TY - ABST T1 - Temporary Territories and Persistent Places: A Bioarchaeological Evaluation of the Association between Monumentality and Territoriality for Foraging Societies of the Prehistoric Ohio Valley A1 - Seidel, Andrew Colin A1 - Carr, Christopher A1 - Stojanowski, Christopher M A1 - Buikstra, Jane E A1 - Aguilera, Miguel KW - Adena KW - Archaeology KW - Biodistance KW - Kentucky KW - Mortuary Practices KW - Physical anthropology AB - Federal legislation prioritizes the repatriation of culturally unidentifiable human remains to federally-recognized Indian tribes that are linked geographically to the region from which the remains were removed. Such linkages are typically based on a Eurocentric notion of the exclusive use and occupancy of an area of land - a space-based approach to land use. Contemporary collaborations between anthropologists and indigenous communities suggest, however, that indigenous patterns of land use are better characterized as place-based and are therefore more complex and fluid than is reflected in current legislation. Despite these insights, space-based approaches remain common within archaeology. One example is the inference of territorial behavior from the presence of monuments within the archaeological record. Drawing on osteological and mortuary data derived from a sample of Adena mounds located in northern Kentucky, this dissertation adopts a place-based approach in order to evaluate the archaeological association between monumentality and territoriality. The relative amounts of skeletal and phenotypic variability present at various spatial scales are quantified and compared and the degree to which mortuary and phenotypic data exhibit spatial structure consistent with the expectations of an isolation-by-distance model is assessed. Results indicate that, while burial samples derived from some mounds exhibit amounts of phenotypic variability that are consistent with the expectations of a territorial model, data from other mounds suggest that multiple groups participated in their construction. Further, the general absence of spatial structure within the phenotypic data suggests that the individuals interred in these mounds are perhaps better characterized as representing an integrated regional population rather than localized groups. Untested archaeological inferences of territoriality may therefore mischaracterize regional population dynamics. In addition, these results suggest that the prioritization criteria for the repatriation of culturally unidentifiable human remains may merit revision. JF - Temporary Territories and Persistent Places: A Bioarchaeological Evaluation of the Association between Monumentality and Territoriality for Foraging Societies of the Prehistoric Ohio Valley PB - Arizona State University UR - http://hdl.handle.net/2286/R.I.53667 N1 - Doctoral Dissertation Anthropology 2019 ER - TY - JOUR T1 - Hydrothermal Plume Fallout, Mass Wasting, and Volcanic Eruptions Contribute to Sediments at Loki's Castle Vent Field, Mohns Ridge JF - Geochemistry, Geophysics, Geosystems Y1 - 2024 A1 - Gartman, A. A1 - Payan, D. A1 - Au, M. A1 - Reeves, E. P. A1 - Jamieson, J. W. A1 - Gini, C. A1 - Roerdink, D. AB - Sediments surrounding hydrothermal vents are important transition spaces between hydrothermal and pelagic environments. These sediments accumulate through diverse processes that include water column plume fallout, volcanic ash deposition, and mass wasting of hydrothermal chimneys and mounds superimposed upon background sedimentation which may originate from pelagic, terrestrial, and volcanic sources. In addition to being a sink for elements discharged from hydrothermal vents, elements may also be scavenged from seawater onto oxidized hydrothermal material. Preservation of these hydrothermal sediments may occur depending on the extent of oxidative and/or reductive dissolution processes after burial. Sediments remaining adjacent to active venting may also be hydrothermally altered after emplacement. To better understand these processes, here we evaluate sediment push cores collected from the Loki's Castle vent field at the intersection of the slow-ultraslow spreading Mohns and Knipovich mid-ocean ridges. All samples were collected within ∼225 m of current high-temperature (299–316°C) “black smoker” fluid discharge. These sediment cores are highly heterogeneous and lack stratigraphic correlation, even for samples taken within meters of each other. Most sediment cores are dominated by either pelagic sediments or mass wasted hydrothermal material, with hydrothermal plume fallout contributing a low proportion of material, and only a single volcanic ash layer occurring in one of the 13 cores. Dominant hydrothermal minerals found include talc, goethite, pyrite, pyrrhotite, and sphalerite. We find that even after several thousand years, most mass wasted hydrothermal material remains minimally altered, with sedimentation rates indistinguishable from background rates within several hundred meters of the hydrothermal vent source. VL - 25 UR - https://onlinelibrary.wiley.com/doi/abs/10.1029/2023GC011094 IS - 2 N1 - _eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1029/2023GC011094 ER - TY - JOUR T1 - Hydrothermal Seepage of Altered Crustal Formation Water Seaward of the Middle America Trench, Offshore Costa Rica JF - Geochemistry, Geophysics, Geosystems Y1 - 2024 A1 - Parsons, Patrice K. F. A1 - Wheat, C. Geoffrey A1 - Fisher, Andrew T. A1 - Silver, Eli A. A1 - Hutnak, Michael KW - formation water KW - hydrogeology KW - hydrothermal KW - Middle American Trench KW - pore water KW - ridge flank AB - Chemical compositions of sediment pore waters are presented from 13 piston and gravity cores that were collected on ∼24 Ma crust of the Cocos Plate seaward of the Middle America Trench and near the onset of crustal faulting from subduction. Cores were collected mainly within a 1.75 km2 area overlying a buried basement topographic high that supports an elevated heat flux, consistent with seawater transport within the upper volcanic crust. Systematic variations in pore water chemical profiles indicate upward seepage speeds (up to 1.7 cm yr−1 providing a net flux of 0.1 L s−1), constrain the chemical composition of the formation water within the underlying upper basaltic basement, and elucidate diagenetic reactions in the sediment. Relative to seawater, formation water has an elevated temperature (70–80°C) and concentrations or values of Ca, chlorinity, Sr, Ba, Li, Fe, Mn, Si, Cs, D/H, and Mo, and lower concentrations or values of Mg, Na, sulfate, alkalinity, TCO2, K, B, F, phosphate, 87Sr/86Sr, δ13C, δ18O, U, and Rb. Although this site is located only 30 km from the trench axis, there is no chemical evidence for subduction-related hydrologic influences. Instead, the data are explained by a combination of seawater-basalt reactions within the upper basement and diffusive exchange with overlying sediment, as part of a shallow, ridge-flank hydrothermal system. It is unclear why this site has an elevated heat flux relative to neighboring crust, but this may result from variations in crustal properties or modification related to flexural faulting outboard of the trench. VL - 25 UR - https://onlinelibrary.wiley.com/doi/abs/10.1029/2023GC011246 IS - 1 N1 - _eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1029/2023GC011246 ER - TY - JOUR T1 - Interactions between local glaciers and adjacent grounded Ross Sea ice in the Royal Society Range, Antarctica JF - Quaternary Science Reviews Y1 - 2024 A1 - Miles, Maraina A1 - Hall, Brenda A1 - Denton, George KW - Alpine glaciers KW - Antarctica KW - Be exposure age dating KW - Last glacial maximum KW - radiocarbon KW - Ross Sea AB - The Antarctic Ice Sheet (AIS) has the potential to exert a major control on future global sea level. Here, we gain insight into the response of the Antarctic Ice Sheet (AIS) to changing climate through assessment of ice-sheet behavior during and since the Last Glacial Maximum (LGM) along the western coast of McMurdo Sound. We examine whether expansion of grounded ice in this sector of the Ross Embayment during the last glaciation was caused by increased flux from East Antarctic outlets and local glaciers or was produced by marine influences, such as lowered sea level or reduced melting of submarine grounded ice. During the LGM, grounded ice derived from the Ross Sea deposited a well-defined drift sheet along the Royal Society headlands on the western coast of McMurdo Sound. Twenty-six new radiocarbon dates of subfossil algae within this drift sheet suggest that the ice sheet was at its maximum extent by at least ∼18.4 ka and maintained this position for about five thousand years. Cross-cutting relationships show that local alpine glaciers did not contribute to the grounded ice but rather fluctuated asynchronously. This same relationship held true during the penultimate glaciation, dated to roughly 137–191 ka with 10Be exposure ages. An explanation for this out-of-phase relationship is that different mechanisms controlled their respective extents. Because they lack significant surface melting ablation zones, the local alpine glaciers, which largely terminate on land, were driven by changes in accumulation. These glaciers likely expanded during warmer times when accumulation was higher. In contrast, marine factors, such as global sea-level change and/or subglacial melting, controlled ice fluctuations in the Ross Embayment, including McMurdo Sound, leading to advance during the LGM. VL - 329 UR - https://www.sciencedirect.com/science/article/pii/S0277379124000921 ER - TY - JOUR T1 - Authigenic uranium deposition in the glacial North Atlantic: Implications for changes in oxygenation, carbon storage, and deep water-mass geometry JF - Quaternary Science Reviews Y1 - 2023 A1 - Zhou, Y. A1 - McManus, J. F. KW - Authigenic uranium KW - Bottom water oxygen KW - Last glacial maximum KW - North Atlantic AB - Oxygen in the ocean has essential ecological and climatic functions, and can be an important indicator of deep-ocean ventilation and carbon storage. Previous studies are divided on whether the subsurface North Atlantic, which today is well-oxygenated, had higher or lower oxygen levels during the Last Glacial Maximum (LGM). Crucially, the limited number of previous reconstructions precludes any conclusions regarding basin-wide patterns in past changes in oxygenation. Authigenic uranium in deep-sea sediments is a sensitive redox tracer that can shed light on bottom water oxygen. Here, we leverage published and new U- and Th-series isotope measurements from North Atlantic sediments to calculate the mass accumulation rate of authigenic uranium (aU MAR) during the Holocene and the LGM. We find that greater aU burial, reflecting lower-than-Holocene oxygen levels and correspondingly greater respired carbon storage, were persistent features of the LGM in the deep North Atlantic. The eastern basin was substantially less well-oxygenated than the western basin. This zonal contrast is possibly related to the farther advance and greater infilling to the east of the mid-Atlantic Ridge of deep waters originating from the Southern Ocean. An alternative explanation is the different residence time in the two basins of deep waters originating from the subpolar North Atlantic. Previous compilations of two nutrient tracers, δ13C and CdW, are consistent with the varying-deep-circulation interpretation of our aU MAR dataset. The observed threshold behavior of aU or the pattern of export productivity, especially at high latitudes, may also have enhanced this west-east difference. VL - 300 UR - https://www.sciencedirect.com/science/article/pii/S0277379122005455 ER - TY - JOUR T1 - Caribbean deepwater snappers: Application of the bomb radiocarbon age estimation validation in understanding aspects of ecology and life history JF - PLOS ONE Y1 - 2023 A1 - Overly, Katherine E. A1 - Shervette, Virginia R. KW - Caribbean KW - Eye lens KW - Eyes KW - Fisheries KW - Larvae KW - Marine fish KW - Otolith KW - Reefs AB - Reef fishes have been utilized as food fish throughout the U.S. Caribbean and Gulf of Mexico waters for centuries, with increasing fishing effort in recent decades. As a result, many species have experienced declines in landings, including deepwater snappers such as queen snapper Etelis oculatus and blackfin snapper Lutjanus buccanella. However, little to no peer-reviewed published research exists on basic life history parameters for either species. Confirming the accuracy of an age estimation method for a fish species is essential for ensuring sustainable fisheries management. This is because in the assessment of fisheries species population age-based parameters, including longevity, age at sexual maturity, growth rate, mortality, age-specific reproductive output, and lifetime reproductive output, are important in understanding overall life history strategies of managed stocks. The past stock assessment on U.S. Caribbean queen snapper utilized an estimated longevity of 8 y, derived from length frequencies for fish from St. Lucia. Blackfin snapper has an estimated longevity of 27 y based on a relatively small study from offshore waters of the southeastern U.S. The focus of our investigation was to estimate maximum longevity of two data-poor species in the U.S. Caribbean. The accuracy of ageing methods was tested via bomb radiocarbon age estimation validation and effects of depth on Δ14C in otolith cores and eye lens core values were examined. Results from our work indicate a maximum validated age of 45 y for queen snapper, and 43 y for blackfin snapper. Our findings indicate queen snapper and blackfin snapper are long-lived (> 40 y). The resulting Δ14C comparison between eye lens cores and otolith cores has important implications for the study of age validation, specifically when deepwater species are involved. VL - 18 UR - https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0295650 IS - 12 N1 - Publisher: Public Library of Science ER - TY - JOUR T1 - Comparability of Radiocarbon Measurements in Dissolved Inorganic Carbon of Seawater Produced at ETH-Zurich JF - Radiocarbon Y1 - 2023 A1 - Castrillejo, Maxi A1 - Hansman, Roberta L. A1 - Graven, Heather D. A1 - Lester, Joanna G. A1 - Bollhalder, Silvia A1 - Kündig, Kayley A1 - Wacker, Lukas KW - 14C KW - comparison KW - DIC KW - dissolved inorganic carbon KW - radiocarbon KW - SEAWATER AB - Radiocarbon observations (Δ14C) in dissolved inorganic carbon (DIC) of seawater provide useful information about ocean carbon cycling and ocean circulation. To deliver high-quality observations, the Laboratory of Ion Beam Physics (LIP) at ETH-Zurich developed a new simplified method allowing the rapid analysis of radiocarbon in DIC of small seawater samples, which is continually assessed by following internal quality controls. However, a comparison with externally produced 14C measurements to better establish an equivalency between methods was still missing. Here, we make the first intercomparison with the National Ocean Sciences Accelerator Mass Spectrometry (NOSAMS) facility based on 14 duplicate seawater samples collected in 2020. We also compare with prior deep-water observations from the 1970s to 1990s. The results show a very good agreement in both comparisons. The mean Δ14C of 12 duplicate samples measured by LIP and NOSAMS were statistically identical within one sigma uncertainty while two other duplicate samples agreed within two sigma. Based on this small number of duplicate samples, LIP values appear to be slightly lower than the NOSAMS values, but more measurements will be needed for confirmation. We also comment on storage and preservation techniques used in this study, including the freezing of samples collected in foil bags. UR - https://www.cambridge.org/core/journals/radiocarbon/article/comparability-of-radiocarbon-measurements-in-dissolved-inorganic-carbon-of-seawater-produced-at-ethzurich/B9F6C6AA45835FA3ED0BF8E0CD9788E3 N1 - Publisher: Cambridge University Press ER - TY - JOUR T1 - Comparing the isotopic and molecular composition of dissolved organic carbon between the oligotrophic South China Sea and the adjacent North Pacific Ocean: Signals of biodegradation, conservative mixing, and terrestrial input JF - Marine Chemistry Y1 - 2023 A1 - Jiang, Peng A1 - Chen, Hongmei A1 - Liu, Zhanfei A1 - Li, Xiaolin KW - carbon isotopes KW - dissolved organic carbon KW - FT-ICR-MS KW - North pacific ocean KW - radiocarbon KW - south china sea AB - The cycling of oceanic dissolved organic carbon (DOC) is a crucial component of the global carbon cycle, yet the identification of sources and the mechanisms of its molecular transformation remain poorly understood. This study compared the isotopic and molecular composition of DOC between the oligotrophic South China Sea (SCS) and the adjacent North Pacific Ocean (NPO), and traced both its allochthonous and autochthonous sources as well as its dynamic cycling processes. DOC was collected through solid-phase extraction (SPE) from water samples of both the SCS and NPO. Carbon content, isotopic ratios, and high-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) measurements revealed that SPE-DOC contained both labile and refractory fractions. According to our mass balance model, the labile fraction of SPE-DOC exhibited a decline from 11.5 to 12.6 μM in surface waters to a negligible concentration below 1000 m. Conversely, the refractory fraction of SPE-RDOC maintained a relatively consistent value, ranging from 12.7 to 19.0 μM across the entire water column. The vertical distribution patterns of the molecular composition and carbon isotopic ratios jointly indicated that the DOC distributions are shaped by distinct biological and physical processes within different biogeochemical realms of the water column. The production and transformation of the relatively labile DOC fractions were the dominant processes in the epipelagic and mesopelagic zones (upper 1000 m). The extent of diapycnal mixing between the SCS and NPO explained the different vertical distributions of refractory DOC molecules in the bathypelagic oceans. The molecular indices of polyphenol compounds, aromaticity, double bond saturation state, terrestrial mass peaks, and δ13C ratios of SPE-DOC indicated contributions from terrestrial sources, likely riverine input, in the SCS. This study sheds light on the molecular evidence of DOC sources, as well as their transformation and conservative mixing processes along the overturning circulation in marginal seas. VL - 257 UR - https://www.sciencedirect.com/science/article/pii/S0304420323001275 ER - TY - JOUR T1 - Duration and ice thickness of a Late Holocene outlet glacier advance near Narsarsuaq, southern Greenland JF - Climate of the Past Y1 - 2023 A1 - Puleo, Peter J. K. A1 - Axford, Yarrow AB - Greenland Ice Sheet (GrIS) outlet glaciers are currently losing mass, leading to sea level rise. Reconstructions of past outlet glacier behavior through the Holocene help us better understand how they respond to climate change. Kiattuut Sermiat, a southern Greenland outlet glacier near Narsarsuaq, is known to have experienced an unusually large Late Holocene advance that culminated at ∼1600 cal yr BP and exceeded the glacier's Little Ice Age extent. We report sedimentary records from two lakes at slightly different elevations in an upland valley adjacent to Kiattuut Sermiat. These reveal when the outlet glacier's surface elevation was higher than during the Little Ice Age and constrain the associated outlet glacier surface elevation. We use bulk sediment geochemistry, magnetic susceptibility, color, texture, and the presence of aquatic plant macrofossils to distinguish between till, glaciolacustrine sediments, and organic lake sediments. Our 14C results above basal till recording regional deglaciation skew slightly old due to a reservoir effect but are generally consistent with regional deglaciation occurring ∼ 11 000 cal yr BP. Neoglacial advance of Kiattuut Sermiat is recorded by deposition of glaciolacustrine sediments in the lower-elevation lake, which we infer was subsumed by an ice-dammed lake that formed along the glacier's margin just after ∼ 3900 cal yr BP. This timing is consistent with several other glacial records in Greenland showing neoglacial cooling driving advance between ∼ 4500–3000 cal yr BP. Given that glaciolacustrine sediments were deposited only in the lower-elevation lake, combined with glacial geomorphological evidence in the valley containing these lakes, we estimate the former ice margin's elevation to have been ∼ 670 m a.s.l., compared with ∼ 420 m a.s.l. today. The ice-dammed lake persisted until the glacier surface fell below this elevation at ∼ 1600 cal yr BP. The retreat timing contrasts with overall evidence for cooling and glacier advance in the region at that time, so we infer that Kiattuut Sermiat's retreat may have resulted from reduced snowfall amounts and/or local glaciological complexity. High sensitivity to precipitation changes could also explain the relatively limited Little Ice Age advance of Kiattuut Sermiat compared with the earlier neoglacial advance. VL - 19 UR - https://cp.copernicus.org/articles/19/1777/2023/ N1 - Publisher: Copernicus GmbH ER - TY - JOUR T1 - Earthquake-enhanced dissolved carbon cycles in ultra-deep ocean sediments JF - Nature Communications Y1 - 2023 A1 - Chu, Mengfan A1 - Bao, Rui A1 - Strasser, Michael A1 - Ikehara, Ken A1 - Everest, Jez A1 - Maeda, Lena A1 - Hochmuth, Katharina A1 - Xu, Li A1 - McNichol, Ann A1 - Bellanova, Piero A1 - Rasbury, Troy A1 - Kölling, Martin A1 - Riedinger, Natascha A1 - Johnson, Joel A1 - Luo, Min A1 - März, Christian A1 - Straub, Susanne A1 - Jitsuno, Kana A1 - Brunet, Morgane A1 - Cai, Zhirong A1 - Cattaneo, Antonio A1 - Hsiung, Kanhsi A1 - Ishizawa, Takashi A1 - Itaki, Takuya A1 - Kanamatsu, Toshiya A1 - Keep, Myra A1 - Kioka, Arata A1 - McHugh, Cecilia A1 - Micallef, Aaron A1 - Pandey, Dhananjai A1 - Proust, Jean Noël A1 - Satoguchi, Yasufumi A1 - Sawyer, Derek A1 - Seibert, Chloé A1 - Silver, Maxwell A1 - Virtasalo, Joonas A1 - Wang, Yonghong A1 - Wu, Ting-Wei A1 - Zellers, Sarah AB - Hadal trenches are unique geological and ecological systems located along subduction zones. Earthquake-triggered turbidites act as efficient transport pathways of organic carbon (OC), yet remineralization and transformation of OC in these systems are not comprehensively understood. Here we measure concentrations and stable- and radiocarbon isotope signatures of dissolved organic and inorganic carbon (DOC, DIC) in the subsurface sediment interstitial water along the Japan Trench axis collected during the IODP Expedition 386. We find accumulation and aging of DOC and DIC in the subsurface sediments, which we interpret as enhanced production of labile dissolved carbon owing to earthquake-triggered turbidites, which supports intensive microbial methanogenesis in the trench sediments. The residual dissolved carbon accumulates in deep subsurface sediments and may continue to fuel the deep biosphere. Tectonic events can therefore enhance carbon accumulation and stimulate carbon transformation in plate convergent trench systems, which may accelerate carbon export into the subduction zones., Earthquakes enhance dissolved carbon production and fuel the microbial activities in hadal trench subsurface sediments, and ultimately strengthen carbon accumulation and transformation in the subduction zones. VL - 14 UR - https://www.nature.com/articles/s41467-023-41116-w ER - TY - JOUR T1 - Geology constrains biomineralization expression and functional trait distribution in the Mountainsnails JF - Journal of Biogeography Y1 - 2023 A1 - Linscott, T. Mason A1 - Recla, Nicole K. A1 - Parent, Christine E. KW - calcareous rock KW - ecophysiological constraint KW - functional biogeography KW - land snail KW - ornamentation KW - random forest KW - resource availability AB - Aim Geographic variation in metabolic resources necessary for functional trait expression can set limits on species distributions. For species that need to produce and maintain biomineralized traits for survival, spatial variation in mineral macronutrients may constrain species distributions by limiting the expression of biomineralized traits. Here, we examine whether Oreohelix land snails that express heavily biomineralized shell ornaments are restricted to CaCO3 rock regions, if they incorporate greater amounts of CaCO3 rock carbon in their shell than less biomineralized smooth forms, and if ornamentation increases shell strength. Location Western United States. Taxon Oreohelix land snails. Methods We used random forest classification models at multiple spatial resolutions to evaluate the contribution of topographic, vegetation, climate, and geologic variables in predicting the presence of heavily biomineralized shell ornaments across the range of Oreohelix. We then measured and compared shell biometric variables, 14C/12C ratios, and peak force for fracture for ornamented and smooth forms from calcareous and non-calcareous substrates. Results Distance to CaCO3 rock was the most important variable in all models and closer proximity to CaCO3 rock was associated with greater probability of local ornamentation classification. Pairwise comparisons of 14C/12C ratios in closely occurring ornamented vs. smooth population pairs revealed ornamented forms incorporate greater CaCO3 rock carbon than smooth forms. Ornamented types measured in this study were generally heavier and required greater peak force for fracture than smooth forms, except when comparing ornamented forms to smooth forms sampled from CaCO3 rock. Main Conclusions Biomineralization expression, species distribution, and trait function appear to be constrained by mineral supply in a highly diverse group of land snails. This trait-environment relationship provides a basis for future investigations of CaCO3 macronutrient constraints on shell form and species distribution in other terrestrial molluscs and has a direct impact on the management of Oreohelix species. VL - 50 UR - https://onlinelibrary.wiley.com/doi/abs/10.1111/jbi.14723 IS - 12 N1 - _eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/jbi.14723 ER - TY - JOUR T1 - Independent age estimates resolve the controversy of ancient human footprints at White Sands JF - Science Y1 - 2023 A1 - Pigati, Jeffrey S. A1 - Springer, Kathleen B. A1 - Honke, Jeffrey S. A1 - Wahl, David A1 - Champagne, Marie R. A1 - ZIMMERMAN, SUSAN R. H. A1 - Gray, Harrison J. A1 - Santucci, Vincent L. A1 - Odess, Daniel A1 - Bustos, David A1 - Bennett, Matthew R. AB - Human footprints at White Sands National Park, New Mexico, USA, reportedly date to between \textasciitilde23,000 and 21,000 years ago according to radiocarbon dating of seeds from the aquatic plant Ruppia cirrhosa. These ages remain controversial because of potential old carbon reservoir effects that could compromise their accuracy. We present new calibrated 14C ages of terrestrial pollen collected from the same stratigraphic horizons as those of the Ruppia seeds, along with optically stimulated luminescence ages of sediments from within the human footprint–bearing sequence, to evaluate the veracity of the seed ages. The results show that the chronologic framework originally established for the White Sands footprints is robust and reaffirm that humans were present in North America during the Last Glacial Maximum. VL - 382 UR - https://www.science.org/doi/10.1126/science.adh5007 N1 - Publisher: American Association for the Advancement of Science ER - TY - JOUR T1 - Lake Dynamics Modulate the Air Temperature Variability Recorded by Sedimentary Aquatic Biomarkers: A Holocene Case Study From Western Greenland JF - Journal of Geophysical Research: Biogeosciences Y1 - 2023 A1 - Cluett, A. A. A1 - Thomas, E. K. A1 - McKay, N. P. A1 - Cowling, O. C. A1 - Castañeda, I. S. A1 - Morrill, C. KW - Alkenone KW - Arctic KW - biogeochemical proxies KW - brGDGT KW - data-model comparison KW - proxy system modeling AB - Quantitative temperature reconstructions from lacustrine organic geochemical proxies including branched glycerol dialkyl glycerol tetraethers (brGDGTs) and alkenones provide key constraints on past continental climates. However, estimation of air temperatures from proxies can be impacted by non-stationarity in the relationships between seasonal air and water temperatures, a factor not yet examined in strongly seasonal high-latitude settings. We pair downcore analyses of brGDGTs and alkenones measured on the same samples through the Holocene with forward-modeled proxy values based on thermodynamic lake model simulations for a western Greenland lake. The measured brGDGT distributions suggest that stable autochthonous (aquatic) production overpowers allochthonous inputs for most samples, justifying the use of the lake model to interpret temperature-driven changes. Conventional calibration of alkenones (detected only after 5.5 thousand years BP) suggests substantially larger temperature variations than conventional calibration of brGDGTs. Comparison of proxy measurements to forward-modeled values suggests variations in brGDGT distributions monotonically reflect multi-decadal summer air temperatures changes, although the length of the ice-free season dampens the influence of air temperatures on water temperatures. Drivers of alkenone variability remain less clear; potential influences include small changes in the seasonality of proxy production or biases toward specific years, both underlain by non-linearity in water-air temperature sensitivity during relevant seasonal windows. We demonstrate that implied temperature variability can differ substantially between proxies because of differences in air-water temperature sensitivity during windows of proxy synthesis without necessitating threshold behavior in the lake or local climate, and recommend that future studies incorporate lake modeling to constrain this uncertainty. VL - 128 UR - https://onlinelibrary.wiley.com/doi/abs/10.1029/2022JG007106 IS - 7 N1 - _eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1029/2022JG007106 ER - TY - JOUR T1 - Machine learning based anomaly detection for sedimentological data: Application to a Holocene multi-proxy paleoenvironmental reconstruction from Laguna Boquita, Jalisco, Mexico JF - Marine Geology Y1 - 2023 A1 - Bianchette, Thomas A. A1 - Pandey, Vijitashwa A1 - Mollan, Calahan A1 - Hall, Sawyer A1 - McCloskey, Terrence A. A1 - Liu, Kam-biu KW - Loss-on-ignition KW - Machine learning KW - Paleoclimate KW - peat KW - Radiocarbon dating KW - x-ray fluorescence AB - Paleoenvironmental reconstructions are critical to determine past climatological and hydrological conditions, such as sea-level rise (SLR) and extreme events including hurricanes and tsunamis. While established quantitative methods, such as principal components analysis and discriminant analysis, have effectively aided reconstructions by demarcating stratigraphic zones, they suffer from limitations due to the underlying assumptions (linearity, normality). Here, we introduce the machine learning technique anomaly detection for sedimentological reconstructions, capable of objectively pinpointing events (anomalies) in sediment cores. We tested this technique on five sediment cores extracted from Laguna Boquita, located along the Pacific coast of Mexico. Each core was subjected to high resolution loss-on-ignition, while the most representative core (core 1) was deemed the training core and scanned with a handheld XRF unit. In general, the sediment cores were dominated by thick units of peat and/or clay, and most cores contained sand layers. This reconstruction represents many environmental settings, ranging from a sandy terrestrial environment (∼6830- ∼ 6370 cal yr BP), organic-rich wetland (∼6370- ∼ 5170 cal yr BP), and clastic-rich backbarrier lagoon (∼5170 cal yr BP to present). The anomaly detection technique proved effective in marking many events, including marine transgression, evidence of SLR, transitions separating dominant depositional environments, and, perhaps most notably, a faded blue clay layer with minimal LOI variability that may represent a shift in backbarrier water level. The anomaly detection also registered anomalies when events were not visually distinct nor present in the LOI datasets (false positives), which represent sediment core sections that require further investigation with multiple proxies. However, anomaly detection failed to register anomalies in certain core sections that should have registered as events due to their distinct nature. Future efforts will look to improve anomaly detection by choosing different train cores and adding additional proxy datasets. VL - 464 UR - https://www.sciencedirect.com/science/article/pii/S0025322723001378 ER - TY - JOUR T1 - Modeling the dynamic penetration depth of post-1950s water in unconfined aquifers using environmental tracers: Central Valley, California JF - Journal of Hydrology Y1 - 2023 A1 - Faulkner, Kirsten E. A1 - Jurgens, Bryant C. A1 - Voss, Stefan A. A1 - Dupuy, Danielle I. A1 - Levy, Zeno F. KW - Environmental tracers KW - Groundwater age KW - Lumped-parameter model AB - The penetration depth of post-1950s recharge (D-1950) in aquifers is a marker that is frequently used to identify groundwater that is susceptible to anthropogenic contamination. Here, we compute D-1950 values at wells, interpolate them in space, and project them across time to map the moving front of modern recharge in four dimensions in the Central Valley aquifer system, California, USA. Tracers of groundwater age (tritium, carbon-14, noble gases, sulfur hexafluoride, and chlorofluorocarbons) were collected at 650 wells spatially distributed throughout the Central Valley and were fit to a lumped-parameter model that assumes a logarithmic age-depth profile in the aquifer. For samples where tritium was present (>0.3 tritium units), the model was used to predict D-1950 at wells screened above or across the modern-premodern interface (n = 484). Wells with samples where tritium was absent (≤0.3 tritium units) were used to define the depth beyond which groundwater is completely premodern (n = 166). Predicted D-1950 values were below the depth of screen bottoms for wells where groundwater is completely modern, and above the depth of screen tops for wells where groundwater is completely premodern. The interpolated surface of D-1950 is dynamic, less prone to extreme values, and produces maps with lower interpolation errors due to a higher spatial density of wells than maps based on the depth of premodern groundwater. Between 2005 and 2025, D-1950 is expected to deepen by 11 and 12 m in the northern and southern parts of the Central Valley, respectively. Areas where D-1950 increases rapidly are likely to see increases in nitrate and other anthropogenic contaminants associated with the downward moving front of modern water. VL - 616 UR - https://www.sciencedirect.com/science/article/pii/S0022169422013889 ER - TY - JOUR T1 - More Frequent Hurricane Passage Across the Bahamian Archipelago During the Little Ice Age JF - Paleoceanography and Paleoclimatology Y1 - 2023 A1 - Winkler, T. S. A1 - van Hengstum, P. J. A1 - Donnelly, J. P. A1 - Wallace, E. J. A1 - Albury, N. A. A1 - D’Entremont, N. A1 - Hawkes, A. D. A1 - Maio, C. V. A1 - Roberts, J. A1 - Sullivan, R. M. A1 - Woodruff, J. D. KW - Bahamas KW - Carbonate KW - common era KW - hurricanes KW - Paleoclimate KW - sedimentology AB - The year 2020 Common Era (CE) experienced the highest number of named tropical cyclones in the Atlantic Ocean since 1850 CE, but the short instrumental record makes it challenging to assess if this level of activity is statistically meaningful. Here, we present two near-annually resolved hurricane reconstructions from sediment archived in two blue holes located only 300 m apart on the northern margin of Grand Bahama. These two blue holes provide a replicated signal of hurricanes passing within a 50–100 km radius over the last 1,800 years, and the long-term reconstructions document multiple 50-to-150-year intervals when hurricane frequency was significantly higher than it has been over the last 100 years. These two records were first merged into a single stack, and then compiled with five other high-resolution reconstructions from across the Bahamian Archipelago to form a single 1500-year record of Bahamian hurricane frequency. This new Bahamian Compilation documents more hurricanes passing ∼75°W from 21°N to 26°N during the Little Ice Age (LIA; 1300–1850 CE) relative to the prior millennium and the last 170 years. The US Eastern Seaboard also experienced heightened hurricane activity during the LIA, whereas the Gulf of Mexico and Southern Caribbean were inactive. This suggests that despite a globally cooler climate, regional climate conditions during the LIA remained favorable for cyclogenesis and intensification along certain Atlantic hurricane pathways. Perhaps heightened Sahel rainfall during the LIA indicates an increase in African Easterly waves, which in turn possibly seeded more tropical cyclones in the Atlantic Main Development Region. VL - 38 UR - https://onlinelibrary.wiley.com/doi/abs/10.1029/2023PA004623 IS - 11 N1 - _eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1029/2023PA004623 ER - TY - JOUR T1 - New insights on black carbon in pelagic Atlantic sediments JF - Marine Chemistry Y1 - 2023 A1 - St.Laurent, Kari A1 - Cantwell, Mark A1 - Lohmann, Rainer KW - Atlantic Ocean KW - BLACK CARBON KW - Polycyclic aromatic hydrocarbons KW - radiocarbon KW - sediments AB - Black carbon (BC) is ubiquitous in pelagic sediments and presumed to have an older radiocarbon age due to long ocean residence times and pre-aging in terrestrial soils. Here, we analyzed sediments from five regions in the subtropical Atlantic Ocean to quantify the black carbon fraction of the total organic carbon pool. Black carbon, derived from the chemothermal oxidation method, comprised between 17 ± 6% of the sedimentary organic carbon in the Northwest Argentina Basin and 65 ± 18% in the Amazon Delta. Black carbon sediment accumulation rates were six times greater in the Sierra Leone Rise (8.4 ± 4.1 mg cm−2 kyr−1) compared to the remote Northwest Argentina Basin (1.3 ± 0.4 mg cm−2 kyr−1), possibly due to enhanced regional atmospheric deposition from annual African grassland fires. The radiocarbon age for BC from subtropical Atlantic sediments were more modern compared to the bulk total organic carbon, and BC source was apportioned as biomass burning byproducts from their stable carbon isotopic signatures and characteristic ratios of polycyclic aromatic hydrocarbons. This study demonstrated that subtropical Atlantic Ocean sediments serve as an important sink for young BC. UR - https://www.sciencedirect.com/science/article/pii/S0304420323001081 ER - TY - JOUR T1 - Organic carbon and planktic foraminifera radiocarbon derived Holocene sediment accumulation rates in the northern slopes of the Gulf of Mexico JF - Deep Sea Research Part I: Oceanographic Research Papers Y1 - 2023 A1 - Schwing, Patrick A1 - Chanton, Jeffrey A1 - Bosman, Samantha A1 - Brooks, Gregg A1 - Larson, Rebekka A. A1 - Romero, Isabel A1 - Diercks, Arne KW - accumulation rates KW - Foraminifera KW - Gulf of Mexico KW - radiocarbon KW - Radiogeochemistry AB - In the context of climate regulation and anthropogenic waste detoxification (e.g. oil spills), estimates of deep ocean sedimentation and carbon sequestration are of the utmost importance. Radiocarbon (14C) is a common radioisotope that can be used to establish millennial scale sediment accumulation rates. The objectives of this study were to: 1) establish ages for co-occurring total organic carbon (TOC) and planktic foraminifera (carbonate) in the northeastern Gulf of Mexico (GoM), 2) use these ages to estimate accumulation rates independently, 3) identify any evidence of redistribution, and 4) examine any offset between TOC and carbonate 14C ages as a tool to potentially identify selective TOC transport. Sediment samples were collected in May 2018 from the RV Point Sur using an Ocean Instruments MC-800 multi corer. Radiocarbon measurements of both planktic foraminifera and TOC subsamples were made at the National Ocean Science Accelerator Mass Spectrometry Facility (NOSAMS). Radiocarbon ages, calibrated using the OxCal 4.4, ranged from recent to 6407 BP. Linear (LAR: 4–24 cm/kyr) and mass accumulation rates (MAR: 1.5–11.5 g/cm2/kyr) were generally consistent with those reported by other recent studies in the GoM. At two sites, C14 ages decreased from the surface to the second sampling increment which was consistent with sediment redistribution. The TOC-carbonate offsets, which are indicative of lateral advection and organic matter aging, were lower than those found in the majority of other regions, which was consistent with less lateral transport or a more oligotrophic setting. The magnitude in radiocarbon age offsets with depth could potentially be used as a relative aging or transport assessment tool in areas with little resuspension. VL - 193 UR - https://www.sciencedirect.com/science/article/pii/S0967063722002722 ER - TY - JOUR T1 - Pre-aged terrigenous organic carbon biases ocean ventilation-age reconstructions in the North Atlantic JF - Nature Communications Y1 - 2023 A1 - Liu, Jingyu A1 - Wang, Yipeng A1 - Jaccard, Samuel L. A1 - Wang, Nan A1 - Gong, Xun A1 - Fang, Nianqiao A1 - Bao, Rui KW - Carbon cycle KW - Marine chemistry KW - Palaeoceanography AB - Changes in ocean ventilation have been pivotal in regulating carbon sequestration and release on centennial to millennial timescales. However, paleoceanographic reconstructions documenting changes in deep-ocean ventilation using 14C dating, may bear multidimensional explanations, obfuscating the roles of ocean ventilation played on climate evolution. Here, we show that previously inferred poorly ventilated conditions in the North Atlantic were linked to enhanced pre-aged organic carbon (OC) input during Heinrich Stadial 1 (HS1). The 14C age of sedimentary OC was approximately 13,345 ± 692 years older than the coeval foraminifera in the central North Atlantic during HS1, which is coupled to a ventilation age of 5,169 ± 660 years. Old OC was mainly of terrigenous origin and exported to the North Atlantic by ice-rafting. Remineralization of old terrigenous OC in the ocean may have contributed to, at least in part, the anomalously old ventilation ages reported for the high-latitude North Atlantic during HS1. VL - 14 UR - https://www.nature.com/articles/s41467-023-39490-6 N1 - Number: 1 Publisher: Nature Publishing Group ER - TY - JOUR T1 - Radiocarbon Constraints on Carbon Release From the Antarctic Ice Sheet Into the Amundsen Sea Embayment JF - Journal of Geophysical Research: Biogeosciences Y1 - 2023 A1 - Fang, Ling A1 - Kim, Minkyoung KW - Antarctica KW - melting ice KW - organic carbon fluxes KW - radiocarbon AB - The Amundsen Sea Embayment in West Antarctica is experiencing rapid ice mass loss, resulting in biogeochemical changes via altered nutrient and organic matter supply. However, organic carbon released from melting ice has not yet been accurately quantified. In this paper, we have integrated new dissolved organic carbon (DOC) data obtained close to the melting Dotson Ice Shelf (DIS) with published radiocarbon (Δ14C) data on sinking and suspended particulate organic carbon (POC), sedimentary OC, DOC and dissolved inorganic carbon to quantify the effect of ice melt to the carbon cycle. Elevated DOC concentrations in deep water near the DIS indicate the transport of carbon sources from the ice shelf to the water column at a rate of 4.6 ± 2.0 × 1010 g C yr−1. Furthermore, Δ14C-DOC measurements suggest there is a possible dark chemoautotrophic production under the influence of meltwater input. The vertical profile of Δ14C in the sedimentary OC from the Sea Ice Zone and the edge of the DIS demonstrates the presence of aged organic carbon sources during warm episodes at ∼11.5 and 15.9 ka BP. Our study indicates that deep water is not only affected by OC discharge from meltwater but also by biological processes due to altered nutrient inputs. Limited data hampers a precise assessment of the influence of meltwater on the carbon cycle. Further sampling in front of the DIS will be beneficial to enhance our understanding of the role of Antarctic Ice Sheet melting in the downstream ecosystem. VL - 128 UR - https://onlinelibrary.wiley.com/doi/abs/10.1029/2022JG007053 N1 - _eprint: https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2022JG007053 ER - TY - JOUR T1 - Radiocarbon dating of the historic grand baobab of Mahajanga, Madagascar JF - Studia Universitatis Babeș-Bolyai Chemia Y1 - 2023 A1 - Patrut, Adrian A1 - Patrut, Roxana T A1 - Rakosy, Laszlo A1 - RATIU, ILEANA ANDREEA A1 - Danthu, Pascal A1 - Leong Pock Tsy, Jean-Michel A1 - von Reden, Karl F AB - The article reports the AMS (accelerator mass spectrometry) radiocarbon investigation of the historic Grand Baobab of Mahajanga. The largest African baobab of Madagascar exhibits a cluster structure, which consists of 6 fused ordinary stems and of 3 small binding stems. Two samples were collected from the largest stem and from a primary branch, out of which several tiny segments were extracted and dated by radiocarbon. The oldest dated sample segment had a radiocarbon date of 214 ± 17 BP, which corresponds to a calibrated age of 265 ± 25 calendar years. The dating results indicate that the Grand Baobab of Mahajanga is 275 ± 25 years old. VL - 68 IS - 1 ER - TY - JOUR T1 - Refractory Dissolved Organic Matter has Similar Chemical Characteristics but Different Radiocarbon Signatures With Depth in the Marine Water Column JF - Global Biogeochemical Cycles Y1 - 2023 A1 - White, Margot E. A1 - Nguyen, Tran B. A1 - Koester, Irina A1 - Lardie Gaylord, Mary C. A1 - Beman, J. Michael A1 - Smith, Kenneth L. A1 - McNichol, Ann P. A1 - Beaupré, Steven R. A1 - Aluwihare, Lihini I. KW - marine dissolved organic matter KW - radiocarbon KW - ramped pyrolysis oxidation AB - The >5,000-year radiocarbon age (14C-age) of much of the 630 ± 30 Pg C oceanic dissolved organic carbon (DOC) reservoir remains an enigma in the marine carbon cycle. The fact that DOC is significantly older than dissolved inorganic carbon at every depth in the ocean forms the basis of our current framing of the marine DOC cycle, where some component persists over multiple cycles of ocean mixing. As a result, 14C-depleted, aged DOC is hypothesized to be present as a uniform reservoir with a constant 14C signature and concentration throughout the water column. However, key requirements of this model, including direct observations of DOC with similar 14C signatures in the surface and deep ocean, have never been met. Despite decades of research, the distribution of Δ14C values in marine DOC remains a mystery. Here, we applied a thermal fractionation method to compare operationally defined refractory DOC (RDOC) from different depths in the North Pacific Ocean. We found that RDOC shares chemical characteristics (as recorded by OC bond strength) throughout the water column but does not share the same 14C signature. Our results support one part of the current paradigm—that RDOC is comprised of structurally related components throughout the ocean that form a “background” reservoir. However, in contrast to the current paradigm, our results are consistent with a vertical concentration gradient and a vertical and inter-ocean Δ14C gradient for RDOC. The observed Δ14C gradient is compatible with the potential addition of pre-aged DOC to the upper ocean. VL - 37 UR - https://onlinelibrary.wiley.com/doi/abs/10.1029/2022GB007603 IS - 4 N1 - _eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1029/2022GB007603 ER - TY - JOUR T1 - Sequential thermal analysis of complex organic mixtures: Procedural standards and improved CO2 purification capacity JF - Radiocarbon Y1 - 2023 A1 - Hanke, Ulrich M. A1 - Gagnon, Alan R. A1 - Reddy, Christopher M. A1 - Gaylord, Mary C. Lardie A1 - Cruz, Anne J. A1 - Galy, Valier A1 - Hansman, Roberta L. A1 - Kurz, Mark D. KW - chemical analysis KW - dirt burner KW - full oxidation (FOX) mode KW - Radiocarbon dating KW - ramped pyrolysis oxidation AB - Sequential thermal analysis allows for deconvoluting the refractory nature and complexity of carbon mixtures embedded in mineral matrices for subsequent offline stable carbon and radiocarbon (14C) isotope analyses. Originally developed to separate Holocene from more ancient sedimentary organic matter to improve dating of marine sediments, the Ramped Pyrolysis and Oxidation (RPO) apparatus, or informally, the “dirt burner” is now used to address pressing questions in the broad field of biogeochemistry. The growing interest in the community now necessitates improved handling and procedures for routine analyses of difficult sample types. Here we report on advances in CO2 purification during sample processing, modifications to the instrumentation at the National Ocean Sciences Accelerator Mass Spectrometry (NOSAMS) facility, and introduce sodium bicarbonate procedural standards with differing natural abundance 14C signatures for blank assessment. Measurements from different environmental samples are used to compare the procedure to the different generations of sequential thermal analyses. With this study, we aim to improve the standardization of the procedures and prepare this instrumentation for innovations in online stable carbon isotopes and direct AMS-interface measurements in the future. VL - 65 UR - https://www.cambridge.org/core/journals/radiocarbon/article/sequential-thermal-analysis-of-complex-organic-mixtures-procedural-standards-and-improved-co2-purification-capacity/E225F01B421614EE176553014E7B38BE IS - 2 N1 - Publisher: Cambridge University Press ER - TY - JOUR T1 - Styles and rates of mesophotic reef accretion on a Caribbean insular slope JF - Coral Reefs Y1 - 2023 A1 - Sherman, Clark E. A1 - Carlo, Milton A1 - Tuohy, Evan A1 - Adey, Walter H. KW - Autochthonous micrite (automicrite) KW - Mesophotic coral ecosystem KW - Reef accretion KW - Reef framework AB - Structural framework is fundamental to the concept of a coral-algal reef. However, our current understanding of reef framework is based largely upon studies of relatively shallow systems that formed at water depths of less than 30 m. There is comparatively limited information on deeper, mesophotic reef frameworks. Short drill cores collected at depths of \textasciitilde 50 m on the steep insular slope of southwest Puerto Rico allow for documentation of the composition and accretion rates of mesophotic reef framework. Framework is dominated by platy agariciid corals (Agaricia spp.) and autochthonous micrite (automicrite) with calcareous algae, corallines and peyssonnelids, forming a secondary component. Conspicuously, well-lithified automicrite constitutes a major structural and volumetric component of the framework. It is composed of magnesian calcite and displays irregular clotted, peloidal and fenestral fabrics, consistent with in situ formation. Radiocarbon ages of corals and automicrite indicate that they have formed recently (< 4 ka) and coevally in their current setting over a period of relative environmental stability. The steep slope gradient and associated dynamic oceanographic conditions may allow for extensive automicrite formation. Mesophotic reef accretion is occurring on the steep slope, though at slow rates of \textasciitilde 0.3 m ka−1. UR - https://doi.org/10.1007/s00338-023-02402-7 ER - TY - JOUR T1 - Surface climate signals transmitted rapidly to deep North Atlantic throughout last millennium JF - Science Y1 - 2023 A1 - Lu, Wanyi A1 - Oppo, Delia W. A1 - Gebbie, Geoffrey A1 - Thornalley, David J. R. AB - Instrumental observations of subsurface ocean warming imply that ocean heat uptake has slowed 20th-century surface warming. We present high-resolution records from subpolar North Atlantic sediments that are consistent with instrumental observations of surface and deep warming/freshening and in addition reconstruct the surface-deep relation of the last 1200 years. Sites from \textasciitilde1300 meters and deeper suggest an \textasciitilde0.5 degrees celsius cooling across the Medieval Climate Anomaly to Little Ice Age transition that began \textasciitilde1350 ± 50 common era (CE), whereas surface records suggest asynchronous cooling onset spanning \textasciitilde600 years. These data suggest that ocean circulation integrates surface variability that is transmitted rapidly to depth by the Atlantic Meridional Ocean Circulation, implying that the ocean moderated Earth’s surface temperature throughout the last millennium as it does today. VL - 382 UR - https://www.science.org/doi/10.1126/science.adf1646 IS - 6672 N1 - Publisher: American Association for the Advancement of Science ER - TY - JOUR T1 - A Tropical Cocktail of Organic Matter Sources: Variability in Supraglacial and Glacier Outflow Dissolved Organic Matter Composition and Age Across the Ecuadorian Andes JF - Journal of Geophysical Research: Biogeosciences Y1 - 2023 A1 - Holt, Amy D. A1 - Kellerman, Anne M. A1 - Battin, Tom. I. A1 - McKenna, Amy M. A1 - Hood, Eran A1 - Andino, Patricio A1 - Crespo-Pérez, Verónica A1 - Peter, Hannes A1 - Schön, Martina A1 - De Staercke, Vincent A1 - Styllas, Michail A1 - Tolosano, Matteo A1 - Spencer, Robert G. M. KW - cryosphere KW - dissolved organic carbon KW - Dissolved organic matter KW - Ecuador KW - FT-ICR MS KW - glaciers KW - δ13C-DOC KW - Δ14C-DOC AB - The biogeochemistry of rapidly retreating Andean glaciers is poorly understood, and Ecuadorian glacier dissolved organic matter (DOM) composition is unknown. This study examined molecular composition and carbon isotopes of DOM from supraglacial and outflow streams (n = 5 and 14, respectively) across five ice capped volcanoes in Ecuador. Compositional metrics were paired with streamwater isotope analyses (δ18O) to assess if outflow DOM composition was associated with regional precipitation gradients and thus an atmospheric origin of glacier DOM. Ecuadorian glacier outflows exported ancient, biolabile dissolved organic carbon (DOC), and DOM contained a high relative abundance (RA) of aliphatic and peptide-like compounds (≥27%RA). Outflows were consistently more depleted in Δ14C-DOC (i.e., older) compared to supraglacial streams (mean −195.2 and −61.3‰ respectively), perhaps due to integration of spatially heterogenous and variably aged DOM pools across the supraglacial environment, or incorporation of aged subglacial OM as runoff was routed to the outflow. Across Ecuador, Δ14C-DOC enrichment was associated with decreased aromaticity of DOM, due to increased contributions of organic matter (OM) from microbial processes or atmospheric deposition of recently fixed and subsequently degraded OM (e.g., biomass burning byproducts). There was a regional gradient between glacier outflow DOM composition and streamwater δ18O, suggesting covariation between regional precipitation gradients and the DOM exported from glacier outflows. Ultimately, this highlights that atmospheric deposition may exert a control on glacier outflow DOM composition, suggesting regional air circulation patterns and precipitation sources in part determine the origins and quality of OM exported from glacier environments. VL - 128 UR - https://onlinelibrary.wiley.com/doi/abs/10.1029/2022JG007188 IS - 5 N1 - _eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1029/2022JG007188 ER - TY - JOUR T1 - An 11,300 yr record of paleoclimatology and paleoceanography of the central California coast in a gravity core from Pioneer Seamount JF - Quaternary International Y1 - 2022 A1 - Barron, John A. A1 - Addison, Jason A. A1 - Heusser, Linda E. A1 - Bukry, David A1 - Schwartz, Valerie A1 - Wagner, Amy AB - Diatom, pollen, silicoflagellate, and biogenic opal analyses from a 155 cm-long gravity core from Pioneer Seamount, offshore Santa Cruz, California (PS1410-06 GC, latitude 37.3°N, longitude 123.4°W, water depth 2165 m) are compiled for the last ~11,300 years and compared with those of ODP 1019 and TN062-O550 from northern California. The relative abundance record of the subtropical diatom Fragilariopsis doliolus has similar bimodal Holocene patterns in all three cores, suggesting that sea surface temperatures (SST) were lower during the middle part of the Holocene than they were during the later and earlier parts. The relative abundance of coastal redwood (Sequoia sempervirens) pollen, a proxy for fog and coastal upwelling, displays stepwise increases in ODP 1019 and TN062-O550 between ~ 4000 and 3000 cal yr. BP, but its relative abundance in PS1410-06 GC increases gradually throughout the past 10,200 yr without any major steps. Similarly, biogenic silica (opal) displays stepwise increases at ~3600 and 2900 cal yr. BP in ODP 1019 and TN062-O550, respectively, whereas opal increases more gradually in PS1410-06 GC during the past 10,100 yr with relatively minor steps at ~3100 and ~2600 cal yr. BP. Together, coastal redwood and opal argue for a more gradual late Holocene increase in coastal upwelling along the coast of central California compared with that off northern California, where onshore-offshore gradients are more distinct. VL - 621 UR - https://linkinghub.elsevier.com/retrieve/pii/S1040618219309449 ER - TY - JOUR T1 - A 4000-year paleoenvironmental reconstruction and extreme event record from Laguna Nuxco, Guerrero, Mexico JF - Palaeogeography, Palaeoclimatology, Palaeoecology Y1 - 2022 A1 - Bianchette, Thomas A. A1 - Liu, Kam-biu A1 - McCloskey, Terrence A. AB - Reconstructing paleoenvironments on Mexico's Pacific coast is crucial to determine past climate conditions and natural hazard periodicities, vital for predicting future activities. Two sediment cores extracted from Laguna Nuxco, a coastal lagoon in Guerrero, were analyzed to provide a 4000-year paleoenvironmental record. Sediments dominated by shelly clay with low water and organic content, high carbonate content, low Ti/Ca ratio and the presence of Anomalocardia subrugosa suggest that a sheltered bay existed from ~4000–~1300 cal yr BP. During this stage, intermittent beach ridge gaps facilitated the deposition of storm-induced shell deposits, likely from tropical cyclones. Frequent thick shell hash deposition toward the top of the lithologic unit indicates heightened storminess likely from an increase in ENSO activity. An intense tropical cyclone, or perhaps multiple storms during an active period deposited a thick shell hash layer at ~1500 cal yr BP, which helped strengthen the beach ridge system and lead to the modern lagoon phase (~1300 cal yr BP to present), as suggested by the presence of Mytella sp. A more isolated lagoon with significant terrestrial sediment input was reflected by the predominance of lagoonal clay with decreased shell and carbonate contents, increased water and organic contents, and increased Ti/Ca ratio. A quiet period with lower tropical cyclone activity occurred from 1300 to 800 cal yr BP and from 300 cal yr BP to the present, as inferred from no or relatively few shell hash deposits, respectively. A period of hyperactivity occurred from 800 to 300 cal yr BP, as evidenced by seven shell hash layers. During the modern lagoon phase, shell hash deposition was not caused by marine inundation processes, but rather ‘blowout’ events driven by intense precipitation during heightened ENSO activity. Findings shed additional light on Late Holocene environmental changes in a dynamic coastal zone related to regional controlling factors such as tropical cyclone activity, ENSO, and beach ridge development. VL - 594 UR - https://linkinghub.elsevier.com/retrieve/pii/S0031018222001031 ER - TY - RPRT T1 - Age and water-quality characteristics of groundwater discharge to the South Loup River, Nebraska, 2019 Y1 - 2022 A1 - Hobza, Christopher M. A1 - Solder, John E. AB - Streams in the Loup River Basin are sensitive to groundwater withdrawals because of the close hydrologic connection between groundwater and surface water. The U.S. Geological Survey, in cooperation with the Upper Loup and Lower Loup Natural Resources Districts, and the Nebraska Environmental Trust, studied the age and water-quality characteristics of groundwater near the South Loup River to assess the possible effects of a multiyear drought on streamflow. Groundwater sampled in wells screened in Quaternary-age deposits displayed a wide range of mean ages (27 to 2,100 years), fraction modern, and susceptibility index values. Groundwater with higher concentrations of chloride and higher specific conductance was indicative of younger groundwater with a narrower age distribution and is more sensitive to climatic disturbances such as short-term drought conditions, based on the calculated susceptibility index. Groundwater samples from wells and springs in Pliocene-age deposits were categorized into two groups with different geochemical and age characteristics. One sample group of springs and wells, called the Western Pliocene, had higher concentrations of chloride and nitrate with young mean ages (18 to 77 years) and narrow age distributions. Groundwater in the Western Pliocene sample group is susceptible to short-term drought. In contrast, the other sample group from Pliocene-age deposits to the east (called Pliocene) had lower concentrations of nitrate, chloride, and mean groundwater ages ranging from 1,900 to 2,900 years old and is less likely to be affected by short-term drought conditions. Groundwater sampled from three wells screened in the Ogallala Formation was shown to have the oldest mean ages ranging from 8,700 to 23,000 years and the lowest calculated susceptibility index values observed in this study. Strong upward hydraulic gradients measured in wells indicated that groundwater from the Ogallala Formation is likely contributing to streamflow of the South Loup River. Continuously measured gage height and specific conductance data indicated groundwater discharge from Quaternary-age deposits was highly responsive to precipitation events. In contrast, groundwater discharge from Pliocene-age deposits (Pliocene sample group) was far less responsive, indicating groundwater discharge from Pliocene-age deposits is likely more resilient to short-term drought conditions. JF - Scientific Investigations Report PB - U.S. Geological Survey CY - Reston, VA SN - 2022-5042 UR - http://pubs.er.usgs.gov/publication/sir20225042 ER - TY - JOUR T1 - Baobabs at the edge: 90-year dynamics of climate variability, growth, resilience, and evolutionary legacy effects JF - Frontiers in Forests and Global Change Y1 - 2022 A1 - Mayne, Diana H. A1 - Karimi, Nisa A1 - Cruywagen, Elsie M. A1 - Cole, Patrick A1 - Goodall, Victoria AB - Climate variability and resilience remain gaps in tree research, challenged by the interacting factors in climate change, long-term resilience and the influence of evolutionary legacy effects. In a multidisciplinary approach using 90-year (1930–2020) climate-growth data, we investigated the dynamics of climate variability on growth and resilience of the tropical African baobab (Adansonia digitata) at the range edge in climate-variable, southeast Africa. The main driver of climate variability, ENSO (El Niño-Southern Oscillation), triggered 83% of droughts exacerbated by positive Indian Ocean Dipole (pIOD) events. Growth over 90 years was positively correlated with maximum temperature and increased after the 1976–1977 Global Warming Shift. The influence of warming was compromised by climate variability and extreme events. Although growth is a measure of adaptive capacity, accelerated growth over the past 20 years contrasted with dehydration, canopy dieback and a novel Didymella pathogen. Resilience was contingent on high genetic diversity (polyploidy and heterozygosity) and Neotropical legacy effects of stem water storage and longevity trade-offs of low growth, recruitment and reproduction. The evolution of resprouting in disturbed, fire-prone ecosystems and bark regeneration increased recovery from disturbance. As resource opportunists, baobabs adopted a fast-slow survival strategy. Rainfall and warming enhanced growth while low and variable rainfall favoured a conservative, low growth-higher survival strategy. Low rainfall, climate extremes and topography increased mortality risk. Mortality was higher at lower elevations on site and regionally. Low growth may conserve the baobab in climate warming but the southern hemisphere tropics is one of two identified global hotspots with amplified hot years. The heightened disturbance predicted from increased climate variability, hot droughts and landfalling tropical cyclones magnifies mortality risk for “Africa’s favourite tree.” VL - 5 UR - https://www.frontiersin.org/articles/10.3389/ffgc.2022.1036636 ER - TY - JOUR T1 - Black carbon and organic carbon dataset over the Third Pole JF - Earth System Science Data Y1 - 2022 A1 - Kang, Shichang A1 - Zhang, Yulan A1 - Chen, Pengfei A1 - Guo, Junming A1 - Zhang, Qianggong A1 - Cong, Zhiyuan A1 - Kaspari, Susan A1 - Tripathee, Lekhendra A1 - Gao, Tanguang A1 - Niu, Hewen A1 - Zhong, Xinyue A1 - Chen, Xintong A1 - Hu, Zhaofu A1 - Li, Xiaofei A1 - Li, Yang A1 - Neupane, Bigyan A1 - Yan, Fangping A1 - Rupakheti, Dipesh A1 - Gul, Chaman A1 - Zhang, Wei A1 - Wu, Guangming A1 - Yang, Ling A1 - Wang, Zhaoqing A1 - Li, Chaoliu AB - Abstract. The Tibetan Plateau and its surroundings, also known as the Third Pole, play an important role in the global and regional climate and hydrological cycle. Carbonaceous aerosols (CAs), including black carbon (BC) and organic carbon (OC), can directly or indirectly absorb and scatter solar radiation and change the energy balance on the Earth. CAs, along with the other atmospheric pollutants (e.g., mercury), can be frequently transported over long distances into the inland Tibetan Plateau. During the last decades, a coordinated monitoring network and research program named “Atmospheric Pollution and Cryospheric Changes” (APCC) has been gradually set up and continuously operated within the Third Pole regions to investigate the linkage between atmospheric pollutants and cryospheric changes. This paper presents a systematic dataset of BC, OC, water-soluble organic carbon (WSOC), and water-insoluble organic carbon (WIOC) from aerosols (20 stations), glaciers (17 glaciers, including samples from surface snow and ice, snow pits, and 2 ice cores), snow cover (2 stations continuously observed and 138 locations surveyed once), precipitation (6 stations), and lake sediment cores (7 lakes) collected across the Third Pole, based on the APCC program. These data were created based on online (in situ) and laboratory measurements. High-resolution (daily scale) atmospheric-equivalent BC concentrations were obtained by using an Aethalometer (AE-33) in the Mt. Everest (Qomolangma) region, which can provide new insight into the mechanism of BC transportation over the Himalayas. Spatial distributions of BC, OC, WSOC, and WIOC from aerosols, glaciers, snow cover, and precipitation indicated different features among the different regions of the Third Pole, which were mostly influenced by emission sources, transport pathways, and deposition processes. Historical records of BC from ice cores and lake sediment cores revealed the strength of the impacts of human activity since the Industrial Revolution. BC isotopes from glaciers and aerosols identified the relative contributions of biomass and fossil fuel combustion to BC deposition on the Third Pole. Mass absorption cross sections of BC and WSOC from aerosol, glaciers, snow cover, and precipitation samples were also provided. This updated dataset is released to the scientific communities focusing on atmospheric science, cryospheric science, hydrology, climatology, and environmental science. The related datasets are presented in the form of excel files. BC and OC datasets over the Third Pole are available to download from the National Cryosphere Desert Data Center (https://doi.org/10.12072/ncdc.NIEER.db0114.2021; Kang and Zhang, 2021). VL - 14 UR - https://essd.copernicus.org/articles/14/683/2022/ IS - 2 ER - TY - JOUR T1 - Carbon Accumulation, Flux, and Fate in Stordalen Mire, a Permafrost Peatland in Transition JF - Global Biogeochemical Cycles Y1 - 2022 A1 - Holmes, M. E. A1 - Crill, P. M. A1 - Burnett, W. C. A1 - McCalley, C. K. A1 - Wilson, R. M. A1 - Frolking, S. A1 - Chang, K.‐Y. A1 - Riley, W. J. A1 - Varner, R. K. A1 - Hodgkins, S. B. A1 - McNichol, A. P. A1 - Saleska, S. R. A1 - Rich, V. I. A1 - Chanton, J. P. AB - Stordalen Mire is a peatland in the discontinuous permafrost zone in arctic Sweden that exhibits a habitat gradient from permafrost palsa, to Sphagnum bog underlain by permafrost, to Eriophorum‐dominated fully thawed fen. We used three independent approaches to evaluate the annual, multi‐decadal, and millennial apparent carbon accumulation rates (aCAR) across this gradient: seven years of direct semi‐continuous measurement of CO2 and CH4 exchange, and 21 core profiles for 210Pb and 14C peat dating. Year‐round chamber measurements indicated net carbon balance of −13 ± 8, −49 ± 15, and −91 ± 43 g C m−2 y−1 for the years 2012–2018 in palsa, bog, and fen, respectively. Methane emission offset 2%, 7%, and 17% of the CO2 uptake rate across this gradient. Recent aCAR indicates higher C accumulation rates in surface peats in the palsa and bog compared to current CO2 fluxes, but these assessments are more similar in the fen. aCAR increased from low millennial‐scale levels (17–29 g C m−2 y−1) to moderate aCAR of the past century (72–81 g C m−2 y−1) to higher recent aCAR of 90–147 g C m−2 y−1. Recent permafrost collapse, greater inundation and vegetation response has made the landscape a stronger CO2 sink, but this CO2 sink is increasingly offset by rising CH4 emissions, dominated by modern carbon as determined by 14C. The higher CH4 emissions result in higher net CO2‐equivalent emissions, indicating that radiative forcing of this mire and similar permafrost ecosystems will exert a warming influence on future climate. Stordalen Mire, a permafrost peatland, has become a stronger carbon sink due to shifts in vegetation and inundation accompanying thaw This stronger carbon sink is offset by an increase in methane emission, resulting in higher net CO2‐equivalent emissions Analysis of respiration products indicates that methane emission from the fen and bog are dominated by modern carbon Stordalen Mire, a permafrost peatland, has become a stronger carbon sink due to shifts in vegetation and inundation accompanying thaw This stronger carbon sink is offset by an increase in methane emission, resulting in higher net CO2‐equivalent emissions Analysis of respiration products indicates that methane emission from the fen and bog are dominated by modern carbon VL - 36 UR - https://onlinelibrary.wiley.com/doi/10.1029/2021GB007113 IS - 1 ER - TY - RPRT T1 - Characterization of the partial oxidation products of crude oil contaminating groundwater at the U.S. Geological Survey Bemidji research site in Minnesota by elemental analysis, radiocarbon dating, nuclear magnetic resonance spectroscopy, and Fourier tran Y1 - 2022 A1 - Thorn, Kevin A. A1 - Islam, Ananna A1 - Kim, Sunghwan AB - In oil spill research, a topic of increasing attention during the last decade has been the environmental impact of the partial oxidation products that result from transformation of the petroleum in freshwater, marine, and terrestrial ecosystems. This report describes the isolation and characterization of the partial oxidation products from crude oil contaminating groundwater at the long-term U.S. Geological Survey Bemidji research site in Minnesota. As the result of a pipeline burst in August 1979, a body of light aliphatic crude oil is present from the land surface to 2 meters below the water table in a shallow sand and gravel aquifer in a remote area outside Bemidji, Minnesota, United States. Biodegradation has resulted in the formation of a plume of dissolved organic carbon (DOC) downgradient from the oil body. Groundwater has also been contaminated in an area known as the spray zone, from vertical infiltration of DOC resulting from biodegradation of oil in the soil column, and possibly from photooxidation of oil at the soil surface. The majority of DOC in the contaminated groundwater is in the form of nonvolatile organic acids (NVOAs) which represent the partial oxidation products of the crude oil constituents. The NVOAs have been classified into three fractions according to their isolation on XAD resins: hydrophobic neutrals (HPON), hydrophobic acids (HPOA), and hydrophilic acids (HPIA). These fractions of NVOAs were isolated from wells downgradient from the oil body (sampling well numbers 533, 532, 530, 515), in the spray zone (603), and from an uncontaminated well upgradient of the oil body (310) between the years 1986 and 1989, and again from wells 530 and 603 in 1998. The samples have been characterized by elemental analysis, radiocarbon dating, carbon-13 nuclear magnetic resonance spectroscopy (13C NMR), and negative-mode (-) electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FTICR-MS), with a particular focus on fractions from wells 310, 530, and 603. All the characterization data indicate that the NVOAs from contaminated wells are distinguishable from the background DOC. Carbon-14 (14C) ages of NVOAs from contaminated wells ranged from 3,615 to 18,985 years before the present, whereas the background DOC from the aquifer was post-bomb (post 1950). By elemental analysis, NVOAs from contaminated wells had higher sulfur but lower nitrogen contents than the background. By electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry, number average molecular weights determined from assigned molecular formulas ranged from 416 to 486 daltons for the HPOA and HPIA fractions from both background and contaminant wells. NVOAs from contaminated wells had significantly greater numbers of assigned molecular formulas containing sulfur, with elevated concentrations of the S1O4-10 species in particular. Compared to the background, HPOA and HPIA fractions from contaminant wells had a broader range of double bond equivalents (DBEs) within On compound classes (n is number of atoms). Additionally, within On compound classes, contaminant well HPOA fractions had a greater abundance of lower n (less than eight) than the background. Contaminant well double bond equivalents versus carbon number (C#) plots of oxygen compound classes suggest oil-derived aliphatic compounds in the range from C12 to C22 in HPOA and HPIA fractions and oil-derived compounds containing aromatic or saturated rings in the approximate range from C20 to C30 are present in HPOA fractions. The data suggest the NVOAs originate from biodegradation of several classes of C12 and greater crude oil constituents: sulfur-containing constituents, including possibly the resins and asphaltenes; constituents containing aromatic rings substituted with methyl groups, including alkylaromatic and naph- thenoaromatic compounds, and C12 to C22 alkyl constituents. The overall similarities of the carbon-13 nuclear magnetic resonance spectra for the well 603 and 530 samples from the two sampling dates suggest that a steady state in the composition of the partial oxidation products in each of the two wells had been reached between 1986–1989 and 1998. JF - Open-File Report PB - U.S. Geological Survey CY - Reston VA SN - 2022-1042 UR - http://pubs.er.usgs.gov/publication/ofr20221042 N1 -

doi: 10.3133/ofr20221042

ER - TY - JOUR T1 - Community practice and religion at an Early Islamic cemetery in highland Central Asia JF - Antiquity Y1 - 2022 A1 - Bullion, Elissa A1 - Maksudov, Farhod A1 - Henry, Edward R. A1 - Merkle, Ann A1 - Frachetti, Michael AB - Archaeological studies of Early Islamic communities in Central Asia have focused on lowland urban communities. Here, the authors report on recent geophysical survey and excavation of an Early Islamic cemetery at Tashbulak in south-eastern Uzbekistan. AMS dating places the establishment of the cemetery in the mid-eighth century AD, making it one of the earliest Islamic burial grounds documented in Central Asia. Burials at Tashbulak conform to Islamic prescriptions for grave form and body deposition. The consistency in ritual suggests the existence of a funerary community of practice, challenging narratives of Islamic conversion in peripheral areas as a process of slow diffusion and emphasising the importance of archaeological approaches for documenting the diversity of Early Islamic communities. VL - 96 UR - https://www.cambridge.org/core/journals/antiquity/article/community-practice-and-religion-at-an-early-islamic-cemetery-in-highland-central-asia/4C292A5614CFA03DF5059B1798B70990/share/d72e17180f49f951c611e728fb3634c79f0618ff IS - 387 ER - TY - JOUR T1 - Comparing paleo-oxygenation proxies (benthic foraminiferal surface porosity, I/Ca, authigenic uranium) on modern sediments and the glacial Arabian Sea JF - Geochimica et Cosmochimica Acta Y1 - 2022 A1 - Lu, Wanyi A1 - Wang, Yi A1 - Oppo, Delia W. A1 - Nielsen, Sune G. A1 - Costa, Kassandra M. KW - 13 Climate Action AB - Oceanic oxygen reconstructions of the last glacial period are needed to understand the mechanisms of glacial deep ocean carbon storage and to validate climate model simulations. However, existing bottom-water oxygen (BWO) reconstructions are ambiguous due to limitations of each paleo-BWO proxy. Here we present data on three proxies for BWO: benthic foraminiferal surface porosity, benthic foraminiferal iodine/calcium (I/Ca), and authigenic uranium (aU), from globally distributed core-top samples, and we evaluate the potential advantages and limitations of these BWO proxies on global and regional scales. All three proxies are most sensitive to changes at relatively low BWO concentrations (<∼50 µmol/kg). Data from globally-distributed core tops confirm that foraminiferal surface porosity is correlated with BWO between 0 and 100 µmol/kg. Our analysis further confirms that benthic surface porosity is predominantly controlled directly by BWO rather than other potential functionalities of surface pores such as organic carbon uptake and respiratory CO2 release. Low benthic I/Ca can identify low BWO (<50 µmol/kg), whereas higher benthic I/Ca values are not associated with specific BWO, possibly due to additional dependence of I/Ca on temperature, salinity, carbonate ion concentration, or water mass mixing at higher BWO. The relationship between aU and BWO is regionally dependent. In the Arabian Sea, variable aU enrichments occur only within the Oxygen Minimum Zone (OMZ), driven by high export production and organic matter fluxes to the sediment. Finally, we combine foraminiferal surface porosity, I/Ca and aU to generate the first quantitative glacial-Holocene BWO reconstructions using a sediment core taken from within the modern Arabian Sea OMZ. All three proxies consistently suggest BWO < 50 μmol/kg in the shallow Arabian Sea during the last ∼30 kyr, with relatively higher BWO during the glacial period than the Holocene. A comparison with the benthic carbon isotope gradient proxy (Δδ13C) confirms that Δδ13C over-estimates BWO in low-oxygen settings possibly due to sediment diagenesis impacts. Our study provides new insights on the merits and limitations of these BWO proxies and confirms the importance of multi-proxy reconstructions for more reliable paleo-BWO estimates. VL - 331 SN - 0016-7037 UR - https://www.sciencedirect.com/science/article/pii/S0016703722002666 ER - TY - JOUR T1 - Contemporary sources dominate carbonaceous aerosol on the North Slope of Alaska JF - Science of The Total Environment Y1 - 2022 A1 - Moffett, Claire E. A1 - Mehra, Manisha A1 - Barrett, Tate E. A1 - Gunsch, Matthew J. A1 - Pratt, Kerri A. A1 - Sheesley, Rebecca J. AB - As the Arctic continues to change and warm rapidly, it is increasingly important to understand the organic carbon (OC) contribution to Arctic aerosol. Biogenic sources of primary and secondary OC in the Arctic will be impacted by climate change, including warming temperatures and earlier snow and ice melt. This study focuses on identifying potential sources and regional influences on the seasonal concentration of organic aerosol through analysis of chemical and isotopic composition. Aerosol samples were collected at two sites on the North Slope of Alaska (Utqiaġvik, UQK, and Oliktok Point, OLK, which is in an Arctic oilfield) over three summers from 2015 to 2017. The elemental carbon (EC) trends at each site were used to understand local combustion influences. Local sources drove EC concentrations at Oliktok Point, where high EC was attributed to oil and gas extraction activity, including diesel combustion emissions. Utqiaġvik had very low EC in the summer. OC was more similar in concentration and well correlated between the two sites with high contributions of contemporary carbon by radiocarbon apportionment (UQK = 74%, OLK = 63%), which could include both marine and terrestrial sources of contemporary carbon (e.g. primary and secondary biogenic, biomass burning and/or associated SOA, and bioaerosols). OC concentrations are strongly correlated to maximum ambient temperatures on the NSA during the summer, which may have implications for predicting future OC aerosol concentrations in a warming Arctic. Biomass burning was determined to be an episodic influence at both sites, based on interpretation of combined aerosol composition, air mass trajectories, and remote sensing of smoke plumes. The results from this study overall strongly suggests contribution from regional sources of contemporary organic aerosol on the NSA, but additional analysis is needed to better constrain contributions from both biogenic sources (terrestrial and/or marine) and bioaerosol to better understand temperature-related aerosol processes in the Arctic. VL - 831 UR - https://linkinghub.elsevier.com/retrieve/pii/S004896972201734X ER - TY - JOUR T1 - Cultural Keystone Places and the Chumash Landscapes of Kumqaq’, Point Conception, California JF - American Antiquity Y1 - 2022 A1 - Rick, Torben C. A1 - Braje, Todd J. A1 - Graham, Lain A1 - Easterday, Kelly A1 - Hofman, Courtney A. A1 - Holguin, Brian E. A1 - Mychajliw, Alexis M. A1 - Reeder-Myers, Leslie A. A1 - Reynolds, Mark D. AB - The places in which people live and spend time are steeped in history, memory, and meaning from the intersection of daily life, environmental interactions, cultural practices, and ritual. Geologic features, plants, animals, and ecosystems merge with these cultural histories, forming critical parts of the landscape and areas of “high cultural salience,” or “cultural keystone places” (CKPs). We identify Kumqaq’ (Point Conception) and the surrounding area in California as a Chumash CKP. Ethnohistoric accounts and contemporary Chumash community members have long demonstrated the importance of Point Conception in Chumash worldview and identity, whereas biologists, ecologists, and conservationists reference the area's rich biodiversity and significance as a biogeographical boundary. Recent archaeological survey of the coastline surrounding Kumqaq’ highlights these connections, identifying over 50 archaeological sites—including shell middens, villages, lithic scatters, and rock art—with at least 9,000 years of occupation. Ongoing collaborations among archaeologists, the Nature Conservancy, and Chumash community members help document and understand the long-term linkages between cultural and biological diversity and how integrating these perspectives can help ensure the resilience of this nexus of human and natural history in the Anthropocene future. VL - 87 UR - https://www.cambridge.org/core/journals/american-antiquity/article/cultural-keystone-places-and-the-chumash-landscapes-of-kumqaq-point-conception-california/16A429D7AA4ACF06CE3005A1578A054B/share/c7af0ac75459bd572e942e9246aa0d3791fae5e1 IS - 3 ER - TY - JOUR T1 - The dynamics of warming during the last deglaciation in high-elevation regions of Eastern Equatorial Africa JF - Quaternary Science Reviews Y1 - 2022 A1 - Garelick, Sloane A1 - Russell, James A1 - Richards, Adin A1 - Smith, Jamila A1 - Kelly, Meredith A1 - Anderson, Nathan A1 - Jackson, Margaret S. A1 - Doughty, Alice A1 - Nakileza, Bob A1 - Ivory, Sarah A1 - Dee, Sylvia A1 - Marshall, Charlie AB - Tropical mountain environments, such as the Rwenzori Mountains in equatorial Africa, are thought to be particularly sensitive to climate change. Ongoing warming in the Rwenzori is impacting local environments and communities through glacial retreat, fires, and flooding. Paleoclimate reconstructions from elsewhere in Africa suggest considerable warming accompanied glacier retreat during the last glacial termination, from ∼21 thousand years before present (ka) through the early to mid-Holocene. Quantifying these changes has been difficult but could help to assess future impacts in the Rwenzori. Here, we present a ∼21 thousand-year (kyr) temperature reconstruction based on the relative abundance of branched glycerol dialkyl glycerol tetraethers (brGDGTs) from Lake Mahoma (2,990 m above sea level; m asl) in the Rwenzori Mountains, Uganda. Our record, paired with existing Rwenzori glacial moraine 10Be exposure ages, suggests that deglacial warming and glacial retreat began by ∼20 ka and accelerated at ∼18–18.5 ka. The timing of the onset of rapid warming matches the timing of the post-glacial rise in radiative forcing from atmospheric greenhouse gases (GHGs) from Antarctic ice cores (Brook et al., 1996; Marcott et al., 2014; Monnin et al., 2004; Schilt et al., 2010). Our temperature reconstruction registers ∼4.9 °C warming from the Last Glacial Maximum (LGM) to the late Holocene. This increase is larger than the average ∼2-4 °C warming observed in records from lower elevation sites in tropical East Africa, but similar to that observed at other high-elevation sites in this region. The increased warming at higher elevations thus confirms that the temperature lapse rate steepened during the LGM over this region. Our results also indicate ∼3 °C of warming during the mid-Holocene relative to the late Holocene. This suggests that the freezing-level height rose above Rwenzori summit elevations at that time, likely causing complete deglaciation of the Rwenzori Mountains from ∼5 to 7 ka. The mid-Holocene is thus a potential analog for the glacial and environmental changes that these mountains are likely to experience in the coming decades. Overall, the timing and magnitude of temperature change observed in our record has important implications for climate model projections of future warming in tropical Africa. VL - 281 UR - https://linkinghub.elsevier.com/retrieve/pii/S0277379122000476 ER - TY - JOUR T1 - Geochemistry and Provenance of Springs in a Baja California Sur Mountain Catchment JF - Groundwater Y1 - 2022 A1 - Lerback, Jory C. A1 - Bowen, Brenda B. A1 - Humphrey, C. E. A1 - Fernandez, Diego. P. A1 - Bernau, Jeremiah A. A1 - Macfarlan, Shane J. A1 - Schniter, Eric A1 - Garcia, J. J. AB - Fractured rock aquifers cover much of Earth's surface and are important mountain sites for groundwater recharge but are poorly understood. To investigate groundwater systematics of a fractured-dominated aquifer in Baja California Sur, Mexico, we examined the spatial patterns of aquifer recharge and connectivity using the geochemistry of springs. We evaluate a range of geochemical data within the context of two endmember hypotheses describing spatial recharge patterns and fracture connectivity. Hypothesis 1 is that the aquifer system is segmented, and springs are fed by local recharge. Hypothesis 2 is that the aquifer system is well connected, with dominant recharge occurring in the higher elevations. The study site is a small <15 km2 catchment. Thirty-four distinct springs and two wells were identified in the study area, and 24 of these sites were sampled for geochemical analyses along an elevation gradient and canyon transect. These analyses included major ion composition, trace element and strontium isotopes, δ18 O and δ2 H isotopes, radiocarbon, and tritium. δ18 O and δ2 H isotopes suggest that the precipitation feeding the groundwater system has at least two distinct sources. Carbon isotopes showed a change along the canyon transect, suggesting that shorter flowpaths feed springs in the top of the transect, and longer flowpaths discharge near the bottom. Geochemical interpretations support a combination of the two proposed hypotheses. Understanding of the connectivity and provenance of these springs is significant as they are the primary source of water for the communities that inhabit this region and may be impacted by changes in recharge and use. VL - 60 UR - https://onlinelibrary.wiley.com/toc/17456584/60/2 IS - 2 ER - TY - JOUR T1 - The giant 1960 tsunami in the context of a 6000‐year record of paleotsunamis and coastal evolution in south‐central Chile JF - Earth Surface Processes and Landforms Y1 - 2022 A1 - Matos‐Llavona, Pedro I. A1 - Ely, Lisa L. A1 - MacInnes, Breanyn A1 - Dura, Tina A1 - Cisternas, Marco A. A1 - Bourgeois, Joanne A1 - Bruce, David A1 - DePaolis, Jessica A1 - Dolcimascolo, Alexander A1 - Horton, Benjamin P. A1 - Melnick, Daniel A1 - Nelson, Alan R. A1 - Szeliga, Walter A1 - Wesson, Robert L. AB - The tsunami associated with the giant 9.5 Mw 1960 Chile earthquake deposited an extensive sand layer above organic‐rich soils near Queule (39.3°S, 73.2°W), south‐central Chile. Using the 1960 tsunami deposits, together with eye‐witness observations and numerical simulations of tsunami inundation, we tested the tsunami inundation sensitivity of the site to different earthquake slip distributions. Stratigraphically below the 1960 deposit are two additional widespread sand layers interpreted as tsunami deposits with maximum ages of 4960–4520 and 5930–5740 cal BP. This >4500‐year gap of tsunami deposits preserved in the stratigraphic record is inconsistent with written and geological records of large tsunamis in south‐central Chile in 1575, 1837, and possibly 1737. We explain this discrepancy by: (1) poor preservation of tsunami deposits due to reduced accommodation space from relative sea‐level fall during the late Holocene; (2) recently evolved coastal geomorphology that increased sediment availability for tsunami deposit formation in 1960; and/or (3) the possibility that the 1960 tsunami was significantly larger at this particular location than other tsunamis in the past >4500 years. Our research illustrates the complexities of reconstructing a complete stratigraphic record of past tsunamis from a single site for tsunami hazard assessment. The coastal geomorphology near Queule, Chile preserves evidence of the giant Mw 9.51960 Chile earthquake and two buried paleotsunami deposits within the last 6000 years. Using the 1960 tsunami deposits, eye‐witness observations, and numerical simulations of tsunami inundation, we tested the sensitivity of the site to different earthquake slip distributions. We consider the role of coastal geomorphic evolution, sea‐level history, and tsunami magnitude in the preservation of paleotsunami depositional records. VL - 47 UR - https://onlinelibrary.wiley.com/doi/10.1002/esp.5363 IS - 8 ER - TY - JOUR T1 - Glacial isostatic adjustment near the center of the former Patagonian Ice Sheet (48°S) during the last 16.5 kyr JF - Quaternary Science Reviews Y1 - 2022 A1 - Troch, Matthias A1 - Bertrand, Sébastien A1 - Lange, Carina B. A1 - Cárdenas, Paola A1 - Arz, Helge A1 - Pantoja-Gutiérrez, Silvio A1 - De Pol-Holz, Ricardo A1 - Kilian, Rolf AB - Our understanding of glacial isostatic rebound across Patagonia is highly limited, despite its importance to constrain past ice volume estimates and better comprehend relative sea-level variations. With this in mind, our research objective is to reconstruct the magnitude and rate of Late Glacial and Holocene glacial isostatic adjustment near the center of the former Patagonian Ice Sheet. We focus on Larenas Bay (48°S; 1.26 km2), which is connected to Baker Channel through a shallow (7.4 m) and narrow (ca. 150 m across) inlet, and hence has the potential to record periods of basin isolation and marine ingression. The paleoenvironmental evolution of the bay was investigated through a sedimentological analysis of a 9.2 m long radiocarbon-dated sediment core covering the last 16.8 kyr. Salinity indicators, including diatom paleoecology, alkenone concentrations and CaCO3 content, were used to reconstruct the bay's connectivity to the fjord. Results indicate that Larenas Bay was a marine environment before 16.5 cal kyr BP and after 9.1 cal kyr BP, but that it was disconnected from Baker Channel in-between. We infer that the postglacial rebound started before 16.5 cal kyr BP and that it outpaced global sea-level rise until slightly before 9.1 cal kyr BP. During the Late Glacial and early Holocene, the center of the former Patagonian Ice Sheet experienced an absolute uplift of ca. 96 m, at an average rate of 1.3 cm/yr. During the remainder of the Holocene, glacial isostatic adjustment continued (ca. 20 m), but at a slower average pace of 0.2 cm/yr. Comparisons between multi-millennial variations in the salinity indicators and existing records of global sea-level rise suggest that the glacial isostatic adjustment rate also fluctuated within these time intervals, likely in response to glacier dynamics. More specifically, most of the glacial isostatic adjustment registered between 16.5 – 9.1 cal kyr BP seems to have occurred before meltwater pulse 1A (14.5 – 14.0 kyr BP). Likewise, it appears that the highest glacial isostatic rebound rates of the last 9.1 kyr occurred during the late Holocene, most likely in response to glacier recession from their Neoglacial maxima. This implies a relatively rapid response of the local solid earth to ice unloading, which agrees with independent modelling studies investigating contemporary uplift. We conclude that the center of the former Patagonian Ice Sheet experienced a glacial isostatic adjustment of ca. 116 m over the last 16.5 kyr, and that >80% occurred during the Late Glacial and early Holocene. VL - 277 UR - https://linkinghub.elsevier.com/retrieve/pii/S0277379121005539 ER - TY - JOUR T1 - Heterogeneous Patterns of Aged Organic Carbon Export Driven by Hydrologic Flow Paths, Soil Texture, Fire, and Thaw in Discontinuous Permafrost Headwaters JF - Global Biogeochemical Cycles Y1 - 2022 A1 - Koch, Joshua C. A1 - Bogard, Matthew J. A1 - Butman, David E. A1 - Finlay, Kerri A1 - Ebel, Brian A1 - James, Jason A1 - Johnston, Sarah Ellen A1 - Jorgenson, M. Torre A1 - Pastick, Neal J. A1 - Spencer, Robert G. M. A1 - Striegl, Robert A1 - Walvoord, Michelle A1 - Wickland, Kimberly P. AB - Climate change is thawing and potentially mobilizing vast quantities of organic carbon (OC) previously stored for millennia in permafrost soils of northern circumpolar landscapes. Climate‐driven increases in fire and thermokarst may play a key role in OC mobilization by thawing permafrost and promoting transport of OC. Yet, the extent of OC mobilization and mechanisms controlling terrestrial‐aquatic transfer are unclear. We demonstrate that hydrologic transport of soil dissolved OC (DOC) from the active layer and thawing permafrost to headwater streams is extremely heterogeneous and regulated by the interactions of soils, seasonal thaw, fire, and thermokarst. Repeated sampling of streams in eight headwater catchments of interior Alaska showed that the mean age of DOC for each stream ranges widely from modern to ∼2,000 years B.P. Together, an endmember mixing model and nonlinear, generalized additive models demonstrated that Δ14C‐DOC signature (and mean age) increased from spring to fall, and was proportional to hydrologic contributions from a solute‐rich water source, related to presumed deeper flow paths found predominantly in silty catchments. This relationship was correlated with and mediated by catchment properties. Mean DOC ages were older in catchments with >50% burned area, indicating that fire is also an important explanatory variable. These observations underscore the high heterogeneity in aged C export and difficulty of extrapolating estimates of permafrost‐derived DOC export from watersheds to larger scales. Our results provide the foundation for developing a conceptual model of permafrost DOC export necessary for advancing understanding and prediction of land‐water C exchange in changing boreal landscapes. In high latitude environments, soils that have been frozen for millennia are thawing, releasing organic carbon (OC). Thawing and export of OC to downstream aquatic ecosystems is a potential biogeochemical feedback that may accelerate climate warming if large amounts of ancient OC are transformed and released to the atmosphere as greenhouse gases. The magnitude and timing of ancient OC thaw and mobilization are not well defined, so predicting these patterns at local to global scales is challenging. Using a suite of diverse headwater catchments in the discontinuous permafrost zone of Alaska, USA, we identify the main controls on the mobilization of ancient OC from thawing landscapes into adjacent streams. Our surveys show that ancient OC export depends on the complex interaction between fire history, soil type and thawing characteristics, and seasonal warming. We find that all of these factors play a role, resulting in highly heterogeneous release of ancient OC to headwater streams. Aged dissolved organic carbon (DOC) in headwater streams in interior Alaska is heterogeneous across permafrost landscapes indicating the interplay of multiple drivers Aged DOC concentrations increase from spring to fall and are highest in catchments with >50% burned extent and dominated by silty uplands Aged DOC is proportional to stream solute loads, indicating that deeper flow paths deliver permafrost C to streams Aged dissolved organic carbon (DOC) in headwater streams in interior Alaska is heterogeneous across permafrost landscapes indicating the interplay of multiple drivers Aged DOC concentrations increase from spring to fall and are highest in catchments with >50% burned extent and dominated by silty uplands Aged DOC is proportional to stream solute loads, indicating that deeper flow paths deliver permafrost C to streams VL - 36 UR - https://onlinelibrary.wiley.com/doi/10.1029/2021GB007242 IS - 4 ER - TY - JOUR T1 - Hydrological and thermodynamic controls on late Holocene gypsum formation by mixing saline groundwater and Dead Sea brine JF - Geochimica et Cosmochimica Acta Y1 - 2022 A1 - Weber, Nurit A1 - Antler, Gilad A1 - Lazar, Boaz A1 - Stein, Mordechai A1 - Yechieli, Yoseph A1 - Gavrieli, Ittai KW - BrinesSaline springs KW - Dead Sea KW - Hydroclimate KW - Lacustrine Gypsum KW - Outsalting KW - Thermodynamic modeling AB - The rapid retreat of the Dead Sea during the past four decades led to the exposure of unique structures of massive gypsum along the shores. Many of these structures (having the shape of mounds) are associated with the activity of Ein Qedem-type saline springs that currently discharge Ca-chloride brine to the lake. Field observations, radiocarbon dating of aragonite (within the gypsum mounds) that yield ancient ages, and the narrow range of 834S and 818O values (d34Sgyp: 14.1-16.9%; d18Ogyp: 14.4-16.5%) indicates that the formation of the gypsum structures is related to the mixing of brines: the Dead Sea brine and ancient (last glacial) Ein Qedem type brine. These are Ca-chloride brines having different salinities and sulfur concentrations that satisfy conditions of an outsalting process whereby supersaturation of gypsum is attained by the mixing of these two brines in the offshore shallow water environment. Thermodynamic calculations (using the PHREEQC software) show that gypsum outsalting occurred when both brines were enriched with sulfate as compared to the present. The Ein-Qedem brine had higher sulfate when subjected to less intensive bacterial sulfate reduction. The Dead Sea was characterized by higher sulfate concentrations during intervals of low lake stands. The conditions of higher sulfate concentrations and enhanced discharge of the saline springs occurred repeatedly in the Dead Sea between -6.6 to 0.6 ka and were intermittent with periods of enhanced supply of sulfate to the lake by freshwaters. VL - 316 UR - https://www.webofscience.com/wos/woscc/full-record/WOS:000730092400010?AlertId=ab9062f8-b111-4f95-a2b8-66e7afac0471&SID=8Dkzxr6qseeJz1VEtb3 ER - TY - JOUR T1 - Iberian hydroclimate variability and the Azores High during the last 1200 years: evidence from proxy records and climate model simulations JF - Climate Dynamics Y1 - 2022 A1 - Thatcher, Diana L. A1 - Wanamaker, A. D. A1 - Denniston, R. F. A1 - Ummenhofer, C. C. A1 - Asmerom, Y. A1 - Polyak, V. J. A1 - Cresswell-Clay, N. A1 - Hasiuk, F. A1 - Haws, J. A1 - Gillikin, D. P. KW - Azores High KW - Hydroclimate KW - last millennium KW - Last Millennium Ensemble KW - Paleoclimate KW - Stalagmite AB - The state of the atmospheric circulation and the associated hydroclimate in the North Atlantic during the last millennium remain the subject of considerable debate in both proxy- and model-based studies. Of particular interest in the Iberian region is the Azores High (AH) system, the southern node of the North Atlantic Oscillation (NAO), an atmospheric dipole closely tied to regional hydroclimate. Hydroclimate-sensitive proxy reconstructions from this region offer some insights into atmospheric dynamics, but large spatiotemporal gaps in these data inhibit a robust evaluation of hydroclimate variability. In this study, we present a continuous, sub-decadally-resolved composite stalagmite carbon isotopic record from three partially overlapping stalagmites from Buraca Gloriosa (BG) cave, western Portugal, situated within the center of the AH, that preserves evidence of regional hydroclimate variability from approximately 800 CE to the present. Chronologies are derived from U/Th dating and annual laminae. Stalagmite carbon isotopic values primarily reflect the amount of effective moisture and reveal generally dry conditions during the Medieval Climate Anomaly (MCA; 850–1250 CE) and Modern Climate/Industrial Era (1850 CE-present), and wetter conditions during the Little Ice Age (LIA; 1400–1850 CE). Multidecadal to centennial variability in the BG record and state-of-the-art last millennium climate model simulations show considerable coherence with precipitation-sensitive records from Spain and Morocco that, like BG, are strongly influenced by the intensity, size, and location of the AH. Model-proxy synthesis suggests that western Portugal was persistently dry during much of the MCA consistent with other NAO reconstructions; however, even considering age uncertainties, the apparent timing in the transition from a relatively dry MCA to a wetter LIA is spatially variable and confirms the non-stationary behavior of the AH system indicated by model output. UR - https://app.dimensions.ai/details/publication/pub.1150271437 ER - TY - JOUR T1 - Ice-sheet expansion from the Ross Sea into McMurdo Sound, Antarctica, during the last two glaciations JF - Quaternary Science Reviews Y1 - 2022 A1 - Heath, Stephanie A1 - Hall, Brenda L. A1 - Denton, George H. A1 - Henderson, Gideon M. A1 - Hendy, Chris H. AB - An understanding of Antarctic Ice Sheet (AIS) behavior is important for future sea-level predictions. Here, we examine past ice-sheet history in the McMurdo Sound region of the western Ross Sea over the last two glacial-interglacial cycles in order to gain insight into the drivers of ice-sheet change. Surficial mapping, along with radiocarbon dates of lacustrine algae and uranium-thorium disequilibrium dates of lacustrine carbonates from ice-dammed lakes, allow reconstruction of the timing and origin of grounded ice in McMurdo Sound during the last glacial maximum (LGM) and penultimate glaciation. During the LGM, ice-surface elevation profiles and distribution of erratics indicate ice flow into southern McMurdo Sound from the Ross Sea, rather than seaward expansion of local glaciers from the Royal Society Range. The grounded ice in McMurdo Sound flowed westward to block the mouths of valleys in the Royal Society Range and to dam proglacial lakes. In Marshall Valley, maximum ice extent during what is termed the Ross Sea glaciation, was achieved by 18 ka and remained close to this position until after 14 ka. The pattern of surficial deposits suggests that ice during the penultimate glaciation, locally named the Marshall glaciation, was slightly more extensive than that of the LGM but had a similar Ross Sea origin. Maximum ice extent in Marshall Valley occurred at ∼145–150 ka; the grounded ice may have receded from the valley mouth shortly after 138 ka. Both ice expansions occurred broadly during times of low Antarctic air temperatures, which have been linked to insolation minima. However, the lack of widespread surface melting ablation zones on the AIS indicates that the link between ice expansion and orbital forcing is likely to be indirect and possibly driven through the ocean. Closer examination of the precise timing of the glacial maxima in Marshall Valley shows that the Marshall glaciation occurred synchronously with the penultimate global maximum; ice recession took place during Termination II. In contrast, maximum ice extent during the Ross Sea glaciation along the Royal Society Range occurred after the global LGM, during Termination I. Deglaciation was primarily an early Holocene event. We attribute this delayed maximum and deglaciation (relative to global events) to the effect of rising accumulation on ice-sheet mass balance. VL - 278 UR - https://linkinghub.elsevier.com/retrieve/pii/S0277379122000105 ER - TY - JOUR T1 - Impact of Indian Ocean surface temperature gradient reversals on the Indian Summer Monsoon JF - Earth and Planetary Science Letters Y1 - 2022 A1 - Weldeab, Syee A1 - Rühlemann, Carsten A1 - Ding, Qinghua A1 - Khon, Vyacheslav A1 - Schneider, Birgit A1 - Gray, William R. AB - Indian Summer Monsoon (ISM) precipitation is the main determinant of livelihood in a densely populated world region. The interannual variability of the ISM is influenced by several modes of climate variability, including anomalous seasonal sea surface temperature (SST) gradient reversals between the eastern, western, and northeastern Indian Ocean. With global warming, the frequency of zonal and meridional Indian Ocean's SST gradient changes is projected to increase but its impact on the ISM is debated. Here we present a 25,000-year proxy record of SST and inferred Ganges-Brahmaputra-Meghna (GBM) River runoff that provides a spatially integrated measure of ISM precipitation changes. This record indicates a monotonic deglacial strengthening of the ISM system when the SST gradient between the Bay of Bengal surface water and the eastern equatorial Indian Ocean was reversed. We posit that the reversal in the meridional SST gradient reduced the impact of Heinrich Event 1 and Younger Dryas on the low elevation part of the ISM domain. Furthermore, the proxy record shows that the strongest Holocene ISM strengthening occurred between 7900±470 and 5700±360 years before present, coinciding with and causally linked to the reversal of the Indian Ocean zonal SST gradient and ensuing changes in the wind fields, a sequence of events that is inferred from and supported by the results of our climate simulation. Our study demonstrates that changes in the Indian Ocean's zonal and meridional thermal gradient strongly shaped the timing of Holocene monsoon strengthening and the response of ISM to the last deglacial freshwater forcing. VL - 578 UR - https://linkinghub.elsevier.com/retrieve/pii/S0012821X21005835 ER - TY - JOUR T1 - Implications of Single-Step Graphitization For Reconstructing Late Holocene Relative Sea-Level Using Radiocarbon-Dated Organic Coastal Sediment JF - Radiocarbon Y1 - 2022 A1 - Sefton, Juliet P. A1 - Kemp, Andrew C. A1 - Elder, Kathryn L. A1 - Hansman, Roberta L. A1 - Roberts, Mark L. KW - age-depth model KW - mangrove KW - Massachusetts KW - Micronesia KW - Salt marsh AB - Late Holocene relative sea-level reconstructions are commonly generated using proxies preserved in salt-marsh and mangrove sediment. These depositional environments provide abundant material for radiocarbon dating in the form of identifiable macrofossils (salt marshes) and bulk organic sediment (mangroves). We explore if single-step graphitization of these samples in preparation for radiocarbon dating can increase the number and temporal resolution of relative sea-level reconstructions without a corresponding increase in cost. Dating of salt-marsh macrofossils from the northeastern United States and bulk mangrove sediment from the Federated States of Micronesia indicates that single-step graphitization generates radiocarbon ages that are indistinguishable from replicates prepared using traditional graphitization, but with a modest increase in error (mean/maximum of 6.25/15 additional 14C yr for salt-marsh macrofossils). Low 12C currents measured on bulk mangrove sediment following single-step graphitization likely render them unreliable despite their apparent accuracy. Simulated chronologies for six salt-marsh cores indicate that having twice as many radiocarbon dates (since single-step graphitization costs ∼50% of traditional graphitization) results in narrower confidence intervals for sample age estimated by age-depth models when the additional error from the single-step method is less than ∼50 14C yr (∼30 14C yr if the chronology also utilizes historical age markers). Since these thresholds are greater than our empirical estimates of the additional error, we conclude that adopting single-step graphitization for radiocarbon measurements on plant macrofossils is likely to increase precision of age-depth models by more than 20/10% (without/with historical age markers). This improvement can be implemented without additional cost. SN - 0033-8222, 1945-5755 UR - https://www.cambridge.org/core/journals/radiocarbon/article/implications-of-singlestep-graphitization-for-reconstructing-late-holocene-relative-sealevel-using-radiocarbondated-organic-coastal-sediment/41F75E6A0679F0E659C96F438452D64C ER - TY - JOUR T1 - Indian monsoon variability during the past ∼8.5 cal kyr as recorded in the sediments of the northeastern Arabian Sea JF - Quaternary International Y1 - 2022 A1 - Ravichandran, M. A1 - Gupta, Anil K. A1 - Mohan, K. A1 - Tiwari, Sameer K. A1 - Lakshumanan, C. A1 - Panigrahi, M.K. AB - We analyzed benthic and planktic foraminifera, total organic carbon and stable isotopes ratios of carbon and oxygen from 100 samples of marine sediment Core ABP, 25/03, off Gujarat in the northeastern Arabian Sea. Factor and cluster analyses of thirty highest-ranked benthic foraminifer species enabled to identify seven biofacies in the study sequence characterizing major changes in deep-sea environments during the past ∼8.5 cal kyr. The benthic foraminiferal data has been combined with population abundances of upwelling indicator planktic foraminifer Globigerina bulloides and mixed layer species from Core ABP, 25/03 and compared with that from ODP Hole 723A and Core ABP, 25/02, western and eastern Arabian Sea, respectively. A major change in benthic foraminifera occurs during ∼8.5 to 6 cal kyr BP, when the summer monsoon was stronger whereas during 6 to 2 cal kyr BP, the data suggest a weak summer monsoon. Planktic foraminifer Globigerina bulloides does not show any significant trend in the study core, but deep thermocline species Neogloboquadrina dutertrei and mixed layer species show significant trend with an inverse correlation with the TOC. This core records high TOC from ∼6.5 to 4 cal kyr BP and during the last 2 cal kyr and low TOC during ∼8.5 to 6.5 cal kyr BP and 4 to 2 cal kyr BP. It is interesting to note intervals of high mixed layer species coincide with high Neogloboquadrina dutertrei percentages and low TOC values at Core ABP, 25/03 during 8.5 to 6.5 cal kyr BP.The faunal data is supported by carbon and oxygen isotope ratios (δ13C and δ18O) of shells of benthic foraminifer Cibicides spp. to strengthen our understanding of changes in the eastern Arabian Sea since ∼8.5 cal kyr BP. UR - https://linkinghub.elsevier.com/retrieve/pii/S104061822200115X ER - TY - JOUR T1 - In-phase millennial-scale glacier changes in the tropics and North Atlantic regions during the HoloceneAbstract JF - Nature Communications Y1 - 2022 A1 - Jomelli, V. A1 - Swingedouw, D. A1 - Vuille, M. A1 - Favier, V. A1 - Goehring, B. A1 - Shakun, J. A1 - Braucher, R. A1 - Schimmelpfennig, I. A1 - Menviel, L. A1 - Rabatel, A. A1 - Martin, L. C. P. A1 - Blard, P.-H. A1 - Condom, T. A1 - Lupker, M. A1 - Christl, M. A1 - He, Z. A1 - Verfaillie, D. A1 - Gorin, A. A1 - Aumaître, G. A1 - Bourles, D. L. A1 - Keddadouche, K. AB - Based on new and published cosmic-ray exposure chronologies, we show that glacier extent in the tropical Andes and the north Atlantic regions (TANAR) varied in-phase on millennial timescales during the Holocene, distinct from other regions. Glaciers experienced an early Holocene maximum extent, followed by a strong mid-Holocene retreat and a re-advance in the late Holocene. We further explore the potential forcing of TANAR glacier variations using transient climate simulations. Since the Atlantic Meridional Overturning Circulation (AMOC) evolution is poorly represented in these transient simulations, we develop a semi-empirical model to estimate the “AMOC-corrected” temperature and precipitation footprint at regional scales. We show that variations in the AMOC strength during the Holocene are consistent with the observed glacier changes. Our findings highlight the need to better constrain past AMOC behavior, as it may be an important driver of TANAR glacier variations during the Holocene, superimposed on other forcing mechanisms. VL - 13 UR - https://www.nature.com/articles/s41467-022-28939-9 IS - 1 ER - TY - JOUR T1 - Large fluxes of continental-shelf-borne dissolved organic carbon in the East China Sea and the Yellow Sea JF - Marine Chemistry Y1 - 2022 A1 - Han, Heejun A1 - Na, Taehee A1 - Cho, Hyung-Mi A1 - Kim, Guebuem A1 - Hwang, Jeomshik AB - Fluxes of dissolved organic carbon (DOC) from continental shelves to the ocean may play a critical role in marine carbon cycling and budget. However, these fluxes have been poorly constrained because complicated biogeochemical reactions of riverine, atmospheric, and marine organic carbon occur in continental shelf-waters. We used multiple tracers of DOC such as stable- and radiocarbon isotope ratios of DOC, fluorescent properties of dissolved organic matter (FDOM), and 228Ra as a water age tracer to investigate the sources and fluxes of DOC in the northwest Pacific continental margin of the East China Sea and the Yellow Sea. Here, we show that there are significant additional (excess) supplies of DOC in the central Yellow Sea relative to the Changjiang (Yangtze River) source, based on these tracers. The marine δ13C signature (−21.1 ± 1.1‰) and the radiocarbon age (2000 ± 400 yr) of DOC suggest that the additional DOC (Δ14DOC = −44‰) is supplied from a combination of newly produced DOC and the degradation of particulate as well as sedimentary organic matter. The flux of this additional DOC produced in the continental shelf of the East China Sea to the open ocean is estimated to be ~1.9 ± 0.8 Tg C yr−1, which is comparable to that from the Changjiang discharge. Our study implies that the fluxes of continental shelf-borne DOC may be important globally and should be considered in estimating global DOC budgets in the marine environment. VL - 240 UR - https://linkinghub.elsevier.com/retrieve/pii/S0304420322000147 ER - TY - JOUR T1 - Late Holocene centennial to millennial-scale variability in lower trophic level productivity off southern Hokkaido, Japan, and its response to dissolved iron-replete Coastal Oyashio dynamics JF - Quaternary Research Y1 - 2022 A1 - Kuwae, Michinobu A1 - Tsugeki, Narumi A1 - Finney, Bruce P. A1 - Tani, Yukinori A1 - Onodera, Jonaotaro A1 - Kiyoto, Mako A1 - Kusaka, Mitsukuni A1 - Sagawa, Takuya A1 - Nakamura, Yugo A1 - Ohnishi, Hiroji A1 - Kuroda, Hiroshi A1 - Okuda, Noboru A1 - Ohta, Tamihisa A1 - Ikehara, Minoru A1 - Irino, Tomohisa AB - Little is known about the dynamics of marine food chains spanning primary to higher trophic levels on centennial and longer timescales, especially where the supply of dissolved iron limits primary productivity. To elucidate the long-term dynamics of biological productivity in the Coastal Oyashio (CO), which is a major pathway for transporting dissolved iron into the western North Pacific from winter to spring, we reconstructed the lower trophic level productivity over the last 3000 years in the CO. Our results demonstrate that the concentrations and mass accumulation rates of both Chl- a (chlorophyll a and its derivatives) and biogenic opal used as proxies of primary productivity, and steryl chlorin esters (SCEs) used as that of zooplankton productivity, show a millennial-scale increasing trend and centennial-scale variability beginning ca. AD 400. SCEs were positively correlated with Chl- a , indicating that changes in zooplankton productivity were induced by bottom-up control of primary productivity. The Chl- a and SCEs showed synchronous centennial-scale patterns with a relative abundance of sea-ice-associated diatom species transported by CO, and with a ventilation index in the Okhotsk Sea Intermediate Water. This synchronous pattern indicates that lower trophic-level productivity during the spring bloom responded to the intensity of iron-replete CO. VL - 107 UR - https://www.cambridge.org/core/journals/quaternary-research/article/late-holocene-centennial-to-millennialscale-variability-in-lower-trophic-level-productivity-off-southern-hokkaido-japan-and-its-response-to-dissolved-ironreplete-coastal-oyashio-dynamics/ ER - TY - JOUR T1 - Late Holocene Paleomagnetic Secular Variation in the Chukchi Sea, Arctic Ocean JF - Geochemistry, Geophysics, Geosystems Y1 - 2022 A1 - West, Gabriel A1 - Nilsson, Andreas A1 - Geels, Alexis A1 - Jakobsson, Martin A1 - Moros, Matthias A1 - Muschitiello, Francesco A1 - Pearce, Christof A1 - Snowball, Ian A1 - O’Regan, Matt AB - The geomagnetic field behavior in polar regions remains poorly understood and documented. Although a number of Late Holocene paleomagnetic secular variation (PSV) records exist from marginal settings of the Amerasian Basin in the Arctic Ocean, their age control often relies on a handful of radiocarbon dates to constrain ages over the past 4,200 years. Here we present well-dated Late Holocene PSV records from two sediment cores recovered from the Chukchi Sea, Arctic Ocean. The records are dated using 26 14C measurements, with local marine reservoir corrections calibrated using tephra layers from the 3.6 cal ka BP Aniakchak eruption in Northern Alaska. These 14C-based chronologies are extended into the post-bomb era using caesium-137 dating, and mercury isochrons. Paleomagnetic measurements and rock magnetic analyses reveal stable characteristic remanent magnetization directions, and a magnetic mineralogy dominated by low-coercivity minerals. The PSV records conform well to global spherical harmonic field model outputs. Centennial to millennial scale directional features are synchronous between the cores and other Western Arctic records from the area. Due to the robust chronology, these new high-resolution PSV records provide a valuable contribution to the characterization of geomagnetic field behavior in the Arctic over the past few thousand years, and can aid in developing age models for suitable sediments found in this region. VL - 23 UR - https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2021GC010187 IS - 5 ER - TY - JOUR T1 - Late Woodland feasting and social networks in the lower Missouri River region JF - North American Archaeologist Y1 - 2022 A1 - Logan, Brad AB - Feasting and its function among small scale societies have received little attention among many descriptive and theoretical studies of this activity. Evidence of feasting focused on large roasting pits by Late Woodland (AD 500–1000) hunter-gatherer-gardeners in the lower Missouri River region on the eastern edge of the Great Plains is presented. Two features at the Quixote site and lipid analyses of stones from them attest single events focused on roasting deer and fish, and perhaps ritual use of red cedar and ceramic pipes. Such features at other Late Woodland sites in the LMRR, specifically the Valley Falls locality of the Delaware River valley in northeastern Kansas, are reinterpreted. Burned stone features at Middle Woodland sites differ and suggest pit roasting was a practice of dispersed Late Woodland groups. Feasting for solidarity forged a social network based on reciprocity, not competition, to mitigate food insecurity among diffuse, low level food producers. VL - 43 UR - https://journals.sagepub.com/doi/10.1177/01976931221104846 IS - 3 ER - TY - ABST T1 - Mangrove Peat Radiocarbon Ages From Snipe and Swan Key, FL Y1 - 2022 A1 - Khan, Nicole S A1 - Toth, Lauren T A1 - Moyer, Ryan P A1 - Shaw, Jaimie E A1 - Capar, Paulina A1 - Kemp, Andrew C A1 - Engelhart, Simon E A1 - Horton, Benjamin P KW - core analysis KW - push coring KW - Radiometric Dating AB - In 2016, researchers collected cores of mangrove peat from two islands in the Florida Keys: Snipe Key (24.679&amp;deg;N, 81.653&amp;deg;W) and Swan Key (25.349N, 80.251W) (Fig. 1). This data release contains the radiocarbon ages and associated data for peat samples analyzed throughout the two cores. These data were used by Khan and others (in preparation) to reconstruct the millennial-scale sea level variability of the two locations. PB - U.S. Geological Survey UR - https://coastal.er.usgs.gov/data-release/doi-P9OOL3L4/ N1 - Medium: csv,xlsx Type: dataset ER - TY - JOUR T1 - Not all permafrost microbiomes are created equal: Influence of permafrost thaw on the soil microbiome in a laboratory incubation study JF - Soil Biology and Biochemistry Y1 - 2022 A1 - Barbato, R.A. A1 - Jones, R.M. A1 - Douglas, T.A. A1 - Doherty, S.J. A1 - Messan, K. A1 - Foley, K.L. A1 - Perkins, E.J. A1 - Thurston, A.K. A1 - Garcia-Reyero, N. AB - Permafrost is thawing at unprecedented rates, significantly altering landscapes and ecosystem trajectories by changing subsurface conditions, vegetation characteristics, and soil properties. Dormant microbes become active as temperatures rise and permafrost soils warm and thaw. To determine the effects of sample location and warming on the permafrost microbiome, we collected permafrost from five distinct locations within the Cold Regions Research and Engineering Laboratory's Permafrost Tunnel (PT) near Fairbanks, Alaska and warmed them in a laboratory incubation study. Heterotrophic respiration was continuously monitored and metagenomes were analyzed at select incubation temperatures. Under frozen conditions, microbial respiration rates from different PT locations were similar, ranging from 2 to 12 mg C–CO2 kg−1 d−1. During thaw, respiration increased in samples from three PT locations, but remained stable for two locations. Analysis of the shotgun metagenomes showed how the microbial communities and their potential function changed as a function of location and incubation temperature. This indicates a differential response of permafrost microbes based on their origin. These findings have important implications for developing accurate forecasts of microbial community assemblages during thaw in that location should be considered as a strong influencing factor. VL - 167 UR - https://linkinghub.elsevier.com/retrieve/pii/S0038071722000621 ER - TY - JOUR T1 - The occupation history of the longest-dwelling Adélie penguin colony reflects Holocene climatic and environmental changes in the Ross Sea, Antarctica JF - Quaternary Science Reviews Y1 - 2022 A1 - Gao, Yuesong A1 - Salvatore, Maria Cristina A1 - Xu, Qibin A1 - Yang, Lianjiao A1 - Sun, Liguang A1 - Xie, Zhouqing A1 - Baroni, Carlo AB - As a result of climate changes, penguins are predicted to be at risk of losing their breeding habitats. Changes in penguin colony distribution suggest that some colonies have withstood environmental changes better than others, serving as initial post-glacial settlements or refuges in adverse climatic conditions. Here we have synthesized over 200 dates (including 91 new dates) of penguin remains and of guano in 107 ornithogenic profiles from abandoned nests on Inexpressible Island, one of the longest persisting Adélie penguin colonies in Antarctica, to investigate the dynamics of population size and the role of this island in the ecological history of this species. The results indicate that, following the retreat of Ross Ice Shelf, the Adélies first colonized this island at ∼8.6 kyr BP, documenting the earliest known breeding site in the Ross Sea since deglaciation. During ∼7-3 kyr BP the reconstructed population on Inexpressible Island was generally consistent with the change in pack ice, reaching relative peaks at 5.5–5.0 and 4.0–3.5 kyr BP. After brief decline at 3.5–3.0 kyr, substantial enlargement of the penguin colony occurred between 3.0 and 1.5 kyr BP, attributed to the immigration from the abandoned colonies along the Scott Coast. During this time, the persistent efficiency of Terra Nova Bay polynya offered conditions favourable to the expansion of the penguin population on Inexpressible Island, which probably represented a refuge area under increased coastal sea-ice. This longest-dwelling penguin colony may provide a valuable refuge for the Adélie penguin if the recurrent Terra Nova Bay polynya persists under future climatic and environmental changes, as occurred in the past. VL - 284 UR - https://linkinghub.elsevier.com/retrieve/pii/S0277379122001251 ER - TY - JOUR T1 - Oceanic passage of hurricanes across Cay Sal Bank in The Bahamas over the last 530 years JF - Marine Geology Y1 - 2022 A1 - Winkler, Tyler S. A1 - van Hengstum, Peter J. A1 - Donnelly, Jeffrey P. A1 - Wallace, Elizabeth J. A1 - D'Entremont, Nicole A1 - Hawkes, Andrea D. A1 - Maio, Christopher V. A1 - Sullivan, Richard M. A1 - Woodruff, Jonathan D. AB - Islands across the Bahamian Archipelago have been devastated by five major hurricanes from 2010 to 2020 CE, including Category 5 Hurricane Dorian in 2019 that inundated parts of Abaco and Grand Bahama with up to 4 m of surge, killing 84 people and leaving >245 others missing. Up to 1 m relative sea-level rise is estimated for The Bahamas by 2100 CE, which could enhance flooding from weaker storms (11,800 years ago). The Anthropocene fraction ranges from <5 to 100%, indicating a wide range in susceptibility to land-surface contamination. The Pleistocene fraction of groundwater exceeds 50% in 7 eastern aquifers that are predominately confined. The Holocene fraction of groundwater exceeds 50% in 5 western aquifers that are predominately unconfined. The sustainability of pumping from these Principal Aquifers depends on rates of recharge and release of groundwater stored in fine-grained layers. VL - 3 SN - 2662-4435 UR - https://www.nature.com/articles/s43247-022-00473-y IS - 1 JO - Commun Earth Environ ER - TY - JOUR T1 - Persistence of old soil carbon under changing climate: The role of mineral-organic matter interactions JF - Chemical Geology Y1 - 2022 A1 - Grant, Katherine E. A1 - Galy, Valier V. A1 - Haghipour, Negar A1 - Eglinton, Timothy I. A1 - Derry, Louis A. AB - Globally, soils store between 1500 and 2800 Pg of organic carbon (OC). The physical and chemical stability of these terrestrial soil carbon stores under plausible climate change scenarios is unclear. Soil organic carbon (SOC), especially in volcanic soils, is stabilized through mineral matrix interactions. How susceptible are these mineral-organic matter interactions to environmental change? Here we present a study of SOC age along a climate gradient of andisols from Kohala volcano on the Island of Hawai'i. We measure carbon isotope composition (14C/12C, 13C/12C) in bulk samples and extracted biomarkers for 4–8 horizons of 15 soil profiles to understand variability in SOC age and persistence across incremental differences in mean annual precipitation. Bulk OC in the subsoil has radiocarbon fraction modern (Fm) values as low as 0.28 to 0.16 (~10,160 to ~14,630 conventional radiocarbon years). Coexisting plant-derived long chain fatty acids (LCFAs) are older, over 22,500 yrs. (Fm = 0.060), implying that these are among the most stable compounds in the soil, while corresponding shorter-chain (C16) fatty acids are much younger, consistent with an origin from active microbial communities assimilating young OC percolating from surface horizons. There is significant Fe loss at higher mean annual precipitation (MAP) (>2200 mm yr−1) sites associated with episodic soil saturation and microbial Fe reduction. %OC is higher at these sites, consistent with the expectation that saturated conditions promote SOC storage. However, in these higher MAP sites iron depletion is associated with much younger bulk SOC and LCFAs 14C ages (~2900 14C years) than at equivalent sample depths in sites that retain most Fe (~14,200 14C years). The remaining mineral matrix consists primarily of Si, Al, and Ti as SRO minerals. The data imply that modest increases in precipitation resulting from environmental change at locations near a potential saturation or redox threshold could result in destabilization of Fe-SOC complexes, rendering previously stabilized carbon available for rapid degradation, potentially irreversibly decreasing the size of the old SOC reservoir. The destabilization of an old, persistent Fe-SOC reservoir can decrease SOC storage and ultimately increase the amount of CO2 released to the atmosphere. VL - 587 UR - https://linkinghub.elsevier.com/retrieve/pii/S0009254121005726 ER - TY - JOUR T1 - Queen triggerfish Balistes vetula: Validation of otolith-based age, growth, and longevity estimates via application of bomb radiocarbon JF - PLOS ONE Y1 - 2022 A1 - Shervette, Virginia R. A1 - Rivera Hernández, Jesús M. ED - Claydon, John A. B. AB - Ensuring the accuracy of age estimation in fisheries science through validation is an essential step in managing species for long-term sustainable harvest. The current study used Δ14 C in direct validation of age estimation for queen triggerfish Balistes vetula and conclusively documented that triggerfish sagittal otoliths provide more accurate and precise age estimates relative to dorsal spines. Caribbean fish samples (n = 2045) ranged in size from 67-473 mm fork length (FL); 23 fish from waters of the southeastern U.S. (SEUS) Atlantic coast ranged in size from 355-525 mm FL. Otolith-based age estimates from Caribbean fish range from 0-23 y, dorsal spine-based age estimates ranged from 1-14 y. Otolith-based age estimates for fish from the SEUS ranged from 8-40 y. Growth function estimates from otoliths in the current study (L∞ = 444, K = 0.13, t0 = -1.12) differed from spined-derived estimates in the literature. Our work indicates that previously reported maximum ages for Balistes species based on spine-derived age estimates may underestimate longevity of these species since queen triggerfish otolith-based ageing extended maximum known age for the species by nearly three-fold (14 y from spines versus 40 y from otoliths). Future research seeking to document age and growth population parameters of Balistes species should strongly consider incorporating otolith-based ageing in the research design. VL - 17 UR - https://dx.plos.org/10.1371/journal.pone.0262281 IS - 1 ER - TY - JOUR T1 - Radiocarbon dating of the historic Emperor’s Beech from Muncel, Baia de Aries, Romania JF - Studia Universitatis Babeș-Bolyai Chemia Y1 - 2022 A1 - Patrut, Adrian A1 - Bocos-Bintintan, Victor A1 - Patrut, Roxana T. A1 - Partila, Doriana A1 - Ratiu, Ileana-Andreea A1 - Rakosy, Laszlo A1 - von Reden, Karl F. AB - The article reports the AMS (accelerator mass spectrometry) radiocarbon dating results of the historic Emperor’s Beech (Fagul Împăratului) from Muncel, Baia de Arieş, Romania. Two wood samples were collected from the large tree, out of which four segments were extracted and analysed by AMS radiocarbon. The oldest dated sample segment had a radiocarbon date of 233 ± 18 BP, which corresponds to a calibrated age of 365 ± 5 years. This value suggests an age of 420 ± 20 years for the Emperor’s Beech. Thus, the historic beech started growing around the year 1600. VL - 67 N1 - Publisher: Babes-Bolyai University ER - TY - JOUR T1 - RADIOCARBON IN DISSOLVED CARBON BY UV OXIDATION: AN UPDATE OF PROCEDURES AND BLANK CHARACTERIZATION AT NOSAMSABSTRACT JF - Radiocarbon Y1 - 2022 A1 - Xu, Li A1 - Roberts, Mark L A1 - Elder, Kathryn L A1 - Hansman, Roberta L A1 - Gagnon, Alan R A1 - Kurz, Mark D AB - This note describes improvements of UV oxidation method that is used to measure carbon isotopes of dissolved organic carbon (DOC) at the National Ocean Sciences Accelerator Mass Spectrometry Facility (NOSAMS). The procedural blank is reduced to 2.6 +/- 0.6 mu g C, with Fm of 0.42 +/- 0.10 and delta C-13 of -28.43 +/- 1.19 parts per thousand. The throughput is improved from one sample per day to two samples per day. VL - 64 UR - https://www.cambridge.org/core/product/identifier/S0033822222000042/type/journal_articlehttps://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0033822222000042 IS - 1 ER - TY - JOUR T1 - Radiocarbon Investigation of the Historic African Baobabs of Omusati, Namibia JF - Forests Y1 - 2022 A1 - Patrut, Adrian A1 - Patrut, Roxana T. A1 - Rakosy, Laszlo A1 - Rakosy, Demetra A1 - Oliver, Willie A1 - Ratiu, Ileana A. A1 - Lowy, Daniel A. A1 - Shiimbi, Gebhardt A1 - Woodborne, Stephan A1 - von Reden, Karl F. AB - The Omusati region belongs to historic Ovamboland, an area of northern Namibia populated by tribes of the Ovambo group. Four very large African baobabs of Omusati played an important role in historic events of the area, such as the tribal wars and the Namibian War of Independence. The four historic baobabs are the Ombalantu baobab (8 stems; circumference 24.50 m), Okahao baobab (4+ stems; around 25 m), Amadhila baobab (12 stems; 25.35 m) and Sir Howard baobab (9 stems; 31.60 m). Two historic baobabs collapsed totally or partially. The stems of the Amadhila baobab toppled and died in 2021, while 3 stems of the Okahao baobab collapsed a long time ago, but are still alive. Our research aimed to determine the architecture and age of these baobabs. Three baobabs (Ombalantu, Amadhila, Sir Howard) exhibit a closed ring-shaped structure, with a false cavity inside. One baobab (Okahao) had an open ring-shaped structure, before its collapse. Several wood cores were extracted from the baobabs and investigated by radiocarbon dating. The dating results indicate ages of 770 ± 50 years for the Ombalantu baobab, 650 ± 50 years for the Okahao baobab, 1100 ± 50 years for the Amadhila baobab and 750 ± 50 years for the Sir Howard baobab. VL - 13 UR - https://www.mdpi.com/1999-4907/13/11/1899 IS - 11 ER - TY - JOUR T1 - Radiocarbon investigation of two large African baobabs from Kizimkazi, Zanzibar, Tanzania JF - Studia Universitatis Babes-Bolyai Chemia Y1 - 2022 A1 - Patrut, Adrian A1 - Patrut, Roxana T. A1 - Rakosy, Laszlo A1 - Ratiu, Ileana-Andreea A1 - Bodis, Jenő A1 - Nassor, Nassor Mahmoud A1 - von Reden, Karl F. AB - The article reports the AMS (accelerator mass spectrometry) radiocarbon dating results of Kizimkazi Big tree and Kizimkazi II baobab, two large African baobabs from Zanzibar, Tanzania. Unfortunately, both baobabs toppled and died in 2018 and 2020, during violent storms. The investigation of the two baobabs evinced that the first of them, which was also the biggest tree of Tanzania, consisted of 5 stems, out of which 2 were false ones, and had a closed ring-shaped structure. The second baobab was composed of 4 fused stems and had a cluster structure. Several wood samples were collected from the two baobabs. Seven segments were extracted from the samples and dated by radiocarbon. The oldest segment from Kizimkazi Big tree had a radiocarbon date of 312 ± 18 BP, corresponding to a calibrated age of 380 ± 10 calendar years. According to dating results, the Kizimkazi Big tree died at the age of 400 ± 25 years. The oldest segment from Kizimkazi II baobab had a radiocarbon date of 137 ± 17 BP, corresponding to a calibrated age of 190 ± 10 calendar years. This value indicates that the Kizimkazi II baobab was 250 ± 25 years old when it died. VL - 67 ER - TY - JOUR T1 - RADIOCARBON INVESTIGATION OF TWO OLD ELMS FROM ROMANIA JF - STUDIA UNIVERSITATIS BABES-BOLYAI CHEMIA Y1 - 2022 A1 - Patrut, A A1 - Patrut, RT A1 - Bocos-Bintintan, V A1 - Ratiu, IA A1 - Rakosy, L A1 - Zdrob, G A1 - Vanca, E A1 - von Reden, KF KW - Age KW - Age determination KW - AMS radiocarbon dating KW - BAOBABS KW - carbon KW - dendrochronology KW - PEDUNCULATE OAK KW - PERFORMANCE KW - Romania KW - Trees KW - Ulmus glabra KW - Ulmus minor AB - The paper reports the AMS (accelerator mass spectrometry) radiocarbon investigation results of two superlative elms from Romana, the very large field elm of Calafat, with a wood volume of 85 m(3), and the wych elm of Sadova. Two wood samples were extracted from each elm and were analysed by AMS radiocarbon. The oldest dated sample from the elm of Calafat had a radiocarbon date of 350 +/- 19 BP, which corresponds to a calibrated age of 415 +/- 25 years, while the oldest sample from the elm of Sadova had a radiocarbon date of 188 +/- 24 BP, corresponding to a calibrated age of 260 +/- 25 years. These values indicate high ages for the two elms, namely 430 +/- 25 years or the elm of Calafat and 400 +/- 25 years for the elm of Sadova. VL - 67 SN - 1224-7154 UR - http://chem.ubbcluj.ro/~studiachemia/issues/chemia2022_1/16Patrut_etal_245_256.pdf IS - 1 ER - TY - JOUR T1 - Radiocarbon measurement of CO2 from carbonate minerals using a hybrid gas ion source with an open split interface JF - Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms Y1 - 2022 A1 - Longworth, Brett E. A1 - Burton, Joshua R. A1 - Pendleton, Simon L. A1 - Moser, Sydney D. A1 - Roberts, Mark L. A1 - Kurz, Mark D. KW - Carbonate KW - Hybrid gas ion source KW - radiocarbon AB - We have developed a method for measuring radiocarbon in carbonate minerals as CO2 gas via a NEC MCSNICS hybrid sputter gas ion source (HGIS). The method uses helium as a carrier gas to displace CO2 from sample vials to an open split, where a glass capillary samples the mixture for delivery directly to the HGIS. This method skips the gas transfer and quantification steps used in a closed inlet HGIS system, simplifying sample measurement. Samples larger than 8 mg carbonate can be measured. Results from measurements of consensus standards (TIRI I, IAEA C2, and an internal modern shell standard), and samples from a marine core (F14C = 0.4–1.15) show that the method agrees well with traditional AMS measurement of the same samples as graphite, and that the 1σ uncertainty is about 1%. We discuss advantages and disadvantages of continuous flow sample introduction, and the effect of reduced precision on calibrated age-depth models produced using gas-source data. VL - 531 UR - https://www.sciencedirect.com/science/article/pii/S0168583X2200218X ER - TY - JOUR T1 - Rapid Degradation of Cellulose Diacetate by Marine MicrobesRapid Degradation of Cellulose Diacetate by Marine Microbes JF - Environmental Science & Technology Letters Y1 - 2022 A1 - Mazzotta, Michael G. A1 - Reddy, Christopher M. A1 - Ward, Collin P. KW - ACETATE KW - BIODEGRADATION AB - The persistence of cellulose diacetate (CDA), a biobased plastic used in textiles and single-use consumer products, in the ocean is currently unknown. Here, we probe the disintegration and degradation of CDA-based materials (25 mu m films, 510 mu m foam, and 97 g/m2 fabric) by marine microbes in a continuous flow seawater mesocosm. Photographic evidence and mass loss measurements demonstrate that CDA-based materials disintegrate in months. Disintegration is marked by the increasing esterase and cellulase activity of the biofilm community, suggesting that marine microbes degrade CDA. The natural abundance stable (13C) and radiocarbon (14C) isotopic signature of carbon dioxide respired during short-term bottle incubations confirms the rapid degradation of both acetyl and cellulosic components of CDA by seawater microbial communities. These findings challenge the paradigm set by governmental agencies and advocacy groups that CDA-based materials persist in the ocean for decades, and represent a positive step toward identifying highutility, biobased plastics with low environmental persistence. VL - 9 UR - https://www.webofscience.com/wos/woscc/full-record/WOS:000730351300001?AlertId=ab9062f8-b111-4f95-a2b8-66e7afac0471&SID=7DMV3hUCqV1Mt8lQGWY IS - 1 ER - TY - JOUR T1 - Reconciling the apparent absence of a Last Glacial Maximum alpine glacial advance, Yukon Territory, Canada, through cosmogenic beryllium-10 and carbon-14 measurements JF - Geochronology Y1 - 2022 A1 - Goehring, Brent M. A1 - Menounos, Brian A1 - Osborn, Gerald A1 - Hawkins, Adam A1 - Ward, Brent AB - We present a new in situ produced cosmogenic beryllium-10 and carbon-14 nuclide chronology from two sets (outer and inner) of alpine glacier moraines from the Grey Hunter massif of southern Yukon Territory, Canada. The chronology of moraines deposited by alpine glaciers outside the limits of the Last Glacial Maximum (LGM) ice sheets potentially provides a less-ambiguous archive of mass balance, and hence climate, than can be inferred from the extents of ice sheets themselves. Results for both nuclides are inconclusive for the outer moraines, with evidence for pre-LGM deposition (beryllium-10) and Holocene deposition (carbon-14). Beryllium-10 results from the inner moraine are suggestive of canonical LGM deposition but with relatively high scatter. Conversely, in situ carbon-14 results from the inner moraines are tightly clustered and suggestive of terminal Younger Dryas deposition. We explore plausible scenarios leading to the observed differences between nuclides and find that the most parsimonious explanation for the outer moraines is that of pre-LGM deposition, but many of the sampled boulder surfaces were not exhumed from within the moraine until the Holocene. Our results thus imply that the inner and outer moraines sampled pre- and post-date the canonical LGM and that moraines dating to the LGM are lacking likely due to overriding by the subsequent Late Glacial/earliest Holocene advance. VL - 4 UR - https://gchron.copernicus.org/articles/4/311/2022/ IS - 1 ER - TY - JOUR T1 - Relative sea-level change in South Florida during the past ~5000 years JF - Global and Planetary Change Y1 - 2022 A1 - Khan, Nicole S. A1 - Ashe, Erica A1 - Moyer, Ryan P. A1 - Kemp, Andrew C. A1 - Engelhart, Simon E. A1 - Brain, Matthew J. A1 - Toth, Lauren T. A1 - Chappel, Amanda A1 - Christie, Margaret A1 - Kopp, Robert E. A1 - Horton, Benjamin P. KW - Holocene KW - mangrove KW - Proxy reconstruction KW - Reproducibility KW - sea level AB - A paucity of detailed relative sea-level (RSL) reconstructions from low latitudes hinders efforts to understand the global, regional, and local processes that cause RSL change. We reconstruct RSL change during the past ~5 ka using cores of mangrove peat at two sites (Snipe Key and Swan Key) in the Florida Keys. Remote sensing and field surveys established the relationship between peat-forming mangroves and tidal elevation in South Florida. Core chronologies are developed from age-depth models applied to 72 radiocarbon dates (39 mangrove wood macrofossils and 33 fine-fraction bulk peat). RSL rose 3.7 m at Snipe Key and 5.0 m at Swan Key in the past 5 ka, with both sites recording the fastest century-scale rate of RSL rise since ~1900 CE (~2.1 mm/a). We demonstrate that it is feasible to produce near-continuous reconstructions of RSL from mangrove peat in regions with a microtidal regime and accommodation space created by millennial-scale RSL rise. Decomposition of RSL trends from a network of reconstructions across South Florida using a spatio-temporal model suggests that Snipe Key was representative of regional RSL trends, but Swan Key was influenced by an additional local-scale process acting over at least the past five millennia. Geotechnical analysis of modern and buried mangrove peat indicates that sediment compaction is not the local-scale process responsible for the exaggerated RSL rise at Swan Key. The substantial difference in RSL between two nearby sites highlights the critical need for within-region replication of RSL reconstructions to avoid misattribution of sea-level trends, which could also have implications for geophysical modeling studies using RSL data for model tuning and validation. VL - 216 UR - https://www.sciencedirect.com/science/article/pii/S0921818122001692 ER - TY - JOUR T1 - Relative sea-level data preclude major late Holocene ice-mass change in Pine Island Bay JF - Nature Geoscience Y1 - 2022 A1 - Braddock, Scott A1 - Hall, Brenda L. A1 - Johnson, Joanne S. A1 - Balco, Greg A1 - Spoth, Meghan A1 - Whitehouse, Pippa L. A1 - Campbell, Seth A1 - Goehring, Brent M. A1 - Rood, Dylan H. A1 - Woodward, John AB - The rapidly retreating Thwaites and Pine Island glaciers together dominate present-day ice loss from the West Antarctic Ice Sheet and are implicated in runaway deglaciation scenarios. Knowledge of whether these glaciers were substantially smaller in the mid-Holocene and subsequently recovered to their present extents is important for assessing whether current ice recession is irreversible. Here we reconstruct relative sea-level change from radiocarbon-dated raised beaches at sites immediately seawards of these glaciers, allowing us to examine the response of the earth to loading and unloading of ice in the Amundsen Sea region. We find that relative sea level fell steadily over the past 5.5 kyr without rate changes that would characterize large-scale ice re-expansion. Moreover, current bedrock uplift rates are an order of magnitude greater than the rate of long-term relative sea-level fall, suggesting a change in regional crustal unloading and implying that the present deglaciation may be unprecedented in the past 5.5 kyr. While we cannot preclude minor grounding-line fluctuations, our data are explained most easily by early Holocene deglaciation followed by relatively stable ice positions until recent times and imply that Thwaites and Pine Island glaciers have not been substantially smaller than present during the past 5.5 kyr. VL - 15 UR - https://www.nature.com/articles/s41561-022-00961-y ER - TY - JOUR T1 - Review article: Existing and potential evidence for Holocene grounding line retreat and readvance in Antarctica JF - The Cryosphere Y1 - 2022 A1 - Johnson, Joanne S. A1 - Venturelli, Ryan A. A1 - Balco, Greg A1 - Allen, Claire S. A1 - Braddock, Scott A1 - Campbell, Seth A1 - Goehring, Brent M. A1 - Hall, Brenda L. A1 - Neff, Peter D. A1 - Nichols, Keir A. A1 - Rood, Dylan H. A1 - Thomas, Elizabeth R. A1 - Woodward, John AB - Widespread existing geological records from above the modern ice sheet surface and outboard of the current ice margin show that the Antarctic Ice Sheet (AIS) was much more extensive at the Last Glacial Maximum (∼20 ka) than at present. However, whether it was ever smaller than present during the last few millennia, and (if so) by how much, is known only for a few locations because direct evidence lies within or beneath the ice sheet, which is challenging to access. Here, we describe how retreat and readvance (henceforth “readvance”) of AIS grounding lines during the Holocene could be detected and quantified using subglacial bedrock, subglacial sediments, marine sediment cores, relative sea-level (RSL) records, geodetic observations, radar data, and ice cores. Of these, only subglacial bedrock and subglacial sediments can provide direct evidence for readvance. Marine archives are of limited utility because readvance commonly covers evidence of earlier retreat. Nevertheless, stratigraphic transitions documenting change in environment may provide support for direct evidence from subglacial records, as can the presence of transgressions in RSL records, and isostatic subsidence. With independent age control, ice structure revealed by radar can be used to infer past changes in ice flow and geometry, and therefore potential readvance. Since ice cores capture changes in surface mass balance, elevation, and atmospheric and oceanic circulation that are known to drive grounding line migration, they also have potential for identifying readvance. A multidisciplinary approach is likely to provide the strongest evidence for or against a smaller-than-present AIS in the Holocene. VL - 16 UR - https://tc.copernicus.org/articles/16/1543/2022/ N1 - Publisher: Copernicus GmbH ER - TY - JOUR T1 - Revised marine reservoir offset (ΔR) values for molluscs and marine mammals from Arctic North America JF - Boreas Y1 - 2022 A1 - Pieńkowski, Anna J. A1 - Coulthard, Roy D. A1 - Furze, Mark F. A. AB - Appropriate marine–terrestrial reservoir offset (ΔR) values are essential for accurate calibration of marine radiocarbon dates. However, ΔR values are only valid for the specific calibration curve that their calculation is based on. Here, we present revised ΔR values for the Marine20 calibration curve from Arctic North America, based on previously published 14C dates on pre-bomb live-collected marine molluscs (n = 124) and cetaceans (beluga whales; tooth dentine; n = 12), and bowhead whale–driftwood age comparisons from the same glacio-isostatically uplifted shorelines (n = 18). Molluscan-based ΔR are: Chukchi/Beaufort sea coasts, 265±116 14C years; NW Canadian Arctic Archipelago, 188±91 14C years; NE Baffin Island, 81±18 14C years; SE Baffin Island, 14±58 14C years; Hudson Strait, −73±64 14C years; Ungava Bay, 0±86 14C years; Foxe Basin, 175±89 14C years; Hudson Bay, −21±72 14C years; James Bay, 209±114 14C years; West Greenland, −93±111 14C years. Species-specific marine mammal ΔR terms are 107±59 14C years for beluga and 24±58 14C years for bowheads. Our revised ΔR values are applicable for as long as the same broad oceanographic conditions (circulation, ventilation) have persisted, i.e. through the Holocene. While molluscan values are applicable to other marine carbonate (e.g. foraminifera), cetacean ΔR are valid only for the species they were calculated for and should not be applied to other marine mammals. Importantly, the ΔR terms calculated here are only valid for Marine20 and should not be used with earlier or later calibration curves. UR - https://onlinelibrary.wiley.com/doi/abs/10.1111/bor.12606 N1 - _eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/bor.12606 ER - TY - JOUR T1 - Sediment Accumulation and Carbon Burial in Four Hadal Trench Systems JF - Journal of Geophysical Research: Biogeosciences Y1 - 2022 A1 - Oguri, Kazumasa A1 - Masqué, Pere A1 - Zabel, Matthias A1 - Stewart, Heather A. A1 - MacKinnon, Gillian A1 - Rowden, Ashley A. A1 - Berg, Peter A1 - Wenzhöfer, Frank A1 - Glud, Ronnie N. KW - focusing factor KW - Hadal trench KW - mass accumulation rate KW - mass-wasting event KW - organic carbon deposition rate KW - radionuclides AB - Hadal trenches are considered to act as depocenters for organic material, although pathways for the material transport and deposition rates are poorly constrained. Here we assess focusing, deposition and accumulation of material and organic carbon in four hadal trench systems underlying different surface ocean productivities; the eutrophic Atacama and Kuril-Kamchatka trenches, the mesotrophic Kermadec trench and the oligotrophic Mariana Trench. The study is based on the distributions of naturally occurring 210Pbex, 137Cs and total organic carbon from recovered sediment cores and by applying previously quantified benthic mineralization rates. Periods of steady deposition and discreet mass-wasting deposits were identified from the profiles and the latter were associated with historic recorded seismic events in the respective regions. During periods without mass wasting, the estimated focusing factors along trench axes were elevated, suggesting more or less continuous downslope focusing of material towards the interior of the trenches. The estimated organic carbon deposition rates during these periods exhibited extensive site-specific variability, but were generally similar to values encountered at much shallower settings such as continental slopes and margins. Organic carbon deposition rates during periods of steady deposition were not mirrored by surface ocean productivity, but appeared confounded by local bathymetry. The inclusion of deposition mediated by mass-wasting events enhanced the sediment and organic carbon accumulations for the past ∼150 years by up to a factor of ∼4. Thus, due to intensified downslope material focusing and infrequent mass-wasting events, hadal trenches are important sites for deposition and sequestration of organic carbon in the deep sea. VL - n/a SN - 2169-8961 UR - https://onlinelibrary.wiley.com/doi/abs/10.1029/2022JG006814 IS - n/a N1 -

e2022JG006814 2022JG006814

ER - TY - JOUR T1 - Sediment organic matter compositional changes in a tropical rift lake as a function of water depth and distance from shore JF - Organic Geochemistry Y1 - 2022 A1 - Kruger, Brittany R. A1 - Werne, Josef P. A1 - Minor, Elizabeth C. KW - -Alcohols KW - C/N ratio KW - carbon isotopes KW - Lake Malawi KW - Protokerogen KW - radiocarbon KW - Sedimentary organic carbon AB - Little is known of modern carbon cycling in East African rift lakes. These large tropical systems with anoxic bottom waters can act as test cases for carbon cycling under future climate change scenarios as well as key sediment repositories for paleolimnology studies and fossil fuel generation. This study is the first to combine stable and radiocarbon isotopic information on bulk sediment and biomarkers (n-alcohols) in an African rift lake by investigating surface sediments collected on a nearshore to offshore transect in northern Lake Malawi. This study is also the first to report radiocarbon content in water column particulate organic, dissolved organic and inorganic carbon from an African rift lake. General surface-sediment trends with increasing water depth were an increase in %TOC, and decreases in grain size, δ13C and C/N. Carbon radioisotope analyses showed that bulk sedimentary organic matter was modern across the transect. Biomarker data indicated a primarily aquatic origin for sedimentary organic matter at offshore sites; terrestrial material dominated the n-alcohol signature closest to the shore. Protokerogen stable isotope signatures were similar, and radiocarbon was somewhat depleted relative to bulk sediment organic matter. As compared to bulk organic matter, lipids were 13C-depleted throughout the sampling transect and 14C-depleted at the most nearshore location. This indicates an aged lipid carbon source and likely significant diagenetic alteration of modern sources prior to deposition in nearshore sediments, perhaps a combination of soil erosion, in-river processing, sediment resuspension and mobilization, and preferential degradation of younger organic matter in the oxic nearshore region. UR - https://www.sciencedirect.com/science/article/pii/S0146638022001619 ER - TY - JOUR T1 - Sources and Behavior of Particulate Organic Carbon in the Yellow Sea and the East China Sea Based on 13C, 14C, and 234Th JF - Frontiers in Marine Science Y1 - 2022 A1 - Seo, Junhyeong A1 - Kim, Guebuem A1 - Hwang, Jeomshik AB - The cycling of particulate organic carbon (POC) in continental shelf regions of the Yellow Sea (YS) and the East China Sea (ECS) was investigated by analyzing the concentrations and carbon isotope signatures (δ13C, Δ14C) of POC, together with the particulate aluminum (Al) concentration and 234Th activity over the period 10–20 August 2020. POC concentrations in the surface layer (0–20 m) were twice as high as those in the middle layer (20–50 m); the highest concentrations of all were observed in the bottom layer (> 50 m) of the YS and the region affected by Changjiang Diluted Water (CDW). Particulate Al concentrations in the bottom layer were three times higher than those in the overlying water column, indicating extensive sediment resuspension. Based on the three-endmember mixing model for the dual carbon isotopes, the estimated contribution of resuspended sedimentary organic carbon to POC ranged from 18% in the surface layer to 65% in the bottom layer. The contribution of riverine input to POC ranged from < 5% in the CDW region to ∼45% in the surface layer of the YS region, whereas that of in situ production was ∼40% in the entire study region. A deficiency of 234Th relative to 238U indicates short residence times of particles in the entire water column (2.6 ± 2.2 d). The flux of POC settling to the seafloor, calculated based on 234Th–238U disequilibrium, was 47–125 mmol m–2 d–1. The POC settling flux was one to two orders of magnitude higher than the burial rate of POC in the underlying sediment, implying the rapid decomposition of POC before incorporation into the sediment. Thus, sediment resuspension is prevalent and an important component of the POC cycling in this shelf region. Overall, our study revealed the complex nature of POC cycling on this shelf, quantified the relative importance of each source of POC, and determined POC flux to the sediment. VL - 9 UR - https://www.frontiersin.org/articles/10.3389/fmars.2022.793556/full ER - TY - JOUR T1 - Subsurface Microbial Community Composition in Anchialine Environments Is Influenced by Original Organic Carbon Source at Time of Deposition JF - Frontiers in Marine Science Y1 - 2022 A1 - Risley, Catherine A. A1 - Tamalavage, Anne E. A1 - van Hengstum, Peter J. A1 - Labonte, Jessica M. AB - Prokaryotes constitute the majority of sedimentary biomass, where they cycle organic carbon and regulate organic matter transformation. The microbes inhabiting sediment are diverse and the factors controlling microbial community composition are not fully understood. Here, we characterized the prokaryotic community using 16S rRNA gene sequencing in 24 stratigraphic layers within a 89 cm (dated to 1900 years old) sediment core from an anchialine sinkhole in the Bahamas with a stratified water column and anoxic bottom water. The microbial community was dominated by members of the Alphaproteobacteria, Dehalococcoidia, Gammaproteobacteria, Bathyarchaeota, and Campylobacter classes. Most interestingly, subsurface microbial community structure could be correlated to previous evidence for timewise changes in the main source of organic matter that was supplied to the sediment accumulating during the last 2000 years, which itself was caused by regional terrestrial vegetation changes. The C:N ratio was correlated to the relative abundance of the microbial classes, and the microbial communities followed three previously determined time periods based on the source of organic matter, which suggests that the carbon source at time of deposition influences the resultant subsurface microbial community composition. These results show that carbon source is a driver of the microbial community composition inhabiting anoxic sediment, which could have implications for improving understanding of carbon cycling in coastal sedimentary basins. VL - 9 UR - https://www.frontiersin.org/articles/10.3389/fmars.2022.872789/full ER - TY - JOUR T1 - Synergy between Sunlight, Titanium Dioxide, and Microbes Enhances Cellulose Diacetate Degradation in the Ocean JF - Environmental Science & Technology Y1 - 2022 A1 - Walsh, Anna N. A1 - Mazzotta, Michael G. A1 - Nelson, Taylor F. A1 - Reddy, Christopher M. A1 - Ward, Collin P. AB - Sunlight chemically transforms marine plastics into a suite of products, with formulation─the specific mixture of polymers and additives─driving rates and products. However, the effect of light-driven transformations on subsequent microbial lability is poorly understood. Here, we examined the interplay between photochemical and biological degradation of fabrics made from cellulose diacetate (CDA), a biobased polymer used commonly in consumer products. We also examined the influence of ∼1% titanium dioxide (TiO2), a common pigment and photocatalyst. We sequentially exposed CDA to simulated sunlight and native marine microbes to understand how photodegradation influences metabolic rates and pathways. Nuclear magnetic resonance spectroscopy revealed that sunlight initiated chain scission reactions, reducing CDA’s average molecular weight. Natural abundance carbon isotope measurements demonstrated that chain scission ultimately yields CO2, a newly identified abiotic loss term of CDA in the environment. Measurements of fabric mass loss and enzymatic activities in seawater implied that photodegradation enhanced biodegradation by performing steps typically facilitated by cellulase. TiO2 accelerated CDA photodegradation, expediting biodegradation. Collectively, these findings (i) underline the importance of formulation in plastic’s environmental fate and (ii) suggest that overlooking synergy between photochemical and biological degradation may lead to overestimates of marine plastic persistence. VL - 56 UR - https://doi.org/10.1021/acs.est.2c04348 N1 - Publisher: American Chemical Society ER - TY - JOUR T1 - Terrestrial organic carbon age and reactivity in the Yellow River fueling efficient preservation in marine sediments JF - Earth and Planetary Science Letters Y1 - 2022 A1 - Zhang, Yushuang A1 - Galy, Valier A1 - Yu, Meng A1 - Zhang, Hailong A1 - Zhao, Meixun AB - The Yellow River is one of the largest suppliers of sediments and organic carbon (OC) to the ocean. Previous studies have revealed that OC transported by the Yellow River largely derives from the erosion of the Chinese Loess Plateau, which is dominated by pre-aged soil carbon and could be efficiently preserved in marine sediments. Here, we used ramped oxidation radiocarbon analysis (RPO-14C) to characterize the age and reactivity distribution of OC in two Yellow River suspended sediment samples and six Bohai Sea and Yellow Sea (BS–YS) surface sediments from a transect along the sediment transport pathway. RPO-14C independently characterizes the full spectrum of OC thermal stability and isotope compositions to reveal the source, age and reactivity structure of OC transported by the Yellow River and preserved in Chinese marginal sea sediments. We calculated the activation energy (E) distribution—a proxy for bonding environment and by extension reactivity—which, combined with 14C and stable carbon isotope (δ 13C) compositions, reveals OC origin and stability. Our data suggest that 96% of OC in Yellow River suspended sediments is biospheric and weathered petrogenic, while unweathered petrogenic OC only accounts for 4% which is almost an order of magnitude lower than the fossil OC estimates (32%) based on compound specific 14C analysis. RPO data reveal the prevalence of aged biospheric loess OC in the Yellow River. We use δ 13C, 14C and RPO-derived activation energy data to quantify the contribution of terrestrial OC to surface sediments in the BS–YS. The resulting estimates of terrestrial OC proto-burial efficiencies yield an average value of 89 ± 30%, revealing overall very high terrestrial OC preservation in the BS–YS. Additionally, and somewhat counter intuitively, we find that the preservation of terrestrial OC decreases with increasing E. This pattern may arise from an enhanced preservation of a pre-aged C4 plants derived fraction of the loess-derived OC associated with secondary clays characterized by smaller grain size and higher surface area. Alternatively, the high E component of the Yellow River OC might comprise partially weathered petrogenic carbon, undergoing further mineralization during transport from rivers to marginal sea sediments via marine organic matter priming. VL - 585 UR - https://linkinghub.elsevier.com/retrieve/pii/S0012821X22001510 ER - TY - JOUR T1 - Understanding the Water Resources of a Mountain‐block Aquifer: Tucson Mountains, Arizona JF - Journal of Contemporary Water Research & Education Y1 - 2022 A1 - Eastoe, Christopher J. A1 - Beisner, Kimberly R. AB - Water resources are limited in arid locations such as Tucson Basin. Residential development in the Tucson Mountains to the west of Tucson, Arizona, is limited by groundwater resources. Groundwater samples were collected from fractured bedrock and alluvial aquifers surrounding the Tucson Mountains to assess water quality and recharge history through measurement of stable O, H, and S isotopes; tritium; and 14C. Most groundwater is a mixture of different ages but is commonly several thousand years old. A few sampling locations indicated a component of water recharged after the above‐ground nuclear testing of the mid 1950s, and these sites may represent locations near where the aquifer receives present‐day recharge. The Tucson Mountains also host sulfide deposits associated with fractures and replacement zones; these locally contribute to poor‐quality groundwater. Projections of future climate predict intensifying drought in southwestern North America. In the study area, a combination of strategies such as rainwater harvesting, exploitation of renewable water, and low groundwater use could be used for sustainable use of the groundwater supply. UR - https://onlinelibrary.wiley.com/doi/10.1111/j.1936-704X.2021.3369.x IS - 175 ER - TY - JOUR T1 - Use of δ18Oatm in dating a Tibetan ice core record of Holocene/Late Glacial climate JF - Proceedings of the National Academy of Sciences Y1 - 2022 A1 - Thompson, Lonnie G. A1 - Severinghaus, Jeffrey P. A1 - Yao, Tandong A1 - Davis, Mary E. A1 - Mosley-Thompson, Ellen A1 - Beaudon, Emilie A1 - Sierra-Hernández, M. Roxana A1 - Porter, Stacy E. AB - Ice cores from the northwestern Tibetan Plateau (NWTP) contain long records of regional climate variability, but refrozen meltwater and dust in these cores has hampered development of robust timescales. Here, we introduce an approach to dating the ice via the isotopic composition of atmospheric O2 in air bubbles (δ18Oatm), along with annual layer counting and radiocarbon dating. We provide a robust chronology for water isotope records (δ18Oice and d-excess) from three ice cores from the Guliya ice cap in the NWTP. The measurement of δ18Oatm, although common in polar ice core timescales, has rarely been used on ice cores from low-latitude, high-altitude glaciers due to (1) low air pressure, (2) the common presence of refrozen melt that adds dissolved gases and reduces the amount of air available for analysis, and (3) the respiratory consumption of molecular oxygen (O2) by micro-organisms in the ice, which fractionates the δ18O of O2 from the atmospheric value. Here, we make corrections for melt and respiration to address these complications. The resulting records of water isotopes from the Guliya ice cores reveal climatic variations over the last 15,000 y, the timings of which correspond to those observed in independently dated lake and speleothem records and confirm that the Guliya ice cap existed before the Holocene. The millennial-scale drivers of δ18Oice are complex and temporally variable; however, Guliya δ18Oice values since the mid-20th century are the highest since the beginning of the Holocene and have increased with regional air temperature. VL - 119 UR - https://www.pnas.org/doi/10.1073/pnas.2205545119 N1 - Publisher: Proceedings of the National Academy of Sciences ER - TY - ICOMM T1 - We're decoding ancient hurricanes' traces on the sea floor – and evidence from millennia of Atlantic storms is not good news for the coast Y1 - 2022 A1 - Winkler, Tyler AB - If you look back at the history of Atlantic hurricanes since the late 1800s, it might seem hurricane frequency is on the rise. The year 2020 had the most tropical cyclones in the Atlantic, with 31, and 2021 had the third-highest, after 2005. The past decade saw five of the six most destructive Atlantic hurricanes in modern history. Then a year like 2022 comes along, with no major hurricane landfalls until Fiona and Ian struck in late September. The Atlantic hurricane season, which ended on Nov. 30, had eight hurricanes and 14 named storms. It’s a reminder that small sample sizes can be misleading when assessing trends in hurricane behavior. There is so much natural variability in hurricane behavior year to year and even decade to decade that we need to look much further back in time for the real trends to come clear. Fortunately, hurricanes leave behind telltale evidence that goes back millennia. Two thousand years of this evidence indicates that the Atlantic has experienced even stormier periods in the past than we’ve seen in recent years. That’s not good news. It tells coastal oceanographers like me that we may be significantly underestimating the threat hurricanes pose to Caribbean islands and the North American coast in the future. JF - The Conversation UR - http://theconversation.com/were-decoding-ancient-hurricanes-traces-on-the-sea-floor-and-evidence-from-millennia-of-atlantic-storms-is-not-good-news-for-the-coast-186899 ER - TY - JOUR T1 - Younger Dryas and early Holocene climate in south Greenland inferred from oxygen isotopes of chironomids, aquatic Moss, and Moss cellulose JF - Quaternary Science Reviews Y1 - 2022 A1 - Puleo, Peter J. K. A1 - Masterson, Andrew L. A1 - Medeiros, Andrew S. A1 - Schellinger, Grace A1 - Steigleder, Regan A1 - Woodroffe, Sarah A1 - Osburn, Magdalena R. A1 - Axford, Yarrow KW - Chironomids KW - Deglaciation KW - diatoms KW - Greenland KW - Holocene KW - Micropaleontology KW - paleoclimatology KW - paleolimnology KW - Stable isotopes KW - Younger Dryas AB - Ice core records have long indicated that the Younger Dryas began and ended with large, abrupt climate shifts over Greenland. Key climatic features remain unknown, including the magnitude of warming during the Younger Dryas-Holocene transition along with the seasonality and spatial variability of Younger Dryas climate changes across Greenland. Here, we use geochemical and paleoecological proxies from lake sediments at Lake N14 in south Greenland to address these outstanding questions. Radiocarbon dating and diatom assemblages confirm early deglaciation and isolation of Lake N14 before ∼13,600 cal yr BP, consistent with previous work. Oxygen isotope ratios (δ18O) of chironomid head capsules, bulk aquatic moss, and aquatic moss-derived cellulose are used to reconstruct oxygen isotopes of past lake water and annual precipitation. Oxygen isotope proxies indicate annual precipitation δ18O values increased by 5.9–7.7‰ at the end of the Younger Dryas. Following the Younger Dryas, moss and cellulose δ18O values show a clear decline in precipitation δ18O values of 2–3‰ from ∼11,540–11,340 cal yr BP that may correspond with the Preboreal Oscillation. Reconstructed precipitation δ18O values then gradually increased from 11,300–10,100 cal yr BP. All three aquatic organic materials register similar shifts in precipitation δ18O values over time, and they closely parallel the δ18O shifts observed in ice cores. This evidence strongly supports the utility of these methods for reconstructing lake water δ18O, and furthermore precipitation δ18O values where lake water reflects precipitation. The relatively large shift in isotopic composition of precipitation at Lake N14 suggests that shifts in temperature, precipitation seasonality, and/or moisture sources at the end of the Younger Dryas were even larger in south Greenland than they were in central Greenland, most likely because of the proximity to major changes in North Atlantic Ocean circulation. The annual air temperature change estimated at Lake N14 at the end of the Younger Dryas is also very large (∼18 ± 7 °C) compared to the summer warming previously inferred from chironomid species assemblages there (∼6 °C). This indicates that the strongest warming at the end of the Younger Dryas occurred in the winter season, consistent with past observations of intensified Younger Dryas seasonality at Lake N14 and elsewhere in Greenland. VL - 296 UR - https://www.sciencedirect.com/science/article/pii/S0277379122004413 ER - TY - JOUR T1 - AGE, GROWTH AND ARCHITECTURE OF THE HISTORIC BIG TREE AT VICTORIA FALLS, ZIMBABWE ASSESSED BY RADIOCARBON DATING JF - Dendrochronologia Y1 - 2021 A1 - Patrut, Adrian A1 - Patrut, Roxana T. A1 - Rakosy, Laszlo A1 - RATIU, ILEANA ANDREEA A1 - Lowy, Daniel A. A1 - von Reden, Karl F. KW - Adansonia digitata KW - Age determination KW - AMS radiocarbon dating KW - growth stop KW - multiple stems KW - tropical trees AB - The article discloses the AMS (accelerator mass spectrometry) radiocarbon dating results of the historic Big Tree at Victoria Falls, Zimbabwe. The research aimed to determine the age, growth and architecture of this renowned African baobab. The superlative baobab is composed of five main stems, three young stems and one false stem. It exhibits an open ring-shaped structure, an architecture that allows baobabs to reach large sizes and old ages. Several wood samples extracted from four stems were dated by radiocarbon. The oldest sample had a radiocarbon date of 978 ± 14 BP, corresponding to a calibrated age of 955 ± 20 calendar years. By this value, the Big Tree at Victoria Falls is 1150 ± 50 years old. We found that the eight common stems belong to three generations, which are 1000-1100, 600-700 and 200-250 years old, respectively. The false stem is 550 years old. The stems belonging to the oldest generation stopped growing over 100 years ago. UR - https://www.sciencedirect.com/science/article/abs/pii/S1125786521000941 ER - TY - JOUR T1 - BOMB-PRODUCED RADIOCARBON ACROSS THE SOUTH PACIFIC GYRE—A NEW RECORD FROM AMERICAN SAMOA WITH UTILITY FOR FISHERIES SCIENCEABSTRACT JF - Radiocarbon Y1 - 2021 A1 - Andrews, Allen H A1 - Prouty, Nancy G A1 - Cheriton, Olivia M AB - Coral skeletal structures can provide a robust record of nuclear bomb produced 14C with valuable insight into air-sea exchange processes and water movement with applications to fisheries science. To expand these records in the South Pacific, a coral core from Tutuila Island, American Samoa was dated with density band counting covering a 59-yr period (1953–2012). Seasonal signals in elemental ratios (Sr/Ca and Ba/Ca) and stable carbon (δ13C) values across the coral core corroborated the well-defined annual band structure and highlighted an ocean climate shift from the 1997–1998 El Niño. The American Samoa coral 14C measurements were consistent with other regional records but included some notable differences across the South Pacific Gyre (SPG) at Fiji, Rarotonga, and Easter Island that can be attributed to decadal ocean climate cycles, surface residence times and proximity to the South Equatorial Current. An analysis of the post-peak 14C decline associated with each coral record indicated 14C levels are beginning to merge for the SPG. This observation, coupled with otolith measurements from American Samoa, reinforces the perspective that bomb 14C dating can be performed on fishes and other marine organisms of the region using the post-peak 14C decline to properly inform fisheries management in the South Pacific. VL - 63 UR - https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0033822221000515 IS - 6 ER - TY - JOUR T1 - Carbon Isotopic and Lithologic Constraints on the Sources and Cycling of Inorganic Carbon in Four Large Rivers in China: Yangtze, Yellow, Pearl, and Heilongjiang JF - Journal of Geophysical Research: Biogeosciences Y1 - 2021 A1 - Shan, Sen A1 - Luo, Chunle A1 - Qi, Yuanzhi A1 - Cai, Wei‐Jun A1 - Sun, Shuwen A1 - Fan, Di A1 - Wang, Xuchen KW - Carbon cycle KW - Chemical weathering KW - inorganic carbon in large rivers KW - radiocarbon KW - stable carbon isotope AB - Transport of terrigenous carbon by rivers has been affected extensively by climate change and anthropogenic activities in China over the last few decades. Here, we present results on carbon isotopes (C-13, C-14) of dissolved and particulate inorganic carbon (DIC and PIC) and combined with major lithologic ions measured in the four largest rivers in China, namely, the Yangtze, Yellow, Pearl, and Heilongjiang rivers, to reveal the sources and transport of terrigenous inorganic carbon in the rivers. The DIC concentrations showed large variations in the four rivers and ranged from 253 to 3,122 mu M. The Yangtze, Yellow and Pearl rivers transported high DIC contents that had low Delta C-14 values of millennium-aged DIC and very old PIC; however, the Heilongjiang River presented a lower DIC concentration with much younger C-14 ages than the global average (1,100 mu M). The strong correlations between the DIC isotope values and major lithological ions (Ca2+ and Mg2+) suggest that chemical weathering played important but variable roles in controlling the production and fate of DIC in the rivers. Using dual isotopes and the MixSIAR model, we calculated that the chemical weathering of carbonate rocks contributed 95 +/- 5% of the riverine DIC to the headwater of the Yangtze River while silicate rock weathering and riverine organic matter respiration contributed 62 +/- 25% and 5 +/- 5% of the DIC in the middle and lower reaches of the river, respectively. In contrast, chemical weathering of silicate rocks contributed the dominant fraction of DIC in the Yellow (55 +/- 17%), Pearl (61 +/- 20%) and Heilongjiang (83 +/- 29%) rivers. VL - 126 UR - https://apps.webofknowledge.com/InboundService.do?product=WOS&Func=Frame&DestFail=http%3A%2F%2Fwww.webofknowledge.com&SrcApp=search&SrcAuth=Alerting&SID=7EQ3XpZtZiWye3DFos4&customersID=Alerting&mode=FullRecord&IsProductCode=Yes&AlertId=4d48b20a-7d27-4fa2- IS - 2 ER - TY - JOUR T1 - Centennial-scale age offsets of plant wax n-alkanes in Adirondack lake sediments JF - Geochimica et Cosmochimica Acta Y1 - 2021 A1 - Freimuth, Erika J. A1 - Diefendorf, Aaron F. A1 - Lowell, Thomas V. A1 - Schartman, Anna K. A1 - Landis, Joshua D. A1 - Stewart, Alexander K. A1 - Bates, Benjamin R. VL - 300 UR - https://apps.webofknowledge.com/InboundService.do?product=WOS&Func=Frame&DestFail=http%3A%2F%2Fwww.webofknowledge.com&SrcApp=search&SrcAuth=Alerting&SID=8FcXJjl9GsiAmhuIO65&customersID=Alerting&mode=FullRecord&IsProductCode=Yes&AlertId=ab9062f8-b111-4f95- ER - TY - JOUR T1 - Characteristics of sediment resuspension on a deep abyssal plain in the Eastern Tropical Pacific Ocean JF - Journal of Sea Research Y1 - 2021 A1 - Kim, Minkyoung A1 - Kim, Hyung Jeek A1 - Ko, Ara A1 - Yoo, Chan Min A1 - Ju, Se-Jong A1 - Hwang, Jeomshik VL - 175 UR - https://www.webofscience.com/wos/woscc/full-record/WOS:000687819300003?AlertId=ab9062f8-b111-4f95-a2b8-66e7afac0471&SID=7DFRqn1B6A3SRDPNEE8 ER - TY - JOUR T1 - Climate control on terrestrial biospheric carbon turnover JF - Proceedings of the National Academy of Sciences Y1 - 2021 A1 - Eglinton, Timothy I. A1 - Galy, Valier V. A1 - Hemingway, Jordon D. A1 - Feng, Xiaojuan A1 - Bao, Hongyan A1 - Blattmann, Thomas M. A1 - Dickens, Angela F. A1 - Gies, Hannah A1 - Giosan, Liviu A1 - Haghipour, Negar A1 - Hou, Pengfei A1 - Lupker, Maarten A1 - McIntyre, Cameron P. A1 - Montluçon, Daniel B. A1 - Peucker-Ehrenbrink, Bernhard A1 - Ponton, Camilo A1 - Schefuß, Enno A1 - Schwab, Melissa S. A1 - Voss, Britta M. A1 - Wacker, Lukas A1 - Wu, Ying A1 - Zhao, Meixun KW - Carbon cycle KW - carbon turnover times KW - fluvial carbon KW - plant biomarkers KW - radiocarbon AB - Terrestrial vegetation and soils hold three times more carbon than the atmosphere. Much debate concerns how anthropogenic activity will perturb these surface reservoirs, potentially exacerbating ongoing changes to the climate system. Uncertainties specifically persist in extrapolating point-source observations to ecosystem-scale budgets and fluxes, which require consideration of vertical and lateral processes on multiple temporal and spatial scales. To explore controls on organic carbon (OC) turnover at the river basin scale, we present radiocarbon (C-14) ages on two groups of molecular tracers of plant-derived carbon-leaf-wax lipids and lignin phenols-from a globally distributed suite of rivers. We find significant negative relationships between the C-14 age of these biomarkers and mean annual temperature and precipitation. Moreover, riverine biospheric-carbon ages scale proportionally with basin-wide soil carbon turnover times and soil C-14 ages, implicating OC cycling within soils as a primary control on exported biomarker ages and revealing a broad distribution of soil OC reactivities. The ubiquitous occurrence of a long-lived soil OC pool suggests soil OC is globally vulnerable to perturbations by future temperature and precipitation increase. Scaling of riverine biospheric-carbon ages with soil OC turnover shows the former can constrain the sensitivity of carbon dynamics to environmental controls on broad spatial scales. Extracting this information from fluvially dominated sedimentary sequences may inform past variations in soil OC turnover in response to anthropogenic and/or climate perturbations. In turn, monitoring riverine OC composition may help detect future climate-change-induced perturbations of soil OC turnover and stocks. VL - 118 UR - https://www.researchgate.net/publication/349357864_Climate_control_on_terrestrial_biospheric_carbon_turnover IS - 8 ER - TY - JOUR T1 - Coal fly ash is a major carbon flux in the Chang Jiang (Yangtze River) basin JF - Proceedings of the National Academy of Sciences Y1 - 2021 A1 - Li, Gen K. A1 - Fischer, Woodward W. A1 - Lamb, Michael P. A1 - West, A. Joshua A1 - Zhang, Ting A1 - Galy, Valier A1 - Wang, Xingchen Tony A1 - Li, Shilei A1 - Qiu, Hongrui A1 - Li, Gaojun A1 - Zhao, Liang A1 - Chen, Jun A1 - Ji, Junfeng AB - Fly ash-the residuum of coal burning-contains a considerable amount of fossilized particulate organic carbon (FOCash) that remains after high-temperature combustion. Fly ash leaks into natural environments and participates in the contemporary carbon cycle, but its reactivity and flux remained poorly understood. We characterized FOCash in the Chang Jiang (Yangtze River) basin, China, and quantified the riverine FOCash fluxes. Using Raman spectral analysis, ramped pyrolysis oxidation, and chemical oxidation, we found that FOCash is highly recalcitrant and unreactive, whereas shale-derived FOC (FOCrock) was much more labile and easily oxidized. By combining mass balance calculations and other estimates of fly ash input to rivers, we estimated that the flux of FOCash carried by the Chang Jiang was 0.21 to 0.42 Mt C center dot y-1 in 2007 to 2008-an amount equivalent to 37 to 72% of the total riverine FOC export. We attributed such high flux to the combination of increasing coal combustion that enhances FOCash production and the massive construction of dams in the basin that reduces the flux of FOCrock eroded from upstream mountainous areas. Using global ash data, a first-order estimate suggests that FOCash makes up to 16% of the present-day global riverine FOC flux to the oceans. This reflects a substantial impact of anthropogenic activities on the fluxes and burial of fossil organic carbon that has been made less reactive than the rocks from which it was derived. VL - 118 UR - http://www.pnas.org/lookup/doi/10.1073/pnas.1921544118https://syndication.highwire.org/content/doi/10.1073/pnas.1921544118http://www.pnas.org/syndication/doi/10.1073/pnas.1921544118 IS - 21 ER - TY - JOUR T1 - Compound-specific radiocarbon reveals sources and land–sea transport of polycyclic aromatic hydrocarbons in an urban estuary JF - Water Research Y1 - 2021 A1 - Ya, Miaolei A1 - Wu, Yuling A1 - Xu, Li A1 - Li, Yongyu A1 - Chen, Hanzhe A1 - Wang, Xinhong AB - As typical chemical indicators of the Anthropocene, polycyclic aromatic hydrocarbons (PAHs) and their environmental behavior in urban estuaries can reveal the influence of anthropogenic activities on coastal zones worldwide. In contrast to conventional approaches based on concentration datasets, we provide a compound-specific radiocarbon ( 14 C) perspective to quantitatively evaluate the sources and land–sea transport of PAHs in an estuarine–coastal surficial sedimentary system impacted by anthropogenic activities and coastal currents. Compound-specific 14 C of PAHs and their 14 C end-member mixing models showed that 67 −73% of fluoranthene and pyrene and 76 −80% of five- and six-ring PAHs in the Jiulong River Estuary (JRE, China) originated from fossil fuels (e.g., coal, oil spill, and petroleum-related emissions). In the adjacent Western Taiwan Strait (WTS), the contributions of fossil fuel to these PAH groups were higher at 74 −79% and 84 −87%, respectively. Furthermore, as a significant biomarker for source al- location of terrigenous organic matter, perylene, a typical five-ring PAH, and its land–sea transport from the basin through the JRE and finally to the WTS was quantitatively evaluated based on the 14 C transport models. In the JRE, fluvial erosions and anthropogenic emissions affected the 14 C signature of perylene ( 14 C perylene , -535 ±5 ‰ ) with contributions of > 38% and < 62%, respectively. From the JRE to the WTS, the decreased 14 C perylene (-735 ±4 ‰ ) could be attributed to the long–range transport of “ocean current- driven” perylene (-919 ±53 ‰ ) with a contribution of 53 ±8%. This compound-specific 14 C approach and PAH transport model help provide a valuable reference for accurately quantifying land–sea transport and burial of organic pollutants in estuarine–coastal sedimentary systems. VL - 198 UR - https://www.sciencedirect.com/science/article/pii/S0043135421003328 ER - TY - DATA T1 - CTD profiles and discrete water-column measurements collected off California and Oregon during NOAA cruise SH-18-12 (USGS field activity 2018-663-FA) from October to November 2018 (ver. 3.0, July 2022) Y1 - 2021 A1 - Prouty, Nancy G A1 - Baker, Miranda C KW - Earth and related environmental sciences KW - Geochemistry AB - Various water column variables, including salinity, dissolved inorganic nutrients, pH, total alkalinity, dissolved inorganic carbon, radio-carbon isotopes were measured in samples collected using a Niskin-bottle rosette at selected depths from sites offshore of California and Oregon from October to November 2018 during NOAA cruise SH-18-12 on the R/V Bell M. Shimada (USGS field activity 2018-663-FA). CTD (Conductivity Temperature Depth) data were also collected at each depth that a Niskin-bottle sample was collected and are presented along with the water sample data. This data release supersedes version 2.0, published in September 2021 at https://doi.org/10.5066/P99DIQZ5. Versioning details are documented in the accompanying VersionHistory_P99MJ096.txt file. PB - U.S. Geological Survey UR - https://www.sciencebase.gov/catalog/item/6281d080d34e3bef0c9a3b17 ER - TY - JOUR T1 - Enhanced iceberg discharge in the western North Atlantic during all Heinrich events of the last glaciation JF - Earth and Planetary Science Letters Y1 - 2021 A1 - Zhou, Yuxin A1 - McManus, Jerry F. A1 - Jacobel, Allison W. A1 - Costa, Kassandra M. A1 - Wang, Shouyi A1 - Alvarez Caraveo, Blanca KW - Heinrich event KW - IRD flux KW - thorium normalization KW - western north atlantic AB - A series of catastrophic iceberg and meltwater discharges to the North Atlantic, termed Heinrich events, punctuated the last ice age. During Heinrich events, coarse terrigenous debris released from the drifting icebergs was preserved in deep-sea sediments, serving as an indicator of iceberg passage. Quantifying the vertical flux of ice-rafted debris (IRD) in open-ocean settings can resolve questions regarding the timing and spatial variation in ice sheet calving intensity. In this study, 230Thxs-based IRD flux throughout the last glacial period was measured in a deep-sea sediment core from the western North Atlantic, and complemented by data spanning 0-32 ka from a sediment core in the Labrador Sea. The cores were recovered from sites downstream from Hudson Strait, a likely conduit for icebergs calving from the Laurentide ice sheet (LIS). We compare our results with equivalent existing data from the eastern North Atlantic and show that the two cores in our study have higher IRD fluxes during all Heinrich events, notably including events H3 (∼31 ka) and H6 (∼60 ka). This study demonstrates that the LIS played a role in all Heinrich events, and raises the likelihood that a single mechanism can account for the genesis of these events. VL - 564 SN - 0012-821X UR - https://www.sciencedirect.com/science/article/pii/S0012821X21001692 JO - Earth and Planetary Science Letters ER - TY - JOUR T1 - ERRONEOUSLY OLD RADIOCARBON AGES FROM TERRESTRIAL POLLEN CONCENTRATES IN YELLOWSTONE LAKE, WYOMING, USA JF - Radiocarbon Y1 - 2021 A1 - Schiller, Christopher M. A1 - Whitlock, Cathy A1 - Elder, Kathryn L. A1 - Iverson, Nels A. A1 - Abbott, Mark B. KW - AMS dating KW - chronology KW - contamination KW - paleoecology KW - pine AB - Accelerator mass spectrometry (AMS) dating of pollen concentrates is often used in lake sediment records where large, terrestrial plant remains are unavailable. Ages produced from chemically concentrated pollen as well as manually picked Pinaceae grains in Yellowstone Lake (Wyoming) sediments were consistently 1700–4300 cal years older than ages established by terrestrial plant remains, tephrochronology, and the age of the sediment-water interface. Previous studies have successfully utilized the same laboratory space and methods, suggesting the source of old-carbon contamination is specific to these samples. Manually picking pollen grains precludes admixture of non-pollen materials. Furthermore, no clear source of old pollen grains occurs on the deglaciated landscape, making reworking of old pollen grains unlikely. High volumes of CO2 are degassed in the Yellowstone Caldera, potentially introducing old carbon to pollen. While uptake of old CO2 through photosynthesis is minor (F14C approximately 0.99), old-carbon contamination may still take place in the water column or in surficial lake sediments. It remains unclear, however, what mechanism allows for the erroneous ages of highly refractory pollen grains while terrestrial plant remains were unaffected. In the absence of a satisfactory explanation for erroneously old radiocarbon ages from pollen concentrates, we propose steps for further study. VL - 63 SN - 0033-8222, 1945-5755 UR - https://www.cambridge.org/core/journals/radiocarbon/article/erroneously-old-radiocarbon-ages-from-terrestrial-pollen-concentrates-in-yellowstone-lake-wyoming-usa/1DAC6B6CCD52443755E7F725B84CFB3F IS - 1 ER - TY - JOUR T1 - Event-dominated transport, provenance, and burial of organic carbon in the Japan Trench JF - Earth and Planetary Science Letters Y1 - 2021 A1 - Schwestermann, T. A1 - Eglinton, T.I. A1 - Haghipour, N. A1 - McNichol, A.P. A1 - Ikehara, K. A1 - Strasser, M. KW - carbon isotopes KW - carbon provenance KW - carbon transfer KW - hadal zone event-stratigraphy KW - Japan Trench KW - ramped Pyr/Ox AB - The delivery of organic carbon (OC) to the ocean's deepest trenches in the hadal zone is poorly understood, but may be important for the carbon cycle, contain crucial information on sediment provenance and event-related transport processes, and provide age constraints on stratigraphic sequences in this terminal sink. In this study, we systematically characterize bulk organic matter (OM) and OC signatures (TOC/TN, delta C-13, C-14), as well as those from application of serial thermal oxidation (ramped pyrolysis/oxidation) of sediment cores recovered along an entire hadal trench encompassing high stratigraphic resolution records spanning nearly 2000 years of deposition. We analyze two cores from the southern and northern Japan Trench, where submarine canyon systems link shelf with trench. We compare results with previously published data from the central Japan Trench, where canyon systems are absent. Our analyses enable refined dating of the stratigraphic record and indicate that event deposits arise from remobilization of relatively surficial sediment coupled with deeper erosion along turbidity current pathways in the southern and central study site and from canyon flushing events in the northern study site. Furthermore, our findings indicate deposition of predominantly marine OC within hemipelagic background sediment as well as associated with event deposits along the entire trench axis. This implies that canyon systems flanking the Japan Trench do not serve as a short-circuit for injection of terrestrial OC to the hadal zone, and that tropical cyclones are not major agents for sediment and carbon transfer into this trench system. These findings further support previous Japan Trench studies interpreting that event deposits originate from the landward trench slope and are earthquake-triggered. The very low terrestrial OC input into the Japan Trench can be explained by the significant distance between trench and hinterland (>180 km), and the physiography of the canyons that do not connect to coast and river systems. We suggest that detailed analyzes of long sedimentary records are essential to understand OC transfer, deposition and burial in hadal trenches. (C) 2021 The Author(s). Published by Elsevier B.V. VL - 563 UR - https://apps.webofknowledge.com/InboundService.do?product=WOS&Func=Frame&DestFail=https%3A%2F%2Fwww.webofknowledge.com&SrcApp=search&SrcAuth=Alerting&SID=8DxHHPXeqJFVJQqBfHD&customersID=Alerting&mode=FullRecord&IsProductCode=Yes&AlertId=4d48b20a-7d27-4fa2 ER - TY - JOUR T1 - Evidence of humans in North America during the Last Glacial Maximum JF - Science Y1 - 2021 A1 - Bennett, Matthew R. A1 - Bustos, David A1 - Pigati, Jeffrey S. A1 - Springer, Kathleen B. A1 - Urban, Thomas M. A1 - Holliday, Vance T. A1 - Reynolds, Sally C. A1 - Budka, Marcin A1 - Honke, Jeffrey S. A1 - Hudson, Adam M. A1 - Fenerty, Brendan A1 - Connelly, Clare A1 - Martinez, Patrick J. A1 - Santucci, Vincent L. A1 - Odess, Daniel AB - Archaeologists and researchers in allied fields have long sought to understand human colonization of North America. Questions remain about when and how people migrated, where they originated, and how their arrival affected the established fauna and landscape. Here, we present evidence from excavated surfaces in White Sands National Park (New Mexico, United States), where multiple in situ human footprints are stratigraphically constrained and bracketed by seed layers that yield calibrated radiocarbon ages between \textasciitilde23 and 21 thousand years ago. These findings confirm the presence of humans in North America during the Last Glacial Maximum, adding evidence to the antiquity of human colonization of the Americas and providing a temporal range extension for the coexistence of early inhabitants and Pleistocene megafauna. VL - 373 UR - https://www.science.org/doi/full/10.1126/science.abg7586 N1 - Publisher: American Association for the Advancement of Science ER - TY - JOUR T1 - A FRAMEWORK FOR TRANSDISCIPLINARY RADIOCARBON RESEARCH: USE OF NATURAL-LEVEL AND ELEVATED-LEVEL -14- C IN ANTARCTIC FIELD RESEARCHABSTRACT JF - Radiocarbon Y1 - 2021 A1 - Venturelli, Ryan A A1 - Vick-Majors, Trista J A1 - Collins, Billy A1 - Gagnon, Alan A1 - Kasic, Kathy A1 - Kurz, Mark D A1 - Li, Wei A1 - Priscu, John A1 - Roberts, Mark A1 - Rosenheim, Brad E KW - AMS KW - contamination KW - LEUCINE KW - radiocarbon AB - Radiocarbon (C-14) is an isotopic tracer used to address a wide range of scientific research questions. However, contamination by elevated levels of C-14 is deleterious to natural-level laboratory workspaces and accelerator mass spectrometer facilities designed to precisely measure small amounts of C-14. The risk of contaminating materials and facilities intended for natural-level C-14 with elevated-level C-14-labeled materials has dictated near complete separation of research groups practicing profoundly different measurements. Such separation can hinder transdisciplinary research initiatives, especially in remote and isolated field locations where both natural-level and elevated-level radiocarbon applications may be useful. This paper outlines the successful collaboration between researchers making natural-level C-14 measurements and researchers using C-14-labeled materials during a subglacial drilling project in West Antarctica (SALSA 2018-2019). Our strict operating protocol allowed us to successfully carry out C-14 labeling experiments within close quarters at our remote field camp without contaminating samples of sediment and water intended for natural level C-14 measurements. Here we present our collaborative protocol for maintaining natural level C-14 cleanliness as a framework for future transdisciplinary radiocarbon collaborations. VL - 63 UR - https://www.cambridge.org/core/product/identifier/S0033822221000552/type/journal_articlehttps://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0033822221000552 IS - 5 ER - TY - JOUR T1 - Geomorphic expression and slip rate of the Fairweather fault, southeast Alaska, and evidence for predecessors of the 1958 rupture JF - Geosphere Y1 - 2021 A1 - Witter, Robert C. A1 - Bender, Adrian M. A1 - Scharer, Katherine M. A1 - DuRoss, Christopher B. A1 - Haeussler, Peter J. A1 - Lease, Richard O. AB - Active traces of the southern Fairweather fault were revealed by light detection and ranging (lidar) and show evidence for transpressional deformation between North America and the Yakutat block in southeast Alaska. We map the Holocene geomorphic expression of tectonic deformation along the southern 30 km of the Fairweather fault, which ruptured in the 1958 moment magnitude 7.8 earthquake. Digital maps of surficial geology, geomorphology, and active faults illustrate both strike-slip and dip-slip deformation styles within a 10°–30° double restraining bend where the southern Fairweather fault steps offshore to the Queen Charlotte fault. We measure offset landforms along the fault and calibrate legacy 14C data to reassess the rate of Holocene strike-slip motion (≥49 mm/yr), which corroborates published estimates that place most of the plate boundary motion on the Fairweather fault. Our slip-rate estimates allow a component of oblique-reverse motion to be accommodated by contractional structures west of the Fairweather fault consistent with geodetic block models. Stratigraphic and structural relations in hand-dug excavations across two active fault strands provide an incomplete paleoseismic record including evidence for up to six surface ruptures in the past 5600 years, and at least two to four events in the past 810 years. The incomplete record suggests an earthquake recurrence interval of ≥270 years—much longer than intervals <100 years implied by published slip rates and expected earthquake displacements. Our paleoseismic observations and map of active traces of the southern Fairweather fault illustrate the complexity of transpressional deformation and seismic potential along one of Earth's fastest strike-slip plate boundaries. VL - 17 SN - 1553-040X UR - https://doi.org/10.1130/GES02299.1 IS - 3 JO - Geosphere ER - TY - RPRT T1 - Hydrogeologic framework, geochemistry, groundwater-flow system, and aquifer hydraulic properties used in the development of a conceptual model of the Ogallala, Edwards-Trinity (High Plains), and Dockum aquifers in and near Gaines, Terry, and Yoakum Counti Y1 - 2021 A1 - Teeple, Andrew P. A1 - Ging, Patricia B. A1 - Thomas, Jonathan V. A1 - Wallace, David S. A1 - Payne, Jason D. AB - In 2014, the U.S. Geological Survey, in cooperation with Llano Estacado Underground Water Conservation District, Sandy Land Underground Water Conservation District, and South Plains Underground Water Conservation District (hereinafter referred to collectively as the “UWCDs”), began a multiphase study in and near Gaines, Terry, and Yoakum Counties, Texas, to develop a regional conceptual model of the hydrogeologic framework, geochemistry, groundwater-flow system, and hydraulic properties, primarily for the High Plains and Edwards-Trinity aquifer system and to a lesser degree for the Dockum aquifer. The High Plains aquifer system (hereinafter referred to as the “Ogallala aquifer”), contained within the Ogallala Formation in Texas, is the shallowest aquifer in the study area and is the primary source of water for agriculture and municipal supply in the areas managed by the UWCDs. Groundwater withdrawals from deeper aquifers (primarily the Edwards-Trinity [High Plains] aquifer system that is hereinafter referred to as the “Edwards-Trinity [High Plains] aquifer”) augmented by lesser amounts from the Dockum aquifer provide additional water sources in the study area. The Edwards-Trinity (High Plains) aquifer is contained within the Trinity and Fredericksburg Groups. The Dockum aquifer, a relatively minor source of water in the study area, is contained in the Dockum Group, which was evaluated as a single unit. The potential for continual declines of the groundwater in the Ogallala aquifer in the study area and the potential changes in water quality resulting from dewatering and increased vertical groundwater movement between adjacent water-bearing units have raised concerns about the amount and quality of available groundwater. The developed conceptual model helped in the understanding of the quantity and quality of the groundwater within the Ogallala, the Edwards-Trinity (High Plains), and to a lesser extent, the Dockum aquifers within the study area. The hydrogeologic framework was used to assess the vertical and lateral extents of hydrogeologic units, bed orientations, unit thicknesses, and location and orientation of paleochannels. In general, the Trinity and Fredericksburg Groups and Ogallala Formation exhibit a slight regional dip (dip angle of about 0.14 degrees) to the southeast with dip directions becoming more to the south with each successively overlying unit (105, 110, and 125 degrees for the bases of the Trinity and Fredericksburg Groups and Ogallala Formation, respectively). In general, the Trinity and Fredericksburg Groups thin to the south and are not present in the southern part of Gaines County, whereas the Ogallala Formation becomes thinner from west to east. The combined thickness of the Trinity and Fredericksburg Groups and Ogallala Formation is generally greatest in the north-central part of the study area and thinnest in the southeastern part of the study area. Paleochannel orientation varied over geologic time as formations were deposited and eroded. Water-quality samples were collected from 51 wells throughout the study area to better understand general water quality and to provide insight into groundwater-flow paths and recharge areas. Groundwater samples were spatially grouped on the basis of similarities found in the physicochemical properties, major ions, trace elements, nutrients, organic compounds, and selected stable isotopes and age tracers. Three groundwater groups were identified in the study area. The first groundwater group (Group 1), represented mostly by groundwater from the Ogallala and Edwards-Trinity (High Plains) aquifers in the northern half of the study area, is considered to be recent recharge, affected by land-use activities, as explained by the younger age, higher concentrations of nitrate plus nitrite, and more frequent detections of organic compounds. Groundwater wells in the second groundwater group (Group 2) are typically in the southwestern and northwestern parts of the study area, and the groundwater in this group is considered to be groundwater recharged during the Pleistocene period, as explained by the relatively old age of the groundwater, high strontium stable isotope ratios, and hydrogen and oxygen stable isotope ratios. The last groundwater group (Group 3) is likely a mixture of groundwater from the first or second groups (or both) with a third, highly mineralized groundwater as explained by having the highest dissolved-solids concentrations in the study area and having some similarities to geochemical characteristics of samples from the first and second groups. A groundwater-flow system analysis was done to understand the flow of groundwater throughout the aquifer system. Groundwater-level altitudes for the Ogallala, Edwards-Trinity (High Plains), and Dockum aquifers are generally higher in the northwestern part of the study area and lower in the southeastern part of the study area. Groundwater generally flows in a northwest to southeast direction across the study area in each of the aquifers. The groundwater-flow paths closely resemble the mapped paleochannels, indicating that within the study area, the groundwater flows preferentially along the paleochannels, especially within the Ogallala aquifer where dewatering of the aquifer results in a greater effect of the base structure on the flow of groundwater. The Ogallala aquifer is unsaturated in localized areas in the study area; unsaturated areas are generally near the southern extent of the Edwards-Trinity (High Plains) aquifer, with the largest unsaturated area west of Seminole, Tex. The saturated thickness of the Ogallala aquifer is thickest (more than 125 feet) southeast of Seminole and west of Brownfield, Tex., near the border between Terry and Yoakum Counties. The saturated thickness of the combined Ogallala and Edwards-Trinity (High Plains) aquifers ranges from less than 10 feet along the far southern edge of the study area to more than 350 feet north and east of Brownfield, Tex., and along the border between Terry and Yoakum Counties. The aquifer hydraulic properties, including hydraulic conductivity and specific yield, were estimated to better understand the ability of groundwater to move through the aquifer system and quantify the volume of available water in storage. The hydraulic-conductivity values varied greatly within the study area (ranging from about 0.03 to about 350 feet per day), and often large variations were found in the same area. Terry County contained the highest and lowest hydraulic conductivity values for the Ogallala aquifer, whereas Yoakum County contained the highest and lowest hydraulic conductivity values for the Edwards-Trinity (High Plains) aquifer. The highest hydraulic-conductivity values for the Dockum aquifer were in Gaines County, whereas the lowest hydraulic-conductivity values were in Terry County. The estimated specific yield values within the study area range from 0.01 to 0.36. Higher specific yield values generally occurred in the western part of the study area except in the Ogallala aquifer where higher specific yield values were in the east. The Ogallala aquifer had the lowest specific yield range and the least specific yield variability among the three aquifers, whereas the Dockum aquifer had the highest specific yield range and the greatest specific yield variability. Using the estimated saturated thickness and estimated specific yield grids, the water volumes of the Ogallala and Edwards-Trinity (High Plains) aquifers and the combined Ogallala and Edwards-Trinity (High Plains) aquifers were estimated. The available water in the Edwards-Trinity (High Plains) aquifer (16.6 million acre-feet) is almost double the available water in the Ogallala aquifer (8.8 million acre-feet). Although the Edwards-Trinity (High Plains) aquifer contains more available groundwater, pumping is more difficult because of the relatively low hydraulic conductivity and specific yield values compared to the Ogallala aquifer. Overall, the available water within the combined Ogallala and Edwards-Trinity (High Plains) aquifers is about 6.6, 10.2, and 8.6 million acre-feet for Gaines, Terry, and Yoakum Counties, respectively. JF - Scientific Investigations Report PB - U.S. Geological Survey CY - Reston, VA SN - 2021-5009 UR - http://pubs.er.usgs.gov/publication/sir20215009 ER - TY - JOUR T1 - Inverted channel variations identified on a distal portion of a bajada in the central Atacama Desert, Chile JF - Geomorphology Y1 - 2021 A1 - Williams, Rebecca M.E. A1 - Irwin, Rossman P. A1 - Noe Dobrea, Eldar Z. A1 - Howard, Alan D. A1 - Dietrich, William E. A1 - Cawley, J.C. AB - In deserts, the interplay between occasional fluvial events and persistent aeolian erosion can form composite modern and relict surfaces, especially on the distal portion of alluvial fans. There, relief inversion of alluvial deposits by differential erosion can form longitudinal ridges. We identified two distinct ridge types formed by relief inversion on converging alluvial fans in the hyperarid Chilean Atacama Desert. Although they are co-located and similar in scale, the ridge types have different ages and formation histories that apparently correspond to minor paleoclimate variations. Gravel-armored ridges are remnants of deflated alluvial deposits with a bimodal sediment distribution (gravel and sand) dated to a minor pluvial phase at the end of the Late Pleistocene (similar to 12 kyr). In contrast, younger (similar to 9 kyr) sulfate-capped ridges formed during a minor arid phase with evaporite deposition in a pre-existing channel that armored the underlying deposits. Collectively, inverted channels at Salar de Llamara resulted from multiple episodes of surface overland flow and standing water spanning several thousand years. Based on ridge relief and age, the minimum long-term deflation rate is 0.1-0.2 m/kyr, driven primarily by wind erosion. This case study is an example of the equifinality concept whereby different processes lead to similar landforms. The complex history of the two ridge types can only be generally constrained in remotely sensed data. In situ observations are required to discern the specifics of the aqueous history, including the flow type, magnitude, sequence, and paleoenvironment. These findings have relevance for interpreting similar landforms on Mars. VL - 393 UR - https://www.webofscience.com/wos/woscc/full-record/WOS:000702871000005?AlertId=4d48b20a-7d27-4fa2-a6a8-37f0daa89864&SID=5CCv4BEH6pVsodTqSwx ER - TY - JOUR T1 - Lacustrine leaf wax hydrogen isotopes indicate strong regional climate feedbacks in Beringia since the last ice age JF - Quaternary Science Reviews Y1 - 2021 A1 - Daniels, W.C. A1 - Russell, J.M. A1 - Morrill, C. A1 - Longo, W.M. A1 - Giblin, A.E. A1 - Holland-Stergar, P. A1 - Welker, J.M. A1 - Wen, X. A1 - Hu, A. A1 - Huang, Y. VL - 269 UR - https://www.webofscience.com/wos/woscc/full-record/WOS:000694971400005?AlertId=4d48b20a-7d27-4fa2-a6a8-37f0daa89864&SID=7FJ1KjxGlxJRYob6iqu ER - TY - JOUR T1 - Limited Presence of Permafrost Dissolved Organic Matter in the Kolyma River, Siberia Revealed by Ramped Oxidation JF - Journal of Geophysical Research: Biogeosciences Y1 - 2021 A1 - Rogers, Jennifer A. A1 - Galy, Valier A1 - Kellerman, Anne M. A1 - Chanton, Jeffrey P. A1 - Zimov, Nikita A1 - Spencer, Robert G. M. VL - 126 UR - https://www.webofscience.com/wos/woscc/full-record/WOS:000677821700019?AlertId=4d48b20a-7d27-4fa2-a6a8-37f0daa89864&SID=8EgwPROzuFaD4cTggN2 IS - 7 ER - TY - JOUR T1 - A maximum rupture model for the central and southern Cascadia subduction zone—reassessing ages for coastal evidence of megathrust earthquakes and tsunamis JF - Quaternary Science Reviews Y1 - 2021 A1 - Nelson, Alan R. A1 - DuRoss, Christopher B. A1 - Witter, Robert C. A1 - Kelsey, Harvey M. A1 - Engelhart, Simon E. A1 - Mahan, Shannon A. A1 - Gray, Harrison J. A1 - Hawkes, Andrea D. A1 - Horton, Benjamin P. A1 - Padgett, Jason S. AB - A new history of great earthquakes (and their tsunamis) for the central and southern Cascadia subduction zone shows more frequent (17 in the past 6700 yr) megathrust ruptures than previous coastal chronologies. The history is based on along-strike correlations of Bayesian age models derived from evaluation of 554 radiocarbon ages that date earthquake evidence at 14 coastal sites. We reconstruct a history that accounts for all dated stratigraphic evidence with the fewest possible ruptures by evaluating the sequence of age models for earthquake or tsunami contacts at each site, comparing the degree of temporal overlap of correlated site age models, considering evidence for closely spaced earthquakes at four sites, and hypothesizing only maximum-length megathrust ruptures. For the past 6700 yr, recurrence for all earthquakes is 370e420 yr. But correlations suggest that ruptures at-1.5 ka and-1.1 ka were of limited extent (<400 km). If so, post-3-ka recurrence for ruptures extending throughout central and southern Cascadia is 510e540 yr. But the range in the times between earthquakes is large: two instances may be-50 yr, whereas the longest are-550 and-850 yr. The closely spaced ruptures about 1.6 ka may illustrate a pattern common at subduction zones of a long gap ending with a great earthquake rupturing much of the subduction zone, shortly followed by a rupture of more limited extent. The ruptures of limited extent support the continued inclusion of magnitude-8 earthquakes, with longer ruptures near magnitude 9, in assessments of seismic hazard in the region. VL - 261 UR - https://apps.webofknowledge.com/InboundService.do?product=WOS&Func=Frame&DestFail=http%3A%2F%2Fwww.webofknowledge.com&SrcApp=search&SrcAuth=Alerting&SID=6DMZZppDlBSzMpeHDG2&customersID=Alerting&mode=FullRecord&IsProductCode=Yes&AlertId=4d48b20a-7d27-4fa2- ER - TY - JOUR T1 - Molluscan aminostratigraphy of the US Mid-Atlantic Quaternary coastal system: Implications for onshore-offshore correlation, paleochannel and barrier island evolution, and local late Quaternary sea-level history JF - Quaternary Geochronology Y1 - 2021 A1 - Wehmiller, John F. A1 - Brothers, Laura L. A1 - Ramsey, Kelvin W. A1 - Foster, David S. A1 - Mattheus, C.R. A1 - Hein, Christopher J. A1 - Shawler, Justin L. AB - The Quaternary record of the US Mid-Atlantic coastal system includes onshore emergent late Pleistocene shoreline deposits, offshore inner shelf and barrier island units, and paleovalleys formed during multiple glacial stage sea-level lowstands. The geochronology of this coastal system is based on uranium series, radiocarbon, amino acid racemization (AAR), and optically stimulated luminescence (OSL) methods. We report over 600 mollusk AAR results from 93 sites between northeastern North Carolina and the central New Jersey shelf, representing samples from both onshore cores or outcrops, sub-barrier and offshore cores, and transported shells from barrier island beaches. AAR age estimates are constrained by paired C-14 analyses on specific shells and associated U-series coral ages from onshore sites. AAR data from offshore cores are interpreted in the context of detailed seismic stratigraphy. The distribution of Pleistocene-age shells on the island beaches is linked to the distribution of inner shelf or sub-barrier source units. Age mixing over a range of time-scales (similar to 1 ka to similar to 100 ka) is identified by AAR results from onshore, beach, and shelf collections, often contributing insights into the processes forming individual barrier islands. The regional aminostratigraphic framework identifies a widespread late Pleistocene (Marine Isotope Stage 5) aminozone, with isolated records of middle and early Pleistocene deposition. AAR results provide age estimates for the timing of formation of the three major paleochannels that underlie the Delmarva Peninsula: Persimmon Point paleochannel >= 800 ka; Exmore paleochannel similar to 400-500 ka (MIS 12); and Eastville paleochannel > 125 ka (MIS 6). The results demonstrate the value of synthesizing abundant AAR chronologic data across various coastal environments, integrating multiple distinct geologic studies. The ages and elevations of the Quaternary units are important for current hypotheses about relative sea level history and crustal dynamics in the region, which was likely influenced by the Laurentide ice sheet, the margin just similar to 400 km to the north. VL - 66 UR - https://www.webofscience.com/wos/woscc/full-record/WOS:000696783400001?AlertId=4d48b20a-7d27-4fa2-a6a8-37f0daa89864&SID=6CdHvzZQLddFkxmd4Jp ER - TY - JOUR T1 - A NEW RAMPED PYROXIDATION/COMBUSTION FACILITY AT 14 CHRONO, BELFAST: SETUP DESCRIPTION AND INITIAL RESULTS JF - Radiocarbon Y1 - 2021 A1 - Keaveney, Evelyn M A1 - Barrett, Gerard T A1 - Allen, Kerry A1 - Reimer, Paula J UR - https://www.cambridge.org/core/product/identifier/S0033822221000461/type/journal_articlehttps://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0033822221000461 ER - TY - JOUR T1 - Permafrost Organic Carbon Turnover and Export Into a High‐Arctic Fjord: A Case Study From Svalbard Using Compound‐specific C-14 Analysis JF - Journal of Geophysical Research: Biogeosciences Y1 - 2021 A1 - Kusch, Stephanie A1 - Rethemeyer, Janet A1 - Ransby, Daniela A1 - Mollenhauer, Gesine VL - 126 UR - https://apps.webofknowledge.com/InboundService.do?product=WOS&Func=Frame&DestFail=http%3A%2F%2Fwww.webofknowledge.com&SrcApp=search&SrcAuth=Alerting&SID=8FcXJjl9GsiAmhuIO65&customersID=Alerting&mode=FullRecord&IsProductCode=Yes&AlertId=ab9062f8-b111-4f95- IS - 3 ER - TY - JOUR T1 - Planktic foraminiferal changes in the western Mediterranean Anthropocene JF - Global and Planetary Change Y1 - 2021 A1 - Pallacks, Sven A1 - Ziveri, Patrizia A1 - Martrat, Belén A1 - Mortyn, P. Graham A1 - Grelaud, Michael A1 - Schiebel, Ralf A1 - Incarbona, Alessandro A1 - Garcia-Orellana, Jordi A1 - Anglada-Ortiz, Griselda VL - 204 UR - https://www.webofscience.com/wos/woscc/full-record/WOS:000687257000005?AlertId=ab9062f8-b111-4f95-a2b8-66e7afac0471&SID=7DFRqn1B6A3SRDPNEE8 ER - TY - JOUR T1 - Plastic Formulation is an Emerging Control of Its Photochemical Fate in the Ocean JF - Environmental Science & Technology Y1 - 2021 A1 - Walsh, Anna N. A1 - Reddy, Christopher M. A1 - Niles, Sydney F. A1 - McKenna, Amy M. A1 - Hansel, Colleen M. A1 - Ward, Collin P. AB - Sunlight exposure is a control of long-term plastic fate in the environment that converts plastic into oxygenated products spanning the polymer, dissolved, and gas phases. However, our understanding of how plastic formulation influences the amount and composition of these photoproducts remains incomplete. Here, we characterized the initial formulations and resulting dissolved photoproducts of four single-use consumer polyethylene (PE) bags from major retailers and one pure PE film. Consumer PE bags contained 15–36% inorganic additives, primarily calcium carbonate (13–34%) and titanium dioxide (TiO2; 1–2%). Sunlight exposure consistently increased production of dissolved organic carbon (DOC) relative to leaching in the dark (3- to 80-fold). All consumer PE bags produced more DOC during sunlight exposure than the pure PE (1.2- to 2.0-fold). The DOC leached after sunlight exposure increasingly reflected the 13C and 14C isotopic composition of the plastic. Ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry revealed that sunlight exposure substantially increased the number of DOC formulas detected (1.1- to 50-fold). TiO2-containing bags photochemically degraded into the most compositionally similar DOC, with 68–94% of photoproduced formulas in common with at least one other TiO2-containing bag. Conversely, only 28% of photoproduced formulas from the pure PE were detected in photoproduced DOC from the consumer PE. Overall, these findings suggest that plastic formulation, especially TiO2, plays a determining role in the amount and composition of DOC generated by sunlight. Consequently, studies on pure, unweathered polymers may not accurately represent the fates and impacts of the plastics entering the ocean. VL - 55 SN - 0013-936X UR - https://doi.org/10.1021/acs.est.1c02272 IS - 18 JO - Environ. Sci. Technol. ER - TY - JOUR T1 - The Preservation of Climate‐Driven Landslide Dams in Western Oregon JF - Journal of Geophysical Research: Earth Surface Y1 - 2021 A1 - Struble, William T. A1 - Roering, Joshua J. A1 - Burns, William J. A1 - Calhoun, Nancy C. A1 - Wetherell, Logan R. A1 - Black, Bryan A. AB - Bedrock landsliding, including the formation of landslide dams, is a predominant geomorphic process in steep landscapes. Clarifying the importance of hydrologic and seismic mechanisms for triggering deep-seated landslides remains an ongoing effort, and formulation of geomorphic metrics that predict dam preservation is crucial for quantifying secondary landslide hazards. Here, we identify >200 landslide-dammed lakes in western Oregon and utilize dendrochronology and enhanced C-14 dating ("wiggle matching") of "ghost forests" to establish slope failure timing at 20 sites. Our dated landslide dataset reveals bedrock landsliding has been common since the last Cascadia Subduction Zone earthquake in January 1700 AD. Our study does not reveal landslides that date to 1700 AD. Rather, we observe temporal clustering of at least four landslides in the winter of 1889/1890 AD, coincident with a series of atmospheric rivers that generated one of the largest regionally recorded floods. We use topographic and field analyses to assess the relation between dam preservation and topographic characteristics of the impounded valleys. In contrast to previous studies, we do not observe systematic scaling between dam size and upstream drainage area, though dam stability indices for our sites correspond with "stable" dams elsewhere. Notably, we observe that dams are preferentially preserved at drainage areas of similar to 1.5 to 13 km(2) and valley widths of similar to 25 to 80 m, which may reflect the reduced downstream influence of debris flows and the accumulation of mature conifer trees upstream from landslide-dammed lake outlets. We suggest that wood accumulation upstream of landslide dams tempers large stream discharges, thus inhibiting dam incision. VL - 126 UR - https://apps.webofknowledge.com/InboundService.do?product=WOS&Func=Frame&DestFail=http%3A%2F%2Fwww.webofknowledge.com&SrcApp=search&SrcAuth=Alerting&SID=8CKLYC3GhfgHnhOJ3m1&customersID=Alerting&mode=FullRecord&IsProductCode=Yes&AlertId=4d48b20a-7d27-4fa2- IS - 4 ER - TY - DATA T1 - Radiocarbon dates, charcoal, and polycyclic aromatic hydrocarbon (PAH) data from Great Dismal Swamp Sites GDS-519 and GDS-520 Y1 - 2021 A1 - Willard, Debra A A1 - Jones, Miriam C A1 - Vachula, Richard S A1 - Balascio, Nicholas L A1 - Canuel, Elizabeth A KW - Climatology AB - Sediment cores were collected in Great Dismal Swamp National Wildlife Refuge in November, 2017 to advance understanding of climate- and land-management driven changes in vegetation, hydrology, and fire regimes. Radiocarbon dates were obtained from samples in two cores (GDS-519-3-21-2017 and GDS-520-3-21-2017) to generate age models for the cores. Bulk sediment samples, charcoal, plant macrofossils, and pollen residue were selected at the USGS in Reston, Virginia and submitted to Beta Analytic, Inc. and the National Ocean Sciences Accelerator Mass Spectrometry (NOSAMS) laboratories for radiocarbon dating. Those laboratories provided both radiocarbon ages and stable carbon isotope (delta 13C) results, which can be used to generate calibrated ages. Bulk density was measured for each core at the USGS in Reston, Virginia. Cores were sectioned at 1-cm increments. One cubic centimeter of wet sediment was extracted from each 1-cm increment downcore and weighed. Samples were subsequently dried at 100 degrees C for at least 24 hours to obtain dry weights, and bulk density was calculated by dividing original 1-cc volume by the dry weight. Polycyclic aromatic hydrocarbons (PAHs) and sedimentary charcoal were analyzed at the Virginia Institute of Marine Science at Gloucester Point, Virginia. PAH analysis began with freeze-drying of samples and extraction of their lipid contents using a Dionex 350 Accelerated Solvent Extractor (9:1; dicholoromethane:methanol). Total lipid extracts were separated into three fractions using silica gel columns and eluents of increasing polarity (F1: hexane, F2: 25% toluene in hexane, F3: methanol). Combined F1 and F2 fractions were analyzed to quantify PAHs using an Agilent 7890A gas chromatograph coupled with a 5975C mass selective detector (GC-MSD). The GC was equipped with a DB-5MS capillary column (30 m length; 320 micrometres outer diameter; 0.25 micrometres film thickness), which was heated using the following temperature program: 16 degrees C/minute to 150 degrees C and 5 degrees C/minute to 300 degrees C. Flow rate was 1.1 mL/minute. Individual PAH abundances were quantified using select ion monitoring mode (SIM) and relative to an external calibration curve constructed with a PAH calibration standard (Sigma-Aldrich CRM47940). Sixteen PAHs were quantified: naphthalene (Na), acenaphthylene (Ayl), acenaphthene (Ace), anthracene (An), phenanthrene (Phe), fluoranthene (Fla), pyrene (Py), benz[a]anthracene (Ba), chrysene (Ch), retene (Ret), benzo[k]fluoranthene (BkF), benzo[a]pyrene (BaP), benzo[b]fluoranthene (BbF), benzo[g,h,i]perylene (Bghi), dibenzo[a,h]anthracene (DiAn), and ideno[1,2,3-cd]pyrene (IP). PAH accumulation rates were quantified using the dry sediment concentration of PAHs and the age-depth model of the sediment cores. Sedimentary charcoal analysis followed a modified version of standard methodologies for isolating and identifying sedimentary charcoal particles. Dried sediment samples were weighed and then subjected to a light chemical treatment (1:1, by volume mixture of 1M sodium hexametaphosphate solution and 2% sodium hypochlorite solution) for 24 hours, in accordance with standard methods (Vachula et al., 2019, 2018). Samples were washed over two nested sieves (63 micrometre and 125 micrometre mesh sizes) to isolate an intermediate size fraction (63-125 micrometres), in which charcoal particles were enumerated using a dissection microscope and gridded petri dishes. Charcoal accumulation rates were quantified using the numeric concentration of charcoal particles, the bulk density of the sediments, and the age-depth model of the sediment cores. References Vachula, R.S., Russell, J.M., Huang, Y. and Richter, N., 2018. Assessing the spatial fidelity of sedimentary charcoal size fractions as fire history proxies with a high-resolution sediment record and historical data. Palaeogeography, Palaeoclimatology, Palaeoecology, 508, pp.166-175. Vachula, R.S., Russell, J.M. and Huang, Y., 2019. Climate exceeded human management as the dominant control of fire at the regional scale in California's Sierra Nevada. Environmental Research Letters, 14(10), p.104011. PB - U.S. Geological Survey UR - https://www.sciencebase.gov/catalog/item/614215cad34e0df5fb947f74 ER - TY - JOUR T1 - RADIOCARBON IN DISSOLVED ORGANIC CARBON BY UV OXIDATION: PROCEDURES AND BLANK CHARACTERIZATION AT NOSAMSABSTRACT JF - Radiocarbon Y1 - 2021 A1 - Xu, Li A1 - Roberts, Mark L A1 - Elder, Kathryn L A1 - Kurz, Mark D A1 - McNichol, Ann P A1 - Reddy, Christopher M A1 - Ward, Collin P A1 - Hanke, Ulrich M KW - blank KW - dissolved organic carbon KW - radiocarbon KW - UV oxidation AB - This study describes a procedural blank assessment of the ultraviolet photochemical oxidation (UV oxidation) method that is used to measure carbon isotopes of dissolved organic carbon (DOC) at the National Ocean Sciences Accelerator Mass Spectrometry Facility (NOSAMS). A retrospective compilation of Fm and δ 13 C results for secondary standards (OX-II, glycine) between 2009 and 2018 indicated that a revised blank correction was required to bring results in line with accepted values. The application of a best-fit mass-balance correction yielded a procedural blank of 22.0 ± 6.0 μg C with Fm of 0.30 ± 0.20 and δ 13 C of-32.0 ± 3.0‰ for this period, which was notably higher and more variable than previously reported. Changes to the procedure, specifically elimination of higher organic carbon reagents and improved sample and reactor handling, reduced the blank to 11.0 ± 2.75 μg C, with Fm of 0.14 ± 0.10 and δ 13 C of-31.0 ± 5.5‰. A thorough determination of the entire sample processing blank is required to ensure accurate isotopic compositions of seawater DOC using the UV oxidation method. Additional efforts are needed to further reduce the procedural blank so that smaller DOC samples can be analyzed, and to increase sample throughput. VL - 63 UR - https://www.cambridge.org/core/journals/radiocarbon/article/abs/radiocarbon-in-dissolved-organic-carbon-by-uv-oxidation-procedures-and-blank-characterization-at-nosams/AA39A2C74772934B44D9BF81C2DF723C IS - 1 ER - TY - JOUR T1 - Revisiting the marine reservoir age in Baja California continental margin sediments using 14C and 210Pb dating JF - Quaternary Geochronology Y1 - 2021 A1 - Treinen-Crespo, Christina A1 - Barbara, Loïc A1 - Villaescusa, Julio A. A1 - Schmidt, Sabine A1 - Pearson, Ann A1 - Carriquiry, José D. AB - Knowledge of the Marine Reservoir Effect (MRE) correction is fundamental in palaeoceanographic research to establish an accurate age-depth model for marine sedimentary records. However, during the last decades different MRE corrections have been applied in inconsistent ways for the same locality and same sediment cores, at Soledad Basin, Baja California, Mexico, creating confusion about the proper correction value of the marine reservoir effect (Delta R) to be applied. In contrast with the empirical approach previously used for assessing the Delta R value in Soledad Basin, in this study we applied an analytical approach based on the concurrent application of AMS-14C and 210Pbxs dating techniques made on sedimentary total organic carbon and foraminifera to determine new regional Delta R values from newly collected sediment cores from this site. Our results from Soledad Basin show a Delta R of 206 +/- 32 years for foraminifera and 706 +/- 42 years for organic carbon. Modeled ages using these results, and compared with those previously applied for the basin, highlight the relevance of the correct use of the local reservoir age as it can generate an offset of approximately 150 years if the other published Delta R were used. These differences can shift core chronologies by several decades and thus yield significant errors in palaeoceanographic reconstructions, which will be important to remedy in future work. VL - 66 UR - https://www.webofscience.com/wos/woscc/full-record/WOS:000696783400003?AlertId=4d48b20a-7d27-4fa2-a6a8-37f0daa89864&SID=6CdHvzZQLddFkxmd4Jp ER - TY - JOUR T1 - Soil Organic Carbon Development and Turnover in Natural and Disturbed Salt Marsh Environments JF - Geophysical Research Letters Y1 - 2021 A1 - Luk, Sheron Y. A1 - Todd‐Brown, Katherine A1 - Eagle, Meagan A1 - McNichol, Ann P. A1 - Sanderman, Jonathan A1 - Gosselin, Kelsey A1 - Spivak, Amanda C. AB - Salt marsh survival with sea-level rise (SLR) increasingly relies on soil organic carbon (SOC) accumulation and preservation. Using a novel combination of geochemical approaches, we characterized fine SOC (≤1 mm) supporting marsh elevation maintenance. Overlaying thermal reactivity, source (δ13C), and age (F14C) information demonstrates several processes contributing to soil development: marsh grass production, redeposition of eroded material, and microbial reworking. Redeposition of old carbon, likely from creekbanks, represented ∼9%–17% of shallow SOC (≤26 cm). Soils stored marsh grass-derived compounds with a range of reactivities that were reworked over centuries-to-millennia. Decomposition decreases SOC thermal reactivity throughout the soil column while the decades-long disturbance of ponding accelerated this shift in surface horizons. Empirically derived estimates of SOC turnover based on geochemical composition spanned a wide range (640–9,951 years) and have the potential to inform predictions of marsh ecosystem evolution. VL - 48 UR - https://onlinelibrary.wiley.com/doi/10.1029/2020GL090287 IS - 2 ER - TY - JOUR T1 - Towards a precise timing of groundwater use in the lower Yellow River area during the late Bronze age: Bayesian inference from the radiocarbon ages of ancient water wells at the Liang'ercun site, north China JF - Quaternary Geochronology Y1 - 2021 A1 - Yu, Shi-Yong A1 - Chen, Xuexiang A1 - Fang, Zhen A1 - Liu, Xiuling A1 - Li, Ming A1 - Guo, Junfeng KW - Geography KW - Multidisciplinary KW - Physical Geosciences VL - 66 UR - https://www.webofscience.com/wos/woscc/full-record/WOS:000684185400002?AlertId=4d48b20a-7d27-4fa2-a6a8-37f0daa89864&SID=D6BWyCypH7Akklkv5hy ER - TY - JOUR T1 - The triple argon isotope composition of groundwater on ten-thousand-year timescales JF - Chemical Geology Y1 - 2021 A1 - Seltzer, Alan M. A1 - Krantz, John A. A1 - Ng, Jessica A1 - Danskin, Wesley R. A1 - Bekaert, David V. A1 - Barry, Peter H. A1 - Kimbrough, David L. A1 - Kulongoski, Justin T. A1 - Severinghaus, Jeffrey P. KW - groundwater KW - Groundwater dating KW - Isotope geochemistry KW - Noble gas AB - Understanding the age and movement of groundwater is important for predicting the vulnerability of wells to contamination, constraining flow models that inform sustainable groundwater management, and interpreting geochemical signals that reflect past climate. Due to both the ubiquity of groundwater with order ten-thousand-year residence times and its importance for climate reconstruction of the last glacial period, there is a strong need for improving geochemical dating tools on this timescale. Whereas 14C of dissolved inorganic carbon and dissolved 4He are common age tracers for Late Pleistocene groundwater, each is limited by systematic uncertainties related to aquifer composition and lithology, and the extent of water-rock interaction. In principle, radiogenic 40Ar in groundwater acquired from decay of 40K in aquifer minerals should be insensitive to some processes that impact 14C and 4He and thus represent a useful, complementary age tracer. In practice, however, detection of significant radiogenic 40Ar signals in groundwater has been limited to a small number of studies of extremely old groundwater (>100 ka). Here we present the first high-precision (<1‰) measurements of triple Ar isotopes (40Ar, 38Ar, 36Ar) in groundwater. We introduce a model that distinguishes radiogenic 40Ar from atmospheric 40Ar by using the non-radiogenic Ar isotopes (36Ar, 38Ar) to correct for mass-dependent fractionation. Using this model, we investigate variability in radiogenic 40Ar excess (Δ40Ar) across 58 groundwater samples collected from 36 wells throughout California (USA). We find that Δ40Ar ranges from ~0‰ (the expected minimum value) to +4.2‰ across three study areas near Fresno, San Diego, and the western Mojave Desert. Based on measurements from a network of 23 scientific monitoring wells in San Diego, we find evidence for a strong dependence of Δ40Ar on aquifer lithology. We suggest that Δ40Ar is fundamentally controlled by the weathering of old K-bearing minerals and thus reflects both the degree of groundwater-rock interaction, which is related to groundwater age, and the integrated flow through different geological formations. Future studies of Late Pleistocene groundwater may benefit from high-precision triple Ar isotope measurements as a new tool to better interpret 14C- and 4He-based constraints on groundwater age and flow. VL - 583 SN - 0009-2541 UR - https://www.sciencedirect.com/science/article/pii/S0009254121004010 JO - Chemical Geology ER - TY - JOUR T1 - Using Radiocarbon to Assess the Abundance, Distribution, and Nature of Labile Organic Carbon in Marine Sediments JF - Global Biogeochemical Cycles Y1 - 2021 A1 - DeMaster, D. J. A1 - Taylor, R. S. A1 - Smith, C. R. A1 - Isla, E. A1 - Thomas, C. J. AB - Positive C-14 gradients have recently been observed within the surface mixed layer of several continental-margin sediments. The best explanation for these positive C-14 gradients is the occurrence and rapid degradation of labile organic carbon (LOC) in the upper 5-10 cm of the seabed. Based on a two-component model for sedimentary organic matter (i.e., a planktonic labile component and an older refractory component), bulk (14)Corg data were used to determine the abundances of LOC within the surface mixed layers of three cores from the West Antarctic Peninsula (WAP) shelf and one core from San Clemente Basin (California Borderland). LOC contents in surface samples from the four stations varied from 0.5 to 1.1 mg/cm(3), comprising 20% (San Clemente Basin) to 80% (WAP, Sta. G) of the total organic carbon. By incorporating a steady state diagenetic model and particle-mixing bioturbation coefficients, the LOC profiles were used to determine LOC turnover times (LOC tau) and LOC e-folding depths. The LOC tau values for the West Antarctic Peninsula sediments varied from 0.09 to 0.59 years, whereas the LOC tau value from the San Clemente Basin core was 63 years. The LOC e-folding depths for the WAP stations varied from 0.8 to 3.4 cm, in contrast to the LOC e-folding depth in San Clemente Basin, which was 4.0 cm. LOC characteristics from the four cores examined in this study were compared to LOC data in the literature as a means of substantiating the overall C-14(org)-based approach and justifying model assumptions. VL - 35 UR - https://onlinelibrary.wiley.com/doi/10.1029/2020GB006676https://onlinelibrary.wiley.com/doi/pdf/10.1029/2020GB006676https://onlinelibrary.wiley.com/doi/pdf/10.1029/2020GB006676https://onlinelibrary.wiley.com/doi/full-xml/10.1029/2020GB006676 IS - 6 ER - TY - JOUR T1 - The Zealandia Switch: Ice age climate shifts viewed from Southern Hemisphere moraines JF - Quaternary Science Reviews Y1 - 2021 A1 - Denton, George H. A1 - Putnam, Aaron E. A1 - Russell, Joellen L. A1 - Barrell, David J. A. A1 - Schaefer, Joerg M. A1 - Kaplan, Michael R. A1 - Strand, Peter D. KW - Climate dynamics KW - Climate modeling KW - Cosmogenic isotopes KW - Geomorphology KW - Glacial KW - Glaciation KW - paleoclimatology KW - Quaternary KW - South Pacific Ocean KW - Southern Hemisphere westerlies KW - Southern Ocean AB - Two fundamental questions about the ice-age climate system await satisfactory resolution. First, if summer solar radiation intensity truly controls the orbital signature of the last glacial cycle, then why were major climatic shifts, including the last termination, globally synchronous? Second, what caused the millennial-scale climate oscillations superimposed on this cycle? We address these questions from a Southern Hemisphere perspective focused on mid-latitude mountain ice fields. We put particular emphasis on the last glacial termination, which involved both orbital-scale and millennial-scale climate elements and has generally well-resolved chronological control. Sustained retreat of mountain glaciers, documented by detailed mapping and chronology of glacial landforms in the Southern Alps and southern Andes, marked the termination of the last ice age, beginning ∼18 kyrs ago and involved a change from glacial to near-interglacial atmospheric temperature within a millennium or two. A rapid poleward shift of the Subtropical Front, delineating the northern margin of the Southern Ocean, ∼18 kyrs ago implies a concurrent poleward shift of the austral westerlies and leads us to hypothesize a southern origin for the dominant phase of the last glacial termination. Together with interhemispheric paleoclimate records and with results of coupled ocean-atmosphere climate modeling, these findings suggest a big, fast, and global end to the last ice age in which a southern-sourced warming episode linked the hemispheres. We posit that a shift in the Southern Ocean circulation and austral westerly wind system, tied to southern orbital forcing, caused this global warming episode by affecting the tropical heat engine and hence global climate. Central to this hypothesis, dubbed the ‘Zealandia Switch’, is the location of the Australia and Zealandia continents relative to Southern Hemisphere oceanic and atmospheric circulation. Coupled ocean-atmosphere climate modeling shows that the locus of the austral westerlies, whether in a more equatorward position representing a glacial-mode climate or in a poleward-shifted position marking interglacial-mode climate, has profound effects on oceanic and associated atmospheric linkages between the tropical Pacific and the Southern Ocean. Shifts in the austral westerlies have global climatic consequences, especially through resulting changes in the greenhouse gas content of the atmosphere and altered heat flux from the tropical Pacific into the Northern and Southern Hemispheres. We suggest that the last glacial termination was a global warming episode that led to extreme seasonality in northern latitudes by stimulating a flush of meltwater and icebergs into the North Atlantic from adjoining ice sheets. This fresh-water influx resulted in widespread North Atlantic sea ice that caused very cold boreal winters, thus amplifying the annual southward shift of the Intertropical Convergence Zone and the monsoonal rain belts. We further suggest that muted manifestations of the Zealandia Switch mechanism were responsible for smaller, recurring millennial-scale climate oscillations within the last glacial cycle. VL - 257 UR - https://www.sciencedirect.com/science/article/pii/S0277379120307332 ER - TY - JOUR T1 - An abrupt cooling event recorded around 73 kyr in western South Atlantic JF - Quaternary International Y1 - 2020 A1 - Camillo, Edmundo A1 - Quadros, Juliana P. A1 - Santarosa, Ana Cláudia A. A1 - Costa, Karen B. A1 - Toledo, Felipe A.L. KW - Artificial neural network KW - C. pelagicus KW - G. inflata N. incompta KW - Oxygen isotope record KW - planktonic foraminifera KW - Toba volcano AB - This paper presents the record of sea surface temperature and planktonic foraminifera cold species for the last 130 kyr of a deep sea marine piston core (GL-854) from western South Atlantic. Our data shows a prominent and consistent feature around 73 kyr when an abrupt drop in sea surface temperature, both artificial neural network and oxygen isotope-based, was recorded. Additionally, our oxygen isotope curve presents a positive excursion and two cold-water planktonic foraminifera (Globoconella inflata and Neogloboquadrina incompta) remarkably increased their abundances. The benthic oxygen isotope record did not indicate any change while planktonic indicators were intensely disturbed. This cooling episode should be explained by a strong and abrupt mechanism able to promptly affect the surface ocean but not the deep ocean. It seems to be one of the coldest intervals during the last 130 kyr. Here, we discuss some hypothesis for this abrupt cooling recorded in the South Atlantic, including the speculative climatic impact of Toba super-eruption. VL - 542 UR - https://www.sciencedirect.com/science/article/pii/S1040618220300902 ER - TY - JOUR T1 - Age validation of yellowfin (Thunnus albacares) and bigeye (Thunnus obesus) tuna of the northwestern Atlantic Ocean JF - Canadian Journal of Fisheries and Aquatic Sciences Y1 - 2020 A1 - Andrews, Allen H. A1 - Pacicco, Ashley A1 - Allman, Robert A1 - Falterman, Brett J. A1 - Lang, Erik T. A1 - Golet, Walter AB - The age and growth of yellowfin (Thunnus albacares) and bigeye (T. obesus) tuna remain problematic because validation of growth zone deposition (opaque and transparent) hasn't been properly evaluated. Otolith growth structure (zone clarity) can be poorly defined for tropical tunas but the use of bomb radiocarbon dating has validated age estimates to 16–18 years for yellowfin and bigeye tuna. Use of the radiocarbon decline period — defined by regional coral and otoliths — provided valid ages through ontogeny. Yellowfin tuna aged 2–18 years (n = 34, 1029–1810 mm FL) and bigeye tuna aged 3–17 years (n = 12, 1280–1750 mm FL) led to birthyears that were coincident with the bomb radiocarbon decline. The results indicate there was no age reading bias for yellowfin tuna and that age estimates of previous studies were likely underestimated for both species. VL - 77 UR - https://www.nrcresearchpress.com/doi/full/10.1139/cjfas-2019-0328 IS - 4 ER - TY - JOUR T1 - Aquifer-Scale Observations of Iron Redox Transformations in Arsenic-Impacted Environments to Predict Future Contamination JF - Environmental Science & Technology Letters Y1 - 2020 A1 - Nghiem, Athena A. A1 - Shen, Yating A1 - Stahl, Mason A1 - Sun, Jing A1 - Haque, Ezazul A1 - DeYoung, Beck A1 - Nguyen, Khue N. A1 - Thi Mai, Tran A1 - Trang, Pham Thi Kim A1 - Pham, Hung Viet A1 - Mailloux, Brian A1 - Harvey, Charles F. A1 - van Geen, Alexander A1 - Bostick, Benjamín C. KW - BANGLADESH KW - BENGAL BASIN KW - groundwater KW - PLEISTOCENE AQUIFER KW - POLLUTION KW - RELEASE KW - RIVER DELTA KW - Sediment KW - TRANSPORT KW - VIETNAM AB - Iron oxides control the mobility of a host of contaminants in aquifer systems, and the microbial reduction of iron oxides in the subsurface is linked to high levels of arsenic in groundwater that affects greater than 150 million people globally. Paired observations of groundwater and solid-phase aquifer composition are critical to understand spatial and temporal trends in contamination and effectively manage changing water resources, yet field-representative mineralogical data are sparse across redox gradients relevant to arsenic contamination. We characterize iron mineralogy using X-ray absorption spectroscopy across a natural gradient of groundwater arsenic contamination in Vietnam. Hierarchical cluster analysis classifies sediments into meaningful groups delineating weathering and redox changes, diagnostic of depositional history, in this first direct characterization of redox transformations in the field. Notably, these groupings reveal a signature of iron minerals undergoing active reduction before the onset of arsenic contamination in groundwater. Pleistocene sediments undergoing postdepositional reduction may be more extensive than previously recognized due to previous misclassification. By upscaling to similar environments in South and Southeast Asia via multinomial logistic regression modeling, we show that active iron reduction, and therefore susceptibility to future arsenic contamination, is more widely distributed in presumably pristine aquifers than anticipated. VL - 7 UR - https://apps.webofknowledge.com/InboundService.do?product=WOS&Func=Frame&DestFail=http%3A%2F%2Fwww.webofknowledge.com&SrcApp=search&SrcAuth=Alerting&SID=8AkJOJLKFU3j5nkGaRI&customersID=Alerting&mode=FullRecord&IsProductCode=Yes&AlertId=4d48b20a-7d27-4fa2- IS - 12 ER - TY - JOUR T1 - Arctic amplification of global warming strengthened by sunlight oxidation of permafrost carbon to CO2 JF - Geophysical Research Letters Y1 - 2020 A1 - Bowen, J. C. A1 - Ward, C. P. A1 - Kling, G. W. A1 - Cory, R. M. AB - Once thawed, up to 15% of the ∼1,000 Pg of organic carbon (C) in arctic permafrost soils may be oxidized to carbon dioxide (CO2) by 2100, amplifying climate change. However, predictions of this amplification strength ignore the oxidation of permafrost C to CO2 in surface waters (photomineralization). We characterized the wavelength dependence of permafrost dissolved organic carbon (DOC) photomineralization and demonstrate that iron catalyzes photomineralization of old DOC (4,000-6,300 a BP) derived from soil lignin and tannin. Rates of CO2 production from photomineralization of permafrost DOC are two-fold higher than for modern DOC. Given that model predictions of future net loss of ecosystem C from thawing permafrost do not include the loss of CO2 to the atmosphere from DOC photomineralization, current predictions of an average of 208 Pg C loss by 2299 may be too low by ~14%. UR - https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2020GL087085 ER - TY - JOUR T1 - Arsenic contamination of Bangladesh aquifers exacerbated by clay layers JF - Nature Communications Y1 - 2020 A1 - Mihajlov, Ivan A1 - Mozumder, M. Rajib H. A1 - Bostick, Benjamín C. A1 - Stute, Martin A1 - Mailloux, Brian J. A1 - Knappett, Peter S. K. A1 - Choudhury, Imtiaz A1 - Ahmed, Kazi Matin A1 - Schlosser, Peter A1 - van Geen, Alexander AB - Confining clay layers typically protect groundwater aquifers against downward intrusion of contaminants. In the context of groundwater arsenic in Bangladesh, we challenge this notion here by showing that organic carbon drawn from a clay layer into a low-arsenic pre-Holocene (>12 kyr-old) aquifer promotes the reductive dissolution of iron oxides and the release of arsenic. The finding explains a steady rise in arsenic concentrations in a pre-Holocene aquifer below such a clay layer and the repeated failure of a structurally sound community well. Tritium measurements indicate that groundwater from the affected depth interval (40–50 m) was recharged >60 years ago. Deeper (55–65 m) groundwater in the same pre-Holocene aquifer was recharged only 10–50 years ago but is still low in arsenic. Proximity to a confining clay layer that expels organic carbon as an indirect response to groundwater pumping, rather than directly accelerated recharge, caused arsenic contamination of this pre-Holocene aquifer. VL - 11 UR - https://www.nature.com/articles/s41467-020-16104-z IS - 1 ER - TY - JOUR T1 - Asian summer monsoon influence on chemical weathering and sediment provenance determined by clay mineral analysis from the Indus Submarine Canyon JF - Quaternary Research Y1 - 2020 A1 - Li, Yuting A1 - Clift, Peter D. A1 - Murray, Richard W. A1 - Exnicios, Elise A1 - Ireland, Thomas A1 - Böning, Philipp KW - Clay minerals KW - Holocene KW - monsoon KW - Provenance KW - Reworking KW - Submarine canyon AB - Clay minerals from the Indus Canyon and eastern clinoform since ~12 ka are uniformly rich in smectite and illite, similar to those from the Holocene Indus flood plains. A systematic enrichment of smectite in the proximal delta compared to the canyon and eastern clinoform argues for preferential capture of smectite close to the river mouth since ~12 ka. There is a rapid shift to a more smectite-rich assemblage in the canyon and eastern clinoform after ~5 ka. This change is probably caused by a change in sediment source, with less direct flux from the Himalaya and more erosion of older, weathered, smectite-rich sediment from the Indus River flood plains, driven by incision of the Indus and its tributaries into the floodplain as summer monsoon rains weakened. This influx of smectite is consistent with lower kaolinite/smectite values since ~5 ka. The onset of large-scale agricultural activities since ~5 ka, especially starting with the Harappan Civilization, may also have enhanced incision and erosion of floodplain sediments over the same time period. This study reports for the first time how monsoon strength variations since ~12 ka affected the clay mineral assemblages and sediment provenance in a major submarine canyon. VL - 93 UR - https://www.cambridge.org/core/journals/quaternary-research/article/asian-summer-monsoon-influence-on-chemical-weathering-and-sediment-provenance-determined-by-clay-mineral-analysis-from-the-indus-submarine-canyon/AA11F458BD5924C1BD9EC9901D1F2941 ER - TY - JOUR T1 - Biomass-Derived Provenance Dominates Glacial Surface Organic Carbon in the Western HimalayaBiomass-Derived Provenance Dominates Glacial Surface Organic Carbon in the Western Himalaya JF - Environmental Science & Technology Y1 - 2020 A1 - Nizam, Sarwar A1 - Sen, Indra S. A1 - Vinoj, Velu A1 - Galy, Valier A1 - Selby, David A1 - Azam, Mohammad F. A1 - Pandey, Satyendra K. A1 - Creaser, Robert A. A1 - Agarwal, Avinash K. A1 - Singh, Akhilendra P. A1 - Bizimis, Michael KW - ; MASS BALANCES KW - AEROSOLS KW - ALBEDO REDUCTION KW - ATMOSPHERIC LEAD KW - BLACK CARBON KW - DUST TRANSPOR KW - isotopic composition KW - PB KW - SNOW ALBEDO KW - TIBETAN PLATEAU AB - The origin, transport pathway, and spatial variability of total organic carbon (OC) in the western Himalayan glaciers are poorly understood compared to those of black carbon (BC) and dust, but it is critically important to evaluate the climatic role of OC in the region. By applying the distribution of OC activation energy; C-14 activity; and radiogenic isotopes of Pb-208/Pb-204, (207)pb/(204)pb and (206)pb/Pb-204 in glacial debris and atmospheric particulate matter (PM10 size fraction), we demonstrate that 98.3 +/- 1.6 and 1.7 +/- 1.6% of OC in western Himalayan glaciers are derived from biomass and petrogenic sources, respectively. The (delta C-13 and N/C composition indicates that the biomass is a complex mixture of C3 vegetation and autochthonous photoautotrophic input modified by heterotrophic microbial activity. The data set reveals that the studied western Himalayan glacier has negligible contributions from fossil-fuel- derived particles, which contrasts to the central and eastern Himalayan glaciers that have significant contributions from fossil fuel sources. We show that this spatial variability of OC sources relates to regional differences in air mass transport pathways and precipitation regimes over the Himalaya. Moreover, our observation suggests that biomass-derived carbon could be the only primary driver of carbon-induced glacier melting in the western Himalaya. VL - 54 UR - https://apps.webofknowledge.com/InboundService.do?product=WOS&Func=Frame&DestFail=http%3A%2F%2Fwww.webofknowledge.com&SrcApp=search&SrcAuth=Alerting&SID=8Aqj2WiW4A71bymjSli&customersID=Alerting&mode=FullRecord&IsProductCode=Yes&AlertId=ab9062f8-b111-4f95- IS - 14 ER - TY - JOUR T1 - Biosignatures Associated with Freshwater Microbialites JF - Life Y1 - 2020 A1 - White, Richard Allen A1 - Soles, Sarah A. A1 - Brady, Allyson L. A1 - Southam, Gordon A1 - Lim, Darlene S.S. A1 - Slater, Greg F. KW - Biosignatures KW - Kelly Lake KW - microbialites KW - Pavilion Lake AB - Freshwater microbialites (i.e., lithifying microbial mats) are quite rare in northern latitudes of the North American continent, with two lakes (Pavilion and Kelly Lakes) of southeastern BC containing a morphological variety of such structures. We investigated Kelly Lake microbialites using carbon isotope systematics, phospholipid fatty acids (PLFAs) and quantitative PCR to obtain biosignatures associated with microbial metabolism. δ13CDIC values (mean δ13CDIC -4.9 ± 1.1‱, n = 8) were not in isotopic equilibrium with the atmosphere; however, they do indicate 13C-depleted inorganic carbon into Kelly Lake. The values of carbonates on microbialite surfaces (δ13C) fell within the range predicted for equilibrium precipitation from ambient lake water δ13CDIC (-2.2 to -5.3‱). Deep microbialites (26 m) had an enriched δ13Ccarb value of -0.3 ± 0.5‱, which is a signature of photoautotrophy. The deeper microbialites (>20 m) had higher biomass estimates (via PLFAs), and a greater relative abundance of cyanobacteria (measured by 16S copies via qPCR). The majority of PLFAs constituted monounsaturated and saturated PLFAs, which is consistent with gram-negative bacteria, including cyanobacteria. The central PLFA δ13C values were highly depleted (-9.3 to -15.7‱) relative to δ13C values of bulk organic matter, suggesting a predominance of photoautotrophy. A heterotrophic signature was also detected via the depleted iso- and anteiso-15:0 lipids (-3.2 to -5.2‱). Based on our carbonate isotopic biosignatures, PLFA, and qPCR measurements, photoautotrophy is enriched in the microbialites of Kelly Lake. This photoautotrophy enrichment is consistent with the microbialites of neighboring Pavilion Lake. This indication of photoautotrophy within Kelly Lake at its deepest depths raises new insights into the limits of measurable carbonate isotopic biosignatures under light and nutrient limitations. VL - 10 UR - https://pubmed.ncbi.nlm.nih.gov/32429118/ IS - 5 ER - TY - JOUR T1 - Carbon cycling in the deep Mariana Trench in the western north Pacific Ocean: Insights from radiocarbon proxy data JF - Deep Sea Research Part I: Oceanographic Research Papers Y1 - 2020 A1 - Shan, Sen A1 - Qi, Yuanzhi A1 - Tian, Jiwei A1 - Wang, Xuchen A1 - Luo, Chunle A1 - Zhou, Chun A1 - Zhang, Xiao-Hua A1 - Xin, Yu A1 - Wang, Yonghong KW - carbon cycling KW - Mariana trench KW - North pacific ocean KW - Particle flux KW - radiocarbon KW - stable carbon isotope AB - The Mariana Trench in the western North Pacific (NP) contains the deepest (11,000 m) point in the ocean and thus remains the least explored environment. Carbon cycling in the deep Mariana Trench is largely unknown and remains a curious mystery. Here, we report radiocarbon (Delta C-14) and stable carbon isotope (delta C-13) compositions of dissolved inorganic and organic carbon (DIC and DOC) and sinking particulate organic carbon (POC) for samples collected at 2000 m, 4000 m and 6000 m from the Mariana Trench in the western NP. DOC had much lower Delta C-14 values (-189 parts per thousand to -538 parts per thousand) than DIC (38 parts per thousand to -236 parts per thousand) and POC (11 parts per thousand-38 parts per thousand) at the same depths, indicating the different cycling processes and time scales of different carbon pools. The C-14 ages of DOC were approximately 1700 years and 4400 years older than those of DIC in the surface (2 m) and deep (10,000 m) waters of the Mariana Trench. Both DOC and DIC Delta C-14 values at hadal depths (>6000 m) in the trench are comparable to values at other sites in the deep NP, suggesting that water movement and mixing at hadal depths in the Mariana Trench are active and follow the deep-water circulation patterns of the NP. POC fluxes at the three deep depths showed large variations, but their modern Delta C-14 values indicate that the effective biological pump that drives fresh surface-produced particles to sink rapidly to deep depths in the trench could provide essential food sources for microbial and benthic communities living in an extremely harsh environment of the Mariana Trench. VL - 164 UR - https://apps.webofknowledge.com/InboundService.do?product=WOS&Func=Frame&DestFail=http%3A%2F%2Fwww.webofknowledge.com&SrcApp=search&SrcAuth=Alerting&SID=5FcsGoXKXNO2xQfU7KW&customersID=Alerting&mode=FullRecord&IsProductCode=Yes&AlertId=4d48b20a-7d27-4fa2- ER - TY - JOUR T1 - Carbon Cycling in the World's Deepest Blue Hole JF - Journal of Geophysical Research: Biogeosciences Y1 - 2020 A1 - Yao, P. A1 - Wang, X. C. A1 - Bianchi, T. S. A1 - Yang, Z. S. A1 - Fu, L. A1 - Zhang, X. H. A1 - Chen, L. A1 - Zhao, B. A1 - Morrison, E. S. A1 - Shields, M. R. A1 - Liu, Y. N. A1 - Bi, N. S. A1 - Qi, Y. Z. A1 - Zhou, S. A1 - Liu, J. W. A1 - Zhang, H. H. A1 - Zhu, C. J. A1 - Yu, Z. G. KW - anoxia KW - carbon cycling KW - dissolved carbon KW - radiocarbon KW - sulfur cycling KW - Yongle blue hole AB - Blue holes are unique geomorphological features with steep biogeochemical gradients and distinctive microbial communities. Carbon cycling in blue holes, however, remains poorly understood. Here we describe potential mechanisms of dissolved carbon cycling in the world's deepest blue hole, the Yongle Blue Hole (YBH), which was recently discovered in the South China Sea. In the YBH, we found some of the lowest concentrations (e.g., 22 μM) and oldest ages (e.g., 6,810 years before present) of dissolved organic carbon, as well as the highest concentrations (e.g., 3,090 μM) and the oldest ages (e.g., 8,270 years before present) of dissolved inorganic carbon observed in oceanic waters. Sharp gradients of dissolved oxygen, H2S, and CH4 and changes in bacterially mediated sulfur cycling with depth indicated that sulfur‐ and/or methane‐based metabolisms are closely linked to carbon cycling in the YBH. Our results showed that the YBH is a unique and easily accessible natural laboratory for examining carbon cycling in anoxic systems, which has potential for understanding carbon dynamics in both paleo and modern oceans—particularly in the context of global change. VL - 125 UR - https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019JG005307 IS - 2 ER - TY - JOUR T1 - Carbon isotope forensics for methane source identification JF - Remediation Journal Y1 - 2020 A1 - Coffin, Richard A1 - Mueller, James AB - Methane (CH4) in ecosystems originates from ancient petroleum formed deep within the earth and/or via microbial fermentation of organic carbon and subsequent reduction of carbon dioxide (CO2). Given the complexity of different ecosystems, origins of CH4 present can be difficult to determine. This issue was realized in a situation where an antimethanogenic in situ chemical reduction (ISCR) remedial amendment containing organic carbon plus zero‐valent iron was applied to treat chlorinated solvents in groundwater at a former dry cleaner facility. The technology rapidly and effectively reduced the concentration of tetrachloroethene in groundwater thus meeting project goals without the stoichiometric accumulation of catabolites such as trichloroethene (TCE), cis‐1,2‐dichloroethene, or vinyl chloride and without excessive methanogenesis (e.g., <2 mg/L) in the treated area. However, approximately 9 months after treatment, increased levels of CH4 (from 5 to 10 mg/L) were observed downgradient from the treated area. The applied remedial amendment contained approximately 60% (weight basis) fermentation organic carbon and was therefore a potential source of this CH4. However, there was <500 mg/L total organic carbon in groundwater emanating from the upgradient treatment area which was unlikely sufficient to produce that much CH4. Moreover, the soil gas also contained benzene, toluene, ethylbenzene, and xylenes and other gasoline constituents. These data suggested that the presence of three gasoline/diesel underground storage tanks that were previously closed in place with no active remediation performed could be the source of elevated CH4. Thirdly, there were sewer lines, utilities, multiple gasoline stations, and industrial activities in the immediate area. With an initial assumption that CH4 source(s) could include the ISCR amendment over stimulation of production, gasoline sourced CH4 from nearby leaking lines, or sewage from local fractured pipes, carbon isotope analyses—radiocarbon (Δ14C) and stable carbon (δ13C)—were coupled with CH4 and CO2 concentration data from groundwater samples to determine the origin of respired carbon. The δ13C range for carbon sources respired in the process would be approximately −26.5‰ to −33.0‰ for the ISCR amendment and total petroleum hydrocarbons (TPH) residuals, respectively. Δ14C is approximately 0‰ and −999‰ for the ISCR amendment (young carbon) and TPH (old carbon), respectively. The isotopic signature of respired gasses confirmed that elevated CH4 downgradient of the treated area originated primarily from sewer gasses (or fermentation of liquids released from sewer lines). This study provides an overview of the capability to apply carbon isotope geochemistry to confirmation of remedial protocols and sources of anthropogenic carbon pools that conclusively identify the origin of CH4 in a complex ecosystem undergoing a remedial action. VL - 30 UR - https://onlinelibrary.wiley.com/doi/10.1002/rem.21640 IS - 2 ER - TY - CHAP T1 - Chapter 30 - Radiocarbon dating of tsunami and storm deposits T2 - Geological Records of Tsunamis and Other Extreme Waves Y1 - 2020 A1 - Kelsey, Harvey M. A1 - Witter, Robert C. ED - Engel, Max ED - Pilarczyk, Jessica ED - May, Simon Matthias ED - Brill, Dominik ED - Garrett, Ed KW - Dating coastal storm deposits KW - Dating tsunami deposits KW - Modeling approaches for dating tsunami deposits KW - Radiocarbon dating KW - Sampling tsunami deposits KW - Tsunami Deposits KW - Tsunami sand AB - Radiocarbon age determinations can be an expedient and accurate means to assign age to deposits of tsunami or storm origin. Essential to the process of incorporating radiocarbon age determinations in tsunami or coastal storm investigations is an awareness on the part of the investigator that a sample will always return an age from a laboratory, but only carefully selected samples inform deposit age. Samples that inform deposit age are of two fundamentally different sample types, in-growth-position samples and detrital samples. For both in-growth-position samples and detrital samples, stratigraphic context is the critical information needed to evaluate how well sample age can constrain deposit age. Well constrained deposit ages require bracketing samples collected to provide both maximum and minimum limiting ages for the deposit(s) of interest. Therefore, sampling should be carried out with the intention of multiple sample submissions for age in order to optimize the potential for acquiring closely limiting ages. If there are multiple age determinations within a stratigraphic sequence that contains tsunami or storm deposits, then the calibrated radiocarbon ages can be, and should be, framed within a Bayesian model structure to better constrain deposit ages. Such models can be further improved by the incorporation of independent stratigraphic age information. JF - Geological Records of Tsunamis and Other Extreme Waves PB - Elsevier SN - 978-0-12-815686-5 UR - https://www.sciencedirect.com/science/article/pii/B9780128156865000304 ER - TY - JOUR T1 - Clumped Isotopes Link Older Carbon Substrates With Slower Rates of Methanogenesis in Northern Lakes JF - Geophysical Research Letters Y1 - 2020 A1 - Douglas, Peter M. J. A1 - Gonzalez Moguel, Regina A1 - Walter Anthony, Katey M. A1 - Wik, Martin A1 - Crill, Patrick M. A1 - Dawson, Katherine S. A1 - Smith, Derek A. A1 - Yanay, Ella A1 - Lloyd, Max K. A1 - Stolper, Daniel A. A1 - Eiler, John M. A1 - Sessions, Alex L. KW - clumped isotopes KW - ebullition flux KW - lakes KW - methane KW - permafrost KW - radiocarbon AB - The release of long‐stored carbon from thawed permafrost could fuel increased methanogenesis in northern lakes, but it remains unclear whether old carbon substrates released from permafrost are metabolized as rapidly by methanogenic microbial communities as recently produced organic carbon. Here, we apply methane (CH4) clumped isotope (Δ18) and 14C measurements to test whether rates of methanogenesis are related to carbon substrate age. Results from culture experiments indicate that Δ18 values are negatively correlated with CH4 production rate. Measurements of ebullition samples from thermokarst lakes in Alaska and glacial lakes in Sweden indicate strong negative correlations between CH4 Δ18 and the fraction modern carbon. These correlations imply that CH4 derived from older carbon substrates is produced relatively slowly. Relative rates of methanogenesis, as inferred from Δ18 values, are not positively correlated with CH4 flux estimates, highlighting the likely importance of environmental variables other than CH4 production rates in controlling ebullition fluxes. VL - 47 UR - https://onlinelibrary.wiley.com/doi/abs/10.1029/2019GL086756 IS - 6 ER - TY - JOUR T1 - Deep Equatorial Pacific Ocean Oxygenation and Atmospheric CO2 Over The Last Ice Age JF - Scientific Reports Y1 - 2020 A1 - Marcantonio, Franco A1 - Hostak, Ryan A1 - Hertzberg, Jennifer E. A1 - Schmidt, Matthew W. AB - Ventilation of carbon stored in the deep ocean is thought to play an important role in atmospheric CO2 increases associated with Pleistocene deglaciations. The presence of this respired carbon has been recorded by an array of paleoceanographic proxies from various locations across the global ocean. Here we present a new sediment core from the Eastern Equatorial Pacific (EEP) Ocean spanning the last 180,000 years and reconstruct high-resolution 230Th-derived fluxes of 232Th and excess barium, along with redox-sensitive uranium concentrations to examine past variations in dust delivery, export productivity, and bottom-water oxygenation, respectively. Our bottom-water oxygenation record is compared to other similar high-resolution records from across the Pacific and in the Southern Ocean. We suggest that the deep Pacific is a site of respired carbon storage associated with periods of decreased global atmospheric CO2 concentration during the LGM, confirming the conclusions from a wealth of previous studies. However, our study is the first to show a similar relationship beyond the last glacial, extending to at least 70,000 years VL - 10 UR - http://www.nature.com/articles/s41598-020-63628-x IS - 1 ER - TY - JOUR T1 - Deglacial temperature controls on no-analog community establishment in the Great Lakes Region JF - Quaternary Science Reviews Y1 - 2020 A1 - Fastovich, David A1 - Russell, James M. A1 - Jackson, Stephen T. A1 - Williams, John W. KW - biomarkers KW - brGDGT KW - Climate sensitivity KW - Lagoons & swamps KW - lakes KW - No-analog KW - North America KW - paleoclimatology KW - Pleistocene KW - pollen KW - sedimentology KW - Temperature KW - vegetation AB - Understanding the drivers of vegetation dynamics and no-analog communities in eastern North America is hampered by a scarcity of independent temperature indicators. We present a new branched glycerol dialkyl glycerol tetraether (brGDGT) temperature record from Bonnet Lake, Ohio (18–8 ka) and report uncertainty estimates based on Bayesian linear regression and bootstrapping. We also reanalyze a previously published brGDGT record from Silver Lake, Ohio, using improved chromatographic methods. All pollen- and brGDGT-based temperature reconstructions showed qualitatively similar deglacial trends but varying magnitudes. Separating 5- and 6- methyl brGDGTs resulted in substantially lower estimates of deglacial temperature variations (6.4 °C) than inferred from earlier brGDGT methods and pollen (11.8 °C, 12.0 °C respectively). Similar trends among proxies suggest good fidelity of brGDGTs to temperature, despite calibration uncertainties. At both sites, the rise and decline of no-analog communities closely track brGDGT-inferred temperatures, with a lag of 0–150 years. The timing of temperature and ecological events varies between Bonnet and Silver Lakes, likely due to age model uncertainties. Climate sensitivity analyses indicate a linear sensitivity of vegetation composition to temperature variations, albeit noisy and significant only with a 500-year bin. The formation of no-analog plant communities in the upper Midwest is closely linked to late-glacial warming, but other factors, such as temperature seasonality or end-Pleistocene megafaunal extinctions, remain viable. VL - 234 UR - https://linkinghub.elsevier.com/retrieve/pii/S0277379119303713 ER - TY - JOUR T1 - Delayed maximum and recession of an East Antarctic outlet glacierAbstract JF - Geology Y1 - 2020 A1 - King, Courtney A1 - Hall, Brenda A1 - Hillebrand, Trevor A1 - Stone, John AB - During the last glaciation, East Antarctic outlet glaciers contributed to a grounded ice sheet in the Ross Embayment. The timing of maximum ice extent, as well as of subsequent deglaciation of these outlets, has implications for the behavior of the Antarctic Ice Sheet (AIS) and its impact on global sea level. We present 45 radiocarbon ages of lacustrine cyanobacteria from the Lake Wellman region alongside Hatherton Glacier, which are the first terrestrial data to both record advance of an Antarctic glacier to its maximum position as well as document a high-resolution chronology of subsequent retreat. Seventeen new exposure ages are widely scattered, but the youngest four are in broad agreement with the radiocarbon data. Hatherton Glacier slowly thickened from 13,000 to 9500 yr B.P. and then thinned steadily until at least ca. 2800 yr B.P. Our work affords evidence of both a delayed maximum and recession of an East Antarctic outlet glacier compared to the global Last Glacial Maximum (LGM) and supports growing evidence of a time-transgressive local LGM within the Ross Sea sector of the ice sheet. Both observations are consistent with the idea that the timing of outlet glacier expansion and timing of recession are controlled by the balance between dynamic thinning from ocean forcing and increased accumulation due to atmospheric warming. VL - 48 UR - https://pubs.geoscienceworld.org/gsa/geology/article/48/6/630/583514/Delayed-maximum-and-recession-of-an-East-Antarctic IS - 6 ER - TY - JOUR T1 - Dissolved black carbon is not likely a significant refractory organic carbon pool in rivers and oceansAbstract JF - Nature Communications Y1 - 2020 A1 - Qi, Yuanzhi A1 - Fu, Wenjing A1 - Tian, Jiwei A1 - Luo, Chunle A1 - Shan, Sen A1 - Sun, Shuwen A1 - Ren, Peng A1 - Zhang, Hongmei A1 - Liu, Jiwen A1 - Zhang, Xiaohua A1 - Wang, Xuchen KW - Changjiang KW - cycle KW - flux KW - HUANGHE RIVERS KW - level KW - particulate KW - quantification KW - radiocarbon KW - sea AB - Rivers are the major carriers of dissolved black carbon (DBC) from land to ocean; the sources of DBC during its continuous transformation and cycling in the ocean, however, are not well characterized. Here, we present new carbon isotope data for DBC in four large and two small mountainous rivers, the Yangtze and Yellow river estuaries, the East China Sea and the North Pacific Ocean. We found that the carbon isotope signatures of DBC are relatively homogeneous, and the DBC C-14 ages in rivers are predominantly young and increase during continuous transport and cycling in the ocean. The results of charcoal leaching experiments indicate that DBC is released from charcoal and degraded by bacteria. Our study suggests that riverine DBC is labile and respired during transport and mixing into the ocean and that residual DBC is cycled and aged on the same time scales as bulk DOC in the ocean. Black carbon is a recalcitrant byproduct of biomass burning that ultimately accumulates in oceanic sinks. Here the authors assessed the sources and cycling of dissolved black carbon in rivers and oceans, finding that oceanic pools are cycled and aged on the same time scales as dissolved organic carbon. VL - 11 UR - http://www.nature.com/articles/s41467-020-18808-8http://www.nature.com/articles/s41467-020-18808-8.pdfhttp://www.nature.com/articles/s41467-020-18808-8.pdfhttp://www.nature.com/articles/s41467-020-18808-8 IS - 1 ER - TY - JOUR T1 - Dual carbon isotope (δ13C and Δ14C) characterization of particulate organic carbon in the Geum and Seomjin estuaries, South Korea JF - Marine Pollution Bulletin Y1 - 2020 A1 - Kang, Sujin A1 - Kim, Jung-Hyun A1 - Ryu, Jong-Sik A1 - Shin, Kyung-Hoon KW - carbon isotopes KW - dam KW - Estuary KW - Geum estuary KW - organic carbon KW - particulate KW - Seomjin estuary AB - We investigated the source, composition, and reactivity of particulate organic carbon (POC) in two contrasting Korean estuary systems, a closed estuary (Geum) (i.e., with an estuary dam at the river mouth) and an open (Seomjin) estuary. A dual isotope (δ13CPOC and Δ14CPOC) approach was applied to surface water samples collected along a salinity gradient in August 2016. Our results indicate that phytoplankton-derived POC was the main contributor to the total POC pool in the reservoir of the Geum estuary, while terrestrial-derived POC predominated the upper Seomjin estuary. A simple binary mixing model using Δ14CPOC revealed a higher modern POC contribution (87–90%) in the Geum estuary reservoir than that (77%) of the upper Seomjin estuary. Accordingly, it appears that an estuary dam can alter the source and reactivity of POC in a reservoir, which can be transferred to the adjacent coastal ecosystem. VL - 150 UR - https://linkinghub.elsevier.com/retrieve/pii/S0025326X19308756 ER - TY - JOUR T1 - Effects of agricultural and tillage practices on isotopic signatures and fluxes of organic and inorganic carbon in headwater streams JF - Aquatic Sciences Y1 - 2020 A1 - Kelsey, Scott A. A1 - Grottoli, Andrea G. A1 - Bauer, James E. A1 - Lorenz, Klaus A1 - Lal, Rattan A1 - Matsui, Yohei A1 - Huey-Sanders, Teresa M. VL - 82 UR - http://link.springer.com/10.1007/s00027-019-0691-7http://link.springer.com/content/pdf/10.1007/s00027-019-0691-7.pdfhttp://link.springer.com/content/pdf/10.1007/s00027-019-0691-7.pdfhttp://link.springer.com/article/10.1007/s00027-019-0691-7/fulltext.html IS - 2 ER - TY - JOUR T1 - Efficient preservation of young terrestrial organic carbon in sandy turbidity-current depositsAbstract JF - Geology Y1 - 2020 A1 - Hage, S. A1 - Galy, V.V. A1 - Cartigny, M.J.B. A1 - Acikalin, S. A1 - Clare, M.A. A1 - Gröcke, D.R. A1 - Hilton, R.G. A1 - Hunt, J.E. A1 - Lintern, D.G. A1 - McGhee, C.A. A1 - Parsons, D.R. A1 - Stacey, C.D. A1 - Sumner, E.J. A1 - Talling, P.J. AB - Burial of terrestrial biospheric particulate organic carbon in marine sediments removes CO2 from the atmosphere, regulating climate over geologic time scales. Rivers deliver terrestrial organic carbon to the sea, while turbidity currents transport river sediment further offshore. Previous studies have suggested that most organic carbon resides in muddy marine sediment. However, turbidity currents can carry a significant component of coarser sediment, which is commonly assumed to be organic carbon poor. Here, using data from a Canadian fjord, we show that young woody debris can be rapidly buried in sandy layers of turbidity current deposits (turbidites). These layers have organic carbon contents 10× higher than the overlying mud layer, and overall, woody debris makes up >70% of the organic carbon preserved in the deposits. Burial of woody debris in sands overlain by mud caps reduces their exposure to oxygen, increasing organic carbon burial efficiency. Sandy turbidity current channels are common in fjords and the deep sea; hence we suggest that previous global organic carbon burial budgets may have been underestimated. VL - 48 UR - https://pubs.geoscienceworld.org/gsa/geology/article/48/9/882/586768/Efficient-preservation-of-young-terrestrial IS - 9 ER - TY - JOUR T1 - Evaluating the effects of regional climate trends along the West Antarctic Peninsula shelf based on the seabed distribution of naturally occurring radioisotopic tracers JF - Marine Geology Y1 - 2020 A1 - Taylor, Richard S. A1 - DeMaster, David J. A1 - Smith, Craig R. A1 - Thomas, Carrie J. KW - Antarctica KW - Climate change KW - Radiochemical flux KW - Sea-ice KW - Seabed AB - Measurements of Th-230, C-14, Pb-210 and Th-234 activities were made on sediment cores collected along a N-S transect exhibiting a gradient in annual sea-ice duration off the West Antarctic Peninsula. The resultant data were used to evaluate the effects of regional warming on particle flux reaching the seabed on timescales from millennial to seasonal. Shelf samples were collected at five stations, over three cruises, between February 2008 and March 2009, as part of the FOODBANCS2 Project. Sea-ice conditions (the number of days ice-free prior to core collection) were evaluated at the five stations to understand the relationship between ice abundance and particle/radionuclide flux. Based on the millennial tracer C-14, rates of sediment accumulation along the peninsula decrease southward, consistent with the observed sea-ice gradient. Th-230 data provide additional evidence on millennial timescales that sediment focusing (i.e., lateral transport) occurs to a greater extent in the northern reaches of the study area compared to the southernmost stations. The distribution of steady-state, Pb-210 flux to the seabed (representing centurial trends) displays a similar trend to C-14, showing higher radionuclide/particle flux in the northern study area (where sea-ice duration is diminished) and lower flux southward as sea-ice duration increases. Additionally, Pb-210 data suggest that lateral transport plays an important role in the sediment distributions of this radiotracer on hundred-year timescales, which is explainable by the relatively short circulation times of peninsular waters relative to Pb-210's half-life. On seasonal and annual time scales, the distribution of steady-state Th-234 flux to the seabed shows an increase in radionuclide flux at the southernmost stations. This increase in radionuclide flux on seasonal and annual time scales is consistent with the warming trend along the peninsula and the reduction in sea-ice duration over the past decade. A significant statistical relationship, however, could not be established between annual sea-ice free days and Th-234-derived particle flux to the seabed. The fluxes/distributions of long-lived particle-reactive tracers (C-14, Th-230, and Pb-210) on the West Antarctic Peninsula shelf appear to be controlled primarily by the long-term pattern of increasing annual sea-ice duration in the southward direction, whereas the fluxes of the short-lived tracer (Th-234) are consistent with the more recent decreases in sea-ice duration (associated with climate change) that have occurred over the past decade, primarily in the southern West Antarctic Peninsula stations. VL - 429 UR - https://www.sciencedirect.com/science/article/pii/S0025322720302036 ER - TY - JOUR T1 - Groundwater as a major source of dissolved organic matter to Arctic coastal waters JF - Nature Communications Y1 - 2020 A1 - Connolly, Craig T. A1 - Cardenas, M. Bayani A1 - Burkart, Greta A. A1 - Spencer, Robert G. M. A1 - McClelland, James W. AB - Groundwater is projected to become an increasing source of freshwater and nutrients to the Arctic Ocean as permafrost thaws, yet few studies have quantified groundwater inputs to Arctic coastal waters under contemporary conditions. New measurements along the Alaska Beaufort Sea coast show that dissolved organic carbon and nitrogen (DOC and DON) concentrations in supra-permafrost groundwater (SPGW) near the land-sea interface are up to two orders of magnitude higher than in rivers. This dissolved organic matter (DOM) is sourced from readily leachable organic matter in surface soils and deeper centuries-to millennia-old soils that extend into thawing permafrost. SPGW delivers approximately 400–2100 m3 of freshwater, 14–71 kg of DOC, and 1–4 kg of DON to the coastal ocean per km of shoreline per day during late summer. These substantial fluxes are expected to increase as massive stocks of frozen organic matter in permafrost are liberated in a warming Arctic. VL - 11 UR - http://www.nature.com/articles/s41467-020-15250-8http://www.nature.com/articles/s41467-020-15250-8.pdfhttp://www.nature.com/articles/s41467-020-15250-8.pdfhttp://www.nature.com/articles/s41467-020-15250-8 IS - 1 ER - TY - JOUR T1 - High dissolved organic radiocarbon in precipitation during winter and its implication on the carbon cycle JF - Science of The Total Environment Y1 - 2020 A1 - Cha, Ji-Yeon A1 - Lee, Seung-Cheol A1 - Lee, Eun-Ju A1 - Go, Minjung A1 - Dasari, Kishore Babu A1 - Yim, Yong-Hyeon A1 - Oh, Neung-Hwan AB - Radiocarbon (14C) analysis is a powerful tool for tracing carbon in the global carbon cycle. Precipitation is a component of the global carbon cycle through which dissolved organic carbon (DOC) enters terrestrial and aquatic ecosystems from the atmosphere. In previous studies, the Δ14C of DOC in rain or snow was negative indicating an input of relatively old organic carbon including fossil fuels, with only a few positive values up to +108‰ showing the signal of recent photosynthesis. However, here we report surprisingly high Δ14C-DOC in bulk precipitation, more than 1000‰ in Seoul, South Korea, especially when the Northwesterly wind blows during winter. In contrast, Δ14C of particulate organic carbon (POC) in bulk precipitation was negative, indicating that the sources of POC and DOC were different. Although the sources of the high Δ14C-DOC are not clear and future studies on them are required, the relatively high Δ14C-DOC in a nearby headwater stream suggests that precipitation DOC has the potential to affect the local carbon cycle, and that stream DOC derived from terrestrial ecosystems could be older than previously thought. The analysis of Δ14C-DOC of precipitation in many other locations is necessary to understand how long carbon stays in terrestrial ecosystems. VL - 742 UR - https://linkinghub.elsevier.com/retrieve/pii/S0048969720337670 ER - TY - JOUR T1 - Holocene earthquake history and slip rate of the southern Teton fault, Wyoming, USAAbstract JF - GSA Bulletin Y1 - 2020 A1 - DuRoss, Christopher B. A1 - Gold, Ryan D. A1 - Briggs, Richard W. A1 - Delano, Jaime E. A1 - Ostenaa, Dean A. A1 - Zellman, Mark S. A1 - Cholewinski, Nicole A1 - Wittke, Seth J. A1 - Mahan, Shannon A. AB - The 72-km-long Teton normal fault bounds the eastern base of the Teton Range in northwestern Wyoming, USA. Although geomorphic surfaces along the fault record latest Pleistocene to Holocene fault movement, the postglacial earthquake history of the fault has remained enigmatic. We excavated a paleoseismic trench at the Buffalo Bowl site along the southernmost part of the fault to determine its Holocene rupture history and slip rate. At the site, ∼6.3 m of displacement postdates an early Holocene (ca. 10.5 ka) alluvial-fan surface. We document evidence of three surface-faulting earthquakes based on packages of scarp-derived colluvium that postdate the alluvial-fan units. Bayesian modeling of radiocarbon and luminescence ages yields earthquake times of ca. 9.9 ka, ca. 7.1 ka, and ca. 4.6 ka, forming the longest, most complete paleoseismic record of the Teton fault. We integrate these data with a displaced deglacial surface 4 km NE at Granite Canyon to calculate a postglacial to mid-Holocene (14.4–4.6 ka) slip rate of ∼1.1 mm/yr. Our analysis also suggests that the postglacial to early Holocene (14.4–9.9 ka) slip rate exceeds the Holocene (9.9–4.6 ka) rate by a factor of ∼2 (maximum of 3); however, a uniform rate for the fault is possible considering the 95% slip-rate errors. The ∼5 k.y. elapsed time since the last rupture of the southernmost Teton fault implies a current slip deficit of ∼4–5 m, which is possibly explained by spatially/temporally incomplete paleoseismic data, irregular earthquake recurrence, and/or variable per-event displacement. Our study emphasizes the importance of minimizing slip-rate uncertainties by integrating paleoseismic and geomorphic data sets and capturing multiple earthquake cycles. VL - 132 UR - https://pubs.geoscienceworld.org/gsa/gsabulletin/article/132/7-8/1566/575767/Holocene-earthquake-history-and-slip-rate-of-the IS - 7-8 ER - TY - JOUR T1 - Holocene occupation history of pygoscelid penguins at Stranger Point, King George (25 de Mayo) Island, northern Antarctic Peninsula JF - The Holocene Y1 - 2020 A1 - Emslie, Steven D A1 - Romero, Matías A1 - Juáres, Mariana A A1 - Argota, Martin R KW - abandoned penguin mounds KW - Holocene penguin colonization KW - marine beach deposit KW - ornithogenic soil KW - Radiocarbon dating KW - South Shetlands KW - West Antarctica AB - We report additional fossil evidence for pygoscelid penguins breeding on King George (25 de Mayo) Island, South Shetland Islands, in the Holocene beginning at ~7000 cal. yr BP. This evidence comes from a raised marine beach deposit formerly studied and described as Pingfo I at Stranger Point, Potter Peninsula. We relocated and exposed deposits at this site and recovered additional samples of penguin bones from five stratigraphic beds that are redescribed here. Most of these bones are from juvenile penguins and exhibit little or no wear indicating minimal transport to the beach deposits. Some of the bones are developed enough to be identifiable to Adélie (Pygoscelis adeliae), Gentoo (Pygoscelis papua), and Chinstrap (Pygoscelis antarctica) penguins, indicating that all three species were breeding at Stranger Point from ~7320 to 4865 cal. yr BP. This breeding occupation corresponds with the first warming and deglaciation that occurred in the northern Antarctic Peninsula by this time and ends with the onset of reglaciation of the Peninsula. At least 31 abandoned penguin mounds and ornithogenic soils also were located and sampled at Stranger Point and indicate that the current occupation of this area by all three pygoscelid penguins dates no older than ~535 cal. yr BP. The absence of ornithogenic soils from earlier Holocene breeding was probably due to glacial activity and soil solifluction during periods of warming in the mid to late Holocene. VL - 30 UR - http://journals.sagepub.com/doi/10.1177/0959683619875814 IS - 1 ER - TY - JOUR T1 - Holocene Rupture History of the Central Teton Fault at Leigh Lake, Grand Teton National Park, WyomingABSTRACT JF - Bulletin of the Seismological Society of America Y1 - 2020 A1 - Zellman, Mark S. A1 - DuRoss, Christopher B. A1 - Thackray, Glenn D. A1 - Personius, Stephen F. A1 - Reitman, Nadine G. A1 - Mahan, Shannon A. A1 - Brossy, Cooper C. AB - Prominent scarps on Pinedale glacial surfaces along the eastern base of the Teton Range confirm latest Pleistocene to Holocene surface‐faulting earthquakes on the Teton fault, but the timing of these events is only broadly constrained by a single previous paleoseismic study. We excavated two trenches at the Leigh Lake site near the center of the Teton fault to address open questions about earthquake timing and rupture length. Structural and stratigraphic evidence indicates two surface‐faulting earthquakes at the site that postdate deglacial sediments dated by radiocarbon and optically stimulated luminescence to ∼10–11  ka⁠. Earthquake LL2 occurred at ∼10.0  ka (9.7–10.4 ka; 95% confidence range) and LL1 at ∼5.9  ka (4.8–7.1 ka; 95%). LL2 predates an earthquake at ∼8  ka identified in the previous paleoseismic investigation at Granite Canyon. LL1 corresponds to the most recent Granite Canyon earthquake at ∼4.7–7.9  ka (95% confidence range). Our results are consistent with the previously documented long‐elapsed time since the most recent Teton fault rupture and expand the fault’s earthquake history into the early Holocen VL - 110 UR - https://pubs.geoscienceworld.org/ssa/bssa/article/110/1/67/575484/Holocene-Rupture-History-of-the-Central-Teton IS - 1 ER - TY - JOUR T1 - Holocene sedimentation in a blue hole surrounded by carbonate tidal flats in The Bahamas: Autogenic versus allogenic processes JF - Marine Geology Y1 - 2020 A1 - van Hengstum, Peter J. A1 - Winkler, Tyler S. A1 - Tamalavage, Anne E. A1 - Sullivan, Richard M. A1 - Little, Shawna N. A1 - MacDonald, Dana A1 - Donnelly, Jeffrey P. A1 - Albury, Nancy A. KW - Carbonate tidal flats KW - carbonates KW - North Atlantic Bahamas KW - sinkhole AB - The sediment in North Atlantic blue holes preserves paleoclimate records. However, accurate paleoclimate reconstructions require an improved understanding of allogenic versus autogenic processes controlling blue hole sedimentation. Here we provide a detailed case study of the Holocene stratigraphy within Freshwater River Blue Hole, which is currently surrounded by carbonate tidal flats in the northern Bahamas (Abaco Island). During the Holocene, concomitant coastal aquifer elevation and relative sea-level rise controlled internal blue hole depositional environments. The general Holocene facies succession observed is: (i) basal detrital and freshwater peat, (ii) palustrine to lacustrine marl, (iii) algal sapropel, and finally (iv) bedded carbonate mud. During the middle Holocene when groundwater levels were lower, small changes in accommodation space that were inherited from the bedrock surface below (<1 m) were able to promote significant lateral facies changes. Multiple cores are needed to characterize these lateral facies changes. Hydrographic characteristics of the coastal aquifer (e.g., vertical position, stratification, salinity) relative to the blue hole benthos exert a fundamental control on (a) benthic flora and meiofauna (e.g., charophytes, ostracodes, foraminifera, gastropods) and (b) organic matter production and preservation from pelagic productivity. Over the last 5000 years, water column stratification in Freshwater River Blue Hole was interrupted on millennial to sub-decadal timescales , which are potentially linked to changing aquifer recharge and rainfall. Lastly, historical intense hurricanes passing closely to the west of the site may have promoted deposition of coarse beds at the site. However, the lack of carbonate tidal flat microfaunal remains (foraminifera: Peneroplis) within these coarse intervals indicates that Freshwater River Blue Hole does not preserve a reliable record of hurricane-induced overwash deposition from the carbonate tidal flats during the last 2300 years. VL - 419 UR - https://linkinghub.elsevier.com/retrieve/pii/S0025322719301811 ER - TY - JOUR T1 - Holocene temperature and landscape history of southwest Greenland inferred from isotope and geochemical lake sediment proxies JF - Quaternary Science Reviews Y1 - 2020 A1 - Lasher, G. Everett A1 - Axford, Yarrow A1 - Masterson, Andrew L. A1 - Berman, Karalyn A1 - Larocca, Laura J. KW - Chironomids KW - glaciers KW - Greenland KW - Isolation basins KW - lake sediments KW - oxygen isotopes KW - Paleotemperatures KW - Stable isotopes AB - Terrestrial temperature reconstructions from the ice-free margins of Greenland are critical for constraining the sensitivity of the Greenland ice sheet to past climate change. Numerous investigations have clarified the glacial history of southwest Greenland in recent decades; however, very few local quantitative temperature reconstructions exist as context for changes in the cryosphere. We examine sedimentary records from two lakes south of Nuuk, Greenland (informally named lakes T1 and T2), and investigate millennial scale Holocene climate change using a multi-proxy approach. Changes in X-Ray fluorescence spectroscopy (XRF), δ15N, δ13C and biogenic silica concentrations of bulk lake sediments mark the transition from a marine environment to isolated lakes as relative sea level fell in the early Holocene. δ18O values of subfossil insects (chironomids) from lakes T1 and T2 decreased by 2–3‰ from c. 8.8 ka BP (minimum limiting age for the onset of lacustrine sediment deposition in lake T2; ka BP = thousands of years before 1950) to 1 ka BP. Existing isotope-independent temperature reconstructions from the west coast of Greenland suggest that these changes in δ18O values accompanied gradual cooling of 2–4 °C, concomitant with decreasing summer insolation. There is widespread regional evidence that this cooling resulted in progressive regrowth of local glaciers and of the ice sheet. The regional consensus on the magnitude of this temperature change indicates that the local, modern modeled temperature - precipitation δ18O relationship cannot be used to quantify millennial-scale temperature changes at these sites through the Holocene. This reinforces that studies utilizing δ18O-based proxies to infer temperature change should carefully assess local isotope-temperature relationships over space and time. VL - 239 UR - https://www.sciencedirect.com/science/article/pii/S0277379120303206 ER - TY - JOUR T1 - The Hooskanaden Landslide: historic and recent surge behavior of an active earthflow on the Oregon Coast JF - Landslides Y1 - 2020 A1 - Alberti, Stefano A1 - Senogles, Andrew A1 - Kingen, Kara A1 - Booth, Adam A1 - Castro, Pete A1 - DeKoekkoek, Jill A1 - Glover-Cutter, Kira A1 - Mohney, Curran A1 - Olsen, Michael A1 - Leshchinsky, Ben AB - This paper presents an analysis of the Hooskanaden Landslide, an earthflow, which experienced a dramatic surge event beginning on February 24, 2019, closing US Highway 101 near mile point 343.5 for nearly 2 weeks. This ~ 1 km long surge event resulted in horizontal displacements of up to 45 m and uplift of 6 m at the toe located on a gravel beach adjacent to the Pacific Ocean. The Hooskanaden Landslide, likely active since the eighteenth century, exhibits regular activity with a recurrence interval of major surge events of approximately every 20 years, transitioning from slow to relatively rapid velocities. During the 2019 event, maximum displacement rates of approximately 60 cm/h were observed, slowly decreasing to 15 cm/h for a sustained period of approximately 2 weeks before the eventual return to baseline conditions (< 0.02 cm/h). UR - http://link.springer.com/10.1007/s10346-020-01466-8 ER - TY - JOUR T1 - Identifying the Greatest Earthquakes of the Past 2000 Years at the Nehalem River Estuary, Northern Oregon Coast, USA JF - Open Quaternary Y1 - 2020 A1 - Nelson, Alan R. A1 - Hawkes, Andrea D. A1 - Sawai, Yuki A1 - Engelhart, Simon E. A1 - Witter, Rob A1 - Grant-Walter, Wendy C. A1 - Bradley, Lee-Ann A1 - Dura, Tina A1 - Cahill, Niamh A1 - Horton, Ben KW - Bayesian transfer function KW - Cascadia subduction zone KW - Coseismic subsidence KW - earthquake hazards KW - Paleoseismology KW - salt-marsh stratigraphy KW - Sea-level changes KW - tidal foraminifera and diatoms AB - We infer a history of three great megathrust earthquakes during the past 2000 years at the Nehalem River estuary based on the lateral extent of sharp (≤3 mm) peat-mud stratigraphic contacts in cores and outcrops, coseismic subsidence as interpreted from fossil diatom assemblages and reconstructed with foraminiferal assemblages using a Bayesian transfer function, and regional correlation of 14C-modeled ages for the times of subsidence. A subsidence contact from 1700 CE (contact A), sometimes overlain by tsunami-deposited sand, can be traced over distances of 7 km. Contacts B and D, which record subsidence during two earlier megathrust earthquakes, are much less extensive but are traced across a 700-m by 270-m tidal marsh. Although some other Cascadia studies report evidence for an earthquake between contacts B and D, our lack of extensive evidence for such an earthquake may result from the complexities of preserving identifiable evidence of it in the rapidly shifting shoreline environments of the lower river and bay. Ages (95% intervals) and subsidence for contacts are: A, 1700 CE (1.1 ± 0.5 m); B, 942–764 cal a BP (0.7 ± 0.4 m and 1.0 m ± 0.4 m); and D, 1568–1361 cal a BP (1.0 m ± 0.4 m). Comparisons of contact subsidence and the degree of overlap of their modeled ages with ages for other Cascadia sites are consistent with megathrust ruptures many hundreds of kilometers long. But these data cannot conclusively distinguish among different types or lengths of ruptures recorded by the three great earthquake contacts at the Nehalem River estuary. VL - 6 UR - http://www.openquaternary.com/articles/10.5334/oq.70/ ER - TY - ABST T1 - Inferring life history characteristics of the oceanic whitetip shark Carcharhinus longimanus from vertebral bomb radiocarbon [Poster] Y1 - 2020 A1 - Passerotti, Michelle S. A1 - Andrews, Allen H. A1 - Natanson, Lisa J. UR - https://hdl.handle.net/1912/27806 ER - TY - JOUR T1 - Inferring Life History Characteristics of the Oceanic Whitetip Shark Carcharhinus longimanus From Vertebral Bomb Radiocarbon JF - Frontiers in Marine Science Y1 - 2020 A1 - Passerotti, Michelle S. A1 - Andrews, Allen H. A1 - Natanson, Lisa J. KW - Age validation KW - Carbon-14 KW - diet KW - family Carcharhinidae KW - migration KW - Vertebrae AB - Oceanic whitetip sharks Carcharhinus longimanus are a cosmopolitan epipelagic species that was once prolific throughout the tropics and subtropics but was recently listed as Critically Endangered by the International Union for the Conservation of Nature and as Threatened under the United States Endangered Species Act. Although historically conspicuous in oceanic fisheries catches, relatively little is known about their habitat use, movement, and life history during migration. Given the paucity of data on migratory patterns and lack of age estimate validation available for this species, we evaluated vertebral growth bands for bomb radiocarbon (C-14) patterns to derive additional information on these metrics. Individual growth bands (n = 62) were milled from vertebrae of eight individuals caught in the northwestern Atlantic Ocean. Age estimates based on vertebral growth bands ranged 1-13 years, with capture dates spanning 1978-2004. Plots of vertebral Delta C-14 relative to regional coral, shark, and fish otolith reference curves suggest age estimates based on presumed annual growth bands were accurate, although specimens were not old enough to capture the most informative portion of the bomb radiocarbon reference period. The magnitude of Delta C-14 varied among individuals, and individual chronologies demonstrated semi-cyclic patterns of Delta C-14 depletion and subsequent enrichment, which may be indicative of changes to diet as a function of annual migratory patterns and is supported by recently published telemetry, diet, and stable isotope studies. Although these data are preliminary in nature, they provide some evidence that Delta C-14 patterns in vertebrae can serve as a multi-purpose tool for life history studies of oceanic sharks. VL - 7 UR - https://www.frontiersin.org/articles/10.3389/fmars.2020.581775/fullhttps://www.frontiersin.org/articles/10.3389/fmars.2020.581775/full ER - TY - JOUR T1 - Influences of upper Floridan aquifer waters on radiocarbon in the otoliths of gray snapper (Lutjanus griseus) in the Gulf of Mexico JF - Radiocarbon Y1 - 2020 A1 - Andrews, Allen H A1 - Barnett, Beverly K A1 - Chanton, Jeffrey P A1 - Thornton, Laura A A1 - Allman, Robert J AB - The otoliths (ear stones) of fishes are commonly used to describe the age and growth of marine and freshwater fishes. These non-skeletal structures are fortuitous in their utility by being composed of mostly inorganic carbonate that is inert through the life of the fish. This conserved record functions like an environmental chronometer and bomb-produced radiocarbon — a 14C signal created by atmospheric testing of thermonuclear devices — can be used as a time-specific marker in validating fish age. However, complications from the hydrogeology of nearshore marine environments can complicate 14C levels, as was the case with gray snapper (Lutjanus griseus) along the Gulf of Mexico coast of Florida. Radiocarbon of these nearshore waters is influenced by freshwater input from the karst topography of the Upper Floridan Aquifer-estuarine waters that are 14C-depleted from surface and groundwater inputs. Some gray snapper likely recruited to this kind of environment where 14C levels were depleted in the earliest otolith growth, although age was validated for individuals that were not exposed to 14C-depleted waters to an age of at least 25 years with support for a 30-year lifespan. UR - https://www.researchgate.net/publication/341180789_INFLUENCES_OF_UPPER_FLORIDAN_AQUIFER_WATERS_ON_RADIOCARBON_IN_THE_OTOLITHS_OF_GRAY_SNAPPER_Lutjanus_griseus_IN_THE_GULF_OF_MEXICO ER - TY - JOUR T1 - Insolation and greenhouse gases drove Holocene winter and spring warming in Arctic Alaska JF - Quaternary Science Reviews Y1 - 2020 A1 - Longo, William M. A1 - Huang, Yongsong A1 - Russell, James M. A1 - Morrill, Carrie A1 - Daniels, William C. A1 - Giblin, Anne E. A1 - Crowther, Josue KW - Alkenone KW - Beringia KW - Continental biomarkers KW - Holocene KW - North America KW - paleoclimatology KW - paleolimnology KW - Proxy data-model comparison KW - seasonality KW - Temperature reconstruction AB - Global surface temperature changes and their drivers during the Holocene Epoch remain controversial. Syntheses of proxy data indicate that global mean annual temperature declined from the mid-Holocene until the Pre-industrial Era, a trend linked to decreasing Northern Hemisphere summer insolation. In contrast, global climate models simulate increasing mean annual temperatures driven by retreating ice sheets and increasing greenhouse gas concentrations. This proxy-model disagreement may originate from a warm season bias in Northern Hemisphere proxy reconstructions, highlighting the need for new proxies that quantify cold season temperature, especially in Arctic regions that were devoid of continental ice sheets during the Holocene. Here, we present a new 16,000-year winter-spring temperature reconstruction derived from the unsaturation ratio of alkenones (U-3(7)K) in a continuous sedimentary sequence from Lake E5, northern Alaska. We employ a thermodynamic lake model to convert alkenone-inferred lake temperatures into winter-spring air temperature anomalies and we contextualize our proxy reconstruction with climate model output from the region. Our reconstruction shows that winter-spring temperatures warmed rapidly during the deglaciation at 16 and 14 thousand years before present and continued to warm gradually throughout the middle and late Holocene (0.12-0.28 degrees C/thousand years) in concert with regional sea surface temperature and sea ice records. Our results are consistent with climate model simulations and we attribute Holocene warming to rising winter-spring insolation, radiative forcing from rising greenhouse gas concentrations and regional feedbacks. Our reconstructed cold season warming equaled or exceeded summer cooling according to a regional synthesis of temperature records, suggesting that seasonal biases in temperature reconstructions may account for proxy-model disagreements in Holocene temperature trends from Eastern Beringia. (C) 2020 Elsevier Ltd. All rights reserved. VL - 242 UR - https://linkinghub.elsevier.com/retrieve/pii/S0277379120304005 ER - TY - JOUR T1 - Late glacial and Holocene paleoenvironments in the midcontinent United States, inferred from Geneva Lake leaf wax, ostracode valve, and bulk sediment chemistry JF - Quaternary Science Reviews Y1 - 2020 A1 - Puleo, Peter J.K. A1 - Axford, Yarrow A1 - McFarlin, Jamie M. A1 - Curry, B. Brandon A1 - Barklage, Mitchell A1 - Osburn, Magdalena R. KW - Holocene KW - Inorganic geochemistry KW - Loess KW - North America KW - Organic geochemistry KW - paleoclimatology KW - paleolimnology KW - Pleistocene KW - sedimentology KW - Stable isotopes AB - Geneva Lake in Wisconsin, USA, is > 20,000 years old and contains a 30-m thick lacustrine sediment record of mid-continent North American climate and environmental change. Here we describe a sediment record from Geneva Lake spanning the past 14,500 years. From scanning X-ray fluorescence, organic C and N concentrations and isotopes, X-ray diffraction, magnetic susceptibility, and grain size of bulk sediments, we infer changes in sediment sources over time including: abrupt decline in inputs of remobilized loess ∼13,400 cal yr BP followed by a gradual transition to organic-rich marl deposition by ∼10,400 cal yr BP as the landscape stabilized following a period of permafrost thaw and vegetation development; deposition of a minerogenic unit at ∼8,200 cal yr BP that may record enhanced eolian activity during the widespread “8.2 ka event; ” and elevated zinc, lead, and arsenic from human activities following regional industrialization. Within the Holocene marl, we also use isotopic (δ18O and δ13C) and trace metal ratio (Sr/Ca and Mg/Ca) analyses of ostracode valves paired with concentrations and hydrogen isotopic composition (δ2H) of leaf wax n-alkanes to infer climate and hydrological change. Groundwater had a large but declining influence on lake water chemistry from 11,800 to 9,700 cal yr BP, precluding inferences of regional climate from our lacustrine proxies during this period. δ2H values of terrestrial n-C29 alkanes show little variability from 9,700 to present, indicating the average isotopic composition of local precipitation was relatively stable, reflecting stable condensation temperatures and source. In contrast, a gradual trend towards more δ18O- and δ2H-depleted lake water and lower lake water Sr/Ca from 9700 cal yr BP to present suggest decreasing evaporation of lake water and increasing precipitation amounts throughout the Holocene and resulting shorter lake water residence times. Lake water Mg/Ca variations over the past 9,700 years broadly parallel regional pollen-based reconstructions of summer temperatures. Neither Mg/Ca nor terrestrial leaf wax δ2H suggest long-term directional shifts in temperature at this site through the middle to late Holocene, as climate became wetter. It appears that precipitation isotopes did not track local temperatures on millennial timescales in this part of mid-continent North America through the Holocene, and instead may have covaried with changes in Northern Hemisphere latitudinal temperature gradients driven by large Arctic temperature changes. VL - 241 UR - https://www.sciencedirect.com/science/article/pii/S0277379120303462 ER - TY - JOUR T1 - A late Holocene subfossil Atlantic white cedar tree-ring chronology from the northeastern United States JF - Quaternary Science Reviews Y1 - 2020 A1 - Pearl, Jessie K. A1 - Anchukaitis, Kevin J. A1 - Donnelly, Jeffrey P. A1 - Pearson, Charlotte A1 - Pederson, Neil A1 - Lardie Gaylord, Mary C. A1 - McNichol, Ann P. A1 - Cook, Edward R. A1 - Zimmermann, George L. KW - coastal KW - Geomorphology KW - Holocene KW - North America KW - paleoclimatology KW - radiogenic isotopes KW - Tree-rings AB - Tree-rings provide precise annually dated climate information, but their application can be limited by the relatively short lifespan of many trees. To overcome this limitation, tree-ring records can be extended over longer time periods by connecting living trees with older “sub-fossil” trees, which can provide information on longer timescales throughout the Holocene. These long chronologies are proxy records of past climate, provide precise chronological information for extreme events, and give insight into the range of natural climate variability prior to the instrumental period. In the densely populated northeastern United States, few tree-ring records are longer than 500 years, and there are no millennial-length tree-ring chronologies for the region. Here, we use a combination of standard dendrochronological and radiocarbon techniques, including use of the 774 CE radiocarbon excursion, to generate an absolutely dated 2500 year-long tree ring record from living, archaeological, and subfossil Atlantic white cedar (Chamaecyparis thyoides) found in the coastal northeastern United States. Our chronology demonstrates the potential to develop multi-millennial Chamaecyparis thyoides tree-ring records to address previously unanswered questions regarding late Holocene hydroclimate, extreme events, and temperature variability in New England. VL - 228 UR - https://linkinghub.elsevier.com/retrieve/pii/S0277379119308108 ER - TY - JOUR T1 - Life and its traces in Antarctica's McMurdo Dry Valley paleolakes: a survey of preservation JF - Micron Y1 - 2020 A1 - Greenfield, Samuel R. A1 - Tighe, Scott W. A1 - Bai, Yu A1 - Goerlitz, David S. A1 - Von Turkovich, Michele A1 - Taatjes, Douglas J. A1 - Dragon, Julie A. A1 - Johnson, Sarah Stewart KW - Antarctica KW - Biosignatures KW - Microbes KW - Paleolakes KW - SEM AB - The extremely cold and arid conditions of Antarctica make it uniquely positioned to investigate fundamental questions regarding the persistence of life in extreme environments. Within the McMurdo Dry Valleys and surrounding mountain ranges are multiple ancient relict lakes, paleolakes, with lacustrine deposits spanning from thousands to millions of years in age. Here we present data from light microscopy, scanning electron microscopy, electron dispersive x-ray spectroscopy, and radiocarbon dating to catalog the remarkable range of life preserved within these deposits. This includes intact microbes and nanobacteria-sized cocci, CaCO3 precipitations consistent with biogenic calcium, previously undescribed net-like structures, possible dormant spores, and long-extinct yet exquisitely preserved non-vascular plants. These images provide an important reference for further microbiome investigations of Antarctic paleolake samples. In addition, these findings may provide a visual reference for the use of subsurface groundwater microbial communities as an analog for paleolake subsurface water on planets such as Mars. VL - 131 UR - https://linkinghub.elsevier.com/retrieve/pii/S0968432819304160 ER - TY - JOUR T1 - Life history of northern Gulf of Mexico Warsaw grouper Hyporthodus nigritus inferred from otolith radiocarbon analysis JF - PLOS ONE Y1 - 2020 A1 - Barnett, Beverly K. A1 - Chanton, Jeffrey P. A1 - Ahrens, Robert A1 - Thornton, Laura A1 - Patterson, William F. ED - Patterson, Heather M. AB - Warsaw grouper, Hyporthodus nigritus, is a western Atlantic Ocean species typically found at depths between 55 and 525 m. It is listed as a species of concern by the U.S. National Marine Fisheries Service and as near threatened by the International Union for the Conservation of Nature. However, little information exists on the species’ life history in the northern Gulf of Mexico (nGOM) and its stock status in that region is currently unknown. Age of nGOM Warsaw grouper was investigated via opaque zone counts in otolith thin sections (max age = 61 y), and then the bomb 14C chronometer was employed to validate the accuracy of age estimates. Otolith cores (n = 14) were analyzed with accelerator mass spectrometry and resulting Δ14C values overlain on a loess regression computed for a regional coral and known-age red snapper Δ14C time series. Residual analysis between predicted Δ14C values from the loess regression versus Warsaw grouper otolith core Δ14C values indicated no significant difference in the two data series. Therefore, the accuracy of otolith-based aging was validated, which enabled growth and longevity estimates to be made for nGOM Warsaw grouper. Dissolved inorganic carbon (DIC) Δ14C values collected from the nGOM support the inference that juvenile Warsaw grouper occur in shelf waters (<200 m) since DIC Δ14C values in this depth range are enriched in 14C and similar to the Δ14C values from otolith cores. A Bayesian model was fit to fishery-dependent age composition data and produced von Bertalanffy growth function parameters of L1 = 1,533 mm, k = 0.14 y-1, and t0 = 1.82 y. Fishing mortality also was estimated in the model, which resulted in a ratio of fishing to natural mortality of 5.1:1. Overall, study results indicate Warsaw grouper is a long-lived species that is estimated to have experienced significant overfishing in the nGOM, with the age of most landed fish being <10 y. VL - 15 UR - https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0228254 IS - 1 ER - TY - JOUR T1 - Local glaciers record delayed peak Holocene warmth in south Greenland JF - Quaternary Science Reviews Y1 - 2020 A1 - Larocca, Laura J. A1 - Axford, Yarrow A1 - Bjørk, Anders A. A1 - Lasher, G. Everett A1 - Brooks, Jeremy P. KW - Equilibrium-line altitudes KW - Greenland KW - Holocene thermal maximum KW - lake sediments KW - Little ice age KW - Mountain glaciers KW - Paleotemperatures AB - Local glaciers and ice caps (GICs) respond sensitively and quickly, on the scale of decades to centuries, to climate variations. Continuous records of past fluctuations in GIC size provide information on the timing and magnitude of Holocene climate shifts, and a longer-term perspective on 21st century glacier retreat. Although there is broad-scale agreement on millennial-scale trends in Holocene climate variability and fluctuations in local GICs in Greenland, regional variations are only loosely constrained. Here we present three Holocene proglacial lake sediment records from South Greenland, an area with abundant local glaciers but few Holocene-length paleoclimate records. In addition, we use geospatial analysis to model past equilibrium-line altitudes (ELAs) and thereby constrain the magnitude of ablation-season temperature change during the warmest and coolest periods of the Holocene. Physical and geochemical sedimentary characteristics show that two of the proglacial lakes continued to receive glacial meltwater input until ∼7.3 and ∼7.1 ka BP. The survival of local glaciers implies that South Greenland remained relatively cool, and that summer temperatures gradually warmed, but did not warm well beyond 1.2 °C above present in the early Holocene. In the mid-Holocene, from ∼7.1 to 5.5 ka BP, organic sedimentation at these two sites indicates that local glaciers became very small, or more likely melted away completely. The glaciers within the third lake’s catchment melted away prior to ∼5.2 ka BP, as sediments deposited earlier in the Holocene could not be dated at this site. We estimate that summer temperatures increased by at least 1.2–1.8 °C above present by ∼7.3–7.1 ka BP. Our results are consistent with other observations that suggest a north-to-south gradient in the timing of Holocene thermal maximum conditions, with southern Greenland experiencing a delayed warming relative to other regions in Greenland. As summer temperatures cooled in the Neoglacial, our records show that sustained glacier regrowth began ∼3.1 ka BP with glaciers in the southernmost catchment, which at present, receive the most precipitation. In the other two catchments, which host smaller glaciers in a drier environment, regrowth began at ∼1.3 and ∼1.2 ka BP, the timing of which is in agreement with other glacial records from the Arctic Atlantic region. Local glaciers reached their maximum late Holocene extents during a cooler, second phase of the Little Ice Age (LIA) ∼0.2-0.1 ka BP, that we estimate was at least 0.4–0.9 °C cooler than present. Overall, these findings improve understanding of the spatio-temporal dynamics of Holocene glacier and climate change in Greenland, potentially yielding valuable information about their future response. VL - 241 UR - https://www.sciencedirect.com/science/article/pii/S0277379120303838 ER - TY - JOUR T1 - Long-term cultural eutrophication in White and Walden Ponds (Concord, Massachusetts, USA), Thoreau's lakes of light JF - Lake and Reservoir Management Y1 - 2020 A1 - Stager, J. Curt A1 - Harvey, Lydia A1 - Chimileski, Scott KW - diatoms KW - eutrophication KW - paleolimnology KW - reclamation KW - Thoreau KW - Walden AB - Two historically important ponds in the vicinity of Boston, MA, were subjected to a comparative paleolimnological investigation of the timing and causes of eutrophication trends in each. The remarkable clarity of White Pond during the early 19th century led Henry David Thoreau to compare it favorably to nearby Walden Pond, but during the 20th century water quality in both ponds declined. Sediment core studies show that cultural eutrophication began at Walden during the 1930s, but no long-term sediment records have been available for White Pond, which makes it more difficult to determine the history and causes of eutrophication there. Here we use microfossil and geochemical analyses of sediment cores to show that major changes in the diatom community of White Pond began around 1900, when fish stocking commenced and soil erosion due to land use in the watershed increased, and that the trend intensified around 1960 and 1990. We also describe efforts to mitigate eutrophication at White Pond, highlight the ecological importance of benthic vegetation in nutrient cycling, and suggest that threats to water quality in both of these ponds will likely increase due to anticipated climatic changes in the region. UR - https://www.tandfonline.com/doi/full/10.1080/10402381.2020.1839606https://www.tandfonline.com/doi/pdf/10.1080/10402381.2020.1839606 ER - TY - JOUR T1 - Minimum limiting deglacial ages for the out-of-phase Saginaw Lobe of the Laurentide Ice Sheet using optically stimulated luminescence (OSL) and radiocarbon methods JF - Quaternary Research Y1 - 2020 A1 - Fisher, Timothy G. A1 - Dziekan, Mitchell R. A1 - McDonald, Jennifer A1 - Lepper, Kenneth A1 - Loope, Henry M. A1 - McCarthy, Francine M.G. A1 - Curry, B. Brandon KW - Deglaciation KW - Lake sediment cores KW - OSL dating KW - Radiocarbon lag KW - Saginaw Lobe KW - Sturgis Moraine AB - Twenty-four new optically stimulated luminescence (OSL) and radiocarbon ages from sediment cores in nine lakes associated with the Shipshewana and Sturgis moraines in northern Indiana and southern Michigan estimate when recession of the Saginaw Lobe of the Laurentide Ice Sheet was underway in the southern Great Lakes region, USA. Average OSL ages of 23.4 ± 2.2 ka for the Shipshewana Moraine and 19.7 ± 2.2 ka for the Sturgis Moraine are considered minimum limiting deglacial ages for these recessional moraines. The much younger radiocarbon ages are consistent with other regional radiocarbon ages from lakes, and record climate amelioration around ~16.5 cal ka BP. Early recession of the interlobate Saginaw Lobe was well underway by 23.4 ± 2.2 ka, when the adjacent Lake Michigan and Huron-Erie lobes were a few hundred kilometers farther south and near their maximum southerly limits. The results provide the first time constraints when sediment from the Lake Michigan and Huron-Erie lobes began filling the accommodation space left by the Saginaw Lobe. The difference between the oldest radiocarbon and OSL age is 7400 yr for the Shipshewana Moraine and 3400 yr for the Sturgis Moraine. VL - 97 UR - https://www.cambridge.org/core/journals/quaternary-research/article/minimum-limiting-deglacial-ages-for-the-outofphase-saginaw-lobe-of-the-laurentide-ice-sheet-using-optically-stimulated-luminescence-osl-and-radiocarbon-methods/EA67A66F68407581E99D7D3A8F1 ER - TY - JOUR T1 - Multiproxy evidence of the Neoglacial expansion of Atlantic Water to eastern Svalbard JF - Climate of the Past Y1 - 2020 A1 - Pawłowska, Joanna A1 - Łącka, Magdalena A1 - Kucharska, Małgorzata A1 - Pawlowski, Jan A1 - Zajączkowski, Marek AB - The main goal of this study is to reconstruct the paleoceanographic development of Storfjorden during the Neoglacial (∼4 cal ka BP). Storfjorden is one of the most important brine factories in the European Arctic and is responsible for deepwater production. Moreover, it is a climate-sensitive area influenced by two contrasting water masses: warm and saline Atlantic Water (AW) and cold and fresh Arctic Water (ArW). Herein, a multiproxy approach was applied to provide evidence for existing interactions between the inflow of AW and sea ice coverage, which are the major drivers of environmental changes in Storfjorden. The sedimentary and microfossil records indicate that a major reorganization of oceanographic conditions in Storfjorden occurred at ∼2.7 cal ka BP. The cold conditions and the less pronounced presence of AW in Storfjorden during the early phase of the Neoglacial were the prerequisite conditions for the formation of extensive sea ice cover. The period after ∼2.7 cal ka BP was characterized by alternating short-term cooling and warming intervals. Warming was associated with pulsed inflows of AW and sea ice melting that stimulated phytoplankton blooms and organic matter supply to the bottom. The cold phases were characterized by heavy and densely packed sea ice, resulting in decreased productivity. The ancient environmental DNA (aDNA) records of foraminifera and diatoms support the occurrence of the major pulses of AW (∼2.3 and ∼1.7 cal ka BP) and the variations in sea ice cover. The episodes of enhanced AW inflow were marked by an increase in the percentage of DNA sequences of monothalamous foraminifera associated with the presence of fresh phytodetritus. Cold and less productive intervals were marked by an increased proportion of monothalamous taxa known only from environmental sequencing. The diatom aDNA record indicates that primary production was continuous during the Neoglacial, regardless of the sea ice conditions. However, the colder periods were characterized by the presence of diatom taxa associated with sea ice, whereas the present-day diatom assemblage is dominated by open-water taxa. VL - 16 UR - https://cp.copernicus.org/articles/16/487/2020/ IS - 2 ER - TY - JOUR T1 - Neotectonic and Paleoseismic Analysis of the Northwest Extent of Holocene Surface Deformation along the Meers Fault, OklahomaABSTRACT JF - Bulletin of the Seismological Society of America Y1 - 2020 A1 - Hornsby, Kristofer T. A1 - Streig, Ashley R. A1 - Bennett, Scott E. K. A1 - Chang, Jefferson C. A1 - Mahan, Shannon AB - The Meers fault (Oklahoma) is one of few seismogenic structures with evidence for Holocene surface rupture in the stable continental region of North America. The 37-kilometer-long southeast section of the full 54-kilometer-long Meers fault is interpreted to be Holocene active. The 17-kilometer-long northwest section is considered Quaternary active, but not Holocene active.We reevaluate surface expression and earthquake timing of the northwest Meers fault to improve seismic source characterization.We use airborne light detection and ranging and historical stereo paired aerial photos to evaluate the fault scarp and local fault zone geomorphology. In the northwest, complex surface deformation includes fault splays, subtle monoclinal warping, and a minor change in fault strike. We interpret that the along strike transition from surface faulting on the southeast Meers fault to surface folding on the northwest Meers fault occurs at the lithologic contact between Permian Post Oak conglomerate and Hennessey shale. We excavated a paleoseismic trench to evaluate the timing of surface-deforming earthquakes on the northwest section of the fault. The excavation revealed weathered Permian Hennessey shale and an ∼1–2-meter-thick veneer of Holocene alluvial deposits that were progressively deformed during two surface-folding earthquakes likely related to blind fault rupture beneath the site. Repeated onlapping to overlapping stratigraphic sequences and associated unconformities are intimately related to folding events along the monocline. OxCal paleoearthquake age modeling indicates that earthquakes occurred 4704–3109 yr B.P. and 5955–4744 yr B.P., and that part of the northwest section of the Meers fault is Holocene active. We find the Holocene-active section of the Meers fault should be lengthened 6.1 km to the northwest, to a total Holocene-active fault length of 43 km. Empirical scaling relationships between surface rupture length and magnitude reveal that the fault could generate an Mw 7.0 earthquake. VL - 110 UR - https://pubs.er.usgs.gov/publication/70208517 IS - 1 ER - TY - JOUR T1 - A new 30,000-year chronology for rapidly deposited sediments on the Lomonosov Ridge using bulk radiocarbon dating and probabilistic stratigraphic alignment JF - Geochronology Y1 - 2020 A1 - Muschitiello, Francesco A1 - O'Regan, Matt A1 - Martens, Jannik A1 - West, Gabriel A1 - Gustafsson, Örjan A1 - Jakobsson, Martin AB - We present a new marine chronostratigraphy from a high-accumulation rate Arctic Ocean core at the intersection of the Lomonosov Ridge and the Siberian margin, spanning the last ∼ 30 kyr. The chronology was derived using a combination of bulk 14C dating and stratigraphic correlation to Greenland ice-core records. This was achieved by applying an appositely developed Markov chain Monte Carlo algorithm for Bayesian probabilistic alignment of proxy records. The algorithm simulates depositionally realistic alignments that are consistent with the available radiocarbon age estimates and allows deriving uncertainty bands associated with the inferred alignment. Current composite chronologies from this region are reasonably consistent with our age model during the Holocene and the later part of deglaciation. However, prior to ∼ 14 kyr BP they yield too old age estimates with offsets that linearly increase up to ∼ 40 kyr near the onset of Marine Isotope Stage (MIS) 2. Our results challenge the robustness of previous regional chronostratigraphies and provide a new stratotype for correlation of sediment cores from this sector of the Lomonosov Ridge and East Siberian slope. In particular, they call for a re-interpretation of events in recent sea-ice proxy reconstructions (Xiao et al., 2015) inaccurately attributed to MIS 3 and the Last Glacial Maximum. VL - 2 UR - https://gchron.copernicus.org/articles/2/81/2020/ IS - 1 ER - TY - JOUR T1 - “New” cyanobacterial blooms are not new: two centuries of lake production are related to ice cover and land use JF - Ecosphere Y1 - 2020 A1 - Ewing, Holly A. A1 - Weathers, Kathleen C. A1 - Cottingham, Kathryn L. A1 - Leavitt, Peter R. A1 - Greer, Meredith L. A1 - Carey, Cayelan C. A1 - Steele, Bethel G. A1 - Fiorillo, Alyeska U. A1 - Sowles, John P. KW - agriculture KW - basin morphometry KW - Cyanobacteria KW - eutrophication KW - Gloeotrichia KW - ice-out KW - land use KW - Maine KW - New Hampshire KW - paleoecology KW - Sediment chemistry KW - watershed AB - Recent cyanobacterial blooms in otherwise unproductive lakes may be warning signs of impending eutrophication in lakes important for recreation and drinking water, but little is known of their historical precedence or mechanisms of regulation. Here, we examined long-term sedimentary records of both general and taxon-specific trophic proxies from seven lakes of varying productivity in the northeastern United States to investigate their relationship to historical in-lake, watershed, and climatic drivers of trophic status. Analysis of fossil pigments (carotenoids and chlorophylls) revealed variable patterns of past primary production across lakes over two centuries despite broadly similar changes in regional climate and land use. Sediment abundance of the cyanobacteriumGloeotrichia,a large, toxic, nitrogen-fixing taxon common in recent blooms in this region, revealed that this was not a new taxon in the phytoplankton communities but rather had been present for centuries. Histories ofGloeotrichiaabundance differed strikingly across lakes and were not consistently associated with most other sediment proxies of trophic status. Changes in ice cover most often coincided with changes in fossil pigments, and changes in watershed land use were often related to changes inGloeotrichiaabundance, although no single climatic or land-use factor was associated with proxy changes across all seven lakes. The degree to which changes in lake sediment records co-occurred with changes in the timing of ice-out or agricultural land use was negatively correlated with the ratio of watershed area to lake area. Thus, both climate and land management appeared to play key roles in regulation of primary production in these lakes, although the manner in which these factors influenced lakes was mediated by catchment morphometry. Improved understanding of the past interactions between climate change, land use, landscape setting, and water quality underscores the complexity of mechanisms regulating lake and cyanobacterial production and highlights the necessity of considering these interactions-rather than searching for a singular mechanism-when evaluating the causes of ongoing changes in low-nutrient lakes. VL - 11 UR - https://esajournals.onlinelibrary.wiley.com/doi/full/10.1002/ecs2.3170 IS - 6 ER - TY - JOUR T1 - Origin of Groundwater Arsenic in a Rural Pleistocene Aquifer in Bangladesh Depressurized by Distal Municipal Pumping JF - Water Resources Research Y1 - 2020 A1 - Mozumder, M. R. H. A1 - Michael, H. A. A1 - Mihajlov, I. A1 - Khan, M. R. A1 - Knappett, P. S. K. A1 - Bostick, B. C. A1 - Mailloux, B. J. A1 - Ahmed, K. M. A1 - Choudhury, I. A1 - Koffman, T. A1 - Ellis, T. A1 - Whaley‐Martin, K. A1 - San Pedro, R. A1 - Slater, G. A1 - Stute, M. A1 - Schlosser, P. A1 - Geen, A. KW - Arsenic KW - Dhaka Bangladesh KW - groundwater pumping KW - modeling AB - Across South Asia, millions of villagers have reduced their exposure to high‐arsenic (As) groundwater by switching to low‐As wells. Isotopic tracers and flow modeling are used in this study to understand the groundwater flow system of a semi‐confined aquifer of Pleistocene (>10 kyr) age in Bangladesh that is generally low in As but has been perturbed by massive pumping at a distance of about 25 km for the municipal water supply of Dhaka. A 10‐ to 15‐m‐thick clay aquitard caps much of the intermediate aquifer (>40‐ to 90‐m depth) in the 3‐km2 study area, with some interruptions by younger channel sand deposits indicative of river scouring. Hydraulic heads in the intermediate aquifer below the clay‐capped areas are 1–2 m lower than in the high‐As shallow aquifer above the clay layer. In contrast, similar heads in the shallow and intermediate aquifer are observed where the clay layer is missing. The head distribution suggests a pattern of downward flow through interruptions in the aquitard and lateral advection from the sandy areas to the confined portion of the aquifer. The interpreted flow system is consistent with 3H‐3He ages, stable isotope data, and groundwater flow modeling. Lateral flow could explain an association of elevated As with high methane concentrations within layers of gray sand below certain clay‐capped portions of the Pleistocene aquifer. An influx of dissolved organic carbon from the clay layer itself leading to a reduction of initially orange sands has also likely contributed to the rise of As. VL - 56 UR - https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2020WR027178 IS - 7 ER - TY - JOUR T1 - Otolith‐Based Age Estimates of Alligator Gar Assessed Using Bomb Radiocarbon Dating to Greater than 60 Years JF - North American Journal of Fisheries Management Y1 - 2020 A1 - Daugherty, Daniel J. A1 - Andrews, Allen H. A1 - Smith, Nathan G. AB - Considerable efforts have been undertaken to characterize population dynamics of the Alligator Gar Atractosteus spatula. Accomplishing this task required identification of suitable structures to estimate age. Buckmeier et al. (2012) validated sagittal otoliths to 31 years—the oldest fish in their study. However, they noted that interpreting annuli became increasingly difficult with age and cautioned that difficulties may result in underestimates of age for older fish. In recent years, sampling efforts have resulted in the collection of otoliths from a number of large (>1,800 mm TL) individuals. Age estimates of these fish ranged to 68 years; however, the accuracy of these ages was unknown. Therefore, we used bomb radiocarbon dating to assess accuracy. The technique measures the time‐specific increase in the radioactive carbon isotope (14C) in calcified aging structures resulting from the testing of thermonuclear devices in the 1950s and 1960s. An abrupt, worldwide increase in environmental radiocarbon occurred in approximately 1958 and acts as a time stamp, providing a reliable means of corroborating the age estimates of long‐lived fishes. Core material (i.e., hatch year), along with a subsample from early growth years, was extracted from the otoliths of 24 Alligator Gar (1,805 to 2,540 mm TL) and analyzed for Δ14C. Estimated age from growth zone counting ranged from 26 to 68 years, corresponding to hatch years spanning from 1946 to 1989. Otolith Δ14C was then plotted against the corresponding hatch years and compared to reference curves for environmental 14C levels across time. Despite evidence of regionally specific trends attributed to differences in groundwater and surface inflows, Δ14C levels in the otoliths were highly correlated with reference data, indicating that age estimates were accurate to within a few years. Thus, our results extend the utility of methods developed by Buckmeier et al. (2012) for Alligator Gar in excess of 60 years and provide greater insight on longevity. VL - 40 UR - https://afspubs.onlinelibrary.wiley.com/doi/full/10.1002/nafm.10390 IS - 3 ER - TY - JOUR T1 - Paleoenvironmental context for the Late Pleistocene appearance of Didymosphenia in a North American alpine lake JF - Aquatic Sciences Y1 - 2020 A1 - Spaulding, Sarah A. A1 - Stone, Jeffery R. A1 - Norton, Stephen A. A1 - Nurse, Andrea A1 - Saros, Jasmine E. AB - The nuisance species Didymosphenia geminata is thought to have been spread by humans across North and South America and New Zealand. This diatom is of interest for its ability to form thick benthic mats in streams, altering ecosystem properties. Little is known, however, about its historic distribution and the parameters that are associated with its growth in absence of human influence. Although it is considered to be native to Arctic regions, its status at lower latitudes is uncertain. We measured the concentration of D. geminata cells in a sediment core from Beauty Lake, WY, a record that dates back to the Late Pleistocene. From approximately 11,233–8750 years before present (ybp), a Didymosphenia maximum persisted, with peak concentrations of 3774±20 valves/mg dry sediment (9985 ybp). The period corresponded to low flux of Al, Fe, and P within the sediments, supporting the importance of low P in controlling distribution. Furthermore, we demonstrate that D. geminata arrived in Beauty Lake shortly after deglaciation of the watershed. This species arrived without the aid of human introduction, implying an inherent ability for dispersal. We also examined the sediment record of nearby Yellowstone Lake, WY for the presence of D. geminata during the same time interval, but cells were not detected. The Yellowstone caldera is composed of rhyolite, a rock rich in silica (Si) and modest amounts of P. We conclude that both watersheds were exposed to the potential colonization by D. geminata, but just as the North Island of New Zealand has not been able to support this diatom because of P concentrations exceeding a threshold, the Yellowstone watershed is not able to support it either. VL - 82 UR - http://link.springer.com/10.1007/s00027-019-0681-9 IS - 1 ER - TY - JOUR T1 - Permafrost Hydrology Drives the Assimilation of Old Carbon by Stream Food Webs in the Arctic JF - Ecosystems Y1 - 2020 A1 - O’Donnell, Jonathan A. A1 - Carey, Michael P. A1 - Koch, Joshua C. A1 - Xu, Xiaomei A1 - Poulin, Brett A. A1 - Walker, Jennifer A1 - Zimmerman, Christian E. AB - Permafrost thaw in the Arctic is mobilizing old carbon (C) from soils to aquatic ecosystems and the atmosphere. Little is known, however, about the assimilation of old C by aquatic food webs in Arctic watersheds. Here, we used C isotopes (δ13C, Δ14C) to quantify C assimilation by biota across 12 streams in arctic Alaska. Streams spanned watersheds with varying permafrost hydrology, from ice-poor bedrock to ice-rich loess (that is, yedoma). We measured isotopic content of (1) C sources including dissolved organic C (DOC), dissolved inorganic C (DIC), and soil C, and (2) stream biota, including benthic biofilm and macroinvertebrates, and resident fish species (Arctic Grayling (Thymallus arcticus) and Dolly Varden (Salvelinus malma)). Findings document the assimilation of old C by stream biota, with depleted Δ14C values observed at multiple trophic levels, including benthic biofilm (14C ages = 5255 to 265 years before present (y BP)), macroinvertebrates (4490 y BP to modern), and fish (3195 y BP to modern). Mixing model results indicate that DOC and DIC contribute to benthic biofilm composition, with relative contributions differing across streams draining ice-poor and ice-rich terrain. DOC originates primarily from old terrestrial C sources, including deep peat horizons (39–47%; 530 y BP) and near-surface permafrost (12–19%; 5490 y BP). DOC also accounts for approximately half of fish isotopic composition. Analyses suggest that as the contribution of old C to fish increases, fish growth and nutritional status decline. We anticipate increases in old DOC delivery to streams under projected warming, which may further alter food web function in Arctic watersheds. VL - 23 UR - https://link.springer.com/article/10.1007%2Fs10021-019-00413-6 IS - 2 ER - TY - JOUR T1 - Provenance of terrigenous sediments in the central Bay of Bengal and its relationship to climate changes since 25 ka JF - Progress in Earth and Planetary Science Y1 - 2020 A1 - Li, Jingrui A1 - Liu, Shengfa A1 - Shi, Xuefa A1 - Chen, Min-Te A1 - Zhang, Hui A1 - Zhu, Aimei A1 - Cui, Jingjing A1 - Khokiattiwong, Somkiat A1 - Kornkanitnan, Narumol AB - Lithogenic grain-size, geochemical elements of core sediments from the central Bay of Bengal (BoB) were analyzed to identify sediment provenance and explore the regional “source-sink” processes since 25 ka. Based on the geochemical compositions of core BoB-88, relative contributions of three end-member sources (Himalayan, Myanmar, Indian Peninsula) were calculated and support the general understanding that Himalayan sources were dominant since the last glacial period, which could reach 70% on average in our study. However, sediments from the Indian Peninsula and Myanmar also contributed nonnegligible materials to the central BoB since 25 ka, especially the former shows an obvious increase since 7.5 ka, which was neglected in the previous studies. To trace the sedimentary processes of different provenance terrigenous materials and reveal their response to climate changes, four typical stages with obvious provenance percent variation, including the Last Glacial Maximum period (LGM), Heinrich 1 (H1), Early Holocene Climate Optimum (EHCO), and mid-late Holocene period, were highlighted and discussed. Sea-level change played a dominant role in the glacial-interglacial scale by controlling the transition of deposition center between the shelf/subaquatic delta and the Bengal Fan, especially for sediment from the Himalayan source, exerting influence on contributions from different provenance end-members between the Holocene and the last glacial period. The opposite directions of the southwest and northeast monsoon current in the BoB have a significant influence on the transfer of the Indian Peninsula and Myanmar materials to the studied core, which led to an increase of up to 11% than the average of the Indian Peninsula and a decrease of up to 9% than the average of the Myanmar source during the Holocene. The balance between sea level (limited transport to the deep sea) and ISM (improved erosion production and output to the BoB) during the mid-late Holocene period maintained the stability of Himalayan source percent. Due to the control of the ISM variations, the Himalayan source showed a decrease of up to 20% and 21% than average during the LGM and H1 period, respectively, and an increase of up to 14% than average during the EHCO. The Myanmar source exhibited fluctuations around the average value during the LGM period, but an obvious increase of up to 21% during the H1 period and a decrease up to 8% during the EHCO, while the Indian Peninsula source percent showed little variations during the LGM and H1, but a decrease of up to 6% during the EHCO. Obvious 1/4 processional and millennial periodic changes (5.0 kyr and 1.1 kyr) of contribution proportions from three end-members provide additional evidences for the climate control on the regional source-sink processes and proved the controlled mechanisms of the orbital parameters and possible influence from the solar activity on millennial scales. VL - 7 UR - https://progearthplanetsci.springeropen.com/articles/10.1186/s40645-020-00328-0 IS - 1 ER - TY - DATA T1 - Radiocarbon dating of deep-sea black corals collected off the southeastern United States Y1 - 2020 A1 - Prouty, Nancy G A1 - Schiff, John A1 - Roark, E. Brendan KW - Ecology KW - Geochemistry KW - marine geology AB - Results of radiocarbon dating of deep-sea (500 m to 700 m) black corals are presented. These corals were collected off the southeastern United States as part of the Southeastern United States Deep-Sea Corals (SEADESC) Initiative. PB - U.S. Geological Survey UR - https://www.sciencebase.gov/catalog/item/5f36d30982cee144fb3874bc ER - TY - JOUR T1 - RADIOCARBON RESERVOIR AGES IN THE HOLOCENE DEAD SEAABSTRACT JF - Radiocarbon Y1 - 2020 A1 - Weber, Nurit A1 - Lazar, Boaz A1 - Stern, Ofra A1 - Burr, George A1 - Gavrieli, Ittai A1 - Roberts, Mark A1 - Kurz, Mark D A1 - Yechieli, Yoseph A1 - Stein, Mordechai KW - aragonite KW - Dead Sea KW - Holocene KW - radiocarbon KW - reservoir ages AB - The sources and fate of radiocarbon (C-14) in the Dead Sea hypersaline solution are evaluated with C-14 measurements in organic debris and primary aragonite collected from exposures of the Holocene Ze'elim Formation. The reservoir age (RA) is defined as the difference between the radiocarbon age of the aragonite at time of its precipitation (representing lake's dissolved inorganic carbon pig) and the age of contemporaneous organic debris (representing atmospheric radiocarbon). Evaluation of the data for the past 6000 yr from Dead Sea sediments reveal that the lake's RA decreased from 2890 yr at 6 cal kyr BP to 2300 yr at present. The RA lies at similar to 2400 yr during the past 3000 yr, when the lake was characterized by continuous deposition of primary aragonite, which implies a continuous supply of freshwater-bicarbonate into the lake. This process reflects the overall stability of the hydrological-climate conditions in the lake's watershed during the late Holocene where bicarbonate originated from dissolution of the surface cover in the watershed that was transported to the Dead Sea by the freshwater runoff. An excellent correlation (R-2=0.98) exists between aragonite ages and contemporaneous organic debris, allowing the estimation of ages of various primary deposits where organic debris are not available. VL - 62 UR - https://apps.webofknowledge.com/InboundService.do?product=WOS&Func=Frame&DestFail=http%3A%2F%2Fwww.webofknowledge.com&SrcApp=search&SrcAuth=Alerting&SID=8AkJOJLKFU3j5nkGaRI&customersID=Alerting&mode=FullRecord&IsProductCode=Yes&AlertId=4d48b20a-7d27-4fa2- IS - 5 ER - TY - JOUR T1 - Ramped thermal analysis for isolating biologically meaningful soil organic matter fractions with distinct residence times JF - SOIL Y1 - 2020 A1 - Sanderman, Jonathan A1 - Grandy, A. Stuart AB - In this work, we assess whether or not ramped thermal oxidation coupled with determination of the radiocarbon content of the evolved CO2 can be used to isolate distinct thermal fractions of soil organic matter (SOM) along with direct information on the turnover rate of each thermal fraction. Using a 30-year time series of soil samples from a well-characterized agronomic trial, we found that the incorporation of the bomb spike in atmospheric 14CO2 into thermal fractions of increasing resistance to thermal decomposition could be successfully modeled. With increasing temperature, which is proportional to activation energy, the mean residence time of the thermal fractions increased from 10 to 400 years. Importantly, the first four of five thermal fractions appeared to be a mixture of fast- and increasingly slower-cycling SOM. To further understand the composition of different thermal fractions, stepped pyrolysis–gas chromatography–mass spectrometry (Py-GC/MS) experiments were performed at five temperatures ranging from 330 to 735 ∘C. The Py-GC/MS data showed a reproducible shift in the chemistry of pyrolysis products across the temperature gradient trending from polysaccharides and lipids at low temperature to lignin- and microbe-derived compounds at middle temperatures to aromatic and unknown compounds at the highest temperatures. Integrating the 14C and Py-GC/MS data suggests the organic compounds, with the exception of aromatic moieties likely derived from wildfire, with centennial residence times are not more complex but may be protected from pyrolysis, and likely also from biological mineralization, by interactions with mineral surfaces. VL - 6 UR - https://soil.copernicus.org/articles/6/131/2020/ IS - 1 ER - TY - JOUR T1 - A refined age calibrated paleosecular variation and relative paleointensity stack for the NW Barents Sea: Implication for geomagnetic field behavior during the Holocene JF - Quaternary Science Reviews Y1 - 2020 A1 - Caricchi, C. A1 - Sagnotti, L. A1 - Campuzano, S.A. A1 - Lucchi, R.G. A1 - MacrÌ, P. A1 - Rebesco, M. A1 - Camerlenghi, A. KW - Arctic region KW - Barents Sea KW - Geomagnetic paleosecular variation KW - Holocene KW - marine sediment cores KW - Paleomagnetism KW - Relative paleointensity AB - Reconstruction of Paleomagnetic Secular Variation (PSV) of the geomagnetic field is fundamental both to assess geodynamo models and to obtain age constraints for rocks, sediments and archaeological material. We present refined age-calibrated Holocene PSV and relative paleointensity (RPI) stack curves derived from Arctic marine sediments (Northwestern Barents Sea). The Holocene sections of four sedimentary cores were correlated on the basis of paleomagnetic trends and age models, and stacked. The resultant composite PSV and RPI Holocene records (NBS stack) and the reconstructed Holocene Virtual Geomagnetic Pole (VGP) path were evaluated in comparison with the most recent paleomagnetic stack curves and geomagnetic field models. The data indicate that during the Holocene time, the VGPs moved within the superficial projection of the inner core tangent cylinder, with the exception of short time intervals around 5600 and 3200 cal yr BP when VGPs extended to lower latitudes. These deviations might reflect regional geomagnetic features, such as persistent geomagnetic flux lobes at core-mantle boundary. Our data confirm that the large VGP shift observed around 5600 cal yr BP is the result of an increased radial magnetic field at the core-mantle boundary over North America, whilst the VGP shift around 3200 cal yr BP represents a major swing to middle latitudes toward the Middle East and might be associated to a regional high paleointensity peak, known as Levantine Iron Age Anomaly (LIAA). VL - 229 UR - https://linkinghub.elsevier.com/retrieve/pii/S0277379119306869 ER - TY - JOUR T1 - The relation of geogenic contaminants to groundwater age, aquifer hydrologic position, water type, and redox conditions in Atlantic and Gulf Coastal Plain aquifers, eastern and south-central USA JF - Science of The Total Environment Y1 - 2020 A1 - Degnan, James R. A1 - Lindsey, Bruce D. A1 - Levitt, Joseph P. A1 - Szabo, Zoltan KW - Arsenic KW - Fluoride KW - Iron KW - Lead-210 KW - pH KW - Polonium-210 AB - Groundwater age distributions developed from carbon-14 (14C), tritium (3H), and helium-4 (4He) concentrations, along with aquifer hydrologic position, water type, and redox conditions, were compared to geogenic contaminants of concern (GCOC) from 252 public-supply wells in six Atlantic and Gulf Coastal Plain unconsolidated-sediment aquifers. Concentrations of one or more GCOCs in 168 (67%) wells exceeded MCLs (maximum contaminant levels), SMCLs (secondary MCLs), or HBSLs (health-based screening levels). Human-health benchmark thresholds (MCLs or HBSLs) were exceeded in 31 (12%) wells, and included 0.8% for fluoride (F), 2.4% for arsenic (As), 4% for lead-210 (210Pb), and 6.7% for polonium-210 (210Po). Values of pH increase with age and were outside the SMCL in 31% of wells (23% < 6.5 and 7.5% > 8.5, SMCL). Among GCOCs with concentrations that increased significantly with groundwater age, the frequency of sentry threshold exceedances (i.e., one-half of MCL, SMCL, or HBSL) included 40% for dissolved solids (DS), 12% for chloride (Cl), 3.6% for F, 4.4% for As, and 9.5% for 210Po. Iron (Fe) concentrations did not correlate with groundwater age, but exceeded sentry thresholds in 29% of wells. Groundwater age, water types, redox, pH, and GCOCs varied because of unique hydrogeologic features of the aquifers (recharge locations and geometry). As expected, primarily confined aquifers had young, oxic, low to near-neutral pH water near the outcrop (recharge area), and older, reduced, high pH water deeper and farther along flow paths. However, unique aquifer hydrogeologic conditions, such as multiple-recharge zones produced anomalous patterns of young and old groundwater at varying depths and locations along flow paths. Evidence for this variability is seen in disequilibrium patterns in the progression of the chemical evolution of groundwater with hydrologic position. When hydrogeologic differences are considered, groundwater age combined with hydrologic-position data, can provide a strong basis for inferring potential occurrence of GCOCs. VL - 723 SN - 0048-9697 UR - https://www.sciencedirect.com/science/article/pii/S0048969720313474 JO - Science of The Total Environment ER - TY - JOUR T1 - Removal of Refractory Dissolved Organic Carbon in the Amundsen Sea, Antarctica JF - Scientific Reports Y1 - 2020 A1 - Fang, Ling A1 - Lee, SangHoon A1 - Lee, Shin-Ah A1 - Hahm, Doshik A1 - Kim, Guebuem A1 - Druffel, Ellen R. M. A1 - Hwang, Jeomshik KW - CIRCUMPOLAR DEEP-WATER KW - cycle KW - DOC KW - glaciers KW - INFLOW KW - MATTER KW - pacific KW - phytoplankton KW - poc KW - radiocarbon AB - The removal mechanism of refractory deep-ocean dissolved organic carbon (deep-DOC) is poorly understood. The Amundsen Sea Polynya (ASP) serves as a natural test basin for assessing the fate of deep-DOC when it is supplied with a large amount of fresh-DOC and exposed to strong solar radiation during the polynya opening in austral summer. We measured the radiocarbon content of DOC in the water column on the western Amundsen shelf. The radiocarbon content of DOC in the surface water of the ASP reflected higher primary production than in the region covered by sea ice. The radiocarbon measurements of DOC, taken two years apart in the ASP, were different, suggesting rapid cycling of DOC. The increase in DOC concentration was less than expected from the observed increase in radiocarbon content from those at the greatest depths. Based on a radiocarbon mass balance, we show that deep-DOC is consumed along with fresh-DOC in the ASP. Our observations imply that water circulation through the surface layer, where fresh-DOC is produced, may play an important role in global DOC cycling. VL - 10 UR - http://www.nature.com/articles/s41598-020-57870-6http://www.nature.com/articles/s41598-020-57870-6.pdfhttp://www.nature.com/articles/s41598-020-57870-6.pdfhttp://www.nature.com/articles/s41598-020-57870-6 IS - 1 ER - TY - JOUR T1 - Resolving sea ice dynamics in the north-western Ross Sea during the last 2.6 ka: From seasonal to millennial timescales JF - Quaternary Science Reviews Y1 - 2020 A1 - Tesi, T. A1 - Belt, S.T. A1 - Gariboldi, K. A1 - Muschitiello, F. A1 - Smik, L. A1 - Finocchiaro, F. A1 - Giglio, F. A1 - Colizza, E. A1 - Gazzurra, G. A1 - Giordano, P. A1 - Morigi, C. A1 - Capotondi, L. A1 - Nogarotto, A. A1 - Köseoğlu, D. A1 - Di Roberto, A. A1 - Gallerani, A. A1 - Langone, L. KW - Fast ice KW - IPSO25 KW - Laminated sediments KW - Ross Sea KW - Sea ice AB - Time-series analyses of satellite images reveal that sea ice extent in the Ross Sea has experienced significant changes over the last 40 years, likely triggered by large-scale atmospheric anomalies. However, resolving how sea ice in the Ross Sea has changed over longer timeframes has until now remained more elusive. Here we used a laminated sediment piston core (14.6 m) collected from the Edisto inlet (Western Ross Sea) to reconstruct fast ice dynamics over the last 2.6 ka. Our goal was to first understand the climate expression of selected well-defined sediment laminae and then use these characteristics for reconstructing past sea ice behaviour across the whole sedimentary sequence. We used the recently established sea ice diatom biomarker proxy IPSO25 in combination with diatom census counts and bulk analyses. Analyses performed on a suite of discrete laminae revealed statistically significant differences between dark and light laminae reflecting different depositional conditions. Based on their respective biogeochemical fingerprints, we infer that dark laminae accumulated during sea ice thaws in early summer. Under these conditions, laminae contain relatively high concentrations of IPSO25 and display an enriched δ13C composition for the bulk organic matter (OM). While diatom assemblages in dark laminae are relatively homogenous, as the thaw continues later in the summer, Corethron pennatum becomes the dominant diatom species, resulting in the formation of light laminae characterized by low IPSO25 concentrations. Since C. pennatum can migrate vertically through the water column to uptake nutrients and avoid competition in oligotrophic waters, its high concentration likely reflects stratified and ice-free surface waters typical of late summer. Down-core trends show that the correlation between sediment brightness and geochemical fingerprint (i.e., IPSO25 and δ13C) holds throughout the record. Based on the knowledge gained at lamina level, our down-core high-resolution reconstruction shows that the summer fast ice coverage changed dramatically during the late Holocene. Specifically, we conclude that the Edisto inlet experienced regular early summer opening between 2.6 ka, and ca. 0.7 ka, after which, coastal fast ice persisted during summer months and ice-free conditions became less frequent. Comparison with previous regional ice core data suggests that the sudden cooling recorded over the Victoria Land Coast region since 0.7 ka might potentially explain our observation of persistent summer fast ice in the Western Ross Sea. Our study has shown that multi-proxy data derived from laminated sediments can provide hitherto unknown detail regarding past summer sea ice dynamics in coastal Antarctic regions. VL - 237 UR - https://linkinghub.elsevier.com/retrieve/pii/S0277379120302614 ER - TY - JOUR T1 - Response of shallow-sea benthic foraminifera to environmental changes off the coast of Goa, eastern Arabian Sea, during the last ∼6100 cal yr BPAbstract JF - Geological Magazine Y1 - 2020 A1 - Saravanan, Ponnusamy A1 - Gupta, Anil K. A1 - Zheng, Hongbo A1 - Panigrahi, Mruganka K. A1 - Tiwari, Sameer K. A1 - Rai, Santosh K. A1 - Prakasam, Muthusamy KW - arabian sea KW - benthic foraminifera KW - Indian monsoon KW - Stable isotopes KW - western continental margin of India AB - We have analysed a 6100-year record of benthic and planktonic foraminifera from inner neritic sediments from Core SK291/GC13, off the Goa coast, eastern Arabian Sea, to understand the response of benthic foraminifera to shallow-marine processes. The benthic foraminiferal assemblage is dominated by Nonion cf. asterizans, Ammonia beccarii, A. gaimardii and Virgulinella fragilis, which have been selected on the basis of a population of 10% or more in any three samples analysed. The planktonic foraminiferal population is sporadic and rare, with Globigerinoides ruber as the predominant species showing a variable trend. The foraminiferal proxies combined with total organic carbon (wt%) and δ13C and δ18O values of Ammonia gaimardii suggest distinct variations, indicating changes in productivity and salinity in the shallow eastern Arabian Sea. The coastal waters off Goa were relatively warmer and less saline between 6100 and 4600, or perhaps to 4200, calibrated years before the present (cal yr BP), corresponding to a stronger monsoon in South and East Asia. The shallow sea was cooler from ~4200 to 2600 cal yr BP in the study area, coinciding with a lower sea surface temperature in the northeastern Arabian Sea and an arid phase in the Indian subcontinent. From 2900 to 2600 cal yr BP the study core exhibits the impacts of short-term cold events, which have earlier been observed in the northeastern Arabian Sea, off Pakistan. During the Little Ice Age, the shallow sea off Goa was less productive. VL - 157 UR - https://www.cambridge.org/core/product/identifier/S0016756819000979/type/journal_article IS - 3 ER - TY - JOUR T1 - Sedimentary evidence of prehistoric distant‐source tsunamis in the Hawaiian Islands JF - Sedimentology Y1 - 2020 A1 - La Selle, SeanPaul A1 - Richmond, Bruce M. A1 - Jaffe, Bruce E. A1 - Nelson, Alan R. A1 - Griswold, Frances R. A1 - Arcos, Maria E. M. A1 - Chagué, Catherine A1 - Bishop, James M. A1 - Bellanova, Piero A1 - Kane, Haunani H. A1 - Lunghino, Brent D. A1 - Gelfenbaum, Guy ED - Costa, Pedro KW - Aleutians KW - deposit KW - distant source KW - extreme events KW - Hawai΄i KW - palaeotsunami AB - Over the past 200 years of written records, the Hawaiian Islands have experienced tens of tsunamis generated by earthquakes in the subduction zones of the Pacific ‘Ring of Fire’ (for example, Alaska–Aleutian, Kuril–Kamchatka, Chile and Japan). Mapping and dating anomalous beds of sand and silt deposited by tsunamis in low‐lying areas along Pacific coasts, even those distant from subduction zones, is critical for assessing tsunami hazard throughout the Pacific basin. This study searched for evidence of tsunami inundation using stratigraphic and sedimentological analyses of potential tsunami deposits beneath present and former Hawaiian wetlands, coastal lagoons, and river floodplains. Coastal wetland sites on the islands of Hawai΄i, Maui, O΄ahu and Kaua΄i were selected based on historical tsunami runup, numerical inundation modelling, proximity to sandy source sediments, degree of historical wetland disturbance, and breadth of prior geological and archaeological investigations. Sand beds containing marine calcareous sediment within peaty and/or muddy wetland deposits on the north and north‐eastern shores of Kaua΄i, O΄ahu and Hawai΄i were interpreted as tsunami deposits. At some sites, deposits of the 1946 and 1957 Aleutian tsunamis are analogues for deeper, older probable tsunami deposits. Radiocarbon‐based age models date sand beds from three sites to ca 700 to 500 cal yr bp, which overlaps ages for tsunami deposits in the eastern Aleutian Islands that record a local subduction zone earthquake. The overlapping modelled ages for tsunami deposits at the study sites support a plausible correlation with an eastern Aleutian earthquake source for a large prehistoric tsunami in the Hawaiian Islands. VL - 67 UR - https://onlinelibrary.wiley.com/doi/10.1111/sed.12623 IS - 3 ER - TY - ABST T1 - Silicified wood from around Old Faithful Geyser, Yellowstone National Park: U.S. Geological Survey data release Y1 - 2020 A1 - Hurwitz, Shaul A1 - Peek, Sara E A1 - Pigati, Jeff A1 - Honke, Jeff A1 - Damby, David E A1 - Stricker, Craig A A1 - King, John AB - Radiocarbon dating of silicified wood was performed at the U.S. Geological Survey’s Radiocarbon Laboratory in Denver, Colorado. All samples were chemically treated using the standard acid-base-acid (ABA) procedure before being combusted online in the presence of excess high-purity oxygen. Water and other contaminant gases were removed using cryogenic separation techniques, and the resulting purified CO2 gas was measured manometrically and converted to graphite using an iron catalyst and hydrogen reduction (Vogel et al., 1984). Graphite targets were then submitted for accelerator mass spectrometry 14C analysis at the National Ocean Sciences Accelerator Mass Spectrometry facility in Woods Hole, Massachusetts. All 14C ages were calibrated using the IntCal13 dataset and CALIB 7.1html (Stuiver and Reimer, 1993; Reimer et al., 2013). Calibrated age ranges are presented in calibrated years before present (BP; 0 yr BP = 1950 A.D.), and uncertainties are given at the 95% (2sigma) confidence level. Select sub-samples of silicified wood were excised with a stainless-steel razor blade and massed into 4 x 6 mm tin capsules (Costech Analytical, Inc, USA). Stable carbon isotope (δ13C) analysis was conducted by continuous flow-isotope ratio mass spectrometry at the U.S. Geological Survey’s Stable Isotope Laboratory in Denver, Colorado using a Carlo Erba NC1500 interfaced to a Micromass Optima mass spectrometer.  Isotopic data are reported in per mil notation after normalization to VPDB with USGS 40 (δ13C = -26.39 ‰) and USGS 41A (δ13C = 36.55 ‰). This research was conducted under Yellowstone Research Permit YELL-SCI-8030. PB - U.S. Geological Survey UR - https://www.sciencebase.gov/catalog/item/get/5eb9b5ba82ce25b5135d2718 N1 - Type: dataset ER - TY - JOUR T1 - Sources and radiocarbon ages of organic carbon in different grain size fractions of Yellow River-transported particles and coastal sediments JF - Chemical Geology Y1 - 2020 A1 - Ge, Tiantian A1 - Xue, Yuejun A1 - Jiang, Xueyan A1 - Zou, Li A1 - Wang, Xuchen KW - organic matter KW - RadiocarbonStable carbon isotope KW - Sediment grain size KW - Yellow River VL - 534 UR - https://www.sciencedirect.com/science/article/pii/S0009254119305819 ER - TY - JOUR T1 - The southern Gulf of Mexico: A baseline radiocarbon isoscape of surface sediments and isotopic excursions at depth JF - PLOS ONE Y1 - 2020 A1 - Bosman, Samantha H. A1 - Schwing, Patrick T. A1 - Larson, Rebekka A. A1 - Wildermann, Natalie E. A1 - Brooks, Gregg R. A1 - Romero, Isabel C. A1 - Sanchez-Cabeza, Joan-Albert A1 - Ruiz-Fernández, Ana Carolina A1 - Machain-Castillo, Maria Luisa A1 - Gracia, Adolfo A1 - Escobar-Briones, Elva A1 - Murawski, Steven A. A1 - Hollander, David J. A1 - Chanton, Jeffrey P. ED - Potter-McIntyre, Sally KW - Gulf of Mexico KW - hydrocarbons KW - Oil spills KW - Oils KW - Petroleum KW - Sediment AB - The southern Gulf of Mexico (sGoM) is home to an extensive oil recovery and development infrastructure. In addition, the basin harbors sites of submarine hydrocarbon seepage and receives terrestrial inputs from bordering rivers. We used stable carbon, nitrogen, and radiocarbon analyses of bulk sediment organic matter to define the current baseline isoscapes of surface sediments in the sGoM and determined which factors might influence them. These baseline surface isoscapes will be useful for accessing future environmental impacts. We also examined the region for influence of hydrocarbon deposition in the sedimentary record that might be associated with hydrocarbon recovery, spillage and seepage, as was found in the northern Gulf of Mexico (nGoM) following the Deepwater Horizon (DWH) oil spill in 2010. In 1979, the sGoM experienced a major oil spill, Ixtoc 1. Surface sediment δ13C values ranged from -22.4‰ to -19.9‰, while Δ14C values ranged from -337.1‰ to -69.2‰. Sediment δ15N values ranged from 2.8‰ to 7.2‰, while the %C on a carbonate-free basis ranged in value of 0.65% to 3.89% and %N ranged in value of 0.09% to 0.49%. Spatial trends for δ13C and Δ14C were driven by water depth and distance from the coastline, while spatial trends for δ15N were driven by location (latitude and longitude). Location and distance from the coastline were significantly correlated with %C and %N. At depth in two of twenty (10%) core profiles, we found negative δ13C and Δ14C excursions from baseline values in bulk sedimentary organic material, consistent with either oil-residue deposition or terrestrial inputs, but likely the latter. We then used 210Pb dating on those two profiles to determine the time in which the excursion-containing horizons were deposited. Despite the large spill in 1979, no evidence of hydrocarbon residue remained in the sediments from this specific time period. VL - 15 UR - https://www.ncbi.nlm.nih.gov/pubmed/32294128 IS - 4 ER - TY - JOUR T1 - Spatial and temporal variability in Mediterranean climate over the last millennium from vermetid isotope records and CMIP5/PMIP3 models JF - Global and Planetary Change Y1 - 2020 A1 - Amitai, Yael A1 - Yam, Ruth A1 - Montagna, Paolo A1 - Devoti, Saverio A1 - Correa, Matthias López A1 - Shemesh, Aldo AB - Stable isotope compositions of oxygen (delta O-18) and carbon (delta C-1(3)) of the aragonite skeleton of the reef-building gastropod Dendropoma petreaum provide high-resolution records of the Mediterranean climate over the last millennium. In particular, the isotopic composition of vermetid cores collected from the west and east Mediterranean reveals that the different regions have had distinct thermal and primary production behaviors throughout the last millennium. The rate of warming in the recent Industrial Period is variable among the different regions of the Mediterranean Sea. The delta O-18-derived Sea Surface Temperature (SST) anomalies show that the Eastern Mediterranean surface temperature is increasing much more rapidly than in the Western Mediterranean. Additionally, the signals of the Little Ice Age and of the Medieval Climate Anomaly are more apparent in the western and in the central Mediterranean while they are almost absent in the eastern Mediterranean. We aim to reconcile the SST temporal and spatial pattern with the variability of the North Atlantic Oscillation (NAO) and the South Asian Monsoon (SAM) climate systems by analyzing coupled atmosphere-ocean models from the CMIP5/PMIP3 projects that simulate the global climate of the past 1000 years. We show that even though the NAO is more dominant in the western Mediterranean SST, its latitudinal movement, on a centennial time scale, is evident in the eastern Mediterranean SST signal. We also discuss the Atlantic water inflow role in the observed similarities of the surface productivity signals and the Suess effect that prevail the Industrial Period signal in all regions of the Mediterranean. VL - 189 UR - https://doi.org/10.1016/j.gloplacha.2020.103159 ER - TY - JOUR T1 - Stable source of Holocene spring precipitation recorded in leaf wax hydrogen-isotope ratios from two New York lakes JF - Quaternary Science Reviews Y1 - 2020 A1 - Schartman, Anna K. A1 - Diefendorf, Aaron F. A1 - Lowell, Thomas V. A1 - Freimuth, Erika J. A1 - Stewart, Alexander K. A1 - Landis, Joshua D. A1 - Bates, Benjamin R. KW - Holocene KW - Hydrogen isotopes KW - late glacial KW - Leaf wax KW - North America KW - Organic geochemistry KW - paleoclimatology KW - Precipitation sourcing AB - Changes in synoptic atmospheric circulation patterns are thought to play a role in establishing millennial scale climate periods during the end of the late glacial and the Holocene. In the northeastern United States, multi-proxy evidence documents fluctuations in effective moisture and temperatures for this time period, but constraining the relationship between atmospheric processes and these climate regimes is not straightforward. Because the hydrogen-isotope ratios of sedimentary terrestrial leaf waxes can reflect precipitation δD, these long-chain hydrocarbon compounds are an excellent tool to investigate moisture sourcing. Here we present lake sediment and leaf wax carbon- and hydrogen-isotope records that span the past ∼14.0 thousand years from Heart Lake and Moose Pond in the Adirondack Mountains (ADK), New York. High initial lake productivity after basin inception is reflected in low C:N ratios (<15), and higher relative short chain n-alkane (n-C17, n-C19, and n-C21) to long chain n-alkane (n-C27, n-C29 and n-C31) concentration ratios. The Holocene record is characterized by low bulk and n-alkane δ13C (∼ −28‰, ∼ −31‰, respectively), high ACL25-35 (∼28), and high relative concentrations of long chain n-alkane homologues, indicating a dominantly terrestrial source of organic matter for this time period. Hydrogen-isotope ratios of n-C29 n-alkane from both lake basins range only ∼20‰ through the Holocene and reconstructed precipitation δD (δDprecip) from both basins is in good agreement with that of modern modeled spring precipitation. This suggests there may have been no major changes in the sourcing of spring precipitation for the ADK throughout the time of record. VL - 240 UR - https://linkinghub.elsevier.com/retrieve/pii/S027737912030319X ER - TY - JOUR T1 - Two-Phase Synthesis of Taxol JF - Journal of the American Chemical Society Y1 - 2020 A1 - Kanda, Yuzuru A1 - Nakamura, Hugh A1 - Umemiya, Shigenobu A1 - Puthukanoori, Ravi Kumar A1 - Murthy Appala, Venkata Ramana A1 - Gaddamanugu, Gopi Krishna A1 - Paraselli, Bheema Rao A1 - Baran, Phil S. KW - 1ST TOTAL-SYNTHESIS KW - ANALOGS KW - chemistry KW - DIMETHYLDIOXIRANE KW - ENANTIOSELECTIVE TOTAL-SYNTHESIS KW - FORMAL TOTAL-SYNTHESIS KW - PINENE PATH KW - RING KW - STEREOCONTROLLED SYNTHESIS KW - TAXANES AB - Taxol (a brand name for paclitaxel) is widely regarded as among the most famed natural isolates ever discovered, and has been the subject of innumerable studies in both basic and applied science. Its documented success as an anticancer agent, coupled with early concerns over supply, stimulated a furious worldwide effort from chemists to provide a solution for its preparation through total synthesis. Those pioneering studies proved the feasibility of retrosynthetically guided access to synthetic Taxol, albeit in minute quantities and with enormous effort. In practice, all medicinal chemistry efforts and eventual commercialization have relied upon natural (plant material) or biosynthetically derived (synthetic biology) supplies. Here we show how a complementary divergent synthetic approach that is holistically patterned off of biosynthetic machinery for terpene synthesis can be used to arrive at Taxol. VL - 142 UR - https://pubs.acs.org/doi/10.1021/jacs.0c03592 IS - 23 ER - TY - JOUR T1 - Yellowstone's Old Faithful Geyser Shut Down by a Severe Thirteenth Century Drought JF - Geophysical Research Letters Y1 - 2020 A1 - Hurwitz, Shaul A1 - King, John C. A1 - Pederson, Gregory T. A1 - Martin, Justin T. A1 - Damby, David E. A1 - Manga, Michael A1 - Hungerford, Jefferson D. G. A1 - Peek, Sara KW - drought KW - Medieval Climate Anomaly KW - mineralization KW - Old Faithful Geyser KW - radiocarbon KW - Yellowstone AB - To characterize eruption activity of the iconic Old Faithful Geyser in Yellowstone National Park over past centuries, we obtained 41 new radiocarbon dates of mineralized wood preserved in the mound of silica that precipitated from erupted waters. Trees do not grow on active geyser mounds, implying that trees grew on the Old Faithful Geyser mound during a protracted period of eruption quiescence. Rooted stumps and root crowns located on higher parts of the mound are evidence that at the time of tree growth, the geyser mound closely resembled its current appearance. The range of calibrated radiocarbon dates (1233–1362 CE) is coincident with a series of severe multidecadal regional droughts toward the end of the Medieval Climate Anomaly, prior to the onset of the Little Ice Age. Climate models project increasingly severe droughts by mid-21st century, suggesting that geyser eruptions could become less frequent or completely cease. VL - 47 UR - https://onlinelibrary.wiley.com/doi/abs/10.1029/2020GL089871 IS - 20 N1 - _eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1029/2020GL089871 ER - TY - JOUR T1 - A 12,700-year history of paleolimnological change from an Andean microrefugium JF - The Holocene Y1 - 2019 A1 - de Novaes Nascimento, Majoi A1 - Laurenzi, Anne Gail A1 - Valencia, Bryan G A1 - Van, Robert A1 - Bush, Mark KW - Andes KW - diatoms KW - drought KW - enso KW - Holocene KW - limnology KW - microrefugia KW - mid-Holocene dry event KW - paleoecology AB - We present a 12,6700-yr limnological history of Lake Miski, a high-elevation lake in a wet section of the Peruvian Andes. While many shallow Andean lakes dried up during the mid-Holocene, loss-on-ignition, magnetic susceptibility, and diatom analysis showed that Lake Miski was a constant feature in the landscape. Overall, fluctuations in the fossil diatom communities of Lake Miski tracked changes in insolation, but this was not the only mechanism influencing observed variability. We identify periods when insolation and interactions with the Pacific Ocean may have played a role in structuring local climate and diatom assemblages. The true mid-Holocene Dry Event (MHDE) is manifested in this record between 8000 and 5000 cal BP, but the carbonate stratigraphy and the diatom community indicated that although the level of the lake decreased, it never completely dried out, instead there was higher availability of planktic habitat and stronger mixing than in much of the Holocene. High rates of biological change observed during the late-Holocene in other records from Peru associated with human amplification of climatic signals were not observed in Lake Miski, as this lake may have been too wet and remote to be strongly influenced by human activity. Because of the presence of a woodland microrefugium, Lake Miski was suggested to have been an unusually climatically stable and wet location during the regional drying associated with the MHDE. Our new limnological information provides additional insights relating to this discussion. The presence of the observed woodland apparently withstood fluctuations that induced state changes in the lake and diatom flora, underscoring that microrefugia do not equate to ‘unchanging’ hydrologies or climates. VL - 29 UR - http://journals.sagepub.com/doi/10.1177/0959683618810400 IS - 2 ER - TY - JOUR T1 - 14C Blank Corrections for 25–100 μg Samples at the National Ocean Sciences AMS Laboratory JF - Radiocarbon Y1 - 2019 A1 - Roberts, M. L. A1 - Elder, K. L. A1 - Jenkins, W. J. A1 - Gagnon, A. R. A1 - Xu, L. A1 - Hlavenka, J. D. A1 - Longworth, B. E. KW - AMS KW - AMS dating KW - blank corrections AB - Replicate radiocarbon (14C) measurements of organic and inorganic control samples, with known Fraction Modern values in the range Fm = 0–1.5 and mass range 6 μg–2 mg carbon, are used to determine both the mass and radiocarbon content of the blank carbon introduced during sample processing and measurement in our laboratory. These data are used to model, separately for organic and inorganic samples, the blank contribution and subsequently “blank correct” measured unknowns in the mass range 25–100 μg. Data, formulas, and an assessment of the precision and accuracy of the blank correction are presented. VL - 61 SN - 0033-8222, 1945-5755 UR - https://www.cambridge.org/core/journals/radiocarbon/article/14c-blank-corrections-for-25100-g-samples-at-the-national-ocean-sciences-ams-laboratory/494B9CF72445198570213B4A2CC303D0 IS - 5 ER - TY - JOUR T1 - An 1800-year record of environmental change from the southern Adirondack Mountains, New York (USA) JF - Journal of Paleolimnology Y1 - 2019 A1 - Grochocki, Konrad K. A1 - Lane, Chad S. A1 - Stager, Jay Curt AB - We analyzed a sediment core from Piseco Lake, New York (USA), to infer late Holocene environmental conditions and look for evidence of prehistoric human activity in the region. We analyzed fossil pollen, charcoal, and geochemistry in sediments deposited over the last ~ 1800 years. The pollen record indicates the area was dominated primarily by Betula (birch), Pinus (pine), and Tsuga (hemlock). Picea (spruce) increased after ~ 1560 cal yr BP and eventually became a major component of the forest. A transition in the fire regime around Piseco Lake occurred after ~ 900 cal yr BP, perhaps associated with drier conditions during the Medieval Climate Anomaly, ca. 1000–600 BP. A fire ca. 580 cal yr BP, along with decline of Tsuga after ~ 520 cal yr BP, may reflect generally dry conditions of the Little Ice Age (600–150 BP). Climate change may have swamped any evidence for low-intensity, prehistoric human activity around Piseco Lake. The rise in Poaceae (grass) and Ambrosia (ragweed) pollen ~ 130 cal yr BP indicates European settlement in the area, and is followed by rapid decline of Tsuga and Pinus, most likely a consequence of logging. Since about 145 cal yr BP, increases in macroscopic charcoal concentrations and changes in sediment geochemistry indicate increased erosion and nutrient influx to Piseco Lake, likely related to anthropogenic activities. VL - 62 UR - http://link.springer.com/10.1007/s10933-019-00093-1 IS - 3 ER - TY - CHAP T1 - A 4000-year history of debris flows in north-central Washington State, U.S.A.: Preliminary results from trenching and surficial geologic mapping at the Pope Creek fan Y1 - 2019 AB - Long-term records of the magnitude and frequency of debris flows on fans are rare, but such records provide critical information needed for debris-flow hazard and risk assessments. This study explores the history of debris flows on a fan with seasonally inhabited cabins at Pope Creek along the Entiat River about 48 km upstream from the town of Entiat, Washington. Motivation for this study was provided by the Duncan Fire, a wildfire which burned the Pope Creek basin in 2014 and resulted in debris flows and water-dominated floods on the fan between August 2014 and October 2016. We excavated and mapped seven 6-m long (2.4 m deep) trenches, mapped deposits on the surface of the fan, and constrained the ages of deposits using radiocarbon dating and the computer program OxCal. Preliminary results indicate that there have been at least 10 debris-flow events (DFEs) since 4000 cal yr BP. The mean recurrence interval between events was 433 +/-44 years, but intervals range from 724 to 20 years. The four most recent events have the shortest recurrence intervals. The largest event had an estimated sediment volume of 97,000 m3 and occurred at about 285 cal yr BP (1665 AD) during the Little Ice Age. The most recent debris-flow event that was triggered by rainstorms following the Duncan Fire was about 8x smaller than the largest event. These results may indicate that the largest DFE was triggered by an exceptional meteorological event that occurred during a cool, wet time, and that smaller DFEs were triggered by less exceptional meteorological events that occurred following wildfires. UR - https://pubs.er.usgs.gov/publication/70203945 ER - TY - JOUR T1 - Abrupt mid-Holocene ice loss in the western Weddell Sea Embayment of Antarctica JF - Earth and Planetary Science Letters Y1 - 2019 A1 - Johnson, Joanne S. A1 - Nichols, Keir A. A1 - Goehring, Brent M. A1 - Balco, Greg A1 - Schaefer, Joerg M. KW - Antarctica KW - cosmogenic dating in situ 14C KW - Holocene KW - Weddell Sea ice sheet AB - The glacial history of the westernmost Weddell Sea sector of Antarctica since the Last Glacial Maximum is virtually unknown, and yet it has been identified as critical for improving reliability of glacio-isostatic adjustment models that are required to correct satellite-derived estimates of ice sheet mass balance. Better knowledge of the glacial history of this region is also important for validating ice sheet models that are used to predict future contribution of the Antarctic ice sheet to sea level rise. Here we present a new Holocene deglacial chronology from a site on the Lassiter Coast of the Antarctic Peninsula, which is situated in the western Weddell Sea sector. Samples from 12 erratic cobbles and 18 bedrock surfaces from a series of presently-exposed ridges were analysed for cosmogenic Be-10 exposure dating, and a smaller suite of 7 bedrock samples for in situ C-14 dating. The resulting Be-10 ages are predominantly in the range 80-690 ka, whereas bedrock yielded much younger in situ C-14 ages, in the range 6.0-7.5 ka for samples collected from 138-385 m above the modern ice surface. From these we infer that the ice sheet experienced a period of abrupt thinning over a short time interval (no more than 2700 years) in the mid-Holocene, resulting in lowering of its surface by at least 250 m. Any late Holocene change in ice sheet thickness - such as re-advance, postulated by several modelling studies - must lie below the present ice sheet surface. The substantial difference in exposure ages derived from Be-10 and C-14 dating for the same samples additionally implies ubiquitous Be-10 inheritance acquired during ice-free periods prior to the last deglaciation, an interpretation that is consistent with our glacial-geomorphological field observations for former cold-based ice cover. The results of this study provide evidence for an episode of abrupt ice sheet surface lowering in the mid-Holocene, similar in rate, timing and magnitude to at least two other locations in Antarctica. VL - 518 UR - https://www.sciencedirect.com/science/article/pii/S0012821X19302638 ER - TY - JOUR T1 - Age, Growth and Death of a National Icon: The Historic Chapman Baobab of Botswana JF - Forests Y1 - 2019 A1 - Patrut, Adrian A1 - Woodborne, Stephan A1 - Patrut, Roxana T. A1 - Hall, Grant A1 - Rakosy, Laszlo A1 - Winterbach, Christiaan A1 - von Reden, Karl F. AB - The year 2016 witnessed the fall of a symbol of the botanical world: the historic Chapman baobab of Botswana. This article presents the results of our investigation of the standing and fallen tree. The Chapman baobab had an open ring-shaped structure composed of six partially fused stems. Several wood samples collected from the stems prior and after their collapse were analysed by using radiocarbon dating. The radiocarbon date of the oldest sample was 1381 ± 22 BP, which corresponds to a calibrated age of 1345 (+10, −15) calendar years. The dating results show that the six stems of the Chapman baobab belonged to three different generations, which were 1350–1400, 800–1000 and 500–600 years old. The growth rate variation of the largest and oldest stem is presented and correlated with the climate evolution in the area over the past 1000 years. The factors that determined the sudden fall and death of the Chapman baobab are also presented and discussed. VL - 10 UR - https://www.mdpi.com/1999-4907/10/11/983 IS - 11 ER - TY - JOUR T1 - Analysis of multiple cosmogenic nuclides constrains Laurentide Ice Sheet history and process on Mt. Mansfield, Vermont's highest peak JF - Quaternary Science Reviews Y1 - 2019 A1 - Corbett, Lee B. A1 - Bierman, Paul R. A1 - Wright, Stephen F. A1 - Shakun, Jeremy D. A1 - Davis, P. Thompson A1 - Goehring, Brent M. A1 - Halsted, Christopher T. A1 - Koester, Alexandria J. A1 - Caffee, Marc W. A1 - Zimmerman, Susan R. KW - Cosmogenic isotopes KW - erosion KW - Geochronology KW - Glaciation KW - Last glacial maximum KW - North America KW - Pleistocene AB - Constraining glacial history and process on Mt Mansfield, the highest peak in Vermont (1339 m a.s.l.), provides insight into how the Laurentide Ice Sheet shaped the underlying landscape, when latest Pleistocene ice retreated, and how upland and lowland glacial histories relate. Here, we quantify in situ cosmogenic 10Be in 20 bedrock and boulder surfaces, as well as in situ cosmogenic 14C in three of those surfaces, to assess subglacial erosion and exposure history. Isotopic concentrations indicate that Mt. Mansfield's lower elevations (∼400–1200 m a.s.l.) were deeply eroded by at least several meters during the last glaciation and then deglaciated rapidly; 10Be ages across this elevation span are indistinguishable and average 13.9 ± 0.6 ka (n = 15), suggesting that 800 m of ice thinning occurred within at most about a millennium. Conversely, the higher elevations (>1200 m a.s.l.) preserve a more complex geomorphic history. Mt. Mansfield's summit surfaces contain 10Be from previous periods of exposure, indicating that the mountaintop landscapes were likely preserved beneath cold-based, weakly-erosive glacial ice. Exposure ages from the shorter-lived isotope, 14C, are younger (9.7 and 11.7 ka), suggesting that Mt. Mansfield's summit was covered until the early Holocene, perhaps by snowfields, ice carapaces, and/or till. Our findings, in context of previous work, suggest that thinning Laurentide ice flowed through the valleys for at most hundreds of years following deglaciation of the uplands, but that the summit remained shielded by ice or sediment for millennia after the valleys became ice-free. VL - 205 UR - https://linkinghub.elsevier.com/retrieve/pii/S0277379118307145 ER - TY - JOUR T1 - Annual radiocarbon measurements in a century-old European beech tree (Fagus sylvatica) from coastal northeastern North America JF - NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS Y1 - 2019 A1 - Gaylord, Mary C. Lardie A1 - Longworth, Brett E. A1 - Murphy, Keelan A1 - Cobb, Caroline A1 - McNichol, Ann P. AB - Radiocarbon (C-14) concentrations of annual tree rings from an European beech tree (Fagus sylvatica) from Woods Hole, MA, USA were analyzed at National Ocean Sciences Accelerator Mass Spectrometry facility (NOSAMS) to construct a C-14 bomb curve record from northeastern North America. The C-14 concentration rises from a pre bomb (1895-1955) average of Fraction Modern ((FC)-C-14) = 0.9764 to a peak of 1.8639 in 1964. After 1964, (FC)-C-14 gradually decreases to 1.0611 in 2014. The annual tree-ring radiocarbon content agrees with the atmospheric radiocarbon content of the Northern Hemisphere and is very similar to the radiocarbon concentration of a red oak (Quercus rubra) tree located in Bear Mountain State Park in New York, USA. Infra-annual tree-ring pairs did not produce evidence of a seasonal effect on the radiocarbon concentration, but there were few samples and more study is warranted. VL - 456 ER - TY - JOUR T1 - Antarctic Relic Microbial Mat Community Revealed by Metagenomics and Metatranscriptomics JF - Frontiers in Ecology and Evolution Y1 - 2019 A1 - Zaikova, Elena A1 - Goerlitz, David S. A1 - Tighe, Scott W. A1 - Wagner, Nicole Y. A1 - Bai, Yu A1 - Hall, Brenda L. A1 - Bevilacqua, Julie G. A1 - Weng, Margaret M. A1 - Samuels-Fair, Maya D. A1 - Johnson, Sarah Stewart AB - Buried upslope from the modern lakes in the McMurdo Dry Valleys of Antarctica are relict lake deposits embedded in valley walls. Within these relict deposits, ancient microbial mats, or paleomats, have been preserved under extremely arid and cold conditions since the receding of larger paleolakes thousands of years ago, and now serve as a sheltered niche for microbes in a highly challenging oligotrophic environment. To explore whether paleomats could be repositories for ancient lake cells or were later colonized by soil microbes, determine what types of metabolic pathways might be present, analyze potential gene expression, and explore whether the cells are in a vegetative or dormant state, we collected paleomat samples from ancient lake facies on the northern slopes of Lake Vanda in Wright Valley in December 2016. Using a gentle lysis technique optimized to preserve longer molecules, combined with a polyenzymatic treatment to maximize yields from different cell types, we isolated high-molecular weight DNA and RNA from ancient paleomat samples. Community composition analysis suggests that the paleomat community may retain a population of indigenous mat cells that may flourish once more favorable conditions are met. In addition to harboring a diverse microbial community, paleomats appear to host heterotrophs in surrounding soils utilizing the deposits as a carbon source. Whole genome long-read PacBio sequencing of native DNA and Illumina metagenomic sequencing of size-sorted DNA (>2,500 nt) indicated possible cell viability, with mat community composed of bacterial taxa. Metagenome assemblies identified genes with predicted roles in nitrogen cycling and complex carbohydrate degradation, and we identified key metabolic pathways such as stress response, DNA repair, and sporulation. Metatranscriptomic data revealed that the most abundant transcripts code for products involved in genetic information processing pathways, particularly translation, DNA replication, and DNA repair. Our results lend new insight into the functional ecology of paleomat deposits, with implications for our understanding of cell biology, Antarctic microbiology and biogeography, and the limits of life in extremely harsh environments. VL - 7 UR - https://www.frontiersin.org/article/10.3389/fevo.2019.00001/full ER - TY - JOUR T1 - The application of delta C-13, TOC and C/N geochemistry of mangrove sediments to reconstruct Holocene paleoenvironments and relative sea levels, Puerto Rico JF - MARINE GEOLOGY Y1 - 2019 A1 - Khan, Nicole S. A1 - Vane, Christopher H. A1 - Engelhart, Simon E. A1 - Kendrick, Chris A1 - Horton, Benjamin P. AB - We assessed the use of delta C-13, TOC and C/N values of bulk sedimentary organic matter (OM) to reconstruct paleoenvironmental and relative sea-level change from mangrove environments in Puerto Rico. The modern distribution of delta C-13, TOC and C/N values was described from 63 vegetation and 59 surface sediment samples collected from three sites containing basin and riverine mangrove stands, and was compared to microfossil (foraminiferal and thecamoebian) assemblages. Four vertically-zoned environments were identified: tidal flat (delta C-13: -18.6 +/- 2.8 parts per thousand; TOC: 10.2 +/- 5.7%; C/N: 12.7 +/- 3.1), mangrove (delta C-13: -26.4 +/- 1.0 parts per thousand; TOC: 33.9 +/- 13.4%; C/N: 24.3 +/- 6.2), brackish transition (delta C-13: -28.8 +/- 0.7 parts per thousand; TOC: 40.8 +/- 11.7%; C/N: 21.7 +/- 3.7), and freshwater swamp (delta C-13: -28.4 +/- 0.4 parts per thousand; TOC: 42.8 +/- 4.8%; C/N: 17.0 +/- 1.1). These environments had distinct delta C-13, TOC and C/N values, with the exception of the brackish transition and freshwater swamp zones that were difficult to distinguish on a geochemical basis alone. The foraminiferal assemblages were complicated by a group that did not show a relationship to elevation due to the presence of calcareous foraminifera occurring above mean higher high water (MHHW), likely resulting from washover or transport by storms. However, the ratio of foraminifera to thecamoebians (F/T) along with delta C-13, TOC and C/N values refines the distinction between brackish and freshwater environments. Using linear discriminant analysis, we applied the delta C-13, TOC, C/N and F/T distributions to a 1.7 m core containing a continuous sequence of Rhizophora mangle peat, which began accumulating at similar to 1650-1930 CE. Together, microfossils, delta C-13, TOC, and C/N values, and the core chronology from Cs-137 and radiocarbon dating revealed that sediments in the core likely accumulated in response to anthropogenic sediment delivery, making it unsuitable for relative sea-level reconstruction. We caution that in the absence of detailed litho-, bio-, chemo-, or chrono-stratigraphic analyses as presented here, care should be taken in interpreting sea-level histories derived from single dates on mangrove peats. VL - 415 ER - TY - JOUR T1 - Arsenic variability and groundwater age in three water supply wells in southeast New Hampshire JF - Geoscience Frontiers Y1 - 2019 A1 - Levitt, Joseph P. A1 - Degnan, James R. A1 - Flanagan, Sarah M. A1 - Jurgens, Bryant C. KW - Age tracers KW - Arsenic variability KW - Geochemical time series KW - Groundwater age modeling AB - Three wells in New Hampshire were sampled bimonthly over three years to evaluate the temporal variability of arsenic concentrations and groundwater age. All samples had measurable concentrations of arsenic throughout the entire sampling period and concentrations in individual wells had a mean variation of more than 7 μg/L. The time series data from this sampling effort showed that arsenic concentrations ranged from a median of 4 μg/L in a glacial aquifer well (SGW-65) to medians of 19 μg/L and 37 μg/L in wells (SGW-93 and KFW-87) screened in the bedrock aquifer, respectively. These high arsenic concentrations were associated with the consistently high pH (median ≥ 8) and low dissolved oxygen (median <0.1 mg/L) in the bedrock aquifer wells, which is typical of fractured crystalline bedrock aquifers in New Hampshire. Groundwater from the glacial aquifer often has high dissolved oxygen, but in this case was consistently low. The pH also is generally acidic in the glacial aquifer but in this case was slightly alkaline (median = 7.5). Also, sorption sites may be more abundant in glacial aquifer deposits than in fractured bedrock which may contribute to lower arsenic concentrations. Mean groundwater ages were less than 50 years old in all three wells and correlated with conservative tracer concentrations, such as chloride; however, mean age was not directly correlated with arsenic concentrations. Arsenic concentrations at KFW-87 did correlate with water levels, in addition, there was a seasonal pattern, which suggests that either the timing of or multiple sampling efforts may be important to define the full range of arsenic concentrations in domestic bedrock wells. Since geochemically reduced conditions and alkaline pHs are common to both bedrock and glacial aquifer wells in this study, groundwater age correlates less strongly with arsenic concentrations than geochemical conditions. There also is evidence of direct hydraulic connection between the glacial and bedrock aquifers, which can influence arsenic concentrations. Correlations between arsenic concentrations and the age of the old fraction of water in SGW-65 and the age of the young fraction of water in SGW-93 suggest that water in the two aquifers may be mixing or at least some of the deeper, older water captured by the glacial aquifer well may be from a similar source as the shallow young groundwater from the bedrock aquifer. The contrast in arsenic concentrations in the two aquifers may be because of increased adsorption capacity of glacio-fluvial sediments, which can limit contaminants more than fractured rock. In addition, this study illustrates that long residence times are not necessary to achieve more geochemically evolved conditions such as high pH and reduced conditions as is typically found with older water in other regions. T3 - Groundwater Arsenic Biogeochemistry VL - 10 SN - 1674-9871 UR - https://www.sciencedirect.com/science/article/pii/S1674987119300313 IS - 5 JO - Geoscience Frontiers ER - TY - NEWS T1 - Baobabs in Trouble: Accelerator Mass Spectrometry Provides Ages of the Most Ancient Trees T2 - The African Physics Newletter Y1 - 2019 A1 - Gledhill, I. JF - The African Physics Newletter UR - https://gallery.mailchimp.com/63e42c583930d9f7a8b637982/files/edd75706-1040-436f-ada1-ba42a1800b8e/Baobab.pdf ER - TY - JOUR T1 - Bigmouth Buffalo Ictiobus cyprinellus sets freshwater teleost record as improved age analysis reveals centenarian longevity JF - Communications Biology Y1 - 2019 A1 - Lackmann, Alec R. A1 - Andrews, Allen H. A1 - Butler, Malcolm G. A1 - Bielak-Lackmann, Ewelina S. A1 - Clark, Mark E. KW - Ageing KW - Conservation biology KW - Freshwater ecology KW - Ichthyology AB - Understanding the age structure and population dynamics of harvested species is crucial for sustainability, especially in fisheries. The Bigmouth Buffalo (Ictiobus cyprinellus) is a fish endemic to the Mississippi and Hudson Bay drainages. A valued food-fish for centuries, they are now a prized sportfish as night bowfishing has become a million-dollar industry in the past decade. All harvest is virtually unregulated and unstudied, and Bigmouth Buffalo are declining while little is known about their biology. Using thin-sectioned otoliths and bomb-radiocarbon dating, we find Bigmouth Buffalo can reach 112 years of age, more than quadrupling previous longevity estimates, making this the oldest known freshwater teleost (~12,000 species). We document numerous populations that are comprised largely (85-90%) of individuals over 80 years old, suggesting long-term recruitment failure since dam construction in the 1930s. Our findings indicate Bigmouth Buffalo require urgent attention, while other understudied fishes may be threatened by similar ecological neglect. VL - 2 UR - https://pubmed.ncbi.nlm.nih.gov/31149641/ IS - 1 ER - TY - JOUR T1 - Bomb Radiocarbon Age Validation of Warsaw Grouper and Snowy Grouper JF - Fisheries Y1 - 2019 A1 - Sanchez, Phillip J. A1 - Pinsky, Jeffrey P. A1 - Rooker, Jay R. AB - Current stock assessments for both the Warsaw Grouper Hyporthodus nigritus and the Snowy Grouper H. niveatus are based on age‐structured population models determined using traditional otolith‐based aging techniques. However, recent studies using bomb radiocarbon validation have shown that many deepwater fishes live much longer than previously estimated when relying on conventional age determination methods. In this study, we conducted bomb radiocarbon age validations of Warsaw Grouper and Snowy Grouper from the Gulf of Mexico. Radiocarbon age validation supported annual growth increment formation for all Warsaw Grouper size classes and medium‐sized Snowy Grouper. Conversely, ages of larger, older Snowy Grouper were greatly underestimated due to difficulty in discriminating annuli. This bomb radiocarbon analysis validates a minimum 56‐year longevity for both Warsaw Grouper and Snowy Grouper, increasing the currently published longevities of 41 and 54 years, respectively. VL - 44 UR - https://onlinelibrary.wiley.com/toc/15488446/44/11 IS - 11 ER - TY - JOUR T1 - CO2-dependent carbon isotope fractionation in Archaea, Part II: The marine water column JF - GEOCHIMICA ET COSMOCHIMICA ACTA Y1 - 2019 A1 - Hurley, Sarah J. A1 - Close, Hilary G. A1 - Elling, Felix J. A1 - Jasper, Claire E. A1 - Gospodinova, Kalina A1 - McNichol, Ann P. A1 - Pearson, Ann AB - Stable carbon isotope ratios of archaeal glycerol dibiphytanyl glycerol tetraether (GDGT) lipids have been proposed as a proxy to infer past changes in the carbon isotope composition (delta C-13) of dissolved inorganic carbon (DIC). The premise for paleo-delta C-13(DIC) reconstructions from GDGTs is based on observations of relatively constant delta C-13(GDGT) values in recent depositional environments. Marine Thaumarchaeota, thought to be the dominant source of GDGTs to marine sediments, fix inorganic carbon using the 3-hydroxypropionate/4-hydroxybutyrate (3HP/4HB) pathway, which is specific to HCO3- as the substrate. Bicarbonate-dependent autotrophy has been the basis for predicting that the stable carbon isotopic composition of GDGTs (delta C-13(GDGT)) should vary in parallel with water column delta C-13(DIC) values, because HCO3- is by far the dominant fraction of DIC in modern seawater. However, this relationship has never been systematically tested. Here we examine the carbon isotopic composition of GDGTs from four water column profiles in the Southwest and Equatorial Atlantic Ocean. Values of delta C-13(GDGT) increase with depth in the water column, in contrast to the characteristic decrease in delta C-13(DIC) values. These divergent trends imply a decrease in the observed total biosynthetic isotope effect (epsilon(Ar)) with depth, i.e., the offset between delta(13)(DIC) and delta C-13(GDGT) is not constant. Instead, we find that values of epsilon(Ar) specifically correlate with oceanographic variables associated with extent of organic remineralization, decreasing as CO2 concentration increases. This observed relationship is consistent in both magnitude and direction with the results of an isotope flux-balance model for Thaumarchaeota that suggests epsilon(Ar) should be sensitive to growth rate (mu) and CO2 availability under conditions of atmospheric pCO(2) < 4 times the pre-anthropogenic Holocene level. Further tests of the sensitivity of epsilon(Ar) to u and CO2 in the modern marine environment will be essential to exploring the potential for a new, archaeal lipid-derived pCO(2) paleobarometer. (C) 2019 Elsevier Ltd. All rights reserved. VL - 261 ER - TY - JOUR T1 - Comparing and improving methods for reconstructing peatland water-table depth from testate amoebae JF - The Holocene Y1 - 2019 A1 - Nolan, Connor A1 - Tipton, John A1 - Booth, Robert K A1 - Hooten, Mevin B A1 - Jackson, Stephen T KW - Bayesian statistics KW - compositional data KW - Holocene KW - hydrology KW - North America KW - Northeast United States KW - Paleoclimate KW - peatlands KW - statistical methods KW - testate amoebae AB - Proxies that use changes in the composition of ecological communities to reconstruct temporal changes in an environmental covariate are commonly used in paleoclimatology and paleolimnology. Existing methods, such as weighted averaging and modern analog technique, relate compositional data to the covariate in very simple ways, and different methods are seldom compared systematically. We present a new Bayesian model that better represents the underlying data and the complexity in the relationships between species’ abundances and a paleoenvironmental covariate. Using testate amoeba–based reconstructions of water-table depth as a test case, we systematically compare new and existing models in a cross-validation experiment on a large training dataset from North America. We then apply the different models to a new 7500-year record of testate amoeba assemblages from Caribou Bog in Maine and compare the resulting water-table depth reconstructions. We find that Bayesian models represent an improvement over existing methods in three key ways: more complete use of the underlying compositional data, full and meaningful treatment of uncertainty, and clear paths toward methodological improvements. Furthermore, we highlight how developing and systematically comparing methods lead to an improved understanding of the proxy system. This paper focuses on testate amoebae and water-table depth, but the framework and ideas are widely applicable to other proxies based on compositional data. VL - 29 UR - https://journals.sagepub.com/doi/10.1177/0959683619846969 IS - 8 ER - TY - JOUR T1 - Coral Skeleton δ15N as a Tracer of Historic Nutrient Loading to a Coral Reef in Maui, Hawaii JF - Scientific Reports Y1 - 2019 A1 - Murray, Joseph A1 - Prouty, Nancy G. A1 - Peek, Sara A1 - Paytan, Adina AB - Excess nutrient loading to nearshore environments has been linked to declining water quality and ecosystem health. Macro-algal blooms, eutrophication, and reduction in coral cover have been observed in West Maui, Hawaii, and linked to nutrient inputs from coastal submarine groundwater seeps. Here, we present a forty-year record of nitrogen isotopes (δ15N) of intra-crystalline coral skeletal organic matter in three coral cores collected at this site and evaluate the record in terms of changes in nitrogen sources. Our results show a dramatic increase in coral δ15N values after 1995, corresponding with the implementation of biological nutrient removal at the nearby Lahaina Wastewater Reclamation Facility (LWRF). High δ15N values are known to be strongly indicative of denitrification and sewage effluent, corroborating a previously suggested link between local wastewater injection and degradation of the reef environment. This record demonstrates the power of coral skeletal δ15N as a tool for evaluating nutrient dynamics within coral reef environments. VL - 9 UR - http://www.nature.com/articles/s41598-019-42013-3 IS - 1 ER - TY - JOUR T1 - Coupled ocean and atmospheric changes during Greenland stadial 1 in southwestern Europe JF - Quaternary Science Reviews Y1 - 2019 A1 - Naughton, F. A1 - Costas, S. A1 - Gomes, S.D. A1 - Desprat, S. A1 - Rodrigues, T. A1 - Sanchez Goñi, M.F. A1 - Renssen, H. A1 - Trigo, R. A1 - Bronk-Ramsey, C. A1 - Oliveira, D. A1 - Salgueiro, E. A1 - Voelker, A.H.L. A1 - Abrantes, F. KW - Climate variability KW - Greenland stadial KW - Iberian margin KW - Jet stream KW - Moisture availability KW - North Atlantic KW - Paleoclimate KW - Westerlies KW - Younger Dryas Complex AB - Paleoclimate reconstructions suggest that the complex variability within the Greenland stadial 1 (GS-1) over western Europe was governed by coupled ocean and atmospheric changes. However, few works from the North Atlantic mid-latitudes document both the GS-1 onset and its termination, which are often considered as single abrupt transition events. Here, we present a direct comparison between marine (alkenone-based sea surface temperatures) and terrestrial (pollen) data, at very high resolution (28 years mean), from the southwestern Iberian shelf record D13882. Our results reveal a rather complex climatic period with internally changing conditions. The GS-1 onset (GS-1a: 12890-12720 yr BP) is marked by a progressive cooling and drying; GS-1b (12720-12390 yr BP) is the coldest and driest phase; GS-1c (12390-12030 yr BP) is marked by a progressive warming and increase in moisture conditions; GS-1 termination (GS-1d: 12030-11770 yr BP) is marked by rapid switches between cool wet, cold dry and cool wet conditions. Although hydroclimate response was very unsteady throughout the GS-1 and in particular during its termination phase, the persistence of an open temperate and Mediterranean forest in southwestern Iberia during the entire episode suggests that at least some moisture was delivered via the Westerlies. We propose coupled ocean and atmospheric mechanisms to reproduce these scenaria. Changes in the strength of the Atlantic Meridional Overturning Circulation (AMOC) as well as variations in the North Atlantic sea-ice growth have favoured the displacement of the polar jet stream's latitudinal position and contributed to a complex spatial pattern and strength of the Westerlies across western Europe. VL - 212 UR - https://www.researchgate.net/publication/332292599_Coupled_ocean_and_atmospheric_changes_during_Greenland_stadial_1_in_southwestern_Europe ER - TY - JOUR T1 - Discovery of an Extensive Deep-Sea Fossil Serpulid Reef Associated With a Cold Seep, Santa Monica Basin, CaliforniaTable_1.docx JF - Frontiers in Marine Science Y1 - 2019 A1 - Georgieva, Magdalena N. A1 - Paull, Charles K. A1 - Little, Crispin T. S. A1 - McGann, Mary A1 - Sahy, Diana A1 - Condon, Daniel A1 - Lundsten, Lonny A1 - Pewsey, Jack A1 - Caress, David W. A1 - Vrijenhoek, Robert C. AB - Multibeam bathymetric mapping of the Santa Monica Basin in the eastern Pacific has revealed the existence of a number of elevated bathymetric features, or mounds, harboring cold seep communities. During 2013–2014, mounds at ∼600 m water depth were observed for the first time and sampled by Monterey Bay Aquarium Research Institute’s ROV Doc Ricketts. Active cold seeps were found, but surprisingly one of these mounds was characterized by massive deposits composed of fossil serpulid worm tubes (Annelida: Serpulidae) exhibiting various states of mineralization by authigenic carbonate. No living serpulids with equivalent tube morphologies were found at the site; hence the mound was termed “Fossil Hill.” In the present study, the identity of the fossil serpulids and associated fossil community, the ages of fossils and authigenic carbonates, the formation of the fossil serpulid aggregation, and the geological structure of the mound are explored. Results indicate that the tubes were most likely made by a deep-sea serpulid lineage, with radiocarbon dating suggesting that they have a very recent origin during the Late Pleistocene, specifically to the Last Glacial Maximum ∼20,000 years ago. Additional U-Th analyses of authigenic carbonates mostly corroborate the radiocarbon dates, and also indicate that seepage was occurring while the tubes were being formed. We also document similar, older deposits along the approximate trajectory of the San Pedro Basin Fault. We suggest that the serpulid tube facies formed in situ, and that the vast aggregation of these tubes at Fossil Hill is likely due to a combination of optimal physical environmental conditions and chemosynthetic production, which may have been particularly intense as a result of sea-level lowstand during the Last Glacial Maximum. VL - 6 UR - https://www.frontiersin.org/article/10.3389/fmars.2019.00115/full ER - TY - JOUR T1 - Dissolved organic carbon in basalt-hosted deep subseafloor fluids of the Juan de Fuca Ridge flank JF - Earth and Planetary Science Letters Y1 - 2019 A1 - Lin, Huei-Ting A1 - Repeta, Daniel J. A1 - Xu, Li A1 - Rappé, Michael S. KW - aromatic organic compound KW - basaltic basement fluid KW - carbon isotopes KW - dissolved organic carbon KW - Juan de Fuca KW - selective removal KW - subseafloor AB - Marine dissolved organic carbon (DOC) is highly depleted in radiocarbon and thus inferred to be largely refractory to removal processes that operate on less than millennial timescales. However, a growing number of reports have shown that a large fraction of marine DOC can be effectively removed during circulation through submarine hydrothermal systems. What is not clear, however, is whether the DOC that remains in hydrothermal fluids is remnant non-reactive DOC from recharged seawater, or DOC that has been largely produced in the subsurface. We collected and characterized warm (∼65 °C) hydrothermal fluids from deep (18, 40, 73, 200 m) within the basalt-hosted basement of the Juan de Fuca Ridge flank in the Northeast Pacific Ocean. DOC concentrations in hydrothermal fluids were 9 to 18 μM, much lower than measured in local deep seawater (37.5 μM). DOC C values of −683‰ to −856‰ were much lower than the C-dissolved inorganic carbon (DIC) values of −880‰ to −918‰, while DOC C values of −23.6‰ to −27.0‰ were much heavier than that of the particulate organic carbon (POC) pool (‰), suggesting that biological production in the subsurface is not a primary source of DOC. Rather, our data suggest that isotopically enriched DOC are selectively removed from recharged seawater, leaving DOC that is very isotopically depleted in the basaltic basement fluids. Despite the removal of 50–75% of DOC in the subsurface, nuclear magnetic resonance (NMR) functional group analyses indicate that aromatic compounds were added to basaltic basement fluids during passage through the deep subseafloor and may partly contribute to the depleted 14C DOC in the ridge-flank basement fluids. VL - 513 UR - https://linkinghub.elsevier.com/retrieve/pii/S0012821X19300998 ER - TY - JOUR T1 - The distribution and magnitude of subglacial erosion on millennial timescales at Engabreen, NorwayAbstract JF - Annals of Glaciology Y1 - 2019 A1 - Rand, Cari A1 - Goehring, Brent M. KW - Beryllium-10 KW - Carbon-14 KW - cosmogenic nuclides KW - Engabreen KW - glacial erosion AB - We quantify the magnitude of millennial-scale glacial erosion at Engabreen, a temperate glacier in coastal northern Norway, using the in situ cosmogenic nuclides carbon-14 (14C) and beryllium-10 (10Be) in bedrock exposed recently by glacial retreat. Nuclide concentrations show no dependence on distance down or across the valley. As such, resulting Holocene erosion depths along two transects perpendicular to glacier flow are highly variable with no systematic distribution, ranging from 0.10 to 2.95 m. We observed 14C–10Be ratios elevated above the production ratio in samples of abraded bedrock, which is counter to the expectation for surfaces covered during the Holocene and exposed only recently. Muon reactions produce nuclides at greater depths than do spallation reactions and 14C at production rates at higher than those of 10Be, resulting in 14C–10Be ratios that increase with depth. Therefore, elevated 14C–10Be ratios indicate that sampled sites were deeply plucked during recent cover, the Little Ice Age in this case, and then rapidly abraded prior to retreat. Our results suggest that, while glacial erosion can generate a u-shaped valley profile over long periods of time (e.g., 105–107 years), the discontinuous nature of glacial plucking produces spatially variable patterns of erosion over shorter millennial timescales. VL - 60 UR - https://www.cambridge.org/core/product/identifier/S0260305519000429/type/journal_article IS - 80 ER - TY - JOUR T1 - Equatorial Pacific seawater pCO2 variability since the last glacial period JF - Scientific Reports Y1 - 2019 A1 - Kubota, Kaoru A1 - Yokoyama, Yusuke A1 - Ishikawa, Tsuyoshi A1 - Sagawa, Takuya A1 - Ikehara, Minoru A1 - Yamazaki, Toshitsugu AB - The ocean may have played a central role in the atmospheric pCO2 rise during the last deglaciation. However, evidence on where carbon was exchanged between the ocean and the atmosphere in this period is still lacking, hampering our understanding of global carbon cycle on glacial–interglacial timescales. Here we report a new surface seawater pCO2 reconstruction for the western equatorial Pacific Ocean based on boron isotope analysis—a seawater pCO2 proxy—using two species of near-surface dwelling foraminifera from the same marine sediment core. The results indicate that the region remained a modest CO2 sink throughout the last deglaciation. VL - 9 UR - http://www.nature.com/articles/s41598-019-49739-0 IS - 1 ER - TY - CONF T1 - Evaluating Playas as Point Sources for Recharge of the High Plains Aquifer, Western Kansas T2 - Joint 53rd Annual South-Central/53rd North-Central/71st Rocky Mtn GSA Section Meeting - 2019 Y1 - 2019 A1 - Stotler, Randy L. A1 - Salley, Kaitlin A. A1 - Johnson, William C. A1 - Ryuh, Yon-Gyung JF - Joint 53rd Annual South-Central/53rd North-Central/71st Rocky Mtn GSA Section Meeting - 2019 PB - Geological Society of America UR - https://www.researchgate.net/publication/333623353_EVALUATING_PLAYAS_AS_SOURCES_OF_RECHARGE_TO_THE_HIGH_PLAINS_AQUIFER_IN_WESTERN_KANSAS ER - TY - JOUR T1 - Evaluating the Radiocarbon Reservoir Effect in Lake Kutubu, Papua New GuineaABSTRACT JF - Radiocarbon Y1 - 2019 A1 - Schneider, Larissa A1 - Pain, Colin F A1 - Haberle, Simon A1 - Blong, Russell A1 - Alloway, Brent V A1 - Fallon, Stewart J A1 - Hope, Geoff A1 - Zawadzki, Atun A1 - Heijnis, Henk AB - Conceptual models predict a tight coupling between the Intertropical Convergence Zone (ITCZ) and the Southern Westerly Winds (SWW) in response to glacial-interglacial transitions, yet little is known about this relationship under Holocene boundary conditions. Here we present a synthesis of Holocene pollen data from the southwest Pacific mid-latitudes that tracks changes in the SWW. Comparison of our SWW paleoclimate records with data tracking the ITCZ, oceanic circulation, and insolation reveals clearly synchronous and in-phase ITCZ-SWW dynamics between 12 and 5 ka, indicating a tight coupling between the tropics and southern mid-latitudes in response to ocean circulation and insolation. An apparent decoupling of the SWW and ITCZ in the Pacific region after 5 ka is attributable to the overriding influence of the El Niño–Southern Oscillation (ENSO) over the proxy data. VL - 61 UR - https://www.cambridge.org/core/product/identifier/S0033822218000498/type/journal_article IS - 1 ER - TY - THES T1 - Evaluation of Compartmentalized Aquifers in the Walla Walla Subbasin of Oregon Using Isotopic and Geochemical Tracers T2 - College of Earth, Ocean, and Atmospheric Sciences Y1 - 2019 A1 - van Stolk, Courtney A. KW - Columbia River Basalt Group KW - Groundwater tracers KW - Stable isotope tracers KW - Walla Walla Valley (Oregon) AB - The Walla Walla Subbasin (WWSB) in Oregon is underlain by formations of the extensive Columbia River Basalt Group (CRBG) which have been deformed by post-Miocene folding and faulting. Extensive irrigation with groundwater from these basalt groups, as well as sedimentary aquifers and surface water diversions from the Walla Walla River, has enabled the WWSB to become a productive agricultural region despite its semi-arid climate. Over the past 10 years water levels in the basalt aquifer have declined to the point where some senior groundwater right holders cannot access their full water allocation. Effective water management depends on an understanding of the flow and recharge pathways in this complex groundwater system. This research uses spatial analysis of geochemical characteristics of groundwater samples to test the hypothesis that local faults create barriers to flow and isolate compartments of groundwater. For this study 31 wells were sampled for analysis of oxygen isotopes, hydrogen isotopes, pH, temperature, and conductivity. At a subset of 18 of those wells, samples were collected for a more extensive array of tests which also included carbon-14, tritium, and ten major ions. These parameters provide information to evaluate the range and distribution of groundwater age, evidence of modern recharge, and the progression of chemical reactions along hypothesized flow paths. Results of these laboratory analyses were compared with a literature review of fault geology and hydrogeology in the CRBG, results of interference pumping tests of basalt wells in the WWSB, and known physical characteristics of the wells sampled. This information was used to test three conceptual models of groundwater flow through the basalt aquifers. The first conceptual model was based on groundwater movement in unfaulted, sloping CRBG terrain where water infiltrates in upland recharge zones where the basalt is exposed, and moves laterally through the sloping interflow zones of the aquifer to wells. The second conceptual model describes local recharge in the vicinity of a well flowing slowly downward through the aquifer until the depth at which is became hydraulically connected to the well. The third model added faults into the model as lateral barriers to flow and vertical conduits to recharge. Comparisons of the monovalent/divalent cation ratios, stable isotope values, and principal component models with well depth, well surface level elevation, and well locations provide insights that conflict with the first two conceptual models and supported the third model. Further comparisons of these parameters with geologic characteristics of these faults from the literature through the lens of the third conceptual model provide a basis for estimating fault hydrogeologic characteristics in the WWSB. JF - College of Earth, Ocean, and Atmospheric Sciences PB - Oregon State University VL - Master of Science (M.S.), Geography UR - https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/qv33s317x ER - TY - JOUR T1 - Evidence for frequent, large tsunamis spanning locked and creeping parts of the Aleutian megathrust JF - GSA Bulletin Y1 - 2019 A1 - Witter, Rob A1 - Briggs, Rich A1 - Engelhart, Simon E. A1 - Gelfenbaum, Guy A1 - Koehler, Rich D. A1 - Nelson, Alan A1 - Selle, SeanPaul La A1 - Corbett, Reide A1 - Wallace, Kristi AB - At the eastern end of the 1957 Andreanof Islands, Alaska, USA, moment magnitude 8.6 earthquake rupture, Driftwood Bay (Umnak Island) and Stardust Bay (Sedanka Island) lie along presently locked and creeping parts of the Aleutian megathrust, respectively, based on satellite geodesy onshore. Both bays, located 200 km apart, face the Aleutian trench and harbor coastal evidence for tsunami inundation in 1957. Here we describe the evidence at Driftwood Bay, including eight sheets of landward-fining, normally-graded marine sand that extend up to 375 m inland and 23 m above mean tide level. Drift logs that corroborate historical accounts of 1957 tsunami runup on Umnak Island’s Pacific coast overlie the youngest sand sheet, which 137Cs activity shows was deposited in the decade before 1963. The older sand sheets probably record tsunamis prior to 1957 because an emergent coastal terrace lacks evidence for storm-wave erosion and overwash since ca. 2 ka. Comparisons of the Driftwood Bay and Stardust Bay tsunami histories suggest that at least twice in the past 1700 years inundation occurred at one site but not the other. In contrast, Bayesian age-depth modeling suggests that the two bays may record five tsunamis like the 1957 tsunami, generated by earthquake ruptures that spanned the presently locked and creeping parts of the Aleutian megathrust. However, serial tsunamis occurring within days to centuries cannot be precluded. Our findings imply 164–257-year recurrence intervals for large eastern Aleutian tsunamis and challenge the notion that creeping parts of the megathrust, inferred from geodesy onshore, pose lower earthquake and tsunami hazards than locked areas. VL - 131 UR - https://pubs.geoscienceworld.org/gsa/gsabulletin/article/131/5-6/707/566656/Evidence-for-frequent-large-tsunamis-spanning IS - 5-6 ER - TY - JOUR T1 - Evidence of Ice Age humans in eastern Beringia suggests early migration to North America JF - Quaternary Science Reviews Y1 - 2019 A1 - Vachula, Richard S. A1 - Huang, Yongsong A1 - Longo, William M. A1 - Dee, Sylvia G. A1 - Daniels, William C. A1 - Russell, James M. KW - Beringia KW - charcoal KW - Fecal sterols KW - Last Glacial KW - Paleofire KW - Polycyclic aromatic hydrocarbons (PAHs) AB - Our understanding of the timing and pathway of human arrival to the Americas remains an important and polarizing topic of debate in archaeology and anthropology. Traditional consensus, supported by archaeological and paleoenvironmental data, favors a 'swift peopling' of the Americas from Asia via the Bering Land Bridge during the last Glacial termination. More recent genetic data and archaeological finds have challenged this view, proposing the 'Beringian standstill hypothesis' (BSH), wherein a population of proto-Americans migrated from Asia during, or even prior to the Last Glacial Maximum (LGM) and lived in Beringia for thousands of years before their eventual spread across the American continents. Using a sediment archive from Lake E5 (68.641667 degrees N, 149.457706 degrees W), located on Alaska's North Slope, we present new data supporting the BSH and shedding new light on the environmental impact of these early American populations. Fecal biomarkers support human presence in the environs of the lake, and our data demonstrate elevated biomass burning in this region during the last Glacial. Elevated burning defies the expectation that natural fires would be less frequent in the Arctic during the last Glacial, thereby suggesting human ignition as the likely culprit. Our data shed new light on the pathway and timing of human migration to the Americas and demonstrate the possibility of the sustainable coexistence of humans and the Ice Age megafauna in Beringia prior to their extinction. (C) 2018 Elsevier Ltd. All rights reserved. VL - 205 UR - https://linkinghub.elsevier.com/retrieve/pii/S0277379118307716https://api.elsevier.com/content/article/PII:S0277379118307716?httpAccept=text/xmlhttps://api.elsevier.com/content/article/PII:S0277379118307716?httpAccept=text/plain ER - TY - JOUR T1 - Examining Coastal Dynamics and Archaeological Site Evidence at a Drowned Cirque Basin Influenced by Earthquakes and Little Ice Age Glaciation JF - Journal of Coastal Research Y1 - 2019 A1 - Maio, Christopher V. A1 - Crowell, Aron L. A1 - Sullivan, Richard M. A1 - Buzard, Richard M. A1 - Whitley, Matthew A. A1 - Bogardus, Reyce C. A1 - Wit, Cary W. de AB - This study contributes baseline information regarding the framework geology, drivers of coastal change, and archaeological record along the fjord-indented coastlines of southcentral Alaska. Field data were collected in July 2015 from James Lagoon, a 30-m-deep drowned cirque valley adjacent to McCarty Fjord in the Nuka Bay region of Kenai Fjords National Park. A 1790 CE terminal moraine deposited by McCarty Glacier extends across the cirque opening and delimits the lagoon. Acoustic surveys of the lagoon reveal bedrock overlain by deltaic, lacustrine, and marine facies containing beds that indicate past submarine landslides. Lagoon and marsh sediment cores contain coarse sand horizons interbedded with silt and peat, evidence of repeated low-frequency, high-intensity events. The largest of the event beds in the marine cores occurs near the surface and is likely associated with the 1964 Great Alaska Earthquake (moment magnitude 9.2). Trees killed during the 1964 earthquake fringe the coastline and indicate ∼2 m of coseismic subsidence. Radiocarbon ages of five exposed subfossil stumps indicate two pre-1964 subsidence events occurring between 1710 and 1789 and 1078 and 1125 median probability calendar year CE (cal CE). A Sugpiaq culture archaeological site dated to 1565 cal CE existed on the western shore of James Lagoon in the interval between these two events, possibly for proximity to an ice floe harbor seal rookery at McCarty Glacier. Archaeological site elevation above mean high water at James Lagoon and around Nuka Bay is inversely related to the extent of cumulative site erosion caused by coastal submergence during the last two great earthquakes. These combined findings lay the groundwork for future research and provide context to ongoing coastal hazards and their effects on cultural resources. VL - 35 UR - https://bioone.org/journals/journal-of-coastal-research/volume-35/issue-4/JCOASTRES-D-18-00074.1/Examining-Coastal-Dynamics-and-Archaeological-Site-Evidence-at-a-Drowned/10.2112/JCOASTRES-D-18-00074.1.full IS - 4 ER - TY - JOUR T1 - Farming strategies of 1st millennium CE agro-pastoralists on the southern foothills of the Tianshan Mountains: A geoarchaeological and macrobotanical investigation of the Mohuchahangoukou (MGK) site, Xinjiang, China JF - PLOS ONE Y1 - 2019 A1 - Li, Yuqi A1 - Storozum, Michael A1 - Tian, Duo A1 - Frachetti, Michael A1 - Su, Kai A1 - Wang, Xin ED - Islam, Rafiq KW - Agricultural irrigation KW - Agricultural soil science KW - agriculture KW - Archaeology KW - Crops KW - Geochemistry KW - Paleopedology KW - Sediment AB - Archaeological evidence emerging over the past decade clearly illustrates that agro-pastoralists living along the foothills of major mountain chains in Central Asia (the so-called “Inner Asian Mountain Corridor” or IAMC) facilitated the spread of domesticated grains through their direct involvement in farming. While the environmental conditions across the northwestern slopes of the IAMC provided adequate resources for incipient farming and herding as early as the mid-3rd mill. BCE, the development of local agricultural strategies on the extremely arid and eroded foothills on the southeastern, leeward side of the mountains remain comparatively less studied. Our study tackles this problem by combining geoarchaeological analysis with conventional macrobotanical identification in the investigation of a 1st-mill. CE agro-pastoralist farming site, Mohuchahangoukou (MGK), located on the arid foothills of the Tianshan range. Our results illustrate how ancient agro-pastoralists at MGK innovated irrigation systems both to combat water shortage and, importantly, to trap sediments carried by flood-water for crop cultivation. By synthesizing currently available data, we estimate that they managed to trap about 40 cm of fine-grained sediment within a span of 200 years or even less. These stone-built field systems helped water a diverse stand of crops and create deeper soils in an otherwise deflated landscape with thin desert soils. Since we detected high levels of salt concentration (>2 dSm-1) in the lower portions of all three test trenches we analyzed, we conclude that soil salinization might have affected the long-term sustainability of this form of irrigated field management. We also infer that, besides engineering efforts, the ancient agro-pastoralists at MGK had to resolve the scheduling conflicts between irrigated farming and animal herding through labor specialization. VL - 14 UR - https://dx.plos.org/10.1371/journal.pone.0217171 IS - 6 ER - TY - JOUR T1 - First record of the extinct ground sloth, Megalonyx jeffersonii, (Xenarthra, Megalonychidae) from New York and contributions to its paleoecology JF - Quaternary International Y1 - 2019 A1 - McDonald, H. Gregory A1 - Feranec, Robert S. A1 - Miller, Norton KW - Megalonyx jeffersonii KW - New York KW - Stable isotopes KW - Synsacrum AB - The first record of the Jefferson ground sloth, Megalonyx jeffersonii, in New York is reported. The specimen consists of a partial synsacrum recovered from a peat deposit near Newburgh, Orange County. Compared to other synsacra of Megalonyx, the number of vertebrae is anomalous with one less caudal vertebra than expected. Stable isotope analysis of the bone shows a δ13C value of 20.5‰ and implies a diet of only C3 plants. The specimen has a radiocarbon date of 11,450 ± 55 BP indicating the presence of this taxon in the region immediately prior to the extinction of the North American Pleistocene megafauna. VL - 530-531 UR - https://linkinghub.elsevier.com/retrieve/pii/S1040618218303252 ER - TY - JOUR T1 - A fluvially derived flood deposit dating to the Kamikaze typhoons near Nagasaki, Japan JF - Natural Hazards Y1 - 2019 A1 - Ladlow, Caroline A1 - Woodruff, Jonathan D. A1 - Cook, Timothy L. A1 - Baranes, Hannah A1 - Kanamaru, Kinuyo AB - Previous studies in western Kyushu revealed prominent marine-derived flood deposits that date to the late thirteenth-century and are interpreted to be a result of two legendary typhoons linked to the failed Mongol invasions of Japan in 1274 and 1281. The regional persistence and prominence of sediments dating to these “Kamikaze” typhoon events (meaning divine wind) raise questions about the origins of these late thirteenth-century deposits. This is due in part to uncertainty in distinguishing between tsunami and storm-induced deposition. To provide additional insight into the true cause of prominent late thirteenth-century flood deposits in western Kyushu, we present a detailed assessment of an additional event deposit dating to the late thirteenth-century from Lake Kawahara near Nagasaki, Japan. This particular deposit thickens landward towards the primary river flowing into Lake Kawahara and exhibits anomalously low Sr/Ti ratios that are consistent with a fluvial rather than a marine sediment source. When combined with previous flood reconstructions, results support the occurrence of an extreme, late thirteenth-century event that was associated with both intense marine- and river-derived flooding. Results therefore contribute to a growing line of evidence for the Kamikaze typhoons resulting in widespread flooding in the region, rather than the late thirteenth-century deposit being associated with a significant tsunami impact to western Kyushu. VL - 99 UR - https://link.springer.com/article/10.1007/s11069-019-03777-z IS - 2 ER - TY - JOUR T1 - Four centuries of vegetation change in the mid-elevation Andean forests of Ecuador JF - Vegetation History and Archaeobotany Y1 - 2019 A1 - Huisman, Seringe N. A1 - Bush, Mark B. A1 - McMichael, Crystal N. H. AB - Mid-elevation Andean ecosystems have immense species richness and endemism. Taxonomic composition is known to change through time on the eastern slopes of the Andes as a result of climatic change and disturbance events, both natural and by human actions. Fossil phytoliths can capture local scale vegetation changes, especially among monocotyledonous plants. Phytolith production is high in grasses and palms, plant groups that are particularly sensitive to climatic changes and disturbance events in Andean ecosystems. Here, we reconstruct four centuries of local-scale vegetation change and the corresponding fire history from lake sediment records retrieved from Lagunas Cormorán and Chimerella, located at ca. 1,700 m a.s.l. in the mid-elevation Andean forests of eastern Ecuador. The charcoal analysis of the lake sediments showed no sign of past fires, and no evidence of cultivation was found at either lake. The phytolith assemblages indicated changes in the relative abundances of palms, grasses and trees over the last few centuries, suggesting that mid-elevation Andean phytolith assemblages are sensitive to local scale vegetation dynamics. The largest change in vegetation occurred at the end of the Little Ice Age, at which point the diversity of palm phytoliths decreases. These phytolith assemblages are probably responding to changes in the cloud base position through time, which strongly influences the distributions of many plants and animals. VL - 28 UR - http://link.springer.com/10.1007/s00334-019-00715-8 IS - 6 ER - TY - JOUR T1 - Four Major Holocene Earthquakes on the Reelfoot Fault Recorded by Sackungen in the New Madrid Seismic Zone, USA JF - Journal of Geophysical Research: Solid Earth Y1 - 2019 A1 - Gold, Ryan D. A1 - DuRoss, Christopher B. A1 - Delano, Jaime E. A1 - Jibson, Randall W. A1 - Briggs, Richard W. A1 - Mahan, Shannon A. A1 - Williams, Robert A. A1 - Corbett, D. Reide AB - Three sequences of well‐documented, major ~M7+ earthquakes (1811–1812, ~1450, and ~900 CE) in the New Madrid seismic zone, USA, contribute significantly to seismic hazard in the region. However, it is unknown whether this <550‐year recurrence interval has been constant throughout the Holocene given limited geomorphic evidence of prior earthquakes. We extend the record of paleoearthquakes along the Reelfoot fault via investigation of ridgetop gravitational failure features, interpreted as sackungen. The sackungen occur in bluffs along the eastern margin of the Mississippi River floodplain and are concentrated near (<15 km) the southwest dipping Reelfoot reverse fault. A paleoseismic trench excavated across sackungen at the Paw Paw site exposed four packages of colluvial sediment that postdate 30‐ to 11‐ka Peoria Loess. We interpret the colluvial packages to have been deposited following episodic failure of the sackungen as a result of strong ground motions from the following sequence of earthquakes: event 4, 1640 ± 1730 BCE; event 3, 270 ± 670 CE; event 2, 1430 ± 380 CE; and event 1, 1810 ± 50 CE (2 sigma). Event timing corresponds to previously documented earthquakes and represents the longest archive of paleoearthquakes on the Reelfoot fault. If the trenched sackungen record all major Reelfoot fault earthquakes, our observations in combination with prior investigations indicate a period of quiescence from at least 11 to 4.4 ka, followed by four major seismic events culminating in the 1811–1812 CE sequence. This clustered earthquake recurrence pattern helps place bounds on seismic hazard and geodynamic models in the New Madrid seismic zone. VL - 124 UR - https://onlinelibrary.wiley.com/doi/abs/10.1029/2018JB016806 IS - 3 ER - TY - JOUR T1 - A fully automated system for the extraction of in situ cosmogenic carbon-14 in the Tulane University cosmogenic nuclide laboratory JF - Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms Y1 - 2019 A1 - Goehring, Brent M. A1 - Wilson, Jim A1 - Nichols, Keir KW - Automation KW - Cosmogenic nuclide KW - In situ carbon-14 AB - During 2015 and culminating in early 2016, we acquired a new Carbon Extraction and Graphitization System (CEGS) from Aeon Laboratories, L.L.C. (hereafter, “Aeon”), and adapted it for in situ cosmogenic sample processing. The Tulane University CEGS (TU-CEGS) is fully automated starting from sample insertion into the tube furnace to generation of graphite material ready for accelerator mass spectrometry cathode preparation. The system implements an integrated sequence of sample processing functions: extraction/collection, purification, measurement, and graphite production, which are all integrated into one unified system. The extraction portion is derived from evolving designs of fusions of quartz via lithium metaborate (LiBO2) flux. A critical analysis of system design in concert with analysis of process parameters yield a nearly order of magnitude increase in sample throughput with total samples processed in our laboratory (320 since installation) with consistent process blank levels (0.98 ± 0.32 × 105 atoms 14C, n = 26) and secondary standard values (0.4953 ± 0.0012 Fm, n = 8). In this paper we detail system design, process algorithm, and line performance including system blanks and the results from the CRONUS-A (6.12 ± 0.32 × 105 atoms g−1 14C, n = 13) interlaboratory comparison material. VL - 455 UR - https://linkinghub.elsevier.com/retrieve/pii/S0168583X19300771 ER - TY - JOUR T1 - Glacial geology and cosmogenic-nuclide exposure ages from the Tucker Glacier - Whitehall Glacier confluence, northern Victoria Land, Antarctica JF - American Journal of Science Y1 - 2019 A1 - Balco, Greg A1 - Todd, Claire A1 - Goehring, Brent M. A1 - Moening-Swanson, Isaac A1 - Nichols, Keir KW - Antarctica KW - cosmogenic-nuclide geochemistry KW - exposure-dating KW - glacial geology KW - Last glacial maximum KW - Ross Sea KW - Tucker Glacier KW - Victoria Land AB - We describe glacial-geological observations and cosmogenic-nuclide exposure ages from the vicinity of the present grounding line of Tucker Glacier, a large alpine glacier flowing from the mountains of northern Victoria Land, East Antarctica, into the outer Ross Sea. These data are relevant for constraining the extent of ice sheet expansion and retreat in the Ross Sea, and associated eustatic sea level impact, between the Last Glacial Maximum (LGM) and the present. In addition, a terrestrial geological record of ice thickness change from this region could provide evidence for or against the hypothesis that rapid eustatic sea-level rise during meltwater pulse 1A (“MWP-1A”) at 14.6 ka was in part the result of rapid, large-scale thinning or breakup of a marine-based portion of the LGM ice sheet in the outer Ross Sea. Glacial-geological observations, exposure ages on glacial deposits, and a novel application of in-situ-produced cosmogenic 14C in quartz-bearing bedrock to identify the limits of LGM ice cover in the absence of direct geomorphic evidence, show that Tucker Glacier near its present grounding line was 300 to 350 m thicker than present during the LGM and thinned steadily between 17 to 5 ka. The largest possible rapid thickness change in the time period 14 to 15 ka that could be accommodated by the exposure-age data is ∼50 m, which is a small fraction of that predicted for the western Ross Sea by model simulations of the Antarctic contribution to MWP-1A. There do exist possible scenarios in which hypothesized marine ice sheet collapse in the outer Ross Sea during MWP-1A might not be recorded by ice thickness changes at Tucker Glacier. However, our record of ice thickness changes spanning this time period is the closest such record to the outer Ross Sea that is likely to exist, and it agrees with all exposure-age deglaciation chronologies from other regions of the Ross embayment in providing no evidence for such an event. VL - 319 UR - http://www.ajsonline.org/lookup/doi/10.2475/04.2019.01 IS - 4 ER - TY - JOUR T1 - Glacial–interglacial Nd isotope variability of North Atlantic Deep Water modulated by North American ice sheet JF - Nature Communications Y1 - 2019 A1 - Zhao, Ning A1 - Oppo, Delia W. A1 - Huang, Kuo-Fang A1 - Howe, Jacob N. W. A1 - Blusztajn, Jerzy A1 - Keigwin, Lloyd D. AB - The Nd isotope composition of seawater has been used to reconstruct past changes in the contribution of different water masses to the deep ocean. In the absence of contrary information, the Nd isotope compositions of endmember water masses are usually assumed constant during the Quaternary. Here we show that the Nd isotope composition of North Atlantic Deep Water (NADW), a major component of the global overturning ocean circulation, was significantly more radiogenic than modern during the Last Glacial Maximum (LGM), and shifted towards modern values during the deglaciation. We propose that weathering contributions of unradiogenic Nd modulated by the North American Ice Sheet dominated the evolution of the NADW Nd isotope endmember. If water mass mixing dominated the distribution of deep glacial Atlantic Nd isotopes, our results would imply a larger fraction of NADW in the deep Atlantic during the LGM and deglaciation than reconstructed with a constant northern endmember. VL - 10 UR - http://www.nature.com/articles/s41467-019-13707-z IS - 1 ER - TY - JOUR T1 - Growth and longevity of Hawaiian grouper (Hyporthodus quernus) — input for management and conservation of a large, slow-growing grouper JF - Canadian Journal of Fisheries and Aquatic Sciences Y1 - 2019 A1 - Andrews, Allen H. A1 - DeMartini, Edward E. A1 - Brodziak, Jon A1 - Nichols, Ryan S. A1 - Humphreys, Robert L. AB - Hawaiian grouper (Hyporthodus quernus) is endemic to the Hawaiian Islands and is regionally important, yet little is known about its life history. This large species is managed within the Deep 7 bottom fish complex, which includes six snapper species that are assumed to have similar life history traits. Previous age estimates were not validated and suggested a maximum age of 34 years. To evaluate the preliminary study and provide a valid basis for life history parameters, we aged otoliths using bomb radiocarbon (14C) dating. Measured 14C values provided ages for smallest to largest fish that differed from the original study. The fundamental information provided here when evaluating Hawaiian grouper conservation status is longevity (valid to 50 years and estimated to 76 years) — no male sampled was <80 cm total length (TL) and younger than 34 years — and age-at-sexual maturity and age-at-sex change, which were indirectly estimated and compared with prior published estimates for this and other groupers. Updated life history parameters (k = 0.078, L∞ = 95.8 cm TL) should be used to improve future management and conservation assessments. VL - 76 UR - https://www.nrcresearchpress.com/doi/full/10.1139/cjfas-2018-0170 IS - 10 ER - TY - CHAP T1 - History and Mystery of Age and Growth Studies in Elasmobranchs: Common Methods and Room for Improvement Y1 - 2019 A1 - Andrews, Allen A1 - Natanson, Lisa A1 - Wintner, Sabine A1 - Passerotti, Michelle AB - Age determination is a fundamental field of study that is of critical importance to management and conservation of a species. Determining population demographics can only be accomplished with the input of age data; yet, despite years of age determination efforts, it continues to be one of the most challenging and nuanced aspects of life history investigation in elasmobranchs. A variety of methods have been used to determine ages in elasmobranchs, some successful and some not. New techniques to obtain accurate and precise ages are being developed, and it is important to recognize the value of both old and new methodologies. SN - 9781315317106 ER - TY - JOUR T1 - Holocene and Last Interglacial climate of the Faroe Islands from sedimentary plant wax hydrogen and carbon isotopes JF - Quaternary Science Reviews Y1 - 2019 A1 - Curtin, Lorelei A1 - D'Andrea, William J. A1 - Balascio, Nicholas A1 - Pugsley, Genevieve A1 - de Wet, Gregory A1 - Bradley, Raymond KW - Holocene KW - interglacial KW - North Atlantic KW - Organic geochemistry KW - paleoclimatology KW - Stable isotopes AB - The Last Interglacial period (LIG) is Earth's most recent globally warm period and is analogous in some ways to projected future global warming. However, questions remain regarding the state of the climate during the LIG in the North Atlantic, a region that is extremely sensitive to changes in oceanic and atmospheric circulation. Here, we present hydrogen and carbon isotope (δD and δ13C) records from a suite of plant wax biomarkers preserved in Holocene and LIG lacustrine sediments from the North Atlantic Faroe Islands and interpret them as qualitative proxies for temperature and hydroclimate variability. These data are used to directly compare LIG and Holocene climate using the same proxy approaches from the same terrestrial location. Measuring multiple isotopes on multiple types of waxes elucidates the sources of homologous plant waxes. We deduce that the δD values of long-chain n-alkanes (C27–C33) and mid-chain n-alkanes (C23–C25) in these sedimentary archives reflect leaf water and lake water δD values, respectively, while the δD values for both long-chain (C28–C30) and mid-chain n-alkanoic acids (C24–C26) primarily represent lake water δD values. Plant wax-inferred δD values of precipitation during the early Holocene (10,100 to 8,200  cal  yr BP) are ∼35‰ more positive than late Holocene values, and decline over the Holocene. δD-inferred hydrologic change and δ13C -inferred plant water use efficiency both indicate that the Faroe Islands became drier throughout the Holocene. Comparison with measurements from LIG plant waxes indicates that late LIG in the Faroe Islands was hydrologically similar to the early-to mid-Holocene (8,200 to 4,000  cal  yr BP), with enriched precipitation isotopes and reduced evapotranspiration indicating a warmer, wetter environment. VL - 223 UR - https://www.sciencedirect.com/science/article/pii/S0277379119304251 ER - TY - JOUR T1 - Holocene glacier fluctuations on the northern flank of Cordillera Darwin, southernmost South America JF - Quaternary Science Reviews Y1 - 2019 A1 - Hall, B.L. A1 - Lowell, T.V. A1 - Bromley, G.R.M. A1 - Denton, G.H. A1 - Putnam, A.E. VL - 222 UR - https://linkinghub.elsevier.com/retrieve/pii/S0277379119303890 ER - TY - JOUR T1 - Holocene paleodepositional changes reflected in the sedimentary microbiome of the Black Sea JF - Geobiology Y1 - 2019 A1 - More, Kuldeep D. A1 - Giosan, Liviu A1 - Grice, Kliti A1 - Coolen, Marco J. L. KW - geomicrobiology KW - palaeo-environment KW - paleoecology KW - sedimentary metagenomes KW - subsurface microbiome KW - sulfur cycle. AB - Subsurface microbial communities are generally thought to be structured through in situ environmental conditions such as the availability of electron acceptors and donors and porosity, but recent studies suggest that the vertical distribution of a subset of subseafloor microbial taxa, which were present at the time of deposition, were selected by the paleodepositional environment. However, additional highly resolved temporal records of subsurface microbiomes and paired paleoenvironmental reconstructions are needed to justify this claim. Here, we performed a highly resolved shotgun metagenomics survey to study the taxonomic and functional diversity of the subsurface microbiome in Holocene sediments underlying the permanently stratified and anoxic Black Sea. Obligate aerobic bacteria made the largest contribution to the observed shifts in microbial communities associated with known Holocene climate stages and transitions. This suggests that the aerobic fraction of the subseafloor microbiome was seeded from the water column and did not undergo post-depositional selection. In contrast, obligate and facultative anaerobic bacteria showed the most significant response to the establishment of modern-day environmental conditions 5.2 ka ago that led to a major shift in planktonic communities and in the type of sequestered organic matter available for microbial degradation. No significant shift in the subseafloor microbiome was observed as a result of environmental changes that occurred shortly after the marine reconnection, 9 ka ago. This supports the general view that the marine reconnection was a gradual process. We conclude that a high-resolution analysis of downcore changes in the subseafloor microbiome can provide detailed insights into paleoenvironmental conditions and biogeochemical processes that occurred at the time of deposition. VL - 17 UR - https://pubmed.ncbi.nlm.nih.gov/30843322/ IS - 4 ER - TY - JOUR T1 - Holocene sea-level variability from Chesapeake Bay Tidal Marshes, USA JF - The Holocene Y1 - 2019 A1 - Cronin, Thomas M A1 - Clevenger, Megan K A1 - Tibert, Neil E A1 - Prescott, Tammy A1 - Toomey, Michael A1 - Hubeny, J Bradford A1 - Abbott, Mark B A1 - Seidenstein, Julia A1 - Whitworth, Hannah A1 - Fisher, Sam A1 - Wondolowski, Nick A1 - Ruefer, Anna KW - chesapeake bay KW - Foraminifera KW - Holocene KW - sea level KW - tidal marsh KW - US East Coast AB - We reconstructed the last 10,000 years of Holocene relative sea-level rise (RSLR) from sediment core records near Chesapeake Bay, eastern United States, including new marsh records from the Potomac and Rappahannock Rivers, Virginia. Results show mean RSLR rates of 2.6 mm yr−1 from 10 to 8 kilo-annum (ka) due to combined final ice-sheet melting during deglaciation and glacio-isostatic adjustment (GIA subsidence). Mean RSLR rates from ~6 ka to present were 1.4 mm yr−1 due mainly to GIA, consistent with other East Coast marsh records and geophysical models. However, a progressively slower mean rate (<1.0 mm yr−1) characterized the last 1000 years when a multi-century-long period of tidal marsh development occurred during the ‘Medieval Climate Anomaly’ (MCA) and ‘Little Ice Age’ (LIA) in the Chesapeake Bay region and other East Coast marshes. This decrease was most likely due to climatic and glaciological processes and, correcting for GIA, represents a fall in global mean sea level (GMSL) near the end of Holocene Neoglacial cooling. These pre-historical climate- and GIA-driven Chesapeake Bay sea-level changes contrast sharply with those based on Chesapeake Bay tide-gauge rates (3.1–4.5 mm yr−1) (back to 1903). After subtracting the GIA subsidence component, these rates can be attributed to long-term (millennial) global factors of accelerated ocean thermal expansion (~1.0 mm yr−1) and mass loss from alpine glaciers and Greenland and Antarctic Ice Sheets (1.5–2.0 mm yr−1). VL - 29 UR - http://journals.sagepub.com/doi/10.1177/0959683619862028 IS - 11 ER - TY - JOUR T1 - Holocene temperature history of northwest Greenland - With new ice cap constraints and chironomid assemblages from Deltaso JF - QUATERNARY SCIENCE REVIEWS Y1 - 2019 A1 - Axford, Y. A1 - Lasher, G. E. A1 - Kelly, M. A. A1 - Osterberg, E. C. A1 - Landis, J. A1 - Schellinger, G. C. A1 - Pfeiffer, A. A1 - Thompson, E. A1 - Francis, D. R. AB - Arctic temperature shifts drive changes in carbon cycling, sea ice extent and Greenland Ice Sheet mass balance, all of which have global ramifications. Paleoclimate data from past warm periods provide a unique means for assessing the sensitivity of these systems to warming climate, but the magnitude and timing of past temperature changes in many parts of the Arctic are poorly known. Here we assess orbital scale Holocene temperature change in northwest Greenland near the margin of the ice sheet using subfossil insect assemblages from lake Deltaso. Based upon sedimentation history in this currently proglacial lake, we also place constraints on Holocene extents of the adjacent North Ice Cap, a large independent ice cap. Reconstructed summer temperatures were warmer than present at the onset of lacustrine sedimentation following regional deglaciation by the Greenland Ice Sheet, sometime between 10.8 and 10.1 ka BP. Deltaso experienced the warmest summer temperatures of the Holocene between similar to 10 and 6.2 ka BP, followed by progressive cooling that continued through the late Holocene as summer insolation declined, culminating in the lowest temperatures during the pre-industrial last millennium. Deltaso chironomids indicate peak early Holocene summer temperatures at least 2.5-3 degrees C warmer than modern and at least 3.5-4 degrees C warmer than the pre-industrial last millennium. We infer based upon lake sediment organic and biogenic content that in response to declining temperatures, North Ice Cap reached its present-day size similar to 1850 AD, having been smaller than present through most of the preceding Holocene. Our synthesis of paleoclimate evidence from northwest Greenland, Ellesmere Island and northern Baffin Bay supports the timing of temperature trends inferred at Deltaso, and suggests that quantitative temperature reconstructions from Deltas(?) may represent a minimum bound on regional early Holocene warming. Collectively, records from the region indicate >4 degrees C summer cooling through the Holocene. Intense early Holocene warmth around northwest Greenland argues against delayed onset of warmer than -present conditions due to the influence of the nearby waning Laurentide Ice Sheet, and has implications for understanding the Greenland Ice Sheet's sensitivity to climate change. (C) 2019 Elsevier Ltd. All rights reserved. VL - 215 ER - TY - JOUR T1 - Holocene Vegetation, Climate, and Carbon History on Western Kodiak Island, Alaska JF - Frontiers in Earth Science Y1 - 2019 A1 - Peteet, Dorothy M. A1 - Nichols, Jonathan E. A1 - Mann, Daniel H. AB - At Phalarope Pond, western Kodiak Island, a multidisciplinary study using pollen and spores, macrofossils, stable isotopes, and carbon accumulation provides the Holocene vegetation and climate history following the deglaciation that began over 16,000 cal years ago (yr BP). Following a cold and dry Younger Dryas, a warm and wet early Holocene was characterized by abundant ferns in a sedge tundra environment with maximum carbon accumulation, similar to high latitude peatlands globally. About 8,700 cal yr BP sedge and ferns declined and climate remained warm as drier conditions prevailed, limiting carbon sequestration. The abrupt shift in D/H isotopes of about 60% indicates a shift to cooler conditions or a more distal moisture source. Neoglaciation beginning about 3,700 cal yr BP is evident from increases in Artemisia, Empetrum and Betula, signifying cooler conditions, while Alnus declines, paralleling regional trends. VL - 7 UR - https://www.frontiersin.org/article/10.3389/feart.2019.00061/full ER - TY - JOUR T1 - A human role in Andean megafaunal extinction? JF - Quaternary Science Reviews Y1 - 2019 A1 - Raczka, M.F. A1 - Mosblech, N.A. A1 - Giosan, L. A1 - Valencia, B.G. A1 - Folcik, A.M. A1 - Kingston, M. A1 - Baskin, S. A1 - Bush, M.B. KW - Andes KW - Deglaciation KW - Ecuador Extinction KW - Fossil pollen KW - Human arrival KW - Pleistocene megafauna KW - Sporormiella AB - A new fossil pollen, Sporormiella, and sediment chemistry record from Lake Llaviucu, Ecuador, spanning the period from 16,280–9000 years Before Present, provides a high-resolution record of paleoecological change in the high Andes. The deglacial transition from super-páramo through páramo grasslands, to Andean forest is traced, with near-modern systems being established by c. 11,900 years ago. It is suggested that forest elements probably existed in microrefugial populations close to the ice front. Sporormiella is used as a proxy for megafaunal abundance, and its decline to background levels is inferred to indicate a local extinction event at c. 12,800 years ago. About 1800 years prior to the extinction, charcoal becomes a regular sedimentary component in this very wet valley. An early date for human activity in the valley is suggested, with the direct implication of humans in the extinction of the megafauna. VL - 205 UR - https://linkinghub.elsevier.com/retrieve/pii/S0277379118307005 ER - TY - JOUR T1 - Illuminating microbial species‐specific effects on organic matter remineralization in marine sediments JF - Environmental Microbiology Y1 - 2019 A1 - Mahmoudi, Nagissa A1 - Enke, Tim N. A1 - Beaupré, Steven R. A1 - Teske, Andreas P. A1 - Cordero, Otto X. A1 - Pearson, Ann UR - https://apps.webofknowledge.com/InboundService.do?product=WOS&Func=Frame&DestFail=http%3A%2F%2Fwww.webofknowledge.com&SrcApp=search&SrcAuth=Alerting&SID=7Bytr67Z6qAbafBcvVL&customersID=Alerting&mode=FullRecord&IsProductCode=Yes&AlertId=ab9062f8-b111-4f95- ER - TY - JOUR T1 - Implications of radiocarbon ages of organic and inorganic carbon in coastal lakes in Florida for establishing a reliable chronology for sediment-based paleoclimate reconstructionAbstract JF - Quaternary Research Y1 - 2019 A1 - Wang, Yang A1 - Das, Oindrila A1 - Xu, Xiaomei A1 - Liu, Jin A1 - Jahan, Shakura A1 - Means, Guy H. A1 - Donoghue, Joseph A1 - Jiang, Shijun AB - Coastal lake sediments are valuable paleoclimate archives provided that they can be accurately dated. Here, we report radiocarbon ages of bulk sediment organic matter (OM), plants, shells, particulate OM, and dissolved OM from coastal lakes in Florida. Bulk sediment OM yielded ages that are consistently older than contemporaneous plants and shells, indicating significant radiocarbon deficiencies in sedimentary OM in these lakes. The data show that the OM radiocarbon deficiency varies over time and with location, making it impossible to determine a proper correction factor for radiocarbon ages of bulk sediments from these lakes. As a result, we consider ages obtained from bulk sediment OM from these lakes unreliable. The age reversals in bulk sediment OM observed in the sediment cores are likely caused by rapid increases in erosion and sedimentation resulting from large storm events. The data also show that sedimentation rate can vary considerably within a given lake, implying that an age-depth model established for one core cannot be directly applied to other cores despite their close proximity. Analyses of shells from one of the lakes suggest that fresh/brackish-water shells may serve as a good substrate for radiocarbon dating owing to a small reservoir effect on inorganic carbon. VL - 91 UR - https://www.cambridge.org/core/product/identifier/S0033589418000960/type/journal_article IS - 2 ER - TY - JOUR T1 - Improved C− efficiency and ion beam currents by modifying SNICS cathode material JF - Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms Y1 - 2019 A1 - Hlavenka, Joshua D. A1 - Abrams, Henry A1 - Roberts, Mark L. A1 - Longworth, Brett E. A1 - Fallon, Stewart KW - Cathode KW - Efficiency KW - Ion source KW - SNICS AB - We investigated the possibility of increasing the C-14 AMS efficiency and maximizing C- beam currents by modifying sample cathode geometry and material. Previously, we reported results which showed an increase in C- beam current and improved ionization efficiency when reducing the cathode sample well diameter from 1 mm to 0.75 mm and using zinc inserts, pressed into the aluminum cathode holder [4]. In this study we expand that effort by using cathodes with inserts made of Fe, Mo, Ni, Ti, Cu, and Zn. We pressed cathodes with 100 mu g of Oxalic Acid I (OX-I) and ran them to exhaustion. C-12 beam currents, C-14 counts, and graphite weight were used to determine ion source efficiency. VL - 439 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=Alerting&SrcApp=Alerting&DestApp=WOS_CPL&DestLinkType=FullRecord&UT=WOS:000455693100015 ER - TY - JOUR T1 - In situ cosmogenic 3He and 36Cl and radiocarbon dating of volcanic deposits refine the Pleistocene and Holocene eruption chronology of SW Peru JF - Bulletin of Volcanology Y1 - 2019 A1 - Bromley, Gordon R. M. A1 - Thouret, Jean-Claude A1 - Schimmelpfennig, Irene A1 - Mariño, Jersy A1 - Valdivia, David A1 - Rademaker, Kurt A1 - del Pilar Vivanco Lopez, Socorro A1 - Team, ASTER A1 - Aumaître, Georges A1 - Bourlès, Didier A1 - Keddadouche, Karim AB - Constraining the age of young lavas, which generally fall outside the effective range of traditional geochronology methods, remains a key challenge in volcanology, limiting the development of high-resolution eruption chronologies. We present an in situ cosmogenic 3He and 36Cl surface-exposure chronology, alongside new minimum-limiting 14C ages, documenting young eruptions at five sites in the Western Cordillera, southern Peru. Four 3He-dated lavas on the Nevado Coropuna volcanic complex (hitherto thought to be dormant) indicate that the central dome cluster is young and potentially active; two Holocene lavas on the easternmost dome are the youngest directly dated lavas in Peru to date. East of Coropuna, lava domes and block-lava flows represent the most extensive output to date of Nevado Sabancaya, one of Peru’s most active volcanoes. Two 3He measurements confirm the Holocene age of these deposits and expand the chronology for one of the youngest major lava fields in Peru. 36Cl surface-exposure ages from the Purupurini dome cluster and Nevado Casiri document middle-late-Holocene episodes of effusive activity, while basal 14C ages from a lava-dammed wetland constrain an effusive eruption at Mina Arcata, north of Coropuna, to the late-glacial period. These new data advance the recent Western Cordillera volcanic record whilst demonstrating both the considerable potential and fundamental limitations of cosmogenic surface-exposure methods for such applications. VL - 81 UR - http://link.springer.com/10.1007/s00445-019-1325-6 IS - 11 ER - TY - JOUR T1 - Influence of Different Acid Treatments on the Radiocarbon Content Spectrum of Sedimentary Organic Matter Determined by RPO/Accelerator Mass SpectrometryABSTRACT JF - Radiocarbon Y1 - 2019 A1 - Bao, Rui A1 - McNichol, Ann P A1 - Hemingway, Jordon D A1 - Lardie Gaylord, Mary C A1 - Eglinton, Timothy I AB - In practice, obtaining radiocarbon (C-14) composition of organic matter (OM) in sediments requires first removing inorganic carbon (IC) by acid-treatment. Two common treatments are acid rinsing and fumigation. Resulting C-14 content obtained by different methods can differ, but underlying causes of these differences remain elusive. To assess the influence of different acid-treatments on C-14 content of sedimentary OM, we examine the variability in C-14 content for a range of marine and river sediments. By comparing results for unacidified and acidified sediments [HCl rinsing (Rinse(HCl)) and HCl fumigation (Fume(HCl))], we demonstrate that the two acid-treatments can affect C-14 content differentially. Our findings suggest that, for low-carbonate samples, Rinse(HCl) affects the Fm values due to loss of young labile organic carbon (OC). Fume(HCl) makes the Fm values for labile OC decrease, leaving the residual OC older. High-carbonate samples can lose relatively old organic components during Rinse(HCl), causing the Fm values of remaining OC to increase. Fume(HCl) can remove thermally labile, usually young, OC and reduce the Fm values. We suggest three factors should be taken into account when using acid to remove carbonate from sediments: IC abundance, proportions of labile and refractory OC, and environmental matrix. VL - 61 UR - https://www.researchgate.net/publication/328913959_Influence_of_different_acid_treatments_on_the_radiocarbon_content_spectrum_of_sedimentary_organic_matter_determined_by_RPOAccelerator_Mass_Spectrometry IS - 2 ER - TY - JOUR T1 - INFLUENCE OF DIFFERENT ACID TREATMENTS ON THE RADIOCARBON CONTENT SPECTRUM OF SEDIMENTARY ORGANIC MATTER DETERMINED BY RPO/ACCELERATOR MASS SPECTROMETRY JF - RADIOCARBON Y1 - 2019 A1 - Bao, Rui A1 - McNichol, Ann P. A1 - Hemingway, Jordon D. A1 - Gaylord, Mary C. Lardie A1 - Eglinton, I, Timothy AB - In practice, obtaining radiocarbon (C-14) composition of organic matter (OM) in sediments requires first removing inorganic carbon (IC) by acid-treatment. Two common treatments are acid rinsing and fumigation. Resulting C-14 content obtained by different methods can differ, but underlying causes of these differences remain elusive. To assess the influence of different acid-treatments on C-14 content of sedimentary OM, we examine the variability in C-14 content for a range of marine and river sediments. By comparing results for unacidified and acidified sediments [HCl rinsing (Rinse(HCl)) and HCl fumigation (Fume(HCl))], we demonstrate that the two acid-treatments can affect C-14 content differentially. Our findings suggest that, for low-carbonate samples, Rinse(HCl) affects the Fm values due to loss of young labile organic carbon (OC). Fume(HCl) makes the Fm values for labile OC decrease, leaving the residual OC older. High-carbonate samples can lose relatively old organic components during Rinse(HCl), causing the Fm values of remaining OC to increase. Fume(HCl) can remove thermally labile, usually young, OC and reduce the Fm values. We suggest three factors should be taken into account when using acid to remove carbonate from sediments: IC abundance, proportions of labile and refractory OC, and environmental matrix. VL - 61 ER - TY - JOUR T1 - Intense Hurricane Activity Over the Past 1500 Years at South Andros Island, The Bahamas JF - Paleoceanography and Paleoclimatology Y1 - 2019 A1 - Wallace, E. J. A1 - Donnelly, J. P. A1 - Hengstum, P. J. A1 - Wiman, C. A1 - Sullivan, R. M. A1 - Winkler, T. S. A1 - d'Entremont, N. E. A1 - Toomey, M. A1 - Albury, N. AB - Hurricanes cause substantial loss of life and resources in coastal areas. Unfortunately, historical hurricane records are too short and incomplete to capture hurricane‐climate interactions on multi‐decadal and longer timescales. Coarse‐grained, hurricane‐induced deposits preserved in blue holes in the Caribbean can provide records of past hurricane activity extending back thousands of years. Here we present a high resolution record of intense hurricane events over the past 1500 years from a blue hole on South Andros Island on the Great Bahama Bank. This record is corroborated by shorter reconstructions from cores collected at two nearby blue holes. The record contains coarse‐grained event deposits attributable to known historical hurricane strikes within age uncertainties. Over the past 1500 years, South Andros shows evidence of four active periods of hurricane activity. None of these active intervals occurred in the past 163 years. We suggest that Intertropical Convergence Zone position modulates hurricane activity on the island based on a correlation with Cariaco Basin titanium concentrations. An anomalous gap in activity on South Andros Island in the early 13th century corresponds to a period of increased volcanism. The patterns of hurricane activity reconstructed from South Andros Island closely match those from the northeastern Gulf of Mexico but are anti‐phased with records from New England. We suggest that either changes in local environmental conditions (e.g., SSTs) or a northeastward shift in storm tracks can account for the increased activity in the western North Atlantic when the Gulf of Mexico and southeastern Caribbean are less active. VL - 34 UR - https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019PA003665 IS - 11 ER - TY - JOUR T1 - Investigating environmental changes as the driving force of agricultural intensification in the lower reaches of the Yellow River: A case study at the Sanyangzhuang site JF - Quaternary International Y1 - 2019 A1 - Qin, Zhen A1 - Storozum, Michael A1 - Liu, Haiwang A1 - Zhang, Xiaohu A1 - Kidder, Tristram R. KW - Agricultural intensification KW - Environmental changes KW - Sanyangzhuang KW - The Yellow River AB - In many different societies around the world, people transitioned from slash-and-burn agriculture to an intensive mode of agricultural production. However, why agriculture was increasingly intensified by early farmers remains less understood. This study investigates the driving forces of agricultural intensification from an environmental perspective. Based on our fieldwork at the Sanyangzhuang site and previous paleoclimatic studies, we reconstruct the depositional processes and climatic changes at Sanyangzhuang and its surrounding area between 5000 yr BP and 2000 yr BP. Data suggest that farmers in the lower reaches of the Yellow River were confronted with increasingly severe Yellow River flooding and drier and colder climate during this time period. The environmental changes increase risks of crop failure and famine, disrupt the equilibrium of the social system and induce a process that brings about initial agricultural intensification. This environmental pressure is aggravated by social/political factors and results in the further development of agricultural intensification. VL - 521 UR - https://linkinghub.elsevier.com/retrieve/pii/S1040618219300655 ER - TY - JOUR T1 - Isolation of quartz for cosmogenic in situ 14C analysis JF - Geochronology Y1 - 2019 A1 - Nichols, Keir A. A1 - Goehring, Brent M. AB - Froth flotation is a commonly used procedure for separating feldspars and micas from quartz for the preparation of quartz mineral separates to carry out cosmogenic nuclide analysis. Whilst extracting carbon from quartz we observed in situ carbon-14 (14C) concentrations which were anomalously high and in excess of theoretical geological maximum concentrations. Further etching of sample material reduced carbon yields and 14C concentrations, yet the latter remained unrealistically high. When quartz from the original whole rock sample was isolated in our laboratory, we observed even lower carbon yields and geologically plausible in situ 14C concentrations. After ruling out unlikely geological scenarios and systematic measurement issues, we decided to investigate the quartz isolation procedure as a potential source of 14C contamination. We hypothesised that laurylamine (dodecylamine), an organic compound used as part of the froth flotation procedure, elevates 14C concentrations if residual laurylamine is present. We demonstrate that laurylamine has a 14C modern carbon source and thus has the potential to influence in situ 14C measurements if present in minute but measurable quantities. Furthermore, we show that insufficient sample etching results in contaminant 14C persisting through the step heating of quartz that is subsequently collected with the in situ component released at 1100 ∘C. We demonstrate that froth flotation contaminates in situ 14C measurements. We provide guidelines for the preparation of quartz based on methods developed in our laboratory and demonstrate that all froth-flotation-derived carbon and 14C is removed when applied. We recommend that the procedures presented be used at a minimum when using froth flotation to isolate quartz for in situ 14C measurements. VL - 1 UR - https://gchron.copernicus.org/articles/1/43/2019/ IS - 1 ER - TY - JOUR T1 - Lake-level variability in Salar de Coipasa, Bolivia during the past ∼40,000 yrAbstract JF - Quaternary Research Y1 - 2019 A1 - Nunnery, J. Andrew A1 - Fritz, Sherilyn C. A1 - Baker, Paul A. A1 - Salenbien, Wout KW - Altiplano KW - Andes KW - Paleoclimate KW - paleohydrology KW - Paleolake KW - South America AB - Various paleoclimatic records have been used to reconstruct the hydrologic history of the Altiplano, relating this history to past variability of the South American summer monsoon. Prior studies of the southern Altiplano, the location of the world’s largest salt flat, the Salar de Uyuni, and its neighbor, the Salar de Coipasa, generally agree in their reconstructions of the climate history of the past ∼24 ka. Some studies, however, have highly divergent climatic records and interpretations of earlier periods. In this study, lake-level variation was reconstructed from a ∼14-m-long sediment core from the Salar de Coipasa. These sediments span the last ∼40 ka. Lacustrine sediment accumulation was apparently continuous in the basin from ∼40 to 6 ka, with dry or very shallow conditions afterward. The fossil diatom stratigraphy and geochemical data (δ13C, δ15N, %Ca, C/N) indicate fluctuations in lake level from shallow to moderately deep, with the deepest conditions correlative with the Heinrich-1 and Younger Dryas events. The stratigraphy shows a continuous lake of variable depth and salinity during the last glacial maximum and latter stages of Marine Oxygen Isotope Stage 3 and is consistent with environmental inferences and the original chronology of a drill core from Salar de Uyuni. VL - 91 UR - https://www.cambridge.org/core/product/identifier/S0033589418001084/type/journal_article IS - 2 ER - TY - JOUR T1 - Laser ablation–accelerator mass spectrometry reveals complete bomb 14C signal in an otolith with confirmation of 60-year longevity for red snapper (Lutjanus campechanus) JF - Marine and Freshwater Research Y1 - 2019 A1 - Andrews, Allen H. A1 - Yeman, Christiane A1 - Welte, Caroline A1 - Hattendorf, Bodo A1 - Wacker, Lukas A1 - Christl, Marcus KW - Age validation KW - Carbon-14 KW - Gulf of Mexico KW - Lutjanidae KW - radiocarbon. AB - Bomb-produced14C has been used to make valid estimates of age for various marine organisms for 25 years, but fish ages that lead to birth years earlier than the period of increase in14C lose their time specificity. As a result, bomb14Cdating is limited to a minimum age from the last year of prebomb levels because the temporal variation in14C in the marine surface layer is negligible for decades before c. 1958. The longevity of red snapper (Lutjanus campechanus) in the Gulf of Mexico remains unresolved despite various forms of support for ages near 50–60 years. Although the age and growth of red snapper have been verified or validated to a limited extent, some scepticism remains about longevity estimates that exceed30 years. In this study, red snapper otoliths were analysed for14C using a novel laser ablation–accelerator mass spectrometry technique to provide a continuousrecordof14C uptake. This approach provided a basis for age validation that extends beyond the normal limits of bomb14C dating with confirmation of a 60-year longevity for red snapper in the Gulf of Mexico. VL - 70 UR - http://www.publish.csiro.au/?paper=MF18265 IS - 12 ER - TY - JOUR T1 - Late Holocene long arid phase in the Indian subcontinent as seen in shallow sediments of the eastern Arabian Sea JF - Journal of Asian Earth Sciences Y1 - 2019 A1 - Saravanan, Ponnusamy A1 - Gupta, Anil K. A1 - Zheng, Hongbo A1 - Panigrahi, Mruganka K. A1 - Prakasam, Muthusamy AB - Multi-proxy record of benthic and planktic foraminifera, total organic carbon and carbon and oxygen isotope ratios from Core SK291/GC15, off the coast of Goa, eastern Arabian Sea reveals significant paleoceanographic and paleoclimatic turnovers during ~6000 to 1700 calibrated years before the Present (cal yr BP). Benthic foraminiferal census data was analyzed with multivariate techniques including factor and cluster analyses of highest ranked species from the studied core that enabled to identify seven biofacies. The record suggests centennial to millennial-scale changes in the surface conditions driven by monsoon-linked upwelling in the eastern Arabian Sea during the studied interval. Various benthic biofacies combined with isotope and planktic foraminiferal data suggest that depletion of dissolved oxygen and increase in organic productivity in the study area was caused by intense monsoonal upwelling since the middle Holocene. The results suggest that during 5400–4700 and 3000–2500 cal yr BP the southwest (SW) monsoon was strong leading to intense upwelling in the study area as reflected by increased Globigerina bulloides percentages. These were generally warmer intervals in the northern hemisphere. The SW monsoon significantly weakened (abrupt decrease in G. bulloides population) during 4700–3400 cal yr BP roughly coinciding with a long arid phase in the Indian subcontinent and a cold interval in Europe. Our record suggests an abrupt increase in SW monsoon intensity during ~3000 to 2500 cal yr BP, when a pronounced change in benthic biofacies is also noted that suggests a major shift in the sub-surface conditions. Our data document a prolong weak SW monsoon phase beginning at ~4600 cal yr BP, little earlier than 4.2 ka event, in the eastern Arabian Sea. VL - 181 UR - https://linkinghub.elsevier.com/retrieve/pii/S1367912019302676 ER - TY - JOUR T1 - Legacy sediment storage in New England river valleys: Anthropogenic processes in a postglacial landscape JF - Geomorphology Y1 - 2019 A1 - Johnson, Kaitlin M. A1 - Snyder, Noah P. A1 - Castle, Stephanie A1 - Hopkins, Austin J. A1 - Waltner, Mason A1 - Merritts, Dorothy J. A1 - Walter, Robert C. KW - Anthropogenic sediment KW - Legacy sedimen KW - Milldams AB - Legacy sediment associated with erosion from land clearing is a common feature in river valleys of the unglaciated Mid-Atlantic Piedmont region. Here, we quantify the volume of legacy sediment storage in three watersheds in New England, a formerly glaciated region with similar history and intensity of forest clearing and milldam construction during the seventeenth to nineteenth centuries. We combine field observations of bank stratigraphy, radiocarbon dating, and mapping of terraces and floodplains using lidar digital elevation models and other GIS datasets. The 68 km2 South River watershed in western Massachusetts exhibits the most extensive evidence for legacy sediment storage. We visited 18 historic dam sites in the watershed and found field evidence for up to 2.2 m of fine sand and silt legacy sediment storage at 14 of the sites. In the 555 km2 Sheepscot River watershed in coastal Maine, we visited 13 historic dam sites and found likely legacy sediment up to 2.3 m thick at six of the dams. In the 171 km2 upper Charles River watershed in eastern Massachusetts, we investigated 14 dam sites, and found legacy sediment up to 1.8 m thick at two of them. Stratigraphically, we identified the base of fine-grained legacy sediment from a change to much coarser grain size (gravel at most sites) or to glacial lacustrine or marine deposits. Along the Sheepscot River, we observed cut timbers underlying historic sediment at several locations, likely associated with sawmill activities. Only at the Charles River were we able to radiocarbon date the underlying gravel layer (1281–1391 calibrated CE). At no site did we find a buried organic-rich Holocene soil, in contrast to the field relations commonly observed in the Mid-Atlantic region. We use lidar elevation data to map planar terrace extents in each watershed, estimate thickness of remaining legacy sediment found stored behind breached or removed milldams, and estimate volumes of remaining legacy sediment storage in valley bottoms for entire watersheds. The maximum volume of stored legacy sediment estimated for the South, Sheepscot, and upper Charles watersheds is 2.5 × 106 m3, 3.7 × 106 m3, and 2.6 × 104 m3, respectively. These volumes of legacy sediment can be translated to an equivalent thickness of soil eroded from each watershed: 37 mm, 7 mm, and 0.2 mm, respectively. We attribute the variation in presence and thickness of legacy sediment at the New England sites to the existence or absence of upstream sediment supply in the form of thick glacial deposits and to sinks such as lakes and wetlands along valley bottoms. Of the three study watersheds, the South River has the most extensive glacial sediments, fewest sinks, and the most legacy sediment in storage along the river corridor. VL - 327 UR - https://linkinghub.elsevier.com/retrieve/pii/S0169555X18304665 ER - TY - BOOK T1 - Mapping Isotopic and Dissolved Organic Matter Baselines in Waters and Sediments of the Gulf of Mexico Y1 - 2019 A1 - Chanton, Jeffrey P. A1 - Jaggi, Aprami A1 - Radović, Jagoš R. A1 - Rosenheim, Brad E. A1 - Walker, Brett D. A1 - Larter, Stephen R. A1 - Rogers, Kelsey A1 - Bosman, Samantha A1 - Oldenburg, Thomas B. P. ED - Murawski, Steven A. ED - Ainsworth, Cameron H. ED - Gilbert, Sherryl ED - Hollander, David J. ED - Paris, Claire B. ED - Schlüter, Michael ED - Wetzel, Dana L. KW - Dissolved organic matter KW - FTICR-MS KW - Gulf baselines KW - High-resolution mass spectrometry KW - organic carbon KW - radiocarbon KW - Ramped pyrolysis KW - Sediment organic matter AB - The Deepwater Horizon oil spill released petroleum hydrocarbons that were depleted in δ13C and Δ14C at depth into the Gulf of Mexico. Stable-carbon and radiocarbon isotopic values and high-resolution mass spectrometry were used to follow the distributions of this petroleum and to track its transformation into petrocarbon, a term used to describe crude oil or transformed crude oil following biodegradation, weathering, oxygenation, or loss of lighter components. The term petrocarbon includes oil- or methane-derived carbon assimilated or incorporated into microbial biomass or into the food web as well as degraded and undegraded petroleum constituents. Here we report (1) the increase in the relative abundance of oxygen-containing carbon compounds making up the dissolved organic matter (DOM) with increasing depth through the water column, indicating the biodegradation of DOM as it was transported to depth in the water column, (2) the finding of 14C depletion in DOM indicating petrocarbon inputs, and (3) the decrease and subsequent increase of 14C in the isotopic composition of sinking particles indicating the capture of petrocarbon in sediment traps. In addition, we discuss the 14C depletion of this material once it is sedimented to the seafloor and the implications for oil spill budgets of seafloor petrocarbon deposition. PB - Springer International Publishing CY - Cham SN - 978-3-030-12962-0 UR - https://link.springer.com/chapter/10.1007/978-3-030-12963-7_10 ER - TY - JOUR T1 - Medieval warmth confirmed at the Norse Eastern Settlement in Greenland JF - Geology Y1 - 2019 A1 - Lasher, G. Everett A1 - Axford, Yarrow AB - Recent work has documented glacier advances in West Greenland coincident with the Medieval Climate Anomaly (MCA) and warmth across much of northern Europe. The North Atlantic Oscillation (NAO) has been invoked to explain antiphasing of temperatures between these North Atlantic regions. Historical and model observations suggest negative correlation between the mode of NAO and both temperature and δ18O values of precipitation over much of Greenland. We test for a hypothesized positive NAO mode and associated cool conditions during the MCA in South Greenland within the Norse Eastern Settlement by reconstructing δ18O values of precipitation at subcentennial resolution over the past 3000 yr using aquatic insect subfossils preserved in lake sediments. More positive δ18O values are found between 900 and 1400 CE, indicating a period of warmth in South Greenland superimposed on late Holocene insolation-forced Neoglacial cooling, and thus not supporting a positive NAO anomaly during the MCA. Highly variable δ18O values record an unstable climate at the end of the MCA, preceding Norse abandonment of Greenland. The spatial pattern of paleoclimate in this region supports proposals that North Atlantic subpolar ocean currents modulated South Greenland’s climate over the past 3000 yr, particularly during the MCA. Terrestrial climate in the Labrador Sea and Baffin Bay regions may be spatially heterogeneous on centennial time scales due in part to the influence of the subpolar gyre. VL - 47 UR - https://pubs.geoscienceworld.org/gsa/geology/article/47/3/267/568708/Medieval-warmth-confirmed-at-the-Norse-Easternhttps://pubs.geoscienceworld.org/gsa/geology/article-pdf/47/3/267/4650216/267.pdfhttps://www.geosociety.org/datarepository/2019096 IS - 3 ER - TY - JOUR T1 - Mid-late Holocene rainfall variation in Taiwan: A high-resolution multi-proxy record unravels the dual influence of the Asian monsoon and ENSO JF - Palaeogeography, Palaeoclimatology, Palaeoecology Y1 - 2019 A1 - Chen, Jinxia A1 - Li, Tiegang A1 - Nan, Qingyun A1 - Shi, Xuefa A1 - Liu, Yanguang A1 - Jiang, Bo A1 - Zou, Jianjun A1 - Selvaraj, Kandasamy A1 - Li, Dongling A1 - Li, ChuanShun KW - C/N ratio KW - Fern spore KW - La Niña KW - Okinawa Trough KW - tropical cyclone AB - Taiwan is particularly sensitive to changes in monsoonal precipitation and to typhoon-induced heavy precipitation events, however, rainfall variability in Taiwan on centennial and millennial time scales during the Holocene has not been well understood. This study describes mid-Holocene rainfall features of Taiwan based on pollen, total organic carbon (TOC), total nitrogen (TN), and C/N ratio records of core MD05-2908. The step-wise increase in sedimentation rate, fern spore percentage and concentration, TOC content, and C/N ratio suggests an increasing terrestrial material supply due to the intensified rainfall in Taiwan since 6800 cal. yr BP. This rainfall pattern shows an inverse pattern to the decreasing East Asian summer monsoon (EASM) strength represented by the multi-proxy records from North China. Variation of the East Asian summer circulation and associated moisture transport may account for the long-term rainfall changes in Taiwan. Superimposed on this trend, we interpreted three prominent rainfall changes, which focus on the periods of 6800–6600, 1090–880 and 490–190 cal. yr BP. These centennial time scale rainfall variations in our records are linked to the intensity of El-Niño Southern Oscillations. VL - 516 UR - https://linkinghub.elsevier.com/retrieve/pii/S0031018218303444 ER - TY - JOUR T1 - The Mighty Susquehanna—Extreme Floods in Eastern North America During the Past Two Millennia JF - Geophysical Research Letters Y1 - 2019 A1 - Toomey, Michael A1 - Cantwell, Meagan A1 - Colman, Steven A1 - Cronin, Thomas A1 - Donnelly, Jeffrey A1 - Giosan, Liviu A1 - Heil, Clifford A1 - Korty, Robert A1 - Marot, Marci A1 - Willard, Debra AB - The hazards posed by infrequent major floods to communities along the Susquehanna River and the ecological health of Chesapeake Bay remain largely unconstrained due to the short length of streamgage records. Here we develop a history of high‐flow events on the Susquehanna River during the late Holocene from flood deposits contained in MD99‐2209, a sediment core recovered in 26 m of water from Chesapeake Bay near Annapolis, Maryland, United States. We identify coarse‐grained deposits left by Hurricane Agnes (1972) and the Great Flood of 1936, as well as during three intervals that predate instrumental flood records (~1800–1500, 1300–1100, and 400–0 CE). Comparison to sedimentary proxy data (pollen and ostracode Mg/Ca ratios) from the same core site indicates that prehistoric flooding on the Susquehanna often accompanied cooler‐than‐usual winter/spring temperatures near Chesapeake Bay—typical of negative phases of the North Atlantic Oscillation and conditions thought to foster hurricane landfalls along the East Coast. VL - 46 UR - https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018GL080890 IS - 6 ER - TY - JOUR T1 - Millennial-scale carbon accumulation and molecular transformation in a permafrost core from Interior Alaska JF - Geochimica et Cosmochimica Acta Y1 - 2019 A1 - Hutchings, J.A. A1 - Bianchi, T.S. A1 - Kaufman, D.S. A1 - Kholodov, A.L. A1 - Vaughn, D.R. A1 - Schuur, E.A.G. KW - amino acids KW - biomarkers KW - branched GDGTs KW - lignin phenols KW - organic carbon KW - permafrost AB - Organic carbon stored in high-latitude permafrost represents a potential positive feedback to climate warming as well as a valuable store of paleoenvironmental information. The below-freezing conditions have effectively removed permafrost organic material from the modern carbon cycle and preserved its pre-freezing bulk and molecular states. The conditions that lead to efficient burial of organic carbon (OC) within permafrost were investigated by measuring OC stocks, past accumulation rates, and biogeochemical composition of a permafrost core taken from Interior Alaska dating back to 40 ka. The post-glacial Marine Isotope Stage 1 is represented by the top 1.2 m of the core and contains 64.7 kg OC/m2 with an accumulation rate of 4.3 g OC/m2/yr. The sediments that accumulated around the Last Glacial Maximum contain 9.9 kg OC/m2 with an accumulation rate of 0.5 g OC/m2/yr. Carbon storage (144.7 kg OC/m2) and accumulation (26.1 g OC/m2/yr) are both observed to be greatest between 35 and 40 ka, late during the Marine Isotope Stage 3 global interstadial. The extent of OC degradation was assessed using lignin and amino acid biomarkers with both approaches indicating well-preserved contemporary active layer and interstadial OC, whereas stadial OC was highly degraded. Lignin compositional indices throughout the core appear altered by sorptive processes that confounded some expected trends in the overall organic matter composition, while amino acids provided a more integrated pattern of change. Significant correlations between carbon-normalized hydroxyproline and total lignin concentrations further support the usefulness of hydroxyproline as an indicator for the abundance of plant organic matter. A novel amino acid plant-microbial index of the ratio of microbial-specific muramic acid and diaminopimelic acid biomarkers to the plant-specific hydroxyproline biomarker, indicate a transition from plant-dominated organic matter in fresh organic soils (index values of 0.01–0.20) to more microbial-dominated organic matter in degraded mineral soils (index values of 0.50–2.50). The branched glycerol dialkyl glycerol tetraether composition is complex and is not immediately compatible with existing temperature transfer functions. Residence time within the active layer is interpreted to integrate key factors such as primary productivity, inorganic sediment delivery, and other climate factors that control soil organic matter degradation. The Marine Isotope Stage 3, mid-Wisconsin interstadial period at this locality was forest-dominated and suggests the currently prevailing tundra ecotone is sensitive to environmental change. The majority of buried permafrost OC is high in degradability and if thawed, would be expected to be highly vulnerable to microbial decomposition. VL - 253 UR - https://www.sciencedirect.com/science/article/pii/S0016703719301863 ER - TY - JOUR T1 - Millennial-scale fluctuations in water volume transported by the Tsushima Warm Current in the Japan Sea during the Holocene JF - Global and Planetary Change Y1 - 2019 A1 - Horikawa, Keiji A1 - Kodaira, Tomohiro A1 - Ikehara, Ken A1 - Murayama, Masafumi A1 - Zhang, Jing KW - Holocene KW - Mg/Ca-derived KW - Neogloboquadrina incompta KW - sea-surface temperature KW - Solar forcing KW - The Japan Sea KW - Tsushima KW - Warm Current AB - Cyclic changes in volume transport of the Tsushima Warm Current (TWC) have been argued from diatom records in the southern Japan Sea off the Japanese islands during the Holocene. Although this phenomenon has not yet been confirmed by various proxy data, determining whether or not these oceanographic changes occurred is crucial for clarifying the nature of oceanographic changes in the southern Japan Sea. Here, we conducted a coupled analysis of Mg/Ca ratios and oxygen isotopes (δ18O) in shallow-dwelling Neogloboquadrina incompta from 13 core-top sediments in southern Japan, and developed a new equation for Mg/Ca temperature calibration (Mg/Ca = 0.311 × exp (0.07 × T)) as a proxy for spring sea surface temperature (SST). Using the newly developed, species-specific Mg/Ca-paleothermometry, we reconstructed SST variability for the past 6800 years from core YK10-7-PC09 in the southern Japan Sea. The Mg/Ca-derived SST record clearly represented five warmer periods at 6200–6000, 4900–4500, 4200–3800, 2600–2100, and 900–400 cal. year BP, almost consistent with previously published diatom records. These warmer events also corresponded to the periods in which warm molluscan assemblages increased at the northern end of the TWC, suggesting that periods of higher SST can be seen as reflecting the increased volume transport of the TWC. We interpreted the results of a model study showing that higher solar irradiance provoked positive Arctic Oscillation (AO)-like spatial patterns and the negative phase of the Pacific Decadal Oscillation (PDO) to mean that increased (reduced) TWC volume transport on the multi-centennial to millennial time scales was caused by high (low) solar insolation via a potential link between AO and PDO. Given that larger and more frequent volcanic eruptions occurred in the mid Holocene than in the late Holocene, volcanic forcing on the TWC volume transport changes would have been more significant during the former, as seen in the highly variable SST from this period and distinct decreases in SST around ~5900 cal. year BP and ~6400 cal. year BP. The millennial-scale fluctuations seen in SSTs in the southern Japan Sea would have had a large impact on the evolution of vegetation and human adaptation in the northern Japanese islands, adjacent to the Japan Sea, over the last 6800 years. VL - 183 UR - https://linkinghub.elsevier.com/retrieve/pii/S0921818118306465 ER - TY - JOUR T1 - Mineral protection regulates long-term global preservation of natural organic carbon JF - Nature Y1 - 2019 A1 - Hemingway, Jordon D. A1 - Rothman, Daniel H. A1 - Grant, Katherine E. A1 - Rosengard, Sarah Z. A1 - Eglinton, Timothy I. A1 - Derry, Louis A. A1 - Galy, Valier V. AB - The balance between photosynthetic organic carbon production and respiration controls atmospheric composition and climate1,2. The majority of organic carbon is respired back to carbon dioxide in the biosphere, but a small fraction escapes remineralization and is preserved over geological timescales3. By removing reduced carbon from Earth’s surface, this sequestration process promotes atmospheric oxygen accumulation2 and carbon dioxide removal1. Two major mechanisms have been proposed to explain organic carbon preservation: selective preservation of biochemically unreactive compounds4,5 and protection resulting from interactions with a mineral matrix6,7. Although both mechanisms can operate across a range of environments and timescales, their global relative importance on 1,000-year to 100,000-year timescales remains uncertain4. Here we present a global dataset of the distributions of organic carbon activation energy and corresponding radiocarbon ages in soils, sediments and dissolved organic carbon. We find that activation energy distributions broaden over time in all mineral-containing samples. This result requires increasing bond-strength diversity, consistent with the formation of organo-mineral bonds8 but inconsistent with selective preservation. Radiocarbon ages further reveal that high-energy, mineral-bound organic carbon persists for millennia relative to low-energy, unbound organic carbon. Our results provide globally coherent evidence for the proposed7 importance of mineral protection in promoting organic carbon preservation. We suggest that similar studies of bond-strength diversity in ancient sediments may reveal how and why organic carbon preservation—and thus atmospheric composition and climate—has varied over geological time. VL - 570 UR - http://www.nature.com/articles/s41586-019-1280-6 IS - 7760 ER - TY - JOUR T1 - Multiple independent records of local glacier variability on Nuussuaq, West Greenland, during the Holocene JF - Quaternary Science Reviews Y1 - 2019 A1 - Schweinsberg, Avriel D. A1 - Briner, Jason P. A1 - Licciardi, Joseph M. A1 - Bennike, Ole A1 - Lifton, Nathaniel A. A1 - Graham, Brandon L. A1 - Young, Nicolás E. A1 - Schaefer, Joerg M. A1 - Zimmerman, Susan H. KW - Cosmogenic 10Be KW - Cosmogenic in situ 14C KW - Greenland KW - Holocene KW - lake sediment KW - Mountain glaciers KW - Neoglaciation AB - The sensitivity of mountain glaciers to small-scale climate fluctuations makes records of their past extent among the best proxies for identifying spatio-temporal climate variability. Here we build on the few existing Holocene records of local glacier change in Greenland by using three independent geochronological methods—proglacial lake sediment analysis, cosmogenic 10Be surface-exposure dating, and in situ 14C burial modeling—to reconstruct continuous records of Holocene glacier variability on Nuussuaq, West Greenland. 