TY - JOUR T1 - Lake Dynamics Modulate the Air Temperature Variability Recorded by Sedimentary Aquatic Biomarkers: A Holocene Case Study From Western Greenland JF - Journal of Geophysical Research: Biogeosciences Y1 - 2023 A1 - Cluett, A. A. A1 - Thomas, E. K. A1 - McKay, N. P. A1 - Cowling, O. C. A1 - Castañeda, I. S. A1 - Morrill, C. KW - Alkenone KW - Arctic KW - biogeochemical proxies KW - brGDGT KW - data-model comparison KW - proxy system modeling AB - Quantitative temperature reconstructions from lacustrine organic geochemical proxies including branched glycerol dialkyl glycerol tetraethers (brGDGTs) and alkenones provide key constraints on past continental climates. However, estimation of air temperatures from proxies can be impacted by non-stationarity in the relationships between seasonal air and water temperatures, a factor not yet examined in strongly seasonal high-latitude settings. We pair downcore analyses of brGDGTs and alkenones measured on the same samples through the Holocene with forward-modeled proxy values based on thermodynamic lake model simulations for a western Greenland lake. The measured brGDGT distributions suggest that stable autochthonous (aquatic) production overpowers allochthonous inputs for most samples, justifying the use of the lake model to interpret temperature-driven changes. Conventional calibration of alkenones (detected only after 5.5 thousand years BP) suggests substantially larger temperature variations than conventional calibration of brGDGTs. Comparison of proxy measurements to forward-modeled values suggests variations in brGDGT distributions monotonically reflect multi-decadal summer air temperatures changes, although the length of the ice-free season dampens the influence of air temperatures on water temperatures. Drivers of alkenone variability remain less clear; potential influences include small changes in the seasonality of proxy production or biases toward specific years, both underlain by non-linearity in water-air temperature sensitivity during relevant seasonal windows. We demonstrate that implied temperature variability can differ substantially between proxies because of differences in air-water temperature sensitivity during windows of proxy synthesis without necessitating threshold behavior in the lake or local climate, and recommend that future studies incorporate lake modeling to constrain this uncertainty. VL - 128 UR - https://onlinelibrary.wiley.com/doi/abs/10.1029/2022JG007106 IS - 7 N1 - _eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1029/2022JG007106 ER - TY - JOUR T1 - Large fluxes of continental-shelf-borne dissolved organic carbon in the East China Sea and the Yellow Sea JF - Marine Chemistry Y1 - 2022 A1 - Han, Heejun A1 - Na, Taehee A1 - Cho, Hyung-Mi A1 - Kim, Guebuem A1 - Hwang, Jeomshik AB - Fluxes of dissolved organic carbon (DOC) from continental shelves to the ocean may play a critical role in marine carbon cycling and budget. However, these fluxes have been poorly constrained because complicated biogeochemical reactions of riverine, atmospheric, and marine organic carbon occur in continental shelf-waters. We used multiple tracers of DOC such as stable- and radiocarbon isotope ratios of DOC, fluorescent properties of dissolved organic matter (FDOM), and 228Ra as a water age tracer to investigate the sources and fluxes of DOC in the northwest Pacific continental margin of the East China Sea and the Yellow Sea. Here, we show that there are significant additional (excess) supplies of DOC in the central Yellow Sea relative to the Changjiang (Yangtze River) source, based on these tracers. The marine δ13C signature (−21.1 ± 1.1‰) and the radiocarbon age (2000 ± 400 yr) of DOC suggest that the additional DOC (Δ14DOC = −44‰) is supplied from a combination of newly produced DOC and the degradation of particulate as well as sedimentary organic matter. The flux of this additional DOC produced in the continental shelf of the East China Sea to the open ocean is estimated to be ~1.9 ± 0.8 Tg C yr−1, which is comparable to that from the Changjiang discharge. Our study implies that the fluxes of continental shelf-borne DOC may be important globally and should be considered in estimating global DOC budgets in the marine environment. VL - 240 UR - https://linkinghub.elsevier.com/retrieve/pii/S0304420322000147 ER - TY - JOUR T1 - Late Holocene centennial to millennial-scale variability in lower trophic level productivity off southern Hokkaido, Japan, and its response to dissolved iron-replete Coastal Oyashio dynamics JF - Quaternary Research Y1 - 2022 A1 - Kuwae, Michinobu A1 - Tsugeki, Narumi A1 - Finney, Bruce P. A1 - Tani, Yukinori A1 - Onodera, Jonaotaro A1 - Kiyoto, Mako A1 - Kusaka, Mitsukuni A1 - Sagawa, Takuya A1 - Nakamura, Yugo A1 - Ohnishi, Hiroji A1 - Kuroda, Hiroshi A1 - Okuda, Noboru A1 - Ohta, Tamihisa A1 - Ikehara, Minoru A1 - Irino, Tomohisa AB - Little is known about the dynamics of marine food chains spanning primary to higher trophic levels on centennial and longer timescales, especially where the supply of dissolved iron limits primary productivity. To elucidate the long-term dynamics of biological productivity in the Coastal Oyashio (CO), which is a major pathway for transporting dissolved iron into the western North Pacific from winter to spring, we reconstructed the lower trophic level productivity over the last 3000 years in the CO. Our results demonstrate that the concentrations and mass accumulation rates of both Chl- a (chlorophyll a and its derivatives) and biogenic opal used as proxies of primary productivity, and steryl chlorin esters (SCEs) used as that of zooplankton productivity, show a millennial-scale increasing trend and centennial-scale variability beginning ca. AD 400. SCEs were positively correlated with Chl- a , indicating that changes in zooplankton productivity were induced by bottom-up control of primary productivity. The Chl- a and SCEs showed synchronous centennial-scale patterns with a relative abundance of sea-ice-associated diatom species transported by CO, and with a ventilation index in the Okhotsk Sea Intermediate Water. This synchronous pattern indicates that lower trophic-level productivity during the spring bloom responded to the intensity of iron-replete CO. VL - 107 UR - https://www.cambridge.org/core/journals/quaternary-research/article/late-holocene-centennial-to-millennialscale-variability-in-lower-trophic-level-productivity-off-southern-hokkaido-japan-and-its-response-to-dissolved-ironreplete-coastal-oyashio-dynamics/ ER - TY - JOUR T1 - Late Holocene Paleomagnetic Secular Variation in the Chukchi Sea, Arctic Ocean JF - Geochemistry, Geophysics, Geosystems Y1 - 2022 A1 - West, Gabriel A1 - Nilsson, Andreas A1 - Geels, Alexis A1 - Jakobsson, Martin A1 - Moros, Matthias A1 - Muschitiello, Francesco A1 - Pearce, Christof A1 - Snowball, Ian A1 - O’Regan, Matt AB - The geomagnetic field behavior in polar regions remains poorly understood and documented. Although a number of Late Holocene paleomagnetic secular variation (PSV) records exist from marginal settings of the Amerasian Basin in the Arctic Ocean, their age control often relies on a handful of radiocarbon dates to constrain ages over the past 4,200 years. Here we present well-dated Late Holocene PSV records from two sediment cores recovered from the Chukchi Sea, Arctic Ocean. The records are dated using 26 14C measurements, with local marine reservoir corrections calibrated using tephra layers from the 3.6 cal ka BP Aniakchak eruption in Northern Alaska. These 14C-based chronologies are extended into the post-bomb era using caesium-137 dating, and mercury isochrons. Paleomagnetic measurements and rock magnetic analyses reveal stable characteristic remanent magnetization directions, and a magnetic mineralogy dominated by low-coercivity minerals. The PSV records conform well to global spherical harmonic field model outputs. Centennial to millennial scale directional features are synchronous between the cores and other Western Arctic records from the area. Due to the robust chronology, these new high-resolution PSV records provide a valuable contribution to the characterization of geomagnetic field behavior in the Arctic over the past few thousand years, and can aid in developing age models for suitable sediments found in this region. VL - 23 UR - https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2021GC010187 IS - 5 ER - TY - JOUR T1 - Late Woodland feasting and social networks in the lower Missouri River region JF - North American Archaeologist Y1 - 2022 A1 - Logan, Brad AB - Feasting and its function among small scale societies have received little attention among many descriptive and theoretical studies of this activity. Evidence of feasting focused on large roasting pits by Late Woodland (AD 500–1000) hunter-gatherer-gardeners in the lower Missouri River region on the eastern edge of the Great Plains is presented. Two features at the Quixote site and lipid analyses of stones from them attest single events focused on roasting deer and fish, and perhaps ritual use of red cedar and ceramic pipes. Such features at other Late Woodland sites in the LMRR, specifically the Valley Falls locality of the Delaware River valley in northeastern Kansas, are reinterpreted. Burned stone features at Middle Woodland sites differ and suggest pit roasting was a practice of dispersed Late Woodland groups. Feasting for solidarity forged a social network based on reciprocity, not competition, to mitigate food insecurity among diffuse, low level food producers. VL - 43 UR - https://journals.sagepub.com/doi/10.1177/01976931221104846 IS - 3 ER - TY - JOUR T1 - Lacustrine leaf wax hydrogen isotopes indicate strong regional climate feedbacks in Beringia since the last ice age JF - Quaternary Science Reviews Y1 - 2021 A1 - Daniels, W.C. A1 - Russell, J.M. A1 - Morrill, C. A1 - Longo, W.M. A1 - Giblin, A.E. A1 - Holland-Stergar, P. A1 - Welker, J.M. A1 - Wen, X. A1 - Hu, A. A1 - Huang, Y. VL - 269 UR - https://www.webofscience.com/wos/woscc/full-record/WOS:000694971400005?AlertId=4d48b20a-7d27-4fa2-a6a8-37f0daa89864&SID=7FJ1KjxGlxJRYob6iqu ER - TY - JOUR T1 - Limited Presence of Permafrost Dissolved Organic Matter in the Kolyma River, Siberia Revealed by Ramped Oxidation JF - Journal of Geophysical Research: Biogeosciences Y1 - 2021 A1 - Rogers, Jennifer A. A1 - Galy, Valier A1 - Kellerman, Anne M. A1 - Chanton, Jeffrey P. A1 - Zimov, Nikita A1 - Spencer, Robert G. M. VL - 126 UR - https://www.webofscience.com/wos/woscc/full-record/WOS:000677821700019?AlertId=4d48b20a-7d27-4fa2-a6a8-37f0daa89864&SID=8EgwPROzuFaD4cTggN2 IS - 7 ER - TY - JOUR T1 - Late glacial and Holocene paleoenvironments in the midcontinent United States, inferred from Geneva Lake leaf wax, ostracode valve, and bulk sediment chemistry JF - Quaternary Science Reviews Y1 - 2020 A1 - Puleo, Peter J.K. A1 - Axford, Yarrow A1 - McFarlin, Jamie M. A1 - Curry, B. Brandon A1 - Barklage, Mitchell A1 - Osburn, Magdalena R. KW - Holocene KW - Inorganic geochemistry KW - Loess KW - North America KW - Organic geochemistry KW - paleoclimatology KW - paleolimnology KW - Pleistocene KW - sedimentology KW - Stable isotopes AB - Geneva Lake in Wisconsin, USA, is > 20,000 years old and contains a 30-m thick lacustrine sediment record of mid-continent North American climate and environmental change. Here we describe a sediment record from Geneva Lake spanning the past 14,500 years. From scanning X-ray fluorescence, organic C and N concentrations and isotopes, X-ray diffraction, magnetic susceptibility, and grain size of bulk sediments, we infer changes in sediment sources over time including: abrupt decline in inputs of remobilized loess ∼13,400 cal yr BP followed by a gradual transition to organic-rich marl deposition by ∼10,400 cal yr BP as the landscape stabilized following a period of permafrost thaw and vegetation development; deposition of a minerogenic unit at ∼8,200 cal yr BP that may record enhanced eolian activity during the widespread “8.2 ka event; ” and elevated zinc, lead, and arsenic from human activities following regional industrialization. Within the Holocene marl, we also use isotopic (δ18O and δ13C) and trace metal ratio (Sr/Ca and Mg/Ca) analyses of ostracode valves paired with concentrations and hydrogen isotopic composition (δ2H) of leaf wax n-alkanes to infer climate and hydrological change. Groundwater had a large but declining influence on lake water chemistry from 11,800 to 9,700 cal yr BP, precluding inferences of regional climate from our lacustrine proxies during this period. δ2H values of terrestrial n-C29 alkanes show little variability from 9,700 to present, indicating the average isotopic composition of local precipitation was relatively stable, reflecting stable condensation temperatures and source. In contrast, a gradual trend towards more δ18O- and δ2H-depleted lake water and lower lake water Sr/Ca from 9700 cal yr BP to present suggest decreasing evaporation of lake water and increasing precipitation amounts throughout the Holocene and resulting shorter lake water residence times. Lake water Mg/Ca variations over the past 9,700 years broadly parallel regional pollen-based reconstructions of summer temperatures. Neither Mg/Ca nor terrestrial leaf wax δ2H suggest long-term directional shifts in temperature at this site through the middle to late Holocene, as climate became wetter. It appears that precipitation isotopes did not track local temperatures on millennial timescales in this part of mid-continent North America through the Holocene, and instead may have covaried with changes in Northern Hemisphere latitudinal temperature gradients driven by large Arctic temperature changes. VL - 241 UR - https://www.sciencedirect.com/science/article/pii/S0277379120303462 ER - TY - JOUR T1 - A late Holocene subfossil Atlantic white cedar tree-ring chronology from the northeastern United States JF - Quaternary Science Reviews Y1 - 2020 A1 - Pearl, Jessie K. A1 - Anchukaitis, Kevin J. A1 - Donnelly, Jeffrey P. A1 - Pearson, Charlotte A1 - Pederson, Neil A1 - Lardie Gaylord, Mary C. A1 - McNichol, Ann P. A1 - Cook, Edward R. A1 - Zimmermann, George L. KW - coastal KW - Geomorphology KW - Holocene KW - North America KW - paleoclimatology KW - radiogenic isotopes KW - Tree-rings AB - Tree-rings provide precise annually dated climate information, but their application can be limited by the relatively short lifespan of many trees. To overcome this limitation, tree-ring records can be extended over longer time periods by connecting living trees with older “sub-fossil” trees, which can provide information on longer timescales throughout the Holocene. These long chronologies are proxy records of past climate, provide precise chronological information for extreme events, and give insight into the range of natural climate variability prior to the instrumental period. In the densely populated northeastern United States, few tree-ring records are longer than 500 years, and there are no millennial-length tree-ring chronologies for the region. Here, we use a combination of standard dendrochronological and radiocarbon techniques, including use of the 774 CE radiocarbon excursion, to generate an absolutely dated 2500 year-long tree ring record from living, archaeological, and subfossil Atlantic white cedar (Chamaecyparis thyoides) found in the coastal northeastern United States. Our chronology demonstrates the potential to develop multi-millennial Chamaecyparis thyoides tree-ring records to address previously unanswered questions regarding late Holocene hydroclimate, extreme events, and temperature variability in New England. VL - 228 UR - https://linkinghub.elsevier.com/retrieve/pii/S0277379119308108 ER - TY - JOUR T1 - Life and its traces in Antarctica's McMurdo Dry Valley paleolakes: a survey of preservation JF - Micron Y1 - 2020 A1 - Greenfield, Samuel R. A1 - Tighe, Scott W. A1 - Bai, Yu A1 - Goerlitz, David S. A1 - Von Turkovich, Michele A1 - Taatjes, Douglas J. A1 - Dragon, Julie A. A1 - Johnson, Sarah Stewart KW - Antarctica KW - Biosignatures KW - Microbes KW - Paleolakes KW - SEM AB - The extremely cold and arid conditions of Antarctica make it uniquely positioned to investigate fundamental questions regarding the persistence of life in extreme environments. Within the McMurdo Dry Valleys and surrounding mountain ranges are multiple ancient relict lakes, paleolakes, with lacustrine deposits spanning from thousands to millions of years in age. Here we present data from light microscopy, scanning electron microscopy, electron dispersive x-ray spectroscopy, and radiocarbon dating to catalog the remarkable range of life preserved within these deposits. This includes intact microbes and nanobacteria-sized cocci, CaCO3 precipitations consistent with biogenic calcium, previously undescribed net-like structures, possible dormant spores, and long-extinct yet exquisitely preserved non-vascular plants. These images provide an important reference for further microbiome investigations of Antarctic paleolake samples. In addition, these findings may provide a visual reference for the use of subsurface groundwater microbial communities as an analog for paleolake subsurface water on planets such as Mars. VL - 131 UR - https://linkinghub.elsevier.com/retrieve/pii/S0968432819304160 ER - TY - JOUR T1 - Life history of northern Gulf of Mexico Warsaw grouper Hyporthodus nigritus inferred from otolith radiocarbon analysis JF - PLOS ONE Y1 - 2020 A1 - Barnett, Beverly K. A1 - Chanton, Jeffrey P. A1 - Ahrens, Robert A1 - Thornton, Laura A1 - Patterson, William F. ED - Patterson, Heather M. AB - Warsaw grouper, Hyporthodus nigritus, is a western Atlantic Ocean species typically found at depths between 55 and 525 m. It is listed as a species of concern by the U.S. National Marine Fisheries Service and as near threatened by the International Union for the Conservation of Nature. However, little information exists on the species’ life history in the northern Gulf of Mexico (nGOM) and its stock status in that region is currently unknown. Age of nGOM Warsaw grouper was investigated via opaque zone counts in otolith thin sections (max age = 61 y), and then the bomb 14C chronometer was employed to validate the accuracy of age estimates. Otolith cores (n = 14) were analyzed with accelerator mass spectrometry and resulting Δ14C values overlain on a loess regression computed for a regional coral and known-age red snapper Δ14C time series. Residual analysis between predicted Δ14C values from the loess regression versus Warsaw grouper otolith core Δ14C values indicated no significant difference in the two data series. Therefore, the accuracy of otolith-based aging was validated, which enabled growth and longevity estimates to be made for nGOM Warsaw grouper. Dissolved inorganic carbon (DIC) Δ14C values collected from the nGOM support the inference that juvenile Warsaw grouper occur in shelf waters (<200 m) since DIC Δ14C values in this depth range are enriched in 14C and similar to the Δ14C values from otolith cores. A Bayesian model was fit to fishery-dependent age composition data and produced von Bertalanffy growth function parameters of L1 = 1,533 mm, k = 0.14 y-1, and t0 = 1.82 y. Fishing mortality also was estimated in the model, which resulted in a ratio of fishing to natural mortality of 5.1:1. Overall, study results indicate Warsaw grouper is a long-lived species that is estimated to have experienced significant overfishing in the nGOM, with the age of most landed fish being <10 y. VL - 15 UR - https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0228254 IS - 1 ER - TY - JOUR T1 - Local glaciers record delayed peak Holocene warmth in south Greenland JF - Quaternary Science Reviews Y1 - 2020 A1 - Larocca, Laura J. A1 - Axford, Yarrow A1 - Bjørk, Anders A. A1 - Lasher, G. Everett A1 - Brooks, Jeremy P. KW - Equilibrium-line altitudes KW - Greenland KW - Holocene thermal maximum KW - lake sediments KW - Little ice age KW - Mountain glaciers KW - Paleotemperatures AB - Local glaciers and ice caps (GICs) respond sensitively and quickly, on the scale of decades to centuries, to climate variations. Continuous records of past fluctuations in GIC size provide information on the timing and magnitude of Holocene climate shifts, and a longer-term perspective on 21st century glacier retreat. Although there is broad-scale agreement on millennial-scale trends in Holocene climate variability and fluctuations in local GICs in Greenland, regional variations are only loosely constrained. Here we present three Holocene proglacial lake sediment records from South Greenland, an area with abundant local glaciers but few Holocene-length paleoclimate records. In addition, we use geospatial analysis to model past equilibrium-line altitudes (ELAs) and thereby constrain the magnitude of ablation-season temperature change during the warmest and coolest periods of the Holocene. Physical and geochemical sedimentary characteristics show that two of the proglacial lakes continued to receive glacial meltwater input until ∼7.3 and ∼7.1 ka BP. The survival of local glaciers implies that South Greenland remained relatively cool, and that summer temperatures gradually warmed, but did not warm well beyond 1.2 °C above present in the early Holocene. In the mid-Holocene, from ∼7.1 to 5.5 ka BP, organic sedimentation at these two sites indicates that local glaciers became very small, or more likely melted away completely. The glaciers within the third lake’s catchment melted away prior to ∼5.2 ka BP, as sediments deposited earlier in the Holocene could not be dated at this site. We estimate that summer temperatures increased by at least 1.2–1.8 °C above present by ∼7.3–7.1 ka BP. Our results are consistent with other observations that suggest a north-to-south gradient in the timing of Holocene thermal maximum conditions, with southern Greenland experiencing a delayed warming relative to other regions in Greenland. As summer temperatures cooled in the Neoglacial, our records show that sustained glacier regrowth began ∼3.1 ka BP with glaciers in the southernmost catchment, which at present, receive the most precipitation. In the other two catchments, which host smaller glaciers in a drier environment, regrowth began at ∼1.3 and ∼1.2 ka BP, the timing of which is in agreement with other glacial records from the Arctic Atlantic region. Local glaciers reached their maximum late Holocene extents during a cooler, second phase of the Little Ice Age (LIA) ∼0.2-0.1 ka BP, that we estimate was at least 0.4–0.9 °C cooler than present. Overall, these findings improve understanding of the spatio-temporal dynamics of Holocene glacier and climate change in Greenland, potentially yielding valuable information about their future response. VL - 241 UR - https://www.sciencedirect.com/science/article/pii/S0277379120303838 ER - TY - JOUR T1 - Long-term cultural eutrophication in White and Walden Ponds (Concord, Massachusetts, USA), Thoreau's lakes of light JF - Lake and Reservoir Management Y1 - 2020 A1 - Stager, J. Curt A1 - Harvey, Lydia A1 - Chimileski, Scott KW - diatoms KW - eutrophication KW - paleolimnology KW - reclamation KW - Thoreau KW - Walden AB - Two historically important ponds in the vicinity of Boston, MA, were subjected to a comparative paleolimnological investigation of the timing and causes of eutrophication trends in each. The remarkable clarity of White Pond during the early 19th century led Henry David Thoreau to compare it favorably to nearby Walden Pond, but during the 20th century water quality in both ponds declined. Sediment core studies show that cultural eutrophication began at Walden during the 1930s, but no long-term sediment records have been available for White Pond, which makes it more difficult to determine the history and causes of eutrophication there. Here we use microfossil and geochemical analyses of sediment cores to show that major changes in the diatom community of White Pond began around 1900, when fish stocking commenced and soil erosion due to land use in the watershed increased, and that the trend intensified around 1960 and 1990. We also describe efforts to mitigate eutrophication at White Pond, highlight the ecological importance of benthic vegetation in nutrient cycling, and suggest that threats to water quality in both of these ponds will likely increase due to anticipated climatic changes in the region. UR - https://www.tandfonline.com/doi/full/10.1080/10402381.2020.1839606https://www.tandfonline.com/doi/pdf/10.1080/10402381.2020.1839606 ER - TY - JOUR T1 - Lake-level variability in Salar de Coipasa, Bolivia during the past ∼40,000 yrAbstract JF - Quaternary Research Y1 - 2019 A1 - Nunnery, J. Andrew A1 - Fritz, Sherilyn C. A1 - Baker, Paul A. A1 - Salenbien, Wout KW - Altiplano KW - Andes KW - Paleoclimate KW - paleohydrology KW - Paleolake KW - South America AB - Various paleoclimatic records have been used to reconstruct the hydrologic history of the Altiplano, relating this history to past variability of the South American summer monsoon. Prior studies of the southern Altiplano, the location of the world’s largest salt flat, the Salar de Uyuni, and its neighbor, the Salar de Coipasa, generally agree in their reconstructions of the climate history of the past ∼24 ka. Some studies, however, have highly divergent climatic records and interpretations of earlier periods. In this study, lake-level variation was reconstructed from a ∼14-m-long sediment core from the Salar de Coipasa. These sediments span the last ∼40 ka. Lacustrine sediment accumulation was apparently continuous in the basin from ∼40 to 6 ka, with dry or very shallow conditions afterward. The fossil diatom stratigraphy and geochemical data (δ13C, δ15N, %Ca, C/N) indicate fluctuations in lake level from shallow to moderately deep, with the deepest conditions correlative with the Heinrich-1 and Younger Dryas events. The stratigraphy shows a continuous lake of variable depth and salinity during the last glacial maximum and latter stages of Marine Oxygen Isotope Stage 3 and is consistent with environmental inferences and the original chronology of a drill core from Salar de Uyuni. VL - 91 UR - https://www.cambridge.org/core/product/identifier/S0033589418001084/type/journal_article IS - 2 ER - TY - JOUR T1 - Laser ablation–accelerator mass spectrometry reveals complete bomb 14C signal in an otolith with confirmation of 60-year longevity for red snapper (Lutjanus campechanus) JF - Marine and Freshwater Research Y1 - 2019 A1 - Andrews, Allen H. A1 - Yeman, Christiane A1 - Welte, Caroline A1 - Hattendorf, Bodo A1 - Wacker, Lukas A1 - Christl, Marcus KW - Age validation KW - Carbon-14 KW - Gulf of Mexico KW - Lutjanidae KW - radiocarbon. AB - Bomb-produced14C has been used to make valid estimates of age for various marine organisms for 25 years, but fish ages that lead to birth years earlier than the period of increase in14C lose their time specificity. As a result, bomb14Cdating is limited to a minimum age from the last year of prebomb levels