@article {gartman_hydrothermal_2024, title = {Hydrothermal Plume Fallout, Mass Wasting, and Volcanic Eruptions Contribute to Sediments at Loki{\textquoteright}s Castle Vent Field, Mohns Ridge}, journal = {Geochemistry, Geophysics, Geosystems}, volume = {25}, number = {2}, year = {2024}, note = {_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1029/2023GC011094}, month = {02/2024}, pages = {e2023GC011094}, abstract = {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{\textquoteright}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{\textendash}316{\textdegree}C) {\textquotedblleft}black smoker{\textquotedblright} 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.}, issn = {1525-2027}, doi = {10.1029/2023GC011094}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1029/2023GC011094}, author = {Gartman, A. and Payan, D. and Au, M. and Reeves, E. P. and Jamieson, J. W. and Gini, C. and Roerdink, D.} } @article {castrillejo_comparability_2023, title = {Comparability of Radiocarbon Measurements in Dissolved Inorganic Carbon of Seawater Produced at ETH-Zurich}, journal = {Radiocarbon}, year = {2023}, note = {Publisher: Cambridge University Press}, month = {03/2023}, pages = {1{\textendash}10}, abstract = {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.}, keywords = {14C, comparison, DIC, dissolved inorganic carbon, radiocarbon, SEAWATER}, issn = {0033-8222, 1945-5755}, doi = {10.1017/RDC.2023.16}, url = {https://www.cambridge.org/core/journals/radiocarbon/article/comparability-of-radiocarbon-measurements-in-dissolved-inorganic-carbon-of-seawater-produced-at-ethzurich/B9F6C6AA45835FA3ED0BF8E0CD9788E3}, author = {Castrillejo, Maxi and Hansman, Roberta L. and Graven, Heather D. and Lester, Joanna G. and Bollhalder, Silvia and K{\"u}ndig, Kayley and Wacker, Lukas} } @article {pigati_independent_2023, title = {Independent age estimates resolve the controversy of ancient human footprints at White Sands}, journal = {Science}, volume = {382}, number = {6666}, year = {2023}, note = {Publisher: American Association for the Advancement of Science}, month = {10/2023}, pages = {73{\textendash}75}, abstract = {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{\textendash}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.}, doi = {10.1126/science.adh5007}, url = {https://www.science.org/doi/10.1126/science.adh5007}, author = {Pigati, Jeffrey S. and Springer, Kathleen B. and Honke, Jeffrey S. and Wahl, David and Champagne, Marie R. and ZIMMERMAN, SUSAN R. H. and Gray, Harrison J. and Santucci, Vincent L. and Odess, Daniel and Bustos, David and Bennett, Matthew R.} } @article {liu_pre-aged_2023, title = {Pre-aged terrigenous organic carbon biases ocean ventilation-age reconstructions in the North Atlantic}, journal = {Nature Communications}, volume = {14}, number = {1}, year = {2023}, note = {Number: 1 Publisher: Nature Publishing Group}, month = {06/2023}, abstract = {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 {\textpm} 692 years older than the coeval foraminifera in the central North Atlantic during HS1, which is coupled to a ventilation age of 5,169 {\textpm} 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.}, keywords = {Carbon cycle, Marine chemistry, Palaeoceanography}, issn = {2041-1723}, doi = {10.1038/s41467-023-39490-6}, url = {https://www.nature.com/articles/s41467-023-39490-6}, author = {Liu, Jingyu and Wang, Yipeng and Jaccard, Samuel L. and Wang, Nan and Gong, Xun and Fang, Nianqiao and Bao, Rui} } @article {white_refractory_2023, title = {Refractory Dissolved Organic Matter has Similar Chemical Characteristics but Different Radiocarbon Signatures With Depth in the Marine Water Column}, journal = {Global Biogeochemical Cycles}, volume = {37}, number = {4}, year = {2023}, note = {_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1029/2022GB007603}, month = {04/2023}, pages = {e2022GB007603}, abstract = {The >5,000-year radiocarbon age (14C-age) of much of the 630 {\textpm} 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{\textemdash}that RDOC is comprised of structurally related components throughout the ocean that form a {\textquotedblleft}background{\textquotedblright} 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.}, keywords = {marine dissolved organic matter, radiocarbon, ramped pyrolysis oxidation}, issn = {1944-9224}, doi = {10.1029/2022GB007603}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1029/2022GB007603}, author = {White, Margot E. and Nguyen, Tran B. and Koester, Irina and Lardie Gaylord, Mary C. and Beman, J. Michael and Smith, Kenneth L. and McNichol, Ann P. and Beaupr{\'e}, Steven R. and Aluwihare, Lihini I.} } @article {hanke_sequential_2023, title = {Sequential thermal analysis of complex organic mixtures: Procedural standards and improved CO2 purification capacity}, journal = {Radiocarbon}, volume = {65}, number = {2}, year = {2023}, note = {Publisher: Cambridge University Press}, month = {03/2023}, pages = {389{\textendash}409}, abstract = {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 {\textquotedblleft}dirt burner{\textquotedblright} 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.}, keywords = {chemical analysis, dirt burner, full oxidation (FOX) mode, Radiocarbon dating, ramped pyrolysis oxidation}, issn = {0033-8222, 1945-5755}, doi = {10.1017/RDC.2023.13}, url = {https://www.cambridge.org/core/journals/radiocarbon/article/sequential-thermal-analysis-of-complex-organic-mixtures-procedural-standards-and-improved-co2-purification-capacity/E225F01B421614EE176553014E7B38BE}, author = {Hanke, Ulrich M. and Gagnon, Alan R. and Reddy, Christopher M. and Gaylord, Mary C. Lardie and Cruz, Anne J. and Galy, Valier and Hansman, Roberta L. and Kurz, Mark D.} } @article {lu_surface_2023, title = {Surface climate signals transmitted rapidly to deep North Atlantic throughout last millennium}, journal = {Science}, volume = {382}, number = {6672}, year = {2023}, note = {Publisher: American Association for the Advancement of Science}, month = {11/2023}, pages = {834{\textendash}839}, chapter = {834}, abstract = {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 {\textpm} 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{\textquoteright}s surface temperature throughout the last millennium as it does today.}, doi = {10.1126/science.adf1646}, url = {https://www.science.org/doi/10.1126/science.adf1646}, author = {Lu, Wanyi and Oppo, Delia W. and Gebbie, Geoffrey and Thornalley, David J. R.} } @article {mayne_baobabs_2022, title = {Baobabs at the edge: 90-year dynamics of climate variability, growth, resilience, and evolutionary legacy effects}, journal = {Frontiers in Forests and Global Change}, volume = {5}, year = {2022}, month = {11/2022}, abstract = {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{\textendash}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 Ni{\~n}o-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{\textendash}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 {\textquotedblleft}Africa{\textquoteright}s favourite tree.{\textquotedblright}}, issn = {2624-893X}, doi = {10.3389/ffgc.2022.1036636}, url = {https://www.frontiersin.org/articles/10.3389/ffgc.2022.1036636}, author = {Mayne, Diana H. and Karimi, Nisa and Cruywagen, Elsie M. and Cole, Patrick and Goodall, Victoria} } @article {2956, title = {Black carbon and organic carbon dataset over the Third Pole}, journal = {Earth System Science Data}, volume = {14}, year = {2022}, month = {Jan-01-2022}, pages = {683 - 707}, abstract = {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 {\textquotedblleft}Atmospheric Pollution and Cryospheric Changes{\textquotedblright} (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).}, doi = {10.5194/essd-14-683-2022}, url = {https://essd.copernicus.org/articles/14/683/2022/}, author = {Kang, Shichang and Zhang, Yulan and Chen, Pengfei and Guo, Junming and Zhang, Qianggong and Cong, Zhiyuan and Kaspari, Susan and Tripathee, Lekhendra and Gao, Tanguang and Niu, Hewen and Zhong, Xinyue and Chen, Xintong and Hu, Zhaofu and Li, Xiaofei and Li, Yang and Neupane, Bigyan and Yan, Fangping and Rupakheti, Dipesh and Gul, Chaman and Zhang, Wei and Wu, Guangming and Yang, Ling and Wang, Zhaoqing and Li, Chaoliu} } @article {2949, title = {Contemporary sources dominate carbonaceous aerosol on the North Slope of Alaska}, journal = {Science of The Total Environment}, volume = {831}, year = {2022}, month = {Jan-07-2022}, pages = {154641}, abstract = {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 (Utqiagvik, 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. Utqiagvik 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.}, issn = {00489697}, doi = {10.1016/j.scitotenv.2022.154641}, url = {https://linkinghub.elsevier.com/retrieve/pii/S004896972201734X}, author = {Moffett, Claire E. and Mehra, Manisha and Barrett, Tate E. and Gunsch, Matthew J. and Pratt, Kerri A. and Sheesley, Rebecca J.} } @article {2974, title = {Cultural Keystone Places and the Chumash Landscapes of Kumqaq{\textquoteright}, Point Conception, California}, journal = {American Antiquity}, volume = {87}, year = {2022}, month = {03/2022}, pages = {487 - 504}, abstract = {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 {\textquotedblleft}high cultural salience,{\textquotedblright} or {\textquotedblleft}cultural keystone places{\textquotedblright} (CKPs). We identify Kumqaq{\textquoteright} (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{\textquoteright}s rich biodiversity and significance as a biogeographical boundary. Recent archaeological survey of the coastline surrounding Kumqaq{\textquoteright} highlights these connections, identifying over 50 archaeological sites{\textemdash}including shell middens, villages, lithic scatters, and rock art{\textemdash}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.}, doi = {10.1017/aaq.2021.154}, url = {https://www.cambridge.org/core/journals/american-antiquity/article/cultural-keystone-places-and-the-chumash-landscapes-of-kumqaq-point-conception-california/16A429D7AA4ACF06CE3005A1578A054B/share/c7af0ac75459bd572e942e9246aa0d3791fae5e1}, author = {Rick, Torben C. and Braje, Todd J. and Graham, Lain and Easterday, Kelly and Hofman, Courtney A. and Holguin, Brian E. and Mychajliw, Alexis M. and Reeder-Myers, Leslie A. and Reynolds, Mark D.} } @article {2960, title = {The dynamics of warming during the last deglaciation in high-elevation regions of Eastern Equatorial Africa}, journal = {Quaternary Science Reviews}, volume = {281}, year = {2022}, month = {Jan-04-2022}, pages = {107416}, abstract = {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{\textendash}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 {\textdegree}C warming from the Last Glacial Maximum (LGM) to the late Holocene. This increase is larger than the average \~{}2-4 {\textdegree}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 {\textdegree}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.}, issn = {02773791}, doi = {10.1016/j.quascirev.2022.107416}, url = {https://linkinghub.elsevier.com/retrieve/pii/S0277379122000476}, author = {Garelick, Sloane and Russell, James and Richards, Adin and Smith, Jamila and Kelly, Meredith and Anderson, Nathan and Jackson, Margaret S. and Doughty, Alice and Nakileza, Bob and Ivory, Sarah and Dee, Sylvia and Marshall, Charlie} } @article {2966, title = {Geochemistry and Provenance of Springs in a Baja California Sur Mountain Catchment}, journal = {Groundwater}, volume = {60}, year = {2022}, month = {Jan-03-2022}, pages = {295 - 308}, abstract = {Fractured rock aquifers cover much of Earth{\textquoteright}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.}, issn = {0017-467X}, doi = {10.1111/gwat.v60.210.1111/gwat.13177}, url = {https://onlinelibrary.wiley.com/toc/17456584/60/2}, author = {Lerback, Jory C. and Bowen, Brenda B. and Humphrey, C. E. and Fernandez, Diego. P. and Bernau, Jeremiah A. and Macfarlan, Shane J. and Schniter, Eric and Garcia, J. J.} } @article {2945, title = {Hydrological and thermodynamic controls on late Holocene gypsum formation by mixing saline groundwater and Dead Sea brine}, journal = {Geochimica et Cosmochimica Acta}, volume = {316}, year = {2022}, month = {Jan-01-2022}, pages = {363 - 383}, abstract = {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.}, keywords = {BrinesSaline springs, Dead Sea, Hydroclimate, Lacustrine Gypsum, Outsalting, Thermodynamic modeling}, issn = {00167037}, doi = {10.1016/j.gca.2021.10.002}, url = {https://www.webofscience.com/wos/woscc/full-record/WOS:000730092400010?AlertId=ab9062f8-b111-4f95-a2b8-66e7afac0471\&SID=8Dkzxr6qseeJz1VEtb3}, author = {Weber, Nurit and Antler, Gilad and Lazar, Boaz and Stein, Mordechai and Yechieli, Yoseph and Gavrieli, Ittai} } @article {thatcher_iberian_2022, title = {Iberian hydroclimate variability and the Azores High during the last 1200 years: evidence from proxy records and climate model simulations}, journal = {Climate Dynamics}, year = {2022}, month = {08/2022}, pages = {1{\textendash}23}, abstract = {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{\textendash}1250 CE) and Modern Climate/Industrial Era (1850 CE-present), and wetter conditions during the Little Ice Age (LIA; 1400{\textendash}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.}, keywords = {Azores High, Hydroclimate, last millennium, Last Millennium Ensemble, Paleoclimate, Stalagmite}, doi = {10.1007/s00382-022-06427-6}, url = {https://app.dimensions.ai/details/publication/pub.1150271437}, author = {Thatcher, Diana L. and Wanamaker, A. D. and Denniston, R. F. and Ummenhofer, C. C. and Asmerom, Y. and Polyak, V. J. and Cresswell-Clay, N. and Hasiuk, F. and Haws, J. and Gillikin, D. P.} } @article {2968, title = {Impact of Indian Ocean surface temperature gradient reversals on the Indian Summer Monsoon}, journal = {Earth and Planetary Science Letters}, volume = {578}, year = {2022}, month = {Jan-01-2022}, pages = {117327}, abstract = {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{\textquoteright}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{\textpm}470 and 5700{\textpm}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{\textquoteright}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.}, issn = {0012821X}, doi = {10.1016/j.epsl.2021.117327}, url = {https://linkinghub.elsevier.com/retrieve/pii/S0012821X21005835}, author = {Weldeab, Syee and R{\"u}hlemann, Carsten and Ding, Qinghua and Khon, Vyacheslav and Schneider, Birgit and Gray, William R.} } @article {2963, title = {Indian monsoon variability during the past \~{}8.5~cal~kyr as recorded in the sediments of the northeastern Arabian Sea}, journal = {Quaternary International}, year = {2022}, month = {Jan-04-2022}, abstract = {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.}, issn = {10406182}, doi = {10.1016/j.quaint.2022.03.016}, url = {https://linkinghub.elsevier.com/retrieve/pii/S104061822200115X}, author = {Ravichandran, M. and Gupta, Anil K. and Mohan, K. and Tiwari, Sameer K. and Lakshumanan, C. and Panigrahi, M.K.} } @article {2965, title = {In-phase millennial-scale glacier changes in the tropics and North Atlantic regions during the HoloceneAbstract}, journal = {Nature Communications}, volume = {13}, year = {2022}, month = {Jan-12-2022}, abstract = {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 {\textquotedblleft}AMOC-corrected{\textquotedblright} 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.}, doi = {10.1038/s41467-022-28939-9}, url = {https://www.nature.com/articles/s41467-022-28939-9}, author = {Jomelli, V. and Swingedouw, D. and Vuille, M. and Favier, V. and Goehring, B. and Shakun, J. and Braucher, R. and Schimmelpfennig, I. and Menviel, L. and Rabatel, A. and Martin, L. C. P. and Blard, P.-H. and Condom, T. and Lupker, M. and Christl, M. and He, Z. and Verfaillie, D. and Gorin, A. and Auma{\^\i}tre, G. and Bourles, D. L. and Keddadouche, K.} } @article {2978, title = {Late Holocene Paleomagnetic Secular Variation in the Chukchi Sea, Arctic Ocean}, journal = {Geochemistry, Geophysics, Geosystems}, volume = {23}, year = {2022}, month = {05/2022}, pages = {1-21}, abstract = {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.}, doi = {10.1029/2021GC010187}, url = {https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2021GC010187}, author = {West, Gabriel and Nilsson, Andreas and Geels, Alexis and Jakobsson, Martin and Moros, Matthias and Muschitiello, Francesco and Pearce, Christof and Snowball, Ian and O{\textquoteright}Regan, Matt} } @article {2951, title = {Not all permafrost microbiomes are created equal: Influence of permafrost thaw on the soil microbiome in a laboratory incubation study}, journal = {Soil Biology and Biochemistry}, volume = {167}, year = {2022}, month = {Jan-04-2022}, pages = {108605}, abstract = {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{\textquoteright}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{\textendash}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.}, issn = {00380717}, doi = {10.1016/j.soilbio.2022.108605}, url = {https://linkinghub.elsevier.com/retrieve/pii/S0038071722000621}, author = {Barbato, R.A. and Jones, R.M. and Douglas, T.A. and Doherty, S.J. and Messan, K. and Foley, K.L. and Perkins, E.J. and Thurston, A.K. and Garcia-Reyero, N.} } @article {2959, title = {The occupation history of the longest-dwelling Ad{\'e}lie penguin colony reflects Holocene climatic and environmental changes in the Ross Sea, Antarctica}, journal = {Quaternary Science Reviews}, volume = {284}, year = {2022}, month = {Jan-05-2022}, pages = {107494}, abstract = {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 Ad{\'e}lie 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 Ad{\'e}lies 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{\textendash}5.0 and 4.0{\textendash}3.5 kyr BP. After brief decline at 3.5{\textendash}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 Ad{\'e}lie penguin if the recurrent Terra Nova Bay polynya persists under future climatic and environmental changes, as occurred in the past.}, issn = {02773791}, doi = {10.1016/j.quascirev.2022.107494}, url = {https://linkinghub.elsevier.com/retrieve/pii/S0277379122001251}, author = {Gao, Yuesong and Salvatore, Maria Cristina and Xu, Qibin and Yang, Lianjiao and Sun, Liguang and Xie, Zhouqing and Baroni, Carlo} } @article {2961, title = {Persistence of old soil carbon under changing climate: The role of mineral-organic matter interactions}, journal = {Chemical Geology}, volume = {587}, year = {2022}, month = {Jan-01-2022}, pages = {120629}, abstract = {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{\textquoteright}i. We measure carbon isotope composition (14C/12C, 13C/12C) in bulk samples and extracted biomarkers for 4{\textendash}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.}, issn = {00092541}, doi = {10.1016/j.chemgeo.2021.120629}, url = {https://linkinghub.elsevier.com/retrieve/pii/S0009254121005726}, author = {Grant, Katherine E. and Galy, Valier V. and Haghipour, Negar and Eglinton, Timothy I. and Derry, Louis A.} } @article {2948, title = {RADIOCARBON IN DISSOLVED CARBON BY UV OXIDATION: AN UPDATE OF PROCEDURES AND BLANK CHARACTERIZATION AT NOSAMSABSTRACT}, journal = {Radiocarbon}, volume = {64}, year = {2022}, month = {Jan-02-2022}, pages = {195 - 199}, abstract = {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.}, issn = {0033-8222}, doi = {10.1017/RDC.2022.4}, url = {https://www.cambridge.org/core/product/identifier/S0033822222000042/type/journal_articlehttps://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0033822222000042}, author = {Xu, Li and Roberts, Mark L and Elder, Kathryn L and Hansman, Roberta L and Gagnon, Alan R and Kurz, Mark D} } @article {2981, title = {Reconciling the apparent absence of a Last Glacial Maximum alpine glacial advance, Yukon Territory, Canada, through cosmogenic beryllium-10 and carbon-14 measurements}, journal = {Geochronology}, volume = {4}, year = {2022}, month = {05/2022}, pages = {311 - 322}, abstract = {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.}, doi = {10.5194/gchron-4-311-2022}, url = {https://gchron.copernicus.org/articles/4/311/2022/}, author = {Goehring, Brent M. and Menounos, Brian and Osborn, Gerald and Hawkins, Adam and Ward, Brent} } @article {2982, title = {Relative sea-level data preclude major late Holocene ice-mass change in Pine Island Bay}, journal = {Nature Geoscience}, volume = {15}, year = {2022}, month = {06/2022}, pages = {568-573}, abstract = {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.}, doi = {10.1038/s41561-022-00961-y}, url = {https://www.nature.com/articles/s41561-022-00961-y}, author = {Braddock, Scott and Hall, Brenda L. and Johnson, Joanne S. and Balco, Greg and Spoth, Meghan and Whitehouse, Pippa L. and Campbell, Seth and Goehring, Brent M. and Rood, Dylan H. and Woodward, John} } @article {johnson_review_2022, title = {Review article: Existing and potential evidence for Holocene grounding line retreat and readvance in Antarctica}, journal = {The Cryosphere}, volume = {16}, number = {5}, year = {2022}, note = {Publisher: Copernicus GmbH}, month = {05/2022}, pages = {1543{\textendash}1562}, abstract = {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 {\textquotedblleft}readvance{\textquotedblright}) 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.}, issn = {1994-0416}, doi = {10.5194/tc-16-1543-2022}, url = {https://tc.copernicus.org/articles/16/1543/2022/}, author = {Johnson, Joanne S. and Venturelli, Ryan A. and Balco, Greg and Allen, Claire S. and Braddock, Scott and Campbell, Seth and Goehring, Brent M. and Hall, Brenda L. and Neff, Peter D. and Nichols, Keir A. and Rood, Dylan H. and Thomas, Elizabeth R. and Woodward, John} } @article {3005, title = {Sediment Accumulation and Carbon Burial in Four Hadal Trench Systems}, journal = {Journal of Geophysical Research: Biogeosciences}, volume = {n/a}, year = {2022}, note = {

e2022JG006814 2022JG006814

}, month = {09/2022}, pages = {e2022JG006814}, abstract = {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.}, keywords = {focusing factor, Hadal trench, mass accumulation rate, mass-wasting event, organic carbon deposition rate, radionuclides}, isbn = {2169-8961}, doi = {10.1029/2022JG006814}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1029/2022JG006814}, author = {Oguri, Kazumasa and Masqu{\'e}, Pere and Zabel, Matthias and Stewart, Heather A. and MacKinnon, Gillian and Rowden, Ashley A. and Berg, Peter and Wenzh{\"o}fer, Frank and Glud, Ronnie N.} } @article {2952, title = {Terrestrial organic carbon age and reactivity in the Yellow River fueling efficient preservation in marine sediments}, journal = {Earth and Planetary Science Letters}, volume = {585}, year = {2022}, month = {Jan-05-2022}, pages = {117515}, abstract = {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{\textendash}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{\textemdash}a proxy for bonding environment and by extension reactivity{\textemdash}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{\textendash}YS. The resulting estimates of terrestrial OC proto-burial efficiencies yield an average value of 89 {\textpm} 30\%, revealing overall very high terrestrial OC preservation in the BS{\textendash}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.}, issn = {0012821X}, doi = {10.1016/j.epsl.2022.117515}, url = {https://linkinghub.elsevier.com/retrieve/pii/S0012821X22001510}, author = {Zhang, Yushuang and Galy, Valier and Yu, Meng and Zhang, Hailong and Zhao, Meixun} } @article {2921, title = {Climate control on terrestrial biospheric carbon turnover}, journal = {Proceedings of the National Academy of Sciences}, volume = {118}, year = {2021}, month = {Nov-02-2022}, pages = {e2011585118}, abstract = {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.}, keywords = {Carbon cycle, carbon turnover times, fluvial carbon, plant biomarkers, radiocarbon}, issn = {0027-8424}, doi = {10.1073/pnas.2011585118}, url = {https://www.researchgate.net/publication/349357864_Climate_control_on_terrestrial_biospheric_carbon_turnover}, author = {Eglinton, Timothy I. and Galy, Valier V. and Hemingway, Jordon D. and Feng, Xiaojuan and Bao, Hongyan and Blattmann, Thomas M. and Dickens, Angela F. and Gies, Hannah and Giosan, Liviu and Haghipour, Negar and Hou, Pengfei and Lupker, Maarten and McIntyre, Cameron P. and Montlu{\c c}on, Daniel B. and Peucker-Ehrenbrink, Bernhard and Ponton, Camilo and Schefu{\ss}, Enno and Schwab, Melissa S. and Voss, Britta M. and Wacker, Lukas and Wu, Ying and Zhao, Meixun} } @article {2930, title = {Coal fly ash is a major carbon flux in the Chang Jiang (Yangtze River) basin}, journal = {Proceedings of the National Academy of Sciences}, volume = {118}, year = {2021}, month = {Jan-05-2023}, pages = {e1921544118}, abstract = {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.}, issn = {0027-8424}, doi = {10.1073/pnas.1921544118}, url = {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}, author = {Li, Gen K. and Fischer, Woodward W. and Lamb, Michael P. and West, A. Joshua and Zhang, Ting and Galy, Valier and Wang, Xingchen Tony and Li, Shilei and Qiu, Hongrui and Li, Gaojun and Zhao, Liang and Chen, Jun and Ji, Junfeng} } @article {2944, title = {A FRAMEWORK FOR TRANSDISCIPLINARY RADIOCARBON RESEARCH: USE OF NATURAL-LEVEL AND ELEVATED-LEVEL -14- C IN ANTARCTIC FIELD RESEARCHABSTRACT}, journal = {Radiocarbon}, volume = {63}, year = {2021}, month = {Jan-10-2021}, pages = {1555 - 1568}, abstract = {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.}, keywords = {AMS, contamination, LEUCINE, radiocarbon}, issn = {0033-8222}, doi = {10.1017/RDC.2021.55}, url = {https://www.cambridge.org/core/product/identifier/S0033822221000552/type/journal_articlehttps://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0033822221000552}, author = {Venturelli, Ryan A and Vick-Majors, Trista J and Collins, Billy and Gagnon, Alan and Kasic, Kathy and Kurz, Mark D and Li, Wei and Priscu, John and Roberts, Mark and Rosenheim, Brad E} } @article {2991, title = {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}, year = {2021}, pages = {85}, institution = {U.S. Geological Survey}, address = {Reston, VA}, abstract = {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 {\textquotedblleft}UWCDs{\textquotedblright}), 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 {\textquotedblleft}Ogallala aquifer{\textquotedblright}), 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 {\textquotedblleft}Edwards-Trinity [High Plains] aquifer{\textquotedblright}) 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.}, isbn = {2021-5009}, doi = {10.3133/sir20215009}, url = {http://pubs.er.usgs.gov/publication/sir20215009}, author = {Teeple, Andrew P. and Ging, Patricia B. and Thomas, Jonathan V. and Wallace, David S. and Payne, Jason D.} } @article {2937, title = {Lacustrine leaf wax hydrogen isotopes indicate strong regional climate feedbacks in Beringia since the last ice age}, journal = {Quaternary Science Reviews}, volume = {269}, year = {2021}, month = {Jan-10-2021}, pages = {107130}, issn = {02773791}, doi = {10.1016/j.quascirev.2021.107130}, url = {https://www.webofscience.com/wos/woscc/full-record/WOS:000694971400005?AlertId=4d48b20a-7d27-4fa2-a6a8-37f0daa89864\&SID=7FJ1KjxGlxJRYob6iqu}, author = {Daniels, W.C. and Russell, J.M. and Morrill, C. and Longo, W.M. and Giblin, A.E. and Holland-Stergar, P. and Welker, J.M. and Wen, X. and Hu, A. and Huang, Y.} } @article {2933, title = {Limited Presence of Permafrost Dissolved Organic Matter in the Kolyma River, Siberia Revealed by Ramped Oxidation}, journal = {Journal of Geophysical Research: Biogeosciences}, volume = {126}, year = {2021}, month = {Jan-07-2021}, issn = {2169-8953}, doi = {10.1029/2020JG005977}, url = {https://www.webofscience.com/wos/woscc/full-record/WOS:000677821700019?AlertId=4d48b20a-7d27-4fa2-a6a8-37f0daa89864\&SID=8EgwPROzuFaD4cTggN2}, author = {Rogers, Jennifer A. and Galy, Valier and Kellerman, Anne M. and Chanton, Jeffrey P. and Zimov, Nikita and Spencer, Robert G. M.} } @article {2929, title = {A maximum rupture model for the central and southern Cascadia subduction zone{\textemdash}reassessing ages for coastal evidence of megathrust earthquakes and tsunamis}, journal = {Quaternary Science Reviews}, volume = {261}, year = {2021}, month = {Jan-06-2021}, pages = {106922}, abstract = {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. }, issn = {02773791}, doi = {10.1016/j.quascirev.2021.106922}, url = {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-}, author = {Nelson, Alan R. and DuRoss, Christopher B. and Witter, Robert C. and Kelsey, Harvey M. and Engelhart, Simon E. and Mahan, Shannon A. and Gray, Harrison J. and Hawkes, Andrea D. and Horton, Benjamin P. and Padgett, Jason S.} } @article {2936, title = {Planktic foraminiferal changes in the western Mediterranean Anthropocene}, journal = {Global and Planetary Change}, volume = {204}, year = {2021}, month = {Jan-09-2021}, pages = {103549}, issn = {09218181}, doi = {10.1016/j.gloplacha.2021.103549}, url = {https://www.webofscience.com/wos/woscc/full-record/WOS:000687257000005?AlertId=ab9062f8-b111-4f95-a2b8-66e7afac0471\&SID=7DFRqn1B6A3SRDPNEE8}, author = {Pallacks, Sven and Ziveri, Patrizia and Martrat, Bel{\'e}n and Mortyn, P. Graham and Grelaud, Michael and Schiebel, Ralf and Incarbona, Alessandro and Garcia-Orellana, Jordi and Anglada-Ortiz, Griselda} } @article {2942, title = {Soil Organic Carbon Development and Turnover in Natural and Disturbed Salt Marsh Environments}, journal = {Geophysical Research Letters}, volume = {48}, year = {2021}, month = {Apr-01-2023}, abstract = {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\%{\textendash}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{\textendash}9,951 years) and have the potential to inform predictions of marsh ecosystem evolution.}, issn = {0094-8276}, doi = {10.1029/2020GL090287}, url = {https://onlinelibrary.wiley.com/doi/10.1029/2020GL090287}, author = {Luk, Sheron Y. and Todd-Brown, Katherine and Eagle, Meagan and McNichol, Ann P. and Sanderman, Jonathan and Gosselin, Kelsey and Spivak, Amanda C.} } @article {2934, title = {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{\textquoteright}ercun site, north China}, journal = {Quaternary Geochronology}, volume = {66}, year = {2021}, month = {Jan-10-2021}, pages = {101214}, keywords = {Geography, Multidisciplinary, Physical Geosciences}, issn = {18711014}, doi = {10.1016/j.quageo.2021.101214}, url = {https://www.webofscience.com/wos/woscc/full-record/WOS:000684185400002?AlertId=4d48b20a-7d27-4fa2-a6a8-37f0daa89864\&SID=D6BWyCypH7Akklkv5hy}, author = {Yu, Shi-Yong and Chen, Xuexiang and Fang, Zhen and Liu, Xiuling and Li, Ming and Guo, Junfeng} } @article {2683, title = {Age validation of yellowfin (Thunnus albacares) and bigeye (Thunnus obesus) tuna of the northwestern Atlantic Ocean}, journal = {Canadian Journal of Fisheries and Aquatic Sciences}, volume = {77}, year = {2020}, month = {Jan-04-2020}, pages = {637 - 643}, abstract = {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{\textquoteright}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{\textendash}18 years for yellowfin and bigeye tuna. Use of the radiocarbon decline period {\textemdash} defined by regional coral and otoliths {\textemdash} provided valid ages through ontogeny. Yellowfin tuna aged 2{\textendash}18 years (n = 34, 1029{\textendash}1810 mm FL) and bigeye tuna aged 3{\textendash}17 years (n = 12, 1280{\textendash}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.}, issn = {0706-652X}, doi = {10.1139/cjfas-2019-0328}, url = {https://www.nrcresearchpress.com/doi/full/10.1139/cjfas-2019-0328}, author = {Andrews, Allen H. and Pacicco, Ashley and Allman, Robert and Falterman, Brett J. and Lang, Erik T. and Golet, Walter} } @article {2675, title = {Biomass-Derived Provenance Dominates Glacial Surface Organic Carbon in the Western HimalayaBiomass-Derived Provenance Dominates Glacial Surface Organic Carbon in the Western Himalaya}, journal = {Environmental Science \& Technology}, volume = {54}, year = {2020}, month = {Sep-07-2021}, pages = {8612 - 8621}, abstract = {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.}, keywords = {; MASS BALANCES, AEROSOLS, ALBEDO REDUCTION, ATMOSPHERIC LEAD, BLACK CARBON, DUST TRANSPOR, isotopic composition, PB, SNOW ALBEDO, TIBETAN PLATEAU}, issn = {0013-936X}, doi = {10.1021/acs.est.0c0271010.1021/acs.est.0c02710.s001}, url = {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-}, author = {Nizam, Sarwar and Sen, Indra S. and Vinoj, Velu and Galy, Valier and Selby, David and Azam, Mohammad F. and Pandey, Satyendra K. and Creaser, Robert A. and Agarwal, Avinash K. and Singh, Akhilendra P. and Bizimis, Michael} } @inbook {2998, title = {Chapter 30 - Radiocarbon dating of tsunami and storm deposits}, booktitle = {Geological Records of Tsunamis and Other Extreme Waves}, year = {2020}, month = {2020/01/01/}, pages = {663 - 685}, publisher = {Elsevier}, organization = {Elsevier}, abstract = {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.}, keywords = {Dating coastal storm deposits, Dating tsunami deposits, Modeling approaches for dating tsunami deposits, Radiocarbon dating, Sampling tsunami deposits, Tsunami Deposits, Tsunami sand}, isbn = {978-0-12-815686-5}, doi = {10.1016/B978-0-12-815686-5.00030-4}, url = {https://www.sciencedirect.com/science/article/pii/B9780128156865000304}, author = {Kelsey, Harvey M. and Witter, Robert C.}, editor = {Engel, Max and Pilarczyk, Jessica and May, Simon Matthias and Brill, Dominik and Garrett, Ed} } @article {2694, title = {Effects of agricultural and tillage practices on isotopic signatures and fluxes of organic and inorganic carbon in headwater streams}, journal = {Aquatic Sciences}, volume = {82}, year = {2020}, month = {Jan-04-2020}, issn = {1015-1621}, doi = {10.1007/s00027-019-0691-7}, url = {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}, author = {Kelsey, Scott A. and Grottoli, Andrea G. and Bauer, James E. and Lorenz, Klaus and Lal, Rattan and Matsui, Yohei and Huey-Sanders, Teresa M.} } @article {2787, title = {Efficient preservation of young terrestrial organic carbon in sandy turbidity-current depositsAbstract}, journal = {Geology}, volume = {48}, year = {2020}, month = {Jan-09-2020}, pages = {882 - 887}, abstract = {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{\texttimes} 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.}, issn = {0091-7613}, doi = {10.1130/G47320.1}, url = {https://pubs.geoscienceworld.org/gsa/geology/article/48/9/882/586768/Efficient-preservation-of-young-terrestrial}, author = {Hage, S. and Galy, V.V. and Cartigny, M.J.B. and Acikalin, S. and Clare, M.A. and Gr{\"o}cke, D.R. and Hilton, R.G. and Hunt, J.E. and Lintern, D.G. and McGhee, C.A. and Parsons, D.R. and Stacey, C.D. and Sumner, E.J. and Talling, P.J.} } @article {2860, title = {High dissolved organic radiocarbon in precipitation during winter and its implication on the carbon cycle}, journal = {Science of The Total Environment}, volume = {742}, year = {2020}, month = {Jan-11-2020}, pages = {140246}, abstract = {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{\textperthousand} showing the signal of recent photosynthesis. However, here we report surprisingly high Δ14C-DOC in bulk precipitation, more than 1000{\textperthousand} 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.}, issn = {00489697}, doi = {10.1016/j.scitotenv.2020.140246}, url = {https://linkinghub.elsevier.com/retrieve/pii/S0048969720337670}, author = {Cha, Ji-Yeon and Lee, Seung-Cheol and Lee, Eun-Ju and Go, Minjung and Dasari, Kishore Babu and Yim, Yong-Hyeon and Oh, Neung-Hwan} } @article {2749, title = {Holocene earthquake history and slip rate of the southern Teton fault, Wyoming, USAAbstract}, journal = {GSA Bulletin}, volume = {132}, year = {2020}, month = {Jan-07-2020}, pages = {1566 - 1586}, abstract = {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{\textendash}4.6 ka) slip rate of \~{}1.1 mm/yr. Our analysis also suggests that the postglacial to early Holocene (14.4{\textendash}9.9 ka) slip rate exceeds the Holocene (9.9{\textendash}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{\textendash}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.}, issn = {0016-7606}, doi = {10.1130/B35363.110.1130/2020020}, url = {https://pubs.geoscienceworld.org/gsa/gsabulletin/article/132/7-8/1566/575767/Holocene-earthquake-history-and-slip-rate-of-the}, author = {DuRoss, Christopher B. and Gold, Ryan D. and Briggs, Richard W. and Delano, Jaime E. and Ostenaa, Dean A. and Zellman, Mark S. and Cholewinski, Nicole and Wittke, Seth J. and Mahan, Shannon A.} } @article {2830, title = {The Hooskanaden Landslide: historic and recent surge behavior of an active earthflow on the Oregon Coast}, journal = {Landslides}, year = {2020}, month = {Jan-06-2022}, abstract = {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).}, issn = {1612-510X}, doi = {10.1007/s10346-020-01466-8}, url = {http://link.springer.com/10.1007/s10346-020-01466-8}, author = {Alberti, Stefano and Senogles, Andrew and Kingen, Kara and Booth, Adam and Castro, Pete and DeKoekkoek, Jill and Glover-Cutter, Kira and Mohney, Curran and Olsen, Michael and Leshchinsky, Ben} } @article {2776, title = {Identifying the Greatest Earthquakes of the Past 2000 Years at the Nehalem River Estuary, Northern Oregon Coast, USA}, journal = {Open Quaternary}, volume = {6}, year = {2020}, month = {Feb-01-2021}, abstract = {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 {\textpm} 0.5 m); B, 942{\textendash}764 cal a BP (0.7 {\textpm} 0.4 m and 1.0 m {\textpm} 0.4 m); and D, 1568{\textendash}1361 cal a BP (1.0 m {\textpm} 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.}, keywords = {Bayesian transfer function, Cascadia subduction zone, Coseismic subsidence, earthquake hazards, Paleoseismology, salt-marsh stratigraphy, Sea-level changes, tidal foraminifera and diatoms}, doi = {10.5334/oq.70}, url = {http://www.openquaternary.com/articles/10.5334/oq.70/}, author = {Nelson, Alan R. and Hawkes, Andrea D. and Sawai, Yuki and Engelhart, Simon E. and Witter, Rob and Grant-Walter, Wendy C. and Bradley, Lee-Ann and Dura, Tina and Cahill, Niamh and Horton, Ben} } @article {2913, title = {Insolation and greenhouse gases drove Holocene winter and spring warming in Arctic Alaska}, journal = {Quaternary Science Reviews}, volume = {242}, year = {2020}, month = {Jan-08-2020}, pages = {106438}, abstract = {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.}, keywords = {Alkenone, Beringia, Continental biomarkers, Holocene, North America, paleoclimatology, paleolimnology, Proxy data-model comparison, seasonality, Temperature reconstruction}, issn = {02773791}, doi = {10.1016/j.quascirev.2020.106438}, url = {https://linkinghub.elsevier.com/retrieve/pii/S0277379120304005}, author = {Longo, William M. and Huang, Yongsong and Russell, James M. and Morrill, Carrie and Daniels, William C. and Giblin, Anne E. and Crowther, Josue} } @article {2760, title = {A late Holocene subfossil Atlantic white cedar tree-ring chronology from the northeastern United States}, journal = {Quaternary Science Reviews}, volume = {228}, year = {2020}, month = {Jan-01-2020}, pages = {106104}, abstract = {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 {\textquotedblleft}sub-fossil{\textquotedblright} 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.}, keywords = {coastal, Geomorphology, Holocene, North America, paleoclimatology, radiogenic isotopes, Tree-rings}, issn = {02773791}, doi = {10.1016/j.quascirev.2019.106104}, url = {https://linkinghub.elsevier.com/retrieve/pii/S0277379119308108}, author = {Pearl, Jessie K. and Anchukaitis, Kevin J. and Donnelly, Jeffrey P. and Pearson, Charlotte and Pederson, Neil and Lardie Gaylord, Mary C. and McNichol, Ann P. and Cook, Edward R. and Zimmermann, George L.} } @article {2820, title = {Life and its traces in Antarctica{\textquoteright}s McMurdo Dry Valley paleolakes: a survey of preservation}, journal = {Micron}, volume = {131}, year = {2020}, month = {Jan-04-2020}, pages = {102818}, abstract = {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.}, keywords = {Antarctica, Biosignatures, Microbes, Paleolakes, SEM}, issn = {09684328}, doi = {10.1016/j.micron.2019.102818}, url = {https://linkinghub.elsevier.com/retrieve/pii/S0968432819304160}, author = {Greenfield, Samuel R. and Tighe, Scott W. and Bai, Yu and Goerlitz, David S. and Von Turkovich, Michele and Taatjes, Douglas J. and Dragon, Julie A. and Johnson, Sarah Stewart} } @article {2848, title = {A new 30,000-year chronology for rapidly deposited sediments on the Lomonosov Ridge using bulk radiocarbon dating and probabilistic stratigraphic alignment}, journal = {Geochronology}, volume = {2}, year = {2020}, month = {Jan-01-2020}, pages = {81 - 91}, abstract = {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.}, doi = {10.5194/gchron-2-81-2020}, url = {https://gchron.copernicus.org/articles/2/81/2020/}, author = {Muschitiello, Francesco and O{\textquoteright}Regan, Matt and Martens, Jannik and West, Gabriel and Gustafsson, {\"O}rjan and Jakobsson, Martin} } @article {2674, title = {{\textquotedblleft}New{\textquotedblright} cyanobacterial blooms are not new: two centuries of lake production are related to ice cover and land use}, journal = {Ecosphere}, volume = {11}, year = {2020}, month = {Jan-06-2020}, abstract = {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.}, keywords = {agriculture, basin morphometry, Cyanobacteria, eutrophication, Gloeotrichia, ice-out, land use, Maine, New Hampshire, paleoecology, Sediment chemistry, watershed}, issn = {2150-8925}, doi = {10.1002/ecs2.v11.610.1002/ecs2.3170}, url = {https://esajournals.onlinelibrary.wiley.com/doi/full/10.1002/ecs2.3170}, author = {Ewing, Holly A. and Weathers, Kathleen C. and Cottingham, Kathryn L. and Leavitt, Peter R. and Greer, Meredith L. and Carey, Cayelan C. and Steele, Bethel G. and Fiorillo, Alyeska U. and Sowles, John P.} } @article {2705, title = {Origin of Groundwater Arsenic in a Rural Pleistocene Aquifer in Bangladesh Depressurized by Distal Municipal Pumping}, journal = {Water Resources Research}, volume = {56}, year = {2020}, month = {Jan-07-2020}, abstract = {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{\textendash}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.}, keywords = {Arsenic, Dhaka Bangladesh, groundwater pumping, modeling}, issn = {0043-1397}, doi = {10.1029/2020WR027178}, url = {https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2020WR027178}, author = {Mozumder, M. R. H. and Michael, H. A. and Mihajlov, I. and Khan, M. R. and Knappett, P. S. K. and Bostick, B. C. and Mailloux, B. J. and Ahmed, K. M. and Choudhury, I. and Koffman, T. and Ellis, T. and Whaley-Martin, K. and San Pedro, R. and Slater, G. and Stute, M. and Schlosser, P. and Geen, A.} } @article {2918, title = {RADIOCARBON RESERVOIR AGES IN THE HOLOCENE DEAD SEAABSTRACT}, journal = {Radiocarbon}, volume = {62}, year = {2020}, month = {Jan-10-2020}, pages = {1453 - 1473}, abstract = {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{\textquoteright}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{\textquoteright}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{\textquoteright}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{\textquoteright}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.}, keywords = {aragonite, Dead Sea, Holocene, radiocarbon, reservoir ages}, issn = {0033-8222}, doi = {10.1017/RDC.2020.28}, url = {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-}, author = {Weber, Nurit and Lazar, Boaz and Stern, Ofra and Burr, George and Gavrieli, Ittai and Roberts, Mark and Kurz, Mark D and Yechieli, Yoseph and Stein, Mordechai} } @article {2877, title = {Ramped thermal analysis for isolating biologically meaningful soil organic matter fractions with distinct residence times}, journal = {SOIL}, volume = {6}, year = {2020}, month = {Jan-01-2020}, pages = {131 - 144}, abstract = {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{\textendash}gas chromatography{\textendash}mass spectrometry (Py-GC/MS) experiments were performed at five temperatures ranging from 330 to 735 oC. 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.}, doi = {10.5194/soil-6-131-2020}, url = {https://soil.copernicus.org/articles/6/131/2020/}, author = {Sanderman, Jonathan and Grandy, A. Stuart} } @article {2781, title = {Resolving sea ice dynamics in the north-western Ross Sea during the last 2.6 ka: From seasonal to millennial timescales}, journal = {Quaternary Science Reviews}, volume = {237}, year = {2020}, month = {Jan-06-2020}, pages = {106299}, abstract = {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.}, keywords = {Fast ice, IPSO25, Laminated sediments, Ross Sea, Sea ice}, issn = {02773791}, doi = {10.1016/j.quascirev.2020.106299}, url = {https://linkinghub.elsevier.com/retrieve/pii/S0277379120302614}, author = {Tesi, T. and Belt, S.T. and Gariboldi, K. and Muschitiello, F. and Smik, L. and Finocchiaro, F. and Giglio, F. and Colizza, E. and Gazzurra, G. and Giordano, P. and Morigi, C. and Capotondi, L. and Nogarotto, A. and K{\"o}seo{\u g}lu, D. and Di Roberto, A. and Gallerani, A. and Langone, L.} } @article {2893, title = {Response of shallow-sea benthic foraminifera to environmental changes off the coast of Goa, eastern Arabian Sea, during the last \~{}6100 cal yr BPAbstract}, journal = {Geological Magazine}, volume = {157}, year = {2020}, month = {Jan-03-2020}, pages = {497 - 505}, abstract = {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.}, keywords = {arabian sea, benthic foraminifera, Indian monsoon, Stable isotopes, western continental margin of India}, issn = {0016-7568}, doi = {10.1017/S0016756819000979}, url = {https://www.cambridge.org/core/product/identifier/S0016756819000979/type/journal_article}, author = {Saravanan, Ponnusamy and Gupta, Anil K. and Zheng, Hongbo and Panigrahi, Mruganka K. and Tiwari, Sameer K. and Rai, Santosh K. and Prakasam, Muthusamy} } @article {2834, title = {Sedimentary evidence of prehistoric distant-source tsunamis in the Hawaiian Islands}, journal = {Sedimentology}, volume = {67}, year = {2020}, month = {Jan-04-2020}, pages = {1249 - 1273}, abstract = {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 {\textquoteleft}Ring of Fire{\textquoteright} (for example, Alaska{\textendash}Aleutian, Kuril{\textendash}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.}, keywords = {Aleutians, deposit, distant source, extreme events, Hawai΄i, palaeotsunami}, issn = {0037-0746}, doi = {10.1111/sed.12623}, url = {https://onlinelibrary.wiley.com/doi/10.1111/sed.12623}, author = {La Selle, SeanPaul and Richmond, Bruce M. and Jaffe, Bruce E. and Nelson, Alan R. and Griswold, Frances R. and Arcos, Maria E. M. and Chagu{\'e}, Catherine and Bishop, James M. and Bellanova, Piero and Kane, Haunani H. and Lunghino, Brent D. and Gelfenbaum, Guy}, editor = {Costa, Pedro} } @article {2667, title = {Sources and radiocarbon ages of organic carbon in different grain size fractions of Yellow River-transported particles and coastal sediments}, journal = {Chemical Geology}, volume = {534}, year = {2020}, month = {Jan-02-2020}, pages = {119452}, keywords = {organic matter, RadiocarbonStable carbon isotope, Sediment grain size, Yellow River}, issn = {00092541}, doi = {10.1016/j.chemgeo.2019.119452}, url = {https://www.sciencedirect.com/science/article/pii/S0009254119305819}, author = {Ge, Tiantian and Xue, Yuejun and Jiang, Xueyan and Zou, Li and Wang, Xuchen} } @article {2669, title = {The southern Gulf of Mexico: A baseline radiocarbon isoscape of surface sediments and isotopic excursions at depth}, journal = {PLOS ONE}, volume = {15}, year = {2020}, month = {Mar-04-2021}, pages = {e0231678}, abstract = {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{\textperthousand} to -19.9{\textperthousand}, while Δ14C values ranged from -337.1{\textperthousand} to -69.2{\textperthousand}. Sediment δ15N values ranged from 2.8{\textperthousand} to 7.2{\textperthousand}, 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.}, keywords = {Gulf of Mexico, hydrocarbons, Oil spills, Oils, Petroleum, Sediment}, doi = {10.1371/journal.pone.023167810.1371}, url = {https://www.ncbi.nlm.nih.gov/pubmed/32294128}, author = {Bosman, Samantha H. and Schwing, Patrick T. and Larson, Rebekka A. and Wildermann, Natalie E. and Brooks, Gregg R. and Romero, Isabel C. and Sanchez-Cabeza, Joan-Albert and Ruiz-Fern{\'a}ndez, Ana Carolina and Machain-Castillo, Maria Luisa and Gracia, Adolfo and Escobar-Briones, Elva and Murawski, Steven A. and Hollander, David J. and Chanton, Jeffrey P.