10Be ages of perched boulders indicate eastern Nuussuaq was deglaciated between ∼11.0 and 10.5 ka. Radiocarbon-dated sediments from two lakes on Nuussuaq contain mineral-rich layers between ∼9.6 and 9.0 and ∼8.7–8.0 cal ka BP that may be correlative with nearby ice sheet moraines deposited in the early Holocene. Multiple proxies for glacier size indicate frequent, high-amplitude glacier fluctuations superimposed on net glacier growth during the late Holocene, with significant ice expansion phases at ∼3.7 ka, 2.8 ka, and throughout the past ∼2 ka. Mean 10Be ages from five nested moraine crests confirm that local glacier extents on Nuussuaq culminated during both the Little Ice Age [∼1470 C.E. (n = 3) and 1750 C.E. (n = 3)] and the preceding centuries (∼520–1320 C.E.; n = 11). Results reveal that local glaciers on Nuussuaq episodically advanced and retreated at centennial timescales throughout the Holocene, most likely in response to regional climate changes in West Greenland superimposed on the progressive insolation-driven cooling trend in the Northern Hemisphere. Our new 10Be moraine chronologies coupled with other glacier-size proxies corroborate an emerging pattern of significant summer cooling and glacier expansion in the centuries prior to the Little Ice Age in the Arctic. VL - 215 UR - https://www.sciencedirect.com/science/article/pii/S0277379118308771 ER - TY - JOUR T1 - MULTI-SUBSTRATE RADIOCARBON DATA CONSTRAIN DETRITAL AND RESERVOIR EFFECTS IN HOLOCENE SEDIMENTS OF THE GREAT SALT LAKE, UTAH JF - RADIOCARBON Y1 - 2019 A1 - Bowen, Gabriel J. A1 - Nielson, Kristine E. A1 - Eglinton, Timothy I. AB - The radiocarbon (C-14) content of simultaneously deposited substrates in lacustrine archives may differ due to reservoir and detrital effects, complicating the development of age models and interpretation of proxy records. Multi-substrate C-14 studies quantifying these effects remain rare, however, particularly for large, terminal lake systems, which are excellent recorders of regional hydroclimate change. We report C-14 ages of carbonates, brine shrimp cysts, algal mat biomass, total organic carbon (TOC), terrestrial macrofossils, and n-alkane biomarkers from Holocene sediments of the Great Salt Lake (GSL), Utah. C-14 ages for co-deposited aquatic organic substrates are generally consistent, with small offsets that may reflect variable terrestrial organic matter inputs to the system. Carbonates and long-chain n-alkanes derived from vascular plants, however, are similar to 1000-4000 C-14 years older than other substrates, reflecting deposition of pre-aged detrital materials. All lacustrine substrates are C-14-depleted compared to terrestrial macrofossils, suggesting that the reservoir age of the GSL was > 1200 years throughout most of the Holocene, far greater than the modern reservoir age of the lake (similar to 300 years). These results suggest good potential for multi-substrate paleoenvironmental reconstruction from Holocene GSL sediments but point to limitations including reservoir-induced uncertainty in( 14)C chronologies and attenuation and time-shifting of some proxy signals due to detrital effects. VL - 61 ER - TY - JOUR T1 - New AMS Dates for Verteba Cave and Stable Isotope Evidence of Human Diet in The Holocene Forest-Steppe, UkraineABSTRACT JF - Radiocarbon Y1 - 2019 A1 - Ledogar, Sarah H A1 - Karsten, Jordan K A1 - Madden, Gwyn D A1 - Schmidt, Ryan A1 - Sokohatskyi, Mykhailo P A1 - Feranec, Robert S KW - archaeometry KW - cave burials KW - Eastern Europe KW - funerary ritual KW - Tripolye culture AB - Excavations at several locations in Verteba Cave have uncovered a large amount of human skeletal remains in association with faunal bones and Tripolye material culture. We aim to establish radiocarbon (14C) dates for eight sites and to evaluate whether these deposits are singular events, or slow accumulations over time. 14C measurements, along with stable carbon and nitrogen isotope data from human and faunal remains, were collected from 18 specimens. Stable isotope values were used to evaluate human and animal diet, and whether freshwater reservoir effects offset measured dates. We found diets of the sampled species had limited to no influence from freshwater resources. Human diet appears to be dominated by terrestrial plants and herbivores. Four new sites were identified as Eneolithic. Comparisons of dates from top and bottom strata for two sites (7 and 20) reveal coeval dates, and we suggest that these deposits represent discrete events rather than slow continuous use. Lastly, we identified dates from the Mesolithic (8490±45 BP, 8765±30 BP), Iron Age (2505±20 BP), Slavic state era (1315±25 BP), and Medieval Period (585±15 BP), demonstrating periodic use of the cave by humans prior to and after the Eneolithic. VL - 61 UR - https://www.cambridge.org/core/product/identifier/S0033822218000528/type/journal_article IS - 1 ER - TY - JOUR T1 - New Last Glacial Maximum ice thickness constraints for the Weddell Sea Embayment, Antarctica JF - The Cryosphere Y1 - 2019 A1 - Nichols, Keir A. A1 - Goehring, Brent M. A1 - Balco, Greg A1 - Johnson, Joanne S. A1 - Hein, Andrew S. A1 - Todd, Claire AB - We describe new Last Glacial Maximum (LGM) ice thickness constraints for three locations spanning the Weddell Sea Embayment (WSE) of Antarctica. Samples collected from the Shackleton Range, Pensacola Mountains, and the Lassiter Coast constrain the LGM thickness of the Slessor Glacier, Foundation Ice Stream, and grounded ice proximal to the modern Ronne Ice Shelf edge on the Antarctic Peninsula, respectively. Previous attempts to reconstruct LGM-to-present ice thickness changes around the WSE used measurements of long-lived cosmogenic nuclides, primarily Be-10. An absence of post-LGM apparent exposure ages at many sites led to LGM thickness reconstructions that were spatially highly variable and inconsistent with flow line modelling. Estimates for the contribution of the ice sheet occupying the WSE at the LGM to global sea level since deglaciation vary by an order of magnitude, from 1.4 to 14.1m of sea level equivalent. Here we use a short-lived cosmogenic nuclide, in situ-produced C-14, which is less susceptible to inheritance problems than Be-10 and other long-lived nuclides. We use in situ C-14 to evaluate the possibility that sites with no post-LGM exposure ages are biased by cosmogenic nuclide inheritance due to surface preservation by cold-based ice and non-deposition of LGM-aged drift. Our measurements show that the Slessor Glacier was between 310 and up to 655m thicker than present at the LGM. The Foundation Ice Stream was at least 800m thicker, and ice on the Lassiter Coast was at least 385m thicker than present at the LGM. With evidence for LGM thickening at all of our study sites, our in situ C-14 measurements indicate that the long-lived nuclide measurements of previous studies were influenced by cosmogenic nuclide inheritance. Our inferred LGM configuration, which is primarily based on minimum ice thickness constraints and thus does not constrain an upper limit, indicates a relatively modest contribution to sea level rise since the LGM of < 4.6 m, and possibly as little as < 1.5 m. VL - 13 UR - http://nora.nerc.ac.uk/id/eprint/526081/ IS - 11 ER - TY - JOUR T1 - On the Origin of Aged Sedimentary Organic Matter Along a River‐Shelf‐Deep Ocean Transect JF - Journal of Geophysical Research: Biogeosciences Y1 - 2019 A1 - Bao, Rui A1 - Zhao, Meixun A1 - McNichol, Ann A1 - Wu, Ying A1 - Guo, Xinyu A1 - Haghipour, Negar A1 - Eglinton, Timothy I. KW - Carbon cycle KW - hydrodynamic processes KW - organic carbon KW - radiocarbon KW - sediments AB - To assess the influences of carbon sources and transport processes on the C-14 age of organic matter (OM) in continental margin sediments, we examined a suite of samples collected along a river-shelf-deep ocean transect in the East China Sea (ECS). Ramped pyrolysis-oxidiation was conducted on suspended particulate matter in the Yangtze River and on surface sediments from the ECS shelf and northern Okinawa Trough. C-14 ages were determined on OM decomposition products within different temperature windows. These measurements suggest that extensive amounts of pre-old (i.e., millennial age) organic carbon (OC) are subject to degradation within and beyond the Yangtze River Delta, and this process is accompanied by an exchange of terrestrial and marine OM. These results, combined with fatty acid concentration data, suggest that both the nature and extent of OM preservation/degradation as well as the modes of transport influence the C-14 ages of sedimentary OM. Additionally, we find that the age of (thermally) refractory OC increases during across-shelf transport and that the age offset between the lowest and highest temperature OC decomposition fractions also increases along the shelf-to-trough transect. Amplified interfraction spread or C-14 heterogeneity is the greatest in the Okinawa Trough. Aged sedimentary OM across the transect may be a consequence of several reasons including fossil OC input, selective degradation of younger OC, hydrodynamic sorting processes, and aging during lateral transport. Consequently, each of them should be considered in assessing the C-14 results of sedimentary OM and its implications for the carbon cycle and interpretation of sedimentary records. VL - 124 UR - https://doi.org/10.1029/2019JG005107 IS - 8 ER - TY - JOUR T1 - Pacific climate influences on ocean conditions and extreme shell growth events in the Northwestern Atlantic (Gulf of Maine) JF - Climate Dynamics Y1 - 2019 A1 - Wanamaker, Alan D. A1 - Griffin, Shelly M. A1 - Ummenhofer, Caroline C. A1 - Whitney, Nina M. A1 - Black, Bryan A1 - Parfitt, Rhys A1 - Lower-Spies, Erin E. A1 - Introne, Douglas A1 - Kreutz, Karl J. AB - The Gulf of Maine is undergoing rapid environmental and ecological changes, yet our spatial and temporal understanding of the climatic and hydrographic variability in this region, including extreme events, is limited and biased to recent decades. In this study, we utilize a highly replicated, multi-century master shell growth chronology derived from the annual increments formed in the shells of the long-lived bivalve Arctica islandica collected in 38 m from the central coastal region in the Gulf of Maine. Our results indicate that shell growth is highly synchronous and inversely related to local seawater temperatures. Using composite analyses of extreme shell growth events from CE 1900 to 2013, we extend our understanding of the factors driving oceanic variability and shell growth in the Northwestern Atlantic back to CE 1761. We suggest that extreme shell growth events are primarily controlled by Gulf of Maine sea surface temperature (SST) and stratification conditions, which in turn appear to be largely influenced by SST patterns in the Pacific Ocean through their influence on mid-latitude atmospheric circulation patterns and the location of the eddy-driven jet. The large-scale jet dynamics during these extreme years manifest as precipitation and moisture transport anomalies and regional SST conditions in the Gulf of Maine that either enhance or inhibit shell growth. Pacific climate variability is thus an important, yet understudied, influence on Gulf of Maine ocean conditions. VL - 52 UR - https://link.springer.com/article/10.1007/s00382-018-4513-8 IS - 11 ER - TY - RPRT T1 - Paleoseismic Investigation of the Levan and Fayette Segments of the Wasatch Fault Zone, Juab and Sanpete Counties, Utah Y1 - 2019 A1 - McDonald, Greg N. A1 - Hiscock, Adam I. A1 - Hylland, Micheal D. PB - Utah Geological Survey UR - https://geodata.geology.utah.gov/pages/view.php?ref=62721 ER - TY - JOUR T1 - Petrocarbon evolution: Ramped pyrolysis/oxidation and isotopic studies of contaminated oil sediments from the Deepwater Horizon oil spill in the Gulf of Mexico JF - PLOS ONE Y1 - 2019 A1 - Rogers, Kelsey L. A1 - Bosman, Samantha H. A1 - Lardie-Gaylord, Mary A1 - McNichol, Ann A1 - Rosenheim, Brad E. A1 - Montoya, Joseph P. A1 - Chanton, Jeffrey P. ED - Cooper, Lee W. KW - C-14 ANALYSES; MARINE SNOW KW - degradation KW - fractionation KW - organic-matter KW - POLYCYCLIC AROMATIC-HYDROCARBONS; MICROBIAL COMMUNITY RESPONSE KW - radiocarbon KW - STABLE CARBON KW - surface sediments AB - Hydrocarbons released during the Deepwater Horizon (DWH) oil spill weathered due to exposure to oxygen, light, and microbes. During weathering, the hydrocarbons' reactivity and lability was altered, but it remained identifiable as "petrocarbon" due to its retention of the distinctive isotope signatures (C-14 and C-13) of petroleum. Relative to the initial estimates of the quantity of oil-residue deposited in Gulf sediments based on 2010-2011 data, the overall coverage and quantity of the fossil carbon on the seafloor has been attenuated. To analyze recovery of oil contaminated deep-sea sediments in the northern Gulf of Mexico we tracked the carbon isotopic composition (C-13 and C-14, radiocarbon) of bulk sedimentary organic carbon through time at 4 sites. Using ramped pyrolysis/oxidation, we determined the thermochemical stability of sediment organic matter at 5 sites, two of these in time series. There were clear differences between crude oil (which decomposed at a lower temperature during ramped oxidation), natural hydrocarbon seep sediment (decomposing at a higher temperature; Delta C-14 = -189 parts per thousand) and our control site (decomposing at a moderate temperature; Delta C-14 = -189 parts per thousand), in both the stability (ability to withstand ramped temperatures in oxic conditions) and carbon isotope signatures. We observed recovery toward our control site bulk Delta C-14 composition at sites further from the wellhead in similar to 4 years, whereas sites in closer proximity had longer recovery times. The thermographs also indicated temporal changes in the composition of contaminated sediment, with shifts towards higher temperature CO2 evolution over time at a site near the wellhead, and loss of higher temperature CO2 peaks at a more distant site. VL - 14 UR - https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0212433 IS - 2 ER - TY - JOUR T1 - Radiocarbon age of different photoreactive fractions of freshwater dissolved organic matter JF - Organic Geochemistry Y1 - 2019 A1 - Ishikawa, Naoto F. A1 - Butman, David A1 - Raymond, Peter A. KW - dissolved organic carbon KW - Mixing model KW - Oxidation time KW - UV irradiation KW - Δ14C AB - Dissolved organic carbon (DOC) plays a major role in aquatic carbon cycling. In order to determine if DOC photolability was related to DOC age, we tested the effect of oxidation time using UV irradiation on natural radiocarbon concentrations (Δ14C) of DOC in six US rivers. The most photo-labile DOC was 14C youngest. After a 100 min UV irradiation, most DOC (>93%) was oxidized in two out of the six rivers studied. On the other hand, the other four rivers still had a considerable amount (>20%) of DOC resistant to UV oxidation, which showed lower Δ14C values than those of bulk DOC. We also found that the concentration and Δ14C value of bulk DOC are controlled by the photochemically intermediate fraction. The results suggest that 14C age of organic matter is not homogeneous within DOC, the degree of which may depend on the characteristics unique to rivers. VL - 135 UR - https://linkinghub.elsevier.com/retrieve/pii/S014663801930107X ER - TY - JOUR T1 - Reconstructing reef fish communities using fish otoliths in coral reef sediments JF - PLOS ONE Y1 - 2019 A1 - Lin, Chien-Hsiang A1 - De Gracia, Brigida A1 - Pierotti, Michele E. R. A1 - Andrews, Allen H. A1 - Griswold, Katie A1 - O’Dea, Aaron ED - Zapalski, Mikołaj K. AB - Little is known about long-term changes in coral reef fish communities. Here we present a new technique that leverages fish otoliths in reef sediments to reconstruct coral reef fish communities. We found over 5,400 otoliths in 169 modern and mid-Holocene bulk samples from Caribbean Panama and Dominican Republic mid-Holocene and modern reefs, demonstrating otoliths are abundant in reef sediments. With a specially-built reference collection, we were able to assign over 4,400 otoliths to one of 56 taxa (35 families) though mostly at genus and family level. Many otoliths were from juvenile fishes for which identification is challenging. Richness (by rarefaction) of otolith assemblages was slightly higher in modern than mid-Holocene reefs, but further analyses are required to elucidate the underlying causes. We compared the living fish communities, sampled using icthyocide, with the sediment otolith assemblages on four reefs finding the otolith assemblages faithfully capture the general composition of the living fish communities. Radiocarbon dating performed directly on the otoliths suggests that relatively little mixing of sediment layers particularly on actively accreting branching coral reefs. All otolith assemblages were strongly dominated by small, fast-turnover fish taxa and juvenile individuals, and our exploration on taxonomy, functional ecology and taphonomy lead us to the conclusion that intense predation is likely the most important process for otolith accumulation in reef sediments. We conclude that otolith assemblages in modern and fossil reef sediments can provide a powerful tool to explore ecological changes in reef fish communities over time and space. VL - 14 UR - https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0218413 IS - 6 ER - TY - JOUR T1 - Salt marsh ecosystem restructuring enhances elevation resilience and carbon storage during accelerating relative sea-level rise JF - Estuarine, Coastal and Shelf Science Y1 - 2019 A1 - Gonneea, Meagan Eagle A1 - Maio, Christopher V. A1 - Kroeger, Kevin D. A1 - Hawkes, Andrea D. A1 - Mora, Jordan A1 - Sullivan, Richard A1 - Madsen, Stephanie A1 - Buzard, Richard M. A1 - Cahill, Niamh A1 - Donnelly, Jeffrey P. KW - 14-Carbon KW - accretion KW - Carbon storage KW - Elevation KW - Salt marsh KW - Sea level index point KW - sea-level rise AB - Salt marshes respond to sea-level rise through a series of complex and dynamic bio-physical feedbacks. In this study, we found that sea-level rise triggered salt marsh habitat restructuring, with the associated vegetation changes enhancing salt marsh elevation resilience. A continuous record of marsh elevation relative to sea level that includes reconstruction of high-resolution, sub-decadal, marsh elevation over the past century, coupled with a lower-resolution 1500-year record, revealed that relative sea-level rose 1.5 ± 0.4 m, following local glacial isostatic adjustment (1.2 mm/yr). As sea-level rise has rapidly accelerated, the high marsh zone dropped 11 cm within the tidal frame since 1932, leading to greater inundation and a shift to flood- and salt-tolerant low marsh species. Once the marsh platform fell to the elevation favored by low-marsh Spartina alterniflora, the elevation stabilized relative to sea level. Currently low marsh accretion keeps pace with sea-level rise, while present day high marsh zones that have not transitioned to low marsh have a vertical accretion deficit. Greater biomass productivity, and an expanding subsurface accommodation space favorable for salt marsh organic matter preservation, provide a positive feed-back between sea-level rise and marsh platform elevation. Carbon storage was 46 ± 28 g C/m2/yr from 550 to 1800 CE, increasing to 129 ± 50 g C/m2/yr in the last decade. Enhanced carbon storage is controlled by vertical accretion rates, rather than soil carbon density, and is a direct response to anthropogenic eustatic sea-level rise, ultimately providing a negative feedback on climate warming. VL - 217 UR - https://linkinghub.elsevier.com/retrieve/pii/S0272771418306851 ER - TY - JOUR T1 - Sea Level Rise Explains Changing Carbon Accumulation Rates in a Salt Marsh Over the Past Two Millennia JF - Journal of Geophysical Research: Biogeosciences Y1 - 2019 A1 - McTigue, Nathan A1 - Davis, Jenny A1 - Rodriguez, Antonio B. A1 - McKee, Brent A1 - Atencio, Anna A1 - Currin, Carolyn KW - Carbon storage KW - Geochronology KW - Salt marsh KW - sea‐level rise AB - High rates of carbon burial observed in wetland sediments have garnered attention as a potential “natural fix” to reduce the concentration of carbon dioxide (CO2) in Earth's atmosphere. A carbon accumulation rate (CAR) can be determined through various methods that integrate a carbon stock over different time periods, ranging from decades to millennia. Our goal was to assess how CAR changed over the lifespan of a salt marsh. We applied a geochronology to a series of salt marsh cores using both 14C and 210Pb markers to calculate CARs that were integrated between 35 and 2,460 years before present. CAR was 39 g C·m−2·year−1 when integrated over millennia but was upward of 148 g C·m−2·year−1 for the past century. We present additional evidence to account for this variability by linking it to changes in relative sea level rise (RSLR), where higher rates of RSLR were associated with higher CARs. Thus, the CAR calculated for a wetland should integrate timescales that capture the influence of contemporary RSLR. Therefore, caution should be exercised not to utilize a CAR calculated over inappropriately short or long timescales as a current assessment or forecasting tool for the climate change mitigation potential of a wetland. VL - 124 UR - https://onlinelibrary.wiley.com/doi/abs/10.1029/2019JG005207 IS - 10 ER - TY - JOUR T1 - Sea-level, monsoonal, and anthropogenic impacts on the millennial-scale variability of siliciclastic sediment input into the western Philippine sea since 27 ka JF - Journal of Asian Earth Sciences Y1 - 2019 A1 - Xu, Zhaokai A1 - Li, Tiegang A1 - Clift, Peter D. A1 - Wan, Shiming A1 - Lim, Dhongil A1 - Chang, Fengming A1 - Sun, Rongtao AB - Multiproxy records from Core MD06-3054 in the western Philippine Sea and published results from the nearby Core MD06-3052, which are both located at the northern margin of the Western Pacific Warm Pool (WPWP), provide precise reconstructions and evidence for the potential controls on continental erosion and weathering intensities in Luzon. These data also constrain sediment source-to-sink processes in the sea since 27 ka at the millennial scale. We demonstrate that the siliciclastic fraction is derived from Luzon volcanic rocks and eolian dust from mainland Asia. Stronger physical erosion and chemical weathering generally occurred during the last glaciation, Heinrich Event 1, the Younger Dryas, and the period from 10.3 to 11.3 ka. In contrast, the Bølling-Allerød was characterized by weaker physical erosion and chemical weathering. During the last glaciation, Heinrich Event 1, and the Younger Dryas, the lower sea level led to enhanced erosion and weathering of the exposed shelf sediments. In contrast, the weaker physical erosion and chemical weathering that occurred during the Bølling-Allerød and the Holocene, except after 2.1 ka, are closely correlated with the higher sea level. The stronger physical erosion and chemical weathering at 10.3–11.3 ka may be derived from the reworking of older sediments during the time of a strengthening summer monsoon. Furthermore, enhanced human activity since 2.1 ka has become the dominant control on erosion in Luzon. Rapid weathering changes in the WPWP during the last deglaciation highlight the high variability in local controls at low latitudes during these periods and the potential influence of controls at high latitudes. VL - 177 UR - https://www.sciencedirect.com/science/article/abs/pii/S1367912019301506 ER - TY - JOUR T1 - Sediment accumulation and sedimentation rates in playas on the High Plains of western Kansas, USA JF - Geomorphology Y1 - 2019 A1 - Bowen, Mark W. A1 - Johnson, William C. KW - 210Pb KW - Agricultural KW - chronology KW - Holocene KW - Radiocarbon dating KW - sedimentation AB - Grassland ecosystems are some of the most modified ecosystems in the world, largely due to conversion to cropland, and the High Plains of the central United States is no exception. Playa wetlands are ubiquitous features of the High Plains and have experienced increased sediment accumulation, which is the primary cause of reduced playa ecosystem function. Seven playas on the High Plains of western Kansas, five with cropland-dominated watersheds and two with grassland-dominated watersheds, were examined to quantify the amount of recent (past ~100–175 yr) sediment accumulated within playas and to establish chronologies of playa filling. Thicknesses of recent sediment were determined in the field, and soil cores were extracted from study playas. Four playa cores were analyzed for 210Pb to establish the chronology of recent sediment accumulation and sedimentation rates. Chronologies of pre-agricultural sediments and sedimentation rates were calculated by 14C dating of buried soils preserved within playa cores. Radiocarbon ages indicate playa stratigraphic records span the Holocene and that these playas have persisted on the landscape since at least the Late Pleistocene. Long-term, natural sedimentation rates were highest during the Pleistocene-Holocene transition and early Holocene, at ~2–4 cm/century. During the middle and late Holocene, sedimentation rates averaged ~1 cm/century. Cropland playas accumulated ~10–15 cm of recent sediment at average rates of ~6.5–10 cm/century, while grassland playas accumulated only ~2 cm of recent sediment. Conversion of watersheds to cropland has greatly accelerated sediment accumulation within playas, which is generally resulting in a decline in critical playa ecosystem functions. VL - 342 UR - https://linkinghub.elsevier.com/retrieve/pii/S0169555X19302612 ER - TY - DATA T1 - Sedimentary Data from Grand Bay, Alabama/Mississippi, 2014–2016 Y1 - 2019 A1 - Marot, Marci A1 - Smith, Christopher G. A1 - McCloskey, Terrence A. A1 - Locker, Stanley D. AB - This data release is an archive of sedimentary field and laboratory analytical data collected in Grand Bay, Alabama/Mississippi from 2014-2016 by scientists from the U.S. Geological Survey St. Petersburg Coastal and Marine Science Center (USGS SPCMSC). This work, a component of the SPCMSC’s Sea-level and Storm Impacts on Estuarine Environments and Shorelines (SSIEES) project, provides the necessary data to quantify sedimentation rates and sediment sources for the marsh and estuary. The SSIEES project objective is to evaluate the exchange of sediment material between the marsh and estuary due to extreme storms and sea-level rise. Micropaleontological data from select cores and surface samples are available in Haller and others (2018, https://doi.org/10.5066/F7MC8X5F, https://doi.org/10.5066/F7445KSG). Single-beam bathymetry of Grand Bay proper and multi-beam bathymetry of several marsh-edge eroding shorelines are reported in Dewitt and others (2017, https://doi.org/10.3133/ds1070) and Stalk and others (2018, https://doi.org/10.5066/F7MC8Z9N), respectively. Subbottom and sidescan sonar data for Grand Bay proper are reported in Locker and others (2018, https://doi.org/10.5066/P9374DKQ). This publication includes data for the sediment cores and surface sediments taken in Grand Bay marsh and estuary during five sampling periods of this study, which were designated as USGS Field Activity Numbers (FAN) 2014-323-FA (project ID 14CCT01), 2015-315-FA (project ID 15CCT02), 2016-331-FA (project ID 16CCT03), 2016-348-FA (project ID 16CCT04), and 2016-358-FA (project ID 16CCT07). Data products include: GPS-derived site locations and elevations; core photographs, logs, and x-radiographs; lithologic, radiochemical, elemental composition, stable isotopic composition, and radiocarbon data; and Federal Geographic Data Committee (FGDC) metadata. Note: This data release was versioned on April 28, 2020. Please see the Suggested Citation section for details. PB - U.S. Geological Survey UR - https://doi.org/10.5066/P9FO8R3Y ER - TY - JOUR T1 - Selective Preservation of Coccolith Calcite in Ontong‐Java Plateau Sediments JF - Paleoceanography and Paleoclimatology Y1 - 2019 A1 - Subhas, Adam V. A1 - McCorkle, Daniel C. A1 - Quizon, Alex A1 - McNichol, Ann P. A1 - Long, Matthew H. KW - BIOMINERALIZATION KW - caco3 dissolution KW - CEARA RISE KW - dissolution kinetics KW - IN-SITU MEASUREMENTS; DEEP-SEA CARBONATES; PLANKTONIC-FORAMINIFERA; EQUATORIAL PACIFIC KW - surface sediments KW - WATER INTERFACE VL - 34 UR - https://apps.webofknowledge.com/InboundService.do?product=WOS&Func=Frame&DestFail=http%3A%2F%2Fwww.webofknowledge.com&SrcApp=search&SrcAuth=Alerting&SID=8DpsdyQUduuojUwg61F&customersID=Alerting&mode=FullRecord&IsProductCode=Yes&AlertId=ab9062f8-b111-4f95- IS - 12 ER - TY - JOUR T1 - Shellfish, Geophytes, and Sedentism on Early Holocene Santa Rosa Island, Alta California, USA JF - The Journal of Island and Coastal Archaeology Y1 - 2019 A1 - Erlandson, Jon M. A1 - Rick, Torben C. A1 - Ainis, Amira F. A1 - Gill, Kristina M. A1 - Jew, Nicholas P. A1 - Reeder-Myers, Leslie A. AB - Archaeobotanical remains recovered from a large ∼8000-year-old-shell midden (CA-SRI-666) on Santa Rosa Island provide the first ancient plant data from this large island, shedding light on ancient patterns of plant use, subsistence, and sedentism. Faunal data from shell midden samples retrieved from three site loci contain evidence for harvesting of rocky intertidal shellfish and estuarine clams and oysters from a paleo-estuary in the vicinity. CA-SRI-666 appears to have been an Early Holocene village site occupied year round. A key to the development of early sedentary societies on the island may have been geophytes, especially Brodiaea-type corms, which provided an abundant source of carbohydrates and calories that complemented marine resources rich in fat and whole animal proteins. Our data demonstrate the value of integrating paleobotanical and zooarchaeological data from island and coastal archaeological sites to help elucidate human social, cultural, and environmental dynamics, including sedentism. UR - https://www.tandfonline.com/doi/abs/10.1080/15564894.2019.1579272?journalCode=uica20 ER - TY - JOUR T1 - Significance of Perylene for Source Allocation of Terrigenous Organic Matter in Aquatic SedimentsSignificance of Perylene for Source Allocation of Terrigenous Organic Matter in Aquatic Sediments JF - Environmental Science & Technology Y1 - 2019 A1 - Hanke, Ulrich M. A1 - Lima-Braun, Ana L. A1 - Eglinton, Timothy I. A1 - Donnelly, Jeffrey P. A1 - Galy, Valier A1 - Poussart, Pascale A1 - Hughen, Konrad A1 - McNichol, Ann P. A1 - Xu, Li A1 - Reddy, Christopher M. AB - Perylene is a frequently abundant, and sometimes the only polycyclic aromatic hydrocarbon (PAH) in aquatic sediments, but its origin has been subject of a longstanding debate in geochemical research and pollutant forensics because its historical record differs markedly from typical anthropogenic PAHs. Here we investigate whether perylene serves as a source-specific molecular marker of fungal activity in forest soils. We use a well-characterized sedimentary record (1735-1999) from the anoxic-bottom waters of the Pettaquamscutt River basin, RI to examine mass accumulation rates and isotope records of perylene, and compare them with total organic carbon and the anthropogenic PAH fluoranthene. We support our arguments with radiocarbon (14C) data of higher plant leaf-wax n-alkanoic acids. Isotope-mass balance-calculations of perylene and n-alkanoic acids indicate that ∼40% of sedimentary organic matter is of terrestrial origin. Further, both terrestrial markers are pre-aged on millennial time-scales prior to burial in sediments and are insensitive to elevated 14C concentrations following nuclear weapons testing in the mid-20th Century. Instead, changes coincide with enhanced erosional flux during urban sprawl. These findings suggest that perylene is definitely a product of soil-derived fungi, and a powerful chemical tracer to study the spatial and temporal connectivity between terrestrial and aquatic environments. VL - 53 UR - https://pubs.acs.org/doi/10.1021/acs.est.9b02344 IS - 14 ER - TY - JOUR T1 - Single step Production of graphite from organic Samples for Radiocarbon Measurements JF - Radiocarbon Y1 - 2019 A1 - Elder, K L A1 - Roberts, M L A1 - Walther, T A1 - Xu, L KW - graphite KW - radiocarbon KW - sealed tube graphite KW - single step graphite AB - We present a new low-cost, high-throughput method for converting many types of organic carbon samples into graphite for radiocarbon (14C) measurements by accelerator mass spectrometry (AMS). The method combines sample combustion and reduction to graphite into a single procedure. In the Single Step method, solid samples are placed directly into Pyrex containing zinc, titanium hydride and iron catalyst. The tube is evacuated, flame sealed, and placed in a muffle furnace for 7 hr. A variety of organic samples have been tested including oxalic acid, sucrose, wood, peat, collagen, humic acid, and contamination swipe samples. The method significantly reduces the time required to produce a graphite sample for 14C measurement, with analytical precision and accuracy approaching that of traditional two-step combustion and hydrogen reduction methods. The details and applicability of the method are presented. VL - 61 UR - https://www.cambridge.org/core/product/identifier/S003382221900136X/type/journal_articlehttps://www.cambridge.org/core/services/aop-cambridge-core/content/view/S003382221900136X IS - 6 ER - TY - JOUR T1 - Sinking particle flux and composition at three sites of different annual sea ice cover in the Amundsen Sea, Antarctica JF - Journal of Marine Systems Y1 - 2019 A1 - Kim, Minkyoung A1 - Yang, Eun J. A1 - Kim, Dongseon A1 - Jeong, Jin-Hyun A1 - Kim, Hyung J. A1 - Park, Jisoo A1 - Jung, Jinyoung A1 - Ducklow, Hugh W. A1 - Lee, SangHoon A1 - Hwang, Jeomshik KW - Amundsen sea KW - Biological pump KW - particulate organic carbon KW - Perennial ice-covered area KW - Polynya AB - This study examines the sinking particle flux and composition of samples collected at three sites in the western Amundsen Sea, Antarctica: a perennial sea-ice-covered area, the central region of the Amundsen Sea polynya, and close to the Dotson Ice Shelf within the polynya. Time series sediment traps were deployed for one year at depths of 400-500 m from February and March 2012. Observations from the three sites confirm previously reported findings that the majority of annual POC (particulate organic carbon) flux in the Amundsen Sea occurs during the austral summer, with much smaller POC fluxes during other seasons. In the perennial ice-covered area, sea ice diatoms were the dominant source of sinking particles. In this region, the summertime POC flux is similar to that in the central polynya. However, the POC flux exhibited large interannual variability, with the reduction in sea ice cover and sufficient insolation being critical to enhanced sinking POC flux. Within the Amundsen Sea polynya, the sinking POC flux was higher in the central region than near the Dotson Ice Shelf, consistent with spatial variability in primary production. The site near the Dotson Ice Shelf had the lowest contribution of diatoms to sinking particles and the smallest POC flux among the three sites. VL - 192 UR - https://www.sciencedirect.com/science/article/pii/S092479631830304X ER - TY - JOUR T1 - Sortable silt records of intermediate-depth circulation and sedimentation in the Southwest Labrador Sea since the Last Glacial Maximum JF - Quaternary Science Reviews Y1 - 2019 A1 - Hoffmann, Sharon S. A1 - Dalsing, Risa E. A1 - Murphy, Sarah C. KW - Holocene KW - labrador sea KW - paleoceanography KW - Sedimentology-marine cores AB - The Labrador Sea is a vital region for the Atlantic Meridional Overturning Circulation (AMOC), where overflow waters from the Nordic Seas mix with locally produced Labrador Sea Water (LSW), before exiting to the interior of the Atlantic Ocean. The dynamical sedimentary proxy of mean sortable silt size () can give information on past changes in deep water circulation speed and the strength of AMOC. We have produced records from two core sites at depths between 1500 and 2000 m on the continental slope east of Newfoundland, to reconstruct changes in intermediate depth water circulation speed, including Glacial North Atlantic Intermediate Water and Labrador Sea Water over the past 22,000 years. Increases in appear to coincide with much of the deglaciation as well as the mid-late Holocene. End-member modeling suggests that ice-rafted debris (IRD) is an important factor in interpreting during the deglaciation. We find that a robust increase in is likely unrelated to IRD during the past 5 ka, and probably reflects increased flow at intermediate depths due to local production of LSW strengthening as Nordic Seas overflows weakened at this depth. Our results highlight both the complications of producing records in IRD-rich, slope environments and the promise that this proxy nevertheless has for reconstructing dynamical changes in deep ocean currents. VL - 206 UR - https://linkinghub.elsevier.com/retrieve/pii/S0277379118306449 ER - TY - JOUR T1 - Sources and sink of black carbon in Arctic Ocean sediments JF - SCIENCE OF THE TOTAL ENVIRONMENT Y1 - 2019 A1 - Ren, Peng A1 - Liu, Yanguang A1 - Shi, Xuefa A1 - Sun, Shuwen A1 - Fan, Di A1 - Wang, Xuchen AB - The concentrations and carbon isotopic (C-13, C-14) compositions of total organic carbon (TOC) and black carbon (BC) were measured for four sediment cores collected from the shelf to slope in the Arctic Ocean. Contents of TOC and BC ranged from 0.46% to 1.94% and 0.04% to 0.13% by dry weight, and BC accounted for 3.5% to 15.2% of the TOC preserved in the shelf and slope sediments. Sediment of the Chukchi shelf contained relatively high BC contents compared with the sediments of the Arctic slope, suggesting strong influence from the river and terrestrial inputs to the shelf region. Radiocarbon measurements revealed that the ages of BC are in the range of 7330 to 29,700 years (before present) and they are 4093 to 7723 years older than the C-14 ages of TOC preserved in the same sediment depths. Based on an isotopic mass balance model, we calculated that fossil fuel combustion contributed 62-96%, and biomass burning contributed 4-38% of the BC pool in the sediments of the study area. This ``slow-cycling'' old BC is an important fraction of the inert organic carbon pool preserved in the sediments, and represents a significant sink of atmospheric CO2 and global carbon cycle. With the thawing permafrost caused by continuous global warming, the size of this BC pool mobilized and exported by rivers to the Arctic Ocean could increase in the future. (C) 2019 Elsevier B.V. All rights reserved. VL - 689 ER - TY - JOUR T1 - Sources of carbon to suspended particulate organic matter in the northern Gulf of Mexico JF - Elem Sci Anth Y1 - 2019 A1 - Rogers, Kelsey L. A1 - Bosman, Samantha H. A1 - Weber, Sarah A1 - Magen, Cedric A1 - Montoya, Joseph P. A1 - Chanton, Jeffrey P. AB - Suspended particulate organic carbon (POCsusp) in the Gulf of Mexico is unique compared to other seas and oceans. In addition to surface primary production, isotopic analysis indicates that microbial cycling of oil and riverine inputs are primary sources of carbon to POCsusp in the Gulf. To characterize POCsusp from seep sites and non-seep north central Gulf (NCG) sites potentially affected by the Deepwater Horizon (DWH) spill, we analyzed 277 and 123 samples for δ13C and Δ1C signatures, respectively. Depth, partitioned into euphotic (300 m), was the main driver of spatial δ13C differences, with deep depths exhibiting 13C depletion. Both deep depths and proximity to sources of natural seepage resulted in 14C depletion. A two-endmember mixing model based on Δ14C indicated that sources to POCsusp were 14–29% fossil carbon at NCG sites and 19–57% at seep sites, with the balance being modern surface production. A six-component Bayesian mixing model MixSIAR, using both 13C and 14C, suggested that riverine inputs were an important carbon source to POCsusp contributing 34–46%. The influence of seeps was localized. Below the euphotic zone at seep sites, 46 ± 5% (n = 9) of the carbon in POCsusp was derived from environmentally degraded, transformed oil; away from seeps, transformed oil contributed 15 ± 4% (n = 39). We hypothesized that, at NCG sites removed from hydrocarbon seep sources, isotopic signatures would be depleted following the spill and then shift towards background-like enriched values over time. At deep depths we observed decreasing Δ14C signatures in POCsusp from 2010 to 2012, followed by isotopic enrichment from 2012 to 2014 and a subsequent recovery rate of 159‰ per year, consistent with this hypothesis and with biodegraded material from DWH hydrocarbons contributing to POCsusp. VL - 7 UR - https://www.elementascience.org/article/10.1525/elementa.389 IS - 1 ER - TY - JOUR T1 - Springwater provenance and flowpath evaluation in Blue Lake, Bonneville basin, Utah JF - Chemical Geology Y1 - 2019 A1 - Lerback, Jory Chapin A1 - Hynek, Scott A. A1 - Bowen, Brenda B. A1 - Bradbury, Christopher D. A1 - Solomon, D. Kip A1 - Fernandez, Diego P. KW - Bonneville basin KW - Geochemistry KW - groundwater KW - Isotope chemistry AB - Water in Utah and Nevada is important for agriculture, municipal use, solute transport, and ecosystem preservation. Large spring wetland systems occur on the playa margin of the Bonneville basin, including Blue Lake, 15 km south of the Bonneville Salt Flats on the Utah-Nevada state border. Large spring systems have historically been studied as water budgets don't apparently balance from direct mountain front recharge (Nelson and Mayo, 2014; Gardner and Heilweil, 2014; and others). Blue Lake is no exception; prior studies here have suggested discharge rates 0.04 - 0.05 km3/yr (Louderback and Rhode, 2009), greater than expected for modelled recharge in the surrounding mountain range (0.03 km3/yr). Three hypothesized recharge mechanisms for Blue Lake are tested: mountain-front recharge, interbasinal groundwater flow, and infiltration from historic Lake Bonneville. Remote sensing suggests that a conservative estimate of Blue Lake discharge constitutes 50-64% of modelled mountain-front recharge (Flint et al., 2011). Major ions, δ18O, δ2H, dissolved gases (14C, 3He, 4He, Ne, Ar, Kr, Xe) and trace elements (Sr and 87Sr/86Sr isotopes) comprehensively constrain recharge conditions, water-rock interactions, flowpaths, and groundwater provenance of this large spring system. 14C signatures suggest that Blue Lake discharge has a transit time between 5,600 and 12,200 years, older than that of Fish Springs. Noble gas concentrations in Blue Lake water suggest an elevated recharge temperature greater than 19°C and low salinity, indicating a deep water table and high geothermal gradient in the recharge area. 87Sr/86Sr ratios of playa-margin springs are elevated from that of mid-playa groundwaters, springwaters from the adjacent mountain range, and alluvial fill groundwater from the valley directly south of Blue Lake. Playa-margin spring Sr isotope values (0.713-0.714) are most similar to direct runoff from the Deep Creek Range granodiorite outcrop (>0.713). Interbasinal groundwater flow in combination with mountain-front recharge is best supported by chemical data rather than mountain-front recharge alone or the slow discharge of regional aquifers recharged by lacustrine infiltration from Lake Bonneville. VL - 529 UR - https://linkinghub.elsevier.com/retrieve/pii/S0009254119303870 ER - TY - JOUR T1 - Stable isotope analyses of ancient and modern Adélie Penguin (Pygoscelis adeliae) mummies from the Ross Sea Region, Antarctica JF - Polar Biology Y1 - 2019 A1 - Kristan, Allyson K. A1 - Emslie, Steven D. A1 - Patterson, William P. AB - We performed stable carbon (δ13C) and nitrogen (δ15N) isotope analyses of 12 ancient Adélie penguin (Pygoscelis adeliae) chick mummies recovered from abandoned colonies in the Ross Sea region, Antarctica, to investigate isotopic variation and fractionation over time. We also examined latitudinal variation in penguin diet to address if the modern dietary pattern (an increase in krill as dominant prey to the north) in this region has existed in the past or if this is a recent phenomenon. The ancient mummies range in age from > 48,000 14C years before present (BP) to ~ 500 calendar years BP. Feather, skin, bone, and toenail samples were analyzed from each individual where available. Identical analyses were performed on five modern mummified Adélie penguin chick carcasses and breast feathers of ten recently dead chicks from each of two active colonies, Cape Hallett and Adélie Cove. We found significantly lower δ15N values in Cape Hallett modern chicks as compared to those from Adélie Cove, indicating an entire trophic-level difference in modern diet that agrees with other studies in this region. The ancient mummies exhibited consistent isotopic fractionation of δ13C among the four different tissues through time. Variation in δ15N and δ13C values was greater in bone and skin than in feather or toenail, but δ15N in all four tissues indicated similar dietary trends with latitude as occurs in this region today. These results provide insight into the dietary variability of Adélie penguins across the Ross Sea region and a framework for similar analyses with other avian species. VL - 42 UR - http://link.springer.com/10.1007/s00300-019-02513-4 IS - 6 ER - TY - JOUR T1 - Sunlight Converts Polystyrene to Carbon Dioxide and Dissolved Organic Carbon JF - Environmental Science & Technology Letters Y1 - 2019 A1 - Ward, Collin P. A1 - Armstrong, Cassia J. A1 - Walsh, Anna N. A1 - Jackson, Julia H. A1 - Reddy, Christopher M. AB - Numerous international governmental agencies that steer policy assume that polystyrene persists in the environment for millennia. Here, we show that polystyrene is completely photochemically oxidized to carbon dioxide and partially photochemically oxidized to dissolved organic carbon. Lifetimes of complete and partial photochemical oxidation are estimated to occur on centennial and decadal time scales, respectively. These lifetimes are orders of magnitude faster than biological respiration of polystyrene and thus challenge the prevailing assumption that polystyrene persists in the environment for millennia. Additives disproportionately altered the relative susceptibility to complete and partial photochemical oxidation of polystyrene and accelerated breakdown by shifting light absorbance and reactivity to longer wavelengths. Polystyrene photochemical oxidation increased approximately 25% with a 10 °C increase in temperature, indicating that temperature is unlikely to be a primary driver of photochemical oxidation rates. Collectively, sunlight exposure appears to be a governing control of the environmental persistence of polystyrene, and thus, photochemical loss terms need to be included in mass balance studies on the environmental fate of polystyrene. The experimental framework presented herein should be applied to a diverse array of polymers and formulations to establish how general these results are for other plastics in the environment. UR - https://pubs.acs.org/doi/abs/10.1021/acs.estlett.9b00532 ER - TY - JOUR T1 - Temperature-controlled tundra fire severity and frequency during the last millennium in the Yukon-Kuskokwim Delta, Alaska JF - The Holocene Y1 - 2019 A1 - Sae-Lim, Jarunetr A1 - Russell, James M A1 - Vachula, Richard S A1 - Holmes, Robert M A1 - Mann, Paul J A1 - Schade, John D A1 - Natali, Susan M KW - alaska KW - Arctic KW - charcoal KW - glycerol dialkyl glycerol tetraethers (GDGTs) KW - late-holocene KW - Paleoclimate KW - Paleofire AB - Wildfire is an important disturbance to Arctic tundra ecosystems. In the coming decades, tundra fire frequency, intensity, and extent are projected to increase because of anthropogenic climate change. To more accurately predict the effects of climate change on tundra fire regimes, it is critical to have detailed knowledge of the natural frequency and extent of past wildfires and how they responded to past climate variability. We present analyses of fire frequency and temperature from a lake sediment core from the Yukon-Kuskokwim (YK) Delta. Our ca. 1000 macroscopic charcoal record shows more frequent but possibly less severe tundra fires during the first half of the last millennium, whereas less frequent, possibly more severe fires characterize the latter half. Our temperature reconstruction, based on distributional changes of branched glycerol dialkyl glycerol tetraethers (brGDGTs), shows slightly warmer conditions from ca. AD 1000 to 1500, and cooler conditions thereafter (ca. AD 1500 to 2000), suggesting that fire frequency increases when climate is relatively warmer in this region. When wildfires occur more frequently, fire severity may decrease because of limited biomass (fuel source) accumulating between fires. The data suggest that tundra ecosystems are highly sensitive to climate change, and that a warmer climate, which is predicted to develop in the near future, will result in more frequent tundra wildfires. VL - 29 UR - http://journals.sagepub.com/doi/10.1177/0959683619838036 IS - 7 ER - TY - JOUR T1 - Temporal constraints on lateral organic matter transport along a coastal mud belt JF - Organic Geochemistry Y1 - 2019 A1 - Bao, Rui A1 - Zhao, Meixun A1 - McNichol, Ann A1 - Galy, Valier A1 - McIntyre, Cameron A1 - Haghipour, Negar A1 - Eglinton, Timothy I. KW - 14C aging KW - Continental shelf seas KW - East China Sea KW - Mud belt KW - organic matter KW - Sediment resuspension AB - Constraints on timescales of lateral transport of sedimentary organic carbon (OC) over continental shelves and associated influences on the distribution and abundance of OC remain sparse. Preferential degradation of labile, young OC during lateral transport results in apparent “diagenetic aging” of OC. Additionally, sediment translocation can also result in “transport time-associated aging” of associated organic matter (OM) as a function of the lateral transport time (LTT). Here, we use a coupled thermal decomposition and radiocarbon (14C) approach to constrain timescales of lateral transport and concomitant loss of OC associated with different grain size fractions of sediments collected from two locations ∼275 km apart along a dispersal pathway on the inner shelf of the East China Sea. The 14C age contrasts between corresponding thermal fractions are used to distinguish these two components of sedimentary OM “aging”. To minimize interferences from hydrodynamic sorting and diagenetic aging of OC accompanying lateral transport, we assess 14C age differences of decomposition products from the most thermally-refractory OC components associated with specific grain size fractions between locations. We show that LTTs vary among different grain size fractions, and examine relationships between LTTs and sedimentary OC loss in order to assess the decomposition of OC as a consequence of lateral transport. We suggest that the decomposition of OC associated with protracted lateral transport exerts a strong influence on OC burial efficiency, with broad implications for carbon cycling over continental shelves. VL - 128 UR - https://www.sciencedirect.com/science/article/pii/S0146638019300075 ER - TY - JOUR T1 - Temporal deconvolution of vascular plant-derived fatty acids exported from terrestrial watersheds JF - Geochimica et Cosmochimica Acta Y1 - 2019 A1 - Vonk, Jorien E. A1 - Drenzek, Nicholas J. A1 - Hughen, Konrad A. A1 - Stanley, Rachel H.R. A1 - McIntyre, Cameron A1 - çon, Daniel B. A1 - Giosan, Liviu A1 - Southon, John R. A1 - Santos, Guaciara M. A1 - Druffel, Ellen R.M. A1 - Andersson, August A. A1 - öld, Martin A1 - Eglinton, Timothy I. KW - british-columbia KW - CARIACO BASIN KW - compound-specific radiocarbon KW - MACKENZIE DELTA KW - marine-sediments KW - odp leg 169s KW - saanich inlet KW - SANTA-MONICA BASIN KW - SOIL ORGANIC-MATTER KW - TROPICAL VEGETATION AB - Relatively little is known about the amount of time that lapses between the photosynthetic fixation of carbon by vascular land plants and its incorporation into the marine sedimentary record, yet the dynamics of terrestrial carbon sequestration have important implications for the carbon cycle. Vascular plant carbon may encounter multiple potential intermediate storage pools and transport trajectories, and the age of vascular plant carbon accumulating in marine sediments will reflect these different pre-depositional histories. Here, we examine down-core C-14 profiles of higher plant leaf wax-derived fatty acids isolated from high fidelity sedimentary sequences spanning the so-called "bomb-spike", and encompassing a ca. 60-degree latitudinal gradient from tropical (Cariaco Basin), temperate (Saanich Inlet), and polar (Mackenzie Delta) watersheds to constrain integrated vascular plant carbon storage/transport times ("residence times"). Using a modeling framework, we find that, in addition to a "young" (conditionally defined as < 50 y) carbon pool, an old pool of compounds comprises 49 to 78 % of the fractional contribution of organic carbon (OC) and exhibits variable ages reflective of the environmental setting. For the Mackenzie Delta sediments, we find a mean age of the old pool of 28 ky (+/- 9.4, standard deviation), indicating extensive pre-aging in permafrost soils, whereas the old pools in Saanich Inlet and Cariaco Basin sediments are younger, 7.9 (+/- 5.0) and 2.4 (+/- 0.50) to 3.2 (+/- 0.54) ky, respectively, indicating less protracted storage in terrestrial reservoirs. The "young" pool showed clear annual contributions for Saanich Inlet and Mackenzie Delta sediments (comprising 24% and 16% of this pool, respectively), likely reflecting episodic transport of OC from steep hillside slopes surrounding Saanich Inlet and annual spring flood deposition in the Mackenzie Delta, respectively. Contributions of 5-10 year old OC to the Cariaco Basin show a short delay of OC inflow, potentially related to transport time to the offshore basin. Modeling results also indicate that the Mackenzie Delta has an influx of young but decadal material (20-30 years of age), pointing to the presence of an intermediate reservoir. Overall, these results show that a significant fraction of vascular plant C undergoes pre-aging in terrestrial reservoirs prior to accumulation in deltaic and marine sediments. The age distribution, reflecting both storage and transport times, likely depends on landscape-specific factors such as local topography, hydrographic characteristics, and mean annual temperature of the catchment, all of which affect the degree of soil buildup and preservation. We show that catchment-specific carbon residence times across landscapes can vary by an order of magnitude, with important implications both for carbon cycle studies and for the interpretation of molecular terrestrial paleoclimate records preserved in sedimentary sequences. VL - 244 UR - https://linkinghub.elsevier.com/retrieve/pii/S0016703718305702https://api.elsevier.com/content/article/PII:S0016703718305702?httpAccept=text/xmlhttps://api.elsevier.com/content/article/PII:S0016703718305702?httpAccept=text/plain ER - TY - JOUR T1 - Testing the Utility of Geochemical Proxies to Reconstruct Holocene Coastal Environments and Relative Sea Level: A Case Study from Hungry Bay, Bermuda JF - Open Quaternary Y1 - 2019 A1 - Kemp, Andrew C. A1 - Vane, Christopher H. A1 - Khan, Nicole S. A1 - Ellison, Joanna C. A1 - Engelhart, Simon E. A1 - Horton, Benjamin P. A1 - Nikitina, Daria A1 - Smith, Struan R. A1 - Rodrigues, Lisa J. A1 - Moyer, Ryan P. KW - mangrove KW - radiocarbon KW - Rock-Eval pyrolysis KW - Sargassum KW - δ13C AB - On low-lying, tropical and sub-tropical coastlines freshwater marshes may be replaced by salt‑tolerant mangroves in response to relative sea-level rise. Pollen analysis of radiocarbon‑dated sediment cores showed that such a change occurred in Hungry Bay, Bermuda during the late Holocene. This well-established paleoenvironmental trajectory provides an opportunity to explore if geochemical proxies (bulk-sediment δ13C and Rock-Eval pyrolysis) can reconstruct known environmental changes and relative sea level. We characterized surface sediment from depositional environments in Bermuda (freshwater wetlands, saline mangroves, and wrack composed of Sargassum natans macroalgae) using geochemical measurements and demonstrate that a multi-proxy approach can objectively distinguish among these environments. However, application of these techniques to the transgressive sediment succession beneath Hungry Bay suggests that freshwater peat and mangrove peat cannot be reliably distinguished in the sedimentary record, possibly because of post‑depositional convergence of geochemical characteristics on decadal to multi‑century timescales and/or the relatively small number of modern samples analyzed. Sediment that includes substantial contributions from Sargassum is readily identified by geochemistry, but has a limited spatial extent. Radiocarbon dating indicates that beginning at –700 CE, episodic marine incursions into Hungry Bay (e.g., during storms) carried Sargassum that accumulated as wrack and thickened through repeated depositional events until ~300 CE. It took a further ~550 years for a peat‑forming mangrove community to colonize Hungry Bay, which then accumulated sediment rapidly, but likely out of equilibrium with regional relative sea-level rise. VL - 5 UR - http://www.openquaternary.com/articles/10.5334/oq.49/ ER - TY - JOUR T1 - Thermal oxidation of carbon in organic matter rich volcanic soils: insights into SOC age differentiation and mineral stabilization JF - Biogeochemistry Y1 - 2019 A1 - Grant, Katherine E. A1 - Galy, Valier V. A1 - Chadwick, Oliver A. A1 - Derry, Louis A. AB - Radiocarbon ages and thermal stability measurements can be used to estimate the stability of soil organic carbon (OC). Soil OC is a complex reservoir that contains a range of compounds with different sources, reactivities, and residence times. This heterogeneity can shift bulk radiocarbon values and impact assessment of OC stability and turnover in soils. Four soil horizons (Oa, Bhs, Bs, Bg) were sampled from highly weathered 350 ka Pololu basaltic volcanics on the Island of Hawaii and analyzed by Ramped PyrOX (RPO) in both the pyrolysis (PY) and oxidation (OX) modes to separate a complex mixture of OC into thermally defined fractions. Fractions were characterized for carbon stable isotope and radiocarbon composition. PY and OX modes yielded similar results. Bulk radiocarbon measurements were modern in the Oa horizon (Fm = 1.013) and got progressively older with depth: the Bg horizon had an Fm value of 0.73. Activation energy distributions (p(E)) calculated using the ‘rampedpyrox’ model yielded consistent mean E values of 140 kJ mol−1 below the Oa horizon. The ‘rampedpyrox’ model outputs showed a mostly bimodal distribution in the p(E) below the Oa, with a primary peak at 135 kJ mol−1 and a secondary peak at 148 kJ mol−1, while the Oa was dominated by a single, higher E peak at 157 kJ mol−1. We suggest that mineral-carbon interaction, either through mineral surface-OC or metal-OC interactions, is the stabilization mechanism contributing to the observed mean E of 140 kJ mol−1 below the Oa horizon. In the Oa horizon, within individual RPO analyses, radiocarbon ages in the individual thermal fractions were indistinguishable (p > 0.1). The flat age distributions indicate there is no relationship between age and thermal stability (E) in the upper horizon (> 25 cm). Deeper in the soil profile higher µEf values were associated with older radiocarbon ages, with slopes progressively steepening with depth. In the deepest (Bg) horizon, there was the largest, yet modest change in Fm of 0.06 (626 radiocarbon years), indicating that older OC is slightly more thermally stable. VL - 144 UR - http://link.springer.com/10.1007/s10533-019-00586-1 IS - 3 ER - TY - JOUR T1 - Timescales of water-quality change in a karst aquifer, south-central Texas JF - Journal of Hydrology X Y1 - 2019 A1 - Musgrove, M. A1 - Solder, J. E. A1 - Opsahl, S. P. A1 - Wilson, J. T. KW - Edwards aquifer KW - Groundwater age KW - Karst KW - Trends KW - Water quality AB - Understanding the drivers and timescales over which groundwater quality changes informs groundwater management, use, and protection. To better understand timescales of water-quality change over short (daily to monthly) and long (seasonal to decadal) timescales, the U.S. Geological Survey’s National Water-Quality Assessment (NAWQA) Enhanced Trends Network (ETN) program instrumented and sampled three wells in the Edwards aquifer in south-central Texas. The wells were instrumented to provide high-frequency continuous (subhourly) water-quality data (temperature, pH, specific conductance, and dissolved oxygen), which were augmented by the collection of discrete samples (about 6 per year) for a range of geochemical constituents (including selected isotopes and age tracers). ETN data (2013–2017) are considered with data from additional sites for the same time period, and also historical records (over more than 80 years) of climatic and hydrologic conditions. During the four-year study, hydrologic conditions transitioned from very dry to very wet. Sites in the updip/unconfined part of the aquifer showed notable changes in water level and geochemistry (1) in response to rainfall/recharge events, and (2) over the multiyear dry/wet cycle. Sites in the downdip/confined part of the aquifer showed changes in water level/spring discharge over similar timescales, although the response is more muted. Geochemistry at the downdip/confined sites, however, varied slowly and minimally, indicating that the geochemical response of the deeper aquifer is decoupled from recent hydrologic responses. Changes at the updip/unconfined sites reflect mixing with recent recharge, whereas the downdip/confined sites were dominated by mineral-solution reactions resulting from longer (decadal) residence times. Mean groundwater ages interpreted from measured age tracers and lumped parameter models range from 7 to >700 years (where mixed with premodern downdip water) but were mostly modern. The aquifer is characterized by updip-to-downdip trends in geochemistry with respect to water-rock interaction and groundwater age. Fourier spectral analysis of historical records indicate hydrologic variability has occurred at dominant periods of 30 and 15 years; in conjunction with age tracers, these results provide insight into timescales at which the aquifer’s public supply is vulnerable to changes in the water quality of recharge. VL - 4 SN - 2589-9155 UR - https://www.sciencedirect.com/science/article/pii/S2589915519300252 JO - Journal of Hydrology X ER - TY - JOUR T1 - Upwelling in the Ocean Basins North of the ACC: 1. On the Upwelling Exposed by the Surface Distribution of C-14 JF - Journal of Geophysical Research: Oceans Y1 - 2019 A1 - Toggweiler, J. R. A1 - Druffel, Ellen R. M. A1 - Key, Robert M. A1 - Galbraith, Eric D. KW - Ocean circulation KW - overturning circulation KW - radiocarbon KW - Upwelling AB - he upwelling associated with the ocean's overturning circulation is hard to observe directly. Here, a large data set of surface C-14 measurements is compiled in order to show where deep water is brought back up to the surface in the ocean basins north of the Antarctic Circumpolar Current (ACC). Maps constructed from the data set show that low-C-14 deep water from the ACC is drawn up to the surface in or near the upwelling zones off Northwest Africa and Namibia in the Atlantic, off Costa Rica and Peru in the Pacific, and in the northern Arabian Sea in the Indian Ocean. Deep water also seems to be reaching the surface in the subarctic Pacific gyre near the Kamchatka Peninsula. The low-C-14 water drawn up to the surface in the upwelling zones is also shown to spread across the ocean basins. It is easily seen, for example, in the western Atlantic off Florida and in the western Pacific off New Guinea and Palau. The spreading allows one to estimate the volumes of upwelling, which, it turns out, are similar to the volumes of large-scale upwelling derived from inverse box models. This means that very large volumes of cool subsurface water are reaching the surface in and near the upwelling zonesmuch larger volumes than would be expected from the local winds. Plain Language Summary The deep layers of the ocean are filled with cold dense water that sinks from the surface near Antarctica and in the northern North Atlantic. This process is understood reasonably well. The countervailing processthe way that the dense water is brought back up to the surfaceis not as well understood. Oceanographers now agree that the ocean's deep water is drawn back up to the surface (upwelled) mainly around Antarctica as part of the wind-driven overturning in the Antarctic Circumpolar Current (ACC). But cool water is also known to reach the surface in upwelling zones around the ocean's margins. Here we map the upwelling north of the ACC with the radioactive isotope carbon-14 and show that the deep water upwelled to the surface around Antarctica seems to be drawn up to the surface a second time in the upwelling zones. The water drawn up to the surface in the upwelling zones then flows back to the North Atlantic and sinks again to complete the cycle. VL - 124 UR - https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018JC014794 IS - 4 ER - TY - JOUR T1 - Upwelling in the Ocean Basins North of the ACC: 2. How Cool Subantarctic Water Reaches the Surface in the Tropics JF - Journal of Geophysical Research: Oceans Y1 - 2019 A1 - Toggweiler, J. R. A1 - Druffel, Ellen R. M. A1 - Key, Robert M. A1 - Galbraith, Eric D. KW - numerical modeling KW - Ocean circulation KW - overturning circulation KW - Upwelling AB - Large volumes of cool water are drawn up to the surface in the tropical oceans. A companion paper shows that the cool water reaches the surface in or near the upwelling zones off northern and southern Africa and Peru. The cool water has a subantarctic origin and spreads extensively across the Atlantic and Pacific basins after it reaches the surface. Here, we look at the spreading in two low-resolution ocean general circulation models and find that the spreading in the models is much less extensive than observed. The problem seems to be the way the upwelling and the spreading are connected (or not connected) to the ocean's large-scale overturning. As proposed here, the cool upwelling develops when warm buoyant water in the western tropics is drawn away to become deep water in the North Atlantic. The drawing away shoals the tropical thermocline in a way that allows cool subantarctic water to be drawn up to the surface along the eastern margins. The amounts of upwelling produced this way exceed the amounts generated by the winds in the upwelling zones by as much as 4 times. Flow restrictions make it difficult for the warm buoyant water in our models to be drawn away. Plain Language Summary A companion paper uses the radioactive isotope carbon-14 to map the upwelling in the ocean basins north of the Antarctic Circumpolar Current (ACC). It shows that deep water drawn up to the surface to the south of the ACC is drawn up to the surface a second time in a number of upwelling areas in the tropics. In this paper, we attempt to simulate the tropical upwelling in an ocean circulation model and find that it is largely missing. Other circulation features are missing as well. The other features operate on the opposite sides of the ocean basins from the upwelling areas and help carry warm water out of the tropics (outflows). The combination of missing elements leads to a hypothesis about the upwelling mechanism. Our hypothesis is that the tropical upwelling is driven by the outflows and the fact that the warm water being carried away ultimately becomes deep water again in the North Atlantic. VL - 124 UR - https://www.researchgate.net/publication/331524382_Upwelling_in_the_Ocean_Basins_north_of_the_ACC_Part_1_On_the_Upwelling_Exposed_by_the_Surface_Distribution_of_D_14_C IS - 4 ER - TY - JOUR T1 - Using Stable Carbon Isotopes to Quantify Radiocarbon Reservoir Age Offsets in the Coastal Black SeaAbstract JF - Radiocarbon Y1 - 2019 A1 - Soulet, Guillaume A1 - Giosan, Liviu A1 - Flaux, Clément A1 - Galy, Valier KW - Black Sea KW - Carbon cycle KW - freshwater reservoir effect KW - Geochronology KW - Reservoir age AB - Constraining radiocarbon (C-14) reservoir age offsets is critical to deriving accurate calendar-age chronologies from C-14 dating of materials which did not draw carbon directly from the atmosphere. The application of C-14 dating to such materials is severely limited in hydrologically sensitive environments like the Black Sea because of the difficulty to quantify reservoir age offsets, which can vary quickly and significantly through time, due to the dynamics of the biogeochemical cycling of carbon. Here we reconstruct C-14 reservoir age offsets (Rshell-atm) of Holocene bivalve shells from the coastal Black Sea relatively to their contemporaneous atmosphere. We show that the C-14 reservoir age offset and the stable carbon isotope composition of bivalve shells are linearly correlated in this region. From a biogeochemical standpoint, this suggests that inorganic stable carbon isotope and C-14 compositions of Black Sea coastal waters are controlled by the balance between autochthonous primary productivity and heterotrophic respiration of allochthonous pre-aged terrestrial organic matter supplied by rivers. This provided an important implication for Black Sea geochronology as the reservoir age offset of C-14-dated bivalve shell can be inferred from its stable carbon isotope composition. Our results provide a fundamental and inexpensive geochemical tool which will considerably improve the accuracy of Holocene calendar age chronologies in the Black Sea. VL - 61 UR - https://www.cambridge.org/core/product/identifier/S0033822218000619/type/journal_articlehttps://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0033822218000619 IS - 1 ER - TY - BOOK T1 - The Utility of Stable and Radioisotopes in Fish Tissues as Biogeochemical Tracers of Marine Oil Spill Food Web Effects Y1 - 2019 A1 - Patterson III, William F. A1 - Chanton, Jeffery P. A1 - Hollander, David J. A1 - Goddard, Ethan A. A1 - Barnett, Beverly K. A1 - Tarnecki, Joseph H. ED - Murawski, Steven A. ED - Ainsworth, Cameron H. ED - Gilbert, Sherryl ED - Hollander, David J. ED - Paris, Claire B. ED - Schlüter, Michael ED - Wetzel, Dana L. KW - Petrocarbon KW - radiocarbon KW - Reef fish KW - Stable isotopes AB - Direct exposure to petroleum compounds was widely reported for a variety of taxa following the DWH. Evidence of exposure ranged from oiling of skin, shells, or feathers, depending on the taxa, to observation of ingested oil in small translucent, invertebrates, to biomarkers of petroleum compounds within an organism’s tissues, such as PAHs in the hepatopancreas of invertebrates or the liver of fishes, or metabolic products of PAH catabolism in the bile of various vertebrate taxa. Development of natural biogeochemical tracers to examine indirect effects, especially over long (months to years) time scales, can be much more problematic. In this chapter, we describe the utility of employing stable isotopes and radioisotopes to 1) examine whether food web effects can be inferred from shifts in stable isotope values measured in vertebrate taxa; 2) examine the assimilation and trophic transfer of petrocarbon in marine food webs; and, 3) serve as long-term biogeochemical tracers either of petrocarbon assimilation or trophic shifts that are indicative of food web effects of marine oil spills. Data and analyses are largely drawn from DWH-related studies but with broader implications to marine oil spills in general. PB - Springer International Publishing CY - Cham SN - 978-3-030-12962-0 UR - https://link.springer.com/chapter/10.1007/978-3-030-12963-7_13 ER - TY - JOUR T1 - 1500 years of lake sedimentation due to fire, earthquakes, floods and land clearance in the Oregon Coast Range: geomorphic sensitivity to floods during timber harvest period JF - Earth Surface Processes and Landforms Y1 - 2018 A1 - Richardson, K.N.D. A1 - Hatten, J.A. A1 - Wheatcroft, R.A. KW - erosion KW - GREAT EARTHQUAKES KW - history KW - NEW-ZEALAND KW - radiocarbon age KW - record KW - TEMPORAL PATTERNS KW - USA KW - WASHINGTON KW - WESTERN OREGON AB - Sediment cores retrieved from landslide-dammed Loon Lake recorded events back to the 5th century AD in a forested, mountainous catchment, thereby providing an opportunity to compare the impacts of known recent perturbations, including floods and timber harvesting with those of an early period in the cores, floods, fires, and earthquakes. High-resolution multi-parameter (grain size, %TC, %TN, and magnetic susceptibility) data allowed the core stratigraphy to be classified as background sedimentation and events. Cs-137 and radiocarbon dating, as well as a varved record in the last 75years provided age control. Mean mass accumulation rate from 1939 to 1978AD, the time of peak timber harvest and a cool wet phase of the Pacific Decadal Oscillation, was 0.79 (0.74-0.92, 95% C.L.) g cm(-2) y(-1), significantly higher than mean rates of both the more recent contemporary period (coincident with the passing of the legislation that regulated harvesting practices in the region), 1979-2012AD, at 0.58 (0.48-0.70) and the entire early period, 0.44 (0.41-0.46). Several event deposits are coeval with independently estimated ages of eight Cascadia subduction zone earthquakes in the early period, including the 1700AD Mw 9.0 event. These deposits are predominantly formed by hyperpycnal flows, as are the known event deposits in the contemporary period. The high mass accumulation rate and greater frequency of thick event deposits during the early contemporary period point to the extraordinary role of timber harvesting in priming the landscape for subsequent sedimentary delivery during floods. Copyright (c) 2017 John Wiley & Sons, Ltd. VL - 43 UR - https://onlinelibrary.wiley.com/doi/abs/10.1002/esp.4335 IS - 7 ER - TY - JOUR T1 - Active Ooid Growth Driven By Sediment Transport in a High-Energy Shoal, Little Ambergris Cay, Turks and Caicos Islands JF - Journal of Sedimentary Research Y1 - 2018 A1 - Trower, Elizabeth J. A1 - Cantine, Marjorie D. A1 - Gomes, Maya L. A1 - Grotzinger, John P. A1 - Knoll, Andrew H. A1 - Lamb, Michael P. A1 - Lingappa, Usha A1 - O'Reilly, Shane S. A1 - Present, Theodore M. A1 - Stein, Nathan A1 - Strauss, Justin V. A1 - Fischer, Woodward W. AB - Ooids are a common component of carbonate successions of all ages and present significant potential as paleoenvironmental proxies, if the mechanisms that control their formation and growth can be understood quantitatively. There are a number of hypotheses about the controls on ooid growth, each offering different ideas on where and how ooids accrete and what role, if any, sediment transport and abrasion might play. These hypotheses have not been well tested in the field, largely due to the inherent challenges of tracking individual grains over long timescales. This study presents a detailed field test of ooid-growth hypotheses on Little Ambergris Cay in the Turks and Caicos Islands, British Overseas Territories. This field site is characterized by westward net sediment transport from waves driven by persistent easterly trade winds. This configuration makes it possible to track changes in ooid properties along their transport path as a proxy for changes in time. Ooid size, shape, and radiocarbon age were compared along this path to determine in which environments ooids are growing or abrading. Ooid surface textures, petrographic fabrics, stable-isotope compositions (δ13C, δ18O, and δ34S), lipid geochemistry, and genetic data were compared to characterize mechanisms of precipitation and degradation and to determine the relative contributions of abiotic (e.g., abiotic precipitation, physical abrasion) and biologically influenced processes (e.g., biologically mediated precipitation, fabric destruction through microbial microboring and micritization) to grain size and character. A convergence of evidence shows that active ooid growth occurs along the transport path in a high-energy shoal environment characterized by frequent suspended-load transport: median ooid size increases by more than 100 μm and bulk radiocarbon ages decrease by 360 yr westward along the ∼ 20 km length of the shoal crest. Lipid and 16S rRNA data highlight a spatial disconnect between the environments with the most extensive biofilm colonization and environments with active ooid growth. Stable-isotope compositions are indistinguishable among samples, and are consistent with abiotic precipitation of aragonite from seawater. Westward increases in ooid sphericity and the abundance of well-polished ooids illustrate that ooids experience subequal amounts of growth and abrasion—in favor of net growth—as they are transported along the shoal crest. Overall, these results demonstrate that, in the Ambergris system, the mechanism of ooid growth is dominantly abiotic and the loci of ooid growth is determined by both carbonate saturation and sediment transport mode. Microbes play a largely destructive, rather than constructive, role in ooid size and fabric. VL - 88 UR - https://pubs.geoscienceworld.org/sepm/jsedres/article/88/9/1132/559083/Active-Ooid-Growth-Driven-By-Sediment-Transport-in IS - 9 ER - TY - JOUR T1 - On the Age and Origin of Lake Ejagham, Cameroon, and Its Endemic FishesAbstract JF - Quaternary Research Y1 - 2018 A1 - Curt Stager, Jay A1 - Alton, Kenneth A1 - Martin, Christopher H. A1 - King, David T. A1 - Petruny, Lucille W. A1 - Wiltse, Brendan A1 - Livingstone, Daniel A. KW - Africa KW - cameroon KW - Cichlid KW - Diatom KW - evolution KW - Lake Ejagham KW - Speciation KW - West African monsoon AB - Lake Ejagham is a small, shallow lake in Cameroon, West Africa, which supports five endemic species of cichlid fishes in two distinct lineages. Genetic evidence suggests a relatively young age for the species flocks, but supporting geologic evidence has thus far been unavailable. Here we present diatom, geochemical, mineralogical, and radiocarbon data from two sediment cores that provide new insights into the age and origin of Lake Ejagham and its endemic fishes. Radiocarbon ages at the base of the longer core indicate that the lake formed approximately 9 ka ago, and the diatom record of the shorter core suggests that hydroclimate variability during the last 3 millennia was similar to that of other lakes in Cameroon and Ghana. These findings establish a maximum age of ca. 9 cal ka BP for the lake and its endemic species and suggest that repeated cichlid speciation in two distinct lineages occurred rapidly within the lake. Local geology and West African paleoclimate records argue against a volcanic, chemical, or climatic origin for Lake Ejagham. Although not conclusive, the morphometry of the lake and possible signs of impact-induced effects on quartz grains are instead more suggestive of a bolide impact. VL - 895716332765461461671825961727356647223 UR - https://www.cambridge.org/core/product/identifier/S0033589417000370/type/journal_articlehttps://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0033589417000370 IS - 01 ER - TY - JOUR T1 - Aging and Molecular Changes of Dissolved Organic Matter Between Two Deep Oceanic End-Members JF - Global Biogeochemical Cycles Y1 - 2018 A1 - Bercovici, S. K. A1 - Koch, B. P. A1 - Lechtenfeld, O. J. A1 - McCallister, S. L. A1 - Schmitt-Kopplin, P. A1 - Hansell, D. A. AB - The global ocean contains a massive reservoir of dissolved organic carbon (DOC), rivaling the atmosphere's pool of CO2. The most recalcitrant fractions have mean radiocarbon ages of ~4,000 years in the Atlantic to ~6,000 years in the Pacific. Knowing the radiocarbon signatures of DOC and the molecular composition of dissolved organic matter (DOM) is crucial to develop understanding of the persistence and lifetime of the DOC pool. In this research, we collected samples from the deep North Pacific in August 2013 (aboard the RV Melville) to couple the Δ14C content of solid‐phase‐extracted DOM (Δ14C‐SPE‐DOM) with its molecular composition in the ocean's oldest deep waters. We find that deep waters in this region held a mean Δ14C‐SPE‐DOM value of −554 ± 9‰ (~6,400 14C years), substantially more depleted than that in the deep Atlantic, which held a mean Δ14C‐SPE‐DOM value of −445 ± 5‰. While we find a more degraded molecular composition of DOM in the deep Pacific than the deep Atlantic, the molecular formulae within the Island of Stability (Lechtenfeld et al., 2014, https://doi.org/10.1016/j.gca.2013.11.009), are largely retained. These results imply that a fraction of deep DOM is resistant to removal and present in both the deep Atlantic and Pacific Oceans. VL - 32 UR - https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2017GB005854 IS - 10 ER - TY - JOUR T1 - Along-slope variations in sediment lithofacies and depositional processes since the Last Glacial Maximum on the northeast Baffin margin, Canada JF - Marine Geology Y1 - 2018 A1 - Jenner, K.A. A1 - Campbell, D.C. A1 - Piper, D.J.W. KW - Baffin Bay KW - Glacigenic debris flow KW - Late Quaternary KW - lithofacies KW - stratigraphy KW - Tan carbonate events AB - Twelve piston cores were used to characterize late Quaternary lithofacies, depositional processes and deglacial history along the Baffin Bay slope between Lancaster Sound and Home Bay. Core investigations show four distinct laterally correlatable lithofacies along the slope – basal and upper diamicton, laminated red brown mud, tan carbonate gravelly, sandy mud and bioturbated brown mud. Basal diamicton largely represents glacigenic debris flow deposits during a glacial advance from Baffin Island at ~25 cal ka. The distribution and character of laminated red brown mud suggests a lateral supply to Baffin Bay slope from ice-proximal meltwater plumes and turbidity currents sourced in glacial ice from both Baffin Bay shelf and Home Bay between 41.5 cal ka to ~14.2 cal ka. An upper diamicton records a lesser, localized glacial advance that ended at about 14.2 cal ka. Tan carbonate mud events represent ice-rafted, enhanced detrital carbonate delivery to the slope between ~25 cal ka and ~11 cal ka. A gradual thinning of these events, from northern to southern Baffin Bay, corroborates a northern Baffin Bay, Lancaster Sound or Nares Strait iceberg source. Proglacial facies seaward of Home Bay contain beds with slightly elevated detrital carbonate that may represent the distal edge of carbonate ice-rafted from Lancaster Sound. Baffin Bay is a type example of a polar glacial basin in which direct glacial supply predominates over the effects of glacial meltwater. As a result, axial supply from the large ice streams north of Baffin Bay (particularly Lancaster Sound) is dominant in the Baffin Bay basin and lateral supply from smaller ice streams on Baffin Island predominates on the NE Baffin Slope. VL - 405 UR - https://linkinghub.elsevier.com/retrieve/pii/S0025322717306321 ER - TY - JOUR T1 - Ancient water wells reveal a prolonged drought in the lower Yellow River area about 2800 years ago JF - Science Bulletin Y1 - 2018 A1 - Yu, Shiyong A1 - Chen, Xuexiang A1 - Liu, Xiuling A1 - Fang, Zhen A1 - Guo, Junfeng A1 - Zhan, Senyang A1 - Fang, Hui A1 - Chen, Fahu AB - Given that the Holocene is the most recent interglacial period that has spurred the development of modern societies, scrutinizing climate changes during this period may provide a knowledge base for better understanding the rise and fall of ancient civilizations. However, our knowledge about the mechanism of millennial-scale climate variability particularly in the absence of major continental ice sheets during the second half of the Holocene remains highly uncertain. Although cold spells manifested as the Bond events have been widely reported in the North Atlantic sector during the mid-to-late Holocene, it is not clear whether or not there is a global expression of these events. Therefore, well-tuned far-field proxy records are indispensable to pinpoint the geographical extent of these climate events. Here we show evidence from ancient water wells in North China for a prolonged drought corresponding to a period of pervasive cooling in the North Atlantic region lasting from about 800 to 550 before the Common Era (BCE). Inferred climatic conditions using a conceptual hydrological model, in line with other proxy records, support the hypothesis of the Sun-climate link probably through the complex ocean-atmospheric interactions in the tropical oceans. Our finding suggests that water well construction represented a major technical invention in human history, which greatly improved the resilience against the depletion of surface water at times when arid climate prevailed. The linked climatic and societal changes demonstrated here can serve as a historical analogue for the socio-economic response to potentially large climate changes in the future. VL - 63 UR - https://linkinghub.elsevier.com/retrieve/pii/S2095927318304651https://api.elsevier.com/content/article/PII:S2095927318304651?httpAccept=text/xmlhttps://api.elsevier.com/content/article/PII:S2095927318304651?httpAccept=text/plain IS - 20 ER - TY - JOUR T1 - Asynchronous behavior of the Antarctic Ice Sheet and local glaciers during and since Termination 1, Salmon Valley, Antarctica JF - Earth and Planetary Science Letters Y1 - 2018 A1 - Jackson, Margaret S. A1 - Hall, Brenda L. A1 - Denton, George H. KW - Antarctic Ice Sheet KW - glacial geomorphology KW - ice sheet stability KW - Termination I AB - The stability of the Antarctic Ice Sheet under future warming remains an open question with broad implications for sea-level prediction and adaptation. In particular, knowledge of whether the ice sheet has the capacity for rapid drawdown or collapse, or whether it can remain stable during periods of warming, is essential for predicting its future behavior. Here we use 55 radiocarbon dates, coupled with geomorphologic mapping, to reconstruct the timing of changes in ice extent and elevation during the last ice-age termination in Salmon Valley, adjacent to McMurdo Sound in the western Ross Sea Embayment. Results indicate that a grounded ice sheet in the Ross Sea Embayment achieved its maximum elevation and extent along the headlands of Salmon Valley at ∼18,000 yr BP, during a period of increasing temperatures and accumulation over the Antarctic continent. This ice remained at or near its maximum on the headlands near the valley mouth until after ∼14,000 yr BP. Removal of grounded Ross Sea ice from Salmon Valley was complete shortly after ∼7900 yr BP, indicating that the grounding line had retreated through southern McMurdo Sound by that time. We suggest the primary driver of Ross Sea ice removal from McMurdo Sound was marine-based, either through basal melting or calving due to sea-level rise. When combined with regional data, the Salmon Valley record suggests that this sector of the Antarctic Ice Sheet did not contribute in a significant way to deglacial meltwater pulses, such as meltwater pulse 1a. In contrast to the Ross Sea ice, our work also shows that local, independent alpine glaciers in Salmon Valley have advanced through the Holocene. Land-terminating glaciers such as these elsewhere in the region show a similar pattern, and may reflect the continued influence of increased accumulation following the termination of the last ice age. VL - 482 UR - https://linkinghub.elsevier.com/retrieve/pii/S0012821X1730674X ER - TY - JOUR T1 - An atmospheric chronology for the glacial-deglacial Eastern Equatorial Pacific JF - Nature Communications Y1 - 2018 A1 - Zhao, Ning A1 - Keigwin, Lloyd D. AB - Paleoclimate reconstructions are only as good as their chronology. In particular, different chronological assumptions for marine sediment cores can lead to different reconstructions of ocean ventilation age and atmosphere-ocean carbon exchange history. Here we build the first high-resolution chronology that is free of the dating uncertainties common in marine sediment records, based on radiocarbon dating twigs found with computed tomography scans in two cores from the Eastern Equatorial Pacific (EEP). With this accurate chronology, we show that the ventilation ages of the EEP thermocline and intermediate waters were similar to today during the Last Glacial Maximum and deglaciation, in contradiction with previous studies. Our results suggest that the glacial respired carbon pool in the EEP was not significantly older than today, and that the deglacial strengthening of the equatorial Pacific carbon source was probably driven by low-latitude processes rather than an increased subsurface supply of upwelled carbon from high-latitude oceans. VL - 9 UR - http://www.nature.com/articles/s41467-018-05574-xhttp://www.nature.com/articles/s41467-018-05574-x.pdfhttp://www.nature.com/articles/s41467-018-05574-xhttp://www.nature.com/articles/s41467-018-05574-x.pdf IS - 1 ER - TY - JOUR T1 - A base-level stratigraphic approach to determining Holocene subsidence of the Ganges-Meghna-Brahmaputra Delta plain JF - EARTH AND PLANETARY SCIENCE LETTERS Y1 - 2018 A1 - Grall, C A1 - Steckler, MS A1 - Pickering, JL A1 - Goodbred, S KW - base level stratigraphic method KW - delta plain KW - Ganges–Brahmaputra–Meghna Delta KW - indicative meaning of sea level index KW - relative sea level KW - subsidence AB - Relative sea level history, which is the result of the combined effects of land subsidence, sediment supply and absolute sea level history may be reconstructed from preserved sediment thicknesses. However, variations in the preserved sediment thicknesses between different sedimentary environments strongly limit the accuracy of this type of geological approach, particularly in fluvial channelized systems, such as delta plains. To address this, we apply three different and independent stratigraphic approaches to the case of the Ganges-Brahmaputra-Meghna Delta (GBMD). Our approach has been made possible by a broad dataset of geological archives we have collected, which includes more than 400 hand-drilled stratigraphic wells, 198 radiocarbon ages, and river seismic reflection data (255 km of high-resolution multichannel seismic images). The seaward gradient of accommodation and the limit of the subsiding delta plain are estimated, assuming that the delta is near or at the base-level, which is considered to be the relative sea-level. First, a statistical analysis of the variability of preserved sediment thicknesses is used to derive the average pattern of accommodation from the Holocene isopach. Secondly, the preserved sediment thicknesses are analyzed by geomorphotectonic domains to estimate an average pattern of accommodation. Thirdly, the burial history of the seismically imaged last glacial incision of the Brahmaputra River is reconstructed. Results suggest that the variability of preserved sediment thicknesses can be up to 35% in a delta plain between river channel and flood plain deposits for the same relative sea-level history. Taking this variability into consideration, the Holocene relative sea-level history of the GBMD and the most likely pattern of subsidence are determined. Results provide evidence of moderate Holocene subsidence over the delta, gently increasing seaward from <0.2 mm/yr landward of the Hinge Zone, which can be considered as the northern limit of the subsiding delta plain, to 2 ± 0.7 mm/yr in the middle fluvial delta to 4 ± 1.4 mm/yr in the lower tidal delta. This enables us to construct the first millennial-scale map of subsidence pattern on the GBMD in which uncertainties on subsidence rates are provided. This map may aid in evaluating the negative impact that human modification may have on subsidence and relative sea level in the GBMD, and thereby help to determine better sustainable coastal management practices for the GBMD and other large delta plains. VL - 499 ER - TY - JOUR T1 - A base-level stratigraphic approach to determining Holocene subsidence of the Ganges–Meghna–Brahmaputra Delta plain JF - Earth and Planetary Science Letters Y1 - 2018 A1 - Grall, C. A1 - Steckler, M.S. A1 - Pickering, J.L. A1 - Goodbred, S. A1 - Sincavage, R. A1 - Paola, C. A1 - Akhter, S.H. A1 - Spiess, V. KW - base level stratigraphic method KW - delta plain KW - Ganges-Brahmaputra-Meghna Delta KW - indicative meaning of sea level index KW - relative sea level KW - subsidence AB - Relative sea level history, which is the result of the combined effects of land subsidence, sediment supply and absolute sea level history may be reconstructed from preserved sediment thicknesses. However, variations in the preserved sediment thicknesses between different sedimentary environments strongly limit the accuracy of this type of geological approach, particularly in fluvial channelized systems, such as delta plains. To address this, we apply three different and independent stratigraphic approaches to the case of the Ganges-Brahmaputra-Meghna Delta (GBMD). Our approach has been made possible by a broad dataset of geological archives we have collected, which includes more than 400 hand-drilled stratigraphic wells, 198 radiocarbon ages, and river seismic reflection data (255 km of high-resolution multichannel seismic images). The seaward gradient of accommodation and the limit of the subsiding delta plain are estimated, assuming that the delta is near or at the base-level, which is considered to be the relative sea-level. First, a statistical analysis of the variability of preserved sediment thicknesses is used to derive the average pattern of accommodation from the Holocene isopach. Secondly, the preserved sediment thicknesses are analyzed by geomorphotectonic domains to estimate an average pattern of accommodation. Thirdly, the burial history of the seismically imaged last glacial incision of the Brahmaputra River is reconstructed. Results suggest that the variability of preserved sediment thicknesses can be up to 35% in a delta plain between river channel and flood plain deposits for the same relative sea-level history. Taking this variability into consideration, the Holocene relative sea-level history of the GBMD and the most likely pattern of subsidence are determined. Results provide evidence of moderate Holocene subsidence over the delta, gently increasing seaward from <0.2 mm/yr landward of the Hinge Zone, which can be considered as the northern limit of the subsiding delta plain, to 2 +/- 0.7 mm/yr in the middle fluvial delta to 4 +/- 1.4 mm/yr in the lower tidal delta. This enables us to construct the first millennial-scale map of subsidence pattern on the GBMD in which uncertainties on subsidence rates are provided. This map may aid in evaluating the negative impact that human modification may have on subsidence and relative sea level in the GBMD, and thereby help to determine better sustainable coastal management practices for the GBMD and other large delta plains. (C) 2018 The Authors. Published by Elsevier B.V. VL - 499 UR - https://www.sciencedirect.com/science/article/pii/S0012821X1830414X ER - TY - JOUR T1 - Bathyal records of enhanced silicate erosion and weathering on the exposed Luzon shelf during glacial lowstands and their significance for atmospheric CO2 sink JF - Chemical Geology Y1 - 2018 A1 - Xu, Zhaokai A1 - Li, Tiegang A1 - Clift, Peter D. A1 - Wan, Shiming A1 - Qiu, Xiaohua A1 - Lim, Dhongil KW - Atmospheric CO2 concentration KW - Chemical weathering KW - East Asian summer monsoon KW - sea level KW - Western Philippine Sea AB - We present a new high-resolution multiproxy data set of mass accumulation rates, Sr-Nd isotopes, as well as major and trace elements for the siliciclastic sediment fraction from International Marine Global Change Study Core MD06-3052, located on the continental slope of the western Philippine Sea. We integrate our new data with published grain sizes and sea surface temperatures from the same core, as well as with Equatorial Pacific sea level, and East Asian summer monsoon precipitation, in order to constrain at high-resolution changes in physical erosion and chemical weathering intensities on Luzon, and sediment source-to-sink processes. We assess the potential significance of chemical weathering of arc silicates in regulating global atmospheric CO2 since 156 kyr BP. Sr-Nd isotopes show that the siliciclastic sediments were dominantly sourced from volcanic rocks exposed on Luzon (~ 68–100%), with a lesser contribution from Asian dust (~ 0–32%). Different indices indicate that stronger physical erosion and chemical weathering occurred during Marine Isotope Stage (MIS) 6 (130–156 kyr BP), as well as in the latter stage of MIS 3 and MIS 2 (14–40 kyr BP). The large sea-level lowstands and associated significant exposure of continental shelf in the western Philippine Sea during these two cold periods should favor physical erosion and chemical weathering of unconsolidated sediments on the exposed shelf. Furthermore, we notice the relatively good coherence between chemical weathering intensities on Luzon and global atmospheric CO2 concentrations over these cold intervals. We suggest that strengthening of chemical weathering of silicates on Luzon and other tropical arcs (within 20° of the Equator) during the Quaternary glacial sea-level lowstands may significantly contribute to the lowering of atmospheric CO2 concentrations during ice ages. We estimate that a significant fraction, up to ~ 16% (i.e., ~ 8 ppmv), of all atmospheric CO2 ultimately sequestered by silicate weathering may be processed through an area corresponding to only ~ 1% of the exorheic drainage area worldwide. VL - 476 UR - https://www.sciencedirect.com/science/article/pii/S0009254117306587 ER - TY - JOUR T1 - Blue marlin ( Makaira nigricans ) longevity estimates confirmed with bomb radiocarbon dating JF - Canadian Journal of Fisheries and Aquatic Sciences Y1 - 2018 A1 - Andrews, Allen H. A1 - Humphreys, Robert L. A1 - Sampaga, Jeffery D. KW - Accelerator mass spectrometry KW - Biology KW - Blue marlin KW - Ecology KW - Fish measurement KW - FisheryLongevity KW - Otolith KW - Radiocarbon dating AB - The longevity of blue marlin (Makaira nigricans) remains unresolved. The use of fin spines and sagittal otoliths for age reading has led to unconfirmed longevity estimates near 20-30 years. Age validation has been elusive because large individuals are uncommonly caught, and a technique that can be applied to structures that provide estimates of age was absent. The use of otolith chemical signatures has been limited by sagittal otoliths that are very small-whole otolith mass of adult blue marlin rarely exceeds 10 mg for the largest fish. Recent advances in the detection limits of radiocarbon (14C) with accelerator mass spectrometry-coupled with recently acquired knowledge of marine bomb 14C signals spanning the tropical Pacific Ocean-have led to an opportunity to age blue marlin from small amounts of otolith material. In this study, otoliths from a recently collected 1245 lb (565 kg) female blue marlin at a measured 146-inch (371 cm) lower jaw fork length were analyzed for 14C. Estimated longevity was either 12-21 or 32-44 years on the basis of bomb 14C dating. Using multiple lines of evidence, it was determined that the young age scenario was most likely, with evidence for an age close to 20 years using a series of deductions in the bomb 14C dating method. VL - 75 UR - http://www.nrcresearchpress.com/doi/10.1139/cjfas-2017-0031http://www.nrcresearchpress.com/doi/pdf/10.1139/cjfas-2017-0031http://www.nrcresearchpress.com/doi/full-xml/10.1139/cjfas-2017-0031 IS - 1 ER - TY - JOUR T1 - Breaching of Mustang Island in response to the 8.2 ka sea-level event and impact on Corpus Christi Bay, Gulf of Mexico: Implications for future coastal change JF - The Holocene Y1 - 2018 A1 - Ferguson, Shannon A1 - Warny, Sophie A1 - Anderson, John B A1 - Simms, Alexander R A1 - White, Crawford KW - barrier island KW - dinoflagellates KW - Gulf of Mexico KW - Holocene KW - North America KW - Sea-level changes AB - The results from an investigation of the coupled Mustang Island–Corpus Christi Bay complex, Gulf of Mexico, shows that the island was eliminated as an effective salinity barrier between 8.86 and 8.17 ka. This event is recorded by a 5-fold increase in dinoflagellate cysts within Corpus Christi Bay. During this time, the bay-head delta shifted 15 km landward and oyster reefs within the bay died off. Our age model indicates that this event most likely resulted from the most rapid period of eustatic rise of the Holocene, which peaked at 8.18–8.31 ka. This event is attributed to late-stage ice sheet disintegration, particularly in North America, by the rapid draining of Lake Agassiz–Ojibway. Local glacial-isostatic factors resulted in a sea-level rise of only 0.2–0.56 m in the western Gulf of Mexico, which was less than needed to submerge the barrier. Rather, it was the marked nature of this sea-level rise that led to the virtual destruction of Mustang Island as an effective salinity barrier. These results provide an analog for predicting coastal morphodynamic response to accelerated sea-level rise and emphasize the need for better understanding of barrier response to sea-level rise and developing improved numerical models for predicting future changes to coastal barrier shorelines. VL - 28 UR - http://journals.sagepub.com/doi/10.1177/0959683617715697 IS - 1 ER - TY - JOUR T1 - A centuries-long delay between a paleo-ice-shelf collapse and grounding-line retreat in the Whales Deep Basin, eastern Ross Sea, Antarctica JF - Scientific Reports Y1 - 2018 A1 - Bart, Philip J. A1 - DeCesare, Matthew A1 - Rosenheim, Brad E. A1 - Majewski, Wojceich A1 - McGlannan, Austin AB - Recent thinning and loss of Antarctic ice shelves has been followed by near synchronous acceleration of ice flow that may eventually lead to sustained deflation and significant contraction in the extent of grounded and floating ice. Here, we present radiocarbon dates from foraminifera that constrain the time elapsed between a previously described paleo-ice-shelf collapse and the subsequent major grounding-line retreat in the Whales Deep Basin (WDB) of eastern Ross Sea. The dates indicate that West Antarctic Ice Sheet (WAIS) grounding-line retreat from the continental shelf edge was underway prior to 14.7 ± 0.4 cal kyr BP. A paleo-ice-shelf collapse occurred at 12.3 ± 0.2 cal kyr BP. The grounding position was maintained on the outer-continental shelf until at least 11.5 ± 0.3 cal kyr BP before experiencing a 200-km retreat. Given the age uncertainties, the major grounding-line retreat lagged ice-shelf collapse by at least two centuries and by as much as fourteen centuries. In the WDB, the centuries-long delay in the retreat of grounded ice was partly due to rapid aggradational stacking of an unusually large volume of grounding-zone-wedge sediment as ice-stream discharge accelerated following ice-shelf collapse. This new deglacial reconstruction shows that ongoing changes to ice shelves may trigger complex dynamics whose consequences are realized only after a significant lag. VL - 8 UR - https://www.nature.com/articles/s41598-018-29911-8 IS - 1 ER - TY - JOUR T1 - Climate variability and cultural eutrophication at Walden Pond (Massachusetts, USA) during the last 1800 years JF - PLOS ONE Y1 - 2018 A1 - Stager, J. Curt A1 - Wiltse, Brendan A1 - Hubeny, J. Bradford A1 - Yankowsky, Eric A1 - Nardelli, David A1 - Primack, Richard ED - Doi, Hideyuki KW - BOREAL LAKES KW - canada KW - CRAWFORD LAKE KW - DEPTH MODELS KW - ENVIRONMENTAL-CHANGE KW - ice-age KW - new-england KW - NORTH-AMERICA KW - NORTHEASTERN UNITED-STATES KW - organic-matter AB - Recent shifts in the ecological condition of Walden Pond, MA, are of potentially wide interest due to the lake's importance as a cultural, historical, and recreational resource in addition to its scientific value as an indicator of local and global environmental change. Algal microfossils in six sediment cores document changes in hydroclimate and trophic status of the lake during the last 1800 years and extend two previous sediment core records of shorter length. Low percentages of planktonic diatoms in the longest cores (WAL-3, WAL-15) indicate shallowing and/or greater water clarity associated with a relatively arid interval during the Medieval Climate Anomaly, ca. A.D. 1150-1300, Cultural eutrophication of the lake since the A.D. 1920s caused diatoms in the genera Asterionella and Synedra to increase in relative abundance at the expense of Cyclotella, Discostella, and the chrysophyte alga Mallomonas allorgel. Percentages of Asterionella and Synedra have remained fairly stable since A.D. 2000 when a previous sediment core study was conducted, but scaled chrysophytes have become more numerous. These findings suggest that, although mitigation efforts have curtailed anthropogenic nutrient inputs to Walden Pond, the lake has not returned to the pre-impact condition described by Henry David Thoreau and may become increasingly vulnerable to further changes in water quality in a warmer and possibly wetter future. VL - 131786944304936355638925103443261363251824210727417625108525645371825392233490545519069849653235772249 UR - https://www.sciencedaily.com/releases/2018/04/180404143418.htm IS - 4 ER - TY - JOUR T1 - Climatic control of Mississippi River flood hazard amplified by river engineering JF - Nature Y1 - 2018 A1 - Munoz, Samuel E. A1 - Giosan, Liviu A1 - Therrell, Matthew D. A1 - Remo, Jonathan W. F. A1 - Shen, Zhixiong A1 - Sullivan, Richard M. A1 - Wiman, Charlotte A1 - O’Donnell, Michelle A1 - Donnelly, Jeffrey P. AB - Over the past century, many of the world’s major rivers have been modified for the purposes of flood mitigation, power generation and commercial navigation1. Engineering modifications to the Mississippi River system have altered the river’s sediment levels and channel morphology2, but the influence of these modifications on flood hazard is debated3,4,5. Detecting and attributing changes in river discharge is challenging because instrumental streamflow records are often too short to evaluate the range of natural hydrological variability before the establishment of flood mitigation infrastructure. Here we show that multi-decadal trends of flood hazard on the lower Mississippi River are strongly modulated by dynamical modes of climate variability, particularly the El Niño–Southern Oscillation and the Atlantic Multidecadal Oscillation, but that the artificial channelization (confinement to a straightened channel) has greatly amplified flood magnitudes over the past century. Our results, based on a multi-proxy reconstruction of flood frequency and magnitude spanning the past 500 years, reveal that the magnitude of the 100-year flood (a flood with a 1 per cent chance of being exceeded in any year) has increased by 20 per cent over those five centuries, with about 75 per cent of this increase attributed to river engineering. We conclude that the interaction of human alterations to the Mississippi River system with dynamical modes of climate variability has elevated the current flood hazard to levels that are unprecedented within the past five centuries. VL - 556 UR - https://www.nature.com/articles/nature26145 IS - 7699 ER - TY - JOUR T1 - The collapse of the North Song dynasty and the AD 1048–1128 Yellow River floods: Geoarchaeological evidence from northern Henan Province, China JF - The Holocene Y1 - 2018 A1 - Storozum, Michael J A1 - Zhen, Qin A1 - Xiaolin, Ren A1 - Haiming, Li A1 - Yifu, Cui A1 - Kui, Fu A1 - Haiwang, Liu KW - floods KW - Geoarchaeology KW - land use KW - North China Plain KW - Song dynasty KW - Yellow River AB - From AD 1048 to 1128, Yellow River flooding killed over a million people, left many more homeless and destitute, and turned parts of the once fertile North China Plain into a silted-up agricultural wasteland. Brought on in part by climate change and the Northern Song dynasty’s (AD 960–1127) mismanagement of the environment, the Yellow River floods likely hastened the collapse of the Northern Song dynasty. Despite the magnitude of this flood event, no sedimentary deposits have yet been linked to these historically recorded floods. In this research paper, we provide archaeological, sedimentary, and radiocarbon evidence of the AD 1048–1128 Yellow River floods at the Dazhanglongcun, Xidacheng, and Daguxiancun sites in Neihuang County, Henan Province. Based on our data, we argue that the AD 1048–1128 Yellow River floods deposited over 5 m of alluvium on villages in the North China Plain, radically changing both the physical and political landscape of Northern Song dynasty China. VL - 28 UR - http://journals.sagepub.com/doi/10.1177/0959683618788682 IS - 11 ER - TY - JOUR T1 - Combining Conflicting Bayesian Models to Develop Paleoseismic Records: An Example from the Wasatch Fault Zone, Utah JF - Bulletin of the Seismological Society of America Y1 - 2018 A1 - DuRoss, Christopher B. A1 - Bennett, Scott E. K. A1 - Briggs, Richard W. A1 - Personius, Stephen F. A1 - Gold, Ryan D. A1 - Reitman, Nadine G. A1 - Hiscock, Adam I. A1 - Mahan, Shannon A. AB - Bayesian statistical analyses of paleoseismic data result in the probabilistic determination of earthquake times using geochronological data evaluated in the context of a stratigraphic model. However, a fundamental problem in paleoseismology is how to use the Bayesian approach to model sparse and/or conflicting geochronological datasets, such as those derived from sites exhibiting episodic sedimentary and pedogenic processes in moderate‐ to high‐energy environments (e.g., a normal‐faulted alluvial fan). Using paleoseismic data for the Corner Canyon site on the Salt Lake City segment of the Wasatch fault zone (Utah), we develop an approach by which multiple Bayesian models are combined to generate an earthquake history at a site. This approach accommodates mutually exclusive interpretations of the geochronological data and thereby limits the influence of sparse data, stratigraphically inconsistent ages, or a single, subjective model interpretation. For the Corner Canyon site, we integrate four OxCal Bayesian models to generate a chronology of six events between ∼4.8 and ∼0.5  ka. Late Holocene (post‐5 ka) mean recurrence and vertical slip‐rate estimates are ∼0.9  ky (0.7–1.0 ky; 95% confidence) and 1.1  mm/yr (0.8–1.7  mm/yr range), respectively. Although our method increases the uncertainty in the timing of individual earthquakes, it more objectively accounts for potential geochronological errors and different interpretations of stratigraphic age control. By relaxing the need to select a single age model, our approach yields more accurate earthquake‐timing results that will better facilitate evaluations of along‐fault event correlation and earthquake rupture length. UR - https://pubs.geoscienceworld.org/ssa/bssa/article/536312/Combining-Conflicting-Bayesian-Models-to-Develop ER - TY - JOUR T1 - Data Constraints on Glacial Atlantic Water Mass Geometry and Properties JF - Paleoceanography and Paleoclimatology Y1 - 2018 A1 - Oppo, Delia W. A1 - Gebbie, Geoffrey A1 - Huang, Kuo‐Fang A1 - Curry, William B. A1 - Marchitto, Thomas M. A1 - Pietro, Kathryn R. AB - The chemical composition of benthic foraminifera from marine sediment cores provides information on how glacial subsurface water properties differed from modern, but separating the influence of changes in the origin and end‐member properties of subsurface water from changes in flows and mixing is challenging. Spatial gaps in coverage of glacial data add to the uncertainty. Here we present new data from cores collected from the Demerara Rise in the western tropical North Atlantic, including cores from the modern tropical phosphate maximum at Antarctic Intermediate Water (AAIW) depths. The results suggest lower phosphate concentration and higher carbonate saturation state within the phosphate maximum than modern despite similar carbon isotope values, consistent with less accumulation of respired nutrients and carbon, and reduced air‐sea gas exchange in source waters to the region. An inversion of new and published glacial data confirms these inferences and further suggests that lower preformed nutrients in AAIW, and partial replacement of this still relatively high‐nutrient AAIW with nutrient‐depleted, carbonate‐rich waters sourced from the region of the modern‐day northern subtropics, also contributed to the observed changes. The results suggest that glacial preformed and remineralized phosphate were lower throughout the upper Atlantic, but deep phosphate concentration was higher. The inversion, which relies on the fidelity of the paleoceanographic data, suggests that the partial replacement of North Atlantic sourced deep water by Southern Ocean Water was largely responsible for the apparent deep North Atlantic phosphate increase, rather than greater remineralization. VL - 33 UR - https://onlinelibrary.wiley.com/doi/abs/10.1029/2018PA003408 IS - 9 ER - TY - JOUR T1 - Decreased sedimentation efficiency of petro- and non-petro-carbon caused by a dispersant for Macondo surrogate oil in a mesocosm simulating a coastal microbial community JF - Marine Chemistry Y1 - 2018 A1 - Xu, Chen A1 - Zhang, Saijin A1 - Beaver, Morgan A1 - Wozniak, Andrew A1 - Obeid, Wassim A1 - Lin, Youmin A1 - Wade, Terry L. A1 - Schwehr, Kathleen A. A1 - Lin, Peng A1 - Sun, Luni A1 - Hatcher, Patrick G. A1 - Chin, Wei-Chun A1 - Chiu, Meng-Hsuen A1 - Knap, Anthony H. A1 - Dean, Kendra A1 - Quigg, Antonietta A1 - Santschi, Peter H. AB - Large amounts of mucous-rich oil-containing marine snow formed in surface waters adjacent to the Deepwater Horizon spill. This marine oil snow (MOS) was implicated in oil delivery to the seafloor. Whether the use of chemical dispersants increased or decreased MOS sedimentation remains controversial. We conducted mesocosm experiments testing the effects of oil and oil plus a dispersant on MOS formation and sedimentation, in coastal seawater. The four treatments used were a surrogate Macondo oil water accommodated fraction (“WAF”), two concentrations of chemically-enhanced WAF (“CEWAF” and diluted CEWAF, “DCEWAF”) containing a dispersant and oil, and Controls (no additions). Based on radiocarbon and 13C NMR results, the presence of dispersants enhanced the amounts of petro-carbon being incorporated into the sinking oil-carrying aggregates (aka MOS). However, most of the chemically-dispersed oil preferentially partitioned into the colloidal and suspended particulate fractions rather than into the rapidly forming MOS. Thus the oil and non-petro-carbon sedimentation efficiency in treatments with a dispersant was much lower, compared to those in the Control and WAF treatments, during the four-day mesocosm experiment. Formation of MOS and its subsequent sinking sequestered the oil in two stages: first via terrestrial-derived detritus containing humic compounds, and subsequently via freshly produced material, such as exopolymeric substances produced by phytoplankton and bacteria. VL - 206 UR - https://linkinghub.elsevier.com/retrieve/pii/S0304420318301415 ER - TY - JOUR T1 - Deglacial floods in the Beaufort Sea preceded Younger Dryas cooling JF - Nature Geoscience Y1 - 2018 A1 - Keigwin, L. D. A1 - Klotsko, S. A1 - Zhao, N. A1 - Reilly, B. A1 - Giosan, L. A1 - Driscoll, N. W. AB - A period of cooling about 13,000 years ago interrupted about 2,000 years of deglacial warming. Known as the Younger Dryas (YD), the event is thought to have resulted from a slowdown of the Atlantic meridional overturning circulation in response to a sudden flood of Laurentide Ice Sheet meltwater that reached the Nordic Seas. Oxygen isotope evidence for a local source of meltwater to the open western North Atlantic from the Gulf of St Lawrence has been lacking. Here we report that the eastern Beaufort Sea contains the long-sought signal of O-18-depleted water. Beginning at similar to 12.94 ± 0.15 thousand years ago, oxygen isotopes in the planktonic foraminifera from two sediment cores as well as sediment and seismic data indicate a flood of meltwater, ice and sediment to the Arctic via the Mackenzie River that lasted about 700 years. The minimum in the oxygen isotope ratios lasted similar to 130 years. We suggest that the floodwater travelled north along the Canadian Archipelago and then through the Fram Strait to the Nordic Seas, where freshening and freezing near sites of deep-water formation would have suppressed convection and caused the YD cooling by reducing the meridional overturning. VL - 11 UR - http://www.nature.com/articles/s41561-018-0169-6http://www.nature.com/articles/s41561-018-0169-6.pdfhttp://www.nature.com/articles/s41561-018-0169-6http://www.nature.com/articles/s41561-018-0169-6.pdf IS - 8 ER - TY - JOUR T1 - The demise of the largest and oldest African baobabs JF - Nature Plants Y1 - 2018 A1 - Patrut, Adrian A1 - Woodborne, Stephan A1 - Patrut, Roxana T. A1 - Rakosy, Laszlo A1 - Lowy, Daniel A. A1 - Hall, Grant A1 - von Reden, Karl F. AB - The African baobab is the biggest and longest-living angiosperm tree. By using radiocarbon dating we identified the stable architectures that enable baobabs to reach large sizes and great ages. We report that 9 of the 13 oldest and 5 of the 6 largest individuals have died, or at least their oldest parts/stems have collapsed and died, over the past 12 years; the cause of the mortalities is still unclear. VL - 4 UR - http://www.nature.com/articles/s41477-018-0170-5 IS - 7 ER - TY - JOUR T1 - Dimensions of Radiocarbon Variability within Sedimentary Organic MatterABSTRACT JF - Radiocarbon Y1 - 2018 A1 - Bao, Rui A1 - McNichol, Ann P A1 - McIntyre, Cameron P A1 - Xu, Li A1 - Eglinton, Timothy I KW - arabian sea KW - grain size KW - hydrodynamic processes KW - organicmatter KW - radiocarbon KW - ramped pyrolysis-oxidation AB - Organic carbon (OC) radiocarbon (14C) signatures in marine surface sediments are highly variable and the causes of this heterogeneity remain ambiguous. Here, we present results from a detailed 14C-based investigation of an Arabian Sea sediment, including measurements on organic matter (OM) in bulk sediment, specific grain size fractions, and OC decomposition products from ramped-pyrolysis-oxidation (RPO). Our results show that 14C ages of OM increase with increasing grain size, suggesting that grain size is an important factor controlling the 14C heterogeneity in marine sediments. Analysis of RPO decomposition products from different grain size fractions reveals an overall increase in age of corresponding thermal fractions from finer to coarser fractions. We suggest that hydrodynamic properties of sediment grains exert the important control on the 14C age distribution of OM among grain size fractions. We propose a conceptual model to account for this dimensionality in 14C variability that invokes two predominant modes of OM preservation within different grain size fractions of Arabian Sea sediment: finer (<63 μm) fractions are influenced by OM-mineral grain aggregation processes, giving rise to relatively uniform 14C ages, whereas OM preserved in coarser (>63 μm) fractions includes materials encapsulated within microfossils and/or entrained fossil (14C-depleted) OC hosted in detrital mineral grains. Our findings highlight the value of RPO for assessment of 14C age variability in sedimentary OC, and for assessing mechanisms of OM preservation in aquatic sediments. VL - 60 UR - https://www.cambridge.org/core/journals/radiocarbon/article/dimensions-of-radiocarbon-variability-within-sedimentary-organic-matter/A81022494F34D8C3B88D39A43112BB08 IS - 03 ER - TY - JOUR T1 - Drought in the northern Bahamas from 3300 to 2500 years ago JF - Quaternary Science Reviews Y1 - 2018 A1 - van Hengstum, Peter J. A1 - Maale, Gerhard A1 - Donnelly, Jeffrey P. A1 - Albury, Nancy A. A1 - Onac, Bogdan P. A1 - Sullivan, Richard M. A1 - Winkler, Tyler S. A1 - Tamalavage, Anne E. A1 - MacDonald, Dana AB - Intensification and western displacement of the North Atlantic Subtropical High (NASH) is projected for this century, which can decrease Caribbean and southeastern American rainfall on seasonal and annual timescales. However, additional hydroclimate records are needed from the northern Caribbean to understand the long-term behavior of the NASH, and better forecast its future behavior. Here we present a multi-proxy sinkhole lake reconstruction from a carbonate island that is proximal to the NASH (Abaco Island, The Bahamas). The reconstruction indicates the northern Bahamas experienced a drought from ∼3300 to ∼2500 Cal yrs BP, which coincides with evidence from other hydroclimate and oceanographic records (e.g., Africa, Caribbean, and South America) for a synchronous southern displacement of the Intertropical Convergence Zone and North Atlantic Hadley Cell. The specific cause of the hydroclimate change in the northeastern Caribbean region from ∼3300 to 2500 Cal yrs BP was probably coeval southern or western displacement of the NASH, which would have increased northeastern Caribbean exposure to subsiding air from higher altitudes. VL - 186 UR - https://linkinghub.elsevier.com/retrieve/pii/S0277379117306273 ER - TY - JOUR T1 - Dual-Isotope Constraints on Seasonally Resolved Source Fingerprinting of Black Carbon Aerosols in Sites of the Four Emission Hot Spot Regions of China JF - Journal of Geophysical Research: Atmospheres Y1 - 2018 A1 - Fang, Wenzheng A1 - Du, Ke A1 - Andersson, August A1 - Xing, Zhenyu A1 - Cho, Chaeyoon A1 - Kim, Sang-Woo A1 - Deng, Junjun A1 - Gustafsson, Örjan KW - aerosol KW - BLACK CARBON KW - carbon isotope KW - china KW - emission sources KW - seasonality AB - Despite much recent efforts, the emission sources of black carbon (BC) aerosols―central input to understanding and predicting environmental and climate impact―remain highly uncertain. Here we present observational δ13C/Δ14C‐based constraints on the sources of BC aerosols over the four seasons in each of the four key hot spot emission regions of China: Beijing‐Tianjin‐Hebei (BTH‐Wuqing; where Wuqing is the sampling location), Yangtze River Delta (YRD‐Haining), Pearl River Delta (PRD‐Zhongshan), and Sichuan Basin (SC‐Deyang). Overall, BC loadings were highest in winter, yet elevated loadings were also observed in other seasons, for example, spring at SC‐Deyang and fall at PRD‐Zhongshan. Annually, the dominant BC sources were coal (50 ± 20%) for BTH‐Wuqing, liquid fossil for YRD‐Haining (46 ± 8%) and PRD‐Zhongshan (48 ± 18%), whereas liquid fossil (42 ± 17%) and biomass burning (41 ± 14%) equally affected SC‐Deyang. There is also different but distinct seasonalities in BC sources for the different sites. As an example, for BTH‐Wuqing coal burning increased from summer to winter, while summer and spring BTH‐Wuqing were more influenced by liquid fossil. In contrast, for YRD‐Haining, the relative importance of emission sources was more constant over the year. These quantitative observational constraints on source‐seasonality of BC aerosols in receptor sites located in China's four key economic zones highlight that regulatory control on BC aerosol emissions from different fuels should consider both seasonal and regional variations. Our results also suggest that models on estimates of BC‐induced climate and air quality should consider variations over both regional and seasonal scales. VL - 123 UR - http://doi.wiley.com/10.1029/2018JD028607 IS - 20 ER - TY - JOUR T1 - Early Holocene sea level in the Canadian Beaufort Sea constrained by radiocarbon dates from a deep borehole in the Mackenzie Trough, Arctic Canada JF - Boreas Y1 - 2018 A1 - O'Regan, Matt A1 - Coxall, Helen A1 - Hill, Philip A1 - Hilton, Robert A1 - Muschitiello, Francesco A1 - Swärd, Henrik AB - Deglacial and Holocene relative sea level (RSL) in the Canadian Beaufort Sea was influenced by the timing and extent of glacial ice in the Mackenzie River corridor and adjacent coastal plains. Considerable evidence indicates extensive ice cover in this region of northwestern Canada during the Late Wisconsinan. However, no absolute ages exist to constrain maximum RSL lowering before the late Holocene (4.2–0 ka). In 1984, the Geological Survey of Canada drilled an 81.5‐m‐deep borehole in the western Mackenzie Trough at 45 m water depth (MTW01). The lower 52.5 m of the borehole was interpreted as a deltaic progradational sequence deposited during a period of rising sea level. The upper 29 m was described as foraminifer‐bearing marine sediments deposited after transgression of the site, when RSL rose above ~−74 m. Here, we present radiocarbon measurements from MTW01, acquired from benthic foraminifera, mollusc fragments and particulate organic carbon in the >63 μm fraction (POC>63 μm) in an attempt to constrain the chronology of sediments within this borehole and date the timing of transgression. The deepest carbonate macrofossil was acquired from 8 m above the transgressive surface (equivalent to 21 m b.s.l.), where mollusc fragments returned a date of 9400 +180–260 cal. a BP (2σ). This provides the oldest constraint on Holocene sea‐level lowering in the region, and implies that transgression at this site occurred prior to the early Holocene. Ages obtained from the lower 52.5 m of the borehole are limited to POC>63 μm samples. These indicate that progradational sediments were deposited rapidly after 24 820 +390–380 cal. a BP (2σ). Due to the incorporation of older reworked organic matter, the actual age of progradation is likely to be younger, occurring after Late Wisconsinan glacial ice retreated from the coast. VL - 47 UR - https://onlinelibrary.wiley.com/doi/10.1111/bor.12335 IS - 4 ER - TY - JOUR T1 - Ecological history of a long-lived conifer in a disjunct population JF - Journal of Ecology Y1 - 2018 A1 - Herring, Erin M. A1 - Gavin, Daniel G. A1 - Dobrowski, Solomon Z. A1 - Fernandez, Matias A1 - Hu, Feng Sheng ED - Gill, Jacquelyn KW - climate KW - disjunction KW - dispersal KW - Holocene KW - Idaho KW - mertensiana KW - Palaeoecology KW - pollen KW - refugia KW - Tsuga AB - In northern Idaho (USA), more than 100 vascular plant species are disjunct >160 km from their main distribution along the Pacific Northwest coast. It remains unclear whether most species within this interior forest disjunction, including Tsuga mertensiana, survived the last glacial period in a north‐Idaho refugium or whether these species colonized the region via long‐distance dispersal during the Holocene. Sediment cores were extracted from three mid‐ to high‐elevation lakes within T. mertensiana‐dominated forests in the Northern Rocky Mountains of Idaho. Pollen and macrofossils were used to reconstruct forest composition, determine the timing of T. mertensiana establishment, examine the hypothesis that the region was a glacial refugium, and contrast how climate, competition and/or dispersal limitation have influenced its modern distribution. The modern distribution of T. mertensiana was analysed by constructing a range map and modelling the potential species distribution. The presence of outlier populations surrounding the Idaho disjunction along with broad areas of unoccupied suitable habitat indicates that the range of T. mertensiana is currently expanding. To assess the accuracy of T. mertensiana pollen at detecting its range limit, a network of pollen surface samples was used to analyse the probability of detecting T. mertensiana pollen as a function of distance from its geographical range limit. Consistent T. mertensiana pollen occurrence at ≥1% abundance is likely only within 42 km of its range limit. Tsuga mertensiana first appears in the pollen and macrofossil record at the highest‐elevation site at c. 4,100 cal year bp, then at the next highest‐elevation site at c. 1,600 cal year bp, and last at the mid‐elevation site at 800 cal year bp. Tsuga mertensiana pollen occurs continuously at ≥1% at all three sites by c. 300 cal year bp suggesting regional presence. The timing of arrival suggests that T. mertensiana is a recent component of the forests of Idaho, having arrived during the Holocene via long‐distance dispersal from coastal populations over 160 km away. Synthesis. Comparison with palaeoclimate reconstructions from the broader region suggests that climate was a greater limiting factor than dispersal in the Holocene establishment in the interior, indicating little difficulty overcoming a large dispersal barrier. However, T. mertensiana remained at low abundances for millennia until Little Ice Age climates promoted its recent increase in abundance. Unoccupied areas of suitable habitat suggest that competition, rather than climate or dispersal, is a limiting range infilling in the interior mesic forests today. VL - 106 UR - https://besjournals.onlinelibrary.wiley.com/doi/full/10.1111/1365-2745.12826 IS - 1 ER - TY - JOUR T1 - The effect of sample drying temperature on marine particulate organic carbon composition JF - Limnology and Oceanography: Methods Y1 - 2018 A1 - Rosengard, Sarah Z. A1 - Lam, Phoebe J. A1 - McNichol, Ann P. A1 - Johnson, Carl G. A1 - Galy, Valier V. AB - Compositional changes in marine particulate organic carbon (POC) throughout the water column trace important processes that underlie the biological pump's efficiency. While labor‐intensive, particle sampling efforts offer potential to expand the empirical POC archive at different stages in the water column, provided that organic composition is sufficiently preserved between sampling and analysis. The standard procedure for preserving organic matter composition in marine samples is to immediately store particles at −80°C to −20°C until they can be freeze‐dried for analysis. This report investigates the effect of warmer drying and storage temperatures on POC composition, which applies to the majority of POC samples collected in the field without intention for organic analysis. Particle samples collected off Woods Hole, Massachusetts were immediately dried at 56°C, at room temperature, or stored in a freezer until freeze‐drying. Results show that oven‐ and air‐drying did not shift the bulk composition (i.e., carbon and nitrogen content and stable isotope composition) of POC in the samples relative to freeze‐drying. Similarly, warmer drying temperatures did not affect POC thermal stability, as inferred by ramped pyrolysis/oxidation, a growing technique that uses a continuous temperature ramp to differentiate components of organic carbon by their decomposition temperature. Oven‐ and air‐drying did depress lipid abundances relative to freeze‐drying, the extent of which depended on compound size and structure. The data suggest that field samples dried at room temperatures and 56°C are appropriate for assessing bulk POC composition and thermal stability, but physical mechanisms such as molecular volatilization bias their lipid composition. VL - 16 UR - https://www.researchgate.net/publication/324893072_The_effect_of_sample_drying_temperature_on_marine_particulate_organic_carbon_composition IS - 5 ER - TY - JOUR T1 - Effects of the Younger Dryas climate event recorded in sediment near the western Irish seaboard JF - Geological Journal Y1 - 2018 A1 - Wood, Bill L. A1 - Williams, D. Michael A1 - Murray, John ED - Somerville, I. KW - Atlantic Ocean KW - Foraminifers KW - Holocene KW - ice rafted debris KW - Ireland KW - sediment core KW - Younger Dryas AB - Results of analyses of a shallow marine sediment vibrocore from the Atlantic seafloor just west of the Aran Islands, western Ireland, are presented. The sediments range from ~16,000 to younger than 9,000 cal BP in age, based on 14C dating of foraminifers and molluscs. One sample within the core is dated at 12804 ± 125 cal BP and lies a very short distance stratigraphically below a conspicuous horizon containing isolated pebbles and sand‐size clasts, in what is an otherwise fine‐grained sequence of sediment. These outsized clasts are interpreted to be ice‐rafted debris. Approximately coeval with this horizon, the diversity and abundance of foraminifers decrease significantly and the foraminifer Nonionellina labradorica makes its first appearance in the core sediment. Stable isotope analysis shows a significant increase in values of δ18O approaching the horizon containing ice‐rafted debris. These results show the effects of a relatively sudden cooling of this part of the Atlantic Ocean at middle latitudes coincident with, or just after, the onset of the Younger Dryas event and demonstrate the extent of floating icebergs and probable later pack ice as a result of this temperature decrease. VL - 53 UR - https://onlinelibrary.wiley.com/doi/10.1002/gj.2918 IS - 2 ER - TY - JOUR T1 - The Effects of Tropical Cyclone-Generated Deposition on the Sustainability of the Pearl River Marsh, Louisiana: The Importance of the Geologic FrameworkPresentation_1.PPTX JF - Frontiers in Ecology and Evolution Y1 - 2018 A1 - McCloskey, Terrence A. A1 - Smith, Christopher G. A1 - Liu, Kam-biu A1 - Nelson, Paul R. AB - Shoreline retreat is a tremendously important issue along the coast of the northern Gulf of Mexico, especially in Louisiana. Although this marine transgression results from a variety of causes, the crucial factor is the difference between marsh surface elevation and rising sea levels. In most cases, the primary cause of a marsh's inability to keep up with sea level is the lack of input of inorganic material. Although tropical cyclones provide an important source of such sediment, little effort has been made to determine the point of origin of the deposited material. In this study we use sedimentary, geochemical and biogeochemical data to identify the bed of the Pearl River and/or Lake Borgne as the source of a ~5 cm thick clastic layer deposited on the surface of the Pearl River marsh on the Louisiana/Mississippi border. Radiochemical chronologies and sedimentary evidence indicate that this layer was associated with the passage of Hurricane Katrina in 2005. As this material would otherwise have been lost to the system, this deposition indicates a net gain to marsh surface elevation. Accretion rates, determined from 137Cs and 14C profiles and the use of the Katrina layer as a stratigraphic marker, indicate that short-term (~50 years) rates are as much as an order of magnitude higher than the long- term (1000s of years) rates. We suggest that the marsh's geologic setting in an incised river valley with steep vertical constraints and a large fluvial discharge, promotes rapid accretion rates, with rates accelerating as the sea moves inland, due to extended hydroperiods and the input of clastic material from both the marine and terrestrial sides. These rates are especially large when compared to accretion occurring in the more common open marshes fringing the Gulf that lack fluvial input. The difference is particularly large when related to marsh recovery/regrowth following the deposition of thick hurricane-generated clastic layers. Given the number of similar incised river valleys along the Gulf Coast, we believe that understanding the processes controlling marsh accretion in such environments is essential in evaluating marsh sustainability on a regional basis. VL - 6 UR - https://www.frontiersin.org/article/10.3389/fevo.2018.00179/full ER - TY - JOUR T1 - The Ephemeral Signature of Permafrost Carbon in an Arctic Fluvial Network JF - Journal of Geophysical Research: Biogeosciences Y1 - 2018 A1 - Drake, Travis W. A1 - Guillemette, François A1 - Hemingway, Jordon D. A1 - Chanton, Jeffery P. A1 - Podgorski, David C. A1 - Zimov, Nikita S. A1 - Spencer, Robert G. M. AB - Arctic fluvial networks process, outgas, and transport significant quantities of terrestrial organic carbon (C), particularly dissolved organic carbon (DOC). The proportion of permafrost C in these fluxes, however, is poorly constrained. A primary obstacle to the quantification of permafrost‐derived DOC is that it is rapidly respired without leaving a unique tracer of its presence. In this study, we investigated the production of bacterial respiratory carbon dioxide (CO2; measured as dissolved inorganic carbon; DIC) during maximum late‐summer thaw in sites spanning a fluvial network (Kolyma Basin, Siberia) to assess whether the biodegradation of permafrost DOC could be detected by the presence of a persistent aged (14C‐depleted) signature on the DIC pool. Using Keeling plot interpretation of DIC produced in bioincubations of river water, we show that bacteria respire varying sources of DOC moving downstream through the fluvial network. Respiration of permafrost (production of aged CO2) was only detected in heavily permafrost thaw influenced sites. In nonpermafrost thaw impacted sites, ambient DIC was modern (14C‐enriched), but rather than precluding the respiration of permafrost OC upstream, we suggest that 14C‐depleted DIC is overwhelmed by modern DIC. Investigation of dissolved organic matter composition via Fourier transform ion cyclotron resonance mass spectrometry highlighted that elevated levels of aliphatic and nitrogen‐containing compounds were associated with the production of aged DIC, providing molecular‐level insight as to why permafrost‐derived dissolved organic matter is rapidly respired. Overall, results from this study demonstrate the difficulty of tracing inputs of a highly reactive substrate to systems with diverse organic matter sources. VL - 123 UR - https://onlinelibrary.wiley.com/doi/abs/10.1029/2017JG004311 IS - 5 ER - TY - JOUR T1 - Evidence for Stable Holocene Basin‐Scale Overturning Circulation Despite Variable Currents Along the Deep Western Boundary of the North Atlantic Ocean JF - Geophysical Research Letters Y1 - 2018 A1 - Hoffmann, Sharon S. A1 - McManus, Jerry F. A1 - Swank, Emerson KW - chemical tracers KW - interglacial KW - Radioactivity and radioisotopes KW - sedimentation (1861) KW - thermohaline AB - While substantial changes in thermohaline circulation related to deglacial climate variability are well established, the role of this circulation in Holocene climate variability remains uncertain. Here we use two dynamical proxies, 231Pa/230Th ratios and mean sortable silt size ( urn:x-wiley:00948276:media:grl58406:grl58406-math-0001), to reconstruct Holocene bottom water circulation at the intermediate‐depth Carolina Slope. We find no substantial change in deep current speed or 231Pa export at this site during the Holocene, suggesting consistent 231Pa export via the Deep Western Boundary Current. urn:x-wiley:00948276:media:grl58406:grl58406-math-0002 shows increasing millennial‐scale variability in the middle‐late Holocene, which may reflect Labrador Sea Water contribution to current speed. We conclude that deepwater export from the North Atlantic has remained remarkably stable during the Holocene, decoupled from changing rates of specific water masses, while production of these water masses varied at millennial to centennial time scales. The persistence of the large‐scale overturning may reflect the ocean's stabilizing influence on Holocene climate. VL - 45 UR - https://onlinelibrary.wiley.com/doi/abs/10.1029/2018GL080187 IS - 24 ER - TY - JOUR T1 - Faunal and stable isotopic analyses of benthic foraminifera from the Southeast Seep on Kimki Ridge offshore southern California, USA JF - Deep Sea Research Part II: Topical Studies in Oceanography Y1 - 2018 A1 - McGann, Mary A1 - Conrad, James E. KW - Beggiatoa KW - benthic foraminifera KW - Calyptogena KW - Kimki Ridge KW - Santa Catalina Basin KW - Southeast Seep KW - Southern California KW - stable carbon isotopes AB - We investigated the benthic foraminiferal faunal and stable carbon and oxygen isotopic composition of a 15-cm push core (NA075-092b) obtained on a Telepresence-Enabled cruise to the Southeast Seep on Kimki Ridge offshore southern California. The seep core was taken at a depth of 973 m in the vicinity of a Beggiatoa bacterial mat and vesicomyid clams (Calyptogena) and compared to previously published data of living assemblages from ~ 714 m, four reference cores obtained at ~ 1030 m, and another one at 739 m. All of the reference sites are also from the Inner Continental Borderland but with no evidence of methane seepage. No endemic species were found at the seep site and most of the taxa recovered there have been reported previously from other seep or low oxygen environments. Q- and R-mode cluster analyses clearly illustrated differences in the faunal assemblages of the seep and non-seep sites. The living assemblage at Southeast Seep was characterized by abundant Takayanagia delicata, Cassidulina translucens, and Spiroplectammina biformis, whereas the non-seep San Pedro Basin reference assemblage was comprised primarily of Chilostomella oolina and Globobulimina pacifica. Density and species richness were lower at the seep site compared to the non-seep site, reflecting the harsher living conditions there. The dead assemblage at the seep site was dominated by Gyroidina turgida compared to Cassidulina translucens at the ~ 1030 m non-seep site and Cassidulina translucens, Pseudoparrella pacifica, and Takayanagia delicata at the 739 m non-seep site. Density was three times lower at Southeast Seep than at the non-seep sites of comparable water depth but species richness was ~ 30% higher. Stable carbon isotopic values were considerably depleted in the seep samples compared to the non-seep samples, with a progression from lightest to heaviest average δ13C values evident at the seep site reflecting microhabitat preference and vital effect: the deep infaunal species of Globobulimina, the shallow infaunal species Uvigerina peregrina, the epifaunal species Cibicidoides wuellerstorfi, and the shallow infaunal but aragonite-shelled species Hoeglundina elegans. The δ13C values downcore among each benthic species indicates ongoing fluid seepage through at least the last 3800 cal yr B.P. at Southeast Seep. Besides the continual local seepage, evidence from δ13C values of planktic foraminifera in the seep core suggest two pulses of methane (at 3000 and 3700 cal yr B.P.) were released that were large enough to influence much of the water column. Paired benthic and planktic foraminiferal stable oxygen isotope records provide evidence that there were no paleoenvironmental changes such as increased bottom-water temperature or changes in oxygen isotopic composition of bottom and pore waters during this 3800-year record to induce the methane releases. Instead, Southeast Seep appears to be the result of local faulting providing pathways for fluid to flow to the seafloor at a fault stepover or transpressional bend in the regional strike-slip system. VL - 150 UR - https://linkinghub.elsevier.com/retrieve/pii/S0967064517301509 ER - TY - JOUR T1 - Fifty-five-year longevity for the largest member of the family Sparidae: the endemic red steenbras Petrus rupestris from South Africa JF - African Journal of Marine Science Y1 - 2018 A1 - Andrews, AH A1 - Smale, MJ A1 - Cowley, PD A1 - Chang, N KW - Age validation KW - bomb radiocarbon dating KW - Carbon-14 KW - copper steenbras KW - endangered species KW - fishery closure KW - otoliths AB - A previous study that explored the age and growth of red steenbras Petrus rupestris (Valenciennes, 1830), a large sparid (family Sparidae, seabreams or porgies) endemic to South Africa and reported to approach 2 m in length, provided estimates as a moderately slow-growing species with a maximum age near 30 years. The stock is considered collapsed and a fishing moratorium was imposed in 2012, resulting in this species being assessed as Endangered by the IUCN. One consideration in addressing population status is validation of life-history traits. In this study, estimates of age for red steenbras from thin-sectioned otoliths were reassessed visually in terms of both the original ages and revised estimates using a different age-reading pattern. The revised ages exceeded the original ages by up to 30 years, with a maximum estimated age of 55 years from a well-defined otolith section that provided a basis for the revised age-reading procedure. Bomb radiocarbon (14C) dating revealed there was an offset in the timing of the 14C rise on the Agulhas Bank that, when coupled with considerations for regional oceanography, provided support for the revised age-reading pattern and an estimated longevity that exceeds 50 years. These findings were further supported by the fortuitous recapture of a tagged red steenbras that was at liberty for 22 years. VL - 40 UR - https://www.tandfonline.com/doi/full/10.2989/1814232X.2018.1520148https://www.tandfonline.com/doi/pdf/10.2989/1814232X.2018.1520148 IS - 4 ER - TY - JOUR T1 - Five Younger Dryas black mats in Mexico and their stratigraphic and paleoenvironmental context JF - Journal of Paleolimnology Y1 - 2018 A1 - Israde-Alcántara, Isabel A1 - Domínguez-Vázquez, G. A1 - Gonzalez, S. A1 - Bischoff, J. A1 - West, A. A1 - Huddart, D. AB - The Younger Dryas interval (YD) was a period of widespread, abrupt climate change that occurred between 12,900 and 11,700 cal yr BP (10,900–10,000 14C BP). Many sites in the Northern Hemisphere preserve a sedimentary record across the onset of the YD interval, including sites investigated in sedimentary basins located in central Mexico (Chapala, Cuitzeo, Acambay), the Basin of Mexico (Tocuila), and northern Mexico (El Cedral). Deposits consist of lacustrine or marginal lake sediments that were deposited during the Pleistocene and the Holocene. At the Tocuila and Acambay sites, Pleistocene fossil vertebrate assemblages, mainly mammoths (Mammuthus columbi), are found in association with a distinctive organic layer, sometimes called the black mat that formed during the YD. At the Chapala, Cuitzeo, Acambay, and Tocuila sites the black mats contain a suite of distinctive microscopic and mineralogical signatures and are accompanied by a sharp change in the depositional environments as supported by diatom and pollen studies reported here. The signatures include magnetic, Fe-rich microspherules, silica melted droplets with aerodynamic shapes (tektites), large amounts of charcoal, and sometimes nanodiamonds (Cuitzeo), all of which were deposited at the onset of the YD. The geochemistry of the microspherules indicates that they are not anthropogenic, authigenic or of cosmic or volcanic origin, and instead, were produced by melting and quenching of terrestrial sediments. Here, we present the stratigraphy at five field sites, the analyses of magnetic microspherules, including major element composition and scanning electron microscopy images. All of these materials are associated with charcoal and soot, which are distinctive stratigraphic markers for the YD layer at several sites in Mexico. VL - 59 UR - http://link.springer.com/10.1007/s10933-017-9982-y IS - 1 ER - TY - JOUR T1 - Fossil Fuel Combustion Emission From South Asia Influences Precipitation Dissolved Organic Carbon Reaching the Remote Tibetan Plateau: Isotopic and Molecular Evidence JF - Journal of Geophysical Research: Atmospheres Y1 - 2018 A1 - Li, Chaoliu A1 - Chen, Pengfei A1 - Kang, Shichang A1 - Yan, Fangping A1 - Tripathee, Lekhendra A1 - Wu, Guangjian A1 - Qu, Bin A1 - Sillanpää, Mika A1 - Yang, Di A1 - Dittmar, Thorsten A1 - Stubbins, Aron A1 - Raymond, Peter A. AB - The dissolved organic carbon in precipitation (water‐soluble organic carbon, WSOC) can provide a carbon subsidy to receiving ecosystems. The concentrations, isotopic signatures (δ13C/Δ14C), and molecular signatures (transform ion cyclotron mass spectrometry) of WSOC being delivered to Nam Co—a remote site on the inland Tibetan Plateau (TP)—were compared to those of WSOC in the snowpack, and in wet deposition from urban cities fringing the TP. The average WSOC concentration at Nam Co (1.0 ± 0.9 mg C L−1) was lower than for the large cities (1.6 to 2.3 mg C L−1) but higher than in the snowpack samples (0.26 ± 0.09 mg C L−1). Based upon radiocarbon data, it is estimated that 15 ± 6% of Nam Co WSOC was fossil derived, increasing to 20 ± 8% for snowpack WSOC, 29 ± 4% for Lhasa WSOC, and 34 ± 8% for the three cities. Transform ion cyclotron mass spectrometry results revealed that the abundance of dissolved black carbon and sulfur‐containing molecules of WSOC increased in the order Nam Co < snow pack < urban. The enrichment in 14C and depletion in dissolved black carbon and sulfurous organic molecules of Nam Co WSOC was suggestive of low, but still detectable inputs of fossil‐derived organics to WSOC on the remote TP. Backward air mass trajectories for the precipitation events at Nam Co suggested that the fossil fuel contributions to WSOC in Nam Co region originated mainly from South Asia. This study provides novel radiocarbon age, chemistry, and source evidence that anthropogenic WSOC is delivered to the remote TP, one of the most remote regions on Earth. VL - 123 UR - http://doi.wiley.com/10.1029/2017JD028181 IS - 11 ER - TY - JOUR T1 - Fossil Fuel-Derived Polycyclic Aromatic Hydrocarbons in the Taiwan Strait, China, and Fluxes across the Air–Water InterfaceFossil Fuel-Derived Polycyclic Aromatic Hydrocarbons in the Taiwan Strait, China, and Fluxes across the AirWater Interface JF - Environmental Science & Technology Y1 - 2018 A1 - Ya, Miaolei A1 - Xu, Li A1 - Wu, Yuling A1 - Li, Yongyu A1 - Zhao, Songhe A1 - Wang, Xinhong AB - On the basis of the application of compound-specific radiocarbon analysis (CSRA) and air–water exchange models, the contributions of fossil fuel and biomass burning derived polycyclic aromatic hydrocarbons (PAHs) as well as their air–water transport were elucidated. The results showed that fossil fuel-derived PAHs (an average contribution of 89%) presented the net volatilization process at the air–water interface of the Taiwan Strait in summer. Net volatile fluxes of the dominant fluorene and phenanthrene (>58% of the total PAHs) were 27 ± 2.8 μg m–2 day–1, significantly higher than the dry deposition fluxes (average 0.43 μg m–2 day–1). The Δ14C contents of selected PAHs (fluorene, phenanthrene plus anthracene, fluoranthene, and pyrene) determined by CSRA in the dissolved seawater ranged from −997 ± 4‰ to −873 ± 6‰, indicating that 89–100% (95 ± 4%) of PAHs were supplied by fossil fuels. The South China Sea warm current originating from the southwest China in summer (98%) and the Min-Zhe coastal current originating from the north China in winter (97%) input more fossil fuel PAHs than the Jiulong River estuary (90%) and Xiamen harbor water (93%). The more radioactive decayed 14C of fluoranthene (a 4-ring PAH) than that of phenanthrene and anthracene (3-ring PAHs) represented a greater fossil fuel contribution to the former in dissolved seawater. VL - 52 UR - https://pubs.acs.org/doi/10.1021/acs.est.8b01331 IS - 13 ER - TY - JOUR T1 - On the Holocene evolution of the Ayeyawady megadelta JF - Earth Surface Dynamics Y1 - 2018 A1 - Giosan, Liviu A1 - Naing, Thet A1 - Min Tun, Myo A1 - Clift, Peter D. A1 - Filip, Florin A1 - Constantinescu, Stefan A1 - Khonde, Nitesh A1 - Blusztajn, Jerzy A1 - Buylaert, Jan-Pieter A1 - Stevens, Thomas A1 - Thwin, Swe AB - The Ayeyawady delta is the last Asian megadelta whose evolution has remained essentially unexplored so far. Unlike most other deltas across the world, the Ayeyawady has not yet been affected by dam construction, providing a unique view on largely natural deltaic processes benefiting from abundant sediment loads affected by tectonics and monsoon hydroclimate. To alleviate the information gap and provide a baseline for future work, here we provide a first model for the Holocene development of this megadelta based on drill core sediments collected in 2016 and 2017, dated with radiocarbon and optically stimulated luminescence, together with a reevaluation of published maps, charts and scientific literature. Altogether, these data indicate that Ayeyawady is a mud-dominated delta with tidal and wave influences. The sediment-rich Ayeyawady River built meander belt alluvial ridges with avulsive characters. A more advanced coast in the western half of the delta (i.e., the Pathein lobe) was probably favored by the more western location of the early course of the river. Radiogenic isotopic fingerprinting of the sediment suggests that the Pathein lobe coast does not receive significant sediment from neighboring rivers. However, the eastern region of the delta (i.e., Yangon lobe) is offset inland and extends east into the mudflats of the Sittaung estuary. Wave-built beach ridge construction during the late Holocene, similar to several other deltas across the Indian monsoon domain, suggests a common climatic control on monsoonal delta morphodynamics through variability in discharge, changes in wave climate or both. Correlation of the delta morphological and stratigraphic architecture information on land with the shelf bathymetry, as well as its tectonic, sedimentary and hydrodynamic characteristics, provides insight on the peculiar growth style of the Ayeyawady delta. The offset between the western Pathein lobe and the eastern deltaic coast appears to be driven by tectonic–hydrodynamic feedbacks as the extensionally lowered shelf block of the Gulf of Mottama amplifies tidal currents relative to the western part of the shelf. This situation probably activates a perennial shear front between the two regions that acts as a leaky energy fence. Just as importantly, the strong currents in the Gulf of Mottama act as an offshore-directed tidal pump that helps build the deep mid-shelf Mottama clinoform with mixed sediments from the Ayeyawady, Sittaung and Thanlwin rivers. The highly energetic tidal, wind and wave regime of the northern Andaman Sea thus exports most sediment offshore despite the large load of the Ayeyawady River. VL - 6 UR - https://esurf.copernicus.org/articles/6/451/2018 IS - 2 ER - TY - JOUR T1 - Holocene history of the Greenland Ice-Sheet margin in Northern Nunatarssuaq, Northwest Greenland JF - arktos Y1 - 2018 A1 - Farnsworth, Lauren B. A1 - Kelly, Meredith A. A1 - Bromley, Gordon R. M. A1 - Axford, Yarrow A1 - Osterberg, Erich C. A1 - Howley, Jennifer A. A1 - Jackson, Margaret S. A1 - Zimmerman, Susan R. AB - Records of past Greenland Ice-Sheet (GrIS) extents are important for understanding the response of the ice sheet to climate conditions, providing a longer term perspective on present ice-margin fluctuations, and evaluating ice-sheet models. We present a record of Holocene GrIS extents in Nunatarssuaq, Northwest Greenland, based on geomorphic mapping combined with 10Be surface exposure dating of rock surfaces and 14C dating of subfossil plants. 10Be ages of boulders and bedrock exposed during deglaciation from the Last Glacial Maximum range from ~ 81 to 15 ka. The apparently old ages of some samples and scatter in the dataset indicate the presence of 10Be inherited from prior periods of exposure and suggest that overriding ice was minimally erosive. Subfossil plants exposed on a debris band in the GrIS margin date to ~ 4.7 cal ka BP and register a time when the Northwest GrIS was smaller than at present. Geomorphic evidence, including a drift sheet, grounding-line moraines, and higher levels of Nordsø, document an advance of the Nuna and Tunge Rampen (GrIS outlet glaciers). 14C ages of in situ subfossil plants and 10Be ages of boulders bracket this advance to ~ 3.2–2.1 ka, a period of regional cooling. Unweathered, lichen-free drift occurs < 50 m beyond the present GrIS margin in most locations. 10Be ages of this drift are 2.2–0.5 ka and likely contain inherited nuclides. 14C ages of in situ subfossil plants atop this drift are between cal AD ~ 1640 and 2001, suggesting recent ice-margin fluctuations. VL - 4 UR - http://link.springer.com/10.1007/s41063-018-0044-0http://link.springer.com/content/pdf/10.1007/s41063-018-0044-0.pdfhttp://link.springer.com/article/10.1007/s41063-018-0044-0/fulltext.htmlhttp://link.springer.com/content/pdf/10.1007/s41063-018-0044-0.pdf IS - 1 ER - TY - JOUR T1 - Holocene mountain glacier history in the Sukkertoppen Iskappe area, southwest Greenland JF - Quaternary Science Reviews Y1 - 2018 A1 - Schweinsberg, Avriel D. A1 - Briner, Jason P. A1 - Miller, Gifford H. A1 - Lifton, Nathaniel A. A1 - Bennike, Ole A1 - Graham, Brandon L. KW - Cosmogenic in situ 14C KW - Glacier fluctuations KW - Greenland KW - Holocene KW - lake sediment KW - Neoglaciation AB - Mountain glaciers and ice caps (GIC) independent of the Greenland Ice Sheet respond rapidly to climate variations and records of their past extent provide information on the natural envelope of climate variability. Here, we use a multi-proxy approach that combines proglacial lake sediment analysis, cosmogenic nuclide surface-exposure dating (in situ 10Be and 14C), and radiocarbon dating of recently ice-entombed moss to generate a centennial-scale record of Holocene GIC fluctuations in southwestern Greenland. Following local deglaciation ∼10-9 ka, sediments from proglacial Crash Lake record a glacier advance at ∼9 ka that is indistinguishable from nearby ice sheet moraines, implying a synchronous response of GIC and the Greenland Ice Sheet to a centennial-scale climate event. Following this local glacier advance, GIC experienced net recession until ∼4.6 ka. Radiocarbon ages of in situ moss (n = 29) and Crash Lake sediments reveal intervals of glacier expansion at ∼1.8, 1.2 and 0.7 ka that are superimposed on an overall trend of net glacier expansion throughout the late Holocene. In situ 14C concentrations from bedrock adjacent to radiocarbon-dated moss samples further constrain the duration of ice cover through the Holocene in this region. We find that our glacier-size proxy records during the past ∼4 ka are broadly consistent with relatively lower temperatures recorded in GISP2 and occur during, or following, intervals of volcanic perturbations. Thus, we speculate that volcanic activity, although less frequent and intense than in the early Holocene and during the Little Ice Age, may have led to centennial-scale variability imprinted on net glacier expansion due to decreasing summer insolation through the late Holocene. VL - 197 UR - https://www.sciencedirect.com/science/article/pii/S0277379118302531 ER - TY - JOUR T1 - How Could a Freshwater Swamp Produce a Chemical Signature Characteristic of a Saltmarsh?How Could a Freshwater Swamp Produce a Chemical Signature Characteristic of a Saltmarsh? JF - ACS Earth and Space Chemistry Y1 - 2018 A1 - McCloskey, Terrence A. A1 - Smith, Christopher G. A1 - Liu, Kam-biu A1 - Marot, Marci A1 - Haller, Christian KW - anoxic KW - diagenesis KW - euxinic KW - florida KW - Molybdenum KW - reactions KW - redox KW - XRF AB - Reduction–oxidation (redox) reaction conditions, which are of great importance for the soil chemistry of coastal marshes, can be temporally dynamic. We present a transect of cores from northwest Florida wherein radical postdepositional changes in the redox regime has created atypical geochemical profiles at the bottom of the sedimentary column. The stratigraphy is consistent along the transect, consisting of, from the bottom upward, carbonate bedrock, a gray clay, an organic mud section, a dense clay layer, and an upper organic mud unit representing the current saltwater marsh. However, the geochemical signature of the lower organic mud unit suggests pervasive redox reactions, although the interval has been identified as representing a freshwater marsh, an unlikely environment for such conditions. Analyses indicate that this discrepancy results from postdepositional diagenesis driven by millennial-scale environmental parameters. Rising sea level that led to the deposition of the capping clay layer, created anaerobic conditions in the freshwater swamp interval, and isolated it hydrologically from the rest of the sediment column. The subsequent infiltration of marine water into this organic material led to sulfate reduction, the buildup of H2S and FeS, and anoxic conditions. Continued sulfidation eventually resulted in euxinic conditions, as evidenced by elevated levels of Fe, S, and especially Mo, the diagnostic marker of euxinia. Because this chemical transformation occurred long after the original deposition the geochemical signature does not reflect soil chemistry at the time of deposition and cannot be used to infer syn-depositional environmental conditions, emphasizing the importance of recognizing diagenetic processes in paleoenvironmental studies. VL - 2 UR - https://pubs.acs.org/doi/10.1021/acsearthspacechem.7b00098 IS - 1 ER - TY - JOUR T1 - Human use of small forage fish: Improved ancient DNA species identification techniques reveal long term record of sustainable mass harvesting of smelt fishery in the northeast Pacific Rim JF - Journal of Archaeological Science Y1 - 2018 A1 - Palmer, Erica A1 - Tushingham, Shannon A1 - Kemp, Brian M. KW - aDNA KW - Ichythyarchaeology KW - Northern California KW - Smelt KW - Species identification AB - The bulk storage and mass capture of small forage fish has played a primary role in the cultural traditions and subsistence practices of many ancient and modern indigenous communities throughout the world. Archaeologists are improving their recognition of human interaction with these fisheries through the application of fine-mesh screening techniques and ichthyofaunal analysis of fish bone. Because of the differing life histories of many of these fish, determining their species from archaeological contexts can improve our resolution of past harvesting and consumption patterns. This has remained a challenge for many categories of fish, such as salmon and smelt. Here, we present an improved genetic species identification process that utilizes ancient DNA amplification techniques involving a reagent-rich PCR protocol (i.e., “Rescue PCR”) and a PCR Enhancer Cocktail P (i.e., PEC-P) to identify smelt and other forage fish bone from five archaeological sites located along the northern California (United States) Pacific coast dating to the Late Period (after 1300 cal BP). Through the application of these novel techniques, our species identification success rate increased to 71.2% overall, with some sites having a remarkable 100% success rate. We identified the species of 104 of 146 fish vertebrae, and determined that inhabitants at these sites harvested primarily surf smelt with potentially less emphasis on night smelt. Observations of herring, perch, sculpin and rainbow trout/steelhead were also made. Along with these small surf fish, we found evidence of larger fish such as shark and Pacific hake (common predatory fish in the area). The study demonstrates a significant breakthrough in ancient DNA identification techniques that resulted in information that speak to the long term continuity of use of mass harvested forage fish by indigenous peoples. The results of this project help establish a better understanding of subsistence and cultural traditions of northern California indigenous communities, with the potential to provide a more global understanding of fishing technologies, sustainability, and mass harvesting of small fishes. VL - 99 UR - https://linkinghub.elsevier.com/retrieve/pii/S0305440318303340 ER - TY - JOUR T1 - The Impact of Aquifer Flushing on Groundwater Arsenic Across a 35‐km Transect Perpendicular to the Upper Brahmaputra River in Assam, India JF - Water Resources Research Y1 - 2018 A1 - Choudhury, R. A1 - Nath, B. A1 - Khan, M. R. A1 - Mahanta, C. A1 - Ellis, T. A1 - Geen, A. KW - aquifer flushing KW - Arsenic KW - groundwater KW - South Asia AB - Well testing in the floodplain of the Brahmaputra River in Golaghat and Jorhat districts of Assam, India, shows that groundwater arsenic (As) concentrations increase with distance from the river. To establish the origin of this pattern, an additional 900 wells <60‐m deep were tested for As and nine sites were drilled along a 35‐km transect perpendicular to the river. The field data show no relation between groundwater As concentrations ranging from <1 to 660 μg/L along the transect and (a) As concentrations of <1–5 mg/kg in cuttings of aquifer sand recovered while drilling or (b) the degree of reduction of iron oxides in these cuttings. The drilling indicates, however, a marked increase in the thickness of a clay layer capping the aquifer starting from <1–5 m near the river to over 60 m at the most distant site toward the base of the Naga foothills. Organic radiocarbon ages of 18–46 kyr obtained from all but one of 13 clay samples indicate pre‐Holocene deposition of the underlying sands across the entire transect. Radiocarbon ages of dissolved inorganic carbon of 0.2, 4.7, and 17.8 kyr were measured in groundwater from three monitoring wells installed to 30–60‐m depth at distances of 10, 20, and 40 km from the river, respectively. A conceptual groundwater flow model consistent with monitored heads and groundwater ages suggests that thick clay layers capping the aquifer further from the river inhibited flushing of the aquifer and, as a result, preserved higher As levels in groundwater. VL - 54 UR - https://onlinelibrary.wiley.com/doi/abs/10.1029/2017WR022485 IS - 10 ER - TY - JOUR T1 - Interstadial Rise and Younger Dryas Demise of Scotland's Last Ice Fields JF - Paleoceanography and Paleoclimatology Y1 - 2018 A1 - Bromley, G. A1 - Putnam, A. A1 - Borns, H. A1 - Lowell, T. A1 - Sandford, T. A1 - Barrell, D. KW - late glacial KW - Loch Lomond Readvance KW - marine reservoir effect KW - moraine chronology KW - radiocarbon KW - seasonality AB - Establishing the atmospheric expression of abrupt climate change during the last glacial termination is key to understanding driving mechanisms. In this paper, we present a new 14C chronology of glacier behavior during late‐glacial time from the Scottish Highlands, located close to the overturning region of the North Atlantic Ocean. Our results indicate that the last pulse of glaciation culminated between ~12.8 and ~12.6 ka, during the earliest part of the Younger Dryas stadial and as much as a millennium earlier than several recent estimates. Comparison of our results with existing minimum‐limiting 14C data also suggests that the subsequent deglaciation of Scotland was rapid and occurred during full stadial conditions in the North Atlantic. We attribute this pattern of ice recession to enhanced summertime melting, despite severely cool winters, and propose that relatively warm summers are a fundamental characteristic of North Atlantic stadials. VL - 33 UR - https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2018PA003341 IS - 4 ER - TY - JOUR T1 - An Investigation of Gas Exchange and Water Circulation in the Amundsen Sea Based On Dissolved Inorganic Radiocarbon JF - Geophysical Research Letters Y1 - 2018 A1 - Kim, Bumsoo A1 - Lee, SangHoon A1 - Kim, Minkyoung A1 - Hahm, Doshik A1 - Rhee, Tae Siek A1 - Hwang, Jeomshik KW - Amundsen sea KW - dissolved inorganic carbon KW - gas exchange KW - radiocarbon KW - water circulation AB - We used radiocarbon isotope ratios in dissolved inorganic carbon to assess gas exchange and water circulation in the western Amundsen Sea. Radiocarbon isotope ratios indicate that Circumpolar Deep Water enters the basin along the seafloor and that the upper layer is formed through modification of this water mass. In the Amundsen Sea Polynya, radiocarbon isotope ratios of surface water are higher than those of underlying Winter Water, implying rapid absorption of atmospheric CO2. A CO2 absorption rate of 45mmol m(-2) d(-1) calculated for a site in the central polynya is higher than that near the Dotson Ice Shelf (28mmolm(-2) d(-1)). The turnover time of water in the Dotson Trough region of the western Amundsen Sea is estimated to be 10-30years, based on results from a box model and radiocarbon mass balance. Plain Language Summary The western Amundsen Sea is experiencing raid physical changes including rapid glacial melting and declining sea ice cover. The suggested heat source is the intrusion of warm Circumpolar Deep Water (CDW) along the seafloor of the Amundsen Shelf. Therefore, understanding the behavior of the intruded CDW, especially how long it stays on the shelf, is important. Physical oceanographic studies have examined the flux of CDW onto and out of the Amundsen Shelf. However, the turnover time of water in the Amundsen Sea is still poorly understood. In this paper, we use radiocarbon isotope signature from dissolved inorganic carbon to examine how rapidly atmospheric CO2 is absorbed into the Amundsen Sea Polynya and how long the water should stay in the western Amundsen Shelf to have the observed radiocarbon isotope signature. Based on our results and the current understanding of the water circulation in the western Amundsen Sea, we found that the water sits on the Amundsen Shelf for a few decades before it moves off shelf. VL - 453 UR - http://apps.webofknowledge.com/InboundService.do?product=WOS&Func=Frame&DestFail=http%3A%2F%2Fwww.webofknowledge.com%3FDestParams%3DUT%253DWOS%25253A000453250000030%2526customersID%253DAlerting%2526smartRedirect%253Dyes%2526action%253Dretrieve%2526mode%25 IS - 22 ER - TY - JOUR T1 - Isotopic composition of sinking particles: Oil effects, recovery andbaselines in the Gulf of Mexico, 2010–2015 JF - Elem Sci Anth Y1 - 2018 A1 - Chanton, Jeffrey P. A1 - Giering, Sarah L. C. A1 - Bosman, Samantha H. A1 - Rogers, Kelsey L. A1 - Sweet, Julia A1 - Asper, Vernon L. A1 - Diercks, Arne R. A1 - Passow, Uta KW - Deep Water Horizon Oil Spill KW - Gulf of Mexico KW - isotopes KW - radiocarbon KW - sediment trap KW - sinking particulates AB - The extensive release of oil during the 2010 Deepwater Horizon spill in the northern Gulf of Mexico perturbed the pelagic ecosystem and associated sinking material. To gauge the recovery and post-spill baseline sources, we measured Δ14C, δ13C and δ34S of sinking particles near the spill site and at a reference site and natural seep site. Particulates were collected August 2010–April 2016 in sediment traps moored at sites with depths of 1160–1660 m. Near the spill site, changes in Δ14C indicated a 3-year recovery period, while δ34S indicated 1–2 years, which agreed with estimates of 1–2 years based on hydrocarbon composition. Under post-spill baseline conditions, carbon inputs to sinking particulates in the northern Gulf were dominated by surface marine production (80–85%) and riverine inputs (15–20%). Near the spill site, Δ14C values were depleted in October 2010 (–140 to –80‰), increasing systematically by 0.07 ± 0.02‰ day–1 until July 2013 when values reached –3.2 ± 31.0‰. This Δ14C baseline was similar to particulates at the reference site (3.8 ± 31.1‰). At both sites, δ13C values stayed constant throughout the study period (–21.9 ± 0.5‰ and –21.9 ± 0.9‰, respectively). δ34S near the spill site was depleted (7.4 ± 3.1‰) during October 2010–September 2011, but enriched (16.9 ± 2.0‰) and similar to the reference site (16.2 ± 3.1‰) during November 2012–April 2015. At the seep site, Δ14C values were –21.7 ± 45.7‰ except during August 2012–January 2013 when a significant Δ14C depletion of –109.0 ± 29.1‰ was observed. We interpret this depletion period, also observed in δ13C data, as caused by the incorporation of naturally seeped oil into sinking particles. Determination of post-spill baselines for these isotopic signatures allows for evaluation of anthropogenic inputs in future. VL - 6 UR - https://www.elementascience.org/article/10.1525/elementa.298 IS - 1 ER - TY - JOUR T1 - Labile organic carbon dynamics in continental shelf sediments after the recent collapse of the Larsen ice shelves off the eastern Antarctic Peninsula: A radiochemical approach JF - Geochimica et Cosmochimica Acta Y1 - 2018 A1 - Isla, E. A1 - DeMaster, D.J. AB - Labile organic carbon (LOC) dynamics (i.e., of recently produced, planktonic material) and sediment dynamics were studied in the seabed using naturally occurring C-14(org), and Pb-210 measurements in the region where the Larsen Ice Shelves A and B were floating almost two decades ago. A non-steady-state diagenetic model was used to estimate sediment mixing coefficients as well as LOC fluxes to the seabed and LOC turnover times (i.e., mean residence times) in a suite of 14 sediment cores from the continental shelf, including a glacial trough. At four of the stations, cores were collected during 2007 and 2011 cruises, enabling a time-series approach for understanding the evolution of sedimentary processes and LOC dynamics in the deposits below a collapsed ice shelf. Sediment mixing coefficients, based on non-steady-state Pb-210 profiles, varied between 0.01 cm(2) y(-1) and 1.6 cm(2) y(-1) in these post-ice shelf sediments. These values were similar to those found in polar deep-sea environments, where sedimentary conditions are less dynamic than in shallower provinces. LOC, whose abundance decreased uniformly with depth, was detected to depths ranging from 2 to 16 cm, with LOC seabed inventories varying from 1.5 to 22 mg LOC cm(-2). Excess Pb-210 and LOC fluxes were relatively uniform across the study area suggesting that similar particle fluxes have taken place within theLarsen system since the disintegration of the various ice shelves. The LOC mean residence time at the different stations varied from 3 y to >60 y. The C-14(org), approach, calculating LOC content based on a two-end member model with planktonic 14C(org) as the labile carbon end member, most closely correlated with the lipid content of the sediment, which has been considered one of the best descriptors of reactive organic matter readily available to benthic consumers. We suggest that the irregular combination of sea ice coverage, organic matter production and supply to the sea floor introduce scatter in the determination of sediment and LOC dynamics such that short-term temporal (<5 years) and spatial trends could not be readily resolved. VL - 242 UR - https://linkinghub.elsevier.com/retrieve/pii/S0016703718304393https://api.elsevier.com/content/article/PII:S0016703718304393?httpAccept=text/xmlhttps://api.elsevier.com/content/article/PII:S0016703718304393?httpAccept=text/plain ER - TY - JOUR T1 - Large Variability of Dissolved Inorganic Radiocarbon in the Kuroshio Extension of the Northwest North PacificABSTRACT JF - Radiocarbon Y1 - 2018 A1 - Ding, Ling A1 - Ge, Tiantian A1 - Gao, Huiwang A1 - Luo, Chunle A1 - Xue, Yuejun A1 - Druffel, Ellen R M A1 - Wang, Xuchen KW - bomb radiocarbon KW - carbon KW - intermediate water KW - MIXED WATER REGION KW - ocean KW - WESTERN BOUNDARY CURRENTS AB - Radiocarbon (C-14) in dissolved inorganic carbon (DIC) was measured for water samples collected from six deep stations in the Kuroshio Extension (KE) region in the northwestern North Pacific in April-May 2015. Vertical profiles of Delta C-14-DIC indicate that bomb-produced Delta C-14 was present from the surface to similar to 1500 m water depth. Large variations in Delta C-14-DIC values (300 parts per thousand) were observed at 500 m water depth among the stations and the differences were likely controlled by transport and mixing dynamics of different water masses in the region. The major Pacific western boundary currents, such as Kuroshio and Oyashio and regional mesoscale eddies, could play important roles affecting the observed Delta C-14-DIC variability. The depth profiles of both Delta C-14-DIC and DIC concentrations can be predicted by the solution mixing model and can be used as conservative tracers of water mass movement and water parcel homogenization in the ocean. VL - 60264317255 UR - https://www.cambridge.org/core/product/identifier/S0033822217001436/type/journal_articlehttps://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0033822217001436 IS - 02 ER - TY - JOUR T1 - Large‐Scale Intrusion of Circumpolar Deep Water on Antarctic Margin Recorded by Stylasterid Corals JF - Paleoceanography and Paleoclimatology Y1 - 2018 A1 - King, Theresa M. A1 - Rosenheim, Brad E. A1 - Post, Alexandra L. A1 - Gabris, Theresa A1 - Burt, Taylor A1 - Domack, Eugene W. AB - We present centennial‐scale radiocarbon (14C) records archived by deep sea stylasterid corals from the outer shelf and upper slope of the Antarctic margin. These novel stylasterids (Errina spp.) were collected from the western Ross Sea shelf (500 m) and slope (1,700 m), as well as the eastern Wilkes Land shelf (670 m). We provide two corals from each region and document an abrupt reversal of 14C ages in the upper (younger) part of each coral. We test the statistical robustness of each record and demonstrate the significance of the age reversals, as well as the ability of these corals to record environmental change. We discuss a variety of possible drivers for this 14C reversal and conclude that it is most likely an encroachment of 14C‐depeleted Circumpolar Deep Water (CDW). This water mass has regionally intruded onto the Antarctic margin in recent decades, facilitating loss of grounded Antarctic ice; which has implications for global sea level, deep‐water formation, and carbon sequestration in the Southern Ocean. Thus, understanding the past variability of CDW on the margin is vital to better constrain climate change trajectories in the near future. We estimate large‐scale encroachment of CDW onto the shelf likely commencing after 1830 CE (±120 year). We present possible drivers for the intrusion, but highlight the need for additional chronologic constraint. This study not only demonstrates the utility of a novel coral taxon but also presents the paleoceanographic community with a testable hypothesis concerning a recent, widespread CDW intrusion. VL - 33 UR - https://onlinelibrary.wiley.com/doi/abs/10.1029/2018PA003439 IS - 11 ER - TY - JOUR T1 - Last Glacial Maximum surface water properties and circulation over Laurentian Fan, western North Atlantic JF - Earth and Planetary Science Letters Y1 - 2018 A1 - Gil, Isabelle M. A1 - Keigwin, Lloyd D. KW - detrital events KW - diatoms KW - ice rafted debris KW - Last glacial maximum KW - Laurentide ice sheet KW - subglacial flows AB - Millennial scale events marked by the contribution of detrital sand are recorded in North Atlantic sediments during the Last Glacial Maximum (LGM), between Heinrich events (HE) 1 and 2, and left their imprint on Laurentian Fan (LF – 43°N) sediments off eastern Canada. The LF counterpart of the well-known detrital events consist of glacial red-brick sediments resulting from subglacial flows separated by olive-grey sediments appears at ∼21.4–19.9 and ∼19.5–18.65 cal kyr BP. High-resolution analyses of diatom assemblages and lithic grains coupled with planktonic oxygen isotopic records reveal that while the red sediment is almost barren of diatoms, foraminifera and lithics (>150 μm), they are abundant in the olive-grey sediment. Diatom assemblages reveal three phases during these events: (1) initial relatively warm/temperate conditions followed by (2) very cold surface water and drifting ice, and (3) a final phase characterized by relatively warmer waters and the appearance of detrital carbonate. Although these events possibly reflect the variability specific to the slope water region, they are likely the response to Atlantic Meridional Overturning Circulation perturbations and ice-sheet instability. Through a chain of mechanisms, meltwater inputs into the North Atlantic led ultimately to an increased volume of tropical waters and part of the heat stored in the subsurface was flushed by a brief convective episode that was not sustained, accounting for the return of cold conditions after the events. The sequence of mechanisms deduced from the paleo data here and elsewhere is consistent with previous modeling results. These data suggest that the detrital events between Heinrich event 1 and 2 may be synchronous across the North Atlantic, and that the LGM was probably not a time of prolonged steady state in the climate system. VL - 500 UR - https://linkinghub.elsevier.com/retrieve/pii/S0012821X18304448 ER - TY - JOUR T1 - Late Holocene paleoceanography in the Chukchi and Beaufort Seas, Arctic Ocean, based on benthic foraminifera and ostracodes JF - arktos Y1 - 2018 A1 - Seidenstein, Julia L. A1 - Cronin, Thomas M. A1 - Gemery, Laura A1 - Keigwin, Lloyd D. A1 - Pearce, Christof A1 - Jakobsson, Martin A1 - Coxall, Helen K. A1 - Wei, Emily A. A1 - Driscoll, Neal W. AB - Calcareous microfossil assemblages in late Holocene sediments from the western Arctic continental shelf provide an important baseline for evaluating the impacts of today’s changing Arctic oceanography. This study compares 14C-dated late Holocene microfaunal assemblages of sediment cores SWERUS-L2-2-PC1, 2-MC4 and 2-KL1 (57 mwd), which record the last 4200 years in the Herald Canyon (Chukchi Sea shelf), and HLY1302-JPC-32, GGC-30, MC-29 (60 mwd), which record the last 3000 years in the Beaufort Sea shelf off the coast of Canada. Foraminiferal and ostracode assemblages are typical of Arctic continental shelf environments with annual sea-ice cover and show relatively small changes in terms of variability of dominant species. Important microfaunal changes in the Beaufort site include a spike in Spiroplectammina biformis coinciding with a decrease in Cassidulina reniforme in the last few centuries suggesting an increase of Pacific Water influence and decreased sea-ice. There is low-amplitude centennial-scale variability in proportions of benthic foraminiferal species, such as C. reniforme. In addition to these species, Cassidulina teretis s.l., Elphidium excavatum clavatum and Stainforthia feylingi are also common at this site. At the Herald Canyon site in the last few centuries, C. reniforme peaks around 150 years BP and then decreases while Spiroplectammina earlandi spikes and Acanthocythereis dunelmensis decreases also suggesting an increase in Pacific Water influence and decreased sea-ice at this site. This site also includes Buccella spp. and Elphidium excavatum clavatum. Differences in benthic foraminifera and ostracode species dominance between the two sites may be due to a greater influence of Pacific Water in the Chukchi shelf, compared to the more distal Beaufort shelf, which is also affected by the Beaufort Gyre and the Mackenzie River. VL - 4 UR - https://link.springer.com/article/10.1007/s41063-018-0058-7 IS - 1 ER - TY - JOUR T1 - Late Pleistocene to Holocene productivity changes in the western equatorial Pacific (Sulu Sea, Philippines) from calcareous nannofossils JF - Marine Micropaleontology Y1 - 2018 A1 - Tangunan, Deborah N. A1 - Peleo-Alampay, Alyssa M. KW - arabian sea KW - EAST-ASIAN MONSOON KW - GLOBAL YOUNGER-DRYAS KW - indian-ocean KW - last deglaciation KW - OCEANIC PRIMARY PRODUCTION KW - south china sea KW - surface sediments KW - UPWELLING SYSTEM KW - YR BP AB - We present a new calcareous nannofossil paleoproductivity reconstruction of the southeastern margin of the Sulu Sea to understand how marine productivity varied through time in one of the major fishing grounds of the Philippine archipelago. The study is based on two sediment cores obtained from two different hydrographic locations in the western equatorial Pacific region: an upwelling region off Zamboanga Peninsula (U-GC12) and a non-upwelling area off Panay Island (NU-GC14), covering the past 18,000 years before present (B.P.). Calcareous nannofossil assemblages in the investigated areas were of low diversity and largely dominated by Gephyrocapsa oceanica and Florisphaera profwida, followed by small placolith-bearing taxa, Emiliania hwcleyi, small Gephyrocapsa, and Reticulofenestra minuta. Upwelling episodes off the Zamboanga Peninsula were recorded several times in the past as shown by an increase in the abundance of high productivity indicator species (G. oceanica, small Gephyrocapsa, E. hwcleyi) and of bulk sediment CaCO3 (%), and a concomitant decline in the total organic carbon (TOC; %). The high abundance of low surface water productivity species F. profunda and Umbellosphaera irregularis indicates a stratified water column with a deeper nutricline, probably caused by the reduced upwelling intensity. This condition was corroborated by the decrease in CaCO3 (%) and an increase in TOC (%). We propose that the modern day high productivity conditions off Zamboanga Peninsula started at 2500 years B.P., whereas the low productivity off Panay Island was recorded from 4000 years B.P., and persists to the present day. Evidence of the Younger Dryas (YD) event was recorded from 11,100 to 10,400 years B.P. in UGC12, synchronous to the YD event reported from other areas in the Northern Hemisphere, and in accordance with the timing in the Sulu Sea as reported from previous studies in this region. This event in the Sulu Sea is characterized by a decrease in total nannofossil abundance and estimated primary productivity, together with an increase in CaCO3 (%) and a decrease in TOC (%). We interpreted that dilution caused by the increase in precipitation experienced in the Southeast Asian region during the YD event could have led to the decline of the total calcareous nannofossils whereas the recorded increase in CaCO3 (%) is attributed to the high abundance of planktonic foraminifera during this interval. VL - 143 UR - https://linkinghub.elsevier.com/retrieve/pii/S0377839816301219https://api.elsevier.com/content/article/PII:S0377839816301219?httpAccept=text/xmlhttps://api.elsevier.com/content/article/PII:S0377839816301219?httpAccept=text/plain ER - TY - JOUR T1 - Linear decline in red snapper (Lutjanus campechanus) otolith Δ14C extends the utility of the bomb radiocarbon chronometer for fish age validation in the Northern Gulf of Mexico JF - ICES Journal of Marine Science Y1 - 2018 A1 - Barnett, Beverly K A1 - Thornton, Laura A1 - Allman, Robert A1 - Chanton, Jeffrey P A1 - Patterson, William F KW - Age validation KW - otoliths KW - radiocarbon KW - red snapper AB - Radiocarbon (D14C) was analyzed in northern Gulf of Mexico (nGOM) red snapper (Lutjanus campechanus) otolith cores (n¼23), otolith edge samples (n¼12), and whole age-0 otoliths (n¼9), with edge samples and whole age-0 otoliths constituting known-age samples. There was no significant difference in the linear relationship of D14C versus year of formation between regional corals and known-age otolith samples, and a linear regression fit to the combined data from 1980 to 2015 extends the utility of the bomb radiocarbon chronometer for age validation. The entire regional coral and known-age otolith data set (1940 to 2015) was then utilized as a reference series to validate otolith-derived red snapper age estimates for cored otolith samples. A loess regression was fit to the reference data and then the sum of squared residuals (SSR) was computed from predicted versus observed birth years for cored adult otolith samples. This process was then repeated for ages biased 61–4 years. Ages with no bias applied had the lowest SSR, thus validating red snapper age estimates and demonstrating the utility of the combined regional coral and known-age red snapper otolith D14C time series for age validation of nGOM marine fishes. VL - 8870697346588911255202655996472975862129455810210311781289189114143320657330766513996026526319911984699 UR - https://academic.oup.com/icesjms/advance-article/doi/10.1093/icesjms/fsy043/4992258http://academic.oup.com/icesjms/advance-article-pdf/doi/10.1093/icesjms/fsy043/24775644/fsy043.pdf ER - TY - JOUR T1 - Longitudinal discontinuities in riverine greenhouse gas dynamics generated by dams and urban wastewater JF - Biogeosciences Y1 - 2018 A1 - Jin, Hyojin A1 - Yoon, Tae Kyung A1 - Begum, Most Shirina A1 - Lee, Eun-Ju A1 - Oh, Neung-Hwan A1 - Kang, Namgoo A1 - Park, Ji-Hyung AB - Surface water concentrations of CO2, CH4, and N2O have rarely been measured simultaneously in river systems modified by human activities, contributing to large uncertainties in estimating global riverine emissions of greenhouse gases (GHGs). Basin-wide surveys of the three GHGs were combined with a small number of measurements of C isotope ratios in dissolved organic matter (DOM), CO2, and CH4 in the Han River basin, South Korea, to examine how longitudinal patterns of the three gases and DOM are affected by four cascade dams along a middle section of the North Han River (hereafter termed “middle reach”) and treated wastewater discharged to the lower Han River (“lower reach”) traversing the Seoul metropolitan area. Monthly monitoring and two-season comparison were conducted at 6 and 15 sites, respectively, to measure surface water gas concentrations and ancillary water quality parameters including concentrations of dissolved organic carbon (DOC) and optical properties of DOM. The basin-wide surveys were complemented with a sampling cruise along the lower reach and synoptic samplings along an urban tributary delivering effluents from a large wastewater treatment plant (WWTP) to the lower reach. The levels of pCO2 were relatively low in the middle reach (51–2465 µatm), particularly at the four dam sites (51–761 µatm), compared with those found in the largely forested upper basin with scattered patches of croplands (163–2539 µatm), the lower reach (78–11298 µatm), and three urban tributaries (2120–11970 µatm). The upper and middle reaches displayed generally low concentration ranges of CH4 and N2O, with some local peaks influenced by agricultural runoff and impoundments. By comparison, the lower reach exhibited exceptionally high concentrations of CH4 (1.2–15766 nmol L−1) and N2O (7.5–1396 nmol L−1), which were significantly correlated with different sets of variables such as DO and PO3−4 for CH4 and NH+4 and NO−3 for N2O. Downriver increases in the levels of DOC and optical properties such as fluorescence index (FI) and protein-like fluorescence indicated an increasing DOM fraction of anthropogenic and microbial origin. The concentrations of the three GHGs and DOC were similar in magnitude and temporal variation at a WWTP discharge and the receiving tributary, indicating a disproportionate contribution of the WWTP effluents to the tributary gas and DOC exports to the lower reach. The values of δ13C in surface water CO2 and CH4 measured during the sampling cruise along the lower reach, combined with δ13C and Δ14C in DOM sampled across the basin, implied a strong influence of the wastewater-derived gases and aged DOM delivered by the urban tributaries. The downstream enrichment of 13C in CO2 and CH4 suggested that the spatial distribution of these gases across the eutrophic lower reach may also be constrained by multiple concomitant processes including outgassing, photosynthesis, and CH4 oxidation. The overall results suggest that dams and urban wastewater may create longitudinal discontinuities in riverine metabolic processes leading to large spatial variations in the three GHGs correlating with different combinations of DOM properties and nutrients. Further research is required to evaluate the relative contributions of anthropogenic and in-stream sources of the three gases and DOM in eutrophic urbanized river systems and constrain key factors for the contrasting impoundment effects such as autotrophy-driven decreases in pCO2 and in-lake production of CH4 and N2O. VL - 15 UR - https://bg.copernicus.org/articles/15/6349/2018/ IS - 20 ER - TY - JOUR T1 - A long-term decrease in the persistence of soil carbon caused by ancient Maya land use JF - Nature Geoscience Y1 - 2018 A1 - Douglas, Peter M. J. A1 - Pagani, Mark A1 - Eglinton, Timothy I. A1 - Brenner, Mark A1 - Curtis, Jason H. A1 - Breckenridge, Andy A1 - Johnston, Kevin AB - The long-term effects of deforestation on tropical forest soil carbon reservoirs are important for estimating the consequences of land use on the global carbon cycle, but are poorly understood. The Maya Lowlands of Mexico and Guatemala provide a unique opportunity to assess this question, given the widespread deforestation by the ancient Maya that began ~4,000 years ago. Here, we compare radiocarbon ages of plant waxes and macrofossils in sediment cores from three lakes in the Maya Lowlands to record past changes in the mean soil transit time of plant waxes (MTTwax). MTTwax indicates the average age of plant waxes that are transported from soils to lake sediments, and comparison of radiocarbon data from soils and lake sediments within the same catchment indicates that MTTwax reflects the age of carbon in deep soils. All three sediment cores showed a decrease in MTTwax, ranging from 2,300 to 800 years, over the past 3,500 years. This decrease in MTTwax, indicating shorter storage times for carbon in lake catchment soils, is associated with evidence for ancient Maya deforestation. MTTwax never recovered to pre-deforestation values, despite subsequent reforestation, implying that current tropical deforestation will have long-lasting effects on soil carbon sinks. VL - 11 UR - https://www.researchgate.net/publication/327119047_A_long-term_decrease_in_the_persistence_of_soil_carbon_caused_by_ancient_Maya_land_use IS - 9 ER - TY - Generic T1 - Maar sediment in central Vietnam Highland near Pleiku: An archive of regional monsoon intensity? Y1 - 2018 A1 - Schimmelmann, A., H. A1 - Nguyễn-Văn, D. A1 - Nguyễn-Thùy, J.P. A1 - Schimmelmann, A.E.K. A1 - Ojala, N. A1 - Nguyễn-Ánh, Q. A1 - Trọng Đỗ, D. A1 - Thùy Nguyễn, P. A1 - Hòa Tạ, V. A1 - Huỳnh-Kim, N. A1 - Quỳnh Phạm-Nữ, B. A1 - Zolitschka, I. KW - flood layer KW - land use KW - monsoon UR - http://eosvnu.net/wp-content/uploads/2018/05/Schimmelmann_2018_Abstract_7IMC.pdf ER - TY - JOUR T1 - Mangrove sediment carbon stocks along an elevation gradient: Influence of the late Holocene marine regression (New Caledonia) JF - Marine Geology Y1 - 2018 A1 - Jacotot, Adrien A1 - Marchand, Cyril A1 - Rosenheim, Brad E. A1 - Domack, Eugene W. A1 - Allenbach, Michel KW - Blue carbon KW - carbon isotopes KW - carbon sequestration KW - Coastal wetlands KW - Sea-level change KW - Semi-arid mangrove forest AB - Among blue carbon ecosystems, mangroves are very efficient in storing carbon in their sediments over decadal to millennial time scales. However, this ability varies with numerous parameters, including climate and sea-level variations. In New Caledonia, mangrove ecosystems develop in semi-arid conditions with a typical zonation: Rhizophora spp. colonize the seaward side of the intertidal area, while Avicennia marina develops at higher elevations, just below the salt-flat. Within this context, we determined both the quantity (organic carbon content and carbon stocks) and the characteristics (carbon over nitrogen ratios (C/N), stable carbon and nitrogen isotopes, radiocarbon age) of the organic matter stored beneath each mangrove stands. Carbon stocks were determined down to different limits with depth: approximate extension of the root systems, one-meter depth, and the hard substrate. Within the extension of the root systems, the sediment carbon stock was lower than 100 MgC ha−1 regardless of the mangrove species. This low value resulted directly from the dry climate that limits mangrove productivity. At depth beneath every zone, a buried layer enriched in mangrove-derived organic matter, with C/N values around 40 and δ13C values around −26‰ was observed. This layer likely resulted from a sea-level high stand during the late Holocene that allowed a long period of stability of the mangrove, slowly accumulating organic matter within the sediment. In this buried layer, the carbon stock was higher than in the upper sediment and reached up to 665, 255 and 300 MgC ha−1 in the salt-flat zone, the A. marina stand and the R. spp. stand, respectively. The highest stock, determined beneath the salt-flat, was suggested to be related to a period of sea-level stability that lasted ~3000 years, whereas beneath the other zones, which are at lower elevations, mangrove colonization was more recent and the sea-level was continuously decreasing till recently. Sea-level variations, and, specifically current sea-level rise, may strongly influence mangrove development due to their migration along the tidal elevation gradient to maintain the biotic conditions needed for their development. VL - 404 UR - https://linkinghub.elsevier.com/retrieve/pii/S0025322717306072 ER - TY - JOUR T1 - Menardiiform planktonic foraminifera stratigraphy from Middle Pleistocene to Holocene in the Western South Atlantic JF - REVISTA BRASILEIRA DE PALEONTOLOGIA Y1 - 2018 A1 - Costa, Karen Badaraco A1 - Camillo Jr, Edmundo A1 - Santarosa, Ana Cláudia Aoki A1 - Iwai, Fabiane Sayuri A1 - Quadros, Juliana Pereira de A1 - Leipnitz, Itamar Ivo A1 - Toledo, Felipe Antonio de Lima AB - We studied the Middle Pleistocene to Holocene menardiiform planktonic foraminifera (MPF) stratigraphy in six continuous deep-sea sediment cores recovered from the Brazilian continental slope to evaluate its use in climatic characterization and as a reliable biostratigraphic tool in the western South Atlantic. For this purpose, an important issue was to construct a robust local biochronological framework for the past 772 ky in the western South Atlantic (Santos Basin). The oxygen isotope chronostratigraphic control allowed us to recalibrate the MPF events in the Santos Basin and identify diachronous bioevents. The bio-horizons found in the Santos Basin, such as the V/W and T/U (bio)zone boundaries, were found in a different chronostratigraphic position compared to previous studies. Results indicate that typical cyclic disappearances and reappearances of the MPF are not synchronous throughout the Atlantic Ocean and should not be employed for ‘climatic zonation’. This asynchronous evidence also provides information on the timing of the mechanisms responsible for the proliferation of these species throughout the Atlantic Ocean. Therefore, we strongly recommend that a local biochronological framework should be used for inter-basin comparisons and also accumulation rate estimates, both for paleoclimatic studies and continental slope geohazard assessment. © 2018, Sociedade Brasileira de Paleontologia. All rights reserved. VL - 21 UR - https://www.researchgate.net/publication/330006751_Menardiiform_planktonic_foraminifera_stratigraphy_from_Middle_Pleistocene_to_Holocene_in_the_Western_South_Atlantic IS - 3 ER - TY - JOUR T1 - Microbial decomposition of marine dissolved organic matter in cool oceanic crust JF - Nature Geoscience Y1 - 2018 A1 - Shah Walter, Sunita R. A1 - Jaekel, Ulrike A1 - Osterholz, Helena A1 - Fisher, Andrew T. A1 - Huber, Julie A. A1 - Pearson, Ann A1 - Dittmar, Thorsten A1 - Girguis, Peter R. KW - carbon KW - community KW - deep-ocean KW - DISTINCT KW - extraction KW - fluid-flow KW - HEAT KW - MID-ATLANTIC RIDGE KW - SEAWATER KW - WESTERN FLANK AB - Marine dissolved organic carbon (DOC) is one of the largest active reservoirs of reduced carbon on Earth. In the deep ocean, DOC has been described as biologically recalcitrant and has a radiocarbon age of 4,000 to 6,000 years, which far exceeds the timescale of ocean overturning. However, abiotic removal mechanisms cannot account for the full magnitude of deep-ocean DOC loss. Deep-ocean water circulates at low temperatures through volcanic crust on ridge flanks, but little is known about the associated biogeochemical processes and carbon cycling. Here we present analyses of DOC in fluids from two borehole observatories installed in crustal rocks west of the Mid-Atlantic Ridge, and show that deep-ocean DOC is removed from these cool circulating fluids. The removal mechanism is isotopically selective and causes a shift in specific features of molecular composition, consistent with microbe-mediated oxidation. We suggest organic molecules with an average radiocarbon age of 3,200 years are bioavailable to crustal microbes, and that this removal mechanism may account for at least 5% of the global loss of DOC in the deep ocean. Cool crustal circulation probably contributes to maintaining the deep ocean as a reservoir of 'aged' and refractory DOC by discharging the surviving organic carbon constituents that are molecularly degraded and depleted in C-14 and C-13 into the deep ocean. VL - 11 UR - http://www.nature.com/articles/s41561-018-0109-5http://www.nature.com/articles/s41561-018-0109-5.pdfhttp://www.nature.com/articles/s41561-018-0109-5http://www.nature.com/articles/s41561-018-0109-5.pdf IS - 5 ER - TY - JOUR T1 - Microbial oxidation of lithospheric organic carbon in rapidly eroding tropical mountain soils JF - Science Y1 - 2018 A1 - Hemingway, Jordon D. A1 - Hilton, Robert G. A1 - Hovius, Niels A1 - Eglinton, Timothy I. A1 - Haghipour, Negar A1 - Wacker, Lukas A1 - Chen, Meng-Chiang A1 - Galy, Valier V. AB - Lithospheric organic carbon (“petrogenic”; OCpetro) is oxidized during exhumation and subsequent erosion of mountain ranges. This process is a considerable source of carbon dioxide (CO2) to the atmosphere over geologic time scales, but the mechanisms that govern oxidation rates in mountain landscapes are poorly constrained. We demonstrate that, on average, 67 ± 11% of the OCpetro initially present in bedrock exhumed from the tropical, rapidly eroding Central Range of Taiwan is oxidized in soils, leading to CO2 emissions of 6.1 to 18.6 metric tons of carbon per square kilometer per year. The molecular and isotopic evolution of bulk OC and lipid biomarkers during soil formation reveals that OCpetro remineralization is microbially mediated. Rapid oxidation in mountain soils drives CO2 emission fluxes that increase with erosion rate, thereby counteracting CO2 drawdown by silicate weathering and biospheric OC burial. VL - 360 UR - https://www.sciencemag.org/lookup/doi/10.1126/science.aao6463 IS - 6385 ER - TY - JOUR T1 - Millennial-scale variations in dustiness recorded in Mid-Atlantic sediments from 0 to 70 ka JF - Earth and Planetary Science Letters Y1 - 2018 A1 - Middleton, Jennifer L. A1 - Mukhopadhyay, Sujoy A1 - Langmuir, Charles H. A1 - McManus, Jerry F. A1 - Huybers, Peter J. KW - helium-3 KW - mass accumulation rate KW - mineral dust KW - North Africa KW - Subtropical North Atlantic KW - thorium-232 AB - Sedimentary records of dust deposition in the subtropical Atlantic provide important constraints on millennial- and orbital-scale variability in atmospheric circulation and North African aridity. Constant flux proxies, such as extraterrestrial helium-3, yield dust flux records that are independent of the biases caused by lateral sediment transport and limited resolution that may be associated with age-model-derived mass accumulation rates. However, Atlantic dust records constrained using constant flux proxies are sparsely distributed and generally limited to the past 20 ka. Here we extend the Atlantic record of North African dust deposition to 70 ka using extraterrestrial helium-3 and measurements of titanium, thorium, and terrigenous helium-4 in two sediment cores collected at 26°N and 29°N on the Mid-Atlantic Ridge and compare results to model estimates for dust deposition in the subtropical North Atlantic. Dust proxy fluxes between 26°N and 29°N are well correlated, despite variability in lateral sediment transport, and underscore the utility of extraterrestrial helium-3 for constraining millennial-scale variability in dust deposition. Similarities between Mid-Atlantic dust flux trends and those observed along the Northwest African margin corroborate previous interpretations of dust flux variability over the past 20 ka and suggest that long distance transport and depositional processes do not overly obscure the signal of North African dust emissions. The 70 ka Mid-Atlantic record reveals a slight increase in North African dustiness from Marine Isotope Stage 4 through the Last Glacial Maximum and a dramatic decrease in dustiness associated with the African Humid Period. On the millennial-scale, the new records exhibit brief dust maxima coincident with North Atlantic cold periods such as the Younger Dryas, and multiple Heinrich Stadials. The correlation between Mid-Atlantic dust fluxes and previous constraints on North African aridity is high. However, precipitation exerts less control on dust flux variability prior to the African Humid Period, when wind variability governs dust emissions from consistently dry dust source regions. Thus, the Mid-Atlantic dust record supports the hypothesis that both aridity and wind strength drive dust flux variability across changing climatic conditions. VL - 482 UR - https://www.sciencedirect.com/science/article/pii/S0012821X17306027 ER - TY - JOUR T1 - Organic Carbon Aging During Across‐Shelf Transport JF - Geophysical Research Letters Y1 - 2018 A1 - Bao, Rui A1 - Uchida, Masao A1 - Zhao, Meixun A1 - Haghipour, Negar A1 - Montlucon, Daniel A1 - McNichol, Ann A1 - Wacker, Lukas A1 - Hayes, John M. A1 - Eglinton, Timothy I. AB - Compound-specific radiocarbon analysis (CSRA) was performed on different grain-size fractions of surficial sediments to examine and compare lateral transport times (LTTs) of organic carbon. 14C aging of long-chain leaf wax fatty acids along two dispersal pathways of fluvially-derived material on adjacent continental margins implies LTTs over distances of ~30 to 500 km that range from hundreds to thousands of years. The magnitude of aging differs among grain size fractions. Our finding suggests that LTTs vary both temporally and spatially as a function of the specific properties of different continental shelf settings. Observations suggest that 14C aging is widespread during lateral transport over continental shelves, with hydrodynamic particle sorting inducing age variations among organic components residing in different grain sizes. Consideration of these phenomena is of importance for understanding carbon cycle processes and interpretation on sedimentary records on continental margins. VL - 45 UR - https://core.ac.uk/download/pdf/222887698.pdf IS - 16 ER - TY - JOUR T1 - Organic matter sources and lateral sedimentation in a Bahamian karst basin (sinkhole) over the late Holocene: Influence of local vegetation and climate JF - Palaeogeography, Palaeoclimatology, Palaeoecology Y1 - 2018 A1 - Tamalavage, Anne E. A1 - van Hengstum, Peter J. A1 - Louchouarn, Patrick A1 - Molodtsov, Sergey A1 - Kaiser, Karl A1 - Donnelly, Jeffrey P. A1 - Albury, Nancy A. A1 - Fall, Patricia L. KW - Caribbean KW - Karst KW - Mixing model KW - Stable isotopes KW - Subtropical landscape AB - Karst basins (e.g., blueholes, sinkholes) accumulate well-preserved sedimentary successions that provide transformative paleoclimatic and paleoenvironmental information. However, the sedimentary processes within these basins are not yet fully understood. Here we present stable carbon isotopic values (δ13Corg) and C:N ratios of bulk organic matter in well-dated sediment cores from Blackwood Sinkhole (Abaco, The Bahamas) to investigate the changing flux of organic matter into the sinkhole during the late Holocene. The provenance of preserved organic matter changed through the late Holocene between three primary sources, as determined by three-endmember mixing modeling: wetland organic matter from the adjacent epikarst surface, authigenic primary productivity in the oligohaline meteoric lens, and terrestrial organic matter from the surrounding landscape. Expansion of wetlands on the adjacent epikarst surface played a critical role by increasing the flux of wetland organic matter to the sinkhole, especially during the last 1000 years. Hurricanes and regional rainfall may have mediated organic matter delivery to the benthos, either through hampering wetland development (prior to 1000 cal yr BP) or by changing dissolved nutrient concentrations available in the basin for primary producers. These results demonstrate that organic matter provenance in karst basins is not constant through time, and is significantly dependent upon both landscape vegetation on the epikarst surface and changing hydrographic conditions that impacts nutrient availability to primary producers. VL - 506 UR - https://linkinghub.elsevier.com/retrieve/pii/S0031018218300683 ER - TY - JOUR T1 - Paleoceanography of northeastern Fram Strait since the last glacial maximum: Palynological evidence of large amplitude changes JF - Quaternary Science Reviews Y1 - 2018 A1 - Falardeau, Jade A1 - de Vernal, Anne A1 - Spielhagen, Robert F. AB - Sea-surface conditions in northeastern Fram Strait since the last glacial maximum (LGM) were reconstructed from cores MSM5/5-712-2 and PS2863/1-2 based on palynological assemblages, ecological preferences of dinocysts and application of the modern analog technique. Dinocyst in LGM sediments are sparse, but their assemblages reflect mild summer conditions. Given the regional context and evidence from other tracers, the dinocyst assemblages of the LGM could relate to regional fluxes of dinocysts during exceptional mild summers. From 19 to 14.7 ka, dinocyst data suggest very cold conditions with extensive sea-ice cover, while abundant reworked palynomorphs indicate intense glacial erosion. An abrupt transition at 14.7-14.5 ka was marked by a peak in summer temperatures coinciding with a rapidly deposited sediment layer related to a regional meltwater plume event in western Svalbard. From 14.7 to 12.6 ka, large seasonal temperature contrasts with mild summers and cold winters together with low salinity indicate continuous melting of the Svalbard Barents Sea ice sheet fostered by warm climate. At 12.6 ka, the regional onset of the Younger Dryas was marked by cooling and increased salinity. On a regional scale, the 12.6-12 ka interval corresponds to an important transition involving enhanced circulation of Arctic waters around Svalbard and establishment of coastal fronts along its northern and western margins. Modern-like oceanic conditions with relatively high salinity and low seasonal temperature contrast developed at about 7.6 ka. Since then, a slight cooling is observed, especially in winter. This study offers a comprehensive picture of the deglacial phases in eastern Fram Strait with unique data on the sea surface salinity, which controls surface water stratification and plays an important role in ocean circulation. (C) 2018 Elsevier Ltd. All rights reserved. VL - 195 UR - https://linkinghub.elsevier.com/retrieve/pii/S0277379117303979https://api.elsevier.com/content/article/PII:S0277379117303979?httpAccept=text/xmlhttps://api.elsevier.com/content/article/PII:S0277379117303979?httpAccept=text/plain ER - TY - JOUR T1 - Paleomagnetism and rock magnetism from sediments along a continental shelf-to-slope transect in the NW Barents Sea: Implications for geomagnetic and depositional changes during the past 15 thousand years JF - Global and Planetary Change Y1 - 2018 A1 - Caricchi, C. A1 - Lucchi, R.G. A1 - Sagnotti, L. A1 - MacrÌ, P. A1 - Morigi, C. A1 - Melis, R. A1 - Caffau, M. A1 - Rebesco, M. A1 - Hanebuth, T.J.J. KW - Barents Sea KW - Kveithola glacial trough KW - Paleomagnetism KW - Rock magnetism AB - Paleomagnetic and rock magnetic data were measured on glaciomarine silty-clay successions along an E-W sediment-core transect across the continental shelf and slope of the Kveithola paleo-ice stream system (south of Svalbard, north-western Barents Sea), representing a stratigraphic interval spanning the last deglaciation and the Holocene. The records indicate that magnetite is the main magnetic mineral and that magnetic minerals are distinctly less abundant on the shelf than at the continental slope. The paleomagnetic properties allow for the reconstruction of a well-defined characteristic remanent magnetization (ChRM) throughout the sedimentary successions. The stratigraphic trends of rock magnetic and paleomagnetic parameters are used for a shelf-slope core correlation and sediment facies analysis is applied for depositional processes reconstruction. The new paleomagnetic records compare to the PSV and RPI variation predicted for the core sites by a simulation using the global geomagnetic field variation models SHA.DIF.14k and CALS7K.2 and closest PSV and RPI regional stack curves. The elaborated dataset, corroborated by available 14C ages, provides a fundamental chronological framework to constrain the coupling of shelf-slope sedimentary processes and environmental changes in the NW Barents Sea region during and after deglaciation. VL - 160 UR - https://linkinghub.elsevier.com/retrieve/pii/S0921818117303077 ER - TY - JOUR T1 - Paleoseismic Results from the Alpine Site, Wasatch Fault Zone: Timing and Displacement Data for Six Holocene Earthquakes at the Salt Lake City–Provo Segment Boundary JF - Bulletin of the Seismological Society of America Y1 - 2018 A1 - Bennett, S. E. K. A1 - DuRoss, C. B. A1 - Gold, R. D. A1 - Briggs, R. W. A1 - Personius, S. F. A1 - Reitman, N. G. A1 - Devore, J. R. A1 - Hiscock, A. I. A1 - Mahan, S. A. A1 - Gray, H. J. A1 - Gunnarson, S. A1 - Stephenson, W. J. A1 - Pettinger, E. A1 - Odum, J. K. AB - To improve the characterization of Holocene earthquakes on the Wasatch fault zone (WFZ), we conducted light detection and ranging (lidar)‐based neotectonic mapping and excavated a paleoseismic trench across an 8‐m‐high fault scarp near Alpine, Utah, located <1  km south of the boundary between the Salt Lake City and Provo segments (SLCS and PS). We document evidence for six paleoearthquakes (AL6–AL1) from scarp‐derived colluvial wedges and crosscutting relations. A ground‐penetrating radar survey across the scarp resolved fault‐zone width, but not paleoearthquake stratigraphy. Bayesian (OxCal) modeling of 13 radiocarbon and 13 optically stimulated luminescence ages indicates that six earthquakes occurred ∼6.2–0.4  ka. Interseismic recurrence ranges from 0.2 to 1.8 ky (mean 1.2 ky). We estimate 6.5±0.7  m of cumulative vertical tectonic displacement across the ≥14‐m‐wide fault zone used near‐field observations of scarp‐derived colluvial‐wedge thicknesses, antithetic faulting, and graben backtilting. This is similar to our independent estimate of 6.5±0.5  m using far‐field observations of the offset ground surface and correlation of alluvial‐fan stratigraphy across the WFZ. These results suggest that colluvial‐wedge thickness at the Alpine site approximates one‐half the original west‐facing fault scarp height. Per‐event vertical displacements range from 0.8 to 1.2 m (mean 1.1 m), which we use to estimate surface rupture lengths that may exceed 50 km from earthquakes as large as moment magnitude (Mw) ∼7.0. The late Holocene average vertical slip rate is 0.9  mm/yr (0.7–1.2  mm/yr range). Earthquake frequency has increased in the past ∼1  ky, whereas displacement per event has been similar for the past ∼6  ky, suggesting that strain accumulation is not the sole factor that controls the frequency and size of earthquakes at the SLCS–PS segment boundary. These findings can be used for a more nuanced characterization of earthquakes at the SLCS–PS boundary and improve earthquake hazard assessments along the Wasatch Front. UR - https://pubs.geoscienceworld.org/ssa/bssa/article/556954/Paleoseismic-Results-from-the-Alpine-Site-Wasatch ER - TY - BOOK T1 - The Potential Impact of Hydrocarbons on Mussels in Port au Port Bay, Newfoundland Y1 - 2018 A1 - Cook, Melissa C. A1 - May, Adam A1 - Kohl, Lucas A1 - Van Biesen, Geert A1 - Parrish, Christopher C. A1 - Morrill, Penny L. KW - Health indices KW - Hydrocarbon contamination KW - Mussels KW - Petroleum KW - Scallops AB - Since 2012, the scallop fishery in Port au Port Bay, Newfoundland, Canada has experienced a drastic decline, while no decline was observed in adjacent St. George's Bay. Local fishermen have raised concerns about an abandoned oil exploration well in the Port au Port Bay. This study investigated the potential impact of petroleum hydrocarbons on sediments and blue mussels [Mytilus edulis] (a proxy organism for scallops) in the area. Sediments from both bays were characterized for their hydrocarbons and compared to potential petroleum hydrocarbon sources. Mussels were analysed for health indices and their 14C content. The results showed that the concentration of hydrocarbons found in the sediments of the fishing ground was within the range of unpolluted marine sediments and that the hydrocarbons present were likely from a mixture of sources. The health indices of the mussels in Port au Port Bay were similar to the health indices of mussels in St. George's Bay and the 14C content of the mussels from both bays was modern. These data suggest that the Port au Port fishing ground was not solely contaminated from crude oil leaking from an oil exploration well, that the mussels were not contaminated with petroleum hydrocarbons, and that Port au Port mussels were just as healthy as the mussels of St. George's Bay. Therefore, whatever caused the scallop decline was most likely scallop- and bay-specific. During this study a fast and efficient method for extracting petroleum hydrocarbons from sediment using accelerated solvent extraction with integrated silica gel was developed. PB - Elsevier VL - 81 SN - 9780128151051 UR - https://linkinghub.elsevier.com/retrieve/pii/S006528811830018Xhttps://api.elsevier.com/content/article/PII:S006528811830018X?httpAccept=text/xmlhttps://api.elsevier.com/content/article/PII:S006528811830018X?httpAccept=text/plain ER - TY - JOUR T1 - Pronounced summer warming in northwest Greenland during the Holocene and Last Interglacial JF - Proceedings of the National Academy of Sciences Y1 - 2018 A1 - McFarlin, Jamie M. A1 - Axford, Yarrow A1 - Osburn, Magdalena R. A1 - Kelly, Meredith A. A1 - Osterberg, Erich C. A1 - Farnsworth, Lauren B. AB - Projections of future rates of mass loss from the Greenland Ice Sheet are highly uncertain because its sensitivity to warming is unclear. Geologic reconstructions of Quaternary interglacials can illustrate how the ice sheet responded during past warm periods, providing insights into ice sheet behavior and important tests for data-model comparisons. However, paleoclimate records from Greenland are limited: Early Holocene peak warmth has been quantified at only a few sites, and terrestrial sedimentary records of prior interglacials are exceptionally rare due to glacial erosion during the last glacial period. Here, we discuss findings from a lacustrine archive that records both the Holocene and the Last Interglacial (LIG) from Greenland, allowing for direct comparison between two interglacials. Sedimentary chironomid assemblages indicate peak July temperatures 4.0 to 7.0 °C warmer than modern during the Early Holocene maximum in summer insolation. Chaoborus and chironomids in LIG sediments indicate July temperatures at least 5.5 to 8.5 °C warmer than modern. These estimates indicate pronounced warming in northwest Greenland during both interglacials. This helps explain dramatic ice sheet thinning at Camp Century in northwest Greenland during the Early Holocene and, for the LIG, aligns with controversial estimates of Eemian warming from ice core data retrieved in northern Greenland. Converging geologic evidence for strong LIG warming is challenging to reconcile with inferred Greenland Ice Sheet extent during the LIG, and the two appear incompatible in many models of ice sheet evolution. An increase in LIG snowfall could help resolve this problem, pointing to the need for hydroclimate reconstructions from the region. VL - 115 UR - http://www.pnas.org/lookup/doi/10.1073/pnas.1720420115https://syndication.highwire.org/content/doi/10.1073/pnas.1720420115http://www.pnas.org/syndication/doi/10.1073/pnas.1720420115 IS - 25 ER - TY - BOOK T1 - Quaternary Glaciation of the Great Lakes Region: Process, Landforms, Sediments, and ChronologyMinimum age of the Mapleton, Tully, and Labrador Hollow moraines indicates correlation with the Port Huron Phase in central New York State Y1 - 2018 A1 - Kehew, Alan E. A1 - Curry, B. Brandon A1 - Kozlowski, Andrew L. A1 - Bird, Brian C. A1 - Lowell, Thomas V. A1 - Smith, Colby A. A1 - Feranec, Robert S. A1 - Graham, Brandon Lars AB - The glaciated terrain along the northern edge of the Appalachian Plateau in the eastern Finger Lakes of central New York has long been recognized as an important location for meltwater routing and for proglacial lake development in the Great Lakes region. Despite recognition of multiple ice margins formed by the Ontario Lobe of the Laurentide ice sheet during the late Wisconsinan, numerical age control of several margins has been elusive, particularly in regard to regional readvances of the Port Bruce (ca. 16,980–18,000 cal [calibrated] yr B.P.) and Port Huron (ca. 14,300– 16,000 cal yr B.P.) Phases. Utilizing light detection and ranging (LiDAR) terrain models in the eastern Finger Lakes area, we identified and described the Mapleton, Tully, and Labrador Hollow moraines. Associated ice-marginal landforms include push moraines, fans, and hummocky topography. In places, these features intrude into the northern heads of through valleys. Coring of three basins directly associated with these landforms yielded more than 20 samples of boreal tree needles and twigs, and Dryas leaves. Accelerated mass spectrometry (AMS) radiocarbon assay results indicate that poststadial lacustrine sedimentation began at ca. 15,000 cal yr B.P., consistent with ages of the Port Huron Phase. PB - Geological Society of America UR - https://pubs.geoscienceworld.org/books/book/2055/chapter/113619040/Minimum-age-of-the-Mapleton-Tully-and-Labrador ER - TY - JOUR T1 - Radiocarbon and Stable Isotope Evidence for Changes in Sediment Mixing in the North Pacific over the Past 30 kyrAbstract JF - Radiocarbon Y1 - 2018 A1 - Costa, Kassandra M A1 - McManus, Jerry F A1 - Anderson, Robert F KW - bioturbation KW - north pacific KW - radiocarbon KW - Stable isotopes AB - Deep-sea sediment mixing by bioturbation is ubiquitous on the seafloor, and it can be an important influence on the fidelity of paleoceanographic records. Bioturbation can be difficult to quantify, especially in the past, but diffusive models based on radioactive tracer profiles have provided a relatively successful approach. However, a singular, constant mixing regime is unlikely to prevail in a region where dynamic oceanographic changes in the bottom water environment are a consequence of paleoclimatic variability. In this study, foraminiferal stable isotopes, radiocarbon (14C) dating, and 230Th fluxes are utilized to understand the sediment mixing history in the easternmost region of the North Pacific. In the uppermost sediment, a 12,000-yr offset between planktonic foraminifera species N. incompta and G. bulloides is observed that coincides with age plateaus at 2000–2500 yr for N. incompta and 15,000–16,000 yr for G. bulloides despite coincident glacial-interglacial shifts in δ18O of benthic species. These age plateaus, particularly for G. bulloides, are a result of changing foraminiferal abundance related to assemblage shifts and carbonate preservation changes since the last glacial period, providing a window into the extent of mixing in the past. The 14C and stable isotope results can be simulated using an iterative model that couples these changes in foraminiferal abundance with variability in mixing depth over time. The best-fit model output suggests that the deepest, or most intense, mixing of the past 30,000 yr (30 kyr) may have occurred during the Holocene. Even though changes in mixing affect the 14C and δ18O of planktonic species that have dramatically varying abundance, substantial age control is nevertheless provided by δ18O measurements on the more consistently abundant benthic foraminifera Uvigerina, thus allowing the construction of a reliable chronology for these cores. VL - 60 UR - https://www.cambridge.org/core/product/identifier/S0033822217000911/type/journal_articlehttps://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0033822217000911 IS - 1 ER - TY - DATA T1 - Radiocarbon, Cesium-137, Grain Size, and X-ray Fluorescence Data for Tsunami Geology Investigation, Driftwood Bay, Umnak Island, Alaska (2018) Y1 - 2018 A1 - Witter, Rob A1 - Gelfenbaum, Guy A1 - Corbett, Reide A1 - Tam, Angela A1 - La Selle, SeanPaul AB - These files provide the complete data release for the paper entitled, "Frequent large tsunamis spanned locked/creeping parts of the Aleutian megathrust." The data set consists of nine tables that include radiocarbon dates, cesium-137 activity, grain size measurements, and scanning X-ray fluorescence element intensity counts. PB - Alaska Science Center, U.S. Geological Survey UR - https://doi.org/10.5066/P9D7KLJV ER - TY - JOUR T1 - Radiocarbon Content of Dissolved Organic Carbon in the South Indian Ocean JF - Geophysical Research Letters Y1 - 2018 A1 - Bercovici, S. K. A1 - McNichol, A. P. A1 - Xu, L. A1 - Hansell, D. A. KW - dissolved organic carbon KW - indian ocean KW - radiocarbon AB - We report four profiles of the radiocarbon content of dissolved organic carbon (DOC) spanning the South Indian Ocean (SIO), ranging from the Polar Front (56°S) to the subtropics (29°S). Surface waters held mean DOC Δ14C values of −426 ± 6‰ (~4,400 14C years) at the Polar Front and DOC Δ14C values of −252 ± 22‰ (~2,000 14C years) in the subtropics. At depth, Circumpolar Deep Waters held DOC Δ14C values of −491 ± 13‰ (~5,400 years), while values in Indian Deep Water were more depleted, holding DOC Δ14C values of −503 ± 8‰ (~5,600 14C years). High‐salinity North Atlantic Deep Water intruding into the deep SIO had a distinctly less depleted DOC Δ14C value of −481 ± 8‰ (~5,100 14C years). We use multiple linear regression to assess the dynamics of DOC Δ14C values in the deep Indian Ocean, finding that their distribution is characteristic of water masses in that region. VL - 45 UR - https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1002/2017GL076295 IS - 2 ER - TY - JOUR T1 - Radiocarbon dating of the old ash of Aiton, Romania JF - Studia Universitatis Babeș-Bolyai Chemia Y1 - 2018 A1 - Patrut, Adrian A1 - Patrut, Roxana T. A1 - Rakosy, Laszlo A1 - Ratiu, Ileana-Andreea A1 - Lowy, Daniel A. A1 - Bodis, Jenő A1 - von Reden, Karl F. AB - The article reports the AMS (accelerator mass spectrometry) radiocarbon investigation results of the old common ash of Aiton. Five wood samples were collected from the trunk of the tree. The deepest ends of the samples were analysed by AMS radiocarbon. We found radiocarbon dates between 165 ± 20 BP and 240 ± 18 BP, which correspond to calibrated ages of 230 – 360 years. These results, combined with a ring counting estimate, indicate an age of 330 ± 30 years for the ash of Aiton. By this value, the ash of Aiton becomes the oldest known common ash with accurate dating results. © 2018, Universitatea Babes-Bolyai, Catedra de Filosofie Sistematica. All rights reserved. VL - 63 UR - https://www.researchgate.net/publication/328588965_Radiocarbon_dating_of_the_old_ash_of_Aiton_Romania IS - 3 ER - TY - JOUR T1 - Rapid precipitation changes in the tropical West Pacific linked to North Atlantic climate forcing during the last deglaciation JF - Quaternary Science Reviews Y1 - 2018 A1 - Xiong, Zhifang A1 - Li, Tiegang A1 - Chang, Fengming A1 - Algeo, Thomas J. A1 - Clift, Peter D. A1 - Bretschneider, Lisa A1 - Lu, Zhengyao A1 - Zhu, Xiao A1 - Frank, Martin A1 - Sauer, Peter E. A1 - Jiang, FuQing A1 - Wan, Shiming A1 - Zhang, Xu A1 - Chen, Shuangxi A1 - Huang, Jie KW - AMOC KW - Chemical weathering KW - enso KW - ITCZ KW - Terrigenous input KW - Western Philippine Sea AB - The cause of rapid hydrological changes in the tropical West Pacific during the last deglaciation remains controversial. In order to test whether these changes were triggered by abrupt climate change events in the North Atlantic Ocean, variations in precipitation during the last deglaciation (18-10 ka) were extracted from proxy records of chemical weathering and terrigenous input in the western Philippine Sea (WPS). The evolution of chemical weathering and terrigenous input since 27 ka was reconstructed using the chemical index of alteration (CIA), elemental ratios (K/Al, TOC/TN and Ti/Ca), δ13Corg, terrigenous fraction abundance and flux data from International Marine Global Change Study Program (IMAGES) core MD06-3054 collected on the upper continental slope of eastern Luzon (northern Philippines). Sediment deposited during the Last Glacial Maximum (LGM) shows weathering equal to or slightly greater than Holocene sediment in the WPS. This unusual state of chemical weathering, which is inconsistent with lower air temperatures and decreased precipitation in Luzon during the LGM, may be due to reworking of poorly consolidated sediments on the eastern Luzon continental shelf during the LGM sea-level lowstand. Rapid changes in chemical weathering, characterized by higher intensity during the Heinrich event 1 (H1) and Younger Dryas (YD) and lower intensity during the Bølling-Allerød (B/A), were linked to rapid variations in precipitation in the WPS during the last deglaciation. The higher terrigenous inputs during the LGM relative to those of the Holocene were controlled by sea-level changes rather than precipitation. The terrigenous inputs show a long-term decline during the last deglaciation, punctuated by brief spikes during the H1 and YD related to sea-level rises and rapid precipitation changes in the WPS, respectively. The proxy records of chemical weathering and terrigenous input from eastern Luzon suggest high rainfall during the H1 and YD events, consistent with inferred rainfall patterns based on Fe/Ca records from offshore Mindanao. Rapid precipitation changes in the WPS did not coincide with migrations of the Intertropical Convergence Zone (ITCZ) but, rather, were related to state shifts of the El Niño-Southern Oscillation (ENSO) during the last deglaciation. Based on proxy records and modeling results, we argue that the Atlantic meridional overturning circulation (AMOC) controlled rapid precipitation changes in the tropical West Pacific through zonal shifts of ENSO or meridional migration of the ITCZ during the last deglaciation. Our findings highlight the dominant role of the North Atlantic Ocean in the tropical hydrologic cycle during the last deglaciation. VL - 197 UR - https://linkinghub.elsevier.com/retrieve/pii/S0277379117309484https://api.elsevier.com/content/article/PII:S0277379117309484?httpAccept=text/xmlhttps://api.elsevier.com/content/article/PII:S0277379117309484?httpAccept=text/plain ER - TY - JOUR T1 - Recent occupation by Adélie Penguins (Pygoscelis adeliae) at Hope Bay and Seymour Island and the ‘northern enigma’ in the Antarctic Peninsula JF - Polar Biology Y1 - 2018 A1 - Emslie, Steven D. A1 - McKenzie, Ashley A1 - Marti, Lucas J. A1 - Santos, Mercedes AB - We excavated active and abandoned Adélie Penguin (Pygoscelis adeliae) colonies at Seymour Island and Hope Bay, Antarctic Peninsula, to determine an occupation history for this species at these sites. Previous research at Hope Bay has indicated an occupation there since the middle Holocene, based on a sediment record from Lake Boeckella. Excavations revealed only shallow and relatively fresh ornithogenic soils in the active colonies at the two localities. At least 53 abandoned pebble mounds were located at Hope Bay of which nine were excavated and four were sampled by probing to recover organic remains to determine their age. Radiocarbon dating of egg membrane, feather, and bone from both sites revealed a young occupation dating to less than ~600 years after correcting for the marine carbon reservoir effect. The mismatch in the geologic record of Adélie Penguin occupation in the northern Antarctic Peninsula, including Lake Boeckella sediments and geologic deposits and lake sediments on King George Island, with more direct evidence of breeding colonies from ornithogenic soils from active and abandoned colonies is hereby referred to as the ‘northern enigma’ as it does not occur in other regions of Antarctica including the southern Antarctic Peninsula, East Antarctica, or the Ross Sea, where the penguin record extends to the early to middle Holocene and matches well with the geologic record of deglaciation and penguin occupation. As yet, there is no convincing explanation for the ‘northern enigma’. VL - 41 UR - http://link.springer.com/10.1007/s00300-017-2170-8 IS - 1 ER - TY - JOUR T1 - Relative sea-level change in Newfoundland, Canada during the past ∼3000 years JF - Quaternary Science Reviews Y1 - 2018 A1 - Kemp, Andrew C. A1 - Wright, Alexander J. A1 - Edwards, Robin J. A1 - Barnett, Robert L. A1 - Brain, Matthew J. A1 - Kopp, Robert E. A1 - Cahill, Niamh A1 - Horton, Benjamin P. A1 - Charman, Dan J. A1 - Hawkes, Andrea D. A1 - Hill, Troy D. A1 - van de Plassche, Orson AB - Several processes contributing to coastal relative sea-level (RSL) change in the North Atlantic Ocean are observed and/or predicted to have distinctive spatial expressions that vary by latitude. To expand the latitudinal range of RSL records spanning the past ∼3000 years and the likelihood of recognizing the characteristic fingerprints of these processes, we reconstructed RSL at two sites (Big River and Placentia) in Newfoundland from salt-marsh sediment. Bayesian transfer functions established the height of former sea level from preserved assemblages of foraminifera and testate amoebae. Age-depth models constrained by radiocarbon dates and chronohorizons estimated the timing of sediment deposition. During the past ∼3000 years, RSL rose by ∼3.0 m at Big River and by ∼1.5 m at Placentia. A locally calibrated geotechnical model showed that post-depositional lowering through sediment compaction was minimal. To isolate and quantify contributions to RSL from global, regional linear, regional non-linear, and local-scale processes, we decomposed the new reconstructions (and those in an expanded, global database) using a spatio-temporal statistical model. The global component confirms that 20th century sea-level rise occurred at the fastest, century-scale rate in over 3000 years (P > 0.999). Distinguishing the contributions from local and regional non-linear processes is made challenging by a sparse network of reconstructions. However, only a small contribution from local-scale processes is necessary to reconcile RSL reconstructions and modeled RSL trends. We identified three latitudinally-organized groups of sites that share coherent regional non-linear trends and indicate that dynamic redistribution of ocean mass by currents and/or winds was likely an important driver of sea-level change in the North Atlantic Ocean during the past ∼3000 years. VL - 201 UR - https://linkinghub.elsevier.com/retrieve/pii/S0277379118304980 ER - TY - JOUR T1 - Remobilization of old permafrost carbon to Chukchi Sea sediments during the end of the last deglaciation JF - Global Biogeochemical Cycles Y1 - 2018 A1 - Martens, Jannik A1 - Wild, Birgit A1 - Pearce, Christof A1 - Tesi, Tommaso A1 - Andersson, August A1 - Broder, Lisa A1 - O’Regan, Matt A1 - Jakobsson, Martin A1 - Sköld, Martin A1 - Gemery, Laura A1 - Cronin, Thomas M. A1 - Semiletov, Igor A1 - Dudarev, Oleg V. A1 - Gustafsson, Örjan KW - carbon isotope KW - climate change feedback KW - coastal erosion KW - Deglaciation KW - past carbon cycling KW - permafrost AB - Climate warming is expected to destabilize permafrost carbon (PF‐C) by thaw‐erosion and deepening of the seasonally thawed active layer and thereby promote PF‐C mineralization to CO2 and CH4. A similar PF‐C remobilization might have contributed to the increase in atmospheric CO2 during deglacial warming after the last glacial maximum. Using carbon isotopes and terrestrial biomarkers (Δ14C, δ13C, and lignin phenols), this study quantifies deposition of terrestrial carbon originating from permafrost in sediments from the Chukchi Sea (core SWERUS‐L2‐4‐PC1). The sediment core reconstructs remobilization of permafrost carbon during the late Allerød warm period starting at 13,000 cal years before present (BP), the Younger Dryas, and the early Holocene warming until 11,000 cal years BP and compares this period with the late Holocene, from 3,650 years BP until present. Dual‐carbon‐isotope‐based source apportionment demonstrates that Ice Complex Deposit—ice‐ and carbon‐rich permafrost from the late Pleistocene (also referred to as Yedoma)—was the dominant source of organic carbon (66 ± 8%; mean ± standard deviation) to sediments during the end of the deglaciation, with fluxes more than twice as high (8.0 ± 4.6 g·m−2·year−1) as in the late Holocene (3.1 ± 1.0 g·m−2·year−1). These results are consistent with late deglacial PF‐C remobilization observed in a Laptev Sea record, yet in contrast with PF‐C sources, which at that location were dominated by active layer material from the Lena River watershed. Release of dormant PF‐C from erosion of coastal permafrost during the end of the last deglaciation indicates vulnerability of Ice Complex Deposit in response to future warming and sea level changes. UR - https://onlinelibrary.wiley.com/doi/abs/10.1029/2018GB005969https://onlinelibrary.wiley.com/doi/pdf/10.1029/2018GB005969https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1029%2F2018GB005969https://onlinelibrary.wiley.com/doi/pdf/10.1029/2018GB005969 ER - TY - JOUR T1 - Residential Coal Combustion as a Source of Levoglucosan in ChinaResidential Coal Combustion as a Source of Levoglucosan in China JF - Environmental Science & Technology Y1 - 2018 A1 - Yan, Caiqing A1 - Zheng, Mei A1 - Sullivan, Amy P. A1 - Shen, Guofeng A1 - Chen, Yingjun A1 - Wang, Shuxiao A1 - Zhao, Bin A1 - Cai, Siyi A1 - Desyaterik, Yury A1 - Li, Xiaoying A1 - Zhou, Tian A1 - Gustafsson, Örjan A1 - Collett, Jeffrey L. AB - Levoglucosan (LG) has been widely identified as a specific marker for biomass burning (BB) sources and frequently utilized in estimating the BB contribution to atmospheric fine particles all over the world. However, this study provides direct evidence to show that coal combustion (CC) is also a source of LG, especially in the wintertime in Northern China, based on both source testing and ambient measurement. Our results show that low-temperature residential CC could emit LG with emission factors (EF) ranging from 0.3 to 15.9 mg kg–1. Ratios of LG to its isomers, mannosan and galactosan, differ between CC and BB emissions, and the wintertime ratios in Beijing ambient PM2.5 and source-specific tracers including carbon isotopic signatures all indicated a significant contribution from CC to ambient levoglucosan in winter in Beijing. The results suggest that LG cannot be used as a distinct source marker for biomass burning in special cases such as some cities in the northern China, where coal is still widely used in the residential and industrial sectors. Biomass burning sources could be overestimated, although such an over-estimation could vary spatially and temporally. VL - 52 UR - https://pubs.acs.org/doi/10.1021/acs.est.7b05858 IS - 3 ER - TY - JOUR T1 - The rise and fall of an ancient Adélie penguin ‘supercolony’ at Cape Adare, Antarctica JF - Royal Society Open Science Y1 - 2018 A1 - Emslie, Steven D. A1 - McKenzie, Ashley A1 - Patterson, William P. KW - population movement KW - Pygoscelis adeliae KW - Ross Sea KW - sea level rise KW - Stable isotopes AB - We report new discoveries and radiocarbon dates on active and abandoned Adélie penguin (Pygoscelis adeliae) colonies at Cape Adare, Antarctica. This colony, first established at approximately 2000 BP (calendar years before present, i.e. 1950), is currently the largest for this species with approximately 338 000 breeding pairs, most located on low-lying Ridley Beach. We hypothesize that this colony first formed after fast ice began blocking open-water access by breeding penguins to the Scott Coast in the southern Ross Sea during a cooling period also at approximately 2000 BP. Our results suggest that the new colony at Cape Adare continued to grow, expanding to a large upper terrace above Ridley Beach, until it exceeded approximately 500 000 breeding pairs (a ‘supercolony’) by approximately 1200 BP. The high marine productivity associated with the Ross Sea polynya and continental shelf break supported this growth, but the colony collapsed to its present size for unknown reasons after approximately 1200 BP. Ridley Beach will probably be abandoned in the near future due to rising sea level in this region. We predict that penguins will retreat to higher elevations at Cape Adare and that the Scott Coast will be reoccupied by breeding penguins as fast ice continues to dissipate earlier each summer, restoring open-water access to beaches there. VL - 5 UR - https://royalsocietypublishing.org/doi/10.1098/rsos.172032 IS - 4 ER - TY - JOUR T1 - Riverine Export of Aged Carbon Driven by Flow Path Depth and Residence Time JF - Environmental Science & Technology Y1 - 2018 A1 - Barnes, Rebecca T. A1 - Butman, David E. A1 - Wilson, Henry F. A1 - Raymond, Peter A. AB - The flux of terrestrial C to rivers has increased relative to preindustrial levels, a fraction of which is aged dissolved organic C (DOC). In rivers, C is stored in sediments, exported to the ocean, or (bio)chemically processed and released as CO2. Disturbance changes land cover and hydrology, shifting potential sources and processing of DOC. To investigate the likely sources of aged DOC, we analyzed radiocarbon ages, chemical, and spectral properties of DOC and major ions from 19 rivers draining the coterminous U.S. and Arctic. DOC optics indicated that the majority is exported as aromatic, high molecular weight, modern molecules while aged DOC tended to consist of smaller, microbial degradation products. Aged DOC exports, observed regularly in arid basins and during base flow in arctic rivers, are associated with higher proportion of mineral weathering products, suggesting deeper flows paths. These patterns also indicate potential for production of microbial byproducts as DOC ages in soil and water with longer periods of time between production and transport. Thus, changes in hydrology associated with landscape alteration (e.g., tilling or shifting climates) that can result in deeper flow paths or longer residence times will likely lead to a greater proportion of aged carbon in riverine exports. VL - 52 UR - https://pubs.acs.org/doi/10.1021/acs.est.7b04717 IS - 3 ER - TY - JOUR T1 - The role of sediment compaction and groundwater withdrawal in local sea-level rise, Sandy Hook, New Jersey, USA JF - Quaternary Science Reviews Y1 - 2018 A1 - Johnson, Christopher S. A1 - Miller, Kenneth G. A1 - Browning, James V. A1 - Kopp, Robert E. A1 - Khan, Nicole S. A1 - Fan, Ying A1 - Stanford, Scott D. A1 - Horton, Benjamin P. KW - Marginal marine KW - North America KW - numerical modeling KW - Quaternary KW - Sea-level change KW - sedimentology AB - The rate of relative sea-level (RSL) rise at Sandy Hook, NJ (4.0 ± 0.5 mm/yr) was higher than The Battery, NY (3.0 ± 0.3 mm/yr) from 1900 to 2012 despite being separated by just 26 km. The difference cannot be explained by differential glacial isostatic adjustment (GIA; 1.4 ± 0.4 and 1.3 ± 0.4 mm/yr RSL rise, respectively) alone. We estimate the contribution of sediment compaction to subsidence at Sandy Hook using high-resolution grain size, percent organic matter, and porosity data from three upper Quaternary (≤13,350 cal yr) cores. The organic matter content (<2%) is too low to contribute to local subsidence. However, numerical modeling of the grain size-depth-age-porosity relationship indicates that compaction of deglacial silts likely reduced the column thickness by 10–20% over the past 13,350 cal yrs. While compaction rates were high immediately after the main silt deposition (13,350–13,150 cal yrs BP), rates decreased exponentially after deposition to an average 20th century rate of 0.16 mm/yr (90% Confidence Interval (C.I.), 0.06–0.32 mm/yr). The remaining ∼0.7 mm/yr (90% C.I. 0.3–1.2 mm/yr) difference in subsidence between Sandy Hook and The Battery is likely due to anthropogenic groundwater withdrawal. Historical data from Fort Hancock wells (2 km to the southeast of the Sandy Hook tide gauge) and previous regional work show that local and regional water extraction lowered the water levels in the aquifers underlying Sandy Hook. We suggest that the modern order of contribution to subsidence (highest to lowest) appears to be GIA, local/regional groundwater extraction, and compaction of thick Quaternary silts. VL - 181 UR - https://linkinghub.elsevier.com/retrieve/pii/S0277379117303657 ER - TY - JOUR T1 - Seafloor fluid seeps on Kimki Ridge, offshore southern California: Links to active strike-slip faulting JF - Deep Sea Research Part II: Topical Studies in Oceanography Y1 - 2018 A1 - Conrad, James E. A1 - Prouty, Nancy G. A1 - Walton, Maureen A.L. A1 - Kluesner, Jared W. A1 - Maier, Katherine L. A1 - McGann, Mary A1 - Brothers, Daniel S. A1 - Roland, Emily C. A1 - Dartnell, Peter KW - California Inner Continental Borderland KW - E/V Nautilus KW - Faulting KW - methane KW - Seepages AB - The Kimki Ridge fluid seeps are located in western Catalina Basin about 60 km southwest of the southern California mainland and at a water depth of approximately 1100 m. Multichannel seismic reflection profiles collected by the U.S. Geological Survey (USGS) in 2014 show acoustic transparency within the Kimki Ridge, suggesting the possibility of fluid seeps and possible sub-seafloor fluid pathways. Subsequent multibeam bathymetric and backscatter intensity data collected during a cooperative University of Washington/USGS cruise in early 2016 show subtle seafloor buildups with high acoustic backscatter (reflectivity) in three places along Kimki Ridge, supporting the existence of fluid seepage. A Remotely Operated Vehicle (ROV) dive, conducted as part of the Nautilus Exploration Program, took place in August 2016 to confirm the presence of these previously unknown seeps and document their characteristics as well as those of any associated biological communities. Two of the three seeps were explored by ROV, and showed abundant evidence of fluid seepage, including characteristic algal mats, chemosynthetic clams, and authigenic carbonate formation. The seeps are comprised of carbonate buildups 1–3 m thick and 300–500 m across. Within these areas, we interpret broad crater-like depressions 30–50 m across and 1–2 m deep to be individual seep vents. The seep areas appear to be broad zones of diffuse seepage that support chemosynthetic biologic communities; however, active venting was not observed. Geochemical analyses of rock samples collected from the seeps indicate microbially driven anaerobic oxidation of methane at or near the sediment water interface. Seismic-reflection profiles show chimney-like fluid pathways along the limbs and in the axis of the fold forming Kimki Ridge, and evidence of methane in shallow sediments can be traced into the adjacent Catalina Basin. A system of closely spaced faults located at the axis of the Kimki Ridge anticline may serve as pathways to allow fluid flow to the seafloor. Our data are consistent with other studies that suggest that transpression is an important component in the formation and localization of fluid seeps in a strike-slip setting, implying that seep formation may be a common occurrence at fault stepovers or transpressional bends in strike-slip systems. VL - 150 UR - https://linkinghub.elsevier.com/retrieve/pii/S0967064517301595 ER - TY - JOUR T1 - Slope failures within and upstream of Lake Quinault, Washington, as uneven responses to Holocene earthquakes along the Cascadia subduction zoneAbstract JF - Quaternary Research Y1 - 2018 A1 - Leithold, Elana L. A1 - Wegmann, Karl W. A1 - Bohnenstiehl, Delwayne R. A1 - Smith, Stephen G. A1 - Noren, Anders A1 - O’Grady, Ryan KW - Cascadia KW - Earthquake KW - lakes KW - Paleoseismic KW - Sediment AB - Investigation of Lake Quinault in western Washington, including a reflection seismic survey, analysis of piston cores, and preliminary mapping in the steep, landslide-prone Quinault River catchment upstream of the lake, reveals evidence for three episodes of earthquake disturbance in the past 3000 yr. These earthquakes triggered failures on the lake’s underwater slopes and delta front, as well as subaerial landsliding, partial channel blockage, and forced fluvial sediment aggradation. The ages of the three Lake Quinault disturbance events overlap with those of coseismically subsided, coastal marsh soils nearby in southwest Washington that are interpreted to record ruptures of the Cascadia megathrust. Absent from Lake Quinault, however, are signals of obvious disturbance from five additional subduction earthquakes inferred to have occurred during the period of record. The lack of evidence for these events may reflect the limitations of the data set derived from the detrital, river-dominated lake stratigraphy but may also have bearing on debates about segmentation and the distribution of slip along the Cascadia subduction zone during prior earthquakes. VL - 89 UR - https://www.cambridge.org/core/product/identifier/S0033589417000965/type/journal_article IS - 1 ER - TY - JOUR T1 - Sources and radiocarbon ages of aerosol organic carbon along the east coast of China and implications for atmospheric fossil carbon contributions to China marginal seas JF - Science of The Total Environment Y1 - 2018 A1 - Yu, Meng A1 - Guo, Zhigang A1 - Wang, Xuchen A1 - Eglinton, Timothy Ian A1 - Yuan, Zineng A1 - Xing, Lei A1 - Zhang, Hailong A1 - Zhao, Meixun KW - AEROSOLS KW - China marginal seas KW - Fossil carbon KW - Radiocarbon (14C) tracer KW - Total organic carbon AB - Aerosol deposition is an important mechanism for the delivery of terrestrial organic carbon (OC) to marginal seas, but OC age characteristics of aerosols are not well constrained and their contributions to sediment OC burial have not been quantified. Total suspended particle samples were collected along the east coast of China at Changdao (CD), Qingdao (QD) and Huaniao Island (HNI), and were analyzed for total organic carbon (TOC) isotopes (13C and 14C) in order to bridge this information gap. TOC δ13C and Δ14C values ranged from − 23.6 to − 30.5‰, and − 153 to − 687‰, respectively, with the latter corresponding to 14C ages ranging from 1280 to 9260 yr. Estimated contributions of fossil carbon to TOC based on 14C mass balance approach ranged from 26 to 73%, with strong seasonal variations in fossil carbon observed at CD. Fossil carbon at CD showed the highest proportion (73%) in winter, reflecting anthropogenic emissions and the lowest proportion (26%) in summer, caused by biomass contribution (annual ave., 52% ± 17%). In contrast, the fossil carbon at both QD (57–64%) and HNI (57–67%) dominated throughout the year, reflecting local anthropogenic influences and long-range transport. Mass balance estimates indicate that atmospheric deposition and riverine export accounted for 31% and 69% of fossil carbon inputs to the China marginal seas (CMS) respectively, with fossil carbon burial efficiencies approaching 100% in the CMS. On a global scale, an atmospheric fossil carbon deposition flux of 17.2 Tg C yr− 1 was estimated, equivalent to 40% of the estimated fluvial flux to the ocean, and potentially accounting for 24–41% of fossil OC burial in marine sediments. Therefore, the atmospheric deposition constitutes an important source of fossil carbon to marine sediments, and could play a key role in regional and global scale OC budgets and biogeochemical cycles. VL - 619-620 UR - https://linkinghub.elsevier.com/retrieve/pii/S004896971733259X ER - TY - JOUR T1 - Spatiotemporal Variation of the Quality, Origin, and Age of Particulate Organic Matter Transported by the Yangtze River (Changjiang) JF - Journal of Geophysical Research: Biogeosciences Y1 - 2018 A1 - Wu, Ying A1 - Eglinton, Timothy I. A1 - Zhang, Jing A1 - Montluçon, Daniel B. KW - Changjiang KW - organic carbon KW - radiocarbon KW - suspended particulate matter KW - Three Gorges Dam AB - Information on the age dynamics of particulate organic matter (POM) in large river systems is currently sparse and represents an important knowledge gap in our understanding of the global carbon cycle. Here we examine variations in organic geochemical characteristics of suspended sediments from the Changjiang (Yangtze River) system collected between 1997 and 2010. Higher particulate organic carbon content (POC%) values were observed in the middle reach, especially after 2003, and are attributed to the increase of in situ (aquatic) primary production associated with decreased total suspended matter concentrations. Corresponding C-14 values from depth profiles taken in 2009 and 2010 indicate spatial and temporal variations in POC sources within the basin. Two isotopic mass balance approaches were explored to quantitatively apportion different sources of Changjiang POM. Results indicate that contributions of biomass and pre-aged soil organic matter are dominant, regardless of hydrological conditions, with soil-derived organic carbon comprising 17-56% of POC based on a Monte Carlo three-end-member mixing model. In contrast, binary mixing model calculations suggest that up to 80% of POC (2009 samples only) derived from biospheric sources. The emplacement of the Three Gorges Dam and resulting trapping of sediment from the upper reach of the watershed resulted in a modification of POM C-14 ages in the reservoir. With the resulting decline in sediment load and increase in the proportion of modern POC in the lower reach, these changes in POM flux and composition of the Changjiang have significant implications for downstream carbon cycle processes. VL - 123 UR - http://doi.wiley.com/10.1029/2017JG004285http://onlinelibrary.wiley.com/wol1/doi/10.1029/2017JG004285/fullpdfhttps://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1029%2F2017JG004285 IS - 9 ER - TY - JOUR T1 - Tectonically-triggered sediment and carbon export to the Hadal zone JF - Nature Communications Y1 - 2018 A1 - Bao, Rui A1 - Strasser, Michael A1 - McNichol, Ann P. A1 - Haghipour, Negar A1 - McIntyre, Cameron A1 - Wefer, Gerold A1 - Eglinton, Timothy I. AB - Sediments in deep ocean trenches may contain crucial information on past earthquake history and constitute important sites of carbon burial. Here we present 14C data on bulk organic carbon (OC) and its thermal decomposition fractions produced by ramped pyrolysis/oxidation for a core retrieved from the >7.5 km-deep Japan Trench. High-resolution 14C measurements, coupled with distinctive thermogram characteristics of OC, reveal hemipelagic sedimentation interrupted by episodic deposition of pre-aged OC in the trench. Low δ13C values and diverse 14C ages of thermal fractions imply that the latter material originates from the adjacent margin, and the co-occurrence of pre-aged OC with intervals corresponding to known earthquake events implies tectonically triggered, gravity-flow-driven supply. We show that 14C ages of thermal fractions can yield valuable chronological constraints on sedimentary sequences. Our findings shed new light on links between tectonically driven sedimentological processes and marine carbon cycling, with implications for carbon dynamics in hadal environments. VL - 9 UR - http://www.nature.com/articles/s41467-017-02504-1http://www.nature.com/articles/s41467-017-02504-1.pdfhttp://www.nature.com/articles/s41467-017-02504-1.pdfhttp://www.nature.com/articles/s41467-017-02504-1 IS - 1 ER - TY - JOUR T1 - Temperature variations in the southern Great Lakes during the last deglaciation: Comparison between pollen and GDGT proxies JF - Quaternary Science Reviews Y1 - 2018 A1 - Watson, Benjamin I. A1 - Williams, John W. A1 - Russell, James M. A1 - Jackson, Stephen T. A1 - Shane, Linda A1 - Lowell, Thomas V. KW - Continental biomarkers KW - GDGT KW - Lagoons and Swamps KW - lakes KW - North America KW - paleoclimatology KW - Pleistocene KW - pollen KW - sedimentology AB - Our understanding of deglacial climate history in the southern Great Lakes region of the United States is primarily based upon fossil pollen data, with few independent and multi-proxy climate reconstructions. Here we introduce a new, well-dated fossil pollen record from Stotzel-Leis, OH, and a new deglacial temperature record based on branched glycerol dialkyl glycerol tetraethers (brGDGTs) at Silver Lake, OH. We compare these new data to previously published records and to a regional stack of pollen-based temperature reconstructions from Stotzel-Leis, Silver Lake, and three other well-dated sites. The new and previously published pollen records at Stotzel-Leis are similar, but our new age model brings vegetation events into closer alignment with known climatic events such as the Younger Dryas (YD). brGDGT-inferred temperatures correlate strongly with pollen-based regional temperature reconstructions, with the strongest correlation obtained for a global soil-based brGDGT calibration (r2 = 0.88), lending confidence to the deglacial reconstructions and the use of brGDGT and regional pollen stacks as paleotemperature proxies in eastern North America. However, individual pollen records show large differences in timing, rates, and amplitudes of inferred temperature change, indicating caution with paleoclimatic inferences based on single-site pollen records. From 16.0 to 10.0ka, both proxies indicate that regional temperatures rose by ∼10 °C, roughly double the ∼5 °C estimates for the Northern Hemisphere reported in prior syntheses. Change-point analysis of the pollen stack shows accelerated warming at 14.0 ± 1.2ka, cooling at 12.6 ± 0.4ka, and warming from 11.6 ± 0.5ka into the Holocene. The timing of Bølling-Allerød (B-A) warming and YD onset in our records lag by ∼300–500 years those reported in syntheses of temperature records from the northern mid-latitudes. This discrepancy is too large to be attributed to uncertainties in radiocarbon dating, and correlation between pollen and brGDGT temperature reconstructions rules out vegetation lags as a cause. However, the YD termination appears synchronous among the brGDGT record, regional pollen stack, and Northern Hemisphere stack. The cause of the larger and lagged temperature changes in the southern Great Lakes relative to Northern Hemisphere averages remains unclear, but may be due to the effects of continentality and ice sheet extent on regional climate evolution. VL - 182 UR - https://linkinghub.elsevier.com/retrieve/pii/S0277379117306467 ER - TY - JOUR T1 - Tracing biogeochemical subsidies from glacier runoff into Alaska's coastal marine food webs JF - Global Change Biology Y1 - 2018 A1 - Arimitsu, Mayumi L. A1 - Hobson, Keith A. A1 - Webber, D'Arcy N. A1 - Piatt, John F. A1 - Hood, Eran W. A1 - Fellman, Jason B. KW - Bayesian isotope mixing model KW - glacier runoff KW - marine ecosystem KW - marine food web KW - δ13C KW - Δ14C KW - δ15N KW - δ2H AB - Nearly half of the freshwater discharge into the Gulf of Alaska originates from landscapes draining glacier runoff, but the influence of the influx of riverine organic matter on the trophodynamics of coastal marine food webs is not well understood. We quantified the ecological impact of riverine organic matter subsidies to glacier‐marine habitats by developing a multi‐trophic level Bayesian three‐isotope mixing model. We utilized large gradients in stable (δ13C, δ15N, δ2H) and radiogenic (Δ14C) isotopes that trace riverine and marine organic matter sources as they are passed from lower to higher trophic levels in glacial‐marine habitats. We also compared isotope ratios between glacial‐marine and more oceanic habitats. Based on isotopic measurements of potential baseline sources, ambient water and tissues of marine consumers, estimates of the riverine organic matter source contribution to upper trophic‐level species including fish and seabirds ranged from 12% to 44%. Variability in resource use among similar taxa corresponded to variation in species distribution and life histories. For example, riverine organic matter assimilation by the glacier‐nesting seabirds Kittlitz's murrelet (Brachyramphus brevirostris) was greater than that of the forest‐nesting marbled murrelet (B. marmoratus). The particulate and dissolved organic carbon in glacial runoff and near surface coastal waters was aged (12100–1500 years BP 14C‐age) but dissolved inorganic carbon and biota in coastal waters were young (530 years BP 14C‐age to modern). Thus terrestrial‐derived subsidies in marine food webs were primarily composed of young organic matter sources released from glacier ecosystems and their surrounding watersheds. Stable isotope compositions also revealed a divergence in food web structure between glacial‐marine and oceanic sites. This work demonstrates linkages between terrestrial and marine ecosystems, and facilitates a greater understanding of how climate‐driven changes in freshwater runoff have the potential to alter food web dynamics within coastal marine ecosystems in Alaska. VL - 24 UR - https://onlinelibrary.wiley.com/doi/full/10.1111/gcb.13875 IS - 1 ER - TY - JOUR T1 - Tropical peatland carbon storage linked to global latitudinal trends in peat recalcitrance JF - Nature Communications Y1 - 2018 A1 - Hodgkins, Suzanne B. A1 - Richardson, Curtis J. A1 - Dommain, René A1 - Wang, Hongjun A1 - Glaser, Paul H. A1 - Verbeke, Brittany A1 - Winkler, B. Rose A1 - Cobb, Alexander R. A1 - Rich, Virginia I. A1 - Missilmani, Malak A1 - Flanagan, Neal A1 - Ho, Mengchi A1 - Hoyt, Alison M. A1 - Harvey, Charles F. A1 - Vining, S. Rose A1 - Hough, Moira A. A1 - Moore, Tim R. A1 - Richard, Pierre J. H. A1 - De La Cruz, Florentino B. A1 - Toufaily, Joumana A1 - Hamdan, Rasha A1 - Cooper, William T. A1 - Chanton, Jeffrey P. AB - Peatlands represent large terrestrial carbon banks. Given that most peat accumulates in boreal regions, where low temperatures and water saturation preserve organic matter, the existence of peat in (sub)tropical regions remains enigmatic. Here we examined peat and plant chemistry across a latitudinal transect from the Arctic to the tropics. Near-surface low-latitude peat has lower carbohydrate and greater aromatic content than near-surface high-latitude peat, creating a reduced oxidation state and resulting recalcitrance. This recalcitrance allows peat to persist in the (sub)tropics despite warm temperatures. Because we observed similar declines in carbohydrate content with depth in high-latitude peat, our data explain recent field-scale deep peat warming experiments in which catotelm (deeper) peat remained stable despite temperature increases up to 9 °C. We suggest that high-latitude deep peat reservoirs may be stabilized in the face of climate change by their ultimately lower carbohydrate and higher aromatic composition, similar to tropical peats. VL - 9 UR - http://www.nature.com/articles/s41467-018-06050-2 IS - 1 ER - TY - JOUR T1 - Unifying Concepts Linking Dissolved Organic Matter Composition to Persistence in Aquatic EcosystemsUnifying Concepts Linking Dissolved Organic Matter Composition to Persistence in Aquatic Ecosystems JF - Environmental Science & Technology Y1 - 2018 A1 - Kellerman, Anne M. A1 - Guillemette, François A1 - Podgorski, David C. A1 - Aiken, George R. A1 - Butler, Kenna D. A1 - Spencer, Robert G. M. AB - The link between composition and reactivity of dissolved organic matter (DOM) is central to understanding the role aquatic systems play in the global carbon cycle; yet, unifying concepts driving molecular composition have yet to be established. We characterized 37 DOM isolates from diverse aquatic ecosystems, including their stable and radiocarbon isotopes (δ13C-dissolved organic carbon (DOC) and Δ14C-DOC), optical properties (absorbance and fluorescence), and molecular composition (ultrahigh resolution mass spectrometry). Isolates encompassed end-members of allochthonous and autochthonous DOM from sites across the United States, the Pacific Ocean, and Antarctic lakes. Modern Δ14C-DOC and optical properties reflecting increased aromaticity, such as carbon specific UV absorbance at 254 nm (SUVA254), were directly related to polyphenolic and polycyclic aromatic compounds, whereas enriched δ13C-DOC and optical properties reflecting autochthonous end-members were positively correlated to more aliphatic compounds. Furthermore, the two sets of autochthonous end-members (Pacific Ocean and Antarctic lakes) exhibited distinct molecular composition due to differences in extent of degradation. Across all sites and end-members studied, we find a consistent shift in composition with aging, highlighting the persistence of certain biomolecules concurrent with degradation time. VL - 52 UR - https://pubs.acs.org/doi/10.1021/acs.est.7b05513 IS - 5 ER - TY - BOOK T1 - Using Stable and Radiocarbon Analyses as a Forensic Tool to Find Evidence of Oil in the Particulates of the Water Column and on the Seafloor Following the 2010 Gulf of Mexico Oil Spill Y1 - 2018 A1 - Bosman, Samantha H. A1 - Chanton, Jeffrey P. A1 - Rogers, Kelsey L. KW - Deepwater Horizon KW - isotopes KW - methane KW - Petrocarbon KW - POCsin KW - POCsusp KW - Sediment AB - Over 600 million liters of oil and copious amounts of methane were released into the Gulf of Mexico between April 20, 2010 and July 15, 2010. We used stable and radiocarbon analyses as a forensic tool to trace these hydrocarbons from the Deepwater Horizon (DwH) well into suspended particulate organic carbon (POCsusp), sinking particulate organic carbon (POCsink), and sedimentary organic carbon on the seafloor. POCsusp samples were considerably depleted both in δ13C and Δ14C relative to surface production, with δ13C and Δ14C values as low as −37.2‰ and −618‰, respectively. POCsink time series data revealed a modern Δ14C value due to a large diatom bloom in early September 2010, but values became depleted as oil contaminated particles continued to descend in the water column until the end of the year. Sediment cores collected in the vicinity of the DwH wellhead revealed evidence of oil contamination in the surface layer (0–1 cm), as indicated by a depletion in Δ14C values compared to the layers below the surface. In addition to providing evidence of oil contamination using stable and radiocarbon analyses, our study was consistent with the existence of a pathway by which spilled oil was deposited onto the seafloor. PB - Elsevier SN - 9780128044346 UR - https://linkinghub.elsevier.com/retrieve/pii/B978012804434600029X ER - TY - JOUR T1 - Variability in carbon uptake and (re)cycling in Antarctic cryptoendolithic microbial ecosystems demonstrated through radiocarbon analysis of organic biomarkers JF - Geobiology Y1 - 2018 A1 - Brady, A. L. A1 - Goordial, J. A1 - Sun, H. J. A1 - Whyte, L. G. A1 - Slater, G. F. AB - Cryptoendolithic lichens and cyanobacteria living in porous sandstone in the high‐elevation McMurdo Dry Valleys are purported to be among the slowest growing organisms on Earth with cycles of death and regrowth on the order of 103–104 years. Here, organic biomarker and radiocarbon analysis were used to better constrain ages and carbon sources of cryptoendoliths in University Valley (UV; 1,800 m.a.s.l) and neighboring Farnell Valley (FV; 1,700 m.a.s.l). Δ14C was measured for membrane component phospholipid fatty acids (PLFA) and glycolipid fatty acids, as well as for total organic carbon (TOC). PLFA concentrations indicated viable cells comprised a minor (<0.5%) component of TOC. TOC Δ14C values ranged from −272‰ to −185‰ equivalent to calibrated ages of 1,100–2,550 years old. These ages may be the result of fractional preservation of biogenic carbon and/or sudden large‐scale community death and extended period(s) of inactivity prior to slow recolonization and incorporation of 14C‐depleted fossil material. PLFA Δ14C values were generally more modern than the corresponding TOC and varied widely between sites; the FV PLFA Δ14C value (+40‰) was consistent with modern atmospheric CO2, while UV values ranged from −199‰ to −79‰ (calibrated ages of 1,665–610 years). The observed variability in PLFA Δ14C depletions is hypothesized to reflect variations in the extent of fixation of modern atmospheric CO2 and the preservation and recycling of older organic carbon by the community in various stages of sandstone recolonization. PLFA profiles and microbial community compositions as determined by molecular genetic characterizations and microscopy differed between the two valleys (e.g., predominance of biomarker 18:2 [>50%] in FV compared to UV), representing microbial communities that may reflect distinct stages of sandstone recolonization and/or environmental conditions. It is thus proposed that Dry Valley cryptoendolithic microbial communities are faster growing than previously estimated. VL - 16 UR - http://doi.wiley.com/10.1111/gbi.2018.16.issue-1 IS - 1 ER - TY - JOUR T1 - Variance and Rate-of-Change as Early Warning Signals for a Critical Transition in an Aquatic Ecosystem State: A Test Case From Tasmania, Australia JF - Journal of Geophysical Research: Biogeosciences Y1 - 2018 A1 - Beck, Kristen K. A1 - Fletcher, Michael-Shawn A1 - Gadd, Patricia S. A1 - Heijnis, Henk A1 - Saunders, Krystyna M. A1 - Simpson, Gavin L. A1 - Zawadzki, Atun KW - carbon and nitrogen stable isotopes KW - critical transitions KW - diatoms KW - early warning signals KW - polleen KW - Tasmania AB - Critical transitions in ecosystem states are often sudden and unpredictable. Consequently, there is a concerted effort to identify measurable early warning signals (EWS) for these important events. Aquatic ecosystems provide an opportunity to observe critical transitions due to their high sensitivity and rapid response times. Using palaeoecological techniques, we can measure properties of time series data to determine if critical transitions are preceded by any measurable ecosystem metrics, that is, identify EWS. Using a suite of palaeoenvironmental data spanning the last 2,400 years (diatoms, pollen, geochemistry, and charcoal influx), we assess whether a critical transition in diatom community structure was preceded by measurable EWS. Lake Vera, in the temperate rain forest of western Tasmania, Australia, has a diatom community dominated by Discostella stelligera and undergoes an abrupt compositional shift at ca. 820 cal yr BP that is concomitant with increased fire disturbance of the local vegetation. This shift is manifest as a transition from less oligotrophic acidic diatom flora (Achnanthidium minutissimum, Brachysira styriaca, and Fragilaria capucina) to more oligotrophic acidic taxa (Frustulia elongatissima, Eunotia diodon, and Gomphonema multiforme). We observe a marked increase in compositional variance and rate‐of‐change prior to this critical transition, revealing these metrics are useful EWS in this system. Interestingly, vegetation remains complacent to fire disturbance until after the shift in the diatom community. Disturbance taxa invade and the vegetation system experiences an increase in both compositional variance and rate‐of‐change. These trends imply an approaching critical transition in the vegetation and the probable collapse of the local rain forest system. VL - 123 UR - http://doi.wiley.com/10.1002/2017JG004135 IS - 2 ER - TY - JOUR T1 - Vegetation responses to late Holocene climate changes in an Andean forest JF - Quaternary Research Y1 - 2018 A1 - Schiferl, Jacob D. A1 - Bush, Mark B. A1 - Silman, Miles R. A1 - Urrego, Dunia H. KW - Cloud forest KW - Dictyocaryum KW - Fossil pollen KW - Little ice age KW - Medieval Climate Anomaly KW - seasonality KW - Tropical ecology AB - A paleoecological record from Lake Palotoa (1370 m elevation) in the Andean foothills of Peru spans the last 3800 years. Lake Palotoa lies near the modern cloud base in a location sensitive to changes in atmospheric moisture. In many areas, these forests have been destroyed, but Lake Palotoa shows no sign of human occupation today or in the past. The modern forest surrounding the lake is dominated by the Andean palm, Dictyocaryum lamarckianum, which is also the most abundant taxon in the fossil pollen record. Fossil pollen data show the vegetation assemblages have not experienced strong compositional changes in the late Holocene. Global-scale climatic events such as the Medieval Climate Anomaly (MCA) and the Little Ice Age (LIA) are identified within the record, though the vegetation responses are subtle. Hedyosmum and Sloanea pollen percentages increase near the onset of the MCA and may reflect decreased seasonality. The LIA coincides with increased Hedyosmum pollen percentages, and increases in Clethra and Begonia, two elements that tend to occupy forests now found at higher elevations. Our findings demonstrate the stability of montane forest systems to natural Holocene climate change. VL - 89 UR - https://www.cambridge.org/core/product/identifier/S0033589417000643/type/journal_article IS - 1 ER - TY - JOUR T1 - 3000 Years of Human Subsistence and Estuarine Resource Exploitation on the Rhode River Estuary, Chesapeake Bay, Maryland JF - Journal of the North Atlantic Y1 - 2017 A1 - Rick, Torben C. A1 - Reeder-Myers, Leslie A. A1 - Carr, Michael J. A1 - Hines, Anson H. AB - Chesapeake Bay is home to highly productive marine ecosystems that were a key part of Native American subsistence for millennia. Despite a number of archaeological projects focused on Chesapeake Bay prehistory, key questions remain about the nature of human use of the estuary through time and across space. Recent work at 7 shell middens on the Rhode River Estuary, MD, provides insight into human subsistence and estuarine res ource exploitation from ∼3200 years ago through the mid-19th century. This is an important diachronic sequence of coastal land use and subsistence for the Chesapeake and helps fill a gap in our understanding of coastal adaptations along North America's Atlantic Coast. Despite climate change, fluctuating sea levels, and the likely appearance of maize agriculture in the area ∼1000 years ago, Native American exploitation of oysters and estuarine resources remained fairly consistent across the Early to Late Woodland. These data stand in contrast to the mid-1800s assemblage, which was likely deposited by 19th-century Euro-Americans and contains overall larger oysters perhaps obtained from deeper waters that may not have been a focus of Native American harvest. When placed in the context of other regional data, our analysis illustrates the value of shell middens for helping understand human subsistence strategies and the historical ecol ogy of the North American Atlantic Coast. VL - 1001 UR - http://www.bioone.org/doi/10.3721/037.002.sp1011 ER - TY - JOUR T1 - The 3.6 ka Aniakchak tephra in the Arctic Ocean: a constraint on the Holocene radiocarbon reservoir age in the Chukchi Sea JF - Climate of the Past Y1 - 2017 A1 - Pearce, Christof A1 - Varhelyi, Aron A1 - Wastegård, Stefan A1 - Muschitiello, Francesco A1 - Barrientos, Natalia A1 - O'Regan, Matt A1 - Cronin, Thomas M. A1 - Gemery, Laura A1 - Semiletov, Igor A1 - Backman, Jan A1 - Jakobsson, Martin AB - The caldera-forming eruption of the Aniakchak volcano in the Aleutian Range on the Alaskan Peninsula at 3.6 cal kyr BP was one of the largest Holocene eruptions worldwide. The resulting ash is found as a visible sediment layer in several Alaskan sites and as a cryptotephra on Newfoundland and Greenland. This large geographic distribution, combined with the fact that the eruption is relatively well constrained in time using radiocarbon dating of lake sediments and annual layer counts in ice cores, makes it an excellent stratigraphic marker for dating and correlating mid–late Holocene sediment and paleoclimate records. This study presents the outcome of a targeted search for the Aniakchak tephra in a marine sediment core from the Arctic Ocean, namely Core SWERUS-L2-2-PC1 (2PC), raised from 57 m water depth in Herald Canyon, western Chukchi Sea. High concentrations of tephra shards, with a geochemical signature matching that of Aniakchak ash, were observed across a more than 1.5 m long sediment sequence. Since the primary input of volcanic ash is through atmospheric transport, and assuming that bioturbation can account for mixing up to ca. 10 cm of the marine sediment deposited at the coring site, the broad signal is interpreted as sustained reworking at the sediment source input. The isochron is therefore placed at the base of the sudden increase in tephra concentrations rather than at the maximum concentration. This interpretation of major reworking is strengthened by analysis of grain size distribution which points to ice rafting as an important secondary transport mechanism of volcanic ash. Combined with radiocarbon dates on mollusks in the same sediment core, the volcanic marker is used to calculate a marine radiocarbon reservoir age offset ΔR = 477 ± 60 years. This relatively high value may be explained by the major influence of typically "carbon-old" Pacific waters, and it agrees well with recent estimates of ΔR along the northwest Alaskan coast, possibly indicating stable oceanographic conditions during the second half of the Holocene. Our use of a volcanic absolute age marker to obtain the marine reservoir age offset is the first of its kind in the Arctic Ocean and provides an important framework for improving chronologies and correlating marine sediment archives in this region. Core 2PC has a high sediment accumulation rate averaging 200 cm kyr throughout the last 4000 years, and the chronology presented here provides a solid base for high-resolution reconstructions of late Holocene climate and ocean variability in the Chukchi Sea. VL - 13 UR - https://cp.copernicus.org/articles/13/303/2017/ IS - 4 ER - TY - JOUR T1 - A ~6000 yr diatom record of mid- to late Holocene fluctuations in the level of Lago Wiñaymarca, Lake Titicaca (Peru/Bolivia)Abstract JF - Quaternary Research Y1 - 2017 A1 - Weide, D. Marie A1 - Fritz, Sherilyn C. A1 - Hastorf, Christine A. A1 - Bruno, Maria C. A1 - Baker, Paul A. A1 - Guedron, Stephane A1 - Salenbien, Wout KW - diatoms KW - Lago Huiñaimarca KW - Lago Wiñaymarca KW - Lake level KW - lake titicaca KW - Mid-Holocene KW - Tropical Andes AB - A multidecadal-scale lake-level reconstruction for Lago Wiñaymarca, the southern basin of Lake Titicaca, has been generated from diatom species abundance data. These data suggest that ~6500 cal yr BP Lago Wiñaymarca was dry, as indicated by a sediment unconformity. At ~4400 cal yr BP, the basin began to fill, as indicated by the dominance of shallow epiphytic species. It remained somewhat saline with extensive wetlands and abundant aquatic plants until ~3800 cal yr BP, when epiphytic species were replaced by planktic saline-indifferent species, suggesting a saline shallow lake. Wiñaymarca remained a relatively shallow lake that fluctuated on a multidecadal scale until ~1250 cal yr BP, when freshwater planktic species increased, suggesting a rise in lake level with a concomitant decrease in salinity. The lake became gradually fresher, dominated by deep, freshwater species from ~850 cal yr BP. By ~80 cal yr BP, saline-tolerant species were rare, and the lake was dominated by freshwater planktic diatoms, resembling the fresh and deep lake of today. These results reveal a more dynamic and chronologically specific record of lake-level fluctuations and associated ecological conditions that provide important new data for paleoclimatologists and archaeologists, to better understand human-environmental dynamics during the mid- to late Holocene. VL - 88 UR - https://www.cambridge.org/core/product/identifier/S0033589417000497/type/journal_article IS - 2 ER - TY - JOUR T1 - A 7000-year history of coastal environmental changes from Mexico’s Pacific coast: A multi-proxy record from Laguna Mitla, Guerrero JF - The Holocene Y1 - 2017 A1 - Bianchette, Thomas A A1 - McCloskey, Terrence A A1 - Liu, Kam-biu KW - El Nino-Southern Oscillation KW - Laguna Mitla KW - mangroves KW - Pacific coast of Mexico KW - Paleoclimate KW - paleoenvironmental reconstruction KW - pollen KW - Sediment KW - tropical cyclones KW - x-ray fluorescence AB - The lack of multi-millennial multi-proxy paleoenvironmental reconstructions from Mexico’s Pacific coast has limited our understanding of the regional response to climate change and sea-level rise. A 479-cm core covering the last 6900 years was extracted from Laguna Mitla in the state of Guerrero on Mexico’s Pacific coast. Beginning as a Rhizophora-dominated salt pan ~6900 yr BP, at ~6500 yr BP, the site transitioned to a mangrove swamp dominated by Laguncularia, which lasted about 300 years. The beach barrier formed from ~6200 to 5200 yr BP, during which time, the site existed as an intermittently sheltered bay, the result of large, rapid changes in wave energy associated with the shifting barrier location and changes in stability. After the beach barrier was stabilized at ~5200 yr BP, water level at the coring site became a function of precipitation rather than sea level. Since that time, deposition has alternated between peat, laid down in a mangrove swamp, and clay intervals characterized by high concentrations of titanium and a predominantly regional pollen signal, representing open-water lagoon phases. Seven periods of increased water level, varying in duration, occurred during the backbarrier period, with El Niño-Southern Oscillation (ENSO) likely the main climatic mechanism causing these periodic shifts in the paleo-precipitation levels. We suggest that the deepest water levels detected over the last ~3200 years correlate with periods of increased ENSO activity. The spatial distribution of tropical cyclone rainfall, which represents a significant percentage of total annual precipitation along Mexico’s Pacific coast, may explain the inconsistencies between our record and paleoclimatic records from Mexico’s interior, but more work is needed to test this hypothesis. VL - 27 UR - http://journals.sagepub.com/doi/10.1177/0959683616687379 IS - 8 ER - TY - JOUR T1 - African Baobabs with a Very Large Number of Stems and False Stems: Radiocarbon Investigation of the Baobab of Warang JF - Studia Universitatis Babeș-Bolyai Chemia Y1 - 2017 A1 - Patrut, Adrian A1 - Garnaud, ébastien A1 - Ka, Oumar A1 - Patrut, Roxana T. A1 - Diagne, Tomas A1 - Lowy, Daniel A. A1 - Forizs, Edit A1 - Bodis, ő A1 - von Reden, Karl F. KW - Adansonia digitata KW - Age determination KW - AMS radiocarbon dating KW - inner cavity KW - multiple stems KW - tropical trees AB - The article presents the AMS (accelerator mass spectrometry) radiocarbon dating results of the baobab of Warang, Senegal. The investigation of the baobab revealed that it consists of 18 partially fused stems, which represents the largest number of stems reported for an African baobab. Three stems build the ring that closes a false cavity, while 15 stems grow outside the ring. Seven wood samples were collected from the false cavity and from the outer part of other stems. The dating results evinced that the stems belong to four different generations, out of which the first generation is around 500 years old. We also documented the presence of false stems, which emerge from a large adjacent stem, are triangular in horizontal section and act as an anchor. The baobab of Warang possesses 12 ordinary stems and 6 false stems. VL - 62 UR - http://chem.ubbcluj.ro/~studiachemia/http://chem.ubbcluj.ro/~studiachemia/chemia2017_1.htmlhttp://www.chem.ubbcluj.ro/~studiachemia/issues/chemia2017_1/09Patrut_etal_111_120.pdf IS - 1 ER - TY - JOUR T1 - Age Constraints on Gulf of Mexico Deep Water Ventilation as Determined by 14C MeasurementsAbstract JF - Radiocarbon Y1 - 2017 A1 - Chapman, Piers A1 - DiMarco, Steven F A1 - Key, Robert M A1 - Previti, Connie A1 - Yvon-Lewis, Shari KW - Gulf of Mexico KW - radiocarbon AMS dating KW - water AB - While the exchange of water through Yucatan Strait is reasonably well known, the age of the deep water in both the Caribbean Sea and Gulf of Mexico is not. We recently measured the radiocarbon (14C) concentrations in deep water in the Gulf of Mexico from a line of stations along 90°30′W. The mean apparent age of water below 900 m, the depth of the Florida Strait sill, was found to be about 740 yr relative to the 1950 14C standard. Depending on how the corrections for biological activity in the upper water are applied, this converts to a “true” age of between 231 ± 28 and 293 ± 74 yr. These ages agree with a previous estimate of the age of the deep water in the Gulf of Mexico based on heat flows, put upper limits on the age of the deep water in the Caribbean Sea, and provide constraints on modelers for the return of deep water from the Gulf of Mexico to the Caribbean. This might be important in the event of a future deep water oil or other chemical spill in the region. UR - https://www.cambridge.org/core/product/identifier/S0033822217000807/type/journal_articlehttps://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0033822217000807 ER - TY - JOUR T1 - Aged dissolved organic carbon exported from rivers of the Tibetan Plateau JF - PLOS ONE Y1 - 2017 A1 - Qu, Bin A1 - Sillanpää, Mika A1 - Li, Chaoliu A1 - Kang, Shichang A1 - Stubbins, Aron A1 - Yan, Fangping A1 - Aho, Kelly Sue A1 - Zhou, Feng A1 - Raymond, Peter A. ED - Lin, Senjie KW - Carbon cycle KW - Carbon dioxide KW - Climate change KW - Rain KW - Rivers KW - Surface water KW - Tibetan people KW - TIBETAN PLATEAU AB - The role played by river networks in regional and global carbon cycle is receiving increasing attention. Despite the potential of radiocarbon measurements (14C) to elucidate sources and cycling of different riverine carbon pools, there remain large regions such as the climate-sensitive Tibetan Plateau for which no data are available. Here we provide new 14C data on dissolved organic carbon (DOC) from three large Asian rivers (the Yellow, Yangtze and Yarlung Tsangpo Rivers) running on the Tibetan Plateau and present the carbon transportation pattern in rivers of the plateau versus other river system in the world. Despite higher discharge rates during the high flow season, the DOC yield of Tibetan Plateau rivers (0.41 gC m-2 yr-1) was lower than most other rivers due to lower concentrations. Radiocarbon ages of the DOC were older/more depleted (511±294 years before present, yr BP) in the Tibetan rivers than those in Arctic and tropical rivers. A positive correlation between radiocarbon age and permafrost watershed coverage was observed, indicating that 14C-deplted/old carbon is exported from permafrost regions of the Tibetan Plateau during periods of high flow. This is in sharp contrast to permafrost regions of the Arctic which export 14C-enriched carbon during high discharge periods. VL - 12 UR - https://dx.plos.org/10.1371/journal.pone.0178166 IS - 5 ER - TY - JOUR T1 - Allochthonous sources and dynamic cycling of ocean dissolved organic carbon revealed by carbon isotopes JF - GEOPHYSICAL RESEARCH LETTERS Y1 - 2017 A1 - Zigah, Prosper K. A1 - McNichol, Ann P. A1 - Xu, Li A1 - Johnson, Carl A1 - Santinelli, Chiara A1 - Karl, David M. A1 - Repeta, Daniel J. KW - ATLANTIC BIGHT KW - BLACK CARBON KW - C-14 KW - HUMIC SUBSTANCES KW - MATTER KW - NORTH PACIFIC-OCEAN KW - RADIOCARBON ANALYSIS KW - SARGASSO SEA KW - SEAWATER KW - SPECTROMETRY AB - We present concentration and isotopic profiles of total, size, and polarity fractionated dissolved organic carbon (DOC) from Station ALOHA (A Long-term Oligotrophic Habitat Assessment), an oligotrophic site in the North Pacific Ocean. The data show that, between the surface and 3500 m, low molecular weight (LMW) hydrophilic DOC, LMW hydrophobic DOC, and high molecular weight (HMW) DOC constitute 22-33%, 45-52%, and 23-35% of DOC, respectively. LMW hydrophilic DOC is more isotopically depleted (delta C-13 of -23.9 parts per thousand to -31.5 parts per thousand and Delta C-14 of -304 parts per thousand to -795 parts per thousand; mean age of 2850 to 15000 years) than the LMW hydrophobic DOC (delta C-13 of -22 parts per thousand to -23 parts per thousand and Delta C-14 of -270 parts per thousand to -568 parts per thousand; 2470 to 6680 years) and HMW DOC (delta C-13 of similar to-21 parts per thousand and Delta C-14 of -24 parts per thousand to -294 parts per thousand; 135-2700 years). Our analyses suggest that a large fraction of DOC may be derived from allochthonous sources such as terrestrial and hydrothermal DOC and cycle on much longer time scales of > 10000 years or enter the ocean as preaged carbon. VL - 44 IS - 5 ER - TY - RPRT T1 - Analysis of piston cores and high-resolution sub-bottom profiler data, Baffin Bay slope, Nunavut Y1 - 2017 A1 - Campbell, D C A1 - Jenner, K A A1 - Higgins, J A1 - Piper, D J W AB - Preface This Open File report summarizes a set of 20 piston cores, up to 822 cm long, taken from the continental slope of Baffin Bay, Canada, in water depths between 833 and 1715 m. It provides down-core lithostratigraphy, physical properties measurements, core photography and core X-radiography, in addition to high-resolution seismic data over most core sites, selected grain size data and portable X-ray fluorescence data. Preliminary along-slope correlation between cores and AMS radiocarbon ages are also provided. Further information on these cores is available through the Expedition Database at http://ed.gdr.nrcan.gc.ca/index_e.php Acknowledgments We thank Dan Meagher, Jesse Sherwin and Meaghan MacQuarrie for assistance with core processing and core logging and Jessica Parkinson and Simon Poirier for core data compilation. Owen Brown completed grain size analyses and Linda Fan assisted with these analyses and plotted the grain size data.We also thank Kate Jarrett for assistance with core subsampling. UR - https://www.researchgate.net/publication/333259233_Analysis_of_piston_cores_and_high-resolution_sub-bottom_profiler_data_Baffin_Bay_slope_Nunavut ER - TY - JOUR T1 - Anthropogenic CO2 accumulation and uptake rates in the Pacific Ocean based on changes in the C-13/C-12 of dissolved inorganic carbon JF - GLOBAL BIOGEOCHEMICAL CYCLES Y1 - 2017 A1 - Quay, P. A1 - Sonnerup, R. A1 - Munro, D. A1 - Sweeney, C. KW - anthropogenic change KW - C-12 KW - C-13 KW - CO2 KW - Pacific Ocean AB - The anthropogenic CO2 accumulation rate for the Pacific Ocean was estimated from the decrease in C-13 of the dissolved inorganic carbon measured on six World Ocean Circulation Experiment cruises during the 1990s and repeated during Climate Variability and Predictability in the 2000s. A mean depth-integrated anthropogenic C-13 change of -8320mdecade(-1) was estimated for the basin by using the multiple linear regression approach. The largest anthropogenic C-13 decreases occurred between 40 degrees S and 60 degrees S, whereas the smallest decreases occurred in the Southern Ocean and subpolar North Pacific. A mean anthropogenic CO2 accumulation rate of 0.410.13molCm(-2)yr(-1) (0.820.26PgCyr(-1)) was determined based on observed C-13 changes and is in agreement with previous observation- and model-based estimates. The mean dissolved inorganic carbon DIC13 inventory change of -178 +/- 43 parts per thousand molm(-2)decade(-1) was primarily the result of air-sea CO2 exchange acting on the measured air-sea C-13 disequilibrium of similar to-1.2 +/- 0.1 parts per thousand. Regional differences between the DIC13 inventory change and air-sea (CO2)-C-13 flux yielded net anthropogenic CO2 uptake rates (independent of pCO(2)) that ranged from similar to 0 to 1molm(-2)yr(-1) and basin-wide mean of 1.2 +/- 1.5PgCyr(-1). High rates of surface ocean DIC increase and C-13 decrease observed in the Drake Passage (53 degrees S-60 degrees S) support above average anthropogenic CO2 accumulation since 2005. Observed C-13 changes in the Pacific Ocean indicate that ocean transport significantly impacted the anthropogenic CO2 distribution and illustrate the utility of C-13 as a tracer to unravel the processes controlling the present and future accumulation of anth ropogenic CO2 in the ocean. VL - 31 ER - TY - JOUR T1 - Assessing the Blank Carbon Contribution, Isotope Mass Balance, and Kinetic Isotope Fractionation of the Ramped Pyrolysis/Oxidation Instrument at NOSAMS JF - Radiocarbon Y1 - 2017 A1 - Hemingway, Jordon D A1 - Galy, Valier V A1 - Gagnon, Alan R A1 - Grant, Katherine E A1 - Rosengard, Sarah Z A1 - Soulet, Guillaume A1 - Zigah, Prosper K A1 - McNichol, Ann P KW - Ramped PyrOx; blank assessment; kinetic fractionation AB - We estimate the blank carbon mass over the course of a typical Ramped PyrOx (RPO) analysis (150-1000 degrees C; 5 degrees C x min(-1)) to be (3.7 +/- 0.6) mu g C with an Fm value of 0.555 +/- 0.042 and a delta C-13 value of (-29.0 +/- 0.1)parts per thousand VPDB. Additionally, we provide equations for RPO Fm and delta C-13 blank corrections, including associated error propagation. By comparing RPO mass-weighted mean and independently measured bulk delta C-13 values for a compilation of environmental samples and standard reference materials (SRMs), we observe a small yet consistent delta C-13 depletion within the RPO instrument (mean-bulk: mu = -0.8 parts per thousand; +/- 1 sigma = 0.9 parts per thousand; n = 66). In contrast, because they are fractionation-corrected by definition, mass-weighted mean Fm values accurately match bulk measurements (mean-bulk: mu = 0.005; +/- 1 sigma = 0.014; n = 36). Lastly, we show there exists no significant intra-sample delta C-13 variability across carbonate SRM peaks, indicating minimal mass-dependent kinetic isotope fractionation during RPO analysis. These data are best explained by a difference in activation energy between C-13- and C-12-containing compounds ((13-12)Delta E) of 0.3-1.8 J x mol(-1), indicating that blank and mass-balance corrected RPO delta C-13 values accurately retain carbon source isotope signals to within 1-2 parts per thousand. VL - 59223–22493970409 UR - https://www.cambridge.org/core/product/identifier/S0033822217000030/type/journal_article IS - 01 JO - Radiocarbon ER - TY - JOUR T1 - ASSESSING THE EFFECTS OF ANTHROPOGENIC EUTROPHICATION ON MARINE BIVALVE LIFE HISTORY IN THE NORTHERN GULF OF MEXICO JF - PALAIOS Y1 - 2017 A1 - HARNIK, PAUL G. A1 - TORSTENSON, MORGAN L. A1 - WILLIAMS, MARIO A. AB - Natural and anthropogenic eutrophication can increase food supply to basal consumers in aquatic food webs. All else being equal, increased food supply is expected to relax life history trade-offs between egg size and number, resulting in a reduction in egg size over time as individuals that produce more numerous, small eggs exhibit greater fitness. We tested this hypothesis by comparing the sizes of larval shells (PI) of the marine bivalve Nuculana acuta in living and death assemblages collected from surficial seafloor sediments on the Alabama continental shelf; PI size is positively correlated with egg size and can be measured from adult shells. We found that the mean PI size of living N. acuta was approximately three microns smaller than that of the associated death assemblage and that this difference was robust to potential taphonomic biases. This life history shift occurred relatively recently as no trend exists in PI size over the past 3100 years. The live-dead disagreement that we observed is consistent with the history of anthropogenic eutrophication in the Mississippi Bight. These data provide a baseline for comparison with other regions in the Gulf of Mexico that have more sustained histories of anthropogenic eutrophication. More broadly, live-dead comparisons of molluscan life history coupled with age dating of molluscan shells can complement community-level metrics when assessing the impacts of anthropogenic eutrophication on coastal ecosystems, and offer a unique study system for investigating life history adaptation in a field context. VL - 32 UR - https://pubs.geoscienceworld.org/palaios/article-lookup?doi=10.2110/palo.2017.033http://pubs.geoscienceworld.org/palaios/sepm/palaios/article-pdf/32/11/678/3994556/i0883-1351-32-11-678.pdf IS - 11 ER - TY - JOUR T1 - Biogeochemical properties of sinking particles in the southwestern part of the East Sea (Japan Sea) JF - Journal of Marine Systems Y1 - 2017 A1 - Minkyoung Kim A1 - Jeomshik Hwang A1 - TaeKeun Rho A1 - Tongsup Lee A1 - Dong-Jin Kang A1 - Kyung-Il Chang A1 - Suyun Noh A1 - HuiTae Joo A1 - Jung Hyun Kwak A1 - Chang-Keun Kang A1 - Kyung-Ryul Kim KW - East Sea (Japan Sea) AB - Abstract This study investigates the biological pump system in the East Sea (Japan Sea) by conducting an analysis of the total particle flux, biogenic material composition, and carbon isotope ratios of sinking particles. The samples were collected for one year starting from March 2011 using time-series sediment traps deployed at depths of 1040 m and 2280 m on bottom-tethered mooring at Station \{EC1\} (37.33°N, 131.45°E; 2300 m water depth) in the Ulleung Basin (UB), southwestern part of the East Sea. The temporal variation in the particulate organic carbon (POC) flux at 1000 m shows a good relationship with the primary production in the corresponding surface water. The ratio of \{POC\} flux at 1000 m to satellite-based primary production in the corresponding region in the \{UB\} was   3%, which is comparable to the values of 2 to 5% estimated from previous studies of other part of the East Sea. The lithogenic material accounted for > 17% of the sinking particles at 1000 m and for a larger fraction of 40 to 60% at 2280 m. The radiocarbon contents of the sinking \{POC\} at both trap depths imply the additional supply of aged POC, with a much greater contribution at 2280 m. Overall, the particle flux in the deep interior of the East Sea appears to be controlled by the supply of complex sources, including aeolian input, the lateral supply of resuspended sediments, and biological production in the surface water. VL - 167 UR - http://www.sciencedirect.com/science/article/pii/S0924796316303608 ER - TY - JOUR T1 - Biological and physical controls on the flux and characteristics of sinking particles on the Northwest Atlantic margin JF - Journal of Geophysical Research: Oceans Y1 - 2017 A1 - Hwang, Jeomshik A1 - Manganini, Steven J. A1 - Park, JongJin A1 - çon, Daniel B. A1 - Toole, John M. A1 - Eglinton, Timothy I. AB - Biogenic matter characteristics and radiocarbon contents of organic carbon (OC) were examined on sinking particle samples intercepted at three nominal depths of 1000 m, 2000 m, and 3000 m (similar to 50 m above the seafloor) during a 3 year sediment trap program on the New England slope in the Northwest Atlantic. We have sought to characterize the sources of sinking particles in the context of vertical export of biogenic particles from the overlying water column and lateral supply of resuspended sediment particles from adjacent margin sediments. High aluminum (Al) abundances and low OC radiocarbon contents indicated contributions from resuspended sediment which was greatest at 3000 m but also significant at shallower depths. The benthic source (i.e., laterally supplied resuspended sediment) of opal appears negligible based on the absence of a correlation with Al fluxes. In comparison, CaCO3 fluxes at 3000 m showed a positive correlation with Al fluxes. Benthic sources accounted for 42 similar to 63% of the sinking particle flux based on radiocarbon mass balance and the relationship between Al flux and CaCO3 flux. Episodic pulses of Al at 3000 m were significantly correlated with the near-bottom current at a nearby hydrographic mooring site, implying the importance of current variability in lateral particle transport. However, Al fluxes at 1000 m and 2000 m were coherent but differed from those at 3000 m, implying more than one mode of lateral supply of particles in the water column. VL - 122 UR - http://doi.wiley.com/10.1002/jgrc.v122.6http://doi.wiley.com/10.1002/2016JC012549http://onlinelibrary.wiley.com/wol1/doi/10.1002/2016JC012549/fullpdfhttps://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2F2016JC012549 IS - 636C5 ER - TY - JOUR T1 - Carbon geochemistry of plankton-dominated samples in the Laptev and East Siberian shelves: contrasts in suspended particle composition JF - Ocean Science Y1 - 2017 A1 - Tesi, Tommaso A1 - Geibel, Marc C. A1 - Pearce, Christof A1 - Panova, Elena A1 - Vonk, Jorien E. A1 - Karlsson, Emma A1 - Salvado, Joan A. A1 - Kruså, Martin A1 - Broder, Lisa A1 - Humborg, Christoph A1 - Semiletov, Igor A1 - Gustafsson, Örjan AB - Recent Arctic studies suggest that sea ice decline and permafrost thawing will affect phytoplankton dynamics and stimulate heterotrophic communities. However, in what way the plankton composition will change as the warming proceeds remains elusive. Here we investigate the chemical signature of the plankton-dominated fraction of particulate organic matter (POM) collected along the Siberian Shelf. POM (> 10 µm) samples were analysed using molecular biomarkers (CuO oxidation and IP25) and dual-carbon isotopes (δ13C and Δ14C). In addition, surface water chemical properties were integrated with the POM (> 10 µm) dataset to understand the link between plankton composition and environmental conditions. δ13C and Δ14C exhibited a large variability in the POM (> 10 µm) distribution while the content of terrestrial biomarkers in the POM was negligible. In the Laptev Sea (LS), δ13C and Δ14C of POM (> 10 µm) suggested a heterotrophic environment in which dissolved organic carbon (DOC) from the Lena River was the primary source of metabolisable carbon. Within the Lena plume, terrestrial DOC probably became part of the food web via bacteria uptake and subsequently transferred to relatively other heterotrophic communities (e.g. dinoflagellates). Moving eastwards toward the sea-ice-dominated East Siberian Sea (ESS), the system became progressively more autotrophic. Comparison between δ13C of POM (> 10 µm) samples and CO2aq concentrations revealed that the carbon isotope fractionation increased moving towards the easternmost and most productive stations. In a warming scenario characterised by enhanced terrestrial DOC release (thawing permafrost) and progressive sea ice decline, heterotrophic conditions might persist in the LS while the nutrient-rich Pacific inflow will likely stimulate greater primary productivity in the ESS. The contrasting trophic conditions will result in a sharp gradient in δ13C between the LS and ESS, similar to what is documented in our semi-synoptic study. VL - 13 UR - https://os.copernicus.org/articles/13/735/2017/ IS - 5 ER - TY - JOUR T1 - Carbon isotope evidence for a northern source of deep water in the glacial western North Atlantic JF - Proceedings of the National Academy of Sciences Y1 - 2017 A1 - Keigwin, Lloyd D. A1 - Swift, Stephen A. KW - carbon isotopes KW - Last glacial maximum KW - ocean ventilation KW - oxygen isotopes KW - western north atlantic AB - The prevailing view of western Atlantic hydrography during the Last Glacial Maximum (LGM) calls for transport and intermixing of deep southern and intermediate northern end members. However, δ13C and Δ14C results on foraminifera from a sediment core at 5.0 km in the northern subtropics show that there may have also been a northern source of relatively young, very dense, nutrient-depleted water during the LGM (18 ky to 21 ky ago). These results, when integrated with data from other western North Atlantic locations, indicate that the ocean was poorly ventilated at 4.2 km, with better ventilation above and below that depth. If this is a signal of water mass source and not nutrient storage, it would indicate that a previously unrecognized deep water end member originated along the western margin of the Labrador Sea, analogous to dense water formation today around Antarctica and in the Okhotsk Sea. VL - 114 UR - http://www.pnas.org/lookup/doi/10.1073/pnas.1614693114https://syndication.highwire.org/content/doi/10.1073/pnas.1614693114http://www.pnas.org/syndication/doi/10.1073/pnas.1614693114 IS - 11 ER - TY - JOUR T1 - Carbon isotope-constrained seasonality of carbonaceous aerosol sources from an urban location (Kanpur) in the Indo-Gangetic Plain JF - Journal of Geophysical Research: Atmospheres Y1 - 2017 A1 - Bikkina, Srinivas A1 - Andersson, August A1 - Ram, Kirpa A1 - Sarin, M. M. A1 - Sheesley, Rebecca J. A1 - Kirillova, Elena N. A1 - Rengarajan, R. A1 - Sudheer, A. K. A1 - Gustafsson, Örjan AB - The Indo-Gangetic Plain (IGP) in northern India, Pakistan and Bangladesh is a major source of carbonaceous aerosols in South Asia. However, poorly constrained seasonality of their sources over the IGP leads to large uncertainty in climate and health effects. Here, we present a first dataset for year-round radiocarbon (Δ14C) and stable carbon (δ13C) based source apportionment of total carbon (TC) in ambient PM10 (n = 17) collected from an urban site (Kanpur: 26.5 °N, 80.3 °E) in the IGP during January 2007-January 2008. The year-round 14C-based fraction biomass (fbio-TC) estimate at Kanpur averages ~77 ± 7%, emphasize an impact of biomass burning emissions (BBEs). The highest fbio-TC(%) is observed in fall season (October-November: 85 ± 6%) followed by winter (December-February: 80 ± 4%) and spring (March-May: 75 ± 8%), while lowest values found in summer (June-September: 69 ± 2%). Since biomass/coal combustion and vehicular emissions mostly contribute to carbonaceous aerosols over the IGP, we predict δ13CTC (δ13Cpred) over Kanpur using known δ13C source signatures and the measured Δ14C value of each sample. The seasonal variability of δ13Cobs - δ13Cpred versus Δ14CTC together with air mass back trajectories and MODIS fire count data reveal that carbonaceous aerosols in winter/fall are significantly influenced by atmospheric aging (downwind transport of crop-residue burning/wood combustion emissions in the northern IGP), while local sources (wheat residue combustion/vehicular emissions) dominate in spring/summer. Given the large temporal and seasonal variability in sources and emission strength of TC over the IGP, 14C-based constraints are, thus, crucial for reducing their uncertainties in carbonaceous aerosol budgets in climate models. Carbon isotope-constrained seasonality of carbonaceous aerosol sources from an urban location (Kanpur) in the Indo-Gangetic Plain: 14Capportionment of carbonaceous aerosol. Available from: https://www.researchgate.net/publication/315970418_Carbon_isotope-constrained_seasonality_of_carbonaceous_aerosol_sources_from_an_urban_location_Kanpur_in_the_Indo-Gangetic_Plain_14Capportionment_of_carbonaceous_aerosol [accessed Jun 2, 2017]. VL - 122 UR - http://doi.wiley.com/10.1002/jgrd.v122.9http://doi.wiley.com/10.1002/2016JD025634http://onlinelibrary.wiley.com/wol1/doi/10.1002/2016JD025634/fullpdfhttps://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2F2016JD025634 IS - 9 ER - TY - JOUR T1 - Carbonization, differential preservation, and sampling biases in domestication studies: An erect knotweed ( Polygonum erectum L.) case study JF - Journal of Archaeological Science: Reports Y1 - 2017 A1 - Mueller, Natalie G. AB - Population morphometrics can be employed to explore the process of domestication, but only after accounting for biases introduced by taphonomic processes and sampling. For every cultivated plant, the challenges associated with carbonization, differential preservation, and sampling bias are different, as are the morphological characteristics of interest in domestication studies. This case study establishes correction factors and sampling parameters for assessing morphological indicators of domestication in erect knotweed (Polygonum erectum L.), an annual plant that was cultivated by Indigenous people in Eastern North America for about 2500 years. Documenting the unique domestication syndrome of erect knotweed creates three different sets of taphonomic and sampling problems that need to be addressed through experimentation and modeling: 1) Assess the morphometric effects of carbonization; 2) assess the effects of differential preservation; and 3) assess the effects of sampling error. The results of this study can be used by other analysts to identify domesticated assemblages of erect knotweed. These analyses also have implications for studies of plant domestication from the morphology of archaeological assemblages in general, especially when nominal variables are used to differentiate wild from domesticated populations (for example, the presence/absence of an abscission scar in cereals or the seed coat texture of chenopods). VL - 13 UR - http://linkinghub.elsevier.com/retrieve/pii/S2352409X16308550http://api.elsevier.com/content/article/PII:S2352409X16308550?httpAccept=text/xmlhttp://api.elsevier.com/content/article/PII:S2352409X16308550?httpAccept=text/plain ER - TY - JOUR T1 - Changes in glacial meltwater alter algal communities in lakes of Scoresby Sund, Renland, East Greenland throughout the Holocene: Abrupt reorganizations began 1000 years before present JF - The Holocene Y1 - 2017 A1 - Slemmons, Krista EH A1 - Medford, Aaron A1 - Hall, Brenda L A1 - Stone, Jeffery R A1 - McGowan, Suzanne A1 - Lowell, Thomas A1 - Kelly, Meredith A1 - Saros, Jasmine E KW - climate KW - Diatom KW - East Greenland KW - glacier KW - Holocene KW - Lake level AB - We investigated the response of lake algal communities to changes in glacial meltwater from the Renland Ice Cap (Greenland) through the Holocene to assess whether influxes always elicit consistent responses or novel responses. We measured sedimentary algal pigments in two proximal lakes, snow-fed Raven and glacier- and snow-fed Bunny Lake, and diatom community structure and turnover in Bunny Lake. Diatom data were not available in Raven Lake. We also modeled lake-level change in Bunny Lake to identify how glacial meltwater may have altered diatom habitat availability through time. Through a series of glacier advances and retreats over the Holocene, the algal response in Bunny Lake was relatively constant until approximately 1015 yr BP, after which there were major changes in sedimentary algal remains. Algal pigment concentrations sharply declined, and diatom species richness increased. Diatom community structure underwent three reorganizations. Until 1015 yr BP, assemblages were dominated by Pinnularia braunii and Aulacoseira pffaffiana. However, approximately 1015–480 yr BP, these species declined and Tabellaria flocculosa and Hannaea arcus became a significant component of the assemblage. Approximately 440 yr BP, A. pfaffiana increased along with species indicating elevated nitrogen. In contrast, the algal pigment records from nearby snow-fed Raven Lake showed different and minimal change through time. Our results suggest that changes in the magnitude and composition of meltwater in our two study lakes were unique over the last 1000 yr BP and elicited a non-linear threshold response absent during other periods of glacier advance and retreat. Deciphering the degree to which glaciers structure algal communities over time has strong implications for lakes as glaciers continue to recede. VL - 27 UR - http://journals.sagepub.com/doi/10.1177/0959683616678468 IS - 7 ER - TY - JOUR T1 - Climate and environmental changes for the past 44 ka clarified by pollen and algae composition in the Ulleung Basin, East Sea (Japan Sea) JF - Quaternary International Y1 - 2017 A1 - Jinxia Chen A1 - Yanguang Liu A1 - Xuefa Shi A1 - Bong-Chool Suk A1 - Jianjun Zou A1 - Zhengquan Yao KW - East Sea (Japan Sea) AB - Abstract The pollen and algae records derived from core KCES-1 in the East Sea (Japan Sea) reveal vegetation and climate changes during the past 44 ka. From 44 to 36 cal ka BP, forest vegetation in the coastal regions of Ulleung Basin was composed predominantly of subalpine conifer forest, open grassland covered the exposed continental shelves, indicating a cool and dry climate. During the period of 36–28.3 cal ka BP, a warmer and wetter climate caused the contraction of subalpine conifer forest in the coastal regions of Ulleung Basin, and the expansion of marsh in the exposed continental shelves. From 28.3 to 17.6 cal ka BP, the sea-level decline restricted the herbs pollen originates in the exposed shelf of East China Sea and Yellow Sea inflow into the East Sea (Japan Sea), and caused the reduction of herbs pollen in the site location. During the time interval of 17.6–15.1 cal ka BP, a great expansion of subalpine conifer forest can be regarded as the consequence of enhanced East Asian winter monsoon (EAWM). The obvious increase in temperate deciduous broadleaved trees, spores and algae can be attributable to the rising of sea level and the warming of climate from 15.1 to 12.1 cal ka BP. During the period of 12.1 to 5.3 cal ka BP, broadleaved taxa increased, especially during the time period of 9.5–5.3 cal ka BP, evergreen broadleaved trees pollen reach the highest values throughout the core, as a result of the Holocene climate optimum condition. Vegetation changes controlled by humid impacts occurred at the late Holocene, as indicated by an increase in Pinus pollen. UR - http://www.sciencedirect.com/science/article/pii/S1040618216300829 ER - TY - JOUR T1 - Climate-related response of dust flux to the central equatorial Pacific over the past 150 kyr JF - Earth and Planetary Science Letters Y1 - 2017 A1 - Jacobel, A.W. A1 - McManus, J.F. A1 - Anderson, R.F. A1 - Winckler, G. KW - abrupt climate change KW - dust KW - equatorial pacific KW - Intertropical Convergence Zone KW - stadial events AB - High resolution paleoclimate records from low latitudes are critical for understanding the role of the tropics in transmitting and generating feedbacks for high-latitude climate change on glacial–interglacial and millennial timescales. Here we present three new records of 230Thxs,0-normalized 232Th-derived dust fluxes from the central equatorial Pacific spanning the last 150 kyr at millennial-resolution. All three dust flux records share the “sawtooth” pattern characteristic of glacial–interglacial cycles in ice volume, confirming a coherent response to global climate forcing on long timescales. These records permit a detailed examination of millennial variability in tropical dust fluxes related to abrupt perturbations in oceanic and atmospheric circulation. Increases in dust flux in association with at least six of the longest Greenland stadials provide evidence that abrupt, high-latitude climate oscillations influenced the atmospheric aerosol load in the equatorial Pacific, with implications for both direct and indirect effects on the tropical energy balance. Our latitudinal transect of cores captures shifts in the position of the Intertropical Convergence Zone (ITCZ) in response to variations in the interhemispheric thermal gradient associated with cooling in Greenland and bipolar seesaw warming in Antarctica. These observations demonstrate that changes in the energy and hydrologic balance of the tropics were repeated features of the penultimate deglaciation, last glacial inception and last glacial cycle, and highlight the role of the tropical atmosphere as a dynamic and responsive component of Earth's climate system. VL - 457 UR - https://doi.org/10.1016/j.epsl.2016.09.042 ER - TY - BOOK T1 - Coastal Research LibraryCoastline Changes of the Baltic Sea from South to EastConstraints of Radiocarbon Dating in Southeastern Baltic Lagoons: Assessing the Vital Effects T2 - Coastline Changes of the Baltic Sea from South to East Y1 - 2017 A1 - Bitinas, Albertas A1 - žeika, Jonas A1 - Buynevich, Ilya V. A1 - šytė, Aldona A1 - Molodkov, Anatoly A1 - ė, Alma ED - Harff, Jan ED - ńczyk, Kazimierz ED - von Storch, Hans KW - Curonian lagoon KW - ESR KW - IR-OSL KW - Molluscs KW - radiocarbon KW - Reservoir effect KW - Vistula lagoon AB - During the past decades, a suite of radiocarbon (14C), infrared optically stimulated luminescence (IR-OSL), and electron spin resonance (ESR) dates were compiled on a variety of materials from the Curonian and Vistula lagoons and spits of the southeastern Baltic Sea. These dated materials generally included lagoon sediments and mollusc shells, along with samples of fossil fish remains, peat, wood, and water bicarbonates. A growing number of 14C dates (conventional and AMS) demonstrates disparities and contradictions with the associated IR-OSL dates and palaeobotanical investigations of contemporary materials. Detailed analyses of 14C, IR-OSL and ESR chronologies and experimental 14C dating of modern live molluscs and water bicarbonates from the Curonian Lagoon and its main tributary – Nemunas-Neris River system – reveals a substantial influx of “old” carbonates into the lagoon. As a result, the uncertainty of reservoir effect added a considerable error to the 14C ages. Moreover, fossil molluscs of the same species extracted from boreholes and outcrops yield significantly younger ages (up to several millennia) than the enclosing sediments. Both of these trends – aging and rejuvenation – highlight an urgent need for constraining the local reservoir correction (ΔR). Several scenarios are presented to explain the impact of vital effects on radiocarbon chronology of carbonates and to offer strategies to account for them in future studies. JF - Coastline Changes of the Baltic Sea from South to East PB - Springer International Publishing CY - Cham SN - 978-3-319-49892-8 UR - http://link.springer.com/10.1007/978-3-319-49894-2_8 ER - TY - JOUR T1 - Comparative growth, age at maturity and sex change, and longevity of Hawaiian parrotfishes with bomb radiocarbon validation JF - Canadian Journal of Fisheries and Aquatic Sciences Y1 - 2017 A1 - DeMartini, Edward E A1 - Andrews, Allen H A1 - Howard, Kathrine G A1 - Taylor, Brett M A1 - Lou, Dongchun A1 - Donovan, Mary K. AB - Growth rates and longevities were estimated for five major fishery species of parrotfishes (“uhu”) at Oahu, Hawai'i. All species grew rapidly with von Bertalanffy Growth Formula (VBGF) k values ≥ 0.4 yr-1. Longevities were found to range broadly among the three SMALL species—4 yr in Calotomus carolinus and 6 and 11 yr in Scarus psittacus and Chlorurus spilurus—and to 15-20 yr in S. rubroviolaceus and Chlorurus perspicillatus for the two LARGE species. Age-reading and growth curves for the latter two LARGE species were validated using bomb radiocarbon dating. Median ages at sexual maturity as females (AM50) and at sex change (from female to terminal phase male, A∆50) were estimated using logistic models. Sexual maturation occurred at 1–2 yr for the SMALL species and at 3–3½ yr in the LARGE species. A∆50 estimates ranged from 2–4 yr in the SMALL species and were about 5 and 7 yr in S. rubroviolaceus and C. perspicillatus, respectively. Estimated milestones poorly corresponded to the current minimum legal size for uhu in Hawai'i (12" or 30.5 cm fork length). Pooling these parrotfishes for management seems generally inappropriate, especially for the two LARGE species. Age-based metrics are more informative than size-based metrics for these fishes UR - http://www.nrcresearchpress.com/doi/10.1139/cjfas-2016-0523 ER - TY - JOUR T1 - Compilation of geophysical, geochronological, and geochemical evidence indicates a rapid Mediterranean-derived submergence of the Black Sea's shelf and subsequent substantial salinification in the early Holocene JF - Marine Geology Y1 - 2017 A1 - Yanchilina, Anastasia G. A1 - Ryan, William B.F. A1 - McManus, Jerry F. A1 - Dimitrov, Petko A1 - Dimitrov, Dimitar A1 - Slavova, Krasimira A1 - Filipova-Marinova, Mariana KW - Black Sea KW - Black Sea transgression KW - Isotope geochemistry KW - Lake transgression KW - Marine-lake connections KW - paleoceanography KW - paleosalinity KW - Reflection profiles AB - Our knowledge of rate and processes in which semi-enclosed environments alternate from lacustrine to marine is commonly limited because of the paucity of specific proxies for sea level and salinity. Here we investigate the timing, rate, and key mechanisms involved in the transformation of the previously isolated Black Sea-Lake to the modern partly-enclosed marine sea using a suite of geophysical, geochemical, and geochronological methods. Cores were collected in transects across shelves of Ukraine, Romania, Bulgaria, and Turkey. Biogenic carbonate from these cores was analyzed for radiocarbon and strontium, oxygen, and carbon isotopes. Strontium results indicate that the submergence of the Black Sea shelf at 9300 calendar years BP was caused by the ingress of Mediterranean water and was abrupt, taking < 40 years. The seismic reflection profiles show a uniform drape of subsequent sediment over aeolian dunes indicating a drowning with no time for erosion accompanying the submergence. Moisture measurements beneath the uniform drape indicate that the shelf was dry before submergence and the shoreline of the Preboreal lake may have regressed to beyond 120 mbsl. Mollusks colonized the newly submerged substrate of the inner shelf at the same time as they colonized the outer shelf. The succession of mollusk species with shells whose strontium isotope composition has a marine component indicates a rising salinity. The transformation of the lake to a sea is affirmed by increases in the shells' strontium and oxygen isotopic ratios towards the external ocean value. Radiocarbon years are calibrated to calendar years by tuning the oxygen and carbon isotope composition of the mollusk record to that of the U/Th dated Sofular Cave stalagmites. The match shows a reduction of the lake's prior high reservoir age accompanying the inflow of the Mediterranean water. In 900 years the salinity reached a threshold that excluded all previous Black Sea lacustrine fauna. These results imply that any substantial postglacial submergence of the Black Sea shelves did not occur prior to entry of Mediterranean water. VL - 383 UR - https://doi.org/10.1016/j.margeo.2016.11.001 ER - TY - JOUR T1 - Comprehensive radiocarbon analysis of benzene polycarboxylic acids (BPCAs) derived from pyrogenic carbon in environmental samples JF - Radiocarbon Y1 - 2017 A1 - Hanke, U M A1 - Wacker, L A1 - Haghipour, N A1 - Schmidt, M W I A1 - Eglinton, T I A1 - McIntyre, C P AB - Compound-specific radiocarbon analysis (CSRA) of benzene polycarboxylic acids (BPCAs) yields molecular-level, source-specific information necessary to constrain isotopic signatures of pyrogenic carbon. However, the purification of individual BPCAs requires a multistep procedure that typically results in only microgram quantities of the target analyte(s). Such small samples are highly susceptible to contamination by extraneous carbon, which needs to be minimized and carefully accounted for in order to yield accurate results. Here, we undertook comprehensive characterization and quantification of contamination associated with molecular radiocarbon (14C) BPCA analyses through systematic processing of multiple authentic standards with both fossil and modern 14C signatures at various concentrations. Using this approach, we precisely apportion the contribution of extraneous carbon with respect to the four implemented subprocedures. Assuming a constant source and quantity of extraneous carbon we correct and statistically evaluate uncertainties in resulting 14C data. Subsequently, we examine the results of triplicate analyses of reference materials representing four different environmental matrices (sediment, soil, aerosol, riverine natural organic matter) and apportion their BPCA sources in terms of carbon residues derived from biomass or fossil fuel combustion. This comprehensive approach to CSRA facilitates retrieval of robust 14C data, with application in environmental studies of the continuum of pyrogenic carbon. VL - 59 UR - https://www.cambridge.org/core/product/identifier/S0033822217000443/type/journal_article IS - 4 ER - TY - JOUR T1 - Constraining the sources and cycling of dissolved organic carbon in a large oligotrophic lake using radiocarbon analyses JF - Geochimica et Cosmochimica Acta Y1 - 2017 A1 - Prosper K. Zigah A1 - Elizabeth C. Minor A1 - Ann P. McNichol A1 - Li Xu A1 - Josef P. Werne KW - atmospheric co2 KW - Carbohydrate-like substance KW - Carboxylic-rich alicyclic molecules (CRAM) KW - Contemporary DOC KW - dissolved inorganic carbon KW - dissolved organic carbon KW - Freshwater carbon cycling KW - Heteropolysaccharides (HPS) KW - High molecular weight DOC KW - Lake Superior KW - Lipid-like fraction KW - Old DOC KW - Oligotrophic lake KW - Protein-like substance KW - radiocarbon KW - Serial thermal oxidation KW - Solid phase extracted DOC KW - Stable isotope KW - Unhydrolysable material AB - Abstract We measured the concentrations and isotopic compositions of solid phase extracted (SPE) dissolved organic carbon (DOC) and high molecular weight (HMW) \{DOC\} and their constituent organic components in order to better constrain the sources and cycling of \{DOC\} in a large oligotrophic lacustrine system (Lake Superior, North America). \{SPE\} \{DOC\} constituted a significant proportion (41-71%) of the lake \{DOC\} relative to \{HMW\} \{DOC\} (10-13%). Substantial contribution of 14C-depleted components to both \{SPE\} \{DOC\} (Δ14C = 25 to 43‰) and \{HMW\} \{DOC\} (Δ14C = 22 to 32‰) was evident during spring mixing, and depressed their radiocarbon values relative to the lake dissolved inorganic carbon (DIC; Δ14C ∼ 59‰). There was preferential removal of 14C-depleted (older) and thermally recalcitrant components from \{HMW\} \{DOC\} and \{SPE\} \{DOC\} in the summer. Contemporary photoautotrophic addition to \{HMW\} \{DOC\} was observed during summer stratification in contrast to \{SPE\} DOC, which decreased in concentration during stratification. Serial thermal oxidation radiocarbon analysis revealed a diversity of sources (both contemporary and older) within the \{SPE\} DOC, and also showed distinct components within the \{HMW\} DOC. The thermally labile components of \{HMW\} \{DOC\} were 14C-enriched and are attributed to heteropolysaccharides (HPS), peptides/amide and amino sugars (AMS) relative to the thermally recalcitrant components reflecting the presence of older material, perhaps carboxylic-rich alicyclic molecules (CRAM). The solvent extractable lipid-like fraction of \{HMW\} \{DOC\} was very 14C-depleted (as old as 1270-2320 14C years) relative to the substances isolated by acid hydrolysis of \{HMW\} DOC. Our data constrain relative influences of contemporary \{DOC\} and old DOC, and \{DOC\} cycling in a modern freshwater ecosystem. VL - 208 UR - http://www.sciencedirect.com/science/article/pii/S0016703717301722 ER - TY - JOUR T1 - Coupling of the Intertropical Convergence Zone and Southern Hemisphere mid-latitude climate during the early to mid-Holocene JF - Geology Y1 - 2017 A1 - Mariani, Michela A1 - Fletcher, Michael-Shawn A1 - Drysdale, Russell N. A1 - Saunders, Krystyna M. A1 - Heijnis, Henk A1 - Jacobsen, Geraldine A1 - Zawadzki, Atun AB - Conceptual models predict a tight coupling between the Intertropical Convergence Zone (ITCZ) and the Southern Westerly Winds (SWW) in response to glacial-interglacial transitions, yet little is known about this relationship under Holocene boundary conditions. Here we present a synthesis of Holocene pollen data from the southwest Pacific mid-latitudes that tracks changes in the SWW. Comparison of our SWW paleoclimate records with data tracking the ITCZ, oceanic circulation, and insolation reveals clearly synchronous and in-phase ITCZ-SWW dynamics between 12 and 5 ka, indicating a tight coupling between the tropics and southern mid-latitudes in response to ocean circulation and insolation. An apparent decoupling of the SWW and ITCZ in the Pacific region after 5 ka is attributable to the overriding influence of the El Niño–Southern Oscillation (ENSO) over the proxy data. VL - 45 UR - https://pubs.geoscienceworld.org/geology/article-lookup?doi=10.1130/G39705.1 IS - 12 ER - TY - JOUR T1 - The De Long Trough: a newly discovered glacial trough on the East Siberian continental margin JF - Climate of the Past Y1 - 2017 A1 - O'Regan, Matt A1 - Backman, Jan A1 - Barrientos, Natalia A1 - Cronin, Thomas M. A1 - Gemery, Laura A1 - Kirchner, Nina A1 - Mayer, Larry A. A1 - Nilsson, Johan A1 - Noormets, Riko A1 - Pearce, Christof A1 - Semiletov, Igor A1 - Stranne, Christian A1 - Jakobsson, Martin AB - Ice sheets extending over parts of the East Siberian continental shelf have been proposed for the last glacial period and during the larger Pleistocene glaciations. The sparse data available over this sector of the Arctic Ocean have left the timing, extent and even existence of these ice sheets largely unresolved. Here we present new geophysical mapping and sediment coring data from the East Siberian shelf and slope collected during the 2014 SWERUS-C3 expedition (SWERUS-C3: Swedish – Russian – US Arctic Ocean Investigation of Climate-Cryosphere-Carbon Interactions). The multibeam bathymetry and chirp sub-bottom profiles reveal a set of glacial landforms that include grounding zone formations along the outer continental shelf, seaward of which lies a  >  65 m thick sequence of glacio-genic debris flows. The glacial landforms are interpreted to lie at the seaward end of a glacial trough – the first to be reported on the East Siberian margin, here referred to as the De Long Trough because of its location due north of the De Long Islands. Stratigraphy and dating of sediment cores show that a drape of acoustically laminated sediments covering the glacial deposits is older than ∼ 50 cal kyr BP. This provides direct evidence for extensive glacial activity on the Siberian shelf that predates the Last Glacial Maximum and most likely occurred during the Saalian (Marine Isotope Stage (MIS) 6). VL - 13 UR - https://cp.copernicus.org/articles/13/1269/2017/ IS - 9 ER - TY - JOUR T1 - The deep distributions of helium isotopes, radiocarbon, and noble gases along the U.S. GEOTRACES East Pacific Zonal Transect (GP16) JF - Marine Chemistry Y1 - 2017 A1 - W. J. Jenkins A1 - Dempsey E. Lott III A1 - Christopher R. German A1 - Kevin L. Cahill A1 - Joanne Goudreau A1 - Brett Longworth AB - Abstract We report the deep distributions of noble gases, helium isotopes, and radiocarbon measured during the U.S. \{GEOTRACES\} \{GP16\} East Pacific Zonal Transect between 152 and 77°W at 12–15°S in the South Pacific. The dominant feature is an intense tongue of hydrothermal effluent that extends > 4000 km westward from the East Pacific Rise (EPR) at   2500 m depth. The patterns reveal significant “downstream” variations in water mass structure, advection, and mixing that belie the simple perception of a continuous plume extending westward from the EPR. For example, one feature observed at 120°W, 14°S has tracer signatures that are consistent with a water mass originating from an area as much as 2000 km south of this section, suggesting a quasi-permanent northward flow on the western flank of the EPR. Helium isotope variations in the plume show a uniquely high 3He/4He source in the tongue compared with typical mid-ocean ridge basalts (MORB), consistent with the anomalously high ratios observed in \{MORB\} glasses from the \{EPR\} segment just south of this transect. The water column data also reveal that the background 3He/4He east of the \{EPR\} is significantly lower than values characteristic of MORB, suggesting an additional, more geographically distributed radiogenic 4He flux of order 107 mol/y into the deep Pacific. In the western end of the section, incoming bottom waters have relatively less hydrothermal hydrothermal helium, more radiocarbon, and more oxygen, as well as negative saturation anomalies for the heavy noble gases (Ar, Kr, and Xe). During the basin-scale upwelling of this water, diapycnal mixing serves to erase these negative anomalies. The relative magnitudes of the increases for the heavy noble gases (Ar, Kr, and Xe) are quantitatively consistent with this process. This leads us to estimate the relatively smaller effects on He and Ne saturations, which range from near zero to 0.2% and 0.3% respectively. With this information, we are able to refine our estimates of the magnitude of 3He and 4He excesses and the absolute 3He/4He ratio of non-atmospheric helium introduced into deep Pacific waters. UR - http://www.sciencedirect.com/science/article/pii/S0304420316302353 ER - TY - JOUR T1 - Deglacial sea level history of the East Siberian Sea and Chukchi Sea margins JF - Climate of the Past Y1 - 2017 A1 - Cronin, Thomas M. A1 - O'Regan, Matt A1 - Pearce, Christof A1 - Gemery, Laura A1 - Toomey, Michael A1 - Semiletov, Igor A1 - Jakobsson, Martin AB - Deglacial (12.8–10.7 ka) sea level history on the East Siberian continental shelf and upper continental slope was reconstructed using new geophysical records and sediment cores taken during Leg 2 of the 2014 SWERUS-C3 expedition. The focus of this study is two cores from Herald Canyon, piston core SWERUS-L2-4-PC1 (4-PC1) and multicore SWERUS-L2-4-MC1 (4-MC1), and a gravity core from an East Siberian Sea transect, SWERUS-L2-20-GC1 (20-GC1). Cores 4-PC1 and 20-GC were taken at 120 and 115 m of modern water depth, respectively, only a few meters above the global last glacial maximum (LGM;  ∼  24 kiloannum or ka) minimum sea level of  ∼  125–130 meters below sea level (m b.s.l.). Using calibrated radiocarbon ages mainly on molluscs for chronology and the ecology of benthic foraminifera and ostracode species to estimate paleodepths, the data reveal a dominance of river-proximal species during the early part of the Younger Dryas event (YD, Greenland Stadial GS-1) followed by a rise in river-intermediate species in the late Younger Dryas or the early Holocene (Preboreal) period. A rapid relative sea level rise beginning at roughly 11.4 to 10.8 ka ( ∼  400 cm of core depth) is indicated by a sharp faunal change and unconformity or condensed zone of sedimentation. Regional sea level at this time was about 108 m b.s.l. at the 4-PC1 site and 102 m b.s.l. at 20-GC1. Regional sea level near the end of the YD was up to 42–47 m lower than predicted by geophysical models corrected for glacio-isostatic adjustment. This discrepancy could be explained by delayed isostatic adjustment caused by a greater volume and/or geographical extent of glacial-age land ice and/or ice shelves in the western Arctic Ocean and adjacent Siberian land areas. VL - 13 UR - https://cp.copernicus.org/articles/13/1097/2017/ IS - 9 ER - TY - JOUR T1 - Deglaciation and ice shelf development at the northeast margin of the Laurentide Ice Sheet during the Younger Dryas chronozone JF - Boreas Y1 - 2017 A1 - Furze, Mark F. A. A1 - ńkowski, Anna J. A1 - McNeely, Morgan A. A1 - Bennett, Robbie A1 - Cage, Alix G. AB - Core 2011804-0010 from easternmost Lancaster Sound provides important insights into deglacial timing and style at the marine margin of the NE Laurentide Ice Sheet (LIS). Spanning 13.2–11.0 cal. ka BP and investigated for ice-rafted debris (IRD), foraminifera, biogenic silica and total organic carbon, the stratigraphy comprises a lithofacies progression from proximal grounding line and sub-ice shelf environments to open glaciomarine deposition; a sequence similar to deposits from Antarctic ice shelves. These results are the first marine evidence of a former ice shelf in the eastern Northwest Passage and are consistent with a preceding phase of ice streaming in eastern Lancaster Sound. Initial glacial float-off and retreat occurred >13.2 cal. ka BP, followed by formation of an extensive deglacial ice shelf during the Younger Dryas, which acted to stabilize the retreating margin of the NE LIS until 12.5 cal. ka BP. IRD analyses of sub-ice shelf facies indicate initial high input from source areas on northern Baffin Island delivered to Lancaster Sound by a tributary ice stream in Admiralty Inlet. After ice shelf break-up, Bylot Island became the dominant source area. Foraminifera are dominated by characteristic ice-proximal glaciomarine benthics (Cassidulina reniforme, Elphidium excavatum f. clavata), complemented by advected Atlantic water (Cassidulina neoteretis, Neogloboquadrina pachyderma) and enhanced current indicators (Lobatula lobatula). The biostratigraphy further supports the ice shelf model, with advection of sparse faunas beneath the ice shelf, followed by increased productivity under open water glaciomarine conditions. The absence of Holocene sediments in the core suggests that the uppermost deposits were removed, most likely due to mass transport resulting from the site's proximity to modern tidewater glacier margins. Collectively, this study presents important new constraints on the deglacial behaviour of the NE Laurentide Ice Sheet, with implications for past ice sheet stability, ice-rafted sediment delivery, and ice−ocean interactions in this complex archipelago setting. UR - http://doi.wiley.com/10.1111/bor.12265 ER - TY - JOUR T1 - Determining rates of sediment accumulation on the Mekong shelf: Timescales, steady-state assumptions, and radiochemical tracers JF - Continental Shelf Research Y1 - 2017 A1 - DeMaster, D.J. A1 - Liu, J.P. A1 - Eidam, E. A1 - Nittrouer, C.A. A1 - Nguyen, T.T. KW - 14C geochronology KW - 210Pb geochronology KW - Deltaic sediment accumulation rates KW - Mekong delta KW - Mekong sediment budget AB - Thirty-two kasten cores, collected from the proximal Mekong continental shelf, have been analyzed for their excess 210Pb distributions in an effort to establish rates of sediment accumulation over the past 100 years. The length of the cores varied from 0.5 to 3 m, and stations sampled topset, foreset, and bottomset beds (water depths 7–21 m). Apparent excess 210Pb sediment accumulation rates ranged from > 10 cm/y (no down-core decrease of excess activity over 300 cm core length) near the Song Hau river mouth, to 1–3 cm/y in topset and foreset beds within 20–50 km of the river mouth, to rates as low as 0.4 cm/y in cores from bottomset beds. The 210Pb sediment accumulation rates yield an overall sediment burial rate of 6.1 × 1013 g/y for the proximal deltaic deposits, which corresponds to 43% of the total modern Mekong sediment burial on the southern Vietnam shelf (1.4 × 1014 g/y; based on our 210Pb and seismic data and 210Pb data from the literature). This shelf burial rate is in reasonable agreement with current long-term estimates of Mekong River sediment discharge (1.3–1.6 × 1014 g/y) from the literature. The inventory of excess 210Pb in the proximal Mekong deltaic deposits indicates that the shoreward flow of offshore water (entrained during river/ocean mixing) is approximately twice the flow of the Mekong freshwater discharge. Organic-carbon 14C ages were measured on 10 cores from the proximal Mekong delta and compared to 210Pb sediment accumulation rates in the same core. The 210Pb accumulation rates in all 10 cores were considered to be more robust and accurate than the 14C geochronologies, primarily because of down-core variations in the source of organic carbon deposited on the seafloor (old terrestrial carbon versus younger marine carbon). Variations in the source of organic carbon accumulating in the seabed were resolved by measuring the δ13C value of the seabed organic carbon. VL - 147 UR - https://www.sciencedirect.com/science/article/pii/S0278434316306732 ER - TY - JOUR T1 - The distribution and utility of sea-level indicators in Eurasian sub-Arctic salt marshes (White Sea, Russia) JF - Boreas Y1 - 2017 A1 - Kemp, Andrew C. A1 - Horton, Benjamin P. A1 - Nikitina, Daria A1 - Vane, Christopher H. A1 - Potapova, Marina A1 - Weber-Bruya, Elizabeth A1 - Culver, Stephen J. A1 - Repkina, Tatyana A1 - Hill, David F. AB - In support of efforts to reconstruct relative sea level (RSL), we investigated the utility of foraminifera, diatoms and bulk‐sediment geochemistry (δ13C, C:N and parameters measured by Rock‐Eval pyrolysis) as sea‐level indicators in Eurasian sub‐Arctic salt marshes. At three salt marshes (<15 km apart) in Dvina Bay (White Sea, Russia), we collected surface sediment samples along transects from subtidal to Taiga forest environments. Foraminifera at all sites formed bipartite assemblages, where elevations below mean high higher water (MHHW) were dominated by Miliammina spp. and elevations between MHHW and the highest occurrence of foraminifera were dominated by Jadammina macrescens and Balticammina pseudomacrescens. Five high‐diversity groups of diatoms were identified and they displayed pronounced variability amongst the study sites. Bulk‐sediment geochemistry recognized two groups (clastic‐dominated environments below MHHW and organic‐rich environments above MHHW). As one group included subtidal elevations and the other included supratidal elevations, we conclude that the measured geochemical parameters are not stand‐alone sea‐level indicators. Core JT2012 captured a regressive sediment succession of clastic, tidal‐flat sediment overlain by salt‐marsh organic silt and freshwater peat. The salt‐marsh sediment accumulated at 2804±52 years before present and preserved foraminifera (Jadammina macrescens and Balticammina pseudomacrescens) with good analogy to modern assemblages indicating that RSL was +2.60±0.47 m at this time. Diatoms confirm that marine influence decreased through time, but the lack of analogy between modern and core assemblages limited their utility as sea‐level indicators. Geochemical parameters also indicate a reduction in marine influence through time. We conclude that RSL reconstructions derived from salt‐marsh sediment preserved beneath Eurasian sub‐Arctic peatlands can provide valuable insight into the spatio‐temporal evolution of the Fennoscandian and Eurasian ice sheets. VL - 46 UR - https://onlinelibrary.wiley.com/doi/10.1111/bor.12233 IS - 3 ER - TY - JOUR T1 - Divergent Evolution of Carbonaceous Aerosols during Dispersal of East Asian Haze JF - Scientific Reports Y1 - 2017 A1 - Fang, Wenzheng A1 - Andersson, August A1 - Zheng, Mei A1 - Lee, Meehye A1 - Holmstrand, Henry A1 - Kim, Sang-Woo A1 - Du, Ke A1 - Gustafsson, Örjan AB - Wintertime East Asia is plagued by severe haze episodes, characterized by large contributions of carbonaceous aerosols. However, the sources and atmospheric transformations of these major components are poorly constrained, hindering development of efficient mitigation strategies and detailed modelling of effects. Here we present dual carbon isotope (δ13C and Δ14C) signatures for black carbon (BC), organic carbon (OC) and water-soluble organic carbon (WSOC) aerosols collected in urban (Beijing and BC for Shanghai) and regional receptors (e.g., Korea Climate Observatory at Gosan) during January 2014. Fossil sources (>50%) dominate BC at all sites with most stemming from coal combustion, except for Shanghai, where liquid fossil source is largest. During source-to-receptor transport, the δ13C fingerprint becomes enriched for WSOC but depleted for water-insoluble OC (WIOC). This reveals that the atmospheric processing of these two major pools are fundamentally different. The photochemical aging (e.g., photodissociation, photooxidation) during formation and transport can release CO2/CO or short-chain VOCs with lighter carbon, whereas the remaining WSOC becomes increasingly enriched in δ13C. On the other hand, several processes, e.g., secondary formation, rearrangement reaction in the particle phase, and photooxidation can influence WIOC. Taken together, this study highlights high fossil contributions for all carbonaceous aerosol sub-compartments in East Asia, and suggests different transformation pathways for different classes of carbonaceous aerosols. VL - 7 UR - http://www.nature.com/articles/s41598-017-10766-4 IS - 1 ER - TY - JOUR T1 - Documenting domestication in a lost crop (Polygonum erectum L.): evolutionary bet-hedgers under cultivation JF - Vegetation History and Archaeobotany Y1 - 2017 A1 - Mueller, Natalie G. KW - Domestication KW - Eastern Agricultural Complex KW - Evolutionary bet-hedging KW - Morphometrics KW - Origins of agriculture AB - This study uses morphometrics and digital image analysis to document domestication syndrome in an annual seed crop, Polygonum erectum L. (erect knotweed), which was cultivated by Native Americans for c. 2,500 years in eastern North America. This plant is one of several seed crops referred to as the Eastern Agricultural Complex, a pre-maize agricultural system that supported societies in a core area centred on the central Mississippi valley for millennia. The extinct domesticated subspecies P. erectum ssp. watsoniae N. G. Muell. described here, exhibits some classic markers of domestication, including larger fruits and reduced germination inhibitors in comparison to its wild progenitor. Domesticated P. erectum also exhibits greatly reduced germination heteromorphism. Germination heteromorphism is the classic example of evolutionary bet-hedging in plants: wild P. erectum sacrifices maximum fitness per generation for a reduction in fitness variance over many generations. It does so by producing two different types of fruits: ones that germinate immediately in the spring after they are produced (smooth morphs), and ones that remain in the soil seed bank for one or more growing seasons before germinating (tubercled morphs). Tubercled morphs allow populations to recover after adverse events. Under cultivation, the selective pressures that maintained this strategy were relaxed as humans saved seeds and created predictable microenvironments for seedlings, resulting in homogenous harvests and reliable germination for ancient farmers. VL - 2621544151612277251256252491314471317501927512453130187936325211846611242525023108578256126282112 UR - http://link.springer.com/10.1007/s00334-016-0592-9http://link.springer.com/content/pdf/10.1007/s00334-016-0592-9.pdfhttp://link.springer.com/content/pdf/10.1007/s00334-016-0592-9.pdfhttp://link.springer.com/article/10.1007/s00334-016-0592-9/fulltext.html IS - 3 ER - TY - JOUR T1 - Dynamics of marsh-mangrove ecotone since the mid-Holocene: A palynological study of mangrove encroachment and sea level rise in the Shark River Estuary, Florida JF - PLOS ONE Y1 - 2017 A1 - Yao, Qiang A1 - Liu, Kam-biu ED - Magar, Vanesa AB - Sea level rise and the associated inland shift of the marsh-mangrove ecotone in south Florida have raised many scientific and management concerns in recent years. Holocene paleoecological records can provide an important baseline to shed light on the long-term dynamics of vegetation changes across this ecotone in the past, which is needed to predict the future. In this study, we present palynological, X-ray fluorescence, and loss-on ignition data from four sedimentary cores recovered from a 20-km marine-to-freshwater transect along the Shark River Estuary, southwest Everglades, to document the patterns and processes of coastal vegetation changes in response to sea level rise since the mid-Holocene. Our record indicates that freshwater marsh progressively replaced marl prairies at the Shark River Estuary between 5700 and 4400 cal yr BP. As marine transgression continued, marine influence reached the threshold necessary for mangroves to establish at the current mouth of the Shark River Slough at 3800 cal yr BP. During the next 3000 years, although sea level rise in the Western North Atlantic slowed down to 0.4 mm/yr, a spatial and temporal gradient was evident as the marsh-mangrove ecotone shifted inland by 20 km from 3800 to 800 cal yr BP, accompanied by a gradual landward replacement of freshwater marsh by mangrove forest. If sea level continues to rise at 2.33 mm/yr in the 21st century in south Florida, it is possible that marine influence will reach the threshold for mangroves to establish in the central Everglades, and we could expect a much more aggressive mangrove encroachment toward the northern and interior parts of south Florida in the next few centuries. UR - https://doi.org/10.1371/journal.pone.0173670 ER - TY - JOUR T1 - Elucidating carbon sources driving microbial metabolism during oil sands reclamation JF - Journal of Environmental Management Y1 - 2017 A1 - Lauren M. Bradford A1 - Lori A. Ziolkowski A1 - Corey Goad A1 - Lesley A. Warren A1 - Gregory F. Slater KW - Phospholipid fatty acids (PLFA) AB - Abstract Microbial communities play key roles in remediation and reclamation of contaminated environments via biogeochemical cycling of organic and inorganic components. Understanding the trends in in situ microbial community abundance, metabolism and carbon sources is therefore a crucial component of effective site management. The focus of this study was to use radiocarbon analysis to elucidate the carbon sources driving microbial metabolism within the first pilot wetland reclamation project in the Alberta oil sands region where the observation of \{H2S\} had indicated the occurrence of microbial sulphate reduction. The reclamation project involved construction of a three compartment system consisting of a freshwater wetland on top of a sand cap overlying a composite tailings (CT) deposit. Radiocarbon analysis demonstrated that both dissolved and sediment associated organic carbon associated with the deepest compartments (the \{CT\} and sand cap) was primarily fossil (Δ14C = −769 to −955‰) while organic carbon in the overlying peat was hundreds to thousands of years old (Δ14C = −250 to −350‰). Radiocarbon contents of sediment associated microbial phospholipid fatty acids (PLFA) were consistent with the sediment bulk organic carbon pools (Peat: Δ14CPLFA = −257‰; Sand cap Δ14CPLFA = −805‰) indicating that these microbes were using sediment associated carbon. In contrast, microbial \{PLFA\} grown on biofilm units installed in wells within the deepest compartments contained much more modern carbon that the associated bulk carbon pools. This implied that the transfer of relatively more modern carbon was stimulating the microbial community at depth within the system. Correlation between cellular abundance estimates based on \{PLFA\} concentrations and the Δ14CPLFA indicated that the utilization of this more modern carbon was stimulating the microbial community at depth. These results highlight the importance of understanding the occurrence and potential outcomes of the introduction of relatively bioavailable carbon to mine wastes in order to predict and manage the performance of reclamation strategies. VL - 188 UR - http://www.sciencedirect.com/science/article/pii/S0301479716309045 ER - TY - JOUR T1 - Equilibrium line altitudes along the Andes during the Last millennium: Paleoclimatic implications JF - The Holocene Y1 - 2017 A1 - Sagredo, Esteban A A1 - Lowell, Thomas V A1 - Kelly, Meredith A A1 - Rupper, Summer A1 - Aravena, Juan Carlos A1 - Ward, Dylan J A1 - Malone, Andrew GO KW - Andes KW - equilibrium line altitude KW - glacial fluctuations KW - glacial reconstruction KW - Holocene KW - last millennium AB - Deciphering the climate changes that influenced the glacial fluctuations of the last millennium requires documenting the spatial and temporal patterns of these glacial events. Here, we estimate the change in equilibrium line altitudes (ELAs) between the most prominent glacial advance of the last millennium and the present for four alpine glaciers located in different climatic regimes along the Andes. For each glacier, we reconstruct scenarios of climatic conditions (temperature and precipitation anomalies) that accommodate the observed ELA changes. We focus on the following glaciers: an alpine glacier in the Cordillera Vilcanota (13°S), Tapado glacier (30°S), Cipreses glacier (34°S), and Tranquilo glacier (47°S). Our results show that the range of possible temperature and precipitation anomalies that accommodate the observed ELA changes overlap significantly at three of the four sites (i.e. Vilcanota, Cipreses, and Tranquilo). Only Tapado glacier exhibits a set of climate anomalies that differs from the other three sites. Assuming no change in precipitation, the estimated ELA changes require a cooling of at least 0.7°C in the Cordillera Vilcanota, 1.0°C at Tapado glacier, 0.6°C at Cipreses glacier, and 0.7°C at Tranquilo glacier. Conversely, assuming no change in temperature, the estimated ELA changes are explained by increases in precipitation exceeding 0.52 m yr−1 (64% of the annual precipitation) in the Cordillera Vilcanota, 0.31 m yr−1 (89%) at Tapado glacier, 0.22 m yr−1 (27%) at Cipreses glacier, and 0.3 m yr−1 (27%) at Tranquilo glacier. By mapping the ELA changes and modeling the potential climate forcing across diverse climate settings, we aim to contribute toward documenting the spatial variability of climate conditions during the last millennium, a key step to decipher the mechanisms underlying the glacial fluctuation that occurred during this period. VL - 27 UR - http://journals.sagepub.com/doi/10.1177/0959683616678458 IS - 7 ER - TY - JOUR T1 - Erosion of modern terrestrial organic matter as a major component of sediments in fjords JF - Geophysical Research Letters Y1 - 2017 A1 - Cui, Xingqian A1 - Bianchi, Thomas S. A1 - Savage, Candida AB - Fjords have recently been recognized as “hot spots” of carbon burial. In this study, we investigated organic carbon (OC) and biomarker radiocarbon values in fjord sediments from New Zealand. Our results showed that OC was mostly modern with the most aged OC in middle reaches of fjords, likely related to hydrodynamic sorting and inputs along adjacent slopes. Radiocarbon ages of sedimentary OC increased from north-to-south, consistent with the Fiordland regional gradients of lower fjord slopes and less rainfall. Our biomarker results suggested that lignin and long-chain fatty acids were preferentially linked with fresh terrestrial debris and degraded soil, respectively, likely due to their chemical and physical properties. Finally, we propose that fjords are a significant sink of modern OC, in contrast to large lowland coastal systems as a major sink of preaged OC. Overall, this study indicated that radiocarbon techniques are critical in investigating carbon dynamics in coastal systems. VL - 442824441945245112168105110293225215662639493436151675187268234320723424507431438414191121427211539259 UR - http://doi.wiley.com/10.1002/2016GL072260http://onlinelibrary.wiley.com/wol1/doi/10.1002/2016GL072260/fullpdfhttps://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2F2016GL072260 IS - 345355903755111181-21212316171193141-2182341 ER - TY - JOUR T1 - Evidence for coseismic subsidence events in a southern California coastal saltmarsh JF - Scientific Reports Y1 - 2017 A1 - Leeper, Robert A1 - Rhodes, Brady A1 - Kirby, Matthew A1 - Scharer, Katherine A1 - Carlin, Joseph A1 - Hemphill-Haley, Eileen A1 - Avnaim-Katav, Simona A1 - MacDonald, Glen A1 - Starratt, Scott A1 - Aranda, Angela KW - Geomorphology KW - Natural hazards KW - Structural geology KW - tectonics AB - Paleoenvironmental records from a southern California coastal saltmarsh reveal evidence for repeated late Holocene coseismic subsidence events. Field analysis of sediment gouge cores established discrete lithostratigraphic units extend across the wetland. Detailed sediment analyses reveal abrupt changes in lithology, percent total organic matter, grain size, and magnetic susceptibility. Microfossil analyses indicate that predominantly freshwater deposits bury relic intertidal deposits at three distinct depths. Radiocarbon dating indicates that the three burial events occurred in the last 2000 calendar years. Two of the three events are contemporaneous with large-magnitude paleoearthquakes along the Newport-Inglewood/Rose Canyon fault system. From these data, we infer that during large magnitude earthquakes a step-over along the fault zone results in the vertical displacement of an approximately 5-km2 area that is consistent with the footprint of an estuary identified in pre-development maps. These findings provide insight on the evolution of the saltmarsh, coseismic deformation and earthquake recurrence in a wide area of southern California, and sensitive habitat already threatened by eustatic sea level rise. VL - 7 UR - http://www.nature.com/articles/srep44615 ER - TY - JOUR T1 - Evolutionary “Bet-Hedgers” under Cultivation: Investigating the Domestication of Erect Knotweed (Polygonum erectum L.) using Growth Experiments JF - Human Ecology Y1 - 2017 A1 - Mueller, Natalie G. KW - Domestication KW - Eastern agricultural complex North America KW - Erect knotweed KW - Evolutionary bet-hedging KW - Experimental archaeology AB - Evolutionary “bet-hedging” refers to situations in which organisms sacrifice mean fitness for a reduction in fitness variance over time. Germination heteromorphism is the quintessential and most well understood bet-hedging strategy. It has evolved in many different plants, including the wild progenitors of some crops. Erect knotweed (Polygonum erectum L.), an annual seed crop, was cultivated in Eastern North America between c. 3000–600 BP. By c. 900 BP, cultivation had produced a domesticated subspecies with greatly reduced germination heteromorphism. Field observations and greenhouse experiments suggest that cultivation eliminated the selective pressures that maintain the bet-hedging strategy in erect knotweed, while humans also directly selected for seeds that germinated reliably and for seedlings with rapid early growth. The protection provided to erect knotweed under cultivation explains the domestication syndrome that has been observed in some archaeological assemblages. Dormancy provides seeds a means of escaping adverse conditions in time, while dispersal provides an escape in space. Farmers relaxed selective pressures that maintained dormancy in erect knotweed by acting as seed dispersers, spreading disturbance-adapted plants to predictable and protected environments, and by saving and exchanging seed stock. Experimental data also indicate that adaptive transgenerational plasticity may have been working against the expression of domestication syndrome in this case. VL - 451072rspb2010070712131513581318177327257912425250103106757712621 UR - http://link.springer.com/10.1007/s10745-016-9881-2http://link.springer.com/content/pdf/10.1007/s10745-016-9881-2.pdfhttp://link.springer.com/content/pdf/10.1007/s10745-016-9881-2.pdfhttp://link.springer.com/article/10.1007/s10745-016-9881-2/fulltext.html IS - 2851313232181233165654 ER - TY - JOUR T1 - The experimental flow to the Colorado River delta: Effects on carbon mobilization in a dry watercourse JF - Journal of Geophysical Research: Biogeosciences Y1 - 2017 A1 - Bianchi, Thomas S. A1 - Butman, David A1 - Raymond, Peter A. A1 - Ward, Nicholas D. A1 - Kates, Rory J. S. A1 - Flessa, Karl W. A1 - Zamora, Hector A1 - Arellano, Ana R. A1 - Ramirez, Jorge A1 - Rodriguez, Eliana KW - carbon cycling KW - Colorado River KW - dry watercourse KW - flooding KW - greenhouse gases KW - mobilization AB - Here we report on the effects of an experimental flood on the carbon cycling dynamics in the dry watercourse of the Colorado River in Mexico. We observed post‐flood differences in the degree of decay, age, and concentration of dissolved organic carbon (DOC), as well as dissolved CH4 and CO2 concentrations throughout the study site. Our results indicate that this flooded waterway was a limited source of CH4 and CO2 to the atmosphere during the event and that DOC age increased with time of flooding. Based on our findings, we suggest that the interplay between storage and mobilization of carbon and greenhouse gases in arid and semiarid regions is potentially sensitive to changing climate conditions, particularly hydrologic variability. Changes in the radiocarbon age of DOC throughout the flooding event suggest that organic matter (OM) that had been stored for long periods (e.g., millennial) was mobilized by the flooding event along with CO2. The OM residing in the dry riverbed that was mobilized into floodwaters had a signature reflective of degraded vascular plant OM and microbial biomass. Whether this microbial OM was living or dead, our findings support previous work in soils and natural waters showing that microbial OM can remain stable and stored in ecosystems for long time periods. As human appropriation of water resources continues to increase, the episodic drying and rewetting of once natural riverbeds and deltas may fundamentally alter the processing and storage of carbon in such systems. VL - 122 UR - https://agupubs.onlinelibrary.wiley.com/doi/10.1002/2016JG003555 IS - 3 ER - TY - JOUR T1 - Extended late Holocene relative sea-level histories for North Carolina, \{USA\} JF - Quaternary Science Reviews Y1 - 2017 A1 - Andrew C. Kemp A1 - Jessica J. Kegel A1 - Stephen J. Culver A1 - Donald C. Barber A1 - David J. Mallinson A1 - Eduardo Leorri A1 - Christopher E. Bernhardt A1 - Niamh Cahill A1 - Stanley R. Riggs A1 - Anna L. Woodson A1 - Ryan P. Mulligan A1 - Benjamin P. Horton KW - Salt marsh AB - Abstract We produced ∼3000-year long relative sea-level (RSL) histories for two sites in North Carolina (USA) using foraminifera preserved in new and existing cores of dated salt-marsh sediment. At Cedar Island, \{RSL\} rose by ∼2.4 m during the past ∼3000 years compared to ∼3.3 m at Roanoke Island. This spatial difference arises primarily from differential \{GIA\} that caused late Holocene \{RSL\} rise to be 0.1–0.2 mm/yr faster at Roanoke Island than at Cedar Island. However, a non-linear difference in \{RSL\} between the two study regions (particularly from ∼0 \{CE\} to ∼1250 CE) indicates that additional local- to regional-scale processes drove centennial-scale \{RSL\} change in North Carolina. Therefore, the Cedar Island and Roanoke Island records should be considered as independent of one another. Between-site differences on sub-millennial timescales cannot be adequately explained by non-stationary tides, sediment compaction, or local sediment dynamics. We propose that a period of accelerating \{RSL\} rise from ∼600 \{CE\} to 1100 \{CE\} that is present at Roanoke Island (and other sites north of Cape Hatteras at least as far as Connecticut), but absent at Cedar Island (and other sites south of Cape Hatteras at least as far as northeastern Florida) is a local-to regional-scale effect of dynamic ocean and/or atmospheric circulation. VL - 160 UR - http://www.sciencedirect.com/science/article/pii/S0277379116304759 ER - TY - JOUR T1 - An Extinct Domesticated Subspecies of Erect Knotweed in Eastern North America: Polygonum erectum subsp. watsoniae (Polygonaceae) JF - Novon: A Journal for Botanical Nomenclature Y1 - 2017 A1 - Mueller, Natalie G. KW - Domestication KW - Eastern Agricultural Complex KW - fruit morphology KW - paleoethnobotany KW - Polygonum AB - This paper provides a description of an extinct domesticated subspecies of erect knotweed (Polygonum erectum L.). Masses of erect knotweed achenes are often recovered from archaeological sites in eastern North America dating to ca. 3000–600 BP. Several paleoethnobotanical assemblages from the later part of this era (ca. 1000–600 BP) contain achenes that are outside the range of natural variation for erect knotweed. The most well preserved of these archaeological assemblages, a desiccated cache of achenes from the Whitney Bluff site, Arkansas (ca. 900 BP), is compared to four closely related species and subspecies of Polygonum L. The Whitney Bluff achenes are most similar to those of P. erectum, but differ from modern fruits of this species in three respects: (1) fruits are larger, (2) average pericarp thickness is reduced, and (3) fruit dimorphism is greatly reduced. These differences are typical of domestication syndrome in annual seed crops. The Whitney Bluff assemblage is described as the type specimen of a domesticated subspecies, P. erectum subsp. watsoniae N. G. Muell. VL - 25 UR - http://www.bioone.org/doi/10.3417/2016005http://www.bioone.org/doi/full-xml/10.3417/2016005 IS - 2 ER - TY - JOUR T1 - Extreme waves in the British Virgin Islands during the last centuries before 1500 CE JF - Geosphere Y1 - 2017 A1 - Atwater, Brian F. A1 - ten Brink, Uri S. A1 - Cescon, Anna Lisa A1 - Feuillet, Nathalie A1 - Fuentes, Zamara A1 - Halley, Robert B. A1 - ñez, Carlos A1 - Reinhardt, Eduard G. A1 - Roger, Jean H. A1 - Sawai, Yuki A1 - Spiske, Michaela A1 - Tuttle, Martitia P. A1 - Wei, Yong A1 - Weil-Accardo, Jennifer AB - Extraordinary marine inundation scattered clasts southward on the island of Anegada, 120 km south of the Puerto Rico Trench, sometime between 1200 and 1480 calibrated years (cal yr) CE. Many of these clasts were likely derived from a fringing reef and from the sandy flat that separates the reef from the island’s north shore. The scattered clasts include no fewer than 200 coral boulders, mapped herein for the first time and mainly found hundreds of meters inland. Many of these are complete colonies of the brain coral Diploria strigosa. Other coral species represented include Orbicella (formerly Montastraea) annu­laris, Porites astreoides, and Acropora palmata. Associated bioclastic carbonate sand locally contains articulated cobble-size valves of the lucine Codakia orbicularis and entire conch shells of Strombus gigas, mollusks that still inhabit the sandy shallows between the island’s north shore and a fringing reef beyond. italicmbricated limestone slabs are clustered near some of the coral boulders. In addition, fields of scattered limestone boulders and cobbles near sea level extend mainly southward from limestone sources as much as 1 km inland. Radiocarbon ages have been obtained from 27 coral clasts, 8 lucine valves, and 3 conch shells. All these additional ages predate 1500 cal yr CE, all but 2 are in the range 1000–1500 cal yr CE, and 16 of 22 brain coral ages cluster in the range 1200–1480 cal yr CE. The event marked by these coral and mollusk clasts likely occurred in the last centuries before Columbus (before 1492 CE). The pre-Columbian deposits surpass Anegada’s previously reported evidence for extreme waves in post-Columbian time. The coarsest of the modern storm deposits consist of coral rubble that lines the north shore and sandy fans on the south shore; neither of these storm deposits extends more than 50 m inland. More extensive overwash, perhaps by the 1755 Lisbon tsunami, is marked primarily by a sheet of sand and shells found mainly below sea level beneath the floors of modern salt ponds. This sheet extends more than 1 km southward from the north shore and dates to the interval 1650–1800 cal yr CE. Unlike the pre-Columbian deposits, it lacks coarse clasts from the reef or reef flat; its shell assemblage is instead dominated by cerithid gastropods that were merely stirred up from a marine pond in the island’s interior. In their inland extent and clustered pre-Columbian ages, the coral clasts and associated deposits suggest extreme waves unrivaled in recent millennia at Anegada. Bioclastic sand coats limestone 4 m above sea level in areas 0.7 and 1.3 km from the north shore. A coral boulder of nearly 1 m3 is 3 km from the north shore by way of an unvegetated path near sea level. As currently understood, the extreme flooding evidenced by these and other clasts represents either an extraordinary storm or a tsunami of nearby origin. The storm would need to have produced tsunami-like bores similar to those of 2013 Typhoon Haiyan in the Philippines. Normal faults and a thrust fault provide nearby tsunami sources along the eastern Puerto Rico Trench. VL - 13 UR - http://geosphere.gsapubs.org/lookup/doi/10.1130/GES01356.1 IS - 2 ER - TY - JOUR T1 - Final Radiocarbon Investigation of Platland Tree, the Biggest African Baobab JF - Studia Universitatis Babeș-Bolyai Chemia Y1 - 2017 A1 - Patrut, Adrian A1 - Woodborne, Stephan A1 - Patrut, Roxana T. A1 - Rakosy, Laszlo A1 - Hall, Grant A1 - Ratiu, Ileana-Andreea A1 - von Reden, Karl F. AB - The article discloses the main results of our new investigation of Platland tree, a.k.a. Sunland baobab, the largest known African baobab. Our recent research was motivated by the three successive splits of 2016 and 2017, which determined the collapse and demise of the stems that have built the main unit of the tree. According to our new findings concerning the architecture of large and old baobabs, we established that Platland tree has a double closed-ring shaped structure and consists of two units/rings that close two separate false cavities. The larger unit was composed of five fused stems, out of which four toppled and died, while the fifth stem is already broken. The smaller unit, which is still standing, consists of three fused stems. We also determined that the larger unit had an age of 800 yr, while the smaller unit is 1100 yr old. VL - 62 UR - https://www.researchgate.net/publication/318354222_Final_Radiocarbon_Investigation_of_Platland_Tree_the_Biggest_African_Baobab IS - 2 ER - TY - JOUR T1 - Greenhouse gas balance over thaw-freeze cycles in discontinuous zone permafrost JF - Journal of Geophysical Research: Biogeosciences Y1 - 2017 A1 - Wilson, R. M. A1 - Fitzhugh, L. A1 - Whiting, G. J. A1 - Frolking, S. A1 - Harrison, M. D. A1 - Dimova, N. A1 - Burnett, W. C. A1 - Chanton, J. P. AB - Peat in the discontinuous permafrost zone contains a globally significant reservoir of carbon that has undergone multiple permafrost-thaw cycles since the end of the mid-Holocene (~3700 years before present). Periods of thaw increase C decomposition rates which leads to the release of CO2 and CH4 to the atmosphere creating potential climate feedback. To determine the magnitude and direction of such feedback, we measured CO2 and CH4 emissions and modeled C accumulation rates and radiative fluxes from measurements of two radioactive tracers with differing lifetimes to describe the C balance of the peatland over multiple permafrost-thaw cycles since the initiation of permafrost at the site. At thaw features, the balance between increased primary production and higher CH4 emission stimulated by warmer temperatures and wetter conditions favors C sequestration and enhanced peat accumulation. Flux measurements suggest that frozen plateaus may intermittently (order of years to decades) act as CO2 sources depending on temperature and net ecosystem respiration rates, but modeling results suggest that—despite brief periods of net C loss to the atmosphere at the initiation of thaw—integrated over millennia, these sites have acted as net C sinks via peat accumulation. In greenhouse gas terms, the transition from frozen permafrost to thawed wetland is accompanied by increasing CO2 uptake that is partially offset by increasing CH4 emissions. In the short-term (decadal time scale) the net effect of this transition is likely enhanced warming via increased radiative C emissions, while in the long-term (centuries) net C deposition provides a negative feedback to climate warming. VL - 122 UR - onlinelibrary.wiley.com/wol1/doi/10.1002/2016JG003600/fullpdf IS - 2 ER - TY - JOUR T1 - Grounding line proximal sediment characteristics at a marine-based, late-stage ice stream margin JF - Journal of Quaternary Science Y1 - 2017 A1 - R?ther, Denise Christina A1 - Winsborrow, Monica A1 - Andreassen, Karin A1 - Forwick, Matthias AB - Geomorphological evidence suggests that ice streams undergo frequent dynamic changes towards the end of their life cycles, but the associated sedimentary characteristics and processes remain poorly understood. Here, we present new sedimentological data from a Late Weichselian marine-based ice stream in upper Bjørnøyrenna, northern Barents Sea, which experienced accelerated flow, intense calving of large icebergs, ice stream stagnation, ice shelf formation and disintegration. Observed till characteristics support the idea of spatially and temporally variable basal drag underneath ice streams. In addition, fast flow may have been accommodated in dilatant deforming till as well as through basal sliding over sticky spots of stiffer till. The grounding zone is shown to be highly transient and spatially variable during the final ice stream readvances, thus making the categories subglacial/proglacial of little value. In line with previous radiocarbon dates, we find that uppermost Bjørnøyrenna was deglaciated before ∼11.3–12.0k cal a BP. Finally, the provenances for the latest ice stream advance and an older ice flow event are inferred based on a novel way of using element geochemistry, helping define ice dome configuration in the northern Barents Sea. VL - 32 UR - http://doi.wiley.com/10.1002/jqs.2939 IS - 4 ER - TY - JOUR T1 - The Growth Stop Phenomenon Of Baobabs (Adansonia Spp.) Identified By Radiocarbon DatingAbstract JF - Radiocarbon Y1 - 2017 A1 - Patrut, Adrian A1 - Woodborne, Stephan A1 - von Reden, Karl F A1 - Hall, Grant A1 - Patrut, Roxana T A1 - Rakosy, Laszlo A1 - Danthu, Pascal A1 - Pock-Tsy, Jean-Michel Leong A1 - Lowy, Daniel A A1 - Margineanu, Dragos KW - Age determination KW - AMS KW - growth stop KW - Radiocarbon dating KW - tropical trees AB - The article reports the growth stop phenomenon, which was documented only for baobabs, i.e. for trees belonging to the Adansonia genus. The identification of growth stop was enabled by radiocarbon dating, which allows a complex investigation of samples collected from the trunk/stems of baobabs. In several cases, the outermost rings of baobabs, which were close to the bark, were found to be old, with ages of several hundreds of years, instead of being very young. Dating results of samples collected from six baobabs are presented. For multistemmed baobabs, the growth stop may occur only for one or several stems. We identified four factors that may induce the growth stop: (i) stress determined by severe climate conditions, (ii) old age, (iii) the need to keep a stable internal architecture, and (iv) the collapse of stems that survive this trauma. Baobabs and their stems affected by growth stop may survive for several centuries, by continuing to produce leaves, flowers, and fruits. This phenomenon was associated with the capacity of baobabs to store large amounts of water in their trunks/stems in the rainy season. This reservoir of water is used during the dry season and allows the trees to survive prolonged drought periods. VL - 59504754164661 UR - https://www.cambridge.org/core/product/identifier/S0033822216000928/type/journal_articlehttps://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0033822216000928 IS - 02 ER - TY - JOUR T1 - A high resolution record of rare earth element compositional changes from the mud deposit on the inner shelf of the East China Sea: Implications for paleoenvironmental changes JF - Quaternary International Y1 - 2017 A1 - Mi, Beibei A1 - Liu, Shengfa A1 - Shi, Xuefa A1 - Li, Xiaoyan A1 - Pan, Hui-Juan A1 - Chen, Min-Te A1 - Wang, Xuchen KW - East China Sea KW - Mud deposit KW - Paleoenvironmental KW - Provenance KW - Rare earth element KW - Sediment AB - A paleoenvironmental reconstruction of the East China Sea (ECS) is presented using rare earth element (REE) analysis of sediments from Core MZ02, which was retrieved from the inner continental shelf's mud area. The analytic results show that the total REEs in the fine sediment vary between 137.76 μg/g and 231.53 μg/g with an average value of 187.69 μg/g. Obvious changes were found during the process of sedimentation. By comparing with the REE compositions from the potential provenances, the ratios of (La/Sm)ucc and (Gd/Yb)ucc revealed that the sediments were mainly derived from river detrital outputs of the Changjiang (Yangtze River), Minjiang and mountainous rivers from western Taiwan Island. The contributions of terrestrial materials from these three main provenances were controlled by sea level change and the Taiwan Warm Current (TWC)-Chinese Coastal Current (CCC) system, which is mainly driven by the East Asian monsoon. The high sedimentation rate during the transgression period between the late Pleistocene and early Holocene (13000–9800 a B.P.) was caused by a well-proportioned mixed provenance from Changjiang, western Taiwanese rivers and Minjiang sediments, due to the lower sea level and the location of the foreshore-nearshore face. Because of the stronger sediment reworking and erosion at the shelf edge during the early Holocene (9800–7300 a B.P.), the strengthening summer East Asian monsoon transported the Minjiang and western Taiwanese river material northeastward, and it became the main sediment source for fine sediments in the shallow sea region of the ECS, while the Changjiang provided a relatively minor amount of detrital sediment to the shelf. The increasing strength of the TWC might have played an important role in sediment dispersal and deposition on the ECS inner shelf during the period 7300–3500 a B.P., thus mountainous river material became the dominant sediment on the shelf of the ECS. Furthermore, the results indicate that the East Asian monsoon and the weakening of the TWC were linked to an abrupt increase in Changjiang-derived terrigenous detritus material since 3500 a B.P.; the source and sink pattern during this period is consistent with the modern sedimentation environment. UR - https://doi.org/10.1016/j.quaint.2016.09.056 ER - TY - JOUR T1 - High-resolution climate of the past ∼7300 years of coastal northernmost California: Results from diatoms, silicoflagellates, and pollen JF - Quaternary International Y1 - 2017 A1 - John A. Barron A1 - David Bukry A1 - Linda E. Heusser A1 - Jason A. Addison A1 - Clark R. Alexander AB - Abstract Piston core TN062-O550, collected about 33 km offshore of Eureka, California, contains a high-resolution record of the climate and oceanography of coastal northernmost California during the past ∼7.34 kyr. Chronology established by nine \{AMS\} ages on a combination of planktic foraminifers, bivalve shell fragments, and wood yields a mean sedimentation rate of 103 cm kyr−1. Marine proxies (diatoms and silicoflagellates) and pollen transported by the nearby Eel River reveal a stepwise development of both modern offshore surface water oceanography and coastal arboreal ecosystems. Beginning at ∼5.4 cal ka the relative abundance of coastal redwood pollen, a proxy for coastal fog, displays a two fold increase suggesting enhanced coastal upwelling. A decline in the relative contribution of subtropical diatoms at ∼5.0 cal ka implies cooling of sea surface temperatures (SSTs). At ∼3.6 cal ka an increase in the relative abundance of alder and oak at the expense of coastal redwood likely signals intensified riverine transport of pollen from inland environments. Cooler offshore \{SSTs\} and increased precipitation characterize the interval between ∼3.6 and 2.8 cal ka. A rapid, stepwise change in coastal climatology and oceanography occurs between ∼2.8 and 2.6 cal ka that suggests an enhanced expression of modern Pacific Decadal Oscillation-like (PDO) cycles. A three-fold increase in the relative abundance of the subtropical diatom Fragilariopsis doliolus at 2.8 cal ka appears to mark an abrupt warming of winter SSTs. Soon afterwards at 2.6 cal ka, a two fold increase in the relative abundance of coastal redwood pollen is suggestive of an abrupt intensification of spring upwelling. After ∼2.8 cal ka a sequence of cool-warm, PDO-like cycles occurs wherein cool cycles are characterized by relative abundance increases in coastal redwood pollen and decreased contributions of subtropical diatoms, whereas opposite proxy trends distinguish warm cycles. UR - http://www.sciencedirect.com/science/article/pii/S1040618216300866 ER - TY - JOUR T1 - Holocene climate and environmental history of East Greenland inferred from lake sediments JF - Journal of Paleolimnology Y1 - 2017 A1 - Lusas, Amanda R. A1 - Hall, Brenda L. A1 - Lowell, Thomas V. A1 - Kelly, Meredith A. A1 - Bennike, Ole A1 - Levy, Laura B. A1 - Honsaker, William KW - De Vries cycle KW - Glacially fed lakes KW - Greenland KW - Holocene KW - Paleoclimate AB - Prediction of future Arctic climate and environmental changes, as well as associated ice-sheet behavior, requires placing present-day warming and reduced ice extent into a long-term context. Here we present a record of Holocene climate and glacier fluctuations inferred from the paleolimnology of small lakes near Istorvet ice cap in East Greenland. Calibrated radiocarbon dates of organic remains indicate deglaciation of the region before ~10,500 years BP, after which time the ice cap receded rapidly to a position similar to or less extensive than present, and lake sediments shifted from glacio-lacustrine clay to relatively organic-rich gyttja. The lack of glacio-lacustrine sediments throughout most of the record suggests that the ice cap was similar to or smaller than present throughout most of the Holocene. This restricted ice extent suggests that climate was similar to or warmer than present, in keeping with other records from Greenland that indicate a warm early and middle Holocene. Middle Holocene magnetic susceptibility oscillations, with a ~200-year frequency in one of the lakes, may relate to solar influence on local catchment processes. Following thousands of years of restricted extent, Istorvet ice cap advanced to within 365 m of its late Holocene limit at ~AD 1150. Variability in the timing of glacial and climate fluctuations, as well as of sediment organic content changes among East Greenland lacustrine records, may be a consequence of local factors, such as elevation, continentality, water depth, turbidity, and seabirds, and highlights the need for a detailed spatial array of datasets to address questions about Holocene climate change. VL - 57 UR - http://link.springer.com/10.1007/s10933-017-9951-5 IS - 4 ER - TY - JOUR T1 - Holocene sea ice variability driven by wind and polynya efficiency in the Ross Sea JF - Nature Communications Y1 - 2017 A1 - Mezgec, K. A1 - Stenni, B. A1 - Crosta, X. A1 - Masson-Delmotte, V. A1 - Baroni, C. A1 - Braida, M. A1 - Ciardini, V. A1 - Colizza, E. A1 - Melis, R. A1 - Salvatore, M. C. A1 - Severi, M. A1 - Scarchilli, C. A1 - Traversi, R. A1 - Udisti, R. A1 - Frezzotti, M. AB - The causes of the recent increase in Antarctic sea ice extent, characterised by large regional contrasts and decadal variations, remain unclear. In the Ross Sea, where such a sea ice increase is reported, 50% of the sea ice is produced within wind-sustained latent-heat polynyas. Combining information from marine diatom records and sea salt sodium and water isotope ice core records, we here document contrasting patterns in sea ice variations between coastal and open sea areas in Western Ross Sea over the current interglacial period. Since about 3600 years before present, an increase in the efficiency of regional latent-heat polynyas resulted in more coastal sea ice, while sea ice extent decreased overall. These past changes coincide with remarkable optima or minima in the abundances of penguins, silverfish and seal remains, confirming the high sensitivity of marine ecosystems to environmental and especially coastal sea ice conditions. VL - 8 UR - http://www.nature.com/articles/s41467-017-01455-x IS - 1 ER - TY - JOUR T1 - Holocene temperatures and isotopes of precipitation in Northwest Greenland recorded in lacustrine organic materials JF - Quaternary Science Reviews Y1 - 2017 A1 - Lasher, G. Everett A1 - Axford, Yarrow A1 - McFarlin, Jamie M. A1 - Kelly, Meredith A. A1 - Osterberg, Erich C. A1 - Berkelhammer, Max B. KW - Chironomids KW - Greenland KW - Holocene KW - paleoclimatology KW - paleolimnology KW - Stable isotopes AB - Reconstructions of Holocene lake water isotopic composition based upon subfossil aquatic organic material offer new insights into Arctic climate. We present quantitative estimates of warmth during the Holocene Thermal Maximum in northwest Greenland, inferred from oxygen isotopes of chironomid head capsules and aquatic moss preserved in lake sediments. delta O-18 values of chironomids from surface sediments of multiple Greenland lakes indicate that these subfossil remains record the delta O-18 values of the lake water in which they grow. Our lake water delta O-18 reconstruction is supported by downcore agreement with delta O-18 values in aquatic moss and chironomid remains. delta O-18 of both organic materials from Secret Lake decrease after 4 ka (ka = thousands of years ago) by 3 parts per thousand into the Neoglacial. We argue that lake water at Secret Lake primarily reflects precipitation delta O-18 values, which is strongly correlated with air temperature in NW Greenland, and that this signal is biased towards summer and early autumn conditions. Other factors may have influenced Secret Lake delta O-18 values through the Holocene, including evaporation of lake water and changing seasonality and source of precipitation. The maximum early Holocene summer and early autumn-biased temperature anomaly at Secret Lake is 2.5-4 degrees C warmer than present from 7.7 (the beginning of our record) to similar to 6 ka. The maximum late Holocene cold anomaly (which includes the Little Ice Age) is 1.5-3 degrees C colder than present. These ranges of possible temperature anomalies reflect uncertainty in the delta O-18 temperature relationship for precipitation at the study site through the Holocene. (C) 2017 Elsevier Ltd. All rights reserved. VL - 170 UR - http://linkinghub.elsevier.com/retrieve/pii/S0277379116305650http://api.elsevier.com/content/article/PII:S0277379116305650?httpAccept=text/xmlhttp://api.elsevier.com/content/article/PII:S0277379116305650?httpAccept=text/plain ER - TY - JOUR T1 - Holocene tephra succession of Puyehue-Cordón Caulle and Antillanca/Casablanca volcanic complexes, southern Andes (40–41°S) JF - Journal of Volcanology and Geothermal Research Y1 - 2017 A1 - J.A. Naranjo A1 - B.S. Singer A1 - B.R. Jicha A1 - H. Moreno A1 - L.E. Lara KW - Chile AB - Abstract Puyehue-Cordón Caulle and Antillanca volcanic complexes are two of at least 50 active frontal arc volcanoes that define the 1400 km-long Southern Volcanic Zone of Chile. Holocene tephra deposits in Chile and Argentina (40–41°S) up to 100 km east of these volcanoes comprise at least five voluminous (  1 to   8 km3) pyroclastic-fall layers that preceded several recently deposited Cordón Caulle pumice fallouts. Field observations of proximal, medium, and distal facies of the deposits, in conjunction with geochronology and geochemistry of the volcanic complexes, indicate that three fall layers are derived from Puyehue volcano (Puyehue 1 and 2, and Mil Hojas), whereas two are sourced from the Antillanca complex (Playas Blanca-Negra, and Nahuel Huapi Tephra), 20 km to the south. The oldest tephra (calibrated 14C age 10.49 ± 0.12 ka, 2σ), found only at medium-distal facies, is deposited directly on granitic moraine boulders and consists of deeply weathered, orange dacitic pumice lapilli. The next prominent tephra at   7 ka comprises dacitic pumice and its age is equivalent to a rhyodacitic dome exposed in the Puyehue summit crater. Above these deposits there are phases of a complex eruption consisting of a conspicuous compositionally-zoned tephra. It also comprises a pyroclastic density current, together with lithic rich and scoriaceous fallout deposits. Mineralogical, geochemical, and Sr isotope evidence, plus the isopach maps, confirm that this sequence of eruptive events is sourced from Antillanca at 1932 ± 68 yrBP. The total volume of this eruptive sequence exceeds 8 km3, making it the largest Holocene eruption from either volcanic complex. This eruption was likely responsible for the destruction of an ancestral Antillanca volcano and the formation of a 4.5 km diameter caldera. A distinctive younger unit in the region is a voluminous rhyodacitic pumice fall (calibrated 14C age 1.11 ± 0.07 ka), above which a series of several alternating dark lithic and pumice lapilli beds accumulated. Correlation with proximal deposits indicates that the 1.11 ka eruption was derived from Puyehue and destroyed   3 km3 of rhyodacitic domes at this volcano summit. Historic explosive activity at the nascent Casablanca volcano and along Cordón Caulle, including the 2011–2012 eruption (  1 km3 of uncompacted pumice), the largest from this fissural zone, emphasizes an increased risk for volcanic hazards in central Chile and Argentina. VL - 332 UR - http://www.sciencedirect.com/science/article/pii/S0377027316301986 ER - TY - JOUR T1 - Hydrologic controls on seasonal and inter-annual variability of Congo River particulate organic matter source and reservoir age JF - Chemical Geology Y1 - 2017 A1 - Hemingway, Jordon D. A1 - Schefuß, Enno A1 - Spencer, Robert G.M. A1 - Dinga, Bienvenu Jean A1 - Eglinton, Timothy I. A1 - McIntyre, Cameron A1 - Galy, Valier V. KW - biomarkers KW - Congo River KW - GDGTs KW - Particulate organic matter KW - radiocarbon AB - We present dissolved organic carbon (DOC) concentrations, particulate organic matter (POM) composition (δ13C, δ15N, ∆14C, N/C), and particulate glycerol dialkyl glycerol tetraether (GDGT) distributions from a 34-month time-series near the mouth of the Congo River. An end-member mixing model using δ13C and N/C indicates that exported POM is consistently dominated by C3 rainforest soil sources, with increasing contribution from C3 vegetation and decreasing contribution from phytoplankton at high discharge. Large C4 inputs are never observed despite covering ≈ 13% of the catchment. Low and variable ∆14C values during 2011 [annual mean = (− 148 ± 82) ‰], when discharge from left-bank tributaries located in the southern hemisphere reached record lows, likely reflect a bias toward pre-aged POM derived from the Cuvette Congolaise swamp forest. In contrast, ∆14C values were stable near − 50‰ between January and June 2013, when left-bank discharge was highest. We suggest that headwater POM is replaced and/or diluted by C3 vegetation and pre-aged soils during transit through the Cuvette Congolaise, whereas left-bank tributaries export significantly less pre-aged material. GDGT distributions provide further evidence for seasonal and inter-annual variability in soil provenance. The cyclization of branched tetraethers and the GDGT-0 to crenarchaeol ratio are positively correlated with discharge (r ≥ 0.70; p-value ≤ 4.3 × 10− 5) due to the incorporation of swamp-forest soils when discharge from right-bank tributaries located in the northern hemisphere is high. Both metrics reach record lows during 2013, supporting our interpretation of increased left-bank contribution at this time. We conclude that hydrologic variability is a major control of POM provenance in the Congo River Basin and that tropical wetlands can be a significant POM source despite their small geographic coverage. VL - 466 UR - https://linkinghub.elsevier.com/retrieve/pii/S0009254117303935 ER - TY - JOUR T1 - Importance of small-scale paleo-oceanographic conditions to interpret changes in size of California mussel (Mytilus californianus). Late Holocene, Santa Cruz island, California JF - Quaternary International Y1 - 2017 A1 - Carola Flores KW - California AB - Abstract Several authors have highlighted the difficulties in disentangling human from natural effects when studying shellfish foraging strategies and archeo-malacogical records. In coastal settings, one of the reasons for this difficulty is the lack of understanding of small-scale oceanographic conditions and their influence on coastal and marine species used by people in the past. The present study evaluated the influence of environmental conditions on shellfish harvesting during the Late Holocene around Santa Cruz Island (Southern California) considering small-scale nearshore oceanographic variability around the Island and its effect on M. californianus (main shellfish species exploited through prehistory along the coast of California). Fluctuations in size and abundance of M. californianus shells through time and local past sea surface temperature (SST) values from oxygen isotope analysis of mussel shells are correlated throughout the stratigraphy of two shell midden sites (2200–500 cal B.P.) nearby coasts with different paleo-oceanographic characteristics. Despite the fact that human harvesting seems to have been the main force shaping length and availability of M. californianus, no clear evidence of human pressure was found on archaeological mussel assemblages. Results also show that fluctuations in regional \{SST\} records (Santa Barbara Basin marine core) do not represent local \{SST\} variations (oxygen isotope analyses on mussel shells), especially if the archaeological site is located on a coast exposed to strong and consistent upwelling activity. By re-evaluating human impact on mussel beds during the Late Holocene around Santa Cruz Island, the research presented here demonstrates the importance of considering small-scale nearshore oceanography for understanding the archaeological evidence of prehistoric human foraging on important intertidal shellfish species. VL - 427, Part A UR - http://www.sciencedirect.com/science/article/pii/S1040618216000665 ER - TY - JOUR T1 - Influence of the megathrust earthquake cycle on upper-plate deformation in the Cascadia forearc of Washington State, USA JF - Geology Y1 - 2017 A1 - Delano, Jaime E. A1 - Amos, Colin B. A1 - Loveless, John P. A1 - Rittenour, Tammy M. A1 - Sherrod, Brian L. A1 - Lynch, Emerson M. AB - The influence of subduction zone earthquake cycle processes on permanent forearc deformation is poorly understood. In the Cascadia subduction zone forearc of Washington State, USA, deformed and incised fluvial terraces serve as archives of longer-term (103–104 yr) strain manifest as both fluvial incision and slip on upper-plate faults. We focus on comparing these geomorphic records in the Wynoochee River valley in the southern Olympic Mountains with short-term (101 yr) deformation driven by interseismic subduction zone coupling. We use optically stimulated luminescence dating and high-resolution elevation data to characterize strath terrace incision and differential uplift across the Canyon River fault, which cuts Wynoochee River terraces. This analysis demonstrates reverse slip rates of ∼0.1–0.3 mm/yr over the past ∼12–37 k.y., which agree with rates predicted by a GPS-constrained boundary element model of interseismic stress from Cascadia subduction zone coupling. Similarly, model-predicted patterns of interseismic uplift mimic the overall pattern of incision in the lower Wynoochee River valley, as revealed by strath elevations dated at 14.1 ± 1.2 ka. Agreement between modeled short-term and observed long-term records of forearc strain suggests that interseismic stress drives slip on upper-plate faults and fluvial incision in Cascadia. Consistency over multiple time scales may indicate relative stability in spatial patterns of subduction zone coupling over at least ∼104 yr intervals. VL - 45 UR - https://digitalcommons.usu.edu/geology_facpub/523/ IS - 11 ER - TY - JOUR T1 - Insights of Pb isotopic signature into the historical evolution and sources of Pb contamination in a sediment core of the southwestern Iberian Atlantic shelf JF - Science of The Total Environment Y1 - 2017 A1 - Mil-Homens, ário A1 - Vale, Carlos A1 - Brito, Pedro A1 - Naughton, Filipa A1 - Drago, Teresa A1 - Raimundo, Joana A1 - Anes, árbara A1 - Schmidt, Sabine A1 - Caetano, Miguel KW - Environment recovery KW - Marine sediments KW - Pb isotopes KW - Roman and modem mining activities KW - Southwestern Iberian shelf KW - Temporal evolution AB - Stable Pb isotopic ratios and concentrations of Al, Cu and Pb were measured in a 5 m long sediment core (VC2B) retrieved at 96 m water depth in the southwestern Iberian Atlantic shelf. Five phases during the last 9.5 kyrs were identified, two of them (Roman Period and modern mining) marked by a decrease of Pb-206/Pb-207 ratios reflecting additional inputs of Pb derived from mining activities. The Roman Period was also characterized by high Pb-208/Pb-206 ratios suggesting the exploitation of the outcropping portion of the orebody intensely weathered when compared with the other formations later mined. The shift of Pb-208/Pb-206 ratios towards linearity took approximately 1.0 kyrs, which may mirror the time of environmental recovery from the impact of Roman mining activities. The application of a mixing model allowed the quantification of the contribution associated with anthropogenic mining activities to the shelf sediments. The maximum values of Pb contamination occurred in the 20th century. This study gives direct evidence of Pb and Cu exploitation over the last 2000 years. The stable Pb isotopic signatures point to legacy of mining activities that are still the prevailing metal source recorded in the southwestern Iberian Atlantic shelf sediments. VL - 586 UR - http://linkinghub.elsevier.com/retrieve/pii/S0048969717302218http://api.elsevier.com/content/article/PII:S0048969717302218?httpAccept=text/plainhttp://api.elsevier.com/content/article/PII:S0048969717302218?httpAccept=text/xml ER - TY - JOUR T1 - Insights of Pb isotopic signature into the historical evolution and sources of Pb contamination in a sediment core of the southwestern Iberian Atlantic shelf JF - Science of The Total Environment Y1 - 2017 A1 - Mário Mil-Homens A1 - Carlos Vale A1 - Pedro Brito A1 - Filipa Naughton A1 - Teresa Drago A1 - Joana Raimundo A1 - Bárbara Anes A1 - Sabine Schmidt A1 - Miguel Caetano KW - Environment recovery AB - Abstract Stable Pb isotopic ratios and concentrations of Al, Cu and Pb were measured in a 5 m long sediment core (VC2B) retrieved at 96 m water depth in the southwestern Iberian Atlantic shelf. Five phases during the last 9.5 kyrs were identified, two of them (Roman Period and modern mining) marked by a decrease of 206Pb/207Pb ratios reflecting additional inputs of Pb derived from mining activities. The Roman Period was also characterized by high 208Pb/206Pb ratios suggesting the exploitation of the outcropping portion of the orebody intensely weathered when compared with the other formations later mined. The shift of 208Pb/206Pb ratios towards linearity took approximately 1.0 kyrs, which may mirror the time of environmental recovery from the impact of Roman mining activities. The application of a mixing model allowed the quantification of the contribution associated with anthropogenic mining activities to the shelf sediments. The maximum values of Pb contamination occurred in the 20th century. This study gives direct evidence of Pb and Cu exploitation over the last 2000 years. The stable Pb isotopic signatures point to legacy of mining activities that are still the prevailing metal source recorded in the southwestern Iberian Atlantic shelf sediments. VL - 586 UR - http://www.sciencedirect.com/science/article/pii/S0048969717302218 ER - TY - JOUR T1 - Investigation of Late Pleistocene and Holocene Activity in the San Gregorio Fault Zone on the Continental Slope North of Monterey Canyon, Offshore Central California JF - Bulletin of the Seismological Society of America Y1 - 2017 A1 - Maier, Katherine L. A1 - Paull, Charles K. A1 - Brothers, Daniel S. A1 - Caress, David W. A1 - McGann, Mary A1 - Lundsten, Eve M. A1 - Anderson, Krystle A1 - Gwiazda, Roberto AB - We provide an extensive high‐resolution geophysical, sediment core, and radiocarbon dataset to address late Pleistocene and Holocene fault activity of the San Gregorio fault zone (SGFZ), offshore central California. The SGFZ occurs primarily offshore in the San Andreas fault system and has been accommodating dextral strike‐slip motion between the Pacific and North American plates since the mid‐Miocene. Our study focuses on the SGFZ where it has been mapped through the continental slope north of Monterey Canyon. From 2009 to 2015, the Monterey Bay Aquarium Research Institute collected high‐resolution multibeam bathymetry and chirp sub‐bottom profiles using an autonomous underwater vehicle (AUV). Targeted samples were collected using a remotely operated vehicle (ROV) to provide radiocarbon age constraints. We integrate the high‐resolution geophysical data with radiocarbon dates to reveal Pleistocene seismic horizons vertically offset less than 5 m on nearly vertical faults. These faults are buried by continuous reflections deposited after ∼17.5  ka and likely following erosion during the last sea‐level lowstand ∼21  ka⁠, bracketing the age of faulting to ∼32–21  ka⁠. Clearly faulted horizons are only detected in a small area where mass wasting exhumed older strata to within ∼25  m of the seafloor. The lack of clearly faulted Holocene deposits and possible highly distributed faulting in the study area are consistent with previous interpretations that late Pleistocene and Holocene activity along the SGFZ may decrease to the south. This study illustrates the complexity of the SGFZ, offshore central California, and demonstrates the utility of very high‐resolution data from combined AUV (geophysical)–ROV (seabed sampling) surveys in offshore studies of fault activity. VL - 107 UR - https://pubs.geoscienceworld.org/bssa/article/107/3/1094-1106/354203 IS - 3 ER - TY - JOUR T1 - Land-use change and managed aquifer recharge effects on the hydrogeochemistry of two contrasting atoll island aquifers, Roi-Namur Island, Republic of the Marshall Islands JF - Applied Geochemistry Y1 - 2017 A1 - Mehrdad Hejazian A1 - Jason J. Gurdak A1 - Peter Swarzenski A1 - Kingsley O. Odigie A1 - Curt D. Storlazzi AB - Abstract Freshwater resources on low-lying atoll islands are highly vulnerable to climate change and sea-level rise. In addition to rainwater catchment, groundwater in the freshwater lens is a critically important water resource on many atoll islands, especially during drought. Although many atolls have high annual rainfall rates, dense natural vegetation and high evapotranspiration rates can limit recharge to the freshwater lens. Here we evaluate the effects of land-use/land-cover change and managed aquifer recharge on the hydrogeochemistry and supply of groundwater on Roi-Namur Island, Republic of the Marshall Islands. Roi-Namur is an artificially conjoined island that has similar hydrogeology on the Roi and Namur lobes, but has contrasting land-use/land-cover and managed aquifer recharge only on Roi. Vegetation removal and managed aquifer recharge operations have resulted in an estimated 8.6 × 105 m3 of potable groundwater in the freshwater lens on Roi, compared to only 1.6 × 104 m3 on Namur. We use groundwater samples from a suite of 33 vertically nested monitoring wells, statistical testing, and geochemical modeling using \{PHREEQC\} to show that the differences in land-use/land-cover and managed aquifer recharge on Roi and Namur have a statistically significant effect on several groundwater-quality parameters and the controlling geochemical processes. Results also indicate a six-fold reduction in the dissolution of carbonate rock in the freshwater lens and overlying vadose zone of Roi compared to Namur. Mixing of seawater and the freshwater lens is a more dominant hydrogeochemical process on Roi because of the greater recharge and flushing of the aquifer with freshwater as compared to Namur. In contrast, equilibrium processes and dissolution-precipitation non-equilibrium reactions are more dominant on Namur because of the longer residence times relative to the rate of geochemical reactions. Findings from Roi-Namur Island support selective land-use/land-cover change and managed aquifer recharge as a promising management approach for communities on other low-lying atoll islands to increase the resilience of their groundwater supplies and help them adapt to future climate change related stresses. VL - 80 UR - http://www.sciencedirect.com/science/article/pii/S0883292716301391 ER - TY - JOUR T1 - Large-scale response of the Eastern Mediterranean thermohaline circulation to African monsoon intensification during sapropel S1 formation JF - Quaternary Science Reviews Y1 - 2017 A1 - T. Tesi A1 - A. Asioli A1 - D. Minisini A1 - V. Maselli A1 - G. Dalla Valle A1 - F. Gamberi A1 - L. Langone A1 - A. Cattaneo A1 - P. Montagna A1 - F. Trincardi KW - Thermohaline circulation AB - Abstract The formation of Eastern Mediterranean sapropels has periodically occurred during intensification of northern hemisphere monsoon precipitation over North Africa. However, the large-scale response of the Eastern Mediterranean thermohaline circulation during these monsoon-fuelled freshening episodes is poorly constrained. Here, we investigate the formation of the youngest sapropel (S1) along an across-slope transect in the Adriatic Sea. Foraminifera-based oxygen index, redox-sensitive elements and biogeochemical parameters reveal – for the first time – that the Adriatic \{S1\} was synchronous with the deposition of south-eastern Mediterranean \{S1\} beds. Proxies of paleo thermohaline currents indicate that the bottom-hugging North Adriatic Dense Water (NAdDW) suddenly decreased at the sapropel onset simultaneously with the maximum freshening of the Levantine Sea during the African Humid Period. We conclude that the lack of the “salty” Levantine Intermediate Water hampered the preconditioning of the northern Adriatic waters necessary for the \{NAdDW\} formation prior to the winter cooling. Consequently, a weak \{NAdDW\} limited in turn the Eastern Mediterranean Deep Water (EMDWAdriatic) formation with important consequences for the ventilation of the Ionian basin as well. Our results highlight the importance of the Adriatic for the deep water ventilation and the interdependence among the major eastern Mediterranean water masses whose destabilization exerted first-order control on \{S1\} deposition. VL - 159 UR - http://www.sciencedirect.com/science/article/pii/S0277379116304012 ER - TY - JOUR T1 - Local and regional wildfire activity in central Maine (USA) during the past 900 years JF - Journal of Paleolimnology Y1 - 2017 A1 - Miller, Daniel R. A1 - Castañeda, Isla S. A1 - Bradley, Raymond S. A1 - MacDonald, Dana AB - Climatic and environmental change has a direct effect on wildfire frequencies and distributions throughout many regions of the world. Reconstructions from natural archives such as lake sediments can extend temporally limited historical records of regional wildfire activity over longer timescales through sedimentary charcoal analysis or examining polycyclic aromatic hydrocarbon (PAH) concentrations. To date, little work has been completed on sedimentary PAH distributions from lacustrine records in the Northeastern United States, making it difficult to assess how accurately PAHs trace fire activity in the region, the spatial scope of the signal (local vs. regional), or if certain compounds do a more adequate job of tracking fire than others. In this study, we examine PAHs and macrocharcoal from a varved sedimentary record from Basin Pond, Fayette, Maine (USA). We find that a drastic increase in the concentrations of 12 measured PAHs occurred during the nineteenth to twentieth centuries due to industrialization of the region. Additionally, elevated concentrations of the PAH retene were found to be coeval with known large-scale regional wildfire events that occurred in 1761–1762, 1825, and 1947 (A.D.). We used the ratio of the PAHs retene and chrysene to infer differences in biomass burning versus anthropogenic combustion sources because retene is associated with conifer resin whereas chrysene is associated with fossil fuel burning. Our new Basin Pond PAH records, along with a local signal of fire occurrence from charcoal analysis, offers the prospect of using this multi-proxy approach as a method for examining long-term wildfire frequency at both the local and regional scale in the Northeastern US. VL - 58 UR - https://link.springer.com/article/10.1007/s10933-017-0002-z IS - 4 ER - TY - JOUR T1 - Local glaciation in West Greenland linked to North Atlantic Ocean circulation during the Holocene JF - Geology Y1 - 2017 A1 - Schweinsberg, Avriel D. A1 - Briner, Jason P. A1 - Miller, Gifford H. A1 - Bennike, Ole A1 - Thomas, Elizabeth K. AB - Recent observations indicate that ice-ocean interaction drives much of the recent increase in mass loss from the Greenland Ice Sheet; however, the role of ocean forcing in driving past glacier change is poorly understood. To extend the observational record and our understanding of the ocean-cryosphere link, we used a multi-proxy approach that combines new data from proglacial lake sediments, C-14-dated in situ moss that recently emerged from beneath cold-based ice caps, and Be-10 ages to reconstruct centennial-scale records of mountain glacier activity for the past similar to 10 k. y. in West Greenland. Proglacial lake sediment records and C-14 dating of moss indicate the onset of Neoglaciation in West Greenland at ca. 5 ka with substantial snowline lowering and glacier expansion at ca. 3.7 ka followed by additional ice expansion phases at ca. 2.9, ca. 1.7, and ca. 1.4 ka and during the Little Ice Age. We find that widespread glacier growth at ca. 3.7 ka in West Greenland coincides with marked cooling and reduced strength of the West Greenland Current in Disko Bugt. The transition to cooler ocean conditions at ca. 3.7 ka identified in Disko Bugt is registered by marine proxy data farther afield in East Greenland and on the northwestern Icelandic shelf, implying large-scale paleoceanographic changes across the North Atlantic during this interval. The similarity between glacier change on West Greenland and multiple marine and terrestrial records across the North Atlantic suggests that glaciers are strongly influenced by changes in ocean circulation and consequently implies that the ocean-cryosphere teleconnection is a persistent feature of the Arctic system. VL - 45 UR - http://geology.gsapubs.org/lookup/doi/10.1130/G38114 IS - 3 ER - TY - JOUR T1 - Micromorphology of late Pleistocene and Holocene sediments and a new interpretation of the Holocene chronology at Anderson Pond, Tennessee, USAAbstract JF - Quaternary Research Y1 - 2017 A1 - Driese, Steven G. A1 - Horn, Sally P. A1 - Ballard, Joanne P. A1 - Boehm, Mathew S. A1 - Li, Zhenghua AB - Thin-section (micromorphological) analysis of samples from the upper 1.5 m of a core obtained in 2007 from Anderson Pond, Tennessee, reveals a coherent but discontinuous record of late Pleistocene and Holocene climate change that supports some interpretations from previous pollen and charcoal analyses but indicates a revised Holocene chronology for this classic pollen site. Legacy sediments recording anthropogenic disturbance compose the upper 65 cm of the core (<160 cal yr BP) and are characterized by mixed, darker-colored, and coarser-grained deposits containing reworked soil aggregates, which sharply overlie finer-grained and lighter-colored, rooted middle Holocene sediments interpreted as a paleosol. These mid-Holocene sediments (95–65 cm; 7100–5600 cal yr BP) record extensive warm-dry subaerial soil conditions during the middle Holocene thermal maximum, manifested by illuviated clay lining root pores, and also contain abundant charcoal. Late Pleistocene sediments (150–95 cm), dark-colored and organic-rich, record open-water conditions and include siliceous aggregate grains at 143–116 cm (14,300–13,900 cal yr BP), recording intense fires. Thin sections are not commonly used in studies of paleoclimate from Quaternary lacustrine sediments, but we advocate for their inclusion in multianalytical approaches because they enhance resolution of depositional and pedogenic processes. VL - 87 UR - https://www.cambridge.org/core/product/identifier/S0033589416000065/type/journal_article IS - 1 ER - TY - JOUR T1 - Millennial mode of variability of sea ice conditions in the Okhotsk Sea during the last glaciation (MIS 4–MIS 2) JF - Quaternary International Y1 - 2017 A1 - Vasilenko, Yuriy P. A1 - Gorbarenko, Sergey A. A1 - Bosin, Aleksandr A. A1 - Shi, Xue-fa A1 - Chen, Min-Te A1 - Zou, Jian-jun A1 - Liu, Yan-guang A1 - Artemova, Antonina V. A1 - Yanchenko, Elena A. A1 - Savenko, Mikhail P. KW - Ice mode KW - Ice-rafted debris KW - Millennial-scale variation KW - Okhotsk Sea KW - Wind mode AB - Coarse fraction (CF) content, grain-size distribution, roundness of CF, gravels and pebbles, and examination of surface of pebbles were studied in core LV28-44-4, recovered from the eastern Okhotsk Sea (OS). The age model of the studied core was based on the AMS 14C data, tephrochronology, δ18O benthic foraminifera record, and correlation of peaks of productivity proxies with long-lasted Dansgaard-Oeschger (DO) interstadials. The results show that sea ice was the main transport agent for CF (ice-rafted debris, IRD) in the eastern OS. Published mineralogical studies of clastic material of the OS indicated that the coast of western Kamchatka was the main source of IRD in the eastern OS. We found 19 peaks of IRD, which mostly coincided with DO stadials. The distribution of CF indicates a different pattern of IRD supply during MIS 4, 3, and 2. Comparison of IRD records in the eastern and central parts of the OS allow us to reconstruct millennial changes in ice and wind modes for MIS 4–MIS 2. Significant strengthening of northeastern and eastern winds during DOSs of MIS 3 and of northern and north-western winds during MIS 2 were observed. VL - 459 UR - https://linkinghub.elsevier.com/retrieve/pii/S1040618216313258 ER - TY - JOUR T1 - Millennial-scale iron fertilization of the eastern equatorial Pacific over the past 100,000 years JF - Nature Geoscience Y1 - 2017 A1 - Loveley, Matthew R. A1 - Marcantonio, Franco A1 - Wisler, Marilyn M. A1 - Hertzberg, Jennifer E. A1 - Schmidt, Matthew W. A1 - Lyle, Mitchell AB - The eastern equatorial Pacific Ocean plays a crucial role in global climate, as it is a substantial source of CO2 to the atmosphere and accounts for a significant portion of global new export productivity. Here we present a 100,000-year sediment core from the eastern equatorial Pacific, and reconstruct dust flux, export productivity and bottom-water oxygenation using excess-230Th-derived fluxes of 232Th and barium, and authigenic uranium concentrations, respectively. We find that during the last glacial period (71,000 to 41,000 years ago), increased delivery of dust to the eastern equatorial Pacific was coeval with North Atlantic Heinrich stadial events. Millennial-scale pulses of increased dust flux coincided with episodes of heightened biological productivity, suggesting that dissolution of dust released iron that promoted ocean fertilization. We also find that periods of low atmospheric CO2 concentrations were associated with suboxic conditions and increased storage of respired carbon in the deep eastern equatorial Pacific. Increases in CO2 concentrations during the deglaciation are coincident with increases in deep Pacific and Southern Ocean water oxygenation levels. We suggest that deep-ocean ventilation was a primary control on CO2 outgassing in this region, with superimposed pulses of high productivity providing a negative feedback. VL - 10 UR - http://www.nature.com/articles/ngeo3024 IS - 10 ER - TY - JOUR T1 - Mobilization and export of millennial-aged organic carbon by the Yellow River JF - Limnology and Oceanography Y1 - 2017 A1 - Xue, Yuejun A1 - Zou, Li A1 - Ge, Tiantian A1 - Wang, Xuchen AB - A combined carbon isotope (13C and 14C) study was carried out to investigate the sources and fate of organic carbon (OC) transported by the Yellow River and preserved in the sediments of the Bohai and Yellow Seas. In 2015, the Yellow River delivered 3.14 × 1010 g C and 4.12 × 1010 g C of dissolved organic carbon (DOC) and particulate organic carbon (POC) to the Bohai Sea. Carbon isotope signatures revealed that the Yellow River transports millennial-aged DOC and POC during all seasons. The values of δ13C-DOC ranged from −24.7‰ to −28.8‰ in the river basin, and −21.0‰ to −27.0‰ in the lower reach. The 14C ages of DOC were 415–1690 yr before present (BP) in the river basin, and they were relatively constant seasonally (1320–1690 yr BP) in the lower reach of the river. In comparison, POC δ13C values in the river were less variable (−22.8‰ to −25.0‰), but much older in both the river basin (4960 ± 1690 yr BP) and in the lower reach (4040 ± 1050 yr BP). Calculations using a dual-isotopic three-end member model revealed that biomass OC derived from C3 plants was the major source of riverine DOC, contributing 65% ± 8% and 52% ± 2% in the river basin and lower reach seasonally. Pre-aged soil OC and fossil OC from weathering contributed 21–42% and 6–14% of the DOC, respectively. In contrast, pre-aged soil OC and fossil OC contributed 60–70% and 17–27% of POC, and biomass OC contributed a minor fraction (13% ± 7%) of riverine POC. Our results further revealed that aged riverine POC had a major influence on OC preservation in the delta and coastal sediments of the Bohai and Yellow Seas. The age of OC in surface sediments varied widely (1610–8275 yr) due to the influence of Yellow River input. Pre-aged soil OC and fossil OC each contributed 32% ± 8% and 22% ± 14% of OC preserved in the sediments. We estimate that about 0.27 Mt yr−1 and 0.07 Mt yr−1 of pre-aged soil OC and fossil OC accumulate in the surface sediments from POC delivered by the modern Yellow River, and 0.013 Mt yr−1 and 0.002 Mt yr−1 of pre-aged soil OC and fossil OC enters the coastal DOC cycle from riverine DOC. The millennial-aged OC delivered to coastal seas by the Yellow River therefore has profound impacts not only on carbon cycling and the carbon budget in the marginal sea, but also on coastal ecosystems and biogeochemical processes. UR - http://doi.wiley.com/10.1002/lno.10579http://onlinelibrary.wiley.com/wol1/doi/10.1002/lno.10579/fullpdfhttps://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Flno.10579 ER - TY - JOUR T1 - More reducing bottom-water redox conditions during the Last Glacial Maximum in the southern Challenger Deep (Mariana Trench, western Pacific) driven by enhanced productivity JF - Deep Sea Research Part II: Topical Studies in Oceanography Y1 - 2017 A1 - Min Luo A1 - Thomas J. Algeo A1 - Hongpeng Tong A1 - Joris Gieskes A1 - Linying Chen A1 - Xuefa Shi A1 - Duofu Chen KW - Laminated diatom mats AB - Abstract The modern southern Mariana Trench is characterized by oligotrophic surface waters, resulting in low primary productivity and well-oxygenated bottom waters. This study investigates changes in the redox conditions of bottom waters in the southern Mariana Trench during the Last Glacial Maximum (LGM) and their potential causes. We measured major, trace, and rare earth elements (REE) in three gravity cores (GC03, GC04, and GC05) and one box core (BC11) retrieved from the southern Challenger Deep at water depths from 5289 to 7118 m. The upper sediment layers of both \{GC05\} and \{BC11\} are dominated by valve fragments of the giant diatom Ethmodiscus rex, forming laminated diatom mats (LDMs). 14C-AMS dates of bulk organic matter show that the \{LDMs\} accumulated between 18.4 and 21.8 kyr B.P., corresponding to the LGM. Modest enrichments of U and Mo along with weak or absent Ce anomalies in the \{LDM\} point to suboxic conditions during the LGM. In contrast, non-LDM samples exhibit little to no enrichment of redox-sensitive elements as well as negative Ce anomalies, indicating deposition under oxic bottom-water conditions. The Ce anomalies are considered valid proxies for bottom-water redox conditions because \{REE\} signatures were acquired in the early diagenetic environment, as indicated by strong P-REE correlations and middle-REE enrichment associated with early diagenetic cycling of Fe-Mn oxyhydroxides in the sediment column followed by capture of the \{REE\} signal by biogenic and/or authigenic apatite. We postulate that the more reducing bottom-water conditions during the \{LGM\} were linked to increased primary productivity induced by enhanced Asian dust input. As shown in earlier studies, the increased primary productivity associated with Ethmodiscus rex blooms in the eastern Philippine Sea played a significant role in capturing atmospheric \{CO2\} during the LGM. Consequently, the magnitude of atmospheric \{CO2\} sequestration by giant diatom blooms during the \{LGM\} may have been greater than previously envisaged. UR - http://www.sciencedirect.com/science/article/pii/S0967064516302892 ER - TY - RPRT T1 - Open-File ReportOpen-File ReportDeepwater Program: Lophelia II, continuing ecological research on deep-sea corals and deep-reef habitats in the Gulf of Mexico Y1 - 2017 A1 - Demopoulos, Amanda W.J. A1 - Ross, Steve W. A1 - Kellogg, Christina A. A1 - Morrison, Cheryl L. A1 - Nizinski, Martha S. A1 - Prouty, Nancy G. A1 - Bourque, Jill R. A1 - Galkiewicz, Julie P. A1 - Gray, Michael A. A1 - Springmann, Marcus J. A1 - Coykendall, D. Katharine A1 - Miller, Andrew A1 - Rhode, Mike A1 - Quattrini, Andrea A1 - Ames, Cheryl L. A1 - Brooke, Sandra D. A1 - McClain-Counts, Jennifer P. A1 - Roark, E. Brendan A1 - Buster, Noreen A. A1 - Phillips, Ryan M. A1 - Frometa, Janessy AB - The deep sea is a rich environment composed of diverse habitat types. While deep-sea coral habitats have been discovered within each ocean basin, knowledge about the ecology of these habitats and associated inhabitants continues to grow. This report presents information and results from the Lophelia II project that examined deep-sea coral habitats in the Gulf of Mexico. The Lophelia II project focused on Lophelia pertusa habitats along the continental slope, at depths ranging from 300 to 1,000 meters. The chapters are authored by several scientists from the U.S. Geological Survey, National Oceanic and Atmospheric Administration, University of North Carolina Wilmington, and Florida State University who examined the community ecology (from microbes to fishes), deep-sea coral age, growth, and reproduction, and population connectivity of deep-sea corals and inhabitants. Data from these studies are presented in the chapters and appendixes of the report as well as in journal publications. This study was conducted by the Ecosystems Mission Area of the U.S. Geological Survey to meet information needs identified by the Bureau of Ocean Energy Management. UR - http://pubs.er.usgs.gov/publication/ofr20171139 ER - TY - JOUR T1 - Paleohydrology of China Lake basin and the context of early human occupation in the northwestern Mojave Desert, USA JF - Quaternary Science Reviews Y1 - 2017 A1 - Rosenthal, Jeffrey S. A1 - Meyer, Jack A1 - Palacios-Fest, Manuel R. A1 - Young, D. Craig A1 - Ugan, Andrew A1 - Byrd, Brian F. A1 - Gobalet, Ken A1 - Giacomo, Jason AB - Considerable prior research has focused on the interconnected pluvial basins of Owens Lake and Searles Lake, resulting in a long record of paleohydrological change in the lower Owens River system. However, the published record is poorly resolved or contradictory for the period encompassing the terminal Pleistocene (22,000 to 11,600 cal BP) and early Holocene (11,600-8200 cal BP). This has resulted in conflicting interpretations about the timing of lacustrine high stands within the intermediate basin of China Lake, which harbors one of the most extensive records of early human occupation in the western Great Basin and California. Here, we report a broad range of radiocarbon-dated paleoenvironmental evidence, including lacustrine deposits and shoreline features, tufa outcrops, and mollusk, ostracode, and fish bone assemblages, as well as spring and other groundwater-related deposits (a.k.a. "black mats") from throughout China Lake basin, its outlet, and inflow drainages. Based on 98 radiocarbon dates, we develop independent evidence for five significant lake-level oscillations between 18,000 and 13,000 cal BP, and document the persistence of groundwater-fed wetlands from the beginning of the Younger Dryas through the early Holocene (12,900-8200 cal BP); including the transition from ground-water fed lake to freshwater marsh between about 13,000 and 12,600 cal BP. Results of this study support and refine existing evidence that shows rapid, high-amplitude oscillations in the water balance of the Owens River system during the terminal Pleistocene, and suggest widespread human use of China Lake basin began during the Younger Dryas. VL - 167 UR - http://linkinghub.elsevier.com/retrieve/pii/S027737911630676Xhttp://api.elsevier.com/content/article/PII:S027737911630676X?httpAccept=text/xmlhttp://api.elsevier.com/content/article/PII:S027737911630676X?httpAccept=text/plain ER - TY - JOUR T1 - The perfect storm: climate change and ancient Maya response in the Puuc Hills region of YucatánAbstract JF - Antiquity Y1 - 2017 A1 - Smyth, Michael P. A1 - Dunning, Nicholas P. A1 - Weaver, Eric M. A1 - van Beynen, Philip A1 - Zapata, David Ortegón KW - drought KW - flooding KW - Maya KW - México KW - speleothem KW - Xcoch KW - Yucatán AB - Climatic fluctuation is often cited as a major factor in the collapse of Maya civilisation during the Terminal Classic Period (e.g. Luzzadder-Beach et al. 2016). Evidence of how people dealt or failed to deal with it has only recently become a more widespread focus for archaeologists. Investigations at Xcoch in the Puuc Hills show the various ways in which resident populations sought to manage water stores when faced with a climate prone to drought and other meteorological extremes. The study also presents results from the analysis of nearby speleothem laminae, which indicate that severe episodes of flooding and droughts may have contributed to a collapse in the population around AD 850. VL - 91 UR - https://www.cambridge.org/core/product/identifier/S0003598X16002660/type/journal_article IS - 356 ER - TY - JOUR T1 - Permafrost Organic Carbon Mobilization From the Watershed to the Colville River Delta: Evidence From 14C Ramped Pyrolysis and Lignin Biomarkers JF - Geophysical Research Letters Y1 - 2017 A1 - Zhang, Xiaowen A1 - Bianchi, Thomas S. A1 - Cui, Xingqian A1 - Rosenheim, Brad E. A1 - Ping, Chien‐Lu A1 - Hanna, Andrea J. M. A1 - Kanevskiy, Mikhail A1 - Schreiner, Kathryn M. A1 - Allison, Mead A. KW - Arctic KW - carbon cycling KW - Colville River KW - Lignin KW - permafrost KW - pyrolysis AB - The deposition of terrestrial‐derived permafrost particulate organic carbon (POC) has been recorded in major Arctic river deltas. However, associated transport pathways of permafrost POC from the watershed to the coast have not been well constrained. Here we utilized a combination of ramped pyrolysis‐oxidation radiocarbon analysis (RPO 14C) along with lignin biomarkers, to track the linkages between soils and river and delta sediments. Surface and deep soils showed distinct RPO thermographs which may be related to degradation and organo‐mineral interaction. Soil material in the bed load of the river channel was mostly derived from deep old permafrost. Both surface and deep soils were transported and deposited to the coast. Hydrodynamic sorting and barrier island protection played important roles in terrestrial‐derived permafrost POC deposition near the coast. On a large scale, ice processes (e.g., ice gauging and strudel scour) and ocean currents controlled the transport and distribution of permafrost POC on the Beaufort Shelf. VL - 44 UR - https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2017GL075543 IS - 22 ER - TY - JOUR T1 - Pleistocene iceberg dynamics on the west Svalbard margin: Evidence from bathymetric and sub-bottom profiler data JF - Quaternary Science Reviews Y1 - 2017 A1 - Fang Zhao A1 - Timothy A. Minshull A1 - Anya J. Crocker A1 - Julian A. Dowdeswell A1 - Shiguo Wu A1 - Simon M. Soryal KW - Pleistocene AB - Abstract Large icebergs leave evidence of their drift via ploughing of the seabed, thereby providing a geological record of episodes of calving from thick ice sheets. We interpret large-scale curvilinear depressions on the western Svalbard margin as ploughmarks produced by the keels of icebergs that grounded on the seafloor as they drifted through this area. Iceberg ploughmarks were identified at modern water depths between 300 m and 1000 m and in two distinct stratigraphic units. Combining data from sediment cores with seismic stratigraphy from sub-bottom profiler data suggests that the ploughmarks developed in two phases: (1) during Marine Isotope Stage (MIS) 6; and (2) during \{MIS\} 2, indicating the presence of large drifting icebergs on the western Svalbard margin during both the Late Saalian and Late Weichselian glaciations. Sediment-core data along the western Svalbard margin indicate a sharp increase in mass-transported sediments dated at 23.7 ± 0.2 ka, consistent with the \{MIS\} 2 age of the younger iceberg-ploughed surface. The ploughmarks are oriented in two main directions: SW-NE and S-N. S-N oriented ploughmarks, which shallow to the north, indicate iceberg drift from the south with a SW–NE component marking the zone of splitting of the West Spitsbergen Current (WSC) into the Yermak Slope Current (YSC) and North Spitsbergen Current (NSC). Large \{MIS\} 6 and \{MIS\} 2 icebergs most likely had an Arctic Ocean source. We suggest that these icebergs probably left the Arctic Ocean southward through Fram Strait and circulated within the Norwegian-Greenland Sea before being transported northwards along the Svalbard margin by the WSC. An additional likely source of icebergs to the western Svalbard margin during \{MIS\} 2 was the ice-sheet terminating in the western Barents Sea, from which icebergs drifted northward. VL - 161 UR - http://www.sciencedirect.com/science/article/pii/S0277379117300860 ER - TY - JOUR T1 - A probabilistic method of assessing carbon accumulation rate at Imnavait Creek Peatland, Arctic Long Term Ecological Research Station, Alaska JF - Journal of Quaternary Science Y1 - 2017 A1 - Nichols, Jonathan E. A1 - Peteet, Dorothy M. A1 - Frolking, Steve A1 - Karavias, John KW - carbon accumulation KW - Imnavait KW - peatlands KW - permafrost KW - radiocarbon KW - Toolik LTER AB - Arctic peatlands are an important part of the global carbon cycle, accumulating atmospheric carbon as organic matter since the Late glacial. Current methods for understanding the changing efficiency of the peatland carbon sink rely on peatlands with an undisturbed stratigraphy. Here we present a method of estimating primary carbon accumulation rate from a site where permafrost processes have either vertically or horizontally translocated nearby carbon‐rich sediment out of stratigraphic order. Briefly, our new algorithm estimates the probability of the age of deposition of a random increment of sediment in the core. The method assumes that if sediment age is measured at even depth increments, dates are more likely to occur during intervals of higher accumulation rate and vice versa. Multiplying estimated sedimentation rate by measured carbon density yields carbon accumulation rate. We perform this analysis at the Imnavait Creek Peatland, near the Arctic Long Term Ecological Research network site at Toolik Lake, Alaska. Using classical radiocarbon age modeling, we find unreasonably high rates of carbon accumulation at various Holocene intervals. With our new method, we find accumulation rate changes that are in improved agreement within the context of other sites throughout Alaska and the rest of the Circum‐Arctic region. VL - 32 UR - https://onlinelibrary.wiley.com/doi/10.1002/jqs.2952 IS - 5 ER - TY - BOOK T1 - Proceedings of the International Ocean Discovery ProgramExpedition 357 methods Y1 - 2017 A1 - Früh-Green, G.L. A1 - Orcutt, B.N. A1 - Green, S.L. A1 - Cotterill, C. A1 - Morgan, S. A1 - Akizawa, N. A1 - Bayrakci, G. A1 - Behrmann, J.-H. A1 - Boschi, C. A1 - Brazleton, W.J. A1 - Cannat, M. A1 - Dunkel, K.G. A1 - Escartin, J. A1 - Harris, M. A1 - Herrero-Bervera, E. A1 - Hesse, K. A1 - John, B.E. A1 - Lang, S.Q. A1 - Lilley, M.D. A1 - Liu, H.-Q. A1 - Mayhew, L.E. A1 - McCaig, A.M. A1 - Menez, B. A1 - Morono, Y. A1 - Quéméneur, M. A1 - Rouméjon, S. A1 - Sandaruwan Ratnayake, A. A1 - Schrenk, M.O. A1 - Schwarzenbach, E.M. A1 - Twing, K.I. A1 - Weis, D. A1 - Whattham, S.A. A1 - Williams, M. A1 - Zhao, R. ED - Früh-Green, G.L. ED - Orcutt, B.N. ED - Green, S.L. ED - Cotterill, C. PB - International Ocean Discovery Program UR - http://publications.iodp.org/proceedings/357/357title.html ER - TY - JOUR T1 - Quantifying bamboo coral growth rate nonlinearity with the radiocarbon bomb spike: A new model for paleoceanographic chronology development JF - Deep Sea Research Part I: Oceanographic Research Papers Y1 - 2017 A1 - Frenkel, M.M. A1 - LaVigne, M. A1 - Miller, H.R. A1 - Hill, T.M. A1 - McNichol, A. A1 - Gaylord, M. Lardie KW - 14C nuclear bomb spike KW - Bamboo coral KW - Chronologies KW - Gorgonin KW - Growth rate KW - paleoceanography KW - radiocarbon AB - Bamboo corals, long-lived cold water gorgonin octocorals, offer unique paleoceanographic archives of the intermediate ocean. These Isididae corals are characterized by alternating gorgonin nodes and high Mg-calcite internodes, which synchronously extend radially. Bamboo coral calcite internodes have been utilized to obtain geochemical proxy data, however, growth rate uncertainty has made it difficult to construct precise chronologies for these corals. Previous studies have relied upon a single tie point from records of the anthropogenic Δ14C bomb spike preserved in the gorgonin nodes of live-collected corals to calculate a mean radial extension rate for the outer ~50 years of skeletal growth. Bamboo coral chronologies are typically constructed by applying this mean extension rate to the entire coral record, assuming constant radial extension with coral age. In this study, we aim to test this underlying assumption by analyzing the organic nodes of six California margin bamboo corals at high enough resolution (<0.5 mm) to identify the Δ14C bomb spike, including two tie points at 1957 and 1970, plus the coral collection date (2007.5) for four samples. Radial extension rates between tie points ranged from 10 to 204 µm/year, with a decrease in growth rate evident between the 1957–1970 and 1970–2007.5 periods for all four corals. A negative correlation between growth rate and coral radius (r =−0.7; p=0.04) was determined for multiple bamboo coral taxa and individuals from the California margin, demonstrating a decline in radial extension rate with specimen age and size. To provide a mechanistic basis for these observations, a simple mathematical model was developed based on the assumption of a constant increase in circular cross sectional area with time to quantify this decline in radial extension rate with coral size between chronological tie points. Applying the area-based model to our Δ14C bomb spike time series from individual corals improves chronology accuracy for all live-collected corals with complete Δ14C bomb spikes. Hence, this study provides paleoceanographers utilizing bamboo corals with a method for reducing age model uncertainty within the anthropogenic bomb spike era (~1957-present). Chronological uncertainty is larger for the earliest portion of coral growth, particularly for skeleton precipitated prior to bomb spike tie points, meaning age estimations for samples living before 1957 remain uncertain. Combining this technique with additional chronological markers could improve age models for an entire bamboo coral. Finally, the relative consistency in growth rate in similarly-aged corals of the same depth and location supports the hypothesis that skeletal growth may be limited by local environmental conditions. UR - https://doi.org/10.1016/j.dsr.2017.04.006 ER - TY - JOUR T1 - Reconstructing Common Era relative sea-level change on the Gulf Coast of Florida JF - Marine Geology Y1 - 2017 A1 - Gerlach, Matthew J. A1 - Engelhart, Simon E. A1 - Kemp, Andrew C. A1 - Moyer, Ryan P. A1 - Smoak, Joseph M. A1 - Bernhardt, Christopher E. A1 - Cahill, Niamh AB - To address a paucity of Common Era data in the Gulf of Mexico, we reconstructed ~ 1.1 m of relative sea-level (RSL) rise over the past ~ 2000 years at Little Manatee River (Gulf Coast of Florida, USA). We applied a regional-scale foraminiferal transfer function to fossil assemblages preserved in a core of salt-marsh peat and organic silt that was dated using radiocarbon and recognition of pollution, 137Cs and pollen chronohorizons. Our proxy reconstruction was combined with tide-gauge data from four nearby sites spanning 1913–2014 CE. Application of an Errors-in-Variables Integrated Gaussian Process (EIV-IGP) model to the combined proxy and instrumental dataset demonstrates that RSL fell from ~ 350 to 100 BCE, before rising continuously to present. This initial RSL fall was likely the result of local-scale processes (e.g., silting up of a tidal flat or shallow sub-tidal shoal) as salt-marsh development at the site began. Since ~ 0 CE, we consider the reconstruction to be representative of regional-scale RSL trends. We removed a linear rate of 0.3 mm/yr from the RSL record using the EIV-IGP model to estimate climate-driven sea-level trends and to facilitate comparison among sites. This analysis demonstrates that since ~ 0 CE sea level did not deviate significantly from zero until accelerating continuously from ~ 1500 CE to present. Sea level was rising at 1.33 mm/yr in 1900 CE and accelerated until 2014 CE when a rate of 2.02 mm/yr was attained, which is the fastest, century-scale trend in the ~ 2000-year record. Comparison to existing reconstructions from the Gulf coast of Louisiana and the Atlantic coast of northern Florida reveal similar sea-level histories at all three sites. We explored the influence of compaction and fluvial processes on our reconstruction and concluded that compaction was likely insignificant. Fluvial processes were also likely insignificant, but further proxy evidence is needed to fully test this hypothesis. Our results indicate that no significant Common Era sea-level changes took place on the Gulf and southeastern Atlantic U.S. coasts until the onset of modern sea-level rise in the late 19th century. VL - 390 UR - https://linkinghub.elsevier.com/retrieve/pii/S0025322716303346 ER - TY - JOUR T1 - Records of continental slope sediment flow morphodynamic responses to gradient and active faulting from integrated AUV and ROV data, offshore Palos Verdes, southern California Borderland JF - Marine Geology Y1 - 2017 A1 - Maier, Katherine L. A1 - Brothers, Daniel S. A1 - Paull, Charles K. A1 - McGann, Mary A1 - Caress, David W. A1 - Conrad, James E. KW - Deep-water channel KW - Gradient KW - Holocene KW - Sediment waves KW - Turbidite Fault AB - Variations in seabed gradient are widely acknowledged to influence deep-water deposition, but are often difficult to measure in sufficient detail from both modern and ancient examples. On the continental slope offshore Los Angeles, California, autonomous underwater vehicle, remotely operated vehicle, and shipboard methods were used to collect a dense grid of high-resolution multibeam bathymetry, chirp sub-bottom profiles, and targeted sediment core samples that demonstrate the influence of seafloor gradient on sediment accumulation, depositional environment, grain size of deposits, and seafloor morphology. In this setting, restraining and releasing bends along the active right-lateral Palos Verdes Fault create and maintain variations in seafloor gradient. Holocene down-slope flows appear to have been generated by slope failure, primarily on the uppermost slope (~ 100–200 m water depth). Turbidity currents created a low relief (< 10 m) channel, up-slope migrating sediment waves (λ = ~ 100 m, h ≤ 2 m), and a series of depocenters that have accumulated up to 4 m of Holocene sediment. Sediment waves increase in wavelength and decrease in wave height with decreasing gradient. Integrated analysis of high-resolution datasets provides quantification of morphodynamic sensitivity to seafloor gradients acting throughout deep-water depositional systems. These results help to bridge gaps in scale between existing deep-sea and experimental datasets and may provide constraints for future numerical modeling studies. VL - 393 UR - https://linkinghub.elsevier.com/retrieve/pii/S0025322716302304 ER - TY - JOUR T1 - Relative sea-level trends in New York City during the past 1500 years JF - The Holocene Y1 - 2017 A1 - Kemp, Andrew C A1 - Hill, Troy D A1 - Vane, Christopher H A1 - Cahill, Niamh A1 - Orton, Philip M A1 - Talke, Stefan A A1 - Parnell, Andrew C A1 - Sanborn, Kelsey A1 - Hartig, Ellen K KW - Bayesian transfer function KW - carbon isotope KW - Foraminifera KW - Salt marsh KW - sedimentation KW - The Bronx AB - New York City (NYC) is threatened by 21st-century relative sea-level (RSL) rise because it will experience a trend that exceeds the global mean and has high concentrations of low-lying infrastructure and socioeconomic activity. To provide a long-term context for anticipated trends, we reconstructed RSL change during the past ~1500 years using a core of salt-marsh sediment from Pelham Bay in The Bronx. Foraminifera and bulk-sediment δ13C values were used as sea-level indicators. The history of sediment accumulation was established by radiocarbon dating and recognition of pollution and land-use trends of known age in down-core elemental, isotopic, and pollen profiles. The reconstruction was generated within a Bayesian hierarchical model to accommodate multiple proxies and to provide a unified statistical framework for quantifying uncertainty. We show that RSL in NYC rose by ~1.70 m since ~575 CE (including ~0.38 m since 1850 CE). The rate of RSL rise increased markedly at 1812–1913 CE from ~1.0 to ~2.5 mm/yr, which coincides with other reconstructions along the US Atlantic coast. We investigated the possible influence of tidal-range change in Long Island Sound on our reconstruction using a regional tidal model, and we demonstrate that this effect was likely small. However, future tidal-range change could exacerbate the impacts of RSL rise in communities bordering Long Island Sound. The current rate of RSL rise is the fastest that NYC has experienced for >1500 years, and its ongoing acceleration suggests that projections of 21st-century local RSL rise will be realized. VL - 27 UR - http://journals.sagepub.com/doi/10.1177/0959683616683263 IS - 8 ER - TY - JOUR T1 - Reversible adsorption and flushing of arsenic in a shallow, Holocene aquifer of Bangladesh JF - Applied Geochemistry Y1 - 2017 A1 - Kathleen A. Radloff A1 - Yan Zheng A1 - Martin Stute A1 - Beth Weinman A1 - Benjamin Bostick A1 - Ivan Mihajlov A1 - Margaret Bounds A1 - M.Moshiur Rahman A1 - M.Rezaul Huq A1 - Kazi M. Ahmed A1 - Peter Schlosser A1 - Alexander van Geen KW - Push–pull tests AB - Abstract The spatial heterogeneity of dissolved arsenic (As) concentrations in shallow groundwater of the Bengal Basin has been attributed to transport of As (and reactive carbon) from external sources or to the release of As from within grey sand formations. We explore the latter scenario in this detailed hydrological and geochemical study along a 300 m transect of a shallow aquifer extending from a groundwater recharge area within a sandy channel bar to its discharge into a nearby stream. Within the 10–20 m depth range, groundwater ages along the transect determined by the 3H–3He method increase from <10 yr in the recharge area to a maximum of 40 yr towards the stream. Concentrations of groundwater As within the same grey sands increase from 10 to 100 to ∼500 μg/L along this transect. Evidence of reversible adsorption of As between the groundwater and sediment was obtained from a series of push–pull experiments, traditional batch adsorption experiments, and the accidental flooding of a shallow monitoring well. Assuming reversible adsorption and a distribution coefficient, Kd, of 0.15–1.5 L/kg inferred from these observations, a simple flushing model shows that the increase in As concentrations with depth and groundwater age at this site, and at other sites in the Bengal and Red River Basins, can be attributed to the evolution of the aquifer over 100–1000 years as aquifer sands are gradually flushed of their initial As content. A wide range of As concentrations can thus be maintained in groundwater with increases with depth governed by the history of flushing and local recharge rates, without external inputs of reactive carbon or As from other sources. VL - 77 UR - http://www.sciencedirect.com/science/article/pii/S0883292715300706 N1 - Environmental and Health Roles of Geogenic Arsenic ER - TY - JOUR T1 - Salt Marsh and Fringing Oyster Reef Transgression in a Shallow Temperate Estuary: Implications for Restoration, Conservation and Blue Carbon JF - Estuaries and Coasts Y1 - 2017 A1 - Ridge, Justin T. A1 - Rodriguez, Antonio B. A1 - Fodrie, F. Joel AB - The importance of intertidal estuarine habitats, like salt marsh and oyster reef, has been well established, as has their ubiquitous loss along our coasts with resultant forfeiture of the ecosystem services they provide. Furthering our understanding of how these habitats are evolving in the face of anthropogenic and climate driven changes will help improve management strategies. Previous work has shown that the growth and productivity of both oyster reefs and salt marshes are strongly linked to elevation in the intertidal zone (duration of aerial exposure). We build on that research by examining the growth of marsh-fringing oyster reefs at yearly to decadal time scales and examine movement of the boundary between oyster reef and salt marsh at decadal to centennial time scales. We show that the growth of marsh-fringing reefs is strongly associated to the duration of aerial exposure, with little growth occurring below mean low water and above mean sea level. Marsh-shoreline movement, in the presence or absence of fringing oyster reefs, was reconstructed using transects of sediment cores. Carbonaceous marsh sediments sampled below the modern fringing oyster reefs indicate that marsh shorelines within Back Sound, North Carolina are predominantly in a state of transgression (landward retreat), and modern oyster-reef locations were previously occupied by salt marsh within the past two centuries. Cores fronting transgressive marsh shorelines absent fringing reefs sampled thinner and less extensive carbonaceous marsh sediment than at sites with fringing reefs. This indicates that fringing reefs are preserving carbonaceous marsh sediment from total erosion as they transgress and colonize the exposed marsh shoreline making marsh sediments more resistant to erosion. The amount of marsh sediment preservation underneath the reef scales with the reef’s relief, as reefs with the greatest relief were level with the marsh platform, preserving a maximum amount of carbonaceous sediments during transgression by buffering the marsh from erosional processes. Thus, fringing oyster reefs not only have the capacity to shelter shorelines but, if located at the ideal tidal elevation, they also keep up with accelerating sea-level rise and cap carbonaceous sediments, protecting them from erosion, as reefs develop along the marsh. VL - 40 UR - http://link.springer.com/10.1007/s12237-016-0196-8 IS - 4 ER - TY - JOUR T1 - Seasonal variability in the source and composition of particulate matter in the depositional zone of Baltimore Canyon, U.S. Mid-Atlantic Bight JF - Deep Sea Research Part I: Oceanographic Research Papers Y1 - 2017 A1 - Prouty, N.G. A1 - Mienis, F. A1 - Campbell-Swarzenski, P. A1 - Roark, E.B. A1 - Davies, A.J. A1 - Robertson, C.M. A1 - Duineveld, G. A1 - Ross, S.W. A1 - Rhode, M. A1 - Demopoulos, A.W.J. KW - Deep-sea ecosystems KW - Geochemical analyses KW - organic matter KW - sediment trap KW - Submarine canyons AB - Submarine canyons are often hotspots of biomass due to enhanced productivity and funneling of organic matter of marine and terrestrial origin. However, most deep-sea canyons remain poorly studied in terms of their role as conduits of terrestrial and marine particles. A multi-tracer geochemical investigation of particles collected yearlong by a sediment trap in Baltimore Canyon on the US Mid-Atlantic Bight (MAB) revealed temporal variability in source, transport, and fate of particulate matter. Both organic biomarker composition (sterol and n-alkanes) and bulk characteristics (δ13C, Δ14C, Chl-a) suggest that while on average the annual contribution of terrestrial and marine organic matter sources are similar, 42% and 52% respectively, marine sources dominate. Elevated Chlorophyll-a and sterol concentrations during the spring sampling period highlight a seasonal influx of relatively fresh phytodetritus. In addition, the contemporaneous increase in the particle reactive micronutrients cadmium (Cd) and molybdenum (Mo) in the spring suggest increased scavenging, aggregation, and sinking of phytodetrital biomass in response to enhanced surface production within the nutricline. While tidally driven currents within the canyon resuspend sediment between 200 and 600 m, resulting in the formation of a nepheloid layer rich in lithogenic material, near-bed sediment remobilization in the canyon depositional zone was minimal. Instead, vertical transport and lateral transport across the continental margin were the dominant processes driving seasonal input of particulate matter. In turn, seasonal variability in deposited particulate organic matter is likely linked to benthic faunal composition and ecosystem scale carbon cycling. VL - 127 UR - https://linkinghub.elsevier.com/retrieve/pii/S0967063717300602 ER - TY - JOUR T1 - Sedimentary record from the Canada Basin, Arctic Ocean: implications for late to middle Pleistocene glacial history JF - Climate of the Past Y1 - 2017 A1 - Dong, Linsen A1 - Liu, Yanguang A1 - Shi, Xuefa A1 - Polyak, Leonid A1 - Huang, Yuanhui A1 - Fang, Xisheng A1 - Liu, Jianxing A1 - Zou, Jianjun A1 - Wang, Kunshan A1 - Sun, Fuqiang A1 - Wang, Xuchen AB - ediment core ARC4-BN05 collected from the Canada Basin, Arctic Ocean, covers the late to middle Quaternary (Marine Isotope Stage – MIS – 1–15, ca. 0.5–0.6 Ma) as estimated by correlation to earlier proposed Arctic Ocean stratigraphies and AMS14C dating of the youngest sediments. Detailed examination of clay and bulk mineralogy along with grain size, content of Ca and Mn, and planktic foraminiferal numbers in core ARC4–BN05 provides important new information about sedimentary environments and provenance. We use increased contents of coarse debris as an indicator of glacier collapse events at the margins of the western Arctic Ocean, and identify the provenance of these events from mineralogical composition. Notably, peaks of dolomite debris, including large dropstones, track the Laurentide Ice Sheet (LIS) discharge events to the Arctic Ocean. Major LIS inputs occurred during the stratigraphic intervals estimated as MIS 3, intra-MIS 5 and 7 events, MIS 8, and MIS 10. Inputs from the East Siberian Ice Sheet (ESIS) are inferred from peaks of smectite, kaolinite, and chlorite associated with coarse sediment. Major ESIS sedimentary events occurred in the intervals estimated as MIS 4, MIS 6 and MIS 12. Differences in LIS vs. ESIS inputs can be explained by ice-sheet configurations at different sea levels, sediment delivery mechanisms (iceberg rafting, suspension plumes, and debris flows), and surface circulation. A long-term change in the pattern of sediment inputs, with an apparent step change near the estimated MIS 7–8 boundary (ca. 0.25 Ma), presumably indicates an overall glacial expansion at the western Arctic margins, especially in North America. VL - 13 UR - https://cp.copernicus.org/articles/13/511/2017/ IS - 5 ER - TY - JOUR T1 - Sequential bioavailability of sedimentary organic matter to heterotrophic bacteria JF - Environmental Microbiology Y1 - 2017 A1 - Mahmoudi, Nagissa A1 - é, Steven R. A1 - Steen, Andrew D. A1 - Pearson, Ann AB - Aquatic sediments harbour diverse microbial communities that mediate organic matter degradation and influence biogeochemical cycles. The pool of bioavailable carbon continuously changes as a result of abiotic processes and microbial activity. It remains unclear how microbial communities respond to heterogeneous organic matrices and how this ultimately affects heterotrophic respiration. To explore the relationships between the degradation of mixed carbon substrates and microbial activity, we incubated batches of organic-rich sediments in a novel bioreactor (IsoCaRB) that permitted continuous observations of CO2 production rates, as well as sequential sampling of isotopic signatures (δ13C, Δ14C), microbial community structure and diversity, and extracellular enzyme activity. Our results indicated that lower molecular weight (MW), labile, phytoplankton-derived compounds were degraded first, followed by petroleum-derived exogenous pollutants, and finally by higher MW polymeric plant material. This shift in utilization coincided with a community succession and increased extracellular enzyme activities. Thus, sequential utilization of different carbon pools induced changes at both the community and cellular level, shifting community composition, enzyme activity, respiration rates, and residual organic matter reactivity. Our results provide novel insight into the accessibility of sedimentary organic matter and demonstrate how bioavailability of natural organic substrates may affect the function and composition of heterotrophic bacterial populations. UR - http://doi.wiley.com/10.1111/1462-2920.13745http://onlinelibrary.wiley.com/wol1/doi/10.1111/1462-2920.13745/fullpdfhttps://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2F1462-2920.13745 ER - TY - JOUR T1 - Short organic carbon turnover time and narrow C-14 age spectra in early Holocene wetland paleosols JF - GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS Y1 - 2017 A1 - Vetter, Lael A1 - Rosenheim, Brad E. A1 - Fernandez, Alvaro A1 - Tornqvist, Torbjoern E. KW - paleosol KW - radiocarbon KW - ramped PyrOx KW - soil organic carbon KW - turnover time AB - Paleosols contain information about the rates of soil organic carbon turnover when the soil was actively forming. However, this temporal information is often difficult to interpret without tight stratigraphic control on the age of the paleosol. Here we apply ramped pyrolysis/oxidation (Ramped PyrOx) C-14 analyses to evaluate age spectra of transgressive early Holocene paleosols from the Mississippi Delta in southeastern Louisiana, USA. We find C-14 age spectra from soil organic matter (SOM) in both paleosols and overlying basal peats that represent variability in age that is close to, or only slightly greater than, analytical uncertainty of C-14 measurements, despite different sources of carbon with likely disparate ages. Such age spectra have not previously been observed in the sedimentary record. Here they indicate vigorous soil carbon turnover prior to burial, which homogenized C-14 ages within SOM across the entire thermochemical spectrum. The weighted bulk C-14 ages from Ramped PyrOx of paleosols and overlying peats are identical within analytical and process-associated uncertainty, and corroborate C-14 ages from charcoal fragments and plant macrofossils from the overlying peat. The youngest ages from Ramped PyrOx age spectra may also potentially be applied as chronometers for stratigraphic burial ages. Our results suggest rapid turnover (<<300 years) of carbon in these soils relative to input of allochthonous carbon, indicating that the C-14 age of different soil components is decoupled from thermochemical stability and instead reflects vigorous turnover processes. The concurrence of paleosol and peat C-14 ages also suggests that pedogenic processes were linked with the development of coastal marshes, and that the priming effect potentially masked the signal of allochthonous carbon inputs during sea level rise. VL - 18 ER - TY - JOUR T1 - Siberian Arctic black carbon sources constrained by model and observation JF - Proceedings of the National Academy of Sciences Y1 - 2017 A1 - Winiger, Patrik A1 - Andersson, August A1 - Eckhardt, Sabine A1 - Stohl, Andreas A1 - Semiletov, Igor P. A1 - Dudarev, Oleg V. A1 - Charkin, Alexander A1 - Shakhova, Natalia A1 - Klimont, Zbigniew A1 - Heyes, Chris A1 - Gustafsson, Örjan KW - Arctic haze KW - atmospheric transport modeling KW - carbon isotopes KW - Climate change KW - emission inventory AB - Black carbon (BC) in haze and deposited on snow and ice can have strong effects on the radiative balance of the Arctic. There is a geographic bias in Arctic BC studies toward the Atlantic sector, with lack of observational constraints for the extensive Russian Siberian Arctic, spanning nearly half of the circum-Arctic. Here, 2 y of observations at Tiksi (East Siberian Arctic) establish a strong seasonality in both BC concentrations (8 ng⋅m−3 to 302 ng⋅m−3) and dual-isotope–constrained sources (19 to 73% contribution from biomass burning). Comparisons between observations and a dispersion model, coupled to an anthropogenic emissions inventory and a fire emissions inventory, give mixed results. In the European Arctic, this model has proven to simulate BC concentrations and source contributions well. However, the model is less successful in reproducing BC concentrations and sources for the Russian Arctic. Using a Bayesian approach, we show that, in contrast to earlier studies, contributions from gas flaring (6%), power plants (9%), and open fires (12%) are relatively small, with the major sources instead being domestic (35%) and transport (38%). The observation-based evaluation of reported emissions identifies errors in spatial allocation of BC sources in the inventory and highlights the importance of improving emission distribution and source attribution, to develop reliable mitigation strategies for efficient reduction of BC impact on the Russian Arctic, one of the fastest-warming regions on Earth. VL - 114 UR - http://www.pnas.org/lookup/doi/10.1073/pnas.1613401114https://syndication.highwire.org/content/doi/10.1073/pnas.1613401114http://www.pnas.org/syndication/doi/10.1073/pnas.1613401114 IS - 7 ER - TY - JOUR T1 - Subduction zone slip variability during the last millennium, south-central Chile JF - Quaternary Science Reviews Y1 - 2017 A1 - Dura, Tina A1 - Horton, Benjamin P. A1 - Cisternas, Marco A1 - Ely, Lisa L. A1 - Hong, Isabel A1 - Nelson, Alan R. A1 - Wesson, Robert L. A1 - Pilarczyk, Jessica E. A1 - Parnell, Andrew C. A1 - Nikitina, Daria KW - Coastal hazards KW - Coastal paleoseismology KW - Diatom paleoecology KW - Prehistoric earthquakes KW - Subduction zone segmentation KW - Tsunami Deposits AB - The Arauco Peninsula (37°-38°S) in south-central Chile has been proposed as a possible barrier to the along-strike propagation of megathrust ruptures, separating historical earthquakes to the south (1960 AD 1837, 1737, and 1575) and north (2010 AD, 1835, 1751, 1657, and 1570) of the peninsula. However, the 2010 (Mw 8.8) earthquake propagated into the Arauco Peninsula, re-rupturing part of the megathrust that had ruptured only 50 years earlier during the largest subduction zone earthquake in the instrumental record (Mw 9.5). To better understand long-term slip variability in the Arauco Peninsula region, we analyzed four coastal sedimentary sections from two sites (Tirúa, 38.3°S and Quidico, 38.1°S) located within the overlap of the 2010 and 1960 ruptures to reconstruct a ∼600-year record of coseismic land-level change and tsunami inundation. Stratigraphic, lithologic, and diatom results show variable coseismic land-level change coincident with tsunami inundation of the Tirúa and Quidico marshes that is consistent with regional historical accounts of coseismic subsidence during earthquakes along the Valdivia portion of the subduction zone (1960 AD and 1575) and coseismic uplift during earthquakes along the Maule portion of the subduction zone (2010 AD, 1835, 1751). In addition, we document variable coseismic land-level change associated with three new prehistoric earthquakes and accompanying tsunamis in 1470–1570 AD, 1425–1455, and 270–410. The mixed record of coseismic subsidence and uplift that we document illustrates the variability of down-dip and lateral slip distribution at the overlap of the 2010 and 1960 ruptures, showing that ruptures have repeatedly propagated into, but not through the Arauco Peninsula and suggesting the area has persisted as a long-term impediment to slip through at least seven of the last megathrust earthquakes (∼600 years). VL - 175 UR - https://linkinghub.elsevier.com/retrieve/pii/S0277379117303505 ER - TY - JOUR T1 - Sub-ice shelf sediment geochronology utilizing novel radiocarbon methodology for highly detrital sediments JF - Geochemistry, Geophysics, Geosystems Y1 - 2017 A1 - Subt, C. A1 - Yoon, H. I. A1 - Yoo, K. C. A1 - Lee, J. I. A1 - Leventer, A. A1 - Domack, E. W. A1 - Rosenheim, B. E. AB - Sub‐ice shelf sediments near Larsen C ice shelf (LIS‐C) show fine‐scale rhythmic laminations that could provide a near‐continuous seasonal‐resolution record of regional ice mass changes. Despite the great potential of these sediments, a dependable Late Quaternary chronology is difficult to generate, rendering the record incomplete. As with many marginal Antarctic sediments, in the absence of preserved carbonate microfossils, the reliability of radiocarbon chronologies depends on presence of high proportions of autochthonous organic carbon with minimized detrital organic carbon. Consequently, acid insoluble organic (AIO) 14C dating works best where high productivity drives high sediment accumulation rates, but can be problematic in condensed sequences with high proportions of detrital organic carbon. Ramped PyrOx 14C dating has progressively been shown to improve upon AIO 14C dates, to the point of matching foraminiferal carbonate 14C dates, through differential thermochemical degradation of organic components within samples. But in highly detrital sediments, proportions of contemporaneously deposited material are too low to fully separate autochthonous organic carbon from detrital carbon in samples large enough to 14C date. We introduce two modifications of the Ramped PyrOx 14C approach applied to highly detrital sediments near LIS‐C to maximize accuracy by utilizing ultra‐small fractions of the highly detrital AIO material. With minimization of the uncertainty cost, these techniques allow us to generate chronologies for cores that would otherwise go undated, pushing the limits of radiocarbon dating to regions and facies with high proportions of pre‐aged detritus. Wider use of these techniques will enable more coordinated a priori coring efforts to constrain regional glacial responses to rapid warming where sediments had previously been thought too difficult to date. VL - 18 UR - https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2016GC006578 IS - 4 ER - TY - JOUR T1 - Technical note: An inverse method to relate organic carbon reactivity to isotope composition from serial oxidation JF - Biogeosciences Y1 - 2017 A1 - Hemingway, Jordon D. A1 - Rothman, Daniel H. A1 - Rosengard, Sarah Z. A1 - Galy, Valier V. VL - 14 UR - https://www.biogeosciences.net/14/5099/2017/https://www.biogeosciences.net/14/5099/2017/bg-14-5099-2017.pdfhttps://www.biogeosciences.net/14/5099/2017/bg-14-5099-2017-supplement.zip IS - 22 ER - TY - JOUR T1 - A Terminal Pleistocene/Early Holocene Environmental Record and Fluted Point from Twain Harte, California JF - PaleoAmerica Y1 - 2017 A1 - Moratto, Michael J. A1 - Davis, Owen K. A1 - Davis-King, Shelly A1 - Meyer, Jack A1 - Rosenthal, Jeffrey A1 - Sylwester, Laurie KW - California prehistory KW - Clovis chronology KW - Geomorphology KW - palynology KW - terminal Pleistocene/early Holocene AB - Although more than 500 Clovis points have been found at no fewer than 60 locations in California, the age of these points remains problematic. Here we report stratified deposits more than 3 meters deep at a site in the central Sierra Nevada from which a Clovis point was recovered in 1969. Five radiocarbon (14C) dates provide temporal control for terminal Pleistocene and early Holocene strata at the site, including the sediments in which the point reposed. We also report the analysis of pollen samples from these strata. Our research indicates that the Clovis point most likely dates to ∼11,900–11,400 cal yr BP. We interpret this, in the context of other fluted-point discoveries, to mean that Clovis lithic technology evidently persisted longer in the Far West than it did elsewhere in the U.S. VL - 3 UR - https://www.tandfonline.com/doi/full/10.1080/20555563.2017.1328959 IS - 3 ER - TY - JOUR T1 - Timing and magnitude of early to middle Holocene warming in East Greenland inferred from chironomids JF - Boreas Y1 - 2017 A1 - Axford, Yarrow A1 - Levy, Laura B. A1 - Kelly, Meredith A. A1 - Francis, Donna R. A1 - Hall, Brenda L. A1 - Langdon, Peter G. A1 - Lowell, Thomas V. ED - ínguez-Rodrigo, M. ED - Baquedano, E. ED - Mabulla, A. ED - ín, F. ED - Egeland, C. P. AB - Much of Greenland experienced summers warmer than present in parts of the early to middle Holocene, during a precession‐driven positive anomaly in summer insolation. However, the magnitude of that warmth remains poorly known, and its timing and spatial pattern are uncertain. Here we describe the first quantitative Holocene palaeotemperature reconstruction from central East Greenland based upon insect (chironomid) assemblages preserved in lake sediments. We postulate that landscapes like our study site, characterized by minimal soil and vegetation development through the Holocene and thus little influenced by some important secondary gradients, are especially well suited to the use of chironomids to reconstruct Holocene temperatures. The inferred timing of warmth at our study site near Scoresby Sund agrees well with other nearby evidence, including glacial geological reconstructions and temperatures inferred from precipitation isotopes at Renland ice cap, supporting the use of chironomids to reconstruct temperatures at this site. We infer highest temperatures from c. 10 to 5.5 ka, followed by gradual cooling after 5.5 ka and progressively colder and less productive conditions after 3.5 ka. Models based upon two independent training sets yield similar inferred temperature trends, and suggest an average summer temperature anomaly from c. 10 to 5.5 ka of 3 to 4 °C relative to the preindustrial last millennium. The estimated overall rate of Neoglacial cooling averaged over the period from 5.5 to 0.5 ka was 0.6 to 0.8 °C per thousand years, more than twice the rate previously estimated for the Arctic as a whole. Given strong apparent spatial variability in Holocene climate around the Arctic, and the utility of palaeoclimate data for improving climate and ice‐sheet models, it should be a priority to further quantify past temperature changes around the margins of the Greenland Ice Sheet, where few quantitative reconstructions exist and future warming will affect global sea level. VL - 4611126123715949514747452279282108875423653331285492025312166523481473253855431029263383391243655482254028102024461441564827316 UR - https://onlinelibrary.wiley.com/doi/abs/10.1111/bor.12247 IS - 4 ER - TY - JOUR T1 - Trends in catchment processes and lake evolution during the late-glacial and early- to mid-Holocene inferred from high-resolution XRF data in the Yellowstone region JF - Journal of Paleolimnology Y1 - 2017 A1 - Lu, Yanbin A1 - Fritz, Sherilyn C. A1 - Stone, Jeffery R. A1 - Krause, Teresa R. A1 - Whitlock, Cathy A1 - Brown, Erik T. A1 - Benes, James V. AB - High-resolution records of geochemical data from four lakes in the Greater Yellowstone region were used to investigate watershed and lake history during the late-glacial and early-Holocene periods. Clastic input to regional lakes was high and variable during the early stages of lake development, when the surrounding landscape was geomorphically unstable and sparsely vegetated, and it decreased as vegetation gradually developed in each catchment. The decrease of clastic input was not regionally synchronous but occurred in a time-transgressive pattern from south to north. Long-term organic matter concentration and diatom production were inversely related to catchment erosion during the early stages of lake development and increased as temperatures warmed and in-lake nutrient concentrations increased. Similarly, calcite production usually was low following lake formation and increased over time, driven by climate change and its associated influences on lake-level, algal production, and lake thermal structure. Overall differences in the timing and pattern of geochemical change indicate that once the landscape had stabilized following deglaciation, changes in the geochemical character of the sediments were strongly influenced by local factors. VL - 58 UR - http://link.springer.com/10.1007/s10933-017-9991-x IS - 4 ER - TY - JOUR T1 - The tropical lapse rate steepened during the Last Glacial Maximum JF - Science Advances Y1 - 2017 A1 - Loomis, Shannon E. A1 - Russell, James M. A1 - Verschuren, Dirk A1 - Morrill, Carrie A1 - De Cort, Gijs A1 - Sinninghe Damsté, Jaap S. A1 - Olago, Daniel A1 - Eggermont, Hilde A1 - Street-Perrott, F. Alayne A1 - Kelly, Meredith A. AB - The gradient of air temperature with elevation (the temperature lapse rate) in the tropics is predicted to become less steep during the coming century as surface temperature rises, enhancing the threat of warming in high-mountain environments. However, the sensitivity of the lapse rate to climate change is uncertain because of poor constraints on high-elevation temperature during past climate states. We present a 25,000-year temperature reconstruction from Mount Kenya, East Africa, which demonstrates that cooling during the Last Glacial Maximum was amplified with elevation and hence that the lapse rate was significantly steeper than today. Comparison of our data with paleoclimate simulations indicates that state-of-the-art models underestimate this lapse-rate change. Consequently, future high-elevation tropical warming may be even greater than predicted. VL - 3 UR - https://advances.sciencemag.org/lookup/doi/10.1126/sciadv.1600815 IS - 1 ER - TY - JOUR T1 - Tropical Pacific climate variability over the last 6000 years as recorded in Bainbridge Crater Lake, Galápagos JF - Paleoceanography Y1 - 2017 A1 - Thompson, Diane M. A1 - Conroy, Jessica L. A1 - Collins, Aaron A1 - Hlohowskyj, Stephan R. A1 - Overpeck, Jonathan T. A1 - Riedinger-Whitmore, Melanie A1 - Cole, Julia E. A1 - Bush, Mark B. A1 - Whitney, H. A1 - Corley, Timothy L. A1 - Kannan, Miriam Steinitz KW - Climate variability KW - El Niño–Southern Oscillation(ENSO) KW - Galápagos archipelago KW - mid‐Holocene KW - monitoring KW - tropical Pacific Ocean AB - Finely laminated sediments within Bainbridge Crater Lake, Galápagos, provide a record of El Niño–Southern Oscillation (ENSO) events over the Holocene. Despite the importance of this sediment record, hypotheses for how climate variability is preserved in the lake sediments have not been tested. Here we present results of long‐term monitoring of the local climate and limnology and a revised interpretation of the sediment record. Brown‐green, organic‐rich, siliciclastic laminae reflect warm, wet conditions typical of El Niño events, whereas carbonate and gypsum precipitate during cool, dry La Niña events and persistent dry periods, respectively. Applying this new interpretation, we find that ENSO events of both phases were generally less frequent during the mid‐Holocene (~6100–4000 calendar years B.P.) relative to the last ~1500 calendar years. Abundant carbonate laminations between 3500 and 3000 calendar years B.P. imply that conditions in the Galápagos region were cool and dry during this period when the tropical Pacific E‐W sea surface temperature (SST) gradient likely strengthened. The frequency of El Niño and La Niña events then intensified dramatically around 1750–2000 calendar years B.P., consistent with a weaker SST gradient and an increased frequency of ENSO events in other regional records. This strong interannual variability persisted until ~700 calendar years B.P., when ENSO‐related variability at the lake decreased as the SST gradient strengthened. Persistent, dry conditions then dominated between 300 and 50 calendar years B.P. (A.D. 1650–1900, ± ~100 years), whereas wetter conditions and frequent El Niño events dominated in the most recent century. VL - 32 UR - https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2017PA003089 IS - 8 ER - TY - JOUR T1 - Turning up the Heat on Organic Matter to Track Carbon JF - Eos Y1 - 2017 A1 - McNichol, Ann A1 - Rosenheim, Brad A1 - Galy, Valier KW - Antarctic sediments KW - Foraminifera KW - radiocarbon KW - stable carbon isotopes VL - 98 UR - https://eos.org/meeting-reports/turning-up-the-heat-on-organic-matter-to-track-carbon ER - TY - JOUR T1 - Two phases of the Holocene East African Humid Period: Inferred from a high-resolution geochemical record off Tanzania JF - Earth and Planetary Science Letters Y1 - 2017 A1 - Liu, Xiting A1 - Rendle-Bühring, Rebecca A1 - Kuhlmann, Holger A1 - Li, Anchun KW - African Humid Period KW - Congo Air Boundary KW - Holocene KW - Intertropical Convergence Zone KW - X-ray fluorescence scanner AB - During the Holocene, the most notably climatic change across the African continent is the African Humid Period (AHP), however the pace and primary forcing for this pluvial condition is still ambiguous, particularly in East Africa. We present a high-resolution marine sediment record off Tanzania to provide insights into the climatic conditions of inland East Africa during the Holocene. Major element ratios (i.e., log-ratios of Fe/Ca and Ti/Ca), derived from X-Ray Fluorescence scanning, have been employed to document variations in humidity in East Africa. Our results show that the AHP is represented by two humid phases: an intense humid period from the beginning of the Holocene to 8 ka (AHP I); and a moderate humid period spanning from 8 to 5.5 ka (AHP II). On the basis of our geochemical record and regime detection, the termination of the AHP initiated at 5.5 ka and ceased around 3.5 ka. Combined with other paleoclimatic records around East Africa, we suggest that the humid conditions in this region responded to Northern Hemisphere (NH) summer insolation. The AHP I and II might have been related to an eastward shift of the Congo Air Boundary and warmer conditions in the western Indian Ocean, which resulted in additional moisture being delivered from the Atlantic and Indian Oceans during the NH summer and autumn, respectively. We further note a drought event throughout East Africa north of 10°S around 8.2 ka, which may have been related to the southward migration of the Intertropical Convergence Zone in response to the NH cooling event. VL - 460 UR - https://linkinghub.elsevier.com/retrieve/pii/S0012821X16307294 ER - TY - JOUR T1 - Utility of salt-marsh foraminifera, testate amoebae and bulk-sediment δ13C values as sea-level indicators in Newfoundland, Canada JF - Marine Micropaleontology Y1 - 2017 A1 - Kemp, Andrew C. A1 - Wright, Alexander J. A1 - Barnett, Robert L. A1 - Hawkes, Andrea D. A1 - Charman, Dan J. A1 - Sameshima, Colby A1 - King, Alexandra N. A1 - Mooney, Hailey C. A1 - Edwards, Robin J. A1 - Horton, Benjamin P. A1 - van de Plassche, Orson AB - We investigated the utility of foraminifera, testate amoebae and bulk-sediment δ13C measurements for reconstructing Holocene relative sea level from sequences of salt-marsh sediment in Newfoundland, Canada. Modern, surface sediment was collected along transects from low to supra-tidal elevations in eastern (at Placentia) and western (at Hynes Brook and Big River) Newfoundland. Consistent with previous work, low-diversity assemblages of foraminifera display an almost binary division into a higher salt-marsh assemblage dominated by Jadammina macrescens and Balticammina pseudomacrescens and a lower salt-marsh assemblage comprised of Miliammina fusca. This pattern and composition resembles those identified at other high latitude sites with cool climates and confirms that foraminifera are sea-level indicators. The lowest occurrence of testate amoebae was at approximately mean higher high water. The composition of high salt-marsh testate amoebae assemblages (Centropyxis cassis type, Trinema spp., Tracheleuglypha dentata type, and Euglypha spp.) in Newfoundland was similar to elsewhere in the North Atlantic, but preservation bias favors removal of species with idiosomic tests over those with xenosomic tests. The mixed high salt-marsh plant community in Newfoundland results in bulk surface-sediment δ13C values that are typical of C3 plants, making them indistinguishable from freshwater sediment. Therefore we propose that the utility of this proxy for reconstructing RSL in eastern North America is restricted to the coastline between Chesapeake Bay and southern Nova Scotia. Using a simple, multi-proxy approach to establish that samples in three radiocarbon-dated sediment cores formed between the lowest occurrence of testate amoebae and the highest occurrence of foraminifera, we generated three example late Holocene sea-level index points at Hynes Brook. VL - 130 UR - https://linkinghub.elsevier.com/retrieve/pii/S0377839816300524 ER - TY - JOUR T1 - Vulnerability of Coral Reefs to Bioerosion From Land‐Based Sources of Pollution JF - Journal of Geophysical Research: Oceans Y1 - 2017 A1 - Prouty, Nancy G. A1 - Cohen, Anne A1 - Yates, Kimberly K. A1 - Storlazzi, Curt D. A1 - Swarzenski, Peter W. A1 - White, Darla KW - aragonite saturation KW - bioerosion KW - coral reefs KW - nutrients KW - submarine groundwater KW - Wastewater AB - Ocean acidification (OA), the gradual decline in ocean pH and [ urn:x-wiley:21699275:media:jgrc22505:jgrc22505-math-0001] caused by rising levels of atmospheric CO2, poses a significant threat to coral reef ecosystems, depressing rates of calcium carbonate (CaCO3) production, and enhancing rates of bioerosion and dissolution. As ocean pH and [ urn:x-wiley:21699275:media:jgrc22505:jgrc22505-math-0002] decline globally, there is increasing emphasis on managing local stressors that can exacerbate the vulnerability of coral reefs to the effects of OA. We show that sustained, nutrient rich, lower pH submarine groundwater discharging onto nearshore coral reefs off west Maui lowers the pH of seawater and exposes corals to nitrate concentrations 50 times higher than ambient. Rates of coral calcification are substantially decreased, and rates of bioerosion are orders of magnitude higher than those observed in coral cores collected in the Pacific under equivalent low pH conditions but living in oligotrophic waters. Heavier coral nitrogen isotope (δ15N) values pinpoint not only site‐specific eutrophication, but also a sewage nitrogen source enriched in 15N. Our results show that eutrophication of reef seawater by land‐based sources of pollution can magnify the effects of OA through nutrient driven‐bioerosion. These conditions could contribute to the collapse of coastal coral reef ecosystems sooner than current projections predict based only on ocean acidification. VL - 122 UR - https://agupubs.onlinelibrary.wiley.com/doi/10.1002/2017JC013264 IS - 12 ER - TY - JOUR T1 - What on Earth Have We Been Burning? Deciphering Sedimentary Records of Pyrogenic CarbonWhat on Earth Have We Been Burning? Deciphering Sedimentary Records of Pyrogenic Carbon JF - Environmental Science & Technology Y1 - 2017 A1 - Hanke, Ulrich M. A1 - Reddy, Christopher M. A1 - Braun, Ana L. L. A1 - Coppola, Alysha I. A1 - Haghipour, Negar A1 - McIntyre, Cameron P. A1 - Wacker, Lukas A1 - Xu, Li A1 - McNichol, Ann P. A1 - Abiven, Samuel A1 - Schmidt, Michael W. I. A1 - Eglinton, Timothy I. AB - Humans have interacted with fire for thousands of years, yet the utilization of fossil fuels marked the beginning of a new era. Ubiquitous in the environment, pyrogenic carbon (PyC) arises from incomplete combustion of biomass and fossil fuels, forming a continuum of condensed aromatic structures. Here, we develop and evaluate 14C records for two complementary PyC molecular markers, benzene polycarboxylic acids (BPCAs) and polycyclic aromatic hydrocarbons (PAHs), preserved in aquatic sediments from a suburban and a remote catchment in the United States (U.S.) from the mid-1700s to 1998. Results show that the majority of PyC stems from local sources and is transferred to aquatic sedimentary archives on subdecadal to millennial time scales. Whereas a small portion stems from near-contemporaneous production and sedimentation, the majority of PyC (∼90%) experiences delayed transmission due to “preaging” on millennial time scales in catchment soils prior to its ultimate deposition. BPCAs (soot) and PAHs (precursors of soot) trace fossil fuel-derived PyC. Both markers parallel historical records of the consumption of fossil fuels in the U.S., yet never account for more than 19% total PyC. This study demonstrates that isotopic characterization of multiple tracers is necessary to constrain histories and inventories of PyC and that sequestration of PyC can markedly lag its production. VL - 51 UR - https://pubs.acs.org/doi/10.1021/acs.est.7b03243 IS - 21 ER - TY - JOUR T1 - Younger-Dryas cooling and sea-ice feedbacks were prominent features of the Pleistocene-Holocene transition in Arctic Alaska JF - Quaternary Science Reviews Y1 - 2017 A1 - Gaglioti, Benjamin V. A1 - Mann, Daniel H. A1 - Wooller, Matthew J. A1 - Jones, Benjamin M. A1 - Wiles, Gregory C. A1 - Groves, Pamela A1 - Kunz, Michael L. A1 - Baughman, Carson A. A1 - Reanier, Richard E. KW - alaska KW - Arctic KW - Bering Strait KW - Climate change KW - dendrochronology KW - north pacific KW - oxygen isotopes KW - Paleoclimate KW - Sea ice KW - Younger Dryas AB - Declining sea-ice extent is currently amplifying climate warming in the Arctic. Instrumental records at high latitudes are too short-term to provide sufficient historical context for these trends, so paleoclimate archives are needed to better understand the functioning of the sea ice-albedo feedback. Here we use the oxygen isotope values of wood cellulose in living and sub-fossil willow shrubs (δ18Owc) (Salix spp.) that have been radiocarbon-dated (14C) to produce a multi-millennial record of climatic change on Alaska's North Slope during the Pleistocene-Holocene transition (13,500–7500 calibrated 14C years before present; 13.5–7.5 ka). We first analyzed the spatial and temporal patterns of δ18Owc in living willows growing at upland sites and found that over the last 30 years δ18Owc values in individual growth rings correlate with local summer temperature and inter-annual variations in summer sea-ice extent. Deglacial δ18Owc values from 145 samples of subfossil willows clearly record the Allerød warm period (∼13.2 ka), the Younger Dryas cold period (12.9–11.7 ka), and the Holocene Thermal Maximum (11.7–9.0 ka). The magnitudes of isotopic changes over these rapid climate oscillations were ∼4.5‰, which is about 60% of the differences in δ18Owc between those willows growing during the last glacial period and today. Modeling of isotope-precipitation relationships based on Rayleigh distillation processes suggests that during the Younger Dryas these large shifts in δ18Owc values were caused by interactions between local temperature and changes in evaporative moisture sources, the latter controlled by sea ice extent in the Arctic Ocean and Bering Sea. Based on these results and on the effects that sea-ice have on climate today, we infer that ocean-derived feedbacks amplified temperature changes and enhanced precipitation in coastal regions of Arctic Alaska during warm times in the past. Today, isotope values in willows on the North Slope of Alaska are similar to those growing during the warmest times of the Pleistocene-Holocene transition, which were times of widespread permafrost thaw and striking ecological changes. VL - 169 UR - https://linkinghub.elsevier.com/retrieve/pii/S0277379117301713 ER - TY - JOUR T1 - 10Be dating reveals early-middle Holocene age of the Drygalski Moraines in central West Greenland JF - Quaternary Science Reviews Y1 - 2016 A1 - Sandra L. Cronauer A1 - Jason P. Briner A1 - Samuel E. Kelley A1 - Susan R.H. Zimmerman A1 - Mathieu Morlighem KW - Holocene AB - Abstract We reconstruct the history of the Greenland Ice Sheet margin on the Nuussuaq Peninsula in central West Greenland through the Holocene using lake sediment analysis and cosmogenic 10Be exposure dating of the prominent Drygalski Moraines. Erratics perched on bedrock outboard of the Drygalski Moraines constrain local deglaciation to ∼9.9 ± 0.6 ka (n = 2). Three Drygalski Moraine crests yield mean 10Be ages of 8.6 ± 0.4 ka (n = 2), 8.5 ± 0.2 ka (n = 3), and 7.6 ± 0.1 ka (n = 2) from outer to inner. Perched erratics between the inner two moraines average 7.8 ± 0.1 ka (n = 2) and are consistent with the moraine ages. Sediments from a proglacial lake with a catchment area extending an estimated 2 km beneath (inland of) the present ice sheet terminus constrain an ice sheet minimum extent from 5.4 ka to 0.6 ka. The moraine chronology paired with the lake sediment stratigraphy reveals that the ice margin likely remained within ∼2 km of its present position from ∼9.9 to 5.4 ka. This unexpected early Holocene stability, preceded by rapid ice retreat and followed by minimum ice extent between ∼5.4 and 0.6 ka, contrasts with many records of early Holocene warmth and the Northern Hemisphere summer insolation maximum. We suggest ice margin stability may instead be tied to adjacent ocean temperatures, which reached an optimum in the middle Holocene. VL - 147 UR - http://www.sciencedirect.com/science/article/pii/S0277379115301050 N1 - Special Issue: \{PAST\} Gateways (Palaeo-Arctic Spatial and Temporal Gateways) ER - TY - JOUR T1 - Abandoned channel fill sequences in the tidal estuary of a small mountainous, dry-summer river JF - SEDIMENTOLOGY Y1 - 2016 A1 - Gray, Andrew B. A1 - Pasternack, Gregory B. A1 - Watson, Elizabeth B. A1 - Goni, Miguel A. KW - Abandoned channels KW - Geomorphology KW - grain-size analysis KW - organic carbon KW - stratigraphy KW - tidal estuaries AB - {This study proposes a modification of the current model for abandoned channel fill stratigraphy produced in unidirectional flow river reaches to incorporate seasonal tidal deposition. Evidence supporting this concept came from a study of two consecutive channel abandonment sequences in Ropers Slough of the lower Eel River Estuary in northern California. Aerial photographs showed that Ropers Slough was abandoned around 1943, reoccupied after the 1964 flood, and abandoned again in 1974 with fill continuing to the present. Planform geomorphic characteristics derived from these images were used in conjunction with sub-centimetre resolution stratigraphic analyses to describe depositional processes and their resultant sedimentary deposits. Both abandonment sequences recorded quasi-annual scale fluvial/tidal deposition couplets. In both cases, tidal deposits contained very little sand, were higher in organic and inorganic carbon content than the sandier, fluvially dominated deposits, and possessed millimetre-scale horizontal laminations. The two abandonment fills differed significantly in terms of the temporal progression of channel narrowing and fluvial sediment deposition characteristics. Aerial photographic analysis showed that the first abandonment sequence led to a more rapid narrowing of Ropers Slough and produced deposits with a positive relationship between grain size/deposit thickness and discharge. The second abandonment resulted in a much slower narrowing of Ropers Slough and generally thinner fluvial deposits with no clear relationship between grain size/deposit thickness and discharge. The delta C-13 values and organic nitrogen to organic carbon ratios of deposits from the first phase overlapped with Eel River suspended sediment characteristics found for low flows (one to five times mean discharge), while those of the second phase were consistent with suspended sediment from higher flows (seven to ten times mean discharge). When considered together, the results indicate that the early fill sequence recorded a reach experiencing regular fluvial deposition through flow conditions during the wet season, while the latter fill sequence records a reach more disconnected from the main stem in terms of flow and sediment. The major factor affecting the difference in sedimentation between the two fill periods appears to have been the morphology of the upstream river bend in relation to the position of the bifurcation node. During the first fill period, the upstream entrance to Ropers Slough seems to have remained open, in part due to the placement of its entrance on the outside of the mainstem river bend, and despite stronger tidal effects caused by a larger tidal prism and closer proximity to the tidal inlet. By the second fill sequence, the upstream bend morphology had altered, placing the entrance to Ropers Slough on the inner bank of the mainstem bend, which resulted in more rapid plug bar formation. The role of tidal effects in the geomorphic trajectory of the two abandonment sequences is unclear, but appears to have been less important than local bifurcation geometry.} VL - 63 ER - TY - JOUR T1 - Accommodation space controls on incised-valley sediment accumulation rates during the Holocene marine transgression (0–11 ka) in Grays Harbor, a large meso-tidal estuary, Washington, \{USA\} JF - Marine Geology Y1 - 2016 A1 - Curt D. Peterson A1 - James B. Phipps KW - Littoral sand sink AB - Abstract Holocene deposits (0–11 ka) that were drill cored (275 samples from 17 sites) in the meso-tidal Grays Harbor estuary were analyzed for 1) sediment texture and source components and 2) calibrated radiocarbon age. These data were used with basin 10 m-contour interval volumes to establish relations between rates of increasing basin accommodation space and sediment volume accumulation. Rates of increasing accommodation space (0.3–2.1 × 106 m3 yr− 1) are based on interval volumes and a sea level curve (0–11.5 ka) for the Grays Harbor basin. Total sediment accumulation rates (0.41–1.4 × 106 m3 yr− 1) are computed for the same 10 m-depth intervals (0–60 m depth MSL) and corresponding 10 m-interval sedimentation durations (0.7–5.0 × 103 ka) from a sediment level curve. The rates of basin increasing accommodation space and total sediment accumulation are positively correlated (R2 = 0.81), but sediment accumulation lagged behind increasing accommodation space (23–37%) during early- and middle-Holocene time (7–10 ka). Slowing rates of sea level rise after 8 ka, permitted combined river and littoral inputs of sediment to reduce basin subtidal water depths (  10 m) to intertidal water depths (  1 m). The ratios between sand and mud components in the analyzed Holocene deposits are negatively correlated to basin water depth. Shallowing tidal flats promoted the export of river mud out of the estuary and the import of littoral sand into the central estuary areas. Variable rates of increasing basin accommodation space 1) directly controlled the total sediment accumulation rate in the evolving basin and 2) indirectly controlled the relative proportions of mud and littoral sand accumulation, due to changing water depths in the basin. The late-Holocene accumulation of littoral sand (52% of total sediment volume) is used to compute the net littoral sand sink (  100 × 106 m3) in the Grays Harbor basin from a potential 1.0 m rise of future sea level following predicted global warming. The contribution of littoral sand from adjacent barrier sand spits (20 km in length) to fill the increasing accommodation space in the Grays Harbor estuary could result in 0.5–1.0 km of shoreline retreat following a 1.0 m rise in sea level. VL - 380 UR - http://www.sciencedirect.com/science/article/pii/S0025322716301268 ER - TY - JOUR T1 - The AD 1755 tsunami deposits onshore and offshore of Algarve (south Portugal): Sediment transport interpretations based on the study of Foraminifera assemblages JF - Quaternary International Y1 - 2016 A1 - Maria Quintela A1 - Pedro J.M. Costa A1 - Francisco Fatela A1 - Teresa Drago A1 - Natalia Hoska A1 - César Andrade A1 - Maria C. Freitas KW - Portugal AB - Abstract Tsunamis are amongst the most catastrophic natural hazards affecting worldwide coastal areas. Their impacts are recorded in the geological archives and its study provides crucial insights into the dynamics and intensity of these events. The accurate establishment of return periods can also be derived using sedimentological data. Onshore tsunami deposits have been extensively described over recent years through the application of a wide range of sedimentological proxies, including micropalaeontological analysis. In this work, the identification of palaeotsunami evidence, in both the onshore and offshore sedimentary record of south Portugal, was performed, relying mostly on the study of Foraminifera assemblages. Three onshore trenches and one offshore core were analyzed and imprints of the \{AD\} 1755 tsunami were observed based in the identification of allochthonous foraminiferal species, increase in the number of broken/abraded tests and its correlation with coarser mean grain size. This was possible after micropalaeontological environmental characterization of both low-energy onshore and offshore present-day sedimentation regimes. In the onshore record, three distinct sediment transport phases were differentiated within the tsunamigenic unit. The basal phase portraying the initial inundation represented by the dominance of marine Foraminifera species in a highly diverse assemblage. The higher energetic character of this phase was also reflected in the identification of the highest number of broken/abraded tests. The intermediate phase reflects an unspecified number of inundation and backwash pulses that were recognized based in the well-balanced presence of estuarine (brackish) and marine species, the sharp decrease in the diversity index and in the number of broken/abraded tests. The final phase recorded in the tsunamigenic unit registers the imprint of the last relevant backwash which was identified based on the dominance of estuarine (brackish) fauna. The overlying unit is dominated by tidal marsh species, demonstrating the start of the coastal system recovery phase. In the offshore record, it was possible to identify 2 distinct historical tsunami events (AD 1755 and \{AD\} 1969). This was achieved through the identification of significant increases in coastal Foraminifera species coupled with the presence of coarser layers. This interpretation was sustained by indirect age-estimation methods (radiocarbon and 210Pb) that ascribed compatible ages to the historical tsunami events. The results obtained in this study stress the relevance and innovative character of this onshore and offshore multiproxy approach in the recognition and understanding of tsunami events. VL - 408, Part A UR - http://www.sciencedirect.com/science/article/pii/S1040618215014159 N1 - QuicklakeH Special Issue: Rapidly changing large lakes and human response ER - TY - JOUR T1 - Age and growth of bluespine unicornfish (Naso unicornis): a half-century life-span for a keystone browser, with a novel approach to bomb radiocarbon dating in the Hawaiian Islands JF - Canadian Journal of Fisheries and Aquatic Sciences Y1 - 2016 A1 - Andrews, A.H. A1 - DeMartini, Edward E. A1 - Eble, Jeff A. A1 - Taylor, Brett M. A1 - Lou, Dong Chun A1 - Humphreys, Robert L. AB - Bluespine unicornfish (Naso unicornis) from Hawaii were aged to >50 years using cross-sectioned sagittal otoliths. Fish length was a poor indicator of age because of rapid and variable early growth, exemplified by fish aged to be 4 years near maximum length. Growth was deterministic with adult ages decoupled from body length. Otolith mass and thickness were evaluated as proxies for age and both were encouraging; thickness explained more variance but mass was easier to measure. An age estimation protocol was validated through ontogeny using bomb radiocarbon (14C) dating. Use of the postbomb 14C decline period from a regional reference chronology enabled age validation of young fish — a novel approach for the Pacific Ocean. A probabilistic procedure for assigning bomb 14C dates (CALIBomb) was used for the first time to determine fish birth years. The age-reading protocol was generally validated, and it was possible to describe length-at-age despite difficulties in counting otolith annuli beyond 30–40 years. Growth curves differed between the sexes, and a four-parameter generalized von Bertalanffy growth function provided the best fit. VL - 73 UR - http://www.nrcresearchpress.com/doi/10.1139/cjfas-2016-0019 IS - 10 ER - TY - JOUR T1 - Age of the Mt. Ortles ice cores, the Tyrolean Iceman and glaciation of the highest summit of South Tyrol since the Northern Hemisphere Climatic Optimum JF - The Cryosphere Y1 - 2016 A1 - Gabrielli, Paolo A1 - Barbante, Carlo A1 - Bertagna, Giuliano A1 - ó, Michele A1 - Binder, Daniel A1 - Carton, Alberto A1 - Carturan, Luca A1 - Cazorzi, Federico A1 - Cozzi, Giulio A1 - Dalla Fontana, Giancarlo A1 - Davis, Mary A1 - De Blasi, Fabrizio A1 - Dinale, Roberto A1 - à, Gianfranco A1 - Dreossi, Giuliano A1 - Festi, Daniela A1 - Frezzotti, Massimo A1 - Gabrieli, Jacopo A1 - Galos, Stephan P. A1 - Ginot, Patrick A1 - Heidenwolf, Petra A1 - Jenk, Theo M. A1 - Kehrwald, Natalie A1 - Kenny, Donald A1 - Magand, Olivier A1 - Mair, Volkmar A1 - Mikhalenko, Vladimir A1 - Lin, Ping Nan A1 - Oeggl, Klaus A1 - Piffer, Gianni A1 - Rinaldi, Mirko A1 - Schotterer, Ulrich A1 - Schwikowski, Margit A1 - Seppi, Roberto A1 - Spolaor, Andrea A1 - Stenni, Barbara A1 - Tonidandel, David A1 - Uglietti, Chiara A1 - Zagorodnov, Victor A1 - Zanoner, Thomas A1 - Zennaro, Piero AB - In 2011 four ice cores were extracted from the summit of Alto dell’Ortles (3859 m), the highest glacier of South Tyrol in the Italian Alps. This drilling site is located only 37 km southwest from where the Tyrolean Iceman, ∼5.3 kyrs old, was discovered emerging from the ablating ice field of Tisenjoch (3210 m, near the Italian–Austrian border) in 1991. The excellent preservation of this mummy suggested that the Tyrolean Iceman was continuously embedded in prehistoric ice and that additional ancient ice was likely preserved elsewhere in South Tyrol. Dating of the ice cores from Alto dell’Ortles based on 210Pb, tritium, beta activity and 14C determinations, combined with an empirical model (COPRA), provides evidence for a chronologically ordered ice stratigraphy from the modern glacier surface down to the bottom ice layers with an age of ∼7 kyrs, which confirms the hypothesis. Our results indicate that the drilling site has continuously been glaciated on frozen bedrock since ∼7 kyrs BP. Absence of older ice on the highest glacier of South Tyrol is consistent with the removal of basal ice from bedrock during the Northern Hemisphere Climatic Optimum (6–9 kyrs BP), the warmest interval in the European Alps during the Holocene. Borehole inclinometric measurements of the current glacier flow combined with surface ground penetration radar (GPR) measurements indicate that, due to the sustained atmospheric warming since the 1980s, an acceleration of the glacier Alto dell’Ortles flow has just recently begun. Given the stratigraphic chronological continuity of the Mt. Ortles cores over millennia, it can be argued that this behaviour has been unprecedented at this location since the Northern Hemisphere Climatic Optimum. VL - 10 UR - http://www.the-cryosphere.net/10/2779/2016/tc-10-2779-2016.pdf IS - 6 ER - TY - JOUR T1 - AMS Radiocarbon Dating of Large Za Baobabs (Adansonia za) of Madagascar. JF - PLoS One Y1 - 2016 A1 - Patrut, Adrian A1 - Patrut, Roxana T A1 - Danthu, Pascal A1 - Leong Pock-Tsy, Jean-Michel A1 - Rakosy, Laszlo A1 - Lowy, Daniel A A1 - von Reden, Karl F KW - Adansonia KW - Calibration KW - Ecology KW - Forests KW - Geography KW - Madagascar KW - Mass Spectrometry KW - Radiometric Dating KW - Time Factors KW - Trees KW - Wood AB -

The article reports the radiocarbon investigation of Anzapalivoro, the largest za baobab (Adansonia za) specimen of Madagascar and of another za, namely the Big cistern baobab. Several wood samples collected from the large inner cavity and from the outer part/exterior of the tree were investigated by AMS (accelerator mass spectrometry) radiocarbon dating. For samples collected from the cavity walls, the age values increase with the distance into the wood up to a point of maximum age, after which the values decrease toward the outer part. This anomaly of age sequences indicates that the inner cavity of Anzapalivoro is a false cavity, practically an empty space between several fused stems disposed in a ring-shaped structure. The radiocarbon date of the oldest sample was 780 ± 30 bp, which corresponds to a calibrated age of around 735 yr. Dating results indicate that Anzapalivoro has a closed ring-shaped structure, which consists of 5 fused stems that close a false cavity. The oldest part of the biggest za baobab has a calculated age of 900 years. We also disclose results of the investigation of a second za baobab, the Big cistern baobab, which was hollowed out for water storage. This specimen, which consists of 4 fused stems, was found to be around 260 years old.