because the temporal variation in14C in the marine surface layer is negligible for decades before c. 1958. The longevity of red snapper (Lutjanus campechanus) in the Gulf of Mexico remains unresolved despite various forms of support for ages near 50–60 years. Although the age and growth of red snapper have been verified or validated to a limited extent, some scepticism remains about longevity estimates that exceed30 years. In this study, red snapper otoliths were analysed for14C using a novel laser ablation–accelerator mass spectrometry technique to provide a continuousrecordof14C uptake. This approach provided a basis for age validation that extends beyond the normal limits of bomb14C dating with confirmation of a 60-year longevity for red snapper in the Gulf of Mexico. VL - 70 UR - http://www.publish.csiro.au/?paper=MF18265 IS - 12 ER - TY - JOUR T1 - Late Holocene long arid phase in the Indian subcontinent as seen in shallow sediments of the eastern Arabian Sea JF - Journal of Asian Earth Sciences Y1 - 2019 A1 - Saravanan, Ponnusamy A1 - Gupta, Anil K. A1 - Zheng, Hongbo A1 - Panigrahi, Mruganka K. A1 - Prakasam, Muthusamy AB - Multi-proxy record of benthic and planktic foraminifera, total organic carbon and carbon and oxygen isotope ratios from Core SK291/GC15, off the coast of Goa, eastern Arabian Sea reveals significant paleoceanographic and paleoclimatic turnovers during ~6000 to 1700 calibrated years before the Present (cal yr BP). Benthic foraminiferal census data was analyzed with multivariate techniques including factor and cluster analyses of highest ranked species from the studied core that enabled to identify seven biofacies. The record suggests centennial to millennial-scale changes in the surface conditions driven by monsoon-linked upwelling in the eastern Arabian Sea during the studied interval. Various benthic biofacies combined with isotope and planktic foraminiferal data suggest that depletion of dissolved oxygen and increase in organic productivity in the study area was caused by intense monsoonal upwelling since the middle Holocene. The results suggest that during 5400–4700 and 3000–2500 cal yr BP the southwest (SW) monsoon was strong leading to intense upwelling in the study area as reflected by increased Globigerina bulloides percentages. These were generally warmer intervals in the northern hemisphere. The SW monsoon significantly weakened (abrupt decrease in G. bulloides population) during 4700–3400 cal yr BP roughly coinciding with a long arid phase in the Indian subcontinent and a cold interval in Europe. Our record suggests an abrupt increase in SW monsoon intensity during ~3000 to 2500 cal yr BP, when a pronounced change in benthic biofacies is also noted that suggests a major shift in the sub-surface conditions. Our data document a prolong weak SW monsoon phase beginning at ~4600 cal yr BP, little earlier than 4.2 ka event, in the eastern Arabian Sea. VL - 181 UR - https://linkinghub.elsevier.com/retrieve/pii/S1367912019302676 ER - TY - JOUR T1 - Legacy sediment storage in New England river valleys: Anthropogenic processes in a postglacial landscape JF - Geomorphology Y1 - 2019 A1 - Johnson, Kaitlin M. A1 - Snyder, Noah P. A1 - Castle, Stephanie A1 - Hopkins, Austin J. A1 - Waltner, Mason A1 - Merritts, Dorothy J. A1 - Walter, Robert C. KW - Anthropogenic sediment KW - Legacy sedimen KW - Milldams AB - Legacy sediment associated with erosion from land clearing is a common feature in river valleys of the unglaciated Mid-Atlantic Piedmont region. Here, we quantify the volume of legacy sediment storage in three watersheds in New England, a formerly glaciated region with similar history and intensity of forest clearing and milldam construction during the seventeenth to nineteenth centuries. We combine field observations of bank stratigraphy, radiocarbon dating, and mapping of terraces and floodplains using lidar digital elevation models and other GIS datasets. The 68 km2 South River watershed in western Massachusetts exhibits the most extensive evidence for legacy sediment storage. We visited 18 historic dam sites in the watershed and found field evidence for up to 2.2 m of fine sand and silt legacy sediment storage at 14 of the sites. In the 555 km2 Sheepscot River watershed in coastal Maine, we visited 13 historic dam sites and found likely legacy sediment up to 2.3 m thick at six of the dams. In the 171 km2 upper Charles River watershed in eastern Massachusetts, we investigated 14 dam sites, and found legacy sediment up to 1.8 m thick at two of them. Stratigraphically, we identified the base of fine-grained legacy sediment from a change to much coarser grain size (gravel at most sites) or to glacial lacustrine or marine deposits. Along the Sheepscot River, we observed cut timbers underlying historic sediment at several locations, likely associated with sawmill activities. Only at the Charles River were we able to radiocarbon date the underlying gravel layer (1281–1391 calibrated CE). At no site did we find a buried organic-rich Holocene soil, in contrast to the field relations commonly observed in the Mid-Atlantic region. We use lidar elevation data to map planar terrace extents in each watershed, estimate thickness of remaining legacy sediment found stored behind breached or removed milldams, and estimate volumes of remaining legacy sediment storage in valley bottoms for entire watersheds. The maximum volume of stored legacy sediment estimated for the South, Sheepscot, and upper Charles watersheds is 2.5 × 106 m3, 3.7 × 106 m3, and 2.6 × 104 m3, respectively. These volumes of legacy sediment can be translated to an equivalent thickness of soil eroded from each watershed: 37 mm, 7 mm, and 0.2 mm, respectively. We attribute the variation in presence and thickness of legacy sediment at the New England sites to the existence or absence of upstream sediment supply in the form of thick glacial deposits and to sinks such as lakes and wetlands along valley bottoms. Of the three study watersheds, the South River has the most extensive glacial sediments, fewest sinks, and the most legacy sediment in storage along the river corridor. VL - 327 UR - https://linkinghub.elsevier.com/retrieve/pii/S0169555X18304665 ER - TY - JOUR T1 - Labile organic carbon dynamics in continental shelf sediments after the recent collapse of the Larsen ice shelves off the eastern Antarctic Peninsula: A radiochemical approach JF - Geochimica et Cosmochimica Acta Y1 - 2018 A1 - Isla, E. A1 - DeMaster, D.J. AB - Labile organic carbon (LOC) dynamics (i.e., of recently produced, planktonic material) and sediment dynamics were studied in the seabed using naturally occurring C-14(org), and Pb-210 measurements in the region where the Larsen Ice Shelves A and B were floating almost two decades ago. A non-steady-state diagenetic model was used to estimate sediment mixing coefficients as well as LOC fluxes to the seabed and LOC turnover times (i.e., mean residence times) in a suite of 14 sediment cores from the continental shelf, including a glacial trough. At four of the stations, cores were collected during 2007 and 2011 cruises, enabling a time-series approach for understanding the evolution of sedimentary processes and LOC dynamics in the deposits below a collapsed ice shelf. Sediment mixing coefficients, based on non-steady-state Pb-210 profiles, varied between 0.01 cm(2) y(-1) and 1.6 cm(2) y(-1) in these post-ice shelf sediments. These values were similar to those found in polar deep-sea environments, where sedimentary conditions are less dynamic than in shallower provinces. LOC, whose abundance decreased uniformly with depth, was detected to depths ranging from 2 to 16 cm, with LOC seabed inventories varying from 1.5 to 22 mg LOC cm(-2). Excess Pb-210 and LOC fluxes were relatively uniform across the study area suggesting that similar particle fluxes have taken place within theLarsen system since the disintegration of the various ice shelves. The LOC mean residence time at the different stations varied from 3 y to >60 y. The C-14(org), approach, calculating LOC content based on a two-end member model with planktonic 14C(org) as the labile carbon end member, most closely correlated with the lipid content of the sediment, which has been considered one of the best descriptors of reactive organic matter readily available to benthic consumers. We suggest that the irregular combination of sea ice coverage, organic matter production and supply to the sea floor introduce scatter in the determination of sediment and LOC dynamics such that short-term temporal (<5 years) and spatial trends could not be readily resolved. VL - 242 UR - https://linkinghub.elsevier.com/retrieve/pii/S0016703718304393https://api.elsevier.com/content/article/PII:S0016703718304393?httpAccept=text/xmlhttps://api.elsevier.com/content/article/PII:S0016703718304393?httpAccept=text/plain ER - TY - JOUR T1 - Large Variability of Dissolved Inorganic Radiocarbon in the Kuroshio Extension of the Northwest North PacificABSTRACT JF - Radiocarbon Y1 - 2018 A1 - Ding, Ling A1 - Ge, Tiantian A1 - Gao, Huiwang A1 - Luo, Chunle A1 - Xue, Yuejun A1 - Druffel, Ellen R M A1 - Wang, Xuchen KW - bomb radiocarbon KW - carbon KW - intermediate water KW - MIXED WATER REGION KW - ocean KW - WESTERN BOUNDARY CURRENTS AB - Radiocarbon (C-14) in dissolved inorganic carbon (DIC) was measured for water samples collected from six deep stations in the Kuroshio Extension (KE) region in the northwestern North Pacific in April-May 2015. Vertical profiles of Delta C-14-DIC indicate that bomb-produced Delta C-14 was present from the surface to similar to 1500 m water depth. Large variations in Delta C-14-DIC values (300 parts per thousand) were observed at 500 m water depth among the stations and the differences were likely controlled by transport and mixing dynamics of different water masses in the region. The major Pacific western boundary currents, such as Kuroshio and Oyashio and regional mesoscale eddies, could play important roles affecting the observed Delta C-14-DIC variability. The depth profiles of both Delta C-14-DIC and DIC concentrations can be predicted by the solution mixing model and can be used as conservative tracers of water mass movement and water parcel homogenization in the ocean. VL - 60264317255 UR - https://www.cambridge.org/core/product/identifier/S0033822217001436/type/journal_articlehttps://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0033822217001436 IS - 02 ER - TY - JOUR T1 - Large‐Scale Intrusion of Circumpolar Deep Water on Antarctic Margin Recorded by Stylasterid Corals JF - Paleoceanography and Paleoclimatology Y1 - 2018 A1 - King, Theresa M. A1 - Rosenheim, Brad E. A1 - Post, Alexandra L. A1 - Gabris, Theresa A1 - Burt, Taylor A1 - Domack, Eugene W. AB - We present centennial‐scale radiocarbon (14C) records archived by deep sea stylasterid corals from the outer shelf and upper slope of the Antarctic margin. These novel stylasterids (Errina spp.) were collected from the western Ross Sea shelf (500 m) and slope (1,700 m), as well as the eastern Wilkes Land shelf (670 m). We provide two corals from each region and document an abrupt reversal of 14C ages in the upper (younger) part of each coral. We test the statistical robustness of each record and demonstrate the significance of the age reversals, as well as the ability of these corals to record environmental change. We discuss a variety of possible drivers for this 14C reversal and conclude that it is most likely an encroachment of 14C‐depeleted Circumpolar Deep Water (CDW). This water mass has regionally intruded onto the Antarctic margin in recent decades, facilitating loss of grounded Antarctic ice; which has implications for global sea level, deep‐water formation, and carbon sequestration in the Southern Ocean. Thus, understanding the past variability of CDW on the margin is vital to better constrain climate change trajectories in the near future. We estimate large‐scale encroachment of CDW onto the shelf likely commencing after 1830 CE (±120 year). We present possible drivers for the intrusion, but highlight the need for additional chronologic constraint. This study not only demonstrates the utility of a novel coral taxon but also presents the paleoceanographic community with a testable hypothesis concerning a recent, widespread CDW intrusion. VL - 33 UR - https://onlinelibrary.wiley.com/doi/abs/10.1029/2018PA003439 IS - 11 ER - TY - JOUR T1 - Last Glacial Maximum surface water properties and circulation over Laurentian Fan, western North Atlantic JF - Earth and Planetary Science Letters Y1 - 2018 A1 - Gil, Isabelle M. A1 - Keigwin, Lloyd D. KW - detrital events KW - diatoms KW - ice rafted debris KW - Last glacial maximum KW - Laurentide ice sheet KW - subglacial flows AB - Millennial scale events marked by the contribution of detrital sand are recorded in North Atlantic sediments during the Last Glacial Maximum (LGM), between Heinrich events (HE) 1 and 2, and left their imprint on Laurentian Fan (LF – 43°N) sediments off eastern Canada. The LF counterpart of the well-known detrital events consist of glacial red-brick sediments resulting from subglacial flows separated by olive-grey sediments appears at ∼21.4–19.9 and ∼19.5–18.65 cal kyr BP. High-resolution analyses of diatom assemblages and lithic grains coupled with planktonic oxygen isotopic records reveal that while the red sediment is almost barren of diatoms, foraminifera and lithics (>150 μm), they are abundant in the olive-grey sediment. Diatom assemblages reveal three phases during these events: (1) initial relatively warm/temperate conditions followed by (2) very cold surface water and drifting ice, and (3) a final phase characterized by relatively warmer waters and the appearance of detrital carbonate. Although these events possibly reflect the variability specific to the slope water region, they are likely the response to Atlantic Meridional Overturning Circulation perturbations and ice-sheet instability. Through a chain of mechanisms, meltwater inputs into the North Atlantic led ultimately to an increased volume of tropical waters and part of the heat stored in the subsurface was flushed by a brief convective episode that was not sustained, accounting for the return of cold conditions after the events. The sequence of mechanisms deduced from the paleo data here and elsewhere is consistent with previous modeling results. These data suggest that the detrital events between Heinrich event 1 and 2 may be synchronous across the North Atlantic, and that the LGM was probably not a time of prolonged steady state in the climate system. VL - 500 UR - https://linkinghub.elsevier.com/retrieve/pii/S0012821X18304448 ER - TY - JOUR T1 - Late Holocene paleoceanography in the Chukchi and Beaufort Seas, Arctic Ocean, based on benthic foraminifera and ostracodes JF - arktos Y1 - 2018 A1 - Seidenstein, Julia L. A1 - Cronin, Thomas M. A1 - Gemery, Laura A1 - Keigwin, Lloyd D. A1 - Pearce, Christof A1 - Jakobsson, Martin A1 - Coxall, Helen K. A1 - Wei, Emily A. A1 - Driscoll, Neal W. AB - Calcareous microfossil assemblages in late Holocene sediments from the western Arctic continental shelf provide an important baseline for evaluating the impacts of today’s changing Arctic oceanography. This study compares 14C-dated late Holocene microfaunal assemblages of sediment cores SWERUS-L2-2-PC1, 2-MC4 and 2-KL1 (57 mwd), which record the last 4200 years in the Herald Canyon (Chukchi Sea shelf), and HLY1302-JPC-32, GGC-30, MC-29 (60 mwd), which record the last 3000 years in the Beaufort Sea shelf off the coast of Canada. Foraminiferal and ostracode assemblages are typical of Arctic continental shelf environments with annual sea-ice cover and show relatively small changes in terms of variability of dominant species. Important microfaunal changes in the Beaufort site include a spike in Spiroplectammina biformis coinciding with a decrease in Cassidulina reniforme in the last few centuries suggesting an increase of Pacific Water influence and decreased sea-ice. There is low-amplitude centennial-scale variability in proportions of benthic foraminiferal species, such as C. reniforme. In addition to these species, Cassidulina teretis s.l., Elphidium excavatum clavatum and Stainforthia feylingi are also common at this site. At the Herald Canyon site in the last few centuries, C. reniforme peaks around 150 years BP and then decreases while Spiroplectammina earlandi spikes and Acanthocythereis dunelmensis decreases also suggesting an increase in Pacific Water influence and decreased sea-ice at this site. This site also includes Buccella spp. and Elphidium excavatum clavatum. Differences in benthic foraminifera and ostracode species dominance between the two sites may be due to a greater influence of Pacific Water in the Chukchi shelf, compared to the more distal Beaufort shelf, which is also affected by the Beaufort Gyre and the Mackenzie River. VL - 4 UR - https://link.springer.com/article/10.1007/s41063-018-0058-7 IS - 1 ER - TY - JOUR T1 - Late Pleistocene to Holocene productivity changes in the western equatorial Pacific (Sulu Sea, Philippines) from calcareous nannofossils JF - Marine Micropaleontology Y1 - 2018 A1 - Tangunan, Deborah N. A1 - Peleo-Alampay, Alyssa M. KW - arabian sea KW - EAST-ASIAN MONSOON KW - GLOBAL YOUNGER-DRYAS KW - indian-ocean KW - last deglaciation KW - OCEANIC PRIMARY PRODUCTION KW - south china sea KW - surface sediments KW - UPWELLING SYSTEM KW - YR BP AB - We present a new calcareous nannofossil paleoproductivity reconstruction of the southeastern margin of the Sulu Sea to understand how marine productivity varied through time in one of the major fishing grounds of the Philippine archipelago. The study is based on two sediment cores obtained from two different hydrographic locations in the western equatorial Pacific region: an upwelling region off Zamboanga Peninsula (U-GC12) and a non-upwelling area off Panay Island (NU-GC14), covering the past 18,000 years before present (B.P.). Calcareous nannofossil assemblages in the investigated areas were of low diversity and largely dominated by Gephyrocapsa oceanica and Florisphaera profwida, followed by small placolith-bearing taxa, Emiliania hwcleyi, small Gephyrocapsa, and Reticulofenestra minuta. Upwelling episodes off the Zamboanga Peninsula were recorded several times in the past as shown by an increase in the abundance of high productivity indicator species (G. oceanica, small Gephyrocapsa, E. hwcleyi) and of bulk sediment CaCO3 (%), and a concomitant decline in the total organic carbon (TOC; %). The high abundance of low surface water productivity species F. profunda and Umbellosphaera irregularis indicates a stratified water column with a deeper nutricline, probably caused by the reduced upwelling intensity. This condition was corroborated by the decrease in CaCO3 (%) and an increase in TOC (%). We propose that the modern day high productivity conditions off Zamboanga Peninsula started at 2500 years B.P., whereas the low productivity off Panay Island was recorded from 4000 years B.P., and persists to the present day. Evidence of the Younger Dryas (YD) event was recorded from 11,100 to 10,400 years B.P. in UGC12, synchronous to the YD event reported from other areas in the Northern Hemisphere, and in accordance with the timing in the Sulu Sea as reported from previous studies in this region. This event in the Sulu Sea is characterized by a decrease in total nannofossil abundance and estimated primary productivity, together with an increase in CaCO3 (%) and a decrease in TOC (%). We interpreted that dilution caused by the increase in precipitation experienced in the Southeast Asian region during the YD event could have led to the decline of the total calcareous nannofossils whereas the recorded increase in CaCO3 (%) is attributed to the high abundance of planktonic foraminifera during this interval. VL - 143 UR - https://linkinghub.elsevier.com/retrieve/pii/S0377839816301219https://api.elsevier.com/content/article/PII:S0377839816301219?httpAccept=text/xmlhttps://api.elsevier.com/content/article/PII:S0377839816301219?httpAccept=text/plain ER - TY - JOUR T1 - Linear decline in red snapper (Lutjanus campechanus) otolith Δ14C extends the utility of the bomb radiocarbon chronometer for fish age validation in the Northern Gulf of Mexico JF - ICES Journal of Marine Science Y1 - 2018 A1 - Barnett, Beverly K A1 - Thornton, Laura A1 - Allman, Robert A1 - Chanton, Jeffrey P A1 - Patterson, William F KW - Age validation KW - otoliths KW - radiocarbon KW - red snapper AB - Radiocarbon (D14C) was analyzed in northern Gulf of Mexico (nGOM) red snapper (Lutjanus campechanus) otolith cores (n¼23), otolith edge samples (n¼12), and whole age-0 otoliths (n¼9), with edge samples and whole age-0 otoliths constituting known-age samples. There was no significant difference in the linear relationship of D14C versus year of formation between regional corals and known-age otolith samples, and a linear regression fit to the combined data from 1980 to 2015 extends the utility of the bomb radiocarbon chronometer for age validation. The entire regional coral and known-age otolith data set (1940 to 2015) was then utilized as a reference series to validate otolith-derived red snapper age estimates for cored otolith samples. A loess regression was fit to the reference data and then the sum of squared residuals (SSR) was computed from predicted versus observed birth years for cored adult otolith samples. This process was then repeated for ages biased 61–4 years. Ages with no bias applied had the lowest SSR, thus validating red snapper age estimates and demonstrating the utility of the combined regional coral and known-age red snapper otolith D14C time series for age validation of nGOM marine fishes. VL - 8870697346588911255202655996472975862129455810210311781289189114143320657330766513996026526319911984699 UR - https://academic.oup.com/icesjms/advance-article/doi/10.1093/icesjms/fsy043/4992258http://academic.oup.com/icesjms/advance-article-pdf/doi/10.1093/icesjms/fsy043/24775644/fsy043.pdf ER - TY - JOUR T1 - Longitudinal discontinuities in riverine greenhouse gas dynamics generated by dams and urban wastewater JF - Biogeosciences Y1 - 2018 A1 - Jin, Hyojin A1 - Yoon, Tae Kyung A1 - Begum, Most Shirina A1 - Lee, Eun-Ju A1 - Oh, Neung-Hwan A1 - Kang, Namgoo A1 - Park, Ji-Hyung AB - Surface water concentrations of CO2, CH4, and N2O have rarely been measured simultaneously in river systems modified by human activities, contributing to large uncertainties in estimating global riverine emissions of greenhouse gases (GHGs). Basin-wide surveys of the three GHGs were combined with a small number of measurements of C isotope ratios in dissolved organic matter (DOM), CO2, and CH4 in the Han River basin, South Korea, to examine how longitudinal patterns of the three gases and DOM are affected by four cascade dams along a middle section of the North Han River (hereafter termed “middle reach”) and treated wastewater discharged to the lower Han River (“lower reach”) traversing the Seoul metropolitan area. Monthly monitoring and two-season comparison were conducted at 6 and 15 sites, respectively, to measure surface water gas concentrations and ancillary water quality parameters including concentrations of dissolved organic carbon (DOC) and optical properties of DOM. The basin-wide surveys were complemented with a sampling cruise along the lower reach and synoptic samplings along an urban tributary delivering effluents from a large wastewater treatment plant (WWTP) to the lower reach. The levels of pCO2 were relatively low in the middle reach (51–2465 µatm), particularly at the four dam sites (51–761 µatm), compared with those found in the largely forested upper basin with scattered patches of croplands (163–2539 µatm), the lower reach (78–11298 µatm), and three urban tributaries (2120–11970 µatm). The upper and middle reaches displayed generally low concentration ranges of CH4 and N2O, with some local peaks influenced by agricultural runoff and impoundments. By comparison, the lower reach exhibited exceptionally high concentrations of CH4 (1.2–15766 nmol L−1) and N2O (7.5–1396 nmol L−1), which were significantly correlated with different sets of variables such as DO and PO3−4 for CH4 and NH+4 and NO−3 for N2O. Downriver increases in the levels of DOC and optical properties such as fluorescence index (FI) and protein-like fluorescence indicated an increasing DOM fraction of anthropogenic and microbial origin. The concentrations of the three GHGs and DOC were similar in magnitude and temporal variation at a WWTP discharge and the receiving tributary, indicating a disproportionate contribution of the WWTP effluents to the tributary gas and DOC exports to the lower reach. The values of δ13C in surface water CO2 and CH4 measured during the sampling cruise along the lower reach, combined with δ13C and Δ14C in DOM sampled across the basin, implied a strong influence of the wastewater-derived gases and aged DOM delivered by the urban tributaries. The downstream enrichment of 13C in CO2 and CH4 suggested that the spatial distribution of these gases across the eutrophic lower reach may also be constrained by multiple concomitant processes including outgassing, photosynthesis, and CH4 oxidation. The overall results suggest that dams and urban wastewater may create longitudinal discontinuities in riverine metabolic processes leading to large spatial variations in the three GHGs correlating with different combinations of DOM properties and nutrients. Further research is required to evaluate the relative contributions of anthropogenic and in-stream sources of the three gases and DOM in eutrophic urbanized river systems and constrain key factors for the contrasting impoundment effects such as autotrophy-driven decreases in pCO2 and in-lake production of CH4 and N2O. VL - 15 UR - https://bg.copernicus.org/articles/15/6349/2018/ IS - 20 ER - TY - JOUR T1 - A long-term decrease in the persistence of soil carbon caused by ancient Maya land use JF - Nature Geoscience Y1 - 2018 A1 - Douglas, Peter M. J. A1 - Pagani, Mark A1 - Eglinton, Timothy I. A1 - Brenner, Mark A1 - Curtis, Jason H. A1 - Breckenridge, Andy A1 - Johnston, Kevin AB - The long-term effects of deforestation on tropical forest soil carbon reservoirs are important for estimating the consequences of land use on the global carbon cycle, but are poorly understood. The Maya Lowlands of Mexico and Guatemala provide a unique opportunity to assess this question, given the widespread deforestation by the ancient Maya that began ~4,000 years ago. Here, we compare radiocarbon ages of plant waxes and macrofossils in sediment cores from three lakes in the Maya Lowlands to record past changes in the mean soil transit time of plant waxes (MTTwax). MTTwax indicates the average age of plant waxes that are transported from soils to lake sediments, and comparison of radiocarbon data from soils and lake sediments within the same catchment indicates that MTTwax reflects the age of