}, editor = {Potter-McIntyre, Sally} } @article {2673, title = {Two-Phase Synthesis of Taxol}, journal = {Journal of the American Chemical Society}, volume = {142}, year = {2020}, month = {Oct-06-2020}, pages = {10526 - 10533}, abstract = {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.}, keywords = {1ST TOTAL-SYNTHESIS, ANALOGS, chemistry, DIMETHYLDIOXIRANE, ENANTIOSELECTIVE TOTAL-SYNTHESIS, FORMAL TOTAL-SYNTHESIS, PINENE PATH, RING, STEREOCONTROLLED SYNTHESIS, TAXANES}, issn = {0002-7863}, doi = {10.1021/jacs.0c0359210.1021/jacs.0c03592.s00110.1021/jacs.0c03592.s002}, url = {https://pubs.acs.org/doi/10.1021/jacs.0c03592}, author = {Kanda, Yuzuru and Nakamura, Hugh and Umemiya, Shigenobu and Puthukanoori, Ravi Kumar and Murthy Appala, Venkata Ramana and Gaddamanugu, Gopi Krishna and Paraselli, Bheema Rao and Baran, Phil S.} } @article {2994, title = {14C Blank Corrections for 25{\textendash}100 μg Samples at the National Ocean Sciences AMS Laboratory}, journal = {Radiocarbon}, volume = {61}, year = {2019}, month = {10/2019}, pages = {1403 - 1411}, abstract = {Replicate radiocarbon (14C) measurements of organic and inorganic control samples, with known Fraction Modern values in the range Fm = 0{\textendash}1.5 and mass range 6 μg{\textendash}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 {\textquotedblleft}blank correct{\textquotedblright} measured unknowns in the mass range 25{\textendash}100 μg. Data, formulas, and an assessment of the precision and accuracy of the blank correction are presented.}, keywords = {AMS, AMS dating, blank corrections}, isbn = {0033-8222, 1945-5755}, doi = {10.1017/RDC.2019.74}, url = {https://www.cambridge.org/core/journals/radiocarbon/article/14c-blank-corrections-for-25100-g-samples-at-the-national-ocean-sciences-ams-laboratory/494B9CF72445198570213B4A2CC303D0}, author = {Roberts, M. L. and Elder, K. L. and Jenkins, W. J. and Gagnon, A. R. and Xu, L. and Hlavenka, J. D. and Longworth, B. E.} } @article {2836, title = {An 1800-year record of environmental change from the southern Adirondack Mountains, New York (USA)}, journal = {Journal of Paleolimnology}, volume = {62}, year = {2019}, month = {Jan-10-2019}, pages = {301 - 314}, abstract = {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{\textendash}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{\textendash}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.}, issn = {0921-2728}, doi = {10.1007/s10933-019-00093-1}, url = {http://link.springer.com/10.1007/s10933-019-00093-1}, author = {Grochocki, Konrad K. and Lane, Chad S. and Stager, Jay Curt} } @article {2646, title = {Abrupt mid-Holocene ice loss in the western Weddell Sea Embayment of Antarctica}, journal = {Earth and Planetary Science Letters}, volume = {518}, year = {2019}, month = {Jan-07-2019}, pages = {127 - 135}, abstract = {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.}, keywords = {Antarctica, cosmogenic dating in situ 14C, Holocene, Weddell Sea ice sheet}, issn = {0012821X}, doi = {10.1016/j.epsl.2019.05.002}, url = {https://www.sciencedirect.com/science/article/pii/S0012821X19302638}, author = {Johnson, Joanne S. and Nichols, Keir A. and Goehring, Brent M. and Balco, Greg and Schaefer, Joerg M.} } @article {2797, title = {Analysis of multiple cosmogenic nuclides constrains Laurentide Ice Sheet history and process on Mt. Mansfield, Vermont{\textquoteright}s highest peak}, journal = {Quaternary Science Reviews}, volume = {205}, year = {2019}, month = {Jan-02-2019}, pages = {234 - 246}, abstract = {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{\textquoteright}s lower elevations (\~{}400{\textendash}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 {\textpm} 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{\textquoteright}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{\textquoteright}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.}, keywords = {Cosmogenic isotopes, erosion, Geochronology, Glaciation, Last glacial maximum, North America, Pleistocene}, issn = {02773791}, doi = {10.1016/j.quascirev.2018.12.014}, url = {https://linkinghub.elsevier.com/retrieve/pii/S0277379118307145}, author = {Corbett, Lee B. and Bierman, Paul R. and Wright, Stephen F. and Shakun, Jeremy D. and Davis, P. Thompson and Goehring, Brent M. and Halsted, Christopher T. and Koester, Alexandria J. and Caffee, Marc W. and Zimmerman, Susan R.} } @article { ISI:000480669600041, title = {Annual radiocarbon measurements in a century-old European beech tree (Fagus sylvatica) from coastal northeastern North America}, journal = {NUCLEAR INSTRUMENTS \& METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS}, volume = {456}, year = {2019}, month = {OCT 1}, pages = {264-270}, abstract = {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.}, issn = {0168-583X}, doi = {10.1016/j.nimb.2019.03.029}, author = {Gaylord, Mary C. Lardie and Longworth, Brett E. and Murphy, Keelan and Cobb, Caroline and McNichol, Ann P.} } @article {2802, title = {Antarctic Relic Microbial Mat Community Revealed by Metagenomics and Metatranscriptomics}, journal = {Frontiers in Ecology and Evolution}, volume = {7}, year = {2019}, month = {Nov-01-2020}, abstract = {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.}, doi = {10.3389/fevo.2019.00001}, url = {https://www.frontiersin.org/article/10.3389/fevo.2019.00001/full}, author = {Zaikova, Elena and Goerlitz, David S. and Tighe, Scott W. and Wagner, Nicole Y. and Bai, Yu and Hall, Brenda L. and Bevilacqua, Julie G. and Weng, Margaret M. and Samuels-Fair, Maya D. and Johnson, Sarah Stewart} } @article {2662, title = {Baobabs in Trouble: Accelerator Mass Spectrometry Provides Ages of the Most Ancient Trees}, year = {2019}, url = {https://gallery.mailchimp.com/63e42c583930d9f7a8b637982/files/edd75706-1040-436f-ada1-ba42a1800b8e/Baobab.pdf}, author = {Gledhill, I.} } @article { ISI:000478786500021, title = {CO2-dependent carbon isotope fractionation in Archaea, Part II: The marine water column}, journal = {GEOCHIMICA ET COSMOCHIMICA ACTA}, volume = {261}, year = {2019}, month = {SEP 15}, pages = {383-395}, abstract = {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.}, issn = {0016-7037}, doi = {10.1016/j.gca.2019.06.043}, author = {Hurley, Sarah J. and Close, Hilary G. and Elling, Felix J. and Jasper, Claire E. and Gospodinova, Kalina and McNichol, Ann P. and Pearson, Ann} } @article {2677, title = {Coupled ocean and atmospheric changes during Greenland stadial 1 in southwestern Europe}, journal = {Quaternary Science Reviews}, volume = {212}, year = {2019}, month = {Jan-05-2019}, pages = {108 - 120}, abstract = {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{\textquoteright}s latitudinal position and contributed to a complex spatial pattern and strength of the Westerlies across western Europe.}, keywords = {Climate variability, Greenland stadial, Iberian margin, Jet stream, Moisture availability, North Atlantic, Paleoclimate, Westerlies, Younger Dryas Complex}, issn = {02773791}, doi = {10.1016/j.quascirev.2019.03.033}, url = {https://www.researchgate.net/publication/332292599_Coupled_ocean_and_atmospheric_changes_during_Greenland_stadial_1_in_southwestern_Europe}, author = {Naughton, F. and Costas, S. and Gomes, S.D. and Desprat, S. and Rodrigues, T. and Sanchez Go{\~n}i, M.F. and Renssen, H. and Trigo, R. and Bronk-Ramsey, C. and Oliveira, D. and Salgueiro, E. and Voelker, A.H.L. and Abrantes, F.} } @article {2853, title = {Discovery of an Extensive Deep-Sea Fossil Serpulid Reef Associated With a Cold Seep, Santa Monica Basin, CaliforniaTable_1.docx}, journal = {Frontiers in Marine Science}, volume = {6}, year = {2019}, month = {Jul-03-2020}, abstract = {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{\textendash}2014, mounds at \~{}600 m water depth were observed for the first time and sampled by Monterey Bay Aquarium Research Institute{\textquoteright}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 {\textquotedblleft}Fossil Hill.{\textquotedblright} 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.}, doi = {10.3389/fmars.2019.00115}, url = {https://www.frontiersin.org/article/10.3389/fmars.2019.00115/full}, author = {Georgieva, Magdalena N. and Paull, Charles K. and Little, Crispin T. S. and McGann, Mary and Sahy, Diana and Condon, Daniel and Lundsten, Lonny and Pewsey, Jack and Caress, David W. and Vrijenhoek, Robert C.} } @article {2795, title = {The distribution and magnitude of subglacial erosion on millennial timescales at Engabreen, NorwayAbstract}, journal = {Annals of Glaciology}, volume = {60}, year = {2019}, month = {Jan-12-2019}, pages = {73 - 81}, abstract = {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{\textendash}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{\textendash}10Be ratios that increase with depth. Therefore, elevated 14C{\textendash}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{\textendash}107 years), the discontinuous nature of glacial plucking produces spatially variable patterns of erosion over shorter millennial timescales.}, keywords = {Beryllium-10, Carbon-14, cosmogenic nuclides, Engabreen, glacial erosion}, issn = {0260-3055}, doi = {10.1017/aog.2019.42}, url = {https://www.cambridge.org/core/product/identifier/S0260305519000429/type/journal_article}, author = {Rand, Cari and Goehring, Brent M.} } @article {2775, title = {Evidence for frequent, large tsunamis spanning locked and creeping parts of the Aleutian megathrust}, journal = {GSA Bulletin}, volume = {131}, year = {2019}, month = {Jan-05-2019}, pages = {707 - 729}, abstract = {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{\textquoteright}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{\textendash}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.}, issn = {0016-7606}, doi = {10.1130/B32031.110.1130/2018296}, url = {https://pubs.geoscienceworld.org/gsa/gsabulletin/article/131/5-6/707/566656/Evidence-for-frequent-large-tsunamis-spanning}, author = {Witter, Rob and Briggs, Rich and Engelhart, Simon E. and Gelfenbaum, Guy and Koehler, Rich D. and Nelson, Alan and Selle, SeanPaul La and Corbett, Reide and Wallace, Kristi} } @article {2747, title = {Four Major Holocene Earthquakes on the Reelfoot Fault Recorded by Sackungen in the New Madrid Seismic Zone, USA}, journal = {Journal of Geophysical Research: Solid Earth}, volume = {124}, year = {2019}, month = {Jun-03-2020}, pages = {3105 - 3126}, abstract = {Three sequences of well-documented, major ~M7+ earthquakes (1811{\textendash}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 {\textpm} 1730 BCE; event 3, 270 {\textpm} 670 CE; event 2, 1430 {\textpm} 380 CE; and event 1, 1810 {\textpm} 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{\textendash}1812 CE sequence. This clustered earthquake recurrence pattern helps place bounds on seismic hazard and geodynamic models in the New Madrid seismic zone.}, issn = {2169-9313}, doi = {10.1029/2018JB016806}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1029/2018JB016806}, author = {Gold, Ryan D. and DuRoss, Christopher B. and Delano, Jaime E. and Jibson, Randall W. and Briggs, Richard W. and Mahan, Shannon A. and Williams, Robert A. and Corbett, D. Reide} } @article {2796, title = {A fully automated system for the extraction of in situ cosmogenic carbon-14 in the Tulane University cosmogenic nuclide laboratory}, journal = {Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms}, volume = {455}, year = {2019}, month = {Jan-09-2019}, pages = {284 - 292}, abstract = {During 2015 and culminating in early 2016, we acquired a new Carbon Extraction and Graphitization System (CEGS) from Aeon Laboratories, L.L.C. (hereafter, {\textquotedblleft}Aeon{\textquotedblright}), 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 {\textpm} 0.32 {\texttimes} 105 atoms 14C, n = 26) and secondary standard values (0.4953 {\textpm} 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 {\textpm} 0.32 {\texttimes} 105 atoms g-1 14C, n = 13) interlaboratory comparison material.}, keywords = {Automation, Cosmogenic nuclide, In situ carbon-14}, issn = {0168583X}, doi = {10.1016/j.nimb.2019.02.006}, url = {https://linkinghub.elsevier.com/retrieve/pii/S0168583X19300771}, author = {Goehring, Brent M. and Wilson, Jim and Nichols, Keir} } @article {2793, title = {Glacial geology and cosmogenic-nuclide exposure ages from the Tucker Glacier - Whitehall Glacier confluence, northern Victoria Land, Antarctica}, journal = {American Journal of Science}, volume = {319}, year = {2019}, month = {Oct-04-2019}, pages = {255 - 286}, abstract = {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 ({\textquotedblleft}MWP-1A{\textquotedblright}) 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.}, keywords = {Antarctica, cosmogenic-nuclide geochemistry, exposure-dating, glacial geology, Last glacial maximum, Ross Sea, Tucker Glacier, Victoria Land}, issn = {0002-9599}, doi = {10.2475/04.2019.01}, url = {http://www.ajsonline.org/lookup/doi/10.2475/04.2019.01}, author = {Balco, Greg and Todd, Claire and Goehring, Brent M. and Moening-Swanson, Isaac and Nichols, Keir} } @article {2791, title = {Holocene paleodepositional changes reflected in the sedimentary microbiome of the Black Sea}, journal = {Geobiology}, volume = {17}, year = {2019}, month = {Sep-07-2020}, pages = {436 - 448}, abstract = {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.}, keywords = {geomicrobiology, palaeo-environment, paleoecology, sedimentary metagenomes, subsurface microbiome, sulfur cycle.}, issn = {1472-4677}, doi = {10.1111/gbi.2019.17.issue-410.1111/gbi.12338}, url = {https://pubmed.ncbi.nlm.nih.gov/30843322/}, author = {More, Kuldeep D. and Giosan, Liviu and Grice, Kliti and Coolen, Marco J. L.} } @article {2713, title = {A human role in Andean megafaunal extinction?}, journal = {Quaternary Science Reviews}, volume = {205}, year = {2019}, month = {Jan-02-2019}, pages = {154 - 165}, abstract = {A new fossil pollen, Sporormiella, and sediment chemistry record from Lake Llaviucu, Ecuador, spanning the period from 16,280{\textendash}9000 years Before Present, provides a high-resolution record of paleoecological change in the high Andes. The deglacial transition from super-p{\'a}ramo through p{\'a}ramo 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.}, keywords = {Andes, Deglaciation, Ecuador Extinction, Fossil pollen, Human arrival, Pleistocene megafauna, Sporormiella}, issn = {02773791}, doi = {10.1016/j.quascirev.2018.12.005}, url = {https://linkinghub.elsevier.com/retrieve/pii/S0277379118307005}, author = {Raczka, M.F. and Mosblech, N.A. and Giosan, L. and Valencia, B.G. and Folcik, A.M. and Kingston, M. and Baskin, S. and Bush, M.B.} } @article {2643, title = {Influence of Different Acid Treatments on the Radiocarbon Content Spectrum of Sedimentary Organic Matter Determined by RPO/Accelerator Mass SpectrometryABSTRACT}, journal = {Radiocarbon}, volume = {61}, year = {2019}, month = {Jan-04-2019}, pages = {395 - 413}, abstract = {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.}, issn = {0033-8222}, doi = {10.1017/RDC.2018.125}, url = {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}, author = {Bao, Rui and McNichol, Ann P and Hemingway, Jordon D and Lardie Gaylord, Mary C and Eglinton, Timothy I} } @article { ISI:000461424500002, title = {INFLUENCE OF DIFFERENT ACID TREATMENTS ON THE RADIOCARBON CONTENT SPECTRUM OF SEDIMENTARY ORGANIC MATTER DETERMINED BY RPO/ACCELERATOR MASS SPECTROMETRY}, journal = {RADIOCARBON}, volume = {61}, number = {2}, year = {2019}, month = {APR}, pages = {395-413}, abstract = {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.}, issn = {0033-8222}, doi = {10.1017/RDC.2018.125}, author = {Bao, Rui and McNichol, Ann P. and Hemingway, Jordon D. and Gaylord, Mary C. Lardie and Eglinton, I, Timothy} } @article {2792, title = {Isolation of quartz for cosmogenic in situ 14C analysis}, journal = {Geochronology}, volume = {1}, year = {2019}, month = {Jan-01-2019}, pages = {43 - 52}, abstract = {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 oC. 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.}, doi = {10.5194/gchron-1-43-2019}, url = {https://gchron.copernicus.org/articles/1/43/2019/}, author = {Nichols, Keir A. and Goehring, Brent M.} } @article {2892, title = {Late Holocene long arid phase in the Indian subcontinent as seen in shallow sediments of the eastern Arabian Sea}, journal = {Journal of Asian Earth Sciences}, volume = {181}, year = {2019}, month = {Jan-09-2019}, pages = {103915}, abstract = {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{\textendash}4700 and 3000{\textendash}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{\textendash}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.}, issn = {13679120}, doi = {10.1016/j.jseaes.2019.103915}, url = {https://linkinghub.elsevier.com/retrieve/pii/S1367912019302676}, author = {Saravanan, Ponnusamy and Gupta, Anil K. and Zheng, Hongbo and Panigrahi, Mruganka K. and Prakasam, Muthusamy} } @book {2719, title = {Mapping Isotopic and Dissolved Organic Matter Baselines in Waters and Sediments of the~Gulf of Mexico}, year = {2019}, pages = {160 - 181}, publisher = {Springer International Publishing}, organization = {Springer International Publishing}, address = {Cham}, abstract = {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.}, keywords = {Dissolved organic matter, FTICR-MS, Gulf baselines, High-resolution mass spectrometry, organic carbon, radiocarbon, Ramped pyrolysis, Sediment organic matter}, isbn = {978-3-030-12962-0}, doi = {10.1007/978-3-030-12963-710.1007/978-3-030-12963-7_10}, url = {https://link.springer.com/chapter/10.1007/978-3-030-12963-7_10}, author = {Chanton, Jeffrey P. and Jaggi, Aprami and Radovi{\'c}, Jago{\v s} R. and Rosenheim, Brad E. and Walker, Brett D. and Larter, Stephen R. and Rogers, Kelsey and Bosman, Samantha and Oldenburg, Thomas B. P.}, editor = {Murawski, Steven A. and Ainsworth, Cameron H. and Gilbert, Sherryl and Hollander, David J. and Paris, Claire B. and Schl{\"u}ter, Michael and Wetzel, Dana L.} } @article {2743, title = {The Mighty Susquehanna{\textemdash}Extreme Floods in Eastern North America During the Past Two Millennia}, journal = {Geophysical Research Letters}, volume = {46}, year = {2019}, month = {Apr-03-2021}, pages = {3398 - 3407}, abstract = {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{\textendash}1500, 1300{\textendash}1100, and 400{\textendash}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{\textemdash}typical of negative phases of the North Atlantic Oscillation and conditions thought to foster hurricane landfalls along the East Coast.}, issn = {0094-8276}, doi = {10.1029/2018GL080890}, url = {https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018GL080890}, author = {Toomey, Michael and Cantwell, Meagan and Colman, Steven and Cronin, Thomas and Donnelly, Jeffrey and Giosan, Liviu and Heil, Clifford and Korty, Robert and Marot, Marci and Willard, Debra} } @article {2764, title = {Mineral protection regulates long-term global preservation of natural organic carbon}, journal = {Nature}, volume = {570}, year = {2019}, month = {Jan-06-2019}, pages = {228 - 231}, abstract = {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{\textquoteright}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{\textemdash}and thus atmospheric composition and climate{\textemdash}has varied over geological time.}, issn = {0028-0836}, doi = {10.1038/s41586-019-1280-6}, url = {http://www.nature.com/articles/s41586-019-1280-6}, author = {Hemingway, Jordon D. and Rothman, Daniel H. and Grant, Katherine E. and Rosengard, Sarah Z. and Eglinton, Timothy I. and Derry, Louis A. and Galy, Valier V.} } @article {2708, title = {Multiple independent records of local glacier variability on Nuussuaq, West Greenland, during the Holocene}, journal = {Quaternary Science Reviews}, volume = {215}, year = {2019}, month = {Jan-07-2019}, pages = {253 - 271}, abstract = {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{\textemdash}proglacial lake sediment analysis, cosmogenic 10Be surface-exposure dating, and in situ 14C burial modeling{\textemdash}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{\textendash}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{\textendash}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.}, keywords = {Cosmogenic 10Be, Cosmogenic in situ 14C, Greenland, Holocene, lake sediment, Mountain glaciers, Neoglaciation}, issn = {02773791}, doi = {10.1016/j.quascirev.2019.05.007}, url = {https://www.sciencedirect.com/science/article/pii/S0277379118308771}, author = {Schweinsberg, Avriel D. and Briner, Jason P. and Licciardi, Joseph M. and Bennike, Ole and Lifton, Nathaniel A. and Graham, Brandon L. and Young, Nicol{\'a}s E. and Schaefer, Joerg M. and Zimmerman, Susan H.} } @article {2794, title = {New Last Glacial Maximum ice thickness constraints for the Weddell Sea Embayment, Antarctica}, journal = {The Cryosphere}, volume = {13}, year = {2019}, month = {Jan-01-2019}, pages = {2935 - 2951}, abstract = {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.}, doi = {10.5194/tc-13-2935-2019}, url = {http://nora.nerc.ac.uk/id/eprint/526081/}, author = {Nichols, Keir A. and Goehring, Brent M. and Balco, Greg and Johnson, Joanne S. and Hein, Andrew S. and Todd, Claire} } @article {2661, title = {On the Origin of Aged Sedimentary Organic Matter Along a River-Shelf-Deep Ocean Transect}, journal = {Journal of Geophysical Research: Biogeosciences}, volume = {124}, year = {2019}, month = {Jun-08-2021}, pages = {2582 - 2594}, abstract = {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.}, keywords = {Carbon cycle, hydrodynamic processes, organic carbon, radiocarbon, sediments}, issn = {2169-8953}, doi = {10.1029/2019JG005107}, url = { https://doi.org/10.1029/2019JG005107}, author = {Bao, Rui and Zhao, Meixun and McNichol, Ann and Wu, Ying and Guo, Xinyu and Haghipour, Negar and Eglinton, Timothy I.} } @article {2701, title = {Pacific climate influences on ocean conditions and extreme shell growth events in the Northwestern Atlantic (Gulf of Maine)}, journal = {Climate Dynamics}, volume = {52}, year = {2019}, month = {Jan-06-2019}, pages = {6339 - 6356}, abstract = {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.}, issn = {0930-7575}, doi = {10.1007/s00382-018-4513-8}, url = {https://link.springer.com/article/10.1007/s00382-018-4513-8}, author = {Wanamaker, Alan D. and Griffin, Shelly M. and Ummenhofer, Caroline C. and Whitney, Nina M. and Black, Bryan and Parfitt, Rhys and Lower-Spies, Erin E. and Introne, Douglas and Kreutz, Karl J.} } @article {2680, title = {Reconstructing reef fish communities using fish otoliths in coral reef sediments}, journal = {PLOS ONE}, volume = {14}, year = {2019}, month = {Feb-06-2020}, pages = {e0218413}, abstract = {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.}, doi = {10.1371/journal.pone.0218413}, url = {https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0218413}, author = {Lin, Chien-Hsiang and De Gracia, Brigida and Pierotti, Michele E. R. and Andrews, Allen H. and Griswold, Katie and O{\textquoteright}Dea, Aaron}, editor = {Zapalski, Miko{\l}aj K.} } @article {2758, title = {Salt marsh ecosystem restructuring enhances elevation resilience and carbon storage during accelerating relative sea-level rise}, journal = {Estuarine, Coastal and Shelf Science}, volume = {217}, year = {2019}, month = {Jan-02-2019}, pages = {56 - 68}, abstract = { 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 {\textpm} 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 {\textpm} 28 g C/m2/yr from 550 to 1800 CE, increasing to 129 {\textpm} 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. }, keywords = {14-Carbon, accretion, Carbon storage, Elevation, Salt marsh, Sea level index point, sea-level rise}, issn = {02727714}, doi = {10.1016/j.ecss.2018.11.003}, url = {https://linkinghub.elsevier.com/retrieve/pii/S0272771418306851}, author = {Gonneea, Meagan Eagle and Maio, Christopher V. and Kroeger, Kevin D. and Hawkes, Andrea D. and Mora, Jordan and Sullivan, Richard and Madsen, Stephanie and Buzard, Richard M. and Cahill, Niamh and Donnelly, Jeffrey P.} } @article {2872, title = {Shellfish, Geophytes, and Sedentism on Early Holocene Santa Rosa Island, Alta California, USA}, journal = {The Journal of Island and Coastal Archaeology}, year = {2019}, month = {Mar-03-2021}, pages = {1 - 21}, abstract = {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.}, issn = {1556-4894}, doi = {10.1080/15564894.2019.1579272}, url = {https://www.tandfonline.com/doi/abs/10.1080/15564894.2019.1579272?journalCode=uica20}, author = {Erlandson, Jon M. and Rick, Torben C. and Ainis, Amira F. and Gill, Kristina M. and Jew, Nicholas P. and Reeder-Myers, Leslie A.} } @article {2757, title = {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}, journal = {Environmental Science \& Technology}, volume = {53}, year = {2019}, month = {Apr-07-2020}, pages = {8244 - 8251}, abstract = {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. }, issn = {0013-936X}, doi = {10.1021/acs.est.9b0234410.1021/acs.est.9b02344.s001}, url = {https://pubs.acs.org/doi/10.1021/acs.est.9b02344}, author = {Hanke, Ulrich M. and Lima-Braun, Ana L. and Eglinton, Timothy I. and Donnelly, Jeffrey P. and Galy, Valier and Poussart, Pascale and Hughen, Konrad and McNichol, Ann P. and Xu, Li and Reddy, Christopher M.} } @article {2642, title = {Temporal constraints on lateral organic matter transport along a coastal mud belt}, journal = {Organic Geochemistry}, volume = {128}, year = {2019}, month = {Jan-02-2019}, pages = {86 - 93}, abstract = {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 {\textquotedblleft}diagenetic aging{\textquotedblright} of OC. Additionally, sediment translocation can also result in {\textquotedblleft}transport time-associated aging{\textquotedblright} 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 {\textquotedblleft}aging{\textquotedblright}. 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.}, keywords = {14C aging, Continental shelf seas, East China Sea, Mud belt, organic matter, Sediment resuspension}, issn = {01466380}, doi = {10.1016/j.orggeochem.2019.01.007}, url = {https://www.sciencedirect.com/science/article/pii/S0146638019300075}, author = {Bao, Rui and Zhao, Meixun and McNichol, Ann and Galy, Valier and McIntyre, Cameron and Haghipour, Negar and Eglinton, Timothy I.} } @article {2628, title = {Temporal deconvolution of vascular plant-derived fatty acids exported from terrestrial watersheds}, journal = {Geochimica et Cosmochimica Acta}, volume = {244}, year = {2019}, month = {Jan-01-2019}, pages = {502 - 521}, abstract = {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.}, keywords = {british-columbia, CARIACO BASIN, compound-specific radiocarbon, MACKENZIE DELTA, marine-sediments, odp leg 169s, saanich inlet, SANTA-MONICA BASIN, SOIL ORGANIC-MATTER, TROPICAL VEGETATION}, issn = {00167037}, doi = {10.1016/j.gca.2018.09.034}, url = {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}, author = {Vonk, Jorien E. and Drenzek, Nicholas J. and Hughen, Konrad A. and Stanley, Rachel H.R. and McIntyre, Cameron and {\c c}on, Daniel B. and Giosan, Liviu and Southon, John R. and Santos, Guaciara M. and Druffel, Ellen R.M. and Andersson, August A. and {\"o}ld, Martin and Eglinton, Timothy I.} } @article {2788, title = {Thermal oxidation of carbon in organic matter rich volcanic soils: insights into SOC age differentiation and mineral stabilization}, journal = {Biogeochemistry}, volume = {144}, year = {2019}, month = {Jan-09-2019}, pages = {291 - 304}, abstract = {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 {\textquoteleft}rampedpyrox{\textquoteright} model yielded consistent mean E values of 140 kJ mol-1 below the Oa horizon. The {\textquoteleft}rampedpyrox{\textquoteright} 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 {\textmu}Ef 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.}, issn = {0168-2563}, doi = {10.1007/s10533-019-00586-1}, url = {http://link.springer.com/10.1007/s10533-019-00586-1}, author = {Grant, Katherine E. and Galy, Valier V. and Chadwick, Oliver A. and Derry, Louis A.} } @article {2644, title = {Upwelling in the Ocean Basins North of the ACC: 1. On the Upwelling Exposed by the Surface Distribution of C-14}, journal = {Journal of Geophysical Research: Oceans}, volume = {124}, year = {2019}, month = {Apr-04-2020}, pages = {2591 - 2608}, abstract = {he upwelling associated with the ocean{\textquoteright}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{\textquoteright}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{\textquoteright}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.}, keywords = {Ocean circulation, overturning circulation, radiocarbon, Upwelling}, issn = {2169-9275}, doi = {10.1029/2018JC014794}, url = {https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018JC014794}, author = {Toggweiler, J. R. and Druffel, Ellen R. M. and Key, Robert M. and Galbraith, Eric D.} } @article {2645, title = {Upwelling in the Ocean Basins North of the ACC: 2. How Cool Subantarctic Water Reaches the Surface in the Tropics}, journal = {Journal of Geophysical Research: Oceans}, volume = {124}, year = {2019}, month = {Apr-04-2020}, pages = {2609 - 2625}, abstract = {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{\textquoteright}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.}, keywords = {numerical modeling, Ocean circulation, overturning circulation, Upwelling}, issn = {2169-9275}, doi = {10.1029/2018JC014795}, url = {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}, author = {Toggweiler, J. R. and Druffel, Ellen R. M. and Key, Robert M. and Galbraith, Eric D.} } @article {2636, title = {Using Stable Carbon Isotopes to Quantify Radiocarbon Reservoir Age Offsets in the Coastal Black SeaAbstract}, journal = {Radiocarbon}, volume = {61}, year = {2019}, month = {Jan-02-2019}, pages = {309 - 318}, abstract = {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.}, keywords = {Black Sea, Carbon cycle, freshwater reservoir effect, Geochronology, Reservoir age}, issn = {0033-8222}, doi = {10.1017/RDC.2018.61}, url = {https://www.cambridge.org/core/product/identifier/S0033822218000619/type/journal_articlehttps://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0033822218000619}, author = {Soulet, Guillaume and Giosan, Liviu and Flaux, Cl{\'e}ment and Galy, Valier} } @book {2720, title = {The Utility of Stable and Radioisotopes in Fish Tissues as Biogeochemical Tracers of Marine Oil Spill Food Web Effects}, year = {2019}, pages = {219 - 238}, publisher = {Springer International Publishing}, organization = {Springer International Publishing}, address = {Cham}, abstract = {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{\textquoteright}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.}, keywords = {Petrocarbon, radiocarbon, Reef fish, Stable isotopes}, isbn = {978-3-030-12962-0}, doi = {10.1007/978-3-030-12963-710.1007/978-3-030-12963-7_13}, url = {https://link.springer.com/chapter/10.1007/978-3-030-12963-7_13}, author = {Patterson III, William F. and Chanton, Jeffery P. and Hollander, David J. and Goddard, Ethan A. and Barnett, Beverly K. and Tarnecki, Joseph H.}, editor = {Murawski, Steven A. and Ainsworth, Cameron H. and Gilbert, Sherryl and Hollander, David J. and Paris, Claire B. and Schl{\"u}ter, Michael and Wetzel, Dana L.} } @article {2864, title = {Active Ooid Growth Driven By Sediment Transport in a High-Energy Shoal, Little Ambergris Cay, Turks and Caicos Islands}, journal = {Journal of Sedimentary Research}, volume = {88}, year = {2018}, month = {Jun-09-2020}, pages = {1132 - 1151}, abstract = {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{\textemdash}in favor of net growth{\textemdash}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.}, issn = {1527-1404}, doi = {10.2110/jsr.2018.59}, url = {https://pubs.geoscienceworld.org/sepm/jsedres/article/88/9/1132/559083/Active-Ooid-Growth-Driven-By-Sediment-Transport-in}, author = {Trower, Elizabeth J. and Cantine, Marjorie D. and Gomes, Maya L. and Grotzinger, John P. and Knoll, Andrew H. and Lamb, Michael P. and Lingappa, Usha and O{\textquoteright}Reilly, Shane S. and Present, Theodore M. and Stein, Nathan and Strauss, Justin V. and Fischer, Woodward W.} } @article {2629, title = {Ancient water wells reveal a prolonged drought in the lower Yellow River area about 2800 years ago}, journal = {Science Bulletin}, volume = {63}, year = {2018}, month = {Jan-10-2018}, pages = {1324 - 1327}, abstract = {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.}, issn = {20959273}, doi = {10.1016/j.scib.2018.09.017}, url = {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}, author = {Yu, Shiyong and Chen, Xuexiang and Liu, Xiuling and Fang, Zhen and Guo, Junfeng and Zhan, Senyang and Fang, Hui and Chen, Fahu} } @article {2624, title = {A base-level stratigraphic approach to determining Holocene subsidence of the Ganges-Meghna-Brahmaputra Delta plain}, journal = {EARTH AND PLANETARY SCIENCE LETTERS}, volume = {499}, year = {2018}, month = {10/01/2018}, pages = {23-36}, chapter = {23}, abstract = {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 {\textpm} 0.7 mm/yr in the middle fluvial delta to 4 {\textpm} 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.}, keywords = {base level stratigraphic method, delta plain, Ganges{\textendash}Brahmaputra{\textendash}Meghna Delta, indicative meaning of sea level index, relative sea level, subsidence}, issn = {0012-821X}, author = {Grall, C and Steckler, MS and Pickering, JL and Goodbred, S} } @article {2623, title = {A base-level stratigraphic approach to determining Holocene subsidence of the Ganges{\textendash}Meghna{\textendash}Brahmaputra Delta plain}, journal = {Earth and Planetary Science Letters}, volume = {499}, year = {2018}, month = {Jan-10-2018}, pages = {23 - 36}, abstract = {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.}, keywords = {base level stratigraphic method, delta plain, Ganges-Brahmaputra-Meghna Delta, indicative meaning of sea level index, relative sea level, subsidence}, issn = {0012821X}, doi = {10.1016/j.epsl.2018.07.008}, url = {https://www.sciencedirect.com/science/article/pii/S0012821X1830414X}, author = {Grall, C. and Steckler, M.S. and Pickering, J.L. and Goodbred, S. and Sincavage, R. and Paola, C. and Akhter, S.H. and Spiess, V.} } @article {2755, title = {Climatic control of Mississippi River flood hazard amplified by river engineering}, journal = {Nature}, volume = {556}, year = {2018}, month = {Jan-04-2018}, pages = {95 - 98}, abstract = {Over the past century, many of the world{\textquoteright}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{\textquoteright}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 Ni{\~n}o{\textendash}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.}, issn = {0028-0836}, doi = {10.1038/nature26145}, url = {https://www.nature.com/articles/nature26145}, author = {Munoz, Samuel E. and Giosan, Liviu and Therrell, Matthew D. and Remo, Jonathan W. F. and Shen, Zhixiong and Sullivan, Richard M. and Wiman, Charlotte and O{\textquoteright}Donnell, Michelle and Donnelly, Jeffrey P.} } @article {2622, title = {Combining Conflicting Bayesian Models to Develop Paleoseismic Records: An Example from the Wasatch Fault Zone, Utah}, journal = {Bulletin of the Seismological Society of America}, year = {2018}, month = {Feb-06-2020}, abstract = {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{\textendash}1.0 ky; 95\% confidence) and 1.1 mm/yr (0.8{\textendash}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.}, issn = {0037-1106}, doi = {10.1785/0120170302}, url = {https://pubs.geoscienceworld.org/ssa/bssa/article/536312/Combining-Conflicting-Bayesian-Models-to-Develop}, author = {DuRoss, Christopher B. and Bennett, Scott E. K. and Briggs, Richard W. and Personius, Stephen F. and Gold, Ryan D. and Reitman, Nadine G. and Hiscock, Adam I. and Mahan, Shannon A.} } @article {2745, title = {Data Constraints on Glacial Atlantic Water Mass Geometry and Properties}, journal = {Paleoceanography and Paleoclimatology}, volume = {33}, year = {2018}, month = {Mar-09-2020}, pages = {1013 - 1034}, abstract = {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.}, issn = {2572-4517}, doi = {10.1029/2018PA003408}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1029/2018PA003408}, author = {Oppo, Delia W. and Gebbie, Geoffrey and Huang, Kuo-Fang and Curry, William B. and Marchitto, Thomas M. and Pietro, Kathryn R.} } @article {2620, title = {Deglacial floods in the Beaufort Sea preceded Younger Dryas cooling}, journal = {Nature Geoscience}, volume = {11}, year = {2018}, month = {08/2018}, pages = {599 - 604}, abstract = {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 {\textpm} 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.}, issn = {1752-0894}, doi = {10.1038/s41561-018-0169-6}, url = {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}, author = {Keigwin, L. D. and Klotsko, S. and Zhao, N. and Reilly, B. and Giosan, L. and Driscoll, N. W.} } @article {2777, title = {Dual-Isotope Constraints on Seasonally Resolved Source Fingerprinting of Black Carbon Aerosols in Sites of the Four Emission Hot Spot Regions of China}, journal = {Journal of Geophysical Research: Atmospheres}, volume = {123}, year = {2018}, month = {Mar-10-2020}, pages = {11,735 - 11,747}, abstract = {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 {\textpm} 20\%) for BTH-Wuqing, liquid fossil for YRD-Haining (46 {\textpm} 8\%) and PRD-Zhongshan (48 {\textpm} 18\%), whereas liquid fossil (42 {\textpm} 17\%) and biomass burning (41 {\textpm} 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{\textquoteright}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.}, keywords = {aerosol, BLACK CARBON, carbon isotope, china, emission sources, seasonality}, doi = {10.1029/2018JD028607}, url = {http://doi.wiley.com/10.1029/2018JD028607}, author = {Fang, Wenzheng and Du, Ke and Andersson, August and Xing, Zhenyu and Cho, Chaeyoon and Kim, Sang-Woo and Deng, Junjun and Gustafsson, {\"O}rjan} } @article {2790, title = {Ecological history of a long-lived conifer in a disjunct population}, journal = {Journal of Ecology}, volume = {106}, year = {2018}, month = {Jan-01-2018}, pages = {319 - 332}, abstract = { 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. }, keywords = {climate, disjunction, dispersal, Holocene, Idaho, mertensiana, Palaeoecology, pollen, refugia, Tsuga}, doi = {10.1111/1365-2745.12826}, url = {https://besjournals.onlinelibrary.wiley.com/doi/full/10.1111/1365-2745.12826}, author = {Herring, Erin M. and Gavin, Daniel G. and Dobrowski, Solomon Z. and Fernandez, Matias and Hu, Feng Sheng}, editor = {Gill, Jacquelyn} } @article {2789, title = {The effect of sample drying temperature on marine particulate organic carbon composition}, journal = {Limnology and Oceanography: Methods}, volume = {16}, year = {2018}, month = {Jan-05-2018}, pages = {286 - 298}, abstract = {Compositional changes in marine particulate organic carbon (POC) throughout the water column trace important processes that underlie the biological pump{\textquoteright}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{\textdegree}C to -20{\textdegree}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{\textdegree}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{\textdegree}C are appropriate for assessing bulk POC composition and thermal stability, but physical mechanisms such as molecular volatilization bias their lipid composition.}, doi = {10.1002/lom3.v16.510.1002/lom3.10245}, url = {https://www.researchgate.net/publication/324893072_The_effect_of_sample_drying_temperature_on_marine_particulate_organic_carbon_composition}, author = {Rosengard, Sarah Z. and Lam, Phoebe J. and McNichol, Ann P. and Johnson, Carl G. and Galy, Valier V.} } @article {2722, title = {The Ephemeral Signature of Permafrost Carbon in an Arctic Fluvial Network}, journal = {Journal of Geophysical Research: Biogeosciences}, volume = {123}, year = {2018}, month = {Jul-05-2018}, pages = {1475 - 1485}, abstract = {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.}, issn = {2169-8953}, doi = {10.1029/2017JG004311}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1029/2017JG004311}, author = {Drake, Travis W. and Guillemette, Fran{\c c}ois and Hemingway, Jordon D. and Chanton, Jeffery P. and Podgorski, David C. and Zimov, Nikita S. and Spencer, Robert G. M.} } @article {2898, title = {Five Younger Dryas black mats in Mexico and their stratigraphic and paleoenvironmental context}, journal = {Journal of Paleolimnology}, volume = {59}, year = {2018}, month = {Jan-01-2018}, pages = {59 - 79}, abstract = {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{\textendash}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.}, issn = {0921-2728}, doi = {10.1007/s10933-017-9982-y}, url = {http://link.springer.com/10.1007/s10933-017-9982-y}, author = {Israde-Alc{\'a}ntara, Isabel and Dom{\'\i}nguez-V{\'a}zquez, G. and Gonzalez, S. and Bischoff, J. and West, A. and Huddart, D.} } @article {2727, title = {On the Holocene evolution of the Ayeyawady megadelta}, journal = {Earth Surface Dynamics}, volume = {6}, year = {2018}, month = {Jan-01-2018}, pages = {451 - 466}, abstract = {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{\textendash}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.}, doi = {10.5194/esurf-6-451-201810.5194/esurf-6-451-2018-supplement}, url = {https://esurf.copernicus.org/articles/6/451/2018}, author = {Giosan, Liviu and Naing, Thet and Min Tun, Myo and Clift, Peter D. and Filip, Florin and Constantinescu, Stefan and Khonde, Nitesh and Blusztajn, Jerzy and Buylaert, Jan-Pieter and Stevens, Thomas and Thwin, Swe} } @article {2709, title = {Holocene mountain glacier history in the Sukkertoppen Iskappe area, southwest Greenland}, journal = {Quaternary Science Reviews}, volume = {197}, year = {2018}, month = {Jan-10-2018}, pages = {142 - 161}, abstract = {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.}, keywords = {Cosmogenic in situ 14C, Glacier fluctuations, Greenland, Holocene, lake sediment, Neoglaciation}, issn = {02773791}, doi = {10.1016/j.quascirev.2018.06.014}, url = {https://www.sciencedirect.com/science/article/pii/S0277379118302531}, author = {Schweinsberg, Avriel D. and Briner, Jason P. and Miller, Gifford H. and Lifton, Nathaniel A. and Bennike, Ole and Graham, Brandon L.} } @article {2767, title = {The Impact of Aquifer Flushing on Groundwater Arsenic Across a 35-km Transect Perpendicular to the Upper Brahmaputra River in Assam, India}, journal = {Water Resources Research}, volume = {54}, year = {2018}, month = {Jun-10-2019}, pages = {8160 - 8173}, abstract = {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{\textendash}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{\textendash}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{\textendash}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{\textendash}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.}, keywords = {aquifer flushing, Arsenic, groundwater, South Asia}, issn = {0043-1397}, doi = {10.1029/2017WR022485}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1029/2017WR022485}, author = {Choudhury, R. and Nath, B. and Khan, M. R. and Mahanta, C. and Ellis, T. and Geen, A.} } @article {2723, title = {Isotopic composition of sinking particles: Oil effects, recovery andbaselines in the Gulf of Mexico, 2010{\textendash}2015}, journal = {Elem Sci Anth}, volume = {6}, year = {2018}, month = {Sep-01-2018}, pages = {43}, abstract = {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{\textendash}April 2016 in sediment traps moored at sites with depths of 1160{\textendash}1660 m. Near the spill site, changes in Δ14C indicated a 3-year recovery period, while δ34S indicated 1{\textendash}2 years, which agreed with estimates of 1{\textendash}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{\textendash}85\%) and riverine inputs (15{\textendash}20\%). Near the spill site, Δ14C values were depleted in October 2010 ({\textendash}140 to {\textendash}80{\textperthousand}), increasing systematically by 0.07 {\textpm} 0.02{\textperthousand} day{\textendash}1 until July 2013 when values reached {\textendash}3.2 {\textpm} 31.0{\textperthousand}. This Δ14C baseline was similar to particulates at the reference site (3.8 {\textpm} 31.1{\textperthousand}). At both sites, δ13C values stayed constant throughout the study period ({\textendash}21.9 {\textpm} 0.5{\textperthousand} and {\textendash}21.9 {\textpm} 0.9{\textperthousand}, respectively). δ34S near the spill site was depleted (7.4 {\textpm} 3.1{\textperthousand}) during October 2010{\textendash}September 2011, but enriched (16.9 {\textpm} 2.0{\textperthousand}) and similar to the reference site (16.2 {\textpm} 3.1{\textperthousand}) during November 2012{\textendash}April 2015. At the seep site, Δ14C values were {\textendash}21.7 {\textpm} 45.7{\textperthousand} except during August 2012{\textendash}January 2013 when a significant Δ14C depletion of {\textendash}109.0 {\textpm} 29.1{\textperthousand} 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.}, keywords = {Deep Water Horizon Oil Spill, Gulf of Mexico, isotopes, radiocarbon, sediment trap, sinking particulates}, doi = {10.1525/elementa.298}, url = {https://www.elementascience.org/article/10.1525/elementa.298}, author = {Chanton, Jeffrey P. and Giering, Sarah L. C. and Bosman, Samantha H. and Rogers, Kelsey L. and Sweet, Julia and Asper, Vernon L. and Diercks, Arne R. and Passow, Uta} } @article {2616, title = {Large Variability of Dissolved Inorganic Radiocarbon in the Kuroshio Extension of the Northwest North PacificABSTRACT}, journal = {Radiocarbon}, volume = {60264317255}, year = {2018}, month = {Jan-04-2018}, pages = {691 - 704}, abstract = {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.}, keywords = {bomb radiocarbon, carbon, intermediate water, MIXED WATER REGION, ocean, WESTERN BOUNDARY CURRENTS}, issn = {0033-8222}, doi = {10.1017/RDC.2017.143}, url = {https://www.cambridge.org/core/product/identifier/S0033822217001436/type/journal_articlehttps://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0033822217001436}, author = {Ding, Ling and Ge, Tiantian and Gao, Huiwang and Luo, Chunle and Xue, Yuejun and Druffel, Ellen R M and Wang, Xuchen} } @article {2751, title = {Large-Scale Intrusion of Circumpolar Deep Water on Antarctic Margin Recorded by Stylasterid Corals}, journal = {Paleoceanography and Paleoclimatology}, volume = {33}, year = {2018}, month = {May-11-2018}, pages = {1306 - 1321}, abstract = {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 ({\textpm}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.}, issn = {2572-4517}, doi = {10.1029/2018PA003439}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1029/2018PA003439}, author = {King, Theresa M. and Rosenheim, Brad E. and Post, Alexandra L. and Gabris, Theresa and Burt, Taylor and Domack, Eugene W.} } @article {2824, title = {Last Glacial Maximum surface water properties and circulation over Laurentian Fan, western North Atlantic}, journal = {Earth and Planetary Science Letters}, volume = {500}, year = {2018}, month = {Jan-10-2018}, pages = {47 - 55}, abstract = {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 {\textendash} 43{\textdegree}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{\textendash}19.9 and \~{}19.5{\textendash}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.}, keywords = {detrital events, diatoms, ice rafted debris, Last glacial maximum, Laurentide ice sheet, subglacial flows}, issn = {0012821X}, doi = {10.1016/j.epsl.2018.07.038}, url = {https://linkinghub.elsevier.com/retrieve/pii/S0012821X18304448}, author = {Gil, Isabelle M. and Keigwin, Lloyd D.} } @article {2742, title = {Late Holocene paleoceanography in the Chukchi and Beaufort Seas, Arctic Ocean, based on benthic foraminifera and ostracodes}, journal = {arktos}, volume = {4}, year = {2018}, month = {Jan-12-2018}, abstract = {Calcareous microfossil assemblages in late Holocene sediments from the western Arctic continental shelf provide an important baseline for evaluating the impacts of today{\textquoteright}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.