VL - 11 IS - 1 ER - TY - JOUR T1 - Anatomy of Labrador Sea Heinrich layers JF - Marine Geology Y1 - 2016 A1 - Reinhard Hesse A1 - Saeed Khodabakhsh KW - Ice-proximal environments AB - Abstract Heinrich layers (H-layers) are distinct, decimetre to centimetre thick layers of ice-rafted debris (IRD) that were deposited in the North Atlantic during the Late and middle Pleistocene. H-layers (H-layers) are characterized by high detrital carbonate and low foraminifera contents. In the Labrador Sea, H-layers reach metre thickness in some proximal core sites near the iceberg source of the Hudson Strait ice stream and show five distinct depositional facies involving sediment lofting and low-density turbidity currents as sediment delivery processes besides ice rafting. Thick massive ice-rafted layers (type I H-layers) occur in the most proximal parts of H-layer 3 and older H-layers. Within 300 km distance from the assumed Hudson Strait ice stream terminus, H-layers somewhat more distal than type I H-layers consist predominantly of stacked thin layers of graded muds containing İRD\} (type İI\} H-layers). The graded muds that are spiked with İRD\} resulted from the deposition of fine-grained lofted sediment that collected dropstones and grains under the iceberg route. At greater distance from the Hudson Strait outlet on the slope and rise south of the strait, H-layers on the levees of tributary canyons to the Northwest Atlantic Mid-Ocean Channel (NAMOC) consist of alternations of thin mud turbidites with intercalated laminae of İRD\} (type İII\} H-layers). On the levees of NAMOC, type İV\} H-layers consist of layers of İRD\} alternating with fewer fine-grained spill-over turbidites, because the spill-over frequency from the deep channel was less than that from the less deep canyons on the slope. Type V is made up of bioturbated hemipelagic muds with coarser İRD\} and occurs in regions between canyons not reached by spill-over turbidity currents and in distal regions of the open ocean or on seamounts. Transport of significant portions of the sediment in H-layers by suspended sediment columns lofted from sand-carrying fresh-water turbidity currents (type II) and by low-density turbidity currents (types İII\} and IV) explains the high percentage of detrital carbonate in the fine (< 63 μm) grain-size fractions (> 80% of the total detrital carbonate of the bulk sediment), which cannot be derived from icebergs alone. It also explains the low magnetic susceptibility and low grey levels on the colour scale compared to H-layers in the North Atlantic east of Greenland. The anomalously great thickness of individual H-layers on the slope and rise off the Hudson Strait as documented in isopach maps reflects the combined effect of the various processes involved in their deposition. Four hypotheses for the origin of H-events are discussed — (i) the binge–purge model, (ii) the subglacial outburst–flow model, (iii) the external forcing model, and (iv) the catastrophic ice-shelf break-up model VL - 380 UR - http://www.sciencedirect.com/science/article/pii/S002532271630113X ER - TY - JOUR T1 - Arctic Deltaic Lake Sediments As Recorders of Fluvial Organic Matter Deposition Y1 - 2016 A1 - Vonk, Jorien E. A1 - Dickens, Angela F. A1 - Giosan, Liviu A1 - Hussain, Zainab A. A1 - Kim, Bokyung A1 - Zipper, Samuel C. A1 - Holmes, Robert M. A1 - Montluçon, Daniel B. A1 - Galy, Valier A1 - Eglinton, Timothy I. AB - Arctic deltas are dynamic and vulnerable regions that play a key role in land-ocean interactions and the global carbon cycle. Delta lakes may provide valuable historical records of the quality and quantity of fluvial fluxes, parameters that are challenging to investigate in these remote regions. Here we study lakes from across the Mackenzie Delta, Arctic Canada, that receive fluvial sediments from the Mackenzie River when spring flood water levels rise above natural levees. We compare downcore lake sediments with suspended sediments collected during the spring flood, using bulk (% organic carbon, % total nitrogen, 13C, 14C) and molecular organic geochemistry (lignin, leaf waxes). High-resolution age models (137Cs, 210Pb) of downcore lake sediment records (n=11) along with lamina counting on high-resolution radiographs show sediment deposition frequencies ranging between annually to every 15 years. Down-core geochemical variability in a representative delta lake sediment core is consistent with historical variability in spring flood hydrology (variability in peak discharge, ice jamming, peak water levels). Comparison with earlier published Mackenzie River depth profiles shows that (i) lake sediments reflect the riverine surface suspended load, and (ii) hydrodynamic sorting patterns related to spring flood characteristics are reflected in the lake sediments. Bulk and molecular geochemistry of suspended particulate matter from the spring flood peak and lake sediments are relatively similar showing a mixture of modern higher-plant derived material, older terrestrial permafrost material, and old rock-derived material. This suggests that deltaic lake sedimentary records hold great promise as recorders of past (century-scale) riverine fluxes and may prove instrumental in shedding light on past behaviour of arctic rivers, as well as how they respond to a changing climate. VL - 4 SN - 2296-6463 UR - http://journal.frontiersin.org/article/10.3389/feart.2016.00077 ER - TY - JOUR T1 - Biospheric and petrogenic organic carbon flux along southeast Alaska JF - Earth and Planetary Science Letters Y1 - 2016 A1 - Xingqian Cui A1 - Thomas S. Bianchi A1 - John M. Jaeger A1 - Richard W. Smith KW - glaciers AB - Abstract Holocene fjords store ca. 11–12% of the total organic carbon (OC) buried in marine sediments with fjords along southeast (SE) Alaska possibly storing half of this \{OC\} (Smith et al., 2015). However, the respective burial of biospheric (OCbio) and petrogenic \{OC\} (OCpetro) remains poorly constrained, particularly across glaciated versus non-glaciated systems. Here, we use surface sediment samples to quantify the sources and burial of sedimentary \{OC\} along \{SE\} Alaska fjord-coastal systems, and conduct a latitudinal comparison across a suite of fjords and river-coastal systems with distinctive \{OC\} sources. Our results for \{SE\} Alaska show that surface sediments in northern fjords (north of Icy Strait) with headwater glaciers are dominated by OCpetro, in contrast to marine and terrestrially-derived fresh \{OC\} in non-glaciated southern fjords. Along the continental shelf of the Gulf of Alaska, terrestrial \{OC\} is exported from rivers. Using end-member mixing models, we determine that glaciated fjords have significantly higher burial rates of \{OCpetro\} ( ∼ 1.1 × 10 3   g \{OC\}   m − 2 yr − 1 ) than non-glaciated fjords and other coastal systems, making \{SE\} Alaska potentially the largest sink of \{OCpetro\} in North America. In contrast, non-glaciated fjords in \{SE\} Alaska are effective in burying marine \{OC\} (OCbio-mari) (13–82 g  \{OC\}   m − 2 yr − 1 ). Globally, \{OC\} in fjord sediments are comprised of a mixture of \{OCpetro\} and fresh OCbio, in contrast to the pre-aged \{OC\} from floodplain river-coastal systems. We find that there may be a general latitudinal trend in the role of fjords in processing OC, where high-latitude temperate glacial fjords (e.g., Yakutat Bay, \{SE\} Alaska) rebury \{OCpetro\} and non-glacial mid-latitude fjords (e.g., Doubtful Sound, Fiordland) sequester \{CO2\} from phytoplankton and/or temperate forests. Overall, we propose that fjords are effective in sequestering \{OCbio\} and re-burying OCpetro. Based on our study, we hypothesize that climate change will have a semi-predictable impact on fjords' \{OC\} cycling in the near future. VL - 452 UR - http://www.sciencedirect.com/science/article/pii/S0012821X16304162 ER - TY - JOUR T1 - Bomb Radiocarbon and the Hawaiian Archipelago: Coral, Otoliths, and SeawaterAbstract JF - Radiocarbon Y1 - 2016 A1 - Andrews, Allen H A1 - Siciliano, Daria A1 - Potts, Donald C A1 - DeMartini, Edward E A1 - Covarrubias, Stephannie AB - Corals of the Hawaiian Archipelago are well situated in the North Pacific Gyre (NPG) to record how bomb-produced radiocarbon has been sequestered and transported by the sea. While this signal can be traced accurately through time in reef-building corals and used to infer oceanographic processes and determine the ages of marine organisms, a comprehensive and validated record has been lacking for the Hawaiian Archipelago. In this study, a coral core from Kure Atoll in the northwestern Hawaiian Islands was used to create a high-resolution bomb 14C record for the years 1939–2002, and was then used with other 14C measurements in fish otoliths and seawater to explore differences and similarities in the bomb 14C signal throughout the Hawaiian Archipelago. The Kure Atoll sample series produced a well-defined bomb 14C curve that, with some exceptions, was similar to other coral 14C records from the Hawaiian Archipelago. Subtle differences in the coral 14C records across the region may be explained by the large-scale ocean circulation patterns and decadal cycles of the NPG. The most rapid increase of 14C, in the 1950s and 1960s, showed similar timing across the Hawaiian Archipelago and provides a robust basis for use of bomb 14C dating to obtain high-precision age determinations of marine organisms. Reference otoliths of juvenile fish demonstrated the use of the post-peak 14C decline period as a viable reference in the age validation of younger and more recently collected fishes, and effectively extended the utility of bomb 14C dating to the latest 30 yr. VL - 58 UR - dx.doi.org/10.1017/RDC.2016.32 IS - 03 ER - TY - JOUR T1 - Bomb-produced radiocarbon in the western tropical Pacific Ocean: Guam coral reveals operation-specific signals from the Pacific Proving Grounds JF - JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS Y1 - 2016 A1 - Andrews, A.H. A1 - Asami, Ryuji A1 - Iryu, Yasufumi A1 - Kobayashi, Donald R. A1 - Camacho, Frank AB - High-resolution radiocarbon (C-14) analyses on a coral core extracted from Guam, a western tropical Pacific island, revealed a series of early bomb-produced C-14 spikes. The typical marine bomb C-14 signal-phase lagged and attenuated relative to atmospheric records-is present in the coral and is consistent with other regional coral records. However, C-14 levels well above what can be attributed to air-sea diffusion alone punctuate this pattern. This anomaly was observed in other Indo-Pacific coral records, but the Guam record is unmatched in magnitude and temporal resolution. The Guam coral Delta C-14 record provided three spikes in 1954-1955, 1956-1957, and 1958-1959 that are superimposed on a normal C-14 record. Relative to mean prebomb levels, the first peak rises an incredible similar to 700 parts per thousand and remained elevated for similar to 1.2 years. A follow up assay with finer resolution increased the peak by similar to 300 parts per thousand. Subsequent spikes were less intense with a rise of similar to 35 and similar to 70 parts per thousand. Each can be linked to thermonuclear testing in the Pacific Proving Grounds at Bikini and Enewetak atolls in Operations Castle (1954), Redwing (1956), and Hardtack I (1958). These C-14 signals can be explained by vaporization of coral reef material in the nuclear fireball, coupled with neutron activation of atmospheric nitrogen (C-14 production), and subsequent absorption of (CO2)-C-14 to form particulate carbonates of close-in fallout. The lag time in reaching Guam and other coral records abroad was tied to ocean surface currents and modeling provided validation of C-14 arrival observations. VL - 121 ER - TY - JOUR T1 - Carbon isotopic (C-14 and C-13) characterization of fossil-fuel derived dissolved organic carbon in wet precipitation in Shandong Province, China JF - JOURNAL OF ATMOSPHERIC CHEMISTRY Y1 - 2016 A1 - Wang, Xuchen A1 - Ge, Tiantian A1 - Xu, Caili A1 - Xue, Yuejun A1 - Luo, Chunle KW - Atmospheric pollution KW - Fossil fuelemission KW - organic carbon KW - radiocarbon KW - Wet precipitation AB - We present results from a 1-year study of radiocarbon and stable carbon isotope measurement of dissolved organic carbon (DOC) of wet precipitation samples collected in the Shandong province of China. A total of 32 rainfall and 4 snow samples were collected from two coastal cities (Qingdao and Yantai) and one inland site (Taian) during 2014. Concentrations of DOC in the rainwater and snow samples varied widely from 28 to 616 mu M. In general, rainwater originating from marine sources had relatively low DOC concentrations compared with continentally generated precipitation. Values of delta C-13-DOC and Delta C-14-DOC in the snow and rainwater ranged from -19.0 to -29.4 % and -23 to -494 %, with corresponding radiocarbon ages of 125 to 5410 years before present. The dominant DOC in the wet precipitation had a relatively old C-14 age (average 2841 years) and a depleted C-13 value (average -24.4 Years), indicating the mixing of contemporary organic carbon with C-14-depleted fossil fuel-derived soluble organic carbon in the atmosphere. Using a dual isotopic two-endmember model, we calculate that 7 % to 52 % of DOC in the snow and rainfall originated from fossil fuels. It is estimated that the flux of DOC in continental rainfall of China is 23 x 10(12) g C yr(-1) and of this, 7.1 x 10(12) g C yr(-1) could be fossil-fuel OC. On a global scale, the DOC flux in rainfall is estimated to be 357 Tg C yr(-1), and 110 Tg C yr(-1) could be fossil fuel-derived. Our study demonstrates that wet precipitation is an important removal process for old fossil fuel carbon from the atmosphere. This removal mechanism could play an important role in the carbon cycle, especially for the anthropogenically derived fraction, and it should be taken into consideration in global carbon cycle models. VL - 73 ER - TY - JOUR T1 - Clumped isotope composition of cold-water corals: A role for vital effects? JF - Geochimica et Cosmochimica Acta Y1 - 2016 A1 - Peter T. Spooner A1 - Weifu Guo A1 - Laura F. Robinson A1 - Nivedita Thiagarajan A1 - Katharine R. Hendry A1 - Brad E. Rosenheim A1 - Melanie J. Leng AB - Abstract The carbonate clumped isotope thermometer is a promising tool for determining past ocean temperatures. It is based on the temperature dependence of rare isotopes ‘clumping’ into the same carbonate ion group in the carbonate mineral lattice. The extent of this clumping effect is independent of the isotope composition of the water from which carbonate precipitates, providing unique advantages over many other paleotemperature proxies. Existing calibrations of this thermometer in cold-water and warm-water corals suggest clumped isotope ‘vital effects’ are negligible in cold-water corals but may be significant in warm-water corals. Here, we test the calibration of the carbonate clumped isotope thermometer in cold-water corals with a recently collected and well characterised sample set spanning a range of coral genera (Balanophyllia, Caryophyllia, Dasmosmilia, Desmophyllum, Enallopsammia and Javania). The clumped isotope compositions (Δ47) of these corals exhibit systematic dependences on their growth temperatures, confirming the basis of the carbonate clumped isotope thermometer. However, some cold-water coral genera show Δ47 values that are higher than the expected equilibrium values by up to 0.05‰ (equivalent to underestimating temperature by ∼9 °C) similar to previous findings for some warm-water corals. This finding suggests that the vital effects affecting corals Δ47 are common to both warm- and cold-water corals. By comparison with models of the coral calcification process we suggest that the clumped isotope offsets in these genera are related to the kinetic isotope effects associated with \{CO2\} hydration/hydroxylation reactions in the corals’ calcifying fluid. Our findings complicate the use of the carbonate clumped isotope thermometer in corals, but suggest that species- or genus-specific calibrations could be useful for the future application of this paleotemperature proxy. VL - 179 UR - http://www.sciencedirect.com/science/article/pii/S0016703716300072 ER - TY - JOUR T1 - Comparison of eastern tropical Pacific TEX 86 and Globigerinoides ruber Mg/Ca derived sea surface temperatures: Insights from the Holocene and Last Glacial Maximum JF - Earth and Planetary Science Letters Y1 - 2016 A1 - Hertzberg, Jennifer E. A1 - Schmidt, Matthew W. A1 - Bianchi, Thomas S. A1 - Smith, Richard W. A1 - Shields, Michael R. A1 - Marcantonio, Franco KW - Foraminifera KW - Holocene KW - LGM; Pacific Ocean KW - Mg/Ca KW - TEX86TEX86 AB - The use of the TEX86TEX86 temperature proxy has thus far come to differing results as to whether TEX86TEX86 temperatures are representative of surface or subsurface conditions. In addition, although TEX86TEX86 temperatures might reflect sea surface temperatures based on core-top (Holocene) values, this relationship might not hold further back in time. Here, we investigate the TEX86TEX86 temperature proxy by comparing TEX86TEX86 temperatures to Mg/Ca temperatures of multiple species of planktonic foraminifera for two sites in the eastern tropical Pacific (on the Cocos and Carnegie Ridges) across the Holocene and Last Glacial Maximum. Core-top and Holocene View the MathML sourceTEX86H temperatures at both study regions agree well, within error, with the Mg/Ca temperatures of Globigerinoides ruber , a surface dwelling planktonic foraminifera. However, during the Last Glacial Maximum, View the MathML sourceTEX86H temperatures are more representative of upper thermocline temperatures, and are offset from G. ruber Mg/Ca temperatures by 5.8 °C and 2.9 °C on the Cocos Ridge and Carnegie Ridge, respectively. This offset between proxies cannot be reconciled by using different TEX86TEX86 temperature calibrations, and instead, we suggest that the offset is due to a deeper export depth of GDGTs at the LGM. We also compare the degree of glacial cooling at both sites based on both temperature proxies, and find that View the MathML sourceTEX86H temperatures greatly overestimate glacial cooling, especially on the Cocos Ridge. This study has important implications for applying the TEX86TEX86 paleothermometer in the eastern tropical Pacific. VL - 434 UR - http://linkinghub.elsevier.com/retrieve/pii/S0012821X15007542http://api.elsevier.com/content/article/PII:S0012821X15007542?httpAccept=text/xmlhttp://api.elsevier.com/content/article/PII:S0012821X15007542?httpAccept=text/plain ER - TY - JOUR T1 - Complex coastal change in response to autogenic basin infilling: An example from a sub-tropical Holocene strandplain JF - Sedimentology Y1 - 2016 A1 - Hein, Christopher J. A1 - FitzGerald, Duncan M. A1 - de Souza, Luis H. P. A1 - Georgiou, Ioannis Y. A1 - Buynevich, Ilya V. A1 - Klein, Antonio H. da F. A1 - de Menezes, ão Thadeu A1 - Cleary, William J. A1 - Scolaro, Thelma L. ED - Mohrig, David AB - Thick bay-fill sequences that often culminate in strandplain development serve as important sedimentary archives of land–ocean interaction, although distinguishing between internal and external forcings is an ongoing challenge. This study employs sediment cores, ground-penetrating radar surveys, radiocarbon dates, palaeogeographic reconstructions and hydrodynamic modelling to explore the role of autogenic processes – notably a reduction in wave energy in response to coastal embayment infilling – in coastal evolution and shoreline morphodynamics. Following a regional 2 to 4 m highstand at ca 5·8 ka, the 75 km2 Tijucas Strandplain in southern Brazil built from fluvial sediments deposited into a semi-enclosed bay. Holocene regressive deposits are underlain by fluvial sands and a Pleistocene transgressive–regressive sequence, and backed by a highstand barrier-island. The strandplain is immediately underlain by 5 to 16 m of seaward-thickening, fluvially derived, Holocene-age, basin-fill mud. Several trends are observed from the landward (oldest) to the seaward (youngest) sections of the strandplain: (i) the upper shoreface and foreshore become finer and thinner and shift from sand-dominated to mud-dominated; (ii) beachface slopes decrease from >11° to ca 7°; and (iii) progradation rates increase from 0·4 to 1·8 m yr−1. Hydrodynamic modelling demonstrates a correlation between progressive shoaling of Tijucas Bay driven by sea-level fall and sediment infilling and a decrease in onshore wave-energy transport from 18 to 4 kW m−1. The combination of allogenic (sediment supply, falling relative sea-level and geology) and autogenic (decrease in wave energy due to bay shoaling) processes drove the development of a regressive system with characteristics that are rare, if not unique, in the Holocene and rock records. These findings demonstrate the complexities in architecture styles of highstand and regressive systems tracts. Furthermore, this article highlights the diverse internal and external processes and feedbacks responsible for the development of these intricate marginal marine sedimentary systems. VL - 63 UR - http://doi.wiley.com/10.1111/sed.12265 IS - 6 ER - TY - JOUR T1 - Conduits, timing and processes of sediment delivery across a high-relief continental margin: Continental shelf to basin in Late Quaternary, Gulf of Papua JF - Marine and Petroleum Geology Y1 - 2016 A1 - Erlangga Septama A1 - Samuel J. Bentley A1 - André W. Droxler KW - Deep-sea AB - Abstract The Gulf of Papua (GoP), between Australia and Papua New Guinea, is the receiving basin for multiple substantial rivers draining southern Papua New Guinea with collective sediment discharge >> 220 million metric tons (Mt) per year, comparable to a continental-scale river, but draining a combined catchment area of only ∼160,000 km2. This study of the deepest marginal basins in the Gulf of Papua was undertaken to build a regional late Quaternary lithofacies and stratigraphic framework to better understand processes, timing, and conduits of sediment delivery from terrestrial and shelf settings to deep marginal basins, using the GoP as a natural laboratory. Methods include observations of sediment-core stratigraphy and physical properties, accelerometer mass spectrometry (AMS) C-14 dates, core x-radiographs and thin sections. Six lithofacies across the deep water Gulf of Papua (GoP) are identified based on core visual and textural observation. Chronological constraints permit an assessment of changes in sediment supply and depositional environments across time and space, from marine isotope stage (MIS) -3 to -1, or in the last 40 cal ka. The sediment delivery to the deep water GoP is dominated by two mechanisms, gravity-driven flows down slopes and into deep sea basin primarily during lowstands in the western portions of the study area, and hemipelagic sediment accumulation during transgression and highstand. Although the sediment flux appears to be overall dominated by sediment-gravity flows, hemipelagic sediment delivery is widespread during periods of sea level highstand. In the eastern portions of the study area, off-shelf sediment delivery continued into the Holocene in sufficient local volumes to produce turbidity currents. This late, localized sediment delivery appears to have been facilitated by oceanographic processes that allowed seaward sediment transport after flooding of the shelf. A simple sediment budget comparing basinal sediment accumulation to modern estimated river-sediment discharge indicates that peak sediment accumulation in proximal basins occurred during MIS-2; and declined thereafter, generally shifting to upper slope locations, except for the eastern margin of Moresby Trough. There, turbidite deposition continued until 7.4 cal ka, well after drowning of the shelf edge. This continued Holocene deep-sea sediment delivery is likely explained by the local narrow shelf width, and the presence of oceanographic processes capable of transporting sediments from shore to shelf edge. VL - 72 UR - http://www.sciencedirect.com/science/article/pii/S0264817216300320 ER - TY - JOUR T1 - Controls on the sources and cycling of dissolved inorganic carbon in the Changjiang and Huanghe River estuaries, China: C-14 and C-13 studies JF - LIMNOLOGY AND OCEANOGRAPHY Y1 - 2016 A1 - Wang, Xuchen A1 - Luo, Chunle A1 - Ge, Tiantian A1 - Xu, Caili A1 - Xue, Yuejun AB - The Changjiang (Yangtze River) and Huanghe (Yellow River) are the two largest rivers in China, and they transport large amounts of terrestrial carbon to the coastal waters of the East China Sea and the Bohai Sea. The sources and cycling of riverine carbon in these two large river estuaries, however, have not been well studied. In this article, we present the results of dual isotope (Delta C-14 and delta C-13) measurements of dissolved inorganic carbon (DIC) collected in the low reaches of the Changjiang and Huanghe and their estuaries during two cruises in 2014. Our results indicate that both the Changjiang and Huanghe carry very high concentrations of DIC ranging from 1384 mu mol kg(-1) to 1732 mu mol kg(-1) and 2711 mu mol kg(-1) to 4120 mu mol kg(-1), respectively, and DIC levels varied with flow rates during high and low discharge periods. The cycling of DIC exhibited conservative behavior in both the Changjiang and Huanghe estuaries, suggesting DIC levels were controlled mainly by physical mixing processes. Delta C-14-DIC values indicate that the Changjiang and Huanghe transport aged DIC (1060-1380 yr old). Both Delta C-14-DIC and delta C-13-DIC values also showed conservative mixing in the two estuaries. Using a dual carbon isotopic model, we calculated that atmospheric CO2 consumed mainly by silicate weathering was a major source, contributing 65.2 +/- 9.0% and 73.4 +/- 3.0% of DIC in the Changjiang and Huanghe, and 96.9-97.7% (by air-sea exchange) of DIC in the coastal waters of the East China Sea (ECS) and Bohai Sea, respectively. Our results indicate that carbonate dissolution was an important (12.3-17.4%) but not major process controlling the high DIC levels in both rivers, as suggested previously. Compared with the large Amazon River, respiration of riverine organic matter (OM) played a less important role, contributing only 15.4-17.2% of DIC in the two Asian rivers. Flux calculations indicate that the Changjiang and Huanghe discharged 1.46 x 10(13) g and 6.28 x 10(11) g DIC into the ECS and Bohai Sea in 2014, which were 9 and 17 times higher than the DOC fluxes in the two rivers. These large fluxes of riverine DIC, especially of aged DIC, could have significant impacts on primary production and carbon cycling in the ECS and Bohai Sea. VL - 61 ER - TY - JOUR T1 - Controls on the stable isotope compositions of travertine from hyperalkaline springs in Oman: Insights from clumped isotope measurements JF - Geochimica et Cosmochimica Acta Y1 - 2016 A1 - E.S. Falk A1 - W. Guo A1 - A.N. Paukert A1 - J.M. Matter A1 - E.M. Mervine A1 - P.B. Kelemen KW - Carbonate AB - Abstract Carbonate formation at hyperalkaline springs is typical of serpentinization in peridotite massifs worldwide. These travertines have long been known to exhibit large variations in their carbon and oxygen isotope compositions, extending from apparent equilibrium values to highly depleted values. However, the exact causes of these variations are not well constrained. We analyzed a suite of well-characterized fresh carbonate precipitates and travertines associated with hyperalkaline springs in the peridotite section of the Samail ophiolite, Sultanate of Oman, and found their clumped isotope compositions vary systematically with formation environments. Based on these findings, we identified four main processes controlling the stable isotope compositions of these carbonates. These include hydroxylation of CO2, partial isotope equilibration of dissolved inorganic carbon, mixing between isotopically distinct carbonate end-members, and post-depositional recrystallization. Most notably, in fresh crystalline films on the surface of hyperalkaline springs and in some fresh carbonate precipitates from the bottom of hyperalkaline pools, we observed large enrichments in Δ47 (up to ∼0.2‰ above expected equilibrium values) which accompany depletions in δ18O and δ13C, yielding about 0.01‰ increase in Δ47 and 1.1‰ decrease in δ13C for every 1‰ decrease in δ18O, relative to expected equilibrium values. This disequilibrium trend, also reflected in preserved travertines ranging in age from modern to ∼40,000 years old, is interpreted to arise mainly from the isotope effects associated with the hydroxylation of \{CO2\} in high-pH fluids and agrees with our first-order theoretical estimation. In addition, in some fresh carbonate precipitates from the bottom of hyperalkaline pools and in subsamples of one preserved travertine terrace, we observed additional enrichments in Δ47 at intermediate δ13C and δ18O, consistent with mixing between isotopically distinct carbonate end-members. Our results suggest that carbonate clumped isotope analysis can be a valuable tool for identifying and distinguishing processes not readily apparent from the carbonate bulk stable isotope compositions alone, e.g., kinetic effects or mixing of different carbonate end-members, which can significantly alter both the apparent formation temperatures and apparent radiocarbon ages. The isotope trends observed in these travertine samples could be applied more broadly to identify extinct hyperalkaline springs in terrestrial and extraterrestrial environments, to better constrain the formation conditions and post-depositional alteration of hyperalkaline spring carbonates, and to extract potential paleoclimate information. VL - 192 UR - http://www.sciencedirect.com/science/article/pii/S0016703716303568 ER - TY - JOUR T1 - Controls on the stratigraphic framework and paleoenvironmental change within a Holocene estuarine system: Pamlico Sound, North Carolina, USA JF - Marine Geology Y1 - 2016 A1 - Nicholas Zaremba A1 - David J. Mallinson A1 - Eduardo Leorri A1 - Stephen Culver A1 - Stanley Riggs A1 - Ryan Mulligan A1 - Eric Horsman A1 - Siddhartha Mitra KW - Coastal geology AB - Abstract This study examines the Holocene stratigraphic record and paleoenvironmental evolution of a large estuarine system, at high temporal and spatial resolution, in the context of changing climate, sea level, and hydrodynamics. New data are used to examine two time periods of increased marine influence within Pamlico Sound in northeastern North Carolina interpreted to be the result of extensive barrier island segmentation synchronous with periods of rapid climate change during the late Holocene. The study reveals the controls on the stratigraphic development and the highly dynamic character of the coastal system in response to climate, and sea-level change as it interacts with paleotopography. These findings can be used to inform projections of future environmental changes. Estuarine waters occupied paleovalleys in the Pamlico Sound region as early as ca. 7500 cal \{BP\} and Pleistocene interfluves separated the paleovalleys from the Atlantic Ocean until ca. 5500 cal BP, when they were flooded by rising sealevel forming the broad, shallow Pamlico Sound. Initial barrier islands and shoals likely formed sometime between 5500 and 5000 cal BP, providing the geomorphic setting for continued estuarine conditions behind the barriers. At ca. 4000 cal BP, an increase in marine influence and sand content is detected in multiple cores, and is correlated to seismic data within the Pamlico Sound basin. This change is interpreted to be the result of increased segmentation of barrier islands (thus a greater number of inlets, or wider inlets), which is consistent with a rapid transgression seen in other areas of the U.S. east coast. The segmentation may have been partially facilitated by a rapid increase in lagoonal area and tidal prism by overtopping of interfluves. Greater barrier island continuity is evident from 3500 to 1200 cal BP, as indicated by muddy deposits with low brackish estuarine foraminiferal assemblages. At ca. 1200 cal BP, seismic, sedimentological and micropaleontological data suggest an increase in wave and current energy and marine influence throughout southeastern Pamlico Sound. These changes are interpreted to represent extensive segmentation of the barrier islands during the Medieval Climate Anomaly (MCA). Since ca. 500 cal BP, the Pamlico Sound system has returned to a more restricted state, as inlets have closed. Currently only three major inlets segment the Outer Banks, the barrier island system fronting Pamlico Sound, but warming climate and increasing rates of sea-level rise suggest that another episode of barrier island segmentation began about a half century ago and appears that it may extend into the near future. VL - 379 UR - http://www.sciencedirect.com/science/article/pii/S0025322716300664 ER - TY - BOOK T1 - Coral Reefs of the WorldCoral Reefs of the Eastern Tropical PacificHolocene Reef Development in the Eastern Tropical Pacific Y1 - 2016 A1 - Toth, Lauren T. A1 - Macintyre, Ian G. A1 - Aronson, Richard B. ED - Glynn, Peter W. ED - Manzello, Derek P. ED - Enochs, Ian C. KW - El Niño KW - Latin American reefs KW - paleoecology KW - Reef accretion KW - Southern Oscillation KW - Upwelling AB - Contrary to early assessments, the eastern tropical Pacific (ETP) is not devoid of well-developed reefs. Significant accumulations of Holocene reef framework are present throughout the region, although they tend to be poorly consolidated, lack the submarine cementation common on most reefs elsewhere in the world, and are subject to considerable bioerosion. These reef frameworks began accreting as early as 7000 years ago. The thickest accumulations of Pocillopora frameworks occur in coastal areas of Mexico, Costa Rica, Panama, and Colombia, but reefs composed of massive corals—species of Porites, Pavona, or Gardineroseris—are present throughout the region. Reef development in the ETP is limited by a variety of characteristics of the physical environment. Because of high turbidity in most areas, reef development is generally restricted to less than ~10 m depth. The spatial extent of reefs in the ETP is also limited from the combined influences of wave action and upwelling. Most reefs in the ETP are only a few hectares in size and the best-developed reefs generally occur in areas sheltered from strong oceanic influence. Upwelling also influences long-term trends in reef development in the region. There does not appear to be a significant impact of upwelling on the millennial-scale growth rates of Panamanian reefs; however, reefs in upwelling environments typically have thinner frameworks than nearby reefs in non-upwelling environments. Furthermore, upwelling may have contributed to a historic shutdown of reef development in Costa Rica and Panama. Although both ecological and oceanographic disturbances have had some impact on the long-term development of reefs in the ETP, the most important control on reef development in this region throughout the Holocene has most likely been the El Niño–Southern Oscillation (ENSO). ENSO activity—especially that of the 1982–83 and 1997–98 El Niño events—has shaped the landscape of coral reefs across the ETP both in recent decades and in the past. Reefs in Pacific Panama and Costa Rica experienced a 2500-year hiatus in vertical growth beginning ~4100 years ago as a result of enhanced ENSO activity. Although the degree of framework accumulation and rate of reef accretion in some parts of the ETP are more similar to that of the western Atlantic than previously thought, the region still remains a marginal environment for reef development. Given the dominant role that climatic variability has played in controlling reef development in the past, the future of reefs in the ETP under accelerating climate change remains uncertain. PB - Springer Netherlands CY - Dordrecht VL - 8 SN - 978-94-017-7498-7 UR - https://link.springer.com/chapter/10.1007%2F978-94-017-7499-4_6 ER - TY - JOUR T1 - Detrital cave sediments record Late Quaternary hydrologic and climatic variability in northwestern Florida, USA JF - Sedimentary Geology Y1 - 2016 A1 - Winkler, Tyler S. A1 - van Hengstum, Peter J. A1 - Horgan, Meghan C. A1 - Donnelly, Jeffrey P. A1 - Reibenspies, Joseph H. KW - Apalachicola KW - florida KW - Karst KW - Phreatic KW - Underwater cave AB - Detrital sediment in Florida's (USA) submerged cave systems may preserve records of regional climate and hydrologic variability. However, the basic sedimentology, mineralogy, stratigraphic variability, and emplacement history of the successions in Florida's submerged caves remains poorly understood. Here we present stratigraphic, mineralogical, and elemental data on sediment cores from two phreatic cave systems in northwestern Florida (USA), on the Dougherty Karst Plain: Hole in the Wall Cave (HITW) and Twin Cave. Water flowing through these caves is subsurface flow in the Apalachicola River drainage basin, and the caves are located just downstream from Jackson Blue (1st magnitude spring, > 2.8 m3 s− 1 discharge). Sedimentation in these caves is dominated by three primary sedimentary styles: (i) ferromanganese deposits dominate the basal recovered stratigraphy, which pass upsection into (ii) poorly sorted carbonate sediment, and finally into (iii) fine-grained organic matter (gyttja) deposits. Resolving the emplacement history of the lower stratigraphic units was hampered by a lack of suitable material for radiocarbon dating, but the upper organic-rich deposits have a punctuated depositional history beginning in the earliest Holocene. For example, gyttja primarily accumulated in HITW and Twin Caves from ~ 5500 to 3500 cal yr. BP, which coincides with regional evidence for water-table rise of the Upper Floridian Aquifer associated with relative sea-level rise in the Gulf of Mexico, and evidence for invigorated drainage through the Apalachicola River drainage basin. Gyttja sediments were also deposited in one of the caves during the Bølling/Allerød climate oscillation. Biologically, these results indicate that some Floridian aquatic cave (stygobitic) ecosystems presently receive minimal organic matter supply in comparison to prehistoric intervals. The pre-Holocene poorly sorted carbonate sediment contains abundant invertebrate fossils, and likely documents a period of enhanced limestone dissolution and cave formation (speleogenesis) during lower paleo water levels. Further work is still required to (a) determine whether precipitation of the ferromanganese deposits is inorganically or biologically mediated, (b) temporally constrain the emplacement history of the primary sedimentary styles, and (c) determine the full geographic extent of these sedimentary signals. However, these preliminary observations suggest that sedimentation in the inland underwater caves of northwestern Florida is related to Quaternary-scale hydrographic variability in the Apalachicola River drainage basin in response to broader ocean and atmospheric forcing. VL - 335 UR - http://linkinghub.elsevier.com/retrieve/pii/S0037073816000312http://api.elsevier.com/content/article/PII:S0037073816000312?httpAccept=text/xmlhttp://api.elsevier.com/content/article/PII:S0037073816000312?httpAccept=text/plain ER - TY - JOUR T1 - Differences in coastal subsidence in southern Oregon (USA) during at least six prehistoric megathrust earthquakes JF - Quaternary Science Reviews Y1 - 2016 A1 - Milker, Yvonne A1 - Nelson, Alan R. A1 - Horton, Benjamin P. A1 - Engelhart, Simon E. A1 - Bradley, Lee-Ann A1 - Witter, Robert C. KW - Cascadia subduction zone KW - Coseismic subsidence KW - Megathrust earthquakes KW - Paleoseismology KW - Salt-marsh foraminifera KW - Sea-level change KW - Transfer functions AB - Stratigraphic, sedimentologic (including CT 3D X-ray tomography scans), foraminiferal, and radiocarbon analyses show that at least six of seven abrupt peat-to-mud contacts in cores from a tidal marsh at Talbot Creek (South Slough, Coos Bay), record sudden subsidence (relative sea-level rise) during great megathrust earthquakes at the Cascadia subduction zone. Data for one contact are insufficient to infer whether or not it records a great earthquake—it may also have formed through local, non-seismic, hydrographic processes. To estimate the amount of subsidence marked by each contact, we expanded a previous regional modern foraminiferal dataset to 174 samples from six Oregon estuaries. Using a transfer function derived from the new dataset, estimates of coseismic subsidence across the six earthquake contacts vary from 0.31 m to 0.75 m. Comparison of subsidence estimates for three contacts in adjacent cores shows within-site differences of ≤0.10 m, about half the ±0.22 m error, although some estimates may be minimums due to uncertain ecological preferences for Balticammina pseudomacrescens in brackish environments and almost monospecific assemblages of Miliammina fusca on tidal flats. We also account for the influence of taphonomic processes, such as infiltration of mud with mixed foraminiferal assemblages into peat, on subsidence estimates. Comparisons of our subsidence estimates with values for correlative contacts at other Oregon sites suggest that some of our estimates are minimums and that Cascadia's megathrust earthquake ruptures have been heterogeneous over the past 3500 years. VL - 142 UR - https://doi.org/10.1016/j.quascirev.2016.04.017 ER - TY - JOUR T1 - DISSOLVED INORGANIC RADIOCARBON IN THE NORTHWEST PACIFIC CONTINENTAL MARGIN JF - RADIOCARBON Y1 - 2016 A1 - Ge, Tiantian A1 - Wang, Xuchen A1 - Zhang, Jing A1 - Luo, Chunle A1 - Xue, Yuejun KW - continental margin KW - dissolved inorganic carbon KW - East China Sea KW - radiocarbon KW - stable carbon isotope AB - This article presents a modified method for extraction of dissolved inorganic carbon (DIC) from seawater for radiocarbon measurement by accelerator mass spectrometry (AMS). Standard tests indicate that the extraction efficiencies of DIC are >96%, and the respective precisions of. Delta C-14-DIC and delta C-13-DIC analyses are 6% and 0.1% or better. Using the method, we report. Delta C-14-DIC profiles collected from the shelf and slope in the East China Sea (ECS) of the northwest Pacific Ocean. Both the DIC concentration and. Delta C-14-DIC in the shelf and slope regions seem primarily affected by the Kuroshio Current. It is estimated that 54-65% of the bottom water in the shelf region could be from the intrusion of Kuroshio intermediate water, which carries a high concentration and low. Delta C-14 values of DIC, and which influenced the DIC and its Delta C-14 signature on the shelf. Compared with the. Delta C-14-DIC profiles at other sites in the northwest Pacific reported previously, it appears that the. Delta C-14-DIC distributions are mainly controlled by the major oceanic currents in the region, and large variations in. Delta C-14-DIC occurred mostly in the upper 800m of the water column. The similarity of. Delta C-14-DIC at depth suggests that the deep-water circulation patterns have been relatively stable in the northwest Pacific Ocean in the last 20 yr. VL - 58 ER - TY - JOUR T1 - Distribution, provenance and early diagenesis of major and trace metals in sediment cores from the Mandovi estuary, western India JF - Estuarine, Coastal and Shelf Science Y1 - 2016 A1 - A. Prajith A1 - V. Purnachandra Rao A1 - P. Chakraborty KW - Western India AB - Abstract Major elements and trace metals were analyzed in four sediment cores recovered along a transect in the Mandovi estuary for their distribution, provenance and early diagenesis. The sediments were clayey silts in cores from the upper/lower estuary and sand-dominated in cores from the middle estuary/bay. Organic carbon (OC) content varied from 0.5 to 4%, with higher values in fine-grained sediments. The mean Fe and Mn contents of sediments from the upper/middle estuary were 3–5 times and 8–13 times, respectively higher than the reference sediment (RS) from the same estuary. The mean Fe and Mn contents of sediments from the lower estuary/bay were close to the RS. Strong inter-metal correlation among Ti, V, Cr and Zr in all the cores indicated their contribution from a common source, probably the laterites from hinterland. Trace metals were more enriched in fine-grained sediments than in sand-dominated sediments. Early diagenetic control on the redistribution of metal is evident in core sediments from the middle estuary to Bay. The distribution of Mo, U and Pb followed that of Fe and Mn in the upper estuary and \{OC\} in the lower estuary/bay. Our results indicated strong anthropogenic contribution of metals from ore deposits in the upper/middle estuary. The Mn and Cr contents of sediment in the upper/middle estuary and Fe in the middle estuary were highly enriched suggestive of ‘significant pollution signal’. More trace metals from the middle estuary were moderately enriched. Speciation studies showed Mn and Pb occurred abundantly in non-residual phases. High Mn content and its high percentage in exchangeable and reductive phases indicate that it was susceptible to be mobilized. However, Fe, Cu and Ni occurred abundantly in residual phases and less percentage of them were expected to be bio-available. VL - 170 UR - http://www.sciencedirect.com/science/article/pii/S0272771416300142 ER - TY - JOUR T1 - Distributions and accumulation rates of polycyclic aromatic hydrocarbons in the northern Gulf of Mexico sediments JF - Environmental Pollution Y1 - 2016 A1 - Puspa L. Adhikari A1 - Kanchan Maiti A1 - Edward B. Overton A1 - Brad E. Rosenheim A1 - Brian D. Marx KW - Radiocarbon (Δ14C) AB - Abstract Sediment samples collected from shelf, slope and interior basin of the northern Gulf of Mexico during 2011–2013, 1–3 years after the Deepwater Horizon (DWH) oil spill, were utilized to characterize \{PAH\} pollution history, in this region. Results indicate that the concentrations of surface ΣPAH43 and their accumulation rates vary between 44 and 160 ng g−1 and 6–55 ng cm−2 y−1, respectively. ΣPAH43 concentration profiles, accumulation rates and Δ14C values are significantly altered only for the sediments in the immediate vicinity of the \{DWH\} wellhead. This shows that the impact of \{DWH\} oil input on deep-sea sediments was generally limited to the area close to the spill site. Further, the \{PAHs\} source diagnostic analyses suggest a noticeable change in \{PAHs\} composition from higher to lower molecular weight dominance which reflects a change in source of \{PAHs\} in the past three years, back to the background composition. Results indicate low to moderate levels of \{PAH\} pollution in this region at present, which are unlikely to cause adverse effects on benthic communities. VL - 212 UR - http://www.sciencedirect.com/science/article/pii/S0269749116300641 ER - TY - JOUR T1 - Dual carbon isotope characterization of total organic carbon in wintertime carbonaceous aerosols from northern India JF - Journal of Geophysical Research: Atmospheres Y1 - 2016 A1 - Bikkina, Srinivas A1 - Andersson, August A1 - Sarin, M. M. A1 - Sheesley, R. J. A1 - Kirillova, E. A1 - Rengarajan, R. A1 - Sudheer, A. K. A1 - Ram, K. A1 - Gustafsson, Örjan AB - Large-scale emissions of carbonaceous aerosols (CA) from South Asia impact both regional climate and air quality, yet their sources are not well constrained. Here we use source-diagnostic stable and radiocarbon isotopes (δ13C and Δ14C) to characterize CA sources at a semiurban site (Hisar: 29.2°N, 75.2°E) in the NW Indo-Gangetic Plain (IGP) and a remote high-altitude location in the Himalayan foothills (Manora Peak: 29.4°N, 79.5°E, 1950 m above sea level) in northern India during winter. The Δ14C of total aerosol organic carbon (TOC) varied from −178‰ to −63‰ at Hisar and from −198‰ to −1‰ at Manora Peak. The absence of significant differences in the 14C-based fraction biomass of TOC between Hisar (0.81 ± 0.03) and Manora Peak (0.82 ± 0.07) reveals that biomass burning/biogenic emissions (BBEs) are the dominant sources of CA at both sites. Combining this information with δ13C, other chemical tracers (K+/OC and SO42−/EC) and air mass back trajectory analyses indicate similar source regions in the IGP (e.g., Punjab and Haryana). These results highlight that CA from BBEs in the IGP are not only confined to the atmospheric boundary layer but also extend to higher elevations of the troposphere, where the synoptic-scale circulations could substantially influence their abundances both to the Himalayas and over the downwind oceanic regions such as the Indian Ocean. Given the vast emissions of CA from postharvest crop residue combustion practices in the IGP during early Northeast Monsoon, this information is important for both improved process and model understanding of climate and health effects, as well as in guiding policy decision aiming at reducing emissions. VL - 121 UR - http://doi.wiley.com/10.1002/2016JD024880https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2F2016JD024880 IS - 9 ER - TY - JOUR T1 - Effects of seafloor diagenesis on planktic foraminiferal radiocarbon ages JF - GEOLOGY Y1 - 2016 A1 - Wycech, Jody A1 - Kelly, D. Clay A1 - Marcott, Shaun AB - Radiocarbon (C-14) ages obtained from planktic foraminiferal calcite are a mainstay for reconstructing ocean-climate change and carbon cycle dynamics of the past 30 k.y., yet the effects of diagenesis on this vital chronometer are poorly constrained. Here, we address this shortcoming by comparing C-14 ages and trace element ratios (Mg/Ca, Mn/Ca) of planktic foraminifera with white, opaque shells deemed well preserved by traditional standards to those with exquisitely preserved translucent shells. Results support a diagenetic mechanism as opaque shells yield C-14 ages invariably older and trace element ratios consistently higher than those of translucent shells. Radiocarbon age offsets are particularly pronounced in mono-specific samples taken from stratigraphic horizons proximal to the delta O-18 maximum marking the Last Glacial Maximum (LGM) and the subsequent deglacial. Radiocarbon-based calendar ages of translucent shells from the two intervals are congruent with the established age ranges for these climate events, whereas those of co-occurring opaque shells overestimate the LGM and deglacial by 8-15 k.y. and 14-22 k.y., respectively. These results demonstrate that the use of translucent foraminifera enhances reproducibility and accuracy of C-14 ages by minimizing the deleterious effects of diagenesis. This study serves as a cautionary tale since white, opaque foraminifera are common in pelagic sediments, and C-14 ages derived from their ostensibly well-preserved shells can lead to discrepancies in the timing of Quaternary climate events and ocean circulation reconstructions. VL - 44 ER - TY - JOUR T1 - Evidence for elevated coastal vulnerability following large-scale historical oyster bed harvesting JF - Earth Surface Processes and Landforms Y1 - 2016 A1 - Brandon, Christine M. A1 - Woodruff, Jonathan D. A1 - Orton, Philip M. A1 - Donnelly, Jeffrey P. AB - Living coastal barriers, such as coral reefs, tidal marshes, mangroves and shellfish beds are widely recognized for their potential role in mitigating flood risk. Limited data exists, however, for assessing the effectiveness of these natural defenses as forms of flood mitigation. In particular, very few mature shellfish beds exist today for modern study due to their destruction in the past few centuries. As an alternative method of study, we present here sedimentary reconstructions of storm overwash from coastal ponds internal to New York Harbor. We use these reconstructions to show that the initial degradation of oyster beds following European settlement of the area coincides with a significant increase in wave-derived overwash deposition at all three of our field sites. Numerical simulations of two flood events of record in the harbor (Hurricane Sandy and a severe winter storm in 1992) were run without and with oyster beds of varying heights (1 m above the seafloor-to-intertidal). Simulations show that the removal of these oyster beds increases wave energy directly off-shore of our field sites by between 30% and 200%. Sedimentary reconstructions and wave modeling experiments therefore both support oyster beds serving as a significant form of coastal protection prior to European disturbance. Copyright © 2016 John Wiley & Sons, Ltd. VL - 41 UR - http://doi.wiley.com/10.1002/esp.v41.8http://doi.wiley.com/10.1002/esp.3931https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fesp.3931 IS - 8 ER - TY - JOUR T1 - Evidence of multiple thermokarst lake generations from an 11 800-year-old permafrost core on the northern Seward Peninsula, Alaska JF - Boreas Y1 - 2016 A1 - Lenz, Josefine A1 - Wetterich, Sebastian A1 - Jones, Benjamin M. A1 - Meyer, Hanno A1 - Bobrov, Anatoly A1 - Grosse, Guido AB - Permafrost degradation influences the morphology, biogeochemical cycling and hydrology of Arctic landscapes over a range of time scales. To reconstruct temporal patterns of early to late Holocene permafrost and thermokarst dynamics, site-specific palaeo-records are needed. Here we present a multi-proxy study of a 350-cm-long permafrost core from a drained lake basin on the northern Seward Peninsula, Alaska, revealing Lateglacial to Holocene thermokarst lake dynamics in a central location of Beringia. Use of radiocarbon dating, micropalaeontology (ostracods and testaceans), sedimentology (grain-size analyses, magnetic susceptibility, tephra analyses), geochemistry (total nitrogen and carbon, total organic carbon, δ13Corg) and stable water isotopes (δ18O, δD, d excess) of ground ice allowed the reconstruction of several distinct thermokarst lake phases. These include a pre-lacustrine environment at the base of the core characterized by the Devil Mountain Maar tephra (22 800±280 cal. a BP, Unit A), which has vertically subsided in places due to subsequent development of a deep thermokarst lake that initiated around 11 800 cal. a BP (Unit B). At about 9000 cal. a BP this lake transitioned from a stable depositional environment to a very dynamic lake system (Unit C) characterized by fluctuating lake levels, potentially intermediate wetland development, and expansion and erosion of shore deposits. Complete drainage of this lake occurred at 1060 cal. a BP, including post-drainage sediment freezing from the top down to 154 cm and gradual accumulation of terrestrial peat (Unit D), as well as uniform upward talik refreezing. This core-based reconstruction of multiple thermokarst lake generations since 11 800 cal. a BP improves our understanding of the temporal scales of thermokarst lake development from initiation to drainage, demonstrates complex landscape evolution in the ice-rich permafrost regions of Central Beringia during the Lateglacial and Holocene, and enhances our understanding of biogeochemical cycles in thermokarst-affected regions of the Arctic. VL - 45 UR - https://onlinelibrary.wiley.com/doi/abs/10.1111/bor.12186 IS - 4 N1 - _eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/bor.12186 ER - TY - JOUR T1 - Factors influencing 14C concentrations of algal and archaeal lipids and their associated sea surface temperature proxies in the Black Sea JF - Geochimica et Cosmochimica Acta Y1 - 2016 A1 - Stephanie Kusch A1 - Janet Rethemeyer A1 - Ellen C. Hopmans A1 - Lukas Wacker A1 - Gesine Mollenhauer KW - sea surface temperature proxies KW - TEX86 KW - Uk37 KW - Uk′37 AB - Abstract Understanding the preservation and deposition history of organic molecules is crucial for the understanding of paleoenvironmental information contained in their abundance ratios such as Uk′37 and \{TEX86\} used as proxies for sea surface temperature (SST). Based on their relatively high refractivity, alkenones and glycerol dialkyl glycerol tetraethers (GDGTs) can survive postdepositional processes like lateral transport, potentially causing inferred \{SSTs\} to be misleading. Likewise, selective preservation of alkenones and \{GDGTs\} may cause biases of the \{SST\} proxies themselves and can lead to decoupling of both proxy records. Here we report compound-specific radiocarbon data of marine biomarkers including alkenones, GDGTs, and low molecular weight (LMW) n-fatty acids from Black Sea sediments deposited under different redox regimes to evaluate the potentially differential preservation of both biomarker classes and its effect on the \{SST\} indices Uk′37 and TEX86. The decadal Δ14C values of alkenones, GDGTs, and \{LMW\} n-fatty acids indicate similar preservation under oxic, suboxic, and anoxic redox regimes and no contribution of pre-aged compounds, e.g., by lateral supply. Moreover, similar 14C concentrations of crenarchaeol, alkenones, and \{LMW\} n-fatty acids imply that the thaumarchaeotal \{GDGTs\} preserved in these sediments are produced in the euphotic zone rather than in subsurface/thermocline waters. However, we observe biomarker-based \{SSTs\} that strongly deviate (ΔSST up to 8.4 °C) from in situ measured mean annual \{SSTs\} in the Black Sea. This is not due to redox-dependent differential biomarker preservation as implied by their Δ14C values and spatial \{SST\} pattern. Since contributions from different sources can largely be excluded, the deviation of the Uk′37 and \{TEX86\} proxy-derived \{SSTs\} from in situ \{SSTs\} requires further study of phylogenetic and other yet unknown environmental controls on alkenone and \{GDGT\} lipid distributions in the Black Sea. VL - 188 UR - http://www.sciencedirect.com/science/article/pii/S001670371630268X ER - TY - JOUR T1 - Fate of terrigenous organic matter across the Laptev Sea from the mouth of the Lena River to the deep sea of the Arctic interior JF - Biogeosciences Y1 - 2016 A1 - Broder, Lisa A1 - Tesi, Tommaso A1 - Salvad?, Joan A. A1 - Semiletov, Igor P. A1 - Dudarev, Oleg V. A1 - Gustafsson, ?rjan AB - Ongoing global warming in high latitudes may cause an increasing supply of permafrost-derived organic carbon through both river discharge and coastal erosion to the Arctic shelves. Mobilized permafrost carbon can be either buried in sediments, transported to the deep sea or degraded to CO2 and outgassed, potentially constituting a positive feedback to climate change. This study aims to assess the fate of terrigenous organic carbon (TerrOC) in the Arctic marine environment by exploring how it changes in concentration, composition and degradation status across the wide Laptev Sea shelf. We analyzed a suite of terrestrial biomarkers as well as source-diagnostic bulk carbon isotopes (δ13C, Δ14C) in surface sediments from a Laptev Sea transect spanning more than 800 km from the Lena River mouth (< 10 m water depth) across the shelf to the slope and rise (2000–3000 m water depth). These data provide a broad view on different TerrOC pools and their behavior during cross-shelf transport. The concentrations of lignin phenols, cutin acids and high-molecular-weight (HMW) wax lipids (tracers of vascular plants) decrease by 89–99 % along the transect. Molecular-based degradation proxies for TerrOC (e.g., the carbon preference index of HMW lipids, the HMW acids ∕ alkanes ratio and the acid ∕ aldehyde ratio of lignin phenols) display a trend to more degraded TerrOC with increasing distance from the coast. We infer that the degree of degradation of permafrost-derived TerrOC is a function of the time spent under oxic conditions during protracted cross-shelf transport. Future work should therefore seek to constrain cross-shelf transport times in order to compute a TerrOC degradation rate and thereby help to quantify potential carbon–climate feedbacks. VL - 13 UR - http://www.biogeosciences.net/13/5003/2016 IS - 17 ER - TY - JOUR T1 - Footprint of roman and modern mining activities in a sediment core from the southwestern Iberian Atlantic shelf JF - Science of The Total Environment Y1 - 2016 A1 - Mário Mil-Homens A1 - Carlos Vale A1 - Filipa Naughton A1 - Pedro Brito A1 - Teresa Drago A1 - Bárbara Anes A1 - Joana Raimundo A1 - Sabine Schmidt A1 - Miguel Caetano KW - mining activities KW - Rare earth elements AB - Abstract A 5-m long sediment core (VC2B), retrieved in the Southwestern Iberian Atlantic shelf, at 96 m water depth, was used to assess major changes in climate and human activities during the last 9.7 kyrs. Analytical measurements included sedimentological (mean grain size, and the contents of sand, silt and clay), geochemical (major, minor, trace and rare earth elements; REEs) and chronological (210Pb and 14C) parameters. Two episodes of increment of fine-grained particles, occurring at 3050 \{BCE\} and 1350 CE, suggest the retreat of the coast line to the present level and the beginning of a wetter phase associated with the “Little Ice Age”. The North American Shale Composite (NASC)-normalized REE-pattern detected in the shelf is similar to that found in the Guadiana estuarine sediments. The possibility of this estuary as a contributor to the sediment load deposited in the adjacent coastal zone was indicated. Trace elements were significantly correlated with Al until 1850 CE, pointing that grain-size rules its distribution in sediments. The depth variation of As, Cu and Pb enrichment factors relative to background values shows two periods of intense human activity that can be mainly linked to mining: (i) across the Roman Period, marked by low enrichments; and (ii) starting on the second half of the 19th century until nowadays with significantly increased enrichments, especially of Pb and Cu. In addition to As, Cu and Pb, this period is also marked by high enrichments of Hg and Zn. Despite the decrease/closure of sulphide massive deposits mining exploitation (e.g., São Domingos, Las Herrerias) during the second half of the 20th century, results showed ongoing input of Pb, Cu, As, Hg and Zn to coastal sediments. Thus, the legacy of contamination by these elements, mainly from leaching of slags and tailings, and remobilization/reworking of contaminated estuarine sediments, is still recorded in marine sediments. VL - 571 UR - http://www.sciencedirect.com/science/article/pii/S0048969716315959 ER - TY - JOUR T1 - Geochemical characterization of inorganic residues on plaster floors from a Maya palace complex at Actuncan, Belize JF - Journal of Archaeological Science: Reports Y1 - 2016 A1 - Lisa J. LeCount A1 - E. Christian Wells A1 - Thomas R. Jamison A1 - David W. Mixter KW - Belize AB - Abstract This report describes the results of a geochemical analysis using a mild acid extraction and inductively coupled plasma-mass spectroscopy of 198 samples from plaster surfaces at the palace complex at Actuncan, a prehispanic Maya city located in a karst landscape of western Belize. Archeologists working in the Maya region of Central America often refer to many different kinds of building complexes as “palaces” without a clear understanding of how they functioned. Often, the rooms inside these structures are devoid of features and artifacts, making it difficult to infer how they were used. Geochemical characterization of inorganic residues on plaster floors as a means of prospecting for activity areas is therefore critical for studying the function and meaning of ancient Maya palaces. At Actuncan, due to the high degree of preservation of many of the floors, overlying plaster surfaces were able to be sampled, thus informing not only how the buildings were used, but how their uses changed over time. Multivariate quantitative modeling and spatial interpolation of the chemical data demonstrate that a variety of domestic, ritual, and possibly administrative activities took place in the palace complex, a finding that challenges previous assessments of palaces as primarily royal residential compounds. VL - 5 UR - http://www.sciencedirect.com/science/article/pii/S2352409X15302261 ER - TY - JOUR T1 - Historical records of organic matter supply and degradation status in the East Siberian Sea JF - Organic Geochemistry Y1 - 2016 A1 - Broder, Lisa A1 - Tesi, Tommaso A1 - Andersson, August A1 - Eglinton, Timothy I. A1 - Semiletov, Igor P. A1 - Dudarev, Oleg V. A1 - Roos, Per A1 - Gustafsson, ?rjan KW - 210Pb KW - Arctic KW - East Siberian Arctic Shelf KW - HMW wax lipids KW - Lignin KW - Monte Carlo KW - δ13C KW - Δ14C AB - Destabilization and degradation of permafrost carbon in the Arctic regions could constitute a positive feedback to climate change. A better understanding of its fate upon discharge to the Arctic shelf is therefore needed. In this study, bulk carbon isotopes as well as terrigenous and marine biomarkers were used to construct two centennial records in the East Siberian Sea. Differences in topsoil and Pleistocene Ice Complex Deposit permafrost concentrations, modeled using δ13C and Δ14C, were larger between inner and outer shelf than the changes over time. Similarly, lignin-derived phenol and cutin acid concentrations differed by a factor of ten between the two stations, but did not change significantly over time, consistent with the dual-carbon isotope model. High molecular weight (HMW) n-alkane and n-alkanoic acid concentrations displayed a smaller difference between the two stations (factor of 3–6). By contrast, the fraction for marine OC drastically decreased during burial with a half-life of 19–27 years. Vegetation and degradation proxies suggested supply of highly degraded gymnosperm wood tissues. Lipid Carbon Preference Index (CPI) values indicated more extensively degraded HMW n-alkanes on the outer shelf with no change over time, whereas n-alkanoic acids appeared to be less degraded toward the core top with no large differences between the stations. Taken together, our results show larger across-shelf changes than down-core trends. Further investigation is required to establish whether the observed spatial differences are due to different sources for the two depositional settings or, alternatively, a consequence of hydrodynamic sorting combined with selective degradation during cross-shelf transport. VL - 91 UR - https://doi.org/10.1016/j.orggeochem.2015.10.008 ER - TY - JOUR T1 - Holocene climate variability from the lake sediment core in Schirmacher Oasis region, East Antarctica: Multiproxy approach JF - Quaternary International Y1 - 2016 A1 - Pawan Govil A1 - Abhijit Mazumder A1 - Rajesh Asthana A1 - Anoop Tiwari A1 - Ravi Mishra KW - Freshwater lakes AB - Abstract A 1.62 m sediment core was retrieved from one of the landlocked freshwater lakes (L-6) in the Schirmacher Oasis (SO), East Antarctica during the 24th Indian Antarctic Expedition (2004–2006). The sediment core samples were analyzed for Total Organic Carbon (TOC), Biogenic Silica (BSi), grain size and elemental concentration ratios (Mg/Ca and Mn/Fe). The sediment core represents the time period of last ∼11.6 cal ka \{BP\} as ascertained by \{AMS\} 14C radiocarbon dates. The sedimentation accumulation rate variation of ∼13.6 cm/ka from ∼11.6 to ∼10 cal ka \{BP\} reveals a warm phase followed by a low sedimentation accumulation rate of ∼2.9 cm/ka from ∼10 ka \{BP\} to ∼3.1 ka BP, indicating a cold period in the region. The sedimentation accumulation rate again increased from ∼3.1 cal ka \{BP\} to recent with a maximum of ∼88 cm/ka which reveals the initiation of glacier retreat or ice-free conditions in the study area. The Total Organic Carbon (TOC) is <2% from ∼10 to ∼3.1 cal ka \{BP\} indicating a prolonged colder phase in the study area. However, elevated TOC, \{BSi\} and Mg/Ca ratio since ∼3.1 cal ka \{BP\} to recent points indicates towards ice-free conditions (continental ice sheet retreat) and subsequently high productivity in the region. Moreover, the productivity was higher at the Pleistocene–Holocene boundary as evidenced by the Mg/CA, Mn/Fe ratio and Biogenic Silica (BSi). The present study identified a colder phase (or re-advancement of continental ice sheet) during the early to mid-Holocene and initiation of ice-free or continental ice-sheet retreat during the late Holocene and their implications on the productivity changes. VL - 425 UR - http://www.sciencedirect.com/science/article/pii/S1040618216304293 ER - TY - JOUR T1 - Hydrogen isotopic analysis with a chromium-packed reactor of organic compounds of relevance to ecological, archaeological, and forensic applications JF - RAPID COMMUNICATIONS IN MASS SPECTROMETRY Y1 - 2016 A1 - Reynard, Linda M. A1 - Tuross, Noreen AB - RationaleThe H-2 values of some nitrogen-containing organic compounds measured by High-Temperature Conversion (HTC) with a glassy carbon reactor have been shown to be inaccurate. A probable explanation for these analytical inaccuracies is the formation of HCN, allowing some hydrogen atoms to escape isotope ratio measurement. We assess this isotopic effect in sample types commonly used for (paleo)ecological, environmental, archaeological, and forensic investigations. MethodsThe H-2(VSMOW-SLAP) values and mass fraction H using a factory-recommended glassy carbon HTC reactor packing were compared with those obtained from using two Cr-containing reactor packings for a variety of N-containing substances, including amino acids, collagen, hair, and silk. Results(2)H(VSMOW-SLAP) values and mass fraction H differed by reactor packing for most, but not all, N-containing samples. The H-2(VSMOW-SLAP) difference was 10-11 for modern collagen and 12-14 parts per thousand for hair, demonstrating that reactor configuration is important for these proteins, and that the use of a chromium-packed reactor may be desirable. In contrast, Bombyx mori cocoon (silk) H-2(VSMOW-SLAP) values did not differ with reactor type. In general, H-2(VSMOW-SLAP) and mass fraction H differences by reactor packing increased with mass fraction nitrogen in the sample. With the Cr-packed reactor hydrogen mass fractions were at theoretically expected values, while the glassy carbon reactor produced lower yields of hydrogen. ConclusionsThe protein and amino acid H-2(VSMOW-SLAP) values measured by factory-recommended online HTC methods differ from those from Cr-containing reactor packing. The magnitude of the differences is variable with sample type; the molecular structure and diagenetic history of each sample may be important. Careful attention to this effect is therefore recommended for the H-2 measurement for all nitrogen-containing analytes. Copyright (c) 2016 John Wiley & Sons, Ltd. VL - 30 ER - TY - JOUR T1 - Hydrothermal iron flux variability following rapid sea level changes JF - GEOPHYSICAL RESEARCH LETTERS Y1 - 2016 A1 - Middleton, Jennifer L. A1 - Langmuir, Charles H. A1 - Mukhopadhyay, Sujoy A1 - McManus, Jerry F. A1 - Mitrovica, Jerry X. AB - Sea level changes associated with Pleistocene glacial cycles have been hypothesized to modulate melt production and hydrothermal activity at ocean ridges, yet little is known about fluctuations in hydrothermal circulation on time scales longer than a few millennia. We present a high-resolution record of hydrothermal activity over the past 50 ka using elemental flux data from a new sediment core from the Mir zone of the TAG hydrothermal field at 26 degrees N on the Mid-Atlantic Ridge. Mir sediments reveal sixfold to eightfold increases in hydrothermal iron and copper deposition during the Last Glacial Maximum, followed by a rapid decline during the sea level rise associated with deglaciation. Our results, along with previous observations from Pacific and Atlantic spreading centers, indicate that rapid sea level changes influence hydrothermal output on mid-ocean ridges. Thus, climate variability may discretize volcanic processing of the solid Earth on millennial time scales and subsequently stimulate variability in biogeochemical interactions with volcanic systems. VL - 43 ER - TY - JOUR T1 - Alutiiq Subsistence Economy at Igvak , a Russian-American Artel in the Kodiak Archipelago JF - Arctic Anthropology Y1 - 2016 A1 - Etnier, Michael A. A1 - Partlow, Megan A. A1 - Foster, Nora R. AB - Igvak was a Russian-American Company fur-hunting outpost (artel) on the south end of Afognak Island that was occupied from the 1790s to about 1830. Midden samples were recovered from deposits adjacent to the Alutiiq workers’ barracks as part of the Dig Afognak program. Although small amounts of European domesticates were identified, the bulk of the diet focused on traditional local foods. The dominant species included cod, harbor seals, and puffins, with a mix of intertidal invertebrates such as mussels, butter clams, and periwinkles. Also common were salmon, cormorants, sea otters, and sea lions. A single species of whale barnacle was identified. The high number of puffin remains may be related to the production of puffin-skin parkas for the Russian-American Company. The site was likely occupied year-round, but the presence of the bones of harbor seal pups and puffin and cormorant chicks confirms a summer occupation. VL - 53 UR - http://aa.uwpress.org/lookup/doi/10.3368/aa.53.2.52 IS - 2 ER - TY - JOUR T1 - Implications of a Bayesian radiocarbon calibration of colonization ages for mammalian megafauna in glaciated New York State after the Last Glacial Maximum JF - Quaternary Research Y1 - 2016 A1 - Robert S. Feranec A1 - Andrew L. Kozlowski KW - New York AB - Abstract To understand what factors control species colonization and extirpation within specific paleoecosystems, we analyzed radiocarbon dates of megafaunal mammal species from New York State after the Last Glacial Maximum. We hypothesized that the timing of colonization and extirpation were both driven by access to preferred habitat types. Bayesian calibration of a database of 39 radiocarbon dates shows that caribou (Rangifer tarandus) were the first colonizers, then mammoth (Mammuthus sp.), and finally American mastodon (Mammut americanum). The timing of colonization cannot reject the hypothesis that colonizing megafauna tracked preferred habitats, as caribou and mammoth arrived when tundra was present, while mastodon arrived after boreal forest was prominent in the state. The timing of caribou colonization implies that ecosystems were developed in the state prior to 16,000 cal yr BP. The contemporaneous arrival of American mastodon with Sporormiella spore decline suggests the dung fungus spore is not an adequate indicator of American mastodon population size. The pattern in the timing of extirpation is opposite to that of colonization. The lack of environmental changes suspected to be ecologically detrimental to American mastodon and mammoth coupled with the arrival of humans shortly before extirpation suggests an anthropogenic cause in the loss of the analyzed species. VL - 85 UR - http://www.sciencedirect.com/science/article/pii/S0033589416000041 ER - TY - JOUR T1 - Incorporation of bomb-produced 14C into fish otoliths: A novel approach for evaluating age validation and bias with an application to yellowfin sole and northern rockfish JF - Ecological Modelling Y1 - 2016 A1 - Kastelle, Craig R. A1 - Helser, Thomas E. A1 - Wischniowski, Stephen G. A1 - Loher, Timothy A1 - Goetz, Betty J. A1 - Kautzi, Lisa A. AB - Fish age validation with bomb-produced radiocarbon (14C) requires a known-age Δ14C reference chronology spanning the era of a marine increase in bomb-produced 14C (1950s to 1960s). Concordance between otolith Δ14C in a validation sample and the reference chronology indicates accurate test ages. Here, we present an information-theoretic approach to hypothesis testing and use Bayesian data analysis with Markov chain Monte Carlo simulation as a probabilistic framework to quantitatively estimate age determination bias and its uncertainty. Using this approach, we compare a new Δ14C reference chronology from the eastern Bering Sea and a previously established reference from the Gulf of Alaska with otolith Δ14C in two validation species, eastern Bering Sea yellowfin sole (Limanda aspera) and Gulf of Alaska northern rockfish (Sebastes polyspinis). Our goals were twofold: (i) to validate the age determination methods for northern rockfish and yellowfin sole using comparisons within oceanic basins, and (ii) to explore the outcome of making naïve comparisons of these validation data sets to reference chronologies across oceanic basins. Based on within-basin comparisons we concluded that estimated ages for eastern Bering Sea yellowfin sole and Gulf of Alaska northern rockfish were accurate. We further concluded that there were important differences in otolith 14C uptake between fish from the two ocean basins. VL - 320 UR - http://www.sciencedirect.com/science/article/pii/S0304380015004354 JO - Incorporation of bomb-produced 14C into fish otoliths: A novel approach for evaluating age validation and bias with an application to yellowfin sole and northern rockfish ER - TY - JOUR T1 - Indus Basin sediment provenance constrained using garnet geochemistry JF - Journal of Asian Earth Sciences Y1 - 2016 A1 - Anwar Alizai A1 - Peter D. Clift A1 - John Still KW - Provenance AB - Abstract The chemical and mineralogical diversity of western Himalayan rivers is the result of each of them draining different tectonic and lithologic units, whose character is partly transferred to the sediments carried by those rivers. Garnet geochemistry was employed to discriminate provenance in the Indus River system. We characterized the geochemistry of garnet sediment grains from the modern Indus and all its major tributaries, as well as the related but ephemeral Ghaggar-Hakra River and dune sand from the Thar Desert. Garnet geochemistry displays a unique signature for the Himalayan rivers on the east of the Indus drainage compared to those in the western drainage. The trunk Indus remains distinct because of the dominant arc-type pyrope-garnet derived from Kohistan and the Karakoram. The Jhellum, which lies just east of the modern Indus has modest concentrations of arc-type pyrope garnets, which are more depleted in the other eastern tributaries. Their presence in the Jhellum reflects recycling of trunk Indus garnets through the Miocene Siwalik Group foreland sedimentary rocks. The Thar Desert dune sample contains significant numbers of grains similar to those in the trunk Indus, likely reworked by monsoon winds from the SW. Our data further indicate the presence of a Himalayan river channel east of the present Indus, close to the delta, in the Nara River valley during the middle Holocene. Sands from this channel cannot be distinguished from the Indus on the basis of their garnet geochemistry alone but we favour their sedimentation from an Indus channel rather than reworking of desert sands by another stream. The garnet geochemistry shows some potential as a provenance tool, but cannot be used alone to uniquely discriminate Indus Basin provenance. VL - 126 UR - http://www.sciencedirect.com/science/article/pii/S1367912016301481 ER - TY - JOUR T1 - Inferring skeletal production from time-averaged assemblages: skeletal loss pulls the timing of production pulses towards the modern period JF - PALEOBIOLOGY Y1 - 2016 A1 - Tomasovych, Adam A1 - Kidwell, Susan M. A1 - Barber, Rina Foygel AB - Age-frequency distributions of dead skeletal material on the landscape or seabed-information on the time that has elapsed since the death of individuals-provide decadal- to millennial-scale perspectives both on the history of production and on the processes that lead to skeletal disintegration and burial. So far, however, models quantifying the dynamics of skeletal loss have assumed that skeletal production is constant during time-averaged accumulation. Here, to improve inferences in conservation paleobiology and historical ecology, we evaluate the joint effects of temporally variable production and skeletal loss on postmortem age-frequency distributions (AFDs) to determine how to detect fluctuations in production over the recent past from AFDs. We show that, relative to the true timing of past production pulses, the modes of AFDs will be shifted to younger age cohorts, causing the true age of past pulses to be underestimated. This shift in the apparent timing of a past pulse in production will be stronger where loss rates are high and/or the rate of decline in production is slow; also, a single pulse coupled with a declining loss rate can, under some circumstances, generate a bimodal distribution. We apply these models to death assemblages of the bivalve Nuculana taphria from the Southern California continental shelf, finding that: (1) an onshore-offshore gradient in time averaging is dominated by a gradient in the timing of production, reflecting the tracking of shallow-water habitats under a sea-level rise, rather than by a gradient in disintegration and sequestration rates, which remain constant with water depth; and (2) loss-corrected model-based estimates of the timing of past production are in good agreement with likely past changes in local production based on an independent sea-level curve. VL - 42 ER - TY - JOUR T1 - The intertropical convergence zone modulates intense hurricane strikes on the western North Atlantic margin JF - Scientific Reports Y1 - 2016 A1 - van Hengstum, Peter J. A1 - Donnelly, Jeffrey P. A1 - Fall, Patricia L. A1 - Toomey, Michael R. A1 - Albury, Nancy A. A1 - Kakuk, Brian KW - Climate-change impacts KW - Forest ecology KW - Ocean sciences KW - Palaeoclimate AB - Most Atlantic hurricanes form in the Main Development Region between 9°N to 20°N along the northern edge of the Intertropical Convergence Zone (ITCZ). Previous research has suggested that meridional shifts in the ITCZ position on geologic timescales can modulate hurricane activity, but continuous and long-term storm records are needed from multiple sites to assess this hypothesis. Here we present a 3000 year record of intense hurricane strikes in the northern Bahamas (Abaco Island) based on overwash deposits in a coastal sinkhole, which indicates that the ITCZ has likely helped modulate intense hurricane strikes on the western North Atlantic margin on millennial to centennial-scales. The new reconstruction closely matches a previous reconstruction from Puerto Rico, and documents a period of elevated intense hurricane activity on the western North Atlantic margin from 2500 to 1000 years ago when paleo precipitation proxies suggest that the ITCZ occupied a more northern position. Considering that anthropogenic warming is predicted to be focused in the northern hemisphere in the coming century, these results provide a prehistoric analog that an attendant northern ITCZ shift in the future may again return the western North Atlantic margin to an active hurricane interval. VL - 6 UR - http://www.nature.com/articles/srep21728http://www.nature.com/articles/srep21728.pdfhttp://www.nature.com/articles/srep21728.pdfhttp://www.nature.com/articles/srep21728 IS - 1 ER - TY - JOUR T1 - IsoCaRB: A novel bioreactor system to characterize the lability and natural carbon isotopic (C-14, C-13) signatures of microbially respired organic matter JF - LIMNOLOGY AND OCEANOGRAPHY-METHODS Y1 - 2016 A1 - Beaupré, Steven R. A1 - Mahmoudi, Nagissa A1 - Pearson, Ann AB - Organic matter is the dominant pool of reduced carbon in marine and freshwater systems. Mineralization of organic matter is largely attributed to complex and diverse microbial communities that mediate degradation and ultimately yield the terminal respiratory product, carbon dioxide (CO2). The factors that constrain the lability and degradation of organic matter remain unclear, but they involve a complex interplay between structural and chemical properties of the compounds, physical properties of the matrices, and the functional potential of the microorganisms that are present. To investigate these relationships, we developed a novel bioreactor system-called Isotopic Carbon Respirometer-Bioreactor (IsoCaRB)-that permits real-time monitoring of microbial CO2 production rates and collects sequential samples of this CO2 for off-line isotopic analyses (C-13, C-14). Application of this system to organic-rich sediments from Salt Pond, MA reveals that organic matter is oxidized both abiotically and microbially, and that the pattern of microbial respiration by the native sediment community is complex, accessing different carbon substrates over the course of incubation. Isotopic measurements show modern organic matter of progressively older ages (<= ca. 50 yr) is consumed, and this material has variable origins (salt marsh grasses, terrestrial, and marine organic matter). Collectively, the IsoCaRB system provides coupled insights into the sources, ages, and inherent biological and abiotic reactivity of natural organic matter. VL - 14 ER - TY - JOUR T1 - Large deglacial shifts of the Pacific Intertropical Convergence Zone JF - Nature Communications Y1 - 2016 A1 - Jacobel, A. W. A1 - McManus, J. F. A1 - Anderson, R. F. A1 - Winckler, G. AB - The position of the Intertropical Convergence Zone (ITCZ) is sensitive to changes in the balance of heat between the hemispheres which has fundamental implications for tropical hydrology and atmospheric circulation. Although the ITCZ is thought to experience the largest shifts in position during deglacial stadial events, the magnitude of shifts has proven difficult to reconstruct, in part because of a paucity of high-resolution records, particularly those including spatial components. Here we track the position of the ITCZ from 150 to 110 ka at three sites in the central equatorial Pacific at sub-millennial time resolution. Our results provide evidence of large, abrupt changes in tropical climate during the penultimate deglaciation, coincident with North Atlantic Heinrich Stadial 11 (∼136–129 ka). We identify this event both as a Northern Hemisphere increase in aeolian dust and as a shift in the mean position of the ITCZ a minimum of 4° southwards at 160° W. VL - 7 UR - http://www.nature.com/doifinder/10.1038/ncomms10449 ER - TY - JOUR T1 - Last Glacial Maximum sea surface temperature and sea-ice extent in the Pacific sector of the Southern Ocean JF - Quaternary Science Reviews Y1 - 2016 A1 - Verena Benz A1 - Oliver Esper A1 - Rainer Gersonde A1 - Frank Lamy A1 - Ralf Tiedemann KW - Pacific Southern Ocean AB - Abstract Sea surface temperatures and sea-ice extent are most critical variables to evaluate the Southern Ocean paleoceanographic evolution in relation to the development of the global carbon cycle, atmospheric \{CO2\} and ocean-atmosphere circulation. Here we present diatom transfer function-based summer sea surface temperature (SSST) and winter sea-ice (WSI) estimates from the Pacific sector of the Southern Ocean to bridge a gap in information that has to date hampered a well-established reconstruction of the last glacial Southern Ocean at circum-Antarctic scale. We studied the Last Glacial Maximum (LGM) at the \{EPILOG\} time slice (19,000–23,000 calendar years before present) in 17 cores and consolidated our \{LGM\} picture of the Pacific sector taking into account published data from its warmer regions. Our data display a distinct east-west differentiation with a rather stable \{WSI\} edge north of the Pacific-Antarctic Ridge in the Ross Sea sector and a more variable \{WSI\} extent over the Amundsen Abyssal Plain. The zone of maximum cooling (>4 K) during the \{LGM\} is in the present Subantarctic Zone and bounded to its south by the 4 °C isotherm. The isotherm is in the \{SSST\} range prevailing at the modern Antarctic Polar Front, representing a circum-Antarctic feature, and marks the northern edge of the glacial Antarctic Circumpolar Current (ACC). The northward deflection of colder than modern surface waters along the South American continent led to a significant cooling of the glacial Humboldt Current surface waters (4–8 K), which affected the temperature regimes as far north as tropical latitudes. The glacial reduction of \{ACC\} temperatures may also have resulted in significant cooling in the Atlantic and Indian Southern Ocean, thus enhancing thermal differentiation of the Southern Ocean and Antarctic continental cooling. The comparison with numerical temperature and sea-ice simulations yields discrepancies, especially concerning the estimates of the sea-ice fields, but some simulations reproduce well our proxy-based temperature data. VL - 146 UR - http://www.sciencedirect.com/science/article/pii/S0277379116302062 ER - TY - JOUR T1 - Late Quaternary evolution of Lago Castor (Chile, 45.6°S): Timing of the deglaciation in northern Patagonia and evolution of the southern westerlies during the last 17 kyr JF - Quaternary Science Reviews Y1 - 2016 A1 - Maarten Van Daele A1 - Sébastien Bertrand A1 - Inka Meyer A1 - Jasper Moernaut A1 - Willem Vandoorne A1 - Giuseppe Siani A1 - Niels Tanghe A1 - Zakaria Ghazoui A1 - Mario Pino A1 - Roberto Urrutia A1 - Marc De Batist KW - Sediment drift AB - Abstract Even though Patagonia is ideally located to study climate of the southern mid-latitudes, many questions on the late Quaternary climate evolution remain unresolved. The timing of maximum glacier extent is still uncertain in vast areas, and the postglacial evolution of the Southern Westerly Wind Belt (SWWB) remains highly debated. Here, we study the sedimentary infill of a glacigenic lake (Lago Castor; 45.6°S, 71.8°W) located at the leeside of the Andes in Chilean Patagonia to i) reconstruct the deglacial evolution of the eastern flank of the Patagonian Ice Sheet (PIS), and ii) discuss postglacial changes in wind strength at a critical location where westerly wind records are critically lacking. A dense grid of high-resolution reflection-seismic data was used to reconstruct the large-scale infill history of the lake, and a radiocarbon dated sediment core penetrating all lacustrine seismic units, was retrieved. Results indicate that the deglaciation of the lake basin and its catchment occurred no later than ∼28 cal kyr \{BP\} (i.e. an early LGM), but possibly even already after \{MIS\} 4. Afterwards, the Lago Castor area was covered by a large proglacial lake that drained – possibly through an outburst flood – when the \{PIS\} outlet glaciers retreated to a critical location. Subsequently, very dry conditions caused the lake to desiccate, as evidenced by an unconformity visible on the seismic profiles and in the sediment core. This dry period likely resulted from the increased orographic effect of the PIS-covered Andes, accompanied by weaker westerlies. From ∼20 kyr \{BP\} onwards, the combination of a shrinking \{PIS\} and a southward shift of the \{SWWB\} resulted in increased precipitation, which caused the lake level to rise. After ∼17 cal kyr BP, lake sedimentation was more directly influenced by the southern westerlies, with the formation of sediment drifts resulting from strong bottom current during periods of intense westerly winds. Our results suggest a progressive increase in wind strength at 46°S from 11.2 to 4.5 cal kyr BP, which supports the hypothesis that the \{SWWB\} broadened during the early and middle Holocene. VL - 133 UR - http://www.sciencedirect.com/science/article/pii/S027737911530202X ER - TY - JOUR T1 - Late Quaternary fingerprints of precession and sea level variation over the past 35 kyr as revealed by sea surface temperature and upwelling records from the Indian Ocean near southernmost Sumatra JF - Quaternary International Y1 - 2016 A1 - Ziye Li A1 - Xuefa Shi A1 - Min-Te Chen A1 - Houjie Wang A1 - Shengfa Liu A1 - Jian Xu A1 - Haiyan Long A1 - Rainer Arief Troa A1 - Rina Zuraida A1 - Eko Triarso KW - Quaternary AB - Abstract We report high-resolution paleoclimatic reconstructions using isotope, alkenone sea surface temperature (SST), productivity, and terrigenous proxy variations over the past 35 kyr from core SO184-10043 (07°18.57′S, 105°03.53′E) in the eastern tropical Indian Ocean offshore of southernmost (S) Sumatra. The core was retrieved at 2171 m water depth, from the monsoon driven seasonal upwelling area off southernmost Sumatra. Our paleoclimatic reconstructions show that an enhanced marine productivity was closely linked to strengthening of coastal upwelling during the increases of boreal summer insolation and associated southeastern (SE) monsoon strength, with pronounced semi-precession cycles (∼11 kyr). In contrast, our record of alkenone \{SSTs\} shows glacial to interglacial, a sea-level variation, but this fluctuates at dominant precession cycles (∼21 kyr). We also observed four \{SST\} “plateaus” with relatively warmer hydrographic stability in our records over the past 35 kyr: 32-27 ka, 24-20 ka, 17-12 ka, and 9-4 ka. The time scale of each plateau is ∼4-6 kyr. Our study indicates that since the last glacial maximum (LGM), the sea level rise has been responsible for the Sunda shelf flooding and the Indonesian Throughflow (ITF) from the South China Sea (SCS) to the eastern Indian Ocean, leaving a dominant fingerprint of a glacial to interglacial increase in \{SSTs\} since ∼9.5 ka We further argue that the a most recent centennial to millennial scale cooling at ∼3.5 ka observed in our \{SST\} record is a widespread event in the tropical Pacific, which has implications for advancing our understanding of the climate dynamics of the tropical oceans at these time scales. VL - 425 UR - http://www.sciencedirect.com/science/article/pii/S1040618216308722 ER - TY - JOUR T1 - A major increase in winter snowfall during the middle Holocene on western Greenland caused by reduced sea ice in Baffin Bay and the Labrador Sea JF - Geophysical Research Letters Y1 - 2016 A1 - Thomas, Elizabeth K. A1 - Briner, Jason P. A1 - Ryan-Henry, John J. A1 - Huang, Yongsong AB - Recent observations indicate that ice-ocean interaction drives much of the recent increase in mass loss from the Greenland Ice Sheet; however, the role of ocean forcing in driving past glacier change is poorly understood. To extend the observational record and our understanding of the ocean-cryosphere link, we used a multi-proxy approach that combines new data from proglacial lake sediments, C-14-dated in situ moss that recently emerged from beneath cold-based ice caps, and Be-10 ages to reconstruct centennial-scale records of mountain glacier activity for the past similar to 10 k. y. in West Greenland. Proglacial lake sediment records and C-14 dating of moss indicate the onset of Neoglaciation in West Greenland at ca. 5 ka with substantial snowline lowering and glacier expansion at ca. 3.7 ka followed by additional ice expansion phases at ca. 2.9, ca. 1.7, and ca. 1.4 ka and during the Little Ice Age. We find that widespread glacier growth at ca. 3.7 ka in West Greenland coincides with marked cooling and reduced strength of the West Greenland Current in Disko Bugt. The transition to cooler ocean conditions at ca. 3.7 ka identified in Disko Bugt is registered by marine proxy data farther afield in East Greenland and on the northwestern Icelandic shelf, implying large-scale paleoceanographic changes across the North Atlantic during this interval. The similarity between glacier change on West Greenland and multiple marine and terrestrial records across the North Atlantic suggests that glaciers are strongly influenced by changes in ocean circulation and consequently implies that the ocean-cryosphere teleconnection is a persistent feature of the Arctic system. VL - 45 UR - http://doi.wiley.com/10.1002/2016GL068513 IS - 3 ER - TY - JOUR T1 - Methane emissions proportional to permafrost carbon thawed in Arctic lakes since the 1950s JF - Nature Geoscience Y1 - 2016 A1 - Walter Anthony, Katey A1 - Daanen, Ronald A1 - Anthony, Peter A1 - Schneider von Deimling, Thomas A1 - Ping, Chien-Lu A1 - Chanton, Jeffrey P. A1 - Grosse, Guido KW - Carbon cycle KW - Climate change KW - Cryospheric science AB - Permafrost thaw exposes previously frozen soil organic matter to microbial decomposition. This process generates methane and carbon dioxide, and thereby fuels a positive feedback process that leads to further warming and thaw1. Despite widespread permafrost degradation during the past ~40 years2, 3, 4, the degree to which permafrost thaw may be contributing to a feedback between warming and thaw in recent decades is not well understood. Radiocarbon evidence of modern emissions of ancient permafrost carbon is also sparse5. Here we combine radiocarbon dating of lake bubble trace-gas methane (113 measurements) and soil organic carbon (289 measurements) for lakes in Alaska, Canada, Sweden and Siberia with numerical modelling of thaw and remote sensing of thermokarst shore expansion. Methane emissions from thermokarst areas of lakes that have expanded over the past 60 years were directly proportional to the mass of soil carbon inputs to the lakes from the erosion of thawing permafrost. Radiocarbon dating indicates that methane age from lakes is nearly identical to the age of permafrost soil carbon thawing around them. Based on this evidence of landscape-scale permafrost carbon feedback, we estimate that 0.2 to 2.5 Pg permafrost carbon was released as methane and carbon dioxide in thermokarst expansion zones of pan-Arctic lakes during the past 60 years. VL - 9 UR - http://www.nature.com/doifinder/10.1038/ngeo2795 ER - TY - JOUR T1 - Micropaleontologic record of Pliocene and Quaternary paleoenvironments in the southern Albemarle Embayment, North Carolina, U.S.A JF - Palaeogeography, Palaeoclimatology, Palaeoecology Y1 - 2016 A1 - Stephen J. Culver A1 - Kathleen M. Farrell A1 - David J. Mallinson A1 - Debra A. Willard A1 - Benjamin P. Horton A1 - Stanley R. Riggs A1 - E. Robert Thieler A1 - John F. Wehmiller A1 - Peter R. Parham A1 - Jessica Pierson Moore A1 - Scott W. Snyder A1 - Caroline Hillier KW - Holocene AB - Abstract The Albemarle Embayment, a Cenozoic depositional basin on the Atlantic coast of the USA, is an ideal setting to understand the temporal and spatial variation of eustatic sea-level fluctuations, glacio-hydro-isostasy, tectonics, subsidence, environments and sedimentation patterns of a passive margin Quaternary section. A NE–SW transect of cores and seismic data in the southern Albemarle Embayment were analyzed using micropaleontologic (foraminifera, diatoms, pollen), sedimentologic, stratigraphic, and geochronologic data to reconstruct the paleoenvironmental evolution and paleoclimates in the nearly 90 m thick Quaternary section. The study area is a very low gradient Quaternary landscape that is cross-cut by several Pleistocene incised valleys; a Holocene barrier island complex forms its eastern margin. In the subsurface, the Albemarle Embayment is bordered to the north by the Norfolk Arch and to the south by the depositionally-constructed Cape Lookout High, which is positioned on the northern flank of the structural Carolina Platform. The Quaternary section overlies mid-Pliocene carbonates in three cores; the contact rises in elevation towards the Cape Lookout High. Fossils and sediment characteristics suggest a subtropical, shallow, high energy marine environment during the Pliocene. Overlying units include incomplete Pleistocene, clastic, transgressive-regressive (T-R) deposits. These have similar ages and stratigraphic signatures as the T-R cycles in the central and north-central Albemarle Embayment, although mid-Pleistocene deposits may be older in the southern region. The bulk of the early and mid-Pleistocene record consists of inner to mid-shelf sand and muddy sand. In contrast, late Pleistocene sands are of inner shelf origin, reflecting the infilling of the basin. Lowstand paleovalleys, with fluvial, wetland and estuarine fill, dissect the early, mid- and late Pleistocene marine units; their locations reflect antecedent topography. Holocene sediments were deposited in shoreface and barrier island environments. Quaternary foraminiferal assemblages in the southern Albemarle Embayment exhibit greater species richness than those in the central and north-central embayment reflecting the presence of a major biogeographic boundary at the same location as the modern biogeographic boundary at Cape Hatteras. VL - 457 UR - http://www.sciencedirect.com/science/article/pii/S0031018216301572 ER - TY - JOUR T1 - Multi-proxy records of Holocene palaeoenvironmental changes in the Varna Lake area, western Black Sea coast JF - Quaternary International Y1 - 2016 A1 - Mariana Filipova-Marinova A1 - Danail Pavlov A1 - Liviu Giosan KW - Geoarchaeology AB - Abstract High-resolution spore-pollen analysis of laminated sediments of newly taken Core-3 (870 cm long) from Varna Lake (northeastern Bulgaria) is combined with multiproxy micropalaeontological analyses of dinoflagellate cysts, acritarchs, and other non-pollen palynomorphs (NPP), including fossil algal and fungal remains. The location of the core is close to several submerged praehistorical sites and the Varna Chalcolithic Necropolis, and permits more precise palaeoecological correlations of obtained results with available archaeological and geochronological data. The established Age vs. Depth Model shows that the formation of the lake started after 7870 cal. \{BP\} due to a rise of the Black Sea level, also known as the First Phase of the Vityazevyan Black Sea Transgression. After ca. 94 y, the Second Phase of the Vityazevyan Black Sea Transgression is registered by a major change in the sedimentation and formation of molluscan shell hash layer of Mytilus galloprovincialis that covers the interval 7776 to 6183 cal. BP. Mixed oak and hornbeam forests dominated the vegetation cover during the Atlantic, Subboreal and Subatlantic chronozones of the Holocene. An important change in the forest composition occurs at ca. 5518 cal. BP, when Carpinus betulus reached its maximum spread due to a climate change. The high-resolution geoarchaeological reconstruction of palaeovegetation also reveals the extent of anthropogenic influence in the Varna Lake area, with deforestation and agricultural practice. Two periods of significant presence of pollen from cultivated cereals, and secondary anthropogenic indicators (weeds and ruderals) were identified. According to the available AMS-radiocarbon data, these periods correspond to the Late Eneolithic and Early Bronze Age. The Transitional period without human activities between these two archaeological periods lasted ca. 319 y and coincides with a rise of the Black Sea level, reflected by the increase of euryhaline marine dinoflagelate cysts Lingulodinium machaerophorum and Spiniferites belerius, and acritarchs Cymatiosphaera globulosa and Micrhystridium cf. ariakense during the First Phase of the Kalamitian Black Sea Transgression. The increased values of Corylus coincidently with decrease of Quercus and Ulmus suggest clearance of forests and enlargement of arable areas during the Late Eneolithic. The NPP-record of spores of coprophyllous fungi Cercophora, Sordaria, Podospora and Chaetomium indicates the presence of domestic animals during the Early Bronze Age. The maximum of Alnus, Ulmus, Fraxinus excelsior-type and Fagus pollen at 717 cal. \{BP\} suggests an increase of humidity and cooling of climate during the Subatlantic. VL - 401 UR - http://www.sciencedirect.com/science/article/pii/S1040618215004954 N1 - Implications for Late Quaternary Sea Level Changes on the Mediterranean and Black Sea Coasts - \{MEDBLACKS2014\} ER - TY - JOUR T1 - A new late Quaternary palaeohydrological record from the humid tropics of northeastern Australia JF - Palaeogeography, Palaeoclimatology, Palaeoecology Y1 - 2016 A1 - M.A. Burrows A1 - H. Heijnis A1 - P. Gadd A1 - S.G. Haberle KW - Late Quaternary AB - Abstract High resolution X-ray fluorescence (XRF) is presented as a robust palaeoclimatic proxy, suitable for use on Late Pleistocene to Holocene sediments located in a volcanic crater on the Atherton Tableland in northeastern Queensland, Australia. The proxy allows identification of wet and dry shifts in a complex sedimentary sequence comprised of peat, gyttja, laminated organic rich muds and fine clastic silt-rich sediments. Significant correlation is found between the \{XRF\} record and other proxies including magnetic susceptibility, humification, grain size, macrocharcoal, δ13C and C/N and pollen. Sixteen wetter periods are identified in the 37 ka sedimentary record for Bromfield Swamp. Three wetter periods commence in late Marine Isotope Stage 3, nine in the early glacial, one in the late de-glacial and four in Holocene. Nineteen drier periods are identified, four in late \{MIS\} 3, seven in the early glacial, one during the LGM, one in the late de-glacial period and six in the Holocene. The \{XRF\} record for Bromfield Swamp is specifically used to identify periods of abrupt climate change. Marked changes in effective precipitation are detected at 32,690, 30,080, 24,660, 21,870, 11,880, 10,020, 9170 and 5120 cal. yr BP. The detection of these abrupt climate events may allow correlation with records from terrestrial sites across the Southern Hemisphere and potentially, the Northern Hemisphere. VL - 451 UR - http://www.sciencedirect.com/science/article/pii/S0031018216001656 ER - TY - JOUR T1 - No iron fertilization in the equatorial Pacific Ocean during the last ice age JF - Nature Y1 - 2016 A1 - Costa, K. M. A1 - McManus, J. F. A1 - Anderson, R. F. A1 - Ren, H. A1 - Sigman, D. M. A1 - Winckler, G. A1 - Fleisher, M. Q. A1 - Marcantonio, F. A1 - Ravelo, A. C. KW - Biogeochemistry KW - Palaeoceanography AB - The equatorial Pacific Ocean is one of the major high-nutrient, low-chlorophyll regions in the global ocean. In such regions, the consumption of the available macro-nutrients such as nitrate and phosphate is thought to be limited in part by the low abundance of the critical micro-nutrient iron1. Greater atmospheric dust deposition2 could have fertilized the equatorial Pacific with iron during the last ice age—the Last Glacial Period (LGP)—but the effect of increased ice-age dust fluxes on primary productivity in the equatorial Pacific remains uncertain3, 4, 5, 6. Here we present meridional transects of dust (derived from the 232Th proxy), phytoplankton productivity (using opal, 231Pa/230Th and excess Ba), and the degree of nitrate consumption (using foraminifera-bound δ15N) from six cores in the central equatorial Pacific for the Holocene (0–10,000 years ago) and the LGP (17,000–27,000 years ago). We find that, although dust deposition in the central equatorial Pacific was two to three times greater in the LGP than in the Holocene, productivity was the same or lower, and the degree of nitrate consumption was the same. These biogeochemical findings suggest that the relatively greater ice-age dust fluxes were not large enough to provide substantial iron fertilization to the central equatorial Pacific. This may have been because the absolute rate of dust deposition in the LGP (although greater than the Holocene rate) was very low. The lower productivity coupled with unchanged nitrate consumption suggests that the subsurface major nutrient concentrations were lower in the central equatorial Pacific during the LGP. As these nutrients are today dominantly sourced from the Subantarctic Zone of the Southern Ocean, we propose that the central equatorial Pacific data are consistent with more nutrient consumption in the Subantarctic Zone, possibly owing to iron fertilization as a result of higher absolute dust fluxes in this region7, 8. Thus, ice-age iron fertilization in the Subantarctic Zone would have ultimately worked to lower, not raise, equatorial Pacific productivity. VL - 529 UR - http://www.nature.com/doifinder/10.1038/nature16453 IS - 7587 ER - TY - JOUR T1 - A Note on Reporting of Reservoir C-14 Disequilibria and Age Offsets JF - RADIOCARBON Y1 - 2016 A1 - Soulet, Guillaume A1 - Skinner, Luke C. A1 - Beaupré, Steven R. A1 - Galy, Valier KW - freshwater effect KW - hardwater effect KW - radiocarbon KW - Reservoir age KW - Reservoir effect KW - ventilation age AB - Reservoir age offsets are widely used to correct marine and speleothem radiocarbon age measurements for various calibration purposes. They also serve as a powerful tracer for carbon cycle dynamics. However, a clear terminology regarding reservoir age offsets is lacking, sometimes leading to miscalculations. This note seeks to provide consistent conventions for reporting reservoir C-14 disequilibria useful to a broad range of environmental sciences. This contribution introduces the (FR)-R-14 and R-14 metrics to express the relative C-14 disequilibrium between two contemporaneous reservoirs and the R metric as the associated reservoir age offset. VL - 58 ER - TY - JOUR T1 - Organic matter cycling across the sulfate-methane transition zone of the Santa Barbara Basin, California Borderland JF - Geochimica et Cosmochimica Acta Y1 - 2016 A1 - Komada, Tomoko A1 - Burdige, David J. A1 - Li, Huan-Lei A1 - Magen, édric A1 - Chanton, Jeffrey P. A1 - Cada, Abraham K. AB - Consumption of sulfate (SO42−) in the sulfate-methane transition zone (SMTZ) has often been considered to be due solely to anaerobic oxidation of methane (AOM). However, recent studies show SO42− fluxes into the SMTZ that exceed methane (CH4) fluxes, thereby challenging this conceptual model. Co-occurrence of organoclastic SO42− reduction (oSR) with AOM in the SMTZ has been hypothesized to be the cause for this flux imbalance, but conclusive evidence is lacking. To address this knowledge gap, we investigated organic matter cycling in the SMTZ of the organic-rich sediments of the Santa Barbara Basin, California Borderland, and examined the occurrence of oSR within this zone using bulk solute profiles and Δ14C and δ13C values of selected carbon pools. We also tested the hypothesis that the SMTZ acts as an oxidation front not just for CH4, but also for dissolved organic carbon (DOC) that is produced below the SMTZ and migrates upward. Mass balance calculations for the SMTZ based on reaction stoichiometry and Δ14C and δ13C values of associated carbon fluxes indicate that ∼35–45% of total SO42− reduction in the SMTZ occurs via oSR, with the remainder attributable to AOM. The δ13C value of net DOC production is distinct from that of the fraction of bulk POC undergoing degradation, suggesting that pore-water DOC represents a compositionally unique slice of the metabolizable POC pool. DOC diffusing upward at 450 cm is virtually free of 14C and contain low levels of short-chain organic acids. Radiocarbon mass balance shows that >30% of this pre-aged, and presumably refractory, DOC is removed from the pore waters within or immediately below the SMTZ. Although the SMTZ does not appear to be a major net DOC oxidation front, these results show that DOC dynamics provide unique insights into organic matter processing in these subsurface sediments. VL - 176 UR - http://linkinghub.elsevier.com/retrieve/pii/S0016703715007164http://api.elsevier.com/content/article/PII:S0016703715007164?httpAccept=text/xmlhttp://api.elsevier.com/content/article/PII:S0016703715007164?httpAccept=text/plain ER - TY - JOUR T1 - Palaeoclimatic changes in Kveithola, Svalbard, during the Late Pleistocene deglaciation and Holocene: Evidences from microfossil and sedimentary records JF - Palaeogeography, Palaeoclimatology, Palaeoecology Y1 - 2016 A1 - Katia Carbonara A1 - Karin Mezgec A1 - Gabriella Varagona A1 - Maria Elena Musco A1 - Renata Giulia Lucchi A1 - Giuliana Villa A1 - Caterina Morigi A1 - Romana Melis A1 - Mauro Caffau KW - Clay minerals AB - Abstract Climate changes are reflected in the Arctic ecosystem history over different timescales. We use a multi proxy-based approach for palaeoenvironmental and palaeoclimatic reconstructions, conducted on sediment cores, compared with summer insolation and Greenland ice core δ18O data in order to establish a framework for climate changes from Late Pleistocene to late Holocene. Our dataset includes the results compiled from a sediment core, collected on the middle slope of the Kveithola Trough Mouth Fan (South of Svalbard) during the \{CORIBAR\} cruise (2013). The studied core presents remarkable lithological and magnetic susceptibility similarities with cores recovered in the same area during the \{SVAIS\} (2007) and the OGS-EGLACOM cruise (2008), allowing the construction of the age model. The results indicate that during the last 14.5 cal ky \{BP\} advances and retreats of the Svalbard Barents Sea Ice Sheet were strictly linked to the interplay of Atlantic and Arctic water inflows to the study area. During the deglaciation, from the Last Glacial Maximum to the onset of the Holocene, the climate underwent a series of abrupt changes including the Bølling-Allerød warm interstadial and the Younger Dryas cold event. During the early Holocene, the investigated area was dominated by enhanced warm Atlantic water inflow, which was concomitant with summer insolation increase, characterizing the Holocene Thermal Maximum. Conversely, the late Holocene was governed by deteriorating climatic conditions, with predominant Arctic/Polar water inflow on the surface water masses off Western Svalbard, possibly associated with summer insolation decline due to orbital forcing. VL - 463 UR - http://www.sciencedirect.com/science/article/pii/S0031018216305533 ER - TY - JOUR T1 - Parent material influence on soil response to vegetation change, Southeastern Minnesota, U.S.A. JF - Geoderma Y1 - 2016 A1 - Joseph A. Mason A1 - Peter M. Jacobs A1 - Kristine E. Gruley A1 - Paul Reyerson A1 - Paul R. Hanson KW - Parent material AB - Abstract Soil morphology changes dramatically across the former transition from forest to grassland in the Midwestern U.S.A. That vegetation boundary shifted as a result of Holocene climatic change and fire suppression following Euroamerican settlement, but the timescale of soil response to those vegetation changes and the factors that influence it are poorly known. On steep colluvial slopes of southeastern Minnesota, Mollisols with thick, dark A horizons typically associated with grassland are found today under deciduous forest. Soils with much thinner and/or lighter-colored A horizons occur immediately up- and downslope of the forest-covered Mollisols. Most of the soils with thick A horizons are not in topographic settings found to favor organic matter accumulation in other landscapes. Principal component analysis highlights important axes of textural and mineralogical variation among horizons of these soils, often related to parent material properties. Soils with and without thick A horizons are separated along one principal component heavily loaded by high pH, reflecting the presence of dolomite fragments in the hillslope sediment that soils with thick, dark A horizons formed in. Stable C isotope analysis reveals that the Mollisols with thick, dark A horizons under forest had C input from vegetation with abundant \{C4\} grasses in the past. Public land survey data also indicate replacement of grassland or savanna by forest since 1854 on colluvial slopes where forest-covered Mollisols occur today. We propose that the soils with thick, dark A horizons under forest today reflect a lagged response to vegetation change, from grassland or savanna to closed forest. Their thick A horizons and some C4-derived organic matter may be preserved because dolomite weathering releases abundant Ca++ and Mg++ that favor aggregation and organic matter stabilization. Soils with thin A horizons just up- or downslope may also have formed partly under grasses, but have responded more quickly and/or more substantially to vegetation change. VL - 275 UR - http://www.sciencedirect.com/science/article/pii/S0016706116301513 ER - TY - JOUR T1 - Plankton biochronology for the last 772,000 years from the western South Atlantic Ocean JF - Marine Micropaleontology Y1 - 2016 A1 - Felipe A.L. Toledo A1 - Juliana P. Quadros A1 - Edmundo Camillo Jr. A1 - Ana Cláudia A. Santarosa A1 - José-Abel Flores A1 - Karen B. Costa KW - Biochronology AB - Abstract Calcareous microfossils have potential in the biostratigraphy of Pleistocene sediments and a clear relationship with paleoceanographic studies. Conversely, there are few quantitative biostratigraphic studies of chronologically-tuned events or sections in the western South Atlantic. In order to improve the stratigraphical framework for South Atlantic paleoceanographic studies, the present work attempts to review the last 772,000 years by carrying out a quantitative analysis of the calcareous nannofossil and planktonic foraminiferal assemblages by comparing them with a high resolution marine isotopic record (δ18O). This work is based on the analysis of two piston cores obtained from the continental slope of the Santos Basin in the Santos Drift, southeastern Brazilian Continental Margin. Twelve Pleistocene calcareous nannofossil events and twenty planktonic foraminifera events calibrated with oxygen isotopes and correlated with literature stratigraphies are discussed. This is the first calcareous plankton biochronology study for the last 772 kyr in the western South Atlantic Ocean. More studies in this region will help to establish a more precise biochronology for these calcareous microfossils. This study also presents six new biostratigraphic events of isotopically-caibrated planktonic foraminifera which can be used as markers in the western South Atlantic. VL - 127 UR - http://www.sciencedirect.com/science/article/pii/S0377839816300561 ER - TY - JOUR T1 - Prehistoric human responses to volcanic tephra fall events in the Ust-Kamchatsk region, Kamchatka Peninsula (Kamchatsky Krai, Russian Federation) during the middle to late Holocene (6000–500 cal BP) JF - Quaternary International Y1 - 2016 A1 - I. Florin Pendea A1 - Hans Harmsen A1 - Dustin Keeler A1 - Ezra B.W. Zubrow A1 - Gregory Korosec A1 - Erika Ruhl A1 - Irina Ponkratova A1 - Eva Hulse KW - Tephra AB - Abstract Prehistoric peoples in Kamchatka coped with recurrent volcanic tephra fall events during the middle to late Holocene. Recent data collected by the International Collaborative Circumpolar Archaeological Project (ICAAP) between 2009 and 2011 explores the long-term relationships between drastic landscape change and concomitant human response. A combination of new archaeological, paleoenvironmental and tephrochronological data demonstrate how the major Ksudach 1750 cal BP (KS1) eruption accelerated settlement relocation from the interior to the paleo-coastline. VL - 394 UR - http://www.sciencedirect.com/science/article/pii/S1040618215007090 N1 - Volcanic Activity and Human Society ER - TY - JOUR T1 - RAPID C-14 ANALYSIS OF DISSOLVED ORGANIC CARBON IN NON-SALINE WATERS JF - RADIOCARBON Y1 - 2016 A1 - Lang, Susan Q. A1 - McIntyre, Cameron P. A1 - Bernasconi, Stefano M. A1 - Fruh-Green, Gretchen L. A1 - Voss, Britta M. A1 - Eglinton, Timothy I. A1 - Wacker, Lukas KW - carbon-cycling KW - dissolved organic carbon KW - method development KW - wet chemical oxidation AB - The radiocarbon content of dissolved organic carbon (DOC) in rivers, lakes, and other non-saline waters can provide valuable information on carbon cycling dynamics in the environment. DOC is typically prepared for C-14 analysis by accelerator mass spectrometry (AMS) either by ultraviolet (UV) oxidation or by freeze-drying and sealed tube combustion. We present here a new method for the rapid analysis of C-14 of DOC using wet chemical oxidation (WCO) and automated headspace sampling of CO2. The approach is an adaption of recently developed methods using aqueous persulfate oxidant to determine the delta C-13 of DOC in non-saline water samples and the C-14 content of volatile organic acids. One advantage of the current method over UV oxidation is higher throughput: 22 samples and 10 processing standards can be prepared in one day and analyzed in a second day, allowing a full suite of C-14 processing standards and blanks to be run in conjunction with samples. A second advantage is that there is less potential for cross-contamination between samples. VL - 58 ER - TY - JOUR T1 - Rapid extraction of dissolved inorganic carbon from seawater and groundwater samples for radiocarbon dating JF - LIMNOLOGY AND OCEANOGRAPHY-METHODS Y1 - 2016 A1 - Gospodinova, K. A1 - McNichol, A. P. A1 - Gagnon, A. A1 - Walter, S. R. Shah AB - We designed and developed a system to efficiently extract dissolved inorganic carbon (DIC) from seawater and groundwater samples for radiocarbon dating. The Rapid Extraction of Dissolved Inorganic Carbon System (REDICS) utilizes a gas-permeable polymer membrane contactor to extract the DIC from an acidified water sample in the form of carbon dioxide (CO2), introduce it to a helium gas stream, cryogenically isolate it, and store it for stable and radiocarbon isotope analysis. The REDICS system offers multiple advantages to the DIC extraction method which has been used for the last several decades at the National Ocean Sciences Accelerator Mass Spectrometry Facility (NOSAMS) at the Woods Hole Oceanographic Institution, including faster DIC extraction, streamlined analysis, and minimized set-up and prep time. The system was tested using sodium carbonate and seawater standards, duplicates of which were also processed on the water stripping line (WSL) at NOSAMS. The results demonstrate that the system successfully extracts, quantifies, and stores more than 99% of the DIC in less than 20 min. Stable and radiocarbon isotope analysis demonstrated system precision of 0.04 parts per thousand and 7.8 parts per thousand, respectively. A Sargasso Sea depth profile was used to further validate the system. The results show high precision for both stable and radiocarbon analysis with pooled standard deviations of 0.02 parts per thousand and 5.6 parts per thousand, respectively. A comparison between the REDICS and WSL analyses indicates a good accuracy for both stable and radio-isotope analysis. VL - 14 ER - TY - JOUR T1 - Recent and Holocene climate change controls on vegetation and carbon accumulation in Alaskan coastal muskegs JF - Quaternary Science Reviews Y1 - 2016 A1 - Dorothy M. Peteet A1 - Jonathan E. Nichols A1 - Christopher M. Moy A1 - Alicia McGeachy A1 - Max Perez KW - Alnus AB - Abstract Pollen, spore, macrofossil and carbon data from a peatland near Cordova, Alaska, reveal insights into the climate–vegetation–carbon interactions from the initiation of the Holocene, c. the last 11.5 ka, to the present (1 ka = 1000 calibrated years before present where 0 = 1950 CE). The Holocene period is characterized by early deposition of gyttja in a pond environment with aquatics such as Nuphar polysepalum and Potamogeton, and a significant regional presence of Alnus crispa subsp. sinuata. Carbon accumulation (50 g/m2/a) was high for a short interval in the early Holocene when Sphagnum peat accumulated, but was followed by a major decline to 13 g/m2/a from 7 to 3.7 ka when Cyperaceae and ericads such as Rhododendron (formerly Ledum) groenlandicum expanded. This shift to sedge growth is representative of many peatlands throughout the south-central region of Alaska, and indicates a drier, more evaporative environment with a large decline in carbon storage. The subsequent return to Sphagnum peat after 4 ka in the Neoglacial represents a widespread shift to moister, cooler conditions, which favored a resurgence of ericads, such as Andromeda polifolia, and increased carbon accumulation rate. The sustained Alnus expansion visible in the top 10 cm of the peat profile is correlative with glacial retreat and warming of the region in the last century, and suggests this colonization will continue as temperature increases and ice melts. VL - 131, Part A UR - http://www.sciencedirect.com/science/article/pii/S0277379115301530 ER - TY - JOUR T1 - Records of continental slope sediment flow morphodynamic responses to gradient and active faulting from integrated AUV and ROV data, offshore Palos Verdes, southern California Borderland JF - Marine Geology Y1 - 2016 A1 - Katherine L. Maier A1 - Daniel S. Brothers A1 - Charles K. Paull A1 - Mary McGann A1 - David W. Caress A1 - James E. Conrad KW - Fault AB - Abstract Variations in seabed gradient are widely acknowledged to influence deep-water deposition, but are often difficult to measure in sufficient detail from both modern and ancient examples. On the continental slope offshore Los Angeles, California, autonomous underwater vehicle, remotely operated vehicle, and shipboard methods were used to collect a dense grid of high-resolution multibeam bathymetry, chirp sub-bottom profiles, and targeted sediment core samples that demonstrate the influence of seafloor gradient on sediment accumulation, depositional environment, grain size of deposits, and seafloor morphology. In this setting, restraining and releasing bends along the active right-lateral Palos Verdes Fault create and maintain variations in seafloor gradient. Holocene down-slope flows appear to have been generated by slope failure, primarily on the uppermost slope (  100–200 m water depth). Turbidity currents created a low relief (< 10 m) channel, up-slope migrating sediment waves (λ =   100 m, h ≤ 2 m), and a series of depocenters that have accumulated up to 4 m of Holocene sediment. Sediment waves increase in wavelength and decrease in wave height with decreasing gradient. Integrated analysis of high-resolution datasets provides quantification of morphodynamic sensitivity to seafloor gradients acting throughout deep-water depositional systems. These results help to bridge gaps in scale between existing deep-sea and experimental datasets and may provide constraints for future numerical modeling studies. UR - http://www.sciencedirect.com/science/article/pii/S0025322716302304 ER - TY - JOUR T1 - Relative sea-level change in northeastern Florida (USA) during the last ∼8.0 ka JF - Quaternary Science Reviews Y1 - 2016 A1 - Hawkes, Andrea D. A1 - Kemp, Andrew C. A1 - Donnelly, Jeffrey P. A1 - Horton, Benjamin P. A1 - Peltier, W. Richard A1 - Cahill, Niamh A1 - Hill, David F. A1 - Ashe, Erica A1 - Alexander, Clark R. KW - Foraminifera KW - Georgia KW - Holocene KW - Salt marsh KW - St. Marys River AB - An existing database of relative sea-level (RSL) reconstructions from the U.S. Atlantic coast lacked valid sea-level index points from Georgia and Florida. This region lies on the edge of the collapsing forebulge of the former Laurentide Ice Sheet making it an important location for understanding glacio-isostatic adjustment and the history of ice-sheet melt. To address the paucity of data, we reconstruct RSL in northeastern Florida (St. Marys) over the last ∼8.0 ka from samples of basal salt-marsh sediment that minimize the influence of compaction. The analogy between modern salt-marsh foraminifera and their fossil counterparts preserved in the sedimentary record was used to estimate paleomarsh surface elevation. Sample ages were determined by radiocarbon dating of identifiable and in-situ plant macrofossils. This approach yielded 25 new sea-level index points that constrain a ∼5.7 m rise in RSL during the last ∼8.0 ka. The record shows that no highstand in sea level occurred in this region over the period of the reconstruction. We compared the new reconstruction to Earth-ice models ICE 6G-C VM5a and ICE 6G-C VM6. There is good fit in the later part of the Holocene with VM5a and for a brief time in the earlier Holocene with VM6. However, there are discrepancies in model-reconstruction fit in the early to mid Holocene in northeastern Florida and elsewhere along the Atlantic coast at locations with early Holocene RSL reconstructions. The most pronounced feature of the new reconstruction is a slow down in the rate of RSL rise from approximately 5.0 to 3.0 ka. This trend may reflect a significant contribution from local-scale processes such as tidal-range change and/or change in base flow of the St. Marys River in response to paleoclimate changes. However, the spatial expression (local vs. regional) of this slow down is undetermined and corroborative records are needed to establish its geographical extent. VL - 142 UR - http://linkinghub.elsevier.com/retrieve/pii/S0277379116301275http://api.elsevier.com/content/article/PII:S0277379116301275?httpAccept=text/xmlhttp://api.elsevier.com/content/article/PII:S0277379116301275?httpAccept=text/plain ER - TY - JOUR T1 - Revisiting the resilience of Late Archaic hunter-gatherers along the Georgia coast JF - Journal of Anthropological Archaeology Y1 - 2016 A1 - John A. Turck A1 - Victor D. Thompson KW - Archaic AB - Abstract This paper addresses fisher-hunter-gatherer settlement and subsistence variability of the Georgia Coast during the Archaic-Woodland transition, framed within ideas derived from Resilience Theory, and focusing on systemic shifts, or “collapse.” A critical examination of these shifts is needed to understand how communities experience change differentially, which in turn can lead to differential community resilience. Analysis of site file and radiocarbon date databases, as well as Bayesian modeling on a subset of dates, was performed at multiple scales and within distinct micro-environmental habitats. Results indicate that as sea levels dropped, there was continuity in Late Archaic occupation within deltaic areas of the coast, with intensive shellfishing occurring earlier (∼5000 cal. BP) and lasting longer (∼3500 cal. BP). In certain habitats, occupation may have continued into the following Early Woodland period. In non-deltaic areas, shellfishing occurs between 4500 and 3800 cal. BP, followed by subsistence changes and population movement. However, some of the post-3800 cal. \{BP\} occupations were fairly substantial. This differential experience of change between deltaic and non-deltaic areas was not accompanied by collapse: both areas had resilient communities. We conclude that inter-village relationships developed during the early Late Archaic period continued into the terminal portion, leading to resilience in the face of change. VL - 43 UR - http://www.sciencedirect.com/science/article/pii/S0278416516300460 ER - TY - JOUR T1 - Scale dependence of environmental and physiological correlates of δ18O and δ13C in the magnesium calcite skeletons of bamboo corals (Gorgonacea; Isididae) JF - Geochimica et Cosmochimica Acta Y1 - 2016 A1 - Ronald E. Thresher A1 - Helen Neil KW - Temperature AB - Abstract We examine in detail δ18O and δ13C in the calcite internodes of bamboo corals as potential proxies of physiological and environmental variability, through (a) a “core top” calibration that includes specimens from a wide range of habitats and environmental conditions and (b) a comparison of high resolution serial point analyses along radial growth axes of a sub-set of specimens with each other, with instrumental temperature and salinity records, with growth rates and with a nominal skeletal proxy for temperature (Mg/Ca) in the same specimens. At the whole-of-specimen level, δ18O and the intercept of the strong within-specimen regression of δ18O against δ13C correlates highly with ambient temperatures at slopes that are identical to those reported for other marine biogenic carbonates (−0.22 per °C). δ13C varies predominantly with apparent specimen-mean growth rate. It also correlates with the slope of the within-specimen covariance between δ18O and δ13C, which in turn is distributed bi-modally among specimens and linked to differences in apparent growth rates. Within-specimens, variability in δ13C, and to a lesser extent δ18O, correlates between specimens collected in the same region and differs between regions, implying an environmental effect, but the factors involved for either isotope ratio are unclear. Correlations between δ18O and temperature (and Mg/Ca) range from positive to negative among specimens and appear to vary over time even within specimens. The mismatch between the consistent temperature-dependence of δ18O at the whole-of-specimen level and the mixed relationship within-specimens can be reconciled by assuming an unknown temperature-dependent factor affecting δ18O during the growth of Isidid calcite. The contrast between the results of the “core top” temperature calibration for δ18O, which are consistent with studies of other carbonates, and the apparently more complex suite of factors affecting both δ13C and δ18O within specimens strongly suggests that calibrations based on a “core top” approach be applied cautiously to environmental reconstructions based on variations of a nominal proxy within specimens. VL - 187 UR - http://www.sciencedirect.com/science/article/pii/S0016703716302678 ER - TY - JOUR T1 - Seasonal variability of stable carbon isotopes (δ13CDIC) in the Skagerrak and the Baltic Sea: Distinguishing between mixing and biological productivity JF - Palaeogeography, Palaeoclimatology, Palaeoecology Y1 - 2016 A1 - Helena L. Filipsson A1 - Daniel C. McCorkle A1 - Andreas Mackensen A1 - Joan M. Bernhard A1 - Lars S. Andersson A1 - Lars-Johan Naustvoll A1 - Angela M. Caballero-Alfonso A1 - Kjell Nordberg A1 - Didrik S. Danielssen KW - Time-series AB - Abstract We documented the annual cycle of the carbon isotopic composition of dissolved inorganic carbon (δ13CDIC) in the water columns of the Skagerrak and Baltic Sea to obtain an increased understanding of the processes involved controlling the carbon isotopic distribution in shelf seas. The lowest δ13CDIC values (− 4.9‰) were found in the low-oxygen, brackish Baltic bottom water whereas the highest values (+ 1.8‰) were observed in the surface water of the Skagerrak during late summer. Photosynthesis drove the high δ13CDIC values (between 1.0 and 1.8‰) noted in the surface waters of both the Skagerrak and the Baltic. The δ13CDIC values below the halocline in the Baltic reflect mixing of brackish water and the more saline water from the Skagerrak, and foremost organic matter remineralization processes that release significant amounts of low-δ13C CO2. Similarly, in the stagnant fjord basins, little deep water exchange and the degradation of terrestrial and marine organic matter set the δ13C composition. Deep-water renewal in the fjord basins resulted in rapid increases of the δ13CDIC on the order of 1‰, whereas remineralization processes caused a decrease in δ13CDIC of 0.1–0.3‰ per month depending on location. The combined effects of water mixing and remineralization processes (estimated using apparent oxygen utilization (AOU) values) yielded the expression: δ13CDIC = 0.032 ∗ S − 0.01 ∗ \{AOU\} − 0.12 for the Baltic – Skagerrak region at water depths below the halocline. UR - http://www.sciencedirect.com/science/article/pii/S0031018216307581 ER - TY - JOUR T1 - Sediment chronology in Antarctic deglacial sediments: Reconciling organic carbon 14 C ages to carbonate 14 C ages using Ramped PyrOx JF - The Holocene Y1 - 2016 A1 - Subt, Cristina A1 - Fangman, Kimberly A A1 - Wellner, Julia S A1 - Rosenheim, Brad E AB - We present the first study which directly compares carbonate radiocarbon (14C) dates with the Ramped PyrOx (RP) radiocarbon dating technique within a single sediment core, and we confirm the utility for the latter constructing chronologies of high latitude, Holocene marine margin sediment successions. Historically, the heavily detrital nature of Antarctic margin sedimentary organic material and lack of carbonate preservation have made these sediments difficult to date accurately. Here, we use archived cores with existing foraminiferal ages to compare with RP dates at equal or similar depth intervals. The lowest temperature RP splits were integrated over narrower intervals than in previous studies to reduce the amount of mixing with older, more thermochemically stable end-members during pyrolytic decomposition. Ages of the low-temperature RP splits coincide with their corresponding carbonate counterparts, suggesting that the RP 14C dating method is a reliable alternative to carbonate dates in sediments where carbonates are absent or not sufficiently preserved for 14C dating. The rarity of calcareous material in most Antarctic sediments often obligates the use of the bulk acid insoluble organic (AIO) fraction of the sediment, which can be problematic because of contamination by older carbon. The bulk AIO 14C ages, which are calculated using the weighted arithmetic mean of all RP splits of individual samples, show that age reversals and biases can occur using bulk AIO dates for age models because of variable proportions of pre-aged organic matter down-core. The application of the RP dating method can reduce these effects to produce a more reliable chronology that is statistically identical to the foraminiferal dating chronology. VL - 26 UR - http://journals.sagepub.com/doi/10.1177/0959683615608688 IS - 2 ER - TY - JOUR T1 - Sediment dynamics and hydrographic conditions during storm passage, Waquoit Bay, Massachusetts JF - Marine Geology Y1 - 2016 A1 - Christopher V. Maio A1 - Jeffrey P. Donnelly A1 - Richard Sullivan A1 - Stephanie M. Madsen A1 - Christopher R. Weidman A1 - Allen M. Gontz A1 - Vitalii A. Sheremet KW - Sediment transport AB - Abstract The impact of storm events on the sediment dynamics of the shallow groundwater fed estuaries of Cape Cod, Massachusetts, \{USA\} is little understood. To address this, the objectives of this study are to assess sediment dynamics during storm passage and determine whether shallow back-barrier lagoons like Waquoit Bay have the preservation potential for a sedimentary archive of hurricanes. When setting out in this study, it was unclear whether paleotempestological methods could be applied successfully to cores collected from the landward reaches of shallow estuaries of southern New England. Water level and bottom current data using Arm-and-Float tide gauges and SeaHorse Tilt Current Meters was collected during Tropical Storm Irene (2011) and coupled with storm surge modeling projections to better elucidate storm-induced sediment transport mechanisms. Three sediment cores were collected at the head of Waquoit Bay, located 2.8 km from the barrier beach. Grain size analysis of sediment cores was conducted with a laser particle size analyzer at 1 cm increments in order to identify coarse grain anomalies, which can act as a storm event proxy. Bayesian statistics were applied to develop age models of two of the cores based on three Pb pollution chronomarkers and 21 continuous flow 14C \{AMS\} ages. The results yield variable sediment accumulation rates between 2 mm/yr to 10 mm/yr, with significantly higher rates occurring in the upper 1 m of sediments. Grain size results are highly variable, and contain numerous large amplitude, short duration fluctuations suggesting that during storm passage coarse sand is deposited in the coring site. The sensitivity of the site to both tropical and extratropical storm events, uncertainties in the age model, and the multiple sediment sources and transport pathways limits the utility of using the Waquoit sediments to determine long-term hurricane frequencies. Results nonetheless provide insights into how extreme storm events impact coastal lagoons. VL - 381 UR - http://www.sciencedirect.com/science/article/pii/S0025322716301438 ER - TY - JOUR T1 - Sedimentation of particulate organic carbon on the Amundsen Shelf, Antarctica JF - Deep Sea Research Part II: Topical Studies in Oceanography Y1 - 2016 A1 - Minkyoung Kim A1 - Jeomshik Hwang A1 - Sang H. Lee A1 - Hyung J. Kim A1 - Dongseon Kim A1 - Eun J. Yang A1 - SangHoon Lee KW - Global carbon cycling AB - Abstract We examined the recent history of sedimentary organic carbon (SOC) accumulation on the western Amundsen Shelf, to help characterize the biological carbon pump in the Amundsen Sea, Antarctica. Vertical sedimentary profiles (in the upper 21-cm) of \{SOC\} content, radio- and stable-carbon isotopes were obtained at four locations in the western Amundsen Sea: near the shelf break, inside the polynya near the Dotson Ice Shelf, and at both the periphery and the center of the Amundsen Sea polynya. Profiles were representative not only of various distances from the coast, but also of various summertime sea ice conditions and bottom depths. The \{SOC\} content (up to 1.1%) and the radiocarbon content were distinctly higher at the periphery and at the center of the polynya than at the other sites. The \{SOC\} and 14C contents were generally consistent with the spatial distribution of primary productivity in the surface water. A linear \{SOC\} accumulation rate of about 1.0 g C m−2 yr−1 was determined from the conventional 14C ages of bulk \{SOC\} below the surface mixed layer at the periphery and at the center of the polynya, for the time period of 3.1–4.7 kyr before present (BP). This linear \{SOC\} accumulation rate was about 20 times greater than the rates determined at the two other sites for the period of 4.6–15.7 kyr BP. Note that all values are for uncorrected 14C ages. At the center of the polynya, a sudden change in \{SOC\} accumulation rate was observed at about 16 cm depth, corresponding to 4.7 kyr BP, implying that changes (during this time period) in physical environments greatly affected primary production, \{SOC\} burial and/or supply of allochthonous particles to this site. The vertical distribution of 14C content in the sediments implies that aged organic matter, likely associated with resuspended sediments, was also being deposited inside the polynya, in addition to autochthonous biogenic particles. If our estimation of \{SOC\} accumulation is extrapolated to the western Amundsen Shelf between 110°W and 120°W, approximately 3×1010 g C yr−1 is buried on the shelf, with  90% of \{SOC\} accumulation occurring in the Amundsen Sea polynya. VL - 123 UR - http://www.sciencedirect.com/science/article/pii/S0967064515002787 N1 - International efforts to understanding of the changing Antarctic climate: The \{KOPRI\} expedition to the Amundsen Sea ER - TY - JOUR T1 - Sedimentation, stratigraphy and physical properties of sediment on the Juan de Fuca Ridge JF - Marine Geology Y1 - 2016 A1 - K.M. Costa A1 - J.F. McManus A1 - B. Boulahanis A1 - S.M. Carbotte A1 - G. Winckler A1 - P.J. Huybers A1 - C.H. Langmuir KW - Oxygen isotope stratigraphy AB - Abstract Sedimentation near mid-ocean ridges may differ from pelagic sedimentation due to the influence of the ridges' rough topography on sediment deposition and transport. This study explores whether the near-ridge environment responds to glacial-interglacial changes in climate and oceanography. New benthic δ18O, radiocarbon, multi-sensor track, and physical property (sedimentation rates, density, magnetic susceptibility) data for seven cores on the Juan de Fuca Ridge provide multiple records covering the past 700,000 years of oceanographic history of the Northeast Pacific Ocean. Systematic variations in sediment density and coarse fraction correspond to glacial-interglacial cycles identified in benthic δ18O, and these observations may provide a framework for mapping the δ18O chronostratigraphy via sediment density to other locations on the Juan de Fuca Ridge and beyond. Sedimentation rates generally range from 0.5 to 3 cm/kyr, with background pelagic sedimentation rates close to 1 cm/kyr. Variability in sedimentation rates close to the ridge likely reflects remobilization of sediment caused by the high relief of the ridge bathymetry. Sedimentation patterns primarily reflect divergence of sedimentation rates with distance from the ridge axis and glacial-interglacial variation in sedimentation that may reflect carbonate preservation cycles as well as preferential remobilization of fine material. VL - 380 UR - http://www.sciencedirect.com/science/article/pii/S0025322716301517 ER - TY - JOUR T1 - Seismic evidence of glacial-age river incision into the Tahaa barrier reef, French Polynesia JF - Marine Geology Y1 - 2016 A1 - Michael R. Toomey A1 - Jonathan D. Woodruff A1 - Jeffrey P. Donnelly A1 - Andrew D. Ashton A1 - J. Taylor Perron KW - Morphology AB - Abstract Rivers have long been recognized for their ability to shape reef-bound volcanic islands. On the time-scale of glacial–interglacial sea-level cycles, fluvial incision of exposed barrier reef lagoons may compete with constructional coral growth to shape the coastal geomorphology of ocean islands. However, overprinting of Pleistocene landscapes by Holocene erosion or sedimentation has largely obscured the role lowstand river incision may have played in developing the deep lagoons typical of modern barrier reefs. Here we use high-resolution seismic imagery and core stratigraphy to examine how erosion and/or deposition by upland drainage networks has shaped coastal morphology on Tahaa, a barrier reef-bound island located along the Society Islands hotspot chain in French Polynesia. At Tahaa, we find that many channels, incised into the lagoon floor during Pleistocene sea-level lowstands, are located near the mouths of upstream terrestrial drainages. Steeper antecedent topography appears to have enhanced lowstand fluvial erosion along Tahaa's southwestern coast and maintained a deep pass. During highstands, upland drainages appear to contribute little sediment to refilling accommodation space in the lagoon. Rather, the flushing of fine carbonate sediment out of incised fluvial channels by storms and currents appears to have limited lagoonal infilling and further reinforced development of deep barrier reef lagoons during periods of highstand submersion. VL - 380 UR - http://www.sciencedirect.com/science/article/pii/S0025322716300548 ER - TY - JOUR T1 - The sources of atmospheric black carbon at a European gateway to the Arctic JF - Nature Communications Y1 - 2016 A1 - Winiger, P A1 - Andersson, A A1 - Eckhardt, S A1 - Stohl, A A1 - Gustafsson, O. AB - Black carbon (BC) aerosols from incomplete combustion of biomass and fossil fuel contribute to Arctic climate warming. Models—seeking to advise mitigation policy—are challenged in reproducing observations of seasonally varying BC concentrations in the Arctic air. Here we compare year-round observations of BC and its δ13C/Δ14C-diagnosed sources in Arctic Scandinavia, with tailored simulations from an atmospheric transport model. The model predictions for this European gateway to the Arctic are greatly improved when the emission inventory of anthropogenic sources is amended by satellite-derived estimates of BC emissions from fires. Both BC concentrations (R2=0.89, P<0.05) and source contributions (R2=0.77, P<0.05) are accurately mimicked and linked to predominantly European emissions. This improved model skill allows for more accurate assessment of sources and effects of BC in the Arctic, and a more credible scientific underpinning of policy efforts aimed at efficiently reducing BC emissions reaching the European Arctic. VL - 7 UR - http://www.nature.com/doifinder/10.1038/ncomms12776 ER - TY - JOUR T1 - South Pacific hydrologic and cyclone variability during the last 3000 years JF - Paleoceanography Y1 - 2016 A1 - Toomey, Michael R. A1 - Donnelly, Jeffrey P. A1 - Tierney, Jessica E. AB - Major excursions in the position of the South Pacific Convergence Zone (SPCZ) and/or changes in its intensity are thought to drive tropical cyclone (TC) and precipitation variability across much of the central South Pacific. A lack of conventional sites typically used for multimillennial proxy reconstructions has limited efforts to extend observational rainfall/TC data sets and our ability to fully assess the risks posed to central Pacific islands by future changes in fresh water availability or the frequency of storm landfalls. Here we use the sedimentary record of Apu Bay, offshore the island of Tahaa, French Polynesia, to explore the relationship between SPCZ position/intensity and tropical cyclone overwash, resolved at decadal time scales, since 3200 years B.P. Changes in orbital precession and Pacific sea surface temperatures best explain evidence for a coordinated pattern of rainfall variability at Tahaa and across the Pacific over the late Holocene. Our companion record of tropical cyclone activity from Tahaa suggests major storm activity was higher between 2600-1500 years B.P., when decadal scale SPCZ variability may also have been stronger. A transition to lower storm frequency and a shift or expansion of the SPCZ toward French Polynesia around 1000 years B.P. may have prompted Polynesian migration into the central Pacific. VL - 31 UR - http://doi.wiley.com/10.1002/2015PA002870 IS - 4 ER - TY - JOUR T1 - Stability of peatland carbon to rising temperatures JF - Nature Communications Y1 - 2016 A1 - Wilson, R. M. A1 - Hopple, A. M. A1 - Tfaily, M. M. A1 - Sebestyen, S. D. A1 - Schadt, C. W. A1 - Pfeifer-Meister, L. A1 - Medvedeff, C. A1 - McFarlane, K. J. A1 - Kostka, J. E. A1 - Kolton, M. A1 - Kolka, R.K. A1 - Kluber, L. A. A1 - Keller, J. K. A1 - Guilderson, T. P. A1 - Griffiths, N. A. A1 - Chanton, J. P. A1 - Bridgham, S. D. A1 - Hanson, P. J. AB - Peatlands contain one-third of soil carbon (C), mostly buried in deep, saturated anoxic zones (catotelm). The response of catotelm C to climate forcing is uncertain, because prior experiments have focused on surface warming. We show that deep peat heating of a 2 m-thick peat column results in an exponential increase in CH4 emissions. However, this response is due solely to surface processes and not degradation of catotelm peat. Incubations show that only the top 20–30 cm of peat from experimental plots have higher CH4 production rates at elevated temperatures. Radiocarbon analyses demonstrate that CH4 and CO2 are produced primarily from decomposition of surface-derived modern photosynthate, not catotelm C. There are no differences in microbial abundances, dissolved organic matter concentrations or degradative enzyme activities among treatments. These results suggest that although surface peat will respond to increasing temperature, the large reservoir of catotelm C is stable under current anoxic conditions. VL - 7 UR - http://www.nature.com/doifinder/10.1038/ncomms13723 ER - TY - JOUR T1 - Stratigraphy, morphology, and geochemistry of late Quaternary buried soils on the High Plains of southwestern Kansas, USA JF - CATENA Y1 - 2016 A1 - Anthony L. Layzell A1 - Rolfe D. Mandel A1 - Tammy M. Rittenour A1 - Jon J. Smith A1 - R. Hunter Harlow A1 - Greg A. Ludvigson KW - Sangamon soil AB - Abstract This study investigated two stratigraphic sequences that record the complex interplay of sedimentation and pedogenesis over the past ca. 84 ka on the High Plains of southwestern Kansas. Up to eight eolian sand and loess units with associated soils were identified in two cores collected from an upland setting. Soil morphological and geochemical data were used to quantitatively assess and compare soil development between multiple buried soils. Chronostratigraphic relationships indicate that 1) loess and eolian sands were episodically deposited during late Marine Isotope Stage (MIS) 5 (ca. 84–70 ka), 2) the Sangamon soil at this site formed between \{MIS\} 3/4 (ca. 70–52 ka), which is consistent with age estimates for renewed Sangamon pedogenesis in the Mississippi River valley, and 3) soil development in the Gilman Canyon Formation began at ca. 44 ka and continued until at least 29.2 ka. Multiple lines of evidence, including grain-size distributions, structure, clay content, and chemical weathering index data, indicate that the morphology and chemistry of the Ak horizon developed in the Gilman Canyon Formation is a product of cumulization by slow loess additions. Similar evidence suggests that cumulization processes are also responsible for the morphology and chemistry of other buried soils in the stratigraphic sequence. Overall, loess inputs during pedogenesis complicate the quantification of weathering processes in these soils. VL - 144 UR - http://www.sciencedirect.com/science/article/pii/S0341816216301655 ER - TY - JOUR T1 - Subsurface Evidence of Storm-Driven Breaching along a Transgressing Barrier System, Cape Cod, U.S.A. JF - Journal of Coastal Research Y1 - 2016 A1 - Maio, Christopher V. A1 - Gontz, Allen M. A1 - Sullivan, Richard M. A1 - Madsen, Stephanie M. A1 - Weidman, Christopher R. A1 - Donnelly, Jeffrey P. KW - coastal change KW - Coastal evolution KW - ground-penetrating radar KW - marine transgression KW - overwash KW - paleochannel KW - paleogeography KW - South Cape Beach AB - Relict and historic tidal channels buried within coastal barriers provide a geologic signature of environmental change, thus enhancing our understanding of how barrier systems respond to extreme storm events. Earliest maps from 1846 depict three inlets along the Waquoit Bay barrier system located on Cape Cod, Massachusetts. These channels were not depicted on maps after 1846, and we lack any information pertaining to them before 1846. The principle objective of this study was to identify the location and map the internal geometry and channel-fill configuration of the buried inlet structures using geophysical and sedimentological data acquisition methods. This was done by collecting 6.2 km of shore-parallel ground-penetrating radar data and five sediment cores ranging in depth from 4 to 5 m. The sediment cores allowed for the ground truthing of the ground-penetrating radar data and provided six samples for radiocarbon dating. The 13 paleochannels identified ranged in depths from 1.3 to 3.7 m below the present beach surface. These appeared in the radar imagery as broad U-shaped cut-and-fill features incised into adjacent barrier facies. The 13 paleochannels composed 24% of the barrier lithosome totaling 704 m in length. Individual channels were primarily less than 65 m in length and between 2.5 and 1.3 m in depth, although an additional 275-m-wide, 3.7-m-deep channel sequence was imaged and likely represents a major and long-lived paleochannel. The results will contribute toward deciphering the evolution of the Waquoit system and identify areas vulnerable to storm-driven coastal change. VL - 318 UR - https://doi.org/10.2112/JCOASTRES-D-14-00109.1 IS - 2 ER - TY - JOUR T1 - Time in tortoiseshell: a bomb radiocarbon-validated chronology in sea turtle scutes JF - Proceedings of the Royal Society of London B: Biological Sciences Y1 - 2016 A1 - Van Houtan, K. S. A1 - Andrews, A. H. A1 - Jones, T. T. A1 - Murakawa, S. K. K. A1 - Hagemann, M. E. AB - Some of the most basic questions of sea turtle life history are also the most elusive. Many uncertainties surround lifespan, growth rates, maturity and spatial structure, yet these are critical factors in assessing population status. Here we examine the keratinized hard tissues of the hawksbill (Eretmochelys imbricata) carapace and use bomb radiocarbon dating to estimate growth and maturity. Scutes have an established dietary record, yet the large keratin deposits of hawksbills evoke a reliable chronology. We sectioned, polished and imaged posterior marginal scutes from 36 individual hawksbills representing all life stages, several Pacific populations and spanning eight decades. We counted the apparent growth lines, microsampled along growth contours and calibrated Δ14C values to reference coral series. We fit von Bertalanffy growth function (VBGF) models to the results, producing a range of age estimates for each turtle. We find Hawaii hawksbills deposit eight growth lines annually (range 5–14), with model ensembles producing a somatic growth parameter (k) of 0.13 (range 0.1–0.2) and first breeding at 29 years (range 23–36). Recent bomb radiocarbon values also suggest declining trophic status. Together, our results may reflect long-term changes in the benthic community structure of Hawaii reefs, and possibly shed light on the critical population status for Hawaii hawksbills. VL - 283 UR - https://www.ncbi.nlm.nih.gov/pubmed/26740617 IS - 1822 N1 - Van Houtan, Kyle SAndrews, Allen HJones, T ToddMurakawa, Shawn K KHagemann, Molly EengResearch Support, U.S. Gov't, Non-P.H.S.England2016/01/08 06:00Proc Biol Sci. 2016 Jan 13;283(1822). pii: 20152220. doi: 10.1098/rspb.2015.2220. U2 - PMC4721088 JO - Time in tortoiseshell: a bomb radiocarbon-validated chronology in sea turtle scutes ER - TY - JOUR T1 - Tracing subarctic Pacific water masses with benthic foraminiferal stable isotopes during the \{LGM\} and late Pleistocene JF - Deep Sea Research Part II: Topical Studies in Oceanography Y1 - 2016 A1 - Mea S. Cook A1 - A. Christina Ravelo A1 - Alan Mix A1 - Ian M. Nesbitt A1 - Nari V. Miller KW - Ocean circulation AB - Abstract As the largest ocean basin, the Pacific helps to set the global climate state, since its circulation affects mean ocean properties, air–sea partitioning of carbon dioxide, and the distribution of global oceanic poleward heat transport. There is evidence that during the Last Glacial Maximum (LGM) the subarctic Pacific contained a better-ventilated, relatively fresh intermediate water mass above  2000 m that may have formed locally. The source and spatial extent of this water mass is not known, nor do we know how formation of this water mass varied during Pleistocene glaciations with different orbital and ice sheet boundary conditions. Here we present a 0.5 My multi-species benthic stable isotope record from Site \{U1345\} (1008 m) on the northern Bering slope and a 1.0 My record from \{U1339\} (1868 m) from the Umnak Plateau in the southeastern basin. We find that the relatively well-ventilated low-δ18O intermediate water reaches 1000 m in the Bering Sea during MIS2, but that the hydrographic divide between this water mass and poorly-ventilated deep water was shallower than 1000 m for earlier glaciations. We also compare Bering Sea piston core and İODP\} Expedition 323 Uvigerina data from the Holocene and \{LGM\} with the modern hydrography, and to previously published profiles from the Okhotsk Sea and Emperor Seamounts. We find that the carbon and oxygen stable isotope signatures of well-ventilated water in the Bering and Okhotsk Seas are distinct, suggesting that there may have been intermediate water formation in both basins during the LGM. VL - 125–126 UR - http://www.sciencedirect.com/science/article/pii/S0967064516300157 N1 - Plio-Pleistocene Paleoceanography of the Bering Sea ER - TY - JOUR T1 - Tracing the intrusion of fossil carbon into coastal Louisiana macrofauna using natural 14C and 13C abundances JF - Deep Sea Research Part II: Topical Studies in Oceanography Y1 - 2016 A1 - Wilson, Rachel M. A1 - Cherrier, Jennifer A1 - Sarkodee-Adoo, Judith A1 - Bosman, Samantha A1 - Mickle, Alejandra A1 - Chanton, Jeffrey P. AB - The Deepwater Horizon oil spill released a large volume of 13C and radiocarbon depleted organic matter to the northern Gulf of Mexico. Evidence of petroleum-derived carbon entering the offshore planktonic foodweb, as well as widespread oiling of coastal areas documented in previous studies suggests that hydrocarbons could have entered the near shore foodweb. To test this hypothesis, we measured radiocarbon (Δ14C%) and stable carbon isotopes (δ13C) in an assortment of fish tissue, invertebrate tissue and shell samples collected within a year of the spill at seven sites from Louisiana to Florida USA across the northern Gulf of Mexico. We observed a west–east gradient with the most depleted radiocarbon values found in Terrebonne Bay, Louisana and increasingly enriched radiocarbon values in organisms collected at sites to the east. Depleted radiocarbon values as low as −10% in invertebrate soft tissue from Terrebonne suggest assimilation of fossil carbon (2.8±1.2%), consistent with the hypothesis that organic matter from petrochemical reservoirs released during the Deepwater Horizon spill entered the coastal food web to a limited extent. Further there was a significant correlation between radiocarbon and δ13C values in invertebrate tissue consistent with this hypothesis. Both oyster tissue and hard head catfish tissue collected in impacted areas of coastal Louisiana were significantly depleted in 14C and 13C relative to organisms collected in the unaffected Apalachicola Bay, Florida (p<0.014). Alternative explanations for these results include the influence of chronic hydrocarbon pollution along the western gulf coast or that the organisms ingest carbon derived from 14C depleted organic matter mobilized during the erosion of coastal marshes in southern Louisiana. VL - 129 JO - Tracing the intrusion of fossil carbon into coastal Louisiana macrofauna using natural 14C and 13C abundances ER - TY - JOUR T1 - Triennial changes in groundwater quality in aquifers used for public supply in California: utility as indicators of temporal trends JF - Environmental Monitoring and Assessment Y1 - 2016 A1 - Kent, Robert A1 - Landon, Matthew K. KW - California groundwater KW - Public supply wells KW - Trend analysis KW - Water-quality monitoring AB - From 2004 to 2011, the U.S. Geological Survey collected samples from 1686 wells across the State of California as part of the California State Water Resources Control Board's Groundwater Ambient Monitoring and Assessment (GAMA) Priority Basin Project (PBP). From 2007 to 2013, 224 of these wells were resampled to assess temporal trends in water quality. The samples were analyzed for 216 water-quality constituents, including inorganic and organic compounds as well as isotopic tracers. The resampled wells were grouped into five hydrogeologic zones. A nonparametric hypothesis test was used to test the differences between initial sampling and resampling results to evaluate possible step trends in water-quality, statewide, and within each hydrogeologic zone. The hypothesis tests were performed on the 79 constituents that were detected in more than 5 % of the samples collected during either sampling period in at least one hydrogeologic zone. Step trends were detected for 17 constituents. Increasing trends were detected for alkalinity, aluminum, beryllium, boron, lithium, orthophosphate, perchlorate, sodium, and specific conductance. Decreasing trends were detected for atrazine, cobalt, dissolved oxygen, lead, nickel, pH, simazine, and tritium. Tritium was expected to decrease due to decreasing values in precipitation, and the detection of decreases indicates that the method is capable of resolving temporal trends. VL - 188 SN - 0167-6369 UR - https://www.proquest.com/docview/1827073834/abstract/EBEC8C6301DE4049PQ/1 IS - 11 ER - TY - JOUR T1 - Twenty-five-year longevity of European hake (Merluccius merluccius) from novel use of bomb radiocarbon dating in the Mediterranean Sea JF - Marine and Freshwater Research Y1 - 2016 A1 - Vitale, Sergio A1 - Andrews, Allen H. A1 - Rizzo, Pietro A1 - Gancitano, Salvatore A1 - Fiorentino, Fabio KW - Age validation KW - Carbon-14 KW - growth KW - lifespan KW - Merlucciidae AB - The high variability of growth and longevity estimates for European hake (Merluccius merluccius) reflects the existence of two opposing hypotheses on growth rates that differ by a factor of 2: (1) a fast-growing hypothesis (FGH) with a maximum age near 15 years; and (2) a slow-growing hypothesis (SGH) with a maximum age near 30 years. A recently established regional radiocarbon (14C) reference led to a first-time application of bomb 14C dating in the Mediterranean Sea to three of the largest-sized and potentially oldest-catch female European hake. Because age reading of otoliths is very subjective and poorly defined, these fish were aged blind with bomb radiocarbon (14C) dating as an independent estimate of validated age. The validated ages were compared with the theoretical maximum ages from the most reliable FGH and SGH von Bertalanffy growth functions. Among the three bomb 14C ages, the most diagnostic length-at-age was an alignment with the bomb 14C rise period for two of the three fish, providing validated ages of 22 years (74.5-cm total length) and 25 years (88-cm total length). The results provide estimates of length-at-age that are in agreement with the SGH and cannot be accounted for by the FGH. VL - 67 UR - https://doi.org/10.1071/MF15376 IS - 7 ER - TY - JOUR T1 - Two black carbon pools transported by the Changjiang and Huanghe Rivers in China JF - GLOBAL BIOGEOCHEMICAL CYCLES Y1 - 2016 A1 - Wang, Xuchen A1 - Xu, Caili A1 - Druffel, Ellen M. A1 - Xue, Yuejun A1 - Qi, Yuanzhi AB - Major rivers play important roles in transporting large amounts of terrestrial organic matter from land to the ocean each year, and the organic matter carried by rivers contains a significant fraction of black carbon (BC). A recent study estimated that 0.027 Gt of BC is transported in the dissolved phase by rivers each year, which accounts for similar to 10% of the global flux of dissolved organic carbon. The relative sources of this large amount of riverine dissolved black carbon (DBC) from biomass burning (young, modern C-14) and fossil fuel (old, C-14 free) combustion are not known. We present radiocarbon measurements of BC in both dissolved and particulate phases transported by the Changjiang and Huanghe Rivers, the two largest rivers in China, during 2015. We show that two, distinct BC pools (young and old) were carried by the rivers. The DBC pool was much younger than the particulate BC (PBC) pool. Mass balance calculations indicate that most (78-85%) of the DBC in the Changjiang and Huanghe Rivers was derived from biomass burning, and only 15-22% was from fossil fuel combustion. In contrast, PBC from biomass burning and fossil fuel combustion were approximately equal in these two rivers. Export of PBC and DBC by the rivers are decoupled, and fluxes of PBC were 4.1 and 6.7 times higher than DBC in the Changjiang and Huanghe Rivers, respectively. The C-14 age differences of the two BC pools suggest that BC derived from biomass burning and fossil fuel combustion are mobilized in different phases and on different time scales in these rivers. VL - 30 ER - TY - JOUR T1 - Unusually large tsunamis frequent a currently creeping part of the Aleutian megathrust JF - Geophysical Research Letters Y1 - 2016 A1 - Witter, Robert C. A1 - Carver, Gary A. A1 - Briggs, Richard W. A1 - Gelfenbaum, Guy A1 - Koehler, Richard D. A1 - La Selle, SeanPaul A1 - Bender, Adrian M. A1 - Engelhart, Simon E. A1 - Hemphill-Haley, Eileen A1 - Hill, Troy D. AB - Current models used to assess earthquake and tsunami hazards are inadequate where creep dominates a subduction megathrust. Here we report geological evidence for large tsunamis, occurring on average every 300–340 years, near the source areas of the 1946 and 1957 Aleutian tsunamis. These areas bookend a postulated seismic gap over 200 km long where modern geodetic measurements indicate that the megathrust is currently creeping. At Sedanka Island, evidence for large tsunamis includes six sand sheets that blanket a lowland facing the Pacific Ocean, rise to 15 m above mean sea level, contain marine diatoms, cap terraces, adjoin evidence for scour, and date from the past 1700 years. The youngest sheet and modern drift logs found as far as 800 m inland and >18 m elevation likely record the 1957 tsunami. Previously unrecognized tsunami sources coexist with a presently creeping megathrust along this part of the Aleutian Subduction Zone. VL - 43 UR - http://doi.wiley.com/10.1002/2015GL066083 IS - 1 ER - TY - JOUR T1 - Variations in microbial carbon sources and cycling in the deep continental subsurface JF - Geochimica et Cosmochimica Acta Y1 - 2016 A1 - Danielle N. Simkus A1 - Greg F. Slater A1 - Barbara Sherwood Lollar A1 - Kenna Wilkie A1 - Thomas L. Kieft A1 - Cara Magnabosco A1 - Maggie C.Y. Lau A1 - Michael J. Pullin A1 - Sarah B. Hendrickson A1 - K. Eric Wommack A1 - Eric G. Sakowski A1 - Esta van Heerden A1 - Olukayode Kuloyo A1 - Borja Linage A1 - Gaetan Borgonie A1 - Tullis C. Onstott AB - Abstract Deep continental subsurface fracture water systems, ranging from 1.1 to 3.3 km below land surface (kmbls), were investigated to characterize the indigenous microorganisms and elucidate microbial carbon sources and their cycling. Analysis of phospholipid fatty acid (PLFA) abundances and direct cell counts detected varying biomass that was not correlated with depth. Compound-specific carbon isotope analyses (δ13C and Δ14C) of the phospholipid fatty acids (PLFAs) and carbon substrates combined with genomic analyses did identify, however, distinct carbon sources and cycles between the two depth ranges studied. In the shallower boreholes at circa 1 kmbls, isotopic evidence indicated microbial incorporation of biogenic \{CH4\} by the in situ microbial community. At the shallowest site, 1.05 kmbls in Driefontein mine, this process clearly dominated the isotopic signal. At slightly deeper depths, 1.34 kmbls in Beatrix mine, the isotopic data indicated the incorporation of both biogenic \{CH4\} and dissolved inorganic carbon (DIC) derived from \{CH4\} oxidation. In both of these cases, molecular genetic analysis indicated that methanogenic and methanotrophic organisms together comprised a small component (<5%) of the microbial community. Thus, it appears that a relatively minor component of the prokaryotic community is supporting a much larger overall bacterial community in these samples. In the samples collected from >3 kmbls in Tau Tona mine (TT107, \{TT109\} Bh2), the \{CH4\} had an isotopic signature suggesting a predominantly abiogenic origin with minor inputs from microbial methanogenesis. In these samples, the isotopic enrichments (δ13C and Δ14C) of the \{PLFAs\} relative to \{CH4\} were consistent with little incorporation of \{CH4\} into the biomass. The most 13C-enriched \{PLFAs\} were observed in \{TT107\} where the dominant CO2-fixation pathway was the acetyl-CoA pathway by non-acetogenic bacteria. The differences in the δ13C of the \{PLFAs\} and the \{DIC\} and \{DOC\} for \{TT109\} Bh2 were ∼−24‰ and 0‰, respectively. The dominant CO2-fixation pathways were 3-HP/4-HB cycle > acetyl-CoA pathway > reductive pentose phosphate cycle. VL - 173 UR - http://www.sciencedirect.com/science/article/pii/S0016703715005852 ER - TY - JOUR T1 - Viable Species of Flamella (Amoebozoa: Variosea) Isolated from Ancient Arctic Permafrost Sediments JF - Protist Y1 - 2016 A1 - Lyubov Shmakova A1 - Natalya Bondarenko A1 - Alexey Smirnov KW - cryptobiosis. AB - Six viable strains of amoebae belonging to the genus Flamella (Amoebozoa, Variosea) were isolated from permafrost sediments sampled in the Russian Arctic region. Two of them are from late Pleistocene permafrost in North-East Siberia, and four - from Holocene and late Pleistocene in North-West Siberia. Light- and electron-microscopic study and molecular phylogeny show that these isolates represent two new species belonging to the genus Flamella. Both species are cyst-forming. This is a remarkable case of high resistance of protozoan cysts, allowing them to survive and recover an amoebae population after a very long, geologically significant period of rest; a “snapshot” of evolution in time. This study directly shows for the first time that amoeba cysts can be conserved not only for years and decades but for many thousand years and then recover, contributing to the formation of an active microbial community. We propose to name the new species as Flamella pleistocenica n.sp. and Flamella beringiania n.sp. Phylogenetic analysis shows that the genus Flamella is a robust and potentially species-rich group of Variosea. VL - 167 UR - http://www.sciencedirect.com/science/article/pii/S1434461015000772 ER - TY - JOUR T1 - A 12,000-yr pollen record off Cape Hatteras — Pollen sources and mechanisms of pollen dispersion JF - Marine Geology Y1 - 2015 A1 - Naughton, F. A1 - Keigwin, L. A1 - Peteet, D. A1 - Costas, S. A1 - Desprat, S. A1 - Oliveira, D. A1 - de Vernal, A. A1 - Voelker, A. A1 - Abrantes, F. AB - Integrating both marine and terrestrial signals from the same sediment core is one of the primary challenges for understanding the role of ocean–atmosphere coupling throughout past climate changes. It is therefore vital to understand how the pollen signal of a given marine record reflects the vegetation changes of the neighboring continent. The comparison between the pollen record of marine core JPC32 (KNR178JPC32) and available terrestrial pollen sequences from eastern North America over the last 12,170 years indicates that the pollen signature off Cape Hatteras gives an integrated image of the regional vegetation encompassing the Pee Dee river, Chesapeake and Delaware hydrographic basins and is reliable in reconstructing the past climate of the adjacent continent. Extremely high quantities of pollen grains included in the marine sediments off Cape Hatteras were transferred from the continent to the sea, at intervals 10,100–8800 cal yr BP, 8300–7500 cal yr BP, 5800–4300 cal yr BP and 2100–730 cal yr BP, during storm events favored by episodes of rapid sea-level rise in the eastern coast of US. In contrast, pollen grains export was reduced during 12,170–10,150 cal yr BP and 4200–2200 cal yr BP, during episodes of intense continental dryness and slow sea level rise episodes or lowstands in the eastern coast of US. The near absence of reworked pollen grains in core JPC32 contrasts with the high quantity of reworked material in nearby but deeper located marine sites, suggesting that the JPC32 record was not affected by the Deep Western Boundary Current (DWBC) since the end of the Younger Dryas and should be considered a key site for studying past climate changes in the western North Atlantic. VL - 367 UR - http://www.sciencedirect.com/science/article/pii/S0025322715001255 JO - A 12,000-yr pollen record off Cape Hatteras — Pollen sources and mechanisms of pollen dispersion ER - TY - JOUR T1 - Accretion history of mid-Holocene coral reefs from the southeast Florida continental reef tract, USA JF - Coral Reefs Y1 - 2015 A1 - Stathakopoulos, A. A1 - Riegl, B. M. KW - Backstepping KW - Holocene KW - Reef accretion KW - Relict reef KW - SE Florida continental reef tract AB - Sixteen new coral reef cores were collected to better understand the accretion history and composition of submerged relict reefs offshore of continental southeast (SE) Florida. Coral radiometric ages from three sites on the shallow inner reef indicate accretion initiated by 8,050 Cal BP and terminated by 5,640 Cal BP. The reef accreted up to 3.75 m of vertical framework with accretion rates that averaged 2.53 m kyr-1. The reef was composed of a nearly even mixture of Acropora palmata and massive corals. In many cases, cores show an upward transition from massives to A. palmata and may indicate local dominance by this species prior to reef demise. Quantitative macroscopic analyses of reef clasts for various taphonomic and diagenetic features did not correlate well with depth/environmental-related trends established in other studies. The mixed coral framestone reef lacks a classical Caribbean reef zonation and is best described as an immature reef and/or a series of fused patch reefs; a pattern that is evident in both cores and reef morphology. This is in stark contrast to the older and deeper outer reef of the SE Florida continental reef tract. Accretion of the outer reef lasted from 10,695–8,000 Cal BP and resulted in a larger and better developed structure that achieved a distinct reef zonation. The discrepancies in overall reef morphology and size as well as the causes of reef terminations remain elusive without further study, yet they likely point to different climatic/environmental conditions during their respective accretion histories. VL - 34872624292351278520242597237061293327511611519362751494811122751520228638172349513073526222412724 UR - http://link.springer.com/10.1007/s00338-014-1233-3http://link.springer.com/content/pdf/10.1007/s00338-014-1233-3 IS - 11 ER - TY - JOUR T1 - African Baobabs with False Inner Cavities: The Radiocarbon Investigation of the Lebombo Eco Trail Baobab JF - PLoS One Y1 - 2015 A1 - Patrut, Adrian A1 - Woodborne, Stephan A1 - von Reden, Karl F. A1 - Hall, Grant A1 - Hofmeyr, Michele A1 - Lowy, Daniel A. A1 - Patrut, Roxana T. AB - The article reports the radiocarbon investigation results of the Lebombo Eco Trail tree, a representative African baobab from Mozambique. Several wood samples collected from the large inner cavity and from the outer part of the tree were investigated by AMS radiocarbon dating. According to dating results, the age values of all samples increase from the sampling point with the distance into the wood. For samples collected from the cavity walls, the increase of age values with the distance into the wood (up to a point of maximum age) represents a major anomaly. The only realistic explanation for this anomaly is that such inner cavities are, in fact, natural empty spaces between several fused stems disposed in a ring-shaped structure. We named them false cavities. Several important differences between normal cavities and false cavities are presented. Eventually, we dated other African baobabs with false inner cavities. We found that this new architecture enables baobabs to reach large sizes and old ages. The radiocarbon date of the oldest sample was 1425 +/- 24 BP, which corresponds to a calibrated age of 1355 +/- 15 yr. The dating results also show that the Lebombo baobab consists of five fused stems, with ages between 900 and 1400 years; these five stems build the complete ring. The ring and the false cavity closed 800-900 years ago. The results also indicate that the stems stopped growing toward the false cavity over the past 500 years. VL - 10 IS - 1 N1 - PT: J; TC: 0; UT: WOS:000348470400021 JO - African Baobabs with False Inner Cavities: The Radiocarbon Investigation of the Lebombo Eco Trail Baobab ER - TY - JOUR T1 - AMS radiocarbon dating of very large Grandidier’s baobabs (Adansonia grandidieri) JF - Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms Y1 - 2015 A1 - Patrut, Adrian A1 - von Reden, Karl F. A1 - Danthu, Pascal A1 - Leong Pock-Tsy, Jean-Michel A1 - Rakosy, Laszlo A1 - Patrut, Roxana T. A1 - Lowy, Daniel A. A1 - Margineanu, Dragos AB - The article reports the AMS radiocarbon investigation of the two largest known Adansonia grandidieri specimens. The two baobabs, which are named Tsitakakoike and Pregnant baobab, are located in Southwestern Madagascar, near Andombiro. A third specimen from this area, the House baobab, was also investigated. According to measurements, Tsitakakoike is the biggest individual above ground level of all Adansonia species. The House baobab was selected for its exposed structure, which is identical to the closed ring-shaped structure with false cavities identified by us in large and old Adansonia digitata specimens. According to our research, Tsitakakoike and the Pregnant baobab have multi-stemmed cylindrical trunks which are mainly hollow; the two very large baobabs also possess a ring-shaped structure. The radiocarbon dates of the oldest wood samples collected from the large trunks were 1274 ± 20 bp for Tsitakakoike and 930 ± 20 bp for the Pregnant baobab. According to their original positions and to the architectures of the two A. grandidieri, the ages of Tsitakakoike and Pregnant baobab would be between 1300 and 1500 years. Therefore, A. grandidieri becomes the third Adansonia species with individuals that can live over 1000 years, according to accurate dating results. VL - 361 N1 - Cu2hzTimes Cited:2Cited References Count:20 JO - AMS radiocarbon dating of very large Grandidier’s baobabs (Adansonia grandidieri) ER - TY - JOUR T1 - Analysis of bomb radiocarbon data for common thresher sharks, Alopias vulpinus, in the northwestern Atlantic Ocean with revised growth curves JF - ENVIRONMENTAL BIOLOGY OF FISHES Y1 - 2015 A1 - Natanson, Lisa J. A1 - Hamady, Li Ling A1 - Gervelis, Brian J. KW - Age KW - Carbon-14 KW - Centra KW - Elasmobranchs KW - Vertebral column AB - Bomb radiocarbon dating was used to determine the periodicity of band pair formation in the vertebral centra of three common thresher sharks (Alopias vulpinus). The traditional interpretation of band pairs were accurate (i.e. annual) up to approximately 14 years of age. In older individuals, band pair counts underestimated age. A new maximum validated age was estimated to be 38 years (an increase of 18 years over the band count estimates). Previously reported length at age estimates for common thresher sharks up to 14 years were used in conjunction with the two older validated estimates to develop a revised growth curve for the species, which was described using the Schnute general model (sexes combined). Updated estimates of age at maturity remained the same for males (8 years) and increased by one year to 13 years for females. The primary finding was the increase in longevity for this species from a band pair count estimate of 24 years to a bomb radiocarbon validated estimate of 38 years, indicating this species lives much longer than previously thought. VL - 99 ER - TY - JOUR T1 - Ancient population genomics and the study of evolution JF - Philosophical Transactions of the Royal Society B: Biological Sciences Y1 - 2015 A1 - Parks, M. A1 - Subramanian, S. A1 - Baroni, C. A1 - Salvatore, M. C. A1 - Zhang, G. A1 - Millar, C. D. A1 - Lambert, D. M. AB - Recently, the study of ancient DNA (aDNA) has been greatly enhanced by the development of second-generation DNA sequencing technologies and targeted enrichment strategies. These developments have allowed the recovery of several complete ancient genomes, a result that would have been considered virtually impossible only a decade ago. Prior to these developments, aDNA research was largely focused on the recovery of short DNA sequences and their use in the study of phylogenetic relationships, molecular rates, species identification and population structure. However, it is now possible to sequence a large number of modern and ancient complete genomes from a single species and thereby study the genomic patterns of evolutionary change over time. Such a study would herald the beginnings of ancient population genomics and its use in the study of evolution. Species that are amenable to such large-scale studies warrant increased research effort. We report here progress on a population genomic study of the Adélie penguin (Pygoscelis adeliae). This species is ideally suited to ancient population genomic research because both modern and ancient samples are abundant in the permafrost conditions of Antarctica. This species will enable us to directly address many of the fundamental questions in ecology and evolution. VL - 370, UR - http://rstb.royalsocietypublishing.org/cgi/doi/10.1098/rstb.2013.0381 IS - 1660, ER - TY - JOUR T1 - Applications and limitations of U–Th disequilibria systematics for determining ages of carbonate alteration minerals in peridotite JF - Chemical Geology Y1 - 2015 A1 - Mervine, Evelyn M. A1 - Sims, Kenneth W.W. A1 - Humphris, Susan E. A1 - Kelemen, Peter B. AB - 238U–234U–230Th dating was conducted on carbonate alteration minerals in the peridotite layer of the Samail Ophiolite, Sultanate of Oman, in order to assess the applicability of U-series dating techniques to these types of Quaternary terrestrial carbonates and also to further constrain natural rates of carbonation of the peridotite. Due to their low U concentrations and relatively high Th/U ratios, Samail carbonates are challenging to date with the 230Th technique because of the sensitivity of ages to corrections for initial 230Th. Uncorrected 230Th ages for Ca-rich travertines are consistently older than previously obtained 14C ages. However, geologically reasonable initial 230Th corrections bring the two sets of ages into concordance. This age concordance suggests that the travertines are generally closed systems, adding a level of credence to the reliability of previously obtained 14C ages. In contrast, uncorrected 230Th ages for Mg-rich carbonate veins are generally younger than previously obtained 14C ages. These young ages are interpreted in terms of remobilization of hexavalent U, which is subsequently deposited as tetravalent U by reduced serpentinization fluids. Two Mg-rich carbonate veins sampled at a roadcut have near-equilibrium (230Th/238U) and (234U/238U) values, which indicate that these veins are > 375,000 years in age, consistent with their “14C dead” (> 50,000 years BP) ages. The variable young and old ages for these Mg-rich carbonate veins indicate that carbonation of the peridotite layer of the Samail Ophiolite is an ongoing process and that there have been multiple generations of subsurface carbonate vein formation. Overall, this study provides insights into some of the challenges associated with applying U-series dating methods to Quaternary terrestrial carbonates, in particular carbonate alteration minerals in peridotites, and highlights some areas where there is room for improvement, such as obtaining better constraints on the isotopic composition of admixed detritus, and also some advantages, such as the ability to identify open system behavior not apparent from 14C dating and stable C and O isotopic analysis alone. VL - 412 UR - http://linkinghub.elsevier.com/retrieve/pii/S0009254115003435 ER - TY - JOUR T1 - Assessment of branched GDGTs as temperature proxies in sedimentary records from several small lakes in southwestern Greenland JF - Organic Geochemistry Y1 - 2015 A1 - Colcord, Devon E. A1 - Cadieux, Sarah B. A1 - Brassell, Simon C. A1 - Castañeda, Isla S. A1 - Pratt, Lisa M. A1 - White, Jeffrey R. AB - This study of five small (<3.0 ha) lakes in southwestern Greenland examines the veracity of branched glycerol dialkyl glycerol tetraethers (br GDGTs) as a temperature proxy in lacustrine systems. The proximity (<5 km) of the lakes suggests that their temperature history, and thus their br GDGT records, should be similar. Distributions of br GDGTs in (i) surface sediments from all five lakes, (ii) 14C-dated sediment cores from two lakes (Upper and Lower EVV Lakes) and (iii) soil samples from the area surrounding the lakes were examined. The temporal records of br GDGT-based temperature for the two cores exhibited both similarities and major discrepancies. The differences between the paleotemperature records for the two lakes suggest that br GDGTs are not solely soil-derived, reflecting air temperature, but also indicate an additional br GDGT contribution from another source. Among the broader suite of lake sediments, there was a strong correlation (R2 0.987) between br GDGT-based surface sediment temperatures and measured summer bottom water temperatures for the four lakes with hypoxic/anoxic bottom waters, including Upper EVV Lake. The correlation suggests production of br GDGTs by anaerobic bacteria within the bottom water and/or sediment–water interface, reflecting environmental temperature for the individual lakes and augmenting the uniform, soil-derived signal. Hence, assessment of br GDGTs in Greenland lake sediments provides evidence for their origin from anaerobic autochthonous bacteria and indicates that interpretation of lacustrine br GDGT-based paleotemperature records requires contextual knowledge of individual lake systems and potential source(s) of sedimentary br GDGTs. VL - 82 UR - http://www.sciencedirect.com/science/article/pii/S0146638015000388 JO - Assessment of branched GDGTs as temperature proxies in sedimentary records from several small lakes in southwestern Greenland ER - TY - JOUR T1 - Bayesian 14C analysis, formation processes, and accumulation rates of the Prisoners Harbor shell midden and village complex, Santa Cruz Island, California JF - Journal of Archaeological Science: Reports Y1 - 2015 A1 - Jew, Nicholas P. A1 - Rick, Torben C. A1 - Glassow, Michael A. A1 - Arnold, Jeanne E. AB - The Prisoners Harbor site (CA-SCRI-240), one of the largest sites on California's Channel Islands and the likely location of the Chumash village Xaxas, played a key role in regional models of emergent complexity and culture contact. Despite substantial excavation at the site, published research has focused on the most recent 500 years of the site's occupation, with comparatively little attention given to the 2–3 millennia preceding this. Here we focus on the formation and chronology of CA-SCRI-240 by presenting a Bayesian analysis of 36 radiocarbon dates from throughout the site's occupation. Comparing three suites of radiocarbon dates, we provide a revised chronology for CA-SCRI-240 and examine site formation processes, sediment deposition rates, and the implications our study holds for reconciling older radiometric dates with large analytical errors and higher precision accelerator mass spectrometry dates. Our analysis suggests that the earliest site occupation was 2750 cal BP, roughly 2000 years later than previously presumed. Sedimentation rates vary throughout the 5.7 m sequence. Deposits for the first 1000 years accumulated slowly followed by relative increase in accumulation rates in the uppermost occupation levels dating to historic times. Our study demonstrates the importance of Bayesian analysis for improving radiocarbon chronologies for large, multi-component sites. VL - 3 UR - http://www.sciencedirect.com/science/article/pii/S2352409X15300420 JO - Bayesian 14C analysis, formation processes, and accumulation rates of the Prisoners Harbor shell midden and village complex, Santa Cruz Island, California ER - TY - JOUR T1 - Beach ridges as paleoseismic indicators of abrupt coastal subsidence during subduction zone earthquakes, and implications for Alaska-Aleutian subduction zone paleoseismology, southeast coast of the Kenai Peninsula, Alaska JF - Megathrust Earthquakes and Sea-level Change: a Tribute to George Plafker Y1 - 2015 A1 - Kelsey, Harvey M. A1 - Witter, Robert C. A1 - Engelhart, Simon E. A1 - Briggs, Richard A1 - Nelson, Alan A1 - Haeussler, Peter A1 - Corbett, D. Reide AB - The Kenai section of the eastern Alaska-Aleutian subduction zone straddles two areas of high slip in the 1964 great Alaska earthquake and is the least studied of the three megathrust segments (Kodiak, Kenai, Prince William Sound) that ruptured in 1964. Investigation of two coastal sites in the eastern part of the Kenai segment, on the southeast coast of the Kenai Peninsula, identified evidence for two subduction zone earthquakes that predate the 1964 earthquake. Both coastal sites provide paleoseismic data through inferred coseismic subsidence of wetlands and associated subsidence-induced erosion of beach ridges. At Verdant Cove, paleo-beach ridges record the paleoseismic history; whereas at Quicksand Cove, buried soils in drowned coastal wetlands are the primary indicators of paleoearthquake occurrence and age. The timing of submergence and death of trees mark the oldest earthquake at Verdant Cove that is consistent with the age of a well documented ∼900-year-ago subduction zone earthquake that ruptured the Prince William Sound segment of the megathrust to the east and the Kodiak segment to the west. Soils buried within the last 400–450 years mark the penultimate earthquake on the southeast coast of the Kenai Peninsula. The penultimate earthquake probably occurred before AD 1840 from its absence in Russian historical accounts. The penultimate subduction zone earthquake on the Kenai segment did not rupture in conjunction with the Prince William Sound to the northeast. Therefore the Kenai segment, which is presently creeping, can rupture independently of the adjacent Prince William Sound segment that is presently locked. VL - 113 UR - http://www.sciencedirect.com/science/article/pii/S0277379115000220 JO - Beach ridges as paleoseismic indicators of abrupt coastal subsidence during subduction zone earthquakes, and implications for Alaska-Aleutian subduction zone paleoseismology, southeast coast of the Kenai Peninsula, Alaska ER - TY - DATA T1 - Carbon Isotope Concentrations in Stream Food Webs of the Arctic Network National Parks, Alaska, 2014-2016 Y1 - 2015 A1 - Carey, Michael P. A1 - O'Donnell, Jonathan A. A1 - Koch, Joshua C. AB - This dataset includes information on the carbon samples that were collected from organic and mineral soils, streams, algae, invertebrates, and fish in the Arctic Network Parks. PB - Alaska Science Center, U.S. Geological Survey UR - https://doi.org/10.5066/p9nauiqr ER - TY - JOUR T1 - Climate forcing of unprecedented intense-hurricane activity in the last 2000 years JF - EARTHS FUTURE Y1 - 2015 A1 - Donnelly, Jeffrey P. A1 - Hawkes, Andrea D. A1 - Lane, Philip A1 - MacDonald, Dana A1 - Shuman, Bryan N. A1 - Toomey, Michael R. A1 - van Hengstum, Peter J. A1 - Woodruff, Jonathan D. KW - Climate change KW - common era KW - Holocene KW - sea surface temperature KW - tropical cyclones AB - How climate controls hurricane variability has critical implications for society is not well understood. In part, our understanding is hampered by the short and incomplete observational hurricane record. Here we present a synthesis of intense-hurricane activity from the western North Atlantic over the past two millennia, which is supported by a new, exceptionally well-resolved record from Salt Pond, Massachusetts (USA). At Salt Pond, three coarse grained event beds deposited in the historical interval are consistent with severe hurricanes in 1991 (Bob), 1675, and 1635 C.E., and provide modern analogs for 32 other prehistoric event beds. Two intervals of heightened frequency of event bed deposition between 1400 and 1675 C.E. (10 events) and 150 and 1150 C.E. (23 events), represent the local expression of coherent regional patterns in intense-hurricane-induced event beds. Our synthesis indicates that much of the western North Atlantic appears to have been active between 250 and 1150 C.E., with high levels of activity persisting in the Caribbean and Gulf of Mexico until 1400 C.E. This interval was one with relatively warm sea surface temperatures (SSTs) in the main development region (MDR). A shift in activity to the North American east coast occurred ca. 1400 C.E., with more frequent severe hurricane strikes recorded from The Bahamas to New England between 1400 and 1675 C.E. A warm SST anomaly along the western North Atlantic, rather than within the MDR, likely contributed to the later active interval being restricted to the east coast. VL - 3 ER - TY - JOUR T1 - Climatic and biotic thresholds of coral-reef shutdown JF - Nature Climate Change Y1 - 2015 A1 - Toth, Lauren T. A1 - Aronson, Richard B. A1 - Cobb, Kim M. A1 - Cheng, Hai A1 - Edwards, R. Lawrence A1 - Grothe, Pamela R. A1 - Sayani, Hussein R. KW - Climate-change ecology KW - Palaeoceanography KW - Palaeoclimate KW - Palaeoecology AB - Climate change is now the leading cause of coral-reef degradation and is altering the adaptive landscape of coral populations1, 2. Increasing sea temperatures and declining carbonate saturation states are inhibiting short-term rates of coral calcification, carbonate precipitation and submarine cementation3, 4, 5. A critical challenge to coral-reef conservation is understanding the mechanisms by which environmental perturbations scale up to influence long-term rates of reef-framework construction and ecosystem function6, 7. Here we reconstruct climatic and oceanographic variability using corals sampled from a 6,750-year core from Pacific Panamá. Simultaneous reconstructions of coral palaeophysiology and reef accretion allowed us to identify the climatic and biotic thresholds associated with a 2,500-year hiatus in vertical accretion beginning ~4,100 years ago8. Stronger upwelling, cooler sea temperatures and greater precipitation—indicators of La Niña-like conditions—were closely associated with abrupt reef shutdown. The physiological condition of the corals deteriorated at the onset of the hiatus, corroborating theoretical predictions that the tipping points of radical ecosystem transitions should be manifested sublethally in the biotic constituents9. Future climate change could cause similar threshold behaviours, leading to another shutdown in reef development in the tropical eastern Pacific. VL - 5 UR - http://www.nature.com/doifinder/10.1038/nclimate2541 IS - 4 ER - TY - JOUR T1 - Coastal evidence for Holocene subduction-zone earthquakes and tsunamis in central Chile JF - Quaternary Science Reviews Y1 - 2015 A1 - Dura, Tina A1 - Cisternas, Marco A1 - Horton, Benjamin P. A1 - Ely, Lisa L. A1 - Nelson, Alan R. A1 - Wesson, Robert L. A1 - Pilarczyk, Jessica E. KW - Coastal hazards KW - Coastal paleoseismology KW - Diatom paleoecology KW - Prehistoric earthquakes KW - Tsunami Deposits AB - The ∼500-year historical record of seismicity along the central Chile coast (30–34°S) is characterized by a series of ∼M 8.0–8.5 earthquakes followed by low tsunamis (<4 m) occurring on the megathrust about every 80 years. One exception is the AD 1730 great earthquake (M 9.0–9.5) and high tsunami (>10 m), but the frequency of such large events is unknown. We extend the seismic history of central Chile through a study of a lowland stratigraphic sequence along the metropolitan coast north of Valparaíso (33°S). At this site, higher relative sea level during the mid Holocene created a tidal marsh and the accommodation space necessary for sediment that preserves earthquake and tsunami evidence. Within this 2600-yr-long sequence, we traced six laterally continuous sand beds probably deposited by high tsunamis. Plant remains that underlie the sand beds were radiocarbon dated to 6200, 5600, 5000, 4400, 3800, and 3700 cal yr BP. Sediment properties and diatom assemblages of the sand beds—for example, anomalous marine planktonic diatoms and upward fining of silt-sized diatom valves—point to a marine sediment source and high-energy deposition. Grain-size analysis shows a strong similarity between inferred tsunami deposits and modern coastal sediment. Upward fining sequences characteristic of suspension deposition are present in five of the six sand beds. Despite the lack of significant lithologic changes between the sedimentary units under- and overlying tsunami deposits, we infer that the increase in freshwater siliceous microfossils in overlying units records coseismic uplift concurrent with the deposition of five of the sand beds. During our mid-Holocene window of evidence preservation, the mean recurrence interval of earthquakes and tsunamis is ∼500 years. Our findings imply that the frequency of historical earthquakes in central Chile is not representative of the greatest earthquakes and tsunamis that the central Chilean subduction zone has produced. VL - 113 UR - https://doi.org/10.1016/j.quascirev.2014.10.015 ER - TY - JOUR T1 - Comparing dust flux records from the Subarctic North Pacific and Greenland: Implications for atmospheric transport to Greenland and for the application of dust as a chronostratigraphic tool JF - PALEOCEANOGRAPHY Y1 - 2015 A1 - Serno, Sascha A1 - Winckler, Gisela A1 - Anderson, Robert F. A1 - Maier, Edith A1 - Ren, Haojia A1 - Gersonde, Rainer A1 - Haug, Gerald H. KW - atmospheric circulation KW - chronostratigrapy KW - eolian dust KW - helium-4 KW - paleoreservoir age KW - Subarctic North Pacific AB - We present a new record of eolian dust flux to the western Subarctic North Pacific (SNP) covering the past 27,000years based on a core from the Detroit Seamount. Comparing the SNP dust record to the North Greenland Ice Core Project (NGRIP) ice core record shows significant differences in the amplitude of dust changes to the two regions during the last deglaciation, while the timing of abrupt changes is synchronous. If dust deposition in the SNP faithfully records its mobilization in East Asian source regions, then the difference in the relative amplitude must reflect climate-related changes in atmospheric dust transport to Greenland. Based on the synchronicity in the timing of dust changes in the SNP and Greenland, we tie abrupt deglacial transitions in the Th-230-normalized He-4 flux record to corresponding transitions in the well-dated NGRIP dust flux record to provide a new chronostratigraphic technique for marine sediments from the SNP. Results from this technique are complemented by radiocarbon dating, which allows us to independently constrain radiocarbon paleoreservoir ages. We find paleoreservoir ages of 745140years at 11,653year B.P., 680228years at 14,630year B.P., and 790498years at 23,290year B.P. Our reconstructed paleoreservoir ages are consistent with modern surface water reservoir ages in the western SNP. Good temporal synchronicity between eolian dust records from the Subantarctic Atlantic and equatorial Pacific and the ice core record from Antarctica supports the reliability of the proposed dust tuning method to be used more widely in other global ocean regions. VL - 30 ER - TY - JOUR T1 - Comparison of large and ultra-small delta c-14 measurements in core top benthic foraminifera from the Okhotsk Sea JF - Radiocarbon Y1 - 2015 A1 - Keigwin, L. D. A1 - Gagnon, A. R. AB - The radiocarbon activity of benthic foraminifera was investigated in surface sediments from a high deposition rate location at a depth of 1000 m in the Okhotsk Sea. Sediments were preserved and stained with Rose Bengal to identify foraminifera that contain cytoplasm. The benthic fauna at this site is dominated by large specimens of Uvigerina peregrina, and bulk samples (similar to 150 individuals) of stained and unstained specimens were dated. The stained sample was about 240 C-14 yr younger than the unstained, and the presence of bomb C-14 is inferred by comparison to water column data in the nearby open North Pacific. Using new methods, multiple measurements were also made on samples of three stained and unstained individuals (as small as 7 mu g C). Results are consistent with those from the bulk samples. This suggests that similar ultra-small measurements could be made at other locations to reveal the age distribution of individuals in a sediment sample in order to assess the extent of bioturbation and the presence of bomb C-14 contamination. VL - 57 IS - 1 N1 - PT: J; TC: 1; UT: WOS:000351052600010 JO - Comparison of large and ultra-small delta c-14 measurements in core top benthic foraminifera from the Okhotsk Sea ER - TY - JOUR T1 - Controls on the distribution and fractionation of yttrium and rare earth elements in core sediments from the Mandovi estuary, western India JF - Continental Shelf Research Y1 - 2015 A1 - Prajith, A. A1 - Rao, V. Purnachandra A1 - Kessarkar, Pratima M. AB - Mineralogy, major elements (Fe, Mn and Al), rare earths and yttrium (REY) of bulk sediments were analyzed in four gravity cores recovered along the main channel of the Mandovi estuary, western India, to determine the sources and controls on REY distribution. The accelerator mass spectrometer (AMS) ages of total organic carbon indicated modern age for the sediments of the upper estuary and, maximum mean ages of 1588 years AD and 539 years AD for the bottom sediments of the cores in the lower estuary and bay, respectively. The sediments of the upper/middle estuary showed abundant hematite, magnetite and goethite and high Fe, Mn, total-REE (ΣREE) and Y, while those in the lower estuary/bay showed abundant silicate minerals and relatively low Fe, Mn, ΣREE and Y. ΣREE showed significant correlation with clay and silt fractions and Y, Al and organic carbon (OC) content of the sediments. The light to heavy REE ratios (LREE/HREE) of sediments were lower than in Post-Archean Australian Shale (PAAS). The PAAS-normalized rare earths and yttrium (REY; Y inserted between Dy and Ho) patterns of sediments showed middle REE (MREE)- and HREE-enrichment with positive Eu anomaly (Eu/Eu⁎) and variable Ce anomaly (Ce/Ce⁎). The REY of sediments is primarily controlled by its texture and REE of source sediment, which is ore material-dominated in the upper/middle estuary and silicate material-dominated in the lower estuary/bay. Low LREE/HREE ratios suggest that very fine-grained sediments were carried away from the estuary because of high-energy conditions. Fractionations of REY (Y/Ho, Sm/Nd, Ce/Ce⁎ and Eu/Eu⁎) are controlled by different mechanisms. High Y/Ho ratios in clayey silts are due to redistribution of Y and Ho by adsorption onto organic-rich, clays. Variations in Sm/Nd ratios are similar to that of Eu/Eu⁎ in cores from the lower estuary/bay and are controlled by mineral constituents of the sediments. Positive Ce and Eu anomalies are inherited from ore material, and ore material and source rocks, respectively. Negative Ce anomaly is related to source rock material and influenced by lanthanum enrichment at certain sediment intervals. VL - 92 UR - http://www.sciencedirect.com/science/article/pii/S0278434314003215 JO - Controls on the distribution and fractionation of yttrium and rare earth elements in core sediments from the Mandovi estuary, western India ER - TY - JOUR T1 - Cryosphere: Antarctic ice growth and retreat JF - Nature Geoscience Y1 - 2015 A1 - Evans, Jeffrey KW - Cryospheric science KW - Palaeoclimate VL - 81008 UR - http://www.nature.com/doifinder/10.1038/ngeo2494 IS - 8 ER - TY - JOUR T1 - Early deglacial onset of southwestern Greenland ice-sheet retreat on the continental shelf JF - QUATERNARY SCIENCE REVIEWS Y1 - 2015 A1 - Winsor, Kelsey A1 - Carlson, Anders E. A1 - Welke, Bethany M. A1 - Reilly, Brendan KW - Davis Strait KW - Deglaciation KW - Greenland KW - Retreat forcings KW - sea level KW - Sedimentation rate AB - The Greenland ice sheet (GrIS) advanced onto the continental shelf during the last glacial period. While deglacial records for when the GrIS withdrew onto the modern coastline are relatively abundant, the timing of early GrIS retreat on the shelf is poorly constrained. Here we use planktic foraminiferal delta O-18, sediment grain size, sedimentation rates, and C-14 ages in southeastern Davis Strait core HU87033-008 to develop an early deglaciation chronology of the southwestern GrIS while on the continental shelf. Sedimentation rates, and especially silt and clay fractions, are high between similar to 20.5 and similar to 17.1 ka, suggesting that the southwestern GrIS margin was near or at the shelf break, where it released subglacially derived sediment-laden meltwater. A peak in sedimentation rates of similar to 110 cm ka(-1) between similar to 19.3 ka and similar to 18.6 ka, combined with an initial decrease in planktic delta O-18 of similar to 0.5 per mil, suggests an early deglacial pull back of the GrIS margin from the shelf break with a concurrent increase in surface ocean meltwater discharge. A subsequent planktic delta O-18 decrease of similar to 1.0 per mil combined with a drop in silt and clay sedimentation rates at 18-17 ka likely record further GrIS retreat inland from the shelf break. Terrestrial Be-10 surface exposure ages indicate that the GrIS margin remained on the continental shelf until similar to 11 ka, yet the cause of this subsequent ice-margin stability on the inner shelf is not known. Our new records provide the first evidence that the southwestern GrIS margin may have begun to deglaciate at the same time as other Northern Hemisphere ice sheets. As Labrador Sea water temperatures likely remained near glacial values until similar to 15 ka, we suggest that initial southwestern GrIS retreat was in response to rising global sea level from retreat of other ice sheets and/or the initial deglacial rise in boreal summer insolation. (C) 2015 Elsevier Ltd. All rights reserved. VL - 128 ER - TY - JOUR T1 - An effective method of UV-oxidation of dissolved organic carbon in natural waters for radiocarbon analysis by accelerator mass spectrometry JF - JOURNAL OF OCEAN UNIVERSITY OF CHINA Y1 - 2015 A1 - Xue Yuejun A1 - Ge Tiantian A1 - Wang Xuchen KW - AMS KW - dissolved organic carbon KW - natural waters KW - radiocarbon KW - UV-oxidation AB - Radiocarbon (C-14) measurement of dissolved organic carbon (DOC) is a very powerful tool to study the sources, transformation and cycling of carbon in the ocean. The technique, however, remains great challenges for complete and successful oxidation of sufficient DOC with low blanks for high precision carbon isotopic ratio analysis, largely due to the overwhelming proportion of salts and low DOC concentrations in the ocean. In this paper, we report an effective UV-Oxidation method for oxidizing DOC in natural waters for radiocarbon analysis by accelerator mass spectrometry (AMS). The UV-oxidation system and method show 95%+/- 4% oxidation efficiency and high reproducibility for DOC in both river and seawater samples. The blanks associated with the method was also low (about 3 A mu g C) that is critical for C-14 analysis. As a great advantage of the method, multiple water samples can be oxidized at the same time so it reduces the sample processing time substantially compared with other UV-oxidation method currently being used in other laboratories. We have used the system and method for C-14 studies of DOC in rivers, estuaries, and oceanic environments and have received promise results. VL - 14 ER - TY - CONF T1 - The End of the Wietenberg Culture in the Light of New 14C dates and its Chronological Relation Towards the Noua Culture. T2 - Bronze Age Chronology in the Carpathian Basin Y1 - 2015 A1 - Ciugudean, Horia A1 - Quinn, Colin P. KW - Bronze Age KW - Bronze Age Chronology KW - Carpathian Basin KW - Noua culture KW - radiocarbon dates KW - Transylvania KW - Wietenberg culture JF - Bronze Age Chronology in the Carpathian Basin SN - 978-606-543-684-8 UR - http://www.academia.edu/25025871/The_End_of_the_Wietenberg_Culture_in_the_Light_of_new_14C_Dates_and_its_Chronological_Relation_towards_the_Noua_Culture ER - TY - CHAP T1 - Field techniques for sea-level reconstruction - Coastal sediment T2 - Handbook of Sea-Level Research Y1 - 2015 A1 - Shennan, I. A1 - Long, A.J. A1 - Horton, B.E. AB - Measuring sea-level change – be that rise or fall – is one of the most pressing scientific goals of our time and requires robust scientific approaches and techniques. This Handbook aims to provide a practical guide to readers interested in this challenge, from the initial design of research approaches through to the practical issues of data collection and interpretation from a diverse range of coastal environments. Building on thirty years of international research, the Handbook comprises 38 chapters that are authored by leading experts from around the world. The Handbook will be an important resource to scientists interested and involved in understanding sea-level changes across a broad range of disciplines, policy makers wanting to appreciate our current state of knowledge of sea-level change over different timescales, and many teachers at the university level, as well as advanced-level undergraduates and postgraduate research students, wanting to learn more about sea-level change. JF - Handbook of Sea-Level Research UR - http://www.wiley.com/WileyCDA/WileyTitle/productCd-1118452585.html ER - TY - JOUR T1 - Forces driving late Pleistocene (ca. 77–12 ka) landscape evolution in the Cimarron River valley, southwestern Kansas JF - Quaternary Research Y1 - 2015 A1 - Layzell, Anthony L. A1 - Mandel, Rolfe D. A1 - Ludvigson, Greg A. A1 - Rittenour, Tammy M. A1 - Smith, Jon J. AB - This study presents stratigraphic, geomorphic, and paleoenvironmental (δ13C) data that provide insight into the late Pleistocene landscape evolution of the Cimarron River valley in the High Plains of southwestern Kansas. Two distinct valley fills (T-1 and T-2) were investigated. Three soils occur in the T-2 fill and five in the T-1 fill, all indicating periods of landscape stability or slow sedimentation. Of particular interest are two cumulic soils dating to ca. 48–28 and 13–12.5 ka. δ13C values are consistent with regional paleoenvironmental proxy data that indicate the prevalence of warm, dry conditions at these times. The Cimarron River is interpreted to have responded to these climatic changes and to local base level control. Specifically, aggradation occurred during cool, wet periods and slow sedimentation with cumulic soil formation occurred under warmer, drier climates. Significant valley incision (~ 25 m) by ca. 28 ka likely resulted from a lowering of local base level caused by deep-seated dissolution of Permian evaporite deposits. VL - 84 JO - Forces driving late Pleistocene (ca. 77–12 ka) landscape evolution in the Cimarron River valley, southwestern Kansas ER - TY - JOUR T1 - Freshening of the Marmara Sea prior to its post-glacial reconnection to the Mediterranean Sea JF - EARTH AND PLANETARY SCIENCE LETTERS Y1 - 2015 A1 - Aloisi, G. A1 - Soulet, G. A1 - Henry, P. A1 - Wallmann, K. A1 - Sauvestre, R. A1 - Vallet-Coulomb, C. A1 - Lecuyer, C. A1 - Bard, E. KW - Black Sea outflow KW - Last glacial maximum KW - Marmara Lake KW - pore water isotope composition AB - During the last glaciation the Marmara Sea was isolated from the Mediterranean Sea because global sea level was below the depth of the Dardanelles sill. Prior to the postglacial reconnection to the Mediterranean Sea (similar to 14.7 cal kyr BP), the surface waters of the Marmara Sea were brackish (Marmara Lake). Freshening of a previously saline Marmara Sea could have happened via spill-out of brackish to fresh water from the surface water of the Black Sea through the Bosphorus Strait. This hypothesis has not been tested against alternative possibilities (salt flushing by river run-off and precipitation). Here we use the dissolved Cl- and stable isotope composition (delta O-18 and delta D) of Marmara Sea sediment pore water to estimate the salinity and stable isotope composition of Marmara Lake bottom water and to evaluate possible freshening scenarios. We use a transport model to simulate pore water Cl-, delta O-18 and delta D in Marmara Sea sediments in the past 130 kyr, which includes the last interglacial (130-75 cal kyr BP), the last glacial (75-14 cal kyr BP) and the current postglacial period. Our results show that the bottom waters of the Marmara Lake were brackish (similar to 4 parts per thousand salinity) and isotopically depleted (delta O-18 similar to -10.2 parts per thousand and delta D similar to -70 parts per thousand, respectively) compared to modern seawater. Their salinity and stable isotope ratios show that they are a mixture of Mediterranean waters and Danube-like waters implying that the freshening took place via spill-out of freshwater through the Bosphorus. Our modelling approach indicates that the transit of fresh water from glacial Eurasia to the Mediterranean via the Marmara Sea started at least 50 cal kyr BP, was continuous throughout most of the last glaciation and persisted up to the post glacial reconnection to the Mediterranean through the Dardanelles sill (14.7 cal kyr BP). These results are consistent with previously published micropaleontological and geochemical investigations of sediment cores that indicate lacustrine conditions in the Marmara Sea from about 75 to 14.7 cal kyr BP. (C) 2015 Elsevier B.V. All rights reserved. VL - 413 ER - TY - RPRT T1 - Geochemical Conditions and the Occurrence of Selected Trace Elements in Groundwater Basins Used for Public Drinking-Water Supply, Desert and Basin and Range Hydrogeologic Provinces, 2006–11: California GAMA Priority Basin Project Y1 - 2015 A1 - Wright, M. T. A1 - Fram, M. S. A1 - Belitz, K. JF - Scientific Investigations Report PB - U.S. Department of the Interior: U.S. Geological Survey VL - 2014–5173 IS - Report JO - Geochemical Conditions and the Occurrence of Selected Trace Elements in Groundwater Basins Used for Public Drinking-Water Supply, Desert and Basin and Range Hydrogeologic Provinces, 2006–11: California GAMA Priority Basin Project ER - TY - JOUR T1 - Glacial-interglacial changes in central tropical Pacific surface seawater property gradients JF - Paleoceanography Y1 - 2015 A1 - Lynch-Stieglitz, Jean A1 - Polissar, Pratigya J. A1 - Jacobel, Allison W. A1 - Hovan, Steven A. A1 - Pockalny, Robert A. A1 - Lyle, Mitchell A1 - Murray, Richard W. A1 - Ravelo, A. Christina A1 - Bova, Samantha C. A1 - Dunlea, Ann G. A1 - Ford, Heather L. A1 - Hertzberg, Jennifer E. A1 - Wertman, Christina A. A1 - Maloney, Ashley E. A1 - Shackford, Julia K. A1 - Wejnert, Katherine A1 - Xie, Ruifang C. AB - Much uncertainty exists about the state of the oceanic and atmospheric circulation in the tropical Pacific over the last glacial cycle. Studies have been hampered by the fact that sediment cores suitable for study were concentrated in the western and eastern parts of the tropical Pacific, with little information from the central tropical Pacific. Here we present information from a suite of sediment cores collected from the Line Islands Ridge in the central tropical Pacific, which show sedimentation rates and stratigraphies suitable for paleoceanographic investigations. Based on the radiocarbon and oxygen isotope measurements on the planktonic foraminifera Globigerinoides ruber, we construct preliminary age models for selected cores and show that the gradient in the oxygen isotope ratio of G. ruber between the equator and 8°N is enhanced during glacial stages relative to interglacial stages. This stronger gradient could reflect enhanced equatorial cooling (perhaps reflecting a stronger Walker circulation) or an enhanced salinity gradient (perhaps reflecting increased rainfall in the central tropical Pacific). VL - 30 UR - http://doi.wiley.com/10.1002/2014PA002746 IS - 5 ER - TY - JOUR T1 - Growth rate determinations from radiocarbon in bamboo corals (genus Keratoisis ) JF - Deep Sea Research Part I: Oceanographic Research Papers Y1 - 2015 A1 - Farmer, Jesse R. A1 - Robinson, Laura F. A1 - önisch, ärbel KW - Bamboo coral KW - Deep-sea coral KW - Growth rates KW - radiocarbon AB - Radiocarbon (14C) measurements are an important tool for determining growth rates of bamboo corals, a cosmopolitan group of calcitic deep-sea corals. Published growth rate estimates for bamboo corals are highly variable, with potential environmental or ecological drivers of this variability poorly constrained. Here we systematically investigate the application of 14C for growth rate determinations in bamboo corals using 55 14C dates on the calcite and organic fractions of six bamboo corals (identified as Keratoisis sp.) from the western North Atlantic Ocean. Calcite 14C measurements on the distal surface of these corals and five previously published bamboo corals exhibit a strong one-to-one relationship with the 14C of dissolved inorganic carbon (DI14C) in ambient seawater (r2=0.98), confirming the use of Keratoisis sp. calcite 14C as a proxy for seawater 14C activity. Radial growth rates determined from 14C age-depth regressions, 14C plateau tuning and bomb 14C reference chronologies range from 12 to 78 µm y−1, in general agreement with previously published radiometric growth rates. We document potential biases to 14C growth rate determinations resulting from water mass variability, bomb radiocarbon, secondary infilling (ontogeny), and growth rate nonlinearity. Radial growth rates for Keratoisis sp. specimens do not correlate with ambient temperature, suggesting that additional biological and/or environmental factors may influence bamboo coral growth rates. VL - 105 UR - http://linkinghub.elsevier.com/retrieve/pii/S0967063715001405http://api.elsevier.com/content/article/PII:S0967063715001405?httpAccept=text/xmlhttp://api.elsevier.com/content/article/PII:S0967063715001405?httpAccept=text/plain ER - TY - BOOK T1 - Handbook of Sea-Level ResearchPre-fieldwork surveys Y1 - 2015 A1 - Witter, Robert C. ED - Shennan, Ian ED - Long, Antony J. ED - Horton, Benjamin P. KW - aerial photography KW - barrier island KW - bathymetric data KW - beach ridge KW - coastal geomorphology KW - geomorphological map KW - LiDAR KW - nautical chart KW - remote sensing KW - satellite imagery AB - Using maps, imagery, tidal measurements, and other historical data to assess the geomorphology of a study area prior to fieldwork helps select optimal sites, identify the most effective field methods to test research hypotheses, highlight the primary geomorphic processes, and may provide preliminary estimates of sea-level change. Here, I review the common types of data useful for pre-fieldwork surveys in sea-level research and discuss the many benefits of assessing the geomorphology of a site in advance of fieldwork. I also review briefly some case studies where historical data led to new directions in research and a scientific breakthrough. PB - John Wiley & Sons, Ltd CY - Chichester, UK SN - 9781118452585 UR - http://doi.wiley.com/10.1002/9781118452547.ch3 ER - TY - JOUR T1 - A high output, large acceptance injector for the NOSAMS Tandetron AMS system JF - Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms Y1 - 2015 A1 - Longworth, Brett E. A1 - von Reden, Karl F. A1 - Long, Pat A1 - Roberts, Mark L. AB - We have completed a major upgrade of the National Ocean Sciences AMS Facility (NOSAMS) Tandetron AMS system in two stages. First, the simultaneous (recombinator) injector was replaced with a fast-cycling sequential injector and changes to the low-energy acceleration section. Data after the injector commissioning show an improvement in background, with mean machine background (commercial graphite) of Fm 0.0004 (62 ka). Second, we replaced the original ion source with a high-output 40 sample MCSNICS source. This improved beam currents and raw ratio fractionation, and increased sample to detection efficiency fivefold. VL - 361 N1 - Cu2hzTimes Cited:0Cited References Count:13 JO - A high output, large acceptance injector for the NOSAMS Tandetron AMS system ER - TY - JOUR T1 - High-frequency surface water changes in the Tagus prodelta off Lisbon, eastern North Atlantic, during the last two millennia JF - Marine Micropaleontology Y1 - 2015 A1 - Bartels-Jónsdóttir, Helga B. A1 - Voelker, Antje H. L. A1 - Abrantes, Fatima G. A1 - Salgueiro, Emilia A1 - Rodrigues, Teresa A1 - Knudsen, Karen Luise AB - A high-resolution sedimentary sequence recovered from the Tagus prodelta has been studied with the objective to reconstruct multi-decadal to centennial-scale climate variability on the western Iberian Margin and to discuss the observations in a wider oceanographic and climatic context. Between ca. 100 BC and AD 400 the foraminiferal fauna and high abundance of Globorotalia inflata indicate advection of subtropical waters via the Azores Current and the winter-time warm Portugal Coastal Current. Between ca. AD 400 and 1350, encompassing the Medieval Climate Anomaly (MCA), enhanced upwelling is indicated by the planktonic foraminiferal fauna, in particular by the high abundance of upwelling indicator species Globigerina bulloides. Relatively light δ18O values and high sea surface temperature (SST) (reconstructed from foraminiferal assemblages) point to upwelling of subtropical Eastern North Atlantic Central Water. Between ca. AD 1350 and 1750, i.e. most of the Little Ice Age, relatively heavy δ18O values and low reconstructed SST, as well as high abundances of Neogloboquadrina incompta, indicate the advection of cold subpolar waters to the area and a southward deflection of the subpolar front in the North Atlantic, as well as changes in the mode of the North Atlantic Oscillation. In addition, the assemblage composition together with the other proxy data reveals less upwelling and stronger river input than during the MCA. Stronger Azores Current influence on the Iberian Margin and strong anthropogenic effect on the climate after AD 1750 is indicated by the foraminiferal fauna. The foraminiferal assemblage shows a significant change in surface water conditions at ca. AD 1900, including enhanced river runoff, a rapid increase in temperature and increased influence of the Azores Current. The Tagus record displays a high degree of similarity to other North Atlantic records, indicating that the site is influenced by atmospheric–oceanic processes operating throughout the North Atlantic, as well as by local changes. VL - 117 UR - http://www.sciencedirect.com/science/article/pii/S0377839815000213 JO - High-frequency surface water changes in the Tagus prodelta off Lisbon, eastern North Atlantic, during the last two millennia ER - TY - JOUR T1 - Holocene variability in the intensity of wind-gap upwelling in the tropical eastern Pacific JF - Paleoceanography Y1 - 2015 A1 - Toth, Lauren T. A1 - Aronson, Richard B. A1 - Cheng, Hai A1 - Edwards, R. Lawrence AB - Wind-driven upwelling in Pacific Panamá is a significant source of oceanographic variability in the tropical eastern Pacific. This upwelling system provides a critical teleconnection between the Atlantic and tropical Pacific that may impact climate variability on a global scale. Despite its importance to oceanographic circulation, ecology, and climate, little is known about the long-term stability of the Panamanian upwelling system or its interaction with climatic forcing on millennial time scales. Using a combination of radiocarbon and U-series dating of fossil corals collected in cores from five sites across Pacific Panamá, we reconstructed the local radiocarbon reservoir correction, ΔR, from ~6750 cal B.P. to present. Because the ΔR of shallow-water environments is elevated by upwelling, our data set represents a millennial-scale record of spatial and temporal variability of the Panamanian upwelling system. The general oceanographic gradient from relatively strong upwelling in the Gulf of Panamá to weak-to-absent upwelling in the Gulf of Chiriquí was present throughout our record; however, the intensity of upwelling in the Gulf of Panamá varied significantly through time. Our reconstructions suggest that upwelling in the Gulf of Panamá is weak at present; however, the middle Holocene was characterized by periods of enhanced upwelling, with the most intense upwelling occurring just after of a regional shutdown in the development of reefs at ~4100 cal B.P. Comparisons with regional climate proxies suggest that, whereas the Intertropical Convergence Zone is the primary control on modern upwelling in Pacific Panamá, the El Niño–Southern Oscillation drove the millennial-scale variability of upwelling during the Holocene. VL - 30 UR - http://doi.wiley.com/10.1002/2015PA002794 IS - 8 ER - TY - JOUR T1 - How Unique was Hurricane Sandy? Sedimentary Reconstructions of Extreme Flooding from New York Harbor JF - Scientific Reports Y1 - 2015 A1 - Brandon, Christine M. A1 - Woodruff, Jonathan D. A1 - Donnelly, Jeffrey P. A1 - Sullivan, Richard M. KW - Environmental sciences KW - Geomorphology KW - Palaeoclimate KW - sedimentology AB - The magnitude of flooding in New York City by Hurricane Sandy is commonly believed to be extremely rare, with estimated return periods near or greater than 1000 years. However, the brevity of tide gauge records result in significant uncertainties when estimating the uniqueness of such an event. Here we compare resultant deposition by Hurricane Sandy to earlier storm-induced flood layers in order to extend records of flooding to the city beyond the instrumental dataset. Inversely modeled storm conditions from grain size trends show that a more compact yet more intense hurricane in 1821 CE probably resulted in a similar storm tide and a significantly larger storm surge. Our results indicate the occurrence of additional flood events like Hurricane Sandy in recent centuries, and highlight the inadequacies of the instrumental record in estimating current flood risk by such extreme events. VL - 4 UR - http://www.nature.com/articles/srep07366http://www.nature.com/articles/srep07366.pdfhttp://www.nature.com/articles/srep07366.pdfhttp://www.nature.com/articles/srep07366 IS - 1 ER - TY - JOUR T1 - HUMAN AND CANID DIETARY RELATIONSHIPS: COMPARATIVE STABLE ISOTOPE ANALYSIS FROM THE KODIAK ARCHIPELAGO, ALASKA JF - JOURNAL OF ETHNOBIOLOGY Y1 - 2015 A1 - West, Catherine F. A1 - France, Christine A. KW - Canis familiaris KW - island ecology KW - Stable isotope analysis KW - Vulpes vulpes AB - Stable carbon and nitrogen isotopes are used to address the dietary relationship between humans and two canid species at the Uyak site (KOD-145) on Kodiak Island, Alaska: dog (Canis familiaris) and red fox (Vulpes vulpes). We assess the relative contribution of marine and terrestrial protein to each species' diet as a measure of their dietary relationship to people, using zooarchaeological data, food web data, and ethnohistoric observations to interpret the results. The results suggest that dogs and foxes had different diets: the dogs are consistently enriched in both C-13 and N-15, which indicates a heavy dependence on marine protein, while the fox samples produced both marine and terrestrial isotope values. Data from this project have the potential to expand our understanding of human-canid relationships in this island environment and in the greater context of island ecology, and contribute some of the first isotopic data for small terrestrial mammals in the Gulf of Alaska. VL - 35 ER - TY - JOUR T1 - Incorporation of bomb-produced 14C into fish otoliths. An example of basin-specific rates from the North Pacific Ocean JF - Canadian Journal of Fisheries and Aquatic Sciences Y1 - 2015 A1 - Wischniowski, Stephen G. A1 - Kastelle, Craig R. A1 - Loher, Timothy A1 - Helser, Thomas E. VL - 72 UR - http://dx.doi.org/10.1139/cjfas-2014-0225 IS - 6 JO - Incorporation of bomb-produced 14C into fish otoliths. An example of basin-specific rates from the North Pacific Ocean ER - TY - JOUR T1 - The influence of ice marginal setting on early Holocene retreat rates in central West Greenland JF - Journal of Quaternary Science Y1 - 2015 A1 - KELLEY, SAMUEL E. A1 - Briner, Jason P. A1 - ZIMMERMAN, SUSAN R. H. AB - Ice sheet reconstructions from diverse ice margin settings, spanning multiple millennia, are needed to assess the reaction of the Greenland Ice Sheet (GrIS) to millennial-scale climatic forcing and to place historical records in a longer-term context. Here we present 18 new cosmogenic 10Be exposure ages and five new radiocarbon ages that constrain the early Holocene retreat of the GrIS in the Disko Bugt region in both a marine and a land-based setting. Results indicate similar rates of early Holocene retreat of ∼40–50 m a−1 from transects in Torsukattak fjord (marine setting) and the Naternaq area (land-based setting). We compile seven previously published chronologies of deglaciation from West Greenland, which yield early Holocene retreat rates ranging from 10 to 65 m a−1, similar to those determined for our two study areas. This work demonstrates that when averaged on millennial timescales, retreat rates were remarkably similar along the western GrIS margin. Furthermore, the retreat rates calculated here demonstrate that terrestrial sectors of ice sheets can retreat at net rates comparable to their marine counterparts. VL - 30 UR - http://doi.wiley.com/10.1002/jqs.2778 IS - 3 ER - TY - JOUR T1 - Isotope-Based Source Apportionment of EC Aerosol Particles during Winter High-Pollution Events at the Zeppelin Observatory, Svalbard JF - Environmental Science & Technology Y1 - 2015 A1 - Winiger, Patrik A1 - Andersson, August A1 - Yttri, Karl E. A1 - Tunved, Peter A1 - Gustafsson, Örjan AB - Black carbon (BC) aerosol particles contribute to climate warming of the Arctic, yet both the sources and the source-related effects are currently poorly constrained. Bottom-up emission inventory (EI) approaches are challenged for BC in general and the Arctic in particular. For example, estimates from three different EI models on the fractional contribution to BC from biomass burning (north of 60° N) vary between 11% and 68%, each acknowledging large uncertainties. Here we present the first dual-carbon isotope-based (Δ14C and δ13C) source apportionment of elemental carbon (EC), the mass-based correspondent to optically defined BC, in the Arctic atmosphere. It targeted 14 high-loading and high-pollution events during January through March of 2009 at the Zeppelin Observatory (79° N; Svalbard, Norway), with these representing one-third of the total sampling period that was yet responsible for three-quarters of the total EC loading. The top-down source-diagnostic 14C fingerprint constrained that 52 ± 15% (n = 12) of the EC stemmed from biomass burning. Including also two samples with 95% and 98% biomass contribution yield 57 ± 21% of EC from biomass burning. Significant variability in the stable carbon isotope signature indicated temporally shifting emissions between different fossil sources, likely including liquid fossil and gas flaring. Improved source constraints of Arctic BC both aids better understanding of effects and guides policy actions to mitigate emissions. VL - 49 UR - http://pubs.acs.org/doi/10.1021/acs.est.5b02644http://pubs.acs.org/doi/pdf/10.1021/acs.est.5b02644 IS - 19 ER - TY - JOUR T1 - Late Holocene glacial advance and ice shelf growth in Barilari Bay, Graham Land, west Antarctic Peninsula JF - GEOLOGICAL SOCIETY OF AMERICA BULLETIN Y1 - 2015 A1 - Christ, Andrew J. A1 - Talaia-Murray, Manique A1 - Elking, Natalie A1 - Domack, Eugene W. A1 - Leventer, Amy A1 - Lavoie, Caroline A1 - Brachfeld, Stefanie A1 - Yoo, Kyu-Cheul A1 - Gilbert, Robert A1 - Jeong, Sun-Mi A1 - Petrushak, Stephen A1 - Wellner, Julia A1 - LARISSA Grp AB - Three marine sediment cores were collected along the length of the fjord axis of Barilari Bay, Graham Land, west Antarctic Peninsula (65 degrees 55'S, 64 degrees 43'W). Multi-proxy analytical results constrained by high-resolution geochronological methods (Pb-210, radiocarbon, Cs-137) in concert with historical observations capture a record of Holocene paleoenvironmental variability. Our results suggest early and middle Holocene (>7022-2815 cal. {[}calibrated] yr B.P.) retreated glacial positions and seasonally open marine conditions with increased primary productivity. Climatic cooling increased sea ice coverage and decreased primary productivity during the Neoglacial (2815 to cal. 730 cal. yr B.P.). This climatic cooling culminated with glacial advance to maximum Holocene positions and expansion of a fjord-wide ice shelf during the Little Ice Age (LIA) (ca. 730-82 cal. yr B.P.). Seasonally open marine conditions were achieved and remnant ice shelves decayed within the context of recent rapid regional warming (82 cal. yr B.P. to present). Our findings agree with previously observed late Holocene cooling and glacial advance across the Antarctic Peninsula, suggesting that the LIA was a regionally significant event with few disparities in timing and magnitude. Comparison of the LIA Antarctic Peninsula record to the rest of the Southern Hemisphere demonstrates close synchronicity in the southeast Pacific and southern most Atlantic region but less coherence for the southwest Pacific and Indian Oceans. Comparisons with the Northern Hemisphere demonstrate that the LIA Antarctic Peninsula record was contemporaneous with pre-LIA cooling and sea ice expansion in the North Atlantic-Arctic, suggesting a global reach for these events. VL - 127 ER - TY - JOUR T1 - Late Holocene precipitation variability recorded in the sediments of Reloncaví Fjord (41°S, 72°W), Chile JF - Quaternary Research Y1 - 2015 A1 - Rebolledo, Lorena A1 - Lange, Carina B. A1 - Bertrand, Sébastien A1 - Muñoz, Praxedes A1 - Salamanca, Marco A1 - Lazo, Pablo A1 - Iriarte, José L. A1 - Vargas, Gabriel A1 - Pantoja, Silvio A1 - Dezileau, Laurent AB - We present reconstructions of late Holocene changes in the source of organic matter and siliceous export production in the Relocanví Fjord (41°S, 72°W), Northern Chilean Patagonia, based on organic carbon content, δ13Corg, N/C ratio, diatom assemblages and biogenic silica contents from three sediment cores. The age models are based on a combination of 210Pb profiles, AMS 14C dating, and on the first occurrence of the diatom Rhizosolenia setigera f. pungens, as a stratigraphic marker in the fjords. The cores span the last 300 to 700 yr. Diatoms dominate the siliceous assemblages in the three cores (98% on average). Our results suggest that precipitation seasonality in the region of Reloncaví was high in CE 1300–1400 and CE 1700–1850, with a clear decreasing trend since CE 1850. The latter trend is in agreement with instrumental records and tree-ring reconstructions. These fluctuations seem to be associated with the Southern Annular Mode (SAM). VL - 84 N1 - Co0ceTimes Cited:1Cited References Count:93 JO - Late Holocene precipitation variability recorded in the sediments of Reloncaví Fjord (41°S, 72°W), Chile ER - TY - JOUR T1 - Low-frequency storminess signal at Bermuda linked to cooling events in the North Atlantic region JF - Paleoceanography Y1 - 2015 A1 - van Hengstum, Peter J. A1 - Donnelly, Jeffrey P. A1 - Kingston, Andrew W. A1 - Williams, Bruce E. A1 - Scott, David B. A1 - Reinhardt, Eduard G. A1 - Little, Shawna N. A1 - Patterson, William P. AB - North Atlantic climate archives provide evidence for increased storm activity during the Little Ice Age (150 to 600 calibrated years (cal years) B.P.) and centered at 1700 and 3000 cal years B.P., typically in centennial-scale sedimentary records. Meteorological (tropical versus extratropical storms) and climate forcings of this signal remain poorly understood, although variability in the North Atlantic Oscillation (NAO) or Atlantic Meridional Overturning Circulation (AMOC) are frequently hypothesized to be involved. Here we present records of late Holocene storminess and coastal temperature change from a Bermudian submarine cave that is hydrographically circulated with the coastal ocean. Thermal variability in the cave is documented by stable oxygen isotope values of cave benthic foraminifera, which document a close linkage between regional temperature change and NAO phasing during the late Holocene. However, erosion of terrestrial sediment into the submarine cave provides a “storminess signal” that correlates with higher-latitude storminess archives and broader North Atlantic cooling events. Understanding the driver of this storminess signal will require higher-resolution storm records to disentangle the contribution of tropical versus extratropical cyclones and a better understanding of cyclone activity during hemispheric cooling periods. Most importantly, however, the signal in Bermuda appears more closely correlated with proxy-based evidence for subtle AMOC reductions than NAO phasing. VL - 30 UR - http://doi.wiley.com/10.1002/2014PA002662https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2F2014PA002662 IS - 2 ER - TY - JOUR T1 - Marine record of Holocene climate, ocean, and cryosphere interactions: Herbert Sound, James Ross Island, Antarctica JF - Quaternary Science Reviews Y1 - 2015 A1 - Minzoni, Rebecca Totten A1 - Anderson, John B. A1 - Fernandez, Rodrigo A1 - Wellner, Julia Smith KW - Antarctic Peninsula KW - diatoms KW - Holocene KW - paleoceanography KW - paleoclimatology AB - The sediment record offshore James Ross Island, northeast Antarctic Peninsula presents an unparalleled opportunity to directly compare marine and terrestrial climate records spanning the Holocene in maritime Antarctica. An 11 m drill core was collected between Herbert Sound and Croft Bay as part of the SHALDRIL NBP-0502 initiative and produced the southernmost sediment record from the eastern side of the AP. Thirty-eight radiocarbon ages are used to construct an age model of centennial-scale resolution. Multi-proxy records, including magnetic susceptibility, pebble content, particle size, total organic carbon, and diatom assemblages, were interrogated in the context of nearby Holocene-age ice core, lake, and drift records from James Ross Island. Differences in the timing and expression of Holocene events reflect marine controls on tidewater glaciers, such as water mass configurations and sea ice. Glacial behavior mimics ice core paleotemperatures during the Holocene, with the exception of distinct ocean warming events. Herbert Sound was fully occupied by grounded ice during the Last Glacial Maximum, and experienced rapid lift-off, followed by a floating ice phase. The canopy of floating ice receded by 10 ± 2.4 cal kyr BP, presumably in response to Early Holocene warming. Herbert Sound and Croft Bay fully deglaciated by 7.2 cal kyr BP, when the Mid Holocene Hypsithermal commenced and the sound became open and productive. An extreme peak in productivity ∼6.1 cal kyr BP indicates an oceanic warming event that is not reflected in atmospheric temperature or lacustrine sediment records. Increase in sea ice cover and ice rafting mark the onset of the Neoglacial ∼2.5 cal kyr BP, when pronounced atmospheric cooling is documented in the James Ross Island ice core. Our comparison facilitates more holistic understanding of atmosphere-ocean-cryosphere interactions that may aid predictions of glacial response to future warming and sea-level scenarios. VL - 129 UR - https://doi.org/10.1016/j.quascirev.2015.09.009 ER - TY - JOUR T1 - Methods and codes for reservoir-atmosphere C-14 age offset calculations JF - QUATERNARY GEOCHRONOLOGY Y1 - 2015 A1 - Soulet, Guillaume KW - Calibration curve KW - Dead carbon fraction KW - Radiocarbon modeling KW - Reservoir age KW - Reservoir effect KW - Uncalibration process AB - Reservoir C-14 age offsets are invaluable tracers for past changes in carbon cycle and oceanic circulation. Reconstruction of reservoir age offsets with time is also required for calibration purposes (reconstruction of atmospheric calibration curve, calibration of non-atmospheric radiocarbon ages). Thus, properly propagating the various uncertainties linked to reservoir age offset is important for proper interpretation. However, approaches for reservoir age offset calculation especially when considering pairs of reservoir-derived C-14 and calenidar ages are usually not detailed and inadequate for proper propagation of uncertainties. Here, the various ways to properly calculate reservoir age offsets are described with a focus on a new approach when considering pairs of C-14 and calendar ages. This approach maps the calendar age distribution onto the C-14 time scale prior to reservoir age offset calculation the ``uncalibration-convolution process{''}. R codes computing reservoir age offsets based on available data are presented. Finally, a case study focusing on the reconstruction of the speleothem-atmosphere C-14 age offsets of speleothem C-14 data used in the latest release of the atmospheric calibration curve is discussed. (C) 2015 Elsevier B.V. All rights reserved. VL - 29 ER - TY - JOUR T1 - Millennial-scale fluctuations of the European Ice Sheet at the end of the last glacial, and their potential impact on global climate JF - QUATERNARY SCIENCE REVIEWS Y1 - 2015 A1 - Toucanne, Samuel A1 - Soulet, Guillaume A1 - Freslon, Nicolas A1 - Jacinto, Ricardo Silva A1 - Dennielou, Bernard A1 - Zaragosi, Sebastien A1 - Eynaud, Frédérique A1 - Bourillet, Jean-Francois A1 - Bayon, Germain KW - Channel River KW - Deglaciation KW - European ice-sheet KW - Meltwater KW - Neodymium KW - Termination AB - Reconstructing Northern Hemisphere ice-sheet oscillations and meltwater routing to the ocean is important to better understand the mechanisms behind abrupt climate changes. To date, research efforts have mainly focused on the North American (Laurentide) ice-sheets (LIS), leaving the potential role of the European Ice Sheet (EIS), and of the Scandinavian ice-sheet (SIS) in particular, largely unexplored. Using neodymium isotopes in detrital sediments deposited off the Channel River, we provide a continuous and well-dated record for the evolution of the EIS southern margin through the end of the last glacial period and during the deglaciation. Our results reveal that the evolution of EIS margins was accompanied with substantial ice recession (especially of the SIS) and simultaneous release of meltwater to the North Atlantic. These events occurred both in the course of the EIS to its LGM position (i.e., during Heinrich Stadial -HS- 3 and HS2; similar to 31-29 ka and similar to 26-23 ka, respectively) and during the deglaciation (i.e., at similar to 22 ka, similar to 20-19 ka and from 18.2 +/- 0.2 to 16.7 +/- 0.2 ka that corresponds to the first part of HS1). The deglaciation was discontinuous in character, and similar in timing to that of the southern LIS margin, with moderate ice-sheet retreat (from 22.5 +/- 0.2 ka in the Baltic lowlands) as soon as the northern summer insolation increase (from similar to 23 ka) and an acceleration of the margin retreat thereafter (from similar to 20 ka). Importantly, our results show that EIS retreat events and release of meltwater to the North Atlantic during the deglaciation coincide with AMOC destabilisation and interhemispheric climate changes. They thus suggest that the EIS, together with the LIS, could have played a critical role in the climatic reorganization that accompanied the last deglaciation. Finally, our data suggest that meltwater discharges to the North Atlantic produced by large-scale recession of continental parts of Northern Hemisphere ice sheets during HS, could have been a possible source for the oceanic perturbations (i.e., AMOC shutdown) responsible for the marine-based ice stream purge cycle, or so-called HE's, that punctuate the last glacial period. (C) 2015 Elsevier Ltd. All rights reserved. VL - 123 ER - TY - JOUR T1 - Multimolecular tracers of terrestrial carbon transfer across the pan-Arctic: C-14 characteristics of sedimentary carbon components and their environmental controls JF - GLOBAL BIOGEOCHEMICAL CYCLES Y1 - 2015 A1 - Feng, Xiaojuan A1 - Gustafsson, Örjan A1 - Holmes, R. Max A1 - Vonk, Jorien E. A1 - van Dongen, Bart E. A1 - Semiletov, Igor P. A1 - Dudarev, Oleg V. A1 - Yunker, Mark B. A1 - Macdonald, Robie W. A1 - Wacker, Lukas A1 - Montluçon, Daniel B. A1 - Eglinton, Timothy I. AB - Distinguishing the sources, ages, and fate of various terrestrial organic carbon (OC) pools mobilized from heterogeneous Arctic landscapes is key to assessing climatic impacts on the fluvial release of carbon from permafrost. Through molecular C-14 measurements, including novel analyses of suberin- and/or cutin-derived diacids (DAs) and hydroxy fatty acids (FAs), we compared the radiocarbon characteristics of a comprehensive suite of terrestrial markers (including plant wax lipids, cutin, suberin, lignin, and hydroxy phenols) in the sedimentary particles from nine major arctic and subarctic rivers in order to establish a benchmark assessment of the mobilization patterns of terrestrial OC pools across the pan-Arctic. Terrestrial lipids, including suberin-derived longer-chain DAs (C-24,C-26,C-28), plant wax FAs (C(24,26,2)8), and n-alkanes (C-27,C-29,C-31), incorporated significant inputs of aged carbon, presumably from deeper soil horizons. Mobilization and translocation of these ``old{''} terrestrial carbon components was dependent on nonlinear processes associated with permafrost distributions. By contrast, shorter-chain (C-16,C-18) DAs and lignin phenols (as well as hydroxy phenols in rivers outside eastern Eurasian Arctic) were much more enriched in C-14, suggesting incorporation of relatively young carbon supplied by runoff processes from recent vegetation debris and surface layers. Furthermore, the radiocarbon content of terrestrial markers is heavily influenced by specific OC sources and degradation status. Overall, multitracer molecular C-14 analysis sheds new light on the mobilization of terrestrial OC from arctic watersheds. Our findings of distinct ages for various terrestrial carbon components may aid in elucidating fate of different terrestrial OC pools in the face of increasing arctic permafrost thaw. VL - 29 ER - TY - JOUR T1 - Multiproxy record of monsoon variability from the Ganga Plain during 400–1200 A.D JF - Updated Quaternary Climatic Research in parts of the Third Pole Selected papers from the HOPE-2013 conference, Nainital, India Y1 - 2015 A1 - Singh, Dhruv Sen A1 - Gupta, Anil K. A1 - Sangode, S. J. A1 - Clemens, Steven C. A1 - Prakasam, M. A1 - Srivastava, Priyeshu A1 - Prajapati, Shailendra K. AB - Understanding on the Indian Summer Monsoon (ISM) variability is chiefly based upon the marine proxies and a few continental records. The Ganga Plain, one of the most densely populated regions of the world marked by intensive cultivation of monsoon dependent crops and a rich cultural history, is not yet well understood in the context of monsoon variability. We present here a 400–1200 A.D. AMS radiocarbon dated record of Ropan Chhapra tal in the Central Ganga Plain using sedimentology, environmental magnetism, and stable isotope of oxygen for ISM variability. The environmental magnetic parameters (χlf, χARM, SIRM/χlf, S-Ratio, B(0)CR and HIRM) inferred antiferromagnetic mineralogy (hematite and/or goethite) independent of grain size variation during 400–900 A.D., depicting climate variability within warm humid to warm arid conditions favouring stronger ISM seasonality. Prevalence of ferrimagnetic mineralogy under less oxygenated conditions intermittently demonstrates an altered catchment regime or possibly in response to stronger winter monsoon. The higher δ18O values around 500, 580 and 740 A.D. indicate warm and arid conditions under weak ISM. The lower δ18O values around 480, 540 and 700 A.D. and from 900 to 1200 A.D. occur during warm and humid conditions indicating maximum intensity of the ISM. Increased silt content from 800 A.D. onwards is due to increased surface runoff in response to enhanced precipitation, and the higher clay percentage around 500, 580 and 740 indicates low-energy (ponding) conditions under weak ISM. The well sorted nature of sediment indicates consistency of the lacustrine environments under fairly uniform energy and constant bottom water conditions, under varied monsoonal intensity. Combinations of sediment textures and stable isotope indicate intense ISM at ∼480 and ∼540 A.D. with flooding around ∼700 A.D. and a weak monsoon at 580 and 740 A.D., with drought at 500 A.D. During ∼900–1200 A.D. the multiproxy record suggests strong summer monsoon synchronous with Medieval Warm Period (MWP), whereas after 1200 A.D. the weak monsoon phase coincides with the onset of the Little Ice Age (LIA). VL - 371 UR - http://www.sciencedirect.com/science/article/pii/S1040618215001470 JO - Multiproxy record of monsoon variability from the Ganga Plain during 400–1200 A.D ER - TY - JOUR T1 - PALEO-STORM INDICATORS WITHIN SASYK LIMAN BAYMOUTH BARRIER, UKRAINE JF - Geology Bulletin Y1 - 2015 A1 - Buynevich, I.V. A1 - Kadurin, S.V. KW - georadar KW - heavy-mineral concentration KW - magnetic susceptibility AB - Sedimentary sequences along continental and insular margins serve as archives of coastal erosion by storms and tsunamis. In areas where overwash is limited or precluded by barrier width and height, such as prograded beach-ridge plains (strandplains), geomorphological (scarps) and lithological (heavy-mineral concentrations) indicators provide the only means of assessing the extent and timing of erosional events. This research presents geological evidence of buried erosional scarps along the Black Sea coast of southwestern Ukraine. A distinct paleo-scarp imaged in shore-normal georadar profile and the associated heavy-mineral horizon (magnetic susceptibility >1,700 SI) indicate a storm event that impacted the shoreline of Sasyk Liman baymouth barrier in historical times. Optical dating offers a more reliable chronology of erosional events, whereas radiocarbon-dated reworked early Holocene shells aid in determining the sources of bioclastic material. VL - 29 ER - TY - JOUR T1 - Palynological reconstruction of environmental changes in coastal wetlands of the Florida Everglades since the mid-Holocene JF - Quaternary Research Y1 - 2015 A1 - Yao, Qiang A1 - Liu, Kam-biu A1 - Platt, William J. A1 - Rivera-Monroy, Victor H. AB - Palynological, loss-on-ignition, and X-ray fluorescence data from a 5.25 m sediment core from a mangrove forest at the mouth of the Shark River Estuary in the southwestern Everglades National Park, Florida were used to reconstruct changes occurring in coastal wetlands since the mid-Holocene. This multi-proxy record contains the longest paleoecological history to date in the southwestern Everglades. The Shark River Estuary basin was formed ~ 5700 cal yr BP in response to increasing precipitation. Initial wetlands were frequently-burned short-hydroperiod prairies, which transitioned into long-hydroperiod prairies with sloughs in which peat deposits began to accumulate continuously about 5250 cal yr BP. Our data suggest that mangrove communities started to appear after ~ 3800 cal yr BP; declines in the abundance of charcoal suggested gradual replacement of fire-dominated wetlands by mangrove forest over the following 2650 yr. By ~ 1150 cal yr BP, a dense Rhizophora mangle dominated mangrove forest had formed at the mouth of the Shark River. The mangrove-dominated coastal ecosystem here was established at least 2000 yr later than has been previously estimated. VL - 83 UR - http://www.sciencedirect.com/science/article/pii/S0033589415000290 IS - 3 JO - Palynological reconstruction of environmental changes in coastal wetlands of the Florida Everglades since the mid-Holocene ER - TY - JOUR T1 - A post-glacial relative sea-level curve from Fiordland, New Zealand JF - Global and Planetary Change Y1 - 2015 A1 - Dlabola, E. K. A1 - Wilson, G. S. A1 - Gorman, A. R. A1 - Riesselman, C. R. A1 - Moy, C. M. AB - The modern fjords of southwest New Zealand were previously stranded lakes isolated from the Tasman Sea by bedrock and moraine sills following the retreat of glaciers at the Last Glacial Maximum. The isolated lake basins were subsequently inundated with sea water when sea-level rise overtopped the sills. A record of the lacustrine-to-marine environmental transition is preserved in the fjord basin sediments and is identified in two New Zealand fjords with high-resolution seismic data and paleoenvironmental analysis of sediment cores. Seismic data are used to constrain the maximum sill depth and microfossil assemblages are used to track the lacustrine-to-marine transition. Chronology is based on fourteen radiocarbon ages. A relative sea-level curve for Fiordland, New Zealand is constructed based on sill depths and age constraints on the marine incursion. The sea-level curve allows insights into estimated uplift rates for Fiordland during the Holocene. From a lowstand of at least 107 mbsl 14,750 yr ago, these data reveal a stepwise transgression. Meltwater Pulse 1b is identified between 12,400 and 11,400 yr ago, with a second acceleration in sea-level rise observed 9700 yr ago. This record contributes a new sea-level curve for a mid-latitude (45°S) Southern Hemisphere location as well as new evidence for Meltwater Pulse 1b. VL - 131 UR - http://www.sciencedirect.com/science/article/pii/S0921818115001071 JO - A post-glacial relative sea-level curve from Fiordland, New Zealand ER - TY - JOUR T1 - Quantification of refractory organic material in Amazon mudbanks of the French Guiana Coast JF - Marine Geology Y1 - 2015 A1 - Williams, Elizabeth K. A1 - Rosenheim, Brad E. A1 - Allison, Mead A1 - McNichol, Ann P. A1 - Xu, Li AB - Sub-oxic overturning mudbanks originating in the Amazon outlet and traveling northwestward along the coast of South America store 3.5 Tg organic carbon on the Amazon shelf, annually. The predominance of old soil carbon burial associated with the sediment has been supported by relatively old bulk radiocarbon ages (~ 2200–3200 14C y) reported, but this amount has yet to be quantified for this dynamic setting. Here, we employ ramped pyrolysis radiocarbon dating to mudbank sediments from three cores to further constrain the amount of refractory sedimentary organic carbon present. Using radiocarbon age as a proxy for reactivity, we find that at least 36% of this organic carbon is pre-aged refractory terrestrial organic carbon, likely sourced from terrestrial soils and averaging ages of 16,100 ± 300 14C y. This implies significant preservation of pre-aged terrestrial soil material in this marine environment despite the mobility and oxygen availability in the muds. Concurrently, an average of 77% of this organic material is aged over 1000 14C y, consistent with previous estimates that the majority of organic carbon buried along the shelf is refractory. Analyses of extracted lignin phenols and terrestrial humic acids also support this preservation of refractory terrestrial material. These data indicate that sediment discharged from the Amazon River may preserve refractory terrestrial carbon in marine sediments at a minimum of 3.1 Tg C/y, which is more efficient than originally thought. VL - 363 UR - http://www.sciencedirect.com/science/article/pii/S0025322715000456 JO - Quantification of refractory organic material in Amazon mudbanks of the French Guiana Coast ER - TY - JOUR T1 - Radiocarbon evidence for a possible abyssal front near 3.1 km in the glacial equatorial Pacific Ocean JF - Earth and Planetary Science Letters Y1 - 2015 A1 - Keigwin, L. D. A1 - Lehman, S. J. AB - We investigate the radiocarbon ventilation age in deep equatorial Pacific sediment cores using the difference in conventional 14C age between coexisting benthic and planktonic foraminifera, and integrate those results with similar data from around the North Pacific Ocean in a reconstruction for the last glaciation (15 to 25 conventional 14C ka). Most new data from both the Equatorial Pacific and the Emperor Seamounts in the northwestern Pacific come from maxima in abundance of benthic taxa because this strategy reduces the effect of bioturbation. Although there remains considerable scatter in the ventilation age estimates, on average, ventilation ages in the Equatorial Pacific were significantly greater below 3.2 km ( ∼ 3080 ± 1125 yrs , n = 15 ) than in the depth interval 1.9 to 3.0 km ( ∼ 1610 ± 250 yrs , n = 12 ). When compared to the average modern seawater Δ C 14 profile for the North Pacific, the Equatorial Pacific glacial data suggest an abyssal front located somewhere between 3.0 and 3.2 km modern water depth. Above that depth, the data may indicate slightly better ventilation than today, and below that depth, glacial Equatorial Pacific data appear to be as old as last glacial maximum (LGM) deep water ages reported for the deep southern Atlantic. This suggests that a glacial reservoir of aged waters extended throughout the circumpolar Southern Ocean and into the Equatorial Pacific. Renewed ventilation of such a large volume of aged (and, by corollary, carbon-rich) water would help to account for the rise in atmospheric pCO2 and the fall in Δ C 14 as the glaciation drew to a close. VL - 425 UR - http://www.sciencedirect.com/science/article/pii/S0012821X15003210 JO - Radiocarbon evidence for a possible abyssal front near 3.1 km in the glacial equatorial Pacific Ocean ER - TY - JOUR T1 - Rapid, high-resolution C-14 chronology of ooids JF - GEOCHIMICA ET COSMOCHIMICA ACTA Y1 - 2015 A1 - Beaupré, Steven R. A1 - Roberts, Mark L. A1 - Burton, Joshua R. A1 - Summons, Roger E. AB - Ooids are small, spherical to ellipsoidal grains composed of concentric layers of CaCO3 that could potentially serve as biogeochemical records of the environments in which they grew. Such records, however, must be placed in the proper temporal context. Therefore, we developed a novel acidification system and employed an accelerator mass spectrometer (AMS) with a gas accepting ion source to obtain radiocarbon (C-14) chronologies extending radially through ooids within one 8-h workday. The method was applied to ooids from Highborne Cay, Bahamas and Shark Bay, Australia, yielding reproducible C-14 chronologies, as well as constraints on the rates and durations of ooid growth and independent estimates of local C-14 reservoir ages. (C) 2015 Elsevier Ltd. All rights reserved. VL - 159 ER - TY - JOUR T1 - Refined bomb radiocarbon dating of two iconic fishes of the Great Barrier Reef JF - Marine and Freshwater Research Y1 - 2015 A1 - Andrews, Allen H. A1 - Choat, John H. A1 - Hamilton, Richard J. A1 - DeMartini, Edward E. VL - 66 IS - 4 N1 - PT: J; TC: 0; UT: WOS:000351621600003 JO - Refined bomb radiocarbon dating of two iconic fishes of the Great Barrier Reef ER - TY - JOUR T1 - Relative sea-level change in Connecticut (USA) during the last 2200 yrs JF - Earth and Planetary Science Letters Y1 - 2015 A1 - Kemp, Andrew C. A1 - Hawkes, Andrea D. A1 - Donnelly, Jeffrey P. A1 - Vane, Christopher H. A1 - Horton, Benjamin P. A1 - Hill, Troy D. A1 - Anisfeld, Shimon C. A1 - Parnell, Andrew C. A1 - Cahill, Niamh KW - Atlantic Ocean KW - Foraminifera KW - Gulf Stream KW - Late Holocene KW - Salt marsh AB - We produced a relative sea-level (RSL) reconstruction from Connecticut (USA) spanning the last ∼2200 yrs that is free from the influence of sediment compaction. The reconstruction used a suite of vertically- and laterally-ordered sediment samples ≤2 cm above bedrock that were collected by excavating a trench along an evenly-sloped bedrock surface. Paleomarsh elevation was reconstructed using a regional-scale transfer function trained on the modern distribution of foraminifera on Long Island Sound salt marshes and supported by bulk-sediment δ13C measurements. The history of sediment accumulation was estimated using an age-elevation model constrained by radiocarbon dates and recognition of pollution horizons of known age. The RSL reconstruction was combined with regional tide-gauge measurements spanning the last ∼150 yrs before being quantitatively analyzed using an error-in-variables integrated Gaussian process model to identify sea-level trends with formal and appropriate treatment of uncertainty and the temporal distribution of data. RSL rise was stable (∼1 mm/yr) from ∼200 BCE to ∼1000 CE, slowed to a minimum rate of rise (0.41 mm/yr) at ∼1400 CE, and then accelerated continuously to reach a current rate of 3.2 mm/yr, which is the fastest, century-scale rate of the last 2200 yrs. Change point analysis identified that modern rates of rise in Connecticut began at 1850–1886 CE. This timing is synchronous with changes recorded at other sites on the U.S. Atlantic coast and is likely the local expression of a global sea-level change. Earlier sea-level trends show coherence north of Cape Hatteras that are contrasted with southern sites. This pattern may represent centennial-scale variability in the position and/or strength of the Gulf Stream. Comparison of the new record to three existing and reanalyzed RSL reconstructions from the same site developed using sediment cores indicates that compaction is unlikely to significantly distort RSL reconstructions produced from shallow (∼2–3 m thick) sequences of salt-marsh peat. VL - 428 UR - http://linkinghub.elsevier.com/retrieve/pii/S0012821X15004690http://api.elsevier.com/content/article/PII:S0012821X15004690?httpAccept=text/xmlhttp://api.elsevier.com/content/article/PII:S0012821X15004690?httpAccept=text/plain ER - TY - JOUR T1 - A sea-level database for the Pacific coast of central North America JF - Quaternary Science Reviews Y1 - 2015 A1 - Engelhart, Simon E. A1 - Vacchi, Matteo A1 - Horton, Benjamin P. A1 - Nelson, Alan R. A1 - Kopp, Robert E. KW - Cascadia subduction zone KW - Glacial isostatic adjustment KW - Holocene KW - Pacific North America KW - Sea-level database AB - A database of published and new relative sea-level (RSL) data for the past 16 ka constrains the sea-level histories of the Pacific coast of central North America (southern British Columbia to central California). Our reevaluation of the stratigraphic context and radiocarbon age of sea-level indicators from geological and archaeological investigations yields 600 sea-level index points and 241 sea-level limiting points. We subdivided the database into 12 regions based on the availability of data, tectonic setting, and distance from the former Cordilleran ice sheet. Most index (95%) and limiting points (54%) are <7 ka; older data come mainly from British Columbia and San Francisco Bay. The stratigraphic position of points was used as a first-order assessment of compaction. Formerly glaciated areas show variable RSL change; where data are present, highstands of RSL occur immediately post-deglaciation and in the mid to late Holocene. Sites at the periphery and distant to formerly glaciated areas demonstrate a continuous rise in RSL with a decreasing rate through time due to the collapse of the peripheral forebulge and the reduction in meltwater input during deglaciation. Late Holocene RSL change varies spatially from falling at 0.7 ± 0.8 mm a−1 in southern British Columbia to rising at 1.5 ± 0.3 mm a−1 in California. The different sea-level histories are an ongoing isostatic response to deglaciation of the Cordilleran and Laurentide Ice Sheets. VL - 113 UR - https://doi.org/10.1016/j.quascirev.2014.12.001 ER - TY - JOUR T1 - Searching for the Oldest Baobab of Madagascar: Radiocarbon Investigation of Large Adansonia rubrostipa Trees JF - PLoS ONE Y1 - 2015 A1 - Patrut, Adrian A1 - von Reden, Karl F. A1 - Danthu, Pascal A1 - Leong Pock-Tsy, Jean-Michel A1 - Patrut, Roxana T. A1 - Lowy, Daniel A. AB - We extended our research on the architecture, growth and age of trees belonging to the genus Adansonia, by starting to investigate large individuals of the most widespread Malagasy species. Our research also intends to identify the oldest baobabs of Madagascar. Here we present results of the radiocarbon investigation of the two most representative Adansonia rubrostipa (fony baobab) specimens, which are located in south-western Madagascar, in the Tsimanampetsotse National Park. We found that the fony baobab called “Grandmother” consists of 3 perfectly fused stems of different ages. The radiocarbon date of the oldest sample was found to be 1136 ± 16 BP. We estimated that the oldest part of this tree, which is mainly hollow, has an age close to 1,600 yr. This value is comparable to the age of the oldest Adansonia digitata (African baobab) specimens. By its age, the Grandmother is a major candidate for the oldest baobab of Madagascar. The second investigated specimen, called the “polygamous baobab”, consists of 6 partially fused stems of different ages. According to dating results, this fony baobab is 1,000 yr old. This research is the first investigation of the structure and age of Malagasy baobabs. VL - 10 UR - http://dx.doi.org/10.1371%2Fjournal.pone.0121170 IS - 3 JO - Searching for the Oldest Baobab of Madagascar: Radiocarbon Investigation of Large Adansonia rubrostipa Trees ER - TY - JOUR T1 - Sediment flux and recent paleoclimate in JordanBasin, Gulf of Maine JF - Continental Shelf Research Y1 - 2015 A1 - Keigwin, Lloyd D. A1 - Pilskaln, Cynthia H. AB - We report planktonic foraminiferal fluxes (accumulation rates) and oxygen isotopes (5180) from a nine-month sediment trap deployment, and 8180 from three sediment cores in Jordan Basin, Gulf of Maine. The sediment trap was deployed at 150 m, about halfway to the basin floor, and samples were collected every three weeks between August 2010 and May 2011. The planktonic foraminiferal fauna in the trap is dominated by Neogloboquadrina incompta that reached a maximum flux in the second half of October. Oxygen isotope ratios on that species indicate that on average during the collecting period it lived in the surface mixed layer, when compared to predicted values based on data from a nearby hydrographic buoy from the same period. New large diameter piston cores from Jordan Basin are 25 and 28 m long. Marine hemipelagic sediments are 25 m thick, and the sharp contact with underlying red deglacial sediments is bracketed by two radiocarbon dates on bivalves that indicate ice-free conditions began 16,900 calibrated years ago. Radiocarbon dating of foraminifera indicates that the basin floor sediments (270-290 m) accumulated at > 3 m/kyr during the Holocene, whereas rates were about one tenth that on the basin slope (230 m). In principle, Jordan Basin sediments have the potential to provide time series with interannual resolution. Our results indicate the Holocene is marked by similar to 2 degrees C variability in SST, and the coldest events of the 20th century, during the mid 1960s and mid 1920s, appear to be recorded in the uppermost 50 cm of the seafloor. (C) 2015 Elsevier Ltd. All rights reserved. VL - 96 N1 - PT: J; TC: 0; UT: WOS:000351249700005 JO - Sediment flux and recent paleoclimate in JordanBasin, Gulf of Maine ER - TY - JOUR T1 - Sedimentary response to Milankovitch-type climatic oscillations and formation of sediment undulations: evidence from a shallow-shelf setting at Gela Basin on the Sicilian continental margin JF - Quaternary Science Reviews Y1 - 2015 A1 - Kuhlmann, Jannis A1 - Asioli, Alessandra A1 - Trincardi, Fabio A1 - Klügel, Andreas A1 - Huhn, Katrin AB - A multi-proxy chronological framework along with sequence-stratigraphic interpretations unveils composite Milankovitch cyclicity in the sedimentary records of the Last Glacial–Interglacial cycle at NE Gela Basin on the Sicilian continental margin. Chronostratigraphic data (including foraminifera-based eco-biostratigraphy and δ18O records, tephrochronological markers and 14C AMS radiometric datings) was derived from the shallow-shelf drill sites GeoB14403 (54.6 m recovery) and GeoB14414 (27.5 m), collected with both gravity and drilled MeBo cores in 193 m and 146 m water depth, respectively. The recovered intervals record Marine Isotope Stages and Substages (MIS) from MIS 5 to MIS 1, thus comprising major stratigraphic parts of the progradational deposits that form the last 100-ka depositional sequence. Calibration of shelf sedimentary units with borehole stratigraphies indicates the impact of higher-frequency (20-ka) sea level cycles punctuating this 100-ka cycle. This becomes most evident in the alternation of thick interstadial highstand (HST) wedges and thinner glacial forced-regression (FSST) units mirroring seaward shifts in coastal progradation. Albeit their relatively short-lived depositional phase, these subordinate HST units form the bulk of the 100-ka depositional sequence. Two mechanisms are proposed that likely account for enhanced sediment accumulation ratios (SAR) of up to 200 cm/ka during these intervals: (1) intensified activity of deep and intermediate Levantine Intermediate Water (LIW) associated to the drowning of Mediterranean shelves, and (2) amplified sediment flux along the flooded shelf in response to hyperpycnal plumes that generate through extreme precipitation events during overall arid conditions. Equally, the latter mechanism is thought to be at the origin of undulated features resolved in the acoustic records of MIS 5 Interstadials, which bear a striking resemblance to modern equivalents forming on late-Holocene prodeltas of other Mediterranean shallow-shelf settings. VL - 108 UR - http://www.sciencedirect.com/science/article/pii/S0277379114004260 JO - Sedimentary response to Milankovitch-type climatic oscillations and formation of sediment undulations: evidence from a shallow-shelf setting at Gela Basin on the Sicilian continental margin ER - TY - JOUR T1 - Sedimentation Pulse in the NE Gulf of Mexico following the 2010 DWH Blowout JF - PLOS ONE Y1 - 2015 A1 - Brooks, Gregg R. A1 - Larson, Rebekka A. A1 - Schwing, Patrick T. A1 - Romero, Isabel A1 - Moore, Christopher A1 - Reichart, Gert-Jan A1 - Jilbert, Tom A1 - Chanton, Jeff P. A1 - Hastings, David W. A1 - Overholt, Will A. A1 - Marks, Kala P. A1 - Kostka, Joel E. A1 - Holmes, Charles W. A1 - Hollander, David ED - Chin, Wei-Chun AB - The objective of this study was to investigate the impacts of the Deepwater Horizon (DWH) oil discharge at the seafloor as recorded in bottom sediments of the DeSoto Canyon region in the northeastern Gulf of Mexico. Through a close coupling of sedimentological, geochemical, and biological approaches, multiple independent lines of evidence from 11 sites sampled in November/December 2010 revealed that the upper ~1 cm depth interval is distinct from underlying sediments and results indicate that particles originated at the sea surface. Consistent dissimilarities in grain size over the surficial ~1 cm of sediments correspond to excess 234Th depths, which indicates a lack of vertical mixing (bioturbation), suggesting the entire layer was deposited within a 4–5 month period. Further, a time series from four deep-sea sites sampled up to three additional times over the following two years revealed that excess 234Th depths, accumulation rates, and 234Th inventories decreased rapidly, within a few to several months after initial coring. The interpretation of a rapid sedimentation pulse is corroborated by stratification in solid phase Mn, which is linked to diagenesis and redox change, and the dramatic decrease in benthic formanifera density that was recorded in surficial sediments. Results are consistent with a brief depositional pulse that was also reported in previous studies of sediments, and marine snow formation in surface waters closer to the wellhead during the summer and fall of 2010. Although sediment input from the Mississippi River and advective transport may influence sedimentation on the seafloor in the DeSoto Canyon region, we conclude based on multidisciplinary evidence that the sedimentation pulse in late 2010 is the product of marine snow formation and is likely linked to the DWH discharge. VL - 10 UR - http://dx.plos.org/10.1371/journal.pone.0132341 IS - 7 ER - TY - JOUR T1 - Single cell genomics indicates horizontal gene transfer and viral infections in a deep subsurface Firmicutes population JF - Frontiers in Microbiology Y1 - 2015 A1 - Labonte, Jessica M. A1 - Field, Erin K. A1 - Lau, Maggie A1 - Chivian, Dylan A1 - Van Heerden, Esta A1 - Wommack, K. Eric A1 - Kieft, Thomas L. A1 - Onstott, Tullis C. A1 - Stepanauskas, Ramunas AB - A major fraction of Earth's prokaryotic biomass dwells in the deep subsurface, where cellular abundances per volume of sample are lower, metabolism is slower, and generation times are longer than those in surface terrestrial and marine environments. How these conditions impact biotic interactions and evolutionary processes is largely unknown. Here we employed single cell genomics to analyze cell-to-cell genome content variability and signatures of horizontal gene transfer (HGT) and viral infections in five cells of Candidatus Desulforudis audaxviator, which were collected from a three km-deep fracture water in the 2.9 Ga-old Witwatersrand Basin of South Africa. Between 0 and 32 % of genes recovered from single cells were not present in the original, metagenomic assembly of Desulforudis, which was obtained from a neighboring subsurface fracture. We found a transposable prophage, a retron, multiple clustered regularly interspaced short palindromic repeats (CRISPRs) and restriction-modification systems, and an unusually high frequency of transposases in the analyzed single cell genomes. This indicates that recombination, HGT and viral infections are prevalent evolutionary events in the studied population of microorganisms inhabiting a highly stable deep subsurface environment. VL - 6 N1 - PT: J; TC: 0; UT: WOS:000352551600004 JO - Single cell genomics indicates horizontal gene transfer and viral infections in a deep subsurface Firmicutes population ER - TY - JOUR T1 - Sinking particle flux in the sea ice zone of the Amundsen Shelf, Antarctica JF - Deep Sea Research Part I: Oceanographic Research Papers Y1 - 2015 A1 - Kim, Minkyoung A1 - Hwang, Jeomshik A1 - Kim, Hyung J. A1 - Kim, Dongseon A1 - Yang, Eun J. A1 - Ducklow, Hugh W. A1 - Hyoung, S. La A1 - Lee, Sang H. A1 - Park, Jisoo A1 - Lee, SangHoon AB - We have examined the flux, biogenic composition, and isotopic values of sinking particles collected by a time-series sediment trap deployed in the sea ice zone (SIZ) of the Amundsen Sea from January 2011 for 1 year. The major portion of the particle flux occurred during the austral summer in January and February when sea ice concentration was reduced to 30 %) and a low bio-Si/POC ratio (<0.5) during the austral winter. CaCO3 content and its contribution to total particle flux was low (~6 %) throughout the study period. Aged POC likely supplied from sediment resuspension accounted for a considerable fraction only from October to December, which was evidenced by a low radiocarbon content and relatively high (30–50 %) content of the non-biogenic components. When compared with POC flux inside the Amundsen Sea polynya obtained by the US Amundsen Sea Polynya International Research Expedition (ASPIRE), the POC flux integrated over the austral summer in the SIZ was virtually identical, although the maximum POC flux was approximately half that inside the Amundsen Sea polynya. This comparatively high POC flux integrated over the austral summer in the SIZ may be caused by phytoplankton blooms persisting over a longer periods and more efficient export of organic matter potentially owing to the diatom-dominant plankton community. If this observation is a general phenomenon on the Amundsen Shelf, the role of the SIZ, compared with the polynyas, need to be examined more carefully when trying to characterize the POC export in this region. VL - 101 N1 - Ck4reTimes Cited:4Cited References Count:38 JO - Sinking particle flux in the sea ice zone of the Amundsen Shelf, Antarctica ER - TY - JOUR T1 - Source-age dynamics of estuarine particulate organic matter using fatty acid delta C-13 and Delta C-14 composition JF - Limnology and Oceanography Y1 - 2015 A1 - McIntosh, Hadley A. A1 - McNichol, Ann P. A1 - Xu, Li A1 - Canuel, Elizabeth A. AB - This study used a multiproxy approach to elucidate the source and age composition of estuarine particulate organic matter (POM) using bulk stable isotopes (C-13(POC)), fatty acid (FA) biomarkers, and compound specific isotopic analyses in surface waters along the Delaware River and Bay (Delaware Estuary, hereafter). C-13 values of FA (C-13(FA)) ranged more widely (-30.9 parts per thousand to -21.8 parts per thousand) than C-13(POC) (-27.5 parts per thousand to -23.5 parts per thousand), providing greater insight about POM sources along the estuary. C-13 values of C-16:0 phospholipid FA (primarily, aquatic sources) increased along the salinity gradient (-29.8 parts per thousand to -23.4 parts per thousand), while C-13(FA) values of long-chain neutral fatty acid (terrestrial sources) decreased (-28.6 parts per thousand to -30.9 parts per thousand). C-13(FA) values for C-18's FA indicated the importance of marsh-derived organic matter within Delaware Estuary. Compound specific radiocarbon analysis showed the heterogeneous age structure of FA associated with POM (FA(POM)). C-14 ages of FA ranged from modern (postbomb) to 1790BP; aged FA (120BP to 1700BP) derived primarily from the watershed, whereas modern FA were produced within Delaware Estuary. C-14 ages of short-chain FA (aquatic sources) reflected differences in the age of dissolved inorganic carbon along the estuary and had older C-14 ages at the river end-member. C-14 ages of FA from terrigenous sources were older than water and sediment residence times indicating this source derived from the watershed. This study is the first to document the complex age distribution of FA(POM) along the estuarine salinity gradient and shows that inorganic carbon sources, watershed inputs and autochthonous production contribute to variation in the ages of POM. VL - 60 IS - 2 N1 - PT: J; TC: 0; UT: WOS:000351126500020 JO - Source-age dynamics of estuarine particulate organic matter using fatty acid delta C-13 and Delta C-14 composition ER - TY - JOUR T1 - South Asian monsoon history over the past 60 kyr recorded by radiogenic isotopes and clay mineral assemblages in the Andaman Sea JF - Geochemistry, Geophysics, Geosystems Y1 - 2015 A1 - Ali, Sajid A1 - Hathorne, Ed C. A1 - Frank, Martin A1 - Gebregiorgis, Daniel A1 - Stattegger, Karl A1 - Stumpf, Roland A1 - Kutterolf, Steffen A1 - Johnson, Joel E. A1 - Giosan, Liviu AB - The Late Quaternary variability of the South Asian (or Indian) monsoon has been linked with glacial-interglacial and millennial scale climatic changes but past rainfall intensity in the river catchments draining into the Andaman Sea remains poorly constrained. Here we use radiogenic Sr, Nd, and Pb isotope compositions of the detrital clay-size fraction and clay mineral assemblages obtained from sediment core NGHP Site 17 in the Andaman Sea to reconstruct the variability of the South Asian monsoon during the past 60 kyr. Over this time interval εNd values changed little, generally oscillating between −7.3 and −5.3 and the Pb isotope signatures are essentially invariable, which is in contrast to a record located further northeast in the Andaman Sea. This indicates that the source of the detrital clays did not change significantly during the last glacial and deglaciation suggesting the monsoon was spatially stable. The most likely source region is the Irrawaddy river catchment including the Indo-Burman Ranges with a possible minor contribution from the Andaman Islands. High smectite/(illite + chlorite) ratios (up to 14), as well as low 87Sr/86Sr ratios (0.711) for the Holocene period indicate enhanced chemical weathering and a stronger South Asian monsoon compared to marine oxygen isotope stages 2 and 3. Short, smectite-poor intervals exhibit markedly radiogenic Sr isotope compositions and document weakening of the South Asian monsoon, which may have been linked to short-term northern Atlantic climate variability on millennial time scales. VL - 16 UR - http://doi.wiley.com/10.1002/2014GC005586 IS - 2 ER - TY - JOUR T1 - Spatial Variation in the Origin of Dissolved Organic Carbon in Snow on the Juneau Icefield, Southeast Alaska JF - Environmental Science & Technology Y1 - 2015 A1 - Fellman, Jason B. A1 - Hood, Eran A1 - Raymond, Peter A. A1 - Stubbins, Aron A1 - Spencer, Robert G.M. AB - Dissolved organic carbon (DOC) plays a fundamental role in the biogeochemistry of glacier ecosystems. However, the specific sources of glacier DOC remain unresolved. To assess the origin and nature of glacier DOC, we collected snow from 10 locations along a transect across the Juneau Icefield, Alaska extending from the coast toward the interior. The Δ14C-DOC of snow varied from −743 to −420‰ showing progressive depletion across the Icefield as δ18O of water became more depleted (R2 = 0.56). Older DOC corresponded to lower DOC concentrations in snow (R2 = 0.31) and a decrease in percent humic-like fluorescence (R2 = 0.36), indicating an overall decrease in modern DOC across the Icefield. Carbon isotopic signatures (13C and 14C) combined with a three-source mixing model showed that DOC deposited in snow across the Icefield reflects fossil fuel combustion products (43–73%) and to a lesser extent marine (21–41%) and terrestrial sources (1–26%). Our finding that combustion aerosols are a large source of DOC to the glacier ecosystem during the early spring (April–May) together with the pronounced rates of glacier melting in the region suggests that the delivery of relic DOC to the ocean may be increasing and consequently impacting the biogeochemistry of glacial and proglacial ecosystems in unanticipated ways. VL - 49 UR - http://pubs.acs.org/doi/10.1021/acs.est.5b02685http://pubs.acs.org/doi/pdf/10.1021/acs.est.5b02685 IS - 19 ER - TY - JOUR T1 - Ultra-Small Graphitization Reactors for Ultra-Microscale C-14 Analysis at the National Ocean Sciences Accelerator Mass Spectrometry (Nosams) Facility JF - Radiocarbon Y1 - 2015 A1 - Walter, Sunita R. Shah A1 - Gagnon, Alan R. A1 - Roberts, Mark L. A1 - McNichol, Ann P. A1 - Gaylord, Mary C. Lardie A1 - Klein, Elizabeth AB - In response to the increasing demand for C-14 analysis of samples containing less than 25 mu g C, ultra-small graphitization reactors with an internal volume of similar to 0.8 mL were developed at NOSAMS. For samples containing 6 to 25 mu g C, these reactors convert CO2 to graphitic carbon in approximately 30 min. Although we continue to refine reaction conditions to improve yield, the reactors produce graphite targets that are successfully measured by AMS. Graphite targets produced with the ultra-small reactors are measured by using the Cs sputter source on the CFAMS instrument at NOSAMS where beam current was proportional to sample mass. We investigated the contribution of blank carbon from the ultra-small reactors and estimate it to be 0.3 +/- 0.1 mu g C with an Fm value of 0.43 +/- 0.3. We also describe equations for blank correction and propagation of error associated with this correction. With a few exceptions for samples in the range of 6 to 7 mu g C, we show that corrected Fm values agree with expected Fm values within uncertainty for samples containing 6-100 mu g C. VL - 57 IS - 1 N1 - PT: J; TC: 1; UT: WOS:000351052600009 JO - Ultra-Small Graphitization Reactors for Ultra-Microscale C-14 Analysis at the National Ocean Sciences Accelerator Mass Spectrometry (Nosams) Facility ER - TY - JOUR T1 - Using Natural Abundance Radiocarbon To Trace the Flux of Petrocarbon to the Seafloor Following the Deepwater Horizon Oil Spill JF - Environmental Science & Technology Y1 - 2015 A1 - Chanton, Jeffrey A1 - Zhao, Tingting A1 - Rosenheim, Brad E. A1 - Joye, Samantha A1 - Bosman, Samantha A1 - Brunner, Charlotte A1 - Yeager, Kevin M. A1 - Diercks, Arne R. A1 - Hollander, David AB - In 2010, the Deepwater Horizon accident released 4.6–6.0 × 1011 grams or 4.1 to 4.6 million barrels of fossil petroleum derived carbon (petrocarbon) as oil into the Gulf of Mexico. Natural abundance radiocarbon measurements on surface sediment organic matter in a 2.4 × 1010 m2 deep-water region surrounding the spill site indicate the deposition of a fossil-carbon containing layer that included 1.6 to 2.6 × 1010 grams of oil-derived carbon. This quantity represents between 0.5 to 9.1% of the released petrocarbon, with a best estimate of 3.0–4.9%. These values may be lower limit estimates of the fraction of the oil that was deposited on the seafloor because they focus on a limited mostly deep-water area of the Gulf, include a conservative estimate of thickness of the depositional layer, and use an average background or prespill radiocarbon value for sedimentary organic carbon that produces a conservative value. A similar approach using hopane tracer estimated that 4–31% of 2 million barrels of oil that stayed in the deep sea settled on the bottom. Converting that to a percentage of the total oil that entered into the environment (to which we normalized our estimate) converts this range to 1.8 to 14.4%. Although extrapolated over a larger area, our independent estimate produced similar values. VL - 49 UR - http://pubs.acs.org/doi/abs/10.1021/es5046524http://pubs.acs.org/doi/pdf/10.1021/es5046524 IS - 2 ER - TY - JOUR T1 - Validated age estimates for large white sharks of the northeastern Pacific Ocean: altered perceptions of vertebral growth shed light on complicated bomb Delta C-14 results JF - Environmental Biology of Fishes Y1 - 2015 A1 - Andrews, Allen H. A1 - Kerr, Lisa A. VL - 98 IS - 3 N1 - PT: J; TC: 0; UT: WOS:000349029800020 JO - Validated age estimates for large white sharks of the northeastern Pacific Ocean: altered perceptions of vertebral growth shed light on complicated bomb Delta C-14 results ER - TY - JOUR T1 - A warm and poorly ventilated deep Arctic Mediterranean during the last glacial period JF - Science Y1 - 2015 A1 - Thornalley, D. J. R. A1 - Bauch, H. A. A1 - Gebbie, G. A1 - Guo, W. A1 - Ziegler, M. A1 - Bernasconi, S. M. A1 - Barker, S. A1 - Skinner, L. C. A1 - Yu, J. AB - Changes in the formation of dense water in the Arctic Ocean and Nordic Seas [the “Arctic Mediterranean” (AM)] probably contributed to the altered climate of the last glacial period. We examined past changes in AM circulation by reconstructing radiocarbon ventilation ages of the deep Nordic Seas over the past 30,000 years. Our results show that the glacial deep AM was extremely poorly ventilated (ventilation ages of up to 10,000 years). Subsequent episodic overflow of aged water into the mid-depth North Atlantic occurred during deglaciation. Proxy data also suggest that the deep glacial AM was ~2° to 3°C warmer than modern temperatures; deglacial mixing of the deep AM with the upper ocean thus potentially contributed to the melting of sea ice, icebergs, and terminal ice-sheet margins. VL - 349 UR - http://www.sciencemag.org/content/349/6249/706.abstract IS - 6249 JO - A warm and poorly ventilated deep Arctic Mediterranean during the last glacial period ER - TY - JOUR T1 - What do benthic ? 13 C and ? 18 O data tell us about Atlantic circulation during Heinrich Stadial 1? JF - Paleoceanography Y1 - 2015 A1 - Oppo, Delia W. A1 - Curry, William B. A1 - McManus, Jerry F. AB - Approximately synchronous with the onset of Heinrich Stadial 1 (HS1), δ13C decreased throughout most of the upper (~1000–2500 m) Atlantic, and at some deeper North Atlantic sites. This early deglacial δ13C decrease has been alternatively attributed to a reduced fraction of high-δ13C North Atlantic Deep Water (NADW) or to a decrease in the NADW δ13C source value. Here we present new benthic δ18O and δ13C records from three relatively shallow (~1450–1650 m) subpolar Northeast Atlantic cores. With published data from other cores, these data form a depth transect (~1200–3900 m) in the subpolar Northeast Atlantic. We compare Last Glacial Maximum (LGM) and HS1 data from this transect with data from a depth transect of cores from the Brazil Margin. The largest LGM-to-HS1 decreases in both benthic δ13C and δ18O occurred in upper waters containing the highest NADW fraction during the LGM. We show that the δ13C decrease can be explained entirely by a lower NADW δ13C source value, entirely by a decrease in the proportion of NADW relative to Southern Ocean Water, or by a combination of these mechanisms. However, building on insights from model simulations, we hypothesize that reduced ventilation due to a weakened but still active Atlantic Meridional Overturning Circulation also contributed to the low δ13C values in the upper North Atlantic. We suggest that the benthic δ18O gradients above ~2300 m at both core transects indicate the depth to which heat and North Atlantic deglacial freshwater had mixed into the subsurface ocean by early HS1. VL - 30 UR - http://doi.wiley.com/10.1002/2014PA002667 IS - 4 ER - TY - JOUR T1 - A 2000-yr reconstruction of air temperature in the Great Basin of the United States with specific reference to the Medieval Climatic Anomaly JF - Quaternary Research Y1 - 2014 A1 - Reinemann, Scott A. A1 - Porinchu, David F. A1 - MacDonald, Glen M. A1 - Mark, Bryan G. A1 - DeGrand, James Q. AB - A sediment core representing the past two millennia was recovered from Stella Lake in the Snake Range of the central Great Basin in Nevada. The core was analyzed for sub-fossil chironomids and sediment organic content. A quantitative reconstruction of mean July air temperature (MJAT) was developed using a regional training set and a chironomid-based WA-PLS inference model (r2jack = 0.55, RMSEP = 0.9°C). The chironomid-based MJAT reconstruction suggests that the interval between AD 900 and AD 1300, corresponding to the Medieval Climate Anomaly (MCA), was characterized by MJAT elevated 1.0°C above the subsequent Little Ice Age (LIA), but likely not as warm as recent conditions. Comparison of the Stella Lake temperature reconstruction to previously published paleoclimate records from this region indicates that the temperature fluctuations inferred to have occurred at Stella Lake between AD 900 and AD 1300 correspond to regional records documenting hydroclimate variability during the MCA interval. The Stella Lake record provides evidence that elevated summer temperature contributed to the increased aridity that characterized the western United States during the MCA. VL - 82 N1 - Aq8ljTimes Cited:0Cited References Count:70 JO - A 2000-yr reconstruction of air temperature in the Great Basin of the United States with specific reference to the Medieval Climatic Anomaly ER - TY - JOUR T1 - Adélie penguin dietary remains reveal Holocene environmental changes in the western Ross Sea (Antarctica) JF - Palaeogeography, Palaeoclimatology, Palaeoecology Y1 - 2014 A1 - Lorenzini, Sandra A1 - Baroni, Carlo A1 - Baneschi, Ilaria A1 - Salvatore, Maria Cristina A1 - Fallick, Anthony E. A1 - Hall, Brenda L. AB - Carbon and nitrogen stable isotope analyses were performed on modern and Holocene Adélie penguin guano samples collected from ornithogenic soils along the Scott Coast (Southern Victoria Land, Antarctica), from Cape Irizar to Dunlop Island, and at Cape Bird (Ross Island). Guano samples also were sieved and sorted under stereomicroscope in order to select penguin dietary remains, such as fish bones and otoliths. Carbon and nitrogen stable isotope composition, coupled with the taxonomic identification of fish otoliths from Scott Coast Holocene samples, indicated a mainly fish-based diet for this area, with Pleuragramma antarcticum as the most eaten prey throughout the investigated period (from 390 cal BP to ca 7300 cal BP). The isotopic values of Ross Island samples (from modern to 3850 cal BP) showed a krill consumption increase in the samples younger than 2000 cal BP, with the maximum in modern samples. Scott Coast and Ross Island Holocene samples showed δ13C and δ15N trends similar to those previously published from Terra Nova Bay (northern Victoria Land), whereas modern samples from Ross Island have similar δ15N composition but different δ13C values. This δ13C divergence started at ca 2000 BP and follows the abandonment of the Scott Coast colonies. The δ13C trend observed in Ross Island and Terra Nova Bay samples and the abandonment of the Scott Coast colonies could suggest the stability and the persistence of the previous oceanographic conditions (i.e. polynya) for the Terra Nova Bay area and the establishment of new conditions for water circulation in the Southern Ross Sea since ~ 2000 BP when persistent sea-ice sealed the Scott Coast. VL - 395 UR - http://www.sciencedirect.com/science/article/pii/S0031018213005440 N1 - id: 2347 JO - Adélie penguin dietary remains reveal Holocene environmental changes in the western Ross Sea (Antarctica) ER - TY - JOUR T1 - Advection and scavenging controls of Pa/Th in the northern NE Atlantic JF - Paleoceanography Y1 - 2014 A1 - Roberts, Natalie L. A1 - McManus, Jerry F. A1 - Piotrowski, Alexander M. A1 - McCave, I. Nicholas AB - Over the last 2 decades, significant advances have been made in reconstructing past rates of ocean circulation using sedimentary proxies for the dynamics of abyssal waters. In this study we combine the use of two rate proxies, sortable silt grain size, and sedimentary 231Pa/230Th, measured on a depth transect of deep-sea sediment cores from the northern NE Atlantic, to investigate ocean circulation changes during the last deglacial. We find that at two deep sites, the core-top 231Pa/230Th ratios reflect Holocene circulation rates, while during Heinrich Stadial 1, the deglacial ratios peaked as the sortable silt grain size decreased, reflecting a general circulation slowdown. However, the peak 231Pa/230Th significantly exceeded the production ratio in both cores, indicating that 231Pa/230Th was only partially controlled by ocean circulation at these sites. This is supported by a record of 231Pa/230Th from an intermediate water depth site, where values also peaked during Heinrich Stadial 1, but were consistently above the production ratio over the last 24 ka, reflecting high scavenging below productive surface waters. At our study sites, we find that preserved sediment component fluxes cannot be used to distinguish between a scavenging or circulation control, although they are consistent with a circulation influence, since the core at intermediate depth with the highest 231Pa/230Th recorded the lowest particle fluxes. Reconstruction of advection rate using 231Pa/230Th in this region is complicated by high productivity, but the data nevertheless contain important information on past deep ocean circulation. VL - 29 UR - http://doi.wiley.com/10.1002/2014PA002633 IS - 6 ER - TY - JOUR T1 - Age and growth of the giant sea bass, Stereolepis gigas JF - California Cooperative Oceanic Fisheries Investigations Reports Y1 - 2014 A1 - A. Hawk, Holly A1 - Allen, Larry KW - Age and growth KW - Carbon-14 KW - lifespan KW - Longevity KW - Otolith KW - Polyprionidae KW - Stereolepis AB - In January 2010, a massive giant sea bass (500 lbs, 227 kg; near maximum reported size of 557 lbs, 253 kg) was captured off Santa Cruz Island by commercial gill-netters. This specimen presented a unique opportunity to estimate and validate of the potential longevity of the largest nearshore teleost of the northeastern Pacific. A transverse section of the sagittal otolith produced consistent counts of 62 opaque annuli along two different axes of the ventral sulcus region, translating into an estimated birth year of 1948. This age estimate was supported by measurements of radiocarbon (14 C) in the other sagittal otolith core (within the first year of growth), relative to D 14 C reference records used for bomb radiocarbon dating. Two otolith core samples produced D 14 C values that were classified as pre-bomb (prior to ,1958–59), indicating a minimum lifespan of 51 years. It is likely that giant sea bass can live more than 60 or 70 years based on growth zone counts, but there is no evidence in the literature or this study to support longevity of 100 years. VL - 55 UR - https://www.researchgate.net/publication/236999608_Bomb_radiocarbon_dating_and_estimated_longevity_of_Giant_Sea_Bass_Stereolepis_gigas ER - TY - JOUR T1 - Amino acid ratios in reworked marine bivalve shells constrain Greenland Ice Sheet history during the Holocene JF - Geology Y1 - 2014 A1 - Briner, J. P. A1 - Kaufman, D. S. A1 - Bennike, O. A1 - Kosnik, M. A. AB - Reconstructions of ice sheet fluctuations during the Holocene, which encompassed cooler and warmer conditions than those that are captured in the historic record, help to elucidate ice margin sensitivity to climate change. We used amino acid geochronology to constrain the history of the western Greenland Ice Sheet margin during intervals of relative warmth in the middle Holocene. We measured the extent of amino acid racemization in 251 ice sheet-reworked marine bivalve shells from three locations spanning western Greenland. A significant relationship between shell age and the ratio of aspartic acid (Asp) isomers (Asp D/L) was revealed using Bayesian model fitting on 20 radiocarbon-dated shell fragments. The range of Asp-inferred bivalve ages at each site corresponds well with independent records of early Holocene ice retreat and late Holocene ice advance. Furthermore, the frequency of Asp-inferred bivalve ages from the three widely separated locations is nearly identical, with most ages between 5 and 3 ka, coinciding with optimum oceanic conditions. Because ice margin changes in western Greenland are tightly linked with oceanographic conditions, the distribution of reworked bivalve ages provides important information about relative ice margin position during smaller-than-present ice sheet configurations. This approach adds a new chronometer to our toolkit for constraining smaller-than-present ice sheet configurations and may have wide applicability around Greenland. Amino acid ratios in reworked marine bivalve shells constrain Greenland Ice Sheet history during the Holocene. Available from: https://www.researchgate.net/publication/270688646_Amino_acid_ratios_in_reworked_marine_bivalve_shells_constrain_Greenland_Ice_Sheet_history_during_the_Holocene [accessed Jun 5, 2017]. VL - 42 UR - http://geology.gsapubs.org/cgi/doi/10.1130/G34843.1 IS - 1 ER - TY - JOUR T1 - Carbonation rates of peridotite in the Samail Ophiolite, Sultanate of Oman, constrained through 14C dating and stable isotopes JF - Geochimica et Cosmochimica Acta Y1 - 2014 A1 - Mervine, Evelyn M. A1 - Humphris, Susan E. A1 - Sims, Kenneth W. W. A1 - Kelemen, Peter B. A1 - W. J. Jenkins AB - Detailed 14C dating as well as stable C and O isotope analyses were conducted on carbonates formed during alteration of the peridotite layer of the Samail Ophiolite, Sultanate of Oman. 14C results obtained in this and previous studies indicate that surface travertines range in age from modern to >45,000 yr BP, indicating long-term deposition and preservation. Travertine deposition rates in two localities were ∼0.1 to 0.3 mm/yr between ∼30,000 and 45,000 yr BP. Using an estimate of total travertine area, this would result in a maximum of ∼1000 to 3000 m3/yr of travertine being deposited throughout the ophiolite during this time period. This travertine deposition would have sequestered a maximum of ∼1 to 3 × 106 kg CO2/yr. Ca-rich carbonate veins that are associated with the surface travertine deposits have ages ranging from ∼4000 to 36,000 yr BP (average: 15,000 yr BP). Mg-rich carbonate veins exposed in outcrops have ages ranging from ∼8000 to 45,000 yr BP (average: 35,000 yr BP). Detailed sampling from numerous locations (3 locations in this study and 10 locations in the previous studies) indicates that no carbonate veins from the natural peridotite weathering surface are older than the ∼50,000 yr BP dating limit of 14C. However, 14C dating of Mg-rich carbonate veins from three roadcut exposures (Qafeefah, Fanja, and Al-Wuqbah) indicates that a significant number of roadcut veins are 14C dead (>50,000 yr BP). A location weighted average indicates that ∼40% of veins sampled at the three roadcuts are 14C dead. An average including veins sampled at both roadcuts and outcrops indicates that overall ∼8% of Mg-rich carbonate veins are 14C dead. Mg-rich carbonate veins are estimated to sequester on the order of 107 kg CO2/yr throughout the ophiolite. VL - 126 UR - http://www.sciencedirect.com/science/article/pii/S0016703713006467 JO - Carbonation rates of peridotite in the Samail Ophiolite, Sultanate of Oman, constrained through 14C dating and stable isotopes ER - TY - JOUR T1 - Centennial-to-millennial hydrologic trends and variability along the North Atlantic Coast, USA, during the Holocene JF - Geophysical Research Letters Y1 - 2014 A1 - Newby, Paige E. A1 - Shuman, Bryan N. A1 - Donnelly, Jeffrey P. A1 - Karnauskas, Kristopher B. A1 - Marsicek, Jeremiah AB - Geophysical and sedimentary records from five lakes in Massachusetts reveal regionally coherent hydrologic variability during the Holocene. All of the lakes have risen since ~9.0 ka, but multicentury droughts after 5.6 ka repeatedly lowered their water levels. Quantified water level histories from the three best-studied lakes share >70% of their reconstructed variance. Four prominent low-water phases at 4.9–4.6, 4.2–3.9, 2.9–2.1, and 1.3–1.2 ka were synchronous across coastal lakes, even after accounting for age uncertainties. The droughts also affected sites up to ~200 km inland, but water level changes at 5.6–4.9 ka appear out of phase between inland and coastal lakes. During the enhanced multicentury variability after ~5.6 ka, droughts coincided with cooling in Greenland and may indicate circulation changes across the North Atlantic region. Overall, the records demonstrate that current water levels are exceptionally high and confirm the sensitivity of water resources in the northeast U.S. to climate change. VL - 41 UR - http://doi.wiley.com/10.1002/2014GL060183https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2F2014GL060183 IS - 12 ER - TY - JOUR T1 - Coastal response to late-stage transgression and sea-level highstand JF - Geological Society of America Bulletin Y1 - 2014 A1 - Hein, C. J. A1 - FitzGerald, D. M. A1 - Thadeu de Menezes, J. A1 - Cleary, W. J. A1 - Klein, A. H. F. A1 - Albernaz, M. B. AB - Coastal morphologic features associated with past shoreline transgressions and sea-level highstands can provide insight into the rates and processes associated with coastal response to the modern global rise in sea level. Along the eastern and southern Brazilian coasts of South America, 6000 years of sea-level fall have preserved late-stage transgressive and sea-level highstand features 1–4 m above present mean sea level and several kilome ters landward of modern shore-lines. GPS with real-time kinematics data, ground-penetrating radar, stratigraphy, and radiocarbon dating within a 2–3-km-wide river-associated strandplain in central Santa Catarina (southern Brazil) uncovered a diverse set of late-stage transgressive and high- stand deposits. Here, the highstand took the forms of (1) an exposed bedrock coast in areas of high wave energy and low sediment supply; (2) a 3.8-m-high transgressive barrier ridge where landward barrier migration was prohibited by the presence of shallow bedrock; and (3) a complete barrier-island complex containing a 5.2-m-high barrier ridge, washover deposits, a paleo-inlet, and a backbarrier lowland, formed in a protected cove with ample sediment supply from small local streams and the erosion of upland sediments. Similar signatures of the mid-Holocene highstand can be traced across all coastal Brazilian states. This study presents the first complete compilation of the diversity of these sedimentary sequences. They are broadly classified here as exposed bedrock coasts (type A), back barrier deposits (type B), transgressive barrier ridges (type C), and barrier-island complexes (type D), according to localized conditions of upland migration potential, wave exposure, and sediment supply. These Brazilian systems present a paradigm for understanding future coastal response to climate change and accelerated sea-level rise: the recognition of a minimum threshold sea-level-rise rate of ~2 mm yr–1 above which transgression proceeded too rapidly for the formation of these stable accretionary shoreline features demonstrates the nonlinearity of coastal response to sea-level change, and the site specificity of conditions associated with the formation of each highstand deposit type, even within a single small embayment, demonstrates the non-uniformity of that response. VL - 126 UR - http://gsabulletin.gsapubs.org/cgi/doi/10.1130/B30836.1 IS - 3-4 ER - TY - JOUR T1 - Composition and origin of authigenic carbonates in the Krishna-Godavari and Mahanadi Basins, eastern continental margin of India JF - Marine and Petroleum Geology Y1 - 2014 A1 - Teichert, B. M. A. A1 - Johnson, J. E. A1 - Solomon, E. A. A1 - Giosan, L. A1 - Rose, K. A1 - Kocherla, M. A1 - Connolly, E. C. A1 - Torres, M. E. AB - The mineralogical and stable isotopic composition of authigenic carbonates from the Krishna-Godavari (KG) and Mahanadi Basin provide a deeper insight into the processes inducing carbonate formation in the sediments of the eastern continental margin of India in the Bay of Bengal. Authigenic carbonate cements, (micro) nodules, bioturbation casts and tubes from 12 core locations drilled during the Indian National Gas Hydrate Program (NGHP) Expedition 01 were investigated for this study. Three main processes responsible for authigenic carbonate precipitation are identified: organoclastic sulfate reduction, anaerobic oxidation of methane and methanogenesis. Evidence of vigorous methane seepage is indicated in carbonates recovered at Sites 7, 10, 12 (KG Basin) and 19 (Mahanadi Basin). These methane-derived carbonates display typical paragenetic carbonate mineralogies (aragonite, high-Mg calcite with >15 Mol% MgCO3, Ca-rich dolomite). Two separate horizons of methane derived-carbonates are correlated between 4 drill holes (up to ∼16 km apart). The upper horizon has been dated with 14C (40,100 – 51,600 a B.P. 1950) clearly indicating that methane seepage has been much more vigorous in the past possibly due to a glacial sea level lowstand. VL - 58 N1 - AAy4wyTimes Cited:5Cited References Count:63 JO - Composition and origin of authigenic carbonates in the Krishna-Godavari and Mahanadi Basins, eastern continental margin of India ER - TY - JOUR T1 - A continental shelf sedimentary record of Little Ice Age to modern glacial dynamics: Bering Glacier, Alaska JF - Continental Shelf Research Y1 - 2014 A1 - Jaeger, John M. A1 - Kramer, Branden AB - The Bering Glacier System is the world's largest surging temperate glacier with seven events occurring over the past century under a range of north Pacific climatic conditions. Onshore records reveal changes in glacial termini positions and evidence of late Holocene glacial advances, but the Little Ice Age (LIA) record of potential glacial surging and associated flooding has not been examined. A 13.6 m-long jumbo core collected on the adjacent continental shelf reveals a 600-yr-long record of sedimentation associated with changing glacifluvial discharge. The chronology is based on 210Pb geochronology and five radiocarbon dates, and the core can be separated into three distinct lithologic units based on the examination of X-radiographs and physical properties: (1) an uppermost unit dating from ∼125 cal yr BP to the present characterized by bioturbated mud interbedded with laminated, thick (5–20 cm) low-bulk density clay-rich beds; (2) a middle unit dating from ∼120–400 cal yr BP that includes numerous interlaminated-to-interbedded low- and high-bulk density beds with infrequent evidence of bioturbation; thick laminated clay-rich beds are rare; (3) a lowermost unit that predates ∼400 cal yr BP and is composed of rare laminated beds grading down into mottled to massive mud. In each of these units, the laminated lithofacies from this mid-shelf location indicates both flood deposition and likely sediment transport in the wave-current bottom-boundary layer. The thick low-density, clay-rich beds in the uppermost unit correlate with historic outburst floods associated with known surge events. Based on previous terrestrial studies, the terminus was at its Holocene Neoglacial maximum extent close to the modern coastline at some point in the middle to late stages of the LIA in southern Alaska (100–350 cal yr BP). During the LIA, preservation of bioturbated intervals is rare while laminated intervals are common. This style of interbedding indicates frequent ( VL - 86 N1 - id: 2324 JO - A continental shelf sedimentary record of Little Ice Age to modern glacial dynamics: Bering Glacier, Alaska ER - TY - JOUR T1 - A continuous multi-millennial record of surficial bivalve mollusk shells from the São Paulo Bight, Brazilian shelf JF - Quaternary Research Y1 - 2014 A1 - Dexter, Troy A. A1 - Kaufman, Darrell S. A1 - Krause Jr, Richard A. A1 - Barbour Wood, Susan L. A1 - Simões, Marcello G. A1 - Huntley, John Warren A1 - Yanes, Yurena A1 - Romanek, Christopher S. A1 - Kowalewski, Michał AB - To evaluate the potential of using surficial shell accumulations for paleoenvironmental studies, an extensive time series of individually dated specimens of the marine infaunal bivalve mollusk Semele casali was assembled using amino acid racemization (AAR) ratios (n = 270) calibrated against radiocarbon ages (n = 32). The shells were collected from surface sediments at multiple sites across a sediment-starved shelf in the shallow sub-tropical São Paulo Bight (São Paulo State, Brazil). The resulting 14C-calibrated AAR time series, one of the largest AAR datasets compiled to date, ranges from modern to 10,307 cal yr BP, is right skewed, and represents a remarkably complete time series: the completeness of the Holocene record is 66% at 250-yr binning resolution and 81% at 500-yr binning resolution. Extensive time-averaging is observed for all sites across the sampled bathymetric range indicating long water depth-invariant survival of carbonate shells at the sediment surface with low net sedimentation rates. Benthic organisms collected from active depositional surfaces can provide multi-millennial time series of biomineral records and serve as a source of geochemical proxy data for reconstructing environmental and climatic trends throughout the Holocene at centennial resolution. Surface sediments can contain time-rich shell accumulations that record the entire Holocene, not just the present. VL - 81 UR - http://www.sciencedirect.com/science/article/pii/S0033589413001646 IS - 2 JO - A continuous multi-millennial record of surficial bivalve mollusk shells from the São Paulo Bight, Brazilian shelf ER - TY - JOUR T1 - Cryostratigraphy and Permafrost Evolution in the Lacustrine Lowlands of West-Central Alaska JF - Permafrost and Periglacial Processes Y1 - 2014 A1 - Kanevskiy, Mikhail A1 - Jorgenson, Torre A1 - Shur, Yuri A1 - O'Donnell, Jonathan A. A1 - Harden, Jennifer W. A1 - Zhuang, Qianlai A1 - Fortier, Daniel AB - The influence of permafrost growth and thaw on the evolution of ice-rich lowland terrain in the Koyukuk-Innoko region of interior Alaska is fundamental but poorly understood. To elucidate this influence, the cryostratigraphy and properties of perennially frozen sediments from three areas in this region are described and interpreted in terms of permafrost history. The upper part of the late Quaternary sediments at the Koyukuk and Innoko Flats comprise frozen organic soils up to 4.5 m thick underlain by ice-rich silt characterised by layered and reticulate cryostructures. The volume of visible segregated ice in silt locally reaches 50 per cent, with ice lenses up to 10 cm thick. A conceptual model of terrain evolution from the Late Pleistocene to the present day identifies four stages of yedoma degradation and five stages of subsequent permafrost aggradation-degradation: (1) partial thawing of the upper ice wedges and the formation of small shallow ponds in the troughs above the wedges; (2) formation of shallow thermokarst lakes above the polygons; (3) deepening of thermokarst lakes and yedoma degradation beneath the lakes; (4) complete thawing of yedoma beneath the lakes; (5) lake drainage; (6) peat accumulation; (7) permafrost aggradation in drained lake basins; (8) formation of permafrost plateaus; and (9) formation and expansion of a new generation of thermokarst features. These stages can occur in differing places and times, creating a highly complex mosaic of terrain conditions, complicating predictions of landscape response to future climatic changes or human impact. Copyright © 2014 John Wiley & Sons, Ltd. VL - 25 UR - http://doi.wiley.com/10.1002/ppp.v25.1http://doi.wiley.com/10.1002/ppp.1800https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fppp.1800 IS - 1 ER - TY - JOUR T1 - Deciphering microbial carbon substrates in PAH contaminated sediments using phospholipid fatty acids, and compound specific δ13C and Δ14C JF - Organic Geochemistry Y1 - 2014 A1 - Morrill, Penny L. A1 - Szponar, Natalie A1 - Johnston, Mathew A1 - Marvin, Chris A1 - Slater, Gregory F. AB - Stable and radiogenic carbon isotopes (δ13C and Δ14C) of organic compounds and phospholipid fatty acids (PLFAs), as well as polycyclic aromatic hydrocarbon (PAH) ratios were used to determine sources and fates of organic contaminants in highly contaminated, and less contaminated sediments of Hamilton Harbour. The highly contaminated sediments had an order of magnitude more total petroleum hydrocarbons (TPHs) compared to the less contaminated sediments. The TPHs extracted from both sites were depleted in 14C (average Δ14C of −775‰ and −973‰, for Sites 1 and 2, respectively) consistent with inputs of fossil derived contaminants. Fossil carbon also contributed to the unextractable residue (Δ14C = −503 ± 55‰) in the sediment at the highly contaminated site relative to the less contaminated site (Δ14C = −132 ± 2‰) indicating inputs of fossil carbon not derived from petroleum or PAHs. Diagnostic PAH ratios (e.g. PAH:NaP between 0.01 and 1), and less negative δ13C (−25.6 ± 0.2‰) of the unextractable residue indicated that a coal derived source was the most likely source of these inputs. Despite the presence of this fossil carbon, there was little evidence of utilization of ancient carbon by the microbial community. The Δ14C of PLFAs from the highly contaminated site were slightly more 14C depleted (Δ14C = −138 ± 20‰) relative to the PLFAs from the less contaminated site (Δ14C = −77 ± 42‰), demonstrating some microbial metabolism of older carbon; however, the majority of the carbon metabolized was modern at both sites, indicating that there was minimal natural attenuation via bioremediation of fossil fuel organic contaminants. VL - 69 UR - http://www.sciencedirect.com/science/article/pii/S0146638014000308 JO - Deciphering microbial carbon substrates in PAH contaminated sediments using phospholipid fatty acids, and compound specific δ13C and Δ14C ER - TY - JOUR T1 - Decreased influence of Antarctic intermediate water in the tropical Atlantic during North Atlantic cold events JF - Earth and Planetary Science Letters Y1 - 2014 A1 - Huang, Kuo-Fang A1 - Oppo, Delia W. A1 - Curry, William B. KW - antarctic intermediate water KW - Atlantic meridional overturning circulation KW - deglacial variability KW - Nd isotopes KW - North Atlantic cold events AB - Antarctic Intermediate Water (AAIW) is a key player in the global ocean circulation, contributing to the upper limb of the Atlantic Meridional Overturning Circulation (AMOC), and influencing interhemispheric heat exchange and the distribution of salinity, nutrients and carbon. However, the deglacial history of AAIW flow into the North Atlantic is controversial. Here we present a multicore-top neodymium isotope calibration, which confirms the ability of unclean foraminifera to faithfully record bottom water neodymium isotopic composition () values in their authigenic coatings. We then present the first foraminifera-based reconstruction of from three sediment cores retrieved from within modern AAIW, in the western tropical North Atlantic. Our records reveal similar glacial and interglacial contributions of AAIW, and a pronounced decrease in the AAIW fraction during North Atlantic deglacial cold episodes, Heinrich Stadial 1 (HS1) and Younger Dryas (YD). Our results suggest two separate phases of reduced fraction of AAIW in the tropical Atlantic during HS1, with a greater reduction during early HS1. If a reduction in AAIW fraction also reflects reduced AMOC strength, this finding may explain why, in many regions, there are two phases of hydrologic change within HS1, and why atmospheric CO2 rose more rapidly during early than late HS1. Our result suggesting less flow of AAIW into the Atlantic during North Atlantic cold events contrasts with evidence from the Pacific, where intermediate-depth records may indicate increased flow of AAIW into the Pacific during the these same events. Antiphased behavior between intermediate depths of the North Atlantic and Pacific implies that the flow of AAIW into Atlantic and Pacific seesawed during the last deglaciation. VL - 389 UR - https://doi.org/10.1016/j.epsl.2013.12.037 ER - TY - JOUR T1 - Deglacial ?18O and hydrologic variability in the tropical Pacific and Indian Oceans JF - Earth and Planetary Science Letters Y1 - 2014 A1 - Gibbons, Fern T. A1 - Oppo, Delia W. A1 - Mohtadi, Mahyar A1 - Rosenthal, Yair A1 - Cheng, Jun A1 - Liu, Zhengyu A1 - Linsley, Braddock K. KW - Deglaciation KW - Eastern Equatorial Pacific KW - heat transport KW - Indo-Pacific KW - δ18O of seawater AB - Evidence from geologic archives suggests that there were large changes in the tropical hydrologic cycle associated with the two prominent northern hemisphere deglacial cooling events, Heinrich Stadial 1 (HS1; ∼19 to 15 kyr BP; kyr BP = 1000 yr before present) and the Younger Dryas (∼12.9 to 11.7 kyr BP). These hydrologic shifts have been alternatively attributed to high and low latitude origin. Here, we present a new record of hydrologic variability based on planktic foraminifera-derived δ18O of seawater (δ18Osw) estimates from a sediment core from the tropical Eastern Indian Ocean, and using 12 additional δ18Osw records, construct a single record of the dominant mode of tropical Eastern Equatorial Pacific and Indo-Pacific Warm Pool (IPWP) hydrologic variability. We show that deglacial hydrologic shifts parallel variations in the reconstructed interhemispheric temperature gradient, suggesting a strong response to variations in the Atlantic Meridional Overturning Circulation and the attendant heat redistribution. A transient model simulation of the last deglaciation suggests that hydrologic changes, including a southward shift in the Intertropical Convergence Zone (ITCZ) which likely occurred during these northern hemisphere cold events, coupled with oceanic advection and mixing, resulted in increased salinity in the Indonesian region of the IPWP and the eastern tropical Pacific, which is recorded by the δ18Osw proxy. Based on our observations and modeling results we suggest the interhemispheric temperature gradient directly controls the tropical hydrologic cycle on these time scales, which in turn mediates poleward atmospheric heat transport. VL - 387 UR - https://doi.org/10.1016/j.epsl.2013.11.032 ER - TY - JOUR T1 - Delta growth and river valleys: the influence of climate and sea level changes on the South Adriatic shelf (Mediterranean Sea) JF - Quaternary Science Reviews Y1 - 2014 A1 - Maselli, V. A1 - Trincardi, F. A1 - Asioli, A. A1 - Ceregato, A. A1 - Rizzetto, F. A1 - Taviani, M. AB - Incised valleys across continental margins represent the response of fluvial systems to changes in their equilibrium dynamics, mainly driven by base level fall forced by glacial–eustatic cycles. The Manfredonia Incised Valley formed during the last glacial sea level lowstand, when most of the southern Adriatic shelf was sub-aerially exposed but the outer shelf remained under water. The pronounced upstream deepening of the valley is ascribed to river incision of the MIS5e highstand coastal prism and related subaqueous clinoform under the influence of MIS5-4 sea level fluctuations, while the downstream shallowing and narrowing mainly reflects the impact of increased rates of sea level fall at the MIS3-2 transition on a flatter mid-outer shelf. Until 15 ka BP, the valley fed an asymmetric delta confined to the mid-outer shelf, testifying that continental and deep marine systems remained disconnected during the lowstand. Sea level rise reached the inner shelf during the Early Holocene, drowning the valley and leading to the formation of a sheltered embayment confined toward the land: at this time part of the incision remained underfilled with a marked bathymetric expression. This mini-basin was rapidly filled by sandy bayhead deltas, prograding from both the northern and southern sides of the valley. In this environment, protected by marine reworking and where sediment dispersal was less effective, the accommodation space was reduced and autogenic processes forced the formation of multiple and coalescing delta lobes. Bayhead delta progradations occurred in few centuries, between 8 and 7.2 ka cal BP, confirming the recent hypothesis that in this area the valley was filled during the formation of sapropel S1. This proximal valley fill, representing the very shallow-water equivalent of the cm-thick sapropel layers accumulated offshore in the deeper southern Adriatic basin, is of key importance in following the signature of the sapropel in a facies-tract ideally from the shoreline to the abyss. VL - 99 UR - http://www.sciencedirect.com/science/article/pii/S0277379114002431 JO - Delta growth and river valleys: the influence of climate and sea level changes on the South Adriatic shelf (Mediterranean Sea) ER - TY - JOUR T1 - A depth refugium from catastrophic coral bleaching prevents regional extinction JF - Ecology Y1 - 2014 A1 - Smith, Tyler B. A1 - Glynn, Peter W. A1 - é, Juan L. A1 - Toth, Lauren T. A1 - Gyory, Joanna KW - Coral bleaching KW - Coral mortality KW - Depth refuge KW - Eastern Tropical Pacific KW - El Nino-Southern Oscillation KW - Extinction KW - Holocene KW - Millepora KW - Refuge AB - Species intolerant of changing climate might avoid extinction within refugia buffered from extreme conditions. Refugia have been observed in the fossil record but are not well documented or understood on ecological time scales. Using a 37-year record from the eastern Pacific across the two most severe El Nin o events on record (1982-1983 and 1997- 1998) we show how an exceptionally thermally sensitive reef-building hydrocoral, Millepora intricata, twice survived catastrophic bleaching in a deeper-water refuge (.11 m depth). During both events, M. intricata was extirpated across its range in shallow water, but showed recovery within several years, while two other hydrocorals without deep-water populations were driven to regional extinction. Evidence from the subfossil record in the same area showed shallow-water persistence of abundant M. intricata populations from 5000 years ago, through severe El Nin o-Southern Oscillation cycles, suggesting a potential depth refugium on a millennial timescale. Our data confirm the deep refuge hypothesis for corals under thermal stress. © 2014 by the Ecological Society of America. VL - 95 UR - http://doi.wiley.com/10.1890/13-0468.1 IS - 6 ER - TY - JOUR T1 - Diverse rupture modes for surface-deforming upper-plate earthquakes in the southern Puget Lowland of Washington State JF - Geosphere Y1 - 2014 A1 - Nelson, Alan R. A1 - Personius, Stephen F. A1 - Sherrod, Brian L. A1 - Kelsey, Harvey M. A1 - Johnson, Samuel Y. A1 - Bradley, Lee-Ann A1 - Wells, Ray E. AB - Earthquake prehistory of the southern Puget Lowland, in the north-south compressive regime of the migrating Cascadia forearc, reflects diverse earthquake rupture modes with variable recurrence. Stratigraphy and Bayesian analyses of previously reported and new 14C ages in trenches and cores along backthrust scarps in the Seattle fault zone restrict a large earthquake to 1040–910 cal yr B.P. (2σ), an interval that includes the time of the M 7–7.5 Restoration Point earthquake. A newly identified surface-rupturing earthquake along the Waterman Point backthrust dates to 940–380 cal yr B.P., bringing the number of earthquakes in the Seattle fault zone in the past 3500 yr to 4 or 5. Whether scarps record earthquakes of moderate (M 5.5–6.0) or large (M 6.5–7.0) magnitude, backthrusts of the Seattle fault zone may slip during moderate to large earthquakes every few hundred years for periods of 1000–2000 yr, and then not slip for periods of at least several thousands of years. Four new fault scarp trenches in the Tacoma fault zone show evidence of late Holocene folding and faulting about the time of a large earthquake or earthquakes inferred from widespread coseismic subsidence ca. 1000 cal yr B.P.; 12 ages from 8 sites in the Tacoma fault zone limit the earthquakes to 1050–980 cal yr B.P. Evidence is too sparse to determine whether a large earthquake was closely predated or postdated by other earthquakes in the Tacoma basin, but the scarp of the Tacoma fault was formed by multiple earthquakes. In the northeast-striking Saddle Mountain deformation zone, along the western limit of the Seattle and Tacoma fault zones, analysis of previous ages limits earthquakes to 1200–310 cal yr B.P. The prehistory clarifies earthquake clustering in the central Puget Lowland, but cannot resolve potential structural links among the three Holocene fault zones. VL - 10 UR - https://pubs.geoscienceworld.org/geosphere/article/10/4/769-796/132175 IS - 4 ER - TY - JOUR T1 - Gas hydrate destabilization and methane release events in the Krishna–Godavari Basin, Bay of Bengal JF - Marine and Petroleum Geology Y1 - 2014 A1 - Joshi, R. K. A1 - Mazumdar, A. A1 - Peketi, A. A1 - Ramamurty, P. B. A1 - Naik, B. G. A1 - Kocherla, M. A1 - Carvalho, Mary Ann A1 - Mahalakshmi, P. A1 - Dewangan, P. A1 - Ramana, M. V. AB - Methane release events have been linked to global warming, alteration of the carbon cycle and influence on biota. However, unequivocal evidence of paleomethane release events are limited. We report several negative carbon stable isotope excursions in planktic and benthic foraminifera in a core (MD161-8) from the Krishna-Godavari (K–G) Basin, Bay of Bengal. The most negative δ13C spikes are recorded during the marine isotope stages MIS-4 and at the transition of MIS-5 to 4. Occurrence of highly 13C depleted (average δ13C = −48 ± 2.4‰ VPDB) authigenic high magnesian calcite are also reported within this time window from the core MD161-8. In the present work an unequivocal explanation for the observed 13C depletion in the marine planktic and benthic foraminifera is difficult to achieve solely from the optical/electron microscopy or C–O stable isotope ratio analyses due to possible influence of diagenetic alteration. We attribute the observed episodic methane expulsion events, as inferred from the negative δ13C excursions and earlier reports on the occurrence chemosynthetic bivalves and Mo concentration anomaly to the destabilization of the base of gas hydrate stability zone (BGHSZ). Sea level drop and shale tectonics induced focused fluid flow are the two possible causes of hydrate destabilization discussed here. Shale tectonics were possibly responsible for creating fault systems which acted as the conduit for gas flow through the sediment column and subsequent seepage. Shale and salt tectonics in the passive continental margins being a globally observed phenomenon, its role as an important driving force for enhanced methane emission needs detailed investigation to understand the climatic perturbations through geologic time. Additional evidence of methane emission from site MD161-15 further supports the link between shale tectonics and methane emission. VL - 58 N1 - AAy4wyTimes Cited:2Cited References Count:97 JO - Gas hydrate destabilization and methane release events in the Krishna–Godavari Basin, Bay of Bengal ER - TY - JOUR T1 - A Geochemical Approach to Determine Sources and Movement of Saline Groundwater in a Coastal Aquifer JF - Groundwater Y1 - 2014 A1 - Anders, Robert A1 - Mendez, Gregory O. A1 - Futa, Kiyoto A1 - Danskin, Wesley R. AB - Geochemical evaluation of the sources and movement of saline groundwater in coastal aquifers can aid in the initial mapping of the subsurface when geological information is unavailable. Chloride concentrations of groundwater in a coastal aquifer near San Diego, California, range from about 57 to 39,400 mg/L. On the basis of relative proportions of major-ions, the chemical composition is classified as Na-Ca-Cl-SO4, Na-Cl, or Na-Ca-Cl type water. ?2H and ?18O values range from ?47.7? to ?12.8? and from ?7.0? to ?1.2?, respectively. The isotopically depleted groundwater occurs in the deeper part of the coastal aquifer, and the isotopically enriched groundwater occurs in zones of sea water intrusion. 87Sr/86Sr ratios range from about 0.7050 to 0.7090, and differ between shallower and deeper flow paths in the coastal aquifer. 3H and 14C analyses indicate that most of the groundwater was recharged many thousands of years ago. The analysis of multiple chemical and isotopic tracers indicates that the sources and movement of saline groundwater in the San Diego coastal aquifer are dominated by: (1) recharge of local precipitation in relatively shallow parts of the flow system; (2) regional flow of recharge of higher-elevation precipitation along deep flow paths that freshen a previously saline aquifer; and (3) intrusion of sea water that entered the aquifer primarily during premodern times. Two northwest-to-southeast trending sections show the spatial distribution of the different geochemical groups and suggest the subsurface in the coastal aquifer can be separated into two predominant hydrostratigraphic layers. VL - 52 UR - http://dx.doi.org/10.1111/gwat.12108 IS - 5 JO - A Geochemical Approach to Determine Sources and Movement of Saline Groundwater in a Coastal Aquifer ER - TY - JOUR T1 - The geochemistry of deep-sea coral skeletons: A review of vital effects and applications for palaeoceanography JF - Deep Sea Research Part II: Topical Studies in Oceanography Y1 - 2014 A1 - Robinson, Laura F. A1 - Adkins, Jess F. A1 - Frank, Norbert A1 - Alexander, C. A1 - Prouty, Nancy A1 - Brendan Roark, E. A1 - de Flierdt, Tina van AB - Deep-sea corals were discovered over a century ago, but it is only over recent years that focused efforts have been made to explore the history of the oceans using the geochemistry of their skeletal remains. They offer a promising archive of past oceanic environments given their global distribution, layered growth patterns, longevity and preservation as well as our ability to date them using radiometric techniques. This paper provides an overview of the current state-of-the-art in terms of geochemical approaches to using deep-sea coral skeletons to explore the history of the ocean. Deep-sea coral skeletons have a wide array of morphologies (e.g., solitary cup corals, branching colonial corals) and materials (calcite, aragonite and proteins). As such their biomineralization strategies are diverse, leading to complex geochemistry within coral skeletons. Notwithstanding these complications, progress has been made on developing methods for reconstructing the oceanographic environment in the past using trace elements and isotopic methods. Promising approaches within certain coral groups include clumped isotopes and Mg/Li for temperature reconstructions, boron isotopes and radiocarbon for carbon cycling, Nd, and radiocarbon for circulation studies and δ15N, P/Ca and Ba/Ca for nutrient tracer studies. Likewise there is now a range of techniques for dating deep-sea corals skeletons (e.g., U-series, radiocarbon), and determining their growth rates (e.g., radiocarbon and 210Pb). Dating studies on historic coral populations in the Atlantic, Southern Ocean and Pacific point to climate and environmental changes being dominant controls on coral populations over millennial and orbital timescales. This paper provides a review of a range of successes and promising approaches. It also highlights areas in which further research would likely provide new insights into biomineralization, palaeoceanography and distribution of past coral populations. VL - 99 N1 - id: 2340 JO - The geochemistry of deep-sea coral skeletons: A review of vital effects and applications for palaeoceanography ER - TY - JOUR T1 - Glacial to deglacial ventilation and productivity changes in the southern Okhotsk Sea JF - Palaeogeography, Palaeoclimatology, Palaeoecology Y1 - 2014 A1 - Okazaki, Yusuke A1 - Kimoto, Katsunori A1 - Asahi, Hirofumi A1 - Sato, Miyako A1 - Nakamura, Yuriko A1 - Harada, Naomi KW - Glacial–deglacial change KW - Okhotsk Sea KW - productivity KW - ventilation AB - As a source region of North Pacific Intermediate Water, the Okhotsk Sea plays an important role in the ventilation of the North Pacific. To understand the detailed oceanographic changes in this marginal sea since the last glaciation, we studied decadal to centennial scale proxy records from new sediment cores from the southwestern Okhotsk Sea. Glacial to Holocene Δ14C records of benthic foraminiferal shells suggested enhanced ventilation in the Okhotsk Sea during the early deglacial period between 18 and 15 ka, corresponding to Heinrich Event 1. Although the Δ14C reconstruction has considerable uncertainties, the Okhotsk Sea may have acted as a source for vigorous ventilation of the subarctic Pacific during this period. CaCO3 preservation events appear to be better explained by the ventilation history of the Okhotsk Sea than by coccolithophores and foraminifera production. CaCO3 preservation started to improve during 18 to 15 ka, and pronounced peaks in the CaCO3 content corresponded to the Bølling–Allerød (15 to 13 ka) and Preboreal (11.5 to 10 ka) warm periods. Diatom and coccolithophore productivity remained low in the Okhotsk Sea throughout the glacial to deglacial periods, different from the situation in the open subarctic Pacific, where high productivity was observed during the Bølling–Allerød period. After the Preboreal period, biogenic opal gradually increased and δ15N decreased in the southern Okhotsk Sea, suggesting that productivity was enhanced by a relaxation of the nitrate limitation. VL - 395 UR - https://doi.org/10.1016/j.palaeo.2013.12.013 ER - TY - JOUR T1 - Heterogeneous reservoirs in the marine carbon cycle Y1 - 2014 A1 - L Follett, Christopher KW - Carbon dioxide content KW - Organic compounds AB - Understanding the fate of primary production in the ocean is a challenging task because once produced, organic material is oxidized over timescales which range from minutes, to millions of years. This timescale diversity is matched by an equal heterogeneity in both the local physical and chemical environment. In this thesis we explore the relationship between the distinct reservoirs of organic carbon in the ocean and their underlying complexity. First, we show how the heterogeneity of portions of the carbon cycle can be packaged in terms of age structured models and their accompanying age and rate distributions. We further relate the moments of the rate distributions to bulk reservoir properties like average age and flux. Explicit relationships are then derived for the specific case of a single turnover time and a lognormal distribution. We apply these ideas to the problem of dissolved organic carbon (DOC) cycling in the ocean. Current models of bulk concentration and isotope data suggest a microbially sourced DOC reservoir consisting of two components. A nearly homogeneous background component with a long turnover time (> 6000 years) is joined by a component of fast turnover time (~ 1 year) and equal concentration in the surface ocean. We confirm the presence of isotopically enriched, modern DOC co-cycling with an isotopically depleted older fraction in the upper ocean. However, our results show that up to 30% of the deep DOC reservoir is modern and supported by a 1 Pg per year carbon flux, ten times higher than inferred from bulk isotope measurements. Isotopically depleted material turns over at an apparent time scale of 30, 000 years, far slower than indicated by bulk isotope measurements. These results are consistent with global DOC measurements and explain both the fluctuations in deep DOC concentration and the anomalous radiocarbon values of DOC in the Southern Ocean. Finally, the thesis explores methods for determining the validity of diffusion limitation as the mechanism behind the power-law slowdown in organic remineralization in sediment. We find that diffusion limitation connects the decay behavior of organic material to the correlations found between mineral surface area and organic matter content in sediments. UR - https://www.researchgate.net/publication/279811318_Heterogeneous_reservoirs_in_the_marine_carbon_cycle ER - TY - JOUR T1 - Hidden cycle of dissolved organic carbon in the deep ocean JF - Proceedings of the National Academy of Sciences Y1 - 2014 A1 - Follett, Christopher L. A1 - Repeta, Daniel J. A1 - Rothman, Daniel H. A1 - Xu, Li A1 - Santinelli, Chiara KW - Carbon cycle KW - carbon isotopes KW - dissolved organic carbon KW - Oceanography KW - radiocarbon AB - Marine dissolved organic carbon (DOC) is a large (660 Pg C) reactive carbon reservoir that mediates the oceanic microbial food web and interacts with climate on both short and long timescales. Carbon isotopic content provides information on the DOC source via [Formula: see text]C and age via [Formula: see text]C. Bulk isotope measurements suggest a microbially sourced DOC reservoir with two distinct components of differing radiocarbon age. However, such measurements cannot determine internal dynamics and fluxes. Here we analyze serial oxidation experiments to quantify the isotopic diversity of DOC at an oligotrophic site in the central Pacific Ocean. Our results show diversity in both stable and radio isotopes at all depths, confirming DOC cycling hidden within bulk analyses. We confirm the presence of isotopically enriched, modern DOC cocycling with an isotopically depleted older fraction in the upper ocean. However, our results show that up to 30% of the deep DOC reservoir is modern and supported by a 1 Pg/y carbon flux, which is 10 times higher than inferred from bulk isotope measurements. Isotopically depleted material turns over at an apparent time scale of 30,000 y, which is far slower than indicated by bulk isotope measurements. These results are consistent with global DOC measurements and explain both the fluctuations in deep DOC concentration and the anomalous radiocarbon values of DOC in the Southern Ocean. Collectively these results provide an unprecedented view of the ways in which DOC moves through the marine carbon cycle. VL - 111 UR - http://www.pnas.org/lookup/doi/10.1073/pnas.1407445111https://syndication.highwire.org/content/doi/10.1073/pnas.1407445111 IS - 47 ER - TY - JOUR T1 - The high-supply, current-dominated continental margin of southeastern South America during the late Quaternary JF - Quaternary Research Y1 - 2014 A1 - Lantzsch, Hendrik A1 - Hanebuth, Till J. J. A1 - Chiessi, Cristiano M. A1 - Schwenk, Tilmann A1 - Violante, Roberto A. AB - The continental margin off the La Plata Estuary (SE South America) is characterized by high fluvial sediment supply and strong ocean currents. High-resolution sediment-acoustic data combined with sedimentary facies analysis, AMS-14C ages, and neodymium isotopic data allowed us to reconstruct late Quaternary sedimentary dynamics in relation to the two major sediment sources, the La Plata Estuary and the Argentine margin. Sediments from these two provinces show completely different dispersal patterns. We show that the northward-trending La Plata paleo-valley was the sole transit path for the huge volumes of fluvial material during lower sea levels. In contrast, material from the Argentine margin sector was transported northwards by the strong current system. Despite the large sediment volumes supplied by both sources, wide parts of the shelf were characterized by either persistent non-deposition or local short-term depocenter formation. The location and formation history of these depocenters were primarily controlled by the interplay of sea level with current strength and local morphology. The high sediment supply was of secondary importance to the stratigraphic construction, though locally resulting in high sedimentation rates. Thus, the shelf system off the La Plata Estuary can be considered as a hydrodynamic-controlled end-member. VL - 81 UR - http://www.sciencedirect.com/science/article/pii/S0033589414000052 IS - 2 JO - The high-supply, current-dominated continental margin of southeastern South America during the late Quaternary ER - TY - JOUR T1 - Holocene earthquakes and right-lateral slip on the left-lateral Darrington-Devils Mountain fault zone, northern Puget Sound, Washington JF - Geosphere Y1 - 2014 A1 - Personius, S. F. A1 - Briggs, R. W. A1 - Nelson, A. R. A1 - Schermer, E. R. A1 - Maharrey, J. Z. A1 - Sherrod, B. L. A1 - Spaulding, S. A. A1 - Bradley, L.-A. AB - Sources of seismic hazard in the Puget Sound region of northwestern Washington include deep earthquakes associated with the Cascadia subduction zone, and shallow earthquakes associated with some of the numerous crustal (upper-plate) faults that crisscross the region. Our paleoseismic investigations on one of the more prominent crustal faults, the Darrington–Devils Mountain fault zone, included trenching of fault scarps developed on latest Pleistocene glacial sediments and analysis of cores from an adjacent wetland near Lake Creek, 14 km southeast of Mount Vernon, Washington. Trench excavations revealed evidence of a single earthquake, radiocarbon dated to ca. 2 ka, but extensive burrowing and root mixing of sediments within 50–100 cm of the ground surface may have destroyed evidence of other earthquakes. Cores in a small wetland adjacent to our trench site provided stratigraphic evidence (formation of a laterally extensive, prograding wedge of hillslope colluvium) of an earthquake ca. 2 ka, which we interpret to be the same earthquake documented in the trenches. A similar colluvial wedge lower in the wetland section provides possible evidence for a second earthquake dated to ca. 8 ka. Three-dimensional trenching techniques revealed evidence for 2.2 ± 1.1 m of right-lateral offset of a glacial outwash channel margin, and 45–70 cm of north-side-up vertical separation across the fault zone. These offsets indicate a net slip vector of 2.3 ± 1.1 m, plunging 14° west on a 286°-striking, 90°-dipping fault plane. The dominant right-lateral sense of slip is supported by the presence of numerous Riedel R shears preserved in two of our trenches, and probable right-lateral offset of a distinctive bedrock fault zone in a third trench. Holocene north-side-up, right-lateral oblique slip is opposite the south-side-up, left-lateral oblique sense of slip inferred from geologic mapping of Eocene and older rocks along the fault zone. The cause of this slip reversal is unknown but may be related to clockwise rotation of the Darrington–Devils Mountain fault zone into a position more favorable to right-lateral slip in the modern N-S compressional stress field. VL - 10 UR - https://pubs.geoscienceworld.org/geosphere/article/10/6/1482-1500/132254 IS - 6 ER - TY - JOUR T1 - Holocene fluctuations of Bregne ice cap, Scoresby Sund, east Greenland: a proxy for climate along the Greenland Ice Sheet margin JF - APEX II: Arctic Palaeoclimate and its Extremes Y1 - 2014 A1 - Levy, Laura B. A1 - Kelly, Meredith A. A1 - Lowell, Thomas V. A1 - Hall, Brenda L. A1 - Hempel, Laura A. A1 - Honsaker, William M. A1 - Lusas, Amanda R. A1 - Howley, Jennifer A. A1 - Axford, Yarrow L. AB - The Greenland Ice Sheet is a major component of the Arctic cryosphere and the magnitude of its response to future climate changes remains uncertain. Longer-term records of climate near the ice sheet margin provide information about natural climate variability and can be used to understand the causes of past changes in the Greenland Ice Sheet. As a proxy for Holocene climate near the ice sheet margin, we reconstruct the fluctuations of Bregne ice cap in the Scoresby Sund region of central east Greenland. Bregne is a small ice cap (2.5 km2 in area) and responds sensitively to summer temperatures. We employ a multi-proxy approach to reconstruct the ice cap fluctuations using geomorphic mapping, 10Be ages of boulders and bedrock and lake sediment records. Past extents of Bregne ice cap are marked by moraines and registered by sediments in downvalley lakes. 10Be ages of bedrock and boulders outboard of the moraines indicate that Bregne ice cap was within ∼250 m of its present-day limit by at least 10.7 ka. Multi-proxy data from sediments in Two Move lake, located downvalley from Bregne ice cap, indicate that the ice cap likely completely disappeared during early and middle Holocene time. Increasing magnetic susceptibility and percent clastic material from ∼6.5 to ∼1.9 cal ka BP in Two Move lake sediments suggest progressively colder conditions and increased snow accumulation on the highlands west of the lake. Laminated silt deposited at ∼2.6 cal ka BP and ∼1.9 cal ka BP to present registers the onset and persistence of Bregne ice cap during the late Holocene. 10Be ages of boulders on an unweathered, unvegetated moraine in the Bregne ice cap forefield range from 0.74 to 9.60 ka. The youngest 10Be age (0.74 ka) likely represents the age of the moraine whereas older ages may be due to 10Be inherited from prior periods of exposure. This late Holocene moraine marks the second largest advance of the ice cap since deglaciation of the region at the end of the last ice age. The oldest moraine in the forefield dates to ≤2.6 cal ka BP. The fluctuations of Bregne ice cap were likely influenced by Northern Hemisphere summer insolation throughout the Holocene and abrupt late Holocene cold events. VL - 92 UR - http://www.sciencedirect.com/science/article/pii/S0277379113002448 JO - Holocene fluctuations of Bregne ice cap, Scoresby Sund, east Greenland: a proxy for climate along the Greenland Ice Sheet margin ER - TY - JOUR T1 - Holocene glacier history of the Lago Argentino basin, Southern Patagonian Icefield JF - Quaternary Science Reviews Y1 - 2014 A1 - Strelin, Jorge A. A1 - Kaplan, Michael R. A1 - Vandergoes, Marcus J. A1 - Denton, George H. A1 - Schaefer, Joerg M. AB - We present new geomorphic, stratigraphic, and chronologic data for Holocene glacier fluctuations in the Lago Argentino basin on the eastern side of the southern Patagonian Andes. Chronologic control is based on 14C and surface-exposure 10Be dating. After the Lateglacial maximum at 13,000 cal yrs BP, the large ice lobes that filled the eastern reaches of Lago Argentino retreated and separated into individual outlet glaciers; this recession was interrupted only by a stillstand or minor readvance at 12,200 cal yrs BP. The eight largest of these individual outlet glaciers are, from north to south: Upsala, Agassiz, Onelli, Spegazzini, Mayo, Ameghino, Perito Moreno, and Grande (formerly Frías). Holocene recession of Upsala Glacier exposed Brazo Cristina more than 10,115 ± 100 cal yrs BP, and reached inboard of the Holocene moraines in Agassiz Este Valley by 9205 ± 85 cal yrs BP; ice remained in an inboard position until 7730 ± 50 cal yrs BP. Several subsequent glacier readvances are well documented for the Upsala and Frías glaciers. The Upsala Glacier readvanced at least seven times, the first being a relatively minor expansion – documented only in stratigraphic sections – between 7730 ± 50 and 7210 ± 45 cal yrs BP. The most extensive Holocene advances of Upsala Glacier resulted in the deposition of the Pearson 1 moraines and related landforms, which are divided into three systems. The Pearson 1a advance occurred about 6000–5000 cal yrs BP and was followed by the slightly less-extensive Pearson 1b and 1c advances dated to 2500–2000 and 1500–1100 cal yrs BP, respectively. Subsequent advances of Upsala Glacier resulted in deposition of the Pearson 2 moraines and corresponding landforms, also separated into three systems, Pearson 2a, 2b, and 2c, constructed respectively at ∼700, >400, and <300 cal yrs BP to the early 20th century. Similar advances are also recorded by moraine systems in front of Grande Glacier and herein separated into the Frías 1 and Frías 2a, 2b, and 2c. The Onelli and Ameghino glacier valleys also preserve older Holocene moraines. In the Agassiz, Spegazzini, and Mayo valleys, ice of the late-Holocene advances appears to have overridden landforms equivalent in age to Pearson 1. Perito Moreno Glacier is an extreme case in which ice of historical (Pearson 2c) advances overrode all older Holocene moraines. Based on the distribution and number of moraines preserved, we infer that the response to climate differed among the Lago Argentino outlet glaciers during the Holocene. This led us to examine the effects of climatic and non-climatic factors on individual glaciers. As a consequence, we detected an important effect of the valley geometry (hypsometry) on the timing and magnitude of glacier response to climate change. These results indicate that caution is needed in correlating moraines among glacier forefields without firm morpho-stratigraphic and age control. Finally, we note important similarities and differences between the overall moraine chronology in the Lago Argentino basin and that in other areas of southern South America and elsewhere in the Southern Hemisphere. VL - 101 UR - http://www.sciencedirect.com/science/article/pii/S0277379114002558 JO - Holocene glacier history of the Lago Argentino basin, Southern Patagonian Icefield ER - TY - JOUR T1 - Holocene Indian Ocean tsunami history in Sri Lanka JF - Geology Y1 - 2014 A1 - Jackson, Kelly L. A1 - Eberli, Gregor P. A1 - Amelung, Falk A1 - McFadden, Melany A. A1 - Moore, Andrew L. A1 - Rankey, Eugene C. A1 - Jayasena, H. A. H. AB - Sediment cores from Karagan Lagoon in southeastern Sri Lanka retrieved deposits from the A.D. 2004 Indian Ocean tsunami and older similar deposits that provide evidence for a tsunami 2417 +/- 152 cal. (calendar) yr B.P. to 2925 +/- 98 cal. yr B.P., and for six tsunamis between 4064 +/- 128 cal. yr B.P. and 6665 +/- 110 cal. yr B.P., a period for which the sediment record appears continuous. Radiocarbon dating indicates that the recurrence interval is variable, ranging from 181-517 yr to 1045 +/- 334 yr, with a mean recurrence interval of 434 +/- 40 yr during the ca. 4000-7000 cal. yr B.P. continuous interval. Assuming that these tsunamis were generated by giant earthquakes along the Sumatra-Andaman subduction zone, a reasonable assumption for this far-field transoceanic location, this record extends the giant-earthquake history for the Indian Ocean region. The longest recurrence interval of more than 1000 yr implies that earthquakes along the subduction zone may reach twice the size of the 2004 earthquake. VL - 42 ER - TY - JOUR T1 - Holocene paleoclimatic variation in the Schirmacher Oasis, East Antarctica: A mineral magnetic approach} JF - POLAR SCIENCE Y1 - 2014 A1 - Phartiyal, Binita KW - Holocene KW - Lacustrine sediments KW - Mineral remanent magnetism KW - Paleoclimate KW - Schirmacher Oasis AB - An analysis of remanent magnetism and radiocarbon ages in the dry lacustrine/sediment fills of the Schirmacher Oasis (SO) in East Antarctica was conducted to reconstruct past climatic condition. The statistically run mineral magnetic data on paleontological statistics software package (multivariate cluster analysis) placed on accelerator mass spectrometer radiocarbon chronology of the three sediment sections, trace 6 phases of climatic fluctuation between 13 and 3 ka, (Phases 1, 3 and 5 represent cold periods while Phases 2, 4, and 6 represent warm periods). One short warm period (Phase 2, ca. 12.5 ka) occurred in the late Pleistocene, and two marked warm periods (Phase 4, 11-8.7 ka; Phase 6, 4.4-3 ka) occurred in the Holocene. High magnetic susceptibility (chi), saturation isothermal remanent magnetism (SIRM), and soft isothermal remanent magnetism (soft IRM) values correspond to colder periods and low values reflect comparatively warmer lacustrine phases. Holocene Optima (Phase 4) and Mid Holocene Hypsithermal (Phase 6) are distinguished by decreased values of concentrations dependent parameters. Remanence is preserved in the low-coercive minerals. Heavy metals in the sediments include, Fe, Rb, Zn, Mo, Co, Pb, Mn, Cu, and As in order of decreasing abundance. (C) 2014 Elsevier B.V. and NIPR. All rights reserved. VL - 8 ER - TY - JOUR T1 - Holocene sea-surface temperature variability in the Chilean fjord region JF - Quaternary Research Y1 - 2014 A1 - Caniupán, Magaly A1 - Lamy, Frank A1 - Lange, Carina B. A1 - Kaiser, Jérôme A1 - Kilian, Rolf A1 - Arz, Helge W. A1 - León, Tania A1 - Mollenhauer, Gesine A1 - Sandoval, Susana A1 - De Pol-Holz, Ricardo A1 - Pantoja, Silvio A1 - Wellner, Julia A1 - Tiedemann, Ralf AB - Here we provide three new Holocene (11–0 cal ka BP) alkenone-derived sea surface temperature (SST) records from the southernmost Chilean fjord region (50–53°S). SST estimates may be biased towards summer temperature in this region, as revealed by a large set of surface sediments. The Holocene records show consistently warmer than present-day SSTs except for the past ~ 0.6 cal ka BP. However, they do not exhibit an early Holocene temperature optimum as registered further north off Chile and in Antarctica. This may have resulted from a combination of factors including decreased inflow of warmer open marine waters due to lower sea-level stands, enhanced advection of colder and fresher inner fjord waters, and stronger westerly winds. During the mid-Holocene, pronounced short-term variations of up to 2.5°C and a cooling centered at ~ 5 cal ka BP, which coincides with the first Neoglacial glacier advance in the Southern Andes, are recorded. The latest Holocene is characterized by two pronounced cold events centered at ~ 0.6 and 0.25 cal ka BP, i.e., during the Little Ice Age. These cold events have lower amplitudes in the offshore records, suggesting an amplification of the SST signal in the inner fjords. VL - 82 UR - http://www.sciencedirect.com/science/article/pii/S0033589414000933 IS - 2 JO - Holocene sea-surface temperature variability in the Chilean fjord region ER - TY - JOUR T1 - Indonesian vegetation response to changes in rainfall seasonality over the past 25,000 years JF - Nature Geoscience Y1 - 2014 A1 - Dubois, Nathalie A1 - Oppo, Delia W. A1 - Galy, Valier V. A1 - Mohtadi, Mahyar A1 - van der Kaars, Sander A1 - Tierney, Jessica E. A1 - Rosenthal, Yair A1 - Eglinton, Timothy I. A1 - L?ckge, Andreas A1 - Linsley, Braddock K. KW - Palaeoclimate KW - Palaeoecology AB - The hydrologic response to climate forcing in the Indo-Pacific warm pool region has varied spatially over the past 25,000 years1, 2, 3, 4, 5. For example, drier conditions are inferred on Java and Borneo for the period following the end of the Last Glacial Maximum, whereas wetter conditions are reconstructed for northwest Australia4. The response of vegetation to these past rainfall variations is poorly constrained. Using a suite of 30 surface marine sediment samples from throughout the Indo-Pacific warm pool, we demonstrate that today the stable isotopic composition of vascular plant fatty acids (δ13Cfa) reflects the regional vegetation composition. This in turn is controlled by the seasonality of rainfall consistent with dry season water stress6. Applying this proxy in a sediment core from offshore northeast Borneo, we show broadly similar vegetation cover during the Last Glacial Maximum and the Holocene, suggesting that, despite generally drier glacial conditions1, 7, there was no pronounced dry season. In contrast, δ13Cfa and pollen data from a core off the coast of Sumba indicate an expansion of C4 herbs during the most recent glaciation, implying enhanced aridity and water stress during the dry season. Holocene vegetation trends are also consistent with a response to dry season water stress. We therefore conclude that vegetation in tropical monsoon regions is susceptible to increases in water stress arising from an enhanced seasonality of rainfall, as has occurred8 in past decades. VL - 7449278721172063253871891072011563523665412739429544323 UR - http://www.nature.com/doifinder/10.1038/ngeo2182 IS - 7 ER - TY - JOUR T1 - Inferring local to regional changes in forest composition from Holocene macrofossils and pollen of a small lake in central Upper Michigan JF - Quaternary Science Reviews Y1 - 2014 A1 - Jackson, Stephen T. A1 - Booth, Robert K. A1 - Reeves, Kelly A1 - Andersen, Jennifer Jewell A1 - Minckley, Thomas A. A1 - Jones, Rachel A. AB - Vegetational response to climatic change involves processes of population and community dynamics within local stands, which scale up to landscape-level changes in vegetation composition and broad-scale changes in species distributions. Understanding these dynamics poses a critical challenge to paleoecological explanation, because of the broad range of scales at which these dynamics take place and interact. We present an 8600-year paleoecological record of local and regional changes in forest composition from a small (2.6 ha) lake in central Upper Michigan. Plant macrofossils provide a spatially precise record of local forest composition, while pollen data provide a spatially integrated record of regional vegetational changes. Temporal patterns among different macrofossil types within species show overall coherence, indicating that changes in macrofossil abundance generally record changes in local tree abundance. Temporal patterns in macrofossil sequences correspond to patterns in pollen sequences, indicating that local changes contributed to the large-scale changes in the surrounding region. The pollen and macrofossil records show nearly continuous turnover in vegetation composition throughout the past 8600 years; the longest period without major compositional change was ca 1600 years, and dynamics at multidecadal to multicentennial scales are observed during many periods. Coordinated application of temporally precise sequences of pollen and macrofossil data at multiple sites can support inferences concerning vegetation dynamics at multiple spatial and temporal scales, and test mechanistic hypotheses. VL - 98 UR - http://www.sciencedirect.com/science/article/pii/S027737911400211X JO - Inferring local to regional changes in forest composition from Holocene macrofossils and pollen of a small lake in central Upper Michigan ER - TY - JOUR T1 - An investigation of size-fractionated organic matter from Lake Superior and a tributary stream using radiocarbon, stable isotopes and NMR JF - Geochimica et Cosmochimica Acta Y1 - 2014 A1 - Zigah, Prosper K. A1 - Minor, Elizabeth C. A1 - Abdulla, Hussain A.N. A1 - Werne, Josef P. A1 - Hatcher, Patrick G. VL - 127 UR - https://linkinghub.elsevier.com/retrieve/pii/S0016703713006765https://api.elsevier.com/content/article/PII:S0016703713006765?httpAccept=text/xmlhttps://api.elsevier.com/content/article/PII:S0016703713006765?httpAccept=text/plain ER - TY - JOUR T1 - An investigation of size-fractionated organic matter from Lake Superior and a tributary stream using radiocarbon, stable isotopes and NMR JF - Geochimica et Cosmochimica Acta Y1 - 2014 A1 - Zigah, Prosper K. A1 - Minor, Elizabeth C. A1 - Abdulla, Hussain A. N. A1 - Werne, Josef P. A1 - Hatcher, Patrick G. AB - This study investigated the concentration and isotopic composition of different size fractions of organic matter (OM) in Lake Superior and in one of its many tributary streams and rivers (Amity Creek, Duluth, Minnesota, USA). Structural compositional drivers of the Δ14C of high molecular weight (HMW, >1 kDa) dissolved organic carbon (DOC) in the lake were also evaluated. Low molecular weight (LMW, 0.7 μm) was generally 13C-depleted (−29 ± 1.2‰) relative to “bulk” (<0.7 μm) DOC (−26.4 ± 0.7‰), “init” (<0.2 μm) DOC (−26.6 ± 0.8‰), HMW DOC (−26.9 ± 0.3‰) and LMW DOC (−26.5 ± 0.9‰), and had more variable 14C content (Δ14C of −94‰ to 53‰; 735 years BP to modern) than the other size fractions. Init DOC (Δ14C of 17–59‰), HMW DOC (Δ14C of 23–64‰) and LMW DOC (Δ14C of 16–62‰) all reflected contemporary (modern) radiocarbon signatures. Bulk DOC (Δ14C of −19‰ to 57‰; 90 years BP to modern) had modern radiocarbon values in the offshore sites (Δ14C of 2–57‰) with pre-aged samples (Δ14C of −8‰ to −19‰) seen at the nearshore site. HMW DOM was relatively N-poor (C:N of 12–19) compared to particulate organic matter (POM, C:N of 8–10) revealing either a more diagenetically altered state or contrasting sources. 13C NMR data showed that biochemical composition of HMW DOC in Lake Superior was dominated by carbohydrates (53–65%) with only trace aromatic components (2–4%). Structurally complex components such as heteropolysaccharides (HPS), amide/peptides and amino sugars (AMS) constitute 75–84% of HMW DOC whereas carboxylic-rich alicyclic molecules (CRAM) made up 16–25% of HMW DOC in the lake. Combined HPS and AMS, O-alkyl carbohydrate carbon, and total carbohydrate carbon contents were significantly positively correlated to the Δ14C of HMW DOC suggesting they contribute a contemporary 14C-enriched component to the HMW DOC in the lake. In contrast, CRAM and aliphatic carbons were significantly inversely correlated with Δ14C of HMW DOC implying that these represent 14C-depleted (older) components of HMW DOC in the lake. At Amity Creek, storm events led to larger loads of bulk DOC and POC, which were both 14C-enriched (modern). However, in baseflow conditions 14C-depleted bulk DOC and POC were exported. LMW DOC from the creek was considerably 14C-depleted compared to concurrent HMW DOC. VL - 127 UR - http://www.sciencedirect.com/science/article/pii/S0016703713006765 JO - An investigation of size-fractionated organic matter from Lake Superior and a tributary stream using radiocarbon, stable isotopes and NMR ER - TY - JOUR T1 - Isotopic evidence for anthropogenic impacts on aquatic food web dynamics and mercury cycling in a subtropical wetland ecosystem in the US JF - Science of The Total Environment Y1 - 2014 A1 - Wang, Yang A1 - Gu, Binhe A1 - Lee, Ming-Kuo A1 - Jiang, Shijun A1 - Xu, Yingfeng AB - Quantifying and predicting the food web consequences of anthropogenic changes is difficult using traditional methods (based on gut content analysis) because natural food webs are variable and complex. Here, stable and radioactive carbon isotopes are used, in conjunction with nitrogen isotopes and mercury (Hg) concentration data, to document the effects of land-use change on food webs and Hg bioaccumulation in the Everglades – a subtropical wetland ecosystem in the US. Isotopic signatures of largemouth bass and sunfish in reference (relatively pristine) wetlands indicate reliance on the food supply of modern primary production within the wetland. In contrast, both fish in areas impacted by agricultural runoff had radiocarbon ages as old as 540 years B.P., and larger isotopic variability than counterparts in reference wetlands, reflecting differences in the food web between impacted and reference wetlands. Consistent with this difference, particulate and dissolved organic matter in impacted areas had old radiocarbon ages (> 600 years B.P.), indicating that old carbon derived from historic peat deposits in the Everglades Agricultural Area was passed along the food chain to consumers. Significant radiocarbon deficiencies in largemouth bass and sunfish, relative to mosquitofish, in impacted areas most likely indicate a reduced dependence on small fish. Furthermore, largemouth bass and sunfish from impacted areas had much lower Hg contents than those from reference wetlands. Taken together, these data suggest a shift toward lower trophic levels and a possible reduction in mercury methylation in impacted wetlands. Our study provides clear evidence that hydrological modification and land-use change in the Everglades have changed the system from one driven primarily by in-situ productivity to one that is partially dependent on allochthonous carbon input from peat soils in the agricultural area and altered the Hg biogeochemical cycle in the wetlands. The results have implications for the restoration and management of wetland ecosystems. VL - 487 UR - http://www.sciencedirect.com/science/article/pii/S0048969714005701 JO - Isotopic evidence for anthropogenic impacts on aquatic food web dynamics and mercury cycling in a subtropical wetland ecosystem in the US ER - TY - JOUR T1 - Late Holocene marine transgression and the drowning of a coastal forest: Lessons from the past, Cape Cod, Massachusetts, USA JF - Palaeogeography, Palaeoclimatology, Palaeoecology Y1 - 2014 A1 - Maio, Christopher V. A1 - Gontz, Allen M. A1 - Weidman, Christopher R. A1 - Donnelly, Jeffrey P. AB - Extra-tropical storms in the spring of 2010 swept the New England coastline resulting in significant erosion along South Cape Beach, a barrier system located on Cape Cod, Massachusetts. The erosion revealed 111 subfossil stumps and a preserved peat outcrop. We hypothesize that the stumps represent an ancient Eastern Red cedar, Juniperus virginiana, stand growing in a back-barrier environment and drowned by episodic storm events and moderate rates of sea-level rise. Stumps, bivalves, and organic sediments, were radiocarbon dated using traditional and continuous-flow Atomic Mass Spectroscopy methods. Six sediment cores elucidated subsurface stratigraphy and environmental setting. Subfossil stumps ranged in age from 413 ± 80 to 1239 ± 53 calibrated years before present. We assume that this age represents the time at which the ancient trees were drowned by marine waters. Based on elevation and age, an 826 year rate of submergence was calculated at 0.73 mm/yr with an R2 value of 0.47. Core stratigraphy, microfossil assemblages, and radiocarbon ages indicate a dynamic barrier environment with frequent overwash and breaching events occurring during the past 500 years. Shoreline change analysis showed that between 1846 and 2008, the shoreline retreated landward by 70 m at a long-term rate of 0.43 m/yr. Future increases in the rate of sea-level rise, coupled with episodic storm events, will lead to the destruction of terrestrial environments at rate orders of magnitude greater than that during the time of the paleoforest. VL - 393 UR - http://www.sciencedirect.com/science/article/pii/S003101821300521X JO - Late Holocene marine transgression and the drowning of a coastal forest: Lessons from the past, Cape Cod, Massachusetts, USA ER - TY - JOUR T1 - Late Holocene sea- and land-level change on the U.S. southeastern Atlantic coast JF - Marine Geology Y1 - 2014 A1 - Kemp, Andrew C. A1 - Bernhardt, Christopher E. A1 - Horton, Benjamin P. A1 - Kopp, Robert E. A1 - Vane, Christopher H. A1 - Peltier, W. Richard A1 - Hawkes, Andrea D. A1 - Donnelly, Jeffrey P. A1 - Parnell, Andrew C. A1 - Cahill, Niamh AB - Late Holocene relative sea-level (RSL) reconstructions can be used to estimate rates of land-level (subsidence or uplift) change and therefore to modify global sea-level projections for regional conditions. These reconstructions also provide the long-term benchmark against which modern trends are compared and an opportunity to understand the response of sea level to past climate variability. To address a spatial absence of late Holocene data in Florida and Georgia, we reconstructed ~ 1.3 m of RSL rise in northeastern Florida (USA) during the past ~ 2600 years using plant remains and foraminifera in a dated core of high salt-marsh sediment. The reconstruction was fused with tide-gauge data from nearby Fernandina Beach, which measured 1.91 ± 0.26 mm/year of RSL rise since 1900 CE. The average rate of RSL rise prior to 1800 CE was 0.41 ± 0.08 mm/year. Assuming negligible change in global mean sea level from meltwater input/removal and thermal expansion/contraction, this sea-level history approximates net land-level (subsidence and geoid) change, principally from glacio-isostatic adjustment. Historic rates of rise commenced at 1850–1890 CE and it is virtually certain (P = 0.99) that the average rate of 20th century RSL rise in northeastern Florida was faster than during any of the preceding 26 centuries. The linearity of RSL rise in Florida is in contrast to the variability reconstructed at sites further north on the U.S. Atlantic coast and may suggest a role for ocean dynamic effects in explaining these more variable RSL reconstructions. Comparison of the difference between reconstructed rates of late Holocene RSL rise and historic trends measured by tide gauges indicates that 20th century sea-level trends along the U.S. Atlantic coast were not dominated by the characteristic spatial fingerprint of melting of the Greenland Ice Sheet. VL - 357 UR - http://www.sciencedirect.com/science/article/pii/S0025322714002187 JO - Late Holocene sea- and land-level change on the U.S. southeastern Atlantic coast ER - TY - JOUR T1 - Late Holocene sea- and land-level change on the U.S. southeastern Atlantic coast JF - Marine Geology Y1 - 2014 A1 - Kemp, Andrew C. A1 - Bernhardt, Christopher E. A1 - Horton, Benjamin P. A1 - Kopp, Robert E. A1 - Vane, Christopher H. A1 - Peltier, W. Richard A1 - Hawkes, Andrea D. A1 - Donnelly, Jeffrey P. A1 - Parnell, Andrew C. A1 - Cahill, Niamh KW - florida KW - Foraminifera KW - Glacio-isostatic adjustment Greenland fingerprint KW - Salt marsh AB - Late Holocene relative sea-level (RSL) reconstructions can be used to estimate rates of land-level (subsidence or uplift) change and therefore to modify global sea-level projections for regional conditions. These reconstructions also provide the long-term benchmark against which modern trends are compared and an opportunity to understand the response of sea level to past climate variability. To address a spatial absence of late Holocene data in Florida and Georgia, we reconstructed ~ 1.3 m of RSL rise in northeastern Florida (USA) during the past ~ 2600 years using plant remains and foraminifera in a dated core of high salt-marsh sediment. The reconstruction was fused with tide-gauge data from nearby Fernandina Beach, which measured 1.91 ± 0.26 mm/year of RSL rise since 1900 CE. The average rate of RSL rise prior to 1800 CE was 0.41 ± 0.08 mm/year. Assuming negligible change in global mean sea level from meltwater input/removal and thermal expansion/contraction, this sea-level history approximates net land-level (subsidence and geoid) change, principally from glacio-isostatic adjustment. Historic rates of rise commenced at 1850–1890 CE and it is virtually certain (P = 0.99) that the average rate of 20th century RSL rise in northeastern Florida was faster than during any of the preceding 26 centuries. The linearity of RSL rise in Florida is in contrast to the variability reconstructed at sites further north on the U.S. Atlantic coast and may suggest a role for ocean dynamic effects in explaining these more variable RSL reconstructions. Comparison of the difference between reconstructed rates of late Holocene RSL rise and historic trends measured by tide gauges indicates that 20th century sea-level trends along the U.S. Atlantic coast were not dominated by the characteristic spatial fingerprint of melting of the Greenland Ice Sheet. VL - 357 UR - http://linkinghub.elsevier.com/retrieve/pii/S0025322714002187http://api.elsevier.com/content/article/PII:S0025322714002187?httpAccept=text/xmlhttp://api.elsevier.com/content/article/PII:S0025322714002187?httpAccept=text/plain ER - TY - JOUR T1 - Late Holocene sedimentation in a high Arctic coastal setting: Simpson Lagoon and Colville Delta, Alaska JF - Continental Shelf Research Y1 - 2014 A1 - Hanna, Andrea J. M. A1 - Allison, Mead A. A1 - Bianchi, Thomas S. A1 - Marcantonio, Franco A1 - Goff, John A. AB - Arctic coastal environments near major river outfalls, like Simpson Lagoon, Alaska and the adjacent Colville River Delta, potentially contain high-resolution sediment records useful in elucidating late Holocene Arctic sediment transport pathways and coupled terrestrial-ocean evidence of paleoclimate variability. This study utilizes a multi-tracer geochronology approach (137Cs, 239,240Pu, and 14C) tailored for high-latitude environments to determine the age models for cores collected from Simpson Lagoon, and to date seismic boundaries in shallow acoustic reflection data (CHIRP) to examine late Holocene infill patterns. Modern (~100 y) sediment accumulation rates range from 5 m of late Holocene interbedded sediments, likely derived primarily from the Colville River, with onset of accumulation occurring prior to ~3500 y BP. A paleo-high in central Simpson Lagoon, separating the two depocenters, was subaerially exposed prior to ~600 y BP. The millimeters-per-year sedimentation rates across the lagoon, coupled with the undisturbed, interbedded sediment record, indicate that these settings hold great potential to develop new Arctic paleoenvironmental records. VL - 74 UR - http://www.sciencedirect.com/science/article/pii/S0278434313004056 JO - Late Holocene sedimentation in a high Arctic coastal setting: Simpson Lagoon and Colville Delta, Alaska ER - TY - JOUR T1 - The late Quaternary environmental evolution of marine Arctic Canada: Barrow Strait to Lancaster Sound JF - Quaternary Science Reviews Y1 - 2014 A1 - Pieńkowski, Anna J. A1 - England, John H. A1 - Furze, Mark F. A. A1 - MacLean, Brian A1 - Blasco, Steve AB - A marine sediment core from the east-central Canadian Arctic Archipelago (Core 86027-154; 74° 22.01′N 89° 51.26′W; 329 m water depth), studied by a multiproxy approach [lithostratigraphy, biogeochemistry, micropalaeontology (dinoflagellate cysts, other non-pollen palynomorphs, benthic and planktonic foraminifera, ostracods)], and encompassing 14 AMS 14C dates, provides valuable insights into regional deglacial to Holocene palaeoenvironments. Six palaeoenvironmental zones are recognized, based on prominent changes in the litho- and biostratigraphy. The waterlain diamicton of Zone I records immediate deglaciation, being derived from lift-off and calving of previously grounded glacial ice. Though deglacial timing is complicated by the sparsity of dating materials and the Portlandia Effect, age–depth model extrapolation places deglaciation at 11.54 cal ka BP. Zone II (11.5–11.0 cal ka BP) represents a distinct progression from initially ice-proximal to increasingly ice-distal conditions, interrupted by an interval of pervasive sea-ice (11.4–11.2 cal ka BP). Noteworthy biological activity commences in Zone III (11.0–9.7 cal ka BP) with a prominent signal of planktonic foraminifera (Neogloboquadrina pachyderma). This likely signifies penetration of deeper, Atlantic-derived water through the central Canadian Arctic Archipelago upon deglaciation, facilitated by the greater, glacioisostatically-induced water depths (+80 m), and implies separation of Laurentide and Innuitian ice sheets by ∼11.0 cal ka BP. Zone IV (9.7–7.2 cal ka BP) records ameliorated, biologically favourable conditions with reduced seasonal sea-ice accompanied by high microfossil species diversity and the presence of subpolar taxa. Zone V (7.2–6.5 cal ka BP) signals the exclusion of Atlantic-derived water, concomitant with increasing sea-ice, simultaneously representing the termination of the dynamic deglacial to early Holocene environments (zones I–IV). Conditions similar to modern typified by uniform sediment characteristics, present-day microfossil assemblage structures, and sparse benthic foraminifera were established by 5.6 cal ka BP (Zone VI). VL - 91 UR - http://www.sciencedirect.com/science/article/pii/S0277379113003752 JO - The late Quaternary environmental evolution of marine Arctic Canada: Barrow Strait to Lancaster Sound ER - TY - JOUR T1 - Late Quaternary sedimentary record and Holocene channel avulsions of the Jamuna and Old Brahmaputra River valleys in the upper Bengal delta plain JF - Tropical Rivers of South and South-east Asia: Landscape evolution, morphodynamics and hazards Y1 - 2014 A1 - Pickering, Jennifer L. A1 - Goodbred, Steven L. A1 - Reitz, Meredith D. A1 - Hartzog, Thomas R. A1 - Mondal, Dhiman R. A1 - Hossain, Md Saddam AB - The first Holocene stratigraphic record of river-channel occupation and switching between the Brahmaputra–Jamuna and Old Brahmaputra paleovalleys is presented here. Motivated by the Brahmaputra River's historic avulsion from the Old Brahmaputra channel to its present-day Jamuna course, we have obtained sediment and radiocarbon samples from 41 boreholes along a 120 km transect crossing these two braided-river valleys. The stratigraphy along this transect reveals sand-dominated Holocene channel systems, each bound by remnant, mud-capped Pleistocene stratigraphy. Using sediment lithology and bulk strontium concentration as a provenance indicator, we define the geometry and channel-occupation history of each paleovalley. The western Brahmaputra–Jamuna valley is broad and somewhat deeper compared with the Old Brahmaputra valley, the latter actually comprising a composite of two narrower sub-valleys bifurcated by an antecedent topographic remnant. The gently sloped valley margins (slope: 0.002 to 0.007) and high width-to-thickness ratio (W/T: ~ 1000) of the Brahmaputra–Jamuna valley suggest that it was filled primarily through lateral channel migration and the reworking of braidbelt and overbank deposits. Conversely, the two Old Brahmaputra sub-valleys have comparatively steeper valley margins (slope: 0.007 to 0.022) and lower width-to-thickness ratios (W/T: ~ 125 and ~ 250), indicating that these were filled primarily through vertical aggradation of channel sands. We attribute this disparity in valley geometry and fill processes to the different occupation histories for each valley. In this case, the much larger Brahmaputra–Jamuna valley represents the principal, if not singular, river course during the last lowstand of sea-level, with a prominent gravel lag underlying the valley. In contrast the smaller Old Brahmaputra valleys do not appear to have been present, or at least well developed, at the last lowstand. Rather these courses were first occupied during the early Holocene transgression, and we infer that the river had been previously excluded from this region by the relatively higher elevation between the Madhupur Terrace and the Shillong Massif. We also demonstrate that the Brahmaputra River experienced 3–4 major avulsions during the Holocene, with considerably longer occupation times within the principal Brahmaputra–Jamuna valley. Together these observations indicate that occupation history and antecedent topography have been important controls on river course mobility and avulsion behavior. VL - 227 UR - http://www.sciencedirect.com/science/article/pii/S0169555X13004868 JO - Late Quaternary sedimentary record and Holocene channel avulsions of the Jamuna and Old Brahmaputra River valleys in the upper Bengal delta plain ER - TY - JOUR T1 - Long-term hydrological changes in the northeastern Gulf of Mexico (ODP-625B) during the Holocene and late Pleistocene inferred from organic-walled dinoflagellate cysts JF - Palaeogeography, Palaeoclimatology, Palaeoecology Y1 - 2014 A1 - Limoges, Audrey A1 - de Vernal, Anne A1 - Van Nieuwenhove, Nicolas AB - Palynological analyses are used in conjunction with oxygen isotopes and Mg/Ca ratios in foraminifers in order to document the response of dinoflagellate cysts (dinocysts) assemblages to changing climate conditions in the northeastern Gulf of Mexico over the Holocene and late Pleistocene. During MIS 6, but also during the cooler phases of MIS 5, Impagidinium species and Operculodinium centrocarpum were dominating the assemblages. By contrast, during the last interglacial (LIG) and the Holocene, assemblages were mainly composed of Spiniferites taxa and characterized by high relative abundance of Spiniferites mirabilis-hyperacanthus, Operculodinium israelianum and/or Polysphaeridium zoharyi. These two periods exhibit ~ 1-2 °C difference in temperature as inferred from Mg/Ca ratios and show significantly distinct assemblages, with higher percentages of S. mirabilis during the LIG and higher percentages of P. zoharyi during the Holocene. This likely denotes important differences in the hydrogeographical conditions (e.g. surface circulation, bathymetric configuration) between the present and last interglacial. The importance of environmental parameters other than temperature and salinity for dinocyst assemblage dynamics is furthermore illustrated. VL - 414 UR - http://www.sciencedirect.com/science/article/pii/S0031018214004258 JO - Long-term hydrological changes in the northeastern Gulf of Mexico (ODP-625B) during the Holocene and late Pleistocene inferred from organic-walled dinoflagellate cysts ER - TY - JOUR T1 - Maximum age and missing time in the vertebrae of sand tiger shark (Carcharias taurus): validated lifespan from bomb radiocarbon dating in the western North Atlantic and southwestern Indian Oceans JF - Marine and Freshwater Research Y1 - 2014 A1 - Passerotti, M. S. A1 - Andrews, A. H. A1 - Carlson, J. K. A1 - Wintner, S. P. A1 - Goldman, K. J. A1 - Natanson, L. J. AB - Bomb radiocarbon analysis of vertebral growth bands was used to validate lifespan for sand tiger sharks (Carcharias taurus) from the western North Atlantic (WNA) and southwestern Indian Oceans (SIO). Visual counts of vertebral growth bands were used to assign age and estimate year of formation (YOF) for sampled growth bands in eight sharks from the WNA and two sharks from the SIO. Carbon-14 results were plotted relative to YOF for comparison with regional Δ14C reference chronologies to assess the accuracy of age estimates. Results from the WNA validated vertebral age estimates up to 12 years, but indicated that ages of large adult sharks were underestimated by 11–12 years. Age was also underestimated for adult sharks from the SIO by 14–18 years. Validated lifespan for C. taurus individuals in the present study reached at least 40 years for females and 34 years for males. Findings indicated that the current age-reading methodology is not suitable for estimating the age of C. taurus beyond ~12 years. Future work should investigate whether vertebrae of C. taurus record age throughout ontogeny, or cease to be a reliable indicator at some point in time. VL - 65 IS - 8 N1 - id: 2352 JO - Maximum age and missing time in the vertebrae of sand tiger shark (Carcharias taurus): validated lifespan from bomb radiocarbon dating in the western North Atlantic and southwestern Indian Oceans ER - TY - JOUR T1 - Microbial biomarkers support organic carbon transport from methane-rich Amazon wetlands to the shelf and deep sea fan during recent and glacial climate conditions JF - Organic Geochemistry Y1 - 2014 A1 - Wagner, Thomas A1 - Kallweit, Wiebke A1 - Talbot, Helen M. A1 - Mollenhauer, Gesine A1 - Boom, Arnoud A1 - Zabel, Matthias AB - We have investigated the delivery of terrestrial organic carbon (OC) to the Amazon shelf and deep sea fan based on soil marker bacteriohopanepolyols (BHPs; adenosylhopane and related compounds) and branched glycerol dialkyl glycerol tetraethers (GDGTs), as well as on 14C dating of bulk organic matter. The microbial biomarker records show persistent burial of terrestrial OC, evidenced by almost constant and high BIT values (0.6) and soil marker BHP concentration [80–230 μg/g TOC (total OC)] on the late Holocene shelf and even higher BIT values (0.8–0.9), but lower and more variable soil-marker BHP concentration (40–100 μg/g TOC), on the past glacial deep sea fan. Radiocarbon data show that OC on the shelf is 3–4 kyr older than corresponding bivalve shells, emphasizing the presence of old carbon in this setting. We observe comparable and unexpectedly invariant BHP composition in both marine sediment records, with a remarkably high relative abundance of C-35 amino BHPs including compounds specific for aerobic methane oxidation on the shelf (avg. 50% of all BHPs) and the fan (avg. 40%). Notably, these marine BHP signatures are strikingly similar to those of a methane-producing floodplain area in one of the Amazonian wetland (várzea) regions. The observation indicates that BHPs in the marine sediments may have initially been produced within wetland regions of the Amazon basin and may therefore document persistent export from terrestrial wetland regions, with subsequent re-working in the marine environment, both during recent and past glacial climate conditions. VL - 67 UR - http://www.sciencedirect.com/science/article/pii/S0146638013002714 JO - Microbial biomarkers support organic carbon transport from methane-rich Amazon wetlands to the shelf and deep sea fan during recent and glacial climate conditions ER - TY - JOUR T1 - Mid- to Late-Holocene Australian–Indonesian summer monsoon variability JF - Quaternary Science Reviews Y1 - 2014 A1 - Steinke, Stephan A1 - Mohtadi, Mahyar A1 - Prange, Matthias A1 - Varma, Vidya A1 - Pittauerova, Daniela A1 - Fischer, Helmut W. AB - The Australian–Indonesian monsoon has a governing influence on the agricultural practices and livelihood in the highly populated islands of Indonesia. However, little is known about the factors that have influenced past monsoon activity in southern Indonesia. Here, we present a ∼6000 years high-resolution record of Australian-Indonesian summer monsoon (AISM) rainfall variations based on bulk sediment element analysis in a sediment archive retrieved offshore northwest Sumba Island (Indonesia). The record suggests lower riverine detrital supply and hence weaker AISM rainfall between 6000 yr BP and ∼3000 yr BP compared to the Late Holocene. We find a distinct shift in terrigenous sediment supply at around 2800 yr BP indicating a reorganization of the AISM from a drier Mid Holocene to a wetter Late Holocene in southern Indonesia. The abrupt increase in rainfall at around 2800 yr BP coincides with a grand solar minimum. An increase in southern Indonesian rainfall in response to a solar minimum is consistent with climate model simulations that provide a possible explanation of the underlying mechanism responsible for the monsoonal shift. We conclude that variations in solar activity play a significant role in monsoonal rainfall variability at multi-decadal and longer timescales. The combined effect of orbital and solar forcing explains important details in the temporal evolution of AISM rainfall during the last 6000 years. By contrast, we find neither evidence for volcanic forcing of AISM variability nor for a control by long-term variations in the El Niño-Southern Oscillation (ENSO). VL - 93 UR - http://www.sciencedirect.com/science/article/pii/S027737911400122X JO - Mid- to Late-Holocene Australian–Indonesian summer monsoon variability ER - TY - JOUR T1 - Modeling environmental factors affecting assimilation of bomb-produced Δ14C in the North Pacific Ocean: Implications for age validation studies JF - Ecological Modelling Y1 - 2014 A1 - Helser, Thomas E. A1 - Kastelle, Craig R. A1 - Lai, Han-lin AB - The bomb-produced radiocarbon (14C) chronometer has become the gold standard for assessing the accuracy of otolith growth ring based fish age estimates. In the northeast Pacific Ocean, nearly a dozen age validation studies have been conducted, ranging from California to Alaska, most of which have relied on a single reference chronology from the Gulf of Alaska. We developed a Bayesian hierarchical model using data sets of bomb-produced radiocarbon in the northeast Pacific Ocean and investigated whether latitude and upwelling exerts an influence on the parameters that describe the rapid Δ14C increase in marine calcium carbonates. Models incorporating both latitude and upwelling as linear covariates of a 4-parameter logistic model were favored based on ΔDIC statistics. There was substantial evidence to support that the timing of the Δ14C pulse was advanced and that total Δ14C uptake increased with increasing latitude. In contrast, increased oceanographic upwelling resulted in lower total radiocarbon input as well as a delay in the timing of the pulse curve, as was demonstrated in the upwelling dominated California Current System. Within the observed latitudinal and upwelling range of the data sets examined in this study the predicted timing of the bomb pulse curve varied by as much as 3 years, which could be misinterpreted as aging error. Our results suggest that new reference chronologies may be needed for regions of the North Pacific Ocean differing in latitude, seasonal upwelling strength and other mixing factors that can potentially change the functional form of the Δ14C curve. VL - 277 UR - http://www.sciencedirect.com/science/article/pii/S0304380014000453 JO - Modeling environmental factors affecting assimilation of bomb-produced Δ14C in the North Pacific Ocean: Implications for age validation studies ER - TY - JOUR T1 - Monsoon-influenced variation in productivity and lithogenic sediment flux since 110 ka in the offshore Mahanadi Basin, northern Bay of Bengal JF - Marine and Petroleum Geology Y1 - 2014 A1 - Phillips, Stephen C. A1 - Johnson, Joel E. A1 - Giosan, Liviu A1 - Rose, Kelly AB - The Indian monsoon drives seasonal changes in precipitation and weathering across India as well as circulation and productivity in the northern Indian Ocean. Variation in paleo-monsoon intensity and its effect on productivity and lithogenic fluxes is poorly constrained in the Bay of Bengal. In this paper, we present analysis of a sediment record from the offshore Mahanadi Basin recovered during the Indian National Gas Hydrate Program Expedition 01 (Site NGHP-01-19B). We reconstruct variation in biogenic and lithogenic components during the last 110 kyr using measurements of total organic carbon (TOC), total nitrogen (TN), TOC/TN, CaCO3, biogenic silica (BSi), δ13TOC, δ15TN, bulk mineralogy from X-ray diffraction, bulk and lithogenic grain size distribution, magnetic susceptibility, bulk density, and Ca, Br, and Zr/Rb from x-ray fluorescence (XRF). The mass-accumulation rate (MAR) of CaCO3, a function of marine productivity, drastically increased between 70 and 10 ka and is correlated to previously-documented elevated Asian dust fluxes and increased Bay of Bengal salinity during a weakened southwest monsoon. Decreased freshwater input over this period likely diminished stratification, allowing for increased mixing and nutrient availability, thus enhancing productivity despite weaker southwest monsoon winds. The MAR of lithogenic material is highest during the Holocene suggesting that sediment supply driven by monsoon intensity is a stronger control on margin sedimentation than sea level at the Mahanadi Basin. Over the entire record, magnetic susceptibility and XRF Zr/Rb are strongly correlated with CaCO3, suggesting higher primary mineral input under a weakened southwest monsoon. TOC/TN and δ13TOC also increase under glacial conditions, suggesting higher relative input of terrestrial C4 organic matter. These results highlight the Mahanadi Basin as a supply-dominated margin where terrigenous sedimentation is strongly influenced by monsoon intensity, and that productivity is limited by variation in monsoon-driven stratification on glacial-interglacial timescales rather than a direct response to monsoon winds. VL - 58 N1 - AAy4wyTimes Cited:4Cited References Count:253 JO - Monsoon-influenced variation in productivity and lithogenic sediment flux since 110 ka in the offshore Mahanadi Basin, northern Bay of Bengal ER - TY - JOUR T1 - A multiple-tracer approach to understanding regional groundwater flow in the Snake Valley area of the eastern Great Basin, USA JF - Applied Geochemistry Y1 - 2014 A1 - Gardner, Philip M. A1 - Heilweil, Victor M. AB - Groundwater in Snake Valley and surrounding basins in the eastern Great Basin province of the western United States is being targeted for large-scale groundwater extraction and export. Concern about declining groundwater levels and spring flows in western Utah as a result of the proposed groundwater withdrawals has led to efforts that have improved the understanding of this regional groundwater flow system. In this study, environmental tracers (δ2H, δ18O, 3H, 14C, 3He, 4He, 20Ne, 40Ar, 84Kr, and 129Xe) and major ions from 142 sites were evaluated to investigate groundwater recharge and flow-path characteristics. With few exceptions, δ2H and δ18O show that most valley groundwater has similar ratios to mountain springs, indicating recharge is dominated by relatively high-altitude precipitation. The spatial distribution of 3H, terrigenic helium (4Heterr), and 3H/3He ages shows that modern groundwater (11 °C to the east of Snake Valley and indicate a hydraulic discontinuity between Snake and Tule Valleys across the northern Confusion Range. The combination of NGTs and 4Heterr shows that the majority of Snake Valley groundwater discharges as springs, evapotranspiration, and well withdrawals within Snake Valley rather than continuing northeastward to discharge at either Fish Springs or the Great Salt Lake Playa. The refined understanding of groundwater recharge and flow paths acquired from this multi-tracer investigation has broad implications for interbasin subsurface flow estimates and future groundwater development. VL - 45 UR - http://www.sciencedirect.com/science/article/pii/S0883292714000390 JO - A multiple-tracer approach to understanding regional groundwater flow in the Snake Valley area of the eastern Great Basin, USA ER - TY - JOUR T1 - New cetacean ΔR values for Arctic North America and their implications for marine-mammal-based palaeoenvironmental reconstructions JF - Quaternary Science Reviews Y1 - 2014 A1 - Furze, Mark F. A. A1 - Pieńkowski, Anna J. A1 - Coulthard, Roy D. AB - Radiocarbon-dated marine mammal remains from emergent Arctic coastlines have frequently been used to reconstruct Holocene sea-ice histories. The use of such reconstructions has hitherto been complicated by uncertain marine reservoir corrections precluding meaningful intercomparisons with data reported in calibrated or sidereal years. Based on an exhaustive compilation of previously published marine mammal radiocarbon dates (both live-harvested materials and subfossils) from the Canadian Arctic Archipelago (CAA), new, statistically-derived δ13C and ΔR values are provided. Average δ13C values are: −16.1 ± 1.1‰ (bone collagen; n = 193) for bowhead (Balaena mysticetus); −14.4 ± 0.5‰ (n = 44; dentine) for beluga (Delphinapterus leucas); −14.8 ± 1.9‰ (teeth and tusks; n = 18) and −18.0 ± 4.7‰ (n = 9; bone collagen) for walrus (Odobenus rosmarus). ΔR values are 170 ± 95 14C years for bowhead (n = 23) and 240 ± 60 14C years for beluga (n = 12). Scarce data preclude calculation of meaningful, statistically robust walrus ΔR. Using the new ΔR values, an expanded and revised database of calibrated bowhead dates (651 dates; many used in previous CAA sea-ice reconstructions) shows pronounced late Quaternary spatio-temporal fluctuations in bone abundance. Though broadly resembling earlier bowhead subfossil frequency data, analysis of the new expanded database suggests early- and mid-Holocene increases in whale abundance to be of longer duration and lower amplitude than previously considered. A more even and persistent spread of infrequent low-abundance remains during “whale free” intervals is also seen. The dominance of three eastern regions (Prince Regent Inlet & Gulf of Boothia; Admiralty Inlet; Berlinguet Inlet/Bernier Bay) in the CAA data, collectively contributing up to 88% of all subfossil remains in the mid-Holocene, is notable. An analysis of calibrated regional sea-level index points suggests that severance of the Admiralty Inlet-Gulf of Boothia marine channel due to isostatically-driven regression may have played a significant role in enhanced whale mortality during this interval. Comparisons between the newly calibrated bowhead data and other regional sea-ice proxy data further highlight spatial and temporal discrepancies, potentially due to regional asynchronicities and variable sensitivities in proxy response to climate and oceanographic forcing. However, the limited number of deglacial–postglacial marine records continues to hamper extensive intercomparisons between marine mammal and other proxy datasets. Nevertheless, an examination of assumptions inherent in linking bowhead subfossil frequencies, population densities, and sea-ice thickness and distribution, shows that such relationships are highly complex. Factors such as broad sea-ice preferences, variable mortality rates and causes, long distance carcass transport, variable coastline and basin/channel geometries, and changing emergence rates all complicate the correlation of whale bone abundance to sea-ice histories. VL - 91 UR - http://www.sciencedirect.com/science/article/pii/S027737911300334X JO - New cetacean ΔR values for Arctic North America and their implications for marine-mammal-based palaeoenvironmental reconstructions ER - TY - JOUR T1 - North Atlantic forcing of tropical Indian Ocean climate JF - Nature Y1 - 2014 A1 - Mohtadi, Mahyar A1 - Prange, Matthias A1 - Oppo, Delia W. A1 - De Pol-Holz, Ricardo A1 - Merkel, Ute A1 - Zhang, Xiao A1 - Steinke, Stephan A1 - ückge, Andreas KW - Palaeoceanography KW - Palaeoclimate AB - The response of the tropical climate in the Indian Ocean realm to abrupt climate change events in the North Atlantic Ocean is contentious. Repositioning of the intertropical convergence zone is thought to have been responsible for changes in tropical hydroclimate during North Atlantic cold spells1, 2, 3, 4, 5, but the dearth of high-resolution records outside the monsoon realm in the Indian Ocean precludes a full understanding of this remote relationship and its underlying mechanisms. Here we show that slowdowns of the Atlantic meridional overturning circulation during Heinrich stadials and the Younger Dryas stadial affected the tropical Indian Ocean hydroclimate through changes to the Hadley circulation including a southward shift in the rising branch (the intertropical convergence zone) and an overall weakening over the southern Indian Ocean. Our results are based on new, high-resolution sea surface temperature and seawater oxygen isotope records of well-dated sedimentary archives from the tropical eastern Indian Ocean for the past 45,000 years, combined with climate model simulations of Atlantic circulation slowdown under Marine Isotope Stages 2 and 3 boundary conditions. Similar conditions in the east and west of the basin rule out a zonal dipole structure as the dominant forcing of the tropical Indian Ocean hydroclimate of millennial-scale events. Results from our simulations and proxy data suggest dry conditions in the northern Indian Ocean realm and wet and warm conditions in the southern realm during North Atlantic cold spells. VL - 509 UR - http://www.nature.com/doifinder/10.1038/nature13196 IS - 7498 ER - TY - JOUR T1 - Oceanographic regimes in the northwest Labrador Sea since Marine Isotope Stage 3 based on dinocyst and stable isotope proxy records JF - APEX II: Arctic Palaeoclimate and its Extremes Y1 - 2014 A1 - Gibb, Olivia T. A1 - Hillaire-Marcel, Claude A1 - de Vernal, Anne AB - Sea surface temperature (SST), salinity and density gradients in the upper water column of the northwest Labrador Sea have been reconstructed based on high resolution analysis of a core (HU2008-029-004PC) spanning the last ∼36 ka, raised off Hudson Strait. The modern analogue technique was applied to dinocyst assemblages and combined with stable isotope data from Neogloboquadrina pachyderma left-coiled (Npl) for this purpose. Three oceanographic regimes were identified, broadly corresponding to the “glacial”, “deglacial” and “postglacial” intervals. The site remained under the direct influence of the Laurentide Ice Sheet (LIS) margin until the postglacial and did not record the Bølling-Allerød warming and weakly recorded the Younger Dryas event. The “glacial” regime lasted until ∼12.2 cal ka BP. It was characterized by generally low concentrations of dinocysts within an assemblage indicative of quasi-perennial sea ice. The “deglacial” regime (ca 12.2–8.3 cal ka BP) was marked by increased biogenic fluxes and more diversified dinocyst assemblages and possibly an enhanced subsurface inflow of North East Atlantic Deep Water. Warm summer (∼11 °C) but low winter (∼0 °C) sea surface temperatures, sea ice cover during about 3 months per year, and low summer salinity (∼28) suggest strong stratification in the upper water layer in relation to meltwater supply from the LIS. Following the final drainage of glacial Lake Agassiz through Hudson Strait, which is dated here at ∼8.3 cal ka BP, and the subsequent LIS collapse, increased summer salinity (up to ∼35) was accompanied by a reduced seasonal gradient of sea surface temperature from winter (∼3.8 °C) to summer (∼8.6 °C) suggesting enhanced penetration of North Atlantic Water. Weakened stratification of the surface water layer then allowed for winter convection and Labrador Sea Water formation, which is consistent with increased Npl-δ13C values in response to higher ventilation of the subsurface water layer. VL - 92 UR - http://www.sciencedirect.com/science/article/pii/S0277379113004915 JO - Oceanographic regimes in the northwest Labrador Sea since Marine Isotope Stage 3 based on dinocyst and stable isotope proxy records ER - TY - JOUR T1 - Organic matter transformation in the peat column at Marcell Experimental Forest: Humification and vertical stratification JF - JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES Y1 - 2014 A1 - Tfaily, Malak M. A1 - Cooper, William T. A1 - Kostka, Joel E. A1 - Chanton, Patrick R. A1 - Schadt, Christopher W. A1 - Hanson, Paul J. A1 - Iversen, Colleen M. A1 - Chanton, Jeffrey P. KW - FT-IR spectroscopy KW - humification KW - NMR spectroscopy KW - organic matter KW - peatlands KW - vertical stratification AB - We characterized peat decomposition at the Marcell Experimental Forest (MEF), Minnesota, USA, to a depth of 2m to ascertain the underlying chemical changes using Fourier transform infrared (FT IR) and C-13 nuclear magnetic resonance (NMR) spectroscopy) and related these changes to decomposition proxies C:N ratio, C-13 and N-15, bulk density, and water content. FT IR determined that peat humification increased rapidly between 30 and 75cm, indicating a highly reactive intermediate-depth zone consistent with changes in C:N ratio, C-13 and N-15, bulk density, and water content. Peat decomposition at the MEF, especially in the intermediate-depth zone, is mainly characterized by preferential utilization of O-alkyl-C, carboxyl-C, and other oxygenated functionalities with a concomitant increase in the abundance of alkyl- and nitrogen-containing compounds. Below 75cm, less change was observed but aromatic functionalities and lignin accumulated with depth. Significant correlations with humification indices, identified by FT IR spectroscopy, were found for C:N ratios. Incubation studies at 22 degrees C revealed the highest methane production rates, greatest CH4:CO2 production ratios, and significant O-alkyl-C utilization within this 30 and 75cm zone. Oxygen-containing functionalities, especially O-alkyl-C, appear to serve as excellent proxies for soil decomposition rate and should be a sensitive indicator of the response of the solid phase peat to increased temperatures caused by climate change and the field study manipulations that are planned to occur at this site. Radiocarbon signatures of microbial respiration products in deeper pore waters at the MEF resembled the signatures of more modern dissolved organic carbon rather than solid phase peat, indicating that recently photosynthesized organic matter fueled the bulk of subsurface microbial respiration. These results indicate that carbon cycling at depth at the MEF is not isolated from surface processes. VL - 119 ER - TY - JOUR T1 - Origin, composition, and transformation of dissolved organic matter in tropical peatlands JF - Geochimica et Cosmochimica Acta Y1 - 2014 A1 - Gandois, L. A1 - Teisserenc, R. A1 - Cobb, A. R. A1 - Chieng, H. I. A1 - Lim, L. B. L. A1 - Kamariah, A. S. A1 - Hoyt, A. A1 - Harvey, C. F. AB - Solid and dissolved organic matter (DOM) compositions were investigated in a pristine and a deforested tropical peat forest in Brunei Darussalam. A combination of elemental (%C, %N, C/N), isotopic (δ15N, δ13C, Δ14C), molecular (lignin phenol biomarkers) and optical (Specific UV Absorbance at 280 nm (SUVA280), fluorescence index (FI)) analyses were performed to characterize DOM in porewater and river water. The DOM composition was compared to vegetation and peat to assess DOM origin and transformations in the ecosystem. Significant relationships were observed between optical properties (SUVA280, FI) and bulk (Δ14C) and molecular (ratio of cinnamyl to vanillyl phenols, C/V) composition of DOM. The radiocarbon content of DOM shows that it is modern at both sites for both surface and deep (to 4.5 m) samples (Δ14C = 74.58 ± 8.53‰ at the pristine site and Δ14C = 87.84 ± 4.5‰ at the deforested site for the first 2 meters), indicating transport of young DOM to deeper layers. Stable carbon-13 content of vegetation, peat and DOM showed only slight fractionation and ranged from −32.2‰ to −28.3‰. Nitrogen showed a greater shift between ecosystem pools. Nitrogen-15 content was higher in the solid peat (δ15N = −0.92 ± 0.49‰ in the pristine site, δ15N = −1.22 ± 1.37‰ in the deforested site) than in DOM (δ15N = −4.2 ± 2.5‰ in the pristine site, δ15N = −4.1 ± 2.3‰ in the deforested site). This difference in δ15N is significantly correlated with the C/N values of peat and DOM and attributable to higher microbial degradation in the peat compared to DOM. Porewater DOM contains less lignin (λ8 = 1.10 ± 0.27 mg 100 mg dw−1 in the pristine site and λ8 = 1.38 ± 0.46 mg 100 mg dw−1 in the deforested site) than does the solid peat (λ8 = 5.66 ± 2.14 mg 100 mg dw−1 in the pristine site and λ8 = 10.29 ± 4.69 mg 100 mg dw−1 in the deforested site). All indicators of lignin degradation (P/(V + S), 3,5Bd/V, (Ad/Al)V, (Ad/Al)S) are significantly higher in DOM than in the solid peat. This shows that lignin can be processed rapidly in the porewater of upper layers of tropical peatlands. Logging activity affected the composition of organic matter at the deforested site. Higher lignin content (λ8) was observed in the solid peat, and the composition of DOM differed greatly in the deforested site: Δ14C, FI, 3,5Bd/V, (Ad/Al)V are significantly different from the pristine site. Thus it appears that the composition of DOM is more sensitive than the solid phase to the effects of land use change on organic matter dynamic in tropical peatlands. VL - 137 UR - http://www.sciencedirect.com/science/article/pii/S0016703714001768 JO - Origin, composition, and transformation of dissolved organic matter in tropical peatlands ER - TY - JOUR T1 - Particle sorting during sediment redistribution processes and the effect on 230 Th-normalized mass accumulation rates JF - Geophysical Research Letters Y1 - 2014 A1 - Marcantonio, Franco A1 - Lyle, Mitchell A1 - Ibrahim, Rami AB - The 230Th method of determining mass accumulation rates (MARs) assumes that little to no fractionation occurs during sediment redistribution processes at the seafloor. We examine 230Th inventories in radiocarbon-dated multicore sediments from paired winnowed and focused sites at Cocos and Carnegie Ridges, Panama Basin. Radiocarbon-derived sand MARs, which likely represent the vertical rain of particles poorly transported by bottom currents, are similar at each of the paired sites but are different using 230Th normalization. 230Th-normalized MARs are about 60% lower at focused sites and likely underestimate vertical MARs, while the reverse is true for winnowed sites. We hypothesize that size fractionation occurs most frequently at lower current velocities, resulting in the coarse fraction being left behind and primarily the fine 230Th-rich grains being transported downslope. 230Th-normalization works well for recording fine-grained (detrital and opal), but not coarse-grained (carbonate), fluxes in regions that have undergone sediment redistribution. VL - 41 UR - http://doi.wiley.com/10.1002/2014GL060477https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2F2014GL060477 IS - 15 ER - TY - JOUR T1 - Phylogeny and phylogeography of functional genes shared among seven terrestrial subsurface metagenomes reveal N-cycling and microbial evolutionary relationships JF - FRONTIERS IN MICROBIOLOGY Y1 - 2014 A1 - Lau, Maggie C. Y. A1 - Cameron, Connor A1 - Magnabosco, Cara A1 - Brown, C. Titus A1 - Schilkey, Faye A1 - Grim, Sharon A1 - Hendrickson, Sarah A1 - Pullin, Michael A1 - Lollar, Barbara Sherwood A1 - Van Heerden, Esta A1 - Kieft, Thomas L. A1 - Onstott, Tullis C. KW - evolution KW - functional genes KW - N-cycle KW - phylogenetics KW - phylogeny KW - phylogeography KW - terrestrial subsurface AB - Comparative studies on community phylogenetics and phylogeography of microorganisms living in extreme environments are rare. Terrestrial subsurface habitats are valuable for studying microbial biogeographical patterns due to their isolation and the restricted dispersal mechanisms. Since the taxonomic identity of a microorganism does not always correspond well with its functional role in a particular community, the use of taxonomic assignments or patterns may give limited inference on how microbial functions are affected by historical, geographical and environmental factors. With seven metagenomic libraries generated from fracture water samples collected from five South African mines, this study was carried out to (1) screen for ubiquitous functions or pathways of biogeochemical cycling of CH4, S, and N; (2) to characterize the biodiversity represented by the common functional genes; (3) to investigate the subsurface biogeography as revealed by this subset of genes; and (4) to explore the possibility of using metagenomic data for evolutionary study. The ubiquitous functional genes are NarV, NPD, PAPS reductase, NifH, NifD, NifK, NifE, and NifN genes. Although these eight common functional genes were taxonomically and phylogenetically diverse and distinct from each other, the dissimilarity between samples did not correlate strongly with geographical or environmental parameters or residence time of the water. Por genes homologous to those of Thermodesulfovibrio yellowstonii detected in all metagenomes were deep lineages of Nitrospirae, suggesting that subsurface habitats have preserved ancestral genetic signatures that inform the study of the origin and evolution of prokaryotes. VL - 5 ER - TY - JOUR T1 - Pore-water chemistry of sediment cores off Mahanadi Basin, Bay of Bengal: Possible link to deep seated methane hydrate deposit JF - Marine and Petroleum Geology Y1 - 2014 A1 - Mazumdar, A. A1 - Peketi, A. A1 - Joao, H. M. A1 - Dewangan, P. A1 - Ramprasad, T. AB - Organoclastic degradation and anaerobic oxidation of methane (AOM) are known to influence sulfate, methane and bicarbonate concentrations of sediment pore-waters. In this work we have analyzed the pore-fluid composition of three piston cores (36–39 m long) collected from water depths ranging from 1429 to 1691 m. We attribute the observed linear sulfate concentration profiles and (ΔCa + ΔAlk)/ΔSO42− ratios dominantly to anaerobic oxidation of methane (AOM) induced sulfate consumption. The gas rich layers just below the base of hydrate stability zone (BGHSZ) is the possible source of the enhanced diffusive flux of biogenic methane ( δ 13 C CH 4 ranging from −99.7 to −106.3‰ VPDB). Occurrences of disseminated gas hydrate in the Mahanadi Basin within the hydrate stability zone (210–220 m thick) supports the link between linear sulfate profile, high rate of AOM and hydrate occurrence. VL - 49 UR - http://www.sciencedirect.com/science/article/pii/S0264817213002638 JO - Pore-water chemistry of sediment cores off Mahanadi Basin, Bay of Bengal: Possible link to deep seated methane hydrate deposit ER - TY - JOUR T1 - Pre-aged plant waxes in tropical lake sediments and their influence on the chronology of molecular paleoclimate proxy records JF - Geochimica et Cosmochimica Acta Y1 - 2014 A1 - Douglas, Peter M. J. A1 - Pagani, Mark A1 - Eglinton, Tim E. A1 - Brenner, Mark A1 - Hodell, David A. A1 - Curtis, Jason H. A1 - Ma, Keith A1 - Breckenridge, Andy AB - Sedimentary records of plant-wax hydrogen (δDwax) and carbon (δ13Cwax) stable isotopes are increasingly applied to infer past climate change. Compound-specific radiocarbon analyses, however, indicate that long time lags can occur between the synthesis of plant waxes and their subsequent deposition in marginal marine sediments. The influence of these time lags on interpretations of plant-wax stable isotope records is presently unconstrained, and it is unclear whether such time lags also affect lacustrine sediments. We present compound-specific radiocarbon (14Cwax) data for n-alkanoic acid plant waxes (n-C26 to n-C30) from: 1) a sediment core from Lake Chichancanab, Yucatan Peninsula, Mexico, 2) soils in the Lake Chichancanab catchment, and 3) surface sediments from three other lakes in southeastern Mexico and northern Guatemala. 14Cwax ages in the surface sediments are consistently older than modern, and may be negatively correlated with mean annual precipitation and positively correlated with lake catchment area. 14Cwax ages in soils surrounding Lake Chichancanab increase with soil depth, consistent with deep, subsoil horizons being the primary source of lacustrine aged plant waxes, which are likely delivered to lake sediments through subsurface transport. Plant waxes in the Lake Chichancanab core are 350 to 1200 years older than corresponding ages of bulk sediment deposition, determined by 14C dates on terrestrial plant macrofossils in the core. A δDwax time series is in closer agreement with other regional proxy hydroclimate records when a plant-wax 14C age model is applied, as opposed to the macrofossil-based core chronology. Inverse modeling of plant-wax age distribution parameters suggests that plant waxes in the Lake Chichancanab sediment core derive predominantly from millennial-age soil carbon pools that exhibit relatively little age variance (< 200 years). Our findings demonstrate that high-temporal-resolution climate records inferred from stable isotope measures on plant waxes in lacustrine sediments may suffer from possible chronologic distortions as a consequence of long residence times of plant waxes in soils. They also underscore the importance of direct radiocarbon dating of these organic molecules. VL - 141 UR - http://www.sciencedirect.com/science/article/pii/S0016703714004451 JO - Pre-aged plant waxes in tropical lake sediments and their influence on the chronology of molecular paleoclimate proxy records ER - TY - JOUR T1 - Preferential burial of permafrost-derived organic carbon in Siberian-Arctic shelf waters JF - JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS Y1 - 2014 A1 - Vonk, Jorien E. A1 - Semiletov, Igor P. A1 - Dudarev, Oleg V. A1 - Eglinton, Timothy I. A1 - Andersson, August A1 - Shakhova, Natalia A1 - Charkin, Alexander A1 - Heim, Birgit A1 - Gustafsson, Örjan KW - biomarkers KW - carbon KW - permafrost KW - radiocarbon AB - The rapidly changing East Siberian Arctic Shelf (ESAS) receives large amounts of terrestrial organic carbon (OC) from coastal erosion and Russian-Arctic rivers. Climate warming increases thawing of coastal Ice Complex Deposits (ICD) and can change both the amount of released OC, as well as its propensity to be converted to greenhouse gases (fueling further global warming) or to be buried in coastal sediments. This study aimed to unravel the susceptibility to degradation, and transport and dispersal patterns of OC delivered to the ESAS. Bulk and molecular radiocarbon analyses on surface particulate matter (PM), sinking PM and underlying surface sediments illustrate the active release of old OC from coastal permafrost. Molecular tracers for recalcitrant soil OC showed ages of 3.4-13 C-14-ky in surface PM and 5.5-18 C-14-ky in surface sediments. The age difference of these markers between surface PM and surface sediments is larger (i) in regions with low OC accumulation rates, suggesting a weaker exchange between water column and sediments, and (ii) with increasing distance from the Lena River, suggesting preferential settling of fluvially derived old OC nearshore. A dual-carbon end-member mixing model showed that (i) contemporary terrestrial OC is dispersed mainly by horizontal transport while being subject to active degradation, (ii) marine OC is most affected by vertical transport and also actively degraded in the water column, and (iii) OC from ICD settles rapidly and dominates surface sediments. Preferential burial of ICD-OC released into ESAS coastal waters might therefore lower the suggested carbon cycle climate feedback from thawing ICD permafrost. VL - 119 ER - TY - JOUR T1 - Radiocarbon age-offsets in an arctic lake reveal the long-term response of permafrost carbon to climate change JF - JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES Y1 - 2014 A1 - Gaglioti, Benjamin V. A1 - Mann, Daniel H. A1 - Jones, Benjamin M. A1 - Pohlman, John W. A1 - Kunz, Michael L. A1 - Wooller, Matthew J. KW - carbon cycling KW - lake sediment KW - paleoclimatology KW - permafrost KW - radiocarbon KW - Younger Dryas AB - Continued warming of the Arctic may cause permafrost to thaw and speed the decomposition of large stores of soil organic carbon (OC), thereby accentuating global warming. However, it is unclear if recent warming has raised the current rates of permafrost OC release to anomalous levels or to what extent soil carbon release is sensitive to climate forcing. Here we use a time series of radiocarbon age-offsets (C-14) between the bulk lake sediment and plant macrofossils deposited in an arctic lake as an archive for soil and permafrost OC release over the last 14,500 years. The lake traps and archives OC imported from the watershed and allows us to test whether prior warming events stimulated old carbon release and heightened age-offsets. Today, the age-offset (2ka; thousand of calibrated years before A.D. 1950) and the depositional rate of ancient OC from the watershed into the lake are relatively low and similar to those during the Younger Dryas cold interval (occurring 12.9-11.7ka). In contrast, age-offsets were higher (3.0-5.0ka) when summer air temperatures were warmer than present during the Holocene Thermal Maximum (11.7-9.0ka) and BOlling-AllerOd periods (14.5-12.9ka). During these warm times, permafrost thaw contributed to ancient OC depositional rates that were similar to 10 times greater than today. Although permafrost OC was vulnerable to climate warming in the past, we suggest surface soil organic horizons and peat are presently limiting summer thaw and carbon release. As a result, the temperature threshold to trigger widespread permafrost OC release is higher than during previous warming events. VL - 119 ER - TY - JOUR T1 - Radiocarbon Data of Funerary Discoveries from Middle Bronze Age Settlement at Miceşti - Cigaş (Alba County, Romania) JF - Annales Universitatis Apulensis Series Historica Y1 - 2014 A1 - Bălan, Gabriel A1 - Quinn, Colin KW - Middle Bronze Age; Wietenberg culture; funerary discoveries; 14C data; chronology AB - In the autumn of 2013 fragments of human bone were selected to date the burials in C.7/2009 and C.11/2012 at Miceşti-Cigaș (fig. 1). The dating of bone collagen provides an accurate means of dating the death of the individual. Radiocarbon dates from bone collagen also are unaffected by the ‘old wood’ phenomenon that can affect conventional charcoal dates. They were calibrated with the Oxcal program, version 4.2.3, resulting a timeframe between 1745-1627 BC (95.4%) / 1736-1645 BC (68.1%) for C.11 and 1880-1693 BC (95.4%) / 1872-1700 BC (68.1%) for C.7 (fig. 1-2). Until now there were only 6 radiocarbon dates obtained on samples taken from Wietenberg sites: Oarța de Sus (two dates: 1. Ly 9190 - “1610-1445 B.C., with maximum probability between 1589-1518-1469 B.C.”; 2. Bln 5626: 3507±37, 1931-1701 BC 2 sigma calibrated); Sighișoara-Cartierul viilor (1685 – 1524 BC) and Rotbav-La pârâuț (three dates: Hd-28203 - 3547±24 BP, 1954- 1774 BC calibrated 2 sigma; Hd-27967 - 3195±19 BP, 1501-1430 BC calibrated 2 sigma; Hd-27989 - 3174±16 BP, 1497-1416 BC calibrated 2 sigma).A partial chronological synchronization between the Wietenberg IV phase and Noua culture has been observed by several scholars. To test this, we draw attention to important radiocarbon dates from sites belonging to Noua culture: Mahala, Crasnaleuca, Miciurin-Odaia and Rotbav-La pârâuț. These radiocarbon dates minimally and definitively place the Noua culture between 1500-1200 BC. There are also some other dates which could suggest the beginning of Noua culture in the 16th century BC (fig. 3).On the basis of the radiocarbon dates belonging to Wietenberg and Noua cultures mentioned above, we consider that the Wietenberg IV phase is part of the Middle Bronze Age, while the beginning of the Late Bronze Age is marked through the presence of Noua culture in Transylvania. If we are to take into account the dates from Miceşti, the first manifestations of the last Wietenberg phase can be placed by the beginning of the 17th century BC. The final part of Wietenberg culture is marked by the emergence of Noua culture before 1500 BC, when, for a short period of time, the two pottery styles coexist. UR - https://www.ceeol.com/search/article-detail?id=308845 IS - 2 ER - TY - JOUR T1 - Radiocarbon dating of planktonic foraminifer shells: A cautionary tale JF - PALEOCEANOGRAPHY Y1 - 2014 A1 - Mekik, Figen AB - Sedimentation rate, bioturbation, winnowing, and calcite dissolution produce significant radiocarbon age offsets among multiple species of coexisting planktonic foraminifers and pteropod fragments. We compare the radiocarbon age of foraminifer species and pteropod fragments with estimates of percent calcite dissolved made with a sedimentary proxy (Globorotalia menardii fragmentation index-MFI) to delineate the effect of dissolution on radiocarbon age of foraminifers. Data from two core top transects on the Rio Grande Rise (RIO) and Ontong Java Plateau (OJP) and from down core sediments of varying sedimentation rates in the tropical Pacific (ME-27, MD98 2177, and MW91-9 56GGC) reveal that sediments with the greatest accumulation rates produce the least age offsets among coexisting species. Age offsets among coexisting foraminifers are about 3500 years on RIO, and 1000 years on OJP. Two core tops from RIO yield an age of the Last Glacial Maximum possibly due to mass displacement of younger sediments downslope. Foraminifer age increases with increasing dissolution and there is a consistent pattern of older foraminifer fragments coexisting with younger whole shells of the same species. The only exception is sediments which have experienced high dissolution where fragments are younger than whole shells. The age offset between fragments of G. menardii and its coexisting whole shells does not exceed the age offset among other coexisting foraminifer species in the same core tops. VL - 29 ER - TY - JOUR T1 - Radiocarbon signatures and size–age–composition relationships of major organic matter pools within a unique California upwelling system JF - Geochimica et Cosmochimica Acta Y1 - 2014 A1 - Walker, B. D. A1 - Guilderson, T. P. A1 - Okimura, K. M. A1 - Peacock, M. B. A1 - McCarthy, M. D. AB - Coastal upwelling zones are among the most productive regions in the world and play a major role in the global carbon cycle. Radiocarbon (as Δ14C) is a powerful tool for tracing the source and fate of suspended particulate and dissolved organic matter (POM, DOM), and has the potential to reconcile key carbon budgets within upwelling systems. However, the extent to which upwelling processes influence the Δ14C signature of surface DIC, or that of POM or DOM remains almost completely unknown. Here we present a time series of stable carbon (δ13C) and Δ14C isotopic data of major water column carbon pools, including dissolved inorganic carbon (DIC), large (0.7–500 μm) and small (0.1–100 μm) POM, and high molecular weight (HMW; ∼1 nm–0.1 μm) DOM from an upwelling center along the Big Sur coast. We show that DIC Δ14C values (ranging between +29‰ and −14‰) are strongly correlated to coastal upwelling processes, and that this 14C-signal readily propagates into both the POM and HMW DOM pool. However, the presence of negative POM and HMW DOM Δ14C values (ranging between +46‰ and −56‰, +6‰ and −123‰ and −1‰ and −150‰, respectively) suggests contributions of “pre-aged” OM, complicating the direct use of “bulk” Δ14C for tracing upwelling-derived carbon production/export. Using a triple-isotope mixing model (δ13C, δ15N, Δ14C) we estimate that 50–90% and 45–51% of large and small POM is newly-produced OM, while between 6–22% and 12–44% of large and small POM are derived from “pre-aged” re-suspended sediments. Finally, we observe quantitative relationships between OM size, composition (C:N ratio) and Δ14C within this upwelling system, possibly representing a new tool for modeling ocean C and N biogeochemical cycles. VL - 126 UR - http://www.sciencedirect.com/science/article/pii/S001670371300611X JO - Radiocarbon signatures and size–age–composition relationships of major organic matter pools within a unique California upwelling system ER - TY - JOUR T1 - Recent unprecedented warming and oligotrophy of the eastern Mediterranean Sea within the last millennium JF - Geophysical Research Letters Y1 - 2014 A1 - Sisma-Ventura, Guy A1 - Yam, Ruth A1 - Shemesh, Aldo AB - The Mediterranean region is a climatic transitional zone between the subtropical/monsoon regime and the temperate westerlies and is subject to forces acting upon the global climate system. Much knowledge about its climate over the last millennium is derived from terrestrial records, whereas changes in sea surface temperatures (SSTs) and in the dissolved inorganic carbon pool (DIC) are poorly known. We present continuous high-resolution reconstructions of SST and δ13CDIC in the eastern Mediterranean (EM) Sea, as inferred from oxygen and carbon isotope records from the skeletons of the reef builder gastropod Dendropoma sp. Spanning the past millennium, the SST reconstruction reveals a 250 year persistent warming trend during which the twentieth century was the warmest on record. Coupled with a distinct trend of 13CDIC depletion and superimposed upon decreased primary production, this climate reconstruction reflects a new state of the EM over the Anthropocene era that exceeds the natural variability of the last millennium. VL - 41 UR - http://doi.wiley.com/10.1002/2014GL060393 IS - 14 ER - TY - JOUR T1 - Record of methane emissions from the West Svalbard continental margin during the last 23.500 yrs revealed by δ13C of benthic foraminifera JF - Global and Planetary Change Y1 - 2014 A1 - Panieri, Giuliana A1 - James, Rachael H. A1 - Camerlenghi, Angelo A1 - Westbrook, Graham K. A1 - Consolaro, Chiara A1 - Cacho, Isabel A1 - Cesari, Valentina A1 - Cervera, Cristina Sanchez AB - The values of δ13C in benthic foraminifera have been measured in a gas-hydrate-bearing sediment core collected from an area of active methane venting on the Vestnesa Ridge (West Svalbard continental margin) to reconstruct the local history of methane emissions over the past 23.500 yrs BP. The chronostratigraphic framework of the core has been derived from AMS 14C dates and biostratigraphic analysis. While foraminifera from some intervals have δ13C within the normal marine range (0 to − 1‰), five intervals are characterized by a much lower δ13C, as low as − 17.4‰. These intervals are interpreted to record the incorporation of 13C-depleted carbon in the presence of methane emissions at the seafloor during biomineralization of the carbonate foraminiferal tests and subsequent secondary mineralization. Methane emission events (MEE) occur from the Last Glacial Maximum (LGM) to the Holocene, with the most prominent one, in terms of δ13C depletion, predating the Bølling–Allerød Interstadial (GI-1 in the Greenland ice core record). The lack of correlation between the values of δ13C and δ18O, however, appears to preclude warming of bottom waters as the principal control on methane release. Rather, it seems likely that methane release is a consequence of episodicity in the supply of gas to the hydrate system and in the processes that enable methane gas to migrate through the hydrate stability field to the seabed, or of other geological processes still under debate. VL - 122 UR - http://www.sciencedirect.com/science/article/pii/S0921818114001799 JO - Record of methane emissions from the West Svalbard continental margin during the last 23.500 yrs revealed by δ13C of benthic foraminifera ER - TY - JOUR T1 - Refining the link between the Holocene development of the Mississippi River Delta and the geologic evolution of Cat Island, MS: implications for delta-associated barrier islands JF - Marine Geology Y1 - 2014 A1 - Miselis, Jennifer L. A1 - Buster, Noreen A. A1 - Kindinger, Jack L. AB - The geologic evolution of barrier islands is profoundly influenced by the nature of the deposits underlying them. Many researchers have speculated on the origin and evolution of Cat Island in Mississippi, but uncertainty remains about whether or not the island is underlain completely or in part by deposits associated with the past growth of the Mississippi River delta. In part, this is due to a lack of comprehensive geological information offshore of the island that could augment previous stratigraphic interpretations based on terrestrial borings. An extensive survey of Cat Island and its surrounding waters was conducted, including shallow-water geophysics (e.g., high-resolution chirp seismic, side-scan sonar, and swath and single-beam bathymetry) and both terrestrial and marine vibracoring. High-resolution seismic data and vibracores from south and east of the island show two horizontally laminated silt units; marine radiocarbon dates indicate that they are St. Bernard delta complex (SBDC) deposits. Furthermore, seismic data reveal that the SBDC deposits taper off toward the southern shoreline of Cat Island and to the west, morphology consistent with the distal edge of a delta complex. The sedimentology and extent of each unit suggest that the lower unit may have been deposited during an earlier period of continuous river flow while the upper unit may represent reduced or sporadic river flow. OSL dates from the island platform (beneath beach ridge complexes) indicate three stages of terrestrial evolution: island emergence resulting from relative sea-level rise (~ 5400 ybp) island aggradation via littoral transport (~ 2500–4000 ybp) and island degradation due to delta-mediated changes in wave direction (present– ~ 3600 ybp). Finally, the combination of terrestrial and marine data shows that portions of Cat Island that are lower in elevation than the central part of the island are younger and are likely underlain by a thin layer of deltaic sediments. This underscores the potential for increased future vulnerability of barrier islands that develop adjacent to major river delta complexes. VL - 355 UR - http://www.sciencedirect.com/science/article/pii/S0025322714001789 JO - Refining the link between the Holocene development of the Mississippi River Delta and the geologic evolution of Cat Island, MS: implications for delta-associated barrier islands ER - TY - JOUR T1 - Seafloor fault ruptures along the North Anatolia Fault in the Marmara Sea, Turkey: Link with the adjacent basin turbidite record JF - Marine Geology Y1 - 2014 A1 - McHugh, Cecilia M. G. A1 - Braudy, Nicole A1 - Çağatay, M. Namik A1 - Sorlien, Christopher A1 - Cormier, Marie-Helene A1 - Seeber, Leonardo A1 - Henry, Pierre AB - The relation between seafloor fault ruptures and the generation of turbidity currents was investigated to better understand the structural growth of tectonic basins with direct implications for earthquake hazard assessment. This study focuses on the Holocene earthquake record of transtensional basins in the Marmara Sea, Turkey, that are associated with the North Anatolian Fault system. The physical and chemical composition of three 10 m-long cores recovered from the Central Basin was studied at high-resolution and turbidite–homogenite units were identified. Turbidite–homogenite units (T–H units) are complex deposits that consist of a sharp basal contact and multiple fining upward beds of sand to coarse silt, above. All are capped by a 25 cm to 75 cm thick layer of medium to fine silt. A chronology developed from radiocarbon and short-lived radioisotopes allowed the correlation of these T–H units to the historical record of earthquakes that in Turkey goes back 2000 years. We found that the best location to recover the most complete sedimentation record is in the deepest part of a basin or “depocenter” where T–H units constitute ~ 80% of the sediments. A very good correlation was established between T–H units in Central Basin and proximal inferred historic epicentres along the central Marmara segment of the North Anatolia Fault that occurred in 1343, 860, 740, and 557 AD, and two more distal earthquakes that occurred in 268 and 1963 (or possibly1964). These sedimentation events can then be referred to as “seismo-turbidites”. The results when compared to findings from other transform basins in Marmara Sea reveal a very good correlation between T–H units and historic ruptures. Most importantly, there is a strong correlation between the inferred locations of historical earthquakes and the preservation of turbidite–homogenite units in the basin adjacent to the inferred rupture. The 740 AD earthquake correlates with T–H units in Izmit Gulf and Central Basin and could represent a multi-segment rupture of the NAF. Generally, T–H units appear to be clustered through the Holocene sections, suggesting temporal earthquake clustering in the Marmara Sea region. Such clustering may account for the lack of T–H units and hence large ruptures through the Central Basin since 1343. VL - 353 UR - http://www.sciencedirect.com/science/article/pii/S0025322714000498 JO - Seafloor fault ruptures along the North Anatolia Fault in the Marmara Sea, Turkey: Link with the adjacent basin turbidite record ER - TY - JOUR T1 - Seasonal variability of organic matter composition in an Alaskan glacier outflow: insights into glacier carbon sources JF - Environmental Research Letters Y1 - 2014 A1 - Spencer, Robert G M A1 - Vermilyea, Andrew A1 - Fellman, Jason A1 - Raymond, Peter A1 - Stubbins, Aron A1 - Scott, Durelle A1 - Hood, Eran KW - alaska KW - dissolved organic carbon KW - glacier KW - organic matter KW - radiocarbon AB - Glacier ecosystems are a significant source of bioavailable, yet ancient dissolved organic carbon (DOC). Characterizing DOC in Mendenhall Glacier out flow (southeast Alaska) we document a seasonal persistence to the radiocarbon-depleted signature of DOC, highlighting ancient DOC as a ubiquitous feature of glacier out flow. We observed no systematic depletion in Δ14C-DOC with increasing discharge during the melt season that would suggest mobilization of an aged subglacial carbon store. However, DOC concentration, δ13C-DOC,Δ14C-DOC and fluorescence signatures appear to have been in fluenced by runoff from vegetated hillslopes above the glacier during onset and senescence of melt. In the peak glacier melt period, the Δ 14 C-DOC of stream samples at the out flow (−181.7 to−355.3‰) was comparable to the Δ 14 C-DOC for snow samples from the accumulation zone (−207.2 to−390.9‰), suggesting that ancient DOC from the glacier surface is exported in glacier runoff. The pre-aged DOC in glacier snow and runoff is consistent with contributions from fossil fuel combustion sources similar to those documented previously in ice cores and thus provides evidence for anthropogenic perturbation of the carbon cycle. Overall, our results emphasize the need to further characterize DOC inputs to glacier ecosystems, particularly in light of predicted changes in glacier mass and runoff in the coming century. VL - 9 UR - http://iopscience.iop.org/article/10.1088/1748-9326/9/5/055005/meta IS - 5 ER - TY - JOUR T1 - Sedimentary and faunal signatures of the post-glacial marine drowning of the Pontocaspian Gemlik “lake” (Sea of Marmara) JF - Quaternary International Y1 - 2014 A1 - Taviani, M. A1 - Angeletti, L. A1 - Cagatay, M. N. A1 - Gasperini, L. A1 - Polonia, A. A1 - Wesselingh, F. P. AB - A Late Pleistocene (Neoeuxinian) Pontocaspian fauna is documented from sediments cored at̴ ∼75 m present water depth in the shallow-silled (∼50 m) Gulf of Gemlik, Sea of Marmara. As determined by AMS-14C dating of Pontocaspian gastropods (15,860 ± 90 BP uncal.), the age of such fauna is consistent with known episodes of Caspian overflow into the Black Sea Basin (Early Hvalynian floods). The fossil mollusc fauna is relatively diverse (12 non-marine taxa), made up of neritid and hydrobioid gastropods, and dreissenid and lymnocardiine bivalves. The presence of hitherto poorly known Pontocaspian taxa in the Sea of Marmara, further documented by the record in Gulf of Gemlik, seems to document that the Neoeuxinian Sea extended south of the Bosporus in the latest Pleistocene. Further, they provide insight into the origin of the modern Black Sea Pontocaspian taxa. The Gemlik Neoeuxinian lacustrine-brackish fauna under scrutiny is the westernmost known expansion of the Pontocaspian domain during the Late Pleistocene. This distinct biogeographic faunal affinity, with all its eastbound implications in terms of landscape and seaway connections, came to an end with the abrupt marine inundation that accompanied the postglacial sea-level rise from the Mediterranean Sea. VL - 345 JO - Sedimentary and faunal signatures of the post-glacial marine drowning of the Pontocaspian Gemlik “lake” (Sea of Marmara) ER - TY - JOUR T1 - Sedimentation patterns on a cold-water coral mound off Mauritania JF - Biology and Geology of Deep-Sea Coral Ecosystems: Proceedings of the Fifth International Symposium on Deep Sea Corals Y1 - 2014 A1 - Eisele, Markus A1 - Frank, Norbert A1 - Wienberg, Claudia A1 - Titschack, Jürgen A1 - Mienis, Furu A1 - Beuck, Lydia A1 - Tisnerat-Laborde, Nadine A1 - Hebbeln, Dierk AB - An unconformity-bound glacial sequence (135 cm thick) of a coral-bearing sediment core collected from the flank of a cold-water coral mound in the Banda Mound Province off Mauritania was analysed. In order to study the relation between coral framework growth and its filling by hemipelagic sediments, U-series dates obtained from the cold-water coral species Lophelia pertusa were compared to 14C dates of planktonic foraminifera of the surrounding matrix sediments. The coral ages, ranging from 45.1 to 32.3 ka BP, exhibit no clear depositional trend, while on the other hand the 14C dates of the matrix sediment provide ages within a much narrower time window of <3000 yrs (34.6–31.8 cal ka BP), corresponding to the latest phase of the coral growth period. In addition, high-resolution computer tomography data revealed a subdivision of the investigated sediment package into three distinct parts, defined by the portion and fragmentation of corals and associated macrofauna as well as in the density of the matrix sediments. Grain size spectra obtained on the matrix sediments show a homogeneous pattern throughout the core sediment package, with minor variations. These features are interpreted as indicators of redeposition. Based on the observed structures and the dating results, the sediments were interpreted as deposits of a mass wasting event, namely a debris flow. During this event, the sediment unit must have been entirely mixed; resulting in averaging of the foraminifera ages from the whole unit and giving randomly distributed coral ages. In this context, for the first time mass wasting is proposed to be a substantial process of mound progradation by exporting material from the mound top to the flanks. Hence, it may not only be an erosional feature but also widening the base of the mound, thus allowing further vertical mound growth. VL - 99 UR - http://www.sciencedirect.com/science/article/pii/S0967064513002762 JO - Sedimentation patterns on a cold-water coral mound off Mauritania ER - TY - JOUR T1 - Silicon isotopes indicate enhanced carbon export efficiency in the North Atlantic during deglaciation JF - Nature Communications Y1 - 2014 A1 - Hendry, Katharine R. A1 - Robinson, Laura F. A1 - McManus, Jerry F. A1 - Hays, James D. KW - Biogeochemistry KW - Cryospheric science KW - Ocean sciences AB - Today’s Sargasso Sea is nutrient starved, except for episodic upwelling events caused by wind-driven winter mixing and eddies. Enhanced diatom opal burial in Sargasso Sea sediments indicates that silicic acid, a limiting nutrient today, may have been more available in subsurface waters during Heinrich Stadials, millennial-scale climate perturbations of the last glacial and deglaciation. Here we use the geochemistry of opal-forming organisms from different water depths to demonstrate changes in silicic acid supply and utilization during the most recent Heinrich Stadial. We suggest that during the early phase (17.5–18 ka), wind-driven upwelling replenished silicic acid to the subsurface, resulting in low Si utilization. By 17 ka, stratification reduced the surface silicic acid supply leading to increased Si utilization efficiency. This abrupt shift in Si cycling would have contributed to high regional carbon export efficiency during the recent Heinrich Stadial, despite being a period of increasing atmospheric CO2. VL - 5 UR - http://www.nature.com/doifinder/10.1038/ncomms4107 ER - TY - JOUR T1 - Sites forlorn: dating intervals of abandonment at three shell middens on Santa Cruz Island, California using Bayesian chronological models JF - Journal of Archaeological Science Y1 - 2014 A1 - Thakar, H. B. AB - Archaeologists interested in variable mobility patterns and the factors that influence them rely on chronometric data to illuminate repetitive cycles of occupation, abandonment, and reoccupation. This article establishes and interrogates Bayesian chronological models in order to provide formal age estimates for two distinct intervals of site abandonment at three substantial multi-component shell middens from Santa Cruz Island, California. The earlier, more protracted interval of abandonment (ca. 2629–1698 cal. BP) following terminal Early Period occupation at each site location represents a temporal datum for a series of significant cultural, demographic, and technological developments throughout the region. I propose that this interval of localized site abandonments indicates a period of reorganization provoked by a shift in the paleoenvironment, a preliminary hypothesis that requires further testing. This research calls for development of similarly rigorous site chronologies on Santa Cruz Island and throughout the region that will shed further light on the validity of the temporal gaps documented in this analysis and most certainly will facilitate the development of additional hypotheses. More broadly, this article highlights the implementation and benefit of a Bayesian approach to building and interrogating site chronologies. VL - 52 N1 - Au6tmTimes Cited:0Cited References Count:55 JO - Sites forlorn: dating intervals of abandonment at three shell middens on Santa Cruz Island, California using Bayesian chronological models ER - TY - JOUR T1 - Source and biolability of ancient dissolved organic matter in glacier and lake ecosystems on the Tibetan Plateau JF - Geochimica et Cosmochimica Acta Y1 - 2014 A1 - Spencer, Robert G.M. A1 - Guo, Weidong A1 - Raymond, Peter A. A1 - Dittmar, Thorsten A1 - Hood, Eran A1 - Fellman, Jason A1 - Stubbins, Aron AB - The Tibetan Plateau is the world’s largest and highest plateau and holds the largest mass of ice on Earth outside the ice-sheets of Greenland and Antarctica, as well as abundant lakes. This study examined the molecular and isotopic signatures of dissolved organic matter (DOM) along with its biolability in glacier ice, glacier-fed streams, and alpine lakes on the Tibetan Plateau. The aim was to assess the sources of DOM and the potential of DOM to provide a carbon subsidy to downstream ecosystems. Tibetan glaciers and glacier streams exhibited low dissolved organic carbon (DOC) concentrations (17.7–27.9 μM) and ancient DOC radiocarbon ages (749–2350 ybp). The optical properties, stable carbon isotope ratios (δ13C-DOC) and the molecular composition (Fourier transform ion cyclotron resonance mass spectrometry) of Tibetan glacier DOM are consistent with data from other glacier systems around the world. The geochemical signatures and the ancient apparent ages of Tibetan glacier DOM suggest a significant fraction is derived from the atmospheric deposition of pre-aged, possibly fossil fuel derived organics. Within the Tibetan alpine lakes, DOC was also ancient (525–675 ybp), due to either inputs of pre-aged organics from glacier runoff, direct deposition, or due to the aging of organics in situ (i.e. a radiocarbon reservoir effect). The glacier ice and glacier stream sites exhibited high biolability of DOC and so provide a carbon subsidy to downstream environments that will change as glaciers on the Tibetan Plateau recede. VL - 142 UR - http://linkinghub.elsevier.com/retrieve/pii/S0016703714005018http://api.elsevier.com/content/article/PII:S0016703714005018?httpAccept=text/xmlhttp://api.elsevier.com/content/article/PII:S0016703714005018?httpAccept=text/plain ER - TY - JOUR T1 - Submarine Paleoseismology Along Populated Transform Boundaries: The Enriquillo-Plantain-Garden Fault, Canal du Sud, Haiti, and the North Anatolian Fault, Marmara Sea, Turkey JF - OCEANOGRAPHY Y1 - 2014 A1 - McHugh, Cecilia M. G. A1 - Seeber, Leonardo A1 - Cormier, Marie-Helene A1 - Hornbach, Matthew AB - Continental transform boundaries cross heavily populated regions and are associated with destructive earthquakes worldwide. The devastating 1999 Turkey earthquakes and the offshore 2010 Haiti earthquake emphasized the urgent need to study the submerged segments of continental transforms. In response, the rapidly evolving field of submarine paleoseismology is focusing its attention on understanding the relationships between sedimentation, seafloor ruptures, and earthquake recurrence intervals along submarine faults. In Canal du Sud, Haiti, the 2010 earthquake-triggered sedimentation events were documented from nearshore to the deep basin by measuring the excess Th-234 in sediment cores. This radioisotope, with a half-life of 24 days, tracked mass wasting, turbidites, turbidite-homogenite units, and a sediment plume that remained in the water column for at least two months after the earthquake. However, the turbidite units in Canal du Sud, Haiti, provide an incomplete record of the region's earthquake history, likely because sedimentation rates are too low for sedimentation events to be triggered by all earthquakes. In contrast, in the Marmara Sea basins, there is very good correlation between turbidites and the historical record of earthquakes dating back 2,000 years. The difference between these correlations is likely related to both sedimentation rates and particulars of the ruptures. Future research along the Enriquillo-Plantain-Garden fault in Haiti and along similar low sedimentation plate boundaries should focus on multiple fault segments in order to obtain complete earthquake recurrence histories. VL - 27 ER - TY - JOUR T1 - Subsurface Evidence of Storm-Driven Breaching along a Transgressing Barrier System, Cape Cod, USA JF - JOURNAL OF COASTAL RESEARCH Y1 - 2014 A1 - Maio, Christopher V. A1 - Gontz, Allen M. A1 - Sullivan, Richard M. A1 - Madsen, Stephanie M. A1 - Weidman, Christopher R. A1 - Donnelly, Jeffrey P. KW - coastal change KW - Coastal evolution KW - ground-penetrating radar KW - marine transgression KW - overwash KW - paleochannel KW - paleogeography KW - South Cape Beach AB - Relict and historic tidal channels buried within coastal barriers provide a geologic signature of environmental change, thus enhancing our understanding of how barrier systems respond to extreme storm events. Earliest maps from 1846 depict three inlets along the Waquoit Bay barrier system located on Cape Cod, Massachusetts. These channels were not depicted on maps after 1846, and we lack any information pertaining to them before 1846. The principle objective of this study was to identify the location and map the internal geometry and channel-fill configuration of the buried inlet structures using geophysical and sedimentological data acquisition methods. This was done by collecting 6.2 km of shoreparallel ground-penetrating radar data and five sediment cores ranging in depth from 4 to 5 m. The sediment cores allowed for the ground truthing of the ground-penetrating radar data and provided six samples for radiocarbon dating. The 13 paleochannels identified ranged in depths from 1.3 to 3.7 m below the present beach surface. These appeared in the radar imagery as broad U-shaped cut-and-fill features incised into adjacent barrier facies. The 13 paleochannels composed 24% of the barrier lithosome totaling 704 m in length. Individual channels were primarily less than 65 m in length and between 2.5 and 1.3 m in depth, although an additional 275-m-wide, 3.7-m-deep channel sequence was imaged and likely represents a major and long-lived paleochannel. The results will contribute toward deciphering the evolution of the Waquoit system and identify areas vulnerable to storm-driven coastal change. VL - 32 ER - TY - JOUR T1 - Ta'u and Ofu/Olosega volcanoes: The ``Twin Sisters'' of Samoa, their P, T, X melting regime, and global implications JF - GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS Y1 - 2014 A1 - Hart, Stanley R. A1 - Jackson, Matthew G. AB - The Samoan islands of Ta'u and Ofu/Olosega (Ofol hereafter) are single shield volcanoes that have erupted alkali basalt for the past 70 and 440 kyr, respectively. They are 20 km apart, and are the easternmost subaerial expressions of the Samoan plume. The isotopic data for these islands are published; we report here the first major and trace element data for Ofol. The two islands are similar isotopically and in trace elements. Their high He-3/He-4 marks them as being a FOZO mantle end-member. By comparing data from both volcanoes, we test the efficacy of melting models in constraining the mantle compositions and their P-T of melting. We show that the mantle sources are similar, with spidergrams that peak at Ta ( 4 x BSE), and Lu similar to 0.5 x BSE. Melts and mantle sources both have Lu/Hf ratios that are too low to support measured Hf-176/Hf-177 ratios, pointing to a young enrichment event in the mantle source. Degrees of melting are 6.5% for Ta'u and 5.2% for Ofol. P-T of melting show a wide, overlapping range, but define a precise array; average values are 1475 degrees C-77 km for Ta'u and 1550 degrees C-110 km for Ofol. The deepest P-T estimate is 4.2 GPa and 1550 degrees C. The P-T array is either a melting adiabat, or a mixing line of melts equilibrated at various depths. Kinetic modeling shows melt re-equilibration will be likely for ascent velocities (m/yr) less than 40/(conduit radius in cm)(2). P-T estimates for melting may typically be minimum values. VL - 15 ER - TY - JOUR T1 - Temporal and spatial distributions of cold-water corals in the Drake Passage: Insights from the last 35,000 years JF - Deep Sea Research Part II: Topical Studies in Oceanography Y1 - 2014 A1 - Margolin, Andrew R. A1 - Robinson, Laura F. A1 - Burke, Andrea A1 - Waller, Rhian G. A1 - Scanlon, Kathryn M. A1 - Roberts, Mark L. A1 - Auro, Maureen E. A1 - van de Flierdt, Tina AB - Scleractinian corals have a global distribution ranging from shallow tropical seas to the depths of the Southern Ocean. Although this distribution is indicative of the corals having a tolerance to a wide spectrum of environmental conditions, individual species seem to be restricted to a much narrower range of ecosystem variables. One way to ascertain the tolerances of corals, with particular focus on the potential impacts of changing climate, is to reconstruct their growth history across a range of environmental regimes. This study examines the spatial and temporal distribution of the solitary scleractinian corals Desmophyllum dianthus, Gardineria antarctica, Balanophyllia malouinensis, Caryophyllia spp. and Flabellum spp. from five sites in the Drake Passage which cross the major frontal zones. A rapid reconnaissance radiocarbon method, cooupled with U-Th dating, extends the age range back more than 100 thousand. Within this age range there are distinct changes in the temporal and spatial distributions of these corals, both with depth and latitude, and on millennial timescales. Two major patterns that emerge are: 1) D. dianthus populations show clear variability in their occurrence through time depending on the latitudinal position within the Drake Passage. North of the Subantarctic Front, D. dianthus first appears in the late deglaciation (~17,000 years ago) and persists to today. South of the Polar Front, in contrast, populations existed during the glacial and early deglacial periods, with only few modern occurrences. A seamount site between the two fronts exhibits characteristics similar to both the north and south sites. This shift across the frontal zones within one species cannot yet be fully explained, but it is likely to be linked to changes in surface productivity, subsurface oxygen concentrations, and carbonate saturation state. 2) at locations where multiple genera were dated, clear differences in age and depth distribution of the populations provide clear evidence that each genus has unique environmental requirements to sustain its population. VL - 99 N1 - id: 2278 JO - Temporal and spatial distributions of cold-water corals in the Drake Passage: Insights from the last 35,000 years ER - TY - JOUR T1 - Timing and preservation mechanism of deglacial pteropod spike from the Andaman Sea, northeastern Indian Ocean JF - BOREAS Y1 - 2014 A1 - Sijinkumar, Adukkam V. A1 - Nath, Bejugam N. A1 - Guptha, Medimi V. S. A1 - Ahmad, Syed M. A1 - Rao, Bandaru R. AB - The aragonite compensation depth (ACD) fluctuated considerably during the last glacial until the Holocene with a dominant pteropod preservation spike during the deglacial period, which is prominently seen in three well-dated cores covering the Andaman Sea, northeastern Indian Ocean. The precise time period of the preservation spike of pteropods is not known but this knowledge is crucial for stratigraphical correlation and also for understanding the driving mechanism. Isotopic and foraminiferal proxies were used to decipher the possible mechanism for pteropods preservation in the Andaman Sea. The poor preservation/absence of pteropods during the Holocene in the Andaman Sea may have implications for ocean acidification, driven by enhanced atmospheric CO2 concentration. Strengthening of the summer monsoon and the resultant high biological productivity may also have played a role in the poor preservation of pteropods. The deglacial pteropod spike is characterized by high abundance/preservation of the pteropods between approximate to 19 and 15cal. ka BP, associated with very low atmospheric CO2 concentration. Isotope data suggest the prevalence of a glacial environment with reduced sea surface temperature, upwelling and enhanced salinity during the pteropod preservation spike. Total planktic foraminifera and Globigerina bulloides abundances are low during this period, implying a weakened summer monsoon and reduced foraminiferal productivity. Based on the preservation record of pteropods, it is inferred that the ACD was probably deepest (>2900m) at 16.5cal. ka BP. The synchronous regional occurrence of the pteropod preservation spike in the Andaman Sea and in the northwestern Indian Ocean could potentially be employed as a stratigraphic marker. VL - 44 ER - TY - JOUR T1 - Transfer of organic carbon through marine water columns to sediments - insights from stable and radiocarbon isotopes of lipid biomarkers JF - Biogeosciences Y1 - 2014 A1 - Wakeham, S. G. A1 - McNichol, A. P. AB - Compound-specific C-13 and C-14 compositions of diverse lipid biomarkers (fatty acids, alkenones, hydrocarbons, sterols and fatty alcohols) were measured in sinking particulate matter collected in sediment traps and from underlying surface sediments in the Black Sea, the Arabian Sea and the Ross Sea. The goal was to develop a multiparameter approach to constrain relative inputs of organic carbon (OC) from marine biomass, terrigenous vascular-plant and relict-kerogen sources. Using an isotope mass balance, we calculate that marine biomass in sediment trap material from the Black Sea and Arabian Sea accounted for 66-100% of OC, with lower terrigenous (3-8 %) and relict (4-16 %) contributions. Marine biomass in sediments constituted lower proportions of OC (66-90 %), with consequentially higher proportions of terrigenous and relict carbon (3-17 and 713 %, respectively). Ross Sea data were insufficient to allow similar mass balance calculations. These results suggest that, whereas particulate organic carbon is overwhelmingly marine in origin, pre-aged allochthonous terrigenous and relict OC become proportionally more important in sediments, consistent with pre-aged OC being better preserved during vertical transport to and burial at the seafloor than the upper-ocean-derived marine OC. VL - 11 IS - 23 N1 - PT: J; TC: 0; UT: WOS:000346357100026 JO - Transfer of organic carbon through marine water columns to sediments - insights from stable and radiocarbon isotopes of lipid biomarkers ER - TY - JOUR T1 - Unusual C35 to C38 alkenones in mid-Holocene sediments from a restricted estuary (Charlotte Harbor, Florida) JF - Organic Geochemistry Y1 - 2014 A1 - van Soelen, E. E. A1 - Lammers, J. M. A1 - Eglinton, T. I. A1 - Sinninghe Damsté, J. S. A1 - Reichart, G. J. AB - Unusual C35 to C38 alkenones were identified in mid-Holocene (8–3.5 kyr BP) sediments from a restricted estuary in southwest Florida (Charlotte Harbor). The distribution was dominated by a C36 diunsaturated (ω15,20) ethyl ketone, identical to the one present in Black Sea Unit 2 sediments. Other unusual alkenones were tentatively assigned as a C35:2 (ω15,20) methyl ketone, a C37:2 (ω17,22) methyl ketone and a C38:2 (ω17,22) ethyl ketone. In late Holocene sediments < 3.5 kyr BP, the common C37 to C39 alkenones were found. Compound-specific 14C, 13C, and D isotope measurements were used to constrain the possible origin of the alkenones. Conventional radiocarbon ages of alkenones and higher plant-derived long chain n-alcohols indicated no significant difference in age between mid-Holocene alkenones and higher plant n-alcohols. Both alcohols and alkenones were offset vs. calibrated ages of shell fragments in the same sediment core, which suggests they were pre-aged by 500–800 yr, implying resuspension and redistribution of the fine-grained sedimentary particles with which they are associated. The hydrogen isotopic (δD) composition (−190‰ to −200‰) of the C37 and C38 alkenones in the late Holocene sediments is in line with values for coastal haptophytes in brackish water. However, the unusual C36 and C38 alkenones from the mid Holocene sediments were enriched in D (by ca. 100‰) vs. the late Holocene alkenones. Also, δ13C values of mid-Holocene alkenones were consistently offset compared with late Holocene alkenones (−21‰ to −22‰ and −22‰ to −23‰, respectively). We suggest that the alkenones in Charlotte Harbor were produced by unknown alkenone-producing haptophyte. VL - 70 UR - http://www.sciencedirect.com/science/article/pii/S0146638014000345 JO - Unusual C35 to C38 alkenones in mid-Holocene sediments from a restricted estuary (Charlotte Harbor, Florida) ER - TY - JOUR T1 - Uplift and subsidence reveal a nonpersistent megathrust rupture boundary (Sitkinak Island, Alaska) JF - Geophysical Research Letters Y1 - 2014 A1 - Briggs, Richard W. A1 - Engelhart, Simon E. A1 - Nelson, Alan R. A1 - Dura, Tina A1 - Kemp, Andrew C. A1 - Haeussler, Peter J. A1 - Corbett, D. Reide A1 - Angster, Stephen J. A1 - Bradley, Lee-Ann AB - We report stratigraphic evidence of land-level change and tsunami inundation along the Alaska-Aleutian megathrust during prehistoric and historical earthquakes west of Kodiak Island. On Sitkinak Island, cores and tidal outcrops fringing a lagoon reveal five sharp lithologic contacts that record coseismic land-level change. Radiocarbon dates, 137Cs profiles, computerized tomography scans, and microfossil assemblages are consistent with rapid uplift circa 290–0, 520–300, and 1050–790 cal yr B.P. and subsidence in A.D. 1964 and circa 640–510 cal yr B.P. Radiocarbon, 137Cs, and 210Pb ages bracketing a sand bed traced 1.5 km inland and evidence for sudden uplift are consistent with Russian accounts of an earthquake and tsunami in A.D. 1788. The mixed uplift and subsidence record suggests that Sitkinak Island sits above a nonpersistent boundary near the southwestern limit of the A.D. 1964 Mw 9.2 megathrust rupture. VL - 41 UR - http://doi.wiley.com/10.1002/2014GL059380 IS - 7 ER - TY - JOUR T1 - Using Natural Abundance Radiocarbon To Trace the Flux of Petrocarbon to the Seafloor Following the Deepwater Horizon Oil Spill JF - Environmental science & technology Y1 - 2014 A1 - Chanton, Jeffrey A1 - Zhao, Tingting A1 - Rosenheim, Brad E. A1 - Joye, Samantha A1 - Bosman, Samantha A1 - Brunner, Charlotte A1 - Yeager, Kevin M. A1 - Diercks, Arne R. A1 - Hollander, David AB - In 2010, the Deepwater Horizon accident released 4.6?6.0 ? 1011 grams or 4.1 to 4.6 million barrels of fossil petroleum derived carbon (petrocarbon) as oil into the Gulf of Mexico. Natural abundance radiocarbon measurements on surface sediment organic matter in a 2.4 ? 1010 m2 deep-water region surrounding the spill site indicate the deposition of a fossil-carbon containing layer that included 1.6 to 2.6 ? 1010 grams of oil-derived carbon. This quantity represents between 0.5 to 9.1% of the released petrocarbon, with a best estimate of 3.0?4.9%. These values may be lower limit estimates of the fraction of the oil that was deposited on the seafloor because they focus on a limited mostly deep-water area of the Gulf, include a conservative estimate of thickness of the depositional layer, and use an average background or prespill radiocarbon value for sedimentary organic carbon that produces a conservative value. A similar approach using hopane tracer estimated that 4?31% of 2 million barrels of oil that stayed in the deep sea settled on the bottom. Converting that to a percentage of the total oil that entered into the environment (to which we normalized our estimate) converts this range to 1.8 to 14.4%. Although extrapolated over a larger area, our independent estimate produced similar values.; In 2010, the Deepwater Horizon accident released 4.6?6.0 ? 1011 grams or 4.1 to 4.6 million barrels of fossil petroleum derived carbon (petrocarbon) as oil into the Gulf of Mexico. Natural abundance radiocarbon measurements on surface sediment organic matter in a 2.4 ? 1010 m2 deep-water region surrounding the spill site indicate the deposition of a fossil-carbon containing layer that included 1.6 to 2.6 ? 