carbon in deep soils. All three sediment cores showed a decrease in MTTwax, ranging from 2,300 to 800 years, over the past 3,500 years. This decrease in MTTwax, indicating shorter storage times for carbon in lake catchment soils, is associated with evidence for ancient Maya deforestation. MTTwax never recovered to pre-deforestation values, despite subsequent reforestation, implying that current tropical deforestation will have long-lasting effects on soil carbon sinks. VL - 11 UR - https://www.researchgate.net/publication/327119047_A_long-term_decrease_in_the_persistence_of_soil_carbon_caused_by_ancient_Maya_land_use IS - 9 ER - TY - JOUR T1 - Land-use change and managed aquifer recharge effects on the hydrogeochemistry of two contrasting atoll island aquifers, Roi-Namur Island, Republic of the Marshall Islands JF - Applied Geochemistry Y1 - 2017 A1 - Mehrdad Hejazian A1 - Jason J. Gurdak A1 - Peter Swarzenski A1 - Kingsley O. Odigie A1 - Curt D. Storlazzi AB - Abstract Freshwater resources on low-lying atoll islands are highly vulnerable to climate change and sea-level rise. In addition to rainwater catchment, groundwater in the freshwater lens is a critically important water resource on many atoll islands, especially during drought. Although many atolls have high annual rainfall rates, dense natural vegetation and high evapotranspiration rates can limit recharge to the freshwater lens. Here we evaluate the effects of land-use/land-cover change and managed aquifer recharge on the hydrogeochemistry and supply of groundwater on Roi-Namur Island, Republic of the Marshall Islands. Roi-Namur is an artificially conjoined island that has similar hydrogeology on the Roi and Namur lobes, but has contrasting land-use/land-cover and managed aquifer recharge only on Roi. Vegetation removal and managed aquifer recharge operations have resulted in an estimated 8.6 × 105 m3 of potable groundwater in the freshwater lens on Roi, compared to only 1.6 × 104 m3 on Namur. We use groundwater samples from a suite of 33 vertically nested monitoring wells, statistical testing, and geochemical modeling using \{PHREEQC\} to show that the differences in land-use/land-cover and managed aquifer recharge on Roi and Namur have a statistically significant effect on several groundwater-quality parameters and the controlling geochemical processes. Results also indicate a six-fold reduction in the dissolution of carbonate rock in the freshwater lens and overlying vadose zone of Roi compared to Namur. Mixing of seawater and the freshwater lens is a more dominant hydrogeochemical process on Roi because of the greater recharge and flushing of the aquifer with freshwater as compared to Namur. In contrast, equilibrium processes and dissolution-precipitation non-equilibrium reactions are more dominant on Namur because of the longer residence times relative to the rate of geochemical reactions. Findings from Roi-Namur Island support selective land-use/land-cover change and managed aquifer recharge as a promising management approach for communities on other low-lying atoll islands to increase the resilience of their groundwater supplies and help them adapt to future climate change related stresses. VL - 80 UR - http://www.sciencedirect.com/science/article/pii/S0883292716301391 ER - TY - JOUR T1 - Large-scale response of the Eastern Mediterranean thermohaline circulation to African monsoon intensification during sapropel S1 formation JF - Quaternary Science Reviews Y1 - 2017 A1 - T. Tesi A1 - A. Asioli A1 - D. Minisini A1 - V. Maselli A1 - G. Dalla Valle A1 - F. Gamberi A1 - L. Langone A1 - A. Cattaneo A1 - P. Montagna A1 - F. Trincardi KW - Thermohaline circulation AB - Abstract The formation of Eastern Mediterranean sapropels has periodically occurred during intensification of northern hemisphere monsoon precipitation over North Africa. However, the large-scale response of the Eastern Mediterranean thermohaline circulation during these monsoon-fuelled freshening episodes is poorly constrained. Here, we investigate the formation of the youngest sapropel (S1) along an across-slope transect in the Adriatic Sea. Foraminifera-based oxygen index, redox-sensitive elements and biogeochemical parameters reveal – for the first time – that the Adriatic \{S1\} was synchronous with the deposition of south-eastern Mediterranean \{S1\} beds. Proxies of paleo thermohaline currents indicate that the bottom-hugging North Adriatic Dense Water (NAdDW) suddenly decreased at the sapropel onset simultaneously with the maximum freshening of the Levantine Sea during the African Humid Period. We conclude that the lack of the “salty” Levantine Intermediate Water hampered the preconditioning of the northern Adriatic waters necessary for the \{NAdDW\} formation prior to the winter cooling. Consequently, a weak \{NAdDW\} limited in turn the Eastern Mediterranean Deep Water (EMDWAdriatic) formation with important consequences for the ventilation of the Ionian basin as well. Our results highlight the importance of the Adriatic for the deep water ventilation and the interdependence among the major eastern Mediterranean water masses whose destabilization exerted first-order control on \{S1\} deposition. VL - 159 UR - http://www.sciencedirect.com/science/article/pii/S0277379116304012 ER - TY - JOUR T1 - Local and regional wildfire activity in central Maine (USA) during the past 900 years JF - Journal of Paleolimnology Y1 - 2017 A1 - Miller, Daniel R. A1 - Castañeda, Isla S. A1 - Bradley, Raymond S. A1 - MacDonald, Dana AB - Climatic and environmental change has a direct effect on wildfire frequencies and distributions throughout many regions of the world. Reconstructions from natural archives such as lake sediments can extend temporally limited historical records of regional wildfire activity over longer timescales through sedimentary charcoal analysis or examining polycyclic aromatic hydrocarbon (PAH) concentrations. To date, little work has been completed on sedimentary PAH distributions from lacustrine records in the Northeastern United States, making it difficult to assess how accurately PAHs trace fire activity in the region, the spatial scope of the signal (local vs. regional), or if certain compounds do a more adequate job of tracking fire than others. In this study, we examine PAHs and macrocharcoal from a varved sedimentary record from Basin Pond, Fayette, Maine (USA). We find that a drastic increase in the concentrations of 12 measured PAHs occurred during the nineteenth to twentieth centuries due to industrialization of the region. Additionally, elevated concentrations of the PAH retene were found to be coeval with known large-scale regional wildfire events that occurred in 1761–1762, 1825, and 1947 (A.D.). We used the ratio of the PAHs retene and chrysene to infer differences in biomass burning versus anthropogenic combustion sources because retene is associated with conifer resin whereas chrysene is associated with fossil fuel burning. Our new Basin Pond PAH records, along with a local signal of fire occurrence from charcoal analysis, offers the prospect of using this multi-proxy approach as a method for examining long-term wildfire frequency at both the local and regional scale in the Northeastern US. VL - 58 UR - https://link.springer.com/article/10.1007/s10933-017-0002-z IS - 4 ER - TY - JOUR T1 - Local glaciation in West Greenland linked to North Atlantic Ocean circulation during the Holocene JF - Geology Y1 - 2017 A1 - Schweinsberg, Avriel D. A1 - Briner, Jason P. A1 - Miller, Gifford H. A1 - Bennike, Ole A1 - Thomas, Elizabeth K. AB - Recent observations indicate that ice-ocean interaction drives much of the recent increase in mass loss from the Greenland Ice Sheet; however, the role of ocean forcing in driving past glacier change is poorly understood. To extend the observational record and our understanding of the ocean-cryosphere link, we used a multi-proxy approach that combines new data from proglacial lake sediments, C-14-dated in situ moss that recently emerged from beneath cold-based ice caps, and Be-10 ages to reconstruct centennial-scale records of mountain glacier activity for the past similar to 10 k. y. in West Greenland. Proglacial lake sediment records and C-14 dating of moss indicate the onset of Neoglaciation in West Greenland at ca. 5 ka with substantial snowline lowering and glacier expansion at ca. 3.7 ka followed by additional ice expansion phases at ca. 2.9, ca. 1.7, and ca. 1.4 ka and during the Little Ice Age. We find that widespread glacier growth at ca. 3.7 ka in West Greenland coincides with marked cooling and reduced strength of the West Greenland Current in Disko Bugt. The transition to cooler ocean conditions at ca. 3.7 ka identified in Disko Bugt is registered by marine proxy data farther afield in East Greenland and on the northwestern Icelandic shelf, implying large-scale paleoceanographic changes across the North Atlantic during this interval. The similarity between glacier change on West Greenland and multiple marine and terrestrial records across the North Atlantic suggests that glaciers are strongly influenced by changes in ocean circulation and consequently implies that the ocean-cryosphere teleconnection is a persistent feature of the Arctic system. VL - 45 UR - http://geology.gsapubs.org/lookup/doi/10.1130/G38114 IS - 3 ER - TY - JOUR T1 - Large deglacial shifts of the Pacific Intertropical Convergence Zone JF - Nature Communications Y1 - 2016 A1 - Jacobel, A. W. A1 - McManus, J. F. A1 - Anderson, R. F. A1 - Winckler, G. AB - The position of the Intertropical Convergence Zone (ITCZ) is sensitive to changes in the balance of heat between the hemispheres which has fundamental implications for tropical hydrology and atmospheric circulation. Although the ITCZ is thought to experience the largest shifts in position during deglacial stadial events, the magnitude of shifts has proven difficult to reconstruct, in part because of a paucity of high-resolution records, particularly those including spatial components. Here we track the position of the ITCZ from 150 to 110 ka at three sites in the central equatorial Pacific at sub-millennial time resolution. Our results provide evidence of large, abrupt changes in tropical climate during the penultimate deglaciation, coincident with North Atlantic Heinrich Stadial 11 (∼136–129 ka). We identify this event both as a Northern Hemisphere increase in aeolian dust and as a shift in the mean position of the ITCZ a minimum of 4° southwards at 160° W. VL - 7 UR - http://www.nature.com/doifinder/10.1038/ncomms10449 ER - TY - JOUR T1 - Last Glacial Maximum sea surface temperature and sea-ice extent in the Pacific sector of the Southern Ocean JF - Quaternary Science Reviews Y1 - 2016 A1 - Verena Benz A1 - Oliver Esper A1 - Rainer Gersonde A1 - Frank Lamy A1 - Ralf Tiedemann KW - Pacific Southern Ocean AB - Abstract Sea surface temperatures and sea-ice extent are most critical variables to evaluate the Southern Ocean paleoceanographic evolution in relation to the development of the global carbon cycle, atmospheric \{CO2\} and ocean-atmosphere circulation. Here we present diatom transfer function-based summer sea surface temperature (SSST) and winter sea-ice (WSI) estimates from the Pacific sector of the Southern Ocean to bridge a gap in information that has to date hampered a well-established reconstruction of the last glacial Southern Ocean at circum-Antarctic scale. We studied the Last Glacial Maximum (LGM) at the \{EPILOG\} time slice (19,000–23,000 calendar years before present) in 17 cores and consolidated our \{LGM\} picture of the Pacific sector taking into account published data from its warmer regions. Our data display a distinct east-west differentiation with a rather stable \{WSI\} edge north of the Pacific-Antarctic Ridge in the Ross Sea sector and a more variable \{WSI\} extent over the Amundsen Abyssal Plain. The zone of maximum cooling (>4 K) during the \{LGM\} is in the present Subantarctic Zone and bounded to its south by the 4 °C isotherm. The isotherm is in the \{SSST\} range prevailing at the modern Antarctic Polar Front, representing a circum-Antarctic feature, and marks the northern edge of the glacial Antarctic Circumpolar Current (ACC). The northward deflection of colder than modern surface waters along the South American continent led to a significant cooling of the glacial Humboldt Current surface waters (4–8 K), which affected the temperature regimes as far north as tropical latitudes. The glacial reduction of \{ACC\} temperatures may also have resulted in significant cooling in the Atlantic and Indian Southern Ocean, thus enhancing thermal differentiation of the Southern Ocean and Antarctic continental cooling. The comparison with numerical temperature and sea-ice simulations yields discrepancies, especially concerning the estimates of the sea-ice fields, but some simulations reproduce well our proxy-based temperature data. VL - 146 UR - http://www.sciencedirect.com/science/article/pii/S0277379116302062 ER - TY - JOUR T1 - Late Quaternary evolution of Lago Castor (Chile, 45.6°S): Timing of the deglaciation in northern Patagonia and evolution of the southern westerlies during the last 17 kyr JF - Quaternary Science Reviews Y1 - 2016 A1 - Maarten Van Daele A1 - Sébastien Bertrand A1 - Inka Meyer A1 - Jasper Moernaut A1 - Willem Vandoorne A1 - Giuseppe Siani A1 - Niels Tanghe A1 - Zakaria Ghazoui A1 - Mario Pino A1 - Roberto Urrutia A1 - Marc De Batist KW - Sediment drift AB - Abstract Even though Patagonia is ideally located to study climate of the southern mid-latitudes, many questions on the late Quaternary climate evolution remain unresolved. The timing of maximum glacier extent is still uncertain in vast areas, and the postglacial evolution of the Southern Westerly Wind Belt (SWWB) remains highly debated. Here, we study the sedimentary infill of a glacigenic lake (Lago Castor; 45.6°S, 71.8°W) located at the leeside of the Andes in Chilean Patagonia to i) reconstruct the deglacial evolution of the eastern flank of the Patagonian Ice Sheet (PIS), and ii) discuss postglacial changes in wind strength at a critical location where westerly wind records are critically lacking. A dense grid of high-resolution reflection-seismic data was used to reconstruct the large-scale infill history of the lake, and a radiocarbon dated sediment core penetrating all lacustrine seismic units, was retrieved. Results indicate that the deglaciation of the lake basin and its catchment occurred no later than ∼28 cal kyr \{BP\} (i.e. an early LGM), but possibly even already after \{MIS\} 4. Afterwards, the Lago Castor area was covered by a large proglacial lake that drained – possibly through an outburst flood – when the \{PIS\} outlet glaciers retreated to a critical location. Subsequently, very dry conditions caused the lake to desiccate, as evidenced by an unconformity visible on the seismic profiles and in the sediment core. This dry period likely resulted from the increased orographic effect of the PIS-covered Andes, accompanied by weaker westerlies. From ∼20 kyr \{BP\} onwards, the combination of a shrinking \{PIS\} and a southward shift of the \{SWWB\} resulted in increased precipitation, which caused the lake level to rise. After ∼17 cal kyr BP, lake sedimentation was more directly influenced by the southern westerlies, with the formation of sediment drifts resulting from strong bottom current during periods of intense westerly winds. Our results suggest a progressive increase in wind strength at 46°S from 11.2 to 4.5 cal kyr BP, which supports the hypothesis that the \{SWWB\} broadened during the early and middle Holocene. VL - 133 UR - http://www.sciencedirect.com/science/article/pii/S027737911530202X ER - TY - JOUR T1 - Late Quaternary fingerprints of precession and sea level variation over the past 35 kyr as revealed by sea surface temperature and upwelling records from the Indian Ocean near southernmost Sumatra JF - Quaternary International Y1 - 2016 A1 - Ziye Li A1 - Xuefa Shi A1 - Min-Te Chen A1 - Houjie Wang A1 - Shengfa Liu A1 - Jian Xu A1 - Haiyan Long A1 - Rainer Arief Troa A1 - Rina Zuraida A1 - Eko Triarso KW - Quaternary AB - Abstract We report high-resolution paleoclimatic reconstructions using isotope, alkenone sea surface temperature (SST), productivity, and terrigenous proxy variations over the past 35 kyr from core SO184-10043 (07°18.57′S, 105°03.53′E) in the eastern tropical Indian Ocean offshore of southernmost (S) Sumatra. The core was retrieved at 2171 m water depth, from the monsoon driven seasonal upwelling area off southernmost Sumatra. Our paleoclimatic reconstructions show that an enhanced marine productivity was closely linked to strengthening of coastal upwelling during the increases of boreal summer insolation and associated southeastern (SE) monsoon strength, with pronounced semi-precession cycles (∼11 kyr). In contrast, our record of alkenone \{SSTs\} shows glacial to interglacial, a sea-level variation, but this fluctuates at dominant precession cycles (∼21 kyr). We also observed four \{SST\} “plateaus” with relatively warmer hydrographic stability in our records over the past 35 kyr: 32-27 ka, 24-20 ka, 17-12 ka, and 9-4 ka. The time scale of each plateau is ∼4-6 kyr. Our study indicates that since the last glacial maximum (LGM), the sea level rise has been responsible for the Sunda shelf flooding and the Indonesian Throughflow (ITF) from the South China Sea (SCS) to the eastern Indian Ocean, leaving a dominant fingerprint of a glacial to interglacial increase in \{SSTs\} since ∼9.5 ka We further argue that the a most recent centennial to millennial scale cooling at ∼3.5 ka observed in our \{SST\} record is a widespread event in the tropical Pacific, which has implications for advancing our understanding of the climate dynamics of the tropical oceans at these time scales. VL - 425 UR - http://www.sciencedirect.com/science/article/pii/S1040618216308722 ER - TY - JOUR T1 - Late Holocene glacial advance and ice shelf growth in Barilari Bay, Graham Land, west Antarctic Peninsula JF - GEOLOGICAL SOCIETY OF AMERICA BULLETIN Y1 - 2015 A1 - Christ, Andrew J. A1 - Talaia-Murray, Manique A1 - Elking, Natalie A1 - Domack, Eugene W. A1 - Leventer, Amy A1 - Lavoie, Caroline A1 - Brachfeld, Stefanie A1 - Yoo, Kyu-Cheul A1 - Gilbert, Robert A1 - Jeong, Sun-Mi A1 - Petrushak, Stephen A1 - Wellner, Julia A1 - LARISSA Grp AB - Three marine sediment cores were collected along the length of the fjord axis of Barilari Bay, Graham Land, west Antarctic Peninsula (65 degrees 55'S, 64 degrees 43'W). Multi-proxy analytical results constrained by high-resolution geochronological methods (Pb-210, radiocarbon, Cs-137) in concert with historical observations capture a record of Holocene paleoenvironmental variability. Our results suggest early and middle Holocene (>7022-2815 cal. {[}calibrated] yr B.P.) retreated glacial positions and seasonally open marine conditions with increased primary productivity. Climatic cooling increased sea ice coverage and decreased primary productivity during the Neoglacial (2815 to cal. 730 cal. yr B.P.). This climatic cooling culminated with glacial advance to maximum Holocene positions and expansion of a fjord-wide ice shelf during the Little Ice Age (LIA) (ca. 730-82 cal. yr B.P.). Seasonally open marine conditions were achieved and remnant ice shelves decayed within the context of recent rapid regional warming (82 cal. yr B.P. to present). Our findings agree with previously observed late Holocene cooling and glacial advance across the Antarctic Peninsula, suggesting that the LIA was a regionally significant event with few disparities in timing and magnitude. Comparison of the LIA Antarctic Peninsula record to the rest of the Southern Hemisphere demonstrates close synchronicity in the southeast Pacific and southern most Atlantic region but less coherence for the southwest Pacific and Indian Oceans. Comparisons with the Northern Hemisphere demonstrate that the LIA Antarctic Peninsula record was contemporaneous with pre-LIA cooling and sea ice expansion in the North Atlantic-Arctic, suggesting a global reach for these events. VL - 127 ER - TY - JOUR T1 - Late Holocene precipitation variability recorded in the sediments of Reloncaví Fjord (41°S, 72°W), Chile JF - Quaternary Research Y1 - 2015 A1 - Rebolledo, Lorena A1 - Lange, Carina B. A1 - Bertrand, Sébastien A1 - Muñoz, Praxedes A1 - Salamanca, Marco A1 - Lazo, Pablo A1 - Iriarte, José L. A1 - Vargas, Gabriel A1 - Pantoja, Silvio A1 - Dezileau, Laurent AB - We present reconstructions of late Holocene changes in the source of organic matter and siliceous export production in the Relocanví Fjord (41°S, 72°W), Northern Chilean Patagonia, based on organic carbon content, δ13Corg, N/C ratio, diatom assemblages and biogenic silica contents from three sediment cores. The age models are based on a combination of 210Pb profiles, AMS 14C dating, and on the first occurrence of the diatom Rhizosolenia setigera f. pungens, as a stratigraphic marker in the fjords. The cores span the last 300 to 700 yr. Diatoms dominate the siliceous assemblages in the three cores (98% on average). Our results suggest that precipitation seasonality in the region of Reloncaví was high in CE 1300–1400 and CE 1700–1850, with a clear decreasing trend since CE 1850. The latter trend is in agreement with instrumental records and tree-ring reconstructions. These fluctuations seem to be associated with the Southern Annular Mode (SAM). VL - 84 N1 - Co0ceTimes Cited:1Cited References Count:93 JO - Late Holocene precipitation variability recorded in the sediments of Reloncaví Fjord (41°S, 72°W), Chile ER - TY - JOUR T1 - Low-frequency storminess signal at Bermuda linked to cooling events in the North Atlantic region JF - Paleoceanography Y1 - 2015 A1 - van Hengstum, Peter J. A1 - Donnelly, Jeffrey P. A1 - Kingston, Andrew W. A1 - Williams, Bruce E. A1 - Scott, David B. A1 - Reinhardt, Eduard G. A1 - Little, Shawna N. A1 - Patterson, William P. AB - North Atlantic climate archives provide evidence for increased storm activity during the Little Ice Age (150 to 600 calibrated years (cal years) B.P.) and centered at 1700 and 3000 cal years B.P., typically in centennial-scale sedimentary records. Meteorological (tropical versus extratropical storms) and climate forcings of this signal remain poorly understood, although variability in the North Atlantic Oscillation (NAO) or Atlantic Meridional Overturning Circulation (AMOC) are frequently hypothesized to be involved. Here we present records of late Holocene storminess and coastal temperature change from a Bermudian submarine cave that is hydrographically circulated with the coastal ocean. Thermal variability in the cave is documented by stable oxygen isotope values of cave benthic foraminifera, which document a close linkage between regional temperature change and NAO phasing during the late Holocene. However, erosion of terrestrial sediment into the submarine cave provides a “storminess signal” that correlates with higher-latitude storminess archives and broader North Atlantic cooling events. Understanding the driver of this storminess signal will require higher-resolution storm records to disentangle the contribution of tropical versus extratropical cyclones and a better understanding of cyclone activity during hemispheric cooling periods. Most importantly, however, the signal in Bermuda appears more closely correlated with proxy-based evidence for subtle AMOC reductions than NAO phasing. VL - 30 UR - http://doi.wiley.com/10.1002/2014PA002662https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2F2014PA002662 IS - 2 ER - TY - JOUR T1 - Late Holocene marine transgression and the drowning of a coastal forest: Lessons from the past, Cape Cod, Massachusetts, USA JF - Palaeogeography, Palaeoclimatology, Palaeoecology Y1 - 2014 A1 - Maio, Christopher V. A1 - Gontz, Allen M. A1 - Weidman, Christopher R. A1 - Donnelly, Jeffrey P. AB - Extra-tropical storms in the spring of 2010 swept the New England coastline resulting in significant erosion along South Cape Beach, a barrier system located on Cape Cod, Massachusetts. The erosion revealed 111 subfossil stumps and a preserved peat outcrop. We hypothesize that the stumps represent an ancient Eastern Red cedar, Juniperus virginiana, stand growing in a back-barrier environment and drowned by episodic storm events and moderate rates of sea-level rise. Stumps, bivalves, and organic sediments, were radiocarbon dated using traditional and continuous-flow Atomic Mass Spectroscopy methods. Six sediment cores elucidated subsurface stratigraphy and environmental setting. Subfossil stumps ranged in age from 413 ± 80 to 1239 ± 53 calibrated years before present. We assume that this age represents the time at which the ancient trees were drowned by marine waters. Based on elevation and age, an 826 year rate of submergence was calculated at 0.73 mm/yr with an R2 value of 0.47. Core stratigraphy, microfossil assemblages, and radiocarbon ages indicate a dynamic barrier environment with frequent overwash and breaching events occurring during the past 500 years. Shoreline change analysis showed that between 1846 and 2008, the shoreline retreated landward by 70 m at a long-term rate of 0.43 m/yr. Future increases in the rate of sea-level rise, coupled with episodic storm events, will lead to the destruction of terrestrial environments at rate orders of magnitude greater than that during the time of the paleoforest. VL - 393 UR - http://www.sciencedirect.com/science/article/pii/S003101821300521X JO - Late Holocene marine transgression and the drowning of a coastal forest: Lessons from the past, Cape Cod, Massachusetts, USA ER - TY - JOUR T1 - Late Holocene sea- and land-level change on the U.S. southeastern Atlantic coast JF - Marine Geology Y1 - 2014 A1 - Kemp, Andrew C. A1 - Bernhardt, Christopher E. A1 - Horton, Benjamin P. A1 - Kopp, Robert E. A1 - Vane, Christopher H. A1 - Peltier, W. Richard A1 - Hawkes, Andrea D. A1 - Donnelly, Jeffrey P. A1 - Parnell, Andrew C. A1 - Cahill, Niamh AB - Late Holocene relative sea-level (RSL) reconstructions can be used to estimate rates of land-level (subsidence or uplift) change and therefore to modify global sea-level projections for regional conditions. These reconstructions also provide the long-term benchmark against which modern trends are compared and an opportunity to understand the response of sea level to past climate variability. To address a spatial absence of late Holocene data in Florida and Georgia, we reconstructed ~ 1.3 m of RSL rise in northeastern Florida (USA) during the past ~ 2600 years using plant remains and foraminifera in a dated core of high salt-marsh sediment. The reconstruction was fused with tide-gauge data from nearby Fernandina Beach, which measured 1.91 ± 0.26 mm/year of RSL rise since 1900 CE. The average rate of RSL rise prior to 1800 CE was 0.41 ± 0.08 mm/year. Assuming negligible change in global mean sea level from meltwater input/removal and thermal expansion/contraction, this