}, issn = {2364-9453}, doi = {10.1007/s41063-018-0058-7}, url = {https://link.springer.com/article/10.1007/s41063-018-0058-7}, author = {Seidenstein, Julia L. and Cronin, Thomas M. and Gemery, Laura and Keigwin, Lloyd D. and Pearce, Christof and Jakobsson, Martin and Coxall, Helen K. and Wei, Emily A. and Driscoll, Neal W.} } @article {2615, title = {Microbial decomposition of marine dissolved organic matter in cool oceanic crust}, journal = {Nature Geoscience}, volume = {11}, year = {2018}, month = {Jan-05-2018}, pages = {334 - 339}, abstract = {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 {\textquoteright}aged{\textquoteright} 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.}, keywords = {carbon, community, deep-ocean, DISTINCT, extraction, fluid-flow, HEAT, MID-ATLANTIC RIDGE, SEAWATER, WESTERN FLANK}, issn = {1752-0894}, doi = {10.1038/s41561-018-0109-5}, url = {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}, author = {Shah Walter, Sunita R. and Jaekel, Ulrike and Osterholz, Helena and Fisher, Andrew T. and Huber, Julie A. and Pearson, Ann and Dittmar, Thorsten and Girguis, Peter R.} } @article {2763, title = {Microbial oxidation of lithospheric organic carbon in rapidly eroding tropical mountain soils}, journal = {Science}, volume = {360}, year = {2018}, month = {Jan-04-2019}, pages = {209 - 212}, abstract = {Lithospheric organic carbon ({\textquotedblleft}petrogenic{\textquotedblright}; 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 {\textpm} 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.}, issn = {0036-8075}, doi = {10.1126/science.aao6463}, url = {https://www.sciencemag.org/lookup/doi/10.1126/science.aao6463}, author = {Hemingway, Jordon D. and Hilton, Robert G. and Hovius, Niels and Eglinton, Timothy I. and Haghipour, Negar and Wacker, Lukas and Chen, Meng-Chiang and Galy, Valier V.} } @article {2621, title = {Paleoseismic Results from the Alpine Site, Wasatch Fault Zone: Timing and Displacement Data for Six Holocene Earthquakes at the Salt Lake City{\textendash}Provo Segment Boundary}, journal = {Bulletin of the Seismological Society of America}, year = {2018}, month = {Feb-10-2018}, abstract = {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{\textendash}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{\textendash}0.4 ka. Interseismic recurrence ranges from 0.2 to 1.8 ky (mean 1.2 ky). We estimate 6.5{\textpm}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{\textpm}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{\textendash}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{\textendash}PS segment boundary. These findings can be used for a more nuanced characterization of earthquakes at the SLCS{\textendash}PS boundary and improve earthquake hazard assessments along the Wasatch Front.}, issn = {0037-1106}, doi = {10.1785/0120160358}, url = {https://pubs.geoscienceworld.org/ssa/bssa/article/556954/Paleoseismic-Results-from-the-Alpine-Site-Wasatch}, author = {Bennett, S. E. K. and DuRoss, C. B. and Gold, R. D. and Briggs, R. W. and Personius, S. F. and Reitman, N. G. and Devore, J. R. and Hiscock, A. I. and Mahan, S. A. and Gray, H. J. and Gunnarson, S. and Stephenson, W. J. and Pettinger, E. and Odum, J. K.} } @book {2833, title = {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}, year = {2018}, publisher = {Geological Society of America}, organization = {Geological Society of America}, abstract = {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{\textendash}18,000 cal [calibrated] yr B.P.) and Port Huron (ca. 14,300{\textendash} 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.}, doi = {10.1130/SPE53010.1130/2018.2530(10)}, url = {https://pubs.geoscienceworld.org/books/book/2055/chapter/113619040/Minimum-age-of-the-Mapleton-Tully-and-Labrador}, author = {Kehew, Alan E. and Curry, B. Brandon and Kozlowski, Andrew L. and Bird, Brian C. and Lowell, Thomas V. and Smith, Colby A. and Feranec, Robert S. and Graham, Brandon Lars} } @article {2909, title = {Radiocarbon, Cesium-137, Grain Size, and X-ray Fluorescence Data for Tsunami Geology Investigation, Driftwood Bay, Umnak Island, Alaska (2018)}, year = {2018}, publisher = {Alaska Science Center, U.S. Geological Survey}, abstract = {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. }, doi = {10.5066/P9D7KLJV}, url = {https://doi.org/10.5066/P9D7KLJV}, author = {Witter, Rob and Gelfenbaum, Guy and Corbett, Reide and Tam, Angela and La Selle, SeanPaul} } @article {2738, title = {Remobilization of old permafrost carbon to Chukchi Sea sediments during the end of the last deglaciation}, journal = {Global Biogeochemical Cycles}, year = {2018}, month = {Jan-12-2019}, abstract = {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 Aller{\o}d 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{\textemdash}ice- and carbon-rich permafrost from the late Pleistocene (also referred to as Yedoma){\textemdash}was the dominant source of organic carbon (66 {\textpm} 8\%; mean {\textpm} standard deviation) to sediments during the end of the deglaciation, with fluxes more than twice as high (8.0 {\textpm} 4.6 g{\textperiodcentered}m-2{\textperiodcentered}year-1) as in the late Holocene (3.1 {\textpm} 1.0 g{\textperiodcentered}m-2{\textperiodcentered}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.}, keywords = {carbon isotope, climate change feedback, coastal erosion, Deglaciation, past carbon cycling, permafrost}, issn = {0886-6236}, doi = {10.1029/2018GB005969}, url = {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}, author = {Martens, Jannik and Wild, Birgit and Pearce, Christof and Tesi, Tommaso and Andersson, August and Broder, Lisa and O{\textquoteright}Regan, Matt and Jakobsson, Martin and Sk{\"o}ld, Martin and Gemery, Laura and Cronin, Thomas M. and Semiletov, Igor and Dudarev, Oleg V. and Gustafsson, {\"O}rjan} } @article {2799, title = {Residential Coal Combustion as a Source of Levoglucosan in ChinaResidential Coal Combustion as a Source of Levoglucosan in China}, journal = {Environmental Science \& Technology}, volume = {52}, year = {2018}, month = {Jun-02-2018}, pages = {1665 - 1674}, abstract = {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{\textendash}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.}, issn = {0013-936X}, doi = {10.1021/acs.est.7b05858}, url = {https://pubs.acs.org/doi/10.1021/acs.est.7b05858}, author = {Yan, Caiqing and Zheng, Mei and Sullivan, Amy P. and Shen, Guofeng and Chen, Yingjun and Wang, Shuxiao and Zhao, Bin and Cai, Siyi and Desyaterik, Yury and Li, Xiaoying and Zhou, Tian and Gustafsson, {\"O}rjan and Collett, Jeffrey L.} } @article {2766, title = {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}, journal = {Science of The Total Environment}, volume = {619-620}, year = {2018}, month = {Jan-04-2018}, pages = {957 - 965}, abstract = {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{\textperthousand}, and - 153 to - 687{\textperthousand}, 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\% {\textpm} 17\%). In contrast, the fossil carbon at both QD (57{\textendash}64\%) and HNI (57{\textendash}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{\textendash}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.}, keywords = {AEROSOLS, China marginal seas, Fossil carbon, Radiocarbon (14C) tracer, Total organic carbon}, issn = {00489697}, doi = {10.1016/j.scitotenv.2017.11.201}, url = {https://linkinghub.elsevier.com/retrieve/pii/S004896971733259X}, author = {Yu, Meng and Guo, Zhigang and Wang, Xuchen and Eglinton, Timothy Ian and Yuan, Zineng and Xing, Lei and Zhang, Hailong and Zhao, Meixun} } @article {2725, title = {Tropical peatland carbon storage linked to global latitudinal trends in peat recalcitrance}, journal = {Nature Communications}, volume = {9}, year = {2018}, month = {Jan-12-2018}, abstract = {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 {\textdegree}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.}, doi = {10.1038/s41467-018-06050-2}, url = {http://www.nature.com/articles/s41467-018-06050-2}, author = {Hodgkins, Suzanne B. and Richardson, Curtis J. and Dommain, Ren{\'e} and Wang, Hongjun and Glaser, Paul H. and Verbeke, Brittany and Winkler, B. Rose and Cobb, Alexander R. and Rich, Virginia I. and Missilmani, Malak and Flanagan, Neal and Ho, Mengchi and Hoyt, Alison M. and Harvey, Charles F. and Vining, S. Rose and Hough, Moira A. and Moore, Tim R. and Richard, Pierre J. H. and De La Cruz, Florentino B. and Toufaily, Joumana and Hamdan, Rasha and Cooper, William T. and Chanton, Jeffrey P.} } @article {2826, title = {Unifying Concepts Linking Dissolved Organic Matter Composition to Persistence in Aquatic EcosystemsUnifying Concepts Linking Dissolved Organic Matter Composition to Persistence in Aquatic Ecosystems}, journal = {Environmental Science \& Technology}, volume = {52}, year = {2018}, month = {Jun-03-2018}, pages = {2538 - 2548}, abstract = {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.}, issn = {0013-936X}, doi = {10.1021/acs.est.7b0551310.1021/acs.est.7b05513.s001}, url = {https://pubs.acs.org/doi/10.1021/acs.est.7b05513}, author = {Kellerman, Anne M. and Guillemette, Fran{\c c}ois and Podgorski, David C. and Aiken, George R. and Butler, Kenna D. and Spencer, Robert G. M.} } @article {2878, title = {Variability in carbon uptake and (re)cycling in Antarctic cryptoendolithic microbial ecosystems demonstrated through radiocarbon analysis of organic biomarkers}, journal = {Geobiology}, volume = {16}, year = {2018}, month = {Jan-01-2018}, pages = {62 - 79}, abstract = {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{\textendash}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{\textperthousand} to -185{\textperthousand} equivalent to calibrated ages of 1,100{\textendash}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{\textperthousand}) was consistent with modern atmospheric CO2, while UV values ranged from -199{\textperthousand} to -79{\textperthousand} (calibrated ages of 1,665{\textendash}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.}, doi = {10.1111/gbi.12263}, url = {http://doi.wiley.com/10.1111/gbi.2018.16.issue-1}, author = {Brady, A. L. and Goordial, J. and Sun, H. J. and Whyte, L. G. and Slater, G. F.} } @article {2896, title = {Variance and Rate-of-Change as Early Warning Signals for a Critical Transition in an Aquatic Ecosystem State: A Test Case From Tasmania, Australia}, journal = {Journal of Geophysical Research: Biogeosciences}, volume = {123}, year = {2018}, month = {Jan-02-2018}, pages = {495 - 508}, abstract = {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.}, keywords = {carbon and nitrogen stable isotopes, critical transitions, diatoms, early warning signals, polleen, Tasmania}, doi = {10.1002/2017JG004135}, url = {http://doi.wiley.com/10.1002/2017JG004135}, author = {Beck, Kristen K. and Fletcher, Michael-Shawn and Gadd, Patricia S. and Heijnis, Henk and Saunders, Krystyna M. and Simpson, Gavin L. and Zawadzki, Atun} } @article {2740, title = {The 3.6 ka Aniakchak tephra in the Arctic Ocean: a constraint on the Holocene radiocarbon reservoir age in the Chukchi Sea}, journal = {Climate of the Past}, volume = {13}, year = {2017}, month = {Jan-01-2017}, pages = {303 - 316}, abstract = {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{\textendash}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 {\textpm} 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.}, doi = {10.5194/cp-13-303-2017}, url = {https://cp.copernicus.org/articles/13/303/2017/}, author = {Pearce, Christof and Varhelyi, Aron and Wasteg{\r a}rd, Stefan and Muschitiello, Francesco and Barrientos, Natalia and O{\textquoteright}Regan, Matt and Cronin, Thomas M. and Gemery, Laura and Semiletov, Igor and Backman, Jan and Jakobsson, Martin} } @article {2784, title = {A ~6000 yr diatom record of mid- to late Holocene fluctuations in the level of Lago Wi{\~n}aymarca, Lake Titicaca (Peru/Bolivia)Abstract}, journal = {Quaternary Research}, volume = {88}, year = {2017}, month = {Jan-09-2017}, pages = {179 - 192}, abstract = {A multidecadal-scale lake-level reconstruction for Lago Wi{\~n}aymarca, the southern basin of Lake Titicaca, has been generated from diatom species abundance data. These data suggest that ~6500 cal yr BP Lago Wi{\~n}aymarca 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. Wi{\~n}aymarca 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.}, keywords = {diatoms, Lago Hui{\~n}aimarca, Lago Wi{\~n}aymarca, Lake level, lake titicaca, Mid-Holocene, Tropical Andes}, issn = {0033-5894}, doi = {10.1017/qua.2017.49}, url = {https://www.cambridge.org/core/product/identifier/S0033589417000497/type/journal_article}, author = {Weide, D. Marie and Fritz, Sherilyn C. and Hastorf, Christine A. and Bruno, Maria C. and Baker, Paul A. and Guedron, Stephane and Salenbien, Wout} } @article {2599, title = {African Baobabs with a Very Large Number of Stems and False Stems: Radiocarbon Investigation of the Baobab of Warang}, journal = {Studia Universitatis Babes-Bolyai Chemia}, volume = {62}, year = {2017}, month = {May-03-2018}, pages = {111 - 120}, abstract = {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.}, keywords = {Adansonia digitata, Age determination, AMS radiocarbon dating, inner cavity, multiple stems, tropical trees}, issn = {12247154}, doi = {10.24193/subbchem10.24193/subbchem.2017.110.24193/subbchem.2017.1.09}, url = {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}, author = {Patrut, Adrian and Garnaud, {\'e}bastien and Ka, Oumar and Patrut, Roxana T. and Diagne, Tomas and Lowy, Daniel A. and Forizs, Edit and Bodis, {\H o} and von Reden, Karl F.} } @article {1093, title = {Assessing the Blank Carbon Contribution, Isotope Mass Balance, and Kinetic Isotope Fractionation of the Ramped Pyrolysis/Oxidation Instrument at NOSAMS}, journal = {Radiocarbon}, volume = {59223{\textendash}22493970409}, year = {2017}, month = {Jan-02-2017}, pages = {179 - 193}, abstract = {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.}, keywords = {Ramped PyrOx; blank assessment; kinetic fractionation}, issn = {0033-8222}, doi = {10.1017/RDC.2017.3}, url = {https://www.cambridge.org/core/product/identifier/S0033822217000030/type/journal_article}, author = {Hemingway, Jordon D and Galy, Valier V and Gagnon, Alan R and Grant, Katherine E and Rosengard, Sarah Z and Soulet, Guillaume and Zigah, Prosper K and McNichol, Ann P} } @article {2882, title = {Carbon geochemistry of plankton-dominated samples in the Laptev and East Siberian shelves: contrasts in suspended particle composition}, journal = {Ocean Science}, volume = {13}, year = {2017}, month = {Jan-01-2017}, pages = {735 - 748}, abstract = {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 {\textmu}m) 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 {\textmu}m) dataset to understand the link between plankton composition and environmental conditions. δ13C and Δ14C exhibited a large variability in the POM (> 10 {\textmu}m) distribution while the content of terrestrial biomarkers in the POM was negligible. In the Laptev Sea (LS), δ13C and Δ14C of POM (> 10 {\textmu}m) 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 {\textmu}m) 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.}, doi = {10.5194/os-13-735-2017}, url = {https://os.copernicus.org/articles/13/735/2017/}, author = {Tesi, Tommaso and Geibel, Marc C. and Pearce, Christof and Panova, Elena and Vonk, Jorien E. and Karlsson, Emma and Salvado, Joan A. and Krus{\r a}, Martin and Broder, Lisa and Humborg, Christoph and Semiletov, Igor and Gustafsson, {\"O}rjan} } @article {2465, title = {Carbon isotope-constrained seasonality of carbonaceous aerosol sources from an urban location (Kanpur) in the Indo-Gangetic Plain}, journal = {Journal of Geophysical Research: Atmospheres}, volume = {122}, year = {2017}, month = {Apr-05-2018}, pages = {4903 - 4923}, abstract = {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 {\textdegree}N, 80.3 {\textdegree}E) in the IGP during January 2007-January 2008. The year-round 14C-based fraction biomass (fbio-TC) estimate at Kanpur averages ~77 {\textpm} 7\%, emphasize an impact of biomass burning emissions (BBEs). The highest fbio-TC(\%) is observed in fall season (October-November: 85 {\textpm} 6\%) followed by winter (December-February: 80 {\textpm} 4\%) and spring (March-May: 75 {\textpm} 8\%), while lowest values found in summer (June-September: 69 {\textpm} 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].}, doi = {10.1002/2016JD025634}, url = {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}, author = {Bikkina, Srinivas and Andersson, August and Ram, Kirpa and Sarin, M. M. and Sheesley, Rebecca J. and Kirillova, Elena N. and Rengarajan, R. and Sudheer, A. K. and Gustafsson, {\"O}rjan} } @article {2741, title = {The De Long Trough: a newly discovered glacial trough on the East Siberian continental margin}, journal = {Climate of the Past}, volume = {13}, year = {2017}, month = {Jan-01-2017}, pages = {1269 - 1284}, abstract = {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 {\textendash} Russian {\textendash} 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 {\textendash} 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).}, doi = {10.5194/cp-13-1269-2017}, url = {https://cp.copernicus.org/articles/13/1269/2017/}, author = {O{\textquoteright}Regan, Matt and Backman, Jan and Barrientos, Natalia and Cronin, Thomas M. and Gemery, Laura and Kirchner, Nina and Mayer, Larry A. and Nilsson, Johan and Noormets, Riko and Pearce, Christof and Semiletov, Igor and Stranne, Christian and Jakobsson, Martin} } @article {Jenkins2017, title = {The deep distributions of helium isotopes, radiocarbon, and noble gases along the U.S. GEOTRACES East Pacific Zonal Transect (GP16)}, journal = {Marine Chemistry}, year = {2017}, pages = {-}, abstract = {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{\textdegree}W at 12{\textendash}15{\textdegree}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 {\textquotedblleft}downstream{\textquotedblright} 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{\textdegree}W, 14{\textdegree}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.}, issn = {0304-4203}, doi = {http://doi.org/10.1016/j.marchem.2017.03.009}, url = {http://www.sciencedirect.com/science/article/pii/S0304420316302353}, author = {W. J. Jenkins and Dempsey E. Lott III and Christopher R. German and Kevin L. Cahill and Joanne Goudreau and Brett Longworth} } @article {2739, title = {Deglacial sea level history of the East Siberian Sea and Chukchi Sea margins}, journal = {Climate of the Past}, volume = {13}, year = {2017}, month = {Jan-01-2017}, pages = {1097 - 1110}, abstract = {Deglacial (12.8{\textendash}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{\textendash}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{\textendash}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.}, doi = {10.5194/cp-13-1097-2017}, url = {https://cp.copernicus.org/articles/13/1097/2017/}, author = {Cronin, Thomas M. and O{\textquoteright}Regan, Matt and Pearce, Christof and Gemery, Laura and Toomey, Michael and Semiletov, Igor and Jakobsson, Martin} } @article {2778, title = {Divergent Evolution of Carbonaceous Aerosols during Dispersal of East Asian Haze}, journal = {Scientific Reports}, volume = {7}, year = {2017}, month = {Jan-12-2017}, abstract = {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.}, doi = {10.1038/s41598-017-10766-4}, url = {http://www.nature.com/articles/s41598-017-10766-4}, author = {Fang, Wenzheng and Andersson, August and Zheng, Mei and Lee, Meehye and Holmstrand, Henry and Kim, Sang-Woo and Du, Ke and Gustafsson, {\"O}rjan} } @article {Bradford2017246, title = {Elucidating carbon sources driving microbial metabolism during oil sands reclamation}, journal = {Journal of Environmental Management}, volume = {188}, year = {2017}, pages = {246 - 254}, abstract = {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{\textperthousand}) while organic carbon in the overlying peat was hundreds to thousands of years old (Δ14C~=~-250 to~-350{\textperthousand}). Radiocarbon contents of sediment associated microbial phospholipid fatty acids (PLFA) were consistent with the sediment bulk organic carbon pools (Peat: Δ14CPLFA~=~-257{\textperthousand}; Sand cap Δ14CPLFA~=~-805{\textperthousand}) 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.}, keywords = {Phospholipid fatty acids (PLFA)}, issn = {0301-4797}, doi = {http://doi.org/10.1016/j.jenvman.2016.11.029}, url = {http://www.sciencedirect.com/science/article/pii/S0301479716309045}, author = {Lauren M. Bradford and Lori A. Ziolkowski and Corey Goad and Lesley A. Warren and Gregory F. Slater} } @article {2765, title = {Hydrologic controls on seasonal and inter-annual variability of Congo River particulate organic matter source and reservoir age}, journal = {Chemical Geology}, volume = {466}, year = {2017}, month = {Jan-09-2017}, pages = {454 - 465}, abstract = {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 {\textpm} 82) {\textperthousand}], 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{\textperthousand} 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 {\texttimes} 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.}, keywords = {biomarkers, Congo River, GDGTs, Particulate organic matter, radiocarbon}, issn = {00092541}, doi = {10.1016/j.chemgeo.2017.06.034}, url = {https://linkinghub.elsevier.com/retrieve/pii/S0009254117303935}, author = {Hemingway, Jordon D. and Schefu{\ss}, Enno and Spencer, Robert G.M. and Dinga, Bienvenu Jean and Eglinton, Timothy I. and McIntyre, Cameron and Galy, Valier V.} } @article {2852, title = {Investigation of Late Pleistocene and Holocene Activity in the San Gregorio Fault Zone on the Continental Slope North of Monterey Canyon, Offshore Central California}, journal = {Bulletin of the Seismological Society of America}, volume = {107}, year = {2017}, month = {Jun-06-2019}, pages = {1094 - 1106}, abstract = {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{\textendash}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){\textendash}ROV (seabed sampling) surveys in offshore studies of fault activity.}, issn = {0037-1106}, doi = {10.1785/0120160261}, url = {https://pubs.geoscienceworld.org/bssa/article/107/3/1094-1106/354203}, author = {Maier, Katherine L. and Paull, Charles K. and Brothers, Daniel S. and Caress, David W. and McGann, Mary and Lundsten, Eve M. and Anderson, Krystle and Gwiazda, Roberto} } @article {Hejazian201758, title = {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}, journal = {Applied Geochemistry}, volume = {80}, year = {2017}, pages = {58 - 71}, abstract = {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~{\texttimes}~105~m3 of potable groundwater in the freshwater lens on Roi, compared to only 1.6~{\texttimes}~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.}, issn = {0883-2927}, doi = {http://doi.org/10.1016/j.apgeochem.2017.03.006}, url = {http://www.sciencedirect.com/science/article/pii/S0883292716301391}, author = {Mehrdad Hejazian and Jason J. Gurdak and Peter Swarzenski and Kingsley O. Odigie and Curt D. Storlazzi} } @article {Tesi2017139, title = {Large-scale response of the Eastern Mediterranean thermohaline circulation to African monsoon intensification during sapropel S1 formation}, journal = {Quaternary Science Reviews}, volume = {159}, year = {2017}, pages = {139 - 154}, abstract = {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 {\textendash} for the first time {\textendash} 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 {\textquotedblleft}salty{\textquotedblright} 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.}, keywords = {Thermohaline circulation}, issn = {0277-3791}, doi = {http://doi.org/10.1016/j.quascirev.2017.01.020}, url = {http://www.sciencedirect.com/science/article/pii/S0277379116304012}, author = {T. Tesi and A. Asioli and D. Minisini and V. Maselli and G. Dalla Valle and F. Gamberi and L. Langone and A. Cattaneo and P. Montagna and F. Trincardi} } @article {2798, title = {Millennial mode of variability of sea ice conditions in the Okhotsk Sea during the last glaciation (MIS 4{\textendash}MIS 2)}, journal = {Quaternary International}, volume = {459}, year = {2017}, month = {Jan-11-2017}, pages = {187 - 200}, abstract = {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{\textendash}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.}, keywords = {Ice mode, Ice-rafted debris, Millennial-scale variation, Okhotsk Sea, Wind mode}, issn = {10406182}, doi = {10.1016/j.quaint.2017.09.039}, url = {https://linkinghub.elsevier.com/retrieve/pii/S1040618216313258}, author = {Vasilenko, Yuriy P. and Gorbarenko, Sergey A. and Bosin, Aleksandr A. and Shi, Xue-fa and Chen, Min-Te and Zou, Jian-jun and Liu, Yan-guang and Artemova, Antonina V. and Yanchenko, Elena A. and Savenko, Mikhail P.} } @article {2527, title = {Mobilization and export of millennial-aged organic carbon by the Yellow River}, journal = {Limnology and Oceanography}, year = {2017}, month = {Jan-04-2017}, abstract = {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 {\texttimes} 1010 g C and 4.12 {\texttimes} 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{\textperthousand} to -28.8{\textperthousand} in the river basin, and -21.0{\textperthousand} to -27.0{\textperthousand} in the lower reach. The 14C ages of DOC were 415{\textendash}1690 yr before present (BP) in the river basin, and they were relatively constant seasonally (1320{\textendash}1690 yr BP) in the lower reach of the river. In comparison, POC δ13C values in the river were less variable (-22.8{\textperthousand} to -25.0{\textperthousand}), but much older in both the river basin (4960 {\textpm} 1690 yr BP) and in the lower reach (4040 {\textpm} 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\% {\textpm} 8\% and 52\% {\textpm} 2\% in the river basin and lower reach seasonally. Pre-aged soil OC and fossil OC from weathering contributed 21{\textendash}42\% and 6{\textendash}14\% of the DOC, respectively. In contrast, pre-aged soil OC and fossil OC contributed 60{\textendash}70\% and 17{\textendash}27\% of POC, and biomass OC contributed a minor fraction (13\% {\textpm} 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{\textendash}8275 yr) due to the influence of Yellow River input. Pre-aged soil OC and fossil OC each contributed 32\% {\textpm} 8\% and 22\% {\textpm} 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.}, doi = {10.1002/lno.10579}, url = {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}, author = {Xue, Yuejun and Zou, Li and Ge, Tiantian and Wang, Xuchen} } @article {Luo2017, title = {More reducing bottom-water redox conditions during the Last Glacial Maximum in the southern Challenger Deep (Mariana Trench, western Pacific) driven by enhanced productivity}, journal = {Deep Sea Research Part II: Topical Studies in Oceanography}, year = {2017}, pages = {-}, abstract = {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.}, keywords = {Laminated diatom mats}, issn = {0967-0645}, doi = {http://doi.org/10.1016/j.dsr2.2017.01.006}, url = {http://www.sciencedirect.com/science/article/pii/S0967064516302892}, author = {Min Luo and Thomas J. Algeo and Hongpeng Tong and Joris Gieskes and Linying Chen and Xuefa Shi and Duofu Chen} } @article {2865, title = {Open-File ReportOpen-File ReportDeepwater Program: Lophelia II, continuing ecological research on deep-sea corals and deep-reef habitats in the Gulf of Mexico}, year = {2017}, abstract = {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.}, doi = {10.3133/ofr20171139}, url = {http://pubs.er.usgs.gov/publication/ofr20171139}, author = {Demopoulos, Amanda W.J. and Ross, Steve W. and Kellogg, Christina A. and Morrison, Cheryl L. and Nizinski, Martha S. and Prouty, Nancy G. and Bourque, Jill R. and Galkiewicz, Julie P. and Gray, Michael A. and Springmann, Marcus J. and Coykendall, D. Katharine and Miller, Andrew and Rhode, Mike and Quattrini, Andrea and Ames, Cheryl L. and Brooke, Sandra D. and McClain-Counts, Jennifer P. and Roark, E. Brendan and Buster, Noreen A. and Phillips, Ryan M. and Frometa, Janessy} } @article {2598, title = {Paleohydrology of China Lake basin and the context of early human occupation in the northwestern Mojave Desert, USA}, journal = {Quaternary Science Reviews}, volume = {167}, year = {2017}, month = {Jan-07-2017}, pages = {112 - 139}, abstract = {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.}, issn = {02773791}, doi = {10.1016/j.quascirev.2017.04.023}, url = {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}, author = {Rosenthal, Jeffrey S. and Meyer, Jack and Palacios-Fest, Manuel R. and Young, D. Craig and Ugan, Andrew and Byrd, Brian F. and Gobalet, Ken and Giacomo, Jason} } @book {2837, title = {Proceedings of the International Ocean Discovery ProgramExpedition 357 methods}, year = {2017}, publisher = {International Ocean Discovery Program}, organization = {International Ocean Discovery Program}, doi = {10.14379/iodp.proc.357.102.2017}, url = {http://publications.iodp.org/proceedings/357/357title.html}, author = {Fr{\"u}h-Green, G.L. and Orcutt, B.N. and Green, S.L. and Cotterill, C. and Morgan, S. and Akizawa, N. and Bayrakci, G. and Behrmann, J.-H. and Boschi, C. and Brazleton, W.J. and Cannat, M. and Dunkel, K.G. and Escartin, J. and Harris, M. and Herrero-Bervera, E. and Hesse, K. and John, B.E. and Lang, S.Q. and Lilley, M.D. and Liu, H.-Q. and Mayhew, L.E. and McCaig, A.M. and Menez, B. and Morono, Y. and Qu{\'e}m{\'e}neur, M. and Roum{\'e}jon, S. and Sandaruwan Ratnayake, A. and Schrenk, M.O. and Schwarzenbach, E.M. and Twing, K.I. and Weis, D. and Whattham, S.A. and Williams, M. and Zhao, R.}, editor = {Fr{\"u}h-Green, G.L. and Orcutt, B.N. and Green, S.L. and Cotterill, C.} } @article {2509, title = {Quantifying bamboo coral growth rate nonlinearity with the radiocarbon bomb spike: A new model for paleoceanographic chronology development}, journal = {Deep Sea Research Part I: Oceanographic Research Papers}, year = {2017}, month = {Jan-04-2017}, abstract = {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 {\textmu}m/year, with a decrease in growth rate evident between the 1957{\textendash}1970 and 1970{\textendash}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.}, keywords = {14C nuclear bomb spike, Bamboo coral, Chronologies, Gorgonin, Growth rate, paleoceanography, radiocarbon}, issn = {09670637}, doi = {10.1016/j.dsr.2017.04.006}, url = {https://doi.org/10.1016/j.dsr.2017.04.006}, author = {Frenkel, M.M. and LaVigne, M. and Miller, H.R. and Hill, T.M. and McNichol, A. and Gaylord, M. Lardie} } @article {2773, title = {Reconstructing Common Era relative sea-level change on the Gulf Coast of Florida}, journal = {Marine Geology}, volume = {390}, year = {2017}, month = {Jan-08-2017}, pages = {254 - 269}, abstract = {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{\textendash}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.}, issn = {00253227}, doi = {10.1016/j.margeo.2017.07.001}, url = {https://linkinghub.elsevier.com/retrieve/pii/S0025322716303346}, author = {Gerlach, Matthew J. and Engelhart, Simon E. and Kemp, Andrew C. and Moyer, Ryan P. and Smoak, Joseph M. and Bernhardt, Christopher E. and Cahill, Niamh} } @article {2467, title = {Siberian Arctic black carbon sources constrained by model and observation}, journal = {Proceedings of the National Academy of Sciences}, volume = {114}, year = {2017}, month = {Feb-02-2018}, pages = {E1054 - E1061}, abstract = {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{\textendash}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.}, keywords = {Arctic haze, atmospheric transport modeling, carbon isotopes, Climate change, emission inventory}, issn = {0027-8424}, doi = {10.1073/pnas.1613401114}, url = {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}, author = {Winiger, Patrik and Andersson, August and Eckhardt, Sabine and Stohl, Andreas and Semiletov, Igor P. and Dudarev, Oleg V. and Charkin, Alexander and Shakhova, Natalia and Klimont, Zbigniew and Heyes, Chris and Gustafsson, {\"O}rjan} } @article {2608, title = {Technical note: An inverse method to relate organic carbon reactivity to isotope composition from serial oxidation}, journal = {Biogeosciences}, volume = {14}, year = {2017}, month = {Jan-01-2017}, pages = {5099 - 5114}, doi = {10.5194/bg-14-5099-201710.5194/bg-14-5099-2017-supplement}, url = {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}, author = {Hemingway, Jordon D. and Rothman, Daniel H. and Rosengard, Sarah Z. and Galy, Valier V.} } @article {2600, title = {Turning up the Heat on Organic Matter to Track Carbon}, journal = {Eos}, volume = {98}, year = {2017}, month = {Jul-09-2018}, keywords = {Antarctic sediments, Foraminifera, radiocarbon, stable carbon isotopes}, doi = {10.1029/2017EO080771}, url = {https://eos.org/meeting-reports/turning-up-the-heat-on-organic-matter-to-track-carbon}, author = {McNichol, Ann and Rosenheim, Brad and Galy, Valier} } @article {2786, title = {Younger-Dryas cooling and sea-ice feedbacks were prominent features of the Pleistocene-Holocene transition in Arctic Alaska}, journal = {Quaternary Science Reviews}, volume = {169}, year = {2017}, month = {Jan-08-2017}, pages = {330 - 343}, abstract = {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{\textquoteright}s North Slope during the Pleistocene-Holocene transition (13,500{\textendash}7500 calibrated 14C years before present; 13.5{\textendash}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 Aller{\o}d warm period (\~{}13.2 ka), the Younger Dryas cold period (12.9{\textendash}11.7 ka), and the Holocene Thermal Maximum (11.7{\textendash}9.0 ka). The magnitudes of isotopic changes over these rapid climate oscillations were \~{}4.5{\textperthousand}, 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.}, keywords = {alaska, Arctic, Bering Strait, Climate change, dendrochronology, north pacific, oxygen isotopes, Paleoclimate, Sea ice, Younger Dryas}, issn = {02773791}, doi = {10.1016/j.quascirev.2017.05.012}, url = {https://linkinghub.elsevier.com/retrieve/pii/S0277379117301713}, author = {Gaglioti, Benjamin V. and Mann, Daniel H. and Wooller, Matthew J. and Jones, Benjamin M. and Wiles, Gregory C. and Groves, Pamela and Kunz, Michael L. and Baughman, Carson A. and Reanier, Richard E.} } @article { ISI:000372268700005, title = {Abandoned channel fill sequences in the tidal estuary of a small mountainous, dry-summer river}, journal = {SEDIMENTOLOGY}, volume = {63}, number = {{1}}, year = {2016}, month = {JAN}, pages = {176-206}, type = {Article}, abstract = {{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.}}, keywords = {Abandoned channels, Geomorphology, grain-size analysis, organic carbon, stratigraphy, tidal estuaries}, issn = {0037-0746}, doi = {10.1111/sed.12223}, author = {Gray, Andrew B. and Pasternack, Gregory B. and Watson, Elizabeth B. and Goni, Miguel A.} } @article {2539, title = {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}, journal = {The Cryosphere}, volume = {10}, year = {2016}, month = {Jan-01-2016}, pages = {2779 - 2797}, abstract = {In 2011 four ice cores were extracted from the summit of Alto dell{\textquoteright}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{\textendash}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{\textquoteright}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{\textendash}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{\textquoteright}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.}, doi = {10.5194/tc-10-2779-2016}, url = {http://www.the-cryosphere.net/10/2779/2016/tc-10-2779-2016.pdf}, author = {Gabrielli, Paolo and Barbante, Carlo and Bertagna, Giuliano and {\'o}, Michele and Binder, Daniel and Carton, Alberto and Carturan, Luca and Cazorzi, Federico and Cozzi, Giulio and Dalla Fontana, Giancarlo and Davis, Mary and De Blasi, Fabrizio and Dinale, Roberto and {\`a}, Gianfranco and Dreossi, Giuliano and Festi, Daniela and Frezzotti, Massimo and Gabrieli, Jacopo and Galos, Stephan P. and Ginot, Patrick and Heidenwolf, Petra and Jenk, Theo M. and Kehrwald, Natalie and Kenny, Donald and Magand, Olivier and Mair, Volkmar and Mikhalenko, Vladimir and Lin, Ping Nan and Oeggl, Klaus and Piffer, Gianni and Rinaldi, Mirko and Schotterer, Ulrich and Schwikowski, Margit and Seppi, Roberto and Spolaor, Andrea and Stenni, Barbara and Tonidandel, David and Uglietti, Chiara and Zagorodnov, Victor and Zanoner, Thomas and Zennaro, Piero} } @article {1280, title = {Arctic Deltaic Lake Sediments As Recorders of Fluvial Organic Matter Deposition}, volume = {4}, year = {2016}, month = {2016}, pages = {77}, abstract = {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.}, isbn = {2296-6463}, doi = {10.3389/feart.2016.00077}, url = {http://journal.frontiersin.org/article/10.3389/feart.2016.00077}, author = {Vonk, Jorien E. and Dickens, Angela F. and Giosan, Liviu and Hussain, Zainab A. and Kim, Bokyung and Zipper, Samuel C. and Holmes, Robert M. and Montlu{\c c}on, Daniel B. and Galy, Valier and Eglinton, Timothy I.} } @article { ISI:000375679100005, title = {Carbon isotopic (C-14 and C-13) characterization of fossil-fuel derived dissolved organic carbon in wet precipitation in Shandong Province, China}, journal = {JOURNAL OF ATMOSPHERIC CHEMISTRY}, volume = {73}, number = {{2}}, year = {2016}, month = {JUN}, pages = {207-221}, type = {Article}, abstract = {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.}, keywords = {Atmospheric pollution, Fossil fuelemission, organic carbon, radiocarbon, Wet precipitation}, issn = {0167-7764}, doi = {10.1007/s10874-015-9323-3}, author = {Wang, Xuchen and Ge, Tiantian and Xu, Caili and Xue, Yuejun and Luo, Chunle} } @article {Spooner2016123, title = {Clumped isotope composition of cold-water corals: A role for vital effects?}, journal = {Geochimica et Cosmochimica Acta}, volume = {179}, year = {2016}, pages = {123 - 141}, abstract = {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 {\textquoteleft}clumping{\textquoteright} 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 {\textquoteleft}vital effects{\textquoteright} 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{\textperthousand} (equivalent to underestimating temperature by \~{}9 {\textdegree}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{\textquoteright} 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.}, issn = {0016-7037}, doi = {http://doi.org/10.1016/j.gca.2016.01.023}, url = {http://www.sciencedirect.com/science/article/pii/S0016703716300072}, author = {Peter T. Spooner and Weifu Guo and Laura F. Robinson and Nivedita Thiagarajan and Katharine R. Hendry and Brad E. Rosenheim and Melanie J. Leng} } @article {2552, title = {Complex coastal change in response to autogenic basin infilling: An example from a sub-tropical Holocene strandplain}, journal = {Sedimentology}, volume = {63}, year = {2016}, month = {Jan-10-2016}, pages = {1362 - 1395}, abstract = {Thick bay-fill sequences that often culminate in strandplain development serve as important sedimentary archives of land{\textendash}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 {\textendash} notably a reduction in wave energy in response to coastal embayment infilling {\textendash} in coastal evolution and shoreline morphodynamics. Following a regional 2 to 4 m highstand at ca 5{\textperiodcentered}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{\textendash}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{\textdegree} to ca 7{\textdegree}; and (iii) progradation rates increase from 0{\textperiodcentered}4 to 1{\textperiodcentered}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.}, doi = {10.1111/sed.12265}, url = {http://doi.wiley.com/10.1111/sed.12265}, author = {Hein, Christopher J. and FitzGerald, Duncan M. and de Souza, Luis H. P. and Georgiou, Ioannis Y. and Buynevich, Ilya V. and Klein, Antonio H. da F. and de Menezes, {\~a}o Thadeu and Cleary, William J. and Scolaro, Thelma L.}, editor = {Mohrig, David} } @article { ISI:000383622900016, title = {Controls on the sources and cycling of dissolved inorganic carbon in the Changjiang and Huanghe River estuaries, China: C-14 and C-13 studies}, journal = {LIMNOLOGY AND OCEANOGRAPHY}, volume = {61}, number = {{4}}, year = {2016}, month = {JUL}, pages = {1358-1374}, type = {Article}, abstract = {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.}, issn = {0024-3590}, doi = {10.1002/lno.10301}, author = {Wang, Xuchen and Luo, Chunle and Ge, Tiantian and Xu, Caili and Xue, Yuejun} } @article {Falk20161, title = {Controls on the stable isotope compositions of travertine from hyperalkaline springs in Oman: Insights from clumped isotope measurements}, journal = {Geochimica et Cosmochimica Acta}, volume = {192}, year = {2016}, pages = {1 - 28}, abstract = {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{\textperthousand} above expected equilibrium values) which accompany depletions in δ18O and δ13C, yielding about 0.01{\textperthousand} increase in Δ47 and 1.1{\textperthousand} decrease in δ13C for every 1{\textperthousand} 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.}, keywords = {Carbonate}, issn = {0016-7037}, doi = {http://doi.org/10.1016/j.gca.2016.06.026}, url = {http://www.sciencedirect.com/science/article/pii/S0016703716303568}, author = {E.S. Falk and W. Guo and A.N. Paukert and J.M. Matter and E.M. Mervine and P.B. Kelemen} } @book {2557, title = {Coral Reefs of the WorldCoral Reefs of the Eastern Tropical PacificHolocene Reef Development in the Eastern Tropical Pacific}, volume = {8}, year = {2016}, pages = {177 - 201}, publisher = {Springer Netherlands}, organization = {Springer Netherlands}, address = {Dordrecht}, abstract = {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{\textemdash}species of Porites, Pavona, or Gardineroseris{\textemdash}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 Ni{\~n}o{\textendash}Southern Oscillation (ENSO). ENSO activity{\textemdash}especially that of the 1982{\textendash}83 and 1997{\textendash}98 El Ni{\~n}o events{\textemdash}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.}, keywords = {El Ni{\~n}o, Latin American reefs, paleoecology, Reef accretion, Southern Oscillation, Upwelling}, isbn = {978-94-017-7498-7}, issn = {2213-719X}, doi = {10.1007/978-94-017-7499-410.1007/978-94-017-7499-4_6}, url = {https://link.springer.com/chapter/10.1007\%2F978-94-017-7499-4_6}, author = {Toth, Lauren T. and Macintyre, Ian G. and Aronson, Richard B.}, editor = {Glynn, Peter W. and Manzello, Derek P. and Enochs, Ian C.} } @article { ISI:000389875700006, title = {DISSOLVED INORGANIC RADIOCARBON IN THE NORTHWEST PACIFIC CONTINENTAL MARGIN}, journal = {RADIOCARBON}, volume = {58}, number = {{3}}, year = {2016}, month = {SEP}, pages = {517-529}, type = {Article}, abstract = {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.}, keywords = {continental margin, dissolved inorganic carbon, East China Sea, radiocarbon, stable carbon isotope}, issn = {0033-8222}, doi = {10.1017/RDC.2016.23}, author = {Ge, Tiantian and Wang, Xuchen and Zhang, Jing and Luo, Chunle and Xue, Yuejun} } @article {2466, title = {Dual carbon isotope characterization of total organic carbon in wintertime carbonaceous aerosols from northern India}, journal = {Journal of Geophysical Research: Atmospheres}, volume = {121}, year = {2016}, month = {Apr-05-2017}, pages = {4797 - 4809}, abstract = {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{\textdegree}N, 75.2{\textdegree}E) in the NW Indo-Gangetic Plain (IGP) and a remote high-altitude location in the Himalayan foothills (Manora Peak: 29.4{\textdegree}N, 79.5{\textdegree}E, 1950 m above sea level) in northern India during winter. The Δ14C of total aerosol organic carbon (TOC) varied from -178{\textperthousand} to -63{\textperthousand} at Hisar and from -198{\textperthousand} to -1{\textperthousand} at Manora Peak. The absence of significant differences in the 14C-based fraction biomass of TOC between Hisar (0.81 {\textpm} 0.03) and Manora Peak (0.82 {\textpm} 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.}, doi = {10.1002/2016JD024880}, url = {http://doi.wiley.com/10.1002/2016JD024880https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002\%2F2016JD024880}, author = {Bikkina, Srinivas and Andersson, August and Sarin, M. M. and Sheesley, R. J. and Kirillova, E. and Rengarajan, R. and Sudheer, A. K. and Ram, K. and Gustafsson, {\"O}rjan} } @article {lenz_evidence_2016, title = {Evidence of multiple thermokarst lake generations from an 11 800-year-old permafrost core on the northern Seward Peninsula, Alaska}, journal = {Boreas}, volume = {45}, number = {4}, year = {2016}, note = {_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/bor.12186}, month = {06/2016}, pages = {584{\textendash}603}, abstract = {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{\textpm}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.}, issn = {1502-3885}, doi = {10.1111/bor.12186}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/bor.12186}, author = {Lenz, Josefine and Wetterich, Sebastian and Jones, Benjamin M. and Meyer, Hanno and Bobrov, Anatoly and Grosse, Guido} } @article {2572, title = {Fate of terrigenous organic matter across the Laptev Sea from the mouth of the Lena River to the deep sea of the Arctic interior}, journal = {Biogeosciences}, volume = {13}, year = {2016}, month = {Jan-01-2016}, pages = {5003 - 5019}, abstract = {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{\textendash}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{\textendash}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{\textendash}climate feedbacks.}, doi = {10.5194/bg-13-5003-201610.5194/bg-13-5003-2016}, url = {http://www.biogeosciences.net/13/5003/2016}, author = {Broder, Lisa and Tesi, Tommaso and Salvad?, Joan A. and Semiletov, Igor P. and Dudarev, Oleg V. and Gustafsson, ?rjan} } @article {2573, title = {Historical records of organic matter supply and degradation status in the East Siberian Sea}, journal = {Organic Geochemistry}, volume = {91}, year = {2016}, month = {Jan-01-2016}, pages = {16 - 30}, abstract = {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{\textendash}6). By contrast, the fraction for marine OC drastically decreased during burial with a half-life of 19{\textendash}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.}, keywords = {210Pb, Arctic, East Siberian Arctic Shelf, HMW wax lipids, Lignin, Monte Carlo, δ13C, Δ14C}, issn = {01466380}, doi = {10.1016/j.orggeochem.2015.10.008}, url = {https://doi.org/10.1016/j.orggeochem.2015.10.008}, author = {Broder, Lisa and Tesi, Tommaso and Andersson, August and Eglinton, Timothy I. and Semiletov, Igor P. and Dudarev, Oleg V. and Roos, Per and Gustafsson, ?rjan} } @article {Govil2016453, title = {Holocene climate variability from the lake sediment core in Schirmacher Oasis region, East Antarctica: Multiproxy approach}, journal = {Quaternary International}, volume = {425}, year = {2016}, pages = {453 - 463}, abstract = {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{\textendash}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{\textendash}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.}, keywords = {Freshwater lakes}, issn = {1040-6182}, doi = {http://doi.org/10.1016/j.quaint.2016.09.032}, url = {http://www.sciencedirect.com/science/article/pii/S1040618216304293}, author = {Pawan Govil and Abhijit Mazumder and Rajesh Asthana and Anoop Tiwari and Ravi Mishra} } @article {10, title = {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}, journal = {Ecological Modelling}, volume = {320}, year = {2016}, pages = {79-91}, abstract = {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 na{\"\i}ve 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.}, issn = {0304-3800}, doi = {10.1016/j.ecolmodel.2015.09.013}, url = {http://www.sciencedirect.com/science/article/pii/S0304380015004354}, author = {Kastelle, Craig R. and Helser, Thomas E. and Wischniowski, Stephen G. and Loher, Timothy and Goetz, Betty J. and Kautzi, Lisa A.} } @article {Benz2016216, title = {Last Glacial Maximum sea surface temperature and sea-ice extent in the Pacific sector of the Southern Ocean}, journal = {Quaternary Science Reviews}, volume = {146}, year = {2016}, pages = {216 - 237}, abstract = {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{\textendash}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~{\textdegree}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{\textendash}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.