1010 grams of oil-derived carbon. This quantity represents between 0.5 to 9.1% of the released petrocarbon, with a best estimate of 3.0?4.9%. These values may be lower limit estimates of the fraction of the oil that was deposited on the seafloor because they focus on a limited mostly deep-water area of the Gulf, include a conservative estimate of thickness of the depositional layer, and use an average background or prespill radiocarbon value for sedimentary organic carbon that produces a conservative value. A similar approach using hopane tracer estimated that 4?31% of 2 million barrels of oil that stayed in the deep sea settled on the bottom. Converting that to a percentage of the total oil that entered into the environment (to which we normalized our estimate) converts this range to 1.8 to 14.4%. Although extrapolated over a larger area, our independent estimate produced similar values. UR - http://dx.doi.org/10.1021/es5046524 JO - Using Natural Abundance Radiocarbon To Trace the Flux of Petrocarbon to the Seafloor Following the Deepwater Horizon Oil Spill ER - TY - JOUR T1 - Validated age and growth estimates for Carcharhinus obscurus in the northwestern Atlantic Ocean, with pre- and post management growth comparisons JF - Environmental Biology of Fishes Y1 - 2014 A1 - Natanson, Lisa J. A1 - Gervelis, Brian J. A1 - Winton, Megan V. A1 - Hamady, Li Ling A1 - Gulak, Simon J. B. A1 - Carlson, John K. KW - Age and growth KW - bomb radiocarbon KW - Dusky shark KW - Elasmobranch KW - Validation KW - Vertebrae AB - Age and growth estimates for the dusky shark, Carcharhinus obscurus, were derived from vertebral centra collected in the northwestern Atlantic Ocean. Sample collection spanned the years prior to and following the implementation ofmanagementmeasures (1963– 2010). Growth was compared pre- and post- population depletion and pre- and post- management to investigate the possibility of density-mediated shifts in age and growth parameters over time. There was no evidence of difference between periods for either sex. Additionally, bomb radiocarbon dating was used to determine the periodicity of band pair formation. Results support the traditional interpretation of annual band pairs up to approximately 11 years of age. After this time, vertebral counts considerably underestimate true age. Maximum validated ages were estimated to be between 38 and 42 years of age (an increase of 15 to 19 years over the band count estimates), confirming longevity to at least 42 years of age. Growth curves estimated using only validated data were compared to those generated using band pair counts. Logistic growth parameters derived from validated vertebral length-at-age data were L∞=261.5 cm FL, Lo=85.5 cm, to=4.89 year and g=0.15 year−1 for the sexes combined. Revised estimates of age at maturity were 17.4 years for males and 17.6 years for females. VL - 97109251443124592565546445894545835645277154931266199319909310036110823842426199561196662521049 UR - http://link.springer.com/10.1007/s10641-013-0189-4http://link.springer.com/content/pdf/10.1007/s10641-013-0189-4 IS - 8C34212 ER - TY - JOUR T1 - Vertebral Bomb Radiocarbon Suggests Extreme Longevity in White Sharks JF - Plos One Y1 - 2014 A1 - Hamady, Li Ling A1 - Natanson, Lisa J. A1 - Skomal, Gregory B. A1 - Thorrold, Simon R. AB - Conservation and management efforts for white sharks (Carcharodon carcharias) remain hampered by a lack of basic demographic information including age and growth rates. Sharks are typically aged by counting growth bands sequentially deposited in their vertebrae, but the assumption of annual deposition of these band pairs requires testing. We compared radiocarbon (Delta C-14) values in vertebrae from four female and four male white sharks from the northwestern Atlantic Ocean (NWA) with reference chronologies documenting the marine uptake of C-14 produced by atmospheric testing of thermonuclear devices to generate the first radiocarbon age estimates for adult white sharks. Age estimates were up to 40 years old for the largest female (fork length [FL]: 526 cm) and 73 years old for the largest male (FL: 493 cm). Our results dramatically extend the maximum age and longevity of white sharks compared to earlier studies, hint at possible sexual dimorphism in growth rates, and raise concerns that white shark populations are considerably more sensitive to human-induced mortality than previously thought. VL - 9 IS - 1 N1 - PT: J; TC: 0; UT: WOS:000329862500089 JO - Vertebral Bomb Radiocarbon Suggests Extreme Longevity in White Sharks ER - TY - JOUR T1 - 11,000 yrs of environmental change in the Northwest Passage: A multiproxy core record from central Parry Channel, Canadian High Arctic JF - Marine Geology Y1 - 2013 A1 - Pieńkowski, A. J. A1 - England, John H. A1 - Furze, Mark F. A. A1 - Blasco, Steve A1 - Mudie, Peta J. A1 - MacLean, Brian AB - Piston core 97022-004PC (74° 48.0′N 97°05.9′W; 267 m water depth) represents a rare paleoenvironmental archive from the understudied west-central Canadian Arctic Archipelago. Lithological, biogeochemical, and microfossil (dinoflagellate cysts, non-pollen palynomorphs, benthic and planktonic foraminifera) characteristics, in combination with a chronostratigraphy based on seventeen radiocarbon dates, show seven prominent paleoenvironmental episodes since the end of the last regional glaciation. The basal diamict (Zone I) records decoupling of previously grounded glacial ice, followed by ice-proximal conditions (Zone IIa) commencing at ~ 10.8 cal ka BP (age-depth model extrapolation). After an interval of pervasive sea-ice (Zone IIb), ice-distal conditions are established (Zone IIc). Although sparse microfossils are present in glaciomarine sediments (Zone II), noticeable biological activity with heightened abundances and diversities across all groups begins in the postglacial Zone III (10.3–10.0 cal ka BP) when planktonic foraminifera (Neogloboquadrina pachyderma) appear. As planktonics are excluded from the study area today (due to shallow inter-channel sills), this likely signals the inflow of relatively warm and saline Atlantic-derived Arctic Intermediate Water below 250 m, presumably facilitated by glacio-isostatically enhanced deglacial water depths. The subsequent Zone IV (10.0–7.0 cal ka BP), characterized by heightened biological productivity in both plankton and benthos and reduced seasonal sea-ice cover, may correspond to a previously proposed Holocene Thermal Maximum. This apparent amelioration ends by the mid Holocene (Zone V; 7.0–5.7 cal ka BP) when Arctic Intermediate Water is excluded from the study area and water depths approach modern values. High-Arctic conditions with seasonal sea-ice cover, a circulation dominated by Arctic Ocean Surface Water, and microfossil assemblages similar to modern are found from ~ 5.7 cal ka BP onwards (Zones VI–VII). As only minor environmental fluctuations are apparent during the late Holocene, shorter-term climatic episodes (e.g. Little Ice Age) are not recognized in this record. VL - 341 UR - http://www.sciencedirect.com/science/article/pii/S0025322713000522 N1 - id: 2343 JO - 11,000 yrs of environmental change in the Northwest Passage: A multiproxy core record from central Parry Channel, Canadian High Arctic ER - TY - CHAP T1 - 14.31 Radiocarbon Dating of Plant Macrofossils from Tidal-Marsh Sediment T2 - Treatise on Geomorphology Y1 - 2013 A1 - Kemp, A. C. A1 - Nelson, A. R. A1 - Horton, B. P. ED - Editor-in-Chief: John, F. Shroder AB - Tidal-marsh sediment is an archive of Holocene environmental changes, including movements of sea and land levels, and extreme events such as hurricanes, earthquakes, and tsunamis. Accurate and precise radiocarbon dating of environmental changes is necessary to estimate rates of change and the recurrence interval (frequency) of events. Plant macrofossils preserved in growth position (or deposited soon after death) in tidal-marsh sediment are ideal samples for dating such changes. In this chapter, we focus on the selection of plant macrofossils for radiocarbon dating and the application of ages from different types of macrofossils to varied research projects, and make recommendations for selection and preparation of tidal-marsh samples for dating. JF - Treatise on Geomorphology PB - Academic Press CY - San Diego N1 - id: 2293 JO - 14.31 Radiocarbon Dating of Plant Macrofossils from Tidal-Marsh Sediment ER - TY - JOUR T1 - 14C and 13C characteristics of higher plant biomarkers in Washington margin surface sediments JF - Geochimica et Cosmochimica Acta Y1 - 2013 A1 - Feng, Xiaojuan A1 - Benitez-Nelson, Bryan C. A1 - Montluçon, Daniel B. A1 - Prahl, Fredrick G. A1 - McNichol, Ann P. A1 - Xu, Li A1 - Repeta, Daniel J. A1 - Eglinton, Timothy I. AB - Plant wax lipids and lignin phenols are the two most common classes of molecular markers that are used to trace vascular plant-derived OM in the marine environment. However, their 13C and 14C compositions have not been directly compared, which can be used to constrain the flux and attenuation of terrestrial carbon in marine environment. In this study, we describe a revised method of isolating individual lignin phenols from complex sedimentary matrices for 14C analysis using high pressure liquid chromatography (HPLC) and compare this approach to a method utilizing preparative capillary gas chromatography (PCGC). We then examine in detail the 13C and 14C compositions of plant wax lipids and lignin phenols in sediments from the inner and mid shelf of the Washington margin that are influenced by discharge of the Columbia River. Plant wax lipids (including n-alkanes, n-alkanoic (fatty) acids, n-alkanols, and n-aldehydes) displayed significant variability in both δ13C (−28.3‰ to −37.5‰) and Δ14C values (−204‰ to +2‰), suggesting varied inputs and/or continental storage and transport histories. In contrast, lignin phenols exhibited similar δ13C values (between −30‰ and −34‰) and a relatively narrow range of Δ14C values (−45‰ to −150‰; HPLC-based measurement) that were similar to, or younger than, bulk OM (−195‰ to −137‰). Moreover, lignin phenol 14C age correlated with the degradation characteristics of this terrestrial biopolymer in that vanillyl phenols were on average ∼500 years older than syringyl and cinnamyl phenols that degrade faster in soils and sediments. The isotopic characteristics, abundance, and distribution of lignin phenols in sediments suggest that they serve as promising tracers of recently biosynthesized terrestrial OM during supply to, and dispersal within the marine environment. Lignin phenol 14C measurements may also provide useful constraints on the vascular plant end member in isotopic mixing models for carbon source apportionment, and for interpretation of sedimentary records of past vegetation dynamics. VL - 105 UR - http://www.sciencedirect.com/science/article/pii/S0016703712006874 N1 - id: 2267 JO - 14C and 13C characteristics of higher plant biomarkers in Washington margin surface sediments ER - TY - JOUR T1 - After the lava flow: The importance of external soil sources for plant colonization of recent lava flows in the central Oregon Cascades, USA JF - Geomorphology Y1 - 2013 A1 - Deligne, Natalia I. A1 - Cashman, Katharine V. A1 - Roering, Joshua J. AB - Effusive volcanic eruptions repave landscapes rapidly with lava flows, resetting broad areas of the underlying landscape and ecosystem. The unique physical properties of lava pose interesting challenges for ecologic recovery, as lava is dense, sterile, and generally inhospitable towards life. In this study we examine two sites of recent volcanism in the central Oregon Cascades, notable for the juxtaposition of barren exposed lava and mature forests on lava flows of the same or roughly the same age. We use a combination of LiDAR analyses, field observations, and soil characterization to examine soil and vegetation at these two sites, and find that the presence of an external sediment or soil source, particularly flood-borne deposits or syn- or post-eruptive tephra, greatly facilitates plant establishment, growth, and survival. The nature of the external sources of sediment or soil dictates the geographic extent of forests on these young lava flows: flood-borne deposits cover localized regions near river channels, while tephra can cover large regions. In general, our results suggest that external sources of soil provide a substrate for plants to grow in along with key nutrients and sufficient moisture retention. We conclude that external sources of soil source are key for the initial recovery following an effusive volcanic disturbance, in particular in temperate climates. Thus, unrelated geomorphic processes, such as past glaciations that provide local sources of mobile sediments, or concurrent volcanic processes, such as tephra production, dictate the presence or absence of forests on young lava flows. VL - 202 UR - http://www.sciencedirect.com/science/article/pii/S0169555X12005582 N1 - id: 2321 JO - After the lava flow: The importance of external soil sources for plant colonization of recent lava flows in the central Oregon Cascades, USA ER - TY - JOUR T1 - AMS radiocarbon investigation of the African baobab: Searching for the oldest tree JF - Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions with Materials and Atoms Y1 - 2013 A1 - Patrut, Adrian A1 - von Reden, Karl F. A1 - Mayne, Diana H. A1 - Lowy, Daniel A. A1 - Patrut, Roxana T. AB - The Glencoe baobab, a very large specimen from South Africa, split twice in 2009. Several wood samples were collected from the eastern cavity, from the outer part of the main section and also from the largest broken segment which was connected to this section. These wood samples were processed and investigated by AMS radiocarbon dating. The radiocarbon date of the oldest sample was found to be 1838 +/- 21 BP, which corresponds to a calibrated age of 1835 +/- 40 years. Thus, the Glencoe baobab becomes the oldest dated baobab and also the oldest angiosperm tree with accurate dating results. The distribution of dating results revealed that the Glencoe baobab is a multi-generation tree, with several standing or collapsed and partially fused stems, showing different ages. (C) 2012 Elsevier B.V. All rights reserved. VL - 294 N1 - id: 2246; PT: J; CT: 12th International Conference on Accelerator Mass Spectrometry (AMS); CY: MAR 20-25, 2011; CL: Wellington, NEW ZEALAND; TC: 0; UT: WOS:000313234300120 JO - AMS radiocarbon investigation of the African baobab: Searching for the oldest tree ER - TY - JOUR T1 - Anatomy of the La Jolla Submarine Canyon system; offshore southern California JF - Marine Geology Y1 - 2013 A1 - Paull, C. K. A1 - Caress, D. W. A1 - Lundsten, E. A1 - Gwiazda, R. A1 - Anderson, K. A1 - McGann, M. A1 - Conrad, J. A1 - Edwards, B. A1 - Sumner, E. J. AB - An autonomous underwater vehicle (AUV) carrying a multibeam sonar and a chirp profiler was used to map sections of the seafloor within the La Jolla Canyon, offshore southern California, at sub-meter scales. Close-up observations and sampling were conducted during remotely operated vehicle (ROV) dives. Minisparker seismic-reflection profiles from a surface ship help to define the overall geometry of the La Jolla Canyon especially with respect to the pre-canyon host sediments. The floor of the axial channel is covered with unconsolidated sand similar to the sand on the shelf near the canyon head, lacks outcrops of the pre-canyon host strata, has an almost constant slope of 1.0° and is covered with trains of crescent shaped bedforms. The presence of modern plant material entombed within these sands confirms that the axial channel is presently active. The sand on the canyon floor liquefied during vibracore collection and flowed downslope, illustrating that the sediment filling the channel can easily fail even on this gentle slope. Data from the canyon walls help constrain the age of the canyon and extent of incision. Horizontal beds of moderately cohesive fine-grained sediments exposed on the steep canyon walls are consistently less than 1.232 million years old. The lateral continuity of seismic reflectors in minisparker profiles indicate that pre-canyon host strata extend uninterrupted from outside the canyon underneath some terraces within the canyon. Evidence of abandoned channels and point bar-like deposits are noticeably absent on the inside bend of channel meanders and in the subsurface of the terraces. While vibracores from the surface of terraces contain thin ( VL - 335 UR - http://www.sciencedirect.com/science/article/pii/S0025322712002150 N1 - id: 2302 JO - Anatomy of the La Jolla Submarine Canyon system; offshore southern California ER - TY - JOUR T1 - Annually Resolved Ice Core Records of Tropical Climate Variability over the Past similar to 1800 Years JF - SCIENCE Y1 - 2013 A1 - Thompson, L. G. A1 - Mosley-Thompson, E. A1 - Davis, M. E. A1 - Zagorodnov, V. S. A1 - Howat, I. M. A1 - Mikhatenko, V. N. A1 - Lin, P. -N. AB - Ice cores from low Latitudes can provide a wealth of unique information about past climate in the tropics, but they are difficult to recover and few exist. Here, we report annually resolved ice core records from the Quelccaya ice cap (5670 meters above sea level) in Peru that extend back similar to 1800 years and provide a high-resolution record of climate variability there. Oxygen isotopic ratios (delta O-18) are linked to sea surface temperatures in the tropical eastern Pacific, whereas concentrations of ammonium and nitrate document the dominant role played by the migration of the Intertropical Convergence Zone in the region of the tropical Andes. Quetccaya continues to retreat and thin. Radiocarbon dates on wetland plants exposed along its retreating margins indicate that it has not been smaller for at least six millennia. VL - 340 ER - TY - JOUR T1 - Applications of accelerator mass spectrometry JF - International Journal of Mass Spectrometry Y1 - 2013 A1 - Kutschera, Walter AB - Applications of accelerator mass spectrometry (AMS) evolved into multi-disciplinary research covering virtually every domain of our environment at large. The possibilities of applications are clearly coupled to technical developments of AMS, which will be covered by the accompanying article of H.-A. Synal. The present review therefore concentrates on describing AMS applications to the largest extent possible. Since the knowledge of the author on the many fields where AMS measurements are performed is, of course, limited, the selection of examples discussed in this review is somewhat biased. In order to compensate for this, a rather long list of references is presented, which should be consulted for a deeper understanding of the respective fields. The seven domains of our environment at large (atmosphere, biosphere, hydrosphere, cryosphere, lithosphere, cosmosphere, and technosphere) are being used as a guideline for the present review. VL - 349-350 N1 - id: 2270 JO - Applications of accelerator mass spectrometry ER - TY - JOUR T1 - Assessing microbial carbon sources and potential PAH degradation using natural abundance 14C analysis JF - Environmental Pollution Y1 - 2013 A1 - Mahmoudi, Nagissa A1 - Fulthorpe, Roberta R. A1 - Burns, Leanne A1 - Mancini, Silvia A1 - Slater, Greg F. AB - Natural abundance 14C analysis was applied to PLFAs collected from an industrial site in southern Ontario in order to assess microbial carbon sources and potential PAH biodegradation in soils. Δ14C of microbial phospholipid fatty acids (PLFA) at the site ranged from +54‰ to −697‰. Comparison of these values to surrounding carbon sources found that microbial carbon sources were derived primarily from vegetation and/or natural organic matter present in the soils rather than PAHs. This study highlights that microbes are able to utilize almost all available pools of organic matter including older pools which are thought to contain recalcitrant compounds. Furthermore, it shows that even with the presence of an active microbial community, there may be little biodegradation of PAHs. This study illustrates challenges in assessing microbial activity in the environment and the advantage of using natural abundance 14C analysis as a tool to elucidate microbial carbon sources. VL - 175 UR - http://www.sciencedirect.com/science/article/pii/S0269749112005453 N1 - id: 2268 JO - Assessing microbial carbon sources and potential PAH degradation using natural abundance 14C analysis ER - TY - JOUR T1 - Bomb radiocarbon dating of the endangered white abalone (Haliotis sorenseni): investigations of age, growth and lifespan JF - Marine and Freshwater Research Y1 - 2013 A1 - Andrews, Allen H. A1 - Leaf, Robert T. A1 - Rogers-Bennett, Laura A1 - Neuman, Melissa A1 - Hawk, Heather A1 - Cailliet, Gregor M. AB - Understanding basic life-history characteristics of white abalone (Haliotis sorenseni), such as estimated lifespan, is critical to making informed decisions regarding the recovery of this endangered species. All predictive modelling tools used to forecast the status and health of populations following restoration activities depend on a validated estimate of adult lifespan. Of the seven Haliotis species in California, white abalone is considered to have the highest extinction risk and was the first marine invertebrate listed as an endangered species under the Federal Endangered Species Act (ESA). Lifespan was previously estimated from observations of early growth; however, no study has generated ages for the largest white abalone. To address questions of age and growth, bomb radiocarbon (C-14) dating was used on shells from large white abalone. Measured bomb C-14 levels were compared to regional C-14 reference records to provide estimates of age, growth and lifespan. Bomb radiocarbon dating indicated that growth was variable among individuals, with a maximum estimated age of 27 years. The findings presented here provide support for previous age and growth estimates and an estimated lifespan near 30 years. These age data support the perception of a critical need for restoring the remnant aging and potentially senescent population. VL - 64 IS - 11 N1 - id: 2351; PT: J; TC: 0; UT: WOS:000326166400004 JO - Bomb radiocarbon dating of the endangered white abalone (Haliotis sorenseni): investigations of age, growth and lifespan ER - TY - JOUR T1 - C-14 and C-13 characteristics of higher plant biomarkers in Washington margin surface sediments JF - GEOCHIMICA ET COSMOCHIMICA ACTA Y1 - 2013 A1 - Feng, Xiaojuan A1 - Benitez-Nelson, Bryan C. A1 - Montluçon, Daniel B. A1 - Prahl, Fredrick G. A1 - McNichol, Ann P. A1 - Xu, Li A1 - Repeta, Daniel J. A1 - Eglinton, Timothy I. AB - Plant wax lipids and lignin phenols are the two most common classes of molecular markers that are used to trace vascular plant-derived OM in the marine environment. However, their C-13 and C-14 compositions have not been directly compared, which can be used to constrain the flux and attenuation of terrestrial carbon in marine environment. In this study, we describe a revised method of isolating individual lignin phenols from complex sedimentary matrices for C-14 analysis using high pressure liquid chromatography (HPLC) and compare this approach to a method utilizing preparative capillary gas chromatography (PCGC). We then examine in detail the C-13 and C-14 compositions of plant wax lipids and lignin phenols in sediments from the inner and mid shelf of the Washington margin that are influenced by discharge of the Columbia River. Plant wax lipids (including n-alkanes, n-alkanoic (fatty) acids, n-alkanols, and n-aldehydes) displayed significant variability in both delta C-13 (-28.3 parts per thousand to -37.5 parts per thousand) and Delta C-14 values (-204 parts per thousand to +2 parts per thousand), suggesting varied inputs and/or continental storage and transport histories. In contrast, lignin phenols exhibited similar delta C-13 values (between -30 parts per thousand and -34 parts per thousand) and a relatively narrow range of Delta C-14 values (-45 parts per thousand to -150 parts per thousand; HPLC-based measurement) that were similar to, or younger than, bulk OM (-195 parts per thousand to -137 parts per thousand). Moreover, lignin phenol C-14 age correlated with the degradation characteristics of this terrestrial biopolymer in that vanillyl phenols were on average similar to 500 years older than syringyl and cinnamyl phenols that degrade faster in soils and sediments. The isotopic characteristics, abundance, and distribution of lignin phenols in sediments suggest that they serve as promising tracers of recently biosynthesized terrestrial OM during supply to, and dispersal within the marine environment. Lignin phenol C-14 measurements may also provide useful constraints on the vascular plant end member in isotopic mixing models for carbon source apportionment, and for interpretation of sedimentary records of past vegetation dynamics. (C) 2012 Elsevier Ltd. All rights reserved. VL - 105 ER - TY - JOUR T1 - A California Current bomb radiocarbon reference chronology and petrale sole (Eopsetta jordani) age validation JF - Canadian Journal of Fisheries and Aquatic Sciences Y1 - 2013 A1 - Haltuch, Melissa A. A1 - Hamel, Owen S. A1 - Piner, Kevin R. A1 - McDonald, Patrick A1 - Kastelle, Craig R. A1 - Field, John C. VL - 70 UR - http://dx.doi.org/10.1139/cjfas-2011-0504 IS - 1 JO - A California Current bomb radiocarbon reference chronology and petrale sole (Eopsetta jordani) age validation ER - TY - JOUR T1 - Carbon isotopic characterization of hydrophobic dissolved organic carbon in rainwater JF - Atmospheric Environment Y1 - 2013 A1 - Avery Jr, G. Brooks A1 - Biswas, K. Farhana A1 - Mead, Ralph A1 - Southwell, Melissa A1 - Willey, Joan D. A1 - Kieber, Robert J. A1 - Mullaugh, Katherine M. AB - The 14C and 13C content of the hydrophobic fraction (C18 extractable) of dissolved organic carbon (DOC) in Wilmington North Carolina USA rainwater was determined for six rain events to elucidate potential sources. A two end member mass-balance calculation indicated that 42–61% of the hydrophobic DOC was of fossil fuel origin compared to previously published values (4–24%) for bulk rain DOC indicating a strong anthropogenic contribution to the hydrophobic component. All fossil fuel derived organic carbon in the bulk DOC (∼15% fossil fuel derived) could be accounted for in the hydrophobic fraction (∼52% fossil fuel derived) which represents approximately 1/3 of the bulk DOC. The δ13C values of the hydrophobic DOC were consistent (−28.8 ± 0.9‰) similar to that for terrestrial and fossil fuel derived organic carbon. This is in contrast to previously published bulk rain DOC δ13C values that displayed a strong influence of air-mass back-trajectory with δ13C values ranging from −20.8‰ (typical of marine organic carbon) for marine air-mass back-trajectory rain to −28.2‰ (typical of terrestrial or fossil fuel derived organic carbon) for terrestrial air-mass back-trajectory rain. The combination of 14C and 13C isotopic data strongly suggests that a large fraction of hydrophobic organic material in rain comes from incompletely combusted fossil fuels. Changes in energy usage patterns and efforts to reduce fossil fuel emissions will alter the abundance of this hydrophobic material in the atmosphere which may impact the spectral distribution of sunlight reaching the earth's surface as well as the degree of oceanic primary productivity. VL - 68 UR - http://www.sciencedirect.com/science/article/pii/S1352231012011223 N1 - id: 2288 JO - Carbon isotopic characterization of hydrophobic dissolved organic carbon in rainwater ER - TY - JOUR T1 - Carbon isotopic evidence for microbial control of carbon supply to Orca Basin at the seawater-brine interface JF - BIOGEOSCIENCES Y1 - 2013 A1 - Shah, S. R. A1 - Joye, S. B. A1 - Brandes, J. A. A1 - McNichol, A. P. AB - Orca Basin, an intraslope basin on the Texas-Louisiana continental slope, hosts a hypersaline, anoxic brine in its lowermost 200m in which limited microbial activity has been reported. This brine contains a large reservoir of reduced and aged carbon, and appears to be stable at decadal time scales: concentrations and isotopic composition of dissolved inorganic (DIC) and organic carbon (DOC) are similar to measurements made in the 1970s. Both DIC and DOC are more ``aged{''} within the brine pool than in overlying water, and the isotopic contrast between brine carbon and seawater carbon is much greater for DIC than DOC. While the stable carbon isotopic composition of brine DIC points towards a combination of methane and organic carbon remineralization as its source, radiocarbon and box model results point to the brine interface as the major source region for DIC, allowing for only limited oxidation of methane diffusing upwards from sediments. This conclusion is consistent with previous studies that identify the seawater-brine interface as the focus of microbial activity associated with Orca Basin brine. Isotopic similarities between DIC and DOC suggest a different relationship between these two carbon reservoirs than is typically observed in deep ocean basins. Radiocarbon values implicate the seawater-brine interface region as the likely source region for DOC to the brine as well as DIC. VL - 10 ER - TY - JOUR T1 - Carbonate as sputter target material for rapid C-14 AMS JF - Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions with Materials and Atoms Y1 - 2013 A1 - Longworth, Brett E. A1 - Robinson, Laura F. A1 - Roberts, Mark L. A1 - Beaupré, Steven R. A1 - Burke, Andrea A1 - W. J. Jenkins AB - This paper describes a technique for measuring the C-14 content of carbonate samples by producing C- ions directly in the negative ion sputter source of an accelerator mass spectrometer CAMS) system. This direct analysis of carbonate material eliminates the time and expense of graphite preparation. Powdered carbonate is mixed with titanium powder, loaded into a target cartridge, and compressed. Beam currents for optimally-sized carbonate targets (0.09-0.15 mg C) are typically 10-20% of those produced by optimally-sized graphite targets (0.5-1 mg C). Modern (>0.8 Fm) samples run by this method have standard deviations of 0.009 Fm or less, and near-modern samples run as unknowns agree with values from traditional hydrolysis/graphite to better than 2%. Targets with as little as 0.06 mg carbonate produce useable ion currents and results, albeit with increased error and larger blank. In its current state, direct sputtering is best applied to problems where a large number of analyses with lower precision are required. These applications could include age surveys of deep-sea corals for determination of historic population dynamics, to identify samples that would benefit from high precision analysis, and for growth rate studies of organisms forming carbonate skeletons. (C) 2012 Elsevier B.V. All rights reserved. VL - 294 N1 - id: 2244; PT: J; CT: 12th International Conference on Accelerator Mass Spectrometry (AMS); CY: MAR 20-25, 2011; CL: Wellington, NEW ZEALAND; TC: 0; UT: WOS:000313234300064 JO - Carbonate as sputter target material for rapid C-14 AMS ER - TY - JOUR T1 - Changes in sub-fossil chironomid assemblages in two Northern Patagonian lake systems associated to the occurrence of historical fires JF - Journal of Paleolimnology Y1 - 2013 A1 - Araneda, A. A1 - Ortega, C. A1 - Jana, P. A1 - Torrejon, F. A1 - Bertrand, S. A1 - Vargas, P. A1 - Fagel, N. A1 - Alvarez, D. A1 - Urrutia, R. AB - Patagonia is commonly seen as an exceptionally pristine area because of its wildlife and practically unpolluted waters. However, during the twentieth century the burning of natural forests was one of the most important human activities in Northern Chilean Patagonia. Some estimations indicate that three million hectares were burned during the first three decades of the century. Hence the objective of this study was to evaluate the impacts of the historical fires in Lake Burgos (45º42′S) and Lake Thompson (45º38′S) in Chilean Patagonia. The impact was measured by evaluating chironomid assemblage since they are sensitive enough to be used as an indicator of aquatic ecosystem health. Fires have a direct and drastic effect on a lake watershed but also indirectly affect a lake ecosystem, changing sedimentation patterns or increasing nutrient inputs. In the studied lakes the periods with higher prevalence of fires were identified by charcoal analysis, while organic matter and magnetic susceptibility allowed the confirmation of pre-fire and post-fire periods. The chironomid composition was evaluated through a PCA and an analysis of similarity (ANOSIM) to test the significance among periods while a Detrended Correspondence Analysis was applied to the chironomid assemblage downcore to assess compositional structure and taxa turnover. In Lake Burgos the ANOSIM test indicated significant differences between the pre-fire and fire periods (p VL - 50 IS - 1 N1 - id: 2121 JO - Changes in sub-fossil chironomid assemblages in two Northern Patagonian lake systems associated to the occurrence of historical fires ER - TY - JOUR T1 - Deciphering hemipelagites from homogenites through anisotropy of magnetic susceptibility. Paleoseismic implications (Sea of Marmara and Gulf of Corinth) JF - Sedimentary Geology Y1 - 2013 A1 - Campos, Corina A1 - Beck, Christian A1 - Crouzet, Christian A1 - Demory, François A1 - Van Welden, Aurélien A1 - Eris, Kadir AB - In closed marine basins and large lakes, gravity re-depositional processes often result in specific turbidites with two abruptly separated layers: a coarse graded lower term and an upper homogenous fine-grained term. An additional mixed term generally occurs in between, indicating to and from particle displacements. The later ones are related to oscillating bottom currents responsible for a high increase of the fine fraction segregation, within the reworked wasted mass. The whole sedimentary event is the association “homogenite + turbidite” (HmTu), which specific a settling condition area here characterized through Anisotropy of Magnetic Susceptibility (AMS). Homogenites's magnetic foliation appears anomalously high with respect to their expected state of compaction, and strikingly higher than hemipelagites's values. We applied this approach to Late Pleistocene/Holocene sediments from the Sea of Marmara and from the Gulf of Corinth. Grain-size and other magnetic parameters related to mineralogy are added to better assess the granular array influence on AMS. As HmTu is considered as often related to earthquake-triggering and tsunami/seiche effects, AMS appears as a useful tool for subaqueous paleoseismic investigations. First, it may evidence the signature of paleo-earthquakes; second, it permits to decipher hemipelagic intervals which are inferred to represent the time elapsed between two successive reworking events. VL - 292 UR - http://www.sciencedirect.com/science/article/pii/S0037073813000614 JO - Deciphering hemipelagites from homogenites through anisotropy of magnetic susceptibility. Paleoseismic implications (Sea of Marmara and Gulf of Corinth) ER - TY - JOUR T1 - The deglaciation and neoglaciation of Upernavik Isstrøm, Greenland JF - Quaternary Research Y1 - 2013 A1 - Briner, Jason P. A1 - åkansson, Lena A1 - Bennike, Ole AB - We constrain the history of the Greenland Ice Sheet margin during the Holocene at Upernavik Isstrøm, a major ice stream in northwestern Greenland. Radiocarbon-dated sediment sequences from proglacial-threshold lakes adjacent to the present ice margin constrain deglaciation of the sites to older than 9.6 ± 0.1 ka. This age of deglaciation is confirmed with 10Be ages of 9.9 ± 0.1 ka from an island adjacent to the historical ice position. The lake sediment sequences also constrain the ice margin to have been less extensive than it is today for the remainder of the Holocene until ~ 1100 to ~ 700 yr ago, when it advanced into two lake catchments. The ice margin retreated back out of these lake catchments in the last decade. The early Holocene deglaciation in Melville Bugt, one of few locations around Greenland where a vast stretch of the current ice margin is marine-based, preceded deglaciation in most other parts of Greenland. Earlier deglaciation in this ice-sheet sector may have been caused by additional ablation mechanisms that apply to marine-based ice margins. Furthermore, despite ice-sheet models depicting this sector of Greenland as relatively stable throughout the Holocene, our data indicate a > 20 km advance-retreat cycle within the last millennium. VL - 80 UR - https://doi.org/10.1016/j.yqres.2013.09.008 IS - 03 ER - TY - JOUR T1 - Diagenetic changes in Lake Superior sediments as seen from FTIR and 2D correlation spectroscopy JF - Organic Geochemistry Y1 - 2013 A1 - Li, Hongyu A1 - Minor, Elizabeth C. A1 - Zigah, Prosper K. AB - Isotopic and elemental analysis, Fourier transform infrared spectroscopy (FTIR), principal components analysis (PCA) and two dimensional (2D) correlation analysis, where core depth was used as perturbation, were used to study the diagenesis of organic matter (OM) in Lake Superior sediments. Changes in OM composition were examined at five lake stations over a depth range of 0–10 cm. PCA results show that depth-related changes among sites are similar, leading to an increased contribution from inorganic (and possibly refractory aromatic organic) components at each site, and a loss of contribution from other organic components. Synchronous spectra reveal that aliphatic esters and carbohydrates are degraded significantly with increasing depth, leading to an increased contribution from clay/biogenic silica/inactive carbohydrates. Asynchronous spectra show that, in general, carboxyl groups, including aliphatic ester and amide in protein, are degraded first, followed by a group of carbohydrates and then aromatic compounds and/or the SiO framework in clay and biogenic silica. Site dependent compositional variation occurs and appears to be influenced by topography and geology, e.g. the delivery of a larger load of terrestrial inorganic silicate minerals to certain sites and re-suspension/re-deposition, leading to less intensive down core variation at mid-lake central and eastern basin sites. The study demonstrates the usefulness of FTIR coupled with PCA and 2D correlation approaches for exploring structural changes in sedimentary material during diagenesis. VL - 58 UR - http://www.sciencedirect.com/science/article/pii/S0146638013000533 N1 - id: 2319 JO - Diagenetic changes in Lake Superior sediments as seen from FTIR and 2D correlation spectroscopy ER - TY - JOUR T1 - Distribution of Radiocarbon Ages in Soil Organic Matter by Thermal Fractionation JF - Radiocarbon Y1 - 2013 A1 - Plante, Alain F. A1 - Beaupré, Steven R. A1 - Roberts, Mark L. A1 - Baisden, Troy VL - 55 IS - 2-3 N1 - id: 2346; PT: J; TC: 0; UT: WOS:000325752100093 JO - Distribution of Radiocarbon Ages in Soil Organic Matter by Thermal Fractionation ER - TY - JOUR T1 - The Duxbury Sunken Forest-Constraints for Local, Late Holocene Environmental Changes Resulting from Marine Transgression, Duxbury Bay, Eastern Massachusetts, USA JF - JOURNAL OF COASTAL RESEARCH Y1 - 2013 A1 - Gontz, Allen M. A1 - Maio, Christopher V. A1 - Rueda, Laura KW - Cape Cod Bay KW - Coastal evolution KW - paleoforest KW - Radiocarbon dating KW - sea level KW - tree stumps AB - The present marine transgression has forced geological and ecological zones vertically higher and landward since the late Pleistocene. A recent investigation in Duxbury Bay, Massachusetts, identified 18 Juniperus virginiana tree stumps emergent on an intertidal flat immediately seaward of a small marsh and pond situated between two eroding drumlins. The position of each stump was mapped with global positioning system (GPS), and its elevation with respect to mean lower low water was surveyed. Samples were selected from four stumps with elevations ranging from 2.03 and 0.75 m above mean lower low water for radiocarbon dating. The samples returned calibrated ages between 2219 +/- 94 and 2867 +/- 79 cal YBP, with the topographically highest sample returning the youngest date. Stump positions suggest a landscape gradient of 1.4 mm/yr between 2000 and 3000 cal YBP. The results are comparable with high-resolution studies of sea level in eastern Massachusetts for the same time period. Comparison of the youngest paleostumps with modern living trees suggests a dramatic change in the landscape gradient, an increase to 1.8 mm/yr. While this is contrary to sea-level studies nearby, it may represent an increase in the energetics of Duxbury Bay and resultant coastal erosion as the bay floods. The site can be used to put the impacts of changing sea-level rates into a landscape evolution framework. VL - 29 ER - TY - JOUR T1 - Environmental isotopes and noble gases in the deep aquifer system of Kazan Trona Ore Field, Ankara, central Turkey and links to paleoclimate JF - Quaternary Research Y1 - 2013 A1 - Arslan, Sebnem A1 - Yazicigil, Hasan A1 - Stute, Martin A1 - Schlosser, Peter AB - Environmental isotopes and noble gases in groundwater samples from the Kazan Trona Ore Field are studied to establish the temperature change between the Holocene and the late Pleistocene. Noble gas temperatures (NGTs) presented in this study add an important facet to the global paleotemperature map in the region between Europe and North Africa. The groundwater system under investigation consists of three different aquifers named shallow, middle and deep in which δ18O and δ2H vary from − 8.10‰ to − 12.80‰ and from − 60.89‰ to − 92.60‰ VSMOW, respectively. The average isotopic depletion between unconfined and confined parts of the system is − 2.5‰ in δ18O and − 20‰ in δ2H. It is not possible to explain this depletion solely with the elevation effect. Recharge temperatures derived from dissolved atmospheric noble gases reflect the current average yearly ground temperatures (13°C) for samples collected near the recharge area but are 3 to 8°C lower than today's temperatures in the deep aquifer system. Low 14C activities and high He excesses in the confined parts of the aquifer system suggest that the water in the deep aquifer was recharged during the last Pleistocene under considerably cooler climatic conditions. VL - 79 UR - http://www.sciencedirect.com/science/article/pii/S0033589412001561 IS - 2 N1 - id: 2269 JO - Environmental isotopes and noble gases in the deep aquifer system of Kazan Trona Ore Field, Ankara, central Turkey and links to paleoclimate ER - TY - JOUR T1 - Evidence for a transgressive barrier within a regressive strandplain system: Implications for complex coastal response to environmental change JF - Sedimentology Y1 - 2013 A1 - Hein, Christopher J. A1 - FitzGerald, Duncan M. A1 - Cleary, William J. A1 - ALBERNAZ, MARCIO B. A1 - De MENEZES, JOAO THADEU A1 - Klein, Antonio H. da F. AB - Clastic, depositional strandplain systems have the potential to record changes in the primary drivers of coastal evolution: climate, sea-level, and the frequency of major meteorological and oceanographic events. This study seeks to use one such record from a southern Brazilian strandplain to highlight the potentially-complex nature of coastal sedimentological response to small changes in these drivers. Following a 2 to 4 m highstand at ca 5·8 ka in southern Brazil, falling sea-level reworked shelf sediment onshore, forcing coastal progradation, smoothing the irregular coastline and forming the 5 km wide Pinheira Strandplain, composed of ca 500 successive beach and dune ridges. Sediment cores, grab samples and >11 km of ground-penetrating radar profiles reveal that the strandplain sequence is composed of well-sorted, fine to very-fine quartz sand. Since the mid-Holocene highstand, the shoreline prograded at a rate of ca 1 to 2 m yr−1 through the deposition of a 4 to 6 m thick shoreface unit; a 1 to 3 m thick foreshore unit containing ubiquitous ridge and runnel facies; and an uppermost beach and foredune unit. However, the discovery of a linear, 100 m wide barrier ridge with associated washover units, a 3 to 4 m deep lagoon and 250 m wide tidal inlet within the strandplain sequence reveals a period of shoreline transgression at 3·3 to 2·8 ka during the otherwise regressive developmental history of the plain. The protected nature of Pinheira largely buffered it from changes in precipitation patterns, wave energy and fluvial sediment supply during the time of its formation. However, multiple lines of evidence indicate that a change in the rate of relative sea-level fall, probably due to either steric or ice-volume effects, may have affected this coastline. Thus, whereas these other potential drivers cannot be fully discounted, this study provides insights into the complexity of decadal-scale to millennial-scale coastal response to likely variability in sea-level change rates. VL - 60 UR - http://doi.wiley.com/10.1111/j.1365-3091.2012.01348.x IS - 2 ER - TY - JOUR T1 - Export of submicron particulate organic matter to mesopelagic depth in an oligotrophic gyre JF - Proceedings of the National Academy of Sciences Y1 - 2013 A1 - Close, H. G. A1 - Shah, S. R. A1 - Ingalls, A. E. A1 - Diefendorf, A. F. A1 - Brodie, E. L. A1 - Hansman, R. L. A1 - Freeman, K. H. A1 - Aluwihare, L. I. A1 - Pearson, A. KW - Biogeochemistry KW - biomarkers KW - carbon isotopes KW - Oceanography AB - Sixty percent of the world ocean by area is contained in oligotrophic gyres [Longhurst A (1995) Prog Oceanog 36:77-16], the biomass of which is dominated by picophytoplankton, including cyanobacteria and picoeukaryotic algae, as well as picoheterotrophs. Despite their recognized importance in carbon cycling in the surface ocean, the role of small cells and their detrital remains in the transfer of particulate organic matter (POM) to the deep ocean remains disputed. Because oligotrophic marine conditions are projected to expand under current climate trends, a better understanding of the role of small particles in the global carbon cycle is a timely goal. Here we use the lipid profiles, radiocarbon, and stable carbon isotopic signatures of lipids from the North Pacific Subtropical Gyre to show that in the surface ocean, lipids from submicron POM (here called extra-small POM) are distinct from larger classes of suspended POM. Remarkably, this distinct extra-small POM signature dominates the total lipids collected at mesopelagic depth, suggesting that the lipid component of mesopelagic POM primarily contains the exported remains of small particles. Transfer of submicron material to mesopelagic depths in this location is consistent with model results that claim the biological origin of exported carbon should be proportional to the distribution of cell types in the surface community, irrespective of cell size [Richardson TL, Jackson GA (2007) Science 315:838-840]. Our data suggest that the submicron component of exported POM is an important contributor to the global biological pump, especially in oligotrophic waters. VL - 110 UR - http://www.pnas.org/cgi/doi/10.1073/pnas.1217514110https://syndication.highwire.org/content/doi/10.1073/pnas.1217514110 IS - 31 ER - TY - JOUR T1 - Extensive recession of Cordillera Darwin glaciers in southernmost South America during Heinrich Stadial 1 JF - Quaternary Science Reviews Y1 - 2013 A1 - Hall, Brenda L. A1 - Porter, Charles T. A1 - Denton, George H. A1 - Lowell, Thomas V. A1 - Bromley, Gordon R. M. AB - The geographic expression and phasing of events during the last termination are important for isolating mechanisms that caused Earth to emerge from the last ice age. Heinrich Stadial 1 (HS1; 14,600–18,000 yr BP) is a key because of the central role that its far-field effects had on the last termination in the Southern Hemisphere. Here, we present new data from Cordillera Darwin that show rapid glacier recession in southern South America during HS1. This retreat was coeval with ice recession elsewhere in South America and New Zealand, with increased upwelling in the Southern Ocean, with warming of SSTs offshore of Chile, and with a rise in atmospheric CO2. Together, these data indicate a coherent and rapid response to the effects of HS1 in the middle and high latitudes of the Southern Hemisphere. VL - 62 UR - http://www.sciencedirect.com/science/article/pii/S0277379112005057 N1 - id: 2331 JO - Extensive recession of Cordillera Darwin glaciers in southernmost South America during Heinrich Stadial 1 ER - TY - JOUR T1 - First high-resolution marinopalynological stratigraphy of Late Quaternary sediments from the central part of the Bulgarian Black Sea area JF - Advancing Pleistocene and Holocene climate change research in the Carpathian-Balkan region Y1 - 2013 A1 - Filipova-Marinova, Mariana A1 - Pavlov, Danail A1 - Coolen, Marco A1 - Giosan, Liviu AB - Spores, pollen and dinoflagellate cysts of Late Pleistocene and Holocene sediments were analyzed from Giant Gravity Core 18 from the Black Sea continental slope, recovered from a water depth of 971 m. The investigated length of the core is 203.5 cm. It includes 3 lithological units: light grey clay, sapropels and coccolith-bearing ooze. The core was sampled at 5–10 cm intervals. Sampling of the interval 141.5–126 cm was carried out at every cm. AMS radiocarbon dating of bulk organic carbon was performed on 18 selected sediment layers. This chronological data allowed the first high-resolution pollen stratigraphy of Late Quaternary sediments from the western Black Sea area to be presented. The percentage spore–pollen diagram is divided into 6 local pollen assemblage zones. The trends in the vegetation dynamics and climate changes and the early history of migration of the majority of the arboreal taxa that nowadays occur in the Eastern Balkan Range were traced out. The palynological record suggests that open oak forests were spread in the Eastern Balkan Range at the beginning of the Holocene and shows early migration of the major temperate arboreal species such as Quercus, Ulmus, Tilia and Carpinus betulus. This vegetation palaeosuccession continues with the spreading of mixed oak forests from 8950 until 2620 cal. BP (8650 ± 40 until 3120 ± 35 14C BP) followed by destructive changes due to human impact and climate deterioration. A cooling of Holocene climate that is well known in the North Atlantic region as the “8200 yrs cold event” is identified for the first time in marine records from the Bulgarian Black Sea area. The assemblages of dinoflagellate cysts and acritarchs were investigated to provide a reconstruction of surface seawater salinity and surface seawater temperature changes. Two main dinoflagellate cyst assemblages, one dominated by fresh- to brackish water species such as Spiniferites cruciformis and Pyxidinopsis psilata and a subsequent one, that is characterized by euryhaline marine Mediterranean species such as Lingulodinium machaerophorum, Spiniferites belerius, Spiniferites bentorii, Operculodinium centrocarpum and acritarchs Cymatiosphaera globulosa testified a change in SSS from low salinity ( VL - 293 UR - http://www.sciencedirect.com/science/article/pii/S1040618212003229 N1 - id: 2330 JO - First high-resolution marinopalynological stratigraphy of Late Quaternary sediments from the central part of the Bulgarian Black Sea area ER - TY - JOUR T1 - A gas-accepting ion source for Accelerator Mass Spectrometry: Progress and applications JF - Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms Y1 - 2013 A1 - Roberts, M. L. A1 - von Reden, K. F. A1 - Burton, J. R. A1 - McIntyre, C. P. A1 - Beaupre, S. R. AB - The National Ocean Sciences Accelerator Mass Spectrometry (NOSAMS) facility at the Woods Hole Oceanographic Institution has developed an Accelerator Mass Spectrometry (AMS) system designed specifically for the analysis of 14C in a continuously flowing stream of carrier gas. A key part of the system is a gas-accepting microwave ion source. Recently, substantial progress has been made in the development of this source, having achieved ion currents rivaling that of a traditional graphite source (albeit at relatively low efficiency). Details and present performance of the gas source are given. Additionally, representative results obtained from coupling the source to both a gas chromatograph and gas bench are presented. VL - 294 N1 - id: 2161 JO - A gas-accepting ion source for Accelerator Mass Spectrometry: Progress and applications ER - TY - JOUR T1 - Great longevity of speckled hind ( Epinephelus drummondhayi), a deep-water grouper, with novel use of postbomb radiocarbon dating in the Gulf of Mexico JF - Canadian Journal of Fisheries and Aquatic Sciences Y1 - 2013 A1 - Andrews, Allen H. A1 - Barnett, Beverly K. A1 - Allman, Robert J. A1 - Moyer, Ryan P. A1 - Trowbridge, Hannah D. A1 - Gillanders, Bronwyn AB - Growth characteristics are poorly understood for speckled hind (Epinephelus drummondhayi), a tropical deep-water grouper of economic importance that is considered overfished. Age has been validated for early growth, but the validity of adult age estimates is unknown. A few studies of growth zones in otoliths have revealed maximum age estimates of 15–35 years, which have been uncritically assumed as longevity. To answer questions about adult age, bomb radiocarbon dating was used to provide validated age estimates. A novel aspect of this study was use of the postbomb radiocarbon decline period (ca. 1980–2004) to age younger fish, an approach that was validated with known-age otoliths. Bomb radiocarbon dating provided valid length-at-age estimates ranging from ∼5 years to more than 45 years. Age was unexpectedly greater than previous estimates for more than half the fish used in this study, and longevity may approach 60–80 years. This study extends the utility of bomb radiocarbon dating by more than 20 years and adds to the growing perspective that deep-water tropical fishes can be long-lived VL - 70 UR - http://www.nrcresearchpress.com/doi/abs/10.1139/cjfas-2012-0537 IS - 8 ER - TY - JOUR T1 - Heightened hurricane activity on the Little Bahama Bank from 1350 to 1650 AD JF - Elsevier Y1 - 2013 A1 - van Hengstum, P.J. A1 - Donnelly, J.P. A1 - Toomey, M.R A1 - Albury, N.A. A1 - Lane, P. A1 - Kakuk, B. KW - Abaco KW - Bahamas KW - Blue hole KW - hurricanes KW - Paleotempestology AB - Deciphering how the climate system has controlled North Atlantic tropical cyclone activity through the Holocene will require a larger observational network of prehistoric hurricane activity. Problematically, the tropical North Atlantic is dominated by carbonate landscapes that typically preserve poorer quality coastal sediment records in comparison to their temperate-region counterparts (e.g., sedimentation continuity and rate). Coastal karst basins (CKBs), such as sinkholes, blueholes, and underwater caves, are widely distributed on carbonate platforms and contain overlooked sedimentary records. Here we present a millennium of hurricane deposits on the Little Bahama Bank archived in a 165 cm core that was extracted from 69 m below sea level in a bluehole on Great Abaco Island, The Bahamas. The coarse- grained overwash deposits associated with both hurricanes Jeanne (2004) and Floyd (1999) were identified using radioisotopes (137Cs,14 C,210Pb), and indicate that the bluehole is sensitive to hurricane- induced sedimentation. Over the last millennium, the Little Bahama Bank experienced heightened hurricane activity from 1350 to 1650 AD. The simplest explanation for this active interval is that favorable climate conditions (El Niño, West African Monsoon, and sea surface temperatures) encouraged North Atlantic hurricane activity at that time. However, asynchronous hurricane activity at similar latitudes in the North Atlantic and Gulf of Mexico suggest that regional oceanography has modulated or amplified regional hurricane activity over the last millennium. VL - 86 ER - TY - JOUR T1 - Heterogeneous rupture in the great Cascadia earthquake of 1700 inferred from coastal subsidence estimates JF - Journal of Geophysical Research: Solid Earth Y1 - 2013 A1 - Wang, Pei-Ling A1 - Engelhart, Simon E. A1 - Wang, Kelin A1 - Hawkes, Andrea D. A1 - Horton, Benjamin P. A1 - Nelson, Alan R. A1 - Witter, Robert C. AB - Past earthquake rupture models used to explain paleoseismic estimates of coastal subsidence during the great A.D. 1700 Cascadia earthquake have assumed a uniform slip distribution along the megathrust. Here we infer heterogeneous slip for the Cascadia margin in A.D. 1700 that is analogous to slip distributions during instrumentally recorded great subduction earthquakes worldwide. The assumption of uniform distribution in previous rupture models was due partly to the large uncertainties of then available paleoseismic data used to constrain the models. In this work, we use more precise estimates of subsidence in 1700 from detailed tidal microfossil studies. We develop a 3-D elastic dislocation model that allows the slip to vary both along strike and in the dip direction. Despite uncertainties in the updip and downdip slip extensions, the more precise subsidence estimates are best explained by a model with along-strike slip heterogeneity, with multiple patches of high-moment release separated by areas of low-moment release. For example, in A.D. 1700, there was very little slip near Alsea Bay, Oregon (~44.4°N), an area that coincides with a segment boundary previously suggested on the basis of gravity anomalies. A probable subducting seamount in this area may be responsible for impeding rupture during great earthquakes. Our results highlight the need for more precise, high-quality estimates of subsidence or uplift during prehistoric earthquakes from the coasts of southern British Columbia, northern Washington (north of 47°N), southernmost Oregon, and northern California (south of 43°N), where slip distributions of prehistoric earthquakes are poorly constrained. VL - 118 UR - http://doi.wiley.com/10.1002/jgrb.50101 IS - 5 ER - TY - JOUR T1 - A High-Throughput, Low-Cost Method for Analysis of Carbonate Samples for C-14 JF - Radiocarbon Y1 - 2013 A1 - Roberts, Mark L. A1 - Beaupré, Steven R. A1 - Burton, Joshua R. VL - 55 IS - 2-3 N1 - id: 2345; PT: J; TC: 0; UT: WOS:000325752100044 JO - A High-Throughput, Low-Cost Method for Analysis of Carbonate Samples for C-14 ER - TY - JOUR T1 - The Holocene onset in the southwestern South Atlantic JF - Palaeogeography, Palaeoclimatology, Palaeoecology Y1 - 2013 A1 - Pivel, M. A. G. A1 - Santarosa, A. C. A. A1 - Toledo, F. A. L. A1 - Costa, K. B. AB - In this paper we present a paleoceanographic reconstruction of the southwestern South Atlantic for the past 13 kyr based on faunal and isotopic analysis of planktonic foraminifera from a high-resolution core retrieved at the South Brazil Bight continental slope. Our record indicates that oceanographic changes in the southwestern South Atlantic during the onset of the Holocene were comparable in strength to those that occurred during the Younger Dryas. Full interglacial conditions started abruptly after 8.2 kyr BP with a sharp change in faunal composition and surface hydrography (SST and SSS). Part of the observed events may be explained in terms of changes in thermohaline circulation while the other part suggests a dominant role of winds. Our data indicate that during the Early Holocene upwelling was significantly strengthened in the South Brazil Bight promoting high productivity and preventing the establishment of the typically interglacial menardiiform species. In general terms, oceanographic changes recorded by core KF02 occurred in synchrony with Antarctica's climate. VL - 374 UR - http://www.sciencedirect.com/science/article/pii/S0031018213000357 N1 - id: 2323 JO - The Holocene onset in the southwestern South Atlantic ER - TY - JOUR T1 - Holocene temperature history at the western Greenland Ice Sheet margin reconstructed from lake sediments JF - Quaternary Science Reviews Y1 - 2013 A1 - Axford, Yarrow A1 - Losee, Shanna A1 - Briner, Jason P. A1 - Francis, Donna R. A1 - Langdon, Peter G. A1 - Walker, Ian R. AB - Predicting the response of the Greenland Ice Sheet to future climate change presents a major challenge to climate science. Paleoclimate data from Greenland can provide empirical constraints on past cryospheric responses to climate change, complementing insights from contemporary observations and from modeling. Here we examine sedimentary records from five lakes near Jakobshavn Isbræ in central West Greenland to investigate the timing and magnitude of major Holocene climate changes, for comparison with glacial geologic reconstructions from the region. A primary objective of this study is to constrain the timing and magnitude of maximum warmth during the early to middle Holocene positive anomaly in summer insolation. Temperature reconstructions from subfossil insect (chironomid) assemblages suggest that summer temperatures were warmer than present by at least 7.1 ka (the beginning of the North Lake record; ka = thousands of years before present), and that the warmest millennia of the Holocene occurred in the study area between 6 and 4 ka. Previous studies in the Jakobshavn region have found that the local Greenland Ice Sheet margin was most retracted behind its present position between 6 and 5 ka, and here we use chironomids to estimate that local summer temperatures were 2–3 °C warmer than present during that time of minimum ice sheet extent. As summer insolation declined through the late Holocene, summer temperatures cooled and the local ice sheet margin expanded. Gradual, insolation-driven millennial-scale temperature trends in the study area were punctuated by several abrupt climate changes, including a major transient event recorded in all five lakes between 4.3 and 3.2 ka, which overlaps in timing with abrupt climate changes previously documented around the North Atlantic region and farther afield at ∼4.2 ka. VL - 59 UR - https://doi.org/10.1016/j.quascirev.2012.10.024 ER - TY - JOUR T1 - Holocene variability in hydrology, vegetation, fire, and eolian activity in the Nebraska Sand Hills, USA JF - The Holocene Y1 - 2013 A1 - Schmieder, Jens A1 - Fritz, Sherilyn C A1 - Grimm, Eric C A1 - Jacobs, Kimberly C A1 - Brown, Kendrick J A1 - Swinehart, James B A1 - Porter, Stephen C KW - diatoms KW - drought KW - Holocene climate change KW - lakes KW - Nebraska Sand Hills KW - pollen AB - This study combined multiple aquatic and terrestrial proxies, including diatoms, pollen, grain size, and bulk-sediment chemistry to reconstruct the history of three lake sites located in the central Sand Hills of Nebraska, USA. Long-term changes in effective moisture are evident at all sites, with significant changes occurring at ~6000, ~4000, and ~ 2000 cal. yr BP. Both aquatic and terrestrial indicators suggest that effective moisture was low between 10,000 and ~6000 cal. yr BP, and that this time interval was the driest period of the Holocene. The dominance of benthic and tychoplanktic diatom taxa indicates relatively shallow lake-level, high sand influx indicates moderately high eolian activity, and the pollen assemblage suggests xeric grasslands with abundant mud flats. About 6000 cal. yr BP, all three sites experienced an increase in effective moisture. Lake-level rise is indicated by increases in planktic and tychoplanktic diatoms relative to benthic taxa, while greater abundance of grass pollen and charcoal, and decreased eolian flux indicate stabilized dunes with dense vegetation sufficient to fuel local fires. A significant hydrologic shift recorded at all sites occurred at ~4000 cal. yr BP. This event was characterized by substantial lake-level rise, yet decreased grass cover and fire frequency, and increased eolian activity. Water-table rise may have been caused by a combination of factors including: (1) formation of dune-dams that blocked old drainage channels, (2) reduced grass cover and hence reduced evapotranspiration, and (3) changes in the frequency and duration of drought. The most likely cause(s) of the differential response of the terrestrial and aquatic systems at this time is not clear, none-the-less the late Holocene was not nearly as dry as the interval prior to 6000 cal. yr BP. The last ~2000 yr were characterized by several short-term fluctuations in lake level, including an interval of drought between 950 and 750 cal. yr BP, coincident with increased eolian activity during the latter part of the Medieval Climatic Anomaly. VL - 23 UR - http://journals.sagepub.com/doi/10.1177/0959683612463100 IS - 4 ER - TY - JOUR T1 - Improving a gas ion source for 14C AMS JF - Proceedings of the Twelfth International Conference on Accelerator Mass Spectrometry, Wellington, New Zealand, 20-25 March 2011 Y1 - 2013 A1 - Fahrni, S. M. A1 - Wacker, L. A1 - Synal, H. A. A1 - Szidat, S. AB - For more than 4 years, gaseous samples of 1–50 μg carbon have been routinely measured with the gas ion source of the small AMS (Accelerator Mass Spectrometer) facility MICADAS (MIni CArbon DAting System) at ETH Zurich. The applied measurement technique offers a simple and fast way of 14C measurements without the need of sample graphitization. A major drawback of gaseous 14C measurements, however, is the relatively low negative ion current, which results in longer measurement times and lower precision compared to graphitized samples. In December 2009, a new, improved Cs sputter ion source was installed at MICADAS and we began to optimize conditions for the measurement of gaseous samples. 12C− currents from the new ion source were improved from initially 3 to 12–15 μA for routine measurements and the negative ion yield was increased by a factor of 2, reaching 8% on average during routine operation. Moreover, the new measurement settings enable a doubled CO2 flow, thus substantially reducing measurement times. The achieved performance allows closing the sample size gap between gaseous and solid samples and makes the gas ion source a promising tool for dating with a measurement precision of 5‰ on samples as small as 50 μg carbon. VL - 294 UR - http://www.sciencedirect.com/science/article/pii/S0168583X12003394 N1 - id: 2304 JO - Improving a gas ion source for 14C AMS ER - TY - JOUR T1 - The Last Glacial: Insights from continuous coring on the New Jersey continental shelf JF - Marine Geology Y1 - 2013 A1 - Christensen, Beth A. A1 - Alexander, Clark A1 - Goff, John A. A1 - Turner, R. Jessica A1 - Austin Jr, James A. AB - Sedimentation on the Pleistocene New Jersey (NJ) shelf is complex, and results from the interaction of processes chiefly driven by glacioeustatic change. Erosion, non-deposition, downcutting and infilling combine to produce a complicated set of reflectors and sedimentary units that are best interpreted in the shallow subsurface with the aid of high resolution seismic reflection profiling. The highly variable lithology on the shelf has historically been an impediment to significant core recovery in this challenging environment. Coring using the AHC-800 drilling system provided continuous downcore recovery at three sites on the outer shelf. The sites targeted fluvial incisions, channel fill and exposure surfaces associated with glacial lowstands. The exceptional cores were analyzed using an integrated approach. Textural and benthic foraminiferal data were evaluated to determine the environment of deposition and estimate paleodepth. Carbon dating of wood and shell material provides the temporal framework for interpretation and K–Ar dating of hornblende crystals provides insights into the source region of sediments. Our integrated analysis indicates the NJ shelf was a dynamic environment from at least 45 ka. Estimates of sea level from this study are consistent with other studies from the Pleistocene NJ Margin. The oldest sediments (> 36 k.y.) recovered by drilling came from below (Site 3) and above (Site 1) R, a time-transgressive regional unconformity. Best estimates are for formation of R on the mid shelf, between MIS3b and the MIS3b/a transition, ~ 45 ka, under neritic conditions. Channels were incised during late MIS2, between ~ 30 and 16 ka. Channel infill was focused in a narrow time frame, during latest MIS 2 (16–14 ka), shortly after the shoreline began to migrate landward. Rates of 1–2 cm/yr are consistent with modern fluvial/ estuarine sedimentation rates. Reinvigoration and infilling of the channels around 14 ka is associated with meltwater pulse 1A. We find no evidence at our study area for jökelhlaup deposition associated with the Intra-Allerød cold period ~ 13 ka. Regional deposition (channel infill and interfluvial regions) was underway by latest MIS2/early MIS1 as sea level transgressed the shelf. The uppermost sediments are of Holocene to Recent age and are routinely and likely rapidly reworked, eroded and mixed by shelf processes. The sediment source during MIS3, as determined by hornblende age dates, was bimodal. Older sediments were derived from the Reading Prong/NJ Highlands and younger sediments were sourced from along the Hudson River. Delivery to the study area was through a more southerly paleo-Hudson position that may have resulted in formation of the outer shelf wedge through deltaic sedimentation during at least MIS 3b–3a. VL - 335 UR - http://www.sciencedirect.com/science/article/pii/S0025322712002381 N1 - id: 2317 JO - The Last Glacial: Insights from continuous coring on the New Jersey continental shelf ER - TY - JOUR T1 - Late Holocene expansion of Istorvet ice cap, Liverpool Land, east Greenland JF - Quaternary Science Reviews Y1 - 2013 A1 - Lowell, Thomas V. A1 - Hall, Brenda L. A1 - Kelly, Meredith A. A1 - Bennike, Ole A1 - Lusas, Amanda R. A1 - Honsaker, William A1 - Smith, Colby A. A1 - Levy, Laura B. A1 - Travis, Scott A1 - Denton, George H. AB - The Greenland Ice Sheet is undergoing dynamic changes that will have global implications if they continue into the future. In this regard, an understanding of how the ice sheet responded to past climate changes affords a baseline for anticipating future behavior. Small, independent ice caps adjacent to the Greenland Ice Sheet (hereinafter called “local ice caps”) are sensitive indicators of the response of Greenland ice-marginal zones to climate change. Therefore, we reconstructed late Holocene ice-marginal fluctuations of the local Istorvet ice cap in east Greenland, using radiocarbon dates of subfossil plants, 10Be dates of surface boulders, and analyses of sediment cores from both threshold and control lakes. During the last termination, the Istorvet ice cap had retreated close to its maximum Holocene position by ∼11,730 cal yr BP. Radiocarbon dates of subfossil plants exposed by recent recession of the ice margin indicate that the Istorvet cap was smaller than at present from AD 200 to AD 1025. Sediments from a threshold lake show no glacial input until the ice cap advanced to within 365 m of its Holocene maximum position by ∼AD 1150. Thereafter the ice cap remained at or close to this position until at least AD 1660. The timing of this, the most extensive of the Holocene, expansion is similar to that recorded at some glaciers in the Alps and in southern Alaska. However, in contrast to these other regions, the expansion in east Greenland at AD 1150 appears to have been very close to, if not at, a maximum Holocene value. Comparison of the Istorvet ice-cap fluctuations with Holocene glacier extents in Southern Hemisphere middle-to-high latitude locations on the Antarctic Peninsula and in the Andes and the Southern Alps suggests an out-of-phase relationship. If correct, this pattern supports the hypothesis that a bipolar see-saw of oceanic and/or atmospheric circulation during the Holocene produced asynchronous glacier response at some localities in the two polar hemispheres. VL - 63 UR - http://www.sciencedirect.com/science/article/pii/S0277379112004830 N1 - id: 2290 JO - Late Holocene expansion of Istorvet ice cap, Liverpool Land, east Greenland ER - TY - JOUR T1 - Late Holocene sedimentation and hydrologic development in a shallow coastal sinkhole on Great Abaco Island, The Bahamas JF - Quaternary International Y1 - 2013 A1 - Kovacs, Shawn E. A1 - van Hengstum, Peter J. A1 - Reinhardt, Eduard G. A1 - Donnelly, Jeffrey P. A1 - Albury, Nancy A. AB - It remains poorly understood how sea level drives environmental change and hydrographic development in coastal karst basins (underwater caves, sinkholes, blueholes, etc.) over millennial timescales. It was previously hypothesized that coastal karst basins (CKBs) transition from vadose, to littoral, then anchialine, and finally submarine environments as sea-level rise inundates coastal karst landscapes, but the initial flooding event of CKBs remains challenging to sample. Runway Sinkhole hosts a modern anchialine ecosystem located ∼225 m from Great Abaco Island coastline in The Bahamas, and its shallow water depth (∼1.8 mbsl) permits an investigation into the early environmental evolution and hydrographic development in a CKBs after inundation by sea-level rise. Four sediment cores were collected from Runway Sinkhole, and late Holocene environmental change was reconstructed with benthic foraminiferal paleoecology, organic matter geochemistry (OM%, δ13Corg, and C:N), X-radiography, and radiocarbon dating. Despite some uncertainties associated with the chronology, it appears that Holocene sea-level rise initially flooded Runway Sinkhole and created a littoral environment at least by ∼3.9 ka, whereafter a detrital peat deposit accumulated in the sinkhole. This detrital peat had a high organic matter content (mean 88%), a δ13Corg value indicative of organic matter derived from C3 plants including mangroves (−28‰), and an unknown calcareous microfossil suggestive of a non-marine habitat in the sinkhole. A shift to carbonate sand deposition, organic matter with more marine-influenced δ13Corg values (−23‰), and expansion of euryhaline (Bolivina striatula, Elphidium poeyanum, and Triloculina bermudezi) and anchialine (Physalidia simplex and Conicospirillina exleyi) benthic foraminifera at ∼1.2 ka marks the onset of modern anchialine environmental conditions at the sediment–water interface (∼1.8 mbsl). These results suggest that relative sea-level rise in the Bahamas forced environmental change in Runway sinkhole at ∼1.2 ka, and indicate that peat deposits in coastal sinkholes must be verified as in-situ before being utilized as sea-level indicators. VL - 317 UR - http://linkinghub.elsevier.com/retrieve/pii/S1040618213007507http://api.elsevier.com/content/article/PII:S1040618213007507?httpAccept=text/xmlhttp://api.elsevier.com/content/article/PII:S1040618213007507?httpAccept=text/plain ER - TY - JOUR T1 - Late Pleistocene–Holocene sedimentary records of climate and lake-level changes in Lake Hazar, eastern Anatolia, Turkey JF - Terrestrial archives of the Mediterranean Y1 - 2013 A1 - Eriş, Kürşad Kadir AB - The sedimentary record of Lake Hazar has been documented by detailed seismo- and chronostratigraphic analyses using high-resolution seismic profiles and sediment cores. In this study, two main seismic stratigraphic units can be confidently correlated with sediment cores using lithology and physical properties. As a result of radiocarbon AMS dating, these sedimentary units presumably cover the period from the late Pleistocene to Holocene. The Holocene sequence of the lake infills can be subdivided into five subunits, each subject to distinctive hydrological and sedimentological processes due to fluctuating lake level. The elevations of these deposits including coastal paleo-terraces provide history of the lake level changes. In Lake Hazar, the maximum lowstand lake level occurred during the transition from the Younger Dryas to Holocene, when the −73 m wave-cut terrace was formed as the main shelf-crossing unconformity surface. The beginning of the Holocene was associated with a abrupt lake level rise and resultant deepening. Analysis of the Lake Hazar terraces has the potential to provide complementary data on the chronology of past lake level and lake volume changes, and their link to past climate change. The continued rising lake level during beginning of the Holocene was modulated by stillstands at −63 m and −56 m, as indicated by broad coastal paleo-terraces across the northern shelf. The main shelf-margin sedimentary system for the Holocene period is composed of three distinct buried deltaic-complexes that were presumably sourced from the Kürkçayı River, the largest input into Lake Hazar. The 3rd millennium crisis at around 3 14C ka BP is recorded in the seismic and core data when the cold and dry climatic condition gave rise to a significant lake level drop. VL - 302 UR - http://www.sciencedirect.com/science/article/pii/S1040618212033915 N1 - id: 2322 JO - Late Pleistocene–Holocene sedimentary records of climate and lake-level changes in Lake Hazar, eastern Anatolia, Turkey ER - TY - JOUR T1 - Late Wisconsinan glaciation and postglacial relative sea-level change on western Banks Island, Canadian Arctic Archipelago JF - Quaternary Research Y1 - 2013 A1 - Lakeman, Thomas R. A1 - England, John H. AB - The study revises the maximum extent of the northwest Laurentide Ice Sheet (LIS) in the western Canadian Arctic Archipelago (CAA) during the last glaciation and documents subsequent ice sheet retreat and glacioisostatic adjustments across western Banks Island. New geomorphological mapping and maximum-limiting radiocarbon ages indicate that the northwest LIS inundated western Banks Island after ~ 31 14C ka BP and reached a terminal ice margin west of the present coastline. The onset of deglaciation and the age of the marine limit (22–40 m asl) are unresolved. Ice sheet retreat across western Banks Island was characterized by the withdrawal of a thin, cold-based ice margin that reached the central interior of the island by ~ 14 cal ka BP. The elevation of the marine limit is greater than previously recognized and consistent with greater glacioisostatic crustal unloading by a more expansive LIS. These results complement emerging bathymetric observations from the Arctic Ocean, which indicate glacial erosion during the Last Glacial Maximum (LGM) to depths of up to 450 m. VL - 80 UR - http://www.sciencedirect.com/science/article/pii/S0033589413000197 IS - 1 N1 - id: 2282 JO - Late Wisconsinan glaciation and postglacial relative sea-level change on western Banks Island, Canadian Arctic Archipelago ER - TY - JOUR T1 - Long-term variations in Iceland–Scotland overflow strength during the Holocene JF - Climate of the Past Y1 - 2013 A1 - Thornalley, D. J. R. A1 - Blaschek, M. A1 - Davies, F. J. A1 - Praetorius, S. A1 - Oppo, D. W. A1 - McManus, J. F. A1 - Hall, I. R. A1 - Kleiven, H. A1 - Renssen, H. A1 - McCave, I. N. AB - The overflow of deep water from the Nordic seas into the North Atlantic plays a critical role in global ocean circulation and climate. Approximately half of this overflow occurs via the Iceland–Scotland (I–S) overflow, yet the history of its strength throughout the Holocene (~ 0–11 700 yr ago, ka) is poorly constrained, with previous studies presenting apparently contradictory evidence regarding its long-term variability. Here, we provide a comprehensive reconstruction of I–S overflow strength throughout the Holocene using sediment grain size data from a depth transect of 13 cores from the Iceland Basin. Our data are consistent with the hypothesis that the main axis of the I–S overflow on the Iceland slope was shallower during the early Holocene, deepening to its present depth by ~ 7 ka. Our results also reveal weaker I–S overflow during the early and late Holocene, with maximum overflow strength occurring at ~ 7 ka, the time of a regional climate thermal maximum. Climate model simulations suggest a shoaling of deep convection in the Nordic seas during the early and late Holocene, consistent with our evidence for weaker I–S overflow during these intervals. Whereas the reduction in I–S overflow strength during the early Holocene likely resulted from melting remnant glacial ice sheets, the decline throughout the last 7000 yr was caused by an orbitally induced increase in the amount of Arctic sea ice entering the Nordic seas. Although the flux of Arctic sea ice to the Nordic seas is expected to decrease throughout the next century, model simulations predict that under high emissions scenarios, competing effects, such as warmer sea surface temperatures in the Nordic seas, will result in reduced deep convection, likely driving a weaker I–S overflow. VL - 9 UR - http://www.clim-past.net/9/2073/2013 IS - 5 ER - TY - JOUR T1 - Maintenance of large deltas through channelization: Nature vs. humans in the Danube delta JF - Anthropocene Y1 - 2013 A1 - Giosan, Liviu A1 - Constantinescu, Stefan A1 - Filip, Florin A1 - Deng, Bing AB - Over the last half century, while the total sediment load of the Danube dramatically decreased due to dam construction on tributaries and its main stem, a grand experiment was inadvertently run in the Danube delta: the construction of a dense network of canals, which almost tripled the water discharge toward the interior of the delta plain. We use core-based and chart-based sedimentation rates and patterns to explore the delta transition from the natural to an anthropogenic regime, to understand the effects of far-field damming and near-field channelization, and to construct a conceptual model for delta development as a function sediment partition between the delta plain and the delta coastal fringe. We show that sediment fluxes increased to the delta plain due to channelization counteracting sea level rise. In turn, the delta coastal fringe was most impacted by the Danube's sediment load collapse. Furthermore, we suggest that morphodynamic feedbacks at the river mouth are crucial in trapping sediment near the coast and constructing wave-dominated deltas or lobes. Finally, we suggest that increased channelization that mimics and enhances natural processes may provide a simple solution for keeping other delta plains above sea level and that abandonment of wave-dominated lobes may be the most long term efficient solution for protecting the internal fluvial regions of deltas and provide new coastal growth downcoast. VL - 1 UR - http://www.sciencedirect.com/science/article/pii/S221330541300012X JO - Maintenance of large deltas through channelization: Nature vs. humans in the Danube delta ER - TY - JOUR T1 - Middle Wisconsin glacial advance into the Appalachian Plateau, Sixmile Creek, Tompkins Co., NY JF - Quaternary Research Y1 - 2013 A1 - Karig, Daniel E. A1 - Miller, Norton G. AB - Areal mapping of the middle Wisconsin varved clay site along Sixmile Creek near Ithaca, New York, has revealed a much more widespread and varied array of sediments than previously thought. Lacustrine clays, some varved, are interbedded with sands and gravels interpreted as sub-aqueous fan deposits, and both are overlain by a deformation till. Nine radiocarbon dates indicate a 34–37 14C ka BP age for the lacustrine sediment, with the deformation till less than a few thousand years younger. Beneath this sequence is a deposit dated at ± 42 14C ka BP. Both strata represent a tundra climate with a mean July temperature of about 10°C. The Sixmile Creek deformation till must correlate with the 35 14C ka BP till along the Genesee River, 125 km to the NW, and defines a Cherrytree stade glacial advance into the Appalachian Plateau, much further south than what has generally been accepted. Such an advance would require drainage from a proglacial lake in the western Ontario basin to flow westward instead of northeastward. The Sixmile strata suggest a colder than accepted middle Wisconsin stage. Recent data indicate that this stage is one of progressive cooling, with large climatic fluctuations. VL - 80 UR - http://www.sciencedirect.com/science/article/pii/S0033589413001002 IS - 3 JO - Middle Wisconsin glacial advance into the Appalachian Plateau, Sixmile Creek, Tompkins Co., NY ER - TY - JOUR T1 - Mid-Late Holocene coastal environmental changes in southeastern Sri Lanka: New evidence for sea level variations in southern Bay of Bengal JF - QUATERNARY INTERNATIONAL Y1 - 2013 A1 - Ranasinghe, R. N. A1 - Ortiz, J. D. A1 - Moore, A. L. A1 - McAdoo, B. A1 - Wells, N. A1 - Siriwardana, C. H. E. R. A1 - Wijesundara, D. T. D. S. AB - The 2004 Indian Ocean tsunami highlighted the need to better understand the dynamics of the South Asian coastlines. Very little knowledge on paleo-coastal variability hinders the development of a paleo-tsunami chronology of the western Bay of Bengal. Also, limited sea level records for the southern Bay of Bengal are remarkably different from rest of the Indian Ocean due to alternating highstands and lowstands during mid-late Holocene. This study was undertaken to recognize how the coastal environment in tectonically stable eastern and southeastern coasts of Sri Lanka changed during mid-late Holocene and to derive evidence of sea level variability. Sediment cores were collected from Kirinda and Panama estuaries, Okanda lagoon and Vakarai beach ridge plain, situated on the eastern and southeastern coasts of Sri Lanka. Physical and chemical variations in sediments, caused by the coastal environmental changes occurred due to fluctuating eustatic sea level, were determined using X-ray fluorescence, visible reflectance, magnetic susceptibility and grain size. Chronology of events were developed using AMS C-14 dates on bulk organic matter, wood, inorganic carbonate and mollusk shells. Results suggest that key periods of transition in the coastal environment in the studied area occurred between about 7300 and 3000 BP. Submergence of coastal environments by mid-Holocene transgression began around 7300 BP. Barrier development initiated at the end of the submergence phase around 4900 BP. Onset of beach ridge development in areas with high sediment supply took place around 4000 BP and continued later than 2400 BP. Marine influence ended around 3000 BP. These coastal environmental changes suggest that Holocene transgression, which started flooding southeastern coastal lowlands, either slowed or the sea level stabilized around 4900 BP. Sea level fell down to its present level at around 3000 BP by the subsequent slow regression. Some cores carry evidence for a possible pause in the transgression or a short lowstand that ended around 5200 BR (c) 2013 Elsevier Ltd and INQUA. All rights reserved. VL - 298 ER - TY - JOUR T1 - A model for drowned terrestrial habitats with associated archeological remains in the northwestern Gulf of Maine, USA JF - Marine Geology Y1 - 2013 A1 - Kelley, Joseph T. A1 - Belknap, Daniel F. A1 - Kelley, Alice R. A1 - Claesson, Stefan H. AB - Marine geophysical techniques and geological measurement of sea-level change allow detailed mapping of seafloor archeological sites and development of models. In the northwestern Gulf of Maine, the lowstand of sea level is only at − 60 m depth, but a prolonged stasis during the late Quaternary sea-level rise, herein termed the slowstand, occurred between 11,500 and 7500 calibrated years before present (cal yr BP) at depths of 15–25 m. This slowdown caused substantial erosion of glacial deposits and formed terrestrial beaches, wetlands and lakes. These landforms attracted people, whose tools were later discovered during present day scallop-fishing activities. Our study areas at the Green Islands and Bass Harbor are within the lowstand and slowstand depth ranges, but at highly exposed and sheltered sites, respectively. The Green Islands site has lost most of its former terrestrial sediment and there is no longer any context for recovered artifacts. At the protected Bass Harbor site, the remains of eroded moraines are associated with drowned spits and a former lacustrine/estuarine basin. Cores at the Bass Harbor location encountered freshwater peat deposits and numerous shallow subtidal shell and plant fossils all deposited during the slowstand. The two most important controls on the preservation of terrestrial landforms and associated human artifacts in the northwestern Gulf of Maine are the rate of sea-level rise and degree of shelter of the site from waves. VL - 338 UR - http://www.sciencedirect.com/science/article/pii/S0025322712002502 N1 - id: 2285 JO - A model for drowned terrestrial habitats with associated archeological remains in the northwestern Gulf of Maine, USA ER - TY - JOUR T1 - Moisture and temperature changes associated with the mid-Holocene Tsuga decline in the northeastern United States JF - Quaternary Science Reviews Y1 - 2013 A1 - Marsicek, Jeremiah P. A1 - Shuman, Bryan A1 - Brewer, Simon A1 - Foster, David R. A1 - Oswald, W. Wyatt AB - A decline of hemlock (Tsuga) populations at ca 5.5 ka (thousands of calibrated radiocarbon years before 1950 AD) stands out as the most abrupt vegetation change of the Holocene in North America, but remains poorly understood after decades of study. Recent analyses of fossil pollen have revealed a concurrent, abrupt oak (Quercus) decline and increases in the abundance of beech (Fagus) and pine (Pinus) on Cape Cod in eastern Massachusetts, but the replacement of drought-tolerant oaks by moisture-sensitive beeches appears inconsistent with low lake levels in the region at the same time. The oak and beech changes are also limited to coastal areas, and the coastal-inland differences require an explanation. Here, we develop a new lake-level reconstruction from Deep Pond, Cape Cod by using a transect of sediment cores and ground-penetrating radar (GPR) profiles to constrain the past elevations of the sandy, littoral zone of the pond. The reconstruction shows that a series of multi-century episodes of low water coincide with the abrupt hemlock and oak declines, and interrupt subsequent phases of hemlock recovery. The lake-level variations equal precipitation deficits of ∼100 mm superimposed on a Holocene long moisture increase of >400 mm. However, because moisture deficits do not easily explain the oak and beech changes, we also evaluate how the climate preferences of the regional vegetation changed over time by matching the fossil pollen assemblages from Deep Pond with their modern equivalents. Reconstructions of the precipitation requirements of the vegetation correlate well even in detail with the lake-level record (r = 0.88 at Deep Pond), and indicate close tracking of effective moisture (precipitation minus evapotranspiration) by the vegetation despite the abrupt species declines, which could have decoupled climate and vegetation trends. Reconstructions of the temperature preferences of the vegetation indicate that coastal sites may have cooled by 0.5–2.5 °C after ca 5.5 ka, while inland sites warmed by 0.5–1 °C. The change in coastal temperature preferences agrees with sea surface cooling in the western Atlantic Ocean of >1 °C. Consequently, the persistence of low hemlock abundance after 5.5 ka in the northeast U.S. may have resulted from oceanic changes that produced multi-century droughts and thus delayed the post-decline recovery of hemlock populations. VL - 80 UR - http://www.sciencedirect.com/science/article/pii/S0277379113003375 JO - Moisture and temperature changes associated with the mid-Holocene Tsuga decline in the northeastern United States ER - TY - JOUR T1 - Molecular and isotopic insights into particulate organic carbon sources and dynamics in Jordan Basin, Gulf of Maine JF - Continental Shelf Research Y1 - 2013 A1 - Hwang, Jeomshik A1 - Montluçon, Daniel B. A1 - Pilskaln, Cynthia H. A1 - Eglinton, Timothy I. AB - The carbon isotope and lipid biomarker composition of suspended particles and surface sediment was measured to examine the impact of sediment supply, redistribution and post-depositional alteration processes on organic matter cycling in the Gulf of Maine, a semi-enclosed shelf sea in the northwest Atlantic. A beam attenuation profile revealed a >50 m-thick benthic nepheloid layer (BNL) in the Jordan Basin at the time of sampling (April 2006). The relatively low radiocarbon content of suspended particulate organic carbon (POC) in the BNL indicates that up to 82% of the POC in this layer was supplied from resuspension of sediment. The concentration of alkenones normalized to POC increased with increasing depth in the water column and was highest in the surface sediment. In contrast to these markers of surface ocean photoautotrophy, the vertical profiles for the concentration and composition of short-chain (C14–C18) n-alkanoic acids provided evidence for enhanced heterotrophic processes near the top of the BNL. Suspended POC samples from two depths within the BNL exhibited marked differences in radiocarbon content and fatty acid composition, suggesting that biological activity and associated processes within the BNL are vertically heterogeneous. VL - 68 UR - http://www.sciencedirect.com/science/article/pii/S0278434313002653 JO - Molecular and isotopic insights into particulate organic carbon sources and dynamics in Jordan Basin, Gulf of Maine ER - TY - JOUR T1 - Old ages of two historical Romanian trees assessed by AMS radiocarbon dating JF - Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions with Materials and Atoms Y1 - 2013 A1 - Patrut, Adrian A1 - von Reden, Karl F. A1 - Lowy, Daniel A. A1 - Patrut, Roxana T. A1 - Vaida, D. Lucian A1 - Margineanu, Dragos AB - Two large Romanian poplars are considered to be associated with significant historical events of the past. In order to verify these claims, wood samples collected from the broken trunks of the two poplars were radiocarbon dated by AMS. The oldest radiocarbon dates were found to be 275 +/- 20 bp for the black poplar of Mocod and 316 +/- 22 bp for the gray poplar of Rafaila. These values correspond to calibrated ages of 365 +/- 10 and 465 +/- 25 years, respectively. The dating results indicate old ages for the two trees, i.e., 455 years for the Mocod poplar and 560 years for the Rafaila poplar. Such age values validate historical information on the two large Romanian trees. (C) 2012 Elsevier B.V. All rights reserved. VL - 294 N1 - id: 2245; PT: J; CT: 12th International Conference on Accelerator Mass Spectrometry (AMS); CY: MAR 20-25, 2011; CL: Wellington, NEW ZEALAND; TC: 0; UT: WOS:000313234300119 JO - Old ages of two historical Romanian trees assessed by AMS radiocarbon dating ER - TY - MAP T1 - Onshore-offshore surficial geologic map of the Newburyport East and northern half of the Ipswich Quadrangles, Massachusetts Y1 - 2013 A1 - Hein, C.J. A1 - FitzGerald, D.M. A1 - Barnhardt, W.A. A1 - Stone, B.D. AB - This geologic map shows the distribution of surficial subaerial and subaqueous materials in the Newburyport East and northern half of the Ipswich 7.5' quadrangles (northeast Massachusetts) and the area of the Gulf of Maine immediately offshore, to an approximate depth of 80 m below modern mean sea level (MSL). This map was compiled from the onshore surficial geologic map of Stone et al. (2006) and the offshore surficial mapping of Barnhardt et al. (2009), and includes newly mapped shallow offshore geologic features. Onshore and offshore units are continuous across the shallow- water zone (0-20 m below MSL). The definition of map units is based on lithologic characteristics (grain size, mineralogy and structure), stratigraphic relationships and relative ages, and sedimentologic processes. The map describes the evolution of the surficial geology in terms of the sediment sources, transportation mechanisms, and depositional, post-depositional and modern processes that have acted on the late Quaternary sediments that compose these units. Cross sections are derived from subsurface data compiled from the literature and collected as part of this study. This maps supersedes MGS OFR 2011-01 JF - Geologic Map UR - https://mgs.geo.umass.edu/biblio/onshore-offshore-surficial-geologic-map-newburyport-east-and-northern-half-ipswich ER - TY - JOUR T1 - Organic carbon export from the Greenland ice sheet JF - Geochimica et Cosmochimica Acta Y1 - 2013 A1 - Bhatia, Maya P. A1 - Das, Sarah B. A1 - Xu, Li A1 - Charette, Matthew A. A1 - Wadham, Jemma L. A1 - Kujawinski, Elizabeth B. AB - Glacial meltwater exports a unique type of organic carbon to marine systems, distinct from non-glacially derived riverine export, potentially capable of stimulating downstream marine primary productivity. Here, we describe for the first time the bulk-level dissolved organic carbon (DOC) and particulate organic carbon (POC) isotopic composition of glacial meltwater draining the Greenland ice sheet (GrIS). These data, in conjunction with an earlier study that investigated the molecular-level composition of GrIS dissolved organic matter, collectively describe the concentration, radiocarbon content, and lability of organic carbon in subglacial discharge from a land-terminating outlet glacier during a melt season. By scaling up our measurements across the ice sheet, we estimate that the annual DOC flux from the GrIS (0.08 Tg/y) is equivalent to that from a small Arctic river (discharge (Q) 200 km3/y). The DOC flux is derived primarily from beneath the glacier (subglacial) (>75%) in the early season, and from surface ice-melt (up to 100%) transmitting through the subglacial environment at the peak of the meltseason. The POC flux is primarily derived from the subglacial environment throughout the meltseason. The early season (low flow) glacier discharge contains higher DOC concentrations (0.5–4.1 mg L−1), and exports more enriched carbon (Δ14CDOC ∼ −250‰) compared to the peak season (high flow) discharge, when the concentrations are lower (0.1–0.6 mg L−1) and the Δ14C is more depleted (Δ14CDOC ∼ −400‰). Conversely, the POC export (1.4–13.2 mg L−1, Δ14CPOC ∼ −250‰) shows no temporal variation in either concentration or radiocarbon content throughout the meltseason. Dissolved ion loads in concomitant samples reflected the seasonal evolution of the subglacial drainage system, confirming the influence of subglacial hydrology on the composition of the bulk carbon pools. Based on this work, we conclude that (1) different mechanisms control the DOC and POC flux from glacial systems; (2) chemically-distinct DOC pools are accessed by seasonally-evolving hydrological flow-paths; and (3) the GrIS can deliver labile carbon, which may also be 14C-depleted, to downstream proglacial and marine environments. VL - 109 UR - http://www.sciencedirect.com/science/article/pii/S0016703713000835 N1 - id: 2276 JO - Organic carbon export from the Greenland ice sheet ER - TY - JOUR T1 - Paleoclimate changes of the last 1000 yr on the eastern Qinghai–Tibetan Plateau recorded by elemental, isotopic, and molecular organic matter proxies in sediment from glacial Lake Ximencuo JF - Palaeogeography, Palaeoclimatology, Palaeoecology Y1 - 2013 A1 - Pu, Yang A1 - Nace, Trevor A1 - Meyers, Philip A. A1 - Zhang, Hucai A1 - Wang, Yongli A1 - Zhang, Chuanlun L. A1 - Shao, Xiaohua AB - Total organic carbon (Corg) and nitrogen (Ntot) concentrations and isotope compositions and n-alkane and n-alkan-ol molecular biomarker compositions were measured in two parallel sediment cores from Lake Ximencuo, a typical glacial lake on the eastern Qinghai–Tibetan Plateau (QTP), to reconstruct local climatic variations during the past 1000 yr. Concentrations of Corg and Ntot vary similarly with changes in precipitation recorded by tree rings in Dulan, northeastern QTP, indicating their close relation to precipitation. Carbon Preference Index (CPI) values of C22–C33 n-alkanes and C22–C28 n-alkan-1-ols and Average Chain Length (ACL) values of C27–C33 n-alkanes generally negatively correlate with δ13Corg and δ15Ntot and also vary comparably with the oxygen isotope temperature record from the Dunde ice core, northeastern QTP. These patterns indicate that high CPI values and negative shifts of the δ13Corg and δ15Ntot correspond to warmer conditions that favor the growth of vascular land plants and that lower values and positive shifts correspond to cooler conditions in the Lake Ximencuo locality. This observation contradicts previous interpretations from peat and modern soil studies that conclude that the CPI indices were controlled by microbial degradation under different climate conditions. Here we propose that the changes of organic matter sources under different climate regimes, combined with physiological adjustments of vascular plants to different air temperatures, might yield different CPI responses to climate changes in glacial plateau lakes. Air temperature and precipitation increases and decreases reconstructed in this 1000-yr study were generally independent of each other, but they both occurred at centennial or multi-centennial scales. The interaction between subtropical (Asian Monsoon) and mid-latitude (Westerly) atmospheric circulation systems probably dominated the local precipitation variations in the Lake Ximencuo catchment, whereas solar insolation, volcanism and greenhouse gas variations were likely responsible for the air temperature changes that are recorded in the lake sediments and that are consistent with regional temperature variations in the eastern QTP. VL - 379–380 UR - http://www.sciencedirect.com/science/article/pii/S0031018213001648 N1 - id: 2310 JO - Paleoclimate changes of the last 1000 yr on the eastern Qinghai–Tibetan Plateau recorded by elemental, isotopic, and molecular organic matter proxies in sediment from glacial Lake Ximencuo ER - TY - JOUR T1 - Persistent export of 231Pa from the deep central Arctic Ocean over the past 35,000 years JF - Nature Y1 - 2013 A1 - Hoffmann, Sharon S. A1 - McManus, Jerry F. A1 - Curry, William B. A1 - Brown-Leger, L. Susan KW - Marine chemistry KW - Palaeoceanography KW - Palaeoclimate AB - The Arctic Ocean has an important role in Earth’s climate, both through surface processes1 such as sea-ice formation and transport, and through the production and export of waters at depth that contribute to the global thermohaline circulation2, 3. Deciphering the deep Arctic Ocean’s palaeo-oceanographic history is a crucial part of understanding its role in climatic change. Here we show that sedimentary ratios of the radionuclides thorium-230 (230Th) and protactinium-231 (231Pa), which are produced in sea water and removed by particle scavenging on timescales of decades to centuries, respectively4, record consistent evidence for the export of 231Pa from the deep Arctic and may indicate continuous deep-water exchange between the Arctic and Atlantic oceans throughout the past 35,000 years. Seven well-dated box-core records provide a comprehensive overview of 231Pa and 230Th burial in Arctic sediments during glacial, deglacial and interglacial conditions. Sedimentary 231Pa/230Th ratios decrease nearly linearly with increasing water depth above the core sites, indicating efficient particle scavenging in the upper water column and greater influence of removal by lateral transport at depth. Although the measured 230Th burial is in balance with its production in Arctic sea water, integrated depth profiles for all time intervals reveal a deficit in 231Pa burial that can be balanced only by lateral export in the water column. Because no enhanced sink for 231Pa has yet been found in the Arctic, our records suggest that deep-water exchange through the Fram strait may export 231Pa. Such export may have continued for the past 35,000 years, suggesting a century-scale replacement time for deep waters in the Arctic Ocean since the most recent glaciation and a persistent contribution of Arctic waters to the global ocean circulation. VL - 497 UR - http://www.nature.com/doifinder/10.1038/nature12145 IS - 7451 ER - TY - JOUR T1 - Pleistocene sequence stratigraphy of the shallow continental shelf, offshore New Jersey: Constraints of Integrated Ocean Drilling Program Leg 313 core holes JF - GEOSPHERE Y1 - 2013 A1 - Miller, Kenneth G. A1 - Sugarman, Peter J. A1 - Browning, James V. A1 - Sheridan, Robert E. A1 - Kulhanek, Denise K. A1 - Monteverde, Donald H. A1 - Wehmiller, John F. A1 - Lombardi, Christopher A1 - Feigenson, Mark D. AB - We used cores and logs from Integrated Ocean Drilling Program (IODP) Expedition 313 to generate biostratigraphic, lithofacies, biofacies, and geochemical data that constrain the ages and paleoenvironments of Pleistocene sequences. We integrate sequence stratigraphy on cores with new seismic stratigraphic data to interpret the Pleistocene history of the Hudson shelf valley and paleoenvironmental and sea-level changes on the inner to middle continental shelf. Improved age control compared to previous studies is provided by integrated calcareous nannofossil biostratigraphy, Sr isotopic stratigraphy, and amino acid racemization. We recognize four upper Pleistocene-Holocene sequences: sequence uP1 is correlated with Marine Isotope Chrons (MIC; ``chron{''} is the correct stratigraphic term for a time unit, not ``stage{''}) 7 or 5e, sequence uP2 with MIC 5c, sequence uP3 with MIC 5a, and sequence uP4 with the latest Pleistocene to Holocene (MIC 1-2). However, within our age resolution it is possible that sequences uP2 and uP3 correlate with MIC 4-3c and 3a, respectively, as suggested by previous studies. Lower Pleistocene sequences lP1 and lP2 likely correlate with peak interglacials (e. g., MIC 31 and MIC 45 or 47, respectively). Thus, we suggest that preservation of sequences occurs only during peak eustatic events (e. g., MIC 45 or 47, MIC 31, and MIC 5), unless they are preserved in eroded valleys. The architecture of the Pleistocene deposits at Sites M27 and M29 is one of thin remnants of highstand and transgressive systems tracts, with lowstand deposits only preserved in the thalwegs of incised valleys. Incised valleys at the bases of sequences uP3 (IODP Site M27) and uP2 (IODP Site M29) document more southward courses of the paleo-Hudson valley, compared to the more southeastward course of the MIC 1-2 paleo-Hudson valley. The patchy distribution of Pleistocene sequences beneath the New Jersey inner-middle continental shelf is due to low accommodation during an interval of large eustatic changes; this predicts that sequences in such settings will be discontinuous, patchy, and difficult to correlate, consistent with previous studies in Virginia and North Carolina. VL - 9 ER - TY - JOUR T1 - Prominent bacterial heterotrophy and sources of C-13-depleted fatty acids to the interior Canada Basin JF - BIOGEOSCIENCES Y1 - 2013 A1 - Shah, S. R. A1 - Griffith, D. R. A1 - Galy, V. A1 - McNichol, A. P. A1 - Eglinton, T. I. AB - In recent decades, the Canada Basin of the Arctic Ocean has experienced rapidly decreasing summer sea ice coverage and freshening of surface waters. It is unclear how these changes translate to deeper waters, particularly as our baseline understanding of organic carbon cycling in the deep basin is quite limited. In this study, we describe full-depth profiles of the abundance, distribution and carbon isotopic composition of fatty acids from suspended particulate matter at a seasonally ice-free station and a semi-permanently ice-covered station. Fatty acids, along with suspended particulate organic carbon (POC), are more concentrated and C-13-enriched under ice cover than in ice-free waters. But this influence, apparent at 50 m depth, does not propagate downward below 150m depth, likely due to the weak biological pump in the central Canada Basin. Branched fatty acids have delta C-13 values that are similar to suspended POC at all depths and are more C-13-enriched than even-numbered saturated fatty acids at depths above 3000 m. These are likely to be produced in situ by heterotrophic bacteria incorporating organic carbon that is isotopically similar to total suspended POC. Below surface waters, there is also the suggestion of a source of saturated even-numbered fatty acids which could represent contributions from laterally advected organic carbon and/or from chemoautotrophic bacteria. At 3000 m depth and below, a greater relative abundance of long-chain (C20-24), branched and unsaturated fatty acids is consistent with a stronger influence of re-suspended sedimentary organic carbon. At these deep depths, two individual fatty acids (C-12 and iso-C-17) are significantly depleted in C-13, allowing for the possibility that methane oxidizing bacteria contribute fatty acids, either directly to suspended particulate matter or to shallow sediments that are subsequently mobilized and incorporated into suspended particulate matter within the deep basin. VL - 10 ER - TY - JOUR T1 - Quantifying overwash flux in barrier systems: An example from Martha's Vineyard, Massachusetts, USA JF - Marine Geology Y1 - 2013 A1 - Carruthers, Emily A. A1 - Lane, D. Philip A1 - Evans, Rob L. A1 - Donnelly, Jeffrey P. A1 - Ashton, Andrew D. KW - barrier system KW - Coastal evolution KW - overwash flux KW - sea-level rise KW - storm impacts AB - Coastal barriers are particularly susceptible to the effects of accelerated sea-level rise and intense storms. Over centennial scales, barriers are maintained via overtopping during storms, which causes deposition of washover fans on their landward sides. Understanding barrier evolution under modern conditions can help evaluate the likelihood of future barrier stability. This study examines three washover fans on the undeveloped south shore of Martha's Vineyard using a suite of vibracores, ground penetrating radar, high resolution dGPS, and LiDAR data. From these data, the volumes of the deposits were determined and range from 2.1 to 2.4 × 104 m3. Two of these overwash events occurred during Hurricane Bob in 1991. The water levels produced by this storm have a calculated return interval of ~ 28 years, implying an onshore sediment flux of 2.4–3.4 m3/m/yr. The third washover was deposited by a nor'easter in January 1997, which has a water level return interval of ~ 6 years, suggesting a flux of 8.5 m3/m/yr. These onshore fluxes are smaller than the erosional flux of sediment resulting from shoreline retreat, suggesting that the barrier is not in long-term equilibrium, a result supported by the thinning of the barrier in recent years. VL - 343 UR - http://linkinghub.elsevier.com/retrieve/pii/S002532271300114Xhttp://api.elsevier.com/content/article/PII:S002532271300114X?httpAccept=text/xmlhttp://api.elsevier.com/content/article/PII:S002532271300114X?httpAccept=text/plain ER - TY - JOUR T1 - Radiocarbon Dating of Basal Peats Supports Separation of Lake Superior from Lakes Michigan-Huron about 1250 years ago JF - Earth and Planetary Science Letters Y1 - 2013 A1 - Yu, Shi-Yong A1 - Colman, Steven M. A1 - Milne, Glenn A. AB - Lake Superior represents an important component of the aquatic ecosystem in North America. Along its south shore, ongoing lake-level rise, accelerated erosion, and wetland loss are major environmental concerns to coastal communities. A better prediction of the future of this shore requires placing the instrumental lake-level records in a geological context. However, our knowledge of the late-Holocene history of the world's largest freshwater body remains fragmentary. Here we present a sedimentary record of late-Holocene relative lake-level changes by dating transgressive basal peats resting directly on a sandy substrate along a bathymetric gradient in Bark Bay Slough, Wisconsin. Our record shows a moderate lake-level rise at 1.4±0.2 mm/yr from about 2200 to 1250 cal yr BP as a result of relatively slow differential uplift of Bark Bay relative to the controlling outlet at Port Huron. The rise accelerated to 2.3±0.2 mm/yr at about 1250 cal yr BP when Sault Ste. Marie emerged as the controlling outlet, thereby separating Superior from Lakes Michigan–Huron and giving rise to the modern hydrographic regime of the upper Great Lakes. The timing of this event in our record is about 1000 yr later than that estimated in most previous studies, but our data complement and confirm the younger age of lake separation inferred using a different methodology. Our results not only provide pertinent information for hydrological regulation, navigation operation, and infrastructural design in the upper Great Lakes, but also provide insight into freshwater wetland succession on flooded coasts. VL - 375 UR - http://www.sciencedirect.com/science/article/pii/S0012821X13003129 JO - Radiocarbon Dating of Basal Peats Supports Separation of Lake Superior from Lakes Michigan-Huron about 1250 years ago ER - TY - RPRT T1 - Recharge Sources and Residence Times of Groundwater as Determined by Geochemical Tracers in the Mayfield Area, Southwestern Idaho, 2011–12 Y1 - 2013 A1 - Hopkins, C. B. JF - Scientific Investigations Report PB - U.S. Department of the Interior: U.S. Geological Survey ER - TY - JOUR T1 - Reconstructing 7000 years of North Atlantic hurricane variability using deep-sea sediment cores from the western Great Bahama Bank JF - Paleoceanography Y1 - 2013 A1 - Toomey, Michael R. A1 - Curry, William B. A1 - Donnelly, Jeffrey P. A1 - van Hengstum, Peter J. AB - [1] Available overwash records from coastal barrier systems document significant variability in North Atlantic hurricane activity during the late Holocene. The same climate forcings that may have controlled cyclone activity over this interval (e.g., the West African Monsoon, El Niño–Southern Oscillation (ENSO)) show abrupt changes around 6000 yrs B.P., but most coastal sedimentary records do not span this time period. Establishing longer records is essential for understanding mid-Holocene patterns of storminess and their climatic drivers, which will lead to better forecasting of how climate change over the next century may affect tropical cyclone frequency and intensity. Storms are thought to be an important mechanism for transporting coarse sediment from shallow carbonate platforms to the deep-sea, and bank-edge sediments may offer an unexplored archive of long-term hurricane activity. Here, we develop this new approach, reconstructing more than 7000 years of North Atlantic hurricane variability using coarse-grained deposits in sediment cores from the leeward margin of the Great Bahama Bank. High energy event layers within the resulting archive are (1) broadly correlated throughout an offbank transect of multi-cores, (2) closely matched with historic hurricane events, and (3) synchronous with previous intervals of heightened North Atlantic hurricane activity in overwash reconstructions from Puerto Rico and elsewhere in the Bahamas. Lower storm frequency prior to 4400 yrs B.P. in our records suggests that precession and increased NH summer insolation may have greatly limited hurricane potential intensity, outweighing weakened ENSO and a stronger West African Monsoon—factors thought to be favorable for hurricane development. VL - 28 UR - http://doi.wiley.com/10.1002/palo.v28.1http://doi.wiley.com/10.1002/palo.20012https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fpalo.20012 IS - 1 ER - TY - JOUR T1 - Reconstructing mid-late Holocene cyclone variability in the Central Pacific using sedimentary records from Tahaa, French Polynesia JF - Quaternary Science Reviews Y1 - 2013 A1 - Toomey, Michael R. A1 - Donnelly, Jeffrey P. A1 - Woodruff, Jonathan D. KW - enso KW - Precession KW - South Pacific KW - tropical cyclones AB - We lack an understanding of the geographic and temporal controls on South Pacific cyclone activity. Overwash records from backbarrier salt marshes and coastal ponds have been used to reconstruct tropical cyclone strikes in the North Atlantic basin. However, these specific backbarrier environments are scarce in the South Pacific, with cyclone records limited primarily to the period of modern observation. This instrumental record suggests a correlation with the El Niño–Southern Oscillation (ENSO), but longer records are necessary to test this relationship over geologic timescales and explore other potential climate drivers of tropical cyclone variability. Deep lagoons behind coral reefs are widespread in the Pacific and provide an alternative setting for developing long-term sedimentary reconstructions of tropical cyclone occurrence. Coarse-grained event deposits within the sediments of a back-reef lagoon surrounding Tahaa reveal a 5000-year record of cyclone occurrences. Timing of recent high-energy deposits matches well with observed tropical cyclone strikes and indicates coarse deposits are storm derived. Longer records show tropical cyclone activity was higher from 5000 to 3800 and 2900 to 500 yrs BP. Comparison to records from the North Pacific (out-of-phase) and North Atlantic (in phase) suggests a coordinated pattern of storm activity across tropical cyclone basins over the mid-late Holocene. The changes in tropical cyclone activity we observe in the South Pacific and across other basins may be related to ENSO as well as precession driven changes in ocean-atmosphere thermal gradients. VL - 77 UR - http://linkinghub.elsevier.com/retrieve/pii/S0277379113002849http://api.elsevier.com/content/article/PII:S0277379113002849?httpAccept=text/xmlhttp://api.elsevier.com/content/article/PII:S0277379113002849?httpAccept=text/plain ER - TY - JOUR T1 - Reconstructing mid-late Holocene cyclone variability in the Central Pacific using sedimentary records from Tahaa, French Polynesia JF - Quaternary Science Reviews Y1 - 2013 A1 - Toomey, Michael R. A1 - Donnelly, Jeffrey P. A1 - Woodruff, Jonathan D. AB - We lack an understanding of the geographic and temporal controls on South Pacific cyclone activity. Overwash records from backbarrier salt marshes and coastal ponds have been used to reconstruct tropical cyclone strikes in the North Atlantic basin. However, these specific backbarrier environments are scarce in the South Pacific, with cyclone records limited primarily to the period of modern observation. This instrumental record suggests a correlation with the El Niño–Southern Oscillation (ENSO), but longer records are necessary to test this relationship over geologic timescales and explore other potential climate drivers of tropical cyclone variability. Deep lagoons behind coral reefs are widespread in the Pacific and provide an alternative setting for developing long-term sedimentary reconstructions of tropical cyclone occurrence. Coarse-grained event deposits within the sediments of a back-reef lagoon surrounding Tahaa reveal a 5000-year record of cyclone occurrences. Timing of recent high-energy deposits matches well with observed tropical cyclone strikes and indicates coarse deposits are storm derived. Longer records show tropical cyclone activity was higher from 5000 to 3800 and 2900 to 500 yrs BP. Comparison to records from the North Pacific (out-of-phase) and North Atlantic (in phase) suggests a coordinated pattern of storm activity across tropical cyclone basins over the mid-late Holocene. The changes in tropical cyclone activity we observe in the South Pacific and across other basins may be related to ENSO as well as precession driven changes in ocean-atmosphere thermal gradients. VL - 77 UR - http://www.sciencedirect.com/science/article/pii/S0277379113002849 JO - Reconstructing mid-late Holocene cyclone variability in the Central Pacific using sedimentary records from Tahaa, French Polynesia ER - TY - JOUR T1 - Resolving varve and radiocarbon chronology differences during the last 2000 years in the Santa Barbara Basin sedimentary record, California JF - Quaternary International Y1 - 2013 A1 - Hendy, Ingrid L. A1 - Dunn, L. A1 - Schimmelmann, A. A1 - Pak, D. K. AB - Santa Barbara Basin (SBB) is well known for producing high quality paleoclimate reconstructions, but the validity of correlations between the basin and other regions rests upon age model accuracy. Yet, the two independent and well-established chronologies based on varve counting and radiocarbon dating do not consistently agree during the last two millennia. Here the validity of age model assumptions is tested including whether 1) the regional reservoir age of surface waters was invariably 641 ± 119 years through time, and/or 2) SBB laminae couplets are consistently annual varves and counted with sufficient precision. This high-resolution 14C study of SBB sediments compares 49 mixed planktonic foraminiferal carbonate and 20 terrestrial organic carbon 14C dates to the varve chronology, to extend the high-resolution paleoclimate chronology of the basin back ∼2000 years. Evidence indicates that regional reservoir ages do not remain constant through time with ΔR, (i.e. regional reservoir age minus variations in the global mixed-layer ocean reservoir age) fluctuating between 80 and 350 years. Second, there is a consistent (R2 = 0.96) undercounting of the varves between 150 and ∼1700 AD based on a new varying ΔR 14C chronology, indicating that some laminae couplets may not be annual. Loss of varves may occur when low riverine input and infrequent winter storm activity during drought intervals fail to supply a siliciclastic layer. VL - 310 UR - http://www.sciencedirect.com/science/article/pii/S1040618212031734 N1 - id: 2289 JO - Resolving varve and radiocarbon chronology differences during the last 2000 years in the Santa Barbara Basin sedimentary record, California ER - TY - JOUR T1 - Sea-level change during the last 2500 years in New Jersey, USA JF - Quaternary Science Reviews Y1 - 2013 A1 - Kemp, Andrew C. A1 - Horton, Benjamin P. A1 - Vane, Christopher H. A1 - Bernhardt, Christopher E. A1 - Corbett, D. Reide A1 - Engelhart, Simon E. A1 - Anisfeld, Shimon C. A1 - Parnell, Andrew C. A1 - Cahill, Niamh AB - Relative sea-level changes during the last ∼2500 years in New Jersey, USA were reconstructed to test if late Holocene sea level was stable or included persistent and distinctive phases of variability. Foraminifera and bulk-sediment δ13C values were combined to reconstruct paleomarsh elevation with decimeter precision from sequences of salt-marsh sediment at two sites using a multi-proxy approach. The additional paleoenvironmental information provided by bulk-sediment δ13C values reduced vertical uncertainty in the sea-level reconstruction by about one third of that estimated from foraminifera alone using a transfer function. The history of sediment deposition was constrained by a composite chronology. An age–depth model developed for each core enabled reconstruction of sea level with multi-decadal resolution. Following correction for land-level change (1.4 mm/yr), four successive and sustained (multi-centennial) sea-level trends were objectively identified and quantified (95% confidence interval) using error-in-variables change point analysis to account for age and sea-level uncertainties. From at least 500 BC to 250 AD, sea-level fell at 0.11 mm/yr. The second period saw sea-level rise at 0.62 mm/yr from 250 AD to 733 AD. Between 733 AD and 1850 AD, sea level fell at 0.12 mm/yr. The reconstructed rate of sea-level rise since ∼1850 AD was 3.1 mm/yr and represents the most rapid period of change for at least 2500 years. This trend began between 1830 AD and 1873 AD. Since this change point, reconstructed sea-level rise is in agreement with regional tide-gauge records and exceeds the global average estimate for the 20th century. These positive and negative departures from background rates demonstrate that the late Holocene sea level was not stable in New Jersey. VL - 81 UR - http://www.sciencedirect.com/science/article/pii/S0277379113003740 JO - Sea-level change during the last 2500 years in New Jersey, USA ER - TY - JOUR T1 - Seasonal climate change across the Roman Warm Period/Vandal Minimum transition using isotope sclerochronology in archaeological shells and otoliths, southwest Florida, USA JF - Quaternary International Y1 - 2013 A1 - Wang, Ting A1 - Surge, Donna A1 - Walker, Karen Jo AB - Archaeological evidence suggests that southwest Florida experienced variably warmer and wetter climate during the Roman Warm Period (RWP; 300 BC–550 AD) relative to the Vandal Minimum (VM; 550–800 AD). This hypothesis was tested by reconstructing seasonal-scale climate conditions for the latter part of the RWP (1–550 AD) by using high-resolution oxygen isotope ratios (δ18O) of archaeological shells (Mercenaria campechiensis) and otoliths (Ariopsis felis). Eight shells radiocarbon-dated to 150–550 AD recorded that the RWP summers at 150–250 AD were insignificantly different from today and the RWP summers at 250–350 AD and 450–550 AD were drier relative to today. Eight otoliths indicate that the winters were variable during the RWP, colder than today at 150–200 AD and 250–300 AD, similar to today at 200–250 AD, 300–350 AD and 450–500 AD, and warmer than today at 500–550 AD. The climate reconstructions agree with archaeological observations and are partially coherent with the history of sea-level change, with a drying and cooling trend at the 95% confidence level across the RWP/VM transition. The climate transition is not only consistent with falling sea level, but also coherent with reduced solar radiation. Reduced solar radiation may have triggered a change in atmospheric circulation patterns that precipitated the observed climate transition. VL - 308 N1 - id: 2298 JO - Seasonal climate change across the Roman Warm Period/Vandal Minimum transition using isotope sclerochronology in archaeological shells and otoliths, southwest Florida, USA ER - TY - JOUR T1 - Sedimentological and geomorphological imprints of Holocene tsunamis in southwestern Spain: An approach to establish the recurrence period JF - Continental Shelf Drowned Landscapes (INQUA-CMP and IGCP-526) Y1 - 2013 A1 - Ruiz, Francisco A1 - Rodríguez-Vidal, Joaquín A1 - Abad, Manuel A1 - Cáceres, Luis M. A1 - Carretero, María I. A1 - Pozo, Manuel A1 - Rodríguez-Llanes, José M. A1 - Gómez-Toscano, Francisco A1 - Izquierdo, Tatiana A1 - Font, Eric A1 - Toscano, Antonio AB - This paper reviews the sedimentological and geomorphological imprints of prehistoric and historical tsunamis in the four main estuaries of SW Spain. These imprints include beach erosion, filling of intertidal channels, deposition of bioclastic layers, washover fans and reworked aeolian sheets and the breaching of spits and tombolos. Most of these imprints were caused by the 218–209 BC and AD 1755 tsunamis, although evidence of other tsunamis has been identified. In these two events, effects on human populations were severe and diverse, such as human loss of life, changes in coastal settlements and international borders, damage to port infrastructure or flooding of marsh and inhabited areas. New radiocarbon reservoir data were included in order to obtain an approach to the recurrence period of these high-energy events (700–1000 years) in this area. VL - 203 UR - http://www.sciencedirect.com/science/article/pii/S0169555X13004650 JO - Sedimentological and geomorphological imprints of Holocene tsunamis in southwestern Spain: An approach to establish the recurrence period ER - TY - JOUR T1 - Sedimentological and Geophysical Signatures of A Relict Tidal Inlet Complex Along A Wave-Dominated Barrier: Assateague Island, Maryland, U.S.A JF - Journal of Sedimentary Research Y1 - 2013 A1 - Seminack, C. T. A1 - Buynevich, I. V. AB - Assateague Island is a classic example of a wave-dominated, retrograding barrier island, with its recent geological history punctuated by episodes of overwash and breaching (comparable to the Outer Banks, North Carolina; northern New Jersey coast; Long Island, New York, etc.). This study aims to provide high-resolution data of a paleo-inlet which may lead to a more precise evolutionary model of other wave-dominated barrier islands. The study focuses on a historically stable segment fronting the Green Run Bay. The site lies north of the historical Green Run Inlet (active until 1880); however, there is no morphological or historical evidence of this inlet occupying the more northerly position, thus suggesting that the study site may represent a relict part of the barrier. High-resolution ground-penetrating radar (GPR) images, complemented with sediment cores and multi-dating techniques, were used to reconstruct the geological legacy of the Green Run Bay segment. The findings indicate that a shallow backbarrier channel, still visible within the Green Run Bay, can be traced to a large (> 380 m wide, 3.0–3.5 m thick) channel cut-and-fill structure beneath the barrier. The channel fill consists of tangential- to sigmoidal-oblique, southward-dipping reflections downlapping onto channel lag facies, which overlie subhorizontal bay-fill strata. Mollusks from the bay fill yield calibrated ages of 4419–2018 yr BP. The paleo-channel facies overlying the bay deposits exhibit a fining-upward sequence, with a mean grain size decreasing from 0.44 to 2.43 φ (0.74 to 0.19 mm). Optically stimulated luminescence dating places the middle part of the inlet fill at 730–590 yr BP. The paleo-channel fill does not extend to the south and therefore is a separate relict feature that predates the historical Green Run Inlet. The paleo-tidal prism of the relict channel was at least 17 × 106 m3, which is comparable to many wave-dominated historical and active inlets along the Atlantic Seaboard. Findings in this study provide the geological background for coastal hazard assessments and offer a mesoscale example of inlet-facies architecture in wave-dominated barrier sequences identified in the rock record. VL - 83 UR - http://jsedres.sepmonline.org/cgi/doi/10.2110/jsr.2013.10http://jsedres.geoscienceworld.org/cgi/doi/10.2110/jsr.2013.10 IS - 2 ER - TY - JOUR T1 - Separation of Lake Superior from Lakes Michigan–Huron about 1250 yr ago JF - Earth and Planetary Science Letters Y1 - 2013 A1 - Yu, Shi-Yong A1 - Colman, Steven M. A1 - Milne, Glenn A. AB - Lake Superior represents an important component of the aquatic ecosystem in North America. Along its south shore, ongoing lake-level rise, accelerated erosion, and wetland loss are major environmental concerns to coastal communities. A better prediction of the future of this shore requires placing the instrumental lake-level records in a geological context. However, our knowledge of the late-Holocene history of the world's largest freshwater body remains fragmentary. Here we present a sedimentary record of late-Holocene relative lake-level changes by dating transgressive basal peats resting directly on a sandy substrate along a bathymetric gradient in Bark Bay Slough, Wisconsin. Our record shows a moderate lake-level rise at 1.4±0.2 mm/yr from about 2200 to 1250 cal yr BP as a result of relatively slow differential uplift of Bark Bay relative to the controlling outlet at Port Huron. The rise accelerated to 2.3±0.2 mm/yr at about 1250 cal yr BP when Sault Ste. Marie emerged as the controlling outlet, thereby separating Superior from Lakes Michigan–Huron and giving rise to the modern hydrographic regime of the upper Great Lakes. The timing of this event in our record is about 1000 yr later than that postulated in most previous studies. Our results not only provide pertinent information for hydrological regulation, navigation operation, and infrastructural design in the upper Great Lakes, but also provide insight into freshwater wetland succession on flooded coasts. VL - 375 N1 - id: 2336 JO - Separation of Lake Superior from Lakes Michigan–Huron about 1250 yr ago ER - TY - JOUR T1 - Should dates trump context? Evaluation of the Cave 7 skeletal assemblage radiocarbon dates JF - Journal of Archaeological Science Y1 - 2013 A1 - Geib, Phil R. A1 - Hurst, Winston B. AB - “Massacre” was the accepted interpretation for a prehistoric skeletal assemblage of around 90 individuals from Cave 7 in the SE Utah of the North American Southwest since the 1890s. Coltrain and others (Journal of Archaeological Science 39, 2220–2230) rejected this account based on a dispersed suite of AMS radiocarbon dates on purified bone collagen from the interred individuals. Since dates from skeletons exhibiting perimortem damage were scattered across some 400 radiocarbon years, Coltrain et al. argued for multiple interments of victims of violence and related kin spread across several centuries. The temporal placement of interment events in Cave 7 clearly cannot be known independent of radiocarbon assays but such assays should not be privileged above contextual information about which individuals were interred together unless verified by an independent dating laboratory. Only by ignoring important information about burial context in the 1893 field record can the dates of Coltrain et al. be accepted as accurate estimates of time of death. We redated residual collagen from 11 of the Cave 7 individuals because of significant contextual anomalies with some of the prior results. The new assays combined with contextual evidence demonstrate that some of Coltrain et al.’s dates are either too old or too young; the dates are neither sufficiently accurate (true estimates of sample age) nor sufficiently precise (small confidence intervals) to refute a single-event massacre or to confirm multiple interment events in Cave 7. Nonetheless, dates that meet these criteria disclose at least two interment events, a large one of mostly adult males, many exhibiting perimortem damage (a massacre assemblage), and a small one consisting of an adult female with three children. A third interment event of a few adult females and child is possible based primarily on context since the date distribution in this case overlaps substantially with that of the massacre victims; context also hints at other interment events. Aside from chronology we clarify the number of Basketmaker individuals interred at the site and the incidence of perimortem violence. A single-event mass killing continues to be the most likely interpretation for around 58 individuals, mostly adult males (at least 35) but also adult females and children. This incident occurred between cal. AD 20–80 and doubtless had a significant social impact at the time because of its scale, reverberating throughout the early farming communities of the Southwest. VL - 40 UR - http://www.sciencedirect.com/science/article/pii/S0305440313000575 IS - 6 N1 - id: 2281 JO - Should dates trump context? Evaluation of the Cave 7 skeletal assemblage radiocarbon dates ER - TY - JOUR T1 - Source, diagenesis, and fluxes of particulate organic carbon along the western Adriatic Sea (Mediterranean Sea) JF - Marine Geology Y1 - 2013 A1 - Tesi, T. A1 - Langone, L. A1 - Giani, M. A1 - Ravaioli, M. A1 - Miserocchi, S. AB - In this study, we investigated the modern organic carbon (OC) cycling along the clinoform-shaped deposit that developed after the attainment of the modern sea-level in the Adriatic Sea (~ 5.5 kyr cal BP). Newly acquired data were combined with published results to characterize the (i) origin, (ii) diagenesis, and (iii) fluxes of OC along the Adriatic clinoform. δ13C, Δ14C, and lignin phenols were used to constrain the composition of OC accumulating in surface sediments. Sediment cores collected at different water depths were used to describe the early diagenesis during burial in different regions. In addition, on the basis of an extensive number of accumulation rates and OC data, we assessed the flux of OC to the seabed and its burial. Our results showed that terrigenous OC is the dominant OC source in the Po prodelta mainly in the form of pre-aged soil-derived OC and vascular plant fragments. Along the clinoform, both Δ14C and the concentration of lignin-derived phenols decreased with increasing distance from the Po prodelta indicating the influence of an additional pool of aged OC that gradually becomes more important because of its selective preservation during the sediment transport. As a result, degradation rates (k) decreased along the clinoform as a function of the sediment oxidative history. The calculated half-life of reactive OC (t1/2) was ~ 14.6 yrs in the Po prodelta whereas topset/forest deposits south of this region exhibited higher values, ~ 100 yrs, indicating the presence of refractory material. In the distal bottomset region, the t1/2 was particularly high ranging from ~ 255 to ~ 912 yrs. Because of the significant southward component of the sediment transport, the OC deposition in the southern surface sediments exceeded the local OC input via rivers (ratio deposition/input 1.2). Conversely, the northern Adriatic was characterized by a marked imbalance (ratio deposition/input 0.3–0.5). According to our calculations, the OC flux to the seabed along the clinoform was ~ 309 Gg of C per year whereas the OC burial was ~ 180 Gg of C per year, corresponding to an overall burial efficiency of ~ 59%. VL - 337 UR - http://www.sciencedirect.com/science/article/pii/S0025322713000273 N1 - id: 2335 JO - Source, diagenesis, and fluxes of particulate organic carbon along the western Adriatic Sea (Mediterranean Sea) ER - TY - JOUR T1 - Stratigraphy and wiggle-matching-based age-depth model of late Holocene marine sediments in Beppu Bay, southwest Japan JF - New Global Perspectives on Paleontology, Stratigraphy, Paleoceanography, Paleoclimatology, and Tectonics in the East Asia and Western Pacific Y1 - 2013 A1 - Kuwae, Michinobu A1 - Yamamoto, Masanobu A1 - Ikehara, Ken A1 - Irino, Tomohisa A1 - Takemura, Keiji A1 - Sagawa, Takuya A1 - Sakamoto, Tatsuhiko A1 - Ikehara, Minoru A1 - Takeoka, Hidetaka AB - We analyzed the lithology, magnetic susceptibility, bulk density, and X-ray radiographs of 14 sediment cores (1–9 m long) from Beppu Bay in the western Seto Inland Sea, Japan, to establish the late Holocene stratigraphy in the deepest part of the bay and to develop an age–depth model for the sediments there. The cores contained 18 thick (major event) high-density layers (16 turbidites and two volcanic ash; >1 cm thick), and both lithological observations and density variations in the hemipelagic mud that is dominant in the cores revealed a further 55 thin (minor event) high-density layers ( VL - 69 UR - http://www.sciencedirect.com/science/article/pii/S1367912012002957 N1 - id: 2295 JO - Stratigraphy and wiggle-matching-based age-depth model of late Holocene marine sediments in Beppu Bay, southwest Japan ER - TY - JOUR T1 - Surface production fuels deep heterotrophic respiration in northern peatlands JF - Global Biogeochemical Cycles Y1 - 2013 A1 - Elizabeth Corbett, J. A1 - Burdige, David J. A1 - Tfaily, Malak M. A1 - Dial, Angela R. A1 - Cooper, William T. A1 - Glaser, Paul H. A1 - Chanton, Jeffrey P. AB - [1] Multiple analyses of dissolved organic carbon (DOC) from pore waters were conducted to define the processes that govern carbon balance in peatlands: (1) source, reactivity, and transport of DOC with respect to vegetation, peat, and age of carbon substrate, (2) reactivity of DOC with respect to molecular size, and (3) lability to photoxidation of surficial DOC. We found that surface organic production fuels heterotrophic respiration at depth in advection-dominated peatlands, especially in fens. Fen DOC was Δ14C enriched relative to the surrounding fen peat, and fen respiration products were similar to this enriched DOC indicating that DOC was the main microbial substrate. Bog DOC was more variable showing either enrichment in ∆14C at depth or ∆14C values that follow peat values. This variability in bogs is probably controlled by the relative importance of vertical transport of labile carbon substrates within the peat profile versus DOC production from bog peat. These results extended our set of observations to 10 years at one bog-fen pair and add two additional bog-fen pairs to our series of observations. Anaerobic incubations of peat, rinsed free of residual DOC, produced DOC and respiration products that were strikingly similar to the peat values in a bog and two fens. This result demonstrated conclusively that downward advection is the process responsible for the presence of modern DOC found at depth in the peat column. Fen DOC has lower C/N values and up to twice as much LMW (<1 kDa) DOC as bogs due to differences in organic inputs and greater microbial processing. Fluorescence irradiation experiments showed that fen DOC is more photolabile than bog DOC. VL - 27 UR - http://doi.wiley.com/10.1002/2013GB004677https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2F2013GB004677 IS - 4 ER - TY - JOUR T1 - Three approaches to radiocarbon calibration of amino acid racemization in Mulinia lateralis from the Holocene of the Chesapeake Bay, USA JF - Amino Acid Racemization Y1 - 2013 A1 - Simonson, Amy E. A1 - Lockwood, Rowan A1 - Wehmiller, John F. AB - A radiocarbon-calibrated aminochronology, based on the bivalve Mulinia lateralis, is presented for Chesapeake Bay core MD03-2661, a 25 m piston core drilled near Kent Island (38°53.21′N; 76°23.89′W) during the 2003 USGS Marion-Dufresne cruise. Three separate approaches were used to calibrate amino acid racemization (AAR) data for aspartic acid with radiocarbon data. For the first approach, a direct or paired analysis calibration incorporated eight articulated specimens, thereby allowing for the application of AAR and radiocarbon analysis of the same specimen and effectively eliminating both intrashell variability and time averaging as factors in the calibration. A second direct approach relied on valves that were bilaterally split to facilitate both AAR and radiocarbon dating, thus effectively eliminating time averaging effects from this calibration. For the third indirect approach, nine independent radiocarbon dates were combined with 129 Asx D/L ratios from the same core depths to produce an indirect calibration model, from which intershell variability and time averaging could be estimated. Variability in AAR ratios was recognized from a myriad of sources, including analytical error, intrashell variability, inherent variability, time averaging, and contamination. The majority of this variability was controlled for through experimental design or by the application of these three independent calibration approaches. The direct calibration of articulated shells and the indirect calibration yielded virtually identical age models, well within their respective 95% confidence intervals. This study establishes an aminostratigraphic reference section for the Holocene record of the Chesapeake Bay and demonstrates the usefulness of multiple calibration approaches and the potential utility of AAR for future studies of sedimentary processes and chronologies in the bay. VL - 16 UR - http://www.sciencedirect.com/science/article/pii/S1871101412001318 N1 - id: 2292 JO - Three approaches to radiocarbon calibration of amino acid racemization in Mulinia lateralis from the Holocene of the Chesapeake Bay, USA ER - TY - JOUR T1 - Transient stratification as the cause of the North Pacific productivity spike during deglaciation JF - Nature Geoscience Y1 - 2013 A1 - Lam, Phoebe J. A1 - Robinson, Laura F. A1 - Blusztajn, Jerzy A1 - Li, Camille A1 - Cook, Mea S. A1 - McManus, Jerry F. A1 - Keigwin, Lloyd D. KW - Biogeochemistry KW - Marine biology KW - Marine chemistry KW - Palaeoceanography AB - During the Bølling–Allerød warm period of the last deglaciation, about 14 kyr ago, there was a strong and pervasive spike in primary productivity in the North Pacific Ocean1. It has been suggested that this productivity event was caused by an influx of the micronutrient iron from surrounding continental shelves as they were flooded by sea-level rise2. Here we test this hypothesis by comparing numerous proxies of productivity with iron flux and provenance measured from a core from the subarctic Pacific Ocean. We find no evidence for an abrupt deglacial pulse of iron from any source at the time of peak productivity. Instead, we argue that the deglacial productivity peak was caused by two stepwise events. First, deep convection during early deglaciation increased nutrient supply to the surface but also increased the depth of the mixed layer, which pushed surface production deeper in the water column and induced light limitation. A subsequent input of meltwater from northern American ice sheets then stratified the water column, which relieved light limitation while leaving the surface waters enriched in nutrients. We conclude that iron plays, at most, a secondary role in controlling productivity during the glacial and deglacial periods in the subarctic Pacific Ocean. VL - 6 UR - http://www.nature.com/doifinder/10.1038/ngeo1873 IS - 8 ER - TY - BOOK T1 - Treatise on Geomorphology8.26 Climate Change Impacts on Cold Climates Y1 - 2013 A1 - Baroni, C. KW - Adélie penguins KW - Antarctica KW - Arctic KW - Cenozoic KW - Climate change KW - Elephant seals KW - glacial history KW - Holocene KW - Icehouse AB - Since the onset of Cenozoic ice sheets, cold climate regions have played a leading role in planetary energy balance, atmospheric and global oceanic circulations. Glacial and periglacial processes in polar regions act as morphogenetic agents for landscape sculpting providing landforms and deposits that represent valuable records for investigating the amplitude of key phases of Cenozoic glacial history. Glacio-eustatic sea-level variations induce revolutionary environmental changes across the entire planet. Changes in periglacial processes also influence cold region hydrology, ecosystems, and soil carbon storage. Climatic and environmental changes in cold regions cause adaptation through ecological and evolutionary responses by organisms. PB - Elsevier SN - 9780080885223 UR - https://doi.org/10.1016/B978-0-12-374739-6.00222-0 ER - TY - JOUR T1 - Tropical cyclone wind speed constraints from resultant storm surge deposition: A 2500 year reconstruction of hurricane activity from St. Marks, FL JF - Geochemistry, Geophysics, Geosystems Y1 - 2013 A1 - Brandon, Christine M. A1 - Woodruff, Jonathan D. A1 - Lane, D. Phil A1 - Donnelly, Jeffrey P. AB - [1] Recent work suggests that the patterns of intense (≥category 3 on the Saffir-Simpson scale) hurricane strikes over the last few millennia might differ from that of overall hurricane activity during this period. Prior studies typically rely on assigning a threshold storm intensity required to produce a sedimentological overwash signal at a particular coastal site based on historical analogs. Here, we improve on this approach by presenting a new inverse-model technique that constrains the most likely wind speeds required to transport the maximum grain size within resultant storm deposits. As a case study, the technique is applied to event layers observed in sediments collected from a coastal sinkhole in northwestern Florida. We find that (1) simulated wind speeds for modern deposits are consistent with the intensities for historical hurricanes affecting the site, (2) all deposits throughout the ∼2500 year record are capable of being produced by hurricanes, and (3) a period of increased intense hurricane frequency is observed between ∼1700 and ∼600 years B.P. and decreased intense storm frequency is observed from ∼2500 to ∼1700 and ∼600 years B.P. to the present. This is consistent with prior reconstructions from nearby sites. Changes in the frequency of intense hurricane strikes may be related to the degree of penetration of the Loop Current in the Gulf of Mexico. VL - 14 UR - http://doi.wiley.com/10.1002/ggge.20217https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fggge.20217 IS - 8 ER - TY - JOUR T1 - An ~11,200 cal yr BP paleolimnological perspective for the archeological findings at Quartz Lake, Alaska JF - Journal of Paleolimnology Y1 - 2012 A1 - Wooller, M. J. A1 - Kurek, J. A1 - Gaglioti, B. V. A1 - Cwynar, L. C. A1 - Bigelow, N. A1 - Reuther, J. D. A1 - Gelvin-Reymiller, C. A1 - Smol, J. P. AB - Wetlands and lakes in the Tanana Valley, Alaska, have provided important resources for prehistoric humans who inhabited this region. We examine an ~11,200 cal yr BP record of environmental and paleolimnological changes from Quartz Lake in the middle Tanana Valley. Our data are also presented in the context of recent archaeological findings in the lake’s general vicinity that have 18 associated AMS 14C dates. We analyzed the stable-carbon and nitrogen isotope composition of total organic matter from the core, coupled with oxygen and carbon isotope analyses of Pisidiidae shells (fingernail clams), in addition to chironomid assemblage changes. Lacustrine sediments began to accumulate at ~11,200 cal yr BP. Initially, autochthonous production was low and allochthonous organic input was negligible between 11,000 and 10,500 cal yr BP, and were associated with relatively cool conditions at Quartz Lake at ~10,700 cal yr BP. After 10,500 cal yr BP, autochthonous production was higher coincident with a shift to chironomid assemblages dominated by taxa associated with warmer summer climates. A decrease in δ13C values of total organic carbon (TOC) and organic content of the sediment between 9,000 and 4,000 cal yr BP may indicate declining autochthonous primary production. This period ended with an abrupt (~7 ‰) decrease in the δ18O values from Pisidiidae shells at ~3,000 cal yr BP, which we hypothesize represented an episodic connection (flood) of the lake with flow from the nearby (~6 km) Tanana River. Our findings coincide with evidence for major flooding at other locations connected to the Tanana River and further afield in Alaska. From ~3,000 cal yr BP Quartz Lake subsequently appeared to become a relatively closed system, as indicated by the δ18OPisidiidae and δ13CPisidiidae data that are positively correlated and generally higher, which also correlates with a shift to moderately higher abundances of littoral chironomids. The cause of the transition to closed-basin conditions may have been geomorphic rather than climatic. This evidence of a progressively stronger evaporative influence on the lake’s closed hydrology after ~3,000 cal yr BP is consistent with our modern δ18O and δD water data from Quartz Lake that plot along a regional evaporative line we base on isotopic measurements from other local lakes and rivers. VL - 48 IS - 1 N1 - id: 2134 JO - An ~11,200 cal yr BP paleolimnological perspective for the archeological findings at Quartz Lake, Alaska ER - TY - JOUR T1 - Anomalous biogeochemical behavior of cadmium in subantarctic surface waters: Mechanistic constraints from cadmium isotopes JF - Earth and Planetary Science Letters Y1 - 2012 A1 - Gault-Ringold, Melanie A1 - Adu, Toyin A1 - Stirling, Claudine H. A1 - Frew, Russell D. A1 - Hunter, Keith A. AB - Cadmium, a highly toxic metal, exhibits a nutrient-type profile in the oceans that is closely correlated to that of the major nutrients phosphate and nitrate. Despite its complexity, the relationship between cadmium and phosphate has been used to infer historic phosphate utilization and biological controls on oceanic CO2 concentrations. Cadmium isotopes offer the potential to constrain the mechanisms controlling cadmium cycling in the oceans, reducing uncertainty associated with the cadmium paleonutrient proxy. Using techniques in double spiking and MC-ICPMS, we report seasonal Cd isotopic and concentration data along with major nutrients and other essential trace metal (Fe, Zn, and Co) concentrations from subantarctic surface waters. We show, for the first time, a 50-fold seasonal decrease in dissolved cadmium concentrations in subantarctic waters that is due to biological uptake. However, this drawdown in Cd is decoupled from phosphate and shows no coincident shift in cadmium isotopic composition. These data, along with the preferential removal of Cd from surface waters relative to Zn, imply that cadmium is supply-limited to phytoplankton and may have a more significant biological role in these low Zn subantarctic surface waters than in regions with higher Zn concentrations. VL - 341–344 UR - http://www.sciencedirect.com/science/article/pii/S0012821X12002890 N1 - id: 2339 JO - Anomalous biogeochemical behavior of cadmium in subantarctic surface waters: Mechanistic constraints from cadmium isotopes ER - TY - JOUR T1 - Anthropogenic aerosols as a source of ancient dissolved organic matter in glaciers JF - Nature Geoscience Y1 - 2012 A1 - Stubbins, Aron A1 - Hood, Eran A1 - Raymond, Peter A. A1 - Aiken, George R. A1 - Sleighter, Rachel L. A1 - Hernes, Peter J. A1 - Butman, David A1 - Hatcher, Patrick G. A1 - Striegl, Robert G. A1 - Schuster, Paul A1 - Abdulla, Hussain A. N. A1 - Vermilyea, Andrew W. A1 - Scott, Durelle T. A1 - Spencer, Robert G. M. KW - Atmospheric chemistry KW - Biogeochemistry KW - Cryospheric science AB - Glacier-derived dissolved organic matter represents a quantitatively significant source of ancient, yet highly bioavailable carbon to downstream ecosystems1. This finding runs counter to logical perceptions of age–reactivity relationships, in which the least reactive material withstands degradation the longest and is therefore the oldest2. The remnants of ancient peatlands and forests overrun by glaciers have been invoked as the source of this organic matter1, 3, 4. Here, we examine the radiocarbon age and chemical composition of dissolved organic matter in snow, glacier surface water, ice and glacier outflow samples from Alaska to determine the origin of the organic matter. Low levels of compounds derived from vascular plants indicate that the organic matter does not originate from forests or peatlands. Instead, we show that the organic matter on the surface of the glaciers is radiocarbon depleted, consistent with an anthropogenic aerosol source. Fluorescence spectrophotometry measurements reveal the presence of protein-like compounds of microbial or aerosol origin. In addition, ultrahigh-resolution mass spectrometry measurements document the presence of combustion products found in anthropogenic aerosols. Based on the presence of these compounds, we suggest that aerosols derived from fossil fuel burning are a source of pre-aged organic matter to glacier surfaces. Furthermore, we show that the molecular signature of the organic matter is conserved in snow, glacier water and outflow, suggesting that the anthropogenic carbon is exported relatively unchanged in glacier outflows. VL - 5 UR - http://www.nature.com/doifinder/10.1038/ngeo1403 IS - 3 ER - TY - JOUR T1 - Apparent oxygen utilization rates calculated from tritium and helium-3 profiles at the Bermuda Atlantic Time-series Study site JF - Biogeosciences Y1 - 2012 A1 - Stanley, R. H. R. A1 - Doney, S. C. A1 - W. J. Jenkins A1 - Lott, D. E., III AB - We present three years of Apparent Oxygen Utilization Rates (AOUR) estimated from oxygen and tracer data collected over the ocean thermocline at monthly resolution between 2003 and 2006 at the Bermuda Atlantic Timeseries Study (BATS) site. We estimate water ages by calculating a transit time distribution from tritium and helium-3 data. The vertically integrated AOUR over the upper 500 m, which is a regional estimate of export, during the three years is 3.1 +/- 0.5 mol O-2 m(-2) yr(-1). This is comparable to previous AOUR-based estimates of export production at the BATS site but is several times larger than export estimates derived from sediment traps or Th-234 fluxes. We compare AOUR determined in this study to AOUR measured in the 1980s and show AOUR is significantly greater today than decades earlier because of changes in AOU, rather than changes in ventilation rates. The changes in AOU are likely a methodological artefact associated with problems with early oxygen measurements. VL - 9 IS - 6 N1 - id: 2253; PT: J; TC: 0; UT: WOS:000305830000003 JO - Apparent oxygen utilization rates calculated from tritium and helium-3 profiles at the Bermuda Atlantic Time-series Study site ER - TY - JOUR T1 - Carbon dynamics in the western Arctic Ocean: insights from full-depth carbon isotope profiles of DIC, DOC, and POC JF - Biogeosciences Y1 - 2012 A1 - Griffith, D. R. A1 - McNichol, A. P. A1 - Xu, L. A1 - McLaughlin, F. A. A1 - Macdonald, R. W. A1 - Brown, K. A. A1 - Eglinton, T. I. AB - Arctic warming is projected to continue throughout the coming century. Yet, our currently limited understanding of the Arctic Ocean carbon cycle hinders our ability to predict how changing conditions will affect local Arctic ecosystems, regional carbon budgets, and global climate. We present here the first set of concurrent, full-depth, dual-isotope profiles for dissolved inorganic carbon (DIC), dissolved organic carbon (DOC), and suspended particulate organic carbon (POCsusp) at two sites in the Canada Basin of the Arctic Ocean. The carbon isotope composition of sinking and suspended POC in the Arctic contrasts strongly with open ocean Atlantic and Pacific sites, pointing to a combination of inputs to Arctic POCsusp at depth, including surface-derived organic carbon (OC), sorbed/advected OC, and OC derived from in situ DIC fixation. The latter process appears to be particularly important at intermediate depths, where mass balance calculations suggest that OC derived from in situ DIC fixation contributes up to 22% of POCsusp. As in other oceans, surface-derived OC is still a dominant source to Arctic POCsusp. Yet, we suggest that significantly smaller vertical POC fluxes in the Canada Basin make it possible to see evidence of DIC fixation in the POCsusp pool even at the bulk isotope level. VL - 9 IS - 3 N1 - id: 2254; PT: J; TC: 4; UT: WOS:000302179500026 JO - Carbon dynamics in the western Arctic Ocean: insights from full-depth carbon isotope profiles of DIC, DOC, and POC ER - TY - JOUR T1 - Carbon isotopic (C-13 and C-14) composition of synthetic estrogens and progestogens JF - RAPID COMMUNICATIONS IN MASS SPECTROMETRY Y1 - 2012 A1 - Griffith, David R. A1 - Wacker, Lukas A1 - Gschwend, Philip M. A1 - Eglinton, Timothy I. AB - RATIONALE Steroids are potent hormones that are found in many environments. Yet, contributions from synthetic and endogenous sources are largely uncharacterized. The goal of this study was to evaluate whether carbon isotopes could be used to distinguish between synthetic and endogenous steroids in wastewater and other environmental matrices. METHODS Estrogens and progestogens were isolated from oral contraceptive pills using semi-preparative liquid chromatography/diode array detection (LC/DAD). Compound purity was confirmed by gas chromatography/flame ionization detection (GC/FID), gas chromatography/time-of-flight mass spectrometry (GC/TOF-MS) and liquid chromatography/mass spectrometry using negative electrospray ionization (LC/ESI-MS). The C-13 content was determined by gas chromatography/isotope ratio mass spectrometry (GC/IRMS) and C-14 was measured by accelerator mass spectrometry (AMS). RESULTS Synthetic estrogens and progestogens are C-13-depleted (delta C-13(estrogen) = 30.0 +/- 0.9 parts per thousand; delta C-13(progestogen) = 30.3 +/- 2.6 parts per thousand) compared with endogenous hormones (delta C-13 similar to -16 to 26 parts per thousand). The C-14 content of the majority of synthetic hormones is consistent with synthesis from C-3 plant-based precursors, amended with `fossil' carbon in the case of EE2 and norethindrone acetate. Exceptions are progestogens that contain an ethyl group at carbon position 13 and have entirely `fossil' C-14 signatures. CONCLUSIONS Carbon isotope measurements have the potential to distinguish between synthetic and endogenous hormones in the environment. Our results suggest that C-13 could be used to discriminate endogenous from synthetic estrogens in animal waste, wastewater effluent, and natural waters. In contrast, C-13 and C-14 together may prove useful for tracking synthetic progestogens. Copyright (c) 2012 John Wiley & Sons, Ltd. VL - 26 ER - TY - JOUR T1 - Central Arctic paleoceanography for the last 50 kyr based on ostracode faunal assemblages JF - Marine Micropaleontology Y1 - 2012 A1 - Poirier, Robert K. A1 - Cronin, Thomas M. A1 - Briggs Jr, William M. A1 - Lockwood, Rowan AB - The paleoceanography of the central Arctic Ocean was reconstructed for the last 50 kyr (Marine Isotope Stages (MIS) 1–3) based on ostracode assemblages from 21 14C-dated sediment cores from the Mendeleev, Lomonosov, and Gakkel Ridges. Arctic sediments deposited during the Holocene interglacial period (MIS 1), the Bølling–Allerød, and larger interstadial Dansgaard–Oeschger (DO) events (3–4, 8, and 12) contain abundant Cytheropteron spp., Henryhowella asperrima, and Krithe spp. at intermediate/deep-depths (~ 1000 to 3000 m). These assemblages suggest a ventilated deep, Arctic Ocean water mass similar to the modern Arctic Ocean Deep Water (AODW) during these time periods. In contrast, sediment deposited during stadial events corresponding to Heinrich events 1, 2, 3, and 4, (also possibly the Younger Dryas; YD), contain abundant Polycope spp. (60–80%) suggesting a greater influence of the Atlantic Layer (AL) on the Arctic Intermediate Water (AIW) and AODW. Reduced sea-ice during the early Holocene, the last deglacial, and MIS 3 interstadials is indicated by the reoccurrence of Acetabulastoma arcticum, an epipelagic species that is parasitic on sea-ice dwelling amphipods. One hypothesis to explain these oceanographic changes during longer stadial events, particularly within the last glacial period (MIS 2), involves sluggish ocean circulation, thicker sea-ice cover, and a deeper halocline with ocean exchange between Greenland Sea and Arctic Ocean deep-water through the Fram Strait. VL - 88–89 UR - http://www.sciencedirect.com/science/article/pii/S0377839812000278 N1 - id: 2283 JO - Central Arctic paleoceanography for the last 50 kyr based on ostracode faunal assemblages ER - TY - JOUR T1 - Changes in planktic foraminiferal faunas, temperature and salinity in the Gulf Stream during the last 30,000 years: influence of meltwater via the Mississippi River JF - Quaternary Science Reviews Y1 - 2012 A1 - Rasmussen, T. L. A1 - Thomsen, E. AB - Variations in the distribution of planktic foraminiferal faunas, temperature and salinity in the surface water of the Gulf Stream during the last 30,000 years have been reconstructed based on a sediment core from the Blake Ridge, subtropical western Atlantic Ocean. Temperatures and salinities were calculated using planktic foraminiferal transfer functions and previously published oxygen isotope values. Productivity was estimated using the >106 μm size fraction of planktic foraminifera. The reconstructed values show that temperature variations have been small during the investigated period with a total range of only 3 °C. The highest temperatures, about 1.5 °C above the present temperature in the area, occurred during the late Glacial, Heinrich event 1 and the mid Holocene time periods. The lowest temperatures, about 1.5 °C below the present temperatures, occurred during the Bølling interstadial. The early Holocene period was relatively cool. The low temperatures during the Bølling interstadial and during the early Holocene are in contrast to the northeastern Atlantic, where the Bølling interstadial was the warmest period of the deglaciation, and the early Holocene the warmest during the Holocene. We attribute the lower temperatures during the Bølling and early Holocene periods to colder meltwater from the Laurentide Ice Sheet flowing into the Gulf of Mexico through the Mississippi River system and carried to the Blake Ridge via the Gulf Stream. VL - 33 UR - http://www.sciencedirect.com/science/article/pii/S0277379111003787 N1 - id: 2150 JO - Changes in planktic foraminiferal faunas, temperature and salinity in the Gulf Stream during the last 30,000 years: influence of meltwater via the Mississippi River ER - TY - JOUR T1 - Characteristics of water-soluble organic carbon associated with aerosol particles in the eastern United States JF - Atmospheric Environment Y1 - 2012 A1 - Wozniak, Andrew S. A1 - Bauer, James E. A1 - Dickhut, Rebecca M. AB - Desorption kinetics and sources (fossil vs. contemporary) of the water soluble organic carbon (WSOC) component of aerosol particles were examined at two sites on the east coast of the United States. Experiments revealed that WSOC is released either rapidly as one homogeneous pool or via biphasic kinetics with one rapidly and one slowly desorbing pool. The majority (>85%) of WSOC was desorbed within the first 15 min of immersion in water, suggesting that this material can be rapidly incorporated into rainwater pre-depositionally or surface waters post-depositionally and transported through watersheds. Radiocarbon (14C) measurements showed that on average 12 ± 4% and 14 ± 2% of WSOC from sites in New York and Virginia, respectively, was derived from fossil sources. By contrast, mass balance calculations revealed water-insoluble organic carbon to have significantly greater fossil contributions. These findings suggest that contemporary biogenic aerosol OC is preferentially incorporated into the aqueous phase and may be transported relatively rapidly through watersheds and aquatic systems. In contrast, the more highly aged and fossil aerosol component remains in particulate form and is more likely to be retained on particles or in soils or aquatic sediments. VL - 46 UR - http://www.sciencedirect.com/science/article/pii/S1352231011010466 N1 - id: 2153 JO - Characteristics of water-soluble organic carbon associated with aerosol particles in the eastern United States ER - TY - JOUR T1 - Characterization of soils beneath a Posidonia oceanica meadow JF - Geoderma Y1 - 2012 A1 - Serrano, O. A1 - Mateo, M. A. A1 - Renom, P. A1 - Julià, R. AB - The study of a 475 cm core (spanning 4316 y BP) sampled in a Posidonia oceanica meadow (Portlligat Bay, NW Mediterranean) allowed us to make the first detailed description of the soil below this endemic seagrass. The sediments under P. oceanica (often referred to as mat or matte) are low density (average bulk density of 0.69 g DW cm− 3) marine soils mainly composed of siliciclastic (46%) and biogenic carbonated (46%) fine-grained sediments (particles 1 mm) and finer organic matter (3% of SOM; VL - 185–186 UR - http://www.sciencedirect.com/science/article/pii/S0016706112001395 N1 - id: 2300 JO - Characterization of soils beneath a Posidonia oceanica meadow ER - TY - JOUR T1 - Chemical and bacteriological analysis of soil from the Middle and Late Weichselian from Western Spitsbergen, Arctic JF - The environment and chronology of the earliest occupation of north-west Europe: current knowledge, problems and new research directions Y1 - 2012 A1 - Singh, Shiv Mohan A1 - Sharma, Jagdev A1 - Gawas-Sakhalkar, Puja A1 - Upadhyay, Ajay K. A1 - Naik, Simantini A1 - Bande, Dnyanesh A1 - Ravindra, Rasik AB - This paper discusses temporal variability in the biogeochemical properties of the deeper permafrost soils of Western Spitsbergen, Arctic, that dates back up to the Middle Weichselian period (44.8 ka BP). Results indicate that during the mid of the last interstadial (∼37 ka BP) the chemical and biological properties of the soils were different from the stadial period that followed. Trace element concentration during the period remained low. Electrical conductivity along with K, Mg, Na, SO4−2, Cl− and HCO3− content of the soils during this period was high. Mineralizable nitrogen, organic carbon, biomass nitrogen and total bacterial counts were also high. These observations concurrently lead to a conclusion that the soils of Western Spitsbergen during the interstadial period were under marine influence. The culturability of bacterial cells was low which increased later with the onset of the stadial. VL - 271 UR - http://www.sciencedirect.com/science/article/pii/S1040618212001541 N1 - id: 2316 JO - Chemical and bacteriological analysis of soil from the Middle and Late Weichselian from Western Spitsbergen, Arctic ER - TY - JOUR T1 - Chemical characteristics of particulate organic matter from a small, mountainous river in the Oregon Coast Range, USA JF - Biogeochemistry Y1 - 2012 A1 - Hatten, J. A. A1 - Goñi, M. A. A1 - Wheatcroft, R. A. VL - 107 N1 - id: 890submittedY JO - Chemical characteristics of particulate organic matter from a small, mountainous river in the Oregon Coast Range, USA ER - TY - JOUR T1 - Chemical weathering and provenance evolution of Holocene–Recent sediments from the Western Indus Shelf, Northern Arabian Sea inferred from physical and mineralogical properties JF - Marine Geology Y1 - 2012 A1 - Limmer, David R. A1 - Köhler, Cornelia M. A1 - Hillier, Stephen A1 - Moreton, Steven G. A1 - Tabrez, Ali R. A1 - Clift, Peter D. AB - We present a multi-proxy mineral record based on X-ray diffraction and diffuse reflectance spectrophotometry analysis for two cores from the western Indus Shelf in order to reconstruct changing weathering intensities, sediment transport, and provenance variations since 13 ka. Core Indus-10 is located northwest of the Indus Canyon and exhibits fluctuations in smectite/(illite + chlorite) ratios that correlate with monsoon intensity. Higher smectite/(illite + chlorite) and lower illite crystallinity, normally associated with stronger weathering, peaked during the Early–Mid Holocene, the period of maximum summer monsoon. Hematite/goethite and magnetic susceptibility do not show clear co-variation, although they both increase at Indus-10 after 10 ka, as the monsoon weakened. At Indus-23, located on a clinoform just west of the canyon, hematite/goethite increased during a period of monsoon strengthening from 10 to 8 ka, consistent with increased seasonality and/or reworking of sediment deposited prior to or during the glacial maximum. After 2 ka terrigenous sediment accumulation rates in both cores increased together with redness and hematite/goethite, which we attribute to widespread cultivation of the floodplain triggering reworking, especially after 200 years ago. Over Holocene timescales sediment composition and mineralogy in two localities on the high-energy shelf were controlled by varying degrees of reworking, as well as climatically modulated chemical weathering. VL - 326–328 UR - http://www.sciencedirect.com/science/article/pii/S0025322712001600 N1 - id: 2271 JO - Chemical weathering and provenance evolution of Holocene–Recent sediments from the Western Indus Shelf, Northern Arabian Sea inferred from physical and mineralogical properties ER - TY - JOUR T1 - Clay mineral variations in Holocene terrestrial sediments from the Indus Basin JF - Quaternary Research Y1 - 2012 A1 - Alizai, Anwar A1 - Hillier, Stephen A1 - Clift, Peter D. A1 - Giosan, Liviu A1 - Hurst, Andrew A1 - VanLaningham, Sam A1 - Macklin, Mark AB - We employed X-ray diffraction methods to quantify clay mineral assemblages in the Indus Delta and flood plains since ~ 14 ka, spanning a period of strong climatic change. Assemblages are dominated by smectite and illite, with minor chlorite and kaolinite. Delta sediments integrate clays from across the basin and show increasing smectite input between 13 and 7.5 ka, indicating stronger chemical weathering as the summer monsoon intensified. Changes in clay mineralogy postdate changes in climate by 5–3 ka, reflecting the time needed for new clay minerals to form and be transported to the delta. Samples from the flood plains in Punjab show evidence for increased chemical weathering towards the top of the sections (6– VL - 77 UR - http://www.sciencedirect.com/science/article/pii/S0033589412000099 IS - 3 N1 - id: 2333 JO - Clay mineral variations in Holocene terrestrial sediments from the Indus Basin ER - TY - JOUR T1 - Climatic and environmental evolution of Lake Iznik (NW Turkey) over the last ∼4700 years JF - Temporal and spatial corridors of Homo sapiens sapiens population dynamics during the Late Pleistocene and Early Holocene Y1 - 2012 A1 - Ülgen, Umut Barış A1 - Franz, Sven Oliver A1 - Biltekin, Demet A1 - Çağatay, M. Namik A1 - Roeser, Patricia Angelika A1 - Doner, Lisa A1 - Thein, Jean AB - Magnetic susceptibility, geochemistry, mineralogy and palynology of sediments from Lake Iznik in Northwestern Anatolia, Turkey, provide a 4700 year record of climatic trends and events. The measured proxies allow a reconstruction of variations in humid/dry periods and lake level changes. The Lake Iznik sedimentary sequence points to an oscillating trend of humid periods interrupted by rapid climate change (RCC) to arid periods. Especially abrupt lithologic and geochemical changes at 4.2 and 3.3 ka calBP may outline intense droughts, which extremely lowered the lake level. For the last 2000 years, the effects of the Roman warm period, Dark Age cold period, Medieval Warm Period and Little Ice Age are recorded within Lake Iznik sediments. Besides many similarities of local climatic periods with other records from the Eastern Mediterranean, there are also differences indicating the complex pattern of the climate in the region. VL - 274 UR - http://www.sciencedirect.com/science/article/pii/S1040618212004363 N1 - id: 2337 JO - Climatic and environmental evolution of Lake Iznik (NW Turkey) over the last ∼4700 years ER - TY - JOUR T1 - Climatic and megaherbivory controls on late-glacial vegetation dynamics: a new, high-resolution, multi-proxy record from Silver Lake, Ohio JF - Quaternary Science Reviews Y1 - 2012 A1 - Gill, Jacquelyn L. A1 - Williams, John W. A1 - Jackson, Stephen T. A1 - Donnelly, Jeffrey P. A1 - Schellinger, Grace C. AB - Novel plant assemblages are a long-recognized feature of late-glacial North America, but identifying their causes has been hampered by inaccurate radiocarbon chronologies and the multiplicity of ecological and climatic events during the late Pleistocene. Recently we reported that the formation of no-analog vegetation may have been linked to declines in Pleistocene megafaunal communities, based on pollen and spores from the coprophilous fungus Sporormiella at sites in Indiana and New York. We present a new, multi-proxy analysis from Silver Lake, OH, which 1) updates the radiocarbon chronology of a classic pollen record with a well-established zone of no-analog vegetation, 2) combines a new sub-centennial pollen record with charcoal, Sporormiella, and x-ray fluorescence (XRF) spectroscopy analyses for an integrated record of landscape change before, during, and after the period of no-analog vegetation, and 3) replicates both the absolute and relative temporal patterns of landscape change at Appleman Lake, IN. At Silver Lake, the decline in Sporormiella at 13.9 ka BP was immediately followed by the formation of novel plant assemblages, as well as the highest-magnitude charcoal peak in the record. Increased Ca and Sr concentrations during the no-analog interval indicate either increased moisture, increased input of nutrients from deciduous litter, or both. The duration of the no-analog assemblages (13.9–11.8 ka BP) roughly corresponds to the period of peak insolation dissimilarity, but is more temporally constrained than previously reported in subcontinental-scale syntheses (17–11 ka BP). We propose a hierarchy of controls on late-glacial plant communities, where biotic interactions such as megaherbivory mediate climate-driven vegetation change. VL - 34 UR - http://www.sciencedirect.com/science/article/pii/S027737911100401X N1 - id: 2141 JO - Climatic and megaherbivory controls on late-glacial vegetation dynamics: a new, high-resolution, multi-proxy record from Silver Lake, Ohio ER - TY - JOUR T1 - Comparative Decalcification Methods, Radiocarbon Dates, and Stable Isotopes of the VIRI Bones JF - Radiocarbon Y1 - 2012 A1 - Tuross, Noreen AB - The Fifth International Radiocarbon Comparison (VIRI) provided a suite of 5 bone samples with consensus ages ranging from 969 to 39,305 14C yr BP (Scott et al. 2010). These bones were used herein in a comparison of decalcification methods using either HCl or EDTA to produce collagen, and the results demonstrate age concordance between both preparation methods and the VIRI consensus values. Additional isotopic analyses of the collagen (13C, 15N, and 18O) illustrate the increasing sensitivity of carbon, nitrogen, and oxygen isotopes in assessing gelatin degradation. VL - 54 UR - https://www.cambridge.org/core/product/identifier/S0033822200047482/type/journal_articlehttps://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0033822200047482 IS - 3-4 ER - TY - JOUR T1 - Composition and fate of gas and oil released to the water column during the Deepwater Horizon oil spill JF - Proceedings of the National Academy of Sciences of the United States of America Y1 - 2012 A1 - Reddy, Christopher M. A1 - Arey, J. Samuel A1 - Seewald, Jeffrey S. A1 - Sylva, Sean P. A1 - Lemkau, Karin L. A1 - Nelson, Robert K. A1 - Carmichael, Catherine A. A1 - McIntyre, Cameron P. A1 - Fenwick, Judith A1 - Ventura, G. Todd A1 - Van Mooy, Benjamin A. S. A1 - Camilli, Richard AB - Quantitative information regarding the endmember composition of the gas and oil that flowed from the Macondo well during the Deepwater Horizon oil spill is essential for determining the oil flow rate, total oil volume released, and trajectories and fates of hydrocarbon components in the marine environment. Using isobaric gas-tight samplers, we collected discrete samples directly above the Macondo well on June 21, 2010, and analyzed the gas and oil. We found that the fluids flowing from the Macondo well had a gas-to-oil ratio of 1,600 standard cubic feet per petroleum barrel. Based on the measured endmember gas-to-oil ratio and the Federally estimated net liquid oil release of 4.1 million barrels, the total amount of C-1-C-5 hydrocarbons released to the water column was 1.7 x 10(11) g. The endmember gas and oil compositions then enabled us to study the fractionation of petroleum hydrocarbons in discrete water samples collected in June 2010 within a southwest trending hydrocarbon-enriched plume of neutrally buoyant water at a water depth of 1,100 m. The most abundant petroleum hydrocarbons larger than C-1-C-5 were benzene, toluene, ethylbenzene, and total xylenes at concentrations up to 78 mu gL(-1). Comparison of the endmember gas and oil composition with the composition of water column samples showed that the plume was preferentially enriched with water-soluble components, indicating that aqueous dissolution played a major role in plume formation, whereas the fates of relatively insoluble petroleum components were initially controlled by other processes. VL - 109 IS - 50 N1 - id: 2247; PT: J; TC: 10; UT: WOS:000312605600028 JO - Composition and fate of gas and oil released to the water column during the Deepwater Horizon oil spill ER - TY - JOUR T1 - Constraining Holocene 10Be production rates in Greenland JF - Journal of Quaternary Science Y1 - 2012 A1 - Briner, Jason P. A1 - Young, ás E. A1 - Goehring, Brent M. A1 - Schaefer, Joerg M. AB - The absence of a production rate calibration experiment on Greenland has limited the ability to link 10Be exposure dating chronologies of ice-margin change to independent records of rapid climate change. We use radiocarbon age control on Holocene glacial features near Jakobshavn Isbræ, western Greenland, to investigate 10Be production rates. The radiocarbon chronology is inconsistent with the 10Be age calculations based on the current globally averaged 10Be production rate calibration data set, but is consistent with the 10Be production rate calibration data set from north-eastern North America, which includes a calibration site nearby on north-eastern Baffin Island. Based on the best-dated feature available from the Jakobshavn Isbræ forefield, we derive a 10Be production rate value of 3.98 ± 0.24 atoms g a−1, using the ‘St’ scaling scheme, which overlaps with recently published reference 10Be production rates. We suggest that these 10Be production rate data, or the very similar data from north-eastern North America, are used on Greenland. Copyright © 2011 John Wiley & Sons, Ltd. VL - 27 UR - http://doi.wiley.com/10.1002/jqs.1562 IS - 1 ER - TY - JOUR T1 - Correction to" Isotopic characterization of aerosol organic carbon components over the eastern United States" (vol 117, D13303, 2012) JF - Journal of Geophysical Research-Atmospheres Y1 - 2012 A1 - Wozniak, Andrew S. A1 - Bauer, James E. A1 - Dickhut, Rebecca M. A1 - Xu, Li A1 - McNichol, Ann P. VL - 117 N1 - id: 2251; PT: J; TC: 0; UT: WOS:000307471700004 JO - Isotopic characterization of aerosol organic carbon components over the eastern United States (vol 117, D13303, 2012) ER - TY - JOUR T1 - Corrigendum to “Timing and duration of North American glacial lake discharges and the Younger Dryas climate reversal” [Quaternary Research 75 (2011) 541–551] JF - Quaternary Research Y1 - 2012 A1 - Rayburn, John A. A1 - Cronin, Thomas M. A1 - Franzi, David A. A1 - Knuepfer, Peter L. K. A1 - Willard, Debra A. VL - 77 UR - http://www.sciencedirect.com/science/article/pii/S0033589411001190 IS - 1 N1 - id: 2156 JO - Corrigendum to “Timing and duration of North American glacial lake discharges and the Younger Dryas climate reversal” [Quaternary Research 75 (2011) 541–551] ER - TY - JOUR T1 - The deglacial to postglacial marine environments of SEBarrow Strait, Canadian Arctic Archipelago JF - Boreas Y1 - 2012 A1 - Pieńkowski, A. J. A1 - England, John H. A1 - Furze, Mark F. A. A1 - Marret, Fabienne A1 - Eynaud, Frédérique A1 - Vilks, Gustav A1 - MacLean, Brian A1 - Blasco, Steve A1 - Scourse, James D. AB - Core 86027-144 (74°15.56?N, 91°14.21?W) represents a rare, continuous record of Late Pleistocene to Holocene sediments from High Arctic Canada extending from the end of the Last Glaciation. Based on microfossils (dinocysts, non-pollen palynomorphs, benthic and planktonic foraminifera), foraminiferal ?18O and ?13C, and sedimentology, seven palaeoenvironmental zones were identified. Zone I (>10.8?cal.?ka BP) records deglaciation, ice-sheet destabilization, float-off and subsequent break-up. Zone II (c.?10.8?10.4?cal.?ka BP) shows ice-proximal to ice-distal glaciomarine conditions, interrupted by pervasive land-fast sea-ice marked by a hiatus in coarse sediment deposition. Significant biological activity starts in Zone III (10.4?9.9?cal.?ka BP), where planktonic foraminifera (Neogloboquadrina pachyderma) suggest early oceanic throughflow. Surface waters flowed NW?SE; however, the deep-water origin remains unclear (potentially NW Arctic Ocean or Baffin Bay). Postglacial amelioration (open-water season greater than present) in Zone IV (9.9?7.8?cal.?ka BP) perhaps corresponds to the regional ?Holocene Thermal Maximum? previously proposed. A transitional period (Zone V; 7.8?6.7?cal. ka BP) of rapid environmental change fluctuating on a scale not observed today is marked by increasing sea-ice and reduced oceanic influence. This probably signals the exclusion of deeper Atlantic water owing to the glacio-isostatic shallowing of inter-island sills, coupled with generally cooling climate. Conditions analogous to those at present, with increased sea-ice and modern microfossil assemblages, commence at c. 6.7?cal.?ka BP (zones VI?VII). Although climate ultimately forces long-term environmental trends, core 86027-144 data imply that regional dynamics, especially changes in sea-level, exert a significant control on marine conditions throughout the Canadian Arctic Archipelago. VL - 41 UR - http://dx.doi.org/10.1111/j.1502-3885.2011.00227.x IS - 2 N1 - id: 2342 JO - The deglacial to postglacial marine environments of SEBarrow Strait, Canadian Arctic Archipelago ER - TY - JOUR T1 - Direct measurement of riverine particulate organic carbon age structure JF - Geophysical Research Letters Y1 - 2012 A1 - Rosenheim, Brad E. A1 - Galy, Valier AB - Carbon cycling studies focusing on transport and transformation of terrigenous carbon sources toward marine sedimentary sinks necessitate separation of particulate organic carbon (OC) derived from many different sources and integrated by river systems. Much progress has been made on isolating and characterizing young biologically-formed OC that is still chemically intact, however quantification and characterization of old, refractory rock-bound OC has remained troublesome. Quantification of both endmembers of riverine OC is important to constrain exchanges linking biologic and geologic carbon cycles and regulating atmospheric CO2 and O-2. Here, we constrain petrogenic OC proportions in suspended sediment from the headwaters of the Ganges River in Nepal through direct measurement using ramped pyrolysis radiocarbon analysis. The unique results apportion the biospheric and petrogenic fractions of bulk particulate OC and characterize biospheric OC residence time. Compared to the same treatment of POC from the lower Mississippi-Atchafalaya River system, contrast in age spectra of the Ganges tributary samples illustrates the difference between small mountainous river systems and large integrative ones in terms of the global carbon cycle. Citation: Rosenheim, B. E., and V. Galy (2012), Direct measurement of riverine particulate organic carbon age structure, Geophys. Res. Lett., 39, L19703, doi:10.1029/2012GL052883. VL - 39 N1 - id: 2248; PT: J; TC: 0; UT: WOS:000309605800002 JO - Direct measurement of riverine particulate organic carbon age structure ER - TY - JOUR T1 - Early stall of West Antarctic Ice Sheet advance on the eastern Ross Sea middle shelf followed by retreat at 27,500 14C yr BP JF - Palaeogeography, Palaeoclimatology, Palaeoecology Y1 - 2012 A1 - Bart, Philip J. A1 - Cone, Amy N. AB - Marine geological and geophysical data suggest that the West Antarctic Ice Sheet (WAIS) deposited three thick seismically-resolvable units in the eastern Ross Sea since the Last Glacial Maximum (LGM) but the chronology of these grounding events is debated. Existing ice-retreat chronologies for the eastern Ross Sea are considered suspect because nearly all have been developed using radiocarbon dating of acid-insoluble organics (AIO) from bulk sediment. We used a new strategy to isolate in situ forams from diamict sediment deposited at the middle-shelf grounding-zone wedge (GZW) — a subaqueous ice-marginal landform previously interpreted to represent deposition during the third grounding event since the LGM advance to the shelf edge. Here we present a synthesis of our new radiocarbon dates of foram tests and AIO with previously published radiocarbon dates. We propose that the WAIS's LGM advance in the eastern-Ross Sea sector reached the middle shelf circa 27,500 14C yr BP and that open-marine sedimentation began shortly thereafter. There is as of yet no clear explanation for why WAIS retreat in this sector of Antarctica apparently began prior to the peak of the last glacial cold period. A precipitation deficit, localized warm water intrusion, an ice dynamic response in the absence of climate forcing or another as of yet unknown forcing mechanism could be responsible. VL - 335-336 UR - http://www.sciencedirect.com/science/article/pii/S0031018211004330 N1 - id: 2170 JO - Early stall of West Antarctic Ice Sheet advance on the eastern Ross Sea middle shelf followed by retreat at 27,500 14C yr BP ER - TY - JOUR T1 - ENSO Drove 2500-Year Collapse of Eastern Pacific Coral Reefs JF - Science Y1 - 2012 A1 - Toth, L. T. A1 - Aronson, R. B. A1 - Vollmer, S. V. A1 - Hobbs, J. W. A1 - Urrego, D. H. A1 - Cheng, H. A1 - Enochs, I. C. A1 - Combosch, D. J. A1 - van Woesik, R. A1 - Macintyre, I. G. AB - Cores of coral reef frameworks along an upwelling gradient in Panamá show that reef ecosystems in the tropical eastern Pacific collapsed for 2500 years, representing as much as 40% of their history, beginning about 4000 years ago. The principal cause of this millennial-scale hiatus in reef growth was increased variability of the El Niño–Southern Oscillation (ENSO) and its coupling with the Intertropical Convergence Zone. The hiatus was a Pacific-wide phenomenon with an underlying climatology similar to probable scenarios for the next century. Global climate change is probably driving eastern Pacific reefs toward another regional collapse. VL - 337318333105323329353215234133898029327161272715118 119109123420422375802767219435149464823345354035608535771415 UR - http://www.sciencemag.org/cgi/doi/10.1126/science.1221168 IS - 609058576041305910598912255331111-125-64469129166932A216274137112 ER - TY - JOUR T1 - Evaluation of sediment trace metal records as paleoproductivity and paleoxygenation proxies in the upwelling center off Concepción, Chile (36°S) JF - Variability of the coastal upwelling and coastal transition zones off central-southern Chile Y1 - 2012 A1 - Muñoz, Praxedes A1 - Dezileau, Laurent A1 - Lange, Carina A1 - Cardenas, Lissette A1 - Sellanes, Javier A1 - Salamanca, Marco A. A1 - Maldonado, Antonio AB - This study analyzes the records of several trace metals sensitive to redox conditions in continental shelf sediments off Concepción, Chile (36°S). The continental margin off Concepción (36°S; 73°W) lies beneath an important upwelling center characterized by high primary production rates and, consequently, high fluxes of organic matter. In spring and summer, this material settles to the seafloor where it decays, producing periods of very low oxygen content in bottom waters (1 mL L−1). The goals of this study were to determine the input of trace metals to the sediment and to decipher how this information can be used to reveal variations in primary productivity or bottom oxygenation. Gravity cores collected at two stations – VG06-2 over the mid-shelf station (88 m water depth, upper boundary of the oxygen minimum zone) and VG06-3 over the outer shelf (120 m water depth, within the oxygen minimum zone) – were sampled for high resolution profiles (1 cm) of trace metals, biogenic opal, stable isotopes, and total organic carbon. The results suggest that the variability in the trace metal distribution on the continental shelf off Concepción is determined by redox conditions and the organic carbon flux to the bottom. Some sections of the sediment cores from the outer shelf showed appreciable authigenic enrichment of U, Cd, and Mo (EF: 5–10, 2–5, and 10–16 respectively) along with heavier values of δ15N, suggesting periods of suboxic conditions. During these periods, fluxes of organic material to the bottom were higher, as indicated by elevated TOC and opal contents. Alternating periods of higher and lower trace metal contents were not observed mid-shelf as they were on the outer shelf. Rather, the mid-shelf samples showed authigenic enrichment of U, Cd, and Mo (EF: 1–6, 4–5, and 10–20, respectively) throughout the core except in a 10-cm-thick gray layer. In general, authigenic enrichment of U, Mo, and Cd occurred at both sites, coincident with olive green layers in the cores. These layers were associated with periods of elevated primary productivity and suboxic conditions. Such periods did not seem to last as long as the oxygenated periods, which had higher inputs of refractive detrital material, coincident with the occurrence of distinct gray sediment layers. VL - 92–95 UR - http://www.sciencedirect.com/science/article/pii/S0079661111000644 N1 - id: 2154 JO - Evaluation of sediment trace metal records as paleoproductivity and paleoxygenation proxies in the upwelling center off Concepción, Chile (36°S) ER - TY - CHAP T1 - Exploring human subsistence at CA-SMI-575NE: An 8400-year-old shell midden on San Miguel Island, California T2 - Exploring Methods of Faunal Analysis: Insights from California Archaeology Y1 - 2012 A1 - Erlandson, Jon M. A1 - Braje, Todd J. ED - Glassow, M. JF - Exploring Methods of Faunal Analysis: Insights from California Archaeology PB - Cotsen Institute of Archaeology Press SN - 9781931745871 N1 - id: 2069 ER - TY - JOUR T1 - Fine scale sediment structure and geochemical signature between eastern and western North Atlantic during Heinrich events 1 and 2 JF - Quaternary Science Reviews Y1 - 2012 A1 - Rashid, H. A1 - Saint-Ange, F. A1 - Barber, D. C. A1 - Smith, M. E. A1 - Devalia, N. AB - Heinrich iceberg-rafting events 1 and 2 (H1 and H2) in the Labrador Sea are identified by their typical nepheloid-flow deposit sedimentary structure, high bulk carbonate, increase in iceberg-rafted detritus (IRD), and depletion of δ18O in the surface-dwelling foraminifer, Neogloboquadrina pachyderma (s). H-layers in this region have sedimentological characteristics different than those in the North Atlantic, and consist of IRD interspersed in pelagic sediments. High resolution 14C-AMS dates allowed us to delineate the leads and lags in instability between different ice-streams of the former Laurentide ice-sheet (LIS). Our data suggest that the discharge from the Hudson Strait ice-stream was followed by Cumberland Sound ice-sheet during H1 and H2. New radiogenic isotopes from the ice-proximal and surficial sediments of the greater Hudson Strait region and Labrador Sea H0, H1 and H2 layers suggest that carbonate-rich layers were only derived from Hudson Strait, not Baffin Bay. Fine scale structure of H1 and H2 intervals in Labrador Sea slope cores is characterized by two lithic peaks dominated by detrital carbonate grains and a single peak in cores from the central Labrador Sea. A similar pattern in the structure of H1 and H2 is observed along the western European margin. These findings contrast with North Atlantic H1 and H2 intervals, which are characterized by a peak of carbonate-rich grains, followed by a peak of quartz and volcanic grains. This comparison with North Atlantic and western European margin cores leads us to suggest that the coupling or lack thereof, between the LIS and European ice-sheet, is related to the depositional processes occurring along the margins, as well as the distance from the sources and the ability of the oceanic currents to disperse icebergs. Any significant change in ice-sheet dynamics would be recorded close to the ice-sheet margin, while distal locations would only record extreme events. We hypothesize that the discordance between the findings reported in the literature is most likely similar to the difference between the upper slope/deep Labrador sites and the Flemish Pass site described in this contribution but requires vigorous testing. VL - 46 UR - http://www.sciencedirect.com/science/article/pii/S0277379112001734 N1 - id: 2308 JO - Fine scale sediment structure and geochemical signature between eastern and western North Atlantic during Heinrich events 1 and 2 ER - TY - JOUR T1 - Geochemical and geological constraints on the composition of marine sediment pore fluid: Possible link to gas hydrate deposits JF - Marine and Petroleum Geology Y1 - 2012 A1 - Mazumdar, A. A1 - Joao, H. M. A1 - Peketi, A. A1 - Dewangan, P. A1 - Kocherla, M. A1 - Joshi, R. K. A1 - Ramprasad, T. AB - Pore water sulfate consumption in marine sediments is controlled by microbially driven sulfate reduction via organo-clastic and methane oxidation processes. In this work, we present sediment pore fluid compositions of 10 long sediment cores and high resolution seismic data from the Krishna–Godavari (K–G) basin, Bay of Bengal. Our results show occurrence of transient (S and kink types) and steady state (quasi-linear) sulfate concentration profiles which are attributed partly to the anaerobic oxidation of methane ( δ 13 C CH 4 : −84.8 to −100.1‰ VPDB) and organo-clastic sulfate reduction. Influence of AOM on alkalinity is evident from the presence of authigenic carbonate layers with highly depleted carbon isotope ratios in core MD161-8. The authigenic carbonates represent the paleo-SMTZs and suggest marked fluctuation in vertical methane flux. Our geophysical data show the acoustic signatures of upward fluid migration from shallow sub-surface, whereas, coring during NGHP expedition-01 confirms the presence of sub-surface gas hydrate deposits in K–G basin which can be linked to deep methane sources. The geochemical analysis suggests that shallow methane source can be attributed to high burial flux of labile organic matter due to high sedimentation rate. Sampling sites with high methane flux from the shallow gas source are characterized by quasi-linear sulfate concentration profile and a shallow sulfate methane transition zone (SMTZ) and may not be necessarily linked to deeper gas hydrate deposits. In contrast, the deep methane source results in a transient kink type sulfate profile and a deeper SMTZ. We have observed a close link between the occurrence of gas hydrate and the S/kink type sulfate profile. We interpret the short lived ‘kink’ in the sulfate profiles as a result of recent enhancement in vertical methane flux possibly driven by reactivation of fault-fractures systems which provide the conduits for fluid flow. VL - 38 UR - http://www.sciencedirect.com/science/article/pii/S0264817212001808 IS - 1 N1 - id: 2306 JO - Geochemical and geological constraints on the composition of marine sediment pore fluid: Possible link to gas hydrate deposits ER - TY - JOUR T1 - Geologic methane seeps along boundaries of Arctic permafrost thaw and melting glaciers JF - Nature Geoscience Y1 - 2012 A1 - Walter Anthony, Katey M. A1 - Anthony, Peter A1 - Grosse, Guido A1 - Chanton, Jeffrey KW - Biogeochemistry KW - Cryospheric science AB - Methane, a potent greenhouse gas, accumulates in subsurface hydrocarbon reservoirs, such as coal beds and natural gas deposits. In the Arctic, permafrost and glaciers form a ‘cryosphere cap’ that traps gas leaking from these reservoirs, restricting flow to the atmosphere. With a carbon store of over 1,200 Pg, the Arctic geologic methane reservoir is large when compared with the global atmospheric methane pool of around 5 Pg. As such, the Earth’s climate is sensitive to the escape of even a small fraction of this methane. Here, we document the release of 14C-depleted methane to the atmosphere from abundant gas seeps concentrated along boundaries of permafrost thaw and receding glaciers in Alaska and Greenland, using aerial and ground surface survey data and in situ measurements of methane isotopes and flux. We mapped over 150,000 seeps, which we identified as bubble-induced open holes in lake ice. These seeps were characterized by anomalously high methane fluxes, and in Alaska by ancient radiocarbon ages and stable isotope values that matched those of coal bed and thermogenic methane accumulations. Younger seeps in Greenland were associated with zones of ice-sheet retreat since the Little Ice Age. Our findings imply that in a warming climate, disintegration of permafrost, glaciers and parts of the polar ice sheets could facilitate the transient expulsion of 14C-depleted methane trapped by the cryosphere cap. VL - 5 UR - http://www.nature.com/doifinder/10.1038/ngeo1480 IS - 6 ER - TY - JOUR T1 - Geological interpretation of a low-backscatter anomaly found on the New Jersey continental margin JF - Marine Geology Y1 - 2012 A1 - Sweeney, Edward M. A1 - Gardner, James V. A1 - Johnson, Joel E. A1 - Mayer, Larry A. AB - An enigmatic low-backscatter, acoustic anomaly occurs on the New Jersey continental margin between Hudson and Wilmington Canyon channels. The presence of the low-backscatter anomaly, as seen with 6.5- and 12-kHz data, indicates a change in the physical properties of the seafloor or near sub-surface. Analyses of seafloor and sub-surface acoustic data with previously collected sediment cores suggest the low-backscatter feature corresponds to an outcrop of older strata uncovered by erosion and non-deposition by the Western Boundary Undercurrent (WBUC). The decrease in backscatter strength is enhanced by the presence of gas in the sub-surface sediments found in the buried Chesapeake Drift. VL - 326–328 UR - http://www.sciencedirect.com/science/article/pii/S0025322712001831 N1 - id: 2328 JO - Geological interpretation of a low-backscatter anomaly found on the New Jersey continental margin ER - TY - JOUR T1 - Insights into the Holocene environmental setting of Terra Nova Bay region (Ross Sea, Antarctica) from oxygen isotope geochemistry of Adélie penguin eggshells JF - The Holocene Y1 - 2012 A1 - Lorenzini, Sandra A1 - Baneschi, Ilaria A1 - Fallick, Anthony E. A1 - Salvatore, Maria Cristina A1 - Zanchetta, Giovanni A1 - Dallai, Luigi A1 - Baroni, Carlo AB - An oxygen isotope record of Adélie penguin (Pygoscelis adeliae) eggshells from Terra Nova Bay (Victoria Land, Antarctica) has been reconstructed in order to provide insights into the palaeoenviroment of this region during the last ~8000 years. The d18O values measured in eggshell carbonate show a great variability over the course of the studied period, with maximum values consistently around +27.5‰. Adopting a metabolic enrichment relative to water source of ~+28.5‰, eggshell d18O values can be interpreted in terms of marine water uptake by the penguins. The spread in d18O of eggshell carbonate at any given time toward more negative values reflects the existence of a low d18O water end member, most plausibly snow or snowmelt. Samples younger than 2000 years are characterized by a general lack of very negative d18O values. As also attested by other proxies, this shift toward more positive isotopic values is likely to be related both to a decreasing contribution of snow or meltwater in the seawaters and consequently to an absence or paucity on the boundary of the nesting sites of snow or snowfall and freshwater that could be directly eaten or drunk by penguins. VL - 22 UR - http://hol.sagepub.com/content/22/1/63.abstract IS - 1 N1 - id: 2348 JO - Insights into the Holocene environmental setting of Terra Nova Bay region (Ross Sea, Antarctica) from oxygen isotope geochemistry of Adélie penguin eggshells ER - TY - JOUR T1 - Isotopic characterization of aerosol organic carbon components over the eastern United States JF - Journal of Geophysical Research-Atmospheres Y1 - 2012 A1 - Wozniak, Andrew S. A1 - Bauer, James E. A1 - Dickhut, Rebecca M. A1 - Xu, Li A1 - McNichol, Ann P. AB - Carbon isotopic signatures (delta C-13, Delta C-14) of aerosol particulate matter total organic carbon (TOC) and operationally defined organic carbon (OC) components were measured in samples from two background sites in the eastern U. S. TOC and water-soluble OC (WSOC) delta C-13 values (-27 to -24 parts per thousand) indicated predominantly terrestrial C-3 plant and fossil derived sources. Total solvent extracts (TSE) and their aliphatic, aromatic, and polar OC components were depleted in delta C-13 (-30 to -26 parts per thousand) relative to TOC and WSOC. Delta C-14 signatures of aerosol TOC and TSE (-476 to +25 parts per thousand) suggest variable fossil contributions (similar to 5-50%) to these components. Aliphatic OC while comprising a small portion of the TOC ( VL - 117 N1 - id: 2252; PT: J; TC: 1; UT: WOS:000306237000001 JO - Isotopic characterization of aerosol organic carbon components over the eastern United States ER - TY - JOUR T1 - An isotopic (Delta C-14, delta C-13, and delta N-15) investigation of the composition of particulate organic matter and zooplankton food sources in Lake Superior and across a size-gradient of aquatic systems JF - BIOGEOSCIENCES Y1 - 2012 A1 - Zigah, P. K. A1 - Minor, E. C. A1 - Werne, J. P. A1 - McCallister, S. Leigh AB - Food webs in aquatic systems can be supported both by carbon from recent local primary productivity and by carbon subsidies, such as material from terrestrial ecosystems, or past in situ primary productivity. The importance of these subsidies to respiration and biomass production remains a topic of debate. While some studies have reported that terrigenous organic carbon supports disproportionately high zooplankton production, others have suggested that phytoplankton preferentially support zooplankton production in aquatic ecosystems. Here we apply natural abundance radiocarbon (Delta C-14) and stable isotope (delta C-13, delta N-15) analyses to show that zooplankton in Lake Superior selectively incorporate recently fixed, locally produced (autochthonous) organic carbon even though other carbon sources are readily available. Estimates from Bayesian isotopic modeling based on Delta C-14 and delta C-13 values show that the average lake-wide median contributions of recent in-lake primary production and terrestrial, sedimentary, and bacterial organic carbon to the bulk POM in Lake Superior were 58%, 5%, 33%, and 3%, respectively. However, isotopic modeling estimates also show that recent in situ production contributed a disproportionately large amount (median, 91%) of the carbon in mesozooplankton biomass in Lake Superior. Although terrigenous organic carbon and old organic carbon from resuspended sediments were significant portions (median, 38%) of the available basal food resources, these contributed only a small amount to mesozooplankton biomass. Comparison of zooplankton food sources based on their radiocarbon composition showed that terrigenous organic carbon was relatively more important in rivers and small lakes, and the proportion of terrestrially derived material used by zooplankton correlated with the hydrologic residence time and the ratio of basin area to water surface area. VL - 9 ER - TY - JOUR T1 - Late-Pleistocene to Holocene sedimentary fills of the Çınarcık Basin of the Sea of Marmara JF - Sedimentary Geology Y1 - 2012 A1 - Eriş, K. Kadir A1 - Çağatay, Namık A1 - Beck, Christian A1 - Mercier de Lepinay, Bernard A1 - Corina, Campos AB - A giant RV Marion Dufresne piston core MD01-2425 recovered from the 1276 m-deep Çınarcık Basin of the Sea of Marmara documents characteristics of deep basin sedimentation influenced by large-scale gravity-controlled mass-wasting processes and associated turbidite deposition during the Late Pleistocene to Holocene. A visual lithological description of the core reveals twenty major seismoturbidite layers (> 20 cm thick), intercalated in hemipelagic-type fine-grained calcareous and slightly siliceous clays. The thickness and frequency of the sesimoturbidite layers deposited during the lacustrine period (prior to 12.3 cal ka BP) is much greater than during the Holocene marine period. The sedimentary processes during deposition of seismoturbidites in the basin have been determined in this study using a combination of grain-size parameters. Often the seismoturbidites show strong grain segregation with a sharp boundary between a coarse lower and a homogeneous upper part. The traction carpet deposits formed at the base of a turbulent suspension and were produced in the lower coarse-grained part, whereas the homogeneous upper part was deposited by uniform suspensions following bedload deposition. VL - 281 UR - http://www.sciencedirect.com/science/article/pii/S0037073812002473 N1 - id: 2309 JO - Late-Pleistocene to Holocene sedimentary fills of the Çınarcık Basin of the Sea of Marmara ER - TY - JOUR T1 - Loess mantle spatial variability and soil horizonation, southern Wisconsin, USA JF - Quaternary International Y1 - 2012 A1 - Jacobs, Peter M. A1 - Mason, Joseph A. A1 - Hanson, Paul R. AB - Loess is an important Quaternary sediment that records evidence of landscape instability in sediment source areas and landscape stability in accumulation areas. In Wisconsin, USA loess mantles glaciogenic deposits dating to the last glaciation, but the landscape distribution and effects of the loess mantle on soil formation have received very little attention. This study investigates the influence of glacial landforms on the spatial pattern of loess thickness and how the presence or absence of a loess mantle overlying glaciogenic sediments has influenced soil profile morphology, namely thickness and nature of horizonation. Loess thickness follows systematic trends along hillslopes, with slope percentage explaining most loess thickness variation between summit and backslope positions. In the presence of a loess mantle, solum and Bt horizon thickness is proportional to the thickness of the loess mantle in well-drained profiles. In the absence of a loess mantle, landscape and sediment characteristics that control permeability and water throughflow appear to be the most important determinants of profile characteristics. The loess mantle modulates soil formation above the lithologic discontinuity with sandy calcareous glacial sediments by controlling soil water behavior and having physical and chemical characteristics conducive to transformation to soil genetic horizons. VL - 265 UR - http://www.sciencedirect.com/science/article/pii/S1040618212000328 N1 - id: 2151 JO - Loess mantle spatial variability and soil horizonation, southern Wisconsin, USA ER - TY - JOUR T1 - Marine climatic seasonality during medieval times (10th to 12th centuries) based on isotopic records in Viking Age shells from Orkney, Scotland JF - Palaeogeography, Palaeoclimatology, Palaeoecology Y1 - 2012 A1 - Surge, Donna A1 - Barrett, James H. AB - Seasonal sea-surface temperature (SST) variability during the Medieval Climate Anomaly (MCA), which corresponds to the height of Viking exploration (800–1200 AD), was estimated using oxygen isotope ratios (δ18O) obtained from high-resolution samples micromilled from archaeological shells of the European limpet, Patella vulgata. Our findings illustrate the advantage of targeting SST archives from fast-growing, short-lived molluscs that capture summer and winter seasons simultaneously. Shells from the 10th to 12th centuries (early MCA) were collected from well-stratified horizons, which accumulated in Viking shell and fish middens at Quoygrew on Westray in the archipelago of Orkney, Scotland. Their ages were constrained based on artifacts and radiocarbon dating of bone, charred cereal grain, and the shells used in this study. We used measured δ18OWATER values taken from nearby Rack Wick Bay (average 0.31 ± 0.17‰ VSMOW, n = 11) to estimate SST from δ18OSHELL values. The standard deviation of δ18OWATER values resulted in an error in SST estimates of ± 0.7 °C. The coldest winter months recorded in the shells averaged 6.0 ± 0.6 °C and the warmest summer months averaged 14.1 ± 0.7 °C. Winter and summer SST during the late 20th century (1961–1990) was 7.77 ± 0.40 °C and 12.42 ± 0.41 °C, respectively. Thus, during the 10th to 12th centuries winters were colder and summers were warmer by ~ 2 °C and seasonality was higher relative to the late 20th century. Without the benefit of seasonal resolution, SST averaged from shell time series would be weighted toward the fast-growing summer season, resulting in the conclusion that the early MCA was warmer than the late 20th century by ~ 1 °C. This conclusion is broadly true for the summer season, but not true for the winter season. Higher seasonality and cooler winters during early medieval times may result from a weakened North Atlantic Oscillation index. VL - 350–352 UR - http://www.sciencedirect.com/science/article/pii/S0031018212003926 N1 - id: 2320 JO - Marine climatic seasonality during medieval times (10th to 12th centuries) based on isotopic records in Viking Age shells from Orkney, Scotland ER - TY - JOUR T1 - Marine radiocarbon reservoir corrections (∆R) for Chesapeake Bay and the Middle Atlantic Coast of North America JF - Quaternary Research Y1 - 2012 A1 - Rick, Torben C. A1 - Henkes, Gregory A. A1 - Lowery, Darrin L. A1 - Colman, Steven M. A1 - Culleton, Brendan J. AB - Radiocarbon dates from known age, pre-bomb eastern oyster (Crassostrea virginica) shells provide local marine reservoir corrections (∆R) for Chesapeake Bay and the Middle Atlantic coastal area of eastern North America. These data suggest subregional variability in ∆R, ranging from 148 ± 46 14C yr on the Potomac River to − 109 ± 38 14C yr at Swan Point, Maryland. The ∆R weighted mean for the Chesapeake's Western Shore (129 ± 22 14C yr) is substantially higher than the Eastern Shore (− 88 ± 23 14C yr), with outer Atlantic Coast samples falling between these values (106 ± 46 and 2 ± 46 14C yr). These differences may result from a combination of factors, including 14C-depleted freshwater that enters the bay from some if its drainages, 14C-depleted seawater that enters the bay at its mouth, and/or biological carbon recycling. We advocate using different subregional ∆R corrections when calibrating 14C dates on aquatic specimens from the Chesapeake Bay and coastal Middle Atlantic region of North America. VL - 77 UR - http://www.sciencedirect.com/science/article/pii/S0033589411001414 IS - 1 N1 - id: 2155 JO - Marine radiocarbon reservoir corrections (∆R) for Chesapeake Bay and the Middle Atlantic Coast of North America ER - TY - JOUR T1 - The Medieval Climate Anomaly in the Iberian Peninsula reconstructed from marine and lake records JF - Quaternary Science Reviews Y1 - 2012 A1 - Moreno, Ana A1 - Pérez, Ana A1 - Frigola, Jaime A1 - Nieto-Moreno, Vanesa A1 - Rodrigo-Gámiz, Marta A1 - Martrat, Belén A1 - González-Sampériz, Penélope A1 - Morellón, Mario A1 - Martín-Puertas, Celia A1 - Corella, Juan Pablo A1 - Belmonte, Ánchel A1 - Sancho, Carlos A1 - Cacho, Isabel A1 - Herrera, Gemma A1 - Canals, Miquel A1 - Grimalt, Joan O. A1 - Jiménez-Espejo, Francisco A1 - Martínez-Ruiz, Francisca A1 - Vegas-Vilarrúbia, Teresa A1 - Valero-Garcés, Blas L. AB - Selected multi-proxy and accurately dated marine and terrestrial records covering the past 2000 years in the Iberian Peninsula (IP) facilitated a comprehensive regional paleoclimate reconstruction for the Medieval Climate Anomaly (MCA: 900–1300 AD). The sequences enabled an integrated approach to land–sea comparisons and, despite local differences and some minor chronological inconsistencies, presented clear evidence that the MCA was a dry period in the Mediterranean IP. It was a period characterized by decreased lake levels, more xerophytic and heliophytic vegetation, a low frequency of floods, major Saharan eolian fluxes, and less fluvial input to marine basins. In contrast, reconstruction based on sequences from the Atlantic Ocean side of the peninsula indicated increased humidity. The data highlight the unique characteristics of the MCA relative to earlier (the Dark Ages, DA: ca 500–900 years AD) and subsequent (the Little Ice Age, LIA: 1300–1850 years AD) colder periods. The reconstruction supports the hypothesis of Trouet et al. (2009), that a persistent positive mode of the North Atlantic Oscillation (NAO) dominated the MCA. VL - 43 UR - http://www.sciencedirect.com/science/article/pii/S0277379112001485 N1 - id: 2334 JO - The Medieval Climate Anomaly in the Iberian Peninsula reconstructed from marine and lake records ER - TY - JOUR T1 - Modern and Fossil Contributions to Polycyclic Aromatic Hydrocarbons in PM2.5 from North Birmingham, Alabama in the Southeastern U.S. JF - ENVIRONMENTAL SCIENCE & TECHNOLOGY Y1 - 2012 A1 - Xu, Li A1 - Zheng, Mei A1 - Ding, Xiang A1 - Edgerton, Eric S. A1 - Reddy, Christopher M. AB - Analyzing the radiocarbon (C-14) content of polycyclic aromatic hydrocarbons (PAHs) in atmospheric particulate matter can provide estimates on the source contributions from biomass burning versus fossil fuel. The relative importance of these two sources to ambient PAHs varies considerably across regions and even countries, and hence there is a pressing need to apportion these sources. In this study, we advanced the radiocarbon analysis from bulk carbon to compound class specific radiocarbon analysis (CCSRA) to determine Delta C-14 and delta C-13 values of PAHs in PM2.5 samples for investigating biomass burning and fossil fuel source contributions to PAHs from one of the Southeastern Aerosol Research and Characterization (SEARCH) sites in North Birmingham (BHM), Alabama during winter (December 2004-February 2005) and summer (June-August 2005) by accelerator mass spectrometry. To compare our ambient samples to known sources, we collected and analyzed fenceline samples from the vicinity of a coke plant in BHM. As expected, PAHs from the coke plant fenceline samples had very low radiocarbon levels. Its Delta C-14 varied from -990 to -970 parts per thousand, indicating that 97 to 99% were of fossil source. PAHs in the ambient PM2.5 had Delta C-14 from -968 to -911 parts per thousand, indicating that 92-97% of PAHs were from fossil fuel combustion. These levels indicated the dominance of fossil sources of ambient PAHs. The radiocarbon level of ambient PAHs was higher in winter than in summer. Winter samples exhibited depleted delta C-13 value and enriched Delta C-14 value because of the increased contribution of PAHs from biomass burning source. However, biomass burning contributed more to heavier PAHs (modern source accounting for 6-8%) than fighter ones with a modern contribution of 3%. VL - 46 ER - TY - JOUR T1 - Molecular records of climate variability and vegetation response since the Late Pleistocene in the Lake Victoria basin, East Africa JF - Quaternary Science Reviews Y1 - 2012 A1 - Berke, Melissa A. A1 - Johnson, Thomas C. A1 - Werne, Josef P. A1 - Grice, Kliti A1 - Schouten, Stefan A1 - Sinninghe Damsté, Jaap S. AB - New molecular proxies of temperature and hydrology are helping to constrain tropical climate change and elucidate possible forcing mechanisms during the Holocene. Here, we examine a ∼14,000 year record of climate variability from Lake Victoria, East Africa, the world's second largest freshwater lake by surface area. We determined variations in local hydroclimate using compound specific δD of terrestrial leaf waxes, and compared these results to a new record of temperature utilizing the TEX86 paleotemperature proxy, based on aquatic Thaumarchaeotal membrane lipids. In order to assess the impact of changing climate on the terrestrial environment, we generated a record of compound specific δ13C from terrestrial leaf waxes, a proxy for ecosystem-level C3/C4 plant abundances, and compared the results to previously published pollen-inferred regional vegetation shifts. We observe a general coherence between temperature and rainfall, with a warm, wet interval peaking ∼10–9 ka and subsequent gradual cooling and drying over the remainder of the Holocene. These results, particularly those of rainfall, are in general agreement with other tropical African climate records, indicating a somewhat consistent view of climate over a wide region of tropical East Africa. The δ13C record from Lake Victoria leaf waxes does not appear to reflect changes in regional climate or vegetation. However, palynological analyses document an abrupt shift from a Poaceae (grasses)-dominated ecosystem during the cooler, arid late Pleistocene to a Moraceae-dominated (trees/shrubs) landscape during the warm, wet early Holocene. We theorize that these proxies are reflecting vegetation in different locations around Lake Victoria. Our results suggest a predominantly insolation-forced climate, with warm, wet conditions peaking at the maximum interhemispheric seasonal insolation contrast, likely intensifying monsoonal precipitation, while maximum aridity coincides with the rainy season insolation and the interhemispheric contrast gradient minima. We interpret a shift in conditions at the Younger Dryas to indicate a limited switch in insolation-dominated control on climate of the Lake Victoria region, to remote teleconnections with the coupled Atlantic and Pacific climate system. VL - 55 UR - http://www.sciencedirect.com/science/article/pii/S0277379112003216 N1 - id: 2318 JO - Molecular records of climate variability and vegetation response since the Late Pleistocene in the Lake Victoria basin, East Africa ER - TY - JOUR T1 - NEW AMS RADIOCARBON DATES FROM LATE PLEISTOCENE MASTODONS AND MAMMOTHS IN NEW YORK STATE, USA JF - RADIOCARBON Y1 - 2012 A1 - Feranec, Robert S. A1 - Kozlowski, Andrew L. VL - 54 ER - TY - JOUR T1 - New Records for Prehistoric Introduction of Neotropical Mammals to the West Indies: Evidence from Carriacou, Lesser Antilles JF - Journal of Biogeography Y1 - 2012 A1 - Giovas, C. M. A1 - LeFebvre, M. J. A1 - Fitzpatrick, S. M. VL - 39 N1 - id: 1873SubmittedY JO - New Records for Prehistoric Introduction of Neotropical Mammals to the West Indies: Evidence from Carriacou, Lesser Antilles ER - TY - JOUR T1 - Optimizing a microwave gas ion source for continuous-flow accelerator mass spectrometry JF - Review of Scientific Instruments Y1 - 2012 A1 - von Reden, K. F. A1 - Roberts, M. L. A1 - Burton, J. R. A1 - é, S. R. AB - A 2.45 GHz microwave ion source coupled with a magnesium charge exchange canal (C × C) has been successfully adapted to a large acceptance radiocarbon accelerator mass spectrometry system at the National Ocean Sciences Accelerator Mass Spectrometry (AMS) Facility, Woods Hole Oceanographic Institution. CO2 samples from various preparation sources are injected into the source through a glass capillary at 370 μl/min. Routine system parameters are about 120–140 μA of negative 12C current after the C × C, leading to about 400 14C counts per second for a modern sample and implying a system efficiency of 0.2%. While these parameters already allow us to perform high-quality AMS analyses on large samples, we are working on ways to improve the output of the ion source regarding emittance and efficiency. Modeling calculations suggest modifications in the extraction triode geometry, shape, and size of the plasma chamber could improve emittance and, hence, ion transport efficiency. Results of experimental tests of these modifications are presented. VL - 835240 UR - http://aip.scitation.org/doi/10.1063/1.3656408http://aip.scitation.org/doi/pdf/10.1063/1.3656408 IS - 2 ER - TY - JOUR T1 - Oxygen control on Holocene cold-water coral development in the eastern Mediterranean Sea JF - Deep Sea Research Part I: Oceanographic Research Papers Y1 - 2012 A1 - Fink, Hiske G. A1 - Wienberg, Claudia A1 - Hebbeln, Dierk A1 - McGregor, Helen V. A1 - Schmiedl, Gerhard A1 - Taviani, Marco A1 - Freiwald, André AB - Continuous sedimentary records from an eastern Mediterranean cold-water coral ecosystem thriving in intermediate water depths (∼600 m) reveal a temporary extinction of cold-water corals during the Early to Mid Holocene from 11.4–5.9 cal kyr BP. Benthic foraminiferal assemblage analysis shows low-oxygen conditions of 2 ml l−1 during the same period, compared to bottom-water oxygen values of 4–5 ml l−1 before and after the coral-free interval. The timing of the corals' demise coincides with the sapropel S1 event, during which the deep eastern Mediterranean basin turned anoxic. Our results show that during the sapropel S1 event low oxygen conditions extended to the rather shallow depths of our study site in the Ionian Sea and caused the cold-water corals temporary extinction. This first evidence for the sensitivity of cold-water corals to low oceanic oxygen contents suggests that the projected expansion of tropical oxygen minimum zones resulting from global change will threaten cold-water coral ecosystems in low latitudes in the same way that ocean acidification will do in the higher latitudes. VL - 62 UR - http://www.sciencedirect.com/science/article/pii/S0967063712000039 N1 - id: 2140 JO - Oxygen control on Holocene cold-water coral development in the eastern Mediterranean Sea ER - TY - JOUR T1 - Pacific cod (Gadus macrocephalus) as a paleothermometer: otolith oxygen isotope reconstruction JF - Journal of Archaeological Science Y1 - 2012 A1 - West, Catherine F. A1 - Wischniowski, Stephen A1 - Johnston, Christopher AB - Stable isotope studies are increasingly important for understanding past environmental and cultural developments along the North Pacific Rim. In this paper, we present methods for using Pacific cod (Gadus macrocephalus) otoliths as a paleothermometer using a case study from Kodiak Island, Alaska. The results of this study indicate that Pacific cod otoliths record variable paleoenvironmental conditions during the Little Ice Age. The broad distribution of Pacific cod and success in using the otoliths as a paleothermometer makes this method widely applicable to researchers working throughout the northern Pacific Rim. VL - 39 UR - http://www.sciencedirect.com/science/article/pii/S0305440312002087 IS - 10 N1 - id: 2303 JO - Pacific cod (Gadus macrocephalus) as a paleothermometer: otolith oxygen isotope reconstruction ER - TY - JOUR T1 - Paleoenvironmental changes on the northeastern and southwestern Black Sea shelves during the Holocene JF - Quaternary International Y1 - 2012 A1 - Ivanova, Elena V. A1 - Murdmaa, Ivar O. A1 - Karpuk, Maria S. A1 - Schornikov, Eugene I. A1 - Marret, Fabienne A1 - Cronin, Thomas M. A1 - Buynevich, Ilya V. A1 - Platonova, Elena A. AB - Four paleoceanographic events are distinguished during the Holocene based on changes in macro- and microfossil assemblages studied from three sediment cores (Ak 521, 522, 2571) from the outer northeast shelf and from core MAR02-45 situated on the southwest shelf of the Black Sea, west to the Bosphorus. The lithology and fossils were previously studied from cores Ak 521 and Ak 522 and MAR02-45. However, high resolution ostracod analyses from the AMS-14C dated core, Ak 2571, allowed for a revision of the taxonomy and paleoecological interpretation of this microfaunal group on the NE shelf. Downcore changes in the relative abundance of the polyhaline ostracods are found to be contemporaneous in all three cores from the NE shelf. As a result, centennial-millennial scale fluctuations of the bottom-water salinity are resolved in the area. A broader scale examination of paleoenvironmental changes between the NE and SW shelves is also made and the surface to bottom salinity gradient is discussed. An uncalibrated radiocarbon based chronology is used throughout this paper to facilitate comparison with the regional chronostratigraphy of marine transgression and regressions in the Black Sea. The calibrated ages corrected for the changes in reservoir age through the Holocene are also provided. The first paleoceanographic event is associated with the pulse of Mediterranean water previously established at about 9.8–9.3 ka BP. This event is clearly observed in the SW region but not on the NE shelf due to a hiatus in the longest core, Ak 521. The second event is represented on both the NE and SW shelves as a replacement of brackish benthic fauna and surface phytoplankton with marine ones between 8.4 and 6.9 ka BP, indicating a gradual increase in salinity. The third event is marked by opposing trends in surface and bottom-water salinity changes. On the NE shelf, bottom-water salinity rose to modern values by ∼ 6.5 ka BP and then decreased within the interval ∼6.4–5.3 ka BP as recorded by the ostracod assemblages. On the SW shelf, surface-water salinity reached modern values by 5.6 ka BP and remained constant until present day as inferred from the dinoflagellate cyst assemblages. The fourth event is marked by a recurring increase in bottom-water salinity to modern values indicated by the polyhaline ostracod assemblages at ∼ 5.3 ka BP in the NE region, after which only minor salinity fluctuations are observed. VL - 261 UR - http://www.sciencedirect.com/science/article/pii/S1040618211006550 N1 - id: 2123 JO - Paleoenvironmental changes on the northeastern and southwestern Black Sea shelves during the Holocene ER - TY - JOUR T1 - Paleoseismic and geomorphologic evidence of recent tectonic activity of the Pozohondo Fault (Betic Cordillera, SE Spain) JF - JOURNAL OF IBERIAN GEOLOGY Y1 - 2012 A1 - Rodriguez-Pascua, M. A. A1 - Perez-Lopez, R. A1 - Garduno-Monroy, V. H. A1 - Giner-Robles, J. L. A1 - Silva, P. G. A1 - Perucha-Atienza, M. A. A1 - Hernandez-Madrigal, V. M. A1 - Bischoff, J. KW - Geomorphology KW - Paleoseismology KW - Prebetic KW - Quaternary KW - SE Spain AB - Instrumental and historical seismicity in the Albacete province (External Prebetic Zone) has been scarcely recorded. However, major strike-slip faults showing NW-SE trending provide geomorphologic and paleoseismic evidence of recent tectonic activity (Late Pleistocene to Present). Moreover, these faults are consistently well oriented under the present stress tensor and therefore, they can trigger earthquakes of magnitude greater than M6, according to the lengths of surface ruptures and active segments recognized in fieldwork. Present landscape nearby the village of Hellin (SE of Albacete) is determined by the recent activity of the Pozohondo Fault (FPH), a NW-SE right-lateral fault with 90 km in length. In this study, we have calculated the Late Quaternary tectonic slip-rate of the FPH from geomorphological, sedimentological, archaeoseimological, and paleoseismological approaches. All of these data suggest that the FPH runs with a minimum slip-rate of 0.1 mm/yr during the last 100 kyrs (Upper Pleistocene-Holocene). In addition, we have recognized the last two major paleoearthquakes associated to this fault. Magnitudes of these paleoearthquakes were gretarer than M6 and their recurrence intervals ranged from 6600 to 8600 yrs for the seismic cycle of FPH. The last earthquake was dated between the 1st and 6th centuries, though two earthquakes could be interpreted in this wide time interval, one at the FPH and other from a far field source. Results obtained here, suggest an increasing of the tectonic activity of the Pozohondo Fault during the last 10,000 yrs. VL - 38 ER - TY - JOUR T1 - Photochemical reactivity of ancient marine dissolved organic carbon JF - Geophysical Research Letters Y1 - 2012 A1 - Beaupré, Steven R. A1 - Druffel, Ellen R. M. AB - Marine dissolved organic carbon (DOC) is the largest reservoir of reduced carbon in seawater and persists up to 4,000-6,000 conventional radiocarbon (C-14) years on average. Photochemical degradation has been suggested as a geochemical sink for these long-lived molecules, yet there have been no studies relating photochemical lability to the C-14-ages of surface DOC. We observed apparent second order (2 degrees) kinetics with respect to DOC and a strong trend from Delta C-14-enriched to depleted values during exhaustive photomineralization of surface marine DOC with high energy UV light. Geochemically, these results suggest that surface DOC is an isotopically-heterogeneous mixture of molecules for which photochemical lability and C-14 ages are correlated. Photochemical mineralization may therefore be an important control on the persistence of C-14-depleted DOC in the ocean. Citation: Beaupre, S. R., and E. R. M. Druffel (2012), Photochemical reactivity of ancient marine dissolved organic carbon, Geophys. Res. Lett., 39, L18602, doi:10.1029/2012GL052974. VL - 39 N1 - id: 2249; PT: J; TC: 0; UT: WOS:000309136800001 JO - Photochemical reactivity of ancient marine dissolved organic carbon ER - TY - JOUR T1 - Postglacial (after 18 ka) deep-sea sedimentation along the Hikurangi subduction margin (New Zealand): Characterisation, timing and origin of turbidites JF - Marine Geology Y1 - 2012 A1 - Pouderoux, Hugo A1 - Proust, Jean-Noël A1 - Lamarche, Geoffroy A1 - Orpin, Alan A1 - Neil, Helen AB - Recent sedimentation along the Hikurangi subduction margin off northeastern New Zealand is investigated using a series of piston cores collected between 2003 and 2008. The active Hikurangi Margin lies along the Pacific–Australia subduction plate boundary and contains a diverse range of geomorphologic settings. Slope basin stratigraphy is thick and complex, resulting from sustained high rates of sedimentation from adjacent muddy rivers throughout the Quaternary. Turbidites deposited since c. 18 ka in the Poverty, Ruatoria and Matakaoa re-entrants are central to this study in that they provide a detailed record of the past climatic conditions and tectonic activity. Here, alternating hemipelagite, turbidite, debrite and tephra layers reflect distinctive depositional modes of marine sedimentation, turbidity current, debris flow and volcanic eruption, respectively. Turbidites dominate the record, ranging in lithofacies from muddy to sandy turbidites, and include some basal-reverse graded turbidites inferred to be derived from hyperpycnal flows. Stacked turbidites are common and indicate multiple gravity-flows over short time periods. The chronology of turbidites is determined by collating an extremely dense set of radiocarbon ages and dated tephra, which facilitate sedimentation rate calculation and identification of the origin of turbidites. Sedimentation rates range from 285 cm/ka during late glacial time (18.5–17 ka) to 15 to 109 cm/ka during postglacial time (17–0 ka). Turbidite deposition is controlled by: (1) the emplacement of slope avalanches reorganising sediment pathways; (2) the postglacial marine transgression leading to a five-fold reduction in sediment supply to the slope due to disconnection of river mouths from the shelf edge, and (3) the Holocene/Pleistocene boundary climate warming resulting in a drastic decrease in the average turbidite grain-size. Flood-induced turbidites are scarce: nine hyperpycnites are recognised since 18 ka and the youngest is correlated to the largest ENSO-related storm event recorded onland (Lake Tutira). Other turbidites contain a benthic foraminiferal assemblage which is strictly reworked from the upper slope and which relates to large earthquakes over the last c. 7 ka. They yield a shorter return time (270–430 years) than the published coastal records for large earthquakes (c. 670 years), but the offshore record is likely to be more complete. The deep-sea sedimentation along the New Zealand active margin illustrates the complex interaction of tectonic and climate in turbidite generation. Climate warming and glacio-eustatic fluctuations are well recorded at a millennial timescale (18 ka), while tectonic deformation and earthquakes appear predominant in fostering turbidite production at a centennial timescale (270–430 years). VL - 295–298 UR - http://www.sciencedirect.com/science/article/pii/S0025322711002507 N1 - id: 2142 JO - Postglacial (after 18 ka) deep-sea sedimentation along the Hikurangi subduction margin (New Zealand): Characterisation, timing and origin of turbidites ER - TY - JOUR T1 - Pre-Columbian fire regimes in lowland tropical rainforests of southeastern Peru JF - Palaeogeography, Palaeoclimatology, Palaeoecology Y1 - 2012 A1 - McMichael, C. H. A1 - Correa-Metrio, A. A1 - Bush, M. B. AB - We document the fire history of the forests of a well-studied ecological research station (Los Amigos) in western Amazonia through soil charcoal analysis, and compare results with data from a nearby lake district known to have supported pre-Columbian human populations. We present novel methods of soil charcoal analysis that improve on its current limitations by accounting for variability in post-fire charcoal deposition, problematic age–depth relationships, and the presence of weathered or regionally-deposited charcoal particles that allow statistical comparisons of fire history characteristics between regions. The fire histories indicate that the research station experienced less intensive historical fire and pre-Columbian disturbance than the lake district. Dated charcoal particles indicated that while soil depth could not be used to predict fire age, fragments below 20 cm depth were generally older than 500 years. Frequent fires have not occurred in either region during the last 1000 years, but fire events in both regions were significantly synchronous from 1000 to 4000 cal. yr BP. The sampling design and methods that provide an ecologically and statistically valid avenue for comparing fire history characteristics between regions can be modified to suit other ecosystems. The results presented here establish confidence that the patterns and processes of the lowland tropical rainforests studied at Los Amigos are not affected by intense or recurrent historical fires. These data also suggest that forests of Madre de Dios, Peru are not post-successional remnants of a ‘cultural parkland’, as suggested by some Amazonian archeologists. VL - 342–343 UR - http://www.sciencedirect.com/science/article/pii/S0031018212002556 N1 - id: 2307 JO - Pre-Columbian fire regimes in lowland tropical rainforests of southeastern Peru ER - TY - JOUR T1 - Radiocarbon and stable-isotope geochemistry of organic and inorganic carbon in Lake Superior JF - GLOBAL BIOGEOCHEMICAL CYCLES Y1 - 2012 A1 - Zigah, Prosper K. A1 - Minor, Elizabeth C. A1 - Werne, Josef P. AB - We present a lake-wide investigation of Lake Superior carbon and organic matter biogeochemistry using radiocarbon, stable isotope, and carbon concentrations. Dissolved inorganic carbon (DIC) abundance in the lake was 121-122 Tg C, with offshore concentration and delta C-13 values being laterally homogenous and tightly coupled to the physical and thermal regime and biochemical processes. Offshore Delta C-14 of DIC (50-65%) exhibited lateral homogeneity and was more C-14 enriched than co-occurring atmospheric CO2 (similar to 38%); nearshore Delta C-14 of DIC (36-38%) was similar to atmospheric CO2. Dissolved organic carbon (DOC) abundance was 14.2-16.4 Tg C. DOC's concentration and delta C-13 were homogenous in June (mixed lake), but varied laterally during August (stratification) possibly due to spatial differences in lake productivity. Throughout sampling, DOC had modern radiocarbon values (14-58%) indicating a semilabile nature with a turnover time of <= 60 years. Lake particulate organic carbon (POC, 0.9-1.3 Tg C) was consistently C-13 depleted relative to DOC. The delta N-15 of epilimnetic particulate organic nitrogen shifted to more negative values during stratification possibly indicating greater use of nitrate (rather than ammonium) by phytoplankton in August. POC's radiocarbon was spatially heterogeneous (Delta C-14 range: 58% to - 303%), and generally C-14 depleted relative to DOC and DIC. POC C-14 depletion could not be accounted for by black carbon in the lake but, because of its spatial and temporal distribution, is attributed to sediment resuspension. The presence of old POC within the epilimnion of the open lake indicates possible benthic-pelagic coupling in the lake's organic carbon cycle; the ultimate fate of this old POC bears further investigation. VL - 26 ER - TY - JOUR T1 - Radiocarbon evidence that carbon from the Deepwater Horizon spill entered the planktonic food web of the Gulf of Mexico JF - Environmental Research Letters Y1 - 2012 A1 - Chanton, J P A1 - Cherrier, J A1 - Wilson, R M A1 - Sarkodee-Adoo, J A1 - Bosman, S A1 - Mickle, A A1 - Graham, W M AB - The Deepwater Horizon (Macondo) oil spill released large volumes of oil and gas of distinct carbon isotopic composition to the northern Gulf of Mexico, allowing Graham et al (2010 Environ. Res. Lett. 5 045301) to use stable carbon isotopes (δ13C) to infer the introduction of spilled oil into the planktonic food web. Surface ocean organic production and measured oil are separated by 5–7‰ in stable carbon isotope (δ13C) space, while in radiocarbon (Δ14C) space these two potential sources are separated by more than 1000‰. Thus radiocarbon isotopes provide a more sensitive tracer by which to infer possible introduction of Macondo oil into the food web. We measured Δ14C and δ13C in plankton collected from within 100 km of the spill site as well as in coastal and offshore DIC (dissolved inorganic carbon or ΣCO2) to constrain surface production values. On average, plankton values were depleted in 14C relative to surface DIC, and we found a significant linear correlation between Δ14C and δ13C in plankton. Cumulatively, these results are consistent with the hypothesis that carbon released from the Deepwater Horizon spill contributed to the offshore planktonic food web. Our results support the findings of Graham et al (2010 Environ. Res. Lett. 5 045301), but we infer that methane input may be important. VL - 7 UR - http://stacks.iop.org/1748-9326/7/i=4/a=045303?key=crossref.bb52d0d288c12eb2c6f2ac2b8f8facea IS - 4 ER - TY - JOUR T1 - Radiocarbon evidence that carbon from the Deepwater Horizon spill entered the planktonic food web of the Gulf of Mexico JF - ENVIRONMENTAL RESEARCH LETTERS Y1 - 2012 A1 - Chanton, J. P. A1 - Cherrier, J. A1 - Wilson, R. M. A1 - Sarkodee-Adoo, J. A1 - Bosman, S. A1 - Mickle, A. A1 - Graham, W. M. KW - carbon isotope KW - Gulf oil spill KW - methane KW - petroleum hydrocarbon KW - radiocarbon AB - The Deepwater Horizon (Macondo) oil spill released large volumes of oil and gas of distinct carbon isotopic composition to the northern Gulf of Mexico, allowing Graham et al (2010 Environ. Res. Lett. 5 045301) to use stable carbon isotopes (delta C-13) to infer the introduction of spilled oil into the planktonic food web. Surface ocean organic production and measured oil are separated by 5-7 parts per thousand in stable carbon isotope (delta C-13) space, while in radiocarbon (Delta C-14) space these two potential sources are separated by more than 1000 parts per thousand. Thus radiocarbon isotopes provide a more sensitive tracer by which to infer possible introduction of Macondo oil into the food web. We measured Delta C-14 and delta C-13 in plankton collected from within 100 km of the spill site as well as in coastal and offshore DIC (dissolved inorganic carbon or Sigma CO2) to constrain surface production values. On average, plankton values were depleted in C-14 relative to surface DIC, and we found a significant linear correlation between Delta C-14 and delta C-13 in plankton. Cumulatively, these results are consistent with the hypothesis that carbon released from the Deepwater Horizon spill contributed to the offshore planktonic food web. Our results support the findings of Graham et al (2010 Environ. Res. Lett. 5 045301), but we infer that methane input may be important. VL - 7 ER - TY - JOUR T1 - Radiocarbon in the Atmosphere and Deep Ocean: New Methods and New Data from the Last Glacial Period to the Holocene JF - XVIII INQUA Congress, 21st–27th July, 2011, Bern, Switzerland Y1 - 2012 A1 - Adkins, Jess VL - 279–280 UR - http://www.sciencedirect.com/science/article/pii/S1040618212005435 N1 - id: 2305 JO - Radiocarbon in the Atmosphere and Deep Ocean: New Methods and New Data from the Last Glacial Period to the Holocene ER - TY - JOUR T1 - Radiocarbon Measurements in the Indian Ocean Aboard RVIB Nathaniel B. Palmer JF - Oceanography Y1 - 2012 A1 - Key, Robert M. A1 - McNichol, Ann VL - 25 IS - 3 N1 - id: 2250; PT: J; TC: 0; SI: SI; UT: WOS:000308774600025 JO - Radiocarbon Measurements in the Indian Ocean Aboard RVIB Nathaniel B. Palmer ER - TY - JOUR T1 - A reconstruction of late Pleistocene relative sea level in the south Bohai Sea, China, based on sediment grain-size analysis JF - Sedimentary Geology Y1 - 2012 A1 - Yi, Liang A1 - Yu, Hongjun A1 - Ortiz, Joseph D. A1 - Xu, Xingyong A1 - Qiang, Xiaoke A1 - Huang, Haijun A1 - Shi, Xuefa A1 - Deng, Chenglong AB - Future anthropogenic sea-level rise and its impact on coastal regions is an important issue facing human civilizations. Due to the short nature of the instrumental record of sea-level change, development of proxies for sea-level change prior to the advent of instrumental records is essential to reconstruct long-term background sea-level changes on local, regional and global scales. Here, we employ numerical methods to partition sediment grain size using a combined database of marine surface and core samples, and to quantitatively reconstruct sea-level variation since the late Pleistocene in the south Bohai Sea, China. Our sea-level reconstruction indicates that relative sea-level changes in the southern Bohai Sea track global sea-level variation for the duration of the record. The results also indicate substantial regression from 70 to 30 cal kyr BP, and potentially subarial exposure from 38 to 20 cal kyr BP. Our results document the feasibility of reconstructing relative sea-level change by numerical partitioning of sediment grain size data, demonstrating the potential for future applications. VL - 281 UR - http://www.sciencedirect.com/science/article/pii/S0037073812002333 N1 - id: 2312 JO - A reconstruction of late Pleistocene relative sea level in the south Bohai Sea, China, based on sediment grain-size analysis ER - TY - JOUR T1 - Re-evaluating the origins of late Pleistocene fire areas on Santa Rosa Island, California, USA JF - Quaternary Research Y1 - 2012 A1 - Rick, Torben C. A1 - Wah, John S. A1 - Erlandson, Jon M. AB - At the close of the Pleistocene, fire regimes in North America changed significantly in response to climate change, megafaunal extinctions, anthropogenic burning and, possibly, even an extraterrestrial impact. On California's Channel Islands, researchers have long debated the nature of late Pleistocene “fire areas,” discrete red zones in sedimentary deposits, interpreted by some as prehistoric mammoth-roasting pits created by humans. Further research found no evidence that these red zones were cultural in origin, and two hypotheses were advanced to explain their origin: natural fires and groundwater processes. Radiocarbon dating, X-ray diffraction analysis, and identification of charcoal from six red zones on Santa Rosa Island suggest that the studied features date between ~ 27,500 and 11,400 cal yr BP and resulted from burning or heating, not from groundwater processes. Our results show that fire was a component of late Pleistocene Channel Island ecology prior to and after human colonization of the islands, with no clear evidence for increased fire frequency coincident with Paleoindian settlement, extinction of pygmy mammoths, or a proposed Younger Dryas impact event. VL - 78 UR - http://www.sciencedirect.com/science/article/pii/S0033589412000786 IS - 2 N1 - id: 2301 JO - Re-evaluating the origins of late Pleistocene fire areas on Santa Rosa Island, California, USA ER - TY - JOUR T1 - Refining the model of barrier island formation along a paraglacial coast in the Gulf of Maine JF - Marine Geology Y1 - 2012 A1 - Hein, Christopher J. A1 - FitzGerald, Duncan M. A1 - Carruthers, Emily A. A1 - Stone, Byron D. A1 - Barnhardt, Walter A. A1 - Gontz, Allen M. KW - barrier-island formation KW - ground-penetrating radar KW - inlet processes KW - inlet-fill sequence KW - paraglacial KW - spit accretion AB - Details of the internal architecture and local geochronology of Plum Island, the longest barrier in the Gulf of Maine, have refined our understanding of barrier island formation in paraglacial settings. Ground-penetrating radar and shallow-seismic profiles coupled with sediment cores and radiocarbon dates provide an 8000-year evolutionary history of this barrier system in response to changes in sediment sources and supply rates as well as variability in the rate of sea-level change. The barrier sequence overlies tills of Wisconsinan and Illinoian glaciations as well as late Pleistocene glaciomarine clay deposited during the post-glacial sea-level highstand at approximately 17 ka. Holocene sediment began accumulating at the site of Plum Island at 7–8 ka, in the form of coarse fluvial channel-lag deposits related to the 50-m wide erosional channel of the Parker River that carved into underlying glaciomarine deposits during a lower stand of sea level. Plum Island had first developed in its modern location by ca. 3.6 ka through onshore migration and vertical accretion of reworked regressive and lowstand deposits. The prevalence of southerly, seaward-dipping layers indicates that greater than 60% of the barrier lithosome developed in its modern location through southerly spit progradation, consistent with a dominantly longshore transport system driven by northeast storms. Thinner sequences of northerly, landward-dipping clinoforms represent the northern recurve of the prograding spit. A 5–6-m-thick inlet-fill sequence was identified overlying the lower stand fluvial deposit; its stratigraphy captures events of channel migration, ebb-delta breaching, onshore bar migration, channel shoaling and inlet infilling associated with the migration and eventual closure of the inlet. This inlet had a maximum cross-sectional area of 2800 m2 and was active around 3.5–3.6 ka. Discovery of this inlet suggests that the tidal prism was once larger than at present. Bay infilling, driven by the import of sediment into the backbarrier environment through tidal inlets, as well as minor sediment contribution from local rivers, led to a vast reduction in the bay tidal prism. This study demonstrates that, prior to about 3 ka, Plum Island and its associated marshes, tidal flats, and inlets were in a paraglacial environment; that is, their main source of sediment was derived from the erosion and reworking of glaciogenic deposits. Since that time, Plum Island has been in a state of dynamic equilibrium with its non-glacial sediment sources and therefore can be largely considered to be in a stable, “post-paraglacial” state. This study is furthermore the first in the Gulf of Maine to show that spit accretion and inlet processes were the dominant mechanisms in barrier-island formation and thus serves as a foundation for future investigations of barrier development in response to backbarrier infilling. VL - 307-310 UR - https://doi.org/10.1016/j.margeo.2012.03.001 ER - TY - JOUR T1 - Sea surface temperature variability and sea-ice extent in the subarctic northwest Pacific during the past 15,000 years JF - Paleoceanography Y1 - 2012 A1 - Max, Lars A1 - Riethdorf, Jan-Rainer A1 - Tiedemann, Ralf A1 - Smirnova, Maria A1 - Lembke-Jene, Lester A1 - Fahl, Kirsten A1 - ürnberg, Dirk A1 - Matul, Alexander A1 - Mollenhauer, Gesine AB - Past changes in North Pacific sea surface temperatures and sea-ice conditions are proposed to play a crucial role in deglacial climate development and ocean circulation but are less well known than from the North Atlantic. Here, we present new alkenone-based sea surface temperature records from the subarctic northwest Pacific and its marginal seas (Bering Sea and Sea of Okhotsk) for the time interval of the last 15 kyr, indicating millennial-scale sea surface temperature fluctuations similar to short-term deglacial climate oscillations known from Greenland ice core records. Past changes in sea-ice distribution are derived from relative percentage of specific diatom groups and qualitative assessment of the IP25biomarker related to sea-ice diatoms. The deglacial variability in sea-ice extent matches the sea surface temperature fluctuations. These fluctuations suggest a linkage to deglacial variations in Atlantic meridional overturning circulation and a close atmospheric coupling between the North Pacific and North Atlantic. During the Holocene the subarctic North Pacific is marked by complex sea surface temperature trends, which do not support the hypothesis of a Holocene seesaw in temperature development between the North Atlantic and the North Pacific. VL - 27 UR - http://doi.wiley.com/10.1029/2012PA002292 IS - 3 ER - TY - JOUR T1 - Seasonal fluxes and source variation of organic carbon transported by two major Chinese Rivers: The Yellow River and Changjiang (Yangtze) River JF - GLOBAL BIOGEOCHEMICAL CYCLES Y1 - 2012 A1 - Wang, Xuchen A1 - Ma, Haiqing A1 - Li, Ronghua A1 - Song, Zhensu A1 - Wu, Jinping AB - A one-year study was carried out to investigate the seasonal fluxes and source variation of organic carbon transported by two major Chinese rivers, the Yellow River and Changjiang. In 2009, the Yellow River and Changjiang transported 3.20 x 10(10) g and 1.58 x 10(12) g DOC and 3.89 x 10(11) g and 1.52 x 10(12) g POC, respectively. The dominant input of the terrestrial organic matter occurred during the high discharge period from June to July for the Yellow River and from June to August for Changjiang, accounting for 36-44% of the DOC and 72-86% of the POC transported by the two rivers in 2009. The Yellow River transported much higher concentrations of inorganic carbon than organic carbon, while a reverse trend was found in the Changjiang, indicating the different sources of carbon discharged by the two rivers. Using radiocarbon and stable carbon isotope measurements, we identified the different sources and seasonal variations of organic carbon transported by the Yellow River and Changjiang. The Yellow River carried old POC with radiocarbon ages ranging from 4000 to 8000 years, while POC transported by Changjiang had a relatively younger C-14 age ranging from 800 to 1060 years. The C-14 ages of DOC were relatively younger (305-1570 years) and showed less variation between the two rivers. The seasonal variations found in C-14 ages of DOC and POC indicate that a large fraction of recent-fixed labile organic carbon was transported by the two rivers in the spring and summer months. The different sources and seasonal variations in both fluxes and sources of organic carbon transported by the Yellow River and Changjiang could have an important influence on the biogeochemical cycle and ecosystems in the estuaries and adjacent coastal waters of the East China Sea. VL - 26 ER - TY - JOUR T1 - A sedimentary-based history of hurricane strikes on the southern Caribbean coast of Nicaragua JF - Quaternary Research Y1 - 2012 A1 - McCloskey, Terrence Allen A1 - Liu, Kam-biu AB - Multi-millennial hurricane landfall records from the western North Atlantic indicate that landfall frequency has varied dramatically over time, punctuated by multi-centennial to millennial scale periods of hyperactivity. We extend the record geographically by presenting a paleostrike record inferred from a four-core transect from a marsh on the Caribbean coast of Nicaragua. Fossil pollen indicates that the site was a highly organic wetland from ~ 5400–4900 cal yr BP, at which time it became a shallow marine lagoon until ~ 2800 cal yr BP when it transitioned back into swamp/marsh, freshening over time, with the present fresh-to-brackish Typha marsh developing over the very recent past. Hurricane Joan, 1988, is recorded as a distinctive light-colored sand–silt–clay layer across the top of the transect, identifiable by abrupt shifts in color from the dark marsh deposits, increased grain size, and two upward-fining sequences, which are interpreted as representing the storm's traction and suspension loads. The six layers identified as hurricane-generated display temporal clustering, featuring a marked increase in landfall frequency ~ 800 cal yr BP. This pattern is anti-phase with the activity pattern previously identified from the northern Caribbean and the Atlantic coast of North America, thereby opposing the view that hyperactivity occurs simultaneously across the entire basin. VL - 78 UR - http://www.sciencedirect.com/science/article/pii/S003358941200083X IS - 3 N1 - id: 2327 JO - A sedimentary-based history of hurricane strikes on the southern Caribbean coast of Nicaragua ER - TY - JOUR T1 - Significance of active growth faulting on marsh accretion processes in the lower Pearl River, Louisiana JF - Geomorphology Y1 - 2012 A1 - Yeager, Kevin M. A1 - Brunner, Charlotte A. A1 - Kulp, Mark A. A1 - Fischer, Dane A1 - Feagin, Rusty A. A1 - Schindler, Kimberly J. A1 - Prouhet, Jeremiah A1 - Bera, Gopal AB - Neotectonic processes influence marsh accretion in the lower Pearl River valley. Active growth faults are suggested by groupings of ponded river channel sections, transverse and linear river channel sections, and down- and across-valley contrasts in channel sinuosity. Seismic profiles identified several likely, fault-induced structural anomalies, two of which parallel the axes of surface distributary networks. Lithostratigraphy and biostratigraphy of six cores from across a suspected fault in the West Middle River, combined with 14C-based age control, yielded evidence of vertical offsets, indicating that this river section is on the plane of a growth fault. These data were used to estimate fault slip rates over two time intervals, 1.2 mm/y over the last 1300 yr, and 0.2 mm yr− 1 over the last 3700 yr, and delineated a sinusoidal pattern of deformation moving distally from the fault, which we interpret as resulting from fault-propagation folding. Higher rates of sediment accumulation (of the order of cm yr− 1 from 210Pbxs and 137Cs activity data) on the down-thrown side are consistent with sedimentary response to increased accommodation space, and mass-based sediment accumulation rates (g cm− 2 yr− 1) exhibit a pattern inverse of that shown by fault-driven sinusoidal deformation. We contend that near-surface growth faults are critically important to driving accretion rates and marsh response to sea-level rise. VL - 153–154 UR - http://www.sciencedirect.com/science/article/pii/S0169555X12001006 N1 - id: 2294 JO - Significance of active growth faulting on marsh accretion processes in the lower Pearl River, Louisiana ER - TY - JOUR T1 - Small-scale lacustrine drifts in Lake Champlain, Vermont JF - Journal of Great Lakes Research Y1 - 2012 A1 - Manley, Patricia L. A1 - Manley, T. O. A1 - Hayo, Kathryn A1 - Cronin, Thomas AB - High resolution CHIRP (Compressed High Intensity Radar Pulse) seismic profiles reveal the presence of two lacustrine sediment drifts located in Lake Champlain's Juniper Deep. Both drifts are positive features composed of highly laminated sediments. Drift B sits on a basement high while Drift A is built on a trough-filling acoustically-transparent sediment unit inferred to be a mass-transport event. These drifts are oriented approximately north–south and are parallel to a steep ridge along the eastern shore of the basin. Drift A, located at the bottom of a structural trough, is classified as a confined, elongate drift that transitions northward to become a system of upslope asymmetric mudwaves. Drift B is perched atop a structural high to the west of Drift A and is classified as a detached elongate drift. Bottom current depositional control was investigated using Acoustic Doppler Current Profilers (ADCPs) located across Drift A. Sediment cores were taken at the crest and at the edges of the Drift A and were dated. Drift source, deposition, and evolution show that these drifts are formed by a water column shear with the highest deposition occurring along its crest and western flank and began developing circa 8700–8800 year BP. VL - 38 N1 - id: 2179 JO - Small-scale lacustrine drifts in Lake Champlain, Vermont ER - TY - JOUR T1 - The Southern Ocean's Role in Carbon Exchange During the Last Deglaciation JF - SCIENCE Y1 - 2012 A1 - Burke, Andrea A1 - Robinson, Laura F. AB - Changes in the upwelling and degassing of carbon from the Southern Ocean form one of the leading hypotheses for the cause of glacial-interglacial changes in atmospheric carbon dioxide. We present a 25,000-year-long Southern Ocean radiocarbon record reconstructed from deep-sea corals, which shows radiocarbon-depleted waters during the glacial period and through the early deglaciation. This depletion and associated deep stratification disappeared by similar to 14.6 ka (thousand years ago), consistent with the transfer of carbon from the deep ocean to the surface ocean and atmosphere via a Southern Ocean ventilation event. Given this evidence for carbon exchange in the Southern Ocean, we show that existing deep-ocean radiocarbon records from the glacial period are sufficiently depleted to explain the similar to 190 per mil drop in atmospheric radiocarbon between similar to 17 and 14.5 ka. VL - 335 ER - TY - JOUR T1 - Stratigraphic evidence for an early Holocene earthquake in Aceh, Indonesia JF - Quaternary Science Reviews Y1 - 2012 A1 - Grand Pre, C. A1 - Horton, B. P. A1 - Kelsey, H. M. A1 - Rubin, C. M. A1 - Hawkes, A. D. A1 - Daryono, M. A1 - Rosenberg, G. A1 - Culver, S. J. AB - The Holocene stratigraphy of the coastal plain of the Aceh Province of Sumatra contains 6 m of sediment with three regionally consistent buried soils above pre-Quaternary bedrock or pre-Holocene unconsolidated sediment. Litho-, bio-, and chronostratigraphic analyses of the lower buried soil reveals a rapid change in relative sea-level caused by coseismic subsidence during an earlyHolocene megathrust earthquake. Evidence for paleoseismic subsidence is preserved as a buried mangrove soil, dominated by a pollen assemblage of Rhizophora and/or Bruguiera/Ceriops taxa. The soil is abruptly overlain by a thin tsunami sand. The sand contains mixed pollen and abraded foraminiferal assemblages of both offshore and onshore environments. The tsunami sand grades upward into mud that contains both well-preserved foraminifera of intertidal origin and individuals of the gastropod Cerithidea cingulata. Radiocarbon ages from the pre- and post-seismic sedimentary sequences constrain the paleoearthquake to 6500–7000 cal. yrs. BP. We use micro-and macrofossil data to determine the local paleoenvironment before and after the earthquake. We estimate coseismic subsidence to be 0.45 ± 0.30 m, which is comparable to the 0.6 m of subsidence observed during the 2004 Aceh–Andaman earthquake on Aceh’s west coast. VL - 54 N1 - id: 2139 JO - Stratigraphic evidence for an early Holocene earthquake in Aceh, Indonesia ER - TY - JOUR T1 - Strengthening of the Northeast Monsoon over the Flores Sea, Indonesia, at the time of Heinrich event 1 JF - Geology Y1 - 2012 A1 - Muller, J. A1 - McManus, J. F. A1 - Oppo, D. W. A1 - Francois, R. AB - Paleoclimate evidence from South America and Asia has been interpreted to indicate that tropical rainfall migrated southward during the Northern Hemisphere cooling associated with Heinrich stadial 1 (HS1), an event of massive iceberg discharge to the North Atlantic ca. 18–15 ka. Although arid conditions associated with such a shift are well documented in southern Asia, as far south as Borneo, debate still exists regarding the precipitation response in southern Indonesia and Australia during HS1. This study utilizes concentrations of the long-lived nuclide 232Th as a proxy for detrital riverine input and 230Th normalization to estimate the history of preserved fluxes reaching the seafloor in the Flores Sea, located between southern Sulawesi and the Lesser Sunda Islands, Indonesia. Because the only source of 232Th to the ocean is continental minerals, this proxy is a robust indicator of continental weathering. The 230Th normalized burial fluxes of lithogenic and biogenic matter demonstrate that both detrital and biogenic fluxes in the Flores Sea were higher during HS1 than any other period in the past 22 k.y. High detrital fluxes indicate enhanced precipitation runoff from surrounding landmasses during a period of maximum southward shift of the Intertropical Convergence Zone. This study further constrains the northern limit of enhanced rainfall associated with a southward shift of Australian monsoon-related rainfall at the time of HS1 and highlights the value of 232Th as a proxy of continental input to deep-sea sediment records. VL - 40 UR - http://geology.gsapubs.org/cgi/doi/10.1130/G32878.1 IS - 7 ER - TY - JOUR T1 - The synchronization of palaeoclimatic events in the North Atlantic region during Greenland Stadial 3 (ca 27.5 to 23.3 kyr b2k) JF - Quaternary Science Reviews Y1 - 2012 A1 - Austin, W. E. N. A1 - Hibbert, F. D. A1 - Rasmussen, S. O. A1 - Peters, C. A1 - Abbott, P. M. A1 - Bryant, C. L. AB - Two high resolution marine sediment cores located 83 km apart in the NE Atlantic have been studied: MD95-2006 (Barra Fan; 57°01.82 N, 10°03.48 W; 2120 m water depth) and MD04-2822 (Rockall Trough; 56°50.54 N, 11°22.96 W; 2344 m water depth). The records are anchored to the NGRIP ice core stratigraphy and GICC05 chronology by the presence of geochemically characterized Fugloyarbanki tephra and further tested by radiocarbon age control. Replicated sea surface temperature (SST) records show evidence for an abrupt and short-lived warming within Greenland Stadial (GS)-3, to which we tentatively assign an age of ca 25.6–24.8 kyr GICC05 b2k. Based on these and another marine palaeoclimate record (LINK17) from the Faroe-Shetland Channel, we propose a new three-fold event stratigraphy for GS-3 within the North East Atlantic region. The recognition of this warming event within GS-3 in NE Atlantic SST records demonstrates that such events may not readily be identified within the coldest stadials of the Greenland ice cores, highlights the need for carefully constructed event stratigraphies (independently tested by the use of tephra isochrones and radiocarbon) and illustrates pervasive millennial-scale climate variability of the North Atlantic region (Dansgaard-Oeschger (D/O) events) is deeply embedded in the dynamics of Atlantic Meridional Overturning Circulation (AMOC). VL - 36 UR - http://www.sciencedirect.com/science/article/pii/S0277379110004452 N1 - id: 2145 JO - The synchronization of palaeoclimatic events in the North Atlantic region during Greenland Stadial 3 (ca 27.5 to 23.3 kyr b2k) ER - TY - RPRT T1 - Test Drilling and Data Collection in the Calaveras County Portion of the Eastern San Joaquin Groundwater Subbasin, California , December 2009 – June 2011 Y1 - 2012 A1 - Metzger, L. F. A1 - Izbicki, J. A. A1 - Nawikas, J. M. JF - Open-File Report PB - U.S. Department of the Interior: U.S. Geological Survey ER - TY - JOUR T1 - A two-dimensional, heart-cutting preparative gas chromatograph facilitates highly resolved single-compound isolations with utility towards compound-specific natural abundance radiocarbon (14C) analyses JF - Journal of Chromatography A Y1 - 2012 A1 - Ball, Gregory Ian A1 - Xu, Li A1 - McNichol, Ann P. A1 - Aluwihare, Lihini I. AB - Motivated by the need to develop clean, high purity preparative enrichments of individual compounds for micro-scale compound-specific natural abundance isotope and radiocarbon (14C) analyses, we describe a new, two-dimensional, heart-cutting, low-bleed, three-oven, single GC preparative system, demonstrate its resolving capabilities as applied to a typically complex environmental sample matrix, and investigate the robustness with which it preserves the authigenic 13C/12C and 14C/12C ratios of individual compounds it targets for preparative enrichment. The system is comprised of a programmable temperature vaporizing (PTV) inlet, a single GC oven, two modular, door-mounted, resistively heated low thermal mass (LTM) columns, a preparative fraction collector (PFC), and a Deans pneumatic switching device which facilitates heart-cutting between the system's 1° and 2° chromatographic dimensions. Further, the system's inlet and trapping parameters are optimized for the efficient preparative enrichment of the methyl ether and ester derivatives of the lignin phenol compound class. The lignin phenols include such compounds as the vanillyl and syringyl aldehydes, ethanones, and acids and are unrivaled biomarkers of terrestrial organic matter, some of which are also important components of fragrances and flavors. Using this suite of compounds, the suitability of this augmented preparative capillary GC (PCGC) system was investigated for micro-scale compound-specific (CS) stable isotope and natural abundance radiocarbon analyses (RA). Analysis of a >300 injection enrichment scheme reveals the instrument to fractionate 13C in predictable ways and to preserve the authigenic Δ14C of compounds it targets for preparative enrichment to within 6.7 ± 5.0‰, demonstrating the promising new utility of such systems towards micro-scale CSRA investigations for which clean and high resolution separation techniques are prerequisite. VL - 1220 UR - http://www.sciencedirect.com/science/article/pii/S0021967311017031 N1 - id: 2152 JO - A two-dimensional, heart-cutting preparative gas chromatograph facilitates highly resolved single-compound isolations with utility towards compound-specific natural abundance radiocarbon (14C) analyses ER - TY - JOUR T1 - Using the N/C ratio to correct bulk radiocarbon ages from lake sediments: Insights from Chilean Patagonia JF - Quaternary Geochronology Y1 - 2012 A1 - Bertrand, Sébastien A1 - Araneda, Alberto A1 - Vargas, Patricia A1 - Jana, Patricia A1 - Fagel, Nathalie A1 - Urrutia, Roberto AB - The offset between AMS radiocarbon ages obtained on bulk lake sediments and the true age of deposition was evaluated at four sites in Northern Chilean Patagonia. Our results show that the bulk radiocarbon ages are systematically older by 300 to 1100 years. In this region free of carbonate and carbonaceous rocks, we argue that this difference results from variable inputs of terrestrial organic carbon from the Holocene soils that cover the lake watersheds. For the four studied lakes, the age offset is clearly related to the fraction of terrestrial carbon preserved in the lake sediments, which was estimated using the N/C ratio of the bulk organic matter. We propose that N/C measurements can be used to significantly improve chronologies based on radiocarbon dating of bulk lake sediments. VL - 12 UR - http://www.sciencedirect.com/science/article/pii/S1871101412001112 N1 - id: 2296 JO - Using the N/C ratio to correct bulk radiocarbon ages from lake sediments: Insights from Chilean Patagonia ER - TY - JOUR T1 - Ventilation changes in the western North Pacific since the last glacial period JF - CLIMATE OF THE PAST Y1 - 2012 A1 - Okazaki, Y. A1 - Sagawa, T. A1 - Asahi, H. A1 - Horikawa, K. A1 - Onodera, J. AB - We reconstructed the ventilation record of deep water at 2100m depth in the mid-latitude western North Pacific over the past 25 kyr from radiocarbon measurements of coexisting planktic and benthic foraminiferal shells in sediment with a high sedimentation rate. The C-14 data on fragile and robust planktic foraminiferal shells were concordant with each other, ensuring high quality of the reconstructed ventilation record. The radiocarbon activity changes were consistent with the atmospheric record, suggesting that no massive mixing of old carbon from the abyssal reservoir occurred throughout the glacial to deglacial periods. margin of the North Pacific, in a deep western boundary current analogous to the present one in the North Atlantic. However, our knowledge of paleo-ventilation, particularly in water deeper than 2000m in the western North Pacific, is limited because of poor preservation of foraminiferal shells in sediment. Here we present a detailed account of ventilation changes in the mid-latitude western North Pacific based on radiocarbon records from coexisting planktic and benthic foraminifera in sediment with high sedimentation rates. Because our ventilation reconstruction is based on radiocarbon data from multiple planktic species in the mid to high-latitude western North Pacific, our record provides robust evidence for the ventilation history in the region. VL - 8 ER - TY - JOUR T1 - 14C-Based source assessment of soot aerosols in Stockholm and the Swedish EMEP-Aspvreten regional background site JF - Atmospheric Environment Y1 - 2011 A1 - Andersson, August A1 - Sheesley, Rebecca J. A1 - Kruså, Martin A1 - Johansson, Christer A1 - Gustafsson, Örjan AB - Combustion-derived soot or black carbon (BC) in the atmosphere has a strong influence on both climate and human health. In order to propose effective mitigation strategies for BC emissions it is of importance to investigate geographical distributions and seasonal variations of BC emission sources. Here, a radiocarbon methodology is used to distinguish between fossil fuel and biomass burning sources of soot carbon (SC). SC is isolated for subsequent off-line 14C quantification with the chemothermal oxidation method at 375 °C (CTO-375 method), which reflects a recalcitrant portion of the BC continuum known to minimize inadvertent inclusion of any non-pyrogenic organic matter. Monitored wind directions largely excluded impact from the Stockholm metropolitan region at the EMEP-Aspvreten rural station 70 km to the south-west. Nevertheless, the Stockholm city and the rural stations yielded similar relative source contributions with fraction biomass (fbiomass) for fall and winter periods in the range of one-third to half. Large temporal variations in 14C-based source apportionment was noted for both the 6 week fall and the 4 month winter observations. The fbiomass appeared to be related to the SC concentration suggesting that periods of elevated BC levels may be caused by increased wood fuel combustion. These results for the largest metropolitan area in Scandinavia combine with other recent 14C-based studies of combustion-derived aerosol fractions to suggest that biofuel combustion is contributing a large portion of the BC load to the northern European atmosphere. VL - 45 UR - http://www.sciencedirect.com/science/article/pii/S1352231010007697 IS - 1 N1 - id: 2148 JO - 14C-Based source assessment of soot aerosols in Stockholm and the Swedish EMEP-Aspvreten regional background site ER - TY - JOUR T1 - Age determination of large live trees with inner cavities: radiocarbon dating of Platland tree, a giant African baobab JF - ANNALS OF FOREST SCIENCE Y1 - 2011 A1 - Patrut, Adrian A1 - von Reden, Karl F. A1 - Van Pelt, Robert A1 - Mayne, Diana H. A1 - Lowy, Daniel A. A1 - Margineanu, Dragos KW - Accelerator mass spectrometry KW - Adansonia digitata KW - Age determination KW - Growth rate KW - Radiocarbon dating AB - Introduction For large trees without a continuous sequence of growth rings in their trunk, such as the African baobab (Adansonia digitata L.), the only accurate method for age determination is radiocarbon dating. As of today, this method was limited to dating samples collected from the remains of dead specimens. Methods Our research extends significantly the dating of such trees to large live specimens with inner cavities. The new approach is based on collecting samples from the cavities and their subsequent radiocarbon dating. Results The giant two-stemmed Platland tree, also known as Sunland baobab, was investigated by using this new approach. AMS radiocarbon dates of the oldest sample segments originating from the two inner cavities indicate that the large stem I (364.5 m(3)) is 750 +/- 75 years old, while the much smaller stem II (136.7 m(3)) has 1,060 +/- 75 years. Results also show that stem I is still growing very fast, while the older stem II slowed down consistently its growth over the past 250 years. The complete mapping of Platland tree determined an overall wood volume of 501.2 m(3). Conclusions Dating results demonstrate that the size-age relation cannot be used for estimating accurately the age of African baobabs. VL - 68 ER - TY - JOUR T1 - Age, growth, and spawning season of red bream (Beryx decadactylus) off the southeastern United States JF - Fishery Bulletin Y1 - 2011 A1 - Friess, C. A1 - Sedberry, G. R. AB - Red bream (Beryx decadactylus) is a commercially important deep-sea benthopelagic fish with a circumglobal distribution on insular and continental slopes and seamounts. In the United States, small numbers are caught incidentally in the wreckfish (Polyprion americanus) fishery which operates off the southeastern coast, but no biological information exists for the management of the U.S. red bream population. For this study, otoliths (n=163) and gonads (n=161) were collected from commercially caught red bream between 2003 and 2008 to determine life history parameters. Specimens ranged in size from 410 to 630 mm fork length and were all determined to be mature by histological examination of the gonads. Females in spawning condition were observed from June through September, and reproductively active males were found year-round. Sectioned otoliths were difficult to interpret, but maximum age estimates were much higher than the 15 years previously reported for this species from the eastern North Atlantic based on whole-otolith analysis. Estimated ages ranged from 8 to 69 years, and a minimum lifespan of 49 years was validated by using bomb radiocarbon dating. Natural mortality was estimated at 0.06/yr. This study shows that red bream are longer lived and more vulnerable to overfishing than previously assumed and should be managed carefully to prevent over-exploitation. VL - 109 UR - http://fishbull.noaa.gov/1091/friess.pdf IS - 1 N1 - id: 2211; Source type: scholarlyjournals; Object type: Article; Object type: Feature; CSAUnique: OB-MD-0015408089; AccNum: 14385075; ISSN: 0090-0656; Peer Reviewed: true JO - Age, growth, and spawning season of red bream (Beryx decadactylus) off the southeastern United States ER - TY - JOUR T1 - The application of foraminifera to reconstruct the rate of 20th century sea level rise, Morbihan Golfe, Brittany, France JF - Quaternary Research Y1 - 2011 A1 - Rossi, V. A1 - Horton, B. P. A1 - Corbett, D. R. A1 - Leorri, E. A1 - Perez-Belmonte, L. A1 - Douglas, B. C. AB - Foraminiferal assemblages preserved within salt-marsh sediment can provide an accurate and precise means to reconstruct relative sea level due to a strong relationship with elevation, which can be quantified using a transfer function. We collected a set of surface samples from two salt marshes in the Morbihan Golfe, France to determine foraminiferal distribution patterns. Dominant taxa included Jadammina macrescens, Trochammina inflata, Haplophragmoides spp. and Miliammina fusca. We developed a foraminifera-based transfer function using a modern training set of 36 samples and 23 species. The strong relationship between observed and predicted values (r(jack)(2) = 0.7) indicated that foraminiferal distribution is primarily controlled by elevation with respect to the tidal frame and precise reconstructions of former sea level are possible (RMSEP(jack) = 0.07 m). The application of the transfer function to a short salt-marsh core (0.32 m) allowed the reconstruction of former sea levels, which were placed in a chronological framework using short-lived radionuclides ((210)Pb and (137)Cs). The agreement between the foraminifera-based sea level curve and the Brest tide-gauge record confirms the reliability of transfer function estimates and the validity of this methodology to extend sea level reconstructions back into the pre-instrumental period. Both instrumental and microfossil records suggest an acceleration of sea level rise during the 20th century. (C) 2010 University of Washington. Published by Elsevier Inc. All rights reserved. VL - 75 IS - 1 N1 - id: 1889; 713FR Times Cited:1 Cited References Count:71submittedY JO - The application of foraminifera to reconstruct the rate of 20th century sea level rise, Morbihan Golfe, Brittany, France ER - TY - JOUR T1 - Associated terrestrial and marine fossils in the late-glacial Presumpscot Formation, southern Maine, USA, and the marine reservoir effect on radiocarbon ages JF - Quaternary Research Y1 - 2011 A1 - Thompson, Woodrow B. A1 - Griggs, Carol B. A1 - Miller, Norton G. A1 - Nelson, Robert E. A1 - Weddle, Thomas K. A1 - Kilian, Taylor M. AB - Excavations in the late-glacial Presumpscot Formation at Portland, Maine, uncovered tree remains and other terrestrial organics associated with marine invertebrate shells in a landslide deposit. Buds of Populus balsamifera (balsam poplar) occurred with twigs of Picea glauca (white spruce) in the Presumpscot clay. Tree rings in Picea logs indicate that the trees all died during winter dormancy in the same year. Ring widths show patterns of variation indicating responses to environmental changes. Fossil mosses and insects represent a variety of species and wet to dry microsites. The late-glacial environment at the site was similar to that of today's Maine coast. Radiocarbon ages of 14 tree samples are 11,907 +/- 31 to 11,650 +/- 50 (14)C yr BP. Wiggle matching of dated tree-ring segments to radiocarbon calibration data sets dates the landslide occurrence at ca. 13,520 + 95/-20 cal yr BP. Ages of shells juxtaposed with the logs are 12,850 +/- 65 (14)C yr BP (Mytilus edulis) and 12,800 +/- 55 (14)C yr BP (Balanus sp.), indicating a marine reservoir age of about 1000 yr. Using this value to correct previously published radiocarbon ages reduces the discrepancy between the Maine deglaciation chronology and the varve-based chronology elsewhere in New England. (C) 2011 University of Washington. Published by Elsevier Inc. All rights reserved. VL - 75 IS - 3 N1 - id: 2011; PT: J; UT: WOS:000290831500018 JO - Associated terrestrial and marine fossils in the late-glacial Presumpscot Formation, southern Maine, USA, and the marine reservoir effect on radiocarbon ages ER - TY - JOUR T1 - Bomb-produced radiocarbon validation of growth-increment crossdating allows marine paleoclimate reconstruction JF - Palaeogeography, Palaeoclimatology, Palaeoecology Y1 - 2011 A1 - Kastelle, Craig R. A1 - Helser, Thomas E. A1 - Black, Bryan A. A1 - Stuckey, Matthew J. A1 - C. Gillespie, Darlene A1 - McArthur, Judy A1 - Little, Diana A1 - D. Charles, Karen A1 - Khan, Reziah S. AB - The bivalve Pacific geoduck (Panopea generosa) has been used in the eastern North Pacific Ocean to create proxies for environmental factors such as temperature and oceanographic conditions. This type of research depends upon accurate age determination of Pacific geoducks, which historically was based on shell growth-increment counts. A recent study comparing age estimates generated by the dendrochronology (tree-ring science) procedure of crossdating to those estimated from growth-increment counts found a significant difference between the methods for geoduck older than 30 years. Compared to the traditional age determination method of counting growth increments, the crossdating method estimates a greater longevity in this species, with some individuals living in excess of 150 years. In the present study, the accuracy of each method was independently assessed using bomb-produced radiocarbon (14C) techniques. Specimens whose birth years were estimated to be within the era of the bomb-produced marine 14C increase and where the differences between ages estimated by the two methods were greatest were selected for 14C analysis. The difference between age estimates from traditional growth-increment counts and those from crossdating was evaluated using their respective 14C chronologies in comparisons to a reference chronology as a standard. The comparisons relied on Bayesian nonlinear models using Markov Chain Monte Carlo simulation. This method of analysis showed that with a 50% probability geoducks were aged correctly when using the crossdating method, compared to the growth increment counts which had a 50% probability of underestimating the age by 4 years. Therefore, the crossdated age estimates were found to be more accurate than increment counts. Furthermore, these results provide new confidence in using Pacific geoduck biochronologies for paleoclimate and paleoenvironmental reconstruction. VL - 311 UR - http://www.sciencedirect.com/science/article/pii/S0031018211004524 IS - 1–2 N1 - id: 2167 JO - Bomb-produced radiocarbon validation of growth-increment crossdating allows marine paleoclimate reconstruction ER - TY - JOUR T1 - Carbonate veins trace seawater circulation during exhumation and uplift of mantle rock: Results from ODP Leg 209 JF - Earth and Planetary Science Letters Y1 - 2011 A1 - Bach, Wolfgang A1 - Rosner, Martin A1 - Jöns, Niels A1 - Rausch, Svenja A1 - Robinson, Laura F. A1 - Paulick, Holger A1 - Erzinger, Jörg AB - Carbonate veins hosted in ultramafic basement drilled at two sites in the Mid Atlantic Ridge 15°N area record two different stages of fluid-basement interaction. A first generation of carbonate veins consists of calcite and dolomite that formed syn- to postkinematically in tremolite–chlorite schists and serpentine schists that represent gently dipping large-offset faults. These veins formed at temperatures between 90 and 170 °C (oxygen isotope thermometry) and from fluids that show intense exchange of Sr and Li with the basement (87Sr/86Sr = 0.70387 to 0.70641, δ7LiL-SVEC = + 3.3 to + 8.6‰). Carbon isotopic compositions range to high δ13CPDB values (+ 8.7‰), indicating that methanogenesis took place at depth. The Sr–Li–C isotopic composition suggests temperatures of fluid-rock interaction that are much higher (T > 350–400 °C) than the temperatures of vein mineral precipitation inferred from oxygen isotopes. A possible explanation for this discrepancy is that fluids cooled conductively during upflow within the presumed detachment fault. Aragonite veins were formed during the last 130 kyrs at low-temperatures within the uplifted serpentinized peridotites. Chemical and isotopic data suggest that the aragonites precipitated from cold seawater, which underwent overall little exchange with the basement. Oxygen isotope compositions indicate an increase in formation temperature of the veins by 8–12 °C within the uppermost ~ 80 m of the subseafloor. This increase corresponds to a high regional geothermal gradient of 100–150 °C/km, characteristic of young lithosphere undergoing rapid uplift. VL - 311 UR - http://www.sciencedirect.com/science/article/pii/S0012821X11005358 IS - 3–4 N1 - id: 2162 JO - Carbonate veins trace seawater circulation during exhumation and uplift of mantle rock: Results from ODP Leg 209 ER - TY - JOUR T1 - Climate related sea-level variations over the past two millennia JF - Proc Natl Acad Sci U S A Y1 - 2011 A1 - Kemp, A. C. A1 - Horton, B. P. A1 - Donnelly, J. P. A1 - Mann, M. E. A1 - Vermeer, M. A1 - Rahmstorf, S. AB - We present new sea-level reconstructions for the past 2100 y based on salt-marsh sedimentary sequences from the US Atlantic coast. The data from North Carolina reveal four phases of persistent sea-level change after correction for glacial isostatic adjustment. Sea level was stable from at least BC 100 until AD 950. Sea level then increased for 400 y at a rate of 0.6 mm/y, followed by a further period of stable, or slightly falling, sea level that persisted until the late 19th century. Since then, sea level has risen at an average rate of 2.1 mm/y, representing the steepest century-scale increase of the past two millennia. This rate was initiated between AD 1865 and 1892. Using an extended semiempirical modeling approach, we show that these sea-level changes are consistent with global temperature for at least the past millennium. VL - 108 UR - http://www.ncbi.nlm.nih.gov/pubmed/21690367 IS - 27 N1 - id: 853; Kemp, Andrew C Horton, Benjamin P Donnelly, Jeffrey P Mann, Michael E Vermeer, Martin Rahmstorf, Stefan Proc Natl Acad Sci U S A. 2011 Jul 5;108(27):11017-22. Epub 2011 Jun 20.3131350submittedY JO - Climate related sea-level variations over the past two millennia ER - TY - JOUR T1 - Coastal subsidence in Oregon, USA, during the giant Cascadia earthquake of AD 1700 JF - Quaternary Science Reviews Y1 - 2011 A1 - Hawkes, A. D. A1 - Horton, B. P. A1 - Nelson, A. R. A1 - Vane, C. H. A1 - Sawai, Y. AB - Quantitative estimates of land-level change during the giant AD 1700 Cascadia earthquake along the Oregon coast are inferred from relative sea-level changes reconstructed from fossil foraminiferal assemblages preserved within the stratigraphic record. A transfer function, based upon a regional training set of modern sediment samples from Oregon estuaries, is calibrated to fossil assemblages in sequences of samples across buried peat-mud and peat-sand contacts marking the AD 1700 earthquake. Reconstructions of sample elevations with sample-specific errors estimate the amount of coastal subsidence during the earthquake at six sites along 400 km of coast. The elevation estimates are supported by lithological, carbon isotope, and faunal tidal zonation data. Coseismic subsidence at Nehalem River, Nestucca River, Salmon River, Alsea Bay, Siuslaw River and South Slough varies between 0.18 m and 0.85 m with errors between 0.18 m and 0.32 m. These subsidence estimates are more precise, consistent, and generally lower than previous semi-quantitative estimates. Following earlier comparisons of semi-quantitative subsidence estimates with elastic dislocation models of megathrust rupture during great earthquakes, our lower estimates for central and northern Oregon are consistent with modeled rates of strain accumulation and amounts of slip on the subduction megathrust, and thus, with a magnitude of 9 for the AD 1700 earthquake. VL - 30 UR - http://www.sciencedirect.com/science/article/pii/S0277379110004130 IS - 3–4 N1 - id: 2143 JO - Coastal subsidence in Oregon, USA, during the giant Cascadia earthquake of AD 1700 ER - TY - JOUR T1 - Contemporary 14C radiocarbon levels of oxygenated polybrominated diphenyl ethers (O-PBDEs) isolated in sponge–cyanobacteria associations JF - Marine pollution bulletin Y1 - 2011 A1 - Guitart, Carlos A1 - Slattery, Marc A1 - Ankisetty, Sridevi A1 - Radwan, Mohamed A1 - Ross, Samir J. A1 - Letcher, Robert J. A1 - Reddy, Christopher M. AB - Considerable debate surrounds the sources of oxygenated polybrominated diphenyl ethers (O-PBDEs) in wildlife as to whether they are naturally produced or result from anthropogenic industrial activities. Natural radiocarbon (14C) abundance has proven to be a powerful tool to address this problem as recently biosynthesized compounds contain contemporary (i.e. modern) amounts of atmospheric radiocarbon; whereas industrial chemicals, mostly produced from fossil fuels, contain no detectable 14C. However, few compounds isolated from organisms have been analyzed for their radiocarbon content. To provide a baseline, we analyzed the 14C content of four O-PBDEs. These compounds, 6-OH-BDE47, 2′-OH-BDE68, 2′,6-diOH-BDE159, and a recently identified compound, 2′-MeO-6-OH-BDE120, were isolated from the tropical marine sponges Dysidea granulosa and Lendenfeldia dendyi. The modern radiocarbon content of their chemical structures (i.e. diphenyl ethers, C12H22O) indicates that they are naturally produced. This adds to a growing baseline on, at least, the sources of these unusual compounds. VL - 62 UR - http://www.sciencedirect.com/science/article/pii/S0025326X11000075 IS - 3 N1 - id: 2192 JO - Contemporary 14C radiocarbon levels of oxygenated polybrominated diphenyl ethers (O-PBDEs) isolated in sponge–cyanobacteria associations ER - TY - JOUR T1 - Controls on dissolved inorganic carbon and δ13C in cave waters from DeSoto Caverns: Implications for speleothem δ13C assessments JF - Geochimica et Cosmochimica Acta Y1 - 2011 A1 - Lambert, W. Joe A1 - Aharon, Paul AB - Unraveling the factors controlling the carbon chemistry and transport of carbon within extant karst systems has important implications concerning the assessment of time-series δ13C records of speleothems. Here we report the results of a 3-year study of total dissolved inorganic carbon [DIC] and δ13CDIC from cave waters at DeSoto Caverns (Southeastern USA) that offer valuable insight on carbon transport and the accompanied isotope fractionations from end-member sources to speleothems. [DIC] and δ13CDIC values of cave waters range from 0.2 to 6.0 mM and 2.7 to −12.9 (‰ VPDB), respectively. [DIC] and δ13CDIC of “seasonal drips” show seasonal, albeit noisy, variability and are inversely related (δ13CDIC = −2.49[DIC] + 0.64, r2 = 0.84). A shallow pool fed by multiple drips shows a bimodal δ13CDIC distribution with an isotopically heavier mode during winter (−4‰ to −5‰ VPDB) relative to summer months (−9‰ to −10‰ VPDB). A multi-year trend of decreasing water availability during the study period is not reflected in a response of cave water carbon chemistry suggesting that rainfall amount may not be a significant controlling factor of the carbon chemistry. Coupled cave air winter ventilation/summer stagnation and varying CO2 fluxes through the soil horizon and epikarst exert the strongest influence on seasonal [DIC] and δ13CDIC variability. Measured values of high [DIC] and low δ13CDIC from cave waters collected during the summer/early fall closely approximate isotopic equilibrium conditions. Conversely, low [DIC] and high δ13CDIC values during winter/early months indicate kinetically enhanced isotopic fractionations within the cave waters. The kinetically enhanced isotopic fractionation of HCO 3 - partitioned between degassed CO2 and precipitated CaCO3 ( 1000 ln α [ ( CO 2 - HCO 3 ) + ( CaCO 3 (AR) - HCO 3 ) ] / 2 ) is greater by about a factor of two (−6.7 ± 0.3‰) relative to the same isotopic fractionation under equilibrium conditions (−3.1‰). VL - 75 UR - http://www.sciencedirect.com/science/article/pii/S0016703710006319 IS - 3 N1 - id: 2195 JO - Controls on dissolved inorganic carbon and δ13C in cave waters from DeSoto Caverns: Implications for speleothem δ13C assessments ER - TY - JOUR T1 - Cryostratigraphy of late Pleistocene syngenetic permafrost (yedoma) in northern Alaska, Itkillik River exposureAbstract JF - Quaternary Research Y1 - 2011 A1 - Kanevskiy, M. A1 - Shur, Y. A1 - Fortier, D. A1 - Jorgenson, M.T. A1 - Stephani, E. AB - Extremely ice-rich syngenetic permafrost, or yedoma, developed extensively under the cold climate of the Pleistocene in unglaciated regions of Eurasia and North America. In Alaska, yedoma occurs in the Arctic Foothills, the northern part of the Seward Peninsula, and in interior Alaska. A remarkable 33-m-high exposure along the lower Itkillik River in northern Alaska opened an opportunity to study the unmodified yedoma, including stratigraphy, particle-size distribution, soil carbon contents, morphology and quantity of segregated, wedge, and thermokarst-cave ice. The exposed permafrost sequence comprised seven cryostratigraphic units, which formed over a period from > 48,000 to 5,000 14C yr BP, including: 1) active layer; 2) intermediate layer of the upper permafrost; 3–4) two yedoma silt units with different thicknesses of syngenetic ice wedges; 5) buried peat layer; 6) buried intermediate layer beneath the peat; and 7) silt layer with short ice wedges. This exposure is comparable to the well known Mus-Khaya and Duvanny Yar yedoma exposures in Russia. Based on our field observations, literature sources, and interpretation of satellite images and aerial photography, we have developed a preliminary map of yedoma distribution in Alaska. VL - 75 UR - https://doi.org/10.1016/j.yqres.2010.12.003 IS - 03 ER - TY - JOUR T1 - A decadally-resolved paleohurricane record archived in the late Holocene sediments of a Florida sinkhole JF - Marine Geology Y1 - 2011 A1 - Lane, Philip A1 - Donnelly, Jeffrey P. A1 - Woodruff, Jonathan D. A1 - Hawkes, Andrea D. KW - Apalachee Bay KW - Gulf of Mexico KW - Holocene KW - hurricane KW - paleohurricane KW - Paleotempestology KW - sinkhole KW - SLOSH KW - storm surge KW - tropical cyclone AB - A 4500-year record of hurricane-induced storm surges is developed from sediment cores collected from a coastal sinkhole near Apalachee Bay, Florida. Recent deposition of sand layers in the upper sediments of the pond was found to be contemporaneous with significant, historic storm surges at the site modeled using SLOSH and the Best Track, post-1851 A.D. dataset. Using the historic portion of the record for calibration, paleohurricane deposits were identified by sand content and dated using radiocarbon-based age models. Marine-indicative foraminifera, some originating at least 5 km offshore, were present in several modern and ancient storm deposits. The presence and long-term preservation of offshore foraminifera suggest that this site and others like it may yield promising microfossil-based paleohurricane reconstructions in the future. Due to the sub-decadal (~ 7 years) resolution of the record and the site's high susceptibility to hurricane-generated storm surges, the average, local frequency of recorded events, approximately 3.9 storms per century, is greater than that of previously published paleohurricane records from the region. The high incidence of recorded events permitted a time series of local hurricane frequency during the last five millennia to be constructed. Variability in the frequency of the largest storm layers was found to be greater than what would likely occur by chance alone, with intervals of both anomalously high and low storm frequency identified. However, the rate at which smaller layers were deposited was relatively constant over the last five millennia. This may suggest that significant variability in hurricane frequency has occurred only in the highest magnitude events. The frequency of high magnitude events peaked near 6 storms per century between 2800 and 2300 years ago. High magnitude events were relatively rare with about 0–3 storms per century occurring between 1900 and 1600 years ago and between 400 and 150 years ago. A marked decline in the number of large storm deposits, which began around 600 years ago, has persisted through present with below average frequency over the last 150 years when compared to the preceding five millennia. VL - 287 UR - http://linkinghub.elsevier.com/retrieve/pii/S0025322711001472http://api.elsevier.com/content/article/PII:S0025322711001472?httpAccept=text/xmlhttp://api.elsevier.com/content/article/PII:S0025322711001472?httpAccept=text/plain IS - 1-4 ER - TY - JOUR T1 - The Deglacial Evolution of North Atlantic Deep Convection JF - SCIENCE Y1 - 2011 A1 - Thornalley, David J. R. A1 - Barker, Stephen A1 - Broecker, Wallace S. A1 - Elderfield, Henry A1 - McCave, I. Nick AB - Deepwater formation in the North Atlantic by open-ocean convection is an essential component of the overturning circulation of the Atlantic Ocean, which helps regulate global climate. We use water-column radiocarbon reconstructions to examine changes in northeast Atlantic convection since the Last Glacial Maximum. During cold intervals, we infer a reduction in open-ocean convection and an associated incursion of an extremely radiocarbon (C-14)-depleted water mass, interpreted to be Antarctic Intermediate Water. Comparing the timing of deep convection changes in the northeast and northwest Atlantic, we suggest that, despite a strong control on Greenland temperature by northeast Atlantic convection, reduced open-ocean convection in both the northwest and northeast Atlantic is necessary to account for contemporaneous perturbations in atmospheric circulation. VL - 331 ER - TY - JOUR T1 - A depositional history of particulate organic carbon in a floodplain lake from the lower Ob’ River, Siberia JF - Geochimica et Cosmochimica Acta Y1 - 2011 A1 - Dickens, Angela F. A1 - Baldock, Jeff A1 - Kenna, Timothy C. A1 - Eglinton, Timothy I. AB - Northern, high latitude soils have stored vast amounts of organic carbon (OC) in permafrost and peats for many millennia, however, climate change may mobilize and release this particulate OC (POC) to arctic rivers. Deltaic and floodplain lakes that receive fluvial sediments, primarily during the spring freshet, may provide records of such changes in riverine POC. Here, we examine properties of OC in a sediment core from a lake in the lower floodplain of the Ob’ River, west Siberia, to determine how the properties of OC deposited in this lake varied over many decades and to evaluate use of this sedimentary OC as a recorder of riverine POC load and properties. The core predates the most recent, dramatic changes in arctic climate and hence may serve as a benchmark against which to contrast future variations in fluvial POC discharge. Elemental, stable carbon and radiocarbon isotopic analyses, along with nuclear magnetic resonance (NMR) spectroscopy and molecular-level information (lignin phenol composition), indicate two major sources of OC to most of the sediments in this lake: plant-derived OC and algal-derived OC. However, a mixing model indicates that the nature and 14C content of these two sources change with depth in the sediment, resulting in three distinct layers: surface horizons, a “high-OC” layer and “mixing” horizons found above and below the high-OC layer. The plant-derived component is significantly aged throughout the core (14C ages of 1300–3900 years) and appears to derive from primarily local, tundra sources, whereas the algal component is modern. Our analysis suggests that the usual mode of OC deposition, as exemplified by the “mixing” and surface horizons, involved mixing of varying amounts of new algal production (35–65%) with aged permafrost- or peat-derived OC. This deposition was interrupted by an event, such as the collapse of a riverbank, which laid down the compositionally distinct “high-OC” layer in which plant-derived OC mixes with aged mineral-soil-derived OC without clear input from algae. The relative amounts of the plant and algal components in the lake sediments appear to be controlled primarily by local hydrological conditions rather than by river-wide processes, suggesting that comparison of sediment records from multiple lakes within a floodplain will be important to assess changes in POC export by arctic rivers. However, the flux and nature of the higher plant-derived OC may carry important information on the sources and dynamics of OC stored within the drainage basin. VL - 75 UR - http://www.sciencedirect.com/science/article/pii/S0016703711003085 IS - 17 N1 - id: 2172 JO - A depositional history of particulate organic carbon in a floodplain lake from the lower Ob’ River, Siberia ER - TY - JOUR T1 - Design and reality: Continuous-flow accelerator mass spectrometry (CFAMS) JF - Proceedings of the 10th European Conference on Accelerators in Applied Research and Technology (ECAART10) Y1 - 2011 A1 - von Reden, Karl F. A1 - Roberts, Mark L. A1 - McIntyre, Cameron P. A1 - Burton, Joshua R. AB - In 2007 we published [1] the design of a novel accelerator mass spectrometry (AMS) system capable of analyzing gaseous samples injected continuously into a microwave plasma gas ion source. Obvious advantages of such a system are drastically reduced processing times and avoidance of potentially contaminating chemical preparation steps. Another paper in these proceedings will present the progress with the development of the microwave gas ion source that has since been built and tested at the National Ocean Sciences AMS Facility in Woods Hole [2]. In this paper we will review the original design and present updates, reflecting our recent encouraging experience with the system. A simple summary: large acceptance ion beam optics design is beneficial to accelerator mass spectrometry in general, but essential to AMS with plasma gas ion sources. VL - 269 UR - http://www.sciencedirect.com/science/article/pii/S0168583X11003703 IS - 24 N1 - id: 2157 JO - Design and reality: Continuous-flow accelerator mass spectrometry (CFAMS) ER - TY - JOUR T1 - The detailed palaeoecology of a mid-Wisconsinan interstadial (ca. 32 000 (14)C a BP) vegetation surface from interior Alaska JF - Journal of Quaternary Science Y1 - 2011 A1 - Wooller, Matthew J. A1 - Zazula, Grant D. A1 - Blinnikov, Misha A1 - Gaglioti, Benjamin V. A1 - Bigelow, Nancy H. A1 - Sanborn, Paul A1 - Kuzmina, Svetlana A1 - La Farge, Catherine AB - We present a multi-proxy reconstruction from a well-preserved vegetation surface (ca. 32 000 (14)C a BP) from the Fox Permafrost tunnel near Fairbanks, Alaska. A thick litter layer of plant material on the vegetation surface is consistent with the vegetation lacking evidence of disturbance. Plant macrofossils and graminoid cuticle analysis show the presence of a graminoid assemblage consistent with phytolith data. The pollen data indicate that trees were not local to the site and that Artemisia sp. was present in the region. The insect and bryophyte reconstructions are consistent with the vascular plant reconstruction, indicating the site was at least periodically wet. delta(13)C values from the graminoids present show a large range encompassing both the wet and dry range displayed by modern graminoids in Alaska. Sequential delta(13)C analyses conducted along the length of leaves attached to the vegetation surface indicate a seasonal shift towards relatively higher water use efficiency. The lower water use efficiency earlier in the growing season may have stemmed from the use of winter season meltwater by plants at the site - a scenario consistent with the site's cryostratigraphy. Our multi-proxy reconstruction contributes to the limited palaeoecological data available for graminoid-dominated vegetation present in Eastern Beringia and particularly the interior of Alaska during the mid-Wisconsinan interstadial. Copyright (C) 2011 John Wiley & Sons, Ltd. VL - 26 IS - 7 N1 - id: 2131; PT: J; TC: 1; UT: WOS:000296091300010 JO - The detailed palaeoecology of a mid-Wisconsinan interstadial (ca. 32 000 (14)C a BP) vegetation surface from interior Alaska ER - TY - JOUR T1 - D/H variation in terrestrial lipids from Santa Barbara Basin over the past 1400 years: A preliminary assessment of paleoclimatic relevance RID C-2752-2008 JF - Organic Geochemistry Y1 - 2011 A1 - Li, Chao A1 - Sessions, Alex L. A1 - Valentine, David L. A1 - Thiagarajan, Nivedita AB - We analyzed D/H ratios of common terrestrial leaf wax lipids in a 1400 year sediment core from the Santa Barbara Basin (SBB) to test whether they accurately record terrestrial climate in Southern California. The D/H ratios of long chain n-alkanes vary substantially with depth, but are poorly correlated with other terrestrial climate proxies. Interference from fossil hydrocarbons may be at least partly responsible. Long chain n-alkanoic acids exhibit nearly constant downcore D/H ratio values. This constancy in the face of known climatic shifts presumably reflects a substantial residence time for leaf wax compounds in terrestrial soil and/or on the basin flanks. Alternatively, the isotopic composition of meteoric waters in Southern California may not covary with climate, particularly aridity. However, the delta D values of n-C(22) and n-C(24) fatty acids, commonly attributed to terrestrial aquatic sources, are partially correlated with Southern California winter Palmer Drought Severity Index, a tree ring-based climatic proxy (R(2) 0.25; p VL - 42 IS - 1 N1 - id: 2050; PT: J; UT: WOS:000286995900002 JO - D/H variation in terrestrial lipids from Santa Barbara Basin over the past 1400 years: A preliminary assessment of paleoclimatic relevance RID C-2752-2008 ER - TY - JOUR T1 - Distribution and significance of heavy-mineral concentrations along the southeast Baltic Sea coast JF - Journal of Coastal Research Y1 - 2011 A1 - Pupienis, D. A1 - Buynevich, I. V. A1 - Bitinas, A. AB - Heavy mineral concentrations (HMCs) in coastal sands are important from both scientific and practical standpoints. On one hand, they may serve as local sources of iron and other economically important metals, and on the other they are good indicators of hydro-meteorological and sedimentological conditions along the coast. A variety of HMC types have been documented in beach, foredune, and relict dune environments of Lithuania. The study region is located along the Curonian Spit (Nida) and mainland coast (Būtingė). The ocean beach sites range from 25 to 35 m in width and are backed by 5-10 m-high foredunes. The Great Dune Ridge on the Curonian Spit consists of relict (mid-late Holocene) dunes which are the highest coastal dunes in Northern Europe (more than 60 m above sea level). The prevailing westerly winds attain speeds of 4.2 m/s in the summer and 5.5 m/s in autumn and winter. Along the southeast Baltic Sea coast, quartz and feldspars-rich sands contain variable amounts (1-8%) of heavy minerals, such as garnet, rutile, zircon, magnetite, ilmenite, hornblende, and other accessory minerals. On the beach, HMCs typically range in thickness from 0.1 to more than 3.0 cm and represent increased wave and run-up regime. Based on previous studies of coastal morphodynamics and field observations during 2005, 2006, 2008 and 2010 enriched horizons near the foot of the foredune are the result of storm reworking and subsequent aeolian deflation. Similar process concentrates almandine garnet and magnetite along the Curonian Lagoon shoreline, on the opposite side from the Nida beach site. Based on their occurrence in the Great Dune Ridge, we suggest that buried HMCs likely represent periods of increased wind activity (storminess). Due to their relatively high fraction of heavy minerals, HMCs have substantially higher magnetic susceptibility (MS) values than background quartz-rich sands and, where well developed, they can be used for spatial correlation of subsurface horizons. Therefore, the MS method was used as a tool for cataloguing the properties of HMCs in the field and in the laboratory. For documenting lithological differences between exposed heavy-mineral concentrations and background quartz-rich sands, this study focused on coastal environments with different sedimentary regimes: 1) surface profile and shallow trenches through the upper berm at Bating (wave run-up setting along the mainland shoreline); 2) a 40-m-long shore-normal beach profile at Nida on the Baltic Sea shoreline of the Curonian Spit, (mixed wave/aeolian conditions) and 3) a short surface profile along a lagoon beach at the base of the Paranidis Dune (the landward side of the spit). The 2008 and 2010 data were compared to previous studies of the HMCs in relict dunes (exclusively aeolian setting). The spatial and temporal distribution of HMCs in different sedimentary environments is a function of: 1) the initial heavy-mineral content prior to high-energy events and 2) hydro-meteorological and sedimentary conditions during the events responsible for removal of lighter minerals and HMC formation as a lag deposit. The thickness, degree of concentration, and rhythmicity of HMC horizons offer opportunities for quantifying the periodicity and intensity of hydrodynamic processes along sandy coasts. IS - SI 64 N1 - id: 2126 JO - Distribution and significance of heavy-mineral concentrations along the southeast Baltic Sea coast ER - TY - CONF T1 - Distribution of radiocarbon ages of soil organic matter by thermal fractionation Y1 - 2011 A1 - Plante, A. F. A1 - Beaupre, S. R. A1 - Fernandez, J. M. A1 - Roberts, M. A1 - Baisden, W. T. AB - Radiocarbon analysis has become an important tool in quantifying the dynamics of soil organic matter within the terrestrial carbon cycle (Trumbore 2009). Measuring radiocarbon concentrations in bulk soil samples provides only the mean age or residence time of the associated organic matter, but it is well recognized that representing soil organic matter as a single, homogeneous pool is inadequate. Significant effort has gone into separating soil organic matter into pools with different intrinsic turnover rates (i.e., radiocarbon concentrations), but the success of these separation methods has been mixed. Using thermal analysis techniques to characterize soil organic matter is rooted in the hypothesized link between the thermal and biogeochemical stability of the organic matter (Plante et al. 2011). Two grassland topsoil samples under contrasting land uses (native vegetation and long-term cultivation) were sampled in 2005 and submitted for radiocarbon analysis. Results of bulk (super 14) C showed a significant shift in radiocarbon age (94 to 79 pMC in the soil from Indian Head, Saskatchewan; 104 to 89 pMC in the soil from Akron, Colorado), attributable to the depletion of labile organic matter during long-term cultivation. Thermogravimetry and evolved gas analysis of these soil samples also showed distinct patterns in mass loss and CO (sub 2) release during thermal analysis, suggesting significant changes in organic matter composition. Four to five "fractions" associated with different CO (sub 2) -evolution regions have been identified and will be analyzed for radiocarbon via NOSAMS's established "dirt burner" method (Rosenheim et al. 2008), consisting of the recently developed discrete CO (sub 2) fraction collector interface between NOSAMS's dirt burner and microwave gas ion source (GIS) continuous flow AMS system (CFAMS). The research question is: Do the differing patterns in CO (sub 2) release during thermal analysis reflect organic matter of different ages Our working hypothesis is that thermally labile soil organic matter (combusting at low temperatures) will consist of younger carbon than thermally resistant organic matter. References: Plante, A. F., J. M. Fernandez, M. L. Haddix, and R. T. Conant. 2011. Biological, chemical and thermal indices of soil organic matter stability in four grassland soils. Soil Biol. Biochem. 43: 1051-1058. Rosenheim, B. E., M. B. Day, E. Domack, H. Schrum, A. Benthien, and J. M. Hayes. 2008. Antarctic sediment chronology by programmed-temperature pyrolysis: Methodology and data treatment. Geochemistry Geophysics Geosystems 9: 1-16. Trumbore, S. 2009. Radiocarbon and soil carbon dynamics. Annu Rev Earth Pl Sc 37: 47-66. PB - American Geophysical Union, Washington, DC, United States (USA) CY - United States (USA) VL - 2011 N1 - id: 2207; Source type: scholarlyjournals; Object type: Article; Object type: Conference Paper; Copyright: GeoRef in Process, Copyright 2012, American Geosciences Institute. After editing and indexing, this record will be added to Georef. Reference includes data supplied by, and/or abstract, Copyright, American Geophysical Union, Washington, DC, United States; CSAUnique: 638157-114; AccNum: 638157-114; CODEN: #07548 ER - TY - JOUR T1 - Drilling predation and taphonomy in modern mollusk death assemblages, San Salvador Island, Bahamas JF - Palaeogeography, Palaeoclimatology, Palaeoecology Y1 - 2011 A1 - Pruss, Sara B. A1 - Stevenson, Marquela A1 - Duffey, Siobhan AB - Studies of modern mollusk death assemblages provide an important framework for evaluating the fossil record. An analysis of 1951 shells from two beaches, Sandy Point and Haitian Boat Beach, on the isolated carbonate platform of San Salvador Island, Bahamas, has yielded significantly different frequencies of predation in bivalve-dominated assemblages. At Sandy Point Beach, bivalves and gastropods had a drilling frequency of 0.11 and 0.07, respectively. At Haitian Boat Beach, bivalves and gastropods showed a higher drilling frequency of 0.37 and 0.22, respectively. The prevalence of beveled drill holes suggests that the dominant predator was a naticid gastropod at both sites. Some ecological and environmental differences between the beaches could account for these disparate signals of predation: at Haitian Boat Beach, there is a higher abundance of the naticid Polinices sp. and it is a lower energy setting than Sandy Point Beach. Furthermore, radiocarbon dating of 17 shells at both beaches yielded a maximum age of > 6000 years before present, suggesting that these assemblages record a complex and long taphonomic history. These results imply that future large-scale coupling of predation studies with age dating of assemblages may provide important insights into the temporal structure of predation as well as the role of taphonomic loss of drilled shells. VL - 311 UR - http://www.sciencedirect.com/science/article/pii/S0031018211004287 IS - 1–2 N1 - id: 2166 JO - Drilling predation and taphonomy in modern mollusk death assemblages, San Salvador Island, Bahamas ER - TY - JOUR T1 - East–West similarities and differences in the surface and deep northern Arabian Sea records during the past 21 Kyr JF - Palaeogeography, Palaeoclimatology, Palaeoecology Y1 - 2011 A1 - Gupta, Anil K. A1 - Mohan, K. A1 - Sarkar, Sudipta A1 - Clemens, Steven C. A1 - Ravindra, Rasik A1 - Uttam, Rajesh K. AB - This study analyses monsoon proxy Globigerina bulloides from Ocean Drilling Program (ODP) Hole 723A (western Arabian Sea) and Hole ABP-25, 02 (northeastern Arabian Sea) as well as dominant benthic foraminifera, pteropods, total organic carbon (TOC), Inorganic Carbon (IC) and stable isotope values of benthic foraminifera from Hole ABP-25, 02 to understand summer monsoon-driven changes in the western and eastern Arabian Sea and their impacts on deep-sea ventilation during the past 21 Kyr. We have also combined published TOC data from ODP Hole 724B to understand if deep-sea conditions in the Arabian Sea were same throughout the region during the studied interval. The summer monsoon was generally weaker during cold intervals including the Last Glacial Maximum, the Younger Dryas and the Bond events of the Holocene. From 20 to 10 Kyr, the deep northeastern Arabian Sea was better oxygenated with less organic carbon supply except during 14–12.5 Kyr when TOC values increased, indicating a weaker summer monsoon and a weak oxygen minimum zone (OMZ). The TOC values and the abundance of the eutrophic benthic foraminiferal species Bulimina aculeata, Melonis barleeanum and Uvigerina peregrina increased during the late Holocene whereas well-oxygenated, low organic carbon benthic species Sphaeroidina bulloides as well as pteropods decreased, indicating an intense OMZ and an increased supply of refractory organic material to the Arabian Sea. It is important to note that although the surface response to monsoon variability was more or less similar in the western and northeastern Arabian Sea, the deep-sea conditions show a marked contrast in the two regions during the past 21 Kyr. VL - 301 UR - http://www.sciencedirect.com/science/article/pii/S0031018211000022 IS - 1-4 N1 - id: 2100 JO - East–West similarities and differences in the surface and deep northern Arabian Sea records during the past 21 Kyr ER - TY - JOUR T1 - Evidence of slumping/sliding in Krishna–Godavari offshore basin due to gas/fluid movements JF - Occurrence and exploration of gas hydrate in the marginal seas and continental margin of the Asia, India and Oceania region Occurrence and exploration of gas hydrate in the marginal seas and continental margin of the Asia, India and Oceania region Y1 - 2011 A1 - Ramprasad, T. A1 - Dewangan, P. A1 - Ramana, M. V. A1 - Mazumdar, A. A1 - Karisiddaiah, S. M. A1 - Ramya, E. R. A1 - Sriram, G. AB - The Krishna–Godavari (KG) offshore basin is one of the promising petroliferous basins of the eastern continental margin of India. Drilling in this basin proved the presence of gas hydrate deposits in the shallow marine sediments beyond 750 m water depths, and provided lithologic and stratigraphic information. We obtained multibeam swath bathymetry covering an area of about 4500 km2 in water depths of 280–1800 m and about 1260 line km of high resolution seismic (HRS) records. The general lithology of midslope deposits is comprised of nannofossil-rich clay, nannofossil-bearing clay and foraminifera-bearing clay. The HRS records and bathymetry reveal evidence of slumping and sliding of the upper and midslope sediments, which result in mass transport deposits (MTD) in the northwestern part of the study area. These deposits exhibit 3–9.5 km widths and extend 10–13 km offshore. The boundaries of the MTDs are often demarcated by sharp truncation of finely layered sediments (FLS) and the MTDs are characterized by acoustically transparent zones in the HRS data. Average thickness of recent MTDs varies with depth, i.e., in the upper slope, the thickness is about 45 m, while in the lower slope it is about 60 m, and in deeper offshore locations they attain a maximum thickness of about 90 m. A direct indication for slumping and mass transportation of deposits is provided by the age reversal in 14C AMS dates observed in a sediment core located in the midslope region. Seismic profiling signatures provide indications of fluid/gas movement. We propose that the presence of steep topographic gradients, high sedimentation rates, a regional fault system, diapirism, fluid/gas movement, and neotectonic activity may have facilitated the slumping/sliding of the upper slope sediments in the KG offshore basin. VL - 28 UR - http://www.sciencedirect.com/science/article/pii/S0264817211000729 IS - 10 N1 - id: 2163 JO - Evidence of slumping/sliding in Krishna–Godavari offshore basin due to gas/fluid movements ER - TY - JOUR T1 - Evolution of a Pharaonic harbor on the Red Sea: Implications for coastal response to changes in sea level and climate JF - GEOLOGY Y1 - 2011 A1 - Hein, Christopher J. A1 - FitzGerald, Duncan M. A1 - Milne, Glenn A. A1 - Bard, Kathryn A1 - Fattovich, Rodolfo AB - The evolution of coastal systems during the Holocene resulted from complex interactions and temporal shifts in the relative contribution of sea-level changes, climate change, and sedimentary processes. Along the Red Sea Coast, a 0.5-2 m highstand of sea level at 5 ka can be directly attributed to far-field effects resulting from the reduction in land ice following the last glacial maximum. At the ancient Egyptian harbor of Mersa/Wadi Gawasis, the site of the world's oldest archaeological evidence of long-distance seafaring, stratigraphic and geomorphologic evidence has been identified for this highstand. Here, wadi sediment input, enhanced by a period of wetter climate of the African Humid Period (early to mid-Holocene), forced the closure of coastal embayments, despite ongoing, relatively rapid sea-level rise. A stable, shallow bay persisted at Mersa/Wadi Gawasis as a result of coincidental aridization and a highstand of sea level during the mid-Holocene. This bay served as the primary harbor for ancient Egyptian trade along the Red Sea coast. During the late Holocene, shoreline progradation was dominated by sea-level fall, driven by isostatic processes. These results demonstrate the interplay of various global (sea level), regional (climate, sea level), and local (sedimentation, bathymetry) controls on the coastal evolution of the Red Sea and how these controls dictated the response of a complex civilization. Furthermore, they highlight the crucial role played by sedimentation in governing coastal response to changing sea levels. VL - 39 ER - TY - JOUR T1 - Fire history and human activities during the last 3300 cal yr BP in Spain's Central Pyrenees: The case of the Estany de Burg JF - Palaeogeography, Palaeoclimatology, Palaeoecology Y1 - 2011 A1 - Bal, Marie-Claude A1 - Pelachs, Albert A1 - Perez-Obiol, Ramon A1 - Julia, Ramon A1 - Cunill, Raquel AB - The study of macroscopic charcoal particles from peat bogs has led to a better understanding of climate, vegetation and fire history, and human impacts. To determine the relationship between human activities and the role of fire events in vegetation change during the last 3300 cal yr BP, we present the results of a multi-proxy approach based on the analysis of sediment characteristics, sedimentary charcoal, organic matter and pollen, as well as historical sources. This multi-proxy research permits high resolution palaeoenvironmental and fire history reconstruction of a mountain area located in the southern central Pyrenees (Spain). In the Pyrenees, fire is typically attributed to human activities since the beginning of the Bronze Age and may be correlated with slash-and-burn cultivation, metallurgy and pasturing activities. The data indicate a good linkage between high fire signals and Poaceae and Cerealia pollen, which reveals the impact of agro-pastoral practices. This study also shows two periods, 2900–2650 cal yr BP and 1850–1550 cal yr BP, for which higher frequencies of fire occurred, suggested by high arboreal pollen (AP) concentrations, and confirming the need for arboreal biomass to sustain fires. From the beginning of the Middle Ages, it seems that a change occurred in the anthropogenic use of fire, from a tool for agro-pastoral forest clearance to a means of maintaining open spaces. VL - 300 UR - http://www.sciencedirect.com/science/article/pii/S0031018210007480 IS - 1–4 N1 - id: 2196 JO - Fire history and human activities during the last 3300 cal yr BP in Spain's Central Pyrenees: The case of the Estany de Burg ER - TY - JOUR T1 - Geological legacy of storm erosion along a high-energy indented coastline: northern Santa Catarina, Brazil JF - Journal of Coastal Research Y1 - 2011 A1 - Buynevich, I. V. A1 - Klein, A. H. F. A1 - FitzGerald, D. M. A1 - Cleary, W. J. A1 - Hein, C. A1 - Veiga, F. A. A1 - Angulo, R. J. A1 - Asp, N. E. A1 - Petermann, R. AB - Along moderate to high-energy sandy coasts of the world, periods of accretion are often punctuated by episodes of erosion and retreat. However documenting the legacy of such events in sand-dominated sequences remains a challenge. The present-day moderate-relief coastlines of Camboriú Peninsula (CP) and the adjacent Navegantes coastal plain in Santa Catarina, Brazil, exhibit a variety of geological features related to recent intense storms, such as the Santa Catarina cyclone of record (March 2004) and subsequent events. These systems offer an opportunity to assess the use of modern indicators of storm erosion as a guide to reconstructing their counterparts from the sedimentary record. The 0.5-2.0-km-long, headland-segmented, coarse-grained, reflective beaches of the Camboriú Peninsula contrast with a 10-km-long, fine-grained, dissipative beach of the Navegantes plain. Morphological indicators of erosion include steep dune and berm scarps, as well as ephemeral washout channels produced by rainfall-induced runoff. Where modified by subsequent deposition, these features can still be identified by their diagnostic reflection geometries and variable-angle truncations (disconformities) in highresolution ground-penetrating radar (GPR) images. In addition to morphological indicators of erosion, coastal sedimentary sequences contain distinct lithological anomalies. Heavy-mineral concentrations (HMCs) are easily identifiable in sediment cores and trenches and produce strong reflections on GPR images. Along Estaleiro Beach (CP), a buried disconformity was identified in GPR images beneath a road, approximately 25 m landward of the November 2004 storm scarp. Its geometry is similar to the recent scarp and its strong geophysical signal return is due to a magnetite-enriched horizon at a depth of 2.6 m. At the Navegantes strandplain, patchy thin layers enriched in fine-grained heavy minerals are common on a gently sloping intertidal beach and near the base of foredunes. Moreover, in the landward portion of the plain that developed during the past 2,000 years, the presence of truncated tangential-oblique reflections in GPR records and HMCs reaching 10-30 cm in thickness indicates past reworking of beach and dune sediments by a series of intense erosional episodes. Low-field magnetic susceptibility measurements of vibracores indicate values from thick HMC layers exceeding 1,000 (*10-5 SI) in contrast to 0−15 (*10-5 SI) for background quartz-rich sands. Given the relatively constant background fraction of heavy minerals in beach sands, the thickness and degree of concentration in HMCs can be used as proxies for the relative impact of high-energy events, including their duration and magnitude. Despite the apparent low preservation potential of these features on high-energy coasts, post-storm accretion and rapid progradation increase their chances of being removed from wave action. IS - SI 64 N1 - id: 2125 JO - Geological legacy of storm erosion along a high-energy indented coastline: northern Santa Catarina, Brazil ER - TY - JOUR T1 - Geological slip rates along the North Anatolian Fault in the Marmara region JF - Tectonics Y1 - 2011 A1 - Gasperini, Luca A1 - Polonia, Alina A1 - Çağatay, M. Namik A1 - Bortoluzzi, Giovanni A1 - Ferrante, Valentina AB - Reliable piercing points on both sides of the Sea of Marmara enabled us to obtain an estimate of the slip-rate over time scales of 10-15 ka on different fault strands of the North Anatolian Fault (NAF) system. We analyzed geomorphic features in the gulfs of Izmit, Gemlik (Sea of Marmara) and Saros (NE Aegean Sea), which were passively displaced by the NAF strands after their abandonment related to the post-glacial sea level rise. Results for the main northern strand, consistently similar on both sides of the Marmara pull-apart, are in the order of 10 mm/yr, about one half of that expected from geodetic measurements and accepted plate-tectonic models. In the southern branch of the NAF, the estimated rate of similar to 4 mm/yr is only slightly higher than that given by geodetic models. Our findings have implications for both neo-tectonic reconstructions of the submerged portion of the NAF system, and fault interactions and seismic hazard estimates in the Marmara region. They suggest that, either the total Anatolia/Eurasia plate motion is more diffuse than previously reported, or geodetic data are not representative of the geological time-scale deformations. Moreover, they suggest that a significant amount of stress is accommodated along the southern strand of the NAF system, on which the last large (M approximate to 7) earthquakes dates back to 1419, 1855 and 1863 AD. VL - 30 N1 - id: 2112; PT: J; TC: 0; J9: TECTONICS; UT: WOS:000296619700001 JO - Geological slip rates along the North Anatolian Fault in the Marmara region ER - TY - BOOK T1 - Geological Society of America Special PapersGeology and Geoarchaeology of the Black Sea Region: Beyond the Flood HypothesisPontic-Baltic pathways for invasive aquatic species: Geoarchaeological implications Y1 - 2011 A1 - Buynevich, Ilya V. A1 - šytė, Aldona A1 - Bitinas, Albertas A1 - Olenin, Sergej A1 - žeika, Jonas A1 - šius, Rimantas AB - An accurate chronology for the exchange of aquatic species between water basins is important for paleoenvironmental reconstruction on both regional and continental scales. During the early Holocene, the range of zebra mussels, Dreissena polymorpha, was limited to the Black, Azov, Caspian, and Aral Seas, as well as the estuaries and lower and middle reaches of the Pontic-Caspian rivers. We present new fi ndings that challenge the currently held view that this species migrated into the Baltic Sea watershed during the early 1800s through the canals joining the tributaries of rivers that drain into the Black and Baltic Sea basins. Geological investigations along the southeast Baltic Sea coast (Curonian and Vistula spits and lagoons) have uncovered shells of D. polymorpha that yielded radiocarbon ages older than 1000 radiocarbon yr B.P. We propose two scenarios to explain the new radiocarbon dates for D. polymorpha. The fi rst scenario involves an anomalously large reservoir effect—as large as 600– 800 yr—however, several lines of evidence cast doubt upon the validity of such a large reservoir correction. The second scenario that might explain the old zebra mussel ages is the earlier arrival of Dreissena polymorpha into the Baltic region. Natural exchange may have been facilitated by the proximity of the tributaries draining thePontic and Baltic watersheds. Human-mediated transport is also considered in association with Viking voyages from the Baltic to the Black and Caspian Seas between A.D. 800 and 1000, and the riverine trade exchange during the Lithuanian expansion into the Pontic steppe in subsequent centuries. It is likely that both scenarios played a role, with implications for late Holocene biogeography and paleoecology of the Pontic-Caspian and Baltic basins. Pontic-Baltic pathways for invasive aquatic species: Geoarchaeological implications (PDF Download Available). Available from: https://www.researchgate.net/publication/256375044_Pontic-Baltic_pathways_for_invasive_aquatic_species_Geoarchaeological_implications [accessed May 25, 2017]. PB - Geological Society of America VL - 473 UR - http://specialpapers.gsapubs.org//content/473http://specialpapers.gsapubs.org/lookup/doi/10.1130/2011.2473(12) ER - TY - BOOK T1 - Geology and Geoarchaeology of the Black Sea Region: Beyond the Flood Hypothesis T2 - Special papers (Geological Society of America) Y1 - 2011 A1 - Buynevich, I. V. A1 - Yanko-Hombach, V. V. A1 - Gilbert, A. S. A1 - and Martin, R. E. JF - Special papers (Geological Society of America) PB - Geological Society of America VL - 473 SN - 9780813724737 N1 - id: 2127 ER - TY - JOUR T1 - Glacial to Holocene swings of the Australian-Indonesian monsoon JF - Nature Geoscience Y1 - 2011 A1 - Mohtadi, Mahyar A1 - Oppo, Delia W. A1 - Steinke, Stephan A1 - Stuut, Jan-Berend W. A1 - De Pol-Holz, Ricardo A1 - Hebbeln, Dierk A1 - Lueckge, Andreas AB - The Australian-Indonesian monsoon is an important component of the climate system in the tropical Indo-Pacific region(1). However, its past variability, relation with northern and southern high-latitude climate and connection to the other Asian monsoon systems are poorly understood. Here we present high-resolution records of monsoon-controlled austral winter upwelling during the past 22,000 years, based on planktic foraminiferal oxygen isotopes and faunal composition in a sedimentary archive collected offshore southern Java. We show that glacial-interglacial variations in the Australian-Indonesian winter monsoon were in phase with the Indian summer monsoon system, consistent with their modern linkage through cross-equatorial surface winds. Likewise, millennial-scale variability of upwelling shares similar sign and timing with upwelling variability in the Arabian Sea. On the basis of element composition and grain-size distribution as precipitation-sensitive proxies in the same archive, we infer that (austral) summer monsoon rainfall was highest during the Bolling-Allerod period and the past 2,500 years. Our results indicate drier conditions during Heinrich Stadial 1 due to a southward shift of summer rainfall and a relatively weak Hadley cell south of the Equator. We suggest that the Australian-Indonesian summer and winter monsoon variability were closely linked to summer insolation and abrupt climate changes in the northern hemisphere. VL - 4 IS - 8 N1 - id: 2012; PT: J; UT: WOS:000293277100016 JO - Glacial to Holocene swings of the Australian-Indonesian monsoon ER - TY - JOUR T1 - Gualas Glacier sedimentary record of climate and environmental change, Golfo Elefantes, Western Patagonia (46.5°S) JF - The Holocene Y1 - 2011 A1 - Fernandez, Rodrigo A1 - Anderson, John A1 - Bertrand, Sébastien A1 - Wellner, Julia AB - Gualas Glacier is an outlet glacier of the Northern Patagonian Icefield, one of the largest temperate ice bodies on Earth. Golfo Elefantes, the depositional basin of Gualas Glacier, has a sedimentary record that spans, with some hiatuses, at least the last ~11.3±3.0 ka. During this period the gulf remained free of ice, as suggested by the absence of proximal glacimarine sediment and till in the sedimentary section. This implies that the arcuate terminal moraines that occur along the edges of Golfo Elefantes were formed during the waning stages of the local glacial maxima (Late Pleistocene) or the early Holocene. Between ~11.3±3.0 ka and ~4.2±0.3–1.4 ka, the basin received low sediment input consisting of fine-grained sediments in the form of low concentration density currents that filled bathymetric lows. Sediment discharge increased several times in the late Holocene (~ UR - http://hol.sagepub.com/content/early/2011/11/22/0959683611425545.abstract N1 - id: 2118 JO - Gualas Glacier sedimentary record of climate and environmental change, Golfo Elefantes, Western Patagonia (46.5°S) ER - TY - JOUR T1 - Gulf of Maine shells reveal changes in seawater temperature seasonality during the Medieval Climate Anomaly and the Little Ice Age JF - Reconstructing mid- to high-latitude marine climate and ocean variability using bivalves, coralline algae, and marine sediment cores from the Northern Hemisphere Y1 - 2011 A1 - Wanamaker Jr, Alan D. A1 - Kreutz, Karl J. A1 - Schöne, Bernd R. A1 - Introne, Douglas S. AB - In this study, we use subannually resolved oxygen isotope values of fossil (dead-collected) and modern (live-caught) bivalve shells (Arctica islandica L.) from the northwestern Atlantic (Gulf of Maine, USA) to reconstruct past seasonal changes in seawater temperature. Our results indicate decreased seasonal temperature amplitude of about 1.6 °C (or ∼ 21%) during Medieval times (ca. AD 1033–1062) compared to shells from the early Little Ice Age (ca. AD 1321–1391) and during the late 19th century (AD 1864–1886). Additionally, seasonal oxygen isotope data suggest that summers were cooler and winters were warmer in the Gulf of Maine during the 11th century compared to summers and winters in the 14th century and the late 19th century. The inferred decreased seasonality during Medieval times likely resulted from increased stratification of the coastal waters due to warmer seawater temperatures. As seawater cooled during the Little Ice Age, we suggest that increased vertical mixing of the coastal surface waters was a major driving factor for the observed increase in the amplitude of the seasonal seawater temperature cycle. VL - 302 UR - http://www.sciencedirect.com/science/article/pii/S0031018210003378 IS - 1–2 N1 - id: 2193 JO - Gulf of Maine shells reveal changes in seawater temperature seasonality during the Medieval Climate Anomaly and the Little Ice Age ER - TY - JOUR T1 - Holocene sea-level change and the emergence of Neolithic seafaring in the Fuzhou Basin (Fujian, China) JF - Quaternary Science Reviews Y1 - 2011 A1 - Rolett, Barry V. A1 - Zheng, Zhuo A1 - Yue, Yuanfu AB - Neolithic seafaring across the Taiwan Strait began approximately 5000 years ago and involved open-sea voyages over distances of at least 130 km. Rapid sea-level rise preceded the emergence of open-sea voyaging, but the possible role of environmental change as a stimulus for the development of seafaring is poorly understood. We investigate this problem by presenting a record of Holocene sea-level change and coastal transformation based on sediment cores obtained from the Fuzhou Basin on the coast of Fujian, China. The cores are located in direct proximity to archaeological sites of the Tanshishan Neolithic culture (5000–4300 cal BP), which is significant for its similarity to the earliest Neolithic cultures of Taiwan. Multiple lines of evidence record the early Holocene inundation of the Fuzhou Basin around 9000 cal BP, the mid-Holocene sea-level highstand, and the final Holocene marine transgression. This final transition is precisely documented, with AMS dates showing the change occurred close to 1900 cal BP. Our paleogeographic reconstruction shows that a large estuary filled the Fuzhou Basin during the mid-Holocene. Tanshishan and Zhuangbianshan, two of the major Fuzhou Basin Neolithic sites, are located today on hills nearly 80 km from the modern coastline. However, when the sites were settled around 5500–5000 cal BP, the marine transgression had transformed these hills into islands in the upper estuary. We suggest that the Neolithic era estuary setting, together with the lack of land suitable for rice paddy agriculture, inhibited intensive food production but favored a maritime orientation and the development of seafaring. VL - 30 UR - http://www.sciencedirect.com/science/article/pii/S0277379111000308 IS - 7–8 N1 - id: 2189 JO - Holocene sea-level change and the emergence of Neolithic seafaring in the Fuzhou Basin (Fujian, China) ER - TY - JOUR T1 - Holocene Southern Ocean surface temperature variability west of the Antarctic Peninsula JF - Nature Y1 - 2011 A1 - Shevenell, A. E. A1 - Ingalls, A. E. A1 - Domack, E. W. A1 - Kelly, C. AB - The disintegration of ice shelves, reduced sea-ice and glacier extent, and shifting ecological zones observed around Antarctica(1,2) highlight the impact of recent atmospheric(3) and oceanic warming(4) on the cryosphere. Observations(1,2) and models(5,6) suggest that oceanic and atmospheric temperature variations at Antarctica's margins affect global cryosphere stability, ocean circulation, sea levels and carbon cycling. In particular, recent climate changes on the Antarctic Peninsula have been dramatic, yet the Holocene climate variability of this region is largely unknown, limiting our ability to evaluate ongoing changes within the context of historical variability and underlying forcing mechanisms. Here we show that surface ocean temperatures at the continental margin of the western Antarctic Peninsula cooled by 3-4 degrees C over the past 12,000 years, tracking the Holocene decline of local (65 degrees S) spring insolation. Our results, based on TEX(86) sea surface temperature (SST) proxy evidence from a marine sediment core, indicate the importance of regional summer duration as a driver of Antarctic seasonal sea-ice fluctuations(7). On millennial timescales, abrupt SST fluctuations of 2-4 degrees C coincide with globally recognized climate variability(8). Similarities between our SSTs, Southern Hemisphere westerly wind reconstructions(9) and El Nino/Southern Oscillation variability(10) indicate that present climate teleconnections between the tropical Pacific Ocean and the western Antarctic Peninsula(11) strengthened late in the Holocene epoch. We conclude that during the Holocene, Southern Ocean temperatures at the western Antarctic Peninsula margin were tied to changes in the position of the westerlies, which have a critical role in global carbon cycling(9,12). VL - 470 IS - 7333 N1 - id: 2053; PT: J; UT: WOS:000287144200042 JO - Holocene Southern Ocean surface temperature variability west of the Antarctic Peninsula ER - TY - JOUR T1 - Interpreting, dating, and reevaluating the botanical assemblage from tell Kedesh: a case study of historical contamination JF - Journal of Archaeological Science Y1 - 2011 A1 - Ksenija, Borojevic AB - Botanical assemblage including charred and mineralized macro plant remains were examined from tell Kedesh in the Upper Galilee, Israel. Flotation samples were collected from various contexts within and outside a large Persian-Hellenistic administrative building complex at tell Kedesh, dated to the 5th to the 2nd century BC, based on the archaeological material. Four AMS radiocarbon dates were obtained on plant macro remains recovered from the flotation samples from the complex. The radiocarbon dates range from the 9th century BC to 17th century AD. The discrepancy among the radiocarbon dates obtained from plant remains and those based on archaeological material can be attributed to bioturbation, including the deep burrowing of harvester ants. The study demonstrates the need for direct radiocarbon dating of the charred plant remains generally assumed to be of ancient origin. This research improves the understanding of depositional and postdepositional processes of plant macro remains and explains their mode of arrival, relevant for the sites with a long occupational history by humans and animals. VL - 38 UR - http://www.sciencedirect.com/science/article/pii/S0305440310004048 IS - 4 N1 - id: 2188 JO - Interpreting, dating, and reevaluating the botanical assemblage from tell Kedesh: a case study of historical contamination ER - TY - JOUR T1 - Late glacial to Holocene sea-level changes in the Sea of Marmara: new evidence from high-resolution seismics and core studies JF - Geo-Marine Letters Y1 - 2011 A1 - Eriş, Kürşad Kadir A1 - Cagatay, M. N. A1 - Akcer, Sena A1 - Gasperini, Luca A1 - Mart, Yosi AB - The late glacial to Holocene sedimentary record of the northern shelf of the Sea of Marmara (SoM) has been documented by detailed seismo-, chrono-, and biostratigraphic analyses using sub-bottom (Chirp) profiles and sediment cores. During MIS 3 and the main part of MIS 2 (60-15 (14)C ka b.p.), disconnection from the Mediterranean and Black seas together with a dry climate resulted in a regression in the SoM, when the Sea was transformed into a brackish lake. The river incisions below 105 m water depth along the northern shelf took place during the last glacial maximum, when the lake level was modulated by stillstands at -98 and -93 m. The post-glacial freshwater transgressive stage of the Marmara 'Lake' occurred between 15 and 13.5 (14)C ka b.p., leading to a rise in water level to -85 m by 13.0 (14)C ka b.p., as evidenced by broad wave-cut terraces along the northern shelf. Since 12 (14)C ka b.p., high-frequency sea-level fluctuations have been identified at the SoM entrance to the Strait of A degrees stanbul (SoI). Thus, wave-cut terraces have been recorded at water depths of -76 and -71 m that, according to an age model for core MD04-2750, have ages of 11.5 and 10.5 (14)C ka b.p., respectively. Ancient shoreline at -65 m along the northern shelf presumably formed soon after the Younger Dryas (YD) at ca. 10.1 (14)C ka b.p. Moreover, there is compelling evidence of Holocene outflow from the Sea of Marmara to the Black Sea. At the SoM entrance to the SoI, the existence of bioherms on the reflector surface together with abundant Brizalina spathulata and Protoglobulimina pupoides in a core suggests a return to higher salinities due to strong Mediterranean water incursion into the SoM at similar to 8.8 (14)C ka b.p. This finding is consistent with earlier suggestions that, after the YD, the Black Sea was flooded by outflow from the SoM as a result of global sea-level rise. VL - 31 IS - 1 N1 - id: 2113; PT: J; TC: 0; J9: GEO-MAR LETT; UT: WOS:000286334700001 JO - Late glacial to Holocene sea-level changes in the Sea of Marmara: new evidence from high-resolution seismics and core studies ER - TY - JOUR T1 - Late Holocene environmental conditions in Coronation Gulf, southwestern Canadian Arctic Archipelago: evidence from dinoflagellate cysts, other non-pollen palynomorphs, and pollen JF - Journal of Quaternary Science Y1 - 2011 A1 - Pieńkowski, A. J. A1 - Mudie, Peta J. A1 - England, John H. A1 - Smith, John N. A1 - Furze, Mark F. A. AB - Boxcore 99LSSL-001 (68.095°?N, 114.186° W; 211?m water depth) from Coronation Gulf represents the first decadal-scale marine palynology and late Holocene sediment record for the southwestern part of the Northwest Passage. The record was studied for organic-walled microfossils (dinoflagellate cysts, non-pollen palynomorphs), pollen, terrestrial spores, and sediment characteristics. 210Pb, 137Cs, and three accelerator mass spectrometry 14C dates constrain the chronology. Three prominent palaeoenvironmental zones were identified. During the interval AD 1470?1680 (Zone I), the climate was warmer and wetter than at present, and environmental conditions were more favourable to biological activity and northward boreal forest migration, with reduced sea-ice and a longer open-water (growing) season. The interval AD 1680?1940 (Zone II) records sea-ice increase, and generally cool, polar conditions during the Little Ice Age. During AD 1940?2000 (Zone III), organic microfossils indicate an extended open-water season and decreased sea-ice, with suggested amelioration surpassing that of Zone I. Although more marine studies are needed to place this record into an appropriate context, the succession from ameliorated (Zone I) to cooler, sea-ice influenced conditions (Zone II) and finally to 20th-century warming (Zone III) corresponds well with several terrestrial climatic records from the neighbouring mainland and Victoria Island, and with lower-resolution marine records to the west. Copyright © 2011 John Wiley & Sons, Ltd. VL - 26 UR - http://dx.doi.org/10.1002/jqs.1503 IS - 8 N1 - id: 2344 JO - Late Holocene environmental conditions in Coronation Gulf, southwestern Canadian Arctic Archipelago: evidence from dinoflagellate cysts, other non-pollen palynomorphs, and pollen ER - TY - JOUR T1 - Late Pleistocene paleoecology of arctic ground squirrel (Urocitellus parryii) caches and nests from Interior Alaska's mammoth steppe ecosystem, USA JF - Quaternary Research Y1 - 2011 A1 - Gaglioti, Benjamin V. A1 - Barnes, Brian M. A1 - Zazula, Grant D. A1 - Beaudoin, Alwynne B. A1 - Wooller, Matthew J. AB - Botanical analyses of fossil and modern arctic ground squirrel (Urocitellus parryii) caches and nests have been used to reconstruct the past vegetation from some parts of Beringia, but such archives are understudied in Alaska. Five modern and four fossil samples from arctic ground squirrel caches and nests provide information on late Pleistocene vegetation in Eastern Beringia. Modern arctic ground squirrel caches from Alaska's arctic tundra were dominated by willow and grass leaves and grass seeds and bearberries, which were widespread in the local vegetation as confirmed by vegetation surveys. Late Pleistocene caches from Interior Alaska were primarily composed of steppe and dry tundra graminoid and herb seeds. Graminoid cuticle analysis of fossil leaves identified Calamagrostis canadensis, Koeleria sp. and Carex albonigra as being common in the fossil samples. Stable carbon isotopes analysis of these graminoid specimens indicated that plants using the C(3) photosynthetic pathways were present and functioning with medium to high water-use efficiency. Fossil plant taxa and environments from ground squirrel caches in Alaska are similar to other macrofossil assemblages from the Yukon Territory, which supports the existence of a widespread mammoth steppe ecosystem type in Eastern Beringia that persisted throughout much of the late Pleistocene. (C) Published by Elsevier Inc. on behalf of University of Washington. VL - 76 IS - 3 N1 - id: 2130; PT: J; TC: 0; UT: WOS:000296672100009 JO - Late Pleistocene paleoecology of arctic ground squirrel (Urocitellus parryii) caches and nests from Interior Alaska's mammoth steppe ecosystem, USA ER - TY - JOUR T1 - Late Quaternary environmental change inferred from phytoliths and other soil-related proxies: Case studies from the central and southern Great Plains, USA JF - Catena Y1 - 2011 A1 - Cordova, Carlos E. A1 - Johnson, William C. A1 - Mandel, Rolfe D. A1 - Palmer, Michael W. AB - This study investigates stable carbon isotopes (delta(13)C), opal phytolith assemblages, burnt phytoliths, microscopic charcoal and Sporormiella spores from modern soils and paleosols in Kansas and Oklahoma. Grass and dicot phytoliths in combination with delta(13)C are used as proxies for reconstructing the structure of grasslands and woodlands. Burnt grass phytoliths and microscopic charcoal are evaluated as proxies for reconstructing paleofire incidence. Concentrations of the fungal spore Sporormiella are used as a proxy for assessing large herbivore activity. These proxies were tested on various modern grassland communities of the central and southern Great Plains, including areas with bison, cattle, and small herbivores, and areas under different fire frequencies. Opal phytolith assemblages and delta(13)C values show that before cal 11 ka, C(3) grasses and woody plants predominated in areas that today are dominated by C(4) grasses. The origin of the shortgrass prairie dates back to about cal 10 ka. The origin of the tallgrass prairie, however, is not clear as phytolith data show variable assemblages throughout the Holocene (mixed-grass, tallgrass, and tallgrass-woodland mosaic). Different proxies (burnt phytoliths vs. charcoal) reveal different fire frequencies, but it is apparent that microfossil evidence for fire incidence is closely related to the abundance of woody plants in the landscape. Before cal 12 ka, soils show somewhat elevated concentration of Spororrniella, but lower concentrations than the modern high-density bison and cattle grazing areas. Throughout the Holocene. Sporormiella frequencies are low, which suggests lower large ungulate densities and perhaps high mobility. (C) 2010 Elsevier B.V. All rights reserved. VL - 85 IS - 2 N1 - id: 1992; PT: J; SI: SI; UT: WOS:000288642200002 JO - Late Quaternary environmental change inferred from phytoliths and other soil-related proxies: Case studies from the central and southern Great Plains, USA ER - TY - JOUR T1 - The marine record of deglaciation of the South Shetland Islands, Antarctica since the Last Glacial Maximum JF - Quaternary Science Reviews Y1 - 2011 A1 - Simms, Alexander R. A1 - Milliken, Kristy T. A1 - Anderson, John B. A1 - Wellner, Julia S. AB - The marine geological record of the glacial-retreat history of the South Shetland Islands is derived from the integration of seismic data, core lithofacies, radiocarbon ages and geomorphological data from two study areas. On the northern shelf, we present one of the first published multibeam bathymetric images of the seafloor. This new image combined with descriptions of new and existing short sediment cores and high-resolution seismic data from the continental shelf north of King George Island are used to map a grounding zone wedge that marks the minimum seaward extent of the South Shetland Ice Cap during the Last Glacial Maximum. Seismic data, multibeam bathymetry, and sediment cores from Maxwell Bay, on the opposite side of King George Island, are used to provide further spatial constrains on the history of grounding and retreat of the ice cap along the southern margin of the South Shetland Islands. During the Last Glacial Maximum the South Shetland Ice Cap extended onto the outer continental shelf, some 50 km north of its present location. The ice grounded on the shelf in troughs in present water depths of almost 400 m. It had a minimum thickness of ∼570 m and was also grounded in the deepest part of fjords and straits between the islands. To the south, the ice cap extended seaward of the mouths of fjords and straits to the steep northern boundary of the Bransfield Strait. Sediment eroded from the fjords and straits was deposited in prominent fans that extend into the Bransfield Strait and show evidence for an ice shelf that covered the Bransfield Strait during the Last Glacial Maximum. A long drill core (SHALDRIL) in Maxwell Bay and several jumbo piston cores yielded carbonate material used to constrain the timing and spatial extent of glacial retreat within Maxwell Bay. The oldest glacimarine sediments in the fjord date back to ∼14.1 to ∼14.8 ka and suggest an initial deglaciation earlier than most previous studies of the South Shetland Islands. Upper Maxwell Bay was ice free by 9.1 ka and most of Maxwell Bay proper was ice free by 5.9 ka except for the smaller tributary fjords of Maxwell Bay. These smaller tributary fjords were ice free by 1.7 ka, but may have been ice free earlier but reoccupied by a neoglacial advance that ended approximately 1.7 ka. VL - 30 UR - http://www.sciencedirect.com/science/article/pii/S0277379111000904 IS - 13–14 N1 - id: 2181 JO - The marine record of deglaciation of the South Shetland Islands, Antarctica since the Last Glacial Maximum ER - TY - JOUR T1 - Methane hydrate-bearing seeps as a source of aged dissolved organic carbon to the oceans JF - Nature Geoscience Y1 - 2011 A1 - Pohlman, John W. A1 - Bauer, James E. A1 - Waite, William F. A1 - Osburn, Christopher L. A1 - Chapman, N. Ross AB - Marine sediments contain about 500-10,000 Gt of methane carbon(1-3), primarily in gas hydrate. This reservoir is comparable in size to the amount of organic carbon in land biota, terrestrial soils, the atmosphere and sea water combined(1,4), but it releases relatively little methane to the ocean and atmosphere(5). Sedimentary microbes convert most of the dissolved methane to carbon dioxide(6,7). Here we show that a significant additional product associated with microbial methane consumption is methane-derived dissolved organic carbon. We use Delta(14)C and delta(13)C measurements and isotopic mass-balance calculations to evaluate the contribution of methane-derived carbon to seawater dissolved organic carbon overlying gas hydrate-bearing seeps in the northeastern Pacific Ocean. We show that carbon derived from fossil methane accounts for up to 28% of the dissolved organic carbon. This methane-derived material is much older, and more depleted in (13)C, than background dissolved organic carbon. We suggest that fossil methane-derived carbon may contribute significantly to the estimated 4,000-6,000 year age of dissolved organic carbon in the deep ocean(8), and provide reduced organic matter and energy to deep-ocean microbial communities. VL - 4 IS - 1 N1 - id: 2030; PT: J; UT: WOS:000285498600015 JO - Methane hydrate-bearing seeps as a source of aged dissolved organic carbon to the oceans ER - TY - JOUR T1 - Micropaleontologic record of Quaternary paleoenvironments in the Central Albemarle Embayment, North Carolina, U.S.A JF - Palaeogeography, Palaeoclimatology, Palaeoecology Y1 - 2011 A1 - Culver, Stephen J. A1 - Farrell, Kathleen M. A1 - Mallinson, David J. A1 - Willard, Debra A. A1 - Horton, Benjamin P. A1 - Riggs, Stanley R. A1 - Thieler, E. Robert A1 - Wehmiller, John F. A1 - Parham, Peter A1 - Snyder, Scott W. A1 - Hillier, Caroline AB - To understand the temporal and spatial variation of eustatic sea-level fluctuations, glacio–hydro–isostacy, tectonics, subsidence, geologic environments and sedimentation patterns for the Quaternary of a passive continental margin, a nearly complete stratigraphic record that is fully integrated with a three dimensional chronostratigraphic framework, and paleoenvironmental information are necessary. The Albemarle Embayment, a Cenozoic regional depositional basin in eastern North Carolina located on the southeast Atlantic coast of the USA, is an ideal setting to unravel these dynamic, interrelated processes. Micropaleontological data, coupled with sedimentologic, chronostratigraphic and seismic data provide the bases for detailed interpretations of paleoenvironmental evolution and paleoclimates in the 90 m thick Quaternary record of the Albemarle Embayment. The data presented here come from a transect of cores drilled through a barrier island complex in the central Albemarle Embayment. This area sits in a ramp-like setting between late Pleistocene incised valleys. The data document the episodic infilling of the Albemarle Embayment throughout the Quaternary as a series of transgressive–regressive (T–R) cycles, characterized by inner shelf, midshelf, and shoreface assemblages, that overlie remnants of fluvial to estuarine valley-fill. Barrier island and marginal marine deposits have a low preservation potential. Inner to mid-shelf deposits of the early Pleistocene are overlain by similar middle Pleistocene shelf sediments in the south of the study area but entirely by inner shelf deposits in the north. Late Pleistocene marine sediments are of inner shelf origin and Holocene deposits are marginal marine in nature. Pleistocene marine sediments are incised, particularly in the northern half of the embayment by lowstand paleovalleys, partly filled by fluvial/floodplain deposits and in some cases, overlain by remnants of transgressive estuarine sediments. The shallowing through time of Quaternary sediments reflects the eastward progradational geometry of the continental shelf. The preservation potential of marginal marine deposits (barrier island, shoreface, backbarrier deposits) is not high, except in topographic lows associated with late Pleistocene paleovalleys and inlets because the current interglacial highstand has not yet reached its highest level. Given the documented increase in rate of relative sea-level rise in this region, shallow marine conditions are likely to return to the central Albemarle Embayment in the near future. VL - 305 UR - http://www.sciencedirect.com/science/article/pii/S0031018211001143 IS - 1–4 N1 - id: 2182 JO - Micropaleontologic record of Quaternary paleoenvironments in the Central Albemarle Embayment, North Carolina, U.S.A ER - TY - JOUR T1 - Multiple-source heterotrophy fueled by aged organic carbon in an urbanized estuary JF - MARINE CHEMISTRY Y1 - 2011 A1 - Griffith, David R. A1 - Raymond, Peter A. KW - (13)C KW - (14)C KW - Carbon cycle KW - Carbon dioxide KW - Chlorophyll KW - dissolved organic carbon KW - Heterotrophy KW - Hudson River Estuary KW - Isotope mixing curves KW - Sewage KW - USA KW - Wastewater AB - The lower Hudson River is a highly urbanized estuary that receives large inputs of treated wastewater. To determine how organic matter from wastewater influences carbon cycling in this type of system, we measured chlorophyll a, pCO(2). dissolved organic carbon (DOC), delta(13)C-DOC, and Delta(14)C-DOC along the salinity gradient and at wastewater treatment plants. Isotopic mixing curves indicate a net removal of DOC that is (13)C enriched and (14)C depleted. The amount of DOC removed was consistent with CO(2) evasion from the estuary. During two transects at average to low flow, the lower Hudson River Estuary was a heterotrophic system with CO(2) evasion balanced by the utilization of aged DOC derived from wastewater and marine phytoplankton that enter the estuary at the seaward end-member. DOC removals were largest during a period of high river flow, when isotopic mixing curves also suggest large contributions from labile terrestrial OC sources. Overall, our results suggest that net heterotrophy in the lower Hudson River Estuary is fueled by aged labile DOC derived from a combination of sources, which are influenced by seasonal phytoplankton blooms, hydrological conditions, and the nature of wastewater inputs. (C) 2010 Elsevier B.V. All rights reserved. VL - 124 ER - TY - JOUR T1 - Paleoecology of mangroves along the Sibun River, Belize JF - Quaternary Research Y1 - 2011 A1 - Monacci, Natalie M. A1 - Meier-Grünhagen, Ursula A1 - Finney, Bruce P. A1 - Behling, Hermann A1 - Wooller, Matthew J. AB - This study examines a sediment core (SR-63) from a mangrove ecosystem along the Sibun River in Belize, which is subject to both changes in sea-level and in the characteristics of the river's drainage basin. Radiocarbon dates from the core show a decreased sedimentation rate from ~ 6 ka to 1 cal ka BP and a marked change in lithology from primarily mangrove peat to fluvial-derived material at ~ 2.5 cal ka BP. Changes in the sedimentation rates observed in mangrove ecosystems offshore have previously been attributed to changes in relative sea-level and the rate of sea-level rise. Pollen analyses show a decreased abundance of Rhizophora (red mangrove) pollen and an increased abundance of Avicennia (black mangrove) pollen and non-mangrove pollen coeval with the decreased sedimentation rates. Elemental ratios ([N:C]a) and stable isotope analyses (δ15N and δ13C) show that changes in the composition of the organic material are also coeval with the change in lithology. The decrease in sedimentation rate at the site of core SR-63 and at offshore sites supports the idea that regional changes in hydrology occurred during the Holocene in Belize, influencing both mainland and offshore mangrove ecosystems. VL - 76 UR - http://www.sciencedirect.com/science/article/pii/S003358941100069X IS - 2 N1 - id: 2099 JO - Paleoecology of mangroves along the Sibun River, Belize ER - TY - JOUR T1 - Past ocean temperatures and coupled U/Th and (super 14) C measurements from deep-sea corals JF - Mineralogical Magazine Y1 - 2011 A1 - Thiagarajan, Nivedita A1 - Adkins, Jess A1 - Eiler, John AB - Deep-sea corals are a unique archive in paleoceanography. They have large banded skeletons that allow for high resolution records and have a high uranium content allowing for accurate calendar ages independent of radiocarbon age measurements. One problem with using deep-sea corals for long records is that it is difficult to date a large numbers of corals accurately and precisely. Unlike sediment cores, fossil fields of corals have no inherent stratigraphy and each individual coral must be separately dated. Here we present the results of 'reconnaissance radiocarbon age analyses' made at NOSAMS on 519 Desmophyllum dianthus (D. dianthus) collected from the New England Seamounts and South of Tasmania. We will also present the results of 80 more deep-sea corals measured on the Gas-Source AMS also at NOSAMS in WHOI. We find that the coral populations respond to rapid climate change events and are sensitive to climatically driven changes in thermohaline circulation, productivity, [O (sub 2) ] and [CO (sub 3) (super 2-) ]. Once dated however, their use as a paleoceanographic archive is complicated by the isotope and trace-metal disequilibria in their skeletons relative to co-existing seawater. However two tracers that overcome these vital effects are paired U-series and radiocarbon dates and clumped isotope measurements. Here we will present preliminary data of YD and H1 corals from the New England Seamounts collected from 1000-2600m of water depth in the North Atlantic where all three tracers are measured in the same corals. We find that the temperature profile of the ocean during both the YD and H1 coral population is constant with depth. The average potential temperature of the Younger Dryas profile is 1.6 + or - 0.5 degrees C while the average potential temperature of the Heinrich 1 profile is 3.1+ or -0.9 degrees C. If one outlier in the H1 profile is removed the average temperature becomes 2.3+ or -0.5 degrees C. We will discuss implications for salinity gradients in the water column during these time periods as well changes in the circulation of the ocean. VL - 75 UR - http://minmag.geoscienceworld.org/content/75/3/1979 IS - 3 N1 - id: 2212; Source type: scholarlyjournals; Object type: Article; Copyright: GeoRef in Process, Copyright 2012, American Geosciences Institute. After editing and indexing, this record will be added to Georef. Abstract, Copyright, Mineralogical Society of Great Britain and Ireland; CSAUnique: 610523-50; AccNum: 610523-50; ISSN: 0026-461X; ElecISSN: 1471-8022; CODEN: MNLMBB; Peer Reviewed: true JO - Past ocean temperatures and coupled U/Th and (super 14) C measurements from deep-sea corals ER - TY - JOUR T1 - Pb isotopic variability in the modern-Pleistocene Indus River system measured by ion microprobe in detrital K-feldspar grains JF - Geochimica et Cosmochimica Acta Y1 - 2011 A1 - Alizai, Anwar A1 - Clift, Peter D. A1 - Giosan, Liviu A1 - VanLaningham, Sam A1 - Hinton, Richard A1 - Tabrez, Ali R. A1 - Danish, Muhammad AB - The western Himalaya, Karakoram and Tibet are known to be heterogeneous with regard to Pb isotope compositions in K-feldspars, which allows this system to be used as a sediment provenance tool. We used secondary ion mass spectrometry to measure the isotopic character of silt and sand-sized grains from the modern Sutlej and Chenab Rivers, together with Thar Desert sands, in order to constrain their origin. The rivers show a clear Himalayan provenance, contrasting with grains from the Indus Suture Zone, but with overlap to known Karakoram compositions. The desert dunes commonly show 207Pb/204Pb and 206Pb/204Pb values that are much higher than those seen in the rivers, most consistent with erosion from Nanga Parbat. This implies at least some origin from the trunk Indus, probably reworked by summer monsoon winds from the SW, a hypothesis supported by bulk Nd and U–Pb zircon dating. Further data collected from Holocene and Pleistocene sands shows that filled and abandoned channels on the western edge of the Thar Desert were sourced from Himalayan rivers before and at 6–8 ka, but that after that time the proportion of high isotopic ratio grains rose, indicating increased contribution from the Thar Desert dunes prior to ∼4.5 ka when flow ceased entirely. This may be linked to climatic drying, northward expansion of the Thar Desert, or changes in drainage style including regional capture, channel abandonment, or active local Thar tributaries. Our data further show a Himalayan river channel east of the present Indus, close to the delta, in the Nara River valley during the middle Holocene. While this cannot be distinguished from the Indus it is not heavily contaminated by reworking from the desert. The Pb system shows some use as a provenance tool, but is not effective at demonstrating whether these Nara sediments represent a Ghaggar-Hakra stream independent from the Indus. Our study highlights an important role for eolian reworking of floodplain sediments in arid rivers such as the Indus. VL - 75 UR - http://www.sciencedirect.com/science/article/pii/S0016703711003164 IS - 17 N1 - id: 2171 JO - Pb isotopic variability in the modern-Pleistocene Indus River system measured by ion microprobe in detrital K-feldspar grains ER - TY - CHAP T1 - Pontic-Baltic pathways for invasive aquatic species: geoarchaeological implications T2 - Geology and Geoarchaeology of the Black Sea Region: Beyond the Flood Hypothesis Y1 - 2011 A1 - Buynevich, I. V. A1 - Damušytė, A. A1 - Bitinas, A. A1 - Olenin, S. A1 - Mažeika, J. A1 - Petrošius, R. ED - Buynevich, I. V. AB - An accurate chronology for the exchange of aquatic species between water basins is important for paleoenvironmental reconstruction on both regional and continental scales. During the early Holocene, the range of zebra mussels, Dreissena polymorpha, was limited to the Black, Azov, Caspian, and Aral Seas, as well as the estuaries and lower and middle reaches of the Pontic-Caspian rivers. We present new findings that challenge the currently held view that this species migrated into the Baltic Sea watershed during the early 1800s through the canals joining the tributaries of rivers that drain into the Black and Baltic Sea basins. Geological investigations along the southeast Baltic Sea coast (Curonian and Vistula spits and lagoons) have uncovered shells of D. polymorpha that yielded radiocarbon ages older than 1000 radiocarbon yr B.P. We propose two scenarios to explain the new radiocarbon dates for D. polymorpha. The first scenario involves an anomalously large reservoir effect—as large as 600–800 yr—however, several lines of evidence cast doubt upon the validity of such a large reservoir correction. The second scenario that might explain the old zebra mussel ages is the earlier arrival of Dreissena polymorpha into the Baltic region. Natural exchange may have been facilitated by the proximity of the tributaries draining the Pontic and Baltic watersheds. Human-mediated transport is also considered in association with Viking voyages from the Baltic to the Black and Caspian Seas between A.D. 800 and 1000, and the riverine trade exchange during the Lithuanian expansion into the Pontic steppe in subsequent centuries. It is likely that both scenarios played a role, with implications for late Holocene biogeography and paleoecology of the Pontic-Caspian and Baltic basins. JF - Geology and Geoarchaeology of the Black Sea Region: Beyond the Flood Hypothesis PB - Geological Society of America N1 - id: 2122 JO - Pontic-Baltic pathways for invasive aquatic species: geoarchaeological implications ER - TY - JOUR T1 - The Posidonia oceanica marine sedimentary record: A Holocene archive of heavy metal pollution JF - Science of The Total Environment Y1 - 2011 A1 - Serrano, O. A1 - Mateo, M. A. A1 - Dueñas-Bohórquez, A. A1 - Renom, P. A1 - López-Sáez, J. A. A1 - Martínez Cortizas, A. AB - The study of a Posidonia oceanica mat (a peat-like marine sediment) core has provided a record of changes in heavy metal abundances (Fe, Mn, Ni, Cr, Cu, Pb, Cd, Zn, As and Al) since the Mid-Holocene (last 4470 yr) in Portlligat Bay (NW Mediterranean). Metal contents were determined in P. oceanica. Both, the concentration records and the results of principal components analysis showed that metal pollution in the studied bay started ca. 2800 yr BP and steadily increased until present. The increase in Fe, Cu, Pb, Cd, Zn and As concentrations since ca. 2800 yr BP and in particular during Greek (ca. 2680–2465 cal BP) and Roman (ca. 2150–1740 cal BP) times shows an early anthropogenic pollution rise in the bay, which might be associated with large- and short-scale cultural and technological development. In the last ca. 1000 yr the concentrations of heavy metals, mainly derived from anthropogenic activities, have significantly increased (e.g. from ~ 15 to 47 μg g− 1 for Pb, ~ 23 to 95 μg g− 1 for Zn and ~ 8 to 228 μg g− 1 for As). Our study demonstrates for the first time the uniqueness of P. oceanica meadows as long-term archives of abundances, patterns, and trends of heavy metals during the Late Holocene in Mediterranean coastal ecosystems. VL - 409 UR - http://www.sciencedirect.com/science/article/pii/S0048969711008242 IS - 22 N1 - id: 2098 JO - The Posidonia oceanica marine sedimentary record: A Holocene archive of heavy metal pollution ER - TY - JOUR T1 - Precipitation as the main driver of Neoglacial fluctuations of Gualas glacier, Northern Patagonian Icefield JF - Climate of the Past Y1 - 2011 A1 - Bertrand, S. A1 - Hughen, K. A. A1 - Lamy, F. A1 - Stuut, J. B. W. A1 - Torrejon, F. A1 - Lange, C. B. AB - Glaciers are frequently used as indicators of climate change. However, the link between past glacier fluctuations and climate variability is still highly debated. Here, we investigate the mid- to late-Holocene fluctuations of Gualas Glacier, one of the northernmost outlet glaciers of the Northern Patagonian Icefield, using a multi-proxy sedimentological and geochemical analysis of a 15 m long fjord sediment core from Golfo Elefantes, Chile, and historical documents from early Spanish explorers. Our results show that the core can be sub-divided in three main lithological units that were deposited under very different hydrodynamic conditions. Between 5400 and 4180 cal yr BP and after 750 cal yr BP, sedimentation in Golfo Elefantes was characterized by the rapid deposition of fine silt, most likely transported by fluvio-glacial processes. By contrast, the sediment deposited between 4130 and 850 cal yr BP is composed of poorly sorted sand that is free of shells. This interval is particularly marked by high magnetic susceptibility values and Zr concentrations, and likely reflects a major advance of Gualas glacier towards Golfo Elefantes during the Neoglaciation. Several thin silt layers observed in the upper part of the core are interpreted as secondary fluctuations of Gualas glacier during the Little Ice Age, in agreement with historical and dendrochronological data. Our interpretation of the Golfo Elefantes glaciomarine sediment record in terms of fluctuations of Gualas glacier is in excellent agreement with the glacier chronology proposed for the Southern Patagonian Icefield, which is based on terrestrial (moraine) deposits. By comparing our results with independent proxy records of precipitation and sea surface temperature, we demonstrate that the fluctuations of Gualas glacier during the last 5400 yr were mainly driven by changes in precipitation in the Andes. N1 - id: 2119 JO - Precipitation as the main driver of Neoglacial fluctuations of Gualas glacier, Northern Patagonian Icefield ER - TY - JOUR T1 - The provenance of vegetation and environmental signatures encoded in vascular plant biomarkers carried by the Ganges–Brahmaputra rivers JF - Earth and Planetary Science Letters Y1 - 2011 A1 - Galy, Valier A1 - Eglinton, Timothy A1 - France-Lanord, Christian A1 - Sylva, Sean AB - Organic matter carried by rivers and deposited in continental and marine sediments contains valuable information on past environmental conditions and their impact on the terrestrial biosphere. In order to use sedimentary records to reconstruct past environmental conditions on the continents, such as vegetation cover and type, or precipitation intensity, we need to understand the provenance of the organic signatures and how they are transferred, and potentially modified, by fluvial transport to the sedimentary reservoir. In particular, we need to understand how environmental conditions are imprinted in the composition of riverine particulate organic carbon. Here we investigate the stable carbon and hydrogen isotopic signatures of vascular plant leaf wax biomarkers in the modern-day Ganges and Brahmaputra river complex, one of the largest fluvial systems on Earth. The distribution of n-alkanes and n-alkanoic acids in Ganges–Brahmaputra river sediments suggests that vascular plant inputs are consistently a significant component of the organic carbon pool. Molecular δ13C measurements reveal that C3 vegetation inputs delivered by the Himalayan rivers are partly degraded and replaced by mixed C3/C4 vegetation input in the floodplain. The hydrogen isotopic composition of long-chain (C24+) n-alkanoic acids, in combination with their stable C isotopic composition, provides constraints on the isotopic composition of the environmental water used by higher plants within the drainage basin. Calculated compositions compare well with the depleted δD isotopic ratios of the river water during the summer monsoon, suggesting that H-isotopic compositions of long-chain alkanoic acids are a valuable proxy for the composition of summer monsoon moisture in the Ganges–Brahmaputra basin. Detailed studies of the “isotopic anatomy” of modern river systems are critical for informed interpretation of marine sedimentary records in river-influenced continental margins. VL - 304 UR - http://www.sciencedirect.com/science/article/pii/S0012821X11000744 IS - 1–2 N1 - id: 2187 JO - The provenance of vegetation and environmental signatures encoded in vascular plant biomarkers carried by the Ganges–Brahmaputra rivers ER - TY - JOUR T1 - Pulleniatina Minimum Events in the Andaman Sea (NE Indian Ocean): Implications for winter monsoon and thermocline changes JF - Marine Micropaleontology Y1 - 2011 A1 - Sijinkumar, A. V. A1 - Nath, B. Nagender A1 - Possnert, G. A1 - Aldahan, A. AB - The late Quaternary record of Pulleniatina obliquiloculata was investigated from two well dated sediment cores from the Andaman Sea (NE Indian Ocean) to examine its paleoceanographic significance and the presence of the Pulleniatina Minimum Events (PME) in the western North Pacific. As in the Pacific, our study shows that PMEs exist in the Indian Ocean albeit with a lower intensity. The Holocene PME occurs between 4.5 and 3.0 cal ka BP with a considerable reduction in P. obliquiloculata abundance, and which matches well with the Pacific records influenced by the Kuroshio Current. Additionally, two significant minimum events of P. obliquiloculata are also seen during the Younger Dryas (YD) and late Last Glacial Maximum (LGM, 20–18 cal ka BP). Overall, the PMEs of the Andaman Sea are not current driven events like in the western Pacific margin either by the weakening of the Kuroshio Current or reduced winter SSTs. The PMEs of the Andaman Sea are characterised by lower abundances of thermocline species indicating the increased depth of the thermocline (DOT) and reduced winter SSTs mainly during the minimum events of the YD and late LGM. The high SSTs during the Holocene PME make this event a mystery. However, the presence of PMEs in the Andaman Sea suggests that these events are not confined to areas influenced by the Kuroshio Current but may be responding to a broad scale oceanographic–climatic process or mechanism which needs to be explored with a detailed study. VL - 81 UR - http://www.sciencedirect.com/science/article/pii/S0377839811000909 IS - 3–4 N1 - id: 2159 JO - Pulleniatina Minimum Events in the Andaman Sea (NE Indian Ocean): Implications for winter monsoon and thermocline changes ER - TY - JOUR T1 - Radiocarbon and 230Th data reveal rapid redistribution and temporal changes in sediment focussing at a North Atlantic drift JF - Earth and Planetary Science Letters Y1 - 2011 A1 - Mollenhauer, Gesine A1 - McManus, Jerry F. A1 - Wagner, Thomas A1 - McCave, I. Nick A1 - Eglinton, Timothy I. AB - In locations of rapid sediment accumulation receiving substantial amounts of laterally transported material the timescales of transport and accurate quantification of the transported material are at the focus of intense research. Here we present radiocarbon data obtained on co-occurring planktic foraminifera, marine haptophyte biomarkers (alkenones) and total organic carbon (TOC) coupled with excess Thorium-230 (230Thxs) measurements on four sediment cores retrieved in 1649–2879m water depth from two such high accumulation drift deposits in the Northeast Atlantic, Björn and Gardar Drifts. While 230Thxs inventories imply strong sediment focussing, no age offsets are observed between planktic foraminifera and alkenones, suggesting that redistribution of sediments is rapid and occurs soon after formation of marine organic matter, or that transported material contains negligible amounts of alkenones. An isotopic mass balance calculation based on radiocarbon concentrations of co-occurring sediment components leads us to estimate that transported sediment components contain up to 12% of fossil organic matter that is free of or very poor in alkenones, but nevertheless appears to consist of a mixture of fresh and eroded fossil material. Considering all available constraints to characterize transported material, our results show that although focussing factors calculated from bulk sediment 230Thxs inventories may allow useful approximations of bulk redeposition, they do not provide a unique estimate of the amount of each laterally transported sediment component. Furthermore, our findings provide evidence that the occurrence of lateral sediment redistribution alone does not always hinder the use of multiple proxies but that individual sediment fractions are affected to variable extents by sediment focussing. VL - 301 UR - http://linkinghub.elsevier.com/retrieve/pii/S0012821X1000717X IS - 1-2 ER - TY - JOUR T1 - Radiocarbon and stable carbon isotopic insights into provenance and cycling of carbon in Lake Superior JF - LIMNOLOGY AND OCEANOGRAPHY Y1 - 2011 A1 - Zigah, Prosper K. A1 - Minor, Elizabeth C. A1 - Werne, Josef P. A1 - McCallister, S. Leigh AB - This study applies radiocarbon and stable carbon isotopic distributions to investigate carbon sources and cycling within Lake Superior. We report the radiocarbon (Delta C-14) and stable carbon isotope (delta C-13) values and the carbon concentrations within dissolved organic carbon (DOC), particulate organic carbon (POC), and dissolved inorganic carbon (DIC) in the lake's western basin water column. Samples were taken during spring mixing and late-summer thermal stratification over a 2-yr period (2007-2009). Distinct processes operating in the surface (photosynthesis) and deep waters (sediment resuspension and pore-water intrusion) control the relative contribution of modern and ancient DOC and POC in the water column. The terrigenous carbon input to the open lake POC varied from 13% +/- 4% during late summer stratification to 9% +/- 3% during spring mixing, with most of the terrestrial carbon being C-14-enriched (modern). The DIC reservoir cycles rapidly, with a bulk Delta C-14(DIC) value that records atmospheric radiocarbon levels from 3 yr prior to sampling. The DOC pool recycles on a longer time scale than does the DIC, with a DOC residence time of <= 60 yr. The suspended POC was in most cases older than co-occurring DOC, most likely as a result of resuspension of lake sediments. VL - 56 ER - TY - JOUR T1 - Radiocarbon and Th-230 data reveal rapid redistribution and temporal changes in sediment focussing at a North Atlantic drift JF - EARTH AND PLANETARY SCIENCE LETTERS Y1 - 2011 A1 - Mollenhauer, Gesine A1 - McManus, Jerry F. A1 - Wagner, Thomas A1 - McCave, I. Nick A1 - Eglinton, Timothy I. KW - alkenones KW - compound-specific radiocarbon dating KW - drift sediments KW - focussing factors KW - Th-230(xs) AB - In locations of rapid sediment accumulation receiving substantial amounts of laterally transported material the timescales of transport and accurate quantification of the transported material are at the focus of intense research. Here we present radiocarbon data obtained on co-occurring planktic foraminifera, marine haptophyte biomarkers (alkenones) and total organic carbon (TOC) coupled with excess Thorium-230 (Th-230(xs)) measurements on four sediment cores retrieved in 1649-2879 m water depth from two such high accumulation drift deposits in the Northeast Atlantic, Bjorn and Gardar Drifts. While Th-230(xs), inventories imply strong sediment focussing, no age offsets are observed between planktic foraminifera and alkenones, suggesting that redistribution of sediments is rapid and occurs soon after formation of marine organic matter, or that transported material contains negligible amounts of alkenones. An isotopic mass balance calculation based on radiocarbon concentrations of co-occurring sediment components leads us to estimate that transported sediment components contain up to 12% of fossil organic matter that is free of or very poor in alkenones, but nevertheless appears to consist of a mixture of fresh and eroded fossil material. Considering all available constraints to characterize transported material, our results show that although focussing factors calculated from bulk sediment Th-230(xs) inventories may allow useful approximations of bulk redeposition, they do not provide a unique estimate of the amount of each laterally transported sediment component. Furthermore, our findings provide evidence that the occurrence of lateral sediment redistribution alone does not always hinder the use of multiple proxies but that individual sediment fractions are affected to variable extents by sediment focussing. (C) 2010 Elsevier B.V. All rights reserved. VL - 301 ER - TY - JOUR T1 - Radiocarbon chronology of the late-glacial Puerto Bandera moraines, Southern Patagonian Icefield, Argentina JF - Quaternary Science Reviews Y1 - 2011 A1 - Strelin, J. A. A1 - Denton, G. H. A1 - Vandergoes, M. J. A1 - Ninnemann, U. S. A1 - Putnam, A. E. AB - We report radiocarbon dates that constrain the timing of the deposition of the late-glacial Puerto Bandera moraine system alongside the western reaches of Lago Argentino adjacent to the Southern Patagonian Icefield. Close maximum-limiting radiocarbon ages (n = 11) for glacier advance into the outer moraines, with a mean value of 11,100 +/- 60 (14)C yrs BP (12,990 +/- 80 cal yrs BP), were obtained from wood in deformation (soft) till exposed beneath flow and lodgment till in Bahia del Quemado on the northeast side of Brazo Norte (North Branch) of western Lago Argentino. Other exposures of this basal deformation till in Bahia del Quemado reveal incorporated clasts of peat, along with larger inclusions of deformed glaciofluvial and lacustrine deposits. Radiocarbon dates of wood included in these reworked peat clasts range from 11,450 +/- 45 (14)C yrs BP to 13,450 +/- 150 (14)C yrs BP (13,315 +/- 60 to 16,440 +/- 340 cal yrs BP). The implication is that, during this interval, glacier fronts were situated inboard of the Puerto Bandera moraines, with the peat clasts and larger proglacial deposits being eroded and then included in the basal till during the Puerto Bandera advance. Minimum-limiting radiocarbon ages for ice retreat come from basal peat in cores sampled in spillways and depressions generated during abandonment of the Puerto Bandera moraines. Glacier recession and subsequent plant colonization were initiated close behind different frontal sectors of these moraines prior to: 10,750 +/- 75 (14)C yrs BP (12,660 +/- 70 cal yrs BP) east of Brazo Rico, 10,550 +/- 55 (14)C yrs BP (12,490 +/- 80 cal yrs BP) in Peninsula Avellaneda, and 10,400 +/- 50 (14)C yrs BP (12,280 +/- 110 cal yrs BP) in Bahia Catalana. In addition, a radiocarbon date indicates that by 10,350 +/- 45 (14)C yrs BP (12,220 +/- 110 cal yrs BP), the Brazo Norte lobe (or former Upsala Glacier) had receded well up the northern branch of Lago Argentino, to a position behind the Herminita moraines. Furthermore, glacier termini had receded to just outboard of the outer Holocene moraines at Lago Frias and Lago Pearson (Anita) prior to 10,400 +/- 40 (14)C yrs BP (12,270 +/- 100 cal yrs BP) and 9040 +/- 45 (14)C yrs BP (10,210 +/- 50 cal yrs BP), respectively. The most extensive recession registered during the early Holocene was in Agassiz Este Valley, where the Upsala Glacier had pulled back behind the outer Holocene moraine, reaching close to the present-day glacier terminus before 8290 +/- 40 (14)C yrs BP (9300 +/- 80 cal yrs BP). The radiocarbon-dated fluctuations of the Lago Argentino glacier in late-glacial time, given here, are in accord with changes in ocean mixed layer properties, predominately temperature, derived from the isotopic record given here of ODP Core 1233, taken a short distance off shore of the Chilean Lake District. It also matches recently published chronologies of late-glacial moraines in the Southern Alps of New Zealand on the opposite side of the Pacific Ocean from Lago Argentino. Finally, the timing of the late-glacial reversal of the Lago Argentino glacier fits the most recent chronology for the culmination of the Antarctic Cold Reversal (ACR) in the deuterium record of the EPICA Dome C ice core from high on the East Antarctic Plateau. Therefore, we conclude that the climate signature of the ACR was widespread in both the ocean and the atmosphere over at least the southern quarter of the globe. (C) 2011 Elsevier Ltd. All rights reserved. VL - 30 IS - 19-20 N1 - id: 1954; PT: J; UT: WOS:000295387000014 JO - Radiocarbon chronology of the late-glacial Puerto Bandera moraines, Southern Patagonian Icefield, Argentina ER - TY - JOUR T1 - Rapid coastal dune migration into temperate and equatorial forests: optical chronology of imaged upper slipface strata JF - Journal of Coastal Research Y1 - 2011 A1 - Buynevich, I. V. A1 - Bitinas, A. A1 - Souza Filho, P. W. M. A1 - Pupienis, D. A1 - Asp, N. E. A1 - Goble, R. J. A1 - Kerber, L. E. AB - This study presents the first sets of optical dates that constrain dunefield evolution along a temperate, forested, microtidal barrier (Curonian Spit, southeast Baltic Sea, Lithuania) and a macrotidal equatorial mangrove coast (Pará State, northern Brazil). In both areas, high-resolution geophysical (georadar) images were used to map the subsurface architecture, relative chronology, and orientation of dune migration surfaces (slipfaces) and vertical accretion strata. Besides relative chronology of dune accretion, subsurface images reveal bounding (superimposition) surfaces indicative of distinct activity phases. A cross-barrier Preila transect on the Curonian Spit, served as the basis for establishing dune chronology in this historically active part of the Great Dune Ridge. Due to barrier width (> 1km) and dune height (>30 m), aeolian sand transfer, rather than overwash and breaching, has been the dominant process of landward migration for this barrier spit since mid-Holocene. OSL dating of the upper sections of buried slipfaces in shallow trenches revealed dune migration of more than 600 m between mid-1500s and late 1700s at the Preila site. These ages are consistent with historical records and the time of burial of a coastal village near the edge of a lagoon by 1797. In equatorial Brazil (Atalaia Beach), large reactivated parabolic dunes have been migrating over coastal roads and mangrove forests over at least the past 150 years. In geophysical images of a parabolic dune, numerous high-amplitude hyperbolic anomalies produced by buried trees contrast with steeply landward-dipping slipface reflections. Due to water table elevation, the lower older part of the dune sequence has been stabilized in the blowout area. Similarly, interdunal lake has partially arrested the migration of a transverse dune ridge, while the adjacent segment continues to advance onto a sparsely vegetated plain. Our preliminary data indicate that whereas the two regions differ markedly in their precipitation patterns, vegetation types, oceanographic setting, and land-use history, both experienced episodes of rapid (average: 1-2 m/year) migration of massive dunes (10-50 m high), which continues locally at the present time. Aside from their implications to coastal evolution, accurate reconstructions of dune dynamics on decadal to centennial time scales should be integrated into coastal development and management strategies. IS - SI 64 N1 - id: 2124 JO - Rapid coastal dune migration into temperate and equatorial forests: optical chronology of imaged upper slipface strata ER - TY - JOUR T1 - Rapid Holocene coastal change revealed by high-resolution micropaleontological analysis, Pamlico Sound, North Carolina, USA JF - Quaternary Research Y1 - 2011 A1 - Grand Pre, Candace A1 - Culver, Stephen J. A1 - Mallinson, David J. A1 - Farrell, Kathleen M. A1 - Corbett, D. Reide A1 - Horton, Benjamin P. A1 - Hillier, Caroline A1 - Riggs, Stanley R. A1 - Snyder, Scott W. A1 - Buzas, Martin A. AB - Foraminiferal analyses of 404 contiguous samples, supported by diatom, lithologic, geochronologic and seismic data, reveal both rapid and gradual Holocene paleoenvironmental changes in an 8.21-m vibracore taken from southern Pamlico Sound, North Carolina. Data record initial flooding of a latest Pleistocene river drainage and the formation of an estuary 9000 yr ago. Estuarine conditions were punctuated by two intervals of marine influence from approximately 4100 to 3700 and 1150 to 500 cal yr BP. Foraminiferal assemblages in the muddy sand facies that accumulated during these intervals contain many well-preserved benthic foraminiferal species, which occur today in open marine settings as deep as the mid shelf, and significant numbers of well-preserved planktonic foraminifera, some typical of Gulf Stream waters. We postulate that these marine-influenced units resulted from temporary destruction of the southern Outer Banks barrier islands by hurricanes. The second increase in marine influence is coeval with increased rate of sea-level rise and a peak in Atlantic tropical cyclone activity during the Medieval Climate Anomaly. This high-resolution analysis demonstrates the range of environmental variability and the rapidity of coastal change that can result from the interplay of changing climate, sea level and geomorphology in an estuarine setting. VL - 76 UR - http://www.sciencedirect.com/science/article/pii/S0033589411000883 IS - 3 N1 - id: 2164 JO - Rapid Holocene coastal change revealed by high-resolution micropaleontological analysis, Pamlico Sound, North Carolina, USA ER - TY - JOUR T1 - Rapid radiocarbon ((14)C) analysis of coral and carbonate samples using a continuous-flow accelerator mass spectrometry (CFAMS) system JF - Paleoceanography Y1 - 2011 A1 - McIntyre, Cameron P. A1 - Roberts, Mark L. A1 - Burton, Joshua R. A1 - McNichol, Ann P. A1 - Burke, Andrea A1 - Robinson, Laura F. A1 - von Reden, Karl F. A1 - W. J. Jenkins AB - Radiocarbon analyses of carbonate materials provide critical information for understanding the last glacial cycle, recent climate history and paleoceanography. Methods that reduce the time and cost of radiocarbon ((14)C) analysis are highly desirable for large sample sets and reconnaissance type studies. We have developed a method for rapid radiocarbon analysis of carbonates using a novel continuous-flow accelerator mass spectrometry (CFAMS) system. We analyzed a suite of deep-sea coral samples and compared the results with those obtained using a conventional AMS system. Measurement uncertainty is VL - 26 N1 - id: 1915; PT: J; UT: WOS:000296649300001 JO - Rapid radiocarbon ((14)C) analysis of coral and carbonate samples using a continuous-flow accelerator mass spectrometry (CFAMS) system ER - TY - JOUR T1 - Rapid wetland expansion during European settlement and its implication for marsh survival under modern sediment delivery rates JF - Geology Y1 - 2011 A1 - Kirwan, M. L. A1 - Murray, A. B. A1 - Donnelly, J. P. A1 - Corbett, D. R. AB - Fluctuations in sea-level rise rates are thought to dominate the formation and evolution of coastal wetlands. Here we demonstrate a contrasting scenario in which land-use-related changes in sediment delivery rates drive the formation of expansive marshland, and vegetation feedbacks maintain their morphology despite recent sediment supply reduction. Stratigraphic analysis and radiocarbon dating in the Plum Island Estuary (Massachusetts, United States) suggest that salt marshes expanded rapidly during the eighteenth and nineteenth centuries due to increased rates of sediment delivery following deforestation associated with European settlement. Numerical modeling coupled with the stratigraphic observations suggests that existing marshland could survive, but not form under the low suspended sediment concentrations observed in the estuary today. These results suggest that many of the expansive marshes that characterize the modern North American coast are metastable relicts of high nineteenth century sediment delivery rates, and that recent observations of degradation may represent a slow return to pre-settlement marsh extent. In contrast to ecosystem management practices in which restoring pre-anthropogenic conditions is seen as a way to increase ecosystem services, our results suggest that widespread efforts to restore valuable coastal wetlands actually prevent some systems from returning to a natural state. VL - 39 IS - 5 N1 - id: 846; 748TX Times Cited:2 Cited References Count:31under reviewY JO - Rapid wetland expansion during European settlement and its implication for marsh survival under modern sediment delivery rates ER - TY - JOUR T1 - Rare earth element geochemistry in the inner shelf of the East China Sea and its implication to sediment provenances JF - Journal of Rare Earths Y1 - 2011 A1 - Xu, Fangjian A1 - Li, Anchun A1 - Li, Tiegang A1 - Xu, Kehui A1 - Chen, Shiyue A1 - Qiu, Longwei A1 - Cao, Yingchang AB - Gravity core EC2005, located in the mud wedge off the Zhejiang-Fujian coast in the inner shelf of the East China Sea (ECS), was analyzed for its lithology, grain size, rare earth elements (REE) and AMS14C dating. Results revealed high-resolution paleoenvironmental evolution and multiple switches of sediment provenances in the inner shelf of ECS. The lithology, grain size and REE concentrations of sediments varied significantly down the core. Mean grain size ranged from 8 to 121 μm, and the values of ΣREE were 152.8–227.9 μg/g. The chondrite- and shale-normalized REE patterns indicated their similarity to the terrigenous sediments in the study area. Between 17.3–12.3 ka BP the sediments in the inner shelf of ECS were mainly originated from local drainage basins. The source then gradually switched to the Yangtze River between 12.3 and 9.8 ka BP. Since about 10–9.8 ka BP, the sediments in the study area were dominantly derived from the Yangtze River. The continuous rising of sea level and formation of coastal current along the inner shelf played a key role in the switches of sediment provenances. VL - 29 UR - http://www.sciencedirect.com/science/article/pii/S1002072110605261 IS - 7 N1 - id: 2177 JO - Rare earth element geochemistry in the inner shelf of the East China Sea and its implication to sediment provenances ER - TY - JOUR T1 - Rates and Mechanisms of Mineral Carbonation in Peridotite: Natural Processes and Recipes for Enhanced, in situ CO 2 Capture and Storage JF - Annual Review of Earth and Planetary Sciences Y1 - 2011 A1 - Kelemen, Peter B. A1 - Matter, Juerg A1 - Streit, Elisabeth E. A1 - Rudge, John F. A1 - Curry, William B. A1 - Blusztajn, Jerzy AB - Near-surface reaction of CO2-bearing fluids with silicate minerals in peridotite and basalt forms solid carbonate minerals. Such processes form abundant veins and travertine deposits, particularly in association with tectonically exposed mantle peridotite. This is important in the global carbon cycle, in weathering, and in understanding physical-chemical interaction during retrograde metamorphism. Enhancing the rate of such reactions is a proposed method for geologic CO2 storage, and perhaps for direct capture of CO2 from near-surface fluids. We review, synthesize, and extend inferences from a variety of sources. We include data from studies on natural peridotite carbonation processes, carbonation kinetics, feedback between permeability and volume change via reaction-driven cracking, and proposed methods for enhancing the rate of natural mineral carbonation via in situ processes ("at the outcrop") rather than ex situ processes ("at the smokestack"). VL - 39 UR - http://www.annualreviews.org/doi/10.1146/annurev-earth-092010-152509 IS - 1 ER - TY - JOUR T1 - A regional-scale climate reconstruction of the last 4000 years from lakes in the Nebraska Sand Hills, USA JF - Quaternary Science Reviews Y1 - 2011 A1 - Schmieder, J. A1 - Fritz, S.C. A1 - Swinehart, J.B. A1 - Shinneman, A.L.C. A1 - Wolfe, A.P. A1 - Miller, G. A1 - Daniels, N. A1 - Jacobs, K.C. A1 - Grimm, E.C. KW - diatoms KW - Droughts KW - Great Plains KW - Holocene KW - lakes KW - Nebraska Sand Hills KW - paleolimnology AB - High-resolution paleohydrological reconstructions were carried out in five shallow lakes in the Nebraska Sand Hills across an eastewest transect in order to 1) determine whether long-term droughts of the past 4000 years were spatially and temporally coherent across the region, 2) distinguish local variation in climate or hydrology from regional patterns of change, and 3) compare the paleolimnological results with the existing dune-inferred drought records. Diatom-inferred lake-level was reconstructed for all sites and compared with other regional records. Alterations between high and low lake-levels were frequent during the past 4000 years, which suggests that shifts between dry and wet periods were prevalent across the Sand Hills. Extended multi-decadal to centennial-scale droughts were more common prior to 2000 years BP, while the last two millennia were hydrologically more variable and climate conditions alternated on shorter timescales. Despite some discrepancies among the five records, the paleohydrological reconstructions refine the Holocene drought history of the Nebraska Sand Hills, particularly between w2200 and 4000 cal a BP. Many of the observed drought events are contemporaneous with severe droughts documented at sites in the northern Great Plains and Rocky Mountains, lending support for the severity and regional significance of these events in western North America. VL - 30 UR - http://linkinghub.elsevier.com/retrieve/pii/S0277379111001132http://api.elsevier.com/content/article/PII:S0277379111001132?httpAccept=text/xmlhttp://api.elsevier.com/content/article/PII:S0277379111001132?httpAccept=text/plain IS - 13-14 ER - TY - JOUR T1 - Repeated century-scale droughts over the past 13,000 yr near the Hudson River watershed, USA JF - Quaternary Research Y1 - 2011 A1 - Newby, Paige E. A1 - Shuman, Bryan N. A1 - Donnelly, Jeffrey P. A1 - MacDonald, Dana AB - Long-term sediment and ground-penetrating radar data from Davis Pond, a small lake near the Hudson River valley, reveal past droughts in a historically humid region that presently supplies water to millions of people in and around New York City. A minimum of eleven sandy paleoshoreline deposits in the lake date from 13.4 to 0.6 cal ka BP. The deposits span 1500 to 200 yr between bracketing radiocarbon ages, and intrude into lacustrine silts up to 9.0 m below the modern lake surface in a transect of six sediment cores. Three low stands, ca. 13.4–10.9, 9.2 and 8.2 cal ka BP indicate low regional moisture balance when low temperatures affected the North Atlantic region. Consistent with insolation trends, water levels rose from ca. 8.0 cal ka BP to present, but five low stands interrupted the rise and are likely associated with ocean–atmosphere interactions. Similar to evidence from other studies, the data from Davis Pond indicate repeated multi-century periods of prolonged or frequent droughts super-imposed on long-term regional trends toward high water levels. The patterns indicate that water supplies in this heavily populated region have continuously varied at multiple time scales and confirm that humid regions such as the northeastern United States are more prone to severe drought than historically expected. VL - 75 UR - http://www.sciencedirect.com/science/article/pii/S0033589411000172 IS - 3 N1 - id: 2183 JO - Repeated century-scale droughts over the past 13,000 yr near the Hudson River watershed, USA ER - TY - CHAP T1 - Resilience and reorganization: Archaeology and the historical ecology of California Channel Island sea mammals T2 - Human Impacts on Seals, Sea Lions, and Sea Otters Y1 - 2011 A1 - Braje, Todd J. A1 - Rick, Torben C. A1 - DeLong, Robert L. A1 - Erlandson, Jon M. ED - Rick, T. C. JF - Human Impacts on Seals, Sea Lions, and Sea Otters PB - University of California Press SN - 9780520267268 N1 - id: 2068 ER - TY - JOUR T1 - Response of a marine-terminating Greenland outlet glacier to abrupt cooling 8200 and 9300 years ago JF - Geophysical Research Letters Y1 - 2011 A1 - Young, ás E. A1 - Briner, Jason P. A1 - Axford, Yarrow A1 - Csatho, Beata A1 - Babonis, Greg S. A1 - Rood, Dylan H. A1 - Finkel, Robert C. AB - Long-term records of Greenland outlet-glacier change extending beyond the satellite era can inform future predictions of Greenland Ice Sheet behavior. Of particular relevance is elucidating the Greenland Ice Sheet's response to decadal- and centennial-scale climate change. Here, we reconstruct the early Holocene history of Jakobshavn Isbræ, Greenland's largest outlet glacier, using 10Be surface exposure ages and 14C-dated lake sediments. Our chronology of ice-margin change demonstrates that Jakobshavn Isbræ advanced to deposit moraines in response to abrupt cooling recorded in central Greenland ice cores ca. 8,200 and 9,300 years ago. While the rapid, dynamically aided retreat of many Greenland outlet glaciers in response to warming is well documented, these results indicate that marine-terminating outlet glaciers are also able to respond quickly to cooling. We suggest that short lag times of high ice flux margins enable a greater magnitude response of marine-terminating outlets to abrupt climate change compared to their land-terminating counterparts. VL - 38 UR - http://doi.wiley.com/10.1029/2011GL049639 IS - 24 ER - TY - JOUR T1 - Response of Jakobshavn Isbrae, Greenland, to Holocene climate change JF - Geology Y1 - 2011 A1 - Young, N. E. A1 - Briner, J. P. A1 - Stewart, H. A. M. A1 - Axford, Y. A1 - Csatho, B. A1 - Rood, D. H. A1 - Finkel, R. C. AB - Rapid fluctuations in the velocity of Greenland Ice Sheet (GIS) outlet glaciers over the past decade have made it difficult to extrapolate ice-sheet change into the future. This significant short-term variability highlights the need for geologic records of preinstrumental GIS margin fluctuations in order to better predict future GIS response to climate change. Using 10Be surface exposure ages and radiocarbon-dated lake sediments, we constructed a detailed chronology of ice-margin fluctuations over the past 10 k.y. for Jakobshavn Isbræ, Greenland's largest outlet glacier. In addition, we present new estimates of corresponding local temperature changes using a continuous record of insect (Chironomidae) remains preserved in lake sediments. We find that following an early Holocene advance just prior to 8 ka, Jakobshavn Isbræ retreated rapidly at a rate of ∼100 m yr−1, likely in response to increasing regional and local temperatures. Ice remained behind its present margin for ∼7 k.y. during a warm period in the middle Holocene with sustained temperatures ∼2 °C warmer than today, then the land-based margin advanced at least 2–4 km between A.D. 1500–1640 and A.D. 1850. The ice margin near Jakobshavn thus underwent large and rapid adjustments in response to relatively modest centennial-scale Holocene temperature changes, which may foreshadow GIS response to future warming. VL - 39 UR - http://geology.gsapubs.org/cgi/doi/10.1130/G31399.1 IS - 2 ER - TY - JOUR T1 - Retreat of the East Antarctic ice sheet during the last glacial termination RID F-5711-2011 JF - Nature Geoscience Y1 - 2011 A1 - Mackintosh, Andrew A1 - Golledge, Nicholas A1 - Domack, Eugene A1 - Dunbar, Robert A1 - Leventer, Amy A1 - White, Duanne A1 - Pollard, David A1 - DeConto, Robert A1 - Fink, David A1 - Zwartz, Dan A1 - Gore, Damian A1 - Lavoie, Caroline AB - The retreat of the East Antarctic ice sheet at the end of the last glacial period has been attributed to both sea-level rise and warming of the ocean at the margin of the ice sheet, but it has been challenging to test these hypotheses. Given the lack of constraints on the timing of retreat, it has been difficult to evaluate whether the East Antarctic ice sheet contributed to meltwater pulse 1a, an abrupt sea-level rise of approximately 20 m that occurred about 14,700 years ago. Here we use terrestrial exposure ages and marine sedimentological analyses to show that ice retreat in Mac. Robertson Land, East Antarctica, initiated about 14,000 years ago, became widespread about 12,000 years ago, and was completed by about 7,000 years ago. We use two models of different complexities to assess the forcing of the retreat. Our simulations suggest that, although the initial stage of retreat may have been forced by sea-level rise, the majority of the ice loss resulted from ocean warming at the onset of the Holocene epoch. In light of our age model we conclude that the East Antarctic ice sheet is unlikely to have been the source of meltwater pulse 1a, and, on the basis of our simulations, suggest that Antarctic ice sheets made an insignificant contribution to eustatic sea-level rise at this time. VL - 4 IS - 3 N1 - id: 2003; PT: J; UT: WOS:000287802300021 JO - Retreat of the East Antarctic ice sheet during the last glacial termination RID F-5711-2011 ER - TY - JOUR T1 - Sea level controls sedimentation and environments in coastal caves and sinkholes JF - Marine Geology Y1 - 2011 A1 - van Hengstum, Peter J. A1 - Scott, David B. A1 - Groecke, Darren R. A1 - Charette, Matthew A. AB - Quaternary climate and sea-level research in coastal karst basins (caves, cenotes, sinkholes, blueholes, etc.) generally focuses on analyzing isotopes in speleothems, or associating cave elevations prior sea-level highstands. The sediments in coastal karst basins represent an overlooked source of climate and sea-level information in the coastal zone, but to accurately interpret these sediments first requires an understanding of the forcing mechanisms that emplace them. In this study, we hypothesize that coastal karst basins transition through vadose, littoral, anchialine, and finally into submarine environments during sea-level rise because groundwater and sea level oscillate in near synchrony in the coastal zone, causing each environment to deposit a unique sedimentary facies. To test this hypothesis, the stratigraphy in twelve sediment cores from a Bermudian underwater cave (Green Bay Cave) was investigated and temporally constrained with twenty radiocarbon dates. The results indicate that we recovered the first succession spanning the entire Holocene from an underwater cave (similar to 13 ka to present). The sediments were characterized with X-radiography, fossil remains, bulk organic matter, organic geochemistry (delta(13)C(org), C:N), and grain size analysis. Four distinct facies represent the four depositional environments: (i) vadose facies (>7.7 ka, calcite rafts lithofacies), (ii) littoral facies (7.7 to 7.3 ka: calcite rafts and mud lithofacies), (iii) anchialine facies (7.3 to 1.6 ka: slackwater and diamict lithofacies), and (iv) submarine facies ( VL - 286 IS - 1-4 N1 - id: 2058; PT: J; UT: WOS:000295104800003 JO - Sea level controls sedimentation and environments in coastal caves and sinkholes ER - TY - JOUR T1 - Siliceous productivity changes in Gulf of Ancud sediments (42°S, 72°W), southern Chile, over the last ∼150 years JF - Fjord Oceanography of the Chilean Patagonia Y1 - 2011 A1 - Rebolledo, Lorena A1 - González, Humberto E. A1 - Muñoz, Praxedes A1 - Iriarte, José L. A1 - Lange, Carina B. A1 - Pantoja, Silvio A1 - Salamanca, Marco AB - We evaluated changes in siliceous export production and the source of organic matter preserved in sediment core MD07-3109H recovered from the Gulf of Ancud, Chiloé Inner Sea (42°S, 72°W, water column depth: 328 m), southern Chile. We analyzed the abundance of siliceous microfossils (diatoms, silicoflagellates, sponge spicules, Chrysophyte cysts, phytoliths), geochemical proxies (weight percent silicon %SiOPAL, organic carbon, total nitrogen, C/N molar), and sediment stable isotopes (δ13Corg, δ15N). Chronology based on 210Pb and 14C provided an accumulated age of 144 years at the base of the core. Sediments of core MD07-3109H are predominantly marine in origin, averaging δ13Corg=–20.75‰±0.82, δ15N=8.7±0.35‰, and C/N=8.76±0.36. Marine diatoms compose 94% of the total assemblage of siliceous microfossils. Our record of productivity based on the mass accumulation rates of organic carbon, total nitrogen, SiOPAL, and total diatoms showed high values between 1863 and 1869 AD followed by a declining trend until 1921 AD, a transition period from 1921 to 1959 AD with fluctuating values, and a clear decreasing pattern from 1960 AD to the present. This marked reduction in productivity was associated with decreased precipitation and Puelo River streamflow (41°S), as well as a warmer and more stratified water column, especially since the 1980s. VL - 31 UR - http://www.sciencedirect.com/science/article/pii/S0278434310002177 IS - 3–4 N1 - id: 2191 JO - Siliceous productivity changes in Gulf of Ancud sediments (42°S, 72°W), southern Chile, over the last ∼150 years ER - TY - JOUR T1 - Solar modulation of North Atlantic central Water formation at multidecadal timescales during the late Holocene JF - Earth and Planetary Science Letters Y1 - 2011 A1 - Morley, Audrey A1 - Schulz, Michael A1 - Rosenthal, Yair A1 - Mulitza, Stefan A1 - Paul, André A1 - Rühlemann, Carsten AB - Understanding natural climate variability in the North Atlantic region is essential not only to assess the sensitivity of atmosphere–ocean climate signal exchange and propagation, but also to help distinguish between natural and anthropogenic climate change. The North Atlantic Oscillation is one of the controlling modes in recent variability of atmosphere–ocean linkages and ice/freshwater fluxes between the Polar and North Atlantic Ocean. Through these processes the NAO influences water mass formation and the strength of the Atlantic Meridional Overturning circulation and thereby variability in ocean heat transport. However, the impact of the NAO as well as other forcing mechanisms on multidecadal timescales such as total solar irradiance on Eastern North Atlantic Central Water production, central water circulation, and climate signal propagation from high to low latitudes in the eastern subpolar and subtropical basins remains uncertain. Here we use a 1200 yr long benthic foraminiferal Mg/Ca based temperature and oxygen isotope record from a ~ 900 m deep sediment core off northwest Africa to show that atmosphere–ocean interactions in the eastern subpolar gyre are transferred at central water depth into the eastern boundary of the subtropical gyre. Further we link the variability of the NAO (over the past 165 yrs) and solar irradiance (Late Holocene) and their control on subpolar mode water formation to the multidecadal variability observed at mid-depth in the eastern subtropical gyre. Our results show that eastern North Atlantic central waters cooled by up to ~ 0.8 ± 0.7 °C and densities decreased by σθ = 0.3 ± 0.2 during positive NAO years and during minima in solar irradiance during the Late Holocene. The presented records demonstrate the sensitivity of central water formation to enhanced atmospheric forcing and ice/freshwater fluxes into the eastern subpolar gyre and the importance of central water circulation for cross-gyre climate signal propagation during the Late Holocene. VL - 308 UR - http://www.sciencedirect.com/science/article/pii/S0012821X11003268 IS - 1–2 N1 - id: 2175 JO - Solar modulation of North Atlantic central Water formation at multidecadal timescales during the late Holocene ER - TY - JOUR T1 - Sources of n-alkanes in an urbanized estuary: Insights from molecular distributions and compound-specific stable and radiocarbon isotopes JF - Marine Chemistry Y1 - 2011 A1 - Ahad, Jason M. E. A1 - Ganeshram, Raja S. A1 - Bryant, Charlotte L. A1 - Cisneros-Dozal, Luz M. A1 - Ascough, Philippa L. A1 - Fallick, Anthony E. A1 - Slater, Greg F. AB - Diagnostic molecular ratios and compound-specific 13C and 14C analyses were used to identify n-alkane sources in surface sediments collected along a transect from an urbanized estuary draining a peat-rich catchment (Tyne, UK). The most abundant homologues were generally C29 or C31, and the carbon preference index (CPI; 1.8 to 6.4) and average chain length (ACL; 28.5 to 29.5) of C25–C33 n-alkanes became progressively lower in samples closer to the mouth of estuary. δ13C signatures of C19–C31 n-alkanes ranged from − 37.1 to − 29.3‰ and in general became more depleted with increasing carbon number. Δ14C values for C21 (− 945 to − 738‰) were significantly more depleted compared to C29 (− 591 to − 65‰) and C31 (− 382 to − 96‰), pointing to a much higher component of fossil (i.e., 14C-free) carbon in the shorter homologue. The radiocarbon contents for these three n-alkanes decreased toward the North Sea, which in conjunction with an up to 4‰ seaward 13C-enrichment in C29 and C31 and seaward decreases in CPI and ACL pointed to petrogenic hydrocarbon contamination in lower estuarine sediments. Independent 13C and 14C mass balances used to calculate the relative proportions of modern (i.e., plant wax) and fossil (i.e., petrogenic) n-alkanes yielded similar results and demonstrated that mixing with marine-derived organic matter (OM) or microbial degradation during estuarine transport led to a seaward decline in modern, longer-chain homologues, resulting in an increasingly larger fossil carbon contribution toward the mouth of estuary. The ability to clearly distinguish anthropogenic from natural inputs suggests that compound-specific radiocarbon analysis can successfully delineate the age of terrigenous OM delivered to the coastal zone even near historically polluted systems such as the Tyne. VL - 126 IS - 1–4 N1 - id: 2169 JO - Sources of n-alkanes in an urbanized estuary: Insights from molecular distributions and compound-specific stable and radiocarbon isotopes ER - TY - JOUR T1 - Stable isotope analysis of dog, fox, and human diets at a Late Holocene Chumash village (CA-SRI-2) on Santa Rosa Island, California JF - Journal of Archaeological Science Y1 - 2011 A1 - Rick, Torben C. A1 - Culleton, Brendan J. A1 - Smith, Carley B. A1 - Johnson, John R. A1 - Kennett, Douglas J. AB - Stable carbon (δ13C) and nitrogen (δ15N) isotope analyses of dog (Canis familiaris), island fox (Urocyon littoralis), and human bone collagen from CA-SRI-2 (AD 130–1830) on Santa Rosa Island, California provide a proxy of diet and the relationships between humans and these animals. Carbon isotopic signatures indicate that Native Americans and their dogs at CA-SRI-2 subsisted almost exclusively on marine resources, while the island fox ate primarily terrestrial foods. Nitrogen isotopes and archaeofaunal remains indicate that humans and dogs also ate higher trophic level foods, including finfishes, marine mammals, and seabirds with smaller amounts of shellfish. The CA-SRI-2 island foxes appear to have eaten higher amounts of terrestrial foods, similar to the diets observed in modern fox populations. These data generally confirm the commensal relationship assumed to exist between domesticated dogs and people, but the carbon isotopic composition of dogs is enriched ∼2‰ compared to humans. We hypothesize that the difference in carbon isotopes between dogs and humans may have resulted from a higher consumption of C3 plants with lower δ13C values by humans, or less likely from the ingestion by dogs of significant amounts of bone collagen, which is enriched by ∼4‰ over associated muscle. VL - 38 UR - http://www.sciencedirect.com/science/article/pii/S0305440311000471 IS - 6 N1 - id: 2180 JO - Stable isotope analysis of dog, fox, and human diets at a Late Holocene Chumash village (CA-SRI-2) on Santa Rosa Island, California ER - TY - JOUR T1 - Stratigraphic record of Holocene coseismic subsidence, Padang, West Sumatra JF - JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH Y1 - 2011 A1 - Dura, Tina A1 - Rubin, Charles M. A1 - Kelsey, Harvey M. A1 - Horton, Benjamin P. A1 - Hawkes, Andrea A1 - Vane, Christopher H. A1 - Daryono, Mudrik A1 - Pre, Candace Grand A1 - Ladinsky, Tyler A1 - Bradley, Sarah AB - Stratigraphic evidence is found for two coseismic subsidence events that underlie a floodplain 20 km south of Padang, West Sumatra along the Mentawai segment (0.5 S- 0.3 S) of the Sunda subduction zone. Each earthquake is marked by a sharp soil-mud contact that represents a sudden change from mangrove to tidal flat. The earthquakes occurred about 4000 and 3000 cal years B.P. based on radiocarbon ages of detrital plant fragments and seeds. The absence of younger paleoseismic evidence suggests that late Holocene relative sea level fall left the floodplain too high for an earthquake to lower it into the intertidal zone. Our results point to a brief, few thousand year window of preservation of subsidence events in tidal-wetland stratigraphic sequences, a result that is generally applicable to other emergent coastlines of West Sumatra. VL - 116 ER - TY - JOUR T1 - Timescale dependence of glacial erosion rates: A case study of Marinelli Glacier, Cordillera Darwin, southern Patagonia JF - Journal of Geophysical Research: Earth Surface Y1 - 2011 A1 - Fernandez, Rodrigo A. A1 - Anderson, John B. A1 - Wellner, Julia S. A1 - Hallet, Bernard AB - Erosion rates have been estimated for a number of glaciated basins around the world, mostly based on modern observations (last few decades) of sediment fluxes to fjords. We use time‐constrained sediment volumes delivered by Marinelli Glacier (55°S), an outlet glacier of the Cordillera Darwin ice cap, southern Patagonian Andes, Tierra del Fuego, to determine erosion rates across different timescales. Sediment volumes are derived using a dense grid of high‐ and low‐frequency single channel seismic data and swath bathymetry data along with piston and Kasten cores. Our results show dramatic differences in erosion rates over different timescales. Erosion rates at Marinelli Glacier diminish about 80% (or by factor of ∼5) with each ten‐fold increase in the time span over which erosion rates are averaged: 29.3 mm/yr for the last 45 years, 5.3 mm/yr for the last 364 years, and 0.5 mm/yr for the last 12,500 years. These results indicate that modern sediment yields and erosion rates from temperate tidewater glaciers can exceed long‐term values over the time of deglaciation after the Last Glacial Maximum (centennial and millennial timescales) by up to 2 orders of magnitude. In view of the low exhumation rates of Cordillera Darwin (∼0.07 mm/yr average for the last 30 Myr), modern erosion rates could be up to 3 orders of magnitude higher than rates over geological time. We conclude that the pattern of erosion rate variation with time reflects the sensitivity of glaciers to climate variability. VL - 116 UR - http://doi.wiley.com/10.1029/2010JF001685 IS - F1 ER - TY - JOUR T1 - Timing and duration of North American glacial lake discharges and the Younger Dryas climate reversal JF - Quaternary Research Y1 - 2011 A1 - Rayburn, John A. A1 - Cronin, Thomas M. A1 - Franzi, David A. A1 - Knuepfer, Peter L. K. A1 - Willard, Debra A. AB - Radiocarbon-dated sediment cores from the Champlain Valley (northeastern USA) contain stratigraphic and micropaleontologic evidence for multiple, high-magnitude, freshwater discharges from North American proglacial lakes to the North Atlantic. Of particular interest are two large, closely spaced outflows that entered the North Atlantic Ocean via the St. Lawrence estuary about 13,200–12,900 cal yr BP, near the beginning of the Younger Dryas cold event. We estimate from varve chronology, sedimentation rates and proglacial lake volumes that the duration of the first outflow was less than 1 yr and its discharge was approximately 0.1 Sv (1 Sverdrup = 106 m3 s−1). The second outflow lasted about a century with a sustained discharge sufficient to keep the Champlain Sea relatively fresh for its duration. According to climate models, both outflows may have had sufficient discharge, duration and timing to affect meridional ocean circulation and climate. In this report we compare the proglacial lake discharge record in the Champlain and St. Lawrence valleys to paleoclimate records from Greenland Ice cores and Cariaco Basin and discuss the two-step nature of the inception of the Younger Dryas. VL - 75 UR - http://www.sciencedirect.com/science/article/pii/S003358941100024X IS - 3 N1 - id: 2184 JO - Timing and duration of North American glacial lake discharges and the Younger Dryas climate reversal ER - TY - JOUR T1 - Trace metal enrichments in Lake Tanganyika sediments: Controls on trace metal burial in lacustrine systems JF - Geochimica et Cosmochimica Acta Y1 - 2011 A1 - Brucker, Rebecca Poulson A1 - McManus, James A1 - Severmann, Silke A1 - Owens, Jeremy A1 - Lyons, Timothy W. AB - We investigate the distributions of several key diagenetic reactants (C, S, Fe) and redox-sensitive trace metals (Mo, Cd, Re, U) in sediments from Lake Tanganyika, East Africa. This study includes modern sediments from a chemocline transect, which spans oxygenated shallow waters to sulfidic conditions at depth, as well as ancient sediments from a longer core (∼2 m) taken at ∼900 m water depth. Modern sediments from depths spanning ∼70–335 m are generally characterized by increasing enrichments of C, S, Mo, Cd, and U with increasing water depth but static Fe distributions. It appears that the sedimentary enrichments of these elements are, to varying degrees, influenced by a combination of organic carbon cycling and sulfur cycling. These modern lake characteristics contrast with a period of high total organic carbon (Corg), total sulfur (STot), and trace metal concentrations observed in the 900 m core, a period which follows the most recent deglaciation (∼18–11 ky). This interval is followed abruptly by an interval (∼11–6 ky) that is characterized by lower C, S, U, and Mo. Consistent with other work we suspect that the low concentrations of S, Mo, and U may indicate a period of intense lake mixing, during which time the lake may have been less productive and less reducing as compared to the present. An alternative, but not mutually exclusive, hypothesis is that changes in the lake’s chemical inventory, driven by significant hydrological changes, could be influencing the distribution of sedimentary trace elements through time. VL - 75 UR - http://www.sciencedirect.com/science/article/pii/S0016703710005739 IS - 2 N1 - id: 2144 JO - Trace metal enrichments in Lake Tanganyika sediments: Controls on trace metal burial in lacustrine systems ER - TY - JOUR T1 - U-series dating of co-seismic gypsum and submarine paleoseismology of active faults in Northern Chile (23°S) JF - Tectonophysics Y1 - 2011 A1 - Vargas, Gabriel A1 - Palacios, Carlos A1 - Reich, Martin A1 - Luo, Shangde A1 - Shen, Chuan-Chou A1 - González, Gabriel A1 - Wu, Yi-Chen AB - The convergence of the Nazca and South American plates along the subduction margin of the central Andes results in large subduction earthquakes and tectonic activity along major fault systems. Despite its relevance, the paleoseismic record of this region is scarce, hampering our understanding about the relationship between the Andes building and earthquake occurrence. In this study, we used the U-series disequilibrium method to obtain absolute ages of paleoearthquake events associated with normal displacements along the active Mejillones and Salar del Carmen faults in the Coastal Range of the Atacama Desert of northern Chile. The 230Th–234U disequilibrium ages in co-seismic gypsum salts sampled along the fault traces together with marine evidences indicate that earthquakes occurred at ca. 29.7 ± 1.7 ka, 11 ± 4 ka and 2.4 ± 0.8 ka. When coupled with paleoseismic marine and radiocarbon (14C) records in the nearby Mejillones Bay evidencing large dislocations along the Mejillones Fault, the geochronological dataset presented here is consistent with the notion that gypsum salts formed during large earthquakes as a result of co-seismic dilatancy pumping of saline waters along the major faults. Based on maximum observed cumulative vertical offsets in the studied faults, this phenomena could have occurred episodically at a rate in the order of 1:40 to 1:50 with respect to the very large subduction earthquakes during the latest Pleistocene–Holocene period. The results presented here reveal that the U-series disequilibrium method can be successfully applied to date the gypsum salts deposited along faults during seismic events, and therefore directly constrain the age of large paleoearthquakes in hyperarid and seismically active zones. VL - 497 UR - http://www.sciencedirect.com/science/article/pii/S0040195110004506 IS - 1–4 N1 - id: 2147 JO - U-series dating of co-seismic gypsum and submarine paleoseismology of active faults in Northern Chile (23°S) ER - TY - JOUR T1 - Using a macroalgal δ15N bioassay to detect cruise ship waste water effluent inputs JF - Marine pollution bulletin Y1 - 2011 A1 - James, Kaldy AB - Green macroalgae bioassays were used to determine if the δ15N signature of cruise ship waste water effluent (CSWWE) could be detected in a small harbor. Opportunistic green macroalgae (Ulva spp.) were collected, cultured under nutrient depleted conditions and characterized with regard to N content and δ15N. Samples of algae were used in controlled incubations to evaluate the direction of isotope shift from exposure to CSWWE. Algae samples exposed to CSWWE exhibited an increase of 1–2.5‰ in δ15N values indicating that the CSWWE had an enriched isotope signature. In contrast, algae samples exposed to field conditions exhibited a significant decrease in the observed δ15N indicating that a light N source was used. Isotopically light, riverine nitrogen derived from N2-fixing trees in the watershed may be a N source utilized by algae. These experiments indicate that the δ15N CSWWE signature was not detectable under the CSWWE loading conditions of this experiment. VL - 62 UR - http://www.sciencedirect.com/science/article/pii/S0025326X11002876 IS - 8 N1 - id: 2176 JO - Using a macroalgal δ15N bioassay to detect cruise ship waste water effluent inputs ER - TY - JOUR T1 - Weathering the storm: Coastal subsistence and ecological resilience on Late Holocene Santa Rosa Island, California JF - Shell Midden Research: An Interdisciplinary Agenda for the Quaternary and Social Sciences Y1 - 2011 A1 - Torben C, Rick AB - Archaeological research on California’s Channel Islands has significantly enhanced understanding of the diversity and variability of coastal hunter-gatherers and the shell middens these people left behind. On the Channel Islands, the Late Holocene was a time of substantial population growth, territoriality, and the emergence of social hierarchies. The role of marine and terrestrial climate change, population growth, human environmental impacts, and other variables in driving Late Holocene cultural and ecological developments is a subject of considerable debate. Analysis of faunal remains (especially finfish and shellfish), complemented by human skeletal and stable isotope analyses, from a massive shell midden and village complex (CA-SRI-2) on Santa Rosa Island provides insight into Late Holocene human responses to coastal resource stress and environmental change. Despite significant population growth, the emergence of social stratification, and increased pressure on local resources and ecosystems, these data demonstrate that there is significant continuity in the coastal resources Channel Island peoples exploited through time. These results document the long-term resilience and adaptability of coastal hunter-gatherers, the marine resources they harvested, and Channel Island ecosystems. VL - 239 UR - http://www.sciencedirect.com/science/article/pii/S1040618210002363 IS - 1–2 N1 - id: 2178 JO - Weathering the storm: Coastal subsistence and ecological resilience on Late Holocene Santa Rosa Island, California ER - TY - CONF T1 - Aeolian sand invasion in coastal regions: geomorphological and geophysical aspects T2 - Schukin Conference on Geomorphology Y1 - 2010 A1 - Buynevich, I. V. A1 - Souza Filho, P. W. M. A1 - Bitinas, A. A1 - Asp, N. E. A1 - Pupienis, D. JF - Schukin Conference on Geomorphology PB - Moscow State University N1 - id: 2128 ER - TY - JOUR T1 - Age and Growth Rate Dynamics of an Old African Baobab Determined by Radiocarbon Dating JF - Radiocarbon Y1 - 2010 A1 - Patrut, A. A1 - Mayne, D. H. A1 - von Reden, K. F. A1 - Lowy, D. A. A1 - Venter, S. A1 - McNichol, A. P. A1 - Roberts, M. L. A1 - Margineanu, D. KW - cal kyr bp KW - Calibration KW - southern-hemisphere AB - In 2008, a large African baobab (Adansonia digitata L.) from Makulu Makete, South Africa, split vertically into 2 sections, revealing a large enclosed cavity. Several wood samples collected from the cavity were processed and radiocarbon dated by accelerator mass spectrometry (AMS) for determining the age and growth rate dynamics of the tree. The C-14 date of the oldest sample was found to be of 1016 +/- 22 BP, which corresponds to a calibrated age of 1000 +/- 15 yr. Thus, the Makulu Makete tree, which eventually collapsed to the ground and died, becomes the second oldest African baobab dated accurately to at least 1000 yr. The conventional growth rate of the trunk, estimated by the radial increase, declined gradually over its life cycle. However, the growth rate expressed more adequately by the cross-sectional area increase and by the volume increase accelerated up to the age of 650 yr and remained almost constant over the past 450 yr. VL - 52 SN - 0033-8222 IS - 2 N1 - Sp. Iss. 1696jn Times Cited:2 Cited References Count:21 JO - Radiocarbon ER - TY - JOUR T1 - Aminostratigraphy of surface and subsurface Quaternary sediments, North Carolina coastal plain, USA JF - Quaternary Geochronology Y1 - 2010 A1 - Wehmiller, J. F. A1 - Thieler, E. R. A1 - Miller, D. A1 - Pellerito, V. A1 - Keeney, V. B. A1 - Riggs, S. R. A1 - Culver, S. A1 - Mallinson, D. A1 - Farrell, K. M. A1 - York, L. L. A1 - Pierson, J. A1 - Parham, P. R. AB - The Quaternary stratigraphy and geochronology of the Albemarle Embayment of the North Carolina (NC) Coastal Plain is examined using amino acid racemization (AAR) in marine mollusks, in combination with geophysical, lithologic, and biostratigraphic analysis of 28 rotasonic cores drilled between 2002 and 2006. The Albemarle Embayment is bounded by structural highs to the north and south, and Quaternary strata thin westward toward the Suffolk paleoshoreline, frequently referred to as the Suffolk Scarp. The Quaternary section is up to similar to 90 m thick, consists of a variety of estuarine, shelf, back-barrier, and lagoonal deposits, and has been influenced by multiple sea-level cycles. The temporal resolution of the amino acid racemization method is tested statistically and with the stratigraphic control provided by this geologic framework, and it is then applied to the correlation and age estimation of subsurface units throughout the region. Over 500 specimens (primarily Mercenaria and Mulinia) from the subsurface section have been analyzed using either gas chromatographic (GC) or reverse-phase liquid chromatographic (RPLC) techniques. The subsurface stratigraphic data are compared with AAR results from numerous natural or excavated exposures from the surrounding region, as well as results from NC beach collections, to develop a comprehensive aminostratigraphic database for the entire Quaternary record within the NC coastal system. Age mixing, recognized in the beach collections, is also seen in subsurface sections, usually where major seismic reflections or core lithology indicate the presence of stratigraphic discontinuities. Kinetic models for racemization are tested within the regional stratigraphic framework, using either radiocarbon or U-series calibrations or comparison with regional biostratigraphy. Three major Pleistocene aminozones [AZ2, AZ3, and AZ4] are found throughout the region, all being found in superposition in several cores. Each can be subdivided, yielding a total of at least eight stratigraphically and statistically distinct aminozones. Kinetic modeling, supplemented with local calibration, indicates that these aminozones represent depositional events ranging from similar to 80 ka to nearly 2 Ma. Three prominent seismic reflections are interpreted to represent the base of the early, middle, and late Pleistocene, respectively, roughly 2 Ma, 800 ka, and 130 ka. The large number of samples and the available stratigraphic control provide new insights into the capabilities and limitations of aminostratigraphic methods in assessing relative and numerical ages of Atlantic Coastal Plain Quaternary deposits. (C) 2009 Elsevier B.V. All rights reserved. VL - 5 IS - 4 N1 - 639btTimes Cited:19Cited References Count:82 JO - Aminostratigraphy of surface and subsurface Quaternary sediments, North Carolina coastal plain, USA ER - TY - JOUR T1 - Ams Radiocarbon Dates from Pleistocene and Holocene Mammals Housed in the New York State Museum, Albany, New York, USA JF - Radiocarbon Y1 - 2010 A1 - Feranec, R. S. A1 - Kozlowski, A. L. VL - 52 SN - 0033-8222 IS - 1 N1 - 586yoTimes Cited:5 Cited References Count:11 JO - Radiocarbon ER - TY - JOUR T1 - Application of bacterial glycerol dialkyl glycerol tetraethers (GDGTs) to develop modern and past temperature estimates from New Zealand lakes JF - Organic Geochemistry Y1 - 2010 A1 - Zink, Klaus- G. A1 - Vandergoes, Marcus J. A1 - Mangelsdorf, Kai A1 - Dieffenbacher-Krall, Ann C. A1 - Schwark, Lorenz AB - Branched isoalkyl glycerol dialkyl glycerol tetraethers (GDGTs) of bacterial origin have been found in high abundance in both modern and glacial sediments of New Zealand South Island freshwater lakes covering a wide range of altitude (101-2000 m). Like isoprenoid GDGTs of archaeal origin, they provide excellent potential for temperature assessment. For this study, their distribution patterns (MBT, methylation ratio and CBT, cyclisation ratio of branched GDGTs) have been successfully used to develop an initial temperature calibration for the study area and to provide preliminary (palaeo)environmental interpretations. MBT data from modern lake sediments correlate well with measured annual air temperature (R(2) 0 74), enabling a regional calibration for reconstructing palaeotemperatures for fossil samples. MBT-derived palaeotemperatures for Alpine Lake, calibrated against mean annual temperature, were determined for the Last Glacial during an early cold phase (between 29,000 and 26,000 years BP) and for later less cold phases (between 23,000 and 18,000 years BP). Compared with the modern temperature regime, the MBT data indicate a decrease of ca 56 and 2 8 degrees C respectively, during this time Modern and past MBT-derived temperatures correlate with chironomid-based temperature reconstructions in the area Archaeal GDGTs, commonly used for the TEX(86) index, are abundant in fossil sediments (Alpine Lake) but scarce in modern sediments, hindering a new local calibration for this palaeotemperature proxy. (C) 2010 Elsevier Ltd All rights reserved VL - 41 IS - 9 N1 - id: 1955; PT: J; CT: 24th International Meeting on Organic Geochemistry; CY: SEP 06-11, 2009; CL: Bremen, GERMANY; UT: WOS:000282671500040 JO - Application of bacterial glycerol dialkyl glycerol tetraethers (GDGTs) to develop modern and past temperature estimates from New Zealand lakes ER - TY - JOUR T1 - The application of intertidal foraminifera to reconstruct coastal subsidence during the giant Cascadia earthquake of AD 1700 in Oregon, USA JF - Quaternary International Y1 - 2010 A1 - Hawkes, A. D. A1 - Horton, B. P. A1 - Nelson, A. R. A1 - Hill, D. F. AB - Changes in species assemblages of intertidal foraminifera can be used to estimate the amount of earthquake-related subsidence during plate-boundary earthquakes at the Cascadia subduction zone. The accuracy and precision of foraminiferal methods in paleoenvironmental reconstruction is underpinned by the relations between contemporary taxa and their environment, which are used to calibrate fossil foraminiferal assemblages in sediment sequences. A contemporary training set of surface sediment samples from five intertidal marshes along the Oregon coast was used to determine foraminiferal distributions and prevailing environmental control(s) along elevational transects. Dominant taxa include Balticammina pseudomacrescens, Trochamminita irregularis, Haplophragmoides wilberti, Trochammina inflata, Jadammina macrescens and Miliammina fusca. Unconstrained cluster analysis and detrended correspondence analysis was used to identify two elevation-dependent faunal zones: Faunal Zone I (upland, high marsh, middle marsh) dominated by Balticammina pseudomacrescens, Haplophragmoides wilberti and Trochammina inflata, and Faunal Zone II (low marsh and tidal flat) dominated by Miliammina fusca. Site-specific differences in assemblages at three marshes enabled further subdivision of Faunal Zone I. Zone la is based on one or more of Balticammina pseudomacrescens, Trochammina inflata, Trochamminita irregularis and Haplophragrnoides sp., and Zone Ib on Jadammina macrescens, Haplophragmoides sp., Trochammina inflata and Miliammina fusca. Canonical correspondence analysis (CCA) and partial CCA of the training set from the Nehalem River marsh transect was used to infer that the zonation of foraminifera is elevation-dependent (39% of explained variance). A transfer function was developed to reconstruct sudden changes in relative sea-level during plate-boundary earthquakes in Oregon. The results indicate a robust performance of the transfer function (r(jack)(2) = 0.82) with the error estimate (RMSEP(jack) = 0.20 m) comparable to local and regional transfer functions from other temperate marshes. To illustrate the potential of the technique, the transfer function was applied to reconstruct subsidence during the AD 1700 earthquake using at Alsea Bay, Oregon. The reconstruction (0.18 +/- 0.20 m) is less than half the subsidence estimate of Nelson et al. [2008. Great-earthquake palogeoesy and tsunamis of the past 2000 years at Alsea Bay, central Oregon coast, USA. Quaternary Science Reviews, 27, 747-768] using their foraminiferal transfer function, perhaps because of differences in taxonomy and the species relationship to elevation. (C) 2009 Elsevier Ltd and INQUA. All rights reserved. VL - 221 IS - 1-2 N1 - id: 1981; PT: J; UT: WOS:000279551800012 JO - The application of intertidal foraminifera to reconstruct coastal subsidence during the giant Cascadia earthquake of AD 1700 in Oregon, USA ER - TY - JOUR T1 - Asphalt volcanoes as a potential source of methane to late Pleistocene coastal waters JF - Nature Geoscience Y1 - 2010 A1 - Valentine, D. L. A1 - Reddy, C. M. A1 - Farwell, C. A1 - Hill, T. M. A1 - Pizarro, O. A1 - Yoerger, D. R. A1 - Camilli, R. A1 - Nelson, R. K. A1 - Peacock, E. E. A1 - Bagby, S. C. A1 - Clarke, B. A. A1 - Roman, C. N. A1 - Soloway, M. AB - Every year, natural petroleum seepage emits 0.2-2 Tg of oil to the ocean(1). Significant oil seepage can build large underwater mounds, consisting of tar deposits with morphologies similar to volcanic lava flows, known as asphalt volcanoes(2,3). Such events are typically accompanied by large fluxes of the greenhouse gas methane(4,5). Marine sediments from the Santa Barbara basin, California, contain a record of elevated methane concentrations(6), anoxia and tar deposition(7) during the Pleistocene epoch that had been attributed to dissolution of methane hydrates. However, the region is known to have exhibited oil seepage in the past(7). Here, we document the discovery of seven extinct asphalt volcanoes off the coast of southern California. The morphology of the deposits and geochemistry of samples taken from the two largest structures supports their classification as asphalt volcanoes, derived from a common source. We estimate that the two structures resulted from seepage of 0.07-0.4 Tg of oil, accompanied by the emission of 0.35-1.8 Tg of methane. Radiocarbon dating of carbonate deposits entrained with the asphalt indicates formation of the volcanoes between 44 and 31 kyr ago. The timing and volume of erupted hydrocarbons from the asphalt structures can explain some or all of the documented methane release and tar accumulation in the Santa Barbara basin during the Pleistocene. VL - 3 IS - 5 N1 - id: 1866; Sp. Iss. SI 589XW Times Cited:0 Cited References Count:28; YY JO - Asphalt volcanoes as a potential source of methane to late Pleistocene coastal waters ER - TY - JOUR T1 - Assessing Microbial Uptake of Petroleum Hydrocarbons in Groundwater Systems Using Natural Abundance Radiocarbon JF - ENVIRONMENTAL SCIENCE & TECHNOLOGY Y1 - 2010 A1 - Ahad, Jason M. E. A1 - Burns, Leanne A1 - Mancini, Silvia A1 - Slater, Greg F. AB - Carbon sources utilized by the active microbial communities in shallow groundwater systems underlying three petroleum service stations were characterized using natural abundance radiocarbon ((14)C). Total organic carbon (TOC) Delta(14)C values ranged from -314 to -972 parts per thousand and petroleum-extracted residues (EXT-RES) ranged from -293 to -971 parts per thousand. Phospholipid fatty acids (PLFAs)-biomarkers for active microbial populations-ranged from -405 to -885 parts per thousand and a comparison of these values with potential carbon sources pointed to significant microbial assimilation of (14)C-free fossil carbon. The most (14)C depleted PLFAs were found in the samples with the highest concentrations of total petroleum hydrocarbons (TPHs). A radiocarbon mass balance indicated up to 43% of the carbon in microbial PLFAs was derived from TPHs, providing direct evidence for biodegradation at two of three sites. At lower levels of TPHs. Delta(14)C values of PLFAs were generally similar to or more enriched than all other carbon in the system indicating microbial utilization of a more (14)C-enriched carbon source and no resolvable evidence for microbial incorporation of petroleum-derived carbon. Results from this study suggest that it is possible to delineate petroleum biodegradation in groundwater systems using these techniques even in complex situations where there exists a wide range in the ages of natural organic matter (i.e., EXT-RES). VL - 44 ER - TY - JOUR T1 - Calibrating a sedimentary record of overwash from Southeastern New England using modeled historic hurricane surges JF - Marine Geology Y1 - 2010 A1 - Boldt, Katherine V. A1 - Lane, Philip A1 - Woodruff, Jonathan D. A1 - Donnelly, Jeffrey P. KW - Holocene KW - hurricane KW - Paleotempestology KW - Salt marsh KW - storm surge KW - tropical cyclone AB - We present a 2000-year record of overwash deposits preserved in a backbarrier salt marsh from southeastern New England. The timing of recent deposits matches well with large hurricane-induced storm surge events documented by local tide gauges in 1991, 1960, 1954, and 1938. Storm surge modeling is used to evaluate the flooding history at the site as well as to assess the pre-instrumental historical record. Storms in 1815, 1727, and 1635 likely caused significant surge that overtopped the barrier, with the timing of coarse-grained overwash deposition correlating well with these events. We infer that twenty-three prehistoric layers mapped across the site were likely also deposited by landfalling hurricanes. Additional records from the area will help to evaluate whether or not temporal trends at the site are a robust representation of hurricane activity for the region. The frequency of overwash at Mattapoisett Marsh, on average 1.5 events per century, is significantly higher than many other overwash-based reconstructions from the western North Atlantic. Further, the Mattapoisett Marsh record does not contain significant multi-centennial gaps in overwash layers. This initial comparison of the data from Mattapoisett marsh with other reconstructions from the western North Atlantic may point toward relatively constant tropical cyclone frequency over the last 2000 years with significant variation in the number of intense tropical cyclones. VL - 275 UR - http://linkinghub.elsevier.com/retrieve/pii/S0025322710001702http://api.elsevier.com/content/article/PII:S0025322710001702?httpAccept=text/xmlhttp://api.elsevier.com/content/article/PII:S0025322710001702?httpAccept=text/plain IS - 1-4 ER - TY - CONF T1 - A Champlain Sea phocid seal fossil from the Champlain Lowland at Plattsburgh, New York Y1 - 2010 A1 - Franzi, David A. A1 - Feranec, Robert A1 - Rayburn, John A. KW - 11 KW - 24 KW - bones KW - Carnivora KW - Cenozoic KW - Champlain Lowland KW - Champlain Sea KW - Chordata KW - Clinton County New York KW - Eutheria KW - lacustrine environment KW - Lake Champlain KW - lake sediments KW - Mammalia KW - New York KW - North America KW - Phoca KW - Phocidae KW - Pinnipedia KW - planar bedding structures KW - Plattsburgh New York KW - Pleistocene KW - Quaternary KW - Quaternary geology KW - rhythmite KW - sedimentary structures KW - sediments KW - taphonomy KW - Tetrapoda KW - Theria KW - United States KW - upper Pleistocene KW - upper Wisconsinan KW - Vertebrata KW - Vertebrate paleontology KW - Wisconsinan AB - A SUNY Plattsburgh environmental geotechnology class uncovered several bones, most likely from a harbor seal (Phoca vitulina), from exposures of Champlain Sea mud at the former Plattsburgh Air Force Base marina. The glacial section at the site contains a complete record of late Wisconsinan deglaciation in the Champlain lowland. A 1.5 to 2.0 meter thick section of fresh water ostracode (Candona subtriangulata) bearing, thinly laminated proglacial lacustrine rhythmites overlie massive gray diamicton near the base of the section. The lacustrine rhythmites contain a 0.0 to 0.2 meter thick layer of medium sand that may record one or more breakout floods from the Ontario and St. Lawrence lowlands. The lacustrine rhythmites grade upward to thinly laminated transitional rhythmites that contain marine and fresh water microfaunal assemblages. Approximately 1.5 to 2.0 meters of thinly laminated to massive, fossiliferous marine mud overlies the transitional facies, which in turn grades upward to an approximately 7-meter thick section of horizontally bedded silt and sand. The seal bones came from massive marine mud just below the transition to silt and sand. The accidental fossil find occurred as the class collected mud samples for a slope stability analysis of the bluffs along the present shoreline of Lake Champlain. The collection consists of the tibia and fibula from both legs, four vertebrae, four ribs, an astragalus, a tarsal bone, a phalange, a molar and half of the mandible with a canine tooth attached. Collagen extracted from a piece of fibula has been sent to the National Ocean Sciences Accelerator Mass Spectrometry Facility (NOSAMS) for radiocarbon dating. The find represents the second phocid fossil recovered from the Champlain lowland. The left tibial shaft from another harbor seal, originally misidentified as a hooded seal (Cystophora cristata), was found in Plattsburgh in 1901. Harbor seals on the east coast of North America presently range from the mid-Atlantic region to the Canadian Arctic. PB - Geological Society of America (GSA), Boulder, CO, United States (USA) CY - United States (USA) VL - 42 N1 - id: 2214; Source type: conferencepapers&proceedings; Object type: Article; Object type: Conference Paper; Copyright: GeoRef, Copyright 2010, American Geological Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States; CSAUnique: 2010-092590; AccNum: 2010-092590; ISSN: 0016-7592; CODEN: GAAPBC ER - TY - JOUR T1 - Climatic controls of interannual variability in regional carbon fluxes from top-down and bottom-up perspectives RID B-8211-2009 JF - Journal of Geophysical Research-Biogeosciences Y1 - 2010 A1 - Desai, Ankur R. A1 - Helliker, Brent R. A1 - Moorcroft, Paul R. A1 - Andrews, Arlyn E. A1 - Berry, Joseph A. AB - Observations of regional net ecosystem exchange (NEE) of CO(2) for 1997-2007 were analyzed for climatic controls on interannual variability (IAV). Quantifying IAV of regional (10(4)-10(6) km(2)) NEE over long time periods is key to understanding potential feedbacks between climate and the carbon cycle. Four independent techniques estimated monthly regional NEE for 10(4) km(2) in a spatially heterogeneous temperate-boreal transition region of the north central United States, centered on the Park Falls, Wisconsin, United States, National Oceanic and Atmospheric Administration tall tower site. These techniques included two bottom-up methods, based on flux tower upscaling and forest inventory based demographic modeling, respectively, and two top-down methods, based on tall tower equilibrium boundary layer budgets and tracer-transport inversion, respectively. While all four methods revealed a moderate carbon sink, they diverged significantly in magnitude. Coherence of relative magnitude and variability of NEE anomalies was strong across the methods. The strongest coherence was a trend of declining carbon sink since 2002. Most climatic controls were not strongly correlated with IAV. Significant controls on IAV were those related to hydrology, such as water table depth, and atmospheric CO(2). Weaker relationships were found with phenological controls such as autumn soil temperature. Hydrologic relationships were strongest with a 1 year lag, potentially highlighting a previously unrecognized predictor of IAV in this region. These results highlight a need for continued development of techniques to estimate regional IAV and incorporation of hydrologic cycling into couple carbon-climate models. VL - 115 N1 - id: 1941; PT: J; UT: WOS:000277259700003 JO - Climatic controls of interannual variability in regional carbon fluxes from top-down and bottom-up perspectives RID B-8211-2009 ER - TY - JOUR T1 - Coastal New England pilot study to determine fossil and biogenic formaldehyde source contributions using radiocarbon JF - JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES Y1 - 2010 A1 - Shen, Haiwei A1 - Heikes, Brian G. A1 - Merrill, John T. A1 - McNichol, Ann P. A1 - Xu, Li AB - Compound specific radiocarbon analyses of atmospheric formaldehyde are reported as fraction modern (Fm) for a limited number of winter and summer air samples collected in coastal southern New England in 2007. The 11 of 13 samples with Fm < 0.2 were collected under the influence of the semipermanent Bermuda high-pressure system with transport from the Washington, D. C., to New York City urban corridor. The two samples with Fm > 0.2 (max similar to 0.35) were collected on days with strong northwesterly flow and the least urban impact. The Fm data were combined with VOC observations from the Rhode Island Department of Environmental Management, estimates of oxygenated VOC (OVOC), and back trajectories to interpret the relative contributions of biogenic and fossil carbon sources. It is argued that CH2O sources were dominated by pollutant VOCs and OVOCs from upwind coastal cities as opposed to more local biogenic VOCs at the times of sample collection. VL - 115 ER - TY - JOUR T1 - Comparative AMS radiocarbon dating of pretreated versus non-pretreated tropical wood samples JF - Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions with Materials and Atoms Y1 - 2010 A1 - Patrut, Adrian A1 - von Reden, Karl F. A1 - Lowy, Daniel A. A1 - Mayne, Diana H. A1 - Elder, Kathryn E. A1 - Roberts, Mark L. A1 - McNichol, Ann P. AB - Several wood samples collected from Dorslandboom, a large iconic African baobab (Adansonia digitata L.) from Namibia, were investigated by AMS radiocarbon dating subsequent to pretreatment and, alternatively, without pretreatment. The comparative statistical evaluation of results showed that there were no significant differences between fraction modern values and radiocarbon dates of the samples analyzed after pretreatment and without pretreatment, respectively. The radiocarbon date of the oldest sample was 993 +/- 20 BP. Dating results also revealed that Dorslandboom is a multi-generation tree, with several stems showing different ages. (C) 2009 Elsevier B.V. All rights reserved. VL - 268 IS - 7-8 N1 - id: 2083; PT: J; CT: 11th International Conference on Accelerator Mass Spectrometry; CY: SEP 14-19, 2008; CL: Rome, ITALY; SP: Univ Salento, CEDAD, Second Univ Naples, CIRCE, INNOVA, Ist Nazl Fis Nucl, LABEC, Abdus Salam Int Ctr Theoret Phys; UT: WOS:000277462300058 JO - Comparative AMS radiocarbon dating of pretreated versus non-pretreated tropical wood samples ER - TY - JOUR T1 - Constant Holocene Southern-Ocean 14C reservoir ages and ice-shelf flow rates Y1 - 2010 A1 - Hall, Brenda L. A1 - Henderson, Gideon M. A1 - Baroni, Carlo A1 - Kellogg, Thomas B. KW - coral KW - marine reservoir effect KW - McMurdo Ice Shelf KW - radiocarbon KW - Southern Ocean KW - U/Th dating AB - Southern Ocean radiocarbon reservoir ages (i.e. non-zero radiocarbon ages in seawater) are the highest in the world's surface ocean. Constraining these reservoir ages at present and in the past is important not only because unknown reservoir ages limit the interpretation of Antarctic radiocarbon chronologies, but also because reservoir ages provide information about ocean circulation (as a recorder of past circulation and as an end member for major deep-water masses in today's ocean). In this study, we use paired U/Th and 14C ages of an unusual set of solitary coral samples trapped by fringing ice shelves in the Ross Sea to provide the first detailed study of Holocene reservoir ages for the Southern Ocean. Our results indicate a relatively constant marine radiocarbon reservoir age of 1144 ± 120 years for the past 6000 years. These results are consistent with extrapolation of the relationship between 14C and alkalinity seen elsewhere, supporting the use of this empirical relationship in high latitudes. The results also suggest constant deep-ocean circulation and air–sea exchange during the Holocene and provide a good target for tuning ocean models of modern circulation. Combining the new ages for corals with their distance from the modern-day ice-shelf grounding line provides some of the first long-term records of ice-shelf velocities for any region and indicates constant flow of the McMurdo Ice Shelf during the Holocene, at a rate similar to that observed today. VL - 296 SN - 0012-821X UR - http://www.sciencedirect.com/science/article/pii/S0012821X10003067 IS - 1–2 ER - TY - JOUR T1 - Constant Holocene Southern-Ocean C-14 reservoir ages and ice-shelf flow rates JF - EARTH AND PLANETARY SCIENCE LETTERS Y1 - 2010 A1 - Hall, Brenda L. A1 - Henderson, Gideon M. A1 - Baroni, Carlo A1 - Kellogg, Thomas B. KW - coral KW - marine reservoir effect KW - McMurdo Ice Shelf KW - radiocarbon KW - Southern Ocean KW - U/Th dating AB - Southern Ocean radiocarbon reservoir ages (i.e. non-zero radiocarbon ages in seawater) are the highest in the world's surface ocean. Constraining these reservoir ages at present and in the past is important not only because unknown reservoir ages limit the interpretation of Antarctic radiocarbon chronologies, but also because reservoir ages provide information about ocean circulation (as a recorder of past circulation and as an end member for major deep-water masses in today's ocean). In this study, we use paired U/Th and C-14 ages of an unusual set of solitary coral samples trapped by fringing ice shelves in the Ross Sea to provide the first detailed study of Holocene reservoir ages for the Southern Ocean. Our results indicate a relatively constant marine radiocarbon reservoir age of 1144 +/- 120 years for the past 6000 years. These results are consistent with extrapolation of the relationship between C-14 and alkalinity seen elsewhere, supporting the use of this empirical relationship in high latitudes. The results also suggest constant deep-ocean circulation and air-sea exchange during the Holocene and provide a good target for tuning ocean models of modern circulation. Combining the new ages for corals with their distance from the modern-day ice-shelf grounding line provides some of the first long-term records of ice-shelf velocities for any region and indicates constant flow of the McMurdo Ice Shelf during the Holocene, at a rate similar to that observed today. (C) 2010 Elsevier B.V. All rights reserved. VL - 296 ER - TY - JOUR T1 - A Continuous-Flow Gas Chromatography C-14 Accelerator Mass Spectrometry System JF - Radiocarbon Y1 - 2010 A1 - McIntyre, C. P. A1 - Galutschek, E. A1 - Roberts, M. L. A1 - von Reden, K. F. A1 - McNichol, A. P. A1 - Jenkins, W. J. KW - ams system KW - gc-ams KW - negative-ion source KW - RADIOCARBON ANALYSIS AB - Gas-accepting ion sources for radiocarbon accelerator mass spectrometry (AMS) have permitted the direct analysis of CO2 gas, eliminating the need to graphitize samples. As a result, a variety of analytical instruments can be interfaced to an AMS system, processing time is decreased, and smaller samples can be analyzed (albeit with lower precision). We have coupled a gas chromatograph to a compact C-14 AMS system fitted with a microwave ion source for real-time compound-specific C-14 analysis. As an initial test of the system, we have analyzed a sample of fatty acid methyl esters and biodiesel. Peak shape and memory was better then existing systems fitted with a hybrid ion source while precision was comparable. C-14/C-12 ratios of individual components at natural abundance levels were consistent with those determined by conventional methods. Continuing refinements to the ion source are expected to improve the performance and scope of the instrument. VL - 52 SN - 0033-8222 IS - 2 N1 - Sp. Iss. 1696jn Times Cited:4 Cited References Count:24 JO - Radiocarbon ER - TY - JOUR T1 - Contrasting multiproxy reconstructions of surface ocean hydrography in the Agulhas Corridor and implications for the Agulhas Leakage during the last 345,000 years JF - PALEOCEANOGRAPHY Y1 - 2010 A1 - Martinez-Mendez, Gema A1 - Zahn, Rainer A1 - Hall, Ian R. A1 - Peeters, Frank J. C. A1 - Pena, Leopoldo D. A1 - Cacho, Isabel A1 - Negre, Cesar AB - Planktonic delta(18)O and Mg/Ca-derived sea surface temperature (SST) records from the Agulhas Corridor off South Africa display a progressive increase of SST during glacial periods of the last three climatic cycles. The SST increases of up to 4 degrees C coincide with increased abundance of subtropical planktonic foraminiferal marker species which indicates a progressive warming due to an increased influence of subtropical waters at the core sites. Mg/Ca-derived SST maximizes during glacial maxima and glacial Terminations to values about 2.5 degrees C above full-interglacial SST. The paired planktonic delta(18)O and Mg/Ca-derived SST records yield glacial seawater delta(18)O anomalies of up to 0.8%, indicating measurably higher surface salinities during these periods. The SST pattern along our record is markedly different from a U(37)(K')-derived SST record at a nearby core location in the Agulhas Corridor that displays SST maxima only during glacial Terminations. Possible explanations are lateral alkenone advection by the vigorous regional ocean currents or the development of SST contrasts during glacials in association with seasonal changes of Agulhas water transports and lateral shifts of the Agulhas retroflection. The different SST reconstructions derived from U(37)(K') and Mg/Ca pose a significant challenge to the interpretation of the proxy records and demonstrate that the reconstruction of the Agulhas Current and interocean salt leakage is not as straightforward as previously suggested. VL - 25 ER - TY - JOUR T1 - Controls on the age of terrigenous organic matter in Black Sea sediments JF - Geochimica et Cosmochimica Acta Y1 - 2010 A1 - Kusch, Stephanie A1 - Rethemeyer, Janet A1 - Schefuß, Enno A1 - Mollenhauer, Gesine N1 - id: 885 ER - TY - JOUR T1 - Coordinated hydrological regimes in the Indo-Pacific region during the past two millennia JF - Paleoceanography Y1 - 2010 A1 - Tierney, J. E. A1 - Oppo, D. W. A1 - Rosenthal, Y. A1 - Russell, J. M. A1 - Linsley, B. K. AB - Instrumental data suggest that major shifts in tropical Pacific atmospheric dynamics and hydrology have occurred within the past century, potentially in response to anthropogenic warming. To better understand these trends, we use the hydrogen isotopic ratios of terrestrial higher plant leaf waxes ( delta D-wax) in marine sediments from southwest Sulawesi, Indonesia, to compile a detailed reconstruction of central Indo-Pacific Warm Pool (IPWP) hydrologic variability spanning most of the last two millennia. Our paleodata are highly correlated with a monsoon reconstruction from Southeast Asia, indicating that intervals of strong East Asian summer monsoon (EASM) activity are associated with a weaker Indonesian monsoon (IM). Furthermore, the centennial-scale oscillations in our data follow known changes in Northern Hemisphere climate ( e. g., the Little Ice Age and Medieval Warm Period) implying a dynamic link between Northern Hemisphere temperatures and IPWP hydrology. The inverse relationship between the EASM and IM suggests that migrations of the Intertropical Convergence Zone and associated changes in monsoon strength caused synoptic hydrologic shifts in the IPWP throughout most of the past two millennia. VL - 25 N1 - id: 795; 565UW Times Cited:0 Cited References Count:42Y JO - Coordinated hydrological regimes in the Indo-Pacific region during the past two millennia ER - TY - JOUR T1 - Deep-sea faunal provinces and their inferred environments in the Indian Ocean based on distribution of Recent benthic foraminifera JF - Palaeogeography Palaeoclimatology Palaeoecology Y1 - 2010 A1 - De, Soma A1 - Gupta, Anil K. AB - Multivariate analysis was performed on percentages of 46 species of unstained deep-sea benthic foraminifera from 131 core-top to near-core-top samples (322-5013 m) from across the Indian Ocean. Faunal data are combined with GEOSECS geochemical data to investigate any relationship between benthic foraminifera (assemblages and species) and deep-sea properties. In general, benthic foraminifera show a good correlation to surface productivity, organic carbon flux to the sea floor, deep-sea oxygenation and, to a lesser extent, to bottom temperature, without correlation with the water depths. The foraminiferal census data combined with geochemical data has enabled the division of the Indian Ocean into two faunal provinces. Province A occupies the northwestern Indian Ocean (Arabian Sea region) where surface primary production has a major maximum during the summer monsoon season and a secondary maximum during winter monsoon season that leads to high organic flux to the seafloor, making the deep-sea one of the most oxygen-deficient regions in the world ocean, with a pronounced oxygen minimum zone (OMZ). This province is dominated by benthic foraminifera characteristic of low oxygen and high organic food flux including Uvigerina peregrina, Robulus nicobarensis, Bolivinita pseudopunctata, Bolivinita sp., Bulimina aculeata, Bulimina alazanensis, Ehrenbergina carinata and Cassidulina carinata. Province B covers southern, southeastern and eastern parts of the Indian Ocean and is dominated by Nuttallides umbonifera, Epistominella exigua, Globocassidulina subglobosa, Uvigerina proboscidea, Cibicides wuellerstorfi, Cassidulina laevigata, Pullenia bulloides, Pullenia osloensis, Pyrgo murrhina, Oridorsalis umbonatus, Gyroidinoides (=Gyroidina) soldanii and Gyroidinoides cf. gemma suggesting well-oxygenated, cold deep water with low (oligotrophic) and pulsed food supply. (C) 2010 Elsevier B.V. All rights reserved. VL - 291 IS - 3-4 N1 - id: 1967; PT: J; UT: WOS:000278782400021 JO - Deep-sea faunal provinces and their inferred environments in the Indian Ocean based on distribution of Recent benthic foraminifera ER - TY - JOUR T1 - Deepwater Formation in the North Pacific During the Last Glacial Termination JF - Science Y1 - 2010 A1 - Okazaki, Y. A1 - Timmermann, A. A1 - Menviel, L. A1 - Harada, N. A1 - Abe-Ouchi, A. A1 - Chikamoto, M. O. A1 - Mouchet, A. A1 - Asahi, H. AB - Between ~17,500 and 15,000 years ago, the Atlantic meridional overturning circulation weakened substantially in response to meltwater discharges from disintegrating Northern Hemispheric glacial ice sheets. The global effects of this reorganization of poleward heat flow in the North Atlantic extended to Antarctica and the North Pacific. Here we present evidence from North Pacific paleo surface proxy data, a compilation of marine radiocarbon age ventilation records, and global climate model simulations to suggest that during the early stages of the Last Glacial Termination, deep water extending to a depth of ~2500 to 3000 meters was formed in the North Pacific. A switch of deepwater formation between the North Atlantic and the North Pacific played a key role in regulating poleward oceanic heat transport during the Last Glacial Termination. VL - 329 UR - http://www.sciencemag.org/cgi/doi/10.1126/science.1190612 IS - 5988 ER - TY - JOUR T1 - Determination of Microbial Carbon Sources and Cycling during Remediation of Petroleum Hydrocarbon Impacted Soil Using Natural Abundance (14)C Analysis of PLFA JF - Environmental science & technology Y1 - 2010 A1 - Cowie, Benjamin R. A1 - Greenberg, Bruce M. A1 - Slater, Gregory F. AB - In a petroleum impacted land-farm soil in Sarnia, Ontario, compound-specific natural abundance radiocarbon analysis identified biodegradation by the soil microbial community as a major pathway for hydrocarbon removal in a novel remediation system. During remediation of contaminated soils by a plant growth promoting rhizobacteria enhanced phytoremediation system (PEPS), the measured Delta(14)C of phospholipid fatty acid (PLEA) biomarkers ranged from -793 parts per thousand to -897 parts per thousand, directly demonstrating microbial uptake and utilization of petroleum hydrocarbons (Delta(14)C(PHC) = -1000 parts per thousand). Isotopic mass balance indicated that more than 80% of microbial PLEA carbon was derived from petroleum hydrocarbons (PHC) and a maximum of 20% was obtained from metabolism of more modern carbon sources. These PLFA from the contaminated soils were the most (14)C-depleted biomarkers ever measured for an in situ environmental system, and this study demonstrated that the microbial community in this soil was subsisting primarily on petroleum hydrocarbons. In contrast, the microbial community in a nearby uncontaminated control soil maintained a more modern. Delta(14)C signature than total organic carbon (Delta(14)C(PLFA) = +36 parts per thousand to -147 parts per thousand, Delta(14)C(TOC) = -148 parts per thousand), indicating preferential consumption of the most modern plant-derived fraction of soil organic carbon. Measurements of delta(13)C and Delta(14)C of soil CO(2) additionally demonstrated that mineralization of PHC contributed to soil CO(2) at the contaminated site. The CO(2) in the uncontaminated control soil exhibited substantially more modern Delta(14)C values, and lower soil CO(2) concentrations than the contaminated soils, suggesting increased rates of soil respiration in the contaminated soils. In combination, these results demonstrated that biodegradation in the soil microbial community was a primary pathway of petroleum hydrocarbon removal in the PEPS system. This study highlights the power of natural abundance radiocarbon for determining microbial carbon sources and identifying biodegradation pathways in complex remediation systems. VL - 44 IS - 7 N1 - id: 2054; PT: J; UT: WOS:000275993700017 JO - Determination of Microbial Carbon Sources and Cycling during Remediation of Petroleum Hydrocarbon Impacted Soil Using Natural Abundance (14)C Analysis of PLFA ER - TY - JOUR T1 - Determination of rare earth, major and trace elements in authigenic fraction of Andaman Sea (Northeastern Indian Ocean) sediments by Inductively Coupled Plasma-Mass Spectrometry JF - Microchemical Journal Y1 - 2010 A1 - Alagarsamy, R. A1 - You, C. F. A1 - Nath, B. N. A1 - Kumar, A. V. S. AB - Downcore variation of rare earth elements (REEs) in the authigenic Fe-Mn oxides of a sediment core (covering a record of last similar to 40 kyr) from the Andaman Sea, a part of the Indian Ocean shows distinctive positive Ce and Eu anomalies. These positive Ce anomalies (Ce* = 1.1 similar to 1.8) are ascribed to be due to oxidation of deep sea sediments. The large positive Eu anomalies (i.e., Eu* > 1.8 to 3.2) occur within a time span near the glacial/interglacial transition (similar to 7000-14,000yr BP) which could be due to the past hydrothermal activity or to the effects arising from sea level changes. During glacial times, the Andaman Sea was almost completely isolated due to low sea level, leading to a reduction in sediment supply from the Ayeyarwady River. The variations of metal abundances (i.e., Ca, Al, Mn, and Fe) in the authigenic fraction provided independent information to evaluate the water column physicochemical changes during the glacial/interglacial transition period. The studied sediment core records changes in riverine inputs and reflects depositional changes related to sea level fluctuations and climatic events over the past 40 kyr in the Andaman Sea. (C) 2009 Elsevier B.V. All rights reserved. VL - 94 IS - 1 N1 - id: 1838; 539FK Times Cited:1 Cited References Count:32Y JO - Determination of rare earth, major and trace elements in authigenic fraction of Andaman Sea (Northeastern Indian Ocean) sediments by Inductively Coupled Plasma-Mass Spectrometry ER - TY - JOUR T1 - Developing graminoid cuticle analysis for application to Beringian palaeoecology JF - Review of palaeobotany and palynology Y1 - 2010 A1 - Gaglioti, B. V. A1 - Severin, K. A1 - Wooller, M. J. AB - Much of Beringia was composed of graminoid (grass and sedge) dominated habitats during the Late-Pleistocene, yet the account of the actual gramioids that were present is relatively vague. The spatial and temporal variabilities of palaeoclimate, mega-fauna. archaeology, and vegetation interactions could be significantly enhanced with accounts of Beringian graminoids. Fossil graminoid foliage is well preserved in permafrost sediments from Beringia and is available for identification using the micro-morphologies of the leaf epidermis (cuticles), which are often consistent with taxonomic identity. We present a scanning electron microscope (SEM) guide to the leaf cuticles of 38 graminoid species shown to be, or suspected of being present in former Eastern Beringian habitats during marine isotope stages (MIS) 2 and 3 (similar to.56,000-12,000 cal. yrs BP). We examine whether modern specimens have sufficient cuticle variability to identify fossil foliage. We surveyed SEM images from herbarium specimens for 50 quantitative and qualitative features on both sides (adaxial and abaxial) of leaves, and entered these into an interactive key program (Delta Editor). Individual species were unique based on the combined presence of 2-4 cuticle features. Replicate samples (n = 5) of 10 species were integrated into a cluster analysis and visually compared using a dendrogram. Overall, fossils that match modern specimens with a Gower's similarity coefficient of 0.80 or higher can be considered a reliable identification match. Several fossil graminoid specimens were compared and identified with our reference collection. Cuticle identification appears to be a viable method for future macrofossil analysis in Beringia. (C) 2010 Elsevier B.V. All rights reserved. VL - 162 IS - 1 N1 - id: 2132; PT: J; TC: 3; UT: WOS:000281181100009 JO - Developing graminoid cuticle analysis for application to Beringian palaeoecology ER - TY - RPRT T1 - Distribution of Isotopic and Environmental Tracers in Groundwater, Northern Ada County, Southwestern Idaho Y1 - 2010 A1 - Adkins, C. B. A1 - Bartolino, J. R. JF - Scientific Investigations Report PB - U.S. Department of the Interior: U.S. Geological Survey VL - 2010–5144 ER - TY - JOUR T1 - Drowned coastal deposits with associated archaeological remains from a sea-level "slowstand": Northwestern Gulf of Maine, USA JF - Geology Y1 - 2010 A1 - Kelley, Joseph T. A1 - Belknap, Daniel F. A1 - Claesson, Stefan AB - Drowned terrestrial wetland environments, such as lakes, marshes, and beaches, were thought to be rare in formerly glaciated regions like the Gulf of Maine (United States). In the northwestern Gulf of Maine, postglacial relative sea-level changes include a "slowstand" between 11.5 ka and 7.5 ka, when the ocean rose VL - 38 IS - 8 N1 - id: 1996; PT: J; UT: WOS:000279847900006 JO - Drowned coastal deposits with associated archaeological remains from a sea-level "slowstand": Northwestern Gulf of Maine, USA ER - TY - JOUR T1 - Environmental anomalies in the northeastern East China Sea during the last 3 000 years: implications for El Nino activity in the Holocene JF - Chinese Journal of Oceanology and Limnology Y1 - 2010 A1 - Chang, Fengming A1 - Li, Tiegang A1 - Zhuang, Lihua A1 - Yan, Jun AB - To reconstruct the productivity changes for the last 10 500 a in the northeastern East China Sea (ECS), biogenic compounds (such as carbonate, organic carbon and opal), marine micropaleontological fossils (planktonic foraminifera, benthic foraminifera, radiolarian and silicoflagellate) and the compositional characters of benthic foraminifera fauna analyses were carried out on a sediment core DOC082 obtained from the western slope of Okinawa Trough (29 degrees 13.93'N, 128 degrees 08.53' E; 1 128 m water depth). The long-term changes of biogenic and micropaleontological proxies display some similarities through the last 10 500 a, which show three different phases: lower values are recorded during the early and middle Holocene (before about 4 000 a BP), followed by an abrupt and remarkable increase at about 4 000 a BP, the late Holocene (after about 3 000 a BP) is characterized by continuously high values. The multi-proxy data of paleoproductivity and percents of benthic foraminifera genera (Uvigerina and Bulimina) show that during the early and middle Holocene (10 500-4 000 a BP) productivity was relatively low with a sudden and distinct increase at about 4 000 a BP, and the late Holocene (3 400-0 a BP) is marked by significantly higher productivity. Also, the radiolarian-based sea surface temperature (SST) records reveal a distinct decline in SST in the late Holocene after 3 200 a BP, very different from the early and middle Holocene. For the last 3 000 a, the enhanced biological productivity and distinctly lower SST indicate a major change of oceanographic conditions in the northeastern ECS. These marine environmental anomalies are consistent with other paleoclimatic records for the late Holocene in the Chinese continent and its surrounding regions. After analyzing the mechanisms of modern productivity and SST changes in the northeastern ECS, and based on the climatic anomalies in the Chinese continent and variations in the Kuroshio Current during modern El Nino periods, we suggest that the anomalous environmental conditions in the northeastern ECS may imply intensified El Nino activity during the late Holocene. VL - 28 IS - 1 N1 - id: 1927; PT: J; UT: WOS:000275654100024 JO - Environmental anomalies in the northeastern East China Sea during the last 3 000 years: implications for El Nino activity in the Holocene ER - TY - JOUR T1 - Eurasian Pastoralists And Their Shifting Regional Interactions at the Steppe Margin: Settlement History At Mukri, Kazakhstan JF - World Archaeology Y1 - 2010 A1 - Frachetti, M. A1 - Benecke, N. A1 - Mar’yashev, A. N. A1 - Doumani, P. VL - 42 IS - 4 N1 - id: 1880In Press ER - TY - JOUR T1 - Evidence for size increase in an exploited mollusc: humped conch (Strombus gibberulus) at Chelechol ra Orrak, Palau from ca. 3000-0 BP JF - JOURNAL OF ARCHAEOLOGICAL SCIENCE Y1 - 2010 A1 - Giovas, Christina M. A1 - Fitzpatrick, Scott M. A1 - Clark, Meagan A1 - Abed, Mira KW - Anthropogenic impacts KW - Humped conch KW - Micronesia KW - Molluscs KW - Pacific Islands KW - Palau AB - Past research has suggested that the humped conch (Strombus gibberulus), a species common in many prehistoric archaeological sites in the Pacific, declines in size and/or abundance over time. Explanations for this phenomenon largely revolve around the possibility that they were overharvested by human populations. In this study, we measured the length and width of over 1400 individual specimens of S. gibberulus shells recovered from the site of Chelechol ra Orrak in Palau, western Micronesia, in deposits dating from ca. 3000 BP to the present. Statistical analysis indicates that in contrast to previous reports, there is a significant size increase for this taxon through time which may be the result of a combination of anthropogenic and environmental factors. We discuss variables influencing mollusc size and suggest that, given the complexities of their interactions and the data limitations of archaeomalacological assemblages, unambiguous determination of the cause(s) of molluscan size change may not always be possible. (C) 2010 Elsevier Ltd. All rights reserved. VL - 37 ER - TY - JOUR T1 - Fire History of a Giant African Baobab Evinced by Radiocarbon Dating JF - Radiocarbon Y1 - 2010 A1 - Patrut, A. A1 - Mayne, D. H. A1 - von Reden, K. F. A1 - Lowy, D. A. A1 - van Pelt, R. A1 - McNichol, A. P. A1 - Roberts, M. L. A1 - Margineanu, D. KW - age calibration KW - bomb c-14 data KW - bombacaceae KW - cal kyr bp KW - southern-hemisphere KW - system AB - The article reports the first radiocarbon dating of a live African baobab (Adansonia digitata L.), by investigating wood samples collected from 2 inner cavities of the very large 2-stemmed Platland tree of South Africa. Some 16 segments extracted from determined positions of the samples, which correspond to a depth of up to 15-20 cm in the wood, were processed and analyzed by accelerator mass spectrometry (AMS). Calibrated ages of segments are not correlated with their positions in the stems of the tree. Dating results indicate that the segments originate from new growth layers, with a thickness of several centimeters, which cover the original old wood. Four new growth layers were dated before the reference year AD 1950 and 2 layers were dated post-AD 1950, in the post-bomb period. Formation of these layers was triggered by major damage inside the cavities. Fire episodes are the only possible explanation for such successive major wounds over large areas or over the entire area of the inner cavities of the Platland tree, able to trigger regrowth. VL - 52 SN - 0033-8222 IS - 2 N1 - Sp. Iss. 1696jn Times Cited:11 Cited References Count:28 JO - Radiocarbon ER - TY - THES T1 - Foraminiferal indicators of paleoceanographic and sea-ice conditions in the Amundsen Gulf and Viscount Melville Sound, Canadian Arctic Y1 - 2010 A1 - Gibb, Olivia T. KW - Biological oceanography KW - Environmental science KW - Paleoclimate Science KW - Paleontology AB - Sediment cores were collected from the Canadian Arctic Archipelago to reconstruct the region's oceanographic and sea ice history via foraminiferal proxies. Foraminiferal species assemblages reflect changes in sea ice cover due to the dissolution of calcareous foraminifera during increased productivity in ice-free waters. The upper five cm of sediment of the core located in the Amundsen Gulf is characterized by a predominantly agglutinated foraminiferal assemblage that spanned the last century, indicative of a seasonally ice-free Amundsen Gulf. In contrast to the recent assemblage, a predominantly calcareous assemblage indicated carbonate preservation within the Amundsen Gulf during a period of perennial ice extending back to the 9th century AD. During the Medieval Warm Period and the Anthropocene, two recent periods of warmer climate, foraminiferal proxies indicated different sea ice regimes. These results suggest that the factors forcing sea ice extent have changed in recent decades. PB - DALHOUSIE UNIVERSITY VL - M.Sc. ER - TY - JOUR T1 - FORAMINIFERAL RECORD OF CHANGES IN SUMMER MONSOON PRECIPITATION JF - Revista Brasileira de Paleontologia Y1 - 2010 A1 - Pivel, M. A. G. A1 - Toledo, F. A. L. A1 - Costa, K. B. AB - Changes in the oxygen isotopic composition of the planktonic foraminifer Globigerinoides ruber and in the foraminifera faunal composition in a core retrieved from the southeastern Brazilian continental margin were used to infer past changes in the hydrological balance and monsoon precipitation in the western