sea-level history approximates net land-level (subsidence and geoid) change, principally from glacio-isostatic adjustment. Historic rates of rise commenced at 1850–1890 CE and it is virtually certain (P = 0.99) that the average rate of 20th century RSL rise in northeastern Florida was faster than during any of the preceding 26 centuries. The linearity of RSL rise in Florida is in contrast to the variability reconstructed at sites further north on the U.S. Atlantic coast and may suggest a role for ocean dynamic effects in explaining these more variable RSL reconstructions. Comparison of the difference between reconstructed rates of late Holocene RSL rise and historic trends measured by tide gauges indicates that 20th century sea-level trends along the U.S. Atlantic coast were not dominated by the characteristic spatial fingerprint of melting of the Greenland Ice Sheet. VL - 357 UR - http://www.sciencedirect.com/science/article/pii/S0025322714002187 JO - Late Holocene sea- and land-level change on the U.S. southeastern Atlantic coast ER - TY - JOUR T1 - Late Holocene sea- and land-level change on the U.S. southeastern Atlantic coast JF - Marine Geology Y1 - 2014 A1 - Kemp, Andrew C. A1 - Bernhardt, Christopher E. A1 - Horton, Benjamin P. A1 - Kopp, Robert E. A1 - Vane, Christopher H. A1 - Peltier, W. Richard A1 - Hawkes, Andrea D. A1 - Donnelly, Jeffrey P. A1 - Parnell, Andrew C. A1 - Cahill, Niamh KW - florida KW - Foraminifera KW - Glacio-isostatic adjustment Greenland fingerprint KW - Salt marsh AB - Late Holocene relative sea-level (RSL) reconstructions can be used to estimate rates of land-level (subsidence or uplift) change and therefore to modify global sea-level projections for regional conditions. These reconstructions also provide the long-term benchmark against which modern trends are compared and an opportunity to understand the response of sea level to past climate variability. To address a spatial absence of late Holocene data in Florida and Georgia, we reconstructed ~ 1.3 m of RSL rise in northeastern Florida (USA) during the past ~ 2600 years using plant remains and foraminifera in a dated core of high salt-marsh sediment. The reconstruction was fused with tide-gauge data from nearby Fernandina Beach, which measured 1.91 ± 0.26 mm/year of RSL rise since 1900 CE. The average rate of RSL rise prior to 1800 CE was 0.41 ± 0.08 mm/year. Assuming negligible change in global mean sea level from meltwater input/removal and thermal expansion/contraction, this sea-level history approximates net land-level (subsidence and geoid) change, principally from glacio-isostatic adjustment. Historic rates of rise commenced at 1850–1890 CE and it is virtually certain (P = 0.99) that the average rate of 20th century RSL rise in northeastern Florida was faster than during any of the preceding 26 centuries. The linearity of RSL rise in Florida is in contrast to the variability reconstructed at sites further north on the U.S. Atlantic coast and may suggest a role for ocean dynamic effects in explaining these more variable RSL reconstructions. Comparison of the difference between reconstructed rates of late Holocene RSL rise and historic trends measured by tide gauges indicates that 20th century sea-level trends along the U.S. Atlantic coast were not dominated by the characteristic spatial fingerprint of melting of the Greenland Ice Sheet. VL - 357 UR - http://linkinghub.elsevier.com/retrieve/pii/S0025322714002187http://api.elsevier.com/content/article/PII:S0025322714002187?httpAccept=text/xmlhttp://api.elsevier.com/content/article/PII:S0025322714002187?httpAccept=text/plain ER - TY - JOUR T1 - Late Holocene sedimentation in a high Arctic coastal setting: Simpson Lagoon and Colville Delta, Alaska JF - Continental Shelf Research Y1 - 2014 A1 - Hanna, Andrea J. M. A1 - Allison, Mead A. A1 - Bianchi, Thomas S. A1 - Marcantonio, Franco A1 - Goff, John A. AB - Arctic coastal environments near major river outfalls, like Simpson Lagoon, Alaska and the adjacent Colville River Delta, potentially contain high-resolution sediment records useful in elucidating late Holocene Arctic sediment transport pathways and coupled terrestrial-ocean evidence of paleoclimate variability. This study utilizes a multi-tracer geochronology approach (137Cs, 239,240Pu, and 14C) tailored for high-latitude environments to determine the age models for cores collected from Simpson Lagoon, and to date seismic boundaries in shallow acoustic reflection data (CHIRP) to examine late Holocene infill patterns. Modern (~100 y) sediment accumulation rates range from 5 m of late Holocene interbedded sediments, likely derived primarily from the Colville River, with onset of accumulation occurring prior to ~3500 y BP. A paleo-high in central Simpson Lagoon, separating the two depocenters, was subaerially exposed prior to ~600 y BP. The millimeters-per-year sedimentation rates across the lagoon, coupled with the undisturbed, interbedded sediment record, indicate that these settings hold great potential to develop new Arctic paleoenvironmental records. VL - 74 UR - http://www.sciencedirect.com/science/article/pii/S0278434313004056 JO - Late Holocene sedimentation in a high Arctic coastal setting: Simpson Lagoon and Colville Delta, Alaska ER - TY - JOUR T1 - The late Quaternary environmental evolution of marine Arctic Canada: Barrow Strait to Lancaster Sound JF - Quaternary Science Reviews Y1 - 2014 A1 - Pieńkowski, Anna J. A1 - England, John H. A1 - Furze, Mark F. A. A1 - MacLean, Brian A1 - Blasco, Steve AB - A marine sediment core from the east-central Canadian Arctic Archipelago (Core 86027-154; 74° 22.01′N 89° 51.26′W; 329 m water depth), studied by a multiproxy approach [lithostratigraphy, biogeochemistry, micropalaeontology (dinoflagellate cysts, other non-pollen palynomorphs, benthic and planktonic foraminifera, ostracods)], and encompassing 14 AMS 14C dates, provides valuable insights into regional deglacial to Holocene palaeoenvironments. Six palaeoenvironmental zones are recognized, based on prominent changes in the litho- and biostratigraphy. The waterlain diamicton of Zone I records immediate deglaciation, being derived from lift-off and calving of previously grounded glacial ice. Though deglacial timing is complicated by the sparsity of dating materials and the Portlandia Effect, age–depth model extrapolation places deglaciation at 11.54 cal ka BP. Zone II (11.5–11.0 cal ka BP) represents a distinct progression from initially ice-proximal to increasingly ice-distal conditions, interrupted by an interval of pervasive sea-ice (11.4–11.2 cal ka BP). Noteworthy biological activity commences in Zone III (11.0–9.7 cal ka BP) with a prominent signal of planktonic foraminifera (Neogloboquadrina pachyderma). This likely signifies penetration of deeper, Atlantic-derived water through the central Canadian Arctic Archipelago upon deglaciation, facilitated by the greater, glacioisostatically-induced water depths (+80 m), and implies separation of Laurentide and Innuitian ice sheets by ∼11.0 cal ka BP. Zone IV (9.7–7.2 cal ka BP) records ameliorated, biologically favourable conditions with reduced seasonal sea-ice accompanied by high microfossil species diversity and the presence of subpolar taxa. Zone V (7.2–6.5 cal ka BP) signals the exclusion of Atlantic-derived water, concomitant with increasing sea-ice, simultaneously representing the termination of the dynamic deglacial to early Holocene environments (zones I–IV). Conditions similar to modern typified by uniform sediment characteristics, present-day microfossil assemblage structures, and sparse benthic foraminifera were established by 5.6 cal ka BP (Zone VI). VL - 91 UR - http://www.sciencedirect.com/science/article/pii/S0277379113003752 JO - The late Quaternary environmental evolution of marine Arctic Canada: Barrow Strait to Lancaster Sound ER - TY - JOUR T1 - Late Quaternary sedimentary record and Holocene channel avulsions of the Jamuna and Old Brahmaputra River valleys in the upper Bengal delta plain JF - Tropical Rivers of South and South-east Asia: Landscape evolution, morphodynamics and hazards Y1 - 2014 A1 - Pickering, Jennifer L. A1 - Goodbred, Steven L. A1 - Reitz, Meredith D. A1 - Hartzog, Thomas R. A1 - Mondal, Dhiman R. A1 - Hossain, Md Saddam AB - The first Holocene stratigraphic record of river-channel occupation and switching between the Brahmaputra–Jamuna and Old Brahmaputra paleovalleys is presented here. Motivated by the Brahmaputra River's historic avulsion from the Old Brahmaputra channel to its present-day Jamuna course, we have obtained sediment and radiocarbon samples from 41 boreholes along a 120 km transect crossing these two braided-river valleys. The stratigraphy along this transect reveals sand-dominated Holocene channel systems, each bound by remnant, mud-capped Pleistocene stratigraphy. Using sediment lithology and bulk strontium concentration as a provenance indicator, we define the geometry and channel-occupation history of each paleovalley. The western Brahmaputra–Jamuna valley is broad and somewhat deeper compared with the Old Brahmaputra valley, the latter actually comprising a composite of two narrower sub-valleys bifurcated by an antecedent topographic remnant. The gently sloped valley margins (slope: 0.002 to 0.007) and high width-to-thickness ratio (W/T: ~ 1000) of the Brahmaputra–Jamuna valley suggest that it was filled primarily through lateral channel migration and the reworking of braidbelt and overbank deposits. Conversely, the two Old Brahmaputra sub-valleys have comparatively steeper valley margins (slope: 0.007 to 0.022) and lower width-to-thickness ratios (W/T: ~ 125 and ~ 250), indicating that these were filled primarily through vertical aggradation of channel sands. We attribute this disparity in valley geometry and fill processes to the different occupation histories for each valley. In this case, the much larger Brahmaputra–Jamuna valley represents the principal, if not singular, river course during the last lowstand of sea-level, with a prominent gravel lag underlying the valley. In contrast the smaller Old Brahmaputra valleys do not appear to have been present, or at least well developed, at the last lowstand. Rather these courses were first occupied during the early Holocene transgression, and we infer that the river had been previously excluded from this region by the relatively higher elevation between the Madhupur Terrace and the Shillong Massif. We also demonstrate that the Brahmaputra River experienced 3–4 major avulsions during the Holocene, with considerably longer occupation times within the principal Brahmaputra–Jamuna valley. Together these observations indicate that occupation history and antecedent topography have been important controls on river course mobility and avulsion behavior. VL - 227 UR - http://www.sciencedirect.com/science/article/pii/S0169555X13004868 JO - Late Quaternary sedimentary record and Holocene channel avulsions of the Jamuna and Old Brahmaputra River valleys in the upper Bengal delta plain ER - TY - JOUR T1 - Long-term hydrological changes in the northeastern Gulf of Mexico (ODP-625B) during the Holocene and late Pleistocene inferred from organic-walled dinoflagellate cysts JF - Palaeogeography, Palaeoclimatology, Palaeoecology Y1 - 2014 A1 - Limoges, Audrey A1 - de Vernal, Anne A1 - Van Nieuwenhove, Nicolas AB - Palynological analyses are used in conjunction with oxygen isotopes and Mg/Ca ratios in foraminifers in order to document the response of dinoflagellate cysts (dinocysts) assemblages to changing climate conditions in the northeastern Gulf of Mexico over the Holocene and late Pleistocene. During MIS 6, but also during the cooler phases of MIS 5, Impagidinium species and Operculodinium centrocarpum were dominating the assemblages. By contrast, during the last interglacial (LIG) and the Holocene, assemblages were mainly composed of Spiniferites taxa and characterized by high relative abundance of Spiniferites mirabilis-hyperacanthus, Operculodinium israelianum and/or Polysphaeridium zoharyi. These two periods exhibit ~ 1-2 °C difference in temperature as inferred from Mg/Ca ratios and show significantly distinct assemblages, with higher percentages of S. mirabilis during the LIG and higher percentages of P. zoharyi during the Holocene. This likely denotes important differences in the hydrogeographical conditions (e.g. surface circulation, bathymetric configuration) between the present and last interglacial. The importance of environmental parameters other than temperature and salinity for dinocyst assemblage dynamics is furthermore illustrated. VL - 414 UR - http://www.sciencedirect.com/science/article/pii/S0031018214004258 JO - Long-term hydrological changes in the northeastern Gulf of Mexico (ODP-625B) during the Holocene and late Pleistocene inferred from organic-walled dinoflagellate cysts ER - TY - JOUR T1 - The Last Glacial: Insights from continuous coring on the New Jersey continental shelf JF - Marine Geology Y1 - 2013 A1 - Christensen, Beth A. A1 - Alexander, Clark A1 - Goff, John A. A1 - Turner, R. Jessica A1 - Austin Jr, James A. AB - Sedimentation on the Pleistocene New Jersey (NJ) shelf is complex, and results from the interaction of processes chiefly driven by glacioeustatic change. Erosion, non-deposition, downcutting and infilling combine to produce a complicated set of reflectors and sedimentary units that are best interpreted in the shallow subsurface with the aid of high resolution seismic reflection profiling. The highly variable lithology on the shelf has historically been an impediment to significant core recovery in this challenging environment. Coring using the AHC-800 drilling system provided continuous downcore recovery at three sites on the outer shelf. The sites targeted fluvial incisions, channel fill and exposure surfaces associated with glacial lowstands. The exceptional cores were analyzed using an integrated approach. Textural and benthic foraminiferal data were evaluated to determine the environment of deposition and estimate paleodepth. Carbon dating of wood and shell material provides the temporal framework for interpretation and K–Ar dating of hornblende crystals provides insights into the source region of sediments. Our integrated analysis indicates the NJ shelf was a dynamic environment from at least 45 ka. Estimates of sea level from this study are consistent with other studies from the Pleistocene NJ Margin. The oldest sediments (> 36 k.y.) recovered by drilling came from below (Site 3) and above (Site 1) R, a time-transgressive regional unconformity. Best estimates are for formation of R on the mid shelf, between MIS3b and the MIS3b/a transition, ~ 45 ka, under neritic conditions. Channels were incised during late MIS2, between ~ 30 and 16 ka. Channel infill was focused in a narrow time frame, during latest MIS 2 (16–14 ka), shortly after the shoreline began to migrate landward. Rates of 1–2 cm/yr are consistent with modern fluvial/ estuarine sedimentation rates. Reinvigoration and infilling of the channels around 14 ka is associated with meltwater pulse 1A. We find no evidence at our study area for jökelhlaup deposition associated with the Intra-Allerød cold period ~ 13 ka. Regional deposition (channel infill and interfluvial regions) was underway by latest MIS2/early MIS1 as sea level transgressed the shelf. The uppermost sediments are of Holocene to Recent age and are routinely and likely rapidly reworked, eroded and mixed by shelf processes. The sediment source during MIS3, as determined by hornblende age dates, was bimodal. Older sediments were derived from the Reading Prong/NJ Highlands and younger sediments were sourced from along the Hudson River. Delivery to the study area was through a more southerly paleo-Hudson position that may have resulted in formation of the outer shelf wedge through deltaic sedimentation during at least MIS 3b–3a. VL - 335 UR - http://www.sciencedirect.com/science/article/pii/S0025322712002381 N1 - id: 2317 JO - The Last Glacial: Insights from continuous coring on the New Jersey continental shelf ER - TY - JOUR T1 - Late Holocene expansion of Istorvet ice cap, Liverpool Land, east Greenland JF - Quaternary Science Reviews Y1 - 2013 A1 - Lowell, Thomas V. A1 - Hall, Brenda L. A1 - Kelly, Meredith A. A1 - Bennike, Ole A1 - Lusas, Amanda R. A1 - Honsaker, William A1 - Smith, Colby A. A1 - Levy, Laura B. A1 - Travis, Scott A1 - Denton, George H. AB - The Greenland Ice Sheet is undergoing dynamic changes that will have global implications if they continue into the future. In this regard, an understanding of how the ice sheet responded to past climate changes affords a baseline for anticipating future behavior. Small, independent ice caps adjacent to the Greenland Ice Sheet (hereinafter called “local ice caps”) are sensitive indicators of the response of Greenland ice-marginal zones to climate change. Therefore, we reconstructed late Holocene ice-marginal fluctuations of the local Istorvet ice cap in east Greenland, using radiocarbon dates of subfossil plants, 10Be dates of surface boulders, and analyses of sediment cores from both threshold and control lakes. During the last termination, the Istorvet ice cap had retreated close to its maximum Holocene position by ∼11,730 cal yr BP. Radiocarbon dates of subfossil plants exposed by recent recession of the ice margin indicate that the Istorvet cap was smaller than at present from AD 200 to AD 1025. Sediments from a threshold lake show no glacial input until the ice cap advanced to within 365 m of its Holocene maximum position by ∼AD 1150. Thereafter the ice cap remained at or close to this position until at least AD 1660. The timing of this, the most extensive of the Holocene, expansion is similar to that recorded at some glaciers in the Alps and in southern Alaska. However, in contrast to these other regions, the expansion in east Greenland at AD 1150 appears to have been very close to, if not at, a maximum Holocene value. Comparison of the Istorvet ice-cap fluctuations with Holocene glacier extents in Southern Hemisphere middle-to-high latitude locations on the Antarctic Peninsula and in the Andes and the Southern Alps suggests an out-of-phase relationship. If correct, this pattern supports the hypothesis that a bipolar see-saw of oceanic and/or atmospheric circulation during the Holocene produced asynchronous glacier response at some localities in the two polar hemispheres. VL - 63 UR - http://www.sciencedirect.com/science/article/pii/S0277379112004830 N1 - id: 2290 JO - Late Holocene expansion of Istorvet ice cap, Liverpool Land, east Greenland ER - TY - JOUR T1 - Late Holocene sedimentation and hydrologic development in a shallow coastal sinkhole on Great Abaco Island, The Bahamas JF - Quaternary International Y1 - 2013 A1 - Kovacs, Shawn E. A1 - van Hengstum, Peter J. A1 - Reinhardt, Eduard G. A1 - Donnelly, Jeffrey P. A1 - Albury, Nancy A. AB - It remains poorly understood how sea level drives environmental change and hydrographic development in coastal karst basins (underwater caves, sinkholes, blueholes, etc.) over millennial timescales. It was previously hypothesized that coastal karst basins (CKBs) transition from vadose, to littoral, then anchialine, and finally submarine environments as sea-level rise inundates coastal karst landscapes, but the initial flooding event of CKBs remains challenging to sample. Runway Sinkhole hosts a modern anchialine ecosystem located ∼225 m from Great Abaco Island coastline in The Bahamas, and its shallow water depth (∼1.8 mbsl) permits an investigation into the early environmental evolution and hydrographic development in a CKBs after inundation by sea-level rise. Four sediment cores were collected from Runway Sinkhole, and late Holocene environmental change was reconstructed with benthic foraminiferal paleoecology, organic matter geochemistry (OM%, δ13Corg, and C:N), X-radiography, and radiocarbon dating. Despite some uncertainties associated with the chronology, it appears that Holocene sea-level rise initially flooded Runway Sinkhole and created a littoral environment at least by ∼3.9 ka, whereafter a detrital peat deposit accumulated in the sinkhole. This detrital peat had a high organic matter content (mean 88%), a δ13Corg value indicative of organic matter derived from C3 plants including mangroves (−28‰), and an unknown calcareous microfossil suggestive of a non-marine habitat in the sinkhole. A shift to carbonate sand deposition, organic matter with more marine-influenced δ13Corg values (−23‰), and expansion of euryhaline (Bolivina striatula, Elphidium poeyanum, and Triloculina bermudezi) and anchialine (Physalidia simplex and Conicospirillina exleyi) benthic foraminifera at ∼1.2 ka marks the onset of modern anchialine environmental conditions at the sediment–water interface (∼1.8 mbsl). These results suggest that relative sea-level rise in the Bahamas forced environmental change in Runway sinkhole at ∼1.2 ka, and indicate that peat deposits in coastal sinkholes must be verified as in-situ before being utilized as sea-level indicators. VL - 317 UR - http://linkinghub.elsevier.com/retrieve/pii/S1040618213007507http://api.elsevier.com/content/article/PII:S1040618213007507?httpAccept=text/xmlhttp://api.elsevier.com/content/article/PII:S1040618213007507?httpAccept=text/plain ER - TY - JOUR T1 - Late Pleistocene–Holocene sedimentary records of climate and lake-level changes in Lake Hazar, eastern Anatolia, Turkey JF - Terrestrial archives of the Mediterranean Y1 - 2013 A1 - Eriş, Kürşad Kadir AB - The sedimentary record of Lake Hazar has been documented by detailed seismo- and chronostratigraphic analyses using high-resolution seismic profiles and sediment cores. In this study, two main seismic stratigraphic units can be confidently correlated with sediment cores using lithology and physical properties. As a result of radiocarbon AMS dating, these sedimentary units presumably cover the period from the late Pleistocene to Holocene. The Holocene sequence of the lake infills can be subdivided into five subunits, each subject to distinctive hydrological and sedimentological processes due to fluctuating lake level. The elevations of these deposits including coastal paleo-terraces provide history of the lake level changes. In Lake Hazar, the maximum lowstand lake level occurred during the transition from the Younger Dryas to Holocene, when the −73 m wave-cut terrace was formed as the main shelf-crossing unconformity surface. The beginning of the Holocene was associated with a abrupt lake level rise and resultant deepening. Analysis of the Lake Hazar terraces has the potential to provide complementary data on the chronology of past lake level and lake volume changes, and their link to past climate change. The continued rising lake level during beginning of the Holocene was modulated by stillstands at −63 m and −56 m, as indicated by broad coastal paleo-terraces across the northern shelf. The main shelf-margin sedimentary system for the Holocene period is composed of three distinct buried deltaic-complexes that were presumably sourced from the Kürkçayı River, the largest input into Lake Hazar. The 3rd millennium crisis at around 3 14C ka BP is recorded in the seismic and core data when the cold and dry climatic condition gave rise to a significant lake level drop. VL - 302 UR - http://www.sciencedirect.com/science/article/pii/S1040618212033915 N1 - id: 2322 JO - Late Pleistocene–Holocene sedimentary records of climate and lake-level changes in Lake Hazar, eastern Anatolia, Turkey ER - TY - JOUR T1 - Late Wisconsinan glaciation and postglacial relative sea-level change on western Banks Island, Canadian Arctic Archipelago JF - Quaternary Research Y1 - 2013 A1 - Lakeman, Thomas R. A1 - England, John H. AB - The study revises the maximum extent of the northwest Laurentide Ice Sheet (LIS) in the western Canadian Arctic Archipelago (CAA) during the last glaciation and documents subsequent ice sheet retreat and glacioisostatic adjustments across western Banks Island. New geomorphological mapping and maximum-limiting radiocarbon ages indicate that the northwest LIS inundated western Banks Island after ~ 31 14C ka BP and reached a terminal ice margin west of the present coastline. The onset of deglaciation and the age of the marine limit (22–40 m asl) are unresolved. Ice sheet retreat across western Banks Island was characterized by the withdrawal of a thin, cold-based ice margin that reached the central interior of the island by ~ 14 cal ka BP. The elevation of the marine limit is greater than previously recognized and consistent with greater glacioisostatic crustal unloading by a more expansive LIS. These results complement emerging bathymetric observations from the Arctic Ocean, which indicate glacial erosion during the Last Glacial Maximum (LGM) to depths of up to 450 m. VL - 80 UR - http://www.sciencedirect.com/science/article/pii/S0033589413000197 IS - 1 N1 - id: 2282 JO - Late Wisconsinan glaciation and postglacial relative sea-level change on western Banks Island, Canadian Arctic Archipelago ER - TY - JOUR T1 - Long-term variations in Iceland–Scotland overflow strength during the Holocene JF - Climate of the Past Y1 - 2013 A1 - Thornalley, D. J. R. A1 - Blaschek, M. A1 - Davies, F. J. A1 - Praetorius, S. A1 - Oppo, D. W. A1 - McManus, J. F. A1 - Hall, I. R. A1 - Kleiven, H. A1 - Renssen, H. A1 - McCave, I. N. AB - The overflow of deep water from the Nordic seas into the North Atlantic plays a critical role in global ocean circulation and climate. Approximately half of this overflow occurs via the Iceland–Scotland (I–S) overflow, yet the history of its strength throughout the Holocene (~ 0–11 700 yr ago, ka) is poorly constrained, with previous studies presenting apparently contradictory evidence regarding its long-term variability. Here, we provide a comprehensive reconstruction of I–S overflow strength throughout the Holocene using sediment grain size data from a depth transect of 13 cores from the Iceland Basin. Our data are consistent with the hypothesis that the main axis of the I–S overflow on the Iceland slope was shallower during the early Holocene, deepening to its present depth by ~ 7 ka. Our results also reveal weaker I–S overflow during the early and late Holocene, with maximum overflow strength occurring at ~ 7 ka, the time of a regional climate thermal maximum. Climate model simulations suggest a shoaling of deep convection in the Nordic seas during the early and late Holocene, consistent with our evidence for weaker I–S overflow during these intervals. Whereas the reduction in I–S overflow strength during the early Holocene likely resulted from melting remnant glacial ice sheets, the decline throughout the last 7000 yr was caused by an orbitally induced increase in the amount of Arctic sea ice entering the Nordic seas. Although the flux of Arctic sea ice to the Nordic seas is expected to decrease throughout the next century, model simulations predict that under high emissions scenarios, competing effects, such as warmer sea