}, keywords = {Pacific Southern Ocean}, issn = {0277-3791}, doi = {http://doi.org/10.1016/j.quascirev.2016.06.006}, url = {http://www.sciencedirect.com/science/article/pii/S0277379116302062}, author = {Verena Benz and Oliver Esper and Rainer Gersonde and Frank Lamy and Ralf Tiedemann} } @article {VanDaele2016130, title = {Late Quaternary evolution of Lago Castor (Chile, 45.6{\textdegree}S): Timing of the deglaciation in northern Patagonia and evolution of the southern westerlies during the last 17 kyr}, journal = {Quaternary Science Reviews}, volume = {133}, year = {2016}, pages = {130 - 146}, abstract = {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{\textdegree}S, 71.8{\textdegree}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 {\textendash} possibly through an outburst flood {\textendash} 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{\textdegree}S from 11.2 to 4.5~cal~kyr BP, which supports the hypothesis that the \{SWWB\} broadened during the early and middle Holocene.}, keywords = {Sediment drift}, issn = {0277-3791}, doi = {http://doi.org/10.1016/j.quascirev.2015.12.021}, url = {http://www.sciencedirect.com/science/article/pii/S027737911530202X}, author = {Maarten Van Daele and S{\'e}bastien Bertrand and Inka Meyer and Jasper Moernaut and Willem Vandoorne and Giuseppe Siani and Niels Tanghe and Zakaria Ghazoui and Mario Pino and Roberto Urrutia and Marc De Batist} } @article {2487, title = {Methane emissions proportional to permafrost carbon thawed in Arctic lakes since the 1950s}, journal = {Nature Geoscience}, volume = {9}, year = {2016}, month = {Oct-08-2017}, pages = {679 - 682}, abstract = {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.}, keywords = {Carbon cycle, Climate change, Cryospheric science}, issn = {1752-0894}, doi = {10.1038/ngeo2795}, url = {http://www.nature.com/doifinder/10.1038/ngeo2795}, author = {Walter Anthony, Katey and Daanen, Ronald and Anthony, Peter and Schneider von Deimling, Thomas and Ping, Chien-Lu and Chanton, Jeffrey P. and Grosse, Guido} } @article {FilipovaMarinova201699, title = {Multi-proxy records of Holocene palaeoenvironmental changes in the Varna Lake area, western Black Sea coast}, journal = {Quaternary International}, volume = {401}, year = {2016}, note = {Implications for Late Quaternary Sea Level Changes on the Mediterranean and Black Sea Coasts - \{MEDBLACKS2014\}}, pages = {99 - 108}, abstract = {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.}, keywords = {Geoarchaeology}, issn = {1040-6182}, doi = {http://doi.org/10.1016/j.quaint.2015.05.009}, url = {http://www.sciencedirect.com/science/article/pii/S1040618215004954}, author = {Mariana Filipova-Marinova and Danail Pavlov and Liviu Giosan} } @article {Burrows2016164, title = {A new late Quaternary palaeohydrological record from the humid tropics of northeastern Australia}, journal = {Palaeogeography, Palaeoclimatology, Palaeoecology}, volume = {451}, year = {2016}, pages = {164 - 182}, abstract = {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.}, keywords = {Late Quaternary}, issn = {0031-0182}, doi = {http://doi.org/10.1016/j.palaeo.2016.03.003}, url = {http://www.sciencedirect.com/science/article/pii/S0031018216001656}, author = {M.A. Burrows and H. Heijnis and P. Gadd and S.G. Haberle} } @article { ISI:000372829700018, title = {A Note on Reporting of Reservoir C-14 Disequilibria and Age Offsets}, journal = {RADIOCARBON}, volume = {58}, number = {{1}}, year = {2016}, month = {MAR}, pages = {205-211}, type = {Article}, abstract = {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.}, keywords = {freshwater effect, hardwater effect, radiocarbon, Reservoir age, Reservoir effect, ventilation age}, issn = {0033-8222}, doi = {10.1017/RDC.2015.22}, author = {Soulet, Guillaume and Skinner, Luke C. and Beaupr{\'e}, Steven R. and Galy, Valier} } @article {Mason20161, title = {Parent material influence on soil response to vegetation change, Southeastern Minnesota, U.S.A.}, journal = {Geoderma}, volume = {275}, year = {2016}, pages = {1 - 17}, abstract = {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.}, keywords = {Parent material}, issn = {0016-7061}, doi = {http://doi.org/10.1016/j.geoderma.2016.04.004}, url = {http://www.sciencedirect.com/science/article/pii/S0016706116301513}, author = {Joseph A. Mason and Peter M. Jacobs and Kristine E. Gruley and Paul Reyerson and Paul R. Hanson} } @article {1034, title = {Rapid extraction of dissolved inorganic carbon from seawater and groundwater samples for radiocarbon dating}, journal = {LIMNOLOGY AND OCEANOGRAPHY-METHODS}, volume = {14}, year = {2016}, month = {01/2016}, pages = {24-30}, type = {Article}, abstract = {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.}, issn = {1541-5856}, doi = {10.1002/lom3.10066}, author = {Gospodinova, K. and McNichol, A. P. and Gagnon, A. and Walter, S. R. Shah} } @article {Maio201667, title = {Sediment dynamics and hydrographic conditions during storm passage, Waquoit Bay, Massachusetts}, journal = {Marine Geology}, volume = {381}, year = {2016}, pages = {67 - 86}, abstract = {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.}, keywords = {Sediment transport}, issn = {0025-3227}, doi = {http://doi.org/10.1016/j.margeo.2016.07.004}, url = {http://www.sciencedirect.com/science/article/pii/S0025322716301438}, author = {Christopher V. Maio and Jeffrey P. Donnelly and Richard Sullivan and Stephanie M. Madsen and Christopher R. Weidman and Allen M. Gontz and Vitalii A. Sheremet} } @article {2468, title = {The sources of atmospheric black carbon at a European gateway to the Arctic}, journal = {Nature Communications}, volume = {7}, year = {2016}, month = {Mar-09-2017}, pages = {12776}, abstract = {Black carbon (BC) aerosols from incomplete combustion of biomass and fossil fuel contribute to Arctic climate warming. Models{\textemdash}seeking to advise mitigation policy{\textemdash}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.}, doi = {10.1038/ncomms12776}, url = {http://www.nature.com/doifinder/10.1038/ncomms12776}, author = {Winiger, P and Andersson, A and Eckhardt, S and Stohl, A and Gustafsson, O.} } @article {2478, title = {Stability of peatland carbon to rising temperatures}, journal = {Nature Communications}, volume = {7}, year = {2016}, month = {Jan-12-2017}, pages = {13723}, abstract = {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{\textendash}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.}, doi = {10.1038/ncomms13723}, url = {http://www.nature.com/doifinder/10.1038/ncomms13723}, author = {Wilson, R. M. and Hopple, A. M. and Tfaily, M. M. and Sebestyen, S. D. and Schadt, C. W. and Pfeifer-Meister, L. and Medvedeff, C. and McFarlane, K. J. and Kostka, J. E. and Kolton, M. and Kolka, R.K. and Kluber, L. A. and Keller, J. K. and Guilderson, T. P. and Griffiths, N. A. and Chanton, J. P. and Bridgham, S. D. and Hanson, P. J.} } @article {2565, title = {Subsurface Evidence of Storm-Driven Breaching along a Transgressing Barrier System, Cape Cod, U.S.A.}, journal = {Journal of Coastal Research}, volume = {318}, year = {2016}, month = {Jan-03-2016}, pages = {264 - 279}, abstract = {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.}, keywords = {coastal change, Coastal evolution, ground-penetrating radar, marine transgression, overwash, paleochannel, paleogeography, South Cape Beach}, issn = {0749-0208}, doi = {10.2112/JCOASTRES-D-14-00109.1}, url = {https://doi.org/10.2112/JCOASTRES-D-14-00109.1}, author = {Maio, Christopher V. and Gontz, Allen M. and Sullivan, Richard M. and Madsen, Stephanie M. and Weidman, Christopher R. and Donnelly, Jeffrey P.} } @article {2577, title = {Twenty-five-year longevity of European hake (Merluccius merluccius) from novel use of bomb radiocarbon dating in the Mediterranean Sea}, journal = {Marine and Freshwater Research}, volume = {67}, year = {2016}, month = {Jan-01-2016}, pages = {1077}, abstract = {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. }, keywords = {Age validation, Carbon-14, growth, lifespan, Merlucciidae}, issn = {1323-1650}, doi = {10.1071/MF15376}, url = {https://doi.org/10.1071/MF15376}, author = {Vitale, Sergio and Andrews, Allen H. and Rizzo, Pietro and Gancitano, Salvatore and Fiorentino, Fabio} } @article {2536, title = {Unusually large tsunamis frequent a currently creeping part of the Aleutian megathrust}, journal = {Geophysical Research Letters}, volume = {43}, year = {2016}, month = {Apr-01-2017}, pages = {76 - 84}, abstract = {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{\textendash}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.}, doi = {10.1002/2015GL066083}, url = {http://doi.wiley.com/10.1002/2015GL066083}, author = {Witter, Robert C. and Carver, Gary A. and Briggs, Richard W. and Gelfenbaum, Guy and Koehler, Richard D. and La Selle, SeanPaul and Bender, Adrian M. and Engelhart, Simon E. and Hemphill-Haley, Eileen and Hill, Troy D.} } @article { ISI:000366502600005, title = {Analysis of bomb radiocarbon data for common thresher sharks, Alopias vulpinus, in the northwestern Atlantic Ocean with revised growth curves}, journal = {ENVIRONMENTAL BIOLOGY OF FISHES}, volume = {99}, number = {{1}}, year = {2015}, month = {DEC}, pages = {39-47}, type = {Article}, abstract = {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.}, keywords = {Age, Carbon-14, Centra, Elasmobranchs, Vertebral column}, issn = {0378-1909}, doi = {10.1007/s10641-015-0452-y}, author = {Natanson, Lisa J. and Hamady, Li Ling and Gervelis, Brian J.} } @article {29, title = {Bayesian 14C analysis, formation processes, and accumulation rates of the Prisoners Harbor shell midden and village complex, Santa Cruz Island, California}, journal = {Journal of Archaeological Science: Reports}, volume = {3}, year = {2015}, pages = {257-264}, abstract = {The Prisoners Harbor site (CA-SCRI-240), one of the largest sites on California{\textquoteright}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{\textquoteright}s occupation, with comparatively little attention given to the 2{\textendash}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{\textquoteright}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.}, issn = {2352-409X}, doi = {10.1016/j.jasrep.2015.06.022}, url = {http://www.sciencedirect.com/science/article/pii/S2352409X15300420}, author = {Jew, Nicholas P. and Rick, Torben C. and Glassow, Michael A. and Arnold, Jeanne E.} } @article {2559, title = {Climatic and biotic thresholds of coral-reef~shutdown}, journal = {Nature Climate Change}, volume = {5}, year = {2015}, month = {Nov-02-2016}, pages = {369 - 374}, abstract = {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 Panam{\'a}. 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{\textemdash}indicators of La Ni{\~n}a-like conditions{\textemdash}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.}, keywords = {Climate-change ecology, Palaeoceanography, Palaeoclimate, Palaeoecology}, issn = {1758-678X}, doi = {10.1038/nclimate2541}, url = {http://www.nature.com/doifinder/10.1038/nclimate2541}, author = {Toth, Lauren T. and Aronson, Richard B. and Cobb, Kim M. and Cheng, Hai and Edwards, R. Lawrence and Grothe, Pamela R. and Sayani, Hussein R.} } @article { ISI:000358041400001, title = {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}, journal = {PALEOCEANOGRAPHY}, volume = {30}, number = {{6}}, year = {2015}, month = {JUN}, pages = {583-600}, type = {Article}, abstract = {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.}, keywords = {atmospheric circulation, chronostratigrapy, eolian dust, helium-4, paleoreservoir age, Subarctic North Pacific}, issn = {0883-8305}, doi = {10.1002/2014PA002748}, author = {Serno, Sascha and Winckler, Gisela and Anderson, Robert F. and Maier, Edith and Ren, Haojia and Gersonde, Rainer and Haug, Gerald H.} } @article {28, title = {Comparison of large and ultra-small delta c-14 measurements in core top benthic foraminifera from the Okhotsk Sea}, journal = {Radiocarbon}, volume = {57}, year = {2015}, note = {PT: J; TC: 1; UT: WOS:000351052600010}, pages = {123-128}, abstract = {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.}, issn = {0033-8222}, doi = {10.2458/azu_rc.57.18153}, author = {Keigwin, L. D. and Gagnon, A. R.} } @article {2469, title = {Isotope-Based Source Apportionment of EC Aerosol Particles during Winter High-Pollution Events at the Zeppelin Observatory, Svalbard}, journal = {Environmental Science \& Technology}, volume = {49}, year = {2015}, month = {Jun-10-2015}, pages = {11959 - 11966}, abstract = {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{\textdegree} 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{\textdegree} 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 {\textpm} 15\% (n = 12) of the EC stemmed from biomass burning. Including also two samples with 95\% and 98\% biomass contribution yield 57 {\textpm} 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.}, issn = {0013-936X}, doi = {10.1021/acs.est.5b02644}, url = {http://pubs.acs.org/doi/10.1021/acs.est.5b02644http://pubs.acs.org/doi/pdf/10.1021/acs.est.5b02644}, author = {Winiger, Patrik and Andersson, August and Yttri, Karl E. and Tunved, Peter and Gustafsson, {\"O}rjan} } @article { ISI:000352212200018, title = {Late Holocene glacial advance and ice shelf growth in Barilari Bay, Graham Land, west Antarctic Peninsula}, journal = {GEOLOGICAL SOCIETY OF AMERICA BULLETIN}, volume = {127}, number = {{1-2}}, year = {2015}, month = {JAN-FEB}, pages = {297-315}, type = {Article}, abstract = {Three marine sediment cores were collected along the length of the fjord axis of Barilari Bay, Graham Land, west Antarctic Peninsula (65 degrees 55{\textquoteright}S, 64 degrees 43{\textquoteright}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.}, issn = {0016-7606}, doi = {10.1130/B31035.1}, author = {Christ, Andrew J. and Talaia-Murray, Manique and Elking, Natalie and Domack, Eugene W. and Leventer, Amy and Lavoie, Caroline and Brachfeld, Stefanie and Yoo, Kyu-Cheul and Gilbert, Robert and Jeong, Sun-Mi and Petrushak, Stephen and Wellner, Julia and LARISSA Grp} } @article { ISI:000368907500001, title = {Multimolecular tracers of terrestrial carbon transfer across the pan-Arctic: C-14 characteristics of sedimentary carbon components and their environmental controls}, journal = {GLOBAL BIOGEOCHEMICAL CYCLES}, volume = {29}, number = {{11}}, year = {2015}, month = {NOV}, pages = {1855-1873}, type = {Article}, abstract = {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 {\textquoteleft}{\textquoteleft}old{{\textquoteright}{\textquoteright}} 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.}, issn = {0886-6236}, doi = {10.1002/2015GB005204}, author = {Feng, Xiaojuan and Gustafsson, {\"O}rjan and Holmes, R. Max and Vonk, Jorien E. and van Dongen, Bart E. and Semiletov, Igor P. and Dudarev, Oleg V. and Yunker, Mark B. and Macdonald, Robie W. and Wacker, Lukas and Montlu{\c c}on, Daniel B. and Eglinton, Timothy I.} } @article {17, title = {Multiproxy record of monsoon variability from the Ganga Plain during 400{\textendash}1200 A.D}, journal = {Updated Quaternary Climatic Research in parts of the Third Pole Selected papers from the HOPE-2013 conference, Nainital, India}, volume = {371}, year = {2015}, pages = {157-163}, abstract = {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{\textendash}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{\textendash}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{\textendash}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).}, issn = {1040-6182}, doi = {10.1016/j.quaint.2015.02.040}, url = {http://www.sciencedirect.com/science/article/pii/S1040618215001470}, author = {Singh, Dhruv Sen and Gupta, Anil K. and Sangode, S. J. and Clemens, Steven C. and Prakasam, M. and Srivastava, Priyeshu and Prajapati, Shailendra K.} } @article {30, title = {A post-glacial relative sea-level curve from Fiordland, New Zealand}, journal = {Global and Planetary Change}, volume = {131}, year = {2015}, pages = {104-114}, abstract = {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{\textdegree}S) Southern Hemisphere location as well as new evidence for Meltwater Pulse 1b.}, issn = {0921-8181}, doi = {10.1016/j.gloplacha.2015.05.010}, url = {http://www.sciencedirect.com/science/article/pii/S0921818115001071}, author = {Dlabola, E. K. and Wilson, G. S. and Gorman, A. R. and Riesselman, C. R. and Moy, C. M.} } @article {2532, title = {South Asian monsoon history over the past 60 kyr recorded by radiogenic isotopes and clay mineral assemblages in the Andaman Sea}, journal = {Geochemistry, Geophysics, Geosystems}, volume = {16}, year = {2015}, month = {Jan-02-2015}, pages = {505 - 521}, abstract = {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.}, doi = {10.1002/2014GC005586}, url = {http://doi.wiley.com/10.1002/2014GC005586}, author = {Ali, Sajid and Hathorne, Ed C. and Frank, Martin and Gebregiorgis, Daniel and Stattegger, Karl and Stumpf, Roland and Kutterolf, Steffen and Johnson, Joel E. and Giosan, Liviu} } @article {15, title = {Ultra-Small Graphitization Reactors for Ultra-Microscale C-14 Analysis at the National Ocean Sciences Accelerator Mass Spectrometry (Nosams) Facility}, journal = {Radiocarbon}, volume = {57}, year = {2015}, note = {PT: J; TC: 1; UT: WOS:000351052600009}, pages = {109-122}, abstract = {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.}, issn = {0033-8222}, doi = {10.2458/azu_rc.57.18118}, author = {Walter, Sunita R. Shah and Gagnon, Alan R. and Roberts, Mark L. and McNichol, Ann P. and Gaylord, Mary C. Lardie and Klein, Elizabeth} } @article {16, title = {A warm and poorly ventilated deep Arctic Mediterranean during the last glacial period}, journal = {Science}, volume = {349}, year = {2015}, pages = {706-710}, abstract = {Changes in the formation of dense water in the Arctic Ocean and Nordic Seas [the {\textquotedblleft}Arctic Mediterranean{\textquotedblright} (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{\textdegree} to 3{\textdegree}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.}, doi = {10.1126/science.aaa9554}, url = {http://www.sciencemag.org/content/349/6249/706.abstract}, author = {Thornalley, D. J. R. and Bauch, H. A. and Gebbie, G. and Guo, W. and Ziegler, M. and Bernasconi, S. M. and Barker, S. and Skinner, L. C. and Yu, J.} } @article {552, title = {Composition and origin of authigenic carbonates in the Krishna-Godavari and Mahanadi Basins, eastern continental margin of India}, journal = {Marine and Petroleum Geology}, volume = {58}, year = {2014}, note = {AAy4wyTimes Cited:5Cited References Count:63}, month = {Dec}, pages = {438-460}, abstract = {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 {\textendash} 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.}, issn = {0264-8172}, doi = {10.1016/j.marpetgeo.2014.08.023}, author = {Teichert, B. M. A. and Johnson, J. E. and Solomon, E. A. and Giosan, L. and Rose, K. and Kocherla, M. and Connolly, E. C. and Torres, M. E.} } @article {2587, title = {Deglacial ?18O and hydrologic variability in the tropical Pacific and Indian Oceans}, journal = {Earth and Planetary Science Letters}, volume = {387}, year = {2014}, month = {Jan-02-2014}, pages = {240 - 251}, abstract = {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.}, keywords = {Deglaciation, Eastern Equatorial Pacific, heat transport, Indo-Pacific, δ18O of seawater}, issn = {0012821X}, doi = {10.1016/j.epsl.2013.11.032}, url = {https://doi.org/10.1016/j.epsl.2013.11.032}, author = {Gibbons, Fern T. and Oppo, Delia W. and Mohtadi, Mahyar and Rosenthal, Yair and Cheng, Jun and Liu, Zhengyu and Linsley, Braddock K.} } @article {2560, title = {A depth refugium from catastrophic coral bleaching prevents regional extinction}, journal = {Ecology}, volume = {95}, year = {2014}, month = {Jan-06-2014}, pages = {1663 - 1673}, abstract = {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. {\textcopyright} 2014 by the Ecological Society of America.}, keywords = {Coral bleaching, Coral mortality, Depth refuge, Eastern Tropical Pacific, El Nino-Southern Oscillation, Extinction, Holocene, Millepora, Refuge}, issn = {0012-9658}, doi = {10.1890/13-0468.1}, url = {http://doi.wiley.com/10.1890/13-0468.1}, author = {Smith, Tyler B. and Glynn, Peter W. and {\'e}, Juan L. and Toth, Lauren T. and Gyory, Joanna} } @article {2585, title = {Indonesian vegetation response to changes in rainfall seasonality over the past 25,000 years}, journal = {Nature Geoscience}, volume = {7449278721172063253871891072011563523665412739429544323}, year = {2014}, month = {Jan-06-2014}, pages = {513 - 517}, abstract = {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.}, keywords = {Palaeoclimate, Palaeoecology}, issn = {1752-0894}, doi = {10.1038/ngeo2182}, url = {http://www.nature.com/doifinder/10.1038/ngeo2182}, author = {Dubois, Nathalie and Oppo, Delia W. and Galy, Valier V. and Mohtadi, Mahyar and van der Kaars, Sander and Tierney, Jessica E. and Rosenthal, Yair and Eglinton, Timothy I. and L?ckge, Andreas and Linsley, Braddock K.} } @article {73, title = {Isotopic evidence for anthropogenic impacts on aquatic food web dynamics and mercury cycling in a subtropical wetland ecosystem in the US}, journal = {Science of The Total Environment}, volume = {487}, year = {2014}, pages = {557-564}, abstract = {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 {\textendash} 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.}, issn = {0048-9697}, doi = {10.1016/j.scitotenv.2014.04.060}, url = {http://www.sciencedirect.com/science/article/pii/S0048969714005701}, author = {Wang, Yang and Gu, Binhe and Lee, Ming-Kuo and Jiang, Shijun and Xu, Yingfeng} } @article {51, title = {Late Holocene marine transgression and the drowning of a coastal forest: Lessons from the past, Cape Cod, Massachusetts, USA}, journal = {Palaeogeography, Palaeoclimatology, Palaeoecology}, volume = {393}, year = {2014}, pages = {146-158}, abstract = {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 {\textpm} 80 to 1239 {\textpm} 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.}, issn = {0031-0182}, doi = {10.1016/j.palaeo.2013.11.018}, url = {http://www.sciencedirect.com/science/article/pii/S003101821300521X}, author = {Maio, Christopher V. and Gontz, Allen M. and Weidman, Christopher R. and Donnelly, Jeffrey P.} } @article {59, title = {Late Holocene sedimentation in a high Arctic coastal setting: Simpson Lagoon and Colville Delta, Alaska}, journal = {Continental Shelf Research}, volume = {74}, year = {2014}, pages = {11-24}, abstract = {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.}, issn = {0278-4343}, doi = {10.1016/j.csr.2013.11.026}, url = {http://www.sciencedirect.com/science/article/pii/S0278434313004056}, author = {Hanna, Andrea J. M. and Allison, Mead A. and Bianchi, Thomas S. and Marcantonio, Franco and Goff, John A.} } @article {42, title = {Late Quaternary sedimentary record and Holocene channel avulsions of the Jamuna and Old Brahmaputra River valleys in the upper Bengal delta plain}, journal = {Tropical Rivers of South and South-east Asia: Landscape evolution, morphodynamics and hazards}, volume = {227}, year = {2014}, pages = {123-136}, abstract = {The first Holocene stratigraphic record of river-channel occupation and switching between the Brahmaputra{\textendash}Jamuna and Old Brahmaputra paleovalleys is presented here. Motivated by the Brahmaputra River{\textquoteright}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{\textendash}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{\textendash}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{\textendash}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{\textendash}4 major avulsions during the Holocene, with considerably longer occupation times within the principal Brahmaputra{\textendash}Jamuna valley. Together these observations indicate that occupation history and antecedent topography have been important controls on river course mobility and avulsion behavior.}, issn = {0169-555X}, doi = {10.1016/j.geomorph.2013.09.021}, url = {http://www.sciencedirect.com/science/article/pii/S0169555X13004868}, author = {Pickering, Jennifer L. and Goodbred, Steven L. and Reitz, Meredith D. and Hartzog, Thomas R. and Mondal, Dhiman R. and Hossain, Md Saddam} } @article {43, title = {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}, journal = {Marine and Freshwater Research}, volume = {65}, year = {2014}, note = {id: 2352}, pages = {674 - 687}, abstract = {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{\textendash}12 years. Age was also underestimated for adult sharks from the SIO by 14{\textendash}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.}, doi = {10.1071/MF13214}, author = {Passerotti, M. S. and Andrews, A. H. and Carlson, J. K. and Wintner, S. P. and Goldman, K. J. and Natanson, L. J.} } @article {554, title = {Monsoon-influenced variation in productivity and lithogenic sediment flux since 110 ka in the offshore Mahanadi Basin, northern Bay of Bengal}, journal = {Marine and Petroleum Geology}, volume = {58}, year = {2014}, note = {AAy4wyTimes Cited:4Cited References Count:253}, month = {Dec}, pages = {502-525}, abstract = {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.}, issn = {0264-8172}, doi = {10.1016/j.marpetgeo.2014.05.007}, author = {Phillips, Stephen C. and Johnson, Joel E. and Giosan, Liviu and Rose, Kelly} } @article {62, title = {A multiple-tracer approach to understanding regional groundwater flow in the Snake Valley area of the eastern Great Basin, USA}, journal = {Applied Geochemistry}, volume = {45}, year = {2014}, pages = {33-49}, abstract = {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 {\textdegree}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.}, issn = {0883-2927}, doi = {10.1016/j.apgeochem.2014.02.010}, url = {http://www.sciencedirect.com/science/article/pii/S0883292714000390}, author = {Gardner, Philip M. and Heilweil, Victor M.} } @article {61, title = {Oceanographic regimes in the northwest Labrador Sea since Marine Isotope Stage 3 based on dinocyst and stable isotope proxy records}, journal = {APEX II: Arctic Palaeoclimate and its Extremes}, volume = {92}, year = {2014}, pages = {269-279}, abstract = {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 {\textquotedblleft}glacial{\textquotedblright}, {\textquotedblleft}deglacial{\textquotedblright} and {\textquotedblleft}postglacial{\textquotedblright} intervals. The site remained under the direct influence of the Laurentide Ice Sheet (LIS) margin until the postglacial and did not record the B{\o}lling-Aller{\o}d warming and weakly recorded the Younger Dryas event. The {\textquotedblleft}glacial{\textquotedblright} 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 {\textquotedblleft}deglacial{\textquotedblright} regime (ca 12.2{\textendash}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 {\textdegree}C) but low winter (\~{}0 {\textdegree}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 {\textdegree}C) to summer (\~{}8.6 {\textdegree}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.}, issn = {0277-3791}, doi = {10.1016/j.quascirev.2013.12.010}, url = {http://www.sciencedirect.com/science/article/pii/S0277379113004915}, author = {Gibb, Olivia T. and Hillaire-Marcel, Claude and de Vernal, Anne} } @article {63, title = {Origin, composition, and transformation of dissolved organic matter in tropical peatlands}, journal = {Geochimica et Cosmochimica Acta}, volume = {137}, year = {2014}, pages = {35-47}, abstract = {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 {\textpm} 8.53{\textperthousand} at the pristine site and Δ14C = 87.84 {\textpm} 4.5{\textperthousand} 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{\textperthousand} to -28.3{\textperthousand}. Nitrogen showed a greater shift between ecosystem pools. Nitrogen-15 content was higher in the solid peat (δ15N = -0.92 {\textpm} 0.49{\textperthousand} in the pristine site, δ15N = -1.22 {\textpm} 1.37{\textperthousand} in the deforested site) than in DOM (δ15N = -4.2 {\textpm} 2.5{\textperthousand} in the pristine site, δ15N = -4.1 {\textpm} 2.3{\textperthousand} 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 {\textpm} 0.27 mg 100 mg dw-1 in the pristine site and λ8 = 1.38 {\textpm} 0.46 mg 100 mg dw-1 in the deforested site) than does the solid peat (λ8 = 5.66 {\textpm} 2.14 mg 100 mg dw-1 in the pristine site and λ8 = 10.29 {\textpm} 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.}, issn = {0016-7037}, doi = {10.1016/j.gca.2014.03.012}, url = {http://www.sciencedirect.com/science/article/pii/S0016703714001768}, author = {Gandois, L. and Teisserenc, R. and Cobb, A. R. and Chieng, H. I. and Lim, L. B. L. and Kamariah, A. S. and Hoyt, A. and Harvey, C. F.} } @article { ISI:000359186200001, title = {Phylogeny and phylogeography of functional genes shared among seven terrestrial subsurface metagenomes reveal N-cycling and microbial evolutionary relationships}, journal = {FRONTIERS IN MICROBIOLOGY}, volume = {5}, year = {2014}, month = {OCT 31}, type = {Article}, abstract = {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.}, keywords = {evolution, functional genes, N-cycle, phylogenetics, phylogeny, phylogeography, terrestrial subsurface}, issn = {1664-302X}, doi = {10.3389/fmicb.2014.00531}, author = {Lau, Maggie C. Y. and Cameron, Connor and Magnabosco, Cara and Brown, C. Titus and Schilkey, Faye and Grim, Sharon and Hendrickson, Sarah and Pullin, Michael and Lollar, Barbara Sherwood and Van Heerden, Esta and Kieft, Thomas L. and Onstott, Tullis C.} } @article { ISI:000348452800012, title = {Preferential burial of permafrost-derived organic carbon in Siberian-Arctic shelf waters}, journal = {JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS}, volume = {119}, number = {{12}}, year = {2014}, month = {DEC}, pages = {8410-8421}, type = {Article}, abstract = {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.}, keywords = {biomarkers, carbon, permafrost, radiocarbon}, issn = {2169-9275}, doi = {10.1002/2014JC010261}, author = {Vonk, Jorien E. and Semiletov, Igor P. and Dudarev, Oleg V. and Eglinton, Timothy I. and Andersson, August and Shakhova, Natalia and Charkin, Alexander and Heim, Birgit and Gustafsson, {\"O}rjan} } @article { ISI:000342993200010, title = {Radiocarbon age-offsets in an arctic lake reveal the long-term response of permafrost carbon to climate change}, journal = {JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES}, volume = {119}, number = {{8}}, year = {2014}, month = {AUG}, pages = {1630-1651}, type = {Article}, abstract = {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.}, keywords = {carbon cycling, lake sediment, paleoclimatology, permafrost, radiocarbon, Younger Dryas}, issn = {2169-8953}, doi = {10.1002/2014JG002688}, author = {Gaglioti, Benjamin V. and Mann, Daniel H. and Jones, Benjamin M. and Pohlman, John W. and Kunz, Michael L. and Wooller, Matthew J.} } @article {74, title = {Radiocarbon signatures and size{\textendash}age{\textendash}composition relationships of major organic matter pools within a unique California upwelling system}, journal = {Geochimica et Cosmochimica Acta}, volume = {126}, year = {2014}, pages = {1-17}, abstract = {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{\textendash}500 μm) and small (0.1{\textendash}100 μm) POM, and high molecular weight (HMW; \~{}1 nm{\textendash}0.1 μm) DOM from an upwelling center along the Big Sur coast. We show that DIC Δ14C values (ranging between +29{\textperthousand} and -14{\textperthousand}) 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{\textperthousand} and -56{\textperthousand}, +6{\textperthousand} and -123{\textperthousand} and -1{\textperthousand} and -150{\textperthousand}, respectively) suggests contributions of {\textquotedblleft}pre-aged{\textquotedblright} OM, complicating the direct use of {\textquotedblleft}bulk{\textquotedblright} Δ14C for tracing upwelling-derived carbon production/export. Using a triple-isotope mixing model (δ13C, δ15N, Δ14C) we estimate that 50{\textendash}90\% and 45{\textendash}51\% of large and small POM is newly-produced OM, while between 6{\textendash}22\% and 12{\textendash}44\% of large and small POM are derived from {\textquotedblleft}pre-aged{\textquotedblright} 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.}, issn = {0016-7037}, doi = {10.1016/j.gca.2013.10.039}, url = {http://www.sciencedirect.com/science/article/pii/S001670371300611X}, author = {Walker, B. D. and Guilderson, T. P. and Okimura, K. M. and Peacock, M. B. and McCarthy, M. D.} } @article {547, title = {Sedimentary and faunal signatures of the post-glacial marine drowning of the Pontocaspian Gemlik {\textquotedblleft}lake{\textquotedblright} (Sea of Marmara)}, journal = {Quaternary International}, volume = {345}, year = {2014}, pages = {11-17}, abstract = {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 {\textpm} 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.}, issn = {1040-6182}, doi = {10.1016/j.quaint.2014.05.045}, author = {Taviani, M. and Angeletti, L. and Cagatay, M. N. and Gasperini, L. and Polonia, A. and Wesselingh, F. P.} } @article {2459, title = {Source and biolability of ancient dissolved organic matter in glacier and lake ecosystems on the Tibetan Plateau}, journal = {Geochimica et Cosmochimica Acta}, volume = {142}, year = {2014}, month = {Jan-10-2014}, pages = {64 - 74}, abstract = {The Tibetan Plateau is the world{\textquoteright}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{\textendash}27.9 μM) and ancient DOC radiocarbon ages (749{\textendash}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{\textendash}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.}, issn = {00167037}, doi = {10.1016/j.gca.2014.08.006}, url = {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}, author = {Spencer, Robert G.M. and Guo, Weidong and Raymond, Peter A. and Dittmar, Thorsten and Hood, Eran and Fellman, Jason and Stubbins, Aron} } @article { ISI:000372038300004, title = {Subsurface Evidence of Storm-Driven Breaching along a Transgressing Barrier System, Cape Cod, USA}, journal = {JOURNAL OF COASTAL RESEARCH}, volume = {32}, number = {{2}}, year = {2014}, month = {MAR}, pages = {264-279}, type = {Article}, abstract = {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.}, keywords = {coastal change, Coastal evolution, ground-penetrating radar, marine transgression, overwash, paleochannel, paleogeography, South Cape Beach}, issn = {0749-0208}, doi = {10.2112/JCOASTRES-D-14-00109.1}, author = {Maio, Christopher V. and Gontz, Allen M. and Sullivan, Richard M. and Madsen, Stephanie M. and Weidman, Christopher R. and Donnelly, Jeffrey P.} } @article { ISI:000351852200011, title = {Timing and preservation mechanism of deglacial pteropod spike from the Andaman Sea, northeastern Indian Ocean}, journal = {BOREAS}, volume = {44}, number = {{2}}, year = {2014}, month = {AUG}, pages = {432-444}, type = {Article}, abstract = {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.}, issn = {0300-9483}, doi = {10.1111/bor.12099}, author = {Sijinkumar, Adukkam V. and Nath, Bejugam N. and Guptha, Medimi V. S. and Ahmad, Syed M. and Rao, Bandaru R.} } @article {2475, title = {Validated age and growth estimates for Carcharhinus obscurus in the northwestern Atlantic Ocean, with pre- and post management growth comparisons}, journal = {Environmental Biology of Fishes}, volume = {97109251443124592565546445894545835645277154931266199319909310036110823842426199561196662521049}, year = {2014}, month = {Jan-08-2014}, pages = {881 - 896}, abstract = {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{\textendash} 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$\infty$=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.}, keywords = {Age and growth, bomb radiocarbon, Dusky shark, Elasmobranch, Validation, Vertebrae}, issn = {0378-1909}, doi = {10.1007/s10641-013-0189-4}, url = {http://link.springer.com/10.1007/s10641-013-0189-4http://link.springer.com/content/pdf/10.1007/s10641-013-0189-4}, author = {Natanson, Lisa J. and Gervelis, Brian J. and Winton, Megan V. and Hamady, Li Ling and Gulak, Simon J. B. and Carlson, John K.} } @article {87, title = {Anatomy of the La Jolla Submarine Canyon system; offshore southern California}, journal = {Marine Geology}, volume = {335}, year = {2013}, note = {id: 2302}, pages = {16-34}, abstract = {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{\textdegree} 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 (}, issn = {0025-3227}, doi = {10.1016/j.margeo.2012.10.003}, url = {http://www.sciencedirect.com/science/article/pii/S0025322712002150}, author = {Paull, C. K. and Caress, D. W. and Lundsten, E. and Gwiazda, R. and Anderson, K. and McGann, M. and Conrad, J. and Edwards, B. and Sumner, E. J.} } @article { ISI:000327567200017, title = {The Duxbury Sunken Forest-Constraints for Local, Late Holocene Environmental Changes Resulting from Marine Transgression, Duxbury Bay, Eastern Massachusetts, USA}, journal = {JOURNAL OF COASTAL RESEARCH}, volume = {29}, number = {{6A, S}}, year = {2013}, month = {NOV}, pages = {168-176}, type = {Article}, abstract = {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.}, keywords = {Cape Cod Bay, Coastal evolution, paleoforest, Radiocarbon dating, sea level, tree stumps}, issn = {0749-0208}, doi = {10.2112/JCOASTRES-D-12-00183.1}, author = {Gontz, Allen M. and Maio, Christopher V. and Rueda, Laura} } @article {107, title = {First high-resolution marinopalynological stratigraphy of Late Quaternary sediments from the central part of the Bulgarian Black Sea area}, journal = {Advancing Pleistocene and Holocene climate change research in the Carpathian-Balkan region}, volume = {293}, year = {2013}, note = {id: 2330}, pages = {170-183}, abstract = {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{\textendash}10 cm intervals. Sampling of the interval 141.5{\textendash}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{\textendash}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 {\textpm} 40 until 3120 {\textpm} 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 {\textquotedblleft}8200 yrs cold event{\textquotedblright} 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 (}, issn = {1040-6182}, doi = {10.1016/j.quaint.2012.05.002}, url = {http://www.sciencedirect.com/science/article/pii/S1040618212003229}, author = {Filipova-Marinova, Mariana and Pavlov, Danail and Coolen, Marco and Giosan, Liviu} } @article {2579, title = {Great longevity of speckled hind ( Epinephelus drummondhayi), a deep-water grouper, with novel use of postbomb radiocarbon dating in the Gulf of Mexico}, journal = {Canadian Journal of Fisheries and Aquatic Sciences}, volume = {70}, year = {2013}, month = {Jan-08-2013}, pages = {1131 - 1140}, abstract = {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{\textendash}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{\textendash}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{\textendash}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}, issn = {0706-652X}, doi = {10.1139/cjfas-2012-0537}, url = {http://www.nrcresearchpress.com/doi/abs/10.1139/cjfas-2012-0537}, author = {Andrews, Allen H. and Barnett, Beverly K. and Allman, Robert J. and Moyer, Ryan P. and Trowbridge, Hannah D. and Gillanders, Bronwyn} } @article {2447, title = {Holocene variability in hydrology, vegetation, fire, and eolian activity in the Nebraska Sand Hills, USA}, journal = {The Holocene}, volume = {23}, year = {2013}, month = {Jan-04-2013}, pages = {515 - 527}, abstract = {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.}, keywords = {diatoms, drought, Holocene climate change, lakes, Nebraska Sand Hills, pollen}, issn = {0959-6836}, doi = {10.1177/0959683612463100}, url = {http://journals.sagepub.com/doi/10.1177/0959683612463100}, author = {Schmieder, Jens and Fritz, Sherilyn C and Grimm, Eric C and Jacobs, Kimberly C and Brown, Kendrick J and Swinehart, James B and Porter, Stephen C} } @article {112, title = {The Last Glacial: Insights from continuous coring on the New Jersey continental shelf}, journal = {Marine Geology}, volume = {335}, year = {2013}, note = {id: 2317}, pages = {78-99}, abstract = {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{\textendash}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{\textendash}14 ka), shortly after the shoreline began to migrate landward. Rates of 1{\textendash}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 j{\"o}kelhlaup deposition associated with the Intra-Aller{\o}d 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{\textendash}3a.}, issn = {0025-3227}, doi = {10.1016/j.margeo.2012.10.015}, url = {http://www.sciencedirect.com/science/article/pii/S0025322712002381}, author = {Christensen, Beth A. and Alexander, Clark and Goff, John A. and Turner, R. Jessica and Austin Jr, James A.} } @article {105, title = {Maintenance of large deltas through channelization: Nature vs. humans in the Danube delta}, journal = {Anthropocene}, volume = {1}, year = {2013}, pages = {35-45}, abstract = {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{\textquoteright}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.}, issn = {2213-3054}, doi = {10.1016/j.ancene.2013.09.001}, url = {http://www.sciencedirect.com/science/article/pii/S221330541300012X}, author = {Giosan, Liviu and Constantinescu, Stefan and Filip, Florin and Deng, Bing} } @article { ISI:000327814700020, title = {Prominent bacterial heterotrophy and sources of C-13-depleted fatty acids to the interior Canada Basin}, journal = {BIOGEOSCIENCES}, volume = {10}, number = {{11}}, year = {2013}, pages = {7065-7080}, type = {Article}, abstract = {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.}, issn = {1726-4170}, doi = {10.5194/bg-10-7065-2013}, author = {Shah, S. R. and Griffith, D. R. and Galy, V. and McNichol, A. P. and Eglinton, T. I.} } @article {79, title = {Sedimentological and geomorphological imprints of Holocene tsunamis in southwestern Spain: An approach to establish the recurrence period}, journal = {Continental Shelf Drowned Landscapes (INQUA-CMP and IGCP-526)}, volume = {203}, year = {2013}, pages = {97-104}, abstract = {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{\textendash}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{\textendash}1000 years) in this area.}, issn = {0169-555X}, doi = {10.1016/j.geomorph.2013.09.008}, url = {http://www.sciencedirect.com/science/article/pii/S0169555X13004650}, author = {Ruiz, Francisco and Rodr{\'\i}guez-Vidal, Joaqu{\'\i}n and Abad, Manuel and C{\'a}ceres, Luis M. and Carretero, Mar{\'\i}a I. and Pozo, Manuel and Rodr{\'\i}guez-Llanes, Jos{\'e} M. and G{\'o}mez-Toscano, Francisco and Izquierdo, Tatiana and Font, Eric and Toscano, Antonio} } @article {106, title = {Should dates trump context? Evaluation of the Cave 7 skeletal assemblage radiocarbon dates}, journal = {Journal of Archaeological Science}, volume = {40}, year = {2013}, note = {id: 2281}, pages = {2754-2770}, abstract = {{\textquotedblleft}Massacre{\textquotedblright} 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{\textendash}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.{\textquoteright}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{\textendash}80 and doubtless had a significant social impact at the time because of its scale, reverberating throughout the early farming communities of the Southwest.}, issn = {0305-4403}, doi = {10.1016/j.jas.2013.01.034}, url = {http://www.sciencedirect.com/science/article/pii/S0305440313000575}, author = {Geib, Phil R. and Hurst, Winston B.} } @article {77, title = {Source, diagenesis, and fluxes of particulate organic carbon along the western Adriatic Sea (Mediterranean Sea)}, journal = {Marine Geology}, volume = {337}, year = {2013}, note = {id: 2335}, pages = {156-170}, abstract = {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{\textendash}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\%.}, issn = {0025-3227}, doi = {10.1016/j.margeo.2013.03.001}, url = {http://www.sciencedirect.com/science/article/pii/S0025322713000273}, author = {Tesi, T. and Langone, L. and Giani, M. and Ravaioli, M. and Miserocchi, S.} } @article {2482, title = {Surface production fuels deep heterotrophic respiration in northern peatlands}, journal = {Global Biogeochemical Cycles}, volume = {27}, year = {2013}, month = {Jan-12-2013}, pages = {1163 - 1174}, abstract = {[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.}, doi = {10.1002/2013GB004677}, url = {http://doi.wiley.com/10.1002/2013GB004677https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002\%2F2013GB004677}, author = {Elizabeth Corbett, J. and Burdige, David J. and Tfaily, Malak M. and Dial, Angela R. and Cooper, William T. and Glaser, Paul H. and Chanton, Jeffrey P.} } @article {124, title = {An ~11,200 cal yr BP paleolimnological perspective for the archeological findings at Quartz Lake, Alaska}, journal = {Journal of Paleolimnology}, volume = {48}, year = {2012}, note = {id: 2134}, pages = {83-99}, abstract = {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{\textquoteright}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 {\textperthousand}) 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{\textquoteright}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.}, doi = {10.1007/s10933-012-9610-9}, author = {Wooller, M. J. and Kurek, J. and Gaglioti, B. V. and Cwynar, L. C. and Bigelow, N. and Reuther, J. D. and Gelvin-Reymiller, C. and Smol, J. P.} } @article {157, title = {Anomalous biogeochemical behavior of cadmium in subantarctic surface waters: Mechanistic constraints from cadmium isotopes}, journal = {Earth and Planetary Science Letters}, volume = {341{\textendash}344}, year = {2012}, note = {id: 2339}, pages = {94-103}, abstract = {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.}, issn = {0012-821X}, doi = {10.1016/j.epsl.2012.06.005}, url = {http://www.sciencedirect.com/science/article/pii/S0012821X12002890}, author = {Gault-Ringold, Melanie and Adu, Toyin and Stirling, Claudine H. and Frew, Russell D. and Hunter, Keith A.} } @article {153, title = {Carbon dynamics in the western Arctic Ocean: insights from full-depth carbon isotope profiles of DIC, DOC, and POC}, journal = {Biogeosciences}, volume = {9}, year = {2012}, note = {id: 2254; PT: J; TC: 4; UT: WOS:000302179500026}, pages = {1217-1224}, abstract = {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.}, issn = {1726-4170}, doi = {10.5194/bg-9-1217-2012}, author = {Griffith, D. R. and McNichol, A. P. and Xu, L. and McLaughlin, F. A. and Macdonald, R. W. and Brown, K. A. and Eglinton, T. I.} } @article { ISI:000309889600007, title = {Carbon isotopic (C-13 and C-14) composition of synthetic estrogens and progestogens}, journal = {RAPID COMMUNICATIONS IN MASS SPECTROMETRY}, volume = {26}, number = {{22}}, year = {2012}, month = {NOV 30}, pages = {2619-2626}, type = {Article}, abstract = {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 {\textquoteleft}fossil{\textquoteright} carbon in the case of EE2 and norethindrone acetate. Exceptions are progestogens that contain an ethyl group at carbon position 13 and have entirely {\textquoteleft}fossil{\textquoteright} 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.}, issn = {0951-4198}, doi = {10.1002/rcm.6385}, author = {Griffith, David R. and Wacker, Lukas and Gschwend, Philip M. and Eglinton, Timothy I.} } @article {130, title = {Chemical and bacteriological analysis of soil from the Middle and Late Weichselian from Western Spitsbergen, Arctic}, journal = {The environment and chronology of the earliest occupation of north-west Europe: current knowledge, problems and new research directions}, volume = {271}, year = {2012}, note = {id: 2316}, pages = {98-105}, abstract = {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.}, issn = {1040-6182}, doi = {10.1016/j.quaint.2012.03.008}, url = {http://www.sciencedirect.com/science/article/pii/S1040618212001541}, author = {Singh, Shiv Mohan and Sharma, Jagdev and Gawas-Sakhalkar, Puja and Upadhyay, Ajay K. and Naik, Simantini and Bande, Dnyanesh and Ravindra, Rasik} } @article {152, title = {Chemical characteristics of particulate organic matter from a small, mountainous river in the Oregon Coast Range, USA}, journal = {Biogeochemistry}, volume = {107}, year = {2012}, note = {id: 890submittedY}, pages = {43-66}, doi = {10.1007/s10533-010-9529-z}, author = {Hatten, J. A. and Go{\~n}i, M. A. and Wheatcroft, R. A.