South Atlantic since the Last Glacial Maximum (LGM). The results suggest a first-order orbital (precessional) control on the South American Monsoon precipitation. This agrees with previous studies based on continental proxies except for LGM estimates provided by pollen records. The causes for this disagreement are discussed. VL - 13 IS - 2 N1 - id: 1974 JO - FORAMINIFERAL RECORD OF CHANGES IN SUMMER MONSOON PRECIPITATION ER - TY - JOUR T1 - Freshwater Outburst from Lake Superior as a Trigger for the Cold Event 9300 Years Ago JF - Science Y1 - 2010 A1 - Yu, Shi-Yong A1 - Colman, Steven M. A1 - Lowell, Thomas V. A1 - Milne, Glenn A. A1 - Fisher, Timothy G. A1 - Breckenridge, Andy A1 - Boyd, Matthew A1 - Teller, James T. AB - Paleoclimate proxy records reveal a pervasive cooling event with a Northern Hemispheric extent similar to 9300 years ago. Coeval changes in the oceanic circulation of the North Atlantic imply freshwater forcing. However, the source, magnitude, and routing of meltwater have remained unknown. Located in central North America, Lake Superior is a key site for regulating the outflow of glacial meltwater to the oceans. Here, we show evidence for an similar to 45-meter rapid lake-level fall in this basin, centered on 9300 calibrated years before the present, due to the failure of a glacial drift dam on the southeast corner of the lake. We ascribe the widespread climate anomaly similar to 9300 years ago to this freshwater outburst delivered to the North Atlantic Ocean through the Lake Huron-North Bay-Ottawa River-St. Lawrence River valleys. VL - 328 IS - 5983 N1 - id: 1950; PT: J; UT: WOS:000278318600030 JO - Freshwater Outburst from Lake Superior as a Trigger for the Cold Event 9300 Years Ago ER - TY - JOUR T1 - From ice age to modern: a record of landscape change in an Andean cloud forest JF - Journal of Biogeography Y1 - 2010 A1 - Valencia, B. G. A1 - Urrego, D. H. A1 - Silman, M. R. A1 - Bush, M. B. AB - Aim VL - 37 IS - 9 N1 - id: 869; 639ND Times Cited:5 Cited References Count:63Y JO - From ice age to modern: a record of landscape change in an Andean cloud forest ER - TY - JOUR T1 - Future of the NOSAMS Tandetron AMS system JF - Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions with Materials and Atoms Y1 - 2010 A1 - von Reden, Karl F. AB - The NOSAMS 3 MV Tandetron AMS system will soon reach its 20th anniversary of operation. A critical review of all aspects of the system is necessary to assess the analytical, economical and operational factors that enter into the consideration of either an upgrade or a replacement of the instrument. Recent in-house experience with the design and construction of a large-acceptance (14)C AMS system gives us a benchmark with which to compare the expected outcome of an upgrade. The present ion analysis efficiency of our Tandetron system is roughly 1%, well below the 4% value of our new system. This affects the lower limit of analyzable sample size, speed of analysis, exposure to systematic errors, and the upper limit of achievable single-sample counting statistics. At first glance it may seem obvious that a replacement (even at higher cost) would be preferable to an upgrade. However, it will be shown that there are good reasons to consider the latter. One of the most compelling is the fact that the Tandetron is a state-of-the-art and superior high-current accelerator design with minimal signs of aging and very low-maintenance. Ion beam modeling calculations show that the main transmission limitation of the instrument is caused by the design of our injector, a four-magnet "Recombinator", making it difficult to perform reliable AMS with negative currents exceeding 80 mu A. To be acceptable, an upgrade should bring the Tandetron to at least 3% ion efficiency by replacing the injector with a properly matched high-transmission device. (C) 2009 Elsevier B.V. All rights reserved. VL - 268 IS - 7-8 N1 - id: 2090; PT: J; CT: 11th International Conference on Accelerator Mass Spectrometry; CY: SEP 14-19, 2008; CL: Rome, ITALY; SP: Univ Salento, CEDAD, Second Univ Naples, CIRCE, INNOVA, Ist Nazl Fis Nucl, LABEC, Abdus Salam Int Ctr Theoret Phys; UT: WOS:000277462300044 JO - Future of the NOSAMS Tandetron AMS system ER - TY - JOUR T1 - Geology of Lonar Crater, India JF - Geological Society of America Bulletin Y1 - 2010 A1 - Maloof, A. C. A1 - Stewart, S. T. A1 - Weiss, B. P. A1 - Soule, S. A. A1 - Swanson-Hysell, N. L. A1 - Louzada, K. L. A1 - Garrick-Bethell, I. A1 - Poussart, P. M. AB - Lonar Crater, India, is one of the youngest and best preserved impact structures on Earth. The 1.88-km-diameter simple crater formed entirely within the Deccan traps, making it a useful analogue for small craters on the basaltic surfaces of the other terrestrial planets and the Moon. In this study, we present a meter-scale-resolution digital elevation model, geological map of Lonar Crater and the surrounding area, and radiocarbon ages for histosols beneath the distal ejecta. Impact-related deformation of the target rock consists of upturned basalt flows in the upper crater walls and recumbent folding around rim concentric, subhorizontal, non-cylindrical fold axes at the crater rim. The rim-fold hinge is preserved around 10%-15% of the crater. Although tearing in the rim-fold is inferred from field and palcomagnetic observations, no tear faults are identified, indicating that large displacements in the crater walls are not characteristic of small craters in basalt. One significant normal fault structure is observed in the crater wall that offsets slightly older layer-parallel slip faults. There is little fluvial erosion of the continuous ejecta blanket. Portions of the ejecta blanket are overlain by aerodynamically and rotationally sculpted glassy impact spherules, in particular in the eastern and western rim, as well as in the depression north of the crater known as Little Lonar. The emplacement of the continuous ejecta blanket can be likened to a radial ground-hugging debris flow, based on the preserved thickness distribution of the ejecta, the efficient exchange of clasts between the ejecta flow and the underlying histosol, and the lack of sorting and stratification in the bulk of the ejecta. The ejecta profile is thickened at the distal edge and similar to fluidized ejecta structures observed on Mars. VL - 122 IS - 1-2 N1 - id: 1846; 539YI Times Cited:0 Cited References Count:100Y JO - Geology of Lonar Crater, India ER - TY - JOUR T1 - Growth rates, stable oxygen isotopes (delta(18)O), and strontium (Sr/Ca) composition in two species of Pacific sclerosponges (Acanthocheatetes wellsi and Astrosclera willeyana) with delta(18)O calibration and application to paleoceanography JF - Journal of Geophysical Research-Oceans Y1 - 2010 A1 - Grottoli, Andrea G. A1 - Adkins, Jess F. A1 - Panero, Wendy R. A1 - Reaman, Daniel M. A1 - Moots, Kate AB - The isotopic and elemental composition of sclerosponge skeletons is used to reconstruct paleoceanographic records. Yet few studies have systematically examined the natural variability in sclerosponge skeletal delta(18)O, growth, and Sr/Ca, and how that may influence the interpretation of sclerosponge proxy records. Here, we analyzed short records in seven specimens of Acanthocheatetes wellsi (high-Mg calcite, 21 mol% Mg) from Palau, four A. wellsi (high-Mg calcite, 21 mol% Mg) from Saipan, and three Astrosclera willeyana (aragonite) sclerosponges from Saipan, as well as one long record in an A. wellsi specimen from Palau spanning 1945-2001.5. In Saipan, species-specific and mineralogical effects appear to have a negligible effect on sclerosponge delta(18)O, facilitating the direct comparison of delta(18)O records between species at a given location. At both sites, A. wellsi delta(18)O and growth rates were sensitive to environmental conditions, but Sr/Ca was not sensitive to the same conditions. High-resolution delta(18)O analyses confirmed this finding as both A. wellsi and A. willeyana deposited their skeleton in accordance with the trends in isotopic equilibrium with seawater, though with a 0.27% offset in the case of A. willeyana. In the high-Mg-calcite species A. wellsi, Mg may be interfering with Sr incorporation into the skeleton. On multidecadal timescales, A. wellsi sclerosponge delta(18)O in Palau tracked the Southern Oscillation Index variability post-1977, but not pre-1977, coincident with the switch in the Pacific Decadal Oscillation (PDO) at similar to 1976. This suggests that water mass circulation in the region is influenced by El Nino-Southern Oscillation variability during positive PDO phases, but not during negative ones. VL - 115 N1 - id: 1962; PT: J; UT: WOS:000278735700001 JO - Growth rates, stable oxygen isotopes (delta(18)O), and strontium (Sr/Ca) composition in two species of Pacific sclerosponges (Acanthocheatetes wellsi and Astrosclera willeyana) with delta(18)O calibration and application to paleoceanography ER - TY - JOUR T1 - Highly episodic fire and erosion regime over the past 2,000 y in the Siskiyou Mountains, Oregon RID A-2851-2009 RID C-9214-2009 JF - Proceedings of the National Academy of Sciences of the United States of America Y1 - 2010 A1 - Colombaroli, Daniele A1 - Gavin, Daniel G. AB - Fire is a primary mode of natural disturbance in the forests of the Pacific Northwest. Increased fuel loads following fire suppression and the occurrence of several large and severe fires have led to the perception that in many areas there is a greatly increased risk of high-severity fire compared with presettlement forests. To reconstruct the variability of the fire regime in the Siskiyou Mountains, Oregon, we analyzed a 10-m, 2,000-y sediment core for charcoal, pollen, and sedimentological data. The record reveals a highly episodic pattern of fire in which 77% of the 68 charcoal peaks before Euro-American settlement cluster within nine distinct periods marked by a 15-y mean interval. The 11 largest charcoal peaks are significantly related to decadal-scale drought periods and are followed by pulses of minerogenic sediment suggestive of rapid sediment delivery. After logging in the 1950s, sediment load was increased fourfold compared with that from the most severe presettlement fire. Less severe fires, marked by smaller charcoal peaks and no sediment pulses, are not correlated significantly with drought periods. Pollen indicators of closed forests are consistent with fire-free periods of sufficient length to maintain dense forest and indicate a fire-triggered switch to more open conditions during the Medieval Climatic Anomaly. Our results indicate that over millennia fire was more episodic than revealed by nearby shorter tree-ring records and that recent severe fires have precedents during earlier drought episodes but also that sediment loads resulting from logging and road building have no precedent in earlier fire events. VL - 107 IS - 44 N1 - id: 1951; PT: J; UT: WOS:000283749000034 JO - Highly episodic fire and erosion regime over the past 2,000 y in the Siskiyou Mountains, Oregon RID A-2851-2009 RID C-9214-2009 ER - TY - JOUR T1 - A High-Performance (14)c Accelerator Mass Spectrometry System JF - Radiocarbon Y1 - 2010 A1 - Roberts, M. L. A1 - Burton, J. R. A1 - Elder, K. L. A1 - Longworth, B. E. A1 - McIntyre, C. P. A1 - von Reden, K. F. A1 - Han, B. X. A1 - Rosenheim, B. E. A1 - W. J. Jenkins A1 - Galutschek, E. A1 - McNichol, A. P. AB - A new and unique radiocarbon accelerator mass spectrometry (AMS) facility has been constructed at the Woods Hole Oceanographic Institution. The defining characteristic of the new system is its large-gap optical elements that provide a larger-than-standard beam acceptance. Such a system is ideally suited for high-throughput, high-precision measurements of (14)C. Details and performance of the new system are presented. VL - 52 IS - 2 N1 - id: 2095; PT: J; CT: 20th International Radiocarbon Conference; CY: MAY 31-JUN 05, 2009; CL: Big Isl, HI; SI: 1; UT: WOS:000285437800005 JO - A High-Performance (14)c Accelerator Mass Spectrometry System ER - TY - JOUR T1 - Holocene changes in Proboscia diatom productivity in shelf waters of the north-western Antarctic Peninsula JF - Antarctic Science Y1 - 2010 A1 - Willmott, V. A1 - Rampen, S. W. A1 - Domack, E. A1 - Canals, M. A1 - Damste, J. S. S. A1 - Schouten, S. AB - Diatoms are important primary producers in present day Antarctic waters but their relative significance in the past is less clear. In this Study We used long-chain diols to reconstruct Proboscia diatom productivity in shelf waters of the western Antarctic Peninsula over the last 8500 yr. Biomarker lipid analysis revealed the presence of a suite of long-chain diols in the sediments, mainly comprising the C-28 and C-30 1,14-diol isomers derived from Proboscia diatoms and C-28 and C-30 1,13-diols derived from other unknown algae. The relative importance of Proboscia diatoms was assessed using the relative abundances of 1, 14-diols versus 1, 13-diols, which showed that Proboscia diatoms were relatively more abundant during the Late Holocene, suggesting that stronger upwelling of circumpolar waters Occurred at that time. The variations in the diol index strongly correlate with melt events in the Siple Dome ice core, Suggesting that the climatic processes responsible for changes in mean summer temperature, open marine influence and atmospheric cyclonic activity recorded at Siple Dome, also controlled the productivity of Proboscia diatoms on the western Antarctic Peninsula region. VL - 22 IS - 1 N1 - id: 789; 559YJ Times Cited:0 Cited References Count:51Y JO - Holocene changes in Proboscia diatom productivity in shelf waters of the north-western Antarctic Peninsula ER - TY - JOUR T1 - Holocene earthquake record offshore Portugal (SW Iberia): testing turbidite paleoseismology in a slow-convergence margin JF - Quaternary Science Reviews Y1 - 2010 A1 - Gracia, Eulalia A1 - Vizcaino, Alexis A1 - Escutia, Carlota A1 - Asioli, Alessandra A1 - Rodes, Angel A1 - Pallas, Raimon A1 - Garcia-Orellana, Jordi A1 - Lebreiro, Susana A1 - Goldfinger, Chris AB - The SW margin of the Iberian Peninsula hosts the present-day boundary between the Eurasian and African Plates. Convergence (4-5 mm/yr) is accommodated through a wide deformation zone characterized by moderate magnitude seismic activity. This zone has also been the source of the most important seismic events in Western Europe, such as the 1755 Lisbon Earthquake and Tsunami and 1969 Horseshoe Earthquake. Despite efforts to identify active seismogenic structures in the Gulf of Cadiz in the last ten years, little is known about its paleoseismic history. The turbidite paleoseismology approach was applied for the first time in a low-rate convergent margin to determine the recurrence interval of large earthquake events that occurred in SW Iberia during the Holocene. Four sediment cores collected at strategically located sites offshore Portugal (i.e. Tagus Abyssal Plain, Infante Don Henrique Basin and Horseshoe Abyssal Plain) reveal that these deep-sea basins preserve a record of episodic deposition of turbidites. In the SW Iberian Margin excluding special climatic events, earthquakes are the most likely triggering mechanism for synchronous, widely-spaced distributed turbidites during the Holocene, when the sea level was relatively stable. Age correlation together with textural, mineralogical, physical properties and geochemical signatures of the new cores complemented by pre-existing multicores and gravity cores reveals a total of 7 widespread turbidite events for the Holocene. Precise dating of the most recent turbidite event (E1) based on (210)Pb and (137)Cs geochronology provides an age of AD 1971 +/- 3. This age corresponds to a high-magnitude instrumental earthquake in the region: the 1969 Horseshoe Earthquake (Mw 8.0). Calibrated (14)C ages of subsequent widespread turbidite events (E3 and E5) correlate with the dates of important historical earthquakes and paleotsunami deposits in the Gulf of Cadiz area, such as AD 1755 and 218 BC, respectively. If older synchronous events (E6, E8, and E10) with ages ranging from 4960-5510 yr BP to 8715-9015 yr BP are also taken into account, a great earthquake recurrence interval of about 1800 years is obtained for the Holocene. Our correlations suggest that the turbidite record may be considered as a proxy for paleoseismic activity in low-convergence rate margins, and a valuable complementary tool in earthquake and tsunami hazard assessment along the coasts of the Iberian Peninsula and North Africa. (C) 2010 Elsevier Ltd. All rights reserved. VL - 29 IS - 9-10 N1 - id: 1959; PT: J; UT: WOS:000277813300008 JO - Holocene earthquake record offshore Portugal (SW Iberia): testing turbidite paleoseismology in a slow-convergence margin ER - TY - JOUR T1 - Holocene evolution of the Indonesian throughflow and the western Pacific warm pool JF - NATURE GEOSCIENCE Y1 - 2010 A1 - Linsley, Braddock K. A1 - Rosenthal, Yair A1 - Oppo, Delia W. AB - High sea surface temperatures in the western Pacific warm pool fuel atmospheric convection and influence tropical climate. This region also hosts the Indonesian throughflow, the network of currents through which surface and thermocline waters are transported from the western equatorial Pacific Ocean into the Indian Ocean. Here we show, using records of the delta O-18 and Mg/Ca of planktonic foraminifera from eight sediment cores, that from about 10,000 to 7,000 years ago, sea surface temperatures in the western sector of the western Pacific warm pool were about 0.5 degrees C higher than during pre-industrial times. We also find that about 9,500 years ago, when the South China and Indonesian seas were connected by rising sea level, surface waters in the Makassar Strait became relatively fresher. We suggest that the permanent reduction of surface salinity initiated the enhanced flow at lower, thermocline depths seen in the modern Indonesian throughflow. However, the uniformly warm sea surface temperatures found upstream and downstream of the Indonesian throughflow indicate that the early Holocene warmth in this region was not directly related to reduced heat transport by the throughflow that may have resulted from surface freshening of the Makassar Strait. Instead, we propose that the elevated temperatures were the result of a westward shift or expansion of the boundaries of the western Pacific warm pool. VL - 3 ER - TY - JOUR T1 - Implications for chloro- and pheopigment synthesis and preservation from combined compound-specific δ13C, δ15N, and Δ14C analysis JF - Biogeosciences Y1 - 2010 A1 - Kusch, S. A1 - Kashiyama, Y. A1 - Ogawa, N. O. A1 - Altabet, M. A1 - Butzin, M. A1 - Friedrich, J. A1 - Ohkouchi, N. A1 - Mollenhauer, G. AB - Chloropigments and their derivative pheopigments preserved in sediments can directly be linked to photosynthesis. Their carbon and nitrogen stable isotopic compositions have been shown to be a good recorder of recent and past surface ocean environmental conditions tracing the carbon and nitrogen sources and dominant assimilation processes of the phytoplanktonic community. In this study we report results from combined compound-specific radiocarbon and stable carbon and nitrogen isotope analysis to examine the time-scales of synthesis and fate of chlorophyll-a and its degradation products pheophytin-a, pyropheophytin-a, and 132,173-cyclopheophorbide-a-enol until burial in Black Sea core-top sediments. The pigments are mainly of marine phytoplanktonic origin as implied by their stable isotopic compositions. Pigment delta15N values indicate nitrate as the major uptake substrate but 15N-depletion towards the open marine setting indicates either contribution from N2-fixation or direct uptake of ammonium from deeper waters. Radiocarbon concentrations translate into minimum and maximum pigment ages of approximately 40 to 1200 years. This implies that protective mechanisms against decomposition such as association with minerals, storage in deltaic anoxic environments, or eutrophication-induced hypoxia and light limitation are much more efficient than previously thought. Moreover, seasonal variations of nutrient source, growth period, and habitat and their associated isotopic variability are likely at least as strong as long-term trends. Combined triple isotope analysis of sedimentary chlorophyll and its primary derivatives is a powerful tool to delineate biogeochemical and diagenetic processes in the surface water and sediments, and to assess their precise time-scales. VL - 7 UR - http://www.biogeosciences.net/7/4105/2010 IS - 12 ER - TY - JOUR T1 - In situ cosmogenic (10)Be production-rate calibration from the Southern Alps, New Zealand RID D-4720-2011 JF - Quaternary Geochronology Y1 - 2010 A1 - Putnam, A. E. A1 - Schaefer, J. M. A1 - Barrell, D. J. A. A1 - Vandergoes, M. A1 - Denton, G. H. A1 - Kaplan, M. R. A1 - Finkel, R. C. A1 - Schwartz, R. A1 - Goehring, B. M. A1 - Kelley, S. E. AB - We present a (10)Be production-rate calibration derived from an early Holocene debris-flow deposit at about 1000 m above sea level in the central Southern Alps, New Zealand, in the mid-latitude Southern Hemisphere. Ten radiocarbon ages on macrofossils from a soil horizon buried by the deposit date the deposit to 9690 +/- 50 calendar years before AD2008. Surface (10)Be concentrations of seven large boulders partially embedded in the stable surface of the deposit are tightly distributed, yielding a standard deviation of similar to 2%. Conversion of the (10)Be measurements to sea level/high-latitude values using each of five standard scaling methods indicates (10)Be production rates of 3.84 +/- 0.08, 3.87 +/- 0.08, 3.83 +/- 0.08, 4.15 +/- 0.09, and 3.74 +/- 0.08 atoms g(-1) a(-1), relative to the '07KNSTD' (10)Be AMS standard, and including only the local time-integrated production-rate uncertainties. When including a sea level high-latitude scaling uncertainty the overall error is similar to 2.5% (1 sigma) for each rate. To test the regional applicability of this production-rate calibration, we measured (10)Be concentrations in a set of nearby moraines deposited before 18060 +/- 200 years before AD2008. The (10)Be ages are only consistent with minimum-limiting (14)C age data when calculated using the new production rates. This also suggests that terrestrial in situ cosmogenic-nuclide production did not change significantly from Last Glacial Maximum to Holocene time in New Zealand. Our production rates agree well with those of a recent calibration study from northeastern North America, but are 12-14% lower than other commonly adopted values. The production-rate values presented here can be used elsewhere in New Zealand for rock surfaces exposed during or since the last glacial period. (C) 2009 Elsevier B.V. All rights reserved. VL - 5 IS - 4 N1 - id: 2031; PT: J; UT: WOS:000280946500002 JO - In situ cosmogenic (10)Be production-rate calibration from the Southern Alps, New Zealand RID D-4720-2011 ER - TY - JOUR T1 - In situ cosmogenic Be-10 production-rate calibration from the Southern Alps, New Zealand JF - QUATERNARY GEOCHRONOLOGY Y1 - 2010 A1 - Putnam, A. E. A1 - Schaefer, J. M. A1 - Barrell, D. J. A. A1 - Vandergoes, M. A1 - Denton, G. H. A1 - Kaplan, M. R. A1 - Finkel, R. C. A1 - Schwartz, R. A1 - Goehring, B. M. A1 - Kelley, S. E. KW - Be-10 KW - C-14 KW - Cosmogenic nuclide KW - Debris flow KW - Holocene KW - Last glacial maximum KW - Moraine KW - Production rate KW - South Island AB - We present a Be-10 production-rate calibration derived from an early Holocene debris-flow deposit at about 1000 m above sea level in the central Southern Alps, New Zealand, in the mid-latitude Southern Hemisphere. Ten radiocarbon ages on macrofossils from a soil horizon buried by the deposit date the deposit to 9690 +/- 50 calendar years before AD2008. Surface Be-10 concentrations of seven large boulders partially embedded in the stable surface of the deposit are tightly distributed, yielding a standard deviation of similar to 2%. Conversion of the Be-10 measurements to sea level/high-latitude values using each of five standard scaling methods indicates Be-10 production rates of 3.84 +/- 0.08, 3.87 +/- 0.08, 3.83 +/- 0.08, 4.15 +/- 0.09, and 3.74 +/- 0.08 atoms g(-1) a(-1), relative to the `07KNSTD' Be-10 AMS standard, and including only the local time-integrated production-rate uncertainties. When including a sea level high-latitude scaling uncertainty the overall error is similar to 2.5% (1 sigma) for each rate. To test the regional applicability of this production-rate calibration, we measured Be-10 concentrations in a set of nearby moraines deposited before 18060 +/- 200 years before AD2008. The Be-10 ages are only consistent with minimum-limiting C-14 age data when calculated using the new production rates. This also suggests that terrestrial in situ cosmogenic-nuclide production did not change significantly from Last Glacial Maximum to Holocene time in New Zealand. Our production rates agree well with those of a recent calibration study from northeastern North America, but are 12-14% lower than other commonly adopted values. The production-rate values presented here can be used elsewhere in New Zealand for rock surfaces exposed during or since the last glacial period. (C) 2009 Elsevier B.V. All rights reserved. VL - 5 ER - TY - JOUR T1 - The influence of sea level and tectonics on Late Pleistocene through Holocene sediment storage along the high-sediment supply Waipaoa continental shelf JF - Marine Geology Y1 - 2010 A1 - Gerber, T. P. A1 - Pratson, L. F. A1 - Kuehl, S. A1 - Walsh, J. P. A1 - Alexander, C. A1 - Palmer, A. AB - We present geophysical and core evidence showing how subsidence caused by forearc shortening has accommodated Late Pleistocene and Holocene sediments supplied to the tectonically active Waipaoa shelf (NZ), limiting off-shelf export during the early sea level highstand. The last glacioeustatic fall and subsequent rise exposed and then flooded a shelf segmented into subbasins separated by zones of uplift, leaving key stratigraphic markers of shoreline regression and transgression that vary strongly in character across the shelf. Highstand sediment isopachs tied to piston cores dated using tephra correlation and a radiocarbon age model provide a sediment budget at similar to 2000yr intervals from the mid-Holocene (similar to 5500 cal.yr BP) to present. Sediment load estimates from our shelf budget are in agreement with published model estimates for suspended sediment discharge from the Waipaoa River for the past 3000yr but, importantly, do not show the 6-fold increase in the Waipaoa's sediment output that began with human settlement 700yr ago and accelerated with deforestation over the last century. Bypassing of Waipaoa sediment to the slope may therefore be a recent phenomenon caused by unnaturally high sediment loads, a conclusion supported by data reported elsewhere in this volume. Our study also reveals evidence for (1) a relatively thick mid-shelf transgressive section deposited during the last eustatic rise that may correlate to estuarine sequences reported from numerous sites on the modern coastline of the North Island, (2) a slight decrease in total basin filling rates during the highstand, and (3) variability in the partitioning of highstand sediments between individual subbasins that may reflect differing degrees of tectonic accommodation. (C) 2009 Elsevier B.V. All rights reserved. VL - 270 IS - 1-4 N1 - id: 1849; Sp. Iss. SI 576IF Times Cited:7 Cited References Count:49Y JO - The influence of sea level and tectonics on Late Pleistocene through Holocene sediment storage along the high-sediment supply Waipaoa continental shelf ER - TY - JOUR T1 - Investigating the influence of hydrogeomorphic setting on the response of lake sedimentation to climatic changes in the Uinta Mountains, Utah, USA JF - Journal of Paleolimnology Y1 - 2010 A1 - Corbett, Lee B. A1 - Munroe, Jeffrey S. AB - Reader Lake and Elbow Lake, two high-altitude lakes in the Uinta Mountains of Utah, are located approximately 2 km apart, at similar elevations, and within identical vegetation communities. Loss on ignition, carbon to nitrogen ratios, biogenic silica, and sediment grain size were analyzed throughout percussion cores retrieved from both lakes to construct continuous time series spanning 14 to ca. 2 ka BP. Given the proximity of the lakes, it is assumed that both were subjected to the same climatic forcing over this time. Accordingly, the first goal of this study was to consider these two multiproxy datasets in concert to yield an integrated paleoclimate record for this region. Close inspection of the records identified discrepancies indicating that the lakes responded to climate changes in different ways despite their proximity and similar setting. Clarifying these differences and understanding why the two lakes behaved differently at certain times was the second goal of this study. Overall, the paleoclimatic records document lake formation in the latest Pleistocene following glacier retreat. Buried glacier ice at the location of Reader Lake may have persisted through the Younger Dryas. Both lakes became biologically productive ca. 11.5 ka BP, and the first appearance of conifer needles indicates that trees had replaced alpine tundra in these watersheds by 10.5 ka BP. The interval from 10 to 6 ka BP was marked by a dramatic increase in precipitation, perhaps related to enhanced monsoonal circulation driven by the insolation maximum. The two lakes recorded this event in notably contrasting ways given their differing hydrogeomorphic settings. Precipitation decreased from 6 to 4 ka BP, and low water levels and drought conditions marked the interval from 4.0 to 2.7 ka BP. The integrated paleoclimate record developed from these cores provides a useful point of comparison with other records from the region. The differences between the records from these closely spaced lakes underscore the need to consider hydrogeomorphic setting when evaluating the suitability of a lake for a paleolimnological study. VL - 44 IS - 1 N1 - id: 2013; PT: J; UT: WOS:000277939200023 JO - Investigating the influence of hydrogeomorphic setting on the response of lake sedimentation to climatic changes in the Uinta Mountains, Utah, USA ER - TY - JOUR T1 - Late Holocene Evolution of the Mekong Subaqueous Delta, Southern Vietnam JF - Marine Geology Y1 - 2010 A1 - Xue, Z. A1 - Liu, J. P. A1 - DeMaster, D. A1 - Van Nguyen, L. A1 - Ta, T. K. O. AB - As Asia's third largest river. with regard to sediment load, the Mekong River delivers approximately 160 million tons of sediment per year to the South China Sea. High-resolution seismic profiling and coring during 2006 and 2007 cruises revealed a low gradient, subaqueous delta system, up to 20 m thick, surrounding the modern Mekong River Delta (MRD) in the west of the South China Sea. Based on clinoform structure, grain size Pb-210, AMS C-14, and delta C-13 results, the subaqueous delta is divided into four zones defined by different sedimentary processes and depositional features. Over the past 3000 yr, the evolution of the MRD has shown a morphological asymmetry indicated by a large down-drift area and a rapid progradation around Cape Camau, similar to 200 km downstream from the river mouth. This asymmetric feature is consistent with increased wave influence. The strong southwestward coastal current, strengthened by the Strong NE monsoon, plays an important role locally in longshore transport of resuspended sediments into the Gulf of Thailand. A late Holocene sediment budget for the MRD has been determined, based on the area and thickness of deltaic sediment. Approximately 80% of Mekong delivered sediment has been trapped within the delta area, which, together with a falling sea-level, resulted in a rapidly prograding MRD over the past 3000 yr. (C) 2009 Elsevier B.V. All rights reserved. VL - 269 IS - 1-2 N1 - id: 848; 560AN Times Cited:0 Cited References Count:53Y JO - Late Holocene Evolution of the Mekong Subaqueous Delta, Southern Vietnam ER - TY - JOUR T1 - Late Quaternary record of pteropod preservation from the Andaman Sea JF - Marine Geology Y1 - 2010 A1 - Sijinkumar, A. V. A1 - Nath, B. Nagender A1 - Guptha, M. V. S. AB - In order to understand the glacial to interglacial fluctuations in pteropod preservation and productivity during the late Quaternary (similar to 54 ka BP to present), we investigated pteropod, organic carbon (Cord and Globigerina bulloides abundance in a deep sea core from the western Andaman Sea. Pteropod abundance and preservation is similar to the "Indo-Pacific carbonate preservation type", showing better preservation during glacial and poor preservation during interglacial periods. The core site appears to have remained below the aragonite compensation depth (ACD) throughout the Holocene, indicated by the total absence of pteropods. Maximum abundance and good preservation of pteropods was observed during stadials such as Younger Dryas (YD), Heinrich Events (HEs) and Last Glacial Maxima (LGM) indicating weaker oxygen minimum zone (OMZ) and deeper ACD. Furthermore, the high relative abundance of mesopelagic pteropods over epipelagic forms suggests a well ventilated water column with weak OMZ particularly during LGM, apparently driven by intense winter monsoon. Increased monsoon-driven productivity was observed during 45-40 ka, of early Marine Isotope stage 2 (MIS 2, 24-22 ka), Bolling/Allered (B/A; 15-13.5 ka), YD and late Holocene as evidenced by Cor, content and G. bulloides. Enhanced pteropod preservation of H1 associated with low C(org) content and G. bulloides suggests that reduced monsoonal driven productivity might have influenced pteropod preservation. Deglacial preservation spike in the Andaman Sea is consistent with other northern Indian Ocean records and elsewhere outside the Indian Ocean implying the event is global in nature, marked by deepening of ACD probably driven by enhancement of winter monsoon on local and changes in intermediate water circulation on regional scale. (C) 2010 Elsevier B.V. All rights reserved. VL - 275 IS - 1-4 N1 - id: 2018; PT: J; UT: WOS:000281217300016 JO - Late Quaternary record of pteropod preservation from the Andaman Sea ER - TY - JOUR T1 - Late-twentieth-century warming in Lake Tanganyika unprecedented since AD 500 JF - Nature Geoscience Y1 - 2010 A1 - Tierney, Jessica E. A1 - Mayes, Marc T. A1 - Meyer, Natacha A1 - Johnson, Christopher A1 - Swarzenski, Peter W. A1 - Cohen, Andrew S. A1 - Russell, James M. AB - Instrumental observations suggest that Lake Tanganyika, the largest rift lake in East Africa, has become warmer, increasingly stratified and less productive over the past 90 years (refs 1,2). These trends have been attributed to anthropogenic climate change. However, it remains unclear whether the decrease in productivity is linked to the temperature rise(3,4), and whether the twentieth-century trends are anomalous within the context of longer-term variability. Here, we use the TEX(86) temperature proxy, the weight per cent of biogenic silica and charcoal abundance from Lake Tanganyika sediment cores to reconstruct lake-surface temperature, productivity and regional wildfire frequency, respectively, for the past 1,500 years. We detect a negative correlation between lake-surface temperature and primary productivity, and our estimates of fire frequency, and hence humidity, preclude decreased nutrient input through runoff as a cause for observed periods of low productivity. We suggest that, throughout the past 1,500 years, rising lake-surface temperatures increased the stratification of the lake water column, preventing nutrient recharge from below and limiting primary productivity. Our records indicate that changes in the temperature of Lake Tanganyika in the past few decades exceed previous natural variability. We conclude that these unprecedented temperatures and a corresponding decrease in productivity can be attributed to anthropogenic global warming, with potentially important implications for the Lake Tanganyika fishery. VL - 3 IS - 6 N1 - id: 2043; PT: J; UT: WOS:000278134100019 JO - Late-twentieth-century warming in Lake Tanganyika unprecedented since AD 500 ER - TY - JOUR T1 - A long history of cloud and forest migration from Lake Consuelo, Peru JF - Quaternary Research Y1 - 2010 A1 - Urrego, D. H. A1 - Bush, M. B. A1 - Silman, M. R. AB - The complete paleoecological history from Lake Consuelo forest yields a record of ground-level cloud formation and changes in its lower altitudinal limit over the last 46,300 cal yr BP. The timing of early lake level fluctuations prior to 37,000 cal yr BP appears sensitive to North Atlantic temperature oscillations, corresponding to Dansgaard-Oeschger interstadials 11, 10 and 8 recorded in GISP2. After the LGM, the first hint of warming is recorded in Lake Consuelo at 22,000 call yr BP and agrees with other estimates for the region. The mid-Holocene (7400-5000 cal yr BP) was the period of highest rates of change and most significant reorganizations in the Consuelo forest. These community changes resulted from a regionally widespread dry period. Results from Lake Consuelo indicate that moisture availability, mediated through cloud cover, played the most significant role in ecological change in this system. Rates of past climate fluctuations never exceeded the forest capacity to accommodate change. Unfortunately, this might not be the case under predicted scenarios for the end of the current century. (C) 2009 University of Washington. Published by Elsevier Inc. All rights reserved. VL - 73 IS - 2 N1 - id: 1903; 564VS Times Cited:8 Cited References Count:85Y JO - A long history of cloud and forest migration from Lake Consuelo, Peru ER - TY - JOUR T1 - Long-term stability in the production of a NW Mediterranean Posidonia oceanica (L.) Delile meadow JF - Palaeogeography Palaeoclimatology Palaeoecology Y1 - 2010 A1 - Mateo, M. A. A1 - Renom, P. A1 - Michener, R. H. AB - Long-term changes in leaf net production of the seagrass Posidonia oceanica (L) Defile. and in the irradiance arriving at the meadow canopy, were investigated in a NW Mediterranean meadow using a palaeoecological approach. We conducted in situ shade experiments to find the relationships between the carbon stable isotope ratio (delta(13)C) of plant tissues, leaf net production, and ambient irradiance. The relationships were highly significant and fitted the Michaelis-Menten equation and power functions. These functions were used to reconstruct light and net production using the delta(13)C of P. oceanica detritus as a palaeoecological proxy along a 150 cm core of P. oceanica matte (a peat-like deposit formed by this endemic seagrass species). The delta(13)C values of sheath detritus along the core (i.e.. the net leaf production) showed a weak but significant decrease towards the present time (R = 0.308: P = 0.02) probably as a result of (1) an increase in DIC availability, and/or (2) a progressive change in the carbon isotopic signature of DIC, both of which are consistent with a rise in anthropogenic atmospheric CO(2). The canopy irradiance, reconstructed for the last 1200 years, showed a mean value of 128 mu E m(-2) s(-1) with a range of 12.5-280 mu E m(-2) s(-1). The reconstruction of the net leaf production for the same period yielded a mean value of 2.5 mg dw day(-1) shoot(-1) with a range of 2.0-2.7 mg dw day(-1) shoot(-1). Both ranges are within the values reported in the literature for present day studies. The absence of significant fluctuations or sudden changes through time suggests remarkable ecosystem stability during the last millennium. (C) 2010 Elsevier B.V. All rights reserved. VL - 291 IS - 3-4 N1 - id: 1911; 611AI Times Cited:3 Cited References Count:116Y JO - Long-term stability in the production of a NW Mediterranean Posidonia oceanica (L.) Delile meadow ER - TY - JOUR T1 - Megadroughts and late Holocene dune activation at the eastern margin of the Great Plains, north-central Kansas, USA JF - Aeolian Research Y1 - 2010 A1 - Hanson, P. R. A1 - Arbogast, A. F. A1 - Johnson, W. C. A1 - Joeckel, R. M. A1 - Young, A. R. AB - Optical and radiocarbon dating indicates that alluvium underlying dunes near Abilene was deposited at or before similar to 45 ka, and that the overlying dunes were active at similar to 1.1-0.5 ka. Geochemical data indicate that the Abilene dune sand is immature and was derived from the underlying Pleistocene alluvium, and not from Holocene age Smoky Hill River deposits. These findings suggest that dune activation was a response to increased aridity and local reduction in vegetation cover as opposed to changes in sediment availability from nearby rivers. The time interval of dune activation at Abilene overlaps Medieval Warm Period megadroughts, similar to the larger and more westerly dune fields on the Great Plains, including the Nebraska Sand Hills and the Great Bend Sand Prairie. The activation of smaller dune fields such as the Abilene dunes near the more humid eastern margin of the Great Plains shows the geographic extent and severity of paleodrought events. Unlike the Duncan dunes, another plains-marginal dune field, however, the Abilene dunes show no evidence for multiple drought events during the Holocene. This difference in dune activity, if it is not a result of sampling or preservation bias, indicates variations in the extent and severity of older drought events at the eastern margin of the Great Plains. Published by Elsevier B.V. VL - 1 IS - 3-4 N1 - 851alTimes Cited:20Cited References Count:35 JO - Megadroughts and late Holocene dune activation at the eastern margin of the Great Plains, north-central Kansas, USA ER - TY - JOUR T1 - Microbial carbon cycling in oligotrophic regional aquifers near the Tono Uranium Mine, Japan as inferred from delta(13)C and Delta(14)C values of in situ phospholipid fatty acids and carbon sources JF - Geochimica et Cosmochimica Acta Y1 - 2010 A1 - Mills, Christopher T. A1 - Amano, Yuki A1 - Slater, Gregory F. A1 - Dias, Robert F. A1 - Iwatsuki, Teruki A1 - Mandernack, Kevin W. AB - Microorganisms are ubiquitous in deep subsurface environments, but their role in the global carbon cycle is not well-understood. The natural abundance delta(13)C and Delta(14)C values of microbial membrane phospholipid fatty acids (PLFAs) were measured and used to assess the carbon sources of bacteria in sedimentary and granitic groundwaters sampled from three boreholes in the vicinity of the Tono Uranium Mine, Gifu, Japan. Sample storage experiments were performed and drill waters analyzed to characterize potential sources of microbial contamination. The most abundant PLFA structures in all waters sampled were 16:0,16:1 omega 7c, cy17:0, and 18:1 omega 7c. A PLFA biomarker for type 11 methanotrophs, 18:1 omega 8c, comprised 3% and 18% of total PLFAs in anoxic sedimentary and granitic waters, respectively, sampled from the KNA-6 borehole. The presence of this biomarker was unexpected given that type II methanotrophs are considered obligate aerobes. However, a bacterium that grows aerobically with CH(4) as the sole energy source and which also produces 56% of its total PLFAs as 18:1 omega 8c was isolated from both waters, providing additional evidence for the presence of type II methanotrophs. The Delta(14)C values determined for type II methanotroph PLFAs in the sedimentary (-86 parts per thousand) and granite (-867 parts per thousand) waters were very similar to the Delta(14)C values of dissolved inorganic carbon (DIC) in each water (similar to-850 parts per thousand). This suggests that type II methanotrophs ultimately derive all their carbon from inorganic sources, whether directly from DIC and/or from CH4 produced by the reduction of DIC. In contrast, delta(13)C values of type II PLFAs in the sedimentary (-93 parts per thousand) and granite (-60 parts per thousand) waters indicate that these organisms use different carbon assimilation schemes in each environment despite very similar delta(13)C(CH4) values (-similar to 95 parts per thousand) for each water. The delta(13)C(PLFA) values (-28 parts per thousand to -45 parts per thousand) of non-methanotrophic bacteria in the KNA-6 LTL water do not clearly distinguish between heterotrophic and autotrophic metabolisms, but Delta(14)C(PLFA) values indicate that >65% of total bacteria filtered from the KNA-6 LTL water are heterotrophs. Ancient Delta(14)C values (similar to-1000 parts per thousand) of some PLFAs suggest that many heterotrophs utilize ancient organic matter, perhaps from lignite seams within the sedimentary rocks. The more negative range of delta(13)C(PLFA) values determined for the KNA-6 granitic water (-42 parts per thousand to -66 parts per thousand) are likely the result of a microbial ecosystem dominated by chemolithoautotrophy, perhaps fuelled by abiogenic H(2). Results of sample storage experiments showed substantial shifts in microbial community composition and delta(13)C(PLFA) values (as much as 5 parts per thousand) during 2-4 days of dark, refrigerated, aseptic storage. However, water samples collected and immediately filtered back in the lab from freshly drilled MSB-2 borehole appeared to maintain the same relative relationships between delta(13)C(PLFA) values for sedimentary and granitic host rocks as observed for samples directly filtered under artesian flow from the KNA-6 borehole of the Tono Uranium Mine. (C) 2010 Elsevier Ltd. All rights reserved. VL - 74 IS - 13 N1 - id: 2057; PT: J; UT: WOS:000278510300008 JO - Microbial carbon cycling in oligotrophic regional aquifers near the Tono Uranium Mine, Japan as inferred from delta(13)C and Delta(14)C values of in situ phospholipid fatty acids and carbon sources ER - TY - JOUR T1 - Mid-Brunhes strengthening of the Indian Ocean Dipole caused increased equatorial East African and decreased Australasian rainfall JF - Geophysical Research Letters Y1 - 2010 A1 - Gupta, Anil K. A1 - Sarkar, Sudipta A1 - De, Soma A1 - Clemens, Steven C. A1 - Velu, Angamuthu AB - The tropical Indian Ocean is an important component of the largest warm pool, marked by changes in sea surface temperatures and depths of thermocline and mixed layer in its western and eastern extremities leading to the development of a dipole mode - the Indian Ocean Dipole (IOD). A narrow band of westerlies (7 degrees N to 7 degrees S) sweep the equatorial Indian Ocean during the April - May and October - November transitions between the summer - and winter-monsoon seasons. These Indian Ocean equatorial westerlies (IEW) are closely related to the IOD, intensifying the upper ocean Eastward Equatorial current also known as Wyrtki jets. The strength of the IOD/IEW determines the moisture content in East Africa. A major decrease in the strength of the IEW (strengthening or positive mode of the IOD) during the mid-Brunhes epoch (similar to 300-250 Kyr BP) coincides with a wetter equatorial East Africa, a drier Australasia and a stronger Indian summer monsoon, indicating that the IOD/IEW play a significant role in driving climate change in East Africa, Australasia and South Asia. Citation: Gupta, A. K., S. Sarkar, S. De, S. C. Clemens, and A. Velu (2010), Mid-Brunhes strengthening of the Indian Ocean Dipole caused increased equatorial East African and decreased Australasian rainfall, Geophys. Res. Lett., 37, L06706, doi: 10.1029/2009GL042225. VL - 37 N1 - id: 1966; PT: J; UT: WOS:000276025100002 JO - Mid-Brunhes strengthening of the Indian Ocean Dipole caused increased equatorial East African and decreased Australasian rainfall ER - TY - JOUR T1 - Millennial-aged organic carbon subsidies to a modern river food web JF - Ecology Y1 - 2010 A1 - Caraco, Nina A1 - Bauer, James E. A1 - Cole, Jonathan J. A1 - Petsch, Steven A1 - Raymond, Peter AB - Recent studies indicate that highly aged material is a major component of organic matter transported by most rivers. However, few studies have used natural (14)C to trace the potential entry of this aged material into modern river food webs. Here we use natural abundance (14)C, (13)C, and deuterium ((2)H) to trace the contribution of aged and contemporary organic matter to an important group of consumers, crustacean zooplankton, in a large temperate river (the Hudson River, New York, USA). Zooplankton were highly (14)C depleted (mean Delta(14)C = -240 parts per thousand) compared to modern primary production in the river or its watershed (Delta(14)C = -60 parts per thousand to +50 parts per thousand). In order to account for the observed (14)C depletion, zooplankton must be subsidized by highly aged particulate organic carbon. IsoSource modeling suggests that the range of the aged dietary subsidy is between similar to 57%, if the aged organic matter source was produced 3400 years ago, and similar to 21%, if the organic carbon used is >= 50 000 years in age, including fossil material that is millions of years in age. The magnitude of this aged carbon subsidy to river zooplankton suggests that modern river food webs may in some cases be buffered from the limitations set by present-day primary production. VL - 91 IS - 8 N1 - id: 2032; PT: J; UT: WOS:000280153500022 JO - Millennial-aged organic carbon subsidies to a modern river food web ER - TY - JOUR T1 - Millennial-scale climate variability during the Last Glacial period in the tropical Andes JF - Quaternary Science Reviews Y1 - 2010 A1 - Fritz, S. C. A1 - Baker, P. A. A1 - Ekdahl, E. A1 - Seltzer, G. O. A1 - Stevens, L. R. AB - Millennial-scale climate variation during the Last Glacial period is evident in many locations worldwide, but it is unclear if such variation occurred in the interior of tropical South America. and, if so, how the low-latitude variation was related to its high-latitude counterpart A high-resolution record, derived from the deep drilling of sediments on the floor of Lake Titicaca in the southern tropical Andes, is presented that shows clear evidence of millennial-scale climate variation between similar to 60 and 20 ka BP This variation is manifested by alternations of two interbedded sedimentary units The two units have distinctive sedimentary, geochemical, and paleobiotic properties that are controlled by the relative abundance of terrigenous or nearshore components versus pelagic components The sediments of more terrigenous or nearshore nature likely were deposited during regionally wetter climates when river transport of water and sediment was higher, whereas the sediments of more pelagic character were deposited during somewhat drier climates regionally. The majority of the wet periods inferred from the Lake Titicaca sediment record are correlated with the cold events in the Greenland ice cores and North Atlantic sediment cores. indicating that increased intensity of the South American summer monsoon was part of near-global scale climate excursions (C) 2010 Elsevier Ltd All rights reserved VL - 29 IS - 7-8 N1 - id: 1886; 584JY Times Cited:5 Cited References Count:59Y JO - Millennial-scale climate variability during the Last Glacial period in the tropical Andes ER - TY - JOUR T1 - Mineral carbonation in peridotite and basalt for CO2 capture and storage JF - Annual Reviews of Earth & Planetary Sciences Y1 - 2010 A1 - Kelemen, P. B. A1 - Matter, J. M. A1 - Streit, L. N1 - id: 845not submitted ER - TY - JOUR T1 - Modern sediment dispersal and accumulation on the outer Poverty continental margin JF - Marine Geology Y1 - 2010 A1 - Alexander, C. R. A1 - Walsh, J. P. A1 - Orpin, A. R. AB - The Poverty margin was sampled in 2005 and 2006 as part of an international initiative to examine the terrestrial and marine sedimentary response to natural and human impacts on dispersal systems at mud-dominated coasts: the NSF MARGINS Source-to-Sink Initiative. Pb-210 accumulation rates generally decrease from similar to 1 g/cm(2) y in the mid-shelf depocenter on the outer shelf to similar to 0.1 g/cm2 y on the mid-slope plateau (range 0.04-2.53 g/cm(2) y). Higher accumulation rates are observed all along the outer Poverty shelf, extending over the shelf break onto the upper Poverty slope in canyons and gullies. Rates are fast in gullies that incise into the shelf edge (0.75-1 g/cm(2) y), particularly in the area between Waipaoa Canyon and Poverty Canyon, and in the axis of Poverty Canyon (1.29-1.89 g/cm(2) y). Below similar to 1200 m water depth, rates in the axis of Poverty Canyon are no more rapid than those found at open slope cores in similar water depths (0.12-0.15 g/cm(2) y). Excess Pb-210 profiles generally exhibit steady state characteristics, except in the axis of Poverty Canyon, where non-steady-state Pb-210 profiles are observed. Cs-137 was not found above minimum detection limits or above statistical background levels in any cores from the Poverty margin. Be-7 was found distributed widely along and across the margin during both summer and winter periods, observed to depths of up to 4cm. Widespread presence of Be-7 on the margin in both winter and summer suggests that terrestrially derived sediment is reaching the outer shelf and upper slope throughout the year. A sediment budget based on Pb-210 accumulation rate data shows that approximately 13-18% of the Waipaoa annual discharge is accumulating on the outer Poverty margin as a whole, and approximately 11-15% of the annual discharge is accumulating on the continental slope alone. Notably, approximately 28% of the sediment annually accumulating in the outer margin is being sequestered in slope gullies and canyons, although they represent only 6% of the area of the outer margin. (C) 2009 Elsevier B.V. All rights reserved. VL - 270 IS - 1-4 N1 - id: 792; Sp. Iss. SI 576IF Times Cited:4 Cited References Count:72Y JO - Modern sediment dispersal and accumulation on the outer Poverty continental margin ER - TY - JOUR T1 - Molecular and Isotopic Analysis of Motor Oil from a Biodiesel-Driven Vehicle JF - Energy & Fuels Y1 - 2010 A1 - Peacock, E. E. A1 - Arey, J. S. A1 - DeMello, J. A. A1 - McNichol, A. P. A1 - Nelson, R. K. A1 - Reddy, C. M. AB - Biodiesel, a mixture of fatty acid methyl esters (FAMEs), is increasingly recognized as a renewable fuel. While some environmental impacts of biodiesel usage have been investigated, accumulation of organic compounds in motor oil, which can subsequently leak onto roads, has not been studied. Because studies have shown that toxic polycyclic aromatic hydrocarbons (PAHs) accumulate in the motor oil of engines fueled with fossil diesel or gasoline, the objective of this study was to determine if this also occurs for engines fueled with biodiesel. Here, we sampled and analyzed motor oil of a biodiesel-powerd 2005 Volkswagen Passat Wagon over 3240 km for personal-use driving. Using gas chromatography with flame ionization detection (GC-FID), we found a total of 0.5% FAMEs in the motor oil after 3240 km. We also used gas chromatography-mass spectrometry and comprehensive two-dimensional gas chromatography and did not detect PAHs or other organic compounds not present in the initial motor oil. Using natural radiocarbon analysis, a powerful technique capable of detecting biodiesel-derived carbon that would be otherwise undetectable by gas chromatography, we found a total of 0.68% biodiesel-derived carbon after 3240 km. This is similar to the amount of FAMEs found in these samples with GC-FID, indicating that the primary source of biodiesel-derived carbon in the motor oil is FAMEs (and not PAHs or other carbonaceous species). This result suggests that used motor oil of biodiesel vehicles can be less toxic based on PAH content than vehicles fueled with fossil diesel or gasoline. VL - 24 N1 - id: 816; 555MH Times Cited:0 Cited References Count:63; YY JO - Molecular and Isotopic Analysis of Motor Oil from a Biodiesel-Driven Vehicle ER - TY - JOUR T1 - A molecular perspective on Late Quaternary climate and vegetation change in the Lake Tanganyika basin, East Africa JF - Quaternary Science Reviews Y1 - 2010 A1 - Tierney, J. E. A1 - Russell, J. M. A1 - Huang, Y. S. AB - Characterizing the nature of past hydrological change and its interactions with vegetation is fundamental to acquiring a better understanding of continental tropical climate dynamics. Here, we outline major shifts in the climate and ecosystem of tropical East Africa for the past 60,000 years (60 ka) by examining molecular records of hydrology, vegetation, and temperature from a sediment sequence from Lake Tanganyika. We demonstrate, via comparison with pollen spectra, that stable carbon isotopes measured on higher plant leaf waxes (delta C-13(wax)) are a reliable proxy for vegetation change. In addition we argue that the D/H ratio of higher plant leaf waxes (delta D-wax) is a robust and independent indicator of past changes in aridity, and is not affected by regional vegetation change directly. Our paired, compound-specific isotope data show that shifts in vegetation lead major changes in hydrology in the Tanganyika basin at several major climate transitions during the past 60,000 years, suggesting that vegetation in the Tanganyika basin is not as sensitive to aridity as previous studies have suggested and that variations in carbon dioxide, temperature, and internal ecosystem dynamics are equally, if not more, important. We hypothesize that regional vegetation change may exert a positive feedback on regional hydrology, thus partially accounting for the abrupt threshold behavior evident in our paleohydrological data. Furthermore, we find that past changes in Tanganyika basin climate and ecology are closely linked to concentrations of atmospheric trace gases, highlighting the paramount influence of global climatic shifts upon regional tropical climate over glacial/interglacial timescales. (C) 2009 Elsevier Ltd. All rights reserved. VL - 29 IS - 5-6 N1 - id: 1850; 574XV Times Cited:0 Cited References Count:111Y JO - A molecular perspective on Late Quaternary climate and vegetation change in the Lake Tanganyika basin, East Africa ER - TY - JOUR T1 - No signature of abyssal carbon n intermediate waters off Chile during deglaciation JF - Nature Geosciences Y1 - 2010 A1 - dePol-Holz, R. A1 - Keigwin, L. A1 - Southon, J. A1 - Hebbeln, D. A1 - Mohtadi, M. VL - 3 N1 - id: 772; YY JO - No signature of abyssal carbon n intermediate waters off Chile during deglaciation ER - TY - JOUR T1 - The Passage of the Bomb Radiocarbon Pulse into the Pacific Ocean JF - Radiocarbon Y1 - 2010 A1 - Jenkins, W. J. A1 - Elder, K. L. A1 - McNichol, A. P. A1 - von Reden, K. KW - AMS KW - antarctic intermediate water KW - anthropogenic co2 KW - atlantic KW - c-14 data KW - carbon KW - distributions KW - graphite KW - south-pacific KW - tritium AB - We report and compare radiocarbon observations made on 2 meridional oceanographic sections along 150 degrees W in the South Pacific in 1991 and 2005. The distributions reflect the progressive penetration of nuclear weapons-produced (14)C into the oceanic thermocline. The changes over the 14 yr between occupations are demonstrably large relative to any possible drift in our analytical standardization. The computed difference field based on the gridded data in the upper 1600 m of the section exhibits a significant decrease over time (approaching 40 to 50 parts per thousand in Delta(14)C) in the upper 200-300 m, consistent with the decadal post-bomb decline in atmospheric (14)C levels. A strong positive anomaly (increase with time), centered on the low salinity core of the Antarctic Intermediate Water (AAIW), approaches 50-60 parts per thousand in Delta(14)C, a clear signature of the downstream evolution of the (14)C transient in this water mass. We use this observation to estimate the transit time of AAIW from its "source region" in the southeast South Pacific and to compute the effective reservoir age of this water mass. The 2 sections show small but significant changes in the abyssal (14)C distributions. Between 1991 and 2005, Delta(14)C has increased by 9 parts per thousand below 2000 m north of 55 degrees S. This change is accompanied overall by a modest increase in salinity and dissolved oxygen, as well as a slight decrease in dissolved silica. Such changes are indicative of greater ventilation. Calculation of "phosphate star" also indicates that this may be due to a shift from the Southern Ocean toward North Atlantic Deep Water as the ventilation source of the abyssal South Pacific. VL - 52 SN - 0033-8222 IS - 3 N1 - Sp. Iss. 2696jo Times Cited:7 Cited References Count:38 JO - Radiocarbon ER - TY - JOUR T1 - Photosynthetic isotope biosignatures in laminated micro-stromatolitic and non-laminated nodules associated with modern, freshwater microbialites in Pavilion Lake, BC RID B-8520-2011 JF - Chemical Geology Y1 - 2010 A1 - Brady, A. L. A1 - Slater, G. F. A1 - Omelon, C. R. A1 - Southam, G. A1 - Druschel, G. A1 - Andersen, D. T. A1 - Hawes, I. A1 - Laval, B. A1 - Lim, D. S. S. AB - The influence of microbial activity on carbonate precipitation was investigated within micro-stromatolitic nodules associated with modem, freshwater microbialites located in Pavilion Lake, B.C. Observed carbonate delta(13)C values enriched by up to +3.6 parts per thousand as compared to predicted abiotic carbonate delta(13)C values from measured dissolved inorganic carbon (mean -1.2 parts per thousand, n=13) were consistent with microbial photosynthetic influence on in situ precipitation within the nodule microenvironment. Estimated carbonate precipitation temperatures within the nodules based on delta(18)O were consistent with recorded summertime temperatures, indicative of precipitation during the period of highest levels of photosynthetic activity. Low delta(13)C values of organic matter within the nodules (-30.6 to 21.1 parts per thousand) and an average inorganic to organic carbon Delta delta(13)C value of 26.8 parts per thousand reflected the preferential uptake of (12)C during non-CO(2) limited photosynthesis, supporting the generation of (13)C-enriched DIC. Microelectrode profiles through the nodules showed oxygen supersaturation of up to similar to 275%, elevated pH compared to ambient water and a lack of any observable dissolved sulphide, Mn or Fe further indicated that photosynthetic activity was the predominant metabolic process within the nodule during light exposure. Microbial phospholipid fatty acid profiles of the nodule communities were indicative of bacteria rather than eukaryotes and PLFA delta(13)C values were depleted relative to the bulk cell by 2.6-6.6 parts per thousand, consistent with a predominance of photosynthetic microbes. Scanning electron microscopy images of the relationship between carbonate minerals and filaments indicated that carbonate precipitation had occurred in situ due to microbial influences on the geochemistry within the nodule microenvironment rather than due to cell surface effects or trapping and binding. The observation of photosynthetically induced (13)C-enrichment of in situ precipitated carbonate within the nodule microenvironment is thus a biosignature of the activity of these surface communities and is consistent with the hypothesized role of biology in the formation of microbialites. (C) 2010 Elsevier B.V. All rights reserved. VL - 274 IS - 1-2 N1 - id: 2056; PT: J; UT: WOS:000279094700005 JO - Photosynthetic isotope biosignatures in laminated micro-stromatolitic and non-laminated nodules associated with modern, freshwater microbialites in Pavilion Lake, BC RID B-8520-2011 ER - TY - JOUR T1 - Postglacial changes in El Nino and La Nina behavior JF - Geology Y1 - 2010 A1 - Makou, Matthew C. A1 - Eglinton, Timothy I. A1 - Oppo, Delia W. A1 - Hughen, Konrad A. AB - Paleoclimate reconstructions suggest distinctive changes in the Ell Nino-Southern Oscillation (ENSO), the dominant mode of tropical climate variability, over the last glacial cycle and throughout the Holocene. However, to the best of our knowledge, no studies provide parallel reconstructions of warm (El Nino) and cold (La Nina) phase variability, thus precluding distinction between variations in ENSO activity and the mean state of the tropical Pacific. Here we provide the first such records, generated using molecular organic geochemical proxies in a sediment core from the Peru margin region. The opposing influences of El Nino and La Nina on coastal upwelling and phytoplankton community structure produce distinct sedimentary sterol records describing the evolution of each ENSO phase. We document changes in surface ocean productivity on the Peru margin over the past 16 ka that indicate enhanced La Nina-like conditions alone during deglaciation, but concomitant increases in both El Nino and La Nina activity during the past 2 ka. We propose that the preponderance of La Nina-like conditions prior to 11.5 ka reflects the influence of waning glacial boundary conditions. By contrast, warm and cold phase covariability during the late Holocene suggests centennial-scale changes in ENSO activity, rather than the Pacific mean state, driven by tropical insolation. VL - 38 IS - 1 N1 - id: 1985; PT: J; UT: WOS:000273346200011 JO - Postglacial changes in El Nino and La Nina behavior ER - TY - JOUR T1 - The potential of New Zealand kauri (Agathis australis) for testing the synchronicity of abrupt climate change during the Last Glacial Interval (60,000-11,700 years ago) JF - Quaternary Science Reviews Y1 - 2010 A1 - Turney, Chris S. M. A1 - Fifield, L. Keith A1 - Hogg, Alan G. A1 - Palmer, Jonathan G. A1 - Hughen, Konrad A1 - Baillie, Mike G. L. A1 - Galbraith, Rex A1 - Ogden, John A1 - Lorrey, Andrew A1 - Tims, Stephen G. A1 - Jones, Richard T. AB - The latter part of the Last Glacial Interval (LGI; 60,000 to 11,700 years ago) experienced a range of climatic and environment extremes. To elucidate the mechanisms of these changes requires records of past variability that are precisely dated and correlated on the same absolute timescale. However, despite decades of research, it is still not possible to align most marine and terrestrial records of past change with ice-core records, largely because of ongoing uncertainties over the conversion of pre-Holocene (14)C ages on to a calendar timescale and uncertainties with in ice-core chronologies. As a result, it is equivocal whether climate changes in both hemispheres during the LGI led, lagged or were synchronous with one another. A decadally-resolved radiocarbon calibration is urgently required to test these models of the Earth system. Here we report radiocarbon measurements obtained from subfossil New Zealand kauri (Agathis australis) spanning a collective 3500 years dated between 25,000 and 45,000 years ago. The results are compared to the recently published international calibration curve IntCal09 and to the marine Cariaco Basin datasets. We show that kauri have considerable potential for development of a Southern Hemisphere component of a unified global calibration curve suite, and that tree-ring sequences can be superposed on other radiocarbon records to constrain atmospheric marine offsets and precisely test the synchronicity of abrupt climate change. (C) 2010 Elsevier Ltd. All rights reserved. VL - 29 IS - 27-28 N1 - id: 1982; PT: J; UT: WOS:000285222000001 JO - The potential of New Zealand kauri (Agathis australis) for testing the synchronicity of abrupt climate change during the Last Glacial Interval (60,000-11,700 years ago) ER - TY - JOUR T1 - The radiocarbon age of organic carbon in marine surface sediments JF - GEOCHIMICA ET COSMOCHIMICA ACTA Y1 - 2010 A1 - Griffith, David R. A1 - Martin, William R. A1 - Eglinton, Timothy I. AB - Long-term carbon cycling and climate change are strongly dependent on organic carbon (OC) burial in marine sediments. Radiocarbon ((14)C) has been widely used to constrain the sources, sinks, and processing of sedimentary OC. To elucidate the dominant controls on the radiocarbon content of total organic carbon ((14)C(TOC)) accumulating in surface sediments we construct a box model that predicts (14)C(TOC) in the sediment mixed layer (measured as fraction modern, Fm). Our model defines three distinct OC pools ({''}degradable,{''} ``semi-labile,{''} and ``refractory{''}) and assumes that (14)C(TOC) flux to sediments is exclusively derived from surface ocean primary productivity, and hence follows a ``generic{''} surface ocean dissolved inorganic carbon (DIC) bomb curve. Model predictions are compared to a set of 75 surface sediment samples, which span a wide geographic range and reflect diverse water column and depositional conditions, and for which sedimentation rate and mixed-layer depth are well characterized. Our model overestimates the Fm value for a majority (65%) of these sites, especially at shallow water depths and for sites characterized by depleted delta(13)C(TOC) values. The model is most sensitive to sedimentation rate and mixed-layer depth. Therefore, slight changes to these parameters can lead to a match between modeled and measured Fm values at many sites. Yet, in some cases, we find that measured Fm values cannot be simulated without large and unrealistic changes to sedimentation rate and mixed-layer depth. These results point to sources of pre-aged OC to surface sediments and implicate soil-derived terrestrial OC, reworked marine OC, and/or anthropogenic carbon as important components of the organic matter present in surface sediments. This approach provides a valuable framework within which to explore controls on sedimentary organic matter composition and carbon burial over a range of spatial and temporal scales. (C) 2010 Elsevier Ltd. All rights reserved. VL - 74 ER - TY - JOUR T1 - Radiocarbon Dating of Individual Lignin Phenols: A New Approach for Establishing Chronology of Late Quaternary Lake Sediments JF - ANALYTICAL CHEMISTRY Y1 - 2010 A1 - Hou, Juzhi A1 - Huang, Yongsong A1 - Brodsky, Corynn A1 - Alexandre, Marcelo R. A1 - McNichol, Ann P. A1 - King, John W. A1 - Hu, Feng Sheng A1 - Shen, Ji AB - The reliability of chronology is a prerequisite for meaningful paleoclimate reconstructions from sedimentary archives. The conventional approach of radiocarbon dating bulk organic carbon in lake sediments is often hampered by the old carbon effect, i.e., the assimilation of ancient dissolved inorganic carbon (DIC) derived from carbonate bedrocks or other sources. Therefore, radiocarbon dating is ideally performed on organic compounds derived from land plants that use atmospheric CO(2) and rapidly delivered to sediments. We demonstrate that lignin phenols isolated from lake sediments using reversed phase high performance liquid chromatography (HPLC) can serve as effective (14)C dating materials for establishing chronology during the late Quaternary. We developed a procedure to purify lignin phenols, building upon a published method. By isolating lignin from standard wood reference substances, we show that our method yields pure lignin phenols and consistent ages as the consensus ages and that our procedure does not introduce radiocarbon contamination. We further demonstrate that lignin phenol ages are compatible with varve counted and macrofossil dated sediment horizons in Steel Lake and Fayetteville Green Lake. Applying the new method to lake sediment cores from Lake Qinghai demonstrates that lignin phenol ages in Lake Qinghai are consistently younger than bulk total organic carbon (TOC) ages which are contaminated by old carbon effect. We also show that the age offset between lignin and bulk organic carbon differs at different Lake Qinghai sedimentary horizons, suggesting a variable hard water effect at different times and that a uniform age correction throughout the core is inappropriate. VL - 82 ER - TY - CONF T1 - Radiocarbon in the Canada Basin: Carbon Transfer Processes in the Changing Arctic T2 - Proceedings from the 2010 AGU Ocean Sciences Meeting Y1 - 2010 A1 - McNichol, A P A1 - Xu, L A1 - Griffith, D R A1 - Eglinton, T I A1 - Macdonald, R A1 - McLaughlin, F A KW - and modeling KW - Biogeochemical cycles KW - carbon cycling KW - processes KW - Radioactivity and radioisotopes AB - We are developing full water column depth [delta]14C profiles for dissolved inorganic carbon (DIC), dissolved organic carbon (DOC) and suspended particulate organic carbon (POC) collected in 2008 from the Canada Basin in the Arctic Ocean. These samples provide an opportunity to study the current distribution of radiocarbon in different carbon pools and set a baseline for future investigations of the carbon cycle in this key oceanic region where climate change is anticipated to have a major and imminent impact on carbon storage and cycling. Our first DI14C depth profile from 75, 150 is similar to one taken in 1992 (Jones et al. 1994) in demonstrating a well-ventilated surface layer overlying an older but recently ventilated deeper basin. Significant increases in DI14C, up to 30 ppt, are observed in the mid-depth region between 500 to 1500 m, roughly coincident with a warm layer underlying cold surface waters. The differences that have occurred over 16 years may lend insight to the observed warming of Atlantic water in the Canada Basin over the past decades. We will present the first DO14C profile from the central Canada Basin. Measurements are being made using a UV oxidation system established at NOSAMS. Most of the samples collected for DO14C measurement were acidified to preserve them. Results from frozen duplicates for a few of the samples will be compared to validate the preservation technique. In most regions of the ocean, the shape of DO14C depth profiles parallel those of DI14C profiles but are shifted to significantly older values. This reflects the fact that general oceanographic circulation and remineralization processes dominate the overall profile, but that the sources of carbon to the DOC pool are more complex than those of DIC. It is unknown whether this will be the case in the Arctic Ocean which, while representing only ~1% of the worlds ocean volume, receives approximately 13% of the global flux of terrigeneous DOC. Jones, G. A. et al. (1994). NIMS B, 92, 426-430. JF - Proceedings from the 2010 AGU Ocean Sciences Meeting PB - American Geophysical Union, 2000 Florida Ave., N.W. Washington DC 20009 USA, [URL:http://www.agu.org] UR - https://search.proquest.com/docview/754883766?accountid=29119 N1 - Date revised - 2010-09-01SuppNotes - Abstracts AvailableLast updated - 2016-12-22 ER - TY - JOUR T1 - Rapid Climatic Signal Propagation from Source to Sink in a Southern California Sediment-Routing System JF - Journal of Geology Y1 - 2010 A1 - Covault, J. A. A1 - Romans, B. W. A1 - Fildani, A. A1 - McGann, M. A1 - Graham, S. A. AB - Terrestrial source areas are linked to deep-sea basins by sediment-routing systems, which only recently have been studied with a holistic approach focused on terrestrial and submarine components and their interactions. Here we compare an extensive piston-core and radiocarbon-age data set from offshore southern California to contemporaneous Holocene climate proxies in order to test the hypothesis that climatic signals are rapidly propagated from source to sink in a spatially restricted sediment-routing system that includes the Santa Ana River drainage basin and the Newport deep-sea depositional system. Sediment cores demonstrate that variability in rates of Holocene deep-sea turbidite deposition is related to complex ocean-atmosphere interactions, including enhanced magnitude and frequency of the North American monsoon and El Nino-Southern Oscillation cycles, which increased precipitation and fluvial discharge in southern California. This relationship is evident because, unlike many sediment-routing systems, the Newport submarine canyon-and-channel system was consistently linked to the Santa Ana River, which maintained sediment delivery even during Holocene marine transgression and highstand. Results of this study demonstrate the efficiency of sediment transport and delivery through a spatially restricted, consistently linked routing system and the potential utility of deep-sea turbidite depositional trends as paleoclimate proxies in such settings. VL - 118 IS - 3 N1 - id: 875; 574IR Times Cited:0 Cited References Count:55Y JO - Rapid Climatic Signal Propagation from Source to Sink in a Southern California Sediment-Routing System ER - TY - JOUR T1 - Recent shoaling of the nutricline and thermocline in the western tropical Pacific JF - Geophysical Research Letters Y1 - 2010 A1 - Williams, Branwen A1 - Grottoli, Andrea G. AB - Long records of subsurface ocean observations are key to constrain our understanding of the climate response of the tropical Pacific to increasing greenhouse gases. Due to the lack of continuous ocean observations, proxies become essential to estimate changes in the tropical thermocline related to changes in Walker circulation. Here, we present high resolution stable nitrogen (delta(15)N) and carbon (delta(13)C) isotope records from three proteinaceous corals spanning the top 105 m of the euphotic zone from an offshore Palauan reef in the western tropical Pacific. Dated with radiocarbon-derived growth chronologies, these isotope records indicate a shoaling of the mean nutricline and thus the thermocline as well, and a likely increase in primary productivity in the western tropical Pacific since the mid-to-late 1970s. Thus, these are the first subsurface proxy data extending below 20 m to support a slowdown of the tropical Pacific Walker circulation during the 20th Century. Citation: Williams, B., and A. G. Grottoli (2010), Recent shoaling of the nutricline and thermocline in the western tropical Pacific, Geophys. Res. Lett., 37, L22601, doi:10.1029/2010GL044867. VL - 37 N1 - id: 1961; PT: J; UT: WOS:000284479000002 JO - Recent shoaling of the nutricline and thermocline in the western tropical Pacific ER - TY - JOUR T1 - Reconnaissance dating A new radiocarbon method applied to assessing the temporal distribution of Southern Ocean deep-sea corals JF - Deep-Sea Research Part I-Oceanographic Research Papers Y1 - 2010 A1 - Burke, Andrea A1 - Robinson, Laura F. A1 - McNichol, Ann P. A1 - W. J. Jenkins A1 - Scanlon, Kathryn M. A1 - Gerlach, Dana S. AB - We have developed a rapid reconnaissance method of preparing graphite for (14)C/(12)C analysis Carbonate (similar to 15 mg) is combusted using an elemental analyzer and the resulting CO(2) is converted to graphite using a sealed tube zinc reduction method Over 85% (n=45 replicates on twenty-one individual corals) of reconnaissance ages measured on corals ranging in age from 500 to 33 000 radiocarbon years (Ryr) are within two standard deviations of ages generated using standard hydrolysis methods on the same corals and all reconnaissance ages are within 300 Ryr of the standard hydrolysis ages Replicate measurements on three individual aragonitic corals yielded ages of 1076 +/- 35 Ryr (standard deviation n=5) 10 739 +/- 47 Ryr (n=8) and 40 146 +/- 3500 Ryr (n=9) No systematic biases were found using different cleaning methods or variable sample sizes Analysis of (13)C/(12)C was made concurrently with the (14)C/(12)C measurement to correct for natural fractionation and for fractionation during sample processing and analysis This technique provides a new rapid method for making accurate percent-level (14)C/(12)C analyses that may be used to establish the rates and chronology of earth system processes where survey-type modes of age estimation are desirable For example applications may include creation of sediment core-top maps preliminary age models for sediment cores and growth rate studies of marine organisms such as corals or mollusks We applied the reconnaissance method to more than 100 solitary deep-sea corals collected in the Drake Passage in the Southern Ocean to investigate their temporal and spatial distribution The corals used in this study are part of a larger sample set and the subset that was dated was chosen based on species as opposed to preservation state so as to exclude obvious temporal biases Similar to studies in other regions the distribution of deep-sea corals is not constant through time across the Drake Passage Most of the corals from the Burdwood Bank (continental shelf of Argentina) have ages ranging between 0 and 2500 calendar years whereas most of the corals from the Sars Seamount in the Drake Passage have ages between 10 000 and 12 500 calendar years Such differences may be caused in part by sampling biases but may also be caused by changes in larval transport nutrient supply or other environmental pressures (C) 2010 Elsevier Ltd All rights reserved VL - 57 IS - 11 N1 - id: 1924; PT: J; UT: WOS:000284750700012 JO - Reconnaissance dating A new radiocarbon method applied to assessing the temporal distribution of Southern Ocean deep-sea corals ER - TY - JOUR T1 - Reconstructing Holocene conditions under the McMurdo Ice Shelf using Antarctic barnacle shells JF - Earth and Planetary Science Letters Y1 - 2010 A1 - Burgess, S. N. A1 - Henderson, G. M. A1 - Hall, B. L. AB - This study evaluates the potential of barnacles for paleoceanographic reconstruction and, in particular, of the Antarctic species Bathylasma corolliforme to reconstruct past under ice shelves Like other barnacle species, this Antarctic barnacle secretes a robust low-Mg calcite shell with distinct growth increments on the external surface indicating growth over a number of years (30-50 in samples studied here). The Bathylasma samples used in this study grew in the Ross Sea and became entrained at the grounding line of a coastal ice shelf in McMurdo Sound, offering potential as an archive of changing conditions in this difficult to access environment under the McMurdo ice shelf. Nine barnacle shells were subsampled at high resolution (60 pun) for delta(18)O and delta(13)C analysis. These samples were dated with (14)C and U-Th techniques, although the later did not yield useful age information due to open-system behaviour of barnacle calcite. Measured delta(18)O values indicate that Bathylasma calcifies close to equilibrium with ambient seawater. One older sample (approximate to 200 ka) has similar delta(18)O and delta(13)C values as the eight Holocene samples, suggesting that barnacle calcite is not prone to significant diagenesis in this setting. Apparent isotope equilibrium and lack of diagenesis make barnacles a promising archive for reconstruction of past ocean conditions. Cycles of delta(18)O observed within each sample sometimes correlate with the external growth ridges, but not always, and have amplitudes of typically 0.6 parts per thousand. This magnitude of variation suggests shell growth during a significant portion of the year. although it remains unclear whether growth continues throughout the year. However, the prominent growth bands suggest at least a signficant seasonal slowing in growth rate. Variations in barnacle delta(18)O within each plate and between plates are too large to be caused by temperature. and instead reflect changes in delta(18)O of the seawater, allowing some assessment of seawater salinity under the ice shelf. Salinities are lowered by addition of meltwaters, but the barnacle delta(18)O data suggest values do not go below 33 parts per thousand.. These data indicate that Bathylasma has potential as an archive of paleoclimate information for shallow/intermediate water depths and, in particular, for difficult to reach environments such as below ice-shelves of Antarctica. Crown Copyright (C) 2010 Published by Elsevier B.V. All rights reserved VL - 298 IS - 3-4 N1 - id: 1960; PT: J; UT: WOS:000283756600013 JO - Reconstructing Holocene conditions under the McMurdo Ice Shelf using Antarctic barnacle shells ER - TY - JOUR T1 - Reduced ice extent on the western Antarctic Peninsula at 700–970 cal. yr B.P. JF - Geology Y1 - 2010 A1 - Hall, B.L. A1 - Koffman, T. A1 - Denton, G.H. AB - Rapid warming and consequent ice-shelf collapse have focused attention on the glacial record of the Antarctic Peninsula. Here, we present the first record of terrestrial organic material exposed by recently retreating ice that bears on past glacier extent and climate in this sensitive region. Radiocarbon dates show that ice on Anvers Island was at or behind its present position at 700–970 cal. yr B.P., coincident with ice reduction elsewhere in the Southern Hemisphere. Moreover, the data indicate that present reduced ice extent on the western Antarctic Peninsula is not unprecedented and is similar to that experienced during at least three periods in the last 5600 yr. VL - 38 UR - http://geology.gsapubs.org/content/38/7/635.abstract IS - 7 ER - TY - JOUR T1 - Reduced North Atlantic Central Water formation in response to early Holocene ice-sheet melting JF - Geophysical Research Letters Y1 - 2010 A1 - Bamberg, A. A1 - Rosenthal, Y. A1 - Paul, A. A1 - Heslop, D. A1 - Mulitza, S. A1 - Ruhlemann, C. A1 - Schulz, M. AB - Central waters of the North Atlantic are fundamental for ventilation of the upper ocean and are also linked to the strength of the Atlantic Meridional Overturning Circulation (AMOC). Here, we show based on benthic foraminiferal Mg/Ca ratios, that during times of enhanced melting from the Laurentide Ice Sheet (LIS) between 9.0-8.5 thousand years before present (ka) the production of central waters weakened the upper AMOC resulting in a cooling over the Northern Hemisphere. Centered at 8.54 +/- 0.2 ka and 8.24 +/- 0.1 ka our dataset records two similar to 150-year cooling events in response to the drainage of Lake Agassiz/Ojibway, indicating early slow-down of the upper AMOC in response to the initial freshwater flux into the subpolar gyre (SPG) followed by a more severe weakening of both the upper and lower branches of the AMOC at 8.2 ka. These results highlight the sensitivity of regional North Atlantic climate change to the strength of central-water overturning and exemplify the impact of both gradual and abrupt freshwater fluxes on eastern SPG surface water convection. In light of the possible future increase in Greenland Ice Sheet melting due to global warming these findings may help us to better constrain and possibly predict future North Atlantic climate change. Citation: Bamberg, A., Y. Rosenthal, A. Paul, D. Heslop, S. Mulitza, C. Ruhlemann, and M. Schulz (2010), Reduced North Atlantic Central Water formation in response to early Holocene ice-sheet melting, Geophys. Res. Lett., 37, L17705, doi: 10.1029/2010GL043878. VL - 37 N1 - id: 874; 649FZ Times Cited:3 Cited References Count:32submittedY JO - Reduced North Atlantic Central Water formation in response to early Holocene ice-sheet melting ER - TY - JOUR T1 - Regional seismic stratigraphy and controls on the Quaternary evolution of the Cape Hatteras region of the Atlantic passive margin, USA JF - Marine Geology Y1 - 2010 A1 - Mallinson, D. J. A1 - Culver, S. J. A1 - Riggs, S. R. A1 - Thieler, E. R. A1 - Foster, D. A1 - Wehmiller, J. A1 - Farrell, K. M. A1 - Pierson, J. AB - Seismic and core data, combined with amino acid racemization and strontium-isotope age data, enable the definition of the Quaternary stratigraphic framework and recognition of geologic controls on the development of the modern coastal system of North Carolina, U.S.A. Seven regionally continuous high amplitude reflections are defined which bound six seismic stratigraphic units consisting of multiple regionally discontinuous depositional sequences and parasequence sets, and enable an understanding of the evolution of this margin. Data reveal the progressive eastward progradation and aggradation of the Quaternary shelf. The early Pleistocene inner shelf occurs at a depth of ca. 20-40 m beneath the western part of the modern estuarine system (Pamlico Sound). A mid- to outer shelf lowstand terrace (also early Pleistocene) with shelf sand ridge deposits comprising parasequence sets within a transgressive systems tract, occurs at a deeper level (ca. 45-70 m) beneath the modern barrier island system (the Outer Banks) and northern Pamlico Sound. Seismic and foraminiferal paleoenvironmental data from cores indicate the occurrence of lowstand strandplain shoreline deposits on the early to middle Pleistocene shelf. Middle to late Pleistocene deposits occur above a prominent unconformity and marine flooding surface that truncates underlying units, and contain numerous filled fluvial valleys that are incised into the early and middle Pleistocene deposits. The stratigraphic framework suggests margin progradation and aggradation modified by an increase in the magnitude of sea-level fluctuations during the middle to late Pleistocene. expressed as falling stage, lowstand, transgressive and highstand systems tracts. Thick stratigraphic sequences occur within the middle Pleistocene section, suggesting the occurrence of high capacity fluvial point sources debouching into the area from the west and north. Furthermore, the antecedent topography plays a significant role in the evolution of the geomorphology and stratigraphy of this marginal system. (C) 2009 Elsevier B.V. All rights reserved. VL - 268 IS - 1-4 N1 - id: 1862; 556RX Times Cited:0 Cited References Count:71Y JO - Regional seismic stratigraphy and controls on the Quaternary evolution of the Cape Hatteras region of the Atlantic passive margin, USA ER - TY - JOUR T1 - Relative sea-level changes, Schuchert Dal, East Greenland, with implications for ice extent in late-glacial and Holocene times JF - Quaternary Science Reviews Y1 - 2010 A1 - Hall, B. L. A1 - Baroni, C. A1 - Denton, G. H. AB - The chronology of late-glacial and Holocene ice fluctuations in East Greenland is important for documenting glacier response to climate change and for determining the mechanisms behind abrupt climate switches. Raised marine sediments and landforms suggest culmination of the late-glacial Milne Land Stade in Schuchert Dal alongside Scoresby Sund before similar to 11,900-12,300 cal yr B.P. Ice in Schuchert Dal apparently receded during the later part of the Younger Dryas, consistent with the idea that this period was characterized by strong seasonality. A stillstand or slight readvance probably interrupted overall recession just prior to 11,000 cal yr B.P. In many locations, ice was back close to present positions by the start of the Holocene. The most extensive glacier advance of the Holocene occurred during the Little Ice Age and was restricted to within a few kilometers of present-day ice margins. (C) 2010 Elsevier Ltd. All rights reserved. VL - 29 IS - 25-26 N1 - id: 1953; PT: J; SI: SI; UT: WOS:000284724400003 JO - Relative sea-level changes, Schuchert Dal, East Greenland, with implications for ice extent in late-glacial and Holocene times ER - TY - JOUR T1 - The role of glacio-eustasy in sequence formation: Mid-Atlantic Continental Margin, USA JF - Marine Geology Y1 - 2010 A1 - McHugh, Cecilia M. A1 - Hartin, Corinne A. A1 - Mountain, Gregory S. A1 - Gould, Helene M. KW - Hudson Canyon; Hudson Shelf Valley KW - Last glacial maximum KW - Mid-Atlantic Continental Margin KW - paleoshoreline KW - sequence stratigraphy AB - Previous studies of the Mid-Atlantic Continental Margin had shown the lack of correlation between Pleistocene glacio-eustatic oscillations and sequence boundaries. This study documents late Pleistocene to Holocene paleoenvironments within a seismic stratigraphic sequence in order to characterize sequence formation and the development of unconformities in response to glacio-eustatic oscillations. The data, high-resolution CHIRP subbottom profiling and 28 vibracores, were collected in water depths of 38 m to 145 m as part of the R/V Endeavor cruise 370 survey to the Mid-Atlantic Continental Margin. Sediment sources, sedimentary and seismic facies associated with the last major glaciation, and oxygen isotope stages OIS 5 to OIS 1 were examined and a chronology was constructed from mollusk assemblages of intertidal origin that allowed tracking the paleoshoreline from 19 to 6 ka BP. The maximum extent of the Last Glacial Maximum (LGM) paleoshoreline at 17 ka BP was documented near the 120 m modern isobath. The shoreline was marked by sediment mounds up to 5 m high and troughs 15 m deep and 1 km wide (interpreted as shoreface and tidal inlet or lagoons) formed from 17 to 15 ka BP. Five kilometers seaward from the LGM shoreline and the head of the Hudson Canyon is a wedge-shaped feature interpreted as a lowstand delta. Sediments older than the last glacial, possibly OIS 3 or OIS 5, onlap a basal unconformity. We correlate this unconformity to a previously identified sequence boundary. Approximately 20 m to 30 m of sediment accumulated on the outer shelf NE of the Hudson Canyon during the last glacial and little deposition has occurred since ~ 11 ka BP. The modern outershelf is covered by ~ 1 m of mollusk-rich glauconitic sand deposited from latest Pleistocene to early Holocene, 15 to 11 ka BP. These results showed a close correspondence between depositional environments and glacio-eustasy but sequence development and sequence boundary formation appeared to be influenced by the incomplete filling of accommodation space due to poor preservation during OIS 2 and low accumulation during the Holocene. VL - 277 UR - http://linkinghub.elsevier.com/retrieve/pii/S0025322710002331http://api.elsevier.com/content/article/PII:S0025322710002331?httpAccept=text/xmlhttp://api.elsevier.com/content/article/PII:S0025322710002331?httpAccept=text/plain IS - 1-4 ER - TY - JOUR T1 - Search for a glacial-age (14)C-depleted ocean reservoir JF - Geophysical Research Letters Y1 - 2010 A1 - Broecker, Wally A1 - Clark, Elizabeth AB - Measurements of the radiocarbon age difference between mixed benthic foraminifera and several coexisting planktic entities were made in hopes of finding evidence for the existence of an isolated glacial-age abyssal ocean reservoir whose demise would explain the large drops in the (14)C to C ratio in atmosphere and surface ocean carbon which occurred during the period of deglaciation. Forty-six new radiocarbon results were obtained at seven depths covering the full range of glacial time (i.e., similar to 27 to 15 (14)C kyrs) from an equatorial Pacific sediment core at 4.4-km water depth. Even though age reversals for foraminifera (but not for coccoliths) at two of the eight depths and large age differences between G. sacculifer and three submixed-layer planktic species mar this data set, there remains little likelihood that such a reservoir existed. Citation: Broecker, W., and E. Clark (2010), Search for a glacial-age (14)C-depleted ocean reservoir, Geophys. Res. Lett., 37, L13606, doi: 10.1029/2010GL043969. VL - 37 N1 - id: 1923; PT: J; UT: WOS:000280043800003 JO - Search for a glacial-age (14)C-depleted ocean reservoir ER - TY - JOUR T1 - Selective preservation of old organic carbon fluvially released from sub-Arctic soils JF - Geophysical Research Letters Y1 - 2010 A1 - Vonk, J. E. A1 - van Dongen, B. E. A1 - Gustafsson, O. AB - Amplified climate warming in the Arctic may cause thaw-remobilization of its large soil organic carbon (SOC) pool. Here we assess the remobilization and preservation of old SOC by the watershed-integrated radiocarbon signature of molecular SOC markers released from northernmost Scandinavia. The radiocarbon analyses revealed a remarkable fractionation for identical vascular plant markers (similar to 420 parts per thousand or similar to 6000 (14)C years) upon settling from surface water to the underlying sediments. From this, we infer fluvial export of two SOC pools; a young surface peat component, and an old deep mineral soil component. The young pool exists as an easily degradable humic suspension, while the old pool is matrix protected from degradation and ballasted for preferential settling. The two soil types with highest OC in Arctic permafrost evidently exhibit different susceptibilities to degradation. Hence, a significant part of the thaw-released OC may simply be fluvially relocated to sediments instead of being emitted to the atmosphere. Citation: Vonk, J.E., B.E. van Dongen, and. Gustafsson (2010), Selective preservation of old organic carbon fluvially released from sub-Arctic soils, Geophys. Res. Lett., 37, L11605, doi:10.1029/2010GL042909. VL - 37 N1 - id: 886; 610KU Times Cited:7 Cited References Count:30Y JO - Selective preservation of old organic carbon fluvially released from sub-Arctic soils ER - TY - THES T1 - Shifting Perceptions of Sacred Spaces: Ceremonial Reuse of Maya Architecture and Monuments at San Bartolo, Guatemala Y1 - 2010 A1 - Craig, Jessica PB - University of Kansas CY - Lawrence VL - Dissertation/Thesis ER - TY - JOUR T1 - Sources of CO2 evasion from two subtropical rivers in North America JF - Biogeochemistry Y1 - 2010 A1 - Zeng, F. W. A1 - Masiello, C. A. AB - We directly measured the partial pressure of dissolved CO2 (pCO(2)) in two humid subtropical rivers in coastal Texas, one highly urbanized (Buffalo Bayou) and one relatively undeveloped (Spring Creek), and analyzed carbon isotopic signatures (Delta C-14 and delta C-13) of riverine dissolved inorganic carbon (DIC) to determine carbon sources sustaining river respiration. Both rivers were highly supersaturated with CO2 at all study sites and on all dates sampled from June 2007 to February 2009. Mean riverine pCO(2) values are 3,052 +/- A 1,364 and 4,702 +/- A 1,980 mu atm for Buffalo Bayou and Spring Creek, respectively. Calculated CO2 emission fluxes per ha of water surface area from these rivers are intermediate between those in tropical and temperate rivers, indicating that globally, humid subtropical rivers may be a significant source of atmospheric CO2. Carbon isotopic signatures revealed that CO2 supersaturation is supported by different carbon sources for the two rivers. In the relatively undeveloped river (Spring Creek), young terrestrial organic matter (OM) is the predominant C source fueling river heterotrophic respiration. In the highly urbanized river (Buffalo Bayou), the high concentration of riverine CO2 is additionally supported by dissolution of CaCO3 likely from pedogenic carbonate, and crushed limestone/dolomite and oyster shells imbedded in old roads in the watershed. Because urban sources of acidity can include HNO3 and H2SO4, whether the limestone/dolomite and shells used by humans act as a net sink or source of atmospheric CO2 needs further study. VL - 100 IS - 1-3 N1 - 646uoTimes Cited:17Cited References Count:55 JO - Sources of CO2 evasion from two subtropical rivers in North America ER - TY - THES T1 - A Source-to-Sink Study of the Mekong River Delta: Hydrology, Delta Evolution, and Sediment Transport Modeling Y1 - 2010 A1 - Xue, Z. PB - North Carolina State University VL - Ph.D. ER - TY - CONF T1 - The southern Svalbard Margin sedimentary system: preliminary results from EGLACOM cruise 2008 T2 - European Geosciences Union, General Assembly 2010 Y1 - 2010 A1 - Melis, R. A1 - Lucchi, R. G. A1 - Giorgetti, G. A1 - Persico, D. A1 - BÁRcena, M. A. A. A1 - Caburlotto, A. A1 - MacrÌ, P. A1 - Villa, G. A1 - Sagnotti, L. A1 - Rebesco, M. JF - European Geosciences Union, General Assembly 2010 CY - Vienna, Austria N1 - id: 873 ER - TY - JOUR T1 - Sr-Nd-Os evidence for a stable erosion regime in the Himalaya during the past 12 Myr JF - EARTH AND PLANETARY SCIENCE LETTERS Y1 - 2010 A1 - Galy, Valier A1 - France-Lanord, Christian A1 - Peucker-Ehrenbrink, Bernhard A1 - Huyghe, Pascale KW - Bengal Fan KW - climate KW - erosion KW - Himalaya KW - Miocene KW - radiogenic isotopes AB - Modern erosion of the Himalaya, the world's largest mountain range, transfers huge dissolved and particulate loads to the ocean. It plays an important role in the long-term global carbon cycle, mostly through enhanced organic carbon burial in the Bengal Fan. To understand the role of past Himalayan erosion, the influence of changing climate and tectonic on erosion must be determined. Here we use a 12 Myr sedimentary record from the distal Bengal Fan (Deep Sea Drilling Project Site 218) to reconstruct the Mio-Pliocene history of Himalayan erosion. We use carbon stable isotopes (delta(13)C) of bulk organic matter as paleo-environmental proxy and stratigraphic tool. Multi-isotopic - Sr, Nd and Os - data are used as proxies for the source of the sediments deposited in the Bengal Fan over time. delta(13)C values of bulk organic matter shift dramatically towards less depleted values, revealing the widespread Late Miocene (ca. 7.4 Ma) expansion of C4 plants in the basin. Sr, Nd and Os isotopic compositions indicate a rather stable erosion pattern in the Himalaya range during the past 12 Myr. This supports the existence of a strong connection between the southern Tibetan plateau and the Bengal Fan. The tectonic evolution of the Himalaya range and Southern Tibet seems to have been unable to produce large re-organisation of the drainage system. Moreover, our data do not suggest a rapid change of the altitude of the southern Tibetan plateau during the past 12 Myr. Variations in Sr and Nd isotopic compositions around the late Miocene expansion of C4 plants are suggestive of a relative increase in the erosion of High Himalaya Crystalline rock (i.e. a simultaneous reduction of both Transhimalayan batholiths and Lesser Himalaya relative contributions). This could be related to an increase in aridity as Suggested by the ecological and sedimentological changes at that time. A reversed trend in Sr and Nd isotopic compositions is observed at the Plio-Pleistocene transition that is likely related to higher precipitation and the development of glaciers in the Himalaya. These almost synchronous moderate changes in erosion pattern and climate changes during the late Miocene and at the Plio-Pleistocene transition support the notion of a dominant control of climate on Himalayan erosion during this time period. However, stable erosion regime during the Pleistocene is suggestive of a limited influence of the glacier development on Himalayan erosion. (C) 2010 Elsevier B.V. All rights reserved. VL - 290 ER - TY - JOUR T1 - Stable isotopes reveal Holocene changes in the diet of Ad,lie penguins in Northern Victoria Land (Ross Sea, Antarctica) JF - Oecologia Y1 - 2010 A1 - Lorenzini, Sandra A1 - Baroni, Carlo A1 - Fallick, Anthony E. A1 - Baneschi, Ilaria A1 - Salvatore, Maria Cristina A1 - Zanchetta, Giovanni A1 - Dallai, Luigi AB - Ad,lie penguin (Pygoscelis adeliae) modern and fossil eggshells and guano samples collected from ornithogenic soils in Terra Nova Bay (Victoria Land, Ross Sea) were processed for carbon and nitrogen isotopic ratios with the aim of detecting past penguin dietary changes. A detailed and greatly expanded Ad,lie penguin dietary record dated back to 7,200 years BP has been reconstructed for the investigated area. Our data indicate a significant dietary shift between fish and krill, with a gradual decrease from past to present time in the proportion of fish compared to krill in Ad,lie penguin diet. From 7,200 to 2,000 years BP, delta(13)C and delta(15)N values indicate fish as the most eaten prey. The dietary contribution of lower-trophic prey in penguin diet started becoming evident not earlier than 2,000 years BP, when the delta(13)C values reveal a change in the penguin feeding behavior. Modern eggshell and guano samples reveal a major dietary contribution of krill but not a krill-dominated diet, since delta(13)C values remain much too high if krill prevail in the diet. According to the Holocene environmental background attested for Victoria Land, Ad,lie penguin dietary shifts between fish and krill seem to reflect penguin paleoecological responses to different paleoenvironmental settings with different conditions of sea-ice extension and persistence. Furthermore, Ad,lie penguin diet appears to be particularly affected by environmental changes in a very specific period within the breeding season, namely the egg-laying period when penguin dietary and feeding habit shifts are clearly documented by the delta(13)C of eggshell carbonate. VL - 164 IS - 4 N1 - id: 2350; PT: J; TC: 6; UT: WOS:000284271900007 JO - Stable isotopes reveal Holocene changes in the diet of Ad,lie penguins in Northern Victoria Land (Ross Sea, Antarctica) ER - TY - JOUR T1 - Stable nitrogen and carbon isotope (delta(15)N and delta(13)C) variability in shallow tropical Pacific soft coral and black coral taxa and implications for paleoceanographic reconstructions JF - Geochimica et Cosmochimica Acta Y1 - 2010 A1 - Williams, Branwen A1 - Grottoli, Andrea G. AB - Soft corals and black corals are useful proxy tools for paleoceanographic reconstructions. However, most work has focused on deep-water taxa and few studies have used these corals as proxy organisms in shallow water ( VL - 74 IS - 18 N1 - id: 1963; PT: J; UT: WOS:000281094900009 JO - Stable nitrogen and carbon isotope (delta(15)N and delta(13)C) variability in shallow tropical Pacific soft coral and black coral taxa and implications for paleoceanographic reconstructions ER - TY - CHAP T1 - Submarine Mass Transport Within Monterey Canyon: Benthic Disturbance Controls on the Distribution of Chemosynthetic Biological Communities T2 - Submarine mass movements and their consequences, 4th International Symposium: Y1 - 2010 A1 - Paull, C. K. A1 - Schlining, B. A1 - Ussler, W. A1 - Lundste, E. A1 - Barry, J. P. A1 - Caress, D. W. A1 - Johnson, J. E. A1 - McGann, M. ED - Mosher, D. C. AB - Documenting mass transport within Monterey Canyon and Fan has been a focus of remotely operated vehicle (ROV) observations, sampling, monitoring, and multibeam mapping studies. These efforts indicate that major mass transport events occur within upper Monterey Canyon (2 km water depths) and onto Monterey Fan for ~100 years. Simultaneous efforts to document the distribution of benthic taxa observed in the video records from 668 ROV dives conducted by the Monterey Bay Aquarium Research Institute (MBARI) provide a uniquely detailed record of the occurrence of chemosynthetic biological communities (CBC). The combined results of these studies provide an understanding of the relationship between disturbance caused by episodic mass wasting events and the distribution of CBC. CBC are common within the canyon's axis below ~2.5 km water depth, but have not been found within the canyon's axis at depths shallower than 2 km. Moreover, CBC occur on the canyon walls at essentially any depth, primarily within young (~hundreds of years old) slump scars. The distribution of CBC provides evidence about the disturbance history of the seafloor. Major mass transport events will destroy communities that lie in their path. Erosion associated with major mass transport events can create environments to support CBC by exposing methane-bearing strata. This can happen as a result of slumping events on the sidewalls of the canyon or where major gravity flow events have excavated the base of canyon walls. Once fresh strata are exposed, geochemical conditions to support CBC will persist for a few centuries. Because CBC are composed of slow-growing and long-lived organisms, it will take decades for these communities to be established. Their existence indicates that environmental stability has occurred over a similar time scale. JF - Submarine mass movements and their consequences, 4th International Symposium: PB - Springer N1 - id: 879 ER - TY - JOUR T1 - Synchronous Deglacial Overturning and Water Mass Source Changes JF - Science Y1 - 2010 A1 - Roberts, N. L. A1 - Piotrowski, A. M. A1 - McManus, J. F. A1 - Keigwin, L. D. AB - Understanding changes in ocean circulation during the last deglaciation is crucial to unraveling the dynamics of glacial-interglacial and millennial climate shifts. We used neodymium isotope measurements on postdepositional iron-manganese oxide coatings precipitated on planktonic foraminifera to reconstruct changes in the bottom water source of the deep western North Atlantic at the Bermuda Rise. Comparison of our deep water source record with overturning strength proxies shows that both the deep water mass source and the overturning rate shifted rapidly and synchronously during the last deglacial transition. In contrast, any freshwater perturbation caused by Heinrich event 1 could have only affected shallow overturning. These findings show how changes in upper-ocean overturning associated with millennial-scale events differ from those associated with whole-ocean deglacial climate events. VL - 327 UR - http://www.sciencemag.org/cgi/doi/10.1126/science.1178068 IS - 5961 ER - TY - JOUR T1 - Temperature and salinity changes in the deglacial North Atlantic JF - Quaternary Science Reviews Y1 - 2010 A1 - Benway, H.M. A1 - McManus, J.F. A1 - Oppo, D.W. A1 - Cullen, J.F. VL - 29 ER - TY - CONF T1 - The Ties That Bind: 3000 Years of Fabric Production and Fiber Use in the Ozark Plateau T2 - 75th annual Conference of the Society for American Archaeology Y1 - 2010 A1 - Horton, Elizabeth T. JF - 75th annual Conference of the Society for American Archaeology CY - St. Louis, Missouri N1 - id: 776 ER - TY - JOUR T1 - Timescales of lateral sediment transport in the Panama Basin as revealed by radiocarbon ages of alkenones, total organic carbon and foraminifera JF - Earth and Planetary Science Letters Y1 - 2010 A1 - Kusch, Stephanie A1 - Eglinton, Timothy I. A1 - Mix, Alan C. A1 - Mollenhauer, Gesine VL - 290 IS - 3-4 N1 - id: 882Y JO - Timescales of lateral sediment transport in the Panama Basin as revealed by radiocarbon ages of alkenones, total organic carbon and foraminifera ER - TY - JOUR T1 - Unique Baltic Outcrops Reveal Millennia of Ecological Changes JF - EOS, TRANSACTIONS AMERICAN GEOPHYSICAL UNION Y1 - 2010 A1 - Buynevich, I. V. A1 - Bitinas, A. A1 - Damušytė, A. A1 - Pupienis, D. AB - Throughout Earth's history, tectonic forces, often violent and unpredictable, have been responsible for exposing geological formations to scientific scrutiny. But forces of uplift are not restricted to plate boundaries. For example, when looking at forested coastal dunes bordering placid Curonian Lagoon along the Lithuanian coast of the Baltic Sea, one hardly suspects that any powerful forces are at work. Yet this is a site where massive migrating hills of sand have put pressure on the deep strata of the ancient lagoon, forcing its sediments to the surface and offering rare access to fossils of the Holocene, which spans the past 10,000 years. VL - 91 IS - 11 N1 - id: 1978 JO - Unique Baltic Outcrops Reveal Millennia of Ecological Changes ER - TY - JOUR T1 - Using proglacial-threshold lakes to constrain fluctuations of the Jakobshavn Isbræ ice margin, western Greenland, during the Holocene JF - Quaternary Science Reviews Y1 - 2010 A1 - Briner, J.P. A1 - Stewart, H.A.M. A1 - Young, N.E. A1 - Philipps, W. A1 - Losee, S. AB - The future response of the Greenland Ice Sheet (GIS) and its potential contribution to sea level rise are uncertain. Rapid changes of Greenland’s outlet glaciers over the past decade have made it difficult to extrapolate ice sheet change into the future. This significant short-term variability highlights the need for longer-term, geologic (e.g., Holocene) records of ice margin fluctuations. However, a major challenge with reconstructing the GIS during the Holocene stems from it having been smaller than it is at present, thus traditional glacial geologic approaches are not suitable. We use radiocarbon-dated sediment sequences from seven proglacial-threshold lakes spanning ∼50 km of the western GIS margin near Jakobshavn Isbræ to constrain the timing of early Holocene deglaciation, the duration that this sector of the western GIS was smaller than its present configuration, and the timing of its advance during Neoglaciation. Our reconstructions suggest deglaciation ∼7300 cal yr BP, minimum ice extent ∼6000–5000 cal yr BP and smaller-than-present ice configuration until at least ∼2300 cal yr BP for the ice margin south of Jakobshavn Isbræ, and until ∼400 cal yr BP for the ice margin north of Jakobshavn Isbræ. One relatively large proglacial lake that became briefly ice-free during the middle Holocene lies in a catchment that likely extends 10s of km inland beneath the GIS, suggesting significant middle Holocene retreat of this portion of the GIS. The overall pattern of ice sheet change is inconsistent with existing ice sheet model reconstructions for this region, but is consistent with numerous paleoclimate proxy and relative sea level data. These continuous lacustrine records corroborate, but provide closer age control than, existing non-continuous records of radiocarbon-dated reworked bivalves from historical moraines in the region. Reconstructing ice margin change from proglacial-threshold lakes is one of few approaches with the potential to constrain smaller-than-present ice sheet extent. VL - 29 UR - https://doi.org/10.1016/j.quascirev.2010.09.005 IS - 27-28 ER - TY - JOUR T1 - Variations in the distribution and radiocarbon age of lignin phenols exported by large river systems JF - Geochimica Et Cosmochimica Acta Y1 - 2010 A1 - Feng, X. J. A1 - Montlucon, D. B. A1 - Eglinton, T. I. VL - 74 SN - 0016-7037 IS - 12, Supplement N1 - Suppl. 1676tl Times Cited:0 Cited References Count:0 JO - Geochim Cosmochim Ac ER - TY - JOUR T1 - Were last glacial climate events simultaneous between Greenland and France? A quantitative comparison using non-tuned chronologies RID E-4539-2011 RID A-2643-2010 JF - Journal of Quaternary Science Y1 - 2010 A1 - Blaauw, Maarten A1 - Wohlfarth, Barbara A1 - Christen, J. Andres A1 - Ampel, Linda A1 - Veres, Daniel A1 - Hughen, Konrad A. A1 - Preusser, Frank A1 - Svensson, Anders AB - Several large abrupt climate fluctuations during the last glacial have been recorded in Greenland ice cores and archives from other regions. Often these Dansgaard-Oeschger events are assumed to have been synchronous over wide areas, and then used as tie-points to link chronologies between the proxy archives. However, it has not yet been tested independently whether or not these events were indeed synchronous over large areas. Here, we compare Dansgaard-Oeschger-type events in a well-dated record from southeastern France with those in Greenland ice cores. Instead of assuming simultaneous climate events between both archives, we keep their age models independent. Even these well-dated archives possess large chronological uncertainties that prevent us from inferring synchronous climate events at decadal to multi-centennial time scales. If possible, comparisons between proxy archives should be based on independent, non-tuned time-scales. Copyright (C) 2009 John Wiley & Sons, Ltd. VL - 25 IS - 3 N1 - id: 1986; PT: J; UT: WOS:000276090800014 JO - Were last glacial climate events simultaneous between Greenland and France? A quantitative comparison using non-tuned chronologies RID E-4539-2011 RID A-2643-2010 ER - TY - CONF T1 - Year-round probing of soot carbon and secondary organic carbon contributions and sources to the South Asian Atmospheric Brown Cloud using radiocarbon (14C) measurements T2 - EGU General Assembly 2010, held 2-7 May, 2010 in Vienna, Austria Y1 - 2010 A1 - Kirillova, Elena A1 - Sheesley, Rebecca J. A1 - Andersson, August A1 - Kruså, Martin A1 - Safai, P. D. A1 - Budhavant, Krishnakant A1 - Rao, P. S. P. A1 - Praveen, P. S. A1 - Gustafsson, Örjan AB - South Asia is one region of vital importance for assessing human impact on radiative forcing by atmospheric aerosols. Previous research in the region has indicated that black carbon is a significant component of the regional aerosol load. In contrast, there is more ambiguous information regarding the contribution of secondary organic aerosols (SOA) to the total carbonaceous (TC) aerosol composition. Here we primarily address the SOA component of the South Asian Atmospheric Brown Cloud (ABC) by a combination of measurements of SOA concentrations and the 14C signature of TC. Atmospheric particulate matter was collected during fourteen-month continuous sampling campaigns Jan 2008 - March 2009 at both the Maldives Climate Observatory at Hannimaadho (MCO-H) and at the Sinhagad hilltop sampling site of the Indian Institute of Tropical Meteorology (SIN) in central-western India. The radiocarbon method is an ideal approach to identify fossil sources (14C "dead") compared to biogenic and biomass combustion products (with a contemporary 14C signal). The radiocarbon source apportionment of TC revealed very similar contribution from biogenic/biomass combustion (60-70%) for Indian SIN site and the MCOH receptor regions for much of the year. However, during the summer monsoon season biomass contribution to TC at the Indian Ocean site increases to 70-80%, while it decreases to 40-50% at the Indian site. Source apportionment of a soot carbon (SC) isolate (CTO-375 method; a tracer of black carbon) shows a similar trend. According to preliminary data in summer biomass contribution is higher at the MCOH receptor site (70%) compared to the SIN background site (45%). These unique year-round 14C data will be interpreted in view of the SOA concentration and the varying origin of the air masses. JF - EGU General Assembly 2010, held 2-7 May, 2010 in Vienna, Austria VL - 12 N1 - id: 870Y JO - Year-round probing of soot carbon and secondary organic carbon contributions and sources to the South Asian Atmospheric Brown Cloud using radiocarbon (14C) measurements ER - TY - JOUR T1 - Younger Dryas Event and formation of peat layers in the northern Yellow Sea JF - Earth Science Frontiers Y1 - 2010 A1 - Li, Tiegang A1 - Chang, Fengming A1 - Yu, Xinke KW - northern Yellow Sea KW - peat layer KW - sea level KW - Younger Dryas Event AB - Peat layer, which formed under the humid climatic conditions and during the stagnated phase of sea level changes, is an important vehicle for information of paleoenvironmental evolution. Results of study on four sections of peat layer from the northern Yellow Sea indicate that all of them are located on the mouth of Bohai Sea strait between 50 and 54 meters water depth. The AMS 14C ages of peat layer are in the range between 10650 and 10100 a BP, which are highly coincident with the age of the Younger Dryas event that was the most significant cold climatic event during the last deglacial warming and occurred between 11000 and 10000 14C a BP. This coincidence indicates that the formation of peat layers in the northern Yellow Sea may be closely correlated with the global impact of Younger Dryas event and can be regard as an evidence of the response of the northern Yellow Sea area to it. The mass appearance of peat layer implies that during the Younger Dryas event a few stagnated periods existed in the postglacial process of sea level rising, the sea level had reached the outside of Bohai Sea strait and may have lingered for about thousand years. The above results and records of pollen suggest that during the period from 10600 to 10200 14C a BP, the northern Yellow Sea was in a cold and humid environment. The humid condition in the northern Yellow Sea area during the Younger Dryas event was distinctly different from the most terrestrial and oceanic records of Younger Dryas event in the global, which shows distinctive effect of Younger Dryas event in different region, and it is irresponsible to diagnose the characteristics of response to Younger Dryas events in different regions based on a single dry and cold mode. VL - 17 SN - 1005-2321 IS - 1 N1 - id: 1969 ER - TY - JOUR T1 - A 2000 year midge-based paleotemperature reconstruction from the Canadian Arctic archipelago JF - Journal of Paleolimnology Y1 - 2009 A1 - Porinchu, D. A1 - MacDonald, G. A1 - Rolland, N. AB - A lake sediment core recovered from Lake V57 on Victoria Island, Nunavut, Canada, spanning the last 2000 years, was analyzed for sub-fossil midge remains and organic-matter content (estimated by loss-on-ignition (LOI)). Significant changes in midge community composition occurred during the last 2000 years, with a distinct midge community appearing after 1600 AD. The chironomid community between 0 and 1600 AD was dominated by Heterotrissocladius, Tanytarsus, Abiskomyia, and Paracladius. At approximately 1600 AD, Heterotrissocladius decreased in relative abundance and taxa such as Corynocera ambigua, C. oliveri, Psectrocladius sordidellus type, and Pentanneurini increased in relative abundance. Previously published midge-based inference models for average July air temperature (AJAT) and summer surface-water temperature (SSWT) were applied to the subfossil midge stratigraphy. The AJAT reconstruction indicates relatively cool conditions existed between 1100 and 1600 AD, with exceptional warming occuring after 1600 AD, as lake productivity inferred from organic-matter content increased concomitantly with midge-inferred AJAT and SSWT. The cooler conditions between 1200 and 1600 AD, and the pattern of warming over recent centuries inferred from Lake V57 is broadly consistent with temperature-sensitive biogenic silica records from other sites in the central Canadian Arctic and the treeline zone to the south suggesting a regionally synchronous response to climate forcing. VL - 41 IS - 1 N1 - id: 1863; 395EF Times Cited:3 Cited References Count:57Y JO - A 2000 year midge-based paleotemperature reconstruction from the Canadian Arctic archipelago ER - TY - JOUR T1 - 2,000-year-long temperature and hydrology reconstructions from the Indo-Pacific warm pool JF - Nature Y1 - 2009 A1 - Oppo, D. W. A1 - Rosenthal, Y. A1 - Linsley, B. K. AB - Northern Hemisphere surface temperature reconstructions suggest that the late twentieth century was warmer than any other time during the past 500 years and possibly any time during the past 1,300 years (refs 1, 2). These temperature reconstructions are based largely on terrestrial records from extra-tropical or high-elevation sites; however, global average surface temperature changes closely follow those of the global tropics(3), which are 75% ocean. In particular, the tropical Indo-Pacific warm pool (IPWP) represents a major heat reservoir that both influences global atmospheric circulation(4) and responds to remote northern high-latitude forcings(5,6). Here we present a decadally resolved continuous sea surface temperature (SST) reconstruction from the IPWP that spans the past two millennia and overlaps the instrumental record, enabling both a direct comparison of proxy data to the instrumental record and an evaluation of past changes in the context of twentieth century trends. Our record from the Makassar Strait, Indonesia, exhibits trends that are similar to a recent Northern Hemisphere temperature reconstruction(2). Reconstructed SST was, however, within error of modern values from about AD 1000 to AD 1250, towards the end of the Medieval Warm Period. SSTs during the Little Ice Age ( approximately AD 1550-1850) were variable, and similar to 0.5 to 1 degrees C colder than modern values during the coldest intervals. A companion reconstruction of delta O-18 of sea water-a sea surface salinity and hydrology indicator-indicates a tight coupling with the East Asian monsoon system and remote control of IPWP hydrology on centennial-millennial timescales, rather than a dominant influence from local SST variation. VL - 460 IS - 7259 N1 - id: 860; ISI Document Delivery No.: 487YE Times Cited: 2 Cited Reference Count: 29 Cited References: *INT AT ENAG WORLD, 2006, GNIP PROGR RES *NAT RES COUNC, 2006, SURF TEMP REC LAST 2 ALDRIAN E, 2003, INT J CLIMATOL, V23, P1435, DOI 10.1002/joc.950 ANAND P, 2003, PALEOCEANOGRAPHY, V18, ARTN 1050 BARSUGLI JJ, 2002, J CLIMATE, V15, P3427 BROCCOLI AJ, 2006, GEOPHYS RES LETT, V33, ARTN L01702 CHIANG JCH, 2005, CLIM DYNAM, V25, P477, DOI 10.1007/s00382-005-0040-5 CONROY JL, 2008, QUATERNARY SCI REV, V27, P1166, DOI 10.1016/j.quascirev.2008.02.015 GORDON AL, 2003, NATURE, V425, P824, DOI 10.1038/nature02038 HAUG GH, 2001, SCIENCE, V293, P1304 JANSEN E, 2007, CLIMATE CHANGE 2007, P466 KAWAHATA H, 2002, DEEP-SEA RES PT II, V49, P2783 LEA DW, 2000, SCIENCE, V289, P1719 LOCARNINI RA, 2006, NOAA ATLAS NESDIS, V61 MANN ME, 2008, P NATL ACAD SCI USA, V105, P13252, DOI 10.1073/pnas.0805721105 MOHTADI M, 2009, PALEOCEANOGRAPHY, V24, ARTN PA1201 MOY CM, 2002, NATURE, V420, P162 NEWTON A, 2006, GEOPHYS RES LETT, V33, ARTN L19710 QU T, 2005, OCEANOGRAPHY, V18, P50 ROSENTHAL Y, 2003, GEOPHYS RES LETT, V30, DOI 10.1029/2002GL016612 SMITH TM, 2008, J CLIMATE, V21, P2283, DOI 10.1175/2007JCLI2100.1 SONTAKKE NA, 1993, J CLIMATE, V6, P1807 STOTT L, 2004, NATURE, V431, P56, DOI 10.1038/nature02903 THUNELL RC, 1984, MICROPALEONTOLOGY, V30, P243 VUILLE M, 2005, J GEOPHYS RES-ATMOS, V110, ARTN D23108 WANG YJ, 2005, SCIENCE, V308, P854, DOI 10.1126/science.1106296 XIE PP, 1996, J CLIMATE, V9, P840 YANCHEVA G, 2007, NATURE, V445, P74, DOI 10.1038/nature05431 ZHANG PZ, 2008, SCIENCE, V322, P940, DOI 10.1126/science.1163965 Oppo, Delia W. Rosenthal, Yair Linsley, Braddock K.; YY JO - 2,000-year-long temperature and hydrology reconstructions from the Indo-Pacific warm pool ER - TY - JOUR T1 - A 24,900-year paleolimnological history from the Peruvian Andes JF - Quaternary Research Y1 - 2009 A1 - Hillyer, R. A1 - Valencia, B. G. A1 - Bush, M. B. A1 - Silman, M. R. A1 - Steinitz-Kannan, M. VL - 71 N1 - id: 1902 ER - TY - JOUR T1 - 5000 year sedimentary record of hurricane strikes on the central coast of Belize JF - Quaternary International Y1 - 2009 A1 - McCloskey, T. A. A1 - Keller, G. AB - The central coast of Belize has been subject to hurricane strikes throughout recorded history with immense human and material cost to the Belizean people. What remains unknown is the long-term frequency of hurricane strikes and the effects such storms may have had on the ancient Maya civilization. Our sedimentary study of major hurricane strikes over the past 5000 years provides preliminary insights. We calculate that over the past 500 years major hurricanes have struck the Belize coast on average once every decade. One giant hurricane with probably particularly catastrophic consequences struck Belize sometime before AD 1500. A temporal clustering of hurricanes suggests two periods of hyperactivity between similar to 4500 and 2500 (14)Cyr BP, which supports a regional model of latitudinal migration of hurricane strike zones. Our preliminary hurricane data, including the extreme apparent size of the giant event, suggest that prehistoric hurricanes were capable of having exerted significant environmental stress in Maya antiquity. (c) 2008 Elsevier Ltd and INQUA. All rights reserved. VL - 195 N1 - id: 2008; PT: J; CT: Workshop on Hurricanes and Typhoons - From the Field Records to the Forecast; CY: SEP 25-28, 2006; CL: Lafayette, LA; SP: United Nat Int Geosci Program, Int Geosphere-Biosphere Programme Past Global Changes; UT: WOS:000263692000006 JO - 5000 year sedimentary record of hurricane strikes on the central coast of Belize ER - TY - CHAP T1 - 8000 Years of Human Settlement and Land Use in Old Ranch Canyon, Santa Rosa Island, California T2 - Proceedings of the Seventh California Islands Symposium Y1 - 2009 A1 - Rick, Torben C. ED - Damiani, Christine C. JF - Proceedings of the Seventh California Islands Symposium PB - Institute for Wildlife Studies CY - Arcata, CA N1 - id: 2074 ER - TY - JOUR T1 - Abrupt climate change as an important agent of ecological change in the Northeast US throughout the past 15,000 years JF - Quaternary Science Reviews Y1 - 2009 A1 - Shuman, B. N. A1 - Newby, P. A1 - Donnelly, J. P. AB - We use a series of tests to evaluate two competing hypotheses about the association of climate and vegetation trends in the northeastern United States over the past 15 kyrs. First, that abrupt climate changes on the scale of centuries had little influence on long-term vegetation trends, and second, that abrupt climate changes interacted with slower climate trends to determine the regional sequence of vegetation phases. Our results support the second. Large dissimilarity between temporally close fossil pollen samples indicates large vegetation changes within 500 years across >4 degrees of latitude at ca 13.25-12.75, 12.0-11.5, 10.5, 8.25, and 5.25 ka. The evidence of vegetation change coincides with independent isotopic and sedimentary indicators of rapid shifts in temperature and moisture balance. In several cases, abrupt changes reversed long-term vegetation trends, such as when spruce (Picea) and pine (Pinus) pollen percentages rapidly declined to the north and increased to the south at ca 13.25-12.75 and 8.25 ka respectively. Abrupt events accelerated other long-term trends, such as a regional increase in beech (Fagus) pollen percentages at 8.5-8.0 ka. The regional hemlock (Tsuga) decline at ca 5.25 ka is unique among the abrupt events, and may have been induced by high climatic variability (i.e., repeated severe droughts from 5.7 to 2.0 ka); autoregressive ecological and evolutionary processes could have maintained low hemlock abundance until ca 2.0 ka. Delayed increases in chestnut (Castanea) pollen abundance after 5.8 and 2.5 ka also illustrate the potential for multi-century climate variability to influence species' recruitment as well as mortality. Future climate changes will probably also rapidly initiate persistent vegetation change, particularly by acting as broad, regional-scale disturbances. (C) 2009 Published by Elsevier Ltd. 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Newby, Paige Donnelly, Jeffrey P. Pergamon-elsevier science ltd Oxford Sp. Iss. SI; YY JO - Abrupt climate change as an important agent of ecological change in the Northeast US throughout the past 15,000 years ER - TY - JOUR T1 - Abrupt mid-Holocene onset of centennial-scale climate variability on the Peru-Chile Margin JF - Geophysical Research Letters Y1 - 2009 A1 - Chazen, C. R. A1 - Altabet, M. A. A1 - Herbert, T. D. AB - Understanding the natural climate variations in the eastern tropical Pacific (ETP) is crucial for predicting the evolution of the El Nino-Southern Oscillation (ENSO). Here we present the first continuous, decadal-resolution Holocene climate record from the Peru-Chile Margin, near the epicenter of the modern ENSO system. Geochemical proxies allow us to reconstruct sea surface temperature, phytoplankton productivity, and thermocline ventilation, variables that are tightly correlated to ENSO events today. Despite the observation that the mean state of all three variables did not change over the past 10,000 years, our data reveal a dramatic increase in climate variability near 5 ka; represented by prolonged periods (50-200 yrs) of climate extremes, which are absent in the early Holocene. These centennial-scale oscillations do not show typical El Nino-La Nina correlations between proxies. We therefore posit that a significant fraction of super-ENSO variance may originate outside the tropics, through processes that ventilate the ETP subsurface waters. Citation: Chazen, C. R., M. A. Altabet, and T. D. Herbert (2009), Abrupt mid-Holocene onset of centennial-scale climate variability on the Peru-Chile Margin, Geophys. Res. Lett., 36, L18704, doi:10.1029/2009GL039749. VL - 36 N1 - id: 1890; 499OY Times Cited:0 Cited References Count:41Y JO - Abrupt mid-Holocene onset of centennial-scale climate variability on the Peru-Chile Margin ER - TY - JOUR T1 - Age Validation of Freshwater Drum using Bomb Radiocarbon JF - Transactions of the American Fisheries Society Y1 - 2009 A1 - Davis-Foust, S. L. A1 - Bruch, R. M. A1 - Campana, S. E. A1 - Olynyk, R. P. A1 - Janssen, J. AB - The ages of freshwater drum Aplodinotus grunniens have typically been estimated by counting the growth increments on their scales or otoliths, but the accuracy of these estimates has not been validated. We used accelerator mass spectrometry (AMS) bomb radiocarbon dating to validate age estimates from sagittal otoliths of freshwater drum from the Lake Winnebago system, Wisconsin. The freshwater drum Delta C-14 chronology from the AMS assay closely reflects the timing and shape of other bomb radiocarbon chronologies, thus validating the accuracy of otolith growth increments to at least age 52 +/- 2 years. The progression of a strong 1983 year-class, which was detected every year sampled over the course of the study (1986, 2003-2007), and indices of year-class abundance calculated from trawling assessments on Lake Winnebago (1986-2007) corroborated otolith ages. Age estimate comparisons between scales, anal spines, dorsal spines, and otoliths showed scales and spines to be completely unreliable as aging structures after age 2. Freshwater drum live to very old ages relative to most other Great Lakes fishes; our oldest specimen based on an otolith age estimate was 58 years old. VL - 138 IS - 2 N1 - id: 802; 477EI Times Cited:1 Cited References Count:58Y JO - Age Validation of Freshwater Drum using Bomb Radiocarbon ER - TY - JOUR T1 - Atlantic hurricanes and climate over the past 1,500 years JF - Nature Y1 - 2009 A1 - Mann, M. E. A1 - Woodruff, J. D. A1 - Donnelly, J. P. A1 - Zhang, Z. H. AB - Atlantic tropical cyclone activity, as measured by annual storm counts, reached anomalous levels over the past decade(1). The short nature of the historical record and potential issues with its reliability in earlier decades, however, has prompted an ongoing debate regarding the reality and significance of the recent rise(2-5). Here we place recent activity in a longer-term context by comparing two independent estimates of tropical cyclone activity over the past 1,500 years. The first estimate is based on a composite of regional sedimentary evidence of landfalling hurricanes, while the second estimate uses a previously published statistical model of Atlantic tropical cyclone activity driven by proxy reconstructions of past climate changes. Both approaches yield consistent evidence of a peak in Atlantic tropical cyclone activity during medieval times (around AD 1000) followed by a subsequent lull in activity. The statistical model indicates that the medieval peak, which rivals or even exceeds (within uncertainties) recent levels of activity, results from the reinforcing effects of La-Nina-like climate conditions and relative tropical Atlantic warmth. 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Woodruff, Jonathan D. Donnelly, Jeffrey P. Zhang, Zhihua National Science Foundation [ATM-0542356, EAR-0519118, OCE-0402746]; YY JO - Atlantic hurricanes and climate over the past 1,500 years ER - TY - JOUR T1 - Bioturbation artifacts in zero-age sediments JF - Paleoceanography Y1 - 2009 A1 - Keigwin, L. D. A1 - Guilderson, T. P. AB - Most seafloor sediments are dated with radiocarbon, and the sediment is assumed to be zero-age (modern) when the signal of atmospheric testing of nuclear weapons is present (Fraction modern (Fm) > 1). Using a simple mass balance, we show that even with Fm > 1, half of the planktonic foraminifera at the seafloor can be centuries old, because of bioturbation. This calculation, and data from four core sites in the western North Atlantic indicate that, first, during some part of the Little Ice Age (LIA) there may have been more Antarctic Bottom Water than today in the deep western North Atlantic. Alternatively, bioturbation may have introduced much older benthic foraminifera into surface sediments. Second, paleo-based warming of Sargasso Sea surface waters since the LIA must lag the actual warming because of bioturbation of older and colder foraminifera. VL - 24 N1 - id: 1826; 535DQ Times Cited:0 Cited References Count:18; YY JO - Bioturbation artifacts in zero-age sediments ER - TY - JOUR T1 - Black carbon in marine particulate organic carbon: Inputs and cycling of highly recalcitrant organic carbon in the Gulf of Maine JF - Marine Chemistry Y1 - 2009 A1 - Flores-Cervantes, D. X. A1 - Plata, D. L. A1 - MacFarlane, J. K. A1 - Reddy, C. M. A1 - Gschwend, P. M. AB - To increase our understanding of the roles of black carbon (BC), a highly sorptive and recalcitrant material, we measured BC concentrations and fluxes in marine particulate organic carbon (POC) out of the water column in the Gulf of Maine (GoM), a representative coastal area downwind of important BC sources of the Northeastern United States. Concentrations ranged from VL - 113 IS - 3-4 N1 - id: 1865; 440SC Times Cited:0 Cited References Count:85; YY JO - Black carbon in marine particulate organic carbon: Inputs and cycling of highly recalcitrant organic carbon in the Gulf of Maine ER - TY - JOUR T1 - Bomb dating and age determination of skates (family Rajidae) off the eastern coast of Canada JF - Ices Journal of Marine Science Y1 - 2009 A1 - McPhie, R. P. A1 - Campana, S. E. AB - Recent declines in abundance of skates off the eastern coast of Canada have heightened the need for validated age and growth estimates in the region. In all, 502 winter (Leucoraja ocellata), little (Leucoraja erinacea), thorny (Amblyraja radiata), and smooth (Malacoraja senta) skate vertebral centra collected seasonally between 1999 and 2004 were sectioned using a mass processing method, then used to reconstruct growth in each species. Bomb rediocarbon (Delta C-14) analysis was used to provide evidence of annual band-pair deposition in thorny skates. Estimates of L-infinity from traditional von Bertalanffy growth models (VBGM) ranged from 60.6 cm (little skate) to 89.7 cm (thorny skate), and K estimates from 0.07 (thorny skate) to 0.19 (little skate). A modified two-parameter VBGM (L-MAX = 94.1 cm) fitted to winter skate lenght-at-age data yielded a value of K to 0.15. Maximum observed ages ranged from 12 (little skate) to 19 years in both winter and thorny skates. The year-specific incorporation of Delta C-14 milled from thorny and winter skate vertebral sections closely resembled shark-derived reference chronology values from the Northwest Atlantic. Pre-bomb Delta C-14 in a thorny skate collected in 1988 and aged at 23 years appeared to validate age interpretations and suggested that thorny skate reach an absolute age of at least 28 years, the oldest validated age reported for any species of batoid. VL - 66 IS - 3 N1 - id: 1856; 421XR Times Cited:3 Cited References Count:82Y JO - Bomb dating and age determination of skates (family Rajidae) off the eastern coast of Canada ER - TY - JOUR T1 - Brown Clouds over South Asia: Biomass or Fossil Fuel Combustion? JF - Science Y1 - 2009 A1 - Gustafsson, O. A1 - Krusa, M. A1 - Zencak, Z. A1 - Sheesley, R. J. A1 - Granat, L. A1 - Engstrom, E. A1 - Praveen, P. S. A1 - Rao, P. S. P. A1 - Leck, C. A1 - Rodhe, H. AB - Carbonaceous aerosols cause strong atmospheric heating and large surface cooling that is as important to South Asian climate forcing as greenhouse gases, yet the aerosol sources are poorly understood. Emission inventory models suggest that biofuel burning accounts for 50 to 90% of emissions, whereas the elemental composition of ambient aerosols points to fossil fuel combustion. We used radiocarbon measurements of winter monsoon aerosols from western India and the Indian Ocean to determine that biomass combustion produced two- thirds of the bulk carbonaceous aerosols, as well as one- half and two- thirds of two black carbon subfractions, respectively. These constraints show that both biomass combustion ( such as residential cooking and agricultural burning) and fossil fuel combustion should be targeted to mitigate climate effects and improve air quality. VL - 323 IS - 5913 N1 - id: 1867; 396JL Times Cited:8 Cited References Count:33Y JO - Brown Clouds over South Asia: Biomass or Fossil Fuel Combustion? ER - TY - JOUR T1 - Carbonaceous aerosol over a Pinus taeda forest in Central North Carolina, USA JF - Atmospheric Environment Y1 - 2009 A1 - Geron, Chris AB - Organic aerosol is the least understood component of ambient fine particulate matter (PM(2.5)). In this study, organic and elemental carbon (OC and EC) within ambient PM(2.5) over a three-year period at a forested site in the North Carolina Piedmont are presented. EC exhibited significant weekday/weekend effects and less significant seasonal effects, in contrast to OC, which showed strong seasonal differences and smaller weekend/weekday effects. Summer OC concentrations are about twice as high as winter concentrations, while EC was somewhat higher in the winter. OC was highly correlated with EC during cool periods when both were controlled by primary combustion sources. This correlation decreased with increasing temperature, reflecting higher contributions from secondary organic aerosol, likely of biogenic origin. PM(2.)5 radiocarbon data from the site confirms that a large fraction of the carbon in PM(2.5) is indeed of biogenic origin, since modern (non-fossil fuel derived) carbon accounted for 80% of the PM(2.5) carbon over the course of a year. OC and EC exhibited distinct diurnal profiles, with summertime OC peaking in late evening and declining until midday, During winter, DC peaked during the early morning hours and again declined until midday. Summertime EC peaked during late morning hours except on weekends. Wintertime EC often peaked in late PM or early AM hours due to local residential wood combustion emissions. The highest short term peaks in OC and EC were associated with wildfire events. These data corroborate recent source apportionment Studies conducted within 20 km of our site, where oxidation products of isoprene, alpha-pinene, and beta-caryophyllene were identified as important precursors to organic aerosols. A large fraction of the carbon in rural southeastern ambient PM(2.5), appears to be of biogenic origin, which is probably difficult to reduce by anthropogenic controls. Published by Elsevier Ltd. VL - 43 IS - 4 N1 - id: 1958; PT: J; UT: WOS:000263188100024 JO - Carbonaceous aerosol over a Pinus taeda forest in Central North Carolina, USA ER - TY - JOUR T1 - Changes in sediment and organic carbon accumulation in a highly-disturbed ecosystem: The Sacramento-San Joaquin River Delta (California, USA) JF - Marine Pollution Bulletin Y1 - 2009 A1 - Canuel, E. A. A1 - Lerberg, E. J. A1 - Dickhut, R. M. A1 - Kuehl, S. A. A1 - Bianchi, T. S. A1 - Wakeham, S. G. AB - We used the Sacramento-San Joaquin River Delta CA (Delta, hereafter) as a model system for understanding how human activities influence the delivery of sediment and total organic carbon (TOC) over the past 50-60 years. Sediment cores were collected from sites within the Delta representing the Sacramento River (SAC), the San Joaquin River (SJR), and Franks Tract (FT), a flooded agricultural tract. A variety of anthropogenic tracers including (CS)-C-137, total DDE (Sigma DDE) and brominated diphenyl ether (BDE) congeners were used to quantify sediment accumulation rates. This information was combined with total organic carbon (TOC) profiles to quantify rates of TOC accumulation. Across the three sites, sediment and TOC accumulation rates were four to eight-fold higher prior to 1972. Changes in sediment and TOC accumulation were coincident with completion of several large reservoirs and increased agriculture and urbanization in the Delta watershed. Radiocarbon content of TOC indicated that much of the carbon delivered to the Delta is "pre-aged" reflecting processing in the Delta watershed or during transport to the sites rather than an input of predominantly contemporary carbon (e.g., 900-1400 years BP in surface sediments and 2200 yrs BP and 3610 yrs BP at the base of the SJR and FT cores, respectively). Together, these data suggest that human activities have altered the amount and age of TOC accumulating in the Delta since the 1940s. (C) 2009 Elsevier Ltd. All rights reserved. VL - 59 IS - 4-7 N1 - id: 1845; Sp. Iss. SI 477XX Times Cited:1 Cited References Count:49Y JO - Changes in sediment and organic carbon accumulation in a highly-disturbed ecosystem: The Sacramento-San Joaquin River Delta (California, USA) ER - TY - JOUR T1 - Chemical and isotopic characterization of size-fractionated organic matter from cryoturbated tundra soils, northern Alaska JF - Journal of Geophysical Research-Biogeosciences Y1 - 2009 A1 - Xu, C. H. A1 - Guo, L. D. A1 - Ping, C. L. A1 - White, D. M. AB - Recent studies indicate a second layer of organic matter often accumulates in the lower active layer and upper permafrost in arctic tundra soils as a result of cryoturbation. In this study, cryoturbated organic matter was characterized using a combination of physical size fractionation and modern analytical techniques for elemental composition (C and N), stable isotopes (delta(13) C and delta N-15), radiocarbon content (Delta C-14), and molecular fingerprinting (pyrolysis-gas chromatography/mass spectrometry, Py-GC/MS). The results indicated that cryoturbated organic matter could be highly bioavailable. Soil organic matter (SOM) associated with fine sand particles was considered to be the organic carbon pool most sensitive to the changing climate. More organic matter is stabilized on clay minerals in arctic tundra soils compared to those in temperate and tropical soils. The bioavailable soluble organic matter extracted from cryoturbated soil was found to have significant long-term effects on carbon cycling. The similar molecular composition between cryoturbated and surface soil organic matter suggests that the vegetation cover has not significantly changed since the early Holocene. Furthermore, the SOM quality in moist acidic tundra was found to be higher than that of wet nonacidic tundra. With thawing permafrost and a deepening of the active layer, cryotrubated organic matter could reenter the biogeochemical cycles in the Arctic, resulting in a positive feedback to climate change. VL - 114 N1 - id: 1828; 475IS Times Cited:0 Cited References Count:61Y JO - Chemical and isotopic characterization of size-fractionated organic matter from cryoturbated tundra soils, northern Alaska ER - TY - JOUR T1 - Chemical and isotopic composition of high-molecular-weight dissolved organic matter from the Mississippi River plume JF - Marine Chemistry Y1 - 2009 A1 - Guo, L. D. A1 - White, D. M. A1 - Xu, C. A1 - Santschi, P. H. AB - In order to examine the source and transformation of high-molecular-weight dissolved organic matter (HMW-DOM) in the mixing zone of the Mississippi River plume, HMW-DOM with sizes between 1 kDa and 0.2 mu m was collected along a salinity gradient using cross-flow ultrafiltration. Isolated OM samples were desalted, freeze-dried and characterized for elemental (C and N) and biochemical composition (proteins, carbohydrates and uronic acids), stable isotopic (delta C-13 and delta N-15) and radiocarbon (Delta C-14) signatures, and relative molecular composition using pyrolysis-gas chromatography/mass spectrometry. The organic carbon content of HMW-DOM samples ranged from 31 to 36 wt.%, indicating that isolated colloids are mostly organic in nature. Contents of N ranged from 1.9% to 3.3%, resulting in a C/N ratio of 19-20 at lower salinity stations with a strong influence by terrestrial DOM and 12-15 at higher salinity stations with more freshly photosynthesized marine DOM. While OC-normalized protein contents decreased with increasing salinity, both carbohydrate and uronic acid contents increased with increasing salinity. Variations of pyrograms demonstrated that the proportion of furfural (an indicator of polysaccharides) in HMW-DOM also increased with increasing salinity, while the proportion of phenols decreased with increasing salinity. Changes in carbohydrate, (acid) polysaccharide and phenol contents of HMW-DOM samples reflect the variation in DOM sources along the salinity gradient, with higher phenol and low polysaccharide contents in lower salinity areas but higher polysaccharide and low phenol contents in coastal waters. Values of delta C-13 increased from -25.24 parts per thousand at the Mississippi River fresh water end-member station to -21.86 parts per thousand at an offshore station in the Gulf of Mexico. Changes in stable isotope composition resemble the changes in molecular composition from freshwater to coastal waters. Values of delta N-15, on the other hand, varied little, from 3.5 parts per thousand to 4.9 parts per thousand without a consistent trend, indicating that delta N-15 is a less sensitive source tracer. Measured radiocarbon signatures (Delta C-14) expressed as apparent C-14 ages ranged from > modern at lower salinity stations to 400-800 y BP at coastal stations. Results of isotopic mass balance revealed that, in addition to end-member organic matter from river and marine sources, at least 10-25% of the HMW-DOM could derive from reworked or regenerated DOM in the Mississippi River plume, most likely through sediment-water interactions and lateral transport. Thus, reworking processes are important in governing the chemical and isotopic composition of DOM in the estuarine mixing zone. (C) 2009 Elsevier B.V. All rights reserved. VL - 114 IS - 3-4 N1 - id: 1827; 465CM Times Cited:1 Cited References Count:51Y JO - Chemical and isotopic composition of high-molecular-weight dissolved organic matter from the Mississippi River plume ER - TY - JOUR T1 - Chemical and isotopic signature of old groundwater and magmatic solutes in a Costa Rican rain forest: Evidence from carbon, helium, and chlorine JF - WATER RESOURCES RESEARCH Y1 - 2009 A1 - Genereux, David P. A1 - Webb, Mathew A1 - Solomon, D. Kip AB - C, He, and Cl concentrations and isotopes in groundwater and surface water in a lowland Costa Rican rain forest are consistent with the mixing of two distinct groundwaters: (1) high-solute bedrock groundwater representing interbasin groundwater flow (IGF) into the rain forest and (2) low-solute local groundwater recharged in the lowlands. In bedrock groundwater, high delta(13)C (-4.89%), low (14)C (7.98 pM), high R/R(A) for He (6.88), and low (36)Cl/Cl (17 x 10(-15)) suggest that elevated tracer concentrations are derived from magmatic outgassing and/or weathering of volcanic rock beneath nearby Volcan Barva. In local groundwater, the magmatic signature is absent, and data suggest atmospheric sources for He and Cl and a biogenic soil gas CO(2) source for dissolved inorganic carbon. Dating of (14)C suggests that the age of bedrock groundwater is 2400-4000 years (most likely at the lower end of the range). Local groundwater has (14)C > 100 pM, indicating the presence of ``bomb carbon'' and thus ages less than similar to 55 years. Overall, data are consistent with a conceptual hydrologic model originally proposed on the basis of water budget and major ion data: (1) large variation in solute concentrations can be explained by mixing of the two distinct groundwaters, (2) bedrock groundwater is much older than local groundwater, (3) elevated solute concentrations in bedrock groundwater are derived from volcanic fluids and/or rock, and (4) local groundwater has not interacted with volcanic rock. Tracers with different capabilities converge on the same hydrologic interpretation. Also, transport of magmatic CO(2) into the lowland rain forest via IGF seems to be significant relative to other large ecosystem-level carbon fluxes. VL - 45 ER - TY - JOUR T1 - A chronology of hurricane landfalls at Little Sippewissett Marsh, Massachusetts, USA, using optical dating JF - Geomorphology Y1 - 2009 A1 - Madsen, A. T. A1 - Duller, G. A. T. A1 - Donnelly, J. P. A1 - Roberts, H. M. A1 - Wintle, A. G. AB - Optical dating has been applied to sediments preserved in Little Sippewissett Marsh, Massachusetts, USA, which are associated with overwashing of the beach barrier during hurricane strikes on the coast. The aims were to determine the hurricane landfall frequency, and make comparisons with independent age control and the historical record. Written sources of hurricane activity along the American east coast are only considered reliable back to the mid 19th century, but the sedimentary record is potentially much longer. Optical dating was applied to quartz grains extracted from thirteen samples within a sediment core from the salt-marsh. Variability in the luminescence characteristics between aliquots was observed and similar to 33% of the measured aliquots were discarded based upon the ratio of the fast component to the medium component. The majority of the samples gave normal dose distributions implying homogeneous resetting of the luminescence signal at the time of deposition, but three of the samples required application of the minimum age model (MAM). Ages ranging between 20 +/- 2 and 594 +/- 38 years were obtained and are broadly in agreement with independent chronologies, thus demonstrating the potential of optical dating in this setting. The hurricane record based upon optical dating extends approximately 300 years further back in time than the official National Oceanic Atmospheric Administration (NOAA) record. The localised nature of hurricane landfalls means that it will be necessary to collect multiple cores from a number of different sites in order to build up a complete hurricane record for this part of the coast. (C) 2009 Elsevier B.V. All rights reserved. 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T. Duller, G. A. T. Donnelly, J. P. Roberts, H. M. Wintle, A. G. National Science Foundation [0519118] The authors wish to acknowledge Dana MacDonald for pollen analysis. This work was supported by National Science Foundation award #0519118. Elsevier science bv Amsterdam Sp. Iss. SI; YY JO - A chronology of hurricane landfalls at Little Sippewissett Marsh, Massachusetts, USA, using optical dating ER - TY - JOUR T1 - Coarse-grained sediment delivery and distribution in the Holocene Santa Monica Basin, California: Implications for evaluating source-to-sink flux at millennial time scales JF - Geological Society of America Bulletin Y1 - 2009 A1 - Romans, B. W. A1 - Normark, W. R. A1 - McGann, M. M. A1 - Covault, J. A. A1 - Graham, S. A. AB - Utilizing accumulations of coarse-grained terrigenous sediment from deep-marine basins to evaluate the relative contributions of and history of controls on sediment flux through a source-to-sink system has been difficult as a result of limited knowledge of event timing. In this study, six new radiocarbon (C-14) dates are integrated with five previously published dates that have been recalibrated from a 12.5-m-thick turbidite section from Ocean Drilling Program (ODP) Site 1015 in Santa Monica Basin, offshore California. This borehole is tied to high-resolution seismic-reflection profiles that cover an 1100 km(2) area of the middle and lower Hueneme submarine fan and most of the basin plain. The resulting stratigraphic framework provides the highest temporal resolution for a thick-bedded Holocene turbidite succession to date, permitting an evaluation of source-to-sink controls at millennial (1000 yr) scales. The depositional history from 7 ka to present indicates that the recurrence interval for large turbidity-current events is relatively constant (300-360 yr), but the volume of sediment deposited on the fan and in the basin plain has increased by a factor of 2 over this period. Moreover, the amount of sand per event on the basin plain during the same interval has increased by a factor of 7. Maps of sediment distribution derived from correlation of seismic-reflection profiles indicate that this trend cannot be attributed exclusively to autogenic processes (e.g., progradation of depocenters). The observed variability in sediment accumulation rates is thus largely controlled by allogenic factors, including: (1) increased discharge of Santa Clara River as a result of increased magnitude and frequency of El Nino-Southern Oscillation (ENSO) events from ca. 2 ka to present, (2) an apparent change in routing of coarse-grained sediment within the staging area at ca. 3 ka (i.e., from direct river input to indirect, littoral cell input into Hueneme submarine canyon), and (3) decreasing rates of sea-level rise (i.e., rate of rise slowed considerably by ca. 3 ka). The Holocene history of the Santa Clara River-Santa Monica Basin source-to-sink system demonstrates the ways in which varying sediment flux and changes in dispersal pathways affect the basinal stratigraphic record. VL - 121 IS - 9-10 N1 - id: 876; 478QZ Times Cited:1 Cited References Count:90Y JO - Coarse-grained sediment delivery and distribution in the Holocene Santa Monica Basin, California: Implications for evaluating source-to-sink flux at millennial time scales ER - TY - JOUR T1 - Comparing glacial and Holocene opal fluxes in the Pacific sector of the Southern Ocean JF - Paleoceanography Y1 - 2009 A1 - Bradtmiller, L. I. A1 - Anderson, R. F. A1 - Fleisher, M. Q. A1 - Burckle, L. H. AB - The silicic acid leakage hypothesis (SALH) predicts that during glacial periods excess silicic acid was transported from the Southern Ocean to lower latitudes, which favored diatom production over coccolithophorid production and caused a drawdown of atmospheric CO2. Downcore records of Th-230-normalized opal (biogenic silica) fluxes from 31 cores in the Pacific sector of the Southern Ocean were used to compare diatom productivity during the last glacial period to that of the Holocene and to examine the evidence for increased glacial Si export to the tropics. Average glacial opal fluxes south of the modern Antarctic Polar Front (APF) were less than during the Holocene, while average glacial opal fluxes north of the APF were greater than during the Holocene. However, the magnitude of the increase north of the APF was not enough to offset decreased fluxes to the south, resulting in a decrease in opal burial in the Pacific sector of the Southern Ocean during the last glacial period, equivalent to approximately 15 Gt opal ka(-1). This is consistent with the work of Chase et al. (2003a), and satisfies the primary requirement of the SALH, assuming that the upwelled supply of Si was approximately equivalent during the Holocene and the glacial period. However, previous results from the equatorial oceans are inconsistent with the other predictions of the SALH, namely that either the C-org:CaCO3 ratio or the rate of opal burial should have increased during glacial periods. We compare the magnitudes of changes in the Southern Ocean and the tropics and suggest that Si escaping the glacial Southern Ocean must have had an alternate destination, possibly the continental margins. There is currently insufficient data to test this hypothesis, but the existence of this sink and its potential impact on glacial pCO(2) remain interesting topics for future study. VL - 24 N1 - id: 836; 455GX Times Cited:0 Cited References Count:97Y JO - Comparing glacial and Holocene opal fluxes in the Pacific sector of the Southern Ocean ER - TY - JOUR T1 - Compound-specific radiocarbon analysis – analytical challenges and applications JF - IOP conference proceedings: Earth and Environmental Sciences Y1 - 2009 A1 - Mollenhauer, G. A1 - Rethemeyer, Janet VL - 5 N1 - id: 884Y JO - Compound-specific radiocarbon analysis – analytical challenges and applications ER - TY - JOUR T1 - Constraining carbon sources and growth rates of freshwater microbialites in Pavilion Lake using 14C analysis JF - Geobiology Y1 - 2009 A1 - Brady, A. L. A1 - Slater, G. A1 - Laval, B. A1 - Lim, D. S. AB - This study determined the natural abundance isotopic compositions (13C, 14C) of the primary carbon pools and microbial communities associated with modern freshwater microbialites located in Pavilion Lake, British Columbia, Canada. The Delta 14C of dissolved inorganic carbon (DIC) was constant throughout the water column and consistent with a primarily atmospheric source. Observed depletions in DIC 14C values compared with atmospheric CO(2) indicated effects due either to DIC residence time and/or inputs of 14C-depleted groundwater. Mass balance comparisons of local and regional groundwater indicate that groundwater DIC could contribute a maximum of 9-13% of the DIC. 14C analysis of microbial phospholipid fatty acids from microbialite communities had Delta 14C values comparable with lake water DIC, demonstrating that lake water DIC was their primary carbon source. Microbialite carbonate was also primarily derived from DIC. However, some depletion in microbialite carbonate 14C relative to lake water DIC occurred, due either to residence time or mixing with a 14C-depleted carbon source. A detrital branch covered with microbialite growth was used to estimate a microbialite growth rate of 0.05 mm year-1 for the past 1000 years, faster than previous estimates for this system. These results demonstrate that the microbialites are actively growing and that the primary carbon source for both microbial communities and recent carbonate is DIC originating from the atmosphere. While these data cannot conclusively differentiate between abiotic and biotic formation mechanisms, the evidence for minor inputs of groundwater-derived DIC is consistent with the previously hypothesized biological origin of the Pavilion Lake microbialites. VL - 7 IS - 5 N1 - id: 2055; PT: J; UT: WOS:000271633500006 JO - Constraining carbon sources and growth rates of freshwater microbialites in Pavilion Lake using 14C analysis ER - TY - JOUR T1 - Coral growth rates from the Holocene Canada Honda fossil reef, Southwestern Dominican Republic: Comparisons with modern counterparts in high sedimentation settings JF - Caribbean Journal of Science Y1 - 2009 A1 - Cuevas, D. N. A1 - Sherman, C. E. A1 - Ramírez, W. A1 - Hubbard, D. K. KW - australia KW - Belize KW - Caribbean KW - community KW - degradation KW - enriquillo valley KW - florida KW - great-barrier-reef KW - linear extension KW - montastraea-annularis KW - paluma shoals KW - record KW - siltation stress KW - skeletal extension KW - turbidity AB - The Holocene Canada Honda fossil reef, located in southwestern Dominican Republic, provides a unique opportunity to examine a well-preserved fossil coral reef that thrived in a high-sedimentation environment between 9,000 to 5,000 years ago. Measurements of coral growth rates from the corals Montastraea faveolata and Siderastrea siderea were conducted and comparisons made with growth rate data of these same species from modern coral reefs throughout the Caribbean. Also, assessments of coral species abundance, morphology, age, and distribution, as well as reef sediment composition, were made to determine the paleoenvironment of reef accretion. This reef is characterized by a high relative abundance of sediment-tolerant coral species that have a tendency to form almost monospecific stands. Individual colonies have a propensity to grow as encrusting, dome-shaped, platy-like forms and specimens of Montastraea faveolata commonly contain bands of sediment incorporated into the skeleton. Calibrated radiocarbon ages of fossil corals range from 9,256 +/- 137 to 6,737 +/- 94.5 BP. Correlation of radiocarbon ages with well-established Holocene sea-level curves indicates that most corals on this reef developed at depths >15m. Measured growth rates in Siderastrea siderea (0.2-0.4 cm/yr) and Montastraea faveolata (0.09-0.44 cm/yr) are relatively low compared with growth rates from modern reef sites, indicating reduced light intensity caused by coral growth at depths greater than 15 m. Reef sediment is characterized by more than 85% carbonate material. A significant portion of the carbonate is allochtonous and was derived from nearby Neogene limestones. The reef was able to survive under high-sedimentation conditions because the high carbonate content of incoming terrigenous sediment would have allowed better light penetration and probable sporadic storms would provide intervening low-sedimentation periods during which reef corals could respond and grow back, keeping-up with sedimentation. VL - 45 SN - 0008-6452 IS - 1 N1 - 695voTimes Cited:0 Cited References Count:47 JO - Caribb J Sci ER - TY - JOUR T1 - Developments in Radiocarbon Technologies: From the Libby Counter to Compound-Specific Ams Analyses JF - Radiocarbon Y1 - 2009 A1 - Povinec, P. P. A1 - Litherland, A. E. A1 - von Reden, K. F. KW - accelerator mass-spectrometry KW - black-sea shelf KW - liquid scintillation techniques KW - low-level c-14 KW - natural-abundance radiocarbon KW - negative-ion source KW - polycyclic aromatic-hydrocarbons KW - proportional counter KW - salt-marsh sediments KW - sedimentary organic-carbon AB - We review developments in radiocarbon measuring techniques from the Libby counter through proportional gas counters and liquid scintillation spectrometers to the more recent developments of accelerator mass spectrometry (AMS), followed by a coupling of gas chromatography with AMS for compound-specific (14)C analyses. While during the first 60 yr of (14)C measurements beta counting, specifically gas counting, was the dominant technique, in the future of (14)C science AMS will be the dominant technology. VL - 51 SN - 0033-8222 IS - 1 N1 - 453wfTimes Cited:15 Cited References Count:273 JO - Radiocarbon ER - TY - JOUR T1 - Distribution of artificial radionuclides in deep sediments of the Mediterranean Sea JF - Science of the Total Environment Y1 - 2009 A1 - Garcia-Orellana, J. A1 - Pates, J. M. A1 - Masque, P. A1 - Bruach, J. M. A1 - Sanchez-Cabeza, J. A. AB - Artificial radionuclides enter the Mediterranean Sea mainly through atmospheric deposition following nuclear weapons tests and the Chernobyl accident, but also through the river discharge of nuclear facility effluents. Previous studies of artificial radionuclides impact of the Mediterranean Sea have focussed on shallow, coastal sediments. However, deep sea sediments have the potential to store and accumulate pollutants, including artificial radionuclides. Deep sea marine sediment cores were collected from Mediterranean Sea abyssal plains (depth >2000 m) and analysed for Pu-239,Pu-240 and Cs-137 to elucidate the concentrations, inventories and sources of these radionuclides in the deepest areas of the Mediterranean. The activity - depth profiles of Pb-210, together with 14 C dating, indicate that sediment mixing redistributes the artificial radionuclides within the first 2.5 cm of the sedimentary column. The excess Pb-210 inventory was used to normalize Pu-239,Pu-240 and Cs-137 inventories for variable sediment fluxes. The Pu-239,Pu-240/Pb-210(xs) ratio was uniform across the entire sea, with a mean value of 1.24 x 10(-3), indicating homogeneous fallout of Pu-239,Pu-240. The Cs-137/Pb-210(xs) ratio showed differences between the eastern (0.049) and western basins (0.030), clearly significant impact of deep sea sediments from the Chernobyl accident. The inventory ratios of Pu-239,Pu-240/Cs-137 were 0.041 and 0.025 in the western and eastern basins respectively, greater than the fallout ratio, 0.021, showing more efficient scavenging of Pu-231,Pu-210 in the water column and major sedimentation of Cs-137 in the eastern basin. Although areas with water depths of >2000 m constitute around 40% of the entire Mediterranean basin, the sediments in these regions only contained 2.7% of the Pu-239,Pu-240 and 0.95% of the Cs-137 deposited across the Sea in 2000. These data show that the accumulation of artificial radionuclides in deep Mediterranean environments is much lower than predicted by other studies from the analysis of continental shelf sediments. (C) 2008 Elsevier B.V, All rights reserved. VL - 407 IS - 2 N1 - id: 871; 389FH Times Cited:2 Cited References Count:63Y JO - Distribution of artificial radionuclides in deep sediments of the Mediterranean Sea ER - TY - JOUR T1 - DNA and lipid molecular stratigraphic records of haptophyte succession in the Black Sea during the Holocene JF - Earth and Planetary Science Letters Y1 - 2009 A1 - Coolen, M. J. L. A1 - Saenz, J. P. A1 - Giosan, L. A1 - Trowbridge, N. Y. A1 - Dimitrov, P. A1 - Dimitrov, D. A1 - Eglinton, T. I. AB - Previous studies suggest that the coccolithophorid haptophyte Emiliania huxleyi entered the Black Sea similar to 3400 yrs ago and since then a coccolith ooze defined as Unit I has developed. Unit I sediments contain long-chain alkenones derived from E huxleyi whereas the alkenone distribution of the deeper coccolith-free sapropel (Unit II) is rather unusual. Alkenone-derived past sea surface temperature (SST) estimates suggest a large difference between Unit II and Unit I, which is likely a result of unusual biological precursors of the alkenones in Unit II. Here, we report a high-resolution stratigraphic analysis of ancient haptophyte DNA to establish the Holocene succession of haptophytes as sources of the alkenones in the Black Sea. Haptophytes related to brackish Isochrysis spp. were the initial sources of alkenones, and appeared immediately after the onset of sapropel deposition (similar to 7550 yrs before present [a BP]). As salinity increased, Isochrysis-related haptophytes were slowly replaced by a complex suite of huxleyi strains as sources of alkenones. Our paleogenetic data showed that E. huxleyi colonized the Black Sea shortly after the onset of sapropel deposition, similar to 4000 yrs earlier than previously recognized based on their preserved coccoliths. E. huxleyi strains were the most likely source of the previously reported abundant and unusual C-36 di-unsaturated "Black Sea alkenone". Strong haptophyte species and strain-specific effects were observed on the level of unsaturation of alkenones which resulted in spurious alkenone-derived SST estimates before 5250 a BP. In contrast, from similar to 5250 a BP onwards a relatively stable haptophyte assemblage dominated by a different suite of E. huxleyi strains yielded robust alkenone-SST values and indicated a gradual cooling from 19 degrees C to similar to 15 degrees C at the top of the record (similar to 450 a BP). Published by Elsevier B.V. VL - 284 IS - 3-4 N1 - id: 1853; 487NY Times Cited:1 Cited References Count:78; YY JO - DNA and lipid molecular stratigraphic records of haptophyte succession in the Black Sea during the Holocene ER - TY - RPRT T1 - Dynamics and Vulnerability of Delta Systems Y1 - 2009 A1 - Overeem, I. A1 - Syvitski, J. P. M. A1 - al, et JF - LOICZ Reports & Studies PB - GKSS Research Center CY - Geesthacht N1 - id: 1898; 35; Y ER - TY - JOUR T1 - Dynamics of particle export on the Northwest Atlantic margin JF - Deep-Sea Research Part I-Oceanographic Research Papers Y1 - 2009 A1 - Hwang, J. A1 - Manganini, S. J. A1 - Montlucon, D. B. A1 - Eglinton, T. I. AB - The Northwest Atlantic margin is characterized by high biological productivity in shelf and slope surface waters. In addition to carbon supply to underlying sediments, the persistent, intermediate depth nepheloid layers emanating from the continental shelves, and bottom nepheloid layers maintained by strong bottom currents associated with the southward flowing Deep Western Boundary Current (DWBC), provide conduits for export of organic carbon over the margin and/or to the interior ocean. As a part of a project to understand dynamics of particulate organic carbon (POC) cycling in this region, we examined the bulk and molecular properties of time-series sediment trap samples obtained at 968 m, 1976 m, and 2938 m depths from a bottom-tethered mooring on the New England slope (water depth, 2988 m). Frequent occurrences of higher fluxes in deep relative to shallower sediment traps and low Delta C-14 values of sinking POC together provide strong evidence for significant lateral transport of aged organic matter over the margin. Comparison of biogeochemical properties such as aluminum concentration and flux, and iron concentration between samples intercepted at different depths shows that particles collected by the deepest trap had more complex sources than the shallower ones. These data also suggest that at least two modes of lateral transport exist over the New England margin. Based on radiocarbon mass balance, about 30% (+/- 10%) of sinking POC in all sediment traps is estimated to be derived from lateral transport of resuspended sediment. A strong correlation between Delta C-14 values and aluminum concentrations suggests that the aged organic matter is associated with lithogenic particles. Our results suggest that lateral transport of organic matter, particularly that resulting from sediment resuspension, should be considered in addition to vertical supply of organic matter derived from primary production, in order to understand carbon cycling and export over continental margins. (C) 2009 Elsevier Ltd. All rights reserved. VL - 56 IS - 10 N1 - id: 1829; 490AT Times Cited:0 Cited References Count:61Y JO - Dynamics of particle export on the Northwest Atlantic margin ER - TY - JOUR T1 - Evidence for calcification depth change of Globorotalia truncatulinoides between deglaciation and Holocene in the Western Atlantic Ocean JF - Marine Micropaleontology Y1 - 2009 A1 - Cleroux, C. A1 - Lynch-Stieglitz, J. A1 - Schmidt, M. W. A1 - Cortijo, E. A1 - Duplessy, J. C. AB - Measurements of the delta O-18 in tests of planktonic and benthic foraminifera in the Florida Straits are used to reconstruct the properties of the water column through time over the last 12 ka (Lynch-Stieglitz et al., in press). The isotopic composition of the foraminifera largely reflects the vertical density gradient. We use this reconstruction and delta O-18 measurements on Globorotalia truncatulinoides in a nearby core to track the depth habitat of this species from the last deglaciation to 1.6 ka B.P. Around 9 ka, G. truncatulinoides was calcifying in much shallower water than during the late Holocene. The downward migration toward its modem habitat is a regional phenomenon over the western tropical Atlantic continental slope. The cause is still unclear but we hypothesize that the shallower calcification depth may be a response to the presence of glacial melt water or to circulation changes. This study points to the value of further study of the ecology, life cycle and calcification depth for G. truncatulinoides and other planktonic foraminifera that are used to reconstruct the history of the thermocline and upper water column structure. Published by Elsevier B.V. VL - 73 IS - 1-2 N1 - id: 1883; 514BR Times Cited:0 Cited References Count:33Y JO - Evidence for calcification depth change of Globorotalia truncatulinoides between deglaciation and Holocene in the Western Atlantic Ocean ER - TY - JOUR T1 - Evidence of centennial-scale drought from southeastern Massachusetts during the Pleistocene/Holocene transition JF - Quaternary Science Reviews Y1 - 2009 A1 - Newby, P. E. A1 - Donnelly, J. P. A1 - Shuman, B. N. A1 - MacDonald, D. AB - A principal method for studying past hydroclimatic change is the reconstruction of paleo-lake levels. Here, we provide high-resolution lake-level records from New Long Pond and Rocky Pond in southeastern Massachusetts, which each contain evidence for multiple, sub-centennial-to-millennial scale low stands during the transition between the Late Pleistocene (15.0 ka) and Middle Holocene (ca 7.0 ka). Data from New Long Pond also demonstrate sedimentary evidence for a drop in water levels in the early to mid AD 20th century, when long-term trends in instrumental data show lower-than-average precipitation in the northeastern United States. Local data show the most precipitous declines in precipitation and groundwater levels are concurrent with the most severe drought in the AD 1960s, which occurred during a period of low sea-surface temperatures in the western North Atlantic. Ground penetrating radar and sediment core data indicate five intervals with numerous paleo-shoreline deposits between ca 15.0 and 7.0 ka, similar to the layer deposited in the AD 1960s. Many of the intervals of low lake levels coincide with proposed meltwater release events or abrupt climate oscillations in the circum North Atlantic. For example, we document at least three low stands during the Younger Dryas (12.9-11.6 ka) and in association with the "9.2" and "8.2" ka events. The combined evidence of (1) concurrent paleo-droughts in southeastern New England with documented North Atlantic abrupt cooling events and (2) recent drought with the modern association of low sea-surface temperatures indicates that freshening and cooling of the western North Atlantic is a viable mechanism for decreasing moisture within the region. Large-scale changes in seasonality and ice sheet extent also may have increased the susceptibility of the northeast to dry conditions triggered by changes in the North Atlantic. (C) 2009 Elsevier Ltd. All rights reserved. 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Donnelly, Jeffrey P. Shuman, Bryan N. MacDonald, Dana Pergamon-elsevier science ltd Oxford Sp. Iss. SI; YY JO - Evidence of centennial-scale drought from southeastern Massachusetts during the Pleistocene/Holocene transition ER - TY - JOUR T1 - Evidence of paleo-cold seep activity from the Bay of Bengal, offshore India JF - Geochemistry Geophysics Geosystems Y1 - 2009 A1 - Mazumdar, A. A1 - Dewangan, P. A1 - Joao, H. M. A1 - Peketi, A. A1 - Khosla, V. R. A1 - Kocherla, M. A1 - Badesab, F. K. A1 - Joshi, R. K. A1 - Roxanne, P. A1 - Ramamurty, P. B. A1 - Karisiddaiah, S. M. A1 - Patil, D. J. A1 - Dayal, A. M. A1 - Ramprasad, T. A1 - Hawkesworth, C. J. A1 - Avanzinelli, R. AB - We report evidence of paleo-cold seep associated activities, preserved in methane-derived carbonates in association with chemosynthetic clams (Calyptogena sp.) from a sediment core in the Krishna-Godavari basin, Bay of Bengal. Visual observations and calculations based on high-resolution wet bulk density profile of a core collected on board R/V Marion Dufresne (May 2007) show zones of sharp increase in carbonate content (10-55 vol%) within 16-20 meters below seafloor (mbsf). The presence of Calyptogena clam shells, chimneys, shell breccias with high Mg calcite cement, and pyrite within this zone suggest seepage of methane and sulfide-bearing fluid to the seafloor in the past. Highly depleted carbon isotopic values (delta C-13 ranges from -41 to -52% VPDB) from these carbonates indicate carbon derived via anaerobic oxidation of methane. Extrapolated mean calendar age (similar to 58.7 ka B. P.) of the clastic sediments at a depth of 16 mbsf is close to the upper limit of the U-Th based depositional age (46.2 +/- 3.7 and 53.0 +/- 1.6 ka) of authigenic carbonates sampled from this level, thereby constraining the younger age limit of the carbonate deposition/methane expulsion events. The observed carbonate deposition might have resulted from the flow of methane-enriched fluids through the fracture network formed because of shale diapirism. VL - 10 N1 - id: 794; 458FC Times Cited:0 Cited References Count:80Y JO - Evidence of paleo-cold seep activity from the Bay of Bengal, offshore India ER - TY - JOUR T1 - Exploring typhoon variability over the mid-to-late Holocene: evidence of extreme coastal flooding from Kamikoshiki, Japan JF - Quaternary Science Reviews Y1 - 2009 A1 - Woodruff, J. D. A1 - Donnelly, J. P. A1 - Okusu, A. AB - Sediment cores from two coastal lakes located on the island of Kamikoshiki in southwestern Japan (Lake Namakoike and Lake Kaiike) provide evidence for the response of a backbarrier beach system to episodic coastal inundation over the last 6400 years. Sub-bottom seismic surveys exhibit acoustically laminated, parallel to subparallel seismic reflectors, intermittently truncated by erosional unconformities. Sediment cores collected from targeted depocenters in both lakes contain finely laminated organic mud interbedded with coarse-grained units, with depths of coarse deposits concurrent with prominent seismic reflectors. The timing of the youngest deposit at Kamikoshiki correlates to the most recently documented breach in the barrier during a typhoon in 1951 AD. Assuming that this modern deposit provides an analog for identifying past events, paleo-typhoons may be reconstructed from layers exhibiting an increase in grain-size, a break in fine-scale stratigraphy, and elevated Sr concentrations. Periods of barrier breaching are concurrent with an increase in El Nino frequency, indicating that the El Nino/Southern Oscillation has potentially played a key role in governing typhoon variability during the mid-to-late Holocene. An inverse correlation is observed between tropical cyclone reconstructions from the western North Atlantic and the Kamikoshiki site, which may indicate an oscillating pattern in tropical cyclone activity between the western Northern Atlantic and the western North Pacific, or at least between the western Northern Atlantic and regions encompassing southern Japan. The two kamikaze typhoons which contributed to the failed Mongol invasions of Japan in 1274 AD and 1281 AD occur during a period with more frequent marine-sourced deposition at the site, suggesting that the events took place during a period of greater regional typhoon activity. (C) 2009 Elsevier Ltd. All rights reserved. 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Donnelly, Jeffrey P. Okusu, Akiko Pergamon-elsevier science ltd Oxford Sp. Iss. SI; YY JO - Exploring typhoon variability over the mid-to-late Holocene: evidence of extreme coastal flooding from Kamikoshiki, Japan ER - TY - JOUR T1 - Field Survey and Geological Effects of the 15 November 2006 Kuril Tsunami in the Middle Kuril Islands JF - Pure and Applied Geophysics Y1 - 2009 A1 - MacInnes, B. T. A1 - Pinegina, T. K. A1 - Bourgeois, J. A1 - Razhigaeva, N. G. A1 - Kaistrenko, V. M. A1 - Kravchunovskaya, E. A. AB - The near-field expression of the tsunami produced by the 15 November 2006 Kuril earthquake (M-w 8.1-8.4) in the middle Kuril Islands, Russia, including runup of up to 20 m, remained unknown until we conducted a post-tsunami survey in the summer of 2007. Because the earthquake occurred between summer field expeditions in 2006 and 2007, we have observations, topographic profiles, and photographs from three months before and nine months after the tsunami. We thoroughly surveyed portions of the islands of Simushir and Matua, and also did surveys on parts of Ketoi, Yankicha, Ryponkicha, and Rasshua. Tsunami runup in the near-field of the middle Kuril Islands, over a distance of about 200 km, averaged 10 m over 130 locations surveyed and was typically between 5 and 15 m. Local topography strongly affected inundation and somewhat affected runup. Higher runup generally occurred along steep, protruding headlands, whereas longer inundation distances occurred on lower, flatter coastal plains. Sediment transport was ubiquitous where sediment was available-deposit grain size was typically sand, but ranged from mud to large boulders. Wherever there were sandy beaches, a more or less continuous sand sheet was present on the coastal plain. Erosion was extensive, often more extensive than deposition in both space and volume, especially in areas with runup of more than 10 m. The tsunami eroded the beach landward, stripped vegetation, created scours and trim lines, cut through ridges, and plucked rocks out of the coastal plain. VL - 166 IS - 1-2 N1 - id: 831; 418XP Times Cited:2 Cited References Count:46Y JO - Field Survey and Geological Effects of the 15 November 2006 Kuril Tsunami in the Middle Kuril Islands ER - TY - JOUR T1 - Fine-scale relief related to Late Holocene channel shifting within the floor of the upper Redondo Fan, offshore Southern California JF - Sedimentology Y1 - 2009 A1 - Normark, William R. A1 - Paull, Charles K. A1 - Caress, David W. A1 - Ussler Iii, William A1 - Sliter, Ray AB - AbstractErosional and depositional bedforms have been imaged at outcrop scale in the upper Redondo Fan, in the San Pedro Basin of offshore Southern California in greater than or equal to 600 m water depths, using an Autonomous Underwater Vehicle developed by the Monterey Bay Aquarium Research Institute. The Autonomous Underwater Vehicle is equipped with multibeam and chirp sub-bottom sonars. Sampling and photographic images using the Monterey Bay Aquarium Research Institute Remotely Operated Vehicle Tiburon provide groundtruth for the Autonomous Underwater Vehicle survey. The 0.3 m vertical and 1.5 m lateral bathymetric resolution and 0.1 m sub-bottom profile resolution provide unprecedented detail of bedform morphology and structure. Multiple channels within the Redondo Fan have been active at different times during the Late Holocene (0 to 3000 yr bp). The currently active channel extending from Redondo Canyon makes an abrupt 90 degree turn at the canyon mouth before resuming a south-easterly course along the east side of the Redondo Fan. This channel is floored by sand and characterized by small steps generally VL - 56 IS - 6 N1 - id: 2216; Source type: scholarlyjournals; Object type: Article; Object type: Feature; CSAUnique: OB-MD-0010477140; AccNum: 11022775; DOI: 10.1111/j.1365-3091.2009.01052.x; ISSN: 0037-0746; Peer Reviewed: true JO - Fine-scale relief related to Late Holocene channel shifting within the floor of the upper Redondo Fan, offshore Southern California ER - TY - JOUR T1 - Fish scales in sediments from off Callao, central Peru JF - DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY Y1 - 2009 A1 - Diaz-Ochoa, J. A. A1 - Lange, C. B. A1 - Pantoja, S. A1 - De lange, G. J. A1 - Gutierrez, D. A1 - Munoz, P. A1 - Salamanca, M. KW - Callao KW - Clupeoid fish KW - Molybdenum KW - Oxygen minimum zone KW - Peru KW - Redox-sensitive trace elements AB - We study fish scales as a proxy of fish abundance and preservation biases together with phosphorus from fish remains (P(fish)) in a sediment core retrieved off Callao, Peru (12 degrees 1'S, 77 degrees 42'W; water depth = 179 m; core length = 52 cm). We interpret our results as a function of changing redox conditions based on ratios of redox-sensitive trace elements (Cu/Al, Mo/Al, Ni/Al, Zn/Al, V/Al), terrigenous indicators (Fe in clays, Ti, Al), and biogenic proxies (CaCO(3), biogenic opal, total nitrogen, organic carbon, barite Ba). The core covers roughly 700 years of deposition, based on (210)Pb activities extrapolated downcore and (14)C dating at selected intervals. Our fish-scale record is dominated by anchovy (Engraulis ringens) scales followed by hake (Merluccius gayii) scales. The core presented an abrupt lithological change at 17 cm (corresponding to the early 19th century). Above that depth, it was laminated and was more organic-rich (10-15% organic carbon) than below, where the core was partly laminated and less organic-rich (< 10%). The lithological shift coincides with abrupt changes in dry bulk density and in the contents of terrigenous and redox-sensitive trace elements, biogenic proxies, and fish scales. The remarkable increase in redox-sensitive trace elements in the upper 17 cm of the core suggests more reducing conditions when compared with deeper and older horizons, and is interpreted as an intensification of the oxygen minimum zone off Peru beginning in the early 19th century. Higher fish-scale contents and higher P(fish)/P(total) ratios were also observed within the upper 17 cm of the core. The behavior of biogenic proxies and redox-sensitive trace elements was similar; more reduced conditions corresponded to higher contents of CaCO(3), C(org), total nitrogen and fish scales, suggesting that these proxies might convey an important preservation signal. (C) 2008 Elsevier Ltd. All rights reserved. VL - 56 ER - TY - JOUR T1 - Fishing from past to present: continuity and resilience of red abalone fisheries on the Channel Islands, California JF - Ecological Applications Y1 - 2009 A1 - Braje, Todd J. A1 - Erlandson, Jon M. A1 - Rick, Torben C. A1 - Dayton, Paul K. A1 - Hatch, Marco B. A. AB - Archaeological data from coastal shell middens provide a window into the structure of ancient marine ecosystems and the nature of human impacts on fisheries that often span millennia. For decades Channel Island archaeologists have studied Middle Holocene shell middens visually dominated by large and often whole shells of the red abalone (Haliotis rufescens). Here we use modern ecological data, historical accounts, commercial red abalone catch records, and zooarchaeological data to examine long-term spatial and temporal variation in the productivity of red abalone fisheries on the Northern Channel Islands, California (USA). Historical patterns of abundance, in which red abalone densities increase from east to west through the islands, extend deep into the Holocene. The correlation of historical and archaeological data argue for long-term spatial continuity in productive red abalone fisheries and a resilience of abalone populations despite dramatic ecological changes and intensive human predation spanning more than 8000 years. Archaeological, historical, and ecological data suggest that California kelp forests and red abalone populations are structured by a complex combination of top-down and bottom-up controls. VL - 19 IS - 4 N1 - id: 2060; PT: J; UT: WOS:000266281400008 JO - Fishing from past to present: continuity and resilience of red abalone fisheries on the Channel Islands, California ER - TY - JOUR T1 - Fishing up the Food Web?: 12,000 Years of Maritime Subsistence and Adaptive Adjustments on California's Channel Islands JF - Pacific Science Y1 - 2009 A1 - Erlandson, Jon M. A1 - Rick, Torben C. A1 - Braje, Todd J. AB - Archaeologists working on California's northern Channel Islands have produced an essentially continuous record of Native American fishing and nearshore ecological changes spanning die last 12,000 years. To search for evidence of Pauly's "fishing down the foodweb" pattern typical of recent historical fisheries, we analyzed variation in the dietary importance of major marine faunal classes (shellfish, fish, marine mammals) on the islands through time. Faunal data suggest that the Island Chumash and their predecessors focused primarily on low-trophic-level shellfish during the Early and Middle Holocene, before shifting their economic focus to finfish and pinnipeds during the Late Holocene. Replicated in faunal sequences from the adjacent mainland, this trans-Holocene pattern suggests that Native Americans fished Lip the food web, a strategy that may have been more sustainable and had fewer ecological repercussions. Emerging technological data suggest, however, that some of the earliest Channel Islanders focused more heavily on higher-trophic-level animals, including marine mammals, seabirds, and waterfowl. These data emphasize the differences between the primarily subsistence-based foraging strategies of ancient Channel Islanders and the globalized market-based fisheries of modern and historic times, with important implications for understanding the long-term evolution and historical ecology of marine ecosystems. VL - 63 IS - 4 N1 - id: 2059; PT: J; UT: WOS:000270849400011 JO - Fishing up the Food Web?: 12,000 Years of Maritime Subsistence and Adaptive Adjustments on California's Channel Islands ER - TY - JOUR T1 - Florida Straits density structure and transport over the last 8,000 years JF - Paleoceanography Y1 - 2009 A1 - Lynch-Stieglitz, J. A1 - Curry, W. B. A1 - Lund, D. C. VL - 24 IS - 3 N1 - id: 837; YY JO - Florida Straits density structure and transport over the last 8,000 years ER - TY - JOUR T1 - Formal definition and dating of the GSSP (Global Stratotype Section and Point) for the base of the Holocene using the Greenland NGRIP ice core, and selected auxiliary records RID B-5560-2008 RID F-1111-2011 JF - Journal of Quaternary Science Y1 - 2009 A1 - Walker, Mike A1 - Johnsen, Sigfus A1 - Rasmussen, Sune Olander A1 - Popp, Trevor A1 - Steffensen, Jorgen-Peder A1 - Gibbard, Phil A1 - Hoek, Wim A1 - Lowe, John A1 - Andrews, John A1 - Bjorck, Svante A1 - Cwynar, Les C. A1 - Hughen, Konrad A1 - Kershaw, Peter A1 - Kromer, Bernd A1 - Litt, Thomas A1 - Lowe, David J. A1 - Nakagawa, Takeshi A1 - Newnham, Rewi A1 - Schwander, Jakob AB - The Greenland ice core from NorthGRIP (NGRIP) contains a proxy climate record across the Pleistocene-Holocene boundary of unprecedented clarity and resolution. Analysis of an array of physical and chemical parameters within the ice enables the base of the Holocene, as reflected in the first signs of climatic warming at the end of the Younger Dryas/Greenland Stadial 1 cold phase, to be located with a high degree of precision. This climatic event is most clearly reflected in an abrupt shift in deuterium excess values, accompanied by more gradual changes in delta(18)O, dust concentration, a range of chemical species, and annual layer thickness. A timescale based on multi-parameter annual layer counting provides an age of 11 700 calendar yr b2k (before AD 2000) for the base of the Holocene, with a maximum counting error of 99 yr. A proposal that an archived core from this unique sequence should constitute the Global Stratotype Section and Point (GSSP) for the base of the Holocene Series/Epoch (Quaternary System/Period) has been ratified by the International Union of Geological Sciences. Five auxiliary stratotypes for the Pleistocene-Holocene boundary have also been recognised. Copyright (C) 2008 John Wiley & Sons, Ltd. VL - 24 IS - 1 N1 - id: 1989; PT: J; UT: WOS:000262615700002 JO - Formal definition and dating of the GSSP (Global Stratotype Section and Point) for the base of the Holocene using the Greenland NGRIP ice core, and selected auxiliary records RID B-5560-2008 RID F-1111-2011 ER - TY - JOUR T1 - Fragmentary Evidence of Great-Earthquake Subsidence during Holocene Emergence, Valdivia Estuary, South Central Chile JF - Bulletin of the Seismological Society of America Y1 - 2009 A1 - Nelson, Alan R. A1 - Kashima, Kaoru A1 - Bradley, Lee-Ann AB - A reconnaissance of Holocene stratigraphy beneath fringing marshes of the Valdivia estuary, where an M 9.5 earthquake caused 1-2 m of regional coseismic subsidence in 1960, shows only fragmentary evidence of prehistoric coseismic subsidence. In most of the 150 hand-driven cores that were examined, a distinct unconformity separates 0.5-1.5 m of late Holocene tidal and floodplain mud, peat, and sand from underlying middle Holocene subtidal mud and sand. At the Las Coloradas site, where stratigraphy is best preserved, two A horizons of marsh and meadow soils abruptly overlain by sand and mud probably record coseismic subsidence shortly followed by tsunamis. The amount of subsidence during the earthquakes proved difficult to reconstruct with a diatom transfer function because of differences between modern and fossil diatom assemblages. Maximum (14)C ages on macrofossils from the two A horizons at the Las Coloradas site of 1.7-1.3 ka and 2.7-1.7 ka allow correlation of the younger horizon with either of two of six (14)C-dated A horizons buried by tsunami sand or post-tsunami tidal sand 200 km to the south at Maullin, and with a lake-wide mass wasting event in Lago Puyehue, 100 km to the southeast. Tidal records of prehistoric coseismic subsidence at Valdivia are scarce because of a sea-level fall of 3-8 m over the past 6000 years, erosion of marsh and meadow soils during subsidence-induced flooding of the estuary, and largely complete land-level recovery during cycles of coseismic subsidence and postseismic uplift. VL - 99 IS - 1 N1 - id: 2020; PT: J; UT: WOS:000266181100006 JO - Fragmentary Evidence of Great-Earthquake Subsidence during Holocene Emergence, Valdivia Estuary, South Central Chile ER - TY - JOUR T1 - From Sheep To (Some) Horses: 4500 Years Of Herd Structure At The Pastoralist Settlement of Begash (southeastern Kazakhstan) JF - Antiquity Y1 - 2009 A1 - Frachetti, M. D. A1 - Benecke, N. VL - 83 IS - 322 N1 - id: 834 ER - TY - THES T1 - A Gendered Model of Prehistoric Resource Depression: A Case Study on the Northwest Coast of North America Y1 - 2009 A1 - Daniels, Phoebe PB - University of Washington CY - Seattle VL - Dissertation/Thesis ER - TY - JOUR T1 - Growth and sexual maturity of the northern propellerclam (Cyrtodaria siliqua) in Eastern Canada, with bomb radiocarbon age validation JF - Marine Biology Y1 - 2009 A1 - Kilada, R. W. A1 - Campana, S. E. A1 - Roddick, D. AB - The northern propellerclam Cyrtodaria siliqua is a common bycatch in the Arctic surfclam, Mactromeris polynyma fishery on Banquereau Bank in Eastern Canada. Samples of the propellerclam from this exploited fishery were used to determine the life history characteristics of the population. The age structure of the population is dominated by old animals to ages exceeding 100 years. We validated the age estimates for the propellerclam through analysis of bomb-produced radiocarbon in the shell growth increments deposited before, during and after the atmospheric atomic bomb testing periods of the 1950s and 1960s. Radiocarbon from shells with presumed birth dates between the late 1950s and 1970s clearly reflected the sharp increase in oceanic radiocarbon attributable to previous nuclear testing, indicating that age estimates based on shell increment counts are accurate. Estimates of von Bertalanffy growth parameters revealed that the growth rate of the population was relatively rapid for the first 20 years of life, slowing down to very low growth rates thereafter. Sexual maturity was estimated as being reached at 28.6 mm in length and 4.7 years in age. Size-weight morphometric relationships were also calculated. VL - 156 IS - 5 N1 - id: 803; 413YA Times Cited:0 Cited References Count:45Y JO - Growth and sexual maturity of the northern propellerclam (Cyrtodaria siliqua) in Eastern Canada, with bomb radiocarbon age validation ER - TY - JOUR T1 - High mitogenomic evolutionary rates and time dependency JF - Trends in Genetics Y1 - 2009 A1 - Subramanian, Sankar A1 - Denver, Dee R. A1 - Millar, Craig D. A1 - Heupink, Tim A1 - Aschrafi, Angelique A1 - Emslie, Steven D. A1 - Baroni, Carlo A1 - Lambert, David M. AB - Using entire modern and ancient mitochondrial genomes of Adelie penguins (Pygoscelis adeliae) that are up to 44000 years old, we show that the rates of evolution of the mitochondrial genome are two to six times greater than those estimated from phylogenetic comparisons. Although the rate of evolution at constrained sites, including nonsynonymous positions and RNAs, varies more than twofold with time (between shallow and deep nodes), the rate of evolution at synonymous sites remains the same. The time-independent neutral evolutionary rates reported here would be useful for the study of recent evolutionary events. VL - 25 IS - 11 N1 - id: 1917; PT: J; NR: 27; TC: 19; J9: TRENDS GENET; PG: 5; GA: 518TW; UT: WOS:000271717800004 JO - High mitogenomic evolutionary rates and time dependency RID B-6647-2008 ER - TY - JOUR T1 - High-sensitivity measurement of diverse vascular plant-derived biomarkers in high-altitude ice cores JF - GEOPHYSICAL RESEARCH LETTERS Y1 - 2009 A1 - Makou, Matthew C. A1 - Thompson, Lonnie G. A1 - Montluçon, Daniel B. A1 - Eglinton, Timothy I. AB - Semi-volatile organic compounds derived from burned and fresh vascular plant sources and preserved in high-altitude ice fields were detected and identified through use of recently developed analytical tools. Specifically, stir bar sorptive extraction and thermal desorption coupled with gas chromatography/time-of-flight mass spectrometry allowed measurement of multiple biomarkers in small sample volumes (<= 30 ml). Among other compounds of interest, several diterpenoids, which suggest inputs from conifers and conifer burning, were identified in post-industrial era and older Holocene ice from the Sajama site in the Bolivian Andes, but not in a glacial period sample, consistent with aridity changes. Differences in biomarker assemblages between sites support the use of these compounds as regionally constrained recorders of vegetation and climate change. This study represents the first application of these analytical techniques to ice core research and the first indication that records of vegetation fires may be reconstructed from diterpenoids in ice. Citation: Makou, M. C., L. G. Thompson, D. B. Montlucon, and T. I. Eglinton (2009), High-sensitivity measurement of diverse vascular plant-derived biomarkers in high-altitude ice cores, Geophys. Res. Lett., 36, L13501, doi: 10.1029/2009GL037643. VL - 36 ER - TY - THES T1 - Historic sediment accretion rates in a Louisiana coastal marsh and implications for sustainability Y1 - 2009 A1 - Smith, Rebekah P. PB - Louisiana State University VL - Dissertation/Thesis ER - TY - JOUR T1 - Holocene Adelie penguin diet in Victoria Land, Antarctica JF - Polar Biology Y1 - 2009 A1 - Lorenzini, Sandra A1 - Olmastroni, Silvia A1 - Pezzo, Francesco A1 - Salvatore, Maria Cristina A1 - Baroni, Carlo AB - Ornithogenic soils (N = 97) dated up to 7000 Before Present (Ebp) were sampled in 16 relict and modern breeding colonies of Ad,lie penguin along the Victoria Land coast (Ross Sea, Antarctica). Taxonomic identification of fish otoliths (N = 677) recovered in these soils allowed to identify the Antarctic silverfish as the most eaten prey (90.1%) throughout the investigated period. A morphometric analysis of the otoliths revealed that the Ad,lie penguin primarily selected prey averaging 67.23 +/- A 23 mm of standard length. Temporal distribution of Pleuragramma antarcticum showed a peak between 2,000 and 4,000 years bp, a period corresponding to the maximum spread of Ad,lie penguin in the Victoria Land. Possible explanations of the variations of the abundance of the fish prey in the diet are discussed in the context of the paleoclimatic events and as possible consequences of dietary shifts due to the temporal variation of prey availability in the Ross Sea ecosystem. VL - 32 IS - 7 N1 - id: 1916; PT: J; NR: 60; TC: 2; J9: POLAR BIOL; PG: 10; GA: 457FQ; UT: WOS:000266914300013 JO - Holocene Adelie penguin diet in Victoria Land, Antarctica ER - TY - JOUR T1 - Holocene sea-level changes along the North Carolina Coastline and their implications for glacial isostatic adjustment models JF - Quaternary Science Reviews Y1 - 2009 A1 - Horton, B. P. A1 - Peltier, W. R. A1 - Culver, S. J. A1 - Drummond, R. A1 - Engelhart, S. E. A1 - Kemp, A. C. A1 - Mallinson, D. A1 - Thieler, E. R. A1 - Riggs, S. R. A1 - Ames, D. V. A1 - Thomson, K. H. AB - We have synthesized new and existing relative sea-level (RSL) data to produce a quality-controlled, spatially comprehensive database from the North Carolina coastline. The RSL database consists of 54 sea-level index points that are quantitatively related to an appropriate tide level and assigned an error estimate, and a further 33 limiting dates that confine the maximum and minimum elevations of RSL The temporal distribution of the index points is very uneven with only five index points older than 4000 cal a BP, but the form of the Holocene sea-level trend is constrained by both terrestrial and marine limiting dates. The data illustrate RSL rapidly rising during the early and mid Holocene from an observed elevation of -35.7 +/- 1.1 m MSL at 11062-10576 cal a BP to -4.2 m +/- 0.4 m MSL at 4240-3592 cal a BP. We restricted comparisons between observations and predictions from the ICE-5G(VM2) with rotational feedback Glacial Isostatic Adjustment (GIA) model to the Late Holocene RSL (last 4000 cal a BP) because of the wealth of sea-level data during this time interval. The ICE-5G(VM2) model predicts significant spatial variations in RSL across North Carolina, thus we subdivided the observations into two regions. The model forecasts an increase in the rate of sea-level rise in Region 1 (Albemarle, Currituck, Roanoke, Croatan, and northern Pamlico sounds) compared to Region 2 (southern Pamlico, Core and Bogue sounds, and farther south to Wilmington). The observations show Late Holocene sea-level rising at 1.14 +/- 0.03 mm year(-1) and 0.82 +/- 0.02 mm year(-1) in Regions 1 and 2, respectively. The ICE-5G(VM2) predictions capture the general temporal trend of the observations, although there is an apparent misfit for index points older than 2000 cal a BR It is presently unknown whether these misfits are caused by possible tectonic uplift associated with the mid-Carolina Platform High or a flaw in the CIA model. A comparison of local tide gauge data with the Late Holocene RSL trends from Regions 1 and 2 support the spatial variation in RSL across North Carolina, and imply an additional increase of mean sea level of greater than 2 mm year(-1) during the latter half of the 20th century; this is in general agreement with historical tide gauge and satellite altimetry data. (C) 2009 Elsevier Ltd. All rights reserved. VL - 28 IS - 17-18 N1 - id: 814; Sp. Iss. SI 484ZD Times Cited:1 Cited References Count:108Y JO - Holocene sea-level changes along the North Carolina Coastline and their implications for glacial isostatic adjustment models ER - TY - JOUR T1 - Human impacts, climate change, and aquatic ecosystem response during the past 2000 yr at Lake Wandakara, Uganda JF - Quaternary Research Y1 - 2009 A1 - Russell, James M. A1 - McCoy, S. J. A1 - Verschuren, D. A1 - Bessems, I. A1 - Huang, Y. AB - Analyses of carbon and hydrogen isotope ratios of terrestrial leaf waxes and the carbon and nitrogen abundance. ratio, and isotopic composition of bulk sediments from Like Wandakara, a crater lake in western Uganda, East Africa. document human and climatic controls on the aquatic system and oil the Surrounding terrestrial vegetation during the past two millennia Our data indicate that Wandakara was a relatively stable, productive lake Surrounded by C(3) vegetation from AD 70 to 1000. Abrupt changes in the delta(13)C of terrestrial leaf waxes indicate a series of abrupt shifts in the relative abundance of C(3) and C(4) vegetation caused by a combination of climate change and human activities around Wandakara beginning at AD 1000. Abrupt shifts in bulk sediment organic geochemistry. particularly C/N ratios and delta(15)N, indicate that human activities at this time caused permanent changes in the limnology of Lake Wandakara. including eutrophication Our results suggest that the biogeochemistry of Like Wandakara was more sensitive to shifting human impacts than to climate variations during the past millennium, highlighting the importance of understanding the intensity of pre-colonial human impacts on Africa's aquatic ecosystems (C) 2009 University of Washington Published by Elsevier Inc All rights reserved VL - 72 IS - 3 N1 - id: 2052; PT: J; UT: WOS:000271254000002 JO - Human impacts, climate change, and aquatic ecosystem response during the past 2000 yr at Lake Wandakara, Uganda ER - TY - JOUR T1 - Implications of Radiocarbon Dates from Potter Creek Cave, Shasta County, California, USA JF - Radiocarbon Y1 - 2009 A1 - Feranec, R. S. KW - account KW - bone KW - pretreatment AB - New dates obtained from the bone collagen of mammals from the deposits in Potter Creek Cave, Shasta County, California, USA, show that these fossils were emplaced over the last 30,000 yr. The dates support the assignment of the fauna in the cave to the late Pleistocene and are contemporaneous to the dates obtained from the fauna of Samwel Cave located 5 km to the north. These new dates do not support previous radiocarbon dates suggesting a Holocene extinction of the extinct bovid Euceratherium collinum, and demonstrate that this and other megafauna were not present in the vicinity after the terminal Pleistocene. VL - 51 SN - 0033-8222 IS - 3 N1 - 544peTimes Cited:1 Cited References Count:16 JO - Radiocarbon ER - TY - JOUR T1 - In situ cosmogenic 10Be production-rate calibration from the Southern Alps, New Zealand JF - Quaternary Geochronology Y1 - 2009 A1 - Putnam, A. E. A1 - Schaefer, J. M. A1 - Barrell, D. J. A. A1 - Vandergoes, M. A1 - Denton, G. H. A1 - Kaplan, M. R. A1 - Finkel, R. C. A1 - Schwartz, R. A1 - Goehring, B. M. A1 - Kelley, S. E. N1 - id: 840In pressY JO - In situ cosmogenic 10Be production-rate calibration from the Southern Alps, New Zealand ER - TY - JOUR T1 - Initial source evaluation of archaeological obsidian from the Kuril Islands of the Russian Far East using portable XRF JF - Journal of Archaeological Science Y1 - 2009 A1 - Phillips, S. C. A1 - Speakman, R. J. AB - Obsidian artifacts recently have been recovered from 18 archaeological sites on eight islands across the Kuril Island archipelago in the North Pacific Ocean, suggesting a wide-ranging distribution of obsidian throughout the island chain over the last 2,500 years. Although there are no geologic sources of obsidian in the Kurils that are known to have been used prehistorically, sources exist in Hokkaido, Japan, and Kamchatka, Russia, the southern and northern geographic regions respectively from which obsidian may have entered the Kuril Islands. This paper reports on the initial sourcing attempt of Kuril Islands obsidian through the analysis of 131 obsidian artifacts. Data from this research were generated through the application of portable XRF technology, and are used to address research questions concerning prehistoric mobility, exchange, and social networking in the Kuril Islands. (C) 2009 Elsevier Ltd. All rights reserved. VL - 36 IS - 6 N1 - id: 832; 433GY Times Cited:2 Cited References Count:66Y JO - Initial source evaluation of archaeological obsidian from the Kuril Islands of the Russian Far East using portable XRF ER - TY - JOUR T1 - Inputs of Fossil Carbon from Wastewater Treatment Plants to US Rivers and Oceans JF - Environmental Science & Technology Y1 - 2009 A1 - Griffith, D. R. A1 - Barnes, R. T. A1 - Raymond, P. A. AB - Every day more than 500 million cubic meters of treated wastewater are discharged into rivers, estuaries, and oceans, an amount slightly less than the average flow of the Danube River. Typically, wastewaters have high organic carbon [OC) concentrations and represent a large fraction of total river flow and a higher fraction of river OC in densely populated watersheds. Here, we report the first direct measurements of radiocarbon (C-14) in municipal wastewater treatment plant (WWTP) effluent. The radiocarbon ages of particulate and dissolved organic carbon (POC and DOC) in effluent are old and relatively uniform across a range of WWTPs in New York and Connecticut. Wastewater DOC has a mean radiocarbon age of 1630 +/- 500 years B.P. and a mean delta C-13 of -26.0 +/- 1 parts per thousand. Mass balance calculations indicate that 25% of wastewater DOC is fossil carbon, which is likely derived from petroleum-based household products such as detergents and pharmaceuticals. These findings warrant reevaluation of the "apparent age" of riverine DOC, the total flux of petroleum carbon to U.S. oceans, and OC source assignments in waters impacted by sewage. VL - 43 IS - 15 N1 - id: 1833; 476XR Times Cited:0 Cited References Count:51Y JO - Inputs of Fossil Carbon from Wastewater Treatment Plants to US Rivers and Oceans ER - TY - JOUR T1 - Intcal09 and Marine09 Radiocarbon Age Calibration Curves, 0-50,000 Years Cal Bp Rid F-4952-2011 Rid B-7298-2008 JF - Radiocarbon Y1 - 2009 A1 - Reimer, P. J. A1 - Baillie, M. G. L. A1 - Bard, E. A1 - Bayliss, A. A1 - Beck, J. W. A1 - Blackwell, P. G. A1 - Ramsey, C. Bronk A1 - Buck, C. E. A1 - Burr, G. S. A1 - Edwards, R. L. A1 - Friedrich, M. A1 - Grootes, P. M. A1 - Guilderson, T. P. A1 - Hajdas, I. A1 - Heaton, T. J. A1 - Hogg, A. G. A1 - Hughen, K. A. A1 - Kaiser, K. F. A1 - Kromer, B. A1 - McCormac, F. G. A1 - Manning, S. W. A1 - Reimer, R. W. A1 - Richards, D. A. A1 - Southon, J. R. A1 - Talamo, S. A1 - Turney, C. S. M. A1 - van der Plicht, J. A1 - Weyhenmeye, C. E. AB - The IntCal04 and Marine04 radiocarbon calibration curves have been updated from 12 cal kBP (cal kBP is here defined as thousands of calibrated years before AD 1950), and extended to 50 cal kBP, utilizing newly available data sets that meet the IntCal Working Group criteria for pristine corals and other carbonates and for quantification of uncertainty in both the (14)C and calendar timescales as established in 2002. No change was made to the curves from 0-12 cal kBP. The curves were constructed using a Markov chain Monte Carlo (MCMC) implementation of the random walk model used for IntCal04 and Marine04. The new curves were ratified at the 20th International Radiocarbon Conference in June 2009 and; ire available in the Supplemental Material at www.radiocarbon.org. VL - 51 SN - 0033-8222 IS - 4 N1 - id: 1983; PT: J; UT: WOS:000274407500002 ER - TY - JOUR T1 - Interhemispheric Atlantic seesaw response during the last deglaciation JF - Nature Y1 - 2009 A1 - Barker, S. A1 - Diz, P. A1 - Vautravers, M. J. A1 - Pike, J. A1 - Knorr, G. A1 - Hall, I. R. A1 - Broecker, W. S. AB - The asynchronous relationship between millennial-scale temperature changes over Greenland and Antarctica during the last glacial period has led to the notion of a bipolar seesaw which acts to redistribute heat depending on the state of meridional overturning circulation within the Atlantic Ocean. Here we present new records from the South Atlantic that show rapid changes during the last deglaciation that were instantaneous (within dating uncertainty) and of opposite sign to those observed in the North Atlantic. Our results demonstrate a direct link between the abrupt changes associated with variations in the Atlantic meridional overturning circulation and the more gradual adjustments characteristic of the Southern Ocean. These results emphasize the importance of the Southern Ocean for the development and transmission of millennial-scale climate variability and highlight its role in deglacial climate change and the associated rise in atmospheric carbon dioxide. VL - 457 IS - 7233 N1 - id: 856; Barker, Stephen Diz, Paula Vautravers, Maryline J Pike, Jennifer Knorr, Gregor Hall, Ian R Broecker, Wallace S England Nature. 2009 Feb 26;457(7233):1097-102.Y JO - Interhemispheric Atlantic seesaw response during the last deglaciation ER - TY - JOUR T1 - Interpreting Nd isotope and Pa-231/Th-230 records in the deep Western North Atlantic JF - Geochimica Et Cosmochimica Acta Y1 - 2009 A1 - Roberts, N. L. A1 - Piotrowski, A. M. A1 - McManus, J. F. A1 - Keigwin, L. D. KW - circulation VL - 73 SN - 0016-7037 IS - 13 N1 - Suppl. S460ys Times Cited:0 Cited References Count:3 JO - Geochim Cosmochim Ac ER - TY - JOUR T1 - Lake Sturgeon Age Validation using Bomb Radiocarbon and Known-Age Fish JF - Transactions of the American Fisheries Society Y1 - 2009 A1 - Bruch, R. M. A1 - Campana, S. E. A1 - Davis-Foust, S. L. A1 - Hansen, M. J. A1 - Janssen, J. AB - Pectoral fin spines have been the accepted structure for estimating the age of various sturgeon species for nearly 100 years, though other structures have also been used (otoliths, pectoral girdle, scutes, and caudal fulcra). Accuracy of age estimates using any of these structures has not been validated, so we report the first use of bomb radiocarbon (C-14) assays to assess the validity of ages estimated using growth increments on pectoral fin spine and otolith frontal cross sections from lake sturgeon Acipenser fulvescens: we also assessed age estimates from pectoral fin spines of known-age lake sturgeon. Growth increments on pectoral fin spine cross sections underestimated true age of fish older than 14 years and error increased with age, whereas otoliths accurately estimated true age up to at least 52 years. Increment formation on pectoral fin spine and otolith cross sections from juvenile lake sturgeon (ages 2-11) was similar, although pectoral spines were clearer and easier to interpret. A power function (true age = [estimated age](1.054796), where estimated age was determined from pectoral spines; r(2) = 0.98) provides a means for correcting existing age estimates obtained from lake sturgeon pectoral fin spines. VL - 138 IS - 2 N1 - id: 1855; 477EI Times Cited:1 Cited References Count:33Y JO - Lake Sturgeon Age Validation using Bomb Radiocarbon and Known-Age Fish ER - TY - JOUR T1 - Land-sea linkage of Holocene paleoclimate on the Southern Bering Continental Shelf JF - Holocene Y1 - 2009 A1 - Katsuki, K. A1 - Khim, B. K. A1 - Itaki, T. A1 - Harada, N. A1 - Sakai, H. A1 - Ikeda, T. A1 - Takahashi, K. A1 - Okazaki, Y. A1 - Asahi, H. AB - Detailed diatom records within surface and core sediments from the Southern Bering Continental Shelf (SBCS) reveal that the Holocene evolution of sea-ice distribution is associated with low pressure patterns. Holocene sea-ice distribution over the SBCS was mainly controlled by the location of the Aleutian Low. The corresponding paleoceanographic and paleoclimate conditions can be divided into three stages. (1) the early Holocene K before 7000 cal. yr BP) was characterized by extensive sea-ice distribution under two low-pressure cells, which covered the western Bering-Sea and the Gulf of Alaska, respectively. (2) Between 3000 and 7000 cal. yr BP, the low-pressure system over the Gulf of Alaska became weak, causing total sea-ice mass over the SBCS to retreat. (3) In the past 3000 years, prevailing southwesterly winds over the SBCS due to the developing Aleutian Low have reduced further sea-ice cover on the SBCS. These paleoclimatic changes were probably a response to ENSO variation. The timings of water mass exchanges on the SBCS coincided with sea-level change along the Alaskan Peninsula. As a result, subsequent morphologic alterations have also influenced the paleoceanographic condition of the SBCS. The effect of the surface coastal water and bottom marine water on the SBCS intensified about 6000 cal. yr BP when sea level increased. VL - 19 IS - 5 N1 - id: 1878; 470HQ Times Cited:1 Cited References Count:76Y JO - Land-sea linkage of Holocene paleoclimate on the Southern Bering Continental Shelf ER - TY - JOUR T1 - Late Holocene Hydrologic and Vegetation Changes at Turneffe Atoll, Belize, Compared with Records from Mainland Central America and Mexico JF - Palaios Y1 - 2009 A1 - Wooller, M. J. A1 - Behling, H. A1 - Guerrero, J. L. A1 - Jantz, N. A1 - Zweigert, M. E. AB - We present pollen and stable isotope (delta C-13, delta O-18, delta N-15) data from a similar to 4 in core (TNF-1) of primarily mangrove peat taken from Turneffe Atoll, Belize. Radiocarbon (accelerator mass spectrometry) dates show that the record represents ca. 5000 years of sediment accumulation. Vegetation composition varied between dominant mangroves (primarily Rhizophora mangle) and Chenopodiaceae-Amaranthaceae, most likely Salicornia bigelovii. The pollen data, along with inferences from stable isotope analyses of bulk peat and fossil leaf fragments, indicate that marked environmental changes occurred at this location over the past ca. 5000 years. There was a transition between ca. 4100 and 2900 cal yr BP, from vegetation dominated by relatively tall mangroves (R. mangle) to one dominated by Chenopodiaceae-Amaranthaceae and then Myrica, most likely wax myrtle (M. cerifera). These changes bracket a period centered at ca. 3500 calibrated years before present, where there is a peak in the delta O-18 of mangrove leaf fragments. This timing corresponds with other paleoenvironmental records of climate drying in Central America and increases the geographic and habitat scope (i.e., mangrove habitat) of records documenting these changes. Interpretations of shifts in mangrove habitat, however, require consideration of additional environmental influences, including changes in groundwater hydrology and relative inputs of seawater and freshwater (i.e., precipitation) during the Holocene. VL - 24 IS - 9-10 N1 - id: 1835; 506UH Times Cited:1 Cited References Count:34Y JO - Late Holocene Hydrologic and Vegetation Changes at Turneffe Atoll, Belize, Compared with Records from Mainland Central America and Mexico ER - TY - JOUR T1 - A late Holocene paleo-productivity record in the western Gulf of Maine, USA, inferred from growth histories of the long-lived ocean quahog (Arctica islandica) JF - INTERNATIONAL JOURNAL OF EARTH SCIENCES Y1 - 2009 A1 - Wanamaker, Alan D. Jr. A1 - Kreutz, Karl J. A1 - Schoene, Bernd R. A1 - Maasch, Kirk A. A1 - Pershing, Andrew J. A1 - Borns, Harold W. A1 - Introne, Douglas S. A1 - Feindel, Scott KW - Arctica islandica KW - Climate variability KW - Gulf of Maine KW - North Atlantic Oscillation (NAO) KW - Paleo-productivity KW - Shell growth AB - To investigate environmental variability during the late Holocene in the western Gulf of Maine, USA, we collected a 142-year-old living bivalve (Arctica islandica) in 2004, and three fossil A. islandica shells of the Medieval Warm Period (MWP) and late MWP / Little Ice Age (LIA) period (corrected C-14(AMS) = 1030 +/- A 78 ad; 1320 +/- A 45 ad; 1357 +/- A 40 ad) in 1996. We compared the growth record of the modern shell with continuous plankton recorder (CPR) time-series (1961-2003) from the Gulf of Maine. A significant correlation (r (2) = 0.55; p < 0.0001) exists between the standardized annual growth index (SGI) of the modern shell and the relative abundance of zooplankton species Calanus finmarchicus. We therefore propose that SGI data from A. islandica is a valid proxy for paleo-productivity of at least one major zooplankton taxa. SGIs from these shells reveal significant periods of 2-6 years (NAO-like) based on wavelet analysis, multitaper method (MTM) analysis and singular spectrum analysis (SSA) during the late Holocene. Based on established physical oceanographic observation in the Gulf of Maine, we suggest that slope water variability coupled with North Atlantic Oscillation (NAO) dynamics is primarily responsible for the observed SGI variability. VL - 98 ER - TY - JOUR T1 - Late Holocene sea-surface temperature and precipitation variability in northern Patagonia, Chile (Jacaf Fjord, 44 degrees S) JF - Quaternary Research Y1 - 2009 A1 - Sepulveda, J. A1 - Pantoja, S. A1 - Hughen, K. A. A1 - Bertrand, S. A1 - Figueroa, D. A1 - Leon, T. A1 - Drenzek, N. J. A1 - Lange, C. AB - A high-resolution multi-proxy study including the elemental and isotopic composition of bulk organic matter, land plant-derived biomarkers, and alkenone-based sea-surface temperature (SST) from a marine sedimentary record obtained from the Jacaf Fjord in northern Chilean Patagonia (similar to 44 degrees 20'S) provided a detailed reconstruction of continental runoff, precipitation, and summer SST spanning the last 1750 yr We observed two different regimes of climate variability in our record a relatively dry/warm period before 900 cal yr BP (lower runoff and average SST 1 degrees C warmer than present day) and a wet/cold period after 750 cal yr BP (higher runoff and average SST 1 degrees C colder than present clay). Relatively colder SSTs were found during 750-600 and 450-250 cal yr BP, where the latter period roughly corresponds to the interval defined for the Little Ice Age (LIA) Similar climatic swings have been observed previously in continental and marine archives of the last two millennia from central and southern Chile, suggesting a strong latitudinal sensitivity to changes in the Southern Westerly Winds, the main Source Of precipitation in southern Chile, and validating the regional nature of the LIA Our results reveal the importance of the Chilean fjord system for recording climate changes of regional and global significance (C) 2009 University of Washington Published by Elsevier Inc All rights reserved. VL - 72 IS - 3 N1 - id: 1858; 512MQ Times Cited:0 Cited References Count:53Y JO - Late Holocene sea-surface temperature and precipitation variability in northern Patagonia, Chile (Jacaf Fjord, 44 degrees S) ER - TY - JOUR T1 - Late Pleistocene-Holocene evolution of the northern shelf of the Sea of Marmara JF - Marine Geology Y1 - 2009 A1 - Cagatay, M. N. A1 - Eris, K. A1 - Ryan, W. B. F. A1 - Sancar, U. A1 - Polonia, A. A1 - Akcer, S. A1 - Biltekin, D. A1 - Gasperini, L. A1 - Gorur, N. A1 - Lericolais, G. A1 - Bard, E. AB - Chirp sub-bottom profiling, multibeam bathymetric mapping and a combination of faunal and isotopic analysis of molluscs and foraminifera in sediment cores on the northern shelf of the Sea of Marmara (SoM) provide evidence of sea-level excursions, water exchanges between the adjacent Mediterranean and Black Seas, and oscillating salinity over the last 160 ka bp. During the marine isotope stages MIS-2, MIS-3, MIS-4 and MIS-6 the SoM disconnected from the Mediterranean Sea and evolved into a lake. During MIS-1, MIS-5 and MIS-7, the SoM reconnected and became salty once again. Sapropels formed shortly after each invasion of Mediterranean saltwater observed in our cores. Concurrent suboxic-dysoxic conditions prevailed over quite shallow substrates on the shelf. Ancient shorelines are pervasive at -85 m on the northern shelf and in the region of Prince Islands coincident with the elevation of the modern bedrock sill in the Canakkale (Dardanelles) Strait. At times when global (eustatic) sea level dropped below this sill, the surface of the SoM stabilized at its outlet and freshened. Thus this particular shoreline is interpreted as the edge of the most recent SoM lake that existed from about 75 ka bp to 12 ka bp. The freshening is observed in very light (-6 parts per thousand) values of delta O-18 measured on freshwater molluscs and the complete absence of foraminifera. Two brief lacustrine episodes during MIS-5 suggest that the level of the Canakkale outlet might have been as shallow as -50 m in the past, a likelihood supported by submerged terraces along its margins bounding the modern central channel and the presence of an euryhaline biofacies in Unit L4.1 corresponding to MIS-5b. delta O-18 profiles and carbon-14 dating show that salinification of the SoM and the blossoming of bioherms evolved rapidly after the latest connection with the Mediterranean at 12 ka bp. However, freshening proceeded more slowly once the connection was severed. (C) 2009 Elsevier B.V. All rights reserved. VL - 265 IS - 3-4 N1 - id: 1843; 500UN Times Cited:1 Cited References Count:80Y JO - Late Pleistocene-Holocene evolution of the northern shelf of the Sea of Marmara ER - TY - JOUR T1 - A Late Prehistoric Bison Processing Camp in the Central Plains: Montana Creek East (14JW46) JF - Plains Anthropologist Y1 - 2009 A1 - Ritterbush, Lauren W. A1 - Logan, Brad VL - 54 IS - 211 N1 - id: 1999 ER - TY - JOUR T1 - Late Quaternary benthic foraminifera from Ocean Drilling Program Hole 716A, Maldives Ridge, southeastern Arabian Sea JF - Micropaleontology Y1 - 2009 A1 - Sarkar, S. A1 - De, S. A1 - Gupta, A. K. KW - benthonic foraminifera KW - equatorial indian-ocean KW - Holocene KW - late neogene KW - monsoon KW - Oxygen minimum zone KW - productivity KW - red-sea KW - south atlantic-ocean KW - Water masses AB - A study on deep-sea benthic foraminifera from the interval similar to 445 ka BP to the Present of the Ocean Drilling Program (ODP) Hole 716A (4 degrees 56.0'N, 73 degrees 17.0'E; preser t water depth 533.3m), Maldives Ridge. southeastern Arabian Sea, documented 201 species belonging to 105 genera. These taxa were examined under scanning electron microscope (SEM) to illustrate their interspecific morphological variations. Several of these species are dominant showing significant down core fluctuations in their abundances whereas some are rare and sporadic. VL - 55 SN - 0026-2803 IS - 1 N1 - 424cdTimes Cited:5 Cited References Count:47 JO - Micropaleontology ER - TY - JOUR T1 - Late Quaternary foraminiferal assemblages from western Ross Sea (Antarctica) in relation to the main glacial and marine lithofacies JF - Marine Micropaleontology Y1 - 2009 A1 - Melis, R. A1 - Salvi, G. AB - investigations oil foraminifers from Upper Pleistocene-Holocene sediments were carried Out On twelve cores from the western Ross Sea continental margin (Drygalski, Joides, North Victoria Land Basins) as part of a "Progetto Nazionale di Ricerche in Antartide" (P.N.R.A.) multidisciplinary project. Data on the foraminiferal frequency, species diversity, tests abundance and their state of preservation were presented as a synthesis of 404 core samples to establish their relationships with the main glacial and marine lithofacies of this area. A total of 126 benthic species. pertaining to 73 genera have been identified; just few taxa, such as Cibicides spp., Globocassidulina spp., Trifarina angulosa and Miliammina spp. being the most ubiquitous and in some cases the dominant species of these paleoenvironments. Two variants of Neogloboquadrina pachyderma, including thin and thick-shelled forms have been recovered. We propose to use these results to provide the degree of glacial control during the Last Glacial Maximum and the following Holocene retreat of the ice sheets. High test fragmentation, low diversity and density tests reflect higher glacial influence of the ice sheet in the Drygalski Basin, whereas the decreasing percentage of fragmentation and a relative increase of density and diversity in Drygalski, Joides and North Victoria Land Basins indicate the paleoenvironmental passage from the ice sheet to the ice shelf condition. The ice shelf retreat is well evidenced in the Joides Basin by a succession of levels barren of foraminifers alternating with high-density levels, rich in T angulosa, followed by a total disappearance of the calcareous foraminifers. Open-marine settings indicative of lower glacial influence and increased corrosiveness of the water masses is testified by the Miliammina foraminiferal assemblage during the Holocene in Drygalski and Joides Basins cores. On the contrary, rich and abundant benthic and planktonic assemblages characterize the Holocene paleoenvironment of the North Victoria Land area, indicating that the water masses were less corrosive with respect to the other areas. In addition to the glacial reworking of the tests, and the dissolution due to the corrosive water mass conditions, the volcaniclastic sediments recovered in the North Victoria Land Basin cores also affected the condition of test preservation. In volcaniclastic sediments, older than about 20 ka BP, the foraminifers concentration tends to zero and, when present, their tests are highly damaged or completely broken. (c) 2008 Elsevier B.V. All rights reserved. VL - 70 IS - 1-2 N1 - id: 1879; 405HR Times Cited:0 Cited References Count:66Y JO - Late Quaternary foraminiferal assemblages from western Ross Sea (Antarctica) in relation to the main glacial and marine lithofacies ER - TY - JOUR T1 - Late Quaternary sediment-accumulation rates within the inner basins of the California Continental Borderland in support of geologic hazard evaluation JF - Geological Society of America Special Papers Y1 - 2009 A1 - Normark, William R. A1 - McGann, Mary A1 - Sliter, Ray W. AB - An evaluation of the geologic hazards of the inner California Borderland requires determination of the timing for faulting and mass-movement episodes during the Holocene. Our effort focused on basin slopes and turbidite systems on the basin floors for the area between Santa Barbara and San Diego, California. Dating condensed sections on slopes adjacent to fault zones provides better control on fault history where high-resolution, seismic-reflection data can be used to correlate sediment between the core site and the fault zones. This study reports and interprets 147 radiocarbon dates from 43 U.S. Geological Survey piston cores as well as 11 dates from Ocean Drilling Program Site 1015 on the floor of Santa Monica Basin. One hundred nineteen dates from 39 of the piston cores have not previously been published. Core locations were selected for hazard evaluation, but despite the nonuniform distribution of sample locations, the dates obtained for the late Quaternary deposits are useful for documenting changes in sediment-accumulation rates during the past 30 ka. Cores from basins receiving substantial sediment from rivers, i.e., Santa Monica Basin and the Gulf of Santa Catalina, show a decrease in sediment supply during the middle Holocene, but during the late Holocene after sea level had reached the current highstand condition, rates then increased partly in response to an increase in El Ni√±o‚ÄìSouthern Oscillation events during the past 3.5 ka. VL - 454 N1 - id: 1906; 10.1130/2009.2454(2.6) ER - TY - JOUR T1 - Mangrove ecosystem changes during the Holocene at Spanish Lookout Cay, Belize JF - Palaeogeography Palaeoclimatology Palaeoecology Y1 - 2009 A1 - Monacci, N. M. A1 - Meier-Grunhagen, U. A1 - Finney, B. P. A1 - Behling, H. A1 - Wooller, M. J. AB - Mangroves are halophytic plants living at the land-sea interface and are therefore natural trackers of sea-level. Multiple proxies of a continuous (8 m) mangrove peat core (BT-79) from Spanish Lookout Cay, Belize illustrate mangrove ecosystem changes during the Holocene. Radiocarbon measurements show this site was colonized by mangroves similar to 8000 cal. yrs BP, with a significant decrease in the peat accumulation rate from similar to 6000 to 1000 cal. yrs BR Stratigraphic characteristics of this peat core such as bulk density, magnetic susceptibility, and loss on ignition show relative uniformity, inferring an uninterrupted mangrove ecosystem during a majority of the Holocene. This is supported by pollen data from BT-79 that show that the site has been consistently dominated by Rhizophora mangle (red mangrove), with Avicennia germinans (black mangrove) and Laguncularia racemosa (white mangrove) present as well. Subfossil R. mangle leaves are used for stable nitrogen, carbon, and oxygen isotope (delta N-15, delta C-13, and delta O-18) analyses. delta N-15 and delta C-13 values provide a proxy of this plant's past physiology and stand structure showing that dwarf (delta N-15 VL - 280 IS - 1-2 N1 - id: 1834; 496QP Times Cited:1 Cited References Count:50Y JO - Mangrove ecosystem changes during the Holocene at Spanish Lookout Cay, Belize ER - TY - JOUR T1 - Marine shellfish harvest on Middle and Late Holocene Santa Barbara Island, California JF - California Archaeology Y1 - 2009 A1 - Rick, Torben C. A1 - Erlandson, Jon M. A1 - Horton, Kristina VL - 1 N1 - id: 2077 ER - TY - CHAP T1 - Methane accumulation and release from deep peat: Measurements, conceptual models, and biogeochemical significance T2 - Carbon Cycling in Northern Peatlands Y1 - 2009 A1 - Glaser, Paul H. A1 - Chanton, Jeffrey P. ED - Baird, A. J. KW - Carbon cycle (Biogeochemistry)—Northern Hemisphere KW - Carbon sequestration—Northern Hemisphere KW - Greenhouse gases—Northern Hemisphere KW - Peatlands—Environmental aspects—Northern Hemisphere AB - Northern peatlands account for more than half the world's wetlands but are currently estimated to contribute only about a third of the total methane emissions from all wetlands. Increasing data on the dynamics of methane gas bubbles in peat deposits now suggest that these estimates may need to be scaled upward. Rates of methanogenesis may remain high in deep peat strata because of the downward transport of labile root exudates permitting the widespread production of gas bubbles. Recent investigations using an array of methods have reported free-phase gas volumes of 10–20% within both deep and shallow peat strata and episodic ebullition fluxes exceeding 35 g CH4 m−2 per event. Gas bubbles accumulate in overpressured pockets that episodically rupture in response to steep declines in atmospheric pressure or declining water tables. Although these ebullition fluxes are highly variable in both time and space, they appear to dominate the annual methane emissions from northern peatlands and represent a major and underappreciated element of the global methane cycle. JF - Carbon Cycling in Northern Peatlands T3 - GEOPHYSICAL MONOGRAPH SERIES PB - American Geophysical Union SN - 9780875904498 N1 - id: 1972 ER - TY - JOUR T1 - Millennial time scale changes in surface to intermediate-deep layer circulation recorded in the sediment cores from the northwestern North Pacific JF - The Quaternary Research Y1 - 2009 A1 - Harada, N. A1 - Kimoto, K. A1 - Okazaki, Y. A1 - Nagashima, K. A1 - Timmermann, A. A1 - Abe-Ouchi, A. VL - 48 IS - 3 N1 - id: 1877 ER - TY - JOUR T1 - Moderate rates of late Quaternary slip along the northwestern margin of the Basin and Range Province, Surprise Valley fault, northeastern California JF - Journal of Geophysical Research-Solid Earth Y1 - 2009 A1 - Personius, Stephen F. A1 - Crone, Anthony J. A1 - Machette, Michael N. A1 - Mahan, Shannon A. A1 - Lidke, David J. AB - The 86-km-long Surprise Valley normal fault forms part of the active northwestern margin of the Basin and Range province in northeastern California. We use trench mapping and radiocarbon, luminescence, and tephra dating to estimate displacements and timing of the past five surface-rupturing earthquakes on the central part of the fault near Cedarville. A Bayesian OxCal analysis of timing constraints indicates earthquake times of 18.2 +/- 2.6, 10.9 +/- 3.2, 8.5 +/- 0.5, 5.8 +/- 1.5, and 1.2 +/- 0.1 ka. These data yield recurrence intervals of 7.3 +/- 4.1, 2.5 +/- 3.2, 2.7 +/- 1.6, and 4.5 +/- 1.5 ka and an elapsed time of 1.2 +/- 0.1 ka since the latest surface-rupturing earthquake. Our best estimate of latest Quaternary vertical slip rate is 0.6 +/- 0.1 mm/a. This late Quaternary rate is remarkably similar to long-term (8-14 Ma) minimum vertical slip rates (>0.4-0.5 +/- 0.3 mm/a) calculated from recently acquired seismic reflection and chronologic and structural data in Surprise Valley and the adjacent Warner Mountains. However, our slip rate yields estimates of extension that are lower than recent campaign GPS determinations by factors of 1.5-4 unless the fault has an unusually shallow (30 degrees-35 degrees) dip as suggested by recently acquired seismic reflection data. Coseismic displacements of 2-4.5 +/- 1 m documented in the trench and probable rupture lengths of 53-65 km indicate a history of latest Quaternary earthquakes of M 6.8-7.3 on the central part of the Surprise Valley fault. VL - 114 N1 - id: 2021; PT: J; UT: WOS:000270058200001 JO - Moderate rates of late Quaternary slip along the northwestern margin of the Basin and Range Province, Surprise Valley fault, northeastern California ER - TY - JOUR T1 - Molecular and isotopic constraints on the sources of suspended particulate organic carbon on the northwestern Atlantic margin JF - Deep-Sea Research Part I-Oceanographic Research Papers Y1 - 2009 A1 - Hwang, J. A1 - Montlucon, D. A1 - Eglinton, T. I. AB - The abundance, carbon isotopic composition (Delta C-14 and delta C-13), and lipid biomarker (alkenones and saturated fatty acids) distributions of suspended particulate organic matter were investigated at three stations centered on the 2000, 3000, and 3500 m isobaths over the New England slope in order to assess particulate carbon sources and dynamics in this highly productive and energetic region. Transmissometry profiles reveal that particle abundances exhibit considerable fine structure, with several distinct layers of elevated suspended particulate matter concentration at intermediate water depths in addition to the presence of a thick bottom nepheloid layer at each station. Excluding surface water samples, the Delta C-14 values of particulate organic carbon (POC) indicated the presence of a pre-aged component in the suspended POC pool (Delta C-14 VL - 56 IS - 8 N1 - id: 774; 471WJ Times Cited:1 Cited References Count:73Y JO - Molecular and isotopic constraints on the sources of suspended particulate organic carbon on the northwestern Atlantic margin ER - TY - JOUR T1 - Molluscs and mass harvesting in the Middle Holocene: Prey size and resource ranking on San Miguel Island, Alta California JF - California Archaeology Y1 - 2009 A1 - Braje, Todd J. A1 - Erlandson, Jon M. VL - 1 IS - 2 N1 - id: 2070 JO - Molluscs and mass harvesting in the Middle Holocene: Prey size and resource ranking on San Miguel Island, Alta California ER - TY - CHAP T1 - Monsoons, Quaternary T2 - Encyclopedia of Paleoclimatology and Ancient Environments Y1 - 2009 A1 - Gupta, A. K. ED - Gornitz, V. JF - Encyclopedia of Paleoclimatology and Ancient Environments T3 - Encyclopedia of Earth Sciences Series PB - Springer SN - 9781402045516 N1 - id: 1971 ER - TY - JOUR T1 - A multi-proxy paleolimnological reconstruction of Holocene climate conditions in the Great Basin, United States JF - Quaternary Research Y1 - 2009 A1 - Reinemann, Scott A. A1 - Porinchu, David F. A1 - Bloom, Amy M. A1 - Mark, Bryan G. A1 - Box, Jason E. AB - A sediment core spanning ~†7000†cal yr BP recovered from Stella Lake, a small sub-alpine lake located in Great Basin National Park, Nevada, was analyzed for subfossil chironomids (non-biting midges), diatoms, and organic content (estimated by loss-on-ignition (LOI)). Subfossil chironomid analysis indicates that Stella Lake was characterized by a warm, middle Holocene, followed by a cool "Neoglacial" period, with the last two millennia characterized by a return to warmer conditions. Throughout the majority of the core the Stella Lake diatom-community composition is dominated by small, periphytic taxa which are suggestive of shallow, cool, alkaline, oligotrophic waters with extensive seasonal ice cover. A reconstruction of mean July air temperature (MJAT) was developed by applying a midge-based inference model for MJAT (two-component WA-PLS) consisting of 79 lakes and 54 midge taxa (rjack2†=†0.55, RMSEP†=†0.9∞C). Comparison of the chironomid-inferred temperature record to existing regional paleoclimate reconstructions suggests that the midge-inferred temperatures correspond well to regional patterns. This multi-proxy record provides valuable insight into regional Holocene climate and environmental conditions by providing a quantitative reconstruction of peak Holocene warmth and aquatic ecosystem response to these changes in the Great Basin, a region projected to experience increased aridity and higher temperatures. VL - 72 IS - 3 N1 - id: 880Y JO - A multi-proxy paleolimnological reconstruction of Holocene climate conditions in the Great Basin, United States ER - TY - JOUR T1 - The Mysterious C-14 Decline JF - Radiocarbon Y1 - 2009 A1 - Broecker, W. AB - Fundamental to the field of radiocarbon dating is not only the establishment of the temporal record of the calendar age-radiocarbon age offsets but also the development of an understanding of their cause. Although part of the decline in the magnitude of this offset over the past 40,000 can be explained by a drop in C-14 production rate associated with a progressive increase in the strength of the Earth's magnetic shielding, it is clear that changes in the distribution of C-14 among the Earth's active carbon reservoirs are also required. In particular, the steep 15% decline in the C-14 to C ratio in atmospheric CO2 and surface ocean Sigma CO2,. which occurred in a 3 kyr-duration interval marking the onset of the last deglaciation, appears to require that a very large amount (at least 5000 gigatons) of C-14-deficient carbon was transferred to or within the ocean during this time interval. As no chemical or stable isotope anomaly associated with this injection appears in either the marine sediment or polar ice records, this injection must involve a transfer within the ocean (i.e. a mixing of 2 ocean reservoirs, one depleted in C-14 and the other enriched in C-14). Although evidence for the existence of a salt-stabilized glacial-age abyssal ocean reservoir exists, a search based on benthic-planktic age differences and C-13 measurements appears to place a limit on its size well below that required to account for the steep C-14 decline. VL - 51 UR - https://journals.uair.arizona.edu/index.php/radiocarbon/article/view/3481 IS - 1 N1 - 453wfTimes Cited:18Cited References Count:30 JO - The Mysterious C-14 Decline ER - TY - CHAP T1 - The nature and origin of decadal to millennial scale climate variability in the southern tropics of South America T2 - Past Climate Variability from the Last Glacial Maximum to the Holocene in South America and Surrounding Regions Y1 - 2009 A1 - Baker, P. A. A1 - Fritz, S. C. A1 - Burns, S. J. A1 - Ekdahl, E. A1 - Rigsby, C. A. ED - Vimeux, F. JF - Past Climate Variability from the Last Glacial Maximum to the Holocene in South America and Surrounding Regions PB - Springer N1 - id: 843 ER - TY - JOUR T1 - A new look at old carbon in active margin sediments RID F-1809-2010 JF - Geology Y1 - 2009 A1 - Drenzek, Nicholas J. A1 - Hughen, Konrad A. A1 - Montluçon, Daniel B. A1 - Southon, John R. A1 - dos Santos, Guaciara M. A1 - Druffel, Ellen R. M. A1 - Giosan, Liviu A1 - Eglinton, Timothy I. AB - Recent studies suggest that as much as half of the organic carbon (OC) undergoing burial in the sediments of tectonically active continental margins may be the product of fossil shale weathering. These estimates rely on the assumption that vascular plant detritus spends little time sequestered in intermediate reservoirs such as soils, freshwater sediments, and river deltas, and thus only minimally contributes to the extraneously old (14)C ages of total organic matter often observed on adjacent shelves. Here we test this paradigm by measuring the (14)C and delta(13)C values of individual higher plant wax fatty acids as well as the d13C values of extractable alkanes isolated from the Eel River margin (California). The isotopic signatures of the long chain fatty acids indicate that vascular plant material has been sequestered for several thousand years before deposition. A coupled molecular isotope mass balance used to reassess the sedimentary carbon budget indicates that the fossil component is less abundant than previously estimated, with pre-aged terrestrial material instead composing a considerable proportion of all organic matter. If these findings are characteristic of other continental margins proximal to small mountainous rivers, then the importance of petrogenic OC burial in marine sediments may need to be reevaluated. VL - 37 IS - 3 N1 - id: 1987; PT: J; UT: WOS:000263842200012 JO - A new look at old carbon in active margin sediments RID F-1809-2010 ER - TY - JOUR T1 - Oceanographic and climatologic controls on the compositions and fluxes of biogenic materials in the water column and sediments of the Cariaco Basin over the Late Holocene JF - Deep-Sea Research Part I-Oceanographic Research Papers Y1 - 2009 A1 - Goñi, M. A. A1 - Aceves, H. A1 - Benitez-Nelson, B. A1 - Tappa, E. A1 - Thunell, R. A1 - Black, D. E. A1 - Muller-Karger, F. A1 - Astor, Y. A1 - Varela, R. AB - Materials collected by sediment traps over a 3-y period and sedimentary horizons from a gravity core covering the last 6000y were used to investigate the effects of climate-related processes such as wind-driven upwelling and regional rainfall on the production, export and burial of particulate organic matter in the Cariaco Basin. A variety of chemical analyses, including organic carbon and nitrogen, biogenic opal, calcite, lithogenic contents, stable carbon isotopic ratios of organic matter and the yields of CuO reaction products derived from distinct biochemicals such as amino acids, fatty acids and lignins, were carried out for this purpose. Principal component analyses were used to investigate the trends in this multivariate data set. These analyses reveal marked temporal differences in the composition of the materials sinking through the water column, which were related to distinct oceanographic and climatic forcings. For example, autorchthonous fluxes, characterized by elevated contents of organic carbon and opal as well as high yields of amino acid and fatty acid reaction products, displayed peaks during periods of intense wind-driven upwelling. In contrast, allochthonous materials, characterized by elevated lithogenic contents and elevated yields of lignin-derived products, were more important during periods of high rainfall, low wind and enhanced stratification. In addition to the strong seasonal contrasts, there was significant temporal variability at both shorter (monthly) and longer (inter-annual) time scales. Hence, other factors, such as zooplankton grazing and El Nino effects on local climatology, may also be important. Examination of the gravity core record yielded several significant trends. For example, there was a marked increase in sediment accumulation rates from 5000 to ca. 700 y before present with concomitant increases in the concentrations of organic carbon, opal and most biomarkers. These results suggest that the Cariaco Basin experienced a marked increase in primary productivity and particle flux to the underlying sediments since the Holocene Thermal Maximum. Also within the sedimentary record, we observed distinct variations in the relative contributions of autochthonous and allochthonous organic matter. The frequency of these variations is roughly 1500y and appears to match ice-rafted debris records from the North Atlantic. Such coincidence indicates cold periods within the Holocene, which are related to minima in insolation, may have led to the southern migration of the inter-tropical convergence zone and the enhancement of wind-driven upwelling, primary productivity and autochthonous organic matter flux to the seabed in the Cariaco Basin. Alternatively, during warm periods, the opposite climatic conditions would have increased both the thermal stratification of the water column and average rainfall in the Cariaco Basin, leading to elevated inputs of allochthonous materials. (C) 2008 Elsevier Ltd. All rights reserved. VL - 56 IS - 4 N1 - id: 1871; 430SK Times Cited:0 Cited References Count:69Y JO - Oceanographic and climatologic controls on the compositions and fluxes of biogenic materials in the water column and sediments of the Cariaco Basin over the Late Holocene ER - TY - JOUR T1 - Palaeoecological potential of the marine organic deposits of Posidonia oceanica: A case study in the NE Iberian Peninsula JF - Palaeogeography Palaeoclimatology Palaeoecology Y1 - 2009 A1 - López-Sáez, J. A. A1 - Lopez-Merino, L. A1 - Mateo, M. A. A1 - Serrano, O. A1 - Perez-Diaz, S. A1 - Serrano, L. AB - A high-resolution sedimentary sequence sampled from the Portlligat Bay (NE Iberian Peninsula) has been studied in order to assess its palaeoecological potential. This sedimentary sequence is considered a very particular one, as it is a peat-like deposit derived from the accumulation of the belowground dead parts of the marine phanerogam Posidonia oceanica through the last 1600 years. This study represents the first attempt to explore the palaeoecological potential of such deposits from a palynological point of view, and has allowed the reconstruction of the vegetation dynamics and changes, human impact and the palaeoclimatic characteristics, demonstrating the value of these sedimentary records in palaeopalynological studies. (C) 2008 Elsevier B.V. All rights reserved. VL - 271 IS - 3-4 N1 - 402ksTimes Cited:20Cited References Count:55 JO - Palaeoecological potential of the marine organic deposits of Posidonia oceanica: A case study in the NE Iberian Peninsula ER - TY - JOUR T1 - Palaeoenvironmental changes from pollen record in deep sea core PC-1 from northern Okinawa Trough, East China Sea during the past 24 ka JF - Chinese Science Bulletin Y1 - 2009 A1 - Xu, HongYan A1 - Chang, Fengming A1 - Luo, YunLi A1 - Sun, XiangJun AB - A pollen record of core PC-1 from the northern Okinawa Trough, East China Sea (ECS), provides information on vegetation and climate changes since 24 cal. kaBP. A total of 103 samples were palynologically analyzed at 8 cm intervals with a time resolution of 230 a. Four pollen zones are recognized: zone I (812-715 cm, 24.2-21.1 cal. kaBP), zone II (715-451 cm, 21.1-15.2 cal. kaBP), zone III (451-251 cm, 15.2-10.8 cal. kaBP), zone IV (251-0 cm, 10.8-0.3 cal. kaBP), corresponding to Late MIS 3, Last Glacial Maximum (LGM), deglaciation and Holocene, respectively. The LGM is characterized by the dominance of herbs, mainly Artemisia, and high pollen influx, implying an open vegetation on the exposed continental shelf and a cool and dry climate. The deglaciation is a climate warming stage with Pinus percentage increased and Artemisia percentage decreased and a rapid sea-level rise. The Holocene is characterized by predominance of tree pollen with rapid increase in Castanea-Castanopsis indicating the development of mixed evergreen and deciduous broad-leaved forest and a warm, humid climate. Low pollen influx during the Holocene probably implies submergence of the continental shelf and retreat of the pollen source area. The vegetation indicated by pollen assemblage found in this upper zone is consistent with the present vegetation found in Kyushu, Japan. Originating from the humid mountain area of North Luzon of the Philippines, Tasmania and New Zealand, Phyllocladus with sporadic occurrence throughout PC-1 core probably suggests the influence of Palaeo-Kuroshio Current or intense summer monsoon. The observed changes in Pinus and Herbs percentage indicate fluctuations of the sea level, and high Pinus percentage corresponds to high sea level. Spectrum analysis of the pollen percentage record reveals many millennial-scale periodicities, such as periodicities of 6.8, 3.85 2.2, 1.6 ka. VL - 54 IS - 20 N1 - id: 1931; PT: J; UT: WOS:000271175500023 JO - Palaeoenvironmental changes from pollen record in deep sea core PC-1 from northern Okinawa Trough, East China Sea during the past 24 ka ER - TY - JOUR T1 - Palaeohydrology of Kangerlussuaq (Soendre Stroemfjord), West Greenland during the last similar to 8000 years JF - Holocene Y1 - 2009 A1 - Aebly, F. A. A1 - Fritz, S. C. AB - Major fluctuations of hydroclimate in West Greenland are recorded in palaeoshoreline terraces that encircle several lakes near Kangerlussuaq, Greenland (67 degree 01'N, 50 degree 40'W). Geomorphic and stratigraphic analyses were used to construct a lake-level curve for Hunde S0, a large closed-basin lake in this region. Changes in lake volume associated with lake-level fluctuations were calculated, and a water-balance model was used to determine the primary factors influencing lake volume and the changes in those factors necessary to affect reconstructed lake-level change. Sensitivity tests suggest that mean annual precipitation and the relative proportion of summer versus winter precipitation are the primary climate drivers of lake-level change. Temperature effects are less important unless coupled with changes in one of the other variables. Two pluvial periods occurred centred around 4600 and 2000 cal. yr BP, with mean annual precipitation estimated at 130 mm and 70 mm higher than modern, respectively. In contrast, a low-stand prior to 6070 cal. yr BP with water levels as much as 18 m below modern was a result of summer temperatures similar to 2-3 degree above modern, coupled with a 14 day increase in the length of the ice-off period and a reduction in mean annual precipitation of similar to 80 mm relative to modern. VL - 19 IS - 1 N1 - id: 2218; Source type: scholarlyjournals; Object type: Article; Object type: Feature; CSAUnique: OB-MD-0009349512; AccNum: 9048978; InputCenter: CS0919076; DOI: 10.1177/0959683608096601; ISSN: 0959-6836; ElecISSN: 1477-0911; Peer Reviewed: true JO - Palaeohydrology of Kangerlussuaq (Soendre Stroemfjord), West Greenland during the last similar to 8000 years ER - TY - CHAP T1 - A Paleocoastal Shell Midden at Seal Cave (CA-SMI-604), San Miguel Island, California T2 - Proceedings of the Seventh California Islands Symposium Y1 - 2009 A1 - Erlandson, Jon M. A1 - Braje, Todd J. A1 - Rick, Torben C. A1 - Davis, Troy A1 - Southon, Troy ED - Damiani, Christine C. JF - Proceedings of the Seventh California Islands Symposium PB - Institute for Wildlife Studies CY - Arcata, CA N1 - id: 2075 ER - TY - JOUR T1 - Paleolimnological records of recent glacier recession in the Rwenzori Mountains, Uganda-D. R. Congo JF - Journal of Paleolimnology Y1 - 2009 A1 - Russell, J. A1 - Eggermont, H. A1 - Taylor, R. A1 - Verschuren, D. AB - The status of tropical glaciers is enormously important to our understanding of past, present, and future climate change, yet lack of continuous quantitative records of alpine glacier extent on the highest mountains of tropical East Africa prior to the 20th century has left the timing and drivers of recent glacier recession in the region equivocal. Here we investigate recent changes (the last 150-700 years) in lacustrine sedimentation, glacier extent, and biogeochemical processes in the Rwenzori Mountains (Uganda- Democratic Republic of Congo) by comparing sedimentological (organic and siliciclastic component determined by loss-on-ignition; LOI) and organic geochemical profiles (carbon and nitrogen abundance, ratio, and isotopic composition of sedimentary organic matter) from lakes occupying presently glaciated catchments against similar profiles from lakes located in catchments lacking glaciers. The siliciclastic content of sediments in the 'glacial lakes' significantly decreases towards the present, whereas 'non-glacial lakes' generally show weak trends in their siliciclastic content over time, demonstrating that changes in the siliciclastic content of glacial lake sediments primarily record fluctuations in glacier extent. Radiometric dating of our sediment cores indicates that prior to their late 19th-century recession Rwenzori glaciers stood at expanded 'Little Ice Age' positions for several centuries under a regionally dry climate regime, and that recession was underway by 1870 AD, during a regionally wet episode. These findings suggest that the influence of late 19th century reductions in precipitation in triggering Rwenzori glacier recession is weaker than previously thought. Our organic geochemical data indicate that glacier retreat has significantly affected carbon cycling in Afroalpine lakes, but trends in aquatic ecosystem functioning are variable among lakes and require more detailed analysis. VL - 41 IS - 2 N1 - id: 2048; PT: J; UT: WOS:000262651500002 JO - Paleolimnological records of recent glacier recession in the Rwenzori Mountains, Uganda-D. R. Congo ER - TY - JOUR T1 - Partitioning of organic matter in continental margin sediments among density fractions JF - Marine Chemistry Y1 - 2009 A1 - Wakeham, S. G. A1 - Canuel, E. A. A1 - Lerberg, E. J. A1 - Mason, P. A1 - Sampere, T. P. A1 - Bianchi, T. S. AB - Hydrodynamic processes sort and redistribute organic matter (OM) and minerals on continental margins. Density fractionations were conducted on sediments from diverse margins (Mexico margin, Gulf of Mexico, Mississippi River delta, Eel River margin) to investigate the nature, provenance and age of OM among density fractions. Mass. elemental (C and N), lignin, and surface area distributions, as well as stable carbon and radiocarbon isotopic compositions were measured, The lowest density fractions (2.5 g cm(-3)) were OC-poor (%OC -200 parts per thousand). Ratios of vanillic acid to vanillin (Ad/Al)v among lignin oxidation products increase with increasing particle density suggesting variable lignin sources or selective degradation of lignin among the different density fractions. (C) 2009 Elsevier B.V. All rights reserved. VL - 115 IS - 3-4 N1 - id: 1844; 521ZI Times Cited:0 Cited References Count:99Y JO - Partitioning of organic matter in continental margin sediments among density fractions ER - TY - JOUR T1 - Permanent storage of carbon dioxide in geological reservoirs by mineral carbonation JF - Nature Geoscience Y1 - 2009 A1 - Matter, J. M. A1 - Kelemen, P. B. AB - Anthropogenic greenhouse-gas emissions continue to increase rapidly despite efforts aimed at curbing the release of such gases. One potentially long-term solution for offsetting these emissions is the capture and storage of carbon dioxide. In principle, fluid or gaseous carbon dioxide can be injected into the Earth's crust and locked up as carbonate minerals through chemical reactions with calcium and magnesium ions supplied by silicate minerals. This process can lead to near-permanent and secure sequestration, but its feasibility depends on the ease and vigour of the reactions. Laboratory studies as well as natural analogues indicate that the rate of carbonate mineral formation is much higher in host rocks that are rich in magnesium-and calcium-bearing minerals. Such rocks include, for example, basalts and magnesium-rich mantle rocks that have been emplaced on the continents. Carbonate mineral precipitation could quickly clog up existing voids, presenting a challenge to this approach. However, field and laboratory observations suggest that the stress induced by rapid precipitation may lead to fracturing and subsequent increase in pore space. Future work should rigorously test the feasibility of this approach by addressing reaction kinetics, the evolution of permeability and field-scale injection methods. VL - 2 IS - 12 N1 - id: 844; 525TO Times Cited:10 Cited References Count:49Y JO - Permanent storage of carbon dioxide in geological reservoirs by mineral carbonation ER - TY - JOUR T1 - Photochemical changes in chemical markers of sedimentary organic matter source and age JF - Marine Chemistry Y1 - 2009 A1 - Mayer, L. M. A1 - Schick, L. L. A1 - Bianchi, T. S. A1 - Wysocki, L. A. AB - Several chemical markers of organic matter source and age are shown to be susceptible to light-induced alteration. To test for the photochemical lability of markers previously employed for sediments from the Louisiana Coastal zone, we subjected sediments under resuspension conditions to Simulated Sunlight, and monitored changes in ON and Br:OC ratios, delta C-13, Delta C-14, and lignin composition. Markers of terrigenous origin (high C:N, lignin) decreased and delta C-13 became enriched in sediments containing primarily terrigencrus organic matter, while a marker of marine organic matter (Br:OC) decreased in samples containing significant contributions from this source. Preferential loss of C-14 from all sediments indicated enhanced photochemical lability of organic matter of relatively recent origin, consistent with the changes in chemical markers. Most, but not all, experimental alterations are consistent with field distributions of these markers. Relatively small experimental changes in the markers in combination with confounding processes in the environment, however. prevent these parallel trends from providing any more than a consistency test for the importance of photochemical reactions in this region. (C) 2009 Elsevier B.V. All rights reserved. VL - 113 IS - 1-2 N1 - id: 793; 425QO Times Cited:0 Cited References Count:40Y JO - Photochemical changes in chemical markers of sedimentary organic matter source and age ER - TY - JOUR T1 - Pleistocene Megafaunal Collapse, Novel Plant Communities, and Enhanced Fire Regimes in North America JF - Science Y1 - 2009 A1 - Gill, J. L. A1 - Williams, J. W. A1 - Jackson, S. T. A1 - Lininger, K. B. A1 - Robinson, G. S. AB - Although the North American megafaunal extinctions and the formation of novel plant communities are well-known features of the last deglaciation, the causal relationships between these phenomena are unclear. Using the dung fungus Sporormiella and other paleoecological proxies from Appleman Lake, Indiana, and several New York sites, we established that the megafaunal decline closely preceded enhanced fire regimes and the development of plant communities that have no modern analogs. The loss of keystone megaherbivores may thus have altered ecosystem structure and function by the release of palatable hardwoods from herbivory pressure and by fuel accumulation. Megafaunal populations collapsed from 14,800 to 13,700 years ago, well before the final extinctions and during the Bolling-Allerod warm period. Human impacts remain plausible, but the decline predates Younger Dryas cooling and the extraterrestrial impact event proposed to have occurred 12,900 years ago. VL - 326 IS - 5956 N1 - id: 769; 521UW Times Cited:4 Cited References Count:30Y JO - Pleistocene Megafaunal Collapse, Novel Plant Communities, and Enhanced Fire Regimes in North America ER - TY - JOUR T1 - Pre-Columbian settlement of Carriacou, West Indies JF - Journal of Field Archaeology Y1 - 2009 A1 - Fitzpatrick, S. M. A1 - Kappers, M. A1 - Kaye, Q. A1 - Giovas, C. M. A1 - LeFebvre, M. J. A1 - Harris, M. H. A1 - Burnett, S. A1 - Pavia, J. A. A1 - Marsaglia, K. A1 - Feathers, J. VL - 34 IS - 3 N1 - id: 830 ER - TY - JOUR T1 - Processes That Initiate Turbidity Currents and Their Influence on Turbidites: A Marine Geology Perspective JF - Journal of Sedimentary Research Y1 - 2009 A1 - Piper, D. J. W. A1 - Normark, W. R. AB - How the processes that initiate turbidity currents influence turbidite deposition is poorly understood, and many discussions in the literature rely on concepts that are overly simplistic. Marine geological studies provide information on the initiation and flow path of turbidity currents, including their response to gradient. In case studies of late Quaternary turbidites on the eastern Canadian and western U.S. margins, initiation processes are inferred either from real-time data for historical flows or indirectly from the age and contemporary paleogeography, erosional features, and depositional record. Three major types of initiation process are recognized: transformation of failed sediment, hyperpycnal flow from rivers or ice margins, and resuspension of sediment near the shelf edge by oceanographic processes. Many high-concentration flows result from hyperpycnal supply of hyperconcentrated bedload, or liquefaction failure of coarse-grained sediment, and most tend to deposit in slope conduits and on gradients VL - 79 IS - 5-6 N1 - id: 877; 451YQ Times Cited:2 Cited References Count:124Y JO - Processes That Initiate Turbidity Currents and Their Influence on Turbidites: A Marine Geology Perspective ER - TY - THES T1 - Proxy Records of Paleohurricanes for the Western and Southern Caribbean Y1 - 2009 A1 - McCloskey, T. A. PB - Louisiana State University CY - Baton Rouge, Louisiana VL - Dissertation/Thesis ER - TY - JOUR T1 - Radiocarbon Analysis of Atmospheric Formaldehyde Using Cystamine Derivatization JF - ANALYTICAL CHEMISTRY Y1 - 2009 A1 - Shen, Haiwei A1 - McNichol, Ann P. A1 - Xu, Li A1 - Gagnon, Alan A1 - Heikes, Brian G. AB - A compound specific radiocarbon analysis method was developed to evaluate the C-14 composition of atmospheric formaldehyde. In this method, gaseous formaldehyde was collected with a high-volume air sampler using glass-fiber filters pretreated with sodium bisulfite. Collected formaldehyde was then released into water and derivatized with cysteamine to thiazolidine. The thiazolidine was extracted into dichloromethane and concentrated by evaporation. Concentrated thiazolidine was separated from other compounds using preparative capillary gas chromatography and uniquely collected as a phosphate salt with a fraction collector. The C-14 composition of the salt was analyzed by accelerator mass spectrometry after combustion to CO2 and subsequent reduction to graphite. In a pilot study, ambient formaldehyde samples collected on the roof of the CACS building at Narragansett Bay Campus, Narragansett, RI, showed a significantly larger fraction of fossil carbon than modern carbon. VL - 81 ER - TY - JOUR T1 - Rapid Response of a Marine Mammal Species to Holocene Climate and Habitat Change JF - Plos Genetics Y1 - 2009 A1 - de Bruyn, Mark A1 - Hall, Brenda L. A1 - Chauke, Lucas F. A1 - Baroni, Carlo A1 - Koch, Paul L. A1 - Hoelzel, A. Rus AB - Environmental change drives demographic and evolutionary processes that determine diversity within and among species. Tracking these processes during periods of change reveals mechanisms for the establishment of populations and provides predictive data on response to potential future impacts, including those caused by anthropogenic climate change. Here we show how a highly mobile marine species responded to the gain and loss of new breeding habitat. Southern elephant seal, Mirounga leonina, remains were found along the Victoria Land Coast (VLC) in the Ross Sea, Antarctica, 2,500 km from the nearest extant breeding site on Macquarie Island (MQ). This habitat was released after retreat of the grounded ice sheet in the Ross Sea Embayment 7,500-8,000 cal YBP, and is within the range of modern foraging excursions from the MQ colony. Using ancient mtDNA and coalescent models, we tracked the population dynamics of the now extinct VLC colony and the connectivity between this and extant breeding sites. We found a clear expansion signal in the VLC population similar to 8,000 YBP, followed by directional migration away from VLC and the loss of diversity at similar to 1,000 YBP, when sea ice is thought to have expanded. Our data suggest that VLC seals came initially from MQ and that some returned there once the VLC habitat was lost, similar to 7,000 years later. We track the founder-extinction dynamics of a population from inception to extinction in the context of Holocene climate change and present evidence that an unexpectedly diverse, differentiated breeding population was founded from a distant source population soon after habitat became available. VL - 5 IS - 7 N1 - id: 1914; PT: J; NR: 58; TC: 11; J9: PLOS GENET; PG: 11; GA: 486SZ; UT: WOS:000269219500031 JO - Rapid Response of a Marine Mammal Species to Holocene Climate and Habitat Change ER - TY - JOUR T1 - Recent occurrence of large jokulhlaups at Lake Tuborg, Ellesmere Island, Nunavut JF - Journal of Paleolimnology Y1 - 2009 A1 - Lewis, Ted A1 - Francus, Pierre A1 - Bradley, Raymond S. AB - The varved sediment record from glacially-fed Lake Tuborg, Ellesmere Island, Nunavut, shows that only three large jokulhlaups have occurred there in the last millennium: 2003, 1993, and 1960. Detailed analyses of sediment microstructure and particle size, combined with in-situ hydrometeorological and limnological process studies, allowed jokulhlaup facies identification and discrimination from deposits from other processes. Deposits from large jokulhlaups are anomalously thick, typically lack internal structure, have sharp bases, and fine upwards. The ice-dammed lake above Lake Tuborg (the source of the jokulhlaups) likely changed its drainage style in 1960, from ice-dam overtopping to ice-dam flotation and glacial tunnel enlargement by melt widening, which allowed the lake to drain completely and catastrophically. Complete drainage of ice-dammed lakes by ice-dam flotation is rare in the region is due to the pervasiveness of cold-based ice. Twentieth century warming is likely responsible for some combination of dam thinning, lake expansion and deepening, and changing the thermal regime at the base of the dam. Anomalously thick individual varves were periodically deposited beginning in the nineteenth century, and their thickness increased with time. This likely reflects a combination of increased ice dam overtopping, subaqueous slope failures, sediment availability and rising air temperature. The varve record presented here significantly correlates with a previous, shorter record from Lake Tuborg. However, generally weak correlations are found between the new varve time series, regional records of air temperature, and glacial melt from ice cores on the Agassiz Ice Cap. It is hypothesized that on short timescales, sedimentation at the coring location reflects a complex and varying integration of multiple hydroclimatic, geomorphic and limnologic influences. VL - 41 IS - 3 N1 - id: 1998; PT: J; UT: WOS:000263543300006 JO - Recent occurrence of large jokulhlaups at Lake Tuborg, Ellesmere Island, Nunavut ER - TY - JOUR T1 - Recently exposed vegetation reveals Holocene changes in the extent of the Quelccaya Ice Cap, Peru JF - QUATERNARY RESEARCH Y1 - 2009 A1 - Buffen, Aron M. A1 - Thompson, Lonnie G. A1 - Mosley-Thompson, Ellen A1 - Huh, Kyung In KW - 14C dating KW - Andes KW - Climate change KW - Glacier retreat KW - Holocene KW - Peru KW - Quelccaya Ice Cap KW - South America KW - Tropical glaciers AB - Radiocarbon dating of well-preserved, in-place vegetation exposed by the retreating Quelccaya Ice Cap of southeastern Peru constrains the last time the ice cap's extent was smaller than at present. Seventeen plant samples from two sites along the central western margin collectively date to 4700 and 5100 cal yr BP and strongly indicate that current ice cap retreat is unprecedented over the past similar to 5 millennia. Seventeen vegetation samples interbedded in a nearby clastic sedimentary sequence suggest ice-free conditions at this site from similar to 5200 to at least similar to 7000 cal yr BP, and place minimum constraint on early- to mid-Holocene ice cap extent. (C) 2009 University of Washington. Published by Elsevier Inc. All rights reserved. VL - 72 ER - TY - JOUR T1 - A record of Lateglacial and early Holocene environmental and ecological change from southwestern Connecticut, USA JF - Journal of Quaternary Science Y1 - 2009 A1 - Oswald, W. W. A1 - Foster, D. R. A1 - Doughty, E. D. A1 - Faison, E. K. AB - Analyses of a sediment core from Highstead Swamp in southwestern Connecticut, USA, reveal Lateglacial and early Holocene ecological and hydrological changes. Lateglacial pollen assemblages are dominated by Picea and Pinus subg. Pinus, and the onset of the Younger Dryas (YD) cold interval is evidenced by higher abundance of Abies and Alnus viridis subsp. crispa. As climate warmed at the end of the YD, Picea and Abies declined and Pinus strobus became the dominant upland tree species. A shift from lacustrine sediment to organic peat at the YD-Holocene boundary Suggests that the lake that existed in the basin during the Lateglacial interval developed into a swamp in response to reduced effective moisture. A change in wetland vegetation from Myrica gale to Alnus incana subsp. rugosa and Sphagnum is consistent with this interpretation of environmental changes at the beginning of the Holocene. Copyright (C) 2009 John Wiley & Sons, Ltd. VL - 24 IS - 6 N1 - id: 783; 494LO Times Cited:0 Cited References Count:27Y JO - A record of Lateglacial and early Holocene environmental and ecological change from southwestern Connecticut, USA ER - TY - JOUR T1 - Regional beryllium-10 production rate calibration for late-glacial northeastern North America JF - Quaternary Geochronology Y1 - 2009 A1 - Balco, Greg A1 - Briner, Jason A1 - Finkel, Robert C. A1 - Rayburn, John A. A1 - Ridge, John C. A1 - Schaefer, Joerg M. AB - The major uncertainty in relating cosmogenic-nuclide exposure ages to ages measured by other dating methods comes from extrapolating nuclide production rates measured at globally scattered calibration sites to the sites of unknown age that are to be dated. This uncertainty can be reduced by locating production rate calibration sites that are similar in location and age to the sites to be dated. We use this strategy to reconcile exposure age and radiocarbon deglaciation chronologies for northeastern North America by compiling (10)Be production rate calibration measurements from independently dated late-glacial and early Holocene ice-marginal landforms in this region. 10Be production rates measured at these sites are 6-12% lower than predicted by the commonly accepted global 10Be calibration data set used with any published production rate scaling scheme. In addition, the regional calibration data set shows significantly less internal scatter than the global calibration data set. Thus, this calibration data set can be used to improve both the precision and accuracy of exposure dating of regional late-glacial events. For example, if the global calibration data set is used to calculate exposure ages, the exposure-age deglaciation chronology for central New England is inconsistent with the deglaciation chronology inferred from radiocarbon dating and varve stratigraphy. We show that using the regional data set instead makes the exposure age and radiocarbon chronologies consistent. This increases confidence in correlating exposure ages of ice-marginal landforms in northeastern North America with glacial and climate events dated by other means. (c) 2008 Elsevier Ltd. All rights reserved. VL - 4 IS - 2 N1 - id: 2034; PT: J; UT: WOS:000265163500003 JO - Regional beryllium-10 production rate calibration for late-glacial northeastern North America ER - TY - JOUR T1 - Relationship between Holocene climate variations over southern Greenland and eastern Baffin Island and synoptic circulation pattern JF - Climate of the Past Y1 - 2009 A1 - Frechette, B. A1 - de Vernal, A. KW - arctic canada KW - cal kyr bp KW - data-base KW - dinoflagellate cyst assemblages KW - high-latitudes KW - modern analogs KW - north-atlantic KW - pollen spectra KW - radiocarbon age calibration KW - sea-surface temperatures AB - Lake pollen records from southwest Greenland and eastern Baffin Island show strong regionalism in climate trends of the last 7000 cal years. July surface air temperature reconstructions from pollen indicate larger amplitude cooling in southwest Greenland (>3.0 degrees C) than in eastern Baffin Island (<1.0 degrees C). This west-east gradient in climate change is consistent with August sea-surface temperature reconstructions from dinocyst records that indicate decreasing temperature and/or strength of the North Atlantic Current to the east during the Holocene while the eastern Canadian margins under the Labrador Current influence display slight warming. Complementary to air and sea-surface temperature records, the lake pollen data led to reconstruct increased cloudiness in southern Greenland, which points to increasing cyclonic activity since 7000 cal years BP west of Greenland. Together, the terrestrial and marine records of the northwest North Atlantic therefore suggest a shift from a dominant NAO+ during the early-mid Holocene to dominant NAO- in the late Holocene. VL - 5 SN - 1814-9324 IS - 3 N1 - 500rkTimes Cited:18 Cited References Count:64 JO - Clim Past ER - TY - JOUR T1 - Report from the International Permafrost Association: Carbon Pools in Permafrost Regions JF - Permafrost and Periglacial Processes Y1 - 2009 A1 - Kuhry, Peter A1 - Ping, Chien-Lu A1 - Schuur, Edward A. G. A1 - Tarnocai, Charles A1 - Zimov, Sergey VL - 20 IS - 2 N1 - id: 2027; PT: J; UT: WOS:000267409000012 JO - Report from the International Permafrost Association: Carbon Pools in Permafrost Regions ER - TY - JOUR T1 - Sediment accumulation on the Southern California Bight continental margin during the twentieth century JF - Special Paper - Geological Society of America Y1 - 2009 A1 - Alexander, Clark R. A1 - Lee, Homa J. AB - Sediment discharged into the portion of the Southern California Bight extending from Santa Barbara to Dana Point enters a complex system of semi-isolated coastal cells, narrow continental shelves, submarine canyons, and offshore basins. On both the Santa Monica and San Pedro margins, (super 210) Pb accumulation rates decrease in an offshore direction (from approximately 0.5 g cm (super -2) yr (super -1) to 0.02 g cm (super -2) yr (super -1) ), in concert with a fining in sediment grain size (from 4.50phi to 8.50phi ), suggesting that offshore transport of wave-resuspended material occurs as relatively dilute nepheloid layers and that hemipalegic sedimentation dominates the supply of sediment to the outer shelf, slope, and basins. Together, these areas are effectively sequestering up to 100% of the annual fluvial input. In contrast to the Santa Monica margin, which does not display evidence of mass wasting as an important process of sediment delivery and redistribution, the San Pedro margin does provide numerous examples of failures and mass wasting, suggesting that intraslope sediment redistribution may play a more important role there. Basin deposits in both areas exhibit evidence of turbidites tentatively associated with both major floods and earthquakes, sourced from either the Redondo Canyon (San Pedro Basin) or Dume Canyon (Santa Monica Basin). On the Palos Verdes shelf, sediment-accumulation rates decrease along and across the shelf away from the White's Point outfall, which has been a major source of contaminants to the shelf deposits. Accumulation rates prior to the construction of the outfall were approximately 0.2 g cm (super -2) yr (super -1) and increased 1.5-3.7 times during peak discharges from the outfall in 1971. The distal rate of accumulation has decreased by approximately 50%, from 0.63 g cm (super -2) yr (super -1) during the period 1971-1992 to 0.29 g cm (super -2) yr (super -1) during the period 1992-2003. The proximal rate of accumulation, however, has only decreased approximately 10%, from 0.83 g cm (super -2) yr (super -1) during the period 1971-1992 to 0.73 g cm (super -2) yr (super -1) during the period 1992-2003. Effluent-affected sediment layers on the Palos Verdes shelf can be identified in seabed profiles of naturally occurring (super 238) U, which is sequestered in reducing sediments. The Santa Clara River shelf, just north and west of the Santa Monica and San Pedro margins, is fine-grained and flood-dominated. Core profiles of excess (super 210) Pb from sites covering the extent of documented major flood deposition exhibit evidence of rapidly deposited sediment up to 25 cm thick. These beds are developing in an active depocenter in water depths of 30-50 m at an average rate of 0.72 g cm (super -2) yr (super -1) . Budget calculations for annual and 50-yr timescale sediment storage on this shelf shows that 20%-30% of the sediment discharge is retained on the shelf, leaving 70%-80% to be redistributed to the outer shelf, slope, Santa Barbara Basin, and Santa Monica Basin. VL - 454 N1 - id: 855; Editor: Lee, Homa J; Normark, William R References: 52; illus. incl. 2 tables, sketch maps Latitude:N332000,N340000 Longitude:W1183000,W1193000Y JO - Sediment accumulation on the Southern California Bight continental margin during the twentieth century ER - TY - JOUR T1 - Sedimentation rates and provenance analysis in the Southwestern Okinawa Trough since the mid-Holocene JF - Chinese Science Bulletin Y1 - 2009 A1 - Li, ChuanShun A1 - Jiang, Bo A1 - Li, Anchun A1 - Li, Tiegang A1 - Jiang, FuQing AB - As a high-sedimentation rate depocenter along the path of the Kuroshio Current, the southwesternmost part of the Okinawa Trough is a key area to understand the Kuroshio history and sediments transportation. A 34.17-m-long sediment core was obtained by the advanced piston corer of Marco Polo/IMAGES XII MARION DUFRESNE during the May 2005 from the Southern Okinawa Trough at site MD05-2908. The recovered sediments were analyzed by AMS (14)C dating, coarse size fraction (> 63 mu m) extraction and moisture content determination in order to study its sedimentation flux and provenance. The depth-age relationship of core MD05-2908 was well constrained by 17 (14)C dating points. The sediments span across the mid-Holocene (6.8 ka B.P.) and have remarkablely high sedimentation rates between 1.8 and 21-2 m/ka, which is well consistent with the modern observations from sediment traps. We identified five 70-200 a periods of abnormally rapid sedimentation events at 6790-6600 a B.P., 5690-5600 a B.P., 4820-4720 a B.P., 1090-880 a B.P., and 260-190 a B.P., during which the highest sedimentation rate is up to 21-2 m/ka. In general, the lithology of the sediments were dominated by silt and clay, associated with less than 5% coarse size fraction (a parts per thousand VL - 54 IS - 7 N1 - id: 1930; PT: J; UT: WOS:000264842600017 JO - Sedimentation rates and provenance analysis in the Southwestern Okinawa Trough since the mid-Holocene ER - TY - JOUR T1 - Sinking deltas due to human activities JF - Nature Geoscience Y1 - 2009 A1 - Syvitski, J. P. M. A1 - Kettner, A. J. A1 - Overeem, I. A1 - Hutton, E. W. H. A1 - Hannon, M. T. A1 - Brakenridge, G. R. A1 - Day, J. A1 - Vorosmarty, C. A1 - Saito, Y. A1 - Giosan, L. A1 - Nicholls, R. J. AB - Many of the world's largest deltas are densely populated and heavily farmed. Yet many of their inhabitants are becoming increasingly vulnerable to flooding and conversions of their land to open ocean. The vulnerability is a result of sediment compaction from the removal of oil, gas and water from the delta's underlying sediments, the trapping of sediment in reservoirs upstream and floodplain engineering in combination with rising global sea level. Here we present an assessment of 33 deltas chosen to represent the world's deltas. We find that in the past decade, 85% of the deltas experienced severe flooding, resulting in the temporary submergence of 260,000 km(2). We conservatively estimate that the delta surface area vulnerable to flooding could increase by 50% under the current projected values for sea-level rise in the twenty-first century. This figure could increase if the capture of sediment upstream persists and continues to prevent the growth and buffering of the deltas. VL - 2 IS - 10 N1 - id: 799; 501BW Times Cited:2 Cited References Count:38; YY JO - Sinking deltas due to human activities ER - TY - JOUR T1 - Source apportionment of elevated wintertime PAHs by compound-specific radiocarbon analysis JF - Atmospheric Chemistry and Physics Y1 - 2009 A1 - Sheesley, R. J. A1 - Krusa, M. A1 - Krecl, P. A1 - Johansson, C. A1 - Gustafsson, O. KW - air-pollution sources KW - atmospheric aerosols KW - BLACK CARBON KW - emissions KW - northern sweden KW - organic-compounds KW - particulate matter KW - polycyclic aromatic-hydrocarbons KW - positive matrix factorization KW - residential wood combustion AB - Natural abundance radiocarbon analysis facilitates distinct source apportionment between contemporary biomass/biofuel ((14)C "alive") versus fossil fuel ((14)C "dead") combustion. Here, the first compound-specific radiocarbon analysis (CSRA) of atmospheric polycyclic aromatic hydrocarbons (PAHs) was demonstrated for a set of samples collected in Lycksele, Sweden a small town with frequent episodes of severe atmospheric pollution in the winter. Renewed interest in using residential wood combustion (RWC) means that this type of seasonal pollution is of increasing concern in many areas. Five individual/paired PAH isolates from three pooled fortnight-long filter collections were analyzed by CSRA: phenanthrene, fluoranthene, pyrene, benzo[b+k] fluoranthene and indeno[cd]pyrene plus benzo[ghi]perylene; phenanthrene was the only compound also analyzed in the gas phase. The measured Delta(14)C for PAHs spanned from -138.3% to 58.0%. A simple isotopic mass balance model was applied to estimate the fraction biomass (fbiomass) contribution, which was constrained to 71-87% for the individual PAHs. Indeno[cd]pyrene plus benzo[ghi]perylene had an fbiomass of 71%, while fluoranthene and phenanthrene (gas phase) had the highest biomass contribution at 87%. The total organic carbon (TOC, defined as carbon remaining after removal of inorganic carbon) fbiomass was estimated to be 77%, which falls within the range for PAHs. This CSRA data of atmospheric PAHs established that RWC is the dominating source of atmospheric PAHs to this region of the boreal zone with some variations among RWC contributions to specific PAHs. VL - 9 SN - 1680-7316 IS - 10 N1 - 452qjTimes Cited:22 Cited References Count:52 JO - Atmos Chem Phys ER - TY - JOUR T1 - Southern Ocean evidence for reduced export of North Atlantic Deep Water during Heinrich event 1 JF - Geology Y1 - 2009 A1 - Robinson, L. F. A1 - van de Flierdt, T. AB - Deep-sea corals form unique, high-resolution archives of ocean circulation that can be dated using the decay of uranium to thorium. They are abundant in the Southern Ocean, and can provide unprecedented insights into ocean circulation and ocean chemistry on sub-millennial time scales in areas where application of traditional paleoceanographic proxies is difficult. Here we present the first coupled neodymium (Nd) isotope and radiocarbon data from deep-sea corals in the Drake Passage (Southern Ocean) adding new constraints on ocean circulation during the last Heinrich event (H1; 16.7 ka). The modern-day Drake Passage water column is homogeneous with respect to Nd isotopes (expressed in epsilon units, e Nd). Its isotopic value of close to -9 is largely controlled by the mixture of North Atlantic Deep Water and Pacific Deep Water. The aragonite of modern Drake Passage corals reflects this water-column value, whereas a fossil coral from H1 is significantly higher at -6.4 +/- 0.4. We interpret this similar to 2.5 epsilon unit shift as a reduction in the influence of North Atlantic-sourced Nd in the Southern Ocean during H1. This interpretation is supported by a series of radiocarbon analyses on the same sample, and is consistent with a twofold or greater reduction in export of North Atlantic waters from the Atlantic Basin. Combining analyses of radiocarbon and Nd isotopes on U-series dated deep-sea coral skeletons holds great potential for quantification of past ocean ventilation rates. VL - 37 IS - 3 N1 - id: 817; 414CT Times Cited:2 Cited References Count:40; YY JO - Southern Ocean evidence for reduced export of North Atlantic Deep Water during Heinrich event 1 ER - TY - JOUR T1 - Southward movement of the Pacific intertropical convergence zone AD 1400-1850 JF - Nature Geoscience Y1 - 2009 A1 - Sachs, J. P. A1 - Sachse, D. A1 - Smittenberg, R. H. A1 - Zhang, Z. H. A1 - Battisti, D. S. A1 - Golubic, S. AB - Tropical rainfall patterns control the subsistence lifestyle of more than one billion people. Seasonal changes in these rainfall patterns are associated with changes in the position of the intertropical convergence zone, which is characterized by deep convection causing heavy rainfall near 10 degrees N in boreal summer and 3 degrees N in boreal winter. Dynamic controls on the position of the intertropical convergence zone are debated, but palaeoclimatic evidence from continental Asia, Africa and the Americas suggests that it has shifted substantially during the past millennium, reaching its southernmost position some time during the Little Ice Age (AD 1400-1850). However, without records from the meteorological core of the intertropical convergence zone in the Pacific Ocean, quantitative constraints on its position are lacking. Here we report microbiological, molecular and hydrogen isotopic evidence from lake sediments in the Northern Line Islands, Galapagos and Palau indicating that the Pacific intertropical convergence zone was south of its modern position for most of the past millennium, by as much as 500 km during the Little Ice Age. A colder Northern Hemisphere at that time, possibly resulting from lower solar irradiance, may have driven the intertropical convergence zone south. We conclude that small changes in Earth's radiation budget may profoundly affect tropical rainfall. VL - 2 IS - 7 N1 - id: 847; 497LS Times Cited:5 Cited References Count:45Y JO - Southward movement of the Pacific intertropical convergence zone AD 1400-1850 ER - TY - JOUR T1 - Spatial variability of late Holocene and 20th century sea-level rise along the Atlantic coast of the United States JF - Geology Y1 - 2009 A1 - Engelhart, Simon E. A1 - Horton, Benjamin P. A1 - Douglas, Bruce C. A1 - Peltier, W. Richard A1 - Törnqvist, Torbjörn E. VL - 37 IS - 12 N1 - id: 1872Y JO - Spatial variability of late Holocene and 20th century sea-level rise along the Atlantic coast of the United States ER - TY - JOUR T1 - Submarine canyon and fan systems of the California Continental Borderland JF - Geological Society of America Special Papers Y1 - 2009 A1 - Normark, William R. A1 - Piper, David J. W. A1 - Romans, Brian W. A1 - Covault, Jacob A. A1 - Dartnell, Peter A1 - Sliter, Ray W. AB - Late Quaternary turbidite and related gravity-flow deposits have accumulated in basins of the California Borderland under a variety of conditions of sediment supply and sea-level stand. The northern basins (Santa Barbara, Santa Monica, and San Pedro) are closed and thus trap virtually all sediment supplied through submarine canyons and smaller gulley systems along the basin margins. The southern basins (Gulf of Santa Catalina and San Diego Trough) are open, and, under some conditions, turbidity currents flow from one basin to another. Seismic-reflection profiles at a variety of resolutions are used to determine the distribution of late Quaternary turbidites. Patterns of turbidite-dominated deposition during lowstand conditions of oxygen isotope stages 2 and 6 are similar within each of the basins. Chronology is provided by radiocarbon dating of sediment from two Ocean Drilling Program sites, the Mohole test-drill site, and large numbers of piston cores. High-resolution, seismic-stratigraphic frameworks developed for Santa Monica Basin and the open southern basins show rapid lateral shifts in sediment accumulation on scales that range from individual lobe elements to entire fan complexes. More than half of the submarine fans in the Borderland remain active at any given position of relative sea level. Where the continental shelf is narrow, canyons are able to cut headward during sea-level transgression and maintain sediment supply to the basins from rivers and longshore currents during highstands. Rivers with high bedload discharge transfer sediment to submarine fans during both highstand and lowstand conditions. VL - 454 N1 - id: 878; 10.1130/2009.2454(2.7) ER - TY - JOUR T1 - Surculichnus bifurcauda n. igen., n. isp., a trace fossil from Late Pleistocene glaciolacustrine varves of the Connecticut River Valley, USA, attributed to notostracan crustaceans based on neoichnological experimentation JF - Palaeogeography Palaeoclimatology Palaeoecology Y1 - 2009 A1 - Knecht, Richard J. A1 - Benner, Jacob S. A1 - Rogers, Christopher A1 - Ridge, John C. AB - New trace fossils found in the Late Pleistocene glaciolacustrine varves of the Connecticut River Valley, Vermont, USA represent the first known notostracan presence in glacial Lake Hitchcock. These unique trace fossils warrant a new ichnogenus and ichnospecies Surculichnus bifurcauda. The New England Varve Chronology (NEVC) constrains the initial presence of S. bifurcauda at similar to 13.3-13.2 kyr. The morphology of S. bifurcauda correlates well with notostracan characteristics and behavior. Sieving of bedding planes that contained S. bifurcauda produced one chitinous fossil that is suggestive of a notostracan telson. Neoichnological experimentation was conducted with the species Triops longicaudatus. During the subadult stage, T longicaudatus produced traces representative of locomotion and feeding behaviors, and at the adult stage reproduced S. bifurcauda, as well as Rusophycus. Possible explanations for the productions of these traces are egg laying or predation behaviors that are both related to maturity. Further research in the paleo- and modern ecology of glacial and nearctic lakes may shed more light on the maker of S. bifurcauda. (C) 2008 Elsevier B.V. All rights reserved. VL - 272 IS - 3-4 N1 - id: 2036; PT: J; UT: WOS:000264010000008 JO - Surculichnus bifurcauda n. igen., n. isp., a trace fossil from Late Pleistocene glaciolacustrine varves of the Connecticut River Valley, USA, attributed to notostracan crustaceans based on neoichnological experimentation ER - TY - RPRT T1 - Terminal Report: Nutrient and Carbon Biogeochemistry of the Sulu Sea (Project No. 96/01/CW) Y1 - 2009 A1 - Jacinto, G. S. A1 - David, L. T. A1 - Peleo-Alampay, A. M. A1 - San Diego-McGlone, M. L. A1 - Siringan, F. P. A1 - Villanoy, C. L. PB - Southeast Asia Regional Committee for START (SARCS) N1 - id: 872 ER - TY - JOUR T1 - Timing and magnitude of recent accelerated sea-level rise (North Carolina, United States) JF - Geology Y1 - 2009 A1 - Kemp, A. C. A1 - Horton, B. P. A1 - Culver, S. J. A1 - Corbett, D. R. A1 - van de Plassche, O. A1 - Gehrels, W. R. A1 - Douglas, B. C. A1 - Parnell, A. C. AB - We provide records of relative sea level since A. D. 1500 from two salt marshes in North Carolina to complement existing tide-gauge records and to determine when recent rates of accelerated sea-level rise commenced. Reconstructions were developed using foraminifera-based transfer functions and composite chronologies, which were validated against regional twentieth century tide-gauge records. The measured rate of relative sea-level rise in North Carolina during the twentieth century was 3.0-3.3 mm/a, consisting of a background rate of similar to 1 mm/a, plus an abrupt increase of 2.2 mm/a, which began between A. D. 1879 and 1915. This acceleration is broadly synchronous with other studies from the Atlantic coast. The magnitude of the acceleration at both sites is larger than at sites farther north along the U. S. and Canadian Atlantic coast and may be indicative of a latitudinal trend. VL - 37 IS - 11 N1 - id: 829; 512AY Times Cited:15 Cited References Count:30Y JO - Timing and magnitude of recent accelerated sea-level rise (North Carolina, United States) ER - TY - JOUR T1 - Timing of post-glacial reinhabitation and ecological development of two New England, USA, drainages based on trace fossil evidence JF - Palaeogeography Palaeoclimatology Palaeoecology Y1 - 2009 A1 - Benner, Jacob S. A1 - Ridge, John C. A1 - Knecht, Richard J. AB - Trace fossils as paleoecological and paleobiogeographical tools in Pleistocene glaciolacustrine sediments have been largely ignored. Combining high resolution varve stratigraphy with trace fossil data can lead to refined paleoenvironmental interpretations during times of rapid climate change. Based on trace fossils from glaciolacustrine varves in the Connecticut and Merrimack River valleys, a new timeline for the reinhabitation of New England by fish and associated invertebrates has been constructed. In addition, it appears that colonization of the recently deglaciated environments occurred in at least four successional stages. If these stages can be recognized elsewhere, it may be possible to accurately model other postglacial migrations using trace fossils and varve chronostratigraphy. (C) 2008 Elsevier B.V. All rights reserved. VL - 272 IS - 3-4 N1 - id: 2035; PT: J; UT: WOS:000264010000007 JO - Timing of post-glacial reinhabitation and ecological development of two New England, USA, drainages based on trace fossil evidence ER - TY - JOUR T1 - Towards a quantitative and independent reconstruction of Holocene temperature and precipitation in Northern Great Plains using novel organic proxies JF - Eos, Transactions, American Geophysical Union Y1 - 2009 A1 - Toney, J. L. A1 - Huang, Y. A1 - Fritz, S. C. A1 - Baker, P. A1 - Grimm, E. C. A1 - Nyren, P. E. VL - 90 IS - 52 N1 - id: 891 ER - TY - JOUR T1 - A trans-Holocene archaeological record of Guadalupe fur seals (Arctocephalus townsendi) on the California coast JF - Marine Mammal Science Y1 - 2009 A1 - Rick, Torben C. A1 - DeLong, Robert L. A1 - Erlandson, Jon M. A1 - Braje, Todd J. A1 - Jones, Terry L. A1 - Kennett, Douglas J. A1 - Wake, Thomas A. A1 - Walker, Phillip L. VL - 25 IS - 2 N1 - id: 2061; PT: J; UT: WOS:000265228700018 JO - A trans-Holocene archaeological record of Guadalupe fur seals (Arctocephalus townsendi) on the California coast ER - TY - JOUR T1 - Using foraminifera to recognize former flood-tide deltas in the Holocene stratigraphic record: examples from the Outer Banks, North Carolina JF - Stratigraphy Y1 - 2009 A1 - Smith, C. G. A1 - Culver, S. J. A1 - Mallinson, D. J. A1 - Riggs, S. R. A1 - Corbett, D. R. VL - 6 N1 - id: 851 ER - TY - JOUR T1 - Validation of yellowedge grouper, Epinephelus flavolimbatus, age using nuclear bomb-produced radiocarbon JF - ENVIRONMENTAL BIOLOGY OF FISHES Y1 - 2009 A1 - Cook, Melissa A1 - Fitzhugh, Gary R. A1 - Franks, James S. KW - Age determination KW - Age validation KW - Gulf of Mexico KW - Longevity KW - RADIOCARBON ANALYSIS KW - Yellowedge grouper AB - Age validation and estimates of longevity of yellowedge grouper (Epinephelus flavolimbatus) from the Gulf of Mexico (GOM) are needed to inform fishery management decisions. Yellowedge grouper sagittal otoliths (n = 100) were collected, aged using conventional means, and cores were submitted for radiocarbon ((14)C) measurement. Radiocarbon values of yellowedge grouper otoliths were compared to established radiocarbon chronologies in the region to validate the age and ageing methodology of this species. The yellowedge grouper chronology displayed a similar sigmoidal trend as previously published chronologies. In addition to the core analysis, multiple areas on otolith sections from eight specimens were analyzed for Delta(14)C to validate age estimates for fish born prior to the (14)C increase. Our results indicate that yellowedge grouper live longer than previously reported (minimum of 40 years based on radiocarbon measurements). The validated ageing methodology supported an estimated maximum longevity of 85 years and established that yellowedge grouper have the longest lifespan currently known for any species of grouper in the GOM. Results also indicate a depth-age interaction in that material extracted from adult otolith sections assigned to post-bomb dates exhibited lower Delta(14)C values than cores (juvenile material) assigned to the same post-bomb dates. This finding is likely explained by lower (14)C levels reported from water masses at deeper depths (> 100 m) which are inhabited by adults. VL - 86 ER - TY - JOUR T1 - Variations of terrigenous material discharges in the South Okinawa trough and its relation to the East Asian summer monsoon since the last millennium JF - Journal of China University of Geosciences Y1 - 2009 A1 - Chen, Jinxia A1 - Li, Tiegang A1 - Qingyun, Nan AB - The top part of a giant IMAGE core MD05-2908 taken from the South Okinawa Trough was investigated for the sake of understanding the climate evolution in Donghai seacoast areas since the last millennium. Sporopollen and organic carbon isotope records of bulk sediments were used as proxies to trace the climate variations and terrigenous materials discharges. Time series were demarcated by 4 AMS 14 C dating ages. Comprehensive data of sporopollen and carbon isotopic composition, together with the paleoenvironmental records show that in the South Okinawa Trough the terrigenous material discharges fluctuated obviously for the past 1000 years. Three relatively high terrigenous material discharge periods, corresponding to 1100-1040 a BP, 960-880 a BP and 800-480 a BP respectively and two quite low terrigenous material discharge periods, namely, 1040-960 a BP and 480-230 a BP, can be identified from our records. In comparison with the stalagmite delta (super 13) C records(which were used to trace the East Asian Summer Monsoon) from Buddha Cave, Shaanxi Province, we found that the variations of terrigenous material discharges might be related closely to variations of the East Asian Summer Monsoon(EASM). Weaker EASM resulted in a convergence rain belt and longer residence time in the South China regions, which increased the efficiency of weathering and denudation of the source area. Moreover, increased rainfall enhanced the land runoff and as a result more terrigenous materials were transported to the South Okinawa Trough. VL - 34 SN - 1000-2383 IS - Generic N1 - id: 1948; Source type: scholarlyjournals; Object type: Article; Copyright: GeoRef in Process, Copyright 2011, American Geosciences Institute. After editing and indexing, this record will be added to Georef.; CSAUnique: 600756-13; AccNum: 600756-13; ISSN: 1000-2383; Peer Reviewed: true ER - TY - JOUR T1 - Vast laminated diatom mat deposits from the west low-latitude Pacific Ocean in the last glacial period JF - Chinese Science Bulletin Y1 - 2009 A1 - Zhai, Bin A1 - Li, Tiegang A1 - Chang, Fengming A1 - Cao, QiYuan AB - Diatoms are one of the predominant contributors to global carbon fixation by accounting for over 40% of total oceanic primary production and dominate export production. They play a significant role in marine biogeochemistry cycle. The diatom mat deposits are results of vast diatoms bloom. By analysis of diatom mats in 136 degrees 00'-140 degrees 00'E, 15 degrees 00'-21 degrees 00'N, Eastern Philippines Sea, we identified the species of the diatoms as giant Ethmodiscus rex (Wallich) Hendey. AMS (14)C dating shows that the sediments rich in diatom mats occurred during 16000-28600 a B.P., which means the bloom mainly occurred during the last glacial period, while there are no diatom mat deposits in other layers. Preliminary analysis indicates that Antarctic Intermediate Water (AAIW) expanded northward and brought silicate-rich water into the area, namely, silicon leakage processes caused the bloom of diatoms. In addition, the increase of iron input is one of the main reasons for the diatom bloom. VL - 54 IS - 23 N1 - id: 1928; PT: J; UT: WOS:000272622100036 JO - Vast laminated diatom mat deposits from the west low-latitude Pacific Ocean in the last glacial period ER - TY - JOUR T1 - Was the Black Sea catastrophically flooded in the early Holocene? JF - Quaternary Science Reviews Y1 - 2009 A1 - Giosan, L. A1 - Filip, F. A1 - Constatinescu, S. AB - A catastrophic flooding of the Black Sea basin was proposed to have occurred during its reconnection to the ocean in the early Holocene. Possible cultural consequences of the flood include the migration of Neolithic farmers from around the Black Sea towards central Europe as well as the creation of flood myths. Stratigraphic and paleo-geomorphologic information from Danube delta aided by radiocarbon ages on articulated mollusks constrain the level in the Black Sea before the marine reconnection to ca 30 m below the present sea level rather than 80 m or lower. If the flood occurred at all, the sea level increase and the flooded area during the reconnection were significantly smaller than previously proposed. (C) 2008 Elsevier Ltd. All rights reserved. VL - 28 IS - 1-2 N1 - id: 866; 399HK Times Cited:0 Cited References Count:56; YY JO - Was the Black Sea catastrophically flooded in the early Holocene? ER - TY - JOUR T1 - Wind-Driven Upwelling in the Southern Ocean and the Deglacial Rise in Atmospheric CO2 JF - Science Y1 - 2009 A1 - Anderson, R. F. A1 - Ali, S. A1 - Bradtmiller, L. I. A1 - Nielsen, S. H. H. A1 - Fleisher, M. Q. A1 - Anderson, B. E. A1 - Burckle, L. H. AB - Wind-driven upwelling in the ocean around Antarctica helps regulate the exchange of carbon dioxide (CO2) between the deep sea and the atmosphere, as well as the supply of dissolved silicon to the euphotic zone of the Southern Ocean. Diatom productivity south of the Antarctic Polar Front and the subsequent burial of biogenic opal in underlying sediments are limited by this silicon supply. We show that opal burial rates, and thus upwelling, were enhanced during the termination of the last ice age in each sector of the Southern Ocean. In the record with the greatest temporal resolution, we find evidence for two intervals of enhanced upwelling concurrent with the two intervals of rising atmospheric CO2 during deglaciation. These results directly link increased ventilation of deep water to the deglacial rise in atmospheric CO2. VL - 323 IS - 5920 N1 - id: 835; 417TP Times Cited:18 Cited References Count:69Y JO - Wind-Driven Upwelling in the Southern Ocean and the Deglacial Rise in Atmospheric CO2 ER - TY - JOUR T1 - 3500 yr record of centennial-scale climate variability from the Western Pacific Warm Pool JF - Geology Y1 - 2008 A1 - Langton, S. J. A1 - Linsley, B. K. A1 - Robinson, R. S. A1 - Rosenthal, Y. A1 - Oppo, D. W. A1 - Eglinton, T. I. A1 - Howe, S. S. A1 - Djajadihardja, Y. S. A1 - Syamsudin, F. AB - We use geochemical data from a sediment core in the shallow-silled and intermittently dysoxic Kau Bay in Halmahera (Indonesia, lat 1 degrees N, long 127.5 degrees E) to reconstruct century-scale climate variability within the Western Pacific Warm Pool over the past similar to 3500 yr. Downcore variations in bulk sedimentary delta N-15 appear to reflect century-scale variability in basin ventilation, attributed to changes in oceanographic conditions related to century-scale fluctuations in El Nino Southern Oscillation (ENSO). We infer an increase in century-scale El Nino activity beginning ca. 1700 yr B.P. with peaks in El Nino activity ca. 1500 yr B.P., 1150 yr B.P., and ca. 700 yr B.P. The Kau Bay results suggest that there was diminished ENSO amplitude or frequency, or a departure from El Nino-like conditions during the Medieval Warm Period, and distinctive, but steadily decreasing, El Nino activity during and after the Little Ice Age. VL - 36 IS - 10 N1 - id: 1894; ISI Document Delivery No.: 357HB Times Cited: 1 Cited Reference Count: 36 Cited References: ALDRIAN E, 2003, INT J CLIMATOL, V23, P1435, DOI 10.1002/joc.950 ALTABET MA, 1994, GLOBAL BIOGEOCHEM CY, V8, P103 ALTABET MA, 2001, LIMNOL OCEANOGR, V46, P368 ARRUDA WZ, 2003, J PHYS OCEANOGR, V33, P2815 BRANDES JA, 1998, LIMNOL OCEANOGR, V43, P1680 BRANDES JA, 2002, GLOBAL BIOGEOCHEMICA, V16 CASCIOTTI KL, 2002, ANAL CHEM, V74, P4905, DOI 10.1021/ac020113w CHRISTIAN JR, 2004, DEEP-SEA RES PT II, V51, P209, DOI 10.1016/j.dsr2.2003.06.002 DEUTSCH C, 2007, NATURE, V445, P163, DOI 10.1038/nature05392 GANESHRAM RS, 2000, PALEOCEANOGRAPHY, V15, P361 GRANGER J, 2004, EOS T AM GEOPHYS U S, V85 GRANGER J, 2004, LIMNOL OCEANOGR, V49, P1763 HAUG GH, 1998, PALEOCEANOGRAPHY, V13, P427 HAUG GH, 2001, SCIENCE, V293, P1304 HODELL DA, 2005, QUATERNARY SCI REV, V24, P1413, DOI 10.1016/j.quascirev.2004.10.013 LIU KK, 1989, LIMNOL OCEANOGR, V34, P820 MAKOU MC, 2007, ORG GEOCHEM, V38, P1680, DOI 10.1016/j.orggeochem.2007.06.003 MARIOTTI A, 1981, PLANT SOIL, V62, P413 MASUMOTO Y, 2001, GEOPHYS RES LETT, V28, P1631 MIDDELBURG JJ, 1990, GEOL ULTRIECTIN, V71, P177 MOY CM, 2002, NATURE, V420, P162 NEWTON A, 2006, GEOPHYS RES LETT, V33, ARTN L19710 REIN B, 2004, GEOPHYS RES LETT, V31, ARTN L17211 REIN B, 2005, PALEOCEANOGRAPHY, V20, ARTN PA4003 REYNOLDS RW, 1994, J CLIMATE, V7, P929 RODBELL DT, 1999, SCIENCE, V283, P516 SIGMAN DM, 2003, GEOCHEM GEOPHY GEOSY, V4, ARTN 1040 SIGMAN DM, 2005, GLOBAL BIOGEOCHEM CY, V19, ARTN GB4022 STOTT L, 2004, NATURE, V431, P56, DOI 10.1038/nature02903 STREETPERROTT FA, 1997, SCIENCE, V278, P1422 THUNELL R, 2004, GLOBAL BIOGEOCHEMICA, V18, UNSP GB3001 UEKI I, 2003, J GEOPHYS RES-OCEANS, V108, ARTN 3243 VANAKEN HMV, 1988, NETHERLANDS J SEA RE, V22, P403, DOI 10.1016/0077-7579(88)90011-7 VANDERWEIJDEN CH, 1989, NETH J SEA RES, V24, P583 VANRIEL PM, 1943, OCEANOGRAPHIC RESU 5, V2 WYRTKI K, 1961, NAGA REPORT, V2 Langton, S. J. Linsley, B. K. Robinson, R. S. Rosenthal, Y. Oppo, D. W. Eglinton, T. I. Howe, S. S. Djajadihardja, Y. S. Syamsudin, F. U.S. National Science Foundation [OCE-0502550, OCE-0502504, OCE-052960] This work was supported by the U.S. National Science Foundation (grants OCE-0502550, OCE-0502504, and OCE-052960). We thank the captain, crew, technicians, and the scientific crew who helped with sample collection on the R/V Baruna Jaya VIII. Geological soc amer, inc Boulder; YY JO - 3500 yr record of centennial-scale climate variability from the Western Pacific Warm Pool ER - TY - THES T1 - A 5000-year history of Caribbean environmental change and hurricane activity reconstructed from coastal lake sediments of the West Indies Y1 - 2008 A1 - Knowles, J. T. PB - Louisiana State University CY - Baton Rouge, Louisiana VL - Dissertation/Thesis UR - http://digitalcommons.lsu.edu/gradschool_dissertations/4026/ ER - TY - JOUR T1 - Abrupt changes in Antarctic Intermediate Water circulation over the past 25,000 years JF - Nature Geoscience Y1 - 2008 A1 - Pahnke, Katharina A1 - Goldstein, Steven L. A1 - Hemming, Sidney R. AB - The circulation of Antarctic Intermediate Water is thought to make an important contribution to the global ocean-climate system, but the details of this interaction are not fully understood. Furthermore, the behaviour of Antarctic Intermediate Water under glacial and interglacial conditions is not well constrained. Here we present a 25,000-year-long record of neodymium isotopic variations-a tracer of water-mass mixing-from the middle depths of the tropical Atlantic Ocean. Our data reveal abruptly enhanced northward advection of Antarctic Intermediate Water during periods of reduced North Atlantic overturning circulation during the last deglaciation. These events coincide with an increase in the formation of Antarctic Intermediate Water and warming in the southwest Pacific Ocean, which suggests a tight link with Southern Hemisphere climate. In contrast, the initial incursion of southern source water into the North Atlantic similar to 19,000 years ago coincided with weak Antarctic Intermediate Water formation in the Pacific and reduced overturning in the North Atlantic. We conclude that reduced competition at intermediate water depth at this time allowed expansion of Antarctic Intermediate Water into the North Atlantic. This early incursion of Antarctic Intermediate Water may have contributed to freshening of the North Atlantic, perhaps spurring the subsequent collapse of North Atlantic deep convection. VL - 1 IS - 12 N1 - id: 2026; PT: J; UT: WOS:000261278700021 JO - Abrupt changes in Antarctic Intermediate Water circulation over the past 25,000 years ER - TY - JOUR T1 - Abrupt climate change and collapse of deep-sea ecosystems JF - Proceedings of the National Academy of Sciences of the United States of America Y1 - 2008 A1 - Yasuhara, M. A1 - Cronin, T. M. A1 - deMenocal, P. B. A1 - Okahashi, H. A1 - Linsley, B. K. AB - We investigated the deep-sea fossil record of benthic ostracodes during periods of rapid climate and oceanographic change over the past 20,000 years in a core from intermediate depth in the northwestern Atlantic. Results show that deep-sea benthic community "collapses" occur with faunal turnover of up to 50% during major climatically driven oceanographic changes. Species diversity as measured by the Shannon-Wiener index falls from 3 to as low as 1.6 during these events. Major disruptions in the benthic communities commenced with Heinrich Event 1, the Inter-Allerod Cold Period (IACP: 13.1 ka), the Younger Dryas (YD: 12.9-11.5 ka), and several Holocene Bond events when changes in deep-water circulation occurred. The largest collapse is associated with the YD/IACP and is characterized by an abrupt two-step decrease in both the upper North Atlantic Deep Water assemblage and species diversity at 13.1 ka and at 12.2 ka. The ostracode fauna at this site did not fully recover until approximate to 8 ka, with the establishment of Labrador Sea Water ventilation. Ecologically opportunistic slope species prospered during this community collapse. Other abrupt community collapses during the past 20 ka generally correspond to millennial climate events. These results indicate that deep-sea ecosystems are not immune to the effects of rapid climate changes occurring over centuries or less. VL - 105 IS - 5 N1 - id: 1884; 261KQ Times Cited:12 Cited References Count:71Y JO - Abrupt climate change and collapse of deep-sea ecosystems ER - TY - THES T1 - Accelerator Mass Spectrometry and Bayesian Data Analysis Y1 - 2008 A1 - Palonen, Vesa PB - University of Helsinki CY - Helsinki, Finland VL - Phd ER - TY - JOUR T1 - Accelerator mass spectrometry C-14 determination in CO2 produced from laser decomposition of aragonite JF - Rapid Communications in Mass Spectrometry Y1 - 2008 A1 - Rosenheim, B. E. A1 - Thorrold, S. R. A1 - Roberts, M. L. AB - The determination of C-14 in aragonite (CaCO3) decomposed thermally to CO2 using an yttrium-aluminum-garnet doped neodymium laser is reported. Laser decomposition accelerator mass spectrometry (LD-AMS) measurements reproduce AMS determinations of C-14 from the conventional reaction of aragonite with concentrated phosphoric acid. The lack of significant differences between these sets of measurements indicates that LD-AMS radiocarbon dating can overcome the significant fractionation that has been observed during stable isotope (C and O) laser decomposition analysis of different carbonate minerals. The laser regularly converted nearly 30% of material removed into CO2 despite it being optimized for ablation, where laser energy breaks material apart rather than chemically altering it. These results illustrate promise for using laser decomposition on the front-end of AMS systems that directly measure CO2 gas. The feasibility of such measurements depends on (1) the improvement of material removal and/or CO2 generation efficiency of the laser decomposition system and (2) the ionization efficiency of AMS systems measuring continuously flowing CO2 Copyright (C) 2008 John Wiley & Sons, Ltd. VL - 22 IS - 21 N1 - id: 1891; 370OU Times Cited:1 Cited References Count:16Y JO - Accelerator mass spectrometry C-14 determination in CO2 produced from laser decomposition of aragonite ER - TY - JOUR T1 - Age validation of Dover sole (Microstomus pacificus) by means of bomb radiocarbon JF - Fishery Bulletin Y1 - 2008 A1 - Kastelle, C. R. A1 - Anderl, D. M. A1 - Kimura, D. K. A1 - Johnston, C. G. KW - alaska KW - gulf KW - lead-radium KW - north pacific KW - otoliths KW - paucispinis KW - pleuronectids KW - pollock theragra-chalcogramma KW - quality-control KW - rockfish sebastes-pinniger AB - We used bomb radiocarbon (C-14) in this age validation study of Dover sole (Microstomus pacificus). The otoliths of Dover sole, a commercially important fish in the North Pacific, are difficult to age and ages derived from the current break-and-burn method were not previously validated. The otoliths used in this study were chosen on the basis of estimated birth year and for the ease of interpreting growth zone patterns. Otolith cores, material representing years 0 through 3, were isolated and analyzed for C-14. Additionally, a small number of otoliths with difficult-to-interpret growth patterns were analyzed for C-14 to help determine age interpretation. The measured Dover sole C-14 values in easier-to-interpret otoliths were compared with a C-14. reference chronology for Pacific halibut (Hippoglossus stenolepis) in the North Pacific, We used an objective statistical analysis where sums of squared residuals between otolith C-14 values of Dover sole and the reference chronology were examined. Our statistical analysis also included a procedure where the Dover sole C-14 values were standardized to the reference chronology. These procedures allowed an evaluation of aging error. The C-14 results indicated that the Dover sole age estimates from the easier-to-interpret otoliths with the break-and-burn method are accurate. This study validated Dover sole ages from 8 to 47 years. VL - 106 SN - 0090-0656 IS - 4 N1 - 371ygTimes Cited:4 Cited References Count:34 JO - Fish B-Noaa ER - TY - JOUR T1 - Antarctic sediment chronology by programmed-temperature pyrolysis: Methodology and data treatment JF - Geochemistry Geophysics Geosystems Y1 - 2008 A1 - Rosenheim, B. E. A1 - Day, M. B. A1 - Domack, E. A1 - Schrum, H. A1 - Benthien, A. A1 - Hayes, J. M. AB - We report a detailed programmed-temperature pyrolysis/ combustion methodology for radiocarbon (C-14) dating of Antarctic sub-ice shelf sediments. The method targets the autochthonous organic component in sediments that contain a distribution of acid-insoluble organic components from several sources of different ages. The approach has improved sediment chronology in organic-rich sediments proximal to Antarctic ice shelves by yielding maximum age constraints significantly younger than bulk radiocarbon dates from the same sediment horizons. The method proves adequate in determining isotope ratios of the pre-aged carbon end-member; however, the isotopic compositions of the low-temperature measurements indicate that no samples completely avoided mixing with some proportion of pre-aged organic material. Dating the unresolved but desired young end-member must rely on indirect methods, but a simple mixing model cannot be developed without knowledge of the sedimentation rate or comparable constraints. A mathematical approach allowing for multiple mixing components yields a maximum likelihood age, a first-order approximation of the relative proportion of the autochthonous component, and the temperature at which allochthonous carbon begins to volatilize and mix with the autochthonous component. It is likely that our estimation of the cutoff temperature will be improved with knowledge of the pyrolysis kinetics of the major components. Chronology is improved relative to bulk acid-insoluble organic material ages from nine temperature interval dates down to two, but incorporation of inherently more pre-aged carbon in the first division becomes more apparent with fewer and larger temperature intervals. VL - 9 N1 - id: 1847; 284ON Times Cited:5 Cited References Count:27Y JO - Antarctic sediment chronology by programmed-temperature pyrolysis: Methodology and data treatment ER - TY - JOUR T1 - Assessing sedimentary records of paleohurricane activity using modeled hurricane climatology JF - Geochemistry Geophysics Geosystems Y1 - 2008 A1 - Woodruff, J. D. A1 - Donnelly, J. P. A1 - Emanuel, K. A1 - Lane, P. AB - Patterns of overwash deposition observed within back-barrier sediment archives can indicate past changes in tropical cyclone activity; however, it is necessary to evaluate the significance of observed trends in the context of the full range of variability under modern climate conditions. Here we present a method for assessing the statistical significance of patterns observed within a sedimentary hurricane-overwash reconstruction. To alleviate restrictions associated with the limited number of historical hurricanes affecting a specific site, we apply a recently published technique for generating a large number of synthetic storms using a coupled ocean- atmosphere hurricane model set to simulate modern climatology. Thousands of overwash records are generated for a site using a random draw of these synthetic hurricanes, a prescribed threshold for overwash, and a specified temporal resolution based on sedimentation rates observed at a particular site. As a test case we apply this Monte Carlo technique to a hurricane- induced overwash reconstruction developed from Laguna Playa Grande (LPG), a coastal lagoon located on the island of Vieques, Puerto Rico in the northeastern Caribbean. Apparent overwash rates in the LPG overwash record are observed to be four times lower between 2500 and 1000 years B. P. when compared to apparent overwash rates during the last 300 years. However, probability distributions based on Monte Carlo simulations indicate that as much as 65% of this drop can be explained by a reduction in the temporal resolution for older sediments due to a decrease in sedimentation rates. Periods of no apparent overwash activity at LPG between 2500 and 3600 years B. P. and 500-1000 years B. P. are exceptionally long and are unlikely to occur (above 99% confidence) under the current climate conditions. In addition, breaks in activity are difficult to produce even when the hurricane model is forced to a constant El Nino state. Results from this study continue to support the interpretation that the western North Atlantic has exhibited significant changes in hurricane climatology over the last 5500 years. VL - 9 N1 - id: 1895; ISI Document Delivery No.: 351AC Times Cited: 2 Cited Reference Count: 46 Cited References: BOVE MC, 1998, B AM METEOROL SOC, V79, P2477 DEMUTH JL, 2006, J APPL METEOROL CLIM, V45, P1573 DONNELLY JP, 2001, GEOL SOC AM BULL, V113, P714 DONNELLY JP, 2001, GEOLOGY, V29, P615 DONNELLY JP, 2001, P NATL ACAD SCI USA, V98, P14218 DONNELLY JP, 2004, GEOPHYS RES LETT, V31, ARTN L05203 DONNELLY JP, 2004, HURRICANES TYPHOONS, P58 DONNELLY JP, 2004, MAR GEOL, V210, P107, DOI 10.1016/j.margeo.2004.05.005 DONNELLY JP, 2005, J COAST RES S, V142, P201 DONNELLY JP, 2007, NATURE, V447, P465, DOI 10.1038/nature05834 ELSNER JB, 2001, GEOPHYS RES LETT, V28, P4123 ELSNER JB, 2001, J CLIMATE, V14, P4341 ELSNER JB, 2008, J APPL METEOROL CLIM, V47, P368, DOI 10.1175/2007JAMC1692.1 EMANUEL K, 2004, J ATMOS SCI, V61, P843 EMANUEL K, 2006, B AM METEOROL SOC, V87, P299, DOI 10.1175/BAMS-87-3-299 EMANUEL K, 2008, B AM METEOROL SOC, V89, P347, DOI 10.1175/BAMS-89-3-347 FRAPPIER A, 2007, TELLUS A, V59, P529, DOI 10.1111/j.1600-0870.2007.00250.x FRAPPIER AB, 2007, GEOLOGY, V35, P111, DOI 10.1130/G23145A.1 GEHRELS WR, 2005, QUATERNARY SCI REV, V24, P2083, DOI 10.1016/j.quascirev.2004.11.016 GOLDENBERG SB, 2001, SCIENCE, V293, P474 GONZALEZ JL, 2006, EOS, V87, P493, DOI 10.1029/2006EO450001 GRAY WM, 1984, MON WEATHER REV, V112, P1649 JELESNIANSKI CP, 1992, NOAA TECH REP NWS, V48 KALNAY E, 1996, B AM METEOROL SOC, V77, P437 LAMBERT WJ, 2008, J PALEOLIMNOL, V39, P117, DOI 10.1007/s10933-007-9101-6 LIGHTY RG, 1982, CORAL REEFS, V1, P125 LIU KB, 1993, GEOLOGY, V21, P793 LIU KB, 2000, QUATERNARY RES, V54, P238 MALMQUIST DL, 1997, 22 C HURR TROP MET A MERCADO A, 1994, NAT HAZARDS, V10, P235, DOI 10.1007/BF00596144 MILLER DL, 2006, P NATL ACAD SCI USA, V103, P14294, DOI 10.1073/pnas.0606549103 MOY CM, 2002, NATURE, V420, P162 NGUETSOP VF, 2004, QUATERNARY SCI REV, V23, P591, DOI 10.1016/j.quascirev.2003.10.007 NOTT J, 2001, NATURE, V413, P508 NOTT J, 2004, ENVIRON INT, V30, P433, DOI 10.1016/j.cnvint.2003.09.010 NOTT J, 2007, EARTH PLANET SC LETT, V255, P367, DOI 10.1016/j.epsl.2006.12.023 NYBERG J, 2002, PALAEOGEOGR PALAEOCL, V183, P25 PIELKE RA, 1999, B AM METEOROL SOC, V80, P2027 PIELKE RA, 2008, NAT HAZARDS REV, V9, P29, DOI 10.1061/(ASCE)1527-6988(2008)9:1(29) RICHEY JN, 2007, GEOLOGY, V35, P423, DOI 10.1130/G23507A.1 SCILEPPI E, 2007, GEOCHEM GEOPHY GEOSY, V8, ARTN Q06011 SIMPSON RH, 1981, HURRICANE ITS IMPACT STOCKDON HF, 2006, COAST ENG, V53, P573, DOI 10.1016/j.coastaleng.2005.12.005 TORNQVIST TE, 2004, GEOL SOC AM BULL, V116, P1026, DOI 10.1130/B2525478.1 WOODRUFF JD, 2008, VIEQUES PUERTO RICO, V36, P391, DOI 10.1130/G24731A.1 WRIGHT CW, 2001, J PHYS OCEANOGR, V31, P2472 Woodruff, Jonathan D. Donnelly, Jeffrey P. Emanuel, Kerry Lane, Philip National Science Foundation ; Risk Prediction Initiative ; National Geographic Society ; Coastal Ocean Institute at WHOI ; Andrew W. Mellon Foundation Endowed Fund for Innovative Research Funding for this research was provided by the Earth Systems History Program of the National Science Foundation, Risk Prediction Initiative, National Geographic Society, Coastal Ocean Institute at WHOI, and the Andrew W. Mellon Foundation Endowed Fund for Innovative Research. We are grateful to E. Bryant, M. Gomes, E. Scileppi, and J. Tierney, who assisted with the field and lab work, and thank A. Solow for informative discussions. Special thanks to J. Elsner for providing the POT modeling code and documentation. This article benefited through constructive reviews by three anonymous referees. Amer geophysical union Washington; YY JO - Assessing sedimentary records of paleohurricane activity using modeled hurricane climatology ER - TY - JOUR T1 - A Be-10 chronology of lateglacial and Holocene mountain glaciation in the Scoresby Sund region, east Greenland: implications for seasonality during lateglacial time JF - Quaternary Science Reviews Y1 - 2008 A1 - Kelly, M. A. A1 - Lowell, T. V. A1 - Hall, B. L. A1 - Schaefer, J. M. A1 - Finkel, R. C. A1 - Goehring, B. M. A1 - Alley, R. B. A1 - Denton, G. H. AB - Thirty-eight new cosmogenic (Be-10) exposure ages from the Scoresby Sund region of east Greenland indicate that prominent moraine sets deposited by mountain glaciers date from 780 to 310 yr, approximately during the Little Ice Age, from 11660 to 10 630 yr, at the end of the Younger Dryas cold interval or during Preboreal time, and from 13 010 to 11630 yr, during lateglacial time. Equilibrium line altitudes (ELAs) interpreted from lateglacial to Early Holocene moraines indicate summertime cooling between similar to 3.9 and 6.6 degrees C relative to today's value, much less than the extreme Younger Dryas cooling registered by Greenland ice cores (mean-annual temperatures of similar to 15 degrees C colder than today's value). This apparent discrepancy between paleotemperature records supports the contention that Younger Dryas cooling was primarily a wintertime phenomenon. Be-10 ages of lateglacial and Holocene moraines show that mountain glaciers during the Little Ice Age were more extensive than at any other time since the Early Holocene Epoch. In addition, 10Be ages of lateglacial moraines show extensive reworking of boulders with cosmogenic nuclides inherited from prior periods of exposure, consistent with our geomorphic observations and cosmogenic-exposure dating studies in other Arctic regions. (C) 2008 Elsevier Ltd. All rights reserved. VL - 27 IS - 25-26 N1 - id: 1868; 389XX Times Cited:7 Cited References Count:75Y JO - A Be-10 chronology of lateglacial and Holocene mountain glaciation in the Scoresby Sund region, east Greenland: implications for seasonality during lateglacial time ER - TY - JOUR T1 - Benthic foraminiferal faunal and isotopic changes as recorded in Holocene sediments of the northwest Indian Ocean JF - Paleoceanography Y1 - 2008 A1 - Gupta, Anil K. A1 - Das, Moumita A1 - Clemens, Steven C. A1 - Mukherjee, Baidehi AB - Historically, the Holocene has been considered an interval of relatively stable climate. However, recent studies from the northern Arabian Sea (Netherlands Indian Ocean Program 905) suggested high-amplitude climate shifts in the early and middle Holocene based on faunal and benthic isotopic proxy records. We examined benthic foraminiferal faunal and stable isotopic data from Ocean Drilling Program (ODP) Site 723 and total organic carbon data from ODP Site 724, Oman Margin (808 and 593 m water depths, respectively). At Site 723 the mid-Holocene shift in delta(18)O values of infaunal benthic species Uvigerina peregrina (1.4 parts per thousand) is 3 times larger than that of epifaunal benthic species Cibicides kullenbergi recorded at Site NIOP 905 off Somalia. However, none of the five other benthic species we measured at Hole 723A exhibits such a shift in delta(18)O. We speculate that the late Holocene delta(18)O decrease in U. peregrina represents species-specific changes in ecological habitat or food preference in response to changes in surface and deep ocean circulation. While the stable isotopic data do not appear to indicate a middle Holocene climatic shift, our total organic carbon and benthic faunal assemblage data do indicate that the early Holocene deep Arabian Sea was influenced by increased ventilation perhaps by North Atlantic Deep Water and/or Circumpolar Deep Water incursions into the Indian Ocean, leading to remineralization of organic matter and a relatively weak early Holocene oxygen minimum zone in the northwest Arabian Sea in spite of strong summer monsoon circulation. VL - 23 IS - 2 N1 - id: 1964; PT: J; UT: WOS:000256362400001 JO - Benthic foraminiferal faunal and isotopic changes as recorded in Holocene sediments of the northwest Indian Ocean ER - TY - JOUR T1 - Biodiesel effects on particulate radiocarbon (C-14) emissions from a diesel engine JF - JOURNAL OF AEROSOL SCIENCE Y1 - 2008 A1 - Bennett, Maren A1 - Volckens, John A1 - Stanglmaier, Rudy A1 - McNichol, Ann P. A1 - Ellenson, William D. A1 - Lewis, Charles W. KW - biofuel KW - EC KW - OC KW - PM KW - source apportionment AB - The relative amount of C-14 in a sample of atmospheric particulate matter (PM), defined as percent modern carbon (pMC), allows the Environmental Protection Agency (EPA) to infer the fraction of PM derived from anthropogenic pollution sources. With increased use of biofuels that contain C-14, the main assumption of the two-source model, that C-14 is solely derived from biogenic emissions, may become invalid. The goal of this study was to determine the C-14 content of PM emitted from an off-highway diesel engine running on commercial grade biodiesel. Tests were conducted with an off-highway diesel engine running at 80% load fueled by various blends of soy-based biodiesel. A dilution tunnel was used to collect PM10 emissions on quartz filters that were analyzed for their C-14 content using accelerator mass spectrometry. A mobility particle sizer and 5-gas analyzer provided supporting information on the particle size distribution and gas-phase emissions. The pMC of PM10 aerosol increased linearly with the percentage of biodiesel present in the fuel. Therefore, PM emissions resulting from increased combustion of biodiesel fuels will likely affect contemporary C-14 apportionment efforts that attempt to split biogenic vs. anthropogenic emissions based on aerosol C-14 content. Increasing the biodiesel fuel content also reduced emissions of total hydrocarbons (THC), PM10 mass, and particulate elemental carbon. Biodiesel had variable results on oxides of nitrogen (NOx) emissions. (C) 2008 Elsevier Ltd. All rights reserved. VL - 39 ER - TY - JOUR T1 - Biogeochemical characterization of carbon sources in the strickland and fly rivers, Papua New Guinea JF - Journal of Geophysical Research-Earth Surface Y1 - 2008 A1 - Alin, S. R. A1 - Aalto, R. A1 - Goñi, M. A. A1 - Richey, J. E. A1 - Dietrich, W. E. AB - [1] The highstanding islands of Oceania are recognized as a source of significant particulate organic carbon delivered to nearshore marine environments. The existing data on carbon export in Oceania are largely derived from small mountainous watersheds ( VL - 113 IS - F1 N1 - id: 1870; 251HH Times Cited:4 Cited References Count:75Y JO - Biogeochemical characterization of carbon sources in the strickland and fly rivers, Papua New Guinea ER - TY - JOUR T1 - Bomb radiocarbon age validation of Pacific ocean perch (Sebastes alutus) using new statistical methods JF - Canadian Journal of Fisheries and Aquatic Sciences Y1 - 2008 A1 - Kastelle, C. R. A1 - Kimura, D. K. A1 - Goetz, B. J. AB - We used bomb-produced radiocarbon (C-14) to validate ages of Pacific ocean perch (Sebastes alutus), which are routinely estimated with the cut-and-burn method at the Alaska Fisheries Science Center (Seattle, Washington, USA). New statistical methods to compare Delta C-14 in validation samples with a reference chronology are introduced: (i) calculating confidence intervals around the LOESS-smoothed Delta C-14 reference chronology using simultaneous inference; (ii) purposely adding biases to the validation sample ages and then analyzing the sum of squared residuals of the validation samples' Delta C-14 about the LOESS-smoothed reference chronology; and (iii) standardizing the Delta C-14 measurements from the validation sample to better fit the reference chronology. Standardized Delta C-14 measurements are particularly useful when researchers suspect that environmental and biological differences between the validation samples and the reference chronology may exist that affect the level, but not the timing, of Delta C-14 in the samples. These new methods can be applied simultaneously. Two previous bomb radiocarbon studies on canary rockfish (Sebastes pinniger) and black drum (Pogonias cromis) were reanalyzed, further illustrating the usefulness of these new methods. VL - 65 IS - 6 N1 - id: 1832; 322ER Times Cited:1 Cited References Count:35Y JO - Bomb radiocarbon age validation of Pacific ocean perch (Sebastes alutus) using new statistical methods ER - TY - JOUR T1 - Bomb radiocarbon chronologies in the Arctic, with implications for the age validation of lake trout (Salvelinus namaycush) and other Arctic species JF - Canadian Journal of Fisheries and Aquatic Sciences Y1 - 2008 A1 - Campana, S. E. A1 - Casselman, J. M. A1 - Jones, C. M. AB - Radiocarbon generated by atmospheric testing of nuclear weapons (bomb radiocarbon) produced a strong signal with an abrupt onset in the 1950s, which serves as a dated marker for tracing oceanic circulation and confirming age in animals forming growth bands. Here, we report the first prebomb and postbomb radiocarbon chronologies for marine and freshwater environments in the Canadian Arctic, extend the radiocarbon chronology for the northwest Atlantic Ocean, and use the onset of the bomb signal to validate our age interpretations of lake trout (Salvelinus namaycush) in Arctic lakes. Both surface and deepwater Arctic chronologies became detectable on or around 1958, similar to the year of onset elsewhere in the world. In contrast, the freshwater Arctic chronology increased sharply in 1957, with a peak value sixfold higher than the adjacent marine environment. The radiocarbon content of the adult otolith core validated our age interpretation criteria for Arctic lake trout to an age of at least 50 years. Otolith growth in such slow-growing fish was so low as to be unresolvable under conventional examination with a dissecting microscope. With these new radiocarbon reference chronologies, age validation of a large number of Arctic organisms should now be possible. VL - 65 IS - 4 N1 - id: 804; 285MD Times Cited:7 Cited References Count:41Y JO - Bomb radiocarbon chronologies in the Arctic, with implications for the age validation of lake trout (Salvelinus namaycush) and other Arctic species ER - TY - JOUR T1 - C-14 as a tracer of labile organic matter in Antarctic benthic food webs JF - Deep-Sea Research Part Ii-Topical Studies in Oceanography Y1 - 2008 A1 - Purinton, B. L. A1 - DeMaster, D. J. A1 - Thomas, C. J. A1 - Smith, C. R. AB - C-14 measurements were made on surface plankton, particle-trap material, surface sediment, benthic invertebrate gut contents, and body tissue samples to assess the effectiveness of this radioisotope as a tracer of labile organic carbon in Antarctic benthic food webs. Samples were collected on five cruises to the West Antarctic Peninsula (WAP) shelf between November 1999 and March 2001 as part of the Food for Benthos on the ANtarctic Continental-Shelf (FOODBANCS) Project. The 14C contents of the body tissues from a variety of deposit feeders (-126 +/- 13 per mil) were substantially enriched relative to the surface sediment (-234 +/- 13 per mil) and statistically similar to the organic matter collected in plankton tows (-135 +/- 10 per mil), indicating that recently produced marine plankton are the primary source of nutrition for these deposit feeders on the West Antarctic shelf. Selective ingestion was the primary feeding strategy used by echiuran worms and certain holothurians (i.e. Peniagone vignoni) for incorporating labile organic carbon into their tissues as demonstrated by the large differences (105 +/- 13 per mil) between surface sediment and gut content C-14 activities. In contrast, digestive and/or assimilatory, selection was the predominant strategy used by an irregular urchin (Amphipneustes lorioli) and several other holothurians (Protelpidia murrayi, Bathyplotes fuscivinculum and the head-clown conveyor belt feeder, Molpadia musculus), as demonstrated by large differences (42 +/- 7 per mil) between the 14C activities of their foregut or whole-gut organic contents and their body tissues. Despite large fluctuations in carbon export from the euphotic zone, benthic feeding strategies remained essentially constant over the 15-month sampling period. No seasonal variation was evident in either the 14C abundance of the deposit-feeder body tissues, or in the 14C abundance of their gut contents. The mean C-14 abundance in the body tissues of the two sub-surface deposit feeders (A. lorioli and M. musculus; mean = -136.2 +/- 8.5 per mil) was distinct (p = 0.0008) from the mean 14C abundance in the body tissues of the four surface deposit feeders (echiuran worm, P vignoni, P. murrayi, and B. fusciviculum; -122.6 +/- 12.3 per mil). The mean 14 C abundance of the gut contents from the sub-surface deposit feeders (-178.0 +/- 18.6 per mil) also was significantly depleted (p = 0.0009) relative to that of the surface deposit feeders (-149.5 +/- 26.6 per mil). The 14C measurements proved to be a much more sensitive tracer for tracking labile organic carbon during ingestive and assimilatory processes than the stable isotopes of carbon or nitrogen. (C) 2008 Elsevier Ltd. All rights reserved. VL - 55 IS - 22-23 N1 - id: 1854; 386VU Times Cited:7 Cited References Count:98Y JO - C-14 as a tracer of labile organic matter in Antarctic benthic food webs ER - TY - BOOK T1 - A canyon through time : archaeology, history, and ecology of the Tecolote Canyon area, Santa Barbara County, California Y1 - 2008 A1 - Erlandson, Jon M. A1 - Rick, Torben C. A1 - Vellanoweth, Ren L. PB - University of Utah Press CY - Salt Lake City N1 - id: 1907 ER - TY - JOUR T1 - Carbonate cycle and its control factors in Kuroshio source region during the last 190ka BP JF - Yanshi Xuebao = Acta Petrologica Sinica Y1 - 2008 A1 - Jingtao, Zhao A1 - Chang, Fengming A1 - Li, Tiegang A1 - Qingyun, Nan A1 - Li, Qing AB - Two deep sea cores (Ph05-5, 16.05 degrees N, 124.34 degrees E, water depth 3382m and WP3:22.15 degrees N, 122.95 degrees E, water depth 2700m) retrieved from the Kuroshio source region of the western Philippine Sea were selected to carry out the CaCO VL - 24 SN - 1000-0569, 1000-0569 IS - 6 N1 - id: 1934; NO: Source type: scholarlyjournals; Object type: Article; Copyright: GeoRef in Process, Copyright 2011, American Geosciences Institute. After editing and indexing, this record will be added to Georef.; CSAUnique: 577070-23; AccNum: 577070-23; ISSN: 1000-0569; Peer Reviewed: true ER - TY - JOUR T1 - Catastrophic hurricane history revealed by organic geochemical proxies in coastal lake sediments: a case study of Lake Shelby, Alabama (USA) JF - Journal of Paleolimnology Y1 - 2008 A1 - Lambert, W. Joe A1 - Aharon, Paul A1 - Rodriguez, Antonio B. AB - We developed a new method for reconstructing millennia-long hurricane records from coastal environments that uses Organic Geochemical Proxies (OGPs) of organic carbon and nitrogen concentrations and their delta C-13 and delta N-15 compositions. The new method is independent of presence/absence of sand layers and improves significantly the severe-storm history resolution. The subject of this investigation is a 1.5 m long sediment core raised at 2.8 m water depth from the center of Lake Shelby, Alabama, a freshwater lake located approximately 250 m from the Gulf of Mexico, from which an overwash sand-layer based record was previously derived. The core contains two distinct sediment units; an upper 62 cm thick, fine-grained, organic-rich lacustrine sapropel (gyttja) that shows no visible structures except one sand lamina at 23.7 cm depth, and an underlying 90 cm thick, organic-poor lagoon/estuary clay unit. The sapropel unit was deposited over a 682 +/- 30 cal year time interval (1320-2002 A.D.) with a mean sedimentation rate of 0.79 +/- 0.04 mm/year. Lake Shelby's water column exhibits two contrasting states based on water chemistry surveys (i) an "isolated", stratified, mode under calm weather conditions with a relatively low trophic state, and (ii) a "flooded" mode occurring during storm surges when nutrient-rich seawater floods the lake. Statistically significant delta C-13 and delta N-15 positive excursions in organic matter, up to maximum values of -25 (parts per thousand PDB) and 4 (parts per thousand Air N-2), respectively, are interpreted as geochemical responses to the marine intrusions that fertilize the lake, increase light availability, and cause eutrophication spikes. Detailed OGPs analyses crossing a sand layer that offers visual evidence of a catastrophic hurricane overwash event at 1717 A.D. exhibit large delta C-13 and delta N-15 positive shifts bounded by rapid returns to base values, thus confirming the validity of the hurricane identification by the OGPs model. Our data indicate that 11 catastrophic hurricanes hit the Alabama coast over the past 682 years with a rough recurrence interval of one in 62 years. VL - 39 IS - 1 N1 - id: 2037; PT: J; UT: WOS:000251730600010 JO - Catastrophic hurricane history revealed by organic geochemical proxies in coastal lake sediments: a case study of Lake Shelby, Alabama (USA) ER - TY - JOUR T1 - Changes in the composition of organic matter from prodeltaic sediments after a large flood event (Po River, Italy) JF - Geochimica et Cosmochimica Acta Y1 - 2008 A1 - Tesi, T. A1 - Langone, L. A1 - Goñi, M. A. A1 - Miserocchi, S. A1 - Bertasi, F. AB - The Po River (Italy) experienced a 100-year flood in October 2000. Surface sediments (0-1 cm) from cross-shelf transects were collected in the Po prodelta area (Adriatic Sea) in December 2000, in order to describe the distribution of organic matter (OM) along the main sediment dispersal system immediately after the flood event. Stations were subsequently reoccupied in October 2001 and April 2002. This sampling program provided a special opportunity to characterize the initial surficial flood deposit and the evolution of its associated OM over the course of 2 years. CuO oxidation, elemental, delta C-13, Delta C-14, and grain-size analyses were carried out to characterize the source, age, and spatial variability of sedimentary OM. Statistical analysis (PERMANOVA) was then applied to investigate temporal changes in different portions of the Po prodelta area. Isotopic and biomarker data suggest that the sedimentary OM in the flood deposit was initially dominated by aged (Delta C-14(Dec-00) = -298.7 +/- 56.3%,), lignin-poor OM (Lambda(Dec-00) = 1.96 +/- 0.33 mg/100 mg OC), adsorbed on the fine material (clay(Dec-00) = 72.1 +/- 4.8%) delivered by the flood. In the 2 years following the flood, post-depositional processes significantly increased the content of lignin (Lambda(Oct-01) = 2.19 +/- 0.51 mg/100 mg OC; Lambda(Apr-02) = 2.61 +/- 0.63 mg/100 mg OC); and coarse material (silt and sand), while decreasing the contributions from aged OC (Delta C-14(Oct-01) = -255.7 +/- 32.8%.; Delta C-14(Apr-02) = -213.2 +/- 30.4%.) and fine fraction (clay(Oct-01) = 54.8 +/- 9.5%; clay(Apr-02) = 44.6 +/- 13.3%). The major changes were observed in the northern and central portions of the prodelta. (c) 2008 Elsevier Ltd. All rights reserved. VL - 72 IS - 8 N1 - id: 888; 290IO Times Cited:4 Cited References Count:66Y JO - Changes in the composition of organic matter from prodeltaic sediments after a large flood event (Po River, Italy) ER - TY - JOUR T1 - Constraints on the Pleistocene chronology of sediments from the Lomonosov Ridge JF - Paleoceanography Y1 - 2008 A1 - O'Regan, M. A1 - King, J. A1 - Backman, J. A1 - Jakobsson, M. A1 - Palike, H. A1 - Moran, K. A1 - Heil, C. A1 - Sakamoto, T. A1 - Cronin, T. M. A1 - Jordan, R. W. AB - [1] Despite its importance in the global climate system, age-calibrated marine geologic records reflecting the evolution of glacial cycles through the Pleistocene are largely absent from the central Arctic Ocean. This is especially true for sediments older than 200 ka. Three sites cored during the Integrated Ocean Drilling Program's Expedition 302, the Arctic Coring Expedition ( ACEX), provide a 27 m continuous sedimentary section from the Lomonosov Ridge in the central Arctic Ocean. Two key biostratigraphic datums and constraints from the magnetic inclination data are used to anchor the chronology of these sediments back to the base of the Cobb Mountain subchron ( 1215 ka). Beyond 1215 ka, two best fitting geomagnetic models are used to investigate the nature of cyclostratigraphic change. Within this chronology we show that bulk and mineral magnetic properties of the sediments vary on predicted Milankovitch frequencies. These cyclic variations record "glacial'' and "interglacial'' modes of sediment deposition on the Lomonosov Ridge as evident in studies of ice-rafted debris and stable isotopic and faunal assemblages for the last two glacial cycles and were used to tune the age model. Potential errors, which largely arise from uncertainties in the nature of downhole paleomagnetic variability, and the choice of a tuning target are handled by defining an error envelope that is based on the best fitting cyclostratigraphic and geomagnetic solutions. VL - 23 IS - 1 N1 - id: 868; 281YL Times Cited:22 Cited References Count:55; YY JO - Constraints on the Pleistocene chronology of sediments from the Lomonosov Ridge ER - TY - JOUR T1 - Contrasting lipid biomarker composition of terrestrial organic matter exported from across the Eurasian Arctic by the five great Russian Arctic rivers JF - Global Biogeochemical Cycles Y1 - 2008 A1 - van Dongen, B. E. A1 - Semiletov, I. A1 - Weijers, J. W. H. A1 - Gustafsson, O. R. AB - Surface sediments outside the great Russian Arctic rivers (GRARs; Ob, Yenisey, Lena, Indigirka, and Kolyma) were investigated for their lipid biomarker composition to elucidate compositional distinctions of the exported organic matter (OM) across this continent-scale climosequence of the Siberian Arctic. The lipid biomarker composition is dominantly terrestrial (high molecular weight (HMW) n-alkanols, n-alkanoic acids, n-alkanes; branched glycerol dialkyl glycerol tetraethers (GDGTs), beta-sitosterol, other sterols, and triterpenoids) with only minor marine contributions (e. g., the ratio of terrigenous-to-aquatic n-alkanes was 17-80, the TOC/TN ratio was 10-16, and the branched and isoprenoid tetraether (BIT) index > 0.88). There is a large contribution of C-23 and C-25 homologues relative to other long-chained n-alkanes, suggesting substantial contribution of probably Sphagnum-derived OM. The C-23 and C-25 contribution decreases eastward, signaling either a decrease in the potential contribution of Sphagnum or a shift within the n-alkane distribution of Sphagnum species or increased aeolian input, due to more arid conditions in the east. Other distinctions in molecular OM composition across the climosequence include increased concentrations of both HMW n-alkanoic acids and beta-sitosterol relative to HMW n-alkanes in the eastern sediments. This suggests that the OM exported by the eastern GRARs is, despite their higher bulk radiocarbon ages, less degraded, which is consistent with increasing permafrost and a shorter annual thaw period in eastern Siberia. Taken together, this benchmark study of the current composition of terrestrially exported OM suggests distinguishing continent-scale trends in molecular composition of the OM across the west-east set of GRARs, which reflects both differences in vegetation and climate. If the climate in the eastern Russian Arctic region becomes more like the current state in the western part, these results would predict a greater degree of decomposition of the old terrestrial OM released by the eastern GRARs and thus greater remineralization and release as CO2 and methane. VL - 22 IS - 1 N1 - id: 819; 261FT Times Cited:10 Cited References Count:112Y JO - Contrasting lipid biomarker composition of terrestrial organic matter exported from across the Eurasian Arctic by the five great Russian Arctic rivers ER - TY - JOUR T1 - Cooling and changing seasonality in the Southern Alps, New Zealand during the Antarctic Cold Reversal JF - Quaternary Science Reviews Y1 - 2008 A1 - Vandergoes, M. J. A1 - Dieffenbacher-Krall, A. C. A1 - Newnham, R. M. A1 - Denton, G. H. A1 - Blaauw, M. AB - A comprehensively C-14 AMS dated pollen and chironomid record from Boundary Stream Tarn provides the first chironomid-derived temperature reconstruction to quantify temperature change during Lateglacial times (17,500-10,000 cal yr BP) in the Southern Alps, New Zealand. The records indicate a ca 1000-year disruption to the Lateglacial warming trend and an overall cooling consistent with the Antarctic Cold Reversal (ACR). The main interval of chironomid-inferred summer temperature depression (similar to 2-3 degrees C) lasted about 700 years during the ACR. Following this cooling event, both proxies indicate a warming step to temperatures slightly cooler than present during the Younger Dryas chronozone (12,900-11,500 cal yr BP). These results highlight a direct linkage between Antarctica and mid-latitude terrestrial climate systems and the largely asynchronous nature of the interhemispheric climate system during the last glacial transition. The greater magnitude of temperature changes shown by the chironomid record is attributed to the response of the proxies to differences in seasonal climate with chironomids reflecting summer temperature and vegetation more strongly controlled by duration of winter or by minimum temperatures. These differences imply stronger seasonality at times during the Lateglacial, which may explain some of the variability between other paleoclimate records from New Zealand and have wider implications for understanding differences between proxy records for abrupt climate change. (C) 2007 Elsevier Ltd. All rights reserved. VL - 27 IS - 5-6 N1 - 293rhTimes Cited:27Cited References Count:64 JO - Cooling and changing seasonality in the Southern Alps, New Zealand during the Antarctic Cold Reversal ER - TY - JOUR T1 - Coupled North Atlantic slope water forcing on Gulf of Maine temperatures over the past millennium JF - Climate Dynamics Y1 - 2008 A1 - Wanamaker, Alan D. A1 - Kreutz, Karl J. A1 - öne, Bernd R. A1 - Pettigrew, Neal A1 - Borns, Harold W. A1 - Introne, Douglas S. A1 - Belknap, Daniel A1 - Maasch, Kirk A. A1 - Feindel, Scott AB - To investigate ocean variability during the last millennium in the Western Gulf of Maine (GOM), we collected a 142-year-old living bivalve (Arctica islandica L.) in 2004, and three fossil A. islandica shells (calibrated 14CAMS = 1030 ± 78 ad; 1320 ± 45 ad; 1357 ± 40 ad) for stable isotope and growth increment analysis. A statistically significant relationship exists between modern GOM temperature records [shell isotope-derived (30 m) (r = −0.79; P < 0.007), Prince 5 (50 m) (r = −0.72; P < 0.019), Boothbay Harbor SST (r = −0.76; P < 0.011)], and Labrador Current (LC) transport data from the Eastern Newfoundland Slope during 1993–2003. In all cases, as LC transport increased, GOM water temperatures decreased the following year. Decadal trends in the North Atlantic Oscillation (NAO) and the Atlantic Multidecadal Oscillation (AMO) influence GOM water temperatures in the most recent period, with water temperatures decreasing during NAO and AMO negative modes most likely linked to LC transport and Gulf Stream interaction. Mean shell-derived isotopic changes (δ18Oc) during the last 1,000 years were +0.47‰ and likely reflect a 1–2°C cooling from 1000 ad to present. Based on these results, we suggest that observed cooling in the GOM during the last millennium was due to increased transport and/or cooling of the LC, and decreased Gulf Stream influence on the GOM. VL - 31 UR - http://www.springerlink.com/index/pdf/10.1007/s00382-007-0344-8 IS - 2 ER - TY - JOUR T1 - Deepwater circulation on Blake Outer Ridge (western North Atlantic) during the Holocene, Younger Dryas, and Last Glacial Maximum JF - Geochemistry Geophysics Geosystems Y1 - 2008 A1 - Evans, H. K. A1 - Hall, I. R. AB - Three depth transects containing a total of 33 sediment cores were investigated along the Blake Outer Ridge in the western subtropical North Atlantic. Sortable silt mean ((SS) over bar) grain size and stable isotope records were used to assess the position and relative intensity of the Western Boundary Undercurrent (WBUC) during the Holocene, the Last Glacial Maximum (LGM), and the Younger Dryas (YD) intervals. The Holocene reconstruction is consistent with modern physical and chemical hydrographic measurements in the area, suggesting a deep position for the fast flowing core of the WBUC (3000-4000 m, deepening to similar to 4500 m water depth on the ridge flanks) and a water column dominated by North Atlantic Deep Water (NADW). The LGM and YD reconstructions show that a comparable hydrographic regime was present during both these intervals, suggesting a similar mode of circulation that was appreciably different from the Holocene reconstruction. The WBUC's zone of maximum flow speed during these intervals is suggested to have shifted above 2500 m water depth, consistent with nutrient depleted Glacial North Atlantic Intermediate Water formation with an increasing influence of Southern Source Water (SSW) beneath. Below 4000 m water depth, (SS) over bar results hint at increased SSW flow vigor during both the LGM and YD with higher flow speeds than during the Holocene. This study provides a framework for aiding the interpretation of time series records of paleocurrent flow speed changes in the region of the WBUC. VL - 9 N1 - id: 839; 281XG Times Cited:1 Cited References Count:84Y JO - Deepwater circulation on Blake Outer Ridge (western North Atlantic) during the Holocene, Younger Dryas, and Last Glacial Maximum ER - TY - JOUR T1 - Deglacial variability in the surface return flow of the Atlantic meridional overturning circulation JF - Paleoceanography Y1 - 2008 A1 - Came, R. E. A1 - Oppo, D. W. A1 - Curry, W. B. A1 - Lynch-Stieglitz, J. AB - [1] Benthic foraminiferal Cd/Ca from a Florida Current sediment core documents the history of the northward penetration of southern source waters within the surface return flow of the Atlantic meridional overturning circulation (AMOC). Cd seawater estimates (Cd-W) indicate that intermediate-depth southern source waters crossed the equator and contributed to the Florida Current during the Bolling-Allerod warm period of the last deglaciation, consistent with evidence of only a modest AMOC reduction compared to today. The Cd-W estimates also provide the first paleoceanographic evidence of a reduction in the influence of intermediate-depth southern source waters within the Florida Current during the Younger Dryas, a deglacial cold event characterized by a weak North Atlantic AMOC. Our results reveal a close correspondence between the northward penetration of intermediate-depth southern source waters and the influence of North Atlantic Deep Water, suggesting a possible link between intermediate-depth southern source waters and the strength of the Atlantic AMOC. VL - 23 IS - 1 N1 - id: 838; 281YL Times Cited:4 Cited References Count:41; YY JO - Deglacial variability in the surface return flow of the Atlantic meridional overturning circulation ER - TY - JOUR T1 - Determination of biodiesel blending percentages using natural abundance radiocarbon analysis: Testing the accuracy of retail biodiesel blends JF - Environmental Science & Technology Y1 - 2008 A1 - Reddy, C. M. A1 - DeMello, J. A. A1 - Carmichael, C. A. A1 - Peacock, E. E. A1 - Xu, L. A1 - Arey, J. S. AB - Blends of biodiesel and petrodiesel are being used increasingly worldwide. Due to several factors, inaccurate blending of these two mixtures can occur. To test the accuracy of biodiesel blending, we developed and validated a radiocarbon-based method and then analyzed a variety of retail biodiesel blends. Error propagation analysis demonstrated that this method calculates absolute blend content with +/- 1% accuracy, even when real-world variability in the component biodiesel and petrodiesel sources is taken into account. We independently confirmed this accuracy using known endmembers and prepared mixtures. This is the only published method that directly quantifies the carbon of recent biological origin in biodiesel blends. Consequently, it robustly handles realistic chemical variability in biological source materials and provides unequivocal apportionment of renewable versus nonrenewable carbon in a sample fuel blend. Analysis of retail biodiesel blends acquired in 2006 in the United States revealed that inaccurate blending happens frequently. Only one out of ten retail samples passed the specifications that the United States Department of Defense requires for blends that are 20% biodiesel (v/v; referred to as B20). VL - 42 IS - 7 N1 - id: 1864; 281JN Times Cited:3 Cited References Count:39; YY JO - Determination of biodiesel blending percentages using natural abundance radiocarbon analysis: Testing the accuracy of retail biodiesel blends ER - TY - JOUR T1 - Differences in sediment organic matter composition and PAH weathering between non-vegetated and recently vegetated fuel oiled sediments JF - International Journal of Phytoremediation Y1 - 2008 A1 - Gregory, Samuel T., III A1 - Nichols, Elizabeth Guthrie AB - We examined polycyclic aromatic hydrocarbon (PAH) attenuation in contaminated field sediments after only 2 years of plant growth. We collected sediments from vegetated and non-vegetated areas at the Indiana Harbor Canal (IHC), an industrialized area with historic petroleum contamination of soils and sediments. PAH concentrations, PAH weathering indices, and organic matter composition in sediments colonized by Phragmites, cattails, or willow trees were compared to the same indices for non-vegetated sediments. We hypothesized that bulk sediment and humin fractions with measurable increases in plant organic matter content would show measurable changes to PAH attenuation as indicated by more weathered PAH diagnostic ratios or reduced PAH concentrations. Carbon-normalized PAH concentrations were lower in vegetated bulk sediments but higher in vegetated humin fractions relative to non-vegetated sediment fractions. Total organic carbon content was not indicative of more weathered N(3)/P(2) ratios or reduced PAH concentrations in vegetated sediment fractions. More weathered N(3)/P(2) ratios were observed with increased modern carbon (plant carbon) content of vegetated sediment fractions. Phragmites sediments contained more modern carbon (plant carbon) and more weathered PAH ratios [C(3)-naphthalenes and C(2)-phenanthrenes (N(3)/P(2))] than willow, cattail, and non-vegetated sediments. VL - 10 IS - 6 N1 - id: 2025; PT: J; UT: WOS:000258774100001 JO - Differences in sediment organic matter composition and PAH weathering between non-vegetated and recently vegetated fuel oiled sediments ER - TY - JOUR T1 - Dogs, humans and island ecosystems: the distribution, antiquity and ecology of domestic dogs (Canis familiaris) on California's Channel Islands, USA JF - Holocene Y1 - 2008 A1 - Rick, Torben C. A1 - Walker, Phillip L. A1 - Willis, Lauren M. A1 - Noah, Anna C. A1 - Erlandson, Jon M. A1 - Vellanoweth, Rene L. A1 - Braje, Todd J. A1 - Kennett, Douglas J. AB - Archaeologists have made significant contributions to our understanding of ancient island environments, including the timing and implications of the introduction of non-native animals (pigs, chickens, rats, etc.) by humans. Here, we focus on the historical ecology and biogeography of domestic dogs (Canis familiaris) on California's Channel Islands during the Holocene. Dogs are the only animal known unequivocally to have been introduced by Native Americans to the islands, but relatively little is known about their distribution, antiquity or influence on native island fauna and flora. We identified a minimum of 96 dogs from 42 archaeological sites on six of the eight islands. Dogs were present for at least 6000 years and appear to have increased in abundance through time. Our analysis suggests that dogs, along with humans and island foxes (Urocyon littoralis), would have had an impact on native animals and ecosystems, especially breeding birds and marine mammals, togs and island foxes likely competed with one another for food, however, and the impacts of dogs on island ecosystems may have been reduced by the presence of island foxes and the symbiotic relationship between dogs and humans. Dogs have been removed from all but one of the islands today, eliminating one of the few terrestrial carnivores present for most of the Holocene. VL - 18 IS - 7 N1 - id: 2063; PT: J; UT: WOS:000260339000006 JO - Dogs, humans and island ecosystems: the distribution, antiquity and ecology of domestic dogs (Canis familiaris) on California's Channel Islands, USA ER - TY - JOUR T1 - Earthquakes generated from bedding plane-parallel reverse faults above an active wedge thrust, Seattle fault zone JF - Geological Society of America Bulletin Y1 - 2008 A1 - Kelsey, Harvey M. A1 - Sherrod, Brian L. A1 - Nelson, Alan R. A1 - Brocher, Thomas M. AB - A key question in earthquake hazard analysis is whether individual faults within fault zones represent independent seismic sources. For the Seattle fault zone, an upper plate structure within the Cascadia convergent margin, evaluating seismic hazard requires understanding how north-side-up, bedding-plane reverse faults, which generate late Holocene fault scarps, interact with the north-vergent master-ramp thrust and overlying backthrust of the fault zone. A regional uplift at A.D. 900-930 involved an earthquake that nucleated at depth and included slip on both the master-ramp thrust and the backthrust. This earthquake also included slip on some of the VL - 120 IS - 11-12 N1 - id: 2019; PT: J; UT: WOS:000260737900015 JO - Earthquakes generated from bedding plane-parallel reverse faults above an active wedge thrust, Seattle fault zone ER - TY - THES T1 - The Effects of Ice Shelf Break-up on Changes in Particulate Carbon Distribution and Composition, Examples from the Larsen System, Antarctica Y1 - 2008 A1 - Roe, K. M. PB - Hamilton College CY - Clinton, New York VL - Dissertation/Thesis ER - TY - JOUR T1 - Environmental and Climatic Controls on the Occurrence and Abundance of Long Chain Alkenones in Lakes of the Interior United States JF - Eos, Transactions, American Geophysical Union Y1 - 2008 A1 - Toney, J. L. A1 - Fritz, S. A1 - Baker, P. A1 - Grim, E. A1 - Nyren, P. A1 - Theroux, S. A1 - Huang, Y. VL - 89 IS - 83 N1 - id: 892 ER - TY - CONF T1 - Environmental Factors Controlling Community Structure, Morphology and Linear Extension of Mid-Holocene Reef Corals from Cañada Honda, Southwestern, Dominican Republic T2 - Proceedings of the 11th International Coral Reef Symposium, Ft. Lauderdale, Florida Y1 - 2008 A1 - Cuevas, D. A1 - Sherman, C. A1 - Ramírez, W. A1 - Hubbard, D. KW - Caribbean KW - Holocene KW - ICRS11 KW - Lessons from the past KW - linear extension KW - siltation AB - The Cañada Honda (CH) fossil coral reef, located in SW Dominican Republic, provides a unique opportunity to examine reef accretion in a high-sedimentation environment between 9.0-5.0 ky ago. Annual linear extension of fossil corals was determined for comparison with data from modern coral reefs. The reef is characterized by the high abundance of sediment-tolerant coral species, their tendency to form almost monospecific stands and grow as domes-cones with ragged margins. Also, colonies of Montastraea faveolata commonly contain bands of sediment incorporated within their skeletons. Calibrated radiocarbon ages of fossil corals range from 9,256±137 to 6,737±94.5 BP. Correlation with Holocene sea-level curves indicates that most corals on CH developed at depths greater than 15m. Growth rates varied from 0.09-0.44 cm/yr and suggest reduced light penetration caused by coral growth at such depths. Reef sediment is characterized by more than 85% carbonate material. A significant portion of the carbonate is allochtonous and was derived from nearby Neogene limestones. The reef was able to survive under these conditions because of the high carbonate content of incoming terrigenous sediment and that storms probably occurred sporadically providing intervening lowsedimentation periods during which reef corals could respond and grow back, “keeping-up” with sedimentation. JF - Proceedings of the 11th International Coral Reef Symposium, Ft. Lauderdale, Florida N1 - id: 1979 ER - TY - JOUR T1 - Episodic reductions in bottom-water currents since the last ice age JF - Nature Geoscience Y1 - 2008 A1 - Praetorius, S. K. A1 - McManus, J. F. A1 - Oppo, D. W. A1 - Curry, W. B. AB - Past changes in the freshwater balance of the surface North Atlantic Ocean are thought to have influenced the rate of deep-water formation, and consequently climate(1,2). Although water-mass proxies are generally consistent with an impact of freshwater input on meridional overturning circulation(3), there has been little dynamic evidence to support this linkage. Here we present a 25,000 year record of variations in sediment grain size from south of Iceland, which indicates vigorous bottom-water currents during both the last glacial maximum and the Holocene period. Together with reconstructions of North Atlantic water-mass distribution, vigorous bottom currents suggest a shorter residence time of northern-source waters during the last glacial maximum, relative to the Holocene period. The most significant reductions in flow strength occur during periods that have been associated with freshening of the surface North Atlantic. The short-term deglacial oscillations in bottom current strength are closely coupled to changes in Greenland air temperature, with a minimum during the Younger Dryas cold reversal and a maximum at the time of rapid warming at the onset of the Holocene. Our results support a strong connection between ocean circulation and rapid climate change. 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McManus, Jerry F. Oppo, Delia W. Curry, William B. Nature publishing group New york; YY JO - Episodic reductions in bottom-water currents since the last ice age ER - TY - JOUR T1 - Eruptive history, geochronology, and magmatic evolution of the Puyehue-Cordon Caulle volcanic complex, Chile JF - Geological Society of America Bulletin Y1 - 2008 A1 - Singer, B. S. A1 - Jicha, B. R. A1 - Harper, M. A. A1 - Naranjo, J. A. A1 - Lara, L. E. A1 - Moreno-Roa, H. AB - Forty-three Ar-40/Ar-39 age determinations of lava flows, domes, ignimbrites, and dikes, plus C-14 dates from seven distal tephra layers, combined with stratigraphy, geochemistry, and Sr and Th isotope data, establish an eruptive chronology for the Puyehue-Cordon Caulle volcanic complex at 40.5 degrees S in the Andean southern volcanic zone (SVZ). The complex preserves similar to 131 km(3) of lava and tephra that erupted from numerous vents widely separated in time and space. Approximately 80% of the total volume consists of basaltic to andesitic lava that formed two broad shield volcanoes between 314 and 70 ka. The modern Puyehue stratovolcano was built on the southerly shield during the past 69 k.y. following a hiatus of 25 k.y. Puyehue has erupted similar to 15 km(3) of basaltic to rhyolitic magma that spans the entire compositional range found in the southern SVZ and evolved via at least six phases including: (1) basaltic andesitic to dacitic lavas between 69 and 32 ka, (2) a shift to bimodal magma compositions that is first expressed by a rhyodacite mingled with inclusions of MgO-rich basaltic andesite at 34 ka, (3) dacitic to rhyolitic flows and domes from 19 to 12 ka, (4) basaltic to basaltic andesitic flows between 15 and 12 ka, (5) subsequent rhyolitic dome growth in several effusive and explosive stages between 7 and 5 ka, followed by (6) a powerful series of phreatomagmatic and sub-Plinian eruptions at ca. 1.1 ka that obliterated the preceding rhyolite domes and formed the present 2.5-km-diameter, 280-m-deep summit crater. Along the Cordon Caulle fissure zone, similar to 5 km(3) of rhyodacitic to rhyolitic lavas, domes, and cones have formed during the past similar to 16.5 k.y., including explosive and effusive eruptions in 1921-1922 and 1960.Eruptive rates were nonuniform over time, with background growth at 0.04 km(3)/k.y. or less, punctuated by spurts at up to 0.90 km(3)/ k.y. The time-averaged rate, 0.42 km(3)/k.y., is nearly double that at the Tatara-San Pedro complex 500 km to the north during the past 300 k.y. These findings indicate that within a single are the magmatic and eruptive fluxes at individual frontal volcanoes can be highly variable. The last three stratocone-building events on Puyehue began during periods of deglaciation, suggesting a relationship between unloading of ice and ease of magma ascent. Puyehue basalt exhibits subtle changes in U-238-Th-230, Sr-87/Sr-86, and trace element composition over time that signal shifts in the composition and degree of melting of the mantle wedge, or the extent to which basalt was modified by assimilation of heterogeneous crustal melts. The complex has become exceptionally bimodal and more explosive over time with recent rhyolites evolving by extreme crystal fractionation of malic magma and lesser volumes of andesite and dacite created via mixing of rhyolite and basalt. Despite the high flux of basalt during the past 300 k.y., no large silicic magma reservoir formed in the upper crust. Instead, U-238-Th-230 data favor rapid ascent of several small bodies of basaltic and silicic magma from the lower crust, promoted perhaps by conduits that reflect strike-slip faulting beneath the complex. VL - 120 IS - 5-6 N1 - 300ujTimes Cited:61Cited References Count:55 JO - Eruptive history, geochronology, and magmatic evolution of the Puyehue-Cordon Caulle volcanic complex, Chile ER - TY - JOUR T1 - Evolution in upper water structure and paleoproductivity in the northern margin of the western pacific warm pool and its forcing mechanism during the last 190 ka B.P.-evidence from nannofossil, foraminifera and their isotope com position JF - Oceanologia et Limnologia Sinica Y1 - 2008 A1 - Zhao, Jingtao A1 - Li, Tiegang A1 - Chang, Fengming A1 - Jiang, Bo VL - 39 IS - 4 N1 - id: 1932 JO - Evolution in upper water structure and paleoproductity in the northern margin of the western pacific warm pool and its forcing mechanism during the last 190 ka B.P.-evidence from nannofossil, foraminifera and their isotope com position ER - TY - JOUR T1 - Five Crescents from Cardwell: Context and Chronology of Chipped Stone Crescents at CA-SMI-679, San Miguel Island, California JF - Pacific Coast Archaeological Society Quarterly Y1 - 2008 A1 - Erlandson, Jon M. A1 - Braje, Todd J. VL - 40 IS - 1 N1 - id: 2065 ER - TY - JOUR T1 - Forty years later: What have we learned about the earliest human occupations of Santa Rosa Island, California? JF - North American Archaeologist Y1 - 2008 A1 - Reeder, Leslie A. A1 - Rick, Torben C. A1 - Erlandson, Jon M. VL - 29 IS - 2 N1 - id: 2078 ER - TY - JOUR T1 - The Global Stratotype Section and Point (GSSP) for the base of the Holocene Series/Epoch (Quaternary System/Period) in the NGRIP ice core RID B-5560-2008 RID F-1111-2011 JF - Episodes Y1 - 2008 A1 - Walker, Mike A1 - Johnsen, Sigfu's A1 - Rasmussen, Sune Olander A1 - Steffensen, Jorgen-Peder A1 - Popp, Trevor A1 - Gibbard, Philip A1 - Hoek, Wim A1 - Lowe, John A1 - Andrews, John A1 - Bjorck, Svante A1 - Cwynar, Les A1 - Hughen, Konrad A1 - Kershaw, Peter A1 - Kromer, Bernd A1 - Litt, Thomas A1 - Lowe, David J. A1 - Nakagawa, Takeshi A1 - Newnham, Rewi A1 - Schwander, Jakob AB - The Greenland ice core from NorthGRIP (NGRIP) contains a proxy climate record across the Pleistocene-Holocene boundary of unprecedented clarity and resolution. Analysis of an array of physical and chemical parameters within the ice enables the base of the Holocene, as reflected in the first signs of climatic warming at the end of the Younger Dryas/Greenland Stadial 1 cold phase, to be located with a high degree of precision. This climatic event is most clearly reflected in an. abrupt shaft in deuterium excess values, accompanied by more gradual changes in delta(18)O, dust concentration, a range of chemical species, and annual layer thickness. A timescale based on multi-parameter annual layer counting provides an age of 11,700 yr b2k (before AD2000) for the base of the Holocene, with, an estimated 2 sigma uncertainty of 99 yr: It is proposed that an archived core from this unique sequence should constitute the Global Stratotype Section and Point (GSSP) for the base of the Holocene Series/Epoch (Quaternary System/Period). VL - 31 SN - 0705-3797 IS - 2 N1 - id: 1988; PT: J; CT: 17th Congress of the International-Union-for-Quaternary-Research; CY: JUL 28-AUG 03, 2007; CL: Cairns, AUSTRALIA; SP: Int Union Quaternary Res; UT: WOS:000258669100017 ER - TY - JOUR T1 - Growth analysis and age validation of a deepwater Arctic fish, the Greenland halibut (Reinhardtius hippoglossoides) JF - Canadian Journal of Fisheries and Aquatic Sciences Y1 - 2008 A1 - Treble, M. A. A1 - Campana, S. E. A1 - Wastle, R. J. A1 - Jones, C. M. A1 - Boje, J. AB - The accuracy of age interpretations on a deep-sea, Arctic fish species, the Greenland halibut (Reinhardtius hippoglossoides) was tested using several age validation methods. Consistent annual growth increments were either not formed or not visible in either whole or sectioned otoliths from three fish marked with oxytetracyline and recaptured after 2-4 years at liberty. Bomb radiocarbon assays based on a local reference chronology indicated that both whole and sectioned otoliths underestimated age by 1-15 years, with an average of 6 years. Growth rates estimated using the tag recapture model GROTAG were consistent with growth rates based on the radiocarbon assays and were less than half that of previously reported growth rates. The failure of otolith sections to provide an accurate age is unusual, but may be symptomatic of very slow-growing species with unusually shaped otoliths. Greenland halibut living in the deep-sea, Arctic environment are slower growing and longer lived than previously suspected, suggesting that the age-structured basis for current fisheries management warrants careful examination. Our results highlight the importance of using rigorous tests of ageing accuracy for exploited species and confirm that such age validation methods can be applied successfully in challenging environments such as the deep sea or the Arctic. VL - 65 IS - 6 N1 - id: 806; 322ER Times Cited:3 Cited References Count:56Y JO - Growth analysis and age validation of a deepwater Arctic fish, the Greenland halibut (Reinhardtius hippoglossoides) ER - TY - JOUR T1 - Holocene erosion of the Lesser Himalaya triggered by intensified summer monsoon JF - Geology Y1 - 2008 A1 - Clift, P. D. A1 - Giosan, L. A1 - Biusztajn, J. A1 - Campbell, I. H. A1 - Allen, C. A1 - Pringle, M. A1 - Tabrez, A. R. A1 - Danish, M. A1 - Rabbani, M. M. A1 - Alizai, A. A1 - Carter, A. A1 - Lueckge, A. AB - Climate is one of the principal controls setting rates of continental erosion. Here we present the results of a provenance analysis of Holocene sediments from the Indus delta in order to assess climatic controls on erosion over millennial time scales. Bulk sediment Nd isotope analysis reveals a number of changes during the late Pleistocene and early Holocene (at 14-20,11-12 and 8-9 ka) away from erosion of the Karakoram and toward more sediment flux from the Himalaya. Radiometric Ar-Ar dating of muscovite and U-Pb dating of zircon sand grains indicate that the Lesser Himalaya eroded relatively more strongly than the Greater Himalaya as global climate warmed and the summer monsoon intensified after 14 ka. Monsoon rains appear to be the primary force controlling erosion across the western Himalaya, at least over millennial time scales. This variation is preserved with no apparent lag in sediments from the delta, but not in the deep Arabian Sea, due to sediment buffering on the continental shelf. VL - 36 IS - 1 N1 - id: 800; 247YL Times Cited:7 Cited References Count:27; YY JO - Holocene erosion of the Lesser Himalaya triggered by intensified summer monsoon ER - TY - JOUR T1 - Holocene multidecadal- to millennial-scale hydrologic variability on the South American Altiplano JF - Holocene Y1 - 2008 A1 - Ekdahl, E. J. A1 - Fritz, S. C. A1 - Baker, P. A. A1 - Rigsby, C. A. A1 - Coley, K. AB - Precipitation on the South American Altiplano varies at a range of temporal scales. A long-term secular increase in moisture availability from the early/mid Holocene to the present, driven by increasing summer insolation resulting from precessional changes in the Earth's orbit, has been documented in earlier studies. However, higher frequency Holocene variability is not yet understood. Here we present high-resolution diatom assemblage data from two small Altiplano lakes, Lago Lagunillas and Lago Umayo, indicating changes in effective moisture in the southern tropical Andes at decadal, centennial and millennial timescales throughout the mid to late Holocene. A strong millennial-scale component, similar in pacing to periods of increased ice-rafted debris flux in the North Atlantic, is observed in both lake records, which suggests that regional precipitation and North Atlantic climate variability are coupled at these scales. The interpretation of the higher frequency variability is hampered by the small number of high-resolution continental and marine records for comparison. VL - 18 IS - 6 N1 - id: 842; ISI Document Delivery No.: 341ZR Times Cited: 1 Cited Reference Count: 49 Ekdahl, Erik J. Fritz, Sherilyn C. Baker, Paul A. Rigsby, Catherine A. Coley, KirstinY JO - Holocene multidecadal- to millennial-scale hydrologic variability on the South American Altiplano ER - TY - JOUR T1 - A Holocene paleotemperature record based on radiolaria from the northern Okinawa Trough (East China Sea) JF - Quaternary International Y1 - 2008 A1 - Chang, Fengming A1 - Li, Tiegang A1 - Zhuang, Lihua A1 - Yan, Jun AB - Using a radiolarian-based transfer function, mean annual sea surface temperature (SST) and seasonal temperature range are reconstructed through the last 10,500yrs in the northern Okinawa Trough. Down-core SST estimates reveal that throughout the Holocene the changes of mean annual SST display a three-step trend: (i) an early Holocene continuous warming between 10,500 and 8500yr BP which ends up with a abrupt cooling at about 8200yr BP; (ii) a relatively stable middle Holocene with high SST that lasted until 3200yr BP; and (iii) a late-Holocene distinct SST decline between 3200 and 500yr BP. This pattern is in agreement with the ice core and terrestrial paleoclimatic records in the Chinese continent and other regions of the world. Five cooling events with abrupt mean annual SST drops, which occur at similar to 300-600, 1400, 3100, 4600-5100 and 8200yr BP, are recognized during the last 10,500yrs. Comparison of our results with records of GISP2 ice core and marine sediment in North Atlantic region suggests these cooling events are strongly coupled, which implies a possible significant climatic correlation between high- and low-latitude areas. (C) 2007 Elsevier Ltd and INQUA. All rights reserved. VL - 183 N1 - id: 1926; PT: J; UT: WOS:000257255700009 JO - A Holocene paleotemperature record based on radiolaria from the northern Okinawa Trough (East China Sea) ER - TY - JOUR T1 - Human impacts on ancient shellfish: a 10,000 year record from San Miguel Island, California JF - Journal of Archaeological Science Y1 - 2008 A1 - Erlandson, Jon M. A1 - Rick, Torben C. A1 - Braje, Todd J. A1 - Steinberg, Alexis A1 - Vellanoweth, Rene L. AB - We use measurements of more than 11,000 marine shells from 41 archaeological components to construct a 10,000 year record of human impacts on ancient mussel and abalone stocks on San Miguel Island, California. General reductions in the mean size of mussel and abalone shells gathered through time are attributed to growing human population and predation pressure. Based on comparison with historically documented changes in shellfish communities caused by the local extinction of sea otters in the 19th century, changes in mean shell size and the abundance of other shellfish species may have been facilitated by Native American predation on sea otters as early as 7500 years ago. Despite having measurable impacts on local ecosystems, Native Americans on San Miguel harvested huge quantities of shellfish throughout the Holocene. Such longterm harvests appear to have been sustained by an early emphasis on fishing at lower trophic levels, by periodically shifting village locations, and by intensifying the use of finfish and sea mammals through time. This pattern of "fishing up the food web" contrasts with many modern fisheries, suggesting that the study of ancient fisheries can help us better manage our own endangered coastal ecosystems. (c) 2008 Elsevier Ltd. All rights reserved. VL - 35 IS - 8 N1 - id: 2064; PT: J; UT: WOS:000257340000006 JO - Human impacts on ancient shellfish: a 10,000 year record from San Miguel Island, California ER - TY - JOUR T1 - The impact of vegetation on sedimentary organic matter composition and PAH desorption JF - Environmental Pollution Y1 - 2008 A1 - Nichols, Elizabeth Guthrie A1 - Gregory, Samuel T. A1 - Musella, Jennifer S. AB - Relationships between sedimentary organic matter (SOM) composition and PAH desorption behavior were determined for vegetated and non-vegetated refinery distillate waste sediments. Sediments were fractionated into size, density, and humin fractions and analyzed for their organic matter content. Bulk sediment and humin fractions differed more in organic matter composition than size/density fractions. Vegetated humin and bulk sediments contained more polar organic carbon, black carbon, and modern (plant) carbon than non-vegetated sediment fractions. Desorption kinetics of phenanthrene, pyrene, chrysene, and C(3)-phenanthrene/anthracenes from humin and bulk sediments were investigated using Tenax (R) beads and a two-compartment, first-order kinetic model. PAH desorption from distillate waste sediments appeared to be controlled by the slow clesorbing fractions of sediment; rate constants were similar to literature values for k(slow) and k(very) (slow). After several decades of plant colonization and growth (Phragmites australis), vegetated sediment fractions more extensively desorbed PAHs and had faster desorption kinetics than non-vegetated sediment fractions. (C) 2008 Elsevier Ltd. All rights reserved. VL - 156 IS - 3 N1 - id: 2024; PT: J; UT: WOS:000261678700045 JO - The impact of vegetation on sedimentary organic matter composition and PAH desorption ER - TY - JOUR T1 - In situ carbonation of peridotite for CO2 storage JF - Proceedings of the National Academy of Sciences of the United States of America Y1 - 2008 A1 - Kelemen, P. B. A1 - Matter, J. AB - The rate of natural carbonation of tectonically exposed mantle peridotite during weathering and low-temperature alteration can be enhanced to develop a significant sink for atmospheric CO2. Natural carbonation of peridotite in the Samail ophiolite, an uplifted slice of oceanic crust and upper mantle in the Sultanate of Oman, is surprisingly rapid. Carbonate veins in mantle peridotite in Oman have an average C-14 age of approximate to 26,000 years, and are not 30-95 million years old as previously believed. These data and reconnaissance mapping show that approximate to 10(4) to 10(5) tons per year of atmospheric CO2 are converted to solid carbonate minerals via peridotite weathering in Oman. Peridotite carbonation can be accelerated via drilling, hydraulic fracture, input of purified CO2 at elevated pressure, and, in particular, increased temperature at depth. After an initial heating step, CO2 pumped at 25 or 30 degrees C can be heated by exothermic carbonation reactions that sustain high temperature and rapid reaction rates at depth with little expenditure of energy. In situ carbonation of peridotite could consume > 1 billion tons of CO2 per year in Oman alone, affording a low-cost, safe, and permanent method to capture and store atmospheric CO2. VL - 105 IS - 45 N1 - id: 779; 373OP Times Cited:12 Cited References Count:37Y JO - In situ carbonation of peridotite for CO2 storage ER - TY - JOUR T1 - In situ carbonation of peridotite for CO2 storage JF - Proceedings of the National Academy of Sciences Y1 - 2008 A1 - Kelemen, P. B. A1 - Matter, J. KW - alteration and weathering KW - carbon capture KW - carbon sequestration KW - exothermic KW - MINERAL AB - The rate of natural carbonation of tectonically exposed mantle peridotite during weathering and low-temperature alteration can be enhanced to develop a significant sink for atmospheric CO2. Natural carbonation of peridotite in the Samail ophiolite, an uplifted slice of oceanic crust and upper mantle in the Sultanate of Oman, is surprisingly rapid. Carbonate veins in mantle peridotite in Oman have an average 14C age of ≈26,000 years, and are not 30–95 million years old as previously believed. These data and reconnaissance mapping show that ≈104 to 105 tons per year of atmospheric CO2 are converted to solid carbonate minerals via peridotite weathering in Oman. Peridotite carbonation can be accelerated via drilling, hydraulic fracture, input of purified CO2 at elevated pressure, and, in particular, increased temperature at depth. After an initial heating step, CO2 pumped at 25 or 30 °C can be heated by exothermic carbonation reactions that sustain high temperature and rapid reaction rates at depth with little expenditure of energy. In situ carbonation of peridotite could consume >1 billion tons of CO2 per year in Oman alone, affording a low-cost, safe, and permanent method to capture and store atmospheric CO2. VL - 105 UR - http://www.pnas.org/cgi/doi/10.1073/pnas.0805794105 IS - 45 ER - TY - JOUR T1 - Incipient Aquaculture in Prehistoric California? Long-term productivity and sustainability vs. immediate returns for the harvest of marine invertebrates JF - Journal of Archaeological Sciences Y1 - 2008 A1 - Whitaker, Adrian R. KW - Conservation KW - Mytilus californianus KW - Optimal foraging theory KW - Resource depression AB - California archaeologists have proposed two alternative methods for harvesting mussels—“stripping” and “plucking”. These two methods are modeled and compared with experimental data from central California (Jones, T.L., Richman, J.R., 1995. On Mussels: Mytilus californianus as a Prehistoric Resource, North American Archaeologist 16, 33–58) and archaeological data from the Punta Gorda Rockshelter, a well-stratified coastal shell midden in northern California. Foragers at the Punta Gorda Rockshelter appear to have practiced a “stripping” technique at approximately 24 month intervals. It is argued that, while this strategy reduced immediate foraging returns, it increased the long-term net productivity of the mussel beds. These findings are discussed in light of the broader literature regarding resource depression and resource cultivation in California prehistory. The conventional interpretation of reductions in the body size in archaeological assemblages is questioned both in terms of rates of return on these individuals and the impact of human predation on local prey populations. VL - 35 IS - 4 N1 - id: 2097 JO - Incipient Aquaculture in Prehistoric California?:Long-term productivity and sustainability vs. immediate returns for the harvest of marine invertebrates ER - TY - JOUR T1 - Increased terrestrial to ocean sediment and carbon fluxes in the northern chesapeake bay associated with twentieth century land alteration JF - Estuaries and Coasts Y1 - 2008 A1 - Saenger, C. A1 - Cronin, T. M. A1 - Willard, D. A1 - Halka, J. A1 - Kerhin, R. AB - We calculated Chesapeake Bay (CB) sediment and carbon fluxes before and after major anthropogenic land clearance using robust monitoring, modeling and sedimentary data. Four distinct fluxes in the estuarine system were considered including (1) the flux of eroded material from the watershed to streams, (2) the flux of suspended sediment at river fall lines, (3) the burial flux in tributary sediments, and (4) the burial flux in main CB sediments. The sedimentary maximum in Ambrosia (ragweed) pollen marked peak land clearance (similar to 1900 A.D.). Rivers feeding CB had a total organic carbon (TOC)/total suspended solids of 0.24 +/- 0.12, and we used this observation to calculate TOC fluxes from sediment fluxes. Sediment and carbon fluxes increased by 138-269% across all four regions after land clearance. Our results demonstrate that sediment delivery to CB is subject to significant lags and that excess post-land clearance sediment loads have not reached the ocean. Post-land clearance increases in erosional flux from watersheds, and burial in estuaries are important processes that must be considered to calculate accurate global sediment and carbon budgets. VL - 31 IS - 3 N1 - id: 812; 316CY Times Cited:1 Cited References Count:54Y JO - Increased terrestrial to ocean sediment and carbon fluxes in the northern chesapeake bay associated with twentieth century land alteration ER - TY - JOUR T1 - Interpreting sea surface temperature from strontium/calcium ratios in Montastrea corals: Link with growth rate and implications for proxy reconstructions JF - Paleoceanography Y1 - 2008 A1 - Saenger, C. A1 - Cohen, A. L. A1 - Oppo, D. W. A1 - Hubbard, D. AB - [1] We analyzed strontium/calcium ratios (Sr/Ca) in four colonies of the Atlantic coral genus Montastrea with growth rates ranging from 2.3 to 12.6 mm a(-1). Derived Sr/Ca-sea surface temperature (SST) calibrations exhibit significant differences among the four colonies that cannot be explained by variations in SST or seawater Sr/Ca. For a single coral Sr/Ca ratio of 8.8 mmol mol(-1), the four calibrations predict SSTs ranging from 24.0 degrees to 30.9 degrees C. We find that differences in the Sr/Ca-SST relationships are correlated systematically with the average annual extension rate (ext) of each colony such that Sr/Ca ( mmol mol(-1)) = 11.82 (+/- 0.13) - 0.058 (+/- 0.004) x ext ( mm a(-1)) - 0.092 (+/- 0.005) x SST (degrees C). This observation is consistent with previous reports of a link between coral Sr/Ca and growth rate. Verification of our growth-dependent Sr/Ca - SST calibration using a coral excluded from the calibration reconstructs the mean and seasonal amplitude of the actual recorded SST to within 0.3 degrees C. Applying a traditional, nongrowth-dependent Sr/Ca - SST calibration derived from a modern Montastrea to the Sr/Ca ratios of a conspecific coral that grew during the early Little Ice Age (LIA) ( 400 years B. P.) suggests that Caribbean SSTs were > 5 degrees C cooler than today. Conversely, application of our growth-dependent Sr/Ca - SST calibration to Sr/Ca ratios derived from the LIA coral indicates that SSTs during the 5-year period analyzed were within error (+/- 1.4 degrees C) of modern values. VL - 23 IS - 3 N1 - id: 864; ISI Document Delivery No.: 333MS Times Cited: 3 Cited Reference Count: 49 Cited References: *DEP CONS CULT AFF, 1986, MAR WAT QUAL MEAS CH *NAT RES COUNC, 2006, SURF TEMP REC LAST 2 BEVINGTON PR, 1969, DATA REDUCTION ERROR, P56 BLACK DE, 2004, PALEOCEANOGRAPHY, V19, ARTN PA2022 BLACK DE, 2007, PALEOCEANOGRAPHY, V22, ARTN PA4204 CARDINAL D, 2001, CHEM GEOL, V176, P213 CARRICARTGANIVET JP, 2004, J EXP MAR BIOL ECOL, V302, P249, DOI 10.1016/j.jembe.2003.10.015 CHIANG JCH, 2002, J GEOPHYS RES-ATMOS, V107, ARTN 4004 COBB KM, 2003, EARTH PLANET SC LETT, V210, P91, DOI 10.1016/S0012-821X(03)00138-9 COHEN AL, 2004, GEOPHYS RES LETT, V31, ARTN L16310 COHEN AL, 2004, MAR ECOL-PROG SER, V271, P147 COHEN AL, 2006, GEOCHEM GEOPHY GEOSY, V7, ARTN Q12004 COHEN AL, 2007, GEOPHYS RES LETT, V34, ARTN L17706 CRONIN TM, 2003, GLOBAL PLANET CHANGE, V36, P17 DEVILLIERS S, 1995, SCIENCE, V269, P1247 DEVILLIERS S, 1999, EARTH PLANET SC LETT, V171, P623 FELIS T, 2004, NATURE, V429, P164, DOI 10.1038/nature02546 GABITOV RI, 2006, GEOCHIM COSMOCHIM S, V70, A187, DOI 10.1016/j.gca.2006.06.377 GAETANI GA, 2006, GEOCHIM COSMOCHIM AC, V70, P4617, DOI 10.1016/j.gca.2006.07.008 GOODKIN NF, 2005, PALEOCEANOGRAPHY, V20, ARTN PA4016 HAASESCHRAMM A, 2003, PALEOCEANOGRAPHY, V18, ARTN 1073 HAASESCHRAMM A, 2005, PALEOCEANOGRAPHY, V20, ARTN PA4015 HAUG GH, 2001, SCIENCE, V293, P1304 HENDY EJ, 2002, SCIENCE, V295, P1511 HERNANDEZGUERRA A, 2000, GEOPHYS RES LETT, V27, P3497 HODELL DA, 2005, QUATERNARY RES, V63, P109, DOI 10.1016/j.yqres.2004.11.004 HUBBARD DK, 2005, J SEDIMENT RES, V75, P97, DOI 10.2110/jsr.2005.009 HUGHEN KA, 2004, RADIOCARBON, V46, P1059 JONES PD, 2004, REV GEOPHYS, V42, ARTN RG2002 LEDER JJ, 1996, GEOCHIM COSMOCHIM AC, V60, P2857 LOUGH JM, 2004, PALAEOGEOGR PALAEOCL, V204, P115, DOI 10.1016/S0031-0182(03)00727-2 LUND DC, 2006, PALEOCEANOGRAPHY, V21, ARTN PA2009 MEIBOM A, 2006, GEOPHYS RES LETT, V33, ARTN L11608 MOHIUDDIN MM, 2004, DEEP-SEA RES PT I, V51, P1659, DOI 10.1016/j.dsr.2004.06.002 NYBERG J, 2002, PALAEOGEOGR PALAEOCL, V183, P25 OSTERMANN DR, 2000, PALEOCEANOGRAPHY, V15, P353 PFLAUMANN U, 2003, PALEOCEANOGRAPHY, V18, ARTN 1065 REYNAUD S, 2007, GEOCHIM COSMOCHIM AC, V71, P354, DOI 10.1016/j.gca.2006.09.009 REYNOLDS RW, 1994, J CLIMATE, V7, P929 ROSENTHAL Y, 1999, ANAL CHEM, V71, P3248 SCHMIDT MW, 2006, GEOCHEM GEOPHY GEOSY, V7, ARTN Q02P10 SMITH JM, 2006, PALEOCEANOGRAPHY, V21, ARTN PA1010 SWART PK, 2002, GEOCHEM GEOPHY GEOSY, V3, ARTN 8402 THUNELL RC, 1984, MICROPALEONTOLOGY, V30, P243 VELLINGA M, 2004, J CLIMATE, V17, P4498 WATANABE T, 2001, MAR GEOL, V173, P21 WEIL E, 1994, B MAR SCI, V55, P151 WINTER A, 2000, GEOPHYS RES LETT, V27, P3365 YOO JM, 1990, J PHYS OCEANOGR, V20, P831 Saenger, Casey Cohen, Anne L. Oppo, Delia W. Hubbard, Dennis Amer geophysical union Washington; YY JO - Interpreting sea surface temperature from strontium/calcium ratios in Montastrea corals: Link with growth rate and implications for proxy reconstructions ER - TY - RPRT T1 - ITUHU SITE (32SN110) 1995 Archeological Excavations, Stutsman County, North Dakota. James River Report Number 5 Y1 - 2008 A1 - Toom, Dennis L. ED - Toom, D. L. JF - James River Report PB - University of North Dakota CY - Grand Forks ND VL - University of North Dakota Anthropology Research Contribution No.411 N1 - id: 771 ER - TY - JOUR T1 - The last reconnection of the Marmara Sea (Turkey) to the World Ocean: A paleoceanographic and paleoclimatic perspective JF - Marine Geology Y1 - 2008 A1 - McHugh, C. M. G. A1 - Gurung, D. A1 - Giosan, L. A1 - Ryan, W. B. F. A1 - Mart, Y. A1 - Sancar, U. A1 - Burckle, L. A1 - Cagatay, M. N. AB - During the late glacial, marine isotope Stage 2, the Marmara Sea transformed into a brackish lake as global sea-level fell below the sill in the Dardanelles Strait. A record of the basin's reconnection to the global ocean is preserved in its sediments permitting the extraction of the paleoceanographic and paleoclimatic history of the region. The goal of this study is to develop a high-resolution record of the lacustrine to marine transition of Marmara Sea in order to reconstruct regional and global climatic events at a millennia] scale. For this purpose, we mapped the paleoshorelines of Marmara Sea along the northern, eastern, and southern shelves at Cekmece. Prince Islands, and Imrali, using data from multibeam bathymetry, high-resolution subbottom profiling (chirp) and ten sediment cores. Detailed sedimentologic, biostratigraphic (foraminifers, mollusk, diatoms), X-ray fluorescence geochemical scanning, and oxygen and carbon stable isotope analyses correlated to a calibrated radiocarbon chronology provided evidence for cold and city conditions prior to 15 ka BP, warm conditions of the Bolling-Allerod from similar to 15 to 13 ka BP, a rapid marine incursion at 12 ka BP, still stand of Marmara Sea and sediment reworking of the paleoshorelines during the Younger Dryas at similar to 11.5 to 10.5 ka BP, and development of strong stratification and influx of nutrients as Black Sea waters spilled into Marmara Sea at 9.2 ka BR Stable environmental conditions developed in Marmara Sea after 6.0 ka BP as sea-level reached its present shoreline and the basin floors filled with sediments achieving their present configuration. (C) 2008 Elsevier B.V. All rights reserved. VL - 255 IS - 1-2 N1 - id: 801; 370ED Times Cited:4 Cited References Count:104; YY JO - The last reconnection of the Marmara Sea (Turkey) to the World Ocean: A paleoceanographic and paleoclimatic perspective ER - TY - JOUR T1 - Late Holocene marine productivity changes in Northern Patagonia-Chile inferred from a multi-proxy analysis of Jacaf channel sediments JF - Estuarine Coastal and Shelf Science Y1 - 2008 A1 - Rebolledo, Lorena A1 - Sepulveda, Julio A1 - Lange, Carina B. A1 - Pantoja, Silvio A1 - Bertrand, Sbastien A1 - Hughen, Konrad A1 - Figueroae, Dante AB - A multi-proxy approach based on organic (organic carbon, alkenones, and C/N) and inorganic geochemical proxies (biogenic opal, inorganic carbon, Fe, Ti, and Ca) preserved in the sediments of the Jacaf channel (CF7-PC33; 44 degrees 21'S, 72 degrees 58'W, 510 m water depth), Chilean fjords, yields evidence of major past productivity fluctuations in accordance with climatic changes over the last similar to 1800 years. The downcore record clearly shows two productivity/climate modes. The first period, prior to 900 cal yr BP, is characterized by decreased marine productivity and a reduced continental signal, pointing to diminished precipitation and runoff. In contrast, the second period between similar to 750 cal yr BP and the late 1800s (top of core) is illustrated by elevated productivity and an increased continental signal, suggesting higher precipitation and runoff. Both time intervals are separated by a relatively abrupt transition of similar to 150 years which roughly coincides with the beginning of the Little Ice Age. The increased content of freshwater diatoms and Chrysophyte cysts that characterize the last 200 years of the latter mode coincides with a significant decrease in the carbonate content of the sediment; together they further indicate increased terrigenous contributions and decreased marine carbonate productivity at the end of the Little Ice Age. The correspondence between our record and other paleoclimate studies carried out in South America and Antarctica demonstrates that the Chilean fjord area of Northern Patagonia is not just sensitive to local climatic variability but also to regional and possibly global variability. (C) 2008 Elsevier Ltd. All rights reserved. VL - 80 IS - 3 N1 - id: 2117; PT: J; TC: 5; J9: ESTUAR COAST SHELF S; UT: WOS:000261562600002 JO - Late Holocene marine productivity changes in Northern Patagonia-Chile inferred from a multi-proxy analysis of Jacaf channel sediments ER - TY - JOUR T1 - A late holocene pollen and charcoal record from La Selva biological station, Costa Rica JF - Biotropica Y1 - 2008 A1 - Kennedy, Lisa M. A1 - Horn, Sally P. AB - Pollen and charcoal analysis of a 5.9-m-long sediment profile from a swamp on an alluvial terrace on the edge of La Selva biological station, Costa Rica (10 degrees 26 ' 23 '' N, 84 degrees 00 ' 24 '' W, 36 m asl), documents three millennia of human and natural disturbance within a lowland tropical rain forest. The record indicates that the highly diverse rain forest that presently surrounds the Cantarrana swamp regrew following forest clearing and maize agriculture that ended only a few centuries ago. The first maize pollen appears in sediments deposited similar to 1070 calendar-year BP. Older sediments below the 'maize zone' contain macroscopic charcoal, abundant microscopic charcoal, and possible pollen indicators of forest clearance, perhaps signaling local cultivation of root crops that left no pollen in the sediments. Interpretation of local archaeology indicates that La Selva reserve may have been most heavily populated during the El Bosque and La Selva regional archaeological phases from 2250-950 yr BP. However, the distribution of maize pollen in the sediments is clear evidence that the reserve was also occupied during the later La Cabana phase (950-400 yr BP), from which few artifacts have yet surfaced. Natural forest disturbance from treefalls and stream dynamics, and hydrological shifts associated with late-Holocene climate variability, form a backdrop to the human land-use history preserved in the Cantarrana sediment profile. VL - 40 IS - 1 N1 - id: 1997; PT: J; UT: WOS:000252319600004 JO - A late holocene pollen and charcoal record from La Selva biological station, Costa Rica ER - TY - JOUR T1 - Late Pleistocene freshwater fish (Cottidae) trackways from New England (USA) glacial lakes and a reinterpretation of the ichnogenus Broomichnium Kuhn JF - Palaeogeography, Palaeoclimatology, Palaeoecology Y1 - 2008 A1 - Benner, Jacob S. A1 - Ridge, John C. A1 - Taft, Natalia K. AB - New trace fossil material from Late Pleistocene glaciolacustrine varves of the Connecticut River Valley, New England, USA represent the first evidence of freshwater sculpin in glacial Lake Hitchcock. Paleobiogeographic data constrain the timing of the last reinhabitation of freshwater cottids from a Wisconsinan glacial refugium. Freshwater sculpin were present in the area of study by ~ 13.7 ky BP, moving approximately 400 km in 5000 yr, and following the ice margin at distances as close as 35 km. The trace fossils warrant erection of a new ichnospecies, Broomichnium flirii isp. nov. Comparison of this new ichnospecies to Broomichnium permianum reveals distinct similarities, and it is possible that the Permian examples of B. permianum also were made by fish, which would reconcile a long-running controversy. Many groups of fish are demersal and make ventral body contact with the substrate and could potentially leave similar traces. Identifying new forms of trace fossils made by fish that use alternative modes of locomotion will prove useful in paleoenvironmental interpretations. VL - 260 IS - 3–4 N1 - id: 2129 JO - Late Pleistocene freshwater fish (Cottidae) trackways from New England (USA) glacial lakes and a reinterpretation of the ichnogenus Broomichnium Kuhn ER - TY - CONF T1 - Late Quaternary paleo-lake fluctuations in westernmost Tibet T2 - 2008 Fall Meeting of the American Geophysical Union (AGU 2008) Y1 - 2008 A1 - Amidon, W. A1 - Blard, P. A1 - Avouac, J. A1 - Schneider, T. ED - San Francisco, California KW - China, People's Rep., Xizang KW - Paleo studies KW - Quaternary JF - 2008 Fall Meeting of the American Geophysical Union (AGU 2008) N1 - id: 1913; TY: CPAPER; NO: Source type: conferencepapers&proceedings; Object type: Conference Paper; CSAUnique: CPI-5461640; AccNum: 5461640(USA) ER - TY - JOUR T1 - Late Quaternary vegetation reconstruction from the Eastern Arc Mountains, Tanzania JF - Quaternary Research Y1 - 2008 A1 - Mumbi, C. T. A1 - Marchant, R. A1 - Hooghiemstra, H. A1 - Wooller, M. J. AB - Pollen, spore, macrofossil and stable isotope (C and N) analyses from a 266-cm sediment core collected from a swamp on the Eastern Arc Mountains, Tanzania, are used to reconstruct vegetation and environmental history. An estimated time scale based on five C-14 ages records approximately 38,000 yr. This palaeorecord is the first from this biodiversity hotspot and importantly extends through the last glacial maximum (LGM). The altitudinal transition from montane to upper montane forest shifted from 1700-1800 in (38,000 C-14 yr BP) to 1800-1900 in (35,000-29,000 C-14 yr BP). From 29,000 to 10,000 C-14 yr BP, it shifted from 1850-1950 in across the LGM to 1750-1800 in (during 10,000-3500 C-14 yr BP), and to present-day elevations at 2000 in during the last 3500 C-14 yr BP. The relative ecosystem stability across the LGM may be explained by the Indian Ocean's influence in maintaining continuous moist forest cover during a period of East African regional climate aridity. During the late Holocene, presence of abundant coprophilous fungi and algal blooms demonstrates increasing human impact. Neurospora spores indicate frequent fires, coinciding with clear signals of decline in Podocarpus and Psychotria trees that possibly represent selective logging. (C) 2007 University of Washington. All rights reserved. VL - 69 IS - 2 N1 - id: 1836; 285PB Times Cited:6 Cited References Count:105Y JO - Late Quaternary vegetation reconstruction from the Eastern Arc Mountains, Tanzania ER - TY - JOUR T1 - Lateral organic carbon supply to the deep Canada Basin JF - Geophysical Research Letters Y1 - 2008 A1 - Hwang, J. A1 - Eglinton, T. I. A1 - Krishfield, R. A. A1 - Manganini, S. J. A1 - Honjo, S. AB - Understanding the processes driving the carbon cycle in the Arctic Ocean is important for assessing the impacts of the predicted rapid and amplified climate change in this region. We analyzed settling particle samples intercepted by a time-series sediment trap deployed in the abyssal Canada Basin ( at 3067 m) in order to examine carbon export to the deep Arctic Ocean. Strikingly old radiocarbon ages ( apparent mean 14 C age = similar to 1900 years) of the organic carbon, abundant lithogenic material (similar to 80%), and mass flux variations temporally decoupled from the cycle of primary productivity in overlying surface waters together suggest that, unlike other ocean basins, the majority of the particulate organic carbon entering the deep Canada Basin is supplied from the surrounding margins. VL - 35 IS - 11 N1 - id: 1830; 314KU Times Cited:7 Cited References Count:33Y JO - Lateral organic carbon supply to the deep Canada Basin ER - TY - JOUR T1 - Life on the edge: early maritime cultures of the Pacific Coast of North America JF - Quaternary Science Reviews Y1 - 2008 A1 - Erlandson, Jon M. A1 - Moss, Madonna L. A1 - Des Lauriers, Matthew AB - A variety of evidence suggests that the Americas may have been colonized, at least in part, by maritime peoples moving around the North Pacific Rim near the end of the Pleistocene. Understanding the geography of late glacial and early postglacial landscapes and the antiquity of human societies along the Pacific Coast continues to be a challenge, however, due to geological dynamics associated with glaciation, tectonism, submergence of coastal lowland landscapes by rising postglacial seas, and coastal erosion. Nonetheless, archaeological research has Pushed back the antiquity of human settlement along the Pacific Coast of North America to the terminal Pleistocene or early Holocene, providing important new data on the nature of the earliest coastal peoples in the Pacific Northwest, Alta California, and Baja California. In this paper, we summarize what is known about the earliest peoples of the Pacific Coast of North America and evaluate the Current viability of the coastal migration theory via a Pacific Rim route. Archaeological evidence now shows that Palaeocoastal peoples occupied each major region of the Pacific Coast by at least 13,000-11,500 calendar years ago (cal BP) (13-11.5 ka), essentially contemporaneous with Clovis and Folsom peoples of the interior. Although it is too early to conclude that the initial human colonization of the Americas took place via a migration by maritime or coastal peoples, it seems increasingly likely that such a migration played a role in the early peopling of the Americas. (c) 2008 Elsevier Ltd. All rights reserved. VL - 27 IS - 23-24 N1 - id: 2062; PT: J; SI: SI; UT: WOS:000261715500012 JO - Life on the edge: early maritime cultures of the Pacific Coast of North America ER - TY - JOUR T1 - Loess record of the Pleistocene-Holocene transition on the northern and central Great Plains, USA JF - Quaternary Science Reviews Y1 - 2008 A1 - Mason, Joseph A. A1 - Miao, Xiaodong A1 - Hanson, Paul R. A1 - Johnson, William C. A1 - Jacobs, Peter M. A1 - Goble, Ronald J. AB - Various lines of evidence support conflicting interpretations of the timing, abruptness. and nature of climate change in the Great Plains during the Pleistocene-Holocene transition. Loess deposits and paleosols on both the central and northern Great Plains provide a valuable record that can help address these issues. A synthesis of new and previously reported optical and radiocarbon ages indicates that the Brady Soil, which marks the boundary between late Pleistocene Peoria Loess and Holocene Bignell Loess, began forming after a reduction in the rate of Peoria Loess accumulation that most likely occurred between 13.5 and 15 cal ka. Brady Soil formation spanned all or part of the Bolling-Allerod episode (approximately 14.7-12.9 cal ka) and all of the Younger Dryas episode (12.9-11.5 cal ka) and extended at least 1000 years beyond the end of the Younger Dryas. The Brady Soil was buried by Bignell Loess sedimentation beginning around 10.5-9 cal ka, and continuing episodically through the Holocene. Evidence for a brief increase in loess influx during the Younger Dryas is noteworthy but very limited. Most late Quaternary loess accumulation in the central Great Plains was nonglacigenic and was under relatively direct climatic control. Thus, Brady Soil formation records climatic conditions that minimized eolian activity and allowed effective pedogenesis, probably through relatively high effective moisture. Optical dating of loess in North Dakota supports correlation of the Leonard Paleosol on the northern Great Plains with the Brady Soil. Thick loess in North Dakota was primarily derived from the Missouri River floodplain; thus, its stratigraphy may in part reflect glacial influence on the Missouri River. Nonetheless, the persistence of minimal loess accumulation and soil formation until 10 cal ka at our North Dakota study site is best explained by a prolonged interval of high effective moisture correlative with the conditions that favored Brady Soil formation. Burial of both the Brady Soil and the Leonard Paleosol by renewed loess influx probably represents eolian system response that occurred when gradual change toward a drier climate eventually crossed the threshold for eolian activity. Overall, the loess-paleosol sequences of the central and northern Great Plains record a broad peak of high effective moisture across the late Pleistocene to Holocene boundary, rather than well-defined climatic episodes corresponding to the Bolling-Allerod and Younger Dryas episodes in the North Atlantic region. (C) 2008 Elsevier Ltd. All rights reserved. VL - 27 IS - 17-18 N1 - id: 1993; PT: J; UT: WOS:000260545800008 JO - Loess record of the Pleistocene-Holocene transition on the northern and central Great Plains, USA ER - TY - JOUR T1 - Matrix protected organic matter in a river dominated margin: A possible mechanism to sequester terrestrial organic matter? JF - Geochimica Et Cosmochimica Acta Y1 - 2008 A1 - Mead, R. N. A1 - Goñi, M. A. AB - The provenance of organic matter in surface sediments from the northern Gulf of Mexico was investigated by analyzing the compositions of lipid biomarkers (n-alkanes, fatty acids, sterols) liberated after a series of chemical treatments designed to remove different organo-mineral matrix associations (i.e. freely extractable, base-hydrolyzable, unhydrolyzable). Bulk analyses of the organic matter (carbon content, carbon:nitrogen ratios, stable and radiocarbon isotopic analyses) were also performed on the intact sediments and their non-hydrolyzable, demineralized residue. We found recognizable lipids from distinct sources, including terrestrial vascular plants, bacteria and marine algae and zooplankton, within each of the isolated fractions. Based on the lipid signatures and bulk compositions, the organic matter within the unhydrolyzable fractions appeared to be the most diagenetically altered, was the oldest in age, and had the highest abundance of terrigenous lipids. In contrast, the base-hydrolyzable fraction was the most diagentically unaltered, had the youngest ages and was most enriched in N and marine lipids. Our results indicate that fresh, autochthonous organic matter is the most important contributor to base-hydrolyzable lipids, whereas highly altered allochthonous sources appear to be predominant source of unhydrolyzable lipids in the surface sediments from the Atchafalaya River shelf. Overall, the lipid biomarker signatures of intact sediments were biased towards the autochthonous source because many of the organic compounds indicative of degraded, terrigenous sources were protected from extraction and saponification by organo-mineral matrices. It is only after these protective matrices were removed by treatment with HCl and HF that these compounds became evident. (C) 2008 Elsevier Ltd. All rights reserved. VL - 72 IS - 11 N1 - id: 827; 309MK Times Cited:5 Cited References Count:71Y JO - Matrix protected organic matter in a river dominated margin: A possible mechanism to sequester terrestrial organic matter? ER - TY - JOUR T1 - Method for determining coal carbon in the reclaimed minesoils contaminated with coal JF - Soil Science Society of America Journal Y1 - 2008 A1 - Ussiri, D. A. N. A1 - Lai, R. KW - BLACK CARBON KW - C-14 KW - FOREST KW - GENESIS KW - MATTER KW - MINING DISTRICT KW - RICH MINE SOILS KW - sediments KW - SITES KW - SOIL ORGANIC-CARBON AB - Minesoils are anthropic soils developed on land disturbed by mining activities. Minesoils developed on the reclaimed surface-mined sites for coal are contaminated with coal particles resulting from mining and reclamation activities. Therefore, the total organic carbon (TOC) pool in these sites is a mixture of coal and plant-derived recent soil organic carbon (SOC). Accurate estimates of SOC pools and C sequestration rates in the reclaimed minesoils (RMS) is limited by the lack of a standard and cost-effective method for determination of coal C concentrations in the RMS. The chemi-thermal method, based on the oxidative resistance of coal, was developed and validated with radiocarbon analysis using selected artificial soil-coal mixtures and minesoil samples. Radiocarbon analysis of RMS samples indicated that minesoils from the top 10-cm depth developing from topsoil applied during reclamation was coal C free. The contribution of coal C and the radiocarbon age of TOC increased with increasing soil depth. The coal C fraction accounted for 0 to 92% of TOC in the RMS samples. The coal C fraction was highly correlated with delta C-13 (r(2) = 0.84), suggesting that stable isotope composition could estimate the coal C concentration in RMS samples. Analysis of coal and artificial soil and coal mixtures indicated that chemi-thermal treatment was effective in removing recent SOC with minimum effect on coal. Analysis of RMS samples indicated that both radiocarbon activity and the chemi-thermal method were effective in estimating coal C concentration in RMS of southeast Ohio. The coal C concentrations for both methods were highly correlated (r(2) = 0.95), suggesting that the chemi-thermal method was as effective as radiocarbon activity measurement in estimating coal C concentration in these soils. VL - 72 SN - 0361-5995 IS - 1 N1 - 24 JO - Soil Sci. Soc. Am. J. ER - TY - JOUR T1 - Micropaleontologic record of late pliocene and quaternary paleoenvironments in the northern Albemarle embayment, North Carolina, USA JF - Palaeogeography Palaeoclimatology Palaeoecology Y1 - 2008 A1 - Culver, S. J. A1 - Farrell, K. M. A1 - Mallinson, D. J. A1 - Horton, B. P. A1 - Willard, D. A. A1 - Thieler, E. R. A1 - Riggs, S. R. A1 - Snyder, S. W. A1 - Wehmiller, J. F. A1 - Bernhardt, C. E. A1 - Hillier, C. AB - Micropaleontological data provide a strong actualistic basis for detailed interpretations of Quaternary paleoenvironmental change. The 90 m-thick Quaternary record of the Albemarle Embayment in the mid-Atlantic coastal plain of the USA provides an excellent opportunity to use such an approach in a region where the details of Quaternary environmental change are poorly known. The foraminiferal record in nine cores from the northern Outer Banks, east of Albemarle Sound, North Carolina, indicates the deposition of subhorizontal, mostly open-marine early to late Pleistocene units unconformably upon a basement of late Pliocene reduced-oxygen, fine-grained, shelf-basin deposits. Pollen data record several warm-cool fluctuations within the early to mid-Pleistocene deposits. Diatom data indicate that some fresh and brackish-water units occur within the generally open-marine Pleistocene succession. A channel cut by the paleo-Roanoke River during the last glacial sea-level lowstand occurs in the northern part of the study area. Pollen indicates that the basal fluvial valley fill accumulated in cooler than modern climate conditions in the latest Pleistocene. Overlying silts and muds accumulated under cool climatic, estuarine conditions according to diatom and pollen data. Radiocarbon ages from the estuarine deposits indicate that the bulk of these sediments accumulated during the latest Pleistocene. The estuarine channel-fill deposits are overlain by Holocene open-marine sands deposited as the rising sea transgressed into the estuary approximately 8.5 to 9.0 kyr BR Within the barrier island drill cores of this study, fully marine sedimentation occurred throughout the Holocene. However, immediately west of the present barrier island, mid- to late Holocene estuarine deposits underlie the modern Albemarle Sound. The islands that currently form a continuous barrier across the mouth of Albemarle Sound have a complex history of Holocene construction and destruction and large portions of them may be less than 3 kyr old. The barrier island sands overlie open-marine sands of Colington Shoal in the north and to the south overlie fluvial and marine sand filling paleo-Roanoke tributary valleys. The Pleistocene sediments underlying the northern Outer Banks study area are mainly of open inner to midshelf origin. If, as is likely, sea level continues to rise, a return to such environmental conditions is likely in the near future. (c) 2008 Elsevier B.V. All rights reserved. VL - 264 IS - 1-2 N1 - id: 815; 331MZ Times Cited:2 Cited References Count:79Y JO - Micropaleontologic record of late pliocene and quaternary paleoenvironments in the northern Albemarle embayment, North Carolina, USA ER - TY - JOUR T1 - Mineralization of ancient carbon i the subsurface of riparian forests JF - Journal of Geophysical Research Y1 - 2008 A1 - Gurwick, Noel P. A1 - McCorkle, Daniel M. A1 - Groffman, Peter M. A1 - Gold, Arthur J. A1 - Kellogg, D. Q. A1 - Seitz-Rundlett, Peter VL - 113 N1 - id: 1193 ER - TY - JOUR T1 - Modern CaCO3 preservation in equatorial Pacific sediments in the context of late-Pleistocene glacial cycles JF - Marine Chemistry Y1 - 2008 A1 - Anderson, R. F. A1 - Fleisher, M. Q. A1 - Lao, Y. A1 - Winckler, G. AB - The CaCO3 content of marine sediments in many regions of the ocean has varied systematically with climate throughout the late-Pleistocene glacial cycles. Both biological productivity and carbonate preservation have been proposed to be the master variable regulating this variability. We have evaluated the preserved flux of CaCO3 in cores from the central equatorial Pacific Ocean (similar to 140 degrees W) using the Th-230-normalization technique. Neither barite fluxes nor Be-10/Th-230 ratios, both geochemical proxies for export production, correlate with CaCO3 fluxes, indicating that productivity is not the principal factor controlling CaCO3 accumulation in these sediments. Preserved fluxes of CaCO3 in central equatorial Pacific sediments correlate in time with the benchmark CaCO3 record from the Cape Basin (South Atlantic Ocean), supporting the view that changes in ocean chemistry (carbonate ion concentration) have controlled the pattern of CaCO3 preservation and accumulation at these sites. Modem CaCO3 preservation in equatorial Pacific sediments has dropped to levels nearly as low as those experienced at any time in the late Pleistocene. Similar changes occurred at the end of each of the late-Pleistocene interglacial periods, from which we infer that ocean carbonate chemistry has already undergone changes that are expected to precede the transition into the next ice age. However, during the late Pleistocene, the time interval between the decrease in CaCO3 preservation and the end of the interglacial has varied substantially from one interglacial to another (from similar to 2000 to similar to 15,000 years), so the late-Holocene decrease in CaCO3 preservation cannot be used to predict the end of the Holocene interglacial period. (C) 2007 Elsevier B.V. All rights reserved. VL - 111 IS - 1-2 N1 - id: 1936; PT: J; UT: WOS:000259418600004 JO - Modern CaCO3 preservation in equatorial Pacific sediments in the context of late-Pleistocene glacial cycles ER - TY - JOUR T1 - The most extensive Holocene advance in the Stauning Alper, East Greenland, occurred in the Little Ice Age JF - Polar Research Y1 - 2008 A1 - Hall, B. L. A1 - Baroni, C. A1 - Denton, G. H. AB - We present glacial geologic and chronologic data concerning the Holocene ice extent in the Stauning Alper of East Greenland. The retreat of ice from the late-glacial position back into the mountains was accomplished by at least 11 000 cal years B.P. The only recorded advance after this time occurred during the past few centuries (the Little Ice Age). Therefore, we postulate that the Little Ice Age event represents the maximum Holocene ice extent in this part of East Greenland. VL - 27 IS - 2 N1 - id: 823; 327VY Times Cited:1 Cited References Count:45Y JO - The most extensive Holocene advance in the Stauning Alper, East Greenland, occurred in the Little Ice Age ER - TY - JOUR T1 - Mutation and evolutionary rates in adelie penguins from the antarctic JF - Plos Genetics Y1 - 2008 A1 - Millar, C. D. A1 - Dodd, A. A1 - Anderson, J. A1 - Gibb, G. C. A1 - Ritchie, P. A. A1 - Baroni, C. A1 - Woodhams, M. D. A1 - Hendy, M. D. A1 - Lambert, D. M. AB - Precise estimations of molecular rates are fundamental to our understanding of the processes of evolution. In principle, mutation and evolutionary rates for neutral regions of the same species are expected to be equal. However, a number of recent studies have shown that mutation rates estimated from pedigree material are much faster than evolutionary rates measured over longer time periods. To resolve this apparent contradiction, we have examined the hypervariable region (HVR I) of the mitochondrial genome using families of Adelie penguins (Pygoscelis adeliae) from the Antarctic. We sequenced 344 bps of the HVR I from penguins comprising 508 families with 915 chicks, together with both their parents. All of the 62 germline heteroplasmies that we detected in mothers were also detected in their offspring, consistent with maternal inheritance. These data give an estimated mutation rate (micro) of 0.55 mutations/site/Myrs (HPD 95% confidence interval of 0.29-0.88 mutations/site/Myrs) after accounting for the persistence of these heteroplasmies and the sensitivity of current detection methods. In comparison, the rate of evolution (k) of the same HVR I region, determined using DNA sequences from 162 known age sub-fossil bones spanning a 37,000-year period, was 0.86 substitutions/site/Myrs (HPD 95% confidence interval of 0.53 and 1.17). Importantly, the latter rate is not statistically different from our estimate of the mutation rate. These results are in contrast to the view that molecular rates are time dependent. VL - 4 IS - 10 N1 - id: 1195; Millar, Craig D Dodd, Andrew Anderson, Jennifer Gibb, Gillian C Ritchie, Peter A Baroni, Carlo Woodhams, Michael D Hendy, Michael D Lambert, David M PLoS Genet. 2008 Oct 3;4(10):e1000209.2546446 JO - Mutation and evolutionary rates in adelie penguins from the antarctic ER - TY - THES T1 - Natural Abundance Radiocarbon Studies of Dissolved Organic Carbon (DOC) in the Marine Environment Y1 - 2008 A1 - de Jesus, Roman P. AB - Marine dissolved organic carbon (DOC), an active reservoir in the global carbon cycle, has an average age of 6000 years and is comprised of biochemicals which may or may not cycle on different time scales. The primary objective of this thesis is to investigate the relationship between radiocarbon (14C) signature and chemical composition of various fractions within DOC. Specifically, this thesis was designed to provide an analytical framework to explicitly explore the relationship between DOC molecular weight, chemical composition, and reactivity. Chapter 2 describes spatial and temporal total organic carbon (TOC) concentration gradients in 2005 from the California Cooperative Fisheries Oceanic Cooperative (CalCOFI) region, which is the main study area for this thesis. Chapter 3 describes a novel solid phase extraction (SPE) method and reports the chemical and isotopic characteristics of fractionated DOC components based on their solubility. These fractions are compared to DOC isolated by the widely applied UF techniques and the results indicate that chemical composition and 14C content were related. Using compound specific isotope analysis (CSIA) of sugars and lipids, Chapter 4 shows that both SPE DOC and UDOC contain specific compounds with similar chemical and isotopic characteristics and residence times. In Chapter 5, CSIA was applied to SPE samples collected from the Delaware River and Estuary and the terrestrially influenced Eel River Margin to examine whether riverine DOC inputs contribute specific compounds or common components to the coastal ocean. Finally, the final chapter discusses the implications and significance of these results for marine DOC cycling. PB - University of California, San Diego VL - Ph.D. ER - TY - JOUR T1 - Near constancy of the Pacific Ocean surface to mid-depth radiocarbon-age difference over the last 20 kyr JF - Earth and Planetary Science Letters Y1 - 2008 A1 - Broecker, W. A1 - Clark, E. A1 - Barker, S. AB - Although C-13 to C-12 and cadmium to calcium ratios provide information regarding the distribution of deep water masses during late glacial time and during the period of deglaciation, our knowledge of the rate at which these water masses were ventilated comes mainly from the difference in radiocarbon-age between coexisting bottom- and surface-dwelling foraminifera. Paired benthic/planktonic foraminiferal radiocarbonage differences covering last 20 kyr in a high-deposition-rate western equatorial Pacific core, MD01-2386, from a water depth of 2.8 km show no significant climate-related variations over this period. This result is surprising for we would have expected a change in this age difference between the last glacial maximum (LGM) and the Holocene and also during the Mystery Interval (17.5-14.5 kyr ago) when the waters in a radiocarbon-depleted abyssal reservoir were presumably being mixed back into the remainder of the ocean. (C) 2008 Elsevier B.V. All rights reserved. VL - 274 IS - 3-4 N1 - id: 770; 390GV Times Cited:2 Cited References Count:27Y JO - Near constancy of the Pacific Ocean surface to mid-depth radiocarbon-age difference over the last 20 kyr ER - TY - CONF T1 - A New Look at Perishable Technologies from the Ozark Plateau: Focus T2 - 31st Annual Conference of the Society of Ethnobiology Y1 - 2008 A1 - Horton, Elizabeth T. JF - 31st Annual Conference of the Society of Ethnobiology CY - Fayetteville, Arkansas N1 - id: 777 ER - TY - JOUR T1 - Northern hemisphere controls on tropical southeast African climate during the past 60,000 years JF - Science Y1 - 2008 A1 - Tierney, Jessica E. A1 - Russell, James M. A1 - Huang, Yongsong A1 - Damste, Jaap S. Sinninghe A1 - Hopmans, Ellen C. A1 - Cohen, Andrew S. AB - The processes that control climate in the tropics are poorly understood. We applied compound-specific hydrogen isotopes (delta D) and the TEX(86) (tetraether index of 86 carbon atoms) temperature proxy to sediment cores from Lake Tanganyika to independently reconstruct precipitation and temperature variations during the past 60,000 years. Tanganyika temperatures follow Northern Hemisphere insolation and indicate that warming in tropical southeast Africa during the last glacial termination began to increase similar to 3000 years before atmospheric carbon dioxide concentrations. delta D data show that this region experienced abrupt changes in hydrology coeval with orbital and millennial-scale events recorded in Northern Hemisphere monsoonal climate records. This implies that precipitation in tropical southeast Africa is more strongly controlled by changes in Indian Ocean sea surface temperatures and the winter Indian monsoon than by migration of the Intertropical Convergence Zone. VL - 322 IS - 5899 N1 - id: 2047; PT: J; UT: WOS:000259902300046 JO - Northern hemisphere controls on tropical southeast African climate during the past 60,000 years ER - TY - JOUR T1 - Origins of archaeal tetraether lipids in sediments: Insights from radiocarbon analysis RID A-6723-2009 JF - Geochimica et Cosmochimica Acta Y1 - 2008 A1 - Shah, Sunita R. A1 - Mollenhauer, Gesine A1 - Ohkouchi, Naohiko A1 - Eglinton, Timothy I. A1 - Pearson, Ann AB - Understanding the supply and preservation of glycerol dibiphytanyl glycerol tetraethers (GDGTs) in marine sediments helps inform their use in paleoceanography. Compound-specific radiocarbon measurements of sedimentary alkenones from multiple environments have been used to gain insight into processes that affect U-37(K') paleotemperature reconstructions. Similar analyses are warranted to investigate how analogous processes affecting GDGTs impact TEX86 paleotemperatures. Here we present radiocarbon measurements on individual GDGTs from Bermuda Rise and Santa Monica Basin sediments and discuss the results in the context of previous studies of co-depositional alkenones and foraminifera. The C-14 contents of GDGTs and planktonic foraminifera in Bermuda Rise are very similar, suggesting a local source; and TEX86-derived temperatures agree more closely with foraminiferal temperatures than do U-37(K') temperatures. In contrast, GDGTs in Santa Monica Basin are depleted in C-14 relative to both alkenones and foraminifera, and TEX86 temperatures agree poorly with known surface water values. We propose three possible factors that could explain these results: (i) GDGTs may be labile relative to alkenones during advective transport through oxic waters; (ii) archaeal production deep in the water column may contribute C-14-depleted GDGTs to sediments; and (iii) some GDGTs also may derive from sedimentary archaeal communities. Each of these three processes is likely to occur with varying relative importance depending on geographic location. The latter two may help to explain why TEX86 temperature reconstructions from Santa Monica Basin do not appear to reflect actual sea surface temperatures. Terrigenous GDGTs are unlikely to be major contributors to Bermuda Rise or Santa Monica Basin sediments, based on values of the BIT index. The results also indicate that the crenarchaeol regioisomer is governed by processes different from other GDGTs. Individual measurements of the crenarchaeol regioisomer are significantly depleted in C-14 relative to co-occurring GDGTs, indicating an alternative origin for this compound that presently remains unknown. Re-examination of the contribution of crenarchaeol regioisomer to the TEX86 index shows that it is a significant influence on the sensitivity of temperature reconstructions. (C) 2008 Elsevier Ltd. All rights reserved. VL - 72 IS - 18 N1 - id: 2051; PT: J; UT: WOS:000259107700010 JO - Origins of archaeal tetraether lipids in sediments: Insights from radiocarbon analysis RID A-6723-2009 ER - TY - JOUR T1 - Oxygen and carbon isotope records of calcareous nannofossils from the west Philippine Sea during the last 190ka JF - Earth Science.Journal of China University of Geoscience Y1 - 2008 A1 - Jingtao, Zhao A1 - Li, Tiegang A1 - Chang, Fengming A1 - Li, Jun KW - 02D KW - 24 KW - algae KW - biochemistry KW - C-13/C-12 KW - carbon KW - Cenozoic KW - Foraminifera KW - Geochemistry KW - Holocene KW - Invertebrata KW - Isotope geochemistry KW - isotope ratios KW - isotopes KW - Last glacial maximum KW - microfossils KW - nannofossils KW - north pacific KW - Northwest Pacific KW - O-18/O-16 KW - oxygen KW - Pacific Ocean KW - paleo-oceanography KW - Philippine Sea KW - Plantae KW - Pleistocene KW - productivity KW - Protista KW - Quaternary KW - Quaternary geology KW - Stable isotopes KW - upper Pleistocene KW - West Pacific AB - The piston core Ph05-5 recovered from the West Philippine Sea(16.049 degrees N, 124.344 degrees E, water depth 3382m) was used to study the delta (super 18) O and delta (super 13) C variations of calcareous nannofossils. The delta (super 18) O values of calcareous nannofossils were obviously lower in Holocene and the last interglaciation than those in the last and the penultimate glaciation. During the last 190 ka the nannofossil delta (super 18) O values were positively correlated with those of planktonic and benthic foraminifera from the same core. But the average delta (super 18) O value of nannofossils was 0.431X10 (super -3) , higher than that of planktonic foraminifera Globigerinoides rubber, and was 0.410X10 (super -3) , lower than that of planktonic foraminifera Neogloboquadrina dutertrei. All the above three average delta (super 18) O values were much lower than those of benthic foraminifera Cibicides wullerstorfi. The change of nannofossil delta (super 13) C values showed similar trends with the absolute abundance of calcareous nannofossils in core Ph05-5, which also indicates the primary productivity variations in the West Philippine Sea. The primary productivity stayed at a stable but relatively low level at MIS 6 and MIS 5e.There was an abrupt rise at the beginning of MIS 5d for the primary productivity which retained high value until 25 ka BP. The primary productivity showed a slight decline during MIS 2 and MIS 1, but still higher than that of MIS 6 and MIS 5e. VL - 33 SN - 1000-2383, 1000-2383 IS - 2 N1 - id: 1933; NO: Source type: scholarlyjournals; Object type: Article; Copyright: GeoRef in Process, Copyright 2011, American Geosciences Institute. After editing and indexing, this record will be added to Georef.; CSAUnique: 570969-5; AccNum: 570969-5; ISSN: 1000-2383; Peer Reviewed: true ER - TY - JOUR T1 - Palaeoclimate - Tree rings floating on ice cores JF - Nature Geoscience Y1 - 2008 A1 - Reimer, Paula J. A1 - Hughen, Konrad A. VL - 1 IS - 4 N1 - id: 1984; PT: J; UT: WOS:000256433500013 JO - Palaeoclimate - Tree rings floating on ice cores ER - TY - JOUR T1 - PALEOPRODUCTIVITY VARIATION AND ITS CORRELATION WITH CLIMATE CHANGES:AN APPROACH OF LONG-CHAIN ALKENONE JF - Quaternary Sciences Y1 - 2008 A1 - Nan, Q. A1 - Li, T. A1 - Chen, Jinxia A1 - Yu, X. A1 - Li, Q. KW - Alkenone KW - ITCZ KW - paleoproductivity KW - SOT KW - the last 7000aB.P. AB - The accurate reconstruction of paleoproductivity is critical for understanding the carbon cycle in the past and for predicting the fate of anthropogenic carbon in the future.Biomarkers in marine sediments are useful tools for paleoenvirionment study and have been used as proxies for total and specific phytoplankton group paleoproductivity.Based on 17 AMS14C age controlling points,we report here molecular abundance data for alkenone and organic carbon isotopic data for bulk samples from a giant piston core MD05-2908(24°48.04'N,122°29.35'E).The aim is to evaluate the paleoproductivity and interpret the climatic-induced controlling factors for the past 7000aB.P.The results showed that the paleoproductivity in the South Okinawa Trough(SOT)fluctuated frequently in the past 7000aB.P.By correlating with the Titanium records from Huguang Marr and Cariaco Basin,we found out that the paleoproductivity was largely controlled by the latitude migration of ITCZ.The rapid southward shift of the ITCZ might have caused longer staying of the rainfall front in the source supply area,thus,led to intensified erosion,brought increased terrigenous material into the ECS and SOT by fluvial the terrigenous materil delivers to the SOT.Terrigenous input on the one hand might have fertilized the sea surface of SOT and stimulated the production,but on the other hand might have diluted the signal of marine derived input to the sediments.The lower production periods in the SOT correlated well with those ice-drift episodes recorded in the high latitude Atlantic Ocean,suggesting the strong relationships between high and low latitude climate. VL - 28 SN - 1001-7410 IS - 3 N1 - id: 1968 ER - TY - THES T1 - Paleotsunami History Recorded in Holocene Coastal Lagoon Sediments, Southeastern Sri Lanka T2 - Marine Geology and Geophysics (Marine) Y1 - 2008 A1 - Jackson, Kelly KW - Coastal Lagoons KW - Holocene KW - Paleotsunamis KW - Sri Lanka KW - Tsunami Deposits KW - Tsunami Sediments KW - Tsunamis AB - Tsunamis are low amplitude, large wavelength waves that can significantly impact coastal regions. Although their destructive impacts are clear from recent events, the frequency with which tsunamis occur is less well constrained. To better understand the tsunami history and coastal impacts in Sri Lanka, this study compares sediments deposited by the December 26, 2004, tsunami to older lagoon sediments in search of evidence for paleotsunami deposits. Results from this study illustrate that the coastal lagoons in Sri Lanka preserve tsunami deposits and can provide the first steps towards constraining the paleotsunami history of the Indian Ocean. Because Sri Lanka is a far field location relative to the Sumatra-Andaman subduction zone, the preserved tsunami deposits are likely mega-tsunami events similar in size and destruction to the December 26, 2004, tsunami. The December 26, 2004, M 9.1?9.3 Sumatra-Andaman earthquake generated a massive tsunami that propagated throughout the Indian Ocean, causing extreme coastal inundation and destruction. The southeastern coastline of Sri Lanka was impacted by the 2004 tsunami where between one and three waves inundated coastal villages, lagoons, and lowlands, killing more than 35,000 people. Karagan Lagoon, located on the southeastern coast of Sri Lanka, was impacted by two waves from this tsunami. Although the lagoon commonly is dominated by organic-rich, siliciclastic clays, silts, and fine sands, the 2004 tsunami deposited a distinct layer of coarse quartz-dominated sand between 1 and 22 cm thick. The base of the 2004 deposit is sharp and erosional and some layers feature faint subparallel laminations. The 2004 tsunami deposit is generally continuous, fines landward, and is confined to the eastern portion of Karagan Lagoon, in the direction from which the tsunami arrived. Sri Lankan lore, in conjunction with reconstructed historical earthquake data, suggests that other tsunamis likely affected Sri Lanka in the past. To test this, twenty-two 1?4 m sediment cores were collected from Karagan Lagoon, providing key information for unraveling the pre-2004 tsunami history of southeastern Sri Lanka. At depth, sixteen cores from Karagan Lagoon contain as many as ten distinct sand layers, including the deposit from the 2004 tsunami. These cores feature siliciclastic clays, silts, and fine sands that dominate the background lagoonal sedimentation that are punctuated by coarse sand layers. These sand-rich layers feature sharp, erosional bases, coarsen and fine upwards, vary in thickness from 1 to 22 cm, and include varying percentages of fine to very coarse sand, with a low-abundance of silt and clay. In the best constrained interval, three coarse sand layers include composition, grain size, grading, and sedimentary structures similar to the sediments deposited by the December 26, 2004, tsunami. The layers are identified in five of the twenty-two cores, although the thicknesses vary. Six additional less well constrained sand layers are present in four of the twenty-two cores. Cores located closer to the lagoon mouth and the eastern coastline (the direction from which the 2004 tsunami arrived) contain more sand layers than cores farther away from the tsunami wave entry point. On the basis of their sedimentary structures, geometry, and extent, these sandy layers are interpreted to represent paleotsunami deposits. AMS radiocarbon dating was used to date the bulk organic sediment from above, between, and below the ten paleotsunami layers in sediment cores from Karagan Lagoon to constrain the timing of events in southeastern Sri Lanka. Material from within the deposit was not dated because it was likely transported from various sources during the event and thus does not represent the age of the tsunami. AMS radiocarbon dates from above and below the paleotsunami layers were calibrated from radiocarbon years before present to calendar years before present (Cal YBP) using OxCal v. 4.0 (Bronk Ramsey, 1995; Bronk Ramsey, 2001) with calibration curve IntCal04 (Reimer et al., 2004). The constraining time intervals of tsunami deposits II?VI were averaged to yield deposits of ages 226, 1641, 4198, 4457, 4924 Cal YBP. Tsunamis VII?X only had sediment dated immediately below the deposit and therefore were deposited prior to 6249, 6455, 6665, and 6840 Cal YBP. In total, ten tsunami deposits, including the 2004 event, are preserved in Karagan Lagoon on the southeastern coast of Sri Lanka. The Karagan Lagoon paleotsunami deposits provide constraints on the recurrence interval of tsunamis similar in magnitude to the 2004 event. The uppermost paleotsunami units were deposited 226, 1641, 4198, 4457, and 4924 Cal YBP, based on AMS radiocarbon dating. Thus, including the 2004 event, six tsunamis affected Karagan Lagoon in the past 5500 years, yielding a recurrence interval of approximately 916 years. Three of the six events, however, occur between ~4000 and 5500 years yielding a recurrence interval of approximately 500 years for this 1500 year period. Four additional older paleotsunami deposits occur in the deeper sections of the cores and were deposited prior to 6249, 6455, 6665, and 6840 Cal YBP, yielding a recurrence interval of approximately 200 years for this time period. Assuming that Karagan Lagoon contains a complete record of tsunami events, the recurrence of tsunamis similar in magnitude to the December 26, 2004, event can occur as often as 200 years. This ?recurrence interval? is illustrated by our data for the time period with increased tsunami activity from ~4000 to 7000 Cal YBP. Tsunamis may potentially affect Sri Lanka at relatively high frequency during certain time intervals though the overall recurrence pattern of these events displays a highly irregular distribution. This extreme variability needs to be taken into consideration when such events are related to earthquake recurrence intervals. Prior to the December 26, 2004, tsunami, paleotsunami deposits in the Indian Ocean were largely unstudied and consequently, Holocene tsunami chronology was incompletely understood for the Indian Ocean. The results from this study represents the first geologic evidence of paleotsunami deposits in Sri Lanka generated by tsunamis during the past 7000 years. The identification of these paleotsunami deposits illustrates that the 2004 tsunami was not a ?one-time event,? but in fact has ancient counterparts. JF - Marine Geology and Geophysics (Marine) PB - University of Miami CY - Miami, FL VL - Master of Science (MS) UR - http://scholarlyrepository.miami.edu/oa_theses/171 ER - TY - JOUR T1 - Pan-Arctic patterns in black carbon sources and fluvial discharges deduced from radiocarbon and PAH source apportionment markers in estuarine surface sediments JF - Global Biogeochemical Cycles Y1 - 2008 A1 - Elmquist, M. A1 - Semiletov, I. A1 - Guo, L. D. A1 - Gustafsson, O. AB - A pan-arctic geospatial picture of black carbon (BC) characteristics was obtained from the seven largest arctic rivers by combining with molecular combustion markers (polycyclic aromatic hydrocarbons) and radiocarbon (C-14) analysis. The results suggested that the contribution from modern biomass burning to BC ranged from low in the Yukon (8%) and Lena (5%) Rivers to high in the Yenisey River (88%). The Mackenzie River contributed almost half of the total arctic fluvial BC export of 202 kton a(-1) (kton = 10(9) g), with the five Russian-Arctic rivers contributing 10-36 kton a(-1) each. The C-14-based source estimate of fluvially exported BC to the Arctic Ocean, weighted by the riverine BC fluxes, amount to about 20% from vegetation/biofuel burning and 80% from C-14-extinct sources such as fossil fuel combustion and relict BC in uplifted source rocks. Combining these pan-arctic data with available estimates of BC export from other rivers gave a revised estimate of global riverine BC export flux of 26 x 10(3) kton a(-1). This is twice higher than a single previous estimate and confirms that river export of BC is a more important pathway of BC to the oceans than direct atmospheric deposition. VL - 22 IS - 2 N1 - id: 820; 307ZP Times Cited:3 Cited References Count:89Y JO - Pan-Arctic patterns in black carbon sources and fluvial discharges deduced from radiocarbon and PAH source apportionment markers in estuarine surface sediments ER - TY - JOUR T1 - Quaternary paleoceanography of the central arctic based on Integrated Ocean Drilling Program Arctic Coring Expedition 302 foraminiferal assemblages JF - Paleoceanography Y1 - 2008 A1 - Cronin, T. M. A1 - Smith, S. A. A1 - Eynaud, F. A1 - O'Regan, M. A1 - King, J. AB - The Integrated Ocean Drilling Program (IODP) Arctic Coring Expedition (ACEX) Hole 4C from the Lomonosov Ridge in the central Arctic Ocean recovered a continuous 18 m record of Quaternary foraminifera yielding evidence for seasonally ice-free interglacials during the Matuyama, progressive development of large glacials during the mid-Pleistocene transition (MPT) similar to 1.2-0.9 Ma, and the onset of high-amplitude 100-ka orbital cycles similar to 500 ka. Foraminiferal preservation in sediments from the Arctic is influenced by primary (sea ice, organic input, and other environmental conditions) and secondary factors (syndepositional, long-term pore water dissolution). Taking these into account, the ACEX 4C record shows distinct maxima in agglutinated foraminiferal abundance corresponding to several interglacials and deglacials between marine isotope stages (MIS) 13-37, and although less precise dating is available for older sediments, these trends appear to continue through the Matuyama. The MPT is characterized by nearly barren intervals during major glacials (MIS 12, 16, and 22-24) and faunal turnover (MIS 12-24). Abundant calcareous planktonic (mainly Neogloboquadrina pachyderma sin.) and benthic foraminifers occur mainly in interglacial intervals during the Brunhes and very rarely in the Matuyama. A distinct faunal transition from calcareous to agglutinated foraminifers 200-300 ka in ACEX 4C is comparable to that found in Arctic sediments from the Lomonosov, Alpha, and Northwind ridges and the Morris Jesup Rise. Down-core disappearance of calcareous taxa is probably related to either reduced sea ice cover prior to the last few 100-ka cycles, pore water dissolution, or both. VL - 23 IS - 1 N1 - id: 813; 281VR Times Cited:10 Cited References Count:84Y JO - Quaternary paleoceanography of the central arctic based on Integrated Ocean Drilling Program Arctic Coring Expedition 302 foraminiferal assemblages ER - TY - THES T1 - Radiocarbon ages on deep water corals from the Ross Sea Y1 - 2008 A1 - Burt, T. PB - Hamilton College CY - Clinton, New York VL - Dissertation/Thesis ER - TY - JOUR T1 - Radiocarbon evidence for the importance of surface vegetation on fermentation and methanogenesis in contrasting types of boreal peatlands JF - Global Biogeochemical Cycles Y1 - 2008 A1 - Chanton, J. P. A1 - Glaser, P. H. A1 - Chasar, L. S. A1 - Burdige, D. J. A1 - Hines, M. E. A1 - Siegel, D. I. A1 - Tremblay, L. B. A1 - Cooper, W. T. AB - We found a consistent distribution pattern for radiocarbon in dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), and methane replicated across spatial and temporal scales in northern peatlands from Minnesota to Alaska. The (14)C content of DOC is relatively modern throughout the peat column, to depths of 3 m. In sedge-dominated peatlands, the (14)C contents of the products of respiration, CH(4) and DIC, are essentially the same and are similar to that of DOC. In Sphagnum- and woody plant-dominated peatlands with few sedges, however, the respiration products are similar but intermediate between the (14)C contents of the solid phase peat and the DOC. Preliminary data indicates qualitative differences in the pore water DOC, depending on the extent of sedge cover, consistent with the hypothesis that the DOC in sedge-dominated peatlands is more reactive than DOC in peatlands where Sphagnum or other vascular plants dominate. These data are supported by molecular level analysis of DOC by ultrahigh-resolution mass spectrometry that suggests more dramatic changes with depth in the composition of DOC in the sedge-dominated peatland pore waters relative to changes observed in DOC where Sphagnum dominates. The higher reactivity of DOC from sedge-dominated peatlands may be a function of either different source materials or environmental factors that are related to the abundance of sedges in peatlands. VL - 22 IS - 4 N1 - id: 1949; PT: J; UT: WOS:000262041000002 JO - Radiocarbon evidence for the importance of surface vegetation on fermentation and methanogenesis in contrasting types of boreal peatlands ER - TY - JOUR T1 - Radiocarbon-based assessment of fossil fuel-derived contaminant associations in sediments JF - Environmental Science & Technology Y1 - 2008 A1 - White, H. K. A1 - Reddy, C. M. A1 - Eclinton, T. I. AB - Hydrophobic organic contaminants (HOCs) are associated with natural organic matter (OM) in the environment via mechanisms such as sorption or chemical binding. The latter interactions are difficult to quantitatively constrain, as HOCs can reside in different OM pools outside of conventional analytical windows. Here, we exploited natural abundance variations in radiocarbon (C-14) to trace various fossil fuel-derived HOCs (C-14- free) within chemically defined fractions of contemporary OM (modern C-14 content) in 13 samples including marine and freshwater sediments and one dust and one soil sample. Samples were sequentially treated by solvent extraction followed by saponification. Radiocarbon analysis of the bulk sample and resulting residues was then performed. Fossil fuel-derived HOCs released by these treatments were quantified from an isotope mass balance approach as well as by gas chromatography-mass spectrometry. For the majority of samples (n = 13), 98-100% of the total HOC pool was solvent extractable. Nonextracted HOCs are only significant (29% of total HOC pool) in one sample containing pp-2,2-bis(chlorophenyl)1,1,1-trichloroethane and its metabolites. The infrequency of significant incorporation of HOCs into nonextracted OM residues suggests that most HOCs are mobile and bioavailable in the environment and, as such, have a greater potential to exert adverse effects. VL - 42 IS - 15 N1 - id: 881; 332HW Times Cited:1 Cited References Count:43Y JO - Radiocarbon-based assessment of fossil fuel-derived contaminant associations in sediments ER - TY - JOUR T1 - A radiocarbon-based assessment of the preservation characteristics of crenarchaeol and alkenones from continental margin sediments JF - Organic Geochemistry Y1 - 2008 A1 - Mollenhauer, G. A1 - Eglinton, T. I. A1 - HopmanSd, E. C. A1 - Damste, J. S. S. AB - Crenarchaeotal glycerol dibiphytanyl glycerol tetraether (GDGT) lipids and alkenones are two types of biomarkers, derived from planktonic marine microorganisms, which are used for reconstruction of sea surface temperature. We determined the radiocarbon contents of the archaeal GDGT crenarchaeol and of alkenones isolated from continental margin sediments. Systematic differences were found between the two biomarkers, with higher radiocarbon content in crenarchaeol than in the phytoplankton-derived alkenones. These differences can be explained by variable contributions of pre-aged, laterally-advected material to the core sites. Crenarchaeol appears to be more efficiently degraded during transport in oxygen-replete environments than alkenones. Whether this reflects the influence of chemical structure or mode of protection (e.g., particle association) is not known. (C) 2008 Elsevier Ltd. All rights reserved. VL - 39 IS - 8 N1 - id: 883; 344AQ Times Cited:11 Cited References Count:33Y JO - A radiocarbon-based assessment of the preservation characteristics of crenarchaeol and alkenones from continental margin sediments ER - TY - JOUR T1 - Radiocarbon-derived sedimentation rates in the Gulf of Mexico JF - Deep-Sea Research Part Ii-Topical Studies in Oceanography Y1 - 2008 A1 - Santschi, P. H. A1 - Rowe, G. T. KW - accumulation KW - ATCHAFALAYA RIVER KW - cores KW - Gulf of Mexico KW - ice-sheet KW - Mass KW - Meltwater KW - MISSISSIPPI RIVER DELTA KW - Nepheloid layer transport KW - Organic carbon burial rates KW - radiocarbon KW - Sedimentation rates KW - TERRIGENOUS ORGANIC-MATTER KW - wasting AB - Sedimentation rates were determined for the northern Gulf of Mexico margin sediments at water depths ranging from 770 to 3560m, using radiocarbon determinations of organic matter. Resulting sedimentation rates ranged from 3 to 15 cm/kyr, decreasing with increasing water depth. These rates agree with long-term sedimentation rates estimated previously using stratigraphic methods, and with estimates of sediment delivery rates by the Mississippi River to the northern Gulf of Mexico, but are generally higher by 1-2 orders of magnitude than those estimated by (210)Pb(xs) methods. Near-surface slope sediments from 2737 to water depth in the Mississippi River fan were much older than the rest. They had minimum (14)C ages of 16-27 kyr and delta(13)C values ranging from -24 parts per thousand to -26.59 parts per thousand, indicating a terrestrial origin of organic matter. The sediments from this site were thus likely deposited by episodic mass wasting of slope sediment through the canyon, delineating the previously suggested main pathway of sediment and clay movement to abyssal Gulf sediments. (C) 2008 Published by Elsevier Ltd. VL - 55 SN - 0967-0645 IS - 24-26 N1 - United States Mineral Management Service [1435-01-99-CT-30991] JO - Deep-Sea Res. Part II-Top. Stud. Oceanogr. ER - TY - JOUR T1 - Reconstructing relative flooding intensities responsible for hurricane-induced deposits from Laguna Playa Grande, Vieques, Puerto Rico JF - Geology Y1 - 2008 A1 - Woodruff, J. D. A1 - Donnelly, J. P. A1 - Mohrig, D. A1 - Geyer, W. R. AB - Extreme coastal flooding, primarily during hurricane strikes, has deposited sand-rich layers in Laguna Playa Grande, a back-barrier lagoon located on the island of Vieques, Puerto Rico. Silici-clastic grain-size distributions within these overwash deposits fine landward (away from the barrier and toward the mainland). A simple advective-settling model can explain this pattern of lateral sorting and is used to constrain the relative magnitude of past flooding events. A deposit associated with the A.D. 1928 San Felipe hurricane is used as a modern analogue to test the technique, which produces reasonable estimates for wave heights that exceed the barrier during the event. A 5000 yr reconstruction of local flooding intensity is developed that provides a measure of the competence for each overwash event to transport coarser-grained sediment a fixed distance into the lagoon. This reconstruction indicates that although the Laguna Playa Grande record exhibits large-scale changes in hurricane frequency on centennial to millennial time scales, the magnitude of these events has stayed relatively constant. Over the last 5000 yr, no evidence exists for an anomalously large hurricane or tsunami event with a competence for sediment transport greater than historical hurricane events. VL - 36 IS - 5 N1 - id: 865; ISI Document Delivery No.: 300VM Times Cited: 3 Cited Reference Count: 19 Cited References: BALDOCK TE, 2005, COAST ENG, V52, P633, DOI 10.1016/j.coastaleng.2005.04.002 BOOSE ER, 2004, ECOL MONOGR, V74, P335 DONNELLY C, 2006, J COASTAL RES, V22, P965, DOI 10.2112/04-0431.1 DONNELLY JP, 2001, GEOLOGY, V29, P615 DONNELLY JP, 2007, NATURE, V447, P465, DOI 10.1038/nature05834 FERGUSON RI, 2004, J SEDIMENT RES, V74, P933 HAUG GH, 2001, SCIENCE, V293, P1304 HOLLAND TK, 2001, COASTAL SEDIMENTS 91, P489 JAFFE BE, 2007, SEDIMENT GEOL, V200, P347, DOI 10.1016/j.sedgeo.2007.01.013 LIU KB, 1993, GEOLOGY, V21, P793 MERCADO A, 1994, NAT HAZARDS, V10, P235, DOI 10.1007/BF00596144 MEYERPETER E, 1948, 2ND P C IAHR STOCKH, V2, P39 MOORE AL, 2007, SEDIMENT GEOL, V200, P336, DOI 10.1016/j.sedgeo.2007.01.012 NOTT J, 2004, ENVIRON INT, V30, P433, DOI 10.1016/j.cnvint.2003.09.010 NYBERG J, 2001, QUATERNARY RES, V56, P87, DOI 10.1006/qres.2001.2249 RUESSINK BG, 1998, J GEOPHYS RES-OCEANS, V103, P3111 SOLA EM, 1995, HISTORIA HURACANES P STOCKDON HF, 2006, COAST ENG, V53, P573, DOI 10.1016/j.coastaleng.2005.12.005 VISSER PJ, 1998, BREACH GROWTH SAND D Woodruff, Jonathan D. Donnelly, Jeffrey P. Mohrig, David Geyer, Wayne R. Geological soc amer, inc Boulder; YY JO - Reconstructing relative flooding intensities responsible for hurricane-induced deposits from Laguna Playa Grande, Vieques, Puerto Rico ER - TY - JOUR T1 - Recycling of graphite during Himalayan erosion: a geological stabilization of carbon in the crust JF - Science Y1 - 2008 A1 - Galy, V. A1 - Beyssac, O. A1 - France-Lanord, C. A1 - Eglinton, T. AB - At geological time scales, the role of continental erosion in the organic carbon (OC) cycle is determined by the balance between recent OC burial and petrogenic OC oxidation. Evaluating its net effect on the concentration of carbon dioxide and dioxygen in the atmosphere requires the fate of petrogenic OC to be assessed. Here, we report a multiscale (nanometer to micrometer) structural characterization of petrogenic OC in the Himalayan system. We show that graphitic carbon is preserved and buried in marine sediments, while the less graphitized forms are oxidized during fluvial transport. Radiocarbon dating indicates that 30 to 50% of the carbon initially present in the Himalayan rocks is conserved during the erosion cycle. Graphitization during metamorphism thus stabilizes carbon in the crust over geological time scales. VL - 322 IS - 5903 N1 - id: 1876; Galy, Valier Beyssac, Olivier France-Lanord, Christian Eglinton, Timothy New York, N.Y. Science. 2008 Nov 7;322(5903):943-5.; YY JO - Recycling of graphite during Himalayan erosion: a geological stabilization of carbon in the crust ER - TY - JOUR T1 - Relative sea-level change, Kjove Land, Scoresby Sund, East Greenland: implications for seasonality in Younger Dryas time JF - Quaternary Science Reviews Y1 - 2008 A1 - Hall, B. A1 - Baroni, C. A1 - Denton, G. A1 - Kelly, M. A. A1 - Lowell, T. AB - The age of the Milne Land Stade (MLS) moraines in the Scoresby Sund region of East Greenland is key for testing the hypothesis that strong seasonality marked abrupt cooling events, such as the Younger Dryas, registered in Greenland ice cores. The relevant chronology is based on 69 radiocarbon dates of shells from raised beaches and deltas related to marine inundation and isostatic rebound that accompanied glacier retreat from the moraines. Taken together, these dates form the basis for a relative sea-level curve that shows very high rates of emergence typical of recently deglaciated regions. Upward extrapolation of this curve suggests that the marine limit (134 m a.s.l.) dates to about 12,400 cal yr B.R The shorelines that mark the marine limit lie within areas that were ice-covered when the glaciers were at the outer limit of the MLS advance; hence, the moraines that form the outer limit must antedate 12,400 cal yr B.R and probably are from earliest Younger Dryas or Allerod time. At Holger Danskes Briller, an inner moraine grades to a massive ice-contact delta, now at 101 m a.s.l., which is dated to 11,000-11,300 cal yr B.P. The age of the outer MLS moraines, along with constraints on the maximum possible Younger Dryas ice extent and snowline lowering are consistent with the idea that East Greenland climate experienced strong seasonality during Younger Dryas time. (C) 2008 Elsevier Ltd. All rights reserved. VL - 27 IS - 25-26 N1 - id: 824; 389XX Times Cited:3 Cited References Count:43Y JO - Relative sea-level change, Kjove Land, Scoresby Sund, East Greenland: implications for seasonality in Younger Dryas time ER - TY - JOUR T1 - Reply to Comment on "The timing and evolution of the post-glacial transgression across the Sea of Marmara shelf south of Istanbul" by Hiscott et al., Marine Geology 248, 228-236 JF - Marine Geology Y1 - 2008 A1 - Eris, K. K. A1 - Ryan, W. B. F. A1 - Cagatay, M. N. A1 - Lericolais, G. A1 - Sancar, U. A1 - Menot, G. A1 - Bard, E. AB - In their comment Hiscott and co-authors adhere rigidly to ages and sources for sedimentary units in the subsurface of the Marmara shelf that they have previously reported in their publications from 2002 through 2007. This adherence is in spite of a superior age-depth model from our 13 m-long sediment core that penetrated deeply into the deposits under consideration and in disregard to the results of subsequent more-detailed and full-coverage mapping of the region under scrutiny. The age revisions are dismissed by the authors of the comment as representing sediments severely disturbed during coring. We rebut this criticism. The Bosporus source attributed by them to the sedimentary units sampled and dated by us appears to be driven by their conception that the Black Sea had a persistent outflow prior to its two-way connection with Marmara. Irrespective of whether the outflow was persistent, our reply shows that the drawing of the isopachs of the sedimentary units by Hiscott and coauthors was accomplished in a fashion to promote the Bosporus source hypothesis regardless of the geographic limits of their survey. The ages assigned to the units are equally indeterminate because the cores used by them have missing core tops of unknown lengths that are not discussed in their publications. Furthermore, the sub-bottom reflectors at the sites where the reflectors were calibrated to their only core without a missing top are actually hidden by the finite width of the bottom reflecting wavelet. (C) 2008 Elsevier B.V. All rights reserved. VL - 254 IS - 3-4 N1 - id: 784; 377ZE Times Cited:0 Cited References Count:33Y JO - Reply to Comment on "The timing and evolution of the post-glacial transgression across the Sea of Marmara shelf south of Istanbul" by Hiscott et al., Marine Geology 248, 228-236 ER - TY - JOUR T1 - Research focus - Tempestuous highs and lows in the Gulf of Mexico JF - Geology Y1 - 2008 A1 - Donnelly, J. P. A1 - Giosan, L. VL - 36 IS - 9 N1 - id: 863; ISI Document Delivery No.: 344QW Times Cited: 3 Cited Reference Count: 25 Cited References: BLUM MD, 2003, T GULF COAST ASS GEO, V53, P64 BLUM MD, 2008, GEOLOGY, V36, P675, DOI 10.1130/G24728A.1 DONNELLY JP, 2007, NATURE, V447, P465, DOI 10.1038/nature05834 GIOSAN L, 2006, GEOLOGY, V34, P757, DOI 10.1130/G22587.1 HUTTON EWH, 2008, COMPUT GEOSCI-UK, V34, P1319, DOI 10.1016/j.cageo.2008.02.013 IVINS ER, 2007, GEOPHYS RES LETT, V34, ARTN L16303 JURKOWSKI G, 1984, J GEOPHYS RES, V89, P6247 KOMAR PD, 2008, J COASTAL RES, V24, P479, DOI 10.2112/07-0894.1 LAMBERT WJ, 2003, T GULF COAST ASS GEO, V53, P433 LIU KB, 2004, HURRICANES TYPHOONS, P13 LOPEZ GI, 2008, J COASTAL RES, P49 MILLIKEN KT, 2008, GEOL S AM S, V443, P1, DOI 10.1130/2008.2443(01) MORTON RA, 2000, J SEDIMENT RES A, V70, P478 OTVOS EG, 1995, J COASTAL RES, V11, P984 OTVOS EG, 1999, J COASTAL RES, V15, P438 OTVOS EG, 2000, GEOMORPHOLOGY, V32, P83 OTVOS EG, 2002, QUATERNARY RES, V57, P425 RODRIGUEZ AB, 2004, J SEDIMENT RES, V74, P405 RODRIGUEZ AB, 2006, J SEDIMENT RES, V76, P257, DOI 10.2110/jsr.2006.018 SHEPARD FP, 1964, SCIENCE, V143, P574 STAPOR FW, 1991, J COASTAL RES, V7, P815 TANNER WF, 1992, B AM METEOROL SOC, V73, P297 TANNER WF, 1995, MAR GEOL, V129, P149 TORNQVIST TE, 2006, GEOLOGY, V34, P697, DOI 10.1130/G22624.1 WRIGHT EE, 2005, J SEDIMENT RES, V75, P621 Donnelly, Jeffrey P. Giosan, Liviu Geological soc amer, inc Boulder; YY JO - Research focus - Tempestuous highs and lows in the Gulf of Mexico ER - TY - JOUR T1 - Robust deterministic model describing the bomb radiocarbon signal for use in fish age validation JF - Transactions of the American Fisheries Society Y1 - 2008 A1 - Hamel, O. S. A1 - Piner, K. R. A1 - Wallace, J. R. AB - The bomb radiocarbon chronometer has become a standard tool for assessing the accuracy of otolith-based fish age estimates. Use of the chronometer depends upon the increase in C-14 that occurred due to the atmospheric testing of nuclear weapons in the middle of the 20th century. In previous analyses, a variety of ad hoc methods have been used to compare test chronologies with reference chronologies. This paper proposes a deterministic coupled-functions model that describes bomb radiocarbon chronologies and standardizes and facilitates comparisons within and across species. In this model, a Gaussian pulse of radiocarbon over time is assumed, and dispersion and dilution are described by continuous exponential decay. The model simplifies to the product of a cumulative normal function and an exponential function; despite its simplicity, the model approximates the observed changes in oceanic radiocarbon quite well. It also allows for statistical testing of the timing of increase between different time series and thus permits quantitative aging validation as well as analysis of geographical differences in the timing of the bomb radiocarbon signal. Estimated model parameters describe the timing of the onset and temporal midpoint of the bomb-related increase in C-14 and the rate of C-14 dispersion or dilution, which corresponds to the observed rate of decline during the postbomb period. Nine published chronologies are used to demonstrate the model and compare it with other published methods of summarizing bomb radiocarbon data for age validation purposes. VL - 137 IS - 3 N1 - id: 775; 306ZU Times Cited:2 Cited References Count:21Y JO - Robust deterministic model describing the bomb radiocarbon signal for use in fish age validation ER - TY - JOUR T1 - Rock magnetic and geochemical record in a sediment core from the eastern Arabian Sea: Diagenetic and environmental implications during the late Quaternary JF - Palaeogeography, Palaeoclimatology, Palaeoecology Y1 - 2008 A1 - Rao, Venigalla Purnachandra A1 - Kessarkar, Pratima Mohan A1 - Patil, Shiva Kumar A1 - Ahmad, Syed Masood AB - Rock magnetic concentration, grain size and mineralogy parameters together with organic carbon, calcium carbonate, redox-sensitive elements, δ18O of Globigerinoides ruber and radiocarbon dating were carried out on a 445 cm long sediment core collected at 1380 m depth off Mangalore, southwestern margin of India. The top 290 cm sediments of the core correspond to the last 18 kaBP. The δ18O and magnetic records exhibit major events at ∼ 16 kaBP, 14.5 kaBP, 11.5 kaBP and 9.8/8.6 kaBP related to start and intensity of the summer monsoon and climate change, and are synchronous with that of the western Arabian Sea and North Atlantic. The sediments with high magnetic susceptibility correlate with high sedimentation rates. The sediments are dominated by fine-grained magnetite, but intervals of 1.2–3.8 kaBP and 10–13.5 kaBP were subjected to diagenetic changes, resulting in the dissolution of fine-grained magnetites and enrichment of redox-sensitive trace elements (Cu, Ni, Zn, V, Mo and U). The sediments between 290 cm and 445 cm correspond to 18–27 kaBP and are characterized by distinct decrease in magnetic concentration, grain size and mineralogy parameters, high organic carbon, low concentrations of redox-sensitive trace elements and abundant pyritized tubules. The reductive diagenetic conditions indicated by rock magnetic properties are in contrast with the weak sub-oxic conditions revealed by low concentrations of trace elements in the sediments. The seasonal organic matter flux produced during the winter monsoon and moderate sedimentation rates favoured reductive diagenesis in the sediments at and below the last glacial maximum (LGM). Intermittent bioturbation, however, allowed oxidants to penetrate into the sediments, remobilized redox-sensitive trace elements into the water column and modified the primary geochemical signal of the sedimentary environment. VL - 270 IS - 1–2 JO - Rock magnetic and geochemical record in a sediment core from the eastern Arabian Sea: Diagenetic and environmental implications during the late Quaternary ER - TY - JOUR T1 - The sedimentary record of glacial retreat, Marinelli Fjord, Patagonia: Regional correlations and climate ties JF - Marine Geology Y1 - 2008 A1 - Boyd, B.L. A1 - Anderson, J.B. A1 - Wellner, J.S. A1 - ández, R.A. AB - The Inland Passage of Chile comprises the most continuous latitudinal transect of ice fields, ice caps, and alpine glaciers in the Southern Hemisphere, providing an excellent natural laboratory for the study of glacial response to climate change during the Holocene. Here we report results from a marine geological investigation of Marinelli Fjord, Tierra del Fuego (54°25 S, 69°35 W) and Ainsworth Fjord, which merges with Marinelli Fjord. Data acquired during July 2005 onboard the RV/IB Nathaniel B. Palmer include high-resolution seismic data, multibeam swath bathymetry data and sediment cores. Post-cruise analyses include detailed seismic facies and lithofacies analysis and radiocarbon dating. The results indicate that a major transition in the glacimarine record from ice-proximal facies to ice-distal facies occurred in the outer basins of the fjord at 15.5 kyr to 12.5 kyr. The ice-proximal facies consists of pebbly mud with abundant laminations and is characterized by high average sedimentation rates (28 mm/yr). In contrast, an ice-distal facies is dominantly bioturbated mud with low average sedimentation rates (0.56 mm/yr). This transition marks the retreat of Marinelli Glacier from the outer basins with no evidence for glacial re-advance. Subsequently, during the mid to late-Holocene, Ainsworth Glacier retreated and exposed Ainsworth Fjord. Our results are consistent with the climatic trends for southern South America where the final deglaciation of the region ended at ~ 12.5 ka. During the Holocene, stable ice conditions persisted until the mid-1960s when Marinelli Glacier began rapidly retreating to its modern day position. VL - 255 UR - http://linkinghub.elsevier.com/retrieve/pii/S0025322708002636http://api.elsevier.com/content/article/PII:S0025322708002636?httpAccept=text/xmlhttp://api.elsevier.com/content/article/PII:S0025322708002636?httpAccept=text/plain IS - 3-4 ER - TY - JOUR T1 - Sex and Symbolism: A Middle Holocene Phallic Artifact from Santa Rosa Island, California JF - Pacific Coast Archaeological Society Quarterly Y1 - 2008 A1 - Rick, Torben C. A1 - Erlandson, Jon M. A1 - Wolff, Christopher B. VL - 40 IS - 1 N1 - id: 2066 ER - TY - JOUR T1 - Shell and Bone Artifacts from Two Middle Holocene Red Abalone Middens on San Miguel Island JF - Pacific Coast Archaeological Society Quarterly Y1 - 2008 A1 - Braje, Todd J. A1 - Erlandson, Jon M. VL - 40 IS - 1 N1 - id: 2067 JO - Shell and Bone Artifacts from Two Middle Holocene Red Abalone Middens on San Miguel Island ER - TY - JOUR T1 - Software development for continuous-gas-flow AMS JF - Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions with Materials and Atoms Y1 - 2008 A1 - von Reden, K. F. A1 - Roberts, M. L. A1 - W. J. Jenkins A1 - Rosenheim, B. E. A1 - McNichol, A. P. A1 - Schneider, R. J. AB - The National Ocean Sciences Accelerator Mass Spectrometry (NOSAMS) Facility at Woods Hole Oceanographic institution is presently completing installation of a novel continuous-flow AMS system. A multi-year development of an AMS microwave gas ion source in collaboration with Atomic Energy Canada Limited (AECL), Chalk River, has preceded this final step of an implementation that is expected to add a new dimension to (14)C AMS. National Instruments, NIM, and CAMAC modules have been programmed with Lab-VIEW on a Windows XP platform to form the basis for data acquisition. In this paper we discuss possible applications and include simulations of expected data acquisition scenarios like real-time AMS analysis of chromatograms. Particular attention will have to be given to issues of synchronization between rapidly changing input amplitudes and signal processing cycles in hardware and software. (C) 2008 Elsevier B.V. All rights reserved. VL - 266 IS - 10 N1 - id: 2091; PT: J; CT: 9th European Conference on Accelerators in Applied Research and Technology; CY: SEP 03-07, 2007; CL: Florence, ITALY; SP: Univ Florence, Dept Phys, Ist Nazl Fis Nucl; UT: WOS:000257185600033 JO - Software development for continuous-gas-flow AMS ER - TY - JOUR T1 - Source and composition of organic matter in the Bari canyon (Italy): Dense water cascading versus particulate export from the upper ocean JF - Deep-Sea Research Part I-Oceanographic Research Papers Y1 - 2008 A1 - Tesi, T. A1 - Langone, L. A1 - Goñi, M. A. A1 - Turchetto, M. A1 - Miserocchi, S. A1 - Boldrin, A. AB - Recent studies in the southern Adriatic Sea have shown that dense water cascading is an effective off-shelf transport mechanism. In order to evaluate the relative importance of different processes affecting the down-slope transfer of organic matter (OM), a multi-proxy biogeochemical study was carried out in the southern Adriatic. Three sediment traps were deployed on the southern slope in March 2004 for 1 year at 35 m above the seabed. Surficial sediments were collected on the shelf and slope along a shore-normal transect. Suspended material in the water column at different water depths was collected along nine shore-normal transects. Organic carbon (OC), total nitrogen (TN), carbon isotopic composition (delta C-13 and Delta C-14) and CuO reaction products were used to identify the OM sources and to asses the relative importance of vertical and lateral particulate fluxes. Both sinking particulates from the euphotic zone and advected material from the seafloor were collected by the moored instrumentations. During low-mass fluxes, the trapped material exhibited the highest Delta C-14 values (from -162.0 parts per thousand to +42.3 parts per thousand) and OC contents (from 1.13% to 2.17%) while the lignin displayed the lowest content (from 0.160 to 0.285 mg 100 mg(-1) OC). However, during dense water cascading events, the down-slope particulate flux showed different compositional features. In this period the trapped material displayed the most depleted Delta C-14 values (from -275.3 parts per thousand to -171.3 parts per thousand.), the lowest OC content (from 0.87% to 1.31%), and the highest lignin content (from 0.230 to 379 mg 100 mg(-1) OC). Holocene sea-level rise has drastically reduced sediment availability to the Bari canyon, and this in turn has affected the OC composition of the material funneled toward the deep Adriatic Sea. Parameters based on lignin CuO products suggest that the terrestrial material exported down the slope is very different from riverine inputs and inner shelf sediments. This indicates that neither river floods nor sediment resuspension from the inner shelf contributes directly to the down-slope flux. Rather, the material collected in the sediment traps exhibits an OM composition comparable to the surface sediments collected in the southern outer shelf. This correspondence suggests that resuspension of sediments by bottom currents in the southern outer shelf significantly contribute to down-slope OM transfer. Finally, the presence of lignin phenols in all cups indicates that lateral fluxes were constantly active on the slope throughout the deployment. (C) 2008 Elsevier Ltd. All rights reserved. VL - 55 IS - 7 N1 - id: 828; 330FL Times Cited:4 Cited References Count:87Y JO - Source and composition of organic matter in the Bari canyon (Italy): Dense water cascading versus particulate export from the upper ocean ER - TY - JOUR T1 - Stratigraphy, pollen history and geochronology of tidal marshes in a Gulf of Maine estuarine system: Climatic and relative sea level impacts JF - MARINE GEOLOGY Y1 - 2008 A1 - Ward, Larry G. A1 - Zaprowski, Brent J. A1 - Trainer, Kevin D. A1 - Davis, P. Thompson KW - accretion KW - climate effects KW - pollen KW - relative sea level KW - salt marshes KW - sedimentology KW - stratigraphy AB - Sedimentologic and stratigraphic characteristics of five tidal marshes in Great Bay Estuary, New Hampshire, which is located on the western boundary of the Gulf of Maine, were assessed from 20 vibracores. detailed descriptions of surficial environments, pollen analyses, and radiocarbon dating. Modern marsh sequences in Great Bay Estuary initiated with a time-transgressive basal peat that formed at the upland-brackish marsh boundary. The oldest basal peat deposit sampled during this study was dated at similar to 4560 cal yr B.P (based on an age of 4060 +/- 40 C-14 yr B.P.). The original tidal marshes that formed in Great Bay Estuary apparently were unable to accrete at a high enough rate to allow seaward expansion, resulting in a transgressive sequence of low marsh or mudflat sediments overlying the basal peat. The transgressive tidal marsh sequence is capped by high marsh sediments that corresponded to a slowing of relative sea-level (RSL) rise in the region and regressive seaward expansion of the tidal marshes. However, significant variations from these transgressive-regressive sequences occur in the Great Bay tidal marshes as a result of more recent marsh expansion and tidal channel migrations. Detailed pollen analyses of a vibracore taken in a tidal marsh along Squamscott River with a sedimentary record spanning the last similar to 3900 cal yr B.P exhibit five well-documented marker horizons including: 1) an increase of Tsuga (hemlock); 2) the appearance of Picea (spruce); 3) Tsuga and Fagus (beech) declines; 4) an increase in Ambrosia (ragweed) coupled with a sudden decrease in Quercus (oak); and 5) the Castanea (chestnut) decline. Using published ages for these pollen horizons and a calibrated 14C age obtained during this study for a basal peat, accretion rates for this marsh system over five time intervals were calculated: 1) 0.4 to 0.5 mm yr(-1) from similar to 3900 to 2850 cal yr B.P.; 2) 0.6 mm yr(-1) from similar to 2850 to similar to 1960 cal yr B.P.; 3) 0.8 mm yr(-1) from similar to 1960 to similar to 580 cal yr B.P.; 4) 0.7 to 0.8 mm yr(-1) from similar to 580 to similar to 210 cal yr B.P.: and 5) 0.8 to 0.9 mm yr(-1) over the last 210 years. The long-term accretion rate for the entire sequence based on the calibrated C-14 age of the basal peat was 0.6 to 0.7 mm yr(-1). This result agrees with accretion rates determined from calibrated C-14 ages from two other tidal marsh systems in Great Bay Estuary with accretion rates between similar to 0.6 to similar to 0.8 mm yr(-1). Higher accretion rates were obtained at a nearby tidal marsh with 1.2 mm yr(-1) for just the marsh and 1.3 mm yr(-1) for the marsh and underlying subtidal sediment. The results of this study indicate that the sedimentology and stratigraphy of moderate-size tidal marshes in rocky, glaciated coasts are highly variable and are strongly influenced by complex interactions among RSL, climatic variations, and anthropogenic influences. For instance, the early development of many of the marshes in the Great Bay Estuary area were likely driven by changes in rates of RSL resulting in transgressive onlap boundaries, subsequently overlain by regressive intertidal marsh sequences. However, more recent changes in tidal marsh sediment composition deposited during a relatively slow, steady RSL rise likely result from other forcings. such as changes in minerogenic and orogenic sediment inputs due to anthropogenic effects, tidal channel migrations, major storms causing erosion of the marsh, or climatic changes causing shifts in sediment delivery or vegetation. (C) 2008 Elsevier B.V. All rights reserved. VL - 256 ER - TY - JOUR T1 - Subdecadally resolved paleoceanography of the Peru margin during the last two millennia JF - Geochemistry Geophysics Geosystems Y1 - 2008 A1 - Agnihotri, R. A1 - Altabet, M. A. A1 - Herbert, T. D. A1 - Tierney, J. E. AB - Using multiproxy sediment core data from the El Nino-Southern Oscillation (ENSO)-sensitive Peru margin, subdecadally resolved (down to similar to 0.6 year) surface productivity and subsurface denitrification are reconstructed for the last similar to 2300 years. Scanning XRF generated major elemental data (Ti, Fe, Si) correlate well with discrete inductively coupled plasma-atomic emission spectometry (ICP-AES) analyses and together with X-radiography (core density) are used as productivity indices. As surface productivity in this marine region is strongly impacted by ENSO, higher (lower) periods of surface productivity are inferred to represent a persistent normal/La Nina (El Nino)-like state. Surface productivity and subsurface denitrification appear to have remained intimately coupled during this period due to direct stimulation of requisite subsurface suboxia and/or hydrographic restructuring. The late Holocene Peru margin is characterized by persistent moderate productivity and subsurface denitrification punctuated at centennial scale by shorter-duration periods of high production and intense denitrification. These centennial-scale events are likely analogous to modern observations of decadal-scale "regime shifts'' but of higher amplitude and provide a background history for future natural changes to this system. Solar (irradiance) variability is suggested to have influenced Peru productivity as evidenced in numerous high-resolution paleorecords from the northern hemisphere. VL - 9 N1 - id: 780; 303SA Times Cited:7 Cited References Count:54Y JO - Subdecadally resolved paleoceanography of the Peru margin during the last two millennia ER - TY - JOUR T1 - Subtropical Atlantic salinity variability and Atlantic meridional circulation during the last deglaciation JF - Geology Y1 - 2008 A1 - Carlson, A. E. A1 - Oppo, D. W. A1 - Came, R. E. A1 - LeGrande, A. N. A1 - Keigwin, L. D. A1 - Curry, W. B. AB - During the last deglaciation (ca. 21-10 ka), freshening of the North Atlantic surface likely caused reductions in Atlantic meridional overturning circulation (AMOC); the mechanisms related to AMOC recovery remain poorly understood. Here we present three new deglacial surface temperature and delta O-18(seawater) (delta O-18(sw)) reconstructions from the western subtropical North and South Atlantic. Similarities to tropical Caribbean and western Atlantic delta O-18(sw) records suggest that a salty surface water mass accumulated in the western Atlantic from 27 degrees S to 33 degrees N during periods of reduced AMOC. However, delta O-18(sw) decreases led deep AMOC resumption by hundreds of years. We suggest that the northward export of salt previously trapped in the western Atlantic resulted in the early establishment of a shallow overturning circulation that eventually culminated in deep AMOC resumption, implying that AMOC may constitute a self-limiting system. 