surface temperatures in the Nordic seas, will result in reduced deep convection, likely driving a weaker I–S overflow. VL - 9 UR - http://www.clim-past.net/9/2073/2013 IS - 5 ER - TY - JOUR T1 - Late-Pleistocene to Holocene sedimentary fills of the Çınarcık Basin of the Sea of Marmara JF - Sedimentary Geology Y1 - 2012 A1 - Eriş, K. Kadir A1 - Çağatay, Namık A1 - Beck, Christian A1 - Mercier de Lepinay, Bernard A1 - Corina, Campos AB - A giant RV Marion Dufresne piston core MD01-2425 recovered from the 1276 m-deep Çınarcık Basin of the Sea of Marmara documents characteristics of deep basin sedimentation influenced by large-scale gravity-controlled mass-wasting processes and associated turbidite deposition during the Late Pleistocene to Holocene. A visual lithological description of the core reveals twenty major seismoturbidite layers (> 20 cm thick), intercalated in hemipelagic-type fine-grained calcareous and slightly siliceous clays. The thickness and frequency of the sesimoturbidite layers deposited during the lacustrine period (prior to 12.3 cal ka BP) is much greater than during the Holocene marine period. The sedimentary processes during deposition of seismoturbidites in the basin have been determined in this study using a combination of grain-size parameters. Often the seismoturbidites show strong grain segregation with a sharp boundary between a coarse lower and a homogeneous upper part. The traction carpet deposits formed at the base of a turbulent suspension and were produced in the lower coarse-grained part, whereas the homogeneous upper part was deposited by uniform suspensions following bedload deposition. VL - 281 UR - http://www.sciencedirect.com/science/article/pii/S0037073812002473 N1 - id: 2309 JO - Late-Pleistocene to Holocene sedimentary fills of the Çınarcık Basin of the Sea of Marmara ER - TY - JOUR T1 - Loess mantle spatial variability and soil horizonation, southern Wisconsin, USA JF - Quaternary International Y1 - 2012 A1 - Jacobs, Peter M. A1 - Mason, Joseph A. A1 - Hanson, Paul R. AB - Loess is an important Quaternary sediment that records evidence of landscape instability in sediment source areas and landscape stability in accumulation areas. In Wisconsin, USA loess mantles glaciogenic deposits dating to the last glaciation, but the landscape distribution and effects of the loess mantle on soil formation have received very little attention. This study investigates the influence of glacial landforms on the spatial pattern of loess thickness and how the presence or absence of a loess mantle overlying glaciogenic sediments has influenced soil profile morphology, namely thickness and nature of horizonation. Loess thickness follows systematic trends along hillslopes, with slope percentage explaining most loess thickness variation between summit and backslope positions. In the presence of a loess mantle, solum and Bt horizon thickness is proportional to the thickness of the loess mantle in well-drained profiles. In the absence of a loess mantle, landscape and sediment characteristics that control permeability and water throughflow appear to be the most important determinants of profile characteristics. The loess mantle modulates soil formation above the lithologic discontinuity with sandy calcareous glacial sediments by controlling soil water behavior and having physical and chemical characteristics conducive to transformation to soil genetic horizons. VL - 265 UR - http://www.sciencedirect.com/science/article/pii/S1040618212000328 N1 - id: 2151 JO - Loess mantle spatial variability and soil horizonation, southern Wisconsin, USA ER - TY - JOUR T1 - Late glacial to Holocene sea-level changes in the Sea of Marmara: new evidence from high-resolution seismics and core studies JF - Geo-Marine Letters Y1 - 2011 A1 - Eriş, Kürşad Kadir A1 - Cagatay, M. N. A1 - Akcer, Sena A1 - Gasperini, Luca A1 - Mart, Yosi AB - The late glacial to Holocene sedimentary record of the northern shelf of the Sea of Marmara (SoM) has been documented by detailed seismo-, chrono-, and biostratigraphic analyses using sub-bottom (Chirp) profiles and sediment cores. During MIS 3 and the main part of MIS 2 (60-15 (14)C ka b.p.), disconnection from the Mediterranean and Black seas together with a dry climate resulted in a regression in the SoM, when the Sea was transformed into a brackish lake. The river incisions below 105 m water depth along the northern shelf took place during the last glacial maximum, when the lake level was modulated by stillstands at -98 and -93 m. The post-glacial freshwater transgressive stage of the Marmara 'Lake' occurred between 15 and 13.5 (14)C ka b.p., leading to a rise in water level to -85 m by 13.0 (14)C ka b.p., as evidenced by broad wave-cut terraces along the northern shelf. Since 12 (14)C ka b.p., high-frequency sea-level fluctuations have been identified at the SoM entrance to the Strait of A degrees stanbul (SoI). Thus, wave-cut terraces have been recorded at water depths of -76 and -71 m that, according to an age model for core MD04-2750, have ages of 11.5 and 10.5 (14)C ka b.p., respectively. Ancient shoreline at -65 m along the northern shelf presumably formed soon after the Younger Dryas (YD) at ca. 10.1 (14)C ka b.p. Moreover, there is compelling evidence of Holocene outflow from the Sea of Marmara to the Black Sea. At the SoM entrance to the SoI, the existence of bioherms on the reflector surface together with abundant Brizalina spathulata and Protoglobulimina pupoides in a core suggests a return to higher salinities due to strong Mediterranean water incursion into the SoM at similar to 8.8 (14)C ka b.p. This finding is consistent with earlier suggestions that, after the YD, the Black Sea was flooded by outflow from the SoM as a result of global sea-level rise. VL - 31 IS - 1 N1 - id: 2113; PT: J; TC: 0; J9: GEO-MAR LETT; UT: WOS:000286334700001 JO - Late glacial to Holocene sea-level changes in the Sea of Marmara: new evidence from high-resolution seismics and core studies ER - TY - JOUR T1 - Late Holocene environmental conditions in Coronation Gulf, southwestern Canadian Arctic Archipelago: evidence from dinoflagellate cysts, other non-pollen palynomorphs, and pollen JF - Journal of Quaternary Science Y1 - 2011 A1 - Pieńkowski, A. J. A1 - Mudie, Peta J. A1 - England, John H. A1 - Smith, John N. A1 - Furze, Mark F. A. AB - Boxcore 99LSSL-001 (68.095°?N, 114.186° W; 211?m water depth) from Coronation Gulf represents the first decadal-scale marine palynology and late Holocene sediment record for the southwestern part of the Northwest Passage. The record was studied for organic-walled microfossils (dinoflagellate cysts, non-pollen palynomorphs), pollen, terrestrial spores, and sediment characteristics. 210Pb, 137Cs, and three accelerator mass spectrometry 14C dates constrain the chronology. Three prominent palaeoenvironmental zones were identified. During the interval AD 1470?1680 (Zone I), the climate was warmer and wetter than at present, and environmental conditions were more favourable to biological activity and northward boreal forest migration, with reduced sea-ice and a longer open-water (growing) season. The interval AD 1680?1940 (Zone II) records sea-ice increase, and generally cool, polar conditions during the Little Ice Age. During AD 1940?2000 (Zone III), organic microfossils indicate an extended open-water season and decreased sea-ice, with suggested amelioration surpassing that of Zone I. Although more marine studies are needed to place this record into an appropriate context, the succession from ameliorated (Zone I) to cooler, sea-ice influenced conditions (Zone II) and finally to 20th-century warming (Zone III) corresponds well with several terrestrial climatic records from the neighbouring mainland and Victoria Island, and with lower-resolution marine records to the west. Copyright © 2011 John Wiley & Sons, Ltd. VL - 26 UR - http://dx.doi.org/10.1002/jqs.1503 IS - 8 N1 - id: 2344 JO - Late Holocene environmental conditions in Coronation Gulf, southwestern Canadian Arctic Archipelago: evidence from dinoflagellate cysts, other non-pollen palynomorphs, and pollen ER - TY - JOUR T1 - Late Pleistocene paleoecology of arctic ground squirrel (Urocitellus parryii) caches and nests from Interior Alaska's mammoth steppe ecosystem, USA JF - Quaternary Research Y1 - 2011 A1 - Gaglioti, Benjamin V. A1 - Barnes, Brian M. A1 - Zazula, Grant D. A1 - Beaudoin, Alwynne B. A1 - Wooller, Matthew J. AB - Botanical analyses of fossil and modern arctic ground squirrel (Urocitellus parryii) caches and nests have been used to reconstruct the past vegetation from some parts of Beringia, but such archives are understudied in Alaska. Five modern and four fossil samples from arctic ground squirrel caches and nests provide information on late Pleistocene vegetation in Eastern Beringia. Modern arctic ground squirrel caches from Alaska's arctic tundra were dominated by willow and grass leaves and grass seeds and bearberries, which were widespread in the local vegetation as confirmed by vegetation surveys. Late Pleistocene caches from Interior Alaska were primarily composed of steppe and dry tundra graminoid and herb seeds. Graminoid cuticle analysis of fossil leaves identified Calamagrostis canadensis, Koeleria sp. and Carex albonigra as being common in the fossil samples. Stable carbon isotopes analysis of these graminoid specimens indicated that plants using the C(3) photosynthetic pathways were present and functioning with medium to high water-use efficiency. Fossil plant taxa and environments from ground squirrel caches in Alaska are similar to other macrofossil assemblages from the Yukon Territory, which supports the existence of a widespread mammoth steppe ecosystem type in Eastern Beringia that persisted throughout much of the late Pleistocene. (C) Published by Elsevier Inc. on behalf of University of Washington. VL - 76 IS - 3 N1 - id: 2130; PT: J; TC: 0; UT: WOS:000296672100009 JO - Late Pleistocene paleoecology of arctic ground squirrel (Urocitellus parryii) caches and nests from Interior Alaska's mammoth steppe ecosystem, USA ER - TY - JOUR T1 - Late Quaternary environmental change inferred from phytoliths and other soil-related proxies: Case studies from the central and southern Great Plains, USA JF - Catena Y1 - 2011 A1 - Cordova, Carlos E. A1 - Johnson, William C. A1 - Mandel, Rolfe D. A1 - Palmer, Michael W. AB - This study investigates stable carbon isotopes (delta(13)C), opal phytolith assemblages, burnt phytoliths, microscopic charcoal and Sporormiella spores from modern soils and paleosols in Kansas and Oklahoma. Grass and dicot phytoliths in combination with delta(13)C are used as proxies for reconstructing the structure of grasslands and woodlands. Burnt grass phytoliths and microscopic charcoal are evaluated as proxies for reconstructing paleofire incidence. Concentrations of the fungal spore Sporormiella are used as a proxy for assessing large herbivore activity. These proxies were tested on various modern grassland communities of the central and southern Great Plains, including areas with bison, cattle, and small herbivores, and areas under different fire frequencies. Opal phytolith assemblages and delta(13)C values show that before cal 11 ka, C(3) grasses and woody plants predominated in areas that today are dominated by C(4) grasses. The origin of the shortgrass prairie dates back to about cal 10 ka. The origin of the tallgrass prairie, however, is not clear as phytolith data show variable assemblages throughout the Holocene (mixed-grass, tallgrass, and tallgrass-woodland mosaic). Different proxies (burnt phytoliths vs. charcoal) reveal different fire frequencies, but it is apparent that microfossil evidence for fire incidence is closely related to the abundance of woody plants in the landscape. Before cal 12 ka, soils show somewhat elevated concentration of Spororrniella, but lower concentrations than the modern high-density bison and cattle grazing areas. Throughout the Holocene. Sporormiella frequencies are low, which suggests lower large ungulate densities and perhaps high mobility. (C) 2010 Elsevier B.V. All rights reserved. VL - 85 IS - 2 N1 - id: 1992; PT: J; SI: SI; UT: WOS:000288642200002 JO - Late Quaternary environmental change inferred from phytoliths and other soil-related proxies: Case studies from the central and southern Great Plains, USA ER - TY - JOUR T1 - Late Holocene Evolution of the Mekong Subaqueous Delta, Southern Vietnam JF - Marine Geology Y1 - 2010 A1 - Xue, Z. A1 - Liu, J. P. A1 - DeMaster, D. A1 - Van Nguyen, L. A1 - Ta, T. K. O. AB - As Asia's third largest river. with regard to sediment load, the Mekong River delivers approximately 160 million tons of sediment per year to the South China Sea. High-resolution seismic profiling and coring during 2006 and 2007 cruises revealed a low gradient, subaqueous delta system, up to 20 m thick, surrounding the modern Mekong River Delta (MRD) in the west of the South China Sea. Based on clinoform structure, grain size Pb-210, AMS C-14, and delta C-13 results, the subaqueous delta is divided into four zones defined by different sedimentary processes and depositional features. Over the past 3000 yr, the evolution of the MRD has shown a morphological asymmetry indicated by a large down-drift area and a rapid progradation around Cape Camau, similar to 200 km downstream from the river mouth. This asymmetric feature is consistent with increased wave influence. The strong southwestward coastal current, strengthened by the Strong NE monsoon, plays an important role locally in longshore transport of resuspended sediments into the Gulf of Thailand. A late Holocene sediment budget for the MRD has been determined, based on the area and thickness of deltaic sediment. Approximately 80% of Mekong delivered sediment has been trapped within the delta area, which, together with a falling sea-level, resulted in a rapidly prograding MRD over the past 3000 yr. (C) 2009 Elsevier B.V. All rights reserved. VL - 269 IS - 1-2 N1 - id: 848; 560AN Times Cited:0 Cited References Count:53Y JO - Late Holocene Evolution of the Mekong Subaqueous Delta, Southern Vietnam ER - TY - JOUR T1 - Late Quaternary record of pteropod preservation from the Andaman Sea JF - Marine Geology Y1 - 2010 A1 - Sijinkumar, A. V. A1 - Nath, B. Nagender A1 - Guptha, M. V. S. AB - In order to understand the glacial to interglacial fluctuations in pteropod preservation and productivity during the late Quaternary (similar to 54 ka BP to present), we investigated pteropod, organic carbon (Cord and Globigerina bulloides abundance in a deep sea core from the western Andaman Sea. Pteropod abundance and preservation is similar to the "Indo-Pacific carbonate preservation type", showing better preservation during glacial and poor preservation during interglacial periods. The core site appears to have remained below the aragonite compensation depth (ACD) throughout the Holocene, indicated by the total absence of pteropods. Maximum abundance and good preservation of pteropods was observed during stadials such as Younger Dryas (YD), Heinrich Events (HEs) and Last Glacial Maxima (LGM) indicating weaker oxygen minimum zone (OMZ) and deeper ACD. Furthermore, the high relative abundance of mesopelagic pteropods over epipelagic forms suggests a well ventilated water column with weak OMZ particularly during LGM, apparently driven by intense winter monsoon. Increased monsoon-driven productivity was observed during 45-40 ka, of early Marine Isotope stage 2 (MIS 2, 24-22 ka), Bolling/Allered (B/A; 15-13.5 ka), YD and late Holocene as evidenced by Cor, content and G. bulloides. Enhanced pteropod preservation of H1 associated with low C(org) content and G. bulloides suggests that reduced monsoonal driven productivity might have influenced pteropod preservation. Deglacial preservation spike in the Andaman Sea is consistent with other northern Indian Ocean records and elsewhere outside the Indian Ocean implying the event is global in nature, marked by deepening of ACD probably driven by enhancement of winter monsoon on local and changes in intermediate water circulation on regional scale. (C) 2010 Elsevier B.V. All rights reserved. VL - 275 IS - 1-4 N1 - id: 2018; PT: J; UT: WOS:000281217300016 JO - Late Quaternary record of pteropod preservation from the Andaman Sea ER - TY - JOUR T1 - Late-twentieth-century warming in Lake Tanganyika unprecedented since AD 500 JF - Nature Geoscience Y1 - 2010 A1 - Tierney, Jessica E. A1 - Mayes, Marc T. A1 - Meyer, Natacha A1 - Johnson, Christopher A1 - Swarzenski, Peter W. A1 - Cohen, Andrew S. A1 - Russell, James M. AB - Instrumental observations suggest that Lake Tanganyika, the largest rift lake in East Africa, has become warmer, increasingly stratified and less productive over the past 90 years (refs 1,2). These trends have been attributed to anthropogenic climate change. However, it remains unclear whether the decrease in productivity is linked to the temperature rise(3,4), and whether the twentieth-century trends are anomalous within the context of longer-term variability. Here, we use the TEX(86) temperature proxy, the weight per cent of biogenic silica and charcoal abundance from Lake Tanganyika sediment cores to reconstruct lake-surface temperature, productivity and regional wildfire frequency, respectively, for the past 1,500 years. We detect a negative correlation between lake-surface temperature and primary productivity, and our estimates of fire frequency, and hence humidity, preclude decreased nutrient input through runoff as a cause for observed periods of low productivity. We suggest that, throughout the past 1,500 years, rising lake-surface temperatures increased the stratification of the lake water column, preventing nutrient recharge from below and limiting primary productivity. Our records indicate that changes in the temperature of Lake Tanganyika in the past few decades exceed previous natural variability. We conclude that these unprecedented temperatures and a corresponding decrease in productivity can be attributed to anthropogenic global warming, with potentially important implications for the Lake Tanganyika fishery. VL - 3 IS - 6 N1 - id: 2043; PT: J; UT: WOS:000278134100019 JO - Late-twentieth-century warming in Lake Tanganyika unprecedented since AD 500 ER - TY - JOUR T1 - A long history of cloud and forest migration from Lake Consuelo, Peru JF - Quaternary Research Y1 - 2010 A1 - Urrego, D. H. A1 - Bush, M. B. A1 - Silman, M. R. AB - The complete paleoecological history from Lake Consuelo forest yields a record of ground-level cloud formation and changes in its lower altitudinal limit over the last 46,300 cal yr BP. The timing of early lake level fluctuations prior to 37,000 cal yr BP appears sensitive to North Atlantic temperature oscillations, corresponding to Dansgaard-Oeschger interstadials 11, 10 and 8 recorded in GISP2. After the LGM, the first hint of warming is recorded in Lake Consuelo at 22,000 call yr BP and agrees with other estimates for the region. The mid-Holocene (7400-5000 cal yr BP) was the period of highest rates of change and most significant reorganizations in the Consuelo forest. These community changes resulted from a regionally widespread dry period. Results from Lake Consuelo indicate that moisture availability, mediated through cloud cover, played the most significant role in ecological change in this system. Rates of past climate fluctuations never exceeded the forest capacity to accommodate change. Unfortunately, this might not be the case under predicted scenarios for the end of the current century. (C) 2009 University of Washington. Published by Elsevier Inc. All rights reserved. VL - 73 IS - 2 N1 - id: 1903; 564VS Times Cited:8 Cited References Count:85Y JO - A long history of cloud and forest migration from Lake Consuelo, Peru ER - TY - JOUR T1 - Long-term stability in the production of a NW Mediterranean Posidonia oceanica (L.) Delile meadow JF - Palaeogeography Palaeoclimatology Palaeoecology Y1 - 2010 A1 - Mateo, M. A. A1 - Renom, P. A1 - Michener, R. H. AB - Long-term changes in leaf net production of the seagrass Posidonia oceanica (L) Defile. and in the irradiance arriving at the meadow canopy, were investigated in a NW Mediterranean meadow using a palaeoecological approach. We conducted in situ shade experiments to find the relationships between the carbon stable isotope ratio (delta(13)C) of plant tissues, leaf net production, and ambient irradiance. The relationships were highly significant and fitted the Michaelis-Menten equation and power functions. These functions were used to reconstruct light and net production using the delta(13)C of P. oceanica detritus as a palaeoecological proxy along a 150 cm core of P. oceanica matte (a peat-like deposit formed by this endemic seagrass species). The delta(13)C values of sheath detritus along the core (i.e.. the net leaf production) showed a weak but significant decrease towards the present time (R = 0.308: P = 0.02) probably as a result of (1) an increase in DIC availability, and/or (2) a progressive change in the carbon isotopic signature of DIC, both of which are consistent with a rise in anthropogenic atmospheric CO(2). The canopy irradiance, reconstructed for the last 1200 years, showed a mean value of 128 mu E m(-2) s(-1) with a range of 12.5-280 mu E m(-2) s(-1). The reconstruction of the net leaf production for the same period yielded a mean value of 2.5 mg dw day(-1) shoot(-1) with a range of 2.0-2.7 mg dw day(-1) shoot(-1). Both ranges are within the values reported in the literature for present day studies. The absence of significant fluctuations or sudden changes through time suggests remarkable ecosystem stability during the last millennium. (C) 2010 Elsevier B.V. All rights reserved. VL - 291 IS - 3-4 N1 - id: 1911; 611AI Times Cited:3 Cited References Count:116Y JO - Long-term stability in the production of a NW Mediterranean Posidonia oceanica (L.) Delile meadow ER - TY - JOUR T1 - Lake Sturgeon Age Validation using Bomb Radiocarbon and Known-Age Fish JF - Transactions of the American Fisheries Society Y1 - 2009 A1 - Bruch, R. M. A1 - Campana, S. E. A1 - Davis-Foust, S. L. A1 - Hansen, M. J. A1 - Janssen, J. AB - Pectoral fin spines have been the accepted structure for estimating the age of various sturgeon species for nearly 100 years, though other structures have also been used (otoliths, pectoral girdle, scutes, and caudal fulcra). Accuracy of age estimates using any of these structures has not been validated, so we report the first use of bomb radiocarbon (C-14) assays to assess the validity of ages estimated using growth increments on pectoral fin spine and otolith frontal cross sections from lake sturgeon Acipenser fulvescens: we also assessed age estimates from pectoral fin spines of known-age lake sturgeon. Growth increments on pectoral fin spine cross sections underestimated true age of fish older than 14 years and error increased with age, whereas otoliths accurately estimated true age up to at least 52 years. Increment formation on pectoral fin spine and otolith cross sections from juvenile lake sturgeon (ages 2-11) was similar, although pectoral spines were clearer and easier to interpret. A power function (true age = [estimated age](1.054796), where estimated age was determined from pectoral spines; r(2) = 0.98) provides a means for correcting existing age estimates obtained from lake sturgeon pectoral fin spines. VL - 138 IS - 2 N1 - id: 1855; 477EI Times Cited:1 Cited References Count:33Y JO - Lake Sturgeon Age Validation using Bomb Radiocarbon and Known-Age Fish ER - TY - JOUR T1 - Land-sea linkage of Holocene paleoclimate on the Southern Bering Continental Shelf JF - Holocene Y1 - 2009 A1 - Katsuki, K. A1 - Khim, B. K. A1 - Itaki, T. A1 - Harada, N. A1 - Sakai, H. A1 - Ikeda, T. A1 - Takahashi, K. A1 - Okazaki, Y. A1 - Asahi, H. AB - Detailed diatom records within surface and core sediments from the Southern Bering Continental Shelf (SBCS) reveal that the Holocene evolution of sea-ice distribution is associated with low pressure patterns. Holocene sea-ice distribution over the SBCS was mainly controlled by the location of the Aleutian Low. The corresponding paleoceanographic and paleoclimate conditions can be divided into three stages. (1) the early Holocene K before 7000 cal. yr BP) was characterized by extensive sea-ice distribution under two low-pressure cells, which covered the western Bering-Sea and the Gulf of Alaska, respectively. (2) Between 3000 and 7000 cal. yr BP, the low-pressure system over the Gulf of Alaska became weak, causing total sea-ice mass over the SBCS to retreat. (3) In the past 3000 years, prevailing southwesterly winds over the SBCS due to the developing Aleutian Low have reduced further sea-ice cover on the SBCS. These paleoclimatic changes were probably a response to ENSO variation. The timings of water mass exchanges on the SBCS coincided with sea-level change along the Alaskan Peninsula. As a result, subsequent morphologic alterations have also influenced the paleoceanographic condition of the SBCS. The effect of the surface coastal water and bottom marine water on the SBCS intensified about 6000 cal. yr BP when sea level increased. VL - 19 IS - 5 N1 - id: 1878; 470HQ Times Cited:1 Cited References Count:76Y JO - Land-sea linkage of Holocene paleoclimate on the Southern Bering Continental Shelf ER - TY - JOUR T1 - Late Holocene Hydrologic and Vegetation Changes at Turneffe Atoll, Belize, Compared with Records from Mainland Central America and Mexico JF - Palaios Y1 - 2009 A1 - Wooller, M. J. A1 - Behling, H. A1 - Guerrero, J. L. A1 - Jantz, N. A1 - Zweigert, M. E. AB - We present pollen and stable isotope (delta C-13, delta O-18, delta N-15) data from a similar to 4 in core (TNF-1) of primarily mangrove peat taken from Turneffe Atoll, Belize. Radiocarbon (accelerator mass spectrometry) dates show that the record represents ca. 5000 years of sediment accumulation. Vegetation composition varied between dominant mangroves (primarily Rhizophora mangle) and Chenopodiaceae-Amaranthaceae, most likely Salicornia bigelovii. The pollen data, along with inferences from stable isotope analyses of bulk peat and fossil leaf fragments, indicate that marked environmental changes occurred at this location over the past ca. 5000 years. There was a transition between ca. 4100 and 2900 cal yr BP, from vegetation dominated by relatively tall mangroves (R. mangle) to one dominated by Chenopodiaceae-Amaranthaceae and then Myrica, most likely wax myrtle (M. cerifera). These changes bracket a period centered at ca. 3500 calibrated years before present, where there is a peak in the delta O-18 of mangrove leaf fragments. This timing corresponds with other paleoenvironmental records of climate drying in Central America and increases the geographic and habitat scope (i.e., mangrove habitat) of records documenting these changes. Interpretations of shifts in mangrove habitat, however, require consideration of additional environmental influences, including changes in groundwater