} } @article {166, title = {Clay mineral variations in Holocene terrestrial sediments from the Indus Basin}, journal = {Quaternary Research}, volume = {77}, year = {2012}, note = {id: 2333}, pages = {368-381}, abstract = {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{\textendash}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{\textendash}}, issn = {0033-5894}, doi = {10.1016/j.yqres.2012.01.008}, url = {http://www.sciencedirect.com/science/article/pii/S0033589412000099}, author = {Alizai, Anwar and Hillier, Stephen and Clift, Peter D. and Giosan, Liviu and Hurst, Andrew and VanLaningham, Sam and Macklin, Mark} } @article {156, title = {Climatic and megaherbivory controls on late-glacial vegetation dynamics: a new, high-resolution, multi-proxy record from Silver Lake, Ohio}, journal = {Quaternary Science Reviews}, volume = {34}, year = {2012}, note = {id: 2141}, pages = {66-80}, abstract = {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{\textendash}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{\textendash}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.}, issn = {0277-3791}, doi = {10.1016/j.quascirev.2011.12.008}, url = {http://www.sciencedirect.com/science/article/pii/S027737911100401X}, author = {Gill, Jacquelyn L. and Williams, John W. and Jackson, Stephen T. and Donnelly, Jeffrey P. and Schellinger, Grace C.} } @article {2523, title = {Constraining Holocene 10Be production rates in Greenland}, journal = {Journal of Quaternary Science}, volume = {27}, year = {2012}, month = {Jan-01-2012}, pages = {2 - 6}, abstract = {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 Isbr{\ae}, 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 Isbr{\ae} forefield, we derive a 10Be production rate value of 3.98 {\textpm} 0.24 atoms g a-1, using the {\textquoteleft}St{\textquoteright} 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 {\textcopyright} 2011 John Wiley \& Sons, Ltd.}, doi = {10.1002/jqs.1562}, url = {http://doi.wiley.com/10.1002/jqs.1562}, author = {Briner, Jason P. and Young, {\'a}s E. and Goehring, Brent M. and Schaefer, Joerg M.} } @article {132, title = {Direct measurement of riverine particulate organic carbon age structure}, journal = {Geophysical Research Letters}, volume = {39}, year = {2012}, note = {id: 2248; PT: J; TC: 0; UT: WOS:000309605800002}, pages = {L19703-L19703}, abstract = {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.}, issn = {0094-8276}, doi = {10.1029/2012GL052883}, author = {Rosenheim, Brad E. and Galy, Valier} } @inbook {1401, title = {Exploring human subsistence at CA-SMI-575NE: An 8400-year-old shell midden on San Miguel Island, California}, booktitle = {Exploring Methods of Faunal Analysis: Insights from California Archaeology}, year = {2012}, note = {id: 2069}, month = {2012}, publisher = {Cotsen Institute of Archaeology Press}, organization = {Cotsen Institute of Archaeology Press}, isbn = {9781931745871}, author = {Erlandson, Jon M. and Braje, Todd J.}, editor = {Glassow, M.} } @article {2488, title = {Geologic methane seeps along boundaries of Arctic permafrost thaw and melting glaciers}, journal = {Nature Geoscience}, volume = {5}, year = {2012}, month = {Aug-05-2013}, pages = {419 - 426}, abstract = {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 {\textquoteleft}cryosphere cap{\textquoteright} 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{\textquoteright}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.}, keywords = {Biogeochemistry, Cryospheric science}, issn = {1752-0894}, doi = {10.1038/ngeo1480}, url = {http://www.nature.com/doifinder/10.1038/ngeo1480}, author = {Walter Anthony, Katey M. and Anthony, Peter and Grosse, Guido and Chanton, Jeffrey} } @article {127, title = {Geological interpretation of a low-backscatter anomaly found on the New Jersey continental margin}, journal = {Marine Geology}, volume = {326{\textendash}328}, year = {2012}, note = {id: 2328}, pages = {46-54}, abstract = {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.}, issn = {0025-3227}, doi = {10.1016/j.margeo.2012.08.007}, url = {http://www.sciencedirect.com/science/article/pii/S0025322712001831}, author = {Sweeney, Edward M. and Gardner, James V. and Johnson, Joel E. and Mayer, Larry A.} } @article {143, title = {The Medieval Climate Anomaly in the Iberian Peninsula reconstructed from marine and lake records}, journal = {Quaternary Science Reviews}, volume = {43}, year = {2012}, note = {id: 2334}, pages = {16-32}, abstract = {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{\textendash}1300 AD). The sequences enabled an integrated approach to land{\textendash}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{\textendash}900 years AD) and subsequent (the Little Ice Age, LIA: 1300{\textendash}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.}, issn = {0277-3791}, doi = {10.1016/j.quascirev.2012.04.007}, url = {http://www.sciencedirect.com/science/article/pii/S0277379112001485}, author = {Moreno, Ana and P{\'e}rez, Ana and Frigola, Jaime and Nieto-Moreno, Vanesa and Rodrigo-G{\'a}miz, Marta and Martrat, Bel{\'e}n and Gonz{\'a}lez-Samp{\'e}riz, Pen{\'e}lope and Morell{\'o}n, Mario and Mart{\'\i}n-Puertas, Celia and Corella, Juan Pablo and Belmonte, {\'A}nchel and Sancho, Carlos and Cacho, Isabel and Herrera, Gemma and Canals, Miquel and Grimalt, Joan O. and Jim{\'e}nez-Espejo, Francisco and Mart{\'\i}nez-Ruiz, Francisca and Vegas-Vilarr{\'u}bia, Teresa and Valero-Garc{\'e}s, Blas L.} } @article {161, title = {Molecular records of climate variability and vegetation response since the Late Pleistocene in the Lake Victoria basin, East Africa}, journal = {Quaternary Science Reviews}, volume = {55}, year = {2012}, note = {id: 2318}, pages = {59-74}, abstract = {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{\textquoteright}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{\textendash}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.}, issn = {0277-3791}, doi = {10.1016/j.quascirev.2012.08.014}, url = {http://www.sciencedirect.com/science/article/pii/S0277379112003216}, author = {Berke, Melissa A. and Johnson, Thomas C. and Werne, Josef P. and Grice, Kliti and Schouten, Stefan and Sinninghe Damst{\'e}, Jaap S.} } @article {155, title = {New Records for Prehistoric Introduction of Neotropical Mammals to the West Indies: Evidence from Carriacou, Lesser Antilles}, journal = {Journal of Biogeography}, volume = {39}, year = {2012}, note = {id: 1873SubmittedY}, pages = {476-487}, doi = {10.1111/j.1365-2699.2011.02630.x}, author = {Giovas, C. M. and LeFebvre, M. J. and Fitzpatrick, S. M.} } @article { ISI:000306950700015, title = {Paleoseismic and geomorphologic evidence of recent tectonic activity of the Pozohondo Fault (Betic Cordillera, SE Spain)}, journal = {JOURNAL OF IBERIAN GEOLOGY}, volume = {38}, number = {{1, SI}}, year = {2012}, pages = {239-251}, type = {Article}, abstract = {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.}, keywords = {Geomorphology, Paleoseismology, Prebetic, Quaternary, SE Spain}, issn = {1698-6180}, doi = {10.5209/rev_JIGE.2012.v38.n1.39216}, author = {Rodriguez-Pascua, M. A. and Perez-Lopez, R. and Garduno-Monroy, V. H. and Giner-Robles, J. L. and Silva, P. G. and Perucha-Atienza, M. A. and Hernandez-Madrigal, V. M. and Bischoff, J.} } @article {2483, title = {Radiocarbon evidence that carbon from the Deepwater Horizon spill entered the planktonic food web of the Gulf of Mexico}, journal = {Environmental Research Letters}, volume = {7}, year = {2012}, month = {Jan-12-2012}, pages = {045303}, abstract = {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{\textendash}7{\textperthousand} in stable carbon isotope (δ13C) space, while in radiocarbon (Δ14C) space these two potential sources are separated by more than 1000{\textperthousand}. 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. }, doi = {10.1088/1748-9326/7/4/045303}, url = {http://stacks.iop.org/1748-9326/7/i=4/a=045303?key=crossref.bb52d0d288c12eb2c6f2ac2b8f8facea}, author = {Chanton, J P and Cherrier, J and Wilson, R M and Sarkodee-Adoo, J and Bosman, S and Mickle, A and Graham, W M} } @article { ISI:000312696400053, title = {Radiocarbon evidence that carbon from the Deepwater Horizon spill entered the planktonic food web of the Gulf of Mexico}, journal = {ENVIRONMENTAL RESEARCH LETTERS}, volume = {7}, number = {{4}}, year = {2012}, month = {OCT-DEC}, type = {Article}, abstract = {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.}, keywords = {carbon isotope, Gulf oil spill, methane, petroleum hydrocarbon, radiocarbon}, issn = {1748-9326}, doi = {10.1088/1748-9326/7/4/045303}, author = {Chanton, J. P. and Cherrier, J. and Wilson, R. M. and Sarkodee-Adoo, J. and Bosman, S. and Mickle, A. and Graham, W. M.} } @article {2556, title = {Refining the model of barrier island formation along a paraglacial coast in the Gulf of Maine}, journal = {Marine Geology}, volume = {307-310}, year = {2012}, month = {Jan-04-2012}, pages = {40 - 57}, abstract = {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{\textendash}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{\textendash}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{\textendash}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, {\textquotedblleft}post-paraglacial{\textquotedblright} 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.}, keywords = {barrier-island formation, ground-penetrating radar, inlet processes, inlet-fill sequence, paraglacial, spit accretion}, issn = {00253227}, doi = {10.1016/j.margeo.2012.03.001}, url = {https://doi.org/10.1016/j.margeo.2012.03.001}, author = {Hein, Christopher J. and FitzGerald, Duncan M. and Carruthers, Emily A. and Stone, Byron D. and Barnhardt, Walter A. and Gontz, Allen M.} } @article {226, title = {14C-Based source assessment of soot aerosols in Stockholm and the Swedish EMEP-Aspvreten regional background site}, journal = {Atmospheric Environment}, volume = {45}, year = {2011}, note = {id: 2148}, pages = {215-222}, abstract = {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 {\textdegree}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.}, issn = {1352-2310}, doi = {10.1016/j.atmosenv.2010.09.015}, url = {http://www.sciencedirect.com/science/article/pii/S1352231010007697}, author = {Andersson, August and Sheesley, Rebecca J. and Krus{\r a}, Martin and Johansson, Christer and Gustafsson, {\"O}rjan} } @article {175, title = {Associated terrestrial and marine fossils in the late-glacial Presumpscot Formation, southern Maine, USA, and the marine reservoir effect on radiocarbon ages}, journal = {Quaternary Research}, volume = {75}, year = {2011}, note = {id: 2011; PT: J; UT: WOS:000290831500018}, pages = {552-565}, abstract = {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{\textquoteright}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.}, issn = {0033-5894}, doi = {10.1016/j.yqres.2011.02.002}, author = {Thompson, Woodrow B. and Griggs, Carol B. and Miller, Norton G. and Nelson, Robert E. and Weddle, Thomas K. and Kilian, Taylor M.} } @article {204, title = {Bomb-produced radiocarbon validation of growth-increment crossdating allows marine paleoclimate reconstruction}, journal = {Palaeogeography, Palaeoclimatology, Palaeoecology}, volume = {311}, year = {2011}, note = {id: 2167}, pages = {126-135}, abstract = {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.}, issn = {0031-0182}, doi = {10.1016/j.palaeo.2011.08.015}, url = {http://www.sciencedirect.com/science/article/pii/S0031018211004524}, author = {Kastelle, Craig R. and Helser, Thomas E. and Black, Bryan A. and Stuckey, Matthew J. and C. Gillespie, Darlene and McArthur, Judy and Little, Diana and D. Charles, Karen and Khan, Reziah S.} } @article {209, title = {Contemporary 14C radiocarbon levels of oxygenated polybrominated diphenyl ethers (O-PBDEs) isolated in sponge{\textendash}cyanobacteria associations}, journal = {Marine pollution bulletin}, volume = {62}, year = {2011}, note = {id: 2192}, pages = {631-636}, abstract = {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.}, issn = {0025-326X}, doi = {10.1016/j.marpolbul.2010.12.022}, url = {http://www.sciencedirect.com/science/article/pii/S0025326X11000075}, author = {Guitart, Carlos and Slattery, Marc and Ankisetty, Sridevi and Radwan, Mohamed and Ross, Samir J. and Letcher, Robert J. and Reddy, Christopher M.} } @article {169, title = {The detailed palaeoecology of a mid-Wisconsinan interstadial (ca. 32 000 (14)C a BP) vegetation surface from interior Alaska}, journal = {Journal of Quaternary Science}, volume = {26}, year = {2011}, note = {id: 2131; PT: J; TC: 1; UT: WOS:000296091300010}, pages = {746-756}, abstract = {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{\textquoteright}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.}, issn = {0267-8179}, doi = {10.1002/jqs.1497}, author = {Wooller, Matthew J. and Zazula, Grant D. and Blinnikov, Misha and Gaglioti, Benjamin V. and Bigelow, Nancy H. and Sanborn, Paul and Kuzmina, Svetlana and La Farge, Catherine} } @article {208, title = {East{\textendash}West similarities and differences in the surface and deep northern Arabian Sea records during the past 21 Kyr}, journal = {Palaeogeography, Palaeoclimatology, Palaeoecology}, volume = {301}, year = {2011}, note = {id: 2100}, pages = {75-85}, abstract = {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{\textendash}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.}, issn = {0031-0182}, doi = {10.1016/j.palaeo.2010.12.027}, url = {http://www.sciencedirect.com/science/article/pii/S0031018211000022}, author = {Gupta, Anil K. and Mohan, K. and Sarkar, Sudipta and Clemens, Steven C. and Ravindra, Rasik and Uttam, Rajesh K.} } @article {211, title = {Geological slip rates along the North Anatolian Fault in the Marmara region}, journal = {Tectonics}, volume = {30}, year = {2011}, note = {id: 2112; PT: J; TC: 0; J9: TECTONICS; UT: WOS:000296619700001}, pages = {TC6001-TC6001}, abstract = {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.}, issn = {0278-7407}, doi = {10.1029/2011TC002906}, author = {Gasperini, Luca and Polonia, Alina and {\c C}a{\u g}atay, M. Namik and Bortoluzzi, Giovanni and Ferrante, Valentina} } @book {1370, title = {Geology and Geoarchaeology of the Black Sea Region: Beyond the Flood Hypothesis}, series = {Special papers (Geological Society of America)}, volume = {473}, year = {2011}, note = {id: 2127}, month = {2011}, pages = {196}, publisher = {Geological Society of America}, organization = {Geological Society of America}, isbn = {9780813724737}, author = {Buynevich, I. V. and Yanko-Hombach, V. V. and Gilbert, A. S. and and Martin, R. E.} } @article {216, title = {Late glacial to Holocene sea-level changes in the Sea of Marmara: new evidence from high-resolution seismics and core studies}, journal = {Geo-Marine Letters}, volume = {31}, year = {2011}, note = {id: 2113; PT: J; TC: 0; J9: GEO-MAR LETT; UT: WOS:000286334700001}, pages = {1-18}, abstract = {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 {\textquoteright}Lake{\textquoteright} 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.}, issn = {0276-0460}, doi = {10.1007/s00367-010-0211-1}, author = {Eri{\c s}, K{\"u}r{\c s}ad Kadir and Cagatay, M. N. and Akcer, Sena and Gasperini, Luca and Mart, Yosi} } @article {213, title = {Late Pleistocene paleoecology of arctic ground squirrel (Urocitellus parryii) caches and nests from Interior Alaska{\textquoteright}s mammoth steppe ecosystem, USA}, journal = {Quaternary Research}, volume = {76}, year = {2011}, note = {id: 2130; PT: J; TC: 0; UT: WOS:000296672100009}, pages = {373-382}, abstract = {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{\textquoteright}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.}, issn = {0033-5894}, doi = {10.1016/j.yqres.2011.08.004}, author = {Gaglioti, Benjamin V. and Barnes, Brian M. and Zazula, Grant D. and Beaudoin, Alwynne B. and Wooller, Matthew J.} } @article { ISI:000290199000003, title = {Multiple-source heterotrophy fueled by aged organic carbon in an urbanized estuary}, journal = {MARINE CHEMISTRY}, volume = {124}, number = {{1-4}}, year = {2011}, month = {MAR 20}, pages = {14-22}, type = {Article}, abstract = {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.}, keywords = {(13)C, (14)C, Carbon cycle, Carbon dioxide, Chlorophyll, dissolved organic carbon, Heterotrophy, Hudson River Estuary, Isotope mixing curves, Sewage, USA, Wastewater}, issn = {0304-4203}, doi = {10.1016/j.marchem.2010.11.003}, author = {Griffith, David R. and Raymond, Peter A.} } @article {227, title = {Pb isotopic variability in the modern-Pleistocene Indus River system measured by ion microprobe in detrital K-feldspar grains}, journal = {Geochimica et Cosmochimica Acta}, volume = {75}, year = {2011}, note = {id: 2171}, pages = {4771-4795}, abstract = {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{\textendash}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{\textendash}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.}, issn = {0016-7037}, doi = {10.1016/j.gca.2011.05.039}, url = {http://www.sciencedirect.com/science/article/pii/S0016703711003164}, author = {Alizai, Anwar and Clift, Peter D. and Giosan, Liviu and VanLaningham, Sam and Hinton, Richard and Tabrez, Ali R. and Danish, Muhammad} } @article {212, title = {The provenance of vegetation and environmental signatures encoded in vascular plant biomarkers carried by the Ganges{\textendash}Brahmaputra rivers}, journal = {Earth and Planetary Science Letters}, volume = {304}, year = {2011}, note = {id: 2187}, pages = {1-12}, abstract = {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{\textendash}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{\textendash}Brahmaputra basin. Detailed studies of the {\textquotedblleft}isotopic anatomy{\textquotedblright} of modern river systems are critical for informed interpretation of marine sedimentary records in river-influenced continental margins.}, issn = {0012-821X}, doi = {10.1016/j.epsl.2011.02.003}, url = {http://www.sciencedirect.com/science/article/pii/S0012821X11000744}, author = {Galy, Valier and Eglinton, Timothy and France-Lanord, Christian and Sylva, Sean} } @article {221, title = {Rapid coastal dune migration into temperate and equatorial forests: optical chronology of imaged upper slipface strata}, journal = {Journal of Coastal Research}, year = {2011}, note = {id: 2124}, pages = {726-730}, abstract = {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 (Par{\'a} 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.}, issn = {0749-0208}, author = {Buynevich, I. V. and Bitinas, A. and Souza Filho, P. W. M. and Pupienis, D. and Asp, N. E. and Goble, R. J. and Kerber, L. E.} } @article {2448, title = {A regional-scale climate reconstruction of the last 4000 years from lakes in the Nebraska Sand Hills, USA}, journal = {Quaternary Science Reviews}, volume = {30}, year = {2011}, month = {Jan-06-2011}, pages = {1797 - 1812}, abstract = {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.}, keywords = {diatoms, Droughts, Great Plains, Holocene, lakes, Nebraska Sand Hills, paleolimnology}, issn = {0277-3791}, doi = {10.1016/j.quascirev.2011.04.011}, url = {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}, author = {Schmieder, J. and Fritz, S.C. and Swinehart, J.B. and Shinneman, A.L.C. and Wolfe, A.P. and Miller, G. and Daniels, N. and Jacobs, K.C. and Grimm, E.C.} } @article {198, title = {Retreat of the East Antarctic ice sheet during the last glacial termination RID F-5711-2011}, journal = {Nature Geoscience}, volume = {4}, year = {2011}, note = {id: 2003; PT: J; UT: WOS:000287802300021}, pages = {195-202}, abstract = {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.}, issn = {1752-0894}, doi = {10.1038/NGEO1061}, author = {Mackintosh, Andrew and Golledge, Nicholas and Domack, Eugene and Dunbar, Robert and Leventer, Amy and White, Duanne and Pollard, David and DeConto, Robert and Fink, David and Zwartz, Dan and Gore, Damian and Lavoie, Caroline} } @article {173, title = {Sea level controls sedimentation and environments in coastal caves and sinkholes}, journal = {Marine Geology}, volume = {286}, year = {2011}, note = {id: 2058; PT: J; UT: WOS:000295104800003}, pages = {35-50}, abstract = {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 (}, issn = {0025-3227}, doi = {10.1016/j.margeo.2011.05.004}, author = {van Hengstum, Peter J. and Scott, David B. and Groecke, Darren R. and Charette, Matthew A.} } @article {185, title = {Siliceous productivity changes in Gulf of Ancud sediments (42{\textdegree}S, 72{\textdegree}W), southern Chile, over the last \~{}150 years}, journal = {Fjord Oceanography of the Chilean Patagonia}, volume = {31}, year = {2011}, note = {id: 2191}, pages = {356-365}, abstract = {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, Chilo{\'e} Inner Sea (42{\textdegree}S, 72{\textdegree}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={\textendash}20.75{\textperthousand}{\textpm}0.82, δ15N=8.7{\textpm}0.35{\textperthousand}, and C/N=8.76{\textpm}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{\textdegree}S), as well as a warmer and more stratified water column, especially since the 1980s.}, issn = {0278-4343}, doi = {10.1016/j.csr.2010.06.015}, url = {http://www.sciencedirect.com/science/article/pii/S0278434310002177}, author = {Rebolledo, Lorena and Gonz{\'a}lez, Humberto E. and Mu{\~n}oz, Praxedes and Iriarte, Jos{\'e} L. and Lange, Carina B. and Pantoja, Silvio and Salamanca, Marco} } @article {228, title = {Sources of n-alkanes in an urbanized estuary: Insights from molecular distributions and compound-specific stable and radiocarbon isotopes}, journal = {Marine Chemistry}, volume = {126}, year = {2011}, note = {id: 2169}, pages = {239-249}, abstract = {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{\textendash}C33 n-alkanes became progressively lower in samples closer to the mouth of estuary. δ13C signatures of C19{\textendash}C31 n-alkanes ranged from - 37.1 to - 29.3{\textperthousand} and in general became more depleted with increasing carbon number. Δ14C values for C21 (- 945 to - 738{\textperthousand}) were significantly more depleted compared to C29 (- 591 to - 65{\textperthousand}) and C31 (- 382 to - 96{\textperthousand}), 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{\textperthousand} 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.}, issn = {0304-4203}, doi = {10.1016/j.marchem.2011.06.002}, author = {Ahad, Jason M. E. and Ganeshram, Raja S. and Bryant, Charlotte L. and Cisneros-Dozal, Luz M. and Ascough, Philippa L. and Fallick, Anthony E. and Slater, Greg F.} } @article {172, title = {U-series dating of co-seismic gypsum and submarine paleoseismology of active faults in Northern Chile (23{\textdegree}S)}, journal = {Tectonophysics}, volume = {497}, year = {2011}, note = {id: 2147}, pages = {34-44}, abstract = {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{\textendash}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 {\textpm} 1.7 ka, 11 {\textpm} 4 ka and 2.4 {\textpm} 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{\textendash}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.}, issn = {0040-1951}, doi = {10.1016/j.tecto.2010.10.017}, url = {http://www.sciencedirect.com/science/article/pii/S0040195110004506}, author = {Vargas, Gabriel and Palacios, Carlos and Reich, Martin and Luo, Shangde and Shen, Chuan-Chou and Gonz{\'a}lez, Gabriel and Wu, Yi-Chen} } @article {1831, title = {A Continuous-Flow Gas Chromatography C-14 Accelerator Mass Spectrometry System}, journal = {Radiocarbon}, volume = {52}, year = {2010}, note = {Sp. Iss. 1696jn Times Cited:4 Cited References Count:24 }, month = {2010}, pages = {295-300}, abstract = {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.}, keywords = {ams system, gc-ams, negative-ion source, RADIOCARBON ANALYSIS}, isbn = {0033-8222}, author = {McIntyre, C. P. and Galutschek, E. and Roberts, M. L. and von Reden, K. F. and McNichol, A. P. and Jenkins, W. J.} } @article {446, title = {Deep-sea faunal provinces and their inferred environments in the Indian Ocean based on distribution of Recent benthic foraminifera}, journal = {Palaeogeography Palaeoclimatology Palaeoecology}, volume = {291}, year = {2010}, note = {id: 1967; PT: J; UT: WOS:000278782400021}, pages = {429-442}, abstract = {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.}, issn = {0031-0182}, doi = {10.1016/j.palaeo.2010.03.012}, author = {De, Soma and Gupta, Anil K.} } @article {398, title = {Determination of Microbial Carbon Sources and Cycling during Remediation of Petroleum Hydrocarbon Impacted Soil Using Natural Abundance (14)C Analysis of PLFA}, journal = {Environmental science \& technology}, volume = {44}, year = {2010}, note = {id: 2054; PT: J; UT: WOS:000275993700017}, pages = {2322-2327}, abstract = {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.}, issn = {0013-936X}, doi = {10.1021/es9029717}, author = {Cowie, Benjamin R. and Greenberg, Bruce M. and Slater, Gregory F.} } @article {425, title = {Developing graminoid cuticle analysis for application to Beringian palaeoecology}, journal = {Review of palaeobotany and palynology}, volume = {162}, year = {2010}, note = {id: 2132; PT: J; TC: 3; UT: WOS:000281181100009}, pages = {95-110}, abstract = {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{\textquoteright}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.}, issn = {0034-6667}, doi = {10.1016/j.revpalbo.2010.06.003}, author = {Gaglioti, B. V. and Severin, K. and Wooller, M. J.} } @article { ISI:000282251700009, title = {Evidence for size increase in an exploited mollusc: humped conch (Strombus gibberulus) at Chelechol ra Orrak, Palau from ca. 3000-0 BP}, journal = {JOURNAL OF ARCHAEOLOGICAL SCIENCE}, volume = {37}, number = {{11}}, year = {2010}, month = {NOV}, pages = {2788-2798}, type = {Article}, abstract = {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.}, keywords = {Anthropogenic impacts, Humped conch, Micronesia, Molluscs, Pacific Islands, Palau}, issn = {0305-4403}, doi = {10.1016/j.jas.2010.06.013}, author = {Giovas, Christina M. and Fitzpatrick, Scott M. and Clark, Meagan and Abed, Mira} } @mastersthesis {1309, title = {Foraminiferal indicators of paleoceanographic and sea-ice conditions in the Amundsen Gulf and Viscount Melville Sound, Canadian Arctic}, volume = {M.Sc.}, year = {2010}, month = {2010}, school = {DALHOUSIE UNIVERSITY}, abstract = {Sediment cores were collected from the Canadian Arctic Archipelago to reconstruct the region{\textquoteright}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.}, keywords = {Biological oceanography, Environmental science, Paleoclimate Science, Paleontology}, author = {Gibb, Olivia T.} } @article {325, title = {Geology of Lonar Crater, India}, journal = {Geological Society of America Bulletin}, volume = {122}, year = {2010}, note = {id: 1846; 539YI Times Cited:0 Cited References Count:100Y}, pages = {109-126}, abstract = {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.}, issn = {0016-7606}, doi = {10.1130/B26474.1}, author = {Maloof, A. C. and Stewart, S. T. and Weiss, B. P. and Soule, S. A. and Swanson-Hysell, N. L. and Louzada, K. L. and Garrick-Bethell, I. and Poussart, P. M.} } @article {380, title = {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}, journal = {Journal of Geophysical Research-Oceans}, volume = {115}, year = {2010}, note = {id: 1962; PT: J; UT: WOS:000278735700001}, pages = {C06008-C06008}, abstract = {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.}, issn = {0148-0227}, doi = {10.1029/2009JC005586}, author = {Grottoli, Andrea G. and Adkins, Jess F. and Panero, Wendy R. and Reaman, Daniel M. and Moots, Kate} } @article {355, title = {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}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {107}, year = {2010}, note = {id: 1951; PT: J; UT: WOS:000283749000034}, pages = {18909-18914}, abstract = {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.}, issn = {0027-8424}, doi = {10.1073/pnas.1007692107}, author = {Colombaroli, Daniele and Gavin, Daniel G.} } @article {246, title = {A High-Performance (14)c Accelerator Mass Spectrometry System}, journal = {Radiocarbon}, volume = {52}, year = {2010}, note = {id: 2095; PT: J; CT: 20th International Radiocarbon Conference; CY: MAY 31-JUN 05, 2009; CL: Big Isl, HI; SI: 1; UT: WOS:000285437800005}, pages = {228-235}, abstract = {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.}, issn = {0033-8222}, doi = {10.2458/azu_js_rc.52.3657}, author = {Roberts, M. L. and Burton, J. R. and Elder, K. L. and Longworth, B. E. and McIntyre, C. P. and von Reden, K. F. and Han, B. X. and Rosenheim, B. E. and W. J. Jenkins and Galutschek, E. and McNichol, A. P.} } @article {427, title = {Holocene earthquake record offshore Portugal (SW Iberia): testing turbidite paleoseismology in a slow-convergence margin}, journal = {Quaternary Science Reviews}, volume = {29}, year = {2010}, note = {id: 1959; PT: J; UT: WOS:000277813300008}, pages = {1156-1172}, abstract = {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.}, issn = {0277-3791}, doi = {10.1016/j.quascirev.2010.01.010}, author = {Gracia, Eulalia and Vizcaino, Alexis and Escutia, Carlota and Asioli, Alessandra and Rodes, Angel and Pallas, Raimon and Garcia-Orellana, Jordi and Lebreiro, Susana and Goldfinger, Chris} } @article {248, title = {In situ cosmogenic (10)Be production-rate calibration from the Southern Alps, New Zealand RID D-4720-2011}, journal = {Quaternary Geochronology}, volume = {5}, year = {2010}, note = {id: 2031; PT: J; UT: WOS:000280946500002}, pages = {392-409}, abstract = {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 {\textquoteright}07KNSTD{\textquoteright} (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.}, issn = {1871-1014}, doi = {10.1016/j.quageo.2009.12.001}, author = {Putnam, A. E. and Schaefer, J. M. and Barrell, D. J. A. and Vandergoes, M. and Denton, G. H. and Kaplan, M. R. and Finkel, R. C. and Schwartz, R. and Goehring, B. M. and Kelley, S. E.} } @article { ISI:000280946500002, title = {In situ cosmogenic Be-10 production-rate calibration from the Southern Alps, New Zealand}, journal = {QUATERNARY GEOCHRONOLOGY}, volume = {5}, number = {{4}}, year = {2010}, month = {AUG}, pages = {392-409}, type = {Article}, abstract = {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 {\textquoteleft}07KNSTD{\textquoteright} 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.}, keywords = {Be-10, C-14, Cosmogenic nuclide, Debris flow, Holocene, Last glacial maximum, Moraine, Production rate, South Island}, issn = {1871-1014}, doi = {10.1016/j.quageo.2009.12.001}, author = {Putnam, A. E. and Schaefer, J. M. and Barrell, D. J. A. and Vandergoes, M. and Denton, G. H. and Kaplan, M. R. and Finkel, R. C. and Schwartz, R. and Goehring, B. M. and Kelley, S. E.} } @article {472, title = {The influence of sea level and tectonics on Late Pleistocene through Holocene sediment storage along the high-sediment supply Waipaoa continental shelf}, journal = {Marine Geology}, volume = {270}, year = {2010}, note = {id: 1849; Sp. Iss. SI 576IF Times Cited:7 Cited References Count:49Y}, pages = {139-159}, abstract = {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{\textquoteright}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.}, issn = {0025-3227}, doi = {10.1016/j.margeo.2009.10.002}, author = {Gerber, T. P. and Pratson, L. F. and Kuehl, S. and Walsh, J. P. and Alexander, C. and Palmer, A.} } @article {245, title = {Late Quaternary record of pteropod preservation from the Andaman Sea}, journal = {Marine Geology}, volume = {275}, year = {2010}, note = {id: 2018; PT: J; UT: WOS:000281217300016}, pages = {221-229}, abstract = {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.}, issn = {0025-3227}, doi = {10.1016/j.margeo.2010.06.003}, author = {Sijinkumar, A. V. and Nath, B. Nagender and Guptha, M. V. S.} } @article {381, title = {Mid-Brunhes strengthening of the Indian Ocean Dipole caused increased equatorial East African and decreased Australasian rainfall}, journal = {Geophysical Research Letters}, volume = {37}, year = {2010}, note = {id: 1966; PT: J; UT: WOS:000276025100002}, pages = {L06706-L06706}, abstract = {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.}, issn = {0094-8276}, doi = {10.1029/2009GL042225}, author = {Gupta, Anil K. and Sarkar, Sudipta and De, Soma and Clemens, Steven C. and Velu, Angamuthu} } @article {241, title = {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)}, journal = {Quaternary Science Reviews}, volume = {29}, year = {2010}, note = {id: 1982; PT: J; UT: WOS:000285222000001}, pages = {3677-3682}, abstract = {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.}, issn = {0277-3791}, doi = {10.1016/j.quascirev.2010.08.017}, author = {Turney, Chris S. M. and Fifield, L. Keith and Hogg, Alan G. and Palmer, Jonathan G. and Hughen, Konrad and Baillie, Mike G. L. and Galbraith, Rex and Ogden, John and Lorrey, Andrew and Tims, Stephen G. and Jones, Richard T.} } @article { ISI:000284192000011, title = {The radiocarbon age of organic carbon in marine surface sediments}, journal = {GEOCHIMICA ET COSMOCHIMICA ACTA}, volume = {74}, number = {{23}}, year = {2010}, month = {DEC 1}, pages = {6788-6800}, type = {Article}, abstract = {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 ({{\textquoteright}{\textquoteright}}degradable,{{\textquoteright}{\textquoteright}} {\textquoteleft}{\textquoteleft}semi-labile,{{\textquoteright}{\textquoteright}} and {\textquoteleft}{\textquoteleft}refractory{{\textquoteright}{\textquoteright}}) and assumes that (14)C(TOC) flux to sediments is exclusively derived from surface ocean primary productivity, and hence follows a {\textquoteleft}{\textquoteleft}generic{{\textquoteright}{\textquoteright}} 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.}, issn = {0016-7037}, doi = {10.1016/j.gca.2010.09.001}, author = {Griffith, David R. and Martin, William R. and Eglinton, Timothy I.} } @conference {1277, title = {Radiocarbon in the Canada Basin: Carbon Transfer Processes in the Changing Arctic}, booktitle = {Proceedings from the 2010 AGU Ocean Sciences Meeting}, year = {2010}, note = {Date revised - 2010-09-01SuppNotes - Abstracts AvailableLast updated - 2016-12-22}, month = {February 2010}, publisher = {American Geophysical Union, 2000 Florida Ave., N.W. Washington DC 20009 USA, [URL:http://www.agu.org]}, organization = {American Geophysical Union, 2000 Florida Ave., N.W. Washington DC 20009 USA, [URL:http://www.agu.org]}, abstract = {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.}, keywords = {and modeling, Biogeochemical cycles, carbon cycling, processes, Radioactivity and radioisotopes}, url = {https://search.proquest.com/docview/754883766?accountid=29119}, author = {McNichol, A P and Xu, L and Griffith, D R and Eglinton, T I and Macdonald, R and McLaughlin, F A} } @article {353, title = {Rapid Climatic Signal Propagation from Source to Sink in a Southern California Sediment-Routing System}, journal = {Journal of Geology}, volume = {118}, year = {2010}, note = {id: 875; 574IR Times Cited:0 Cited References Count:55Y}, pages = {247-259}, abstract = {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.}, issn = {0022-1376}, doi = {10.1086/651539}, author = {Covault, J. A. and Romans, B. W. and Fildani, A. and McGann, M. and Graham, S. A.} } @article {234, title = {Recent shoaling of the nutricline and thermocline in the western tropical Pacific}, journal = {Geophysical Research Letters}, volume = {37}, year = {2010}, note = {id: 1961; PT: J; UT: WOS:000284479000002}, pages = {L22601-L22601}, abstract = {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.}, issn = {0094-8276}, doi = {10.1029/2010GL044867}, author = {Williams, Branwen and Grottoli, Andrea G.} } @article {506, title = {Reconnaissance dating A new radiocarbon method applied to assessing the temporal distribution of Southern Ocean deep-sea corals}, journal = {Deep-Sea Research Part I-Oceanographic Research Papers}, volume = {57}, year = {2010}, note = {id: 1924; PT: J; UT: WOS:000284750700012}, pages = {1510-1520}, abstract = {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}, issn = {0967-0637}, doi = {10.1016/j.dsr.2010.07.010}, author = {Burke, Andrea and Robinson, Laura F. and McNichol, Ann P. and W. J. Jenkins and Scanlon, Kathryn M. and Gerlach, Dana S.} } @article {2464, title = {The role of glacio-eustasy in sequence formation: Mid-Atlantic Continental Margin, USA}, journal = {Marine Geology}, volume = {277}, year = {2010}, month = {Jan-11-2010}, pages = {31 - 47}, abstract = {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.}, keywords = {Hudson Canyon; Hudson Shelf Valley, Last glacial maximum, Mid-Atlantic Continental Margin, paleoshoreline, sequence stratigraphy}, issn = {00253227}, doi = {10.1016/j.margeo.2010.08.009}, url = {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}, author = {McHugh, Cecilia M. and Hartin, Corinne A. and Mountain, Gregory S. and Gould, Helene M.} } @article {236, title = {Selective preservation of old organic carbon fluvially released from sub-Arctic soils}, journal = {Geophysical Research Letters}, volume = {37}, year = {2010}, note = {id: 886; 610KU Times Cited:7 Cited References Count:30Y}, abstract = {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.}, issn = {0094-8276}, doi = {10.1029/2010gl042909}, author = {Vonk, J. E. and van Dongen, B. E. and Gustafsson, O.} } @conference {1793, title = {The southern Svalbard Margin sedimentary system: preliminary results from EGLACOM cruise 2008}, booktitle = {European Geosciences Union, General Assembly 2010}, year = {2010}, note = {id: 873}, month = {2010}, address = {Vienna, Austria}, author = {Melis, R. and Lucchi, R. G. and Giorgetti, G. and Persico, D. and B{\'A}Rcena, M. A. A. and Caburlotto, A. and Macr{\`I}, P. and Villa, G. and Sagnotti, L. and Rebesco, M.} } @article { ISI:000275306200022, title = {Sr-Nd-Os evidence for a stable erosion regime in the Himalaya during the past 12 Myr}, journal = {EARTH AND PLANETARY SCIENCE LETTERS}, volume = {290}, number = {{3-4}}, year = {2010}, month = {FEB 20}, pages = {474-480}, type = {Article}, abstract = {Modern erosion of the Himalaya, the world{\textquoteright}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.}, keywords = {Bengal Fan, climate, erosion, Himalaya, Miocene, radiogenic isotopes}, issn = {0012-821X}, doi = {10.1016/j.epsl.2010.01.004}, author = {Galy, Valier and France-Lanord, Christian and Peucker-Ehrenbrink, Bernhard and Huyghe, Pascale} } @article {233, title = {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}, journal = {Geochimica et Cosmochimica Acta}, volume = {74}, year = {2010}, note = {id: 1963; PT: J; UT: WOS:000281094900009}, pages = {5280-5288}, abstract = {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 (}, issn = {0016-7037}, doi = {10.1016/j.gca.2010.06.026}, author = {Williams, Branwen and Grottoli, Andrea G.} } @conference {958, title = {Year-round probing of soot carbon and secondary organic carbon contributions and sources to the South Asian Atmospheric Brown Cloud using radiocarbon (14C) measurements}, booktitle = {EGU General Assembly 2010, held 2-7 May, 2010 in Vienna, Austria}, volume = {12}, year = {2010}, note = {id: 870Y}, month = {05/2010}, abstract = {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.}, author = {Kirillova, Elena and Sheesley, Rebecca J. and Andersson, August and Krus{\r a}, Martin and Safai, P. D. and Budhavant, Krishnakant and Rao, P. S. P. and Praveen, P. S. and Gustafsson, {\"O}rjan} } @article {256, title = {Bioturbation artifacts in zero-age sediments}, journal = {Paleoceanography}, volume = {24}, year = {2009}, note = {id: 1826; 535DQ Times Cited:0 Cited References Count:18; YY}, abstract = {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.}, issn = {0883-8305}, doi = {10.1029/2008pa001727}, author = {Keigwin, L. D. and Guilderson, T. P.} } @article {480, title = {Black carbon in marine particulate organic carbon: Inputs and cycling of highly recalcitrant organic carbon in the Gulf of Maine}, journal = {Marine Chemistry}, volume = {113}, year = {2009}, note = {id: 1865; 440SC Times Cited:0 Cited References Count:85; YY}, pages = {172-181}, abstract = {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}, issn = {0304-4203}, doi = {10.1016/j.marchem.2009.01.012}, author = {Flores-Cervantes, D. X. and Plata, D. L. and MacFarlane, J. K. and Reddy, C. M. and Gschwend, P. M.} } @article {332, title = {Brown Clouds over South Asia: Biomass or Fossil Fuel Combustion?}, journal = {Science}, volume = {323}, year = {2009}, note = {id: 1867; 396JL Times Cited:8 Cited References Count:33Y}, pages = {495-498}, abstract = {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.}, issn = {0036-8075}, doi = {10.1126/science.1164857}, author = {Gustafsson, O. and Krusa, M. and Zencak, Z. and Sheesley, R. J. and Granat, L. and Engstrom, E. and Praveen, P. S. and Rao, P. S. P. and Leck, C. and Rodhe, H.} } @article {514, title = {Carbonaceous aerosol over a Pinus taeda forest in Central North Carolina, USA}, journal = {Atmospheric Environment}, volume = {43}, year = {2009}, note = {id: 1958; PT: J; UT: WOS:000263188100024}, pages = {959-969}, abstract = {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.}, issn = {1352-2310}, doi = {10.1016/j.atmosenv.2008.10.053}, author = {Geron, Chris} } @article {272, title = {Chemical and isotopic characterization of size-fractionated organic matter from cryoturbated tundra soils, northern Alaska}, journal = {Journal of Geophysical Research-Biogeosciences}, volume = {114}, year = {2009}, note = {id: 1828; 475IS Times Cited:0 Cited References Count:61Y}, abstract = {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.}, issn = {0148-0227}, doi = {10.1029/2008jg000846}, author = {Xu, C. H. and Guo, L. D. and Ping, C. L. and White, D. M.} } @article {479, title = {Chemical and isotopic composition of high-molecular-weight dissolved organic matter from the Mississippi River plume}, journal = {Marine Chemistry}, volume = {114}, year = {2009}, note = {id: 1827; 465CM Times Cited:1 Cited References Count:51Y}, pages = {63-71}, abstract = {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.}, issn = {0304-4203}, doi = {10.1016/j.marchem.2009.04.002}, author = {Guo, L. D. and White, D. M. and Xu, C. and Santschi, P. H.} } @article { ISI:000269036900005, title = {Chemical and isotopic signature of old groundwater and magmatic solutes in a Costa Rican rain forest: Evidence from carbon, helium, and chlorine}, journal = {WATER RESOURCES RESEARCH}, volume = {45}, year = {2009}, month = {AUG 11}, type = {Article}, chapter = {W08413}, abstract = {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 {\textquoteleft}{\textquoteleft}bomb carbon{\textquoteright}{\textquoteright} 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.}, issn = {0043-1397}, doi = {10.1029/2008WR007630}, author = {Genereux, David P. and Webb, Mathew and Solomon, D. Kip} } @article {326, title = {Coarse-grained sediment delivery and distribution in the Holocene Santa Monica Basin, California: Implications for evaluating source-to-sink flux at millennial time scales}, journal = {Geological Society of America Bulletin}, volume = {121}, year = {2009}, note = {id: 876; 478QZ Times Cited:1 Cited References Count:90Y}, pages = {1394-1408}, abstract = {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.}, issn = {0016-7606}, doi = {10.1130/B26393.1}, author = {Romans, B. W. and Normark, W. R. and McGann, M. M. and Covault, J. A. and Graham, S. A.} } @article {424, title = {Distribution of artificial radionuclides in deep sediments of the Mediterranean Sea}, journal = {Science of the Total Environment}, volume = {407}, year = {2009}, note = {id: 871; 389FH Times Cited:2 Cited References Count:63Y}, pages = {887-898}, abstract = {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.}, issn = {0048-9697}, doi = {10.1016/J.Scitotenv.2008.09.018}, author = {Garcia-Orellana, J. and Pates, J. M. and Masque, P. and Bruach, J. M. and Sanchez-Cabeza, J. A.} } @article {497, title = {DNA and lipid molecular stratigraphic records of haptophyte succession in the Black Sea during the Holocene}, journal = {Earth and Planetary Science Letters}, volume = {284}, year = {2009}, note = {id: 1853; 487NY Times Cited:1 Cited References Count:78; YY}, pages = {610-621}, abstract = {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.}, issn = {0012-821X}, doi = {10.1016/j.epsl.2009.05.029}, author = {Coolen, M. J. L. and Saenz, J. P. and Giosan, L. and Trowbridge, N. Y. and Dimitrov, P. and Dimitrov, D. and Eglinton, T. I.} } @article { ISI:000268272100013, title = {Fish scales in sediments from off Callao, central Peru}, journal = {DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY}, volume = {56}, number = {{16}}, year = {2009}, month = {JUL 15}, pages = {1113-1124}, type = {Article}, abstract = {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{\textquoteright}S, 77 degrees 42{\textquoteright}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.}, keywords = {Callao, Clupeoid fish, Molybdenum, Oxygen minimum zone, Peru, Redox-sensitive trace elements}, issn = {0967-0645}, doi = {10.1016/j.dsr2.2008.09.015}, author = {Diaz-Ochoa, J. A. and Lange, C. B. and Pantoja, S. and De lange, G. J. and Gutierrez, D. and Munoz, P. and Salamanca, M.} } @article {540, title = {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}, journal = {Journal of Quaternary Science}, volume = {24}, year = {2009}, note = {id: 1989; PT: J; UT: WOS:000262615700002}, pages = {3-17}, abstract = {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.}, issn = {0267-8179}, doi = {10.1002/jqs.1227}, author = {Walker, Mike and Johnsen, Sigfus and Rasmussen, Sune Olander and Popp, Trevor and Steffensen, Jorgen-Peder and Gibbard, Phil and Hoek, Wim and Lowe, John and Andrews, John and Bjorck, Svante and Cwynar, Les C. and Hughen, Konrad and Kershaw, Peter and Kromer, Bernd and Litt, Thomas and Lowe, David J. and Nakagawa, Takeshi and Newnham, Rewi and Schwander, Jakob} } @article {442, title = {In situ cosmogenic 10Be production-rate calibration from the Southern Alps, New Zealand}, journal = {Quaternary Geochronology}, year = {2009}, note = {id: 840In pressY}, doi = {10.1016/j.quageo.2009.12.001}, author = {Putnam, A. E. and Schaefer, J. M. and Barrell, D. J. A. and Vandergoes, M. and Denton, G. H. and Kaplan, M. R. and Finkel, R. C. and Schwartz, R. and Goehring, B. M. and Kelley, S. E.} } @article {402, title = {Inputs of Fossil Carbon from Wastewater Treatment Plants to US Rivers and Oceans}, journal = {Environmental Science \& Technology}, volume = {43}, year = {2009}, note = {id: 1833; 476XR Times Cited:0 Cited References Count:51Y}, pages = {5647-5651}, abstract = {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.}, issn = {0013-936X}, doi = {10.1021/As9004043}, author = {Griffith, D. R. and Barnes, R. T. and Raymond, P. A.} } @article {1846, title = {Intcal09 and Marine09 Radiocarbon Age Calibration Curves, 0-50,000 Years Cal Bp Rid F-4952-2011 Rid B-7298-2008}, journal = {Radiocarbon}, volume = {51}, year = {2009}, note = {id: 1983; PT: J; UT: WOS:000274407500002}, month = {2009}, pages = {1111-1150}, abstract = {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.}, isbn = {0033-8222}, author = {Reimer, P. J. and Baillie, M. G. L. and Bard, E. and Bayliss, A. and Beck, J. W. and Blackwell, P. G. and Ramsey, C. Bronk and Buck, C. E. and Burr, G. S. and Edwards, R. L. and Friedrich, M. and Grootes, P. M. and Guilderson, T. P. and Hajdas, I. and Heaton, T. J. and Hogg, A. G. and Hughen, K. A. and Kaiser, K. F. and Kromer, B. and McCormac, F. G. and Manning, S. W. and Reimer, R. W. and Richards, D. A. and Southon, J. R. and Talamo, S. and Turney, C. S. M. and van der Plicht, J. and Weyhenmeye, C. E.} } @article {283, title = {Late Holocene Hydrologic and Vegetation Changes at Turneffe Atoll, Belize, Compared with Records from Mainland Central America and Mexico}, journal = {Palaios}, volume = {24}, year = {2009}, note = {id: 1835; 506UH Times Cited:1 Cited References Count:34Y}, pages = {650-656}, abstract = {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.}, issn = {0883-1351}, doi = {10.2110/palo.2009.p09-036r}, author = {Wooller, M. J. and Behling, H. and Guerrero, J. L. and Jantz, N. and Zweigert, M. E.