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Oppo, Delia W. Came, Rosemarie E. LeGrande, Allegra N. Keigwin, Lloyd D. Curry, William B. Geological soc amer, inc Boulder; YY JO - Subtropical Atlantic salinity variability and Atlantic meridional circulation during the last deglaciation ER - TY - CONF T1 - Taphonomy and ages of bivalve shells from San Salvador Island, Bahamas Y1 - 2008 A1 - Pruss, Sara B. KW - 10 KW - abrasion KW - absolute age KW - Bahamas KW - beachrock KW - Bivalvia KW - C-14 KW - carbon KW - carbonate rocks KW - Caribbean region KW - Cenozoic KW - Chione KW - dates KW - Gastropoda KW - Glycymeris KW - Heterodonta KW - Holocene KW - interpretation KW - Invertebrata KW - Invertebrate paleontology KW - isotopes KW - lithification KW - living taxa KW - Mollusca KW - Quaternary KW - radioactive isotopes KW - San Salvador KW - sedimentary rocks KW - sediments KW - shells KW - taphonomy KW - upper Holocene KW - Veneridae KW - Veneroida KW - West Indies AB - Paleontological interpretations of taphonomic processes can be complimented by examining abrasion and age of shells in modern settings. A preliminary analysis of the ages of bivalves from Haitian Boat Beach (just east of Barkers Point, northwest coast of San Salvador Island, Bahamas) provides a range of ages of shell material exposed on modern beaches of San Salvador Island and provides estimates of the timing of beach rock lithification. At Haitian Boat Beach Beach, bivalves and gastropods were collected from shell accumulations preserved on the beach as well as within a single 3 to 5-cm thick horizon of beach rock. The ages of 2 valves (Genus Chione) from the beach and 4 valves (Genus Chione and Genus Glycymeris) from the beach rock were analyzed. Two of the most abraded shells were selected for analysis from the beach in an attempt to get a maximum age of beach shell material. These shells were radiocarbon dated by measuring carbon-14 at NOSAMS and converted to calendar years using the CALIB program of Stuiver and Reimer (1993). Two abraded valves collected from the beach yielded calendar year ages BP of 512 and 549 years. The beach rock valves yielded calendar year ages BP of 143, 129, and 1628. These results suggest lithification of beach rock was initiated PB - Geological Society of America (GSA), Boulder, CO, United States (USA) CY - United States (USA) VL - 40 N1 - id: 2219; Source type: conferencepapers&proceedings; Object type: Article; Object type: Conference Paper; Copyright: GeoRef, Copyright 2008, American Geological Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States; CSAUnique: 2010-024085; AccNum: 2010-024085; ISSN: 0016-7592; CODEN: GAAPBC ER - TY - JOUR T1 - Terrigenous organic matter in sediments from the Fly River delta-clinoform system (Papua New Guinea) JF - Journal of Geophysical Research-Earth Surface Y1 - 2008 A1 - Goñi, M. A. A1 - Monacci, N. A1 - Gisewhite, R. A1 - Crockett, J. A1 - Nittrouer, C. A1 - Ogston, A. A1 - Alin, S. R. A1 - Aalto, R. AB - Although an inordinate fraction of the global sediment flux to the ocean occurs in tropical mountainous river margins, little is known regarding the sources and fate of organic matter in these systems. To address these knowledge gaps, the distribution and composition of organic matter in sediments from the Fly River delta-clinoform were examined in the context of the source-to-sink study of the Papuan Continuum. The significant contrasts in the texture of seabed sediments measured across the study area coincided with stark contrasts in concentration and composition of the sedimentary organic matter. Coarser sediments displayed significantly lower organic carbon and nitrogen contents, more enriched stable carbon and nitrogen compositions, lower lignin product yields, and distinctly different lignin and nonlignin product compositions than their fine-textured counterparts. Compositional differences were also measured between high-and low-density fractions of selected sediment samples. Subsurface sediments showed marked compositional variations that were predominantly associated with changes in the texture of the deposits. Most sediments were characterized by moderate carbon loadings (0.5-1.0 mg C m(-2)), although several samples from the outer topset region, an area of sediment bypass, were characterized by lower carbon loadings indicative of enhanced carbon losses. Overall, the organic matter in both surface and subsurface sediments appeared to have predominantly a terrigenous origin, with no evidence for dilution and/or replacement by marine carbon. The measured compositions were consistent with contributions from modern vascular plant detritus, aged soil organic matter, and very old or fossil organic matter devoid of recognizable biochemicals. VL - 113 IS - F1 N1 - id: 826; 257VD Times Cited:8 Cited References Count:78Y JO - Terrigenous organic matter in sediments from the Fly River delta-clinoform system (Papua New Guinea) ER - TY - JOUR T1 - TRACING PAST CIRCULATION CHANGES IN THE WESTERN SOUTH ATLANTIC BASED ON PLANKTONIC FORAMINIFERA JF - Revista Brasileira de Paleontologia Y1 - 2008 A1 - Toledo, F. A. L. A1 - Costa, K. B. A1 - Pivel, M. A. G. A1 - Campos, E. AB - In this study, we traced past oceanographic changes in the southeastern Brazilian Continental Margin based on the ratio between two planktonic foraminifera species (Globigerina bulloides and Globigerinoides ruber), along a core located close to the transition between the tropical and subtropical biogeographic provinces. Each species is representative of a biogeographic province and has excluding ecological preferences. According to our interpretation, periods of low G. bulloides/G. ruber values would characterize a stronger influence of the warm, oligotrophic tropical water and, conversely, periods of high G. bulloides/G. ruber values correspond to a stronger influence of colder and nutrient-richer waters. Changes in the relative influence of the different water masses are strongly dependent on the regional wind field which affects the upper-level circulation mostly by the latitudinal displacement of the bifurcation of the South Equatorial Current which, in turn, has strong impacts on the Brazil Current’s strength and on the intensity of the upwelling regime in the study area. The analysis of the last 30 kyr record, suggests that productivity was highly increased both around the Last Glacial Maximum and the Younger Dryas event. In between these events, the record suggests that productivity was severely decreased during deglaciation. Also, our record suggests a gradual decrease in productivity from 11 kyr BP through the Holocene which can be explained by a progressively stronger Brazil Current resulting from a southward displacement of the Intertropical Convergence Zone. Our results are consistent with other studies providing estimates of changes in trade wind strength and in the extent of the climatic belts through time. VL - 11 IS - 3 N1 - id: 1973 JO - TRACING PAST CIRCULATION CHANGES IN THE WESTERN SOUTH ATLANTIC BASED ON PLANKTONIC FORAMINIFERA ER - TY - JOUR T1 - A validated description of age and growth of western Atlantic bluefin tuna (Thunnus thynnus) JF - Canadian Journal of Fisheries and Aquatic Sciences Y1 - 2008 A1 - Neilson, J. D. A1 - Campana, S. E. AB - Current stock assessments of western Atlantic bluefin tuna (Thunnus thymus) use age-structured population analyses, but the age assignment in the population model is made using all age-length relationship derived from mark and recapture studies largely completed during the 1970s. In our study, the deposition of bomb radiocarbon was used as a dated mark to validate age inferences of bluefin tuna and to compare the validated ages with those predicted from the age-length relationship. The results support the view that the age-length relationship currently in use for the assessment overestimates growth rate and the ultimate size of the fish. These findings have implications for the estimation of stock productivity and may negatively impact the rebuilding schedules established by fisheries managers. VL - 65 IS - 8 N1 - id: 805; 348EN Times Cited:4 Cited References Count:12Y JO - A validated description of age and growth of western Atlantic bluefin tuna (Thunnus thynnus) ER - TY - JOUR T1 - Very high-resolution seismo-acoustic imaging of seagrass meadows (Mediterranean Sea): Implications for carbon sink estimates JF - Geophysical Research Letters Y1 - 2008 A1 - Lo Iacono, C. A1 - Mateo, M. A. A1 - Gracia, E. A1 - Guasch, L. A1 - Carbonell, R. A1 - Serrano, L. A1 - Serrano, O. A1 - Danobeitia, J. KW - cycle AB - Posidonia oceanica is a widespread coastal Mediterranean seagrass which accumulates in its subsurface large quantities of organic material derived from its roots, rhizomes and leaf sheaths embedded in sandy sediments. These organic deposits may be up to several meters thick as they accumulate over thousands of years forming the matte, whose high content in organic carbon plays a major role in the global ocean carbon cycle. In this study, very highresolution seismo-acoustic methods were applied to image the subsurface features of a P. oceanica seagrass meadow at Portlligat (Cadaque's, Girona, Spain), in the NW-Mediterranean Sea. Our findings yield fresh insights into the settling of the P. oceanica meadow in the study area, and define with unprecedented detail the potential volume occupied by the matte. A strong reflector, located from 4.3 to 11.7 m depth, was recognized in several seismo-acoustic profiles as the substratum on which P. oceanica first settled in the study area. A 3D bathymetric model of this substratum allowed us to reconstruct the Portlligat palaeo-environment prior to the settling of P. oceanica, which corresponded to a shallow coastal setting protected from the open sea. A core drilled in the meadow at Portlligat revealed the presence of a 6 m thick dense matte composed of medium to coarse sandy sediments mixed with plant debris and bioclasts. Radiocarbon datings revealed a constant accretion rate of the matte of about 1.1 m/kyr. Gravelly bioclastic deposits observed at the base of the core correspond to the base of the matte and gave a date of 5616 +/- 46 Cal yr BP. For the first time, very high-resolution marine geophysical techniques allowed us to accurately define the volume occupied by P. oceanica matte, which in the study area reaches up to almost 220,000 +/- 17,400 m(3). This result is an important step forward in our efforts to estimate the size of the carbon sink represented by P. oceanica meadows along the Mediterranean coasts significantly contributing to the biosphere carbon cycle. VL - 35 SN - 0094-8276 IS - 18 N1 - id: 896; 351AE Times Cited:1 Cited References Count:14 ER - TY - CONF T1 - 14C and 13C isotopic characterization of organic carbon in surface waters of the South Atlantic Bight T2 - ASLO Aquatic Sciences Meeting Y1 - 2007 A1 - De Alteris, J. A. A1 - Bauer, J. E. A1 - Perkey, D. W. A1 - Keesee, E. J. A1 - Cai, W. J. JF - ASLO Aquatic Sciences Meeting CY - Santa Fe, NM N1 - id: 1026 ER - TY - JOUR T1 - 14C Groundwater age and the importance of chemical fluxes across aquifer boundaries in confined Cretaceous aquifers of North Carolina, USA JF - Radiocarbon Y1 - 2007 A1 - Kennedy, C. D. A1 - Genereux, D. P. VL - 49 IS - 3 N1 - id: 1192 ER - TY - JOUR T1 - A 1,500-year record of North Atlantic storm activity based on optically dated relict beach scarps JF - Geology Y1 - 2007 A1 - Buynevich, I. V. A1 - FitzGerald, D. M. A1 - Goble, R. J. KW - barrier KW - erosion KW - ground-penetrating radar KW - heavy minerals KW - Maine KW - OSL dating AB - Understanding of long-term dynamics of intense coastal storms is important for determining the frequency and impact of these events on sandy coasts. We use optically stimulated luminescence (OSL) dates on relict scarps within a prograded barrier sequence to reconstruct the chronology of large-magnitude erosional events in the western Gulf of Maine. OSL dates obtained on quartz-rich sediments immediately overlying relict scarps indicate severe beach erosion and retreat due to erosional events ca. 1550, 390, 290, and 150 cal yr B.P. Our data provide new evidence of increased storm activity (most likely frequency and/or intensity of extratropical storms) during the past 500 yr, which was preceded by a relatively calm period lasting ∼1000 yr. The width of the coastal sequence preserved between successive paleoscarps shows strong correlation with the time interval elapsed between storms. Our findings indicate that diagnostic geophysical and sedimentological signatures of severe erosional events offer new opportunities for assessing the impact and timing of major storms along sandy coasts. VL - 35 IS - 6 N1 - id: 1083 JO - A 1,500-year record of North Atlantic storm activity based on optically dated relict beach scarps ER - TY - JOUR T1 - A 190% drop in atmosphere's Delta(14) C during the "Mystery Interval" (17.5 to 14.5 kyr) JF - Earth and Planetary Science Letters Y1 - 2007 A1 - Broecker, Wallace A1 - Barker, Stephen AB - Reconstructions of atmospheric Delta(14)C for the deglacial period reveal a 190 +/- 10%. drop between 17.5 and 14.5 kyr before present, during the 'mystery interval'. While it appears that the major contributor must be the mixing between an isolated low radiocarbon abyssal reservoir and the remainder of the ocean, a combination of (14)C measurements on coexisting benthic and planktic foraminifera shells and (13)C/(12)C measurements on benthic foraminifera make it difficult to identify a sufficiently large volume for this reservoir. An alternative scenario, based on higher (14)C production rates between about 38 and 18 kyr ago, would escape the need for a large, isolated reservoir prior to the mystery interval but instead would call for a better ventilated ocean afterwards. The addition of (14) C-deficient sedimentary carbon appears not to be an important contributor. While the unlikely explanation that the half-life of (14)C is 15% greater than the accepted value (5730 yr) would eliminate the steady decrease in the (14)C/C over the last 40 kyr, it would not explain the steep drop which occurred between 17.5 and 14.5 kyr. (c) 2007 Elsevier B.V. All rights reserved. VL - 256 IS - 1-2 N1 - id: 1921; PT: J; UT: WOS:000246051000009 JO - A 190% drop in atmosphere's Delta(14) C during the "Mystery Interval" (17.5 to 14.5 kyr) ER - TY - JOUR T1 - A 28-ka history of sea surface temperature, primary productivity and planktonic community variability in the western Arabian Sea JF - Paleoceanography Y1 - 2007 A1 - Pourmand, Ali A1 - Marcantonio, Franco A1 - Bianchi, Thomas S. A1 - Canuel, Elizabeth A. A1 - Waterson, Elizabeth J. AB - Uranium series radionuclides and organic biomarkers, which represent major groups of planktonic organisms, were measured in western Arabian Sea sediments that span the past 28 ka. Variability in the past strength of the southwest and northeast monsoons and its influence on primary productivity, sea surface temperature (SST), and planktonic community structure were investigated. The average alkenone-derived SST for the last glacial period was ∼3°C lower than that measured for the Holocene. Prior to the deglacial, the lowest SSTs coincide with the highest measured fluxes of organic biomarkers, which represent primarily a planktonic suite of diatoms, coccolithophorids, dinoflagellates, and zooplankton. We propose that intensification of winter northeast monsoon winds during the last glacial period resulted in deep convective mixing, cold SSTs and enhanced primary productivity. In contrast, postdeglacial (<17 ka) SSTs are warmer during times in which biomarker fluxes are high. Associated with this transition is a planktonic community structure change, in which the ratio of the average cumulative flux of diatom biomarkers to the cumulative flux of coccolithophorid biomarkers is twice as high during the deglacial and Holocene than the average ratio during the last glacial period. We suggest that this temporal transition represents a shift from a winter northeast monsoon-dominated (pre-17 ka) to a summer southwest monsoon-dominated (post-17 ka) wind system. VL - 22 UR - http://doi.wiley.com/10.1029/2007PA001502https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1029%2F2007PA001502 IS - 4 ER - TY - JOUR T1 - Abrupt climate change in southeast tropical Africa influenced by Indian monsoon variability and ITCZ migration JF - Geophysical Research Letters Y1 - 2007 A1 - Tierney, J. E. A1 - Russell, J. M. AB - The timing and magnitude of abrupt climate change in tropical Africa during the last glacial termination remains poorly understood. High-resolution paleolimnological data from Lake Tanganyika, Southeast Africa show that wind-driven seasonal mixing in the lake was reduced during the Younger Dryas, Inter-Allerod Cool Period, Older Dryas, and Heinrich Event 1, suggesting a weakened southwest Indian monsoon and a more southerly position of the Inter-Tropical Convergence Zone over Africa during these intervals. These events in Lake Tanganyika, coeval with millennial and centennial-scale climate shifts in the high latitudes, suggest that changes in ITCZ location and Indian monsoon strength are important components of abrupt global climate change and that their effects are felt south of the equator in Africa. However, we observe additional events in Lake Tanganyika of equal magnitude that are not correlated with high-latitude changes, indicating the potential for abrupt climate change to originate from within tropical systems. VL - 34 IS - 15 N1 - id: 1851; 201ZV Times Cited:4 Cited References Count:31Y JO - Abrupt climate change in southeast tropical Africa influenced by Indian monsoon variability and ITCZ migration ER - TY - JOUR T1 - Age under-estimation in New Zealand porbeagle sharks (Lamna nasus): is there an upper limit to ages that can be determined from shark vertebrae? JF - Marine and Freshwater Research Y1 - 2007 A1 - Francis, M. P. A1 - Campana, S. E. A1 - Jones, C. M. AB - Annual deposition of growth bands in vertebrae has been validated for many shark species, and is now widely regarded as the norm. However, vertebrae are part of the shark's axial skeleton, and band deposition may stop in old sharks when somatic growth ceases. We aged vertebral sections from New Zealand porbeagle sharks (Lamna nasus) under reflected white light and using X-radiographs. Bomb radiocarbon assays supported vertebral age estimates up to similar to 20 years, but not at older ages. The results suggest that older porbeagles were under-aged by as much as 50% from vertebral band counts, presumably because band width declined to a point where it became unresolvable. This has important implications for growth studies on other long-lived sharks. Estimated ages at sexual maturity were 8-11 years for males and 15-18 years for females, and longevity may be similar to 65 years. New Zealand and North Atlantic porbeagles differ in these parameters, and in length at maturity and maximum length, suggesting genetic isolation of the two populations. VL - 58 IS - 1 N1 - id: 1857; 131AF Times Cited:5 Cited References Count:60Y JO - Age under-estimation in New Zealand porbeagle sharks (Lamna nasus): is there an upper limit to ages that can be determined from shark vertebrae? ER - TY - JOUR T1 - Aging of marine organic matter during cross-shelf lateral transport in the Benguela upwelling system revealed by compound-specific radiocarbon dating JF - Geochemistry Geophysics Geosystems Y1 - 2007 A1 - Mollenhauer, G. A1 - Inthorn, M. A1 - Vogt, T. A1 - Zabel, M. A1 - Damste, J. S. S. A1 - Eglinton, T. I. KW - alkenones KW - atlantic-ocean KW - burial KW - carbon accumulation KW - coastal KW - compound-specific radiocarbon dating KW - continental-margin KW - ionization mass-spectrometry KW - membrane-lipids KW - namibia KW - sea sediments KW - Sediment transport AB - Organic matter accumulation and burial on the Namibian shelf and upper slope are spatially heterogeneous and strongly controlled by lateral transport in subsurface nepheloid layers. Much of the material deposited in depo-centers on the slope ultimately derives from the shelf. Supply of organic matter from the shelf involves selective transport of organic matter. We studied these selective transport processes by analyzing the radiocarbon content of co-occurring sediment fractions. Here we present radiocarbon data for total organic carbon as well as three tracers of surface ocean productivity (phytoplankton-derived alkenones, membrane lipids of pelagic crenarchaeota (crenarchaeol), and calcareous microfossils of planktic foraminifera) in core-top and near-surface sediment samples. The samples were collected on the Namibian margin along a shelf-slope transect (85 to 1040 m) at 24 degrees S and from the upper slope depo-center at 25.5 degrees S. In core-top sediments, alkenone ages gradually increased from modern to 3490 radiocarbon years with distance from shore and with water depth. Crenarchaeol, while younger than alkenones, also increased in age with distance offshore. It was concluded that the observed ages were a consequence of cross-shelf transport and associated aging of organic matter. Radiocarbon ages of preserved lipid biomarkers in sediments thus at least partially depend on the relative amount of laterally supplied, pre-aged material present in a sample, highlighting the importance of nepheloid transport for the sedimentation of organic matter over the Namibian margin. VL - 8 SN - 1525-2027 N1 - 213qvTimes Cited:3 Cited References Count:60 JO - Geochem Geophy Geosy ER - TY - JOUR T1 - Amplitude and timing of temperature and salinity variability in the subpolar North Atlantic over the past 10 k.y. JF - Geology Y1 - 2007 A1 - Came, R. E. A1 - Oppo, D. W. A1 - McManus, J. F. KW - Björn Drift KW - Mg/Ca KW - Neogloboquadrina pachyderma dextral KW - Ocean Drilling Program Site 984 KW - paleotemperature AB - Paired planktic foraminiferal δ18O and Mg/Ca data reveal trends of increasing temperatures (∼3 °C) and salinities in the subpolar North Atlantic over the course of the Holocene, which were punctuated by abrupt events. The trends likely reflect an insolation-forced northward retreat of the boundary between polar and North Atlantic subsurface waters. The superimposed variability does not appear to be periodic, but tends to recur within a broad millennial band. The records provide convincing evidence of open-ocean cooling (nearly 2 °C) and freshening during the 8.2 ka event, and suggest similar conditions at 9.3 ka. However, the two largest temperature oscillations in our record (∼2 °C) occurred during the past 4 k.y., suggesting a recent increase in temperature variability relative to the mid-Holocene, perhaps in response to neoglaciation, which began at about this time. VL - 35 IS - 4 N1 - id: 983 JO - Amplitude and timing of temperature and salinity variability in the subpolar North Atlantic over the last 10,000 years ER - TY - JOUR T1 - THE ANALYSIS OF STABLE ISOTOPES FROM CALIFORNIA COASTAL ARCHAEOLOGICAL SITES: IMPLICATIONS FOR UNDERSTANDING HUMAN CULTURAL DEVELOPMENTS AND ENVIRONMENTAL CHANGE JF - Proceedings of the Society for California Archaeology Y1 - 2007 A1 - Robbins, John A. A1 - Rick, Torben C. VL - 20 N1 - id: 2079 ER - TY - JOUR T1 - Archaeological investigations in Jedediah Smith Campground and Hiouchi Flat JF - Redwood National and State Park Y1 - 2007 A1 - Tushingham, Shannon VL - I IS - Auger Testing N1 - id: 1158 ER - TY - BOOK T1 - The Archaeology and Historical Ecology of Late Holocene San Miguel Island Y1 - 2007 A1 - Rick, Torben C. PB - Cotsen Institute of Archaeology, University of California CY - Los Angeles N1 - id: 1086 ER - TY - ART T1 - Are tsunamis always sedimentologically important events? A case study of sedimentological and geochemical analyses of coastal lagoons, Sri Lanka Y1 - 2007 A1 - Jackson, K. L. A1 - Rankey, E. C. A1 - Eberli, G. P. A1 - Amelung, F. A1 - Andres, M. S. A1 - Peterson, L. P. A1 - Swart, P. K. A1 - Jayasena, H. A. H. A1 - Kehelpannala, K. V. W. PB - American Association of Petroleum Geologists Abstracts with Programs CY - Long Beach, CA N1 - id: 1144; Annual Meeting ER - TY - CONF T1 - Assessing environmental factors associated with changes in the growth rate of a bivalve mollusk species through the Holocene T2 - First International Sclerochronology Conference Y1 - 2007 A1 - Krause R.A, Jr. A1 - Huntley, J. W. A1 - Kowalewski, M. A1 - Romanek, C. R. A1 - Kaufmann, D. S. A1 - Simoes, M. G. JF - First International Sclerochronology Conference CY - St. Petersburg, FL USA N1 - id: 1169 ER - TY - JOUR T1 - Atlantic meridional overturning circulation during the Last Glacial Maximum JF - Science Y1 - 2007 A1 - Lynch-Stieglitz, J. A1 - Adkins, J. F. A1 - Curry, W. B. A1 - Dokken, T. A1 - Hall, I. R. A1 - Herguera, J. C. A1 - Hirschi, J. J. M. A1 - Ivanova, E. V. A1 - Kissel, C. A1 - Marchal, O. A1 - Marchitto, T. M. A1 - McCave, I. N. A1 - McManus, J. F. A1 - Mulitza, S. A1 - Ninnemann, U. A1 - Peeters, F. A1 - Yu, E. F. A1 - Zahn, R. AB - The circulation of the deep Atlantic Ocean during the height of the last ice age appears to have been quite different from today. We review observations implying that Atlantic meridional overturning circulation during the Last Glacial Maximum was neither extremely sluggish nor an enhanced version of present-day circulation. The distribution of the decay products of uranium in sediments is consistent with a residence time for deep waters in the Atlantic only slightly greater than today. However, evidence from multiple water-mass tracers supports a different distribution of deep-water properties, including density, which is dynamically linked to circulation. 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Curry, William B. Dokken, Trond Hall, Ian R. Herguera, Juan Carlos Hirschi, Joel J. -M. Ivanova, Elena V. Kissel, Catherine Marchal, Olivier Marchitto, Thomas M. McCave, I. Nicholas McManus, Jerry F. Mulitza, Stefan Ninnemann, Ulysses Peeters, Frank Yu, Ein-Fen Zahn, Rainer Amer assoc advancement science Washington; YY JO - Atlantic meridional overturning circulation during the Last Glacial Maximum ER - TY - JOUR T1 - Biomarker evidence for the co-occurrence of three races (A, B and L) of Botryococcus braunii in El Junco Lake, Galapagos JF - Organic Geochemistry Y1 - 2007 A1 - Zhang, Z. H. A1 - Metzger, P. A1 - Sachs, J. P. AB - In spite of the fact that individual races of Botryococcus braunii are widely distributed in lakes, reports of the co-existence of different chemical races are rare. Here we report biomarker evidence for the co-occurrence of three different races of B. braunii (A, B and L) in the water column and sediments of El Junco Lake, a freshwater crater lake at 700 m elevation on San Cristobal Island, Galapagos. We also show the existence of lycopadienes and lycopatrienes in suspended particles and sediments. Biomarker indicators of the three races were: cis and trans C-25-C-31 n-alkadienes and a C-29 triene for race A, a series of C34H58 botryococcenes for race B, and a C40H78 hydrocarbon, trans, trans-lycopadiene accompanied by minor amounts of isomers for race L. Epoxides derived from n-alkadienes and trans, trans-lycopadiene, specific to races A and L respectively, were also detected. Several previously unreported lycopadienes and lycopatrienes were identified in both the water column and sediment, and are believed to represent by-products and intermediates, respectively, of trans, trans-lycopadiene synthesis. Botryococcene and lycopadiene concentrations reached 16.7 and 0.8 mg/g dry sediment in near-surface sediments, and varied over more than three orders of magnitude, while n-alkadienes were present in trace quantities. Pyrolysates from the kerogen fraction of sediment contained lycopadiene and alkadiene related lipids along with chemically resistant polymers of R braunii cell walls. Apparently n-alkadienes, botryococcenes and lycopadienes and -trienes can survive in oxic sediments for several decades, and the down core variation in these lipids likely reflects changes in lake hydrology, alternately favoring the bloom or near-extinction of R braunii race B. (C). 2007 Elsevier Ltd. All rights reserved. VL - 38 IS - 9 N1 - id: 590; 218MC Times Cited:7 Cited References Count:72 JO - Biomarker evidence for the co-occurrence of three races (A, B and L) of Botryococcus braunii in El Junco Lake, Galapagos ER - TY - RPRT T1 - Calcification in sclersoponges: implications for reconstructing CO2 fluxes in the tropics Y1 - 2007 A1 - Grottoli, A. G. JF - ASLO CY - Santa Fe, NM N1 - id: 1132 ER - TY - THES T1 - Carbon, chlorine, and oxygen isotopes as tracers of interbasin groundwater flow at La Selva Biological Station, Costa Rica Y1 - 2007 A1 - Webb, Mathew PB - North Carolina State University CY - Raleigh, NC VL - Masters ER - TY - JOUR T1 - Carbon export and cycling by the York, Tanana and Porcupine Rivers, Alaska, 2001-2005 JF - Water Resources Res. Y1 - 2007 A1 - Striegl, R. G. A1 - Dornblaser, M. M. A1 - Aiken, G. R. A1 - Wickland, K. P. A1 - Raymond, P. A. VL - 43 N1 - id: 1162 ER - TY - THES T1 - Carbon in riparian subsurface ecosystems: Sources, lability, and spatial patterns Y1 - 2007 A1 - Gurwick, N. P. PB - Cornell University CY - Ithaca, NY VL - Ph.D. ER - TY - JOUR T1 - Carbon isotope variation in modern soils of the tallgrass prairie: Analogues for the interpretation of isotopic records derived from paleosols JF - Quaternary International Y1 - 2007 A1 - Johnson, W. C. A1 - Willey, K. L. A1 - Macpherson, G. L. AB - Use of stable carbon isotope data from paleosols to reconstruct past plant community structure (C-3 vs. C-4) has become commonplace. In an effort to improve our ability to make isotope-based reconstructions and to better appreciate the pitfalls, investigations were conducted on both modern soils and paleosols in the Kansas grasslands.Stable carbon isotope data were derived from soils and vegetation on the near-pristine, C-4-dominated grassland of the Konza Tallgrass Prairie Long-Term Ecological Research (LTER) site in northeastern Kansas. In order to evaluate variation of delta C-13 within the landscape, two levels of sampling were employed: 2 m-deep upland cores extracted to assess variation with depth in the soil profile, and, to assess variability across the landscape, surface samples along two transects and from within a 660 x 690 m grid. For transect and grid points, both the upper 2cm of sediment and the aboveground biomass were collected. Core samples taken at Konza reveal that soil organic carbon was depleted in C-13 within the upper 10-20cm relative to the remainder of the soil solum below, a phenomenon previously reported. In transects and the sample grid, soil organic carbon from soil surfaces was consistently more depleted in C-13 than aboveground tissue of associated vegetation samples. Slope, azimuth, and insolation were computed from field data and a highresolution DEM of the sample grid, but these variables offered no significant explanation of the spatial variability in delta C-13 data from soil organic carbon. The observation that modern landscape position has little effect on delta C-13 over short distances, at least in a C4-dominated community, lends support to the application of delta C-13 analysis to buried soils for paleoenvironmental reconstruction where paleolandscape position is often unknown.Stable carbon isotope data were derived from paleosols at from the Beisel-Steinle site located to the west of Konza in central Kansas. Three soils were examined: the interstadial paleosol within the Gilman Canyon Formation (c. 38-27k cal yr BP), the Late Pleistocene-Holocene Brady Soil, and the modern surface soil. With the exception of isotopic depletion at the top of the surface soil, all three soils exhibited similar delta C-13 values of about14 parts per thousand, the same value realized in the soil cores from Konza, suggesting close similarity among the plant communities of the interstade, the Late Pleistocene-Early Holocene transition, and pristine prairie of today.This investigation emphasizes the need for additional research into the variation in stable carbon isotope signals vertically within the profile and across the landscape. Issues include the source of the near-surface depletion zone, the relationship between isotopic values in the soil versus those of the vegetation, and variation in Soil delta 13C values delta 13C throughout the landscape. (c) 2006 Elsevier Ltd and INQUA. All rights reserved. VL - 162 N1 - 158nkTimes Cited:9Cited References Count:144 JO - Carbon isotope variation in modern soils of the tallgrass prairie: Analogues for the interpretation of isotopic records derived from paleosols ER - TY - JOUR T1 - Carbon nanotube foils for electron stripping in tandem accelerators JF - Nucl. Inst. & Meth. in Physics Research B. Y1 - 2007 A1 - von Reden, K. A1 - Zhang, M. A1 - Meigs, M. A1 - Sichel, E. A1 - Fang, S. A1 - Baughman, R. VL - 261 N1 - id: 690 ER - TY - JOUR T1 - Caribbean sclerosponge radiocarbon measurements re-interpreted in terms of U/Th age models JF - Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions with Materials and Atoms Y1 - 2007 A1 - Rosenheim, B. E. A1 - Swart, P. K. AB - Previously unpublished AMS radiocarbon measurements of a sclerosponge from tongue of the ocean (TOTO), Bahamas, as well as preliminary data from an investigation of the radiocarbon records of sclerosponges living at different depths in the adjacent Bahamas basin, Exuma Sound, are interpreted in terms of U-series age models. The data are compared to an existing Caribbean sclerosponge radiocarbon bomb curve measured using standard gas proportional beta counting and used to interpret a Pb-210 age model. The Delta C-14 records from the sclerosponges illustrate a potential for use of radiocarbon both as a tracer of subsurface water masses or as an additional age constraint on recently sampled sclerosponges. By using an independent age model, this study lays the framework for utilizing sclerosponges from different locations in the tropics and subtropics and different depths within their wide depth range (0-250 m) to constrain changes in production of subtropical underwater in the Atlantic Ocean. This framework is significant because the proxy approach is necessary to supplement the short and coarse time series being used to constrain variability in the formation of Caribbean subtropical underwater, the return flow of a shallow circulation cell responsible for nearly 10% of the heat transported poleward in the N. Atlantic. (c) 2007 Elsevier B.V. All rights reserved. VL - 259 IS - 1 N1 - id: 785; 182WV Times Cited:2 Cited References Count:30Y JO - Caribbean sclerosponge radiocarbon measurements re-interpreted in terms of U/Th age models ER - TY - JOUR T1 - Century-to-millennial scale climatic variability in Lake Malawi revealed by isotope records JF - Earth and Planetary Science Letters Y1 - 2007 A1 - Barker, P. A. A1 - Leng, M. J. A1 - Gasse, F. A1 - Huang, Y. AB - Diatom-based oxygen isotope data ( delta super(1) super(8)O sub(d) sub(i) sub(a) sub(t) sub(o) sub(m)) from Lake Malawi show multi-centennial scale wet-dry intervals spaced approximately every 2.3 ka throughout a 25 ka sequence. The delta super(1) super(8)O sub(d) sub(i) sub(a) sub(t) sub(o) sub(m) record is supported by a lower resolution deuterium ( delta D sub(p) sub(a))isotope curve derived from palmitic acid. We interpret these isotope data in terms of major shifts in precipitation and evaporation moderated by seasonal controls on the host organisms. Dry periods marked by relatively positive isotope values, represent the extension of abrupt Holocene events noted from northern and equatorial Africa to 10-15 super(o)S. These events in Lake Malawi correspond to cool episodes in Greenland, thereby demonstrating teleconnections generated by meridional temperature gradients. Sea surface temperatures are likely to be the primary transmitter of deglacial climate changes, although trade wind strength and direction is critical in controlling precipitation patterns in tropical regions. Conversely, the global hydrological cycle, driven by low latitude regions represents an important positive feedback amplifying deglacial processes. VL - 261 IS - 1-2 N1 - id: 2222; Source type: scholarlyjournals; Object type: Article; Object type: Feature; CSAUnique: OB-MD-0006626237; AccNum: 7631572; DOI: 10.1016/j.epsl.2007.06.010; ISSN: 0012-821X; Peer Reviewed: true JO - Century-to-millennial scale climatic variability in Lake Malawi revealed by isotope records ER - TY - RPRT T1 - Chapter B--Field Trip Day 2: Quaternary Geology of Lake Alamosa and the Costilla Plain, southern Colorado Y1 - 2007 A1 - Machette, M. N. A1 - Marchetti, D. W. A1 - Thompson, R. A. A1 - Kirkham, R. M. ED - Machette, M. N. JF - Quaternary geology of the San Luis Basis, southern Colorado and Northern New Mexico--Rocky Mountain Section Friends of the Pleistocene Guidebook: U. S. Geological Survey Open-File Report 2007-1193 N1 - id: 626 ER - TY - RPRT T1 - Chapter E--Holocene sand deposits in the San Luis Basin, east of Alamosa Colorado Y1 - 2007 A1 - Machette, M. N. A1 - Puseman, K. ED - Machette, M. N. JF - Quaternary geology of the San Luis Basis, southern Colorado and Northern New Mexico--Rocky Mountain Section Friends of the Pleistocene Guidebook: U. S. Geological Survey Open-File Report 2007-1193 N1 - id: 627 ER - TY - RPRT T1 - Chapter F--Late Pleistocene to early Holocene paleoecology of the "Mr. Peat" wetland deposit, Alamosa County, Colorado Y1 - 2007 A1 - Schumann, R. R. A1 - Machette, M. N. ED - Machette, M. N. JF - Quaternary geology of the San Luis Basin, southern Colorado and Northern New Mexico--Rocky Mountain Section Friends of the Pleistocene Guidebook: U. S. Geological Survey Open-File Report 2007-1193 N1 - id: 628 ER - TY - THES T1 - Climate change impact research in U.S. national parks Y1 - 2007 A1 - Ironside, Kirsten PB - NAU Environmental Sciences Program, 5/7 VL - Masters ER - TY - JOUR T1 - Coastal subsistence and landscape evolution on Eastern Santa Rosa Island, California: perspectives from CA-SRI-667 JF - Proceedings of the Society for California Archaeology Y1 - 2007 A1 - Wolff, Christopher B. A1 - Aland, Amanda A1 - Rick, Torben C. VL - 20 N1 - id: 2080 JO - Coastal subsistence and landscape evolution on Eastern Santa Rosa Island, California: perspectives from CA-SRI-667 ER - TY - JOUR T1 - Comment on "Anomalous radiocarbon ages for foraminifera shells" by W. Broecker et al.: A correction to the western tropical Pacific MD9821-81 record JF - Paleoceanography Y1 - 2007 A1 - Stott, Lowell D. VL - 22 IS - 1 N1 - id: 2017; PT: J; UT: WOS:000244478900001 JO - Comment on "Anomalous radiocarbon ages for foraminifera shells" by W. Broecker et al.: A correction to the western tropical Pacific MD9821-81 record ER - TY - JOUR T1 - Computer simulation of MC-SNICS for performance improvements JF - Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions with Materials and Atoms Y1 - 2007 A1 - Han, B. X. A1 - Southon, J. R. A1 - Roberts, M. L. A1 - von Reden, K. F. AB - Increasing ion source current output while keeping the beam emittance small is a key for improving measurement throughput and quality of an accelerator mass spectrometry (AMS) system. The NEC MC-SNICS ion sources have widely been used for AMS around the world. In this work, a computer simulation study on MC-SNICS ion source was carried out using the code PBGUNS. The primary Cs+ beam is simulated as space-charge limited emission from the ionizer surface. The secondary negative ion beam is simulated in the presence of the space-charge induced by both the primary and the secondary beam. Two different configurations of the MC-SNICS have been studied: the original factory version and the UC Irvine modified version. The latter has a 0.668 in. radius spherical ionizer and an immersion lens at cathode potential with the original Cs focus lens removed. Simulation showed that the modified version provides more intense and better focused Cs+ beam at the cathode target, hence higher negative ion production from the sample by sputtering. The new arrangement of Einzel-preacceleration section of the MC-SNICS at UC Irvine was also simulated and discussed. Simulation results are in good agreement with the experimental observations made at UC Irvine. Hints for selection of an immersion lens geometry have been obtained. (c) 2007 Elsevier B.V. All rights reserved. VL - 261 IS - 1-2 N1 - 200swTimes Cited:8Cited References Count:8 JO - Computer simulation of MC-SNICS for performance improvements ER - TY - JOUR T1 - Constraining global air-sea gas exchange for CO2 with recent bomb 14C measurements JF - Global Biogeochemical Cycles Y1 - 2007 A1 - Sweeney, C. A1 - Gloor, E. A1 - Jacobson, A. J. A1 - Key, R. M. A1 - McKinley, G. A1 - Sarmiento, J. L. A1 - Wanninkhof, R. VL - 21 N1 - id: 1052 ER - TY - JOUR T1 - Constraints on the origin of sedimentary organic carbon in the Beaufort Sea from coupled molecular 13C and 14C measurements JF - Marine Chemistry Y1 - 2007 A1 - Drenzek, Nicholas J. A1 - Montluçon, Daniel B. A1 - Yunker, Mark B. A1 - Macdonald, Robie W. A1 - Eglinton, Timothy I. VL - 103 N1 - id: 1030 ER - TY - JOUR T1 - Contributions of toluene and alpha-pinene to SOA formed in an irradiated toluene/alpha-pinene/NOx/air mixture: Comparison of results using C-14 content and SOA organic tracer methods JF - Environmental Science & Technology Y1 - 2007 A1 - Offenberg, J. H. A1 - Lewis, C. W. A1 - Lewandowski, M. A1 - Jaoui, M. A1 - Kleindienst, T. E. A1 - Edney, E. O. AB - An organic tracer method, recently proposed for estimating individual contributions of toluene and alpha-pinene to secondary organic aerosol (SOA) formation, was evaluated by conducting a laboratory study where a binary hydrocarbon mixture, containing the anthropogenic aromatic hydrocarbon, toluene, and the biogenic monoterpene, alpha-pinene, was irradiated in air in the presence of NOx to form SOA. The contributions of toluene and alpha-pinene to the total SOA concentration, calculated using the organic tracer method, were compared with those obtained with a more direct C-14 content method. In the study, SOA to SOC ratios of 2.07 +/- 0.08 and 1.41 +/- 0.04 were measured for toluene and alpha-pinene SOA, respectively. The individual tracer-based SOA contributions of 156 mu g m(-3) for toluene and 198 mu g m(-3) for alpha-pinene, which together accounted for 82% of the gravimetrically determined total SOA concentration, compared well with the C-14 values of 182 and 230 mu g m(-3) measured for the respective SOA precursors. While there are uncertainties associated with the organic tracer method, largely due to the chemical complexity of SOA forming chemical mechanisms, the results of this study suggest the organic tracer method may serve as a useful tool for determining whether a precursor hydrocarbon is a major SOA contributor. VL - 41 IS - 11 N1 - id: 1882; 172ZM Times Cited:13 Cited References Count:19Y JO - Contributions of toluene and alpha-pinene to SOA formed in an irradiated toluene/alpha-pinene/NOx/air mixture: Comparison of results using C-14 content and SOA organic tracer methods ER - TY - JOUR T1 - Cooling of Northwest Atlantic slope waters during the Holocene JF - Geophysical Research Letters Y1 - 2007 A1 - Sachs, J. P. KW - circulation KW - deposition KW - ice KW - labrador sea KW - ocean KW - oscillation KW - sea-surface KW - stratigraphy KW - Temperature KW - variability AB - [1] Climate of the last 11,000 years, the Holocene, is usually described as warm and stable. Benchmark temperature records from central Greenland ice cores show none of the large, abrupt variations that characterized the prior 100,000 years of glacial climate. Nor do they show any substantial trend, indicating at most 1 degrees-3 degrees C of cooling. Here we show that the slope waters east of the United States and Canada cooled 4 degrees-10 degrees C during the Holocene. Declining insolation, increasing convection in the Labrador Sea, and equatorward shifting of the Gulf Stream path may have caused the cooling. VL - 34 SN - 0094-8276 IS - 3 N1 - 136deTimes Cited:35 Cited References Count:33 JO - Geophys Res Lett ER - TY - JOUR T1 - Demise of a submarine canyon? Evidence for highstand infilling on the Waipaoa River continental margin, New Zealand JF - Geophysical Research Letters Y1 - 2007 A1 - Walsh, J. P. A1 - Alexander, C. R. A1 - Gerber, T. A1 - Orpin, A. R. A1 - Sumners, B. W. AB - Submarine canyons are major geomorphologic features on the Earth's surface. Their formation has received considerable debate, but their demise has received less attention. Research of modern canyons with cores and moorings has documented active sediment transport and deposition, but extrapolation of these local observations over larger areas is precluded by complex canyon geomorphology. High-resolution multibeam and chirp data presented here provide convincing evidence of an infilling canyon head on the Waipaoa River margin of New Zealand. Tens of meters of Holocene sediment have accumulated on the outer shelf and in Lachlan canyon as a result of off-shelf sediment transport. Regardless of the ultimate fate of this system over geological time scales, this research demonstrates highstand sedimentation as a possible mechanism for canyon burial and cause of canyon demise, which has important implications for the evolution of canyons globally. VL - 34 IS - 20 N1 - id: 791; 228BW Times Cited:4 Cited References Count:42Y JO - Demise of a submarine canyon? Evidence for highstand infilling on the Waipaoa River continental margin, New Zealand ER - TY - CONF T1 - Deposition and reactivity of aerosol-derived organic carbon in temperate watersheds T2 - ASLO Aquatic Sciences Meeting Y1 - 2007 A1 - Wozniak, A. W. A1 - Bauer, J. E. A1 - Dickhut, R. M. A1 - Keesee, E. J. JF - ASLO Aquatic Sciences Meeting CY - Santa Fe, NM N1 - id: 1029 ER - TY - JOUR T1 - Detection of silica-mediated dissolution of magnetic grains in sediments using FORC diagrams JF - Geophysical Research Letters Y1 - 2007 A1 - Wetter, L. A1 - Verosub, K. A1 - Russell, J. KW - dissolution KW - FORC AB - Recently silica-mediated dissolution has been recognized as a potentially important factor influencing magnetic studies of marine and lacustrine sediments. Although direct evidence for the dissolution of magnetic particles in silica-rich environments is lacking, the process is expected to produce changes in the magnetic grain-size distribution, a hypothesis that is tested in this study on sediments from Lake Tanganyika, East Africa, using First Order Reversal Curves (FORCs). Results from different magnetic intensity zones within the studied samples clearly show changes in the grain-size distribution of magnetic minerals. In particular, zones with high biogenic silica content (BSi) correlated with depletion in fine-grained magnetic material, whereas zones with lower BSi showed no depletion. These results are consistent with the idea that silica-mediated dissolution results in the preferential removal of fine-grained magnetic material, and indicate that FORC diagrams are effective in characterizing silica-mediated dissolution in sediments. VL - 34 IS - 12 N1 - 182vvTimes Cited:3Cited References Count:8 JO - Detection of silica-mediated dissolution of magnetic grains in sediments using FORC diagrams ER - TY - JOUR T1 - Diagenetic and sedimentological controls on the composition of organic matter preserved in California Borderland Basin sediments JF - Limnology and Oceanography Y1 - 2007 A1 - Mollenhauer, G. A1 - Eglinton, T. I. KW - c-14 measurements KW - compound-specific radiocarbon KW - continental-margin KW - fatty-acids KW - marine-sediments KW - monica basin KW - oxic degradation KW - oxygen exposure time KW - santa-barbara basin KW - surface sediments AB - Compound-specific radiocarbon (C-14) contents, stable carbon isotopes, and abundances of phytoplankton and vascular plant derived lipid biomarkers (alkenones and fatty acids) were obtained from Santa Barbara Basin and Santa Monica Basin sediments, along with radiocarbon contents of planktic foraminifera and total organic carbon. We investigated core-top and prebomb sediment intervals at sites from the flanks and depocenters of the basins deposited under contrasting bottom water oxygen concentrations. Bulk organic matter generally has the lowest radiocarbon levels of all sediment constituents measured, whereas planktic foraminifera tend to be the most radiocarbon enriched. Alkenones are systematically depleted in radiocarbon with respect to foraminifera. Short-chain (C-14, C-16, C-18) fatty acids decrease rapidly in absolute abundance and relative to longer-chain (> C-24) homologues from core-top to prebomb samples. The loss of short-chain fatty acids with depth is associated with C-13 depletion of short-chain fatty acids, indicating preferential preservation of terrestrially derived fatty acids. Short-chain fatty acids tend to be more C-14-enriched relative to alkenones in core-top sediments, whereas longer-chain homologues are generally the most radiocarbon depleted of the lipids studied here. Less refractory compounds (e.g., short-chain fatty acids) are thus enriched in radiocarbon with respect to more recalcitrant biomarkers (alkenones, long-chain fatty acids). The lower C-14 content of more refractory compounds reflects a larger proportion of laterally supplied, preaged material. Greater preservation of labile organic compounds observed at the depocenters than in flank sediments results in the presence of "younger" biomarkers, underlining the important influence of selective degradation of labile compounds on their radiocarbon ages. VL - 52 SN - 0024-3590 IS - 2 N1 - 149kgTimes Cited:43 Cited References Count:67 JO - Limnol Oceanogr ER - TY - JOUR T1 - Distribution and sub-bottom features of Holocene oyster deposits in the York River, Virginia and the rate of degradations of oyster shell JF - Geological Society of America Abstracts with Programs Y1 - 2007 A1 - Stackhouse, B. L. A1 - Lockwood, R. VL - 39 N1 - id: 587 ER - TY - JOUR T1 - Distribution and turnover of carbon in natural and constructed wetlands in the Florida Everglades JF - Applied Geochemistry Y1 - 2007 A1 - Stern, J. A1 - Wang, Y. A1 - Gu, B. A1 - Newman, J. AB - Stable and radiocarbon isotopic contents of dissolved organic C (DOC), dissolved inorganic C (DIC), particulate organic C (POC) and plants were used to examine the source and turnover rate of C in natural and constructed wetlands in the Florida Everglades. DOC concentrations decreased, with P concentrations, along a water quality gradient from the agriculturally impacted areas in the northern Everglades to the more pristine Everglades National Park. delta C-13 values of DOC in the area reflect contributions of both wetland vegetation and sugarcane from agriculture. Radiocarbon ages of DOC, POC and DIC in the Everglades ranged from 2.01 ka BP to ">modern". The old C-14 ages of DOC and POC were found in impacted areas near the Everglades Agricultural Area (EAA) in the northern Everglades. In contrast, DOC and POC in pristine marsh areas had near modern or ">modern" C-14 ages. These data indicate that a major source of POC and DOC in impacted areas is the degradation of historic peat deposits in the EAA. In the pristine areas of the marsh, DOC represents a mix of modern and historic C sources, whereas POC comes from modern primary production as indicated by positive A C-14 values, suggesting that DOC is transported farther away from its source than POC. High A C-14 values of DIC indicate that dissolution of limestone bedrock is not a significant source of DIC in the Everglades wetlands. As a restored wetland moves towards its "original" or "natural" state, the C-14 signatures of DOC should approach that of modern atmosphere. In addition, measurements of concentration and C isotopic composition of DOC in two small constructed wetlands (i.e., test cells) indicate that these freshwater wetland systems contain a labile DOC pool with rapid turnover times of 26-39 days and that the test cells are overall net sinks of DOC. (C) 2007 Elsevier Ltd. All rights reserved. VL - 22 IS - 9 N1 - 216vhTimes Cited:23Cited References Count:36 JO - Distribution and turnover of carbon in natural and constructed wetlands in the Florida Everglades ER - TY - JOUR T1 - Early Maritime Technology on California’s San Miguel Island: Arena Points from JF - Current Research in the Pleistocene Y1 - 2007 A1 - Erlandson, Jon M. A1 - Braje, Todd VL - 24 N1 - id: 2071 ER - TY - JOUR T1 - Electromagnetic field modeling and ion optics calculations for a continuous-flow AMS system JF - Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions with Materials and Atoms Y1 - 2007 A1 - Han, B. X. A1 - von Reden, K. F. A1 - Roberts, M. L. A1 - Schneider, R. J. A1 - Hayes, J. M. A1 - W. J. Jenkins AB - A continuous-flow C-14 AMS (CFAMS) system is under construction at the NOSAMS facility. This system is based on a NEC Model 1.5SDH-10.5 MV Pelletron accelerator and will utilize a combination of a microwave ion source (MIS) and a charge exchange canal (CXC) to produce negative carbon ions from a continuously flowing stream Of CO2 gas. For high-efficiency transmission of the large emittance, large energy-spread beam from the ion source unit, a large-acceptance and energy-achromatic injector consisting of a 45 degrees electrostatic spherical analyzer (ESA) and a 90 degrees double-focusing magnet has been designed. The 45 degrees ESA is rotatable to accommodate a 134-sample MC-SNICS as a second ion source. The high-energy achromat (90 degrees double focusing magnet and 90 degrees ESA) has also been customized for large acceptance. Electromagnetic field modeling and ion optics calculations of the beamline were done with Infolytica MagNet, ElecNet, and Trajectory Evaluator. PBGUNS and SIMION were used for the modeling of ion source unit. (c) 2007 Elsevier B.V. All rights reserved. VL - 259 IS - 1 N1 - id: 1698; 182WV Times Cited:6 Cited References Count:14 JO - Electromagnetic field modeling and ion optics calculations for a continuous-flow AMS system ER - TY - CONF T1 - The Environmental Anomalies in the Northeastern East China Sea during the Last 3000 Years: Implications for El Nino Activity in the Holocene T2 - 9th International Conference on Paleoceanography (ICP 9) Y1 - 2007 A1 - Chang, F. A1 - Zhuang, L. A1 - Li, T. A1 - Yan, J. A1 - Li, Q. ED - Shanghai International Convention Center, Shanghai KW - Donghai Sea KW - Holocene KW - Multidisciplinary KW - Paleo studies KW - Paleoenvironments KW - U 7000 JF - 9th International Conference on Paleoceanography (ICP 9) N1 - id: 1935; TY: CPAPER; NO: Source type: conferencepapers&proceedings; Object type: Conference Paper; CSAUnique: CPI-4728602; AccNum: 4728602(China) ER - TY - JOUR T1 - Evaluation of gas chromatographic isotope fractionation and process contamination by carbon in compound-specific radiocarbon analysis JF - Analytical Chemistry Y1 - 2007 A1 - Zencak, Z. A1 - Reddy, C. M. A1 - Teuten, E. L. A1 - Xu, L. A1 - McNichol, A. P. A1 - Gustafsson, O. AB - The relevance of both modern and fossil carbon contamination as well as isotope fractionation during preparative gas chromatography for compound-specific radiocarbon analysis (CSRA) was evaluated. Two independent laboratories investigated the influence of modern carbon contamination in the sample cleanup procedure and preparative capillary gas chromatography (pcGC) of a radiocarbon-dead 3,3',4,4',5,5'-hexachlorobiphenyl (PCB 169) reference. The isolated samples were analyzed for their C-14/C-12 ratio by accelerator mass spectrometry. Sample Delta C-14 values of -996 +/- 20 and -985 +/- 20% agreed with a Delta C-14 of -995 +/- 20% for the unprocessed PCB 169, suggesting that no significant contamination by nonfossil carbon was introduced during the sample preparation process at either laboratory. A reference compound containing a modern C-14/C-12 ratio (vanillin) was employed to evaluate process contamination from fossil C. No negative bias due to fossil C was observed (sample Delta C-14 value of 165 +/- 20% agreed with Delta C-14 of 155 +/- 12% for the unprocessed vanillin). The extent of isotopic fractionation that can be induced during pcGC was evaluated by partially collecting the vanillin model compound of modern C-14/C-12 abundance. A significant change in the delta C-13 and delta C-14 values was observed when only parts of the eluting peak were collected (delta C-13 values ranged from -15.75 to -49.91% and delta C-14 values from -82.4 to +4.71%). Delta C-14 values, which are normalized to a delta C-13 of -25%, did not deviate significantly (-58.9 to -5.8%, considering the uncertainty of similar to +/- 20%). This means that normalization of radiocarbon results to a delta C-13 of -25%, normally performed to remove effects of environmental isotope fractionation on C-14-based age determinations, also cor-rects sufficiently for putative isotopic fractionation that may occur during pcGC isolation of individual compounds for CSRA. VL - 79 IS - 5 N1 - id: 615; 140ID Times Cited:11 Cited References Count:32 JO - Evaluation of gas chromatographic isotope fractionation and process contamination by carbon in compound-specific radiocarbon analysis ER - TY - RPRT T1 - Evolution and latitudinal diversity gradient: Speciation, extinction, and biogeography Y1 - 2007 A1 - Mittelbach, G. G. A1 - Schemske, D. W. A1 - Cornell, H. V. A1 - Allen, A. P. A1 - Brown, J. M. A1 - Bush, M. B. JF - Ecology Letters VL - on-line N1 - id: 456 ER - TY - JOUR T1 - Exploring relationships between watershed properties and holocene loss-on-ignition records in high-elevation lakes, southern uinta mountains, Utah, USA JF - Arctic Antarctic and Alpine Research Y1 - 2007 A1 - Munroe, Jeffrey S. AB - Sediment cores were retrieved from 12 lakes in the southern Uinta Mountains ranging in elevation from 2960 to 3475 m. Organic content was determined by loss-on-ignition (LOI) at 1-cm intervals (n = 2850), corresponding to 20 to similar to 100 yrs per sample. This data set was used to explore relationships between watershed variables and LOI records. Average LOI values are strongly correlated with lake elevation, elevation of the watershed, extent of late-lying snow and bare rock in the watershed, and the area of upstream lakes. Average LOI values are not significantly correlated with lake depth, or with lake or watershed area. The 12 LOI records can be visually divided into 3 groups with contrasting patterns: Steady, Trending, and Rising. Steady lakes have the lowest average LOI values, and are located in watersheds with the highest maximum elevations and the largest area of upstream lakes and late-lying snow. The most significant determinant on average LOI and LOI pattern is hydrologic through-flow as revealed by the configuration and number of inlets and outlets. The repetition of Steady, Trending, and Rising LOI patterns in different parts of the range, combined with contrasting LOI patterns in adjacent lakes, suggests that watershed characteristics strongly influence organic sedimentation. VL - 39 IS - 4 N1 - id: 2014; PT: J; CT: Uinta Interdisciplinary Assessment Symposium (UINTAS 2006); CY: MAY , 2006; CL: Snowbird, UT; UT: WOS:000250962500006 JO - Exploring relationships between watershed properties and holocene loss-on-ignition records in high-elevation lakes, southern uinta mountains, Utah, USA ER - TY - MAP T1 - Field and laboratory data from an earthquake history study of scarps of the Lake Creek-Boundary Creek fault between the Elwha River and Siebert Creek, Clallam County, Washington Y1 - 2007 A1 - Nelson, A. R. A1 - Personius, S. F. A1 - Buck, Jason A1 - Bradley, L. A. A1 - Wells, R. E. A1 - Schermer, E. R. JF - U. S. Geological Survey Scientific Investigations Report 2004 N1 - id: 433 ER - TY - JOUR T1 - Flux and age of dissolved organic carbon exported to the Arctic Ocean: A carbon isotopic study of the five largest arctic rivers RID C-4087-2009 RID C-5396-2008 JF - Global Biogeochemical Cycles Y1 - 2007 A1 - Raymond, Peter A. A1 - McClelland, J. W. A1 - Holmes, R. M. A1 - Zhulidov, A. V. A1 - Mull, K. A1 - Peterson, B. J. A1 - Striegl, R. G. A1 - Aiken, G. R. A1 - Gurtovaya, T. Y. AB - The export and Delta C-14-age of dissolved organic carbon (DOC) was determined for the Yenisey, Lena, Ob', Mackenzie, and Yukon rivers for 2004 - 2005. Concentrations of DOC elevate significantly with increasing discharge in these rivers, causing approximately 60% of the annual export to occur during a 2-month period following spring ice breakup. We present a total annual flux from the five rivers of similar to 16 teragrams (Tg), and conservatively estimate that the total input of DOC to the Arctic Ocean is 25 - 36 Tg, which is similar to 5-20% greater than previous fluxes. These fluxes are also similar to 2.5 x greater than temperate rivers with similar watershed sizes and water discharge. Delta C-14-DOC shows a clear relationship with hydrology. A small pool of DOC slightly depleted in Delta C-14 is exported with base flow. The large pool exported with spring thaw is enriched in D14C with respect to current-day atmospheric Delta C-14-CO2 values. A simple model predicts that similar to 50% of DOC exported during the arctic spring thaw is 1 - 5 years old, similar to 25% is 6 - 10 years in age, and 15% is 11 - 20 years old. The dominant spring melt period, a historically undersampled period, exports a large amount of young and presumably semilabile DOC to the Arctic Ocean. VL - 21 IS - 4 N1 - id: 2033; PT: J; UT: WOS:000250704000002 JO - Flux and age of dissolved organic carbon exported to the Arctic Ocean: A carbon isotopic study of the five largest arctic rivers RID C-4087-2009 RID C-5396-2008 ER - TY - JOUR T1 - Flux and fate of Yangtze river sediment delivered to the East China Sea JF - Geomorphology Y1 - 2007 A1 - Liu, J. P. A1 - Xu, K. H. A1 - Li, A. C. A1 - Milliman, J. D. A1 - Velozzi, D. M. A1 - Xiao, S. B. A1 - Yang, Z. S. AB - Numerous cores and dating show the Yangtze River has accumulated about 1.16 x 10(12) t sediment in its delta plain and proximal subaqueous delta during Holocene. High-resolution seismic profiling and coring in the southern East China Sea during 2003 and 2004 cruises has revealed an elongated (similar to 800 km) distal subaqueous mud wedge extending from the Yangtze River mouth southward off the Zhejiang and Fujian coasts into the Taiwan Strait. Overlying what appears to be a transgressive sand layer, this distal clinoform thins offshore, from similar to 40 in thickness between the 20 and 30 m water depth to < 1-2 in between 60 and 90 m water depth, corresponding to an across shelf distance of less than 100 km. Total volume of this distal mud wedge is about 4.5 x 10(11) m(3), equivalent to similar to 5.4 x 10(11) t of sediment. Most of the sediment in this mud wedge comes from the Yangtze River, with some input presumably coming from local smaller rivers. Thus, the total Yangtze-derived sediments accumulated in its deltaic system and East China Sea inner shelf have amounted to about 1.7 x 10(12) t. Preliminary analyses suggest this longshore and across-shelf transported clinoform mainly formed in the past 7000 yrs after postglacial sea level reached its mid-Holocene highstand, and after re-intensification of the Chinese longshore current system. Sedimentation accumulation apparently increased around 2000 yrs BP, reflecting the evolution of the Yangtze estuary and increased land erosion due to human activities, such as fanning and deforestation. The southward-flowing China Coastal Current, the northward-flowing Taiwan Warm Current, and the Kuroshio Current appear to have played critical roles in transporting and trapping most of Yangtze-derived materials in the inner shelf, and hence preventing the sediment escape into the deep ocean. (c) 2006 Elsevier B.V. All rights reserved. VL - 85 IS - 3-4 N1 - 244vyTimes Cited:286Cited References Count:84 JO - Flux and fate of Yangtze river sediment delivered to the East China Sea ER - TY - CHAP T1 - The Geographic, Geological and Oceanographic Setting of the Indus River T2 - Large Rivers Y1 - 2007 A1 - Inam, A. A1 - Clift, P. D. A1 - Giosan, L. ED - Gupta, A. JF - Large Rivers PB - Wiley Press N1 - id: 867; Y ER - TY - JOUR T1 - Global human impacts or climate change? : explaining the Sooty Shearwater decline at the Minard site, Washington State, USA JF - Journal of Archaeological Science Y1 - 2007 A1 - Bovy, K. M. AB - Sooty Shearwater (Puffinus griseus) remains decrease throughout the occupation (AD 1000-1600) of the Minard site (45-GH-15) on the southern Washington coast, USA. Given that New Zealand is one of the major breeding locations for this long-distant migrant, the decline at the Minard site may be due to human impacts on a global scale. In particular, the Maori practice of muttonbirding, the killing and preparation of fledgling shearwaters for storage, may have affected the number of summer migrants reaching the Pacific Northwest Coast. A second hypothesis attributes the decline in Sooty Shearwaters at the site to increasing sea surface temperatures and/or increased frequency of ENSO events during this period. Understanding how Sooty Shearwaters responded to human hunting and/or climate events in the past may be useful for the current management of this species, which has faced dramatic declines in recent decades. (c) 2006 Elsevier Ltd. All rights reserved. VL - 34 IS - 7 N1 - id: 445; 170KG Times Cited:4 Cited References Count:104 JO - Global human impacts or climate change? : explaining the Sooty Shearwater decline at the Minard site, Washington State, USA ER - TY - JOUR T1 - High-resolution proxy record of Holocene climate from a loess section in Southwestern Nebraska, USA JF - Palaeogeography Palaeoclimatology Palaeoecology Y1 - 2007 A1 - Miao, Xiaodong A1 - Mason, Joseph A. A1 - Johnson, William C. A1 - Wang, Hong AB - Multi-proxy analysis was used to produce a high-resolution paleoclimatic record from an exceptionally thick section of the Holocene Bignell Loess near Wauneta, Southwestern Nebraska, in the central Great Plains. The Wauneta section has excellent age control, based on optically stimulated luminescence (OSL) and radiocarbon dating, and records multiple episodes of rapid loess deposition alternating with slower deposition and soil formation. The lowermost and uppermost OSL ages obtained from the Bignell Loess are 10,250 +/- 610 years (5.9 in depth) and 100 +/- 10 years (0.1 in depth), respectively. As a result, the Holocene has been temporally confined. Stratigraphically, the Bignell Loess overlies the Late Pleistocene Peoria Loess (deposited similar to 21-14 ka), and the two units are separated by the Brady Soil which is distinguished by its color and other pedogenic features. L*a*b* color parameters and organic carbon content of Bignell Loess are sensitive proxies to differentiate drought-induced aeolian sediment layers from the intercalated soil horizons. Soil organic carbon-derived delta(13)C data suggest that the C(3)-dominated floral environment during Peoria Loess deposition shifted dramatically to a C(4)-dominated environment during Brady Soil formation in response to a warming trend. Even greater C(4) abundance characterized the late Holocene. High-resolution delta(13)C data support the contention that C(3) vs. C(4) vegetation change in the Holocene reflects ecosystem response to frequent vegetation disturbance under and conditions. Time series analysis reveals that delta(13)C and color parameters display high frequency variation with periodicities of 103-118 years and 103 years, respectively. Similar periodicities were also reported in studies of North Dakota takes, though the physical mechanism responsible is uncertain. Comparison of Bignell Loess color and tropical Pacific sea surface temperatures (SSTs) allows evaluation of a proposed teleconnection between drought in the Great Plains and La Nina-like conditions in the tropical Pacific. The loess color index and eastern tropical Pacific SST display broad similarities through the late Pleistocene and Holocene that are consistent with this teleconnection. On the other hand, drought centered at 3800 years ago is not consistent with the teleconnection, and the end of early Holocene aridity at the Wauneta section, around 6500 years ago, is much earlier than the corresponding rise in SST and increase in El Nino frequency in the eastern tropical Pacific. (c) 2006 Elsevier B.V. All rights reserved. VL - 245 IS - 3-4 N1 - id: 1994; PT: J; UT: WOS:000245026900004 JO - High-resolution proxy record of Holocene climate from a loess section in Southwestern Nebraska, USA ER - TY - CHAP T1 - Historical ecology and human impacts on coastal ecosystems of the Santa Barbara Channel region, California T2 - Ancient Human Impacts on Marine Environments: A Global Perspective Y1 - 2007 A1 - Rick, Torben C. A1 - Erlandson, Jon M. A1 - Braje, Todd J. A1 - Estes, James A1 - Graham, Michael A1 - Vellanoweth, Rene ED - Rick, T. C. JF - Ancient Human Impacts on Marine Environments: A Global Perspective PB - University of California Press CY - Berkeley N1 - id: 577 ER - TY - RPRT T1 - Holocene fire and occupation in Amazonia: Records from two lake districts Y1 - 2007 A1 - Bush, M. B. A1 - Silman, M. R. A1 - de Toledo, M. B. A1 - Listopad, C. R. S. A1 - Gosling, W. D. A1 - Williams, C. A1 - De Oliveira, P. E. A1 - Krisel, C. JF - Philosophical Transactions of the Royal Society of London VL - Ser. B. N1 - id: 454 ER - TY - JOUR T1 - Holocene Reworking of a Sand Sheet in the Merrimack Embayment, Western Gulf of Maine JF - Journal of Coastal Research Y1 - 2007 A1 - Hein, C. J. A1 - FitzGerald, D. M. A1 - Barnhardt, W. KW - backscatter KW - bedforms KW - shallow seismic KW - shelf sediment transport AB - Recent bathymetric, backscatter, and seafloor sediment samples demonstrate that a large sand sheet was formed in the inner shelf by the reworking of the Merrimack River lowstand delta (deposited 12 kya; currently at 45 m depth) and braid plain during the Holocene transgression. Asymmetric bedforms and distinct grain size distributions suggest the sand sheet is actively being reworked by inner-shelf processes.Bottom sediments range from silty sand at the submerged delta to coarse sand and fine gravel in the innermost shelf (depth: 10-50 m). Coarse-grained sand comprises an expansive (32 km(2)) featureless sand sheet centered off the Merrimack River. Fine-grained sand discontinuously overlies this sand sheet in many locations and forms long wavelength (100 - 800 m), low amplitude (1-2 m), asymmetrical bedforms. Sets of these bedforms are oriented from slightly oblique offshore to onshore; several bedform sets are located within I km and oriented orthogonally to one another. Along the paleo-delta front north-northwest oriented bedforms are dominant. Inshore of these features, the bedforms become more closely spaced and have orientations to the west and west-southwest. Preliminary data suggest that the combined forces of instantaneous storm-wave generated shear stress and storm-induced currents associated with high energy northeast storm events may be responsible for sand sheet reworking and bedform development. SN - 0749-0208 IS - SI 50 N1 - Sp. Iss. 50V16hi Times Cited:2 Cited References Count:22 JO - J Coastal Res ER - TY - JOUR T1 - Holocene sea-level oscillations and environmental changes on the Eastern Black Sea shelf JF - Palaeogeography Palaeoclimatology Palaeoecology Y1 - 2007 A1 - Ivanova, E. V. A1 - Murdmaa, I. O. A1 - Chepalyga, A. L. A1 - Cronin, T. M. A1 - Pasechnik, I. V. A1 - Levchenko, O. V. A1 - Howe, S. S. A1 - Manushkina, A. V. A1 - Platonova, E. A. AB - A multi-proxy study of four sediment cores from the Eastern (Caucasian) Black Sea shelf revealed five transgressive-regressive cycles overprinted on the general trend of glacioeustatic sea-level rise during the last 11,000 C-14 yr. These cycles are well represented in micro-and macrofossil assemblages, sedimentation rates, and gain size variations. The oldest recovered sediments were deposited in the Neoeuxinian semi-freshwater basin (similar to 10,500-9000 C-14 yr BP) and contain a Caspian-type mollusk fauna dominated by Dreissena rostriformis. Low delta O-18 and delta C-13 values are measured on this species. The first appearance of marine mollusks and ostracodes from the Mediterranean is established in this part of the Black Sea at similar to 8200 C-14 yr BP, i.e., about 1000-2000 yr later than the appearance of marine microfossils in the deeper part of the sea. The Early Holocene (Bugazian to Vityazevian) condensed section of shell and shelly mud sediments with at least two hiatuses represent a high-energy shelf-edge facies. It contains a transitional assemblage representing a mixture of Caspian and Mediterranean fauna. This pattern suggests a dual-flow regime via the Bosphorus after 8200 C-14 yr BR Caspian species disappear and oligolialine species decrease in abundance during the Vityazevian-Prekalamitian cycle. Later, during the Middle to Late Holocene, low sea-level stands are characterized by shell layers, whereas silty mud with various mollusk and ostracode assemblages rapidly accumulated during transgressions. Restricted mud accumulation, as well as benthic faunal composition and abundance, suggest high-energy and well-ventilated bottom water during low sea-level stands. A trend of O-18 enrichment in mollusk shells points to an increase in bottom-water salinity during the Vityazevian to Kalamitian transgressions (similar to 7000 to 5700 C-14 yr BP) due to a more open connection with the Mediterranean, while a pronounced increase in polyhaline species abundance is established during the Kalamitian to Djemetean transgressions (similar to 6400 to 2700 C-14 yr BP). However, the composition of the faunal assemblage indicates that bottom-water salinity never exceeded modem values of 18-20 psu. (c) 2006 Elsevier B.V. All rights reserved. VL - 246 IS - 2-4 N1 - 156gzTimes Cited:22Cited References Count:51 JO - Holocene sea-level oscillations and environmental changes on the Eastern Black Sea shelf ER - TY - CONF T1 - Holocene sedimentation in a kettle lpond breached by rising sea level on Cape Cod T2 - Northeast Section Meeting, Geological Society of America Y1 - 2007 A1 - Bratton, John F. JF - Northeast Section Meeting, Geological Society of America CY - Durham, NH VL - 39 N1 - id: 1065; 1 ER - TY - JOUR T1 - Household and Community Archaeology at the Chumash Village of Niaqla, Santa Rosa Island, California JF - Journal of Field Archaeology Y1 - 2007 A1 - Rick, Torben C. VL - 32 IS - 3 N1 - id: 2072 ER - TY - JOUR T1 - Human responses to Middle Holocene climate change on California's Channel Islands JF - Quaternary Science Reviews Y1 - 2007 A1 - Kennett, D. J. A1 - Kennettb, J. P. A1 - Erlandson, J. M. A1 - Cannariato, K. G. AB - High-resolution archaeological and paleoenvironmental records from California's Channel Islands provide a unique opportunity to examine potential relationships between climatically induced environmental changes and prehistoric human behavioral responses. Available climate records in western North America (7-3.8 ka) indicate a severe dry interval between 6.3 and 4.8 ka embedded within a generally warm and dry Middle Holocene. Very dry conditions in western North America between 6.3 and 4.8 ka correlate with cold to moderate sea-surface temperatures (SST) along the southern California Coast evident in Ocean Drilling Program (ODP) Core 893A/B (Santa Barbara Basin). An episode of inferred high marine productivity between 6.3 and 5.8 ka corresponds with the coldest estimated SSTs of the Middle Holocene, otherwise marked by warm/low productivity marine conditions (7.5-3.8 ka). The impact of this severe aridity on humans was different between the northern and southern Channel Islands, apparently related to degree of island isolation, size and productivity of islands relative to population, fresh water availability, and on-going social relationships between island and continental populations. Northern Channel Islanders seem to have been largely unaffected by this severe and phase. In contrast, cultural changes on the southern Channel Islands were likely influenced by the climatically induced environmental changes. We suggest that productive marine conditions coupled with a dry terrestrial climate between 6.3 and 5.8 ka stimulated early village development and intensified fishing on the more remote southern islands. Contact with people on the adjacent southern California Coast increased during this time with increased participation in a down-the-line trade network extending into the western Great Basin and central Oregon. Genetic similarities between Middle Holocene burial populations on the southern Channel Islands and modern California Uto-Aztecan populations suggest Middle Holocene movement of people at this time from southern California desert environs westward to the southern islands, a migration perhaps stimulated by increased continental aridity. (c) 2006 Elsevier Ltd. All rights reserved. VL - 26 IS - 3-4 N1 - 158ghTimes Cited:49Cited References Count:167 JO - Human responses to Middle Holocene climate change on California's Channel Islands ER - TY - JOUR T1 - Intense hurricane activity over the past 5,000 years controlled by El Nino and the West African monsoon JF - Nature Y1 - 2007 A1 - Donnelly, J. P. A1 - Woodruff, J. D. AB - The processes that control the formation, intensity and track of hurricanes are poorly understood. It has been proposed that an increase in sea surface temperatures caused by anthropogenic climate change has led to an increase in the frequency of intense tropical cyclones, but this proposal has been challenged on the basis that the instrumental record is too short and unreliable to reveal trends in intense tropical cyclone activity. Storm-induced deposits preserved in the sediments of coastal lagoons offer the opportunity to study the links between climatic conditions and hurricane activity on longer timescales, because they provide centennial- to millennial-scale records of past hurricane landfalls. Here we present a record of intense hurricane activity in the western North Atlantic Ocean over the past 5,000 years based on sediment cores from a Caribbean lagoon that contain coarse-grained deposits associated with intense hurricane landfalls. The record indicates that the frequency of intense hurricane landfalls has varied on centennial to millennial scales over this interval. Comparison of the sediment record with palaeo-climate records indicates that this variability was probably modulated by atmospheric dynamics associated with variations in the El Nino/Southern Oscillation and the strength of the West African monsoon, and suggests that sea surface temperatures as high as at present are not necessary to support intervals of frequent intense hurricanes. To accurately predict changes in intense hurricane activity, it is therefore important to understand how the El Nino/Southern Oscillation and the West African monsoon will respond to future climate change. VL - 447 IS - 7143 N1 - Donnelly, Jeffrey PWoodruff, Jonathan DengResearch Support, Non-U.S. Gov'tResearch Support, U.S. Gov't, Non-P.H.S.England2007/05/25 09:00Nature. 2007 May 24;447(7143):465-8. JO - Intense hurricane activity over the past 5,000 years controlled by El Nino and the West African monsoon ER - TY - JOUR T1 - Last millennia sedimentary record on a micro-tidal, low-accumulation prodelta (Tet NW Mediterranean) JF - Marine Geology Y1 - 2007 A1 - Bourrin, F. A1 - Monaco, A. A1 - Aloisi, J. C. A1 - Sanchez-Cabeza, J. A. A1 - Lofi, J. A1 - Heussner, S. A1 - de Madron, X. D. A1 - Jeanty, G. A1 - Buscail, R. A1 - Saragoni, G. AB - Statistical sequential analysis was performed on a series of sediment cores collected from the Tet prodelta in the Gulf of Lions, northwestern Mediterranean Sea, between October 2003 and October 2004. Seabed changes during that period were correlated to hydrodynamic conditions (waves and currents) and river discharge. Low sediment supply prevents full preservation of new sediment strata on this low-accumulation prodelta located on a microtidal, storm-dorninated inner shelf. Severe meteorological events caused a rapid succession of erosion and deposition phases. For example, the December 2003 flood and storm produced a flood layer deposit that persisted for 2 months with only slight transformations due to early diagenesis and/or bioturbation, until a new, storm event eroded this layer. A typical sedimentary sequence was observed for the secular deposits composed of a 10-cm-thick sandy layer overlaying siltyclayey layers. These characteristic features were used to analyse the last millennia sedimentary record of the Tet prodelta. The low preservation of freshly deposited sediments and variable sedimentation rates during the last millennia period yield a sedimentary sequence formed by the outcropping of muddy prodeltaic units intersected by heterogeneous siltysandy units similar to those formed under present day hydrodynamic conditions. No flood layer was found related to catastrophic flooding of the last century in the sedimentary record. The Little lee Age (similar to 1550-1850 AD) probably favoured the formation of a well-developed muddy prodelta in the mouth of the Tet River. Later on, the decrease of sediment supply by rivers due to climate change and/or human activities (damming, irrigation), and the increase of the number of high-energy storms reaching the coast, induced a coarsening of the top sediment layer on this prodelta. This modem change of the substrate is also observed in the composition of benthic biota found in the substrate. (c) 2007 Elsevier B.V All rights reserved. VL - 243 IS - 1-4 N1 - id: 1904; 210TU Times Cited:8 Cited References Count:68Y JO - Last millennia sedimentary record on a micro-tidal, low-accumulation prodelta (Tet NW Mediterranean) ER - TY - JOUR T1 - Late Holocene barrier island collapse; Outer Banks, North Carolina, USA JF - The Sedimentary Record Y1 - 2007 A1 - Culver, Stephen J. A1 - Grand Pre, Candace A. A1 - Mallinson, David J. A1 - Riggs, Stanley R. A1 - Corbett, D. Reide A1 - Foley, Jennifer A1 - Hale, Michael A1 - Metger, Lauren A1 - Ricardo, John A1 - Rosenberger, Jeb A1 - Smith, Christopher G. A1 - Smith, Curtis W. A1 - Snyder, Scott W. A1 - Twamley, David A1 - Farrell, Kathleen A1 - Horton, Benjamin KW - 24, Quaternary geology KW - algae KW - assemblages KW - barrier islands KW - Cenozoic KW - changes KW - clastic sediments KW - cores KW - diatoms KW - erosion KW - Foraminifera KW - geologic hazards KW - Holocene KW - hurricanes KW - Invertebrata KW - landform evolution KW - lithofacies KW - littoral KW - microfossils KW - North Carolina KW - Outer Banks KW - Pamlico Sound KW - Plantae KW - preservation KW - Protista KW - Quaternary KW - salinity KW - sand KW - sea-level KW - sediments KW - United States KW - upper Holocene KW - Vibroseis AB - We document here the threat of large scale destruction (collapse) of barrier islands based on the study of many cores taken along the Outer Banks and in Pamlico Sound, North Carolina.Around 1,100 cal yr BP, probably as the result of hurricane activity, portions of the southern Outer Banks must have collapsed to allow normal salinity waters to bathe southern Pamlico Sound for several hundred years. Such collapse could occur again during our current regime of global warming, rising sea level and increased tropical cyclone activity. The economic effect of barrier island break collapse on Outer Banks communities would be devastating. VL - 5 IS - 4 N1 - id: 1887; ISSN: 1543-8740 Language: English References: 16; illus. incl. strat. col., geol. sketch map United States (USA) Latitude:N350000,N353000 Longitude:W0753000,W0760000 ER - TY - JOUR T1 - Late Holocene fine-grained sediments of the Balearic Abyssal Plain, Western Mediterranean Sea JF - Marine Geology Y1 - 2007 A1 - Zuniga, D. A1 - Garcia-Orellana, J. A1 - Calafat, A. A1 - Price, N. B. A1 - Adatte, T. A1 - Sanchez-Vidal, A. A1 - Canals, M. A1 - Sanchex-Cabeza, J. A. A1 - Masque, P. A1 - Fabres, J. AB - The Late Holocene fine-grained sedimentation in the deep central Balearic Abyssal Plain, Western Mediterranean Sea, has been studied after the analysis of high quality sediment cores from three multicoring stations, named A, B and C. The coring stations are 25 km apart from each other and form a triangle that is at the greatest distance from the nearest landmasses. The sediments consist of foraminifer-pteropod oozes (layers U1 and U4 from bottom to top), two pteropod oozes (U2 and U5) and a turbidite layer (U3). The same sequence has been identified in the three cores. The turbidite layer U3 that lies on top of U2 (C-14 AMS dated at 1814 cal yrs BP) ranges from 5 to I I cm thick and is clearly distinguished from the dominating hemipelagic sediments by colour variations, higher water content and the absence of planktonic foraminifer shells. Rather uniform values of organic carbon and nitrogen are also characteristic of the U3 turbidite unit, likely because of homogenisation during transport and emplacement. In addition, U3 unit shows higher contents of terrigenous elements such as K and Fe. Otherwise, the presence of zeolites in the turbidite layer supports the hypothesis of the Sardinian continental margin, where pyroclastic deposits are known, as the most likely source area for U3. Our results demonstrate the ability of turbidity currents originating on the margins surrounding the Balearic Abyssal Plain to reach the very centre of the basin during high sea level still stands as the present one. (c) 2006 Elsevier B.V. All rights reserved. VL - 237 IS - 1-2 N1 - id: 624; 139VA Times Cited:6 Cited References Count:57 JO - Late Holocene fine-grained sediments of the Balearic Abyssal Plain, Western Mediterranean Sea ER - TY - JOUR T1 - Late Quaternary environmental and human events at En Gedi, reflected by the geology and archaeology of the Moringa Cave (Dead Sea area, Israel) JF - Quaternary Research Y1 - 2007 A1 - Lisker, S. A1 - Porat, R. A1 - Davidovich, U. A1 - Eshel, H. A1 - Lauritzen, S. E. A1 - Frumkin, A. AB - The Moringa Cave within Pleistocene sediments in the En Gedi area of the Dead Sea Fault Escarpment contains a sequence of various Pleistocene lacustrine deposits associated with higher-than-today lake levels at the Dead Sea basin. In addition it contains Chalcolithic remains and 5th century BC burials attributed to the Persian period, cemented and covered by Late Holocene travertine flowstone. These deposits represent a chain of Late Pleistocene and Holocene interconnected environmental and human events, echoing broader scale regional and global climate events. A major shift between depositional environments is associated with the rapid fall of Lake Lisan level during the latest Pleistocene. This exposed the sediments, providing for cave formation processes sometime between the latest Pleistocene (ca. 15 ka) and the Middle Holocene (ca. 4500 BC), eventually leading to human use of the cave. The Chalcolithic use of the cave can be related to a relatively moist desert environment, probably related to a shift in the location of the northern boundary of the Saharo-Arabian desert belt. The travertine layer was U-Th dated 2.46 +/- 0.10 to 2.10 +/- 0.04 ka, in agreement with the archaeological finds from the Persian period. Together with the inner consistency of the dating results, this strongly supports the reliability of the radiometric ages. The 2.46-2.10 ka travertine deposition within the presently dry cave suggests a higher recharge of the Judean Desert aquifer, correlative to a rising Dead Sea towards the end of the 1 st millennium BC. This suggests a relatively moist local and regional climate facilitating human habitation of the desert. (c) 2007 University of Washington. All rights reserved. VL - 68 IS - 2 N1 - 207wkTimes Cited:3Cited References Count:55 JO - Late Quaternary environmental and human events at En Gedi, reflected by the geology and archaeology of the Moringa Cave (Dead Sea area, Israel) ER - TY - CHAP T1 - Late quaternary lake and swamp sediments: records of climate and environment T2 - Central America: Geology, Resources, Hazards Y1 - 2007 A1 - Horn, S. P. ED - Bundschuh, J. JF - Central America: Geology, Resources, Hazards PB - Taylor & Francis/Balkema CY - Leiden, The Netherlands VL - 1 N1 - id: 622 ER - TY - JOUR T1 - Late quaternary paleoseismology of the southern Steens fault zone, northern Nevada JF - Bulletin of the Seismological Society of America Y1 - 2007 A1 - Personius, Stephen F. A1 - Crone, Anthony J. A1 - Machette, Michael N. A1 - Mahan, Shannon A. A1 - Kyung, Jai Bok A1 - Cisneros, Hector A1 - Lidke, David J. AB - The 192-km-long Steens fault zone is the most prominent normal fault system in the northern Basin and Range province of western North America. We use trench mapping and radiometric dating to estimate displacements and timing of the last three surface-rupturing earthquakes (E1-E3) on the southern part of the fault south of Denio, Nevada. Coseismic displacements range from 1.1 to 2.2 +/- 0.5 m, and radiometric ages indicate earthquake times of 11.5 +/- 2.0 ka (E3), 6.1 +/- 0.5 ka (E2), and 4.6 +/- 1.0 ka (E1). These data yield recurrence intervals of 5.4 +/- 2.1 k.y. between E3 and E2, 1.5 +/- 1.1 k.y. between E2 and E1, and an elapsed time of 4.6 +/- 1.0 k.y. since El. The recurrence data yield variable interval slip rates (between 0.2 +/- 0.22 and 1.5 +/- 2.3 mm/yr), but slip rates averaged over the past similar to 18 k.y. (0.24 +/- 0.06 mm/year) are similar to long-term (8.5-12.5 Ma) slip rates (0.2 +/- 0.1 mm/yr) measured a few kilometers to the north. We infer from the lack of significant topographic relief across the fault in Bog Hot Valley that the fault zone is propagating southward and may now be connected with a fault at the northwestern end of the Pine Forest Range. Displacements documented in the trench and a rupture length of 37 km indicate a history of three latest Quaternary earthquakes with magnitudes of M 6.6-7.1 on the southern part of the Steens fault zone. VL - 97 IS - 5 N1 - id: 2022; PT: J; UT: WOS:000249930900021 JO - Late quaternary paleoseismology of the southern Steens fault zone, northern Nevada ER - TY - THES T1 - Late-glacial through Holocene stratigraphy and lake-level record ofRangeley Lake, Western Maine Y1 - 2007 A1 - Metcalfe, Elisabet PB - University of Maine VL - Master's ER - TY - JOUR T1 - A late-glacial transition from Picea glauca to Picea mariana in southern New England JF - Quaternary Research Y1 - 2007 A1 - Lindbladh, M. A1 - Oswald, W. W. A1 - Foster, D. R. A1 - Faison, E. K. A1 - Hou, J. Z. A1 - Huang, Y. S. AB - Picea is an important taxon in late-glacial pollen records from eastern North America, but little is known about which species of Picea were present. We apply a recently developed palynological method for discriminating the three Picea species in eastern North America to three records from New England. Picea glauca was dominant at similar to 14,500-14,000 cal yr BP, followed by a transition to Picea mariana between similar to 14,000 and 13,500 cal yr BP. Comparison of the pollen data with hydrogen isotope data shows clearly that this transition began before the beginning of the Younger Dryas Chronozone. The ecological changes of the late-glacial interval were not a simple oscillation in the position of a single species' range, but rather major changes in vegetation structure and composition occurring during an interval of variations in several environmental factors, including climate, edaphic conditions, and atmospheric CO2 levels. (c) 2007 University of Washington. All rights reserved. VL - 67 IS - 3 N1 - id: 1841; 160RU Times Cited:5 Cited References Count:61Y JO - A late-glacial transition from Picea glauca to Picea mariana in southern New England ER - TY - JOUR T1 - Linking lithology and land use to sources of dissolved and particulate organic matter in headwaters of a temperate, passive-margin river system JF - Geochimica Et Cosmochimica Acta Y1 - 2007 A1 - Longworth, B. E. A1 - Petsch, S. T. A1 - Raymond, P. A. A1 - Bauer, J. E. KW - ATCHAFALAYA RIVER KW - ATMOSPHERIC O-2 KW - BLACK SHALE KW - continental-shelf KW - GULF-OF-MEXICO KW - marine-sediments KW - MINERAL KW - SPACE-TIME CLIMATE KW - STABLE-ISOTOPES KW - surface sediments KW - SURFACES AB - A number of rivers have been found to transport highly aged organic matter [OM]; however, the sources of this aged material remain a matter of debate. One potential source may be erosion and weathering of headwater lithologies rich in ancient sedimentary OM. In this study, waters, suspended particulates, streambed sediments, rocks and soils from fourteen small headwater watersheds of a mid-size, temperate, passive margin river were sampled and characterized by Delta C-14, delta C-13, and POC/TPN ratios to identify sources of particulate and dissolved OM delivered to the river mainstem. These headwater sites encompass a range in lithology (OM-rich shales, OM-lean carbonate/mudstone facies, and OM-free crystalline rocks) and land use types (forested and agricultural), and allow investigation of the influence of agriculture and bedrock types on stream OM characteristics. Streams draining large areas of both agricultural land use and OM-rich lithology contain particulate OM [POM] that is more C-14-depleted than streams draining forested, shale-free watersheds. However, this is not sufficient to account for the significantly lower Delta C-14-POC measured in the river mainstern. Dissolved OM [DOM] Delta C-14 are in all cases enriched compared to POM from the same stream, but are otherwise highly variable and unrelated to either land use or lithology. POC/TPN ratios were likewise highly variable. POC and DOC delta C-13 signatures were similar across all watersheds. Based on isotope mass balance, C-14-free fossil OM sources contribute 0-12% of total stream POM. Although these results do not unequivocally separate the influences of land use and lithology, watershed coverage by shale and agriculture are both important controls on stream A Delta C-14-POC. Thus export of aged, particle-associated OM may be a feature of river systems along both passive and active continental margins. (C) 2007 Elsevier Ltd. All rights reserved. VL - 71 SN - 0016-7037 IS - 17 N1 - 30 JO - Geochim. Cosmochim. Acta ER - TY - JOUR T1 - Lithological anomalies in a relict coastal dune: Geophysical and paleoenvironmental markers JF - Geophysical Research Letters Y1 - 2007 A1 - Buynevich, I. V. A1 - Bitinas, A. A1 - Pupienis, D. AB - Ground exposures of migration surfaces (slipfaces) of a relict Holocene coastal dune along the southeastern Baltic Sea coast provide an ideal opportunity for establishing the causes of prominent reflections on geophysical profiles. High-amplitude reflections on high-resolution ground-penetrating radar (GPR) images correlate well with two major lithological anomalies: 1) paleosols developed on dune slipfaces, and 2) slipfaces consisting of heavy-mineral concentrations (HMCs). Paleosols serve as indicators of dune stability, represent datable chronostratigraphic surfaces, and help reconstruct dune paleo-morphology. HMCs have substantially higher magnetic susceptibility values than background quartz-rich sands and, where they are well-developed, can be also used for spatial correlation. Based on their occurrence at the study site, these enriched horizons likely represent periods of increased wind activity ( storminess). Multiple HMCs upwind of paleosol P1 ( 800 670 cal years BP) likely reflect periods of intensified wind activity along the southeast Baltic region during the Medieval Warm Period. VL - 34 IS - 9 N1 - 168ajTimes Cited:18Cited References Count:38 JO - Lithological anomalies in a relict coastal dune: Geophysical and paleoenvironmental markers ER - TY - JOUR T1 - Little Ice Age drought in equatorial Africa: Intertropical Convergence Zone migrations and El Nino-Southern Oscillation variability RID C-1423-2010 JF - Geology Y1 - 2007 A1 - Russell, J. M. A1 - Johnson, T. C. AB - High-resolution analyses of the Mg concentration in authigenic calcite in five cores from Lake Edward provide a water balance history of central equatorial Africa spanning the past 1400 yr. A high ratio of Mg to Ca (%Mg) indicates strong droughts in central Africa during the Little Ice Age (A.D. 1400-1750), in contrast to records from Lake Naivasha, Kenya, which suggest a wet Little Ice Age. This spatial pattern in Africa likely arose due to coupled changes in the high latitudes, the position of the Intertropical Convergence Zone, and the Ell Ni (n) over tildeo-Southern Oscillation (ENSO) system. Our results further suggest that the patterns and variability of twentieth-century rainfall in central Africa have been unusually conducive to human welfare in the context of the past 1400 yr. VL - 35 IS - 1 N1 - id: 2049; PT: J; UT: WOS:000243483800006 JO - Little Ice Age drought in equatorial Africa: Intertropical Convergence Zone migrations and El Nino-Southern Oscillation variability RID C-1423-2010 ER - TY - JOUR T1 - Little Ice Age drought in quatorial Africa: ITCZ migrations and ENSO variability JF - geology Y1 - 2007 A1 - Russell, J. M. A1 - Johnson, T. C. VL - 35 N1 - id: 1005 ER - TY - JOUR T1 - Long-term settlement, mobility, and landscape formation of Eastern Eurasian pastoralists from 2500 CAL B.C JF - Journal of Field Archaeology Y1 - 2007 A1 - Frachetti, M. D. A1 - Mar’yashev, A. N. VL - 32 IS - 3 N1 - id: 1881 ER - TY - JOUR T1 - Marine radiocarbon evidence for the mechanism of deglacial atmospheric CO2 rise JF - Science Y1 - 2007 A1 - Marchitto, T. M. A1 - Lehman, S. J. A1 - Ortiz, J. D. A1 - Fluckiger, J. A1 - van Geen, A. AB - We reconstructed the radiocarbon activity of intermediate waters in the eastern North Pacific over the past 38,000 years. Radiocarbon activity paralleled that of the atmosphere, except during deglaciation, when intermediate-water values fell by more than 300 per mil. Such a large decrease requires a deglacial injection of very old waters from a deep-ocean carbon reservoir that was previously well isolated from the atmosphere. The timing of intermediate-water radiocarbon depletion closely matches that of atmospheric carbon dioxide rise and effectively traces the redistribution of carbon from the deep ocean to the atmosphere during deglaciation. VL - 316 IS - 5830 N1 - Marchitto, Thomas MLehman, Scott JOrtiz, Joseph DFluckiger, Jacquelinevan Geen, AlexanderengResearch Support, U.S. Gov't, Non-P.H.S.2007/05/15 09:00Science. 2007 Jun 8;316(5830):1456-9. Epub 2007 May 10. JO - Marine radiocarbon evidence for the mechanism of deglacial atmospheric CO2 rise ER - TY - JOUR T1 - Middle Holocene subsistence and land use on Southeast Anchorage, Santa Rosa Island, California JF - Journal of California and Great Basin Anthropology Y1 - 2007 A1 - Wolff, Christopher B. A1 - Rick, Torben C. A1 - Aland, Amanda AB - California's Channel Islands have a lengthy archaeological record, spanning roughly 13,000 calendar years. However, relatively little is known about cultural developments during the Middle Holocene, resulting in a substantial gap in our understanding of the prehistory of California. Our research at CA-SRI-667, a large dune site with three components dated between about 6,200 and 4,300 cal B.P., demonstrates significant environmental changes occurred through time. Faunal remains and artifacts from the site document the decline of a local estuary, intensive dune building episodes, and the presence of relatively mobile human settlement systems. These data illustrate the dynamic nature of Middle Holocene human settlement and subsistence strategies, and associated environmental changes on California's Channel Islands. VL - 27 UR - http://www.jstor.org/stable/27825866 IS - 2 N1 - id: 2082 JO - Middle Holocene subsistence and land use on Southeast Anchorage, Santa Rosa Island, California ER - TY - RPRT T1 - A Mid-Holocene environmental change in Amazonian savannas Y1 - 2007 A1 - de Toledo, M. B. A1 - Bush, M. B. JF - Journal of Biogeography VL - on-line N1 - id: 455 ER - TY - JOUR T1 - Mobilization pathways of organic carbon from permafrost to arctic rivers in a changing climate JF - Geophysical Research Letters Y1 - 2007 A1 - Guo, L. D. A1 - Ping, C. L. A1 - Macdonald, R. W. AB - [1] Arctic warming may cause the release of vast amounts of soil organic carbon (SOC) from permafrost, which will manifest itself in the fluxes and composition of organic carbon in northern rivers and Arctic coastal regions. To elucidate the transport pathways of SOC, radiocarbon composition was measured for dissolved organic carbon (DOC), particulate organic carbon (POC), sediments and SOC from the Mackenzie, Sagavanirktok, and Yukon river basins, and soil leaching experiments were conducted. The radiocarbon ages of riverine suspended POC and sediments ranged from 4430 to similar to 7970 yr BP, while DOC was much younger (390-1440 yr BP) except samples from the Sag River. Soil leaching experiments released VL - 34 IS - 13 N1 - id: 773; 187WS Times Cited:23 Cited References Count:29Y JO - Mobilization pathways of organic carbon from permafrost to arctic rivers in a changing climate ER - TY - JOUR T1 - A multiproxy peat record of Holocene mangrove palaeoecology from Twin Cays, Belize JF - The HoloceneThe Holocene Y1 - 2007 A1 - Wooller, Matthew J. A1 - Morgan, Rebecca A1 - Fowell, Sarah A1 - Behling, Hermann A1 - Fogel, Marilyn AB - The extent and function of coastal mangrove ecosystems are likely to be influenced by future changes in sea level. Multiple proxies of past mangrove ecosystems preserved in a 780 cm long peat core (TCC2) taken from Twin Cays, Belize, record palaeoecological changes since ~8000 cal. yr BP. The proxies included pollen and the stable-isotope (C, N and O) compositions of mangrove leaf fragments. Rhizophora mangle (red mangrove) has been dominant at this site on Twin Cays for over ~8000 years. Variations in δ13 C and δ15N suggest past changes in stand structure between dwarf, transition and tall R. mangle through the Holocene. Marked changes in the δ18O (up to ~4?) of mangrove leaf fragments throughout TCC2 most likely record variations in the proportion of seawater versus precipitation taken up by past mangroves, reflecting the degree of inundation of the site with seawater resulting from changes in the rate of Holocene sea-level rise. Notably, a decline in peat accumulation rate at ~7200 cal. yr BP correlates with a decrease in the rate of rise in sea level. This was not accompanied by a marked change in the pollen assemblages. However, changes in assemblage composition began to occur ~6300 cal. yr BP, with an increase in Myrsine-type and Avicennia germinans (black mangrove) pollen. An increase in the δ18O between 6100 and 5300 cal. yr BP, which correlates with other records from Central America, indicates a significant increase in the rate of rise in sea level.The extent and function of coastal mangrove ecosystems are likely to be influenced by future changes in sea level. Multiple proxies of past mangrove ecosystems preserved in a 780 cm long peat core (TCC2) taken from Twin Cays, Belize, record palaeoecological changes since ~8000 cal. yr BP. The proxies included pollen and the stable-isotope (C, N and O) compositions of mangrove leaf fragments. Rhizophora mangle (red mangrove) has been dominant at this site on Twin Cays for over ~8000 years. Variations in δ13 C and δ15N suggest past changes in stand structure between dwarf, transition and tall R. mangle through the Holocene. Marked changes in the δ18O (up to ~4?) of mangrove leaf fragments throughout TCC2 most likely record variations in the proportion of seawater versus precipitation taken up by past mangroves, reflecting the degree of inundation of the site with seawater resulting from changes in the rate of Holocene sea-level rise. Notably, a decline in peat accumulation rate at ~7200 cal. yr BP correlates with a decrease in the rate of rise in sea level. This was not accompanied by a marked change in the pollen assemblages. However, changes in assemblage composition began to occur ~6300 cal. yr BP, with an increase in Myrsine-type and Avicennia germinans (black mangrove) pollen. An increase in the δ18O between 6100 and 5300 cal. yr BP, which correlates with other records from Central America, indicates a significant increase in the rate of rise in sea level. VL - 17 SN - 0959-6836 UR - http://journals.sagepub.com/doi/abs/10.1177/0959683607082553 IS - 8 ER - TY - RPRT T1 - Naze Site (32SN246) 1994 Archeological Excavations Stutsman County, North Dakota. James River Report Number 4 Y1 - 2007 A1 - Toom, Dennis L. PB - University of North Dakota CY - Grand Rapids, ND VL - University of North Dakota Anthropology Research Contribution No.410 N1 - id: 296 ER - TY - CONF T1 - The nitrogen isotope biogeochemistry of Long Island Sound; insights into mechanisms of 15N enrichment in eutrophication-impacted estuaries T2 - ASLO Meeting Y1 - 2007 A1 - Altabet, M. A. A1 - Varekamp, J. C. JF - ASLO Meeting CY - New Orelans, LA N1 - id: 752 ER - TY - CHAP T1 - North Atlantic intermediate depth variability during the Younger Dryas; evidence from benthic foraminiferal Mg/Ca and the GFDL R30 coupled climate model T2 - Geophysical Monograph, vol. 173 Y1 - 2007 A1 - Came, Rosemarie E. A1 - Curry, William B. A1 - Oppo, Delia W. A1 - Broccoli, Anthony J. A1 - Stouffer, Ronald J. A1 - Lynch-Stieglitz, Jean ED - Schmittner, Andreas KW - 24, Quaternary geology KW - Atlantic Ocean KW - benthic environment KW - Cenozoic KW - chemical ratios KW - Foraminifera KW - Glaciation KW - Gulf of Mexico KW - ice cores KW - Invertebrata KW - isotope ratios KW - isotopes KW - Little Bahama Bank KW - Mg/Ca KW - microfossils KW - North Atlantic KW - O-18/O-16 KW - oxygen KW - paleo-oceanography KW - paleobathymetry KW - paleosalinity KW - paleotemperature KW - Pleistocene KW - Protista KW - Quaternary KW - Stable isotopes KW - Straits of Florida KW - upper KW - upper Weichselian KW - Weichselian KW - Younger Dryas JF - Geophysical Monograph, vol. 173 PB - American Geophysical Union CY - Washington SN - 9780875904382 N1 - id: 857; American Geophysical Union 2005 fall meeting, San Francisco, CA, United States, Dec 5-9, 2005 NSF grants OCE-0096495, ATM-0502428, OCE-0096472, OCE-0220776 and ATM-0501351 References: 72; illus.; Y ER - TY - CHAP T1 - Oceanic dispersal and accumulation of river sediment T2 - Continental-Margin Sedimentation: from Sediment Transport to Sequence Stratigraphy Y1 - 2007 A1 - Sommerfield, C. K. A1 - Agston, A. S. A1 - Mullenbach, B. L. A1 - Drake, D. E. A1 - Alexander, C. R. A1 - Nittrouer, C. A. A1 - Borgeld, J. C. A1 - Wheatcroft, R. A. A1 - Leithold, E. L. ED - Nittrouer, C. A. JF - Continental-Margin Sedimentation: from Sediment Transport to Sequence Stratigraphy PB - Blackwell Publishing Ltd. CY - Oxford VL - IAS Special Publication N1 - id: 1119 ER - TY - CHAP T1 - One if by land, two if by sea: who were the first Californians? T2 - California Prehistory:Colonization, Culture and Complexity Y1 - 2007 A1 - Erlandson, Jon M. A1 - Rick, Torben C. A1 - Jones, Terry L. A1 - Porcasi, Judith ED - Jones, Terry L. JF - California Prehistory:Colonization, Culture and Complexity PB - AltaMira Press N1 - id: 2081 ER - TY - JOUR T1 - Organic matter origin and distribution in suspended particulate materials and surficial sediments from the western Adriatic Sea (Italy) JF - Estuarine Coastal and Shelf Science Y1 - 2007 A1 - Tesi, T. A1 - Miserocchi, S. A1 - Goñi, M. A. A1 - Langone, L. A1 - Boldrin, A. A1 - Turchetto, M. AB - In this study, organic carbon (OC), total nitrogen (TN), stable carbon isotopic (delta C-13(OC)) and CuO reaction product compositions were used to identify the sources of organic matter (OM) and to quantify the relative importance of allochthonous and autochthonous contributions to the western Adriatic Sea, Italy. Suspended particulate material (195 samples) and surficial sediments (0- 1 cm, 70 samples) from shallow cross-shelf transects were collected in February and May 2003, respectively. Vertical water column profiles were acquired along the same transects. Data include depth, potential temperature, salinity, density and chlorophyll fluorimetry. Along the western Adriatic shelf in the near-shore region, the phytoplankton growth was influenced by dynamics of the buoyant plumes from the Po and Appennine rivers. A small amount of very fine terrigenous material remained suspended within the coastal current and was exported southward along the shelf to the slope. High variability in the bulk composition was detected in the Po prodelta surficial sediments, whereas the western Adriatic shelf, although a larger area, exhibited a narrower range of values. A significant decoupling was observed between suspended particles in the water column and surficial deposits. The organic material collected in the water column was compositionally heterogeneous, with contributions from marine phytoplankton, riverine-estuarine phytoplankton and soil-derived OM. Frequent physical reworking of surficial sediments likely leads to the efficient oxidation of marine OC, resulting in the observed accumulation and preservation of refractory soil-derived OC delivered by the Po and Appennine rivers. (c) 2007 Elsevier Ltd. All rights reserved. VL - 73 IS - 3-4 N1 - id: 1869; 179HX Times Cited:12 Cited References Count:61Y JO - Organic matter origin and distribution in suspended particulate materials and surficial sediments from the western Adriatic Sea (Italy) ER - TY - JOUR T1 - Paleoecology and ecosystem restoration: case studies from Chesapeake Bay and the Florida Everglades JF - Frontiers in Ecology and the Environment Y1 - 2007 A1 - Willard, D. A. A1 - Cronin, T. M. AB - Climate extremes that cause droughts, floods, or large temperature fluctuations can complicate ecosystem restoration efforts focused on local and regional human disturbance. Restoration targets are often based primarily on monitoring data and modeling simulations, which provide information on species' short-term response to disturbance and environmental variables. Consequently, the targets may be unsustainable under the spectrum of natural variability inherent in the system or under future climate change. Increasingly, ecologists and restoration planners recognize the value of the long temporal perspective provided by paleoecological data. Advances in paleoclimatology, including better climate proxy methods and temporal resolution, contribute to our understanding of ecosystem response to anthropogenic and climatic forcing at all time scales. We highlight paleoecological research in the Chesapeake Bay and the Florida Everglades and summarize the resulting contributions to restoration planning. Integration of paleoecological, historic, monitoring, and modeling efforts will lead to the development of sustainable, adaptive management strategies for ecosystem restoration. VL - 5 IS - 9 N1 - id: 811; 227MD Times Cited:5 Cited References Count:51Y JO - Paleoecology and ecosystem restoration: case studies from Chesapeake Bay and the Florida Everglades ER - TY - JOUR T1 - Paleoenvironmental change in the middle Okinawa Trough since the last deglaciation: Evidence from the sedimentation rate and planktonic foraminiferal record JF - Palaeogeography Palaeoclimatology Palaeoecology Y1 - 2007 A1 - Xiang, R. A1 - Sun, Y. B. A1 - Li, T. G. A1 - Oppo, D. W. A1 - Chen, M. H. A1 - Zheng, F. AB - Well-dated, high-resolution records of planktonic foraminifera and oxygen isotopes from two sediment cores, A7 and E017, in the middle Okinawa Trough reveal strong and rapid millennial-scale climate changes since similar to 18 to 17 thousand years before present (kyr B.P.). Sedimentation rate shows a sudden drop at similar to 11.2 cal. kyr B.P. due to a rapid rise of sea level after the Younger Dryas (YD) and consequently submergence of the large continental shelf on the East China Sea (ECS) and the retreat of the estuary providing sediment to the basin. During the last deglaciation, the relative abundance of warm and cold species of planktonic foraminifera fluctuates strongly, consistent with the timing of sea surface temperature (SST) variations determined from Mg/Ca measurements of planktonic foraminifera from one of the two cores. These fluctuations are coeval with climate variation recorded in the Greenland ice cores and North Atlantic sediments, namely Heinrich event 1 (H1), Bolling-Allerod (B/A) and YD events. At about 9.4 kyr B.P., a sudden change in the relative abundance of shallow to deep planktonic species probably indicates a sudden strengthening of the Kuroshio Current in the Okinawa Trough, which was synchronous with a rapid sea-level rise at 9.5-9.2 kyr B.P. in the ECS, Yellow Sea (YS) and South China Sea (SCS). The abundance of planktonic foraminiferal species, together with Mg/Ca based SST, exhibits millennial-scale oscillations during the Holocene, with 7 cold events (at about 1.7, 2.3-4.6, 6.2, 7.3, 8.2, 9.6, 10.6 cal. kyr BP) superimposed on a Holocene warming trend. This Holocene trend, together with centennial-scale SST variations superimposed on the last deglacial trend, suggests that both high and low latitude influences affected the climatology of the Okinawa Trough. (c) 2006 Elsevier B.V. All rights reserved. VL - 243 IS - 3-4 N1 - 134kzTimes Cited:48Cited References Count:62 JO - Paleoenvironmental change in the middle Okinawa Trough since the last deglaciation: Evidence from the sedimentation rate and planktonic foraminiferal record ER - TY - JOUR T1 - Paleoenvironmental proxy records from Lake Hovsgol, Mongolia, and a synthesis of Holocene climate change in the Lake Baikal watershed JF - Quaternary Research Y1 - 2007 A1 - Prokopenko, A. A. A1 - Khursevich, G. K. A1 - Bezrukova, E. V. A1 - Kuzmin, M. I. A1 - Boes, X. A1 - Williams, D. F. A1 - Fedenya, S. A. A1 - Kulagina, N. V. A1 - Letunova, P. P. A1 - Abzaeva, A. A. AB - Here we discuss palcoenvironmental evolution in the Baikal region during the Holocene using new records of aquatic (diatom) and terrestrial vegetation changes from Hovsgol, Mongolia's largest and deepest lake. We reconcile previous contradictory Baikal timescales by constraining reservoir corrections of AMS dates on bulk sedimentary organic carbon. Synthesis of the Holocene records in the Baikal watershed reveals a northward progression in landscape/vegetation changes and an anti-phase behavior of diatom and biogenic silica proxies in neighboring rift lakes. In Lake Baikal, these proxies appear to be responsive to annual temperature increases after 6 ka, whereas in Lake Hovsgol they respond to higher precipitation/runoff from 11 to 7 ka. Unlike around Lake Baikal, warmer summers between 6 and 3.5 ka resulted in the decline, not expansion, of forest vegetation around Lake Hovsgol, apparently as a result of higher soil temperatures and lower moisture availability. The regional climatic proxy data are consistent with a series of 500-yr time slice Holocene GCM simulations for continental Eurasia. Our results allow reevaluation of the concepts of 'the Holocene optimum' and a 'maximum of the Asian summer monsoon', as applied to palcoclimate records from continental Asia. (c) 2007 University of Washington. All rights reserved. VL - 68 IS - 1 N1 - 187enTimes Cited:71Cited References Count:58 JO - Paleoenvironmental proxy records from Lake Hovsgol, Mongolia, and a synthesis of Holocene climate change in the Lake Baikal watershed ER - TY - JOUR T1 - Paleoenvironmental significance of the eastern mud snail, Ilyanassa obsolete (Say, 1822), from a microtidal coastal sequence of southern New England JF - The Nautilus Y1 - 2007 A1 - Buynevich, I. V. VL - 121 UR - http://biodiversitylibrary.org/page/8496891 N1 - id: 1082 JO - Paleoenvironmental significance of the eastern mud snail, Ilyanassa obsolete (Say, 1822), from a microtidal coastal sequence of southern New England ER - TY - MAP T1 - Paleoseismology of the Nephi segment of the Wasatch fault zone, Juab County, Utah--Preliminary results from two large exploratory trenches at Willow Creek Y1 - 2007 A1 - Machette, M. N. A1 - Crone, A. J. A1 - Personius, S. F. A1 - Dart, R. L. A1 - Lidke, D. J. A1 - Mahan, S. A. A1 - Olig, S. S. PB - U. S. Geological Survey N1 - id: 1116; Investigations Map 2966, 2 oversize plates ER - TY - JOUR T1 - Placing late Neanderthals in a climatic context RID A-5197-2008 JF - Nature Y1 - 2007 A1 - Tzedakis, P. C. A1 - Hughen, K. A. A1 - Cacho, I. A1 - Harvati, K. AB - Attempts to place Palaeolithic finds within a precise climatic framework are complicated by both uncertainty over the radiocarbon calibration beyond about 21,500 (14)C years BP(1) and the absence of a master calendar chronology for climate events from reference archives such as Greenland ice cores or speleothems(2). Here we present an alternative approach, in which (14)C dates of interest are mapped directly onto the palaeoclimate record of the Cariaco Basin by means of its (14)C series(3), circumventing calendar age model and correlation uncertainties, and placing dated events in the millennial-scale climate context of the last glacial period. This is applied to different sets of dates from levels with Mousterian artefacts, presumably produced by late Neanderthals, from Gorham's Cave in Gibraltar: first, generally accepted estimates of about 32,000 (14)C years BP for the upper-most Mousterian levels(4,5); second, a possible extended Middle Palaeolithic occupation until about 28,000 (14)C years BP(6); and third, more contentious evidence for persistence until about 24,000 (14)C years BP(6). This study shows that the three sets translate to different scenarios on the role of climate in Neanderthal extinction. The first two correspond to intervals of general climatic instability between stadials and interstadials that characterized most of the Middle Pleniglacial and are not coeval with Heinrich Events. In contrast, if accepted, the youngest date indicates that late Neanderthals may have persisted up to the onset of a major environmental shift, which included an expansion in global ice volume and an increased latitudinal temperature gradient. More generally, our radiocarbon climatostratigraphic approach can be applied to any 'snapshot' date from discontinuous records in a variety of deposits and can become a powerful tool in evaluating the climatic signature of critical intervals in Late Pleistocene human evolution. VL - 449 IS - 7159 N1 - id: 1991; PT: J; UT: WOS:000249394500047 JO - Placing late Neanderthals in a climatic context RID A-5197-2008 ER - TY - JOUR T1 - Planktonic foraminifera, calcareous nannoplankton and ascidian variations during the last 25 kyr in the Southwestern Atlantic: A paleoproductivity signature? JF - Marine Micropaleontology Y1 - 2007 A1 - Toledo, Filipe A. L. A1 - Chachao, Mario A1 - Costa, Karen B. A1 - Pivel, Maria A. G. VL - 64 N1 - id: 1061 ER - TY - THES T1 - Population dynamics, structure and per-recruit analysis of yellowedge grouper, Epinephelus flavolimbatus, from the northern Gulf of Mexico Y1 - 2007 A1 - Cook, M. PB - University of Southern Mississippi CY - Hattiesburg, MS VL - Ph.D. ER - TY - JOUR T1 - Post-glacial changes in spatial patterns of vegetation across southern New England JF - Journal of Biogeography Y1 - 2007 A1 - Oswald, W. W. A1 - Faison, E. K. A1 - Foster, D. R. A1 - Doughty, E. D. A1 - Hall, B. R. A1 - Hansen, B. C. S. AB - Aim We analysed lake-sediment pollen records from eight sites in southern New England to address: (1) regional variation in ecological responses to post-glacial climatic changes, (2) landscape-scale vegetational heterogeneity at different times in the past, and (3) environmental and ecological controls on spatial patterns of vegetation. Location The eight study sites are located in southern New England in the states of Massachusetts and Connecticut. The sites span a climatic and vegetational gradient from the lowland areas of eastern Massachusetts and Connecticut to the uplands of north-central and western Massachusetts. Tsuga canadensis and Fagus grandifolia are abundant in the upland area, while Quercus, Carya and Pinus species have higher abundances in the lowlands. Methods We collected sediment cores from three lakes in eastern and north-central Massachusetts (Berry East, Blood and Little Royalston Ponds). Pollen records from those sites were compared with previously published pollen data from five other sites. Multivariate data analysis (non-metric multi-dimensional scaling) was used to compare the pollen spectra of these sites through time. Results Our analyses revealed a sequence of vegetational responses to climate changes occurring across southern New England during the past 14,000 calibrated radiocarbon years before present (cal yr BP). Pollen assemblages at all sites were dominated by Picea and Pinus banksiana between 14,000 and 11,500 cal yr BP; by Pinus strobus from 11,500 to 10,500 cal yr BP; and by P. strobus and Tsuga between 10,500 and 9500 cal yr BP. At 9500-8000 cal yr BP, however, vegetation composition began to differentiate between lowland and upland sites. Lowland sites had higher percentages of Quercus pollen, whereas Tsuga abundance was higher at the upland sites. This spatial heterogeneity strengthened between 8000 and 5500 cal yr BP, when Fagus became abundant in the uplands and Quercus pollen percentages increased further in the lowland records. The differentiation of upland and lowland vegetation zones remained strong during the mid-Holocene Tsuga decline (5500-3500 cal yr BP), but the pattern weakened during the late-Holocene (3500-300 cal yr BP) and European-settlement intervals. Within-group similarity declined in response to the uneven late-Holocene expansion of Castanea, while between-group similarity increased due to homogenization of the regional vegetation by forest clearance and ongoing disturbances. Main conclusions The regional gradient of vegetation composition across southern New England was first established between 9500 and 8000 cal yr BP. The spatial heterogeneity of the vegetation may have arisen at that time in response to the development or strengthening of the regional climatic gradient. Alternatively, the differentiation of upland and lowland vegetation types may have occurred as the climate ameliorated and an increasing number of species arrived in the region, arranging themselves in progressively more complex vegetation patterns across relatively stationary environmental gradients. The emergence of a regional vegetational gradient in southern New England may be a manifestation of the increasing number of species and more finely divided resource gradient. VL - 34 IS - 5 N1 - id: 1840; 157BN Times Cited:5 Cited References Count:70Y JO - Post-glacial changes in spatial patterns of vegetation across southern New England ER - TY - JOUR T1 - The power of radiocarbon in biogeochemical studies of the marine carbon cycle: insights from studies of dissolved and particulate organic carbon (DOC and POC) JF - Chem Rev Y1 - 2007 A1 - McNichol, A. P. A1 - Aluwihare, L. I. VL - 107 IS - 2 N1 - McNichol, Ann PAluwihare, Lihini IengResearch Support, U.S. Gov't, Non-P.H.S.Review2007/02/16 09:00Chem Rev. 2007 Feb;107(2):443-66. JO - The power of radiocarbon in biogeochemical studies of the marine carbon cycle: insights from studies of dissolved and particulate organic carbon (DOC and POC) ER - TY - MAP T1 - Preliminary geologic map of the north-central part of the Alamosa 1/2 degree x 1 degree quadrangle, Alamosa and Conejos Counties, Colorado Y1 - 2007 A1 - Machette, M. N. A1 - Thompson, R. A. PB - U. S. Geological Survey Open-File Report N1 - id: 629; 1 sheet, 1:50,000 scale ER - TY - JOUR T1 - Preservation of black carbon in the shelf sediments of the East China Sea JF - Chinese Science Bulletin Y1 - 2007 A1 - Wang, X. C. A1 - Li, A. C. AB - Concentrations and carbon isotopic (C-14, C-13) compositions of black carbon (BC) were measured for three sediment cores collected from the Changjiang River estuary and the shelf of the East China Sea. BC concentrations ranged from 0.02 to 0.14 mg/g (dry weight), and accounted for 5% to 26% of the sedimentary total organic carbon (TOC) pool. Among the three sediment cores collected at each site, sediment from the Changjiang River estuary had relatively high BC contents compared with the sediments from the East China Sea shelf, suggesting that the Changjiang River discharge played an important role in the delivery of BC to the coastal region. Radiocarbon measurements indicate that the ages of BC are in the range of 6910 to 12250 years old B. P. (before present), that is in general, 3700 to 9000 years older than the C-14 ages of TOC in the sediments. These variable radiocarbon ages suggest that the BC preserved in the sediments was derived from the products of both biomass fire and fossil fuel combustion, as well as from ancient rock weathering. Based on an isotopic mass balance model, we calculated that fossil fuel combustion contributed most (60%. 80%) of the BC preserved in these sediments and varied with depth and locations. The deposition and burial of this "slow-cycling" BC in the sediments of the East China Sea shelf represent a significant pool of carbon sink and could greatly influence carbon cycling in the region. VL - 52 IS - 22 N1 - 232knTimes Cited:13Cited References Count:28 JO - Preservation of black carbon in the shelf sediments of the East China Sea ER - TY - JOUR T1 - Progress on a gas-accepting ion source for continuous-flow accelerator mass spectrometry JF - Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions with Materials and Atoms Y1 - 2007 A1 - Roberts, M. L. A1 - Schneider, R. J. A1 - von Reden, K. F. A1 - Wills, J. S. C. A1 - Han, B. X. A1 - Hayes, J. M. A1 - Rosenheim, B. E. A1 - W. J. Jenkins AB - A gas-accepting microwave-plasma ion source is being developed for continuous-flow accelerator mass spectrometry (AMS). Characteristics of the ion source will be presented. Schemes for connecting a gas or liquid chromatograph to the ion source will also be discussed. (c) 2007 Ellsevier B.V. All rights reserved. VL - 259 IS - 1 N1 - 182wvTimes Cited:24Cited References Count:12 JO - Progress on a gas-accepting ion source for continuous-flow accelerator mass spectrometry ER - TY - JOUR T1 - Quantification and radiocarbon source apportionment of black carbon in atmospheric aerosols using the CTO-375 method JF - Atmospheric Environment Y1 - 2007 A1 - Zencak, Z. A1 - Elmquist, M. A1 - Gustafsson, O. AB - To make progress towards linking the atmosphere and biogeosphere parts of the black carbon (BC) cycle, a chemothermal oxidation method (CTO-375), commonly applied for isolating BC from complex geomatrices such as soils, sediments and aquatic particles, was applied to investigate the BC also in atmospheric particles. Concentrations and C-14-based source apportionment of CTO-375 based BC was established for a reference aerosol (NIST RM-8785) and for wintertime aerosols collected in Stockholm and in a Swedish background area. The results were compared with thermal-optical (OC/EC) measurements. For NIST RM-8785, a good agreement was found between the BCCTO-375 concentration and the reported elemental carbon (EC) concentration measured by the "Speciation Trends Network - National Institute of Occupational Safety and Health" method (ECNIOSH) with BCCTO-375 of 0.054+/-0.002gg(-1) and ECNIOSH of 0.067+/-0.008gg(-1). In contrast, there was an average factor of ca. 20 difference between BC(CTO-37)5 and ECNIOSH for the ambient Scandinavian wintertime aerosols, presumably reflecting a combination of BCCTO-375 isolating only the recalcitrant soot-BC portion of the BC continuum and the ECNIOSH metric inadvertently including some intrinsically non-pyrogenic organic matter. Isolation of BCCTO-375 with subsequent off-line radiocarbon analysis yielded fraction modern values (fM) for total organic carbon (TOC) of 0.93 (aerosols from a Swedish background area), and 0.58 (aerosols collected in Stockholm); whereas the fM for BCCTO-375 isolates were 1.08 (aerosols from a Swedish background area), and 0.87 (aerosols collected in Stockholm). This radiocarbon-based source apportionment suggests that contribution from biomass combustion to cold-season atmospheric BCCTO-375 in Stockholm was 70% and in the background area 88%. (C) 2007 Elsevier Ltd. All rights reserved. VL - 41 IS - 36 N1 - id: 818; 243XB Times Cited:8 Cited References Count:58Y JO - Quantification and radiocarbon source apportionment of black carbon in atmospheric aerosols using the CTO-375 method ER - TY - JOUR T1 - Quantity, C-14 age and lability of desorbed soil organic carbon in fresh water and seawater JF - Organic Geochemistry Y1 - 2007 A1 - Butman, D. A1 - Raymond, P. A. A1 - Oh, N. H. A1 - Mull, K. AB - Soil organic carbon (OC) resulting from terrestrial photosynthesis is one of the largest reactive pools of sequestered atmospheric CO2. As an intermediate storage mechanism for organic material through time, the vertical distribution of carbon in a soil profile generally shows an age continuum with depth. Aged soil carbon is often the result of sorptive preservation, a physical mechanism that protects organic matter (OM) from microbial decay. Sorptive preservation is, however, a reversible process. Upon desorption, previously protected OM could be available for decomposition. Here we present simple fresh and salt water desorption experiments designed to determine the amount, 14C age and lability of “reversible” OM. Results suggest that 1.1–3.9% and 1.5–6.7% of OC, and 0.7–3% and 0.6–5% of total soil nitrogen can be desorbed using fresh and salt water, respectively. Radiocarbon data suggest this desorbed carbon is Δ14C-enriched compared to the bulk soil, with Δ14C values close to modern atmospheric Δ14CO2 at the soil surface, and aging with depth. Of this extractable aged carbon, upwards of 23–56% is labile across all treatments and with depth. Additional carbon is extracted with salt water compared to fresh water and this surplus is non-labile and younger than the labile component. Radiocarbon dating shows that the 14C age of soil carbon increases with depth and that there is a pool of Δ14C-depleted OC that is readily remineralized upon entering an aquatic/marine environment. These results indicate that eroded soil particles can release OC and organic N when entering rivers and oceans and that up to 50% of this carbon is available for aquatic metabolism. VL - 38 IS - 9 N1 - id: 1161 JO - Quantity, C-14 age and lability of desorbed soil organic carbon in fresh water and seawater. Organic Geochemistry ER - TY - JOUR T1 - Quaternary depositional patterns and sea-level fluctuations, northeastern North Carolina JF - Quaternary Research Y1 - 2007 A1 - Parham, P. R. A1 - Riggs, S. R. A1 - Culver, S. J. A1 - Mallinson, D. J. A1 - Wehmiller, J. F. AB - A detailed record of late Quaternary sea-level oscillations is preserved within the upper 45 in of deposits along an eight kin transect across Croatan Sound, a drowned tributary of the Roanoke/Albemarle drainage system, northeastern North Carolina. Drill-hole and seismic data reveal nine relatively complete sequences filling an antecedent valley comprised of discontinuous middle and early Pleistocene deposits. On interfluves, lithologically similar marine deposits of different sequences occur stacked in vertical succession and separated by ravinement surfaces. Within the paleo-drainage, marine deposits are separated by fluvial and/or estuarine sediments deposited during periods of lowered sea level. Foraminiferal and molluscan fossil assemblages indicate that marine facies were deposited in a shallow-marine embayment with open connection to shelf waters. Each sequence modifies or truncates portions of the preceding sequence or sequences. Sequence boundaries are the product of a combination of fluvial, estuarine, and marine erosional processes. Stratigraphic and age analyses constrain the ages of sequences to late Marine Isotope Stage (MIS) 6 and younger (similar to 140 ka to present), indicating multiple sea-level oscillations during this interval. Elevations of highstand deposits associated with late MIS 5 and MIS 3 imply that sea level was either similar to present during those times, or that the region may have been influenced by glacio-isostatic uplift and Subsidence. (c) 2006 University of Washington. All rights reserved. VL - 67 IS - 1 N1 - 131tvTimes Cited:18Cited References Count:56 JO - Quaternary depositional patterns and sea-level fluctuations, northeastern North Carolina ER - TY - RPRT T1 - Quaternary geology of the San Luis Basin, southern Colorado and Northern New Mexico--Rocky Mountain Section Friends of the Pleistocene Guidebook Y1 - 2007 A1 - Machette, M. N. A1 - Coates, M. M. A1 - Johnson, M. J. JF - U. S. Geological Survey Open-File Report 2007-1193 N1 - id: 625 ER - TY - JOUR T1 - Quaternary glaciation and hydrologic variation in the South American tropics as reconstructed from the Lake Titicaca drilling project JF - Quaternary Research Y1 - 2007 A1 - Fritz, S. C. A1 - Baker, P. A. A1 - Seltzer, G. O. A1 - Ballantyne, A. A1 - Tapia, P. A1 - Cheng, H. A1 - Edwards, R. L. AB - A 136-m-long drill core of sediments was recovered from tropical high-attitude Lake Titicaca, Bolivia-Peru, enabling a reconstruction of past climate that spans four cycles of regional glacial advance and retreat and that is estimated to extend continuously over the last 370,000 yr. Within the errors of the age model, the periods of regional glacial advance and retreat are concordant respectively with global glacial and interglacial stages. Periods of ice advance in the southern tropical Andes generally were periods of positive water balance, as evidenced by deeper and fresher conditions in Lake Titicaca. Conversely, reduced glaciation occurred during periods of negative water balance and shallow closed-basin conditions in the lake. The apparent coincidence of positive water balance of Lake Titicaca and glacial growth in the adjacent Andes with Northern Hemisphere ice sheet expansion implies that regional water balance and glacial mass balance are strongly influenced by global-scale temperature changes, as well as by precessional forcing of the South American summer monsoon. (c) 2007 University of Washington. All rights reserved. VL - 68 IS - 3 N1 - id: 841; 227AJ Times Cited:9 Cited References Count:63Y JO - Quaternary glaciation and hydrologic variation in the South American tropics as reconstructed from the Lake Titicaca drilling project ER - TY - JOUR T1 - Radiocarbon age of late glacial deep water from the equatorial Pacific JF - Paleoceanography Y1 - 2007 A1 - Broecker, W. A1 - Clark, E. A1 - Barker, S. A1 - Hajdas, I. A1 - Bonani, G. A1 - Moreno, E. AB - Radiocarbon age differences for pairs of coexisting late glacial age benthic and planktic foraminifera shells handpicked from 10 sediment samples from a core from a depth of 2.8 km in the western equatorial Pacific are not significantly different from that of 1600 years calculated from measurements on prenuclear seawater. This places a lower limit on the depth of the interface for the hypothetical radiocarbon-depleted glacial age seawater reservoir required to explain the 190% drop in the (14)C/C for atmospheric CO(2), which occurred during the mystery interval (17.5 to 14.5 calendar years ago). These measurements restrict the volume of this reservoir to be no more than 35% that of the ocean. Further, (14)C measurements on a single Last Glacial Maximum age sample from a central equatorial Pacific core from a depth of 4.4 km water fail to reveal evidence for the required 5- to 7-kyr age difference between benthic and planktic foraminifera shells if the isolated reservoir occupied only one third of the ocean. Nor does the (13)C record for benthic forams from this abyssal core yield any evidence for the excess respiration CO(2) expected to be produced during thousands of years of isolation. Nor, as indicated by the presence of benthic foraminifera, was the dissolved oxygen used up in this abyssal water. VL - 22 IS - 2 N1 - id: 413; 165MC Times Cited:10 Cited References Count:18 JO - Radiocarbon age of late glacial deep water from the equatorial Pacific ER - TY - JOUR T1 - Radiocarbon age offsets of foraminifera resulting from differential dissolution and fragmentation within the sedimentary bioturbated zone JF - Paleoceanography Y1 - 2007 A1 - Barker, Stephen A1 - Broecker, Wallace A1 - Clark, Elizabeth A1 - Hajdas, Irka AB - Shells of coexisting species of planktonic foraminifera from the Ontong Java Plateau reveal radiocarbon age offsets of up to 2200 years. Similar offsets are found between fragments and whole shells of single species. Steady state modelling of dissolution and bioturbation within the sedimentary mixed layer predicts age differences of up to several kiloyears due to the interplay between differential dissolution and fragmentation of foraminifer shells and bioturbation. The observation that fragile foraminiferal shells are systematically older than those of more robust species is more difficult to explain. Mechanisms of chemical erosion, interface dissolution, and sediment redistribution are all apparently unable to explain this phenomenon. A possible solution is presented in which a particular species may be represented by two distinct classes of shells which are more or less robust. In this case, differential dissolution and fragmentation causes an increase in the mean age as the fragile class contributes less to the remaining intact shells. This study highlights the vulnerability of low sedimentation rate cores to the effects of dissolution and bioturbation. VL - 22 IS - 2 N1 - id: 1920; PT: J; UT: WOS:000246308600002 JO - Radiocarbon age offsets of foraminifera resulting from differential dissolution and fragmentation within the sedimentary bioturbated zone ER - TY - JOUR T1 - Radiocarbon analysis confirms the annual nature of sagebrush growth rings JF - Radiocarbon Y1 - 2007 A1 - Biondi, F. A1 - Strachan, S. D. J. A1 - Mensing, S. A1 - Piovesan, G. AB - In the Great Basin of North America, big sagebrush (Artemisia tridentata Nutt.) growth rings can be used to reconstruct environmental changes with annual resolution in areas where there is otherwise little such information available. We tested the annual nature of big sagebrush wood layers using accelerator mass spectrometry (AMS) radiocarbon dating. Four cross-sections from 3 sagebrush plants were collected near Ely, Nevada, USA, and analyzed using dendrochronological methods. Ten C-14 measurements were then used to trace the location of the 1963-64 "bomb spike." Although the number of rings on each section did not exceed 60, crossdating was possible within a section and between sections. Years assigned to individual wood layers by means of crossdating aligned with their expected C-14 values, matching the location of the C-14 peak. This result confirmed the annual nature of growth rings formed by big sagebrush, and will facilitate the development of spatially explicit, well-replicated proxy records of environmental change, such as wildfire regimes, in Great Basin valleys. VL - 49 UR - https://journals.uair.arizona.edu/index.php/radiocarbon/article/view/3015/2773 IS - 3 N1 - 258usTimes Cited:9Cited References Count:48 JO - Radiocarbon analysis confirms the annual nature of sagebrush growth rings ER - TY - JOUR T1 - Radiocarbon and stable isotope geochemistry of organic matter in the Amazon headwaters, Peruvian Andes JF - Global Biogeochemical Cycles Y1 - 2007 A1 - Townsend-Small, A. A1 - Noguera, J. L. A1 - McClain, M. E. A1 - Brandes, J. A. KW - amino-acids KW - atlantic-ocean KW - carbon KW - drainage-basin KW - land-use KW - nitrogen KW - particulate KW - river system KW - sediments KW - streams AB - [1] We used delta C-13, delta N-15, and Delta C-14 to determine the sources of riverine organic matter in the Pozuzo River, a tributary of the Pachitea River located in the mountainous headwaters of the Amazon. Particulate organic matter (POM) Delta C-14 decreased downstream, suggesting that young organic matter (OM) introduced in small headwaters is respired preferentially in rivers or is diluted downstream with older material. The delta C-13 and delta N-15 of POM in headwater rivers were heterogeneous and also isotopically distinct from the main stem, suggesting that differences in landscape processes in small catchments impact the concentration and composition of POM in streams. The delta C-13 of dissolved organic matter (DOM) closely mirrored that of POM in the headwaters, with an apparent decoupling of dissolved and particulate OM in the river main stem. The delta C-13 of POM sampled in 2004 had a much different relationship with altitude than observed during previous years: In 2004, a very dry year, we observed enrichment from the headwaters to the main stem, and the opposite pattern in 2002, when rain fell heavily throughout the sampling campaign. This suggests that during dry conditions, in-stream processes ( such as resuspension or photosynthesis) may control riverine POM composition as opposed to terrestrial processes, which dominate during high runoff. Thus a decrease in runoff in Andean headwaters could result in less terrestrial POM transfer to rivers in the Andes foothills and lowland Amazon with a corresponding decrease in aquatic CO2 evasion. VL - 21 SN - 0886-6236 IS - 2 N1 - 185aaTimes Cited:12 Cited References Count:37 JO - Global Biogeochem Cy ER - TY - CONF T1 - Radiocarbon and Th-230 data reveal temperal changes in sediment focusing at ODP site 984, Poster T2 - EGU General Assembly Y1 - 2007 A1 - Mollenhauer, Gesine A1 - McManus, J. F. A1 - Wagner, T. A1 - McCave, I. N. A1 - Eglinton, T. I. JF - EGU General Assembly CY - Vienna, Austria N1 - id: 547 ER - TY - JOUR T1 - Radiocarbon dating of a very large African baobab JF - Tree Physiology Y1 - 2007 A1 - Patrut, A. A1 - von Reden, K. F. A1 - Pohlman, J. W. A1 - Wittmann, R. A1 - Mitchell, C. S. A1 - Lowy, D. A. A1 - Alberts, A. H. A1 - Gerlach, D. A1 - Xu, L. KW - Adansonia digitata KW - Age KW - Age determination KW - amazonia KW - c-14 content KW - cal kyr bp KW - Calibration KW - dendrochronology KW - dendroclimatology KW - holocene logs KW - location-dependent differences KW - southern-hemisphere KW - tasmanian conifers KW - Trees KW - tropical trees AB - In late 2004, Grootboom, probably the largest known African baobab (Adansonia digitata L.), collapsed unexpectedly in northeastern Namibia. Ten wood samples collected from different areas of the trunk were processed and investigated by accelerator mass spectrometry radiocarbon dating. The radiocarbon dates of three samples were greater than 1000 years BP (radiocarbon years before present, i.e., before AD 1950). The corresponding calibrated calendar age of the oldest sample was 1275 +/- 50 years, making Grootboom the oldest known angiosperm tree with reliable dating results. Variations in radiocarbon dates among the wood samples indicated that, morphologically, Grootboom was a quintuple tree, whereas genetically, it was a single individual. Ages of extreme lateral samples revealed that, over the past 500-600 years, Grootbooom had almost ceased growing, providing information about climate changes in central southern Africa. The sudden demise of Grootboom coincided with the spread of the poorly studied baobab disease, which has become epidemic in Namibia. VL - 27 SN - 0829-318x IS - 11 N1 - 230afTimes Cited:35 Cited References Count:43 JO - Tree Physiol ER - TY - CHAP T1 - Radiocarbon dating of deep-sea sediments T2 - Paleoceanography of the Late Cenozoic Y1 - 2007 A1 - Hughen, K. A. ED - Hillaire-Marcel, Claude JF - Paleoceanography of the Late Cenozoic PB - Elsevier VL - 1: Methods N1 - id: 552 ER - TY - JOUR T1 - Rapid sea level rise and ice sheet response to 8,200-year climate event JF - Geophysical Research Letters Y1 - 2007 A1 - Cronin, T. M. A1 - Vogt, P. R. A1 - Willard, D. A. A1 - Thunell, R. A1 - Halka, J. A1 - Berke, M. A1 - Pohlman, J. AB - The largest abrupt climatic reversal of the Holocene interglacial, the cooling event 8.6 - 8.2 thousand years ago (ka), was probably caused by catastrophic release of glacial Lake Agassiz-Ojibway, which slowed Atlantic meridional overturning circulation (AMOC) and cooled global climate. Geophysical surveys and sediment cores from Chesapeake Bay reveal the pattern of sea level rise during this event. Sea level rose similar to 14 m between 9.5 to 7.5 ka, a pattern consistent with coral records and the ICE- 5G glacio-isostatic adjustment model. There were two distinct periods at similar to 8.9 - 8.8 and similar to 8.2 - 7.6 ka when Chesapeake marshes were drown as sea level rose rapidly at least similar to 12 mm yr(-1). The latter event occurred after the 8.6 - 8.2 ka cooling event, coincided with extreme warming and vigorous AMOC centered on 7.9 ka, and may have been due to Antarctic Ice Sheet decay. VL - 34 IS - 20 N1 - id: 810; 225MA Times Cited:4 Cited References Count:32Y JO - Rapid sea level rise and ice sheet response to 8,200-year climate event ER - TY - JOUR T1 - Reactivation of Coastal Dunes Documented by Subsurface Imaging of the Great Dune Ridge, Lithuania JF - Journal of Coastal Research Y1 - 2007 A1 - Buynevich, I. A1 - Bitinas, A. A1 - Pupienis, D. KW - curonian spit KW - gpr KW - medieval KW - reflection geometry KW - slipface KW - truncation AB - Large coastal and inland dunefields often consist of multiple generations defined by periods of stability and reactivation. Where earlier phases of aeolian activity are masked by subsequent deposition, continuous high-resolution geophysical images help to reconstruct the history of landscape change. Ground-penetrating radar (GPR) profiles from relict Holocene dunes on the northern Curonian Spit, Lithuania reveal distinct contacts between older deposits (barrier-spit facies, older aeolian strata, paleosols) and overlying dune sands. Early stages of dune migration began prior to 6,000 years B.P. followed by several periods of stabilisation and subsequent reactivation. Parabolic and transverse dunes, some attaining heights of 40-60 m, have migrated to the east in response to westerly winds from the Baltic Sea. In several places, similar to a number of sites in Northern Europe, the upper sections of large dunes have been deflated leaving near-horizontal exposures where subsurface imaging extends the continuity of key stratigraphic horizons. Within dune sequences, oblique lateral accretion surfaces indicate the direction of earlier migration phases and exhibit distinct meso-scale geometries. In GPR images and shallow trenches, buried slipfaces have dip angles varying from 10-15 degrees to 31-34 degrees, the latter being similar to the angle of repose maintained by modem unvegetated dunes. A series of cores taken through sequences of stacked buried slipfaces show little visible variation in sediment properties with depth, suggesting that minor changes in texture, mineralogy and grain packing may be responsible for individual reflections in geophysical records. Occasionally, laterally extensive horizons enriched in heavy minerals produce prominent subsurface reflections and are indicative of periods of increased wind activity. SN - 0749-0208 N1 - Sp. Iss. 50V16hi Times Cited:10 Cited References Count:30 JO - J Coastal Res ER - TY - RPRT T1 - A regional study of Holocene climate change and human occupation in Peruvian Amazonia Y1 - 2007 A1 - Bush, M. B. A1 - Listopad, M. C. S. A1 - Silman, M. R. JF - Journal of Biogeography VL - on-line article N1 - id: 453 ER - TY - CONF T1 - Regional variability in the ages and reactivities of riverine dissolved and particulate organic matter exported to a temperate ocean margin T2 - ASLO Aquatic Sciences Meeting Y1 - 2007 A1 - Bauer, J. E. A1 - Raymond, P. A. A1 - Cole, J. J. A1 - Petsch, S. T. A1 - Longworth, B. E. A1 - Caraco, N. F. A1 - Keesee, E. J. JF - ASLO Aquatic Sciences Meeting CY - Santa Fe, NM N1 - id: 477 ER - TY - JOUR T1 - Relationships between carbon isotopic composition and mode of binding of natural organic matter in selected marine sediments Y1 - 2007 A1 - White, Helen K. A1 - Reddy, Christopher M. A1 - Eglinton, Timothy I. AB - We have investigated the relationships between radiocarbon (14C) and stable carbon (13C) isotopic composition and the different modes of binding of organic matter (OM) in surficial sediments selected from near-shore and continental margin sites that vary in terms of input and depositional conditions. To improve our understanding of the entire OM pool, isotopic analysis of sedimentary sub-fractions, as opposed to individual compounds, was performed. This was achieved by sequentially treating sediments via solvent extraction to examine unbound compounds, followed by saponification to cleave ester linked moieties. Isotopic analysis was performed on the bulk sediment and resulting residues. The molecular composition of the extracts was examined using gas chromatography/mass spectrometry (GC/MS) and the relative contributions of terrestrial and marine biomarkers were assessed. Radiocarbon abundances (Δ14C) of the bulk sediment reflect a mixture of modern, pre-aged and fossil carbon. Offsets in Δ14C between the bulk sediment and sediment residues demonstrate varying associations of these carbon pools. For the majority of sites, a negative offset between extracted (EX-RES) and saponified (SA-RES) sediment residues results from the removal of relatively 14C-rich material during saponification. Saponification extracts (SAEs) are mainly composed of short chain (n-C12 to n-C24) alkanoic acids with an even/odd dominance, indicating a predominantly marine algal or microbial source. This provides evidence for the protection of labile marine carbon by chemical binding. This study bridges the gap between molecular level and bulk OM analysis of marine sediments. VL - 38 SN - 0146-6380 UR - http://www.sciencedirect.com/science/article/pii/S0146638007001751 IS - 11 ER - TY - JOUR T1 - Reply to comment by L. D. Stott on "Anomalous radiocarbon ages for foraminifera shells": A correction to the western tropical Pacific MD9821-81 record JF - Paleoceanography Y1 - 2007 A1 - Broecker, W. S. A1 - Barker, S. VL - 22 IS - 1 N1 - id: 2015; PT: J; UT: WOS:000244478900002 JO - Reply to comment by L. D. Stott on "Anomalous radiocarbon ages for foraminifera shells": A correction to the western tropical Pacific MD9821-81 record ER - TY - RPRT T1 - Report of archaeological field research in 2006, including geological descriptions of archaeological locales Y1 - 2007 A1 - Fitzhugh, B. A1 - Etnier, M. A1 - MacInnes, B. A1 - Phillips, S. C. A1 - Taylor, J. W. JF - Kuril Biocomplexity Project (NSF 0508109, PI: Fitzhugh) N1 - id: 833Unpublished project report ER - TY - JOUR T1 - Response of vegetation and fire to Little Ice Age climate change: regional continuity and landscape heterogeneity JF - Landscape Ecology Y1 - 2007 A1 - Hotchkiss, S. C. A1 - Calcote, R. A1 - Lynch, E. A. AB - Late-Holocene climatic conditions in the upper Great Lakes region have changed sufficiently to produce significant changes in vegetation and fire regimes. The objective of this study was to determine how the vegetation mosaic and fire regimes on an oak (Quercus spp.)- and pine (Pines spp.)-dominated sand plain in northwestern Wisconsin responded to climatic changes of the past 1,200 years. We used pollen and charcoal records from a network of sites to investigate the range of natural variability of vegetation on a 1,500-km(2) landscape on the southern part of the sand plain. A major vegetation shift from jack pine (Pines banksiana) and red pine (P. resinosa) to increased abundance of white pine (P. strobus) occurred between 700 and 600 calendar years before present (cal yr BP), apparently corresponding to more mesic conditions regionally. A decrease in charcoal accumulation rate also occurred at most sites but was not synchronous with the vegetation change. At some sites there were further changes in vegetation and fire regimes occurring similar to 500-300 cal yr BP, but these changes were not as strong or unidirectional as those that occurred 700-600 cal yr BP. Our results suggest that both the composition and the distribution of vegetation of the southern part of the sand plain have been sensitive to relatively small climatic changes, and that the vegetation at the time of European settlement was a transitory phenomenon, rather than a long-term stable condition. VL - 22 N1 - Suppl. 1239unTimes Cited:25Cited References Count:92 JO - Response of vegetation and fire to Little Ice Age climate change: regional continuity and landscape heterogeneity ER - TY - JOUR T1 - A review of modern coral delta18O and Delta14C proxy records JF - Earth-Science Reviews Y1 - 2007 A1 - Grottoli, Andrea G. A1 - Eakin, C. Mark VL - 81 N1 - id: 653 ER - TY - JOUR T1 - Salinity changes in the western tropical South Atlantic during the last 30 kyr JF - Global and Planetary Change Y1 - 2007 A1 - Toledo, F. A. L. A1 - Costa, K. B. A1 - Pivel, M. A. G. AB - The hydrographic changes in the western tropical South Atlantic during the last 30 kyr were reconstructed based in the faunal and isotopic analyses of planktonic foraminifera of three cores taken along the Brazilian Continental Margin between 14 degrees S and 25 degrees S. The application of the SIMMAX-MAT method on faunal counts data provided the sea surface temperature estimates. Sea surface salinity estimates were based on the oxygen isotope composition of Globigerinoides ruber (white). Additionally, the abundance record of the planktonic foraminifera Globorotalia truncatulinoides (right) was used as a proxy for vertical mixing of surface waters. Sea surface temperature estimates suggest a relative stability of the area during the last 30 kyr. However, significant changes in the isotopic composition of G. ruber (white) suggest that the isotopic signal is dominated by the influence of sea surface salinity changes. The observed salinity changes are related to both the local hydrological balance and global circulation. Orbital forcing and sea surface salinity changes were responsible for considerable changes in the stability of the upper water column and consequently in the depth of the mixed layer, as indicated by the abundance record of G. truncatulinoides (right). (c) 2007 Elsevier B.V All rights reserved. VL - 57 IS - 3-4 N1 - 181bjTimes Cited:28Cited References Count:59 JO - Salinity changes in the western tropical South Atlantic during the last 30 kyr ER - TY - JOUR T1 - Sea level rise in Tampa Bay JF - Eos, Transactions, American Geophysical Union Y1 - 2007 A1 - Cronin, Thomas M. A1 - Edgar, N. Terence A1 - Brooks, Gregg A1 - Hastings, David A1 - Larson, Rebekka A1 - Hine, Albert A1 - Locker, Stanley A1 - Suthard, Beau A1 - Flower, Benjamin A1 - Hollander, David A1 - Wehmiller, John A1 - Willard, Debra A. A1 - Smith, Shannon VL - 88 IS - 10 N1 - id: 1899; References: 14; illus. incl. geol. sketch map Latitude:N272700,N280200 Longitude:W0822200,W0825100Y JO - Sea level rise in Tampa Bay ER - TY - JOUR T1 - Sea-level history of the Gulf of Mexico since the Last Glacial Maximum with implications for the melting history of the Laurentide Ice Sheet JF - Quaternary Science Reviews Y1 - 2007 A1 - Simms, Alexander R. A1 - Lambeck, Kurt A1 - Purcell, Anthony A1 - Anderson, John B. A1 - Rodriguez, Antonio B. AB - Sea-level records from the Gulf of Mexico at the Last Glacial Maximum, 20 ka, are up to 35 m higher than time-equivalent sea-level records from equatorial regions. The most popular hypothesis for explaining this disparity has been uplift due to the forebulge created by loading from Mississippi River sediments. Using over 50 new radiocarbon dates as well as existing published data obtained from shallowmarine deposits within the northern Gulf of Mexico and numerical models simulating the impact of loading due to the Mississippi Fan and glacio-hydro-isostasy, we test several possible explanations for this sea-level disparity.. We find that neither a large radiocarbon reservoir, sedimentary loading due to the Mississippi Fan, nor large-scale regional uplift can explain this disparity. We do find that with an appropriate model for the Laurentide Ice Sheet, the observations from the Gulf of Mexico can be explained by the process of glaciohydro-isostasy. Our analysis suggests that in order to explain this disparity one must consider a Laurentide Ice Sheet reconstruction with less ice from 15 ka to its disappearance 6 ka and more ice from the Last Glacial Maximum to 15 ka than some earlier models have suggested. This supports a Laurentide contribution to meltwater pulse 1-A, which could not have come entirely from its southern sector. (c) 2007 Elsevier Ltd. All rights reserved. VL - 26 IS - 7-8 N1 - id: 2038; PT: J; UT: WOS:000248732200007 JO - Sea-level history of the Gulf of Mexico since the Last Glacial Maximum with implications for the melting history of the Laurentide Ice Sheet ER - TY - JOUR T1 - Searching for a suitable gas ion source for C-14 accelerator mass spectrometry JF - Preceeding of PNNIB-11 (9/2006) Y1 - 2007 A1 - von Reden, K. A1 - Roberts, M. A1 - Han, B. A1 - Schneider, R. A1 - Wills, J. VL - A.I.P. Preceedings Series IS - in press N1 - id: 689 ER - TY - JOUR T1 - Seaward-branching coastal-plain and Piedmont incised-valley systems through multiple sea-level cycles: Late Quaternary examples from Mobile Bay and Mississippi Sound, USA JF - Journal of Sedimentary Research Y1 - 2007 A1 - Greene, D. Lawrence, Jr. A1 - Rodriguez, Antonio B. A1 - Anderson, John B. AB - Most incised valleys become more organized seaward through tributaries merging with the main trunk valley. Late Quaternary incised valleys on the Mississippi and Alabama inner continental shelf branch seaward, although they do coalesce towards the shelf break where they feed shelf-edge deltas. To link fluvial systems with their associated previously mapped incised valleys on the shelf, and evaluate the contribution of small coastal-plain valley systems to the lowstand systems tract, high-resolution seismic data and cores were collected from Mobile Bay, eastern Mississippi Sound, and the Mobile bay-head delta. These data show four unconformity-bounded stacked units, and this study focuses on the upper two regionally mappable units. The upper two unconformities were sampled in core as exposure surfaces, and, on the basis of stratigraphic position, depth of incision, and C-14 dates, are interpreted as sequence boundaries. The shallowest sequence boundary (A) formed in response to the Oxygen Isotope Stage 2 sea-level lowstand, while the underlying sequence boundary (B) formed in response to an earlier lowstand (Stage 6?). A map of Sequence Boundary B shows a network of seaward-branching valleys, 20-35 m deep and 0.6-7.7 km wide, that extend across Mobile Bay and Mississippi Sound. These valleys, which are bounded by well-developed terraces, are extensions of the piedmont Mobile fluvial system and the coastal-plain Fowl and La Batre fluvial systems. A map of the Stage 2 Sequence Boundary shows that all systems generally reoccupied their previous valley positions and are separated by interfluve plateaus. Valley fill between Sequence Boundary B and the Stage 2 Sequence Boundary is generally composed of a basal unit of alluvial sediments overlain by bay-head delta deposits; however, Stage 2 to 1 valley fill is composed entirely (if central-basin sediments. The presence of bay-head delta deposits on the inner shelf indicates this depositional environment backstepped across the estuaries to modern positions. Backstepping likely occurred as the low-gradient paleovalleys were inundated, resulting in rapid rates of transgression. Fluvial gradients measured on Sequence Boundary B and the Stage 2 Sequence Boundary, below the modern Mobile bay-head delta plain and the estuaries, are very low (1.3-0.3 m/km). The Mobile bay-head delta and upper Mobile Bay are confined by steep topography, which opens basinward into the low-gradient shorelines surrounding lower Mobile Bay and Mississippi Sound. During falling sea level, channel branching likely occurred as the low-gradient fluvial systems extended basinward beyond the confined topography. These channels incised as sea level fell below the steeper shelf break during the lowstand. Stage 2 valley morphology is partially influenced by the position of the underlying Stage 6 valleys. Both coastal-plain and piedmont valley systems exhibit compound fill, indicating that differentiation between these types of incised valleys cannot be based on valley-fill architecture alone. VL - 77 IS - 1-2 N1 - id: 2039; PT: J; UT: WOS:000246987600011 JO - Seaward-branching coastal-plain and Piedmont incised-valley systems through multiple sea-level cycles: Late Quaternary examples from Mobile Bay and Mississippi Sound, USA ER - TY - JOUR T1 - Sedimentary evidence of hurricane strikes in western Long Island, New York JF - Geochemistry Geophysics Geosystems Y1 - 2007 A1 - Scileppi, E. A1 - Donnelly, J. P. KW - barrier-island KW - climate KW - Coastal geology KW - fire-island KW - global change : climate variability KW - hurricane KW - hydrology : extreme events KW - hydrology : hydroclimatology KW - ice-age KW - New York KW - new-england KW - new-jersey KW - past 5,000 years KW - Salt marsh KW - salt-marsh KW - sea-level rise KW - sedimentation KW - tidal marsh KW - tropical cyclones AB - [1] Evidence of historical landfalling hurricanes and prehistoric storms has been recovered from backbarrier environments in the New York City area. Overwash deposits correlate with landfalls of the most intense documented hurricanes in the area, including the hurricanes of 1893, 1821, 1788, and 1693 A. D. There is little evidence of intense hurricane landfalls in the region for several hundred years prior to the late 17th century A. D. The apparent increase in intense hurricane landfalls around 300 years ago occurs during the latter half of the Little Ice Age, a time of lower tropical sea surface temperatures. Multiple washovers laid down between similar to 2200 and 900 cal yr B. P. suggest an interval of frequent intense hurricane landfalls in the region. Our results provide preliminary evidence that fluctuations in intense hurricane landfall in the northeastern United States were roughly synchronous with hurricane landfall fluctuations observed for the Caribbean and Gulf Coast, suggesting North Atlantic - wide changes in hurricane activity. VL - 8 SN - 1525-2027 N1 - 182vrTimes Cited:48 Cited References Count:59 JO - Geochem Geophy Geosy ER - TY - JOUR T1 - Sedimentary iron cycling and the origin and preservation of magnetization in platform carbonate muds, Andros Island, Bahamas JF - Earth and Planetary Science Letters Y1 - 2007 A1 - Maloof, A. C. A1 - Kopp, R. E. A1 - Grotzinger, J. P. A1 - Fike, D. A. A1 - Bosak, T. A1 - Vali, H. A1 - Poussart, P. M. A1 - Weiss, B. P. A1 - Kirschvink, J. L. AB - Carbonate muds deposited on continental shelves are abundant and well-preserved throughout the geologic record because shelf strata are difficult to subduct and peritidal carbonate units often form thick, theologically strong units that resist penetrative deformation. Much of what we know about pre-Mesozoic ocean chemistry, carbon cycling, and global change is derived from isotope and trace element geochemistry of platform carbonates. Paleomagnetic data from the same sediments would be invaluable, placing records of paleolatitude, paleogeography, and perturbations to the geomagnetic field in the context and relative chronology of chemostratigraphy. To investigate the depositional and early diagenetic processes that contribute to magneitzation in carbonates, we surveyed over 500 core and surface samples of peritidal, often microbially bound carbonate muds spanning the last similar to 1000 yr and deposited on top of Pleistocene aeolianites in the Triple Goose Creek region of northwest Andros Island, Bahamas. Sedimentological, geochemical, magnetic and ferromagnetic resonance properties divide the sediment columns into three biogeochemical zones. In the upper sediments, the dominant magnetic mineral is magnetite, produced by magnetotactic bacteria and dissimiliatory microbial iron metabolism. At lower depths, above or near mean tide level, microbial iron reduction dissolves most of the magnetic particles in the sediment. In some cores, magnetic iron sulfides precipitate in a bottom zone of sulfate reduction, likely coupled to the oxidation of decaying mangrove roots. The remanent magnetization preserved in all oriented samples appears indistinguishable from the modem local geomagnetic field, which reflects the post-depositional origin of magnetic particles in the lower zone of the parasequence. While we cannot comment on the effects of late-stage diagenesis or metamorphism on remanence in carbonates, we postulate that early-cemented, thin-laminated parasequence tops in ancient peritidal carbonates are mostly likely to preserve syn-depositional paleomagnetic directions and magnetofossil stratigraphies. (c) 2007 Published by Elsevier B.V. VL - 259 IS - 3-4 N1 - id: 787; 197DX Times Cited:9 Cited References Count:47Y JO - Sedimentary iron cycling and the origin and preservation of magnetization in platform carbonate muds, Andros Island, Bahamas ER - TY - JOUR T1 - Selective degradation of organic compounds in sediments from the California Borderland Basins: evidence from compound specific Delta 14C and delta 13C analyses JF - Limnology and Oceanography Y1 - 2007 A1 - Mollenhauer, Gesine A1 - Eglinton, Timothy I. VL - 52 N1 - id: 544 ER - TY - JOUR T1 - Source apportionment of atmospheric PAHs in the western Balkans by natural abundance radiocarbon analysis JF - Environmental Science and Technology Y1 - 2007 A1 - Zencak, Zdenek A1 - Klanova, Jana A1 - Holoubek, Ivan A1 - Gustafsson, Örjan VL - 41 IS - 11 N1 - id: 519 JO - Source apportionment of atmospheric PAHs in the estern Balkans by natural abundance radiocarbon analysis ER - TY - JOUR T1 - Source, transport and fate of terrestrial organic carbon on the western Mediterranean Sea, Gulf of Lions, France JF - Marine Chemistry Y1 - 2007 A1 - Tesi, T. A1 - Miserocchi, S. A1 - Goñi, M. A. A1 - Langone, L. AB - As part of the EuroSTRATAFORM project, a multi-proxy study was conducted in order to investigate origin, transport and deposition of riverine organic matter in the Gulf of Lions. Surface sediments (0-1 cm) from the Rhone prodelta area and along the sediment dispersal system were collected in September 2004 and in April 2005. Lignin, elemental and stable carbon isotopic analyses were carried out to characterize the source of sedimentary organic material and to facilitate evaluation of temporal and spatial variability. Large contrasts in the organic matter composition of prodelta sediments were observed as a result of the preferential transport of the finest material. In our hypothesis, woody debris, rich in organic matter, hydraulically behaves like very fine sand and is retained within the prodelta area. In contrast, the organic matter adsorbed onto finer particles is selectively transported away from the prodelta along the sediment dispersal system, explaining the distinct organic matter composition observed in the offshore regions. (c) 2007 Elsevier B.V. All rights reserved. VL - 105 IS - 1-2 N1 - id: 825; 176SJ Times Cited:15 Cited References Count:70Y JO - Source, transport and fate of terrestrial organic carbon on the western Mediterranean Sea, Gulf of Lions, France ER - TY - JOUR T1 - Spatial complexity of 'Little Ice Age' climate in East Africa: sedimentary records from two crater lake basins in western Uganda JF - Holocene Y1 - 2007 A1 - Russell, J. M. A1 - Verschuren, D. A1 - Eggermont, H. AB - Lithostratigraphic analyses of the sedimentary record from two contrasting crater lake basins in western Uganda, Africa, provide evidence for three major century-scale and intervals during the last 2000 year. Variations in sedimentation and salt mineralogy of hypersaline Lake Kitagata, and a succession of fine-grained lake sediments and peat in the freshwater Lake Kibengo, suggest century-scale droughts centred on AD 0, similar to 1100, similar to 1550 and 1750. These results broadly support data from nearby Lake Edward on the timing of drought in western Uganda, but contrast with lake sediment records from eastern equatorial Africa. In particular, our results suggest regional variability of East African climate during the main phase of the 'Little Ice Age' (AD similar to 1500 to 1800), with westernmost East Africa experiencing drought while areas farther east were wet. This spatial pattern highlights the strongly regional nature of century-scale climate changes over the African continent, and holds implications for the mechanisms governing African rainfall during the 'Little Ice Age'. VL - 17 IS - 2 N1 - 144ztTimes Cited:36Cited References Count:55 JO - Spatial complexity of 'Little Ice Age' climate in East Africa: sedimentary records from two crater lake basins in western Uganda ER - TY - JOUR T1 - Stable carbon isotope compositions of Eastern Beringian grasses and sedges: Investigating their potential as paleoenvironmental indicators JF - Arctic Antarctic and Alpine Research Y1 - 2007 A1 - Wooller, M. J. A1 - Zazula, G. D. A1 - Edwards, M. A1 - Froese, D. G. A1 - Boone, R. D. A1 - Parker, C. A1 - Bennett, B. AB - The nature of vegetation cover present in Beringia during the last glaciation remains unclear. Uncertainty rests partly with the limitations of conventional paleoecological methods. A lack of sufficient taxonomic resolution most notably associated with the grasses and sedges restricts the paleoccological inferences that can be made. Stable isotope measurements of subfossil plants are frequently used to enhance paleoenvironmental reconstructions. We present an investigation of the stable carbon isotope composition (delta C-13) of modern and subfossil grasses and sedges (graminoids) from Eastern Beringia. Modern grasses from wet habitats had a mean delta C-13 of -29.1 parts per thousand. (standard deviation [SD] = 2.1 parts per thousand, n = 75), while those from dry habitats had a mean of -26.9 parts per thousand (SD = 1.19, n = 27). Sedges (n = -50) from dry, wet, marsh, and sand dune habitats had specific habitat ranges. Four modern C-4 grasses had delta C-13 values typical Of C4 plants. Analyses were also conducted using subfossil graminoid remains from several sedimentary paleoecological contexts (e.g., arctic ground squirrel nests, loess, permafrost, and paleosols) in Eastern Beringia. Results from these subfossil samples, ranging in age from > 40,000 to ca. 11,000 cal. yr BP, illustrate that the delta C-13 of graminoid remains has altered during the past. The range of variation in the subfossil samples is within the range from modern graminoid specimens from dry and wet habitats. The results indicate that stable isotopes could contribute to a comprehensive and multiproxy reconstruction of Beringian paleoenvironments. VL - 39 IS - 2 N1 - 170fwTimes Cited:20Cited References Count:73 JO - Stable carbon isotope compositions of Eastern Beringian grasses and sedges: Investigating their potential as paleoenvironmental indicators ER - TY - RPRT T1 - Stable-and radiocarbon isotopes in corals and adjacent natural waters: reconstructing land-use change and the land-ocean carbon cycle Y1 - 2007 A1 - Moyer, R. P. A1 - Grottoli, A. G. JF - ASLO CY - Santa Fe, NM N1 - id: 654 ER - TY - CHAP T1 - Status of the Black Sea flood hypothesis T2 - The Black Sea Flood Question: Changes in Coastline, Climate and Human Settlement Y1 - 2007 A1 - Ryan, W. B. F. ED - Yanko-Hombach, V. JF - The Black Sea Flood Question: Changes in Coastline, Climate and Human Settlement PB - Springer N1 - id: 854 ER - TY - JOUR T1 - Strandplain evolution along the southern coast of Santa Caterina, Brazil JF - Journal of Coastal Research Y1 - 2007 A1 - FitzGerald, D. M. A1 - Cleary, W. J. A1 - Buynevich, I. V. A1 - Hein, C. J. A1 - Kleins, A. H. F. A1 - Asp, N. A1 - Angulo, R. VL - Special Issue 50 N1 - id: 1099 ER - TY - JOUR T1 - Stratigraphy and environmental reconstruction at the middle Wisconsinan Gilman Canyon Formation type locality, Buzzard's Roost, southwestern Nebraska, USA JF - Quaternary Research Y1 - 2007 A1 - Johnson, W. C. A1 - Willey, K. L. A1 - Mason, J. A. A1 - May, D. W. AB - The middle Wisconsinan Gilman Canyon Formation at the Buzzard's Roost type locality in southwestern Nebraska was investigated to document the stratigraphy and to reconstruct the environmental and climate record. The Gilman Canyon Formation was subdivided into three loess units and three soils, with radiocarbon ages constraining it between about 40 ka and 25 ka. Stable carbon isotope ratios, magnetic susceptibility, and carbon content were used to define and characterize soils within both the Gilman Canyon Formation and underlying Illinoian Loveland Loess. At the height of soil development within the Gilman Canyon Formation, climate was supporting C-4-dominated grassland, with July temperatures equal to or exceeding those of today. Soil-forming intervals within the Loveland Loess, including the Sangamon Soil, also exhibited relative increases in C-4 biomass. Climate, as recorded in the Gilman Canyon Formation, is corroborated by regional proxy data. The formation accumulated during MIS 3, and concurrent soil formation coincided with a summer insolation maximum. (c) 2007 University of Washington. All rights reserved. VL - 67 IS - 3 N1 - 160ruTimes Cited:17Cited References Count:115 JO - Stratigraphy and environmental reconstruction at the middle Wisconsinan Gilman Canyon Formation type locality, Buzzard's Roost, southwestern Nebraska, USA ER - TY - JOUR T1 - A study of secondary organic aerosol formation in the anthropogenic-influenced southeastern United States JF - Journal of Geophysical Research-Atmospheres Y1 - 2007 A1 - Weber, R. J. A1 - Sullivan, A. P. A1 - Peltier, R. E. A1 - Russell, A. A1 - Yan, B. A1 - Zheng, M. A1 - de Gouw, J. A1 - Warneke, C. A1 - Brock, C. A1 - Holloway, J. S. A1 - Atlas, E. L. A1 - Edgerton, E. KW - AMBIENT AEROSOL KW - atmosphere KW - C-14 KW - emissions KW - evolution KW - GASOLINE KW - OXIDATION KW - PARTICLES KW - RATIOS KW - ZURICH AB - [1] The formation of secondary organic aerosol (SOA) in an anthropogenic-influenced region in the southeastern United States is investigated by a comparison with urban plumes in the northeast. The analysis is based on measurements of fine-particle organic compounds soluble in water (WSOC) as a measure of secondary organic aerosol. Aircraft measurements over a large area of northern Georgia, including the Atlanta metropolitan region, and in plumes from New York City and surrounding urban regions in the northeast show that fine-particle WSOC are spatially correlated with vehicle emission tracers (e.g., CO), yet the measurements indicate that vehicles do not directly emit significant particulate WSOC. In addition to being correlated, WSOC concentrations were in similar proportions to anthropogenic tracers in both regions, despite biogenic volatile organic compounds (VOCs) that were on average 10-100 times higher over northern Georgia. In contrast, radiocarbon analysis on WSOC extracted from integrated filters deployed in Atlanta suggests that roughly 70-80% of the carbon in summertime WSOC is modern. If both findings are valid, the combined results indicate that in northern Georgia, fine-particle WSOC was secondary and formed through a process that involves mainly modern biogenic VOCs but which is strongly linked to an anthropogenic component that may largely control the mass of SOA formed. Independent of the radiocarbon results, a strong association between SOA and anthropogenic sources has implications for control strategies in urban regions with large biogenic VOC emissions. VL - 112 SN - 2169-897X IS - D13 N1 - 263D13302 JO - J. Geophys. Res.-Atmos. ER - TY - JOUR T1 - A study of secondary organic aerosol formation in the anthropogenic-influenced southeastern United States JF - Journal of Geophysical Research-Atmospheres Y1 - 2007 A1 - Weber, R. J. A1 - Sullivan, A. P. A1 - Peltier, R. E. A1 - Russell, A. A1 - Yan, B. A1 - Zheng, M. A1 - de Gouw, J. A1 - Warneke, C. A1 - Brock, C. A1 - Holloway, J. S. A1 - Atlas, E. L. A1 - Edgerton, E. AB - [1] The formation of secondary organic aerosol (SOA) in an anthropogenic-influenced region in the southeastern United States is investigated by a comparison with urban plumes in the northeast. The analysis is based on measurements of fine-particle organic compounds soluble in water (WSOC) as a measure of secondary organic aerosol. Aircraft measurements over a large area of northern Georgia, including the Atlanta metropolitan region, and in plumes from New York City and surrounding urban regions in the northeast show that fine-particle WSOC are spatially correlated with vehicle emission tracers (e.g., CO), yet the measurements indicate that vehicles do not directly emit significant particulate WSOC. In addition to being correlated, WSOC concentrations were in similar proportions to anthropogenic tracers in both regions, despite biogenic volatile organic compounds (VOCs) that were on average 10-100 times higher over northern Georgia. In contrast, radiocarbon analysis on WSOC extracted from integrated filters deployed in Atlanta suggests that roughly 70-80% of the carbon in summertime WSOC is modern. If both findings are valid, the combined results indicate that in northern Georgia, fine-particle WSOC was secondary and formed through a process that involves mainly modern biogenic VOCs but which is strongly linked to an anthropogenic component that may largely control the mass of SOA formed. Independent of the radiocarbon results, a strong association between SOA and anthropogenic sources has implications for control strategies in urban regions with large biogenic VOC emissions. VL - 112 IS - D13 N1 - id: 788; 187XB Times Cited:47 Cited References Count:39Y JO - A study of secondary organic aerosol formation in the anthropogenic-influenced southeastern United States ER - TY - CHAP T1 - Submarine canyon and fan systems of the California Continental Borderland, Chapter 3-7 T2 - Earth Science in the Urban Ocean: The Southern California Contental Borderlands Y1 - 2007 A1 - Normark, W. R. A1 - Piper, D. J. W. A1 - Romans, B. W. A1 - Covault, J. A. A1 - Dartnell, P. A1 - Sliter, R. W. ED - Paper, Geological Society of America Special JF - Earth Science in the Urban Ocean: The Southern California Contental Borderlands N1 - id: 992 ER - TY - JOUR T1 - Surface currents in the western North Atlantic during the Last Glacial Maximum JF - Geochemistry Geophysics Geosystems Y1 - 2007 A1 - LeGrande, A. N. A1 - Lynch-Stieglitz, J. AB - [1] During the last ice age, the density gradient across the Florida Current was reduced, implying a reduction in the flow of the Gulf Stream through the Florida Straits. Here we investigate the possibility that a significant portion of this wind-driven western boundary flow bypassed the Florida Straits during glacial times due to either changes in bathymetry induced by the sea level drop or changes in wind patterns. Down core records of the oxygen isotope ratios of the planktonic foraminifer Globorotalia truncatulinoides are used to locate the density gradients and thus the locations of upper ocean currents in the western North Atlantic. We find that western boundary flow was largely confined within the Florida Straits during the Last Glacial Maximum as it is today. This finding supports the idea that the reduced density gradient across the Florida Current represents a reduction in the surface branch of the surface to deep meridional overturning circulation in the Atlantic rather than a reduction in the proportion of the wind-driven flow carried by the Florida Current. VL - 8 IS - 1 N1 - 131djTimes Cited:2Cited References Count:16 JO - Surface currents in the western North Atlantic during the Last Glacial Maximum ER - TY - CHAP T1 - Tectonics and relative sea-level change T2 - Encyclopedia of Quaternary Science Y1 - 2007 A1 - Nelson, A. R. ED - Scott, Elias JF - Encyclopedia of Quaternary Science PB - Elsevier N1 - id: 998 ER - TY - CONF T1 - Terrestrial subsidies of aquatic metabolism and food webs: A turorial and review T2 - American Society of Limnology and Oceanography; Aquatic Science meeting Y1 - 2007 A1 - Cole, J. J. AB - 69 JF - American Society of Limnology and Oceanography; Aquatic Science meeting CY - Santa Fe, NM N1 - id: 480 ER - TY - JOUR T1 - Is there a thorium-230 deficit in Arctic sediments? JF - Earth and Planetary Science Letters Y1 - 2007 A1 - Hoffmann, S. S. A1 - McManus, J. F. VL - 258 IS - 3-4 N1 - id: 711 ER - TY - JOUR T1 - The timing and evolution of the post-glacial transgression across the Sea of Marmara shelf south of Istanbul JF - Marine Geology Y1 - 2007 A1 - Eris, K. K. A1 - Ryan, W. B. F. A1 - Cagatay, M. N. A1 - Sancar, U. A1 - Lericolais, G. A1 - Menot, G. A1 - Bard, E. AB - High-resolution seismic reflection profiles and analyses of the sedimentary substrate at the Sea of Marmara (SoM) entrance to the Strait of Istanbul (Sol, Bosphorus) provide a detailed record of the transgression that took place after the SoM reconnected with the Mediterranean. The sediments progressively fill a paleo shelf valley that incised the margin from the Sol to the shelf break at the time of the pre-Holocene lowstand. We map seven seismic reflection units that can be confidently correlated to sediment cores by lithology and physical properties. Sediments in the cores are dated by radiocarbon methods. Early channel and levee deposits within the paleo valley belong to the Younger Dryas cold stage and record outflow from the Black Sea via the Sol. Small clinoform packages on the valley margin formed in proximity to climbing paleo shorelines. The elevations of these deposits conform to the sealevel history recorded in Barbados corals. The younger part of the succession includes a subaqueous prodelta sourced from the Kurbagalidere River. Its relatively young age when the Holocene sea had almost reached its modem level suggests that the thick progradational and aggradational clinoform development was primarily a response to sediment supply rather than the filling of expanding accommodation space. Our findings refute the hypothesis of Aksu et al. (Aksu, A.E., Hiscott, R.N., Mudie., P.J., Rochon, A., Kaminski, M.A., Abrojano, T., Yasar, D., 2002a. Persistent Holocene outflow fromn the Black Sea to the Eastern Mediterranean contradicts Noah's Flood hypothesis, GSA Today 10,(6), 3-7., Aksu, A.E., Hiscott, R.N., Kaminski, M.A., Mudie, P.J., Gillespie, H., Abrojano, T., Yasar, D., 2002b. Last glacial-Holocene paleoceanography of the Black Sea and Marmara Sea: stable isotopic, foraminiferal and coccolith evidence. Mar. Geol., 190, 119-149.) and Hiscott et al. (Hiscott, R.N., Aksu, A.E., Yasar, D., Kaminski, M.A., Mudie, P.J., Kostylev, V.E., MacDonald, J.C. Isler, F.I., Lord, A.R., 2002. Deltas south of the Bosphorus Strait record persistent Black Sea outflow to the Marmara Sea since similar to 10 ka, Mar. Geol., 190,95-118., Hiscott, R.N., Aksu, A.E., Mudie., P.J., Kaminski, M.A., Abrajano, T, Yasar, D., Rochon, A., 2007. The Marmara Sea gateway since similar to 16 ky BP: non-catastrophic causes of paleoceanographic events in the Black Sea at 8.4 and 7.15 ky BR In Yanko-Hombach,V, Gilbert, A.S., Dolukhanov, P.M. (Eds.), The Black Sea Flood Question, Springer, The Netherlands, 89-117.) that this deposit was supplied from the Sol and that its presence requires a persistent Black Sea outflow since 10 C-14 ka bp (not corrected from the reservoir age or calibrated). (c) 2007 Elsevier B.V All rights reserved. VL - 243 IS - 1-4 N1 - 210tuTimes Cited:36Cited References Count:52 JO - The timing and evolution of the post-glacial transgression across the Sea of Marmara shelf south of Istanbul ER - TY - JOUR T1 - Tropical Pacific - mid-latitude teleconnections in medieval times JF - Climatic Change Y1 - 2007 A1 - Graham, N. E. A1 - Hughes, M. K. A1 - Ammann, C. M. A1 - Cobb, K. M. A1 - Hoerling, M. P. A1 - Kennett, D. J. A1 - Kennett, J. P. A1 - Rein, B. A1 - Stott, L. A1 - Wigand, P. E. A1 - Xu, T. Y. AB - Terrestrial and marine late Holocene proxy records from the western and central US suggest that climate between approximately 500 and 1350 A.D. was marked by generally arid conditions with episodes of severe centennial-scale drought, elevated incidence of wild fire, cool sea surface temperatures (SSTs) along the California coast, and dune mobilization in the western plains. This Medieval Climate Anomaly (MCA) was followed by wetter conditions and warming coastal SSTs during the transition into the "Little Ice Age" (LIA). Proxy records from the tropical Pacific Ocean show contemporaneous changes indicating cool central and eastern tropical Pacific SSTs during the MCA, with warmer than modern temperatures in the western equatorial Pacific. This pattern of mid-latitude and tropical climate conditions is consistent with the hypothesis that the dry MCA in the western US resulted (at least in part) from tropically forced changes in winter NH circulation patterns like those associated with modern La Nina episodes. We examine this hypothesis, and present other analyses showing that the imprint of MCA climate change appears in proxy records from widely distributed regions around the planet, and in many cases is consistent with a cool medieval tropical Pacific. One example, explored with numerical model results, is the suggestion of increased westerlies and warmer winter temperatures over northern Europe during medieval times. An analog technique for the combined use of proxy records and model results, Proxy Surrogate Reconstruction (PSR), is introduced. VL - 83 IS - 1-2 N1 - 160ufTimes Cited:125Cited References Count:151 JO - Tropical Pacific - mid-latitude teleconnections in medieval times ER - TY - JOUR T1 - Ultra-microscale analysis of lipids by 14C-AMS: Assessment and correction for sample processing blanks JF - Radiocarbon Y1 - 2007 A1 - Shah, S. R. A1 - Pearson, A. VL - 49 N1 - id: 501 ER - TY - JOUR T1 - A unique Yellow River-derived distal subaqueous delta in the Yellow Sea JF - Marine Geology Y1 - 2007 A1 - Yang, Z. S. A1 - Liu, J. P. AB - Newly acquired high-resolution Chirp sonar profiles reveal a unique Yellow River-derived, alongshore distributed, bidirectional (landward and seaward) across-shelf transported, omega-shaped (Omega") distal subaqueous deltaic lobe deposited around the eastern tip of the Shandong Peninsula in the Yellow Sea. This clinoform deposit directly overlies the postglacial transgressive surface, featured by convex-up seafloor morphology, up to 40 in thick locally. Radiocarbon-14 dates from the underlain pre-Holocene and transgressive sediments indicate this distal lobe has formed since the middle-Holocene highstand under a relatively stable sea level. This along-shelf distributed distal clinoform has been deposited mainly by the resuspended Yellow River sediments carried down by the coastal current, interacting with the local waves, tides and upwelling. Collectively, over the past 7000 years, nearly 30% of the Yellow River-derived sediment has been re-suspended and transported out of the Bohai Sea into the Yellow Sea. Overall, the Yellow River-derived sediment could reach the -80 m water depth in the central South Yellow Sea, about 700 kin from the river mouth; in contrast, a very small fraction of the modem riverine sediment could escape the outer shelf or reach the Okinawa Trough. (c) 2007 Elsevier B.V. All rights reserved. VL - 240 IS - 1-4 N1 - 178psTimes Cited:88Cited References Count:39 JO - A unique Yellow River-derived distal subaqueous delta in the Yellow Sea ER - TY - JOUR T1 - Validated age, growth, and mortality estimates of the ocean quahog (Arctica islandica) in the western Atlantic JF - Ices Journal of Marine Science Y1 - 2007 A1 - Kilada, R. W. A1 - Campana, S. E. A1 - Roddick, D. AB - The age structure of offshore (Sable Bank) and inshore (St Mary's Bay) populations of eastern Canadian ocean quahogs (Arctica islandica), and of a northwestern Iceland population, is investigated. Age estimates for eastern Canadian ocean quahogs were validated through analysis of bomb-produced C-14 in quahog shell growth increments deposited before, during, and after the atmospheric atomic bomb testing periods of the 1950s and 1960s. Delta 14C from shells with presumed birthdates between the late 1950s and 1970s clearly reflects the sharp increase in oceanic radiocarbon attributable to nuclear testing. The results validate our age interpretations of Sable Bank quahogs to an age of 45 y, and support longevity estimates of more than 200 y for the same population. Longevity calculations for the other populations exceeded 60 y. Von Bertalanffy growth parameters were estimated for the three populations, the growth rate of all three was relatively rapid for the first 20 - 30 y of life, but thereafter was very slow. The instantaneous rate of natural mortality (M), calculated using the age-frequency distribution of the unexploited populations, was estimated to be 0.03 and 0.10 for the Sable Bank and St Mary's Bay populations, respectively. VL - 64 IS - 1 N1 - id: 807; 173HY Times Cited:6 Cited References Count:51Y JO - Validated age, growth, and mortality estimates of the ocean quahog (Arctica islandica) in the western Atlantic ER - TY - CONF T1 - Variability of major carbon pools in the Mississippi River: importance of tributary inputs and regional land use on carbon and organic matter biogeochemistry T2 - ASLO Aquatic Sciences Meeting Y1 - 2007 A1 - Perkey, D. W. A1 - Bauer, J. E. A1 - Keesee, E. J. JF - ASLO Aquatic Sciences Meeting CY - Santa Fe, NM N1 - id: 484 ER - TY - CHAP T1 - Variability of the marine ITCZ over the eastern Pacific during the past 30,000 years: Regional perspective and global context T2 - The Hadley Circulation: Present, Past and Future Y1 - 2007 A1 - Koutavas, Athanasios A1 - Lynch-Stieglitz, Jean ED - Bradley, R. S. JF - The Hadley Circulation: Present, Past and Future PB - Kluwer Academic Publishers N1 - id: 642 ER - TY - JOUR T1 - 14C methane and DIC in the deep terrestrial subsurface: implications for microbial methanogenesis JF - Geomicrobiology Journal Y1 - 2006 A1 - Slater, Greg F. A1 - Lippmann-Pipke, Johanna A1 - Moser, Duane P. A1 - Reddy, Christopher M. A1 - Onstott, T. C. A1 - Lacrampe-Couloume, Georges A1 - Lollar, Barbara Sherwood VL - 23 N1 - id: 1100 ER - TY - JOUR T1 - A 5,000-year record of coastal settlement on Anacapa Island, California JF - Journal of California and Great Basin Anthropology Y1 - 2006 A1 - Rick, Torben C. VL - 26 N1 - id: 1088 ER - TY - JOUR T1 - A 6,000 year old red abalone midden from Otter Point, San Miguel Island, California JF - North American Archaeologist Y1 - 2006 A1 - Vellanoweth, Rene L. A1 - Rick, Torben C. A1 - Erlandson, Jon M. A1 - Reynolds, Gnessa VL - 27 N1 - id: 1090 ER - TY - JOUR T1 - Abrupt tropical climate change: past and present JF - Proc Natl Acad Sci U S A Y1 - 2006 A1 - Thompson, L. G. A1 - Mosley-Thompson, E. A1 - Brecher, H. A1 - Davis, M. A1 - Leon, B. A1 - Les, D. A1 - Lin, P. N. A1 - Mashiotta, T. A1 - Mountain, K. AB - Three lines of evidence for abrupt tropical climate change, both past and present, are presented. First, annually and decadally averaged delta(18)O and net mass-balance histories for the last 400 and 2,000 yr, respectively, demonstrate that the current warming at high elevations in the mid- to low latitudes is unprecedented for at least the last 2 millennia. Second, the continuing retreat of most mid- to low-latitude glaciers, many having persisted for thousands of years, signals a recent and abrupt change in the Earth's climate system. Finally, rooted, soft-bodied wetland plants, now exposed along the margins as the Quelccaya ice cap (Peru) retreats, have been radiocarbon dated and, when coupled with other widespread proxy evidence, provide strong evidence for an abrupt mid-Holocene climate event that marked the transition from early Holocene (pre-5,000-yr-B.P.) conditions to cooler, late Holocene (post-5,000-yr-B.P.) conditions. This abrupt event, approximately 5,200 yr ago, was widespread and spatially coherent through much of the tropics and was coincident with structural changes in several civilizations. These three lines of evidence argue that the present warming and associated glacier retreat are unprecedented in some areas for at least 5,200 yr. The ongoing global-scale, rapid retreat of mountain glaciers is not only contributing to global sea-level rise but also threatening freshwater supplies in many of the world's most populous regions. VL - 103 IS - 28 N1 - Thompson, Lonnie GMosley-Thompson, EllenBrecher, HenryDavis, MaryLeon, BlancaLes, DonLin, Ping-NanMashiotta, TracyMountain, KeithengResearch Support, Non-U.S. Gov'tResearch Support, U.S. Gov't, Non-P.H.S.2006/07/04 09:00Proc Natl Acad Sci U S A. 2006 Jul 11;103(28):10536-43. Epub 2006 Jun 30. U2 - PMC1484420 JO - Abrupt tropical climate change: past and present ER - TY - CONF T1 - Abrupt vegetation changes in tropical South America over the last 120,000 years T2 - EOS Abstracts, 2006 Ocean Sciences Meeting Y1 - 2006 A1 - Hughen, K. A. A1 - Drenzek, N. A1 - Bice, M. A1 - Eglinton, T. I. JF - EOS Abstracts, 2006 Ocean Sciences Meeting CY - Honolulu, HI N1 - id: 1078 ER - TY - JOUR T1 - Absence of 14C in PM2.5 Emissions from Gasohol Combustion in Small Engines JF - Aerosol Science and Technology Y1 - 2006 A1 - Lewis, C. W. A1 - Volkens, J. A1 - Braddock, J. N. A1 - Crews, W. S. A1 - Lonneman, W. A. A1 - McNichol, A. P. N1 - id: 1699 ER - TY - JOUR T1 - Age mixing among sympatrick bivalves and brachiopods from the Brazilian South Atlantic JF - Geological Society of America Abstracts with Programs Y1 - 2006 A1 - Krause R.A, Jr. A1 - Barbour-Wood, S. A1 - Kowalewski, M. A1 - Simoes, M. G. A1 - Kaufman, D. A1 - Romanek, C. S. A1 - Wehmiller, J. R. VL - 38 IS - 7 N1 - id: 1170 JO - Age mixing among sympatrick bivalves and brachiopods from the Brazilian South Atlantic ER - TY - JOUR T1 - Ahead of the Game: Middle and upper palaeolithic hunting behaviors in the southern Caucasus JF - Current Anthropology Y1 - 2006 A1 - Adler, Daniel S. A1 - Bar-Oz, Guy A1 - Belfer-Cohen, Anna A1 - Bar-Yosef, Ofer VL - 47 IS - 1 N1 - id: 1137 JO - Ahead of the Game: Middle and upper palaeolithic hunting behaviors in the southern Caucasus ER - TY - JOUR T1 - Alkenone-based reconstruction of late-Holocene surface temperature and salinity changes in Lake Qinghai, China JF - Geophysical Research Letters Y1 - 2006 A1 - Liu, Z. A1 - Henderson, A. C. G. A1 - Huang, Y. VL - 33 N1 - id: 1157 ER - TY - JOUR T1 - Anomalous radiocarbon ages for foraminifera shells JF - Paleoceanography Y1 - 2006 A1 - Broecker, W. A1 - Barker, S. A1 - Clark, E. A1 - Hajdas, I. A1 - Bonani, G. AB - The causes for discordant radiocarbon results on multiple species of planktonic foraminifera from high-sedimentation-rate marine sediments are investigated. We have documented two causes for these anomalous results. One is the addition of secondary radiocarbon for which we have, to date, only one firm example. It involves an opal-rich sediment. The other is the incorporation of reworked material. Again, we have, to date, only one firm example. It involves a rapidly deposited ocean margin sediment. However, we have three other examples where reworking is the most likely explanation. On the basis of this study it is our conclusion that, where precise radiocarbon dating of high-deposition-rate marine sediment is required, a prerequisite is to demonstrate that concordant ages can be obtained on pairs of fragile and robust planktic shells. For sediment rich in opal, it is advisable to check for secondary calcite by comparing ages obtained on acid-leached samples with those on unleached samples. VL - 21 IS - 2 N1 - id: 980; 041JB Times Cited:7 Cited References Count:7 JO - Anomalous radiocarbon ages for foraminifera shells ER - TY - JOUR T1 - Anthropogenic markers in the Holocene stratigraphic sequence of the Gulf of Trieste (northern Adriatic Sea) JF - Marine Geology Y1 - 2006 A1 - Covelli, S. A1 - Fontolan, G. A1 - Faganeli, J. A1 - Ogrinc, N. AB - The Gulf of Trieste is a shallow serni-enclosed marine basin in the northernmost part of the Adriatic Sea that has been affected by the relative rise in sea-level during the Holocene. The sedimentary sequences in three cores, ranging in length from 130 to 320 cm, were investigated through the variability in grain-size parameters, major (Al, Fe, S, N, Ca and Mg) and trace (Ti, Mn, Cr, Ni, Cu, Zn and Hg) elements, organic and inorganic C, delta C-13 and C-14 dating in order to obtain information on paleoenvironmental evolution and the historical development of heavy metal contamination. The potential sources of pollution are: urban sewage from nearly 400,000 inhabitants, industrial effluents, and 500 yr of Hg mining activity in the Idrija region (western Slovenia), located in the upper basin of the Isonzo river, the main freshwater input to the coastal zone. The conventional 14 C ages of bulk sedimentary OC in the basal part of the three cores were 9030 +/- 70 (GTI), 8270 +/- 50 (GT2) and 9160 +/- 120 (GT3) yr BP. An upward increase in highly negative delta C-13(org) values from the core bottoms indicates that lacustrine-swamp conditions in the study area were rapidly followed by a typical marine depositional environment. Cluster analysis performed on the geochemical data for all subsamples of the three cores identifies several groups with a clear stratigraphic meaning. Factor analysis of the data shows related element groups that can be interpreted as being related to, for instance, the natural contribution from alummosilicates and carbonates, from organic matter (peat) and the more recent anthropogenic "impact". Predicted natural linear relationships for metal-Al were obtained from the core subsamples and they can be used as a baseline to evaluate metal enrichments on a regional scale. Results show that more recent sediments in the central sector of the Gulf of Trieste are slightly enriched in Cu (max Enrichment Factor EF=2.1) and Zn (max EF=1.6), and noticeably contaminated by Hg (up to 23.32 mu g g(-1)) to a maximum depth of 90 cm and up to 60 times above the estimated regional background (0.13 mu g g(-1)). The Hg historical trend is well correlated with extraction activity at the Idrija mine, thus allowing indicative sedimentation rate estimation and tentative assessment of the rate of Hg accumulation in bottom sediments (from 1.77 to 31.49 mg m(-2) yr(-1) at the surface). The large inventory of Hg in the core GT2 appeared to be the result of proximity to the fluvial source, which is still active in supplying Hg to the coastal areas and makes the Gulf of Trieste one of the most Hg contaminated area in the whole Mediterranean basin. (c) 2006 Elsevier B.V. All rights reserved. VL - 230 IS - 1-2 N1 - 069seTimes Cited:37Cited References Count:61 JO - Anthropogenic markers in the Holocene stratigraphic sequence of the Gulf of Trieste (northern Adriatic Sea) ER - TY - RPRT T1 - The ARCADIA cruise: Assessing long-term changes in tropical reef coral distribution along the Atlantic Continental Margin, southeastern United States Y1 - 2006 A1 - Piniak, G. A. JF - Project report to NOAA Office of Ocean Exploration CY - Silver Spring, MD N1 - id: 1103 ER - TY - CONF T1 - Archaeological geology of the central Penobscot River Valley, Maine, USA T2 - 2006 Philadelphia Annual Meeting Y1 - 2006 A1 - Kelley, Alice R. JF - 2006 Philadelphia Annual Meeting CY - Philadelphia, PA N1 - id: 1172 ER - TY - JOUR T1 - Aspartic acid racemization dating of Holocene brachiopods and bivalves from the southern Brazilian shelf, South Atlantic JF - Quaternary Research Y1 - 2006 A1 - Barbour-Wood, S. L. A1 - Krause R.A, Jr. A1 - Kowalewski, M. A1 - Wehmiller, J. F. A1 - Simoes, M. G. KW - Amino acid racemization KW - Aspartic KW - Bouchardia KW - Brachiopods KW - Brazil KW - Holocene KW - Mollusks KW - Radiocarbon dating KW - Semele KW - Ubatuba Bay AB - The extent of racemization of aspartic acid (Asp) has been used to estimate the ages of 9 shells of the epifaunal calcitic brachiopod Bouchardia rosea and 9 shells of the infaunal aragonitic bivalve Semele casali. Both taxa were collected concurrently from the same sites at depths of 10 m and 30 m off the coast of Brazil. Asp D/L values show an excellent correlation with radiocarbon age at both sites and for both taxa (r2Site 9 B. rosea = 0.97, r2Site 1 B. rosea = 0.997, r2Site 9 S. casali = 0.9998, r2Site 1 S. casali = 0.93). The Asp ratios plotted against reservoir-corrected AMS radiocarbon ages over the time span of multiple millennia can thus be used to develop reliable and precise geochronologies not only for aragonitic mollusks (widely used for dating previously), but also for calcitic brachiopods. At each collection site, Bouchardia specimens display consistently higher D/L values than specimens of Semele. Thermal differences between sites are also notable and in agreement with theoretical expectations, as extents of racemization for both taxa are greater at the warmer, shallower site than at the cooler, deeper one. In late Holocene marine settings, concurrent time series of aragonitic and calcitic shells can be assembled using Asp racemization dating, and parallel multi-centennial to multi-millennial records can be developed simultaneously for multiple biomineral systems. VL - 66 IS - 2 N1 - id: 1168 JO - Aspartic acid racemization dating of Holocene brachiopods and bivalves from the southern Brazilian shelf, South Atlantic ER - TY - CONF T1 - Atmospheric fossil sources of river and estuarine organic carbon transported to the coastal ocean T2 - Ocean Sciences Meeting Y1 - 2006 A1 - Wozniak, A. S. A1 - Bauer, J. E. A1 - Dickhut, R. M. A1 - Keesee, E. J. JF - Ocean Sciences Meeting CY - Honolulu, HI N1 - id: 1028 ER - TY - CHAP T1 - Behavioral ecology and the transition from hunting and gathering to Agriculture T2 - Behavioral Ecology and the Transition to Agriculture Y1 - 2006 A1 - Winterhalder, B. A1 - Kennett, D. J. ED - Kennett, D. J. JF - Behavioral Ecology and the Transition to Agriculture PB - University of California Press CY - Berkeley, CA N1 - id: 467 ER - TY - BOOK T1 - Behavioral Ecology and the Transition to Agriculture Y1 - 2006 A1 - Kennett, D. J. A1 - Winterhalder, B. PB - University of California Press CY - Berkeley, CA N1 - id: 459 ER - TY - JOUR T1 - Bioreactivity of estuarine dissolved organic matter: A combined geochemical and microbiological approach JF - Limnology and Oceanography Y1 - 2006 A1 - McCallister, S. L. A1 - Bauer, J. E. A1 - Canuel, E. A. KW - acids KW - bacteria KW - bay KW - bioavailability KW - carbon-isotope analysis KW - extraction KW - food webs KW - sediments AB - An integrated multidisciplinary study utilizing geochemical and microbial ecological approaches was conducted to characterize the origins, chemical nature, and quantities of dissolved and particulate organic matter (OM) utilized by heterotrophic bacteria in a temperate estuary. C: N, stable isotope (delta C-13), and lipid biomarker analyses revealed differences in the inferred reactivity of autochthonous versus allochthonous OM sources. Isotopic comparison of OM size fractions and bacterial nucleic acids suggests that high-molecular-weight dissolved OM (DOM) is consistently linked to bacterial biomass synthesis along the estuarine salinity gradient. Polyunsaturated fatty acids (as percent of total fatty acids, FA) were a reliable predictor of DOM decomposition in bioassays, thus providing an indicator directly linking DOM reactivity to its composition. Significant positive correlations between FA diagnostic of bacterial sources and lipid biomarker compounds diagnostic of planktonic origin indicate a systematic bacterial response to autochthonous DOM sources along the estuarine continuum. These findings further suggest that, although the geochemical signature of algal-derived OM in the dissolved phase may appear quantitatively insignificant, this fraction may nevertheless represent a principal source of bioreactive OM to heterotrophic bacteria in estuarine waters. VL - 51 SN - 0024-3590 IS - 1 N1 - 040scTimes Cited:39 Cited References Count:32 JO - Limnol Oceanogr ER - TY - JOUR T1 - Bomb dating and age validation using the spines of spiny dogfish (Squalus acanthias) JF - Environmental Biology of Fishes Y1 - 2006 A1 - Campana, S. E. A1 - Jones, C. A1 - McFarlane, G. A. A1 - Myklevoll, S. AB - Bomb radiocarbon has previously been used to validate the age of large pelagic sharks based on incorporation into vertebrae. However, not all sharks produce interpretable vertebral growth bands. Here we report the first application of bomb radiocarbon as an age validation method based on date-specific incorporation into spine enamel. Our results indicate that the dorsal spines of spiny dogfish, Squalus acanthias, recorded and preserved a bomb radiocarbon pulse in growth bands formed during the 1960s with a timing which was very similar to that of marine carbonates. Using radiocarbon assays of spine growth bands known to have formed in the 1960s and 1970s as a dated marker, we confirm the validity of spine enamel growth band counts as accurate annual age indicators to an age of at least 45 year. Radiocarbon incorporation into northeast Atlantic dogfish spines occurred in similar years as those in the northwest Atlantic and northeast Pacific, although the amount of radiocarbon differed in keeping with the radiocarbon content of the different water masses. Published reports suggesting that Pacific dogfish are longer lived and slower growing than their Atlantic counterparts appear to be correct, and are not due to errors in interpreting the spine growth bands. Radiocarbon assays of fin spine enamel appears to be well suited to the age validation of sharks with fin spines which inhabit the upper 200 m of the ocean. VL - 77 IS - 3-4 N1 - 107bsTimes Cited:38Cited References Count:25 JO - Bomb dating and age validation using the spines of spiny dogfish (Squalus acanthias) ER - TY - JOUR T1 - Bomb radiocarbon dating calibrates beluga (Delphinapterus leucas) age estimates JF - Canadian Journal of Zoology-Revue Canadienne De Zoologie Y1 - 2006 A1 - Stewart, R. E. A. A1 - Campana, S. E. A1 - Jones, C. M. A1 - Stewart, B. E. AB - The ages of many mammals are estimated by counting growth layers in tooth sections, yet validation of age estimation techniques using free-ranging mammals has been problematic. Contrary to age estimates for most other animals in which it is assumed that one bipartite growth increment forms annually, beluga whale (Delphinapterus leucas (Pallas, 1776)) age estimates have been calculated assuming that two growth layer groups (GLGs) form each year. Here we report the age validation for belugas based on date-specific incorporation of atomic bomb radiocarbon into tooth GLGs. Radiocarbon assays of dentinal layers formed in belugas harvested between 1895 and 2001 indicated that radiocarbon from atmospheric testing of nuclear weapons was incorporated into growing teeth and retained for the remaining life of the animal. Comparison of age determined by bomb radiocarbon with age determined by GLG counts indicated that GLGs form annually, not semiannually, and provide an accurate indicator of age for belugas up to at least 60 years old. Radiocarbon signatures of belugas were temporally and metabolically stable and were apparently derived more from the radiocarbon content of their prey than from water. Our understanding of many facets of beluga population dynamics is altered by the finding that this species lives twice as long as previously thought. VL - 84 IS - 12 N1 - 140vdTimes Cited:51Cited References Count:73 JO - Bomb radiocarbon dating calibrates beluga (Delphinapterus leucas) age estimates ER - TY - RPRT T1 - Calibration and natural variability of skeletal stable carbon isotopes in the Pacific sclerosponge acanthocheatetes wellsi: implications for reconstructing CO2 uptake in coastal tropical environments Y1 - 2006 A1 - Grottoli, A. G. JF - Ocean Sciences Meeting CY - Honolulu N1 - id: 1133 ER - TY - JOUR T1 - Carbon flow in salt marsh sediments: Natural-level radiocarbon as a tracer for incorporation of petroleum-derived carbon into bacteria JF - Geochim. Cosmochim. Acta Y1 - 2006 A1 - Wakeham, S. G. A1 - McNichol, A. P. A1 - Kostka, J. A1 - Pease, T. K. VL - 70 N1 - id: 762 ER - TY - CHAP T1 - Carbon flux in seagrass ecosystems T2 - Seagrasses: Biology, Ecology and Conservation. Y1 - 2006 A1 - Mateo, M. A. A1 - Cebrián, J. A1 - Dunton, K. A1 - Mutchler, T. ED - Larkum, A. W. D. JF - Seagrasses: Biology, Ecology and Conservation. PB - Springer CY - The Netherlands N1 - id: 2006 ER - TY - JOUR T1 - Carbon isotopic constraints on relict organic carbon contributions to Ross Sea sediments JF - G-cubed Y1 - 2006 A1 - Ohkouchi, N. A1 - Eglinton, T. I. VL - 7 N1 - id: 759 ER - TY - JOUR T1 - Carbon remineralization in the Amazon-Guianas tropical mobile mudbelt: A sedimentary incinerator JF - Continental Shelf Research Y1 - 2006 A1 - Aller, R. C. A1 - Blair, N. E. AB - The Amazon River spawns a vast mobile mudbelt extending similar to 1600 km from the equator to the Orinoco delta. Deposits along the Amazon-Guianas coastline are characterized by some of the highest C-org remineralization rates reported for estuarine, deltaic, or shelf deposits, however, paradoxically, except where stabilized by mangroves or intertidal algal mats, they are usually suboxic and nonsulfidic. A combination of tides, wind-driven waves, and coastal currents forms massive fluid muds and mobile surface sediment layers similar to 0.5-2m, thick which are dynamically refluxed and frequently reoxidized. Overall, the seabed functions as a periodically mixed batch reactor, efficiently remineralizing organic matter in a gigantic sedimentary incinerator of global importance. Amazon River material entering the head of this dynamic dispersal system carries an initial terrestrial sedimentary Corg loading of similar to 0.7 mg Cm-2 particle surface area. Total C-org loading is lowered to similar to 0.2 mg Cm-2 in the proximal delta topset, similar to 60-70% of which remains of terrestrial origin. Loading decreases further to 0.12-0.14 mg Cm-2 (similar to 60% terrestrial) in mudbanks similar to 600 km downdrift along French Guiana, values comparable to those found in the oligotrophic deepsea. DOC/Sigma CO2 ratios in pore waters of French Guiana mudbanks indicate that > 90% of metabolized organic substrates are completely oxidized. Within the Amazon delta topset at the head of the dispersal system, both terrestrial and marine organic matter contribute substantially to early diagenetic remineralization, although reactive marine substrate dominates (similar to 60-70%). The conditional rate constant for terrestrial C-org in the delta topset is similar to 0.2 a(-1). As sedimentary C-org is depleted during transit, marine sources become virtually the exclusive substrate for remineralization except very near the mangrove shoreline. The delta C-13 and Delta C-14 values of pore water Sigma CO2 in mudbanks demonstrate that the primary source of remineralized organic matter within similar to 1 km of shore is a small quantity of bomb signature marine plankton (+ 80 parts per thousand). Thus, fresh marine organic material is constantly entrained into mobile deposits and increasingly drives early diagenetic reactions along the transit path. Relatively refractory terrestrial C-org is lost more slowly but steadily during sedimentary refluxing and suboxic diagenesis. Amazon Fan deposits formed during low sea level stand largely bypassed this suboxic sedimentary incinerator and stored material with up to similar to 3X the modern high stand inner shelf C-org load (Keil et al., 1997b. Proceedings of the Ocean Drilling Program, Scientific Results. Vol. 155. pp. 531-537). Sedimentary dynamics, including frequency and magnitude of remobilization, and the nature of dispersal systems are clearly key controls on diagenetic processes, biogeochemical cycling, and global C storage along the continental margins. (c) 2006 Elsevier Ltd. All rights reserved. VL - 26 IS - 17-18 N1 - id: 979; 109UE Times Cited:28 Cited References Count:93 JO - Carbon remineralization in the Amazon-Guianas tropical mobile mudbelt: A sedimentary incinerator ER - TY - JOUR T1 - Carbon stable isotope composition of DNA isolated from an incipient paleosol JF - Geology Y1 - 2006 A1 - Jahren, A. H. A1 - Kelm, K. A1 - Wendland, B. A1 - Petersen, G. A1 - Seberg, O. AB - We determined the carbon isotope (delta(13)C) value of double-stranded DNA (dsDNA) isolated from the organic horizons of a Delaware soil that is actively being covered by an encroaching sand dune. The soil belongs to a Nymphaea odorata Ait. (water lily) wetland, and we regard its active acquisition of a thick (similar to 24 cm) surface mantle to embody the process of palleopedogenesis; therefore, we have termed it an "incipient paleosol." In this study, we compared the delta(13)C value of paleosoll dsDNA to the bulk delta(13)C value of N. odorata, as well as to the delta(13)C value of plants that had colonized the surface mantle. The isotopic offset between palleosol delta(13)C(dsDNA) and N. odorata delta(13)Ca(tissue) was identical to the relationship between delta(13)C(dsDNA) and delta(13)C(tissue) for tracheophytes, which we had previously determined. In contrast, the isotopic offset between paleosol delta(13)C(dsDNA) and the delta(13)C(tissue) of plants colonizing the surface mantle differed from this relationship by as much as 41%. Similarly, the delta(13)C value of bulk palleosoll organic matter was extremely heterogeneous and varied across 6%. All palleosol DNA pollymerase chain reaction (PCR) products produced clear, sharp, 350 base-pair (bp) fragments of rbcL, a gene shared by all photosynthetic organisms. These results open the exciting possibility that stable isotope analysis of dsDNA isolated from palleosol organic matter can be used to infer the delta(13)C value of the plant that dominated the nucleic acid contribution. VL - 34 IS - 5 N1 - 039nnTimes Cited:4Cited References Count:19 JO - Carbon stable isotope composition of DNA isolated from an incipient paleosol ER - TY - JOUR T1 - Characterizing biodegration and microbial metabolic activity in situ using natural abundance, molecular-level 14C analysis JF - Organic Geochemistry Y1 - 2006 A1 - Slater, G. F. A1 - Nelson, R. K. A1 - Kile, B. M. A1 - Reddy, C. M. VL - 37 N1 - id: 614 ER - TY - JOUR T1 - Chemical composition of the graphitic black carbon fraction in riverine and marine sediments at submicron scales using carbon X-ray spectromicroscopy JF - Geochimica et Cosmochimica Acta Y1 - 2006 A1 - Haberstroh, P. R. A1 - Brandes, J. A. A1 - Gelinas, Y. A1 - Dickens, A. F. A1 - Wirick, S. VL - 70 N1 - id: 1703 ER - TY - CONF T1 - The Chilean Fjords T2 - Abstracts, EGU General Assembly Y1 - 2006 A1 - Lange, C. B. A1 - Pantoja, S. A1 - Sepulveda, J. A1 - Rebolledo, L. A1 - Smith-Wellner, J. A1 - Anderson, J. B. A1 - Hughen, K. A. JF - Abstracts, EGU General Assembly CY - Vienna, Austria N1 - id: 561 ER - TY - JOUR T1 - Chronologie des variations climatiques repides pendant la derniere periode glaciaire JF - Comptes Rendus de l'Academie des Sciences Y1 - 2006 A1 - Bard, E. A1 - Rostek, F. A1 - G, Menot-Combes VL - 5 N1 - id: 398 JO - Chronologie des variations climatiques repides pendant la derniere periode glaciaire ER - TY - JOUR T1 - A climatic driver for abrupt mid-Holocene vegetation dynamics and the hemlock decline in New England JF - Ecology Y1 - 2006 A1 - Foster, D. R. A1 - Oswald, W. W. A1 - Faison, E. K. A1 - Doughty, E. D. A1 - Hansen, B. C. KW - *Climate KW - *Ecosystem KW - Geologic Sediments KW - new england KW - Tsuga/*physiology AB - The mid-Holocene decline of eastern hemlock is widely viewed as the sole prehistorical example of an insect- or pathogen-mediated collapse of a North American tree species and has been extensively studied for insights into pest-host dynamics and the consequences to terrestrial and aquatic ecosystems of dominant-species removal. We report paleoecological evidence implicating climate as a major driver of this episode. Data drawn from sites across a gradient in hemlock abundance from dominant to absent demonstrate: a synchronous, dramatic decline in a contrasting taxon (oak); changes in lake sediments and aquatic taxa indicating low water levels; and one or more intervals of intense drought at regional to continental scales. These results, which accord well with emerging climate reconstructions, challenge the interpretation of a biotically driven hemlock decline and highlight the potential for climate change to generate major, abrupt dynamics in forest ecosystems. VL - 87 SN - 0012-9658 (Print)0012-9658 (Linking) IS - 12 N1 - Foster, David ROswald, W Wyatt Faison, Edward K Doughty, Elaine D Hansen, Barbara C S eng Research Support, Non-U.S. Gov't Research Support, U.S. Gov't, Non-P.H.S. 2007/01/26 09:00 Ecology. 2006 Dec;87(12):2959-66. ER - TY - JOUR T1 - Coherence between solar activity and the East Asian winter monsoon variability in the past 8000 years from Yangtze River-derived mud in the East China Sea JF - Palaeogeography Palaeoclimatology Palaeoecology Y1 - 2006 A1 - Xiao, S. B. A1 - Li, A. C. A1 - Liu, J. P. A1 - Chen, M. H. A1 - Xie, Q. A1 - Jiang, F. Q. A1 - Li, T. G. A1 - Xiang, R. A1 - Chen, Z. AB - AMS(14)C dating and grain-size analysis for Core PC-6, located in the middle of a mud area on the inner shelf of the East China Sea (ECS), were used to rebuild the Holocene history of the East Asian winter monsoon (EAWM). The 7.5-m core recorded the history of environmental changes during the postglacial transgression. The core's mud section (the upper 450 cm) has been formed mainly by suspended sediment delivered from the Yangtze River mouth by the ECS Winter Coastal Current (ECSWCC) since 7.6 kyr BP. Using a mathematical method called "grain size vs. standard deviatioW', we can divide the Core PC-6's grain-size distribution into two populations at about 28 mu m. The fine population (< 28 mu m) is considered to be transported by the ECSWCC as suspended loads. Content of the fine population changes little and represents a stable sedimentary environment in accord with the present situation. Thus, variation of mean grain-size from the fine population would reflect the strength of ECSWCC, which is mainly controlled by the East Asian winter monsoon.Abrupt increasing mean grain size in the mud section is inferred to be transported by sudden strengthened ECSWCC, which was caused by the strengthened EAWM. Thus, the high resolution mean grain-size variation might serve as a proxy for reconstruction of the EAWM. A good correlation between sunspot change and the mean grain-size of suspended fine population suggests that one of the primary controls on centennial- to decadal-scale changes of the EAWM in the past 8 ka is the variations of sun irradiance, i.e., the EAWM will increase in intensity when the number of sunspots decreases. Spectral analyses of the mean grain-size time series of Core PC-6 show statistically significant periodicities centering on 2463, 1368, 128, 106, 100, 88-91, 7678, and 70-72 years. The EAWM and the East Asian summer monsoon (EASM) agree with each other well on these cycles, and the East Asian Monsoon (EAM) and the Indian Monsoon also share in concurrent cycles in Holocene, which are in accord with the changes of the sun irradiance. (c) 2005 Elsevier B.V. All rights reserved. VL - 237 IS - 2-4 N1 - 072kpTimes Cited:52Cited References Count:61 JO - Coherence between solar activity and the East Asian winter monsoon variability in the past 8000 years from Yangtze River-derived mud in the East China Sea ER - TY - CONF T1 - Continental slope sediment delivery and storage on an active margin: the Waipaoa Margin example T2 - 2006 AGU meeting Y1 - 2006 A1 - Alexander, C. A1 - Walsh, J. P. A1 - Sumner, B. A1 - Orpin, A. R. A1 - Kuehl, S. A. JF - 2006 AGU meeting CY - San Francisco, CA N1 - id: 1121 ER - TY - RPRT T1 - Corals and sclerosponges as geochemical recorders of past climate change Y1 - 2006 A1 - Grottoli, A. G. JF - AAPG/SEMP Course 19 CY - Houston, TX N1 - id: 1134 ER - TY - JOUR T1 - Cosmogenic isotope 14C: production and carbon cycle JF - PAGES Newsletter Y1 - 2006 A1 - Hughen, K. A. VL - 14 N1 - id: 1075 ER - TY - CONF T1 - Cross-shelf lateral transport in the Benguela Upwelling System: Aging of marine organic matter in the benthic boundary layer T2 - Ocean Sciences Meeting Y1 - 2006 A1 - Mollenhauer, Gesine A1 - Inthorn, Maik A1 - Zabel, Matthias A1 - Damste, Jaap Sinninghe A1 - Eglinton, Timothy I. JF - Ocean Sciences Meeting CY - Honollulu, Hawaii USA N1 - id: 545 ER - TY - JOUR T1 - Deglaciation and Holocene climate change in the western Peruvian Andes JF - Quaternary Research Y1 - 2006 A1 - Weng, C. Y. A1 - Bush, M. B. A1 - Curtis, J. H. A1 - Kolata, A. L. A1 - Dillehay, T. D. A1 - Binford, M. W. AB - Pollen, charcoal, magnetic susceptibility, and bulk density data provide the first paleoecological record spanning the last 33,000 years from the western cordillera of the Peruvian Andes. Sparse super-puna vegetation existed before 30,000 cat yr B.P. around Lake Compuerta (3950 m elevation), prior to a sedimentary hiatus that lasted until c. 16,200 cat yr B.P. When sedimentation resumed, a glacial foreland or super-puna flora is represented in which Polylepis was a significant element. Glacial outwash, marked by high sedimentary magnetic susceptibility, increased from c. 16,200 cat yr B.P. and reached a peak at c. 13,200 cat yr B.P. Between c. 12,500 cat yr B.P. and 10,000 cat yr B.P., magnetic susceptibility was reduced. Vegetation shifts suggest a cool dry time, consistent with regional descriptions of the Younger Dryas event. Deglaciation resumes by 10,000 cat yr B.P. and the last ice is lost from the catchnient at similar to 7500 cat yr B.P. During the early Holocene warm and dry period between 10,000 and 5500 cat yr B.P., Alnus expanded in downslope forests. Alnus declined in abundance at 5500 cat yr B.P. when wetter and cooler conditions returned and human activity intensified. Maize (Zea mays) pollen first occurred in the core at similar to 2600 cat yr B.P., indicating a minimum age for local agriculture. An increase in Alnus pollen abundance at similar to 1000 cat yr B.P. could be due to human activity or perhaps due to a regional climate change associated with cultural turnover elsewhere in the Andes at this time. (c) 2006 University of Washington. All rights reserved. VL - 66 IS - 1 N1 - 058upTimes Cited:27Cited References Count:55 JO - Deglaciation and Holocene climate change in the western Peruvian Andes ER - TY - JOUR T1 - Depth limit for reef building corals in the Au'au Channel, S. E. Hawaii JF - Coral Reefs Y1 - 2006 A1 - Grigg, R. W. VL - 25 N1 - id: 1085 ER - TY - RPRT T1 - Determination of carbon dioxide, hydrographic and chemical parameters during the R/V Nathaniel B. Palmer cruise in the southern Indian Ocean (WOCE section S041) Y1 - 2006 A1 - Takahashi, R. A1 - Millero, F. J. A1 - Key, R. M. A1 - Chipman, D. A1 - Peltola, E. A1 - Rubin, S. A1 - Sweeney, C. A1 - Sutherland, S. N1 - id: 1053 ER - TY - JOUR T1 - Diageneitc and sedimentological controls on the composition of organic matter preserved in California Borderland Basin sediments JF - Limnology & Oceanography Paleoceanography, submitted Y1 - 2006 A1 - Mollenhauer, Gesine A1 - Eglinton, Timothy I. N1 - id: 1705 ER - TY - JOUR T1 - Dissolved and particulate organic matter source-age characterization in the upper and lower Chesapeake Bay: A combined isotope and biochemical approach JF - Limnology and Oceanography Y1 - 2006 A1 - Loh, A. N. A1 - Bauer, J. E. A1 - Canuel, E. A. KW - biomarkers KW - carbon KW - delta-c-13 KW - lipid-composition KW - ocean KW - radiocarbon KW - river KW - san-francisco KW - sediments KW - variability AB - In order to characterize the sources and ages of organic matter contributing to river and estuarine outflow waters, the present study investigated Delta C-14 and delta C-13 signatures of the major operationally defined biochemical classes of ultrafiltered dissolved organic matter (UDOM) in conjunction with lipid biomarker and elemental compositions of UDOM and suspended particulate organic matter (POM) in the Chesapeake Bay. Freshwater (Susquehanna River) UDOM was dominated by a molecularly uncharacterized (MUC) fraction, followed by total carbohydrate (TCHO), total hydrolysable amino acid (THAA) and total lipid (TLE) components. In contrast, UDOM at the bay mouth (salinity similar to 22-24) was comprised mainly of TCHO, followed by MUC, THAA, and TLE. The Delta C-14 and delta C-13 signatures of both UDOM and its major biochemical classes indicate that Susquehanna DOM is derived in part from old allochthonous terrestrial sources, whereas young marine sources dominate at the bay mouth. In contrast to the other biochemical classes, lipophilic DOM at both sites was very old (similar to 5,000-7,000 years B.P.). In addition, factor analysis of lipid biomarker compounds revealed unique signatures for the UDOM and POM pools that imply disparate source and/or recycling properties as well as potential influences due to physical partitioning. Lipid biomarker compounds showed that although autochthonous riverine/estuarine sources dominated both the UDOM and POM pools, terrigenous lipids were elevated in the Susquehanna during high flow conditions. The presence of lipid biomarkers diagnostic of "fresh" algal material in UDOM further suggested its greater reactivity than POM. The observed biochemical and lipid biomarker compositions and isotopic signatures of UDOM and POM are consistent with previous findings suggesting that these two major organic matter pools have dissimilar reactivities and cycling times, and they derive from comparatively unique source-age materials in rivers and estuaries. VL - 51 SN - 0024-3590 IS - 3 N1 - 045nhTimes Cited:24 Cited References Count:37 JO - Limnol Oceanogr ER - TY - CONF T1 - Do inland waters matter in the regional or global C balance: A review and turorial T2 - American Society of Limnology and Oceanography Summer Meeting Y1 - 2006 A1 - Cole, J. J. JF - American Society of Limnology and Oceanography Summer Meeting CY - Victoria, Canada N1 - id: 479 ER - TY - CONF T1 - The early history of Long Island Sound T2 - The last deglaciation Y1 - 2006 A1 - Varekamp, J. C. A1 - Thomas, E. JF - The last deglaciation CY - Lamont Doherty Earth Observatory, Columbia Univ., NY N1 - id: 1185 ER - TY - JOUR T1 - Early Holocene land use and subsistence on eastern Santa Rosa Island, California JF - Current Research in the Pleistocene Y1 - 2006 A1 - Rick, T. C. A1 - Kennett, D. J. A1 - Erlandson, J. M. VL - 22 N1 - id: 1021 ER - TY - JOUR T1 - Early holocene openlands in southern New England JF - Ecology Y1 - 2006 A1 - Faison, E. K. A1 - Foster, D. R. A1 - Oswald, W. W. A1 - Hansen, B. C. A1 - Doughty, E. KW - *Ambrosia KW - *Pollen KW - Ecosystem KW - Geography KW - new england KW - Paleontology AB - The pre-historical vegetation structure in temperate forest regions is much debated among European and North American ecologists and conservationists. Frans Vera's recent hypothesis that large mammals created mosaics of forest and openland vegetation in both regions throughout the Holocene has been particularly controversial and has provoked new approaches to conservation management. Thirty years earlier, American paleoecologists Herb Wright and Margaret Davis debated whether abundant ragweed pollen at Rogers Lake, Connecticut at 9500 yr BP signified local forest openings or long-distance transport of pollen from Midwestern prairies. Using new pollen records from Harvard Forest and the North American Pollen Database, we address this question and offer insights to the openland discussion. Ragweed and other forbs exceed 3.5% at five sites in a restricted area of southern New England between 10,100 and 7700 yr BP. Strong evidence suggests this pollen originated from the landscapes surrounding these sites (supporting Davis), as ragweed pollen percentages do not increase with longitude from New England to the Midwest. Ragweed pollen percentages are also unrelated to basin size and therefore unrelated to the proportion of extraregional pollen in New England. High forbs values were associated with increases in oak, decreases in white pine, and relatively high charcoal values. Modern pollen records with similar forb and tree percentages occur along the Prairie Peninsula region of the Upper Midwest. However, the closest analogue to the southern New England early Holocene assemblages comes from Massachusetts' Walden Pond in the early 18th century. These results and the affiliation of ragweed for open, disturbed habitats suggest that oak-pine forests with large openings persisted for over 2000 years due to dry conditions and perhaps increased fire frequency. This conclusion is corroborated by independent lake level and climate reconstructions. Because these early Holocene openlands have no detectable analogue in New England for the past 7000 years before European settlement, we suggest that all important openlands today are almost exclusively a legacy of Colonial agriculture and should be managed accordingly. Nonetheless, our results may have implications for forest dynamics accompanying projected climate change to more arid conditions in New England over the next century. VL - 87 SN - 0012-9658 (Print)0012-9658 (Linking) IS - 10 N1 - Faison, E KFoster, D R Oswald, W W Hansen, B C S Doughty, E eng Research Support, Non-U.S. Gov't Research Support, U.S. Gov't, Non-P.H.S. 2006/11/09 09:00 Ecology. 2006 Oct;87(10):2537-47. ER - TY - CONF T1 - Effects of differential degradation of marine organic compounds on preserved radiocarbon ages and biomarker-based SST reconstructions, Poster T2 - EGU General Assembly Y1 - 2006 A1 - Mollenhauer, Gesine A1 - Sinninghe, Jaap S. A1 - Eglinton, Timothy I. JF - EGU General Assembly CY - Vienna, Austria N1 - id: 1072 ER - TY - CONF T1 - Elemental and isotopic characterization of organic matter and carbon in the South Atlantic bight, a net heterotrophic ocean margin T2 - Ocean Sciences Meeting Y1 - 2006 A1 - De Alteris, J. A1 - Bauer, J. E. A1 - Perkey, D. W. A1 - Keesee, E. J. A1 - Cai, W. J. JF - Ocean Sciences Meeting CY - Honolulu, HI N1 - id: 481 ER - TY - CONF T1 - Environmental impact on LIS from the early colonial society T2 - Long Island Sound Research Conference Y1 - 2006 A1 - Thomas, E. A1 - Varekamp, J. C. JF - Long Island Sound Research Conference CY - Groton, CT N1 - id: 750 ER - TY - CONF T1 - Evaluating the Holocene c=dynamics of oceanographic processes in the Southeast Brazilian Bight using accumulations of calcitic and aragonitic shells T2 - American Geophysical Union, Fall Meeting Y1 - 2006 A1 - Krause R.A, Jr. A1 - Barbour-Wood, S. A1 - Kowalewski, M. A1 - Simoes, M. G. A1 - Kaufman, D. A1 - Romanek, C. S. A1 - Wehmiller, J. F. AB - PP43A-01233 JF - American Geophysical Union, Fall Meeting CY - San Francisco, CA, USA N1 - id: 716 ER - TY - JOUR T1 - Evaluation of ageing accuracy of bocaccio (Sebastes paucispinis) rockfish using bomb radiocarbon JF - Fisheries Research Y1 - 2006 A1 - Piner, K. R. A1 - Wallace, J. R. A1 - Hamel, O. S. A1 - Mikus, R. AB - The accuracy of bocaccio rockfish age assignments was evaluated using radiocarbon levels measured in otoliths collected from fish taken off the coast of Washington state (USA). Otoliths from 24 randomly selected fish with estimated birth years from 1950 to 1977, based on paired otolith age estimates, were used in this study. The level of radiocarbon measured in the core of each otolith was compared to a reference radiocarbon chronology based on radiocarbon levels in otoliths from known-age Pacific halibut. The degree of graphical phase correspondence between the two series was sufficient to support the hypothesis that the annuli were formed yearly in bocaccio otoliths but were somewhat difficult to identify. Statistical analysis of the ageing errors could not document a bias in production ageing of bocaccio. Pre-bomb radiocarbon levels measured in otolith cores confirm that bocaccio can live at least 37 years. Published by Elsevier B.V. VL - 77 IS - 2 N1 - 011qtTimes Cited:10Cited References Count:40 JO - Evaluation of ageing accuracy of bocaccio (Sebastes paucispinis) rockfish using bomb radiocarbon ER - TY - CHAP T1 - An evolutionary model for the origins of agriculture on the Pacific coast of southern Mexico T2 - Behavioral Ecology and the Transition to Agriculture Y1 - 2006 A1 - Kennett, D. J. A1 - Voorhies, B. A1 - Martorana, D. ED - Kennett, D. J. JF - Behavioral Ecology and the Transition to Agriculture PB - University of California Press CY - Berkeley, CA N1 - id: 465 ER - TY - JOUR T1 - Flooding of Bering Strait and Holocene climate in the Chukchi Sea JF - Geology Y1 - 2006 A1 - Keigwin, L. D. A1 - Donnelly, J. P. A1 - Cook, M. S. A1 - Driscoll, N. W. A1 - Brigham-Grette, J. VL - 34 N1 - id: 678 ER - TY - JOUR T1 - Foraminiferal and sedimentary record of Late Holocene barrier island evolution, Pea Island, North Carolina: The role of storm overwash, inlet processes, and anthropogenic modification JF - Journal of Coastal Research Y1 - 2006 A1 - Culver, S. J. A1 - Ames, D. V. A1 - Corbett, D. R. A1 - Mallinson, D. J. A1 - Riggs, S. R. A1 - Smith, C. G. A1 - Vance, D. J. AB - Foraminiferal and sedimentary data, supplemented with geochemical dating and ground-penetrating radar transects, show that the barrier island at Pea Island National Wildlife Refuge just north of Rodanthe, North Carolina, has been dominated by a combination of inlet and overwash processes for at least 1000 years. The stratigraphic record of several vibracores does not preserve every, or even many, overwash events but, instead, is characterized by three to four fining-upward sequences. The last three commence with overwash sand or gravel that is overlain by a variety of finer-grained estuarine, inlet, and marsh deposits. The dynamic nature of this segment of the Outer Banks was muted in the late 1930s by construction of artificial barrier dune ridges, extensive planting of grass and shrubs, and construction of Highway 12 in 1953. Subsequently, the road and barrier dune ridge were rebuilt and relocated several times following storm events. VL - 22 IS - 4 N1 - 070tkTimes Cited:19Cited References Count:33 JO - Foraminiferal and sedimentary record of Late Holocene barrier island evolution, Pea Island, North Carolina: The role of storm overwash, inlet processes, and anthropogenic modification ER - TY - CONF T1 - The formation history of Long Island Sound T2 - Long Island Sound Research Conference Y1 - 2006 A1 - Varekamp, J. C. A1 - Thomas, E. A1 - Lewis, R. A1 - Altabet, M. JF - Long Island Sound Research Conference CY - Groton, CT N1 - id: 1187 ER - TY - JOUR T1 - Geomorphologic controls on the age of particulate organic carbon from small mountainous and upland rivers JF - Global Biogeochemical Cycles Y1 - 2006 A1 - Leithold, E. L. A1 - Blair, N. E. A1 - Perkey, D. W. KW - 14C KW - kerogen recycling KW - particulate organic carbon AB - To assess the role that erosion processes play in governing the character of particulate organic carbon (POC) discharged from small mountainous and upland rivers, a suite of watersheds from Oregon, California, and New Zealand was investigated. The rivers share similar geology, tectonic setting, and climate, but have sediment yields that range over 3 orders of magnitude. The (14)C age of the POC loads is highly correlated with sediment yield. Carbon isotope mass balances reveal that the rivers carry bimodal mixtures of modern-plant-and ancient-rock-derived OC. At lower yields, modern plant OC dominates the material delivered to the river by sheetwash and shallow landsliding. With increasing yield, a progressively larger part of the POC is contributed directly from bedrock erosion via deep gully incision. Our results support the inference that active margin watersheds are important sources of aged POC to the ocean. VL - 20 IS - 3 N1 - 082xbTimes Cited:78Cited References Count:77 JO - Geomorphologic controls on the age of particulate organic carbon from small mountainous and upland rivers ER - TY - CONF T1 - A geostatistical approach to watershed sources of aged riverine organic matter to the Hudson-Mohawk River system T2 - American Geophysical Union Fall Meeting Y1 - 2006 A1 - Longworth, B. E. A1 - Petsch, S. T. A1 - Raymond, P. A. A1 - Bauer, J. E. JF - American Geophysical Union Fall Meeting CY - San Francisco, CA N1 - id: 483 ER - TY - JOUR T1 - Great earthquakes of variable magnitude at the Cascadia subduction zone JF - Quaternary Research Y1 - 2006 A1 - Nelson, A. R. A1 - Kelsey, H. M. A1 - Witter, R. C. AB - Comparison of histories of great earthquakes and accompanying tsunamis at eight coastal sites suggests plate-boundary ruptures of varying length, implying great earthquakes of variable magnitude at the Cascadia subduction zone. Inference of rupture length relies on degree of overlap on radiocarbon age ranges for earthquakes and tsunamis, and relative amounts of coseismic subsidence and heights of tsunamis. Written records of a tsunami in Japan provide the most conclusive evidence for rupture of much of the plate boundary during the earthquake of 26 January 1700. Cascadia stratigraphic evidence dating from about 1600 cal yr B.P., similar to that for the 1700 earthquake, implies a similarly long rupture with substantial subsidence and a high tsunami. Correlations are consistent with other long ruptures about 1350 cal yr B.P., 2500 cal yr B.P., 3400 cal yr B.P., 3800 cal yr B.P., 4400 cal yr B.P., and 4900 cal yr B.P. A rupture about 700-1100 cal yr B.P. was limited to the northern and central parts of the subduction zone, and a northern rupture about 2900 cal yr B.P. may have been similarly limited. Times of probable short ruptures in southern Cascadia include about I 100 cal yr B.P., 1700 cal yr B.P., 3200 cal yr B.P., 4200 cal yr B.P., 4600 cal yr B.P., and 4700 cal yr B.P. Rupture patterns suggest that the plate boundary in northern Cascadia usually breaks in long ruptures during the greatest earthquakes. Ruptures in southernmost Cascadia vary in length and recurrence intervals more than ruptures in northern Cascadia. Published by University of Washington. VL - 65 IS - 3 N1 - 046pgTimes Cited:70Cited References Count:66 JO - Great earthquakes of variable magnitude at the Cascadia subduction zone ER - TY - JOUR T1 - Gulf Stream density structure and transport during the past millennium JF - Nature Y1 - 2006 A1 - Lund, D. C. A1 - Lynch-Stieglitz, J. A1 - Curry, W. B. AB - The Gulf Stream transports approximately 31 Sv (1 Sv = 10(6) m(3) s(-1)) of water and 1.3 x 10(15) W of heat into the North Atlantic ocean. The possibility of abrupt changes in Gulf Stream heat transport is one of the key uncertainties in predictions of climate change for the coming centuries. Given the limited length of the instrumental record, our knowledge of Gulf Stream behaviour on long timescales must rely heavily on information from geologic archives. Here we use foraminifera from a suite of high-resolution sediment cores in the Florida Straits to show that the cross-current density gradient and vertical current shear of the Gulf Stream were systematically lower during the Little Ice Age (ad approximately 1200 to 1850). We also estimate that Little Ice Age volume transport was ten per cent weaker than today's. The timing of reduced flow is consistent with temperature minima in several palaeoclimate records, implying that diminished oceanic heat transport may have contributed to Little Ice Age cooling in the North Atlantic. The interval of low flow also coincides with anomalously high Gulf Stream surface salinity, suggesting a tight linkage between the Atlantic Ocean circulation and hydrologic cycle during the past millennium. VL - 444 IS - 7119 N1 - Lund, David CLynch-Stieglitz, JeanCurry, William BengResearch Support, U.S. Gov't, Non-P.H.S.England2006/12/01 09:00Nature. 2006 Nov 30;444(7119):601-4. JO - Gulf Stream density structure and transport during the past millennium ER - TY - JOUR T1 - The historical fur trade and climate change JF - EOS Y1 - 2006 A1 - Varekamp, J. C. VL - 87 IS - 52 N1 - id: 725 ER - TY - JOUR T1 - Holocene elephant seal distribution implies warmer-than-present climate in the Ross Sea JF - Proceedings of the National Academy of Sciences of the United States of America Y1 - 2006 A1 - Hall, B. L. A1 - Hoelzel, A. R. A1 - Baroni, C. A1 - Denton, G. H. A1 - Le Boeuf, B. J. A1 - Overturf, B. A1 - Topf, A. L. AB - We show that southern elephant seal (Mirounga leonina) colonies existed proximate to the Ross Ice Shelf during the Holocene, well south of their core sub-Antarctic breeding and molting grounds. We propose that this was due to warming (including a previously unrecognized period from approximate to 1,100 to 2,300 C-14 yr B.P.) that decreased coastal sea ice and allowed penetration of warmer-than-present climate conditions into the Ross Embayment. If, as proposed in the literature, the ice shelf survived this period, it would have been exposed to environments substantially warmer than present. VL - 103 IS - 27 N1 - id: 1918; PT: J; NR: 25; TC: 14; J9: P NATL ACAD SCI USA; PG: 5; GA: 064DM; UT: WOS:000239069400013 JO - Holocene elephant seal distribution implies warmer-than-present climate in the Ross Sea ER - TY - CHAP T1 - Hudson River Paleoecology from Marshes T2 - Hudson River Fishes and their Environment. Y1 - 2006 A1 - Peteet, D. A1 - Pederson, D. A1 - Kurdyla, D. A1 - Guilderson, T. ED - Waldman, J. R. JF - Hudson River Fishes and their Environment. PB - American Fisheries Society Monograph N1 - id: 1165 ER - TY - JOUR T1 - Human Impacts on Rapa, French Polynesia JF - Antiquity Y1 - 2006 A1 - Kennett, D. J. A1 - Anderson, A. A1 - Prebble, M. A1 - Conte, E. A1 - Southon, J. VL - 80 N1 - id: 1020 ER - TY - CHAP T1 - The ideal free distribution, food production, and the colonization of Oceania T2 - Behavioral Ecology and the Transition to Agriculture Y1 - 2006 A1 - Kennett, D. J. A1 - Anderson, A. A1 - Winterhalder, B. ED - Kennett, D. J. JF - Behavioral Ecology and the Transition to Agriculture PB - University of California Press CY - Berkeley, CA N1 - id: 466 ER - TY - JOUR T1 - Incorporation of aged dissolved organic carbon (DOC) onto oceanic particulate organic carbon (POC): an experimental approach using carbon isotopes JF - Marine Chemistry Y1 - 2006 A1 - Hwang, J. A1 - Druffel, E. R. M. A1 - Bauer, J. E. VL - 98 N1 - id: 682 ER - TY - JOUR T1 - The influence of seasonal precipitation and temperature regimes on lake levels in the northeastern United States during the Holocene JF - Quaternary Research Y1 - 2006 A1 - Shuman, B. A1 - Donnelly, J. P. AB - AMS-dated sediment cores combined with ground-penetrating radar profiles from two lakes in southeastern Massachusetts demonstrate that regional water levels rose and fell multiple times during the Holocene when the known climatic controls (i.e., ice extent and insolation) underwent unidirectional changes. The lakes were lowest between 10,000 and 9000 and between 5500 and 3000 cat yr B.P. Using a heuristic moisture-budget model, we explore the hypothesis that changes in seasonal precipitation regimes, driven by monotonic trends in ice extent and insolation, plausibly explain the multiple lake-level changes. Simulated lake levels resulting from low summer precipitation rates match observed low lake levels of 10,000-9000 cat yr B.P., whereas a model experiment that simply shifts the seasonality of the modem Massachusetts precipitation regime (i.e., moving the peak monthly precipitation from winter to summer) produces levels that are similar to 2 in lower than today as observed for 5500-3000 cat yr BY, The influence of the Laurentide ice sheet could explain dry summers before ca. 8000 cat yr B.P. A later shift from a summer-wet to a winter-wet moisture-balance regime could have resulted from insolation-driven changes in the influence of the Bermuda subtropical high. Temperature changes probably further modified lake levels by affecting snowmelt and transpiration. (c) 2005 Published by University of Washington. VL - 65 IS - 1 N1 - 003pfTimes Cited:40Cited References Count:48 JO - The influence of seasonal precipitation and temperature regimes on lake levels in the northeastern United States during the Holocene ER - TY - JOUR T1 - IntCal04 Update: The future of radiocarbon calibration JF - PAGES Newsletter Y1 - 2006 A1 - Reimer, P. A1 - Hughen, K. A. VL - 14 N1 - id: 557 ER - TY - JOUR T1 - Intra-shell radiocarbon variability in marine mollusks JF - Radiocarbon Y1 - 2006 A1 - Culleton, B. J. A1 - Kennett, D. J. A1 - Ingram, B. L. A1 - Erlandson, J. M. A1 - Southon, J. VL - 48 IS - 3 N1 - id: 1019 ER - TY - JOUR T1 - Intrinsic bacterial biodegradation of petroleum contamination demonstrated in situ using natural abundance, molecular-level 14C analysis JF - Organic Geochemistry Y1 - 2006 A1 - Slater, Gregory F. A1 - Nelson, Robert K. A1 - Kile, Brian M. A1 - Reddy, Christopher M. VL - 37 N1 - id: 594 ER - TY - CONF T1 - Investigating the temperoral relationship between the synthesis and sediment incorporation of vascular plant biomarkers using molecular level 14C analysis T2 - EOS Abstracts, 2006 AGU Ocean Sciences Meeting Y1 - 2006 A1 - Drenzek, N. A1 - Poussart, P. A1 - Lima, A. L. A1 - Hughens, K. A1 - Reddy, C. A1 - Eglinton, T. I. JF - EOS Abstracts, 2006 AGU Ocean Sciences Meeting CY - Honolulu, HI N1 - id: 562 ER - TY - JOUR T1 - Las morenas de Punta Banderas, Lago Argentino JF - Proceedings of the XVI Congreso Geologico Argentino Y1 - 2006 A1 - Strelin, J. A1 - Denton, G. H. VL - CD-ROM IS - 269 N1 - id: 707 ER - TY - CONF T1 - Late Holocene climate variability of South America reconstructed by a multi-proxy analysis of Chilean fjord sediments T2 - Abstracts, EGU General Assembly Y1 - 2006 A1 - Bertrand, S. A1 - Hughen, K. A. A1 - Giosan, L. A1 - Tierney, J. A1 - Sepfulveda, J. A1 - Pantoja, S. JF - Abstracts, EGU General Assembly CY - Vienna, Austria N1 - id: 560 ER - TY - CONF T1 - The late Pleistocene-Holocene history of Long Island Sound T2 - LISRC proceedings Y1 - 2006 A1 - Varekamp, J. C. A1 - Thomas, E. A1 - Groner, M. JF - LISRC proceedings N1 - id: 1175 ER - TY - THES T1 - Late Quaternary sea-level lowstand environments and chronology of outer Saco Bay, Maine Y1 - 2006 A1 - Lee, K. PB - University of Maine CY - Orono, ME VL - Masters ER - TY - JOUR T1 - Late-Quaternary paleoenvironmental evolution of Lesina lagoon (sosuthern Italy) from subsurface data JF - Sedimentary Geology Y1 - 2006 A1 - Lucchi, Marianna Ricci A1 - Fiorini, Flavia A1 - Colalongo, Maria Luisa A1 - Curzi, Pietro Vittorio KW - Foraminifers KW - Late Quaternary KW - Lesina lagoon (Italy) KW - Ostracods KW - Sea-level changes AB - Integrated sedimentological and micropaleontological (foraminifers and ostracods) analyses of two 55 m long borehole cores (S3 and S4) drilled in the subsurface of Lesina lagoon (Gargano promontory—Italy) has yielded a facies distribution characteristic of alluvial, coastal and shallow-marine sediments. Stratigraphic correlation between the two cores, based on strong similarity in facies distribution and AMS radiocarbon dates, indicates a Late Pleistocene to Holocene age of the sedimentary succession. Two main depositional sequences were deposited during the last 60-ky. These sequences display poor preservation of lowstand deposits and record two major transgressive pulses and subsequent sea-level highstands. The older sequence, unconformably overlying a pedogenized alluvial unit, consists of paralic and marine units (dated by AMS radiocarbon at about 45–50,000 years BP) that represent the landward migration of a barrier-lagoon system. These units are separated by a ravinement surface (RS1). Above these tansgressive deposits, highstand deposition is characterised by progradation of the coastal sediments. The younger sequence, overlying an unconformity of tectonic origin, is a 10 m-thick sedimentary body, consisting of fluvial channel sediments overlain by transgressive–regressive deposits of Holocene age. A ravinement surface (RS2), truncating the transgressive (lagoonal and back-barrier) deposits in core S4, indicates shoreface retreat and landward migration of the barrier/lagoon system. The overlying beach, lagoon and alluvial deposits are the result of mid-Holocene highstand sedimentation and coastal progradation. VL - 183 N1 - id: 1060 JO - Late-Quaternary paleoenvironmental evolution of Lesina lagoon (sosuthern Italy) from subsurface data ER - TY - CONF T1 - Long Island Sound - a human dominated estuary T2 - AGU spring meeting, 2006 Y1 - 2006 A1 - Varekamp, J. C. A1 - Thomas, E. JF - AGU spring meeting, 2006 CY - Baltimore, MD N1 - id: 1186 ER - TY - JOUR T1 - MAGic: A Phanerozoic model for the geochemical cycling of major rock-forming components JF - American Journal of Science Y1 - 2006 A1 - Arvidson, R. S. A1 - Mackenzie, F. T. A1 - Guidry, M. KW - ATMOSPHERIC CARBON-DIOXIDE KW - CENOZOIC EVOLUTION KW - Clay minerals KW - CO2 KW - DOLOMITE PROBLEM KW - marine-sediments KW - REVISED MODEL KW - SEAWATER CHEMISTRY KW - SECULAR VARIATION KW - time AB - A dynamical model (MAGic) is presented that describes the elemental cycling of sedimentary materials involving sodium, potassium, calcium, magnesium, chloride, carbon, oxygen, iron, sulfur and phosphorous through much of the Phanerozoic. The model incorporates the basic reactions controlling atmospheric carbon dioxide and oxygen concentrations, continental and seafloor weathering of silicate and carbonate rocks, net ecosystem productivity, basalt-seawater exchange reactions, precipitation and diagenesis of chemical sediments and authigenic silicates, oxidation-reduction reactions involving carbon, sulfur, and iron, and subduction-decarbonation reactions. Although MAGic contains feedback and forcing functions adapted from the GEOCARB models (Berner, 1991, 1994; Berner and Kothavala, 2001), these functions are incorporated in a reservoir-reaction scheme that is considerably more detailed. Coupled reservoirs include shallow and deep cratonic silicate and carbonate rocks and sediments, seawater, atmosphere, oceanic sediments and basalts, and the shallow mantle. Model results are reasonably consistent with recently published constraints provided by fluid inclusion, isotopic, floral, and mineralogical records. We have used these results to evaluate sensitivity to uncertainties in the history of the earth-ocean-atmosphere system over the past 500 Ma: the advent of pelagic carbonate sedimentation, the importance of burial versus early diagenetic dolomite formation, the importance of reverse weathering, and the relationship of these processes to seafloor spreading rates. Results include a general pattern of dolomite abundance during periods of elevated seafloor spreading and alkalinity production, elevated atmospheric CO2 concentrations for most of the Phanerozoic similar to those predicted by GEOCARB, and covariance of seawater sulfate to calcium ratios with magnesium to calcium ratios. These trends are broadly consistent with proxies for seawater composition and the mass-age data of the rock record itself. VL - 306 SN - 0002-9599 IS - 3 N1 - 53 JO - Am. J. Sci. ER - TY - CONF T1 - Marine 14C calibration and activity record for the past 50,000 years from the Cariaco Basin, Abstract T2 - Eos Trans AGU 87, Fall Meeting Supple. Y1 - 2006 A1 - Hughen, K. A. A1 - Southon, J. A1 - Lehman, S. J. A1 - Jenkins, W. JF - Eos Trans AGU 87, Fall Meeting Supple. CY - San Francisco, CA N1 - id: 1076 ER - TY - CONF T1 - Marine 14C data sets: contributions to calibration and Earth Systems research, Abstract T2 - 19th International Radiocarbon Conference Y1 - 2006 A1 - Hughen, K. A. JF - 19th International Radiocarbon Conference CY - Oxford, UK N1 - id: 1077 ER - TY - JOUR T1 - Marine-derived 14C calibration and activity record for the past 50,000 years updated from the Cariaco Basin JF - Quaternary Science Reviews Y1 - 2006 A1 - Hughen, K. A. A1 - Southon, J. A. A1 - Lehman, S. J. A1 - Bertrand, C. J. H. A1 - Turnbull, J. VL - 25 N1 - id: 553 ER - TY - CONF T1 - Mechanism of 15N enrichment in eutrophication-impacted estuaries T2 - ASLO Ocean Sciences meeting Y1 - 2006 A1 - Varekamp, J. C. A1 - Altabet, M. A. A1 - Thomas, C. R. JF - ASLO Ocean Sciences meeting CY - Honolulu, HI N1 - id: 745 ER - TY - CONF T1 - Mercury contamination in Connecticut and Long Island Sound from historic hat-making sources T2 - GSA Annual Meeting Y1 - 2006 A1 - Goldoff, B. A1 - Varekamp, J. C. A1 - Neupane, A. JF - GSA Annual Meeting CY - Philadelphia, PA N1 - id: 747 ER - TY - CONF T1 - Mercury contamination in Long Island Sounds, USA, from the historic hat-making industry T2 - ISEG7 meeting Y1 - 2006 A1 - Varekamp, J. C. JF - ISEG7 meeting CY - Beijing, China N1 - id: 746 ER - TY - JOUR T1 - Meridional overturning circulation in the South Atlantic at the last glacial maximum JF - Geochemistry Geophysics Geosystems Y1 - 2006 A1 - Lynch-Stieglitz, J. A1 - Curry, W. B. A1 - Oppo, D. W. A1 - Ninneman, U. S. A1 - Charles, C. D. A1 - Munson, J. AB - The geostrophic shear associated with the meridional overturning circulation is reflected in the difference in density between the eastern and western margins of the ocean basin. Here we examine how the density difference across 30 degrees S in the upper 2 km of the Atlantic Ocean ( and thus the magnitude of the shear associated with the overturning circulation) has changed between the last glacial maximum and the present. We use oxygen isotope measurements on benthic foraminifera to reconstruct density. Today, the density in upper and intermediate waters along the eastern margin in the South Atlantic is greater than along the western margin, reflecting the vertical shear associated with the northward flow of surface and intermediate waters and the southward flowing North Atlantic Deep Waters below. The greater density along the eastern margin is reflected in the higher delta(18)O values for surface sediment benthic foraminifera than those found on the western margin for the upper 2 km. For the last glacial maximum the available data indicate that the eastern margin foraminifera had similar delta(18)O to those on the western margin between 1 and 2 km and that the gradient was reversed relative to today with the higher delta(18)O values in the western margin benthic foraminifera above 1 km. If this reversal in benthic foraminifera delta(18)O gradient reflects a reversal in seawater density gradient, these data are not consistent with a vigorous but shallower overturning cell in which surface waters entering the Atlantic basin are balanced by the southward export of Glacial North Atlantic Intermediate Water. VL - 7 N1 - 092siTimes Cited:17Cited References Count:46 JO - Meridional overturning circulation in the South Atlantic at the last glacial maximum ER - TY - JOUR T1 - Mid-Holocene El Nino-Southern Oscillation (ENSO) attenuation revealed by individual foraminifera in eastern tropical Pacific sediments JF - Geology Y1 - 2006 A1 - Koutavas, A. A1 - deMenocal, P. B. A1 - Olive, G. C. A1 - Lynch-Stieglitz, J. AB - Holocene reconstructions of the Ell Nino-Southern Oscillation (ENSO) provide valuable perspective on its recent evolution and can be important for assessing its future. Optimal assessment of past ENSO variability requires observations from its center of action in the eastern equatorial Pacific, but these are limited due to paucity of high-resolution paleoceanographic archives (e.g., corals). Here we use a new approach to quantify past ENSO variance based on the oxygen isotopic composition (delta O-18) of individual foraminifera (Globigerinoides ruber) from deep-sea sediments in the ENSO source region.. Individual G. ruber foraminifera behave as monthly recorders of sea-surface conditions, including ENSO extremes, circumventing the lack of annual resolution in the sediments. Intrapopulation delta O-18 distributions derived with this method from a core near the Galapagos Islands reveal mid-Holocene reductions in variance or 50%, requiring drastic attenuation of the ENSO amplitude. Furthermore, Mg/Ca thermometry indicates that mid-Holocene background conditions were accompanied by a stronger zonal temperature gradient that coincided with a northward-displaced Intertropical Convergence Zone (ITCZ). The results suggest that the position of the ITCZ is an important factor in the low-frequency modulation of ENSO and could influence its future evolution. VL - 34 IS - 12 N1 - 113wzTimes Cited:128Cited References Count:26 JO - Mid-Holocene El Nino-Southern Oscillation (ENSO) attenuation revealed by individual foraminifera in eastern tropical Pacific sediments ER - TY - JOUR T1 - Modern saltmarsh diatom distributions of the Outer Banks, North Carolina, and the development of a transfer function for high resolution reconstructions of sea level JF - Estuarine Coastal and Shelf Science Y1 - 2006 A1 - Horton, B. P. A1 - Corbett, R. A1 - Culver, S. J. A1 - Edwards, R. J. A1 - Hillier, C. AB - We collected modern diatom samples from Currituck Barrier Island, Oregon inlet and Pea Island marshes, Outer Banks, North Carolina, USA, which have different salinity regimes due to their varying distances from a major barrier island inlet. Multivariate analyses separate the saltmarsh diatom assemblages into distinct elevational zones, dominated by differing abundances of polyhalobous, mesohalobous and oliohalobous taxa. suggesting that the distribution of saltmarsh diatoms is a direct function of elevation, with the most important controlling factors being the duration and frequency of subaerial exposure.We developed the first diatom-based transfer function for the east coast of North America to reconstruct former sea levels based upon the relationship between diatom assemblage and elevation. Results imply that this is possible to a precision of +/- 0.08 m, superior to most similar studies from temperate, mid-latitude environments. The transfer function is used to construct a relative sea-level curve from fossil assemblages from Salvo. North Carolina. These results suggest a sea-level rise of 0.7 m over the last c. 150 years, at an average of c. 3.7 mm year(-1). This is consistent with existing sea-level data, and illustrates the utility of the transfer function approach. (c) 2006 Elsevier Ltd. All rights reserved. VL - 69 IS - 3-4 N1 - 090jmTimes Cited:37Cited References Count:74 JO - Modern saltmarsh diatom distributions of the Outer Banks, North Carolina, and the development of a transfer function for high resolution reconstructions of sea level ER - TY - RPRT T1 - The Montana Creek Sites: Archaeological Investigations at Lovewell Reservoir, Jewell County, Kansas-2004 Y1 - 2006 A1 - Ritterbush, Lauren W. A1 - Logan, Brad PB - Nebraska-Kansas Area Office, Bureau of Reclamation. Dept. of Sociology, Anthropology and Social Work, Kansas State University CY - Manhattan N1 - id: 619 ER - TY - CONF T1 - Monthly resolved stable oxygen isotope record in a Palauan sclerosponge Acanthocheatetes wellsi for the period of 1977-2001 T2 - 10th International Coral Reef Symposium Y1 - 2006 A1 - Grottoli, Andrea G. JF - 10th International Coral Reef Symposium N1 - id: 1131 ER - TY - JOUR T1 - A multiproxy palaeoecological record of Holocene lake sediments from the Rio Tapajos, eastern Amazonia JF - Palaeogeography Palaeoclimatology Palaeoecology Y1 - 2006 A1 - Irion, G. A1 - Bush, M. B. A1 - de Mello, J. A. N. A1 - Stuben, D. A1 - Neumann, T. A1 - Muller, G. A1 - De, J. O. A1 - Junk, J. W. AB - Two sediment cores up to 42 m in length were raised from the wide, deep, section of the lower Tapajos River, Amazonia, referred to as Lago Tapajos. These cores reveal a history of subtle environmental change that began with the formation of Lago Tapajos as sea level rose about 11,000 years ago. The sediments of the lake were deposited fairly quickly-at a rate of ca. 4 m per millennium and are uniformly fine grained, with low organic content. The fossil pollen record derived from these sediments reveals that forest surrounded this site throughout the Holocene. The largest change in the core took place between ca. 5500 and 4200 cal. years BP and reflects a transition from coarser to finer sediments. Coincident with the change in sediment is a slight transition in the pollen spectra with an increase in Poaceae abundance at the expense of the pioneer tree Cecropia cecropia. A tentative explanation is offered in which increased human activity, possibly spurred by climatic change, resulted in the formation of some local grasslands. However, despite the apparent actions of humans, there is no indication of basin-wide transformation of landscapes in this record. The Holocene persistence of forest as the dominant landscape matrix around Lago Tapajos is supported by low delta C-13 values and by the constant geochemistry and mineralogy of the lake sediments. (c) 2006 Elsevier B.V. All rights reserved. VL - 240 IS - 3-4 N1 - 097fbTimes Cited:40Cited References Count:78 JO - A multiproxy palaeoecological record of Holocene lake sediments from the Rio Tapajos, eastern Amazonia ER - TY - CONF T1 - Multiproxy records of eutrophication in Long Island Sound T2 - GSA Annual Meeting Y1 - 2006 A1 - Varekamp, Thomas E. A1 - Avener, J. C. JF - GSA Annual Meeting CY - Philadelphia, PA N1 - id: 748 ER - TY - JOUR T1 - The mystery interval 1.5 to 14.5 kyrs ago JF - Pages News Y1 - 2006 A1 - Denton, G. H. A1 - Broecker, W. S. A1 - Alley, R. B. VL - 14 N1 - id: 701 ER - TY - JOUR T1 - National register evaluation and geoarchaeological analysis of the sites and shovel testing at Fort Riley, Kansas JF - Center for Environmental Management of Military Lands, Colorado State Univ. Y1 - 2006 A1 - Sherman, Stephen A. A1 - Johnson, William C. VL - TPS 06-13 N1 - id: 696 ER - TY - JOUR T1 - Natural 14C in Saccoglossus Bromophenolosus compared to its surrounding sediments JF - Marine Ecology Progress Series Y1 - 2006 A1 - Teuten, E. L. A1 - King, G. M. A1 - Reddy, C. M. VL - 324 N1 - id: 613 ER - TY - JOUR T1 - Natural abundance radiocarbon as a tracer of assimilation of petrolleum carbon by bacteria in salt marsh sediments JF - Geochim. Cosmochim. Acta Y1 - 2006 A1 - Wakeham, S. G. A1 - McNichol, A. P. A1 - Kostka, J. A1 - Pease, T. K. VL - 70 N1 - id: 520 ER - TY - JOUR T1 - Natural-abundance radiocarbon as a tracer of assimilation of petroleum carbon by bacteria in salt marsh sediments JF - Geochimica Et Cosmochimica Acta Y1 - 2006 A1 - Wakeham, S. G. A1 - McNichol, A. P. A1 - Kostka, J. E. A1 - Pease, T. K. AB - The natural abundance of radiocarbon ((14)C) provides unique insight into the source and cycling of sedimentary organic matter. Radiocarbon analysis of bacterial phospholipid lipid fatty acids (PLFAs) in salt-marsh sediments of southeast Georgia (USA)-one heavily contaminated by petroleum residues-was used to assess the fate of petroleum-derived carbon in sediments and incorporation of fossil carbon into microbial biomass. PLFAs that are common components of eubacterial cell membranes (e.g., branched C(15) and C(17), 10-methyl-C(16)) were depleted in (14)C in the contaminated sediment (mean Delta(14)C value of +25 +/- 19 parts per thousand for bacterial PLFAs) relative to PLFAs in uncontaminated "control" sediment (Delta(14)C = +101 +/- 12 parts per thousand). We suggest that the (14)C-depletion in bacterial PLFAs at the contaminated site results from microbial metabolism of petroleum and subsequent incorporation of petroleum-derived carbon into bacterial membrane lipids. A mass balance calculation indicates that 6-10% of the carbon in bacterial PLFAs at the oiled site could derive from petroleum residues. These results demonstrate that even weathered petroleum may contain components of sufficient lability to be a carbon source for biomass production by marsh sediment microorganisms. Furthermore, a small but significant fraction of fossil carbon is assimilated even in the presence of a much larger pool of presumably more-labile and faster-cycling carbon substrates. (c) 2006 Elsevier Inc. All rights reserved. VL - 70 IS - 7 N1 - 030olTimes Cited:27Cited References Count:65 JO - Natural-abundance radiocarbon as a tracer of assimilation of petroleum carbon by bacteria in salt marsh sediments ER - TY - JOUR T1 - New evidence for remnant deposits recorded by columnar sediments in the shelf of the northern South China Sea JF - Marine Geology & Quaternary Geology Y1 - 2006 A1 - Xiao, S. B. A1 - Chen, M. H. A1 - Lu, J. VL - 26 SN - 0256-1492 IS - 3 N1 - id: 568 JO - New evidence for remnant deposits recorded by columnar sediments in the shelf of the northern South China Sea ER - TY - CONF T1 - New middle and late Holocene radiocarbon dates for alluvial deposits containing the Sand Creek pit hearths of northwestern Nebraska, U.S.A T2 - 14th Annual Island in the Planes Archeological and Historical Symposium Program and Abstracts Y1 - 2006 A1 - LaGarry, L. A. A1 - LaGarry, H. E. A1 - Wandsnider, L. A1 - Richardson, E. L. JF - 14th Annual Island in the Planes Archeological and Historical Symposium Program and Abstracts N1 - id: 517 ER - TY - JOUR T1 - Non-pollen palynomorphs from organic deposits of Posidonia oceanica: a new tool for palaeoenvironmental studies in marine peat-like deposits JF - Palyno-Bulletin Y1 - 2006 A1 - López-Sáez, J. A. A1 - López-García, P. A1 - Pozuelo, R. A1 - Mateo, M. A. A1 - Renom, P. A1 - Garrido, D. AB - The in situ accumulation of large quantities of biogenic materials over millennia is very relevant and occurs only in a limited number of ecosystems. Peat bogs are probably the bestknown example among terrestrial ecosystems (e.g. Aaby & Berglund, 1986) and coral reefs among marine ecosystems (e.g. Clausen & Roth, 1975). In situ organic accumulations in the marine environment are rare, having been described for mangroves and seagrass species. The Mediterranean seagrass Posidonia oceanica accumulates large quantities of organic debris. Roots, rhizomes and leaf sheaths are progressively buried fonning a bioconstruction called 'matte'. The organic material remains with little morphological alteration for millennia (Mateo et aI. , 1997), constitnting a marine peat-like deposit with a great interest from a palaeoenvironmental point of view. The present paper evaluates the palaeoecological potential of the organic deposits generated by the marine phanerogame Posidonia oceanica in the Bay of Port Lligat, Girona, NE Spain. This stndy discusses the detailed evolution of the vegetation in the landscape of the area. VL - 2 IS - 1-4 N1 - id: 2005 JO - Non-pollen palynomorphs from organic deposits of Posidonia oceanica: a new tool for palaeoenvironmental studies in marine peat-like deposits ER - TY - JOUR T1 - The North Anatolian fault in the Gulf of Izmit (Turkey): Rapid vertical motion in response to minor bends of a non-vertical continental transform JF - Journal of Geophysical Research Y1 - 2006 A1 - Cormier, M. H. A1 - Seeber, L. A1 - McHugh, C. M. G. A1 - Polonia, A. A1 - Cagatay, M. N. A1 - Emre, O. A1 - Gasperini, L. A1 - Gorur, N. A1 - Bortoluzzi, G. A1 - Bonatti, E. A1 - Ryan, W. B. F. A1 - Newman, K. R. VL - 111 N1 - id: 532 ER - TY - JOUR T1 - Ongoing build-up of refractory organic carbon in boreal soils during the Holocene JF - Science Y1 - 2006 A1 - Smittenberg, R. H. A1 - Eglinton, T. I. A1 - Schouten, S. A1 - Sinninghe-Damste, J. S. VL - 314 N1 - id: 1146 ER - TY - CONF T1 - Organic Carbon in Rivers (Plenary Lecture) T2 - Geochemical Earth Reference Model (GERM) Workshop Y1 - 2006 A1 - Raymond, P. A. JF - Geochemical Earth Reference Model (GERM) Workshop CY - Lamont-Doherty N1 - id: 488 ER - TY - JOUR T1 - Origin of PCDD in ball clay assessed with compound-specifric chlorine isotope analysis and radiocarbon dating JF - Environmental Science and Technology Y1 - 2006 A1 - Holmstrand, H. D. A1 - Gadomski, D. A1 - Mandalakis, M. A1 - Tysklind, M. A1 - Irvine, R. A1 - Andersson, P. A1 - Gustafsson, O. VL - 40 N1 - id: 1040 ER - TY - ART T1 - Paleotsunami deposits in coastal lagoons, Sri Lanka: Are tsunamis always sedimentologically important events? Y1 - 2006 A1 - Jackson, K. L. A1 - Rankey, E. C. A1 - Eberli, G. P. A1 - Amelung, F. A1 - Andres, M. S. A1 - Peterson, L. C. A1 - Swart, P. K. A1 - Jayasena, H. A. H. A1 - Kehelpannala, K. V. W. PB - EOS Trans. AGU Fall Meeting Suppl. Abstracts N1 - id: 664 ER - TY - JOUR T1 - Pedological properties of the eroding coastline along the Beaufort Sea, Alaska JF - Eos Trans. AGU Fall Meeting Supplement Y1 - 2006 A1 - Ping, C. L. A1 - Dou, F. A1 - Jorgenson, G. A1 - Michaelson, J. A1 - Lynn, L. A. A1 - Shur, Y. A1 - Kanevsky, M. VL - 87 IS - 52 N1 - id: 1002 ER - TY - JOUR T1 - Postglacial climate reconstruction based on compound-specific D/H ratios of fatty acids from Blood Pond, New England JF - Geochemistry Geophysics Geosystems Y1 - 2006 A1 - Hou, J. Z. A1 - Huang, Y. S. A1 - Wang, Y. A1 - Shuman, B. A1 - Oswald, W. W. A1 - Faison, E. A1 - Foster, D. R. KW - atmospheric processes : paleoclimatology KW - eastern north-america KW - fatty acids KW - geochemistry : organic and biogenic geochemistry KW - geochemistry : stable isotope geochemistry KW - Holocene KW - hydrogen isotope KW - hydrogen isotope ratios KW - lacustrine organic-matter KW - lake-sediments KW - Paleoclimate KW - record KW - Stable isotopes KW - united-states KW - vegetation history KW - younger-dryas AB - We determined hydrogen isotope ratios of individual fatty acids in a sediment core from Blood Pond, Massachusetts, USA, in order to reconstruct climate changes during the past 15 kyr. In addition to palmitic acid (C-16 n-acid), which has been shown to record lake water D/H ratios, our surface sediments and down core data indicate that behenic acid (C-22 n-acid), produced mainly by aquatic macrophytes, is also effective for capturing past environmental change. Calibration using surface sediments from two transects across eastern North America indicates that behenic acid records delta D variation of lake water. Down core variations in delta D values of behenic acid and pollen taxa are consistent with the known climate change history of New England. By evaluating the hypothesis that D/H fractionations of long chain even numbered fatty acids (C-24-C-32 n-acids) relative to lake water provide independent estimates of relative humidity during the growing season, we find that differences between lake-level records and isotopically inferred humidity estimates may provide useful insight into seasonal aspects of the hydrologic cycle. Combined analyses of D/H of short and long chain fatty acids from lake sediment cores thus allow reconstructions of both past temperature and growing season relative humidity. Comparison of delta D records from two lakes in New England provides critical information on regional climate variation and abrupt climate change, such as the 8.2 ka event. VL - 7 SN - 1525-2027 IS - 3 N1 - 031uaTimes Cited:32 Cited References Count:43 JO - Geochem Geophy Geosy ER - TY - CHAP T1 - Pre-Columbian maize agriculture in Costa Rice: Pollen and other evidence from lake and swamp sediments T2 - Histories of Maize: Multidisciplinary Approaches to the Prehistory, Biogeography, Domestication, and Evolution of Maize Y1 - 2006 A1 - Horn, S. P. ED - Staller, J. JF - Histories of Maize: Multidisciplinary Approaches to the Prehistory, Biogeography, Domestication, and Evolution of Maize PB - Elsevier Press CY - San Diego, CA N1 - id: 1113 ER - TY - JOUR T1 - Quantifying archaeal community autotrophy in the mesopelogic ocean using natural radiocarbon JF - Proc. Natl. Acad. Sci. USA Y1 - 2006 A1 - Ingalls, A. E. A1 - Shah, S. R. A1 - Hansman, R. L. A1 - Aluwihare, L. I. A1 - Santos, G. M. A1 - Druffel, E. R. M. A1 - Pearson, A. VL - 103 N1 - id: 502 ER - TY - JOUR T1 - Rapid lateral particle transport in the Argentine Basin: Molecular 14C and 230Th evidence JF - Deep-Sea Research I Y1 - 2006 A1 - Mollenhauer, Gesine A1 - McManus, Jerry F. A1 - Benthien, Albert A1 - Muller, Peter J. A1 - Eglinton, Timothy I. VL - 53 N1 - id: 543 ER - TY - JOUR T1 - Rapid sea-level rise and Holocene climate in the Chukchi Sea JF - Geology Y1 - 2006 A1 - Keigwin, L. D. A1 - Donnelly, J. P. A1 - Cook, M. S. A1 - Driscoll, N. W. A1 - Brigham-Grette, J. AB - Three new sediment cores from the Chukchi Sea preserve a record of local paleoenvironment, sedimentation, and flooding of the Chukchi Shelf (similar to-50 m) by glacial-eustatic sea-level rise. Radiocarbon dates on foraminifera provide the first marine evidence that the sea invaded Hope Valley (southern Chukchi Sea, -53 m) as early as 12 ka. The lack of significant sediment accumulation since ca. 7 ka in Hope Valley, southeastern Chukchi Shelf, is consistent with decreased sediment supply and fluvial discharge to the shelf as deglaciation of Alaska concluded. Abundant benthic foraminifera from a site west of Barrow Canyon indicate that surface waters were more productive 4-6 ka, and this productivity varied on centennial time scales. An offshore companion to this core contains a 20 m record of the Holocene. These results show that carefully selected core sites from the western Arctic Ocean can have a temporal resolution equal to the best cores from other regions, and that these sites can be exploited for high-resolution studies of the paleoenvironment. VL - 34 IS - 10 N1 - 089zkTimes Cited:67Cited References Count:18 JO - Rapid sea-level rise and Holocene climate in the Chukchi Sea ER - TY - JOUR T1 - Rapid subsidence and sedimentation from oblique slip near a bend on the North Anatolian transform fault in the Marmara Sea, Turkey JF - Geology Y1 - 2006 A1 - Seer, L. A1 - Cormier, M. H. A1 - McHugh, C. A1 - Emre, O. A1 - Polonia, A. A1 - Sorlien, C. VL - 34 IS - 11 N1 - id: 533 ER - TY - JOUR T1 - Recent investigations of maritime archaic structures at White Point, Northern Labrador JF - Provincial Archaeology Office of Newfoundland and Labrador Archaeological Review Y1 - 2006 A1 - Wolff, Christopher B. VL - online N1 - id: 410 ER - TY - JOUR T1 - Reduced agulhas leakage at the LGM inferred from an integrated provenance and flux dtudy JF - Earth & Planatary Science Letters Y1 - 2006 A1 - Franzese, A. M. A1 - Hemming, S. R. A1 - Goldstein, S. L. A1 - Anderson, R. F. VL - 250 N1 - id: 632 ER - TY - JOUR T1 - Refining the radiocarbon dating of Antarctic marine sediments via stepped combustion JF - Eps Trans AGU Y1 - 2006 A1 - Schrum, H. A1 - Hayes, J. A1 - Domack, E. VL - 87 IS - 36 N1 - id: 702 ER - TY - JOUR T1 - A revised late Holocene sea-level record for northern Massachusetts, USA JF - Journal of Coastal Research Y1 - 2006 A1 - Connelly, J. P. VL - 22 N1 - id: 497 ER - TY - JOUR T1 - The rise and fall of the refugial hypothesis JF - Biota Neotropica Y1 - 2006 A1 - Bush, M. B. A1 - De Oliveira, P. E. VL - 6 IS - 1 N1 - id: 457 JO - The rise and fall of the refugial hypothesis ER - TY - JOUR T1 - Rotasonic vibracores from northeastern North Carolina, cores OBX-10 through OBX-18 JF - NCGS Open-file Report Y1 - 2006 A1 - Hoffman, C. W. A1 - Farrell, K. M. A1 - Pierson, J. A. A1 - Ward, A. N. A1 - Nickerson, J. G. A1 - Brooks, R. W. A1 - Ganey, J. G. VL - II IS - 2006-04 N1 - id: 704 ER - TY - JOUR T1 - Sea surface temperatures of southern middle-latitudes 0-160 by BP JF - Paleoceanography Y1 - 2006 A1 - Pahnke, K. A1 - Sachs, J. P. VL - 21 N1 - id: 591 ER - TY - JOUR T1 - Sea-level and tectonic control of middle to late Pleistocene turbidite systems in Santa Monica Basin, offshore California JF - Sedimentology Y1 - 2006 A1 - Normark, W. R. A1 - Piper, D. J. W. A1 - Sliter, R. AB - Small turbidite systems offshore from southern California provide an opportunity to track sediment from river source through the turbidity-current initiation process to ultimate deposition, and to evaluate the impact of changing sea level and tectonics. The Santa Monica Basin is almost a closed system for terrigenous sediment input, and is supplied principally from the Santa Clara River. The Hueneme fan is supplied directly by the river, whereas the smaller Mugu and Dume fans are nourished by southward longshore drift. This study of the Late Quaternary turbidite fill of the Santa Monica Basin uses a dense grid of high-resolution seismic-reflection profiles tied to new radiocarbon ages for Ocean Drilling Program (ODP) Site 1015 back to 32 ka. Over the last glacial cycle, sedimentation rates in the distal part of Santa Monica Basin averaged 2-3 mm yr(-1), with increases at times of extreme relative sea-level lowstand. Coarser-grained mid-fan lobes prograded into the basin from the Hueneme, Mugu and Dume fans at times of rapid sea-level fall. These pulses of coarse-grained sediment resulted from river channel incision and delta cannibalization. During the extreme lowstand of the last glacial maximum, sediment delivery was concentrated on the Hueneme Fan, with mean depositional rates of up to 13 mm yr(-1) on the mid- and upper fan. During the marine isotope stage (MIS) 2 transgression, enhanced rates of sedimentation of > 4 mm yr(-1) occurred on the Mugu and Dume fans, as a result of distributary switching and southward littoral drift providing nourishment to these fan systems. Longer-term sediment delivery to Santa Monica Basin was controlled by tectonics. Prior to MIS 10, the Anacapa ridge blocked the southward discharge of the Santa Clara River into the Santa Monica Basin. The pattern and distribution of turbidite sedimentation was strongly controlled by sea level through the rate of supply of coarse sediment and the style of initiation of turbidity currents. These two factors appear to have been more important than the absolute position of sea level. VL - 53 IS - 4 N1 - 063ieTimes Cited:24Cited References Count:38 JO - Sea-level and tectonic control of middle to late Pleistocene turbidite systems in Santa Monica Basin, offshore California ER - TY - JOUR T1 - Sea-level variation during the holocene deduced from the morphologic and stratigraphic evolution of Morgan Peninsula, Alabama, USA JF - Journal of Sedimentary Research Y1 - 2006 A1 - Rodriguez, A. B. A1 - Meyer, C. T. AB - Recent Gulf of Mexico shoreline studies interpret middle to late Holocene sea level as failing from a level above present elevation or stable at present elevation; however, the architecture of Morgan Peninsula, Alabama, does not support this. Morgan Peninsula is a beach-ridge strandplain composed of two obliquely aligned Holocene beach-ridge sets. Ground-penetrating radar profiles discriminate between parallel, even to wavy reflectors of the eolian dune environment and the underlying seaward-dipping, complex sigmoidal-oblique reflectors of the foreshore and upper-shoreface environment. The contact between foreshore and eolian facies in beach ridges can be used as a sea-level indicator. The average elevation of this contact in Morgan Peninsula rises throughout shoreline accretion, which occurred throughout the last 5.4 ka, suggesting that there was continual sea-level rise during this time. Morgan Peninsula is a useful modern analog to ancient shoreface-shelf parasequences and demonstrates the significant internal complexities that can exist in these deposits. Erosional discontinuities imaged in the Holocene foreshore-upper shoreface environment are laterally continuous, extend to elevations above mean sea level, and correlate to beach ridges and the transition between beach-ridge sets. An increase in the wave regime or fluctuations in sediment supply appear to be likely mechanisms for forming erosional discontinuities below beach ridges. The erosional surface separating beach-ridge sets may have formed by increased storm activity and associated barrier breaching, or a reconfiguration of the Mobile Bay tidal-delta complex superimposed on a gradual rate of sea-level rise. This boundary is recognized by a change in beach-ridge orientation at the surface and an increase in the aggradational component of shoreline accretion. VL - 76 IS - 1-2 N1 - id: 2040; PT: J; UT: WOS:000235746800018 JO - Sea-level variation during the holocene deduced from the morphologic and stratigraphic evolution of Morgan Peninsula, Alabama, USA ER - TY - JOUR T1 - On sediment accumulation rates and stratigraphic completeness: Lessons from Holocene ocean margins JF - Continental Shelf Research Y1 - 2006 A1 - Sommerfield, C. K. AB - Stratigraphic completeness is a fundamental consideration when deciphering the mass accumulation history of sediments and the geologic record of earth and ocean processes. In this study, stratigraphic completeness was examined in the context of late Holocene sedimentary successions using published sediment accumulation rates for five ocean margin systems (Amazon shelf, Hudson estuary, northern California shelf, Mid-Atlantic slope, Santa Monica Bay). Plots of mass accumulation rate versus time span of averaging were used to determine how rates scale with measurement period, and to estimate levels of stratigraphic completeness for comparison within and among margin systems. Statistically significant inverse correlations between accumulation rate and time span of averaging are indicated for all but one of these systems-most of the sedimentary records examined are stratigraphically incomplete. At the 10(3)-yr level of resolution, completeness is 20-48% for strongly tidal estuarine (Hudson estuary) and deltaic shelf (Amazon shelf) sites, 51-91% for accretionary shelves (northern California shelf) and slopes (Mid-Atlantic slope), and 85-100% for a sediment-starved slope (Santa Monica bay). Mass accumulation rates converge to a relatively narrow range (0.01-0.1 g cm(-2) yr(-1)) at the 10(4)-yr level of resolution, consistent with the notion that there are universal controls on sediment accumulation rate, i.e., rate of sea-level rise and sediment supply. Among sites on the Amazon and northern California shelves, within-system completeness varies by similar to 10-20% on account of site-specific sedimentary processes that preferentially trap or disperse suspended sediment. Overall, stratigraphic completeness increases with water depth shelf-to-slope, yet depth is not a robust predictor of completeness in general owing to differences in strata-forming processes among shallow-marine environments. Significantly, completeness varies inversely with instantaneous deposition rate as the most sediment-rich systems tend to exhibit the most incomplete sedimentary records. The findings of this study emphasize the importance of considering time span and fidelity when interpreting the accumulation history of modern and Holocene sedimentary strata. (c) 2006 Elsevier Ltd. All rights reserved. VL - 26 IS - 17-18 N1 - 109ueTimes Cited:24Cited References Count:61 JO - On sediment accumulation rates and stratigraphic completeness: Lessons from Holocene ocean margins ER - TY - JOUR T1 - Sediment Cd and Mo accumulation in the oxygen-minimum zone off western Baja California linked to global climate over the past 52 kyr JF - Paleoceanography Y1 - 2006 A1 - Dean, W. E. A1 - Zheng, Y. A1 - Ortiz, J. D. A1 - van Geen, A. KW - continental-margin KW - enhanced preservation KW - late pleistocene KW - marine-sediments KW - nitrogen isotope KW - northeast pacific waters KW - organic-carbon preservation KW - productivity variations KW - santa-barbara basin KW - suboxic sediments AB - [ 1] Concentrations of organic carbon (orgC), cadmium (Cd), and molybdenum (Mo) were measured in two sediment cores raised from depths of 430 and 700 m within the oxygen-minimum zone (OMZ) off southern Baja California at a temporal resolution of similar to 0.5 kyr over the past 52 kyr. These records are supplemented with diffuse spectral reflectance (DSR) measurements obtained on board ship soon after collection at a resolution of similar to 0.05 kyr. In the core from 700 m depth, a component extracted from the DSR data and the three geochemical proxies generally vary in concert with each other and over a wide range ( 4 - 22% orgC; 1 - 40 mg/kg Cd; 5 120 mg/kg Mo). Intervals of increased orgC, Cd, and Mo accumulation generally correspond to warm periods recorded in the oxygen-isotopic composition of Greenland ice, with the exception of the Bolling/Allerod which is only weakly expressed off Baja California. Concentrations of the biogenic proxies are higher in the core from 430 m depth, but erratic sediment accumulation before 15 ka precludes dating of the older intervals that are laminated and contain elevated orgC, Cd, and Mo concentrations. The new data provide further evidence of an intimate teleconnection between global climate and the intensity of the OMZ and/or productivity along the western margin of North America. On the basis of a comparison with Cd and Mo records collected elsewhere in the region, we conclude that productivity may actually have varied off southern Baja California by no more than a factor of 2 over the past 52 kyr. VL - 21 SN - 0883-8305 IS - 4 N1 - 110idTimes Cited:34 Cited References Count:68 JO - Paleoceanography ER - TY - JOUR T1 - Sedimentary facies and climate control on formation of vivianite and siderite microconcretions in sediments of Lake Baikal, Siberia JF - Journal of Paleolimnology Y1 - 2006 A1 - Sapota, T. A1 - Aldahan, A. A1 - Al-Aasm, I. S. AB - Authigenic vivianite and siderite microconcretions were found, respectively, in hemipelagic and deltaic facies of 600-m-long BDP-98 sediment section from Lake Baikal. Textural investigations of these microconcretions show that they are typically < 1 mm in size, irregular in shape and composed of aggregated crystallites. Dissimilar orientation of vivianite and siderite crystallites suggests formation at different depths in the sediment; up to tens of centimeters for vivianite and tens of meters for siderite. Chemical analyses of both the vivianite and the siderite indicate cation composition characterized by minor amounts of Mn, Ca and Mn apart from the dominating Fe. Rather limited and distinctive carbon isotopic composition of the siderite, with delta C-13(VPDB) values between about +13 and +16 degrees, implies formation of the mineral in the methanogenic zone of diagenesis. Isotopic composition of oxygen in the siderite (delta O-18(VPDB) values between about -10 and -11 degrees) is consistent with crystallization temperature at about 10-30 degrees C and water delta O-18(SMOW) values between about -10 and -16 degrees. The distribution of the authigenic minerals in the section suggests changes in both sedimentary facies and climate, where vivianite formation was controlled by hemipelagic depositional conditions during the Pliocene and Quaternary, whereas siderite reflects impact of deltaic conditions during the Miocene. VL - 36 IS - 3 N1 - 092qrTimes Cited:32Cited References Count:37 JO - Sedimentary facies and climate control on formation of vivianite and siderite microconcretions in sediments of Lake Baikal, Siberia ER - TY - JOUR T1 - Sedimentary features of the Yangtze River-derived along-shelf clinoform deposit in the East China Sea JF - Continental Shelf Research Y1 - 2006 A1 - Liu, J. P. A1 - Li, A. C. A1 - Xu, K. H. A1 - Veiozzi, D. M. A1 - Yang, Z. S. A1 - Milliman, J. D. A1 - DeMaster, D. AB - A predominant sigmoidal clinoform deposit extends from the Yangtze River mouth southwards 800 kin along the Chinese coast. This clinoform is thickest (similar to 40m) between the 20 and 30 m isobaths and progressively thins offshore, reaching water depths of 60 and 90 m and distances up to 100 km offshore. Clay mineral, heavy metal, geochemical and grain-size analyses indicate that the Yangtze River is the primary source for this longshore-transported clinoform deposit. (210)Pb chronologies show the highest accumulation rates (> 3 cm/yr) occur immediately adjacent to the Yangtze subaqueous delta (north of 30 degrees N), decreasing southward alongshore and eastward offshore. The interaction of strong tides, waves, the China Coastal Current, winter storms, and offshore upwelling appear to have played important roles in trapping most Yangtze-derived sediment on the inner shelf and transporting it to the south. (c) 2006 Elsevier Ltd. All rights reserved. VL - 26 IS - 17-18 N1 - 109ueTimes Cited:158Cited References Count:62 JO - Sedimentary features of the Yangtze River-derived along-shelf clinoform deposit in the East China Sea ER - TY - JOUR T1 - Sedimentology, physical properties and age of mass transport deposits associated with the Marques de Pombal Fault, Southwest Portuguese Margin JF - Norwegian Journal of Geology Y1 - 2006 A1 - Vizcaino, Alexis A1 - Gracia, Eulalia A1 - Pallas, Raimon A1 - Garcia-Orellana, Jordi A1 - Escutia, Carlota A1 - Casas, David A1 - Willmott, Veronica A1 - Diez, Susana A1 - Asioli, Alessandra A1 - Danobeitia, Juanjo VL - 86 N1 - id: 623 ER - TY - CONF T1 - Shell fragmentation as an indicator of benthic conditions T2 - GSA Annual Meeting Y1 - 2006 A1 - Best, Mairi M. R. A1 - Bibeau, Karine A1 - Spitzberg, Daniel A1 - Thomas, Ellen A1 - Varekamp, Johan C. A1 - Bernatis, Jennifer JF - GSA Annual Meeting CY - Philadelphia, PA N1 - id: 749 ER - TY - JOUR T1 - Solid-state 13C NMR analysis of size and density fractions of marine sediments: Insight into organic carbon sources and preservation mechanisms JF - Geochimica et Cosmochimica Acta Y1 - 2006 A1 - Dickens, A. F. A1 - Baldock, J. A. A1 - Smernik, R. J. A1 - Wakeham, S. G. A1 - Arnarson, T. S. A1 - Gelinas, Y. A1 - Hedges, J. I. VL - 70 N1 - id: 1702 ER - TY - JOUR T1 - Source and transport of terrigenous organic matter of the upper Yukon River: evidence from isotope (13C, 14C and 15N) composition of dissolved, colloidal and particulate phases JF - Global Biogeochemical Cycles Y1 - 2006 A1 - Guo, L. A1 - Macdonald, R. W. VL - 20 N1 - id: 1129 ER - TY - CONF T1 - Sources age and composition of dissolved and particulate organic matter delivered to a passive margin river system T2 - ASLO/AGU Ocean Science Meeting Y1 - 2006 A1 - Petsch, S. T. A1 - Gordon, E. S. A1 - Longworth, B. E. A1 - Schillawki, S. E. A1 - Raymond, P. A. JF - ASLO/AGU Ocean Science Meeting CY - Honolulu, HI N1 - id: 485 ER - TY - JOUR T1 - Sources and potential transformation of estuarine dissolved and particulate organic matter: a multi-tracer approach JF - Organic Geochemistry Y1 - 2006 A1 - McCallister, S. L. A1 - Bauer, J. E. A1 - Ducklow, H. W. A1 - Canuel, E. A. VL - 37 N1 - id: 597 ER - TY - CONF T1 - Sources, fate and turnover of terrestrial organic carbon in rivers (Lecture) T2 - Organic Geochemistry Gordon Conference Y1 - 2006 A1 - Raymond, P. A. A1 - Oh, N. H. JF - Organic Geochemistry Gordon Conference CY - Plymouth, NH N1 - id: 491 ER - TY - CONF T1 - Sources, fate and turnover of terrestrial organic carbon in rivers T2 - Goldschmidt Conference Y1 - 2006 A1 - Raymond, P. A. JF - Goldschmidt Conference CY - Melbourne, Australia N1 - id: 489 ER - TY - JOUR T1 - Spacial and temporal variation in cores from Lake Titicaca, Bolivia/Peru during the last 13,000 yrs JF - Quaternary International Y1 - 2006 A1 - Fritz, S. C. A1 - Baker, P. A. A1 - Tapia, P. A1 - Garland, J. VL - 158 N1 - id: 588 ER - TY - RPRT T1 - Stable carbon isotopes in coastal Puerto Rico corals and adjacent natural waters: implications for land-ocean connectivity and land-use history Y1 - 2006 A1 - Moyer, R. P. A1 - Grottoli, A. G. JF - Ocean Sciences Meeting CY - Honolulu VL - Abstract #OS25J-14 N1 - id: 655 ER - TY - JOUR T1 - Stable isotopes from marine shells, ancient environments, and human subsistence on Middle Holocene Santa Rosa Island, California, U.S.A JF - Journal of Island and Coastal Archaeology Y1 - 2006 A1 - Rick, Torben C. A1 - Robbins, John A. A1 - Ferguson, Kurth M. VL - 1 N1 - id: 578 ER - TY - JOUR T1 - Submarine earthquake geology along the North Anatolia Fault in the Marmara Sea, Turkey: A model for transform basin sedimentation JF - Earth and Planetary Science Letters Y1 - 2006 A1 - McHugh, C. M. G. A1 - Seeber, L. A1 - Cormier, M. H. A1 - Dutton, J. A1 - Cagatay, N. A1 - Polonia, A. A1 - Ryan, W. B. F. A1 - Gorur, N. AB - The submerged portions of the North Anatolia Fault system beneath the Marmara Sea were studied with high-resolution multibeam bathymetry, subbottom profiling and sediment cores. The major objectives were to learn about the seismic and tectonic history of the fault from the stratigraphic record at a scale similar to paleoseismic studies on land and to develop tools for submarine earthquake geology that can be applied to fault-controlled basins in general. We focused on Holocene sediment in several Marmara Sea basins of different sizes. The approach was to test whether: (1) the depocenters of the larger basins contain a record of all historic Ms > 7 earthquakes within the Marmara Sea region; (2) the small transform basins record earthquakes that rupture through them; (3) vertical and strike-slip Holocene deformation can be quantified; and (4) the effects of an earthquake generally includes both primary structural features due to rupture of the sea floor, such as strata offset, scarps and tilting, as well as secondary effects due to shaking, such as mass-wasting and gravitational flows. We found evidence of earthquakes that we correlate with historic events in 181 AD, 740 AD, 1063 AD, 1343 AD, 1509 AD, 1766 AD, 1894 AD and 1912 AD. The geologic evidence is primarily from those basins adjacent to the rupture as inferred from historic data. This suggests that coseismic deformation of the sea floor along the rupture is a critical factor in the sedimentary record. We propose a qualitative sedimentation model that relates this coseismic deformation to mass-wasting of the slope, scour of the basin floor, seiche motions and homogenite deposition. Frequent earthquake activity sheds sediments from the flanks, contributes to the much thicker sediment on the basin floor and decreases the likelihood of sediment failures in response to normal marine gravity-driven processes. The surveying techniques and approaches used have therefore the potential of documenting earthquake ruptures of fault segments and to extend the earthquake record far before the known history, thus improving hazard evaluations and the fundamental understanding of earthquake process. (c) 2006 Elsevier B.V. All rights reserved. VL - 248 IS - 3-4 N1 - 085kgTimes Cited:55Cited References Count:98 JO - Submarine earthquake geology along the North Anatolia Fault in the Marmara Sea, Turkey: A model for transform basin sedimentation ER - TY - JOUR T1 - Temporal and spatial complexity in post-glacial shelf sedimentation on the tectonically active, Poverty Bay continental margin of New Zealand JF - Continental Shelf Research Y1 - 2006 A1 - Orpin, A. R. A1 - Alexander, C. A1 - Carter, L. A1 - Kuehl, S. A1 - Walsh, J. P. VL - 26 N1 - id: 634 ER - TY - JOUR T1 - Tracking the weathering of an oil spill with comprehensive two-dimensional gas chromatography JF - Environmental Forensics Y1 - 2006 A1 - Nelson, R. K. A1 - Kile, B. M. A1 - Plata, D. L. A1 - Sylva, S. P. A1 - Xu, L. A1 - Reddy, C. M. A1 - Gaines, R. B. A1 - Frysinger, G. S. A1 - Reichenbach, S. E. AB - Comprehensive two-dimensional gas chromatography (GC x GC) was used to investigate the Bouchard 120 oil spill. The latter occurred on April 25, 2003, when the barge Bouchard 120 spilled similar to 375,000 liters of No. 6 fuel oil into Buzzards Bay, Massachusetts. In order to gain a better understanding of the natural processes affecting the fate of the spilled product, we collected and analyzed oil-covered rocks from Nyes Neck beach in North Falmouth, Massachusetts. Here we discuss the data from samples collected on May 9, 2003, and six months later, on November 23, 2003. Along with standard two-dimensional gas chromatographic analysis, we employed unique data-visualization techniques such as difference, ratio, and addition chromatograms to highlight how evaporation, water washing, and biodegradation weathered the spilled oil. These approaches provide a new perspective to studying oil spills and aid attempts to remediate them. VL - 7 IS - 1 N1 - 032ldTimes Cited:62Cited References Count:21 JO - Tracking the weathering of an oil spill with comprehensive two-dimensional gas chromatography ER - TY - ART T1 - Tsunami sediemnts in coastal lagoons, Sri Lanka: implications for paleotsunamis Y1 - 2006 A1 - Jackson, K. L. A1 - Amelung, F. A1 - Andres, M. S. A1 - Eberli, G. P. A1 - Jayasena, H. A. H. A1 - Kehelpannala, K. V. W. PB - American Association of Petroleum Geologists Abstracts with Programs CY - Houston, TX N1 - id: 665; Annual Meeting ER - TY - CONF T1 - Two ecological shifts in Long Island Sound during the industrial period T2 - Long Island Sound Research Center Y1 - 2006 A1 - Thomas, E. A1 - Varekamp, J. C. A1 - Mecray, E. L. A1 - Buchholtzten-Brink, M. R. L. A1 - Cooper, S. A1 - Brinkhuis, H. A1 - Sangioirgio, F. JF - Long Island Sound Research Center CY - Groton, CT N1 - id: 751 ER - TY - CONF T1 - An updated 14C calibration and activity record for the past 50,000 years from marine Cariaco Basin, Abstract T2 - 19th International Radiocarbon Conference Y1 - 2006 A1 - Hughen, K. A. A1 - Southon, J. A. A1 - Lehman, S. J. A1 - Bertrand, C. J. H. A1 - Turnbull, J. JF - 19th International Radiocarbon Conference CY - Oxford, UK N1 - id: 559 ER - TY - RPRT T1 - Using packrat middens to assess how grazing influences vegetation change in Glen Canyon National Recreation Area, Utah Y1 - 2006 A1 - Fisher, J. A1 - Cole, K. L. A1 - Anderson, R. S. JF - USGS open-file report 2006-1183 N1 - id: 1105 ER - TY - JOUR T1 - Variability in radiocarbon ages of biochemical compound classes of high molecular weight dissolved organic matter in estuaries JF - Estuarine Coastal and Shelf Science Y1 - 2006 A1 - Wang, X. C. A1 - Callahan, J. A1 - Chen, R. F. AB - High molecular weight dissolved organic matter (HMW-DOM, > 1000 Da) represents a major fraction (> 30%) of dissolved organic carbon (DOC) in the ocean and thus plays an important role in the global biogeochemical cycling of carbon and many other elements. Its organic sources and formation mechanisms, however, are still not well understood especially in estuarine and coastal regions where multiple natural and anthropogenic sources contribute to total HMW-DOM. In this paper we report our measurements of natural radiocarbon (C-14) abundances and stable carbon isotope (C-13) compositions of the major biochemical compound classes: amino acids, carbohydrates and lipids separated from eight HMW-DOM samples collected from five US estuaries as part of our on-going study of sources, distribution and transport of chromophoric dissolved organic matter (CDOM) in estuarine and coastal waters. Distinct differences in both C-14 and C-13 values were found among the bulk HMW-DOM samples as well as the individual compound classes. Radiocarbon ages of the major compound classes varied by as much as 27,000 years in a single sample. The calculated average radiocarbon ages of the compound fractions of HMW-DOM indicate that the total lipid fraction is very "old", while the acid-insoluble fraction is slightly younger. Total amino acid and carbohydrate fractions, however, have relatively modern apparent C-14 ages. The significant variability in C-14 ages among the compound classes indicates not only multiple organic carbon sources but also different formation and turnover pathways controlling the cycling of different biochemical components of HMW-DOM in estuarine and coastal waters. (c) 2006 Elsevier Ltd. All rights reserved. VL - 68 IS - 1-2 N1 - 057ogTimes Cited:6Cited References Count:41 JO - Variability in radiocarbon ages of biochemical compound classes of high molecular weight dissolved organic matter in estuaries ER - TY - CONF T1 - Variability in the character, age and reactivity of organic matter exported from rivers and estuaries to ocean margins T2 - Ocean Sciences Meeting Y1 - 2006 A1 - Bauer, J. E. A1 - Cole, J. J. A1 - Caraco, N. F. A1 - Raymond, P. A. A1 - Keesee, E. J. A1 - Fernald, S. A1 - Mull, K. JF - Ocean Sciences Meeting CY - Honolulu, HI N1 - id: 476 ER - TY - CONF T1 - Western Atlantic intertropical convergence zone variability over the last full glacial cycle, Abstract T2 - Eos Trans. AGU 87, Fall Meeting Suppl. Y1 - 2006 A1 - Drenzek, N. A1 - Hughe, K. A1 - Sessions, A. A1 - Bice, M. A1 - Eglinton, T. I. JF - Eos Trans. AGU 87, Fall Meeting Suppl. CY - San Francisco, CA N1 - id: 558 ER - TY - JOUR T1 - Young Danube delta documents stable Black Sea level since the middle Holocene: Morphodynamic, paleogeographic, and archaeological implications JF - Geology Y1 - 2006 A1 - Giosan, L. A1 - Donnelly, J. P. A1 - Constantinescu, S. A1 - Filip, F. A1 - Ovejanu, I. A1 - Vespremeanu-Stroe, A. A1 - Vespremeanu, E. A1 - Duller, G. A. T. AB - New radiocarbon and optical dates show that the Holocene Danube delta started to build out of a Black Sea embayment similar to 5200 yr ago. Delta lobe development phases differ by as much as 5 k.y. from previously proposed ages. The new chronology allows for a better understanding of the Danube delta paleogeography, including the demise of Istria, the main ancient Greek-Roman city in the region. Prior reconstructions of sea level in the Black Sea inferred fluctuations to 15 m in range; however, stratigraphy of beach ridges in the delta shows that the relative Black Sea level for the past 5 k.y. was stable in the Danube delta region within -2 m and +1.5 of the current level. Hydroisostatic effects related to a proposed catastrophic reconnection of the Black Sea to the World Ocean in the early Holocene may have been responsible for the sea level reaching the highstand earlier than estimated by models. The new sea-level data suggest that submergence at several ancient settlements around the Black Sea may be better explained by local factors such as subsidence rather than by basin-wide sea-level fluctuations. VL - 34 IS - 9 N1 - 084aqTimes Cited:63Cited References Count:35 JO - Young Danube delta documents stable Black Sea level since the middle Holocene: Morphodynamic, paleogeographic, and archaeological implications ER - TY - JOUR T1 - A 17,000 year history of Andean climatic and vegetation change from Laguna de Chochos, Peru JF - Journal of Quaternary Science Y1 - 2005 A1 - Bush, M. B. A1 - Hansen, B. C. S. A1 - Rodbell, D. T. A1 - Seltzer, G. O. A1 - Young, K. R. A1 - Leon, B. A1 - Abbott, M. B. A1 - Silman, M. R. A1 - Gosling, W. D. AB - The manifestation of major climatic events such as the timing of deglaciation and whether, or not, the Younger Dryas affected Andean systems has garnered considerable recent attention. Even the Holocene is rapidly emerging as a time of considerable interest in Neotropical palaeoclimatology and palaeoecology. The Holocene of the Neotropics is now revealed as a time of some temperature change with precipitation:evaporation ratios fluctuating markedly. Major changes in lake level, ice-accumulation, and vegetation are indicative of changes both in precipitation and temperature regimes. Although global-scale forcing mechanisms may underlie some of these changes, e.g. the precessional rhythm, other variability appears to be localised. In a record from near the upper forest limit of the eastern Peruvian Andes, pollen, charcoal, and sedimentary data suggest that the deglaciational period from ca. 17 000 to ca. 11 500 cal. yr BP was a period of rapid climatic oscillations, set against an overall trend of warming. A warm-dry event is evident between ca. 9500 and ca. 7300 cal. yr BP, and comparisons with other regional archives suggest that it was regional in scale. A ca. 1500-yr periodicity in the magnetic susceptibility data is evident between 12 000 and 6000 cal. yr BP, reaching a peak intensity during the dry event. A weaker oscillation with a 500–600-yr periodicity is present throughout much of the Holocene. The uppermost sample of the pollen analysis reveals deforestation as modern human land use simplified the landscape. VL - 20 IS - 7-8 N1 - id: 1015 JO - A 17,000 year history of Andean climatic and vegetation change from Laguna de Chochos, Peru ER - TY - JOUR T1 - A 2000-year reconstruction of forest disturbance from southern Pacific Costa Rica JF - Palaeogeography Palaeoclimatology Palaeoecology Y1 - 2005 A1 - Anchukaitis, K. J. A1 - Horn, S. P. AB - We reconstruct prehistoric and historic human forest disturbance and vegetation change in southern Pacific Costa Rica, in the vicinity of the Las Cruces Biological Station and the La Amistad International Park and Biosphere Reserve. Pollen and charcoal in sediments from Laguna Santa Elena reveal a nearly continuous record of human alteration of these tropical forests over the past two millennia. The basal portion of the core shows nearly intact premontane forests approximately 1800 cal. year B.P., although there is evidence of human presence on the landscape in the form of maize pollen and charcoal. Clearing for agriculture resulted in the dominance of disturbance taxa in the watershed beginning at least 1400 cal. year B.P. The pollen record reveals a possible, brief hiatus in human occupation of the watershed at approximately 540 cal. year B.P., although secondary succession began to occur in the Laguna Santa Elena watershed prior to that time, beginning about 700 cal. year B.P. Three eruptions of nearby Volcan Baru which we date to approximately 610, 1080, and 1440 cal. year B.P., apparently had little direct effect on the prehistoric populations in the immediate vicinity of the lake. Historic and modern land clearance has perpetuated a modem vegetation assemblage of disturbance and successional taxa, (c) 2005 Elsevier B.V. All rights reserved. VL - 221 IS - 1-2 N1 - id: 1112; 931QJ Times Cited:14 Cited References Count:114 JO - A 2000-year reconstruction of forest disturbance from southern Pacific Costa Rica ER - TY - CONF T1 - A 2.45 GHz Ion Source for use in Accelerator Mass Spectrometry T2 - 11th International Conference on Ion Ssources Y1 - 2005 A1 - von Reden, K. F. A1 - Schneider, R. J. A1 - Roberts, M. L. A1 - Han, B. X. A1 - Wills, J. JF - 11th International Conference on Ion Ssources CY - Caen, France N1 - id: 1707 ER - TY - CONF T1 - 3-D Electromagnetic Field Modeling and Ion Optics Calculations for a Continuous-Flow AMS System T2 - 10th International Conference on Accelerator Mass Spectrometry Y1 - 2005 A1 - Han, B. X. A1 - von Reden, K. F. A1 - Roberts, M. L. A1 - Schneider, R. J. A1 - Hayes, J. M. JF - 10th International Conference on Accelerator Mass Spectrometry CY - Berkeley, California N1 - id: 1708 ER - TY - JOUR T1 - The 8200 year B. P. event in the slop water system, western sublpolar North Atlantic JF - Paleoceanography Y1 - 2005 A1 - Keigwin, L. D. A1 - Sachs, J. P. A1 - Rosenthal, Y. A1 - Boyle, E. A. VL - 20 N1 - id: 1097 ER - TY - JOUR T1 - Abundance, composition, and vertical transport of PAHs in marsh sediments JF - Environ Sci Technol Y1 - 2005 A1 - White, H. K. A1 - Xu, L. A1 - Lima, A. L. A1 - Eglinton, T. I. A1 - Reddy, C. M. AB - Petroleum-derived hydrocarbons continue to persist in Wild Harbor, West Falmouth, MA, following a spill of No. 2 fuel oil in 1969 from the barge Florida. Recent analysis of marsh sediments revealed that residues of degraded oil are present with concentrations of total petroleum hydrocarbons as high as approximately 9 mg g(-1). Polycyclic aromatic hydrocarbons (PAHs) constitute only a minor fraction of these residues with maximum concentrations of 134 mirog g(-1), but their fate is of interest because of their potential toxicity to organisms. As compared to typical unweathered No. 2 fuel oil, the current distribution of PAHs in the sediments reflects substantial weathering by abiotic and biotic processes, specifically a preferential loss of naphthalenes relative to phenanthrenes, as well as isomer-specific biodegradation of alkylated PAHs. Based on comparison to results from an earlier study, it appears that little or no change has occurred to the distribution of PAHs since 1989, indicating that weathering at this site has stalled or is now proceeding at a significantly slower rate. To assess whether sediment-water partitioning and molecular diffusion in the interstitial medium are now the dominant processes controlling the vertical distribution of PAHs, downcore profiles were compared to a numerical model. While in some cases the model accurately reproduced the measured data, there were instances where the distribution of PAHs was slightly under or overestimated. Reasons for these discrepancies are discussed and are likely due to bioturbation, colloid-facilitated transport, or both. Assessment of the influence of these processes on the spilled oil expands our understanding of the overall fate of these compounds and their potential long-term effects on the environment. VL - 39 IS - 21 N1 - White, Helen KXu, LiLima, Ana Lucia CEglinton, Timothy IReddy, Christopher MengResearch Support, Non-U.S. Gov'tResearch Support, U.S. Gov't, Non-P.H.S.2005/11/22 09:00Environ Sci Technol. 2005 Nov 1;39(21):8273-80. JO - Abundance, composition, and vertical transport of PAHs in marsh sediments ER - TY - JOUR T1 - Age and origin of Late Quaternary eolianite, Kaiehu Point (Moomomi), Molokai, Hawaii JF - Journal of Coastal Research Y1 - 2005 A1 - Fletcher, C. H. A1 - Murray-Wallace, C. V. A1 - Glenn, C. R. A1 - Sherman, C. E. A1 - Popp, B. A1 - Hessler, A. KW - Amino acid racemization KW - aminostratigraphy KW - bermuda KW - carbonate lithofacies KW - cementation KW - cliche paleosols KW - eolianite KW - hawaii KW - island KW - Late Quaternary KW - limestone petrology KW - Marine KW - molokai KW - oahu KW - precipitation KW - sea level KW - sea-level KW - south-australia KW - Stable isotopes KW - stratigraphy AB - A well-preserved, vertically stacked succession of two genetically distinct eolianites and associated caliche paleosol units, capped by modern and Holocene coastal dunes, occurs at Kaiehu Point, west Molokai, Hawaii. The Pleistocene eolianite facies comprise well-cemented, medium grained skeletal carbonate sand and their morphostratigraphic context implies formation at times of lower than present sea level. Amino acid racernization (AAR) evidence suggests eolianite formation late in marine Oxygen Isotope Stage (OIS) 5, but lacks the precision to uniquely define in which isotopic substage the deposits formed. Coupled with the AAR results, the morphostratigraphic evidence, would suggest that the Lower Eolianite formed in OIS 5c and the Middle Eolianite during 5a with their superposed caliche paleosols having formed in subsequent stadial stages. The unconsolidated coastal sand dunes of Holocene age contain reworked Late Pleistocene skeletal carbonate sand based on AAR evidence. The most likely source of the reworked carbonate is from the erosion of the eolianites at Kaiehu Point. The Pleistocene eolianite-caliche paleosol sediments reveal variable Mg-content, stable isotope ratios and petrological characteristics consistent with changing degrees of weathering intensity and meteoric diagenesis. These changes are attributed to orographic effects resulting from relative sea-level changes. Accordingly, a two-phase model is favored for the formation of the eolianite-paleosol successions at Kaiehu Point, west Molokai. Eolianite sedimentation is initiated at times of marginally lower sea levels promoting the landward migration of bioclastic sand to form extensive eolian sandsheets. This is followed by a more pronounced phase of pedogenesis associated with a further fall in sea level and concomitant increased rainfall due to enhanced orographic effects. VL - SI SN - 0749-0208 IS - 42 N1 - Sp. Iss. 42947fu Times Cited:3 Cited References Count:50 JO - J Coastal Res ER - TY - JOUR T1 - Age validation of canary rockfish (Sebastes pinniger) from off the Oregon coast (USA) using the bomb radiocarbon method JF - Canadian Journal of Fisheries and Aquatic Sciences Y1 - 2005 A1 - Piner, K. R. A1 - Hamel, O. S. A1 - Menkel, J. L. A1 - Wallace, J. R. A1 - Hutchinson, C. E. AB - The alternating translucent and opaque banding pattern in canary rockfish (Sebastes pinniger) otoliths, aged using a break-and-burn methodology, are annual markings. To validate age assignment, we compared measured radiocarbon levels in canary rockfish otolith cores with a reference chronology developed from known age Pacific halibut (Hippoglossus stenolepis). An average 2- to 3-year phase shift was detected between the canary rockfish and a Pacific halibut reference chronology that was likely the result of differences in the regional oceanography or underageing bias. The assumption of ageing bias consistency was tested with two sampling designs. The first design controled for age-related ageing error, and the second design related birth year to estimated age. No change in the magnitude of ageing bias as a function of age was detected. VL - 62 IS - 5 N1 - 932zxTimes Cited:27Cited References Count:27 JO - Age validation of canary rockfish (Sebastes pinniger) from off the Oregon coast (USA) using the bomb radiocarbon method ER - TY - CONF T1 - The American Mediterranean: the influence of human populations on the ecosystem of Long Island Sound T2 - Living on the Edge Y1 - 2005 A1 - Thomas, E. A1 - Varekamp, J. C. A1 - Thaler, B. A1 - Sangiorgio, F. JF - Living on the Edge VL - Abstract N1 - id: 1184 ER - TY - JOUR T1 - Amplitude and timing of sea-surface temperature change in the northern South China Sea: Dynamic link to the East Asian monsoon JF - Geology Y1 - 2005 A1 - Oppo, D. W. A1 - Sun, Y. B. AB - Magnesium/calcium (Mg/Ca) ratios of foraminiferal shells from a sediment core from the northern South China Sea, a semi-enclosed basin in the western tropical Pacific, document variations in sea-surface temperature (SST) during the past 145 k.y. Glacial SSTs were 4 degrees C colder than interglacial SSTs. During the last deglaciation, most of the warming was accomplished in a single abrupt step after continental ice-sheet decay had already begun, but warming and ice-sheet demise were nearly synchronous during the penultimate deglaciation. Abrupt SST changes of the past 15 k.y. were apparently synchronous with events in East Asian monsoon rainfall, suggesting that variations in monsoon winds and their influence on surface circulation of the western Pacific exerted a strong control on northern South China Sea SSTs. We suggest that this link persisted for the previous 130 k.y., during which time orbital-scale 2-3 degrees C SST changes and several small (<= 2 degrees C) abrupt SST events occurred in the northern South China Sea. The similar timing of northern South China Sea SST, on a benthic delta O-18 time scale, to a well-dated speleothem record from eastern China suggests that the demise of ice sheets associated with the penultimate deglaciation did not precede Northern Hemisphere summer insolation increase. Our results suggest that surface waters had higher delta O-18 values during times of strong summer monsoon than during times of weak monsoon, likely reflecting a redistribution of O-18 depleted rainfall from land during times of strong summer monsoons, to the western Pacific during times of weaker summer monsoons. VL - 33 IS - 10 N1 - 969rmTimes Cited:66Cited References Count:38 JO - Amplitude and timing of sea-surface temperature change in the northern South China Sea: Dynamic link to the East Asian monsoon ER - TY - JOUR T1 - Are bacteria actively degrading petroleum residues from the West Falmouth oil spill? New insights from 14C analysis of bacterial lipids JF - Environmental Science and Technology Y1 - 2005 A1 - Slater, G. F. A1 - White, H. K. A1 - Eglinton, T. I. A1 - Reddy, C. M. VL - 39 N1 - id: 1189 ER - TY - JOUR T1 - Assessing in situ mineralization of recalcitrant organic compounds in vadose zone sediments using delta(13)C and (14)C measurements JF - Journal of Contaminant Hydrology Y1 - 2005 A1 - Kirtland, B. C. A1 - Aelion, C. M. A1 - Stone, P. A. AB - Few techniques exist to measure the biodegradation of recalcitrant organic compounds such as chlorinated hydrocarbons (CHC) in situ, yet predictions of biodegradation rates are needed for assessing monitored natural attenuation. Traditional techniques measuring O(2), CO(2), or chemical concentrations (in situ respiration, metabolite and soil air monitoring) may not be sufficiently sensitive to estimate biodegradation rates for these compounds. This study combined isotopic measurements ((14)C and delta(13)C Of CO(2) and delta(13)C of CHCs) in conjunction with traditional methods to assess in situ biodegradation of perchloroethylene (PCE) and its metabolites in PCE-contaminated vadose zone sediments. CHC, ethene, ethane, methane, O(2), and CO(2) concentrations were measured over 56 days using gas chromatography (GC). 613C of PCE, trichloroethylene (TCE) and cis- 1,2-dichloroethylene (DCE), delta(13)C and (14)C of vadose zone CO(2) and sediment organic matter, and delta(13)C, (14)C, and deltaD of methane were measured using a GC-isotope ratio mass spectrometer or accelerator mass spectrometer. PCE metabolites accounted for 0.2% to 18% of CHC concentration suggesting limited reductive dechlorination. Metabolites TCE and DCE were significantly enriched in (13)C with respect to PCE indicating metabolite biodegradation. Average delta(13)C-CO(2) in source area wells (-23.5parts per thousand) was significantly lower compared to background wells (- 18.4%o) indicating CHC mineralization. Calculated CHC mineralization rates were 0.003 to 0.01 mg DCE/kg soil/day based on lower (14)C values Of CO(2) in the contaminated wells (63% to 107% modem carbon (pMC) relative to the control well (117 pMC). Approximately 74% of the methane was calculated to be derived from in situ CHC biodegradation based on the (14)C measurement of methane (29 pMC). (14)C-CO(2) analyses was a sensitive measurement for quantifying in situ recalcitrant organic compound mineralization in vadose zone sediments for which limited methodological tools exist. (C) 2004 Elsevier B.V All rights reserved. VL - 76 IS - 1-2 N1 - 883lpTimes Cited:11Cited References Count:52 JO - Assessing in situ mineralization of recalcitrant organic compounds in vadose zone sediments using delta(13)C and (14)C measurements ER - TY - CONF T1 - Assessing variability in the character and reactivity of DOM and POM delivered to the oceans by rivers and estuaries T2 - Gordon Research Conference on Chemical Oceanography Y1 - 2005 A1 - Bauer, J. E. JF - Gordon Research Conference on Chemical Oceanography CY - Meredith, NH N1 - id: 1025 ER - TY - JOUR T1 - Bacterial incorporation of relict carbon in the hydrothermal environment of Guaymas Basin JF - Geochimica Et Cosmochimica Acta Y1 - 2005 A1 - Pearson, A. A1 - Seewald, J. S. A1 - Eglinton, T. I. AB - Radiocarbon analyses of bulk carbon and individual organic compounds are presented for the hydrothermal environment of the Rebecca's Roost vent in the southern trough of the Guaymas Basin hydrothermal field. The Delta(14)C values of CO, and CH4 in the hottest hydrothermal fluids (317 degrees C) are nearly "radiocarbon dead" (-944 parts per thousand and -923 parts per thousand, respectively). In contrast, the Delta(14)C values of sediments and individual fatty acids (-418 parts per thousand to -227 parts per thousand) obtained from a bacterial mat located south of the vent site are similar to values previously reported for hydrothermal petroleum in this environment and are more depleted in C-14 than overlying waters. Hydrothermal fluids moving through the sediments appear to supply C-14 of intermediate age to the bacteria. This carbon may take the form of, or may be supplied by processes similar to, the generation of hydrothermal petroleum. Although the bacterial mat visibly was dominated by Beggiatoa spp., such mats are known to include numerous other species. Individual compound data show that preaged carbon is being consumed by the integrated bacterial assemblage. Values of delta(13)C and Delta(14)C indicate that petroleum-derived carbon is incorporated directly into fresh bacterial biomass. Subsequently, some of this newly synthesized material also is consumed by heterotrophs, as eukaryotic sterols from the same sample also have C-14-depleted values (Delta(14)C = -136 parts per thousand to -110 parts per thousand). Therefore, the entire system may operate as a complex consortium to transform relict carbon back into biomass. Bacterial consumption of relict carbon occurs despite the ample supply of fresh carbon delivered from the productive, overlying water column. Copyright (c) 2005 Elsevier Ltd. VL - 69 IS - 23 N1 - 999tpTimes Cited:36Cited References Count:69 JO - Bacterial incorporation of relict carbon in the hydrothermal environment of Guaymas Basin ER - TY - JOUR T1 - Basal inflection-control led shelf-edge wedges off New Jersey track sea-level fall JF - Geology Y1 - 2005 A1 - Gulick, S. P. S. A1 - Goff, J. A. A1 - Austin, J. A. A1 - Alexander, C. R. A1 - Nordfjord, S. A1 - Fulthorpe, C. S. AB - A key marker for examining the latest Pleistocene history of the New Jersey margin is the high-amplitude, long-recognized R-horizon reflector. This time-transgressive surface was formed 4733 ka and represents the integrated topographic and bathymetric surface developed during the complicated sea-level oscillation associated with the regression that preceded the Last Glacial Maximum (LGM). From landward to seaward across the outer shelf, the R reflector changes from subhorizontal, in most locations < 9 m beneath the modern seafloor, to seaward dipping, forming the base of two of flapping sediment wedges: the previously described outer-shelf wedge and a deep-shelf wedge seaward of it. This transition occurs across two inflection zones, where the dip of the R reflector steepens seaward, that can be traced for tens of kilometers along strike and mark the landward limits of these wedges. These inflection zones are possibly former wave-dominated shorefaces; these represent the primary topographic elements present during the last regression. We speculate that these inflections dictated both the locations for deposition of the two prograding, of flapping wedges that developed during the complex sea-level fall prior to the LGM and their successive erosion before and after the LGM. We suggest that such inflection zones and their associated wedges are important markers of regression in clastic-dominated outer-shelf settings along passive margins. VL - 33 IS - 5 N1 - 922awTimes Cited:19Cited References Count:24 JO - Basal inflection-control led shelf-edge wedges off New Jersey track sea-level fall ER - TY - JOUR T1 - Basin-wide sedimentation changes and deglacial lake-level rise in the Hovsgol basin, NW Mongolia JF - Quaternary International Y1 - 2005 A1 - Prokopenko, A. A. A1 - Kuzmin, M. I. A1 - Wlliams, D. F. A1 - Gelety, V. F. A1 - Kalmychkov, G. V. A1 - Gvozdkov, A. N. A1 - Solotchin, P. A. AB - A study of 15 gravity cores reveals consistent patterns of lithologic change throughout the Lake Hovsgol basin. Sediments of the last glacial are composed of calcareous clayey silt with an admixture of coarse material from sand to gravel. During the last deglaciation, a basin-wide deposition of finely laminated carbonate mud took place and was ultimately succeeded by the deposition of diatomaccous clayey ooze during the entire Holocene interval. Diatom productivity in Lake Hovsgol during the early Holocene was higher than today, but declined by ca. 6.6 cal ka BP. Sedimentation rate estimates for post-glacial section range from 1.5 to over 6.7 cm/ka for different parts of Lake Hovsgol. Rates appear to have decreased in the late Holocene.The last glacial maximum (LGM) corresponded to a dramatic low stand of Lake Hovsgol on the order of 100 m below today's level, as reflected by littoral facies retrieved in cores from intermediate depths. Age dating of plant fragments in these sediments suggests that lake level started rising no later than 15.4 cal ka BP. By the beginning of the Holocene, Lake Hovsgol evolved from a low-level closed basin lake to an overflowing freshwater lake. The observed dramatic lithologic change and evidence for lake-level change suggest that Lake Hovsgol may in fact serve as a sensitive 'water gauge' in continental interior Asia and that the Hovsgol sedimentary record preserves reliable proxies for past changes in effective moisture balance in the Lake Baikal catchment area. (c) 2004 Elsevier Ltd and INQUA. All rights reserved. VL - 136 N1 - 926rlTimes Cited:51Cited References Count:16 JO - Basin-wide sedimentation changes and deglacial lake-level rise in the Hovsgol basin, NW Mongolia ER - TY - JOUR T1 - Beads, bifaces, and boats: an early maritime adaptation on the south coast of San Miguel Island, California JF - American Anthropologist Y1 - 2005 A1 - Erlandson, Jon M. A1 - Braje, Todd J. A1 - Rick, Torben C. A1 - Peterson, Jenna VL - 107 IS - 4 N1 - id: 442 ER - TY - CONF T1 - Beam Profile Measurements for a MC-SNICS Source with Spherical Ionizer T2 - 10th International Conference on Accelerator Mass Spectrometry Y1 - 2005 A1 - von Reden, K. F. A1 - Griffin, V. S. A1 - Roberts, M. L. JF - 10th International Conference on Accelerator Mass Spectrometry CY - Berkeley, California N1 - id: 1706 ER - TY - JOUR T1 - Biogeochemical investigations of marine methane seeps, Hydrate Ridge, Oregon JF - Journal of Geophysical Research-Biogeosciences Y1 - 2005 A1 - Valentine, D. L. A1 - Kastner, M. A1 - Wardlaw, G. D. A1 - Wang, X. C. A1 - Purdy, A. A1 - Bartlett, D. H. KW - anaerobic oxidation KW - authigenic carbonates KW - cascadia convergent margin KW - community structure KW - dissolved organic-carbon KW - fluid-flow KW - ne pacific KW - odp site 892b KW - phylogenetic analysis KW - sulfate-reducing bacteria AB - [1] A series of biogeochemical studies were conducted at the southern summit of Hydrate Ridge, offshore Oregon. Using the submersible DSV Alvin, sediment push cores were collected from two distinct seep environments characterized by the presence of clam fields (CF) or microbial mats (MM) at the sediment-water interface; samples were also collected from a nearby reference site characterized by a barren surface at the sediment-water interface. Sediment samples from each setting were analyzed for the depth distributions of total organic carbon (concentrations, delta C-13 and Delta C-14), total sedimentary nitrogen, and microbial abundance. Pore fluids were extracted and analyzed for sulfate, alkalinity, sulfide, organic carbon, and volatile organic acids. These depth distributions clearly indicate the presence of three distinctive biogeochemical settings in the surface sediments of Hydrate Ridge, and provide the basis for a comparative biogeochemical analysis. Both CF and MM sites display properties indicating enhanced microbial activity in the subsurface, compared with the reference site. MM sites display evidence of net biomass production in the subsurface; however, a loss of sediment nitrogen relative to the reference site indicates that mineralization is also enhanced. Calculations based on the removal of nitrogen indicate that greater than 30% of autochthonous organic material is lost to enhanced mineralization in the top 23 cm of one MM site. An isotope mass balance of sediment-bound organic carbon indicates a mixed source, including methane and allochthonous organic carbon dissolved in the seep fluids. The concentrations of organic carbon dissolved in seep fluids reach values of 22 mM and provide a first indication that advective transport of dissolved organic carbon from great depth may supply an important source of energy and carbon to "methane seep'' communities. VL - 110 SN - 0148-0227 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=Alerting&SrcApp=Alerting&DestApp=WOS&DestLinkType=FullRecord;UT=WOS:000240984200001 IS - G2 N1 - 090wnTimes Cited:19 Cited References Count:72 JO - J Geophys Res-Biogeo ER - TY - JOUR T1 - Blank correction for Delta 14C measurements in organic compound classes of oceanic particulate matter JF - Radiocarbon Y1 - 2005 A1 - Hwang, Jeomshik A1 - Druffel, Ellen R. M. VL - 47 IS - 1 N1 - id: 1054 ER - TY - JOUR T1 - Calculation of hydrogen isotopic fractionations in biogeochemical systems JF - Geochimica Et Cosmochimica Acta Y1 - 2005 A1 - Sessions, A. L. A1 - Hayes, J. M. AB - Hydrogen-isotopic data are often interpreted using mathematical approximations originally intended for other isotopes. One of the most common. apparent in literature over the last several decade's. assumes that delta values of reactants and products are separated by a constant fractionation factor delta(p) = delta(r) + epsilon(p/r). Because of the large fractionations that affect hydrogen isotopes, such approximations can lead to substantial errors. Here we review and develop general equations for isotopic mass balances that include the differential fractionation of each component in a mixture and discuss their use in three geochemical applications. For the fractionation of a single component. the reactant and product are related by delta(p) = a(p/r)delta(r) + epsilon(p/r), where alpha and epsilon refer to the same fractionation. Regression of delta(p) on delta(r) should give equivalent fractionations based on the intercept and slope, but this has not generally been recognized in studies of D/H fractionation. In a mixture of two components, each of which is fractionated during mixing, there is no unique solution for the three unknown variables (two fractionation factors and the elemental mixing ratio of the two hydrogen sources). The flow of H from CH4 and H2O to bacterial lipids in the metabolism of Methylococcus capsulatus provides an example of such a case. Data and conclusions from an earlier study of that system (Sessions et al., 2002) are reexamined here. Several constraints on the variables are available based on plausible ranges for fractionation factors. A possible refinement to current experimental procedures is the measurement of three different isotopes, which would allow unique determination of all variables. Copyright (C) 2005 Elsevier Ltd. VL - 69 IS - 3 N1 - 892wiTimes Cited:55Cited References Count:21 JO - Calculation of hydrogen isotopic fractionations in biogeochemical systems ER - TY - JOUR T1 - Carbon and nitrogen isotope compositions of organic matter in coastal marine sediments (the Gulf of Trieste, N Adriatic Sea): indicators of sources and preservation JF - Marine Chemistry Y1 - 2005 A1 - Ogrinc, N. A1 - Fontolan, G. A1 - Faganeli, J. A1 - Covelli, S. AB - Terrestrial organic carbon (OC) preserved in marine sediments is an important reservoir in the global carbon cycle, but remains poorly constrained. We determined the elemental and C- and N-isotopic compositions of organic material (OM) in surface sediments and sediment cores from the Gulf of Trieste (N Adriatic), an area characterized by relatively high riverine input. This multiple tracer approach permits evaluation of how sensitive each tracer is for constraining the terrestrial component of OM. Using the relevant terrestrial and marine OM end-members, we estimate that the terrestrial contribution ranges from about 90% at the mouth of the Isonzo River and decreases to <= 10% in the center of the Gulf. In the southern part of the Gulf, 32-44% of terrestrial OC is contributed from smaller rivers, while the delta(15)N values of OM reflect more effective nutrient utilization. Analyses of different size fractions show that smaller particles are consistently more organic-rich and tend to be transported further from the river mouth, depending on river discharge. In the size fraction 2-16 mu m, elemental ratios and delta(13)C(org) and delta(15)N isotopic signatures are consistent with a sedimentary OM pool dominated by bacterially derived biomass. Radiocarbon analyses of sedimentary OC yield depleted Delta(14)C values (-338.7 parts per thousand to -429.4 parts per thousand), indicating a significant fraction of relatively old OC. The natural abundance of C-13 and C-14 tracers suggests a two-component mixture of ancient and modem C in the sediments down to approximately 60 cm sub-bottom, with an estimated similar to 45% of sedimentary OC probably being derived from ancient sedimentary OC (kerogen). In addition, there is a significant change in the source of organic material downcore in these sediments which, along with geological evidence, indicate contributions from freshwater swamps typical of coastal lakes with intermittent connections to the sea (brackish) prior to similar to 9000 BP. Depth variations in a core from a salt marsh further indicate temporal variability of OM deposition and transformations in a changing brackish-marine environment in the past. (C) 2004 Elsevier B.V. All rights reserved. VL - 95 IS - 3-4 N1 - 934goTimes Cited:76Cited References Count:77 JO - Carbon and nitrogen isotope compositions of organic matter in coastal marine sediments (the Gulf of Trieste, N Adriatic Sea): indicators of sources and preservation ER - TY - JOUR T1 - Carbon isotopes from fossil packrat pellets and elevational movements of Utah agave plants reveal the Younger Dryas cold period in Grand Canyon, Arizona JF - Geology Y1 - 2005 A1 - Cole, K. L. A1 - Arundel, S. T. AB - Carbon isotopes in rodent fecal pellets were measured on packrat (Neotoma spp.) middens from the Grand Canyon, Arizona. The pellet samples reflect the abundance of cold-intolerant C4 and Crassulacean acid metabolism (CAM) plant species relative to the predominant C3 vegetation in the packrat diet. The temporal sequence of isotopic results suggests a temperature decline followed by a sharp increase corresponding to the Boiling/ Allerod-Younger Dryas-early Holocene sequence. This pattern was then tested using the past distribution of Utah agave (Agave utahensis). Spatial analyses of the range of this temperature-sensitive CAM species demonstrate that its upper elevational limit is controlled by winter minimum temperature. Applying this paleotemperature proxy to the past ellevational limits of Utah agave suggests that minimum winter temperatures were similar to 8 degrees C below modern values during the Last Glacial Maximum, 4.5-6.5 degrees C below modern during the Bolling/Allerod, and 7.5-8.7 degrees C below modern during the early Younger Dryas. As the Younger Dryas terminated, temperatures warmed similar to 4 degrees C between ca. 11.8 ka and 11.5 ka. These extreme fluctuations in winter minimum temperature have not been generally accepted for terrestrial paleoecological records from the and southwestern United States, likely because of large statistical uncertainties of older radiocarbon results and reliance on proxies for summer temperatures, which were less affected. VL - 33 IS - 9 N1 - 960jfTimes Cited:22Cited References Count:26 JO - Carbon isotopes from fossil packrat pellets and elevational movements of Utah agave plants reveal the Younger Dryas cold period in Grand Canyon, Arizona ER - TY - CONF T1 - Carbon Isotopes in Riverine Systems T2 - Lindeman Speaker, Department of Ecology, Evolution and Behavior Y1 - 2005 A1 - Raymond, P. A. JF - Lindeman Speaker, Department of Ecology, Evolution and Behavior CY - University of Minnesota N1 - id: 487 ER - TY - JOUR T1 - Catastrophic meltwater discharge down the Hudson River Valley: A potential trigger for the Intra-Allerod cold period JF - Geology Y1 - 2005 A1 - Donnelly, J. P. A1 - Driscoll, N. A1 - Uchupi, E. A1 - Keigwin, L. A1 - Schwab, W. A1 - Thieler, E. R. A1 - Swift, S. VL - 33 N1 - id: 1033 ER - TY - JOUR T1 - Coastal foraging at Otter Cave: a 6600 year old shell midden on San Miquel Island, California JF - Journal of California and Great Basin Anthropology Y1 - 2005 A1 - Erlandson, Jon M. A1 - Vellanoweth, Rene L. A1 - Rick, Torben C. A1 - Batterson, Melissa R. VL - 25 N1 - id: 580 ER - TY - JOUR T1 - The composition and transport of organic carbon in rainfall: insights from the natural (13C and 14C) isotopes of carbon JF - Geophysical Research Letters Y1 - 2005 A1 - Raymond, P. A. VL - 32 N1 - id: 599 ER - TY - CHAP T1 - Computer Control T2 - Electrostatic accelerators: fundamentals and applications Y1 - 2005 A1 - Roberts, M. L. ED - Hellborg, R. JF - Electrostatic accelerators: fundamentals and applications PB - Springer SN - 3540239839 N1 - id: 1686 ER - TY - CONF T1 - Continuous-Flow Accelerator Mass Spectrometry T2 - the International Symposium on Utilization of Accelerators Y1 - 2005 A1 - Roberts, M. L. A1 - von Reden, K. F. A1 - Han, B. X. A1 - Schneider, R. J. A1 - Benthien, A. A1 - Hayes, J. M. JF - the International Symposium on Utilization of Accelerators T3 - IAEA-CN-115-09 CY - Dubrovnik Croatia N1 - id: 767 ER - TY - JOUR T1 - Contribution of biomass burning to polycyclic aromatic hydrocarbons in European background aerosols JF - Environmental Science and Technology Y1 - 2005 A1 - Mandalakis, M. A1 - Gustafsson, O. A1 - Alsberg, T. A1 - Reddy, C. A1 - Xu, L. A1 - Klanova, J. A1 - Holoubek, I. A1 - Stephanou, E. VL - 39 IS - 9 N1 - id: 510 ER - TY - JOUR T1 - Cross-formational flow and salinity sources inferred from a combined study of helium concentrations, isotopic ratios, and major elements in the Marshall aquifer, southern Michigan JF - Geochemistry Geophysics Geosystems Y1 - 2005 A1 - Ma, L. A1 - Castro, M. C. A1 - Hall, C. M. A1 - Walter, L. M. AB - Helium data and major ion chemistry are presented for the shallow Marshall aquifer in southern Michigan. This data set is subsequently analyzed in conjunction with major element data sets from deeper and shallower water levels previously collected in this area. He excesses and isotopic ratios suggest the presence of tritiogenic He-3 in young waters in the Marshall aquifer. He excesses in old groundwater samples are mostly of crustal origin although the presence of a significant mantle He component in some samples cannot be ruled out. He excesses in the Marshall aquifer are unusually high for such shallow depths ( <= 300 m) and reach over two and three orders of magnitude above those of air- saturated water ( ASW) for He-3 and He-4, respectively. He isotopes require a source external to the aquifer, partly supplied by underlying formations within the sedimentary sequence, partly from the crystalline basement. Calibration of He concentrations observed in the Marshall aquifer requires He fluxes of 1 x 10(-13) and 1.6 x 10(-6) cm(3) STP cm(-2) yr(-1) for He-3 and He-4, respectively. These He fluxes are far greater than those reported in other sedimentary basins around the world ( e. g., Paris Basin, Gulf Coast Basin) at similar and far greater depths. Such high He fluxes present at such shallow depths within the Michigan Basin strongly suggest the presence of a dominant vertical water flow component and further indicate that impact of recharge water at depth is minor. Upward cross- formational flow is also likely responsible for the extremely high salinities present in the shallow subsurface of the Michigan Basin. The observed positive correlation between helium and bromide strongly suggests that these two very distinct conservative tracers both originate at greater depths and further suggests that advection is the dominant transport mechanism within the basin. The occurrence of large- scale cross- formational flow is also consistent with the evolution displayed by the major ion chemistry throughout most of the sedimentary sequence, indicating that solutes from shallow levels carry the signature of deep formation brines. VL - 6 IS - 10 N1 - 973vwTimes Cited:18Cited References Count:63 JO - Cross-formational flow and salinity sources inferred from a combined study of helium concentrations, isotopic ratios, and major elements in the Marshall aquifer, southern Michigan ER - TY - JOUR T1 - A decrease in discharge-normalized DOC export by the Yukon River during summer through autumn JF - Geophysical Research Letters Y1 - 2005 A1 - Striegl, R. G. A1 - Aiken, G. R. A1 - Dornblaser, M. M. A1 - Raymond, P. A. A1 - Wickland, K. P. KW - alaska KW - arctic-ocean KW - climate-change KW - CO2 KW - discontinuous permafrost KW - dissolved organic-carbon KW - flux KW - MATTER KW - tundra AB - Climate warming is having a dramatic effect on the vegetation distribution and carbon cycling of terrestrial subarctic and arctic ecosystems. Here, we present hydrologic evidence that warming is also affecting the export of dissolved organic carbon and bicarbonate (DOC and HCO3-) at the large basin scale. In the 831,400 km(2) Yukon River basin, water discharge (Q) corrected DOC export significantly decreased during the growing season from 1978 - 80 to 2001 - 03, indicating a major shift in terrestrial to aquatic C transfer. We conclude that decreased DOC export, relative to total summer through autumn Q, results from increased flow path, residence time, and microbial mineralization of DOC in the soil active layer and groundwater. Counter to current predictions, we argue that continued warming could result in decreased DOC export to the Bering Sea and Arctic Ocean by major subarctic and arctic rivers, due to increased respiration of organic C on land. VL - 32 SN - 0094-8276 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=Alerting&SrcApp=Alerting&DestApp=WOS&DestLinkType=FullRecord;UT=WOS:000233354500009 IS - 21 N1 - 985cuTimes Cited:163 Cited References Count:28 JO - Geophys Res Lett ER - TY - JOUR T1 - The deglacial history of surface and intermediate water of the Bering Sea JF - Deep-Sea Research Part Ii-Topical Studies in Oceanography Y1 - 2005 A1 - Cook, M. S. A1 - Keigwin, L. D. A1 - Sancetta, C. A. AB - The lithology of deglacial sediments from the Bering Sea includes intervals of laminated or dysaerobic sediments. These intervals are contemporaneous with the occurrence of laminated sediments from the California margin and Gulf of California, which suggests widespread low-oxygen conditions at intermediate depths in the North Pacific Ocean. The cause could be reduced intermediate water ventilation, increased organic carbon flux, or a combination of the two. We infer abrupt decreases of planktonic foraminifer delta(18)O at 14,400 and 11,650 yr BP, which may be a combination of both freshening and warming. On the Shirshov Ridge, the abundance of sea-ice diatoms of the genus Nitzschia reach local maxima twice during the deglaciation, the latter of which may be an expression of the Younger Dryas. These findings expand the extent of the expression of deglacial millennial-scale climate events to include the northernmost Pacific. (c) 2005 Elsevier Ltd. All rights reserved. VL - 52 IS - 16-18 N1 - 995ksTimes Cited:51Cited References Count:52 JO - The deglacial history of surface and intermediate water of the Bering Sea ER - TY - JOUR T1 - The demise of the alga Botryococcus Braunii from a Norwegian fjord is due to early eutrophication JF - The Holocene Y1 - 2005 A1 - Smittenberg, R. H. A1 - Baas, M. A1 - Schouten, S. A1 - Sinninghe-Damste, J. S. VL - 15 N1 - id: 1148 ER - TY - JOUR T1 - Detailed compositional analysis of gas seepage at the National Carbon Storage Test Site, Teapot Dome, Wyoming, USA JF - Applied Geochemistry Y1 - 2005 A1 - Klusman, Ronald W. VL - 21 N1 - id: 1038 JO - Detailed compositional analysis of gas seepage at the National Carbon Storage Test Site, Teapot Dome, Wyoming, USA ER - TY - JOUR T1 - Determination of microbial carbon sources in petroleum contaminated sediments using molecular 14C analysis JF - Environmental Science and Technology Y1 - 2005 A1 - Slater, G. F. A1 - White, H. K. A1 - Eglinton, T. I. A1 - Reddy, C. M. VL - 39 N1 - id: 595 ER - TY - JOUR T1 - Determination of Microbial Carbon Sources in Petrolleum Contaminated Sediments Using Molecular 14C Analysis JF - Environ. Sci. Technol Y1 - 2005 A1 - Slater, G. F. A1 - White, H. K. A1 - Eglinton, T. I. A1 - Reddy, C. M. VL - 39 N1 - id: 1225 ER - TY - CONF T1 - Dissolved and particulate organic matter source-age characterization in river and estuarine outflow waters: a combined isotope and biochemical approach T2 - ASLO Summer Meeting Y1 - 2005 A1 - Loh, A. N. A1 - Bauer, J. E. A1 - Canuel, E. A. JF - ASLO Summer Meeting CY - Santiago de Compostela, Spain N1 - id: 482 ER - TY - CONF T1 - The early geological history of Long Island Sound T2 - AGU Fall meeting Y1 - 2005 A1 - Varekamp, J. C. A1 - Thomas, E. JF - AGU Fall meeting CY - San Francisco, CA N1 - id: 744 ER - TY - JOUR T1 - Effects of natural sunlight on decomposition of estuarine dissolved organic C, N and P and bacterial growth JF - Aquatic Microbial Ecology Y1 - 2005 A1 - McCallister, S. L. A1 - Bauer, J. E. A1 - Kelly, J. A1 - Ducklow, H. W. VL - 40 N1 - id: 1101 ER - TY - CONF T1 - The environmental history of Long Island Sound with evidence for human impacts T2 - Living on the Edge Symposium Y1 - 2005 A1 - Varekamp, J. C. A1 - Thomas, E. JF - Living on the Edge Symposium VL - Abstract N1 - id: 743 ER - TY - JOUR T1 - An equatorial harmonic of the high latitude 1500-year cycle JF - Geophysical Research Letters Y1 - 2005 A1 - Russell, J. M. A1 - Johnson, T. C. VL - 32 N1 - id: 1006 ER - TY - JOUR T1 - An evaluation of 14C age relationships between co-occurring foraminifera, alkenones, and total organic carbon in continental margin sediments JF - Paleoceanography Y1 - 2005 A1 - Mollenhauer, Gesine A1 - Kienast, Markus A1 - Lamy, Frank A1 - Meggers, Helge A1 - Schneider, Ralph R. A1 - Hayes, John M. A1 - Eglinton, Timothy I. VL - 20 N1 - id: 492 ER - TY - JOUR T1 - Evidence from ophiolites, blueschists, and ultrahigh-pressure metamorphic terrances that the modern episode of subduction tectonics began in Neoproterozoic time JF - Geological Society of America Y1 - 2005 A1 - Stern, Robert J. VL - 33 N1 - id: 1551 ER - TY - JOUR T1 - Evidence from the Northeastern Atlantic basin for variability in the rate of the meridional overturning circulation through the last deglaciation JF - Earth and Planetary Science Letters Y1 - 2005 A1 - Gherardi, J. M. A1 - Labeyrie, L. A1 - McManus, J. F. A1 - Francois, R. A1 - Skinner, L. C. A1 - Cortijo, E. AB - A first study from the subtropical western Atlantic, using Pa-231/Th-230 ratios as a kinematic proxy for deep water circulation, provided compelling evidence for a strong link between climate and the rate of Meridional Overturning Circulation (MOC) over the last deglaciation. However, these results warrant confirmation from additional locations and water depths because the interpretation of the sedimentary Pa-231/Th-230 ratio in terms of circulation vigor can be biased by variations in particle flux and composition. We have measured Pa-231/Th-230 in a core from the Iberian margin, in the Northeastern Atlantic basin, and have compared these new results to the data from the western Atlantic basin. We find that the reduction in the circulation during H1 and YD and the subsequent increases first recognized in the sediment deposited on Ben-nuda Rise are also evident in the eastern basin, in a totally different sedimentary regime, confirming that sedimentary Pa-231/Th-230 ratios record basin-wide changes in deep water circulation. However, some differences between the eastern and western records are also recognized, providing preliminary evidence to differentiate between renewal rates in the two North Atlantic basins and between shallower and deeper overturning. Our results suggest the possible existence of two sources of Glacial North Atlantic Intermediate Deep Water (GNAIW), one in the south Labrador Sea and another west of Rockall Plateau. Both sources contributed to the meridional overturning but the two had different sensitivity to meltwater from the Laurentide and the Fermoscandian ice sheets during the deglaciation. These results indicate that additional information on the geometry and strength of the ventilation of the deep Atlantic can be obtained by contrasting the evolution of sediment Pa-231/Th-230 in different sections of the Atlantic Ocean. (C) 2005 Elsevier B.V. All rights reserved. VL - 240 IS - 3-4 N1 - 995vhTimes Cited:93Cited References Count:69 JO - Evidence from the Northeastern Atlantic basin for variability in the rate of the meridional overturning circulation through the last deglaciation ER - TY - JOUR T1 - Evidence of past intense tropical cyclones from backbarrier salt pond sediments: A case study from Isla de Culebrita, Puerto Rico, USA JF - Journal of Coastal Research Y1 - 2005 A1 - Donnelly, J. P. KW - Caribbean KW - climate KW - coast KW - deposits KW - florida KW - grain-size analysis KW - Holocene KW - hurricane KW - hurricanes KW - new-jersey KW - record KW - south-carolina KW - storm KW - tsunami AB - Tropical cyclones pose a significant threat to lives and resources in heavily-populated regions and can extensivelymodify coastal landforms. In appropriate depositional environments a sedimentological record of past tropical cyclones can be preserved. Given the relative rarity of landfalling tropical cyclones and the shortness of the instrumental record, little is known about past patterns of hurricane activity. The development of long-term records of tropical cyclone activity will make it possible to examine how past climate change may have influenced the frequency, intensity, and locations (origin, tracks) of hurricanes. Previous work has shown that intense hurricane strikes produce a distinctive sedimentary signature that can be used to reconstruct long-term records of these events. Numerous coastal salt ponds and lagoons in eastern Puerto Rico and the U.S. Virgin Islands are well situated to receive allocthonous sediments during intense tropical cyclone landfalls. Coastal salt ponds, normally low-energy environments, are dominated by fine-grained organic sediments, with the exception of episodic deposition of coarser-grained mineral sediments from the beach and nearshore during extreme storms. Sediment obtained from a series of cores taken from Big Culebrita Salt Pond on the Isla de Culebrita, Puerto Rico reveal a record of flooding-induced sedimentation within mangrove and salt-pond sediments dating back more than 2000 years. Reconstructing the history of storm-surge deposition from backbarrier salt-pond sediments may allow for the reconstruction of a millennial-scale record of tropical cyclones for the northeastern Caribbean and other regions. VL - SI42 SN - 0749-0208 UR - http://www.jstor.org/stable/25736985 N1 - Sp. Iss. 42947fu Times Cited:16 Cited References Count:40 JO - J Coastal Res ER - TY - JOUR T1 - The Fe3+/ΣFe ratios of MORB glasses and their implications for mantle melting JF - Geochimica et Cosmochimica Acta Y1 - 2005 A1 - Bezos, Antoine A1 - Humler, Eric AB - The Fe3+/ΣFe ratio of 104 MORB glasses from the Pacific, the Atlantic, the Indian, and the Red Sea spreading centers have been determined using wet chemical Fe2+ analyses and electron microprobe FeOtotal measurements. The data provide a new estimate for the MORB oxygen fugacity (fO2) of 0.41 ± 0.43 (1sigma, N = 100) log units below the fayalite-magnetite-quartz buffer (FMQ), equivalent to a Fe3+/ΣFe = 0.12 ± 0.02 (1sigma, N = 104). This new fO2 estimate is 0.8 log units more oxidized than the average fO2 proposed by Christie et al. (1986) (FMQ-1.20 ± 0.44; Fe3+/ΣFe = 0.07 ± 0.01; N = 87). This slight difference may be related in part to the 3.5% underestimation of the Fe2+ concentration determined by Christie et al. (1986) compared with this study. MORB oxygen fugacity does not display any significant difference between the three main oceanic domains, or between enriched and depleted MORB. Yet, the iron red-ox state ratio shows a broad increase during fractional crystallization. Detailed study of magmatic suites highlights the lack of systematic Fe3+/ΣFe ratio fractionation during differentiation. Despite the large variations of inferred partial melting degrees (from 5 to 20%), the present data set does not provide any evidence of Fe3+/ΣFe relationships with partial melting proxies such as Na8.0. Based on the Fe3+ systematics during partial melting, it is suggested that the oxidation state of MORB reflects a “buffered mantle melting process” resulting in the apparent compatible behavior of Fe3+ during partial melting, and in the relatively constant Fe3+/ΣFe ratio irrespective of the extent of melting. This result implies that partial melting processes may be open relative to oxygen. We propose a model where the Fe3+/ΣFe ratio in the melt is buffered during partial melting. The MORB Fe2O3 systematics can be accounted for by using a fO2 of FMQ-1 that is equivalent to the average fO2 reported for abyssal peridotites. VL - 69 N1 - id: 1578 JO - The Fe3+/EFe ratios of MORB glasses and their implications for mantle melting ER - TY - JOUR T1 - Fluctuations in export productivity over the last century from sediments of a southern Chilean fjord (44 degrees S) JF - Estuarine Coastal and Shelf Science Y1 - 2005 A1 - Sepulveda, J. A1 - Pantoja, S. A1 - Hughen, K. A1 - Lange, C. A1 - Gonzalez, F. A1 - Munoz, P. A1 - Rebolledo, L. A1 - Castro, R. A1 - Contreras, S. A1 - Avila, A. A1 - Rossel, P. A1 - Lorca, G. A1 - Salamanca, M. A1 - Silva, N. AB - Here we present the first reconstruction of changes in surface primary production during the last century from the Puyuhuapi fjord in southern Chile, using a variety of parameters (diatoms, biogenic silica, total organic carbon, chlorins, and proteins) as productivity proxies. Two sediment cores from the head and the center of the fjord were analyzed and compared to gain insights on past changes in productivity in these two different depositional environments. Higher sedimentation rates found at the head of the fjord result from the combination of a shallower water column and a restricted circulation by the occurrence of a sill. Additionally, sediment mixing depths estimated from (210)Pb data suggest that suboxic conditions may dominate the bottom water and the sediment-water interface in this location.Productivity of the Puyuhuapi fjord during the last century was characterized by a constant increase from the late 19th century to the early 1980s, then decreased until the late 1990s, and then rose again to present-day values. The influence of rainfall on productivity was most noticeable during periods of low rainfall, which coincided with decreased overall productivity within the Puyuhuapi fjord. Simultaneous variations in productivity and rainfall in the study area suggest that marine productivity could respond to atmospheric-oceanic interactions at a local scale. At a regional scale, marine productivity of the area may be related to other large-scale processes such as the El Nino Southern Oscillation. (c) 2005 Elsevier Ltd. All rights reserved. VL - 65 IS - 3 N1 - 975sfTimes Cited:22Cited References Count:53 JO - Fluctuations in export productivity over the last century from sediments of a southern Chilean fjord (44 degrees S) ER - TY - JOUR T1 - Foraminiferal isotope anomalies from northwestern Pacific marginal sediments JF - Geochemistry Geophysics Geosystems Y1 - 2005 A1 - Ohkushi, K. A1 - Ahagon, N. A1 - Uchida, M. A1 - Shibata, Y. KW - atmospheric processes : paleoclimatology KW - benthic foraminifera KW - California KW - carbon isotopes KW - corals KW - Foraminifera KW - gas-hydrate KW - kuril trench KW - marine geology and geophysics : marine sediments : processes and transport KW - methane hydrate KW - methane release KW - northwestern pacific ocean KW - sea-level record KW - tokachi-oki earthquake KW - western north pacific KW - Younger Dryas AB - [1] We evaluated the influence of methane release from methane hydrate reservoirs in the northwestern Pacific continental margin on stable isotope values. We analyzed stable isotopes of foraminifera from a piston core collected at 1066-m water depth off eastern Hokkaido, northern Japan. Carbon isotope signals indicated that planktonic and benthic foraminifera in several glacial sediment layers in the core were highly depleted in C-13; both the planktonic and benthic foraminiferal delta C-13 values ranged from about -10 parts per thousand to -2 parts per thousand. Most foraminiferal tests in these horizons were brown as a result of postdepositional alteration. Foraminiferal oxygen isotopes fluctuated abnormally in the glacial sediment layers, showing small ( about 0.5 parts per thousand) positive shifts relative to normal glacial values. We attributed the positive shifts to authigenic carbonate formation in the foraminiferal tests. The authigenic carbonates have formed when rising methane, from methane hydrate in the sediment, became oxidized as it came in contact with dissolved sulfate near the seafloor. Episodic methane-release events may be associated with great plate-boundary earthquakes with epicenters near the coring site. VL - 6 SN - 1525-2027 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=Alerting&SrcApp=Alerting&DestApp=WOS&DestLinkType=FullRecord;UT=WOS:000228479400002 IS - 4 N1 - 917qmTimes Cited:9 Cited References Count:48 JO - Geochem Geophy Geosy ER - TY - JOUR T1 - From Pleistocene mariners to complex hunter-gatherers: the archaeology of the California Channel Islands JF - Journal of World Prehistory Y1 - 2005 A1 - Rick, Torben C. A1 - Erlandson, Jon M. A1 - Vellanoweth, Rene L. VL - 19 N1 - id: 581 ER - TY - JOUR T1 - A geoarchaeological chronology of Holocene dune building on San Miguel Island, California JF - Holocene Y1 - 2005 A1 - Erlandson, J. M. A1 - Rick, T. C. A1 - Peterson, C. AB - A data base of 114 C-14 dates from 40 archaeological sites in San Miguel Island sand dunes provides a general chronology for Holocene dune building. Although rising seas have probably submerged earlier evidence, postglacial dune building on San Miguel began as early as 10 000 years ago. More intensive dune building dates to the middle and late Holocene, including large parabolic dunes that traverse the island and climb some of the highest landforms. Native American peoples lived on and altered island sand dunes for nearly 10 000 years, and native burning and other landscape alterations may have contributed to periodic destabilization of island dunefields. Accumulation of cultural debris also facilitated anthropogenic soil formation in many coastal localities, however, and over the millennia midden debris protected large expanses of the island's coastal perimeter from wind erosion. With the introduction of sheep c. AD 1850, destabilization and erosion of dune soils caused by overgrazing and other human impacts reached unprecedented levels, devastating the island's natural ecology. In recent decades, with the removal of sheep and other exotic animals from the island, the dunes have begun to restabilize. VL - 15 IS - 8 N1 - 992ziTimes Cited:23Cited References Count:31 JO - A geoarchaeological chronology of Holocene dune building on San Miguel Island, California ER - TY - JOUR T1 - Geochemical and hydrogeological contrasts between shallow and deeper aquifers in two villages of Araihazar, Bangladesh: Implications for deeper aquifers as drinking water sources JF - Geochimica et Cosmochimica Acta Y1 - 2005 A1 - Zheng, Y. A1 - van Geen, A. A1 - Stute, M. A1 - Dhar, R. A1 - Mo, Z. A1 - Cheng, Z. A1 - Horneman, A. A1 - Gavrieli, I. A1 - Simpson, H. J. A1 - Versteeg, R. A1 - Steckler, M. A1 - Grazioli-Venier, A. A1 - Goodbred, S. A1 - Shahnewaz, M. A1 - Shamsudduha, M. A1 - Hoque, M. A. A1 - Ahmed, K. M. AB - Sediment and groundwater profiles were compared in two villages of Bangladesh to understand the geochemical and hydrogeological factors that regulate dissolved As concentrations in groundwater. In both villages, fine-grained sediment layers separate shallow aquifers ( 50 ka ago and a groundwater age of thousands of years. In the other village (Bay), the sediment is VL - 69 IS - 22 N1 - id: 604; 999UZ Times Cited:59 Cited References Count:49 JO - Geochemical and hydrogeological contrasts between shallow and deeper aquifers in two villages of Araihazar, Bangladesh: Implications for deeper aquifers as drinking water sources ER - TY - JOUR T1 - Geochemical characteristics of recent 2 ka mud on the inner shelf of the East China Sea JF - GEOCHIMICA Y1 - 2005 A1 - Xiao, S. B. A1 - Li, A. C. A1 - Jiang, F. A1 - Xu, F. J. A1 - Zheng, F. A1 - Chen, Z. KW - East China Sea continental shelf KW - factor analysis KW - geochemical characteristics KW - particle size AB - The particle size of DD2 in the northern part of the muddy area along the continental margin of the East China Sea was analyzed. AMS 14 C age test and the main elements, trace elements The relationship between the content of each element and the particle size was discussed and analyzed. The relationship between them was discussed by R factor analysis. Studies have shown that nearly 2 ka to DD2 The majority of the main elements and trace elements in the pores are stable; the content of most of the elements with the grain size becomes increasing, while the content of Sr and SiO 2 The decreasing tendency of CaO, Na 2 O, Hf, Zr and Ti is poor in particle size. The results of factor analysis show that the chemical composition of DD2 pore can be It is divided into four kinds of combination types: the main characteristics of the distribution of elements in sediments are reflected, and the samples are not treated by salt beforehand to cause the combination of main elements and trace elements The Zr, Hf and Nb elements are enriched in the specific particle size components (silt), and the addition of calcareous biological components and the redistribution of elements during early diagenesis Wait. The results show that Rb, Cu, Ni, V, P, Sc, Fe 2 O 3 , Cr, K 2 O, Nb, Co, Th, Ti and Al 2 O 3 are relatively inactive elements in DD 2 pores, They can be compared with the modern Yangtze River, the Yellow River sediments, for genetic analysis. The Ti J Zr and Cr J Th ratios indicate that the pore deposits are mainly derived from the granitic Source area. VL - 34 IS - 6 N1 - id: 570 JO - Geochemical characteristics of recent 2 ka mud on the inner shelf of the East China Sea ER - TY - JOUR T1 - Geologic implications of Late Quaternary isostatic adjustment in the Penobscot/Kennebec River system, Maine JF - Geological Society of America Abstracts with Programs Y1 - 2005 A1 - Kelley, Alice R. A1 - Kelly, Joseph T. A1 - Belknap, Daniel F. A1 - Gontz, Allen M. VL - 37 IS - 1 N1 - id: 1173 ER - TY - JOUR T1 - Glacial water mass geometry and the distribution of d 13 C of SCO 2 in the western Atlantic Ocean JF - Paleoceanography Y1 - 2005 A1 - Curry, W. B. A1 - Oppo, D. W. VL - 20 N1 - id: 416 ER - TY - JOUR T1 - Global methane emission through mud volcanoes and its past and present impact on the Earth's climate-a comment JF - International Journal of Earth Sciences Y1 - 2005 A1 - Milkov, A. V. A1 - Etiope, G. VL - 94 IS - 3 N1 - 940vyTimes Cited:11Cited References Count:15 JO - Global methane emission through mud volcanoes and its past and present impact on the Earth's climate-a comment ER - TY - RPRT T1 - Global ocean data analysis project (GLODAP): Results and data, ORNL/CDIAC-145, NDP-145 Y1 - 2005 A1 - Sabine, C. L. A1 - Key, R. M. A1 - Kozyr, A. A1 - Feely, R. A. A1 - Wanninkhof, R. A1 - Millero, F. J. A1 - Peng, T. H. A1 - Bullister, J. L. A1 - Lee, K. N1 - id: 529 ER - TY - JOUR T1 - A high-resolution geochemical record from Lake Edward, Uganda Congo and the timing and causes of tropical African drought during the late Holocene JF - Quaternary Science Reviews Y1 - 2005 A1 - Russell, J. M. A1 - Johnson, T. C. AB - High-resolution analyses of the elemental composition of calcite and biogenic silica (BSi) content in piston cores from Lake Edward, equatorial Africa, document complex interactions between climate variability and lacustrine geochemistry over the past 5400 years. Correlation of these records from Lake Edward to other climatically-forced geochemical and lake level records from Lakes Naivasha, Tanganyika, and Turkana allows us to develop a chronology of drought events in equatorial East Africa during the late Holocene. Major drought events of at least century-scale duration are recorded in lacustrine records at about 850, 1500, similar to 2000, and 4100 cal year BP. Of these, the most severe event occurred between about 2050 and 1850 cal year BP, during which time Lake Edward stood about 15 in below its present level. Numerous additional droughts of less intensity and/or duration are present in the Lake Edward record, some of which may be correlated to other lacustrine climate records from equatorial East Africa. These events are superimposed on a long-term trend of increasingly and conditions from 5400 to about 2000 cal year BP, followed by a shift toward wetter climates that may have resulted from an intensification of the winter Indian monsoon. Although the causes of decade- to century-scale climate variability in the East African tropics remain obscure, time-series spectral analysis suggests no direct linkage between solar output and regional rainfall. Rather, significant periods of similar to 725, similar to 125, 63-72, 31-25, and 19-16 years suggest a tight linkage between the Indian Ocean and African rainfall, and could result from coupled ocean-atmosphere variability inherent to the tropical monsoon system. (c) 2004 Elsevier Ltd. All rights reserved. VL - 24 IS - 12-13 N1 - 933pzTimes Cited:63Cited References Count:74 JO - A high-resolution geochemical record from Lake Edward, Uganda Congo and the timing and causes of tropical African drought during the late Holocene ER - TY - JOUR T1 - High-resolution historical records from Pettaquamscutt River basin sediments; 2. Chronology and record of 137Cs released by the Chernobyl accident JF - Geochimica et Cosmochimica Acta Y1 - 2005 A1 - Lima, A. L. A1 - Hubeny, J. B. A1 - Reddy, C. M. A1 - King, J. W. A1 - Hughen, K. A. A1 - Eglinton, T. I. VL - 69 N1 - id: 555 ER - TY - JOUR T1 - Holocene aminochronology and time-averaging fro Chesapeake Bay mulinia JF - Geological Society of America Abstracts with Programs Y1 - 2005 A1 - Edwards, A. L. A1 - Wehmiller, J. R. A1 - Lockwood, R. A1 - Kaufman, D. A1 - Bright, J. A1 - Cronin, T. A1 - Willard, D. VL - 37 N1 - id: 585 ER - TY - JOUR T1 - Holocene hydrologic variation at Lake Titicaca, Bolivia/Peru, and its relationship to North Atlantic climate variation JF - Journal of Quaternary Science Y1 - 2005 A1 - Baker, P. A. A1 - Fritz, S. C. A1 - Garland, J. A1 - Ekdahl, E. AB - A growing number of sites in the Northern Hemisphere show centennial- to millennial-scale climate variation that has been correlated with change in solar variability or with change in North Atlantic Circulation. However, it is unclear how (or whether) these oscillations in the climate system are manifest in the Southern Hemisphere because of a lack of sites with suitably high sampling resolution. In this paper, we reconstruct the lake-level history of Lake Titicaca, using the carbon isotopic content of sedimentary organic matter, to evaluate centennial- to millennial-scale precipitation variation and its phasing relative to sites in the Northern Hemisphere. The pattern and timing of lake-level change in Lake Titicaca is similar to the ice-rafted debris record of Holocene Bond events, demonstrating a possible coupling between precipitation variation on the Altiplano and North Atlantic sea-surface temperatures (SSTs). The cold periods of the Holocene Bond events correspond with periods of increased precipitation on the Altiplano. Holocene precipitation variability on the Altiplano is anti-phased with respect to precipitation in the Northern Hemisphere monsoon region. More generally, the tropical Andes underwent large changes in precipitation on centennial-to-millennial timescales during the Holocene. Copyright (C) 2005 John Wiley & Sons, Ltd. VL - 20 IS - 7-8 N1 - id: 1095; 000CQ Times Cited:21 Cited References Count:46 JO - Holocene hydrologic variation at Lake Titicaca, Bolivia/Peru, and its relationship to North Atlantic climate variation ER - TY - JOUR T1 - Holocene molluscan aminostratigraphy of Chesapeake Bay sediments JF - Geological Society of America Abstracts with Programs Y1 - 2005 A1 - Edwards, A. L. A1 - Lockwood, R. A1 - Wehmiller, J. A1 - Cronin, T. A1 - Kaufman, D. A1 - Bright, J. VL - 37 N1 - id: 586 ER - TY - CONF T1 - The Holocene radiocarbon reservoir effect in the western Ross Sea T2 - Annual West Antarctic Ice Sheet Meeting Y1 - 2005 A1 - Hall, Brenda L. A1 - Henderson, Gideon M. A1 - Baroni, Carlo A1 - Kellog, Thomas JF - Annual West Antarctic Ice Sheet Meeting CY - Sterling, VA N1 - id: 434 ER - TY - CONF T1 - Holocene terebratulid brachiopods from the southern Brazilian Shelf (South Atlantic): Ecology, taphonomy, and time-averaging T2 - Fifth International Brachiopod Congress Y1 - 2005 A1 - Kowalewski, M. A1 - Simoes, M. G. A1 - Barbour-Wood, S. L. A1 - Krause R.A, Jr. A1 - Rodriguez, S. C. A1 - Wehmiller, J. F. A1 - Rodland, D. L. A1 - Carroll, M. JF - Fifth International Brachiopod Congress PB - Harper, D. A. T. Long, S. L. McCorrey, M. CY - Copenhagen N1 - id: 1171; Abstracts, p. 34-35 ER - TY - JOUR T1 - A hydrogen-rich early Earth atmosphere JF - Science Y1 - 2005 A1 - Tian, F. A1 - Toon, O. B. A1 - Pavlov, A. A. A1 - De Sterck, H. AB - We show that the escape of hydrogen from early Earth's atmosphere likely occurred at rates slower by two orders of magnitude than previously thought. The balance between slow hydrogen escape and volcanic outgassing could have maintained a hydrogen mixing ratio of more than 30%. The production of prebiotic organic compounds in such an atmosphere would have been more efficient than either exogenous delivery or synthesis in hydrothermal systems. The organic soup in the oceans and ponds on early Earth would have been a more favorable place for the origin of life than previously thought. VL - 308 IS - 5724 N1 - Tian, FengToon, Owen BPavlov, Alexander ADe Sterck, HengResearch Support, U.S. Gov't, Non-P.H.S.2005/04/09 09:00Science. 2005 May 13;308(5724):1014-7. Epub 2005 Apr 7. JO - A hydrogen-rich early Earth atmosphere ER - TY - JOUR T1 - Impact of millennial-scale Holocene climate variability on eastern North American terrestrial ecosystems: pollen-based climatic reconstruction JF - Global and Planetary Change Y1 - 2005 A1 - Willard, D. A. A1 - Bernhardt, C. E. A1 - Korejwo, D. A. A1 - Meyers, S. R. AB - We present paleoclimatic evidence for a series of Holocene millennial-scale cool intervals in eastern North America that occurred every similar to 1400 years and lasted similar to 300-500 years, based on pollen data from Chesapeake Bay in the mid-Atlantic region of the United States. The cool events are indicated by significant decreases in pine pollen, which we interpret as representing decreases in January temperatures of between 0.2 degrees and 2 degrees C. These temperature decreases include excursions during the Little Ice Age (similar to 1300-1600 AD) and the 8 ka cold event. The timing of the pine minima is correlated with a series of quasi-periodic cold intervals documented by various proxies in Greenland, North Atlantic, and Alaskan cores and with solar minima interpreted from cosmogenic isotope records. These events may represent changes in circumpolar vortex size and configuration in response to intervals of decreased solar activity, which altered jet stream patterns to enhance meridional circulation over eastern North America. (c) 2004 Elsevier B.V All rights reserved. VL - 47 IS - 1 N1 - 944zeTimes Cited:48Cited References Count:68 JO - Impact of millennial-scale Holocene climate variability on eastern North American terrestrial ecosystems: pollen-based climatic reconstruction ER - TY - JOUR T1 - Impact of vegetation on sedimentary organic matter composition and polycyclic aromatic hydrocarbon attenuation JF - Environ Sci Technol Y1 - 2005 A1 - Gregory, S. T. A1 - Shea, D. A1 - Guthrie-Nichols, E. KW - Biodegradation, Environmental KW - Environmental Monitoring KW - Geologic Sediments/chemistry KW - Magnetic Resonance Spectroscopy KW - Mass Spectrometry KW - Plants KW - Polycyclic Aromatic Hydrocarbons/*isolation & purification/*metabolism KW - Refuse Disposal KW - Soil Pollutants/*isolation & purification/*metabolism AB - Results from natural and engineered phytoremediation systems provide strong evidencethatvegetated soils mitigate polycyclic aromatic hydrocarbon (PAH) contamination. However, the mechanisms by which PAH mitigation occurs and the impact of plant organic matter on PAH attenuation remain unclear. This study assessed the impact of plant organic matter on PAH attenuation in labile and refractory sediments fractions from a petroleum distillate waste pit that has naturally revegetated. Samples were collected in distinct zones of barren and vegetated areas to assess changes to organic matter composition and PAH content as vegetation colonized and became established in the waste pit. Sediments were fractionated into bulk sediment and humin fractions and analyzed for organic matter composition by isotope ratio mass spectrometry (delta (13)C), 13C nuclear magnetic resonance (13C NMR), delta 14C AMS (accelerator mass spectrometry), and percent organic carbon (%TOC). Gas chromatography mass spectrometry (GC/ MS) of lipid extracts of SOM fractions provided data for PAH distribution histograms, compound weathering ratios, and alkylated and nonalkylated PAH concentrations. Inputs of biogenic plant carbon, PAH weathering, and declines in PAH concentrations are most evidentfor vegetated SOM fractions, particularly humin fractions. Sequestered PAH metabolites were also observed in vegetated humin. These results show that plant organic matter does impact PAH attenuation in both labile and refractory fractions of petroleum distillate waste. VL - 39 SN - 0013-936X (Print)0013-936X (Linking) UR - https://www.ncbi.nlm.nih.gov/pubmed/16082958 IS - 14 N1 - Gregory, Samuel TShea, Damian Guthrie-Nichols, Elizabeth eng Research Support, U.S. Gov't, Non-P.H.S. 2005/08/09 09:00 Environ Sci Technol. 2005 Jul 15;39(14):5285-92. ER - TY - JOUR T1 - Increased productivity in the subantarctic ocean during Heinrich events JF - Nature Y1 - 2005 A1 - Sachs, J. P. A1 - Anderson, R. F. AB - Massive iceberg discharges from the Northern Hemisphere ice sheets, 'Heinrich events', coincided with the coldest periods of the last ice age. There is widespread evidence for Heinrich events and their profound impact on the climate and circulation of the North Atlantic Ocean, but their influence beyond that region remains uncertain. Here we use a combination of molecular fingerprints of algal productivity and radioisotope tracers of sedimentation to document eight periods of increased productivity in the subpolar Southern Ocean during the past 70,000 years that occurred within 1,000-2,000 years of a Northern Hemisphere Heinrich event. We discuss possible causes for such a link, including increased supply of iron from upwelling and increased stratification during the growing season, which imply an alteration of the global ocean circulation during Heinrich events. The mechanisms linking North Atlantic iceberg discharges with subantarctic productivity remain unclear at this point. We suggest that understanding how the Southern Ocean was altered during these extreme climate perturbations is critical to understanding the role of the ocean in climate change. VL - 434 IS - 7037 N1 - Sachs, Julian PAnderson, Robert FengResearch Support, Non-U.S. Gov'tResearch Support, U.S. Gov't, Non-P.H.S.England2005/04/29 09:00Nature. 2005 Apr 28;434(7037):1118-21. JO - Increased productivity in the subantarctic ocean during Heinrich events ER - TY - JOUR T1 - Input of particulate organic and dissolved inorganic carbon from the Amazon to the Atlantic Ocean JF - Geochemistry Geophysics Geosystems Y1 - 2005 A1 - Druffel, E. R. M. A1 - Bauer, J. E. A1 - Griffin, S. KW - accumulation KW - amazon KW - C-14 KW - carbon cycling KW - CO2 KW - continental-shelf KW - poc KW - radiocarbon KW - river system KW - Sediment KW - total co(2) KW - water AB - We report concentrations and isotope measurements (radiocarbon and stable carbon) of dissolved inorganic carbon (DIC) and suspended particulate organic carbon (POC) in waters collected from the mouth of the Amazon River and the North Brazil Current. Samples were collected in November 1991, when the Amazon hydrograph was at its annual minimum and the North Brazil Current had retroflected into the equatorial North Atlantic. The DIC D 14 C results revealed postbomb carbon in river and ocean waters, with slightly higher values at the river mouth. The low DIC delta(13)C signature of the river end-member (-11%) demonstrates that about half of the DIC originated from the remineralization of terrestrially derived organic matter. A linear relationship between DIC and salinity indicates that DIC was mixed nearly conservatively in the transition zone from the river mouth to the open ocean, though there was a small amount (<= 10%) of organic matter remineralization in the mesohaline region. The POC Delta(14)C values in the river mouth were markedly lower than those values from the western Amazon region (Hedges et al., 1986). We conclude that the dominant source of POC near the river mouth and in the inner Amazon plume during November 1991 was aged, resuspended material of significant terrestrial character derived from shelf sediments, while the outer plume contained mainly marine-derived POC. VL - 6 SN - 1525-2027 N1 - 909pwTimes Cited:17 Cited References Count:21 JO - Geochem Geophy Geosy ER - TY - CONF T1 - An investigation of accurate gas exchange measurements for determing a large river carbon isotope mass balance T2 - 37th Liege International Colloquium on Gas Transfer at Water Survaces Y1 - 2005 A1 - Raymond, P. A. A1 - McGillis, W. R. A1 - Bauer, J. E. A1 - Caraco, N. F. A1 - Cole, J. J. JF - 37th Liege International Colloquium on Gas Transfer at Water Survaces CY - Liege, Belgium N1 - id: 490 ER - TY - BOOK T1 - The Island Chumash: Behavioral Ecology of a Maritime Society Y1 - 2005 A1 - Kennett, D. J. PB - University of California Press CY - Berkeley, CA N1 - id: 1017 ER - TY - JOUR T1 - Isolation and Characterization of a Genetically Tractable Photoautotrophic Fe(II)-Oxidizing Bacterium, Rhodopseudomonaspalustris Strain TIE-1 JF - Applied and Environmental Microbiology Y1 - 2005 A1 - Jiao, Yongqin A1 - Kappler, Andreas A1 - Croal, Laura R. A1 - Newman, Dianne K. VL - 71 N1 - id: 1576 ER - TY - JOUR T1 - On the isolation of elemental carbon (EC) for micro-molar 14C accelerator mass spectrometry: development of a hybrid reference material for 14C-EC accuracy asssurance, and a critical evaluation of the thermal optical kinetic (TOK EC isolation procedure JF - Atmospheric Chemistry and Physics Y1 - 2005 A1 - Currie, L. A. A1 - Kessler, J. D. VL - 5 N1 - id: 631 ER - TY - JOUR T1 - Isotopic constraints on the fate of petroleum residues sequestered in salt marsh sedimetns JF - Environmental Science and Technology Y1 - 2005 A1 - White, H. K. A1 - Reddy, C. M. A1 - Eglinton, T. I. VL - 39 N1 - id: 969 JO - Isotopic constraints on the fate of petroleum residues sequestered in salt marsh sedimetns ER - TY - JOUR T1 - Lacustrine loss-on-ignition recrods from the southern Uinta Mountains JF - Geological Society of America Abstracts with Programs Y1 - 2005 A1 - Munroe, Jeffrey S. VL - 37 IS - 7 N1 - id: 694 ER - TY - JOUR T1 - Last deglaciation in the Okinawa Trough: Subtropical northwest Pacific link to Northern Hemisphere and tropical climate JF - Paleoceanography Y1 - 2005 A1 - Sun, Y. B. A1 - Oppo, D. W. A1 - Xiang, R. A1 - Liu, W. G. A1 - Gao, S. KW - cal kyr bp KW - deep-ocean circulation KW - equatorial current KW - kuroshio current KW - late pleistocene KW - oxygen-isotope KW - planktonic-foraminifera KW - radiocarbon age calibration KW - south china sea KW - surface-water AB - [1] Detailed deglacial and Holocene records of planktonic delta O-18 and Mg/Ca - based sea surface temperature (SST) from the Okinawa Trough suggest that at similar to 18 to 17 thousand years before present (kyr B. P.), late spring/ early summer SSTs were approximately 3 degrees C cooler than today, while surface waters were up to 1 practical salinity unit saltier. These conditions are consistent with a weaker influence of the summer East Asian Monsoon (EAM) than today. The timing of suborbital SST oscillations suggests a close link with abrupt changes in the EAM and North Atlantic climate. A tropical influence, however, may have resulted in subtle decoupling between the North Atlantic and the Okinawa Trough/EAM during the deglaciation. Okinawa Trough surface water trends in the Holocene are consistent with model simulations of an inland shift of intense EAM precipitation during the middle Holocene. Millennial-scale alternations between relatively warm, salty conditions and relatively cold, fresh conditions suggest varying influence of the Kuroshio during the Holocene. VL - 20 SN - 0883-8305 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=Alerting&SrcApp=Alerting&DestApp=WOS&DestLinkType=FullRecord;UT=WOS:000232654500001 IS - 4 N1 - 975ipTimes Cited:53 Cited References Count:55 JO - Paleoceanography ER - TY - JOUR T1 - The last glacial maximum: stability and change in an Andean cloud forest JF - Journal of Quaternary Science Y1 - 2005 A1 - Urrego, D. H. A1 - Silman, M. R. A1 - Bush, M. B. VL - 20 N1 - id: 458 ER - TY - JOUR T1 - Late neogene and quaternary evolution of the northern Albermarle Embayment (mid-Atlantic continental margin, USA) JF - Marine Geology Y1 - 2005 A1 - Mallinson, D. A1 - Riggs, S. A1 - Culver, S. A1 - Thieler, R. A1 - Foster, D. R. A1 - Corbett, D. R. A1 - Farrell, K. A1 - J, Wehmiller VL - 217 N1 - id: 1160 ER - TY - JOUR T1 - Late-glacial and Holocene record of lake levels of Mathews Pond and Whitehead Lake, northern Maine, USA JF - Journal of Paleolimnology Y1 - 2005 A1 - Dieffenbacher-Krall, A. C. A1 - Nurse, A. M. AB - Paleohydrology studies at Mathews Pond and Whitehead Lake in northern Maine revealed synchronous changes in lake levels from about 12,000 C-14 yrs BP to the present. We analyzed gross sediment structure, organic and carbonate content, mineral grain size, and macrofossils of six cores from each of the two lakes, and obtained 72 radiocarbon dates. Interpretation of this paleo-environmental data suggests that the lateglacial and Younger Dryas climate was dry, and lake levels were low. Early Holocene lake levels were considerably higher but declined for an interval from about 8000 to 7200 14 C yrs BP. Sediment of both lakes contains evidence of a dry period at similar to 7400 C-14 yrs BP (8200 cal yr). Lake levels of both sites declined abruptly about 4800 14 C yrs BP and remained low until 3000 14 C yrs BP. Modern lake levels were achieved only within the past 600 years. The west-to-east, time-transgressive nature of lake-level changes from several sites across northeastern North America suggests periodic changes in atmospheric circulation patterns as a driving force behind observed moisture balance changes. VL - 34 IS - 3 N1 - 953ghTimes Cited:21Cited References Count:81 JO - Late-glacial and Holocene record of lake levels of Mathews Pond and Whitehead Lake, northern Maine, USA ER - TY - JOUR T1 - Late-Quaternary lowstands of lake Bosumtwi, Ghana: evidence from high-resolution seismic-reflection and sediment-core data JF - Palaeogeography Palaeoclimatology Palaeoecology Y1 - 2005 A1 - Brooks, K. A1 - Scholz, C. A. A1 - King, J. W. A1 - Peck, J. A1 - Overpeck, J. T. A1 - Russell, J. M. A1 - Amoako, P. Y. O. AB - Results from the first high-resolution, single-channel seismic-reflection survey of tropical Lake Bosumtwi, Ghana, and sedimentological data from a C-14-dated sediment piston core were used to revise and extend the basin's late-Quaternary lake level history. We report four seismic sequence boundaries and an exposure surface from a sediment core. which are interpreted as erosional surfaces formed at times of drastic low lake level. The youngest erosional surf-ace occurs as much as 31 In below present lake level (bpll) and up to 0.7 in below the present sediment-water interface. This most recent unconformity observed in the seismic data is interpreted to be coeval with the basin-wide late-Holocene dry period between 0.5 and 1 cal ky BP (calendar years before present). Another exposure surface observed in a sediment core is based on an abrupt contact separating low density, wet, clay rich sediments from underlying high density, compact, silt-rich and rootlet-rich sediments, and is interpreted to have developed prior to 16.8 cal ky BP when the lake was similar to60 in bpll. Three older, erosional surfaces occur at depths of similar to92 +/- 3, 102 +/- 3, and 107 +/- 4 in bpll, suggesting numerous lowstands in Lake Bosumtwi during the late-Pleistocene. By extrapolation of average sedimentation rates (0.41 m/ky) from the upper similar to10.5 m of sediment, we estimate the ages of these older lowstands to be similar to65, similar to86 similar to108 cal ky BP. The lowstands of Lake Bosumtwi evidenced from the seismic and sediment core data are interpreted as a response to increased aridity in this part of the equatorial tropics and may correlate to other observed continent-wide shifts in African climate over the past 100 ky and possibly to rapid climatic shifts observed at high latitudes. Determining the precise timing of these lowstands will ultimately reveal much about the drought dynamics of tropical and subtropical Africa. (C) 2004 Elsevier B.V. All rights reserved. VL - 216 IS - 3-4 N1 - 892ujTimes Cited:21Cited References Count:54 JO - Late-Quaternary lowstands of lake Bosumtwi, Ghana: evidence from high-resolution seismic-reflection and sediment-core data ER - TY - JOUR T1 - Latest Holocene evolution and human disturbance of a channel segment in the Hudson River Estuary JF - Marine Geology Y1 - 2005 A1 - Klingbeil, A. D. A1 - Sommerfield, C. K. AB - The latest Holocene sedimentary record of a cohesive channel and subtidal shoal in the lower Hudson River Estuary was examined to elucidate natural (sea-level rise, sediment transport) and anthropogenic (bulkheading, dredging) influences oil the recent morphodynamic evolution of the system. To characterize the seafloor and shallow subbottom, similar to 100 km of high-resolution seismic reflection profiles (chirp) were collected within a 20-km reach of the estuary and correlated with sediment lithologies provided by eight vibracores recovered along seismic lines. Sediment geochronology with Cs-137 and C-14 was used to estimate intermediate and long-term sedimentation rates, respectively, and historical bathyrnetric data were analyzed to identify regional patterns of accretion and erosion, and to quantify changes in channel geometry and sediment volume.The shoal lithosome originated around 4 ka presumably with decelerating eustatic sea level rise during the latest Holocene. Long-term sedimentation rates on the shoal (2.3-2.6 mm/yr) are higher than in the channel (2 mm/yr) owing to hydrodynamic conditions that preferentially sequester suspended sediment on the western side of the estuary. As a result, the shoal accretes oblique to the principal axis of tidal transport, and more rapidly than the channel to produce an asymmetric cross-section. Shoal deposits consist of tidally bedded muds and are stratified by minor erosion surfaces that seismic profiles reveal to extend for I Os of meters to kilometers. The frequency and continuity of these Surfaces suggest that the surficial shoal is catastrophically stripped on decadal-centennial time scales by elevated tidal flows. tidal erosion maintains the shoal at a uniform depth below sea level and prevents it from transitioning to an intertidal environment. Consequently, the long-term sedimentation rate approximates the rate of sea-level rise in the lower estuary (1-3 mm/yr). VL - 218 IS - 1-4 N1 - 942iaTimes Cited:11Cited References Count:49 JO - Latest Holocene evolution and human disturbance of a channel segment in the Hudson River Estuary ER - TY - JOUR T1 - Long range transport of biomass aerosol to Greenland: Multi-spectroscopic investigation of particles deposited in the snow JF - Journal of Radioanalytical and Nuclear Chemistry Y1 - 2005 A1 - Currie, L. A. A1 - Kessler, J. D. A1 - Fletcher, R. A. A1 - Dibb, J. E. AB - Recent developments in radiometrics and mass spectrometry techniques for ultra-sensitive analysis of radionuclides in the marine environment are reviewed. In the radiometrics sector the dominant development has been the utilization of large HPGe detectors in underground laboratories with anti-cosmic or anti-Compton shielding for the analysis of short and medium-lived radionuclides in the environment. In the mass spectrometry sector, applications of inductively coupled plasma mass spectrometry (ICP-MS) and accelerator mass spectrometry (AMS) for the analysis of long-lived radionuclides in the environment are the most important recent achievements. The recent developments do not only considerably decrease the detection limits for several radionuclides (up to several orders of magnitude), but they also enable to decrease sample volumes so that sampling, e.g., of the water column can be much easier and more effective. A comparison of radiometrics and mass spectrometry results for the analysis of radionuclides in the marine environment shows a reasonable agreement - within quoted uncertainties, for wide range of activities and different sample matrices analyzed. VL - 263 IS - 2 N1 - 899oqTimes Cited:2Cited References Count:28 JO - Long range transport of biomass aerosol to Greenland: Multi-spectroscopic investigation of particles deposited in the snow ER - TY - JOUR T1 - Long term calibration of the Noble gas temperature system in a shallow unconfined Pleistocene aquifer JF - Eos Trans. AGU Fall Meeting Supplement Y1 - 2005 A1 - Hall, C. M. A1 - Castro, M. C. A1 - Lohmann, K. C. A1 - Ma, L. VL - 86 IS - 52 N1 - id: 438 ER - TY - CHAP T1 - Microbial transformations of organic matter in black shales and implications for global biogeochemical cycles T2 - Geobiology: Objectives, Concepts, Perspectives Y1 - 2005 A1 - Petsch, S. T. A1 - Edwards, K. J. A1 - Eglinton, T. I. ED - Noffke, N. JF - Geobiology: Objectives, Concepts, Perspectives PB - Elsevier N1 - id: 758 ER - TY - JOUR T1 - Mid-Holocene hydrologic change and hypolimnion formation in Lake Erie JF - Journal of Great Lakes Research Y1 - 2005 A1 - Clotts, R. A. A1 - McCambridge, C. E. A1 - Barrera, E. A1 - Saylor, B. Z. A1 - Palmer, D. F. A1 - Coakley, J. P. VL - 31 N1 - id: 688 ER - TY - CONF T1 - Millennial scale variability in tropical South American vegetation during the last glaciation T2 - Eos Trans. AGU, 86(52), Fall Meeting Suppl. Y1 - 2005 A1 - Hughen, K. A. A1 - Drenzek, N. A1 - Bice, M. A1 - Eglinton, T. I. JF - Eos Trans. AGU, 86(52), Fall Meeting Suppl. CY - San Francisco, CA N1 - id: 563 ER - TY - JOUR T1 - Molecular and stable isotope compositions of natural gas hydrates: A revised global dataset and basic interpretations in the context of geological settings JF - Organic Geochemistry Y1 - 2005 A1 - Milkov, A. V. AB - A global dataset of molecular and stable isotope compositions of gases released from 209 different specimens of natural gas hydrate is presented and discussed. The 26 hydrate-bearing areas from 21 geographic regions are grouped into high gas flux (HGF) settings, low gas flux (LGF) settings and hydrated gas accumulations (HGA). Methane (CH4) is the most abundant hydrate-bound gas, while CO2 and C2+ hydrocarbon gases are frequently present in small amounts. Non-hydrocarbon gases, such as H2S, are uncommon. The stable isotope composition of hydrate-bound gases varies significantly (e.g., delta(13)C of CH4 from -74.7 to -39.60 parts per thousand), suggesting that gases of both microbial and thermogenic origin form gas hydrates. Hydrate-bound gases are derived from autochthonous [Located predominantly within the gas hydrate stability zone (GHSZ)] and allochthonous (located in deep sediments) sources. The occurrence and concentration of gas hydrates in sediments are controlled not by the origin of gases, but rather by their sources, which in turn strongly depend on geological setting. Allochthonous gases (microbial and/or thermogenic) dominate in HGF and HGA settings where they are focused in the shallow GHSZ along faults, within mud volcanoes, in permeable carrier beds and other geological features from underlying petroleum systems. Relatively high concentrations of gas hydrate (average 5-15% of pores and locally up to 100 parts per thousand of volume) occurring over small areas are typical of HGF and HGA settings. In contrast, autochthonous and diffuse allochthonous gases (mostly microbial) occur in stratigraphically and structurally simple LGF settings and result in relatively low concentrations of gas hydrate (average similar to 2% of pores in the GHSZ) spread over large areas. The major implication of this finding is that successful prediction of resource and geohazard potential of gas hydrates is possible only if regional petroleum systems extending well below the GHSZ are properly evaluated. In addition to the diagnosis of origins and sources of hydrate-bound gases, molecular and isotopic data help to better identify hydrate-bearing intervals and provide valuable insights into the dynamics of hydrate-bearing sites. (C) 2005 Elsevier Ltd. All rights reserved. VL - 36 IS - 5 N1 - 929dvTimes Cited:101Cited References Count:138 JO - Molecular and stable isotope compositions of natural gas hydrates: A revised global dataset and basic interpretations in the context of geological settings ER - TY - JOUR T1 - Morphodynamics and evolution of Danube delta JF - Journal of Sedimentary Research Y1 - 2005 A1 - Giosan, L. A1 - Vespremeanu, E. A1 - Donnelly, J. P. A1 - Bhattacharya, J. A1 - Buonaiuto, F. VL - SP 83 N1 - id: 499 ER - TY - JOUR T1 - Moving-wire device for carbon isotopic analyses of nanogram quantities of nonvolatile organic carbon JF - Anal Chem Y1 - 2005 A1 - Sessions, A. L. A1 - Sylva, S. P. A1 - Hayes, J. M. AB - We describe a moving-wire analyzer for measuring 13C in dissolved, involatile organic materials. Liquid samples are first deposited and dried on a continuously spooling nickel wire. The residual sample is then combusted as the wire moves through a furnace, and the evolved CO2 is analyzed by continuous-flow isotope ratio mass spectrometry. A typical analysis requires 1 microL of sample solution and produces a CO2 peak approximately 5 s wide. The system can measure "bulk" delta13C values of approximately 10 nmol of organic carbon with precision better than 0.2 per thousand. For samples containing approximately 1 nmol of C, precision is approximately 1 per thousand. Precision and sensitivity are limited mainly by background noise derived from carbon within the wire. Instrument conditions minimizing that background are discussed in detail. Accuracy is better than 0.5 per thousand for nearly all dissolved analytes tested, including lipids, proteins, nucleic acids, sugars, halocarbons, and hydrocarbons. The sensitivity demonstrated here for 13C measurements represents a approximately 1000-fold improvement relative to existing elemental analyzers and should allow the use of many new preparative techniques for collecting and purifying nonvolatile biochemicals for isotopic analysis. VL - 77 IS - 20 N1 - Sessions, Alex LSylva, Sean PHayes, John MengResearch Support, U.S. Gov't, Non-P.H.S.2005/10/15 09:00Anal Chem. 2005 Oct 15;77(20):6519-27. JO - Moving-wire device for carbon isotopic analyses of nanogram quantities of nonvolatile organic carbon ER - TY - JOUR T1 - The multi-centennial dynamics of an upwelling system revealed by stable isotope and trace element sclerochronology of amino-acid dated bivalve and brachiopod shells JF - Geological Society of America Abstracts with Programs Y1 - 2005 A1 - Krause, R. A., Jr. A1 - Barbour-Wood, S. A1 - Romanek, C. S. A1 - Kowalewski, M. A1 - Simoes, M. G. A1 - Wehmiller, J. F. VL - 37 IS - 7 N1 - id: 717 JO - The multi-centennial dynamics of an upwelling system revealed by stable isotope and trace element sclerochronology of amino-acid dated bivalve and brachiopod shells ER - TY - JOUR T1 - Multiple sources for late-Holocene tsunamis at Discovery Bay, Washington State, USA JF - Holocene Y1 - 2005 A1 - Williams, H. F. L. A1 - Hutchinson, I. A1 - Nelson, A. R. AB - Nine muddy sand beds interrupt a 2500- yr- old sequence of peat deposits beneath a tidal marsh at the head of Discovery Bay on the south shore of the Strait of Juan de Fuca, Washington. An inferred tsunami origin for the sand beds is assessed by means of six criteria. Although all the sand beds contain marine diatoms and almost all the beds display internal strati. cation, the areal extent of the oldest beds is too limited to confirm their origin as tsunami deposits. The ages of four beds overlap with known late Holocene tsunamis generated by plate- boundary earthquakes at the Cascadia subduction zone. Diatom assemblages in peat deposits bracketing these four beds do not indicate concurrent change in elevation at Discovery Bay. Diatoms in the peat bracketing a tsunami bed deposited about 1000 cal. yr BP indicate a few decimeters of submergence, suggesting deformation on a nearby upper- plate fault. Other beds may mark tsunamis caused by more distant upper- plate earthquakes or local submarine landslides triggered by earthquake shaking. Tsunamis from both subduction zone and upper- plate sources pose a significant hazard to shoreline areas in this region. VL - 15 IS - 1 N1 - 894xjTimes Cited:37Cited References Count:67 JO - Multiple sources for late-Holocene tsunamis at Discovery Bay, Washington State, USA ER - TY - RPRT T1 - Natural variability in skeletal growth rate, stable isotopes, and Sr/Ca composition in two species of Pacific sclerosponges (Acnathocheatetes wellsi and Astroclera welleyana) Y1 - 2005 A1 - Grottoli, A. G. A1 - Adkins, J. F. A1 - Moots, K. JF - Benthic Ecology Meetings CY - Williamsburg, VA N1 - id: 1135 ER - TY - JOUR T1 - Noble gases and stable isotopes in a shallow aquifer in southern Michigan: Implications for noble gas paleotemperature reconstructions for cool climates JF - Geophysical Research Letters Y1 - 2005 A1 - Hall, C. M. A1 - Castro, M. C. A1 - Lohmann, K. C. A1 - Ma, L. KW - water AB - Noble gas data from the Glacial Drift, the shallowest aquifer in southern Michigan confirm findings by Ma et al. (2004) that modern noble gas temperatures (NGTs) are systematically below the current mean annual air temperature (MAAT) which, in turn, is similar to the ground temperature of these recharge waters. By tracking noble gas concentrations as well as stable isotope ratios through an autumn, winter, spring and into summer, we show that although water in this aquifer is modern, noble gases do not track the atmosphere on a short time scale. Specifically, excess He-3 and He-4 indicate that the gas environment at the water table is integrating conditions over years or decades rather than weeks or months. Our results are interpreted using various NGT interpretational models and possible mechanisms for the production of low apparent NGTs are discussed. VL - 32 SN - 0094-8276 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=Alerting&SrcApp=Alerting&DestApp=WOS&DestLinkType=FullRecord;UT=WOS:000232177300004 IS - 18 N1 - 968qnTimes Cited:26 Cited References Count:14 JO - Geophys Res Lett ER - TY - CHAP T1 - Once spilled, still found: metal contamination in Connecticut wetlands and Long Island Sound sediment from historic industries, Chapter 9 T2 - Our Changing Coasts Y1 - 2005 A1 - Varekamp, J. C. A1 - Mecray, E. L. A1 - Zierzow, T. ED - Visiglione, Whitelaw JF - Our Changing Coasts PB - E. Elgar N1 - id: 724 ER - TY - JOUR T1 - One-year record of organic and elemental carbon in fine particles in downtown Beijing and Shanghai JF - Atmospheric Chemistry and Physics Y1 - 2005 A1 - Yang, F. A1 - He, K. A1 - Ye, B. A1 - Chen, X. A1 - Cha, L. A1 - Cadle, S. H. A1 - Chan, T. A1 - Mulawa, P. A. AB - Weekly PM2.5 samples were collected for one year ( 1999 - 2000) in Beijing and Shanghai and the carbonaceous species analyzed to investigate and compare their time series patterns and possible sources in the two biggest cities of China. Weekly carbonaceous concentrations varied in wide ranges with 8.6 - 59 mu g m(-3) for OC and 1.5-25.4 mu g m(-3) for EC in Beijing, and with 5.1 - 38.4 mu g m(-3) for OC and 2.3 - 13.0 mu g m(-3) for EC in Shanghai. Similar weekly and seasonal variations of OC and EC concentrations were found in each city though major combustion sources presented source-dependent emission characteristics and seasonal differences in emission amount for carbonaceous species. Both OC and EC maintained much higher concentrations in late fall through winter, probably due to enhanced emissions coupled with unfavorable meteorological conditions. In Beijing, the C-14 analysis of limited samples suggested there was a significant contribution ( 33 - 48%) of modern carbon to the total fine carbonaceous PM burden with higher fractions in the harvest seasons. The high mass ratios of excessive potassium to EC in both Beijing and Shanghai also indicated that biomass burning had important contribution to fine carbonaceous particles. VL - 5 N1 - 936dsTimes Cited:77Cited References Count:45 JO - One-year record of organic and elemental carbon in fine particles in downtown Beijing and Shanghai ER - TY - CONF T1 - Organic matter inputs and metabolism in a large river estuary (the Hudson): Insights from natural abundance isotopes and whole system metabolism T2 - American Society of Limnology and Oceanography Y1 - 2005 A1 - Caraco, N. F. A1 - Cole, J. J. A1 - Raymond, P. A. A1 - Bauer, J. E. JF - American Society of Limnology and Oceanography CY - Salt Lake City, UT N1 - id: 478 ER - TY - JOUR T1 - Otolith science entering the 21st century JF - Marine and Freshwater Research Y1 - 2005 A1 - Campana, S. E. AB - A review of 862 otolith-oriented papers published since the time of the 1998 Otolith Symposium in Bergen, Norway suggests that there has been a change in research emphasis compared to earlier years. Although close to 40% of the papers could be classifed as ‘annual age and growth’ studies, the remaining papers were roughly equally divided between studies of otolith microstructure, otolith chemistry and non-ageing applications. A more detailed breakdown of subject areas identified 15 diverse areas of specialisation, including age determination, larval fish ecology, population dynamics, species identification, tracer applications and environmental reconstructions. For each of the 15 subject areas, examples of representative studies published in the last 6 years were presented, with emphasis on the major developments and highlights. Among the challenges for the future awaiting resolution, the development of novel methods for validating the ages of deepsea fishes, the development of a physiologically-based otolith growth model, and the identification of the limits (if any) of ageing very old fish are among the most pressing. VL - 56 IS - 5 N1 - id: 1044 JO - Otoligh science entering the 21st centure ER - TY - JOUR T1 - The Paleoproterozoic snowball Earth: a climate disaster triggered by the evolution of oxygenic photosynthesis JF - Proc Natl Acad Sci U S A Y1 - 2005 A1 - Kopp, R. E. A1 - Kirschvink, J. L. A1 - Hilburn, I. A. A1 - Nash, C. Z. AB - Although biomarker, trace element, and isotopic evidence have been used to claim that oxygenic photosynthesis evolved by 2.8 giga-annum before present (Ga) and perhaps as early as 3.7 Ga, a skeptical examination raises considerable doubt about the presence of oxygen producers at these times. Geological features suggestive of oxygen, such as red beds, lateritic paleosols, and the return of sedimentary sulfate deposits after a approximately 900-million year hiatus, occur shortly before the approximately 2.3-2.2 Ga Makganyene "snowball Earth" (global glaciation). The massive deposition of Mn, which has a high redox potential, practically requires the presence of environmental oxygen after the snowball. New age constraints from the Transvaal Supergroup of South Africa suggest that all three glaciations in the Huronian Supergroup of Canada predate the Snowball event. A simple cyanobacterial growth model incorporating the range of C, Fe, and P fluxes expected during a partial glaciation in an anoxic world with high-Fe oceans indicates that oxygenic photosynthesis could have destroyed a methane greenhouse and triggered a snowball event on time-scales as short as 1 million years. As the geological evidence requiring oxygen does not appear during the Pongola glaciation at 2.9 Ga or during the Huronian glaciations, we argue that oxygenic cyanobacteria evolved and radiated shortly before the Makganyene snowball. VL - 102 IS - 32 N1 - Kopp, Robert EKirschvink, Joseph LHilburn, Isaac ANash, Cody ZengResearch Support, Non-U.S. Gov'tResearch Support, U.S. Gov't, Non-P.H.S.2005/08/03 09:00Proc Natl Acad Sci U S A. 2005 Aug 9;102(32):11131-6. Epub 2005 Aug 1. U2 - PMC1183582 JO - The Paleoproterozoic snowball Earth: a climate disaster triggered by the evolution of oxygenic photosynthesis ER - TY - JOUR T1 - Pre- and post-industrial environmental changes as revealed by the biogeochemical sedimentary record of Drammensfjord, Norway JF - Marine Geology Y1 - 2005 A1 - Smittenberg, R. H. A1 - Baas, M. A1 - Green, M. J. A1 - Hopmans, E. C. A1 - Schouten, S. A1 - Damste, J. S. S. AB - The biogeochemical sedimentary record of the anoxic Drammensfjord, Norway, was investigated on a decadal to centennial time scale over the last millennium, in order to reconstruct the pre-industrial fjord environment and ecosystem and human-induced environmental changes. The sediments were dated by a combination of C-14 and Pb-210 analysis and varve counting. Analysis of the bulk sedimentary parameters and of the biomarker distribution revealed that the sedimentary organic matter of the fjord is primarily of terrigetious origin, indicating that the fjord was oligotrophic or mesotrophic. The fjord's bottom water has been continuously euxinic since at least 1000 AD, but photic zone euxinia occurred only irregularly in the fjord. The organic matter flux and composition remained virtually invariable until the 18th century. After that time, the flux of material derived from coniferous trees started to increase, indicated by elevated concentrations of dehydroabietic acid and related compounds, but also by raising levels of C-24 n-alcohols and fatty acids. This marked the onset of sawmill activities in the hinterland. After the beginning of the industrial revolution, around 1850, the flux of organic waste from sawmills and paper mills increased substantially. It is suggested that slow bacterial degradation of this relatively nutrient-poor organic waste caused a gradual eutrophication trend, which is reflected in substantial increased bacterial and moderately increased other aquatic biomarker accumulation rates. After the industrial revolution, this trend accelerated and was possibly enhanced by a growing population of the area with accompanymg agricultural and domestic waste. This promoted primary productivity and changed the phytoplankton composition in the fjord.(C) 2004 Elsevier B.V. All rights reserved. VL - 214 IS - 1-3 N1 - 890unTimes Cited:23Cited References Count:105 JO - Pre- and post-industrial environmental changes as revealed by the biogeochemical sedimentary record of Drammensfjord, Norway ER - TY - CONF T1 - Preliminary report on the archaeology and paleoecology of the Abalone Rocks Estuary, Santa Rosa Island, California T2 - Proceedings of the Sixth California Islands Symposium Y1 - 2005 A1 - Rick, T. C. A1 - Kennett, D. J. A1 - Erlandson, J. M. ED - Carcelon, D. JF - Proceedings of the Sixth California Islands Symposium PB - National Park Service Technical Publications, Institute for Wildlife Studies, Arcata, California CY - Santa Barbara Museum of Natural History VL - CHIS-05-01 N1 - id: 468 ER - TY - CONF T1 - Preliminary research results indicate modern sedimentation ont he continental slope seaward of theWaipoao River, New Zealand T2 - New Zealand Marine Science Society Annual Meeting Y1 - 2005 A1 - Alexander, C. A. A1 - Walsh, J. P. A1 - Orpin, A. R. A1 - Sumners, B. W. A1 - Gerber, T. P. A1 - Kuehl, S. A. JF - New Zealand Marine Science Society Annual Meeting CY - Wellington, NZ N1 - id: 637 ER - TY - CONF T1 - Progress on a Gas Ion Source for Continuous-Flow Accelerator Mass Spectrometry T2 - 10th International Conference on Accelerator Mass Spectrometry Y1 - 2005 A1 - Roberts, M. L. A1 - Schneider, R. J. A1 - von Reden, K. F. A1 - Han, B. X. A1 - Rosenheim, B. E. A1 - Hayes, J. M. ED - Knezovich, J. ED - et al. JF - 10th International Conference on Accelerator Mass Spectrometry CY - Berkeley, California N1 - id: 768 ER - TY - JOUR T1 - Provenance analysis of mud along the Min-zhe coast since 2 ka BP JF - Acta Sedimentologica Sinica Y1 - 2005 A1 - Xiao, S. B. A1 - Li, A. C. A1 - Jiang, F. VL - 23 IS - 22 N1 - id: 567 JO - Provenance analysis of mud along the Min-zhe coast since 2 ka BP ER - TY - JOUR T1 - The Puerto Bandera Moraines, Lago Argentino JF - Actas Del XVI Congreso Geologico Argentina, La Plata Y1 - 2005 A1 - Strelin, Jorge A1 - Denton, George N1 - id: 573 ER - TY - JOUR T1 - Radiocarbon dating and the "old shell" problem: direct dating of artifacts and cultural chronologies in coastal and other aquatic regions JF - Journal of Archaeological Science Y1 - 2005 A1 - Rick, T. C. A1 - Vellanoweth, R. L. A1 - Erlandson, J. M. AB - Archaeologists have long recognized the problem of the "old wood" effect in radiocarbon dating charcoal and wood samples, the age of which may be hundreds of years older than their use by humans. Such problems have resulted in significant changes in how most researchers select wood and charcoal samples for C-14 dating, with many now using relatively short-lived carbonized materials for dating. Despite the significant strides made in our understanding of the potential biases of the "old wood" effect, little emphasis has been placed on the possible impacts of dating "old shell" in archaeological deposits. The use of marine shell for C-14 dating is widespread in coastal areas around the world, including a growing emphasis on the dating of individual shell artifacts via Accelerator Mass Spectrometry (AMS). In dating shell artifacts, we have obtained several dates older than associated C-14 dates for short-lived subsistence remains from the same deposits, including great disparities (> 10,000 years) and more subtle differences (>= 100 years). These discrepancies appear to be due to the use of old shells by humans to make beads and other artifacts, including shells collected from fossil deposits, older archaeological sites, and beaches. The problems caused by the use of old shells to make beads and other artifacts are surmountable through careful sample selection, analysis of multiple 14 C dates on a variety of materials, and proper calibration procedures. (c) 2005 Elsevier Ltd. All rights reserved. VL - 32 IS - 11 N1 - 970xgTimes Cited:33Cited References Count:40 JO - Radiocarbon dating and the "old shell" problem: direct dating of artifacts and cultural chronologies in coastal and other aquatic regions ER - TY - JOUR T1 - Radiocarbon dating of alkenones from marine sediments: I. Isolation protocol JF - Radiocarbon Y1 - 2005 A1 - Ohkouchi, N. A1 - Xu, L. A1 - Reddy, C. M. A1 - Montlucon, D. A1 - Eglinton, T. I. KW - AMS KW - carbon KW - indicators KW - proxy KW - records KW - tool AB - The chemical and isotopic compositions of long-chain (C-36-C-39) unsaturated ketones (alkenones), a unique class of algal lipids, encode surface ocean properties useful for paleoceanographic reconstruction. Recently, we have sought to extend the utility of alkenones as oceanic tracers through measurement of their radiocarbon contents. Here. we describe a method for isolation of alkenones from sediments as a compound class based on a sequence of wet chemical techniques. The steps involved, which include silica gel column chromatography, urea adduction, and silver nitrate-silica gel column chromatography, exploit various structural attributes of the alkenones. Amounts of purified alkenones estimated by GC/FID measurements were highly correlated with CO2 yields after sample combustion, indicating purities of greater than 90% for samples containing >= 100 mu g C. The degree of alkenone unsaturation (U-37(K')) also varied minimally through the procedure. We also describe a high-performance liquid chromatography (HPLC) method to isolate individual alkenones for molecular-level structural and isotopic determination. VL - 47 SN - 0033-8222 IS - 3 N1 - 993nkTimes Cited:13 Cited References Count:22 JO - Radiocarbon ER - TY - JOUR T1 - Radiocarbon dating of alkenones from marine sediments: II. Assessment of carbon process blanks JF - Radiocarbon Y1 - 2005 A1 - Mollenhauer, G. A1 - Montlucon, D. A1 - Eglinton, T. I. KW - c-14 ams KW - organic-compounds KW - records KW - samples KW - system KW - tool AB - We evaluate potential process blanks associated with radiocarbon measurement of microgram to milligram quantities of alkenones at the National Ocean Sciences Accelerator Mass Spectrometry (NOSAMS) facility. Two strategies to constrain the contribution of blanks to alkenone C-14 dates were followed: 1) dating of samples of known age and 2) multiple measurements of identical samples. We show that the potential contamination associated with the procedure does not lead to a systematic bias of the results of alkenone dating to either younger or older ages. Our results indicate that alkenones record Delta(14)C of ambient DIC with an accuracy of approximately 10 parts per thousand. A conservative estimate of measurement precision is 17 parts per thousand for modern samples. Alkenone C-14 ages are expected to be reliable within 500 yr for samples younger than 10,500 C-14 yr. VL - 47 SN - 0033-8222 IS - 3 N1 - 993nkTimes Cited:13 Cited References Count:20 JO - Radiocarbon ER - TY - JOUR T1 - Radiocarbon dating of alkenones from marine sediments-III. Influence of solvent extractions procedures on 14C measurements of foraminifera JF - Radiocarbon Y1 - 2005 A1 - Ohkouchi, N. A1 - Eglinton, T. I. A1 - Hughen, K. A. A1 - Roosen, E. A1 - Keigwin, L. VL - 47 N1 - id: 554 ER - TY - JOUR T1 - Radiocarbon variability in the western North Atlantic during the last deglaciation JF - Science Y1 - 2005 A1 - Robinson, L. F. A1 - Adkins, J. F. A1 - Keigwin, L. D. A1 - Southon, J. A1 - Fernandez, D. P. A1 - Wang, S. L. A1 - Scheirer, D. S. AB - We present a detailed history of glacial to Holocene radiocarbon in the deep western North Atlantic from deep-sea corals and paired benthic-planktonic foraminifera. The deglaciation is marked by switches between radiocarbon-enriched and -depleted waters, leading to large radiocarbon gradients in the water column. These changes played an important role in modulating atmospheric radiocarbon. The deep-ocean record supports the notion of a bipolar seesaw with increased Northern-source deep-water formation linked to Northern Hemisphere warming and the reverse. In contrast, the more frequent radiocarbon variations in the intermediate/deep ocean are associated with roughly synchronous changes at the poles. VL - 310 IS - 5753 N1 - Robinson, Laura FAdkins, Jess FKeigwin, Lloyd DSouthon, JohnFernandez, Diego PWang, S-LScheirer, Daniel SengResearch Support, Non-U.S. Gov'tResearch Support, U.S. Gov't, Non-P.H.S.2005/12/03 09:00Science. 2005 Dec 2;310(5753):1469-73. Epub 2005 Nov 3. JO - Radiocarbon variability in the western North Atlantic during the last deglaciation ER - TY - CONF T1 - Rapid lateral particle transport in the Argintine Basin: Th-230 and molecular C-14 Evidence, Poster T2 - EGU General Assembly Y1 - 2005 A1 - Mollenhauer, Gesine A1 - McManus, J. F. A1 - Benthien, A. A1 - Muller, P. J. A1 - Eglinton, T. I. JF - EGU General Assembly CY - Vienna, Austria N1 - id: 548 ER - TY - JOUR T1 - Rapid viscoelastic uplift in southeast Alaska caused by post-Little Ice Age glacial retreat JF - Earth and Planetary Science Letters Y1 - 2005 A1 - Larsen, C. F. A1 - Motyka, R. J. A1 - Freymueller, J. T. A1 - Echelmeyer, K. A. A1 - Ivins, E. R. AB - Our observations show that extreme uplift in southeast Alaska began about 1770 AD, with relative sea level (RSL) change to 5.7 m and current uplift rates to 32 mm/yr. This region experienced widespread glacial melting following the Little Ice Age (LIA), with the collapse of the Glacier Bay Icefield alone equivalent to 8 mm of global sea level rise. Geodynamic modelling links the uplift to post-LIA isostatic rebound, with the extreme uplift signal and a priori knowledge of ice load changes requiring the presence of a low viscosity asthenosphere (3.7 X 10(18) Pa s). These crustal deformations are triggered by climate change through glacier wastage. (c) 2005 Elsevier B.V. All rights reserved. VL - 237 IS - 3-4 N1 - 968ijTimes Cited:109Cited References Count:44 JO - Rapid viscoelastic uplift in southeast Alaska caused by post-Little Ice Age glacial retreat ER - TY - JOUR T1 - Reassessing human settlement on the south coast of San Miguel Island, California: The use of 14C dating as a reconnaissance tool JF - Radiocarbon Y1 - 2005 A1 - Braje, Todd J. A1 - Erlandson, Jon M. A1 - Rick, Torben C. AB - Californias San Miguel Island contains over 600 archaeological sites, some occupied as early as 12,000 yr ago and most located along the islands north coast. Archaeologists have long believed the south coast to have been marginal or largely uninhabited. Burial of some landforms by sand dunes deposited after historical overgrazing, the lack of systematic survey, and a dearth of radiocarbon dating have also contributed to an underestimation of the intensity of human land use along the south coast of San Miguel Island. Our recent reconnaissance and dating of shell middens on the islands south coast indicate more intensive occupation than previously thought, with numerous south coast sites spanning at least the past 9000 yr, and demonstrate the utility of combining systematic archaeological reconnaissance and radiometrics in reconstructions of human settlement and historical ecology in coastal environments. VL - 47 UR - https://journals.uair.arizona.edu/index.php/radiocarbon/article/view/2795/2560 N1 - id: 579 JO - Reassessing human settlement on the south coast of San Miguel Island, California: The use of 14C dating as a reconnaissance tool ER - TY - JOUR T1 - Recent 2000-year geological records of mud in the inner shelf of the East China Sea and their climatic implications JF - Chinese Science Bulletin Y1 - 2005 A1 - Xiao, S. B. A1 - Li, A. C. A1 - Jiang, F. Q. A1 - Li, T. G. A1 - Huang, P. A1 - Xu, Z. K. AB - AXIS(14)C dating and grain-size analysis for Core DD2, located at the north of the Yangtze River-derived mud off the Zhejiang-Fujian coasts in the inner shelf of the East China Sea, provide us a high-resolution grain-size distribution curve varying with depth and time. Data in the upper mud layer of Core DD2 indicate that there are at least 9 abrupt grain-size increasing in recent 2000 years, with each corresponding very well with the low-temperature events in Chinese history, which might result from the periodical strengthening of the East Asian Winter Monsoon (EAWM), including the first-revealed maximum temperature lowering event at around 990 a BP. At the same time, the finer grain size section in Core DD2 agrees well with the Sui-Tang Warming Period (600-1000 a AD) defined previously by Zhu Kezhen, during which the climate had a warm, cold and warm fluctuation, with a dominated cooling period of 750-850 a AD. The Little Ice Age (LIA) can also be identified in the core. It starts around 1450 a AD and was followed by a subsequent cooling events at 1510, 1670 and 1840 a AD. Timing of these cold events revealed here still needs to be further verified owing to some current uncertainty of dating we used in this study. VL - 50 IS - 5 N1 - 923yeTimes Cited:20Cited References Count:58 JO - Recent 2000-year geological records of mud in the inner shelf of the East China Sea and their climatic implications ER - TY - JOUR T1 - Recent 8 ka mud records of the East Asian Winter Monsoon from the inner shelf of the East China Sea JF - Earth Science - Journal of China University of Geosciences Y1 - 2005 A1 - Xiao, S. B. A1 - Li, A. C. A1 - Chen, M. H. A1 - Liu, J. P. A1 - Jiang, F. G. A1 - Li, T. G. A1 - Xie, Q. A1 - Xiang, R. A1 - Chen, Z. VL - 30 IS - 5 N1 - id: 569 JO - Recent 8 ka mud records of the East Asian Winter Monsoon from the inner shelf of the East China Sea ER - TY - JOUR T1 - Recent and modern marine erosion on the New Jersey outer shelf JF - Marine Geology Y1 - 2005 A1 - Goff, J. A. A1 - Austin, J. A. A1 - Gulick, S. A1 - Nordfjord, S. A1 - Christensen, B. A1 - Sommerfield, C. A1 - Olson, H. A1 - Alexander, C. AB - Recent chirp seismic reflection data combined with multibeam bathymetry, backscatter, and analysis of grab samples and short cores provide evidence of significant recent erosion on the outer New Jersey shelf. The timing of erosion is constrained by two factors: (1) truncation at the seafloor of what is interpreted to be the transgressive ravinement surface at the base of the surficial sand sheet, and (2) truncation of apparently moribund sand ridges along erosional swales oriented parallel to the primary direction of modem bottom flow and oblique to the strike of the sand ridges. These observations place the erosion in a marine setting, post-dating the passage of the shoreface ravinement and the evolution of sand ridges that form initially in the near shore environment. Also truncated by marine erosion are shallowly buried, fluvial channel systems, formed during the Last Glacial Maximum and filled during the transgression, and a regional reflector "R" that is > &SIM; 40 kyr. Depths of erosion range from a few meters to > 10 m. The seafloor within eroded areas is often marked by "ribbon" morphology, seen primarily in the backscatter data as areas of alternating high and low backscatter elongated in the direction of primary bottom flow. Ribbons are more occasionally observed in the bathymetry; where observed, crests exhibit low backscatter and troughs exhibit high backscatter. Sampling reveals that the high backscatter areas of the ribbons consist of a trimodal admixture of mud, sand and shell hash, with a bimodal distribution of abraded and unabraded sand grains and microfauna. The shell hash is interpreted to be an erosional lag, while the muds and unabraded grains are, in this non-depositional environment, evidence of recent erosion at the seafloor of previously undisturbed strata. The lower-backscatter areas of the ribbon morphology were found to be a well-sorted medium sand unit only a few 10's of cm thick overlying the shelly/muddy/sandy material. Concentrations of well-rounded gravels and cobbles were also found in eroded areas with very high backscatter, and at least one of these appears to be derived from the base of an eroded fluvial channel. Seafloor reworking over the transgressive evolution of the shelf appears to have switched from sand ridge evolution, which is documented to &SIM; 40 m water depth, to more strictly erosional modification at greater water depths. We suggest that this change may be related to the reduction with water depth in the effectiveness of sediment resuspension by waves. Resuspension is a critical factor in the grain size sorting during transport by bottom currents over large bedforms like sand ridges. Otherwise, we speculate, displacement of sand by unidirectional currents will erode the seafloor. © 2005 Elsevier B.V. All rights reserved. VL - 216 IS - 4 N1 - 925kdTimes Cited:42Cited References Count:53 JO - Recent and modern marine erosion on the New Jersey outer shelf ER - TY - JOUR T1 - Redox stratification and anoxia of the early Precambrian oceans: Implications for carbon isotope excursions and oxidation events JF - Precambrian Research Y1 - 2005 A1 - Aharon, P. AB - An updated compendium of delta(13)C data offer compelling evidence that delta(13)C positive excursions of unsurpassed magnitude in the recorded Earth history (> 8 parts per thousand, and up to 18 parts per thousand PDB) occurred in the early Proterozoic (the Lomagundi event). Questions whether or not these unprecedented positive VC shifts were contemporaneous in various basins and represent local or global events remain unresolved. The framework of major geologic events that occurred in the Paleoproterozoic argues against a Snowball Earth scenario as a backdrop to these exceptional C-13-enrichments. Substantial increases of carbon flux ratio (F-o/F-c, eight times the Phanerozoic average) and organic carbon burial rate (F-o, three times the Phanerozoic average) are required to account for the observed C-13-enrichments under steady-state and dynamic equilibrium modes, respectively. These enhanced ratios and rates are conditional on the availability of a flux of nutrients to the contemporaneous biota producers in excess of the riverine flux, and a decoupling of the P and C cycles. It is argued that these two conditions were met between 2.25 and 2.11 Ga in a redox-stratified ocean with weak upwelling and sluggish meridional surface circulation. The alternative, that the major disturbance in the terrestrial carbon cycle occurred in a rapidly ventilated ocean, is assessed as being unlikely. A large pulse of O-2 equivalent to six to seven times the present terrestrial oxygen budget was rapidly scavenged and spent in the oxidation of reduced Fe and S transported to the shelves by rivers. This contention is consistent with data inferring low oxygen levels (10(-5) to 10(-2) PAL) in the Paleoproterozoic atmosphere and the occurrence of ocean anoxia until the late Precambrian. (c) 2005 Elsevier B.V. All rights reserved. VL - 137 IS - 3-4 N1 - id: 1585; 940DR Times Cited:19 Cited References Count:78 JO - Redox stratification and anoxia of the early Precambrian oceans: Implications for carbon isotope excursions and oxidation events ER - TY - JOUR T1 - Sedimentation and carbon burial on the northern California continental shelf: the signatures of land-use change JF - Continental Shelf Research Y1 - 2005 A1 - Leithold, E. L. A1 - Perkey, D. W. A1 - Blair, N. E. A1 - Creamer, T. N. AB - The burial of organic carbon (OC) on continental margins is strongly coupled to the supply and accumulation of inorganic mineral particles. It follows that carbon burial on the margins should be impacted by changes in riverine sediment delivery, yet these impacts have not been well documented. In this study, an similar to2000-year record of sedimentation and carbon burial on the continental shelf offshore from the Eel River in northern California was examined. The record reveals a 6-11-fold increase in the rate of sediment accumulation on the mid-shelf beginning about 1955, and a concomitant decrease in grain size and increase in flood-layer preservation. At the same time. the age of buried wood fragments abruptly decreased and their stable carbon isotopic composition became enriched in C-13. We argue that these changes can be explained largely as the result of altered land use in the Eel watershed during the past century and its impacts on shelf sediment dispersal processes.Sedimentary OC on the Eel shelf consists primarily of discrete wood fragments associated with coarse-silt- and sandsized particles, and of organic matter strongly bound to clay-sized mineral grains. The clay fraction is a particularly sensitive recorder of environmental change in the Eel system. Above the 1995 horizon, the clay fraction shows an abrupt decrease in OC concentration and loading (OC content normalized to particle surface area) attendant with the increased accumulation rate. Kerogen carbon constitutes a relatively constant proportion of the clay-associated OC throughout the similar to2000-year record. Increases in mass wasting and input of bedrock material following the onset of intensive industrial logging in the Eel watershed may have resulted in a lower loading of terrestrial plant OC in the clay fraction deposited after 1955 as suggested by isotopic mass balance calculations.The Eel River is representative of small mountainous watersheds worldwide that deliver a major portion of the sediment and carbon flux to the margins and that have been strongly impacted by land-use change during the past century. Our results suggest that such changes leave a distinctive mark in both the sedimentological and geochemical records preserved offshore. (C) 2004 Elsevier Ltd. All rights reserved. VL - 25 IS - 3 N1 - 894cyTimes Cited:29Cited References Count:109 JO - Sedimentation and carbon burial on the northern California continental shelf: the signatures of land-use change ER - TY - JOUR T1 - On the sedimentological origin of downcore variations of bulk sedimentary nitrogen isotope ratios JF - Paleoceanography Y1 - 2005 A1 - Kienast, M. A1 - Higginson, M. J. A1 - Mollenhauer, G. A1 - Eglinton, T. I. A1 - Chen, M. T. A1 - Calvert, S. E. AB - The bulk sedimentary nitrogen isotopic composition of two cores from nearby sites on the northern slope of the South China Sea (Site 17940 and Ocean Drilling Program (ODP) Site 1144) differs by up to >2‰ during the last glacial period. Given their close proximity, both core sites are located in the same biogeographic zone and nutrient regime, and it is thus unlikely that this offset is due to a true gradient in surface ocean conditions. In an attempt to resolve this offset, we have investigated the possible effects of two sedimentological parameters that can affect bulk sedimentary δ15N, namely, the variable contribution of inorganic N to bulk N in the sediment and the grain-size dependence of bulk δ15N. We find that neither effect, singly or in combination, is sufficient to explain the significant δ15N offset between the two down-core records. By elimination the most likely explanation for the observed discrepancy is a different origin of both the organic and inorganic nitrogen at each site. This study adds to the growing body of evidence highlighting the complex nature and origin of the sedimentary components in sediment drifts, such as ODP Site 1144. VL - 20 N1 - id: 1066 JO - On the sedimentological origin of downcore variations of bulk sedimentary nitrogen isotope ratios ER - TY - JOUR T1 - Solar influence on the Indian summer monssoon during the Holocene JF - Geophysical Research Letters Y1 - 2005 A1 - Gupta, Anil K. A1 - Das, Moumita A1 - Anderson, David M. VL - 32 N1 - id: 535 ER - TY - CONF T1 - Source, timing and depositional environments of Paleochannel incision and infill on the New Jersey Shelf T2 - 2005 National GSA Meeting Y1 - 2005 A1 - Alexander, C. A1 - Christensen, B. A1 - Turner, J. A1 - Goff, J. A1 - Austin J.A, Jr. A1 - Venherm, C. A1 - Nordfjord, S. A1 - Sommerfield, C. A1 - Gulick, S. A1 - Fulthorpe, C. JF - 2005 National GSA Meeting CY - Salat Lake City, UT N1 - id: 638 ER - TY - CHAP T1 - Status of the U. S. canary rockfish resource in 2005 T2 - Status of the Pacific Coast Groundfish Fishery Through 2005, Stock Assessment and Fishery Evaluation: Stock Assessments and Rebuilding Analyses Y1 - 2005 A1 - Methot, R. A1 - Stewart, I. J. ED - Council, Pacific Fishery Management JF - Status of the Pacific Coast Groundfish Fishery Through 2005, Stock Assessment and Fishery Evaluation: Stock Assessments and Rebuilding Analyses CY - Portland, OR VL - 6 N1 - id: 539 ER - TY - JOUR T1 - Subducting oceanic crust: The source of deep diamonds JF - Geology Y1 - 2005 A1 - Tappert, R. A1 - Stachel, T. A1 - Harris, J. W. A1 - Muehlenbachs, K. A1 - Ludwig, T. A1 - Brey, G. P. AB - Inclusions of majoritic garnet in diamonds from the Jagersfontein kimberlite formed at unusually great depths of similar to 250 to > 500 km in the asthenosphere and transition zone. The original host rocks were derived from a much shallower, basaltic (eclogitic) source. The presence of negative Eu anomalies in all majoritic garnets requires a crustal origin, thereby linking these very deep diamond sources to subducting oceanic crust. The carbon isotope values (delta(13)C) of the host diamonds fall within a narrow range at similar to -20%, which is fundamentally different from the broad range (-24% to -2%) and bimodal distribution of carbon isotopes of Jagersfontein diamonds that formed in the shallower lithosphere. This indicates that majoritic garnet-bearing diamonds at Jagersfontein inherited their light carbon isotopic composition directly from organic matter contained in a subducting slab. These diamonds were likely formed by direct conversion from graphite, well within the diamond stability field. VL - 33 IS - 7 N1 - 938hnTimes Cited:65Cited References Count:26 JO - Subducting oceanic crust: The source of deep diamonds ER - TY - CHAP T1 - Submerged paleoshorelines in the southern and western Black Sea - implications for inundated prehistoric archaeological sites T2 - The Black Sea Flood Questions: Changes in Coastline, Climate, and Human Settlement Y1 - 2005 A1 - Coleman, Dwight F. A1 - Ballard, Robert D. ED - V, Yanko-Hombach JF - The Black Sea Flood Questions: Changes in Coastline, Climate, and Human Settlement PB - Springer, Dordrecht CY - The Netherlands N1 - id: 1058 ER - TY - JOUR T1 - The supply and preservation of ancient and modern components of organic carbon on the Canadian Beaufort Shelf of the Arctic Ocean JF - Marine Chemistry Y1 - 2005 A1 - Goñi, M. A. A1 - Yunker, M. B. A1 - Macdonald, R. W. A1 - Eglinton, T. I. VL - 93 N1 - id: 757 ER - TY - JOUR T1 - Ten years of compound-specific radiocarbon analysis JF - Oceanography Y1 - 2005 A1 - Ingalls, A. E. A1 - Pearson, A. VL - 18 N1 - id: 504 ER - TY - JOUR T1 - Terrace inundation as an autocyclic mechanism for parasequence formation: Galveston Estuary, Texas, USA JF - Journal of Sedimentary Research Y1 - 2005 A1 - Rodriguez, A. B. A1 - Anderson, J. B. A1 - Simms, A. R. AB - Architecture of late Quaternary incised-valley fills is commonly attributed to the interplay between sea-level rise, sediment supply, and hydrodynamic processes. Inundation of fluvial terraces is commonly overlooked as an autocyclic mechanism for formation of parasequences. If the rate of sea-level rise and sediment supply is constant, architecture of terraced incised-valley fills will likely show backstepping parasequences. The control that variable antecedent topography has on architecture of incised-valley fills is examined in the Trinity incised valley, Texas. The Trinity valley is characterized by a series of downward-stepping terraces, and the Galveston Estuary formed above this irregular antecedent topography. Flooding surfaces, recognized in core by a decrease in sedimentation rates and a change from delta-plain to central-basin facies, formed at similar to -14 m, 8,200 cal. yr BP and similar to -10 m, 7,700 cal. yr BP, matching depths of the relatively flat fluvial terraces. Flooding surfaces formed rapidly and represent entire reorganization of the estuarine complex. Across the -10 m flooding surface, the river mouth and bay-head delta shifted landward at a rate of similar to 6.5 km per century and the associated barrier shoreline was stranded on the inner continental shelf, forming Heald Bank. Flooding surfaces formed as the rate of sea-level rise was decreasing, and are not associated with a decrease in sediment delivery to the estuary. As sea level inundates relatively flat fluvial terraces, rates of transgression rapidly increase, resulting in a sudden increase in accommodation space and an associated landward shift in coastal facies. Backstepping parasequences are inherent to the architecture of terraced incised-valley fills. VL - 75 IS - 4 N1 - id: 2041; PT: J; UT: WOS:000230261600008 JO - Terrace inundation as an autocyclic mechanism for parasequence formation: Galveston Estuary, Texas, USA ER - TY - JOUR T1 - Toward a Neoproterozoic composite carbon-isotope record JF - Geological Society of America Bulletin Y1 - 2005 A1 - Halverson, G. P. A1 - Hoffman, P. F. A1 - Schrag, D. P. A1 - Maloof, A. C. A1 - Rice, A. H. N. AB - Glacial deposits of Sturtian and Marinoan age occur in the well-studied Neoproterozoic successions of northern Namibia, South Australia, and northwestern Canada. In all three regions, the Marinoan glaciation is presaged by a large negative delta(13)C anomaly, and the cap carbonates to both glacial units share a suite of unique sedimentological, stratigraphic, and geochemical features. These global chronostratigraphic markers are the bases of a new correlation scheme for the Neoproterozoic that corroborates radiometric data that indicate that there were three glacial epochs between ca. 750 and 580 Ma. Intraregional correlation of Neoproterozoic successions in the present-day North Atlantic region suggests that glacial diamictite pairs in the Polarisbreen Group in northeastern Svalbard and the Tillite Group in eastern Greenland were deposited during the Marinoan glaciation, whereas the younger of a pair of glacials (Mortensnes Formation) in the Vestertana Group of northern Norway was deposited during the third (Gaskiers) Neoproterozoic glaciation. Gaskiers-aged glacial deposits are neither globally distributed nor overlain by a widespread cap carbonate but are associated with an extremely negative delta(13)C anomaly. The chronology developed here provides the framework for a new, high-resolution model carbon-isotope record for the Neoproterozoic comprising new delta(13)C (carbonate) data from Svalbard (Akademikerbreen Group) and Namibia (Otavi Group) and data in the literature from Svalbard, Namibia, and Oman. A new U-Pb zircon age of 760 +/- 1 Ma from an ash bed in the Ombombo Subgroup in Namibia provides the oldest direct time-calibration point in the compilation, but the time scale of this preliminary delta(13)C record remains poorly constrained. VL - 117 IS - 9-10 N1 - 960jtTimes Cited:414Cited References Count:174 JO - Toward a Neoproterozoic composite carbon-isotope record ER - TY - JOUR T1 - Tsunami history of an Oregon coastal lake reveals a 4600 yr record of great earthquakes on the Cascadia subduction zone JF - Geological Society of America Bulletin Y1 - 2005 A1 - Kelsey, H. M. A1 - Nelson, A. R. A1 - Hemphill-Haley, E. A1 - Witter, R. C. AB - Bradley Lake, on the southern Oregon coastal plain, records local tsunamis and seismic shaking on the Cascadia subduction zone over the last 7000 yr. Thirteen marine incursions delivered landward-thinning sheets of sand to the lake from nearshore, beach, and dune environments to the west. Following each incursion, a slug of marine water near the bottom of the freshwater take instigated a few-year-to-several-decade period of a brackish (<= 4 parts per thousand salinity) lake. Four additional disturbances without marine incursions destabilized sideslopes and bottom sediment, producing a suspension deposit that blanketed the lake bottom.Considering the magnitude and duration of the disturbances necessary to produce Bradley Lake's marine incursions, a local tsunami generated by a great earthquake on the Cascadia subduction zone is the only accountable mechanism. Extreme ocean levels must have been at least 5-8 m above sea level, and the cumulative duration of each marine incursion must have been at least 10 min. Disturbances without marine incursions require seismic shaking as well.Over the 4600 yr period when Bradley Lake was an optimum tsunami recorder, tsunamis from Cascadia plate-boundary earthquakes came in clusters. Between 4600 and 2800 cal yr B.P., tsunamis occurred at the average frequency of similar to 3-4 every 1000 yr. Then, starting similar to 2800 cal yr B.P., there was a 930-1260 yr interval with no tsunamis. That gap was followed by a similar to 1000 yr period with 4 tsunamis. In the last millennium, a 670-750 yr gap preceded the A.D. 1700 earthquake and tsunami. The A.D. 1700 earthquake may be the first of a new cluster of plate-boundary earthquakes and accompanying tsunamis.Local tsunamis entered Bradley Lake an average of every 390 yr, whereas the portion of the Cascadia plate boundary that underlies Bradley Lake ruptured in a great earthquake less frequently, about once every 500 yr. Therefore, the entire length of the subduction zone does not rupture in every earthquake, and Bradley Lake has recorded earthquakes caused by rupture along the entire length of the Cascadia plate boundary as well as earthquakes caused by rupture of shorter segments of the boundary. The tsunami record from Bradley Lake indicates that at times, most recently similar to 1700 yr B.P., overlapping or adjoining segments of the Cascadia plate boundary ruptured within decades of each other. VL - 117 IS - 7-8 N1 - 938hsTimes Cited:103Cited References Count:73 JO - Tsunami history of an Oregon coastal lake reveals a 4600 yr record of great earthquakes on the Cascadia subduction zone ER - TY - JOUR T1 - Two abundant bioaccumulated halogenated compounds are natural products JF - Science Y1 - 2005 A1 - Teuten, E. L. A1 - Xu, L. A1 - Reddy, C. M. AB - Methoxylated polybrominated diphenyl ethers (MeO-PBDEs) have been found bioaccumulated in the tissues of a variety of aquatic animals and at concentrations comparable to those of anthropogenic halogenated organic compounds, including polychlorinated biphenyls (PCBs). The origin of the MeO-PBDEs has been uncertain; circumstantial evidence supports a natural and/or an industrial source. By analyzing the natural abundance radiocarbon content of two MeO-PBDEs isolated from a True's beaked whale (Mesoplodon mirus), we show that these compounds were naturally produced. VL - 307 IS - 5711 N1 - Teuten, Emma LXu, LiReddy, Christopher MengResearch Support, Non-U.S. Gov'tResearch Support, U.S. Gov't, Non-P.H.S.2005/02/12 09:00Science. 2005 Feb 11;307(5711):917-20. JO - Two abundant bioaccumulated halogenated compounds are natural products ER - TY - JOUR T1 - Unusually high helium fluxes in the shallow Marshall aquifer in southern Michigan: implications for cross-formational flow and salinity sources JF - Eos Trans. AGU Fall Meeting Supplement Y1 - 2005 A1 - Ma, L. A1 - Castro, M. C. A1 - Hall, C. M. A1 - Walter, L. M. VL - 86 IS - 52 N1 - id: 437 JO - Unusually high helium fluxes in the shallow Marshall aquifer in southern Michigan: implications for cross-formational flow and salinity sources ER - TY - JOUR T1 - Using comprehensive two-dimensional gas chromatography retention indices to estimate environmental partitioning properties for a complete set of diesel fuel hydrocarbons JF - Analytical Chemistry Y1 - 2005 A1 - Arey, J. S. A1 - Nelson, R. K. A1 - Xu, L. A1 - Reddy, C. M. AB - Comprehensive two-dimensional gas chromatography (GC x GC) provides nearly complete composition data for some complex mixtures such as petroleum hydrocarbons. However, the potential wealth of physical property information contained in the corresponding two-dimensional chromatograms is largely untapped. We developed a simple but robust method to estimate GC x GC retention indices for diesel-range hydrocarbons. By exploiting n-alkanes as reference solutes in both dimensions, calculated retention indices were insensitive to uncertainty in the enthalpy of gas-stationary-phase transfer for a suite of representative diesel components. We used the resulting two-dimensional retention indices to estimate the liquid vapor pressures, aqueous solubilities, air-water partition coefficients, octanol-water partition coefficients, and vaporization enthalpies of a nearly complete set of diesel fuel hydrocarbons. Partitioning properties were typically estimated within a factor of 2; this is not as accurate as some previous estimation or measurement methods. However, these relationships may allow powerful and incisive analysis of phase-transfer processes affecting petroleum hydrocarbon mixtures in the environment. For example, GC x GC retention data might be used to quantitatively deconvolve the effects of water washing and evaporation on environmentally released diesel fuels. VL - 77 IS - 22 N1 - id: 1700; 985UM Times Cited:30 Cited References Count:56 JO - Using comprehensive two-dimensional gas chromatography retention indices to estimate environmental partitioning properties for a complete set of diesel fuel hydrocarbons ER - TY - JOUR T1 - Volatiles in subduction zone magmas: concentrations and fluxes based on melt inclusion and volcanic gas data JF - Journal of Volcanology and Geothermal Research Y1 - 2005 A1 - Wallace, P. J. AB - Owing to advances in microanalytical techniques over the last 15 years, there is a growing database on the volatile contents of subduction-related magmas as recorded in melt (glass) inclusions trapped in phenocrysts in volcanic rocks. Basaltic. magma from subduction zones show a wide range of water contents, ranging from as high as 6-8 to <0.5 wt.% H2O. Variations are related in some places to primary factors such as proximity to the arc front or extent of subduction-related mantle enrichment inferred from trace element systematics. Some low values of H2O in melt inclusions result from shallow degassing before crystallization and entrapment of inclusions. The dissolved CO2 contents of melt inclusions from basaltic arc lavas range from Mow detection (similar to25 ppm) to nearly 2500 ppm. This variability is caused by degassing of low-solubility CO2 before inclusions are trapped. The estimated primary CO2 content of arc basaltic magma inferred front global arc volcanic CO2 emissions and magma flux is >3000 ppm, suggesting that no melt inclusions sample undegassed arc magmas. The Cl and S contents of arc basaltic magmas are greater than midocean ridge basalts, indicating that these volatiles are also recycled from subducted sediment and altered oceanic crust back into the mantle wedge. Comparison of the fluxes of volatiles subducted back into the mantle along subduction zones and returned from the mantle to the surface reservoir (crust, ocean, and atmosphere) via magmatism suggests that there is an approximate balance for structurally bound H2O and Cl. In contrast, similar to50% of subducted C appears to be returned to the deep mantle by subduction, but uncertainties are relatively large. For S, the amount returned to the surface reservoir by subduction zone magmatism is only similar to15-30% of the total amount being subducted. Dacitic and rhyolitic magmas in arcs contain 1-6 wt.% H2O, a range that overlaps considerably with the values for basaltic magmas. Either basaltic parents for these differentiated magmas are relatively H2O-poor, or intermediate to silicic arc magmas form through open-system processes involving variable amounts of crustal melting, mixing with basalt and basaltic differentiates, and fluxing of CO2-rich vapor from mafic magma recharged into silicic magma bodies. Consideration of H2O-CO2 relations and gaseous SO2 emissions for intermediate to silicic arc magmas shows that such magmas are typically vapor-saturated during crystallization in the middle to upper crust. Gas emissions thus reflect migration and accumulation of volatiles within complex open magmatic systems. (C) 2004 Elsevier B.V. All rights reserved. VL - 140 IS - 1-3 N1 - 889fwTimes Cited:418Cited References Count:157 JO - Volatiles in subduction zone magmas: concentrations and fluxes based on melt inclusion and volcanic gas data ER - TY - JOUR T1 - When did oxygen appear in the atmosphere? JF - Geological Society of America Y1 - 2005 A1 - Ono, Shuhei VL - Abstracts with Programs N1 - id: 1577 ER - TY - JOUR T1 - 14C activity and global carbon cycle changes over the past 50,000 years JF - Science Y1 - 2004 A1 - Hughen, K. A1 - Lehman, S. A1 - Southon, J. A1 - Overpeck, J. A1 - Marchal, O. A1 - Herring, C. A1 - Turnbull, J. AB - A series of 14C measurements in Ocean Drilling Program cores from the tropical Cariaco Basin, which have been correlated to the annual-layer counted chronology for the Greenland Ice Sheet Project 2 (GISP2) ice core, provides a high-resolution calibration of the radiocarbon time scale back to 50,000 years before the present. Independent radiometric dating of events correlated to GISP2 suggests that the calibration is accurate. Reconstructed 14C activities varied substantially during the last glacial period, including sharp peaks synchronous with the Laschamp and Mono Lake geomagnetic field intensity minimal and cosmogenic nuclide peaks in ice cores and marine sediments. Simulations with a geochemical box model suggest that much of the variability can be explained by geomagnetically modulated changes in 14C production rate together with plausible changes in deep-ocean ventilation and the global carbon cycle during glaciation. VL - 303 IS - 5655 N1 - Hughen, KLehman, SSouthon, JOverpeck, JMarchal, OHerring, CTurnbull, Jeng2004/01/13 05:00Science. 2004 Jan 9;303(5655):202-7. JO - 14C activity and global carbon cycle changes over the past 50,000 years ER - TY - JOUR T1 - The 14C AMS system at the University of Georgia JF - Nuclear Instruments and Methods in Physics Research Y1 - 2004 A1 - Roberts, M. L. A1 - Culp, R. A. A1 - Dvoracek, D. K. A1 - Hodgins, G. W. L. A1 - Neary, M. P. A1 - Noakes, J. E. VL - B 233-224 IS - 50-54 N1 - id: 1809 ER - TY - JOUR T1 - The 14C AMS system at The University of Georgia JF - Proceedings of the Ninth International Conference on Accelerator Mass Spectrometry Y1 - 2004 A1 - Roberts, M. L. A1 - Culp, R. A. A1 - Dvoracek, D. K. A1 - Hodgins, G. W. L. A1 - Neary, M. P. A1 - Noakes, J. E. AB - The Center for Applied Isotope Studies at the University of Georgia has installed a compact 14C accelerator mass spectrometry (AMS) system manufactured by the National Electrostatics Corporation, Middleton, Wisconsin. The system utilizes a 134 sample ion source and a 500 kV Pelletron. In terms of cost and size, the new system is a significant advance over previous technology. Details and performance of the new system will be presented. VL - 223-224 N1 - id: 2103 JO - The 14C AMS system at The University of Georgia ER - TY - JOUR T1 - 14C Measurements JF - Aerosol Science & Technol Y1 - 2004 A1 - Tanner, R. L. A1 - Parkhurst, W. J. A1 - McNichol, A. P. VL - 38 IS - S1 N1 - id: 972 ER - TY - JOUR T1 - 215-kyr sea-level oscillations from marine and continental layers in Argentarola cave speleothems (Italy) JF - Global and Planetry Changes Y1 - 2004 A1 - Antonioli, F. A1 - E, Bard A1 - Silenzi, S. A1 - Potter, E. K. A1 - Improta, S. KW - Italy KW - Sea-level change KW - Submerged speleothems KW - Tyrrhenian sea AB - Several Quaternary sea-level changes are recorded by speleothems in the Argentarola Cave (Italy), which is currently flooded by the Mediterranean Sea. Speleothems with a sequence of continental layers and marine biogenic overgrowths (serpulid colonies), all presently covered by living serpulids, were sampled at water depths between −3.5 and −21.7 m. The composite sequence contains five marine and four continental layers, formed over the last 215 ka. The Mediterranean Sea flooded the cave during two short periods of MIS 7 (7.3 and 7.1), as well as during an episode at the end of MIS 6 and during MIS 5, when a thick biogenic overgrowth grew during MIS 5.2 and 5.4. Thin continental layers also formed during the LGM. This final speleothem layer was interrupted during the Holocene sea-level rise, but at different times in each speleothem. A Holocene sea-level curve has been constructed from this same layer. A thin marine layer, found only in the deeper stalagmites at −21.5 and −21.7 m, is tentatively related to the short marine transgression of Termination II, after 145 ka BP and before MIS 5.5. The island of Argentarola lies in a tectonically stable area and our data generally agree with the results obtained by other authors on speleothems from the Bahamas. The data presented here are compared with the SPECMAP curve and other recently published sea-level curves. VL - 43 N1 - id: 973 JO - 215-kyr sea-level oscillations from marine and continental layers in Argentarola cave speleothems (Italy) ER - TY - JOUR T1 - 48,000 years of climate and forest change from a biodiversity hotspot JF - Science Y1 - 2004 A1 - Bush, M. B. A1 - Silman, M. R. A1 - Urrego, D. H. AB - A continuous 48,000-year-long paleoecological record from Neotropical lower montane forest reveals a consistent forest presence and an ice-age cooling of ∼5° to 9°C. After 30,000 years of compositional stability, a steady turnover of species marks the 8000-year-long transition from ice-age to Holocene conditions. Although the changes were directional, the rates of community change were no different during this transitional period than in the preceding 30,000-year period of community stability. The warming rate of about 1°C per millennium during the Pleistocene-Holocene transition was an order of magnitude less than the projected changes for the 21st century. VL - 303 IS - 5659 N1 - id: 1016 JO - 48,000 years of climate and forest change from a biodiversity hotspot ER - TY - JOUR T1 - 50,000-Year-Old Plant May Warn of Death of Tropical Ice Caps JF - Newswise Y1 - 2004 A1 - Thompson, Lonnie VL - 13 Dec. 2004 N1 - id: 1224 ER - TY - JOUR T1 - An 8700 year old shell midden from the south coast of San Miguel Island, California JF - Current Research in the Pleistocene Y1 - 2004 A1 - Braje, Todd J. A1 - Erlandson, Jon M. A1 - Rick, Torben C. VL - 21 N1 - id: 1091 JO - An 8700 year old shell midden from the south coast of San Miguel Island, California ER - TY - JOUR T1 - Abrupt tropical vegetation response to rapid climate changes JF - Science Y1 - 2004 A1 - Hughen, K. A. A1 - Eglinton, T. I. A1 - Xu, L. A1 - Makou, M. AB - Identifying leads and lags between high- and low-latitude abrupt climate shifts is needed to understand where and how such events were triggered. Vascular plant biomarkers preserved in Cariaco basin sediments reveal rapid vegetation changes in northern South America during the last deglaciation, 15,000 to 10,000 years ago. Comparing the biomarker records to climate proxies from the same sediment core provides a precise measure of the relative timing of changes in different regions. Abrupt deglacial climate shifts in tropical and high-latitude North Atlantic regions were synchronous, whereas changes in tropical vegetation consistently lagged climate shifts by several decades. VL - 304 IS - 5679 N1 - Hughen, Konrad AEglinton, Timothy IXu, LiMakou, MatthewengResearch Support, Non-U.S. Gov't2004/05/25 05:00Science. 