hydrology and relative inputs of seawater and freshwater (i.e., precipitation) during the Holocene. VL - 24 IS - 9-10 N1 - id: 1835; 506UH Times Cited:1 Cited References Count:34Y JO - Late Holocene Hydrologic and Vegetation Changes at Turneffe Atoll, Belize, Compared with Records from Mainland Central America and Mexico ER - TY - JOUR T1 - A late Holocene paleo-productivity record in the western Gulf of Maine, USA, inferred from growth histories of the long-lived ocean quahog (Arctica islandica) JF - INTERNATIONAL JOURNAL OF EARTH SCIENCES Y1 - 2009 A1 - Wanamaker, Alan D. Jr. A1 - Kreutz, Karl J. A1 - Schoene, Bernd R. A1 - Maasch, Kirk A. A1 - Pershing, Andrew J. A1 - Borns, Harold W. A1 - Introne, Douglas S. A1 - Feindel, Scott KW - Arctica islandica KW - Climate variability KW - Gulf of Maine KW - North Atlantic Oscillation (NAO) KW - Paleo-productivity KW - Shell growth AB - To investigate environmental variability during the late Holocene in the western Gulf of Maine, USA, we collected a 142-year-old living bivalve (Arctica islandica) in 2004, and three fossil A. islandica shells of the Medieval Warm Period (MWP) and late MWP / Little Ice Age (LIA) period (corrected C-14(AMS) = 1030 +/- A 78 ad; 1320 +/- A 45 ad; 1357 +/- A 40 ad) in 1996. We compared the growth record of the modern shell with continuous plankton recorder (CPR) time-series (1961-2003) from the Gulf of Maine. A significant correlation (r (2) = 0.55; p < 0.0001) exists between the standardized annual growth index (SGI) of the modern shell and the relative abundance of zooplankton species Calanus finmarchicus. We therefore propose that SGI data from A. islandica is a valid proxy for paleo-productivity of at least one major zooplankton taxa. SGIs from these shells reveal significant periods of 2-6 years (NAO-like) based on wavelet analysis, multitaper method (MTM) analysis and singular spectrum analysis (SSA) during the late Holocene. Based on established physical oceanographic observation in the Gulf of Maine, we suggest that slope water variability coupled with North Atlantic Oscillation (NAO) dynamics is primarily responsible for the observed SGI variability. VL - 98 ER - TY - JOUR T1 - Late Holocene sea-surface temperature and precipitation variability in northern Patagonia, Chile (Jacaf Fjord, 44 degrees S) JF - Quaternary Research Y1 - 2009 A1 - Sepulveda, J. A1 - Pantoja, S. A1 - Hughen, K. A. A1 - Bertrand, S. A1 - Figueroa, D. A1 - Leon, T. A1 - Drenzek, N. J. A1 - Lange, C. AB - A high-resolution multi-proxy study including the elemental and isotopic composition of bulk organic matter, land plant-derived biomarkers, and alkenone-based sea-surface temperature (SST) from a marine sedimentary record obtained from the Jacaf Fjord in northern Chilean Patagonia (similar to 44 degrees 20'S) provided a detailed reconstruction of continental runoff, precipitation, and summer SST spanning the last 1750 yr We observed two different regimes of climate variability in our record a relatively dry/warm period before 900 cal yr BP (lower runoff and average SST 1 degrees C warmer than present day) and a wet/cold period after 750 cal yr BP (higher runoff and average SST 1 degrees C colder than present clay). Relatively colder SSTs were found during 750-600 and 450-250 cal yr BP, where the latter period roughly corresponds to the interval defined for the Little Ice Age (LIA) Similar climatic swings have been observed previously in continental and marine archives of the last two millennia from central and southern Chile, suggesting a strong latitudinal sensitivity to changes in the Southern Westerly Winds, the main Source Of precipitation in southern Chile, and validating the regional nature of the LIA Our results reveal the importance of the Chilean fjord system for recording climate changes of regional and global significance (C) 2009 University of Washington Published by Elsevier Inc All rights reserved. VL - 72 IS - 3 N1 - id: 1858; 512MQ Times Cited:0 Cited References Count:53Y JO - Late Holocene sea-surface temperature and precipitation variability in northern Patagonia, Chile (Jacaf Fjord, 44 degrees S) ER - TY - JOUR T1 - Late Pleistocene-Holocene evolution of the northern shelf of the Sea of Marmara JF - Marine Geology Y1 - 2009 A1 - Cagatay, M. N. A1 - Eris, K. A1 - Ryan, W. B. F. A1 - Sancar, U. A1 - Polonia, A. A1 - Akcer, S. A1 - Biltekin, D. A1 - Gasperini, L. A1 - Gorur, N. A1 - Lericolais, G. A1 - Bard, E. AB - Chirp sub-bottom profiling, multibeam bathymetric mapping and a combination of faunal and isotopic analysis of molluscs and foraminifera in sediment cores on the northern shelf of the Sea of Marmara (SoM) provide evidence of sea-level excursions, water exchanges between the adjacent Mediterranean and Black Seas, and oscillating salinity over the last 160 ka bp. During the marine isotope stages MIS-2, MIS-3, MIS-4 and MIS-6 the SoM disconnected from the Mediterranean Sea and evolved into a lake. During MIS-1, MIS-5 and MIS-7, the SoM reconnected and became salty once again. Sapropels formed shortly after each invasion of Mediterranean saltwater observed in our cores. Concurrent suboxic-dysoxic conditions prevailed over quite shallow substrates on the shelf. Ancient shorelines are pervasive at -85 m on the northern shelf and in the region of Prince Islands coincident with the elevation of the modern bedrock sill in the Canakkale (Dardanelles) Strait. At times when global (eustatic) sea level dropped below this sill, the surface of the SoM stabilized at its outlet and freshened. Thus this particular shoreline is interpreted as the edge of the most recent SoM lake that existed from about 75 ka bp to 12 ka bp. The freshening is observed in very light (-6 parts per thousand) values of delta O-18 measured on freshwater molluscs and the complete absence of foraminifera. Two brief lacustrine episodes during MIS-5 suggest that the level of the Canakkale outlet might have been as shallow as -50 m in the past, a likelihood supported by submerged terraces along its margins bounding the modern central channel and the presence of an euryhaline biofacies in Unit L4.1 corresponding to MIS-5b. delta O-18 profiles and carbon-14 dating show that salinification of the SoM and the blossoming of bioherms evolved rapidly after the latest connection with the Mediterranean at 12 ka bp. However, freshening proceeded more slowly once the connection was severed. (C) 2009 Elsevier B.V. All rights reserved. VL - 265 IS - 3-4 N1 - id: 1843; 500UN Times Cited:1 Cited References Count:80Y JO - Late Pleistocene-Holocene evolution of the northern shelf of the Sea of Marmara ER - TY - JOUR T1 - A Late Prehistoric Bison Processing Camp in the Central Plains: Montana Creek East (14JW46) JF - Plains Anthropologist Y1 - 2009 A1 - Ritterbush, Lauren W. A1 - Logan, Brad VL - 54 IS - 211 N1 - id: 1999 ER - TY - JOUR T1 - Late Quaternary benthic foraminifera from Ocean Drilling Program Hole 716A, Maldives Ridge, southeastern Arabian Sea JF - Micropaleontology Y1 - 2009 A1 - Sarkar, S. A1 - De, S. A1 - Gupta, A. K. KW - benthonic foraminifera KW - equatorial indian-ocean KW - Holocene KW - late neogene KW - monsoon KW - Oxygen minimum zone KW - productivity KW - red-sea KW - south atlantic-ocean KW - Water masses AB - A study on deep-sea benthic foraminifera from the interval similar to 445 ka BP to the Present of the Ocean Drilling Program (ODP) Hole 716A (4 degrees 56.0'N, 73 degrees 17.0'E; preser t water depth 533.3m), Maldives Ridge. southeastern Arabian Sea, documented 201 species belonging to 105 genera. These taxa were examined under scanning electron microscope (SEM) to illustrate their interspecific morphological variations. Several of these species are dominant showing significant down core fluctuations in their abundances whereas some are rare and sporadic. VL - 55 SN - 0026-2803 IS - 1 N1 - 424cdTimes Cited:5 Cited References Count:47 JO - Micropaleontology ER - TY - JOUR T1 - Late Quaternary foraminiferal assemblages from western Ross Sea (Antarctica) in relation to the main glacial and marine lithofacies JF - Marine Micropaleontology Y1 - 2009 A1 - Melis, R. A1 - Salvi, G. AB - investigations oil foraminifers from Upper Pleistocene-Holocene sediments were carried Out On twelve cores from the western Ross Sea continental margin (Drygalski, Joides, North Victoria Land Basins) as part of a "Progetto Nazionale di Ricerche in Antartide" (P.N.R.A.) multidisciplinary project. Data on the foraminiferal frequency, species diversity, tests abundance and their state of preservation were presented as a synthesis of 404 core samples to establish their relationships with the main glacial and marine lithofacies of this area. A total of 126 benthic species. pertaining to 73 genera have been identified; just few taxa, such as Cibicides spp., Globocassidulina spp., Trifarina angulosa and Miliammina spp. being the most ubiquitous and in some cases the dominant species of these paleoenvironments. Two variants of Neogloboquadrina pachyderma, including thin and thick-shelled forms have been recovered. We propose to use these results to provide the degree of glacial control during the Last Glacial Maximum and the following Holocene retreat of the ice sheets. High test fragmentation, low diversity and density tests reflect higher glacial influence of the ice sheet in the Drygalski Basin, whereas the decreasing percentage of fragmentation and a relative increase of density and diversity in Drygalski, Joides and North Victoria Land Basins indicate the paleoenvironmental passage from the ice sheet to the ice shelf condition. The ice shelf retreat is well evidenced in the Joides Basin by a succession of levels barren of foraminifers alternating with high-density levels, rich in T angulosa, followed by a total disappearance of the calcareous foraminifers. Open-marine settings indicative of lower glacial influence and increased corrosiveness of the water masses is testified by the Miliammina foraminiferal assemblage during the Holocene in Drygalski and Joides Basins cores. On the contrary, rich and abundant benthic and planktonic assemblages characterize the Holocene paleoenvironment of the North Victoria Land area, indicating that the water masses were less corrosive with respect to the other areas. In addition to the glacial reworking of the tests, and the dissolution due to the corrosive water mass conditions, the volcaniclastic sediments recovered in the North Victoria Land Basin cores also affected the condition of test preservation. In volcaniclastic sediments, older than about 20 ka BP, the foraminifers concentration tends to zero and, when present, their tests are highly damaged or completely broken. (c) 2008 Elsevier B.V. All rights reserved. VL - 70 IS - 1-2 N1 - id: 1879; 405HR Times Cited:0 Cited References Count:66Y JO - Late Quaternary foraminiferal assemblages from western Ross Sea (Antarctica) in relation to the main glacial and marine lithofacies ER - TY - JOUR T1 - Late Quaternary sediment-accumulation rates within the inner basins of the California Continental Borderland in support of geologic hazard evaluation JF - Geological Society of America Special Papers Y1 - 2009 A1 - Normark, William R. A1 - McGann, Mary A1 - Sliter, Ray W. AB - An evaluation of the geologic hazards of the inner California Borderland requires determination of the timing for faulting and mass-movement episodes during the Holocene. Our effort focused on basin slopes and turbidite systems on the basin floors for the area between Santa Barbara and San Diego, California. Dating condensed sections on slopes adjacent to fault zones provides better control on fault history where high-resolution, seismic-reflection data can be used to correlate sediment between the core site and the fault zones. This study reports and interprets 147 radiocarbon dates from 43 U.S. Geological Survey piston cores as well as 11 dates from Ocean Drilling Program Site 1015 on the floor of Santa Monica Basin. One hundred nineteen dates from 39 of the piston cores have not previously been published. Core locations were selected for hazard evaluation, but despite the nonuniform distribution of sample locations, the dates obtained for the late Quaternary deposits are useful for documenting changes in sediment-accumulation rates during the past 30 ka. Cores from basins receiving substantial sediment from rivers, i.e., Santa Monica Basin and the Gulf of Santa Catalina, show a decrease in sediment supply during the middle Holocene, but during the late Holocene after sea level had reached the current highstand condition, rates then increased partly in response to an increase in El Ni√±o‚ÄìSouthern Oscillation events during the past 3.5 ka. VL - 454 N1 - id: 1906; 10.1130/2009.2454(2.6) ER - TY - JOUR T1 - The last reconnection of the Marmara Sea (Turkey) to the World Ocean: A paleoceanographic and paleoclimatic perspective JF - Marine Geology Y1 - 2008 A1 - McHugh, C. M. G. A1 - Gurung, D. A1 - Giosan, L. A1 - Ryan, W. B. F. A1 - Mart, Y. A1 - Sancar, U. A1 - Burckle, L. A1 - Cagatay, M. N. AB - During the late glacial, marine isotope Stage 2, the Marmara Sea transformed into a brackish lake as global sea-level fell below the sill in the Dardanelles Strait. A record of the basin's reconnection to the global ocean is preserved in its sediments permitting the extraction of the paleoceanographic and paleoclimatic history of the region. The goal of this study is to develop a high-resolution record of the lacustrine to marine transition of Marmara Sea in order to reconstruct regional and global climatic events at a millennia] scale. For this purpose, we mapped the paleoshorelines of Marmara Sea along the northern, eastern, and southern shelves at Cekmece. Prince Islands, and Imrali, using data from multibeam bathymetry, high-resolution subbottom profiling (chirp) and ten sediment cores. Detailed sedimentologic, biostratigraphic (foraminifers, mollusk, diatoms), X-ray fluorescence geochemical scanning, and oxygen and carbon stable isotope analyses correlated to a calibrated radiocarbon chronology provided evidence for cold and city conditions prior to 15 ka BP, warm conditions of the Bolling-Allerod from similar to 15 to 13 ka BP, a rapid marine incursion at 12 ka BP, still stand of Marmara Sea and sediment reworking of the paleoshorelines during the Younger Dryas at similar to 11.5 to 10.5 ka BP, and development of strong stratification and influx of nutrients as Black Sea waters spilled into Marmara Sea at 9.2 ka BR Stable environmental conditions developed in Marmara Sea after 6.0 ka BP as sea-level reached its present shoreline and the basin floors filled with sediments achieving their present configuration. (C) 2008 Elsevier B.V. All rights reserved. VL - 255 IS - 1-2 N1 - id: 801; 370ED Times Cited:4 Cited References Count:104; YY JO - The last reconnection of the Marmara Sea (Turkey) to the World Ocean: A paleoceanographic and paleoclimatic perspective ER - TY - JOUR T1 - Late Holocene marine productivity changes in Northern Patagonia-Chile inferred from a multi-proxy analysis of Jacaf channel sediments JF - Estuarine Coastal and Shelf Science Y1 - 2008 A1 - Rebolledo, Lorena A1 - Sepulveda, Julio A1 - Lange, Carina B. A1 - Pantoja, Silvio A1 - Bertrand, Sbastien A1 - Hughen, Konrad A1 - Figueroae, Dante AB - A multi-proxy approach based on organic (organic carbon, alkenones, and C/N) and inorganic geochemical proxies (biogenic opal, inorganic carbon, Fe, Ti, and Ca) preserved in the sediments of the Jacaf channel (CF7-PC33; 44 degrees 21'S, 72 degrees 58'W, 510 m water depth), Chilean fjords, yields evidence of major past productivity fluctuations in accordance with climatic changes over the last similar to 1800 years. The downcore record clearly shows two productivity/climate modes. The first period, prior to 900 cal yr BP, is characterized by decreased marine productivity and a reduced continental signal, pointing to diminished precipitation and runoff. In contrast, the second period between similar to 750 cal yr BP and the late 1800s (top of core) is illustrated by elevated productivity and an increased continental signal, suggesting higher precipitation and runoff. Both time intervals are separated by a relatively abrupt transition of similar to 150 years which roughly coincides with the beginning of the Little Ice Age. The increased content of freshwater diatoms and Chrysophyte cysts that characterize the last 200 years of the latter mode coincides with a significant decrease in the carbonate content of the sediment; together they further indicate increased terrigenous contributions and decreased marine carbonate productivity at the end of the Little Ice Age. The correspondence between our record and other paleoclimate studies carried out in South America and Antarctica demonstrates that the Chilean fjord area of Northern Patagonia is not just sensitive to local climatic variability but also to regional and possibly global variability. (C) 2008 Elsevier Ltd. All rights reserved. VL - 80 IS - 3 N1 - id: 2117; PT: J; TC: 5; J9: ESTUAR COAST SHELF S; UT: WOS:000261562600002 JO - Late Holocene marine productivity changes in Northern Patagonia-Chile inferred from a multi-proxy analysis of Jacaf channel sediments ER - TY - JOUR T1 - A late holocene pollen and charcoal record from La Selva biological station, Costa Rica JF - Biotropica Y1 - 2008 A1 - Kennedy, Lisa M. A1 - Horn, Sally P. AB - Pollen and charcoal analysis of a 5.9-m-long sediment profile from a swamp on an alluvial terrace on the edge of La Selva biological station, Costa Rica (10 degrees 26 ' 23 '' N, 84 degrees 00 ' 24 '' W, 36 m asl), documents three millennia of human and natural disturbance within a lowland tropical rain forest. The record indicates that the highly diverse rain forest that presently surrounds the Cantarrana swamp regrew following forest clearing and maize agriculture that ended only a few centuries ago. The first maize pollen appears in sediments deposited similar to 1070 calendar-year BP. Older sediments below the 'maize zone' contain macroscopic charcoal, abundant microscopic charcoal, and possible pollen indicators of forest clearance, perhaps signaling local cultivation of root crops that left no pollen in the sediments. Interpretation of local archaeology indicates that La Selva reserve may have been most heavily populated during the El Bosque and La Selva regional archaeological phases from 2250-950 yr BP. However, the distribution of maize pollen in the sediments is clear evidence that the reserve was also occupied during the later La Cabana phase (950-400 yr BP), from which few artifacts have yet surfaced. Natural forest disturbance from treefalls and stream dynamics, and hydrological shifts associated with late-Holocene climate variability, form a backdrop to the human land-use history preserved in the Cantarrana sediment profile. VL - 40 IS - 1 N1 - id: 1997; PT: J; UT: WOS:000252319600004 JO - A late holocene pollen and charcoal record from La Selva biological station, Costa Rica ER - TY - JOUR T1 - Late Pleistocene freshwater fish (Cottidae) trackways from New England (USA) glacial lakes and a reinterpretation of the ichnogenus Broomichnium Kuhn JF - Palaeogeography, Palaeoclimatology, Palaeoecology Y1 - 2008 A1 - Benner, Jacob S. A1 - Ridge, John C. A1 - Taft, Natalia K. AB - New trace fossil material from Late Pleistocene glaciolacustrine varves of the Connecticut River Valley, New England, USA represent the first evidence of freshwater sculpin in glacial Lake Hitchcock. Paleobiogeographic data constrain the timing of the last reinhabitation of freshwater cottids from a Wisconsinan glacial refugium. Freshwater sculpin were present in the area of study by ~ 13.7 ky BP, moving approximately 400 km in 5000 yr, and following the ice margin at distances as close as 35 km. The trace fossils warrant erection of a new ichnospecies, Broomichnium flirii isp. nov. Comparison of this new ichnospecies to Broomichnium permianum reveals distinct similarities, and it is possible that the Permian examples of B. permianum also were made by fish, which would reconcile a long-running controversy. Many groups of fish are demersal and make ventral body contact with the substrate and could potentially leave similar traces. Identifying new forms of trace fossils made by fish that use alternative modes of locomotion will prove useful in paleoenvironmental interpretations. VL - 260 IS - 3–4 N1 - id: 2129 JO - Late Pleistocene freshwater fish (Cottidae) trackways from New England (USA) glacial lakes and a reinterpretation of the ichnogenus Broomichnium Kuhn ER - TY - CONF T1 - Late Quaternary paleo-lake fluctuations in westernmost Tibet T2 - 2008 Fall Meeting of the American Geophysical Union (AGU 2008) Y1 - 2008 A1 - Amidon, W. A1 - Blard, P. A1 - Avouac, J. A1 - Schneider, T. ED - San Francisco, California KW - China, People's Rep., Xizang KW - Paleo studies KW - Quaternary JF - 2008 Fall Meeting of the American Geophysical Union (AGU 2008) N1 - id: 1913; TY: CPAPER; NO: Source type: conferencepapers&proceedings; Object type: Conference Paper; CSAUnique: CPI-5461640; AccNum: 5461640(USA) ER - TY - JOUR T1 - Late Quaternary vegetation reconstruction from the Eastern Arc Mountains, Tanzania JF - Quaternary Research Y1 - 2008 A1 - Mumbi, C. T. A1 - Marchant, R. A1 - Hooghiemstra, H. A1 - Wooller, M. J. AB - Pollen, spore, macrofossil and stable isotope (C and N) analyses from a 266-cm sediment core collected from a swamp on the Eastern Arc Mountains, Tanzania, are used to reconstruct vegetation and environmental history. An estimated time scale based on five C-14 ages records approximately 38,000 yr. This palaeorecord is the first from this biodiversity hotspot and importantly extends through the last glacial maximum (LGM). The altitudinal transition from montane to upper montane forest shifted from 1700-1800 in (38,000 C-14 yr BP) to 1800-1900 in (35,000-29,000 C-14 yr BP). From 29,000 to 10,000 C-14 yr BP, it shifted from 1850-1950 in across the LGM to 1750-1800 in (during 10,000-3500 C-14 yr BP), and to present-day elevations at 2000 in during the last 3500 C-14 yr BP. The relative ecosystem stability across the LGM may be explained by the Indian Ocean's influence in maintaining continuous moist forest cover during a period of East African regional climate aridity. During the late Holocene, presence of abundant coprophilous fungi and algal blooms demonstrates increasing human impact. Neurospora spores indicate frequent fires, coinciding with clear signals of decline in Podocarpus and Psychotria trees that possibly represent selective logging. (C) 2007 University of Washington. All rights reserved. VL - 69 IS - 2 N1 - id: 1836; 285PB Times Cited:6 Cited References Count:105Y JO - Late Quaternary vegetation reconstruction from the Eastern Arc Mountains, Tanzania ER - TY - JOUR T1 - Lateral organic carbon supply to the deep Canada Basin JF - Geophysical Research Letters Y1 - 2008 A1 - Hwang, J. A1 - Eglinton, T. I. A1 - Krishfield, R. A. A1 - Manganini, S. J. A1 - Honjo, S. AB - Understanding the processes driving the carbon cycle in the Arctic Ocean is important for assessing the impacts of the predicted rapid and amplified climate change in this region. We analyzed settling particle samples intercepted by a time-series sediment trap deployed in the abyssal Canada Basin ( at 3067 m) in order to examine carbon export to the deep Arctic Ocean. Strikingly old radiocarbon ages ( apparent mean 14 C age = similar to 1900 years) of the organic carbon, abundant lithogenic material (similar to 80%), and mass flux variations temporally decoupled from the cycle of primary productivity in overlying surface waters together suggest that, unlike other ocean basins, the majority of the particulate organic carbon entering the deep Canada Basin is supplied from the surrounding margins. VL - 35 IS - 11 N1 - id: 1830; 314KU Times Cited:7 Cited References Count:33Y JO - Lateral organic carbon supply to the deep Canada Basin ER - TY - JOUR T1 - Life on the edge: early maritime cultures of the Pacific Coast of North America JF - Quaternary Science Reviews Y1 - 2008 A1 - Erlandson, Jon M. A1 - Moss, Madonna L. A1 - Des Lauriers, Matthew AB - A variety of evidence suggests that the Americas may have been colonized, at least in part, by maritime peoples moving around the North Pacific Rim near the end of the Pleistocene. Understanding the geography of late glacial and early postglacial landscapes and the antiquity of human societies along the Pacific Coast continues to be a challenge, however, due to geological dynamics associated with glaciation, tectonism, submergence of coastal lowland landscapes by rising postglacial seas, and coastal erosion. Nonetheless, archaeological research has Pushed back the antiquity of human settlement along the Pacific Coast of North America to the terminal Pleistocene or early Holocene, providing important new data on the nature of the earliest coastal peoples in the Pacific Northwest, Alta California, and Baja California. In this paper, we summarize what is known about the earliest peoples of the Pacific Coast of North America and evaluate the Current viability of the coastal migration theory via a Pacific Rim route. Archaeological evidence now shows that Palaeocoastal peoples occupied each major region of the Pacific Coast by at least 13,000-11,500 calendar years ago (cal BP) (13-11.5 ka), essentially contemporaneous with Clovis and Folsom peoples of the interior. Although it is too early to conclude that the initial human colonization of the Americas took place via a migration by maritime or coastal peoples, it seems increasingly likely that such a migration played a role in the early peopling of the Americas. (c) 2008 Elsevier Ltd. All rights reserved. VL - 27 IS - 23-24 N1 - id: 2062; PT: J; SI: SI; UT: WOS:000261715500012 JO - Life on the edge: early maritime cultures of the Pacific Coast of North America ER - TY - JOUR T1 - Loess record of the Pleistocene-Holocene transition on the northern and central Great Plains, USA JF - Quaternary Science Reviews Y1 - 2008 A1 - Mason, Joseph A. A1 - Miao, Xiaodong A1 - Hanson, Paul R. A1 - Johnson, William C. A1 - Jacobs, Peter M. A1 - Goble, Ronald J. AB - Various lines of evidence support conflicting interpretations of the timing, abruptness. and nature of climate change in the Great Plains during the Pleistocene-Holocene transition. Loess deposits and paleosols on both the central and northern Great Plains provide a valuable record that can help address these issues. A synthesis of new and previously reported optical and radiocarbon ages indicates that the Brady Soil, which marks the boundary between late Pleistocene Peoria Loess and Holocene Bignell Loess, began forming after a reduction in the rate of Peoria Loess accumulation that most likely occurred between 13.5 and 15 cal ka. Brady Soil formation spanned all or part of the Bolling-Allerod episode (approximately 14.7-12.9 cal ka) and all of the Younger Dryas episode (12.9-11.5 cal ka) and extended at least 1000 years beyond