} } @article {473, title = {Late Pleistocene-Holocene evolution of the northern shelf of the Sea of Marmara}, journal = {Marine Geology}, volume = {265}, year = {2009}, note = {id: 1843; 500UN Times Cited:1 Cited References Count:80Y}, pages = {87-100}, abstract = {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.}, issn = {0025-3227}, doi = {10.1016/j.margeo.2009.06.011}, author = {Cagatay, M. N. and Eris, K. and Ryan, W. B. F. and Sancar, U. and Polonia, A. and Akcer, S. and Biltekin, D. and Gasperini, L. and Gorur, N. and Lericolais, G. and Bard, E.} } @article {1842, title = {Late Quaternary benthic foraminifera from Ocean Drilling Program Hole 716A, Maldives Ridge, southeastern Arabian Sea}, journal = {Micropaleontology}, volume = {55}, year = {2009}, note = {424cdTimes Cited:5 Cited References Count:47 }, month = {2009}, pages = {23-48}, abstract = {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{\textquoteright}N, 73 degrees 17.0{\textquoteright}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.}, keywords = {benthonic foraminifera, equatorial indian-ocean, Holocene, late neogene, monsoon, Oxygen minimum zone, productivity, red-sea, south atlantic-ocean, Water masses}, isbn = {0026-2803}, author = {Sarkar, S. and De, S. and Gupta, A. K.} } @inbook {1407, title = {Methane accumulation and release from deep peat: Measurements, conceptual models, and biogeochemical significance}, booktitle = {Carbon Cycling in Northern Peatlands}, series = {GEOPHYSICAL MONOGRAPH SERIES}, year = {2009}, note = {id: 1972}, month = {2009}, pages = {145-158}, publisher = {American Geophysical Union}, organization = {American Geophysical Union}, abstract = {Northern peatlands account for more than half the world{\textquoteright}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{\textendash}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.}, keywords = {Carbon cycle (Biogeochemistry){\textemdash}Northern Hemisphere, Carbon sequestration{\textemdash}Northern Hemisphere, Greenhouse gases{\textemdash}Northern Hemisphere, Peatlands{\textemdash}Environmental aspects{\textemdash}Northern Hemisphere}, isbn = {9780875904498}, author = {Glaser, Paul H. and Chanton, Jeffrey P.}, editor = {Baird, A. J.} } @inbook {1410, title = {Monsoons, Quaternary}, booktitle = {Encyclopedia of Paleoclimatology and Ancient Environments}, series = {Encyclopedia of Earth Sciences Series}, year = {2009}, note = {id: 1971}, month = {2009}, pages = {589-594}, publisher = {Springer}, organization = {Springer}, isbn = {9781402045516}, author = {Gupta, A. K.}, editor = {Gornitz, V.} } @article {317, title = {A new look at old carbon in active margin sediments RID F-1809-2010}, journal = {Geology}, volume = {37}, year = {2009}, note = {id: 1987; PT: J; UT: WOS:000263842200012}, pages = {239-242}, abstract = {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.}, issn = {0091-7613}, doi = {10.1130/G25351A.1}, author = {Drenzek, Nicholas J. and Hughen, Konrad A. and Montlu{\c c}on, Daniel B. and Southon, John R. and dos Santos, Guaciara M. and Druffel, Ellen R. M. and Giosan, Liviu and Eglinton, Timothy I.} } @article {509, title = {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}, journal = {Deep-Sea Research Part I-Oceanographic Research Papers}, volume = {56}, year = {2009}, note = {id: 1871; 430SK Times Cited:0 Cited References Count:69Y}, pages = {614-640}, abstract = {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.}, issn = {0967-0637}, doi = {10.1016/j.dsr.2008.11.010}, author = {Go{\~n}i, M. A. and Aceves, H. and Benitez-Nelson, B. and Tappa, E. and Thunell, R. and Black, D. E. and Muller-Karger, F. and Astor, Y. and Varela, R.} } @article {330, title = {Pleistocene Megafaunal Collapse, Novel Plant Communities, and Enhanced Fire Regimes in North America}, journal = {Science}, volume = {326}, year = {2009}, note = {id: 769; 521UW Times Cited:4 Cited References Count:30Y}, pages = {1100-1103}, abstract = {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.}, issn = {0036-8075}, doi = {10.1126/science.1179504}, author = {Gill, J. L. and Williams, J. W. and Jackson, S. T. and Lininger, K. B. and Robinson, G. S.} } @article {1854, title = {Pre-Columbian settlement of Carriacou, West Indies}, journal = {Journal of Field Archaeology}, volume = {34}, year = {2009}, note = {id: 830}, month = {2009}, pages = {247-266}, author = {Fitzpatrick, S. M. and Kappers, M. and Kaye, Q. and Giovas, C. M. and LeFebvre, M. J. and Harris, M. H. and Burnett, S. and Pavia, J. A. and Marsaglia, K. and Feathers, J.} } @article { ISI:000268455600046, title = {Radiocarbon Analysis of Atmospheric Formaldehyde Using Cystamine Derivatization}, journal = {ANALYTICAL CHEMISTRY}, volume = {81}, number = {{15}}, year = {2009}, month = {AUG 1}, pages = {6310-6316}, type = {Article}, abstract = {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.}, issn = {0003-2700}, doi = {10.1021/ac9004666}, author = {Shen, Haiwei and McNichol, Ann P. and Xu, Li and Gagnon, Alan and Heikes, Brian G.} } @article {363, title = {Sinking deltas due to human activities}, journal = {Nature Geoscience}, volume = {2}, year = {2009}, note = {id: 799; 501BW Times Cited:2 Cited References Count:38; YY}, pages = {681-686}, abstract = {Many of the world{\textquoteright}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{\textquoteright}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{\textquoteright}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.}, issn = {1752-0894}, doi = {10.1038/Ngeo629}, author = {Syvitski, J. P. M. and Kettner, A. J. and Overeem, I. and Hutton, E. W. H. and Hannon, M. T. and Brakenridge, G. R. and Day, J. and Vorosmarty, C. and Saito, Y. and Giosan, L. and Nicholls, R. J.} } @article {1841, title = {Source apportionment of elevated wintertime PAHs by compound-specific radiocarbon analysis}, journal = {Atmospheric Chemistry and Physics}, volume = {9}, year = {2009}, note = {452qjTimes Cited:22 Cited References Count:52 }, month = {2009}, pages = {3347-3356}, abstract = {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.}, keywords = {air-pollution sources, atmospheric aerosols, BLACK CARBON, emissions, northern sweden, organic-compounds, particulate matter, polycyclic aromatic-hydrocarbons, positive matrix factorization, residential wood combustion}, isbn = {1680-7316}, author = {Sheesley, R. J. and Krusa, M. and Krecl, P. and Johansson, C. and Gustafsson, O.} } @article {364, title = {Southward movement of the Pacific intertropical convergence zone AD 1400-1850}, journal = {Nature Geoscience}, volume = {2}, year = {2009}, note = {id: 847; 497LS Times Cited:5 Cited References Count:45Y}, pages = {519-525}, abstract = {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{\textquoteright}s radiation budget may profoundly affect tropical rainfall.}, issn = {1752-0894}, doi = {10.1038/Ngeo554}, author = {Sachs, J. P. and Sachse, D. and Smittenberg, R. H. and Zhang, Z. H. and Battisti, D. S. and Golubic, S.} } @article {315, title = {Timing and magnitude of recent accelerated sea-level rise (North Carolina, United States)}, journal = {Geology}, volume = {37}, year = {2009}, note = {id: 829; 512AY Times Cited:15 Cited References Count:30Y}, pages = {1035-1038}, abstract = {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.}, issn = {0091-7613}, doi = {10.1130/G30352a.1}, author = {Kemp, A. C. and Horton, B. P. and Culver, S. J. and Corbett, D. R. and van de Plassche, O. and Gehrels, W. R. and Douglas, B. C. and Parnell, A. C.} } @article {1839, title = {Towards a quantitative and independent reconstruction of Holocene temperature and precipitation in Northern Great Plains using novel organic proxies}, journal = {Eos, Transactions, American Geophysical Union}, volume = {90}, year = {2009}, note = {id: 891}, month = {2009}, pages = {Fall Meet. Suppl., Abstract PP21D-06}, author = {Toney, J. L. and Huang, Y. and Fritz, S. C. and Baker, P. and Grimm, E. C. and Nyren, P. E.} } @article {433, title = {Was the Black Sea catastrophically flooded in the early Holocene?}, journal = {Quaternary Science Reviews}, volume = {28}, year = {2009}, note = {id: 866; 399HK Times Cited:0 Cited References Count:56; YY}, pages = {1-6}, abstract = {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.}, issn = {0277-3791}, doi = {10.1016/J.Quascirev.2008.10.012}, author = {Giosan, L. and Filip, F. and Constatinescu, S.} } @article {365, title = {Abrupt changes in Antarctic Intermediate Water circulation over the past 25,000 years}, journal = {Nature Geoscience}, volume = {1}, year = {2008}, note = {id: 2026; PT: J; UT: WOS:000261278700021}, pages = {870-874}, abstract = {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.}, issn = {1752-0894}, doi = {10.1038/ngeo360}, author = {Pahnke, Katharina and Goldstein, Steven L. and Hemming, Sidney R.} } @article {435, title = {A Be-10 chronology of lateglacial and Holocene mountain glaciation in the Scoresby Sund region, east Greenland: implications for seasonality during lateglacial time}, journal = {Quaternary Science Reviews}, volume = {27}, year = {2008}, note = {id: 1868; 389XX Times Cited:7 Cited References Count:75Y}, pages = {2273-2282}, abstract = {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{\textquoteright}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{\textquoteright}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.}, issn = {0277-3791}, doi = {10.1016/j.quascirev.2008.08.004}, author = {Kelly, M. A. and Lowell, T. V. and Hall, B. L. and Schaefer, J. M. and Finkel, R. C. and Goehring, B. M. and Alley, R. B. and Denton, G. H.} } @article {387, title = {Benthic foraminiferal faunal and isotopic changes as recorded in Holocene sediments of the northwest Indian Ocean}, journal = {Paleoceanography}, volume = {23}, year = {2008}, note = {id: 1964; PT: J; UT: WOS:000256362400001}, pages = {PA2214-PA2214}, abstract = {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.}, issn = {0883-8305}, doi = {10.1029/2007PA001546}, author = {Gupta, Anil K. and Das, Moumita and Clemens, Steven C. and Mukherjee, Baidehi} } @article {274, title = {Biogeochemical characterization of carbon sources in the strickland and fly rivers, Papua New Guinea}, journal = {Journal of Geophysical Research-Earth Surface}, volume = {113}, year = {2008}, note = {id: 1870; 251HH Times Cited:4 Cited References Count:75Y}, abstract = {[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 (}, issn = {0148-0227}, doi = {10.1029/2006jf000625}, author = {Alin, S. R. and Aalto, R. and Go{\~n}i, M. A. and Richey, J. E. and Dietrich, W. E.} } @article {310, title = {Bomb radiocarbon age validation of Pacific ocean perch (Sebastes alutus) using new statistical methods}, journal = {Canadian Journal of Fisheries and Aquatic Sciences}, volume = {65}, year = {2008}, note = {id: 1832; 322ER Times Cited:1 Cited References Count:35Y}, pages = {1101-1112}, abstract = {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{\textquoteright} 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.}, issn = {0706-652X}, doi = {10.1139/F08-038}, author = {Kastelle, C. R. and Kimura, D. K. and Goetz, B. J.} } @article {492, title = {Changes in the composition of organic matter from prodeltaic sediments after a large flood event (Po River, Italy)}, journal = {Geochimica et Cosmochimica Acta}, volume = {72}, year = {2008}, note = {id: 888; 290IO Times Cited:4 Cited References Count:66Y}, pages = {2100-2114}, abstract = {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.}, issn = {0016-7037}, doi = {10.1016/J.Gca.2008.02.005}, author = {Tesi, T. and Langone, L. and Go{\~n}i, M. A. and Miserocchi, S. and Bertasi, F.} } @article {271, title = {Contrasting lipid biomarker composition of terrestrial organic matter exported from across the Eurasian Arctic by the five great Russian Arctic rivers}, journal = {Global Biogeochemical Cycles}, volume = {22}, year = {2008}, note = {id: 819; 261FT Times Cited:10 Cited References Count:112Y}, abstract = {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.}, issn = {0886-6236}, doi = {10.1029/2007gb002974}, author = {van Dongen, B. E. and Semiletov, I. and Weijers, J. W. H. and Gustafsson, O. R.} } @article {354, title = {Differences in sediment organic matter composition and PAH weathering between non-vegetated and recently vegetated fuel oiled sediments}, journal = {International Journal of Phytoremediation}, volume = {10}, year = {2008}, note = {id: 2025; PT: J; UT: WOS:000258774100001}, pages = {473-485}, abstract = {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.}, issn = {1522-6514}, doi = {10.1080/15226510802114862}, author = {Gregory, Samuel T., III and Nichols, Elizabeth Guthrie} } @article {1872, title = {Environmental and Climatic Controls on the Occurrence and Abundance of Long Chain Alkenones in Lakes of the Interior United States}, journal = {Eos, Transactions, American Geophysical Union}, volume = {89}, year = {2008}, note = {id: 892}, month = {2008}, pages = {Fall Meet. Suppl., Abstract 2008}, author = {Toney, J. L. and Fritz, S. and Baker, P. and Grim, E. and Nyren, P. and Theroux, S. and Huang, Y.} } @article {1871, title = {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}, journal = {Episodes}, volume = {31}, year = {2008}, note = {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}, month = {2008}, pages = {264-267}, abstract = {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).}, isbn = {0705-3797}, author = {Walker, Mike and Johnsen, Sigfu{\textquoteright}s and Rasmussen, Sune Olander and Steffensen, Jorgen-Peder and Popp, Trevor and Gibbard, Philip and Hoek, Wim and Lowe, John and Andrews, John and Bjorck, Svante and Cwynar, Les and Hughen, Konrad and Kershaw, Peter and Kromer, Bernd and Litt, Thomas and Lowe, David J. and Nakagawa, Takeshi and Newnham, Rewi and Schwander, Jakob} } @article {321, title = {Holocene erosion of the Lesser Himalaya triggered by intensified summer monsoon}, journal = {Geology}, volume = {36}, year = {2008}, note = {id: 800; 247YL Times Cited:7 Cited References Count:27; YY}, pages = {79-82}, abstract = {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.}, issn = {0091-7613}, doi = {10.1130/G24315a.1}, author = {Clift, P. D. and Giosan, L. and Biusztajn, J. and Campbell, I. H. and Allen, C. and Pringle, M. and Tabrez, A. R. and Danish, M. and Rabbani, M. M. and Alizai, A. and Carter, A. and Lueckge, A.} } @article {502, title = {The impact of vegetation on sedimentary organic matter composition and PAH desorption}, journal = {Environmental Pollution}, volume = {156}, year = {2008}, note = {id: 2024; PT: J; UT: WOS:000261678700045}, pages = {928-935}, abstract = {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.}, issn = {0269-7491}, doi = {10.1016/j.envpol.2008.05.011}, author = {Nichols, Elizabeth Guthrie and Gregory, Samuel T. and Musella, Jennifer S.} } @article {474, title = {The last reconnection of the Marmara Sea (Turkey) to the World Ocean: A paleoceanographic and paleoclimatic perspective}, journal = {Marine Geology}, volume = {255}, year = {2008}, note = {id: 801; 370ED Times Cited:4 Cited References Count:104; YY}, pages = {64-82}, abstract = {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{\textquoteright}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.}, issn = {0025-3227}, doi = {10.1016/j.margeo.2008.07.005}, author = {McHugh, C. M. G. and Gurung, D. and Giosan, L. and Ryan, W. B. F. and Mart, Y. and Sancar, U. and Burckle, L. and Cagatay, M. N.} } @article {437, title = {Loess record of the Pleistocene-Holocene transition on the northern and central Great Plains, USA}, journal = {Quaternary Science Reviews}, volume = {27}, year = {2008}, note = {id: 1993; PT: J; UT: WOS:000260545800008}, pages = {1772-1783}, abstract = {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.}, issn = {0277-3791}, doi = {10.1016/j.quascirev.2008.07.004}, author = {Mason, Joseph A. and Miao, Xiaodong and Hanson, Paul R. and Johnson, William C. and Jacobs, Peter M. and Goble, Ronald J.} } @article {491, title = {Matrix protected organic matter in a river dominated margin: A possible mechanism to sequester terrestrial organic matter?}, journal = {Geochimica Et Cosmochimica Acta}, volume = {72}, year = {2008}, note = {id: 827; 309MK Times Cited:5 Cited References Count:71Y}, pages = {2673-2686}, abstract = {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.}, issn = {0016-7037}, doi = {10.1016/j.gca.2008.03.007}, author = {Mead, R. N. and Go{\~n}i, M. A.} } @article {1880, title = {Mineralization of ancient carbon i the subsurface of riparian forests}, journal = {Journal of Geophysical Research}, volume = {113}, year = {2008}, note = {id: 1193}, month = {2008}, pages = {13 pages}, author = {Gurwick, Noel P. and McCorkle, Daniel M. and Groffman, Peter M. and Gold, Arthur J. and Kellogg, D. Q. and Seitz-Rundlett, Peter} } @article {298, title = {Mutation and evolutionary rates in adelie penguins from the antarctic}, journal = {Plos Genetics}, volume = {4}, year = {2008}, note = {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}, pages = {e1000209}, abstract = {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.}, issn = {1553-7404 (Electronic) 1553-7390 (Linking)}, doi = {10.1371/journal.pgen.1000209}, author = {Millar, C. D. and Dodd, A. and Anderson, J. and Gibb, G. C. and Ritchie, P. A. and Baroni, C. and Woodhams, M. D. and Hendy, M. D. and Lambert, D. M.} } @article {270, title = {Pan-Arctic patterns in black carbon sources and fluvial discharges deduced from radiocarbon and PAH source apportionment markers in estuarine surface sediments}, journal = {Global Biogeochemical Cycles}, volume = {22}, year = {2008}, note = {id: 820; 307ZP Times Cited:3 Cited References Count:89Y}, abstract = {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.}, issn = {0886-6236}, doi = {10.1029/2007gb002994}, author = {Elmquist, M. and Semiletov, I. and Guo, L. D. and Gustafsson, O.} } @article {385, title = {Radiocarbon evidence for the importance of surface vegetation on fermentation and methanogenesis in contrasting types of boreal peatlands}, journal = {Global Biogeochemical Cycles}, volume = {22}, year = {2008}, note = {id: 1949; PT: J; UT: WOS:000262041000002}, pages = {GB4022-GB4022}, abstract = {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.}, issn = {0886-6236}, doi = {10.1029/2008GB003274}, author = {Chanton, J. P. and Glaser, P. H. and Chasar, L. S. and Burdige, D. J. and Hines, M. E. and Siegel, D. I. and Tremblay, L. B. and Cooper, W. T.} } @article {320, title = {Reconstructing relative flooding intensities responsible for hurricane-induced deposits from Laguna Playa Grande, Vieques, Puerto Rico}, journal = {Geology}, volume = {36}, year = {2008}, note = {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}, pages = {391-394}, abstract = {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.}, issn = {0091-7613}, doi = {10.1130/g24731a.1}, author = {Woodruff, J. D. and Donnelly, J. P. and Mohrig, D. and Geyer, W. R.} } @article {333, title = {Recycling of graphite during Himalayan erosion: a geological stabilization of carbon in the crust}, journal = {Science}, volume = {322}, year = {2008}, note = {id: 1876; Galy, Valier Beyssac, Olivier France-Lanord, Christian Eglinton, Timothy New York, N.Y. Science. 2008 Nov 7;322(5903):943-5.; YY}, pages = {943-5}, abstract = {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.}, issn = {1095-9203 (Electronic) 0036-8075 (Linking)}, doi = {10.1126/science.1161408}, author = {Galy, V. and Beyssac, O. and France-Lanord, C. and Eglinton, T.} } @article {324, title = {Research focus - Tempestuous highs and lows in the Gulf of Mexico}, journal = {Geology}, volume = {36}, year = {2008}, note = {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}, pages = {751-752}, issn = {0091-7613}, doi = {10.1130/focus092008.1}, author = {Donnelly, J. P. and Giosan, L.} } @article {510, title = {Source and composition of organic matter in the Bari canyon (Italy): Dense water cascading versus particulate export from the upper ocean}, journal = {Deep-Sea Research Part I-Oceanographic Research Papers}, volume = {55}, year = {2008}, note = {id: 828; 330FL Times Cited:4 Cited References Count:87Y}, pages = {813-831}, abstract = {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.}, issn = {0967-0637}, doi = {10.1016/j.dsr.2008.03.007}, author = {Tesi, T. and Langone, L. and Go{\~n}i, M. A. and Turchetto, M. and Miserocchi, S. and Boldrin, A.} } @article {273, title = {Terrigenous organic matter in sediments from the Fly River delta-clinoform system (Papua New Guinea)}, journal = {Journal of Geophysical Research-Earth Surface}, volume = {113}, year = {2008}, note = {id: 826; 257VD Times Cited:8 Cited References Count:78Y}, abstract = {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.}, issn = {0148-0227}, doi = {10.1029/2006jf000653}, author = {Go{\~n}i, M. A. and Monacci, N. and Gisewhite, R. and Crockett, J. and Nittrouer, C. and Ogston, A. and Alin, S. R. and Aalto, R.} } @article {1876, title = {Very high-resolution seismo-acoustic imaging of seagrass meadows (Mediterranean Sea): Implications for carbon sink estimates}, journal = {Geophysical Research Letters}, volume = {35}, year = {2008}, note = {id: 896; 351AE Times Cited:1 Cited References Count:14}, month = {2008}, abstract = {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{\textquoteright}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.}, keywords = {cycle}, isbn = {0094-8276}, author = {Lo Iacono, C. and Mateo, M. A. and Gracia, E. and Guasch, L. and Carbonell, R. and Serrano, L. and Serrano, O. and Danobeitia, J.} } @article {1900, title = {14C Groundwater age and the importance of chemical fluxes across aquifer boundaries in confined Cretaceous aquifers of North Carolina, USA}, journal = {Radiocarbon}, volume = {49}, year = {2007}, note = {id: 1192}, month = {2007}, pages = {1181-1203}, author = {Kennedy, C. D. and Genereux, D. P.} } @article {974, title = {A 1,500-year record of North Atlantic storm activity based on optically dated relict beach scarps}, journal = {Geology}, volume = {35}, year = {2007}, note = {id: 1083}, pages = {543-546}, abstract = {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.}, keywords = {barrier, erosion, ground-penetrating radar, heavy minerals, Maine, OSL dating}, doi = {10.1130/G23636A.1}, author = {Buynevich, I. V. and FitzGerald, D. M. and Goble, R. J.} } @article {1531, title = {Calcification in sclersoponges: implications for reconstructing CO2 fluxes in the tropics}, year = {2007}, note = {id: 1132}, month = {2007}, pages = {68}, address = {Santa Fe, NM}, author = {Grottoli, A. G.} } @mastersthesis {1312, title = {Carbon in riparian subsurface ecosystems: Sources, lability, and spatial patterns}, volume = {Ph.D.}, year = {2007}, month = {2007}, school = {Cornell University}, address = {Ithaca, NY}, author = {Gurwick, N. P.} } @article {499, title = {Century-to-millennial scale climatic variability in Lake Malawi revealed by isotope records}, journal = {Earth and Planetary Science Letters}, volume = {261}, year = {2007}, note = {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}, pages = {93-103}, abstract = {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.}, issn = {0012-821X}, doi = {10.1016/j.epsl.2007.06.010}, author = {Barker, P. A. and Leng, M. J. and Gasse, F. and Huang, Y.} } @article {1887, title = {Constraining global air-sea gas exchange for CO2 with recent bomb 14C measurements}, journal = {Global Biogeochemical Cycles}, volume = {21}, year = {2007}, note = {id: 1052}, month = {2007}, author = {Sweeney, C. and Gloor, E. and Jacobson, A. J. and Key, R. M. and McKinley, G. and Sarmiento, J. L. and Wanninkhof, R.} } @article {263, title = {Demise of a submarine canyon? Evidence for highstand infilling on the Waipaoa River continental margin, New Zealand}, journal = {Geophysical Research Letters}, volume = {34}, year = {2007}, note = {id: 791; 228BW Times Cited:4 Cited References Count:42Y}, abstract = {Submarine canyons are major geomorphologic features on the Earth{\textquoteright}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.}, issn = {0094-8276}, doi = {10.1029/2007gl031142}, author = {Walsh, J. P. and Alexander, C. R. and Gerber, T. and Orpin, A. R. and Sumners, B. W.} } @article {604, title = {Distribution and turnover of carbon in natural and constructed wetlands in the Florida Everglades}, journal = {Applied Geochemistry}, volume = {22}, year = {2007}, note = {216vhTimes Cited:23Cited References Count:36}, month = {Sep}, pages = {1936-1948}, abstract = {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.}, issn = {0883-2927}, doi = {10.1016/j.apgeochem.2007.04.007}, author = {Stern, J. and Wang, Y. and Gu, B. and Newman, J.} } @article {403, title = {Evaluation of gas chromatographic isotope fractionation and process contamination by carbon in compound-specific radiocarbon analysis}, journal = {Analytical Chemistry}, volume = {79}, year = {2007}, note = {id: 615; 140ID Times Cited:11 Cited References Count:32}, pages = {2042-2049}, abstract = {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{\textquoteright},4,4{\textquoteright},5,5{\textquoteright}-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.}, issn = {0003-2700}, doi = {10.1021/Ac061821a}, author = {Zencak, Z. and Reddy, C. M. and Teuten, E. L. and Xu, L. and McNichol, A. P. and Gustafsson, O.} } @article {390, title = {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}, journal = {Global Biogeochemical Cycles}, volume = {21}, year = {2007}, note = {id: 2033; PT: J; UT: WOS:000250704000002}, pages = {GB4011-GB4011}, abstract = {The export and Delta C-14-age of dissolved organic carbon (DOC) was determined for the Yenisey, Lena, Ob{\textquoteright}, 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.}, issn = {0886-6236}, doi = {10.1029/2007GB002934}, author = {Raymond, Peter A. and McClelland, J. W. and Holmes, R. M. and Zhulidov, A. V. and Mull, K. and Peterson, B. J. and Striegl, R. G. and Aiken, G. R. and Gurtovaya, T. Y.} } @inbook {1423, title = {The Geographic, Geological and Oceanographic Setting of the Indus River}, booktitle = {Large Rivers}, year = {2007}, note = {id: 867; Y}, month = {2007}, publisher = {Wiley Press}, organization = {Wiley Press}, author = {Inam, A. and Clift, P. D. and Giosan, L.}, editor = {Gupta, A.} } @inbook {1455, title = {Historical ecology and human impacts on coastal ecosystems of the Santa Barbara Channel region, California}, booktitle = {Ancient Human Impacts on Marine Environments: A Global Perspective}, year = {2007}, note = {id: 577}, month = {2007}, publisher = {University of California Press}, organization = {University of California Press}, address = {Berkeley}, author = {Rick, Torben C. and Erlandson, Jon M. and Braje, Todd J. and Estes, James and Graham, Michael and Vellanoweth, Rene}, editor = {Rick, T. C.} } @article {1481, title = {Holocene fire and occupation in Amazonia: Records from two lake districts}, volume = {Ser. B.}, year = {2007}, note = {id: 454}, month = {2007}, author = {Bush, M. B. and Silman, M. R. and de Toledo, M. B. and Listopad, C. R. S. and Gosling, W. D. and Williams, C. and De Oliveira, P. E. and Krisel, C.} } @article {477, title = {Late Holocene fine-grained sediments of the Balearic Abyssal Plain, Western Mediterranean Sea}, journal = {Marine Geology}, volume = {237}, year = {2007}, note = {id: 624; 139VA Times Cited:6 Cited References Count:57}, pages = {25-36}, abstract = {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.}, issn = {0025-3227}, doi = {10.1016/J.Margeo.2006.10.034}, author = {Zuniga, D. and Garcia-Orellana, J. and Calafat, A. and Price, N. B. and Adatte, T. and Sanchez-Vidal, A. and Canals, M. and Sanchex-Cabeza, J. A. and Masque, P. and Fabres, J.} } @article {267, title = {Mobilization pathways of organic carbon from permafrost to arctic rivers in a changing climate}, journal = {Geophysical Research Letters}, volume = {34}, year = {2007}, note = {id: 773; 187WS Times Cited:23 Cited References Count:29Y}, abstract = {[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}, issn = {0094-8276}, doi = {10.1029/2007gl030689}, author = {Guo, L. D. and Ping, C. L. and Macdonald, R. W.} } @article {505, title = {Organic matter origin and distribution in suspended particulate materials and surficial sediments from the western Adriatic Sea (Italy)}, journal = {Estuarine Coastal and Shelf Science}, volume = {73}, year = {2007}, note = {id: 1869; 179HX Times Cited:12 Cited References Count:61Y}, pages = {431-446}, abstract = {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.}, issn = {0272-7714}, doi = {10.1016/j.ecss.2007.02.008}, author = {Tesi, T. and Miserocchi, S. and Go{\~n}i, M. A. and Langone, L. and Boldrin, A. and Turchetto, M.} } @article {515, title = {Quantification and radiocarbon source apportionment of black carbon in atmospheric aerosols using the CTO-375 method}, journal = {Atmospheric Environment}, volume = {41}, year = {2007}, note = {id: 818; 243XB Times Cited:8 Cited References Count:58Y}, pages = {7895-7906}, abstract = {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.}, issn = {1352-2310}, doi = {10.1016/j.atmosenv.2007.06.006}, author = {Zencak, Z. and Elmquist, M. and Gustafsson, O.} } @article {1896, title = {Radiocarbon dating of a very large African baobab}, journal = {Tree Physiology}, volume = {27}, year = {2007}, note = {230afTimes Cited:35 Cited References Count:43 }, month = {Nov}, pages = {1569-1574}, abstract = {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.}, keywords = {Adansonia digitata, Age, Age determination, amazonia, c-14 content, cal kyr bp, Calibration, dendrochronology, dendroclimatology, holocene logs, location-dependent differences, southern-hemisphere, tasmanian conifers, Trees, tropical trees}, isbn = {0829-318x}, author = {Patrut, A. and von Reden, K. F. and Pohlman, J. W. and Wittmann, R. and Mitchell, C. S. and Lowy, D. A. and Alberts, A. H. and Gerlach, D. and Xu, L.} } @article {1903, title = {A review of modern coral delta18O and Delta14C proxy records}, journal = {Earth-Science Reviews}, volume = {81}, year = {2007}, note = {id: 653}, month = {2007}, pages = {67-91}, author = {Grottoli, Andrea G. and Eakin, C. Mark} } @article {285, title = {Seaward-branching coastal-plain and Piedmont incised-valley systems through multiple sea-level cycles: Late Quaternary examples from Mobile Bay and Mississippi Sound, USA}, journal = {Journal of Sedimentary Research}, volume = {77}, year = {2007}, note = {id: 2039; PT: J; UT: WOS:000246987600011}, pages = {139-158}, abstract = {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.}, issn = {1527-1404}, doi = {10.2110/jsr.2007.016}, author = {Greene, D. Lawrence, Jr. and Rodriguez, Antonio B. and Anderson, John B.} } @article {500, title = {Sedimentary iron cycling and the origin and preservation of magnetization in platform carbonate muds, Andros Island, Bahamas}, journal = {Earth and Planetary Science Letters}, volume = {259}, year = {2007}, note = {id: 787; 197DX Times Cited:9 Cited References Count:47Y}, pages = {581-598}, abstract = {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.}, issn = {0012-821X}, doi = {10.1016/j.epsl.2007.05.021}, author = {Maloof, A. C. and Kopp, R. E. and Grotzinger, J. P. and Fike, D. A. and Bosak, T. and Vali, H. and Poussart, P. M. and Weiss, B. P. and Kirschvink, J. L.} } @article {905, title = {Source apportionment of atmospheric PAHs in the western Balkans by natural abundance radiocarbon analysis}, journal = {Environmental Science and Technology}, volume = {41}, year = {2007}, note = {id: 519}, pages = {3850-3855}, doi = {10.1021/es0628957}, author = {Zencak, Zdenek and Klanova, Jana and Holoubek, Ivan and Gustafsson, {\"O}rjan} } @article {483, title = {Source, transport and fate of terrestrial organic carbon on the western Mediterranean Sea, Gulf of Lions, France}, journal = {Marine Chemistry}, volume = {105}, year = {2007}, note = {id: 825; 176SJ Times Cited:15 Cited References Count:70Y}, pages = {101-117}, abstract = {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.}, issn = {0304-4203}, doi = {10.1016/j.marchem.2007.01.005}, author = {Tesi, T. and Miserocchi, S. and Go{\~n}i, M. A. and Langone, L.} } @article {1536, title = {Stable-and radiocarbon isotopes in corals and adjacent natural waters: reconstructing land-use change and the land-ocean carbon cycle}, year = {2007}, note = {id: 654}, month = {2007}, pages = {126}, address = {Santa Fe, NM}, author = {Moyer, R. P. and Grottoli, A. G.} } @article {613, title = {Tropical Pacific - mid-latitude teleconnections in medieval times}, journal = {Climatic Change}, volume = {83}, year = {2007}, note = {160ufTimes Cited:125Cited References Count:151}, month = {Jul}, pages = {241-285}, abstract = {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.}, issn = {0165-0009}, doi = {10.1007/s10584-007-9239-2}, author = {Graham, N. E. and Hughes, M. K. and Ammann, C. M. and Cobb, K. M. and Hoerling, M. P. and Kennett, D. J. and Kennett, J. P. and Rein, B. and Stott, L. and Wigand, P. E. and Xu, T. Y.} } @article {1493, title = {Calibration and natural variability of skeletal stable carbon isotopes in the Pacific sclerosponge acanthocheatetes wellsi: implications for reconstructing CO2 uptake in coastal tropical environments}, year = {2006}, note = {id: 1133}, month = {2006}, address = {Honolulu}, author = {Grottoli, A. G.} } @article {1949, title = {Chemical composition of the graphitic black carbon fraction in riverine and marine sediments at submicron scales using carbon X-ray spectromicroscopy}, journal = {Geochimica et Cosmochimica Acta}, volume = {70}, year = {2006}, note = {id: 1703}, month = {2006}, pages = {1483-1494}, author = {Haberstroh, P. R. and Brandes, J. A. and Gelinas, Y. and Dickens, A. F. and Wirick, S.} } @article {1013, title = {Chronologie des variations climatiques repides pendant la derniere periode glaciaire}, journal = {Comptes Rendus de l{\textquoteright}Academie des Sciences}, volume = {5}, year = {2006}, note = {id: 398}, pages = {13-19}, doi = {10.1016/j.crpv.2005.11.002}, author = {Bard, E. and Rostek, F. and G, Menot-Combes} } @article {1526, title = {Corals and sclerosponges as geochemical recorders of past climate change}, year = {2006}, note = {id: 1134}, month = {2006}, address = {Houston, TX}, author = {Grottoli, A. G.} } @article {1951, title = {Depth limit for reef building corals in the Au{\textquoteright}au Channel, S. E. Hawaii}, journal = {Coral Reefs}, volume = {25}, year = {2006}, note = {id: 1085}, month = {2006}, pages = {77-84}, author = {Grigg, R. W.} } @inbook {1451, title = {Hudson River Paleoecology from Marshes}, booktitle = {Hudson River Fishes and their Environment.}, year = {2006}, note = {id: 1165}, month = {2006}, pages = {113-128}, publisher = {American Fisheries Society Monograph}, organization = {American Fisheries Society Monograph}, author = {Peteet, D. and Pederson, D. and Kurdyla, D. and Guilderson, T.}, editor = {Waldman, J. R.} } @conference {1665, title = {Late Holocene climate variability of South America reconstructed by a multi-proxy analysis of Chilean fjord sediments}, booktitle = {Abstracts, EGU General Assembly}, year = {2006}, note = {id: 560}, month = {2006}, address = {Vienna, Austria}, author = {Bertrand, S. and Hughen, K. A. and Giosan, L. and Tierney, J. and Sepfulveda, J. and Pantoja, S.} } @conference {1671, title = {The late Pleistocene-Holocene history of Long Island Sound}, booktitle = {LISRC proceedings}, year = {2006}, note = {id: 1175}, month = {2006}, pages = {27-32}, author = {Varekamp, J. C. and Thomas, E. and Groner, M.} } @article {2438, title = {MAGic: A Phanerozoic model for the geochemical cycling of major rock-forming components}, journal = {American Journal of Science}, volume = {306}, year = {2006}, note = {53}, month = {Mar}, pages = {135-190}, abstract = {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.}, keywords = {ATMOSPHERIC CARBON-DIOXIDE, CENOZOIC EVOLUTION, Clay minerals, CO2, DOLOMITE PROBLEM, marine-sediments, REVISED MODEL, SEAWATER CHEMISTRY, SECULAR VARIATION, time}, isbn = {0002-9599}, doi = {10.2475/ajs.306.3.135 }, author = {Arvidson, R. S. and Mackenzie, F. T. and Guidry, M.} } @conference {1686, title = {Mercury contamination in Connecticut and Long Island Sound from historic hat-making sources}, booktitle = {GSA Annual Meeting}, year = {2006}, note = {id: 747}, month = {2006}, address = {Philadelphia, PA}, author = {Goldoff, B. and Varekamp, J. C. and Neupane, A.} } @conference {1694, title = {Monthly resolved stable oxygen isotope record in a Palauan sclerosponge Acanthocheatetes wellsi for the period of 1977-2001}, booktitle = {10th International Coral Reef Symposium}, year = {2006}, note = {id: 1131}, month = {2006}, pages = {572-579}, author = {Grottoli, Andrea G.} } @article {1022, title = {Non-pollen palynomorphs from organic deposits of Posidonia oceanica: a new tool for palaeoenvironmental studies in marine peat-like deposits}, journal = {Palyno-Bulletin}, volume = {2}, year = {2006}, note = {id: 2005}, pages = {38-40}, abstract = {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 {\textquoteright}matte{\textquoteright}. 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.}, author = {L{\'o}pez-S{\'a}ez, J. A. and L{\'o}pez-Garc{\'\i}a, P. and Pozuelo, R. and Mateo, M. A. and Renom, P. and Garrido, D.} } @article {1960, title = {The North Anatolian fault in the Gulf of Izmit (Turkey): Rapid vertical motion in response to minor bends of a non-vertical continental transform}, journal = {Journal of Geophysical Research}, volume = {111}, year = {2006}, note = {id: 532}, month = {2006}, author = {Cormier, M. H. and Seeber, L. and McHugh, C. M. G. and Polonia, A. and Cagatay, M. N. and Emre, O. and Gasperini, L. and Gorur, N. and Bortoluzzi, G. and Bonatti, E. and Ryan, W. B. F. and Newman, K. R.} } @article {1947, title = {Origin of PCDD in ball clay assessed with compound-specifric chlorine isotope analysis and radiocarbon dating}, journal = {Environmental Science and Technology}, volume = {40}, year = {2006}, note = {id: 1040}, month = {2006}, pages = {3730-3755}, author = {Holmstrand, H. D. and Gadomski, D. and Mandalakis, M. and Tysklind, M. and Irvine, R. and Andersson, P. and Gustafsson, O.} } @article {1953, title = {Reduced agulhas leakage at the LGM inferred from an integrated provenance and flux dtudy}, journal = {Earth \& Planatary Science Letters}, volume = {250}, year = {2006}, note = {id: 632}, month = {2006}, pages = {72-88}, author = {Franzese, A. M. and Hemming, S. R. and Goldstein, S. L. and Anderson, R. F.} } @article {1948, title = {Rotasonic vibracores from northeastern North Carolina, cores OBX-10 through OBX-18}, journal = {NCGS Open-file Report}, volume = {II}, year = {2006}, note = {id: 704}, month = {2006}, pages = {1 CD ROM}, author = {Hoffman, C. W. and Farrell, K. M. and Pierson, J. A. and Ward, A. N. and Nickerson, J. G. and Brooks, R. W. and Ganey, J. G.} } @article {1913, title = {Sedimentology, physical properties and age of mass transport deposits associated with the Marques de Pombal Fault, Southwest Portuguese Margin}, journal = {Norwegian Journal of Geology}, volume = {86}, year = {2006}, note = {id: 623}, month = {2006}, pages = {177-186}, author = {Vizcaino, Alexis and Gracia, Eulalia and Pallas, Raimon and Garcia-Orellana, Jordi and Escutia, Carlota and Casas, David and Willmott, Veronica and Diez, Susana and Asioli, Alessandra and Danobeitia, Juanjo} } @article {1956, title = {Solid-state 13C NMR analysis of size and density fractions of marine sediments: Insight into organic carbon sources and preservation mechanisms}, journal = {Geochimica et Cosmochimica Acta}, volume = {70}, year = {2006}, note = {id: 1702}, month = {2006}, pages = {666-686}, author = {Dickens, A. F. and Baldock, J. A. and Smernik, R. J. and Wakeham, S. G. and Arnarson, T. S. and Gelinas, Y. and Hedges, J. I.} } @article {1950, title = {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}, journal = {Global Biogeochemical Cycles}, volume = {20}, year = {2006}, note = {id: 1129}, month = {2006}, author = {Guo, L. and Macdonald, R. W.} } @conference {1790, title = {Sources age and composition of dissolved and particulate organic matter delivered to a passive margin river system}, booktitle = {ASLO/AGU Ocean Science Meeting}, year = {2006}, note = {id: 485}, month = {2006}, address = {Honolulu, HI}, author = {Petsch, S. T. and Gordon, E. S. and Longworth, B. E. and Schillawki, S. E. and Raymond, P. A.} } @article {1952, title = {Spacial and temporal variation in cores from Lake Titicaca, Bolivia/Peru during the last 13,000 yrs}, journal = {Quaternary International}, volume = {158}, year = {2006}, note = {id: 588}, month = {2006}, pages = {23-29}, author = {Fritz, S. C. and Baker, P. A. and Tapia, P. and Garland, J.} } @article {1527, title = {Stable carbon isotopes in coastal Puerto Rico corals and adjacent natural waters: implications for land-ocean connectivity and land-use history}, volume = {Abstract $\#$OS25J-14}, year = {2006}, note = {id: 655}, month = {2006}, address = {Honolulu}, author = {Moyer, R. P. and Grottoli, A. G.} } @article {593, title = {Submarine earthquake geology along the North Anatolia Fault in the Marmara Sea, Turkey: A model for transform basin sedimentation}, journal = {Earth and Planetary Science Letters}, volume = {248}, year = {2006}, note = {085kgTimes Cited:55Cited References Count:98}, month = {Aug 30}, pages = {661-684}, abstract = {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.}, issn = {0012-821x}, doi = {10.1016/j.epsl.2006.05.038}, author = {McHugh, C. M. G. and Seeber, L. and Cormier, M. H. and Dutton, J. and Cagatay, N. and Polonia, A. and Ryan, W. B. F. and Gorur, N.} } @article {707, title = {Tracking the weathering of an oil spill with comprehensive two-dimensional gas chromatography}, journal = {Environmental Forensics}, volume = {7}, year = {2006}, note = {032ldTimes Cited:62Cited References Count:21}, month = {Mar}, pages = {33-44}, abstract = {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.}, issn = {1527-5922}, doi = {10.1080/15275920500506758}, author = {Nelson, R. K. and Kile, B. M. and Plata, D. L. and Sylva, S. P. and Xu, L. and Reddy, C. M. and Gaines, R. B. and Frysinger, G. S. and Reichenbach, S. E.} } @article {679, title = {Young Danube delta documents stable Black Sea level since the middle Holocene: Morphodynamic, paleogeographic, and archaeological implications}, journal = {Geology}, volume = {34}, year = {2006}, note = {084aqTimes Cited:63Cited References Count:35}, month = {Sep}, pages = {757-760}, abstract = {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.}, issn = {0016-8505}, doi = {10.1130/G22587.1}, author = {Giosan, L. and Donnelly, J. P. and Constantinescu, S. and Filip, F. and Ovejanu, I. and Vespremeanu-Stroe, A. and Vespremeanu, E. and Duller, G. A. T.} } @article {979, title = {A 17,000 year history of Andean climatic and vegetation change from Laguna de Chochos, Peru}, journal = {Journal of Quaternary Science}, volume = {20}, year = {2005}, note = {id: 1015}, pages = {703-714}, abstract = {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{\textendash}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.}, doi = {10.1002/jqs.983}, author = {Bush, M. B. and Hansen, B. C. S. and Rodbell, D. T. and Seltzer, G. O. and Young, K. R. and Leon, B. and Abbott, M. B. and Silman, M. R. and Gosling, W. D.} } @article {1998, title = {Age and origin of Late Quaternary eolianite, Kaiehu Point (Moomomi), Molokai, Hawaii}, journal = {Journal of Coastal Research}, volume = {SI}, year = {2005}, note = {Sp. Iss. 42947fu Times Cited:3 Cited References Count:50 }, month = {Spr}, pages = {97-112}, abstract = {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.}, keywords = {Amino acid racemization, aminostratigraphy, bermuda, carbonate lithofacies, cementation, cliche paleosols, eolianite, hawaii, island, Late Quaternary, limestone petrology, Marine, molokai, oahu, precipitation, sea level, sea-level, south-australia, Stable isotopes, stratigraphy}, isbn = {0749-0208}, author = {Fletcher, C. H. and Murray-Wallace, C. V. and Glenn, C. R. and Sherman, C. E. and Popp, B. and Hessler, A.} } @article {684, title = {Basal inflection-control led shelf-edge wedges off New Jersey track sea-level fall}, journal = {Geology}, volume = {33}, year = {2005}, note = {922awTimes Cited:19Cited References Count:24}, month = {May}, pages = {429-432}, abstract = {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.}, issn = {0091-7613}, doi = {10.1130/G21310.1}, author = {Gulick, S. P. S. and Goff, J. A. and Austin, J. A. and Alexander, C. R. and Nordfjord, S. and Fulthorpe, C. S.} } @article {660, title = {Basin-wide sedimentation changes and deglacial lake-level rise in the Hovsgol basin, NW Mongolia}, journal = {Quaternary International}, volume = {136}, year = {2005}, note = {926rlTimes Cited:51Cited References Count:16}, month = {Jul}, pages = {59-69}, abstract = {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{\textquoteright}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 {\textquoteright}water gauge{\textquoteright} 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.}, issn = {1040-6182}, doi = {10.1016/j.quaint.2004.11.008}, author = {Prokopenko, A. A. and Kuzmin, M. I. and Wlliams, D. F. and Gelety, V. F. and Kalmychkov, G. V. and Gvozdkov, A. N. and Solotchin, P. A.} } @conference {1576, title = {Beam Profile Measurements for a MC-SNICS Source with Spherical Ionizer}, booktitle = {10th International Conference on Accelerator Mass Spectrometry}, year = {2005}, note = {id: 1706}, month = {2005}, address = {Berkeley, California}, author = {von Reden, K. F. and Griffin, V. S. and Roberts, M. L.} } @article {1984, title = {Contribution of biomass burning to polycyclic aromatic hydrocarbons in European background aerosols}, journal = {Environmental Science and Technology}, volume = {39}, year = {2005}, note = {id: 510}, month = {2005}, pages = {2976-2982}, author = {Mandalakis, M. and Gustafsson, O. and Alsberg, T. and Reddy, C. and Xu, L. and Klanova, J. and Holoubek, I. and Stephanou, E.} } @article {594, title = {Evidence from the Northeastern Atlantic basin for variability in the rate of the meridional overturning circulation through the last deglaciation}, journal = {Earth and Planetary Science Letters}, volume = {240}, year = {2005}, note = {995vhTimes Cited:93Cited References Count:69}, month = {Dec 15}, pages = {710-723}, abstract = {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.}, issn = {0012-821x}, doi = {10.1016/j.epsl.2005.09.061}, author = {Gherardi, J. M. and Labeyrie, L. and McManus, J. F. and Francois, R. and Skinner, L. C. and Cortijo, E.} } @article {598, title = {Fluctuations in export productivity over the last century from sediments of a southern Chilean fjord (44 degrees S)}, journal = {Estuarine Coastal and Shelf Science}, volume = {65}, year = {2005}, note = {975sfTimes Cited:22Cited References Count:53}, month = {Nov}, pages = {587-600}, abstract = {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.}, issn = {0272-7714}, doi = {10.1016/j.ecss.2005.07.005}, author = {Sepulveda, J. and Pantoja, S. and Hughen, K. and Lange, C. and Gonzalez, F. and Munoz, P. and Rebolledo, L. and Castro, R. and Contreras, S. and Avila, A. and Rossel, P. and Lorca, G. and Salamanca, M. and Silva, N.} } @article {493, title = {Geochemical and hydrogeological contrasts between shallow and deeper aquifers in two villages of Araihazar, Bangladesh: Implications for deeper aquifers as drinking water sources}, journal = {Geochimica et Cosmochimica Acta}, volume = {69}, year = {2005}, note = {id: 604; 999UZ Times Cited:59 Cited References Count:49}, pages = {5203-5218}, abstract = {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}, issn = {0016-7037}, doi = {10.1016/J.Gca.2005.06.001}, author = {Zheng, Y. and van Geen, A. and Stute, M. and Dhar, R. and Mo, Z. and Cheng, Z. and Horneman, A. and Gavrieli, I. and Simpson, H. J. and Versteeg, R. and Steckler, M. and Grazioli-Venier, A. and Goodbred, S. and Shahnewaz, M. and Shamsudduha, M. and Hoque, M. A. and Ahmed, K. M.} } @article {1987, title = {Geologic implications of Late Quaternary isostatic adjustment in the Penobscot/Kennebec River system, Maine}, journal = {Geological Society of America Abstracts with Programs}, volume = {37}, year = {2005}, note = {id: 1173}, month = {2005}, pages = {24}, author = {Kelley, Alice R. and Kelly, Joseph T. and Belknap, Daniel F. and Gontz, Allen M.