2004 Jun 25;304(5679):1955-9. Epub 2004 May 20. JO - Abrupt tropical vegetation response to rapid climate changes ER - TY - JOUR T1 - Across-shelf sediment transport since the Last Glacial Maximum, southern California margin JF - Geology Y1 - 2004 A1 - Sommerfield, C. K. A1 - Lee, H. J. AB - Correlation of continental shelf-slope stratigraphy in Santa Monica Bay (southern California) with Ocean Drilling Program records for nearby slope-basin sites has illuminated the timing and scale of terrigenous sediment dispersal on margin since the Last Glacial Maximum (LGM). Marine flooding surfaces preserved in a transgressive sequence on the Santa Monica Shelf provide a key link between base-level elevation and sediment transport across shelf. Sediment-accumulation rates at slope-basin sites were maximal ca. 15-10 ka, well after the LGM, decreased during the 12-9 ka transition from fluvial-estuarine to fully marine conditions on the shelf, and decelerated throughout the Holocene to 30%-75% of their values at the LGM. The deceleration is interpreted to manifest a landward shift in the margin depocenter with the onset of transgressive sedimentation beginning when sea level surmounted the shelf edge ca. 13 ka, as predicted by sequence-stratigraphic models. However, the records make clear that factors other than base level modulated slope-basin accumulation rates during the deglaciation. VL - 32 IS - 4 N1 - 808fbTimes Cited:19Cited References Count:36 JO - Across-shelf sediment transport since the Last Glacial Maximum, southern California margin ER - TY - CONF T1 - Advective controls on the age of marine sedimentary organic matter T2 - Gordon Research Conference Organic Geochemistry Y1 - 2004 A1 - Mollenhauer, Gesine A1 - Eglinton, Timothy I. A1 - Hayes, John M. JF - Gordon Research Conference Organic Geochemistry CY - Holderness School, New Hampshsire, USA N1 - id: 1068 ER - TY - JOUR T1 - Age and preservation of Amphistegina (foraminifera) in Hawaiian beach sand: implication for sand turnover rate and resource renewal JF - Marine Micropaleontology Y1 - 2004 A1 - Resig, J. M. AB - Radiocarbon dating of tests of Amphistegina spp. from the surface sand of Hawaiian beaches has revealed ages up to 1500 years or more. Preservation is related to age: the residual umbos are older than the intact tests. The antiquity of some of the tests suggests that predictions of a sand turnover rate of less than 100 years time based on Amphistegina productivity studies are in error and that the majority of tests produced in nearshore environments of Hawaii do not accumulate on the beach. (C) 2003 Elsevier B.V. All rights reserved. VL - 50 IS - 3-4 N1 - id: 178; 800DG Times Cited:3 Cited References Count:30 JO - Age and preservation of Amphistegina (foraminifera) in Hawaiian beach sand: implication for sand turnover rate and resource renewal ER - TY - JOUR T1 - Age of the Palos Verdes submarine debris avalanche, southern California JF - Marine Geology Y1 - 2004 A1 - Normark, W. R. A1 - McGann, M. A1 - Sliter, R. VL - 203 N1 - id: 990 ER - TY - JOUR T1 - Alabama Gulf Coast groundwaters: 4He and 14C as groundwater-dating tools JF - Geology Y1 - 2004 A1 - Carey, Anne A1 - Dowling, Carolyn B. A1 - Poreda, Robert J. KW - 14C KW - 4He KW - age dating KW - Baldwin County Alabama KW - groundwater AB - Analyses of 4He and 14C in groundwaters from a Miocene quartz aquifer on the Alabama Gulf Coast show the usefulness of 4He for dating these Holocene groundwaters. In this aquifer system of low alkalinities and low pHs, radiocarbon ages can be used without model correction. The groundwaters studied ranged from 42.3% to 95.5% modern carbon and yielded uncorrected ages of 375–6790 yr. Radiogenic 4He ages ranged from >50–7500 yr. VL - 32 IS - 4 N1 - id: 1222 JO - Alabama Gulf Coast groundwaters: 4He and 14C as groundwater-dating tools ER - TY - JOUR T1 - AMS 14C measurement and preparative techniques at NIES-TERRA JF - Nuclear Instruments and Methods in Physics Research B Y1 - 2004 A1 - Yoneda, Minoru A1 - Shibata, Yasuyuki A1 - Tanaka, Atsushi A1 - Uehiro, Takashi A1 - Morita, Masatoshi A1 - Uchida, Masao A1 - Kobayashi, Toshiyuki A1 - Kobayashi, Chiaki A1 - Suzuki, Ryo A1 - Miyamoto, Keisuke A1 - Hancock, Boze A1 - Dibden, Chris A1 - Edmonds, John S. AB - The AMS facility at the National Institute for Environmental Studies (NIES) has now been operating for five years since 1997. This AMS-dedicated facility named NIES-TERRA (Tandem accelerator for Environmental Research and Radiocarbon Analysis) consists of a 5MV tandem Pelletron (15SDH-2), a solid ion source with sequential injection system, a gas ion source with a simultaneous injection system, and a gas ionization detector. Typical precision with 14C measurements is around 0.5% and the background level has been achieved at around 50 kBP. Our main target is radiocarbon in environmental sciences, while other cosmogenic isotopes (10Be and 26Al) have been measured. Recently we have improved our preparation laboratory to increase sample throughput. CO2 production and purification using a commercial elemental analyzer connected to cryogenic traps (EA–CT) were investigated. We used a modified elemental analyzer with a chemical trap for separation and this is expected to reduce memory effect and background in comparison with an analyzer using gas-chromatography. This newly designed EA–CT system showed high precision and accuracy. Source of background contamination was also discussed based on the analysis of various amounts of standard materials. VL - 223-224 N1 - id: 1492 JO - AMS 14C measurement and preparative techniques at NIES-TERRA ER - TY - CONF T1 - Anthropogenic eutrophication of Long Island Sound: effects on diatom communities through time T2 - 7th Biennial Long Island Sound reserach conference proceedings Y1 - 2004 A1 - Cooper, S. R. A1 - Thomas, E. A1 - Varekamp, J. C. A1 - Sangiorgio, F. JF - 7th Biennial Long Island Sound reserach conference proceedings N1 - id: 1181 ER - TY - CONF T1 - Anthropogenic influences on benthis foraminiferal faunas in Long Island Sound T2 - 7th Biennial Long Island Sound reserach conference, Program and Abstracts Y1 - 2004 A1 - Thomas, E. A1 - Varekamp, J. C. A1 - Thaler, B. A1 - Acosta, Z. JF - 7th Biennial Long Island Sound reserach conference, Program and Abstracts N1 - id: 1183 ER - TY - JOUR T1 - Archean Tectonics 2004: A review JF - Precambrian Research Y1 - 2004 A1 - Van Kranendonk, M. VL - 131 N1 - id: 1601 ER - TY - JOUR T1 - Artifacts from a submerged prehistoric site on the Coos Bay Estuary, southern Oregon coast JF - Journal of California and Great Basin Anthropology Y1 - 2004 A1 - Minor, Rick A1 - Nelson, Alan R. VL - 24 IS - 1 N1 - id: 993 ER - TY - JOUR T1 - Assessing sources and agesof organic matter supporting river and estuarine bacterial production: a multiple isotope (Delta14C, delta13C and delta15N) approach JF - Limnology and Oceanography Y1 - 2004 A1 - McCallister, S. L. A1 - Bauer, J. E. A1 - Cherrier, J. C. A1 - Ducklow, H. W. VL - 49 N1 - id: 1153 ER - TY - JOUR T1 - A backbarrier overwash record of intense storms from Brigantine, New Jersey JF - Marine Geology Y1 - 2004 A1 - Donnelly, J. P. A1 - Butler, J. A1 - Roll, S. A1 - Wengren, M. A1 - Webb, T. AB - Analysis of aerial photographs and historic charts indicates that the barrier beach at Brigantine, NJ has migrated landward 300 to 400 m since 1869, primarily as a result of overwash during hurricanes and winter storms. A series of vibracores from the backbarrier salt marsh reveals a millennial-scale stratigraphic record of overwash deposition. Carbon-14 (C-14) and Cesium-137 (Cs-137) radioisotopic methods were used to date over-wash deposits (washovers). The ages of recent washovers are consistent with deposition during intense storms in 1938, 1944, 1950, and 1962. An additional overwash deposit recovered in five of the sediment cores was likely deposited by an intense hurricane strike in 1821 or possibly in 1788. Two prehistoric overwash fans were likely deposited by intense storms striking the New Jersey Coast in the 7th to l4th centuries and 6th to 7th centuries A.D. The landward barrier migration indicates that the older overwash sediments were likely transported a considerably greater distance than the more recent overwash fans. The greater distance of transport may indicate that the prehistoric storms that deposited overwash fans across the study site were more intense than the most intense storm to strike this coast in the historic period, the hurricane of 182 1. The spatially variable occurrence of overwash deposition at this site points to a need for multisite stratigraphic surveys of extensive stretches of the coast in order to develop reliable records of past intense storm frequency from backbarrier environments. (C) 2004 Elsevier B.V. All rights reserved. VL - 210 IS - 1-4 N1 - Sp. Iss. SI853thTimes Cited:74Cited References Count:37 JO - A backbarrier overwash record of intense storms from Brigantine, New Jersey ER - TY - CHAP T1 - Backbarrier sedimentary records of intense hurricane landfalls in the northeastern United States T2 - Hurricanes and Typhoons: Past, Present, and Potential Y1 - 2004 A1 - Donnelly, J. P. A1 - Iii, Webb T. ED - Murnane, R. JF - Hurricanes and Typhoons: Past, Present, and Potential PB - Columbia Press CY - New York, NY N1 - id: 500 ER - TY - JOUR T1 - Benthic foraminifera in the changing ecosystem of Long Island Sound, abstract JF - EOS Trans. AGU Y1 - 2004 A1 - Thaler, B. A1 - Thomas, E. A1 - Varekamp, J. C. VL - 85 IS - 17 N1 - id: 1182 ER - TY - JOUR T1 - Busted balls shell midden (CA-SMI-606): an early coastal site on San Miguel Island, California JF - North American Archaeologist Y1 - 2004 A1 - Erlandson, Jon M. A1 - Rick, Torben C. A1 - Batterson, Melissa R. VL - 25 N1 - id: 583 ER - TY - JOUR T1 - Carbonatization of oceanic crust by the seafloor hydrothermal activity and its significance as a CO2 sink in the Early Archean JF - Geochimica Et Cosmochimica Acta Y1 - 2004 A1 - Nakamura, K. A1 - Kato, Y. AB - Early Archean (3.46 Ga) hydrothermally altered basaltic rocks exposed near Marble Bar, eastern Pilbara Craton, have been studied in order to reveal geological and geochemical natures of seafloor hydrothermal carbonatization and to estimate the CO2 flux sunk into the altered oceanic crust by the carbonatization. The basaltic rocks are divided into basalt and dolerite, and the basalt is further subdivided into type I, having original igneous rock textures, and type II, lacking these textures due to strong hydrothermal alteration. Primary clinopyroxene phenocrysts are preserved in some part of the dolerite samples, and the alteration mineral assemblage of dolerite (chlorite + epidote + albite +/- quartz actinolite) indicates that the alteration. condition was typical greenschist facies. In other samples, all primary minerals were completely replaced by secondary minerals, and the alteration mineral assemblage of the type I and type II basalts (chlorite + K-mica + quartz + carbonate minerals +/- albite) is characterized by the presence of K-mica and carbonate minerals and the absence of Ca-Al silicate minerals such as epidote and actinolite, suggesting the alteration condition of high CO2 fugacity. The difference of the alteration mineral assemblages between basalt and dolerite is probably attributed to the difference of water/rock ratio that, in turn, depends on their porosity.Carbonate minerals in the carbonatized basalt include calcite, ankerite, and siderite, but calcite is quite dominant: The delta(13)C values of the carbonate minerals are -0.3 +/- 1.2parts per thousand and mostly within the range of marine carbonate; indicating that the carbonate minerals were formed by seafloor hydrothermal alteration and that carbonate carbon in the altered basalt was derived from seawater. Whole-rock chemical composition of the basaltic rocks is essentially similar to that of modern mid-ocean ridge basalt (MORB) except for highly mobile elements such as K2O, Rb, Sr, and Ba. Compared to the least altered dolerite, all altered basalt samples are enriched in K2O, Rb, and Ba, and are depleted in Na2O, reflecting the presence of K-mica replacing primary plagioclase. In addition, noticeable CO2 enrichment is recognized in the basalt due to the ubiquitous presence of carbonate minerals, but there was essentially neither gain nor loss of CaO. This suggests that the CO2 in the hydrothermal fluid (seawater) was trapped by using Ca originally contained in the basalt. The CaO/CO2, ratios of the basalt are generally the same as that of pure calcite, indicating that Ca in the basalt was almost completely converted to calcite during the carbonatization, although Mg and Fe were mainly redistributed into noncarbonate minerals such as chlorite.The carbon flux into the Early Archean oceanic crust by the seafloor hydrothermal carbonatization is estimated to be 3.8 X 10(13) mol/yr, based on the average carbon content of altered oceanic crust of 1.4 X 10(-3) mol/g, the alteration depth of 500 m, and the spreading rate of 1.8 X 10(11) cm(2)/yr. This flux is equivalent to or greater than the present-day total carbon flux. It is most likely that the seafloor hydrothermal carbonatization played an important role as a sink of atmospheric and oceanic CO2 in the Early Archean: Copyright (C) 2004 Elsevier Ltd. VL - 68 IS - 22 N1 - 869juTimes Cited:55Cited References Count:67 JO - Carbonatization of oceanic crust by the seafloor hydrothermal activity and its significance as a CO2 sink in the Early Archean ER - TY - JOUR T1 - Carbon-isotopic shifts associated with heterotrophy and biosynthetic pathways in direct- and indirect-developing sea urchins JF - Marine Ecology Progress Series Y1 - 2004 A1 - Villinski, J. C. A1 - Hayes, J. M. A1 - Villinski, J. T. A1 - Brassell, S. C. A1 - Raff, R. A. AB - Natural abundances of C-13 were measured in bulk biomass and in individual lipids isolated from 2 species of sea urchins, Heliocidaris erythrogramma and H. tuberculata, and from calcareous and green benthic algae on which they were feeding. Planktonic larvae of H. erythrogramma are lecithotrophic whereas those of H. tuberculata are planktotrophic. The organisms were collected from a subtidal environment in Botany Bay, Sydney, Australia. The biomass of both consumers was enriched in C-13 relative to their diets by up to 1.8parts per thousand. The carbon skeletons of sterols from the urchins derive at least in part from de novo biosynthesis by the urchins. Depending on chain length and degree of unsaturation, carboxylic acids from the urchins derive from de novo blosynthesis (14:0, unsaturated acids), from the diet (18:0), or from both these sources (16:0). H. tuberculata synthesizes a greater distribution and proportion of unsaturated carboxylic acids. Odd-C and branched-chain carboxylic acids derive in part from bacterial sources and are enriched in C-13 relative to algal lipids and depleted relative to those in urchins. Only H. erythrogramma, which uses wax esters-as storage lipids in its relatively large and buoyant eggs, produces significant quantities of n-alkanols; n-alkanols in H, tuberculata derive from the diet. In terms of molecular distributions and isotopic compositions, the lipids in fecal matter from both heterotrophs resemble those of the diet rather than those of the urchins. VL - 275 N1 - 847vnTimes Cited:4Cited References Count:34 JO - Carbon-isotopic shifts associated with heterotrophy and biosynthetic pathways in direct- and indirect-developing sea urchins ER - TY - CHAP T1 - CA-SMI-548: A 9500 year old shell midden at Running Springs, San Miquel Island, California T2 - Emerging from the Ice Age: Early Holocene Occupations on the Central California Coast Y1 - 2004 A1 - Erlandson, Jon M. A1 - Rick, Torben C. A1 - Vellanoweth, Rene L. A1 - Largaespada, Tony ED - Bertrando, Ethan JF - Emerging from the Ice Age: Early Holocene Occupations on the Central California Coast PB - San Luis Obispo County Archaeological Society Occasional Paper VL - 17 N1 - id: 584 ER - TY - JOUR T1 - Characterization of Siberian Arctic coastal sediments: Implications for terrestrial organic carbon export JF - Global Biogeochemical Cycles Y1 - 2004 A1 - Guo, L. D. A1 - Semiletov, I. A1 - Gustafsson, O. A1 - Ingri, J. A1 - Andersson, P. A1 - Dudarev, O. A1 - White, D. KW - arctic ocean KW - BLACK CARBON KW - climate KW - CO2 KW - continental-shelf KW - flux KW - isotopic composition KW - lena river KW - MATTER KW - ocean KW - organic carbon KW - quantification KW - Sediment AB - Surface sediments were collected during the 2000 TransArctic Expedition along the Siberian Arctic coastline, including the Ob, Yenisey, Khatanga, Lena, and Indigirka estuaries. Sediments were characterized for elemental composition (total organic carbon, TOC, black carbon, BC, and total N, as well as major and trace elements), isotopic signature (delta(13)C, delta(15)N, Delta(14)C, epsilon(Nd), Sr-87/Sr-86), and organic molecular composition to better understand river export variations over the large spatial scale of the Siberian Arctic. On average, 79 +/- 9% of the total C in sediments was organic while 21 +/- 9% was inorganic. BC made up 9 +/- 4% of the TOC pool, with a general increasing trend from west to east along the Siberian coast. The combined Nd- and Sr-isotopes (epsilon(Nd) and Sr-87/Sr-86) were used to define two distinct sediment sources between east and west Siberian regions with the Khatanga River as a boundary. Data from pyrolysis-GC/MS of the sedimentary organic carbon (SOC) indicated an increase in the freshness of the organic matter from west to east on the Siberian Arctic coast, with increasing relative abundance of furfurals (polysaccharides) with respect to nitriles. Values for the delta(13)C of SOC ranged from -27.1% (mostly terrigenous) to -23.8%, while delta(15)N increased from east to west (3.1 to 5.2%) with a significant correlation with C/N ratio. Values for the Delta(14)C of SOC ranged from -805 to -279%, with a consistent trend increasing from the east (Indigirka River) to the west (Ob River). These D 14 C values corresponded to a 14 C age of 2570 +/- 30 yBP in the Ob estuary and 13,050 +/- 50 yBP in the Indigirka estuary. Most importantly, D 14 C values were significantly correlated with the ratio of BC/TOC (R-2 = 0.91, n = 6), consistent with the distribution pattern of increasing permafrost zone from the west to the east along the Siberian coast. Together, our results suggest that older OC was derived from the release of recalcitrant BC during permafrost thawing and riverbank and coastal erosion, likely enhanced by ongoing environmental changes in the northern ecosystem. VL - 18 SN - 0886-6236 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=Alerting&SrcApp=Alerting&DestApp=WOS&DestLinkType=FullRecord;UT=WOS:000220432900001 IS - 1 N1 - 806knTimes Cited:99 Cited References Count:51 JO - Global Biogeochem Cy ER - TY - JOUR T1 - Chronology of sediment deposition in Upper Klamath Lake, Oregon JF - Journal of Paleolimnology Y1 - 2004 A1 - Colman, S. M. A1 - Bradbury, J. P. A1 - McGeehin, J. P. A1 - Holmes, C. W. A1 - Sarna-Wojcicki, A. M. A1 - Edgington, D. AB - A combination of tephrochronology and 14C, 210Pb, and 137Cs measurements provides a robust chronology for sedimentation in Upper Klamath Lake during the last 45 000 years. Mixing of surficial sediments and possible mobility of the radio-isotopes limit the usefulness of the 137Cs and 210Pb data, but 210Pb profiles provide reasonable average sediment accumulation rates for the last 100–150 years. Radiocarbon ages near the top of the core are somewhat erratic and are too old, probably as a result of detrital organic carbon, which may have become a more common component in recent times as surrounding marshes were drained. Below the tops of the cores, radiocarbon ages in the center of the basin appear to be about 400 years too old, while those on the margin appear to be accurate, based on comparisons with tephra layers of known age.Taken together, the data can be combined into reasonable age models for each site. Sediments have accumulated at site K1, near the center of the basin, about 2 times faster than at site CM2, on the margin of the lake. The rates are about 0.10 and 0.05 cm/yr, respectively. The chronological data also indicate that accumulation rates were slower during the early to middle Holocene than during the late Holocene, consistent with increasing wetness in the late Holocene. VL - 31 IS - 2 N1 - id: 182 JO - Chronology of sediment deposition in Upper Klamath Lake, Oregon ER - TY - JOUR T1 - Co2 and 3He in hydrothermal plumes: implications for mid-ocean ridge CO2 flux JF - Earth and Planetary Science Letters Y1 - 2004 A1 - Resing, Joseph A. A1 - Lupton, John E. A1 - Feely, Richard A. A1 - Lilley, Marvin D. VL - 226 N1 - id: 1518 ER - TY - JOUR T1 - The CO2-He-Ar-H2O systematics of the Manus back-arc basin: Resolving source composition from degassing and contamination effects JF - Geochimica Et Cosmochimica Acta Y1 - 2004 A1 - Shaw, A. M. A1 - Hilton, D. R. A1 - Macpherson, C. G. A1 - Sinton, J. M. AB - We report new stepped heating He, Ar, CO2 and water data on a petrogenetically diverse suite of lavas from the Manus back-arc basin, where a plume component has previously been identified. The aim of this study is to evaluate the superimposed effects of degassing and contamination in order to identify mantle source characteristics. CO2 abundances and carbon isotopes in both the vesicle ([CO2] up to 180ppm; delta(13)C as low as -33.6 parts per thousand) and glass ([CO2] up to 270ppm; delta(13)C as low as -34.3parts per thousand) phases reveal that samples have been modified by varying degrees of degassing. High water concentration samples (back-arc basin basalts (BABB) and arc type samples) show the highest degrees of degassing (i.e. lower delta(13)C values and lower CO2 contents). The results are modelled for both the glass and vesicle phases using batch and fractional degassing models. Parental melt compositions can be constrained to show the following CO2 concentration trend: are-type > BABB s.r. (southern rift) > MORB-2, E-MORB, X-BABB (extreme BABB), BABB > MORB-1 and MORB-smt. He-4/Ar-40* ratios of samples (14.6-1100) are consistent with residual volatiles from a degassed source. Variations in CO2/(3) He values are likely due to degassing, followed by contamination from a crustal source (either the subducting Solomon Sea Plate or the pre-existing crust through which the lavas erupt), as evidenced by high K2O/TiO2 ratios and low delta(13)C. The CO2/(3) He of the Manus plume is best estimated by the MORB-smt and MORB-1 samples at 3.1 +/- 0.6 X 10(9). This value is similar to previous estimates of plume CO2/(3) He values, which are either equal to or slightly greater than the upper mantle average of 2 X 10(9). Copyright (C) 2004 Elsevier Ltd. VL - 68 IS - 8 N1 - 813fdTimes Cited:30Cited References Count:76 JO - The CO2-He-Ar-H2O systematics of the Manus back-arc basin: Resolving source composition from degassing and contamination effects ER - TY - JOUR T1 - Collapse and rapid resumption of Atlantic meridional circulation linked to deglacial climate changes JF - Nature Y1 - 2004 A1 - McManus, J. F. A1 - Francois, R. A1 - Gherardi, J. M. A1 - Keigwin, L. D. A1 - Brown-Leger, S. AB - The Atlantic meridional overturning circulation is widely believed to affect climate. Changes in ocean circulation have been inferred from records of the deep water chemical composition derived from sedimentary nutrient proxies, but their impact on climate is difficult to assess because such reconstructions provide insufficient constraints on the rate of overturning. Here we report measurements of 231Pa/230Th, a kinematic proxy for the meridional overturning circulation, in a sediment core from the subtropical North Atlantic Ocean. We find that the meridional overturning was nearly, or completely, eliminated during the coldest deglacial interval in the North Atlantic region, beginning with the catastrophic iceberg discharge Heinrich event H1, 17,500 yr ago, and declined sharply but briefly into the Younger Dryas cold event, about 12,700 yr ago. Following these cold events, the 231Pa/230Th record indicates that rapid accelerations of the meridional overturning circulation were concurrent with the two strongest regional warming events during deglaciation. These results confirm the significance of variations in the rate of the Atlantic meridional overturning circulation for abrupt climate changes. VL - 428 IS - 6985 N1 - McManus, J FFrancois, RGherardi, J-MKeigwin, L DBrown-Leger, SengResearch Support, Non-U.S. Gov'tResearch Support, U.S. Gov't, Non-P.H.S.England2004/04/23 05:00Nature. 2004 Apr 22;428(6985):834-7. JO - Collapse and rapid resumption of Atlantic meridional circulation linked to deglacial climate changes ER - TY - JOUR T1 - Comments on potential geologic and seismic hazards affecting coastal Ventura County, CCalifornia JF - U. S. Geological Survey OFR 1004-1286 Y1 - 2004 A1 - Ross, S. D. Boore A1 - Fisher, M. A1 - Frankel, A. A1 - Geist, E. A1 - Hudnut, K. A1 - Kayen, R. A1 - Lee, H. A1 - Normark, W. R. A1 - Wong, F. N1 - id: 420 ER - TY - CONF T1 - A comparative analysis of time averaging for bivalves and brachiopods from a modern tropical shelf T2 - Geological Society of America, Abstracts with Programs Y1 - 2004 A1 - Krause R.A, Jr. A1 - Barbourl-Wood, S. L. A1 - Wehmiller, J. F. A1 - Kowalewski, M. A1 - Simoes, M. G. AB - 36(5):383 JF - Geological Society of America, Abstracts with Programs CY - Denver, CO, USA N1 - id: 718 ER - TY - JOUR T1 - Compound-specific radiocarbon dating of the varved Holocene sedimentary record of Saanich Inlet, Canada JF - Paleoceanography Y1 - 2004 A1 - Smittenberg, R. H. A1 - Hopmans, E. C. A1 - Schouten, S. A1 - Hayes, J. M. A1 - Eglinton, T. I. A1 - Damste, J. S. S. KW - british-columbia KW - compound-specific radiocarbon dating KW - crenarchaeol KW - ionization mass-spectrometry KW - marine-sediments KW - mediterranean sea KW - membrane-lipids KW - ne pacific KW - odp leg 169s KW - organic-matter KW - pacific-ocean KW - rapid isolation KW - Reservoir age KW - reservoir ages KW - saanich inlet AB - [1] The radiocarbon contents of various biomarkers extracted from the varve-counted sediments of Saanich Inlet, Canada, were determined to assess their applicability for dating purposes. Calibrated ages obtained from the marine planktonic archaeal biomarker crenarchaeol compared favorably with varve-count ages. The same conclusion could be drawn for a more general archaeal biomarker (GDGT-0), although this biomarker proved to be less reliable due to its less-specific origin. The results also lend support to earlier indications that marine crenarchaeota use dissolved inorganic carbon (DIC) as their carbon source. The average reservoir age offset DeltaR of 430 years, determined using the crenarchaeol radiocarbon ages, varied by +/-110 years. This may be caused by natural variations in ocean-atmosphere mixing or upwelling at the NE Pacific coast but variability may also be due to an inconsistency in the marine calibration curve when used at sites with high reservoir ages. VL - 19 SN - 0883-8305 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=Alerting&SrcApp=Alerting&DestApp=WOS&DestLinkType=FullRecord;UT=WOS:000221326700001 IS - 2 N1 - 819piTimes Cited:18 Cited References Count:69 JO - Paleoceanography ER - TY - JOUR T1 - The constancy of upper mantle fO2 through time inferred from V/Sc ratios in basalts JF - Earth and Planetary Science Letters Y1 - 2004 A1 - Li, Zheng-Xue Anser A1 - Lee, Cin-Ty Aeolus VL - 228 N1 - id: 1580 ER - TY - JOUR T1 - Controls on the variability of organic matter and dissolved inorganic carbon ages in northeast U.S. rivers JF - Marine Chemistry Y1 - 2004 A1 - Raymond, P. A. A1 - Bauer, J. E. A1 - Caraco, N. F. A1 - Cole, J. J. A1 - Longworth, B. E. A1 - Petsch, S. T. VL - 92 N1 - id: 967 ER - TY - JOUR T1 - Coupling instrumental and geological records of sea-level change: Evidence from southern New England of an increase in the rate of sea-level rise in the late 19th century JF - Geophysical Research Letters Y1 - 2004 A1 - Donnelly, J. P. A1 - Cleary, P. A1 - Newby, P. A1 - Ettinger, R. KW - accretion KW - cal yr ad KW - climate-ocean variations KW - connecticut KW - long-island sound KW - salt-marsh AB - We construct a high-resolution relative sea-level record for the past 700 years by dating basal salt-marsh peat samples above a glacial erratic in an eastern Connecticut salt marsh, to test whether or not the apparent recent acceleration in the rate of sea-level rise (SLR) is coeval with climate warming. The data reveal an average SLR rate of 1.0 +/- 0.2 mm/year from about 1300 to 1850 A. D. Coupling of the regional tide-gauge data (1856 to present) with this marsh-based record indicates that the nearly three-fold increase in the regional rate of SLR to modern levels likely occurred in the later half of the 19th century. Thus the timing of the observed SLR rate increase is coincident with the onset of climate warming, indicating a possible link between historic SLR increases and recent temperature increases. VL - 31 SN - 0094-8276 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=Alerting&SrcApp=Alerting&DestApp=WOS&DestLinkType=FullRecord;UT=WOS:000220432600003 IS - 5 N1 - 806kkTimes Cited:94 Cited References Count:20 JO - Geophys Res Lett ER - TY - JOUR T1 - Dating the rise of atmospheric oxygen JF - Nature Y1 - 2004 A1 - Bekker, A. A1 - Holland, H. D. A1 - Wang, P. L. A1 - Rumble, D. A1 - Stein, H. J. A1 - Hannah, J. L. A1 - Coetzee, L. L. A1 - Beukes, N. J. AB - Several lines of geological and geochemical evidence indicate that the level of atmospheric oxygen was extremely low before 2.45 billion years (Gyr) ago, and that it had reached considerable levels by 2.22 Gyr ago. Here we present evidence that the rise of atmospheric oxygen had occurred by 2.32 Gyr ago. We found that syngenetic pyrite is present in organic-rich shales of the 2.32-Gyr-old Rooihoogte and Timeball Hill formations, South Africa. The range of the isotopic composition of sulphur in this pyrite is large and shows no evidence of mass-independent fractionation, indicating that atmospheric oxygen was present at significant levels (that is, greater than 10(-5) times that of the present atmospheric level) during the deposition of these units. The presence of rounded pebbles of sideritic iron formation at the base of the Rooihoogte Formation and an extensive and thick ironstone layer consisting of haematitic pisolites and oolites in the upper Timeball Hill Formation indicate that atmospheric oxygen rose significantly, perhaps for the first time, during the deposition of the Rooihoogte and Timeball Hill formations. These units were deposited between what are probably the second and third of the three Palaeoproterozoic glacial events. VL - 427 IS - 6970 N1 - id: 1534; Bekker, A Holland, H D Wang, P-L Rumble, D 3rd Stein, H J Hannah, J L Coetzee, L L Beukes, N J England Nature. 2004 Jan 8;427(6970):117-20. JO - Dating the rise of atmospheric oxygen ER - TY - JOUR T1 - Decline of surface temperature and salinity in the western tropical Pacific Ocean in the Holocene epoch JF - Nature Y1 - 2004 A1 - Stott, L. A1 - Cannariato, K. A1 - Thunell, R. A1 - Haug, G. H. A1 - Koutavas, A. A1 - Lund, S. AB - In the present-day climate, surface water salinities are low in the western tropical Pacific Ocean and increase towards the eastern part of the basin. The salinity of surface waters in the tropical Pacific Ocean is thought to be controlled by a combination of atmospheric convection, precipitation, evaporation and ocean dynamics, and on interannual timescales significant variability is associated with the El Nino/Southern Oscillation cycles. However, little is known about the variability of the coupled ocean-atmosphere system on timescales of centuries to millennia. Here we combine oxygen isotope and Mg/Ca data from foraminifers retrieved from three sediment cores in the western tropical Pacific Ocean to reconstruct Holocene sea surface temperatures and salinities in the region. We find a decrease in sea surface temperatures of approximately 0.5 degrees C over the past 10,000 yr, whereas sea surface salinities decreased by approximately 1.5 practical salinity units. Our data imply either that the Pacific basin as a whole has become progressively less salty or that the present salinity gradient along the Equator has developed relatively recently. VL - 431 IS - 7004 N1 - Stott, LowellCannariato, KevinThunell, RobertHaug, Gerald HKoutavas, AthanasiosLund, SteveengResearch Support, U.S. Gov't, Non-P.H.S.England2004/09/03 05:00Nature. 2004 Sep 2;431(7004):56-9. JO - Decline of surface temperature and salinity in the western tropical Pacific Ocean in the Holocene epoch ER - TY - JOUR T1 - Deep global cycling of carbon constrained by the solidus of anhydrous, carbonated eclogite under upper mantle conditions JF - Earth and Planetary Science Letters Y1 - 2004 A1 - Dasgupta, R. A1 - Hirschmann, M. M. A1 - Withers, A. C. AB - We present partial melting experiments that constrain the near solidus phase relations of carbonated eclogite from 2 to 8.5 GPa. The starting material was prepared by adding 5 wt.% CO2 in the form of a mixture of Fe-Mg-Ca-Na-K carbonates to an eclogite from Salt Lake crater, Oahu, Hawaii and is a reasonable approximation of carbonated oceanic crust from which siliceous hydrous fluids have been extracted during subduction. Melt-present versus melt-absent conditions are distinguished based on textural criteria. Garnet and clinopyroxene appear in all the experiments. Between 2 and 3 GPa, the subsolidus assemblage also includes ilmenite+/-calcio-dolomite(ss)+/-CO2, whereas above the solidus (1050-1075 degreesC at 3 GPa) calcio-dolomitic liquid appears. From 3 to 4.5 GPa, dolomite(ss) is stable at the solidus and the near-solidus melt becomes increasingly dolomitic. The appearance of dolomite above 3 GPa is accompanied by a negative Clapeyron slope of the solidus, with a minimum located between 995 and 1025 degreesC at ca. 4 GPa. Above 4 GPa, the solidus rises with increasing pressure to 1245+35 degreesC at 8.5 GPa and magnesite becomes the subsolidus carbonate. Dolomitic melt coexists with magnesite+garnet+cpx+rutile along the solidus from 5 to 8.5 GPa.Comparison of our results to other recent experimental studies [T. Hammouda, High-pressure melting of carbonated eclogite and experimental constraints on carbon recycling and storage in the mantle, Earth Planet. Sci. Lett. 214 (2003) 357-368; G.M. Yaxley, G.P. Brey, Phase relations of carbonate-beating eclogite assemblages from 2.5 to 5.5 GPa: implications for petropnesis of carbonatites, Contrib. Mineral. Petrol. 146 (2004) 606-6191 shows that carbonate minerals are preserved in anhydrous or slightly hydrous carbonated eclogite to temperatures >1100 and >1200 degreesC at 5 and 9 GPa, respectively. Thus, deep subduction of carbonate is expected along any plausible subduction geotherm. If extrapolated to higher pressures, the carbonated eclogite solidus is likely to intersect the oceanic geotherm at a depth close to 400 km. Carbonated eclogite bodies entering the convecting upper mantle will thus release carbonate melt near the top of the mantle transition zone and may account for anomalously slow seismic velocities at depths of 280-400 km. Upon release, this small volume, highly reactive melt could be an effective agent of deep mantle metasomatism. Comparison of the carbonated eclogite solidus with that of peridotite-CO2 shows a shallower solidus-geotherm intersection for the latter. This implies that carbonated peridotite is a more likely proximal source of magmatic carbon in oceanic provinces. However, carbonated eclogite is a potential source of continental carbonatites, as its solidus crosses the continental shield geotherm at ca. 4 GPa. Transfer of eclogite-derived carbonate melt to peridotite may account for the geochemical characteristics of some oceanic island basalts (OIBs) and their association with high CaO and CO2. (C) 2004 Elsevier B.V. All rights reserved. VL - 227 IS - 1-2 N1 - 864qyTimes Cited:192Cited References Count:49 JO - Deep global cycling of carbon constrained by the solidus of anhydrous, carbonated eclogite under upper mantle conditions ER - TY - JOUR T1 - Deglacial history of the Ecuadorian Andes and implication for climate variations: Preliminary results JF - Eos Trans. AGU Fall Meeting Supplement Y1 - 2004 A1 - Hall, M. A1 - Rinterknecht, V. R. A1 - Schaefer, J. M. A1 - R, Seager A1 - Greene, A. VL - 85 IS - 47 N1 - id: 1003 ER - TY - JOUR T1 - Deglacial sea surface temperatures of the western tropical Pacific: A new look at old coral JF - Paleoceanography Y1 - 2004 A1 - Cohen, A. L. A1 - Hart, S. R. KW - bolling-allerod KW - climate-change KW - coral sr/ca KW - diagenesis KW - ion microprobe KW - last deglaciation KW - paleotemperature proxy KW - radiocarbon KW - record KW - sea surface temperature KW - sr/ca KW - strontium KW - symbiotic coral KW - trace-elements KW - tropical pacific AB - Using Secondary Ion Mass Spectrometry ( SIMS) ion microprobe techniques, we generated annual Sr/Ca cycles with subweekly resolution from chunks of Porites coral retrieved from a Tahiti barrier reef drill core (149degreesW, 17degreesS), representing the period 13,650 to 13,100 years B.P. The centers of pristine skeletal septa were selectively targeted with a 10 mum diameter ion beam spot, avoiding adjacent pore spaces occupied by secondary aragonite needles. Applying a Sr/Ca-sea surface temperature (SST) calibration equation derived from modern Tahiti Porites having the same low growth rate as the fossil specimens, we obtained SSTs similar to0.5degrees-1.5degreesC cooler during the Bolling-Allerod relative to the present day, with no significant change in seasonality. On the contrary, we estimate that analysis of bulk samples would yield excessively cool Sr/Ca-based SST estimates due to the occupation by secondary aragonite crystals of up to 50% of the skeletal pore space in the ancient samples. We find that growth rate effects on coral Sr/Ca further depress the apparent mean annual derived SSTs (by >3degreesC) and amplify the apparent seasonality by selectively enhancing wintertime cooling. Our microscale analysis of pristine skeleton and application of an appropriate growth-dependent calibration yield Sr/Ca-derived SSTs that are in good agreement with those derived from Mg/Ca ratios of calcitic foraminifera which indicate a continuous postglacial warming of the western tropical Pacific, in phase with the warming of the tropical Atlantic. VL - 19 SN - 0883-8305 IS - 4 N1 - 885czTimes Cited:30 Cited References Count:37 JO - Paleoceanography ER - TY - CHAP T1 - Dynamics of tidal salt barren formation and the record of present-day sea level change T2 - The Ecogeomorphology of Tidal Marshes, American Geophysical Union Y1 - 2004 A1 - Hsieh, Y. P. ED - Fagherazzi, S. JF - The Ecogeomorphology of Tidal Marshes, American Geophysical Union N1 - id: 1164 ER - TY - JOUR T1 - Early diagenetic remineralization of sedimentary organic C in the Gulf of Papua deltaic complex (Papua New Guinea): Net loss of terrestrial C and diagenetic fractionation of C isotopes JF - Geochimica et Cosmochimica Acta Y1 - 2004 A1 - Aller, R. C. A1 - Blair, N. E. AB - Oceania supplies similar to40% of the global riverine flux of organic carbon, approximately half of which is injected onto broad continental shelves and processed in shallow deltaic systems. The Gulf of Papua, on the south coast of the large island of New Guinea, is one such deltaic clinoform complex. It receives similar to4 Mt yr(-1) particulate terrestrial organic carbon with initial particle C-org loading similar to0.7 mg m(-2). C-org loading is reduced to similar to0.3 mg m(-2) in the topset-upper foreset zones of the delta despite additional inputs of mangrove and planktonic detritus, and high net sediment accumulation rates of 1-4 cm yr(-1) . Carbon isotopic analyses (delta(3)C, Delta(14)C) of SigmaCO(2) and C-org demonstrate rapid ( VL - 68 IS - 8 N1 - id: 976; 813FD Times Cited:44 Cited References Count:72 JO - Early diagenetic remineralization of sedimentary organic C in the Gulf of Papua deltaic complex (Papua New Guinea): Net loss of terrestrial C and diagenetic fractionation of C isotopes ER - TY - CONF T1 - The early history of Long Island Sound T2 - 7th Biennial Long Island Sound research conference, Program/Abstracts Y1 - 2004 A1 - Varekamp, J. C. A1 - Thomas, E. A1 - Groner, M. JF - 7th Biennial Long Island Sound research conference, Program/Abstracts N1 - id: 741 ER - TY - JOUR T1 - Enhanced marine productivity off western North America during warm climate intervals of the past 52 kyr JF - Geology Y1 - 2004 A1 - Ortiz, J. D. A1 - O'Connell, S. A1 - DelViscio, J. A1 - Dean, W. E. A1 - Carriquiry, J. A1 - Marchitto, T. M. A1 - Zheng, Y. A1 - van Geen, A. VL - 32 IS - 6 N1 - id: 603 ER - TY - JOUR T1 - Episodic methane release events from Last Glacial marginal sediments in the western North Pacific JF - Geochemistry Geophysics Geosystems Y1 - 2004 A1 - Uchida, M. A1 - Shibata, Y. A1 - Ohkushi, K. A1 - Ahagon, N. A1 - Hoshiba, M. KW - atmospheric composition and structure : geochemical cycles KW - atmospheric methane KW - carbon isotopes KW - carbon isotopic fractionation KW - climate-change KW - cold seeps KW - diploptene KW - Foraminifera KW - gas-hydrate KW - geochemistry : isotopic composition/chemistry KW - geochemistry : organic geochemistry KW - hydrocarbons KW - interglacial KW - intermediate water KW - methane hydrate KW - santa-barbara basin KW - sea sediments KW - subduction zone KW - western north pacific AB - [1] According to recent observations of anomalous bottom-simulating reflections (BSR),the northwest Pacific marginal sediments around Japan main islands bear large abundances of methane hydrate [Satoh, 2002]. During the Last Glacial, direct and indirect evidence accumulated from geochemical data suggests that methane episodically released from hydrate trapped in the seafloor sediments [ Dickens et al., 1995; Hinrichs et al., 2003; Kennett et al., 2000]. Here we show that marginal sediments from the western North Pacific contain a hopanoid 17alpha( H), 21beta(H)-hop-22(29)-ene ( diploptene) derived from the activity of methanotrophic bacteria in water column and/or surface sediment during a warming period (Interstadial 3) in the Last Glacial. The carbon isotopic compositions of diploptene range between - 41.0parts per thousand and - 27.9parts per thousand ( relative to PDB). In the horizon indicative of a contribution of methanotrophic bacteria, foraminiferal isotope signals were also found with highly depleted C-13 compositions of planktonic foraminifera ( similar to - 1.9parts per thousand, PDB) and benthic foraminifera ( similar to - 0.8parts per thousand, PDB), suggesting indirect records of enhanced incorporation of C-13-depleted CO2 formed by methanotrophic process that use C-12-enriched methane as their main source of carbon. From combined isotopic data of molecular ( diploptene) and foraminifera, the most prominent signal of methane release was detected in the sediments deposited around 25.4 cal. kyr BP ( similar to 100 year time span), corresponding to the Interstadial 3. This is the first evidence of methane hydrate instability in the open western North Pacific during the Last Glacial. Considering the glacial-interglacial hydrographic conditions in this region, the instability of methane hydrate may be modulated by intermediate water warming and/or the lowering of sea level. Our results suggest that the western North Pacific marginal regions may be a profound effect on rapid global warming climate changes during the Last Glacial. VL - 5 SN - 1525-2027 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=Alerting&SrcApp=Alerting&DestApp=WOS&DestLinkType=FullRecord;UT=WOS:000223543700001 IS - 8 N1 - 849mvTimes Cited:13 Cited References Count:73 JO - Geochem Geophy Geosy ER - TY - JOUR T1 - The eutrophication of Long Island Sound, abstract JF - EOS Trans. AGU Y1 - 2004 A1 - Varekamp, J. C. A1 - Lugolobi, F. A1 - Thomas, E. A1 - Mecray, E. A1 - Buchholtz ten Brink, M. R. VL - 85 IS - 17 N1 - id: 740 ER - TY - JOUR T1 - Eutrophication of western Long Island Sound JF - GSA Annual Meeting Y1 - 2004 A1 - Thomas, E. A1 - Varekamp, J. C. A1 - Acosta, Z. A1 - Thaler, B. A1 - Cooper, S. A1 - Sangiorgio, F. VL - Abstracts 36 IS - 6 N1 - id: 739 ER - TY - JOUR T1 - Evaluation of ocean carbon cycle models with data-based metrics JF - Geophysical Research Letters Y1 - 2004 A1 - Matsumoto, K. A1 - Sarmiento, J. L. A1 - Key, R. M. A1 - Aumont, O. A1 - Bullister, J. L. A1 - Caldeira, K. A1 - Campin, J. M. A1 - Doney, S. C. A1 - Drange, H. A1 - Dutay, J. C. A1 - Follows, M. A1 - Gao, Y. A1 - Gnanadesikan, A. A1 - Gruber, N. A1 - Ishida, A. A1 - Joos, F. A1 - Lindsay, K. A1 - Maier-Reimer, E. A1 - Marshall, J. C. A1 - Matear, R. J. A1 - Monfray, P. A1 - Mouchet, A. A1 - Najjar, R. A1 - Plattner, G. K. A1 - Schlitzer, R. A1 - Slater, R. A1 - Swathi, P. S. A1 - Totterdell, I. J. A1 - Weirig, M. F. A1 - Yamanaka, Y. A1 - Yool, A. A1 - Orr, J. C. KW - anthropogenic co2 KW - pacific-ocean KW - radiocarbon AB - New radiocarbon and chlorofluorocarbon-11 data from the World Ocean Circulation Experiment are used to assess a suite of 19 ocean carbon cycle models. We use the distributions and inventories of these tracers as quantitative metrics of model skill and find that only about a quarter of the suite is consistent with the new data-based metrics. This should serve as a warning bell to the larger community that not all is well with current generation of ocean carbon cycle models. At the same time, this highlights the danger in simply using the available models to represent the state-of-the-art modeling without considering the credibility of each model. VL - 31 SN - 0094-8276 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=Alerting&SrcApp=Alerting&DestApp=WOS&DestLinkType=FullRecord;UT=WOS:000220743900001 IS - 7 N1 - 811adTimes Cited:110 Cited References Count:17 JO - Geophys Res Lett ER - TY - JOUR T1 - Evidence for Late Holocene earthquakes on the Utsalady Point Fault, northern puget lowland, Washington JF - Bulletin of the Seismological Society of America Y1 - 2004 A1 - Johnson, S. Y. A1 - Nelson, A. R. A1 - Personius, S. F. A1 - Wells, R. E. A1 - Kelsey, H. N. A1 - Sherrod, B. L. A1 - Okumura, K. A1 - Koehler, R. A1 - Witter, R. C. A1 - Bradley, L. A. A1 - Harding, D. J. AB - Trenches across the Utsalady Point fault in the northern Puget Lowland of Washington reveal evidence of at least one and probably two late Holocene earthquakes. The "Teeka"' and "Duffers" trenches were located along a 1.4-km-long. 1- to 4-m-high, northwest-trending, southwest-facing. topographic scarp recognized from Airborne Laser Swath Mapping. Glaciomarine drift exposed in the trenches reveals evidence of about 95 to 150 cm of vertical and 200 to 220 cm of left-lateral slip in the Teeka trench. Radiocarbon ages from a buried soil A horizon and overlying slope colluvium alone, with the historical record of earthquakes suggest that this faulting occurred 100 to 400 calendar years B.P. (A.D. 1550 to 1850). In the Duffers trench, 370 to 450 cm of vertical separation is accommodated by faulting (similar to210 cm) and folding (similar to160 to 240 cm), with probable but undetermined amounts of lateral slip. Stratigraphic relations and radiocarbon ages from buried soil, colluvium. and fissure fill in the hanging wall suggest the deformation at Duffers is most likely from two earthquakes that occurred between 100 to 500 and 1100 to 2200 calendar years B.P., but deformation during a single earthquake is also possible. For the two-earthquake hypothesis, deformation at Teeka trench in the first event involved folding but not faulting. Regional relations suggest that the earthquake(s) were M greater than or equal to similar to6.7 and that offshore rupture may have produced tsunamis. Based on this investigation and related recent studies, the maximum recurrence interval for large ground-rupturing crustal-fault earthquakes in the Puget Lowland is about 400 to 600 years or less. VL - 94 IS - 6 N1 - 887giTimes Cited:18Cited References Count:46 JO - Evidence for Late Holocene earthquakes on the Utsalady Point Fault, northern puget lowland, Washington ER - TY - CONF T1 - Evidence of historical wet period deposits in central Long Island Sound: source and transport processes based on mercury profiles and sedimentology T2 - 7th biennial Long Island Sound research conference, Program and abstrracts Y1 - 2004 A1 - Carey, D. A. A1 - Varekamp, J. C. JF - 7th biennial Long Island Sound research conference, Program and abstrracts N1 - id: 734 ER - TY - JOUR T1 - The evolution of the Earth surface sulfur reservoir JF - American Journal of Science Y1 - 2004 A1 - Canfield, D. E. AB - The surface sulfur reservoir is in intimate contact with the mantle. Over long time scales, exchange with the mantle has influenced the surface reservoir size and possibly its isotopic composition. Processes delivering sulfur to the Earth surface from the mantle include volcanic outgassing, hydrothermal input, and ocean crust weathering. The sulfide fixed in ocean crust as a consequence of hydrothermal sulfate reduction, and subduction of sedimentary sulfides, represent return pathways of sulfur to the mantle. The importance of these different pathways in influencing the size of the surface sulfur reservoir depends on the particulars of ocean and atmosphere chemistry. During times of banded iron formation when the oceans contained dissolved iron, sulfide from submarine hydrothermal activity was precipitated on the seafloor and subsequently subducted back into the mantle and, therefore, had little impact on the surface sulfur reservoir size. With sulfidic ocean bottom water conditions, which may have occurred through long stretches of the Mesoproterozoic and Neoproterozoic, significant amounts of sulfide is subducted into the mantle. When the oceans are oxic, sulfide subduction is unimportant, and an additional source, ocean crust weathering, delivers sulfur to the Earth surface. Thus, under oxic conditions the surface environment accumulates sulfur, and probably has for most of the last 700 million years.Mass balance modeling suggests that the surface sulfur reservoir may have peaked in size in the early Mesoproterozoic, declined to a minimum in the Neoproterozoic, and increased to its present size through the Phanerozoic. The exchange of sulfur between the mantle and the surface environment can also influence the isotopic composition of the surface reservoir. Modeling shows that the subduction of S-34- depleted sulfur through the Mesoproterzoic could have significantly increased the average delta(34)S of the surface reservoir into the late Neoproterozoic. The preserved isotope record through the Neoproterozoic is well out of balance, with the average delta(34)S for sulfate and sulfide both exceeding the modem crustal average. This imbalance could be explained, at least partly, if the crustal average was more S-34-enriched than at present, as the modeling presented here suggests. VL - 304 IS - 10 N1 - 889sqTimes Cited:142Cited References Count:59 JO - The evolution of the Earth surface sulfur reservoir ER - TY - JOUR T1 - Export of young terrigenous dissolved organic carbon from rivers to the Arctic Ocean JF - Geophysical Research Letters Y1 - 2004 A1 - Benner, R. A1 - Benitez-Nelson, B. A1 - Kaiser, K. A1 - Amon, R. M. W. AB - Soils in the drainage basins of Arctic rivers are a major global reservoir of aged organic carbon. The fate of this old carbon is of growing concern as the effects of climate change become more evident in the Arctic. We report natural abundance C-14 data indicating that dissolved organic carbon (DOC) from several Eurasian and North American rivers is predominantly young and largely derived from recently-fixed C in plant litter and upper soil horizons. Concentrations of dissolved lignin phenols, unique organic tracers of terrestrial plant material, and C-14 content in DOC were strongly correlated throughout the Arctic Ocean, indicating terrigenous DOC is mostly young and widely distributed in polar surface waters. These young ages of terrigenous DOC in rivers and the ocean indicate little of the old carbon stored in Arctic soils is currently being mobilized in the dissolved component of continental runoff. VL - 31 IS - 5 N1 - id: 646; 806KJ Times Cited:60 Cited References Count:34 JO - Export of young terrigenous dissolved organic carbon from rivers to the Arctic Ocean ER - TY - NEWS T1 - Fate of mercury in Long Island Sound T2 - Newsday Magazine Y1 - 2004 A1 - Varekamp, J. C. JF - Newsday Magazine ER - TY - CHAP T1 - Flexible strategies for resource defense on the northern channel islands of California: An agent-based model T2 - The Archaeology of Insularity: Examining the Past in Island Environments Y1 - 2004 A1 - Kennett, D. J. A1 - Clifford, R. ED - Fitzpatrick, Scott JF - The Archaeology of Insularity: Examining the Past in Island Environments PB - Greenwood Press CY - West Port, CT N1 - id: 470 ER - TY - JOUR T1 - From bedrock to burial: the evolution of particulate organic carbon across coupled watershed-continental margin systems JF - Marine Chemistry Y1 - 2004 A1 - Blair, N. E. A1 - Leithold, E. L. A1 - Aller, R. C. AB - Deltas sequester nearly half of the organic carbon (OC) buried in the marine environment. The composition of the buried organic matter reflects both watershed and seabed processes. A conceptual model is presented that describes the evolution of particulate organic carbon (POC) as it travels from its terrestrial source to its burial at sea. Alterations to the POC occur primarily in bioactive reservoirs, such as soils and the surface mixed layer (SML) of the seabed, where new organic matter can be added and older material degraded. Bypassing or rapid passage through the reservoirs is a key parameter because it avoids change. The Eel River of northern California and the Amazon River systems illustrate the importance of reservoir transit time and storage in determining the character of POC delivered to the continental margin. The Eel exemplifies a bypass system. Mass-wasting processes on land deliver unaltered bedrock along with OC derived from extant vegetation directly to the river channel without significant storage in soils. Rapid burial on the shelf occurs as a result of flood events. As a consequence, the buried material appears to be a simple mixture of carbon derived from kerogen (bedrock C), and modem terrestrial and marine sources. This is predicted to be a characteristic of the many similar short rivers on active margins that supply >40% of the fluvial sediment to the world's ocean. Extensive storage and processing of OC in lowland soils is a characteristic of the large Amazon watershed. Upland POC compositions are either overprinted or replaced by lowland sources. Upon delivery to the shelf, over half of the riverine POC is lost as a result of residence in sediment layers that are periodically reworked over time scales of days to months. The addition of fresh reactive marine OC, exposure to oxygen, and the regeneration of metal oxidants during resuspension events fuel the oxidation of the niverme organic matter. The nature of the watershed-shelf processes likely produce a complex mixture of organics possessing a continuum of ages and reactivities. The model illustrates the need to develop tools to measure residence times of particles in the various reservoirs so that the behavior of POC can be calibrated as it moves through a sedimentary system. The ultimate goal is to be able to use the organic geochemistry of soils and sediments to quantitatively infer the history of processes that determine both the composition and amount of POC present in different depositional environments. (C) 2004 Elsevier B.V. All rights reserved. VL - 92 IS - 1-4 N1 - id: 978; 882IA Times Cited:50 Cited References Count:118 JO - From bedrock to burial: the evolution of particulate organic carbon across coupled watershed-continental margin systems ER - TY - JOUR T1 - A gas ion source for continuous-flow AMS JF - Proceedings of the Ninth International Conference on Accelerator Mass Spectrometry Y1 - 2004 A1 - Schneider, R. J. A1 - Kim, S. W. A1 - von Reden, K. F. A1 - Hayes, J. M. A1 - Wills, J. S. C. A1 - Griffin, V. S. A1 - Sessions, A. L. A1 - Sylva, S. AB - The first gas-fed ion source for radiocarbon AMS applications (without sputtering) has been operated at the Woods Hole NOSAMS Facility. A three-year, off-line test program resulted in positive carbon ion currents up to 1 mA and negative ion currents up to 80 μA. Recently, the compact, permanent-magnet microwave plasma ion source and magnesium vapor charge-exchange canal were coupled to the recombinator injector of the 2.5 MV Tandetron. When the ion source was operated on CO2 at a flow rate of about 200 μl per minute, negative carbon ion beams up to 20 μA were obtained, at an energy of 35 keV. Radiocarbon measurements were performed on standard reference gases and the dynamic response to square-wave pulses of gas was determined. Time constants in the ion source are less than 1 s, which should allow analysis of chromatographic peaks of CO2 with very little broadening. A combustion device has been constructed to generate CO2 for direct injection into the source. Argon carrier gas is used to buffer the pressure at one atmosphere in the sample gas injector. A dedicated ion-beam injector, with higher angular acceptance and higher transmitted currents, is being constructed for the AMS system. VL - 223-224 N1 - id: 2104 JO - A gas ion source for continuous-flow AMS ER - TY - JOUR T1 - Glacial intermediate water ventilation in the northwestern Pacific based on AMS radiocarbon dating JF - Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions with Materials and Atoms Y1 - 2004 A1 - Ohkushi, K. A1 - Uchida, M. A1 - Ahagon, N. A1 - Mishima, T. A1 - Kanematsu, T. AB - C-14 ages of benthic foraminifera and planktonic foraminifera in sediment core PC4 (41degrees07.10'N, 142degrees24.17'E) collected from the northwestern Pacific were measured by accelerator mass spectrometry. The purpose of this study was to investigate the changes in intermediate water ventilation in the northwestern Pacific during the last glacial period. We used age differences between benthic foraminifera and planktonic foraminifera from the same sediment horizons to estimate the ventilation time of intermediate water. Planktonic C-14 ages show that the core recorded paleoenvironmental changes during the last 35 kyr. Glacial benthic-planktonic age differences were smaller in the early deglacial period (15000-17000 cal yr BP) than in the period (19000-30000 cal yr BP) before and during the last glacial maximum. The results at intermediate depths are consistent with those from a Pacific deep-water site. (C) 2004 Elsevier B.V. All rights reserved. VL - 223 IS - 460-465 N1 - 852jtTimes Cited:7Cited References Count:13 JO - Glacial intermediate water ventilation in the northwestern Pacific based on AMS radiocarbon dating ER - TY - JOUR T1 - A global ocean carbon climatology: Results from global data analysis project (GLODAP) JF - Global Biogeochemical Cycles Y1 - 2004 A1 - Kay, R. M. A1 - Kozyr, A. A1 - Sabine, C. L. A1 - Lee, K. A1 - Wanninkhof, R. A1 - Bullister, J. L. A1 - Feely, R. A. A1 - Millero, F. J. A1 - Mordy, C. A1 - Peng, T. H. VL - 18 N1 - id: 527 ER - TY - JOUR T1 - Great earthquakes and tsunamis of the past 2000 years at the Salmon River estuary, central Oregon coast, USA JF - Bulletin of the Seismological Society of America Y1 - 2004 A1 - Nelson, A. R. A1 - Asquith, A. C. A1 - Grants, W. C. AB - Four buried tidal marsh soils at a protected inlet near the mouth of the Salmon River yield definitive to equivocal evidence for coseismic subsidence and burial by tsunami-deposited sand during great earthquakes at the Cascadia subduction zone. An extensive, landward-tapering sheet of sand overlies a peaty tidal-marsh soil over much of the lower estuary. Limited pollen and macrofossil data suggest that the soil suddenly subsided 0.3-1.0 m shortly before burial. Regional correlation of similar soils at tens of estuaries to the north and south and precise C-14 ages from one Salmon River site imply that the youngest soil subsided during the great earthquake of 26 January A.D. 1700. Evidence for sudden subsidence of three older soils during great earthquakes is more equivocal because older-soil stratigraphy can be explained by local hydrographic changes in the estuary. Regional C-14 correlation of two of the three older soils with soils at sites that better meet criteria for a great-earthquake origin is consistent with the older soils recording subsidence and tsunamis during at least two great earthquakes. Pollen evidence of sudden coseismic subsidence from the older soils is inconclusive, probably because the amount of subsidence was small (<0.5 m). The shallow depths of the older soils yield rates of relative sea-level rise substantially less than rates previously calculated for Oregon estuaries. VL - 94 IS - 4 N1 - 855anTimes Cited:18Cited References Count:80 JO - Great earthquakes and tsunamis of the past 2000 years at the Salmon River estuary, central Oregon coast, USA ER - TY - JOUR T1 - H2-rich fluids from serpentinization: geochemical and biotic implications JF - Proc Natl Acad Sci U S A Y1 - 2004 A1 - Sleep, N. H. A1 - Meibom, A. A1 - Fridriksson, T. A1 - Coleman, R. G. A1 - Bird, D. K. AB - Metamorphic hydration and oxidation of ultramafic rocks produces serpentinites, composed of serpentine group minerals and varying amounts of brucite, magnetite, and/or FeNi alloys. These minerals buffer metamorphic fluids to extremely reducing conditions that are capable of producing hydrogen gas. Awaruite, FeNi3, forms early in this process when the serpentinite minerals are Fe-rich. Olivine with the current mantle Fe/Mg ratio was oxidized during serpentinization after the Moon-forming impact. This process formed some of the ferric iron in the Earth's mantle. For the rest of Earth's history, serpentinites covered only a small fraction of the Earth's surface but were an important prebiotic and biotic environment. Extant methanogens react H2 with CO2 to form methane. This is a likely habitable environment on large silicate planets. The catalytic properties of FeNi3 allow complex organic compounds to form within serpentinite and, when mixed with atmospherically produced complex organic matter and waters that circulated through basalts, constitutes an attractive prebiotic substrate. Conversely, inorganic catalysis of methane by FeNi3 competes with nascent and extant life. VL - 101 IS - 35 N1 - Sleep, N HMeibom, AFridriksson, ThColeman, R GBird, D KengResearch Support, U.S. Gov't, Non-P.H.S.2004/08/25 05:00Proc Natl Acad Sci U S A. 2004 Aug 31;101(35):12818-23. Epub 2004 Aug 23. U2 - PMC516479 JO - H2-rich fluids from serpentinization: geochemical and biotic implications ER - TY - JOUR T1 - Holocene development of the Yellow River's subaqueous delta, North Yellow Sea JF - Marine Geology Y1 - 2004 A1 - Liu, J. P. A1 - Milliman, J. D. A1 - Gao, S. A1 - Cheng, P. VL - 209 IS - 1-4 N1 - id: 650 ER - TY - JOUR T1 - Holocene evolution of the east Texas coast and inner continental shelf: Along-strike variability in coastal retreat rates JF - Journal of Sedimentary Research Y1 - 2004 A1 - Rodriguez, A. B. A1 - Anderson, J. B. A1 - Siringan, F. P. A1 - Taviani, M. AB - The low gradient east Texas coast and inner-continental shelf, from Sabine Lake at the Texas-Louisiana border to the western end of Galveston Island, experienced extreme along-strike variations in rates of Holocene coastal retreat. Around 7.7 ka a barrier shoreline was located approximately 55 klm offshore. Toward the western end of Galveston Island, the shoreline retreated 55 km, occupying a position on the lagoon side of the Island by about 5.3 ka. Toward the Texas-Louisiana border, the shoreline retreated more gradually, occupying a position seaward of Sabine Bank by 5.3 ka. Between 4.7 ka and 2.8 ka the shoreline at Sabine Bank retreated -30 km, while Galveston Island prograded seaward. Bolivar Peninsula began to accrete around 1.5 ka. Heald and Sabine banks, located on the inner continental shelf above terraced fluvial deposits of the Trinity-Sabine incised valley, are the only preserved remnants of these former shoreline positions. Fluctuating rates of sea-level rise were not the forcing mechanism behind episodes of rapid shoreline retreat because these events were localized. Rather, along-strike variations in the rate of transgression were caused by the variable inner-shelf gradients, which increase towards the west, and the orientation of the Sabine incised valley and associated terraced fluvial deposits, which trend northeast-southwest (parallel to shore). As shorelines retreated over fluvial deposits, these served as local sand sources that enabled barrier islands to persist offshore, out of equilibrium with sea level. Once these sand sources became depleted, and/or sea level reached some critical threshold, barrier shorelines became stranded offshore as banks, and new shorelines formed landward. The geologic setting of coastal areas, specifically antecedent topography, plays a primary role in controlling coastal evolution. To accurately forecast long-term (centennial to millennial) coastal evolution, it is essential that impacts associated with variations in the underlying geology of coastal areas be incorporated into coastal forecasting models. VL - 74 IS - 3 N1 - id: 2042; PT: J; UT: WOS:000221339900007 JO - Holocene evolution of the east Texas coast and inner continental shelf: Along-strike variability in coastal retreat rates ER - TY - JOUR T1 - Holocene fault scarps near Tacoma, Washington, USA JF - Geology Y1 - 2004 A1 - Sherrod, B. L. A1 - Brocher, T. M. A1 - Weaver, C. S. A1 - Bucknam, R. C. A1 - Blakely, R. J. A1 - Kelsey, H. M. A1 - Nelson, A. R. A1 - Haugerud, R. AB - Airborne laser mapping confirms that Holocene active faults traverse the Puget Sound metropolitan area, northwestern continental United States. The mapping, which detects forest-floor relief of as little as 15 cm, reveals scarps along geophysical lineaments that separate areas of Holocene uplift and subsidence. Along one such line of scarps, we found that a fault warped the ground surface between A.D. 770 and 1160. This reverse fault, which projects through Tacoma, Washington, bounds the southern and western sides of the Seattle uplift. The northern flank of the Seattle uplift is bounded by a reverse fault beneath Seattle that broke in A.D. 900-930. Observations of tectonic scarps along the Tacoma fault demonstrate that active faulting with associated surface rupture and ground motions pose a significant hazard in the Puget Sound region. VL - 32 IS - 1 N1 - 765ehTimes Cited:50Cited References Count:22 JO - Holocene fault scarps near Tacoma, Washington, USA ER - TY - JOUR T1 - Holocene relative sea-level history of the Southern Victoria Land Coast, Antarctica JF - Global and Planetary Change Y1 - 2004 A1 - Hall, B. L. A1 - Baroni, C. A1 - Denton, G. H. AB - More than 130 radiocarbon dates of penguin remains and guano, sealskin, shells, and seaweed from raised beach ridges afford relative sea-level information for southern Victoria Land. A new relative sea-level curve suggests that the final unloading of grounded ice from the coast took place about 6600 C-14 years BP, in keeping with previous estimates of the timing of deglaciation. Since this time, the coast has experienced 32 m of relative sea-level fall at rates ranging from 2 to 15 mm/year, consistent with glacioisostatic rebound. (C) 2004 Elsevier B.V. All rights reserved. VL - 42 IS - 1-4 N1 - 845idTimes Cited:40Cited References Count:25 JO - Holocene relative sea-level history of the Southern Victoria Land Coast, Antarctica ER - TY - JOUR T1 - Hydrologic variation during the last 170,000 years in the southern hemisphere tropics of South America JF - Quaternary Research Y1 - 2004 A1 - Fritz, S. C. A1 - Baker, P. A. A1 - Lowenstein, T. K. A1 - Seltzer, G. O. A1 - Rigsby, C. A. A1 - Dwyer, G. S. A1 - Tapia, P. M. A1 - Arnold, K. K. A1 - Ku, T. L. A1 - Luo, S. D. AB - Despite the hypothesized importance of the tropics in the global climate system, few tropical paleoclimatic records extend to periods earlier than the last glacial maximum (LGM), about 20,000 years before present. We present a well-dated 170,000-year time series of hydrologic variation from the southern hemisphere tropics of South America that extends from modem times through most of the penultimate glacial period. Alternating mud and salt units in a core from Salar de Uyuni, Bolivia reflect alternations between wet and dry periods. The most striking feature of the sequence is that the duration of paleolakes increased in the late Quaternary. This change may reflect increased precipitation, geomorphic or tectonic processes that affected basin hydrology, or some combination of both. The dominance of salt between 170,000 and 140,000 yr ago indicates that much of the penultimate glacial period was dry, in contrast to wet conditions in the LGM. Our analyses also suggest that the relative influence of insolation forcing on regional moisture budgets may have been stronger during the past 50,000 years than in earlier times. (C) 2003 University of Washington. All rights reserved. VL - 61 IS - 1 N1 - 776jhTimes Cited:98Cited References Count:43 JO - Hydrologic variation during the last 170,000 years in the southern hemisphere tropics of South America ER - TY - JOUR T1 - Inhibited eclogite formation: The key to the rapid growth of strong and buoyant Archean continental crust JF - Geology Y1 - 2004 A1 - Bjornerud, M. G. A1 - Austrheim, H. AB - Subduction is the principal mechanism by which the hydrosphere and interior of Earth interact. Today, subduction involves the dehydration of ocean crust at depths of 60-120 km depending on the age of the slab. Release of the water leads to generation of arc magmas (future continental crust), and the slab is then transformed into denser eclogite that helps to pull more of the slab into the trench. However, it is unlikely that the first continental crust formed this way. Growing geochemical evidence indicates that large volumes of continental crust were produced over a short period of time in the Archean, when the planet was probably too hot for modern plate tectonics to operate. A significant increase in the kinetics of eclogite-forming reactions may have been the key to the transition from Archean to modern tectonics. Under the higher geothermal gradients of the Archean, tectonically buried ocean crust would have been severely dehydrated before reaching eclogite facies pressures. Because rapid eclogitization is dependent on water as a medium for advective ion transport, the very shallow dehydration in the Archean may have inhibited the formation of eclogite facies minerals. The importance of water in eclogite metamorphism is illustrated by a complex of partly eclogitized malic granulites in Holsnoy, western Norway, in which reaction progress was limited by the availability of water. When water is scarce or absent, metastable granulite facies mineral assemblages can persist at eclogite facies depths owing to the extremely slow reaction kinetics when diffusion is the only chemical transport mechanism. Such dehydrated but uneclogitized mafic crust would have been very strong and too buoyant to sink into the mantle, and it may have formed the substrate for the first continental lithosphere. VL - 32 IS - 9 N1 - id: 1507; 851PG Times Cited:12 Cited References Count:29 JO - Inhibited eclogite formation: The key to the rapid growth of strong and buoyant Archean continental crust ER - TY - JOUR T1 - Isotopic order, biogeochemical processes, and earth history - Goldschmidt Lecture, Davos, Switzerland, August 2002 JF - Geochimica Et Cosmochimica Acta Y1 - 2004 A1 - Hayes, J. M. AB - The impetus to interpret carbon isotopic signals comes from an understanding of isotopic fractionations imposed by living organisms. That understanding rests in turn on studies of enzymatic isotope effects, on fruitful concepts of isotopic order, and on studies of the distribution of (13)C both between and within biosynthetic products. In sum, these studies have shown that the isotopic compositions of biological products are governed by reaction kinetics and by pathways of carbon flow.Isotopic compositions of individual compounds can indicate specific processes or environments. Examples include biomarkers which record the isotopic compositions of primary products in aquatic communities, which indicate that certain bacteria have used methane as a carbon source, and which show that some portions of marine photic zones have been anaerobic. In such studies, the combination of structural and isotopic lines of evidence reveals relationships between compounds and leads to process-related thinking. These are large steps. Reconstruction of the sources and histories of molecular fossils redeems much of the early promise of organic geochemistry by resolving and clarifying paleoenviron-mental signals. In turn, contemplation of this new information is driving geochemists to study microbial ecology and evolution, oceanography, and sedimentology. Copyright (C) 2004 Elsevier Ltd. VL - 68 IS - 8 N1 - 813fdTimes Cited:17Cited References Count:70 JO - Isotopic order, biogeochemical processes, and earth history - Goldschmidt Lecture, Davos, Switzerland, August 2002 ER - TY - JOUR T1 - Late Archean Microbial Ecology: An Integration of Molecular, Isotopic, and Lithologic Studies JF - PH.D. thesis, Earth Sciences, the Pennsylvania State University Y1 - 2004 A1 - Eigenbrode, Jennifer N1 - id: 1581 ER - TY - JOUR T1 - A late Pleistocene-Holocene noble gas paleotemperature record in southern Michigan JF - Geophysical Research Letters Y1 - 2004 A1 - Ma, L. A1 - Castro, M. C. A1 - Hall, C. M. AB - Noble gas temperatures (NGTs) and C-14 derived ages in groundwaters of the Michigan Basin reveal a ground temperature of similar to1degreesC toward the end of the Last Glacial Maximum (LGM) suggesting that groundwater recharge occurred under the Laurentide Ice Sheet (LIS) cover. In addition to the general warming observed since the LGM, the NGT record indicates an abrupt warming event between similar to12.8 and 11.1 kyrs BP, correlative to the Bolling-Allerod (BOA) warm phases. Ice-sheet-linked changes in freshwater delivery to the North Atlantic, together with changes in the North Atlantic Deep Water (NADW) circulation are possible causes of such abrupt climate shifts in northeastern US. Pleistocene waters yielding the lowest NGTs have the highest delta(18)O and deltaD values, suggesting an atmospheric circulation pattern distinct from today, with a stronger moisture component from the Gulf of Mexico, possibly due to the presence of the LIS which weakened the Pacific westerly flow. VL - 31 IS - 23 N1 - 881pcTimes Cited:31Cited References Count:24 JO - A late Pleistocene-Holocene noble gas paleotemperature record in southern Michigan ER - TY - JOUR T1 - Late Quaternary deposition in the Inner Basins of the California Continental Borderland: Part A. Santa Monica Basin JF - U. S. Geological Survey Scientific Investigations Report 2004 Y1 - 2004 A1 - Normark, W. R. A1 - McGann, M. VL - 5183 N1 - id: 417 ER - TY - CHAP T1 - Late Quaternary sedimentation and deformation in Santa Monica and Catalina Basins, offshore southern California T2 - Geology and Tectonics of Santa Cataline Island and the California Continental Borderland Y1 - 2004 A1 - Normark, W. R. A1 - Baher, S. A1 - Sliter, R. ED - Guidebook, South Coast Geological Society Annual Field Trip JF - Geology and Tectonics of Santa Cataline Island and the California Continental Borderland CY - Santa Ana, California N1 - id: 991 ER - TY - THES T1 - Late-glacial climate as inferred from chironomid assemblages in lake sediments from Aroostook County, northeastern Maine Y1 - 2004 A1 - Chase, G. PB - University of Maine CY - Orono, Maine VL - M.S. ER - TY - CONF T1 - Long Island Sound: diatoms from sediment cores as part of environmental and ecological change studies, abstracts T2 - Mid-Atlantic ecology conference: sustainable landscapes Y1 - 2004 A1 - Cooper, S. R. A1 - Thomas, E. A1 - Varekamp, J. C. JF - Mid-Atlantic ecology conference: sustainable landscapes CY - Franklin & Marshall College, Lancaster, PA N1 - id: 735 ER - TY - JOUR T1 - Mangrove ecocystem dynamics and elemental cycling at Twin Cays, Belize, during the Holocene JF - Journal of Quaternary Science Y1 - 2004 A1 - Wooller, M. J. A1 - Behling, H. A1 - Smallwood, B. J. A1 - Fogel, M. KW - Holocene KW - isotopes;pollen KW - mangroves KW - Palaeoecology AB - Existing at the transition between the terrestrial environment and hydrosphere, mangroves are sensitive to environmental change (e.g. sea-level rise). We present pollen and stable isotope data from a core (TCC1) of continuous (10 m) mangrove peat from Twin Cays, ∼12 km off of the coast of Belize, Central America. Radiocarbon dates on fragments of mangrove leaves preserved in TCC1 show that the core provides an 8600 14C year record of mangrove ecosystem changes. Variation in the stable carbon and nitrogen isotope composition (δ13C = ∼−30 to −25‰; δ15N = ∼−6 to 2‰) of mangrove leaves imply that the stand structure and nutrient status of the mangroves at the site have changed during the Holocene. Pollen data from the same core show that the floral composition of the site has changed at points during the Holocene, most notably a brief (∼240 years) switch at ∼3860 14C yr BP to dominance by a species of Myrsine (not currently present at the site). Our results are consistent with significant environmental changes (either marked disturbance from hurricanes or fluctuations in sea-level) through the Holocene. VL - 19 IS - 7 N1 - id: 1149 JO - Mangrove ecocystem dynamics and elemental cycling at Twin Cays, Belize, during the Holocene ER - TY - CHAP T1 - Mantle Samples Included in Volcanic Rocks: Xenoliths and Diamonds T2 - Treatise on Geochemistry Y1 - 2004 A1 - Pearson, D. G. A1 - Canil, D. A1 - Shirey, S. B. ED - Holland, H. D. JF - Treatise on Geochemistry CY - Elsevier Ltd, Oxford VL - 2 N1 - id: 1575 ER - TY - CONF T1 - Mercury contamination in wetlands T2 - Meeting of the Atlantic Chaopter of the Soc. of Env. Toxicology and Health Y1 - 2004 A1 - Varekamp, J. C. JF - Meeting of the Atlantic Chaopter of the Soc. of Env. Toxicology and Health CY - Rhode Island N1 - id: 742 ER - TY - CONF T1 - Mercury in Connecticut and Long Island Sound: impact of historic hatting industries T2 - American Geophyscial Union, Joint Assembly Y1 - 2004 A1 - Bronsther, R. A1 - Welsh, P. A1 - Varekamp, J. C. JF - American Geophyscial Union, Joint Assembly PB - American Geophysical Union (AGU) VL - 85 IS - 17 N1 - id: 733 JO - Mercury in Connecticut and Long Island Sound: impact of historic hatting industries, abstract ER - TY - CHAP T1 - Natural radiocarbon distribution in the deep ocean T2 - Global Environmental Change in the Ocean and on Land Y1 - 2004 A1 - Matsumoto, K. A1 - Key, R. M. ED - Shiyomi, M. JF - Global Environmental Change in the Ocean and on Land PB - Terrapub CY - Tokyo N1 - id: 1050 ER - TY - CHAP T1 - Natural Radiocarbon Distribution in the Deep Ocean T2 - Global Environmental Change in the Ocean and on Land Y1 - 2004 A1 - Matsumoto, Katsumi
 A1 - Key, Robert M. ED - Shiyomi, M. JF - Global Environmental Change in the Ocean and on Land PB - Terrapub VL - Submitted SN - 9784887041332 ER - TY - JOUR T1 - A new Holocene relative sea-level curve for Terra Nova Bay, Victoria Land, Antarctica JF - Journal of Quaternary Science Y1 - 2004 A1 - Baroni, C. A1 - Hall, B. L. AB - More than 100 radiocarbon dates of penguin guano and remains, shells and seal skin afford ages for raised beaches adjacent to Terra Nova Bay, Antarctica. These dates permit construction of a new relative sea-level curve that bears on the timing of deglaciation. Recession of the Ross Sea ice-sheet grounding line from Terra Nova Bay occurred no earlier than 7200 C-14 yr (8000 cal. yr) BP. Retreat along the Victoria Land coast may have been rapid, possibly contributing to eustatic sea-level rise centred at ca. 7600 cal. yr BP. The presence of a significant amount of ice remaining in the Ross Sea Embayment in Holocene time lessens the chance that Antarctica contributed significantly to meltwater pulse 1A several thousand years earlier. Copyright (C) 2004 John Wiley Sons, Ltd. VL - 19 IS - 4 N1 - 833xiTimes Cited:38Cited References Count:36 JO - A new Holocene relative sea-level curve for Terra Nova Bay, Victoria Land, Antarctica ER - TY - JOUR T1 - New insights into the burial history of organic carbon on the early Earth JF - Geochemistry Geophysics Geosystems Y1 - 2004 A1 - Bjerrum, C. J. A1 - Canfield, D. E. AB - [1] The isotope record of organic matter and calcium carbonate is often used to infer the burial history of organic carbon through time. As organic carbon burial is widely held to control long-term oxygen production, the isotope record also relates to the production rates of oxygen on Earth. Current interpretations of the record suggest a long-term consistency in the proportion of total carbon buried as organic carbon (f ratio), with some important periods of much higher burial proportions. The isotope record is analyzed here with a new carbon isotope mass balance model, which considers submarine hydrothermal weathering of ocean crust as a significant removal pathway of inorganic carbon. With this model the f ratio is considerably reduced if isotopically depleted inorganic carbon is precipitated during hydrothermal weathering and if hydrothermal weathering dominates inorganic carbon removal from the surface environment. In contrast to previous calculations, our analysis of the carbon isotope record shows that organic carbon burial in the Archean accounted for only between 0% and 10% of the total carbon burial. These low burial proportions would have contributed to a slow accumulation of atmospheric oxygen in the Archean. VL - 5 N1 - id: 1506; 846RU Times Cited:14 Cited References Count:44 JO - New insights into the burial history of organic carbon on the early Earth ER - TY - CONF T1 - Nitrogen isotopic ratio records the eutrophication history of Long Island sound T2 - American Geophyscial Union, Joint Assembly Y1 - 2004 A1 - Altabet, M. A1 - Varekamp, J. C. AB - Increasing coastal population and industrialization has led to the steady degradation of the Long Island Sound (LIS) environment. Increased nutrient loading from sewage inputs has resulted in eutrophication and decreased summertime subsurface oxygen concentration particularly at its western end. It is critical to develop a detailed history of these environmental changes, both to understand causative processes and for design of optimal and cost effective remediation plans. We are developing a detailed time line of environmental changes in LIS over the last few centuries based on the study of geochemical and paleo-ecological proxies in geographically distributed sediment cores. Sediment nitrogen isotopic ratio (d15N) in particular is being used as an indicator of perturbations of the nitrogen biogeochemistry. Higher d15N is expected from sewage inputs as well as from the initiation of subsurface denitrification during low O2 conditions. Contemporary correlation between eutrophication intensity and d15N is seen in sediment core top data which show a substantial 4 per mil increase in d15N going from eastern to western LIS. This observation is consistent with greater nutrient loading toward New York City with its greater coastal population density. Downcore data from a site in western LIS show 4 per mil lower d15N prior to 200 years ago, documenting the point at which significant anthropogenic impact began. Increasing d15N over the last 200 years correlate with productivity proxies and other proxies for anthropogenic influence JF - American Geophyscial Union, Joint Assembly PB - American Geophysical Union (AGU) VL - 85 IS - 17 N1 - id: 732 JO - Nitrogen isotopic ratio records the eutrophication history of Long Island sound, abstract ER - TY - JOUR T1 - NotCal04-Comparison/Calibration 14 C records 26-50 cal kBP JF - Radiocarbon Y1 - 2004 A1 - van der Plicht, J. A1 - Beck, J. W. A1 - Bard, E. A1 - Baillie, M. G. L. A1 - Blackwell, P. G. A1 - Buck, C. E. A1 - Friedrich, M. A1 - Guilderson, T. P. A1 - Hughen, K. A. A1 - Kromer, B. VL - 46 N1 - id: 399 ER - TY - JOUR T1 - Oceanic ventilation and biogeochemical cycling: Understanding the physical mechanisms that produce realistic distributions of tracers and productivity JF - Global Biogeochemical Cycles Y1 - 2004 A1 - Gnanadesikan, A. A1 - Dunne, J. P. A1 - Key, R. M. A1 - Matsumoto, K. A1 - Sarmiento, J. L. A1 - Slater, R. D. A1 - Swathi, P. S. KW - Biogeochemical cycles KW - bottom water formation KW - circulation models KW - diffusion KW - particle export KW - pycnocline KW - sensitivity KW - Temperature KW - vertical exchange KW - weddell sea KW - World Ocean AB - [1] Differing models of the ocean circulation support different rates of ventilation, which in turn produce different distributions of radiocarbon, oxygen, and export production. We examine these fields within a suite of general circulation models run to examine the sensitivity of the circulation to the parameterization of subgridscale mixing and surface forcing. We find that different models can explain relatively high fractions of the spatial variance in some fields such as radiocarbon, and that newer estimates of the rate of biological cycling are in better agreement with the models than previously published estimates. We consider how different models achieve such agreement and show that they can accomplish this in different ways. For example, models with high vertical diffusion move young surface waters into the Southern Ocean, while models with high winds move more young North Atlantic water into this region. The dependence on parameter values is not simple. Changes in the vertical diffusion coefficient, for example, can produce major changes in advective fluxes. In the coarse-resolution models studied here, lateral diffusion plays a major role in the tracer budget of the deep ocean, a somewhat worrisome fact as it is poorly constrained both observationally and theoretically. VL - 18 SN - 0886-6236 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=Alerting&SrcApp=Alerting&DestApp=WOS&DestLinkType=FullRecord;UT=WOS:000224876500001 IS - 4 N1 - 867xpTimes Cited:66 Cited References Count:42 JO - Global Biogeochem Cy ER - TY - JOUR T1 - Organic carbon accumulation in the South Atlantic Ocean: 1st modern, mid-Holocene and Last Glacial distribution JF - Global and Planetary Change Y1 - 2004 A1 - Mollenhauer, Gesine A1 - Schneider, Ralph R. A1 - Jennerjahn, Tim A1 - Muller, Peter J. A1 - Wefer, Gerold VL - 40 N1 - id: 1704 ER - TY - JOUR T1 - Pacific halibut (Hippoglossus stenolepis) chronology of bomb radiocarbon in otoliths from 1944-1981 and a validation of ageing methods JF - Journal of Fish Biology Y1 - 2004 A1 - Piner, K. P. A1 - Wischniowski, S. G. VL - 64 N1 - id: 1063 ER - TY - CONF T1 - Paleochannel incision and infill on the New Jersey shelf: timing, character and depositional environment T2 - 2005 SE GSA Meeting Y1 - 2004 A1 - Alexander, C. A1 - Christensen, C. A1 - Goff, J. A1 - Austin J.A, Jr. A1 - Venherm, C. A1 - Nordfjord, S. A1 - Gulick, S. A1 - Sommerfield, C. A1 - Fulthorpe, C. A1 - Schock, S. JF - 2005 SE GSA Meeting CY - Biloxi, MS N1 - id: 1120 ER - TY - JOUR T1 - Paleoclimate. A better radiocarbon clock JF - Science Y1 - 2004 A1 - Bard, E. A1 - Rostek, F. A1 - Menot-Combes, G. VL - 303 IS - 5655 N1 - id: 974; Bard, Edouard Rostek, Frauke Menot-Combes, Guillemette New York, N.Y. Science. 2004 Jan 9;303(5655):178-9. JO - Paleoclimate. A better radiocarbon clock ER - TY - CONF T1 - The paleo-environmental history of Long Island Sound as traced by organic carbon, biogenic silica and stable isotope/trace element studies in sediment cores T2 - 6th Biennual LIS Res. Conf. Proc. Y1 - 2004 A1 - Varekamp, J. C. A1 - Thomas, E. A1 - Lugolobi, F. A1 - Buchholtz ten Brink, M. R. JF - 6th Biennual LIS Res. Conf. Proc. N1 - id: 1174 ER - TY - CONF T1 - Paleoproductivity indicators in Long Island Sound T2 - American Geophyscial Union, Joint Assembly Y1 - 2004 A1 - Andersen, N. A1 - Varekamp, J. C. AB - Oxygen depletion in bottom waters is considered to be the most pressing environmental problem affecting Long Island Sound (LIS). Summer anoxia occurs as a result of two factors: 1) Stratification of the water column due to warming of the shallow water preventing mixing and thus homogeneous distribution of oxygen. 2) Eutrophication resulting in increased primary productivity leading to a greater oxygen demand in the bottom waters as the larger amount of organic matter decays. The goal of this project is to create a paleoproductivity record for LIS and to attempt to link recent increases in productivity with anthropogenic nutrient sources, most notably wastewater treatment plant effluent. Two cores, WLIS-75 from the western narrows and B1GGC1 from near the mouth of the Housatonic River, have been analyzed for biogenic silica (BSi), total carbon, nitrogen, and sulfur. The BSi data was obtained through analyses of timed sequential extracts from an alkaline solution that reacted with the sediment at 85 C. Sediment densities were calculated from measured core water contents and assumed dry rock densities. A preliminary age model was developed using the onset of mercury pollution (about 1820 AD) as a reference point. At around 1800, the C, N, S and BSi concentrations all start to increase. In WLIS-75, BSi was higher throughout the core compared to core B1GGC1, suggesting an overall higher rate of productivity in the western section of LIS. In both cores the mass accumulation rates of BSi, C, N, and S increased exponentially over the last 300 years. A coarse layer was deposited around 1950-1960 in core WLIS-75, and is marked by abundant coarse debris of rocks and coal fragments. This layer may represent a flood deposit or stem from local (illegal?) dumping; its presence impacts the data for the last 30-40 years of the core. A strong correlation between total S and total C is observed, suggesting that Sulfide formation is limited by the amount of labile organic matter present. The data from the two cores show strong evidence for eutrophication over the last 200 years, with a strong increase in the N supply. JF - American Geophyscial Union, Joint Assembly PB - American Geophysical Union (AGU) VL - 85 IS - 17 N1 - id: 1180 JO - Paleoproductivity indicators in Long Island Sound, abstract ER - TY - BOOK T1 - The Phanerozoic Carbon Cycle Y1 - 2004 A1 - Berner, Robert A. PB - Oxford University Press CY - New York, NY N1 - id: 1555 ER - TY - JOUR T1 - Photosynthetic microbial mats in the 3,416-Myr-old ocean JF - Nature Y1 - 2004 A1 - Tice, M. M. A1 - Lowe, D. R. AB - Recent re-evaluations of the geological record of the earliest life on Earth have led to the suggestion that some of the oldest putative microfossils and carbonaceous matter were formed through abiotic hydrothermal processes. Similarly, many early Archaean (more than 3,400-Myr-old) cherts have been reinterpreted as hydrothermal deposits rather than products of normal marine sedimentary processes. Here we present the results of a field, petrographic and geochemical study testing these hypotheses for the 3,416-Myr-old Buck Reef Chert, South Africa. From sedimentary structures and distributions of sand and mud, we infer that deposition occurred in normal open shallow to deep marine environments. The siderite enrichment that we observe in deep-water sediments is consistent with a stratified early ocean. We show that most carbonaceous matter was formed by photosynthetic mats within the euphotic zone and distributed as detrital matter by waves and currents to surrounding environments. We find no evidence that hydrothermal processes had any direct role in the deposition of either the carbonaceous matter or the enclosing sediments. Instead, we conclude that photosynthetic organisms had evolved and were living in a stratified ocean supersaturated in dissolved silica 3,416 Myr ago. VL - 431 IS - 7008 N1 - Tice, Michael MLowe, Donald RengResearch Support, Non-U.S. Gov'tResearch Support, U.S. Gov't, Non-P.H.S.England2004/10/01 05:00Nature. 2004 Sep 30;431(7008):549-52. JO - Photosynthetic microbial mats in the 3,416-Myr-old ocean ER - TY - JOUR T1 - Phylogenetically specific spearation of rRNA from prokaryotes for isotopic analysis JF - Marine Chemistry Y1 - 2004 A1 - Pearson, Ann A1 - Sessions, Alex L. A1 - Edwards, Katrina J. A1 - Hayes, John M. VL - 92 N1 - id: 1805 ER - TY - JOUR T1 - Plans for Expanded 14C Analyses at the NOSAMS Facility--a status and progress report. 9th International Conference on Accelerator Mass Spectrometry, Nagoya, Japan, 9/2002 JF - Nuclear Instruments and Methods in Physics Research Y1 - 2004 A1 - von Reden, K. A1 - Donoghue, J. A1 - Elder, K. A1 - Gagnon, A. A1 - Gerlach, D. A1 - Griffin, V. S. A1 - Healy, R. A1 - Long, P. A1 - McNichol, A. P. A1 - Percy, D. A1 - Roberts, M. L. A1 - Schneider, R. J. A1 - Xu, L. A1 - Hayes, J. VL - B 223-224 N1 - id: 1810 ER - TY - JOUR T1 - Prehistoric marine mammal overkill in the northeastern Pacific: A review of new evidence JF - Journal of California and Great Basin Anthropology Y1 - 2004 A1 - Jones, T. L. A1 - Hildebrandt, W. R. A1 - Kennett, D. J. A1 - Porcasi, J. J. VL - 24 N1 - id: 469 ER - TY - JOUR T1 - Present status of radiocarbon calibration and comparison records based on Polynesian corals and Iberian Margin sediments JF - Radiocarbon Y1 - 2004 A1 - Bard, E. A1 - Menot-Combes, G. A1 - Rostek, F. AB - In this paper, we present updated information and results of the radiocarbon records based on Polynesian corals and on Iberian Margin planktonic foraminifera. The latter record was first published by Bard et al. (2004a,b), with the subsequent addition of some data by Shackleton et al. (2004). These data sets are compared with the IntCal98 record (Stuiver et al. 1998) and with data sets based on other archives, such as varves of Lake Suigetsu (Kitagawa and van der Plicht 1998, 2000), speleothems from the Bahamas (Beck et al. 2001), and Cariaco sediments (Hughen et al. 2004). Up to 26,000 cal BP, the Iberian Margin data agree within the errors of the other records. By contrast, in the interval between 33,000 and 41,000 cal BP, the Iberian Margin record runs between the Lake Suigetsu and Bahamian speleothem data sets, but it agrees with the few ImCal98 coral data and the Cariaco record. VL - 46 UR - https://journals.uair.arizona.edu/index.php/radiocarbon/article/view/4176/3601 IS - 3 N1 - 956zfTimes Cited:30Cited References Count:33 JO - Present status of radiocarbon calibration and comparison records based on Polynesian corals and Iberian Margin sediments ER - TY - JOUR T1 - Quartz content and the quartz-to-plagioclase ratio determined by X-ray diffraction: a proxy for ice rafting in the northern North Atlantic? JF - Earth and Planetary Science Letters Y1 - 2004 A1 - Moros, M. A1 - McManus, J. F. A1 - Rasmussen, T. A1 - Kuijpers, A. A1 - Dokken, T. A1 - Snowball, I. A1 - Jansen, E. A1 - Neilsen, T. VL - 218 IS - 3-4 N1 - id: 713 ER - TY - CHAP T1 - Quaternary sea level history of the United States T2 - The Quaternary period in the United States, Developments in Quaternary science Y1 - 2004 A1 - Muhs, D. R. A1 - Wehmiller, J. F. A1 - Simmons, K. R. A1 - York, L. L. ED - Gillespie, A. R. JF - The Quaternary period in the United States, Developments in Quaternary science PB - Elsevier CY - Amsterdam N1 - id: 706 ER - TY - CONF T1 - Radiocarbon ages of marine bimarkers and co-occurring foraminifera: evidence for differential particle transport on continental margins, Poster T2 - Eighth International Conference on Palaeoceanography Y1 - 2004 A1 - Mollenhauer, Gesine A1 - Eglinton, Timothy I. A1 - Hayes, John M. A1 - Kienast, Markus A1 - Lamy, Frank A1 - Meggers, Helge A1 - Schneider, Ralph R. JF - Eighth International Conference on Palaeoceanography CY - Biarritz, France N1 - id: 549 ER - TY - JOUR T1 - Radiocarbon and stable isotope constraints on Last Glacial Maximum and Younger Dryas ventilation in the western North Atlantic JF - Paleoceanography Y1 - 2004 A1 - Keigwin, L. D. KW - benthic foraminifera KW - deep-sea sediments KW - ice-age KW - Ocean circulation KW - ocean ventilation KW - pacific-ocean KW - radiocarbon KW - SARGASSO SEA KW - southern-ocean KW - Thermohaline circulation KW - united-states KW - water circulation KW - western north atlantic AB - [1] Foraminiferal abundance, C-14 ventilation ages, and stable isotope ratios in cores from high deposition rate locations in the western subtropical North Atlantic are used to infer changes in ocean and climate during the Younger Dryas (YD) and Last Glacial Maximum (LGM). The delta(18)O of the surface dwelling planktonic foram Globigerinoides ruber records the present-day decrease in surface temperature (SST) of similar to 4 degreesC from Gulf Stream waters to the northeastern Bermuda Rise. If during the LGM the modern delta(18)O/salinity relationship was maintained, this SST contrast was reduced to 2 degreesC. With LGM to interglacial delta(18)O changes of at least 2.2parts per thousand, SSTs in the western subtropical gyre may have been as much as 5 degreesC colder. Above similar to 2.3 km, glacial delta(13)C was higher than today, consistent with nutrient-depleted ( younger) bottom waters, as identified previously. Below that, delta(13)C decreased continually to - 0.5parts per thousand, about equal to the lowest LGM delta(13)C in the North Pacific Ocean. Seven pairs of benthic and planktonic foraminiferal C-14 dates from cores > 2.5 km deep differ by 1100 +/- 340 years, with a maximum apparent ventilation age of similar to 1500 years at 4250 m and at similar to 4700 m. Apparent ventilation ages are presently unavailable for the LGM < 2.5 km because of problems with reworking on the continental slope when sea level was low. Because LGM δC-13 is about the same in the deep North Atlantic and the deep North Pacific, and because the oldest apparent ventilation ages in the LGM North Atlantic are the same as the North Pacific today, it is possible that the same water mass, probably of southern origin, flowed deep within each basin during the LGM. Very early in the YD, dated here at 11.25 +/- 0.25 ( n = 10) conventional C-14 kyr BP ( equal to 12.9 calendar kyr BP), apparent ventilation ages < 2.3 km water depth were about the same as North Atlantic Deep Water today. Below similar to 2.3 km, four YD pairs average 1030 +/- 400 years. The oldest apparent ventilation age for the YD is 1600 years at 4250 m. This strong contrast in ventilation, which indicates a front between water masses of very different origin, is similar to glacial profiles of nutrient-like proxies. This suggests that the LGM and YD modes of ocean circulation were the same. VL - 19 SN - 0883-8305 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=Alerting&SrcApp=Alerting&DestApp=WOS&DestLinkType=FullRecord;UT=WOS:000225033500003 IS - 4 N1 - 870dfTimes Cited:72 Cited References Count:60 JO - Paleoceanography ER - TY - JOUR T1 - Radiocarbon apportionment of fossil versus biofuel combustion sources of polycyclic aromatic hydrocarbons in the Stockholm metropolitan area JF - Environ Sci Technol Y1 - 2004 A1 - Mandalakis, M. A1 - Gustafsson, O. A1 - Reddy, C. M. A1 - Xu, L. KW - *Bioelectric Energy Sources KW - *Fossil Fuels KW - Biomass KW - Carbon Radioisotopes KW - Cities KW - Environmental Monitoring KW - Fresh Water KW - Geologic Sediments/*analysis KW - Polycyclic Aromatic Hydrocarbons/*analysis/isolation & purification KW - Sweden KW - Water Pollutants, Chemical/*analysis/isolation & purification AB - Source-diagnostic markers and the isotopic composition of polycyclic aromatic hydrocarbons (PAHs) were examined in surface sediments from the greater Stockholm waterways to deduce the contribution from biomass sources to the environmental PAH load. The summed concentration of 20 PAHs ranged from 0.8 to 45.1 microg/g (dry weight) and exhibited a steep decline with increasing distance from the city center evidencing that sources within the metropolitan area of Stockholm dominate its PAH burden. Several diagnostic PAH ratios indicated an overwhelming predominance of pyrogenic sources over the petrogenic ones, while retene and 1,7-dimethylphenanthrene were unable to correctly evaluate the contribution from biomass combustion. The stable carbon isotope composition (delta13C) of individual PAHs ranged from -24.8 to -27.0% but also was proved inefficient to discriminate between different types of fuels due to the overlapping signals in various sources. The delta14C values of PAHs ranged between -550.4 and -934.1%, indicating a clear predominance of fossil fuel sources. By using an isotopic mass balance approach, we estimated that on average 17+/-9% of PAHs derived from biomass combustion. This radiocarbon apportionment, in conjunction with detailed energy statistics for the Stockholm region, revealed that the ambient PAH burden is roughly similar, per unit energy produced, from fossil fuels and biofuels. Societies' shifting energy policies toward a larger reliance on biofuels may thus not lead to further deterioration of air quality and respiratory ailments for the urban population. VL - 38 SN - 0013-936X (Print)0013-936X (Linking) UR - https://www.ncbi.nlm.nih.gov/pubmed/15543735 IS - 20 N1 - Mandalakis, ManolisGustafsson, Orjan Reddy, Christopher M Xu, Li eng Comparative Study Research Support, Non-U.S. Gov't Research Support, U.S. Gov't, Non-P.H.S. 2004/11/17 09:00 Environ Sci Technol. 2004 Oct 15;38(20):5344-9. ER - TY - JOUR T1 - Radiocarbon calibration beyond 20,000 B.P. by means of planktonic foraminifera of the Iberian Margin JF - Quaternary Research Y1 - 2004 A1 - Bard, E. A1 - Rostek, F. A1 - Menot-Combes, G. KW - Dansgaard-Oeschger events KW - Heinrich events KW - Laschamp magnetic excursion KW - Last glacial cycle KW - North Atlantic KW - Radiocarbon calibration AB - We present a new set of 14C ages obtained by accelerator mass spectrometry (AMS) on planktonic foraminifera from a deep-sea core collected off the Iberian Margin (MD952042). This site, at 37°N, is distant from the high-latitude zones where 14C reservoir age is large and variable. Many independent proxies — alkenones, magnetic susceptibility, ice-rafted debris, foraminifera stable isotopes, abundances of foraminifera, pollen, and dinoflagellates — show abrupt changes correlative with Dansgaard-Oeschger and Heinrich events of the last glacial period. The good stratigraphic agreement of all proxies — from the fine to the coarse-size fractions — indicates that the foraminifera 14C ages are representative of the different sediment fractions. To obtain reliable 14C ages of foraminifera beyond 20,000 14C yr B.P., we leached the shells prior to carbonate hydrolysis and subsequent analysis. For a calendar age scale, we matched the Iberian Margin U37K′ profile with that of Greenland Summit δ18O. Both are proxies for temperature, which in models varies synchronously in the two areas. The match creates no spurious jumps in sedimentation rate and requires only a limited number of tie points. Except for ages older than 40,000 14C yr B.P., Greenland's GISP2 and GRIP records yield similar calendars. The 14C and imported calendar ages of the Iberian Margin record are then compared to data — from lacustrine annual varves and from corals and speleothems dated by U–Th — previously used to extend the calibration beyond 20,000 14C yr B.P. The new record follows a smooth pattern between 23,000 and 50,000 cal yr B.P. We find good agreement with the previous data sets between 23,000 and 31,000 cal yr B.P. In the interval between 33,000 and 41,000 cal yr B.P., for which previous records disagree by up to 5000 cal yr, the Iberian Margin record closely follows the polynomial curve that was previously defined by an interpolation of the coral ages and runs between the Lake Suigetsu and the Bahamian speleothem data sets. VL - 61 IS - 2 N1 - id: 401 JO - Radiocarbon calibration beyond 20,000 B.P. by means of planktonic foraminifera of the Iberian Margin ER - TY - CONF T1 - Radiocarbon content of alkenones, foraminifera and bulk OC in oxic and anoxic sediments from the California Borderland Basins, Poster T2 - Gordon Research Conference Organic Geochemistry Y1 - 2004 A1 - Mollenhauer, Gesine A1 - Eglinton, Timothy I. JF - Gordon Research Conference Organic Geochemistry CY - Holderness School, New Hampshire, USA N1 - id: 550 ER - TY - JOUR T1 - Radiocarbon dating of diatom-bound organic compounds JF - Marine Chemistry Y1 - 2004 A1 - Ingalls, A. E. A1 - Anderson, R. F. A1 - Pearson, A. AB - Here we present a new method for obtaining radiocarbon dates for the organic compounds intrinsic to diatom frustules. This method will improve age models for sediment cores that lack calcium carbonate and improve current interpretations of diatom-based paleoproxies. In preparation for radiocarbon dating by Accelerator Mass Spectrometry, compounds intrinsic to diatom frustules are released from their opal matrix by dissolution in HF and then purified using preparative liquid chromatography-mass spectrometry (LC-MS). The method was applied to one sample from each of three cores (NBP9802 Station 7 GC2; TN057-13 PC4; Ell-2) and a plankton tow (CRS 746, FOODBANCS) collected in the Southern Ocean. In each sample, radiocarbon ages of diatom-bound organic compounds differed from those obtained from foraminiferal CaCO3. Agreement between the foraminifera and compound-specific date was best in cores Ell-2 and TN057-13. In contrast, compound-specific C-14 ages obtained from NBP9802 differed substantially from those measured for foraminiferal CaCO3. The influence of background contamination was assessed throughout all stages of the method and cannot be responsible for the discrepancy observed. Possible reasons for the disagreement between the ages of foraminifera and diatom-bound compounds are discussed in the context of sediment dynamics. These preliminary results suggest that our diatom-based dating method represents a major step forward in our ability interpret sediment records in the Southern Ocean and therefore our understanding of the role of the Southern Ocean in past climate. (C) 2004 Elsevier B.V. All rights reserved. VL - 92 IS - 1-4 N1 - 882iaTimes Cited:34Cited References Count:33 JO - Radiocarbon dating of diatom-bound organic compounds ER - TY - JOUR T1 - Radiocarbon evidence for a naturally-produced, bioaccumulation halogenated organic compound JF - Environmental Science and Technology Y1 - 2004 A1 - Reddy, C. M. A1 - Xu, L. A1 - O'Neil, G. W. A1 - Nelson, R. K. A1 - Eglinton, T. I. A1 - Faulkner, D. J. A1 - Norstrom, R. A1 - Ross, P. S. A1 - Tittlemier, S. A. VL - 38 IS - 7 N1 - id: 1806 ER - TY - JOUR T1 - Radiocarbon studies of Long Island Sound sediments JF - EOS Trans. AGU Y1 - 2004 A1 - Groner, M. A1 - Thomas, E. A1 - Varekamp, J. C. VL - 85 IS - 17 N1 - id: 737 ER - TY - JOUR T1 - Reconsidering Melt-water Pulses 1A and 1B: Global impacts of rapid sea-level rise JF - Journal of Ocean University of China Y1 - 2004 A1 - Liu, J. P. A1 - Milliman, J. D. VL - 3 IS - 3 N1 - id: 649 ER - TY - JOUR T1 - Red abalone bead production and exchange on California's northern channel islands JF - North American Archaeologist Y1 - 2004 A1 - Rick, Torben C. VL - 25 N1 - id: 574 ER - TY - JOUR T1 - Relations between environmental black carbon sorption and geochemical sorbent characteristics JF - Environmental Science & Technology Y1 - 2004 A1 - Cornelissen, G. A1 - Kukulska, Z. A1 - Kalaitzidis, S. A1 - Christanis, K. A1 - Gustafsson, O. AB - Pyrogenic carbon particles in sediments (soot and charcoal, collectively termed "black carbon" or BC) appear to be efficient sorbents of many hydrophobic organic compounds, so they may play an important role in the fate and toxicity of these substances. To properly model toxicant sorption behavior, it is important to (i) quantify the magnitude of the role of BC in sorption and (ii) elucidate which geochemical BC characteristics determine the strength of environmental BC sorption. Sorption isotherms of d(10)-phenanthrene (d(10)-PHE) were determined over a wide concentration range (0.0003-20 mug/L), for five sediments with widely varying characteristics. From the sorption isotherms, we determined Freundlich coefficients of environmental BC sorption, K-F,BC(env). These varied from 10(4.7) to 10(5.5). From the data, it could be deduced that BC was responsible for 49-85% of the total d(10)-PHE sorption at a concentration of 1 ng/L. At higher concentrations, the importance of BC for the sorption process diminished to <20% at 1 mug/L and 0-1% at 1 mg/L. There were no significant relationships between BC sorption strength and the tested geochemical BC characteristics [the fraction of small (<38 mum) BC particles, the BC resistance to high-temperature oxidation, the fraction of biomass-derived BC, the native polycyclic aromatic hydrocarbon and total organic carbon contents]. Because of the limited variation in BC sorption strength with widely varying BC characteristics, the presented BC sorption coefficients may putatively be used as generic starting points for environmental modeling purposes. VL - 38 IS - 13 N1 - 834fgTimes Cited:90Cited References Count:48 JO - Relations between environmental black carbon sorption and geochemical sorbent characteristics ER - TY - JOUR T1 - The Remarkable Metrological History of Radiocarbon Dating [II] JF - J Res Natl Inst Stand Technol Y1 - 2004 A1 - Currie, L. A. AB - This article traces the metrological history of radiocarbon, from the initial breakthrough devised by Libby, to minor (evolutionary) and major (revolutionary) advances that have brought (14)C measurement from a crude, bulk [8 g carbon] dating tool, to a refined probe for dating tiny amounts of precious artifacts, and for "molecular dating" at the 10 microg to 100 microg level. The metrological advances led to opportunities and surprises, such as the non-monotonic dendrochronological calibration curve and the "bomb effect," that gave rise to new multidisciplinary areas of application, ranging from archaeology and anthropology to cosmic ray physics to oceanography to apportionment of anthropogenic pollutants to the reconstruction of environmental history. Beyond the specific topic of natural (14)C, it is hoped that this account may serve as a metaphor for young scientists, illustrating that just when a scientific discipline may appear to be approaching maturity, unanticipated metrological advances in their own chosen fields, and unanticipated anthropogenic or natural chemical events in the environment, can spawn new areas of research having exciting theoretical and practical implications. VL - 109 IS - 2 N1 - Currie, Lloyd Aeng2004/01/01 00:00J Res Natl Inst Stand Technol. 2004 Apr 1;109(2):185-217. doi: 10.6028/jres.109.013. Print 2004 Mar-Apr. U2 - PMC4853109 JO - The Remarkable Metrological History of Radiocarbon Dating [II] ER - TY - JOUR T1 - Role of bottom water transport and diapycnic mixing in determing the radiocarbon distribution in the Pacific JF - J. Geophys. Res. Y1 - 2004 A1 - Roussenov, V. A1 - Williams, R. G. A1 - Follows, M. J. A1 - Key, R. M. VL - 109 N1 - id: 526 ER - TY - CHAP T1 - Sampling Mantle Heterogeneity through Oceanic Basalts: Isotopes and Trace Elements T2 - Treatise on Geochemistry Y1 - 2004 A1 - Hofmann, A. W. ED - Holland, H. D. JF - Treatise on Geochemistry T3 - The Mantle and Core PB - Max-Plank-Institut fur Chemie; Earth Observatory, Palisades, NY, USA CY - Mainz, Germany; Palisades, NY. USE VL - 2.03 N1 - id: 1525 ER - TY - JOUR T1 - Sensitivity of present and future surface temperatures to precipitation characteristics JF - Climate Research Y1 - 2004 A1 - Lynn, Barry H. A1 - Druyan, Leonard A1 - Hogrefe, Christian A1 - Dudhia, Jimy A1 - Rosenzweig, Cynthia A1 - Goldberg, Richard A1 - Rind, David A1 - Healy, Richard A1 - Rosenthal, Joyce A1 - Kinney, Patrick AB - A model simulation study shows that different diurnal cycles of precipitation are consistent with radically different present and future climate characteristics. In projected future climate scenarios, divergence in the time of day and type of precipitation had very divergent impacts on the radiation balance and consequently on surface temperatures. The relationship between the diurnal cycle of precipitation versus the present and future climate was examined using the GISS-MM5 (Goddard Institute for Space Studies Mesoscale Model 5) regional climate modeling system with 2 alternative moist convection schemes. June-August (JJA) mean surface temperatures of the 1990s, 2050s, and 2080s were simulated over the eastern US on a double nested 108/36 km domain, with the 36 km domain centered over the eastern US. In the 1990s, one model version simulated maxima in (convective) precipitation during the early morning, while the second model simulated the hour of precipitation maxima with considerable spatial variability (in better agreement with observations). In the futuristic climate scenarios, differences in the time of day of precipitation had very important impacts on the radiation balance at the surface. One version gave more precipitation at night and fewer clouds during the day, promoting higher surface temperatures. The alternative version created more precipitation during the day, consistent with diminished absorption of solar radiation at the surface and consequently lower surface temperatures. The results demonstrate the importance of improving cumulus parameterizations in regional mesoscale and global climate models and suggest that such improvements would lead to greater confidence in model projections of climate change. VL - 28 N1 - id: 1696 JO - Sensitivity of present and future surface temperatures to precipitation characteristics ER - TY - BOOK T1 - Shoreline Changes on the Elizabeth Islands over the Past 5000 Years Y1 - 2004 A1 - Gaines, Sarah PB - Cuttyhunk Historical Society CY - Cuttyhunk, MA N1 - id: 715 ER - TY - CHAP T1 - Social and economic dynamics on Late Holocene San Miguel Island, California T2 - Foundations of Chumash Complexity Y1 - 2004 A1 - Rick, Torben C. ED - Arnold, Jeanne JF - Foundations of Chumash Complexity PB - UCLA Cotsen Institute of Archaeology CY - Los Angeles N1 - id: 575 ER - TY - JOUR T1 - Spatial variations in a condensed interval between estuarine and open-marine settings: Holocene Hudson River estuary and adjacent continental shelf JF - Geology Y1 - 2004 A1 - McHugh, C. M. G. A1 - Pekar, S. F. A1 - Christie-Blick, N. A1 - Ryan, W. B. F. A1 - Carbotte, S. A1 - Bell, R. AB - An interval of stratigraphic condensation extending for 300 km from the fluvially dominated Hudson River estuary to the adjacent continental shelf reveals stratal relationships within an unconformity-rellated depositional sequence that are commonly difficult to resolve in seismic reflection profiles and outcrop. High-resolution side-scan sonar and bathymetry, more than 100 sediment cores similar to2 m long, and radioisotope (C-14, Cs-137) age control show that much of the valley was filled by ca. 3 to 1 ka. The present rate of sediment accumulation averages 1 mm/yr, corresponding with a sea-level rise of similar to1.2 mm/yr relative to local bedrock. Condensation is manifested today by sedimentary bypass in most parts of the estuary and by the trapping of available sediment (1.2-5.6 x 10(5) t/yr [metric tons]) along narrow reaches and primarily in the vicinity of the estuarine turbidity maximum, a part of the estuary located upstream of the salinity intrusion similar to25 km from the mouth (3.0 x 10(5) t/yr). Shelf condensation is due to sediment starvation. The condensed interval merges updip with a nascent sequence boundary as the estuary reaches its final filling phase and downdip with the sequence boundary that developed at the Last Glacial Maximum. Delta progradation may take place as available shelf accommodation is filled, but such sediments are expected to be removed once sea level begins to fall. This sedimentation pattern, in which a condensed interval merges with different sequence boundaries, is consistent with the stratigraphic record of the Atlantic margin back to the Paleogene and may be typical of sediment-starved margins. VL - 32 IS - 2 N1 - 772lcTimes Cited:10Cited References Count:30 JO - Spatial variations in a condensed interval between estuarine and open-marine settings: Holocene Hudson River estuary and adjacent continental shelf ER - TY - JOUR T1 - Stable carbon and nitrogen isotopic compositions of organic compound classes in high molecular weight dissolved organic matter from four U. S. estuaries JF - Geochimica et Cosmochimica Acta Y1 - 2004 A1 - Wang, X. C. A1 - Altabet, A. M. A1 - Callahan, J. A1 - Chen, R. F. VL - 68 N1 - id: 515 ER - TY - JOUR T1 - Stable carbon and oxygen isotope records in a Palau sclerosponge JF - Geochimica Et Cosmochimica Acta Y1 - 2004 A1 - Grottoli, A. G. A1 - Gibb, O. VL - 68 SN - 0016-7037 IS - 11, Supplement N1 - Suppl. S827th Times Cited:0 Cited References Count:0 JO - Geochim Cosmochim Ac ER - TY - JOUR T1 - Stable carbon isotope ratios in lake and swamp sediments as a proxy for prehistoric forest clearance and crop cultivation in the Neotropics JF - Journal of Paleolimnology Y1 - 2004 A1 - Lane, C. S. A1 - Horn, S. P. A1 - Mora, C. I. AB - Close correspondence between stable carbon isotope ratios (delta(13)C), pollen, and charcoal profiles in sediment cores from Laguna Zoncho and Machita swamp, Costa Rica, shows that prehistoric forest clearance and crop cultivation can be detected in the stable carbon isotope ratios of total organic carbon (delta(13)C(TOC)). Analyses of delta(13)C(TOC) complement evidence from pollen, charcoal, and phytoliths and provide a proxy that is sensitive to the intensity and/or proximity to core sites of prehistoric forest clearance and agriculture in watersheds. Stable carbon isotope analyses are particularly useful in situations in which other evidence of forest clearance and agriculture is limited. VL - 32 IS - 4 N1 - 881ycTimes Cited:30Cited References Count:36 JO - Stable carbon isotope ratios in lake and swamp sediments as a proxy for prehistoric forest clearance and crop cultivation in the Neotropics ER - TY - JOUR T1 - Style, context, and chronology of a wooden canoe model from Santa Rosa Island, California JF - Journal of California and Great Basin Anthropology Y1 - 2004 A1 - Rick, Torben C. A1 - Johnson, John R. A1 - Erlandson, Jon M. A1 - Gamble, Lynn H. VL - 24 IS - 2 N1 - id: 1092 ER - TY - JOUR T1 - Temporal variability of Delta 14C, delta13C, and C/N in sinking particulate organic matter at a deep time series station in the northeast Pacific Ocean JF - Global Biogeochemical Cycles Y1 - 2004 A1 - Hwang, Jeomshik A1 - Druffel, Ellen R. M. A1 - Griffin, Sheila A1 - L, Smith Kenneth, Jr. A1 - Baldwin, Roberta J. A1 - Bauer, James E. VL - 18 N1 - id: 531 ER - TY - CONF T1 - Time averaging on a shallow subtropical shelf: the search for a taphomomic clock T2 - Geological Society of America, Abstracts with Programs Y1 - 2004 A1 - Barbour-Wood, S. L. A1 - Krause R.A, Jr. A1 - Kowalewski, M. A1 - Wehmiller, J. F. A1 - Simoes, M. G. AB - 36(2):134 JF - Geological Society of America, Abstracts with Programs CY - Washington, DC, USA N1 - id: 719 ER - TY - CONF T1 - The urban sea: anthropogenic influences on benthic foraminifera in Long Island Sound T2 - IGC 32 Y1 - 2004 A1 - Thomas, E. A1 - Varekamp, J. C. A1 - Thaler, B. A1 - Groner, M. JF - IGC 32 CY - Florence, Italy N1 - id: 738 ER - TY - CONF T1 - The use of stable carbon isotopes in foraminiferal calcite to trace changes in biological oxygen demand in Long Island Sound T2 - 6th Biennual LIS Res. Conf. Proc. Y1 - 2004 A1 - Lugolobi, F. A1 - Varekamp, J. C. A1 - Thomas, E. A1 - Buchholtz ten Brink, M. R. JF - 6th Biennual LIS Res. Conf. Proc. N1 - id: 723 ER - TY - JOUR T1 - Variable ageing and storage of dissolved organic components in the open ocean JF - Nature Y1 - 2004 A1 - Loh, A. N. A1 - Bauer, J. E. A1 - Druffel, E. R. M. AB - Seawater dissolved organic matter (DOM) is the largest reservoir of exchangeable organic carbon in the ocean, comparable in quantity to atmospheric carbon dioxide(1,2). The composition, turnover times and fate of all but a few planktonic constituents of this material are, however, largely unknown(3,4). Models of ocean carbon cycling are thus limited by the need for information on temporal scales of carbon storage in DOM subcomponents, produced via the 'biological pump', relative to their recycling by bacteria(3,4). Here we show that carbohydrate- and protein-like substances in the open Atlantic and Pacific oceans, though often significantly aged, comprise younger fractions of the DOM, whereas dissolved lipophilic material exhibits up to similar to90 per cent fossil character. In contrast to the millennial mean ages of DOM observed throughout the water column, weighted mean turnover times of DOM in the surface ocean are only decadal in magnitude. An observed size-age continuum further demonstrates that small dissolved molecules are the most highly aged forms of organic matter, cycling much more slowly than larger, younger dissolved and particulate precursors, and directly links oceanic organic matter age and size with reactivity(3,5). VL - 430 IS - 7002 N1 - 847daTimes Cited:93Cited References Count:30 JO - Variable ageing and storage of dissolved organic components in the open ocean ER - TY - JOUR T1 - Vegetation and climate changes around the Lama Lake, Taymyr Peninsula, Russia during the Late Pleistocene and Holocene JF - HIgh resolution lake sediment records in climate and Environment variability studies:European lake drilling program Y1 - 2004 A1 - Andreev, A.A. A1 - Tarasov, P.E. A1 - Klimanov, V.A. A1 - Melles, M. A1 - Lisitsyna, O.M. A1 - Hubberten, H.-W. AB - A continuous lacustrine sequence from the western part of Lama Lake (69°32′N, 90°12′E), complemented by a peat sequence from the lake catchment provides the first detailed environmental reconstruction for the Late Glacial and Holocene on the Taymyr Peninsula. Scarce steppe-like communities with Artemisia, Poaceae, and Cyperaceae dominated during the Late Glacial. Tundra-like communities with Betula nana, Dryas, and Salix grew on more mesic sites. There are distinct climatic signals, which may be correlated with the Bølling and Allerød warming and Middle and Younger Dryas cooling. The Late Glacial/Preboreal transition, at about 10,000 14C yr BP, was characterized by changes from predominantly open herb communities to shrub tundra ones. Larch forest might have been established as early as 9700–9600 14C yr BP, whilst shrub alder came to the area ca 9500–9400 14C yr BP, and spruce did not reach area before ca 9200 14C yr BP. Spruce-larch forests with shrub alder and tree birch dominated the vegetation around the Lama Lake from ca 9000 14C yr BP. Dwarf birch communities were also broadly distributed. The role of spruce in the forest gradually decreased after 4500 14C yr BP. The vegetation cover in the Lama Lake area became similar to the modern larch-spruce forest ca 2500 14C yr BP. A pollen-based biome reconstruction supports a quantitative interpretation of the pollen spectra. Climate reconstructions obtained with information-statistical and plan-functional-type methods show very similar trends in reconstructed July temperature since ca 12,300 14C yr BP, while precipitation anomalies are less coherent, especially during the Late Glacial–Holocene transition. VL - 122 SN - 1040-6182 IS - 1 ER - TY - JOUR T1 - Vegetation and sedimentation in the Lake Edward Basin, Uganda-Congo during the late Pleistocene and early Holocene JF - Journal of Paleolimnology Y1 - 2004 A1 - Beuning, K. R. M. A1 - Russell, J. M. AB - New palynological and sedimentological data obtained from the basal 3 m of core E96-2P from Lake Edward, Uganda-Congo record conditions wetter than present in the Edward basin from similar to11000 to 6700 yr BP, in phase with other climate and vegetation records of northern hemispheric East Africa. Dominant pollen taxa include Celtis spp., Alchornea spp., Olea spp., and Moraceae indicating a moist semi-deciduous tropical forest. More xeric indicators such as Amaranthaceae and Asteraceae together with Poaceae comprise less than 5% of the pollen sum throughout this interval as compared with between 44 and 50% during a lake lowstand at similar to2000 cal yr BP and at the core top ( near modern). The differences between these two assemblages suggest a similar to25 to 60% increase in annual precipitation during the early- to mid-Holocene as compared to modern (1500-2000 vs. 1200 mm/yr today). Early Holocene sediments in E96-2P are composed of laminated diatom oozes with moderately high total sulfur concentrations (2.8-4.7%) and no authigenic calcite, also indicative of conditions wetter than present. Between similar to9000 and 6700 yr BP, palynological and sedimentary proxies indicate sub-millennial-scale events related to changes in riverine discharge and runoff in the Edward basin. We attribute the variability in runoff, and hence precipitation, to Holocene variability in Indian or Atlantic Ocean SSTs or to shifts in the relative contribution of Indian and Atlantic moisture sources to the western Rift of equatorial Africa. VL - 32 IS - 1 N1 - 814suTimes Cited:11Cited References Count:77 JO - Vegetation and sedimentation in the Lake Edward Basin, Uganda-Congo during the late Pleistocene and early Holocene ER - TY - JOUR T1 - Ventilation of the glacial deep Pacific Ocean JF - Science Y1 - 2004 A1 - Broecker, W. A1 - Barker, S. A1 - Clark, E. A1 - Hajdas, I. A1 - Bonani, G. A1 - Stott, L. AB - Measurements of the age difference between coexisting benthic and planktic foraminifera from western equatorial Pacific deep-sea cores suggest that during peak glacial time the radiocarbon age of water at 2-kilometers depth was no greater than that of today. These results make unlikely suggestions that a slowdown in deep-ocean ventilation was responsible for a sizable fraction of the increase of the ratio of carbon-14 (14C) to carbon in the atmosphere and surface ocean during glacial time. Comparison of 14C ages for coexisting wood and planktic foraminifera from the same site suggests that the atmosphere to surface ocean 14C to C ratio difference was not substantially different from today's. VL - 306 IS - 5699 N1 - Broecker, WallaceBarker, StephenClark, ElizabethHajdas, IrkaBonani, GeorgesStott, Lowelleng2004/11/13 09:00Science. 2004 Nov 12;306(5699):1169-72. JO - Ventilation of the glacial deep Pacific Ocean ER - TY - CONF T1 - Western Long Island Sound: evidence from diatom studies of eutrophication and environmental change in the 19th centure T2 - AERS fall meeting Y1 - 2004 A1 - Cooper, S. R. A1 - Thomas, E. A1 - Varekamp, J. C. A1 - Sangiorgio, F. JF - AERS fall meeting CY - New Jersey Meadowland Commission, Lyndhurst, NJ N1 - id: 736 ER - TY - CONF T1 - 14C activity and global carbon cycle changes over the past 50,000 years T2 - Abstracts, 18th International Radiocarbon Conf. Y1 - 2003 A1 - Hughen, K. A. A1 - Lehman, S. J. A1 - Southon, J. A1 - Overpeck, J. T. A1 - Marchal, O. A1 - Herring, C. A1 - Turnbull, J. JF - Abstracts, 18th International Radiocarbon Conf. CY - Wellington, NZ N1 - id: 1079 ER - TY - JOUR T1 - A 1600-year history of the Labrador Current off Nova Scotia JF - Climate Dynamics Y1 - 2003 A1 - Keigwin, L. D. A1 - Sachs, J. P. A1 - Rosenthal, Y. AB - A multicore from Emerald Basin, on the continental margin off Nova Scotia, has a modern C-14 age at the top, and other C-14 dates indicate a linear sedimentation rate of similar to30 cm/ka to 1600 calendar years BP. This rate is great enough to record century-to-millennial scale changes in the surface and deep (similar to250 m) waters in the basin that are influenced by the Labrador Current. We applied five proxies for seawater temperature changes to the sediments of Emerald Basin, including the percent abundance and the oxygen isotope ratio (delta(18)O) of the polar planktonic foraminifer N. pachyderma (s.), the unsaturation ratio of alkenones (U-37(k')) produced by prymnesiophyte phytoplankton, and the delta(18)O and Mg/Ca of benthic foraminifera. All five proxies indicate the ocean warmed suddenly sometime in the past 150 years or so. The exact timing of this event is uncertain because C-14 dating is inaccurate in recent centuries, but this abrupt warming probably correlates with widespread evidence for warming in the Arctic in the nineteenth century. Because the Canadian Archipelago is one of the two main sources for the Labrador Current, warming and melting of ice caps in that region may have affected Labrador Current properties. Before this recent warming, sea surface temperature was continually lower by 1-2 degreesC, and bottom water was colder by about 6 degreesC in Emerald Basin. These results suggest that there was no Medieval Warm Period in the coastal waters off Nova Scotia. Because there is also no evidence of medieval warming in the Canadian archipelago, it seems likely that coastal waters from Baffin Bay to at least as far south as Nova Scotia were continually cold for similar to1500 of the past 1600 years. VL - 21 IS - 1 N1 - 698thTimes Cited:25Cited References Count:31 JO - A 1600-year history of the Labrador Current off Nova Scotia ER - TY - JOUR T1 - 1999 RV Melville Baja California cruise, on the preservation of laminated sediments along the western margin of North America JF - Paleoceanography Y1 - 2003 A1 - van Geen, A. A1 - Zheng, Y. A1 - Bernhard, J. M. A1 - Cannariato, K. G. A1 - Carriquiry, J. A1 - Dean, E. A1 - Eakins, B. W. A1 - Ortiz, J. D. A1 - Pike, J. VL - 18 IS - 4 N1 - id: 1102 ER - TY - JOUR T1 - A 725 yr cycle in the climate of central Africa during the late Holocene JF - Geology Y1 - 2003 A1 - Russell, J. M. A1 - Johnson, T. C. A1 - Talbot, M. R. AB - High-resolution analyses of the chemical and stable isotope composition of endogenic calcite from Lake Edward, an equatorial rift take in central Africa, reveal large oscillations in African climate and moisture balance over the past 5400 yr. These oscillations indicate a series of droughts from 4900 to 400 yr B.P. that define a drought period of similar to725 yr. This period may be correlated to variations in the Indian Ocean monsoons, as documented by similar periods in sea-surface salinity records from the northern Indian Ocean. The similarities in periodicity of the Lake Edward and Indian Ocean records may indicate that low-frequency variability within the Indian and Pacific Oceans dominates millennial-scale African moisture balance and the Holocene climate of the tropical Indian Ocean. VL - 31 IS - 8 N1 - 710ajTimes Cited:27Cited References Count:34 JO - A 725 yr cycle in the climate of central Africa during the late Holocene ER - TY - JOUR T1 - Abrupt changes in the Asian southwest monsoon during the Holocene and their links to the North Atlantic Ocean JF - Nature Y1 - 2003 A1 - Gupta, A. K. A1 - Anderson, D. M. A1 - Overpeck, J. T. AB - During the last ice age, the Indian Ocean southwest monsoon exhibited abrupt changes that were closely correlated with millennial-scale climate events in the North Atlantic region(1-3), suggesting a mechanistic link. In the Holocene epoch, which had a more stable climate, the amplitude of abrupt changes in North Atlantic climate was much smaller, and it has been unclear whether these changes are related to monsoon variability. Here we present a continuous record of centennial-scale monsoon variability throughout the Holocene from rapidly accumulating and minimally bioturbated sediments in the anoxic Arabian Sea. Our monsoon proxy record reveals several intervals of weak summer monsoon that coincide with cold periods documented in the North Atlantic region(4)-including the most recent climate changes from the Medieval Warm Period to the Little Ice Age and then to the present. We therefore suggest that the link between North Atlantic climate and the Asian monsoon is a persistent aspect of global climate. VL - 421 IS - 6921 N1 - 637uwTimes Cited:483Cited References Count:30 JO - Abrupt changes in the Asian southwest monsoon during the Holocene and their links to the North Atlantic Ocean ER - TY - JOUR T1 - Acceptance of the 2002 V. M. Goldschmidt Award JF - Geochimica Et Cosmochimica Acta Y1 - 2003 A1 - Hayes, J. M. VL - 67 IS - 13 N1 - 693mfTimes Cited:0Cited References Count:0 JO - Acceptance of the 2002 V. M. Goldschmidt Award ER - TY - JOUR T1 - Accumulation of biogenic and lithogenic material in the Pacific sector of the Southern Ocean during the past 40,000 years JF - Deep-Sea Research Part Ii-Topical Studies in Oceanography Y1 - 2003 A1 - Chase, Z. A1 - Anderson, R. F. A1 - Fleisher, M. Q. A1 - Kubik, P. W. KW - antarctic circumpolar current KW - atmospheric co2 KW - biological productivity KW - Deep-sea KW - interglacial changes KW - Last glacial maximum KW - marine-sediments KW - organic-carbon KW - pa-231/th-230 ratio KW - terrigenous sediment AB - The (230)Th-normalization technique was applied to surface sediments and down-core records from the Pacific sector of the Southern Ocean between 120degreesW and 170degreesW in order to reconstruct vertical rain rates, corrected for lateral redistribution of sediment. Preserved rain rates of opal, organic carbon and biogenic Ba all indicate that biological productivity south of the Antarctic Polar Front (APF) was much lower than today during the Last Glacial Maximum (LGM), probably in response to increased ice cover. However, by analogy with modern opal fluxes south of the ACC, we show that year-round ice cover is not a prerequisite for very low rates of opal accumulation. Available records from north of the APF indicate little to no change in opal export, in contrast to records from the Indian and Atlantic sectors, which show enhanced opal export north of the APF during the LGM. Glacial records from north of 66degreesS in the Pacific all show lithogenic fluxes that were greater than today, but significantly lower than lithogenic fluxes in the glacial Atlantic and Indian sectors. Together, these new records from the Pacific sector show that during the LGM the three basins of the Southern Ocean were significantly more differentiated than today. The observed inter-basin distribution of lithogenic fluxes and opal burial, and the presumed geographical distribution of increased dust input to the Southern Ocean during the LGM, are consistent with an Atlantic-Indian-Pacific gradient in the degree of iron-stimulated diatom productivity within the zone lying between the APF and the Subantarctic Front. Previous studies, which focused primarily on the Atlantic sector, may have overestimated the glacial increase in the strength of the biological pump in the Southern Ocean. (C) 2002 Elsevier Science Ltd. All rights reserved. VL - 50 SN - 0967-0645 IS - 3-4 N1 - 662agTimes Cited:82 Cited References Count:86 JO - Deep-Sea Res Pt Ii ER - TY - JOUR T1 - Age determination, validation and growth of Grand Bank yellowtail flounder (Limanda ferruginea) JF - Ices Journal of Marine Science Y1 - 2003 A1 - Dwyer, K. S. A1 - Walsh, S. J. A1 - Campana, S. E. AB - Yellowtail flounder (Limanda ferruginea) (Storer, 1839) on the Grand Bank off Newfoundland were traditionally aged using surface-read whole otoliths. Age determination of otoliths from recaptures of fish tagged in the early 1990s indicated that the traditional ageing technique was underestimating the ages of yellowtail flounder when compared with the time at liberty. Age comparisons between whole and thin-sectioned otoliths showed agreement in age readings up to 7 years; thereafter whole otoliths tended to give much lower ages than those estimated by thin sections. Length-frequency analysis of pelagic and demersal juveniles, captive rearing of juveniles and marginal increment analysis all corroborated age determination based on thin sections. Tag-recaptures and bomb radiocarbon assays validated age interpretations based on thin sections in young and old yellowtail flounder, respectively. Ages were validated up to 25 years for females and 21 years for males. However, because of increased narrowing of annuli in thin-sectioned otoliths from old fish, even thin sections may underestimate the true age of the fish. von Bertalanfly growth curve parameters (combined sexes) were L-infinity = 55.6 cm total length, K = 0.16 and t(0) = -0.003. These results challenge the conventional view that yellowtail flounder on the Grand Banks are a relatively fast growing, short-lived species. Crown Copyright (C) 2003 Published by Elsevier Ltd on behalf of International Council for the Exploration of the Sea. All rights reserved. VL - 60 IS - 5 N1 - 723jaTimes Cited:43Cited References Count:57 JO - Age determination, validation and growth of Grand Bank yellowtail flounder (Limanda ferruginea) ER - TY - CONF T1 - Alkenone radiocarbon stratigraphy at high resolution continental margin sites T2 - EGS-AGU-EUG Joint Assembly Y1 - 2003 A1 - Mollenhauer, Gesine A1 - Eglinton, Timothy I. A1 - Freudenthal, Tim A1 - Lamy, Frank JF - EGS-AGU-EUG Joint Assembly CY - Nice, France N1 - id: 1071 ER - TY - JOUR T1 - The amplitude and phasing of climate change during the last deglaciation in the Sulu Sea, western equatorial Pacific JF - Geophysical Research Letters Y1 - 2003 A1 - Rosenthal, Y. A1 - Oppo, D. W. A1 - Linsley, B. K. KW - china KW - enso KW - level KW - monsoon KW - record KW - surface temperature AB - [1] Variations in tropical sea surface temperature patterns and the phasing relative to climate change in higher-latitudes provide insight into the mechanisms of climate change on both orbital and shorter time-scales. Here, we present well-dated, high-resolution records of planktonic foraminiferal delta(18)O and Mg/Ca-based SST spanning the last deglaciation from the Sulu Sea, located in the western equatorial Pacific. The results indicate that the last glacial maximum was 2.3 +/- 0.5degreesC cooler than present in the Sulu Sea with a concomitant decrease in sea surface salinity. The similarity between variations in surface salinity in the Sulu Sea, the western and eastern equatorial Pacific, and the Greenland ice-core record suggests that the observed changes in salinity reflect large-scale rearrangement of atmospheric patterns, which were coherent and synchronous throughout the Northern Hemisphere. The results suggest that the glacial equatorial Pacific climate was strongly influenced by both tropical, and extra-tropical forcing, although it is not clear whether interannual (ENSO) variability is a good analogue of glacial-interglacial climate change. VL - 30 SN - 0094-8276 IS - 8 N1 - 677zxTimes Cited:122 Cited References Count:18 JO - Geophys Res Lett ER - TY - CHAP T1 - Analog for Holocene and future Climate? T2 - Geophysical Monograph 137, Earth's Climate and Orbital Eccentricity: The Marine Isotope State 11 Questions Y1 - 2003 A1 - McManus, J. F. A1 - Oppo, D. W. A1 - Cullen, J. L. A1 - Healey, S. L. ED - Droxler, A. JF - Geophysical Monograph 137, Earth's Climate and Orbital Eccentricity: The Marine Isotope State 11 Questions N1 - id: 1166 ER - TY - CONF T1 - Ancient organic matter sources to the Hudson-Mohawk River system: implications of riverine transport of ancient organic matter for the global biogeochemical T2 - American Geophysical Union (AGU) Y1 - 2003 A1 - Longworth, B. E. A1 - Raymond, P. A. A1 - Petsch, S. T. JF - American Geophysical Union (AGU) CY - San Francisco, CA N1 - id: 1027 ER - TY - JOUR T1 - Anthropogenically induced changes in sediment and biogenic silica fluxes in Chesapeake Bay JF - Geology Y1 - 2003 A1 - Colman, S. M. A1 - Bratton, J. F. AB - Sediment cores as long as 20 m, dated by C-14, Pb-210, and Cs-137 methods and pollen stratigraphy, provide a history of diatom productivity and sediment-accumulation rates in Chesapeake Bay. We calculated the flux of biogenic silica and total sediment for the past 1500 yr for two high-sedimentation-rate sites in the mesohaline section of the bay. The data show that biogenic silica flux to sediments, an index of diatom productivity in the bay, as well as its variability, were relatively low before European settlement of the Chesapeake Bay watershed. In the succeeding 300400 yr, the flux of biogenic silica has increased by a factor of 4 to 5. Biogenic silica fluxes still appear to be increasing, despite recent nutrient-reduction efforts. The increase in diatom-produced biogenic silica has been partly masked (in concentration terms) by a similar increase in total sediment flux. This history suggests the magnitude of anthropogenic disturbance of the estuary and indicates that significant changes had occurred long before the twentieth century. VL - 31 IS - 1 N1 - 632uhTimes Cited:47Cited References Count:35 JO - Anthropogenically induced changes in sediment and biogenic silica fluxes in Chesapeake Bay ER - TY - JOUR T1 - An assessment of the Late Holocene record of severe storm impacts from Lake Shelby, Alabama JF - Gulf Coast Association of Geological Societies Transactions Y1 - 2003 A1 - Lambert, W. Joe A1 - Aharon, Paul A1 - Rodriguez, Antonio B. AB - The historical record of severe storms on the Gulf Coast extends back only about 100 years. To better predict how the Gulf Coast will be impacted by future climate change and associated changes in storm frequency it is necessary to extend the severe storm record back to the time when global climate was different than today. A 3200-year record of severe storm impacts was reported from Lake Shelby, AL, using sand layers as proxies of storm intensity and frequency (Liu and Fearn, 1993). To enhance the understanding of the Lake Shelby environment and changes that may occur during severe storms seismic data, water chemistry profiles, sediment cores, radiocarbon dates, and geochemical measurements were obtained. The results indicate that Lake Shelby is a stratified lake in terms of salinity and dissolved oxygen. The lake floor is composed of two general lithologies, gyttja located below about 2 m water depth, and sand located along the entire perimeter of the lake. Radiocarbon dates and stable isotope data indicate that the lake was a brackish water lagoon prior to 80014C yrs BP when it became isolated and transformed into a lacustrine environment. Interpretation of sand layers recognized in sediment cores from Lake Shelby as indicators of severe storms may be ambiguous. New data suggest that severe-storm records based on geochemical stratigraphy may provide higher resolution and confidence than conventional overwash techniques. VL - 53 N1 - id: 1111 JO - An assessment of the Late Holocene record of severe storm impacts from Lake Shelby, Alabama ER - TY - JOUR T1 - Asynchronous alkenone and foraminifera records from the Benguela Upwelling System JF - Geochimica et Cosmochimica Acta Y1 - 2003 A1 - Mollenhauer, Gesine A1 - Eglinton, Timothy I. A1 - Ohkouchi, Naohiko A1 - Schneider, Ralph R. A1 - Muller, Peter J. A1 - Grootes, Pieter M. A1 - Rullkotter, Jurgen VL - 67 IS - 12 N1 - id: 1067 ER - TY - JOUR T1 - Atlantic Ocean circulation during the Younger Dryas: Insights from a new Cd/Ca record from the western subtropical South Atlantic JF - Paleoceanography Y1 - 2003 A1 - Came, R. E. A1 - Oppo, D. W. A1 - Curry, W. B. AB - [Benthic foraminiferal Cd/ Ca from an intermediate depth, western South Atlantic core documents the history of southward penetration of North Atlantic Intermediate Water ( NAIW). Cd seawater estimates ( Cd-W) for the last glacial are consistent with the production of NAIW and its export into the South Atlantic. At similar to 14.5 ka concurrently with the onset of the Bolling- Allerod to Younger Dryas cooling, the NAIW contribution to the South Atlantic began to decrease, marking the transition from a glacial circulation pattern to a Younger Dryas circulation. High Cd-W in both the deep North Atlantic and the intermediate South Atlantic imply reduced export of deep and intermediate water during the Younger Dryas and a significant decrease in northward oceanic heat transport. A modern circulation was achieved at similar to 9 ka, concurrently with the establishment of Holocene warmth in the North Atlantic region, further supporting a close linkage between deepwater variability and North Atlantic climate. VL - 18 IS - 4 N1 - 749rtTimes Cited:30Cited References Count:39 JO - Atlantic Ocean circulation during the Younger Dryas: Insights from a new Cd/Ca record from the western subtropical South Atlantic ER - TY - JOUR T1 - Biomass burning and oceanic primary production estimates in the Sulu Sea area over the last 380 kyr and the East Asian monsoon dynamics JF - Marine Geology Y1 - 2003 A1 - Beaufort, L. A1 - de Garidel-Thoron, T. A1 - Linsley, B. A1 - Oppo, D. A1 - Buchet, N. KW - arabian sea KW - atlantic KW - climatic-change KW - EARLY HOLOCENE KW - EQUATORIAL KW - fire KW - GLACIAL MAXIMUM KW - indian-ocean KW - late pleistocene KW - Late Quaternary KW - monsoon KW - nannoplankton KW - Pleistocene KW - SOUTH CHINA KW - Sulu Sea KW - WEST-JAVA AB - Coccolithophorid assemblages and micro-charcoal content were analysed in giant piston core MD97-2141 recovered in the Sulu Sea (Philippines). These proxies help to reconstruct respectively the dynamics of the oceanic primary production (PP) and biomass burning in that area. PP in the Sulu Sea intensifies during the East Asian winter monsoon (EAWM) and therefore PP constitutes a proxy for EAWM dynamics. Most of the precipitation in the Sulu Sea region occurs during the East Asian summer monsoon (EASM). Because the intensity of biomass burning is related to dryness of the surrounding area, the sedimentary micro-charcoal content can be used as an inverse proxy for EASM intensity. Our results show that the EAWM intensifies during glacial times in agreement with previous studies. Precessional forcing appears to act directly on EAWN because of the early response of PP in that frequency band. The micro-charcoal record exhibits complex dynamics, which we attribute to the competing influence of the long-term El Nino Southern Oscillation (ENSO)-like forcing and the glacial/interglacial cycle on EASM. These influences create an unusual frequency spectrum with power around 30 kyr and 19 kyr attributed to the non-linear response to the 100-kyr cycle (glacial) and the 23-kyr (ENSO) cycle. A factor of two increase in the amplitude of the micro-charcoal variability between 51 and 10 ka BP could correspond to Homo sapiens biomass burning in the style of the fire-stick farming of the Australian Aborigines. We also find, on precession cycles, an opposite phase between EASM and EAWM records and an advance of -delta(18)O and delta(18)O respectively by 2000 yr. (C) 2003 Elsevier B.V. All rights reserved. VL - 201 SN - 0025-3227 IS - 1-3 N1 - Symposium on Asian Monsoons and Global Linkages on Milankovitch and Sub-Milankovitch Time ScalesMAY 09-11, 2001 BEIJING, PEOPLES R CHINA 70 JO - Mar. Geol. ER - TY - JOUR T1 - Calcium carbonate budget in the Atlantic Ocean based on water column inorganic carbon chemistry JF - Global Biogeochemical Cycles Y1 - 2003 A1 - Chung, S. N. A1 - Lee, K. A1 - Feely, R. A. A1 - Sabine, C. L. A1 - Millero, F. J. A1 - Wanninkhof, R. A1 - Bullister, J. L. A1 - Key, R. M. A1 - Peng, T. H. KW - alkalinity KW - anthropogenic co2 KW - caco3 dissolution KW - calcium carbonate budget KW - chemical lysocline KW - Deep-sea KW - dioxide system KW - dissociation-constants KW - dissolution kinetics KW - dissolution of calcium carbonate KW - eastern north-atlantic KW - ocean carbon cycle KW - organic-carbon KW - pacific-ocean KW - saturation state of seawater AB - [1] Recent independent lines of evidence suggest that the dissolution of calcium carbonate (CaCO3) particles is substantial in the upper ocean above the calcite 100% saturation horizon. This shallow-water dissolution of carbonate particles is in contrast with the current paradigm of the conservative nature of pelagic CaCO3 at shallow water depths. Here we use more than 20,000 sets of carbon measurements in conjunction with CFC and C-14 data from the WOCE/JGOFS/OACES global CO2 survey to estimate in situ dissolution rates of CaCO3 in the Atlantic Ocean. A dissolution rate is estimated from changes in alkalinity as a parcel of water ages along an isopycnal surface. The in situ CaCO3 dissolution increases rapidly at the aragonite 100% saturation horizon. Estimated dissolution rates north of 40degreesN are generally higher than the rates to the south, which is partly attributable to the production of exported CaCO3 being higher in the North Atlantic than in the South Atlantic. As more CaCO3 particles move down the water column, more particles are available for in situ dissolution. The total water column CaCO3 dissolution rate in the Atlantic Ocean is determined on an annual basis by integrating estimated dissolution rates throughout the entire water column and correcting for alkalinity input of approximately 5.6 x 10(12) mol C yr(-1) from CaCO3-rich sediments. The resulting water column dissolution rate of CaCO3 for the Atlantic Ocean is approximately 11.1 x 10(12) mol C yr(-1). This corresponds to about 31% of a recent estimate (35.8 x 10(12) mol C yr(-1)) of net CaCO3 production by Lee [2001] for the same area. Our calculation using a large amount of high-quality water column alkalinity data provides the first basin-scale estimate of the CaCO3 budget for the Atlantic Ocean. VL - 17 SN - 0886-6236 IS - 4 N1 - 732egTimes Cited:44 Cited References Count:73 JO - Global Biogeochem Cy ER - TY - CONF T1 - Carbon cycling in Long Island Sound over the last 1000 years T2 - AGU, Fall meeting Y1 - 2003 A1 - Lugolobi, F. A1 - Varekamp, J. C. A1 - Thomas, E. A1 - Buchholtz ten Brink, M. L. A1 - Mecray, E. JF - AGU, Fall meeting CY - San Francisco, CA N1 - id: 1179 ER - TY - JOUR T1 - Carbon isotopic compositions of prokaryotic lipids as tracers of carbon cycling in diverse settings JF - Chemical Geology Y1 - 2003 A1 - Pancost, R. D. A1 - Damste, J. S. S. AB - Recent work has highlighted the ubiquity of bacteria and archaea and continues to affirm their significance in diverse biogeochemical processes. The delta(13)C values and distributions of diagnostic lipids derived from such microorganisms can provide insights into prokaryotic processes in modem settings and are one of the few means by which past prokaryotic processes in depositional settings can be elucidated. Here we present a brief review of prokaryotic lipids commonly observed in sediments and the controls on their carbon isotopic compositions. We then present two case studies-one of Mediterranean cold seeps at which anaerobic oxidation of methane occurs and one of a Holocene peat deposit in which a variety of aerobic and anaerobic microorganisms govern the degradation of organic matter. These two studies illustrate the potential utility of compound-specific carbon isotope analyses to deconvolute pathways of carbon flow in microbial communities. (C) 2002 Elsevier Science B.V. All rights reserved. VL - 195 IS - 1-4 N1 - id: 1331; 666LX Times Cited:59 Cited References Count:144 JO - Carbon isotopic compositions of prokaryotic lipids as tracers of carbon cycling in diverse settings ER - TY - JOUR T1 - The Catfish Lake scarp: preliminary field data and implications for earthquake hazards posed by the Tacoma fault JF - U. S. Geological Survey Open-File Report Y1 - 2003 A1 - Sherrod, B. L. A1 - Nelson, A. R. A1 - Kelsey, H. M. A1 - Brocher, T. M. A1 - Blakely, R. J. A1 - Weaver, C. S. A1 - Rountree, N. K. A1 - Rhea, S. A1 - Jackson, B. S. VL - 03-0455 N1 - id: 430 ER - TY - JOUR T1 - Changes in the 13C/12C of dissolved inorganic carbon in the ocean as a tracer of anthropogenic CO2 uptake JF - Global Biogeochemical Cycles Y1 - 2003 A1 - Quay, P. A1 - Sonnerup, R. A1 - Westby, T. A1 - Stutsman, J. A1 - McNichol, A. VL - 17 N1 - id: 1546 ER - TY - JOUR T1 - Changes of the 13C/12C of dissolved inorganic carbon in the ocean as a tracer of anthropogenic C)2 uptake JF - Global Biogeochemical Cycles Y1 - 2003 A1 - Quay, P. D. A1 - Sonnerup, T. A1 - Westby, J. A1 - Stutsman, J. A1 - McNichol, A. P. VL - 17 IS - 1004 N1 - id: 1689 ER - TY - JOUR T1 - Climate and the collapse of Mayan civilization JF - Science Y1 - 2003 A1 - Haug, G. H. A1 - Gunther, D. A1 - Peterson, L. C. A1 - Sigman, D. M. A1 - Hughen, K. A. VL - 299 N1 - id: 556 ER - TY - CONF T1 - COMPARE04-Comparison/calibration of 14C records 26-50 ka T2 - Abstracts, 18th International Radiocarbon Conf. Y1 - 2003 A1 - van der Plicht, J. A1 - Hughen, K. A. A1 - Guilderson, T. P. A1 - Reimer, P. JF - Abstracts, 18th International Radiocarbon Conf. CY - Wellington, NZ N1 - id: 564 ER - TY - CONF T1 - A comparison of rates of time averaging between the bivalve Macoma cleryana and brachiopod Bouchardia rosea on a shallow subtropical shelf T2 - Geological Society of America, Abstracts with Programs Y1 - 2003 A1 - Barbour-Wood, S. L. A1 - Krause R.A, Jr. A1 - Kowalewski, M. A1 - Wehmiller, J. F. A1 - Simoes, M. G. A1 - Goodfriend, G. A. AB - 35(6):273 JF - Geological Society of America, Abstracts with Programs CY - Seattle, WA, USA N1 - id: 720 ER - TY - JOUR T1 - Composition and syngeneity of molecular fossils from the 2.78 to 2.45 billion-year-old Mount Bruce Supergroup, Pilbara Craton, Western Australia JF - Geochimica Et Cosmochimica Acta Y1 - 2003 A1 - Brocks, J. J. A1 - Buick, R. A1 - Logan, G. A. A1 - Summons, R. E. AB - Shales of very low metamorphic grade from the 2.78 to 2.45 billion-year-old (Ga) Mount Bruce Supergroup, Pilbara Craton, Western Australia, were analyzed for solvent extractable hydrocarbons. Samples were collected from ten drill cores and two mines in a sampling area centered in the Hamersley Basin near Wittenoom and ranging 200 km to the southeast, 100 km to the southwest and 70 km to the northwest. Almost all analyzed kerogenous sedimentary rocks yielded solvent extractable organic matter. Concentrations of total saturated hydrocarbons were commonly in the range of 1 to 20 ppm ( mug/g rock) but reached maximum values of 1000 ppm. The abundance of aromatic hydrocarbons was similar to1 to 30 ppm. Analysis of the extracts by gas chromatography-mass spectrometry (GC-MS) and GC-MS metastable reaction monitoring (MRM) revealed the presence of n-alkanes, mid- and end-branched monomethylalkanes, omega-cyclohexylalkanes, acyclic isoprenoids, diamondoids, tri- to pentacyclic terpanes, steranes, aromatic steroids and polyaromatic hydrocarbons. Neither plant biomarkers nor hydrocarbon distributions indicative of Phanerozoic contamination were detected. The host kerogens of the hydrocarbons were depleted in C-13 by 2 to 21parts per thousand relative to n-alkanes, a pattern typical of, although more extreme than, other Precambrian samples. Acyclic isoprenoids showed carbon isotopic depletion relative to n-alkanes and concentrations of 2alpha-methylhopanes were relatively high, features rarely observed in the Phanerozoic but characteristic of many other Precambrian bitumens. Molecular parameters, including sterane and hopane ratios at their apparent thermal maxima, condensate-like alkane profiles, high mono- and triaromatic steroid maturity parameters, high methyladamantane and methyldiamantane indices and high methylphenanthrene maturity ratios, indicate thermal maturities in the wet-gas generation zone. Additionally, extracts from shales associated with iron ore deposits at Tom Price and Newman have unusual polyaromatic hydrocarbon patterns indicative of pyrolytic dealkylation.The saturated hydrocarbons and biomarkers in bitumens from the Fortescue and Hamersley Groups are characterized as 'probably syngenetic with their Archean host rock' based on their typical Precambrian molecular and isotopic composition, extreme maturities that appear consistent with the thermal history of the host sediments, the absence of biomarkers diagnostic of Phanerozoic age, the absence of younger petroleum source rocks in the basin and the wide geographic distribution of the samples. Aromatic hydrocarbons detected in shales associated with iron ore deposits at Mt Tom Price and Mt Whaleback are characterized as 'clearly Archean' based on their hypermature composition and covalent bonding to kerogen. Copyright (C) 2003 Elsevier Ltd. VL - 67 IS - 22 N1 - 741dvTimes Cited:124Cited References Count:102 JO - Composition and syngeneity of molecular fossils from the 2.78 to 2.45 billion-year-old Mount Bruce Supergroup, Pilbara Craton, Western Australia ER - TY - CONF T1 - Compound specific radiocarbon dating of alkenones: methodological considerations and applications in paleoceanography T2 - 18th International Radiocarbon Conference Y1 - 2003 A1 - Mollenhauer, Gesine A1 - Eglinton, Timothy I. A1 - Schneider, Ralph R. A1 - Meggers, Helge A1 - Lamy, Frank A1 - Ohkouchi, Nao A1 - Hayes, John M. JF - 18th International Radiocarbon Conference CY - Wellington, New Zealand N1 - id: 1070 ER - TY - CONF T1 - Continuous-Flow Accelerator Mass Spectrometry T2 - International Symposium on Radiation Physics Y1 - 2003 A1 - Roberts, M. L. A1 - Benthien, A. A1 - Schneider, R. J. A1 - von Reden, K. F. A1 - Hayes, J. M. JF - International Symposium on Radiation Physics CY - Mexico City, Mexico N1 - id: 1683 ER - TY - JOUR T1 - Contrasting He-C relationships in Nicaragua and Costa Rica: insights into C cycling through subduction zones JF - Earth and Planetary Science Letters Y1 - 2003 A1 - Shaw, A. M. A1 - Hilton, D. R. A1 - Fischer, T. P. A1 - Walker, J. A. A1 - Alvarado, G. E. AB - We report He-3/He-4 ratios, relative He, Ne, and CO2 abundances as well as delta(13)C values for volatiles from the volcanic output along the Costa Rica and Nicaragua segments of the Central American arc utilising fumaroles, geothermal wells, water springs and bubbling hot springs. CO2/He-3 ratios are relatively constant throughout Costa Rica (av. 2.1 X 10(10)) and Nicaragua (av. 2.5 X 10(10)) and similar to arcs worldwide (similar to1.5 X 10(10)). delta(13)C values range from -6.8parts per thousand (MORB-like) to -0.1parts per thousand (similar to marine carbonate (0parts per thousand)). He-3/He-4 ratios are essentially MORB-like (8 +/- R-A) with some samples showing evidence of crustal He additions - water spring samples are particularly susceptible to modification. The He-CO2 relationships are consistent with an enhanced input of slab-derived C to magma sources in Nicaragua ((L+S)/M = 16; where L, M and S represent the fraction of CO2 derived from limestone and/or marine carbonate (L), the mantle (M) and sedimentary organic C (S) sources) relative to Costa Rica ((L+S)/M = 10). This is consistent with prior studies showing a higher sedimentary flux to the arc volcanics in Nicaragua (as traced by Ba/La, Be-10 and La/Yb). Possible explanations include: (1) offscraping of the uppermost sediments in the Costa Rica forearc, and (2) a cooler thermal regime in the Nicaragua subduction zone, preserving a higher proportion of melt-inducing fluids to subarc depths, leading to a higher degree of sediment transfer to the subarc mantle. The absolute flux Of CO2 from the Central American arc as determined by correlation spectrometry methods (5.8 X 10(10) mol/yr) and CO2/He-3 ratios (7.1 X 10(10) mol/yr) represents approximately 14-18% of the amount of CO2 input at the trench from the various slab contributors (carbonate sediments, organic C, and altered oceanic crust). Although the absolute flux is comparable to other arcs, the efficiency Of CO2 recycling through the Central American are is surprisingly low (14-18% vs. a global average of similar to50%). This may be attributed to either significant C loss in the forearc region, or incomplete decarbonation of carbonate sediments at subarc depths. The implication of the latter case is that a large fraction of C (up to 86%) may be transferred to the deep mantle (depths beyond the source of arc magmas). (C) 2003 Elsevier B.V. All rights reserved. VL - 214 IS - 3-4 N1 - 725paTimes Cited:98Cited References Count:50 JO - Contrasting He-C relationships in Nicaragua and Costa Rica: insights into C cycling through subduction zones ER - TY - CHAP T1 - Cosmochemical Estimates of Mantle Composition T2 - Treatise on Geochemistry Y1 - 2003 A1 - Palme, H. A1 - O'Neill, H. St C. ED - Holland, H. D. JF - Treatise on Geochemistry PB - Elsevier Ltd, Oxford VL - 2 N1 - id: 1583 ER - TY - JOUR T1 - Dates, demography, and disease: Cultural contacts and possible evidence for old world epidemics among the island Chumash JF - Pacific Coast Archaeological Society Quarterly Y1 - 2003 A1 - Erlandson, J. M. A1 - Rick, T. C. A1 - Kennett, D. J. A1 - Walker, P. L. VL - 37 IS - 3 N1 - id: 1022 ER - TY - JOUR T1 - Decadal timescale shift in the 14C record of a central equatorial Pacific coral JF - Radiocarbon Y1 - 2003 A1 - Grottoli, A. G. A1 - Gille, S. T. A1 - Druffel, E. R. M. A1 - Dunbar, R. B. VL - 45 IS - 1 N1 - id: 1130 ER - TY - JOUR T1 - Deep sea records from the southeast Labrador Ocean circulation changes and ice-rafting events during hte last 160,000 years JF - Paleoceanography Y1 - 2003 A1 - Rasmussen, T. L. A1 - Oppo, D. W. A1 - Thompson, E. A1 - Lehman, S. J. VL - 18 N1 - id: 989 ER - TY - JOUR T1 - Early cave occupations on San Miguel Island, California JF - Current Research in the Pleistocene Y1 - 2003 A1 - Rick, Torben C. A1 - Erlandson, Jon M. A1 - Vellanoweth, Rene L. VL - 20 N1 - id: 1093 ER - TY - JOUR T1 - East Asian monsoon forcing of suborbital variability in the Sulu Sea during Marine Isotope Stage 3: Link to Northern Hemisphere climate JF - Geochemistry Geophysics Geosystems Y1 - 2003 A1 - Dannenmann, S. A1 - Linsley, B. K. A1 - Oppo, D. W. A1 - Rosenthal, Y. A1 - Beaufort, L. KW - 1620 global change : climate dynamics (3309) KW - 4267 oceanography : general : paleoceanography KW - dissolution KW - equatorial pacific KW - eurasian snow cover KW - isotope stage 3 KW - last glacial period KW - late pleistocene KW - Mg/Ca KW - millennial-scale climate change KW - oxygen isotopes KW - paleoceanography KW - planktonic-foraminifera KW - records KW - se asian monsoon KW - south china sea KW - summer monsoon KW - surface temperature-variations AB - [1] We have generated a new high-resolution record of variations in planktonic foraminiferal oxygen isotopes (delta(18)O) and Mg/Ca from a sediment core (IMAGES 97-2141) in the Sulu Sea located in the Philippine archipelago of western tropical Pacific. This record reveals distinct, suborbital-scale delta(18)O changes, most notably during Marine Isotope Stage 3 (MIS3) (similar to30,000 to 60,000 years B.P.). The amplitudes of these delta(18)O fluctuations (0.4 to 0.7parts per thousand) exceed that which can be attributed to sea level changes and must be due to changes in sea surface conditions. In the same interval, variations in planktonic foraminifera Mg/Ca suggest that suborbital surface ocean temperature variations of 1 to 1.5degreesC in the Sulu Sea were not in phase with delta(18)O. Combined, this evidence indicates that the MIS3 millennial delta(18)O events in the Sulu Sea were primarily the result of changes in surface water salinity, which today is directly related to the East Asian Monsoon (EAM) and its influence on the balance between surface water contributions from the South China Sea and Western Pacific Warm Pool (WPWP). Within dating uncertainties the MIS3 Sulu Sea delta(18)O suborbital variability indicates that times of fresher surface conditions in the Sulu Sea coincide with similar conditions in the WPWP [Stott et al., 2002] and also with intensifications of the summer EAM as recorded in the U-Th dated Chinese (Hulu Cave) speleothem delta(18)O record [Wang et al., 2001] and thus by inference with interstadials in the Greenland Ice core records. Combined, these results indicate that pronounced suborbital variability in the summer EAM and Intertropical Convergence Zone (ITCZ) during MIS3 was tightly coupled with climate conditions in the northern high latitudes. VL - 4 SN - 1525-2027 N1 - 631mwTimes Cited:41 Cited References Count:53 JO - Geochem Geophy Geosy ER - TY - JOUR T1 - Ecosystem modulation of dissolved carbon age in a temperate marsh-dominated estuary JF - Ecosystems Y1 - 2003 A1 - Raymond, P. A. A1 - Hopkinson, C. S. AB - We measured the concentrations and isotopic values (Delta(14)C and delta(13)C) of dissolved inorganic, dissolved organic, and particulate organic carbon (DIC, DOC, and POC, respectively) in the Parker River watershed and estuary in Massachusetts, USA, to determine the age of carbon (C) entering the estuary and how estuarine processing affects the quantity and apparent age of C transported to the Gulf of Maine. The watershed measurements indicated the transport of Delta(14)C-enriched modern DIC and DOC and variably aged POC from the watershed to the estuary. The transport of organic matter from the watershed was dominated by DOC transport, with POC making up less than 10% of the total. Surveys within the watershed aimed at determining which land-use type dominated the DOC export indicated that wetlands, although they made up only around 20% of the land use, could be responsible for approximately 75% of the DOC export. We therefore conclude that the wetland land uses of the Parker River watershed are exporting mainly Delta(14)C-enriched modem DOC. DIC isotopes indicate that the source of DIC in the Parker River watershed is dominated by the weathering of noncarbonate parent material by Delta(14)C-enriched carbon dioxide (CO2) originating from the respiration of young organic matter in soils. Transects in the estuary displayed net additions of all C species. For DOC and DIC, the export of this internally added DOC and DIC was approximately equal to the amount being exported from the watershed, showing the importance of focusing on estuaries when estimating the export of C to the coastal ocean. With respect to DIC, the total input is even larger when the atmospheric exchange of excess PCO2 is calculated. The Delta(14)C -DOC and Delta(14)C-DIC transects indicate that the internally added DOC and DIC is Delta(14)C-enriched modern material. The source of this material is the fringing marshes and estuarine phytoplankton, with the relative importance of these two sources changing over time. Taken together, the bulk C and Delta(14)C measurements show that the estuary is adding significant quantities of young DOC despite the presence of vast quantities of old marsh peat flanking the entire estuary. Furthermore, the DIC data indicate that Delta(14)C-enriched modern material is what is fueling the majority of heterotrophic respiration within the system. VL - 6 IS - 7 N1 - 746zrTimes Cited:42Cited References Count:73 JO - Ecosystem modulation of dissolved carbon age in a temperate marsh-dominated estuary ER - TY - CHAP T1 - Emergence of Late Holocene sociopolitical complexity on Santa Rosa and San Miquel Islands T2 - Catalist to Complexity: The Late Holocene Archaeology of the California Coast: Perspectives in California Archaeology Y1 - 2003 A1 - Kennett, D. J. A1 - Conlee, C. A. ED - Erlandson, J. M. JF - Catalist to Complexity: The Late Holocene Archaeology of the California Coast: Perspectives in California Archaeology PB - Institute of Archaeology, University of California CY - Los Angeles, CA N1 - id: 472 ER - TY - JOUR T1 - Eutrophication and carbon sources in Chesapeake Bay over the last 2700 yr: human impacts in context JF - Geochimica et Cosmochimica Acta Y1 - 2003 A1 - Bratton, John F. A1 - Colman, Steven M. A1 - Seal, Robert R. AB - To compare natural variability and trends in a developed estuary with human-influenced patterns, stable isotope ratios (δ13C and δ15N) were measured in sediments from five piston cores collected in Chesapeake Bay. Mixing of terrestrial and algal carbon sources primarily controls patterns of δ13Corg profiles, so this proxy shows changes in estuary productivity and in delivery of terrestrial carbon to the bay. Analyses of δ15N show periods when oxygen depletion allowed intense denitrification and nutrient recycling to develop in the seasonally stratified water column, in addition to recycling taking place in surficial sediments. These conditions produced 15N-enriched (heavy) nitrogen in algal biomass, and ultimately in sediment. A pronounced increasing trend in δ15N of +4‰ started in about A.D. 1750 to 1800 at all core sites, indicating greater eutrophication in the bay and summer oxygen depletion since that time. The timing of the change correlates with the advent of widespread land clearing and tillage in the watershed, and associated increases in erosion and sedimentation. Isotope data show that the region has experienced up to 13 wet-dry cycles in the last 2700 yr. Relative sea-level rise and basin infilling have produced a net freshening trend overprinted with cyclic climatic variability. Isotope data also constrain the relative position of the spring productivity maximum in Chesapeake Bay and distinguish local anomalies from sustained changes impacting large regions of the bay. This approach to reconstructing environmental history should be generally applicable to studies of other estuaries and coastal embayments impacted by watershed development. VL - 67 IS - 18 N1 - id: 541 JO - Eutrophication and carbon sources in Chesapeake Bay over the last 2,700 years: Human impacts in context ER - TY - CONF T1 - Evaluating system-specific variability in riverine organic matter ages: implications for determining terrestrial contributions to oceanic DOC T2 - Symposium on New Approaches in Marine Organic Biogeochemistry Y1 - 2003 A1 - Raymond, P. A. JF - Symposium on New Approaches in Marine Organic Biogeochemistry CY - Friday Harbor Laboratory, Seattle, WA N1 - id: 486 ER - TY - JOUR T1 - Evolution of a habitable planet JF - Annual Review of Astronomy and Astrophysics Y1 - 2003 A1 - Kasting, J. F. A1 - Catling, D. AB - Giant planets have now been discovered around other stars, and it is only a matter of time until Earth-sized planets are detected. Whether any of these planets are suitable for life depends on their volatile abundances, especially water, and on their climates. Only planets within the liquid-water habitable zone (HZ) can support life on their surfaces and, thus, can be analyzed remotely to determine whether they are inhabited. Fortunately, current models predict that HZs are relatively wide around main-sequence stars not too different from our sun. This conclusion is based on studies of how our own planet has evolved over time. Earth's climate has remained conducive to life for the past 3.5 billion years or more, despite a large increase in solar luminosity, probably because of previous higher concentrations Of CO2 and/or CH4. Both these gases are involved in negative feedback loops that help to stabilize the climate. In addition to these topics, we also briefly discuss the rise of atmospheric O-2 and O-3, along with their possible significance as indicators of life on other planets. VL - 41 N1 - 742axTimes Cited:217Cited References Count:146 JO - Evolution of a habitable planet ER - TY - BOOK T1 - Evolution of Sedimentary Rocks T2 - Treatise on Geochemistry Y1 - 2003 A1 - Veizer, J. A1 - Mackenzie, F. T. ED - Turekian, K. K. JF - Treatise on Geochemistry PB - Elsevier Ltd, Oxford VL - 7 N1 - id: 1604 ER - TY - JOUR T1 - Extensive deposits on the Pacific plate from Late Pleistocene North American glacial lake outbursts JF - Journal of Geology Y1 - 2003 A1 - Normark, W. R. A1 - Reid, J. A. AB - One of the major unresolved issues of the Late Pleistocene catastrophic-flood events in the northwestern United States (e.g., from glacial Lake Missoula) has been what happened when the flood discharge reached the ocean. This study compiles available 3.5-kHz high-resolution and airgun seismic reflection data, long-range sidescan sonar images, and sediment core data to define the distribution of flood sediment in deepwater areas of the Pacific Ocean. Upon reaching the ocean at the mouth of the Columbia River near the present-day upper continental slope, sediment from the catastrophic floods continued flowing downslope as hyperpycnally generated turbidity currents. The turbidity currents resulting from the Lake Missoula and other latest Pleistocene floods followed the Cascadia Channel into and through the Blanco Fracture Zone and then flowed west to the Tufts Abyssal Plain. A small part of the flood sediment, which was stripped off the main flow at a bend in the Cascadia Channel at its exit point from the Blanco Fracture Zone, continued flowing more than 400 km to the south and reached the Escanaba Trough, a rift valley of the southern Gorda Ridge. Understanding the development of the pathway for the Late Pleistocene flood sediment reaching Escanaba Trough provides insight for understanding the extent of catastrophic flood deposits on the Pacific plate. VL - 111 IS - 6 N1 - 758frTimes Cited:37Cited References Count:53 JO - Extensive deposits on the Pacific plate from Late Pleistocene North American glacial lake outbursts ER - TY - MAP T1 - Field and laboratory data from an earthquake history study of the Waterman Point fault, Kitsap County, Washington Y1 - 2003 A1 - Nelson, A. R. A1 - Johnson, S. Y. A1 - Kelsey, S. K. A1 - Wells, R. E. A1 - Sherrod, B. L. A1 - Bradley, L. A. A1 - Okumura, K. A1 - Bogar, R. JF - U. S. Geological Survey Miscellaneous Field Studies N1 - id: 429 ER - TY - JOUR T1 - Fossil Sources of Ambient Aerosol Carbon Based on 14C Measurements JF - Aerosol Science and Technology Y1 - 2003 A1 - Tanner, R. L. A1 - Parker, W. J. A1 - McNichol, A. P. N1 - id: 1690 ER - TY - JOUR T1 - Geochemistry of hydrothermally altered oceanic crust: DSDP/ODP Hole 504B - Implications for seawater-crust exchange budgets and Sr- and Pb-isotopic evolution of the mantle JF - Geochemistry, Geophysics, Geosystems G3 Y1 - 2003 A1 - Bach, Wolfgang A1 - Peucker-Ehrenbrink, Bernhard A1 - Hart, STanly R. A1 - Blusztajn, Jerzy S. VL - 4 N1 - id: 1536 JO - Geochemistry of hydrothermally altered oceanic crust: DSDP/ODP Hole 504B - Implications for seawater-crust exchange budgets and Sr- and Pb-isotopic evolution of the mantle ER - TY - JOUR T1 - Glacial-interglacial dynamics of the eastern equatorial Pacific cold tongue Intertropical Convergence Zone system reconstructed from oxygen isotope records JF - Paleoceanography Y1 - 2003 A1 - Koutavas, A. A1 - Lynch-Stieglitz, J. AB - We use planktonic oxygen isotope (delta(18)O) records spanning the last 30,000 years (kyr) to constrain the magnitude and spatial pattern of glacial cooling in the upwelling environment of the eastern equatorial Pacific (EEP). Fourteen new downcore delta(18)O records were obtained from surface-dwelling planktonic foraminifera Globigerinoides sacculifer and Globigerinoides ruber in eight cores from the upwelling tongue of the EEP. All sites have sedimentation rates exceeding 5 cm/kyr and, with one exception, lie above the modern depth of the foraminiferal lysocline. Sites directly underlying the cool band of upwelling immediately south of the equator record mean late Holocene (LH)-Last Glacial Maximum (LGM) delta(18)O amplitudes ranging between 1.0 and 1.3parts per thousand. We estimate that mean sea surface temperatures (SST) in this region during the LGM were on average 1.5 +/- 0.5degreesC lower than the LH. Larger delta(18)O amplitudes are observed in sites north of the equator, indicating a spatial pattern of reduced meridional SST gradient across the equator during the LGM. This result is supported by comparison of Mg/Ca SST reconstructions from two sites straddling the equator. We interpret the reduction of this gradient during the LGM as evidence for a less intense cold tongue-Intertropical Convergence Zone (ITCZ) frontal system, a more southerly position of the ITCZ, and weaker southeast equatorial trades in the EEP. VL - 18 IS - 4 N1 - 756nfTimes Cited:56Cited References Count:100 JO - Glacial-interglacial dynamics of the eastern equatorial Pacific cold tongue Intertropical Convergence Zone system reconstructed from oxygen isotope records ER - TY - JOUR T1 - Global MORB chemistry compilation at the segment scale JF - Database available at http://www.petdb.org. Y1 - 2003 A1 - Su, Y. A1 - Langmuir, C. H. N1 - id: 1600 ER - TY - JOUR T1 - Heterogeneity in the radiocarbon content of Polycyclic aromatic hydrocarbons in household soot JF - Environmental Forensics Y1 - 2003 A1 - Reddy, C. M. A1 - Xu, L. A1 - O'Connor, R. VL - 4 N1 - id: 507 ER - TY - JOUR T1 - High-temperature seafloor hydrothermal circulation over geologic time and archean banded iron formations JF - Geophysical Research Letters Y1 - 2003 A1 - Lowell, R. P. A1 - Keller, S. M. AB - Under the assumption of simple plate tectonics with a range of continental growth scenarios, we construct models of global lithospheric heat loss, hydrothermal heat loss and hydrothermal iron flux to the ocean as functions of geologic time from 4.0 Ga to present. The models show that lithospheric heat loss scales with the square root of the plate creation rate, whereas hydrothermal heat loss scales linearly with that rate. Thus during the Archean lithospheric and hydrothermal heat losses were approximate to3 and approximate to10 times greater than present, respectively. Straightforward extrapolation of hydrothermal Fe flux from the present to the Archean using these models indicates that hydrothermal Fe may not have been sufficient to supply the large Superior-type Banded Iron Formations deposited between 2.7 and 1.8 Ga. VL - 30 IS - 7 N1 - 669jkTimes Cited:5Cited References Count:31 JO - High-temperature seafloor hydrothermal circulation over geologic time and archean banded iron formations ER - TY - JOUR T1 - Hydrothermal alteration of upper oceanic crust formed at a fast-spreading ridge: mineral, chemical, and isotopic evidence from ODP Site 801 JF - Chemical Geology Y1 - 2003 A1 - Alt, J. C. A1 - Teagle, D. A. H. AB - ODP Hole 801C penetrates >400 m into 170-Ma oceanic basement formed at a fast-spreading ridge. Most basalts are slightly (10-20%) recrystallized to saponite, calcite, minor celadonite and iron oxyhydroxides, and trace pyrite. Temperatures estimated from oxygen isotope data for secondary minerals are 5-100 degreesC, increasing downward. At the earliest stage, dark celadonitic alteration halos formed along fractures and celadonite, and quartz and chalcedony formed in veins from low-temperature ( VL - 201 IS - 3-4 N1 - id: 1537; 748HG Times Cited:42 Cited References Count:56 JO - Hydrothermal alteration of upper oceanic crust formed at a fast-spreading ridge: mineral, chemical, and isotopic evidence from ODP Site 801 ER - TY - JOUR T1 - Isotopic and geochemical assessment of in situ biodegradation of chlorinated hydrocarbons JF - Environ Sci Technol Y1 - 2003 A1 - Kirtland, B. C. A1 - Aelion, C. M. A1 - Stone, P. A. A1 - Hunkeler, D. AB - Currently there is no in situ method to detect and quantify complete mineralization of chlorinated hydrocarbons (CHCs) to CO2. Combined isotopic measurements in conjunction with traditional chemical techniques were used to assess in situ biodegradation of trichloroethylene (TCE) and carbon tetrachloride (CT). Vadose zone CHC, ethene, ethane, methane, O2, and CO2 concentrations were analyzed using gas chromatography over 114 days at the Savannah River Site. delta13C of CHC and delta13C and 14C of vadose zone CO2, sediment organic matter, and groundwater dissolved inorganic carbon (DIC)were measured. Intermediate metabolites of TCE and CT accounted for < or = 10% of total CHCs. Delta13C of cis-1,2-dichloroethylene (DCE) was always heavier than TCE indicating substantial DCE biodegradation. 14C-CO2 values ranged from 84 to 128 percent modern carbon (pMC), suggesting that plant root-respired CO2 was dominant. 14C-CO2 values decreased over time (up to 12 pMC), and contaminated groundwater 14C-DIC (76 pMC) was substantially depleted relative to the control (121 pMC). 14C provided a direct measure of complete CHC mineralization in vadose zone and groundwater in situ and may improve remediation strategies. VL - 37 IS - 18 N1 - Kirtland, Brian CAelion, C MarjorieStone, Peter AHunkeler, DanielengResearch Support, Non-U.S. Gov'tResearch Support, U.S. Gov't, Non-P.H.S.2003/10/04 05:00Environ Sci Technol. 2003 Sep 15;37(18):4205-12. JO - Isotopic and geochemical assessment of in situ biodegradation of chlorinated hydrocarbons ER - TY - JOUR T1 - KN167-KN168A/B: AHC-800 coring on the New Jersey Shelf for ONR's Geoclutter Initiative, R/V KNORR JF - Cruise Report Y1 - 2003 A1 - Alexander, C. R. A1 - Austin J.A, Jr. N1 - id: 635 ER - TY - CHAP T1 - La colonisation et les fortifications de Rapa T2 - Bilan de la recherche archeologique en Polynesie francaise Y1 - 2003 A1 - Kennett, D. J. A1 - Anderson, A. J. A1 - Prebble, M. A1 - Conte, E. ED - Marchesi, H. JF - Bilan de la recherche archeologique en Polynesie francaise PB - Service de la Culture et du Patrimoine CY - Papeete, Tahiti N1 - id: 471 ER - TY - JOUR T1 - Late Holocene earthquakes on the Toe Jam Hill fault, Seattle fault zone, Bainbridge Island, Washington JF - Geological Society of America Bulletin Y1 - 2003 A1 - Nelson, A. R. A1 - Johnson, S. Y. A1 - Kelsey, H. M. A1 - Wells, R. E. A1 - Sherrod, B. L. A1 - Pezzopane, S. K. A1 - Bradley, L. A. A1 - Koehler, R. D. A1 - Bucknam, R. C. AB - Five trenches across a Holocene fault scarp yield the first radiocarbon-measured earthquake recurrence intervals for a crustal fault in western Washington. The scarp, the first to be revealed by laser imagery, marks the Toe Jam Hill fault, a north-dipping backthrust to the Seattle fault. Folded and faulted strata, liquefaction features, and forest soil A horizons buried by hanging-wall-collapse colluvium record three, or possibly four, earthquakes between 2500 and 1000 yr ago. The most recent earthquake is probably the 1050-1020 cal. (calibrated) yr B.P. (A.D. 900930) earthquake that raised marine terraces and triggered a tsunami in Puget Sound. Vertical deformation estimated from strati-graphic and surface offsets at trench sites suggests late Holocene earthquake magnitudes near M7, corresponding to surface ruptures >36 km long. Deformation features recording poorly understood latest Pleistocene earthquakes suggest that they were smaller than late Holocene earthquakes. Postglacial earthquake recurrence intervals based on 97 radiocarbon ages, most on detrital charcoal, range from similar to12,000 yr to as little as a century or less; corresponding fault-slip rates are 0.2 mm/ yr for the past 16,000 yr and 2 mm/yr for the past 2500 yr. Because the Toe Jam Hill fault is a backthrust to the Seattle fault, it may not have ruptured during every earthquake on the Seattle fault. But the earthquake history of the Toe Jam Hill fault is at least a partial proxy for the history of the rest of the Seattle fault zone. VL - 115 IS - 11 N1 - 740qwTimes Cited:41Cited References Count:53 JO - Late Holocene earthquakes on the Toe Jam Hill fault, Seattle fault zone, Bainbridge Island, Washington ER - TY - JOUR T1 - Late-Holocene climate and ecosystem history from Chesapeake Bay sediment cores, USA JF - Holocene Y1 - 2003 A1 - Willard, D. A. A1 - Cronin, T. M. A1 - Verardo, S. AB - Palaeoclimate records from late-Holocene sediments in Chesapeake Bay, the largest estuary in the USA, provide evidence that both decadal to centennial climate variability and European colonization had severe impacts on the watershed and estuary. Using pollen and dinoflagellate cysts as proxies for mid-Atlantic regional precipitation, estuarine salinity and dissolved oxygen (DO) during the last 2300 years, we identified four dry intervals, centred on AD 50 (P1/D1), AD 1000 (P2/D2), AD 1400 (P3) and AD 1600 (P4). Two centennial-scale events, P1/D1 and P2/D2, altered forest composition and led to increased salinity and DO levels in the estuary. Intervals P3 and P4 lasted several decades, leading to decreased production of pine pollen. Periods of dry mid-Atlantic climate correspond to 'megadroughts' identified from tree-ring records in the southeastern and central USA. The observed mid-Atlantic climate variability may be explained by changes in atmospheric circulation resulting in longer-term, perhaps amplified, intervals of meridional flow. After European colonization in the early seventeenth century, forest clearance for agriculture, timber and urbanization altered estuarine water quality, with dinoflagellate assemblages indicating reduced DO and increased turbidity. VL - 13 IS - 2 N1 - 650thTimes Cited:56Cited References Count:101 JO - Late-Holocene climate and ecosystem history from Chesapeake Bay sediment cores, USA ER - TY - JOUR T1 - Late-Quaternary cold events recorded in the Southern Ocean sediments, Pacific Sector JF - Terra Antartica Y1 - 2003 A1 - Langone, L. A1 - Capotondi, L. A1 - Giglio, F. A1 - Focaccia, P. A1 - C, Morigi A1 - Ravaioli, M. VL - 9 N1 - id: 1000 JO - Late-Quaternary cold events recorded in the Southern Ocean sediments, Pacific Sector ER - TY - JOUR T1 - Lipid-Like material as the source of the uncharacterized organic carbon in the ocean? JF - Science Y1 - 2003 A1 - Hwang, Jeomshik A1 - Druffel, Ellen R. M. VL - 299 N1 - id: 530 ER - TY - JOUR T1 - Magnitude and variability of Holocene sediment accumulation in Santa Monica Bay, California JF - Mar Environ Res Y1 - 2003 A1 - Sommerfield, C. K. A1 - Lee, H. J. AB - The spatial variability of Holocene (past 10,000 years) sediment accumulation in Santa Monica Bay (California) was examined to identify controls sediment trapping in a bathymetrically complex coastal embayment and to provide geologic context for the post-industrial sedimentary record and associated pollution gradients. Sediment chronologies based on downcore AMS 14C dates were used to quantify long-term (millennia) accumulation rates in an effort to elucidate particle-transport pathways and sinks. Sediment accumulation rates for the full range of bayfloor environments (50-630 m water depths) range from 22 to 102 mg/cm(2)/year (15-88 mm/100 year), have an overall mean of 51+/-21 mg/cm(2)/year (1 sigma, n=11), and are comparable to rates reported for adjacent borderland basins. Maximal accumulation rates on the Malibu shelf and within a reentrant to Redondo canyon are interpreted to reflect (1) proximity to sediment sources and (2) localized oceanographic and topographic conditions conducive to sediment trapping and deposition. The 14C-derived accumulation rates are 2-10 times lower than rates determined through (210)Pb geochronology for the same sites in a related study, revealing that Holocene sediment accumulation has been non-steady-state. Santa Monica Bay is an important sink for suspended matter; averaged over the past several millennia a mass of sediment equivalent to 10-80% of the modern annual river supply is sequestered yearly. Net influx of suspended matter derived from the adjacent Palos Verdes shelf is evinced by a concentration gradient of p,p'-DDE in bayfloor sediments, whereas the distribution of anthropogenic silver suggests transport from Santa Monica shelf to the southeastern boundary of the bay. The results of this study provide new insight to the long-term fates of particulate matter in Los Angeles coastal waters. VL - 56 IS - 1-2 N1 - Sommerfield, Christopher KLee, Homa JengResearch Support, U.S. Gov't, Non-P.H.S.England2003/03/22 04:00Mar Environ Res. 2003 Jul-Aug;56(1-2):151-76. JO - Magnitude and variability of Holocene sediment accumulation in Santa Monica Bay, California ER - TY - BOOK T1 - Mantle Volatiles--Distribution and Consequences T2 - Treatise on Geochemistry Y1 - 2003 A1 - Luth, R. W. ED - Turekian, K. K. JF - Treatise on Geochemistry PB - Elsevier Ltd CY - Oxford VL - 2 N1 - id: 1597 ER - TY - MAP T1 - Map and data for Quaternary faults and folds in Washington State Y1 - 2003 A1 - Lidke, D. J. A1 - Johnson, S. Y. A1 - McCory, P. A. A1 - Personius, S. F. A1 - Nelson, A. R. A1 - Dart, R. L. A1 - Bradley, L. A. A1 - Haller, K. M. A1 - Machette, M. N. JF - Geological Survey Open-File Report N1 - id: 997 ER - TY - MAP T1 - Maps and data from a trench investigation of the Utsalady Point fault, Whidbey Island, Washington Y1 - 2003 A1 - Johnson, S. Y. A1 - Nelson, A. R. A1 - Personius, S. F. A1 - Wells, R. E. A1 - Kelsey, H. M. A1 - Sherrod, B. L. A1 - Okumura, K. A1 - Koehler, R., III A1 - Witter, R. C. A1 - Bradley, L. A. A1 - Harding, D. J. JF - U. S. Geological Survey Miscellaneous Field Studies N1 - id: 996 ER - TY - JOUR T1 - Mercury contamination chronologies from Connecticut wetlands and Long Island Sound sediments JF - Environmental Geology Y1 - 2003 A1 - Varekamp, J. C. A1 - Kreulen, B. A1 - ten Brink, M. R. B. A1 - Mecray, E. L. AB - Sediment cores were used to investigate the mercury deposition histories of Connecticut and Long Island Sound. Most cores show background (pre-1800s) concentrations (50-100 ppb Hg) below 30-50 cm depth, strong enrichments up to 500 ppb Hg in the core tops, with lower Hg concentrations in the surface sediments (200-300 ppb Hg). A sediment core from the Housatonic River has peak levels of 1,500 ppb Hg, indicating the presence of a Hg point source in this watershed. The Hg records were translated into Hg contamination chronologies through Pb-210 dating. The onset of Hg contamination occurred in similar to1840-1850 in eastern Connecticut, whereas in the Housatonic River the onset is dated at around 1820. The mercury accumulation profiles show periods of peak contamination at around 1900 and at 1950-1970. Peak Hg* (Hg* = Hg measured minus Hg background) accumulation rates in the salt marshes vary; dependent on the sediment character, between 8 and 44 ng Hg/cm(2) per year, whereas modern Hg* accumulation rates range from 4-17 ng Hg/cm(2) per year; time-averaged Hg* accumulation rates are 15 ng Hg/cm(2) per year. These Hg* accumulation rates in sediments are higher than the observed Hg atmospheric deposition rates (about 1-2 ng Hg/cm(2) per year), indicating that contaminant Hg from the watershed is focused into the coastal zone. The Long Island Sound cores show similar Hg profiles as the marsh cores, but time-averaged Hg* accumulation rates are higher than in the marshes (26 ng Hg/cm(2) a year) because of-the different sediment characteristics. In-situ atmospheric deposition of Hg in the marshes and in Long Island Sound is only a minor component of the total Hg budget. The 1900 peak of Hg contamination is most likely related to climatic factors (the wet period of the early 1900s) and the 1950-1970 peak was caused by strong anthropogenic Hg emissions at that time. Spatial trends in total Hg burdens in cores are largely related to sedimentary parameters (amount of clay) except for the high inventories of the Housatonic River, which are related to Hg releases from hat-making in the town of Danbury. Much of the contaminated sediment transport in the Housatonic River Basin occurs during floods; creating distinct layers of Hg-contaminated sediment in western Long Island Sound. The drop of about 40% in Hg accumulation rates between the 1960s and 1990s seems largely the result of reduced Hg emissions and to a much lesser extent of climatic factors. VL - 43 IS - 3 N1 - 643lmTimes Cited:22Cited References Count:45 JO - Mercury contamination chronologies from Connecticut wetlands and Long Island Sound sediments ER - TY - JOUR T1 - Microbial dolomite crusts from the carbonate platform off western India JF - Sedimentology Y1 - 2003 A1 - Rao, V. P. A1 - Kessarkar, P. M. A1 - Krumbein, W. E. A1 - Krajewski, K. P. A1 - Schneider, R. J. AB - The occurrence of Late Pleistocene dolomite crusts that occur at 64 m depth on the carbonate platform off western India is documented. Dolomite is the most predominant mineral in the crusts. In thin section, the crust consists of dolomitized microlaminae interspersed with detrital particles. Under scanning electron microscopy, these laminae are made up of tubular filaments or cellular structures of probable cyanobacterial origin. Dolomite crystals encrust or overgrow the surfaces of the microbial filaments and/or cells; progressive mineralization obliterates their morphology. Well-preserved microbial mats, sulphide minerals (pyrrhotite and marcasite) and the stable isotope composition of dolomite in the crusts indicate hypersaline and anoxic conditions during dolomite formation. The crusts are similar to dolomite stromatolites, and biogeochemical processes related to decaying microbial mats under anoxic conditions probably played an important role in dolomite precipitation. The dolomite is therefore primary and/or very early diagenetic in origin. The dolomite crusts are interpreted to be a composite of microbial dolomite overprinted by early burial organic dolomite. The results of this study suggest that a microbial model for dolomite formation may be relevant for the origin of ancient massive dolomites in marine successions characterized by cryptalgal laminites. The age of the crusts further suggests that the platform was situated at shallow subtidal depths during the Last Glacial Maximum. VL - 50 IS - 5 N1 - 724ejTimes Cited:19Cited References Count:69 JO - Microbial dolomite crusts from the carbonate platform off western India ER - TY - JOUR T1 - Mid-depth circulation in the northwest Pacific during the last deglaciation: Evidence from foraminiferal radiocarbon ages JF - Geophysical Research Letters Y1 - 2003 A1 - Ahagon, N. A1 - Ohkushi, K. A1 - Uchida, M. A1 - Mishima, T. AB - Sediment cores (MR01-K03 PC4/PC5, 1366 m water depth) collected from off northern Japan were studied using coexisting planktonic and benthic foraminiferal radiocarbon measurements to reconstruct the history of mid-depth circulation in the northwest Pacific. Reconstructed ventilation ages indicate that, consistent with data from a previous radiocarbon study at a shallower site, there was significant variation in mid-depth circulation during the last deglaciation, especially in the Bolling-Allerod (13-15 ka) and Younger Dryas (11.5-13 ka) intervals. Our record indicates that the ventilation changes in the North Pacific were antiphase to those of the North Atlantic, suggesting that atmospheric moisture transport associated with the Asian Monsoon might have played a great role in millennium-scale ventilation changes in the North Pacific during the last deglaciation. VL - 30 IS - 21 N1 - id: 405; 742FU Times Cited:19 Cited References Count:23 JO - Mid-depth circulation in the northwest Pacific during the last deglaciation: Evidence from foraminiferal radiocarbon ages ER - TY - JOUR T1 - Mid-holocene climate change in Lake Bosumtwi, Ghana JF - Quaternary Research Y1 - 2003 A1 - Russell, J. A1 - Talbot, M. R. A1 - Haskell, B. J. AB - Lake Bosumtwi is one of the most widely studied palaeoclimate archives in West Africa. Results from numerous AMS C-14 dates of samples from four piston cores from Lake Bosumtwi show that an abrupt sedimentary transition from a mid-Holocene sapropel to calcareous laminated muds occurred at about 3200 cal yr B.P. High-resolution analyses of the nitrogen isotopic composition of organic matter across this transition confirm its abrupt nature, and suggest that the change may signal a step toward increased aridity and intensified surface winds that affected western equatorial Africa from Ghana to the Congo basin. Northern and Eastern Africa experienced a similar abrupt shift toward aridity during the late Holocene, but at about 5000 cal yr B.P., a difference in timing that illustrates the regional nature of climate changes during the Holocene and the importance of feedback mechanisms in regulating Holocene climate variability. Furthermore, an abrupt change at about 3000 cal yr B.P. occurs at several sites adjacent to the tropical and subtropical Atlantic, which may hint at major changes in the surface temperatures of the tropical Atlantic and/or Pacific at this time. (C) 2003 University of Washington. Published by Elsevier Inc. All rights reserved. VL - 60 IS - 2 N1 - 716arTimes Cited:43Cited References Count:39 JO - Mid-holocene climate change in Lake Bosumtwi, Ghana ER - TY - JOUR T1 - Modeling the d180 in precipitation over the Americas: 1. Simulation of the stable isotope in Andean ice cores JF - JGR Y1 - 2003 A1 - Vuille, M. A1 - Bradley, R. S. A1 - Healy, R. A1 - Werner, M. A1 - Handy, D. R. A1 - Thompson, L. G. A1 - Keimig, F. VL - 108 IS - D6 N1 - id: 1771 ER - TY - JOUR T1 - Modeling the d18O in precipitation over the Americas: 1. Simulation of the stable isotope in Andean ice cores JF - JGR Y1 - 2003 A1 - Vuille, M. A1 - Bradley, R. S. A1 - Healy, R. A1 - Werner, M. A1 - Hardy, D. R. A1 - Thompson, L. G. A1 - Keimig, F. VL - 108 IS - D6 N1 - id: 1691 ER - TY - JOUR T1 - Modeling the d18O in precipitation over the Americas: 2. Interannual variability and climatic controls JF - JGR Y1 - 2003 A1 - Vuille, M. A1 - Bradley, R. S. A1 - Werner, M. A1 - Healy, R. A1 - Keimig, F. VL - 108 IS - D6 N1 - id: 1692 ER - TY - NEWS T1 - Muckrakers discover history in Long Island Sound T2 - New York Times Y1 - 2003 A1 - Varekamp, J. C. JF - New York Times CY - New York, NY ER - TY - JOUR T1 - Multiple sulfur isotopes and the evolution of the atmosphere JF - Earth and Planetary Science Letters Y1 - 2003 A1 - Farquhar, J. A1 - Wing, B. A. AB - Interest in multiple sulfur isotope analyses has been fueled by recent reports of mass-independent sulfur isotope signatures in the geologic record. A non-zero multiple isotopic signature of sulfur (Delta(33)S and Delta(36)S) is produced primarily through photochemical reactions, and it is an almost perfect tracer of the source of sulfur. Once the signature is passed on to a given sulfur reservoir, it will be preserved unless there is addition of sulfur with a different Delta(33)S or Delta(36)S. In the geological record, this signature has been used to study the evolution of the Earth's atmosphere and to trace movement of sulfur through geological systems early in Earth's history. Recently, small but significant mass-independent sigriatures have been reported for some younger samples, raising the possibility of additional applications of multiple isotope studies. The purpose of this review is to introduce and discuss the implications of multiple isotope studies and to focus attention on these anomalous, but not uncommon isotopic signatures. (C) 2003 Elsevier Science B.V. All rights reserved. VL - 213 IS - 1-2 N1 - 708vdTimes Cited:280Cited References Count:56 JO - Multiple sulfur isotopes and the evolution of the atmosphere ER - TY - CONF T1 - Niaqla revisited: Archaeology and ethnohistory of a Chumash Village on Santa Rosa Island, California T2 - Society for California Archaeology 16 Y1 - 2003 A1 - Rick, Torben C. JF - Society for California Archaeology 16 N1 - id: 576 ER - TY - JOUR T1 - Palaeo-oceanography: Deepwater variability in the Holocene epoch JF - Nature Y1 - 2003 A1 - Oppo, D. W. A1 - McManus, J. F. A1 - Cullen, J. L. VL - 422 IS - 6929 N1 - Oppo, Delia WMcManus, Jerry FCullen, James LengEngland2003/03/21 04:00Nature. 2003 Mar 20;422(6929):277. JO - Palaeo-oceanography: Deepwater variability in the Holocene epoch ER - TY - CONF T1 - The paleo environmental history of Long Island Sound, Abstract T2 - Long Island Sound Lobster Research meeting Y1 - 2003 A1 - Varekamp, J. C. A1 - Thomas, E. A1 - Buchholtz ten Brink, M. F. A1 - Altabet, M. A1 - Cooper, S. JF - Long Island Sound Lobster Research meeting CY - Groton, CT N1 - id: 1178 ER - TY - JOUR T1 - Paleoenvironmental inferences from core Anta95-1 (Granite Harobr, Sw Ross Sea-Antarctica) JF - Terra Antarctica reports Y1 - 2003 A1 - Orsini, G. A1 - Giglio, F. A1 - Langone, L. A1 - Ravaioli, M. VL - 8 N1 - id: 1001 ER - TY - JOUR T1 - Penetration of anthropogenic carbon into organic particles of the deep ocean JF - Geophysical Research Letters Y1 - 2003 A1 - Druffel, E. R. M. A1 - Bauer, J. E. A1 - Griffin, S. A1 - Hwang, J. KW - bomb radiocarbon KW - C-14 KW - CO2 KW - delta-c-13 KW - MATTER KW - NORTH PACIFIC-OCEAN KW - SARGASSO SEA KW - Sediment KW - variability KW - water AB - [1] In the late 1980s, bomb C-14 was present in suspended particulate organic carbon (POC) from the North Central Pacific (NCP) and Sargasso Sea ( SS) throughout most of the water column, demonstrating that deep POC had exchanged with atmospheric CO2 in the past 30 years. Upon reoccupation of these sites in 1999 and 2000, respectively, we observed that the delta(13)C values of suspended POC were lower than those measured a decade earlier. This demonstrates that anthropogenic CO2 from fossil fuel and biomass burning has penetrated a major organic matter pool in the deep ocean. Delta(14)C measured in the suspended POC showed similar or higher values in the deep Sargasso Sea and decreased values in the deep NCP compared to those measured previously. We use a box model to show that the differences in the radiocarbon results are likely due to the presence of resuspended sediment that is laterally advected from the continental margin to the deep Sargasso Sea. VL - 30 SN - 0094-8276 IS - 14 N1 - 709dpTimes Cited:12 Cited References Count:29 JO - Geophys Res Lett ER - TY - JOUR T1 - Persistence of Gulf Stream separation during the Last Glacial Period: Implications for current separation theories JF - Journal of Geophysical Research-Oceans Y1 - 2003 A1 - Matsumoto, K. A1 - Lynch-Stieglitz, J. KW - cape-hatteras KW - deep-ocean KW - gulf stream separation KW - Last glacial maximum KW - marine sediment cores KW - north-atlantic KW - Ocean circulation KW - oxygen isotope composition KW - oxygen isotopic composition KW - past 21,000 years KW - planktonic foraminifera KW - planktonic-foraminifera KW - SARGASSO SEA KW - western boundary current KW - western boundary undercurrent KW - wind-driven AB - [1] We present stable oxygen isotope ratio (delta(18)O) measurements on deep-dwelling planktonic foraminifera from the western margin of the North Atlantic in order to reconstruct the latitude at which the Gulf Stream separated from the western boundary of the Atlantic Ocean in the past. The modern separation latitude can be reconstructed within one degree from delta(18)O measured on the fossil shells of deep-dwelling planktonic foraminifera Globorotalia truncatulinoides from the Holocene sediments representing the past 10,000 years of mild climate conditions similar to today. The separation latitude is captured in a sharp delta(18)O gradient, which reflects the prominent hydrographic change across the boundary between the warm waters south and east of the Gulf Stream and the cold Slope Water to the north. The latitudinal delta(18)O profile from approximately the Last Glacial Maximum shows that the Gulf Stream separated from the coast near Cape Hatteras at almost the same latitude as it does today. We assess our finding in light of existing Gulf Stream separation theories and conclude that one of the theories, the wind-induced separation mechanism, is not consistent with our paleoceanographic reconstruction. VL - 108 SN - 0148-0227 IS - C6 N1 - 690nvTimes Cited:14 Cited References Count:56 JO - J Geophys Res-Oceans ER - TY - JOUR T1 - The persistence of memory: The fate of ancient sedimentary organic carbon in a modern sedimentary system JF - Geochimica Et Cosmochimica Acta Y1 - 2003 A1 - Blair, N. E. A1 - Leithold, E. L. A1 - Ford, S. T. A1 - Peeler, K. A. A1 - Holmes, J. C. A1 - Perkey, D. W. AB - The cycle of organic carbon burial and exhumation moderates atmospheric chemistry and global climate over geologic timescales. The burial of organic carbon occurs predominantly at sea in association with clay-sized particles derived from the erosion of uplifted continental rocks. It follows that the history of the fine-grained particles on land may bear on the nature of the organic carbon buried. In this study, the evolution of clay-associated organic matter was followed from bedrock source to the seabed in the Eel River sedimentary system of northern California using natural abundance C-13 and C-14 tracers. Approximately half of the fine-grained organic carbon delivered to the shelf is derived from ancient sedimentary organic carbon found in the uplifted Mesozoic-Tertiary Franciscan Complex of the watershed. The short residence time of friable soils on steep hill slopes, coupled with rapid sediment accumulation rates on the shelf-slope, act to preserve the ancient organic carbon. A comparable quantity of modem organic carbon is added to particles in the watershed and on the shelf and slope. The bimodal mixture of ancient and modem C in soils and sediments may be characteristic of many short, mountainous rivers. If the Eel River chemistry is typical of such rivers, more than 40 Tg of ancient organic C may be delivered to the world's oceans each year. A flux of that magnitude would have a significant influence on marine and global C-cycles. Copyright (C) 2003 Elsevier Science Ltd. VL - 67 IS - 1 N1 - 634jvTimes Cited:143Cited References Count:63 JO - The persistence of memory: The fate of ancient sedimentary organic carbon in a modern sedimentary system ER - TY - JOUR T1 - A possible record of the Younger Dryas event in deep-sea sediments of the Southern Ocean (Pacific sector) JF - Palaeogeography Palaeoclimatology Palaeoecology Y1 - 2003 A1 - Morigi, C. A1 - Capotondi, L. A1 - Giglio, F. A1 - Langone, L. A1 - Brilli, M. A1 - Turi, B. A1 - Ravaioli, M. AB - The oxygen isotope record combined with radiocarbon dating from two deep-sea cores collected along a transect between New Zealand and the Ross Sea are used to establish a reliable chronostratigraphy for the last 14 kyr. After an integrated geochemical and micropaleontological analysis in this timeframe we detected a cooling interval dated between 12.5 cal kyr BP and 11.4 cal kyr BP. The age control suggests that this event started 1.5 kyr after the onset of the Antarctic Cold Reversal previously observed in several Antarctic ice cores. We infer that the observed cool event corresponds to the Younger Dryas event defined in Northern Europe. This suggests that climate change recorded in this sector of the Southern Hemisphere still shows some synchronicity with Northern Hemisphere variations and that the decoupling of climate change between the two hemispheres likely occurred south of the Polar Front. (C) 2003 Elsevier B.V. All rights reserved. VL - 198 IS - 1-2 N1 - 723feTimes Cited:15Cited References Count:55 JO - A possible record of the Younger Dryas event in deep-sea sediments of the Southern Ocean (Pacific sector) ER - TY - JOUR T1 - Post little ice age uplift at Juneau, Alaska reconstructed from dendrochronology and geomorphology JF - Quaternary Research Y1 - 2003 A1 - Motyka, R. J. VL - 59 N1 - id: 698 ER - TY - JOUR T1 - On the preservation of laminated sediments along the western margin of North America JF - Paleoceanography Y1 - 2003 A1 - van Geen, A. A1 - Zheng, Y. A1 - Bernhard, J. M. A1 - Cannariato, K. G. A1 - Carriquiry, J. A1 - Dean, W. E. A1 - Eakins, B. W. A1 - Ortiz, J. D. A1 - Pike, J. VL - 18 IS - 4 N1 - id: 1128 ER - TY - JOUR T1 - Quantitative estimates of time-averaging in terebratulidbrachiopod shell accumulations from a modern tropical shelf JF - Paleobiology Y1 - 2003 A1 - Carroll, M. A1 - Kowalewski, M. A1 - Simoes, M. G. A1 - Goodfriend, G. A. AB - Quantitative estimates of time-averaging in marine shellaccumulations available to date are limited primarily toaragonitic mollusk shells. We assessed time-averaging in Holoceneassemblages of calcitic brachiopod shells by direct dating ofindividual specimens of the terebratulid brachiopod Bouchardiarosea. The data were collected from exceptional (brachiopod-rich)shell assemblages, occurring surficially on a tropical mixedcarbonate-siliciclastic shelf (the Southeast Brazilian Bight, SWAtlantic), a setting that provides a good climatic andenvironmental analog for many Paleozoic brachiopod shell beds ofNorth America and Europe. A total of 82 individual brachiopodshells, collected from four shallow (5-25 m) nearshore ( VL - 29 IS - 3 N1 - id: 2231; Source type: scholarlyjournals; Object type: Article; Object type: Feature; CSAUnique: BONE5712965; AccNum: 5712965; DOI: 10.1043/0094-8373(2003)029(0381:QEOTIT)2.0.CO;2; ISSN: 0094-8373; Peer Reviewed: true JO - Quantitative estimates of time-averaging in terebratulidbrachiopod shell accumulations from a modern tropical shelf ER - TY - CONF T1 - Radiocarbon ages of marine biomarkers and co-occurring foraminifera: evidence for differential particle transport on continental margins T2 - AGU Fall Meeting 2003 Y1 - 2003 A1 - Mollenhauer, Gesine A1 - Eglinton, Timothy I. A1 - Hayes, John M. A1 - Keinast, Markus A1 - Lamy, Frank A1 - Meggers, Helge A1 - Schneider, Ralph R. JF - AGU Fall Meeting 2003 CY - San Francisco, USA N1 - id: 1069 ER - TY - JOUR T1 - Radiocarbon dating of individual fatty acids as a tool for refining Antarctic margin sediment chronologies JF - Radiocarbon Y1 - 2003 A1 - Ohkouchi, N. A1 - Eglinton, T. I. A1 - Hayes, J. M. KW - carbon KW - ice-sheet KW - marine-sediments KW - north-atlantic KW - organic-matter KW - ross-sea KW - southern-ocean AB - We have measured the radiocarbon contents of individual, solvent-extractable, short-chain (C-14, C-16, and C-18) fatty acids isolated from Ross Sea surface sediments. The corresponding C-14 ages are equivalent to that of the post-bomb dissolved inorganic carbon (DIC) reservoir. Moreover, molecular C-14 variations in surficial (upper 15 cm) sediments indicate that these compounds may prove useful for reconstructing chronologies of Antarctic margin sediments containing uncertain (and potentially variable) quantities of relict organic carbon. A preliminary molecular C-14 chronology suggests that the accumulation rate of relict organic matter has not changed during the last 500 C-14 yr. The focus of this study is to determine the validity of compound-specific C-14 analysis as a technique for reconstructing chronologies of Antarctic margin sediments. VL - 45 SN - 0033-8222 IS - 1 N1 - 735tqTimes Cited:25 Cited References Count:29 JO - Radiocarbon ER - TY - THES T1 - A radiocarbon method and multi-tracer approach to quantifying groundwater discharge to coastal waters Y1 - 2003 A1 - Gramling, Carolyn PB - MIT/WHOI CY - Cambridge, MA/Woods Hole, MA VL - PH.D. ER - TY - JOUR T1 - Sea-level changes and depositional environments in the Izmit Gulf, eastern Marmara Sea, during the late glacial-Holocene period JF - Marine Geology Y1 - 2003 A1 - Cagatay, M. N. A1 - Gorur, N. A1 - Polonia, A. A1 - Demirbag, E. A1 - Sakinc, M. A1 - Cormier, M. H. A1 - Capotondi, L. A1 - McHugh, C. A1 - Emre, O. A1 - Eris, K. AB - Offshore and onshore stratigraphic studies, together with high-resolution shallow seismic reflection profiling and multibeam bathymetric mapping, were carried out in the western and central part of the Izmit Gulf. These studies indicate that the Izmit Gulf was a lacustrine environment as part of the Marmara 'Lake' during the late glaciation and early deglaciation until similar to12 kyr BP, when the Marmara Basin was inundated by the Mediterranean waters. Correlation of C-14-dated onshore and offshore stratigraphic units in the Western Izmit Gulf indicates that generally coarse late glacial sediments overlie a marked erosional surface formed during the low water level of the Marmara 'Lake'. These coarse sediments are succeeded by 10.4-7 kyr BP old transgressive, and by late Holocene post-transgression mud units. The bathymetry and sub-bottom Chirp profiles clearly show that the paleoshoreline of the Gulf was located at -85 m, having been controlled by the bedrock sill depth of the Canakkale Strait. Another paleoshoreline observed at -65 m on the northern margin of the Western Izmit and Karamursel basins was probably formed during the Younger Dryas sea-level stillstand. The shelf areas during this time were colonized by bioherms, which were subsequently drowned and disappeared after a further rise of the sea level. The presence of a -65 in marine paleoshoreline in the Karamursel Basin indicates that the sill restricting this basin to the west was much deeper than its present -55 in level and was located further south. The Golcuk Basin, restricted by a -38 in sill to its west, was probably not flooded by marine waters until similar to9 kyr BP. (C) 2003 Published by Elsevier B.V. VL - 202 IS - 3-4 N1 - 749gpTimes Cited:52Cited References Count:30 JO - Sea-level changes and depositional environments in the Izmit Gulf, eastern Marmara Sea, during the late glacial-Holocene period ER - TY - JOUR T1 - Sediment characteristics at selected sites of the Ross Sea continental shelf: does the sedimentary record reflect water column fluxes? JF - Antarctic Science Y1 - 2003 A1 - Frignani, M. A1 - Giglio, F. A1 - Accornero, A. A1 - Langone, L. A1 - Ravaioli, M. VL - 15 IS - 1 N1 - id: 440 ER - TY - CONF T1 - Sedimentology and age control of late Quaternary New Jersey shelf deposits T2 - AGU Fall 2003 Meeting Y1 - 2003 A1 - Alexander, C. A1 - Sommerfield, C. A1 - Austin J.A, Jr. A1 - Christensen, B. A1 - Fulthorpe, C. A1 - Goff, J. A1 - Gulick, S. A1 - Nordfjord, S. A1 - Nielson, D. A1 - Schock, S. JF - AGU Fall 2003 Meeting CY - San Francisco, CA N1 - id: 636 ER - TY - JOUR T1 - Soil-productivity relationships and organic matter turnover in dry tropical forests of the Florida Keys JF - Plant and Soil Y1 - 2003 A1 - Ross, M. S. A1 - Coultas, C. L. A1 - Hsieh, Y. P. AB - Soils and aboveground production in five types of upland forest in the Florida Keys were examined. Throughout the habitat gradient represented by these forest types, the soils were predominantly shallow and organic, forming in place directly on the limestone bedrock. However, the well-drained soils in the most productive broadleaved forests were deep enough to qualify as Histosols (Folists). Soils decreased in electrical conductivity and increased in nutrient content with increasing aboveground production. At 3-12 Mg ha(-1) yr(-1), production was within the range reported for dry tropical forests. Measured rates of decomposition were moderate or fast, and estimates of the organic C turnover of several soils based on their bomb radiocarbon signature were 100 years or less. In the face of these rapid turnover rates, we attribute the development of organic soils to the absence of mineral residues from weathering of the underlying limestone bedrock. Fast turnover of organic matter, and rapid and efficient cycling of nutrients are necessary to sustain the high production rates obtained on these shallow organic soils. VL - 253 IS - 2 N1 - 702ymTimes Cited:12Cited References Count:46 JO - Soil-productivity relationships and organic matter turnover in dry tropical forests of the Florida Keys ER - TY - JOUR T1 - Stratigraphic evolution of the late Holocene Ganges-Brahmaputra lower delta plain JF - Sedimentary Geology Y1 - 2003 A1 - Allison, M. A. A1 - Khan, S. R. A1 - Goodbred, S. L. A1 - Kuehl, S. A. KW - Ganges–Brahmaputra KW - Late Holocene KW - Stratigraphic evolution AB - Sediment cores from the Ganges-Brahmaputra delta in Bangladesh were examined for sedimentological character, clay mineralogy, elemental trends (C, N, S), and C-14 geochronology to develop a model for the sedimentary sequence resulting from lower delta plain progradation in the late Holocene. A widespread facies succession from Muddy Sand to Interbedded Mud records progradation of shoal-island complexes and the transition from subtidal to intertidal conditions. Mangrove-vegetated islands and peninsulas represent the final phase of progradation; a Mottled Mud that is deposited by penetration of turbid coastal water into the mangroves during high water events. Organic matter preservation is generally low ( < 1% TOC) in most of these well-drained deposits that are characterized by a permeable, silt-dominated granulometry. Clay mineralogy in the cores records the relative influence of smectite and kaolinite-rich Ganges sediments and illite and chlorite-rich Brahmaputra material. The lower delta plain west of the modem river mouths was deposited as a Ganges-dominated delta in three phases since 5000 cal years BP, with Brahmaputra influence confined to the Meghna estuary area and to the supratidal section of western delta deposits. Evolution of the lower delta plain in the late Holocene was influenced by regional subsidence patterns in the tectonically active Bengal Basin, which controlled distributary channel avulsion and migration, and the creation of accommodation space. (C) 2002 Elsevier Science B.V. All rights reserved. VL - 155 IS - 3-4 N1 - 642qaTimes Cited:92Cited References Count:84 JO - Stratigraphic evolution of the late Holocene Ganges-Brahmaputra lower delta plain ER - TY - JOUR T1 - Suitability of glycerin-preserved otoliths for age validation using bomb radiocarbon JF - Journal of Fish Biology Y1 - 2003 A1 - Campana, S. E. A1 - Stanley, R. D. A1 - Wischniowski, S. AB - The effect of glycerin storage on the bomb radiocarbon content of otoliths was determined experimentally. Storage in either pre- or post-bomb glycerin had no detectable effect on the bomb radiocarbon content of either pre- or post-bomb otoliths. Therefore bomb-dated age validation studies need not be restricted to freshly-collected samples or dry otoliths, implying that the large numbers of glycerin-archived otoliths around the world are suitable for age validation studies using bomb radiocarbon. (C) 2003 The Fisheries Society of the British Isles. VL - 63 IS - 4 N1 - 734gqTimes Cited:5Cited References Count:9 JO - Suitability of glycerin-preserved otoliths for age validation using bomb radiocarbon ER - TY - JOUR T1 - Tufts submarine fan: Turbidity-current gateway to Escanaba Trough JF - U. S. Geological Survey Bulletin 2216 Y1 - 2003 A1 - Reid, J. A. A1 - Normark, W. R. VL - Bulletin 2216 IS - Version 1.0 N1 - id: 418 ER - TY - JOUR T1 - Using radiocarbon to apportion sources of polycyclic aromatic hydrocarbons in household soot JF - Environmental Forensics Y1 - 2003 A1 - Reddy, C. M. A1 - Xu, L. A1 - O'Connor, R. AB - To determine whether polycyclic aromatic hydrocarbons (FAHs) in household soot were derived from the combustion of scrap wood or creosote that was impregnated in the wood (or some combination of both), the molecular composition and radiocarbon (C-14) content of the total carbon and several PAHs in the soot was investigated. The 5730-year half-life of C-14 makes it an ideal marker for identifying creosote-derived PAHs (C-14-free) versus those derived from the combustion of wood (contemporary C-14). The C-14 abundance of phenanthrene, fluoranthene, pyrene, and retene was determined by accelerator mass spectrometry after solvent extraction and purification by preparative capillary gas chromatography. The molecular analysis (presence of retene and 1,7-dimethylphenanthrene) and bulk C-14 content (contemporary) of the soot indicated that wood combustion was a strong source of carbon to the soot. The C-14 of retene in two soot samples was also contemporary, indicating that it was derived from the combustion of the scrap wood. These results are consistent with previous work that has suggested that retene is an excellent marker of wood combustion. However, the C-14 content of phenanthrene, fluoranthene, and pyrene in one soot sample was much lower and revealed that these compounds had a mixed creosote and wood source. Using an isotopic mass balance approach, we estimate that 40 to 70% of phenanthrene, fluoranthene, and pyrene were derived from the combustion of the scrap wood. The results of this study show that molecular marker and bulk C-14 analysis can be potentially misleading in apportioning sources of every PAH, and that molecular-level C-14 analysis of PAHs can be a powerful tool for environmental forensics. VL - 4 IS - 3 N1 - 731ytTimes Cited:16Cited References Count:42 JO - Using radiocarbon to apportion sources of polycyclic aromatic hydrocarbons in household soot ER - TY - JOUR T1 - Variations in the hydrological regime of Kara-Bogaz-Gol Gulf Lake Issyk-Kul, and the Aral Sea assessed based on data of bottom sediment studies JF - Water Resources Y1 - 2003 A1 - Ferronskii, V. I. A1 - Polyakov, V. A. A1 - Brezgunov, V. S. A1 - Vlasova, L. S. A1 - Karpychev, Yu A. A1 - Bobkov, A. F. A1 - Romaniovskii, V. V. A1 - Johnson, T. C. A1 - Ricketts, R. D. A1 - Rasmussen, K. A. VL - 30 N1 - id: 493 ER - TY - JOUR T1 - An 11,000 year lithostratigraphic and paleohydrologic record from equatorial Africa: Lake Edward, Uganda-Congo JF - Paleogeography, Paleoclimatology, Palaeoecology Y1 - 2002 A1 - Russell, J. M. A1 - Johnson, T. C. A1 - Kelts, K. R. A1 - Laerdal, T. A1 - Talbot, M. R. VL - 193 N1 - id: 1010 ER - TY - CONF T1 - The 14C AMS system at the University of Georgia T2 - International Conference on Accelerator Mass Spectrometry Y1 - 2002 A1 - Roberts, M. L. A1 - Culp, R. A. A1 - Dvoracek, D. K. A1 - Hodgins, G. W. L. A1 - Neary, M. P. A1 - Noakes, J. E. JF - International Conference on Accelerator Mass Spectrometry CY - Nagoya, Japan N1 - id: 1684 ER - TY - CHAP T1 - A 20,000-yr sedimentological record from Lake Malawi, East Africa: the Late-Pleistocene/Holocene transition in the southern tropics T2 - The East African Great Lakes: Limnology, Palaeoclimatology and Biodiversity Y1 - 2002 A1 - Barry, S. L. A1 - Filippi, M. L. A1 - Talbot, M. A1 - Johnson, T. C. ED - Odada, E. O. JF - The East African Great Lakes: Limnology, Palaeoclimatology and Biodiversity T3 - Advances in global change research PB - Kluwer Academic Publishers, Dordrecht SN - 6610618461 N1 - id: 1478 ER - TY - CHAP T1 - A 24,600 year diatom record from the northern basin of Lake Malawi T2 - The East African Great Lakes, Limnology, Palaeoclimatology and Biodiversity Y1 - 2002 A1 - Gasse, F. A1 - Barker, P. A1 - Johnson, T. C. ED - Odada, E. O. JF - The East African Great Lakes, Limnology, Palaeoclimatology and Biodiversity T3 - Advances in global change research PB - Kluwer Academic Publishers, Dordrecht SN - 6610618461 N1 - id: 1479 ER - TY - JOUR T1 - A 4000-Year Lacustrine Record of Environmental Change in the Southern Maya Lowlands, Petén, Guatemala JF - Quaternary Research Y1 - 2002 A1 - Rosenmeier, Michael F. A1 - Hodell, David A. A1 - Brenner, Mark A1 - Curtis, Jason H. A1 - Guilderson, Thomas P. AB - A 4000-yr sediment core record from Lake Salpetén, Guatemala, provides evidence for Maya-induced forest clearance and consequent soil erosion between ∼1700 cal yr B.C. and 850 cal yr A.D. Radiocarbon ages of wood, seeds, and charcoal support an age-depth model with average errors of ±110 cal yr. Relatively low carbonate δ18O values between 1300 and 400 cal yr B.C. coincide with pollen evidence for forest loss, consistent with increased surface and groundwater flow to the lake. Minimum δ18O values between 400 cal yr B.C. and 150 cal yr A.D. suggest a high lake level, as do 14C-dated aquatic gastropods as much as 7.5 m above the present lake stage. High lake levels resulted from reduced evaporation-to-precipitation ratios, increased hydrologic input caused by anthropogenic deforestation, or both. The Preclassic abandonment (150 A.D.) and Early Classic/Late Classic boundary (550 A.D.) are marked by relatively high δ18O values indicating reduced lake levels. Oxygen isotope composition increased further coincident with the Terminal Classic Maya demographic decline between 800 and 900 A.D. This period of high δ18O may have been caused by the greater aridity that has been documented in northern Yucatán lakes or by decreased hydrologic input to the lake as a consequence of forest recovery. Reduced soil erosion after 850 cal yr A.D. coincided with the Terminal Classic Maya demographic decline and permitted forest recovery and resumption of organic sedimentation. VL - 57 IS - 2 N1 - id: 2106 JO - A 4000-Year Lacustrine Record of Environmental Change in the Southern Maya Lowlands, Petén, Guatemala ER - TY - JOUR T1 - A 6100 14C year record of El Nino activity from the Galapagos Islands JF - Journal of Paleolimnology Y1 - 2002 A1 - Riedinger, M. A. A1 - Steinitz-Kannan, M. A1 - Last, W. M. A1 - Brenner, M. VL - 27 N1 - id: 1485 ER - TY - JOUR T1 - Abundant brachiopods on a tropical, upwelling-influenced shelf (Southeast Brazilian Bight, South Atlantic JF - Palaios Y1 - 2002 A1 - Kowalewski, M. A1 - Simeos, M. G. A1 - Carroll, M. A1 - Rodland, D. L. AB - Rhynchonelliform brachiopods were diverse and often dominant benthos of tropical seas in the Paleozoic. In contrast, they are believed to be rare in open habitats of modern oceans, especially at low latitudes. This study documents numerous occurrences of rhynchonelliform brachiopods on a modern tropical shelf, particularly in areas influenced by upwelling. Extensive sampling of the outer shelf and coastal bays of the Southeast Brazilian Bight revealed dense populations of terebratulid brachiopods (>103 individuals / m2 of seafloor) between 24° and 26°S. On the outer shelf, brachiopods are more abundant than bivalves and gastropods combined. However, brachiopod diversity is low: only four species belonging to the genera Bouchardia, Terebratulina, Argyrotheca, and Platidia were identified among over 16000 examined specimens. Brachiopods occur preferentially on carbonate bottoms and include two substrate-related associations: Bouchardia (40–70% CaCO3 weight content) and Terebratulina-Argyrotheca (70–95% CaCO3). All four species display a broad bathymetric range that contrasts with a narrow depth tolerance postulated for many Paleozoic rhynchonelliforms. The most abundant populations occur in the depth range between 100 and 200 m, and coincide with zones of shelf-break upwelling, where relatively colder and nutrient-rich water masses of the South Atlantic Central Water are brought upward by cyclonic meanders of the South Brazil Current (a western boundary current that flows poleward along the coast of Brazil). This is consistent with previous biological and paleontological studies that suggest upwelling may play a role in sustaining brachiopod-dominated benthic associations. The presence of abundant brachiopods in the open habitats of the tropical shelf of the western South Atlantic contrasts with current understanding of their latitudinal distribution and points to major gaps in our knowledge of their present-day biogeography. The ecological importance of rhynchonelliform brachiopods in modern oceans and their role as producers of biogenic sedimentary particles may be underestimated. VL - 17 IS - 3 N1 - id: 1416 JO - Abundant brachiopods on a tropical, upwelling-influenced shelf (Southeast Brazilian Bight, South Atlantic ER - TY - RPRT T1 - Akata Site (32SN121) 1996 Archeological Excavations. Anthropology Research, Department of Anthropology, University of North Dakota, Grand Forks (Report) Y1 - 2002 A1 - Toom, Dennis L. PB - Dakotas Area Office, U. S. Bureau of Reclamation CY - Bismarck, ND VL - in prep N1 - id: 1362 ER - TY - JOUR T1 - The andesite aqueduct: prespectives on the evolution of intermediate magmatism in west-central (105-99 degrees W) Mexico JF - Contributions to Mineralogy and Petrology Y1 - 2002 A1 - Carmichael, I. S. E. VL - 143 N1 - id: 1588 ER - TY - JOUR T1 - The Antarctic ice sheet during the last glacial maximum and its subsequent retreat histroy: a review JF - Quaternary Science Reviews Y1 - 2002 A1 - Anderson, J. B. A1 - Shipp, S. S. A1 - Lowe, A. L. A1 - Wellner, J. S. A1 - Mosola, A. AB - An emerging body of evidence from studies of the last glacial/interglacial cycle suggests that the East and West Antarctic ice sheets have not advanced and retreated in concert. The West Antarctic ice sheet advanced to the outer shelf in most regions during the Last Glacial Maximum (LGM). The retreat from the shelf commenced shortly after the LGM and continued into the late Holocene. The West Antarctic Ice Sheet in Ross and Amundsen seas slid across a deforming bed, at least during the final phases of extended glaciation. This implies that at this time the ice sheet had a low profile. Differences in the number and locations of grounding-zone wedges and smaller grounding zone features from trough to trough imply that individual West Antarctic Ice Sheet ice streams retreated episodically. Details concerning the expansion, retreat, and behavior of the East Antarctic Ice Sheet (EAIS) are more sparse. The picture emerging is that the EAIS did not expand to the continental shelf edge during the LGM; rather, it achieved a maximum extent of a mid-shelf position in some locations, while in other areas the ice terminus was situated near its present location. The timing of retreat along sectors within the EAIS appears diachronous, and in places occurred prior to the LGM. The Antarctic Peninsula shelf contained considerably more ice during the LGM than previously proposed. The results presented in this paper support more recent published ice-sheet models that call for greater contributions of melting ice from West Antarctica, including the Antarctic Peninsula, to the post-glacial rise in sea level. VL - 21 IS - 1-3 N1 - id: 1126 JO - The Antarctic ice sheet during the last glacial maximum and its subsequent retreat histroy: a review ER - TY - JOUR T1 - On the antiquity of the single-piece shell fishhook: AMS radiocarbon evidence from the southern California coast JF - Journal of Archaeological Sciences Y1 - 2002 A1 - Rick, T. C. A1 - Vellanoweth, R. L. A1 - Erlandson, J. M. A1 - Kennett, D. J. VL - 29 N1 - id: 1024 ER - TY - CONF T1 - Assessing the linkages among climate variability, land-use change, and the sedimentary regime of the Upper Chesapeak Bay T2 - Proceedings Coastal Environment 2002 Y1 - 2002 A1 - Barros, A. P. A1 - Gordon, S. J. JF - Proceedings Coastal Environment 2002 PB - WIT Press N1 - id: 1218 ER - TY - CONF T1 - Benthic foraminifera in Long Island Sound as indicators of eutrophication T2 - GSA Annual meeting Y1 - 2002 A1 - Abramson, I. A1 - Thomas, E. A1 - Varekamp, J. C. A1 - Buchholtz ten Brink, M. R. JF - GSA Annual meeting CY - Denver, CO N1 - id: 731 ER - TY - CHAP T1 - Biogenic silica profiles in the sediments of large tropical lakes: examples from East Africa T2 - Sedimentation in Continental Rifts Y1 - 2002 A1 - Johnson, T. C. ED - Renaut, R. W. JF - Sedimentation in Continental Rifts PB - Spec. Publ. Society Economic Paleontologists and Mineralogists N1 - id: 343 ER - TY - JOUR T1 - Birth of the modern Chesapeake Bay estuary between 7.4 and 8.2 ka and implications for global sea-level rise JF - Geo-Marine Letters Y1 - 2002 A1 - Bratton, John F. A1 - Colman, Steven M. A1 - Thieler, E. Robert A1 - Seal, Robert R. AB - Two major pulses of sea-level rise are thought to have taken place since the last glacial maximum — meltwater pulses (mwp) 1A (12 cal ka) and 1B (9.5 cal ka). Between mwp 1B and about 6 cal ka, many of the complex coastal ecosystems which ring the world’s oceans began to form. Here we report data for rhenium, carbon isotopes, total organic carbon, and fossil oysters from Chesapeake Bay which span the transition from fresh to brackish water conditions in the bay in the mid-Holocene. These data constrain sea-level change and resulting environmental change in the bay. They indicate that the transition was rapid, and that it was produced by (1) a third pulse of rapid eustatic sea-level rise, or (2) a geometry of the prehistoric Chesapeake Bay basin which predisposed it to a nonlinear response to a steadily rising sea level. Similar nonlinear changes in vulnerable coastal environments are likely to take place in the future due to polar warming, regardless of the timing or rate of sea-level rise. VL - 22 IS - 4 N1 - id: 540 JO - Birth of the modern Chesapeake Bay estuary 7,400 to 8,200 years ago and implications for global sea-level rise ER - TY - JOUR T1 - Blackwood Creek Stream restoration project design draft report JF - U.S. Forest Service Lake Tahoe Basin Management Unit, South Lake Tahoe, CA Y1 - 2002 A1 - Beck, Nicole A1 - Hydrology, Swanson N1 - id: 350 ER - TY - RPRT T1 - Blackwood Creek Strem restoration project design draft report Y1 - 2002 A1 - Beck, N. A1 - Hydrology, S. ED - Unit, U. S. Forest Service Lake Tahoe Basin Management CY - South Lake, Tahoe, CA N1 - id: 1140 ER - TY - JOUR T1 - Bomb dating and age determination of large pelagic sharks JF - Canadian Journal of Fisheries and Aquatic Sciences Y1 - 2002 A1 - Campana, S. E. A1 - Natanson, L. J. A1 - Myklevoll, S. AB - Despite their notoriety and role as apex predators, the longevity of large pelagic sharks such as the porbeagle (Lamna nasus) and shortfin mako (Isurus oxyrinchus) is unknown. Vertebral growth bands provide an accurate indicator of age in young porbeagle, but age validation has never been reported for any large shark species past the age of sexual maturity. Here, we report the first application of bomb radiocarbon as an age validation method for long-lived sharks based on date-specific incorporation of radiocarbon into vertebral growth bands. Our results indicate that porbeagle vertebrae recorded and preserved a bomb radiocarbon pulse in growth bands formed during the 1960s. Through comparison of radiocarbon assays in young, known-age porbeagle collected in the 1960s with the corresponding growth bands in old porbeagle collected later, we confirm the validity of porbeagle vertebral growth band counts as accurate annual age indicators to an age of at least 26 years. The radiocarbon signatures of porbeagle vertebral growth bands appear to be temporally and metabolically stable and derived mainly from the radiocarbon content of their prey. Preliminary radiocarbon assays of shortfin mako vertebrae suggest that current methods for determining shortfin mako age are incorrect. VL - 59 IS - 3 N1 - 548ceTimes Cited:98Cited References Count:16 JO - Bomb dating and age determination of large pelagic sharks ER - TY - CONF T1 - Bomb radiocarbon and anthropogenic CO2 in ocean biogeochemical models T2 - AGU/ASLO Conference Y1 - 2002 A1 - Matsumoto, K. A1 - Sarmiento, J. A1 - Key, R. A1 - Slater, C. A1 - Sabine, C. JF - AGU/ASLO Conference CY - Honolulu, HI N1 - id: 320 ER - TY - JOUR T1 - A Budget of Carbonate and Terrigenous Sediments, Hanalei Bay, Kauai, Hawaiian Islands JF - Marine Geology Y1 - 2002 A1 - Calhoun, R. S. A1 - Fletcher, C. H. A1 - Harney, J. N. AB - The sediment budget of Hanalei Bay on the north shore of Kauai was calculated using sedimentological and geophysical methods. The calculations of the budget subsequently allowed an interpretation of the Holocene history of the bay. The bay sediments are easily separated into marine (carbonate) and terrigenous (siliciclastic) grains. Surficial sediments are dominated by carbonate grains (∼70%) of coralline algae, coral, and mollusc fragments as well as foraminifera, Halimeda, bryozoa, and echinoderm tests. However, siliciclastic grains (e.g. olivine, plagioclase, volcanic lithics) from the Hanalei River watershed draining shield volcanic highlands are the most common individual grain type (∼27%) and form a zone of high concentration from the mouth of the Hanalei River into the center of the bay. Flooding in the bay by the post-glacial sea-level rise began soon after 11.7 kyears. The resulting marine environment caused the net deposition of 45.5±1.5×106 m3 of sediment in the bay and approximately 33.7±11.2×106 m3 of sediment on the Hanalei coastal plain. The total volume of carbonate sediment stored in the bay and coastal plain is greater than the volume likely to have been produced exclusively within the bay during the same time. Calculations indicate that approximately 2490 m3 year−1 have been imported into the bay or coastal plain and deposited since 11,700 years ago. The majority of this sediment influx is likely delivered from the east by the strong tradewind-driven littoral currents that characterize Kauai's north shore. Net carbonate sediment deposition in Hanalei Bay peaked at a rate of 15,500 m3 year−1 between 5000 and 3000 years ago (when sea level may have been 2 m above present) diminishing to 3890 m3 year−1 from 1000 years ago to the present. This influx is likely to have played a significant role in the mid to late Holocene progradation of the Hanalei shoreline. N1 - id: 105 JO - A Budget of Carbonate and Terrigenous Sediments, Hanalei Bay, Kauai, Hawaiian Islands ER - TY - CHAP T1 - Carbon isotopic composition of DOM T2 - Biogeochemistry of Marine Dissolved Organic Matter Y1 - 2002 A1 - Bauer, J. E. ED - Hansell, D. A. JF - Biogeochemistry of Marine Dissolved Organic Matter PB - Elsevier Science Publishers N1 - id: 687 ER - TY - JOUR T1 - Challenges in radiocarbon dating organic carbon in opal-rich marine sediments JF - Radiocarbon Y1 - 2002 A1 - Zheng, Y. A1 - Anderson, R. F. A1 - Froelich, P. N. A1 - Beck, W. A1 - McNichol, A. P. A1 - Guilderson, T. AB - We explored the reliability of radiocarbon ages obtained on organic carbon phases in opal-rich Southern Ocean sediments. Paired biogenic carbonate and total organic carbon (TOC) C-14 analyses for three Southern Ocean cores showed that the TOC ages were systematically younger than the carbonate ages. Carbonate ages were consistent with oxygen isotopic and bio-stratigraphy, indicating error in TOC ages that could be explained by 5-24% of modern carbon contamination of TOC samples. Two possible sources of contamination are: 1) adsorption of atmospheric CO2 or volatile organic compounds to reactive opal surface sites, and 2) fixation of atmospheric CO2 by chemosynthetic bacteria during core storage. In an effort to reduce the modem carbon contamination, diatoms were separated from sediments, purified, and pre-oxidized by concentrated nitric and perchloric acids to permit dating of opal-intrinsic organic carbon (similar to0.1-0.3% by weight). C-14 ages of chemically pre-oxidized opal showed a significant amount of modem carbon contamination, from 11 to 32%, indicating adsorption from the atmosphere of modem carbon onto opal surfaces that were previously cleaned by acid oxidation. Several experiments designed to eliminate the modern C contamination were attempted, but so far we have not been able to obtain a radiocarbon age on C-14-dead Southern Ocean opal-rich sediments, either bulk TOC or purified diatom opal samples, as old as our procedural blank. VL - 44 UR - https://journals.uair.arizona.edu/index.php/radiocarbon/article/view/4084/3509 IS - 1 N1 - 591keTimes Cited:13Cited References Count:28 JO - Challenges in radiocarbon dating organic carbon in opal-rich marine sediments ER - TY - JOUR T1 - Changes in the 13C/12C of dissolved inorganic carbon in the ocean as a tracer of anthropogenic CO2 uptake JF - Global Biogeochemical Cycles Y1 - 2002 A1 - Quay, P. D. A1 - Sonnerup, R. A1 - Westby, T. A1 - Stutsman, J. A1 - McNichol, A. P. VL - 17 IS - 1 N1 - id: 1715 ER - TY - JOUR T1 - Chemical and carbon isotopic evidence for the source and fate of dissolved organic matter in the northern Everglades JF - Biogeochemistry Y1 - 2002 A1 - Wang, Y. A1 - Hsieh, Y. P. A1 - Landing, W. M. A1 - Choi, Y. H. A1 - Salters, V. A1 - Campbell, D. VL - 61 N1 - id: 616 JO - Chemical and carbon isotopic evidence for the source and fate of dissolved organic matter in the northern Everglades ER - TY - JOUR T1 - Chemical composition and cycling of dissolved organic matter in the Mid-Atlantic Bight JF - Deep-Sea Research Part Ii-Topical Studies in Oceanography Y1 - 2002 A1 - Aluwihare, L. I. A1 - Repeta, D. J. A1 - Chen, R. F. AB - This study focuses on the chemical characterization of high molecular-weight dissolved organic matter (HMW DOM) isolated from the Middle Atlantic Bight in April 1994 and March 1996. Using proton nuclear magnetic resonance spectroscopy ((HNMR)-H-1) and monosaccharide analysis we compared both spatial and temporal variations in the chemical structure of HMW DOM across this region. Our analyses support the presence of at least two compositionally distinct components to HMW DOM. The major component is acyl polysaccharide (APS), a biopolymer rich in carbohydrates, acetate and lipid, accounting for between 50% and 80% of the total high molecular-weight dissolved organic carbon (HMW DOC) in surface samples. APS is most abundant in fully marine, surface-water samples, and is a product of autochthonous production. Organic matter with spectral properties characteristic of humic substances is the second major component of HMW DOM. Humic substances are most abundant (up to 49% of the total carbon) in samples collected from estuaries, near the coast, and in deep water, suggesting both marine and perhaps terrestrial sources. Radiocarbon analyses of neutral monosaccharides released by the hydrolysis of APS have similar and modern (average 71parts per thousand) Delta(14)C values. Radiocarbon data support our suggestion that these sugars occur as part of a common macromolecule, with an origin via recent biosynthesis. Preliminary radiocarbon data for total neutral monosaccharides isolated from APS at 300 and 750m show this fraction to be substantially enriched relative to total HMW DOC and DOC. The relatively enriched radiocarbon values of APS at depth suggest APS is rapidly transported into the deep ocean. (C) 2002 Elsevier Science Ltd. All rights reserved. VL - 49 IS - 20 N1 - 607kxTimes Cited:74Cited References Count:44 JO - Chemical composition and cycling of dissolved organic matter in the Mid-Atlantic Bight ER - TY - JOUR T1 - Chemostratigraphy of Paleoproterozoic carbonate successions of the Wyoming Craton: tectonic forcing of biogeochemical change? JF - Precambrian Research Y1 - 2002 A1 - Bekker, A. A1 - Karhu, J. A. A1 - Eriksson, A. A1 - Kaufman, A. J. KW - Biogeochemistry KW - Chemostratigraphy KW - Kenorland KW - Paleoproterozoic KW - Wyoming AB - The Archean Wyoming Craton is flanked on the south and east by belts of Paleoproterozoic supracrustal successions whose correlation is complicated by lack of geochronologic constraints and continuous outcrop. However, carbonate units in these successions may be correlated by integrating carbon isotope stratigraphy with lithostratigraphy. The ∼10 km thick Paleoproterozoic Snowy Pass Supergroup in the Medicine Bow Mountains was deposited on the present-day southern flank of the Wyoming Craton; it contains three discrete levels of glacial diamictite correlative with those in the Huronian Supergroup, on the southern margin of the Superior Craton. The Nash Fork Formation of the upper Snowy Pass Supergroup is significantly younger than the uppermost diamictite and was deposited after the end of the Paleoproterozoic glacial epoch. Carbonates at the base of the Nash Fork Formation record remarkable 13C-enrichment, up to +28‰ (V-PDB), whereas those from overlying members of the lower Nash Fork Formation have δ13C values between +6 and +8‰. Carbonates from the upper Nash Fork Formation above the carbonaceous shale have carbon isotope values ranging between 0 and +2.5‰. The transition from high carbon isotope values to those near 0‰ in the Nash Fork Formation is similar to that at the end of the ca. 2.2–2.1 Ga carbon isotope excursion in Fennoscandia. This chemostratigraphic trend and deposition of BIFs, Mn-rich lithologies, carbonaceous shales and phosphorites at the end of the global ca. 2.2–2.1 Ga carbon isotope excursion are likely related to ocean overturn associated with the final breakup of the Kenorland supercontinent. Correlative carbonates from the Slaughterhouse Formation in the Sierra Madre, WY, and from the Whalen Group in the Rawhide Creek area in the Hartville Uplift, WY, have highly positive carbon isotope values. In contrast, carbonates from other exposures of the Whalen Group in the Hartville Uplift and all carbonate units in the Black Hills, SD, have carbon isotope values close to 0‰. Combined with existing geochronologic and stratigraphic constraints, these data suggest that the Slaughterhouse Formation and the succession exposed in the Rawhide Creek area of the Hartville Uplift are correlative with the lower and middle Nash Fork Formation and were deposited during the ca. 2.2–2.1 Ga carbon isotope excursion. The Estes and Roberts Draw formations in the Black Hills and carbonates from other exposures in the Hartville Uplift postdate the ca. 2.2–2.1 Ga positive carbon isotope excursion and are most likely correlative with the upper Nash Fork Formation. The passive margin, on which the carbonates with highly positive carbon isotope values were deposited, extended around the southern flank of the Wyoming Craton through the Sierra Madre, Medicine Bow Mountains and Hartville Uplift. The presence of carbonates with carbon isotope values close to 0‰ in the upper Nash Fork Formation and the Whalen Group indicates that the passive margin persisted on the southern flank of the Wyoming Craton after the carbon isotope excursion. Rifting in the Black Hills, likely related to the final breakup of the Kenorland, succeeded the carbon isotope excursion, since the Estes and Roberts Draw formations, deposited during rifting and ocean opening on the eastern flank of the Wyoming Craton, postdate the carbon isotope excursion. VL - 120 IS - 3-4 N1 - id: 1586 JO - Chemostratigraphy of Paleoproterozoic carbonate successions of the Wyoming Craton: tectonic forcing of biogeochemical change? ER - TY - JOUR T1 - Composition, age, provenance of organic matter in N. W. African dust over the Atlantic Ocean JF - Geochemistry, Geophysics, Geosystems G3 Y1 - 2002 A1 - Eglinton, T. I. A1 - Eglinton, G. A1 - Dupont, L. A1 - Montlucon, D. A1 - Sholkovitz, E. A1 - Reddy, C. M. VL - 3 IS - 8 N1 - id: 611 ER - TY - JOUR T1 - Compositional characterization of prehistoric ceramics: A new approach JF - Journal of Archaeological Sciences Y1 - 2002 A1 - Kennett, D. J. A1 - Sakai, S. A1 - Neff, H. A1 - Gossett, R. A1 - Larson, D. O. VL - 29 N1 - id: 474 ER - TY - JOUR T1 - Converting AMS data to radiocarbon values: considerations and conventions JF - Radiocarbon Y1 - 2002 A1 - McNichol, A. P. A1 - Jull, A. J. T. A1 - Burr, G. S. VL - 43 IS - 2A N1 - id: 1818 ER - TY - JOUR T1 - A Critical Evaluation of Interlaboratory Data on Total, Elemental, and Isotopic Carbon in the Carbonaceous Particle Reference Material, NIST SRM 1649a JF - J Res Natl Inst Stand Technol Y1 - 2002 A1 - Currie, L. A. A1 - Benner, B. A., Jr. A1 - Kessler, J. D. A1 - Klinedinst, D. B. A1 - Klouda, G. A. A1 - Marolf, J. V. A1 - Slater, J. F. A1 - Wise, S. A. A1 - Cachier, H. A1 - Cary, R. A1 - Chow, J. C. A1 - Watson, J. A1 - Druffel, E. R. A1 - Masiello, C. A. A1 - Eglinton, T. I. A1 - Pearson, A. A1 - Reddy, C. M. A1 - Gustafsson, O. A1 - Quinn, J. G. A1 - Hartmann, P. C. A1 - Hedges, J. I. A1 - Prentice, K. M. A1 - Kirchstetter, T. W. A1 - Novakow, T. A1 - Puxbaum, H. A1 - Schmid, H. AB - Because of increased interest in the marine and atmospheric sciences in elemental carbon (EC), or black carbon (BC) or soot carbon (SC), and because of the difficulties in analyzing or even defining this pervasive component of particulate carbon, it has become quite important to have appropriate reference materials for intercomparison and quality control. The NIST "urban dust" Standard Reference Material((R)) SRM 1649a is useful in this respect, in part because it comprises a considerable array of inorganic and organic species, and because it exhibits a large degree of ((14)C) isotopic heterogeneity, with biomass carbon source contributions ranging from about 2 % (essentially fossil aliphatic fraction) to about 32 % (polar fraction). A primary purpose of this report is to provide documentation for the new isotopic and chemical particulate carbon data for the most recent (31 Jan. 2001) SRM 1649a Certificate of Analysis. Supporting this is a critical review of underlying international intercomparison data and methodologies, provided by 18 teams of analytical experts from 11 institutions. Key results of the intercomparison are: (1) a new, Certified Value for total carbon (TC) in SRM 1649a; (2) (14)C Reference Values for total carbon and a number of organic species, including for the first time 8 individual PAHs; and (3) elemental carbon (EC) Information Values derived from 13 analytical methods applied to this component. Results for elemental carbon, which comprised a special focus of the intercomparison, were quite diverse, reflecting the confounding of methodological-matrix artifacts, and methods that tended to probe more or less refractory regions of this universal, but ill-defined product of incomplete combustion. Availability of both chemical and (14)C speciation data for SRM 1649a holds great promise for improved analytical insight through comparative analysis (e.g., fossil/biomass partition in EC compared to PAH), and through application of the principle of isotopic mass balance. VL - 107 IS - 3 N1 - Currie, L ABenner, B A JrKessler, J DKlinedinst, D BKlouda, G AMarolf, J VSlater, J FWise, S ACachier, HCary, RChow, J CWatson, JDruffel, E R MMasiello, C AEglinton, T IPearson, AReddy, C MGustafsson, OQuinn, J GHartmann, P CHedges, J IPrentice, K MKirchstetter, T WNovakow, TPuxbaum, HSchmid, Heng2002/01/01 00:00J Res Natl Inst Stand Technol. 2002 Jun 1;107(3):279-98. doi: 10.6028/jres.107.022. Print 2002 May-Jun. U2 - PMC4861351 JO - A Critical Evaluation of Interlaboratory Data on Total, Elemental, and Isotopic Carbon in the Carbonaceous Particle Reference Material, NIST SRM 1649a ER - TY - CHAP T1 - Data report: Australian Bight T2 - Proc. ODP, Sci. Results Y1 - 2002 A1 - Hine, A. C. A1 - Brooks, G. R. A1 - Mallinson, D. A1 - Brunner, C. A. A1 - James, N. P. A1 - Feary, D. A. A1 - Holbourn, A. E. A1 - Drexler, T. M. A1 - Howd, P. ED - Hine, A. C. JF - Proc. ODP, Sci. Results VL - 182 N1 - id: 271 ER - TY - JOUR T1 - Differences in 14C age between stratigraphically associated charcoal and marine shell from the archaic period site of kilometer 4, southern Peru: old wood or old water? JF - Radiocarbon Y1 - 2002 A1 - Kennett, D. J. A1 - Ingram, B. L. A1 - Southon, J. R. A1 - Wise, K. VL - 44 IS - 1 N1 - id: 1023 ER - TY - CONF T1 - The distribution and inventory of bomb produced radiocarbon in the Pacific Ocean T2 - AGU/ASLO Conference Y1 - 2002 A1 - Key, R. M. JF - AGU/ASLO Conference CY - Honolulu, HI N1 - id: 1448 ER - TY - JOUR T1 - Drowned reefs and antecedent karst topography, Au'au Channel, S. E. Hawaiian Island JF - EOS Y1 - 2002 A1 - Grigg, R. W. A1 - Grossman, E. E. A1 - al, et VL - 83 IS - 4 N1 - id: 662 ER - TY - THES T1 - The dynamics of pore water dissolved organic carbon and the fate of organic matter in anoxic marine sediments: As assessment using carbon isotopes and ultrafiltration. PhD thesis Y1 - 2002 A1 - Seagle, Carol A. PB - University of North Carolina at Chapel Hill CY - Chapel Hill, North Carolina VL - PhD ER - TY - JOUR T1 - El Nino-like pattern in Ice Age Tropical Pacific Sea surace temperature JF - Science Y1 - 2002 A1 - Koutavas, Athanasios A1 - Lynch-Stieglitz, Jean A1 - Marchitto, Thomas M. A1 - Sachs, Julian P. AB - Sea surface temperatures (SSTs) in the cold tongue of the eastern equatorial Pacific exert powerful controls on global atmospheric circulation patterns. We examined climate variability in this region from the Last Glacial Maximum (LGM) to the present, using a SST record reconstructed from magnesium/calcium ratios in foraminifera from sea-floor sediments near the Galápagos Islands. Cold-tongue SST varied coherently with precession-induced changes in seasonality during the past 30,000 years. Observed LGM cooling of just 1.2°C implies a relaxation of tropical temperature gradients, weakened Hadley and Walker circulation, southward shift of the Intertropical Convergence Zone, and a persistent El Niño–like pattern in the tropical Pacific. This is contrasted with mid-Holocene cooling suggestive of a La Niña–like pattern with enhanced SST gradients and strengthened trade winds. Our results support a potent role for altered tropical Pacific SST gradients in global climate variations. VL - 297 IS - 5579 N1 - id: 644 JO - El Nino-like pattern in Ice Age Tropical Pacific Sea surace temperature ER - TY - CONF T1 - ENSO mid-Holocene onset: constraints from an open ocean record in the eastern equatorial Pacific T2 - AGU Y1 - 2002 A1 - Richaud, M. A1 - Loubere, P. JF - AGU N1 - id: 352 ER - TY - JOUR T1 - Eolian processes, ground cover, and the archaeology of coastal dunes: a taphonomic case study from San Miguel Island, California, U.S.A JF - Geoarchaeology Y1 - 2002 A1 - Rick, Torben C. VL - 17 IS - 8 N1 - id: 1089 ER - TY - CONF T1 - Eutrophication of Long Island Sound as traced by benthic foraminifera T2 - Long Island Sound/NEERS Research Conference Y1 - 2002 A1 - Thomas, E. A1 - Abramson, I. A1 - Varekamp, J. C. A1 - Buchholtz ten Brink, M. R. JF - Long Island Sound/NEERS Research Conference CY - Groton, CT N1 - id: 727 ER - TY - JOUR T1 - Field and laboratory data from an earthquake history study of the Toe Jam Hill fault, Bainbridge Island, Washington JF - U.S. Geological Survey Open-File Report Y1 - 2002 A1 - Nelson, A. R. A1 - Johnson, S. Y. A1 - Wells, R. E. A1 - Kelsey, H. M. A1 - Pezzopane, S. K. A1 - Sherrod, B. L. A1 - Bradley, L. A. A1 - Iii, Koehler R. D. A1 - Bucknam, R. C. A1 - Haugerud, R. A. A1 - LaPrade, W. T. VL - 02-60 N1 - id: 428 ER - TY - JOUR T1 - Field and Laboratory data from an earthquake history study of the Toe Jam Hill fault, Bainbridge Island, Washington JF - U.S. Geological Survey Open-File Report 02-60 Y1 - 2002 A1 - Nelson, A. R. A1 - Johnson, S. Y. A1 - Wells, R. E. A1 - Pezzopane, S. K. A1 - Kelsey, H. M. A1 - Sherrod, B. L. A1 - Bradley, L. A. A1 - Koehler, R. D., III A1 - Bucknam, R. C. A1 - Haugerud, R. A. A1 - LaPrade, W. T. N1 - id: 259 ER - TY - CHAP T1 - Foragers of the Congo: the early settlement of the Ituri forest T2 - Under the Canopy: The Archaeology of Tropical Rain Forests Y1 - 2002 A1 - Mercader, J. ED - Mercader, J. JF - Under the Canopy: The Archaeology of Tropical Rain Forests PB - Rutgers University Press CY - New Brunswick N1 - id: 1197 ER - TY - CONF T1 - Fossil sources of PM2.5 aerosol carbon based on 14C measurements T2 - PM2.5 and electric power generation: recent findings and implications Y1 - 2002 A1 - Tanner, R. L. A1 - Parkhurst, W. J. A1 - McNichol, A. P. JF - PM2.5 and electric power generation: recent findings and implications CY - Pittsburgh, PA N1 - id: 353 ER - TY - JOUR T1 - A high-resolution paleoclimate record spanning the past 25,000 years in southern East Africa JF - Science Y1 - 2002 A1 - Johnson, T. C. A1 - Brown, E. T. A1 - McManus, J. A1 - Barry, S. A1 - Barker, P. A1 - Gasse, F. AB - High-resolution profiles of the mass accumulation rate of biogenic silica and other geochemical proxies in two piston cores from northern Lake Malawi provide a climate signal for this part of tropical Africa spanning the past 25,000 years. The biogenic silica mass accumulation rate was low during the relatively dry late Pleistocene, when the river flux of silica to the lake was suppressed. Millennial-scale fluctuations, due to upwelling intensity, in the late Pleistocene climate of the Lake Malawi basin appear to have been closely linked to the Northern Hemisphere climate until 11 thousand years ago. Relatively cold conditions in the Northern Hemisphere coincided with more frequent north winds over the Malawi basin, perhaps resulting from a more southward migration of the Intertropical Convergence Zone. VL - 296 IS - 5565 N1 - Johnson, Thomas CBrown, Erik TMcManus, JamesBarry, SylviaBarker, PhilipGasse, FrancoisengResearch Support, U.S. Gov't, Non-P.H.S.2002/04/06 10:00Science. 2002 Apr 5;296(5565):113-32. JO - A high-resolution paleoclimate record spanning the past 25,000 years in southern East Africa ER - TY - CONF T1 - The historical record of water quality in Long Island Sound T2 - Long Island Sound workshop Y1 - 2002 A1 - Varekamp, J. C. A1 - Thomas, E. A1 - Mecray, E. L. A1 - Buchholtz ten Brink, M. F. JF - Long Island Sound workshop PB - Batelle Laboratories CY - Groton, CT N1 - id: 726 ER - TY - JOUR T1 - Holocene chronology of a continental shelf mudbelt off southwestern Africa JF - The Holocene Y1 - 2002 A1 - Meadows, M. E. A1 - Rogers, J. A1 - Lee-Throp, J. A. A1 - Bateman, M. D. A1 - Dingle, R. V. AB - The Holocene lithostratigraphy and geochronology of sediments on an inner continental-shelf mudbelt off the west coast of southern Africa is presented. Based on a study of seven large gravity cores, numerous grab samples and two vibracores, two distinctive sections of the mudbelt have been identi” ed. The northern section is associated with the Orange River prodelta, and is dominated by laminated clay-rich sediments, while the southern section off Namaqualand is associated with more homogeneous muds. AMS radiocarbon ages of 31 samples from these cores are problematic due to the absence of expected modern material at the sedimentocean interface and numerous age reversals and inconsistencies in some of the cores. Possible mechanisms to explain the apparently anomalously old surface and near-surface samples are suggested. Most likely expla nations appear to lie in a combination of sediment-retrieval problems, the periodic loss of ” ne particulate organic carbon from within the water column, the sampling of possible relic sediments and, most likely of all, the incorporation into the sediments of 14C-depleted terrigenous organic matter. The age reversals are especially evident in the laminated sediments, and the entrainment of ‘old’ carbon from the terrestrial source of these sediments is offered as the most parsimonious explanation. Stable carbon isotope analyses and a single lumi nescence age support the contention that radiocarbon date inconsistencies are a consequence of terrestrial inputs of carbon which is non-contemporaneous with the actual time of sedimentation. In studies of offshore accumulations of terrigenous material, the marine-derived organic fraction may therefore prove a more reliable measure of radiocarbon chronology. N1 - id: 220 JO - Holocene chronology of a continental shelf mudbelt off southwestern Africa ER - TY - CHAP T1 - Holocene moisture changes and fire frequency at Rio Rubens Bog, Southern Patagonia T2 - Fire History Y1 - 2002 A1 - Huber, U. M. A1 - Markgraf, V. ED - Swetnam, T. T. JF - Fire History PB - Academic Press N1 - id: 233 ER - TY - THES T1 - Implications of environmental change for energy flow through natural systems: Freshwater wetlands and coastal zones Y1 - 2002 A1 - Chasar, L. PB - Florida State University VL - PhD ER - TY - JOUR T1 - In situ calcium carbonate dissolution in the Pacific Ocean JF - Global Biogeochemical Cycles Y1 - 2002 A1 - Feely, R. A. A1 - Sabine, C. L. A1 - Lee, K. A1 - Millero, F. J. A1 - Lamb, M. F. A1 - Greeley, D. A1 - Bullister, J. L. A1 - Key, R. M. A1 - Peng, T. H. A1 - Kozyr, A. A1 - Ono, T. A1 - Wong, C. S. KW - anthropogenic co(2) KW - anthropogenic co2 KW - aragonite saturation KW - atmospheric carbon KW - caco(3) dissolution KW - calcite saturation KW - carbonate lysocline KW - chemical lysocline KW - coccolithophore emiliania-huxleyi KW - indian-ocean KW - north pacific KW - organic-matter KW - Pacific Ocean KW - panama basin KW - particulate matter AB - Over the past several years researchers have been working to synthesize the WOCE/JGOFS global CO(2) survey data to better understand carbon cycling processes in the oceans. The Pacific Ocean data set has over 35,000 sample locations with at least two carbon parameters, oxygen, nutrients, CFC tracers, and hydrographic parameters. In this paper we estimate the in situ CaCO(3) dissolution rates in the Pacific Ocean water column. Calcium carbonate dissolution rates ranging from 0.01-1.1 mumol kg(-1) yr(-1) are observed in intermediate and deepwater beginning near the aragonite saturation horizon. In the North Pacific Intermediate Water between 400 and 800 m, CaCO(3) dissolution rates are more than 7 times faster than observed in middle and deep water depths (average=0.051 m mol kg(-1) yr(-1)). The total amount of CaCO(3) that is dissolved within the Pacific is determined by integrating excess alkalinity throughout the water column. The total inventory of CaCO(3) added by particle dissolution in the Pacific Ocean, north of 40degreesS, is 157 Pg C. This amounts to an average dissolution rate of approximately 0.31 Pg C yr(-1). This estimate is approximately 74% of the export production of CaCO(3) estimated for the Pacific Ocean. These estimates should be considered to be upper limits for in situ carbonate dissolution in the Pacific Ocean, since a portion of the alkalinity increase results from inputs from sediments. VL - 16 SN - 0886-6236 IS - 4 N1 - 649rqTimes Cited:86 Cited References Count:60 JO - Global Biogeochem Cy ER - TY - JOUR T1 - Increase in the Asian southwest monsoon during the past four centuries JF - Science Y1 - 2002 A1 - Anderson, D. M. A1 - Overpeck, J. T. A1 - Gupta, A. K. AB - Climate reconstructions reveal unprecedented warming in the past century; however, little is known about trends in aspects such as the monsoon. We reconstructed the monsoon winds for the past 1000 years using fossil Globigerina bulloides abundance in box cores from the Arabian Sea and found that monsoon wind strength increased during the past four centuries as the Northern Hemisphere warmed. We infer that the observed link between Eurasian snow cover and the southwest monsoon persists on a centennial scale. Alternatively, the forcing implicated in the warming trend (volcanic aerosols, solar output, and greenhouse gases) may directly affect the monsoon. Either interpretation is consistent with the hypothesis that the southwest monsoon strength will increase during the coming century as greenhouse gas concentrations continue to rise and northern latitudes continue to warm. VL - 297 IS - 5581 N1 - id: 536; Anderson, David M Overpeck, Jonathan T Gupta, Anil K New York, N.Y. Science. 2002 Jul 26;297(5581):596-9. JO - Increase in the Asian southwest monsoon during the past four centuries ER - TY - JOUR T1 - Influence of Vegetation Change on Watershed Hydrology: Implications for Paleoclimatic Interpretation of Lacustrine d180 Records JF - Journal of Paleolimnology Y1 - 2002 A1 - Rosenmeier, M. F. A1 - Hodell, D. A. A1 - Brenner, M. A1 - Curtis, J. H. A1 - Martin, J. B. A1 - Anselmetti, F. S. A1 - Ariztegui, D. A1 - Guilderson, T. P. VL - 27 N1 - id: 1386 ER - TY - JOUR T1 - Inorganic carbon in the Indian Ocean: Distribution and dissolution processes JF - Global Biogeochemical Cycles Y1 - 2002 A1 - Sabine, C. L. A1 - Key, R. M. A1 - Feely, R. A. A1 - Greeley, D. KW - alkalinity KW - anthropogenic co2 KW - arabian sea KW - calcium carbonate KW - Carbon cycle KW - dioxide system KW - dissociation KW - indian ocean KW - pressure KW - saturation state KW - SEAWATER KW - Temperature KW - thermodynamics KW - total alkalinity KW - total co2 KW - water AB - This study uses nearly 25,000 carbon measurements from the WOCE/JGOFS global CO2 survey to examine the distribution of dissolved inorganic carbon (DIC) and total alkalinity (TA) in the Indian Ocean. Shallow and intermediate distributions of inorganic carbon do not strictly follow temperature and salinity because of differing surface gradients and vertical biological processes that work to modify the circulation derived features. Anthropogenic CO2 has increased the shallow DIC by as much as 3%, decreasing the vertical DIC gradient. Deep ocean DIC and TA increase toward the north because of the decomposition and dissolution of organic and inorganic particles. Calcite saturation depths range from 2900-3900 m with the deepest saturation depth in the central Indian Ocean. Variations of aragonite saturation depth (200-1400 m) are similar to calcite, but the deepest saturations are in the southwestern Indian Ocean. The shallowest aragonite saturation depths are found in the Bay of Bengal. In the northern Arabian Sea and Bay of Bengal, the current aragonite saturations are 100 and 200 m shallower, respectively, than in preindustrial times. Estimates of carbonate dissolution rates on isopycnal surfaces range from 0.017 to 0.083 mumol kg(-1) yr(-1) in deep waters. Upper water column dissolution rates range from 0 to 0.73 mumol kg(-1) yr(-1), with a local maximum occurring in intermediate waters just below the aragonite saturation horizon. Dissolution is also generally higher north of the Chemical Front at 10-20degreesS. There is some evidence for significant sedimentary sources in the northern Indian Ocean. VL - 16 SN - 0886-6236 IS - 4 N1 - 643rkTimes Cited:50 Cited References Count:72 JO - Global Biogeochem Cy ER - TY - RPRT T1 - Ituhu Site (32SN110) 1995 Archeological Excavations. Anthropology Research, Department of Anthropology, University of North Dakota, Grand Forks (Report) Y1 - 2002 A1 - Toom, Dennis L. PB - Dakotas Area Office, U. S. Bureau of Reclamation CY - Bismarck, ND VL - in prep N1 - id: 202 ER - TY - RPRT T1 - James River Archeological Project 1994-2000, Background and General Research Design - Stutsman County, North Dakota Y1 - 2002 A1 - Toom, Dennis L. PB - U.S. Bureau of Reclamation, Dakota Area Office CY - Bismarck, ND 58502 VL - Contribution Nos. 379-381 N1 - id: 1221 ER - TY - RPRT T1 - Keyhole Reservoir 2001 Archeological Site Evaluations, Crook County, Wyoming Y1 - 2002 A1 - Jackson, Michael L. A1 - Toom, Dennis L. PB - Anthropology Research, Department of Anthropology, University of North Dakota, Grand Forks CY - Grand Forks, ND VL - in prep N1 - id: 1432 ER - TY - JOUR T1 - Kilimanjaro ice core records: evidence of holocene climate change in tropical Africa JF - Science Y1 - 2002 A1 - Thompson, L. G. A1 - Mosley-Thompson, E. A1 - Davis, M. E. A1 - Henderson, K. A. A1 - Brecher, H. H. A1 - Zagorodnov, V. S. A1 - Mashiotta, T. A. A1 - Lin, P. N. A1 - Mikhalenko, V. N. A1 - Hardy, D. R. A1 - Beer, J. AB - Six ice cores from Kilimanjaro provide an approximately 11.7-thousand-year record of Holocene climate and environmental variability for eastern equatorial Africa, including three periods of abrupt climate change: approximately 8.3, approximately 5.2, and approximately 4 thousand years ago (ka). The latter is coincident with the "First Dark Age," the period of the greatest historically recorded drought in tropical Africa. Variable deposition of F- and Na+ during the African Humid Period suggests rapidly fluctuating lake levels between approximately 11.7 and 4 ka. Over the 20th century, the areal extent of Kilimanjaro's ice fields has decreased approximately 80%, and if current climatological conditions persist, the remaining ice fields are likely to disappear between 2015 and 2020. VL - 298 IS - 5593 N1 - Thompson, Lonnie GMosley-Thompson, EllenDavis, Mary EHenderson, Keith ABrecher, Henry HZagorodnov, Victor SMashiotta, Tracy ALin, Ping-NanMikhalenko, Vladimir NHardy, Douglas RBeer, Jurgeng2002/10/19 04:00Science. 2002 Oct 18;298(5593):589-93. JO - Kilimanjaro ice core records: evidence of holocene climate change in tropical Africa ER - TY - RPRT T1 - Kirschenman III Site (32SN247) 1994 Archeological Excavation. Anthropology Research, Department of Anthropology, University of North Dakota, Grand Forks (Report) Y1 - 2002 A1 - Toom, Dennis L. PB - Dakotas Area Office, U. S. Bureau of Reclamation CY - Bismarck, ND VL - in prep N1 - id: 201 ER - TY - JOUR T1 - A late glacial-Holocene tephrochronology for glacial lakes in southern Ecuador JF - Quaternary Research Y1 - 2002 A1 - Rodbell, D. T. A1 - Bagnato, S. A1 - Nebolini, J. C. A1 - Seltzer, G. O. A1 - Abbott, M. B. AB - Despite the presence of numerous active volcanoes in the northern half of Ecuador, few, if any, distal tephras have been previously recognized in the southern one third of the country. In this article, we document the presence of thin (0.1-1.0-cm-thick) distal tephras comprising glass and/or phenocrysts of hornblende and feldspar in sediment cores from five glacial lakes and one bog in Las Cajas National Park (2degrees40'-3degrees00'S, 79degrees00'-79degrees25'W). The lake cores contain from 5 to 7 tephras, and each has a diagnostic major element geochemistry as determined from electron microprobe analysis of similar to710 glass shards and similar to440 phenocrysts of feldspar and hornblende. The loss of sodium with exposure to the electron microbeam causes a 10 +/- 7 wt.% (+/-1sigma) reduction in Na content, which we empirically determined and corrected for before correlating tephras among the sediment cores. We use a similarity coefficient to correlate among the sediment cores; pair-wise comparison of all tephras generally yields an unambiguous correlation among the cores. Six tephras can be traced among all or most of the cores, and several tephras are present in only one or two of the cores. Twenty-six accelerator mass spectrometry (14)C dates on macrofossils preserved in the sediment cores provide the basis for establishing a regional tephrochronology. The widespread tephras were deposited similar to9900, 8800,7300,5300,2500, and 2200 cal yr B.P. The oldest tephras were deposited similar to15,500 and 15,100 cal yr B.P., but these are not found in all cores. Two of the tephras appear correlative with volcaniclastic strata on the flanks of Volcan Cotopaxi and one tephra may correlate with strata on the flanks of Volcan Ninahuilca; both volcanoes are in central Ecuador. The absence of tephras in sediment cores correlative with the numerous eruptions of active volcanoes of the past two millennia implies that the earlier eruptions, which did deposit tephras in the lakes, must have been either especially voluminous, or southerly winds must have prevailed at the time of the eruption, or both. (C) 2002 University of Washington. VL - 57 IS - 3 N1 - 555kpTimes Cited:25Cited References Count:23 JO - A late glacial-Holocene tephrochronology for glacial lakes in southern Ecuador ER - TY - JOUR T1 - Late Pleistocene-Holocene paleoceanography and ventilation of the Gulf of California JF - Journal of Oceanography Y1 - 2002 A1 - Keigwin, L. D. AB - Sediment cores collected in 1990 from the Gulf of California have been studied using stable isotope and radiocarbon techniques to reconstruct the climate and ventilation histories since the last glacial maximum. Benthic foraminiferal delta(18)O from core tops in a water depth range of 145 to 1442 m increases by about 2parts per thousand with increasing depth. This is consistent with a composite temperature profile constructed from several hydrocasts in the various gulf basins. However, the delta18O water/salinity relationship is not sufficiently linear in gulf locations or in nearby open Pacific Geochemical Ocean Sections Study (GEOSECS) stations to be useful in solving paleotemperature equations. Of the most common benthic foraminifera, only Planulina ariminensis has delta(13)C that is consistent with the measured delta(13)C of SigmaCO(2). Several cores in the depth range 500 to 900 m have the laminated Holocene and Bolling/Allerod sediments, and the nonlaminated glacial age and Younger Dryas sediments that are typical of the gulf and other locations such as Santa Barbara Basin. The best of those, Jumbo Piston Core (JPC) 56 from 818 m water depth on the western margin of Guaymas Basin, was sampled for intensive study. Oxygen isotope ratios in benthic and planktonic foraminifera show little evidence for deglacial temperature oscillations. Carbon isotope ratios are generally lower during warm epochs, but the most striking result is strongly lowered benthic and planktonic delta(13)C about 9500 years ago. This may reflect water column oxidation of locally released methane. Neither benthic delta(13)C in depth section nor paired benthic and planktonic (14)C data in JPC56 are consistent with increased intermediate water ventilation during the glacial maximum and Younger Dryas. Likewise, (14)C data from 5 pairs of foraminifera from the Okhotsk Sea fail to support better ventilation in that basin during the last glacial maximum. VL - 58 IS - 2 N1 - 554heTimes Cited:53Cited References Count:48 JO - Late Pleistocene-Holocene paleoceanography and ventilation of the Gulf of California ER - TY - CHAP T1 - Late Quaternary sedimentation and climate in the Lake Edward and George area, Uganda-Congo T2 - The East African Great Lakes: Limnology, Palaeolimnology, and Biodiversity Y1 - 2002 A1 - Laerdal, T. A1 - Talbot, M. R. A1 - Russell, J. M. ED - Olago, D. JF - The East African Great Lakes: Limnology, Palaeolimnology, and Biodiversity PB - Kluwer Academic Publishers CY - Dordrecht, The Netherlands N1 - id: 1012 ER - TY - JOUR T1 - Late-Quaternary lowstands of Lake Titicaca: evidence from high-resolution seismic data JF - Palaeogeography Palaeoclimatology Palaeoecology Y1 - 2002 A1 - D'Agostino, K. A1 - Seltzer, G. A1 - Baker, P. A1 - Fritz, S. A1 - Dunbar, R. KW - Andes KW - bolivian altiplano KW - central andes KW - climatic-change KW - Holocene KW - lacustrine KW - lake level change KW - lake titicaca KW - level KW - malawi KW - Peru KW - record KW - seismic reflection data KW - tropical paleoclimate KW - tropical south-america AB - Approximately 600 km of high-resolution seismic reflection data were collected to investigate the late-Quaternary stratigraphic development of Lake Titicaca. The focus of this report is on two seismic sequence boundaries, which are interpreted as erosional surfaces formed at times of low lake level. The younger erosional surface occurs as much as 90 in below the present lake level and up to 8 in below the present sediment-water interface. This erosional surface is interpreted to be coeval with a well-documented early- to mid-Holocene lowstand, dated between similar to 8000 and 3600 cal yr BP. An earlier and previously unknown erosional surface occurs at a sub-bottom depth of approximately 30 m, and as much as 240 in below the present lake level, which implies a major late-Pleistocene lowstand of Lake Titicaca. By extrapolation of sedimentation rates from the upper similar to 14 in of sediment, we estimate the age of this older lowstand at > 90 000 cal yr BP. Both lowstands of Lake Titicaca indicated by the seismic data are likely to have been a response to climatic change in the region. (C) 2002 Elsevier Science B.V. All rights reserved. VL - 179 SN - 0031-0182 IS - 1-2 N1 - 560qxTimes Cited:31 Cited References Count:33 JO - Palaeogeogr Palaeocl ER - TY - CHAP T1 - The limits of paleontological resolution T2 - High Resolution Approachews in Paleontology: Kluwer Academic/Plenum Y1 - 2002 A1 - Kowalewski, M. A1 - Bambach, R. K. ED - Harries, P. J. JF - High Resolution Approachews in Paleontology: Kluwer Academic/Plenum T3 - Topic in Geobiology CY - New York N1 - id: 1415 ER - TY - RPRT T1 - Linking vertical advection and diet to juvenile salmon condition and parasite load: A study using 14C, 13C, and 15N Y1 - 2002 A1 - Casillas, E. A1 - Rau, G. H. A1 - al, et ED - Abstract, Ocean Sciences Meeting JF - Transactions, American Geophysical Union N1 - id: 1142 ER - TY - JOUR T1 - Los Cerritos: an early fishing-farming community on the Pacific Coast of Mexico JF - Antiquity Y1 - 2002 A1 - Kennett, D. J. A1 - Voorhies, B. A1 - McClure, S. B. VL - 76 N1 - id: 473 ER - TY - CONF T1 - Major Prehistoric Ceramic Series in the Middle Missouri Subarea of the Plains T2 - 2002 Conference on the ceramics of the Northeastern Plains and adjacent areas Y1 - 2002 A1 - Toom, Dennis L. JF - 2002 Conference on the ceramics of the Northeastern Plains and adjacent areas CY - University of Winnipeg, Winnipeg, Manitoba N1 - id: 1434 ER - TY - CONF T1 - A marine record of Holocene climate events in tropical South America, abstract T2 - Eos Trans. AGU 83, Fall Meeting Suppl Y1 - 2002 A1 - Haug, G. H. A1 - Gunther, D. A1 - Hughen, K. A. A1 - Peterson, L. C. A1 - Rohl, U. JF - Eos Trans. AGU 83, Fall Meeting Suppl CY - San Francisco, CA N1 - id: 1080 ER - TY - MPCT T1 - Mercury from hatting industry in Connecticut Y1 - 2002 A1 - Varekamp, J. C. CY - USA ER - TY - CONF T1 - Mercury in Connecticut and Long Island Sound sediment T2 - Long Island Sound/NEERS Research Conference Y1 - 2002 A1 - Varekamp, J. C. A1 - Buchholtz ten Brink, M. R. JF - Long Island Sound/NEERS Research Conference CY - Groton, CT N1 - id: 729 ER - TY - NEWS T1 - Mercury issues from old industries Y1 - 2002 A1 - Varekamp, J. C. CY - Chicago, IL ER - TY - NEWS T1 - Mercury legacy from hatmaking in Danbury, CT T2 - Hartford Courant Y1 - 2002 A1 - Varekamp, J. C. JF - Hartford Courant CY - Hartford, CT ER - TY - JOUR T1 - A middle archaic archaeological site on the Est Coast of Mexico JF - Latin American Antiquity Y1 - 2002 A1 - Voorhies, B. A1 - Kennett, D. J. A1 - Jones, J. G. A1 - Wake, T. A. VL - 13 IS - 2 N1 - id: 475 ER - TY - CHAP T1 - The Middle Stone Age occupation of Atlantic central Africa: new evidence from Equatorial Guinea and Cameroon T2 - Under the Canopy: The Archaeology of Tropical Rain Forests Y1 - 2002 A1 - Mercader, J. A1 - Marti, R. ED - Mercader, J. JF - Under the Canopy: The Archaeology of Tropical Rain Forests PB - Rutgers University Press CY - New Brunswick N1 - id: 1196 ER - TY - JOUR T1 - The nature of 'stone-lines' in the African Quaternary record: archaeological resolution at the rainforest site of Mosumu, Equatorial Guinea JF - Quaternary International Y1 - 2002 A1 - Mercader, J. A1 - Marti, R. A1 - Martinez, J. L. A1 - Brooks, A. KW - Age KW - behavior KW - cameroon KW - congo KW - ituri KW - layers KW - origin KW - tools KW - vegetation AB - 'Stone-lines' are widespread Quaternary features that appear in tropical and subtropical regions. They have a diverse nature and genesis, and are frequently associated with archaeological assemblages. However, archaeological deposition and 'stone-line' configuration may be unrelated geological events separated by thousands of years. The energetics involved in 'stone-line' formation, coarse and fine material translocation across space and in depth, and overall assemblage integrity vary from one site to another. This paper presents quantitative and spatial geoarchaeological data from the site of Mosumu, in the tropical rain forest of continental Equatorial Guinea. Mosumu yielded Middle and Later Stone Age assemblages dated to at least the last 30,000 years in a 'stone-line' context. Special attention to the study of vertical and horizontal variations of artifacts, sedimentary features, and taphonomic indicators allows analysis of the nature, meaning, and archeological resolution at this site. The results are placed in the wider debate over the meaning of 'stone-lines' in the African Quaternary record. (C) 2002 Elsevier Science Ltd and INQUA. All rights reserved. VL - 89 SN - 1040-6182 N1 - 536zcTimes Cited:15 Cited References Count:89 JO - Quatern Int ER - TY - RPRT T1 - Nelson Site (32SN113) 2000 Archeological Excavations. Anthropology Research, Department of Anthropology, University of North Dakota, Grand Forks (Report) Y1 - 2002 A1 - Toom, Dennis L. PB - Dakotas Area Office, U. S. Bureau of Reclamation CY - Bismarck, ND VL - in prep. N1 - id: 203 ER - TY - JOUR T1 - Noble gases and volatile recycling at subduction zones JF - Noble Gases in Geochemistry and Cosmochemistry Y1 - 2002 A1 - Hilton, D. R. A1 - Fischer, T. P. A1 - Marty, B. VL - 47 N1 - Bw12hTimes Cited:243Cited References Count:219Reviews in Mineralogy & Geochemistry JO - Noble gases and volatile recycling at subduction zones ER - TY - JOUR T1 - Numerical models, geochemistry and the zero-paradox noble-gas mantle JF - Philos Transact A Math Phys Eng Sci Y1 - 2002 A1 - Ballentine, C. J. A1 - Van Keken, P. E. A1 - Porcelli, D. A1 - Hauri, E. H. AB - Numerical models of whole-mantle convection demonstrate that degassing of the mantle is an inefficient process, resulting in ca. 50% of the (40)Ar being degassed from the mantle system. In this sense the numerical simulations are consistent with the (40)Ar mass balance between the atmosphere and mantle reservoir. These models, however, are unable to preserve the large-scale heterogeneity predicted by models invoking geochemical layering of the mantle system. We show that the three most important noble-gas constraints on the geochemically layered mantle are entirely dependent on the (3)He concentration of the convecting mantle derived from the (3)He flux into the oceans and the average ocean-crust generation rate. A factor of 3.5 increase in the convecting-mantle noble-gas concentration removes all requirements for: a (3)He flux into the upper mantle from a deeper high (3)He source; a boundary in the mantle capable of separating heat from helium; and a substantial deep-mantle reservoir to contain a hidden (40)Ar rich reservoir. We call this model concentration for the convecting mantle the 'zero-paradox' concentration. The time-integrated flux of (3)He into the oceans is a robust observation, but only representative of the ocean-floor activity over the last 1000 years. In contrast, ocean-floor generation occurs over tens of millions of years. We argue that combining these two observations to obtain the (3)He concentration of the mantle beneath mid-ocean ridges is unsound. Other indicators of mantle (3)He concentration suggest that the real value may be at least a factor of two higher. As the zero-paradox concentration is approached, the noble-gas requirement for mantle layering is removed. We further consider the role that recycled material plays in ocean-island-basalt generation and show that a source with high (3)He and (3)He/(4)He must exist within the mantle. Nevertheless, only a small amount of this material is required to generate both the observed ocean-island (3)He/(4)He ratios and the concentrations inferred from basalt samples for this mantle source. VL - 360 IS - 1800 N1 - id: 1579; Ballentine, Chris J Van Keken, Peter E Porcelli, Don Hauri, Erik H England Philos Transact A Math Phys Eng Sci. 2002 Nov 15;360(1800):2611-31. JO - Numerical models, geochemistry and the zero-paradox noble-gas mantle ER - TY - JOUR T1 - Oak, chestnut and fire: climatic and cultural controls of long-term forest dynamics in New England, USA JF - Journal of Biogeography Y1 - 2002 A1 - Foster, D. R. A1 - Clayden, S. A1 - Orwig, D. A. A1 - Hall, B. AB - Aim Despite decades of study we have limited insights into the nature of the pre-European landscape of the north-eastern USA and the forces and changes that shaped modern forest patterns. Information on such long-term forest dynamics would provide critical insights into the relationships among environmental change, land-use history and biotic responses and is greatly needed for conservation planning. To address these issues we used modern, historical, and palaeoecological approaches to reconstruct the 3500-year history of a New England upland region dominated by oak and (formerly) chestnut forests and to interpret the interactions among climate change, natural and human disturbance, and site factors in controlling vegetation patterns and dynamics at different spatial scales.Location The study focused on a broad upland ridge dominated by oak forests in the north-central Massachusetts town of New Salem. Detailed palaeoecological analyses were undertaken of wetland (Chamberlain Swamp) and lake (Lily Pond) basins in order to reconstruct local to regional scale vegetation dynamics, which were interpreted within the context of regional vegetation data from central Massachusetts.Methods Palaeoecological methods were used to reconstruct the vegetation, fire and land-use history of the local and subregional vegetation from the two basins and to place these in the context of regional information on vegetation and climate change based on other published data. Historical information including maps, archaeological and census data, and vegetation information were gathered for the landscape and areas surrounding the coring sites. Vegetation sampling in transects adjacent to the swamp coring area included tree cores for dendrochronological reconstructions.Results Stand, landscape and regional forest dynamics were most strongly driven by climate, notably an apparent cooling and increase in moisture availability c. 1500 yr BP, and European land-use activities commencing 260 yr BP. However, the abundance of oak and chestnut (fire-tolerant, sprouting species) and the distribution of hemlock (fire-intolerant) at a stand to landscape scale were also influenced by fire, which, in turn, varied with climate and human activity. Despite, or perhaps as a consequence of ongoing disturbance by fire and presumably windstorms in this hurricane-prone region, the pre-European period was marked by two 1000+ year periods of remarkably stable forest composition, separated by an abrupt compositional shift. In contrast, over the past 260 years the vegetation has changed rather continuously in response to human activity, producing stand, landscape and regional patterns that are novel as well as recent in origin.The results indicate that chestnut was a major component of some pre-European landscapes in New England, in part because of occasional fire, and that cultural and physical factors have interacted over millennia to control vegetation patterns and dynamics. Our analyses also suggest that the composition of low diversity forests can be remarkably stable over millennia. The range of ecological, cultural and management insights afforded by this study underscores the fundamental utility of very long-term research in science and policy development. VL - 29 IS - 10-11 N1 - 618gtTimes Cited:53Cited References Count:126 JO - Oak, chestnut and fire: climatic and cultural controls of long-term forest dynamics in New England, USA ER - TY - CHAP T1 - Ocean circulation: thermohaline circulation T2 - Encyclopedia of Ocean Sciences Y1 - 2002 A1 - Toggweiler, J. R. A1 - Key, R. M. ED - Steele, J. JF - Encyclopedia of Ocean Sciences PB - Academic Press CY - London N1 - id: 521 ER - TY - JOUR T1 - The Ocean Margins Program: an interdisciplinary study of carbon sources, transformations, and sinks in a temperate continental margin system JF - Deep-Sea Research Part Ii-Topical Studies in Oceanography Y1 - 2002 A1 - Verity, P. G. A1 - Bauer, J. E. A1 - Flagg, C. N. A1 - DeMaster, D. J. A1 - Repeta, D. J. KW - cape-hatteras KW - chesapeake bay KW - co2 fluxes KW - coastal zone KW - dissolved organic-carbon KW - gulf-stream KW - middle atlantic bight KW - north-carolina KW - slope sediments KW - united-states AB - The cycling of carbon on the US east coast shelf and upper slope has been studied for 20 years in a variety of interdisciplinary programs focused on the, Mid and South Atlantic Bights. The culmination of this research was a comprehensive field study conducted in 1996 to ascertain whether the Cape Hatteras shelf was a net source or sink for atmospheric CO(2), and the associated transformations and pathways of inorganic and organic carbon. The rationale, objectives, design, and overview of the Ocean Margins Program are given here as a framework to interpret the results of the papers presented in this special issue. (C) 2002 Elsevier Science Ltd. All rights reserved. VL - 49 SN - 0967-0645 IS - 20 N1 - 607kxTimes Cited:26 Cited References Count:96 JO - Deep-Sea Res Pt Ii ER - TY - JOUR T1 - Ocean ventilation and sedimentation since the glacial maximum at 3 km in the western North Atlantic JF - Geochemistry Geophysics Geosystems Y1 - 2002 A1 - Keigwin, L. D. A1 - Schlegel, M. A. KW - abyssal circulation KW - benthic foraminifera KW - c-14 ages KW - Calibration KW - climate-change KW - deep-water KW - Holocene KW - Last glacial maximum KW - ocean ventilation KW - radiocarbon KW - radiocarbon age KW - sea KW - sediment drifts KW - Younger Dryas AB - [1] Stable isotope, sedimentological, and radiocarbon data from cores at similar to 3 km water depth on the Blake Ridge, western subtropical North Atlantic, reveal the history of deep water ventilation since the last glacial maximum (LGM). Bulk sediment accumulation rates varied locally by a factor of 2 under the influence of bottom currents in this sediment drift environment, but the sand flux, mostly foraminifera, was nearly identical at a given time. This suggests that the rain rate of foraminifera (mostly planktonic) was constant, that transport of foraminifera was negligible, and that current-controlled differences in clay and silt transport drive bulk accumulation. In two of the cores, flux peaks in the benthic foraminifera Cibicidoides and Uvigerina peregrina occurred during the Younger Dryas (YD) cold event, and at 18.2, 19.6, 21.1, 25.0, and 28.1 ka. Radiocarbon measurements on those benthic foraminifera show the ventilation age of bottom waters was similar to 1000 years during the YD, and for older events it was as great as 2000 years. These results contrast with Holocene ventilation, which was similar to 500 years and 700 years at 1500 years and similar to 7100 years before present, respectively. VL - 3 SN - 1525-2027 IS - 6 N1 - 565rlTimes Cited:26 Cited References Count:43 JO - Geochem Geophy Geosy ER - TY - JOUR T1 - Organic carbon deposition on the North Carolina continental slope off Cape Hatteras (USA) JF - Deep-Sea Research Part Ii-Topical Studies in Oceanography Y1 - 2002 A1 - Thomas, C. J. A1 - Blair, N. E. A1 - Alperin, M. J. A1 - DeMaster, D. J. A1 - Jahnke, R. A. A1 - Martens, C. S. A1 - Mayer, L. KW - anaerobic methane oxidation KW - early diagenesis KW - margin KW - marine-sediments KW - MATTER KW - middle-atlantic-bight KW - sea-floor KW - shelf KW - south KW - waters AB - The continental slope off Cape Hatteras, NC is a region of high sediment accumulation and organic matter deposition. Sediment accumulation rates range from 3 to 151 cm kyr(-1). Organic carbon deposition rates are 5-13 moles C m(-2) yr(-1), the highest reported for the slope off the eastern US. Burial efficiencies are 3-40%. The organic matter deposited is marine in origin and a mix of old and young particles. High organic carbon deposition rates support remineralization throughout the upper 2-3 m of sediment. Deep bioirrigation to depths of 60-100 cm within the seabed affects the biogeochemistry of the sediments by extending the zone of sulfate reduction and by steepening DIC porewater gradients through the non-local exchange of porewater. Stable and radiocarbon isotope mixing curves for porewater dissolved inorganic carbon (DIC) indicate that the dominant source of DIC accumulating in the upper 2-3 m of the seabed is of nearly uniform delta(13)C (-21.10parts per thousand) and Delta(14)C (-546parts per thousand.). (C) 2002 Elsevier Science Ltd. All rights reserved. VL - 49 SN - 0967-0645 IS - 20 N1 - 607kxTimes Cited:31 Cited References Count:77 JO - Deep-Sea Res Pt Ii ER - TY - CHAP T1 - Ostracoda and paleoceanography T2 - American Geophysical Union Monograph - The Ostracoda: Applications in Quaternay Research Y1 - 2002 A1 - Cronin, T. M. A1 - Boomer, I. A1 - Dwyer, G. S. A1 - Rodriguez-Lazaro, J. ED - Holmes, J. A. JF - American Geophysical Union Monograph - The Ostracoda: Applications in Quaternay Research N1 - id: 1473 ER - TY - JOUR T1 - Paleoceanographic proxies in Long Island Sound, CT, USA JF - Geochimica Et Cosmochimica Acta Y1 - 2002 A1 - Thomas, E. A1 - Lugolobi, F. A1 - Varekamp, J. C. VL - 66 SN - 0016-7037 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=Alerting&SrcApp=Alerting&DestApp=WOS&DestLinkType=FullRecord;UT=WOS:000177423401511 IS - 15a N1 - Suppl. 1583rx Times Cited:0 Cited References Count:0 JO - Geochim Cosmochim Ac ER - TY - CONF T1 - Paleoenvironmental history of Long Island Sound T2 - Long Island Sound/NEERS Research Conference AGU Fall Meeting Y1 - 2002 A1 - Varekamp, J. C. A1 - Thomas, E. A1 - Lugolobi, F. A1 - Buchholtz ten Brink, M. R. JF - Long Island Sound/NEERS Research Conference AGU Fall Meeting CY - Groton, CT San Francisco, CA N1 - id: 1177 ER - TY - CONF T1 - Plans for expanded 14C analyses at the NOSAMS facility - a status and progress report T2 - International Conference on Accelerator Mass Spectrometry Y1 - 2002 A1 - von Reden, K. F. A1 - Donoghue, J. A1 - Elder, K. A1 - Gagnon, A. A1 - Gerlach, D. A1 - Griffin, V. A1 - Healy, R. A1 - Long, P. A1 - McNichol, A. A1 - Percy, D. A1 - Roberts, M. L. A1 - Schneider, R. J. A1 - Xu, L. A1 - Hayes, J. M. JF - International Conference on Accelerator Mass Spectrometry CY - Nagoya, Japan N1 - id: 1685 ER - TY - JOUR T1 - Pleistocene chronology of continental margin sedimentation: New insights into traditional models, New Jersey JF - Marine Geology Y1 - 2002 A1 - McHugh, C. M. G. A1 - Olson, H. C. KW - baltimore canyon KW - coastal-plain KW - glacioeustasy KW - global sea-level KW - isotopes KW - late quaternary sedimentation KW - mass-wasting KW - new-york KW - north-atlantic KW - northwest atlantic KW - passive margin KW - Pleistocene KW - sedimentary processes KW - sequence stratigraphy KW - shelf KW - slope AB - Commonly accepted models for the evolution of continental margins link sediment erosion, transport and deposition to eustasy. To test these models, we constructed an oxygen isotope record from 520 m of Pleistocene sediment recovered by the Ocean Drilling Program Leg 174A from the New Jersey continental slope. The delta(18)O record was calibrated to SPECMAP oxygen isotope time scale [Imbrie et al. (1984), in: Berger et al. (Eds.), Milankovitch and Climate, 269-305] with radiocarbon ages, nannoplankton biostratigraphy, magnetostratigraphy, and opal and calcium carbonate stratigraphy. Sixteen glacial/interglacial fluctuations of global ice volume have been recorded in the Pleistocene: oxygen isotope stages (OIS) 1 (partial), 2-4, 5 (partial) and 8 throughout 18. Contrary to predicted sedimentation models, a classification of mass-wasting deposits, based on variations in the styles of soft-sediment deformation and grain size, shows that: (1) mass-wasting is not restricted to glacial times but is present during both glacial and interglacial stages; (2) glacial stages are dominated by fine-grained sediments some of which were deposited by gravity flows; and (3) the transitions from glacial to interglacial stages are characterized by the deposition of coarse sands. The sedimentary record shows large-scale trends that do not fit the traditional models of higher glacial sedimentation rates since there is no consistent variation in sediment accumulation between glacial and interglacial stages. Instead there are longer-term sedimentation patterns. Uniform sedimentation rates of 62 cm/kyr characterize the early middle Pleistocene (OIS 12-18), followed by varying rates from low to very high for three consecutive time periods: OIS 11 to 9 (98-560 cm/kyr), OIS 8 (52-560 cm/kyr), and OIS 5 to 2 (37-353 cm/kyr). Each of these depositional units is contained within one seismic-stratigraphic sequence and bounded by sequence boundaries. Their deposition was influenced by the supply of sediment rather than eustasy. Sediment supply was modulated by: (1) the transition from the dominance of obliquity to that of eccentricity (OIS 18-12 to OIS 11-1); and (2) the proximity of the ice sheet (located similar to 150 km away from the paleoshoreline during the last glacial maximum). (C) 2002 Elsevier Science B.V. All rights reserved. VL - 186 SN - 0025-3227 IS - 3-4 N1 - 582qnTimes Cited:33 Cited References Count:89 JO - Mar Geol ER - TY - JOUR T1 - Possible biological or physical explanations for decadal scale trends in North Pacific nutrient concentrations and oxygen utilization JF - Deep-Sea Research Part Ii-Topical Studies in Oceanography Y1 - 2002 A1 - Keller, K. A1 - Slater, R. D. A1 - Bender, M. A1 - Key, R. M. KW - anthropogenic co2 invasion KW - atmospheric co2 KW - carbon-cycle KW - el-nino KW - hydrographic data KW - organic-matter KW - redfield ratios KW - sargasso-sea KW - subtropical gyre KW - vertical fluxes AB - We analyze North Pacific GEOSECS (1970s) and WOCE (1990s) observations to examine potential decadal trends of the marine biological carbon pump. Nitrate concentrations ([NO3]) and apparent oxygen utilization (AOU) decreased significantly in intermediate waters (by -0.6 and -2.9 mu mol kg(-1) respectively, at sigma (theta) = 27.4 kg m(-3), corresponding to approximate to 1050 m). In shallow waters (above roughly 750 m) [NO3-] and AOU increased, though the changes were not statistically significant. A sensitivity study with an ocean general circulation model indicates that reasonable perturbations of the biological carbon pump due to changes in export production or remineralization. efficiency are insufficient to account for the intermediate water tracer trends. However, changes in water ventilation rates could explain the intermediate water tracer trends and would be consistent with trends of water age derived from radiocarbon. Trends in AOU and [NO3-] provide relatively poor constraints on decadal scale trends in the marine biological carbon pump for two reasons. First, most of the expected changes due to decadal scale perturbations of the marine biota occur in shallow waters, where the available data are typically too sparse to account for the strong spatial and temporal variability. Second, alternative explanations for the observed tracer trends (e.g., changes in the water ventilation rates) cannot be firmly rejected. Our data analysis does not disprove the null-hypothesis of an unchanged biological carbon pump in the North Pacific. (C) 2001 Published by Elsevier Science Ltd. VL - 49 SN - 0967-0645 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=Alerting&SrcApp=Alerting&DestApp=WOS&DestLinkType=FullRecord;UT=WOS:000173008600015 IS - 1-3 N1 - 507ceTimes Cited:24 Cited References Count:71 JO - Deep-Sea Res Pt Ii ER - TY - JOUR T1 - Precambrian marine carbonate isotope database: Version 1.1 JF - Geochemistry Geophysics Geosystems Y1 - 2002 A1 - Shields, G. A1 - Veizer, J. KW - 1010 geochemistry : chemical evolution KW - 1030 geochemistry : geochemical cycles (0330) KW - 1040 geochemistry : isotopic composition/chemistry KW - 1050 geochemistry : marine geochemistry (4835,4850) KW - calcite KW - carbonates KW - cycle KW - dolomite KW - evolution KW - Geochemistry KW - isotope stratigraphy KW - oceans KW - precambrian KW - SEAWATER KW - sediments KW - strontium KW - sulfur KW - time AB - [1] We present a compilation of strontium, carbon, and oxygen isotope compositions of roughly 10,000 marine carbonate rocks of Archean - Ordovician age (3800 Ma - 450 Ma). The Precambrian Marine Carbonate Isotope Database (PMCID) has been compiled from 152 published and 3 unpublished articles and books of the past 40 years. Also included are 30 categories of relevant "metadata'' that allow detailed comparisons and quality assessments of the isotope data to be made. The PMCID will be updated periodically as new data and better age constraints come to light. Here we outline the structure of the first published version of the database and its inherent merits and limitations. VL - 3 SN - 1525-2027 N1 - 561enTimes Cited:103 Cited References Count:26 JO - Geochem Geophy Geosy ER - TY - CONF T1 - Prehistoric cereamics in the upper James River region of the northeastern plains T2 - Conference on the ceramics of the northeastern plains and adjacent areas Y1 - 2002 A1 - Toom, Dennis L. A1 - Schneider, Frederick E. JF - Conference on the ceramics of the northeastern plains and adjacent areas CY - University of Winnipeg, Winnipeg, Manitoba N1 - id: 1436 ER - TY - JOUR T1 - Prehistoric horticulture in the northeastern plains JF - Plains Anthropologist Y1 - 2002 A1 - Schneider, Frederick E. VL - 47 IS - 180 N1 - id: 1437 ER - TY - CHAP T1 - Radiocarbon analysis, calibration and applications T2 - Current methods in geochronology: Temporal resolution in geology, palaeontology, archaeoloty, and anthropology Y1 - 2002 A1 - Kromer, B. A1 - Hughen, K. ED - Copeland, P. JF - Current methods in geochronology: Temporal resolution in geology, palaeontology, archaeoloty, and anthropology PB - Kluwer Academic Press N1 - id: 326 ER - TY - JOUR T1 - Radiocarbon as a tool to apportion the sources of polycyclic aromatic hydrocarbons and black carbon in environmental samples JF - Environmental Science & Technology Y1 - 2002 A1 - Reddy, C. M. A1 - Pearson, A. A1 - Xu, L. A1 - McNichol, A. P. A1 - Benner, B. A. A1 - Wise, S. A. A1 - Klouda, G. A. A1 - Currie, L. A. A1 - Eglinton, T. I. AB - To determine the relative inputs of polycyclic aromatic hydrocarbons (PAHs) and black carbon (BC) in environmental samples from the combustion of fossil fuels and biomass we have developed two independent analytical methods for determining the C-14 abundance of PAHs and BC. The 5730 yr half-life of C-14 makes it an ideal tracer for identifying combustion products derived from fossil fuels (C-14-free) versus those stemming from modern biomass (contemporary C-14). The C-14 abundance of PAHs in several environmental Standard Reference Materials was measured by accelerator mass spectrometry after extraction and then purification by high-performance liquid chromatography and preparative capillary gas chromatography. This method yields pure compounds that allow for a high degree of confidence in the C-14 results. The PAHs data were then used to compare and evaluate results from an operationally defined thermal oxidation method used to isolate a BC fraction. The C-14 compositions of PAHs and BC were very similar and suggest that the thermal oxidation method employed for isolating BC is robust and free from interferences by non-BC components. In addition, these data indicate that both the PAHs and the BC species derive mostly from fossil fuels and/or their combustion products. VL - 36 IS - 8 N1 - 541gfTimes Cited:133Cited References Count:59 JO - Radiocarbon as a tool to apportion the sources of polycyclic aromatic hydrocarbons and black carbon in environmental samples ER - TY - JOUR T1 - Radiocarbon content of synthetic and natural semi-volatile halogenated organic compounds JF - Environ Pollut Y1 - 2002 A1 - Reddy, C. M. A1 - Xu, L. A1 - Eglinton, T. I. A1 - Boon, J. P. A1 - Faulkner, D. J. KW - Animals KW - Carbon Radioisotopes/*analysis KW - Environmental Pollutants/*analysis KW - Hydrocarbons, Halogenated/chemical synthesis/*chemistry KW - Insecticides/chemistry KW - Polychlorinated Biphenyls/chemistry KW - Porifera/*chemistry KW - Toxaphene/chemistry AB - Some halogenated organic compounds, such as polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs) and polybrominated diphenyl ethers (PBDEs), have been suggested to have natural sources but separating these compounds from their commercially synthesized counterparts is difficult. Molecular-level 14C analysis may be beneficial since most synthetic compounds are manufactured from petrochemicals (14C-free) and natural compounds should have "modern" or "contemporary" 14C levels. As a baseline study, we measured, for the first time, the 14C abundance in commercial PCB and PBDE mixtures, a number of organochlorine pesticides, as well as one natural product 2-(3',5'-dibromo-2'-methoxyphenoxy)-3,5-dibromoanisole. The latter compound was isolated from a marine sponge and is similar in structure to a PBDE. All of the synthetic compounds were 14C-free except for the pesticide toxaphene. which had a modern 14C abundance, as did the brominated natural compound. The result for toxaphene was not surprising since it was commercially synthesized by the chlorination of camphene derived from pine trees. These results suggest that measuring the 14C content of halogenated organic compounds may be quite useful in establishing whether organic compounds encountered in the environment have natural or synthetic origins (or both) provided that any synthetic counterparts derive from petrochemical feedstock. VL - 120 SN - 0269-7491 (Print)0269-7491 (Linking) UR - https://www.ncbi.nlm.nih.gov/pubmed/12395826 IS - 2 N1 - Reddy, Christopher MXu, Li Eglinton, Timothy I Boon, Jan P Faulkner, D John eng Research Support, Non-U.S. Gov't Research Support, U.S. Gov't, Non-P.H.S. England 2002/10/25 04:00 Environ Pollut. 2002;120(2):163-8. ER - TY - JOUR T1 - Radiocarbon dates bason on organic matter in diatom frustules, Abstract JF - EOS. Trans. AGU Y1 - 2002 A1 - Donoghue, Joanne C. A1 - Hayes, John M. A1 - Manganini, Steven J. A1 - Francois, Roger AB - OS42E-156 VL - 83 IS - 4 N1 - id: 1720 ER - TY - JOUR T1 - Radiocarbon Dates of Corals, Gastropods and Forminifers from Saurashtra Peninsula, Gujarat and Their Implications for Sea-level Studies JF - Journal Geological Society of India Y1 - 2002 A1 - Mathur, U. B. A1 - Pandey, D. K. VL - 60 N1 - id: 1219 ER - TY - JOUR T1 - Radiocarbon dating, chronologic framework, and changes in accumulation rates of Holocene estuarine sediments from Chesapeake Bay JF - Quaternary Research Y1 - 2002 A1 - Colman, S. M. A1 - Baucom, P. C. A1 - Bratton, J. F. A1 - Cronin, T. M. A1 - McGeehin, J. P. A1 - Willard, D. A1 - Zimmerman, A. R. A1 - Vogt, P. R. AB - Rapidly accumulating Holocene sediments in estuaries commonly are difficult to sample and date. In Chesapeake Bay, we obtained sediment cores as much as 20 m in length and used numerous radiocarbon ages measured by accelerator mass spectrometry methods to provide the first detailed chronologies of Holocene sediment accumulation in the bay. Carbon in these sediments is a complex mixture of materials from a variety of sources. Analyses of different components of the sediments show that total organic carbon ages are largely unreliable, because much of the carbon (including coal) has been transported to the bay from upstream sources and is older than sediments in which it was deposited. Mollusk shells (clams, oysters) and foraminifera appear to give reliable results, although reworking and burrowing are potential problems. Analyses of museum specimens collected alive before atmospheric nuclear testing suggest that the standard reservoir correction for marine samples is appropriate for middle to lower Chesapeake Bay. The biogenic carbonate radiocarbon ages are compatible with (210)Pb and (137)Cs data and pollen stratigraphy from the same sites.Post-settlement changes in sediment transport and accumulation is an important environmental issue in many estuaries, including the Chesapeake. Our data show that large variations in sediment mass accumulation rates occur among sites. At shallow water sites, local factors seem to control changes in accumulation rates with time. Our two relatively deep-water sites in the axial channel of the bay have different long-term average accumulation rates, but the history of sediment accumulation at these sites appears to reflect overall conditions in the bay. Mass accumulation rates at the two deep-water sites rapidly increased by about fourfold coincident with widespread land clearance for agriculture in the Chesapeake watershed. VL - 57 IS - 1 N1 - 517wpTimes Cited:57Cited References Count:33 JO - Radiocarbon dating, chronologic framework, and changes in accumulation rates of Holocene estuarine sediments from Chesapeake Bay ER - TY - CONF T1 - Radiocarbon dating of alkenones in sediments from the Namibian continental margin T2 - European Geophysical Society, XXVII General Assembly Y1 - 2002 A1 - Mollenhauer, Gesine A1 - Eglinton, Timothy I. A1 - Ohkouchi, Nao A1 - Grootes, Pieter M. A1 - Muller, Peter J. A1 - Rullkotter, Jurgen A1 - Schneider, Ralph R. JF - European Geophysical Society, XXVII General Assembly CY - Nice, France N1 - id: 546 ER - TY - CONF T1 - Radiocarbon in a Fanning Island coral: Inter-decadal variability in waters upwelling in the central equatorial Pacific from 1922-1955 T2 - ALSO/AGU Ocean Sciences Meeting Y1 - 2002 A1 - Grottoli, A. G. A1 - Gille, S. T. A1 - Druffel, E. R. M. A1 - Dunbar, R. B. JF - ALSO/AGU Ocean Sciences Meeting CY - Honolulu, HI N1 - id: 658 ER - TY - CONF T1 - Radiochemical measurements from FOODBANCS: Examining carbon cycling and benth-pelagic coupling on the Antarctic continental shelf T2 - AGU/ASLO Ocean Sciences Meeting Y1 - 2002 A1 - DeMaster, D. J. A1 - Thomas, J. A1 - al, et JF - AGU/ASLO Ocean Sciences Meeting CY - Honolulu, HI N1 - id: 1143 ER - TY - ADVS T1 - Rainwater as a Removal Mechanism for Fossil Fuel Derived Atmospheric Organic Carbon Y1 - 2002 A1 - Avery, Brooks U5 - Video/DVD ER - TY - JOUR T1 - Rapid isolation of biomarkers for compound specific radiocarbon dating using high-performance liquid chromatography and flow injection analysis - atmoospheric pressure chemical ionisation mass spectrometry JF - Journal of Chromatography A Y1 - 2002 A1 - Smittenberg, R. H. A1 - Hopmans, E. C. A1 - Schouten, S. A1 - Sinninghe-Damste, J. S. VL - 978 N1 - id: 669 ER - TY - JOUR T1 - Rate of plate creation and destruction: 180 Ma to present JF - Geological Society of America Bulletin Y1 - 2002 A1 - Rowley, D. B. AB - One of the primary measures of plate tectonics is the history of production of new oceanic lithosphere. As shown by B. Parsons, a direct estimate of the rate of plate creation can be derived from the area/age versus age distribution of the modern oceanic lithosphere. Inversion of the most recent area versus age data (digital isochrons by R.D. Muller et al.) yields a result that the rate of oceanic plate production has not varied significantly since 180 Ma from a mean rate of 3.4 km(2)/yr. Reconstruction of the cumulative area of subducted lithosphere over the past 90 m.y. is in excellent agreement with a fixed rate of ridge production. The conclusion that the rate of ridge production has not varied significantly contrasts markedly with most existing estimates in which the rate is modeled as decreasing by 50% or more since ca. 100 Ma. A constant rate of ridge production has important implications for models of sea level and p(CO2), among other phenomena that have been linked to variations in global rates of seafloor spreading. VL - 114 IS - 8 N1 - 583daTimes Cited:142Cited References Count:20 JO - Rate of plate creation and destruction: 180 Ma to present ER - TY - JOUR T1 - Rates of evolution in ancient DNA from Adelie penguins JF - Science Y1 - 2002 A1 - Lambert, D. M. A1 - Ritchie, P. A. A1 - Millar, C. D. A1 - Holland, B. A1 - Drummond, A. J. A1 - Baroni, C. AB - Well-preserved subfossil bones of Adelie penguins, Pygoscelis adeliae, underlie existing and abandoned nesting colonies in Antarctica. These bones, dating back to more than 7000 years before the present, harbor some of the best-preserved ancient DNA yet discovered. From 96 radiocarbon-aged bones, we report large numbers of mitochondrial haplotypes, some of which appear to be extinct, given the 380 living birds sampled. We demonstrate DNA sequence evolution through time and estimate the rate of evolution of the hypervariable region I using a Markov chain Monte Carlo integration and a least-squares regression analysis. Our calculated rates of evolution are approximately two to seven times higher than previous indirect phylogenetic estimates. VL - 295 IS - 5563 N1 - Lambert, D MRitchie, P AMillar, C DHolland, BDrummond, A JBaroni, CengResearch Support, Non-U.S. Gov'tResearch Support, U.S. Gov't, P.H.S.2002/03/23 10:00Science. 2002 Mar 22;295(5563):2270-3. JO - Rates of evolution in ancient DNA from Adelie penguins ER - TY - JOUR T1 - Reassessment of Lake Victoria–Upper Nile River paleohydrology from oxygen isotope records of lake-sediment cellulose JF - Geology Y1 - 2002 A1 - Beuning, K. R. M. A1 - Kelts, K. R. A1 - Russell, J. M. A1 - Wolfe, B. B. KW - cellulose KW - East Africa KW - isotope KW - oxygen KW - paleohydrology AB - Reconstruction of lake-water δ18O from analysis of cellulose δ18O in two sediment cores from Lake Victoria, East Africa, shows a large shift to lower values during the terminal Pleistocene. This shift records the transition from closed- to open-basin conditions following desiccation at the Last Glacial Maximum. Although oxygen isotope analysis of cellulose from one core had placed this overflow at 8 ka (7200 14C yr B.P.), reevaluation of the age model for this core, in addition to new stratigraphic and chronological evidence from a second core, suggests that basin overflow was established much earlier, ca. 13 ka. Our refined view of the timing of Lake Victoria overflow inferred from the oxygen isotope records is consistent with other paleolimnological studies, indicating that lake-sediment cellulose is an effective and sensitive isotopic archive of major hydrologic events in this region. VL - 30 IS - 6 N1 - id: 1011 JO - Oxygen isotope stratigraphy of sediment cellulose from two cores, Lake Victoria, East Africa ER - TY - CONF T1 - Sea level rise in Long Island Sound over the last millennium T2 - Long Island Sound/NEERS Research Conference AGU Fall meeting Y1 - 2002 A1 - Thomas, E. A1 - Varekamp, J. C. JF - Long Island Sound/NEERS Research Conference AGU Fall meeting CY - Groton, CT San Francisco, CA N1 - id: 728 ER - TY - JOUR T1 - Separating natural and bomb-produced radiocarbon in the ocean: The potential alkalinity method JF - Global Biogeochemical Cycles Y1 - 2002 A1 - Rubin, S. I. A1 - Key, R. M. KW - bomb-produced radiocarbon KW - CO2 KW - indian-ocean KW - inventory KW - natural radiocarbon KW - pacific-ocean KW - potential alkalinity method KW - radiocarbon inventory KW - radiocarbon separation KW - silicate method KW - thermocline KW - ventilation KW - woce AB - [1] The use of radiocarbon (Delta(14)C) as a tracer for oceanic processes generally requires differentiation of naturally occurring radiocarbon from the bomb component produced by atmospheric nuclear weapons testing. We present a new separation method based on the strong linear correlation between Delta(14)C and potential alkalinity. Unlike previous techniques the new algorithm is applicable at all latitudes. Additionally, the potential alkalinity method provides an estimate of surface ocean prebomb Delta(14)C concentrations. Predictions with the technique appear to be unbiased and have uncertainties which are less than previous techniques. VL - 16 SN - 0886-6236 IS - 4 N1 - 646xuTimes Cited:44 Cited References Count:35 JO - Global Biogeochem Cy ER - TY - JOUR T1 - The Shandong mud wedge and post-glacial sediment accumulation in the Yellow Sea JF - Geo-Marine Letters Y1 - 2002 A1 - Liu, J. P. A1 - Milliman, J. D. A1 - Gao, S. AB - Two well-defined deltaic sequences in the Bohai Sea and in the South Yellow Sea represent post-glacial accumulation of Yellow River-derived sediments. Another prominent depocenter on this epicontinental shelf, a pronounced clinoform in the North Yellow Sea, wraps around the northeastern and southeastern end of the Shandong Peninsula, extending into the South Yellow Sea. This Shandong mud wedge is 20 to 40 m thick and contains an estimated 300 km(3) of sediment. Radiocarbon dating, shallow seismic profiles, and regional sea-level history suggest that the mud wedge formed when the rate of post-glacial sea-level rise slackened and the summer monsoon intensified, at about 11 ka. Geomorphic configuration and mineralogical data indicate that present-day sediment deposited on the Shandong mud wedge comes not only from the Yellow River but also from coastal erosion and local rivers. Basin-wide circulation in the North Yellow Sea may transport and redistribute fine sediments into and out of the mud wedge. VL - 21 IS - 4 N1 - 538tcTimes Cited:56Cited References Count:34 JO - The Shandong mud wedge and post-glacial sediment accumulation in the Yellow Sea ER - TY - JOUR T1 - Shelf record of climatic changes in flood magnitude and frequency, north-coastal California JF - Geology Y1 - 2002 A1 - Sommerfield, C. K. A1 - Drake, D. E. A1 - Wheatcroft, R. A. AB - Continental-shelf deposits off the Eel River, north-coastal California, document a recent increase in the magnitude and frequency of major hydrologic floods (greater than or equal to10 yr recurrence interval). The shelf record reveals a sudden, three-fold increase in sedimentation rate ca. 1954 and a concomitant increase in the frequency of preserved flood beds. Comparison of sedimentary and river-discharge records reveals that major floods after ca. 1950 had a more pronounced effect on coastal sediment delivery and accumulation offshore than previous recorded events of similar magnitude, and that stratigraphic preservation of flood events is highly dependent on flood frequency and net sedimentation rate. We contend that this change in marine sedimentation is a response to documented climatic phenomena that have increased the frequency of major floods throughout the western United States during the past half century, together with intrabasinal impacts of extreme floods in 1955 and 1964. Anthropogenic increase in watershed-sediment production is a probable secondary factor. VL - 30 IS - 5 N1 - 551ucTimes Cited:46Cited References Count:34 JO - Shelf record of climatic changes in flood magnitude and frequency, north-coastal California ER - TY - JOUR T1 - Slip rates of the Karakorum fault, Ladakh, India, determined using cosmic ray exposure dating of debris flows and moraines JF - Journal of Geophysical Research-Solid Earth Y1 - 2002 A1 - Brown, E. T. A1 - Bendick, R. A1 - Bourles, D. L. A1 - Gaur, V. A1 - Molnar, P. A1 - Raisbeck, G. M. A1 - Yiou, F. AB - We measure an average slip rate of 4+/-1 mm yr(-1) along the Karakorum fault, heretofore considered one of Earth's greatest strike-slip faults and thought by many to play a key role in Asian deformation kinematics. Levees of a debris flow, and contours of the fan on which it was deposited, have been displaced 40+/-5 m. Concentrations of Be-10 in boulders from the debris flow yield ages of 11-14 ka, implying a slip rate of 4+/-1 mm yr(-1) during that period. A fresher debris flow has been offset 2-2.5 m since 1-2 ka, implying the occurrence of an earthquake with Msimilar to7 since that time. Concentrations of Be-10 in boulders on the crest of the most extensive moraine near Leh imply that the most recent major glacial advance occurred at 90+/-15 ka. This is consistent with the inference of others that alpine glaciers in this region have not necessarily expanded in concert with Northern Hemisphere continental ice sheets. If features, including lateral moraines, that Liu inferred to have been offset 300-350 m by the Karakorum fault date from the same period, they too imply a slip rate of 3-4 mm yr(-1). This slip rate is comparable to rates of extension across grabens within Tibet. With recent evidence that slip along the Altyn Tagh fault occurs at similar to10 mm yr(-1), our rate suggests that slip along the boundaries of Tibet is not significantly more rapid than extension within the plateau. Hence, plate tectonics, in the strictest sense, ought not be applied to Tibet, because Tibet does not behave as a rigid plate. VL - 107 IS - B9 N1 - 634wuTimes Cited:104Cited References Count:72 JO - Slip rates of the Karakorum fault, Ladakh, India, determined using cosmic ray exposure dating of debris flows and moraines ER - TY - JOUR T1 - Spatial and temporal offsets between proxy records in a sediment drift JF - Science Y1 - 2002 A1 - Ohkouchi, N. A1 - Eglinton, T. I. A1 - Keigwin, L. D. A1 - Hayes, J. M. AB - Chronologies for Late Quaternary marine sediment records are usually based on radiocarbon ages of planktonic foraminifera. Signals carried by other sedimentary components measured in parallel can provide complementary paleoclimate information. A key premise is that microfossils and other indicators within a given sediment horizon are of equal age. We show here that haptophyte-derived alkenones isolated from Bermuda Rise drift sediments are up to 7000 years older than coexisting planktonic foraminifera. This temporal offset, which is apparently due to lateral transport of alkenones on fine-grained particles from the Nova Scotian margin, markedly influences molecular estimates of sea surface temperatures. More broadly, the observation raises questions about both the temporal and the geographic delity of paleoenvironmental records encoded by readily transported components of sediments. VL - 298 IS - 5596 N1 - 612mqTimes Cited:147Cited References Count:38 JO - Spatial and temporal offsets between proxy records in a sediment drift ER - TY - CONF T1 - Stable carbon isotope record in a Palau Sclerosponge T2 - Fall AGU Y1 - 2002 A1 - Grottoli, A. G. JF - Fall AGU CY - San Francisco, CA N1 - id: 657 ER - TY - JOUR T1 - Stable chlorine and carbon isotopic compositions of selected semi-volatile organochlorine compounds JF - Organic Geochemistry Y1 - 2002 A1 - Drenzek, N. J. A1 - Tarr, C. H. A1 - Eglinton, T. I. A1 - Heraty, L. J. A1 - Sturchio, N. C. A1 - Shiner, V. J. A1 - Reddy, C. M. KW - aroclors KW - fractionation KW - hydrocarbons KW - intrinsic bioremediation KW - samples KW - solvents KW - trichloroethene AB - To assess whether the isotopic composition of semi-volatile organochlorine compounds (SVOCs) may be a useful tool, we measured the bulk delta(37)Cl and delta(13)C values of several pesticides and Aroclor mixtures from different suppliers. Overall, the delta(37)Cl and delta(13)C values ranged from -5.10 to + 1.22% and -31.63 to -22.39%, respectively. These values are narrower than the ranges observed previously for volatile organic contaminants (VOCs). In particular, the isotopic compositions of the Aroclor mixtures were very tightly constrained for both chlorine and carbon, We also observed that SVOCs synthesized from hexachlorocyclopentadiene had the most enriched delta(37)Cl values. These data provide a baseline for future work employing isotope ratios to study the environmental fate of SVOCs. (C) 2002 Elsevier Science Ltd. All rights reserved. VL - 33 SN - 0146-6380 IS - 4 N1 - 545bnTimes Cited:41 Cited References Count:25 JO - Org Geochem ER - TY - JOUR T1 - Stable isotope composition of Littoridina australis from the coast of Buenos Aires province, Argentina, during Holocene climatic fluctuations JF - Geobios Y1 - 2002 A1 - Aguirre, M. L. A1 - Zanchetta, G. A1 - Fallick, A. E. KW - Argentina KW - Holocene KW - Littoridina australis KW - Molluscs KW - Palaeoenvironments KW - Stable isotopes AB - Stable isotope (carbon and oxygen) analyses were performed on Littoridina australis shells collected from molluscan concentrations within Holocene littoral deposits along the Bonaerensian coastal area of Argentina (south-western Atlantic). Isotope data allow us to define two very different areas: the Samborombon Bay, where isotope composition of shells was mainly governed by mixing between marine and freshwater, and the Mar Chiquita lagoon, where the original brackish environment was dominated by evaporation of water that originated high isotope shell values. In both areas some isotope profiles show short and quite large oscillations in delta(18)O. Their origin may be tentatively explained as due to the changes in moisture regime that control freshwater supply. The results suggest that these deposits can represent natural archives potentially useful for palaeoclimate reconstruction. (C) 2002 Editions scientifiques et medicales Elsevier SAS. All rights reserved. VL - 35 IS - 1 N1 - 563lxTimes Cited:9Cited References Count:27 JO - Stable isotope composition of Littoridina australis from the coast of Buenos Aires province, Argentina, during Holocene climatic fluctuations ER - TY - JOUR T1 - Super ENSO and global climate oscillations at millennial time scales JF - Science Y1 - 2002 A1 - Stott, L. A1 - Poulsen, C. A1 - Lund, S. A1 - Thunell, R. AB - The late Pleistocene history of seawater temperature and salinity variability in the western tropical Pacific warm pool is reconstructed from oxygen isotope (delta18O) and magnesium/calcium composition of planktonic foraminifera. Differentiating the calcite delta18O record into components of temperature and local water delta18O reveals a dominant salinity signal that varied in accord with Dansgaard/Oeschger cycles over Greenland. Salinities were higher at times of high-latitude cooling and were lower during interstadials. The pattern and magnitude of the salinity variations imply shifts in the tropical Pacific ocean/atmosphere system analogous to modern El Nino-Southern Oscillation (ENSO). El Nino conditions correlate with stadials at high latitudes, whereas La Nina conditions correlate with interstadials. Millennial-scale shifts in atmospheric convection away from the western tropical Pacific may explain many paleo-observations, including lower atmospheric CO2, N2O, and CH4 during stadials and patterns of extratropical ocean variability that have tropical source functions that are negatively correlated with El Nino. VL - 297 IS - 5579 N1 - Stott, LowellPoulsen, ChristopherLund, SteveThunell, Roberteng2002/07/13 10:00Science. 2002 Jul 12;297(5579):222-6. JO - Super ENSO and global climate oscillations at millennial time scales ER - TY - RPRT T1 - Tahuka Site (32SN121) 1998 Archeological Excavations. Anthropology Research, Department of Anthropology, University of North Dakota, Grand Forks (Report) Y1 - 2002 A1 - Toom, Dennis L. PB - Dakotas Area Office, U. S. Bureau of Reclamation CY - Bismarck, ND VL - in prep N1 - id: 1363 ER - TY - JOUR T1 - Temporal and regional variability in sources and cycling of DOC and POC in the northwest Atlantic continental shelf and slope JF - Deep-Sea Research II Y1 - 2002 A1 - Bauer, J. E. A1 - Druffel, E. R. M. A1 - Wolgast, D. M. A1 - Griffin, S. VL - 49 IS - 20 N1 - id: 685 JO - Temporal and spatial variability in sources and cycling of DOC and POC in the northwest Atlantic continental margin ER - TY - JOUR T1 - Test of negative ion beams from a microwave ion source with a charge exchange canal for accelerator mass spectrometry applications JF - Review of Scientific Instruments Y1 - 2002 A1 - Kim, S. W. A1 - Schneider, R. J. A1 - von Reden, K. F. A1 - Hayes, J. M. A1 - Wills, J. S. C. AB - A test facility has been constructed to evaluate negative ion beams from small gaseous samples for accelerator mass spectrometry applications. The positive ion beams from the microwave ion source are passed into a charge-exchange canal (CXC) where the ions exchange electrons with magnesium vapor and become negatively charged. Positive molecular ions were: either neutralized or broken up into atomic ions and neutral atoms and molecules by collision processes. Most of the resulting particles were suspected to be neutrals. In studies with injections of CO2 pulses, the resulting positive and negative C-12 current peaks gave a 0.09% yield of C- ions from CO2 molecules, which includes a charge-exchange efficiency of 10%. Since nitrogen does not form a stable negative ion, N-14 background is virtually eliminated after the beam goes through the CXC, which is necessary for radiocarbon measurements. (C) 2002 American Institute of Physics. VL - 73 IS - 2 N1 - 2522wyTimes Cited:8Cited References Count:7 JO - Test of negative ion beams from a microwave ion source with a charge exchange canal for accelerator mass spectrometry applications ER - TY - RPRT T1 - U. S. WOCE Indian Ocean survey: Final report for radiocarbon, Ocean Tracer Laboratory Tech. Report #902-1 Y1 - 2002 A1 - Key, R. M. A1 - Quay, P. D. N1 - id: 528 ER - TY - JOUR T1 - Uncertainties and novel prospects in the study of the soil carbon dynamics JF - Chemosphere Y1 - 2002 A1 - Wang, Y. A1 - Hsieh, Y. P. KW - Carbon Dioxide/chemistry/metabolism KW - Carbon Radioisotopes/analysis KW - Carbon/*chemistry/metabolism KW - Ecosystem KW - Kinetics KW - Models, Chemical KW - Plants/metabolism KW - Seasons KW - Soil/*analysis AB - Establishment of the Kyoto Protocol has resulted in an effort to look towards living biomass and soils for carbon sequestration. In order for carbon credits to be meaningful, sustained carbon sequestration for decades or longer is required. It has been speculated that improved land management could result in sequestration of a substantial amount of carbon in soils within several decades and therefore can be an important option in reducing atmospheric CO2 concentration. However, evaluation of soil carbon sources and sinks is difficult because the dynamics of soil carbon storage and release is complex and still not well understood. There has been rapid development of quantitative techniques over the past two decades for measuring the component fluxes of the global carbon cycle and for studying the soil carbon cycle. Most significant development in the soil carbon cycle study is the application of accelerator mass spectrometry (AMS) in radiocarbon measurements. This has made it possible to unravel rates of carbon cycling in soils, by studying natural levels of radiocarbon in soil organic matter and soil CO2. Despite the advances in the study of the soil carbon cycle in the recent decades, tremendous uncertainties exist in the sizes and turnover times of soil carbon pools. The uncertainties result from lack of standard methods and incomplete understanding of soil organic carbon dynamics, compounded by natural variability in soil carbon and carbon isotopic content even within the same ecosystem. Many fundamental questions concerning the dynamics of the soil carbon cycle have yet to be answered. This paper reviews and synthesizes the isotopic approaches to the study of the soil carbon cycle. We will focus on uncertainties and limitations associated with these approaches and point out areas where more research is needed to improve our understanding of this important component of the global carbon cycle. VL - 49 SN - 0045-6535 (Print)0045-6535 (Linking) UR - https://www.ncbi.nlm.nih.gov/pubmed/12430658 IS - 8 N1 - Wang, YangHsieh, Yuch-Ping eng England 2002/11/15 04:00 Chemosphere. 2002 Dec;49(8):791-804. ER - TY - CONF T1 - An unexplored sedimentary record for the study of environmental change in Mediterranean environments: Posidonia oceanica (L.) Delile peats T2 - The Study of Environmental Change Using Isotope Techniques. IAEA C&S Papers Series Y1 - 2002 A1 - Mateo, M. A. A1 - Renom, P. A1 - Julià, R. A1 - Romero, J. A1 - Michener, R. JF - The Study of Environmental Change Using Isotope Techniques. IAEA C&S Papers Series CY - Vienna N1 - id: 351 ER - TY - CONF T1 - The use of carbon isotopes to trace changes in biological oxygen demand in Long Island Sound T2 - Long Island Sound/NEERS Research Conference Y1 - 2002 A1 - Lugolobi, F. A1 - Varekamp, J. C. A1 - Thomas, E. JF - Long Island Sound/NEERS Research Conference CY - Groton, CT N1 - id: 730 ER - TY - JOUR T1 - Vapour undersaturation in primitive mid-ocean-ridge basalt and the volatile content of Earth's upper mantle JF - Nature Y1 - 2002 A1 - Saal, A. E. A1 - Hauri, E. H. A1 - Langmuir, C. H. A1 - Perfit, M. R. AB - The analysis of volatiles in magmatic systems can be used to constrain the volatile content of the Earth's mantle and the influence that magmatic degassing has on the chemistry of the oceans and the atmosphere. But most volatile elements have very low solubilities in magmas at atmospheric pressure, and therefore virtually all erupted lavas are degassed and do not retain their primary volatile signatures. Here we report the undersaturated pre-eruptive volatile content for a suite of mid-ocean-ridge basalts from the Siqueiros intra-transform spreading centre. The undersaturation leads to correlations between volatiles and refractory trace elements that provide new constraints on volatile abundances and their behaviour in the upper mantle. Our data generate improved limits on the abundances of carbon dioxide, water, fluorine, sulphur and chlorine in the source of normal mid-ocean-ridge basalt. The incompatible behaviour of carbon dioxide, together with the CO(2)/Nb and CO(2)/Cl ratios, permit estimates of primitive carbon dioxide and chlorine to be made for degassed and chlorine-contaminated mid-ocean-ridge basalt magmas, and hence constrain degassing and contamination histories of mid-ocean ridges. VL - 419 IS - 6906 N1 - Saal, Alberto EHauri, Erik HLangmuir, Charles HPerfit, Michael RengEngland2002/10/09 04:00Nature. 2002 Oct 3;419(6906):451-5. JO - Vapour undersaturation in primitive mid-ocean-ridge basalt and the volatile content of Earth's upper mantle ER - TY - JOUR T1 - Volcanic gases, black smokers, and the Great Oxidation Event JF - Geochimica Et Cosmochimica Acta Y1 - 2002 A1 - Holland, H. D. KW - atmospheric oxygen KW - carbon KW - chemistry KW - east pacific rise KW - evolution KW - hydrothermal vent fluids KW - midocean ridges KW - precambrian cherts KW - south-africa KW - sulfur cycle AB - This paper proposes that gradual changes in the composition of volatiles that have been added to the atmosphere-ocean system are responsible for the Great Oxidation Event (G.O.E.) ca. 2.3 Ga. Before ca. 2.3 Ga, the composition of these volatiles was probably such that 20% of the carbon gases could be reduced to organic matter and all of the sulfur gases could be reduced to pyrite. Since 2.3 Ga, the composition of these volatiles has been such that 20% of the carbon gases could be reduced to organic matter, but only a fraction of the sulfur gases could be reduced to pyrite. This change led to the oxygenation of the atmosphere and to a large increase in the SO4-2 concentration of seawater. A considerable body of observational data supports these proposals. Copyright (C) 2002 Elsevier Science Ltd. VL - 66 SN - 0016-7037 IS - 21 N1 - 608ztTimes Cited:295 Cited References Count:57 JO - Geochim Cosmochim Ac ER - TY - JOUR T1 - Were glacial iceberg surges in the North Atlantic triggered by global climatic warming? JF - Marine Geology Y1 - 2002 A1 - Moros, M. A1 - Kuijpers, A. A1 - Snowball, I. A1 - Lassen, S. A1 - Backstrom, D. A1 - Gingele, F. A1 - McManus, J. F. VL - 192 IS - 4 N1 - id: 712 ER - TY - JOUR T1 - The West Falmouth oil spill after thirty years: the persistence of petroleum hydrocarbons in marsh sediments JF - Environ Sci Technol Y1 - 2002 A1 - Reddy, C. M. A1 - Eglinton, T. I. A1 - Hounshell, A. A1 - White, H. K. A1 - Xu, L. A1 - Gaines, R. B. A1 - Frysinger, G. S. KW - *Accidents KW - Chromatography, Gas KW - Environmental Monitoring KW - Geologic Sediments/*chemistry KW - Hydrocarbons/*analysis KW - Massachusetts KW - Petroleum/*analysis KW - Ships KW - Time Factors KW - Water Pollutants, Chemical/*analysis AB - The long-term fate of petroleum hydrocarbons in marsh sediments (West Falmouth, MA) contaminated in 1969 by the spill of the barge Florida was investigated. A 36-cm-long sediment core was collected in August 2000, and sediment extracts were analyzed by gas chromatography (GC) and comprehensive two-dimensional gas chromatography (GC x GC). The latter technique is capable of separating 1 order of magnitude more compounds than the former and was used to observe whether any compositional changes in the unresolved complex mixture (UCM) occurred. No evidence of petroleum residues was detected in the top 6 cm (0-6 cm) and the lower 8 cm (28-36 cm) of the core. However, the central sections 16-28 cm) were dominated by a UCM in the boiling range of n-C13-n-C25 alkanes, consistent with a No. 2 fuel oil source. The 12-14- and 14-16-cm sections had the highest concentrations of UCM approximately 8 mg g(-1)). These values are similar to concentrations observed shortly after the spill. Initial GC x GC analysis revealed that only the n-alkanes were completely degraded, and contrary to previous studies, pristane and phytane as well as numerous other branched alkanes are still present in the sediments. These results suggestthatatthis site hydrocarbon contamination will persist indefinitely in the sedimentary record. VL - 36 SN - 0013-936X (Print)0013-936X (Linking) UR - https://www.ncbi.nlm.nih.gov/pubmed/12487296 IS - 22 N1 - Reddy, Christopher MEglinton, Timothy I Hounshell, Aubrey White, Helen K Xu, Li Gaines, Richard B Frysinger, Glenn S eng Research Support, Non-U.S. Gov't Research Support, U.S. Gov't, Non-P.H.S. 2002/12/19 04:00 Environ Sci Technol. 2002 Nov 15;36(22):4754-60. ER - TY - JOUR T1 - WOCE radiocarbon IV: Pacific Ocean results; P10, P13N, P14C, P18, P19 & S4P JF - Radiocarbon Y1 - 2002 A1 - Key, R. M. A1 - Quay, P. D. A1 - Schlosser, P. A1 - McNichol, A. P. A1 - von Reden, K. F. A1 - Schneider, R. J. A1 - Elder, K. L. A1 - Stuiver, M. A1 - Ostlund, H. G. AB - The World Ocean Circulation Experiment, carried out between 1990 and 1997, provided the most comprehensive oceanic survey of radiocarbon to date. Approximately 10,000 samples were collected in the Pacific Ocean by U.S. investigators for both conventional large volume P counting and small volume accelerator mass spectrometry analysis techniques. Results from six cruises are presented. The data quality is as good or better than previous large-scale surveys. The C-14 distribution for the entire WOCE Pacific data set is graphically described using mean vertical profiles and sections, and property-property plots. VL - 44 UR - https://journals.uair.arizona.edu/index.php/radiocarbon/article/view/4097 IS - 1 N1 - 591keTimes Cited:33Cited References Count:56 JO - WOCE radiocarbon IV: Pacific Ocean results; P10, P13N, P14C, P18, P19 & S4P ER - TY - CHAP T1 - Woodlands in ancient and modern times in the territory of Sagalassos T2 - Sagalassos VI. Report on the survey and excavation campaigns of 1998, 1999 and 2000 Y1 - 2002 A1 - Vermoere, M. A1 - Vanhecke, L. A1 - Paulissen, E. A1 - Waelkens, M. A1 - Smets, E. ED - Monographiae, Acta Archaeologica Lovaniensia JF - Sagalassos VI. Report on the survey and excavation campaigns of 1998, 1999 and 2000 PB - Leuven University Press VL - 14 N1 - id: 346 ER - TY - JOUR T1 - 14C-dead living biomass: evidence for microbial assimilation of ancient organic carbon during shale weathering JF - Science Y1 - 2001 A1 - Petsch, S. T. A1 - Eglington, T. I. A1 - Edwards, K. J. AB - Prokaryotes have been cultured from a modern weathering profile developed on a approximately 365-million-year-old black shale that use macromolecular shale organic matter as their sole organic carbon source. Using natural-abundance carbon-14 analysis of membrane lipids, we show that 74 to 94% of lipid carbon in these cultures derives from assimilation of carbon-14-free organic carbon from the shale. These results reveal that microorganisms enriched from shale weathering profiles are able to use a macromolecular and putatively refractory pool of ancient organic matter. This activity may facilitate the oxidation of sedimentary organic matter to inorganic carbon when sedimentary rocks are exposed by erosion. Thus, microorganisms may play a more active role in the geochemical carbon cycle than previously recognized, with profound implications for controls on the abundance of oxygen and carbon dioxide in Earth's atmosphere over geologic time. VL - 292 IS - 5519 N1 - Petsch, S TEglington, T IEdwards, K JengHistorical ArticleResearch Support, Non-U.S. Gov'tResearch Support, U.S. Gov't, Non-P.H.S.2001/04/03 10:00Science. 2001 May 11;292(5519):1127-31. Epub 2001 Mar 29. JO - 14C-dead living biomass: evidence for microbial assimilation of ancient organic carbon during shale weathering ER - TY - JOUR T1 - A 160,000-year record of tropical climate variability from Salar de Uyuni, Bolivia JF - EOS, Transactions, American Geophysical Union Y1 - 2001 A1 - Fritz, S. C. A1 - Baker, P. A. A1 - Dwyer, G. S. VL - 80 N1 - id: 1474 ER - TY - JOUR T1 - A 700 year sedimentary record of intense hurricane landfalls in southern New England JF - GSA Bulletin Y1 - 2001 A1 - Donnelly, Jeffrey P. A1 - Bryant, Sarah Smith A1 - Butler, Jessica A1 - Dowling, Jennifer A1 - Fan, Linda A1 - Hausmann, Neil A1 - Newby, Paige A1 - Shuman, Bryan A1 - Stern, Jennifer A1 - Westover, Karlyn A1 - Webb, Thompson, III VL - 113 N1 - id: 1343 ER - TY - BOOK T1 - Abrupt climate change and pre-Columbian cultural collapse T2 - Interhemispheric Climate Linkages Y1 - 2001 A1 - Brenner, M. A1 - Hodell, D. A. A1 - Curtis, J. H. A1 - Rosenmeier, M. A1 - Binford, M. W. A1 - Abbott, M. B. JF - Interhemispheric Climate Linkages PB - Academic Press N1 - id: 1408 ER - TY - JOUR T1 - Accumulation rates and sources of sediments and organic carbon on the Palos Verdes shelf based on multiple radioisotopic tracers (137Cs, 239,240Pu, 210Pb, 234Th, 238U and 14C) JF - Marine Chemistry Y1 - 2001 A1 - Santschi, P. H. A1 - Guo, L. A1 - Asbill, S. A1 - Allison, M. A1 - Kepple, B. A1 - Wen, L. S. AB - We report here bioturbation and sediment accumulation rates determined from replicate sediment cores at four different sampling sites on the Palos Verdes shelf, Southern California, using bomb fallout and natural radionuclides (137Cs, 239,240Pu, 210Pb, 234Th, and 14C), along with supporting measurements of organic carbon (OC), porosity and granulometry. Present-day particle reworking, on time scales of several months, is restricted to the upper 3 cm, with rates ranging from 13 to 200 cm2/year, as deduced from 234Thxs profiles. There is little evidence that particle reworking reached depths significantly greater than 5 cm. Post-1963 (or post-1971) sediment accumulation rates ranged from 0.7 to 1.4 g/cm2/year (equivalent to 1.1–1.8 cm/year for surficial sediments), as calculated from Pu and Cs isotope profiles, with little change over time or distance from the outfall. Lateral transport of older sediment and multiple sediment sources on the Palos Verdes shelf is suggested from radiocarbon measurements on foraminifera and bulk sedimentary organic matter at two sampling sites, which showed variable, old and refractory sources of OC. Pre-1953 sediments accumulated at rates that were at least 0.4 g/cm2/year (≥0.3 cm/year), based on 210Pbxs dating. Given the abundance of sediment sources to the Palos Verdes shelf, the high sedimentation rates, and shallow particle mixed layers, contaminant-enriched layers should continue to move deeper into the sediments. VL - 73 IS - 2 N1 - id: 1309 JO - Accumulation rates and sources of sediments and organic carbon on the Palos Verdes shelf based on multiple radioisotopic tracers (137Cs, 239,240Pu, 210Pb, 234Th, 238U and 14C) ER - TY - JOUR T1 - Across forests and savannas: Later Stone Age assemblages from Ituri and Semliki, Northeast Domacratic Republic of Congo JF - Journal of Antropological Research Y1 - 2001 A1 - Mercader, J. A1 - Brooks, A. VL - 57 IS - 2 N1 - id: 1217 ER - TY - JOUR T1 - Algal and archaeal polyisoprenoids in a recent marine sediment: Molecular isotopic evidence for anaerobic oxidation of methane JF - Geochemistry Geophysics Geosystems Y1 - 2001 A1 - Bian, L. Q. A1 - Hinrichs, K. U. A1 - Xie, T. M. A1 - Brassell, S. C. A1 - Iversen, H. A1 - Fossing, H. A1 - Jorgensen, B. B. A1 - Hayes, J. M. AB - Analyses of C-13 contents of individual organic molecules in a marine sediment show that crocetane, 2,6,11,15-tetramethylhexadecane, an isomer of phytane, is produced by microorganisms that use methane as their main source of carbon. The sediments lie at a water depth of 68 m in the Kattegat, the strait between Denmark and Sweden. Crocetane appears first 185 cm below the sediment-water interface, in the zone marking the transition from sulfate reduction to methanogenesis. Its delta C-13 value is -90 +/- 10 parts per thousand versus Vienna Pee Dee Belemnite (VPDB). Its structure, which includes four isoprene units arranged symmetrically around a tail-to-tail linkage, suggests that it is produced by a member of the archaea. Growing at the intersection of the diffusion gradients for sulfate and methane in sedimentary pore waters, the source organism apparently function as a methane-consuming member of the microbial consortium responsible for the anaerobic oxidation of methane [Hoehler et al., 1994], in which, as first demonstrated quantitatively in these sediments [Iversen and Jorgensen, 1985], electrons are transferred from methane to sulfate. The presence of archaeal biomass throughout the sediment section is indicated by significant concentrations of 2,6,10,15,19-pentamethylicosane (PMI) and of ether-bound phytane and biphytane. The PMI reaches a minimum delta value of -47 parts per thousand well below the transition zone. Its isotopic depletion could reflect either methanogenic or methanotrophic sources. The ether-bound lipids are isotopically uniform throughout the section and are presumed to derive from archaea that utilize a carbon source unaffected by the oxidation of methane. VL - 2 IS - 2000GC000112 N1 - 458jvTimes Cited:51Cited References Count:79 JO - Algal and archaeal polyisoprenoids in a recent marine sediment: Molecular isotopic evidence for anaerobic oxidation of methane ER - TY - JOUR T1 - Amino acid composition and diagenesis in the shells of terebratulid brachiopod Bouchardia rosea (SW Atlantic) JF - Geological Society of America Abstracts with Programs Y1 - 2001 A1 - Carroll, M. A1 - Kowalewski, M. A1 - Simeos, M. G. A1 - Goodfriend, G. A. VL - 33 IS - A10 N1 - id: 1417 ER - TY - JOUR T1 - AMS radiocarbon dating of a shell fishhook from Santa Rosa Island, California JF - Radiocarbon Y1 - 2001 A1 - Rick, T. C. AB - Several single-piece shell fishhooks from CA-SRI-43 on Santa Rosa Island were dated by association to roughly 5500 cal BP and were argued to be among the oldest specimens in the region. Direct accelerator mass spectrometry (AMS) radiocarbon dating of one of these hooks provided a date of 560 cal BP, however, making it about 5000 yr younger than originally presumed. This younger date is more consistent with the regional shell fishhook chronology and demonstrates the importance of obtaining direct AMS C-14 dates to refine artifact and site chronologies. VL - 43 SN - 0033-8222 IS - 1 N1 - 458qxTimes Cited:7 Cited References Count:18 JO - Radiocarbon ER - TY - CONF T1 - The Beadmaker Site: A plains village site at Heart Butte Reservoir, North Dakota T2 - 2001 Fall meeting of the North Dakota Archeological Association Y1 - 2001 A1 - Jackson, Michael L. JF - 2001 Fall meeting of the North Dakota Archeological Association CY - Bismarck, ND N1 - id: 297 ER - TY - JOUR T1 - Benthic remineralization and burial of biogenic SiO2, CaCO3, organic carbon, and detrital material in the Southern Ocean along a transect at 170oW JF - Deep-Sea Res. Y1 - 2001 A1 - Sayles, F. L. A1 - Martin, W. R. A1 - Chase, Z. A1 - Anderson, R. F. VL - Part-II IS - 48 N1 - id: 276 ER - TY - CONF T1 - Biogenic silica and organic carbon in sediments from the Pacific Sector of the Southern Ocean T2 - Antarctic Earth Sciences at the close of a Millenium: Proceedings 8th International Symposium on Artarctic Earth Sciences Y1 - 2001 A1 - Giglio, F. A1 - Langone, L. A1 - Morigi, C. A1 - Frignani, M. A1 - Ravaioli, M. ED - Gamble, J. A. JF - Antarctic Earth Sciences at the close of a Millenium: Proceedings 8th International Symposium on Artarctic Earth Sciences PB - Royal Society of New Zealand Bulletin VL - 8th N1 - id: 284 ER - TY - CONF T1 - Bomb 14C versus anthropogenic CO2 in OCMIP ocean biogeochemical models T2 - Global Change Open Science Conference Y1 - 2001 A1 - Matsumoto, K. A1 - Sarmiento, J. L. A1 - Key, R. M. A1 - Slater, R. D. A1 - Sabine, C. L. JF - Global Change Open Science Conference CY - Amsterdam, the Netherlands N1 - id: 1446 ER - TY - CONF T1 - Brachiopod shell taphonomy in subtropical siliciclastic environments: preliminary field results T2 - Reuniao Anal de Sociedade Brasileira de Paleontologia, Paleo-2001 Y1 - 2001 A1 - Simoes, M. G. A1 - Kowalewski, M. A1 - Carroll, M. A1 - Rodland, D. L. A1 - Mello, L. H. C. JF - Reuniao Anal de Sociedade Brasileira de Paleontologia, Paleo-2001 PB - Boletim de Resumos CY - Rio Claro, SP N1 - id: 281 ER - TY - RPRT T1 - A budget of Holocene carbonate sediments, Kailua Bay, Oahu, Hawaiian Islands Y1 - 2001 A1 - Harney, Jodi N. A1 - Fletcher, Charles H. PB - University of Hawaii CY - Honolulu, HI N1 - id: 329 ER - TY - JOUR T1 - Carbon dioxide cycling and implications for climate on ancient Earth JF - Journal of Geophysical Research-Planets Y1 - 2001 A1 - Sleep, N. H. A1 - Zahnle, K. AB - The crustal Urey cycle of CO2 involving silicate weathering and metamorphism acts as a dynamic climate buffer. In this cycle, warmer temperatures speed silicate weathering and carbonate formation, reducing atmospheric CO2 and thereby inducing global cooling. Over long periods of time, cycling of CO2 into and out of the mantle also dynamically buffers CO2. In the mantle cycle, CO2 is outgassed at ridge axes and island arcs, while subduction of carbonatized oceanic basalt and pelagic sediments returns CO2 to the mantle. Negative feedback is provided because the amount of basalt carbonatization depends on CO2 in seawater and therefore on CO2 in the air. On the early Earth, processes involving tectonics were more vigorous than at present, and the dynamic mantle buffer dominated over the crustal one. The mantle cycle would have maintained atmospheric and oceanic CO2 reservoirs at levels where the climate was cold in the Archean unless another greenhouse gas was important. Reaction of CO2 with impact ejecta and its eventual subduction produce even lower levels of atmospheric CO2 and small crustal carbonate reservoirs in the Hadean. Despite its name, the Hadean climate would have been freezing unless tempered by other greenhouse gases. VL - 106 IS - E1 N1 - 395tjTimes Cited:185Cited References Count:101 JO - Carbon dioxide cycling and implications for climate on ancient Earth ER - TY - JOUR T1 - Carbon isotope geochemistry of the Santa Clara River JF - Global Biogeochemical Cycles Y1 - 2001 A1 - Masiello, C. A. A1 - Druffel, E. R. M. AB - The Santa Clara River is a prototypical small mountainous river, with a headwater height greater than 1000 m and a basin area smaller than 10,000 m(2). Although individual small mountainous rivers export trivial amounts of sediment and carbon to the ocean, as a group these rivers may export a major fraction las much as 50%) of the total global river sediment flux [Milliman and Syvitski, 1992], making their geochemistry relevant the study of the ocean's carbon cycle. In addition, many small rivers export sediment in a few high flux events, causing massive, sporadic discharge of carbon onto coastal shelves, discharge conditions very different from those of large rivers. This class of rivers is an end-member of the river-ocean carbon exchange system, opposite the Earth's largest river, the Amazon. The carbon mass and isotopic properties of the Santa Clara River are significantly different from previously studied large rivers. During the 1997-1998 winter, all Santa Clara carbon pools were old, with flux-weighted average Delta (14)C values of -428 +/- 76 parts per thousand for particulate organic carbon, -73 +/- 31 parts per thousand for dissolved organic carbon, and -644 +/- 58 parts per thousand for black carbon. The age of exported carbon is primarily due to the deep erosion of old soils and not to inclusion of fossil fuel carbon. Additionally, the delta (13)C signatures of exported carbon pools were high relative to terrestrial carbon, bearing a signature quite similar to marine carbon (average particulate organic carbon (POC) delta (13)C = -22.2 +/- 0.8 parts per thousand). The Santa Clara's estuary is small and drains onto the narrow eastern Pacific coastal margin, exporting this old soil organic matter directly into the ocean. If the Santa Clara export patterns are representative of this class of rivers, they may be a significant source of refractory terrestrial carbon to the ocean. VL - 15 IS - 2 N1 - 441mbTimes Cited:116Cited References Count:34 JO - Carbon isotope geochemistry of the Santa Clara River ER - TY - JOUR T1 - Carbon Isotope Ratios of Organic Compound Fractions Separated From Sinking Particulate Organic Matter at a Deep Sea Station in the Northeast Pacific JF - EOS Y1 - 2001 A1 - Druffel, E. R. A1 - Grottoli, A. G. A1 - Gille, S. T. A1 - Dunbar, R. B. N1 - id: 256 ER - TY - JOUR T1 - Carbonate 14C Background: Does it have Multiple Personalities? JF - Radiocarbon Y1 - 2001 A1 - Nadeau, Marie-Josee A1 - Grootes, Pieter M. A1 - Voelker, Antje A1 - Bruhn, Frank A1 - Duhr, Alexander A1 - Oriwall, Angelika VL - 43 IS - 2A N1 - id: 1501 ER - TY - JOUR T1 - Chronology of the Palmer Deep Site, Antarctic Peninsula: A Holocene Paleoenvironmental reference for the circum-Antarctic JF - The Holocene Y1 - 2001 A1 - Domack, E. W. A1 - Leventer, A. A1 - Dunbar, R. A1 - Taylory, R. A1 - Brachfeld, S. A1 - Sjunneskog, C. VL - 11 IS - 1 N1 - id: 119 ER - TY - JOUR T1 - Chronology of the Palmer Deep Site, Antarctic Peninsula: A Holocene Paleoenvironmental reference for the circum-Antarctic JF - The Holocene Y1 - 2001 A1 - Domack, E. W. A1 - Leventer, A. A1 - Dunbar, R. A1 - Taylor, R. A1 - Brachfeld, S. A1 - Sjunneskog, C. AB - Palmer Deep sediment cores are used to produce the first high-resolution, continuous late Pleistocene to Holocene time-series from the Antarctic marine system. The sedimentary record is dated using accelerator mass spectrometer radiocarbon methods on acid insoluble organic matter and foraminiferal calcite. Fifty-four radiocarbon analyses are utilized in the dating which provides a calibrated timescale back to 13 ka BP. Reliability of resultant ages on organic matter is assured because duplicates produce a standard deviation from the surface age of less than laboratory error (i.e., ±50 years). In addition, surface organic matter ages at the site are in excellent agreement with living calcite ages at the accepted reservoir age of 1260 years for the Antarctic Peninsula. Spectral analyses of the magnetic susceptibility record against the age model reveal unusually strong periodicity in the 400,–200 and 50-70 year frequency bands, similar to other high-resolution records from the Holocene but, so far, unique for the circum-Antarctic. Here we show that comparison to icecore records of specific climatic events (e.g., the ’Little Ice Age‘, Neoglacial, Hypsithermal, and the Bølling/Allerød to Younger Dryas transition) provides improved focus upon the relative timing of atmosphere/ocean changes between the northern anid southern high latitudes. N1 - id: 1319 JO - Chronology of the Palmer Deep Site, Antarctic Peninsula: A Holocene Paleoenvironmental reference for the circum-Antarctic ER - TY - CHAP T1 - Climate change in the circum-Caribbean (late Pleistocene-to-Present) and implications for regional biogeography T2 - Biogeography of the West Indies: Patterns and Perspectives, 2nd Edition Y1 - 2001 A1 - Curtis, J. H. A1 - Brenner, M. A1 - Hodell, D. A. ED - Woods, C. A. JF - Biogeography of the West Indies: Patterns and Perspectives, 2nd Edition PB - CRC Press CY - Boca Raton, FL N1 - id: 265 ER - TY - JOUR T1 - Climatic significance of large lakes on the Altiplano of South America JF - EOS, Transactions, American Geophysical Union Y1 - 2001 A1 - Baker, P. A. A1 - Seltzer, G. O. A1 - Fritz, S. C. A1 - Rigsby, C. A. A1 - Dwyer, G. S. VL - 82 N1 - id: 333 JO - Climatic significance of large lakes on the Altiplano of South America ER - TY - JOUR T1 - Comparative analysis of methane-oxidizing archaea and sulfate-reducing bacteria in anoxic marine sediments JF - Appl Environ Microbiol Y1 - 2001 A1 - Orphan, V. J. A1 - Hinrichs, K. U. A1 - Ussler, W. A1 - Paull, C. K. A1 - Taylor, L. T. A1 - Sylva, S. P. A1 - Hayes, J. M. A1 - DeLong, E. F. AB - The oxidation of methane in anoxic marine sediments is thought to be mediated by a consortium of methane-consuming archaea and sulfate-reducing bacteria. In this study, we compared results of rRNA gene (rDNA) surveys and lipid analyses of archaea and bacteria associated with methane seep sediments from several different sites on the Californian continental margin. Two distinct archaeal lineages (ANME-1 and ANME-2), peripherally related to the order Methanosarcinales, were consistently associated with methane seep marine sediments. The same sediments contained abundant (13)C-depleted archaeal lipids, indicating that one or both of these archaeal groups are members of anaerobic methane-oxidizing consortia. (13)C-depleted lipids and the signature 16S rDNAs for these archaeal groups were absent in nearby control sediments. Concurrent surveys of bacterial rDNAs revealed a predominance of delta-proteobacteria, in particular, close relatives of Desulfosarcina variabilis. Biomarker analyses of the same sediments showed bacterial fatty acids with strong (13)C depletion that are likely products of these sulfate-reducing bacteria. Consistent with these observations, whole-cell fluorescent in situ hybridization revealed aggregations of ANME-2 archaea and sulfate-reducing Desulfosarcina and Desulfococcus species. Additionally, the presence of abundant (13)C-depleted ether lipids, presumed to be of bacterial origin but unrelated to ether lipids of members of the order Desulfosarcinales, suggests the participation of additional bacterial groups in the methane-oxidizing process. Although the Desulfosarcinales and ANME-2 consortia appear to participate in the anaerobic oxidation of methane in marine sediments, our data suggest that other bacteria and archaea are also involved in methane oxidation in these environments. VL - 67 IS - 4 N1 - Orphan, V JHinrichs, K UUssler, W 3rdPaull, C KTaylor, L TSylva, S PHayes, J MDelong, E FengComparative StudyResearch Support, Non-U.S. Gov'tResearch Support, U.S. Gov't, Non-P.H.S.2001/04/03 10:00Appl Environ Microbiol. 2001 Apr;67(4):1922-34. U2 - PMC92814 JO - Comparative analysis of methane-oxidizing archaea and sulfate-reducing bacteria in anoxic marine sediments ER - TY - JOUR T1 - Composition of hydrothermal vent microbial communities as revealed by analyses of signature lipids, stable carbon isotopes, and Aquificales cultures JF - Applied and Environmental Microbiology Y1 - 2001 A1 - Jahnke, Linda L. A1 - Eder, Wolfgang A1 - Huber, Robert A1 - Hope, Janet M. A1 - Hinrichs, Kai-Uwe A1 - Hayes, John M. A1 - Des Marais, David J. A1 - Cady, Sherry L. A1 - Summons, Roger E. VL - 67 N1 - id: 1783 ER - TY - JOUR T1 - Compound-specific D/H ratios of lipid biomarkers from sediments as a proxy for environmental and climatic conditions JF - Geochimica Et Cosmochimica Acta Y1 - 2001 A1 - Sauer, P. E. A1 - Eglinton, T. I. A1 - Hayes, J. M. A1 - Schimmelmann, A. A1 - Sessions, A. L. AB - Hydrogen isotope ratios (D/H) of lipid biomarkers extracted from aquatic sediments were measured to determine whether they can be used as a proxy for D/H of environmental water. Values of deltaD were determined by using a recently developed isotope-ratio-monitoring gas chromatograph-mass spectrometer system (irmGCMS) and were confirmed by conventional hydrogen isotopic measurements (i.e., combustion followed by reduction) on individual compounds isolated by preparative capillary gas chromatography. Diverse lipids (alkanes, n-alkanols, sterols, and pentacyclic triterpenols) were analyzed to examine hydrogen-isotopic controls on lipids of varying origin and biosynthetic pathway. For algal sterols (24-methylcholest-3 beta -ol, 24-ethylcholest-5,22-dien-3 beta -ol, and 4,23,24-trimethylcholesterol, or dinosterol), the fractionation between sedimentary lipids and environmental water was -201 +/- 10 parts per thousand and was similar in both marine and freshwater sites. In a sediment from a small lake in a forested catchment, triterpenols from terrestrial sources were enriched in D by 30 parts per thousand relative to algal sterols. Apparent fractionation factors for n-alkyl lipids were smaller than those of triterpenols and were more variable, probably reflecting multiple sources for these compounds. We conclude that hydrogen-isotopic analyses of algal sterols provide a viable means of reconstructing D/H of environmental waters. Results are less ambiguous than reconstructions based on analyses of kerogen or other operationally defined organic matter fractions. Copyright (C) 2001 Elsevier Science Ltd. VL - 65 IS - 2 N1 - 395npTimes Cited:209Cited References Count:64 JO - Compound-specific D/H ratios of lipid biomarkers from sediments as a proxy for environmental and climatic conditions ER - TY - JOUR T1 - Contribution of "old" carbon from natural marine hydrocarbon seeps to sedimentary and dissolved organic carbon pools in the Gulf of Mexico JF - Geophysical Research Letters Y1 - 2001 A1 - Wang, X. C. A1 - Chen, R. F. A1 - Whelan, J. A1 - Eglinton, L. AB - Natural radiocarbon (C-14) abundances and stable carbon isotope (delta C-13) compositions were measured for sediment total organic carbon (TOC), and total lipid fractions of sediments, bottom water, and hydrate-water collected from two hydrocarbon seepage sites in Green Canyon, Northern Gulf of Mexico to determine the contribution of "old" carbon from seeps to sediment TOC and dissolved organic carbon (DOC) pools. Our results indicate that 40-60% of the organic carbon preserved in the sediments and 30% of the DOC in the deep water above the seeps were seep-derived C-14-depleted organic carbon. This new evidence along with our previous studies suggest that natural marine hydrocarbon seepage could be a significant source contributing "old" carbon to the marine environment. Our findings suggest that the global importance and the long-term impact of this contribution to biogeochemical carbon cycling in the ocean need to be more thoroughly investigated. VL - 28 IS - 17 N1 - 467jmTimes Cited:20Cited References Count:25 JO - Contribution of "old" carbon from natural marine hydrocarbon seeps to sedimentary and dissolved organic carbon pools in the Gulf of Mexico ER - TY - JOUR T1 - Converting AMS data to radiocarbon values: Considerations and conventions JF - Radiocarbon Y1 - 2001 A1 - McNichol, A. P. A1 - Jull, A. J. T. A1 - Burr, G. S. KW - accelerator mass-spectrometry KW - NOSAMS KW - ratio AB - We summarize the basic operation of accelerator mass spectrometry (AMS) systems used to measure radiocarbon and discuss the calculations used to convert AMS output to C-14 data. VL - 43 SN - 0033-8222 IS - 2a N1 - 1531yc Times Cited:24 Cited References Count:19 JO - Radiocarbon ER - TY - JOUR T1 - Correction of H3+ contributions in hydrogen isotope ratio monitoring mass spectrometry JF - Anal Chem Y1 - 2001 A1 - Sessions, A. L. A1 - Burgoyne, T. W. A1 - Hayes, J. M. AB - Two fundamentally different approaches, termed "pointwise" and "peakwise," are currently used to correct hydrogen isotope ratio monitoring data for the presence of H3+ ion contributions. Consideration of the underlying assumptions shows that the peakwise approach is valid only for peaks with the same functional shape and only when background signals do not vary. The pointwise correction is much more versatile and can be used even when peak shapes and sizes, as well as background signals, vary significantly. It is not exact and is limited in accuracy by (1) the signal-broadening effects of electronic time constants, (2) the analog-to-digital conversion frequency, and (3) the highest frequency of the sample signal. To minimize errors for typical gas chromatographic signals, time constants of <500 ms and analog-to-digital sampling intervals of < or =250 ms are needed. Errors are further minimized by matching sample and standard peaks in both amplitude and D/H ratio. Using the pointwise algorithm, we demonstrate that a series of 14 homologous n-alkanes varying in concentration over a 5-fold range can be analyzed with a mean precision of 2.3 per thousand and no systematic errors. VL - 73 SN - 0003-2700 (Print)0003-2700 (Linking) UR - https://www.ncbi.nlm.nih.gov/pubmed/11199965 IS - 2 N1 - Sessions, A LBurgoyne, T W Hayes, J M eng 2001/02/24 12:00 Anal Chem. 2001 Jan 15;73(2):192-9. ER - TY - CONF T1 - On the d13C:PO4 relationahip in the modern and glacial ocean T2 - Fall AGU Meeting Y1 - 2001 A1 - Toggweiler, J. R. A1 - Key, R. M. A1 - McNeil, B. JF - Fall AGU Meeting CY - San Francisco, CA N1 - id: 1447 ER - TY - JOUR T1 - Dating modern deltas: progress, problems and prognostics JF - Annual Review of Earth and Atmospheric Sciences Y1 - 2001 A1 - Stanley, D. J. AB - Radiocarbon dating is the method most frequently used to date Holocene deltaic sequences, but less than one quarter of 14C dates are within ±500 years of predicted age. Such dates tend to be unreliable, in other words, often too old and commonly inverted upsection, and core sample dates obtained near deltaic plain surfaces may be as old as mid- to late Holocene. Stratigraphic irregularities result primarily from downslope reworking of upland alluvial sediment, with displacement of “old carbon” in the sediment that accumulates in lower valleys and deltaic plains. Use of dates that are too old results in inaccurately calculated rates (most often too low) of relative sea-level rise and/or land subsidence. More reliable timing of deltaic sediment requires a multiple-method dating approach, including, where possible, identification of associated archaeological material. Developing an accurate dating strategy is a critical step for implementing reliable coastal protection measures needed for the rapidly increasing human populations in these low-lying, vulnerable nearshore settings. VL - 28 N1 - id: 1378 JO - Dating modern deltas: progress, problems and prognostics ER - TY - JOUR T1 - Decadal record of climate variability spanning the last 700 years in the southern tropics of East Africa JF - Geology Y1 - 2001 A1 - Johnson, T. C. A1 - Barry, S. L. A1 - Chan, Y. A1 - Wilkinson, P. VL - 29 N1 - id: 1477 ER - TY - CHAP T1 - The deglaciation of eastern Maine: in Deglacial history and relative sea-level changes, northern New England and adjacent Canada T2 - Deglacial history and relative sea-level changes, northern New England and adjacent Canada Y1 - 2001 A1 - Dorion, C. C. A1 - Kaplan, M. R. A1 - Kreutz, K. J. A1 - Balco, G. A1 - Wright, J. A1 - Borns, H. W., Jr. ED - Weddle, T. K. JF - Deglacial history and relative sea-level changes, northern New England and adjacent Canada T3 - Special papers (Geological Society of America) PB - Geological Society of America SN - 0813723515 N1 - id: 1310 ER - TY - CONF T1 - Deposition of Bomb C-14 in Continental Slope Sediments: Use of Radiocarbon in Understanding Benthic Food Web Dynamics T2 - Aquatic Sciences Meeting, ASLO Y1 - 2001 A1 - DeMaster, D. J. A1 - Blair, N. E. A1 - Smith, C. R. A1 - Fornes, W. L. A1 - Thomas, C. J. A1 - Plaia, G. JF - Aquatic Sciences Meeting, ASLO CY - Albuquerque, NM N1 - id: 1368 ER - TY - JOUR T1 - Determination of the the H3 factor in hydrogen isotope ratio monitoring mass spectrometry JF - Anal Chem Y1 - 2001 A1 - Sessions, A. L. A1 - Burgoyne, T. W. A1 - Hayes, J. M. AB - The H3 factor, K, is a parameter required in high-precision, mass spectrometric analyses of hydrogen isotopic abundances. When H2 is used as the sample gas, R* = R - Ki2, where R* is the true HD/H2 ratio, R is the observed (mass 3)/(mass 2) ion-current ratio, and i2 is the ion current at mass 2. Four different methods for the determination of K were defined and tested under conditions characteristic of isotope ratio monitoring systems. Three of these were peak-based. The fourth employed steady flows of H2 from a conventional inlet system. Results obtained using the latter method were more precise (standard deviation of K = 0.1 versus approximately 0.6 ppm mV(-1) for the peak-based methods). However, use of the resulting values of K for correction of isotope ratio monitoring GC/MS results led to systematic errors as large as 9 per thousand, whereas use of the peak-based values led to no systematic errors. Values of K were only weakly dependent on the pressure of He, declining approximately 5% for each 10-fold increase in P(He). Small variations in partial pressures of H2O and CH4, potential contaminants under isotope ratio monitoring conditions, had no significant effect on values of K. VL - 73 SN - 0003-2700 (Print)0003-2700 (Linking) UR - https://www.ncbi.nlm.nih.gov/pubmed/11199966 IS - 2 N1 - Sessions, A LBurgoyne, T W Hayes, J M eng 2001/02/24 12:00 Anal Chem. 2001 Jan 15;73(2):200-7. ER - TY - JOUR T1 - Development of a Carbon Isotope-Based Tracer of Groundwater Fluxes into Estuaries and the Coastal Ocean JF - EOS Y1 - 2001 A1 - McCorkle, D. C. A1 - Gramling, C. M. A1 - Mulligan, A. E. A1 - Woods, T. L. VL - 82 IS - 20 N1 - id: 1409 ER - TY - JOUR T1 - Diastems and time-averaging: The limits of resolution in stratigraphy and paleontology JF - Geological Society of America Abstracts with Programs Y1 - 2001 A1 - Kowalewski, M. A1 - Bambach, R. K. VL - 33 IS - A32 N1 - id: 282 JO - Diastems and time-averaging: The limits of resolution in stratigraphy and paleontology ER - TY - JOUR T1 - Drainage of late Wisconsin glacial lakes and the morphology and late quaternary stratigraphy of the New Jersey-southern New England continental shelf and slope JF - Marine Geology Y1 - 2001 A1 - Uchupi, E. A1 - Driscoll, N. A1 - Ballard, R. D. A1 - Bolmer, S. T. AB - We propose that late Wisconsin deposition and erosion (Hudson Shelf and Block Island valleys) on the shelf and slope from New Jersey to southern New England were a consequence of the catastrophic drainage of glacial lakes behind terminal moraine systems and the huge volume of water stored beneath the Laurentian ice sheet and subsequent erosion of the lake sediments by flash floods. The morphology imparted by glaciation regulated the discharge associated with the ablation of the glaciers. Associated with the deposits west of Hudson Shelf Valley are the remains of mammoth and mastodon which were transported from their living habitats along the lake shores to their present burial sites on the shelf. The floods also triggered gravity flows on the upper continental slope which made possible the transportation of coarse debris over hundreds of km into the deep-sea. That these catastrophic hood morphologies can still be recognized on the middle to outer shelf suggest that much of its surface was little modified during the late Pleistocene/Holocene transgression. Thus the late Pleistocene/Holocene transgression may have been characterized by short periods when sea level rose rapidly allowing for the preservation of relict features. (C) 2001 Elsevier Science B.V. All rights reserved. VL - 172 IS - 1-2 N1 - 400trTimes Cited:50Cited References Count:115 JO - Drainage of late Wisconsin glacial lakes and the morphology and late quaternary stratigraphy of the New Jersey-southern New England continental shelf and slope ER - TY - CONF T1 - The Effect of Different Acid Treatments on the Radiocarbon Age of Sedimentary Organic Matter T2 - EOS, Transactions, American Geophysical Union Y1 - 2001 A1 - Batista, F A1 - McNichol, A P A1 - Gerlach, D S KW - A, Atlantic KW - Acidification KW - Brackish KW - Brackishwater environment KW - carbon cycling KW - Chronostratigraphy KW - Estuarine sedimentation KW - organic carbon KW - organic matter KW - Palaeoceanography KW - Radioactivity and radioisotopes KW - Radiocarbon dating KW - Sediment chemistry KW - Stable isotopes AB - To date the bulk organic carbon in marine sediments it is necessary to first remove any inorganic carbon present by acidification. We tested three different acid treatments to see how the different methods affected the stable and radio-carbon isotopic values of the remaining organic matter. The standard NOSAMS method is to react the sediment with repeated aliquots of1.2N HCl until no visible dissolution reaction is present. The remaining sediment is then rinsed with distilled water. This method leaves a carbonate-free sediment that is easy to combust but suffers from the possible removal of acid-soluble organic matter. We compared this method to two methods that do not require rinsing of the sediments after acid treatment--a vapor phase acidification method using concentrated HCl (Hedges and Stern, 1984) and an in situ acidification with sulfurous acid (Verardo et al., 1990). Scaling these methods up to deal with the amount of sediment required for a radiocarbon date can present challenges that are not evident when dealing with the small quantities required for a percent organic carbon measurement. Vapor phase acidification of high carbonate sediments leaves hygroscopic salts that can impede sample combustion. Sulfurous acid is a weak acid and it is very difficult to determine when all the carbonate has been removed from a sediment sample. We tested sediments from 6 locations in (or near) the Atlantic Ocean that represented riverine, estuarine, and marine environments as well as a range of both organic and inorganic concentrations. We will present the isotopic results for these sediments and evaluate what is the most appropriate method to use. Hedges J.I. and J.H. Stern (1984) Limnol. Oceanogr. 29, 657-663. Verardo D.J., P.N. Froelich and A. McIntyre (1990) Deep-Sea Res. 37, 157-165. JF - EOS, Transactions, American Geophysical Union PB - American Geophysical Union, 2000 Florida Ave., N.W. Washington DC 20009 USA, [mailto:service@agu.org] UR - https://search.proquest.com/docview/19468089?accountid=29119 N1 - Date revised - 2007-02-01SuppNotes - Session: OS41A 9 The Truth About Paleoceanographic Proxies - What Are They Really Telling Us III Posters.Last updated - 2016-05-27 ER - TY - JOUR T1 - Effects of biosynthesis and physiology on relative abundances and isotopic compositions of alkenones JF - Geochemistry Geophysics Geosystems Y1 - 2001 A1 - Gonzalez, E. L. A1 - Riebesell, U. A1 - Hayes, J. M. A1 - Laws, E. A. KW - algae KW - alkenones KW - anhydrase KW - biogeochemical processes KW - biosynthesis KW - calcification KW - carbon-13 KW - emiliania-huxleyi prymnesiophyceae KW - fractionation KW - Haptophytes KW - inorganic carbon utilization KW - instruments and techniques KW - isoprenoid biosynthesis KW - marine diatom KW - paleoceanography KW - photosynthesis KW - physiology KW - phytoplankton KW - sea surface temperature AB - The number of double bonds in long-chain, unsaturated ketones (alkenones) produced by some members of the Haptophyceae is correlated with the ambient temperature at the time of synthesis. For these same organisms the depletion of carbon-13 in biosynthetic products relative to dissolved inorganic carbon is related directly to the specific growth rate and inversely to the concentration of dissolved carbon dioxide. This report summarizes issues relating to the physiology, metabolism, and biochemistry of alkenone producers and how they affect the abundances and isotopic compositions of alkenones. These considerations show that an understanding of cellular responses to parameters governing uptake of inorganic carbon (C-i), isotopic fractionation, growth under diverse nutrient conditions, and genetic variability, both in the field and in culture, is necessary for developing a conceptual understanding of the biological significance of the epsilonp and U-37(K') indices. Emiliana huxleyi is the best known alkenone producer and can serve as a model organism for these studies. This report identifies knowledge gaps and appropriate objectives for both field- and laboratory-based research. VL - 2 SN - 1525-2027 IS - Working Group Report, Workshop on Alkenone-Based Paleoceanographic Indicators, 2000GC000052 N1 - 458kdTimes Cited:6 Cited References Count:39 JO - Geochem Geophy Geosy ER - TY - JOUR T1 - Estimates of anthropogenic carbon uptake from four three-dimensional global ocean models JF - Global Biogeochemical Cycles Y1 - 2001 A1 - Orr, J. C. A1 - Maier-Reimer, E. A1 - Mikolajewicz, U. A1 - Monfray, P. A1 - Sarmiento, J. L. A1 - Toggweiler, J. R. A1 - Taylor, N. K. A1 - Palmer, J. A1 - Gruber, N. A1 - Sabine, C. L. A1 - Le Quere, C. A1 - Key, R. M. A1 - Boutin, J. AB - We have compared simulations of anthropogenic CO2 in the four three-dimensional ocean models that participated in the first phase of the Ocean Carbon-Cycle Model Intercomparison Project (OCMIP), as a means to identify their major differences. Simulated global uptake agrees to within +/- 19%, giving a range of 1.85 +/-0.35 Pg C yr(-1) for the 1980-1989 average, Regionally, the Southern Ocean dominates the present-day air-sea flux of anthropogenic CO2 in all models, with one third to one half of the global uptake occurring south of 30 degreesS. The highest simulated total uptake in the Southern Ocean was 70% larger than the lowest. Comparison with recent data-based estimates of anthropogenic CO2 suggest that most of the models substantially overestimate storage in the Southern Ocean; elsewhere they generally underestimate storage by less than 20%. Globally, the OCMIP models appear to bracket the real ocean's present uptake, based on comparison of regional data-based estimates of anthropogenic CO2 and bomb C-14. Column inventories of bomb C-14 have become more similar to those for anthropogenic CO2 with the time that has elapsed between the Geochemical Ocean Sections Study (1970s) and World Ocean Circulation Experiment (1990s) global sampling campaigns. Our ability to evaluate simulated anthropogenic CO2 would improve if systematic errors associated with the data-based estimates could be provided regionally. VL - 15 IS - 1 N1 - 417rwTimes Cited:187Cited References Count:64 JO - Estimates of anthropogenic carbon uptake from four three-dimensional global ocean models ER - TY - JOUR T1 - Evaluation of a protocol for the quantification of black carbon in sediments, soils, and aquatic sediments JF - Global Biogeochem. Cycles Y1 - 2001 A1 - Gustafsson, O. A1 - Bucheli, T. D. A1 - Kululska, M. A1 - Andersson, C. A1 - Largeau, C. A1 - Rouzard, J. N. A1 - Reddy, C. M. A1 - Eglinton, T. I. VL - 15 N1 - id: 1439 ER - TY - THES T1 - Fluttuazioni tardo quaternarie dei flussi sedimentari di componenti biogene nel settore pacifico dell'Oceano Meridionale--Thesis Y1 - 2001 A1 - Focaccia, P. PB - Universita di Balogna CY - Balogna, Italy VL - Dissertation/Thesis ER - TY - CHAP T1 - Fractionation of the isotopes of carbon and hydrogen in biosynthetic processes T2 - Stable Isotope Geochemistry, Reviews in Mineralogy and Geochemistry Y1 - 2001 A1 - Hayes, John M. ED - Valley, John W. JF - Stable Isotope Geochemistry, Reviews in Mineralogy and Geochemistry PB - Mineralogical Society of America CY - Washington, DC VL - 43 N1 - id: 1709 ER - TY - JOUR T1 - Geometry, numerical models and revised slip rates for the Reelfoot blind thrust and truishear fault-propagation fold, New Medrid Seismic zone JF - Engineering Geology Y1 - 2001 A1 - Champion, J. A1 - Mueller, K. A1 - Tate, A. A1 - Guccione, M. J. AB - The geometry and structural relief of late Holocene sediments folded across the Reelfoot scarp are characterized with trench excavations, shallow borings, a digital elevation model (DEM) of topography and Reelfoot Lake (RL) bathymetry. Results suggest the scarp forms by heterogeneous shear in the forelimb of a fault-propagation fold. Seismic data and the accompanying structural analysis support the argument that the Reelfoot fault does not offset the surface, and that the Reelfoot scarp is a fold limb. Structural relief measured across the Reelfoot scarp is slightly higher than previous determinations and varies from 7 to 11 m along the western shoreline of RL. Numerical models based on trishear kinematics constrain growth of the Reelfoot monocline and indicate that the underlying Reelfoot thrust fault is steeply dipping. The shallowest portion of the central Reelfoot thrust segment dips 75° where the fault tip has propagated upward from 911 m to its current location 465 m beneath the surface. The models indicate that the shallowest section of the southern thrust segment in the Reelfoot thrust system dips even more steeply at 80° but has propagated upward only a few tens of meters to its present location 1016 m beneath the surface. The thrust is flatter at deeper levels based on the location of earthquake hypocenters. Strain across the Reelfoot scarp is partitioned into two or three separate fold scarps that collectively record a late Holocene fault slip rate of 3.9±0.1 mm/yr. The slip rate is based on 9 m of structural relief, the 2290±60 ybp age of folded sediment and a 75° dip for the fault. This implies a rate of horizontal contraction in the seismic zone of ∼1.0 mm/yr. This rate is strongly dependent on the dip of the thrust calculated by the structural analysis. The numerical models argue for reactivation of faults that previously offset Paleozoic strata. VL - 62 IS - 1-3 N1 - id: 1381 JO - Geometry, numerical models and revised slip rates for the Reelfoot blind thrust and truishear fault-propagation fold, New Medrid Seismic zone ER - TY - CONF T1 - Greenhouse warming and the impact of sea level rise on water resources on the coastal plain of the gulf coast, U.S.A T2 - Annual PIs meeting of the DOE National Institute for Global Environmental Change Southeast Regional Center Y1 - 2001 A1 - Carey, Anne JF - Annual PIs meeting of the DOE National Institute for Global Environmental Change Southeast Regional Center CY - Duke, University N1 - id: 344 ER - TY - RPRT T1 - Heart Butte Reservoir 1998-2000 Archeological Investigations, Grant County, North Dakota Y1 - 2001 A1 - Jackson, Michael A. A1 - Bales, Jennifer R. PB - Department of Anthropology, University of North Dakota, Grand Forks CY - Bismarck, ND VL - in prep N1 - id: 200 ER - TY - JOUR T1 - High frequency dynamics of the East Asian Monsoon during the last 200,000 years JF - Paleoceanography Y1 - 2001 A1 - Garidel-Thoron, T. de A1 - Beaaufort, L. A1 - Linsley, B. K. A1 - Dannenmann, S. VL - 16 IS - 5 N1 - id: 272 ER - TY - JOUR T1 - The history of South American tropical precipitation for the past 25,000 years JF - Science Y1 - 2001 A1 - Baker, P. A. A1 - Seltzer, G. O. A1 - Fritz, S. C. A1 - Dunbar, R. B. A1 - Grove, M. J. A1 - Tapia, P. M. A1 - Cross, S. L. A1 - Rowe, H. D. A1 - Broda, J. P. AB - Long sediment cores recovered from the deep portions of Lake Titicaca are used to reconstruct the precipitation history of tropical South America for the past 25,000 years. Lake Titicaca was a deep, fresh, and continuously overflowing lake during the last glacial stage, from before 25,000 to 15,000 calibrated years before the present (cal yr B.P.), signifying that during the last glacial maximum (LGM), the Altiplano of Bolivia and Peru and much of the Amazon basin were wetter than today. The LGM in this part of the Andes is dated at 21,000 cal yr B.P., approximately coincident with the global LGM. Maximum aridity and lowest lake level occurred in the early and middle Holocene (8000 to 5500 cal yr B.P.) during a time of low summer insolation. Today, rising levels of Lake Titicaca and wet conditions in Amazonia are correlated with anomalously cold sea-surface temperatures in the northern equatorial Atlantic. Likewise, during the deglacial and Holocene periods, there were several millennial-scale wet phases on the Altiplano and in Amazonia that coincided with anomalously cold periods in the equatorial and high-latitude North Atlantic, such as the Younger Dryas. VL - 291 IS - 5504 N1 - id: 369; Baker, P A Seltzer, G O Fritz, S C Dunbar, R B Grove, M J Tapia, P M Cross, S L Rowe, H D Broda, J P New York, N.Y. Science. 2001 Jan 26;291(5504):640-3. JO - The history of South American tropical precipitation for the past 25,000 years ER - TY - JOUR T1 - The Holocene paleolimnology of Lake Issyk-Kul, Kyrgystan: trace element and stable isotope composition of ostracods JF - Paleogeography, Palaeoclimatology, Palaeocecology Y1 - 2001 A1 - Ricketts, R. D. A1 - Johnson, T. C. A1 - Brown, E. T. A1 - Rasmussen, K. A. A1 - Romanovsky, V. V. AB - The stable isotope and trace element geochemistry of ostracode shells from Lake Issyk-Kul, Kyrgyzstan, provide an important new paleoclimate record for central Asia. The δ18O, δ13C, Sr/Ca, Mg/Ca and U/Ca composition of shells from the species Candona neglecta found in two piston cores constrains the paleohydrology of the lake from 8700 to 1000 calendar yr before present. These data, combined with robust chronologies based on 16 AMS 14C dates, suggest that the region went from a relatively moist climate in the early Holocene to a more arid climate in the late Holocene. Intense freshwater input, presumably glacial runoff, flowed into the lake from 8700 to 8300 cal yr BP as evident from the δ18O and δ13C values. From 8300 to 6900 cal yr BP δ18O and Sr/Ca values indicate that the lake was relatively fresh and an open basin, and U/Ca values suggest that the lake was well-mixed with well-oxygenated bottom waters. There is a transition zone between 6900 and 4900 cal yr BP when δ18O and Sr/Ca values rapidly increase and Mg/Ca and U/Ca values rapidly decrease. During this period the lake evolved from an open, freshwater, well-mixed lake to a closed, more saline, less well-mixed lake. For the remainder of the record δ18O, Sr/Ca, Mg/Ca and U/Ca are relatively constant, implying conditions similar to modern conditions, although the slight increasing trend in Sr/Ca may suggest an increase in salinity over this period. The δ13C values were approximately in equilibrium with atmospheric CO2 in the early part of the record but became relatively negative in the later part of the record. This indicates that the dominant mechanism controlling the isotopic composition of dissolved inorganic carbon shifted from exchange with the atmosphere to variations in biological productivity. VL - 176 IS - 1-4 N1 - id: 341 JO - The Holocene paleolimnology of Lake Issyk-Kul, Kyrgystan: trace element and stable isotope composition of ostracods ER - TY - JOUR T1 - Holocene–late Pleistocene non-tropical carbonate sediments and tectonic history of the western rift basin margin of the southern Gulf of California JF - Sedimentary Geology Y1 - 2001 A1 - Halfar, J. A1 - Godinez-Orta, L. A1 - Goodfriend, G. A. A1 - Mucciarone, D. A. A1 - Ingle, J. C. A1 - Holden, P. AB - Using high-resolution seismic reflection profiling and dating of (1) shallow marine vibracores and (2) sediments collected from uplifted marine terraces we reconstruct the tectonic history and sediment accumulation patterns of Holocene to late Pleistocene warm-temperate to subtropical carbonates in the southern Gulf of California, Mexico. The study was conducted in the vicinity of La Paz where carbonates form along the fault bounded narrow western shelf of the tectonically active Gulf of California rift basin. The non-tropical nature of the setting is responsible for (1) poor cementation of the bioclastic carbonates, and (2) a composition which is dominated by rhodoliths (coralline red algae), corals and mollusks. Unrimmed carbonate flats forming in small pocket bays and a rhodolith bioherm, which has a surface area of more than 20 km2 and is up to 16 m thick, constitute the major carbonate factories. Holocene carbonate accumulation rates were deduced from seismic and core data and are highest on the rhodolith bioherm (260 cm/ka) and in subtidal zones of pocket bays (210 cm/ka), and lowest on the inner and middle shelf (100 cm/ka). Taken together, rates of carbonate accumulation are intermediate in magnitude between higher rates recorded in fully tropical carbonate settings and lower rates typical of cool-water carbonates. Seismic reflection profiles demonstrate that Isla Espiritu Santo in the center of the study area is a west dipping fault block, which is tectonically influenced by two distinct faults, the La Paz and Espiritu Santo faults. The latter fault accommodates at least 700 m of east-side down normal offset, and forms a steep eastern escarpment leading into the La Paz slope basin. Some of the sediments produced in the shallow carbonate factories of the narrow La Paz shelf are transported across this escarpment and are redeposited in the slope basin at a water depth of 750 m. Uranium-series dates of marine terraces exposed on Isla Espiritu Santo indicate that late Pleistocene uplift along the eastern side of the island could be as high as 310 mm/ka whereas downdropping along the western side of the island occurred at a rate of up to 15 mm/ka. Isla Espiritu Santo therefore constitutes part of the uplifted shoulder of the western margin of the Gulf of California rift basin. Patterns of vertical tectonic movements of Isla Espiritu Santo together with fault offsets on the surrounding seafloor and slump features on steep submarine slopes, point to continuous activity of the La Paz and Espiritu Santo faults. Results of this study will assist in recognizing and interpreting similar settings along ancient non-tropical rift basin margins worldwide and especially in the Neogene of the Gulf of California. VL - 144 IS - 1-2 N1 - id: 1316 JO - Holocene–late Pleistocene non-tropical carbonate sediments and tectonic history of the western rift basin margin of the southern Gulf of California ER - TY - JOUR T1 - Hydrology, vegetation, and climate change in the southern Everglades during the Holocene JF - Bulletin of American Paleontology Y1 - 2001 A1 - Winkler, M. G. A1 - Sanford, P. R. A1 - Kaplan, S. W. AB - Paleoecological study of 18 AMS-dated sediment cores from the southern Everglades provides evidence of a shifting mosaic of biotic communities in the past similar to those on the Everglades landscape today. Our results also indicate initiation of Everglades peatlands at 5900 yr B. P., the importance of fire (from charcoal analysis) as a structuring agent in the tropical Everglades, evidence of past plant communities (Isoetes marshes) not present in the modern landscape, and the introduction of exotic plants (Schinus, Casuarina, etc.) today. Past vegetation changes are documented by pollen and sclereid changes. Past water level changes are documented by plant community changes, diatom species and habitat changes, sponge spicule changes, and by intervals of peat (wet) or marl (dry) deposition in the sediment cores. Marl deposition dominates today at these sites in the southern Everglades, a long-term trend exacerbated by human impacts. The Everglades may become less complex in the near future as introduced plants outcompete native vegetation and decreased water levels result in decreased peat production. A rewatering plan must include both wet and dry seasonal cycles in order to preserve the shifting mosaic nature of the landscape and to maintain the Everglades as a functional habitat for both plants and animals. VL - 361 N1 - id: 125 JO - Hydrology, vegetation, and climate change in the southern Everglades during the Holocene ER - TY - JOUR T1 - Hypothesized climate forcing time series for the last 500 years JF - Journal of Geophysical Research-Atmospheres Y1 - 2001 A1 - Robertson, A. A1 - Overpeck, J. A1 - Rind, D. A1 - Mosley-Thompson, E. A1 - Zielinski, G. A1 - Lean, J. A1 - Koch, D. A1 - Penner, J. A1 - Tegen, I. A1 - Healy, R. AB - A new compilation of annually resolved time series of atmospheric trace gas concentrations, solar irradiance, tropospheric aerosol optical depth, and stratospheric (volcanic) aerosol optical depth is presented for use in climate modeling studies of the period 1500 to 1999 A.D. Atmospheric CO2 CH4, and N2O concentrations over this period are well established on the basis of fossil air trapped in ice cores and instrumental measurements over the last few decades. Estimates of solar irradiance, ranging between 1364.2 and 1368.2 W/m(2), are presented using calibrated historical observations of the Sun back to 1610, along with cosmogenic isotope variations extending back to 1500. Tropospheric aerosol distributions are calculated by scaling the modern distribution of sulfate and carbonaceous aerosol optical depths back to 1860 using reconstructed regional CO2 emissions; prior to 1860 the anthropogenic tropospheric aerosol optical depths are assumed to be zero. Finally, the first continuous, annually dated record of zonally averaged stratospheric (volcanic) optical depths back to 1500 is constructed using sulfate flux data from multiple ice cores from both Greenland and Antarctica, in conjunction with historical and instrumental (satellite and pyrheliometric) observations. The climate forcings generated here are currently being used as input to a suite of transient (time dependent) paleoclimate model simulations of the past 500 years. These forcings are also available for comparison with instrumental and proxy paleoclimate data of the same period. VL - 106 IS - D14 N1 - 456yeTimes Cited:108Cited References Count:89 JO - Hypothesized climate forcing time series for the last 500 years ER - TY - JOUR T1 - Identification of a novel alkenone in Black Sea sediments JF - Organic Geochemistry Y1 - 2001 A1 - Xu, L. A1 - Reddy, C. M. A1 - Farrington, J. W. A1 - Frysinger, G. S. A1 - Gaines, R. B. A1 - Johnson, C. G. A1 - Nelson, R. K. A1 - Eglinton, T. I. AB - We report the identification of a novel long-chain ketone in Holocene Black Sea sediments. Based on chemical properties, and chromatographic and mass spectrometric characteristics, this compound has been identified as a diunsaturated C-36 ethyl ketone. Further analyses indicated the position and configuration of the double bonds, and the novel alkenone was determined to be hexatriaconta-(16E,21E)-dien-3-one. While this compound is present in only trace quantities in Unit I sediments, it is the most abundant alkenone in portions of Unit II. Its presence thus apparently pre-dates the invasion of Emiliania huxleyi in the Black Sea. The down-core profiles and isotopic compositions suggest that the precursor for the C-36:2 alkenone may be distinct from that of the C37-39 alkenones, however the biological origin of this novel compound is presently unknown. (C) 2001 Elsevier Science Ltd. All rights reserved. VL - 32 IS - 5 N1 - id: 1946; PT: J; UT: WOS:000168692100002 JO - Identification of a novel alkenone in Black Sea sediments ER - TY - JOUR T1 - The impact of sea ice concentration accuracies on climate model simulations with the GISS GCM JF - Journal of Climate Y1 - 2001 A1 - Parkinson, C. L. A1 - Rind, D. A1 - Healy, R. J. A1 - Martinson, D. G. AB - The Goddard Institute for Space Studies global climate model (GISS GCM) is used to examine the sensitivity of the simulated climate to sea ice concentration specifications in the type of simulation done in the Atmospheric Model Intercomparison Project (AMIP), with specified oceanic boundary conditions. Results show that sea ice concentration uncertainties of +/-7% can affect simulated regional temperatures by more than 6 degreesC, and biases in sea ice concentrations of +7% and -7% alter simulated annually averaged global surface air temperatures by -0.10 degrees and +0.17 degreesC, respectively, over those in the control simulation. The resulting 0.27 degreesC difference in simulated annual global surface air temperatures is reduced by a third, to 0.18 degreesC, when considering instead biases of +4% and -4%. More broadly, least squares fits through the temperature results of 17 simulations with ice concentration input changes ranging from increases of 50% versus the control simulation to decreases of 50% yield a yearly average global impact of 0.0107 degreesC warming for every 1% ice concentration decrease, that is, 1.07 degreesC warming for the full +50% to -50% range. Regionally and on a monthly average basis, the differences can be far greater, especially in the polar regions, where wintertime contrasts between the +50% and -50% cases can exceed 30 degreesC. However, few statistically significant effects are found outside the polar latitudes, and temperature effects over the nonpolar oceans tend to be under 1 degreesC, due in part to the specification of an unvarying annual cycle of sea surface temperatures. The +/-7% and +/-4% results provide bounds on the impact (on GISS GCM simulations making use of satellite data) of satellite-derived ice concentration inaccuracies, +/-7% being the current estimated average accuracy of satellite retrievals and +/-4% being the anticipated improved average accuracy for upcoming satellite instruments. Results show that the impact on simulated temperatures of imposed ice concentration changes is least in summer, encouragingly the same season in which the satellite accuracies are thought to be worst. Hence, the impact of satellite inaccuracies is probably less than the use of an annually averaged satellite inaccuracy would suggest. VL - 14 IS - 12 N1 - id: 1944; PT: J; UT: WOS:000169239100008 JO - The impact of sea ice concentration accuracies on climate model simulations with the GISS GCM ER - TY - JOUR T1 - Implications of the carbon isotope and mineral inclusion record for the formation of diamonds in the mantle underlying a mobile belt: Venetia, South Africa JF - Geochimica Et Cosmochimica Acta Y1 - 2001 A1 - Deines, P. A1 - Viljoen, F. A1 - Harris, J. W. AB - A total of 199 diamonds from the Venetia kimberlite, South Africa, whose mineral inclusion chemistry had already been measured, were analyzed for their carbon isotopic composition. Silicate inclusions in these diamonds either belong to a peridotitic (P-Type), an eclogitic (E-Type) or transitional, websteritic (W-Type), paragenesis.The carbon isotopic composition of 161 P-Type diamonds ranges from delta C-13 = -2.23 to - 18 parts per thousand vs. PDB. The large number of samples available and the wide range in delta C-13 permitted, for the first time, a detailed analysis of the relationships between P-Type inclusion chemistry and the carbon isotopic composition of the diamond host. The delta C-13 Sampling frequency distribution is multi-modal. Examination of the inclusion chemistry (chromite, olivine, garnet) as a function of the carbon isotope composition mode to which the host belongs, as well as multivariate regression analyses, revealed no correlation between inclusion chemistry and C-13 content. The inclusion compositions in diamonds of low C-13 content are not distinctive. For a given carbon isotopic composition the combination of Ni/Fe and Mg/(Mg + Fe) of olivine inclusions varies systematically along fractionation trends. The composition of the olivine inclusions and the C-13 content of their hosts can be interpreted as reflecting similar petrogenetic processes occurring in several mantle environments into which carbon of variable isotopic composition was introduced. The iron/magnesium distribution between coexisting garnets and olivines permits an estimate of their pressure/temperature equilibration conditions. Diamonds whose inclusions were equilibrated at lower temperatures and pressures tend to have, on average, lower C-13 contents. The compositions of coexisting olivines and chromites suggest oxygen fugacities between 2.9 and 5.8 log units below the quartz-fayalite-magnetite buffer at 50 kbar, and temperatures between 1280 and 1490 degreesC prevailed during diamond formation. Inclusions from diamonds of lower C-13 content do not indicate systematically lower fO(2) values during their formation. The fO(2)/T conditions determined suggest minimal (0.0 to -0.5 parts per thousand) isotope fractionation between a C-H-O vapor phase (carbon dioxide, carbon monoxide, methane, water, hydrogen) and diamond. The large C-13 depletion of some Venetia P-Type diamonds appears to be unrelated to the composition of their inclusions, igneous fractionation trends, oxygen fugacity, and vapor isotope fractionation processes. This conclusion is consistent with evidence deduced from more limited data sets from other kimberlites. VL - 65 IS - 5 N1 - 412wtTimes Cited:31Cited References Count:90 JO - Implications of the carbon isotope and mineral inclusion record for the formation of diamonds in the mantle underlying a mobile belt: Venetia, South Africa ER - TY - JOUR T1 - Initiation of the Australian summer monsoon 14,000 years ago JF - Quaternary International Y1 - 2001 A1 - Wyrwoll, K. H. A1 - Miller, G. H. AB - Definitive evidence for the onset of monsoon moisture in northern Australia following the and phase of the Last Glacial Maximum has been elusive, in large part due to the lack of long, continuous sediment records. Here we report new evidence from two separate drainage basins in the Kimberley region of monsoonal northwestern Australia. At both sites, radiocarbon ages on (basal) biogenic materials in flood deposits indicate stream flow, as high or higher than maximum historic levels, began about 14 cal ka BP. These results suggest that the Australian summer monsoon was fully active several millennia earlier than previously expected. The early onset of the monsoon and the widespread evidence for diminished monsoon activity in the late Holocene cannot be reconciled with primary forcing of the Australian monsoon by changes in low-latitude summer insolation over Australia. (C) 2001 Elsevier Science Ltd and INQUA. All rights reserved. VL - 83-5 IS - 1 N1 - 478pnTimes Cited:78Cited References Count:42 JO - Initiation of the Australian summer monsoon 14,000 years ago ER - TY - CHAP T1 - Installation of a 134-sample MC-SNICS at the NOSAMS facility and first results T2 - Symposium of NorthEastern Accelerator Personnel, Oak Ridge National Lab., USA, October 25-28, 1999 Y1 - 2001 A1 - Bellino, Mary A1 - von Reden, Karl F. A1 - Schneider, Robert J. A1 - Long, Patricia Long A1 - Healy, Richard ED - Hensley, D. K. JF - Symposium of NorthEastern Accelerator Personnel, Oak Ridge National Lab., USA, October 25-28, 1999 PB - World Scientific CY - Oak Ridge, TN N1 - id: 1718 ER - TY - CONF T1 - Isotopes as tracers of the oceanic circulation: results from the world ocean circulation experiment T2 - International Conference on the Study of Environmental Change Using Isotope Techniques, I.A.E.A. Y1 - 2001 A1 - Schlosser, P. A1 - Jenkins, W. J. A1 - Key, R. A1 - Lupton, J. JF - International Conference on the Study of Environmental Change Using Isotope Techniques, I.A.E.A. N1 - id: 318 ER - TY - CHAP T1 - Isotopic Evolution of the Biogeochemical Carbon Cycle During the Precambrian T2 - Reviews in Mineralogy & Geochemistry, Stable Isotope Geochemistry Y1 - 2001 A1 - Des Marais, David J. ED - Valley, John W. JF - Reviews in Mineralogy & Geochemistry, Stable Isotope Geochemistry PB - Mineralogical Society of America CY - Washington, DC VL - 43 N1 - id: 1556 ER - TY - JOUR T1 - The last interglacial to glacial transition, Togiak Bay, Southwestern Alaska JF - Quaternary Research Y1 - 2001 A1 - Kaufman, D. S. A1 - Manley, W. F. A1 - Wolfe, A. P. A1 - Hu, F. S. A1 - Preece, S. J. A1 - Westgate, J. A. A1 - Forman, S. L. AB - An 18-m-high coastal bluff at Togiak Bay (northwestern Bristol Bay, southwestern Alaska) exposes marine, lacustrine, fluvial, glacial, volcanic, and organic deposits that record the ∼50,000-year-long transition from the peak of the last interglaciation to the early Wisconsin glaciation. The base of the section is dominated by stratified sand and silt extending up to 4.3 m above sea level; marine diatoms are present, and pollen assemblages are characterized by relatively high percentages of Picea, Alnus, and Betula and low percentages of Poaceae and Cyperaceae. The marine sediment was probably deposited during the peak of marine oxygen-isotope stage (OIS) 5e. An infrared stimulated luminescence (IRSL) age of 151,000±13,000 yr from near the base of the exposure is permissive of this correlation. The marine sand and silt are overlain by 0.8 m of peaty silt with diatoms that record a transition from marine to lacustrine conditions. During this interval, Poaceae and Cyperaceae dominate the pollen assemblages, and Picea and shrubs are nearly absent, suggesting that herb tundra occupied the landscape. This interval probably encompasses OIS 5d on the basis of the herb tundra and an IRSL age of 119,000±10,000 yr from 60 cm below the marine/lacustrine transition. The organic mud is overlain by 3.1 m of stratified sand and organic silt that apparently record shallowing of the lake; reappearance of spruce and shrubs (=OIS 5c?); and subsequent deepening of the lake (=OIS 5b?); followed by aggradation of a floodplain (=OIS 5a?), which was dry at the time basaltic lava buried the site. Thermoluminescence analyses on lava-baked sediment indicate that the eruption occurred 70,000±10,000 yr ago. Sometime thereafter, but prior to 53,600 14C yr B.P. an outlet of the Ahklun Mountains ice cap advanced over the site and deposited ∼7 m of bouldery ice-contact drift. The sedimentary sequence contains at least four tephra beds. Major- and trace-element chemistry provide a basis for correlating two of the tephras with tephra beds at nearby sites. The tephras, luminescence ages, and correlations with marine isotope stages provide the geochronological control to place the Togiak Bay section into a global context. The site serves as an important new reference section for late Pleistocene paleoenvironmental change in eastern Beringia. VL - 55 IS - 2 N1 - id: 1392 JO - The last interglacial to glacial transition, Togiak Bay, Southwestern Alaska ER - TY - JOUR T1 - Late quaternary climate and hydrology of tropical South America inferred from an isotopic and chemical model of Lake Titicaca, Bolivia and Peru JF - Quaternary Research Y1 - 2001 A1 - Cross, S. L. A1 - Baker, P. A. A1 - Seltzer, G. O. A1 - Fritz, S. C. A1 - Dunbar, R. B. AB - A simple mass balance model provides insight into the hydrologic, isotopic, and chemical responses of Lake Titicaca to past climatic changes. Latest Pleistocene climate of the Altiplano is assumed to have been 20% wetter and 5 degreesC colder than today, based on previous modeling. Our simulation of lacustrine change since 15,000 cal yr B.P. is forced by these modeled climate changes. The latest Pleistocene Lake Titicaca was deep, fresh, and overflowing. The latest Pleistocene riverine discharge from the lake was about 8 times greater than the modern average, sufficient to allow the expansion of the great paleolake Tauca on the central Altiplano. The lake delta O-18 value averaged about -13 parts per thousand SMOW (the modern value is about -4.2 parts per thousand). The early Holocene decrease in precipitation caused Lake Titicaca to fall below its outlet and contributed to a rapid desiccation of paleolake Tauca. Continued evaporation caused the 100-m drop in lake level, but only a slight(1-2 parts per thousand) increase (relative to modern) in delta O-18 Of early Holocene lake waters. This Holocene lowstand level of nearly 100 m was most likely produced by a precipitation decrease, relative to modern, of about 40%, The lake was saline as recently as 2000 cal yr B.P. The timing of these hydrologic changes is in general agreement with calculated changes of insolation forcing of the South American summer monsoon, (C) 2001 University of Washington. VL - 56 IS - 1 N1 - 452lzTimes Cited:50Cited References Count:46 JO - Late quaternary climate and hydrology of tropical South America inferred from an isotopic and chemical model of Lake Titicaca, Bolivia and Peru ER - TY - JOUR T1 - Late Quaternary water-level variations and vegetation history at Crooked Pond, southeastern Massachusetts JF - Quaternary Research Y1 - 2001 A1 - Shuman, B. A1 - Bravo, J. A1 - Kaye, J. A1 - Lynch, J. A. A1 - Newby, P. A1 - Webb, T. AB - Sediment cores collected along a transect in Crooked Pond, southeastern Massachusetts, provide evidence of water-level changes between 15,000 cal yr B.P. and present. The extent of fine-grained, detrital, organic accumulation in the basin, inferred from sediment and pollen stratigraphies, varied over time and indicates low water levels between 11,200 and 8000 cal yr B.P. and from ca. 5300 to 3200 cal yr B.P. This history is consistent with the paleohydrology records from nearby Makepeace Cedar Swamp and other sites from New England and eastern Canada and with temporal patterns of regional changes in effective soil moisture inferred from pollen data. The similarities among these records indicate that (1) regional conditions were drier than today when white pine (Pinus strobus) grew abundantly in southern New England (11,200 to 9500 cal yr B.P.); (2) higher moisture levels existed between 8000 and 5500 cal yr B.P., possibly caused by increased meridonal circulation as the influence of the Laurentide ice sheet waned; and (3) drier conditions possibly contributed to the regional decline in hemlock (Tsuga) abundances at 5300 cal yr B.P. Although sea-level rise may have been an influence, moist climatic conditions during the late Holocene were the primary reason for a dramatic rise in water-table elevations. (C) 2001 University of Washington. VL - 56 IS - 3 N1 - id: 1379; 493FU Times Cited:43 Cited References Count:41 JO - Late Quaternary water-level variations and vegetation history at Crooked Pond, southeastern Massachusetts ER - TY - JOUR T1 - A marine record of holocene climate events in tropical South America JF - Science Y1 - 2001 A1 - Haug, G. H. A1 - Hughen, K. A. A1 - Sigman, D. M. A1 - Peterson, L. C. A1 - Rohl, U. VL - 293 N1 - id: 1466 ER - TY - JOUR T1 - Metamorphic devolatilization of subducted oceanic metabasalts: implications for seismicity, arc magmatism and volatile recycling JF - Earth and Planetary Science Letters Y1 - 2001 A1 - Kerrick, D. M. A1 - Connolly, J. A. D. AB - Subducted oceanic metabasalts are believed to be a primary source of volatiles for are magmatism and fluid-induced seismicity. From phase equilibria computed for an average oceanic metabasalt we present a model for subduction zone devolatilization for pressures up to 6 GPa (similar to 180 km). Along high temperature geotherms complete dehydration occurs under forearcs, whereas dehydration does not occur along low temperature geotherms. For intermediate geotherms, major dehydration occurs under subarcs and provides a subjacent H2O source for are volcanism. Decarbonation is negligible along cold and intermediate geotherms and limited along high temperature geotherms. Because decarbonation is limited for all subducted carbonate-bearing lithologies, transfer of CO2 from subducted slabs to are magmas may be triggered by aqueous fluid infiltration. Metabasalt devolatilization could induce seismicity in forearcs (high temperature geotherms) and subarcs (intermediate geotherms); however, because of the lack of devolatilization, metabasalts would not be a fluid source for seismicity with low temperature geotherms. Along low temperature geotherms, limited devolatilization of subducted oceanic metabasalts and marine sediments in forearcs and subarcs provides a mechanism for return of volatiles to the deeper mantle. (C) 2001 Elsevier Science B.V. All rights reserved. VL - 189 IS - 1-2 N1 - 446xmTimes Cited:202Cited References Count:49 JO - Metamorphic devolatilization of subducted oceanic metabasalts: implications for seismicity, arc magmatism and volatile recycling ER - TY - JOUR T1 - Millennial-scale dynamics of the East Asian winter monsoon during the last 200,000 years JF - Paleoceanography Y1 - 2001 A1 - de Garidel-Thoron, Thibault A1 - Beaufort, Luc VL - 16 N1 - id: 251 ER - TY - CONF T1 - Multiple anthropogenic tracer distributions in the ocean T2 - Sixth International CO2 Conference Y1 - 2001 A1 - Sabine, C. L. A1 - Key, R. M. A1 - Bullister, J. L. A1 - Feely, R. A. A1 - Lamb, M. F. A1 - Millero, F. J. A1 - Wanninkhof, R. A1 - Peng, T. H. A1 - Lee, K. A1 - Kozyr, A. A1 - Gruber, N. JF - Sixth International CO2 Conference CY - Sendai, Japan N1 - id: 319 ER - TY - CONF T1 - A new method for separating bomb-produced and natural D14C, Global Change T2 - Open Science Conference Y1 - 2001 A1 - Key, R. M. JF - Open Science Conference CY - Amsterdam, the Netherlands N1 - id: 1445 ER - TY - JOUR T1 - New records show pronounced changes in Arctic Ocean circulation and climate (cover article) JF - EOS, Transactions, American Geophysical Union Y1 - 2001 A1 - Darby, D. A1 - Bischof, J. A1 - Cutter, G. A1 - de Vernal, A. A1 - Hillaire-Marcel, C. A1 - Dwyer, G. A1 - McManus, J. A1 - Polyak, L. A1 - Osterman, L. A1 - Poore, R. VL - 82 N1 - id: 332 ER - TY - JOUR T1 - New techniques define combustion product signatures in sediments JF - Woods Hole Oceanographic Institution 2000 annual report Y1 - 2001 A1 - Eglinton, T. I. N1 - id: 1487 ER - TY - CHAP T1 - Ocean Circulation and Climate T2 - Observing and Modelling the Global Ocean Y1 - 2001 A1 - Schlosser, P. A1 - Bullister, J. L. A1 - Fine, R. A1 - Jenkins, W. J. A1 - Key, R. A1 - Lupton, J. A1 - Roether, W. A1 - Smethie, W. M., Jr. ED - Siedler, G. JF - Observing and Modelling the Global Ocean PB - Academic Press N1 - id: 309 ER - TY - BOOK T1 - Ocean process tracers: Radiocarbon T2 - Encyclopedia of Ocean Sciences Y1 - 2001 A1 - Key, R. M. ED - Steele, J. JF - Encyclopedia of Ocean Sciences PB - Academic Press CY - London N1 - id: 310 ER - TY - CHAP T1 - Ocean Process Tracers: Single compound radiocarbon measurements T2 - Encyclopedia of Ocean Sciences Y1 - 2001 A1 - Eglinton, T. I. A1 - Pearson, A. JF - Encyclopedia of Ocean Sciences PB - Academic Press CY - London N1 - id: 1420 ER - TY - CONF T1 - Oceanic changes in the southern Pacific Ocean during the last deglaciation time, as recorded by planktic foraminifers and oxigen isotopes. --Extended abstract T2 - ANTOSTRAT Symposium on "The geologic record of the Antarctic ice sheet from drilling, coring and seismic studies" Y1 - 2001 A1 - Morigi, C. A1 - Capotondi, L. A1 - Giglio, F. A1 - Langone, L. A1 - Brilli, M. A1 - Turi, B. A1 - Ravaioli, M. JF - ANTOSTRAT Symposium on "The geologic record of the Antarctic ice sheet from drilling, coring and seismic studies" CY - Erice, Italy N1 - id: 1428 ER - TY - JOUR T1 - Optical dating, ages, and scatter from tsunami-laid sands from Bradley Lake, Oregon JF - Quaternary Science Reviews Y1 - 2001 A1 - Ollerhead, Jeff A1 - Huntley, David J. A1 - Nelson, Alan R. A1 - Kelsey, Harvey M. VL - 20 N1 - id: 1406 ER - TY - JOUR T1 - Optical dating of tsunami-laid sand from an Oregon coastal lake JF - Quaternary Science Reviews Y1 - 2001 A1 - Ollerhead, J. A1 - Huntley, D. J. A1 - Nelson, A. R. A1 - Kelsey, H. M. AB - Optical ages for five samples of tsunami-laid sand from an Oregon coastal lake were determined using an infrared optical-dating method on K-feldspar separates and, as a test of accuracy, compared to ages determined by AMS C-14 dating or detrital plant fragments found in the same beds. Two optical ages were about 20% younger than calibrated C-14 ages of about 3.1 and 4.3 ka. Correction of the optical ages using measured anomalous fading rates brings them into agreement with the C-14 ages. The approach used holds significant promise for improving the accuracy of infrared optical-dating methods.Luminescence data for the other three samples result in optical age limits much greater than the C-14 ages. These data provide a textbook demonstration of the correlation between scatter in the luminescence intensity of individual sample aliquots and their normalization values that is expected when the samples contain sand grains not adequately exposed to daylight just prior to or during deposition and burial. Thus, the data for these three samples suggest that the tsunamis eroded young and old sand deposits before dropping the sand in the lake. (C) 2001 Elsevier Science Ltd. All rights reserved. VL - 20 IS - 18 N1 - 500nqTimes Cited:24Cited References Count:39 JO - Optical dating of tsunami-laid sand from an Oregon coastal lake ER - TY - JOUR T1 - Origins of lipid biomarkers in Santa Monica Basin surface sediment: A case study using compound-specific D14C analysis JF - Geochimica et Cosmochimica Acta Y1 - 2001 A1 - Pearson, A. A1 - McNichol, A. P. A1 - Benitez-Nelson, B. C. A1 - Hayes, J. M. A1 - Eglinton, T. I. VL - 65 IS - 18 N1 - id: 1419 ER - TY - CONF T1 - Paleoceanographic changes in the Southern Ocean, during the last deglaciation time, as recorded by planktic foraminifers and oxygen isotopes--Poster T2 - ANTOSTRAT Symposium on "The geologic record of the Antarctic ice sheet from drilling, coring and seismic studies"--Poster Y1 - 2001 A1 - Morigi, C. A1 - Capotondi, L. A1 - Giglio, F. A1 - Langone, L. A1 - Turi, B. A1 - Brilli, M. A1 - Ravaioli, M. JF - ANTOSTRAT Symposium on "The geologic record of the Antarctic ice sheet from drilling, coring and seismic studies"--Poster CY - Erice, Italy N1 - id: 1424 ER - TY - CONF T1 - Paleoclimate through the ages from the Cariaco Basin, Abstract T2 - American Geophysical Union Y1 - 2001 A1 - Hughen, K. A. A1 - Peterson, L. C. A1 - Black, D. A1 - Haug, G. A1 - Poore, R. JF - American Geophysical Union CY - Boston, MA N1 - id: 1467 ER - TY - JOUR T1 - Paleoproterozoic Huronian basin: product of a Wilson cycle punctuarted by glaciations and a meteorite impact JF - Sedimentary Geology Y1 - 2001 A1 - Young, G. M. A1 - Long, D. G. F. A1 - Fedo, C. M. A1 - Nesbitt, H. W. KW - Geochemistry KW - Glaciation KW - Impact KW - Paleoproterozoic KW - Wilson cycle AB - The Huronian Supergroup (∼2.4–2.2 Ga) comprises up to 12 km of mainly sedimentary supracrustal rocks. The oldest Huronian unit, the Livingstone Creek Formation, is chemically and mineralogically immature. Significant chemical weathering and deposition of U-rich quartz pebble conglomerates followed deposition of the Livingstone Creek Formation and extrusion of the overlying, rift-related lavas of the Thessalon Formation. Much of the succeeding Huronian comprises climatically(?)-controlled tripartite cycles, each of which begins with glaciogenic diamictites, followed by mudstones and cross bedded arenaceous units. Huronian deposition is interpreted as the result of a partial Wilson cycle, involving rifting and development of a southward-facing passive margin. The ∼2.4 Ga Murray and Creighton granites have been considered by others to be co-eval with an early orogenic episode (Blezardian). Expected unconformities are, however, lacking and these granites, together with co-eval volcanic rocks and abundant soft sediment deformation structures are considered to be due to anorogenic processes during Huronian basin subsidence. The main deformation of the Huronian is probably related to the Penokean orogeny (∼1.89–1.8 Ga). Geochemical investigations have contributed to paleoclimatic and provenance studies and have helped to define basin-wide metasomatic events. A large impact at ∼1.85 Ga likely played an important role in formation of the Sudbury Igneous Complex (SIC) and deposition of fallback breccias of the Onaping Formation (basal Whitewater Group in the Sudbury basin). Overlying sedimentary rocks of the Whitewater Group are considered to be a fortuitously-preserved portion of a widespread flysch apron that spread across the southern margin of the Superior Province as a foreland basin fill, in response to the closure phase of the Wilson cycle during the Penokean orogeny. Geochronological data suggest that these events occurred during the Penokean orogeny. VL - 141-142 N1 - id: 1606 JO - Paleoproterozoic Huronian basin: product of a Wilson cycle punctuarted by glaciations and a meteorite impact ER - TY - JOUR T1 - Persistent solar influence on North Atlantic climate during the Holocene JF - Science Y1 - 2001 A1 - Bond, G. A1 - Kromer, B. A1 - Beer, J. A1 - Muscheler, R. A1 - Evans, M. N. A1 - Showers, W. A1 - Hoffmann, S. A1 - Lotti-Bond, R. A1 - Hajdas, I. A1 - Bonani, G. AB - Surface winds and surface ocean hydrography in the subpolar North Atlantic appear to have been influenced by variations in solar output through the entire Holocene. The evidence comes from a close correlation between inferred changes in production rates of the cosmogenic nuclides carbon-14 and beryllium-10 and centennial to millennial time scale changes in proxies of drift ice measured in deep-sea sediment cores. A solar forcing mechanism therefore may underlie at least the Holocene segment of the North Atlantic's "1500-year" cycle. The surface hydrographic changes may have affected production of North Atlantic Deep Water, potentially providing an additional mechanism for amplifying the solar signals and transmitting them globally. VL - 294 IS - 5549 N1 - id: 1397; Bond, G Kromer, B Beer, J Muscheler, R Evans, M N Showers, W Hoffmann, S Lotti-Bond, R Hajdas, I Bonani, G New York, N.Y. Science. 2001 Dec 7;294(5549):2130-6. Epub 2001 Nov 15. JO - Persistent solar influence on North Atlantic climate during the Holocene ER - TY - JOUR T1 - Pleistocene glacial history of the southern Ahklun Mountains, southwestern Alaska: Soil-development, morphometric, and radiocarbon constraints JF - Quaternary Science Reviews Y1 - 2001 A1 - Manley, W. F. A1 - Kaufman, D. S. A1 - Briner, J. P. AB - Four new AMS ages, glacial mapping, and measurements of soil development, loess thickness, and moraine morphology constrain the age and extent of at least three Quaternary advances by outlet lobes of an ice cap over the Ahklun Mountains of southwestern Alaska. The relative-age data are from 107 sites correlated to 25 ice-marginal positions in the Kanektok, Goodnews, Togiak, and Kulukak River valleys and along the southeastern flank of the range. Radiocarbon ages provide minimum ages for six — and a maximum age for one — of the former ice margins. Soil and morphometric parameters subdivide the ice limits into three relative-age groups. One to three pre-Wisconsin advances, probably middle Pleistocene in age, are represented by drift with relatively thick B horizons (60±5 cm, with Bt horizons), thick loess caps (80±12 cm), and broad moraines (135±134 m) with gentle side slopes (7±5°). An extensive early Wisconsin (sensu lato, s.l.) advance, >39.9 ka, and three associated stillstands or readvances are characterized by intermediate soil and morphometric parameters (Bw and weak Bt horizons with thicknesses of 40±11 cm; loess thicknesses of 69±46 cm; crest widths of 38±13 m; and slope angles of 14±4°). The maximum late Wisconsin advance, >16.9 ka, and two readvances or stillstands are associated with thin (20±5 cm), weakly to moderately developed Bw horizons, thin loess caps (28±8 cm), narrow crest widths (28±9 m), and steep slope angles (18±3°). The data confirm that early-Wisconsin glaciers in southeast Beringia were much more extensive than late Wisconsin glaciers, which were apparently limited by availability of moisture. VL - 20 IS - 103 N1 - id: 1204 JO - Pleistocene glacial history of the southern Ahklun Mountains, southwestern Alaska: Soil-development, morphometric, and radiocarbon constraints ER - TY - JOUR T1 - Pollen record of the last 500 years from the Doninos coastal lagoon (NW Iberian Peninsula): Changes in the pollinic catchment size versus paleoecological interpretation JF - Journal of Coastal Research Y1 - 2001 A1 - Santos, L. A1 - Bao, R. A1 - Goni, M. F. S. KW - charcoal KW - coastal lagoon KW - diatoms KW - human impact KW - Late Holocene KW - late-holocene KW - nw iberian peninsula KW - pollen KW - representation KW - source area KW - vegetation KW - vegetation history AB - Pollen, diatom, charcoal and sedimentological analyses of a 4.20-m long core collected in the margin of the Doninos coastal lagoon, northwest Iberian Peninsula, provide information about the environmental evolution of this lagoon during the last 530 yr BP. During this time period, local environmental changes, such as changes in the sand-barrier permeability, alluvial sedimentation and/or anthropogenic activity, played a major role in the evolution of this coastal system. This scenario allows us to test the degree the pollinic signal recorded in the sediments of coastal lagoons is reshaped by the influence of local processes.Diatom and sedimentological data as well as historical archives indicate the development of a lacustrine system at the bottom of the sequence. Therefore, the coring site might be included in the lagoon itself. Pollen data seems to reflect the regional vegetation as a consequence of the large pollinic catchment area. Local Castanea cultivation and anthropogenic deforestation are also recorded. At the top of the sequence, diatom facies suggest increased marine influence at this time as a consequence of the more common events of breaching of a retrograding barrier. This, plus natural silting up by alluvial sedimentation and man-induced drying up of the lagoonal margins, lead to a progressive decrease in the water body extension. The coring point is now outside of the lagoon, implying a reduction in the pollinic catchment area that gave rise to a gradual increase in the local pollinic rainfall of periphytic vegetation. From the pollen diagram of this coastal deposit signatures of regional vegetation are swamped by local pollen input. The fluctuations in the percentages of the different pollen taxa are related to the complex interaction between basin size, human activities and breaching of the barrier. Caution must therefore be taken with direct paleoclimatic inferences from pollinic studies in coastal lagoons as an alternative where other continental deposits are lacking. VL - 17 SN - 0749-0208 IS - 3 N1 - 479bdTimes Cited:6 Cited References Count:46 JO - J Coastal Res ER - TY - CONF T1 - Possible record of the yunger dryas event in sediments of the Southern Ocean (Pacific Sector)--Poster T2 - AUG Y1 - 2001 A1 - Morigi, C. A1 - Capotondi, L. A1 - Langone, L. A1 - Giglio, F. A1 - Ravaioli, M. JF - AUG CY - Nice N1 - id: 1423 ER - TY - CONF T1 - Possible record of the yunger dryas event in sediments of the southern ocean (Pacific sector)--abstract T2 - AUG Y1 - 2001 A1 - Morigi, C. A1 - Capotondi, L. A1 - Langone, L. A1 - Giglio, F. A1 - Ravaioli, M. JF - AUG CY - Nice, France N1 - id: 1427 ER - TY - JOUR T1 - Post-glacial eruptive history of the western volcanic zone, Iceland JF - EOS Trans. Amer. Geophys. Union Y1 - 2001 A1 - Sinton, John M. A1 - Gronvold, Karl VL - 82 suppl. IS - F1218 N1 - id: 355 ER - TY - JOUR T1 - Pre-Columbian fish farming in the Amazon JF - Expedition Y1 - 2001 A1 - Erickson, Clark L. VL - 43 IS - 1 N1 - id: 1481 ER - TY - JOUR T1 - Pre-Columbian roads of the Amazon JF - Expedition Y1 - 2001 A1 - Erickson, Clark L. VL - 43 IS - 2 N1 - id: 1482 ER - TY - JOUR T1 - Pre-late Wisconsin glacial history, coastal Ahklun Mountains, southwestern Alaska-New amino acid, thermoluminescence, and 40Ar/30Ar results JF - Quaternary Science Reviews Y1 - 2001 A1 - Kaufman, D. S. A1 - Manley, W. F. A1 - Forman, S. L. A1 - Layer, P. AB - New stratigraphic and geochronologic data from the Togiak Bay area of southwestern Alaska indicate that glaciers advanced from the southern Ahklun Mountains at least three and as many as six times prior to the late Wisconsin. The oldest glaciations are represented by glacial–marine sediment in coastal exposures on Hagemeister Island. The extent of amino acid (isoleucine) epimerization in fossil molluscs indicates that at least one, and possibly four, older middle Pleistocene glacial intervals are represented, with age estimates spanning ∼500–280 ka and averaging ∼400±100 ka. The youngest glacial-marine drift on Hagemeister Island may correlate with the eruption of the Togiak tuya. A new 40Ar/39Ar age on basalt that overlies pillow lava indicates that the volcano erupted through glacial ice at least 300 m thick 263±22 ka. The youngest drift in the region overlies the Old Crow tephra (140±10 ka) and a 70±10 ka basaltic lava flow dated by thermoluminescence analysis of underlying baked sediment. The drift delimits flat piedmont lobes that spread out onto the continental shelf and terminated >100 km from their source areas during the early Wisconsin (sensu lato). The glacial-geologic evidence suggests that major expansions of glaciers were out of phase with global ice volume. VL - 20 IS - 1-3 N1 - id: 1203 JO - Pre-late Wisconsin glacial history, coastal Ahklun Mountains, southwestern Alaska-New amino acid, thermoluminescence, and 40Ar/30Ar results ER - TY - JOUR T1 - Proceedings of a Workshop on Alkenone-Based Paleoceanographic Indicators (Introduction to special issue of journal) JF - Geochem. Geophys. Geosyst. Y1 - 2001 A1 - Eglinton, T. I. A1 - Conte, M. H. A1 - Eglinton, G. A1 - Hayes, John M. VL - 2 IS - 2000GC000122 N1 - id: 1739 ER - TY - JOUR T1 - Radiocarbon and stable carbon isotopic evidence for transport and transformation of DOC, DIC and CH4 in a northern Minnesota peatland JF - Global Biogeochemical Cycles Y1 - 2001 A1 - Chasar, L. S. A1 - Chanton, J. P. A1 - Glaser, P. H. A1 - Siegel, D. I. A1 - Rivers, J. S. VL - 14 N1 - id: 98 ER - TY - JOUR T1 - Radiocarbon Dating of Wood Samples and Plutonium Sediment Disturbance Studies at the Queen Anne's Revence Wreck Site JF - Southeastern Geology Y1 - 2001 A1 - Martens, Christopher S. A1 - McNichol, Ann P. VL - 40 IS - 1 N1 - id: 1200 ER - TY - JOUR T1 - Radiocarbon in a Fanning Island Coral: Inter-decadal Variability in Waters Upwelling in the Central Equatorial Pacific from 1922 - 1955 JF - EOS Y1 - 2001 A1 - Grottoli, A. G. A1 - Gille, S. T. A1 - Druffel, E. R. M. A1 - Dunbar, R. B. N1 - id: 1399 ER - TY - JOUR T1 - Rapid shoreward encroachment of salt marsh cordgrass in response to accelerated sea-level rise JF - Proc Natl Acad Sci U S A Y1 - 2001 A1 - Donnelly, J. P. A1 - Bertness, M. D. AB - The distribution of New England salt marsh communities is intrinsically linked to the magnitude, frequency, and duration of tidal inundation. Cordgrass (Spartina alterniflora) exclusively inhabits the frequently flooded lower elevations, whereas a mosaic of marsh hay (Spartina patens), spike grass (Distichlis spicata), and black rush (Juncus gerardi) typically dominate higher elevations. Monitoring plant zonal boundaries in two New England salt marshes revealed that low-marsh cordgrass rapidly moved landward at the expense of higher-marsh species between 1995 and 1998. Plant macrofossils from sediment cores across modern plant community boundaries provided a 2,500-year record of marsh community composition and documented the migration of cordgrass into the high marsh. Isotopic dating revealed that the initiation of cordgrass migration occurred in the late 19th century and continued through the 20th century. The timing of the initiation of cordgrass migration is coincident with an acceleration in the rate of sea-level rise recorded by the New York tide gauge. These results suggest that increased flooding associated with accelerating rates of sea-level rise has stressed high-marsh communities and promoted landward migration of cordgrass. If current rates of sea-level rise continue or increase slightly over the next century, New England salt marshes will be dominated by cordgrass. If climate warming causes sea-level rise rates to increase significantly over the next century, these cordgrass-dominated marshes will likely drown, resulting in extensive losses of coastal wetlands. VL - 98 IS - 25 N1 - Donnelly, J PBertness, M DengResearch Support, Non-U.S. Gov't2001/11/29 10:00Proc Natl Acad Sci U S A. 2001 Dec 4;98(25):14218-23. Epub 2001 Nov 27. U2 - PMC64662 JO - Rapid shoreward encroachment of salt marsh cordgrass in response to accelerated sea-level rise ER - TY - THES T1 - Ricostruzioni paleoambientali nel Mare di Ross (Antartide) attraverso lo studio di associazioni di foraminiferi--Thesis Y1 - 2001 A1 - Orsini, G. PB - Universita di Bologna CY - Bologna, Italy VL - Dissertation/Thesis ER - TY - RPRT T1 - The search for early shell middens on San Miguel Island, California Y1 - 2001 A1 - Erlandson, Jon M. PB - University of Oregon CY - Eugene, Oregon N1 - id: 331 ER - TY - JOUR T1 - Sedimentary evidence of intense hurricane strikes from New Jersey JF - Geology Y1 - 2001 A1 - Donnelly, J. P. A1 - Roll, S. A1 - Wengren, M. A1 - Butler, J. A1 - Lederer, R. A1 - Webb, T. AB - Nine Vibracores from the backbarrier marsh at Whale Beach, New Jersey, reveal three large-scale overwash deposits associated with historic and prehistoric storms. The uppermost and smallest overwash fan was deposited in the Ash Wednesday northeaster of March 5-8, 1962, A second more substantial overwash fan between 100 and 35 cm depth dates to the late eighteenth or early nineteenth century. This fan was most likely deposited during the 1821 hurricane, the only intense hurricane to make landfall in New jersey in the past 350 yr, A third, larger overwash fan between 200 and 300 cm depth was deposited between A.D. 1278 and 1438 and is likely the result of a prehistoric intense hurricane strike. The combination of historical and stratigraphic evidence indicates that two intense hurricanes (winds > 50 m s(-1)) have likely made landfall on the southern New Jersey coast in the past 700 yr, resulting in an annual landfall probability of 0.3%. VL - 29 IS - 7 N1 - 449elTimes Cited:102Cited References Count:14 JO - Sedimentary evidence of intense hurricane strikes from New Jersey ER - TY - CONF T1 - A Silent Tandetron AMS System T2 - Proceedings of the 31st SNEAP Y1 - 2001 A1 - von Reden, K. F. A1 - Schneider, R. J. JF - Proceedings of the 31st SNEAP PB - World Scientific Publishing Co. CY - Julich, Germany N1 - id: 1680 ER - TY - JOUR T1 - A solid state 13C NMR study of kerogen degradation during black shale weathering JF - Geochim. Cosmochim. Acta Y1 - 2001 A1 - Petsch, S. T. A1 - Smernik, R. J. A1 - Eglinton, T. I. A1 - Oades, J. M. VL - 65 N1 - id: 277 ER - TY - CONF T1 - Stratigraphic Development of a Northeastern South Carolina Barrier Island: Waites Island T2 - Geological Society of America National Meeting, Abstracts with Program Y1 - 2001 A1 - Wright, E. A1 - Harris, M. S. A1 - Sapp, A. A1 - Lewis, K. A1 - Kruse, S. A1 - Edgar, T. JF - Geological Society of America National Meeting, Abstracts with Program CY - Boston, MA N1 - id: 1410 ER - TY - RPRT T1 - Stratigraphy, paleoceanography, chronology, and paleoenvironment during deglaciation of eastern Maine, Report Y1 - 2001 A1 - Dorion, C. C. A1 - Balco, G. A1 - Kaplan, M. R. A1 - Kreutz, K. J. A1 - Wright, J. A1 - Borns, H. W. JF - Deglacial History and Relative Sea Level Changes, Northern New England and adjacent Canada PB - Geological Society of America CY - Boulder, CO VL - 242 N1 - id: 1333 ER - TY - THES T1 - Studi paleoambientali nel settore Pacifico dell'Oceano Meridionale attraverso indagini geochimiche--thesis Y1 - 2001 A1 - Giuliana, Tino PB - Universita di Bologna CY - Balogna, Italy VL - Dissertation/Thesis ER - TY - JOUR T1 - Subdivision of glacial deposits in southeastern Peru based on pedogenic development and radiometric ages JF - Quaternary Research Y1 - 2001 A1 - Goodman, A. Y. A1 - Rodbell, D. T. A1 - Seltzer, G. O. A1 - Mark, B. G. AB - The Cordillera Vilcanota and Quelccaya Ice Cap region of southern Peru (13 degrees 30'-14 degrees 00'S; 70 degrees 40'-71 degrees 25'W) contains a detailed record of late Quaternary glaciation in the tropical Andes, Quantification of soil development on 19 moraine crests and radiocarbon ages are used to reconstruct the glacial history. Secondary iron and day increase linearly in Quelccaya soils and clay accumulates at a linear rate in Vilcanota soils, which may reflect the semicontinuous addition of eolian dust enriched in secondary iron to all soils. In contrast, logarithmic rates of iron buildup in soils in the Cordillera Vilcanota reflect chemical weathering; high concentrations of secondary iron in Vilcanota tills may mask the role of eolian input to these soils. Soil-age estimates from extrapolation of field and laboratory data suggest that the most extensive late Quaternary glaciation occurred >70,000 yr B.P. This provides one of the first semiquantitative age estimates for maximum ice extent in southern Peru and is supported by a minimum-limiting age of similar to 41,520 C-14 yr B.P. A late glacial readvance culminated similar to 16,650 cal yr B.P. in the Cordillera Vilcanota, Following rapid deglaciation of unknown extent, an advance of the Quelccaya Ice Cap occurred between similar to 13,090 and 12,800 cal yr B.P., which coincides approximately with the onset of the Younger Dryas cooling in the North Atlantic region. Moraines deposited <394 cal yr B.P. in the Cordillera Vilcanota and <300 cal yr B.P. on the west side of the Quelccaya Ice Cap correlate with Little Ice Age moraines of other regions. (C) 2001 University or Washington. VL - 56 IS - 1 N1 - 452lzTimes Cited:27Cited References Count:51 JO - Subdivision of glacial deposits in southeastern Peru based on pedogenic development and radiometric ages ER - TY - JOUR T1 - Thirty thousand year record of climate from the Galapagos Islands and links with high latitudes JF - EOS Y1 - 2001 A1 - Koutavas, A. A1 - Lynch-Stieglitz, J. A1 - Sachs, J. P. A1 - Marchitto, T. M. AB - Fall Meeting Supplement F737 VL - 82 IS - 47 N1 - id: 255 JO - Thirty thousand year record of climate from the Galapagos Islands and links with high latitudes ER - TY - CONF T1 - Time-averaged shell accumulations as records of past levels of marine benthic productivity: Implications for conservation biology and ecosystem restoration efforst T2 - North American Paleontologial Convention, Programs and Abstracts Y1 - 2001 A1 - Kowalewski, M. A1 - Avila-Serrano, G. A. A1 - Flessa, K. W. A1 - Goodfriend, A. G. JF - North American Paleontologial Convention, Programs and Abstracts PB - Paleobios VL - 21 (supple. no. 2) N1 - id: 283 ER - TY - CONF T1 - Time-Averaging in articulate brachiopod accumulations: A quantitative estimate of temporal resolution from a Holocene tropical shelf (Southern Brazil) T2 - North American Paleontological Convention, Programs and Abstracts Y1 - 2001 A1 - Carroll, M. A1 - Kowalewski, M. A1 - Simoes, M. G. A1 - Goodfriend, G. A. JF - North American Paleontological Convention, Programs and Abstracts PB - Paleobios VL - 21 (supple. no. 2) N1 - id: 1418 ER - TY - JOUR T1 - Tropical climate changes at millennial and orbital timescales on the Bolivian Altiplano JF - Nature Y1 - 2001 A1 - Baker, P. A. A1 - Rigsby, C. A. A1 - Seltzer, G. O. A1 - Fritz, S. C. A1 - Lowenstein, T. K. A1 - Bacher, N. P. A1 - Veliz, C. AB - Tropical South America is one of the three main centres of the global, zonal overturning circulation of the equatorial atmosphere (generally termed the 'Walker' circulation1). Although this area plays a key role in global climate cycles, little is known about South American climate history. Here we describe sediment cores and down-hole logging results of deep drilling in the Salar de Uyuni, on the Bolivian Altiplano, located in the tropical Andes. We demonstrate that during the past 50,000 years the Altiplano underwent important changes in effective moisture at both orbital (20,000-year) and millennial timescales. Long-duration wet periods, such as the Last Glacial Maximum—marked in the drill core by continuous deposition of lacustrine sediments—appear to have occurred in phase with summer insolation maxima produced by the Earth's precessional cycle. Short-duration, millennial events correlate well with North Atlantic cold events, including Heinrich events 1 and 2, as well as the Younger Dryas episode. At both millennial and orbital timescales, cold sea surface temperatures in the high-latitude North Atlantic were coeval with wet conditions in tropical South America, suggesting a common forcing. VL - 409 N1 - id: 388 JO - Tropical climate changes at millennial and orbital timescales revealed by deep drilling on the South American altiplano ER - TY - JOUR T1 - Tropical cooling and the isotopic composition of precipitation in general circulation model simullations of the ice age climate JF - Climate Dynamics Y1 - 2001 A1 - Charles, C. D. A1 - Rind, D. A1 - Healy, R. A1 - Webb, R. VL - 17 N1 - id: 1716 ER - TY - JOUR T1 - Use of 14C and 13C natural abundances for evaluating riverine, estuarine, and coastal DOC and POC sources and cycling: Review and Synthesis JF - Org. Geochem Y1 - 2001 A1 - Raymond, P. A. A1 - Bauer, J. E. VL - 32 N1 - id: 278 ER - TY - JOUR T1 - Use of bomb radiocarbon to validate otolith section ages of red snapper Lutjanus campechanus from the northern Gulf of Mexico JF - Limnology and Oceanography Y1 - 2001 A1 - Baker, M. S. A1 - Wilson, C. A. AB - The red snapper Lutjanus campechanus is an important recreational and commercial fish species in the northern Gulf of Mexico. Management approaches have varied in part because of uncertainty of their longevity. Snapper ages have been based on presumed otolith annuli; however, this methodology has not been validated for all age classes. A recent technique to validate otolith age utilizes the increase in oceanic C-14 resulting from atmospheric testing of nuclear bombs during the 1950s and 1960s. Analyses of annuli from living corals and fish otoliths from 1900 to the present have documented that elevated C-14 input has occurred throughout the world's oceans. We validated otolith section age estimates through accelerator mass spectrometry analysis of bomb-produced C-14 in red snapper (otoliths) hatched before, during, and after the nuclear testing periods. Delta C-14 data from the otoliths of red snapper with presumed birth dates between 1960 and 1973 clearly reflect the sharp increase in oceanic radiocarbon attributable to previous nuclear testing. Similarities between the otolith and nearby coral Delta C-14 chronologies suggest that annulus-based age estimates of red snapper are valid on average to within 1-3 yr. In addition, this study provides the first carbonate bomb radiocarbon time series from the northern Gulf of Mexico. VL - 46 IS - 7 N1 - 491vzTimes Cited:36Cited References Count:22 JO - Use of bomb radiocarbon to validate otolith section ages of red snapper Lutjanus campechanus from the northern Gulf of Mexico ER - TY - JOUR T1 - U-Th dating of carbonate platform and slope sediments JF - Geochimica Et Cosmochimica Acta Y1 - 2001 A1 - Henderson, G. M. A1 - Slowey, N. C. A1 - Fleisher, M. Q. AB - Absolute chronology of marine sediment beyond the C-14 age range provides a test for models of climate change and has many other applications. U-Th techniques have been used for such chronology by dating corals, but extending these techniques to marine sediment is complicated by the presence of significant initial Th-230-both in detrital material and scavenged from seawater. In this study, we investigate four methods of solving the initial Th-230 problem for a particular type of marine sediment-the aragonite-rich sediments of carbonate platforms and slopes. Bulk sediment U-Th analyses can be corrected for initial Th to yield ages with approximate to2 to 3 kyr precision for highstand periods when sediment aragonite contents are particularly high. Uncertainty on the corrections causes inadequate precision for sediment from other periods, however. Removal of scavenged Th before analysis would enable a dramatic increase in this precision but has not proved successful despite a range of chemical leach approaches. Using heavy liquids to separate the various carbonate minerals found in Bahamas sediment enables an isochron approach to correct for initial Th, but the presence of initial Th from two sources requires correction or removal of one source of initial Th before the other is deconvolved by the isochron. Quantitative removal of detrital material before isochron analysis proves a successful approach. Such isochron data demonstrate that, although sediment remains closed to U-Th on a centimetre scale, nuclides are moved from grain to grain by alpha -recoil. Such intergrain exchange is expected to be observed in all sediments containing mineral grains with different U concentrations. Measured U-234/U-238 allows the recoil movement to be corrected and results in isochron ages with precision sometimes as low as 3 kyr. The accuracy of this approach has been proved by dating samples within the 14C age range. Sediments spanning the penultimate deglaciation have also been dated. After a small correction for bioturbation, the age for this event is found to be 135.2 +/- 3.5 ka. TWs date is approximate to8 kyr before the peak in northern hemisphere insolation and suggests that deglaciation is initiated by a mechanism in the southern hemisphere or tropics. This isochron approach shows considerable promise for dating of sediments older than this event, which will provide further information about the timing and mechanisms of global climate change. Copyright (C) 2001 Elsevier Science Ltd. VL - 65 IS - 16 N1 - 462zlTimes Cited:49Cited References Count:44 JO - U-Th dating of carbonate platform and slope sediments ER - TY - CONF T1 - Validation of compound-specific 14C dating using the varved sedimentary record of Saanich Inlet, Canada T2 - Proceedings of the 20th international meeting on organic geochemistry Y1 - 2001 A1 - Smittenberg, R. H. A1 - Hopmans, E. C. A1 - Eglinton, T. I. A1 - Hayes, J. M. A1 - Whiticar, M. J. A1 - Schouten, S. A1 - Sinninghe Damsté, J. S. JF - Proceedings of the 20th international meeting on organic geochemistry CY - Nancy, France N1 - id: 270 ER - TY - JOUR T1 - Vegetation succession and carbon sequestration in a coastal wetland in northwestern Florida: evidence from carbon isotopes JF - Global Biogeochemical Cycles Y1 - 2001 A1 - Choi, Y. A1 - Wang, Y. A1 - Hsieh, Y. P. A1 - Robinson, L. VL - 15 IS - 2 N1 - id: 267 ER - TY - JOUR T1 - Were Rhyolitic Glasses in the Vedde Ash and in the North Atlantic's Ash Zone 1 produced by the Same Volcanic Eruption? JF - Quaternary Science Reviews Y1 - 2001 A1 - Bond, G. C. A1 - Mandeville, C. A1 - Hoffmann, S. AB - New evidence from North Atlantic deep-sea sediment cores suggests that rhyolitic glass shards in Ash Zone 1 and in the Vedde Ash may not have been produced by the same eruption as has been widely assumed. Our argument is based on (1) a marine ice-rafted deposit approximately 1000 years older than the Vedde Ash contains rhyolitic shards with the same major element chemistry as the Vedde Ash itself and (2) coincidence of Ash Zone 1 with an abrupt increase in discharge of glacial icebergs into the North Atlantic. Hence, we cannot rule out the possibility that Vedde-like rhyolitic glasses were erupted onto Icelandic glaciers before eruption of the Vedde Ash, stored in the glacial ice, then dispersed by icebergs into the North Atlantic and deposited partly or entirely as Ash Zone 1. While not disproving that Ash Zone 1 and the Vedde Ash came from the same eruption, our findings indicate that further study is needed to establish the exact relation between the two ash deposits. VL - 20 N1 - id: 253 JO - Were Rhyolitic Glasses in the Vedde Ash and in the North Atlantic's Ash Zone 1 produced by the Same Volcanic Eruption? ER - TY - CHAP T1 - 14C Dating of sediment of the Uppermost Cape Fear Slide Plain: Constraints on the timing of this massive submarine landslide (Book Section) T2 - Scientific Results of the Ocean Drilling Program, Leg 164 Y1 - 2000 A1 - Rodriquez, N. M. A1 - Paull, C. K. ED - Paull, C. K. JF - Scientific Results of the Ocean Drilling Program, Leg 164 T3 - Ocean Drilling Program CY - College Station, TX VL - 164 N1 - id: 1342 ER - TY - JOUR T1 - Acceptance of the 1997 Alfred E. Treibs Award JF - Geochimica Et Cosmochimica Acta Y1 - 2000 A1 - Hayes, J. M. VL - 64 IS - 4 N1 - 287naTimes Cited:0Cited References Count:0 JO - Acceptance of the 1997 Alfred E. Treibs Award ER - TY - JOUR T1 - Age and composition of carbonate shoreface sediments, Kailua Bay, Oahu, Hawaii JF - Coral Reefs Y1 - 2000 A1 - Harney, J. N. A1 - Grossman, E. E. A1 - Richmond, B. M. A1 - Fletcher, C. H. AB - The origin, age, and dynamics of carbonate sediments in Kailua Bay on Oahu, Hawaii, are described. The shoreface (from shoreline to 4 km offshore) consists of a broad (5 km(2)) fringing coral reef ecosystem bisected by a sinuous, shore-normal, sand-filled paleostream channel 200-300 m wide. The median grain diameter of surface sands is finest on the beach face (<0.3 mm) and increases offshore along the channel axis. Kailua sands are >90% biogenic carbonate, dominated by skeletal fragments of coralline algae (e.g. Porolithon, up to 50%) followed by the calcareous green alga Halimeda (up to 32%), coral fragments (1-24%), mollusc fragments (6-21%), and benthic foraminifera (1-10%). Sand composition and age across the shoreface are correlated to carbonate production. Corals and coralline algae, principal builders of the reef framework, are younger and more abundant in sands along the channel axis and in offshore reefal areas, while Halimeda, molluscs, and foraminifera are younger and more dominant in nearshore waters shoreward of the main region of framework building. Shoreface sediments are relatively old. Of 20 calibrated radiocarbon dates on skeletal constituents of sand, only three are younger than 500 years B.P.; six are 500-1000 years B.P.; six are 1000-2000 years B.P.; and five are 2000-5000 years B.P. Dated fine sands are older than medium to coarse sands and hence may constitute a reservoir of fossil carbonate that is distributed over the entire shoreface. Dominance of fossiliferous sand indicates long storage times for carbonate grains, which tend to decrease in size with age, such that the entire period of relative sea-level inundation (similar to 5000 years) is represented in the sediment. Despite an apparently healthy modern coral ecosystem, the surficial sand pool of Kailua Bay is dominated by sand reflecting an antecedent system, possibly one that existed under a + 1-2 m sea-level high stand during the mid- to late Holocene. VL - 19 IS - 2 N1 - 341wmTimes Cited:32Cited References Count:43 JO - Age and composition of carbonate shoreface sediments, Kailua Bay, Oahu, Hawaii ER - TY - CHAP T1 - Amino acid racemization in ostracodes T2 - Perspectives in Amino Acid and Protein Geochemistry Y1 - 2000 A1 - Kaufman, D. S. ED - Goodfriend, G. A. JF - Perspectives in Amino Acid and Protein Geochemistry PB - Oxford University Press SN - 0195135075 N1 - id: 1390 ER - TY - JOUR T1 - An artificial landscape-scale fishery in the Bolivian Amazon JF - Nature Y1 - 2000 A1 - Erickson, C. L. AB - Historical ecologists working in the Neotropics argue that the present natural environment is an historical product of human intentionality and ingenuity, a creation that is imposed, built, managed and maintained by the collective multigenerational knowledge and experience of Native Americans. In the past 12,000 years, indigenous peoples transformed the environment, creating what we now recognize as the rich ecological mosaic of the Neotropics. The prehispanic savanna peoples of the Bolivian Amazon built an anthropogenic landscape through the construction of raised fields, large settlement mounds, and earthen causeways. I have studied a complex artificial network of hydraulic earthworks covering 525 km2 in the Baures region of Bolivia. Here I identify a particular form of earthwork, the zigzag structure, as a fish weir, on the basis of form, orientation, location, association with other hydraulic works and ethnographic analogy. The native peoples used this technology to harvest sufficient animal protein to sustain large and dense populations in a savanna environment. VL - 408 IS - 6809 N1 - Erickson, C LengHistorical ArticleResearch Support, Non-U.S. Gov'tResearch Support, U.S. Gov't, Non-P.H.S.England2000/11/23 11:00Nature. 2000 Nov 9;408(6809):190-3. JO - An artificial landscape-scale fishery in the Bolivian Amazon ER - TY - THES T1 - Black carbon in lacustrine and coastal marine sediments, Thesis Y1 - 2000 A1 - Muri, G. PB - University of Ljubljana, Slovenia CY - Ljubljana, Slovenia VL - PhD ER - TY - JOUR T1 - Characterising the Namaqualand mudbelt of southern Africa: chronology, palynology and palaeoenvironments JF - South African Geographical Journal Y1 - 2000 A1 - Gray, C. E. D. A1 - Meadows, M. E. A1 - Lee-Thorp, J. A. A1 - Rogers, J. VL - 82 IS - 136-141 N1 - id: 219 ER - TY - JOUR T1 - Chesapeake Bay sedimentary record of Holocene climatic variability and human ecosystem disturbance JF - Geology Y1 - 2000 A1 - Cronin, T. A1 - Willard, D. A1 - Karlsen, A. A1 - Ishman, S. A1 - Verardo, S. A1 - McGeehin, J. A1 - Kerhin, R. A1 - Holmes, C. A1 - Colman, S. M. A1 - Zimmerman, A. VL - 28 N1 - id: 184 ER - TY - CHAP T1 - Chronostratigraphy of sediments in the southern Gulf of California, based on amino acid racemization analysis of mollusks and rhodolith (Book Section) T2 - Perspectives in Amino Acid and Protein Geochemistry Y1 - 2000 A1 - Goodfriend, G. A. A1 - Halfar, J. A1 - Godinez-Orta, L. ED - Goodfriend, G. A. JF - Perspectives in Amino Acid and Protein Geochemistry PB - Oxford University Press, NY N1 - id: 174 ER - TY - CHAP T1 - Climate change in the northern American tropics since the last ice age: implications for environment and culture (Book Section) T2 - Imperfect Balance: Landscape transformations in the Precolumbian Americas Y1 - 2000 A1 - Hodell, D. A. A1 - Brenner, M. A1 - Curtis, J. H. ED - Lentz, D. L. JF - Imperfect Balance: Landscape transformations in the Precolumbian Americas PB - Columbia University Press CY - NY N1 - id: 198 ER - TY - JOUR T1 - Climate, fire, and vegetation between about 13,000 and 9,200 14C yr. B. P JF - Quaternary Research Y1 - 2000 A1 - Moreno, P. I. VL - 54 N1 - id: 237 ER - TY - JOUR T1 - A continuous high-resolution record of late Pleistocene climate variability from the Estacia basin, New Mexico JF - Geological Society of America Bulletin Y1 - 2000 A1 - Allen, B. D. A1 - Anderson, R. Y. KW - Lacustrine sediments KW - Last glacial maximum KW - ostracodes KW - Paleoclimate KW - trace metals AB - Lake sediments that accumulated in the Estancia basin, central New Mexico, provide a detailed record of submillennial latest Pleistocene climatic oscillations. Sedimentologic, biologic, and geochemical proxies for changes in salinity and lake level were used to identify episodes of wet and dry climate that occurred between 24 and 12 k.y. B.P., as dated by 14C by means of accelerator mass spectrometry from shoreline and basin-center deposits. These dates determine the timing and duration of the episodes of wet and dry climate. The lake expanded and contracted repeatedly during the last glacial maximum and fluctuated near its highest elevation several times during the interval ca. 20 to 15 k.y. B.P. A pronounced lowstand lasting ∼1 k.y. occurred between ca. 15 and 14 k.y. B.P., followed by two more highstands of the lake between ca. 14 and 12.5 k.y. B.P. Desiccation of the perennial lake after 12 k.y. B.P. was followed by a final, poorly dated highstand at ca. 10 k.y. B.P. The record of lake-level fluctuations from the Estancia basin provides a high-resolution record of changes in water budget in a basin, the comparatively simple physiography and hydrogeology of which ensured a direct response to the strong climatic fluctuations that occurred during the last glacial maximum and termination. VL - 112 IS - 9 N1 - id: 239 JO - A continuous high-resolution record of late Pleistocene climate variability from the Estacia basin, New Mexico ER - TY - JOUR T1 - d13C values and radiocarbon dates of microbial biomarkers as tracers fro carbon recycling in peat deposits JF - Geology Y1 - 2000 A1 - Pancost, R. D. A1 - van Geel, B. A1 - Baas, M. A1 - Damste Sinninghe, J. S. VL - 28 N1 - id: 1330 ER - TY - CONF T1 - Deep Sea Sediments off Baja California Reflect Greenland Ice Core climate cycles T2 - Geological Society of America, Annual meeting Y1 - 2000 A1 - Ortiz, J. A1 - O'Connell, S. A1 - van Geen, A. A1 - Party, Melville ' Shipboard Scientific JF - Geological Society of America, Annual meeting PB - Geological Society of America CY - Reno, NV N1 - id: 110 ER - TY - JOUR T1 - Detecting holocene changes in thermohaline circulation JF - Proc Natl Acad Sci U S A Y1 - 2000 A1 - Keigwin, L. D. A1 - Boyle, E. A. KW - *Climate KW - *Plankton KW - Animals KW - Atlantic Ocean KW - carbon isotopes KW - ice KW - oxygen isotopes KW - time AB - Throughout the last glacial cycle, reorganizations of deep ocean water masses were coincident with rapid millennial-scale changes in climate. Climate changes have been less severe during the present interglacial, but evidence for concurrent deep ocean circulation change is ambiguous. VL - 97 SN - 0027-8424 (Print)0027-8424 (Linking) UR - https://www.ncbi.nlm.nih.gov/pubmed/10677463 IS - 4 N1 - Keigwin, L DBoyle, E A eng Research Support, U.S. Gov't, Non-P.H.S. 2000/03/04 09:00 Proc Natl Acad Sci U S A. 2000 Feb 15;97(4):1343-6. ER - TY - JOUR T1 - Differences in great earthquake rupture extent inferred from tsunami-laid sand and foraminiferal assemblages at Alsea Bay, central Oregon coast JF - Geological Society of America Abstracts with Programs Y1 - 2000 A1 - Nelson, A. R. A1 - Jennings, A. E. VL - 33 IS - 7 N1 - id: 257 ER - TY - JOUR T1 - Ecosystem development and response to climatic change: a comparative study of forest-lake ecosystems on different substrates JF - Evolution and Behavior Y1 - 2000 A1 - Ewing, Holly A. N1 - id: 1384 ER - TY - JOUR T1 - Enormous Ganges-Brahmaputra sediment discharge during strengthened early Holocene monsoon JF - Geology Y1 - 2000 A1 - Goodbred, S. L., Jr. A1 - Kuehl, S. A. AB - Rivers are the main source of terrigenous sediment delivered to continental margins and thus exert a major control on coastal evolution and sequence development. However, little is known about past changes in fluvial sediment loads despite the recognition of significant variation under changing climatic regimes. In this study we present the first quantified estimate of sediment discharge for a major river system under conditions of an intensified early Holocene monsoon. Development of the Ganges-Brahmaputra River delta began ca. 11000 yr B.P., when rising sea level flooded the Bengal basin, thereby trapping most of the river's discharge on the inner margin. Chronostratigraphic data from these deltaic deposits are used to calculate the rates of sediment storage on the margin, which provide a minimum estimate of the river's past sediment load. Results reveal that ∼5 × 1012 m3 of sediment was stored in the Bengal basin from ca. 11000 to 7000 yr B.P., which corresponds to a mean load of 2.3 × 109 t/yr. In comparison, modern sediment load of the Ganges-Brahmaputra is ∼1 × 109 t/yr, ranking it first among the world's rivers and underscoring the significance of a two-fold increase sustained over 4 k.y. Furthermore, the timing of immense discharge in the early Holocene strongly suggests its relation to a stronger than present southwest monsoon in South Asia. Similar patterns of high monsoon-related sediment discharge have been noted throughout the tropics and subtropics, suggesting a widespread fluviosedimentary response, the potential magnitude of which is showcased by the Ganges-Brahmaputra system. VL - 28 IS - 12 N1 - id: 147 JO - Enormous Ganges-Brahmaputra sediment discharge during strengthened early Holocene monsoon ER - TY - RPRT T1 - Environmental changes in the last centure in Little Trout Lake, Inkspot Bay, Great Corn and Little Corn Lakes, Lac du Flambeau Tribal Lands, Wisconsin. Report Y1 - 2000 A1 - Winkler, M. G. A1 - Sanford, P. R. VL - Final Report to Water Resources Division, Lac du Flambeau Tribe N1 - id: 128 ER - TY - RPRT T1 - Erosional scour and geologic evolution of Croatan Sound, northeastern North Caroline: N.C Y1 - 2000 A1 - Riggs, S. R. A1 - Rudolph, G. L. A1 - Ames, D. V. PB - Department of Transportation VL - FHA/NC/2000-02 N1 - id: 243 ER - TY - JOUR T1 - An estimate of the anthropogenic offset of oceanic d13CDIC based on the ventilation of the California Current at 42N JF - Global Biogeochem. Cycles Y1 - 2000 A1 - Ortiz, J. D. A1 - Mix, A. C. A1 - Wheeler, P. A1 - Key, R. M. VL - 14 IS - 3 N1 - id: 307 ER - TY - JOUR T1 - Evidence from U-Th dating against Northern Hemisphere forcing of the penultimate deglaciation JF - Nature Y1 - 2000 A1 - Henderson, G. M. A1 - Slowey, N. C. AB - Milankovitch proposed that summer insolation at mid-latitudes in the Northern Hemisphere directly causes the ice-age climate cycles. This would imply that times of ice-sheet collapse should correspond to peaks in Northern Hemisphere June insolation. But the penultimate deglaciation has proved controversial because June insolation peaks 127 kyr ago whereas several records of past climate suggest that change may have occurred up to 15 kyr earlier. There is a clear signature of the penultimate deglaciation in marine oxygen-isotope records. But dating this event, which is significantly before the 14C age range, has not been possible. Here we date the penultimate deglaciation in a record from the Bahamas using a new U-Th isochron technique. After the necessary corrections for alpha-recoil mobility of 234U and 230Th and a small age correction for sediment mixing, the midpoint age for the penultimate deglaciation is determined to be 135 +/- 2.5 kyr ago. This age is consistent with some coral-based sea-level estimates, but it is difficult to reconcile with June Northern Hemisphere insolation as the trigger for the ice-age cycles. Potential alternative driving mechanisms for the ice-age cycles that are consistent with such an early date for the penultimate deglaciation are either the variability of the tropical ocean-atmosphere system or changes in atmospheric CO2 concentration controlled by a process in the Southern Hemisphere. VL - 404 IS - 6773 N1 - HendersonSloweyengEngland2000/03/15 09:00Nature. 2000 Mar 2;404(6773):61-6. JO - Evidence from U-Th dating against Northern Hemisphere forcing of the penultimate deglaciation ER - TY - JOUR T1 - Further evidence of abrupt Holocene drowning of the Black Sea shelf JF - Marine Geology Y1 - 2000 A1 - Ballard, R. D. A1 - Coleman, D. F. A1 - Rosenberg, G. D. AB - A 1999 survey of the Black Sea continental shelf off the north central Turkish seaport of Sinop using a side-scan sonar, small remotely operated vehicles, and a series of dredge lowerings located, inspected and sampled an exposed high-energy paleoshoreline at a depth of 155 m. Radiocarbon dating of mollusk shells collected from this ancient beach revealed that the marine flooding of the Black Sea took place between 7460 and 6820 yr B.P. tall ages are reported in radiocarbon years, not calendar years, without correction for reservoir age or dendro-calibration) changing it from a lacustrine to marine environment. This relic surface remained in contact with the bottom waters of the Black Sea for a long period of time before being draped by a thin layer of sapropel mud. Wood samples recovered from this same location were very well preserved and yielded dates as old as 3580 yr B.P. (C) 2000 Elsevier Science B.V. All rights reserved. VL - 170 IS - 3-4 N1 - 380xeTimes Cited:71Cited References Count:8 JO - Further evidence of abrupt Holocene drowning of the Black Sea shelf ER - TY - THES T1 - Geochemical and Lithological Records of the Hypsithermal and Nipissing Flood Event from Lake Erie--Thesis Y1 - 2000 A1 - Kempthorne, Rebecca PB - University of Akron CY - Akron, Ohio VL - M.S. ER - TY - JOUR T1 - A giant vampire (Mammalia, Chiroptera) in the Late Holocene from the Argentinean pampas: paleoenvironmental significance JF - Palaeogeography Palaeoclimatology Palaeoecology Y1 - 2000 A1 - Pardinas, U. F. J. A1 - Tonni, E. P. AB - The first fossil desmodontine record and the only well documented chiropteran fossil record from Argentina is described. A complete left upper canine was collected at Centinela del Mar (38 degrees 21'S58 degrees W, General Alvarado County, Buenos Aires Province) from fossil-bearing sediments referred to the Late Holocene. The tooth size is 25% larger than that of the modern vampire bat. Desmodus rotundus. We assign this tooth to Desmodus cf. D. draculae, an extinct species recorded in the Pleistocene-Holocene of South America (Brazil and Venezuela). The southernmost distribution of present-day Desmodus extends to northeast Buenos Aires province (35 degrees S). The presence of Desmodus some 600 km south of this present-day limit (July minimal isotherm of 10 degrees C) indicates that around 300 years BP the southeastern Buenos Aires province was at least 2 degrees C higher than modern July isotherm. The Desmodus tooth is associated with sigmodontine rodents characteristic of subtropical and temperate-warm areas (e.g., Pseudoryzomys simplex, Bibimys cf. B. torresi), and provides additional evidence to support this hypothesis. A correlation with a global warming phase is discussed. (C) 2000 Elsevier Science B.V. All rights reserved. VL - 160 IS - 3-4 N1 - 330jhTimes Cited:12Cited References Count:40 JO - A giant vampire (Mammalia, Chiroptera) in the Late Holocene from the Argentinean pampas: paleoenvironmental significance ER - TY - JOUR T1 - Glacial deep water geometry: South Atlantic Benthic foraminiferal Cd/Ca and delta13C evidence JF - Paleoceanography Y1 - 2000 A1 - Oppo, Delia W. A1 - Horowitz, Michael VL - 15 IS - 2, April 2000 N1 - id: 13050883-8305/00/1999PA000436 ER - TY - CONF T1 - Glacial-Interglacial variations in the accumulation rates of major biogenic components in the Southern Pacific Ocean sediments--Abstract T2 - Third International SO-JGOFS Symposium Y1 - 2000 A1 - Giglio, F. A1 - Langone, L. A1 - Ravaioli, M. A1 - Frignani, M. A1 - Mangini, A. A1 - Fonti, P. JF - Third International SO-JGOFS Symposium CY - Brest N1 - id: 287 ER - TY - RPRT T1 - Global Distribution of Total Inorganic Carbon and Total Alkalinity Below the Deepest Winter Mixed Layer Depths Y1 - 2000 A1 - Goyet, C. A1 - Healy, R. A1 - Ryan, J. AB - Modeling the global ocean-atmosphere carbon dioxide system is becoming increasingly important to greenhouse gas policy. These models require initialization with realistic three- dimensional (3-D) oceanic carbon fields. This report presents an approach to establishing these initial conditions from an extensive global database of ocean carbon dioxide (CO2) system measurements and well-developed interpolation methods. These methods are limited to waters below the deepest mixed layer. The data used for these interpolations include the recent high-quality data sets from the World Ocean Circulation Experiment (WOCE), Joint Global Ocean Flux Study (JGOFS), and Ocean-Atmosphere Carbon Exchange Study (OACES) programs. Prior to analysis, all carbon data were adjusted to established reference material listed in http://andrew.ucsd.edu/co2qc/. The interpolation methodology employs correlation between CO2 system properties and other more widely measured properties: potential temperature, salinity, and apparent oxygen utilization. The correlations are computed for each profile, and the coefficients are interpolated to the 1°×1°×32 vertical-layer grid at a monthly temporal resolution. Finally, the gridded coefficients are applied to a global monthly climatology of ocean temperature, salinity, and oxygen to compute total CO2 (TCO2) and total alkalinity (TALK) for the 3-D grid. This approach offers advantages over spin up of a single profile in defining spatial variation in CO2 system properties because it reduces initialization time and provides a more accurate carbon field. The results provide an unprecedented "view" of the global distribution of TALK and TCO2 in the ocean. These results as well as those from the monthly mixed layer depths can be used in diagnostic and prognostic global ocean models. The data set of the gridded climatological fields of TCO2, TALK, and mixed layer depths is available free of charge as a numeric data package from the Carbon Dioxide Information Analysis Center (CDIAC). The interpolated data set includes seasonal TCO2 and TALK fields as well as the coefficients used to estimate these concentrations and the monthly mixed layer depths. PB - Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory CY - Oak Ridge, Temessee VL - ORNIJCDIAC-127 NDP-076 N1 - id: 1970 ER - TY - RPRT T1 - Gulf of Mexico Intraslope Basins (BIB) Phase 1 Project Atlas Y1 - 2000 A1 - Damuth, J. E. A1 - Olson, H. C. A1 - Moss, G. PB - Institute for Geophysics, University of Texas at Austin Department of Geology and Geophysics, University of Texas at Arlington N1 - id: 354 ER - TY - CONF T1 - High resolution proxy record of late Quaternary climate change from Soledad Basis, northwest Mexico, Abstract T2 - UK Pages Y1 - 2000 A1 - Pike, J. A1 - van Geen, A. A1 - Beaufort, L. A1 - Party, Shipboard Scientific JF - UK Pages N1 - id: 111 ER - TY - JOUR T1 - Holocene and recent rates of sediment accumulation in southern Lake Michigan JF - Quaternary Science Reviews Y1 - 2000 A1 - Colman, S. M. A1 - King, J. W. A1 - Jones, G. A. A1 - Reynolds, R. L. A1 - Bothner, M. H. VL - 19 N1 - id: 183 ER - TY - JOUR T1 - Holocene cirque glacier activity in Western Spitsbergen, Svalbard: sediment records from pro-glacial Linnevatnet JF - The Holocene Y1 - 2000 A1 - Snyder, J. A. A1 - Werner, A. A1 - Miller, G. H. VL - 5 N1 - id: 234 ER - TY - JOUR T1 - Holocene climate in the western Great Lakes national parks and lakeshores: Implications for future climate change JF - Conservation Biology Y1 - 2000 A1 - Davis, M. A1 - Douglas, C. A1 - Calcote, R. A1 - Cole, K. L. A1 - Winkler, M. G. A1 - Flakne, R. AB - We reconstruct Holocene climate history (last 10,000 years) for each of the U.S. National Park Service units in the western Great Lakes region in order to evaluate their sensitivity to global warming. Annual precipitation, annual temperature, and July and January temperatures were reconstructed by comparing fossil pollen in lake sediment with pollen in surface samples, assuming that ancient climates were similar to modern climate near analogous surface samples. In the early Holocene, most of the parks experienced colder winters, warmer summers, and lower precipitation than today. An exception is Voyageurs National Park in northern Minnesota where, by 8000 years ago, January temperatures were higher than today. The combination of high mean annual temperature and lower precipitation at Voyageurs resulted in a dry period between 8000 and 5000 years ago, similar to the Prairie Period in regions to the south and west. A mid-Holocene warm-dry period also occurred at other northern and central parks but was much less strongly developed. In southern parks there was no clear evidence of a mid-Holocene warm-dry period. These differences suggest that global model predictions of a warm, dry climate in the northern Great Plains under doubled atmospheric CO2 may be more applicable to Voyageurs than to the other parks. The contrast in reconstructed temperatures at Voyageurs and Isle Royale indicates that the ameliorating effect of the Great Lakes on temperatures has been in effect throughout the Holocene and presumably will continue in the future, thus reducing the potential for species loss caused by future temperature extremes. Increased numbers of mesic trees at all of the parks in the late Holocene reflect increasing annual precipitation. This trend toward more mesic conditions began 6000 years ago in the south and 4000 years ago in the north and increased sharply in recent millennia at parks located today in lake-effect snow belts. This suggests that lake-effect snowfall is sensitive to continental-scale changes in climate and could be affected by future climate change. Plant and animal species sensitive to changes in the moisture regime could thus be endangered within the Great Lakes parks. VL - 14 IS - 4 N1 - 338uvTimes Cited:47Cited References Count:46 JO - Holocene climate in the western Great Lakes national parks and lakeshores: Implications for future climate change ER - TY - JOUR T1 - The Holocene history of Lake Victoria, East Africa JF - Ambio Y1 - 2000 A1 - Johnson, T. C. A1 - Kelts, K. A1 - Odada, E. O. VL - 29 N1 - id: 340 ER - TY - JOUR T1 - Holocene hydrological reconstructions from stable isotopes and paleolimnology, Cordillera Real, Bolivia JF - Quarternary Science Reviews Y1 - 2000 A1 - Abbott, M. B. A1 - Wolfe, A. P. A1 - Aravena, R. A1 - Wolfe, A. P. A1 - Seltzer, G. O. AB - Multiproxy analyses of sediment cores from Lago Taypi Chaka Kkota (LTCK) Cordillera Real, Bolivia, provide a record of drier conditions following late Pleistocene deglaciation culminating in pronounced aridity between 6.2 and 2.3 ka B.P. Today LTCK is a glacial-fed lake that is relatively insensitive to changes in P–E because it is largely buffered from dry season draw-down through the year-round supply of glacial meltwater. This was not the case during the middle to late Holocene when glaciers were absent from the watershed. Lake-water δFull-size image (<1 K) values inferred from δFull-size image (<1 K) analysis of sediment cellulose range from −12.9 to −5.3‰ and average −8.7‰ between 6.2 and 2.3 ka B.P. Modern lake-water δFull-size image (<1 K) from LTCK averages −14.8‰ which is compatible with the δFull-size image (<1 K) value of −14.3‰ for the surface sediment cellulose. Analyses of δFull-size image (<1 K) from modern surface waters in 23 lakes that span the range from glacial-fed to closed basin vary from −16.6 to −2.5‰. This approximates the magnitude of the down-core shift in δFull-size image (<1 K) values in LTCK during the middle to late Holocene from −12.9 to −5.3‰. Strong paleohydrologic change during the middle Holocene is also evident in diatom assemblages that consist of shallow-water, non-glacial periphytic taxa and bulk organic δFull-size image (<1 K) and δFull-size image (<1 K) that show increases likely resulting from degradation of lacustrine organic matter periodically exposed to subaerial conditions. Neoglaciation began after 2.3 ka B.P. as indicated by changes in the composition of the sediments, lower δFull-size image (<1 K) values, and a return to diatom assemblages characteristic of the glacial sediments that formed during the Late Pleistocene. Collectively, these data indicate that the past 2.3 ka B.P. have been the wettest interval during the Holocene. Millennial-scale shifts in the paleohydrologic record of LTCK during the early to middle Holocene conform to other regional paleoclimatic time-series, including Lake Titicaca and Nevado Sajama, and may be driven by insolation and resultant changes in atmospheric circulation and moisture supply. In contrast, an apparent 1200-year lag in the onset of wetter conditions at LTCK (2.3 ka B.P.) compared to Lake Titicaca (3.5 ka B.P.) provides evidence for variable sub-regional hydrologic response to climate change during the middle to late Holocene. VL - 19 IS - 17-18 N1 - id: 1206 JO - Palaeolimnology, Cordillera Real Bolivia ER - TY - JOUR T1 - Holocene lake sediment records of Arctic hydrology JF - Journal of Paleolimnology Y1 - 2000 A1 - MacDonald, G. M. A1 - Felzer, B. A1 - Finney, B. P. A1 - Forman, S. L. KW - Arctic KW - Climate change KW - Holocene KW - paleohydrology KW - paleolimnology AB - Although paleoclimatic research in the Arctic has most often focused on variations in temperature, the Arctic has also experienced changes in hydrologic balance. Changes in Arctic precipitation and evaporation rates affects soils, permafrost, lakes, wetlands, rivers, ice and vegetation. Changes in Arctic soils, permafrost, runoff, and vegetation can influence global climate by changing atmospheric methane and carbon dioxide concentrations, thermohaline circulation, and high latitude albedo. Documenting past variations in Arctic hydrological conditions is important for understanding Arctic climate and the potential response and role of the Arctic in regards to future climate change. Methods for reconstructing past changes in Arctic hydrology from the stratigraphic, isotopic, geochemical and fossil records of lake sediments are being developed, refined and applied in a number of regions. These records suggest that hydrological variations in the Arctic have been regionally asynchronous, reflecting the impacts of different forcing factors including orbitally controlled insolation changes, changes in geography related to coastal emergence, ocean currents, sea ice extent, and atmospheric circulation. Despite considerable progress, much work remains to be done on the development of paleohydrological proxies and their application to the Arctic. VL - 24 IS - 1 N1 - id: 375 JO - S. L. Holocene lake sediment records of Arctic hydrology ER - TY - JOUR T1 - Ice core evidence for climate change in the Tropics: implications for our future JF - Quaternary Science Reviews Y1 - 2000 A1 - Thompson, L. G. AB - Reliable meteorological observations for climate reconstruction are limited or absent prior to A.D. 1850 for much of the Earth and particularly in both tropical South America and the Tibetan Plateau region of central Asia. Over 50% of the Earth's surface lies between 30 degrees N and 30 degrees S and 75% of the world's inhabitants live and conduct their activities in these tropical regions. Thus, much of the climatic activity of significance to humanity, such as variations in the occurrence and intensity of the El Nino-Southern Oscillation and monsoons, are largely confined to lower latitudes. Moreover, the variability of these tropical systems and particularly that of the tropical hydrological system in response to regional and global climate forcing are not well understood. Fortunately, ice core records are also available from selected high altitude, low and mid-latitude ice caps. The ice core studies described here were undertaken as part of a long-term program to acquire the global-scale, high-resolution climatic and environmental history essential for understanding more fully the linkages between the low and the high latitudes. Two ice core records, one covering the last full glacial cycle from the Guliya Ice Cap, China (35 degrees N; 6200 m asl) and one from Huascaran, Peru, which reveal significant cooling during the Last Glacial Cycle Maximum (LGM similar to 20,000 yr BP) are compared with preliminary data coming from the new Sajama, Bolivia (18 degrees S, 6550 m asl) and the Dasuopu, Himalaya (China, 28 degrees N, 7200 m asl) cores. Lower delta(18)O values (equivalent to cooling of similar to 8 degrees C) contribute to the growing body of evidence that the tropical climate was cooler and more variable during the last glacial cycle and has renewed current interest in the tropical water vapor cycle. The new tropical ice core records raise additional questions about our understanding of the role of the tropics in global climate. Unfortunately, as a result of recent warming, all known tropical glaciers and ice caps are retreating and soon will no longer continue to preserve viable paleoclimatic records. The characteristics of the current warming will be examined and compared to earlier periods of climatic warming such as the transition form the last glacial into the current interglacial as well as other periods within the Holocene. It is important to distinguish natural variation in the climate system from the anthropogenic influences superimposed during the: last century. These tropical ice cores offer long-term perspectives of accumulation, temperature, atmospheric dust and "greenhouse" gas concentrations against which recent variations may be assessed, with particular relevance for lower latitude regions where most people live. (C) 1999 Elsevier Science Ltd. All rights reserved. VL - 19 IS - 1-5 N1 - 268pvTimes Cited:145Cited References Count:54 JO - Ice core evidence for climate change in the Tropics: implications for our future ER - TY - JOUR T1 - Ice Core Paleoclimate Records in Tropical South America Since the Last Glacial Maximum JF - Journal of Quaternary Science Y1 - 2000 A1 - Thompson, L. G. A1 - Mosley-Thompson, E. A1 - Henderson, K. A. VL - 15 IS - 4 N1 - id: 245 ER - TY - JOUR T1 - Identification of a novel alkenone in Black Sea sediments JF - Organic Geochemistry Y1 - 2000 A1 - Xu, L. A1 - Reddy, C. M. A1 - Farrington, J. W. A1 - Frysinger, G. S. A1 - Gaines, R. B. A1 - Johnson, C. G. A1 - Nelson, R. K. A1 - Eglinton, T. I. KW - Alkenone KW - Black Sea KW - Haptophytes KW - Holocene KW - Sediment KW - Structure characterization AB - We report the identification of a novel long-chain ketone in Holocene Black Sea sediments. Based on chemical properties, and chromatographic and mass spectrometric characteristics, this compound has been identified as a di-unsaturated C36 ethyl ketone. Further analyses indicated the position and configuration of the double bonds, and the novel alkenone was determined to be hexatriaconta-(16E,21E)-dien-3-one. While this compound is present in only trace quantities in Unit I sediments, it is the most abundant alkenone in portions of Unit II. Its presence thus apparently pre-dates the invasion of Emiliania huxleyi in the Black Sea. The down-core profiles and isotopic compositions suggest that the precursor for the C36:2 alkenone may be distinct from that of the C37-39 alkenones, however the biological origin of this novel compound is presently unknown. VL - 32 N1 - id: 1719 JO - Identification of a novel alkenone in Black Sea sediments ER - TY - JOUR T1 - Identification of Seasonal-to-Decadal Timescale Variations in the Zonal Currents of the Central Equatorial Pacific Prior to 1955 Using A14C in Coral JF - EOS Y1 - 2000 A1 - Grottoli, A. G. A1 - Druffel, E. R. M. A1 - Gille, S. T. A1 - Dunbar, R. B. AB - F767 VL - 81 IS - 48 N1 - id: 254 ER - TY - CONF T1 - Identification of seasonal-to-decadal timescale variations in the zonal currents of the central equatorial Pacific T2 - International Coral Reef Symposium Y1 - 2000 A1 - Grottoli, A. G. A1 - Druffel, E. R. M. A1 - Gille, S. T. A1 - Dunbar, R. B. JF - International Coral Reef Symposium CY - Bali N1 - id: 1401 ER - TY - THES T1 - Implementazione di sistemi di datazione con il 14C ed estensione all 'impiego di piccole quantita di materiale, Thesis Y1 - 2000 A1 - Salvatore, Improta PB - Universita degli studi di Roma La Sapienza CY - Roma VL - Dissertation/Thesis ER - TY - JOUR T1 - The Indian Ocean 13C Suess effect JF - Global Biogeochemical Cycles Y1 - 2000 A1 - Sonnerup, R. E. A1 - Quay, P. D. A1 - McNichol, A. P. VL - 14 N1 - id: 1816 ER - TY - JOUR T1 - Installation of a 134-sample MC-SNICS ion source at NOSAMS and first results JF - Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions with Materials and Atoms Y1 - 2000 A1 - von Reden, K. F. A1 - Bellino, M. A1 - Long, P. A1 - Schneider, R. J. A1 - Loger, R. KW - AMS KW - beam extraction/injection KW - C-14 KW - ion sources KW - ocean KW - pacific AB - In April 1999, the National Ocean Sciences AMS (NOSAMS) facility received the shipment of a 134-sample MC-SNICS ion source from the National Electrostatics Corporation (NEC). It replaced one of the two 59-sample spherical ionizer sources (US-AMS Model 3090A, HVEE Model 846). In this paper, we will describe the adaptation of the NEC ion source to the US-AMS/HVEE recombinator injector at NOSAMS. This is the first lime that the two leading sputter ion source designs are directly comparable on the same system. We will present ion beam optics calculations for both in comparison with measured results. Once fully operational, the new ion source will assume all of the sputter sample measurements at NOSAMS, while the remaining 59-sample source will be replaced by the newly developed microwave gas ion source. One of the most desirable features of the MC-SNICS design is the smaller cathode geometry. At comparable extracted currents, the surface diameter of the pressed samples is reduced from 1.5 to 1 mm. A new, automatic sample pressing procedure is being developed for this design. This will improve the capability for preparing and analyzing smaller sputter samples (carbon weight <100 g). Our US-AMS cathodes showed considerable reduction in the extracted currents when the sample diameter was reduced to 1 mm, even with samples of normal size (>200 mug C). (C) 2000 Elsevier Science B.V. All rights reserved. VL - 172 SN - 0168-583X N1 - 8th International Conference on Accelerator Mass SpectrometrySEP 06-10, 1999 VIENNA, AUSTRIA JO - Nucl. Instrum. Methods Phys. Res. Sect. B-Beam Interact. Mater. Atoms ER - TY - JOUR T1 - Isotopic evidence for Late Glacial and Holocene climatic change in the tropical Andes JF - Geology Y1 - 2000 A1 - Seltzer, G. A1 - Rodbell, D. A1 - Burns, S. VL - 28 IS - 35-38 N1 - id: 1338 ER - TY - JOUR T1 - Lake Erie: The Impact of Mid-Holocene Flooding by Upper Great Lake Waters JF - EOS, Transactions, American Geophysical Union Y1 - 2000 A1 - Kempthorne, R. A. A1 - Barrera, E. A1 - Coakley, J. P. A1 - Palmer, D. F. VL - 81 IS - 19 N1 - id: 248 ER - TY - JOUR T1 - Late glacial paleohydrology and vegetational change in Salada Medinana, Central Ebro Basin, Spain JF - Quarternary International Y1 - 2000 A1 - Valero-Garces, B. L. VL - 73/74 N1 - id: 382 ER - TY - JOUR T1 - A late Holocene pollen record from Torrey Pine State Reserve, California JF - Quaternary Research Y1 - 2000 A1 - Cole, K. L. A1 - Wahl, Eugene VL - 53 N1 - id: 214 ER - TY - CHAP T1 - Late Pleistocene and Holocene geological evolution of the central Penobscot River Valley: Surficial geology, geoarchaeology, and water supply (Book Section) T2 - Guidebook for Field Trips in Coastal and East-Central Maine: NEIGC 92nd Annual Meeting Y1 - 2000 A1 - Kelly, A. R. A1 - Dorion, C. C. A1 - Balco, G. A1 - Dieffenbacher-Krall, A. A1 - Garrett, P. A1 - Locke, D. A1 - Tolman, A. ED - Yates, M. G. JF - Guidebook for Field Trips in Coastal and East-Central Maine: NEIGC 92nd Annual Meeting CY - Orono, ME N1 - id: 152 ER - TY - CONF T1 - Late Quaternary sedimentary fluctuations of biogenic fluxes driven by climatic changes in the Southern Ocean--abstract T2 - XXV General Assembly of European Geophysical Society Y1 - 2000 A1 - Langone, L. A1 - Giglio, F. A1 - Ravaioli, M. A1 - Frignani, M. A1 - Marozzi, G. A1 - Rovatti, G. JF - XXV General Assembly of European Geophysical Society CY - Nice, France N1 - id: 288 ER - TY - JOUR T1 - Lipids as a Common Interest of Microorganisms and Geochemists (Commentary) JF - Proc. National Academy Sciences USE Y1 - 2000 A1 - Hayes, John M. VL - 98 N1 - id: 1778 ER - TY - CHAP T1 - Lomas de ocupacion en los Llanos de Moxos (Book Section) T2 - La Arqueologia de las Tierras Bajas Y1 - 2000 A1 - Erickson, Clark L. ED - Duran Coirolo, Alicia JF - La Arqueologia de las Tierras Bajas PB - Comision Nacional de Arqueologia, Ministerio de Educacion y Cultura CY - Montevideo, Uruguay N1 - id: 180 ER - TY - CHAP T1 - Los caminos prehispanicos de la amazonia boliviana (Book Section) T2 - Vias Precolombinas: los caminos, los ingenieros y los viajeros Y1 - 2000 A1 - Erickson, Clark L. ED - Herrera, Leonor JF - Vias Precolombinas: los caminos, los ingenieros y los viajeros PB - Instituto Colombiano de Antropología y Historia CY - Bogata, Colombia N1 - id: 179 ER - TY - JOUR T1 - Low-level (submicromole) environmental 14C metrology JF - Nucl. Instr. and Meth. in Phys. Res. Y1 - 2000 A1 - Currie, L. A. A1 - Kessler, J. D. A1 - Marolf, J. V. A1 - McNichol, A. P. A1 - Stuart, D. R. A1 - Donoghue, J. C. VL - B IS - 172 N1 - id: 1713 ER - TY - JOUR T1 - Mapping of C4 plant input from North West Africa into North East Atlantic Sediments JF - Geochimica et Cosmochima Acta Y1 - 2000 A1 - Huang, Yongsong A1 - Dupont, Lydie A1 - Sarnthein, Michael A1 - Hayes, John M. A1 - Eglinton, Geoffrey VL - 64 N1 - id: 1777 ER - TY - JOUR T1 - Mass spectra of sn-2hydroxyarchaeol, a Polar-lipid Biomarker for Anaerobic Methanotrophy JF - Geochem. Geophys. Geosyst. Y1 - 2000 A1 - Hinrichs, Kai-Uwe A1 - Pancost, Richard D. A1 - Summons, Roger E. A1 - Sprott, G. Dennis A1 - Sylva, Sean P. A1 - Sinninghe-Damste, Jaap S. A1 - Hayes, John M. VL - 1 IS - 2000GC000042 N1 - id: 1735 ER - TY - JOUR T1 - Memorial to Henry G. Thode, 1910-1997 JF - Geological Society of America Memorials Y1 - 2000 A1 - Shaw, Denis M. A1 - Epstein, Sam A1 - Hayes, John M. VL - 31 N1 - id: 1737 ER - TY - JOUR T1 - Molecular and isotopic analysis of anaerobic methane-oxidizing communities in marine sediments JF - Organic Geochemistry Y1 - 2000 A1 - Hinrichs, K. U. A1 - Summons, R. E. A1 - Orphan, V. A1 - Sylva, S. P. A1 - Hayes, J. M. AB - Convergent lines of molecular, carbon-isotopic, and phylogenetic evidence have previously indicated (Hinrichs, K.U., Hayes, J.M., Sylva, S.P., Brewer. P.G.. DeLong, E.F., 1999. Methane-consuming archaebacteria in marine sediments. Nature 398, 802-805.) that archaea are involved in the anaerobic oxidation of methane in sediments from the Eel River Basin. offshore northern California. Now, further studies of those same sediments and of sediments from a methane seep in the Santa Barbara Basin have confirmed and extended those results. Mass spectrometric and chromatographic analyses of an authentic standard of sn-2-hydroxyarchaeol (hydroxylated at C-3 in the sn-2 phytanyl moiety) have confirmed our previous, tentative identification of this compound but shown that the previously examined product was the mono-TMS, rather than di-TMS, derivative. Further analyses of C-13-depleted lipids, appreciably more abundant in samples from the Santa Barbara Basin, have shown that the archaeal lipids are accompanied by two sets of products that are only slightly less depleted in C-13. These are additional glycerol ethers and fatty acids. The alkyl substituents in the ethers (mostly monoethers, with some diethers) are non-isoprenoidal. The carbon-number distributions and isotopic compositions of the alkyl substituents and of the fatty acids are similar, suggesting strongly that they are produced by the same organisms. Their structures, n-alkyl and methyl-branched n-alkyl, require a bacterial rather than archaeal source. The non-isoprenoidal glycerol ethers are novel constituents in marine sediments but have been previously reported in thermophilic, sulfate- and nitrate-reducing organisms which lie near the base of the rRNA-based phylogenetic tree. Based on previous observations that the anaerobic oxidation of methane involves a net transfer of electrons from methane to sulfate, it appears likely that the non-archaeal, C-13-depleted lipids are products of one or more previously unknown sulfate-reducing bacteria which grow syntrophically with the methane-utilizing archaea. Their products account for 50% of the fatty acids in the sample from the Santa Barbara Basin. At all methane-seep sites examined, the preservation of aquatic products is apparently enhanced because the methane-oxidizing consortium utilizes much of the sulfate that would otherwise be available for remineralization of materials from the water column. Crown Copyright (C) 2000 Published by Elsevier Science Ltd. All rights reserved. VL - 31 IS - 12 N1 - 384quTimes Cited:204Cited References Count:49 JO - Molecular and isotopic analysis of anaerobic methane-oxidizing communities in marine sediments ER - TY - JOUR T1 - The N and W Iceland Shelf: insights into Last Glacial Maximum ice extent and deglaciation based on acoustic stratigraphy and basal radiocarbon AMS dates JF - Quaternary Science Reviews Y1 - 2000 A1 - Andrews, J. T. A1 - Hardardottir, J. A1 - Helgadottir, G. A1 - Jennings, A. E. A1 - Geirsdottir, A. A1 - Sveinbjornsdottir, A. E. A1 - Schoolfield, S. A1 - Kristjansdottir, G. B. A1 - Smith, L. M. A1 - Thors, K. A1 - Syvitski, J. P. M. AB - We present 32 AMS radiocarbon dates collected from sediments obtained during cruises of CSS Hudson (1993, RV Jan Mayen (1996), and Bjarni Saemundsson (1997). The radiocarbon dates were obtained on samples from the basal part of sediment cores collected across an area between 64 and 67 degrees N and 18-29 degrees W. Core sites were based on 3.5 kHz acoustic subbottom surveys. The 3.5 kHz subbottom profiles indicate that several of the troughs contain greater than or equal to 30 m of Quaternary sediment. At many sites, the acoustic surveys suggest the presence of one or more strong reflectors which can be traced over extended areas ( > 100 km) of the seafloor. These may represent large-scale volcanic ash falls, such as the Vedde ash and its correlatives, as well as other regionally significant tephras. We report dates from seven areas; (1) Northern troughs - Eyjafjardarall, Hunafloadjup, and Reykjafjardarall: (2) Hunafloi area and inner shelf and fjords; (3) Djupall area; (4) Isafjardardjup area; (5) Kolluall; (6) western shelf break and slope; and 7) Jokuldjup. The dates range in age from Marine Isotope Stages 3-1. Five cores have basal dates greater than or equal to 16 ka and thus provide information on the timing and environments during the deglaciation, Several dates of similar to 12 ka indicate that the inner shelf may have been largely ice-free by that time. Estimates of average sediment accumulation rates vary between 4 and 90 cm/kyr, with modal estimates of 30-30 cm/kyr, (C) 2000 Elsevier Science Ltd. All rights reserved. VL - 19 IS - 7 N1 - 298udTimes Cited:71Cited References Count:75 JO - The N and W Iceland Shelf: insights into Last Glacial Maximum ice extent and deglaciation based on acoustic stratigraphy and basal radiocarbon AMS dates ER - TY - JOUR T1 - A New Estimate of the Holocene Lowstand Level of Lake Titicaca and Implications for Tropical Paleohydrology JF - The Holocene Y1 - 2000 A1 - Cross, S. C. A1 - Baker, P. A. A1 - Seltzer, G. O. A1 - Fritz, S. C. VL - 10 N1 - id: 1339 ER - TY - JOUR T1 - The NOSAMS sample preparation laboratory in the next millenium: Progress after the WOCE program JF - Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions with Materials and Atoms Y1 - 2000 A1 - Gagnon, A. R. A1 - McNichol, A. P. A1 - Donoghue, J. C. A1 - Stuart, D. R. A1 - von Reden, K. AB - Since 1991, the primary charge of the National Ocean Sciences AMS (NOSAMS) facility at the Woods Hole Oceanographic Institution has been to supply high throughput, high precision AMS C-14 analyses for seawater samples collected as part of the World Ocean Circulation Experiment (WOCE). Approximately 13,000 samples taken as part of WOCE should be fully analyzed by the end of Y2K. Additional sample sources and techniques must be identified and incorporated if NOSAMS is to continue in its present operation mode.A trend in AMS today is the ability to routinely process and analyze radiocarbon samples that contain tiny amounts (<100 g) of carbon. The capability to mass-produce small samples for C-14 analysis has been recognized as a major facility goal. The installation of a new 134-position MC-SNICS ion source, which utilizes a smaller graphite target cartridge than presently used, is one step towards realizing this goal. New preparation systems constructed in the sample preparation laboratory (SPL) include an automated bank of 10 small-volume graphite reactors, an automated system to process organic carbon samples, and a multi-dimensional preparative capillary gas chromatograph (PCGC). (C) 2000 Elsevier Science B.V. All rights reserved. VL - 172 IS - 172 N1 - 372jrTimes Cited:20Cited References Count:12 JO - The NOSAMS sample preparation laboratory in the next millenium: Progress after the WOCE program ER - TY - JOUR T1 - Oceanic uptake of CO2 re-estimated through d13C in WOCE samples JF - Nuclear Instruments and Methods in Physics Research Y1 - 2000 A1 - Lerperger, M. A1 - McNichol, A. P. A1 - Peden, J. A1 - Gagnon, A. R. A1 - Elder, K. L. A1 - Kutschera, W. A1 - Rom, W. A1 - Steier, P. VL - B (172) IS - 1-4 N1 - id: 1817 ER - TY - CONF T1 - An ocean-wide DIC-13 data set T2 - AGU Ocean Sciences Meeting Y1 - 2000 A1 - McNichol, A. P. A1 - Quay, P. D. A1 - Stuart, D. R. A1 - Sonnerup, R. E. A1 - Key, R. M. JF - AGU Ocean Sciences Meeting CY - San Antonio, TX N1 - id: 1444 ER - TY - CONF T1 - An Ocean-Wide DIC-13 Data Set T2 - 2000 Ocean Sciences Meeting, San Antonio, TX (USA), 24-28 Jan 2000 Y1 - 2000 A1 - McNichol, A P A1 - Quay, P D A1 - Stuart, D R A1 - Sonnerup, R E A1 - Key, R M KW - carbon cycling KW - Carbon dioxide KW - Deep water KW - dissolved inorganic carbon KW - ISW, Indian Ocean KW - Marine KW - Mass Spectrometry KW - Ocean circulation KW - Phosphates KW - PS, Antarctic Ocean KW - Q2 09146:TSD distribution, water masses and circulation KW - Stable isotopes KW - Standardization KW - Water masses KW - World Ocean KW - World Ocean Circulation Experiment (WOCE) AB - High quality DIC-13 measurements were made throughout the world's oceans at the University of Washington (UW) and the National Ocean Sciences Accelerator Mass Spectrometry (NOSAMS) Facility during both the OACES and WOCE programs. We are currently merging these two data sets which represent 25000 individual DIC- 13 measurements from 1260 stations. We will present the inter-laboratory calibration and standardization data. Based on 135 measurements on CO2 gas extracted at UW, the mean offset between the two labs is 0.01 o/oo, similar to the offset observed from an exchange of DIC standards (0.012 o/oo). Stations measured by both laboratories will also be examined for offsets, although one comparison in the Indian Ocean shows no significant differences. We will present our progress towards a global atlas of DIC-13, primarily maps of the merged data sets in the Pacific, Southern, and Indian Oceans. In this poster we will concentrate on regions that have been under-sampled in the past, e.g. the Southern Ocean. Additionally, we will examine the relationship of DIC-13 to PO4 and to DIC-14. A preliminary analysis of DIC-13 and PO4 from three WOCE lines in the Pacific indicates that the expected relationship is observed in the deep waters and that the data from different water masses occupy well-defined regions of the graph. We are examining the potential for using the relationship between DIC-14 and DIC-13 to improve our understanding of the penetration of bomb radiocarbon into the ocean as well as fundamental processes in the deep ocean. The relationship is complex yet the data from shallow to intermediate depths (100 to 1000m) follow two distinct parallel lines that are related to the hemisphere in which JF - 2000 Ocean Sciences Meeting, San Antonio, TX (USA), 24-28 Jan 2000 PB - American Geophysical Union, 2000 Florida Ave., N.W. Washington, DC 20009 USA UR - https://search.proquest.com/docview/19610793?accountid=29119 N1 - Date revised - 2007-04-01SuppNotes - Abstracts available.Last updated - 2016-12-21 ER - TY - JOUR T1 - An organic tracer for surface ocean radiocarbon JF - Paleoceanography Y1 - 2000 A1 - Pearson, A. A1 - Eglinton, T. I. A1 - McNichol, A. P. AB - The Delta(14)C of surface water dissolved inorganic carbon (DIC) in the Southern California Eight was compared to Delta(14)C as recorded by the sterols in Santa Monica and Santa Barbara Basin sediments. All of the C-26, C-27, C-28, and C-29 sterols as well as dinosterol had C-14 concentrations equal to surface water DIG, indicating that all of the major sterols were derived from phytoplanktonic production. There is no detectable terrestrial component. Their tracer capability was confirmed by comparing the "bomb C-14"-derived change in surface water Delta(14)C(DIC) With the change in Delta(14)C(sterol). The "prebomb" Delta(14)C(DIC) was similar to 82 parts per thousand, and prebomb sterols averaged -75 +/- 19 parts per thousand. The Delta(14)C value in 1996 was +71 parts per thousand, Eighteen measurements representing eight different sterols from the sediment-water interface of both Santa Monica and Santa Barbara Basins averaged +62 +/- 23 parts per thousand. When three of these values were eliminated because of suspected contamination, the remaining data averaged +71 +/- 12 parts per thousand. The entire compound class could serve as an excellent proxy for the C-14 concentration of ocean surface waters. VL - 15 IS - 5 N1 - 358wyTimes Cited:37Cited References Count:58 JO - An organic tracer for surface ocean radiocarbon ER - TY - JOUR T1 - Organogenic dolomitization in peritidal to deep-sea sediments JF - Journal of Sedimentary Research Y1 - 2000 A1 - Mazzullo, S. J. AB - Presumed barriers to early dolomitization in normal seawater-derived pore fluids at earth-surface temperatures appear to be overcome within some anoxic, organic-rich sediments as a result of bacterial sulfate reduction and methanogenesis, These processes may promote early dolomitization, particularly during methanogenesis and late stages of sulfate reduction, by concurrently raising and sustaining high pH and high total alkalinity and CO32- concentrations in pore fluids, and by simultaneously either decreasing Mg and Ca hydration or by promoting crystal surface reactions with less hydrated Mg-Ca neutral ion pairs. Volumetrically significant quantities of dolomite are associated with sulfate reduction and/or methanogenesis within peritidal, shallow-marine, and deep-sea deposits. Average concentrations of organogenic dolomite are as much as 70% in some Holocene peritidal deposits, and 28% in Mesozoic to Quaternary deep-sea sediments.Organogenic dolomites are mainly cements, and contain relatively low concentrations of Sr and Mn, Sulfate-reduction dolomites generally are Fe-deficient because of concurrent pyrite precipitation, whereas methanogenetic dolomites may be somewhat more ferroan as Fe substitutes for depleting Mg. Sources of Mg and Ca for dolomite are diffusion from overlying seawater and/or dissolution of precursor carbonate sediments. Dolomites are characterized by a wide range in delta(13)C values wherein those of sulfate reduction versus methanogenetic origin typically are C-13-depleted and C-13-enriched, respectively. The extent of C-13 depletion or enrichment, however, depends on the extent of organodiagenetic reactions and amount of C-13 contributed by seawater diffusion, and commonly results in overlap of delta(13)C(dolomite) values. The range of delta(18)O(dolomite) values is somewhat more restricted, and generally reflects differences in pore-fluid temperature and salinity. Some of the unresolved issues in organogenic dolomitization are: the relative efficiencies of sulfate reduction versus methanogenesis in promoting dolomitization, depths of dolomite formation inferred on the basis of delta(18)O(dolomite) values and probable sources of Mg and Ca, and the mode of dolomitization with progressive burial into methanogenetic zones. VL - 70 IS - 1 N1 - A287nxTimes Cited:125Cited References Count:106 JO - Organogenic dolomitization in peritidal to deep-sea sediments ER - TY - JOUR T1 - The origin of Antarctic precipitation: a modelling approach JF - Tellus Series B-Chemical and Physical Meteorology Y1 - 2000 A1 - Delaygue, G. A1 - Masson, V. A1 - Jouzel, J. A1 - Koster, R. D. A1 - Healy, R. J. AB - The contribution of different moisture sources to Antarctic precipitation for present-day and glacial conditions is estimated with the NASA/GISS Atmospheric General Circulation Model. Despite its low horizontal resolution (8 degrees x 10 degrees), this model simulates reasonably well the broad features of the observed present-day hydrological cycle. Simulated present-day Antarctic precipitation is dominated throughout the year by moisture from a subtropical/midlatitude band (30 degrees S-60 degrees S). The moisture supplied to a given coastal area of Antarctica originates mostly in the adjacent oceanic basin; closer to the pole, other oceanic basins can also contribute significantly. Replacing the present-day sea surface temperatures (SSTs) and sea ice cover in the GCM with those from the CLIMAP oceanic reconstruction for the last glacial maximum (LGM), greatly increases the simulated latitudinal temperature gradient, with the consequence of slightly enhancing the contribution of low latitude moisture to Antarctic precipitation. It also changes the seasonality of the different contributions and thus their budget, particularly in coastal regions. Because the nature of LGM tropical SSTs is still under debate, Ne performed an additional LGM simulation in which the tropical SSTs are reduced relative to those of CLIMAP. The resulting decrease in the latitudinal gradient brings the relative contributions to Antarctic precipitation more in line with those of the present-day simulation. VL - 52 IS - 1 N1 - id: 1942; PT: J; UT: WOS:000085432600002 JO - The origin of Antarctic precipitation: a modelling approach ER - TY - JOUR T1 - The origin of n-alkanes in Santa Monica Basin surface sediment: A model based on compount-specific Delta14C and delta13C data JF - Org. Geochem Y1 - 2000 A1 - Pearson, A. A1 - Eglinton, T. I. VL - 31 N1 - id: 364 ER - TY - JOUR T1 - Osmium isotopes demonstrate distal trnasport of contaminated sediments in Chesapeake Bay JF - Environmental Science Technology Y1 - 2000 A1 - Helz, G. R. A1 - Adelson, J. M. A1 - Miller, C. V. A1 - Cornwell, J. C. A1 - Hill, J. M. A1 - Horan, M. A1 - Walker, R. J. VL - 34 IS - 2528-2534 N1 - id: 1371 ER - TY - JOUR T1 - Ostracode Mg/Ca ratios suggest warmer-than-present early and middle Holocene in the western Arctic Ocean JF - EOS, Transactions, American Geophysical Union Y1 - 2000 A1 - Dwyer, G. S. VL - 81 IS - 4 N1 - id: 1475 ER - TY - CONF T1 - OxCal analyses and varve-based sedimentation rates constrain the times of 14C-dated tsunamis in southern Oregon T2 - Abstract for Geological Society of America Penbrose Conference on Great Cascadia Earthquake Tricentennial Seaside Y1 - 2000 A1 - Nelson, A. R. A1 - Kelsey, H. M. A1 - Hemphill-Haley, Eileen A1 - Witter, R. C. JF - Abstract for Geological Society of America Penbrose Conference on Great Cascadia Earthquake Tricentennial Seaside CY - Seaside, Oregon N1 - id: 1405 ER - TY - CONF T1 - Paleoceanographic changes in the Southern Ocean (Pacific sector) during the last 14 Ka.--Poster T2 - Third International SO-JGOFS Symposium Y1 - 2000 A1 - Morigi, C. A1 - Capotondi, L. A1 - Ravaioli, M. A1 - Giglio, F. A1 - Turi, B. A1 - Brilli, M. A1 - Langone, L. JF - Third International SO-JGOFS Symposium CY - Brest N1 - id: 1422 ER - TY - THES T1 - Paleoclimate signals in a speleothem from Belize, Senior Thesis Y1 - 2000 A1 - Gaines, Sarah M. PB - Princeton University CY - Princeton, NJ VL - Dissertation/Thesis ER - TY - CONF T1 - Palynlogical evidence for human occupation between 2550 and 1270 years BP recorded in two mountain wetlands (near Sagalassos, western Taurus range, SW Turkey) T2 - International Symposium on High Mountain Lakes and Streams Y1 - 2000 A1 - Vermoere, M. A1 - Waelkens, M. A1 - E, Smets JF - International Symposium on High Mountain Lakes and Streams N1 - id: 1370 ER - TY - RPRT T1 - Particle mixing and sediment accumulation rates of Peconic Estuary sediments: A sediment accretion study in support of the Peconic Estuary Program (Report) Y1 - 2000 A1 - Cochran, J. K. A1 - Hirschberg, D. J. A1 - Amiel, D. VL - Proj #0014400598181563 N1 - id: 1344 ER - TY - JOUR T1 - Postglacial and Late Holocene earthquakes on the Toe Jam strand of the Seattle fault, Bainbridge Island Washington JF - Geological Society of America Abstracts with Programs Y1 - 2000 A1 - Nelson, A. R. A1 - Johnson, S. Y. A1 - Pezzopane, S. K. A1 - Wells, R. E. A1 - Kelsey, H. M. A1 - Sherrod, B. L. A1 - Koehler, R. D. A1 - Bradley, L. A. A1 - Bucknam, R. C. A1 - LaPrade, W. T. A1 - Cox, J. W. A1 - Narwold, C. F. VL - 32 N1 - id: 258 ER - TY - JOUR T1 - Postglacial climate and vegetation history, north-central Kola Peninsula, Russia: pollen and diatom records from Lake Yarnyshnoe-3 JF - Boreas Y1 - 2000 A1 - Snyder, J. A. A1 - MacDonald, G. M. A1 - Forman, S. L. A1 - Tarasov, G. A. A1 - Mode, W. N. KW - atlantic KW - finnish lapland KW - Holocene KW - late pleistocene KW - norway KW - sea KW - sediments KW - varanger-peninsula KW - western part KW - younger-dryas AB - A sediment core from Lake Yamyshnoe-3 (69 degrees 04'N; 36 degrees 04'E), an emerged coastal lake from the tundra of the north-central Kola Peninsula, has been analyzed for fossil pollen and diatoms. The pollen record shows the Younger Dryas event marked by increasing Artemisia coupled with decreases in Poaceae, Cyperaceae and Salix at c. 10 700 to 10 000 BP. This core provides the first well-defined palynological record of the Younger Dryas event on the Kola Peninsula. Stomates from Pinus were recovered from the core interval between 8000 and 6000 BP. The stomates, coupled with elevated values of pine pollen, indicate that Pinus sylvestris grew near the arctic coastline of the central Kola Peninsula in the middle Holocene. However, the small number of stomates suggests that pines were not plentiful. The diatom record from the core reflects basin isolation from the sea and indicates additional limnological changes during the climate transition between c. 5000 and 4000 BP. The broadly similar climate and vegetation history on the north-central Kola Peninsula and in Fennoscandia demonstrates the propagation of late glacial and Holocene climate events from the North Atlantic region into the Eurasian Arctic. VL - 29 SN - 0300-9483 IS - 4 N1 - 378dxTimes Cited:28 Cited References Count:82 JO - Boreas ER - TY - JOUR T1 - Procesos y formas periglaciares en la montana mediterranea JF - Instituto de Estudios Turolenses, Teruel Y1 - 2000 A1 - Garcia-Ruiz, J. M. N1 - id: 371 ER - TY - JOUR T1 - Processes and rates of Holocene sedimentation in Santa Monica Bay, CA JF - EOS Y1 - 2000 A1 - Sommerfield, C. K. A1 - Lee, H. J. VL - Transactions of the American Geophysical Union IS - 80:49 N1 - id: 139 ER - TY - JOUR T1 - Quantitative estimates of time-averaging in articulate brachiopod accumulations from a Holocene tropical shelf (Southern Brazil) JF - Geological Society of America Abstracts with Programs Y1 - 2000 A1 - Carroll, M. A1 - Kowalewski, M. A1 - Simoes, M. G. A1 - Goodfriend, G. A. VL - 32 N1 - id: 124 ER - TY - THES T1 - Quaternary Geology of Central Sheboygan County, Wisconsin, Thesis Y1 - 2000 A1 - Chapel, Dawn PB - University of Wisconsin CY - Madison, Wisconsin VL - MS ER - TY - JOUR T1 - Quaternary palaeohydrological evolution of a playa lake: Salada Mediana, central Ebro Basin, Spain JF - Sedimentology Y1 - 2000 A1 - Valero-Garces, B. L. A1 - Delgado-Huertas, A. A1 - Navas, A. A1 - Machin, J. A1 - Gonzalez-Samperiz, P. A1 - Kelts, K. AB - Sedimentary features, mineralogy, bulk geochemical composition, stable isotope analyses and pollen data from sediment cores were used to reconstruct the Late Quaternary depositional evolution of the Salada Mediana playa lake (central Ebro Basin, northeastern Spain). The 150-cm-long sediment core sequence is composed of gypsum- and dolomite-rich muds (Lower and Middle sections) and black, laminated, calcite-bearing sediments (Upper section). The Salada Mediana formed as a karstic depression in the Miocene gypsum substratum during the Late Pleistocene. The Lower section was deposited in a sulphate-carbonate saline lake that ended with a period of desiccation and basin floor deflation. Subsequent deposition (Middle section) took place in a playa-lake system. Two cycles of lower water table and expanded saline mud flats occurred. The Holocene sequence is missing, probably as a result of aeolian erosion. Sedimentation resumed only a few centuries ago, and saline pan environments dominated until modern times. The Salada Mediana facies succession was mainly governed by fluctuations in the hydrological balance, brine composition, and salinity; however, aeolian processes (detrital input and deflation) and recycling of previously precipitated salts also played a significant role. VL - 47 IS - 6 N1 - 383xwTimes Cited:31Cited References Count:76 JO - Quaternary palaeohydrological evolution of a playa lake: Salada Mediana, central Ebro Basin, Spain ER - TY - JOUR T1 - The radiocarbon age of calcite dissolving at the sea floor: Estimates from pore water data JF - Geochimica Et Cosmochimica Acta Y1 - 2000 A1 - Martin, W. R. A1 - McNichol, A. P. A1 - McCorkle, D. C. AB - We measured the radiocarbon content and stable isotopic composition of pore water and bottom water Sigma CO2, sedimentary organic carbon, and CaCO3 at two sites on the Ceara Rise, one underlying bottom water that is supersaturated with respect to calcite (Site B), the other underlying undersaturated bottom water (Site G). The results were combined with pore water O-2, Sigma CO2, and Ca2+ profiles (Martin and Sayles, 1996) to estimate the radiocarbon content of the CaCO3 that is dissolving in the sediment mixed layer. At Site G, the CaCO3 that is dissolving in the upper 2 cm of the sediments is clearly younger (richer in C-14) than the bulk sedimentary CaCO3, indicating that nonhomogeneous CaCO3 dissolution occurs there. The case for nonhomogeneous dissolution is much weaker at the site underlying supersaturated bottom water. The results indicate that nonhomogeneous dissolution occurs in sediments underlying undersaturated bottom water, that the dissolution is rapid relative to the rate of homogenization of the CaCO3 in the mixed layer by bioturbation, and that the dissolution rate of CaCO3 decreases as it ages in the sediment mixed layer. The results support the hypothesis, based on solid phase analyses, that the preferential dissolution of young (i.e., radiocarbon-rich) CaCO3 leads to a pattern of increasing radiocarbon age of mixed-layer CaCO3 as the degree of undersaturation of bottom water increases (Keir, 1984; Broecker et al., 1991). Copyright (C) 2000 Elsevier Science Ltd. VL - 64 IS - 8 N1 - 303ueTimes Cited:26Cited References Count:31 JO - The radiocarbon age of calcite dissolving at the sea floor: Estimates from pore water data ER - TY - CONF T1 - Radiocarbon calibration and abruptchanges in atmospheric 14Cconcentration during Marine Isotope Stage 3 T2 - American Geophysical Union Y1 - 2000 A1 - Hughen, K. A. A1 - Southon, J. A1 - Lehman, S. J. A1 - Peterson, L. C. A1 - Overpeck, J. T. JF - American Geophysical Union CY - San Francisco, CA N1 - id: 327 ER - TY - JOUR T1 - The radiocarbon content of individual lignin-derived phenols: Technique and initial results JF - Radiocarbon Y1 - 2000 A1 - McNichol, A. P. A1 - Ertel, J. R. A1 - Eglinton, T. I. KW - AMS KW - isotope-ratio KW - NOSAMS KW - oxidation-products AB - We present a method for the isolation of phenolic compounds derived from lignin for radiocarbon analysis. These phenols are generated by chemical oxidation of polymeric materials and derivatized for separation and recovery by preparative capillary gas chromatography (PCGC). This technique yields tens of micrograms of pure, stable compounds that can he converted to graphite and analyzed by accelerator mass spectrometry (AMS). Analysis of model flavor compounds and dated woods indicates that, in most cases, the radiocarbon (C-14) contents of the individual compounds, corrected for the contribution of the derivative, agree with that of the bulk material to within 20 parts per thousand. VL - 42 SN - 0033-8222 IS - 2 N1 - 365vkTimes Cited:19 Cited References Count:17 JO - Radiocarbon ER - TY - JOUR T1 - Radiocarbon dated Pinus sylvertis L. wood from beyond treeline on the Kola Peninsula, Russia JF - The Holocene Y1 - 2000 A1 - MacDonald, G. M. A1 - Gervalis, B. A1 - Snyder, J. A. A1 - Tarasov, G. A. A1 - Borisova, O. A. AB - Radiocarbon dates were obtained from 24 samples of Pinus sylvestris L. (Scots pine) wood recovered from sites beyond the modern conifer tree-line on the Kola Peninsula of Russia. Twenty-one of the samples came from the shallow waters and eroding peats at the edges of two small lakes at 68°439N, 35°109E, located north of the modern conifer tree-line. Three samples came from a small pond located above the modern elevational limits of Pinus sylvestris at 68°259N, 35°199E. The radiocarbon dates indicate that pine trees grew approximately 20 km north of the mapped modern limits of the species from 6680 BP to 3830 BP. Pine trees were also growing some 40 m above their modern elevational limits between 5890 BP and 3450 BP. Nineteen of the samples date from 6680 BP to 5070 BP, suggesting that the density of trees north of the modern tree-line was greatest between 7000 and 5000 BP. The timing of tree-line advance and greatest density on the Kola Peninsula are in agreement with the results of similar studies from northern Fennoscandia which indicate that maximum northern and elevational extension of tree-line occurred between 7000 BP and 4000 BP. The general agreement between tree-line reconstructions suggests that the climatic changes that promoted mid-Holocene tree-line extension along the North Atlantic margins in northern Fennoscandia propagated eastward to the Kola Peninsula. The late timing of initial pine expansion on the Kola and in adjacent northern Fennoscandia remains problematic and may relate to lower winter insolation, temperature regimes in the adjacent oceans or slow rates of migration. VL - 10 UR - http://journals.sagepub.com/doi/abs/10.1191/095968300667807510 N1 - id: 376 JO - Radiocarbon dated Pinus sylvertis L. wood from beyond treeline on the Kola Peninsula, Russia ER - TY - JOUR T1 - Radiocarbon dates in China's Holocene Yangtze delta: record of sediment storage and reworking, not timing of deposition JF - Journal Coastal Res. Y1 - 2000 A1 - Stanley, D. J. A1 - Chen, Z. VL - 16 IS - 4 N1 - id: 230 ER - TY - CHAP T1 - Radiocarbon dating of Marion-Dufresne cores MD99-2204, 2207, and 2209, Chesapeake Bay T2 - Initial Report on IMAGES V Cruise of the Marion-Dufresne to the Chesapeake Bay June 20-22, 1999 Y1 - 2000 A1 - Colman, S. M. A1 - Bratton, J. F. A1 - Baucom, P. C. ED - Cronin, T. M. JF - Initial Report on IMAGES V Cruise of the Marion-Dufresne to the Chesapeake Bay June 20-22, 1999 PB - U. S. Geological Survey VL - Open-File Report 00-306 N1 - id: 1414 ER - TY - JOUR T1 - Radiocarbon dating the artifically contained surfaces of the Rhone deltaic plain, southern France JF - Journal Coastal Res. Y1 - 2000 A1 - Stanley, D. J. VL - 16 IS - 4 N1 - id: 1377 ER - TY - CONF T1 - The radiocarbon gradient at the Antarctic Polar Front T2 - AGU Ocean Sciences Meeting Y1 - 2000 A1 - Schneider, R. J. A1 - McNichol, A. P. A1 - von Reden, K. F. A1 - Elder, K. L. A1 - Gagnon, A. R. A1 - Key, R. M. A1 - Quay, P. D. A1 - Schlosser, P. M. JF - AGU Ocean Sciences Meeting CY - San Antonio, TX N1 - id: 317 ER - TY - JOUR T1 - Radiocarbon-Based Estimates of the Groundwater Contribution to Estuarine Freshwater Budgets: An Example from Pages Creek, North Carolina JF - EOS Y1 - 2000 A1 - McCorkle, D. C. A1 - Gramling, C. M. A1 - Mulligan, A. E. A1 - Woods, T. L. A1 - Lott, D. E. VL - 81 IS - 19 N1 - id: 1315 ER - TY - JOUR T1 - Rapid ice margin fluctuations during the Bolling/Allerod and Younger Dryas intervals in the Peruvian Andes JF - Quaternary Research Y1 - 2000 A1 - Rodbell, D. T. A1 - Seltzer, G. O. VL - 54 N1 - id: 392 ER - TY - JOUR T1 - Rapid ice margin fluctuations during the Younger Dryas in the tropical Andes JF - Quaternary Research Y1 - 2000 A1 - Rodbell, D. T. A1 - Seltzer, G. O. AB - Radiocarbon dated lacustrine sequences in Peru show that the chronology of glaciation during the late glacial in the tropical Andes was significantly out-of-phase with the record of climate change in the North Atlantic region. Fluvial incision of glacial-lake deposits in the Cordillera Blanca, central Peru, has exposed a glacial outwash gravel; radiocarbon dates from peat stratigraphically bounding the gravel imply that a glacier advance culminated between similar to 11,280 and 10,990 C-14 yr B.P.; rapid ice recession followed. Similarly, in southern Peru, ice readvanced between similar to 11,500 and 10,900 C-14 yr B.P. as shown by a basal radiocarbon date of similar to 10,870 C-14 yr B.P. from a lake within 1 ion of the Quelccaya Ice Cap. By 10,900 C-14 yr B.P, the ice front had retreated to nearly within its modern limits. Thus, glaciers in central and southern Peru advanced and retreated in near lockstep with one another. The Younger Dryas in the Peruvian Andes was apparently marked by retreating ice fronts in spite of the cool conditions that are inferred from the partial derivative O-18 record of Sajama ice. This retreat was apparently driven by reduced precipitation, which is consistent with interpretations of other paleoclimatic indicators from the region and which may have been a nonlinear response to steadily decreasing summer insolation. (C) 2000 University of Washington. VL - 54 IS - 3 N1 - 388erTimes Cited:61Cited References Count:66 JO - Rapid ice margin fluctuations during the Younger Dryas in the tropical Andes ER - TY - JOUR T1 - Responces of a saline lake ecosystems in semi-arid regions to irrigation and climate variability. The history of Salada Chiprana, Central Ebro Basin, Spain JF - Ambio Y1 - 2000 A1 - Valero-Garces, B. L. A1 - Navas, A. A1 - Machin, J. A1 - Stevenson, T. A1 - Davis, B. IS - 344-350 N1 - id: 385 ER - TY - JOUR T1 - Shared Technologies: Later Stone Age Forager-Farmer Interaction and Metallurgy in the Ituri Rainforest, Democratic Republic of Congo JF - Azania Y1 - 2000 A1 - Mercader, J. A1 - Rovira, S. A1 - Gomez, P. VL - 35 N1 - id: 396 ER - TY - JOUR T1 - The significance of large sediment supply, active tectonism, and eustasy on margin sequence development: Late Quaternary stratigraphy and evolution of the Ganges-Brahmaputra delta JF - Sedimentary Geology Y1 - 2000 A1 - Goodbred, S. L. A1 - Kuehl, S. A. AB - Borehole data from the Ganges-Brahmaputra delta system unveil an intriguing Late Quaternary history controlled by immense sediment discharge, tectonics, and eustasy. Sea level first intersected a major portion of the lowstand surface similar to 10,000-11,000 cal yr BP, marking the onset of sediment trapping and delta growth. Despite rapid sea-level rise (>1 cm/yr), sediment load was sufficient to maintain relative shoreline stability during this time. By similar to 7000 cal yr BP, accommodation was quickly infilled with slowed sea-level rise, leading to upstream channel migration and widespread dispersal of sands. This forced coastal progradation along the western delta front where the Ganges was situated, and much of the river's fine-grained discharge bypassed the subaerial delta and formed a prograding deltaic clinoform on the shelf. Concurrently, Brahmaputra sediments were sequestered to an inland tectonic basin, thus starving the adjacent shoreline and leading to transgression along the eastern delta. By similar to 5000 cal yr BP, the two rivers had migated or changed course to discharge along the eastern delta shoreline which began to prograde into what is now the modern river-mouth estuary. Present delta configuration appears to have developed by similar to 3000 cal yr BP. Evolution of the tectonically active Ganges-Brahmaputra (G-B) system reveals important similarities and differences with other deltas. Overall facies succession follows that of basic models, progressing from an alluvial valley to coastal marine delta front to a prograding subaerial delta plain. However, the timing, thickness, and controls of these deposits differ. Immense sediment discharge from the Ganges and Brahmaputra rivers allowed initial delta growth 2000-3000 yr earlier than the global average, despite debouching onto a canyon-incised, high-energy margin. Subsequently, a thick (similar to 50 m) transgressive systems tract was formed during the early Holocene phase of delta aggradation, contrasting with extensive shoreline retreat documented along most margins. Highstand progradation of coastal and shelf sequences ensued by the middle Holocene, but subsiding inland basins also favored accumulation of a thick (to 40 m) highstand sequence in the: lower floodplains. Unlike many other delta systems, subsidence in the subaerial G-B delta is not dominated by compaction, but rather by plate-driven tectonic processes that generate rates up to 4 mm/year. Overall, the huge sediment load, tectonic subsidence, major seismic events, and a nearshore canyon system have led to widespread sediment dispersal and sequence formation across the subaerial delta, shelf, and deep-sea Bengal Fan throughout the Late Quaternary. (C) 2000 Elsevier Science B.V. All rights reserved. VL - 133 IS - 3-4 N1 - 337jeTimes Cited:203Cited References Count:63 JO - The significance of large sediment supply, active tectonism, and eustasy on margin sequence development: Late Quaternary stratigraphy and evolution of the Ganges-Brahmaputra delta ER - TY - CONF T1 - Sonota Complex Sites in Eastern North Dakota T2 - 2000 Plains Conference, 58th Annual Meeting of the Plains Anthropological Society Y1 - 2000 A1 - Toom, Dennis L. A1 - Jackson, Michael A. JF - 2000 Plains Conference, 58th Annual Meeting of the Plains Anthropological Society CY - St. Paul, MN N1 - id: 205 ER - TY - THES T1 - Sources, distribution and transformations of PAH in the Gulf of Triests (northern Adriatic), Thesis Y1 - 2000 A1 - Notar, M. PB - University of Ljubljana, Slovenia CY - Ljubljana, Slovenia VL - Dissertation/Thesis ER - TY - JOUR T1 - Stable- and radio-carbon isotopic composition of porewater DOC in an organic-rich marine sediment JF - EOS Y1 - 2000 A1 - Alperin, M. J. A1 - Hee, C. A. A1 - Albert, D. A. A1 - Martens, C. S. VL - 81 IS - 699 N1 - id: 1438 JO - Stable- and radio-carbon isotopic composition of porewater DOC in an organic-rich marine sediment ER - TY - CHAP T1 - Stable carbon isotope record of middle to late Holocene climate changes from land snail shells at HInds Cave, Texas (Book Section) T2 - Holocene Environmental Change on the Great Plains of North America Y1 - 2000 A1 - Goodfriend, G. A. A1 - Ellis, G. L. ED - Wolfe, S. JF - Holocene Environmental Change on the Great Plains of North America PB - Quaternary Internation VL - 67 N1 - id: 175 ER - TY - JOUR T1 - Stable chlorine isotopic compositions of aroclors and aroclor-contaminated sediments JF - Environmental Science & Technology Y1 - 2000 A1 - Reddy, C. M. A1 - Heraty, L. J. A1 - Holt, B. D. A1 - Sturchio, N. C. A1 - Eglinton, T. I. A1 - Drenzek, N. J. A1 - Xu, L. A1 - Lake, J. L. A1 - Maruya, K. A. AB - An exploratory investigation was conducted to evaluate if stable chlorine isotopic ratios of polychlorinated biphenyls (PCBs) could be useful in studying the processes that determine their transport and fate in the environment First, we determined the variability of delta(37)Cl in the source materials for PCBs. Second, we determined if the delta(37)Cl values of contaminated environmental samples fell outside the range in source variability. The isotopic variability among the source materials (Aroclors) was rather small; delta(37)- Cl values ranged from -3.37 to -2.11% (mean and standard deviation, -2.78 +/- 0.39%, n = 12). There was no correlation between the delta(37)Cl values and percentages of chlorine in the mixtures. We also found very similar values in several Clophen mixtures and one Phenoclor. The delta(37)Cl values in the total PCBs isolated from Aroclor-contaminated sediments from the Hudson River, New Bedford Harbor, and Turtle River Estuary ranged from -4.54 to -2.25% (n = 19). While most of the delta(37)Cl values were within 2 standard deviations of the mean Aroclor value (our assumed estimate for overall source variability), two of the PCB contaminated sediment samples from New Bedford Harbor did appear to be isotopically distinct. The PCBs in these sediments had lower amounts of less chlorinated congeners (when compared to the source material) and were likely isotopically affected by alteration processes that preferentially removed these congeners. Compound specific measurements of two congeners in Aroclor 1268 suggest that there are no large congener-specific differences in the stable chlorine isotope ratios in Aroclors. This study shows that the delta(37)Cl Values of PCBs may be a potentially useful diagnostic tool in studying the transport and fate of PCBs and indicates that additional research is warranted. VL - 34 IS - 13 N1 - 330rcTimes Cited:39Cited References Count:16 JO - Stable chlorine isotopic compositions of aroclors and aroclor-contaminated sediments ER - TY - CONF T1 - Status of the WOCE tracer synthesis effort, Invited presentation T2 - WOCE Data Products Committee Meeting 13 Y1 - 2000 A1 - Key, R. M. JF - WOCE Data Products Committee Meeting 13 CY - College Station, TX N1 - id: 1457 ER - TY - JOUR T1 - Systematics, distributional and palaeoenvironmental aspects of Littoridina australis(D'Orbigny, 1835) (Mesogastropoda) in the Marine Quaternary of Argentina (South America) JF - Geobios Y1 - 2000 A1 - Aguirre, M. L. A1 - Farinati, E. A. KW - Hydrobiidae KW - Late Quaternary KW - Littoridina australis KW - Palaeoecology KW - Southwestern Atlantic KW - Systematics AB - LittoridinaSouleyet, 1852 (Mesogastropoda, Hydrobiidae) is the best represented genus among themolluscan taxa recorded in the marine late Quaternary from Argentina. It is distinguished by its ubiquity and high abundance along the coastal area from Río de La Plata down to southern Buenos Aires Province, both in beach ridge and coastal lagoon and estuarine facies and tidal flats. It is practically absent in Holocene littoral depositis from Patagonia and a very scarce component of the Pleistocene deposits from the whole Argentine coast. At present it is not recorded along the Argentine Sea or occurs only rarely in scarce quantities and restricted distribution, always associated to marginal marine environments. Most specimens collected from the marine Quaternary are assignable to Littoridina australis (D'Orbigny, 1835), a dominant species (50-> 80%) in the Holocene from La Plata down to Bahía San Blas (Buenos Aires Province). Due to the similarity of the original illustrations and of the type material of L. australis crassa, L. isabelleana, L. australis nana and L. conexa with L. australis, these taxa are considered synonyms. L. australis is proposed as a polytipic species with three main morphs (ecomorphs) which represent adaptations to different environmental conditions, mostly of salinty: ‘A’ (wide and short, very scarce, similar to L. charruana and L. conexa), ‘B’ (identical to the lectotypo de L. australis, similar to L. australis crassa; predominant) and ‘C’ (strongly elongated, similar to L. isabelleana and L. australis nana, with variations according to size; scarce). At present ‘B’ is dominant in mixohaline conditions, ‘C’ in polyhaline environments and ‘A’ in oligo-mixohaline sites. The morphological variations observed within the abundant material (fossil and modern), geographically and through time, would be a consequence of the influence over the littoral benthonic communities of environmental and climatic changes occurred during the late Quaternary: A trend was observed towards a major abundance of the morph ‘C’ (polyhaline) in the northern sector of the distribution, Samborombón Bay, and before ca. 5 ka A.P., whilst the morph ‘B’ (mixohaline) predominates in the central and southern sectors of the distribution, Mar Chiquita and Bahía Blanca, and is dominant after ca. 4.5 ka. This in turn would be a response to a progressive decrease of salinity along the littoral zone following the Climatic Optimum (Holocene ‘Hypsithermal’, >7-5 ka A.P.), in coincidence with the sea-level (and temperature) decreasing trend until the present. VL - 33 IS - 5 N1 - id: 1372 JO - Aspectos sistematicos, de distribucion y paleombientales de Littorindina australis (d'Orbigny, 1835) (Hydorbiidae, Mesogastropoda) del Cuaternario marino de la Argentina (Sudamerica) ER - TY - CONF T1 - Ten years after - the WOCE AMS radiocarbon program T2 - Accelerator Mass Spectrometer Conference Y1 - 2000 A1 - McNichol, A. P. A1 - Schneider, R. J. A1 - von Reden, K. F. A1 - Gagnon, A. R. A1 - Elder, K. L. A1 - Key, R. M. A1 - Quay, P. D. JF - Accelerator Mass Spectrometer Conference N1 - id: 316 ER - TY - JOUR T1 - Ten years after - The WOCE AMS radiocarbon program JF - Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions with Materials and Atoms Y1 - 2000 A1 - McNichol, A. P. A1 - Schneider, R. J. A1 - von Reden, K. F. A1 - Gagnon, A. R. A1 - Elder, K. L. A1 - Key, R. M. A1 - Quay, P. D. AB - The National Ocean Sciences Accelerator Mass Spectrometry (NOSAMS) Facility is measuring all of the samples collected as part of the US WOCE Program - over 13,000 samples. We designed our extraction lines so that we also measure precise, oceanographically useful delta C-13-Sigma CO2 values. We have completed the analysis of samples from the Pacific and Southern Oceans and are processing those from the Indian Ocean now. At present, this constitutes the world's largest AMS data set. Reviews of the Pacific radiocarbon data are available and demonstrate the increased penetration of the "bomb signal" into the water column since the 1970s. Stable isotope data are being combined with those collected as part of NOAA's Ocean-Atmosphere Carbon Exchange Study to study the ocean's role in the anthropogenic CO2 cycle. The relationship of delta C-13 to other chemical tracers, e.g., PO4, O-2 and chlorofluorocarbons, will further our understanding of basic oceanographic processes. We present preliminary results from these studies as well as investigate the relationship of C-14 to C-13 in the ocean. (C) 2000 Elsevier Science B.V. All rights reserved. VL - 172 IS - 1-4 N1 - 372jrTimes Cited:14Cited References Count:12 JO - Ten years after - The WOCE AMS radiocarbon program ER - TY - JOUR T1 - Tests of positive ion beams from a microwave ion source for AMS JF - Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions with Materials and Atoms Y1 - 2000 A1 - Schneider, R. J. A1 - von Reden, K. F. A1 - Hayes, J. M. A1 - Wills, J. S. C. A1 - Kern, W. G. E. A1 - Kim, S. W. AB - A test facility has been constructed to evaluate high-current positive ion beams from small gaseous samples for AMS applications. The major components include a compact permanent magnet microwave ion source built at the AECL Chalk River Laboratory and now on loan from the University of Toronto, and a double-focusing spectrometer magnet on loan from Argonne National Laboratory. Samples are introduced by means of a silica capillary injection system. Loop injection into a carrier gas provides a stable feed for the microwave driven plasma. The magnetic analysis system is utilized to isolate carbon ions derived from CO? samples from other products of the plasma discharge, including argon ions of the carrier gas. With a smaller discharge chamber, we hope to exceed a conversion efficiency of 14% for carbon ions produced per atom, which we reported at AMS-7. The next step will be to construct an efficient charge-exchange cell, to produce negative ions for injection into the WHOI recombinator injector. (C) 2000 Elsevier Science B.V. All rights reserved. VL - 172 IS - 252-256 N1 - 372jrTimes Cited:16Cited References Count:4 JO - Tests of positive ion beams from a microwave ion source for AMS ER - TY - CONF T1 - The tie-in of a varve-count chronology and radiocarbon dates: a method for addressing 14C-reservoir age T2 - Climate Conference, LDGO Y1 - 2000 A1 - Schimmelmann, A. A1 - Lange, Carina B. JF - Climate Conference, LDGO CY - Columbia University, New York N1 - id: 199 ER - TY - ART T1 - Trophic Transfer of Anthropogenic Contaminants to Salt-Marsh Bacteria: A Molecular Radiocarbon Approach (Poster) Y1 - 2000 A1 - Pease, Tamara A1 - Wakeham, Stuart PB - Skidaway Institute of Oceanography, Savannah, GA 31411 N1 - id: 222; Presented at the Gordon Research Conference in Organic Geochemistry ER - TY - JOUR T1 - Turbidite Megabeds in an Oceanic Rift Valley Recording Jokulhlaups of Late Pleistocene Glacial Lakes of the Western United States JF - Journal of Geology Y1 - 2000 A1 - Zuffa, G. G. A1 - Normark, W. R. A1 - Serra, F. A1 - Brunner, C. A. AB - Escanaba Trough is the southernmost segment of the Gorda Ridge and is filled by sandy turbidites locally exceeding 500 m in thickness. New results from Ocean Drilling Program (ODP) Sites 1037 and 1038 that include accelerator mass spectrometry (AMS) 14C dates and revised petrographic evaluation of the sediment provenance, combined with high-resolution seismic-reflection profiles, provide a lithostratigraphic framework for the turbidite deposits. Three fining-upward units of sandy turbidites from the upper 365 m at ODP Site 1037 can be correlated with sediment recovered at ODP Site 1038 and Deep Sea Drilling Program (DSDP) Site 35. Six AMS 14C ages in the upper 317 m of the sequence at Site 1037 indicate that average deposition rates exceeded 10 m/k.yr. between 32 and 11 ka, with nearly instantaneous deposition of one approximately 60-m interval of sand. Petrography of the sand beds is consistent with a Columbia River source for the entire sedimentary sequence in Escanaba Trough. High-resolution acoustic stratigraphy shows that the turbidites in the upper 60 m at Site 1037 provide a characteristic sequence of key reflectors that occurs across the floor of the entire Escanaba Trough. Recent mapping of turbidite systems in the northeast Pacific Ocean suggests that the turbidity currents reached the Escanaba Trough along an 1100-km-long pathway from the Columbia River to the west flank of the Gorda Ridge. The age of the upper fining-upward unit of sandy turbidites appears to correspond to the latest Wisconsinan outburst of glacial Lake Missoula. Many of the outbursts, or jokulhlaups, from the glacial lakes probably continued flowing as hyperpycnally generated turbidity currents on entering the sea at the mouth of the Columbia River. VL - 108 IS - 3 N1 - id: 162; J Geol. 2000 May;108(3):253-274. JO - Turbidite Megabeds in an Oceanic Rift Valley Recording Jokulhlaups of Late Pleistocene Glacial Lakes of the Western United States ER - TY - JOUR T1 - Un registro de 8,000 anos del paleoclima del noroeste de Yucatan, Mexico JF - Revista de la Universidad Autonoma de Yucatan Y1 - 2000 A1 - Brenner, M. A1 - Leyden, B. W. A1 - Curtis, J. H. A1 - Medina-Gonzalez, R. M. A1 - Dahlin, B. H. KW - Ciencias de la atmósfera KW - Geología KW - México KW - Paleoclima KW - Península de Yucatán KW - Yucatán VL - 15 IS - 213 N1 - id: 264 JO - Un registro de 8,000 anos del paleoclima del noroeste de Yucatan, Mexico ER - TY - ART T1 - Use of bomb produced C-14 to validate otolith section age estimates of red snapper Lutjanus compechanus from the northern Gulf of Mexico, Artwork Y1 - 2000 A1 - Baker, M. Scott