the end of the Younger Dryas. The Brady Soil was buried by Bignell Loess sedimentation beginning around 10.5-9 cal ka, and continuing episodically through the Holocene. Evidence for a brief increase in loess influx during the Younger Dryas is noteworthy but very limited. Most late Quaternary loess accumulation in the central Great Plains was nonglacigenic and was under relatively direct climatic control. Thus, Brady Soil formation records climatic conditions that minimized eolian activity and allowed effective pedogenesis, probably through relatively high effective moisture. Optical dating of loess in North Dakota supports correlation of the Leonard Paleosol on the northern Great Plains with the Brady Soil. Thick loess in North Dakota was primarily derived from the Missouri River floodplain; thus, its stratigraphy may in part reflect glacial influence on the Missouri River. Nonetheless, the persistence of minimal loess accumulation and soil formation until 10 cal ka at our North Dakota study site is best explained by a prolonged interval of high effective moisture correlative with the conditions that favored Brady Soil formation. Burial of both the Brady Soil and the Leonard Paleosol by renewed loess influx probably represents eolian system response that occurred when gradual change toward a drier climate eventually crossed the threshold for eolian activity. Overall, the loess-paleosol sequences of the central and northern Great Plains record a broad peak of high effective moisture across the late Pleistocene to Holocene boundary, rather than well-defined climatic episodes corresponding to the Bolling-Allerod and Younger Dryas episodes in the North Atlantic region. (C) 2008 Elsevier Ltd. All rights reserved. VL - 27 IS - 17-18 N1 - id: 1993; PT: J; UT: WOS:000260545800008 JO - Loess record of the Pleistocene-Holocene transition on the northern and central Great Plains, USA ER - TY - JOUR T1 - Last millennia sedimentary record on a micro-tidal, low-accumulation prodelta (Tet NW Mediterranean) JF - Marine Geology Y1 - 2007 A1 - Bourrin, F. A1 - Monaco, A. A1 - Aloisi, J. C. A1 - Sanchez-Cabeza, J. A. A1 - Lofi, J. A1 - Heussner, S. A1 - de Madron, X. D. A1 - Jeanty, G. A1 - Buscail, R. A1 - Saragoni, G. AB - Statistical sequential analysis was performed on a series of sediment cores collected from the Tet prodelta in the Gulf of Lions, northwestern Mediterranean Sea, between October 2003 and October 2004. Seabed changes during that period were correlated to hydrodynamic conditions (waves and currents) and river discharge. Low sediment supply prevents full preservation of new sediment strata on this low-accumulation prodelta located on a microtidal, storm-dorninated inner shelf. Severe meteorological events caused a rapid succession of erosion and deposition phases. For example, the December 2003 flood and storm produced a flood layer deposit that persisted for 2 months with only slight transformations due to early diagenesis and/or bioturbation, until a new, storm event eroded this layer. A typical sedimentary sequence was observed for the secular deposits composed of a 10-cm-thick sandy layer overlaying siltyclayey layers. These characteristic features were used to analyse the last millennia sedimentary record of the Tet prodelta. The low preservation of freshly deposited sediments and variable sedimentation rates during the last millennia period yield a sedimentary sequence formed by the outcropping of muddy prodeltaic units intersected by heterogeneous siltysandy units similar to those formed under present day hydrodynamic conditions. No flood layer was found related to catastrophic flooding of the last century in the sedimentary record. The Little lee Age (similar to 1550-1850 AD) probably favoured the formation of a well-developed muddy prodelta in the mouth of the Tet River. Later on, the decrease of sediment supply by rivers due to climate change and/or human activities (damming, irrigation), and the increase of the number of high-energy storms reaching the coast, induced a coarsening of the top sediment layer on this prodelta. This modem change of the substrate is also observed in the composition of benthic biota found in the substrate. (c) 2007 Elsevier B.V All rights reserved. VL - 243 IS - 1-4 N1 - id: 1904; 210TU Times Cited:8 Cited References Count:68Y JO - Last millennia sedimentary record on a micro-tidal, low-accumulation prodelta (Tet NW Mediterranean) ER - TY - JOUR T1 - Late Holocene barrier island collapse; Outer Banks, North Carolina, USA JF - The Sedimentary Record Y1 - 2007 A1 - Culver, Stephen J. A1 - Grand Pre, Candace A. A1 - Mallinson, David J. A1 - Riggs, Stanley R. A1 - Corbett, D. Reide A1 - Foley, Jennifer A1 - Hale, Michael A1 - Metger, Lauren A1 - Ricardo, John A1 - Rosenberger, Jeb A1 - Smith, Christopher G. A1 - Smith, Curtis W. A1 - Snyder, Scott W. A1 - Twamley, David A1 - Farrell, Kathleen A1 - Horton, Benjamin KW - 24, Quaternary geology KW - algae KW - assemblages KW - barrier islands KW - Cenozoic KW - changes KW - clastic sediments KW - cores KW - diatoms KW - erosion KW - Foraminifera KW - geologic hazards KW - Holocene KW - hurricanes KW - Invertebrata KW - landform evolution KW - lithofacies KW - littoral KW - microfossils KW - North Carolina KW - Outer Banks KW - Pamlico Sound KW - Plantae KW - preservation KW - Protista KW - Quaternary KW - salinity KW - sand KW - sea-level KW - sediments KW - United States KW - upper Holocene KW - Vibroseis AB - We document here the threat of large scale destruction (collapse) of barrier islands based on the study of many cores taken along the Outer Banks and in Pamlico Sound, North Carolina.Around 1,100 cal yr BP, probably as the result of hurricane activity, portions of the southern Outer Banks must have collapsed to allow normal salinity waters to bathe southern Pamlico Sound for several hundred years. Such collapse could occur again during our current regime of global warming, rising sea level and increased tropical cyclone activity. The economic effect of barrier island break collapse on Outer Banks communities would be devastating. VL - 5 IS - 4 N1 - id: 1887; ISSN: 1543-8740 Language: English References: 16; illus. incl. strat. col., geol. sketch map United States (USA) Latitude:N350000,N353000 Longitude:W0753000,W0760000 ER - TY - JOUR T1 - Late Holocene fine-grained sediments of the Balearic Abyssal Plain, Western Mediterranean Sea JF - Marine Geology Y1 - 2007 A1 - Zuniga, D. A1 - Garcia-Orellana, J. A1 - Calafat, A. A1 - Price, N. B. A1 - Adatte, T. A1 - Sanchez-Vidal, A. A1 - Canals, M. A1 - Sanchex-Cabeza, J. A. A1 - Masque, P. A1 - Fabres, J. AB - The Late Holocene fine-grained sedimentation in the deep central Balearic Abyssal Plain, Western Mediterranean Sea, has been studied after the analysis of high quality sediment cores from three multicoring stations, named A, B and C. The coring stations are 25 km apart from each other and form a triangle that is at the greatest distance from the nearest landmasses. The sediments consist of foraminifer-pteropod oozes (layers U1 and U4 from bottom to top), two pteropod oozes (U2 and U5) and a turbidite layer (U3). The same sequence has been identified in the three cores. The turbidite layer U3 that lies on top of U2 (C-14 AMS dated at 1814 cal yrs BP) ranges from 5 to I I cm thick and is clearly distinguished from the dominating hemipelagic sediments by colour variations, higher water content and the absence of planktonic foraminifer shells. Rather uniform values of organic carbon and nitrogen are also characteristic of the U3 turbidite unit, likely because of homogenisation during transport and emplacement. In addition, U3 unit shows higher contents of terrigenous elements such as K and Fe. Otherwise, the presence of zeolites in the turbidite layer supports the hypothesis of the Sardinian continental margin, where pyroclastic deposits are known, as the most likely source area for U3. Our results demonstrate the ability of turbidity currents originating on the margins surrounding the Balearic Abyssal Plain to reach the very centre of the basin during high sea level still stands as the present one. (c) 2006 Elsevier B.V. All rights reserved. VL - 237 IS - 1-2 N1 - id: 624; 139VA Times Cited:6 Cited References Count:57 JO - Late Holocene fine-grained sediments of the Balearic Abyssal Plain, Western Mediterranean Sea ER - TY - JOUR T1 - Late Quaternary environmental and human events at En Gedi, reflected by the geology and archaeology of the Moringa Cave (Dead Sea area, Israel) JF - Quaternary Research Y1 - 2007 A1 - Lisker, S. A1 - Porat, R. A1 - Davidovich, U. A1 - Eshel, H. A1 - Lauritzen, S. E. A1 - Frumkin, A. AB - The Moringa Cave within Pleistocene sediments in the En Gedi area of the Dead Sea Fault Escarpment contains a sequence of various Pleistocene lacustrine deposits associated with higher-than-today lake levels at the Dead Sea basin. In addition it contains Chalcolithic remains and 5th century BC burials attributed to the Persian period, cemented and covered by Late Holocene travertine flowstone. These deposits represent a chain of Late Pleistocene and Holocene interconnected environmental and human events, echoing broader scale regional and global climate events. A major shift between depositional environments is associated with the rapid fall of Lake Lisan level during the latest Pleistocene. This exposed the sediments, providing for cave formation processes sometime between the latest Pleistocene (ca. 15 ka) and the Middle Holocene (ca. 4500 BC), eventually leading to human use of the cave. The Chalcolithic use of the cave can be related to a relatively moist desert environment, probably related to a shift in the location of the northern boundary of the Saharo-Arabian desert belt. The travertine layer was U-Th dated 2.46 +/- 0.10 to 2.10 +/- 0.04 ka, in agreement with the archaeological finds from the Persian period. Together with the inner consistency of the dating results, this strongly supports the reliability of the radiometric ages. The 2.46-2.10 ka travertine deposition within the presently dry cave suggests a higher recharge of the Judean Desert aquifer, correlative to a rising Dead Sea towards the end of the 1 st millennium BC. This suggests a relatively moist local and regional climate facilitating human habitation of the desert. (c) 2007 University of Washington. All rights reserved. VL - 68 IS - 2 N1 - 207wkTimes Cited:3Cited References Count:55 JO - Late Quaternary environmental and human events at En Gedi, reflected by the geology and archaeology of the Moringa Cave (Dead Sea area, Israel) ER - TY - CHAP T1 - Late quaternary lake and swamp sediments: records of climate and environment T2 - Central America: Geology, Resources, Hazards Y1 - 2007 A1 - Horn, S. P. ED - Bundschuh, J. JF - Central America: Geology, Resources, Hazards PB - Taylor & Francis/Balkema CY - Leiden, The Netherlands VL - 1 N1 - id: 622 ER - TY - JOUR T1 - Late quaternary paleoseismology of the southern Steens fault zone, northern Nevada JF - Bulletin of the Seismological Society of America Y1 - 2007 A1 - Personius, Stephen F. A1 - Crone, Anthony J. A1 - Machette, Michael N. A1 - Mahan, Shannon A. A1 - Kyung, Jai Bok A1 - Cisneros, Hector A1 - Lidke, David J. AB - The 192-km-long Steens fault zone is the most prominent normal fault system in the northern Basin and Range province of western North America. We use trench mapping and radiometric dating to estimate displacements and timing of the last three surface-rupturing earthquakes (E1-E3) on the southern part of the fault south of Denio, Nevada. Coseismic displacements range from 1.1 to 2.2 +/- 0.5 m, and radiometric ages indicate earthquake times of 11.5 +/- 2.0 ka (E3), 6.1 +/- 0.5 ka (E2), and 4.6 +/- 1.0 ka (E1). These data yield recurrence intervals of 5.4 +/- 2.1 k.y. between E3 and E2, 1.5 +/- 1.1 k.y. between E2 and E1, and an elapsed time of 4.6 +/- 1.0 k.y. since El. The recurrence data yield variable interval slip rates (between 0.2 +/- 0.22 and 1.5 +/- 2.3 mm/yr), but slip rates averaged over the past similar to 18 k.y. (0.24 +/- 0.06 mm/year) are similar to long-term (8.5-12.5 Ma) slip rates (0.2 +/- 0.1 mm/yr) measured a few kilometers to the north. We infer from the lack of significant topographic relief across the fault in Bog Hot Valley that the fault zone is propagating southward and may now be connected with a fault at the northwestern end of the Pine Forest Range. Displacements documented in the trench and a rupture length of 37 km indicate a history of three latest Quaternary earthquakes with magnitudes of M 6.6-7.1 on the southern part of the Steens fault zone. VL - 97 IS - 5 N1 - id: 2022; PT: J; UT: WOS:000249930900021 JO - Late quaternary paleoseismology of the southern Steens fault zone, northern Nevada ER - TY - THES T1 - Late-glacial through Holocene stratigraphy and lake-level record ofRangeley Lake, Western Maine Y1 - 2007 A1 - Metcalfe, Elisabet PB - University of Maine VL - Master's ER - TY - JOUR T1 - A late-glacial transition from Picea glauca to Picea mariana in southern New England JF - Quaternary Research Y1 - 2007 A1 - Lindbladh, M. A1 - Oswald, W. W. A1 - Foster, D. R. A1 - Faison, E. K. A1 - Hou, J. Z. A1 - Huang, Y. S. AB - Picea is an important taxon in late-glacial pollen records from eastern North America, but little is known about which species of Picea were present. We apply a recently developed palynological method for discriminating the three Picea species in eastern North America to three records from New England. Picea glauca was dominant at similar to 14,500-14,000 cal yr BP, followed by a transition to Picea mariana between similar to 14,000 and 13,500 cal yr BP. Comparison of the pollen data with hydrogen isotope data shows clearly that this transition began before the beginning of the Younger Dryas Chronozone. The ecological changes of the late-glacial interval were not a simple oscillation in the position of a single species' range, but rather major changes in vegetation structure and composition occurring during an interval of variations in several environmental factors, including climate, edaphic conditions, and atmospheric CO2 levels. (c) 2007 University of Washington. All rights reserved. VL - 67 IS - 3 N1 - id: 1841; 160RU Times Cited:5 Cited References Count:61Y JO - A late-glacial transition from Picea glauca to Picea mariana in southern New England ER - TY - JOUR T1 - Linking lithology and land use to sources of dissolved and particulate organic matter in headwaters of a temperate, passive-margin river system JF - Geochimica Et Cosmochimica Acta Y1 - 2007 A1 - Longworth, B. E. A1 - Petsch, S. T. A1 - Raymond, P. A. A1 - Bauer, J. E. KW - ATCHAFALAYA RIVER KW - ATMOSPHERIC O-2 KW - BLACK SHALE KW - continental-shelf KW - GULF-OF-MEXICO KW - marine-sediments KW - MINERAL KW - SPACE-TIME CLIMATE KW - STABLE-ISOTOPES KW - surface sediments KW - SURFACES AB - A number of rivers have been found to transport highly aged organic matter [OM]; however, the sources of this aged material remain a matter of debate. One potential source may be erosion and weathering of headwater lithologies rich in ancient sedimentary OM. In this study, waters, suspended particulates, streambed sediments, rocks and soils from fourteen small headwater watersheds of a mid-size, temperate, passive margin river were sampled and characterized by Delta C-14, delta C-13, and POC/TPN ratios to identify sources of particulate and dissolved OM delivered to the river mainstem. These headwater sites encompass a range in lithology (OM-rich shales, OM-lean carbonate/mudstone facies, and OM-free crystalline rocks) and land use types (forested and agricultural), and allow investigation of the influence of agriculture and bedrock types on stream OM characteristics. Streams draining large areas of both agricultural land use and OM-rich lithology contain particulate OM [POM] that is more C-14-depleted than streams draining forested, shale-free watersheds. However, this is not sufficient to account for the significantly lower Delta C-14-POC measured in the river mainstern. Dissolved OM [DOM] Delta C-14 are in all cases enriched compared to POM from the same stream, but are otherwise highly variable and unrelated to either land use or lithology. POC/TPN ratios were likewise highly variable. POC and DOC delta C-13 signatures were similar across all watersheds. Based on isotope mass balance, C-14-free fossil OM sources contribute 0-12% of total stream POM. Although these results do not unequivocally separate the influences of land use and lithology, watershed coverage by shale and agriculture are both important controls on stream A Delta C-14-POC. Thus export of aged, particle-associated OM may be a feature of river systems along both passive and active continental margins. (C) 2007 Elsevier Ltd. All rights reserved. VL - 71 SN - 0016-7037 IS - 17 N1 - 30 JO - Geochim. Cosmochim. Acta ER - TY - JOUR T1 - Lithological anomalies in a relict coastal dune: Geophysical and paleoenvironmental markers JF - Geophysical Research Letters Y1 - 2007 A1 - Buynevich, I. V. A1 - Bitinas, A. A1 - Pupienis, D. AB - Ground exposures of migration surfaces (slipfaces) of a relict Holocene coastal dune along the southeastern Baltic Sea coast provide an ideal opportunity for establishing the causes of prominent reflections on geophysical profiles. High-amplitude reflections on high-resolution ground-penetrating radar (GPR) images correlate well with two major lithological anomalies: 1) paleosols developed on dune slipfaces, and 2) slipfaces consisting of heavy-mineral concentrations (HMCs). Paleosols serve as indicators of dune stability, represent datable chronostratigraphic surfaces, and help reconstruct dune paleo-morphology. HMCs have substantially higher magnetic susceptibility values than background quartz-rich sands and, where they are well-developed, can be also used for spatial correlation. Based on their occurrence at the study site, these enriched horizons likely represent periods of increased wind activity ( storminess). Multiple HMCs upwind of paleosol P1 ( 800 670 cal years BP) likely reflect periods of intensified wind activity along the southeast Baltic region during the Medieval Warm Period. VL - 34 IS - 9 N1 - 168ajTimes Cited:18Cited References Count:38 JO - Lithological anomalies in a relict coastal dune: Geophysical and paleoenvironmental markers ER - TY - JOUR T1 - Little Ice Age drought in equatorial Africa: Intertropical Convergence Zone migrations and El Nino-Southern Oscillation variability RID C-1423-2010 JF - Geology Y1 - 2007 A1 - Russell, J. M. A1 - Johnson, T. C. AB - High-resolution analyses of the Mg concentration in authigenic calcite in five cores from Lake Edward provide a water balance history of central equatorial Africa spanning the past 1400 yr. A high ratio of Mg to Ca (%Mg) indicates strong droughts in central Africa during the Little Ice Age (A.D. 1400-1750), in contrast to records from Lake Naivasha, Kenya, which suggest a wet Little Ice Age. This spatial pattern in Africa likely arose due to coupled changes in the high latitudes, the position of the Intertropical Convergence Zone, and the Ell Ni (n) over tildeo-Southern Oscillation (ENSO) system. Our results further suggest that the patterns and variability of twentieth-century rainfall in central Africa have been unusually conducive to human welfare in the context of the past 1400 yr. VL - 35 IS - 1 N1 - id: 2049; PT: J; UT: WOS:000243483800006 JO - Little Ice Age drought in equatorial Africa: Intertropical Convergence Zone migrations and El Nino-Southern Oscillation variability RID C-1423-2010 ER - TY - JOUR T1 - Little Ice Age drought in quatorial Africa: ITCZ migrations and ENSO variability JF - geology Y1 - 2007 A1 - Russell, J. M. A1 - Johnson, T. C. VL - 35 N1 - id: 1005 ER - TY - JOUR T1 - Long-term settlement, mobility, and landscape formation of Eastern Eurasian pastoralists from 2500 CAL B.C JF - Journal of Field Archaeology Y1 - 2007 A1 - Frachetti, M. D. A1 - Mar’yashev, A. N. VL - 32 IS - 3 N1 - id: 1881 ER - TY - JOUR T1 - Las morenas de Punta Banderas, Lago Argentino JF - Proceedings of the XVI Congreso Geologico Argentino Y1 - 2006 A1 - Strelin, J. A1 - Denton, G. H. VL - CD-ROM IS - 269 N1 - id: 707 ER - TY - CONF T1 - Late Holocene climate variability of South America reconstructed by a multi-proxy analysis of Chilean fjord sediments T2 - Abstracts, EGU General Assembly Y1 - 2006 A1 - Bertrand, S. A1 - Hughen, K. A. A1 - Giosan, L. A1 - Tierney, J. A1 - Sepfulveda, J. A1 - Pantoja, S. JF - Abstracts, EGU General Assembly CY - Vienna, Austria N1 - id: 560 ER - TY - CONF T1 - The late Pleistocene-Holocene history of Long Island Sound T2 - LISRC proceedings Y1 - 2006 A1 - Varekamp, J. C. A1 - Thomas, E. A1 - Groner, M. JF - LISRC proceedings N1 - id: 1175 ER - TY - THES T1 - Late Quaternary sea-level lowstand environments and chronology of outer Saco Bay, Maine Y1 - 2006 A1 - Lee, K. PB - University of Maine CY - Orono, ME VL - Masters ER - TY - JOUR T1 - Late-Quaternary paleoenvironmental evolution of Lesina lagoon (sosuthern Italy) from subsurface data JF - Sedimentary Geology Y1 - 2006 A1 - Lucchi, Marianna Ricci A1 - Fiorini, Flavia A1 - Colalongo, Maria Luisa A1 - Curzi, Pietro Vittorio KW - Foraminifers KW - Late Quaternary KW - Lesina lagoon (Italy) KW - Ostracods KW - Sea-level changes AB - Integrated sedimentological and micropaleontological (foraminifers and ostracods) analyses of two 55 m long borehole cores (S3 and S4) drilled in the subsurface of Lesina lagoon (Gargano promontory—Italy) has yielded a facies distribution characteristic of alluvial, coastal and shallow-marine sediments. Stratigraphic correlation between the two cores, based on strong similarity in facies distribution and AMS radiocarbon dates, indicates a Late Pleistocene to Holocene age of the sedimentary succession. Two main depositional sequences were deposited during the last 60-ky. These sequences display poor preservation of lowstand deposits and record two major transgressive pulses and subsequent sea-level highstands. The older sequence, unconformably overlying a pedogenized alluvial unit, consists of paralic and marine units (dated by AMS radiocarbon at about 45–50,000 years BP) that represent the landward migration of a barrier-lagoon system. These units are separated by a ravinement surface (RS1). Above these tansgressive deposits, highstand deposition is characterised by progradation of the coastal sediments. The younger sequence, overlying an unconformity of tectonic origin, is a 10 m-thick sedimentary body, consisting of fluvial channel sediments overlain by transgressive–regressive deposits of Holocene age. A ravinement surface (RS2), truncating the transgressive (lagoonal and back-barrier) deposits in core S4, indicates shoreface retreat and landward migration of the barrier/lagoon system. The overlying beach, lagoon and alluvial deposits are the result of mid-Holocene highstand sedimentation and coastal progradation. VL - 183 N1 - id: 1060 JO - Late-Quaternary paleoenvironmental evolution of Lesina lagoon (sosuthern Italy) from subsurface data ER - TY - CONF T1 - Long Island Sound - a human dominated estuary T2 - AGU spring meeting, 2006 Y1 - 2006 A1 - Varekamp, J. C. A1 - Thomas, E. JF - AGU spring meeting, 2006 CY - Baltimore, MD N1 - id: 1186 ER - TY - JOUR T1 - Lacustrine loss-on-ignition recrods from the southern Uinta Mountains JF - Geological Society of America Abstracts with Programs Y1 - 2005 A1 - Munroe, Jeffrey S. VL - 37 IS - 7 N1 - id: 694 ER - TY - JOUR T1 - Last deglaciation in the Okinawa Trough: Subtropical northwest Pacific link to Northern Hemisphere and tropical climate JF - Paleoceanography Y1 - 2005 A1 - Sun, Y. B. A1 - Oppo, D. W. A1 - Xiang, R. A1 - Liu, W. G. A1 - Gao, S. KW - cal kyr bp KW - deep-ocean circulation KW - equatorial current KW - kuroshio current KW - late pleistocene KW - oxygen-isotope KW - planktonic-foraminifera KW - radiocarbon age calibration KW - south china sea KW - surface-water AB - [1] Detailed deglacial and Holocene records of planktonic delta O-18 and Mg/Ca - based sea surface temperature (SST) from the Okinawa Trough suggest that at similar to 18 to 17 thousand years before present (kyr B. P.), late spring/ early summer SSTs were approximately 3 degrees C cooler than today, while surface waters were up to 1 practical salinity unit saltier. These conditions are consistent with a weaker influence of the summer East Asian Monsoon (EAM) than today. The timing of suborbital SST oscillations suggests a close link with abrupt changes in the EAM and North Atlantic climate. A tropical influence, however, may have resulted in subtle decoupling between the North Atlantic and the Okinawa Trough/EAM during the deglaciation. Okinawa Trough surface water trends in the Holocene are consistent with model simulations of an inland shift of intense EAM precipitation during the middle Holocene. Millennial-scale alternations between relatively warm, salty conditions and relatively cold, fresh conditions suggest varying influence of the Kuroshio during the Holocene. VL - 20 SN - 0883-8305 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=Alerting&SrcApp=Alerting&DestApp=WOS&DestLinkType=FullRecord;UT=WOS:000232654500001 IS - 4 N1 - 975ipTimes Cited:53 Cited References Count:55 JO - Paleoceanography ER - TY - JOUR T1 - The last glacial maximum: stability and change in an Andean cloud forest JF - Journal of Quaternary Science Y1 - 2005 A1 - Urrego, D. H. A1 - Silman, M. R. A1 - Bush, M. B. VL - 20 N1 - id: 458 ER - TY - JOUR T1 - Late neogene and quaternary evolution of the northern Albermarle Embayment (mid-Atlantic continental margin, USA) JF - Marine Geology Y1 - 2005 A1 - Mallinson, D. A1 - Riggs, S. A1 - Culver, S. A1 - Thieler, R. A1 - Foster, D. R. A1 - Corbett, D. R. A1 - Farrell, K. A1 - J, Wehmiller VL - 217 N1 - id: 1160 ER - TY - JOUR T1 - Late-glacial and Holocene record of lake levels of Mathews Pond and Whitehead Lake, northern Maine, USA JF - Journal of Paleolimnology Y1 - 2005 A1 - Dieffenbacher-Krall, A. C. A1 - Nurse, A. M. AB - Paleohydrology studies at Mathews Pond and Whitehead Lake in northern Maine revealed synchronous changes in lake levels from about 12,000 C-14 yrs BP to the present. We analyzed gross sediment structure, organic and carbonate content, mineral grain size, and macrofossils of six cores from each of the two lakes, and obtained 72 radiocarbon dates. Interpretation of this paleo-environmental data suggests that the lateglacial and Younger Dryas climate was dry, and lake levels were low. Early Holocene lake levels were considerably higher but declined for an interval from about 8000 to 7200 14 C yrs BP. Sediment of both lakes contains evidence of a dry period at similar to 7400 C-14 yrs BP (8200 cal yr). Lake levels of both sites declined abruptly about 4800 14 C yrs BP and remained low until 3000 14 C yrs BP. Modern lake levels were achieved only within the past 600 years. The west-to-east, time-transgressive nature of lake-level changes from several