} } @article {541, title = {Holocene hydrologic variation at Lake Titicaca, Bolivia/Peru, and its relationship to North Atlantic climate variation}, journal = {Journal of Quaternary Science}, volume = {20}, year = {2005}, note = {id: 1095; 000CQ Times Cited:21 Cited References Count:46}, pages = {655-662}, abstract = {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.}, issn = {0267-8179}, doi = {10.1002/Jqs.987}, author = {Baker, P. A. and Fritz, S. C. and Garland, J. and Ekdahl, E.} } @article {1995, title = {Impact of vegetation on sedimentary organic matter composition and polycyclic aromatic hydrocarbon attenuation}, journal = {Environ Sci Technol}, volume = {39}, year = {2005}, note = {Gregory, Samuel TShea, Damian Guthrie-Nichols, Elizabeth eng Research Support, U.S. Gov{\textquoteright}t, Non-P.H.S. 2005/08/09 09:00 Environ Sci Technol. 2005 Jul 15;39(14):5285-92. }, month = {Jul 15}, pages = {5285-92}, abstract = {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.}, keywords = {Biodegradation, Environmental, Environmental Monitoring, Geologic Sediments/chemistry, Magnetic Resonance Spectroscopy, Mass Spectrometry, Plants, Polycyclic Aromatic Hydrocarbons/*isolation \& purification/*metabolism, Refuse Disposal, Soil Pollutants/*isolation \& purification/*metabolism}, isbn = {0013-936X (Print)0013-936X (Linking)}, doi = {10.1021/es048028o }, url = {https://www.ncbi.nlm.nih.gov/pubmed/16082958}, author = {Gregory, S. T. and Shea, D. and Guthrie-Nichols, E.} } @article {2003, title = {Input of particulate organic and dissolved inorganic carbon from the Amazon to the Atlantic Ocean}, journal = {Geochemistry Geophysics Geosystems}, volume = {6}, year = {2005}, note = {909pwTimes Cited:17 Cited References Count:21 }, month = {Mar 18}, abstract = {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.}, keywords = {accumulation, amazon, C-14, carbon cycling, CO2, continental-shelf, poc, radiocarbon, river system, Sediment, total co(2), water}, isbn = {1525-2027}, doi = {10.1029/2004GC000842}, author = {Druffel, E. R. M. and Bauer, J. E. and Griffin, S.} } @article {1964, title = {Last deglaciation in the Okinawa Trough: Subtropical northwest Pacific link to Northern Hemisphere and tropical climate}, journal = {Paleoceanography}, volume = {20}, year = {2005}, note = {975ipTimes Cited:53 Cited References Count:55 }, month = {Oct 7}, abstract = {[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.}, keywords = {cal kyr bp, deep-ocean circulation, equatorial current, kuroshio current, late pleistocene, oxygen-isotope, planktonic-foraminifera, radiocarbon age calibration, south china sea, surface-water}, isbn = {0883-8305}, doi = {10.1029/2004PA001061}, url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2\&SrcAuth=Alerting\&SrcApp=Alerting\&DestApp=WOS\&DestLinkType=FullRecord;UT=WOS:000232654500001}, author = {Sun, Y. B. and Oppo, D. W. and Xiang, R. and Liu, W. G. and Gao, S.} } @article {1997, title = {Morphodynamics and evolution of Danube delta}, journal = {Journal of Sedimentary Research}, volume = {SP 83}, year = {2005}, note = {id: 499}, month = {2005}, pages = {391-410}, author = {Giosan, L. and Vespremeanu, E. and Donnelly, J. P. and Bhattacharya, J. and Buonaiuto, F.} } @article {1524, title = {Natural variability in skeletal growth rate, stable isotopes, and Sr/Ca composition in two species of Pacific sclerosponges (Acnathocheatetes wellsi and Astroclera welleyana)}, year = {2005}, note = {id: 1135}, month = {2005}, address = {Williamsburg, VA}, author = {Grottoli, A. G. and Adkins, J. F. and Moots, K.} } @article {574, title = {Pre- and post-industrial environmental changes as revealed by the biogeochemical sedimentary record of Drammensfjord, Norway}, journal = {Marine Geology}, volume = {214}, year = {2005}, note = {890unTimes Cited:23Cited References Count:105}, month = {Jan 30}, pages = {177-200}, abstract = {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{\textquoteright}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.}, issn = {0025-3227}, doi = {10.1016/j.margeo.2004.10.029}, author = {Smittenberg, R. H. and Baas, M. and Green, M. J. and Hopmans, E. C. and Schouten, S. and Damste, J. S. S.} } @conference {1752, title = {Preliminary research results indicate modern sedimentation ont he continental slope seaward of theWaipoao River, New Zealand}, booktitle = {New Zealand Marine Science Society Annual Meeting}, year = {2005}, note = {id: 637}, month = {2005}, address = {Wellington, NZ}, author = {Alexander, C. A. and Walsh, J. P. and Orpin, A. R. and Sumners, B. W. and Gerber, T. P. and Kuehl, S. A.} } @article {573, title = {Recent and modern marine erosion on the New Jersey outer shelf}, journal = {Marine Geology}, volume = {216}, year = {2005}, note = {925kdTimes Cited:42Cited References Count:53}, month = {May 15}, pages = {275-296}, abstract = {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{\textquoteright}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.}, issn = {0025-3227}, doi = {10.1016/j.margeo.2005.02.015}, author = {Goff, J. A. and Austin, J. A. and Gulick, S. and Nordfjord, S. and Christensen, B. and Sommerfield, C. and Olson, H. and Alexander, C.} } @article {1994, title = {Solar influence on the Indian summer monssoon during the Holocene}, journal = {Geophysical Research Letters}, volume = {32}, year = {2005}, note = {id: 535}, month = {2005}, pages = {1-4}, author = {Gupta, Anil K. and Das, Moumita and Anderson, David M.} } @conference {1789, title = {Source, timing and depositional environments of Paleochannel incision and infill on the New Jersey Shelf}, booktitle = {2005 National GSA Meeting}, year = {2005}, note = {id: 638}, month = {2005}, address = {Salat Lake City, UT}, author = {Alexander, C. and Christensen, B. and Turner, J. and Goff, J. and Austin J.A, Jr. and Venherm, C. and Nordfjord, S. and Sommerfield, C. and Gulick, S. and Fulthorpe, C.} } @article {1996, title = {The supply and preservation of ancient and modern components of organic carbon on the Canadian Beaufort Shelf of the Arctic Ocean}, journal = {Marine Chemistry}, volume = {93}, year = {2005}, note = {id: 757}, month = {2005}, pages = {53-73}, author = {Go{\~n}i, M. A. and Yunker, M. B. and Macdonald, R. W. and Eglinton, T. I.} } @article {2049, title = {Characterization of Siberian Arctic coastal sediments: Implications for terrestrial organic carbon export}, journal = {Global Biogeochemical Cycles}, volume = {18}, year = {2004}, note = {806knTimes Cited:99 Cited References Count:51 }, month = {Mar 10}, abstract = {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.}, keywords = {arctic ocean, BLACK CARBON, climate, CO2, continental-shelf, flux, isotopic composition, lena river, MATTER, ocean, organic carbon, quantification, Sediment}, isbn = {0886-6236}, doi = {10.1029/2003GB002087}, url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2\&SrcAuth=Alerting\&SrcApp=Alerting\&DestApp=WOS\&DestLinkType=FullRecord;UT=WOS:000220432900001}, author = {Guo, L. D. and Semiletov, I. and Gustafsson, O. and Ingri, J. and Andersson, P. and Dudarev, O. and White, D.} } @article {629, title = {Collapse and rapid resumption of Atlantic meridional circulation linked to deglacial climate changes}, journal = {Nature}, volume = {428}, year = {2004}, note = {McManus, J FFrancois, RGherardi, J-MKeigwin, L DBrown-Leger, SengResearch Support, Non-U.S. Gov{\textquoteright}tResearch Support, U.S. Gov{\textquoteright}t, Non-P.H.S.England2004/04/23 05:00Nature. 2004 Apr 22;428(6985):834-7.}, month = {Apr 22}, pages = {834-7}, abstract = {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.}, issn = {0028-0836 (Linking)}, doi = {10.1038/nature02494}, author = {McManus, J. F. and Francois, R. and Gherardi, J. M. and Keigwin, L. D. and Brown-Leger, S.} } @article {2022, title = {Comments on potential geologic and seismic hazards affecting coastal Ventura County, CCalifornia}, journal = {U. S. Geological Survey OFR 1004-1286}, year = {2004}, note = {id: 420}, month = {2004}, pages = {19 p.}, author = {Ross, S. D. Boore and Fisher, M. and Frankel, A. and Geist, E. and Hudnut, K. and Kayen, R. and Lee, H. and Normark, W. R. and Wong, F.} } @article {2048, title = {Deglacial history of the Ecuadorian Andes and implication for climate variations: Preliminary results}, journal = {Eos Trans. AGU Fall Meeting Supplement}, volume = {85}, year = {2004}, note = {id: 1003}, month = {2004}, author = {Hall, M. and Rinterknecht, V. R. and Schaefer, J. M. and R, Seager and Greene, A.} } @conference {1619, title = {The early history of Long Island Sound}, booktitle = {7th Biennial Long Island Sound research conference, Program/Abstracts}, year = {2004}, note = {id: 741}, month = {2004}, author = {Varekamp, J. C. and Thomas, E. and Groner, M.} } @article {2039, title = {Evaluation of ocean carbon cycle models with data-based metrics}, journal = {Geophysical Research Letters}, volume = {31}, year = {2004}, note = {811adTimes Cited:110 Cited References Count:17 }, month = {Apr 2}, abstract = {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.}, keywords = {anthropogenic co2, pacific-ocean, radiocarbon}, isbn = {0094-8276}, doi = {10.1029/2003GL018970}, url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2\&SrcAuth=Alerting\&SrcApp=Alerting\&DestApp=WOS\&DestLinkType=FullRecord;UT=WOS:000220743900001}, author = {Matsumoto, K. and Sarmiento, J. L. and Key, R. M. and Aumont, O. and Bullister, J. L. and Caldeira, K. and Campin, J. M. and Doney, S. C. and Drange, H. and Dutay, J. C. and Follows, M. and Gao, Y. and Gnanadesikan, A. and Gruber, N. and Ishida, A. and Joos, F. and Lindsay, K. and Maier-Reimer, E. and Marshall, J. C. and Matear, R. J. and Monfray, P. and Mouchet, A. and Najjar, R. and Plattner, G. K. and Schlitzer, R. and Slater, R. and Swathi, P. S. and Totterdell, I. J. and Weirig, M. F. and Yamanaka, Y. and Yool, A. and Orr, J. C.} } @article {464, title = {A gas ion source for continuous-flow AMS}, journal = {Proceedings of the Ninth International Conference on Accelerator Mass Spectrometry}, volume = {223-224}, year = {2004}, note = {id: 2104}, pages = {149-154}, abstract = {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.}, issn = {0168-583X}, doi = {10.1016/j.nimb.2004.04.031}, author = {Schneider, R. J. and Kim, S. W. and von Reden, K. F. and Hayes, J. M. and Wills, J. S. C. and Griffin, V. S. and Sessions, A. L. and Sylva, S.} } @article {724, title = {Great earthquakes and tsunamis of the past 2000 years at the Salmon River estuary, central Oregon coast, USA}, journal = {Bulletin of the Seismological Society of America}, volume = {94}, year = {2004}, note = {855anTimes Cited:18Cited References Count:80}, month = {Aug}, pages = {1276-1292}, abstract = {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.}, issn = {0037-1106}, doi = {10.1785/012003210}, author = {Nelson, A. R. and Asquith, A. C. and Grants, W. C.} } @article {2041, title = {Holocene development of the Yellow River{\textquoteright}s subaqueous delta, North Yellow Sea}, journal = {Marine Geology}, volume = {209}, year = {2004}, note = {id: 650}, month = {2004}, pages = {45-67}, author = {Liu, J. P. and Milliman, J. D. and Gao, S. and Cheng, P.} } @inbook {1446, title = {Late Quaternary sedimentation and deformation in Santa Monica and Catalina Basins, offshore southern California}, booktitle = {Geology and Tectonics of Santa Cataline Island and the California Continental Borderland}, year = {2004}, note = {id: 991}, month = {2004}, pages = {291-317}, address = {Santa Ana, California}, author = {Normark, W. R. and Baher, S. and Sliter, R.}, editor = {Guidebook, South Coast Geological Society Annual Field Trip} } @article {2014, title = {NotCal04-Comparison/Calibration 14 C records 26-50 cal kBP}, journal = {Radiocarbon}, volume = {46}, year = {2004}, note = {id: 399}, month = {2004}, pages = {1225{\textendash}1238}, author = {van der Plicht, J. and Beck, J. W. and Bard, E. and Baillie, M. G. L. and Blackwell, P. G. and Buck, C. E. and Friedrich, M. and Guilderson, T. P. and Hughen, K. A. and Kromer, B.} } @article {2052, title = {Oceanic ventilation and biogeochemical cycling: Understanding the physical mechanisms that produce realistic distributions of tracers and productivity}, journal = {Global Biogeochemical Cycles}, volume = {18}, year = {2004}, note = {867xpTimes Cited:66 Cited References Count:42 }, month = {Oct 20}, abstract = {[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.}, keywords = {Biogeochemical cycles, bottom water formation, circulation models, diffusion, particle export, pycnocline, sensitivity, Temperature, vertical exchange, weddell sea, World Ocean}, isbn = {0886-6236}, doi = {10.1029/2003GB002097}, url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2\&SrcAuth=Alerting\&SrcApp=Alerting\&DestApp=WOS\&DestLinkType=FullRecord;UT=WOS:000224876500001}, author = {Gnanadesikan, A. and Dunne, J. P. and Key, R. M. and Matsumoto, K. and Sarmiento, J. L. and Slater, R. D. and Swathi, P. S.} } @conference {1734, title = {Paleochannel incision and infill on the New Jersey shelf: timing, character and depositional environment}, booktitle = {2005 SE GSA Meeting}, year = {2004}, note = {id: 1120}, month = {2004}, address = {Biloxi, MS}, author = {Alexander, C. and Christensen, C. and Goff, J. and Austin J.A, Jr. and Venherm, C. and Nordfjord, S. and Gulick, S. and Sommerfield, C. and Fulthorpe, C. and Schock, S.} } @article {2010, title = {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}, journal = {Nuclear Instruments and Methods in Physics Research}, volume = {B 223-224}, year = {2004}, note = {id: 1810}, month = {2004}, pages = {50-54}, author = {von Reden, K. and Donoghue, J. and Elder, K. and Gagnon, A. and Gerlach, D. and Griffin, V. S. and Healy, R. and Long, P. and McNichol, A. P. and Percy, D. and Roberts, M. L. and Schneider, R. J. and Xu, L. and Hayes, J.} } @inbook {1444, title = {Quaternary sea level history of the United States}, booktitle = {The Quaternary period in the United States, Developments in Quaternary science}, year = {2004}, note = {id: 706}, month = {2004}, pages = {147-183}, publisher = {Elsevier}, organization = {Elsevier}, address = {Amsterdam}, author = {Muhs, D. R. and Wehmiller, J. F. and Simmons, K. R. and York, L. L.}, editor = {Gillespie, A. R.} } @article {2040, title = {Radiocarbon apportionment of fossil versus biofuel combustion sources of polycyclic aromatic hydrocarbons in the Stockholm metropolitan area}, journal = {Environ Sci Technol}, volume = {38}, year = {2004}, note = {Mandalakis, ManolisGustafsson, Orjan Reddy, Christopher M Xu, Li eng Comparative Study Research Support, Non-U.S. Gov{\textquoteright}t Research Support, U.S. Gov{\textquoteright}t, Non-P.H.S. 2004/11/17 09:00 Environ Sci Technol. 2004 Oct 15;38(20):5344-9. }, month = {Oct 15}, pages = {5344-9}, abstract = {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{\textquoteright} 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.}, keywords = {*Bioelectric Energy Sources, *Fossil Fuels, Biomass, Carbon Radioisotopes, Cities, Environmental Monitoring, Fresh Water, Geologic Sediments/*analysis, Polycyclic Aromatic Hydrocarbons/*analysis/isolation \& purification, Sweden, Water Pollutants, Chemical/*analysis/isolation \& purification}, isbn = {0013-936X (Print)0013-936X (Linking)}, doi = {10.1021/es049088x}, url = {https://www.ncbi.nlm.nih.gov/pubmed/15543735}, author = {Mandalakis, M. and Gustafsson, O. and Reddy, C. M. and Xu, L.} } @article {2051, title = {Radiocarbon studies of Long Island Sound sediments}, journal = {EOS Trans. AGU}, volume = {85}, year = {2004}, note = {id: 737}, month = {2004}, author = {Groner, M. and Thomas, E. and Varekamp, J. C.} } @article {796, title = {Relations between environmental black carbon sorption and geochemical sorbent characteristics}, journal = {Environmental Science \& Technology}, volume = {38}, year = {2004}, note = {834fgTimes Cited:90Cited References Count:48}, month = {Jul 1}, pages = {3632-3640}, abstract = {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.}, issn = {0013-936x}, doi = {10.1021/es0498742}, author = {Cornelissen, G. and Kukulska, Z. and Kalaitzidis, S. and Christanis, K. and Gustafsson, O.} } @article {280, title = {Sensitivity of present and future surface temperatures to precipitation characteristics}, journal = {Climate Research}, volume = {28}, year = {2004}, note = {id: 1696}, pages = {53-65}, abstract = {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.}, doi = {10.3354/cr028053}, author = {Lynn, Barry H. and Druyan, Leonard and Hogrefe, Christian and Dudhia, Jimy and Rosenzweig, Cynthia and Goldberg, Richard and Rind, David and Healy, Richard and Rosenthal, Joyce and Kinney, Patrick} } @book {1373, title = {Shoreline Changes on the Elizabeth Islands over the Past 5000 Years}, year = {2004}, note = {id: 715}, month = {2004}, publisher = {Cuttyhunk Historical Society}, organization = {Cuttyhunk Historical Society}, address = {Cuttyhunk, MA}, author = {Gaines, Sarah} } @article {2050, title = {Stable carbon and oxygen isotope records in a Palau sclerosponge}, journal = {Geochimica Et Cosmochimica Acta}, volume = {68}, year = {2004}, note = {Suppl. S827th Times Cited:0 Cited References Count:0 }, month = {Jun}, pages = {A474-A474}, isbn = {0016-7037}, doi = {10.1016/j.gca.2004.05.010}, author = {Grottoli, A. G. and Gibb, O.} } @article {2024, title = {Style, context, and chronology of a wooden canoe model from Santa Rosa Island, California}, journal = {Journal of California and Great Basin Anthropology}, volume = {24}, year = {2004}, note = {id: 1092}, month = {2004}, pages = {301-307}, author = {Rick, Torben C. and Johnson, John R. and Erlandson, Jon M. and Gamble, Lynn H.} } @article {2047, title = {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}, journal = {Global Biogeochemical Cycles}, volume = {18}, year = {2004}, note = {id: 531}, month = {2004}, pages = {1-9}, author = {Hwang, Jeomshik and Druffel, Ellen R. M. and Griffin, Sheila and L, Smith Kenneth, Jr. and Baldwin, Roberta J. and Bauer, James E.} } @conference {1817, title = {The urban sea: anthropogenic influences on benthic foraminifera in Long Island Sound}, booktitle = {IGC 32}, year = {2004}, note = {id: 738}, month = {2004}, address = {Florence, Italy}, author = {Thomas, E. and Varekamp, J. C. and Thaler, B. and Groner, M.} } @article {630, title = {Abrupt changes in the Asian southwest monsoon during the Holocene and their links to the North Atlantic Ocean}, journal = {Nature}, volume = {421}, year = {2003}, note = {637uwTimes Cited:483Cited References Count:30}, month = {Jan 23}, pages = {354-357}, abstract = {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.}, issn = {0028-0836}, doi = {10.1038/nature01340}, author = {Gupta, A. K. and Anderson, D. M. and Overpeck, J. T.} } @article {2075, title = {Asynchronous alkenone and foraminifera records from the Benguela Upwelling System}, journal = {Geochimica et Cosmochimica Acta}, volume = {67}, year = {2003}, note = {id: 1067}, month = {2003}, pages = {2157-2171}, author = {Mollenhauer, Gesine and Eglinton, Timothy I. and Ohkouchi, Naohiko and Schneider, Ralph R. and Muller, Peter J. and Grootes, Pieter M. and Rullkotter, Jurgen} } @article {2078, title = {Climate and the collapse of Mayan civilization}, journal = {Science}, volume = {299}, year = {2003}, note = {id: 556}, month = {2003}, pages = {1731-1735}, author = {Haug, G. H. and Gunther, D. and Peterson, L. C. and Sigman, D. M. and Hughen, K. A.} } @conference {1592, title = {COMPARE04-Comparison/calibration of 14C records 26-50 ka}, booktitle = {Abstracts, 18th International Radiocarbon Conf.}, year = {2003}, note = {id: 564}, month = {2003}, address = {Wellington, NZ}, author = {van der Plicht, J. and Hughen, K. A. and Guilderson, T. P. and Reimer, P.} } @conference {1593, title = {A comparison of rates of time averaging between the bivalve Macoma cleryana and brachiopod Bouchardia rosea on a shallow subtropical shelf}, booktitle = {Geological Society of America, Abstracts with Programs}, year = {2003}, note = {id: 720}, month = {2003}, address = {Seattle, WA, USA}, abstract = {35(6):273}, author = {Barbour-Wood, S. L. and Krause R.A, Jr. and Kowalewski, M. and Wehmiller, J. F. and Simoes, M. G. and Goodfriend, G. A.} } @article {2079, title = {Decadal timescale shift in the 14C record of a central equatorial Pacific coral}, journal = {Radiocarbon}, volume = {45}, year = {2003}, note = {id: 1130}, month = {2003}, pages = {91-99}, author = {Grottoli, A. G. and Gille, S. T. and Druffel, E. R. M. and Dunbar, R. B.} } @article {937, title = {Late-Quaternary cold events recorded in the Southern Ocean sediments, Pacific Sector}, journal = {Terra Antartica}, volume = {9}, year = {2003}, note = {id: 1000}, pages = {100-105}, author = {Langone, L. and Capotondi, L. and Giglio, F. and Focaccia, P. and C, Morigi and Ravaioli, M.} } @article {2072, title = {Paleoenvironmental inferences from core Anta95-1 (Granite Harobr, Sw Ross Sea-Antarctica)}, journal = {Terra Antarctica reports}, volume = {8}, year = {2003}, note = {id: 1001}, month = {2003}, pages = {133-138}, author = {Orsini, G. and Giglio, F. and Langone, L. and Ravaioli, M.} } @article {2083, title = {Penetration of anthropogenic carbon into organic particles of the deep ocean}, journal = {Geophysical Research Letters}, volume = {30}, year = {2003}, note = {709dpTimes Cited:12 Cited References Count:29 }, month = {Jul 23}, pages = {1744}, abstract = {[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.}, keywords = {bomb radiocarbon, C-14, CO2, delta-c-13, MATTER, NORTH PACIFIC-OCEAN, SARGASSO SEA, Sediment, variability, water}, isbn = {0094-8276}, doi = {10.1029/2003GL017423}, author = {Druffel, E. R. M. and Bauer, J. E. and Griffin, S. and Hwang, J.} } @article {644, title = {A possible record of the Younger Dryas event in deep-sea sediments of the Southern Ocean (Pacific sector)}, journal = {Palaeogeography Palaeoclimatology Palaeoecology}, volume = {198}, year = {2003}, note = {723feTimes Cited:15Cited References Count:55}, month = {Sep 15}, pages = {265-278}, abstract = {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.}, issn = {0031-0182}, doi = {10.1016/S0031-0182(03)00404-8}, author = {Morigi, C. and Capotondi, L. and Giglio, F. and Langone, L. and Brilli, M. and Turi, B. and Ravaioli, M.} } @article {360, title = {Quantitative estimates of time-averaging in terebratulidbrachiopod shell accumulations from a modern tropical shelf}, journal = {Paleobiology}, volume = {29}, year = {2003}, note = {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}, pages = {381-402}, abstract = {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 (}, issn = {0094-8373, 0094-8373}, doi = {10.1043/0094-8373(2003)029(0381:QEOTIT)2.0.CO;2}, author = {Carroll, M. and Kowalewski, M. and Simoes, M. G. and Goodfriend, G. A.} } @mastersthesis {1311, title = {A radiocarbon method and multi-tracer approach to quantifying groundwater discharge to coastal waters}, volume = {PH.D.}, year = {2003}, month = {2003}, school = {MIT/WHOI}, address = {Cambridge, MA/Woods Hole, MA}, author = {Gramling, Carolyn} } @article {645, title = {Sea-level changes and depositional environments in the Izmit Gulf, eastern Marmara Sea, during the late glacial-Holocene period}, journal = {Marine Geology}, volume = {202}, year = {2003}, note = {749gpTimes Cited:52Cited References Count:30}, month = {Nov 30}, pages = {159-173}, abstract = {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 {\textquoteright}Lake{\textquoteright} 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 {\textquoteright}Lake{\textquoteright}. 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.}, issn = {0025-3227}, doi = {10.1016/S0025-3227(03)00259-7}, author = {Cagatay, M. N. and Gorur, N. and Polonia, A. and Demirbag, E. and Sakinc, M. and Cormier, M. H. and Capotondi, L. and McHugh, C. and Emre, O. and Eris, K.} } @article {2080, title = {Sediment characteristics at selected sites of the Ross Sea continental shelf: does the sedimentary record reflect water column fluxes?}, journal = {Antarctic Science}, volume = {15}, year = {2003}, note = {id: 440}, month = {2003}, pages = {133-139}, author = {Frignani, M. and Giglio, F. and Accornero, A. and Langone, L. and Ravaioli, M.} } @conference {1785, title = {Sedimentology and age control of late Quaternary New Jersey shelf deposits}, booktitle = {AGU Fall 2003 Meeting}, year = {2003}, note = {id: 636}, month = {2003}, address = {San Francisco, CA}, author = {Alexander, C. and Sommerfield, C. and Austin J.A, Jr. and Christensen, B. and Fulthorpe, C. and Goff, J. and Gulick, S. and Nordfjord, S. and Nielson, D. and Schock, S.} } @article {894, title = {Stratigraphic evolution of the late Holocene Ganges-Brahmaputra lower delta plain}, journal = {Sedimentary Geology}, volume = {155}, year = {2003}, note = {642qaTimes Cited:92Cited References Count:84}, month = {Feb 1}, pages = {317-342}, abstract = {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.}, keywords = {Ganges{\textendash}Brahmaputra, Late Holocene, Stratigraphic evolution}, issn = {0037-0738}, doi = {10.1016/S0037-0738(02)00185-9}, author = {Allison, M. A. and Khan, S. R. and Goodbred, S. L. and Kuehl, S. A.} } @inbook {1405, title = {A 24,600 year diatom record from the northern basin of Lake Malawi}, booktitle = {The East African Great Lakes, Limnology, Palaeoclimatology and Biodiversity}, series = {Advances in global change research}, year = {2002}, note = {id: 1479}, month = {2002}, publisher = {Kluwer Academic Publishers, Dordrecht}, organization = {Kluwer Academic Publishers, Dordrecht}, isbn = {6610618461}, author = {Gasse, F. and Barker, P. and Johnson, T. C.}, editor = {Odada, E. O.} } @article {532, title = {A 4000-Year Lacustrine Record of Environmental Change in the Southern Maya Lowlands, Pet{\'e}n, Guatemala}, journal = {Quaternary Research}, volume = {57}, year = {2002}, note = {id: 2106}, pages = {183-190}, abstract = {A 4000-yr sediment core record from Lake Salpet{\'e}n, 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 {\textpm}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 Yucat{\'a}n 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.}, issn = {0033-5894}, doi = {10.1006/qres.2001.2305}, author = {Rosenmeier, Michael F. and Hodell, David A. and Brenner, Mark and Curtis, Jason H. and Guilderson, Thomas P.} } @conference {1572, title = {Assessing the linkages among climate variability, land-use change, and the sedimentary regime of the Upper Chesapeak Bay}, booktitle = {Proceedings Coastal Environment 2002}, year = {2002}, note = {id: 1218}, month = {2002}, pages = {183-192}, publisher = {WIT Press}, organization = {WIT Press}, author = {Barros, A. P. and Gordon, S. J.} } @article {903, title = {Challenges in radiocarbon dating organic carbon in opal-rich marine sediments}, journal = {Radiocarbon}, volume = {44}, year = {2002}, note = {591keTimes Cited:13Cited References Count:28}, pages = {123-136}, abstract = {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.}, issn = {0033-8222}, url = {https://journals.uair.arizona.edu/index.php/radiocarbon/article/view/4084/3509}, author = {Zheng, Y. and Anderson, R. F. and Froelich, P. N. and Beck, W. and McNichol, A. P. and Guilderson, T.} } @article {2114, title = {Compositional characterization of prehistoric ceramics: A new approach}, journal = {Journal of Archaeological Sciences}, volume = {29}, year = {2002}, note = {id: 474}, month = {2002}, pages = {443-455}, author = {Kennett, D. J. and Sakai, S. and Neff, H. and Gossett, R. and Larson, D. O.} } @article {668, title = {A Critical Evaluation of Interlaboratory Data on Total, Elemental, and Isotopic Carbon in the Carbonaceous Particle Reference Material, NIST SRM 1649a}, journal = {J Res Natl Inst Stand Technol}, volume = {107}, year = {2002}, note = {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.}, month = {May-Jun}, pages = {279-98}, abstract = {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.}, issn = {1044-677X (Linking)}, doi = {10.6028/jres.107.022}, author = {Currie, L. A. and Benner, B. A., Jr. and Kessler, J. D. and Klinedinst, D. B. and Klouda, G. A. and Marolf, J. V. and Slater, J. F. and Wise, S. A. and Cachier, H. and Cary, R. and Chow, J. C. and Watson, J. and Druffel, E. R. and Masiello, C. A. and Eglinton, T. I. and Pearson, A. and Reddy, C. M. and Gustafsson, O. and Quinn, J. G. and Hartmann, P. C. and Hedges, J. I. and Prentice, K. M. and Kirchstetter, T. W. and Novakow, T. and Puxbaum, H. and Schmid, H.} } @article {2119, title = {Drowned reefs and antecedent karst topography, Au{\textquoteright}au Channel, S. E. Hawaiian Island}, journal = {EOS}, volume = {83}, year = {2002}, note = {id: 662}, month = {2002}, pages = {82}, author = {Grigg, R. W. and Grossman, E. E. and al, et} } @article {703, title = {A high-resolution paleoclimate record spanning the past 25,000 years in southern East Africa}, journal = {Science}, volume = {296}, year = {2002}, note = {Johnson, Thomas CBrown, Erik TMcManus, JamesBarry, SylviaBarker, PhilipGasse, FrancoisengResearch Support, U.S. Gov{\textquoteright}t, Non-P.H.S.2002/04/06 10:00Science. 2002 Apr 5;296(5565):113-32.}, month = {Apr 05}, pages = {113-32}, abstract = {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.}, issn = {0036-8075 (Linking)}, doi = {10.1126/science.1070057}, author = {Johnson, T. C. and Brown, E. T. and McManus, J. and Barry, S. and Barker, P. and Gasse, F.} } @article {2120, title = {In situ calcium carbonate dissolution in the Pacific Ocean}, journal = {Global Biogeochemical Cycles}, volume = {16}, year = {2002}, note = {649rqTimes Cited:86 Cited References Count:60 }, month = {Dec 31}, abstract = {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.}, keywords = {anthropogenic co(2), anthropogenic co2, aragonite saturation, atmospheric carbon, caco(3) dissolution, calcite saturation, carbonate lysocline, chemical lysocline, coccolithophore emiliania-huxleyi, indian-ocean, north pacific, organic-matter, Pacific Ocean, panama basin, particulate matter}, isbn = {0886-6236}, doi = {10.1029/2002GB001866}, author = {Feely, R. A. and Sabine, C. L. and Lee, K. and Millero, F. J. and Lamb, M. F. and Greeley, D. and Bullister, J. L. and Key, R. M. and Peng, T. H. and Kozyr, A. and Ono, T. and Wong, C. S.} } @article {338, title = {Increase in the Asian southwest monsoon during the past four centuries}, journal = {Science}, volume = {297}, year = {2002}, note = {id: 536; Anderson, David M Overpeck, Jonathan T Gupta, Anil K New York, N.Y. Science. 2002 Jul 26;297(5581):596-9.}, pages = {596-9}, abstract = {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.}, issn = {1095-9203 (Electronic) 0036-8075 (Linking)}, doi = {10.1126/science.1072881}, author = {Anderson, D. M. and Overpeck, J. T. and Gupta, A. K.} } @article {2099, title = {Influence of Vegetation Change on Watershed Hydrology: Implications for Paleoclimatic Interpretation of Lacustrine d180 Records}, journal = {Journal of Paleolimnology}, volume = {27}, year = {2002}, note = {id: 1386}, month = {2002}, pages = {117-131}, author = {Rosenmeier, M. F. and Hodell, D. A. and Brenner, M. and Curtis, J. H. and Martin, J. B. and Anselmetti, F. S. and Ariztegui, D. and Guilderson, T. P.} } @article {2096, title = {Inorganic carbon in the Indian Ocean: Distribution and dissolution processes}, journal = {Global Biogeochemical Cycles}, volume = {16}, year = {2002}, note = {643rkTimes Cited:50 Cited References Count:72 }, month = {Oct-Nov}, abstract = {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.}, keywords = {alkalinity, anthropogenic co2, arabian sea, calcium carbonate, Carbon cycle, dioxide system, dissociation, indian ocean, pressure, saturation state, SEAWATER, Temperature, thermodynamics, total alkalinity, total co2, water}, isbn = {0886-6236}, doi = {10.1029/2002GB001869}, author = {Sabine, C. L. and Key, R. M. and Feely, R. A. and Greeley, D.} } @conference {1682, title = {A marine record of Holocene climate events in tropical South America, abstract}, booktitle = {Eos Trans. AGU 83, Fall Meeting Suppl}, year = {2002}, note = {id: 1080}, month = {2002}, address = {San Francisco, CA}, author = {Haug, G. H. and Gunther, D. and Hughen, K. A. and Peterson, L. C. and Rohl, U.} } @conference {1744, title = {Plans for expanded 14C analyses at the NOSAMS facility - a status and progress report}, booktitle = {International Conference on Accelerator Mass Spectrometry}, year = {2002}, note = {id: 1685}, month = {2002}, address = {Nagoya, Japan}, author = {von Reden, K. F. and Donoghue, J. and Elder, K. and Gagnon, A. and Gerlach, D. and Griffin, V. and Healy, R. and Long, P. and McNichol, A. and Percy, D. and Roberts, M. L. and Schneider, R. J. and Xu, L. and Hayes, J. M.} } @conference {1765, title = {Radiocarbon dating of alkenones in sediments from the Namibian continental margin}, booktitle = {European Geophysical Society, XXVII General Assembly}, year = {2002}, note = {id: 546}, month = {2002}, address = {Nice, France}, author = {Mollenhauer, Gesine and Eglinton, Timothy I. and Ohkouchi, Nao and Grootes, Pieter M. and Muller, Peter J. and Rullkotter, Jurgen and Schneider, Ralph R.} } @conference {1768, title = {Radiocarbon in a Fanning Island coral: Inter-decadal variability in waters upwelling in the central equatorial Pacific from 1922-1955}, booktitle = {ALSO/AGU Ocean Sciences Meeting}, year = {2002}, note = {id: 658}, month = {2002}, address = {Honolulu, HI}, author = {Grottoli, A. G. and Gille, S. T. and Druffel, E. R. M. and Dunbar, R. B.} } @article {618, title = {The Shandong mud wedge and post-glacial sediment accumulation in the Yellow Sea}, journal = {Geo-Marine Letters}, volume = {21}, year = {2002}, note = {538tcTimes Cited:56Cited References Count:34}, month = {Mar}, pages = {212-218}, abstract = {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.}, issn = {0276-0460}, doi = {10.1007/s00367-001-0083-5}, author = {Liu, J. P. and Milliman, J. D. and Gao, S.} } @article {985, title = {Slip rates of the Karakorum fault, Ladakh, India, determined using cosmic ray exposure dating of debris flows and moraines}, journal = {Journal of Geophysical Research-Solid Earth}, volume = {107}, year = {2002}, note = {634wuTimes Cited:104Cited References Count:72}, month = {Sep}, pages = {ESE 7-1{\textendash}ESE 7-13}, abstract = {We measure an average slip rate of 4+/-1 mm yr(-1) along the Karakorum fault, heretofore considered one of Earth{\textquoteright}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.}, issn = {2169-9313}, doi = {10.1029/2000JB000100}, author = {Brown, E. T. and Bendick, R. and Bourles, D. L. and Gaur, V. and Molnar, P. and Raisbeck, G. M. and Yiou, F.} } @conference {1796, title = {Stable carbon isotope record in a Palau Sclerosponge}, booktitle = {Fall AGU}, year = {2002}, note = {id: 657}, month = {2002}, address = {San Francisco, CA}, author = {Grottoli, A. G.} } @article {1010, title = {Temporal and regional variability in sources and cycling of DOC and POC in the northwest Atlantic continental shelf and slope}, journal = {Deep-Sea Research II}, volume = {49}, year = {2002}, note = {id: 685}, pages = {4419}, chapter = {4387}, doi = {10.1016/S0967-0645(02)00123-6}, author = {Bauer, J. E. and Druffel, E. R. M. and Wolgast, D. M. and Griffin, S.} } @article {2108, title = {Were glacial iceberg surges in the North Atlantic triggered by global climatic warming?}, journal = {Marine Geology}, volume = {192}, year = {2002}, note = {id: 712}, month = {2002}, pages = {393-417}, author = {Moros, M. and Kuijpers, A. and Snowball, I. and Lassen, S. and Backstrom, D. and Gingele, F. and McManus, J. F.} } @article {2104, title = {The West Falmouth oil spill after thirty years: the persistence of petroleum hydrocarbons in marsh sediments}, journal = {Environ Sci Technol}, volume = {36}, year = {2002}, note = {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{\textquoteright}t Research Support, U.S. Gov{\textquoteright}t, Non-P.H.S. 2002/12/19 04:00 Environ Sci Technol. 2002 Nov 15;36(22):4754-60. }, month = {Nov 15}, pages = {4754-60}, abstract = {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.}, keywords = {*Accidents, Chromatography, Gas, Environmental Monitoring, Geologic Sediments/*chemistry, Hydrocarbons/*analysis, Massachusetts, Petroleum/*analysis, Ships, Time Factors, Water Pollutants, Chemical/*analysis}, isbn = {0013-936X (Print)0013-936X (Linking)}, doi = {10.1021/es020656n}, url = {https://www.ncbi.nlm.nih.gov/pubmed/12487296}, author = {Reddy, C. M. and Eglinton, T. I. and Hounshell, A. and White, H. K. and Xu, L. and Gaines, R. B. and Frysinger, G. S.} } @article {406, title = {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)}, journal = {Marine Chemistry}, volume = {73}, year = {2001}, note = {id: 1309}, pages = {125-152}, abstract = {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{\textendash}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.}, doi = {10.1016/S0304-4203(00)00101-8}, author = {Santschi, P. H. and Guo, L. and Asbill, S. and Allison, M. and Kepple, B. and Wen, L. S.} } @article {2162, title = {Amino acid composition and diagenesis in the shells of terebratulid brachiopod Bouchardia rosea (SW Atlantic)}, journal = {Geological Society of America Abstracts with Programs}, volume = {33}, year = {2001}, note = {id: 1417}, month = {2001}, author = {Carroll, M. and Kowalewski, M. and Simeos, M. G. and Goodfriend, G. A.} } @conference {1578, title = {Biogenic silica and organic carbon in sediments from the Pacific Sector of the Southern Ocean}, booktitle = {Antarctic Earth Sciences at the close of a Millenium: Proceedings 8th International Symposium on Artarctic Earth Sciences}, volume = {8th}, year = {2001}, note = {id: 284}, month = {2001}, pages = {35}, publisher = {Royal Society of New Zealand Bulletin}, organization = {Royal Society of New Zealand Bulletin}, author = {Giglio, F. and Langone, L. and Morigi, C. and Frignani, M. and Ravaioli, M.}, editor = {Gamble, J. A.} } @article {2154, title = {Carbon Isotope Ratios of Organic Compound Fractions Separated From Sinking Particulate Organic Matter at a Deep Sea Station in the Northeast Pacific}, journal = {EOS}, year = {2001}, note = {id: 256}, month = {2001}, author = {Druffel, E. R. and Grottoli, A. G. and Gille, S. T. and Dunbar, R. B.} } @article {2137, title = {Carbonate 14C Background: Does it have Multiple Personalities?}, journal = {Radiocarbon}, volume = {43}, year = {2001}, note = {id: 1501}, month = {2001}, pages = {169-176}, author = {Nadeau, Marie-Josee and Grootes, Pieter M. and Voelker, Antje and Bruhn, Frank and Duhr, Alexander and Oriwall, Angelika} } @article {2140, title = {Development of a Carbon Isotope-Based Tracer of Groundwater Fluxes into Estuaries and the Coastal Ocean}, journal = {EOS}, volume = {82}, year = {2001}, note = {id: 1409}, month = {2001}, pages = {S152}, author = {McCorkle, D. C. and Gramling, C. M. and Mulligan, A. E. and Woods, T. L.} } @conference {1278, title = {The Effect of Different Acid Treatments on the Radiocarbon Age of Sedimentary Organic Matter}, booktitle = {EOS, Transactions, American Geophysical Union}, year = {2001}, note = {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}, month = {January 2001}, publisher = {American Geophysical Union, 2000 Florida Ave., N.W. Washington DC 20009 USA, [mailto:service@agu.org]}, organization = {American Geophysical Union, 2000 Florida Ave., N.W. Washington DC 20009 USA, [mailto:service@agu.org]}, abstract = {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.}, keywords = {A, Atlantic, Acidification, Brackish, Brackishwater environment, carbon cycling, Chronostratigraphy, Estuarine sedimentation, organic carbon, organic matter, Palaeoceanography, Radioactivity and radioisotopes, Radiocarbon dating, Sediment chemistry, Stable isotopes}, url = {https://search.proquest.com/docview/19468089?accountid=29119}, author = {Batista, F and McNichol, A P and Gerlach, D S} } @article {2147, title = {Effects of biosynthesis and physiology on relative abundances and isotopic compositions of alkenones}, journal = {Geochemistry Geophysics Geosystems}, volume = {2}, year = {2001}, note = {458kdTimes Cited:6 Cited References Count:39 }, month = {Jan 29}, pages = {art. no.-2000GC000052}, abstract = {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{\textquoteright}) 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.}, keywords = {algae, alkenones, anhydrase, biogeochemical processes, biosynthesis, calcification, carbon-13, emiliania-huxleyi prymnesiophyceae, fractionation, Haptophytes, inorganic carbon utilization, instruments and techniques, isoprenoid biosynthesis, marine diatom, paleoceanography, photosynthesis, physiology, phytoplankton, sea surface temperature}, isbn = {1525-2027}, doi = {10.1029/2000GC000052}, author = {Gonzalez, E. L. and Riebesell, U. and Hayes, J. M. and Laws, E. A.} } @article {771, title = {Estimates of anthropogenic carbon uptake from four three-dimensional global ocean models}, journal = {Global Biogeochemical Cycles}, volume = {15}, year = {2001}, note = {417rwTimes Cited:187Cited References Count:64}, month = {Mar}, pages = {43-60}, abstract = {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{\textquoteright}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.}, issn = {0886-6236}, doi = {10.1029/2000gb001273}, author = {Orr, J. C. and Maier-Reimer, E. and Mikolajewicz, U. and Monfray, P. and Sarmiento, J. L. and Toggweiler, J. R. and Taylor, N. K. and Palmer, J. and Gruber, N. and Sabine, C. L. and Le Quere, C. and Key, R. M. and Boutin, J.} } @article {2145, title = {Evaluation of a protocol for the quantification of black carbon in sediments, soils, and aquatic sediments}, journal = {Global Biogeochem. Cycles}, volume = {15}, year = {2001}, note = {id: 1439}, month = {2001}, pages = {881-890}, author = {Gustafsson, O. and Bucheli, T. D. and Kululska, M. and Andersson, C. and Largeau, C. and Rouzard, J. N. and Reddy, C. M. and Eglinton, T. I.} } @article {413, title = {Geometry, numerical models and revised slip rates for the Reelfoot blind thrust and truishear fault-propagation fold, New Medrid Seismic zone}, journal = {Engineering Geology}, volume = {62}, year = {2001}, note = {id: 1381}, pages = {31-49}, abstract = {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{\textdegree} 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{\textdegree} 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{\textpm}0.1 mm/yr. The slip rate is based on 9 m of structural relief, the 2290{\textpm}60 ybp age of folded sediment and a 75{\textdegree} 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.}, doi = {10.1016/S0013-7952(01)00048-5}, author = {Champion, J. and Mueller, K. and Tate, A. and Guccione, M. J.} } @article {340, title = {The history of South American tropical precipitation for the past 25,000 years}, journal = {Science}, volume = {291}, year = {2001}, note = {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.}, pages = {640-3}, abstract = {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.}, issn = {0036-8075 (Print) 0036-8075 (Linking)}, doi = {10.1126/science.291.5504.640}, author = {Baker, P. A. and Seltzer, G. O. and Fritz, S. C. and Dunbar, R. B. and Grove, M. J. and Tapia, P. M. and Cross, S. L. and Rowe, H. D. and Broda, J. P.} } @article {411, title = {Holocene{\textendash}late Pleistocene non-tropical carbonate sediments and tectonic history of the western rift basin margin of the southern Gulf of California}, journal = {Sedimentary Geology}, volume = {144}, year = {2001}, note = {id: 1316}, pages = {149-157-161-178}, abstract = {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.}, doi = {10.1016/S0037-0738(01)00139-7}, author = {Halfar, J. and Godinez-Orta, L. and Goodfriend, G. A. and Mucciarone, D. A. and Ingle, J. C. and Holden, P.} } @article {409, title = {Identification of a novel alkenone in Black Sea sediments}, journal = {Organic Geochemistry}, volume = {32}, year = {2001}, note = {id: 1946; PT: J; UT: WOS:000168692100002}, pages = {633-645}, abstract = {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.}, issn = {0146-6380}, doi = {10.1016/S0146-6380(01)00019-5}, author = {Xu, L. and Reddy, C. M. and Farrington, J. W. and Frysinger, G. S. and Gaines, R. B. and Johnson, C. G. and Nelson, R. K. and Eglinton, T. I.} } @conference {1695, title = {Multiple anthropogenic tracer distributions in the ocean}, booktitle = {Sixth International CO2 Conference}, year = {2001}, note = {id: 319}, month = {2001}, address = {Sendai, Japan}, author = {Sabine, C. L. and Key, R. M. and Bullister, J. L. and Feely, R. A. and Lamb, M. F. and Millero, F. J. and Wanninkhof, R. and Peng, T. H. and Lee, K. and Kozyr, A. and Gruber, N.} } @conference {1717, title = {Oceanic changes in the southern Pacific Ocean during the last deglaciation time, as recorded by planktic foraminifers and oxigen isotopes. --Extended abstract}, booktitle = {ANTOSTRAT Symposium on "The geologic record of the Antarctic ice sheet from drilling, coring and seismic studies"}, year = {2001}, note = {id: 1428}, month = {2001}, pages = {137}, address = {Erice, Italy}, author = {Morigi, C. and Capotondi, L. and Giglio, F. and Langone, L. and Brilli, M. and Turi, B. and Ravaioli, M.} } @conference {1733, title = {Paleoceanographic changes in the Southern Ocean, during the last deglaciation time, as recorded by planktic foraminifers and oxygen isotopes--Poster}, booktitle = {ANTOSTRAT Symposium on "The geologic record of the Antarctic ice sheet from drilling, coring and seismic studies"--Poster}, year = {2001}, note = {id: 1424}, month = {2001}, pages = {137}, address = {Erice, Italy}, author = {Morigi, C. and Capotondi, L. and Giglio, F. and Langone, L. and Turi, B. and Brilli, M. and Ravaioli, M.} } @article {2131, title = {Pollen record of the last 500 years from the Doninos coastal lagoon (NW Iberian Peninsula): Changes in the pollinic catchment size versus paleoecological interpretation}, journal = {Journal of Coastal Research}, volume = {17}, year = {2001}, note = {479bdTimes Cited:6 Cited References Count:46 }, month = {Sum}, pages = {705-713}, abstract = {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. }, keywords = {charcoal, coastal lagoon, diatoms, human impact, Late Holocene, late-holocene, nw iberian peninsula, pollen, representation, source area, vegetation, vegetation history}, isbn = {0749-0208}, author = {Santos, L. and Bao, R. and Goni, M. F. S.} } @conference {1747, title = {Possible record of the yunger dryas event in sediments of the Southern Ocean (Pacific Sector)--Poster}, booktitle = {AUG}, year = {2001}, note = {id: 1423}, month = {2001}, address = {Nice}, author = {Morigi, C. and Capotondi, L. and Langone, L. and Giglio, F. and Ravaioli, M.} } @conference {1746, title = {Possible record of the yunger dryas event in sediments of the southern ocean (Pacific sector)--abstract}, booktitle = {AUG}, year = {2001}, note = {id: 1427}, month = {2001}, address = {Nice, France}, author = {Morigi, C. and Capotondi, L. and Langone, L. and Giglio, F. and Ravaioli, M.} } @article {2127, title = {Post-glacial eruptive history of the western volcanic zone, Iceland}, journal = {EOS Trans. Amer. Geophys. Union}, volume = {82 suppl.}, year = {2001}, note = {id: 355}, month = {2001}, author = {Sinton, John M. and Gronvold, Karl} } @article {2160, title = {Radiocarbon and stable carbon isotopic evidence for transport and transformation of DOC, DIC and CH4 in a northern Minnesota peatland}, journal = {Global Biogeochemical Cycles}, volume = {14}, year = {2001}, note = {id: 98}, month = {2001}, pages = {1095-1105}, author = {Chasar, L. S. and Chanton, J. P. and Glaser, P. H. and Siegel, D. I. and Rivers, J. S.} } @article {2146, title = {Radiocarbon in a Fanning Island Coral: Inter-decadal Variability in Waters Upwelling in the Central Equatorial Pacific from 1922 - 1955}, journal = {EOS}, year = {2001}, note = {id: 1399}, month = {2001}, author = {Grottoli, A. G. and Gille, S. T. and Druffel, E. R. M. and Dunbar, R. B.