 A1 - Wilson, Charles A. PB - 53rd Annual Gulf and Carribbean Fisheries Institute Meeting CY - Biloxi, MS ER - TY - CONF T1 - Use of Natural C-14 Measurements to Examine Benthic Food Webs T2 - National AGU/ASLO Meeting Y1 - 2000 A1 - DeMaster, D. J. A1 - Fornes, W. L. A1 - Smith, C. R. A1 - Plaia, G. A1 - Blair, N. E. A1 - Levin, L. A. JF - National AGU/ASLO Meeting CY - San Antonio, TX N1 - id: 1367 ER - TY - CONF T1 - Ventilation of the deep Pacific Ocean, invited talk T2 - AGU Ocean Sciences Meeting Y1 - 2000 A1 - Key, R. M. JF - AGU Ocean Sciences Meeting CY - San Antonio, TX N1 - id: 315 ER - TY - JOUR T1 - Was it melt-water outflor or ice-sheet discharge? A high-resolution study of ice-sheet discharge from the high-latitude sector of the LIS during the LGM JF - EOS Y1 - 2000 A1 - Rashid, H. A1 - Hesse, R. A1 - Piper, D. J. W. VL - 81 IS - 19 N1 - id: 138 ER - TY - JOUR T1 - What can paired measurements of foraminifera d13C and sedimentary 231 Pa/230Th tell us about the link between thermohaline circulation and rapid climate oscillations? JF - EOS Y1 - 2000 A1 - McManus, J. F. A1 - Francois, R. A1 - Marchal, O. VL - 81 N1 - id: 169 ER - TY - JOUR T1 - Years of Sediment, Vegetation, and Water-Level Changes at the Makepeace Cedar Swamp, Southern Massachusetts JF - Quaternary Research Y1 - 2000 A1 - Newby, P. E. A1 - Killoran, P. A1 - Waldorf, M. R. A1 - Shuman, B. N. A1 - Webb, R. S. A1 - Webb, T., III VL - 53 N1 - id: 231 ER - TY - JOUR T1 - A 0.5-million-year record of millennial-scale climate variability in the north atlantic JF - Science Y1 - 1999 A1 - McManus, J. F. A1 - Oppo, D. W. A1 - Cullen, J. L. AB - Long, continuous, marine sediment records from the subpolar North Atlantic document the glacial modulation of regional climate instability throughout the past 0.5 million years. Whenever ice sheet size surpasses a critical threshold indicated by the benthic oxygen isotope (delta18O) value of 3.5 per mil during each of the past five glaciation cycles, indicators of iceberg discharge and sea-surface temperature display dramatically larger amplitudes of millennial-scale variability than when ice sheets are small. Sea-surface temperature oscillations of 1 degrees to 2 degreesC increase in size to approximately 4 degrees to 6 degreesC, and catastrophic iceberg discharges begin alternating repeatedly with brief quiescent intervals. The glacial growth associated with this amplification threshold represents a relatively small departure from the modern ice sheet configuration and sea level. Instability characterizes nearly all observed climate states, with the exception of a limited range of baseline conditions that includes the current Holocene interglacial. VL - 283 SN - 1095-9203 (Electronic)0036-8075 (Linking) UR - https://www.ncbi.nlm.nih.gov/pubmed/9974387 IS - 5404 N1 - McManusOppo Cullen eng 1999/02/12 03:03 Science. 1999 Feb 12;283(5404):971-5. ER - TY - JOUR T1 - 2-Methylhopanoids as biomarkers for cyanobacterial oxygenic photosynthesis JF - Nature Y1 - 1999 A1 - Summons, R. E. A1 - Jahnke, L. L. A1 - Hope, J. M. A1 - Logan, G. A. AB - Oxygenic photosynthesis is widely accepted as the most important bioenergetic process happening in Earth's surface environment(1). It is thought to have evolved within the cyanobacterial lineage, but it has been difficult to determine when it began. Evidence based on the occurrence and appearance of stromatolites(2) and microfossils' indicates that phototrophy occurred as long ago as 3,465 Myr although no definite physiological inferences can be he made from these objects. Carbon isotopes and other geological phenomena(4,5) provide clues but are also equivocal, Biomarkers are potentially useful because the three domains of extant life-Bacteria, Archaea and Eukarya-have signature membrane lipids with recalcitrant carbon skeletons. These lipids turn into hydrocarbons in sediments and can be found wherever the record is sufficiently well preserved. Here we show that 2-methylbacteriohopanepolyols occur in a high proportion of cultured cyanobacteria and cyanobacterial mats, Their 2-methylhopane hydrocarbon derivatives are abundant in organic-rich sediments as old as 2,500 Myr. These biomarkers may help constrain the age of the oldest cyanobacteria and the advent of oxygenic photosynthesis. They could also be used to quantify the ecological importance of cyanobacteria through geological time. VL - 400 IS - 6744 N1 - 223rtTimes Cited:510Cited References Count:28 JO - 2-Methylhopanoids as biomarkers for cyanobacterial oxygenic photosynthesis ER - TY - JOUR T1 - 87Sr/86Sr, delta 18O evolution of Phanerozoic seawater JF - Chemical Geology Y1 - 1999 A1 - Veizer, Jan A1 - Davin, Ala A1 - Azmy, Karem A1 - Bruckschen, Peter A1 - Buhl, Dieter A1 - Bruhn, Frank A1 - Carden, Giles A. F. A1 - Diener, Andreas A1 - Ebneth, Stefan A1 - Godderis, Yves A1 - Jasper, Torsten A1 - Korte, Christoph A1 - Pawellek, Frank A1 - Podlaha, Olaf G. A1 - Strauss, Harald VL - 161 N1 - id: 1603 ER - TY - JOUR T1 - The abundance of 13C in marine organic matter and isotopic fractionation in the global biogeochemical cycle of carbon during the past 800 Ma JF - Chemical Geology Y1 - 1999 A1 - Hayes, John M. A1 - Strauss, Harald A1 - Kaufman, Alan J. VL - 161 N1 - id: 1547 ER - TY - CONF T1 - The Antarctic Radiocarbon Storage Ring T2 - 8th International Conference on Accelerator Mass Spectrometry Y1 - 1999 A1 - Schneider, Robert J. A1 - McNichol, Ann P. A1 - von Reden, Karl F. A1 - Elder, Kathryn L. A1 - Gagnon, Alan R. A1 - Key, Robert M. A1 - Quay, Paul D. JF - 8th International Conference on Accelerator Mass Spectrometry CY - Vienna, Austria N1 - id: 1791 ER - TY - CONF T1 - Application of a compact microwave ion source to radiocarbon analysis T2 - The eighth international conference on heavy-ion accelerator technology Y1 - 1999 A1 - Schneider, R. J. A1 - von Reden, K. F. A1 - Hayes, J. M. A1 - Wills, J. S. C. ED - Shepard, K. W. KW - carbon KW - ion sources KW - mass spectroscopy KW - spectrochemical analysis KW - tandem accelerators AB - The compact, high current, 2.45 GHz microwave-driven plasma ion source which was built for the Chalk River TASCC facility is presently being adapted for testing as a gas ion source for accelerator mass spectrometry, at the Woods Hole Oceanographic Institution accelerator mass spectrometer. The special requirements for producing carbon-ion beams from micromole quantities of carbon dioxide produced from environmental samples will be discussed. These samples will be introduced into the ion source by means of argon carrier gas and a silicon capillary injection system. Following the extraction of positive ions from the source, negative ion formation in a charge exchange vapor will effectively remove the argon from the carbon beam. Simultaneous injection of the three carbon isotopes into the accelerator is planned. JF - The eighth international conference on heavy-ion accelerator technology PB - American Institute of Physics N1 - id: 1977 ER - TY - CONF T1 - Application of Compact Microwave Ion Source to Radiocarbon Analysis T2 - 8th International Conference on Heavy Ion Accelerator Technology Y1 - 1999 A1 - Schneider, R. J. A1 - von Reden, K. F. A1 - Hayes, J. M. A1 - Wills, J. S. C. ED - Shepard, K. JF - 8th International Conference on Heavy Ion Accelerator Technology PB - American Institute of Physics CY - Argonne National Lab. VL - Conference Proceedings 473 N1 - id: 1824 ER - TY - RPRT T1 - An Archaeological Investigation of Late Archaic Cerros de Trincheras Sites in Chihuahua, Mexico Y1 - 1999 A1 - Hard, R. A1 - Roney, J. PB - University of Texas, Center for Archaeological Research N1 - id: 1389 ER - TY - JOUR T1 - Assessing the importance of subtropical waters in ventilating the Equatorial Pacific thermocline: A combined transient-tracer approach JF - International WOCE Newsletter Y1 - 1999 A1 - Peacock, S. A1 - Jenkins, W. A1 - Key, R. A1 - Broecker, W. VL - 35 N1 - id: 1465 ER - TY - JOUR T1 - Assessment of a hard water dating problem in Wonder Lake, Denali National Park, Alaska JF - Geographie Physique et Quatenaire Y1 - 1999 A1 - Child, J. C. A1 - Werner, A. VL - 53 N1 - id: 1383 ER - TY - CONF T1 - Biogenic silica and organic carbon in sediments from the Pacific sector of the Southern Ocean.--Abstract T2 - 8th International Symposium on Antarctic Earch Sciences Y1 - 1999 A1 - Giglio, F. A1 - Frignani, M. A1 - Langone, L. A1 - Morigi, C. A1 - Pianosi, G. A1 - Ravaioli, M. JF - 8th International Symposium on Antarctic Earch Sciences CY - Victoria University of Wellington, Wellington, New Zealand N1 - id: 286 ER - TY - JOUR T1 - Biogenic silica records from the BDP-93 drill site and adjacent areas of the Selenga Delta, Lake Baikal, Siberia JF - Journal of Paleolimnology Y1 - 1999 A1 - Colman, S. M. A1 - Peck, J. A. A1 - Hatton, J. A1 - Karabanov, E. B. A1 - King, J. W. VL - 21 N1 - id: 186 ER - TY - JOUR T1 - Carbon isotopes as tracers of groundwater discharge into the coastal ocean: A preliminary study of saltmarsh groundwater from North Inlet, SC JF - EOS Y1 - 1999 A1 - Gramling, C. M. A1 - McCorkle, D. C. VL - 80 IS - 17 N1 - id: 1314 ER - TY - CONF T1 - Carbon sequestration and vegetation succession in a coastal wetland in northwest Florida (abstract) T2 - Spring meeting of American Geophysical Union Y1 - 1999 A1 - Choi, Y. A1 - Wang, Y. A1 - Hsieh, Y. A1 - Robinson, L. JF - Spring meeting of American Geophysical Union PB - EOS, Transactions CY - Boston, MA VL - 80 N1 - id: 164 ER - TY - RPRT T1 - Climate and fisheries on the south east Australian continental shelf and slope (final report) Y1 - 1999 A1 - Koslow, J. A. A1 - Thresher, R. PB - Fisheries Research and Development Corporation N1 - id: 109 ER - TY - JOUR T1 - Climate and lake-level history of the northern Altiplano Bolivia, as recorded in Holocene sediments of the Rio Desaguadero JF - Journal of Sedimentary Research Y1 - 1999 A1 - Baucom, P. C. A1 - Rigsby, C. A. AB - Strata exposed in terraces and modern cutbanks along the Rio Desaguadero contain a variety of lithofacies that were deposited in four distinct facies associations. These facies associations document a history of aggradation and downcutting that is Linked to Holocene climate change on the Altiplano.Braided stream, meandering stream, deltaic and shoreline, and la custrine sediments preserved in multi-level terraces in the northern Rio Desaguadero valley record two high-water intervals: one between 4500 and 3900 yr BP and another between 2000 and 2200 yr BP. These wet periods were interrupted by three periods of fluvial downcutting, centered at approximately 4000 yr BP, 3600 Sr BP, and after 2000 yr BP. Braided-river sediments preserved in a single terrace level in the southern Rio Desaguadero valley record a history of nearly continuous fluvial sedimentation from at least 7000 yr BP until approximately 3200 yr BP that was followed by a single episode (post-3210 ST BP) of down cutting and lateral migration.The deposition and subsequent fluvial downcutting of the northern strata was controlled by changes in effective moisture that can he correlated to Holocene water level fluctuations of Lake Titicaca, The deposition and dissection of braided-stream sediments to the south are more likely controlled by a combination of base-level change and sediment input from the Rio Mauri. VL - 69 IS - 3 N1 - A197atTimes Cited:30Cited References Count:61 JO - Climate and lake-level history of the northern Altiplano Bolivia, as recorded in Holocene sediments of the Rio Desaguadero ER - TY - JOUR T1 - Climate change in the Lake Valencia Basin, Venezuela, approximately 12,600 yr BP to present JF - The Holocene Y1 - 1999 A1 - Curtis, J. H. A1 - Brenner, M. A1 - Hodell, D. A. VL - 9 N1 - id: 197 ER - TY - CONF T1 - Combined use of bomb radiocarbon and tritium to place constraints on the relative importance of northern- and southern- derived waters in ventilating the equatorial Pacific thermocline T2 - WOCE-AIMS Tracer Workshop Y1 - 1999 A1 - Peacock, S. A1 - Key, R. A1 - Jenkins, W. A1 - Broecker, W. JF - WOCE-AIMS Tracer Workshop CY - Bremen, Germany N1 - id: 314 ER - TY - JOUR T1 - A continuous Holocene glacial record inferred from proglacial lake sediments in Banff National Park, Albert, Canada JF - Quaternary Research Y1 - 1999 A1 - Leonard, Eric M. A1 - Reasoner, Mel A. KW - Canadian Rocky Mountains KW - glacial history KW - glaciolacustrine sedimentation KW - Holocene; Altithermal AB - Sediment cores from three proglacial lakes in northern Banff National Park, Alberta, preserve a record of Holocene glacial activity upvalley which is more continuous and better dated than available surficial records. Dating of the cores is based on tephrochronology and 16 AMS14C ages of terrestrial macrofossils. All cores contain a threefold sequence of lacustrine sediments overlying a late Pleistocene diamicton. Basal lacustrine sediments >10,10014C yr old contain little organic matter. Sediment composition indicates a large glacigenic contribution. A sharp increase in organic content marks the beginning of the Altithermal interval at all three lakes. This transition occurred abruptly at about 10,10014C yr B.P. at Crowfoot Lake and possibly more gradually at the other lakes. Altithermal sediments contain relatively little glacigenic material, and during most of the Altithermal, glaciers may have been absent above Crowfoot and Bow Lakes. Glaciers draining into Hector Lake appear to have persisted through the Altithermal. A subsequent decrease in organic content in each lake, reflecting increased clastic sedimentation, marks the end of the Altithermal and the onset of Neoglacial ice advances. The transition took place between about 5800 and 400014C yr B.P. and may be time-transgressive, beginning earlier in Hector Lake than in Crowfoot Lake. Changing Neoglacial clastic sedimentation rates through the Neoglacial interval indicate two main periods of increased glacier extent, between ca. 3000 and 1800 varve yr ago (ca. 2900–190014C yr B.P.) and during the last several hundred years. During the intervening period glaciers were less extensive, but much more extensive than during the recessions of the Altithermal interval. VL - 51 IS - 1 N1 - id: 48; illus. incl. 4 tables, sketch maps, 42 refs. JO - A continuous Holocene glacial record inferred from proglacial lake sediments in Banff National Park, Albert, Canada ER - TY - JOUR T1 - Cool surface waters of the subtropical North Pacific Ocean during the last glacial JF - Nature Y1 - 1999 A1 - Lee, K. E. A1 - Slowey, N. C. AB - One of the most controversial results of the CLIMAP(1,2) project's reconstruction of past sea surface temperature (SST) is that large areas of the subtropical Pacific Ocean were warmer during the last glacial period than they are today. This finding has important implications because SST patterns at low to subtropical latitudes strongly influence climate, and SST changes are closely linked with climate fluctuations(3-5). Until now, a lack of well-preserved, high-resolution marine sediment cores from the region has hindered efforts to confirm these unexpectedly high ice-age SST estimates. Here we use both the oxygen-isotope compositions and species assemblages of planktonic foraminifera in a shallow-water core with high deposition rates near Hawaii to estimate glacial SST of the subtropical North Pacific Ocean, Contrary to the CLIMAP results(2), our data indicate that the annual average SST in this region was similar to 2 degrees C cooler during the last glaciation than it is today, These results help to reconcile the marine SST record with inferences drawn from snowline depressions on Hawaii during the last glacial(3,6), and should ultimately yield improved estimates of global climate sensitivity by providing important new constraints on climate model simulations of ice-age cycles. VL - 397 IS - 6719 N1 - 166knTimes Cited:31Cited References Count:29 JO - Cool surface waters of the subtropical North Pacific Ocean during the last glacial ER - TY - CHAP T1 - Coupled inner shelf--shoreline sediment responses to small-scale Holocene sea-level fluctuations; North Carolina coastal zone T2 - The non-steady state of the inner shelf and shoreline: coastal change on the time scale of decades to millennia in the late Quaternary Y1 - 1999 A1 - Riggs, S. R. ED - Fletcher, C. H. JF - The non-steady state of the inner shelf and shoreline: coastal change on the time scale of decades to millennia in the late Quaternary PB - University of Hawaii, Honolulu N1 - id: 1393 ER - TY - JOUR T1 - Deep-sea sedimentary record of the late Wisconsin cataclysmic floods from the Columbia River JF - Geology Y1 - 1999 A1 - Brunner, C. A. A1 - Normark, W. R. A1 - Zuffa, G. G. A1 - Serra, F. AB - New results from Ocean Drilling Program Site 1037 and U.S. Geological Survey high-resolution seismic-reflection profiles confirm the great thickness, fast deposition rate, distant source, and convolute path of turbidites that fill the Escanaba Trough, the rift valley of the southernmost segment of the Gorda Ridge. Accelerator mass spectrometry C-14 measurements provide the first direct dating of the Escanaba Trough turbidites, demonstrating an average deposition rate faster than 10 m/k.y. between 32 and 11 ka and as fast as 15 m/k.y. during the oxygen isotope stage 2 lowstand, In the upper 60 m of sediment, the petrology of turbidite sand beds, which are as much as 12 m thick, show that the dominant source for the turbidites is from the Columbia River, which is more than 800 km to the north, rather than from the much closer rivers of northern California. New high-resolution seismic-reflection profiles show that, except for areas of very recent volcanism, the entire Escanaba Trough below 3200 m water depth is floored by the turbidite sequence that was cored in the upper 60 m at Site 1037B, The ages of the upper 120 m of turbidites correspond with the ages of channeled scabland deposits associated with latest Quaternary jokulhlaups from glacial Lake Missoula, The age and source characteristics suggest that these megaturbidite beds in Escanaba Trough are most likely deposits formed by hyperpycnally generated turbidity currents as the largest of the Lake Missoula floods entered the sea. VL - 27 IS - 5 N1 - 193qfTimes Cited:40Cited References Count:19 JO - Deep-sea sedimentary record of the late Wisconsin cataclysmic floods from the Columbia River ER - TY - JOUR T1 - Deglaciation of the northwestern White Mountains, New Hampshire JF - Geographie Physique Et Quaternaire Y1 - 1999 A1 - Thompson, W. B. A1 - Fowler, B. K. A1 - Dorion, C. C. KW - canada KW - chronology KW - climate KW - last termination KW - new-england KW - record KW - tills AB - The mode of deglaciation in the northwestern White Mountains of New Hampshire has been controversial since the mid 1800's. Early workers believed that active ice deposited the Bethlehem Moraine complex in the Ammonoosuc River basin during recession of the last ice sheet. In the 1930's this deglaciation model was replaced by the concept of widespread simultaneous stagnation and downwastage of Late Wisconsinan ice. The present authors reexamined the Bethlehem Moraine complex and support the original interpretation of a series of moraines deposited by active ice. We found other moraine clusters of similar age to the northeast in the Johns River and lsrael River basins. lce-marginal deposits that probably correlate with the Bethlehem Moraine also occur west of Littleton. The Bethlehem Moraine complex and equivalent deposits in adjacent areas were formed by readvance and oscillatory retreat of the Connecticut Valley lobe of the Laurentide Ice Sheet. This event is called the Littleton-Bethlehem Readvance. Throughout the study area, sequences of glaciolacustrine deposits and meltwater drainage channels indicate progressive northward recession of the glacier margin. Radiocarbon dates from nearby New England and Quebec suggest that the ice sheet withdrew from this part of the White Mountains between about 12,500 and 12,000 (14)C yr BP. We attribute the Littleton-Bethlehem Readvance to a brief climatic cooling during Older Dyas time, close to 12,000 BP. VL - 53 SN - 0705-7199 IS - 1 N1 - 218kbTimes Cited:18 Cited References Count:56 JO - Geogr Phys Quatern ER - TY - JOUR T1 - Deltas, radiocarbon dating, and measurements of sediment storage and subsidence JF - Geology Y1 - 1999 A1 - Stanley, D. J. A1 - Hait, A. K. VL - 28 N1 - id: 1376 ER - TY - THES T1 - Diagenetic Zonation and Authigenic Carbonate Formation within Methane- and Gas Hydrate-Bearing Sedimentary Sections, Offshore, Southeastern North America, Thesis Y1 - 1999 A1 - Rodriques, N. M. PB - University of North Carolina CY - Chapel Hill, NC VL - Dissertation/Thesis ER - TY - CONF T1 - The distribution and carbon isotopic composition of dissolved organic matter in Florida Everglades (abstract) T2 - The Sixth Symposium on Biogeochemistry of Wetlands Y1 - 1999 A1 - Wang, Y. A1 - Hsieh, Y. P. A1 - Landing, W. M. A1 - Salters, V. A1 - Cooper, W. A1 - Proctor, L. JF - The Sixth Symposium on Biogeochemistry of Wetlands N1 - id: 165 ER - TY - RPRT T1 - Environmental changes in the last centure in Little Trout Lake and Inkspot Bay, Lac du Flambeau Tribal Lands, Wisconsin. Preliminary Results Report Y1 - 1999 A1 - Winkler, M. G. A1 - Sanford, P. R. PB - Water Resources Division, Lac du Flambeau Tribe N1 - id: 1320 ER - TY - JOUR T1 - Evidence for Late Pleistocene-Holocene Intermediate-Water variability in the North Atlantic JF - EOS Y1 - 1999 A1 - McManus, J. F. A1 - Oppo, D. W. A1 - Curry, W. A1 - Marchitto, T. A1 - Cullen, J. L. VL - 80 N1 - id: 172 ER - TY - JOUR T1 - Extreme 13C carb enrichment in ca. 2.0 Ga magnesite-stromatolite--dolomite--"red beds" association in a global context: a case for the world-wide signal enhanced by a local environment JF - Earth-Science Reviews Y1 - 1999 A1 - Melezhik, Victor A. A1 - Fallick, Anthony E. A1 - Medvedev, Pavel V. A1 - Makarikhin, Vladimir V. VL - 48 N1 - id: 1567 ER - TY - JOUR T1 - Fault slip rates in the modern new madrid seismic zone JF - Science Y1 - 1999 A1 - Mueller, K. A1 - Champion, J. A1 - Guccione, M. A1 - Kelson, K. AB - Structural and geomorphic analysis of late Holocene sediments in the Lake County region of the New Madrid seismic zone indicates that they are deformed by fault-related folding above the blind Reelfoot thrust fault. The widths of narrow kink bands exposed in trenches were used to model the Reelfoot scarp as a forelimb on a fault-bend fold; this, coupled with the age of folded sediment, yields a slip rate on the blind thrust of 6.1 +/- 0.7 mm/year for the past 2300 +/- 100 years. An alternative method used structural relief across the scarp and the estimated dip of the underlying blind thrust to calculate a slip rate of 4.8 +/- 0.2 mm/year. Geometric relations suggest that the right lateral slip rate on the New Madrid seismic zone is 1.8 to 2.0 mm/year. VL - 286 SN - 1095-9203 (Electronic)0036-8075 (Linking) UR - https://www.ncbi.nlm.nih.gov/pubmed/10550047 IS - 5442 N1 - MuellerChampion Guccione Kelson eng 1999/11/05 Science. 1999 Nov 5;286(5442):1135-8. ER - TY - THES T1 - Fluttuazioni tardo quaternarie dei flussi sedimentari di carbonio organico e silice biogena nel settore pacifico dell'Oceano Meridionale--Thesis Y1 - 1999 A1 - Pianosi, G. PB - Universita di Bologna CY - Bologna, Italy VL - Dissertation/Thesis ER - TY - JOUR T1 - Fractionation of hydrogen isotopes in lipid biosynthesis JF - Organic Geochemistry Y1 - 1999 A1 - Sessions, A. L. A1 - Burgoyne, T. W. A1 - Schimmelmann, A. A1 - Hayes, J. M. AB - Isotopic compositions of carbon-bound hydrogen in individual compounds from eight different organisms were measured using isotope-ratio-monitoring gas chromatography-mass spectrometry. This technique is capable of measuring D/H ratios at natural abundance in individual lipids yielding as little as 20 nmol of H-2, and is applicable to a wide range of compounds including hydrocarbons, sterols, and fatty acids. The hydrogen isotopic compositions of lipids are controlled by three factors: isotopic compositions of biosynthetic precursors, fractionation and exchange accompanying biosynthesis, and hydrogenation during biosynthesis. delta D values of lipids from the eight organisms examined here suggest that all three processes are important for controlling natural variations in isotopic abundance. n-Alkyl lipids are depleted in D relative to growth water by 113-262 parts per thousand, while polyisoprenoid lipids are depleted in D relative to growth water by 142-376 parts per thousand. Isotopic variations within compound classes (e.g., n-alkanes) are usually less than similar to 50 parts per thousand, but variations as large as 150 parts per thousand are observed among isoprenoid lipids from a single organism. Phytol is consistently depleted in D by up to 50 parts per thousand relative to other isoprenoid lipids. Inferred isotopic fractionations between cellular water and lipids are greater than those indicated by previous studies. (C) 1999 Elsevier Science Ltd. All rights reserved. VL - 30 IS - 9 N1 - 254efTimes Cited:281Cited References Count:26 JO - Fractionation of hydrogen isotopes in lipid biosynthesis ER - TY - JOUR T1 - The geochemistry of redox sensitive trace metals in sediments JF - Geochimica Et Cosmochimica Acta Y1 - 1999 A1 - Morford, J. L. A1 - Emerson, S. AB - We analyzed the redox sensitive elements V, Mo, U, Re and Cd in surface sediments from the Northwest African margin, the U.S. Northwest margin and the Arabian Sea to determine their response under a range of redox conditions. Where oxygen penetrates 1 cm or less into the sediments, Mo and V diffuse to the overlying water as Mn is reduced and remobilized. Authigenic enrichments of U, Re and Cd are evident under these redox conditions. With the onset of sulfate reduction, all of the metals accumulate authigenically with Re being by far the most enriched. General trends in authigenic metal accumulation are described by calculating authigenic fluxes for the 3 main redox regimes: oxic, reducing where oxygen penetrates less than or equal to 1 cm, and anoxic conditions. Using a simple diagenesis model and global estimates of organic carbon rain rate and bottom water oxygen concentrations, we calculate the area of sediments below 1000 m water depth in which oxygen penetration is less than or equal to 1 cm to be 4% of the ocean floor. We conclude that sediments where oxygen penetrates less than or equal to 1 cm release Mn, V and Mo to seawater at rates of 140%-260%, 60%-150% and 5%-10% of their respective riverine fluxes, using the authigenic metal concentrations and accumulation rates from this work and other literature. These sediments are sinks for Re, Cd and U, with burial fluxes of 70%-140%, 30%-80% and 20%-40%, respectively, of their dissolved riverine inputs. We modeled the sensitivity of the response of seawater Re, Cd and V concentrations to changes in the area of reducing sediments where oxygen penetrates less than or equal to 1 cm. Our analysis suggests a negligible change in seawater Re concentration, whereas seawater concentrations of Cd and V could have decreased and increased, respectively, by 5%-10% over 20 kyr if the area of reducing sediments increased by a factor of 2 and by 10%-20% if the area increased by a factor of 3. The concentration variations for a factor of 2 increase in the area of reducing sediments are at about the level of uncertainty of Cd/Ca and V/Ca ratios observed in foraminifera shells over the last 40 kyr. This implies that the area of reducing sediments in the ocean deeper than 1000 m (4%) has not been greater than twice the present value in the recent past. Copyright (C) 1999 Elsevier Science Ltd. VL - 63 IS - 11-12 N1 - 227ktTimes Cited:455Cited References Count:92 JO - The geochemistry of redox sensitive trace metals in sediments ER - TY - THES T1 - The Geochemistry of Redox Sensitive Trace Metals: Thesis Y1 - 1999 A1 - Morford, J. L. PB - University of Washington VL - PhD ER - TY - JOUR T1 - A geostrophic transport estimate for the Florida Current from the oxygen isotope composition of benthic foraminifera JF - Paleoceanography Y1 - 1999 A1 - Lynch-Stieglitz, J. A1 - Curry, W. B. A1 - Slowey, N. AB - We present a new method for the quantitative reconstruction of upper ocean flows for during times in the past. For the warm (T>5 degrees C) surface ocean, density can be accurately reconstructed from calcite precipitated in equilibrium with seawater, as both of these properties increase with decreasing temperature and increasing salinity. Vertical density profiles can be reconstructed from the oxygen isotopic composition of benthic foraminifera. The net volume transport between two vertical density profiles can be calculated using the geostrophic method. Using benthic foraminifera from surface sediment samples from either side of the Florida Straits (Florida Keys and Little Bahama Bank), we reconstruct two vertical density profiles and calculate a volume transport of 32 Sv using this method. This agrees well with estimates from physical oceanographic methods of 30-32 Sv for the mean annual volume transport. We explore the sensitivity of this technique to various changes in the relationship between temperature and salinity as well as salinity and the oxygen isotopic composition of seawater. VL - 14 IS - 3 N1 - 198xcTimes Cited:81Cited References Count:45 JO - A geostrophic transport estimate for the Florida Current from the oxygen isotope composition of benthic foraminifera ER - TY - JOUR T1 - Glacial modulation of rapid climate change during the last 0.5 million years JF - PAGES newsletter Y1 - 1999 A1 - McManus, J. F. A1 - Oppo, D. W. A1 - Cullen, J. L. VL - 7 N1 - id: 168 ER - TY - THES T1 - High Molecular Weight Dissolved Organic Matter in Seawater: Chemical Structure, Sources, and Cycling, Thesis Y1 - 1999 A1 - Aluwihare, Lihini I. PB - MIT/WHOI Joint Program CY - Cambridge, MA/Woods Hole, MA VL - PhD N1 - id: 150; Chemical Oceanography JO - High Molecular Weight Dissolved Organic Matter in Seawater: Chemical Structure, Sources, and Cycling, Thesis ER - TY - JOUR T1 - A high resolution ~15,000 year record of El-Nino driven alluviation in southwestern Ecuador JF - Science Y1 - 1999 A1 - Rodbell, D. T. A1 - Seltzer, G. O. A1 - Anderson, D. M. A1 - Abbott, M. B. A1 - Enfield, D. B. A1 - Newman, J. H. VL - 283 N1 - id: 393 ER - TY - JOUR T1 - Holocene and modern sediment budgets for the Ganges-Brahmaputra River: Evidence for highstand dispersal to floodplain, shelf, and deep-sea depocenters JF - Geology Y1 - 1999 A1 - Goodbred, S. L. A1 - Kuehl, S. A. VL - 27 IS - 6 N1 - id: 149 ER - TY - JOUR T1 - Holocene depositional patterns, neotectonics and Sundarban Mangroves in the western Ganges-Brahmaputra delta JF - Jour. Coastal Res. Y1 - 1999 A1 - Stanley, D. J. A1 - Hait, A. VL - 16 N1 - id: 229 ER - TY - JOUR T1 - Holocene Environmental changes in the Lake Erie Basis JF - International Association for Great Lakes Research Program and Abstract Y1 - 1999 A1 - Kepthorne, R. A. A1 - Barrera, E. A1 - Coakley, J. P. A1 - Tevesz, M. J. S. A1 - Miller, B. B. VL - A-58 N1 - id: 249 ER - TY - JOUR T1 - Holocene surface faulting in the Seattle fault zone, Bainbridge Island, Washington JF - Seismological Research Letters Y1 - 1999 A1 - Nelson, A. R. A1 - Pezzopane, S. K. A1 - Bucknam, R. C. A1 - Koehler, R. D. A1 - Narwold, C. F. A1 - Kelsey, H. M. A1 - Sherrod, B. L. A1 - LaPrade, W. T. A1 - Wells, R. E. A1 - Johnson, S. Y. VL - 70 IS - 2 N1 - id: 1404 ER - TY - CONF T1 - Installation and First Results of a 134-Sample MC-SNICS Ion Source at NOSAMS T2 - 8th International Conference on Accelerator Mass Spectrometry Y1 - 1999 A1 - von Reden, K. F. A1 - Schneider, R. J. A1 - McNichol, A. P. A1 - Elder, K. F. A1 - Gagnon, A. R. JF - 8th International Conference on Accelerator Mass Spectrometry CY - Vienna, Austria N1 - id: 1802 ER - TY - CHAP T1 - Installation of a 134-Sample MC-SNICS Ion Source at NOSAMS and first results T2 - Accelerator Mass Spectrometry, Proceedings of the Eighth International Conference on Accelerator Mass Spectrometry Y1 - 1999 A1 - von Reden, Karl F. A1 - Bellino, Mary A1 - Long, Patricia A1 - Schneider, Robert J. A1 - Loger, Roger ED - Kutschera, W. JF - Accelerator Mass Spectrometry, Proceedings of the Eighth International Conference on Accelerator Mass Spectrometry PB - North-Holland CY - Vienna, Austria N1 - id: 1724 ER - TY - JOUR T1 - Interdisciplinary environmental project probes Chesapeake Bay down to the core JF - EOS Y1 - 1999 A1 - Cronin, T. A1 - Colman, S. M. A1 - Willard, D. A1 - Kerhin, R. A1 - Holmes, C. A1 - Karlsen, A. A1 - Ishman, S. A1 - Bratton, J. VL - Transactions of the American Geophysical Union IS - 80 N1 - id: 185 ER - TY - JOUR T1 - Interpreting carbon-isotope excursions: carbonates and organic matter JF - Chemical Geology Y1 - 1999 A1 - Kump, L. R. A1 - Arthur, M. A. AB - Variations in the carbon isotopic compositions of marine carbonate and organic carbon provide a record of changes in the fraction of organic carbon buried through time and may provide clues to changes in rates of weathering and sources of organic carbon. Paired carbonate and organic carbon isotope determinations provide a possibility of interpreting not only changes in the global carbon cycle through time, but changes in atmospheric pCO(2) as well. Interpretations of these types of data are typically rather qualitative; a quantitative basis is required to develop a better understanding of changes in the carbon cycle. For this purpose, we employ a simple model of the global carbon cycle which is subjected to a number of different perturbations, each lasting 500 ky, i.e., much longer than the residence times of carbon and phosphorus in the ocean-atmosphere system. In addition to standard considerations of carbon mass and isotopic fluxes to the ocean-atmosphere system from weathering and volcanism and fluxes of organic carbon and carbonate-carbon to sediments, the model ;incorporates sensitivity of the photosynthetic carbon isotope effect to changes in pCO(2). The inclusion of this parameter leads to unexpected carbon isotope responses to forcing that causes increased rates of organic carbon burial. A series of simple to more complex simulations illustrates the significant effects of varying differences between the carbon isotopic composition of sedimented carbonate and organic carbon (Delta(B)). With constant Delta(B) a 50% increase in organic carbon burial produces a parallel increase in carbonate and organic carbon isotopic compositions. However, the same simulation with Delta(B) responsive to pCO(2) changes produces an initial parallel delta(13)C increase, but this is followed by an even greater C-13-enrichment in organic carbon because pCO(2) falls in response to increased organic carbon burial. The counterintuitive overall result of the enhanced organic carbon burial event is that the carbonate carbon isotopic composition actually decreases because of the more substantial increase in delta(13)C(org). In addition, we illustrate the effects on carbon isotopic compositions of the oceanic inorganic carbon reservoir and buried organic matter of a 50% increase in volcanic CO2 outgassing, a 50% increase in weathering rate (with coupled phosphate and riverine carbon flux responses), a 50% decrease in shale-associated organic carbon weathering, a 50% decrease in silicate weathering rate, and the possible effects of the rise in abundance of C-4 plants in the late Miocene to Recent. We compare the model simulated carbon isotopic responses for some of these experiments to paired carbonate- and organic-carbon records to illustrate how these records might be interpreted in light of the model response. (C) 1999 Elsevier Science B.V. All rights reserved. VL - 161 IS - 1-3 N1 - 243xyTimes Cited:398Cited References Count:64 JO - Interpreting carbon-isotope excursions: carbonates and organic matter ER - TY - THES T1 - An investigation of a transition in glacial landforms in southeastern Main. Thesis Y1 - 1999 A1 - Lurvey, L. Kirk PB - University of Maine VL - M.S. ER - TY - JOUR T1 - Isotopic and molecular fractionation in combustion; three routes to molecular marker validation, including direct molecular 'dating' (GC/AMS) JF - Atmospheric Environment Y1 - 1999 A1 - Currie, L. A. A1 - Klouda, G. A. A1 - Benner, B. A. A1 - Garrity, K. A1 - Eglinton, T. I. AB - The identification of unique isotopic, elemental, and molecular markers for sources of combustion aerosol has growing practical importance because of the potential effects of fine particle aerosol on health, visibility and global climate. It is urgent, therefore, that substantial efforts be directed toward the validation of assumptions involving the use of such tracers for source apportionment. We describe here three independent routes toward carbonaceous aerosol molecular marker identification and validation: (1) tracer regression and multivariate statistical techniques applied to field measurements of mixed source, carbonaceous aerosols; (2) a new development in aerosol (14)C metrology: direct, pure compound accelerator mass spectrometry (AMS) by off-line GC/AMS ('molecular dating'); and (3) direct observation of isotopic and molecular source emissions during controlled laboratory combustion of specific fuels. Findings from the combined studies include. independent support for benzo(ghi)perylene as a motor vehicle tracer from the first (statistical) and second (direct 'dating') studies; a new indication, from the third (controlled combustion) study, of a relation between (13)C isotopic fractionation and PAH molecular fractionation, also linked with fuel and stage of combustion; and quantitative data showing the influence of both fuel type and combustion conditions on the yields of such species as elemental carbon and PAH, reinforcing the importance of exercising caution when applying presumed conservative elemental or organic tracers to fossil or biomass burning field data as in the first study. Published by Elsevier Science Ltd. VL - 33 IS - 17 N1 - 208duTimes Cited:38Cited References Count:31 JO - Isotopic and molecular fractionation in combustion; three routes to molecular marker validation, including direct molecular 'dating' (GC/AMS) ER - TY - CONF T1 - The Last Deglaciation in Southern Chile T2 - Development of Paleoceanography as a New Field of Science Y1 - 1999 A1 - Anderson, D. M. A1 - Archer, R. B. JF - Development of Paleoceanography as a New Field of Science CY - Stockholm VL - 27 N1 - id: 145 ER - TY - JOUR T1 - Late Pleistocene-Holocene sea-level change and the New Jersey coastline JF - Trans. Am. Geophys. Un. Y1 - 1999 A1 - Miller, K. G. A1 - Sugarman, P. J. A1 - Sheridan, R. E. A1 - Ashley, G. M. IS - Spring Meeting, 1999 N1 - id: 163 ER - TY - JOUR T1 - Late Quaternary stratigraphy of Marresale, Yamal Peninsula, Russia: new constraints on the footprint of the Eurasian ice sheet JF - Geology Y1 - 1999 A1 - Forman, S. L. A1 - Ingolfsson, O. A1 - Manley, W. F. A1 - Lokrantz, H. VL - 27 N1 - id: 370 ER - TY - JOUR T1 - Late Quaternary stratigraphy, Paleoclimate and neotectonism of the Persian (Arabian) Gulf region JF - Marine Geology Y1 - 1999 A1 - Uchupi, E. A1 - Swift, S. A. A1 - Ross, D. A. AB - The last glacial deposits in the Persian (Arabian) Gulf consist of a > 22,000 year old paralic terrigenous sequence in the Mesopotamia Shelf, the foredeep in front of the Iranian Zagros Mountains and the northern side of the Biaban Shelf. Elsewhere, the Gulf, and probably the Biaban Shelf, were mantled by > 30,000 year old carbonates. Comparison of C-14 data from foraminifera from the last glacial terrigenous unit in the foredeep off Iran with curves published by Hopley [Hopley, D., 1982. The Geomorphology of the Great Barrier Reef: Quaternary Development of Coral Reefs. Wiley, New York, 453 pp.] and Chapell et al. [Chapell, J., Omura, A., Tezer, E., McCulloch, M., Pandolfi, J., Ota, Y., Pillans, B., 1996. Reconciliation of late Quaternary sea levels derived from coral terraces at Huon Peninsula with deep sea oxygen isotope records. Earth Planet. Sci. Lett. 141, 227-236.] indicates that the region may have experienced uplift during the last glacial, whereas other geologic data indicate that the foredeep has had a history of continuous subsidence during the Cenozoic. A possible explanation for this discrepancy is that the foraminifera analyzed are not in place, but were reworked into shallower water during the Holocene transgression. However, the foraminifera analyzed do not display any evidence of wear, indicating that such transport was limited. A third alternative is that sea level during the last glacial was much higher than indicated by the curves of Hopley and Chapell et al.At the peak of the last glaciation 21,000 to 20,000 years ago, when sea level was 120 m lower than now, the Gulf was a waterless basin and deposition was negligible. On the Biaban Shelf, the Holocene transgressive sequence resting unconformably on last glacial sediments consists of 14,000 year old carbonates, a > 11,000 year old terrigenous delta on the northern end of the Biaban Shelf and 11,000-10,000 year old intertidal-tidal aragonite deposited in a dry climate. On the northeast side of the Gulf, the last glacial sediments are covered by 10,000 to 7000 year old aragonite muds (younging toward the northwest). Resting on the aragonites on the Biaban Shelf and on the northeast and northwest sides of the Gulf are marls deposited under the present humid climate. The southwest side of the Gulf continued to be a site of carbonate deposition throughout the Holocene. Comparison of AMS C-14 measurements of the late Holocene marls with the sea level curve of Fairbanks [Fairbanks, R.G., 1989. A 17,000 year glacio-eustatic sea level record; influence of glacial melting rates and the Younger Dryas event and deep-ocean circulation. Nature 342, 637-642.] indicates that the axial zone of the Gulf off Iran experienced subsidence during the Holocene. This subsidence coupled with a rapid rise in sea level during a major glacial melt 9500 to 8500 years ago, when global sea level rose from -50 to -28 m, led to the replacement of marl with a shallow (8-25 m) water fauna by a 'deep' (> 50 m) water one. Similar measurements and other geologic data indicate that the Mesopotamia Shelf and the mouth of the Mesopotamian Depression on the northwest side of the Gulf underwent both subsidence and uplift during the Cenozoic. These vertical oscillations, however, were more subdued than these in the foredeep off iran. The Arabian Shelf along the Gulfs southwest side appears to have experienced minor uplift during the Cenozoic. (C) 1999 Elsevier Science B.V. All rights reserved. VL - 160 IS - 1-2 N1 - 214vaTimes Cited:31Cited References Count:58 JO - Late Quaternary stratigraphy, Paleoclimate and neotectonism of the Persian (Arabian) Gulf region ER - TY - CONF T1 - Late Wisconsian deep-sea sedimentary record from convulsive geologic events, Northeast Pacific T2 - IAS 19 Regional Meeting of Sedimentology Y1 - 1999 A1 - Serra, Francesca A1 - Normark, William R. A1 - Zuffa, Gian Gaspare A1 - Brunner, Charlotte A. JF - IAS 19 Regional Meeting of Sedimentology CY - Copenhagen VL - Abstracts N1 - id: 1471 ER - TY - JOUR T1 - Linking the 10Be continental record of Lake Baikal to marine and ice archives for the last 50 ka: Implication for the global dust-aerosol input JF - Geophysical Research Letters Y1 - 1999 A1 - Aldahan, A. A1 - Possnert, G. A1 - Peck, J. A1 - King, J. A1 - Colman, S. AB - We present here a 10Be profile from the continental sediments of Lake Baikal (the world's largest fresh water lake), which, for the first time, shows the ≈ 40 ka 10Be enhancement and a pattern that strongly matches those from the marine and ice records for the last 50 ka. This finding provides a new horizon for global and regional correlation of continental archives. Additionally, our VADM-predicted 10Be production confirms and further strengthens a common global cause (geomagnetic field intensity) for the change in atmospheric 10Be over the last 50 ka. We also show that most of the 10Be inventory to the lake has been provided by riverine input, but with a significant addition from direct precipitation and dust-aerosol fallout. We estimate a higher dust-aerosol contribution of 10Be during the Holocene and interstadial stage 3 (22–50 ka) as compared with the glacial period (12–22 ka). VL - 26 N1 - id: 1353 JO - Linking the 10Be continental record of Lake Baikal to marine and ice archives for the last 50 ka: Implication for the global dust-aerosol input ER - TY - JOUR T1 - Long-term fluxes and budget of ferric iron: implication for the redox states of the Earth's mantle and atmosphere JF - Earth and Planetary Science Letters Y1 - 1999 A1 - Lecuyer, C. A1 - Ricard, Y. AB - Net flux of ferric iron from the subducted oceanic crust to the mantle has been estimated to constrain the evolution of the redox state of the Earth's mantle. The main mechanism responsible for the transfer of ferric iron towards the mantle is the production of magnetite during the hydrothermal alteration of the oceanic crust. Both modeling and compilation of chemical data lead to a flux of 21 x 10(3) kg s(-1) of ferric iron transported by the subducted oceanic crust. The net flux of ferric iron towards the deep mantle is estimated to be 12 x 10(3) kg s(-1) when corrected from the production rates of basic magmas at oceanic ridges, island arcs, and hot spots. We discuss several hypotheses. Ferric iron could react at depth with reduced species that buffer the redox state of the mantle to its present-day value. One possible mechanism could be the reaction of this ferric iron with the core that would have been reduced by only 500 m since 2 Ga. At the opposite, we may also consider that ferric iron accumulates in the deep mantle, being possibly accepted by the structure of spinel, garnet, and perovskite. The transfer of ferric iron from subducted slabs to the mantle contributes from 10 to 25% in the global budget of the ferric iron component of the mantle. The long-term loss of ferric iron from the Earth's surface may be considered as a plausible mechanism to regulate the photosynthetic production of molecular oxygen. (C) 1999 Elsevier Science B.V. All rights reserved. VL - 165 IS - 2 N1 - 160gtTimes Cited:87Cited References Count:66 JO - Long-term fluxes and budget of ferric iron: implication for the redox states of the Earth's mantle and atmosphere ER - TY - JOUR T1 - Marine and meteoric diagenesis of pleistocene carbonates from a nearshore submarine terrace, Ohau, Hawaii JF - Journal of Sedimentary Research Y1 - 1999 A1 - Sherman, C. E. A1 - Fletcher, C. H. A1 - Rubin, K. H. VL - 69 IS - 5 N1 - id: 298 ER - TY - JOUR T1 - Marine and meteoric diagenesis of Pleistocene carbonates from a nearshore submarine terrace, Oahu, Hawaii JF - Journal of Sedimentary Research Y1 - 1999 A1 - Sherman, C. E. A1 - Fletcher, C. H. A1 - Rubin, K. H. KW - barrier-reef KW - calcite KW - corals KW - fringing-reef KW - Holocene KW - oxygen isotopes KW - platform KW - recrystallization KW - sea-level KW - stabilization AB - The nearshore slope of Oahu consists of a shallowly dipping shelf extending from the shoreline out to the similar to -20 m contour, where there is a sharp break in slope down to similar to -30 m, Limestones recovered in a series of short cores taken from this nearshore terrace are typical of shallow-marine reef environments and comprise either a branching-coral or massive-coral facies, The composition as well as shoreward zonation of facies suggests that the terrace represents an in situ fossil reef complex. Th-U ages of in situ corals are all Pleistocene and suggest that the bulk of the feature formed during marine oxygen isotope stage 7. Later accretion along the seaward front of the terrace occurred during marine oxygen isotope substages 5a and/or 5c. Deposition during these interglacial highstands has not previously been documented in the sea-level record on Oahu,Although the diagenetic record in the cored samples is incomplete, three periods of diagenesis are identified: early shallow marine, meteoric, and post-meteoric shallow marine. Early shallow-marine diagenesis includes cementation by aragonite and Mg calcite in an active marine phreatic zone and predominantly micritization in a stagnant marine phreatic zone. Meteoric processes occurred in the vadose zone and include precipitation of calcite (needle fibers, meniscus cements, micritic networks), neomorphism, and dissolution. All limestones are now in an active marine phreatic zone. Evidence of post-meteoric shallow-marine diagenesis is found in last-generation Mg calcite cements and internal sediments occurring directly on limestone substrates that have otherwise been stabilized to calcite. The present seafloor is undergoing extensive biological and physical erosion. No Holocene limestones were recovered. Petrographic and geochemical signatures of subaerial exposure and meteoric diagenesis are recognized within the upper several centimeters of all cores. Thus, the present seafloor in the study area is a flooded Pleistocene subaerial exposure surface. VL - 69 SN - 1073-130x IS - 5 N1 - A237cq Times Cited:42 Cited References Count:79 JO - J Sediment Res ER - TY - JOUR T1 - Measured and predicted sediment yield from a subtropical, heavy rainfall, steep-sided river basin: Hanalei, Kauai, Hawaiian Islands JF - Geomorphology Y1 - 1999 A1 - Calhoun, R. S. A1 - Fletcher, C. H. AB - To determine the sediment yield of the 54.4 km(2) Hanalei River basin, we employ three methods: (1) the Universal Soil Loss Equation (USLE), which uses natural characteristics of the basin such as the amount of rain, slope steepness and length values, and soil types to predict sediment erosion in a basin; (2) the thickness and calibrated radiocarbon age of fluvial deposits cored from the coastal plain; and (3) field measurements of suspended sediment in the river. Method 1 (USLE) provides a model prediction of sediment yield that we test with observational data of methods 2 and 3. Several curves, including one by the US Soil Conservation Service, predict a sediment delivery ratio (measured sediment yield: gross erosion) between approximately 15% and 50%. With 5260 +/- 2210 Mg (metric tons) yr(-1) of suspended sediment in the Hanalei River and 2300 +/- 700 Mg yr(-1) deposited on the coastal plain, however, the delivery of sediment in the Hanalei basin ranged between 45% and 101% of the maximum predicted USLE value (88 +/- 103 Mg km(-2) yr(-1)). This higher than predicted yield may be the result of mass movement. We are not able to differentiate, however, between erosion and mass movement as the principle agent of denudation. Our measurements indicate a total sediment yield of 140 +/- 55 Mg km(-2) yr(-1) for the Hanalei Valley. (C) 1999 Elsevier Science B.V. All rights reserved. VL - 30 IS - 3 N1 - 267flTimes Cited:14Cited References Count:37 JO - Measured and predicted sediment yield from a subtropical, heavy rainfall, steep-sided river basin: Hanalei, Kauai, Hawaiian Islands ER - TY - JOUR T1 - Methane-consuming archaebacteria in marine sediments JF - Nature Y1 - 1999 A1 - Hinrichs, K. U. A1 - Hayes, J. M. A1 - Sylva, S. P. A1 - Brewer, P. G. A1 - DeLong, E. F. AB - Large amounts of methane are produced in marine sediments but are then consumed before contacting aerobic waters or the atmosphere. Although no organism that can consume methane anaerobically has ever been isolated, biogeochemical evidence indicates that the overall process involves a transfer of electrons from methane to sulphate and is probably mediated by several organisms, including a methanogen (operating in reverse) and a sulphate-reducer (using an unknown intermediate substrate). Here we describe studies of sediments related to a decomposing methane hydrate. These provide strong evidence that methane is being consumed by archaebacteria that are phylogenetically distinct from known methanogens. Specifically, lipid biomarkers that are commonly characteristic of archaea are so strongly depleted in carbon-13 that methane must be the carbon source, rather than the metabolic product, for the organisms that have produced them. Parallel gene surveys of small-subunit ribosomal RNA (16S rRNA) indicate the predominance of a new archael group which is peripherally related to the methanogenic orders Methanomicrobiales and Methanosarcinales. VL - 398 IS - 6730 N1 - Hinrichs, K UHayes, J MSylva, S PBrewer, P GDeLong, E FengResearch Support, Non-U.S. Gov'tResearch Support, U.S. Gov't, Non-P.H.S.England1999/05/11 02:03Nature. 1999 Apr 29;398(6730):802-5. JO - Methane-consuming archaebacteria in marine sediments ER - TY - JOUR T1 - Millennial-scale climate changes in ventilation of the thermocline, intermediate and deep waters of the glacial North Atlantic JF - Geophysical Monograph series Y1 - 1999 A1 - Curry, W. B. A1 - Marchitto, T. M. A1 - McManus, J. F. A1 - Oppo, D. W. A1 - L, Laarkamp K. VL - AGU Chapman Conference volume 112 N1 - id: 207 ER - TY - CHAP T1 - New Developments at the NOSAMS Facility T2 - Proceeding of the International Workshop on Frontiers in Accelerator Mass Spectrometry Y1 - 1999 A1 - von Reden, K. F. A1 - Schneider, R. J. A1 - McNichol, A. P. A1 - Hayes, J. M. A1 - Pearson, A. A1 - Eglinton, T. I. ED - Science, Japan International ED - Technology Exchange, Center JF - Proceeding of the International Workshop on Frontiers in Accelerator Mass Spectrometry PB - National Institute for Environmental Studies, Tsukuba, National Museum of Japanese History CY - Tsukuba, Japan N1 - id: 1723(JISTEC) ER - TY - CONF T1 - New Developments at the NOSAMS Facility T2 - International Workshop on Frontiers in Accelerator Mass Spectrometry Y1 - 1999 A1 - von Reden, K. F. A1 - Schneider, R. J. A1 - McNichol, A. P. A1 - Hayes, J. M. A1 - Pearson, A. A1 - Eglinton, T. I. ED - Shibata, Y. JF - International Workshop on Frontiers in Accelerator Mass Spectrometry PB - National Institute for Environmental Studies Reprot CY - Tsukuba, Japan N1 - id: 1679 ER - TY - CHAP T1 - The North Atlantic's 1-2 kyr climate rhythm: Relation to Heinrich events, Dansgaard/Oeschger cycles and the Little Ice Age (Book Section) T2 - Mechanisms of global climate change at mellennial time scales Y1 - 1999 A1 - Bond, G. C. A1 - Showers, W. A1 - Elliot, M. A1 - Evans, M. A1 - Lotti, R. A1 - Hajdas, I. A1 - Bonani, G. A1 - Johnson, S. ED - Webb, R. ED - D, Keigwin L. JF - Mechanisms of global climate change at mellennial time scales T3 - Geophysical Monograph Series 112 N1 - id: 216 ER - TY - CHAP T1 - The overturning circulation of the glacial Atlantic: A view from the top T2 - Reconstructing Ocean History: A Window into the Future Y1 - 1999 A1 - Lynch-Stieglitz, J. A1 - Curry, W. B. A1 - Slowey, N. A1 - Schmidt, G. A. ED - Abrantes, F. JF - Reconstructing Ocean History: A Window into the Future PB - Kluwer Academic/Plenum CY - New York N1 - id: 1364 ER - TY - CONF T1 - The overturning circulation of the glacial Atlantic: A view from the top T2 - Sixth International Conference on Paleoceanography Y1 - 1999 A1 - Lynch-Stieglitz, J. A1 - Curry, W. B. A1 - Slowey, N. C. JF - Sixth International Conference on Paleoceanography N1 - id: 1337 ER - TY - CONF T1 - Paleoceanographic changes in the Southern Ocean (Pacific Sector) during the last 14 ka.- -Abstract T2 - Third International SO-JGOFS Symposium Y1 - 1999 A1 - Morigo, C. A1 - Capotondi, L. A1 - Ravaioli, M. A1 - Giglio, F. A1 - Turi, B. A1 - Brilli, M. A1 - Langone, L. JF - Third International SO-JGOFS Symposium CY - Brest N1 - id: 1426 ER - TY - JOUR T1 - Paleoclimate of Southwestern China for the past 50,000 yr inferred from lake sediment records JF - Quaternary Research Y1 - 1999 A1 - Hodell, D. A. A1 - Brenner, M. A1 - Kanfoush, S. L. A1 - Curtis, J. H. A1 - Stoner, J. S. A1 - Song, X. L. A1 - Yuan, W. A1 - Whitmore, T. J. AB - Long sediment cores (12.5 and 13.5 m) from two lakes in Yunnan Province were used to infer the paleoclimate of southwest China over the past 50,000 yr, During the Holocene and marine isotope stage (MIS 3), bio-induced carbonate precipitation and organic matter (OM) production was high, suggesting warm temperatures and high primary productivity. In contrast, sediment inorganic carbon (IC) and organic carbon (OC) concentrations were low in last glacial deposits from 38,000 to 12,000 cal yr B.P., indicating cool temperatures and low productivity. The 50,000-yr record has alternating peaks of carbonate and coarse-grain (>38 mu m) quartz that reflect warm, moist interglacial or interstadial conditions alternating with cold, dry glacial or stadial conditions, respectively. Spectral analysis of the carbonate and quartz signals reveals power concentrated at periods of 7200 and 8900 cal yr, respectively, that may reflect a nonlinear climate response to precessional forcing at a time of reduced eccentricity modulation (McIntyre and Molfino, 1996). Oxygen isotope values of calcite from Yunnan lake cores indicate the summer monsoon was weak during the last glaciation from 50,000 to 12,000 cal yr B.P. The summer monsoon intensified between 12,000 and 8000 cal yr B.P., but weakened gradually in response to insolation forcing during the mid-to-late Holocene. Our results support the Overpeck ef al. (1996) model that posits a weak summer monsoon during the last glaciation that responded nonlinearly to insolation forcing when its intensity was affected by Eurasian snow cover and ice-sheet extent. The summer monsoon intensified and responded linearly to seasonal insolation forcing in the Holocene when ice volume diminished. (C) 1999 University of Washington. VL - 52 IS - 3 N1 - 255ltTimes Cited:85Cited References Count:58 JO - Paleoclimate of Southwestern China for the past 50,000 yr inferred from lake sediment records ER - TY - JOUR T1 - Paleoenvironmental changes during the last 17,000 years in western Patagonia JF - Bamberger Geographische Schriften Y1 - 1999 A1 - Markgraf, V. A1 - Bianchi, M. M. VL - 19 N1 - id: 1382 ER - TY - CONF T1 - Paleoenvironments of Capitol Reef National Park reconstructed from fossil packrate middens T2 - 4th biennial Conference on Research on the Colorado Plateau Y1 - 1999 A1 - Cole, K. L. A1 - Murray, L. K. ED - Riper, van JF - 4th biennial Conference on Research on the Colorado Plateau CY - USGS Colorado Plateau Field Station, Flagstaff, AZ N1 - id: 1369 ER - TY - JOUR T1 - Peat accumulation and succession following permafrost thaw in the boreal peatlands of Manitoba, Canada JF - Ecoscience Y1 - 1999 A1 - Camill, P. AB - Permafrost thaw in boreal peatlands may be widespread as climate warms over the next century. Thaw will lead to dramatic changes in vegetation, and an understanding of the patterns and rates of succession following thaw is important for assessing future ecosystem changes, such as carbon accumulation and the likelihood of permafrost formation during climate warming. This paper describes the autogenic processes of peat accumulation and succession from recently thawed, aquatic Sphagnum communities to lawn and hummock Sphagnum communities favorable for permafrost formation. Peat cores were used to construct bulk density profiles in aquatic, lawn, and hummock habitats. Soil bulk density increased over time from the edges to the centers of thawed bogs. These changes corresponded to changes from aquatic to lawn/hummock communities. Macrofossils from Pb-210-dated peat cores were used to document historical changes to hummock communities. Succession to hummock communities capable of forming permafrost was less than 80 years. Picea mariana seedlings colonized emergent Sphagnum hummocks in collapse scars, which may lead to permafrost formation. However, permafrost formation in today's discontinuous permafrost landscape is unlikely during future climate warming because of limited tree establishment and shifting mean annual temperature isotherms. VL - 6 IS - 4 N1 - 299bzTimes Cited:22Cited References Count:55 JO - Peat accumulation and succession following permafrost thaw in the boreal peatlands of Manitoba, Canada ER - TY - CONF T1 - Planktic foraminifera and oxygen isotope as proxies for paleoceanographic reconstruction in the Southern Ocean during the last deglacial time--Abstract T2 - Convegno Glaciologia e Paleoclima Y1 - 1999 A1 - Morigi, C. A1 - Capotondi, L. A1 - Ravaioli, M. A1 - Giglio, F. A1 - Turi, B. A1 - Brilli, M. A1 - Frignani, M. A1 - Langone, L. JF - Convegno Glaciologia e Paleoclima CY - Padova N1 - id: 1425 ER - TY - JOUR T1 - Preliminary evidence of early deglaciation in southern Chile JF - Palaeogeography Palaeoclimatology Palaeoecology Y1 - 1999 A1 - Anderson, D. M. A1 - Archer, R. B. AB - The end of the last ice age in the channels of southern Chile is recorded by resumed sedimentation in formerly ice-filled basins. To identify the timing of initial ice retreat in Southern Chile, we examined ice-proximal sediments from a proglacial lake along the eastern margin of the Magallanes ice sheet, an environment thought to be sensitive to initial melting (Porter, S.C,, Clapperton, C.M., Sugden, D.E., 1992. Chronology and dynamics of deglaciation along and near the Strait of Magellan, southernmost South America. Sver. Geol. Unders. 81, 233-239). AMS-radiocarbon dates of the supra-till deposits in two cores indicate that sedimentation resumed 18 radiocarbon kyr. Deposition in kettle-holes and bogs on the adjacent land surfaces began at the same time or earlier (17-25 radiocarbon kyr) (Clapperton, C.M., Sugden, D.E., Kaufman, D.S., McCulloch, R.D., 1995. The last glaciation in central Magellan Strait, Southernmost Chile. Quat. Res. 44, 133-148). Our preliminary interpretation is that these events indicate initial deglaciation in the region and the formation of a large proglacial lake, followed several thousand years later by the invasion of salt water as sea level rose. Deglaciation in southers Chile occurred too early to be forced by the resumption of North Atlantic Deep Water formation, sea level rise, or northern hemisphere summer insolation, and we suggest instead that southern insolation played a role. The time of initial deglaciation in southern Chile (21-27 calendar kyr) occurred as southern hemisphere annual insolation increased from a minimum at 29 calendar kyr (6 W/m(2) less than today at 80 degrees S). (C) 1999 Elsevier Science B.V. All rights reserved. VL - 146 IS - 1-4 N1 - 160wbTimes Cited:13Cited References Count:25 JO - Preliminary evidence of early deglaciation in southern Chile ER - TY - CONF T1 - A preliminary model-data comparison for bomb-14C in the Pacific thermocline T2 - WOCE-AIMS Tracer Workshop Y1 - 1999 A1 - Rogers, K. A1 - Peacock, S. A1 - Latif, M. A1 - Key, R. M. JF - WOCE-AIMS Tracer Workshop CY - Bremen, Germany N1 - id: 313 ER - TY - JOUR T1 - Radiocarbon age anomalies in land snail shells from Texas: Ontogenetic, individual, and geographic patterns of variation JF - Radiocarbon Y1 - 1999 A1 - Goodfriend, G. A. A1 - Ellis, G. L. A1 - Toolin, L. J. KW - Carbonate AB - Accelerator mass spectrometric (AMS) radiocarbon analyses of live-collected, prebomb samples of shell carbonates of the land snails Rabdotus dealbatus and R. alternatus from Texas were carried out to quantify the characteristic age anomalies of land snails from limestone areas. Age anomalies are similar for the two species; they average +700 yr and vary by +/-180 yr (1 sigma) among samples. Serial analysis of I shell reveals a significant ontogenetic trend in C-14 age anomalies, with older apparent ages (up to 1200 yr) in the apical part of the shell and younger and uniform ages in the last whorl. No trend in age anomalies was found across a broad range of rainfall conditions (from 300 to 1000 mm mean annual rainfall). VL - 41 SN - 0033-8222 IS - 2 N1 - 228qgTimes Cited:28 Cited References Count:18 JO - Radiocarbon ER - TY - JOUR T1 - Radiocarbon analysis of Pinus lagunae tree rings: Implications for tropical dendrochronology JF - Radiocarbon Y1 - 1999 A1 - Biondi, F. AB - A promising species for tropical dendrochronology is Pinus lagunae, a pine tree found in Baja California Sur (Mexico) around lat 23.5 degrees N. In 1995, we sampled a total of 27 wood cores from 13 Pinus lagunae trees in Sierra La Victoria (23 degrees 36'N, 109 degrees 56'W),just north of Sierra La Laguna, at an elevation of 1500-1600 m. Selected trees were locally dominant, but their ring-width patterns could not be crossdated. To test the hypothesis that visible growth layers in Pinus lagunae are formed annually, we measured radiocarbon amounts in individual rings by means of accelerator mass spectrometry (AMS). Twenty-three C-14 measurements were used to trace the location of the 1963-64 "bomb spike" in 3 wood increment cores. By comparing the location of that Delta(14)C extreme with the number of visible radial wood increments, it was possible to conclude that 2 cores had a number of locally absent rings, while the 3rd one included a few years with more than one growth layer. Therefore, ring-width patterns of sampled Pinus lagunae were not consistent from one tree to another, most likely because of climatic regime in combination with microsite features. While the possibility of generating Pinus lagunae tree-ring chronologies cannot entirely be ruled out, the development of dendrochronological proxy records of climate from coniferous species in tropical North America should focus on species and sites that experience a more pronounced seasonality. VL - 41 UR - https://journals.uair.arizona.edu/index.php/radiocarbon/article/view/3814 IS - 3 N1 - 289tcTimes Cited:16Cited References Count:31 JO - Radiocarbon analysis of Pinus lagunae tree rings: Implications for tropical dendrochronology ER - TY - JOUR T1 - Rapid strand-plain accretion in the northeastern Nile Delta in the 9th century A. D. and the demise of the port of Pelusium JF - Geology Y1 - 1999 A1 - Goodfriend, G. A. A1 - Stanley, D. J. VL - 27 N1 - id: 177 ER - TY - JOUR T1 - Reconstructing the oceanic 13C Suess effect JF - Global Biogeochemical Cycles Y1 - 1999 A1 - Sonnerup, R. E. A1 - Quay, P. D. A1 - McNichol, A. P. A1 - Bullister, J. L. A1 - Westby, T. A. A1 - Anderson, H. L. VL - 13 N1 - id: 1710 ER - TY - CONF T1 - Records of Heinrich Events at the confluence of the distal Northwest Atlantic Mid-Ocean Channel, and the Immarssauk Mid-Ocean Channel of the North Atlantic, Europ. Union T2 - Geoscience 10th Annual Meeting Y1 - 1999 A1 - Rashid, H. A1 - Hesse, R. A1 - Piper, D. J. W. JF - Geoscience 10th Annual Meeting VL - Abstract 4 N1 - id: 137; 1 ER - TY - JOUR T1 - Registro micropaleontologico de los cambios naturales y antropicos (500 anos BP-presente) en us ecosistema de lagoon (Doninos, NO Peninsula Iberica) JF - Actas XV Jornadas Sociedad Espanola de Paleontologia Y1 - 1999 A1 - Bao, R. A1 - Santos, L. A1 - Sanchez-Goni, M. F. VL - Temas Geologico-Mineros ITGE, 26, Madrid N1 - id: 151 ER - TY - CONF T1 - Relative Sea-Level Rise and the Development of Channel-Fill and Shallow-Water Sequences on Cape Cod, Massachusetts T2 - American Geophysical Union, Spring Meeting Y1 - 1999 A1 - Gutierrez, B. T. A1 - Aubrey, D. G. A1 - Driscoll, N. W. A1 - Uchupi, E. JF - American Geophysical Union, Spring Meeting CY - Boston, MA N1 - id: 120 ER - TY - JOUR T1 - Research of natural processes taking place in Issyk-Kul Lake and Issyk-Kul Hollow by means of isotopic methods JF - Science and New Technologies Y1 - 1999 A1 - Johnson, T. J. A1 - Rasmussen, K. A. A1 - Romanovsky, V. V. IS - Special Issue No. 1 N1 - id: 210 ER - TY - JOUR T1 - Retreat of a tidewater margin of the Laurentide ice sheet in eastern coastal Maine ca. 14 to 13,000 14C yrs BP JF - Geological Society of America Bulletin Y1 - 1999 A1 - Kaplan, M. F. VL - 111 N1 - id: 104 ER - TY - JOUR T1 - The role of oceanic forcing in mid-Holocene Northern Hemisphere climatic change JF - Paleoceanography Y1 - 1999 A1 - Kerwin, M. W. A1 - Overpeck, J. T. A1 - Webb, R. S. A1 - DeVernal, A. A1 - Rind, D. H. A1 - Healy, R. J. AB - Previous model investigations suggested that changes in orbital forcing and feedbacks associated with northward expansion of the boreal forest were both required to explain the full magnitude of enhanced high-latitude Northern Hemisphere summer warming at 6 ka, thus implying that biospheric feedbacks (decreased planetary albedo associated with forest expansion) may be large in the future [Foley ct at., 1994; TEMPO (Testing Earth System Models with Paleo-Observations), 1996]. Before the magnitude of past biospheric and other feedbacks can be estimated with confidence, however, the role of realistic high-latitude oceanic forcing (i.e., sea surface temperature (SST) increases and sea ice reductions) should also be considered. Here we review existing paleoceanographic observations that suggest portions of the North Atlantic were up to 4 degrees C warmer than today at 6 ka. We then combine our estimates of mid-Holocene North Atlantic SST and sea ice conditions with new climate model simulations to suggest that a significant portion of high-latitude summer warming at 6 ka in the Northern Hemisphere can be accounted for by altered orbital forcing, SSTs, and sea ice relative to today. Our results underscore the importance of incorporating realistic boundary conditions when using paleoenvironmental data to evaluate the climate system's sensitivity to altered forcing and suggest that high-latitude oceanic feedbacks were major contributors to enhanced high-latitude summer warming in the Northern Hemisphere at 6 ka. VL - 14 IS - 2 N1 - id: 1943; PT: J; UT: WOS:000079325100009 JO - The role of oceanic forcing in mid-Holocene Northern Hemisphere climatic change ER - TY - JOUR T1 - S4I Final report for AMS 14C samples JF - Ocean Tracer Laboratory Tech. Rep. Y1 - 1999 A1 - Key, R. M. VL - 99 IS - 2 N1 - id: 325 ER - TY - JOUR T1 - Sedimentary facies analyses as paleohydrological proxies for saline alkes, Central Ebro Basin, Spain. Fourth workshop of the European Lake Drilling Programme JF - Terra Nostra Y1 - 1999 A1 - Valero-Garces, B. L. VL - 99/10 N1 - id: 383 ER - TY - JOUR T1 - Sedimentary organic matter preservation: A test for selective degradation under oxic conditions JF - American Journal of Science Y1 - 1999 A1 - Hedges, J. I. A1 - Hu, F. S. A1 - Devol, A. H. A1 - Hartnett, H. E. A1 - Tsamakis, E. A1 - Keil, R. G. AB - We report here a test of the hypothesis that the extent of organic matter preservation in continental margin sediments is controlled by the average period accumulating particles reside in oxic porewater immediately beneath the water/sediment interface. Oxygen penetration depths, organic element compositions, and mineral surface areas were determined for 16 sediment cores collected along an offshore transect across the Washington continental shelf, slope, and adjacent Cascadia Basin. Individual amino acid, sugar, and pollen distributions were analyzed for a 11 to 12 cm horizon from each core, and (14)C-based sediment accumulation rates and stable carbon isotope compositions were determined from depth profiles within a subset of six cores from representative sites. Sediment accumulation rates decreased, and dissolved O(2) penetration depths increased offshore along the sampling transect. As a result, oxygen exposure times (OET) increased seaward from decades (mid-shelf and upper slope) to more than a thousand years (outer Cascadia Basin). Organic contents and compositions were essentially constant within individual sediment cores but varied consistently with location. In particular, organic carbon/surface area ratios decreased progressively offshore and with increasing OET. Three independent compositional parameters demonstrated that the remnant organic matter in farther offshore sediments is more degraded. Both concentration and compositional patterns indicated that sedimentary organic matter exhibits a distinct and reproducible "oxic effect" OET helps integrate and explain organic matter preservation in accumulating continental margin sediments and hence provides a useful tool for assessing transfer of organic matter from the biosphere to the geosphere. VL - 299 IS - 7-9 N1 - 263rmTimes Cited:194Cited References Count:104 JO - Sedimentary organic matter preservation: A test for selective degradation under oxic conditions ER - TY - CONF T1 - Sedimentological and carbon-isotopic record of late Holocene climate in the sediments of Soda Lake Carrizo Plain, California. Abstracts T2 - Geological Society of America, Annual Meeting Y1 - 1999 A1 - Eigenbrode, J. L. A1 - Pratt, L. M. A1 - Rhodes, D. D. A1 - Arrowsmith, J. R. A1 - Mora, G. JF - Geological Society of America, Annual Meeting T3 - Session 147 CY - Denver, Colorado N1 - id: 224 ER - TY - THES T1 - Sedimentological, carbon-isotopic, and molecular records of late Holocene climate in the sediments of Soda Lake, Carrizo Plain, California. Thesis Y1 - 1999 A1 - Eigenbrode, J.L. A1 - Pratt, L.M. A1 - Rhodes, D.D. A1 - Arrowsmith, J.R. A1 - Mora, G. PB - Indiana University VL - M.S., Unpublished ER - TY - CHAP T1 - A Silent Tandetron AMS System T2 - Symposium of North Eastern Accelerator Personnel, October 13-15, 1997, SNEAP XXXI Y1 - 1999 A1 - von Reden, Karl F. A1 - Schneider, Robert J. ED - Dworschak, F. JF - Symposium of North Eastern Accelerator Personnel, October 13-15, 1997, SNEAP XXXI PB - World Scientific Publishing Co. CY - Forschungszentrum Julich, Germany N1 - id: 1722 ER - TY - JOUR T1 - Similar glacial and Holocene deep water circulation inferred from southeast Pacific benthic foraminiferal carbon isotope composition JF - Paleoceanography Y1 - 1999 A1 - Matsumoto, K. A1 - Lynch-Stieglitz, J. AB - We present Holocene and last glacial maximum (LGM) oxygen and carbon isotope measurements on Planulina wuellerstorfi in six southeast Pacific cores. Sedimentation rates are low in this part of the ocean, acid measurements were made on individual foraminiferal shells in order to identify the Holocene and glacial individuals on the basis of their extreme delta(18)O. The new delta(13)C data were combined with previous P. wuellerstorfi data for interpretation of global thermohaline circulation. Data from the Southern Ocean were examined closely for regional coherency and a few anomalous delta(13)C values suspected of having productivity overprint were removed. The resulting global delta(13)C distributions and gradients indicate that the deep water circulation was similar during the Holocene and LGM. This interpretation brings delta(13)C data to a better agreement with Cd/Ca data and marks a sharp contrast with a widely held view based on delta(13)C measurements that the glacial Southern Ocean was the terminus of the thermohaline circulation. The proposed presence of glacial North Atlantic Deep Water does not necessarily contradict the postulated presence of Glacial North Atlantic Intermediate Water. VL - 14 IS - 2 N1 - 179kdTimes Cited:61Cited References Count:90 JO - Similar glacial and Holocene deep water circulation inferred from southeast Pacific benthic foraminiferal carbon isotope composition ER - TY - JOUR T1 - Simulated time-dependent climate response to solar radiative forcing since 1600 JF - Journal of Geophysical Research-Atmospheres Y1 - 1999 A1 - Rind, D. A1 - Lean, J. A1 - Healy, R. AB - Estimated solar irradiance variations since 1500 have been used to force the GISS atmospheric GCM coupled to a mixed layer "q-flux" ocean with heat diffusion through the bottom of the mixed layer. The goal is to assess solar-induced climate change in preindustrial and postindustrial epochs. Six simulations and control runs were made to test the effects of different initial conditions, estimates of initial solar forcing conditions, and ocean heat uptake. The results show that an estimated solar forcing increase of 0.25% accounts for a 0.45 degrees C temperature increase since 1600 and an increase of about 0.2 degrees C over the past 100 years. Global surface temperatures lag solar fluctuations by up to 10 years; the lag is greater over the oceans and so is the correlation due to reduced noise. With only a mixed layer ocean the phase lag is 5 years less. Solar forcing and water vapor feedback each directly account for 35% of the temperature response, with cloud cover changes contributing 20% and sea ice/snow cover 10%. Uncertainty in the initial radiation imbalance or solar forcing affects the surface temperatures for 60-90 years. Modeled and observed periodicities show dominance of long-period forcing (>50 years), as provided by the solar input in these experiments. Tropical temperatures correlate best with solar forcing, due to the influence of water vapor feedback, especially at these multidecadal periods. Sea ice and extratropical temperatures have less long-period power, while high-frequency fluctuations dominate simulated cloud cover variations, which are relatively independent of solar forcing changes. Global and extratropical precipitation increase as the climate warms, but not low and subtropical precipitation, due to conflicting influences of absolute temperature and temperature gradient changes. Solar forcing by itself was not sufficient to produce the rapid warming during the last several decades. A comparison experiment varying trace gas forcing suggests that if the solar estimate is correct, then negative forcing by tropospheric aerosols (and perhaps volcanoes, ozone, and land use changes) has been about -1.2 W m(-)2 since 1700, implying approximately equal contribution from direct and indirect tropospheric aerosol effects. VL - 104 IS - D2 N1 - id: 1945; PT: J; UT: WOS:000078242200003 JO - Simulated time-dependent climate response to solar radiative forcing since 1600 ER - TY - JOUR T1 - The slope water current over the Laurentian Fan on interunnual to millennial timescales JF - Science Y1 - 1999 A1 - Keigwin, L. D. A1 - Pickart, R. S. VL - 286 N1 - id: 113 ER - TY - JOUR T1 - Spatial distribution of carbon and oxygen isotopes in laterally extensive carbonate-cemented layers: Implications for mode of growth and subsurface identification JF - Journal of Sedimentary Research Y1 - 1999 A1 - Klein, J. S. A1 - Mozley, P. A1 - Campbell, A. A1 - Cole, R. AB - Carbonate concretions and laterally extensive cemented layers are common features in the Prairie Canyon Member of the Mancos Shale at its type locality in western Colorado. Stable-isotope and petrographic data were obtained from these cemented zones in an attempt to determine: (1) how the cemented layers form, (2) whether or not they can be chemically correlated, and (3) if it is possible to differentiate them from concretions in the subsurface. The cement in both the layers and concretions consists of ferroan dolomite and lesser amounts of stoichiometric dolomite and ankerite. Samples for stable-isotope analysis were drilled from 10 grids, with a typical grid spacing of 10 cm x 10 cm, Gridded samples were obtained from two continuous cemented layers at several locations along the layers (2.3 m to 1.5 km apart on the same layer), and from isolated and stratabound concretions,Taken together, all the cements (regardless of spatial position) show a remarkably linear correlation (R-2 = 0.98) between delta(13)C and delta(18)O, Systematic center-to-edge decreases in both delta(13)C and delta(18)O occur in each of the cemented zones and are persistent over lateral intervals of at least 1.5 km, The cores of the cemented zones have positive delta(13)C values (up to > 10 parts per thousand PDB), which result from incorporation of C-13-enriched carbon during methanogenesis. The edges of the cemented zones have negative delta(13)C values (down to < -9 parts per thousand PDB), which suggests incorporation of C-13-depleted carbon from thermocatalytic decarboxylation reactions. Oxygen isotope paleothermometry indicates that precipitation may have started at moderate temperatures (similar to 25 degrees C) and ended at temperatures as high as 92 degrees C,The spatial distribution of the isotopic data in the cemented layers can be explained as resulting from the coalescence of stratabound concretions, followed by growth above and below the coalesced concretions. Such growth may have occurred in a complex: manner, in which early cements precipitated throughout the thickness of the layer but were more abundant in the core zone. Given the lateral persistence of the pattern of isotopic variation in the cemented layers, geochemical correlation of the layers may be possible in the subsurface. In addition, because laterally persistent cemented layers in the Prairie Canyon Member exhibit patterns of isotopic variation different from concretions (layers have a more asymmetrical vertical distribution), it should be possible to distinguish between the two styles of cementation from subsurface core data alone. VL - 69 IS - 1 N1 - A157gxTimes Cited:36Cited References Count:39 JO - Spatial distribution of carbon and oxygen isotopes in laterally extensive carbonate-cemented layers: Implications for mode of growth and subsurface identification ER - TY - RPRT T1 - The speciation and sources of dissolved phosphorus in the Everglades (Report) Y1 - 1999 A1 - Copper, W. A1 - Hsieh, Y. P. A1 - Landing, W. M. A1 - Proctor, L. A1 - Salters, V. A1 - Wang, Y. N1 - id: 1348 ER - TY - CONF T1 - Stable isotope and trace element composition of ostracodes from Lake Issyk Kul, Kyrgyzstan T2 - American Geophysical Union Fall Meeting Y1 - 1999 A1 - Ricketts, R. D. A1 - Rasmussen, K. A. A1 - Brown, E. T. A1 - Johnson, T. J. JF - American Geophysical Union Fall Meeting CY - San Francisco, California N1 - id: 1366 ER - TY - CONF T1 - Ten Years After--The WOCE AMS Radiocarbon Program T2 - 8th International Conference on Accelerator Mass Spectrometry Y1 - 1999 A1 - McNichol, A. A1 - Schneider, R. A1 - von Reden, K. A1 - Gagnon, A. A1 - Elder, K. A1 - Key, R. A1 - Quay, P. JF - 8th International Conference on Accelerator Mass Spectrometry CY - Vienna, Austria N1 - id: 1757 ER - TY - JOUR T1 - Terminal Proterozoic Mid-Shelf Benthic Microbial Mats in the Centralian Supervasin and their Environmental Significance JF - Geochimica et Cosmochimica Acta Y1 - 1999 A1 - Logan, Graham A. A1 - Calver, Clive R. A1 - Gorjan, Paul A1 - Summons, Roger E. A1 - Hayes, John M. A1 - Walter, Malcolm R. VL - 63 N1 - id: 1734 ER - TY - JOUR T1 - Terrace Construction in Northern Chihuahua, Mexico at 1150 B.C. and the Present JF - Journal of Field Archaeology Y1 - 1999 A1 - Hard, R. A1 - Roney, J. A1 - Zapata, J. A1 - Moses, B. VL - 26 N1 - id: 238 ER - TY - JOUR T1 - The uptake of carbon during alteration of ocean crust JF - Geochimica Et Cosmochimica Acta Y1 - 1999 A1 - Alt, J. C. A1 - Teagle, D. A. H. AB - The distributions and abundances of alteration types and carbonate minerals in sections of upper ocean crust have been measured in order to determine the carbon budget in altered ocean crust. Our results show that the ocean crust is a sink for carbon, with an annual storage rate of 3.4 x 10(12) mol C y(-1), in close agreement with a previous estimate by Staudigel et al. (1989). This surpasses the total production rate of carbon in new oceanic crust and, besides accounting for uptake of all CO2 lost via degassing at MOR, results in a net sink in the oceanic crust of 1.5-2.4 x 10(12) mol C y(-1). This sink is significant for global carbon budgets, and subduction of altered ocean crust may be an important source of CO2 to the atmosphere and/or recycling into the mantle. The bulk CO2 content of the crust decreases with depth, with most of the carbon taken up in the permeable upper few hundred meters of the volcanic section at low temperatures (0-60 degrees C) during aging of crust away from spreading ridges. The abundances of carbonate veins and the bulk CO2 contents of the upper crust are greater in older (110-165 Ma) than younger (6Ma) crust, suggesting progressive uptake of carbon by the upper ocean crust. Precipitation of carbonates within the crust is essentially complete within 100 Ma, and perhaps as soon as a few tens of million years after formation of the crust. Copyright (C) 1999 Elsevier Science Ltd. VL - 63 IS - 10 N1 - 221egTimes Cited:188Cited References Count:45 JO - The uptake of carbon during alteration of ocean crust ER - TY - JOUR T1 - Use of Hydrogen and Carbon Stable Isotopes in the Characterization of Oils from the Potiguar Basin (onshore), Northeastern Brazil JF - Bulletin of the American Association of Petroleum Geologists Y1 - 1999 A1 - Neto, Eugenio Vaz dos Santos A1 - Hayes, John M. VL - 83 N1 - id: 1732 ER - TY - JOUR T1 - Variability in shallow- and intermediate-water hydrography during the last climate cycle of the Quaternary JF - EOS Y1 - 1999 A1 - McManus, J. F. A1 - Healey, S. L. A1 - Oppo, D. W. A1 - Curry, W. B. VL - 80 N1 - id: 170 ER - TY - THES T1 - Warm-temperate to subtropical shallow water carbonates of the southern Gulf of California and geochemistry of rhodoliths (Thesis) Y1 - 1999 A1 - Halfar, J. PB - Stanford University CY - Stanford, CA VL - PhD ER - TY - JOUR T1 - Weaker Gulf Stream in the Florida straits during the last glacial maximum JF - Nature Y1 - 1999 A1 - Lynch-Stieglitz, J. A1 - Curry, W. B. A1 - Slowey, N. AB - As it passes through the Florida Straits, the Gulf Stream consists of two main components: the western boundary flow of the wind-driven subtropical gyre and the northward-flowing surface and intermediate waters which are part of the 'global conveyor belt' compensating for the deep water that is exported from the North Atlantic Ocean(1), The mean flow through the Straits is largely in geostrophic balance and is thus reflected in the contrast in seawater density across the Straits(2). Here we use oxygen-isotope ratios of benthic foraminifera which lived along the ocean margins on the boundaries of the Florida Current during the Last Glacial Maximum to determine the density structure in the water and thereby reconstruct transport through the Straits using the geostrophic method-a technique which has been used successfully for estimating present-day flow(3). Our data suggest that during the Last Glacial Maximum, the density contrast across the Florida Straits was reduced, with the geostrophic flow, referenced to the bottom of the channel, at only about two-thirds of the modern value. If the wind-driven western boundary flow was not lower during the Last Glacial Maximum than today, these results indicate a significantly weaker conveyor-belt component of the Gulf Stream compared to present-day values. Whereas previous studies based on tracers suggested that deep waters of North Atlantic origin were not widespread during glacial times, indicating either a relatively weak or a shallow overturning cell, our results provide evidence that the overturning cell was indeed weaker during glacial times. VL - 402 IS - 6762 N1 - 264pcTimes Cited:122Cited References Count:31 JO - Weaker Gulf Stream in the Florida straits during the last glacial maximum ER - TY - JOUR T1 - A Younger Dryas Temperature Reversal in the Eastern Equatorial Pacific, EOS, Transactions JF - AGU, 1999 Fall Meeting Y1 - 1999 A1 - Koutavas, A. A1 - Lynch-Stieglitz, J. VL - 80 N1 - id: 167; 46 JO - A Younger Dryas Temperature Reversal in the Eastern Equatorial Pacific, EOS, Transactions ER - TY - JOUR T1 - A 25,000-year tropical climate history from bolivian ice cores JF - Science Y1 - 1998 A1 - Thompson, L. G. A1 - Davis, M. E. A1 - Mosley-Thompson, E. A1 - Sowers, T. A. A1 - Henderson, K. A. A1 - Zagorodnov, V. S. A1 - Lin, P. A1 - Mikhalenko, V. N. A1 - Campen, R. K. A1 - Bolzan, J. F. A1 - Cole-Dai, J. A1 - Francou, B. AB - Ice cores that were recovered from the summit of Sajama mountain in Bolivia provide carbon-14-dated tropical records and extend to the Late Glacial Stage (LGS). Oxygen isotopic ratios of the ice decreased 5.4 per mil between the early Holocene and the Last Glacial Maximum, which is consistent with values from other ice cores. The abrupt onset and termination of a Younger Dryas-type event suggest atmospheric processes as the probable drivers. Regional accumulation increased during the LGS, during deglaciation, and over the past 3000 years, which is concurrent with higher water levels in regional paleolakes. Unlike polar cores, Sajama glacial ice contains eight times less dust than the Holocene ice, which reflects wetter conditions and extensive snow cover. VL - 282 SN - 1095-9203 (Electronic)0036-8075 (Linking) UR - https://www.ncbi.nlm.nih.gov/pubmed/9836630 IS - 5395 N1 - ThompsonDavis Mosley-Thompson Sowers Henderson Zagorodnov Lin Mikhalenko Campen Bolzan Cole-Dai Francou eng 1998/12/04 03:02 Science. 1998 Dec 4;282(5395):1858-64. ER - TY - CONF T1 - AMS measurement of T2 - Sixteenth International Radiocarbon Conference Y1 - 1998 A1 - von Reden, K. F. A1 - McNichol, A. P. A1 - Pearson, A. A1 - Schneider, R. J. JF - Sixteenth International Radiocarbon Conference CY - Groningen VL - 40(1) N1 - id: 1643 ER - TY - JOUR T1 - AMS Measurement of small samples with high-current system: (Proceedings of the 16th International Radiocarbon Conference, 1997) JF - Radiocarbon Y1 - 1998 A1 - von Reden, K. F. A1 - McNichol, A. A1 - Pearson, A. A1 - Schneider, R. VL - 40 IS - 1 N1 - id: 1815 ER - TY - CHAP T1 - Arid phases in the western Mediterranean region during the last glacial cycle reconstructed from Lacustrine records T2 - Paleohydrology and Environmental Change Y1 - 1998 A1 - Valerol-Garces, B. L. A1 - Zeroual, E. A1 - Kelts, K. ED - Eenito, G. JF - Paleohydrology and Environmental Change PB - Wiley & Sons CY - London N1 - id: 1211 ER - TY - JOUR T1 - Carbon cycling in sediments from the western equatorial Atlantic: Stable and radiocarbon isotopes in pore waters on the Ceara Rise JF - EOS Y1 - 1998 A1 - McNichol, A. P. A1 - McCorkle, D. C. A1 - Martin, W. R. A1 - Berry, J. N. VL - 79 IS - 1 N1 - id: 108 ER - TY - JOUR T1 - Challenges in application of radiocarbon dating of organic carbon phases in opal-rich marine sediments from the Southern Ocean JF - Trans. AGU 79 Y1 - 1998 A1 - Zheng, Y. A1 - Anderson, R. F. A1 - Froelich, P. N. A1 - Beck, W. A1 - McNichol, A. P. A1 - Guilderson, T. N1 - id: 266 ER - TY - JOUR T1 - The chemical composition of subducting sediment and its consequences for the crust and mantle JF - Chemical Geology Y1 - 1998 A1 - Plank, T. A1 - Langmuir, C. H. AB - Subducted sediments play an important role in are magmatism and crust-mantle recycling. Models of continental growth, continental composition, convergent margin magmatism and mantle heterogeneity all require a better understanding of the mass and chemical fluxes associated with subducting sediments. We have evaluated subducting sediments on a global basis in order to better define their chemical systematics and to determine both regional and global average compositions. We then use these compositions to assess the importance of sediments to are volcanism and crust-mantle recycling, and to re-evaluate the chemical composition of the continental crust. The large variations in the chemical composition of marine sediments are for the most part linked to the main lithological constituents. The alkali elements (K, Rb and Cs) and high field strength elements (Ti, Nb, Hf, Zr) an closely linked to the detrital phase in marine sediments; Th is largely detrital but may be enriched in the hydrogenous Fe-Mn component of sediments; REE patterns are largely continental, but abundances are closely linked to fish debris phosphate; U is mostly detrital, but also dependent on the supply and burial rate of organic matter; Ba is linked to both biogenic barite and hydrothermal components; Sr is linked to carbonate phases. Thus, the important geochemical tracers follow the lithology of the sediments. Sediment lithologies are controlled in turn by a small number of factors: proximity of detrital sources (volcanic and continental); biological productivity and preservation of carbonate and opal; and sedimentation rate. Because of the link with lithology and the wealth of lithological data routinely collected for ODP and DSDP drill cores, bulk geochemical averages can be calculated to better than 30% for most elements from fewer than ten chemical analyses for a typical drill core (100-1000 m). Combining the geochemical systematics with convergence rate and other parameters permits calculation of regional compositional fluxes for subducting sediment. These regional fluxes can be compared to the compositions of are volcanics to asses the importance of sediment subduction to are volcanism. For the 70% of the trenches worldwide where estimates can be made, the regional fluxes also provide the basis for a global subducting sediment (GLOSS) composition and flux. GLOSS is dominated by terrigenous material (76 wt% terrigenous, 7 wt% calcium carbonate, 10 wt% opal, 7 wt% mineral-bound H2O+), and therefore similar to upper continental crust (UCC) in composition. Exceptions include enrichment in Ba, Mn and the middle and heavy REE, and depletions in detrital elements diluted by biogenic material (alkalis, Th, Zr, Hf). Sr and Pb are identical in GLOSS and UCC as a result of a balance between dilution and enrichment by marine phases. GLOSS and the systematics of marine sediments provide an independent approach to the composition of the upper continental crust for detrital elements. Significant discrepancies of up to a factor of two exist between the marine sediment data and current upper crustal estimates for Cs, Nb, Ta and Ti. Suggested revisions to UCC include Cs (7.3 ppm), Nb (13.7 ppm), Ta (0.96 ppm) and TiO2 (0.76 wt%). These revisions affect recent bulk continental crust estimates for La/Nb and U/Nb, and lead to an even greater contrast between the continents and mantle for these important trace element ratios. GLOSS and the regional sediment data also provide new insights into the mantle sources of oceanic basalts.The classical geochemical distinction between 'pelagic' and 'terrigenous' sediment sources is not valid and needs to be replaced by a more comprehensive understanding of the compositional variations in complete sedimentary columns. In addition, isotopic arguments based on surface sediments alone can lead to erroneous conclusions. Specifically, the Nd/Hf ratio of GLOSS relaxes considerably the severe constraints on the amount of sediment recycling into the mantle based on earlier estimates from surface sediment compositions. (C) 1998 Elsevier Science B.V. All rights reserved. VL - 145 IS - 3-4 N1 - Zv404Times Cited:1407Cited References Count:173 JO - The chemical composition of subducting sediment and its consequences for the crust and mantle ER - TY - JOUR T1 - CO2 fluxes from mid-ocean ridges, arcs and plumes JF - Chemical Geology Y1 - 1998 A1 - Marty, B. A1 - Tolstikhin, I. N. AB - Estimates of CO2 emissions at spreading centres, convergent margins, and plumes have been reviewed and upgraded using observed CO2/He-3 ratios in magmatic volatiles, He-3 content estimates in the magmatic sources, and magma emplacement rates in the different tectonic settings. The effect of volatile fractionation during magma degassing, investigated using new rare gas and CO2 abundances determined simultaneously for a suite of Mid-Ocean Ridge (MOR) basalt glasses, is not the major factor controlling the spread of data, which mainly result from volatile heterogeneity in the mantle source. The computed C flux at ridges (2.2 +/- 0.9) x 10(12) mol/a, is essentially similar to previous estimates based on a mon restricted data base. Variation of the C flux in the past can be simply scaled to that of spreading rate since the computed C depends mainly on the volatile content of the mantle source, which can be considered constant during the last 10(8) a. The flux of CO2 from arcs may be approximated using the CO2/He-3 ratios of volcanic gases at arcs and the magma emplacement rate, assuming that the He-3 content of the mantle end-member is that of the MORE source. The resulting flux is similar to 2.5 x 10(12) mol/a, with approx. 80% of carbon being derived from the subducting plate. The flux of CO2 from plumes, based on time-averaged magma production rates and on estimated contributions of geochemical sources to plume magmatism, is less than or equal to 3 x 10(12) mol/a. Significant enhancements of the CO2 flux from plumes might have occurred in the past during giant magma emplacements, depending on the duration of these events, although the time-integrated effect does not appear important. The global magmatic flux of CO2 into the atmosphere and the hydrosphere is found to be 6 x 10(12) mol/a, with a range of (4-10) x 10(12) mol/a. Improvement on the precision of this estimate is linked to a better understanding of the volatile inventory at arcs on one hand, and on the dynamics of plumes and their mantle source contribution on the other hand. (C) 1998 Elsevier Science B.V. All rights reserved. VL - 145 IS - 3-4 N1 - Zv404Times Cited:212Cited References Count:109 JO - CO2 fluxes from mid-ocean ridges, arcs and plumes ER - TY - CONF T1 - The concentration and isotopic composition of dissolved inorganic carbon in ground water and submarine ground water discharge: Preliminary results from Onslow Bay, NC and North Inlet, SC T2 - Conference on Southeast Coastal Ocean Research Y1 - 1998 A1 - McCorkle, D. C. A1 - Gramling, C. JF - Conference on Southeast Coastal Ocean Research T3 - Program and Abstracts, Coastal Ocean Boundaries and Interactions and Assessments (COBIA) CY - Savannah, GA N1 - id: 1313 ER - TY - CONF T1 - Controls of chemical and isotopic composition of Lake water, Peten, Guatemala and implications for Holocene climatic variability in Central America. Abstracts with Programs T2 - Geological Society of America Annual Meeting Y1 - 1998 A1 - Martin, J. B. A1 - Rosenmeier, M. F. A1 - Hodell, D. A. A1 - Brenner, M. A1 - Curtis, J. H. JF - Geological Society of America Annual Meeting VL - 30 N1 - id: 140 ER - TY - CHAP T1 - A Correction for Aberrations in the Woods Hole Recombinator T2 - Symposium of North-Eastern Accelerator Personnel, SNEAP 1996 Y1 - 1998 A1 - Schneider, R. J. A1 - von Reden, K. F. ED - von Reden, Karl F. JF - Symposium of North-Eastern Accelerator Personnel, SNEAP 1996 PB - World Scientific CY - Woods Hole, MA N1 - id: 1823 ER - TY - JOUR T1 - A Correction for Aberrations in the Woods Hole Recombinator. Symposium of North-Eastern Accelerator Personnel JF - World Scientific Y1 - 1998 A1 - Schneider, R. J. A1 - von Reden, K. F. VL - SNEAP 1996 N1 - id: 1793 ER - TY - JOUR T1 - A Correction for Aberrations in the Woods Hole Recombinator. Symposium of North-Eastern Accelerator Personnel JF - World Scientific Y1 - 1998 A1 - Schneider, Robert J. A1 - McNichol, Ann P. A1 - von Reden, Karl F. A1 - Elder, Kathryn L. A1 - Gagnon, Allan R. A1 - Key, Robert M. A1 - Quay, Paul D. VL - SNEAP 1996 N1 - id: 1664 ER - TY - JOUR T1 - Cultural and climatic history of Coba, a lowland Maya city in Quintana Roo, Mexico JF - Quaternary Research Y1 - 1998 A1 - Leyden, B. W. A1 - Brenner, M. A1 - Dahlin, B. H. AB - Lake Coba, within the archaeological site of Coba, provides evidence bearing on lowland Maya development, Palynological and geochemical data record multidecadal precipitation cycles from a 8.80-m, >8370-yr lake-sediment sequence terminating on bedrock. Late Classic sedimentation rates are rapid, but an anthropogenically derived colluvium layer is lacking, Initial vegetation was medium semi-deciduous and swamp forest. Forest clearance began 1650 B.C. (Early Preclassic) and maize first occurred at 850 B.C. (Middle Preclassic). Lakeside milpas existed until A.D. 720 (Late Classic) and then were moved from the city center as urbanization intensified and Lake Coba was diked as a reservoir. Coba was at most briefly vacated during the Classic Collapse and was abandoned after A.D. 1240, although some habitation persisted. The paleoecological record matches the archaeological history for Coba, but pervasive disturbance muted the climatic signal, as the Late Classic drought is barely evident. The question whether economic trees were maintained within the city is unresolved, Maize cultivation allowed the Maya to develop a complex society and support a large population, but dependence on maize was ultimately doomed by variable rainfall. Precipitation in extreme years was insufficient to support crops, while native vegetation was not directly affected by drought that devastated Maya agriculture, (C) 1998 University of Washington. VL - 49 IS - 1 N1 - Yz880Times Cited:59Cited References Count:46 JO - Cultural and climatic history of Coba, a lowland Maya city in Quintana Roo, Mexico ER - TY - JOUR T1 - Decadal to millennial variability of fluviomarine sedimentation on the northern California continental shelf JF - EOS Y1 - 1998 A1 - Sommerfield, C. K. VL - Transactions of the American Geophysical Union IS - 79:45 N1 - id: 1328 ER - TY - JOUR T1 - Early diagenetic minerals and variables influencing their distributions in two long cores (>40m), Mississippi River delta plain JF - Journal of Sedimentary Research Y1 - 1998 A1 - Bailey, A. M. A1 - Roberts, H. H. A1 - Blackson, J. M. AB - Two long (>40 m) continuous push cores of sediments from the Mississippi Delta Plain, one at a northern freshwater site and one at a southern marine-influenced site, have provided samples of individual concretions and homogenized bulk samples for a study of early diagenesis. Early (<10,000 y) diagenetic minerals are abundant and include: siderite>pyrite>calcite nearly equal dolomite>vivianite approximately hematite. Siderite formed postburial and contains bands of clastic minerals and accessory diagenetic calcite and dolomite, as well as Ca, Mg, and Mn substituted in the lattice. Values for delta 13 C increase with increasing depth to +11 per mil (PDB) at a depth of 40 m, reflecting the increasing role of methanogenesis with depth. From analyses of bulk samples, pyrite concentrations are higher in organic-rich horizons, do not vary appreciably with depth below one meter when adjusted for organic-carbon control, and are generally higher in the marine-influenced core than at the freshwater site. Conversely, concentrations of siderite are higher in fine-grained siliciclastic horizons, increase with depth to about 20 m, and do not vary with the extent of marine influence in these cores. To a first approximation, distributions of pyrite appear to be controlled by variations in organic carbon concentration in sulfate-sufficient systems that formed through marine incursion into organic-rich layers that cap sediment packages in the deltaic system. Residual pyritic S is sulfate-controlled and lower in the northern, more freshwater organic-rich sediments. Siderite formation appears to be focused in sulfate-deficient systems that formed when siliciclastic wedges that constitute the central parts of sediment packages prograded into lacustrine or bay environments. Low sulfate levels in these horizons in both cores facilitated similar levels of siderite. A juxtaposition of marine versus freshwater diagenetic mineral suites in adjacent horizons resulted from these interactions between physical and geochemical processes. VL - 68 IS - 1 N1 - id: 5 JO - Early diagenetic minerals and variables influencing their distributions in two long cores (>40m), Mississippi River delta plain ER - TY - CONF T1 - Early results from the WOCE radiocarbon program T2 - TYKKI workshop invited talk Y1 - 1998 A1 - Key, Robert M. JF - TYKKI workshop invited talk CY - Tokyo, Japan N1 - id: 312 ER - TY - JOUR T1 - Early to middle Holocene climatic variability in Central America: evidence from lacustrine sediments in the Peten, Guatemala JF - EOS: Transactions American Geophysical Union Y1 - 1998 A1 - Rosenmeier, M. F. A1 - Hodel, D. A. A1 - Martin, J. B. A1 - Brenner, M. A1 - Curtis, J. H. VL - 79 N1 - id: 1209 ER - TY - RPRT T1 - Environmental changes since deglaciation in Voyageurs National Park: A summary for park personnel in Holocene Paleoenvironnments in Western Great Lakes Park. Report Y1 - 1998 A1 - Winkler, M. G. A1 - Sanford, P. R. PB - National Park Service VL - 9; Final report N1 - id: 129 ER - TY - JOUR T1 - Evaluating reproducibility of seawater, inorganic and organic carbon 14C results at the National Ocean Sciences AMS Facility (NOSAMS) JF - Radiocarbon Y1 - 1998 A1 - Elder, K. L. A1 - McNichol, A. P.
 A1 - Gagnon, A. R. VL - 40 IS - 1 ER - TY - JOUR T1 - Evidence for episodic calcium-carbonate dissolution in the subpolar North Atlantic during the last glaciation JF - EOS Y1 - 1998 A1 - McManus, J. F. A1 - Lohmann, G. P. IS - 79 N1 - id: 171 ER - TY - CHAP T1 - Geoforma Ediciones, Logrono, Barcelona T2 - Investigaciones recientes de la Geomorfologia esponola Y1 - 1998 A1 - Valero-Garces, B. L. A1 - Matri Bono, C. A1 - Kelts, K. ED - Ortiz, A. G. JF - Investigaciones recientes de la Geomorfologia esponola N1 - id: 384 ER - TY - JOUR T1 - Glacial-age hydrography of the far northwest Pacific Ocean JF - Paleoceanography Y1 - 1998 A1 - Keigwin, L. D. AB - Stable isotope data on benthic foraminifera from more than 30 cores on the northern Emperor Seamounts and in the Okhotsk Sea are synthesized in paleohydrographic profiles spanning the depth range 1000-4000 m. Holocene (core-top) benthic foraminiferal delta(18)O and delta(13)C data are calibrated to modern hydrographic properties through measurements of delta(13)C of Sigma CO2 and delta(18)O of seawater. Cibicidoides stable isotope ratios are close to the delta(13)C and equilibrium delta(18)O of seawater, whereas Uvigerina delta(18)O and delta(13)C are variably offset from Cibicidoides. Glacial maximum delta(13)C of Cibicidoides displays a different vertical profile than that of the Holocene. When results are adjusted by +0.32 parts per thousand to account for the secular change in delta(13)C during the last glacial maximum, the data coincide with the modern seawater and foraminiferal curves deeper than similar to 2 km. However, at shallower depths delta(13)C gradually increases by as much as 1 parts per thousand above the modern value. Furthermore, above 2 km the benthic delta(18)O decreases by similar to 0.5 parts per thousand. These results are consistent with a benthic front at similar to 2 km in the North Pacific [see Herguera et al., 1992], but they differ from interpretations based on trace metal data which indicate a source of nutrient-depleted deep water during glaciation. The isotopic data suggest that during glaciation there was a better ventilated watermass at intermediate depths in the far northwestern Pacific, it was relatively fresher than deep waters there, and deep waters were as nutrient-rich as today. VL - 13 IS - 4 N1 - 105bqTimes Cited:192Cited References Count:61 JO - Glacial-age hydrography of the far northwest Pacific Ocean ER - TY - JOUR T1 - Glacioisostasy and lake-level change at Moosehead lake, Maine JF - Quaternary Research Y1 - 1998 A1 - Balco, G. A1 - Belknap, D. F. A1 - Kelley, J. T. AB - Reconstructions of glacioisostatic rebound based on relative sea level in Maine and adjacent Canada do not agree well with existing geophysical models. In order to understand these discrepancies better, we investigated the lake-level history of 40-km-long Moosehead Lake in northwestern Maine. Glacioisostasy has affected the level of Moosehead Lake since deglaciation ca. 12,500 C-14 yr B.P. Lowstand features at the southeastern end and an abandoned outlet at the northwestern end of the lake indicate that the lake basin was tilted down to the northwest, toward the retreating ice sheet, by 0.7 m/km at 10,000 C-14 yr B.P. Water level then rose rapidly in the southeastern end of the lake, and the northwestern outlet was abandoned, indicating rapid relaxation of landscape tilt. Lowstand features at the northwestern end of the lake suggest that the lake basin was tilted to the southeast at ca. 8750 C-14 yr B.P., possibly as the result of a migrating isostatic forebulge. After 8000 C-14 yr B.P., water level at the southeastern end was again below present lake level and rose gradually thereafter. We found no evidence suggesting that postglacial climate change significantly affected lake level. The rebound history inferred from lake-level data is consistent with previous interpretations of nearby relative sealevel data, which indicate a significantly steeper and faster-moving ice-proximal depression and ice-distal forebulge than geophysical models predict. (C) 1998 University of Washington. VL - 49 IS - 2 N1 - Zm315Times Cited:9Cited References Count:46 JO - Glacioisostasy and lake-level change at Moosehead lake, Maine ER - TY - CONF T1 - High-precision Measurements of 14C as a Circulation Tracer in the Pacific, Indian, and Southern Oceans with Accelerator Mass Spectrometry (AMS) T2 - 8th International Conference on Heavy Ion Accelerator Technology Y1 - 1998 A1 - von Reden, K. F. A1 - Peden, J. C. A1 - Schneider, R. J. A1 - Bellino, M. A1 - Donoghue, J. A1 - Elder, K. L. A1 - Gagnon, A. R. A1 - Long, P. A1 - McNichol, A. P. A1 - Morin, T. A1 - Stuart, D. A1 - Hayes, J. M. A1 - Key, R. M. ED - Shepard, K. American Institute of Physics JF - 8th International Conference on Heavy Ion Accelerator Technology CY - Argonne National Lab N1 - id: 1636 ER - TY - JOUR T1 - High-precision radiocarbon age calibration for terrestrial and marine samples JF - Radiocarbon Y1 - 1998 A1 - Stuiver, M. A1 - Reimer, P. J. A1 - Braziunas, T. F. KW - ad 1950-500 bc KW - c-14 data KW - decadal calibration KW - reservoir ages KW - time scale AB - Single-year and decadal radiocarbon tree-ring ages are tabulated and discussed in terms of C-14 age calibration. The single-year data form the basis of a detailed 14C age calibration curve for the cal AD 1510-1954 interval ("cal" denotes calibrated). The Seattle decadal data set (back to 11,617 cal sp, with 0 sp = AD 1950) is a component of the integrated decadal INTCAL98 C-14 age curve (Stuiver et al. 1998). Atmospheric C-14 ages can be transformed into C-14 ages of the global ocean using a carbon reservoir model. INTCAL98 C-14 ages, used for these calculations, yield global ocean C-14 ages differing slightly from previously published ones (Stuiver and Braziunas 1993b). We include discussions of offsets, error multipliers, regional C-14 age differences and marine C-14 age response to oceanic and atmospheric forcing. VL - 40 SN - 0033-8222 IS - 3 N1 - 155qrTimes Cited:705 Cited References Count:31 JO - Radiocarbon ER - TY - JOUR T1 - Historical geomorphic processes and human activities in the Central Spanish Pyrenees JF - Mountain Research and Development Y1 - 1998 A1 - Garcia-Ruiz, J. M. A1 - Valero-Garces, B. L. AB - In the Central Spanish Pyrenees there is a great diversity of geomorphic processes due to topographic and climatic heterogeneity and altitudinal gradient. Human activity during the last 4,000 years has contributed to the disturbance of the original landscape and its hydro-morphological dynamics. The upper forest belt was destroyed by fire during the Middle Ages in order to provide summer pastures to transhumant livestock. The hillslopes below 1,600 m were cultivated and frequently burnt to improve the soil and pasture quality, even on steep slopes. The most evident consequence of this has been the increase in the sources of sediment. In the subalpine belt, mass movements and dense rill networks have caused severe soil erosion and the expansion of gelifluxion terracettes; in the middle mountain belt overland flow has resulted in stoniness of the soil surface, and debris flows have occurred on hillslopes and along river channels. This paper discusses the effects of human activity on the geomorphic processes in the study area. VL - 18 IS - 4 N1 - 142mnTimes Cited:49Cited References Count:62 JO - Historical geomorphic processes and human activities in the Central Spanish Pyrenees ER - TY - THES T1 - Holocene Evolution of Lake Erie Environments: inferrences from stable isotopes of cored sediments offshore Fairport Harbor, Ohio--Thesis Y1 - 1998 A1 - McCambridge, Constance PB - University of Akron CY - Akron, Ohio VL - M. S. ER - TY - JOUR T1 - How much deep water is formed in the Southern Ocean? JF - Journal of Geophysical Research-Oceans Y1 - 1998 A1 - Broecker, W. S. A1 - Peacock, S. L. A1 - Walker, S. A1 - Weiss, R. A1 - Fahrbach, E. A1 - Schroeder, M. A1 - Mikolajewicz, U. A1 - Heinze, C. A1 - Key, R. A1 - Peng, T. H. A1 - Rubin, S. AB - Three tracers are used to place constraints on the production rate of ventilated deep water in the Southern Ocean. The distribution of the water mass tracer PO4* ("phosphate star") in the deep sea suggests that the amount of ventilated deep water produced in the Southern Ocean is equal to or greater than the outflow of North Atlantic Deep Water from the Atlantic. Radiocarbon distributions yield an export flux of water from the North Atlantic which has averaged about 15 Sv over the last several hundred years. CFC inventories are used as a direct indicator of the current production rate of ventilated deep water in the Southern Ocean. Although coverage is as yet sparse, it appears that the CFC inventory is not inconsistent with the deep water production rate required by the distributions of PO4* and radiocarbon. It has been widely accepted that the major part of the deep water production in the Southern Ocean takes place in the Weddell Sea. However, our estimate of the Southern Ocean ventilated deep water flux is in conflict with previous estimates of the flux of ventilated deep water from the Weddell Sea, which lie in the range 1-5 Sv. Possible reasons for this difference are discussed. VL - 103 IS - C8 N1 - Zz547Times Cited:115Cited References Count:44 JO - How much deep water is formed in the Southern Ocean? ER - TY - JOUR T1 - Impact of human activity on regional forest composition and dynamics in central New England JF - Ecosystems Y1 - 1998 A1 - Fuller, T. L.
 A1 - Foster, D. R.
 A1 - McLachlan, T. S.
 A1 - Drake, N. KW - awenda provincial park KW - eastern north-america KW - european settlement KW - forest dynamics KW - history KW - human disturbance KW - lake sediment KW - land-use KW - new england KW - paleoecology KW - patterns KW - rates of change KW - united-states KW - vegetation dynamics AB - Historical and ecological data from north-central Massachusetts suggest that widespread and intensive human disturbance after European settlement led to a shift in forest composition and obscured regional patterns of species abundance. A paleoecological approach was required to place recent forest dynamics in a long-term context. Pollen and charcoal data from 11 small lakes in north-central Massachusetts were used to reconstruct local vegetation dynamics and fire histories across the region over the past 1000 years. The sites are located across an environmental gradient. Paleoecological data indicate that prior to European settlement, there was regional variation in forest composition corresponding to differences in climate, substrate, and fire regime. Oak, chestnut, and hickory were abundant at low elevations, whereas hemlock, beech, sugar maple, and yellow birch were common at high elevations. Fire appears to have been more frequent and/or intense at lower elevations, maintaining high abundances of oak, and archaeological data suggest Native American populations were greater in these areas. A change in forest composition at higher elevations, around 550 years before present, may be related to the Little Ice Age (a period of variable climate), fire, and/or activity by Native Americans, and led to regional convergence in forest composition. After European settlement, forest composition changed markedly in response to human disturbance and there was a sharp increase in rates of vegetation change. Regional patterns were obscured further, leading to homogenization of broad-scale forest composition. There is no indication from the pollen data that forests are returning to pre-European settlement forest composition, and rates of vegetation change remain high, reflecting continuing disturbance on the landscape, despite regional reforestation. VL - 1 SN - 1432-9840 IS - 1 ER - TY - JOUR T1 - Influence of oxygen exposure time on organic carbon preservation in continental margin sediments JF - Nature Y1 - 1998 A1 - Hartnett, H. E. A1 - Keil, R. G. A1 - Hedges, J. I. A1 - Devol, A. H. AB - Today, over 90% of all organic carbon burial in the ocean occurs in continental margin sediments(1). This burial is intrinsically linked to the cycling of biogeochemically important elements (such as N, P, S, Fe and Mn) and, on geological timescales, largely controls the oxygen content of the atmosphere(2-4). Currently there is a volatile debate over which processes govern sedimentary organic carbon preservation(5-8). In spite of numerous studies demonstrating empirical relationships between organic carbon burial and such factors as primary productivity(9), the flux of organic carbon through the water column(10), sedimentation rate(11,12), organic carbon degradation rate(13), and bottom-water oxygen concentration(8,14), the mechanisms directly controlling sedimentary organic carbon preservation remain unclear. Furthermore, as organic carbon burial is the process that, along with pyrite burial(15), balances O-2 concentrations in the atmosphere, it is desirable that any mechanism proposed to control organic carbon preservation include a feedback buffering atmospheric oxygen concentrations over geological time. Here we compare analyses of sediments underlying two regions of the eastern North Pacific Ocean, one which has oxygen-depleted bottom waters and one with typical oxygen distributions. Organic carbon burial efficiency is strongly correlated with the length of time accumulating particles are exposed to molecular oxygen in sediment pore waters. Oxygen exposure time effectively incorporates other proposed environmental variables(8-14), and may exert a direct control on sedimentary organic carbon preservation and atmospheric oxygen concentrations. VL - 391 IS - 6667 N1 - Yv594Times Cited:355Cited References Count:27 JO - Influence of oxygen exposure time on organic carbon preservation in continental margin sediments ER - TY - JOUR T1 - Isotopic Biogeochemistry of the Neocomian Lacustrine and Upper Aptian Marine-Evaporitic Sediments of the Potiguar Basin, Northeastern Brazil JF - Organic Geochemistry Y1 - 1998 A1 - Neto, Eugenio Vaz dos Santos A1 - Hayes, John M. A1 - Takaki, Tikae VL - 28 N1 - id: 1729 ER - TY - CONF T1 - Late Holocene climatic variability in Central America: evidence from lacustrine sediments in the Peten, Guatemala and implications for Maya cultural evolution; Procedings of the PEP 1 T2 - PEP 1 (Pole-Equator-Pole, Paleoclimate of the Americas) Y1 - 1998 A1 - Rosenmeier, M. F. A1 - Hodell, D. A. A1 - Martin, J. B. A1 - Brenner, M. A1 - Curtis, J. H. JF - PEP 1 (Pole-Equator-Pole, Paleoclimate of the Americas) CY - Merida, Venezualla N1 - id: 141 ER - TY - CONF T1 - Late Pleistocene Mammuthus primigenious from coastal mMaine T2 - 33rd annual meeting, Geological Society of America, Northeastern Section Y1 - 1998 A1 - Hoyle, B. G. A1 - Fisher, D. C. A1 - Dorion, C. C. A1 - Churchill, L. L. A1 - W, Borns H., Jr. A1 - Nelson, R. E. JF - 33rd annual meeting, Geological Society of America, Northeastern Section PB - Geological Society of America CY - Portland, ME N1 - id: 21 ER - TY - JOUR T1 - Le torbiditi dell'Escanaba Trough (Juan de Fuca Plate, Pacifico nordorientale): registrazione sedimentaria di piene fluviali catastrofiche del Fiume Columbia durante le fasi di deglaciazione tardo quaternaria JF - Giornale di Geologia Y1 - 1998 A1 - Brunner, C. A. A1 - Normark, W. R. A1 - Zuffa, G. G. A1 - Serra, F. VL - 60 N1 - id: 1470 JO - Le torbiditi dell'Escanaba Trough (Juan de Fuca Plate, Pacifico nordorientale): registrazione sedimentaria di piene fluviali catastrofiche del Fiume Columbia durante le fasi di deglaciazione tardo quaternaria ER - TY - JOUR T1 - Manzala lagoon, Nile delta, Egypt: modern sediment accumulation based on radioactive tracers JF - Environmental Geology Y1 - 1998 A1 - Benninger, L. K. A1 - Suayah, I. B. A1 - Stanley, D. J. AB - This study was undertaken to determine whether recent anthropogenic changes in the Nile basin have affected the modern rate of sediment accumulation in the Nile delta. Excess (210)pb, Cs-137, and Pu-239,Pu-240 were used to develop a sediment chronology for a core from central Manzala lagoon, the delta sector which has had the highest average rate of sediment accumulation during the Holocene (to about 0.7 cm year(-1)). Excess Pb-210 was detected in the top 32 cm of the core, yielding an accumulation rate of 1.2 cm year(-1), higher than the mean rate for the Holocene. A high Cs-137/Pu-239,Pu-240 ratio requires a reactor source (possibly Chernobyl) for these nuclides. Low concentrations of excess (210)pb and weapons-fallout nuclides precluded recognition of changes in sediment accumulation rate in Manzala lagoon during this century and may limit the use of tracer radionuclides for modern sediment chronology in the Nile delta. VL - 34 IS - 2-3 N1 - id: 1283; Zq055 Times Cited:9 Cited References Count:37 JO - Manzala lagoon, Nile delta, Egypt: modern sediment accumulation based on radioactive tracers ER - TY - JOUR T1 - A massive terraced village complex in Chihuahua, Mexico, 3000 years before present JF - Science Y1 - 1998 A1 - Hard, R. J. A1 - Roney, J. R. AB - Cerro Juanaquena is a residential complex with 8 kilometers of terrace walls in northwestern Mexico that was occupied at similar to 3000 calendar years before present based on radiocarbon dates on maize (Zea mays L.), Most other similar sized terrace complex sites that have been found date to similar to 1000 years before present, Cerro Juanaquena was contemporaneous with 10 other sites in the southwestern United States that have yielded 18 of the earliest maize or squash radiocarbon dates yet, and it is by far the largest and most complex site, The archaeological evidence from this site, combined with other recent data, implies that highly variable combinations of population aggregation, agricultural dependence, and degrees of sedentism were present during the time maize was being introduced into the American Southwest. VL - 279 IS - 5357 N1 - Zb612Times Cited:32Cited References Count:59 JO - A massive terraced village complex in Chihuahua, Mexico, 3000 years before present ER - TY - RPRT T1 - Method and Technology of AMS Y1 - 1998 A1 - von Reden, K. F. PB - University of Mass., Dartmouth CY - Dartmouth, MA N1 - id: 1677 ER - TY - CONF T1 - Microscale AMS 14C Measurement at NOSAMS T2 - 16th International 14C Conference Y1 - 1998 A1 - Pearson, Ann A1 - McNichol, Ann P. A1 - Schneider, Robert J. A1 - von Reden, Karl F. JF - 16th International 14C Conference N1 - id: 1502 ER - TY - JOUR T1 - Microscale AMS 14C measurements at NOSAMS JF - Radiocarbon Y1 - 1998 A1 - Pearson, A. A1 - McNichol, A. P. A1 - Schneider, R. J. A1 - von Reden, K. F. A1 - Zheng, Y. VL - 40 IS - 1 N1 - id: 1621 ER - TY - JOUR T1 - Microscale AMS 14C measurements at NOSAMS: (Proceedings of the 16th International Radiocarbon Conference, 1997) JF - Radiocarbon Y1 - 1998 A1 - Pearson, A. A1 - McNichol, A. P. A1 - Schneider, R. J. A1 - von Reden, K. F. A1 - Zheng, Y. VL - 40 IS - 1 N1 - id: 1814 ER - TY - CONF T1 - Microscale AMS (super 14) C measurement at NOSAMS Y1 - 1998 A1 - Pearson, Ann A1 - McNichol, Ann P. A1 - Schneider, Robert J. A1 - von Reden, Karl F. A1 - Zheng, Yan KW - 03 KW - absolute age KW - accelerator mass spectroscopy KW - accuracy KW - C-14 KW - C-14/C-12 KW - carbon KW - Carbon dioxide KW - combustion KW - data processing KW - Geochronology KW - graphite KW - isotope fractionation KW - isotopes KW - mass spectroscopy KW - mathematical methods KW - methods KW - native elements KW - radioactive isotopes KW - sample preparation KW - size KW - spectroscopy KW - Stable isotopes AB - Techniques for making precise and accurate radiocarbon accelerator mass spectrometry (AMS) measurements on samples containing less than a few hundred micrograms of carbon are being developed at the NOSAMS facility. A detailed examination of all aspects of the sample preparation and data analysis process shows encouraging results. Small quantities of CO (sub 2) are reduced to graphite over cobalt catalyst at an optimal temperature of 605 degrees C. Measured (super 14) C/ (super 12) C ratios of the resulting targets are affected by machine-induced isotopic fractionation, which appears directly related to the decrease in ion current generated by the smaller sample sizes. It is possible to compensate effectively for this fractionation by measuring samples relative to small standards of identical size. Examination of the various potential sources of background (super 14) C contamination indicates that the sample combustion process is the largest contributor, adding ca. 1 mu g of carbon with a less-than-modern (super 14) C concentration. PB - University of Arizona, Department of Geosciences, Tucson, AZ, United States (USA) CY - United States (USA) VL - 40 UR - http://hdl.handle.net/10150/653650 N1 - id: 2237; Source type: conferencepapers&proceedings; Object type: Article; Object type: Conference Paper; Copyright: GeoRef, Copyright 2007, American Geological Institute.; CSAUnique: 1999-044438; AccNum: 1999-044438; ISSN: 0033-8222; CODEN: RACAAT ER - TY - JOUR T1 - Millennial-scale changes in North Atlantic circulation since the last glaciation JF - Nature Y1 - 1998 A1 - Marchitto, T. M. A1 - Curry, W. B. A1 - Oppo, D. W. AB - Ocean circulation is closely linked to climate change on glacial-interglacial and shorter timescales. Extensive reorganizations in the circulation of deep and intermediate-depth waters in the Atlantic Ocean have been hypothesized for both the last glaciation(1-6) and the subsequent Younger Dryas cold interval(3,6-10), but there has been little palaeoceanographic study of the subtropical gyres(11-13). These gyres are the dominant oceanic features of wind-driven circulation, and as such they reflect changes in climate and are a significant control on nutrient cycling and, possible, atmospheric CO2 concentrations. Here we present Cd/Ca ratios in the shells of benthic foraminifera from the Bahama banks that confirm previous suggestions(11,12) that nutrient concentrations in the North Atlantic subtropical gyre were much lower during the Last Glacial Maximum than they are today (up to 50% lower according to our data). These contrasting nutrient burdens imply much shorter residence times for waters within the thermocline of the Last Glacial Maximum. Below the glacial thermocline, nutrient concentrations were reduced owing to the presence of Glacial North Atlantic Intermediate Water. A high-resolution Cd/Ca record from an intermediate depth indicates decreased nutrient concentrations during the Younger Dryas interval as well, mirroring opposite changes at a nearby deep site(3,9). Together, these observations suggest that the formation of deep and intermediate waters-North Atlantic Deep Water and Glacial North Atlantic Intermediate Water, respectively-wax and wane alternately on both orbital and millennial timescales. VL - 393 IS - 6685 N1 - Zt988Times Cited:106Cited References Count:30 JO - Millennial-scale changes in North Atlantic circulation since the last glaciation ER - TY - JOUR T1 - A multi-proxy study of Holocene environmental change in the Maya lowlands of Peten, Guatemala JF - Journal of Paleolimnology Y1 - 1998 A1 - Curtis, J. H. A1 - Brenner, M. A1 - Hodell, D. A. A1 - Balser, R. A. A1 - Islebe, G. A. A1 - Hooghiemstra, H. AB - We used multiple variables in a sediment core from Lake Peten-Itza, Peten, Guatemala, to infer Holocene climate change and human influence on the regional environment. Multiple proxies including pollen, stable isotope geochemistry, elemental composition, and magnetic susceptibility in samples from the same core allow differentiation of natural versus anthropogenic environmental changes. Core chronology is based on AMS (14)C measurement of terrestrial wood and charcoal and thus avoids the vagaries of hard-water-lake error. During the earliest Holocene, prior to similar to 9000 (14)C yr BP, the coring site was not covered by water and all proxies suggest that climatic conditions were relatively dry. Water covered the coring site by similar to 9000 (14)C yr BP, coinciding with filling of other lakes in Peten and farther north on the Yucatan Peninsula. During the early Holocene (similar to 9000 to similar to 6800 (14)C yr BP), pollen data suggest moist conditions, but high delta(18)O values are indicative of relatively high E/P. This apparent discrepancy may be due to a greater fractional loss of the lake's water budget to evaporation during the early stages of lake filling. Nonetheless, conditions were moist enough to support semi-deciduous lowland forest. Decrease in delta(18)O values and associated change in ostracod species at similar to 6800 (14)C yr BP suggest a transition to even moister conditions. Decline in lowland forest taxa beginning similar to 5780 (14)C yr BP may indicate early human disturbance. By similar to 2800 (14)C yr BP, Maya impact on the environment is documented by accelerated forest clearance and associated soil erosion. Multiple proxies indicate forest recovery and soil stabilization beginning similar to 1100 to 1000 (14)C yr BP, following the collapse of Classic Maya civilization. VL - 19 IS - 2 N1 - Zj856Times Cited:92Cited References Count:96 JO - A multi-proxy study of Holocene environmental change in the Maya lowlands of Peten, Guatemala ER - TY - JOUR T1 - A new model for Proterozoic ocean chemistry JF - Nature Y1 - 1998 A1 - Canfield, D. E. AB - There was a significant oxidation of the Earth's surface around 2 billion years ago (2 Gyr)(1-4). Direct evidence for this oxidation comes, mostly, from geological records of the redox-sensitive elements Fe and U reflecting the conditions prevailing during weathering(1-3). The oxidation event was probably driven by an increased input of oxygen to the atmosphere arising from an increased sedimentary burial of organic matter between 2.3 and 2.0 Gyr(5). This episode was postdated by the final large precipitation of banded iron formations around 1.8 Gyr(1,2). It is generally believed that banded iron formations precipitated from an ocean whose bottom waters contained significant concentrations of dissolved ferrous iron, and that this sedimentation process terminated when aerobic bottom waters developed, oxidizing the iron and thus removing it from solution(1,2). In contrast, I argue here that anoxic bottom waters probably persisted until well after the deposition of banded iron formations ceased; I also propose that sulphide, rather than oxygen, was responsible for removing iron from deep ocean water. The sulphur-isotope record supports this hypothesis as it indicates increasing concentrations of oceanic sulphate, starting around 2.3 Gyr(6), leading to increasing rates of sulphide production by sulphate reduction. The increase in sulphide production became sufficient, around 1.8 Gyr,to precipitate the total flux of iron into the oceans. I suggest that aerobic deep-ocean waters did not develop until the Neoproterozoic era (1.0 to similar to 0.54 Gyr), in association with a second large oxidation of the Earth's surface. This new model is consistent with the emerging view of Precambrian sulphur geochemistry and the chemical events leading to the evolution of animals, and it is fully testable by detailed geochemical analyses of preserved deep-water marine sediments. VL - 396 IS - 6710 N1 - 145klTimes Cited:530Cited References Count:29 JO - A new model for Proterozoic ocean chemistry ER - TY - JOUR T1 - North Atlantic gyre ventilation and intermediate water formation during the last glaciation and Younger Dryas JF - Nature Y1 - 1998 A1 - Marchitto, T. M. A1 - Curry, W. B. A1 - W, Oppo D. VL - 393 N1 - id: 208 ER - TY - CONF T1 - NOSAMS Controls with LabView T2 - Proceedings of the 30th Symposium of Northeastern Accelerator Personnel - Woods Hole, 1996 Y1 - 1998 A1 - von Reden, K. F. ED - von Reden, K. F. JF - Proceedings of the 30th Symposium of Northeastern Accelerator Personnel - Woods Hole, 1996 PB - World Scientific Publishing Co., Singapore N1 - id: 1764 ER - TY - JOUR T1 - NOSAMS Controls with LabView JF - World Scientific Y1 - 1998 A1 - von Reden, K. F. N1 - id: 1675 ER - TY - CHAP T1 - NOSAMS Controls with LabView T2 - Symposium of North-Eastern Accelerator Personnel, Woods Hole Oceanographic Institution, Woods Hole, USE, October 27-30, 1996, SNEAP XXX Y1 - 1998 A1 - von Reden, K. F. ED - von Reden, K. F. JF - Symposium of North-Eastern Accelerator Personnel, Woods Hole Oceanographic Institution, Woods Hole, USE, October 27-30, 1996, SNEAP XXX PB - World Scientific Publishing Co. CY - Woods Hole, MA N1 - id: 1721 ER - TY - CONF T1 - The NOSAMS Sample Preparation Laboratory: Systems and graphite performance analysis T2 - 16th International 14C Conference Y1 - 1998 A1 - Gagnon, A. R. A1 - McNichol, A. P. A1 - Donaghue, J. C. A1 - Morin, T. J. A1 - Peden, J. C. JF - 16th International 14C Conference CY - Groninghen N1 - id: 1628 ER - TY - JOUR T1 - Overview of the eruption of Soufriere Hills volcano, Montserrat, 18 July 1995 to December 1997 JF - Geophysical Research Letters Y1 - 1998 A1 - Young, S. R. A1 - Sparks, R. S. J. A1 - Aspinall, W. P. A1 - Lynch, L. L. A1 - Miller, A. D. A1 - Robertson, R. E. A. A1 - Shepherd, J. B. AB - The onset of phreatic volcanic activity at the Soufriere Hills volcano, Montserrat on 18 July 1995 followed a three-year period of heightened volcano-seismic activity beneath the island. Phreatic explosions gave way to continuous eruption of juvenile andesitic magma in the form of a lava dome on or around 15 November 1995. Magma production rate has varied, leading to changes in eruptive style. An explosive eruption on 17 September 1996 followed a period of enhanced dome growth and large-scale gravitational collapses from its eastern flank. Increasing dome volume led to stressing and overtopping of the confining crater walls to the southwest, north and west during early 1997. Sustained high magma production rate since June 1997 has led to three periods of major gravitational dome collapses followed by vulcanian explosive eruptions. Dome growth re-started immediately after the cessation of the latest of these explosive phases in October 1997 and continues as of December 1997. VL - 25 IS - 18 N1 - 119mkTimes Cited:102Cited References Count:7 JO - Overview of the eruption of Soufriere Hills volcano, Montserrat, 18 July 1995 to December 1997 ER - TY - JOUR T1 - P10 Final report for AMS 14C samples JF - Ocean Tracer Laboratory Tech. Rep. Y1 - 1998 A1 - Key, R. M. VL - 98 IS - 4B N1 - id: 1463 ER - TY - JOUR T1 - P10 Final report for large volume 14C samples JF - Ocean Tracer Laboratory Tech. Rep. Y1 - 1998 A1 - Key, R. M. VL - 98 IS - 4A N1 - id: 1462 ER - TY - JOUR T1 - P17N Final report for AMS 14C samples JF - Ocean Tracer Laboratory Tech. Rep. Y1 - 1998 A1 - Key, R. M. VL - 98 IS - 1 N1 - id: 1460 ER - TY - JOUR T1 - P18 Final report for AMS 14C samples JF - Ocean Tracer Laboratory Technical Report Y1 - 1998 A1 - Key, R. M. A1 - D, Quay P. VL - 98 IS - 5 N1 - id: 1464 JO - P18 Final report for AMS 14C samples ER - TY - JOUR T1 - P19C Final report for AMS 14C samples JF - Ocean Tracer Laboratory Tech. Rep. Y1 - 1998 A1 - Key, R. M. VL - 98 IS - 2 N1 - id: 1461 ER - TY - JOUR T1 - Paleoclimatic Assessment of Cretaceous Lacustrine and Marine-Evaporitic Sequences from the Potiguar Basin Based on the Hydrogen Isotopic Compositions of Saturated Hydrocarbons JF - Revista Latino Americana de Geoquimica Ogranica Y1 - 1998 A1 - Neto, Eugenio Vaz dos Santos A1 - Hayes, John M. A1 - Takaki, Tikae VL - 4 N1 - id: 1776 ER - TY - JOUR T1 - Physical controls on dissolved inorganic radiocarbon variability in the California Current JF - Deep-Sea Research Part Ii-Topical Studies in Oceanography Y1 - 1998 A1 - Masiello, C. A. A1 - Druffel, E. R. M. A1 - Bauer, J. E. AB - We present depth profiles of Delta(14)C and delta(13)C Of dissolved inorganic carbon (DIC) at Station M in the Eastern North Pacific. Several seasonal profiles are presented for the time period between 1991 and 1996. Comparison with GEOSECS data clearly shows changes in ocean radiocarbon profiles since 1973. The Delta(14)C Of DIC shows the most variability at depths of 450, 85, and 25 m, and the lowest variability at depths of 1600 and 2500 m. The largest variability in DIC Delta(14)C occurs at 450 m, a depth marked by large fluctuations in the radiocarbon signatures of the source waters. The likely controls of DIC Delta(14)C variability are physical changes in the circulation of the California Current System. A simple two-box model is used to show the importance of wind driven mixing at the surface. We discuss the likely effects of mesoscale eddies and ENSO on the DIC Delta(14)C values at this site. We also show that remineralization of organic carbon (dissolved or particulate) is not responsible for the variability in the Delta(14)C Of DIC observed at Station M. (C) 1998 Elsevier Science Ltd. All rights reserved. VL - 45 IS - 4-5 N1 - 102ttTimes Cited:21Cited References Count:43 JO - Physical controls on dissolved inorganic radiocarbon variability in the California Current ER - TY - JOUR T1 - Preparation for continuous flow accelerator mass spectrometry Radiocarbon JF - Radiocarbon Y1 - 1998 A1 - Schneider, R. J. A1 - Hayes, J. M. A1 - von Reden, K. F. A1 - McNichol, A. P. A1 - Eglinton, T. A1 - Wills, J. S. C. VL - 1 IS - 95-102 N1 - id: 1623 ER - TY - CONF T1 - The Proceedings of the 30th Symposium of North-Eastern Accelerator Personnel T2 - 30th Symposium of North-Eastern Accelerator Personnel Y1 - 1998 A1 - von Reden, K. F.
 A1 - Schneider, R. J. JF - 30th Symposium of North-Eastern Accelerator Personnel PB - World Scientific Publishing Co. ER - TY - JOUR T1 - Proceedings of the 30th Symposium of Northeastern Accelerator Personnel - Woods Hole, 1996 JF - World Scientific Y1 - 1998 A1 - von Reden, K. F. A1 - Schneider, R. J. N1 - id: 1674 ER - TY - CONF T1 - Proceedings of the 8th International Conference on Heavy Ion Accelerator Technology T2 - American Institute of Physics, Conference Proceeding Series Y1 - 1998 A1 - Schneider, R. J. A1 - von Reden, K. F. A1 - Hayes, J. M. A1 - Wills, J. S. C. JF - American Institute of Physics, Conference Proceeding Series CY - Argonne National Lab N1 - id: 1624; submitted ER - TY - JOUR T1 - Pyroclastic stratigraphy of the Soufriere Hills volcano, Montserrat - Implications for the present eruption JF - Geophysical Research Letters Y1 - 1998 A1 - Roobol, M. J. A1 - Smith, A. L. AB - The stratigraphy of the Soufriere Hills volcano is dominated by dense-andesite block and ash flow deposits. Forty-one radiocarbon ages permit a reconstruction of the eruptive history over the past 31,000 years. A single stratigraphic member yielding radiocarbon ages of 22,000 to 20,000 years B.P. is composed of block and ash flow deposits with semi-vesiculated clasts concentrated in the upper third of each deposit. The present eruption is also producing block and ash flow deposits with both dense and semi-vesiculated clasts. It marks a return to a more explosive driven type of activity as occurred 22,000 to 20,000 years ago. Deposits of this member have a broad sheet-like form and volumes in excess of any produced so far by the present eruption. VL - 25 IS - 18 N1 - 119mkTimes Cited:24Cited References Count:9 JO - Pyroclastic stratigraphy of the Soufriere Hills volcano, Montserrat - Implications for the present eruption ER - TY - JOUR T1 - Quantitative Production of H2 by Pyrolysis of Gas Chromatographic Effluents JF - Analytical Chemistry Y1 - 1998 A1 - Burgoyne, Thomas W. A1 - Hayes, John M. VL - 70 N1 - id: 1731 JO - Quantitative Production of H2 by Pyrolysis of Gas Chromatographic Effluents ER - TY - CONF T1 - Radiocarbon in the North Pacific: What we have learned since GEOSECS T2 - Seventh Annual PICES Meeting Y1 - 1998 A1 - Key, Robert M. JF - Seventh Annual PICES Meeting CY - Fairbanks, AK N1 - id: 311 ER - TY - JOUR T1 - Radiometrically determined sedimentary fluxes in the sub-polar North Atlantic during the last 140,000 years JF - Earth and Planetary Science Letters Y1 - 1998 A1 - McManus, J. F. A1 - Anderson, R. F. A1 - Broecker, W. S. A1 - Fleisher, M. Q. A1 - Higgins, S. M. AB - We have examined the record of sediment input during the last 140000 years in a deep-sea core from 49 degrees 27'N, 22 degrees 16'W in the eastern North Atlantic. Using uranium-series disequilibria to constrain time, we have calculated mass fluxes of total sediment, as well as mass and particle fluxes of major sedimentary components. Sediment accumulation rates were generally lower and relatively constant during broadly defined interglacial intervals, driven primarily by the burial of biogenic material. Accumulation rates were higher and more variable during glacial intervals, and were influenced primarily by terrigenous material. Peaks in bulk mass fluxes were associated with particular episodes (Heinrich events) within the last glacial and during each of the last two deglaciations. The flux of ice-rafted debris, as uniquely identified by coarse detrital fragments, was higher during layers representing each of the glacial Heinrich events, with modest increases during events H3 and H6 and dramatic increases during the others, confirming the widespread interpretation of these layers as episodes of enhanced iceberg delivery. The burial flux of foraminifera was markedly lower during each of the glacial Heinrich events, also confirming the original identification of these layers as barren intervals. Ice-rafting events within marine isotope stage 5 left neither a large detrital nor biogenic flux imprint at our study site. Variations in the burial rates of non-carbonate sediments were largely responsible for overall changes in sediment accumulation throughout the last climate cycle. Ice-rafting was apparently an important delivery mechanism for this terrigenous material. The instantaneous chronometer established here for the last 140000 years in the subpolar North Atlantic allows the transformation of existing and subsequent data from relative values to absolute burial fluxes. (C) 1998 Elsevier Science B.V. VL - 155 IS - 1-2 N1 - Ze160Times Cited:70Cited References Count:55 JO - Radiometrically determined sedimentary fluxes in the sub-polar North Atlantic during the last 140,000 years ER - TY - JOUR T1 - A reassessment of the sources and importance of land-derived organic matter in surface sediments from the Gulf of Mexico JF - Geochimica Et Cosmochimica Acta Y1 - 1998 A1 - Goñi, M. A. A1 - Ruttenberg, K. C. A1 - Eglinton, T. I. AB - Organic matter in surface sediments from two onshore-offshore transects in the northwestern Gulf of Mexico was characterized by a variety of techniques, including elemental, stable carbon, radiocarbon, and molecular-level analyses. In spite of the importance of the Mississippi River as a sediment source, there is little evidence for a significant terrigenous input based on the low carbon:nitrogen ratios (8-5) and the enriched delta(13)C values of bulk sedimentary organic carbon (-19.7 parts per thousand to -21.7 parts per thousand). Radiocarbon analyses, on the other hand, yield depleted Delta(14)C values (-277 parts per thousand to -572 parts per thousand) which indicate that a significant fraction of the sedimentary organic carbon (OC) in all these surface sediments must be relatively old and most likely of allochthonous origin. CuO oxidations yield relatively low quantities of lignin products (0.4-1.4 mg/100 mg OC) along with compounds derived from proteins, polysaccharides, and lipids. Syringyl:vanillyl and cinnamyl:vanillyl ratios (averaging 1.6 and 0.5, respectively) and acid:aldehyde ratios for both vanillyl and syringyl phenols (averaging 0.8 and 1.2, respectively) indicate that the lignin present in sediments originates from nonwoody angiosperm sources and is highly degraded. The delta(13)C values of lignin phenols in shelf sediments are relatively depleted in (13)C (averaging -26.3 parts per thousand) but are increasingly enriched in (13)C at the slope sites (averaging -17.5 parts per thousand for the two deepest stations). We interpret these molecular and isotopic compositions to indicate that a significant fraction (greater than or equal to 50%) of the lignin and, by inference, the land-derived organic carbon in northwestern Gulf of Mexico sediments ultimately originated from C(4) plants. The source of this material is likely to be soil organic matter eroded from the extensive grasslands of the Mississippi River drainage basin. Notably, the mixed C(4) and C(3) source and the highly degraded state of this material hampers its recognition and quantification in shelf and slope sediments. Our data are consistent with higher than previously estimated inputs of land-derived organic carbon to regions of the ocean, such as the Gulf of Mexico, with significant sources of terrigenous C(4)-derived organic matter. Copyright (C) 1998 Elsevier Science Ltd. VL - 62 IS - 18 N1 - 156xvTimes Cited:251Cited References Count:133 JO - A reassessment of the sources and importance of land-derived organic matter in surface sediments from the Gulf of Mexico ER - TY - CONF T1 - Reproducibility of seawater, inorganic and organic 14C results at NOSAMS T2 - Sixteenth International 14C Conference Y1 - 1998 A1 - Elder, K. L. A1 - McNichol, A. P. A1 - Gagnon, A. R. JF - Sixteenth International 14C Conference CY - Groningen VL - 40(1) N1 - id: 1625 ER - TY - THES T1 - Ritual, Power, and the Development of a Complex Society: The Island of the Sun and the Tiwanaku State, Thesis Y1 - 1998 A1 - Seddon, Matthew T. PB - University of Chicago CY - Chicago, ILL VL - Ph.D. Unpublished ER - TY - JOUR T1 - Sea level higher than present 3500 years ago on the northern main Hawaiian Islands JF - Geology Y1 - 1998 A1 - Grossman, E. E. A1 - Fletcher, C. H. AB - New data from an emerged coastal bench and associated fossil beach on Kapapa Island (Oahu), Hawaii, preserve a detailed history of middle to late Holocene sea level. These include 29 new calibrated radiocarbon ages and elevations indicating mean sea level reached a maximum position of 2.00 +/- 0.35 m ca. 3500 yr B.P. These results correlate with additional evidence from Hawaii and other Pacific islands and provide constraints on Oahu's long-term uplift rate (0.03-0.07 mm/yr), previously based solely on Pleistocene age shorelines. Our sea-level reconstruction is consistent with geophysical model predictions of Earth's geoid response to the last deglaciation and with observations of increased Antarctic ice volume during the late Holocene. VL - 26 IS - 4 N1 - Zg996Times Cited:34Cited References Count:25 JO - Sea level higher than present 3500 years ago on the northern main Hawaiian Islands ER - TY - JOUR T1 - Sea-level rise on eastern China's Yangtze delta JF - Journal of Coastal Research Y1 - 1998 A1 - Chen, Z. Y. A1 - Stanley, D. J. KW - delta flooding KW - Holocene KW - neolithic sites KW - peat KW - radiocarbon dates KW - relative sea level KW - sea-level curve KW - subsidence KW - taihu lake KW - yangtze delta AB - The Yangtze delta is a densely populated, low-lying region highly vulnerable to flooding, high tides and typhoons. All previous studies indicated that relative sea level was higher from similar to 7500-4000 yrs. BP, then lowered and stabilized at about present msl during the past 3000 yrs. To the contrary, we find that sea level has been rising relative to the southern Yangtze delta plain based on new sea-level data derived from dated peats, reassessment of earlier sea-level curves and measurement of delta plain subsidence and analysis of prehistoric habitat bases from similar to 7000 to 3000 yrs. BP. Consequences of this relative rise include difficulty in expelling water from the low-lying delta plain to the coast and associated flood damage. Emplacement of the 3-Gorges Dam on the Yangtze will control flooding of the Yangtze river but decrease sediment accumulation on the delta plain that, in turn, is likely to accelerate saline inundation of this vital breadbasket. VL - 14 SN - 0749-0208 IS - 1 N1 - Yt592Times Cited:46 Cited References Count:27 JO - J Coastal Res ER - TY - JOUR T1 - Status Report of the National Ocean Sciences AMS Facility at Woods Hole Oceanographic Institution: Operations and Recent Developments JF - 15th International Conference on the Applications of Accelerators in Research and Industry Y1 - 1998 A1 - Bellino, M. A1 - von Reden, K. F. A1 - Schneider, R. J. A1 - Peden, J. C. A1 - Donoghue, J. A1 - Elder, K. L. A1 - Gagnon, A. R. A1 - Long, P. A1 - McNichol, A. P. A1 - Odegaard, A. P. A1 - Stuart, D. A1 - Handwork, S. A1 - Hayes, J. M. VL - A.I.P. Conference Proceedings IS - 475, part 2 N1 - id: 1647 ER - TY - CONF T1 - (super 14) C AMS measurements of Y1 - 1998 A1 - von Reden, Karl F. A1 - McNichol, Ann P. A1 - Pearson, Ann A1 - Schneider, Robert J. KW - 03 KW - absolute age KW - accelerator mass spectroscopy KW - C-14 KW - carbon KW - dilution KW - Geochronology KW - ions KW - isotopes KW - mass spectroscopy KW - precision KW - radioactive isotopes KW - sample preparation KW - spectroscopy KW - volume AB - The NOSAMS facility at Woods Hole Oceanographic Institution has started to develop and apply techniques for measuring very small samples on a standard Tandetron accelerator mass spectrometry (AMS) system with high-current hemispherical Cs sputter ion sources. Over the past year, results on samples ranging from 7 to 160 mu g C showed both the feasibility of such analyses and the present limitations on reducing the size of solid carbon samples. One of the main factors affecting the AMS results is the dependence of a number of the beam optics parameters on the extracted ion beam current. The extracted currents range from 0.5 to 10 mu A of (super 12) C (super -) for the sample sizes given above. We here discuss the setup of the AMS system and methods for reliable small-sample measurements and give the AMS-related limits to sample size and the measurement uncertainties. PB - University of Arizona, Department of Geosciences, Tucson, AZ, United States (USA) CY - United States (USA) VL - 40 N1 - id: 2239; Source type: conferencepapers&proceedings; Object type: Article; Object type: Conference Paper; Copyright: GeoRef, Copyright 2007, American Geological Institute.; CSAUnique: 1999-044459; AccNum: 1999-044459; ISSN: 0033-8222; CODEN: RACAAT ER - TY - CONF T1 - Synthesis and modeling of the WOCE radiocarbon data set T2 - WOCE Conference Y1 - 1998 A1 - Key, Robert M. JF - WOCE Conference CY - Halifax, Canada N1 - id: 1443 ER - TY - JOUR T1 - Target preparation for continuous flow accelerator mass spectrometry JF - Radiocarbon Y1 - 1998 A1 - Schneider, R. J. A1 - Hayes, J. M. A1 - von Reden, K. F. A1 - McNichol, A. P. A1 - Eglinton, T. I. A1 - Wills, J. S. C. KW - gas KW - ion-source AB - For very small samples, it is difficult to prepare graphitic targets that will yield a useful and steady sputtered ion beam. Working with materials separated by preparative capillary gas chromatography, we have succeeded with amounts as small as 20 mu g C. This seems to be a practical limit, as it involves 1) multiple chromatographic runs with trapping of effluent fractions, 2) recovery and combustion of the fractions, 3) graphitization and 4) compression of the resultant graphite/cobalt matrix into a good sputter target. Through such slow and intricate work, radiocarbon ages of lignin derivatives and hydrocarbons from coastal sediments have been determined. If this could be accomplished as an "online" measurement by flowing the analytes directly into a microwave gas ion source, with a carrier gas, then the number of processing steps could be minimized. Such a system would be useful not just for chromatographic effluents, but for any gaseous material, such as CO2 produced from carbonates. We describe tests using such an ion source. VL - 40 SN - 0033-8222 IS - 1 N1 - 1 Sp. Iss. SI113kt Times Cited:11 Cited References Count:10 JO - Radiocarbon ER - TY - JOUR T1 - Technology revolutionizes tracer oceanography during WOCE JF - International WOCE Newsletter Y1 - 1998 A1 - Key, R. M. A1 - McNichol, A. VL - 30 N1 - id: 324 JO - Technology revolutionizes tracer oceanography during WOCE ER - TY - JOUR T1 - Temporal variations of bomb radiocarbon inventory in the Pacific Ocean JF - Marine Chemistry Y1 - 1998 A1 - Peng, T. H. A1 - Key, R. M. A1 - Ostlund, H. G. AB - The natural and anthropogenic components of the radiocarbon measurements from seawater samples can be successfully separated by an improved method, which is based on a very well-defined relationship between natural radiocarbon and dissolved silica observed mainly during the GEOSECS survey for waters beneath 1000 m depth. This relationship is further reconfirmed by the C-14 measurements from large volume samples taken in the deep waters in the Pacific Ocean during the recent WOCE survey program. Analysis of upper ocean C-14 measurements made along 152 degrees W, and north of 20 degrees N, in the northeastern Pacific Ocean during the NOAA's CGC91 cruise, which is a part of the WOCE survey program, indicates that the bomb C-14 inventory in this part of the ocean has increased by 22% since the GEOSECS measurements made in 1974, This increase is consistent with the model prediction of 25% for the northern hemisphere ocean. Change of the surface water bomb Delta(14)C values during this period is insignificant, This feature is also consistent with the model simulation. Results of this new analysis will provide useful information of the temporal variations of bomb C-14 inventory in the ocean, in addition to the spatial distribution, which can be used as powerful constraints in calibrating the global ocean carbon cycle models, especially those based on three-dimensional ocean general circulation models, for estimating the uptake of CO2 by the ocean. (C) 1998 Elsevier Science B.V. VL - 60 IS - 1-2 N1 - Zm128Times Cited:22Cited References Count:18 JO - Temporal variations of bomb radiocarbon inventory in the Pacific Ocean ER - TY - JOUR T1 - Three Holocene tephras identified in lacustrine sediment cores from the Wonder Lake area, Denali National Park and Preserve AK JF - Arctic and Alpine Research Y1 - 1998 A1 - Child, J. C. A1 - Beget, J. A1 - Werner, A. VL - 30 N1 - id: 235 ER - TY - JOUR T1 - Un registro de 6,000 anos de manifestaciones intensas del fenomeno de El Nino en sedimentos de lagunas de las Islas Galapagos JF - Bulletin de l'Institut Francais d'Etudes Andines Y1 - 1998 A1 - Steinitz-Kannan, M. A1 - Riedinger, M. A. A1 - Last, W. M. A1 - Brenner, M. A1 - Miller, M. C. VL - 27 IS - 3 N1 - id: 196 ER - TY - RPRT T1 - Una Investigacion Arqueologica de los Sitios Cerros con Trincheras del Arcaico Tardio en Chihuahua, Mexico: Las Investigaciones de Campo de 1997 Y1 - 1998 A1 - Hard, R. A1 - Roney, J. PB - University of Texas, Center for Archaeological Research N1 - id: 242 ER - TY - JOUR T1 - Water-induced errors in continuous-flow carbon isotope ratio mass spectrometry JF - Anal Chem Y1 - 1998 A1 - Leckrone, K. J. A1 - Hayes, J. M. AB - Formation of HCO2+ from CO2 and background H2O in isotope ratio mass spectrometers has been examined in detail. The process is troublesome because its product is not resolved from 13C16O2+. The resulting, artifactual enhancement of the mass 45 ion current (and analogous enhancement of the mass 46 ion current by transfer of hydrogen to mass 45 species) can cause systematic errors in analyses of 13C based on measurement of ion current ratios in the mass spectrum of CO2. Such errors are neutralized when isotopic analyses are based on differential comparisons in which ion currents and background water levels are precisely equal during admission and ionization of both sample and standard gases. In continuous-flow systems, however, that requirement is generally not met. The resulting systematic error is proportional to the 18/44 ion current ratio. When the widely used MAT252 mass spectrometer is tuned to yield maximum sensitivity, the constant of proportionality is 26 +/- 2/1000 (i.e., the error will be 0.26/1000 if the mass 18 ion current is 100 times smaller than that at mass 44). Errors can be reduced 5-fold when the ion-source residence time of CO2+ is decreased by use of stronger ion-extraction potential gradients. Under those same conditions, sensitivity is decreased by 60%. For operation at highest sensitivity, carrier gas dew points on the order of -70 degrees C are required to obtain errors < or = 0.1/1000 for samples yielding mass 44 ion currents of 10 nA. Carrier gas dew points < or = -80 degrees C are conveniently reached by use of a Nafion dryer operated at approximately 0 degree C. VL - 70 IS - 13 N1 - Leckrone, K JHayes, J MengResearch Support, Non-U.S. Gov'tResearch Support, U.S. Gov't, Non-P.H.S.1998/07/17Anal Chem. 1998 Jul 1;70(13):2737-44. JO - Water-induced errors in continuous-flow carbon isotope ratio mass spectrometry ER - TY - JOUR T1 - Water-level changes in Lake Baikal, Siberia: Tectonics versus climate JF - Geology Y1 - 1998 A1 - Colman, S. M. VL - 26 N1 - id: 187 ER - TY - RPRT T1 - Western Great Lakes paleoecology study, global climate change initiative. In Holocene Paleoenvironments in Western Great Lakes Parks. Report Y1 - 1998 A1 - Winkler, M. G. A1 - Sanford, P. R. PB - National Park Service & USGS Biological Resources Div., Northern Prairie Wildlife Research Center CY - Columbia, Missouri VL - Final report N1 - id: 130 ER - TY - JOUR T1 - Yangtze delta inundation and the discontinuity between Neolithic and younger cultures, China JF - Geoarchaeology Y1 - 1998 A1 - Stanley, D. J. A1 - Chen, Z. A1 - Song, J. VL - 14 IS - 15-26 N1 - id: 228 ER - TY - CONF T1 - 14C AMS measurement of C AMS measurement of C AMS measurement of T2 - 16th International Radiocarbon Conference, Groningen Y1 - 1997 A1 - von Reden, K. A1 - McNichol, A. A1 - Pearson, A. A1 - Schneider, R. JF - 16th International Radiocarbon Conference, Groningen VL - Book of Abstracts N1 - id: 952 ER - TY - JOUR T1 - A 3,500 14C yr. high-resolution record of lake level changes in Lake Titicaca, South America JF - Quaternary Research Y1 - 1997 A1 - Abbott, M. B. A1 - Binford, M. W. A1 - Brenner, M. A1 - Kelts, K. R. AB - Sediment cores collected from the southern basin of Lake Titicaca (Bolivia/Peru) on a transect from 4.6 m above overflow level to 15.1 m below overflow level are used to identify a new century-scale chronology of Holocene lake-level variations. The results indicate that lithologic and geochemical analyses on a transect of cores can be used to identify and date century-scale lake-level changes. Detailed sedimentary analyses of subfacies and radiocarbon dating were conducted on four representative cores. A chronology based on 60 accelerator mass spectrometer radiocarbon measurements constrains the timing of water-level fluctuations. Two methods were used to estimate the14C reservoir age. Both indicate that it has remained nearly constant at ∼25014C yr during the late Holocene. Core studies based on lithology and geochemistry establish the timing and magnitude of five periods of low lake level, implying negative moisture balance for the northern Andean altiplano over the last 3500 cal yr. Between 3500 and 3350 cal yr B.P., a transition from massive, inorganic-clay facies to laminated organic-matter-rich silts in each of the four cores signals a water-level rise after a prolonged mid-Holocene dry phase. Evidence of other significant low lake levels occurs 2900–2800, 2400–2200, 2000–1700, and 900–500 cal yr B.P. Several of the low lake levels coincided with cultural changes in the region, including the collapse of the Tiwanaku civilization. VL - 47 N1 - id: 173; jpc JO - A 3,500 14C yr. high-resolution record of lake level changes in Lake Titicaca, South America ER - TY - JOUR T1 - An abrupt drowning of the Black Sea shelf JF - Marine Geology Y1 - 1997 A1 - Ryan, W. B. F. A1 - Pitman, W. C. A1 - Major, C. O. A1 - Shimkus, K. A1 - Moskalenko, V. A1 - Jones, G. A. A1 - Dimitrov, P. A1 - Gorur, N. A1 - Sakinc, M. A1 - Yuce, H. AB - During latest Quaternary glaciation, the Black Sea became a giant freshwater lake. The surface of this lake drew down to levels more than 100 m below its outlet. When the Mediterranean rose to the Bosporus sill at 7,150 yr BP1, saltwater poured through this spillway to refill the lake and submerge, catastrophically, more than 100,000 km(2) of its exposed continental shelf. The permanent drowning of a vast terrestrial landscape may possibly have accelerated the dispersal of early neolithic foragers and farmers into the interior of Europe at that time. (C) 1997 Elsevier Science B.V. VL - 138 IS - 1-2 N1 - Xj245Times Cited:283Cited References Count:35 JO - An abrupt drowning of the Black Sea shelf ER - TY - CONF T1 - AMS measurements of the 14C distribution in the Pacific Ocean T2 - Proceedings of the Seventh International Conference on Accelerator Mass Spectrometry Y1 - 1997 A1 - von Reden, K. F. A1 - McNichol, A. P. A1 - Peden, J. C. A1 - Elder, K. L. A1 - Gagnon, A. R. A1 - Schneider, R. J. ED - Jull, A. J. T. JF - Proceedings of the Seventh International Conference on Accelerator Mass Spectrometry CY - Tucson, AZ VL - B123 N1 - id: 1644; B123 ER - TY - JOUR T1 - AMS measurements of the 14C distribution in the Pacific Ocean JF - Nuclear Instruments and Methods in Physics Research Y1 - 1997 A1 - von Reden, K. F. A1 - McNichol, A. P. A1 - Peden, J. C. A1 - Elder, K. L. A1 - Gagnon, A. R. A1 - Schneider, R. J. VL - B123 N1 - id: 1673 ER - TY - JOUR T1 - Biostratigraphy and sedimentation rates of the Amazon Deep Sea Fan JF - Proceedings of the Ocean Drilling Program: Scientific Results Y1 - 1997 A1 - Mikkelsen, N. A1 - Maslin, M. A1 - Firaudeau, J. A1 - Showers, W. J. VL - 155 N1 - id: 71 ER - TY - JOUR T1 - Carbon isotopic fractionation associated with lipid biosynthesis by a cyanobacterium: relevance for interpretation of biomarker records JF - Geochim Cosmochim Acta Y1 - 1997 A1 - Sakata, S. A1 - Hayes, J. M. A1 - McTaggart, A. R. A1 - Evans, R. A. A1 - Leckrone, K. J. A1 - Togasaki, R. K. KW - *Biomass KW - Acetic Acid/metabolism KW - Alkanes/*analysis/chemistry KW - Biomarkers/chemistry KW - carbon isotopes KW - Carbon/*chemistry KW - Chlorophyll/metabolism KW - Cyanobacteria/chemistry/*metabolism KW - Geologic Sediments/*chemistry KW - Lipids/*biosynthesis KW - NASA Discipline Exobiology KW - Non-NASA Center KW - Palmitic Acid/metabolism KW - Phytol/metabolism KW - Pigments, Biological/metabolism AB - For the cyanobacterium Synechocystis UTEX 2470, grown photoautotrophically to a logarithmic stage of growth, the total lipid extract is depleted in 13C by 4.8% relative to average biomass. Depletions observed for acetogenic (straight-chain) lipids range from 7.6 (hexadecanoic acid) to 9.9% (a C16 n-alkyl chain bound in a polar-lipid fraction), with a mass-weighted average of 9.1%. Polyisoprenoid lipids fall into two isotopic groups, with phytol, diplopterol, and diploptene depleted by 6.4-6.9% and bishomohopanol (produced from the extracts by the preparative degradation of bacteriohopanepolyol) depleted by 8.4%. Analysis of the pattern of depletions indicates that two carbon positions in each C5 biomonomer leading to polyisoprenoid products are probably depleted in 13C relative to average biomass. The depletion of bacteriohopanepolyol relative to other polyisoprenoids can be ascribed to changes that occur over the life of each cell: (1) the 13C content of carbon flowing to lipid biosynthesis decreases as the cell size increases and (2) a greater proportion of the bacteriohopanepolyol which, unlike other polyisoprenoids, is present mainly in the cytoplasm rather than in membranes and is synthesized when cells are larger. Chlorophyll a is depleted relative to average biomass by O.7%. Given the observed depletion of 13C in phytol, the heteroaromatic, chlorophyllide portion of chlorophyll must be enriched in 13C by 2.7%. This enrichment is large relative to that in chlorophyllides produced by eukaryotes and may be related to a parallel enrichment of 13C in cyanobacterial glutamic acid. As in many previous investigations of cyanobacterial lipids, long-chain n-alkanes (C22-C29) are found in the extracts. They are, however, enriched in 13C relative to biomass and have isotopic compositions suggesting that they are contaminants of petrochemical origin. Available results indicate that cyanobacterial lipids will be depleted relative to dissolved CO2 that has served as a carbon source by 22-30% and that a wider range of depletions will be characteristic of eukaryotic products. The absence of long-chain n-alkanes in cyanobacteria reduces the possibility that petroleum ever formed from pre-eukaryotic sedimentary debris. VL - 61 SN - 0016-7037 (Print)0016-7037 (Linking) UR - https://www.ncbi.nlm.nih.gov/pubmed/11540730 IS - 24 N1 - Sakata, SHayes, J M McTaggart, A R Evans, R A Leckrone, K J Togasaki, R K eng Research Support, U.S. Gov't, Non-P.H.S. 1997/01/01 00:00 Geochim Cosmochim Acta. 1997;61(24):5379-89. ER - TY - RPRT T1 - Changes in the Pacific Ocean distribution of radiocarbon since GEOSECS, 1997 Y1 - 1997 A1 - Key, R. M. PB - U. S. WOCE Office CY - College Station, TX VL - 9 N1 - id: 323 ER - TY - JOUR T1 - Climate variation and the rise and fall of an Andean civilization JF - Quaternary Research Y1 - 1997 A1 - Binford, M. W. A1 - Kolata, A. L. A1 - Brenner, M. A1 - Janusek, J. W. A1 - Seddon, M. T. A1 - Abbott, M. A1 - Curtis, J. H. AB - Paleolimnological and archaeological records that span 3500 years from Lake Titicaca and the surrounding Bolivian-Peruvian altiplano demonstrate that the emergence of agriculture (ca. 1500 B.C.) and the collapse of the Tiwanaku civilization (ca. A.D. 1100) coincided with periods of abrupt, profound climate change, The timing and magnitude of climate changes are inferred from stratigraphic evidence of lake-level variation recorded in C-14-dated lake-sediment cores. Paleolake levels provide estimates of drainage basin water balance. Archaeological evidence establishes spatial and temporal patterns of agricultural field use and abandonment. Prior to 1500 B.C., aridity in the altiplano precluded intensive agriculture. During a wetter period from 1500 B.C. to A.D. 1100, the Tiwanaku civilization and its immediate predecessors developed specialized agricultural methods that stimulated population growth and sustained large human settlements, A prolonged drier period (ca. A.D. 1100-1400) caused declining agricultural production, field abandonment, and cultural collapse. (C) 1997 University of Washington. VL - 47 IS - 2 N1 - Wu887Times Cited:148Cited References Count:53 JO - Climate variation and the rise and fall of an Andean civilization ER - TY - JOUR T1 - Consistent Fractionation of 13C in Nature and in the Laboratory: Growth-rate Effects in Some Haptophyte Algae JF - Global Biogeochemical Cycles Y1 - 1997 A1 - Bidigare, Robert R. A1 - Fluegge, Arnim A1 - Freeman, Katherine H. A1 - Hanson, Kristi L. A1 - Hayes, John M. A1 - Hollander, David A1 - Jasper, John P. A1 - King, Linda L. A1 - Laws, Edward A. A1 - Milder, Jeffrey A1 - Millero, Frank J. A1 - Pancost, Richard A1 - Popp, Brian N. A1 - Sternberg, Paul A. A1 - Wakeham, Stuart G. AB - The carbon isotopic fractionation accompanying formation of biomass by alkenone-producing algae in natural marine environments varies systematically with the concentration of dissolved phosphate. Specifically, if the fractionation is expressed by єP ≈ δe − δp, where δe and δp are the δ13C values for dissolved CO2 and for algal biomass (determined by isotopic analysis of C37 alkadienones), respectively, and if Ce is the concentration of dissolved CO2, μmol kg−1, then b = 38 + 160*[PO4], where [PO4] is the concentration of dissolved phosphate, μM, and b = (25 − єp)Ce. The correlation found between b and [PO4] is due to effects linking nutrient levels to growth rates and cellular carbon budgets for alkenone-containing algae, most likely by trace-metal limitations on algal growth. The relationship reported here is characteristic of 39 samples (r2 = 0.95) from the Santa Monica Basin (six different times during the annual cycle), the equatorial Pacific (boreal spring and fall cruises as well as during an iron-enrichment experiment), and the Peru upwelling zone. Points representative of samples from the Sargasso Sea ([PO4] ≤ 0.1 μM) fall above the b = f[PO4] line. Analysis of correlations expected between μ (growth rate), єp, and Ce shows that, for our entire data set, most variations in єp result from variations in μ rather than Ce. Accordingly, before concentrations of dissolved CO2 can be estimated from isotopic fractionations, some means of accounting for variations in growth rate must be found, perhaps by drawing on relationships between [PO4] and Cd/Ca ratios in shells of planktonic foraminifera. VL - 11 N1 - id: 1727 JO - Consistent Fractionation of 13C in Nature and in the Laboratory: Growth-rate Effects in Some Haptophyte Algae ER - TY - CONF T1 - A correction for aberrations in the WHOI Recombinator Injector T2 - Symposium of North Eastern Accelerator Personnel Y1 - 1997 A1 - von Reden, K. F.
 A1 - Schneider, R. J. JF - Symposium of North Eastern Accelerator Personnel PB - World Scientific Publishing Co. ER - TY - JOUR T1 - Corrections for contamination background in AMS 14C measurements JF - Nuclear Instruments and Methods in Physics Research B Y1 - 1997 A1 - Brown, T. A. A1 - Southon, J. R. AB - Measurements of ratios were made on samples of Oxalic Acid and 14C “dead” materials spanning the mass range from 10 μg to ∼1 mg. These measurements have allowed the determination of both the amount, and the 14C content, of the contaminant carbon introduced during sample processing in our laboratory. These data were used to correct measured ratios obtained from ANU Sucrose and “∼ one-half-life old” test samples for the influence of the contaminant. The test samples spanned the 10 μg to ∼1 mg mass range and the corrections were made using three different formulae. The results obtained from these calculations allow the accuracy of these background correction formulae to be evaluated. VL - 123 N1 - id: 1493 JO - Corrections for contamination background in AMS 14C measurements ER - TY - CONF T1 - Determination of the radiocarbon ages of individual PAH extracted from urban aerosol and marine sediment T2 - 16th International Radiocarbon Conference Y1 - 1997 A1 - Pearson, A. A1 - Eglinton, T. I. A1 - McNichol, A. P. A1 - Currie, L. A. A1 - Schneider, R. J. A1 - von Reden, K. F. A1 - Benner, B. A. A1 - Wise, S. A. JF - 16th International Radiocarbon Conference CY - Groningen VL - Book of Abstracts N1 - id: 951 ER - TY - JOUR T1 - Detritus dynamics in the seagrass Posidonia oceanica: Elements for an ecosystem carbon and nutrient budget JF - Marine Ecology-Progress Series Y1 - 1997 A1 - Mateo, M. A. A1 - Romero, J. AB - Leaf decay, leaf Litter export, burial in belowground sinks, and respiratory consumption of detritus were examined at 2 different depths in a Posidonia oceanica (L.) Delile meadow off the Medes Islands, NW Mediterranean. At 5 m, the amount of exported leaf Litter represented carbon, nitrogen and phosphorus losses of 7, 9 and 6 % of the plant primary production, respectively. About 26 % of the carbon produced by the plant in 1 yr was immobilized by burial in the belowground compartment, i.e. as roots and rhizomes. Annual nitrogen and phosphorus burial in the sediment was 8 and 5 % of total N and P needs, respectively. Respiratory consumption (aerobic) of carbon leaf detritus represented 17% of the annual production. An additional, but very substantial, loss of carbon as very fine particulate organic matter has been estimated at ca 48%. At 13 m the pattern of carbon losses was similar, but the lesser effect of wave action (relative to that at 5 m) reduced exportation, hence increasing the role of respiratory consumption. Data on carbon losses indicated that only a small part of the plant production was actually available to fuel the food web of this ecosystem. Total nutrient losses were in the range of 21 to 47 % of annual needs. From differences found in N and P concentrations between living and dead tissues, it is suggested that important nutrient recycling (50 to 70%) may be due either to reclamation or to leaching immediately after plant death. VL - 151 IS - 1-3 N1 - id: 2004; PT: J; UT: WOS:A1997XE68700005 JO - Detritus dynamics in the seagrass Posidonia oceanica: Elements for an ecosystem carbon and nutrient budget ER - TY - JOUR T1 - Dynamic changes of the Holocene Mississippi River delta plain: The delta cycle JF - Journal of Coastal Research Y1 - 1997 A1 - Roberts, H. H. KW - barrier KW - delta cycle KW - lacustrine deltas KW - progradation KW - shoreline change KW - subsidence AB - Previous geologic research on Holocene Mississippi River deltaic deposits has verified that the present delta plain and associated nearshore barrier islands and submarine shoals are either direct or indirect products of cyclic delta-building events that have operated on a variety of temporal and spatial scales. A major depositional element of the modern delta plain is the delta complex, of which there are six: (1) Maringouin, (2) Teche, (3) St. Bernard, (4) Lafourche, (5) Balize, and (6) Atchafalaya. Major delta-building events have occurred at a frequency of one every 1-2 kyr. Deposits associated with the six major delta complexes are fundamental constructional units of the delta plain, which collectively covers an area of similar to 30,000 km(2). Sedimentary deposits associated with these delta-building events range in thickness from about 10 to 100 m. Their construction is modulated by stream capture, which develops a new delta complex by way of a new river course. Delta complexes may be comprised of one or more delta lobes. As a product of this delta switching, the depositional architecture of the delta plain consists of laterally offset and stacked delta lobes. Within delta lobes are subdeltas and even smaller crevasse-splays. These smaller scale deltas sedimentologically and geomorphically mimic their larger delta lobe counterparts, but they are considerably thinner, cover less area, and have a shorter period of development and abandonment. Subdeltas are usually < 10 m thick and may fill shallow bays that cover over 300 km(2). They build and deteriorate on time-scales of 150-200 years. Crevasse-splays or overbank splays are < 5 m thick, cover only a few square kilometers, and are abandoned after several decades of active growth.Each delta evolves through a rapid regressional phase as water and sediment are captured from an antecedent river course. If highstand conditions persist long enough, deltas may prograde to the outer shelf to form wedges of deltaic sediment much thicker than their inner shelf counterparts. The delta-building process starts with the filling of interior lakes (lacustrine deltas), which is followed by bayhead delta-building at the coast, and finally by progradation across the marine shelf(shelf delta). Delta complexes and delta lobes, as well as their smaller counterparts, experience three phases of growth and abandonment: (1) rapid growth with increasing-to-stable discharge, (2) relative stability during initial stages of waning discharge, when sediment input balances the collective effects of subsidence, and (3) abandonment, followed by rapid subsidence-driven subaerial delta deterioration. In the rapid growth stage, formerly eroding-subsiding coastal environments experience delta plain accretion and coastal progradation from renewed sediment input. On the abandonment side of the cycle, marine processes overwhelm fluvial processes and rework the delta perimeter. Forced by the combined processes of subsidence, the delta surface undergoes progressive submergence. Transgressive sand bodies created by wave reworking of the delta evolve from headland beaches and spits, to barrier islands, and finally to submarine shoals as the abandonment phase is completed. VL - 13 SN - 0749-0208 UR - http://www.jstor.org/stable/4298659 IS - 3 N1 - Xq326Times Cited:167 Cited References Count:74 JO - J Coastal Res ER - TY - JOUR T1 - Eastern Mississippi Delta; late Wisconsin unconformity, overlying transgressive facies, sea level and subsidence JF - Engineering Geology Y1 - 1997 A1 - Stanley, D. J. A1 - Warne, A. G. A1 - Dunbar, J. B. VL - 45 IS - 1-4 N1 - id: 79 ER - TY - JOUR T1 - Efficiency and temperature dependence of water removal by membrane dryers JF - Anal Chem Y1 - 1997 A1 - Leckrone, K. J. A1 - Hayes, J. M. AB - The vapor pressure of water in equilibrium with sorption sites within a Nafion membrane is given by log P(WN) = -3580/T + 10.01, where P(WN) is expressed in Torr and T is the membrane temperature, in kelvin. The efficiency of dryers based on selective permeation of water through Nafion can thus be enhanced by cooling the membrane. Residual water in effluents exceeds equilibrium levels if insufficient time is allowed for water to diffuse to the membrane surface as gas passes through the dryer. For tubular configurations, this limitation can be avoided if L > or = Fc(10(3.8)/120 pi D), where L is the length of the tubular membrane, in centimeters, Fc is the gas flow rate, in mL/ min, and D is the diffusion coefficient for water in the carrier gas at the operating temperature of the dryer, in cm2/s. An efficient dryer that at room temperature dries gas to a dew point of -61 degrees C is described; the same dryer maintained at 0 degrees C yields a dew point of -80 degrees C and removes water as effectively as Mg(ClO4)2 or a dry ice/acetone slush. The use of Nafion membranes to construct devices capable of delivering gas streams with low but precisely controlled humidities is discussed. VL - 69 IS - 5 N1 - Leckrone, K JHayes, J MengComparative StudyResearch Support, U.S. Gov't, Non-P.H.S.1997/03/01 00:00Anal Chem. 1997 Mar 1;69(5):911-8. JO - Efficiency and temperature dependence of water removal by membrane dryers ER - TY - JOUR T1 - Eruption of Soufriere Hills Volcano in Montserrat JF - EOS Y1 - 1997 A1 - Young, S. R. A1 - Sparks, S. A1 - Robertson, R. A1 - Lynch, L. A1 - Aspinall, W. AB - On July 18,1995, the Soufriere Hills volcano in Montserrat erupted for the first time in recorded history. The eruption began with intense fumarolic venting and phreatic explosions following 3 years of elevated seismicity. An andesite lava dome emerged on November 15, 1995, and continued to grow, with several periods of copious pyroclastic flow generation and an explosive eruption on September 17, 1996. The largest pyroclastic flows to date (on June 25, 1997) and a period of vulcanian explosions with fountain collapse (during early August 1997) indicate continued escalation of the eruption. VL - 78 IS - 38 N1 - id: 99 JO - Eruption of Soufriere Hills Volcano in Montserrat ER - TY - CONF T1 - Evaluating reproducibility of seawater, inorganic and organic carbon 14C results at the National Ocean Sciences AMS Facility (NOSAMS) T2 - 16th International Radiocarbon Conference Y1 - 1997 A1 - Elder, K. L. A1 - McNichol, A. P. A1 - Gagnon, A. R. JF - 16th International Radiocarbon Conference T3 - Book of Abstracts CY - Groningen N1 - id: 956 ER - TY - RPRT T1 - The evaluation of geochemical indicators of anoxia in the Chesapeak Bay. Report Y1 - 1997 A1 - Adelson, Jordan Michael N1 - id: 1374; rpc ER - TY - JOUR T1 - Evidence for earliest olive oil production in submerged settlements off the Carmel coast, Israel JF - Journal of Archaeological Science Y1 - 1997 A1 - Galili, E. A1 - Stanley, D. J. A1 - Sharvit, Y. A1 - Weinstein, E. M. AB - Thousands of crushed olive stones with olive pulp are concentrated in pits at the Kfar Samir prehistoric settlement off the Carmel coast south of Haifa. Observations at this site, and at other Late Neolithic to Early Chalcolithic offshore settlements in this region, record an olive-oil technology that began along the Carmel coastal plain as early as 6500 years ago. This is about 500 years earlier than previously held. These new finds help define the technology of olive-oil production and refine the chronological definition of cultural units along the southern Levant coast during the 7th millenniumbp, a time of major transition between the end of the Neolithic and beginning of the Chalcolithic. N1 - id: 81 JO - Evidence for earliest olive oil production in submerged settlements off the Carmel coast, Israel ER - TY - JOUR T1 - The first trans-Arctic 14C section: comparison of the mean ages of the deep waters in the Eurasian and Canadian Basins of the Arctic Ocean; in Proceedings of the 7th International Conference on Accelerator Mass Spectrometry JF - Nuclear Instruments and Methods Y1 - 1997 A1 - Schlosser, P. A1 - Kromer, B. A1 - Ekwurzel, B. A1 - Bonisch, G. A1 - McNichol, A. A1 - Schneider, R. A1 - von Reden, K. A1 - Ostlund, H. A1 - Swift, J. VL - B IS - 123 N1 - id: 1751 ER - TY - JOUR T1 - The first trans-Arctic 14C section: comparison of the mean ages of the deep waters in the Eurasian and Canadian basins fo the Arctic Ocean JF - Nuclear Instruments and Methods in Physics Research Y1 - 1997 A1 - Schlosser, Peter A1 - Kromer, Bernd A1 - Ekwurzel, Brenda A1 - Bonisch, Gerhard A1 - McNichol, Ann A1 - Schneider, Robert A1 - von Reden, Karl A1 - Ostlund, H. G. A1 - Swift, J. H. VL - 123 IS - 431-437 N1 - id: 67 ER - TY - JOUR T1 - Foraminiferal constraints on very high-resolution seismic stratigraphy and late Quaternary glacial history, New Jersey continental shelf JF - Palaios Y1 - 1997 A1 - Lagoe, M. B. A1 - Davies, T. A. A1 - Austin, J. K. A1 - Olson, H. C. AB - Internal stratigraphy of a Late Quaternary sediment wedge on the New Jersey outer continental shelf has been investigated using regional and 3-D seismic surveys, sediment cores and foraminiferal biofacies analysis. Results from the study help constrain Late Wisconsinan glacial/deglacial history in this area. Three major reflectors (channels, S and R) define 5 stratigraphic units: S1-modern sediments; S2-sands overlying a channelized surface (Channels reflector); S3-muds, clays and sandy muds below the channelized surface and above reflector S; S4-an unsampled unit between reflectors S and R; and S5-sands underlying reflector R, the fatter surface defining the base of the sediment wedge. Multivariate quantitative analysis delineates four major faunal groups characterizing these stratigraphic units. Faunal patterns are interpreted in terms of modern foraminiferal distributions, planktonic/benthic ratios and faunal abundance patterns. Group A dominates units S2 and S5 and is characterized by Cibicides lobatulus and Cassidulina islandica. The fauna indicates middle neritic water depths, moderate to high current energy, and moderate accumulation rates. Group B dominates unit S3 (muddy unit) and is characterized by Elphidium excavatum s.l., Buccella frigida, Fursenkoina fusiformis and miliolid spp. This fauna represents an environment with no modern analogue on the New Jersey continental shelf reflecting middle neritic, low-energy conditions and the accumulation of predominantly muddy sediments. Group C dominates the modern sediment veneer (unit S1), and its diverse fauna is consistent with modern faunal distributions and environmental conditions. Group D consists of a low-diversity fauna dominated by Fursenkoina fusiformis and Nonionella sp., which characterizes a few samples in unit S3. Environmental conditions are probably similar to those described for faunal group B. The distribution and interpretation of these faunas, combined with preliminary C-14 AMS dates, indicate that the Quaternary history of the outer-shelf sediment wedge involves a middle Wisconsinan unconformity (R), overlain by an unsampled unit (S4) and several meters of mud (S3). This relationship may represent a middle Wisconsinan outwash event. The muddy deposit was later incised by the ''Channels'' horizon, possibly reflecting the Late Wisconsinan maximum lowering of sea level. This horizon is overlain by sandy transgressive deposits associated with rising sea level, presumably during the Holocene. VL - 12 IS - 3 N1 - Xf026Times Cited:19Cited References Count:39 JO - Foraminiferal constraints on very high-resolution seismic stratigraphy and late Quaternary glacial history, New Jersey continental shelf ER - TY - JOUR T1 - A high-resolution paleoenvironmental record from Bainbridge Crater Lake, Galapagos Islands JF - Wurzburger Geographische Manuscripte, Heft Y1 - 1997 A1 - Reidinger, M. A1 - Steinitz-Kannan, M. A1 - Last, W. A1 - Brenner, M. VL - 41 N1 - id: 356 ER - TY - JOUR T1 - Hold-up and memory effect for carbon in a compact microwave ion source JF - Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions with Materials and Atoms Y1 - 1997 A1 - Schneider, R. J. A1 - vonReden, K. F. A1 - Wills, J. S. C. A1 - Diamond, W. T. A1 - Lewis, R. A1 - Savard, G. A1 - Schmeing, H. AB - The production of C+ in a microwave ion source injected with a gaseous CO2 sample has been investigated as an alternative to sample graphitization, A continuous flow of argon gas maintained the discharge, and 20 mu L Of CO2 gas at approximately 1 atm was pulsed into the source through a sample valve closely coupled to the plasma chamber, The C+ component of the beam fell to 1% of its original intensity less than 10 s after the valve was operated. in a separate experiment, the microwave ion source was operated with pure CO2 feed gas and the extracted beam was magnetically analyzed. Efficient breakup of the molecules was observed. These results are considered promising for such applications as accelerator mass spectrometry of C isotopes in gaseous samples. VL - 123 IS - 1-4 N1 - Wt653Times Cited:13Cited References Count:7 JO - Hold-up and memory effect for carbon in a compact microwave ion source ER - TY - JOUR T1 - Holocene Evolution of Lake Erie Environments JF - Geological Society of America, Abstracts with Programs Y1 - 1997 A1 - McCambridge, C. A1 - Barrera, E. A1 - Tevesz, M. A1 - Fuller, J. VL - 29 IS - 6 N1 - id: 250 ER - TY - JOUR T1 - An isotopic biogeochemical study of Neoproterozoic and Early Cambrian sediments from the Centralian Superbasin, Australia JF - Geochim Cosmochim Acta Y1 - 1997 A1 - Logan, G. A. A1 - Summons, R. E. A1 - Hayes, J. M. KW - Alkanes/analysis/chemistry KW - Animals KW - australia KW - biomarkers KW - carbon isotopes KW - Carbon/analysis/*chemistry KW - Cyanobacteria KW - Eukaryota KW - Feces KW - Fossils KW - Geologic Sediments/*analysis/chemistry KW - Hydrocarbons/analysis KW - NASA Discipline Exobiology KW - Non-NASA Center KW - Paleontology KW - phytoplankton KW - SEAWATER KW - Terpenes/analysis KW - Zooplankton AB - Organic matter from Neoproterozoic and Early Cambrian sediments of the Amadeus and Officer basins of the Centralian Superbasin, Australia, has been studied for biomarker distributions and the carbon isotopic compositions of kerogen and individual hydrocarbons. These sediments represent both shallow and deep water marine facies in the older sections and marine and saline lacustrine carbonate deposits in the Cambrian. Hydrocarbon biomarker patterns were found to be quite consistent with the known sedimentary environments and provide valuable insights into the biogeochemical changes which accompanied the transition from a microbially-dominated ocean to the early stages of metazoan radiation. In particular, carbon isotopic data for n-alkyl and isoprenoid lipids presented here, and in earlier studies, showed a reversal in carbon isotopic ordering between the Proterozoic and Phanerozoic. By comparison with the delta 13C of kerogen, n-alkyl lipids from deep-water Proterozoic sediments were enriched in 13C and appear to be derived mainly from heterotrophs whilst open marine Phanerozoic counterparts are 13C depleted and evidently derived mainly from autotrophs. Data from the samples studied here are consistent with a model invoking a change in the redox structure of the ocean, possibly aided by the innovation of faecal pellets. VL - 61 SN - 0016-7037 (Print)0016-7037 (Linking) UR - https://www.ncbi.nlm.nih.gov/pubmed/11540731 IS - 24 N1 - Logan, G ASummons, R E Hayes, J M eng Research Support, U.S. Gov't, Non-P.H.S. 1997/01/01 00:00 Geochim Cosmochim Acta. 1997;61(24):5391-409. ER - TY - JOUR T1 - Isotopic stratigraphy of Amazon Fan sediments JF - Proceedings of the Ocean Drilling Program: Scientific Results Y1 - 1997 A1 - Showers, W. J. A1 - Schneider, R. A1 - Mikkelsen, N. A1 - Maslin, M. VL - 155 N1 - id: 1277 ER - TY - CONF T1 - Late Plains Woodland Occupation of the Kirschenman III Site in the James River Valley, North Dakota T2 - 1997 Plains Conference, 55th Annual Meeting of the Plains Anthropological Society Y1 - 1997 A1 - Toom, Dennis L. JF - 1997 Plains Conference, 55th Annual Meeting of the Plains Anthropological Society CY - Boulder, CO N1 - id: 204 ER - TY - CHAP T1 - Late Quaternary climate, fire, and vegetation dynamics (Book Section) T2 - Sediment Records of Biomass Burning and Global Change Y1 - 1997 A1 - Winkler, M. G. ED - Clark, J. S. JF - Sediment Records of Biomass Burning and Global Change PB - Springer-Verlag CY - Berlin N1 - id: 134 ER - TY - THES T1 - Late quaternary evolution of the Central Texas shelf: Sequence Stratigraphic Implications, Thesis Y1 - 1997 A1 - Eckles, Brenda AB - This study documents the evolution of the interdeltaic central Texas continental shelf over the last 350,000 years. The dataset consists of high-resolution seismic data, platform boring descriptions, oxygen isotope analyses, and radiocarbon dates. A strong correlation exists between seismic facies and lithofacies enabling seven stages of evolution to be mapped. The distribution of these facies is primarily controlled by fourth-order glacio-eustatic cycles. Seismic stratigraphy, oxygen isotope analyses, and radiocarbon dating were integrated to develop an independent sea-level curve for the area. Longshore and surface currents transport large volumes of sand into the area which is deposited as widespread, thick $(>$10 meters) barrier-bar highstand sand bodies on the inner shelf. Sediments are deposited and preserved in a repetitive manner during each glacio-eustatic cycle. This implies a predictable pattern of deposition, therefore, allowing for the development of depositional models that can be applied to ancient deposits in the exploration for hydrocarbons. VL - Dissertation/Thesis ER - TY - JOUR T1 - Late Quaternary Western Atlantic Paleoceanography and terrigenous sedimentation on the Amazon Fan: a view from delta d180 and d13C of planktonic foraminifera and bulk organic matter d13C JF - Proceedings of the Ocean Drilling Program: Scientific Results Y1 - 1997 A1 - Schneider, R. R. A1 - Muller, P. J. A1 - Schlunz, B. A1 - Segl, M. A1 - Showers, W. J. A1 - Wefer, G. VL - 155 N1 - id: 1278 ER - TY - JOUR T1 - Lignin phenols in sediments of Lake Baikal, Siberia: application to paleoenvironmental studies JF - Organic Geochemistry Y1 - 1997 A1 - Orem, W. H. A1 - Colman, S. M. A1 - Lerch, H. E. AB - Sediments from three cores obtained from distinct depositional environments in Lake Baikal, Siberia were analyzed for organic carbon, total nitrogen and lignin phenol concentration and composition. Results were used to examine changes in paleoenvironmental conditions during climatic cycles of the late Quaternary (<125 ka). Average organic carbon, and total nitrogen concentrations, atomic C/N ratios and organic carbon accumulation rates were significantly higher in the Holocene compared with the late Pleistocene, reflecting overall warmer temperatures and increased runoff during the Holocene. A Holocene maximum in organic carbon was observed at about 6 ka, and may represent the warmest/wettest period of the Holocene. At one site (Academician Ridge) pronounced late Pleistocene maxima in organic carbon and biogenic silica were observed at about 80-85 ka, probably indicative of an interstadial period with enhanced aquatic productivity. Total sedimentary lignin phenol contents were generally lower in the late Pleistocene compared to the Holocene, but with several peaks in concentration during the late Pleistocene. These late Pleistocene peaks in total sedimentary lignin content (dated at about 80, 50 and 30 ka) directly precede or occur during peaks in sedimentary biogenic silica contents. These periods likely represent relatively warm interstadial times, with increased precipitation producing the observed increase in terrestrial runoff and aquatic productivity. Lignin phenol ratios (S/V, C/V and P/V) were used to examine changes in terrestrial vegetation type resulting from changes in paleoenvironmental conditions during the late Pleistocene. A degree of caution must be used in the interpretation of these ratios with regard to vegetation sources and paleoenvironmental conditions, because of potential compositional changes in lignin resulting from biodegradation. Nevertheless, results show that long glacial periods were characterized by terrestrial vegetation composed of a mix of non-woody angiosperm vegetation and minor gymnosperm forest. Shorter interstadial periods are defined by a change to dominant gymnosperm forest and were observed at about 80, 75, 63, 50 and 30 ka, ranging from about 2-6 kyr in duration. These interstadial periods of the late Pleistocene defined by lignin phenol ratios generally occur during longer periods of enhanced sedimentary biogenic silica content (about 10-15 ka in duration), providing corroborative evidence of these warm interstadial periods. (C) 1997 Elsevier Science Ltd. VL - 27 IS - 3-4 N1 - Yq252Times Cited:29Cited References Count:61 JO - Lignin phenols in sediments of Lake Baikal, Siberia: application to paleoenvironmental studies ER - TY - JOUR T1 - Mass transport deposits of Amazon Fans JF - Proceedings of the Ocean Drilling Program: Scientific Results Y1 - 1997 A1 - Piper, D. J. A1 - Pirmez, C. A1 - Flood, R. A1 - Long, D. A1 - Manely, P. A1 - Normark, W. A1 - Showers, W. VL - 155 N1 - id: 1279 ER - TY - JOUR T1 - Mediterranean deltas: subsidence as a major control of relative sea-level rise JF - Bulletin de l'Institut oceanographique(Monaco) Y1 - 1997 A1 - Stanley, D. J. N1 - id: 1284 ER - TY - JOUR T1 - Molecular radiocarbon dating of archeological artifacts and marine muds JF - Woods Hole Oceanographic Institution 1996 Annual Report Y1 - 1997 A1 - Eglinton, T. I. N1 - id: 368 ER - TY - CONF T1 - The National Ocean Sciences AMS (NOSAMS) Sample Preparation Laboratory: Systems and Graphite Performance Analysis T2 - International Radiocarbon Conference Y1 - 1997 A1 - Gagnon, A. R. A1 - McNichol, A. P. A1 - Donoghue, J. C. A1 - Morin, T. J. A1 - Peden, J. C. JF - International Radiocarbon Conference CY - Groningen, Nethlands N1 - id: 962 ER - TY - CONF T1 - The NOSAMS sample preparation laboratory: overview of systems and techniques T2 - 16th International Radiocarbon Conference Y1 - 1997 A1 - Gagnon, A. R. A1 - McNichol, A. A1 - Donoghue, J. C. A1 - Merkle, K. M. A1 - Morin, T. J. JF - 16th International Radiocarbon Conference PB - Book of Abstracts CY - Groningen N1 - id: 955 ER - TY - JOUR T1 - P13N final report for AMS 14C samples JF - Ocean Tracer Laboratory Technical Report Y1 - 1997 A1 - Key, R. M. A1 - Quay, P. D. VL - 97 IS - 3 N1 - id: 1254 JO - P13N final report for AMS 14C samples ER - TY - JOUR T1 - P14C final report for AMS 14C samples JF - Ocean Tracer Laboratory Tech. Report Y1 - 1997 A1 - Key, R. M. VL - 97 IS - 4 N1 - id: 1255 ER - TY - JOUR T1 - P16A17A final report for AMS 14C samples JF - Ocean Tracer Laboratory Tech. Report Y1 - 1997 A1 - Key, R. M. VL - 97 IS - 2 N1 - id: 1253 ER - TY - THES T1 - Paleoceanographic Variability on a Millennial Scale: A High Resolution Record of the Latest Deglaciation from the Blake Outer Ridge, Western North Atlantic, Thesis Y1 - 1997 A1 - Schlegel, Mary Ann VL - MS ER - TY - JOUR T1 - Paleoclimatic implications of Holocene lake-level fluctuations, Owasco Lake, New York: Comment JF - Geology Y1 - 1997 A1 - Balco, G. A1 - Belknap, D. F. A1 - Kelley, J. T. VL - 25 IS - 4 N1 - Wu319Times Cited:0Cited References Count:7 JO - Paleoclimatic implications of Holocene lake-level fluctuations, Owasco Lake, New York: Comment ER - TY - JOUR T1 - Paleoclimatic implications of silicieous microfossil succession in late Quaternary sediments in Lake Baikal, Siberia JF - Journal of Paleolimnology Y1 - 1997 A1 - Julius, M. L. A1 - Stoermer, E. F. A1 - Colman, S. M. A1 - Moore, T. C. VL - 18 N1 - id: 1354 ER - TY - JOUR T1 - Paleocology research in Great Lakes (U.S.A.)National Parks JF - Abstracts for American Society of Limnology and Oceanography Y1 - 1997 A1 - Winkler, M. G. N1 - id: 1300 ER - TY - RPRT T1 - Paleoecological research at Isle Royale, Apostle Islands, and Voyageurs National Parks. Report Y1 - 1997 A1 - Winkler, M. G. A1 - Sanford, P. R. N1 - id: 1321 ER - TY - RPRT T1 - Paleogeography and sedimentary evolution of Nauset Marsh estuary, Cape Cod, MA. Final Report to the National Park Service Y1 - 1997 A1 - Allen, J. R. A1 - Boothroyd, J. N1 - id: 1311 ER - TY - JOUR T1 - Paleolimnology research at Isle Royale, Apostle Island, and Voyageurs National Parks JF - USGS Biological Resources Division, Global Change Research Program Y1 - 1997 A1 - Winkler, M. G. A1 - Sanford, P. R. VL - Summary Report N1 - id: 1299 ER - TY - CONF T1 - Possible role of climate in the collapse of the Akkadian Empire: evidence from Gulf of Oman marine sediments T2 - AGU Fall Meeting Y1 - 1997 A1 - Cullen, H. JF - AGU Fall Meeting CY - San Francisco, California N1 - id: 1235 ER - TY - JOUR T1 - Postglacial relative sea level history from sediment and diatom rcords of emerged coastal lakes, north-central Kola Peninsula, Russia JF - Boreas Y1 - 1997 A1 - Snyder, J. A. A1 - Forman, S. L. A1 - Mode, W. N. A1 - Tarasov, G. A. VL - 26 N1 - id: 379 ER - TY - JOUR T1 - Precise temporal correlation of Holocene mollusc shells using sclerochronology JF - Palaeogeography, Paleoclimatology, Paleoecology Y1 - 1997 A1 - Marchitto, T. M. A1 - Jones, G. A. A1 - Goodfriend, G. A. A1 - Weidman, C. R. A1 - Jirikowic, J. N1 - id: 1293 ER - TY - RPRT T1 - Preliminary paleoecology study of Salt Pond and Nauset Lagoon, Cape Cod National Seashore (Report) Y1 - 1997 A1 - Cole, K. A1 - Winkler, M. G. A1 - Sanford, P. R. PB - National Park Service, North Atlantic Region VL - Final Report N1 - id: 131 ER - TY - JOUR T1 - Preliminary results of the first drilling on Lake Baikal, Buguldeika site, southeastern Siberia JF - Quaternary International Y1 - 1997 A1 - Baikal Members, B. D. Drilling Project AB - The Baikal Drilling Project (BDP) is a multinational effort to investigate the paleoclimatic history and tectonic evolution of the Baikal sedimentary basin during the Late Neogene. In March 1993 the Baikal drilling system was successfuly deployed from a barge frozen into position over a topographic high, termed the Buguldeika saddle, in the southern basin of Lake Baikal. The BDP-93 scientific team, made up of Russian, American and Japanese scientists, successfully recovered the first long (>100 m) hydraulic piston cores from two holes in 354 m of water. High quality cores of 98 m (Hole 1) and 102 m (Hole 2), representing sedimentation over the last 500,000 years, were collected in 78 mm diameter plastic liners with an average recovery of 72% and 90%, respectively. Magnetic susceptibility logging reveals an excellent hole-to-hole correlation. In this report the scientific team describes the preliminary analytical results from BDP-93 hole 1 cores. Radiocarbon dating by accelerator mass spectrometry provides an accurate chronology for the upper portion of Hole 1. Detailed lithologic characteristics, rock magnetic properties and inorganic element distributions show a significant change to the depositional environment occuring at 50 m subbottom depth, approximately 250,000 BP. This change may be due to uplift and rotation of the horst block in the Buguldeika saddle. The sedimentary section above 50 m is pelitic with varve-like laminae, whereas the section below 50 m contains a high proportion of sand and gravel horizons often organized into turbidite sequences. Accordingly, high resolution seismic records reveal a change in sonic velocity at this depth. It is inferred that sedimentation prior to 250 ka BP was from the west via the Buguldeika river system. After 250 ka BP the Buguldeika saddle reflects an increase in hemipelagic sediments admixed with fine-grained material from the Selenga River drainage basin, east of Lake Baikal. Variations in the spore-pollen assemblage, diatoms, biogenic silica content, rock magnetic properties, clay mineralogy and organic carbon in the upper 50 m of BDP-93-1 reveal a detailed record of climate change over approximately the last 250,000 years. These variables alternate in a pattern characteristic of glacial/interglacial climatic fluctuations. The present age model suggests that the climate signal recorded in Lake Baikal sediments is similar to Late Quaternary signals recorded in Chinese loess sections and in marine sediments. VL - 37 N1 - id: 188 JO - Preliminary results of the first drilling on Lake Baikal, Buguldeika site, southeastern Siberia ER - TY - JOUR T1 - Preliminary results of the first scientific drilling on Lake Baikal, Buguldeika site, southeastern Siberia JF - Quaternary International Y1 - 1997 A1 - Colman, S. A1 - Grachev, M. A1 - Hearn, P. A1 - Horie, S. A1 - Kawai, T. A1 - Kuzmin, M. A1 - Logachov, N. A1 - Fialkov, V. A1 - Gorigljad, A. A1 - Tomilov, B. A1 - Khakhaev, B. A1 - Kochikov, S. A1 - Lykov, V. A1 - Pevzner, L. A1 - Bucharov, A. A1 - Karabanov, E. A1 - Logachev, N. A1 - Mats, V. A1 - Bardardinov, A. A1 - Baranova, E. A1 - Khlystov, O. A1 - Khrachenko, V. A1 - Shimaraeva, M. A1 - Stolbova, E. A1 - Komakova, E. A1 - Efremova, S. A1 - Gvozdkov, A. A1 - Kravchinski, V. A1 - Peck, J. A1 - Fileva, T. A1 - Kashik, S. A1 - Khramtsova, T. A1 - Kalashnikova, I. A1 - Rasskazova, T. A1 - Tatarnikova, V. A1 - Yuretich, R. A1 - Mazilov, V. A1 - Takemura, K. A1 - Bobrov, V. A1 - Gunicheva, T. A1 - Haraguchi, H. A1 - Ito, S. A1 - Kocho, T. A1 - Kuzmin, M. A1 - Markova, M. A1 - Pampura, V. A1 - Proidakova, O. A1 - Ishiwatari, R. A1 - Sawatari, H. A1 - Takeuchi, A. A1 - Toyoda, K. A1 - Vorobieva, S. A1 - Ikeda, A. A1 - Marui, A. A1 - Nakamura, T. A1 - Ogura, K. A1 - Ohta, T. A1 - King, J. A1 - Sakai, H. A1 - Yokoyama, T. A1 - Hayashida, A. A1 - Bezrukova, E. A1 - Fowell, S. A1 - Fuji, N. A1 - Letunova, P. A1 - Misharina, V. A1 - Miyoshi, N. A1 - Chernyaeva, G. A1 - Ignatova, I. A1 - Likhoshvai, E. A1 - Stoermer, E. A1 - Granina, L. A1 - Levina, O. A1 - Dolgikh, P. A1 - Lazo, F. A1 - Lutskaia, N. A1 - Orem, W. A1 - Wada, E. A1 - Williams, D. A1 - Yamada, K. A1 - Yamada, S. A1 - Callander, E. A1 - Golobokoval, L. A1 - Shanks, P. A1 - Dorofeeva, R. A1 - Duchkov, A. KW - asia KW - tectonics AB - The Baikal Drilling Project (BDP) is a multinational effort to investigate the paleoclimatic history and tectonic evolution of the Baikal sedimentary basin during the Late Neogene. In March 1993 the Baikal drilling system was successfuly deployed from a barge frozen into position over a topographic high, termed the Buguldeika saddle, in the southern basin of Lake Baikal. The BDP-93 scientific team, made up of Russian, American and Japanese scientists, successfully recovered the first long (>100 m) hydraulic piston cores from two holes in 354 m of water. High quality cores of 98 m (Hole 1) and 102 m (Hole 2), representing sedimentation over the last 500,000 years, were collected in 78 mm diameter plastic liners with an average recovery of 72% and 90%, respectively. Magnetic susceptibility logging reveals an excellent hole-to-hole correlation. In this report the scientific team describes the preliminary analytical results from BDP-93 hole 1 cores. Radiocarbon dating by accelerator mass spectrometry provides an accurate chronology for the upper portion of Hole 1. Detailed lithologic characteristics, rock magnetic properties and inorganic element distributions show a significant change to the depositional environment occuring at 50 m subbottom depth, approximately 250,000 BP. This change may be due to uplift and rotation of the horst block in the Buguldeika saddle. The sedimentary section above 50 m is pelitic with varve-like laminae, whereas the section below 50 m contains a high proportion of sand and gravel horizons often organized into turbidite sequences. Accordingly, high resolution seismic records reveal a change in sonic velocity at this depth. It is inferred that sedimentation prior to 250 ka BP was from the west via the Buguldeika river system. After 250 ka BP the Buguldeika saddle reflects an increase in hemipelagic sediments admired with fine-grained material from the Selenga River drainage basin, east of Lake Baikal. Variations in the spore-pollen assemblage, diatoms, biogenic silica content, rock magnetic properties, clay mineralogy and organic carbon in the upper 50 m of BDP-93-1 reveal a detailed record of climate change over approximately the last 250,000 years. These variables alternate in a pattern characteristic of glacial/interglacial climatic fluctuations. The present age model suggests that the climate signal recorded in Lake Baikal sediments is similar to Late Quaternary signals recorded in Chinese loess sections and in marine sediments. Copyright (C) 1996 INQUA/Elsevier Science Ltd VL - 37 SN - 1040-6182 IS - 17 March N1 - Vq100Times Cited:44 Cited References Count:29 JO - Quatern Int ER - TY - JOUR T1 - Productivity-induced sulphur enrichment of hydrocarbon-rich sediments from the Kimmeridge Clay Formation JF - Chem Geol Y1 - 1997 A1 - Lallier-Verges, E. A1 - Hayes, J. M. A1 - Boussafir, M. A1 - Zaback, D. A. A1 - Tribovillard, N. P. A1 - Connan, J. A1 - Bertrand, P. AB - This work aims to highlight the relationship between primary productivity, sulphate reduction and organic carbon preservation in cyclic marine sediments from the Kimmeridge Clay Formation. A concomitant increase of the total sulphur content with the preserved organic content (TOC), shows the progressive supply of both metabolisable organic matter and resistant organic matter is linked to primary productivity. However, variations in sulphate reduction efficiency, based on elemental abundance and isotopic composition of sulphur, reveal that the proportion of metabolisable vs. resistant organic matter has varied along the cycles. This is interpreted in terms of the variation in organic delivery. Organic sulphur content is found to be proportional to the organic matter content, whereas concentrations of pyritic sulphur are constant at very high (> 10% TOC) values. This result is explained by a limitation of available iron for pyritisation at times of very high organic flux. Under such conditions, HS- in excess could be responsible for the early formation of organo-sulphur compounds and thus for the preservation of highly aliphatic (i.e. lipid-rich) organic matter. VL - 134 N1 - Lallier-Verges, EHayes, J MBoussafir, MZaback, D ATribovillard, N PConnan, JBertrand, PengResearch Support, Non-U.S. Gov'tNetherlands1997/01/01 00:00Chem Geol. 1997;134:277-88. JO - Productivity-induced sulphur enrichment of hydrocarbon-rich sediments from the Kimmeridge Clay Formation ER - TY - JOUR T1 - Radiocarbon chronology of Namaqualand mudbelt sediments: problems and prospects JF - South African Journal of Science Y1 - 1997 A1 - Meadows, M. E. A1 - Dingle, R. V. A1 - Rogers, J. A1 - Mills, E. G. KW - accumulation rates KW - ages KW - Marine AB - This paper presents the first radiocarbon-dated chronology of the mudbelt which occupies the continental shelf around southern Africa. The results confirm the Holocene age of the superficial deposits and suggest that laminations in the sediments of the mudbelt off the Orange River mouth are recent and terrestrially derived. Two anomalies are, however, apparent in the chronology. First, the surface sediments do not provide recent or contemporary radiocarbon ages, as would be expected. Second, the laminated sediments yield ages which are not in stratigraphic sequence and appear to be clustered around the period 1000 to 1700 sri Possible reasons for these anomalies are discussed together with alternative means of deriving a more accurate and reliable chronology for the mudbelt sediments. VL - 93 SN - 0038-2353 IS - 7 N1 - Yb537Times Cited:7 Cited References Count:18 JO - S Afr J Sci ER - TY - THES T1 - Radiolarian Population Changes in the Glacial-Deglacial North Atlantic Ocean: Evidence for Changes in Ocean Circulation, Thesis Y1 - 1997 A1 - French, P. L. PB - University of Maine VL - M. S. ER - TY - JOUR T1 - Recent subsidence of the northern Suez canal JF - Nature Y1 - 1997 A1 - Stanley, D. J. A1 - Goodfriend, G. A. VL - 388 IS - 6640 N1 - Xm528Times Cited:16Cited References Count:10 JO - Recent subsidence of the northern Suez canal ER - TY - JOUR T1 - Regional, Holocene records of the human dimension of global change: Sea-level and land-use change in prehistoric Mexico JF - Global and Planetary Change Y1 - 1997 A1 - Sluyter, A. AB - Regional, Holocene records hold particular relevance for understanding the reciprocal nature of global environmental change and one of its major human dimensions: ''sustainable agriculture'', i.e., food production strategies which entail fewer causes of and are less susceptible to environmental change. In an epoch of accelerating anthropogenic transformation, those records reveal the protracted regional causes and consequences of change (often agricultural) in the global system as well as informing models of prehistoric, intensive agriculture which, because of long tenures and high productivities, suggest strategies for sustainable agricultural in the present. This study employs physiographic analysis and the palynological, geochemical record from cores of basin fill to understand the reciprocal relation between environmental and land-use change in the Gulf of Mexico tropical lowland, focusing on a coastal basin sensitive to sea-level change and containing vestiges of prehistoric settlement and wetland agriculture. Fossil pollen reveals that the debut of maize cultivation in the Laguna Catarina watershed dates to ca. 4100 BC, predating the earliest evidence for that cultivar anywhere else in the lowlands of Middle America. Such an early date for a cultivar so central to Neotropical agroecology and environmental change, suggests the urgency of further research in the study region. Moreover, the longest period of continuous agriculture in the basin lasted nearly three millennia (ca. 2400 BC-AD 550) despite eustatic sea-level rise. Geochemical fluxes reveal the reciprocity between land-use and environmental change: slope destabilization, basin aggradation, and eutrophication. The consequent theoretical implications pertain to both applied and basic research. Redeploying ancient agroecologies in dynamic environments necessitates reconstructing the changing operational contexts of putative high productivity and sustainability. Adjusting land use in the face of global warming and eustatic sea-level rise necessitates understanding sediment influxes to coastal basins which, in turn, depend on vegetation, climate, and land use in watersheds. VL - 14 IS - 3-4 N1 - Wk148Times Cited:17Cited References Count:116 JO - Regional, Holocene records of the human dimension of global change: Sea-level and land-use change in prehistoric Mexico ER - TY - CONF T1 - Reproducibility of 14C AMS analyses at NOSAMS T2 - 16th International Radiocarbon Conference Y1 - 1997 A1 - Elder, K. L. A1 - Gagnon, A. R. A1 - McNichol, A. P. JF - 16th International Radiocarbon Conference PB - Book of Abstracts CY - Groningen N1 - id: 961 ER - TY - JOUR T1 - Sedimentology of terrigenous mud from the Orange River delta and the inner shelf off Namaqualand, South Africa JF - South African Geographical Journal Y1 - 1997 A1 - Mabote, M. A1 - Rogers, J. A1 - Meadows, M. E. AB - Sediment cores, from the inner shelf off the Namaqualand continental shelf have been examined using radiographic and grain-size techniques. Size-frequency distributions reveal that the sediments are poly modal, with a dominant very fine-silt mode being between 8-4μm, and suggest that the weak, poleward-flowing De Decker Current causes southward dispersal of terrigenous mud off the Orange River mouth. It appears that this current is not strong enough to transport material coarser than very fine silt. Material >63μm in size is rare, but may be indicative of storm events. Quartz and mica in the sediments are related to the semi-arid climate of Namaqualand, where they are entrained by adiabatic Berg winds moving offshore from the interior. Sponge spicules indicate the presence of filter-feeding animals (epifauna). Planktonic foraminifera may be indicative of relatively high productivity associated with nutrient-rich upwelling waters, which support an enormous population of plankton. The presence of faecal pellets is associated with the presence of burrowing infauna. Authigenic gypsum is associated with the presence of anaerobic conditions in the sediments. Two of the lithofacies identified in these fine-grained deposits are: (a) laminated mud and (b) homogeneous mud. Primary sedimentary structures are present, particularly in the portion of the mudbelt closest to the Orange Delta, where the mud is well laminated. Laminations decrease in abundance southward from the delta, where the muddy sediment is increasingly bioturbated (burrowed) by infauna, probably by polychaete worms. VL - 79 IS - 2 N1 - id: 218 JO - Sedimentology of terrigenous mud from the Orange River delta and the inner shelf off Namaqualand, South Africa ER - TY - JOUR T1 - Source and contribution of terrigenous organic carbon to surface sediments in the Gulf of Mexico JF - Nature Y1 - 1997 A1 - Goñi, M. A. A1 - Ruttenberg, K. C. A1 - Eglinton, T. I. AB - The sources and burial professes of organic matter in marine sediments are not well understood, yet they are important if we are to have a better understanding of the global carbon cycle(1). In particular, the nature and fraction of the terrestrial organic carbon preserved in marine sediments is poorly constrained. Here we use the chemical and stable carbon isotope signatures of oxidation products from a macromolecular component (lignin)(2) of the terrigenous organic matter preserved in offshore surface sediments in the Gulf of Mexico to complement similar data from an existing onshore transect(3) in this region. The complete onshore-offshore data set, along with radiocarbon dates of the bulk organic material at the same sites, allows the differentiation of material originating from plants that photosynthesize using the C-4 mechanism from those that undergo C-3 photosynthesis. We conclude that the offshore lignins derive from erosion of the extensive grassland (C-4) soils Of the Mississippi River drainage basin, and that the nearshore lignins originate largely from C-3 plant detritus from coastal forests and swamps, This distribution is probably due to the hydrodynamic sorting of the different source materials(4) during their seaward transport, These results suggest that previous studies(3,5) have significantly underestimated the terrigenous fraction of organic matter in offshore sediments by not recognizing the contribution of C-4 vegetation to the carbon-isotope composition. Such an underestimate may force revisions in the assessment of past marine primary productivity and associated organic carbon fluxes(6), and of organic matter preservation/remineralization(7) and nutrient cycling(8) in marine sediments. VL - 389 IS - 6648 N1 - Xw772Times Cited:194Cited References Count:30 JO - Source and contribution of terrigenous organic carbon to surface sediments in the Gulf of Mexico ER - TY - JOUR T1 - Stratigraphic evolution of the inner continental shelf in response to late Quaternary relative sea-level change, northwestern Gulf of Maine JF - Geological Society of America Bulletin Y1 - 1997 A1 - Barnhardt, W. A. A1 - Belknap, D. F. A1 - Kelley, J. T. AB - Accumulations of deltaic and littoral sediments on the inner continental shelf of Maine, Gulf of Maine, preserve a record of postglacial sea-level changes and shoreline migrations, The depositional response of coastal environments to a cycle of regression, lowstand, and transgression was examined with seismic-reflection profiles, vibracores, and radiocarbon dates collected from sediments at the mouths of the Kennebec and Penobscot Rivers, Sequence-stratigraphic analysis of these data reveals two distinctly different successions of late Quaternary deposits that represent end members in an evolutionary model for this glaciated coast. Seaward of the Kennebec River, coarse-grained shorelines with foreset beds occur at depths of 20-60 m and outline the lobate margin of the Kennebec River paleodelta, a complex, rock-framed accumulation of glaciomarine and deltaic sediments capped by estuarine and marine deposits, Sand derived from this system today supports large barrier spits and extensive salt marshes, In contrast, the mouth of the Penobscot River is characterized by thick deposits of glaciomarine mud overlain by marine mud of Holocene age, including gas-charged zones that have locally evolved into fields of pockmarks, The distinct lark of sand and gravel seaward of the Penobscot River and its abundance seaward of the Kennebec River probably reflect differences in sediment som ces and the physiography of the two watersheds, The contrasting stratigraphic framework of the se systems demonstrates the importance of understanding local and regional differences in sediment supply, sea-level change, bedrock structure, and exposure to waves and tides in older to model river-mouth deposition on glaciated coasts.Evolution of shelf deposits was largely controlled by relative sea level, which locally fell from a highstand (+60 to +70 m at 14 ka) contemporary with deglaciation to a lowstand (-55 m at 10.8 ka), The sea-level lowering was accompanied by fluvial incision of older deposits, producing a regressive, basal unconformity, Major rivers deposited abundant sediment over this surface, Sea level then rose at varying rates, extensively reworking formerly emergent parts of the shelf and producing a shoreface ravinement surface in areas exposed to waves, A tidal ravinement surface has developed in sheltered embayments where erosion is due mainly to tidal currents. Incised valleys in both settings preserve transgressive estuarine deposits that contain lagoonal bivalves and salt-marsh foraminifera at depths of 15-30 m, These deposits accumulated ca, 9.2-7.3 ka, locally a period of relatively slow sea-level rise. VL - 109 IS - 5 N1 - Wy671Times Cited:38Cited References Count:65 JO - Stratigraphic evolution of the inner continental shelf in response to late Quaternary relative sea-level change, northwestern Gulf of Maine ER - TY - JOUR T1 - Synchronous, high-frequency oscillations in tropical sea surface temperatures and North Atlantic Deep Water production during the last glacial cycle JF - Paleoceanography Y1 - 1997 A1 - Curry, W. B. A1 - Oppo, D. W. AB - Stable isotopic measurements of G. sacculifer and C. wuellerstorfi in a core from the western equatorial Atlantic imply that there are parallel, suborbital oscillations in surface water hydrography and deep water circulation occurring during oxygen isotope stages 2 and 3. Low values of G. sacculifer delta(18)O accompany high values of C. wuellerstorfi delta(13)C, linking warmer sea surface temperatures (SSTs) in the tropics with increased production of lower North Atlantic Deep Water (NADW). The amplitude of the delta(18)O oscillations is 0.6 parts per thousand (or 2 degrees-3 degrees C), which is superimposed on a glacial/interglacial amplitude of about 2.1 parts per thousand,. Using the G. sacculifer delta(18)O data, we calculate that surface waters were colder during stage 2 than calculated by CLIMAP [1976, 1981]. The longer-period (> 2 kyr) oscillations in air temperature recorded in the Greenland and Antarctic ice cores appear to correlate with oscillations in sea surface temperature in the equatorial Atlantic. The magnitude of these oscillations in tropical SST is too large to have resulted from changes in meridional heat transport caused by the global conveyor alone. The apparent synchroneity of equatorial SST and polar air temperature changes, as well as the amplitude of the SST changes at the equator, are consistent with the climate effects expected from changes in the atmosphere's greenhouse gas content (H(2)0(vapor), CO2, and CH4). VL - 12 IS - 1 N1 - Wd891Times Cited:109Cited References Count:63 JO - Synchronous, high-frequency oscillations in tropical sea surface temperatures and North Atlantic Deep Water production during the last glacial cycle ER - TY - CONF T1 - Target preparation for continuous flow accelerator mass spectrometry T2 - 16th International Radiocarbon Conference Y1 - 1997 A1 - Schneider, R. J. A1 - Hayes, J. M. A1 - Eglinton, T. I. A1 - McNichol, A. P. A1 - von Reden, K. F. JF - 16th International Radiocarbon Conference CY - Groningen VL - Book of Abstracts N1 - id: 953 ER - TY - JOUR T1 - Target preparation for continuous flow accelerator mass spectrometry JF - Radiocarbon Y1 - 1997 A1 - Schneider, R. J. A1 - Hayes, J. M. A1 - von Reden, K. F. A1 - McNichol, A. P. A1 - Eglinton, T. I. VL - 40 N1 - id: 1661 ER - TY - JOUR T1 - Target preparation for continuous flow accelerator mass spectrometry: (Proceedings of the 16th International Radiocarbon Conference, 1997) JF - Radiocarbon Y1 - 1997 A1 - Schneider, R. J. A1 - Hayes, J. M. A1 - von Reden, K. F. A1 - McNichol, A. P. A1 - Eglinton, T. VL - 40 N1 - id: 1752 ER - TY - THES T1 - An updated high resolution chronology of deglaciation and accompanying marine transgression in Maine, Thesis Y1 - 1997 A1 - Dorion, C. C. PB - University of Maine CY - Orono, Maine VL - Dissertation/Thesis ER - TY - JOUR T1 - Variability in radiocarbon ages of individual organic compounds from marine sediments JF - Science Y1 - 1997 A1 - Eglinton, T. I. A1 - BenitezNelson, B. C. A1 - Pearson, A. A1 - McNichol, A. P. A1 - Bauer, J. E. A1 - Druffel, E. R. M. AB - Organic carbon (OC) from multiple sources can be delivered contemporaneously to aquatic sediments. The influence of different OC inputs on carbon-14-based sediment chronologies is illustrated in the carbon-14 ages of purified, source-specific (biomarker) organic compounds from near-surface sediments underlying two contrasting marine systems, the Black Sea and the Arabian Sea, In the Black Sea, isotopic heterogeneity of n-alkanes indicated that OC was contributed from both fossil and contemporary sources. Compounds reflecting different source inputs to the Arabian Sea exhibit a 10,000-year range in conventional carbon-14 ages. Radiocarbon measurements of biomarkers of marine photoautotrophy enable sediment chronologies to be constructed independent of detrital OC influences. VL - 277 IS - 5327 N1 - Xq247Times Cited:175Cited References Count:37 JO - Variability in radiocarbon ages of individual organic compounds from marine sediments ER - TY - RPRT T1 - Western Great Lakes Paleoecology Study. Report Y1 - 1997 A1 - Winkler, M. G. A1 - Sanford, P. R. PB - National Biological Service Global Climate Change Initiative VL - Interim Report N1 - id: 1322 ER - TY - JOUR T1 - Western Great Lakes regional paleoenvironmental changes: island and inland contrasts JF - Ecological Society of America Bulletin Y1 - 1997 A1 - Winkler, M. G. A1 - Sanford, P. R. A1 - Cole, K. L. A1 - Flakne, R. L. N1 - id: 1301 ER - TY - JOUR T1 - Western South Atlantic deepwater hydrography derived from benthic Cd/Ca and stable isotope data JF - Supplement to EOS Y1 - 1997 A1 - Horowitz, M. A1 - Oppo, D. W. VL - 17 IS - 78 N1 - id: 1269 ER - TY - JOUR T1 - A 27,000 year record of Red Sea Outflow: Implication for timing of post-glacial monsoon intensification JF - Geophysical Research Letters Y1 - 1996 A1 - Naqvi, W. A. A1 - Fairbanks, R. G. AB - We reconstruct here the history of the Red Sea Outflow (RSO) over the past 27,000 years from an AMS C-14-dated high-resolution delta(13)C record of benthic foraminifera from the inner Gulf of Aden assuming the dominance of circulation over productivity in regulating benthic delta(13)C. The results reveal that, following a period of suppressed RSO due to shallow sill 24,000-18,000 yr BP, the Red Sea was vigorously flushed for similar to 2,000 years before a major monsoon intensification caused the cessation of deep water formation from 15,500 to 7,300 yr BP. It appears that the monsoon intensification did lag behind insolation until 15,500 yr BP. Between 15,500 and the present, however, there was no lag in conflict with the previous reports, implying a negligible dampening effect of continental albedo during this period. However, since our analysis is confined to a single depth horizon and our record is sensitive to sea level, it has some limitations as an indicator of monsoon intensity. VL - 23 IS - 12 N1 - Up857Times Cited:16Cited References Count:27 JO - A 27,000 year record of Red Sea Outflow: Implication for timing of post-glacial monsoon intensification ER - TY - JOUR T1 - An 84-kyr paleomagnetic record from the sediments of Lake Baikal, Siberia JF - Journal of Geophysical Research-Solid Earth Y1 - 1996 A1 - Peck, J. A. A1 - King, J. W. A1 - Colman, S. M. A1 - Kravchinsky, V. A. AB - We have conducted a paleomagnetic study of sediment cores obtained from the Selenga prodelta region of Lake Baikal, Russia. This record, which spans approximately the last 84 kyr, contributes to a better understanding of the nature of geomagnetic field behavior in Siberia and is a useful correlation and dating tool. We demonstrate that the Lake Baikal sediments are recording variations in the geomagnetic field. The directional record displays secular variation behavior with a geomagnetic excursion at 20 ka and additional excursions appearing as large-amplitude secular variation at 41, 61, and 67 ka. Smoothing of the geomagnetic excursion behavior occurs in Lake Baikal sediments owing to the intermediate sedimentation rate (13 cm kyr(-1)). The Lake Baikal relative paleointensity record correlates to absolute paleointensity data for the last 10 kyr and to relative paleointensity records from the Mediterranean Sea and Indian Ocean for the last 84 kyr. This correlation suggests a strong global (i.e., dipole) component to these records and further supports the reliability of sediments as recorders of relative geomagnetic paleointensity. We show that a relative geomagnetic intensity stratigraphy has a potential resolution of 7 kyr by correlating continental and marine records. The geomagnetic intensity stratigraphy helps constrain the age of the difficult to date Lake Baikal sediments. VL - 101 IS - B5 N1 - Ul090Times Cited:76Cited References Count:48 JO - An 84-kyr paleomagnetic record from the sediments of Lake Baikal, Siberia ER - TY - CHAP T1 - Agroecological perspectives on the decline of the Tiwanaku State (Book Section) T2 - Tiwanaku and its Hinterland: Archaeology and Paleoecology of an Andean Civilization Y1 - 1996 A1 - Kolata, Alan L. A1 - Ortloff, Charles R. ED - Kolata, Alan L. JF - Tiwanaku and its Hinterland: Archaeology and Paleoecology of an Andean Civilization PB - Smithsonian Institution Press, Washington, DC VL - 1 N1 - id: 1258 ER - TY - CONF T1 - Altithermal of the Canadian Rockies; timing and internal structure; evidence from lake sediments T2 - 14th biennial meeting of the American Quaternary Association Y1 - 1996 A1 - Leonard, Eric A1 - Resoner, Mel JF - 14th biennial meeting of the American Quaternary Association CY - Flagstaff, AZ VL - 14 N1 - id: 1262 ER - TY - CONF T1 - AMS measurements of the 14C distribution in the Pacific Ocean T2 - 7th International Conference on Accelerator Mass Spectrometry Y1 - 1996 A1 - von Reden, K. F. A1 - McNichol, A. P. A1 - Schneider, R. J. JF - 7th International Conference on Accelerator Mass Spectrometry PB - Radiocarbon CY - Tucson, AZ VL - 38 N1 - id: 950; 1 ER - TY - JOUR T1 - AMS radiocarbon analyses from Lake Baikal, Siberia: Challenges of dating sediments from a large, oligotrophic lake JF - Quaternary Science Reviews Y1 - 1996 A1 - Colman, S. M. A1 - Jones, G. A. A1 - Rubin, M. A1 - King, J. W. A1 - Peck, J. A. A1 - Orem, W. H. AB - A suite of 146 new accelerator-mass spectrometer (AMS) radiocarbon ages provides the first reliable chronology for late Quaternary sediments in Lake Baikal. In this large, highly oligotrophic lake, biogenic and authigenic carbonate are absent, and plant macrofossils are extremely rare. Total organic carbon is therefore the primary material available for dating. Several problems are associated with the TOC ages. One is the mixture of carbon sources in TOC, not all of which are syndepositional in age. This problem manifests itself in apparent ages for the sediment surface that are greater than zero. However, because most of the organic carbon in Lake Baikal sediments is algal (autochthonous) in origin, this effect is limited to about 1000+/-500 years, which can be corrected, at least for young deposits. The other major problem with dating Lake Baikal sediments is the very low carbon contents of glacial-age deposits, which makes them extremely susceptible to contamination with modern carbon. This problem can be minimized by careful sampling and handling procedures.The ages show almost an order of magnitude difference in sediment-accumulation rates among different sedimentary environments in Lake Baikal, from about 0.04 mm/year on isolated banks such as Academician Ridge, to nearly 0.3 mm/year in the turbidite depositional areas beneath the deep basin floors, such as the Central Basin. The new AMS ages clearly indicate that the dramatic increase in diatom productivity in the lake, as evidenced by increases in biogenic silica and organic carbon, began about 13 ka, in contrast to previous estimates of 7 ka for the age of this transition. Holocene net sedimentation rates may be less than, equal to, or greater than those in the late Pleistocene, depending on the site. This variability reflects the balance between variable terrigenous sedimentation and increased biogenic sedimentation during interglaciations. The ages reported here, and the temporal and spatial variation in sedimentation rates that they imply, provide opportunities for paleoenvironmental reconstructions at different time scales and resolutions. Published by Elsevier Science Ltd VL - 15 IS - 7 N1 - Vp609Times Cited:112Cited References Count:29 JO - AMS radiocarbon analyses from Lake Baikal, Siberia: Challenges of dating sediments from a large, oligotrophic lake ER - TY - JOUR T1 - Automated systems and techniques utilized at the NOSAMS sample preparation laboratory: An update of productivity and quality issues JF - Radiocarbon Y1 - 1996 A1 - Gagnon, A. R. A1 - McNichol, A. P. A1 - Hutton, D. L. A1 - Osborne, E. A. A1 - Donoghue, J. C. VL - 38 IS - 1 N1 - id: 959 ER - TY - RPRT T1 - Cape May site report Y1 - 1996 A1 - Miller, K. G. A1 - Liu, C. A1 - Browning, J. V. A1 - Pekar, S. A1 - Sugarman, P. A1 - Van Fossen, M. C. A1 - Mullikin, L. A1 - Queen, D. A1 - Feigenson, M. D. A1 - Aubry, M. P. A1 - Burckle, L. D. A1 - Powars, D. A1 - Heibel, T. PB - Proc. ODP, Init. Repts CY - College Station, TX VL - 150X and suppl. N1 - id: 55 ER - TY - JOUR T1 - Carbon isotopes and the rise of atmospheric oxygen JF - Geology Y1 - 1996 A1 - Karhu, J. A. A1 - Holland, H. D. AB - New data for the isotopic composition of carbon in carbonate sediments deposited between 2.6 and 1.6 Ga indicate that the value of delta(13)C in these sediments underwent a very large positive excursion between 2.22 and 2.06 Ga. A reassessment of the earlier delta(13)C data for carbonate sediments shows that this excursion was probably worldwide, and that it was preceded and followed by several hundred million years during which the delta(13)C of carbonate sediments differed little from that of modern carbonates. The large delta(13)C excursion between 2.22 and 2.06 Ga was probably related to an abnormally high rate of organic carbon deposition, which generated an abnormally high rate of O-2 production, We estimate that the total excess O-2 produced during the excursion was between 12 and 22 times the present atmospheric O-2 inventory. The delta(13)C data therefore suggest that the O-2 content of the atmosphere increased very significantly between 2.22 and 2.06 Ga. This inference is supported strongly by several other lines of evidence. VL - 24 IS - 10 N1 - Vm224Times Cited:257Cited References Count:44 JO - Carbon isotopes and the rise of atmospheric oxygen ER - TY - CONF T1 - Catastrophic discharge of fluvial sediment to the ocean; evidence of jokulhlaups events in the Alsek Sea Valley, Southeast Alaska (USA) T2 - International symposium on Erosion and sediment yield; global and regional perspectives Y1 - 1996 A1 - Milliman, J. D. A1 - Snow, J. A1 - Jaeger, J. A1 - Nittrouer, C. A. ED - Webb, B. W. JF - International symposium on Erosion and sediment yield; global and regional perspectives PB - IAHS-AISH CY - Exeter, United Kingdom VL - 236 N1 - id: 28 ER - TY - JOUR T1 - Character, paleoenvironment, rate of accumulation, and evidence for seismic triggering of Holocene turbidites, Canada Abyssal Plain, Arctic Ocean JF - Marine Geology Y1 - 1996 A1 - Grantz, A. A1 - Phillips, R. L. A1 - Mullen, M. W. A1 - Starratt, S. W. A1 - Jones, G. A. A1 - Naidu, A. S. A1 - Finney, B. P. AB - Four box cores and one piston core show that Holocene sedimentation on the southern Canada Abyssal Plain for the last 8010 +/- 120 yr has consisted of a continuing rain of pelagic organic and ice-rafted elastic sediment with a net accumulation rate during the late Holocene of less than or equal to 10 mm/1000 yr, and episodically emplaced turbidites 1-5 m thick deposited at intervals of 830 to 3450 yr (average 2000 yr). The average net accumulation rate of the mixed sequence of turbidites and thin pelagite interbeds in the cores is about 1.2 m/1000 yr.Physiography suggests that the turbidites originated on the Mackenzie Delta or its clinoform, and delta(13)C values of -27 to -25 parts per thousand in the turbidites are compatible with a provenance on a delta. Extant displaced neritic and lower slope to basin plain calcareous benthic foraminifers coexist in the turbidite units. Their joint occurence indicates that the turbidites originated on the modern continental shelf and entrained sediment from the slope and rise enroute to their final resting place on the Canada Abyssal Plain. The presence of Middle Pleistocene diatoms in the turbidites suggests, in addition, that the turbidites may have originated in shallow submarine slides beneath the upper slope or outer shelf. Small but consistent differences in organic carbon content and delta(13)C values between the turbidite units suggest that they did not share an identical provenance, which is at least compatible with an origin in slope failures.The primary provenance of the ice-rafted component of the pelagic beds was the glaciated terrane of northwestern Canada; and the provenance of the turbidite units was Pleistocene and Holocene sedimentary deposits on the outer continental shelf and upper slope of the Mackenzie Delta. Largely local derivation of the sediment of the Canada Abyssal Plain indicates that sediment accumulation rates in the Arctic Ocean are valid only for regions with similar depositional sources and processes, and that these rates cannot be extrapolated regionally. The location of an elliptical zone of active seismicity over the inferred provenance of the turbidites suggests that they were triggered by large earthquakes.Distal turbidite sediment accumulation rates were more than two orders of magnitude greater than pelagic sediment accumulation rates on the Canada Abyssal Plain during the last 8000 years. This disparity reconciles the discrepancy between the high accumulation rates assumed by some for the Arctic Ocean because of the numerous major rivers and large ice sheets that discharge into this small mediterranean basin and the low pelagic sedimentation rates that have been reported from the Arctic Ocean. VL - 133 IS - 1-2 N1 - Uy014Times Cited:36Cited References Count:46 JO - Character, paleoenvironment, rate of accumulation, and evidence for seismic triggering of Holocene turbidites, Canada Abyssal Plain, Arctic Ocean ER - TY - CHAP T1 - Chemical Composition of Volcanic Gases T2 - Monitoring and Mitigation of Volcano Hazards Y1 - 1996 A1 - Giggenbach, W. F. ED - Scarpa, S. JF - Monitoring and Mitigation of Volcano Hazards PB - Springer Verlag CY - Berlin N1 - id: 1590 ER - TY - JOUR T1 - Chemical weathering and controls on atmospheric O2 and CO2: Fundamental principles were enunciated by J. J. Ebelmen in 1845 JF - Geochimica et Cosmochimica Acta Y1 - 1996 A1 - Berner, Robert A. A1 - Maasch, Kirk A. VL - 60 N1 - id: 1533 JO - Chemical weathering and controls on atmospheric O2 and CO2: Fundamental principles were enunciated by J. J. Ebelmen in 1845 ER - TY - JOUR T1 - Climate connections between the hemisphere revealed by deep sea sediment core ice core correlations JF - Earth and Planetary Science Letters Y1 - 1996 A1 - Charles, C. D. A1 - LynchStieglitz, J. A1 - Ninnemann, U. S. A1 - Fairbanks, R. G. AB - Correlation of Southern Ocean deep sea sediment core records with ice core records of polar climate delineates with unprecedented detail the relationship between high latitude climate and the ocean's thermohaline circulation over the last 80,000 years. Our observations suggest that, while North Atlantic Deep Water variability manifests itself clearly in Southern Ocean nutrient proxy records over periods as short as 500 yr, this deep water variability did not promote a direct link between climate variability in the high latitudes of the two hemispheres on millennial timescales. In particular, the proxy records indicate that, on average, northern hemisphere climate fluctuations lagged those of the southern hemisphere by 1500 yr. VL - 142 IS - 1-2 N1 - Uz230Times Cited:201Cited References Count:33 JO - Climate connections between the hemisphere revealed by deep sea sediment core ice core correlations ER - TY - JOUR T1 - A comparison of methods for the measurement of dissolved organic carbon in natural waters JF - Marine Chemistry Y1 - 1996 A1 - Peltzer, E. T. A1 - Fry, B. A1 - Doering, P. H. A1 - McKenna, J. H. A1 - Norrman, B. A1 - Zweifel, U. L. AB - A small suite of natural samples spanning a wide range of DOC concentrations and salinities were analyzed by three high-temperature combustion (HTC) techniques and persulfate oxidation, One of the HTC techniques, sealed-tube combustion (STC), served as a referee method, Using this method, it was possible to obtain absolute DOC concentrations for the natural samples free of any analytical blank offset, Prior to the comparison of samples, an exchange of carbon-free water and calibration standards showed that all methods were equally well calibrated, Linear correlation analysis was used to differentiate whether the differences observed between methods was due to variable oxidation yields or to an artifact of the instrument blank, Agreement among the various methods was quite good, but yields for all methods decreased compared to the STC technique at concentrations of > 400 mu M C. Persulfate results were found to be very similar to HTC results. Finally, carbon-free distilled water prepared by UV/H2O2 oxidation or Milli-Q systems had near-zero DOC concentrations and was adequate for blank correction of all the various techniques yielding DOC concentrations in excellent agreement with the referee method. VL - 54 IS - 1-2 N1 - Vj296Times Cited:50Cited References Count:49 JO - A comparison of methods for the measurement of dissolved organic carbon in natural waters ER - TY - JOUR T1 - Compound specific radiocarbon analysis as a tool to quantitatively apportion modern and fossil sources of polycyclic aromatic hydrocarbons in environmental matrices. JF - Abstracts of Papers of the American Chemical Society Y1 - 1996 A1 - Eglinton, T. I. A1 - Pearson, A. A1 - McNichol, A. P. A1 - Currie, L. A. A1 - Benner, B. A. A1 - Wise, S. A. VL - 212 SN - 0065-7727 IS - 2 N1 - 1Va915 Times Cited:0 Cited References Count:0 JO - Abstr Pap Am Chem S ER - TY - JOUR T1 - Concentrations of carbonyl compounds and the carbon isotopy of formaldehyde at a coastal site in Nova Scotia during the NARE summer intensive JF - Journal of Geophysical Research: AtmospheresJ. Geophys. Res. Y1 - 1996 A1 - Tanner, Roger L. A1 - Zielinska, Barbara A1 - Uberna, Ewa A1 - Harshfield, Gregory A1 - McNichol, Ann P. KW - 0315 Biosphere/atmosphere interactions KW - 0345 Pollution: urban and regional KW - 0365 Troposphere: composition and chemistry KW - 0394 Instruments and techniques VL - 101 SN - 2156-2202 UR - http://dx.doi.org/10.1029/95JD03574 IS - D22 ER - TY - JOUR T1 - Concentrations of carbonyl compounds and the carbon isotopy of formaldehyde at a coastal site in Nova Scotia during the NARE summer intensive JF - Journal of Geophysical Research-Atmospheres Y1 - 1996 A1 - Tanner, R. L. A1 - Zielinska, B. A1 - Uberna, E. A1 - Harshfield, G. A1 - McNichol, A. P. AB - The concentrations of gaseous atmospheric carbonyl compounds have been measured at a coastal site on the southern tip of Nova Scotia during August 1993 as part of the National Oceanic and Atmospheric Administration's North Atlantic Regional Experiment (NARE) summer intensive. The DNPH-cartridge technique was used for sampling, with analysis by HPLC with UV absorbance detection. The carbon isotopic content of formaldehyde was measured using a novel collection technique on bisulfite-coated fillers followed by accelerator mass spectrometric determination of C-14 content and C-13/C-12 isotopic ratios. Results from this study indicate that quantifiable levels above about 100 parts per trillion by volume were found at the Chebogue Point, Nova Scotia, site for several carbonyls, formaldehyde, acetaldehyde, acetone, propionaldehyde, methyl ethyl ketone, and benzaldehyde, for most 6-hour sampling periods. Six-hour averaged formaldehyde levels of <0.5 to about 3.5 parts per billion were found during periods of local influence and during influence of continental air masses crossing eastern Canada and northeastern US. In contrast, background levels of formaldehyde of 200-400 pptv were found under conditions of predominantly marine back trajectories. Large fractions of contemporary carbon (of the order of 80%) were found in collected formaldehyde samples for all transport regimes and formaldehyde concentrations, suggesting that biogenic sources of hydrocarbon precursors to formaldehyde predominated during the summer season. VL - 101 IS - D22 N1 - Vz788Times Cited:38Cited References Count:42 JO - Concentrations of carbonyl compounds and the carbon isotopy of formaldehyde at a coastal site in Nova Scotia during the NARE summer intensive ER - TY - CONF T1 - Correlated temperature and icerafting records, early deglacial warming, and meltwater signals in V29-191, eastern North Atlantic Ocean T2 - American Quaternary Association Conference Y1 - 1996 A1 - Lagerklint, I. Marianne JF - American Quaternary Association Conference PB - American Quaternary Association VL - 14 N1 - id: 1260 JO - Correlated temperature and icerafting records, early deglacial warming, and meltwater signals in V29-191, eastern North Atlantic Ocean ER - TY - CONF T1 - Dating of explosive volcanic events associated with dome growth at Soufriere Hills volcano, Montserrat T2 - Proceedings of the Special Symposium on Volcanism in Montserrat, Second Caribbean Conference on Natural Hazards and Hazard Management Y1 - 1996 A1 - Young, S. R. A1 - Hoblitt, R. P. A1 - Smith, A. L. A1 - Devine, J. D. A1 - Wadge, G. A1 - Shepherd, J. B. JF - Proceedings of the Special Symposium on Volcanism in Montserrat, Second Caribbean Conference on Natural Hazards and Hazard Management T3 - Montserrat Volcano Observatory Open File Report 96/22 CY - Kingston, Jamaica N1 - id: 1306 ER - TY - CONF T1 - Deep water formation and exchange rates in the Arctic Ocean: Implications from the distribution of 14C T2 - 7th International Conference on Accelerator Mass Spectrometry Y1 - 1996 A1 - Schlosser, P. A1 - Kromer, B. A1 - Ekwurzel, B. A1 - Boenisch, G. A1 - McNichol, A. A1 - Schneider, R. A1 - von Reden, K. A1 - Oestlund, G. JF - 7th International Conference on Accelerator Mass Spectrometry PB - Radiocarbon CY - Tucson, AZ VL - 38 N1 - id: 947; 1 ER - TY - RPRT T1 - The development of Ryder Pond in the Cape Cod National Seashore and determination of the causes of recent Ryder Pondwater chemistry changes. Report Y1 - 1996 A1 - Winkler, Marjorie G. PB - University of Wisconsin Center for Climatic Research CY - Madison, WI VL - NPS/NESO-RNR/NRTR/97-01 N1 - id: 92 ER - TY - CONF T1 - Diatom and sediment evidence for late Holocene hydrologic changes, Everglades National Park T2 - ASLO Meeting Y1 - 1996 A1 - Winkler, M. G. A1 - Kaplan, S. JF - ASLO Meeting CY - Milwaukee, WI N1 - id: 1303 ER - TY - JOUR T1 - Direct U-Th dating of marine sediments from the two most recent interglacial periods JF - Nature Y1 - 1996 A1 - Slowey, N. C. A1 - Henderson, G. M. A1 - Curry, W. B. AB - A KNOWLEDGE of the age of marine sediments is necessary to determine the timing of events and rates of processes in the marine realm, and the relationships among marine and other climatically sensitive records. The establishment of an accurate chronology for Pleistocene marine sediments beyond the range of radiocarbon dating (approximately the past 45 kyr) has therefore been a goal of palaeoceanographers for decades. Early attempts(1,2) based on measurements of the radionuclides Th-230 and Pa-231 mere beset with problems, and subsequent studies focused on tying fluctuations in marine sediment oxygen-isotope records to events such as the formation of col al reef terraces and changes in the Earth's magnetic polarity(3,4), and tuning the resultant chronologies to the Earth's orbitally driven insolation variations(5-8). But these chronologies (especially the age and duration of the last interglacial period) have been challenged by several studies(9-12), raising questions about the fundamental cause of Pleistocene climate fluctuations. Here we report the direct U-Th dating of aragonite-rich marine sediments from the Bahamas, and present an accurately dated marine oxygen-isotope record for the last two interglacials. We obtain dates of 120-127 kyr BP for the last interglacial and 189-190 kyr np for the late stage 7 interglacial. These dates are in accord with the general theory of orbitally forced climate fluctuations and demonstrate the potential of our direct-dating approach for developing an absolute chronology for the Pleistocene marine oxygen-isotope record. VL - 383 IS - 6597 N1 - Vh315Times Cited:39Cited References Count:40 JO - Direct U-Th dating of marine sediments from the two most recent interglacial periods ER - TY - JOUR T1 - Distribution of otoliths in surficial sediments of the U. S. Atlantic continental shelf and slope and potential for reconstructing Holocene fish stocks JF - Paleoceanography Y1 - 1996 A1 - Elder, K. L. A1 - Jones, G. A. A1 - Bolz, G. VL - 11 IS - 3 N1 - id: 1755 ER - TY - JOUR T1 - The early and middle Weichselian interstadials in the central area of the Scandinavian glaciations JF - Quaternary Science Reviews Y1 - 1996 A1 - Donner, J. AB - In the central parts of the Scandinavian glaciations, in Norway, Sweden and Finland, there are a number of Early Weichselian sites with fresh-water sediments, which, by comparison with sites further south, can be correlated with either the Brorup or Odderade interstadials. Few of these sites can with any certainty be correlated with just one of the two. In northern Jutland and at the coast of south-western Norway there are Early Weichselian marine sediments, some of those in Norway having been interpreted as interstadial.Middle Weichselian fresh-water sediments have only been found in Denmark and southern Sweden, whereas marine sediments occur in northern Jutland and at the coast in Norway, in the same areas as the Early Weichselian marine sediments. Most of the Middle Weichselian sites must be referred to as representing an interstadial complex, as a close correlation with the five interstadials identified in northwest Germany and The Netherlands is not possible.A close correlation has been made between the fluctuations in the deep-sea oxygen-isotope curve and the Weichselian history in Scandinavia, the justification for which is discussed. Copyright (C) 1996 Elsevier Science Ltd VL - 15 IS - 5-6 N1 - Vl592Times Cited:10Cited References Count:56 JO - The early and middle Weichselian interstadials in the central area of the Scandinavian glaciations ER - TY - JOUR T1 - East Asian monsoon variations; linkage to northern hemisphere millenniallll-scale climate oscillations JF - Supplement to EOS Y1 - 1996 A1 - Oppo, D. W. A1 - Deiner, L. A1 - Curry, W. B. A1 - Norris, R. D. VL - 77 N1 - id: 56 ER - TY - JOUR T1 - Effects of turbidity flows on organic matter accumulation, sulfate reduction, and methane generation in deep-sea sediments on the Iberia Abyssal Plain JF - Organic Geochemistry Y1 - 1996 A1 - Meyers, P. A. A1 - Silliman, J. E. A1 - Shaw, T. J. AB - Non-steady-state sedimentation has affected preservation of organic matter in a Pliocene-Pleistocene turbidite sequence sampled by the Ocean Drilling Program at four closely spaced drill sites on the Iberia Abyssal Plain. Organic carbon concentrations average ca. 0.7% in sediments from Sites 897 and 898 and ca. 0.4% at Sites 899 and 900. Headspace concentrations of interstitial methane exceed 100,000 ppm in sediments from Sites 897 and 898 but are essentially zero in those from Sites 899 and 900. Methane concentrations do not rise until interstitial sulfate concentrations are virtually depleted, suggesting the presence of deep in situ methanogenic bacterial activity at Sites 897 and 898 and its absence at Sites 899 and 900. Two factors associated with the turbidity flows that created the sedimentary sequence evidently influenced post-depositional diagenesis at these sites. The principal factor is that the rapidly deposited turbidite sequences at Sites 897 and 898 protected organic matter from early oxic degradation and thereby permitted subsequent anoxic degradation to proceed. In contrast, organic matter in the more slowly deposited turbidites at Sites 899 and 900 was oxidized soon after deposition and was therefore not available for later microbial utilization. A lesser factor is that the turbidity flows may have obtained their entrained organic matter from different environments and consequently delivered organic matter with different characteristics. Both factors contributed to heterogeneity of the types and amounts of organic matter that accumulated in these deep-sea sediments, and this variability has influenced subsequent sulfate reduction and methanogenesis. Copyright (C) 1996 Elsevier Science Ltd. VL - 25 IS - 1-2 N1 - Wd943Times Cited:22Cited References Count:33 JO - Effects of turbidity flows on organic matter accumulation, sulfate reduction, and methane generation in deep-sea sediments on the Iberia Abyssal Plain ER - TY - CONF T1 - Evolution of the 14C signal in the surface North Atlantic Ocean T2 - 7th International Conference on Accelerator Mass Spectrometry Abstract Radiocarbon Y1 - 1996 A1 - Weidman, C. R. A1 - Jones, G. A. JF - 7th International Conference on Accelerator Mass Spectrometry Abstract Radiocarbon CY - Tucson, AZ VL - 38 N1 - id: 89; 1 ER - TY - CONF T1 - Expanded Small Sample Capabilities at NOSAMS: Preparation and Analysis of Conventional Graphite Targets Containing 0.15 mg Carbon T2 - 7th International Conference on Accelerator Mass Spectrometry Y1 - 1996 A1 - Pearson, A. A1 - McNichol, A. P. A1 - Schneider, R. J. A1 - von Reden, K. F. JF - 7th International Conference on Accelerator Mass Spectrometry PB - Radiocarbon CY - Tucson, AZ VL - 38 N1 - id: 946; 1 ER - TY - JOUR T1 - Fluxes of mantle and subducted carbon along convergent plate boundaries JF - Geophysical Research Letters Y1 - 1996 A1 - Sano, Y. A1 - Williams, S. N. AB - The potential impact of increases in atmospheric CO2 is a topic of considerable controversy. Even though volcanic emission of CO2 may be very small as compared to anthropogenic emissions, evaluation of natural degassing of CO2 is important for any model of the geochemical C cycle and evolution of the Earth's atmosphere. We report here the mantle C flux in subduction zones based on He and C isotopes and CO2/He-3 ratios of high-temperature volcanic gases and medium- and low-temperature fumaroles in circum-Pacific volcanic regions. The calculated volcanic C flux of 3.1x10(12) mol/a from subduction zones is larger than the flux of 1.5x10(12) mol/a from mid-ocean ridges, while contributions from the mantle in subduction zone is only 0.30x10(12) mol/a, equivalent to about 20% of the C flux in mid-ocean ridges. Since the estimated mantle C flux in hot spot regions is insignificant, 0.029x10(12) mol/a, we propose that the global mantle C flux is 1.8x10(12) mol/a in total. The flux, if accumulated over 4.5 billion year of geological time, amounts to 8.3x10(21) mol which agrees well with 9x10(21) mol of the present inventory of C at the Earth's surface. This may support a continuous degassing model of C or the idea that subducted C is recycled into the lower mantle. VL - 23 IS - 20 N1 - Vl370Times Cited:137Cited References Count:39 JO - Fluxes of mantle and subducted carbon along convergent plate boundaries ER - TY - JOUR T1 - Forcing of Atlantic Equatorial and Subpolar Millennial Cycles by Precession JF - Science Y1 - 1996 A1 - McIntyre, A. A1 - Molfino, B. AB - Abundance cycles of the marine alga Florisphaera profunda centered on a period of 7600 carbon-14 years (8400 calendar years) are present in high-resolution records from the equatorial Atlantic spanning 0 to 45,000 years ago. These cycles correlate with Heinrich events 1 through 5, which document rapid changes in continental ice melting around the subpolar North Atlantic. These variations in F. profunda are a direct response to modulation in zonal wind-driven divergence produced by a precessional component of orbital variation during a time of reduced eccentricity modulation. VL - 274 SN - 1095-9203 (Electronic)0036-8075 (Linking) UR - https://www.ncbi.nlm.nih.gov/pubmed/8943191 IS - 5294 N1 - McIntyreMolfino eng 1996/12/13 Science. 1996 Dec 13;274(5294):1867-70. ER - TY - JOUR T1 - Gas chromatographic isolation of individual compounds from complex matrices for radiocarbon dating JF - Anal Chem Y1 - 1996 A1 - Eglinton, T. I. A1 - Aluwihare, L. I. A1 - Bauer, J. E. A1 - Druffel, E. R. A1 - McNichol, A. P. AB - This paper describes the application of a novel, practical approach for isolation of individual compounds from complex organic matrices for natural abundance radiocarbon measurement. This is achieved through the use of automated preparative capillary gas chromatography (PCGC) to separate and recover sufficient quantities of individual target compounds for (14)C analysis by accelerator mass spectrometry (AMS). We developed and tested this approach using a suite of samples (plant lipids, petroleums) whose ages spanned the (14)C time scale and which contained a variety of compound types (fatty acids, sterols, hydrocarbons). Comparison of individual compound and bulk radiocarbon signatures for the isotopically homogeneous samples studied revealed that Delta(14)C values generally agreed well (+/-10%). Background contamination was assessed at each stage of the isolation procedure, and incomplete solvent removal prior to combustion was the only significant source of additional carbon. Isotope fractionation was addressed through compound-specific stable carbon isotopic analyses. Fractionation of isotopes during isolation of individual compounds was minimal (<5 per thousand for delta(13)C), provided the entire peak was collected during PCGC. Trapping of partially coeluting peaks did cause errors, and these results highlight the importance of conducting stable carbon isotopic measurements of each trapped compound in concert with AMS for reliable radiocarbon measurements. The addition of carbon accompanying derivatization of functionalized compounds (e.g., fatty acids and sterols) prior to chromatographic separation represents a further source of potential error. This contribution can be removed using a simple isotopic mass balance approach. Based on these preliminary results, the PCGC-based approach holds promise for accurately determining (14)C ages on compounds specific to a given source within complex, heterogeneous samples. VL - 68 IS - 5 N1 - Eglinton, T IAluwihare, L IBauer, J EDruffel, E RMcNichol, A Peng1996/03/01 00:00Anal Chem. 1996 Mar 1;68(5):904-12. doi: 10.1021/ac9508513. JO - Gas chromatographic isolation of individual compounds from complex matrices for radiocarbon dating ER - TY - JOUR T1 - Gas venting and late Quaternary sedimentation in the Persian (Arabian) Gulf JF - Marine Geology Y1 - 1996 A1 - Uchupi, E. A1 - Swift, S. A. A1 - Ross, D. A. AB - High resolution 3.5 kHz echo sounding profiles and piston cores were used to reconstruct the microtopography and late Quaternary depositional history of the Persian Gulf. Perversive throughout the seafloor of the Gulf is an extensive network of pockmarks formed by seepages of thermogenic gas. These gas seeps and bottom water exiting the Gulf via the Strait of Hormuz are the most significant processes controlling present-day sedimentation in the region. Erosion by these seeps has been so intense in the Baiban Shelf in the Strait of Hormuz as to create a ''hoodoo'' like terrain on the outer shelf. The surfical geology of the Gulf documents a short lived transgression 29,400 to 22,800 years ago during the Wisconsin regression which began 125,000 years ago, the Wisconsin regressive maxima when sea level dropped to -120/-130 m about 21,000/20,000 years ago and the climate was dry and eolian and paralic sedimentation characterized the Gulf, the Holocene transgression 18,000 to 12,000 years ago when the climate was more humid than during the climax of the Wisconsin regression, a dry phase 12,000 to 9000 years ago when the Persian Gulf was a site of eolian and carbonate deposition, and the present sediment cycle during the last 9000 years under a more humid regime. It was during the present cycle that southeast trending marl lobes were deposited off Iran, Arabia acquired its hyper-arid climate about 3000 years ago and the Gulf attained its present configuration about 1000 years ago as a result of the construction of the Tigris Euphrates Delta at its head and tectonism and aggradation along its Arabian and Iranian flanks. VL - 129 IS - 3-4 N1 - Tv774Times Cited:49Cited References Count:82 JO - Gas venting and late Quaternary sedimentation in the Persian (Arabian) Gulf ER - TY - JOUR T1 - Highly Variable Late Pleistocene and Holocene Sedimentation Rates In AMS C14-Dated Boxcores From the Central Arctic Ocean JF - EOS Y1 - 1996 A1 - Darby, D. A. Bischof J. F. Jones G. A. VL - 77 IS - 46 N1 - id: 906 ER - TY - JOUR T1 - A history of Pacific Northwest earthquakes recorded in Holocene sediments from Lake Washington JF - Journal of Geophysical Research-Solid Earth Y1 - 1996 A1 - Karlin, R. E. A1 - Abella, S. E. B. AB - Large earthquakes can trigger slumping of the steep walls of lake basins and landslides in the drainage area, resulting in turbidite deposition in the lake and increased detrital flux from inlets. Holocene sediments in piston cores from Lake Washington contain a series of terrigenous layers that were episodically deposited in the lake. Sedimentological, geochemical, and paleomagnetic analyses on nine piston cores show that the detrital layers are temporally and areally correlatable, indicating basinwide disruptions. These layers are opaque on X-radiographs, are coincident with magnetic susceptibility peaks, have abundant aluminosilicate minerals, are relatively coarse grained, and have low organic carbon and biogenic silica contents. The thicknesses and geographic distributions of the layers suggest that they are not due to floods or delta destabilization. Side scan swath imagery and subbottom profiling show that large slumps, subaqueous landslides, and debris flows are common along the margins of the lake. A detailed chronology, established from 21 radiocarbon ages on five cores, show that a prominent turbidite was deposited about 1000-1100 years ago. This turbidite apparently was triggered by a large earthquake that probably occurred on the Seattle fault. Other depositional events in the sediment record at 1500-1700, 2400-2500, and 2800-3200 years ago coincide with periods of landsliding that have been previously inferred from the dating of drowned trees in the lake. More than 30 depositional events have occurred in the last 12,000 years and 21 disturbances have occurred since the deposition of the Mazama ash about 7,600 years ago. If all the events are due to earthquakes, the Puget Sound region has been subject to major shaking every 300 to 400 years. The strong intensities needed to trigger subaqueous slides may not be generated by just local sources such as the Seattle fault but could also be caused by great subduction earthquakes occurring along the coast. VL - 101 IS - B3 N1 - Ua372Times Cited:19Cited References Count:57 JO - A history of Pacific Northwest earthquakes recorded in Holocene sediments from Lake Washington ER - TY - JOUR T1 - Holocene climatic and human influences on lakes of the Yucatan Peninsula, Mexico: An interdisciplinary, palaeolimnological approach JF - Holocene Y1 - 1996 A1 - Whitmore, T. J. A1 - Brenner, M. A1 - Curtis, J. H. A1 - Dahlin, B. H. A1 - Leyden, B. W. AB - We used palaeolimnological techniques to examine effects of Holocene climate change and human influence on lakes of the Yucatan Peninsula, Mexico. The three study lakes are located along a west-east transect that represents a gradient of increasing modern precipitation and density of former Maya settlement. At Lake Coba, an 880-cm sediment core yields a complete record of lacustrine sedimentation that began when the lake first filled similar to 8000 BP as groundwater level rose in response to rising sea level and increased precipitation. Diatom, ostracod, and delta(18)O evidence indicate that Lake Coba was initially shallow and saline. Coba, presently in the region of greatest rainfall, showed more episodic water-level changes than Lake San Jose Chulchaca or Lake Sayaucil. High lake level and fresh water were evident at 440 cm (similar to 2600 BP), followed by a decline in water levels and an increase in total ionic salinity to the present time. In a 613-cm core from Sayaucil, in the intermediate precipitation zone, total salinity was high between 600 and 400 cm (similar to 3050 and 2000 BP), followed by consistently higher water levels. Salinity was high in the lower portion of a 110-cm San Jose Chulchaca core (beginning similar to 1860 BP), followed by a gradual and consistent freshening of water to the present time.Trophic state changes and human influence on lakes were evaluated using diatom, delta(18)O, total P, sedimentary organic matter, and preliminary pollen data. Maximal human disturbance at Lake Coba, a densely settled Maya urban site, occurred during a deep-water event at 440 cm, followed by a decline in human influence and trophic state to the present time. Trophic state and linear sedimentation rates in Sayaucil increased significantly above 400 cm (after similar to 2000 BP), probably associated with initial Maya settlement near Xtojil and subsequent small-scale farming. Limnological disturbance may have preceded the period of maximal human occupation because initial land clearance and consequent soil erosion probably affected water quality substantially. San Jose Chulchaca lacks archaeological evidence of human occupation in the drainage, and shows gradual changes in trophic state not caused by human disturbance. With the exception of a C-14 date on wood from the base of the Coba core, C-14 dates and chronologies may be artificially old as a consequence of hard-water-lake error. Trophic state changes in the study lakes were generally consistent with known patterns of human settlement and population change. Late-Holocene water-level fluctuations were most pronounced in Lake Coba in eastern Yucatan, where modern rainfall is currently greatest, but lake level is generally lower than during much of the past. Lake level was relatively constant in Sayaucil in the central peninsula, whereas lake level in San Jose Chulchaca in the arid western portion of the peninsula increased gradually over time. VL - 6 IS - 3 N1 - Vh189Times Cited:56Cited References Count:65 JO - Holocene climatic and human influences on lakes of the Yucatan Peninsula, Mexico: An interdisciplinary, palaeolimnological approach ER - TY - JOUR T1 - Holocene paleoclimatic changes in the Lake Winnebago basin, east-central Wisconsin JF - Abstracts with Programs - Geological Society of America Y1 - 1996 A1 - Haase, Alisa A. A1 - Smith, G. L. A1 - Hardacker, E. P. VL - 28 IS - 6 N1 - id: 77 ER - TY - JOUR T1 - Holocene sea-level rise recorded by a radiocarbon-dated mussel in a submerged speleothem beneath the Mediterranean Sea JF - Quaternary Research Y1 - 1996 A1 - Fabrizio, A. A1 - Oliverio, M. VL - 45 IS - 2 N1 - id: 1241 ER - TY - JOUR T1 - A Holocene vegetation history from lowland Guatemala JF - Holocene Y1 - 1996 A1 - Islebe, G. A. A1 - Hooghiemstra, H. A1 - Brenner, M. A1 - Curtis, J. H. A1 - Hodell, D. A. AB - A 5.45-m core from Lake Peten-Irza, lowland Guatemala, contains a near-complete record of Holocene sedimentation. The age-depth relationship for the core is based on AMS C-14 dating of terrestrial wood fragments and provides a reliable chronology in this karst region where hard-water lake error has typically confounded sediment geochronology. In the basal part of the sequence, pollen of the Moraceae-Urticaceae group dominate, indicating the presence of widespread tropical forest during the early Holocene (c. 8600-5600 yr BP). Relative abundance of pollen of high forest taxa declined beginning as early as 5600 yr BP, indicating climatic drying or perhaps initial land clearance. Deforestation by prehistoric Mayan inhabitants is documented clearly in the pollen record beginning about 2000 pr BP (106 cal BC-122 cal Ao, 95.4%, 2 sigmas) by the appearance of disturbance taxa (e.g. Ambrosia and Poaceae) and presence of Zea. Forest regrowth occurred following the Classic Maya collapse, c. AD 900, as reflected by a relative increase in Moraceae-Urticaceae pollen. VL - 6 IS - 3 N1 - Vh189Times Cited:103Cited References Count:44 JO - A Holocene vegetation history from lowland Guatemala ER - TY - JOUR T1 - Increased continental-margin slumping frequency during sea-level lowstands above gas hydrate-bearing sediments JF - Geology Y1 - 1996 A1 - Paull, C. K. A1 - Buelow, W. J. A1 - Ussler, W. A1 - Borowski, W. S. AB - We present C-14 data on sediment samples from cores of the upper 7 m of the sediment column overlying a major continental-rise gas hydrate field on the southern Carolina Rise and inner Blake Ridge offshore the southeastern United States. The data show that glacial-age sediments are underrepresented in the cores. The observation is consistent with a previously predicted association between sea-level lowstands and increased frequency of sea-floor slumping on continental margins containing gas hydrates. VL - 24 IS - 2 N1 - Tt580Times Cited:86Cited References Count:26 JO - Increased continental-margin slumping frequency during sea-level lowstands above gas hydrate-bearing sediments ER - TY - RPRT T1 - Informe Final: Geocronologia de las aquas subterraneas del Salar Punta Negra, Antofagasta, II Region. Preparado para Minera Escondida Ltda. (Report) Y1 - 1996 A1 - Salamanca, Marco PB - Minera Escondid Ltda N1 - id: 181 ER - TY - JOUR T1 - Initial results from paleoclimatic drilling and geophysical studies of Washoe Lake, Nevada JF - USGS Circular 1119, Water Resources Division Y1 - 1996 A1 - Karlin, R. A1 - Trexler, J. A1 - Petersen, R. N1 - id: 1245 ER - TY - JOUR T1 - Inorganic radiocarbon in time-series trap samples: implication of seasonal variation of 14C in the upper ocean JF - Radiocarbon Y1 - 1996 A1 - Honda, Makio C. VL - 38 IS - 3 N1 - id: 27 ER - TY - JOUR T1 - Isolation of Individual Organic Compounds for AMS Radiocarbon Analysis--A Novel Approach JF - Radiocarbon Y1 - 1996 A1 - Eglinton, T. I. A1 - McNichol, A. P. A1 - Benitez-Nelson, B. C. A1 - Pearson, A. A1 - von Reden, K. F. A1 - Schneider, R. J. A1 - Bauer, J. E. A1 - Druffel, E. R. M. VL - 38 IS - 1 N1 - id: 1650 ER - TY - CONF T1 - Isolation of Individual Organic Compounds for AMS Radiocarbon Analysis -- A Novel Approach T2 - 7th International Conference on Accelerator Mass Spectrometry Y1 - 1996 A1 - Eglinton, T. I. A1 - McNichol, A. P. A1 - Benitez-Nelson, B. C. A1 - Pearson, A. A1 - von Reden, K. F. A1 - Schneider, R. J. A1 - Bauer, J. E. A1 - Druffel, E. R. M. JF - 7th International Conference on Accelerator Mass Spectrometry PB - Radiocarbon CY - Tucson, AZ VL - 38 N1 - id: 1800; 1 ER - TY - CONF T1 - Kinematic Effects in the Sputtering of Carbon Isotopes T2 - 7th International Conference on Accelerator Mass Spectrometry Y1 - 1996 A1 - Schneider, R. J. A1 - Hartman, J. A1 - von Reden, K. F. A1 - McNichol, A. P. JF - 7th International Conference on Accelerator Mass Spectrometry PB - Radiocarbon CY - Tucson, AZ VL - 38 N1 - id: 1801; 1 ER - TY - JOUR T1 - Kinematic Effects in the Sputtering of Carbon Isotopes JF - Radiocarbon Y1 - 1996 A1 - Schneider, R. J. A1 - Hartman, J. A1 - von Reden, K. F. A1 - McNichol, A. P. VL - 1 IS - 108 N1 - id: 1660 ER - TY - CONF T1 - The "Lake" of Mayran: Reconstructing an Environmental History from Alluvial, Lacustrine, and Soils Records in Northern Mexico T2 - Annual Meeting, Sociedad Mexicana de Antropologia Y1 - 1996 A1 - Butzer, K. W. Frederick C. D. Cordova C. E. Butzer E. K. Abbott y J. T. JF - Annual Meeting, Sociedad Mexicana de Antropologia CY - Tepic (Noyarit) N1 - id: 903; Symposium: "El Hombre y el Lago: Ayer y Hoy" ER - TY - JOUR T1 - Large-volume WOCE radiocarbon sampling in the Pacific Ocean JF - Radiocarbon Y1 - 1996 A1 - Stuiver, M. A1 - Ostlund, H. G. A1 - Key, R. M. A1 - Reimer, P. J. KW - geosecs AB - At the University of Miami Tritium Laboratory and the University of Washington Quaternary Isotope Laboratory, more than 1000 large-volume Pacific Ocean radiocarbon samples were measured for the WOCE program. Here we present a comprehensive data set, and a brief discussion of our findings. VL - 38 SN - 0033-8222 IS - 3 N1 - Xd080Times Cited:12 Cited References Count:8 JO - Radiocarbon ER - TY - JOUR T1 - Late holocene coastal plain stratigraphy and sea-level history at Hanalei, Kauai, Hawaiian islands JF - Quaternary Research Y1 - 1996 A1 - Calhoun, R. S. A1 - Fletcher, C. H. AB - Fluvial, marine, and mixed fluvial-marine deposition on the coastal plain of Hanalei Bay on the north shore of Kauai, Hawaii, records a middle- to late-Holocene fall of relative sea level. Radiocarbon dating of the regression boundary preserved in the stratigraphy of the coastal plain documents a seaward shift of the shoreline beginning at least 4800-4580 cal yr B.P. and continuing until at least 2160-1940 cal yr B.P. Marine sands stranded in the backshore and coastal plain environment are buried by fluvial floodplain and channel sands, silts, and muds. In places, erosion at the regression contact exposed older marine sands thus increasing the hiatus at the regression disconformity, The shoreline regression is best explained as the result of a fall in relative sea level. The age and elevation of the cored regression boundary at sites that have not been influenced by erosion are consistent with a middle-to late-Holocene highstand of relative sea level as predicted by geophysical models of whole Earth deformation related to deglaciation. (C) 1996 University of Washington. VL - 45 IS - 1 N1 - Uf728Times Cited:21Cited References Count:35 JO - Late holocene coastal plain stratigraphy and sea-level history at Hanalei, Kauai, Hawaiian islands ER - TY - CHAP T1 - Late Quaternary deep circulation in the western equatorial Atlantic (Book Section) T2 - The South Atlantic: Present and Past Circulation Y1 - 1996 A1 - Curry, W. B. ED - Berger, W. JF - The South Atlantic: Present and Past Circulation N1 - id: 1336 ER - TY - THES T1 - Late Quaternary stratigraphy, sea-level history and paleoclimatology of the southeast Florida outer continental shelf, Thesis Y1 - 1996 A1 - Toscano, M. A. PB - University of South Florida CY - St. Petersburg, FL VL - Unpublished Ph.D. dissertation ER - TY - JOUR T1 - The Little Ice Age and Medieval Warm Period in the Sargasso Sea JF - Science Y1 - 1996 A1 - Keigwin, L. D. AB - Sea surface temperature (SST), salinity, and flux of terrigenous material oscillated on millennial time scales in the Pleistocene North Atlantic, but there are few records of Holocene variability. Because of high rates of sediment accumulation, Holocene oscillations are well documented in the northern Sargasso Sea. Results from a radiocarbon-dated box core show that SST was approximately 1°C cooler than today approximately 400 years ago (the Little Ice Age) and 1700 years ago, and approximately 1°C warmer than today 1000 years ago (the Medieval Warm Period). Thus, at least some of the warming since the Little Ice Age appears to be part of a natural oscillation. VL - 274 SN - 1095-9203 (Electronic)0036-8075 (Linking) UR - https://www.ncbi.nlm.nih.gov/pubmed/8929406 IS - 5292 N1 - Keigwineng 1996/11/29 Science. 1996 Nov 29;274(5292):1504-8. ER - TY - JOUR T1 - A long pollen record from lowland Amazonia: Forest and cooling in glacial times JF - Science Y1 - 1996 A1 - Colinvaux, P. A. A1 - DeOliveira, P. E. A1 - Moreno, J. E. A1 - Miller, M. C. A1 - Bush, M. B. AB - A continuous pollen history of more than 40,000 years was obtained from a lake in the lowland Amazon rain forest. Pollen spectra demonstrate that tropical rain forest occupied the region continuously and that savannas or grasslands were not present during the last glacial maximum. The data suggest that the western Amazon forest was not fragmented into refugia in glacial times and that the lowlands were not a source of dust. Glacial age forests were comparable to modern forests but also included species now restricted to higher elevations by temperature, suggesting a cooling of the order of 5 degrees to 6 degrees C. VL - 274 IS - 5284 N1 - Vk748Times Cited:350Cited References Count:42 JO - A long pollen record from lowland Amazonia: Forest and cooling in glacial times ER - TY - JOUR T1 - Molecular breakup of CO2 and hold-up time in a microwave ion source Y1 - 1996 A1 - Wills, J. S. C. A1 - Diamond, W. T. A1 - Lewis, R. A. A1 - Schmeing, H. A1 - von Reden, K. F. A1 - Schneider, R. J. N1 - id: 949 ER - TY - JOUR T1 - Neolithic migrations as a function of sea level-controlled topography in the Yangtze Delta, China JF - Geology Y1 - 1996 A1 - Stanley, D. J. A1 - Chen, Zhongyuan VL - 24 IS - 12 N1 - id: 1282 ER - TY - JOUR T1 - Ocean Tracer Laboratory Tech. Report JF - P17E19S final report for AMS 14C samples Y1 - 1996 A1 - Key, R. M. VL - 97 IS - 1 N1 - id: 1252 ER - TY - CONF T1 - ODP drilling on the Amazon Fan; initial results on growth pattern and timing of fan sedimentation T2 - Annual Meeting Abstracts--American Association of Petroleum Geologists and Society of Economic Paleontologists and Mineralogists Y1 - 1996 A1 - Flood, R. D. A1 - Piper, D. J. W. JF - Annual Meeting Abstracts--American Association of Petroleum Geologists and Society of Economic Paleontologists and Mineralogists PB - American Association of Petroleum Geologists and Society of Economic Paleontologists and Mineralogists CY - San Diego, CA VL - 5 N1 - id: 23 ER - TY - BOOK T1 - One thousand years of change in the Great Lakes Region. A pilot project of the NBS Landscape Use History of North America (LUHNA) publ. electronically on the World Wide Web Y1 - 1996 A1 - Cole, K. L. A1 - Davis, M. B. A1 - Winkler, M. G. N1 - id: 1323; http://www.nbs.gov/luhna/cole ER - TY - RPRT T1 - P16 S17S TUNES-2 final report for AMS 14C samples (Report) Y1 - 1996 A1 - Key, R. M. JF - Ocean Tracer Laboratory Tech. Report VL - 96 N1 - id: 1250 ER - TY - JOUR T1 - P16A17A Final report for large volume samples and D14C measurements JF - Ocean Tracer Laboratory Tech. Rep. Y1 - 1996 A1 - Key, R. M. VL - 96 IS - 7 N1 - id: 1454 ER - TY - JOUR T1 - P16C TUNES-3 final report for AMS 14C samples JF - Ocean Tracer Laboratory Technical Report Y1 - 1996 A1 - Key, R. M. A1 - Quay, P. VL - 96 IS - 6 N1 - id: 1453 JO - P16C TUNES-3 final report for AMS 14C samples ER - TY - RPRT T1 - P16C TUNES-3 final report for AMS 14C samples (Report) Y1 - 1996 A1 - Key, R. M. A1 - Quay, P. JF - Ocean Tracer Laboratory Tech. Report VL - 96 N1 - id: 1251 ER - TY - JOUR T1 - P16S17S TUNES-2 final report for AMS 14C samples JF - Ocean Tracer Laboratory Tech. Rep. Y1 - 1996 A1 - Key, R. M. VL - 96 IS - 5 N1 - id: 1452 ER - TY - JOUR T1 - P16S17S TUNES-2 final report for large volume samples JF - Ocean Tracer Laboratory Tech. Rep. Y1 - 1996 A1 - Key, R. M. VL - 96 IS - 4 N1 - id: 1451 ER - TY - JOUR T1 - P17C TUNES-1 final report for AMS 14C samples JF - Ocean Tracer Laboratory Tech. Report Y1 - 1996 A1 - Key, R. M. VL - 96 IS - 3 N1 - id: 1249 ER - TY - JOUR T1 - P17C TUNES-1 final report for large volume samples JF - Ocean Tracer Laboratory Tech. Rept Y1 - 1996 A1 - Key, R. M. VL - 96 IS - 2 N1 - id: 1449 ER - TY - JOUR T1 - P17E19S Final report for large volume samples and D14C measurements JF - Ocean Tracer Laboratory Tech. Rep. Y1 - 1996 A1 - Key, R. M. VL - 96 IS - 8 N1 - id: 1455 ER - TY - JOUR T1 - P17N Final report for large volume samples JF - Ocean Tracer Laboratory Tech. Rep. Y1 - 1996 A1 - Key, R. M. VL - 96 IS - 11 N1 - id: 1459 ER - TY - JOUR T1 - P19C Final report for large volume samples and D14C measurements JF - Ocean Tracer Laboratory Tech. Rep. Y1 - 1996 A1 - Key, R. M. VL - 96 IS - 10 N1 - id: 1458 ER - TY - JOUR T1 - P6 final report for AMS 14C samples JF - Ocean Tracer Laboratory Tech. Rep. Y1 - 1996 A1 - Key, R. M. VL - 96 IS - 9 N1 - id: 1456 ER - TY - RPRT T1 - The paleoecology and pH history of Ike Walton Lake and comparison with the recent history of Zee Lake. Report Y1 - 1996 A1 - Winkler, M. G. PB - Lac du Flambeau Water Resources Program Contract #1243 VL - Final Report N1 - id: 1325 ER - TY - CONF T1 - Paleoecology of the Everglades National Park Paper T2 - Florida Bay Science Conference Y1 - 1996 A1 - Winkler, M. G. A1 - Sanford, P. R. A1 - Kaplan, S. W. JF - Florida Bay Science Conference CY - Florida N1 - id: 1298 ER - TY - RPRT T1 - Paleoecology of the Everglades National Park. Report Y1 - 1996 A1 - Winkler, M. G. A1 - Sanford, P. R. A1 - Kaplan, S. PB - National Park Service, Everglades National Park CY - Homestead, Florida VL - Technical Report 97-006 N1 - id: 1324 ER - TY - JOUR T1 - PC17 TUNES-1 final report for AMS 14C samples JF - Ocean Tracer Laboratory Tech. Rept. Y1 - 1996 A1 - Key, R. M. VL - 96 IS - 3 N1 - id: 1450 ER - TY - BOOK T1 - Petroleum Geochemistry and Geology Y1 - 1996 A1 - Hunt, John M. PB - W. H. Freeman & Company CY - New York, NY N1 - id: 1558 ER - TY - JOUR T1 - Post-bomb radiocarbon records of surface corals from the tropical Atlantic Ocean JF - Radiocarbon Y1 - 1996 A1 - Druffel, E. R. M. KW - atmosphere KW - banded corals KW - bermuda KW - C-14 KW - pacific KW - rings KW - ventilation AB - Delta(14)C records are reported for post-bomb corals from three sites in the tropical Atlantic Ocean. In corals from 18 degrees S in the Brazil Current, Delta(14)C values increased from ca.-58 parts per thousand in the early 1950s to +138 parts per thousand by 1974, then decreased to 110 parts per thousand by 1982 Shorter records from 8 degrees S off Brazil and from the Cape Verde Islands (17 degrees N) showed initially higher Delta(14)C values before 1965 than those at 18 degrees S, but showed lower rates of increase of Delta(14)C during the early 1960s. There is general agreement between the coral results and Delta(14)C of dissolved inorganic carbon (DIC) measured in seawater previously for locations in the tropical Atlantic Ocean. Delta(14)C values at our tropical ocean sites increased at a slower rate than those observed previously in the temperate North Atlantic (Florida and Bermuda), owing to the latter's proximity to the bomb C-14 input source in the northern hemisphere. Model results show that from 1960-1980 the Cape Verde coral and selected DIC Delta(14)C values from the North Equatorial Current agree with that calculated for the North Atlantic based on an isopycnal mixing model with a constant water mass renewal rate between surface and subsurface waters. This is in contrast to Delta(14)C values in Bermuda corals that showed higher post-bomb values than those predicted using a constant water mass renewal rate, hence indicating that ventilation in the western north Atlantic Ocean had decreased by a factor of 3 during the 1960s and 1970s (Druffel 1989). VL - 38 SN - 0033-8222 IS - 3 N1 - Xd080Times Cited:25 Cited References Count:20 JO - Radiocarbon ER - TY - JOUR T1 - A preliminary palynological study of the late Pleistocene to Holocene history of the Lake Winnebago basin, Wisconsin JF - Abstracts with Programs - Geological Society of America Y1 - 1996 A1 - Ormseth, B. L. A1 - Smith, G. L. VL - 28 IS - 6 N1 - id: 76 ER - TY - JOUR T1 - Preparative capillary gas chromatographic isolation of individual compounds from complex matrices for radiocarbon dating JF - Analytical Chemistry Y1 - 1996 A1 - Eglinton, T. I. A1 - Aluwihare, L. I. A1 - Bauer, J. E. A1 - Druffel, E. R. M. A1 - McNichol, A. P. VL - 68 N1 - id: 1340 ER - TY - JOUR T1 - Progress of the NOSAMS Facility WOCE 14C Data Analysis JF - Radiocarbon Y1 - 1996 A1 - von Reden, K. F. A1 - McNichol, A. P. A1 - Schneider, R. J. VL - 38 IS - 1 N1 - id: 1672 ER - TY - CONF T1 - Progress of the NOSAMS Facility WOCE 14C data analysis T2 - 7th International Conference on Accelerator Mass Spectrometry Y1 - 1996 A1 - von Reden, K. F. A1 - McNichol, A. P. A1 - Schneider, R. J. JF - 7th International Conference on Accelerator Mass Spectrometry PB - Radiocarbon CY - Tucson, AZ VL - 38 N1 - id: 948; 1 ER - TY - CONF T1 - Progress of the NOSAMS Facility WOCE 14C Data Analysis T2 - Workshop on Applications of AMS to Global Climate Change Y1 - 1996 A1 - von Reden, K. F. A1 - McNichol, A. P. A1 - Schneider, R. J. JF - Workshop on Applications of AMS to Global Climate Change PB - Radiocarbon CY - La Jolla VL - 38 N1 - id: 1768; 1 ER - TY - CONF T1 - Progress of the NOSAMS Facility WOCE 14C Data Analysis, Workshop on Applications of AMS to Global Climate Change T2 - Workshop on Applications of AMS to Global Climate Change Y1 - 1996 A1 - von Reden, K. F. A1 - McNichol, A. P. A1 - Schneider, R. J. JF - Workshop on Applications of AMS to Global Climate Change PB - Radiocarbon CY - La Jolla VL - 38 N1 - id: 954; 8 ER - TY - CONF T1 - Progress of the NOSAMS facility WOCE (super 14) C data analysis Y1 - 1996 A1 - von Reden, K. F. A1 - McNichol, A. P. A1 - Schneider, Robert J. KW - 02D KW - 07 KW - accelerator mass spectroscopy KW - C-14 KW - carbon KW - Isotope geochemistry KW - isotopes KW - mass spectroscopy KW - Oceanography KW - Pacific Ocean KW - progress report KW - radioactive isotopes KW - report KW - sea water KW - spectroscopy PB - University of Arizona, Department of Geosciences, Tucson, AZ, United States (USA) CY - United States (USA) VL - 38 N1 - id: 2242; Source type: conferencepapers&proceedings; Object type: Article; Object type: Conference Paper; Copyright: GeoRef, Copyright 2007, American Geological Institute.; CSAUnique: 1999-071631; AccNum: 1999-071631; ISSN: 0033-8222; CODEN: RACAAT ER - TY - JOUR T1 - Radiocarbon measurements of atmospheric volatile organic compounds: Quantifying the biogenic contribution JF - Environmental Science & Technology Y1 - 1996 A1 - Klouda, G. A. A1 - Lewis, C. W. A1 - Rasmussen, R. A. A1 - Rhoderick, G. C. A1 - Sams, R. L. A1 - Stevens, R. K. A1 - Currie, L. A. A1 - Donahue, D. J. A1 - Jull, A. J. T. A1 - Seila, R. L. AB - The radiocarbon (C-14) abundance of atmospheric volatile organic compounds (VOC) gives a quantitative estimate of contributions from biomass and fossil-mass sources, important information for effective regulation of ozone precursors. We report here details of a methodology to perform such measurements and the first exploratory C-14 results on VOC fractions separated from two composited urban tropospheric air samples, collected during the summer (1992) in Atlanta, GA. The upper limit of the percentage of VOC originating from biomass sources during the morning and evening hours in Atlanta were 9 and 17%, respectively, measurements reported at the 95% confidence level. However, due to the level of the process blank and its uncertainty, in both cases the percentage can be as low as zero. The results of these experiments, designed to (i) evaluate the entire [C-14]VOC measurement process and (ii) obtain reliable estimates of biogenic contributions to atmospheric VOC, emphasize how important controls are throughout this multi-step chemical process to ensure quality data. VL - 30 IS - 4 N1 - Uc413Times Cited:26Cited References Count:25 JO - Radiocarbon measurements of atmospheric volatile organic compounds: Quantifying the biogenic contribution ER - TY - CHAP T1 - Recession of the late Wisconsinan Ice Sheet from the northwestern White Mountains, New Hampshire (Book Section) T2 - New England Intercollegiate Geological Conference Guidebook for Field Trips in Northern New Hampshire and Adjacent regions of Maine and Vermont Y1 - 1996 A1 - Thompson, W. B. A1 - Fowler, B. K. A1 - Flanagan, S. M. A1 - Dorion, C. C. ED - Van Baalen, M. R. JF - New England Intercollegiate Geological Conference Guidebook for Field Trips in Northern New Hampshire and Adjacent regions of Maine and Vermont N1 - id: 18 ER - TY - JOUR T1 - Reworking and discontinuities in Holocene sedimentation in the Nile Delta: Documentation from amino acid racemization and stable isotopes in mollusk shells JF - Marine Geology Y1 - 1996 A1 - Goodfriend, G. A. A1 - Stanley, D. J. AB - The late Holocene sedimentary history of the northwestern edge of the Nile Delta is reconstructed from amino acid racemization, radiocarbon, and stable isotope analysis of a series of bivalve shells from a core taken at the edge of Lake Maryut near Alexandria. Amino acid racemization, confirmed by radiocarbon and stable isotope analysis, indicates that in many parts of the core mixed-age mollusk assemblages are present. Dating of the time of sediment accumulation at various levels in the core is therefore based on the age of the youngest shells, which are identified by amino acid racemization analysis (lowest D/L values). AMS radiocarbon analysis is used to determine the ages of the shells, except for the most recent sediments (last 100 yr), for which aspartic acid racemization provides more precise ages.Amino acid racemization analysis of 59 shells from 21 levels in the 4.8 m Holocene sequence in the core enabled identification of a large hiatus. Holocene sedimentation started at ca. 2400 BC, apparently corresponding to a westward shift of the course of the Canopic Nile distributary which lies to the east. Deposition continued at a rate of 1.4 mm per year, ceasing at ca. 550 BC, at which time the Canopic Nile shifted eastward again and subsequently became defunct. A marine connection during this period is indicated by stable isotope values of shells. Sediment accumulation began again only at the end of the 19th century, when a series of irrigation canals was connected to the Lake Maryut basin. Stable isotope values indicate a strong freshwater influence. Deposition has continued to the present at a very high rate (19 mm per year) due to supply of sediments by agricultural activity.The relative ease with which racemization analyses can be carried out permits detailed analysis of core chronostratigraphy, leading to more accurate reconstruction of core chronology: hiatuses can be pinpointed and documented, and age mixtures can be identified, with appropriate individual shells being selected for AMS radiocarbon analysis. Aspartic acid racemization analysis permits dating of samples from the last several hundred years, a period for which radiocarbon analyses provide poor precision. VL - 129 IS - 3-4 N1 - Tv774Times Cited:35Cited References Count:30 JO - Reworking and discontinuities in Holocene sedimentation in the Nile Delta: Documentation from amino acid racemization and stable isotopes in mollusk shells ER - TY - CONF T1 - Ryder Pond: A drought-induced natural acidification experiment T2 - Ecological Society of America (ESA) meeting Y1 - 1996 A1 - Winkler, M. G. A1 - Portnoy, J. JF - Ecological Society of America (ESA) meeting CY - Providence, RI N1 - id: 94 ER - TY - JOUR T1 - Seasonal oxygen depletion in continental-shelf waters of Louisiana; historical record of benthic foraminifers JF - Geology Y1 - 1996 A1 - Sen Gupta, B. K. A1 - Turner, R. E. A1 - Rabalais, N. N. VL - 24 IS - 3 N1 - id: 85 ER - TY - JOUR T1 - Seasonal variability of particulate organic radiocarbon in the northeastern Pacific JF - Journal of Geophysical Research Y1 - 1996 A1 - Druffel, Ellen R. M. A1 - Bauer, J. E. A1 - Williams, P. M. A1 - Griffin, S. A1 - Wolgast, D. VL - 101 IS - C9 N1 - id: 1239 ER - TY - JOUR T1 - Sediment dispersal along northern Israel coast during the early Holocene: Geological and archaeological evidence JF - Marine Geology Y1 - 1996 A1 - Stanley, D. J. A1 - Galili, E. AB - geological and archaeological study of finds at Atlit-Yam, a Pre-Pottery Neolithic settlement submerged off the Carmel coast of northern Israel, provides new information on sediment provenance and dispersal in the southern Levant. Clay mineral analyses of mud-rich samples collected in a water well (ca. 8100-7550 yrs B.P.) at this site are useful for determining the early Holocene circulation pattern along this margin. Analyses record the predominance of fluvial sediment from proximal Carmel highland sources to the east, as indicated by illite, and of marine sediment from the north and northeast, as indicated by kaolinite. This north-to-south coastal transport is in marked contrast to the present south-to-north dispersal pattern where smectite-rich Nile material is derived from distal sources and carried hundreds of kilometers to the Carmel margin. The interpreted coastal circulation pattern indicates that although the modern Nile delta, major source of sediment in the eastern Mediterranean, had begun to form about 8000-7500 yrs ago, it had not yet begun to supply substantial amounts of sediment to as far north as the Carmel coast by the time the water well was abandoned. The Atlit-Yam site serves as a unique geochronologic gauge valuable for interpreting climatic, oceanographic and sedimentologic conditions in the SE Mediterranean which, as recently as 7500 yrs ago, were markedly different than those prevailing at present. VL - 130 IS - 1-2 N1 - Ue849Times Cited:13Cited References Count:30 JO - Sediment dispersal along northern Israel coast during the early Holocene: Geological and archaeological evidence ER - TY - JOUR T1 - Sedimentary carbon-isotope systematics on the Amazon shelf JF - Geo-Marine Letters Y1 - 1996 A1 - Sommerfield, C. K. A1 - Nittrouer, C. A. A1 - DeMaster, D. J. AB - Sedimentary carbon systematics on the Amazon continental shelf were investigated using C-14 and delta(13)C measurements of sedimentary organic materials. Mass balance calculations indicate that the C-14 content of modern shelf muds results from burial of old (similar to 5000 yr BP) terrestrial soil carbon and bomb-C-14-enriched marine carbon, implying that most of the bomb-labeled riverine particulate carbon is not buried on the shelf. The C-14 signature of Amazon shelf deposits records the effects of both biogeochemical and sedimentary processes active in this dynamic environment. VL - 16 IS - 1 N1 - Ty588Times Cited:12Cited References Count:33 JO - Sedimentary carbon-isotope systematics on the Amazon shelf ER - TY - JOUR T1 - Sedimentology of the Krakatau 1883 submarine pyroclastic deposits JF - Bulletin of Volcanology Y1 - 1996 A1 - Mandeville, C. W. A1 - Carey, S. A1 - Sigurdsson, H. AB - The majority of tephra generated during the paroxysmal 1883 eruption of Krakatau volcano, Indonesia, was deposited in the sea within a 15-km radius of the caldera. Two syneruptive pyroclastic facies have been recovered in SCUBA cores which sampled the 1883 subaqueous pyroclastic deposit. The most commonly recovered facies is a massive textured, poorly sorted mixture of pumice and lithic lapilli-to-block-sized fragments set in a silty to sandy ash matrix. This facies is indistinguishable from the 1883 subaerial pyroclastic flow deposits preserved on the Krakatau islands on the basis of grain size and component abundances. A less common facies consists of well-sorted, planar-laminated to low-angle cross-bedded, vitric-enriched silty ash. Entrance of subaerial pyroclastic flows into the sea resulted in subaqueous deposition of the massive facies primarily by deceleration and sinking of highly concentrated, deflated components of pyroclastic flows as they traveled over water. The basal component of the deposit suggests no mixing with seawater as inferred from retention of the fine ash fraction, high temperature of emplacement, and lack of traction structures, and no significant hydraulic sorting of components. The laminated facies was most likely deposited from low-concentration pyroclastic density currents generated by shear along the boundary between the submarine pyroclastic flows and seawater. The Krakatau deposits are the first well-documented example of true submarine pyroclastic flow deposition from a modern eruption, and thus constitute an important analog for the interpretation of ancient sequences where subaqueous deposition has been inferred based on the facies characteristics of encapsulating sedimentary sequences. VL - 57 IS - 7 N1 - Uk310Times Cited:57Cited References Count:59 JO - Sedimentology of the Krakatau 1883 submarine pyroclastic deposits ER - TY - CONF T1 - Stable and radio-carbon isotope measurements in the Pacific Ocean; contributions from NOSAMS Y1 - 1996 A1 - McNichol, A. P. A1 - von Reden, K. F. A1 - Schneider, R. J. A1 - Key, R. M. A1 - Jones, G. A. KW - 02D KW - 07 KW - accelerator mass spectroscopy KW - C-13/C-12 KW - C-14 KW - carbon KW - chemical analysis KW - geochemical indicators KW - high-resolution methods KW - Isotope geochemistry KW - isotope ratios KW - isotopes KW - marine geology KW - mass spectroscopy KW - National Ocean Sciences Accelerator Mass Spectrometry KW - NOSAMS KW - Oceanography KW - Pacific Ocean KW - radioactive isotopes KW - radioactive tracers KW - sampling KW - sea water KW - spectroscopy KW - Stable isotopes KW - tracers KW - Woods Hole Oceanographic Institution PB - American Geophysical Union, Washington, DC, United States (USA) CY - United States (USA) VL - 77 N1 - id: 2240; Source type: conferencepapers&proceedings; Object type: Article; Object type: Conference Paper; Copyright: GeoRef, Copyright 2007, American Geological Institute.; CSAUnique: 1997-047916; AccNum: 1997-047916; ISSN: 0096-3941; CODEN: EOSTAJ ER - TY - JOUR T1 - Stable and radio-carbon isotope measurements in the Pacific Ocean: Contribution from NOSAMS JF - Supplement to Trans. Amer. Geophysical Union Y1 - 1996 A1 - McNichol, A. P. A1 - Key, R. A1 - Jones, G. VL - 76 IS - 3 N1 - id: 1266 ER - TY - CONF T1 - Stable and radiocarbon isotope measurements in the Pacific Ocean: Contributions from NOSAMS T2 - AGU/ASLO 1996 Ocean Sciences Meeting Y1 - 1996 A1 - McNichol, A. P. A1 - von Reden, K. F. A1 - Schneider, R. J. A1 - Key, R. M. A1 - Jones, G. A. JF - AGU/ASLO 1996 Ocean Sciences Meeting CY - San Diego, CA N1 - id: 960 ER - TY - JOUR T1 - Surficial geology of the middle and upper continental slope, northern Gulf of Mexico; the important role of episodic fluid venting JF - AAPG Bulletin Y1 - 1996 A1 - Roberts, H. H. VL - 80 IS - 9 N1 - id: 1272 ER - TY - JOUR T1 - TIMS U-Th dated early Holocene sea-level record from submerged fossil reefs, southeast Florida margin JF - Abstracts with Programs--Geological Society of America Y1 - 1996 A1 - Lundberg, J. A1 - Toscano, M. A. VL - 28 IS - 7 N1 - id: 1263 JO - TIMS U-Th dated early Holocene sea-level record from submerged fossil reefs, southeast Florida margin ER - TY - JOUR T1 - Uranium-series disequilibrium, sedimentation, diatom frustules, and paleoclimate change in Lake Baikal JF - Earth and Planetary Science Letters Y1 - 1996 A1 - Edgington, D. N. A1 - Robbins, J. A. A1 - Colman, S. M. A1 - Orlandini, K. A. A1 - Gustin, M. P. AB - The large volume of water, approximately one-fifth of the total surface fresh water on the planet, contained in Lake Baikal in southeastern Siberia is distinguished by having a relatively high concentration of uranium (ca. 2 nM), and, together with the surface sediments, an unusually high U-234/U-238 alpha activity ratio of 1.95. About 80% of the input of 234 uranium to the lake, with a U-234/U-238 ratio of 2.0, comes from the Selenga River, Profiles of uranium, as well as the extent of isotopic disequilibrium in a 9 m sediment core collected on Academic Ridge, generally show high values during interglacial periods corresponding to high diatom frustule numbers (DiFr) and biogenic silica (BSi) data that have been reported elsewhere. During glacial periods (low DiFr and BSi), uranium progeny (U-234 and Th-230) were in secular equilibrium with low concentrations of their parent U-238. Radionuclide distributions were interpreted in terms of a quantitative model allowing for adsorption of riverine inputs of uranium onto two classes of sedimenting particles with differing U-238/Th-232 ratios and uranium progeny in secular equilibrium. If the U-234/U-238 activity ratio of adsorbed uranium has remained constant, mean sedimentation rates can be independently estimated as 3.6 +/- 0.6 and 3.7 +/- 0.9 cm . kyr(-1) for the decay of U-234 and in-growth of Th-230, respectively. These rates are consistent with a mean rate of 3.76 cm . kyr(-1), calculated by optimization of the correspondence between adsorbed U-238 and delta(18)O in dated oceanic sediments, The adsorbed uranium apparently tracks variable river flow during interglacials and is drastically reduced during periods of glaciation. Evidently, uranium has not been significantly redistributed within Baikal sediments over at least the past 250 kyr and is a unique, biologically non-essential, tracer for climate-sensitive processes, which provide their own internal geochronometers, potentially useful for ages up to 1 Myr BP. VL - 142 IS - 1-2 N1 - Uz230Times Cited:61Cited References Count:29 JO - Uranium-series disequilibrium, sedimentation, diatom frustules, and paleoclimate change in Lake Baikal ER - TY - JOUR T1 - WOCE AMS Radiocarbon I: Pacific Ocean results (P6, P16, and P17) JF - Radiocarbon Y1 - 1996 A1 - Key, R. M. A1 - Quay, P. D. A1 - Jones, G. A. A1 - McNichol, A. P. A1 - von Reden, K. F. A1 - Schneider, R. J. AB - AMS radiocarbon results from the World Ocean Circulation Experiment in the Pacific Ocean show dramatic changes in the inventory and distribution of bomb-produced 14C since the time of the GEOSECS survey (8/73-6/74). Nearsurface 4C values for the eastern portion of both the northern and southern subtropical gyres decreased by 25-50%, with the change being greater in the north. Equatorial near-surface values have increased by ca. 25%. Changes in the 250-750-m depth range are dramatically different between the northern and southern basins. The intermediate and mode waters of the southern basin have increased by as much as 75%o since GEOSECS. Waters of similar density in the northern hemisphere are not exposed to the Southern Ocean circulation regime and are significantly less ventilated, showing maximum changes of ca. 50%. VL - 38 UR - https://journals.uair.arizona.edu/index.php/radiocarbon/article/view/1918 IS - 3 N1 - id: 38 JO - WOCE AMS Radiocarbon I: Pacific Ocean results (P6, P16, and P17) ER - TY - JOUR T1 - WOCE Pacific Ocean radiocarbon program JF - Radiocarbon Y1 - 1996 A1 - Key, R. M. KW - sciences-ams-facility AB - Fieldwork for the World Ocean Circulation Experiment (WOCE) radiocarbon program was recently completed. Ca. 9000 samples were collected for analysis using both conventional B-counting techniques and the newer AMS technique. The mean uncertainty for the beta analyses is 3 parts per thousand; for AMS analyses, ca. 4.5 parts per thousand. VL - 38 SN - 0033-8222 IS - 3 N1 - Xd080Times Cited:21 Cited References Count:40 JO - Radiocarbon ER - TY - CONF T1 - Age and paleoclimate of submerged late Pleistocene reef system, Southeast Florida shelf; implications for substage 5A sea level T2 - Geological Society of America, 1995 annual meeting Y1 - 1995 A1 - Toscano, M. A. A1 - Lundberg, J. A1 - Hine, A. C. JF - Geological Society of America, 1995 annual meeting CY - New Orleans, LA VL - 27 N1 - id: 1242; 6 ER - TY - JOUR T1 - Amazon continental margin high resolution records of the penultimate interglacial JF - Eos, Transactions, American Geophysical Union Y1 - 1995 A1 - Showers, W. J. A1 - Genna, B. A1 - Price, P. VL - 76 IS - 17 N1 - id: 1276 ER - TY - CONF T1 - Amazon Continental Margin High Resolution Records of Western Tropical Atlantic circulation over the past 130 ky T2 - International Conference of Paleoceanography Y1 - 1995 A1 - Showers, William J. A1 - Genna, Bernard A1 - Price, Pamela JF - International Conference of Paleoceanography CY - Halifax, Canada N1 - id: 1280 ER - TY - JOUR T1 - Climate-Change - the North Pacific through the Millennia JF - Nature Y1 - 1995 A1 - Keigwin, L. D. VL - 377 IS - 6549 N1 - Rz336Times Cited:6Cited References Count:14 JO - Climate-Change - the North Pacific through the Millennia ER - TY - JOUR T1 - Climatically Linked Carbon-Isotope Variation during the Past 430,000 Years in Southern-Ocean Sediments JF - Paleoceanography Y1 - 1995 A1 - Singer, A. J. A1 - Shemesh, A. AB - We use the isotopic composition of carbon from organic matter enclosed within diatom frustules as a proxy for paleoproductivity and paleo-dissolved carbon dioxide concentrations in ocean surface waters. A Southern Ocean record from south of the Antarctic Polar Front and spanning 430,000 years of carbon isotopic variation in diatomaceous organic matter is presented for the first time. The most refractory diatomaceous organic matter fraction was extracted and analyzed to avoid problems associated with diagenesis. The results clearly indicate cyclic changes in organic carbon isotopic ratios, with C-13 depleted values associated with all of the last five glacial periods, reflecting changes in surface water properties and primary productivity. Changes in dissolved carbon dioxide concentrations are the most probable cause of these cycles, but the possible effect of seawater pH changes cannot be excluded. VL - 10 IS - 2 N1 - Rd382Times Cited:54Cited References Count:43 JO - Climatically Linked Carbon-Isotope Variation during the Past 430,000 Years in Southern-Ocean Sediments ER - TY - JOUR T1 - Coastal Massachusetts Pond Development - Edaphic, Climatic, and Sea-Level Impacts since Deglaciation JF - Journal of Paleolimnology Y1 - 1995 A1 - Winkler, M. G. A1 - Sanford, P. R. AB - Kettle ponds in the Cape Cod National Seashore in southeastern Massachusetts differ in their evolution due to depth of the original ice block, the clay content of outwash in their drainage basins, and their siting in relation to geomorphic changes caused by sea-level rise, barrier beach formation, and saltmarsh development. Stratigraphic records of microfossil, carbon isotope, and sediment changes also document late-glacial and Holocene climatic changes.The ponds are separated into 3 groups, each of which follow different development scenarios. Group I ponds date from the late-glacial. They formed in clay-rich outwash, have perched aquifers and continuous lake sediment deposition. The earliest pollen and macrofossil assemblages in Group I pond sediments suggest tundra and spruce-willow parklands before 12 000 yr B.P., boreal forest between 12 000 and 10 500 yr B.P., bog/heath initiation and expansion during the Younger Dryas between 11 000 and 10 000 yr B.P., northern conifer forest between 10 500 and 9500 yr B.P., and establishment of the Cape oak and pitch pine barrens vegetation after 9500 yr B.P. Sedimentation rate changes suggest lowered freshwater levels between 9000 and 5000 yr B.P. caused by decreased precipitation on the Atlantic Coastal Plain. Lake sediment deposition began in the middle Holocene in Group II ponds which formed in clay-poor outwash. These ponds date from about 6000-5000 yr B.P. In these ponds sediment deposition began as sea level rose and the freshwater lens intersected the dry basins. The basal radiocarbon dates of these ponds and stable carbon isotope analyses of the pond sediments suggest a sea-level curve for Cape Cod Bay. Holocene topographic changes in upland and the landscape surrounding the ponds is reconstructed for this coastal area.Group III ponds in the late Holocene landscape of the Provincelands dunes originated as interdunal bogs about 1000 yr B.P. and became ponds more recently as water-levels increased. Feat formation in the Provincelands reflects climatic changes evident on both sides of the Atlantic region. VL - 14 IS - 3 N1 - Td951Times Cited:1Cited References Count:62 JO - Coastal Massachusetts Pond Development - Edaphic, Climatic, and Sea-Level Impacts since Deglaciation ER - TY - JOUR T1 - Continental climate response to orbital forcing from biogenic silica records in Lake Baikal, Siberia JF - Nature Y1 - 1995 A1 - Colman, S. M. A1 - Peck, J. A. A1 - B, Karabanov E. A1 - Carter, S. J. A1 - Bradbury, J. P. A1 - King, J. W. A1 - Williams, D. F. VL - 378 N1 - id: 1357 ER - TY - THES T1 - Development and application of the mollusc Arctica islandicaas a paleoceanographic tool for the North Atlantic Ocean, Thesis Y1 - 1995 A1 - Weidman, C. R. PB - MIT CY - Cambridge, MA and Woods Hole, MA VL - Ph.D. dissertation ER - TY - CONF T1 - Developments at the NOSAMS Facility During 1995 T2 - Symposium of Northeastern Accelerator Personnel Y1 - 1995 A1 - von Reden, K. F. A1 - Cohen, G. J. A1 - Dalton, M. J. A1 - Peden, J. C. A1 - Schneider, R. J. JF - Symposium of Northeastern Accelerator Personnel CY - Durham, NC N1 - id: 1799 ER - TY - JOUR T1 - The eastern chenier plain; an update on downrift coastal progradation associated with the building of a new Holocene delta lobe in the Mississippi delta complex JF - AAPG Bulletin Y1 - 1995 A1 - Roberts, Harry H. A1 - Huh, O. K. VL - 79 IS - 10 N1 - id: 64 ER - TY - THES T1 - The effects of islands on the recession of the late Wisconsinan ice sheet margin in the De Geer Sea, Maine, Thesis Y1 - 1995 A1 - Donner, J. PB - University of Maine CY - Orono, Maine VL - Dissertation/Thesis ER - TY - CONF T1 - Environmental History of the Lake Winnebago Basin: 15,000 Years Ago to 1850 T2 - Wisconsin Academy of Sciences, Arts and Letters, 125th Annual Conference Y1 - 1995 A1 - Smith, G. L. Fitzgerald T. M. Gruber M. M. Smith S. R. JF - Wisconsin Academy of Sciences, Arts and Letters, 125th Annual Conference CY - Madison, Wisconsin N1 - id: 916 ER - TY - THES T1 - Evolution, environment, and isotope systematics of a glauconite deposit on the modern sea floor along the southeastern United States continental margin, Thesis Y1 - 1995 A1 - am Ende, B. A. PB - University of North Carolina, Chapel Hill, NC VL - Ph.D. N1 - id: 1; Department of Geology ER - TY - CONF T1 - A first look at changes in Pacific 14C levels between GEOSECS and WOCE T2 - International Association for the Physical Sciences of Oceans, General Assembly, 5-12 August 1995, Honolulu, Hawaii Y1 - 1995 A1 - Key, R. M. A1 - Toggweiler, J. R. JF - International Association for the Physical Sciences of Oceans, General Assembly, 5-12 August 1995, Honolulu, Hawaii PB - International Association for the Physical Sciences of Oceans (IAPSO) CY - Honolulu, Hawaii VL - 130 N1 - id: 40 JO - A first look at changes in Pacific 14C levels between GEOSECS and WOCE ER - TY - JOUR T1 - Geological framework, processes, and rates of subsidence in the Mississippi River delta plain JF - AAPG Bulletin Y1 - 1995 A1 - Penland, P. Shea A1 - Jeffress, Williams S. A1 - Roberts, Harry H. A1 - Bailey, Alan A1 - Kuecher, Gerald J. A1 - Suhayda, Joseph N. A1 - Ramsey, Karen E. VL - 79 IS - 10 N1 - id: 65 ER - TY - JOUR T1 - Glacial-Interglacial Differences in Circulation and Carbon Cycling within the Upper Western North-Atlantic JF - Paleoceanography Y1 - 1995 A1 - Slowey, N. C. A1 - Curry, W. B. AB - We investigated glacial-interglacial changes in the circulation and carbon cycling in the western North Atlantic subtropical gyre using hydrographic data and downcore records of the stable isotopic compositions of individual shells of Bahamian benthic foraminifera. Potential temperature-salinity-depth relations show that modern thermocline (similar to 200-1000 m) and deep (similar to 1000-2000 m) waters in the Providence Channels, Bahamas, originate in the Sargasso Sea and are typical of the subtropical gyre. Gradients in the stable isotopic compositions of late Holocene Planulina and Cibicidoides species from the bank margins (similar to 400 to 1500 m depth) reflect temperature, nutrient, and isotopic gradients of modern subtropical gyre waters. The difference between the delta(18)O of glacial maximum and late Holocene foraminifera is similar to 2.1 parts per thousand for the upper 900 m of the water column and similar to 1.6 parts per thousand for deeper waters, indicating that these waters were similar to 4 degrees C and similar to 2 degrees C cooler, respectively, during glacial time. The glacial temperature gradient (dT/dz) was similar to today, while the base of the thermocline was similar to 100 m shallower. These results differ significantly from our earlier results from multiple shell delta(18)O analyses, which implied upper thermocline waters were only similar to 1 degrees C cooler and dT/dz was greater during the glacial maximum. The difference occurs because bioturbation adversely affects multiple shell analyses of glacial-aged samples from shallow water depths. At all depths above 1500 m, foraminiferal delta(13)C are greater during the glacial maximum than the late Holocene by at least 0.1 to 0.2 parts per thousand (as much as 0.6 parts per thousand in the lower thermocline), indicating that nutrient concentrations throughout the thermocline were reduced and there was no oxygen minimum zone during the glacial maximum. This suggests greater, more uniform ventilation of the thermocline. Results of single and multiple shell delta(13)C analyses of glacial age foraminifera compare favorably because samples most affected by mixing correspond to water depths where the glacial-interglacial change of delta(13)C was small. Cooler upper ocean waters during the glacial maximum reflect cooler temperatures at the ocean surface where isopycnal surfaces outcrop, including large areas of the subtropical ocean. A shallower thermocline base is consistent with southward migration of the northern edge of the subtropical gyre or increased mode water production. Enhanced thermocline ventilation is consistent with more vigorous winds and all isopycnal surfaces outcropping in the area of Ekman downwelling. VL - 10 IS - 4 N1 - Rm032Times Cited:80Cited References Count:86 JO - Glacial-Interglacial Differences in Circulation and Carbon Cycling within the Upper Western North-Atlantic ER - TY - CONF T1 - The Hemispherical Ionizer Sputter Sources at the Woods Hole AMS Facility T2 - 29th Symposium of NorthEastern Accelerator Personnel Y1 - 1995 A1 - von Reden, K. F. ED - Westerfeld, C. JF - 29th Symposium of NorthEastern Accelerator Personnel PB - World Scientific Publishing Co. CY - Durham, NC N1 - id: 1671 ER - TY - CONF T1 - Improvements in procedural blanks at NOSAMS: Reflections of improvements in sample preparation and accelerator operation T2 - 15th International 14C Conference Y1 - 1995 A1 - McNichol, A. P. A1 - Gagnon, A. R. A1 - Osborne, E. a A1 - Hutton, D. L. A1 - von Reden, K. F. A1 - Schneider, R. J. JF - 15th International 14C Conference PB - Radiocarbon VL - 37 N1 - id: 1641; 15th International Radiocarbon Conference, Glasgow, Scotland, August 15-19, 1994 ER - TY - JOUR T1 - Improvements in procedural blanks at NOSAMS: Reflections of improvements in sample preparation and accelerator operation JF - Radiocarbon Y1 - 1995 A1 - McNichol, A. P. A1 - Gagnon, A. R. A1 - Osborne, E. A. A1 - Hutton, D. L. A1 - vonReden, K. F. A1 - Schneider, R. J. KW - SPECTROMETRY AB - During the four years the Sample Preparation Laboratory (SPL) at the National Ocean Sciences Accelerator Mass Spectrometer (NOSAMS) Facilty has been in operation we have accumulated much data from which we can assess our progress. We evaluate our procedural blanks here and describe modifications in our procedures that have improved our analyses of older samples. In the SPL, we convert three distinct types of samples-seawater, CaCO3 and organic carbon-to CO2 prior to preparing graphite for the accelerator and have distinct procedural blanks for each procedure. Dissolved inorganic carbon (Sigma CO2) is extracted from acidified seawater samples by sparging with a nitrogen carrier gas. We routinely analyze ''line blanks'' by processing CO2 from a C-14-dead source through the entire stripping procedure. Our hydrolysis blank, IAEA C-1, is prepared by acidifying in vacuo with 100% H3PO4 at 60 degrees C overnight, identical to our sample preparation. We use a dead graphite, NBS-21, or a commercially available carbon powder for our organic combustion blank; organic samples are combusted at 850 degrees C for 5 h using CuO to provide the oxidant. Analysis of our water stripping data suggests that one step in the procedure contributes the major portion of the line blank. At present, the contribution from the line blank has no effect on our seawater analyses (fraction modern (fm) between 0.7 and 1.2). Our hydrolysis blanks can have an fm value as low as 0.0006, but are more routinely between 0.0020 and 0.0025. The fm of our best organic combustion blanks is higher than those routinely achieved in other laboratories and we are currently altering our methods to reduce it. VL - 37 SN - 0033-8222 IS - 2 N1 - Ud868Times Cited:16 Cited References Count:6 JO - Radiocarbon ER - TY - THES T1 - Intracrystalline proteins in aragonite-needle mud from Florida Bay: an immunological and biogeochemica study, Thesis Y1 - 1995 A1 - Hawkins, Sharon PB - University of North Carolina at Chapel Hill CY - Ann Arbor, MI VL - M.S. ER - TY - JOUR T1 - Late Pleistocene Oxygen-Isotope Records of Biogenic Silica from the Atlantic Sector of the Southern-Ocean JF - Paleoceanography Y1 - 1995 A1 - Shemesh, A. A1 - Burckle, L. H. A1 - Hays, J. D. AB - We determined the isotopic composition of oxygen in marine diatoms in eight deepsea cores recovered from the Atlantic sector of the Southern Ocean. The analytical reproducibility and core-to-core consistency of the isotopic signal suggests that diatom delta(18)O can be used as a new paleocenographic tool to reconstruct past variations in surface water characteristics and to generate O-18 -isotope-based stratigraphy for the Southern Ocean. The data indicate that diatom delta(18)O reflects sea surface temperature and seawater isotopic composition and that diatoms retain their isotopic signal on timescales of a least 430 ka. The delta(18)O analyses of different diatom assemblages reveal that the isotopic signal is free of species effects and that the common Antarctic species have the same water-opal fractionation. The transition from the last glacial maximum (LGM) to the Holocene is fully recorded in high sedimentation rate cores. An O-18 enrichment during the LGM, a post-LGM meltwater spike and an input of meltwater during the late Holocene are the main isotopic features observed in down core records. The origin of this meltwater was very likely melting icebergs and/or continental ice or by melting sea ice that had accumulated snow. The most pronounced meltwater effects are recorded in cores that are associated with the Weddel gyre. Our results provide the basis for extending isotope studies to oceanic regions devoid of carbonate; further, isotopic stratigraphies may be constructed for records and regions where they were previously not possible. VL - 10 IS - 2 N1 - Rd382Times Cited:82Cited References Count:23 JO - Late Pleistocene Oxygen-Isotope Records of Biogenic Silica from the Atlantic Sector of the Southern-Ocean ER - TY - CONF T1 - Late Pleistocene to Holocene Diatom Assemblages of the Lake Winnebago Basin, Wisconsin T2 - North-Central/South-Central Section, Geological Society of America Y1 - 1995 A1 - Smith, S. R. Smith G. L. JF - North-Central/South-Central Section, Geological Society of America CY - Lincoln, Nebraska VL - 27 N1 - id: 915 ER - TY - JOUR T1 - Late Pleistocene to Holocene paleolimnolgy of the Lake Winnebago Basin, based on ostracods JF - Abstracts with Programs - Geological Society of America Y1 - 1995 A1 - Gruber, M. M. A1 - Smith, G. L. VL - 27 IS - 3 N1 - id: 75 ER - TY - CONF T1 - Late Pleistocene to Holocene Paleolimnology of the Lake Winnebago Basin, Based on Ostracods T2 - North-Central/South-Central Section,Geological Society of America Y1 - 1995 A1 - Gruber, M. M. A1 - Smith, G. L. JF - North-Central/South-Central Section,Geological Society of America CY - Lincoln, Nebraska VL - 27 N1 - id: 909 ER - TY - CONF T1 - Late Quaternary Depositional History of the Lake Winnebago Basin T2 - North-Central/South_Central Section, Geological Society of America Y1 - 1995 A1 - Fitzgerald, T. M. A1 - Smith, G. L. JF - North-Central/South_Central Section, Geological Society of America CY - Lincoln, Nebraska VL - 27 N1 - id: 908 ER - TY - JOUR T1 - Late Quaternary Paleolimnology of the Lake Winnebago Basin, Based on Ostracodes Y1 - 1995 A1 - Gruber, M. M. Smith G. L. N1 - id: 910 ER - TY - JOUR T1 - Late Quaternary Relative Sea-Level Change in the Western Gulf of Maine - Evidence for a Migrating Glacial Forebulge JF - Geology Y1 - 1995 A1 - Barnhardt, W. A. A1 - Gehrels, W. R. A1 - Belknap, D. F. A1 - Kelley, J. T. AB - New radiocarbon-dated cores obtained by Vibracorers in the western Gulf of Maine confirm that a short-lived, relative sea-level lowstand of similar to-55 m occurred at 11-10.5 ka. These cores and younger salt-marsh data also reveal that rates of transgression varied throughout the Holocene, probably due to local variations in glacial isostasy. The isostatic component is resolved by subtracting published approximations of eustatic sea level from our well-determined observations of local relative sea level. A large peek in the isostatic curve coincides with the lowstand and is interpreted as a forebulge 20-25 m in amplitude. Forebulge migration is estimated at 7-11 km/100 yr, based on the timing of lowstands across the region. VL - 23 IS - 4 N1 - Qr847Times Cited:69Cited References Count:32 JO - Late Quaternary Relative Sea-Level Change in the Western Gulf of Maine - Evidence for a Migrating Glacial Forebulge ER - TY - CONF T1 - Late Wisconsinan stratigraphy and deglaciation chronology of the lower Aroostook River Valley, Maine T2 - Geological Society of America, Northeastern Section, 30th annual meeting Y1 - 1995 A1 - Strasser, J. C. A1 - Weddle, T. K. A1 - Dorion, C. C. JF - Geological Society of America, Northeastern Section, 30th annual meeting CY - Cromwell, Connecticut VL - 27 N1 - id: 1238 ER - TY - JOUR T1 - The Marine Record of Deglaciation from the Continental-Margin Off Nova-Scotia JF - Paleoceanography Y1 - 1995 A1 - Keigwin, L. D. A1 - Jones, G. A. AB - Continental margin sediments off Nova Scotia accumulate at high rates (up to 360 cm kyr(-1)) and contain a history of millennial-scale environmental changes which are dominated by the proximity of the Laurentide ice sheet during the latest Quaternary. Using ratios of oxygen, accelerator mass spectrometer radiocarbon dating, micropaleontology, and sedimentology, we document these changes in six piston cores ranging in water depth from similar to 450 to similar to 4300 m. We find that maximum delta(18)O in N. pachyderma occurred about 15 ka and preceded the maximum abundance of this species in these cores by similar to 1000 years. Between 13 and 14 ka we find a second peak in abundance of N. pachyderma, minimum delta(18)O, and two pulses of ice rafting. The sediment lithology supports terrestrial studies which indicate that there was a general withdrawal of ice beyond the upper Paleozoic and Mesozoic red beds by 14 ka in southeastern Canada, so the ice rafting events between 13 and 14 ka probably reflect ice stream activity in the St. Lawrence valley. The Younger Dryas event is recognized as a peak in abundance of N. pachyderma and ice rafting (dated as similar to 11.3 ka), but meltwater discharge to the Gulf of St. Lawrence was either too small or occurred over too long a time to leave a distinct delta(18)O minium off Nova Scotia. At 7.1 ka, in the middle of Holocene warming, we find a third peak in abundance of N. pachyderma and another delta(18)O minimum but no ice rafting. We interpret these data as evidence of a late-occurring meltwater event which, if correct, could have originated in the Great Lakes, in the Labrador-Ungava region, or in both. The final millennial-scale phenomenon off Nova Scotia is the onset of ''Neoglaciation,'' marked by increased ice rafting and increased % N. pachyderma beginning about 5 kyr ago. VL - 10 IS - 6 N1 - Th675Times Cited:85Cited References Count:77 JO - The Marine Record of Deglaciation from the Continental-Margin Off Nova-Scotia ER - TY - CONF T1 - Marsh accretion and relative sea level rise since AD 1000 T2 - Geological Society of America, 1995 annual meeting Y1 - 1995 A1 - Varekamp, J. C. A1 - E, Thoma JF - Geological Society of America, 1995 annual meeting PB - Geological Society of America (GSA) Boulder, CO, USA CY - New Orleans, LA, USA VL - 27 N1 - id: 1290; 6 ER - TY - JOUR T1 - Measurements of the OX-II/OX-1 ratio as a quality control parameter at NOSAMS JF - Radiocarbon Y1 - 1995 A1 - Schneider, R. J. A1 - McNichol, A. P. A1 - Nadeau, M. J. A1 - von Reden, K. F. VL - 37 IS - 3 N1 - id: 1630 ER - TY - CONF T1 - Measurements of the OX-II/OX-I ratio as a quality control parameter at NOSAMS T2 - 15th International Radiocarbon Conference Y1 - 1995 A1 - Schneider, R. J. A1 - McNichol, A. P. A1 - Nadeau, M. J. A1 - von Reden, K. F. JF - 15th International Radiocarbon Conference CY - Glasgow, Scotland N1 - id: 944 ER - TY - JOUR T1 - Mud volcanoes in the Gulf of Mexico; a mechanism for mixing sediments of different ages in slope environments JF - Gulf Coast Association of Geological Societies Transactions Y1 - 1995 A1 - Kohl, Barry A1 - Roberts, Harry H. AB - The extrusion of older, unconsolidated sediments onto the seafloor during the Quaternary is one explanation for frequent occurrences of displaced fossil microfaunas encountered at depth in wells drilled on the flanks of salt diapirs in the continental slope environment. Samples from mud volcanoes on the Louisiana continental slope were collected in 1992 and 1993 for foraminiferal studies by using the Johnson Sea-Link I & II manned submersibles. Age dating by use of planktonic foraminifera has shown that sediments ranging in age from middle Miocene to Pleistocene are being deposited on the modern seafloor by active mud vents/volcanoes. These sediments, when buried by modern pelagic or more rapidly deposited terrigenous clastics, would be anomalous when encountered in coreholes or exploratory wells. Vents, as shown by seismic sections, are associated with faults which provide the connection to older subsurface fine-grained sediments that are: 1) mobilized by gas and fluids, 2) carried to the surface, and 3) ejected onto the seafloor to form mud volcanoes and fine-grained sediment flows. The mud volcanoes are in water depths ranging from 300 to 690 meters located in Garden Banks Block 382, Green Canyon Blocks 143 and 272, and Mississippi Canyon Block 929. This study is part of an ongoing investigation of the geology around cold vents which support chemosynthetic faunal communities in the Gulf of Mexico. These results have important implications for age dating subsurface sediments encountered in wells and coreholes on the continental slope. VL - 45 UR - http://archives.datapages.com/data/gcags/data/045/045001/0351.htm N1 - id: 63 JO - Mud volcanoes in the Gulf of Mexico; a mechanism for mixing sediments of different ages in slope environments ER - TY - CONF T1 - Multiple Indicator Approach to Interpreting Abrupt Climate Changes in the North Atlantic. Program and Abstracts T2 - 5th International Conference on Paleoceanography Y1 - 1995 A1 - Kellog, T. B. A1 - Wright, J. D. A1 - Kellogg, D. E. A1 - Lagerklint, I. M. A1 - French, P. L. JF - 5th International Conference on Paleoceanography CY - Halifax, Nova Scotia N1 - id: 96 ER - TY - CONF T1 - Negative ion sources for dating a very small radiocarbon samples T2 - 15th International Radiocarbon Conference Y1 - 1995 A1 - Nadeau, M. J. A1 - Schneider, R. J. A1 - von Reden, K. R. JF - 15th International Radiocarbon Conference CY - Glasgow, Scotland N1 - id: 943 ER - TY - JOUR T1 - North Atlantic Deep Water variability during stage 3 JF - Eos, Transactions, American Geophysical Union Y1 - 1995 A1 - Oppo, D. W. A1 - Lehman, S. J. A1 - Curry, J. A1 - Lynch, Stieglitz A1 - Fairbanks, R. G. VL - 76 IS - 17 N1 - id: 58 ER - TY - JOUR T1 - Origin of Carbon in Fumarolic Gas from Island Arcs JF - Chemical Geology Y1 - 1995 A1 - Sano, Y. A1 - Marty, B. AB - We have measured He-3/He-4 ratios, delta(13)C-values and CO2/He-3 ratios of fumaroles and hot spring gases in three volcanic areas in Japan. The He-3/He-4 ratios, delta(13)C-values and CO2/He-3 ratios vary from 2.02 R(atm) to 7.55 R(atm) -9.7 parts per thousand to -2.7 parts per thousand and from 7.74.10(9) to 1.18.10(11), respectively. Based on these data and those in the literature, we present the first quantitative estimates of the upper mantle, sediment and limestone including slab components in CO2 of volcanic and hydrothermal fluids from subduction zones. Taking compiled C isotopic data of limestone and organic sediment, assuming that the CO2/He-3 ratio and delta(13)C-value of mid-ocean ridge basalt (MORB) are representative of the upper-mantle component, and that later isotopic and elemental fractionations are minimal, it is possible to deconvolve each fraction of C on the basis of simple mixing equations. Up to 20% of the carbon in high-temperature volcanic gases in subduction zones is derived from a MORB-type source, while the major fraction of the gases is attributable to CO2 produced by decarbonation of subducted marine limestone and slab carbonate. VL - 119 IS - 1-4 N1 - Qc329Times Cited:227Cited References Count:46 JO - Origin of Carbon in Fumarolic Gas from Island Arcs ER - TY - CONF T1 - Paleodischarge events on the Amazon Fan during the last glacial T2 - AGU Annual Fall Meeting Y1 - 1995 A1 - Showers, William J. A1 - Genna, Bernard A1 - Price, Pamela A1 - Flood, Roger A1 - Piper, David JF - AGU Annual Fall Meeting CY - San Francisco, California N1 - id: 1281 ER - TY - JOUR T1 - Paleosol evidence of anthropogenic impact on late Holocene landscape instability around an Anasazi site in Kane County, Utah JF - Abstracts with Programs - Geological Society of America Y1 - 1995 A1 - Kulp, T. R. A1 - Rigsby, C. A. VL - 27 IS - 6 N1 - id: 1271 JO - Paleosol evidence of anthropogenic impact on late Holocene landscape instability around an Anasazi site in Kane County, Utah ER - TY - JOUR T1 - Possible Role of Climate in the Collapse of Classic Maya Civilization JF - Nature Y1 - 1995 A1 - Hodell, D. A. A1 - Curtis, J. H. A1 - Brenner, M. AB - THE Maya civilization developed around 3,000 years ago in Mesoamerica, and after flourishing during the so-called Classic period, it collapsed around 750-900 AD(1). It has been speculated(2-6) that climate change may have played a part in this collapse. But efforts to reconstruct the last three millennia of Mesoamerican climate using palynological methods have met with equivocal success, because human-mediated deforestation has altered regional vegetation in ways that mimic climate shifts, making it difficult to discriminate between natural and anthropogenic changes(7-15). Here we use temporal variations in oxygen isotope and sediment composition in a 4.9-m sediment core from Lake Chichancanab, Mexico, to reconstruct a continuous record of Holocene climate change for the central Yucatan peninsula. The interval between 1,300 and 1,100 yr up (AD 800-1,000) was the driest of the middle to late Holocene epoch, and coincided with the collapse of Classic Maya civilization, This continuous climate proxy record thus provides evidence of climate deterioration in the Maya region during the terminal Classic period. VL - 375 IS - 6530 N1 - Rb101Times Cited:439Cited References Count:41 JO - Possible Role of Climate in the Collapse of Classic Maya Civilization ER - TY - JOUR T1 - Radiocarbon Ages of Pre-Bomb Clams and the Hard-Water Effect in Lakes Michigan and Huron JF - Journal of Paleolimnology Y1 - 1995 A1 - Rea, D. K. A1 - Colman, S. M. AB - Five radiocarbon ages, all determined by accelerator mass spectrometry, have been obtained for two pre-bomb bivalves from Lake Michigan and one from Lake Huron. After correcting those ages for the fractionation of C-14 in calcite and for the radioactively inert CO2 in the atmosphere, we find residual ages, caused by the hard water effect, of about 250 years for Lake Michigan and 440 years for Lake Huron. VL - 14 IS - 1 N1 - Rq668Times Cited:22Cited References Count:13 JO - Radiocarbon Ages of Pre-Bomb Clams and the Hard-Water Effect in Lakes Michigan and Huron ER - TY - CONF T1 - Routine 14C AMS at 0.2% precision - Do we need it, can it be done? T2 - 109th American Chemical Society National Meeting Y1 - 1995 A1 - von Reden, K. F. JF - 109th American Chemical Society National Meeting CY - Anaheim, CA N1 - id: 945 ER - TY - RPRT T1 - Sampling Cruise 6, North Atlantic Tracer Release Experiment, R/V Seward Johnson, Cruise 9404 Y1 - 1995 A1 - Ledwell, J. R. A1 - Donoghue, T. A1 - Donoghue, J. A1 - Sundermeyer, M. PB - Woods Hole Oceanographic Institution CY - Woods Hole, MA N1 - id: 1754 ER - TY - JOUR T1 - A Sea-Level Rise Curve from Guilford, Connecticut, USA JF - Marine Geology Y1 - 1995 A1 - Nydick, K. R. A1 - Bidwell, A. B. A1 - Thomas, E. A1 - Varekamp, J. C. AB - High-resolution stratigraphic studies based on sediment chemistry, lithology, macroflora, and benthic foraminiferal assemblages in three peat cores from coastal salt marshes at Guilford, Connecticut, show that coastal marshes are ephemeral environments. Marsh-wide environmental variations were common, and century-long episodes of relative submergence alternated with emergence. Despite about 2 m of relative sea-level rise (RSLR) in Connecticut over the last 1500 years, the marshes have expanded both landwards and seawards, and marsh accretion has been outpaced only marginally by RSLR.We used radiocarbon dating and the level of anthropogenic markers (metal pollution, as dated with Pb-210) in the cores for age control. For most of the last 1000 years the rate of RSLR was between 1.3 and 1.8 mm/yr, but over the last 300-400 years it increased to 2.9-3.3 mm/yr, and has been faster than the accretion rate, especially in the middle marsh. The net-submergence rate or ''submergence index'' (ratio of the rate of RSLR and marsh-accretion rate) averaged about 1.15 over the last 1000 years, and increased to about 1.5 over the last 200 years.The rate of RSLR was very sluggish during the early part of the Little Ice Age, but we found a slightly higher rate during the Little Climate Optimum; this excursion is close to the noise level, however. The most significant observation is that RSLR increased strongly around A.D. 1650. The onset of this acceleration falls in the middle to end of the Little Ice Age, and thus preceded the period of modern global warming that started late last century and that has been tentatively correlated with anthropogenic emissions of greenhouse gases. VL - 124 IS - 1-4 N1 - Rl477Times Cited:71Cited References Count:81 JO - A Sea-Level Rise Curve from Guilford, Connecticut, USA ER - TY - RPRT T1 - Status of understanding of the saturated-zone ground-water flow system at Yucca Mountain, Nevada, as of 1995, Report Y1 - 1995 A1 - Steinkampf, W. C. N1 - id: 1285 ER - TY - JOUR T1 - Stratigraphic Evidence of Changes in Amazon Shelf Sedimentation during the Late Holocene JF - Marine Geology Y1 - 1995 A1 - Sommerfield, C. K. A1 - Nittrouer, C. A. A1 - Figueiredo, A. G. AB - Late Holocene sedimentation on the Amazon shelf was investigated using a combination of seismic, sedimentological, and geochronological methods. Piston cores collected in the subaqueous delta region during A Multidisciplinary Amazon Shelf Sediment Study (AmasSeds) penetrated a regionally traceable (1.25 x 10(4) km(2)) seismic discontinuity, which corresponds to a dense relict-mud reflector overlain by acoustically transparent sediment. Distinct offsets in profiles of wet-bulk density, P-wave velocity, and Pb-210 activity are noted in cores at the reflector horizon (unconformity), signifying a past change in sedimentation conditions on the shelf. Bulk-sediment C-14 dating indicates net depositional conditions for the subaqueous delta from >1800 yr B.P. to 700 yr B.P. and a net erosional phase from about 700 yr B.P. to 100 yr ago. Sedimentological evidence of the erosional phase includes lag deposits and burrows present at the unconformity surface in piston cores. The deposits above and below the unconformity are similar with respect to grain-size parameters and sedimentary structures, suggesting that environmental conditions during the two depositional periods were similar. According to C-14 dates of coastal deposits, the shoreline of Amapa State, Brazil served as a major depocenter of Amazon mud during the erosional phase on the shelf. Pb-210 geochronology indicates that the most recent phase of sediment accumulation in the study area commenced about 100 yr ago, resulting in rapid progradation of topset deposits and burial of relict strata. In the present environment, oceanographic and meteorologic processes cause along-shelf variations in sediment dispersal and depositional patterns, and about 1400 km(2) of the erosional relict deposits are still exposed at the seabed. The short time scales over which Amazon shelf strata respond to changes in the physical environment preclude the influence of relative sea-level cyclicity on recent sedimentation patterns. During the late Holocene, sedimentation and strata formation on the Amazon shelf are linked to fluvial, oceanographic and meteorologic processes that affect sediment supply, deposition and erosion. VL - 125 IS - 3-4 N1 - Rt489Times Cited:33Cited References Count:65 JO - Stratigraphic Evidence of Changes in Amazon Shelf Sedimentation during the Late Holocene ER - TY - JOUR T1 - Suborbital Timescale Variability of North-Atlantic Deep-Water during the Past 200,000 Years JF - Paleoceanography Y1 - 1995 A1 - Oppo, D. W. A1 - Lehman, S. J. AB - We generated similar to 200-kyr-long proxy records of surface and deepwater variability from a subpolar North Atlantic core (V29-202), enabling us to assess the linkage between surface and deepwater changes on suborbital timescales. In particular, we used a benthic delta(13)C record to evaluate the deep water response to Dansgaard-Oeschger temperature oscillations and to Heinrich events, times of massive iceberg delivery to the North Atlantic. We found that the reduction of North Atlantic Deep Water (NADW) production was generally associated with cold or dropping sea surface temperatures (SSTs) as indicated by planktonic foraminiferal assemblages. The NADW contribution to the site did not drop appreciably during Heinrich events H4 through H2, probably because these events followed intervals of prolonged surface cooling already characterized by low rates of NADW production. By contrast NADW reduction appears to have been synchronous with H5. SST rise associated with both Dansgaard-Oeschger oscillations and Heinrich events was usually accompanied by increasing NADW strength. In a few cases the NADW recovery appeared to lag the SST rise; however, the apparent delay is most likely an artefact of the sedimentary record (low concentrations of benthic foraminifera). As a result of low benthic foraminiferal abundances during stage 6, the stage 6 benthic foraminiferal delta(13)C record is of lower resolution than the younger part of the record. The stage 6 proxy records for surface hydrography nevertheless reveal millennial-scale oscillations similar to those seen in stage 3. The available delta(13)C data suggest that NADW weakened in association with the cold portions of stage 6 SST oscillations. We also sought to confirm a recent study which concluded that there was little NADW variability during the peak of the last interglaciation, marine oxygen isotope substage 5e (Eemian). Isotope stage 5 was marked by a trend of increasing benthic delta(13)C in V29-202. Rising delta(13)C through isotope stage 5 is also seen in tropical surface water records and at some deep Atlantic sites and may reflect the common derivation of these water masses. Variations of greater than or equal to 0.5 parts per thousand superimposed on this rising delta(13)C trend within substage 5e in V29-202 are so far not evident in tropical feed waters and may therefore indicate that NADW production was weaker during the late than mid-Eemian. VL - 10 IS - 5 N1 - Rx409Times Cited:145Cited References Count:39 JO - Suborbital Timescale Variability of North-Atlantic Deep-Water during the Past 200,000 Years ER - TY - JOUR T1 - Systematic decrease of high delta 13C values with burial in late archaean (2.8 Ga) diagenetic dolomite: evidence for methanogenesis from the Crixas Greenstone Belt, Brazil JF - Precambrian Research Y1 - 1995 A1 - Dix, G. R. A1 - Thomson, M. L. A1 - Longstaffe, F. J. A1 - McNutt, R. H. VL - 70 N1 - id: 1589 ER - TY - JOUR T1 - Tree Survival and Growth on Land Reclaimed in Accord with Public-Law-95-87 JF - Journal of Environmental Quality Y1 - 1995 A1 - Chaney, W. R. A1 - Pope, P. E. A1 - Byrnes, W. R. AB - The objective of this study was to determine survival and growth of black walnut (Juglans nigra L.) and northern red oak (Quercus alba L.) 12 yr after planting on a surface-mined site in southern Indiana reclaimed according to specifications of Public Law 95-87, the Surface Mining Control and Reclamation Act of 1977. A stocking level adequate to meet the requirements for forest land use (1112 trees/ha, or 450 trees/acre) was attained only for black walnut and only if competing ground cover vegetation was controlled in the tree rows. Height of both tree species was significantly greater when ground cover vegetation was controlled during the first 2 yr, but the growth rate, approximately 10 cm/yr, was very slow. VL - 24 SN - 0047-2425 IS - 4 N1 - Rj934Times Cited:17 Cited References Count:18 JO - J Environ Qual ER - TY - JOUR T1 - Two-step deglaciation of the southeastern Barents Sea JF - Geology Y1 - 1995 A1 - Polyak, L. A1 - Lehman, S. J. A1 - Gataulin, V. A1 - Jull, A. J. T. VL - 23 IS - 6 N1 - id: 62 ER - TY - CONF T1 - Using sclerochronology of the mollusc Arctica islandica as a paleoceanographic tool T2 - 5th International Conference on Paleoceanography Y1 - 1995 A1 - Marchitto, T. M. A1 - Jones, G. A. A1 - Goodfriend, G. A. A1 - Weidman, C. R. A1 - Jirikowic, J. JF - 5th International Conference on Paleoceanography CY - Halifax, NS N1 - id: 1294 ER - TY - JOUR T1 - Variability in the Benguela Current upwelling system over the past 70,000 years JF - Progress in Oceanography Y1 - 1995 A1 - Summerhayes, C. P. A1 - Kroon, D. A1 - Rosell-Mele, A. A1 - Jordan, R. W. A1 - Schrader, H. J. A1 - Hearn, R. A1 - Villanueva, J. A1 - Grimali, J. O. A1 - Eglinton, G. AB - This study was designed to see if the intensity and location of upwelling in the Benguela Current Upwelling System off Namibia changed significantly during the last 70,000 years. Most of the analytical work focused on geochemical, micropalaeontological and stable isotopic analyses of a 6.5m long combined pilot and piston core, PGPC12, from 1017m on the continental slope close to Walvis Bay. The slope sediments are rich in organic matter. Most of it is thought to represent deposition beneath a productive shelf edge upwelling system, but some is supplied by downslope near-bottom flow of material probably resuspended on the outer continental shelf. Temporal changes in upwelling intensity as represented by fluctuations in the accumulation of organic matter do not show the simple 'classical' pattern of less upwelling and lower productivity in interglacials and more upwelling and higher productivity in glacials, but instead show a pattern of higher frequency fluctuations. The broad changes in organic carbon accumulation reach maxima at times when the earth-sun distance was greatest, indicating that this accumulation responded to changes in the precession index; at these times monsoons would have been weakest and Trade Winds strongest. Maximum accumulation of organic matter on the slope occurred in the last interstadial (isotope stage 3), and coincided with coldest sea surface temperatures as recorded by alkenone data (U(37)(k)), and by nannofossil assemblages. It is attributed largely to increased productivity in situ, rather than the lateral supply of material eroded from older organic rich deposits exposed by the lowering of sealevel at that time. The enhanced productivity is attributed to a strengthening of upwelling-favourable winds in this area in response to the minimal solar insolation typical of this period. Diatoms generally are not abundant in these sediments, so appear to be unreliable indicators of productivity over the continental slope. When sealevel was lowest (isotope stages 2 and 4) organic matter previously deposited on the continental shelf was eroded and dumped on the continental slope; this reworked material constitutes up to 43% of the flux of organic matter to the slope at these times. This process did not affect the slope in stage 3, when sealevel fell by only 50m. The accumulation of terrigenous material was highest in stages 2 and 4. The available data suggest that the terrigenous influx at those times was primarily aeolian. We interpret this to mean that more of the winds then came from the east ('Berg' winds), bringing an influx of aeolian dust from the hinterland; these easterlies were less favoarable for upwelling than were the more southerly Trade Winds that dominated during stage 3. Carbonate accumulation was least in stages 2 and 4, largely in response to dissolution induced by CO(2)-rich bottom waters. VL - 35 IS - 3 N1 - V07zbTimes Cited:100Cited References Count:147 JO - Variability in the Benguela Current upwelling system over the past 70,000 years ER - TY - JOUR T1 - Ventilation of the deep Pacific Ocean JF - Supplement to Trans. American Geophysic. Union Y1 - 1995 A1 - Key, R. M. A1 - Rooth, C. A1 - Ostlund, G. A1 - Stuiver, M. VL - 76 IS - 3 N1 - id: 41 JO - Ventilation of the deep Pacific Ocean ER - TY - JOUR T1 - AMS C14 Dating of the Holocene Climatic Optimum in the North Pacific and Atlantic Oceans JF - EOS,Transactions,American Geophysical Union Y1 - 1994 A1 - Kuzmin, Y. V. A1 - Jones, G. A. A1 - Elder, K. L. VL - 75 IS - 3 N1 - id: 913 JO - AMS C14 Dating of the Holocene Climatic Optimum in the North Pacific and Atlantic Oceans ER - TY - JOUR T1 - Analysis of a large hydrochemical data base for the Death Valley region, Nevada and California JF - Eos, Transactions, American Geophysical Union Y1 - 1994 A1 - Perfect, D. L. A1 - Steinkampf, W. C. A1 - Turner, A. K. VL - 75 IS - 44 N1 - id: 1286 ER - TY - JOUR T1 - Application of AMS 14C dating to continental margin sediments off Nova Scotia JF - Eos, Transactions, American Geophysical Union Y1 - 1994 A1 - Keigwin, L. D. A1 - Jones, G. A. VL - 75 IS - 3 N1 - id: 1247 ER - TY - JOUR T1 - The Application of AMS to Organic Geochemistry--Constraints Imposed by Sample Preparation and Machine Operations JF - EOS, Transactions of the American Geophysical Union Y1 - 1994 A1 - McNichol, A. P. A1 - von Reden, K. F. A1 - Schneider, R. J. A1 - Jones, G. A. VL - 75 IS - 3 N1 - id: 1798 ER - TY - JOUR T1 - An assessment of the effect of chemical scavenging within hydrothermal plumes upon ocean geochemistry JF - Earth and Planetary Science Letters Y1 - 1994 A1 - Kadko, D. VL - 120 N1 - id: 1594 ER - TY - JOUR T1 - Automated Sample Processing at the National Ocean Sciences Ams Facility JF - Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions with Materials and Atoms Y1 - 1994 A1 - Cohen, G. J. A1 - Hutton, D. L. A1 - Osborne, E. A. A1 - vonReden, K. F. A1 - Gagnon, A. R. A1 - McNichol, A. P. A1 - Jones, G. A. AB - The high throughput and high precision requirements for the NOSAMS facility have made it essential to automate many of the stages in sample processing. These automated procedures increase the sample capacity for the lab while reducing errors in sample preparation. Automation has also allowed sample histories to be recorded and saved in Sybase, a relational data base. VL - 92 IS - 1-4 N1 - Nv547Times Cited:9Cited References Count:1 JO - Automated Sample Processing at the National Ocean Sciences Ams Facility ER - TY - JOUR T1 - Biogenic Silica in Lake Baikal Sediments - Results from 1990-1992 American Cores JF - Journal of Great Lakes Research Y1 - 1994 A1 - Carter, S. J. A1 - Colman, S. M. KW - accumulation KW - Holocene KW - Lake Baikal KW - marine-sediments KW - opal KW - Paleoclimate KW - sediments KW - silica AB - The Lake Baikal Paleoclimate Project is a joint Russian-American program established to study the paleoclimate of Central Asia. During three summer field seasons, duplicate Russian and American coves were taken at a number of sites in different sedimentary environments in the lake. Eight cores returned to the U.S. were quantitatively analyzed for biogenic silica using a single-step 5-hour alkaline leach, followed by dissolved silicon analysis by inductively-coupled-plasma atomic-emission spectroscopy. Sediments of Holocene age in these cores have biogenic silica maxima that range from about 15 to 80 percent. An underlying zone in each core with low biogenic-silica concentrations (0 to 5 percent) dates from the last glacial maximum. The transition from the last glaciation to the present interglaciation, recorded by biogenic silica, began about 13,000 years ago. Biogenic silica profiles from these cores appear to be a good measure of past diatom productivity and a useful basis for paleoclimatic interpretations. VL - 20 SN - 0380-1330 IS - 4 N1 - Px453Times Cited:46 Cited References Count:20 JO - J Great Lakes Res ER - TY - MGZN T1 - Carbon and Radiocarbon in the Northeast Pacific: Implications for Abyssal Ventilation and Biogenic Input Y1 - 1994 A1 - Key, R. M. A1 - Rooth, C. G. A. A1 - Feely, R. JF - 15th International Radiocarbon Conference, Glasgow, Scotland N1 - id: 911 ER - TY - JOUR T1 - Chronology, sedimentology, and faunal assemblages of glaciomarine sediments in Maine JF - Geological Society of America, Abstracts with Programs Y1 - 1994 A1 - Dorion, C. C. VL - 25 IS - 2 N1 - id: 17 ER - TY - JOUR T1 - Comparative-Study of Fe-C Bead and Graphite Target Performance with the National-Ocean-Science-Ams (Nosams) Facility Recombinator Ion-Source JF - Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions with Materials and Atoms Y1 - 1994 A1 - Klinedinst, D. B. A1 - McNichol, A. P. A1 - Currie, L. A. A1 - Schneider, R. J. A1 - Klouda, G. A. A1 - vonReden, K. F. A1 - Verkouteren, R. M. A1 - Jones, G. A. AB - An accelerator mass spectrometry (AMS) experiment was designed to investigate C-14 target performance for two target types over a range of isotopic concentrations and sample sizes, with a special focus on the ability to measure C-14 in environmental samples having only microgram amounts of carbon. The findings were positive, showing that precision, accuracy, and stability were adequate to determine C-14 to 1% or better in samples containing as little as 25 mug carbon. Satisfactory Poisson uncertainty and target stability were demonstrated down to a level of 7 mug carbon, but experimental data showed that accurate measurements at that level require detailed knowledge of blank variability and mass dependence of the modern carbon calibration factor. VL - 92 IS - 1-4 N1 - Nv547Times Cited:23Cited References Count:13 JO - Comparative-Study of Fe-C Bead and Graphite Target Performance with the National-Ocean-Science-Ams (Nosams) Facility Recombinator Ion-Source ER - TY - JOUR T1 - Constraints Imposed by Sample Preparation and Machine Operations JF - EOS, Transactions of the American Geophysical Union Y1 - 1994 A1 - McNichol, A. P. A1 - von Reden, K. F. A1 - Schneider, R. J. A1 - Jones, G. A. VL - 75 IS - 3 N1 - id: 937 ER - TY - JOUR T1 - Contamination in Boston Harbor and Massachusetts Bay JF - United States Geological Survey Yearbook Y1 - 1994 A1 - Bothner, M. H. A1 - Butman, B. A1 - Signell, R. P. N1 - id: 1231 ER - TY - JOUR T1 - Control and automation of the Accelerator Mass Spectrometry Facility at Woods Hole Oceanographic Institution JF - Symposium of Northeastern Accelerator Personnel Y1 - 1994 A1 - Cohen, G. C. A1 - von Reden, K. F. N1 - id: 1649 ER - TY - JOUR T1 - The Deep-water Radiocarbon Minimum in the Northeastern Pacific Ocean; Early WOCE Results JF - EOS, Transactions, American Geophysical Union; Ocean Sciences Mtg., San Diego, Feb.21-25, 1994 Y1 - 1994 A1 - Key, R. M. A1 - Toggweiller, J. R. VL - 75 IS - 3 N1 - id: 912 JO - The Deep-water Radiocarbon Minimum in the Northeastern Pacific Ocean; Early WOCE Results ER - TY - JOUR T1 - Deglaciation, Lake Levels, and Meltwater Discharge in the Lake-Michigan Basin JF - Quaternary Science Reviews Y1 - 1994 A1 - Colman, S. M. A1 - Clark, J. A. A1 - Clayton, L. A1 - Hansel, A. K. A1 - Larsen, C. E. AB - The deglacial history of the Lake Michigan basin, including discharge and routing of meltwater, is complex because of the interaction among (1) glacial retreats and re-advances in the basin (2) the timing of occupation and the isostatic adjustment of lake outlets and (3) the depositional and erosional processes that left evidence of past lake levels. In the southern part of the basin, a restricted area little affected by differential isostasy, new studies of onshore and offshore areas allow refinement of a lake-level history that has evolved over 100 years. Important new data include the recognition of two periods of influx of meltwater from Lake Agassiz into the basin and details of the highstands gleaned from sedimentological evidence. Major disagreements still persist concerning the exact timing and lake-level changes associated with the Algonquin phase, approximately 11,000 BP. A wide variety of independent data suggests that the Lake Michigan Lobe was thin, unstable, and subject to rapid advances and retreats. Consequently, lake-level changes were commonly abrupt and stable shorelines were short-lived. The long-held beliefs that the southern part of the basin was stable and separated from deformed northern areas by a hinge-line discontinuity are becoming difficult to maintain. Numerical modeling of the ice-earth system and empirical modeling of shoreline deformation are both consistent with observed shoreline tilting in the north and with the amount and pattern of modern deformation shown by lake-level gauges. New studies of subaerial lacustrine features suggest the presence of deformed shorelines higher than those originally ascribed to the supposed horizontal Glenwood level. Finally, the Lake Michigan region as a whole appears to behave in a similar manner to other areas, both local (other Great Lakes) and regional (U.S. east coast), that have experienced major isostatic changes. Detailed sedimentological and dating studies of field sites and additional development of geophysical models offer hope for reconciling the field data with our understanding of earth theology. VL - 13 IS - 9-10 N1 - Qq080Times Cited:30Cited References Count:48 JO - Deglaciation, Lake Levels, and Meltwater Discharge in the Lake-Michigan Basin ER - TY - THES T1 - The deglaciation of southeastern Washington County, Maine. Thesis Y1 - 1994 A1 - Kaplan, M. PB - University of Maine, Orono CY - Orono, Maine VL - Unpublished ER - TY - RPRT T1 - The development of the Gull Pond Chain of Lakes and the Herring River Basin in the Cape Cod National Seashore. Report Y1 - 1994 A1 - Winkler, M. G. N1 - id: 93 ER - TY - CONF T1 - Do AMS measurements approach a Gaussian distribution? T2 - 15th International Radiocarbon Conference Y1 - 1994 A1 - Jirikowic, J. L. A1 - Schneider, R. J. A1 - von Reden, K. F. A1 - Jones, G. A. JF - 15th International Radiocarbon Conference CY - Glasgow, Scotland N1 - id: 940 ER - TY - CHAP T1 - Glacial geology of the Penobscot River basin between Millinocket and Medway (Book Section) T2 - New England Intercollegiate Geological Conference Guidebook for Field Trips in North Central Maine Y1 - 1994 A1 - Weddle, T. K. A1 - Lowell, T. V. A1 - Dorion, C. C. ED - Hanson, L. S. JF - New England Intercollegiate Geological Conference Guidebook for Field Trips in North Central Maine N1 - id: 19 ER - TY - JOUR T1 - Glacial/interglacial slope sedimentation changes on the Pleistocene NJ margin, ODP Site 904A JF - Eos, Transactions, American Geophysical Union Y1 - 1994 A1 - Christensen, B. A. A1 - Thunell, R. A1 - Miller, K. G. A1 - Smith, N. A1 - Cockrell, K. VL - 75 IS - 16 N1 - id: 54 ER - TY - CHAP T1 - Global methanotrophy at the Archean-Proterozoic transition T2 - Early Life on Earth. Nobel Symposium Y1 - 1994 A1 - Hayes, J. M. ED - Bengston, S. JF - Early Life on Earth. Nobel Symposium PB - Columbia University Press, New York VL - 84 N1 - id: 1565 ER - TY - JOUR T1 - High Precision Sea Water 14C Analyses at the National Ocean Sciences AMS Facility JF - EOS, Transactions of the American Geophysical Union Y1 - 1994 A1 - von Reden, K. F. A1 - Jones, G. A. A1 - Schneider, R. J. A1 - McNichol, A. P. VL - 75 IS - 3 N1 - id: 939 ER - TY - JOUR T1 - High resolution sediment changes on the Pleistocene NJ upper slope JF - Eos, Transactions, American Geophysical Union Y1 - 1994 A1 - Christensen, B. A. A1 - Hoppie, B. W. A1 - Miller, K. G. A1 - Thunell, R. C. A1 - Le, J. VL - 75 IS - 44 N1 - id: 53 ER - TY - CONF T1 - High-latitude ocean radiocarbon time histories from AMS-dating of long-lived molluscs T2 - AGU Ocean Sciences Meeting Y1 - 1994 A1 - Weidman, C. R. A1 - Jones, G. A. JF - AGU Ocean Sciences Meeting CY - San Diego, CA N1 - id: 90 ER - TY - JOUR T1 - High-precision AMS radiocarbon measurements of central Arctic Ocean seawaters JF - Nuclear Instruments and Methods in Physics Research Y1 - 1994 A1 - Jones, G. A. A1 - Gagnon, A. R. A1 - Schneider, R. J. A1 - von Reden, K. F. A1 - McNichol, A. P. VL - B92 N1 - id: 52 ER - TY - JOUR T1 - High-precision sea water 14C analyses by accelerator mass spectrometry. 15th International Radiocarbon Conference, Glasgow, Scotland, August 15-19 JF - EOS, Transactions of the American Geophysical Union Y1 - 1994 A1 - von Reden, K. F. A1 - Jones, G. A. A1 - Schneider, R. J. A1 - McNichol, A. P. VL - 75 IS - 3 N1 - id: 941 ER - TY - JOUR T1 - High-Resolution Climate Records from the North-Atlantic during the Last Interglacial JF - Nature Y1 - 1994 A1 - McManus, J. F. A1 - Bond, G. C. A1 - Broecker, W. S. A1 - Johnsen, S. A1 - Labeyrie, L. A1 - Higgins, S. AB - THE two deep ice cores recovered by the GRIP(1) and GISP(2) projects at Summit, Greenland, agree in detail over the past 100,000 years(3) and demonstrate dramatic climate variability in the North Atlantic region during the last glacial, before the current period of Holocene stability. This glacial climate instability has subsequently been documented in the marine sedimentary record of surface-ocean conditions in the North Atlantic(4). Before 100 kyr ago the two ice core records are discrepant, however, casting doubt on whether the oxygen isotope fluctuations during the last interglacial (Eemian) seen in the GRIP core(1,5) represent a true climate signal. Here we present high-resolution records of foraminiferal assemblages and ice-rafted detritus from two North Atlantic cores for the interval 65 kyr to 135 kyr ago, extending the surface-ocean record back to the Eemian. The correlation between our records and the Greenland ice-core records is good throughout the period in which the two ice cores agree, suggesting a regionally coherent climate response. During the Eemian, our marine records show a more stable climate than that implied by the GRIP ice core, suggesting that localized phenomena may be responsible for the variability in the latter record during the Eemian. VL - 371 IS - 6495 N1 - Ph254Times Cited:313Cited References Count:25 JO - High-Resolution Climate Records from the North-Atlantic during the Last Interglacial ER - TY - JOUR T1 - A history of past earthquakes in the Puget Sound area recorded in Holocene sediments from Lake Washington JF - Open-File Report, U. S. Geological Survey Y1 - 1994 A1 - Karlin, R. E. A1 - Abella, S. E. B. N1 - id: 31 ER - TY - JOUR T1 - Holocene neotectonic deformation and earthquake history in sediments from Lake Washington JF - Abstracts with Programs - Geological Society of America Y1 - 1994 A1 - Karlin, R. A1 - Holmes, M. A1 - Abella, S. VL - 26 IS - 7 N1 - id: 32 ER - TY - JOUR T1 - Hydrochemical data base for the Death Valley region, California and Nevada JF - Open-File Report--U. S. Geological Survey Y1 - 1994 A1 - Perfect, D. L. A1 - Faunt, C. C. A1 - Steinkampf, W. C. A1 - Turner, A. K. N1 - id: 1287 ER - TY - JOUR T1 - Integrated Dating Techniques to Determine the Age of a Glauconite Deposit on the Modern Seafloor JF - EOS, Transactions,American Geophysical Union Y1 - 1994 A1 - am Ende, B. A. A1 - Paull, C. K. A1 - Benninger, L. VL - 75 IS - 3 N1 - id: 901 JO - Integrated Dating Techniques to Determine the Age of a Glauconite Deposit on the Modern Seafloor ER - TY - JOUR T1 - Internal and External Checks in the Nosams Sample Preparation Laboratory for Target Quality and Homogeneity JF - Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions with Materials and Atoms Y1 - 1994 A1 - Osborne, E. A. A1 - McNichol, A. P. A1 - Gagnon, A. R. A1 - Hutton, D. L. A1 - Jones, G. A. AB - In the NOSAMS sample preparation laboratory (SPL) we have developed rigorous internal procedures aimed at ensuring that sample preparation introduces as little error into our analyses as possible and identifying problems rapidly. Our three major CO2 preparation procedures are: stripping inorganic carbon from seawater, hydrolyzing CaCO3, and oxidizing organic matter. For seawater, approximately 10% of our analyses are standards or blanks which we use to demonstrate extraction of virtually all the inorganic carbon. Analysis of the stable carbon isotopic composition of the CO2 extracted from our standards indicates a precision of better than 0.15-0.20 parts per thousand. We also routinely process C-14-free CO2 in our stripping lines to demonstrate the absence of a significant process-dependent blank. For organic combustions and CaCO3 hydrolyses, we use the carbon yield (% organic carbon (OC) or % CaCO3 by weight) as a check on our sample procedures. We have analyzed the blank contribution of these procedures as a function of sample size. Our organic carbon blank is constant at approximately 0.4% modem for samples containing greater than 1 mg C and our carbonate blank is less than 0.2% modern for samples containing more than 0.5 mg C. We use a standard Fe/H-2 catalytic reduction to prepare graphite from CO2. We check the completeness of our reactions with the pressure data stored during the reaction as well as use a robot to determine a gravimetric yield. All graphite undergoes a visual inspection and is rejected if any heterogeneities are present. We have recombusted graphite made from CO2 with deltaC-13 values ranging from -42 to 1 parts per thousand and determined that the deltaC-13 of the recombusted carbon agrees with that from the pure gas to within 0.05 parts per thousand, demonstrating little or no fractionation during the treatment of the sample. The deltaC-13 we measure on the CO2 generated from more than 75% of our samples is compared to the deltaC-13 measured on the AMS as a further check of our procedures. As further external checks, we analyzed the International Atomic Energy Association (IAEA) samples during the establishment of our laboratory and are presently participating in the third international radiocarbon intercalibration (TIRI) exercise. VL - 92 IS - 1-4 N1 - Nv547Times Cited:14Cited References Count:5 JO - Internal and External Checks in the Nosams Sample Preparation Laboratory for Target Quality and Homogeneity ER - TY - CONF T1 - La Curva Di Risalta Del Mare Tirreno Negli Ultimi 40 KA Ottenuta Mediante Datazioni Di Speleotemi Sommersi E Dati Archeologici T2 - International Meeting on Underwater Geology Y1 - 1994 A1 - Alessio, M. A1 - Allegri, L. A1 - Antonioli, F. A1 - Belluomini, G. A1 - Improta, S. A1 - Manfra, L. A1 - Martinez, M. P. JF - International Meeting on Underwater Geology CY - Palinuro N1 - id: 899 ER - TY - JOUR T1 - Lake-Level History of Lake-Michigan for the Past 12,000 Years - the Record from Deep Lacustrine Sediments JF - Journal of Great Lakes Research Y1 - 1994 A1 - Colman, S. M. A1 - Forester, R. M. A1 - Reynolds, R. L. A1 - Sweetkind, D. S. A1 - King, J. W. A1 - Gangemi, P. A1 - Jones, G. A. A1 - Keigwin, L. D. A1 - Foster, D. S. KW - lake michigan KW - ostracodes KW - radiocarbon KW - sedimentology KW - sediments KW - southern AB - Collection and analysis of an extensive set of seismic-reflection profiles and cores from southern Lake Michigan have provided new data that document the history of the lake basin for the past 12,000 years. Analyses of the seismic data, together with radiocarbon dating, magnetic, sedimentologic, isotopic, and paleontologic studies of core samples, have allowed us to reconstruct lake-level changes during this recent part of the lake's history.The post-glacial history of lake-level changes in the Lake Michigan basin begins about 11.2 ka with the fall from the high Calumet level, caused by the retreat of the Two Rivers glacier, which had blocked the northern outlet of the lake. This lake-level fall was temporarily reversed by a major influx of water from glacial Lake Agassiz (about 10.6 ka), during which deposition of the distinctive gray Wilmette Bed of the Lake Michigan Formation interrupted deposition of red glaciolacustrine sediment. Lake level then continued to fall, culminating in the opening of the North Bay outlet at about 10.3 ka. During the resulting Chippewa low phase, lake level was about 80 m lower than it is today in the southern basin of Lake Michigan. The rise of the early Holocene lake level, controlled primarily by isostatic rebound of the North Bay outlet, resulted in a prominent, planar, transgressive unconformity that eroded most of the shoreline features below present lake level. Superimposed on this overall rise in lake level, a second influx of water from Lake Agassiz temporarily raised lake levels an unknown amount about 9.1 ka. At about 7 ka, lake level may have fallen below the level of the outlet because of sharply drier climate. Sometime between 6 and 5 ka, the character of the lake changed dramatically, probably due mostly to climatic causes, becoming highly undersaturated with respect to calcium carbonate and returning primary control of lake level to the isostatically rising North Bay outlet. Post-Nipissing (about 5 ka) lake level has fallen about 6 m due to erosion of the Port Huron outlet, a trend around which occurred relatively small (+/- approximately 2 m), short-term fluctuations controlled mainly by climatic changes. These cyclic fluctuations are reflected in the sedimentological and sediment-magnetic properties of the sediments. VL - 20 SN - 0380-1330 IS - 1 N1 - Nl348Times Cited:47 Cited References Count:29 JO - J Great Lakes Res ER - TY - JOUR T1 - Latest Quaternary Sedimentation in the Kerch Strait Area of the Black Sea Shelf: Response to Glacial Sea Level Fluctuation JF - EOS,Transactions,American Geophysical Union Y1 - 1994 A1 - Major, C. O. A1 - Ryan, W. B. F. A1 - Pitman, W. C., III A1 - Shimkus, K. M. A1 - Jones, G. A. A1 - O'Connell, S. VL - 75 IS - 16 N1 - id: 914 ER - TY - JOUR T1 - The limnological and climate history of Lake Michigan from ostracode, stable-isotope, and magnetic susceptibility records JF - Journal of Great Lakes Research Y1 - 1994 A1 - Forester, R. M. A1 - Colman, S. M. A1 - Reynolds, R. L. A1 - Jones, G. A. A1 - Keigwin, L. D. A1 - Foster, D. S. VL - 20 N1 - id: 1358 ER - TY - JOUR T1 - Methods for Data Screening, Flagging and Error Analysis at the National-Ocean-Sciences-Ams-Facility JF - Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions with Materials and Atoms Y1 - 1994 A1 - Schneider, R. J. A1 - Jones, G. A. A1 - McNichol, A. P. A1 - vonReden, K. F. A1 - Elder, K. L. A1 - Huang, K. A1 - Kessel, E. D. AB - All data collection, from sample submittal through processing into targets and AMS analysis, is integrated within a large relational database (Sybase). Over 50 tables are linked through key fields. Through structured queries, the information is analysed and presented for a wide variety of applications. Benefits include enhanced quality control, more complete reports to users and more accurate transfer of data among the several laboratories on the network. VL - 92 IS - 1-4 N1 - Nv547Times Cited:14Cited References Count:4 JO - Methods for Data Screening, Flagging and Error Analysis at the National-Ocean-Sciences-Ams-Facility ER - TY - RPRT T1 - The modern limnology of the interdunal Provincelands Ponds in the Cape Cod National Seashore. Technical Report. Final Report Y1 - 1994 A1 - Winkler, M. G. PB - National Park Service, North Atlantic Region VL - NPS/NAROSS/NRTR-94/20 N1 - id: 136 ER - TY - JOUR T1 - The National Ocean Sciences Accelerator Mass Spectrometry Facility: Recent Developments JF - EOS, Transactions of the American Geophysical Union Y1 - 1994 A1 - Schneider, R. J. A1 - Jones, G. A. A1 - von Reden, K. F. A1 - McNichol, A. P. VL - 75 IS - 3 N1 - id: 938 ER - TY - CONF T1 - ODP Initial Reports, Leg 150X T2 - Ocean Drilling Program Y1 - 1994 A1 - Miller, K. G. A1 - Liu, C. A1 - Browning, J. V. A1 - Pekar, S. F. A1 - Sugarman, P. J. A1 - Van Fossen, M. C. A1 - Mullikin, L. A1 - Queen, D. A1 - Feigenson, M. D. A1 - Aubry, M. P. A1 - Burckle, L. D. A1 - Powars, D. A1 - Heibel, T. JF - Ocean Drilling Program CY - College Station, TX N1 - id: 1347 ER - TY - JOUR T1 - Optimized Data Analysis for AMS Radiocarbon Dating JF - Nuclear Instruments & Methods in Physics Research Section B - Beam Interactions with Materials and Atoms Y1 - 1994 A1 - Séguin, F. H. A1 - Schneider, R. J. A1 - Jones, G. A. A1 - von Reden, K. F. VL - 92 SN - 0168-583X IS - 1-4 N1 - id: 1617; PBS Record: 240; (03) FH Seguin/Mit/Cambridge, MA 02139 USA (42) English Article (44) NV547 ER - TY - THES T1 - Paleoceanographic conditions of the late Wisconsinan marine transgression and regression in eastern coastal Maine: stable isotopic evidence. Thesis Y1 - 1994 A1 - Kreutz, K. J. PB - University of Maine CY - Orono, Maine VL - Dissertation/Thesis ER - TY - THES T1 - A paleoenvironmental study of the southern Champlain Sea, Thesis Y1 - 1994 A1 - Schlegel, Mary Ann PB - MIT CY - Woods Hole, MA VL - Dissertation/Thesis ER - TY - JOUR T1 - Performance Characteristics of the 3-MV Tandetron AMS System at the National Ocean Sciences AMS Facility JF - Nuclear Instruments & Methods in Physics Research Section B - Beam Interactions with Materials and Atoms Y1 - 1994 A1 - von Reden, K. F. A1 - Schneider, R. J. A1 - Cohen, G. J. A1 - Jones, G. A. KW - ACCELERATOR MASS-SPECTROMETER VL - 92 SN - 0168-583X IS - 1-4 N1 - id: 1619; PBS Record: 60; (03) KF Vonreden/Woods Hole Oceanog Inst/Natl Ocean Sci Accelerator/Mass Spectrometry Facil/Woods Hole, MA 02540 USA (42) English Article (44) NV547 ER - TY - CONF T1 - Progress at the Woods Hole AMS Facility T2 - 13th International Conference on the Applications of Accelerators in Research and Industry Y1 - 1994 A1 - Schneider, R. J. JF - 13th International Conference on the Applications of Accelerators in Research and Industry CY - Denton, TX N1 - id: 964 ER - TY - JOUR T1 - Radiocarbon Chronology of Black-Sea Sediments JF - Deep-Sea Research Part I-Oceanographic Research Papers Y1 - 1994 A1 - Jones, G. A. A1 - Gagnon, A. R. AB - Accelerator Mass Spectrometer (AMS) radiocarbon analyses have been made on 102 samples from 12 sediment cores and 23 samples from two water column profiles. These materials, collected during the first leg of the 1988 joint U.S.-Turkish Black Sea Expedition, provide the most comprehensive radiocarbon chronology of Black Sea sediments vet attempted. Radiocarbon analyses from carefully collected box cores and a molluse shell collected live in 1931 suggest the prebomb surface waters had a DELTAC-14 value of -55 parts per thousand (460 years) and that the maximum detrital correction for radiocarbon ages of Unit I sediments is 580 years for the organic carbon and 260 years for the carbonate fractions. Evidence does not support the 1430-2000 year pre-bomb surface water and/or detrital corrections argued for in past studies. The best estimates for the age of the beginning of the final invasion of the coccolithophore Emiliania huxleyi (Unit 1/2 boundary of Ross and DEGENS, 1974, The Black Sea-geology, chemistry and biology, pp. 183-199) and the age of the first invasion of E. huxleyi (Unit I/II boundary of HAY et al., 1991, Deep-Sea Research, 38, S1211-S1235) are 1635 +/- 60 and 2720 +/- 160 years BP, respectively. Sapropel formation began at approximately 7540 +/- 130 years BP at all depths in the basin, a pattern in disagreement with those predicted by existing time-evolution models of sapropel formation for this basin. Our data suggest that the oxic-anoxic interface has remained relatively stable throughout the Holocene, is controlled largely by the physical oceanography of the basin, and has not evolved as assumed by previous workers. VL - 41 IS - 3 N1 - Nm252Times Cited:121Cited References Count:44 JO - Radiocarbon Chronology of Black-Sea Sediments ER - TY - CONF T1 - Radiocarbon Dating of Marine Deposits on Submerged Speleothems and Sea-Level Oscillation T2 - 15th International Radiocarbon Conference Y1 - 1994 A1 - Alessio, M. A1 - Allegri, L. A1 - Antonioli, F. A1 - Belluomini, G. A1 - Improta, S. A1 - Manfra, L. JF - 15th International Radiocarbon Conference CY - Glasgow, Scotland N1 - id: 900 ER - TY - MGZN T1 - Radiocarbon Studies of Particulate Organic Carbon in the Eastern North Pacific Ocean Y1 - 1994 A1 - Druffel, E. R. M. A1 - Griffin, S. A1 - Bauer, J. E. A1 - Williams, P. M. A1 - Wolgast, D. M. A1 - Lee, C. JF - 15th International Radiocarbon Conference, Glasgow, Scotland N1 - id: 907 ER - TY - CONF T1 - Radiocarbon studies of particulate organic carbon in the eastern North Pacific Ocean T2 - 1994 ocean sciences meeting Y1 - 1994 A1 - Druffel, E. R. M. A1 - Bauer, J. E. A1 - Williams, P. M. A1 - Griffin, S. A1 - Wolgast, C. Lee A1 - Wakeham, S. G. ED - University of California at Irvine, Department of Geosciences JF - 1994 ocean sciences meeting CY - San Diego, CA VL - 75 N1 - id: 1240; 3 ER - TY - THES T1 - Radiocarton Dating of Pollen by Accelerator Mass Spectrometry Y1 - 1994 A1 - Brown, Thomas Alexander PB - University of Washington VL - Ph.d N1 - id: 1494; Geophysics Program ER - TY - JOUR T1 - Rapid analysis of seawater samples at the National Ocean Sciences Accelerator Mass Spectrometry Facility, Woods Hole, MA JF - Radiocarbon Y1 - 1994 A1 - McNichol, A. P. A1 - Jones, G. A. A1 - Hutton, D. L. A1 - Gagnon, A. R. A1 - Key, R. M. VL - 36 IS - 2 N1 - id: 305 ER - TY - JOUR T1 - The Rapid Preparation of Seawater Sigma-Co2 for Radiocarbon Analysis at the National Ocean Sciences Ams Facility JF - Radiocarbon Y1 - 1994 A1 - McNichol, A. P. A1 - Jones, G. A. A1 - Hutton, D. L. A1 - Gagnon, A. R. A1 - Key, R. M. KW - accelerator mass-spectrometry KW - C-14 KW - samples AB - We have established a laboratory for extracting Sigma CO2 from seawater samples for AMS analysis of the radiocarbon content. The seawater samples are collected at sea, poisoned and stored until analysis in the laboratory. Each sample is acidified; the inorganic carbon is stripped out as CO2 with an inert carrier gas and then converted to graphite. We present results for Buzzards Bay surface H2O and Na2CO3 standards that demonstrate we strip > 98% of inorganic carbon from seawater. Stable isotope analyses are performed to better than 0.2 parts per thousand, and the reproducibility of C-14 measurements on Buzzards Bay seawater is better than 13 parts per thousand. Finally, we compare data from samples collected in 1991 to those collected in the 1970s and to large volume samples. VL - 36 SN - 0033-8222 IS - 2 N1 - Pz926Times Cited:61 Cited References Count:14 JO - Radiocarbon ER - TY - JOUR T1 - Redifinition of the "Blake Event" based on new paleomagnetic results from deep sea sediments of the Blake-Bahama Outer Ridge JF - Eos, Transactions, American Geophysical Union Y1 - 1994 A1 - Henyey, S. A1 - Lund, S. P. A1 - Schwart, M. A1 - Keigwin, L. VL - 75 IS - 44 N1 - id: 33 ER - TY - JOUR T1 - A rock-magnetic record from Lake Baikal, Siberia: Evidence for Late Quaternary climate change JF - Earth and Planetary Science Letters Y1 - 1994 A1 - Peck, J. A. A1 - King, J. W. A1 - Colman, S. M. A1 - Kravchinsky, V. A. VL - 1222 N1 - id: 15 ER - TY - JOUR T1 - The Role of the Deep-Ocean in North-Atlantic Climate-Change between 70-Kyr and 130-Kyr Ago JF - Nature Y1 - 1994 A1 - Keigwin, L. D. A1 - Curry, W. B. A1 - Lehman, S. J. A1 - Johnsen, S. AB - THE suggestion(1) that changes in North Atlantic Deep Water (NADW) production are linked through surface heat flux to the atmospheric temperature over Greenland is supported by earlier indications(2,3) that NADW production decreased during glacial times, and by the subsequent finding(4-6) that it declined during the Younger Dryas cool period at the end of the last glaciation. Changes in North Atlantic surface temperatures have been found? to mirror high-frequency temperature changes recorded in Greenland ice cores over the past 80 kyr, but the connection to abyssal circulation has yet to be established, except for one or two isolated oscillations(8,9). Here we present carbon and oxygen isotope analyses of benthic foraminifera in a high-resolution North Atlantic deepsea sediment core for the period 70-130 kyr ago. These data allow us to reconstruct the history of NADW production, which shows a close correlation with Greenland climate variability for much of this time interval, suggesting that the climate influence of NADW variability was widespread. We see no evidence, however, for changes in NADW production during substage 5e (the Eemian interglacial period), in contrast with recent ice-core data(10) which suggest severe climate instability in Greenland during this time period. Our results may support suggestions, based on data from a second ice core, that this apparent instability is am artefact caused by ice flow(11). Alternatively, the Eemian climate instability may have had a different origin from the subsequent climate events. VL - 371 IS - 6495 N1 - Ph254Times Cited:159Cited References Count:32 JO - The Role of the Deep-Ocean in North-Atlantic Climate-Change between 70-Kyr and 130-Kyr Ago ER - TY - JOUR T1 - A Sediment Budget for Southern Lake-Michigan - Source and Sink Models for Different Time Intervals JF - Journal of Great Lakes Research Y1 - 1994 A1 - Colman, S. M. A1 - Foster, D. S. KW - deposition KW - erosion KW - Holocene KW - lake michigan KW - sediment budget KW - sediments AB - We have constructed a sediment budget for the southern Lake Michigan basin for sand and for mud during three time periods: the past 100, 5,000, and 10,000 years. For the modern (100-year) sediment budget, accountable sediment sources add up to 93 percent of the calculated sinks. The mud budget has a source deficit of about 40%, probably due to errors in mu&sand ratios and (or) to other sources not included in our model, especially erosion of the lake floor, which accompanies bluff recession. Two terms dominate the modem sediment-budget equation: (1) bluff erosion, which is an order of magnitude larger than either rivers or aerosols as a source, and (2) deposition in the deep basin, which is more than two orders of magnitude greater as a sink than suspended sediment transport out of the basin. About half of the sand derived from bluff erosion is deposited in the deep lake; the other half must be deposited in nearshore sand bodies, beaches, and dunes. Despite the uncertainties in our estimates of sediment sources and sinks, the attempt to reconstruct sediment budgets for time intervals of 100, 5,000, and 10,000 years leads to important insights about erosion and sedimentation processes. Bluff erosion is the dominant source of both sand and mud in the basin. The deep lake floor is the primary sink for mud, whereas both the deep lake and nearshore areas are important sinks for sand. On a long-term basis, rates of bluff erosion have progressively decreased and are apparently independent of anthropogenic effects. Rates of sediment accumulation in the lake basin mirror the decrease in rates of bluff erosion for prehistoric time, but have increased markedly since human settlement, probably because of anthropogenic effects on river and aerosolic inputs. VL - 20 SN - 0380-1330 IS - 1 N1 - Nl348Times Cited:17 Cited References Count:29 JO - J Great Lakes Res ER - TY - JOUR T1 - Sensing plant community and climate change by charcoal-carbon isotope analysis JF - Ecoscience Y1 - 1994 A1 - Winkler, M. G. KW - c-3/c-4 plants KW - midwestern u. s. KW - paleoclimatology KW - paleovegetation KW - sediment charcoal KW - stable carbon isotopes AB - Mass spectrometric carbon isotope (delta C-13) analyses of charcoal-carbon found in lake sediments provide evidence of paleoclimate and paleovegetation independent of pollen. By chemically separating the microscopic charcoal-carbon, which originates from upland fires, from total carbon in lake, ocean, or ice cores, changes in C-3/C-4 biomass of upland plant communities can be measured, wet or dry climates identified, and the evolution of specific plant assemblages traced. In the North American Midwest, delta C-13 values of lake sediment charcoal-carbon from Lake Mendota, Wisconsin, U. S. A., document two shifts from C-3 (forests) to C-4 (prairie grasses) plants since deglaciation: an abrupt change at about 8.5 ka (8 500 years BP) and a longer duration change between 6 and 3 ka. A pine-savannah is interpreted for the earlier date while oak-savannah dominated the landscape between 6 and 3 ka. C-4 biomass, which was almost non-existent in the region before 8.5 ka, increased to more than 50% between 6 and 3 ka. Spruce-tundra parkland evident in the Midwest before about 12 ka contained no C-4 grasses and was probably similar in composition to modern North American tundra-parkland which has no C-4 biomass. The climate inferred from the delta C-13 data compares well with climate inferred from pollen and sediment data from the same core and supports climate model simulations of decreased effective moisture during the middle Holocene in the North American Midwest. The delta C-13 results also suggest future landscape changes should greenhouse-gas warming occurs. Savannah, with increased C-4 biomass, could again become prevalent in the North American Midwest. VL - 1 SN - 1195-6860 IS - 4 N1 - V19xpTimes Cited:10 Cited References Count:44 JO - Ecoscience ER - TY - JOUR T1 - Sources of Urban Contemporary Carbon Aerosol JF - Environmental Science & Technology Y1 - 1994 A1 - Hildemann, L. M. A1 - Klinedinst, D. B. A1 - Klouda, G. A. A1 - Currie, L. A. A1 - Cass, G. R. AB - Emissions from the major sources of fine carbonaceous aerosol in the Los Angeles basin atmosphere have been analyzed to determine the amounts of the C-12 and C-14 isotopes present. From these measurements, an inventory of the fossil carbon and contemporary carbon particle emissions to the Los Angeles atmosphere has been created. In the winter, more than half of the fine primary carbonaceous aerosol emissions are from sources containing contemporary carbon, including fireplaces, charbroilers, paved road dust, cigarette smoke, and brake lining dust, while in the summer at least one-third of the carbonaceous particle emissions are contemporary. Using a mathematical model for atmospheric transport, predictions are made of the atmospheric fine particulate fossil carbon and contemporary carbon concentrations expected due to primary source emissions. Model predictions are in reasonable agreement with the measured radiocarbon content of the fine ambient aerosol samples. It is concluded that the high fraction of contemporary carbon measured historically in Los Angeles is not due to local emission sources of biogenic material; rather, it is due to a combination of local anthropogenic pollution sources and background marine aerosol advected into the city. VL - 28 IS - 9 N1 - Pe258Times Cited:111Cited References Count:45 JO - Sources of Urban Contemporary Carbon Aerosol ER - TY - JOUR T1 - Subsidence in the Mississippi River Delta - Important influences of valley filling by cyclic deposition, primary consolidation phenomena, and early diagenesis JF - Transactions of the Gulf Coast Association of Geological Societies Y1 - 1994 A1 - Roberts, H. H. A1 - Bailey, A. A1 - Kuecher, G. J. VL - XLIV N1 - id: 1273 ER - TY - JOUR T1 - A synthesis of post-glacial diatom records from Lake Baikal JF - Journal of Paleolimnology Y1 - 1994 A1 - Bradbury, J. Platt A1 - Bezrukova, Ye V. A1 - Chernyaeva, G. P. A1 - Colman, S. M. A1 - Khursevich, G. A1 - King, J. W. A1 - Likoshway, Y. V. KW - Climate change KW - diatoms KW - Holocene KW - Lake Baikal KW - paleolimnology KW - palynology AB - The biostratigraphy of fossil diatoms contributes important chronologic, paleolimnologic, and paleoclimatic information from Lake Baikal in southeastern Siberia. Diatoms are the dominant and best preserved microfossils in the sediments, and distinctive assemblages and species provide inter-core correlations throughout the basin at millennial to centennial scales, in both high and low sedimentation-rate environments. Distributions of unique species, once dated by radiocarbon, allow diatoms to be used as dating tools for the Holocene history of the lake. Diatom, pollen, and organic geochemical records from site 305, at the foot of the Selenga Delta, provide a history of paleolimnologic and paleoclimatic changes from the late glacial (15 ka) through the Holocene. Before 14 ka diatoms were very rare, probably because excessive turbidity from glacial meltwater entering the lake impeded productivity. Between 14 and 12 ka, lake productivity increased, perhaps as strong winds promoted deep mixing and nutrient regeneration. Pollen evidence suggests a cold shrub — steppe landscape dominated the central Baikal depression at this time. As summer insolation increased, conifers replaced steppe taxa, but diatom productivity declined between 11 and 9 ka perhaps as a result of increased summer turbidity resulting from violent storm runoff entering the lake via short, steep drainages. After 8 ka, drier, but more continental climates prevailed, and the modern diatom flora of Lake Baikal came to prominence. On Academician Ridge, a site of slow sedimentation rates, Holocene diatom assemblages at the top of 10-m cores reappear at deeper levels suggesting that such cores record at least two previous interglacial (or interstadial?) periods. Nevertheless, distinctive species that developed prior to the last glacial period indicate that the dynamics of nutrient cycling in Baikal and the responsible regional climatic environments were not entirely analogous to Holocene conditions. During glacial periods, the deep basin sediments of Lake Baikal are dominated by rapidly deposited clastics entering from large rivers with possibly glaciated headwaters. On the sublacustrine Academician Ridge (depth = 300 m), however, detailed analysis of the diatom biostratigraphy indicates that diastems (hiatuses of minor duration) and (or) highly variable rates of accumulation complicate paleolimnologic and paleoclimatic reconstructions from these records. VL - 10 IS - 3 N1 - id: 16 JO - A synthesis of post-glacial diatom records from Lake Baikal ER - TY - MGZN T1 - Thermocline Ventilation Rates in the North Pacific Y1 - 1994 A1 - Sonnerup, R. E. A1 - Quay, P. D. A1 - Bullister, J. L. A1 - Key, R. M. A1 - McNichol, A. P. A1 - Jones, G. A. JF - American Geophysical Union, San Francisco N1 - id: 917 ER - TY - JOUR T1 - Tic, Toc, Dic, Doc, Pic, Poc - Unique Aspects in the Preparation of Oceanographic Samples for C-14 Ams JF - Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions with Materials and Atoms Y1 - 1994 A1 - McNichol, A. P. A1 - Osborne, E. A. A1 - Gagnon, A. R. A1 - Fry, B. A1 - Jones, G. A. AB - The radiocarbon content of discrete carbon pools (total (T), dissolved (D), and particulate (P) inorganic (I) and organic (O) carbon (C)) is a useful tracer of carbon cycling within the modem and past ocean. The isolation of different carbon pools in the ocean environment and conversion to CO2 presents unique analytical problems for the radiocarbon chemist. In general, isolation and preparation of inorganic carbon presents few problems; dissolved carbon is easily extracted by acidifying the sample and stripping with an inert gas. Carbon is also readily isolated from particulate carbonate samples; in this case, CO2 is prepared by hydrolysis of the substrate with phosphoric acid. The isolation and preparation of organic carbon presents a much greater problem. Dissolved organic carbon (DOC) must first be isolated from DIC and then oxidized in the presence of very high salt concentrations. We present results from a closed-tube combustion method in which the DIC-free seawater is evaporated to dryness, transferred to a clean combustion tube, and oxidized overnight at 550-degrees-C. Combustion of total organic carbon (TOC) in sediments with a high inorganic carbon content is also difficult. Removal of CaCO3 with acid leaves severely deliquescent salts which, if not thoroughly dried, cause combustion tubes to explode. Removal of the salts by rinsing can also remove significant amounts of organic matter. Finally, we present results from a local coastal region. VL - 92 IS - 1-4 N1 - Nv547Times Cited:82Cited References Count:9 JO - Tic, Toc, Dic, Doc, Pic, Poc - Unique Aspects in the Preparation of Oceanographic Samples for C-14 Ams ER - TY - JOUR T1 - Two episodes of meltwater influx from glacial Lake Agassiz into the Lake Michigan basin: Contrasts in climatic and oceanographic effects JF - Geology Y1 - 1994 A1 - Colman, S. M. A1 - Keigwin, L. D. A1 - Forester, R. M. VL - 22 N1 - id: 189 ER - TY - BOOK T1 - AMS Pulse, Supplement 1993 Y1 - 1993 A1 - NOSAMS, / PB - National Ocean Sciences Accelerator Mass Spectrometry Facility CY - Woods Hole, MA UR - https://hdl.handle.net/1912/24698 ER - TY - BOOK T1 - AMS Pulse Vol. 1, No. 4, Spring 1993 Y1 - 1993 A1 - NOSAMS, / PB - National Ocean Sciences Accelerator Mass Spectrometry Facility CY - Woods Hole, MA UR - https://hdl.handle.net/1912/24694 ER - TY - BOOK T1 - AMS Pulse Vol. 2, No. 1, Summer 1993 Y1 - 1993 A1 - NOSAMS, / PB - National Ocean Sciences Accelerator Mass Spectrometry Facility CY - Woods Hole, MA UR - https://hdl.handle.net/1912/24697 ER - TY - JOUR T1 - Ams-Graphite Target Production Methods at the Woods-Hole Oceanographic Institution during 1986-1991 JF - Radiocarbon Y1 - 1993 A1 - Gagnon, A. R. A1 - Jones, G. A. KW - accelerator mass-spectrometry KW - facility KW - ocean KW - radiocarbon KW - samples KW - sediments AB - In July 1986, an AMS radiocarbon target preparation laboratory was established at the Woods Hole Oceanographic Institution to produce graphite to be analyzed at the NSF-Accelerator Facility for Radioisotope Analysis at the University of Arizona (Tucson). By June 1991, 923 graphite targets had been prepared and 847 analyzed. Our lab procedures during this time included the careful documentation of weights of all starting samples, catalysts and final graphite yields, as well as the volume of CO2 gas evolved during CaCO3 hydrolysis or closed-tube organic carbon combustions. From these data, we evaluate the methods used in general and in our lab. VL - 35 SN - 0033-8222 IS - 2 N1 - Lg927Times Cited:12 Cited References Count:14 JO - Radiocarbon ER - TY - CONF T1 - Comparative study of Fe-C Bead vs. graphite target performance with the NOSAMS Facility recombinator ion source T2 - 6th International Conference on Accelerator Mass Spectrometry Y1 - 1993 A1 - Kleindinst, D. B. A1 - McNichol, A. P. A1 - Currie, L. A. A1 - Jones, G. A. A1 - Verkouteren, R. M. A1 - von Reden, K. F. A1 - Klouda, G. A. A1 - Schneider, R. J. JF - 6th International Conference on Accelerator Mass Spectrometry CY - Canberra, Australia N1 - id: 931 ER - TY - MGZN T1 - Dating the Climatic Optimum with AMS Y1 - 1993 A1 - Elder, K. L. JF - AMS Pulse, The National Ocean Sciences Accelerator Mass Spectrometry Facility Newsletter VL - Spring 1993 N1 - id: 1645 ER - TY - JOUR T1 - Deep-sea sediments reveal JF - Oceanus Y1 - 1993 A1 - Lehman, Scott J. A1 - Keigwin, L. D. VL - 35 IS - 4 N1 - id: 1248 JO - Deep-sea sediments reveal ER - TY - CONF T1 - Development of the mollusc Artica islandica as a paleoceanographic tool for reconstructing annual and seasonal records of 14C and delta 18O in the mid- to high- latitude North Atlantic Ocean T2 - International Symposium on Applications of Isotope Techniques in the Study of Past and Current Environmental Changes in the Hydrosphere and the Atmosphere Y1 - 1993 A1 - Weidman, C. R. A1 - Jones, G. A. JF - International Symposium on Applications of Isotope Techniques in the Study of Past and Current Environmental Changes in the Hydrosphere and the Atmosphere PB - International Atomic Energy Agency CY - Vienna, Austria VL - SMm-329 N1 - id: 1292 ER - TY - JOUR T1 - First results in from Pacific 14C Program JF - WOCE Notes Y1 - 1993 A1 - Key, R. M. A1 - Toggweiler, J. R. VL - 5 IS - 3 N1 - id: 39 JO - First results in from Pacific 14C Program ER - TY - CONF T1 - The high-precision AMS 14C program on seawater at the National Ocean Sciences AMS Facility T2 - European Community Workshop on Development of Ocean Tracer Measurements Y1 - 1993 A1 - von Reden, K. F. A1 - Jones, G. A. A1 - Schneider, R. J. A1 - McNichol, A. P. JF - European Community Workshop on Development of Ocean Tracer Measurements CY - Bremen, Germany N1 - id: 1767 ER - TY - CONF T1 - High-precision AMS radiocarbon measurements of seawater at the National Ocean Sciences AMS Facility T2 - 6th International Conference on Accelerator Mass Spectrometry Y1 - 1993 A1 - Jones, G. A. A1 - Schneider, R. J. A1 - McNichol, A. P. A1 - von Reden, K. F. JF - 6th International Conference on Accelerator Mass Spectrometry CY - Canberra, Australia N1 - id: 929 ER - TY - JOUR T1 - A history of past earthquakes recorded in Holocene sediments from Lake Washington JF - Eos, Transactions, American Geophysical Union Y1 - 1993 A1 - Karlin, R. A1 - Abella, S. VL - 74 IS - 43 N1 - id: 30 ER - TY - CONF T1 - Internal and external checks in the NOSAMS Sample Preparation Laboratory for target quality and homogeneity T2 - 6th International Conference on Accelerator Mass Spectrometry Y1 - 1993 A1 - McNichol, A. P. A1 - Gagnon, A. R. A1 - Osborne, E. A. A1 - Hutton, D. L. A1 - Jones, G. A. JF - 6th International Conference on Accelerator Mass Spectrometry CY - Canberra, Australia N1 - id: 958 ER - TY - CONF T1 - Laboratory automation at the National Ocean Sciences AMS Facility T2 - 6th Internation Conference on Accelerator Mass Spectrometry Y1 - 1993 A1 - Cohen, G. J. A1 - Hutton, D. L. A1 - von Reden, K. F. A1 - Osborne, E. A. A1 - McNichol, A. P. A1 - Jones, G. A. JF - 6th Internation Conference on Accelerator Mass Spectrometry CY - Canberra, Australia N1 - id: 927 ER - TY - CONF T1 - Methods for data screening, flagging and error analysis at the National Ocean Sciences AMS Facility T2 - 6th International Conference on Accelerator Mass Spectrometry Y1 - 1993 A1 - Schneider, R. J. A1 - Jones, G. A. A1 - McNichol, A. P. A1 - von Reden, K. F. A1 - Elder, K. L. A1 - Kessel, E. D. JF - 6th International Conference on Accelerator Mass Spectrometry CY - Canberra, Australia N1 - id: 933 ER - TY - JOUR T1 - The National Ocean Sciences Accelerator Mass Spectrometry Facility JF - WOCE Notes Y1 - 1993 A1 - Jones, G. A. A1 - McNichol, A. P. A1 - von Reden, K. F. A1 - Schneider, R. J. VL - 5 N1 - id: 1639 ER - TY - CONF T1 - The National Ocean Sciences Accelerator Mass Spectrometry Facility and the WOCE Hydrographic Program. Measurement of 14C in seawater by AMS T2 - Third Scientific Meeting, Oceanography Society Y1 - 1993 A1 - McNichol, A. P. A1 - Jones, G. A. A1 - Schneider, R. J. A1 - von Reden, K. F. A1 - Key, R. M. JF - Third Scientific Meeting, Oceanography Society CY - Seattle, WA VL - 95 N1 - id: 1656 ER - TY - JOUR T1 - The National Ocean Sciences Accelerator Mass Spectrometry Facility (WOCE) JF - WOCE Notes Y1 - 1993 A1 - Jones, G. A. A1 - McNichol, A. P. A1 - von Reden, K. F. A1 - Schneider, R. J. VL - 5 N1 - id: 1651 ER - TY - CONF T1 - The National Ocean Sciences AMS Facility at Woods Hole Oceanographic Institution T2 - 6th International Conference on Accelerator Mass Spectrometry Y1 - 1993 A1 - Jones, G. A. A1 - Schneider, R. J. A1 - von Reden, K. F. A1 - McNichol, A. P. A1 - Gagnon, A. R. A1 - Cohen, G. J. A1 - Osborne, E. A. A1 - Hutton, D. L. A1 - Kessel, E. D. A1 - Elder, K. L. JF - 6th International Conference on Accelerator Mass Spectrometry CY - Canberra, Australia N1 - id: 930 ER - TY - CONF T1 - The National Ocean Sciences AMS System at Woods Hole Oceanographic Institution T2 - European Community Workshop on Tracers in Physical Oceanography Y1 - 1993 A1 - von Reden, K. F. A1 - Jones, G. A. A1 - Schneider, R. J. A1 - McNichol, A. P. JF - European Community Workshop on Tracers in Physical Oceanography CY - Bremen, Germany N1 - id: 935 ER - TY - MGZN T1 - Neo-Atlantic Climatic Episode and the Middle Missouri Villagers Y1 - 1993 A1 - Toom, D. L. JF - 51st Plains Anthropological Conference N1 - id: 918 ER - TY - CONF T1 - A new high-temporal resolution paleoceanographic tool for the northern North Atlantic: the mollusc Arctica islandica T2 - International Council for the Exploration of the Sea (ICES) Statutory Meeting Y1 - 1993 A1 - Weidman, C. R. A1 - Jones, G. A. JF - International Council for the Exploration of the Sea (ICES) Statutory Meeting CY - Dublin, Ireland VL - 1993/K N1 - id: 1295; 17 ER - TY - CONF T1 - Optimized data analysis for radiocarbon dating T2 - 6th International Conference on Accelerator Mass Spectrometry Y1 - 1993 A1 - Sequin, F. H. A1 - Schneider, R. J. A1 - Jones, G. A. A1 - von Reden, K. F. JF - 6th International Conference on Accelerator Mass Spectrometry CY - Canberra, Australia N1 - id: 934 ER - TY - CONF T1 - Performance characteristics of the 3MV tandetron AMS system at the National Ocean Sciences AMS Facility T2 - 6th International Conference on Accelerator Mass Spectrometry Y1 - 1993 A1 - von Reden, K. F. A1 - Schneider, R. J. A1 - Cohen, G. J. A1 - Jones, G. A. JF - 6th International Conference on Accelerator Mass Spectrometry CY - Canberra, Australia N1 - id: 936 ER - TY - JOUR T1 - Plankton Environment and Marine Sediment Record of the Archipelago de Magallanes, Chile JF - EOS,Transactions,American Geophysical Union Y1 - 1993 A1 - Anderson, D. M. A1 - Archer, R. B. VL - 74 IS - 3 N1 - id: 902 JO - Plankton Environment and Marine Sediment Record of the Archipelago de Magallanes, Chile ER - TY - JOUR T1 - Progress report for the WOCE radiocarbon program JF - WOCE Notes Y1 - 1993 A1 - Key, R. M. A1 - Toggweiler, J. R. VL - 5 N1 - id: 322 JO - Progress report for the WOCE radiocarbon program ER - TY - MGZN T1 - Putting Ourselves to the Test: Analysis of the IAEA Intercomparison Samples Y1 - 1993 A1 - McNichol, A. P. JF - AMS Pulse VL - 1 N1 - id: 1612 ER - TY - JOUR T1 - Radiocarbon ages from two submerged strandline features in the western Gulf of Maine and a sea-level curve for the northeastern Massachusetts coastal region JF - Quaternary Research Y1 - 1993 A1 - Oldale, R. N. A1 - Colman, S. M. A1 - Jones, G. A. VL - 40 IS - 1 N1 - id: 10 ER - TY - JOUR T1 - Radiocarbon dating of Lake Baikal sediments--A progress report JF - Russian Geology and Geophysics Y1 - 1993 A1 - Colman, S. M. A1 - Kuptsov, V. M. A1 - Jones, G. A. A1 - Carter, S. J. VL - 34 N1 - id: 191 ER - TY - CONF T1 - Radiocarbon time histories from long-lived molluscs using accelerator mass-spectrometry T2 - 6th International Conference on Accelerator Mass Spectrometry Y1 - 1993 A1 - Weidman, C. R. A1 - Jones, G. A. JF - 6th International Conference on Accelerator Mass Spectrometry CY - Sydney, Australia N1 - id: 1296 ER - TY - CONF T1 - Role of the United States National Ocean Sciences Accelerator Mass Spectrometry Facility in Global Climate Change Studies T2 - International Symposium on Applications of Isotope Techniques in Studying Past and Current Environmental Change in the Hydrosphere and the Atmosphere Y1 - 1993 A1 - Jones, G. A. A1 - Schneider, R. J. A1 - von Reden, K. F. A1 - McNichol, A. P. JF - International Symposium on Applications of Isotope Techniques in Studying Past and Current Environmental Change in the Hydrosphere and the Atmosphere CY - Vienna N1 - id: 928 ER - TY - RPRT T1 - Sampling the marine gashydrate reservoir: Assessing the methane inventory, internal dynamics, and potential of methane discharges to the atmosphere. Final progress report Y1 - 1993 A1 - Paull, C. PB - California University CY - Davis, CA VL - DOEER61010T11 N1 - id: 59 ER - TY - JOUR T1 - A shell-derived time history of bomb 14C on Georges Bank and its Labrador Sea implications JF - Journal of Geophysical Research Y1 - 1993 A1 - Weidman, C. R. A1 - Jones, G. A. AB - Bomb-produced radiocarbon has been used in the past as an important tracer of ocean circulation and as a valuable tool for calculating CO2 air-sea exchange. However, previous studies of the ocean's time-varying bomb 14C record have been confined exclusively to analyzing banded corals, and thus their application has been limited to the lower latitudes. The first time history of bomb 14C from the high-latitude North Atlantic Ocean is obtained from a 54-year-old mollusc specimen, (Bivalvia) Arctica islandica, which was collected live from Georges Bank (41°N) in 1990. The annual growth bands of its shell were analyzed for Δ14C using accelerator mass spectrometry, producing a Δ14C time history from 1939 to 1990. The depleted condition of the Georges Bank bomb 14C signal relative to two coral-derived North Atlantic Δ14C time histories suggests a significant deepwater source for the waters on Georges Bank. Supported by previous work linking the origin of waters on Georges Bank to the Labrador Sea, the Δ14C budget on Georges Bank is modeled as Labrador Sea water, which largely becomes confined to the shelf and partially equilibrates with the atmosphere during a 1-year transit time from the Labrador Sea to Georges Bank. This model is also used to estimate a time history of bomb 14C for the Labrador Sea. Prebomb Δ14C values calculated for the surface Labrador Sea suggest that a greater inventory of bomb 14C has accumulated here than has previously been reported. However, the estimated prebomb average Δ14C (−70.6‰) for this period is nearly identical to the −70‰ previously calculated for the prebomb source of North Atlantic Deep Water and is in agreement with Transient Tracers in the Ocean subsurface tritium data from the central Labrador Sea. Deduced variations in the ventilation and/or 14CO2 uptake rates in the Labrador Sea correspond with observed changes in surface salinity of the Labrador Sea, suggesting a reduction in deepwater formation during the late 1960s and 1970s. VL - 98 IS - C8 N1 - id: 88 JO - A shell-derived time history of bomb 14C on Georges Bank and its Labrador Sea implications ER - TY - CONF T1 - The 59-sample, hemispherical ionizer ion sources at the Woods Hole Accelerator Mass Spectrometer T2 - Twelfth International Conference on the Application of Accelerators in Research and Industry Y1 - 1992 A1 - von Reden, K. F. JF - Twelfth International Conference on the Application of Accelerators in Research and Industry CY - Denton, Texas N1 - id: 1797 ER - TY - BOOK T1 - Abundances and Isotopic Compositions of Carbon and Sulfur Species in Whole Rock and Kerogen Samples T2 - The Proterozoic Biosphere Y1 - 1992 A1 - Strauss, H. A1 - Moore, T. B. ED - Klein, C. ED - Klein, C. JF - The Proterozoic Biosphere PB - Cambridge University Press N1 - id: 1599 ER - TY - JOUR T1 - Accelerator Mass-Spectrometry - Tracking Carbon in the Marine-Environment JF - Oceanus Y1 - 1992 A1 - Schneider, R. J. A1 - Jones, G. A. VL - 35 SN - 0029-8182 IS - 4 N1 - Kl777Times Cited:0 Cited References Count:0 JO - Oceanus ER - TY - CONF T1 - The AMS Accelerator at Woods Hole Oceanographic Institution T2 - Symposium of North Eastern Accelerator Personnel Y1 - 1992 A1 - Schneider, R. J. A1 - von Reden, K. F. A1 - Cohen, G. J. A1 - Jones, G. A. ED - Benson, J. JF - Symposium of North Eastern Accelerator Personnel PB - World Scientific Publishing Co. CY - Singapore N1 - id: 1794 ER - TY - BOOK T1 - AMS Pulse Vol. 1, No. 3, Winter 1992 Y1 - 1992 A1 - NOSAMS, / PB - National Ocean Sciences Accelerator Mass Spectrometry Facility CY - Woods Hole, MA UR - https://hdl.handle.net/1912/24696 ER - TY - BOOK T1 - AMS Pulse Vol. 1, Nos. 1 and 2, Fall 1992 Y1 - 1992 A1 - NOSAMS, / PB - National Ocean Sciences Accelerator Mass Spectrometry Facility CY - Woods Hole, MA UR - https://hdl.handle.net/1912/24695 ER - TY - CONF T1 - Application of AMS to Oceanography: Progress at the National Ocean Sciences AMS Facility (abstract) T2 - AMS Symposium Division of Nuclear Chemistry and Technology, 203rd American Chemical Society National Meeting Y1 - 1992 A1 - McNichol, A. P. A1 - Jones, G. A. A1 - Schneider, R. J. A1 - von Reden, K. F. JF - AMS Symposium Division of Nuclear Chemistry and Technology, 203rd American Chemical Society National Meeting N1 - id: 1796 ER - TY - MGZN T1 - Climatic History and Darwinian Causes of High Amazonian Diversity Y1 - 1992 A1 - Colinvaux, P. JF - 8th International Palynological Congress, Aix-en-Provence, France N1 - id: 904 ER - TY - JOUR T1 - Geochemistry of Precambrian carbonates: IV. Early Paleoproterozoic (2.25 +/-0.25 Ga) seawater JF - Geochimica et Cosmochimica Acta Y1 - 1992 A1 - Veizer, J. A1 - Clayton, K. R. N. A1 - Hinton, R. W. VL - 56 N1 - id: 1602 ER - TY - JOUR T1 - Illumination of a Black-Box - Analysis of Gas-Composition during Graphite Target Preparation JF - Radiocarbon Y1 - 1992 A1 - McNichol, A. P. A1 - Gagnon, A. R. A1 - Jones, G. A. A1 - Osborne, E. A. KW - deposition AB - We conducted a study of relative gas composition changes of CO2, CO and CH4 during the formation of graphite targets using different temperatures, catalysts and methods. Reduction with H-2 increases the reaction rate without compromising the quality of the AMS target produced. Methane is produced at virtually any temperature, and the amount produced is greater at very low temperatures. The reduction of CO to graphite is very slow when H-2 is not included in the reaction. VL - 34 SN - 0033-8222 IS - 3 N1 - Kf389Times Cited:63 Cited References Count:10 JO - Radiocarbon ER - TY - JOUR T1 - Initial Dating and Paleoenvironmental Results From Lake Baikal, Southeastern Siberia JF - Abstracts With Programs of the American Quaternary Association Y1 - 1992 A1 - Colman, S. M. A1 - Karabanov, E. B. A1 - Williams, D. F. A1 - Hearn, P. P., Jr. A1 - King, J. W. A1 - Orem, W. H. A1 - Bradbury, J. P. A1 - Shanks, W. C., III A1 - Jones, G. A. A1 - Carter, S. J. VL - xx N1 - id: 905 ER - TY - CHAP T1 - Major events in the geological development of the Precambrian Earth T2 - The Proterozoic Biosphere Y1 - 1992 A1 - Lowe, D. R. ED - Schopf, J. W. JF - The Proterozoic Biosphere PB - Cambridge University Press N1 - id: 1584 ER - TY - JOUR T1 - The National Ocean Sciences Accelerator Mass Spectrometer for Precision C-14 at Woods Hole Oceanographic Institution -- Status and new results JF - EOS, Transactions of the American Geophysical Union Y1 - 1992 A1 - von Reden, K. F. A1 - Jones, G. A. A1 - Schneider, R. J. A1 - McNichol, A. P. A1 - Cohen, G. J. VL - 72 N1 - id: 926 ER - TY - JOUR T1 - The new National Ocean Sciences Accelerator Mass Spectrometer Facility at Woods Hole Oceanographic Institution-Progress and first results (Proceedings of the 14th International Radiocarbon Conference, 1991) JF - Radiocarbon Y1 - 1992 A1 - von Reden, K. F. A1 - Jones, G. A. A1 - Schneider, R. J. A1 - McNichol, A. P. A1 - Cohen, G. J. A1 - Purser, K. H. VL - 34 N1 - id: 1787 ER - TY - CONF T1 - The new National Ocean Sciences Accelerator Mass Spectrometer Facility at Woods Hole Oceanographic Institution - Progress and First Results T2 - 14th International Radiocarbon Conference 1991 Y1 - 1992 A1 - von Reden, K. F. A1 - Jones, G. A. A1 - Schneider, R. J. A1 - McNichol, A. P. A1 - Cohen, G. J. A1 - Purser, K. H. ED - Long, A. JF - 14th International Radiocarbon Conference 1991 PB - Radiocarbon VL - 34 N1 - id: 1618 ER - TY - JOUR T1 - The occurrence of extralimital boreal mollusks in West Greenland during the Holocene (abstract) JF - EOS, Transactions, American Geophysical Union Y1 - 1992 A1 - Jones, G. A. A1 - Elder, K. L. VL - 72 IS - 259 N1 - id: 1758 ER - TY - JOUR T1 - Oceanic Crustal Thickness from Seismic Measurements and Rare-Earth Element Inversions JF - Journal of Geophysical Research-Solid Earth Y1 - 1992 A1 - White, R. S. A1 - Mckenzie, D. A1 - Onions, R. K. AB - Seismic refraction results show that the igneous section of oceanic crust averages 7.1 +/- 0.8 km thick away from anomalous regions such as fracture zones and hot-spots, with extremal bounds of 5.0-8.5 km. Rare earth element inversions of the melt distribution in the mantle source region suggest that sufficient melt is generated under normal oceanic spreading centers to produce an 8.3 +/- 1.5 km thick igneous crust. The difference between the thickness estimates from seismics and from rare earth element inversions is not significant given the uncertainties in the mantle source composition, though it is of the magnitude that would be expected if partial melt fractions of about 1% remain in the mantle and are not extracted to the overlying crust. The inferred igneous thickness increases to 10.3 +/- 1.7 km (seismic measurements) and 10.7 +/- 1.6 km (rare earth element inversions) where spreading centers intersect the regions of hotter than normal mantle surrounding mantle plumes. This is consistent with melt generation by decompression of the hotter mantle as it rises beneath spreading centers. Maximum inferred melt volumes are found on aseismic ridges directly above the central rising cores of mantle plumes, and average 20 +/- 1 and 18 +/- 1 km for seismic profiles and rare earth element inversions respectively. Both seismic measurements and rare earth element inversions show evidence for variable local crustal thinning beneath fracture zones, though some basalts recovered from fracture zones are indistinguishable geochemically from those generated on normal ridge segments away from fracture zones. This is consistent with a model where the melt generated beneath spreading ridges is redistributed to intrusive centers along the ridge axis, from where it may flow laterally along the axis at crustal or surface levels. The melt may sometimes flow into the bathymetric lows associated with fracture zones. Oceanic crust created at very slow-spreading ridges, and in regions adjacent to some continental margins where rifting was initially very slow, exhibits anomalously thin crust from seismic measurements and unusually small amounts of melt generation from rare earth element inversions. We attribute the decreased mantle melting on very slow-spreading ridges to the conductive heat loss that enables the mantle to cool as it rises beneath the rift. VL - 97 IS - B13 N1 - Kd951Times Cited:645Cited References Count:119 JO - Oceanic Crustal Thickness from Seismic Measurements and Rare-Earth Element Inversions ER - TY - CONF T1 - Operation of the Woods Hole AMS System T2 - 12th International Conference on the Application of Accelerators in Research and Industry Y1 - 1992 A1 - Schneider, R. J. JF - 12th International Conference on the Application of Accelerators in Research and Industry CY - Denton, Texas N1 - id: 963 ER - TY - CONF T1 - Planung, Aufbau und Betrieb der Woods Hole AMS Anlage T2 - AMS Symposium at Christian-Ausust University Y1 - 1992 A1 - von Reden, K. F. JF - AMS Symposium at Christian-Ausust University CY - Kiel, Germany N1 - id: 1668 ER - TY - JOUR T1 - Rapid Analysis of Seawater Inorganic Carbon at the National Ocean Sciences AMS Facility: Progress and Preliminary Results (abstract) JF - EOS, Transactions of the American Geophysical Union Meeting Y1 - 1992 A1 - McNichol, A. P. A1 - Jones, G. A. A1 - Schneider, R. J. A1 - von Reden, K. F. A1 - Key, R. M. VL - 72 IS - 65 N1 - id: 1655 ER - TY - JOUR T1 - Sedimentary Cycling and Environmental-Change in the Late Proterozoic - Evidence from Stable and Radiogenic Isotopes JF - Geochimica Et Cosmochimica Acta Y1 - 1992 A1 - Derry, L. A. A1 - Kaufman, A. J. A1 - Jacobsen, S. B. AB - We report C, Sr, and O isotopic as well as selected major and trace element data from Late Proterozoic (ca. 900-540 Ma) marine carbonates in three widely separated basins. The isotopic and elemental data are used to evaluate effects of post-depositional alteration of Sr-87/Sr-86 and delta-C-13. Using our present best estimates for unaltered samples, we construct a new delta-C-13-curve for 850 500 Ma marine carbonates using data in this paper and from literature sources. Delta-C-13 values are high (+4 to +8 parts per thousand) during most of the late Riphean (ca. 900-600 Ma) with brief negative excursions likely associated with glacial periods. Similarly, in the Vendian delta-C-13 falls sharply (from late Riphean highs) to < -3 parts per thousand around the Varanger glaciation (ca. 600 Ma), and then returns to high values (+4 to +2 parts per thousand) remaining until the Precambrian-Cambrian boundary where the curve drops to a value of about -1 parts per thousand in Lower Cambrian carbonates. Coupling of the Sr and C isotopic data is used to develop a simple model for evaluating organic carbon (C(org)) burial in Late Proterozoic oceans. These calculations indicate that C(org) burial rates were lower than present-day values during much of the late Riphean, at the same time that erosion rates were low. Excess O2 produced by the burial of C(org) was likely balanced by oxidation of reduced hydrothermal fluids and weathering reactions. Near the time of the Varanger glaciation, C(org) burial rates dropped but quickly recovered and reached a maximum (a factor of 2-4 greater than present day) in Vendian sediments. High C(org) burial rates were probably driven by high sedimentation rates, and possibly high productivity. The high C(org) burial rate likely gave rise to a large flux of O2; high values of delta-S-34 in Late Proterozoic marine sulfates suggest that this O2 flux was not balanced by increased sulfate formation. Further, the Sr-isotopic record indicates that excess O2 was not balanced by oxidation of submarine hydrothermal fluids. Increased oxidative weathering was probably an important sink for O2; nonetheless, we conclude that a significant and rapid increase in atmospheric O2 occurred in the Vendian. These results have important implications for environmental changes during the first appearance of an Ediacaran metazoan fauna. VL - 56 IS - 3 N1 - Hj963Times Cited:357Cited References Count:100 JO - Sedimentary Cycling and Environmental-Change in the Late Proterozoic - Evidence from Stable and Radiogenic Isotopes ER - TY - JOUR T1 - Variability of the delta13C of dissolved inorganic carbon at a site in the North Pacific Ocean JF - Geochimica et Cosmochimica Acta Y1 - 1992 A1 - McNichol, A. P. A1 - Druffel, E. R. M. VL - 56 N1 - id: 1746 ER - TY - CONF T1 - AMS radiocarbon results obtained from graphite targets produced at the Woods Hole Oceanographic Institution between 1986 and 1991 T2 - 14th Internation Radiocarbon Conference Y1 - 1991 A1 - Gagnon, A. R. A1 - Jones, G. A. JF - 14th Internation Radiocarbon Conference CY - Tucson, AZ N1 - id: 957 ER - TY - CHAP T1 - Carbon cycling in coastal sediments: 2. An investigation of the sources of CO2 to pore water using carbon isotopes T2 - Organic Substances and Sediments in Water, Processes and Analytical Y1 - 1991 A1 - McNichol, A. P. A1 - Druffel, E. R. M. A1 - Lee, C. ED - Baker, R. A. JF - Organic Substances and Sediments in Water, Processes and Analytical PB - CRC Press CY - Boca Raton, FL VL - 2 N1 - id: 1743 ER - TY - JOUR T1 - Carbon cycling in coastal sediments: 2. Estimating remineralization in Buzzards Bay, MA--A comment JF - Geochimica et Cosmochimica Y1 - 1991 A1 - Rowe, G. T. A1 - McNichol, A. P. VL - 55 N1 - id: 1786 ER - TY - JOUR T1 - Carbon isotope anomalies in carbonates of the Karelian Complex JF - Geochemistry International Y1 - 1991 A1 - Yudovich, Y. E. A1 - Makarikhin, V. V. A1 - Medvedev, P. V. A1 - Sukhanov, N. V. VL - 28 N1 - id: 1607 JO - Carbon isotope anomalies in carbonates of the Karelian Complex ER - TY - JOUR T1 - The compressibility of silicate liquids containing Fe2O3 and the effect of composition, temperature, oxygen fugacity and pressure on their redox states JF - Contributions to Mineralogy and Petrology Y1 - 1991 A1 - Kress, V. C. A1 - Carmichael, I. S. E. VL - 108 N1 - id: 1582 JO - The compressibility of silicate liquids containing Fe203 and the effect of composition, temperature, oxygen fugacity and pressure on their redox states ER - TY - JOUR T1 - Illumination of a black box: Gas composition changes during graphite target preparation for AMS (Proceedings of the 14th International Radiocarbon Conference, 1991) JF - Radiocarbon Y1 - 1991 A1 - McNichol, A. P. A1 - Gagnon, A. R. A1 - Jones, G. A. A1 - Osborne, E. A. VL - 34 N1 - id: 1745 ER - TY - RPRT T1 - Measuring 14C in seawater by Accelerator Mass Spectrometry Y1 - 1991 A1 - McNichol, A. P. A1 - Jones, G. A. PB - WOCE Hydrographic Programme Office/Woods Hole Oceanographic Institution CY - Woods Hole, MA VL - WOCE Report No. 68/91 N1 - id: 1610 ER - TY - JOUR T1 - A Model for Atmospheric Co2 over Phanerozoic Time JF - American Journal of Science Y1 - 1991 A1 - Berner, R. A. AB - A new model has been constructed for calculating the level of atmospheric CO2 over Phanerozoic time which is much simpler mathematically than the BLAG model, but more complex geologically and biologically. Mathematical simplification comes about by following the cycle of carbon only, lumping all carbonate minerals together, combining the ocean and atmosphere into one reservoir, and calculating atmospheric CO2 level as a series of successive ocean-atmosphere steady states. The isotope mass balance model of Garrels and Lerman (1984) is expanded to include the effect of changing area, elevation, and position of the continents as well as the evolution of land plants as they affect weathering rate, and changes in seafloor area generation rate and the relative importance of deep sea versus shallow platform carbonate deposition as they affect global degassing. Atmospheric CO2 level is calculated from a weathering feedback function for silicates which varies with time as vascular land plants arise and evolve.Results suggest that there has been a notable pattern of varying atmospheric CO2 level over the past 570 my with high levels during the Mesozoic and early Paleozoic and low levels during the Permo-Carboniferous and late Cenozoic. Sensitivity analysis shows that, within reasonable limits of the principal governing parameters, this qualitative trend of varying CO2 is relatively insensitive to the actual values chosen for these parameters. Causes of the CO2 variation are multiple, and no single geological or biological process can be called upon to explain all CO2 variation for all time.The calculated trend of CO2 over time agrees well with independent estimations of paleoclimates. Thus, the greenhouse theory of paleoclimate on a long geological time scale is supported by the results of the present study. VL - 291 IS - 4 N1 - Ff648Times Cited:412Cited References Count:61 JO - A Model for Atmospheric Co2 over Phanerozoic Time ER - TY - CONF T1 - The optimization of target production for AMS T2 - 14th International Radiocarbon Conference Y1 - 1991 A1 - McNichol, A. P. A1 - Gagnon, A. R. A1 - Jones, G. A. A1 - Schneider, R. J. A1 - von Reden, K. F. JF - 14th International Radiocarbon Conference CY - Tucson, AZ N1 - id: 922 ER - TY - CHAP T1 - Quantification and characterization of porewater organic colloids T2 - Organic Substances and Sediments in Water. Processes and Analytical Y1 - 1991 A1 - Chin, Y. P. A1 - McNichol, A. P. A1 - Gschwend, P. M. ED - Baker, R. A. JF - Organic Substances and Sediments in Water. Processes and Analytical PB - CRC Press CY - Boca Raton, FL VL - 2 N1 - id: 1744 ER - TY - CHAP T1 - Radiocarbon T2 - WOCE Hydrographic Operations and Methods Manual Y1 - 1991 A1 - Key, R. M. JF - WOCE Hydrographic Operations and Methods Manual PB - WOCE Hydrographic Program Office Technical Report N1 - id: 321 ER - TY - JOUR T1 - Response of G. quinqueloba to Hypsithermal warming in the Norwegian-Greenland Sea (abstract) JF - EOS, Transactions, American Geophysical Union Y1 - 1991 A1 - Jones, G. A. A1 - Elder, K. L. VL - 71 IS - 268 N1 - id: 1759 ER - TY - CONF T1 - Response of the Norwegian-Greenland Sea to Mid-Holocen warming (abstract) T2 - 20th Arctic Workshoip, INSTAAR Y1 - 1991 A1 - Jones, G. A. A1 - Elder, K. L. JF - 20th Arctic Workshoip, INSTAAR CY - Fairbanks, AL N1 - id: 1760 ER - TY - CONF T1 - A triple-isotope injector for Accelerator Mass Spectrometry: Conference Record of the 1991 IEEE Particle Accelerator Conference T2 - IEEE Particle Accelerator Conference Y1 - 1991 A1 - Schneider, R. J. A1 - von Reden, K. F. A1 - Purser, K. H. JF - IEEE Particle Accelerator Conference CY - San Francisco, CA VL - 2 N1 - id: 923 ER -