} } @mastersthesis {1310, title = {Studi paleoambientali nel settore Pacifico dell{\textquoteright}Oceano Meridionale attraverso indagini geochimiche--thesis}, volume = {Dissertation/Thesis}, year = {2001}, month = {2001}, school = {Universita di Bologna}, address = {Balogna, Italy}, author = {Giuliana, Tino} } @article {622, title = {Subdivision of glacial deposits in southeastern Peru based on pedogenic development and radiometric ages}, journal = {Quaternary Research}, volume = {56}, year = {2001}, note = {452lzTimes Cited:27Cited References Count:51}, month = {Jul}, pages = {31-50}, abstract = {The Cordillera Vilcanota and Quelccaya Ice Cap region of southern Peru (13 degrees 30{\textquoteright}-14 degrees 00{\textquoteright}S; 70 degrees 40{\textquoteright}-71 degrees 25{\textquoteright}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.}, issn = {0033-5894}, doi = {10.1006/qres.2001.2221}, author = {Goodman, A. Y. and Rodbell, D. T. and Seltzer, G. O. and Mark, B. G.} } @conference {1810, title = {Time-averaged shell accumulations as records of past levels of marine benthic productivity: Implications for conservation biology and ecosystem restoration efforst}, booktitle = {North American Paleontologial Convention, Programs and Abstracts}, volume = {21 (supple. no. 2)}, year = {2001}, note = {id: 283}, month = {2001}, pages = {80-81}, publisher = {Paleobios}, organization = {Paleobios}, author = {Kowalewski, M. and Avila-Serrano, G. A. and Flessa, K. W. and Goodfriend, A. G.} } @conference {1811, title = {Time-Averaging in articulate brachiopod accumulations: A quantitative estimate of temporal resolution from a Holocene tropical shelf (Southern Brazil)}, booktitle = {North American Paleontological Convention, Programs and Abstracts}, volume = {21 (supple. no. 2)}, year = {2001}, note = {id: 1418}, month = {2001}, pages = {40}, publisher = {Paleobios}, organization = {Paleobios}, author = {Carroll, M. and Kowalewski, M. and Simoes, M. G. and Goodfriend, G. A.} } @article {864, title = {Age and composition of carbonate shoreface sediments, Kailua Bay, Oahu, Hawaii}, journal = {Coral Reefs}, volume = {19}, year = {2000}, note = {341wmTimes Cited:32Cited References Count:43}, month = {Jul}, pages = {141-154}, abstract = {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.}, issn = {0722-4028}, doi = {10.1007/s003380000085}, author = {Harney, J. N. and Grossman, E. E. and Richmond, B. M. and Fletcher, C. H.} } @inbook {1424, title = {Amino acid racemization in ostracodes}, booktitle = {Perspectives in Amino Acid and Protein Geochemistry}, year = {2000}, note = {id: 1390}, month = {2000}, pages = {145}, publisher = {Oxford University Press}, organization = {Oxford University Press}, isbn = {0195135075}, author = {Kaufman, D. S.}, editor = {Goodfriend, G. A.} } @article {2197, title = {Characterising the Namaqualand mudbelt of southern Africa: chronology, palynology and palaeoenvironments}, journal = {South African Geographical Journal}, volume = {82}, year = {2000}, note = {id: 219}, month = {2000}, author = {Gray, C. E. D. and Meadows, M. E. and Lee-Thorp, J. A. and Rogers, J.} } @inbook {1409, title = {Chronostratigraphy of sediments in the southern Gulf of California, based on amino acid racemization analysis of mollusks and rhodolith (Book Section)}, booktitle = {Perspectives in Amino Acid and Protein Geochemistry}, year = {2000}, note = {id: 174}, month = {2000}, pages = {320-330}, publisher = {Oxford University Press, NY}, organization = {Oxford University Press, NY}, author = {Goodfriend, G. A. and Halfar, J. and Godinez-Orta, L.}, editor = {Goodfriend, G. A.} } @article {328, title = {Enormous Ganges-Brahmaputra sediment discharge during strengthened early Holocene monsoon}, journal = {Geology}, volume = {28}, year = {2000}, note = {id: 147}, pages = {1083-1086}, abstract = {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{\textquoteright}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{\textquoteright}s past sediment load. Results reveal that \~{}5 {\texttimes} 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 {\texttimes} 109 t/yr. In comparison, modern sediment load of the Ganges-Brahmaputra is \~{}1 {\texttimes} 109 t/yr, ranking it first among the world{\textquoteright}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.}, doi = {10.1130/​0091-7613(2000)​28<1083:EGSDDS>​2.0.CO;2}, author = {Goodbred, S. L., Jr. and Kuehl, S. A.} } @conference {1639, title = {Glacial-Interglacial variations in the accumulation rates of major biogenic components in the Southern Pacific Ocean sediments--Abstract}, booktitle = {Third International SO-JGOFS Symposium}, year = {2000}, note = {id: 287}, month = {2000}, address = {Brest}, author = {Giglio, F. and Langone, L. and Ravaioli, M. and Frignani, M. and Mangini, A. and Fonti, P.} } @article {1492, title = {Global Distribution of Total Inorganic Carbon and Total Alkalinity Below the Deepest Winter Mixed Layer Depths}, volume = {ORNIJCDIAC-127 NDP-076}, year = {2000}, note = {id: 1970}, month = {2000}, institution = {Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory}, address = {Oak Ridge, Temessee}, abstract = {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{\textdegree}{\texttimes}1{\textdegree}{\texttimes}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.}, author = {Goyet, C. and Healy, R. and Ryan, J.} } @article {911, title = {Identification of a novel alkenone in Black Sea sediments}, journal = {Organic Geochemistry}, volume = {32}, year = {2000}, note = {id: 1719}, pages = {633-645}, abstract = {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.}, keywords = {Alkenone, Black Sea, Haptophytes, Holocene, Sediment, Structure characterization}, doi = {10.1016/S0146-6380(01)00019-5}, author = {Xu, L. and Reddy, C. M. and Farrington, J. W. and Frysinger, G. S. and Gaines, R. B. and Johnson, C. G. and Nelson, R. K. and Eglinton, T. I.} } @article {2196, title = {Identification of Seasonal-to-Decadal Timescale Variations in the Zonal Currents of the Central Equatorial Pacific Prior to 1955 Using A14C in Coral}, journal = {EOS}, volume = {81}, year = {2000}, note = {id: 254}, month = {2000}, abstract = {F767}, author = {Grottoli, A. G. and Druffel, E. R. M. and Gille, S. T. and Dunbar, R. B.} } @conference {1651, title = {Identification of seasonal-to-decadal timescale variations in the zonal currents of the central equatorial Pacific}, booktitle = {International Coral Reef Symposium}, year = {2000}, note = {id: 1401}, month = {2000}, address = {Bali}, author = {Grottoli, A. G. and Druffel, E. R. M. and Gille, S. T. and Dunbar, R. B.} } @inbook {1425, title = {Late Pleistocene and Holocene geological evolution of the central Penobscot River Valley: Surficial geology, geoarchaeology, and water supply (Book Section)}, booktitle = {Guidebook for Field Trips in Coastal and East-Central Maine: NEIGC 92nd Annual Meeting}, year = {2000}, note = {id: 152}, month = {2000}, address = {Orono, ME}, author = {Kelly, A. R. and Dorion, C. C. and Balco, G. and Dieffenbacher-Krall, A. and Garrett, P. and Locke, D. and Tolman, A.}, editor = {Yates, M. G.} } @conference {1674, title = {Late Quaternary sedimentary fluctuations of biogenic fluxes driven by climatic changes in the Southern Ocean--abstract}, booktitle = {XXV General Assembly of European Geophysical Society}, year = {2000}, note = {id: 288}, month = {2000}, address = {Nice, France}, author = {Langone, L. and Giglio, F. and Ravaioli, M. and Frignani, M. and Marozzi, G. and Rovatti, G.} } @article {804, title = {The N and W Iceland Shelf: insights into Last Glacial Maximum ice extent and deglaciation based on acoustic stratigraphy and basal radiocarbon AMS dates}, journal = {Quaternary Science Reviews}, volume = {19}, year = {2000}, note = {298udTimes Cited:71Cited References Count:75}, month = {Mar}, pages = {619-631}, abstract = {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.}, issn = {0277-3791}, doi = {10.1016/S0277-3791(99)00036-0}, author = {Andrews, J. T. and Hardardottir, J. and Helgadottir, G. and Jennings, A. E. and Geirsdottir, A. and Sveinbjornsdottir, A. E. and Schoolfield, S. and Kristjansdottir, G. B. and Smith, L. M. and Thors, K. and Syvitski, J. P. M.} } @article {808, title = {The NOSAMS sample preparation laboratory in the next millenium: Progress after the WOCE program}, journal = {Nuclear Instruments \& Methods in Physics Research Section B-Beam Interactions with Materials and Atoms}, volume = {172}, year = {2000}, note = {372jrTimes Cited:20Cited References Count:12}, month = {Oct}, pages = {409-415}, abstract = {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.}, issn = {0168-583x}, doi = {10.1016/S0168-583x(00)00201-9}, author = {Gagnon, A. R. and McNichol, A. P. and Donoghue, J. C. and Stuart, D. R. and von Reden, K.} } @article {2188, title = {Oceanic uptake of CO2 re-estimated through d13C in WOCE samples}, journal = {Nuclear Instruments and Methods in Physics Research}, volume = {B (172)}, year = {2000}, note = {id: 1817}, month = {2000}, pages = {501-512}, author = {Lerperger, M. and McNichol, A. P. and Peden, J. and Gagnon, A. R. and Elder, K. L. and Kutschera, W. and Rom, W. and Steier, P.} } @conference {1732, title = {Paleoceanographic changes in the Southern Ocean (Pacific sector) during the last 14 Ka.--Poster}, booktitle = {Third International SO-JGOFS Symposium}, year = {2000}, note = {id: 1422}, month = {2000}, address = {Brest}, author = {Morigi, C. and Capotondi, L. and Ravaioli, M. and Giglio, F. and Turi, B. and Brilli, M. and Langone, L.} } @mastersthesis {1308, title = {Paleoclimate signals in a speleothem from Belize, Senior Thesis}, volume = {Dissertation/Thesis}, year = {2000}, month = {2000}, pages = {54}, school = {Princeton University}, address = {Princeton, NJ}, author = {Gaines, Sarah M.} } @article {2198, title = {Procesos y formas periglaciares en la montana mediterranea}, journal = {Instituto de Estudios Turolenses, Teruel}, year = {2000}, note = {id: 371}, month = {2000}, pages = {63-79}, author = {Garcia-Ruiz, J. M.} } @article {2206, title = {Quantitative estimates of time-averaging in articulate brachiopod accumulations from a Holocene tropical shelf (Southern Brazil)}, journal = {Geological Society of America Abstracts with Programs}, volume = {32}, year = {2000}, note = {id: 124}, month = {2000}, pages = {A13-A14}, author = {Carroll, M. and Kowalewski, M. and Simoes, M. G. and Goodfriend, G. A.} } @article {749, title = {Quaternary palaeohydrological evolution of a playa lake: Salada Mediana, central Ebro Basin, Spain}, journal = {Sedimentology}, volume = {47}, year = {2000}, note = {383xwTimes Cited:31Cited References Count:76}, month = {Dec}, pages = {1135-1156}, abstract = {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.}, issn = {0037-0746}, doi = {10.1046/j.1365-3091.2000.00346.x}, author = {Valero-Garces, B. L. and Delgado-Huertas, A. and Navas, A. and Machin, J. and Gonzalez-Samperiz, P. and Kelts, K.} } @article {1033, title = {Radiocarbon dated Pinus sylvertis L. wood from beyond treeline on the Kola Peninsula, Russia}, journal = {The Holocene}, volume = {10}, year = {2000}, note = {id: 376}, pages = {143-147}, abstract = {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{\textdegree}439N, 35{\textdegree}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{\textdegree}259N, 35{\textdegree}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.}, url = {http://journals.sagepub.com/doi/abs/10.1191/095968300667807510}, author = {MacDonald, G. M. and Gervalis, B. and Snyder, J. A. and Tarasov, G. A. and Borisova, O. A.} } @conference {1767, title = {The radiocarbon gradient at the Antarctic Polar Front}, booktitle = {AGU Ocean Sciences Meeting}, year = {2000}, note = {id: 317}, month = {2000}, address = {San Antonio, TX}, author = {Schneider, R. J. and McNichol, A. P. and von Reden, K. F. and Elder, K. L. and Gagnon, A. R. and Key, R. M. and Quay, P. D. and Schlosser, P. M.} } @article {2187, title = {Radiocarbon-Based Estimates of the Groundwater Contribution to Estuarine Freshwater Budgets: An Example from Pages Creek, North Carolina}, journal = {EOS}, volume = {81}, year = {2000}, note = {id: 1315}, month = {2000}, pages = {S249}, author = {McCorkle, D. C. and Gramling, C. M. and Mulligan, A. E. and Woods, T. L. and Lott, D. E.} } @article {2184, title = {Shared Technologies: Later Stone Age Forager-Farmer Interaction and Metallurgy in the Ituri Rainforest, Democratic Republic of Congo}, journal = {Azania}, volume = {35}, year = {2000}, note = {id: 396}, month = {2000}, pages = {107-122}, author = {Mercader, J. and Rovira, S. and Gomez, P.} } @article {815, title = {The significance of large sediment supply, active tectonism, and eustasy on margin sequence development: Late Quaternary stratigraphy and evolution of the Ganges-Brahmaputra delta}, journal = {Sedimentary Geology}, volume = {133}, year = {2000}, note = {337jeTimes Cited:203Cited References Count:63}, month = {Jun 15}, pages = {227-248}, abstract = {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{\textquoteright}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.}, issn = {0037-0738}, doi = {10.1016/S0037-0738(00)00041-5}, author = {Goodbred, S. L. and Kuehl, S. A.} } @inbook {1408, title = {Stable carbon isotope record of middle to late Holocene climate changes from land snail shells at HInds Cave, Texas (Book Section)}, booktitle = {Holocene Environmental Change on the Great Plains of North America}, volume = {67}, year = {2000}, note = {id: 175}, month = {2000}, pages = {47-60}, publisher = {Quaternary Internation}, organization = {Quaternary Internation}, author = {Goodfriend, G. A. and Ellis, G. L.}, editor = {Wolfe, S.} } @conference {1804, title = {Ten years after - the WOCE AMS radiocarbon program}, booktitle = {Accelerator Mass Spectrometer Conference}, year = {2000}, note = {id: 316}, month = {2000}, author = {McNichol, A. P. and Schneider, R. J. and von Reden, K. F. and Gagnon, A. R. and Elder, K. L. and Key, R. M. and Quay, P. D.} } @article {810, title = {Ten years after - The WOCE AMS radiocarbon program}, journal = {Nuclear Instruments \& Methods in Physics Research Section B-Beam Interactions with Materials and Atoms}, volume = {172}, year = {2000}, note = {372jrTimes Cited:14Cited References Count:12}, month = {Oct}, pages = {479-484}, abstract = {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{\textquoteright}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{\textquoteright}s Ocean-Atmosphere Carbon Exchange Study to study the ocean{\textquoteright}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.}, issn = {0168-583x}, doi = {10.1016/S0168-583x(00)00093-8}, author = {McNichol, A. P. and Schneider, R. J. and von Reden, K. F. and Gagnon, A. R. and Elder, K. L. and Key, R. M. and Quay, P. D.} } @article {2207, title = {87Sr/86Sr, delta 18O evolution of Phanerozoic seawater}, journal = {Chemical Geology}, volume = {161}, year = {1999}, note = {id: 1603}, month = {1999}, pages = {59-88}, author = {Veizer, Jan and Davin, Ala and Azmy, Karem and Bruckschen, Peter and Buhl, Dieter and Bruhn, Frank and Carden, Giles A. F. and Diener, Andreas and Ebneth, Stefan and Godderis, Yves and Jasper, Torsten and Korte, Christoph and Pawellek, Frank and Podlaha, Olaf G. and Strauss, Harald} } @conference {1564, title = {The Antarctic Radiocarbon Storage Ring}, booktitle = {8th International Conference on Accelerator Mass Spectrometry}, year = {1999}, note = {id: 1791}, month = {1999}, address = {Vienna, Austria}, author = {Schneider, Robert J. and McNichol, Ann P. and von Reden, Karl F. and Elder, Kathryn L. and Gagnon, Alan R. and Key, Robert M. and Quay, Paul D.} } @conference {1579, title = {Biogenic silica and organic carbon in sediments from the Pacific sector of the Southern Ocean.--Abstract}, booktitle = {8th International Symposium on Antarctic Earch Sciences}, year = {1999}, note = {id: 286}, month = {1999}, pages = {119}, address = {Victoria University of Wellington, Wellington, New Zealand}, author = {Giglio, F. and Frignani, M. and Langone, L. and Morigi, C. and Pianosi, G. and Ravaioli, M.} } @article {2235, title = {Carbon isotopes as tracers of groundwater discharge into the coastal ocean: A preliminary study of saltmarsh groundwater from North Inlet, SC}, journal = {EOS}, volume = {80}, year = {1999}, note = {id: 1314}, month = {1999}, pages = {S107}, author = {Gramling, C. M. and McCorkle, D. C.} } @article {2219, title = {Fault slip rates in the modern new madrid seismic zone}, journal = {Science}, volume = {286}, year = {1999}, note = {MuellerChampion Guccione Kelson eng 1999/11/05 Science. 1999 Nov 5;286(5442):1135-8. }, month = {Nov 05}, pages = {1135-8}, abstract = {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.}, isbn = {1095-9203 (Electronic)0036-8075 (Linking)}, doi = {10.1126/science.286.5442.1135 }, url = {https://www.ncbi.nlm.nih.gov/pubmed/10550047}, author = {Mueller, K. and Champion, J. and Guccione, M. and Kelson, K.} } @article {2238, title = {Holocene and modern sediment budgets for the Ganges-Brahmaputra River: Evidence for highstand dispersal to floodplain, shelf, and deep-sea depocenters}, journal = {Geology}, volume = {27}, year = {1999}, note = {id: 149}, month = {1999}, pages = {559-562}, author = {Goodbred, S. L. and Kuehl, S. A.} } @conference {1653, title = {Installation and First Results of a 134-Sample MC-SNICS Ion Source at NOSAMS}, booktitle = {8th International Conference on Accelerator Mass Spectrometry}, year = {1999}, note = {id: 1802}, month = {1999}, address = {Vienna, Austria}, author = {von Reden, K. F. and Schneider, R. J. and McNichol, A. P. and Elder, K. F. and Gagnon, A. R.} } @article {798, title = {Isotopic and molecular fractionation in combustion; three routes to molecular marker validation, including direct molecular {\textquoteright}dating{\textquoteright} (GC/AMS)}, journal = {Atmospheric Environment}, volume = {33}, year = {1999}, note = {208duTimes Cited:38Cited References Count:31}, month = {Aug}, pages = {2789-2806}, abstract = {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 ({\textquoteright}molecular dating{\textquoteright}); 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 {\textquoteright}dating{\textquoteright}) 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.}, issn = {1352-2310}, doi = {10.1016/S1352-2310(98)00325-2}, author = {Currie, L. A. and Klouda, G. A. and Benner, B. A. and Garrity, K. and Eglinton, T. I.} } @conference {1731, title = {Paleoceanographic changes in the Southern Ocean (Pacific Sector) during the last 14 ka.- -Abstract}, booktitle = {Third International SO-JGOFS Symposium}, year = {1999}, note = {id: 1426}, month = {1999}, address = {Brest}, author = {Morigo, C. and Capotondi, L. and Ravaioli, M. and Giglio, F. and Turi, B. and Brilli, M. and Langone, L.} } @conference {1742, title = {Planktic foraminifera and oxygen isotope as proxies for paleoceanographic reconstruction in the Southern Ocean during the last deglacial time--Abstract}, booktitle = {Convegno Glaciologia e Paleoclima}, year = {1999}, note = {id: 1425}, month = {1999}, pages = {70-71}, address = {Padova}, author = {Morigi, C. and Capotondi, L. and Ravaioli, M. and Giglio, F. and Turi, B. and Brilli, M. and Frignani, M. and Langone, L.} } @article {2237, title = {Radiocarbon age anomalies in land snail shells from Texas: Ontogenetic, individual, and geographic patterns of variation}, journal = {Radiocarbon}, volume = {41}, year = {1999}, note = {228qgTimes Cited:28 Cited References Count:18 }, month = {1999}, pages = {149-156}, abstract = {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).}, keywords = {Carbonate}, isbn = {0033-8222}, author = {Goodfriend, G. A. and Ellis, G. L. and Toolin, L. J.} } @article {2236, title = {Rapid strand-plain accretion in the northeastern Nile Delta in the 9th century A. D. and the demise of the port of Pelusium}, journal = {Geology}, volume = {27}, year = {1999}, note = {id: 177}, month = {1999}, pages = {147-150}, author = {Goodfriend, G. A. and Stanley, D. J.} } @conference {1776, title = {Relative Sea-Level Rise and the Development of Channel-Fill and Shallow-Water Sequences on Cape Cod, Massachusetts}, booktitle = {American Geophysical Union, Spring Meeting}, year = {1999}, note = {id: 120}, month = {1999}, address = {Boston, MA}, author = {Gutierrez, B. T. and Aubrey, D. G. and Driscoll, N. W. and Uchupi, E.} } @conference {1805, title = {Ten Years After--The WOCE AMS Radiocarbon Program}, booktitle = {8th International Conference on Accelerator Mass Spectrometry}, year = {1999}, note = {id: 1757}, month = {1999}, address = {Vienna, Austria}, author = {McNichol, A. and Schneider, R. and von Reden, K. and Gagnon, A. and Elder, K. and Key, R. and Quay, P.} } @article {2227, title = {Terminal Proterozoic Mid-Shelf Benthic Microbial Mats in the Centralian Supervasin and their Environmental Significance}, journal = {Geochimica et Cosmochimica Acta}, volume = {63}, year = {1999}, note = {id: 1734}, month = {1999}, pages = {1345-1358}, author = {Logan, Graham A. and Calver, Clive R. and Gorjan, Paul and Summons, Roger E. and Hayes, John M. and Walter, Malcolm R.} } @article {2246, title = {Challenges in application of radiocarbon dating of organic carbon phases in opal-rich marine sediments from the Southern Ocean}, journal = {Trans. AGU 79}, year = {1998}, note = {id: 266}, month = {1998}, author = {Zheng, Y. and Anderson, R. F. and Froelich, P. N. and Beck, W. and McNichol, A. P. and Guilderson, T.} } @conference {1595, title = {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}, booktitle = {Conference on Southeast Coastal Ocean Research}, series = {Program and Abstracts, Coastal Ocean Boundaries and Interactions and Assessments (COBIA)}, year = {1998}, note = {id: 1313}, month = {1998}, pages = {29}, address = {Savannah, GA}, author = {McCorkle, D. C. and Gramling, C.} } @article {2257, title = {A Correction for Aberrations in the Woods Hole Recombinator. Symposium of North-Eastern Accelerator Personnel}, journal = {World Scientific}, volume = {SNEAP 1996}, year = {1998}, note = {id: 1664}, month = {1998}, pages = {123-128}, author = {Schneider, Robert J. and McNichol, Ann P. and von Reden, Karl F. and Elder, Kathryn L. and Gagnon, Allan R. and Key, Robert M. and Quay, Paul D.} } @article {2435, title = {Evaluating reproducibility of seawater, inorganic and organic carbon 14C results at the National Ocean Sciences AMS Facility (NOSAMS)}, journal = {Radiocarbon}, volume = {40}, year = {1998}, month = {1998}, pages = {223-230}, author = {Elder, K. L. and McNichol, A. P.
 and Gagnon, A. R.} } @conference {1646, title = {High-precision Measurements of 14C as a Circulation Tracer in the Pacific, Indian, and Southern Oceans with Accelerator Mass Spectrometry (AMS)}, booktitle = {8th International Conference on Heavy Ion Accelerator Technology}, year = {1998}, note = {id: 1636}, month = {1998}, address = {Argonne National Lab}, author = {von Reden, K. F. and Peden, J. C. and Schneider, R. J. and Bellino, M. and Donoghue, J. and Elder, K. L. and Gagnon, A. R. and Long, P. and McNichol, A. P. and Morin, T. and Stuart, D. and Hayes, J. M. and Key, R. M.}, editor = {Shepard, K. American Institute of Physics} } @article {720, title = {Historical geomorphic processes and human activities in the Central Spanish Pyrenees}, journal = {Mountain Research and Development}, volume = {18}, year = {1998}, note = {142mnTimes Cited:49Cited References Count:62}, month = {Nov}, pages = {309-320}, abstract = {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.}, issn = {0276-4741}, doi = {10.2307/3674096}, author = {Garcia-Ruiz, J. M. and Valero-Garces, B. L.} } @conference {1715, title = {The NOSAMS Sample Preparation Laboratory: Systems and graphite performance analysis}, booktitle = {16th International 14C Conference}, year = {1998}, note = {id: 1628}, month = {1998}, address = {Groninghen}, author = {Gagnon, A. R. and McNichol, A. P. and Donaghue, J. C. and Morin, T. J. and Peden, J. C.} } @article {825, title = {A reassessment of the sources and importance of land-derived organic matter in surface sediments from the Gulf of Mexico}, journal = {Geochimica Et Cosmochimica Acta}, volume = {62}, year = {1998}, note = {156xvTimes Cited:251Cited References Count:133}, month = {Sep}, pages = {3055-3075}, abstract = {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.}, issn = {0016-7037}, doi = {10.1016/S0016-7037(98)00217-8}, author = {Go{\~n}i, M. A. and Ruttenberg, K. C. and Eglinton, T. I.} } @conference {1778, title = {Reproducibility of seawater, inorganic and organic 14C results at NOSAMS}, booktitle = {Sixteenth International 14C Conference}, volume = {40(1)}, year = {1998}, note = {id: 1625}, month = {1998}, pages = {223-230}, address = {Groningen}, author = {Elder, K. L. and McNichol, A. P. and Gagnon, A. R.} } @article {738, title = {Sea level higher than present 3500 years ago on the northern main Hawaiian Islands}, journal = {Geology}, volume = {26}, year = {1998}, note = {Zg996Times Cited:34Cited References Count:25}, month = {Apr}, pages = {363-366}, abstract = {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{\textquoteright}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{\textquoteright}s geoid response to the last deglaciation and with observations of increased Antarctic ice volume during the late Holocene.}, issn = {0091-7613}, doi = {10.1130/0091-7613(1998)026<0363:Slhtpy>2.3.Co;2}, author = {Grossman, E. E. and Fletcher, C. H.} } @article {2276, title = {Status Report of the National Ocean Sciences AMS Facility at Woods Hole Oceanographic Institution: Operations and Recent Developments}, journal = {15th International Conference on the Applications of Accelerators in Research and Industry}, volume = {A.I.P. Conference Proceedings}, year = {1998}, note = {id: 1647}, month = {1998}, pages = {644-647}, author = {Bellino, M. and von Reden, K. F. and Schneider, R. J. and Peden, J. C. and Donoghue, J. and Elder, K. L. and Gagnon, A. R. and Long, P. and McNichol, A. P. and Odegaard, A. P. and Stuart, D. and Handwork, S. and Hayes, J. M.} } @article {819, title = {An abrupt drowning of the Black Sea shelf}, journal = {Marine Geology}, volume = {138}, year = {1997}, note = {Xj245Times Cited:283Cited References Count:35}, month = {Apr}, pages = {119-126}, abstract = {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.}, issn = {0025-3227}, doi = {10.1016/S0025-3227(97)00007-8}, author = {Ryan, W. B. F. and Pitman, W. C. and Major, C. O. and Shimkus, K. and Moskalenko, V. and Jones, G. A. and Dimitrov, P. and Gorur, N. and Sakinc, M. and Yuce, H.} } @conference {1560, title = {AMS measurements of the 14C distribution in the Pacific Ocean}, booktitle = {Proceedings of the Seventh International Conference on Accelerator Mass Spectrometry}, volume = {B123}, year = {1997}, note = {id: 1644; B123}, month = {1997}, pages = {438-442}, address = {Tucson, AZ}, author = {von Reden, K. F. and McNichol, A. P. and Peden, J. C. and Elder, K. L. and Gagnon, A. R. and Schneider, R. J.}, editor = {Jull, A. J. T.} } @article {2280, title = {AMS measurements of the 14C distribution in the Pacific Ocean}, journal = {Nuclear Instruments and Methods in Physics Research}, volume = {B123}, year = {1997}, note = {id: 1673}, month = {1997}, pages = {438-442}, author = {von Reden, K. F. and McNichol, A. P. and Peden, J. C. and Elder, K. L. and Gagnon, A. R. and Schneider, R. J.} } @conference {1630, title = {Evaluating reproducibility of seawater, inorganic and organic carbon 14C results at the National Ocean Sciences AMS Facility (NOSAMS)}, booktitle = {16th International Radiocarbon Conference}, series = {Book of Abstracts}, year = {1997}, note = {id: 956}, month = {1997}, pages = {45}, address = {Groningen}, author = {Elder, K. L. and McNichol, A. P. and Gagnon, A. R.} } @article {535, title = {Evidence for earliest olive oil production in submerged settlements off the Carmel coast, Israel}, journal = {Journal of Archaeological Science}, year = {1997}, note = {id: 81}, pages = {1141-1150}, abstract = {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.}, doi = {10.1006/jasc.1997.0193}, author = {Galili, E. and Stanley, D. J. and Sharvit, Y. and Weinstein, E. M.} } @conference {1699, title = {The National Ocean Sciences AMS (NOSAMS) Sample Preparation Laboratory: Systems and Graphite Performance Analysis}, booktitle = {International Radiocarbon Conference}, year = {1997}, note = {id: 962}, month = {1997}, address = {Groningen, Nethlands}, author = {Gagnon, A. R. and McNichol, A. P. and Donoghue, J. C. and Morin, T. J. and Peden, J. C.} } @conference {1714, title = {The NOSAMS sample preparation laboratory: overview of systems and techniques}, booktitle = {16th International Radiocarbon Conference}, year = {1997}, note = {id: 955}, month = {1997}, pages = {50}, publisher = {Book of Abstracts}, organization = {Book of Abstracts}, address = {Groningen}, author = {Gagnon, A. R. and McNichol, A. and Donoghue, J. C. and Merkle, K. M. and Morin, T. J.} } @article {2298, title = {Precise temporal correlation of Holocene mollusc shells using sclerochronology}, journal = {Palaeogeography, Paleoclimatology, Paleoecology}, year = {1997}, note = {id: 1293}, month = {1997}, author = {Marchitto, T. M. and Jones, G. A. and Goodfriend, G. A. and Weidman, C. R. and Jirikowic, J.} } @article {2305, title = {Preliminary results of the first scientific drilling on Lake Baikal, Buguldeika site, southeastern Siberia}, journal = {Quaternary International}, volume = {37}, year = {1997}, note = {Vq100Times Cited:44 Cited References Count:29 }, month = {1997}, pages = {3-17}, abstract = {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}, keywords = {asia, tectonics}, isbn = {1040-6182}, author = {Colman, S. and Grachev, M. and Hearn, P. and Horie, S. and Kawai, T. and Kuzmin, M. and Logachov, N. and Fialkov, V. and Gorigljad, A. and Tomilov, B. and Khakhaev, B. and Kochikov, S. and Lykov, V. and Pevzner, L. and Bucharov, A. and Karabanov, E. and Logachev, N. and Mats, V. and Bardardinov, A. and Baranova, E. and Khlystov, O. and Khrachenko, V. and Shimaraeva, M. and Stolbova, E. and Komakova, E. and Efremova, S. and Gvozdkov, A. and Kravchinski, V. and Peck, J. and Fileva, T. and Kashik, S. and Khramtsova, T. and Kalashnikova, I. and Rasskazova, T. and Tatarnikova, V. and Yuretich, R. and Mazilov, V. and Takemura, K. and Bobrov, V. and Gunicheva, T. and Haraguchi, H. and Ito, S. and Kocho, T. and Kuzmin, M. and Markova, M. and Pampura, V. and Proidakova, O. and Ishiwatari, R. and Sawatari, H. and Takeuchi, A. and Toyoda, K. and Vorobieva, S. and Ikeda, A. and Marui, A. and Nakamura, T. and Ogura, K. and Ohta, T. and King, J. and Sakai, H. and Yokoyama, T. and Hayashida, A. and Bezrukova, E. and Fowell, S. and Fuji, N. and Letunova, P. and Misharina, V. and Miyoshi, N. and Chernyaeva, G. and Ignatova, I. and Likhoshvai, E. and Stoermer, E. and Granina, L. and Levina, O. and Dolgikh, P. and Lazo, F. and Lutskaia, N. and Orem, W. and Wada, E. and Williams, D. and Yamada, K. and Yamada, S. and Callander, E. and Golobokoval, L. and Shanks, P. and Dorofeeva, R. and Duchkov, A.} } @article {759, title = {Recent subsidence of the northern Suez canal}, journal = {Nature}, volume = {388}, year = {1997}, note = {Xm528Times Cited:16Cited References Count:10}, month = {Jul 24}, pages = {335-336}, issn = {0028-0836}, doi = {10.1038/40997}, author = {Stanley, D. J. and Goodfriend, G. A.} } @conference {1777, title = {Reproducibility of 14C AMS analyses at NOSAMS}, booktitle = {16th International Radiocarbon Conference}, year = {1997}, note = {id: 961}, month = {1997}, pages = {45}, publisher = {Book of Abstracts}, organization = {Book of Abstracts}, address = {Groningen}, author = {Elder, K. L. and Gagnon, A. R. and McNichol, A. P.} } @article {760, title = {Source and contribution of terrigenous organic carbon to surface sediments in the Gulf of Mexico}, journal = {Nature}, volume = {389}, year = {1997}, note = {Xw772Times Cited:194Cited References Count:30}, month = {Sep 18}, pages = {275-278}, abstract = {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.}, issn = {0028-0836}, doi = {10.1038/38477}, author = {Go{\~n}i, M. A. and Ruttenberg, K. C. and Eglinton, T. I.} } @article {2333, title = {Automated systems and techniques utilized at the NOSAMS sample preparation laboratory: An update of productivity and quality issues}, journal = {Radiocarbon}, volume = {38}, year = {1996}, note = {id: 959}, month = {1996}, pages = {38-39}, author = {Gagnon, A. R. and McNichol, A. P. and Hutton, D. L. and Osborne, E. A. and Donoghue, J. C.} } @article {853, title = {Character, paleoenvironment, rate of accumulation, and evidence for seismic triggering of Holocene turbidites, Canada Abyssal Plain, Arctic Ocean}, journal = {Marine Geology}, volume = {133}, year = {1996}, note = {Uy014Times Cited:36Cited References Count:46}, month = {Jul}, pages = {51-73}, abstract = {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.}, issn = {0025-3227}, doi = {10.1016/0025-3227(96)00015-1}, author = {Grantz, A. and Phillips, R. L. and Mullen, M. W. and Starratt, S. W. and Jones, G. A. and Naidu, A. S. and Finney, B. P.} } @inbook {1406, title = {Chemical Composition of Volcanic Gases}, booktitle = {Monitoring and Mitigation of Volcano Hazards}, year = {1996}, note = {id: 1590}, month = {1996}, pages = {221-256}, publisher = {Springer Verlag}, organization = {Springer Verlag}, address = {Berlin}, author = {Giggenbach, W. F.}, editor = {Scarpa, S.} } @article {851, title = {Reworking and discontinuities in Holocene sedimentation in the Nile Delta: Documentation from amino acid racemization and stable isotopes in mollusk shells}, journal = {Marine Geology}, volume = {129}, year = {1996}, note = {Tv774Times Cited:35Cited References Count:30}, month = {Jan}, pages = {271-283}, abstract = {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.}, issn = {0025-3227}, doi = {10.1016/0025-3227(96)83348-2}, author = {Goodfriend, G. A. and Stanley, D. J.} } @article {2310, title = {Seasonal oxygen depletion in continental-shelf waters of Louisiana; historical record of benthic foraminifers}, journal = {Geology}, volume = {24}, year = {1996}, note = {id: 85}, month = {1996}, pages = {227-230}, author = {Sen Gupta, B. K. and Turner, R. E. and Rabalais, N. N.} } @article {2339, title = {Seasonal variability of particulate organic radiocarbon in the northeastern Pacific}, journal = {Journal of Geophysical Research}, volume = {101}, year = {1996}, note = {id: 1239}, month = {1996}, pages = {20543-20552}, author = {Druffel, Ellen R. M. and Bauer, J. E. and Williams, P. M. and Griffin, S. and Wolgast, D.} } @article {854, title = {Sediment dispersal along northern Israel coast during the early Holocene: Geological and archaeological evidence}, journal = {Marine Geology}, volume = {130}, year = {1996}, note = {Ue849Times Cited:13Cited References Count:30}, month = {Feb}, pages = {11-17}, abstract = {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.}, issn = {0025-3227}, doi = {10.1016/0025-3227(95)00167-0}, author = {Stanley, D. J. and Galili, E.} } @article {861, title = {Uranium-series disequilibrium, sedimentation, diatom frustules, and paleoclimate change in Lake Baikal}, journal = {Earth and Planetary Science Letters}, volume = {142}, year = {1996}, note = {Uz230Times Cited:61Cited References Count:29}, month = {Jul}, pages = {29-42}, abstract = {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.}, issn = {0012-821x}, doi = {10.1016/0012-821x(96)00085-4}, author = {Edgington, D. N. and Robbins, J. A. and Colman, S. M. and Orlandini, K. A. and Gustin, M. P.} } @article {2342, title = {Amazon continental margin high resolution records of the penultimate interglacial}, journal = {Eos, Transactions, American Geophysical Union}, volume = {76}, year = {1995}, note = {id: 1276}, month = {1995}, pages = {174}, author = {Showers, W. J. and Genna, B. and Price, P.} } @conference {1556, title = {Amazon Continental Margin High Resolution Records of Western Tropical Atlantic circulation over the past 130 ky}, booktitle = {International Conference of Paleoceanography}, year = {1995}, note = {id: 1280}, month = {1995}, address = {Halifax, Canada}, author = {Showers, William J. and Genna, Bernard and Price, Pamela} } @conference {1652, title = {Improvements in procedural blanks at NOSAMS: Reflections of improvements in sample preparation and accelerator operation}, booktitle = {15th International 14C Conference}, volume = {37}, year = {1995}, note = {id: 1641; 15th International Radiocarbon Conference, Glasgow, Scotland, August 15-19, 1994}, month = {1995}, pages = {683-691}, publisher = {Radiocarbon}, organization = {Radiocarbon}, author = {McNichol, A. P. and Gagnon, A. R. and Osborne, E. a and Hutton, D. L. and von Reden, K. F. and Schneider, R. J.} } @article {2348, title = {Improvements in procedural blanks at NOSAMS: Reflections of improvements in sample preparation and accelerator operation}, journal = {Radiocarbon}, volume = {37}, year = {1995}, note = {Ud868Times Cited:16 Cited References Count:6 }, month = {1995}, pages = {683-691}, abstract = {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 {\textquoteright}{\textquoteright}line blanks{\textquoteright}{\textquoteright} 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.}, keywords = {SPECTROMETRY}, isbn = {0033-8222}, author = {McNichol, A. P. and Gagnon, A. R. and Osborne, E. A. and Hutton, D. L. and vonReden, K. F. and Schneider, R. J.} } @article {2350, title = {Late Pleistocene to Holocene paleolimnolgy of the Lake Winnebago Basin, based on ostracods}, journal = {Abstracts with Programs - Geological Society of America}, volume = {27}, year = {1995}, note = {id: 75}, month = {1995}, pages = {54}, author = {Gruber, M. M. and Smith, G. L.} } @conference {1670, title = {Late Pleistocene to Holocene Paleolimnology of the Lake Winnebago Basin, Based on Ostracods}, booktitle = {North-Central/South-Central Section,Geological Society of America}, volume = {27}, year = {1995}, note = {id: 909}, month = {1995}, address = {Lincoln, Nebraska}, author = {Gruber, M. M. and Smith, G. L.} } @article {2349, title = {Late Quaternary Paleolimnology of the Lake Winnebago Basin, Based on Ostracodes}, year = {1995}, note = {id: 910}, month = {1995}, author = {Gruber, M. M. Smith G. L.} } @article {741, title = {Late Quaternary Relative Sea-Level Change in the Western Gulf of Maine - Evidence for a Migrating Glacial Forebulge}, journal = {Geology}, volume = {23}, year = {1995}, note = {Qr847Times Cited:69Cited References Count:32}, month = {Apr}, pages = {317-320}, abstract = {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.}, issn = {0091-7613}, doi = {10.1130/0091-7613(1995)023<0317:Lqrslc>2.3.Co;2}, author = {Barnhardt, W. A. and Gehrels, W. R. and Belknap, D. F. and Kelley, J. T.} } @conference {1736, title = {Paleodischarge events on the Amazon Fan during the last glacial}, booktitle = {AGU Annual Fall Meeting}, year = {1995}, note = {id: 1281}, month = {1995}, address = {San Francisco, California}, author = {Showers, William J. and Genna, Bernard and Price, Pamela and Flood, Roger and Piper, David} } @article {2345, title = {Two-step deglaciation of the southeastern Barents Sea}, journal = {Geology}, volume = {23}, year = {1995}, note = {id: 62}, month = {1995}, pages = {567-571}, author = {Polyak, L. and Lehman, S. J. and Gataulin, V. and Jull, A. J. T.} } @conference {1821, title = {Using sclerochronology of the mollusc Arctica islandica as a paleoceanographic tool}, booktitle = {5th International Conference on Paleoceanography}, year = {1995}, note = {id: 1294}, month = {1995}, address = {Halifax, NS}, author = {Marchitto, T. M. and Jones, G. A. and Goodfriend, G. A. and Weidman, C. R. and Jirikowic, J.} } @article {850, title = {Variability in the Benguela Current upwelling system over the past 70,000 years}, journal = {Progress in Oceanography}, volume = {35}, year = {1995}, note = {V07zbTimes Cited:100Cited References Count:147}, pages = {207-251}, abstract = {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 {\textquoteright}classical{\textquoteright} 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 ({\textquoteright}Berg{\textquoteright} 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.}, issn = {0079-6611}, doi = {10.1016/0079-6611(95)00008-5}, author = {Summerhayes, C. P. and Kroon, D. and Rosell-Mele, A. and Jordan, R. W. and Schrader, H. J. and Hearn, R. and Villanueva, J. and Grimali, J. O. and Eglinton, G.} } @article {848, title = {Automated Sample Processing at the National Ocean Sciences Ams Facility}, journal = {Nuclear Instruments \& Methods in Physics Research Section B-Beam Interactions with Materials and Atoms}, volume = {92}, year = {1994}, note = {Nv547Times Cited:9Cited References Count:1}, month = {Jun}, pages = {129-133}, abstract = {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.}, issn = {0168-583x}, doi = {10.1016/0168-583x(94)95991-9}, author = {Cohen, G. J. and Hutton, D. L. and Osborne, E. A. and vonReden, K. F. and Gagnon, A. R. and McNichol, A. P. and Jones, G. A.} } @article {2377, title = {High-precision AMS radiocarbon measurements of central Arctic Ocean seawaters}, journal = {Nuclear Instruments and Methods in Physics Research}, volume = {B92}, year = {1994}, note = {id: 52}, month = {1994}, pages = {426-430}, author = {Jones, G. A. and Gagnon, A. R. and Schneider, R. J. and von Reden, K. F. and McNichol, A. P.} } @article {847, title = {Internal and External Checks in the Nosams Sample Preparation Laboratory for Target Quality and Homogeneity}, journal = {Nuclear Instruments \& Methods in Physics Research Section B-Beam Interactions with Materials and Atoms}, volume = {92}, year = {1994}, note = {Nv547Times Cited:14Cited References Count:5}, month = {Jun}, pages = {158-161}, abstract = {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.}, issn = {0168-583x}, doi = {10.1016/0168-583x(94)95997-8}, author = {Osborne, E. A. and McNichol, A. P. and Gagnon, A. R. and Hutton, D. L. and Jones, G. A.} } @article {2383, title = {Lake-Level History of Lake-Michigan for the Past 12,000 Years - the Record from Deep Lacustrine Sediments}, journal = {Journal of Great Lakes Research}, volume = {20}, year = {1994}, note = {Nl348Times Cited:47 Cited References Count:29 }, month = {1994}, pages = {73-92}, abstract = {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{\textquoteright}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. }, keywords = {lake michigan, ostracodes, radiocarbon, sedimentology, sediments, southern}, isbn = {0380-1330}, author = {Colman, S. M. and Forester, R. M. and Reynolds, R. L. and Sweetkind, D. S. and King, J. W. and Gangemi, P. and Jones, G. A. and Keigwin, L. D. and Foster, D. S.} } @article {838, title = {Radiocarbon Chronology of Black-Sea Sediments}, journal = {Deep-Sea Research Part I-Oceanographic Research Papers}, volume = {41}, year = {1994}, note = {Nm252Times Cited:121Cited References Count:44}, month = {Mar}, pages = {531-557}, abstract = {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.}, issn = {0967-0637}, doi = {10.1016/0967-0637(94)90094-9}, author = {Jones, G. A. and Gagnon, A. R.} } @article {1364, title = {Radiocarbon Studies of Particulate Organic Carbon in the Eastern North Pacific Ocean}, year = {1994}, note = {id: 907}, month = {1994}, author = {Druffel, E. R. M. and Griffin, S. and Bauer, J. E. and Williams, P. M. and Wolgast, D. M. and Lee, C.} } @conference {1770, title = {Radiocarbon studies of particulate organic carbon in the eastern North Pacific Ocean}, booktitle = {1994 ocean sciences meeting}, volume = {75}, year = {1994}, note = {id: 1240; 3}, month = {1994}, pages = {236}, address = {San Diego, CA}, author = {Druffel, E. R. M. and Bauer, J. E. and Williams, P. M. and Griffin, S. and Wolgast, C. Lee and Wakeham, S. G.}, editor = {University of California at Irvine, Department of Geosciences} } @article {2371, title = {Rapid analysis of seawater samples at the National Ocean Sciences Accelerator Mass Spectrometry Facility, Woods Hole, MA}, journal = {Radiocarbon}, volume = {36}, year = {1994}, note = {id: 305}, month = {1994}, pages = {237-246}, author = {McNichol, A. P. and Jones, G. A. and Hutton, D. L. and Gagnon, A. R. and Key, R. M.} } @article {2369, title = {The Rapid Preparation of Seawater Sigma-Co2 for Radiocarbon Analysis at the National Ocean Sciences Ams Facility}, journal = {Radiocarbon}, volume = {36}, year = {1994}, note = {Pz926Times Cited:61 Cited References Count:14 }, month = {1994}, pages = {237-246}, abstract = {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.}, keywords = {accelerator mass-spectrometry, C-14, samples}, isbn = {0033-8222}, author = {McNichol, A. P. and Jones, G. A. and Hutton, D. L. and Gagnon, A. R. and Key, R. M.} } @article {846, title = {Tic, Toc, Dic, Doc, Pic, Poc - Unique Aspects in the Preparation of Oceanographic Samples for C-14 Ams}, journal = {Nuclear Instruments \& Methods in Physics Research Section B-Beam Interactions with Materials and Atoms}, volume = {92}, year = {1994}, note = {Nv547Times Cited:82Cited References Count:9}, month = {Jun}, pages = {162-165}, abstract = {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.}, issn = {0168-583x}, doi = {10.1016/0168-583x(94)95998-6}, author = {McNichol, A. P. and Osborne, E. A. and Gagnon, A. R. and Fry, B. and Jones, G. A.} } @article {2393, title = {Ams-Graphite Target Production Methods at the Woods-Hole Oceanographic Institution during 1986-1991}, journal = {Radiocarbon}, volume = {35}, year = {1993}, note = {Lg927Times Cited:12 Cited References Count:14 }, month = {1993}, pages = {301-310}, abstract = {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.}, keywords = {accelerator mass-spectrometry, facility, ocean, radiocarbon, samples, sediments}, isbn = {0033-8222}, author = {Gagnon, A. R. and Jones, G. A.} } @conference {1655, title = {Internal and external checks in the NOSAMS Sample Preparation Laboratory for target quality and homogeneity}, booktitle = {6th International Conference on Accelerator Mass Spectrometry}, year = {1993}, note = {id: 958}, month = {1993}, pages = {75}, address = {Canberra, Australia}, author = {McNichol, A. P. and Gagnon, A. R. and Osborne, E. A. and Hutton, D. L. and Jones, G. A.} } @conference {1700, title = {The National Ocean Sciences AMS Facility at Woods Hole Oceanographic Institution}, booktitle = {6th International Conference on Accelerator Mass Spectrometry}, year = {1993}, note = {id: 930}, month = {1993}, pages = {46}, address = {Canberra, Australia}, author = {Jones, G. A. and Schneider, R. J. and von Reden, K. F. and McNichol, A. P. and Gagnon, A. R. and Cohen, G. J. and Osborne, E. A. and Hutton, D. L. and Kessel, E. D. and Elder, K. L.} } @article {2401, title = {Illumination of a Black-Box - Analysis of Gas-Composition during Graphite Target Preparation}, journal = {Radiocarbon}, volume = {34}, year = {1992}, note = {Kf389Times Cited:63 Cited References Count:10 }, month = {1992}, pages = {321-329}, abstract = {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.}, keywords = {deposition}, isbn = {0033-8222}, author = {McNichol, A. P. and Gagnon, A. R. and Jones, G. A. and Osborne, E. A.} } @conference {1562, title = {AMS radiocarbon results obtained from graphite targets produced at the Woods Hole Oceanographic Institution between 1986 and 1991}, booktitle = {14th Internation Radiocarbon Conference}, year = {1991}, note = {id: 957}, month = {1991}, pages = {198}, address = {Tucson, AZ}, author = {Gagnon, A. R. and Jones, G. A.} } @article {2407, title = {Illumination of a black box: Gas composition changes during graphite target preparation for AMS (Proceedings of the 14th International Radiocarbon Conference, 1991)}, journal = {Radiocarbon}, volume = {34}, year = {1991}, note = {id: 1745}, month = {1991}, pages = {321-329}, author = {McNichol, A. P. and Gagnon, A. R. and Jones, G. A. and Osborne, E. A.} } @conference {1722, title = {The optimization of target production for AMS}, booktitle = {14th International Radiocarbon Conference}, year = {1991}, note = {id: 922}, month = {1991}, pages = {224}, address = {Tucson, AZ}, author = {McNichol, A. P. and Gagnon, A. R. and Jones, G. A. and Schneider, R. J. and von Reden, K. F.} } @inbook {1391, title = {Quantification and characterization of porewater organic colloids}, booktitle = {Organic Substances and Sediments in Water. Processes and Analytical}, volume = {2}, year = {1991}, note = {id: 1744}, month = {1991}, pages = {107-126}, publisher = {CRC Press}, organization = {CRC Press}, address = {Boca Raton, FL}, author = {Chin, Y. P. and McNichol, A. P. and Gschwend, P. M.}, editor = {Baker, R. A.} }