sites across northeastern North America suggests periodic changes in atmospheric circulation patterns as a driving force behind observed moisture balance changes. VL - 34 IS - 3 N1 - 953ghTimes Cited:21Cited References Count:81 JO - Late-glacial and Holocene record of lake levels of Mathews Pond and Whitehead Lake, northern Maine, USA ER - TY - JOUR T1 - Late-Quaternary lowstands of lake Bosumtwi, Ghana: evidence from high-resolution seismic-reflection and sediment-core data JF - Palaeogeography Palaeoclimatology Palaeoecology Y1 - 2005 A1 - Brooks, K. A1 - Scholz, C. A. A1 - King, J. W. A1 - Peck, J. A1 - Overpeck, J. T. A1 - Russell, J. M. A1 - Amoako, P. Y. O. AB - Results from the first high-resolution, single-channel seismic-reflection survey of tropical Lake Bosumtwi, Ghana, and sedimentological data from a C-14-dated sediment piston core were used to revise and extend the basin's late-Quaternary lake level history. We report four seismic sequence boundaries and an exposure surface from a sediment core. which are interpreted as erosional surfaces formed at times of drastic low lake level. The youngest erosional surf-ace occurs as much as 31 In below present lake level (bpll) and up to 0.7 in below the present sediment-water interface. This most recent unconformity observed in the seismic data is interpreted to be coeval with the basin-wide late-Holocene dry period between 0.5 and 1 cal ky BP (calendar years before present). Another exposure surface observed in a sediment core is based on an abrupt contact separating low density, wet, clay rich sediments from underlying high density, compact, silt-rich and rootlet-rich sediments, and is interpreted to have developed prior to 16.8 cal ky BP when the lake was similar to60 in bpll. Three older, erosional surfaces occur at depths of similar to92 +/- 3, 102 +/- 3, and 107 +/- 4 in bpll, suggesting numerous lowstands in Lake Bosumtwi during the late-Pleistocene. By extrapolation of average sedimentation rates (0.41 m/ky) from the upper similar to10.5 m of sediment, we estimate the ages of these older lowstands to be similar to65, similar to86 similar to108 cal ky BP. The lowstands of Lake Bosumtwi evidenced from the seismic and sediment core data are interpreted as a response to increased aridity in this part of the equatorial tropics and may correlate to other observed continent-wide shifts in African climate over the past 100 ky and possibly to rapid climatic shifts observed at high latitudes. Determining the precise timing of these lowstands will ultimately reveal much about the drought dynamics of tropical and subtropical Africa. (C) 2004 Elsevier B.V. All rights reserved. VL - 216 IS - 3-4 N1 - 892ujTimes Cited:21Cited References Count:54 JO - Late-Quaternary lowstands of lake Bosumtwi, Ghana: evidence from high-resolution seismic-reflection and sediment-core data ER - TY - JOUR T1 - Latest Holocene evolution and human disturbance of a channel segment in the Hudson River Estuary JF - Marine Geology Y1 - 2005 A1 - Klingbeil, A. D. A1 - Sommerfield, C. K. AB - The latest Holocene sedimentary record of a cohesive channel and subtidal shoal in the lower Hudson River Estuary was examined to elucidate natural (sea-level rise, sediment transport) and anthropogenic (bulkheading, dredging) influences oil the recent morphodynamic evolution of the system. To characterize the seafloor and shallow subbottom, similar to 100 km of high-resolution seismic reflection profiles (chirp) were collected within a 20-km reach of the estuary and correlated with sediment lithologies provided by eight vibracores recovered along seismic lines. Sediment geochronology with Cs-137 and C-14 was used to estimate intermediate and long-term sedimentation rates, respectively, and historical bathyrnetric data were analyzed to identify regional patterns of accretion and erosion, and to quantify changes in channel geometry and sediment volume.The shoal lithosome originated around 4 ka presumably with decelerating eustatic sea level rise during the latest Holocene. Long-term sedimentation rates on the shoal (2.3-2.6 mm/yr) are higher than in the channel (2 mm/yr) owing to hydrodynamic conditions that preferentially sequester suspended sediment on the western side of the estuary. As a result, the shoal accretes oblique to the principal axis of tidal transport, and more rapidly than the channel to produce an asymmetric cross-section. Shoal deposits consist of tidally bedded muds and are stratified by minor erosion surfaces that seismic profiles reveal to extend for I Os of meters to kilometers. The frequency and continuity of these Surfaces suggest that the surficial shoal is catastrophically stripped on decadal-centennial time scales by elevated tidal flows. tidal erosion maintains the shoal at a uniform depth below sea level and prevents it from transitioning to an intertidal environment. Consequently, the long-term sedimentation rate approximates the rate of sea-level rise in the lower estuary (1-3 mm/yr). VL - 218 IS - 1-4 N1 - 942iaTimes Cited:11Cited References Count:49 JO - Latest Holocene evolution and human disturbance of a channel segment in the Hudson River Estuary ER - TY - JOUR T1 - Long range transport of biomass aerosol to Greenland: Multi-spectroscopic investigation of particles deposited in the snow JF - Journal of Radioanalytical and Nuclear Chemistry Y1 - 2005 A1 - Currie, L. A. A1 - Kessler, J. D. A1 - Fletcher, R. A. A1 - Dibb, J. E. AB - Recent developments in radiometrics and mass spectrometry techniques for ultra-sensitive analysis of radionuclides in the marine environment are reviewed. In the radiometrics sector the dominant development has been the utilization of large HPGe detectors in underground laboratories with anti-cosmic or anti-Compton shielding for the analysis of short and medium-lived radionuclides in the environment. In the mass spectrometry sector, applications of inductively coupled plasma mass spectrometry (ICP-MS) and accelerator mass spectrometry (AMS) for the analysis of long-lived radionuclides in the environment are the most important recent achievements. The recent developments do not only considerably decrease the detection limits for several radionuclides (up to several orders of magnitude), but they also enable to decrease sample volumes so that sampling, e.g., of the water column can be much easier and more effective. A comparison of radiometrics and mass spectrometry results for the analysis of radionuclides in the marine environment shows a reasonable agreement - within quoted uncertainties, for wide range of activities and different sample matrices analyzed. VL - 263 IS - 2 N1 - 899oqTimes Cited:2Cited References Count:28 JO - Long range transport of biomass aerosol to Greenland: Multi-spectroscopic investigation of particles deposited in the snow ER - TY - JOUR T1 - Long term calibration of the Noble gas temperature system in a shallow unconfined Pleistocene aquifer JF - Eos Trans. AGU Fall Meeting Supplement Y1 - 2005 A1 - Hall, C. M. A1 - Castro, M. C. A1 - Lohmann, K. C. A1 - Ma, L. VL - 86 IS - 52 N1 - id: 438 ER - TY - JOUR T1 - Late Archean Microbial Ecology: An Integration of Molecular, Isotopic, and Lithologic Studies JF - PH.D. thesis, Earth Sciences, the Pennsylvania State University Y1 - 2004 A1 - Eigenbrode, Jennifer N1 - id: 1581 ER - TY - JOUR T1 - A late Pleistocene-Holocene noble gas paleotemperature record in southern Michigan JF - Geophysical Research Letters Y1 - 2004 A1 - Ma, L. A1 - Castro, M. C. A1 - Hall, C. M. AB - Noble gas temperatures (NGTs) and C-14 derived ages in groundwaters of the Michigan Basin reveal a ground temperature of similar to1degreesC toward the end of the Last Glacial Maximum (LGM) suggesting that groundwater recharge occurred under the Laurentide Ice Sheet (LIS) cover. In addition to the general warming observed since the LGM, the NGT record indicates an abrupt warming event between similar to12.8 and 11.1 kyrs BP, correlative to the Bolling-Allerod (BOA) warm phases. Ice-sheet-linked changes in freshwater delivery to the North Atlantic, together with changes in the North Atlantic Deep Water (NADW) circulation are possible causes of such abrupt climate shifts in northeastern US. Pleistocene waters yielding the lowest NGTs have the highest delta(18)O and deltaD values, suggesting an atmospheric circulation pattern distinct from today, with a stronger moisture component from the Gulf of Mexico, possibly due to the presence of the LIS which weakened the Pacific westerly flow. VL - 31 IS - 23 N1 - 881pcTimes Cited:31Cited References Count:24 JO - A late Pleistocene-Holocene noble gas paleotemperature record in southern Michigan ER - TY - JOUR T1 - Late Quaternary deposition in the Inner Basins of the California Continental Borderland: Part A. Santa Monica Basin JF - U. S. Geological Survey Scientific Investigations Report 2004 Y1 - 2004 A1 - Normark, W. R. A1 - McGann, M. VL - 5183 N1 - id: 417 ER - TY - CHAP T1 - Late Quaternary sedimentation and deformation in Santa Monica and Catalina Basins, offshore southern California T2 - Geology and Tectonics of Santa Cataline Island and the California Continental Borderland Y1 - 2004 A1 - Normark, W. R. A1 - Baher, S. A1 - Sliter, R. ED - Guidebook, South Coast Geological Society Annual Field Trip JF - Geology and Tectonics of Santa Cataline Island and the California Continental Borderland CY - Santa Ana, California N1 - id: 991 ER - TY - THES T1 - Late-glacial climate as inferred from chironomid assemblages in lake sediments from Aroostook County, northeastern Maine Y1 - 2004 A1 - Chase, G. PB - University of Maine CY - Orono, Maine VL - M.S. ER - TY - CONF T1 - Long Island Sound: diatoms from sediment cores as part of environmental and ecological change studies, abstracts T2 - Mid-Atlantic ecology conference: sustainable landscapes Y1 - 2004 A1 - Cooper, S. R. A1 - Thomas, E. A1 - Varekamp, J. C. JF - Mid-Atlantic ecology conference: sustainable landscapes CY - Franklin & Marshall College, Lancaster, PA N1 - id: 735 ER - TY - CHAP T1 - La colonisation et les fortifications de Rapa T2 - Bilan de la recherche archeologique en Polynesie francaise Y1 - 2003 A1 - Kennett, D. J. A1 - Anderson, A. J. A1 - Prebble, M. A1 - Conte, E. ED - Marchesi, H. JF - Bilan de la recherche archeologique en Polynesie francaise PB - Service de la Culture et du Patrimoine CY - Papeete, Tahiti N1 - id: 471 ER - TY - JOUR T1 - Late Holocene earthquakes on the Toe Jam Hill fault, Seattle fault zone, Bainbridge Island, Washington JF - Geological Society of America Bulletin Y1 - 2003 A1 - Nelson, A. R. A1 - Johnson, S. Y. A1 - Kelsey, H. M. A1 - Wells, R. E. A1 - Sherrod, B. L. A1 - Pezzopane, S. K. A1 - Bradley, L. A. A1 - Koehler, R. D. A1 - Bucknam, R. C. AB - Five trenches across a Holocene fault scarp yield the first radiocarbon-measured earthquake recurrence intervals for a crustal fault in western Washington. The scarp, the first to be revealed by laser imagery, marks the Toe Jam Hill fault, a north-dipping backthrust to the Seattle fault. Folded and faulted strata, liquefaction features, and forest soil A horizons buried by hanging-wall-collapse colluvium record three, or possibly four, earthquakes between 2500 and 1000 yr ago. The most recent earthquake is probably the 1050-1020 cal. (calibrated) yr B.P. (A.D. 900930) earthquake that raised marine terraces and triggered a tsunami in Puget Sound. Vertical deformation estimated from strati-graphic and surface offsets at trench sites suggests late Holocene earthquake magnitudes near M7, corresponding to surface ruptures >36 km long. Deformation features recording poorly understood latest Pleistocene earthquakes suggest that they were smaller than late Holocene earthquakes. Postglacial earthquake recurrence intervals based on 97 radiocarbon ages, most on detrital charcoal, range from similar to12,000 yr to as little as a century or less; corresponding fault-slip rates are 0.2 mm/ yr for the past 16,000 yr and 2 mm/yr for the past 2500 yr. Because the Toe Jam Hill fault is a backthrust to the Seattle fault, it may not have ruptured during every earthquake on the Seattle fault. But the earthquake history of the Toe Jam Hill fault is at least a partial proxy for the history of the rest of the Seattle fault zone. VL - 115 IS - 11 N1 - 740qwTimes Cited:41Cited References Count:53 JO - Late Holocene earthquakes on the Toe Jam Hill fault, Seattle fault zone, Bainbridge Island, Washington ER - TY - JOUR T1 - Late-Holocene climate and ecosystem history from Chesapeake Bay sediment cores, USA JF - Holocene Y1 - 2003 A1 - Willard, D. A. A1 - Cronin, T. M. A1 - Verardo, S. AB - Palaeoclimate records from late-Holocene sediments in Chesapeake Bay, the largest estuary in the USA, provide evidence that both decadal to centennial climate variability and European colonization had severe impacts on the watershed and estuary. Using pollen and dinoflagellate cysts as proxies for mid-Atlantic regional precipitation, estuarine salinity and dissolved oxygen (DO) during the last 2300 years, we identified four dry intervals, centred on AD 50 (P1/D1), AD 1000 (P2/D2), AD 1400 (P3) and AD 1600 (P4). Two centennial-scale events, P1/D1 and P2/D2, altered forest composition and led to increased salinity and DO levels in the estuary. Intervals P3 and P4 lasted several decades, leading to decreased production of pine pollen. Periods of dry mid-Atlantic climate correspond to 'megadroughts' identified from tree-ring records in the southeastern and central USA. The observed mid-Atlantic climate variability may be explained by changes in atmospheric circulation resulting in longer-term, perhaps amplified, intervals of meridional flow. After European colonization in the early seventeenth century, forest clearance for agriculture, timber and urbanization altered estuarine water quality, with dinoflagellate assemblages indicating reduced DO and increased turbidity. VL - 13 IS - 2 N1 - 650thTimes Cited:56Cited References Count:101 JO - Late-Holocene climate and ecosystem history from Chesapeake Bay sediment cores, USA ER - TY - JOUR T1 - Late-Quaternary cold events recorded in the Southern Ocean sediments, Pacific Sector JF - Terra Antartica Y1 - 2003 A1 - Langone, L. A1 - Capotondi, L. A1 - Giglio, F. A1 - Focaccia, P. A1 - C, Morigi A1 - Ravaioli, M. VL - 9 N1 - id: 1000 JO - Late-Quaternary cold events recorded in the Southern Ocean sediments, Pacific Sector ER - TY - JOUR T1 - Lipid-Like material as the source of the uncharacterized organic carbon in the ocean? JF - Science Y1 - 2003 A1 - Hwang, Jeomshik A1 - Druffel, Ellen R. M. VL - 299 N1 - id: 530 ER - TY - JOUR T1 - A late glacial-Holocene tephrochronology for glacial lakes in southern Ecuador JF - Quaternary Research Y1 - 2002 A1 - Rodbell, D. T. A1 - Bagnato, S. A1 - Nebolini, J. C. A1 - Seltzer, G. O. A1 - Abbott, M. B. AB - Despite the presence of numerous active volcanoes in the northern half of Ecuador, few, if any, distal tephras have been previously recognized in the southern one third of the country. In this article, we document the presence of thin (0.1-1.0-cm-thick) distal tephras comprising glass and/or phenocrysts of hornblende and feldspar in sediment cores from five glacial lakes and one bog in Las Cajas National Park (2degrees40'-3degrees00'S, 79degrees00'-79degrees25'W). The lake cores contain from 5 to 7 tephras, and each has a diagnostic major element geochemistry as determined from electron microprobe analysis of similar to710 glass shards and similar to440 phenocrysts of feldspar and hornblende. The loss of sodium with exposure to the electron microbeam causes a 10 +/- 7 wt.% (+/-1sigma) reduction in Na content, which we empirically determined and corrected for before correlating tephras among the sediment cores. We use a similarity coefficient to correlate among the sediment cores; pair-wise comparison of all tephras generally yields an unambiguous correlation among the cores. Six tephras can be traced among all or most of the cores, and several tephras are present in only one or two of the cores. Twenty-six accelerator mass spectrometry (14)C dates on macrofossils preserved in the sediment cores provide the basis for establishing a regional tephrochronology. The widespread tephras were deposited similar to9900, 8800,7300,5300,2500, and 2200 cal yr B.P. The oldest tephras were deposited similar to15,500 and 15,100 cal yr B.P., but these are not found in all cores. Two of the tephras appear correlative with volcaniclastic strata on the flanks of Volcan Cotopaxi and one tephra may correlate with strata on the flanks of Volcan Ninahuilca; both volcanoes are in central Ecuador. The absence of tephras in sediment cores correlative with the numerous eruptions of active volcanoes of the past two millennia implies that the earlier eruptions, which did deposit tephras in the lakes, must have been either especially voluminous, or southerly winds must have prevailed at the time of the eruption, or both. (C) 2002 University of Washington. VL - 57 IS - 3 N1 - 555kpTimes Cited:25Cited References Count:23 JO - A late glacial-Holocene tephrochronology for glacial lakes in southern Ecuador ER - TY - JOUR T1 - Late Pleistocene-Holocene paleoceanography and ventilation of the Gulf of California JF - Journal of Oceanography Y1 - 2002 A1 - Keigwin, L. D. AB - Sediment cores collected in 1990 from the Gulf of California have been studied using stable isotope and radiocarbon techniques to reconstruct the climate and ventilation histories since the last glacial maximum. Benthic foraminiferal delta(18)O from core tops in a water depth range of 145 to 1442 m increases by about 2parts per thousand with increasing depth. This is consistent with a composite temperature profile constructed from several hydrocasts in the various gulf basins. However, the delta18O water/salinity relationship is not sufficiently linear in gulf locations or in nearby open Pacific Geochemical Ocean Sections Study (GEOSECS) stations to be useful in solving paleotemperature equations. Of the most common benthic foraminifera, only Planulina ariminensis has delta(13)C that is consistent with the measured delta(13)C of SigmaCO(2). Several cores in the depth range 500 to 900 m have the laminated Holocene and Bolling/Allerod sediments, and the nonlaminated glacial age and Younger Dryas sediments that are typical of the gulf and other locations such as Santa Barbara Basin. The best of those, Jumbo Piston Core (JPC) 56 from 818 m water depth on the western margin of Guaymas Basin, was sampled for intensive study. Oxygen isotope ratios in benthic and planktonic foraminifera show little evidence for deglacial temperature oscillations. Carbon isotope ratios are generally lower during warm epochs, but the most striking result is strongly lowered benthic and planktonic delta(13)C about 9500 years ago. This may reflect water column oxidation of locally released methane. Neither benthic delta(13)C in depth section nor paired benthic and planktonic (14)C data in JPC56 are consistent with increased intermediate water ventilation during the glacial maximum and Younger Dryas. Likewise, (14)C data from 5 pairs of foraminifera from the Okhotsk Sea fail to support better ventilation in that basin during the last glacial maximum. VL - 58 IS - 2 N1 - 554heTimes Cited:53Cited References Count:48 JO - Late Pleistocene-Holocene paleoceanography and ventilation of the Gulf of California ER - TY - CHAP T1 - Late Quaternary sedimentation and climate in the Lake Edward and George area, Uganda-Congo T2 - The East African Great Lakes: Limnology, Palaeolimnology, and Biodiversity Y1 - 2002 A1 - Laerdal, T. A1 - Talbot, M. R. A1 - Russell, J. M. ED - Olago, D. JF - The East African Great Lakes: Limnology, Palaeolimnology, and Biodiversity PB - Kluwer Academic Publishers CY - Dordrecht, The Netherlands N1 - id: 1012 ER - TY - JOUR T1 - Late-Quaternary lowstands of Lake Titicaca: evidence from high-resolution seismic data JF - Palaeogeography Palaeoclimatology Palaeoecology Y1 - 2002 A1 - D'Agostino, K. A1 - Seltzer, G. A1 - Baker, P. A1 - Fritz, S. A1 - Dunbar, R. KW - Andes KW - bolivian altiplano KW - central andes KW - climatic-change KW - Holocene KW - lacustrine KW - lake level change KW - lake titicaca KW - level KW - malawi KW - Peru KW - record KW - seismic reflection data KW - tropical paleoclimate KW - tropical south-america AB - Approximately 600 km of high-resolution seismic reflection data were collected to investigate the late-Quaternary stratigraphic development of Lake Titicaca. The focus of this report is on two seismic sequence boundaries, which are interpreted as erosional surfaces formed at times of low lake level. The younger erosional surface occurs as much as 90 in below the present lake level and up to 8 in below the present sediment-water interface. This erosional surface is interpreted to be coeval with a well-documented early- to mid-Holocene lowstand, dated between similar to 8000 and 3600 cal yr BP. An earlier and previously unknown erosional surface occurs at a sub-bottom depth of approximately 30 m, and as much as 240 in below the present lake level, which implies a major late-Pleistocene lowstand of Lake Titicaca. By extrapolation of sedimentation rates from the upper similar to 14 in of sediment, we estimate the age of this older lowstand at > 90 000 cal yr BP. Both lowstands of Lake Titicaca indicated by the seismic data are likely to have been a response to climatic change in the region. (C) 2002 Elsevier Science B.V. All rights reserved. VL - 179 SN - 0031-0182 IS - 1-2 N1 - 560qxTimes Cited:31 Cited References Count:33 JO - Palaeogeogr Palaeocl ER - TY - CHAP T1 - The limits of paleontological resolution T2 - High Resolution Approachews in Paleontology: Kluwer Academic/Plenum Y1 - 2002 A1 - Kowalewski, M. A1 - Bambach, R. K. ED - Harries, P. J. JF - High Resolution Approachews in Paleontology: Kluwer Academic/Plenum T3 - Topic in Geobiology CY - New York N1 - id: 1415 ER - TY - RPRT T1 - Linking vertical advection and diet to juvenile salmon condition and parasite load: A study using 14C, 13C, and 15N Y1 - 2002 A1 - Casillas, E. A1 - Rau, G. H. A1 - al, et ED - Abstract, Ocean Sciences Meeting JF - Transactions, American Geophysical Union N1 - id: 1142 ER - TY - JOUR T1 - Los Cerritos: an early fishing-farming community on the Pacific Coast of Mexico JF - Antiquity Y1 - 2002 A1 - Kennett, D. J. A1 - Voorhies, B. A1 - McClure, S. B. VL - 76 N1 - id: 473 ER - TY - JOUR T1 - The last interglacial to glacial transition, Togiak Bay, Southwestern Alaska JF - Quaternary Research Y1 - 2001 A1 - Kaufman, D. S. A1 - Manley, W. F. A1 - Wolfe, A. P. A1 - Hu, F. S. A1 - Preece, S. J. A1 - Westgate, J. A. A1 - Forman, S. L. AB - An 18-m-high coastal bluff at Togiak Bay (northwestern Bristol Bay, southwestern Alaska) exposes marine, lacustrine, fluvial, glacial, volcanic, and organic deposits that record the ∼50,000-year-long transition from the peak of the last interglaciation to the early Wisconsin glaciation. The base of the section is dominated by stratified sand and silt extending up to 4.3 m above sea level; marine diatoms are present, and pollen assemblages are characterized by relatively high percentages of Picea, Alnus, and Betula and low percentages of Poaceae and Cyperaceae. The marine sediment was probably deposited during the peak of marine oxygen-isotope stage (OIS) 5e. An infrared stimulated luminescence (IRSL) age of 151,000±13,000 yr from near the base of the exposure is permissive of this correlation. The marine sand and silt are overlain by 0.8 m of peaty silt with diatoms that record a transition from marine to lacustrine conditions. During this interval, Poaceae and Cyperaceae dominate the pollen assemblages, and Picea and shrubs are nearly absent, suggesting that herb tundra occupied the landscape. This interval probably encompasses OIS 5d on the basis of the herb tundra and an IRSL age of 119,000±10,000 yr from 60 cm below the marine/lacustrine transition. The organic mud is overlain by 3.1 m of stratified sand and organic silt that apparently record shallowing of the lake; reappearance of spruce and shrubs (=OIS 5c?); and subsequent deepening of the lake (=OIS 5b?); followed by aggradation of a floodplain (=OIS 5a?), which was dry at the time basaltic lava buried the site. Thermoluminescence analyses on lava-baked sediment indicate that the eruption occurred 70,000±10,000 yr ago. Sometime thereafter, but prior to 53,600 14C yr B.P. an outlet of the Ahklun Mountains ice cap advanced over the site and deposited ∼7 m of bouldery ice-contact drift. The sedimentary sequence contains at least four tephra beds. Major- and trace-element chemistry provide a basis for correlating two of the tephras with tephra beds at nearby sites. The tephras, luminescence ages, and correlations with marine isotope stages provide the geochronological control to place the Togiak Bay section into a global context. The site serves as an important new reference section for late Pleistocene paleoenvironmental change in eastern Beringia. VL - 55 IS - 2 N1 - id: 1392 JO - The last interglacial to glacial transition, Togiak Bay, Southwestern Alaska ER - TY - JOUR T1 - Late quaternary climate and hydrology of tropical South America inferred from an isotopic and chemical model of Lake Titicaca, Bolivia and Peru JF - Quaternary Research Y1 - 2001 A1 - Cross, S. L. A1 - Baker, P. A. A1 - Seltzer, G. O. A1 - Fritz, S. C. A1 - Dunbar, R. B. AB - A simple mass balance model provides insight into the hydrologic, isotopic, and chemical responses of Lake Titicaca to past climatic changes. Latest Pleistocene climate of the Altiplano is assumed to have been 20% wetter and 5 degreesC colder than today, based on previous modeling. Our simulation of lacustrine change since 15,000 cal yr B.P. is forced by these modeled climate changes. The latest Pleistocene Lake Titicaca was deep, fresh, and overflowing. The latest Pleistocene riverine discharge from the lake was about 8 times greater than the modern average, sufficient to allow the expansion of the great paleolake Tauca on the central Altiplano. The lake delta O-18 value averaged about -13 parts per thousand SMOW (the modern value is about -4.2 parts per thousand). The early Holocene decrease in precipitation caused Lake Titicaca to fall below its outlet and contributed to a rapid desiccation of paleolake Tauca. Continued evaporation caused the 100-m drop in lake level, but only a slight(1-2 parts per thousand) increase (relative to modern) in delta O-18 Of early Holocene lake waters. This Holocene lowstand level of nearly 100 m was most likely produced by a precipitation decrease, relative to modern, of about 40%, The lake was saline as recently as 2000 cal yr B.P. The timing of these hydrologic changes is in general agreement with calculated changes of insolation forcing of the South American summer monsoon, (C) 2001 University of Washington. VL - 56 IS - 1 N1 - 452lzTimes Cited:50Cited References Count:46 JO - Late quaternary climate and hydrology of tropical South America inferred from an isotopic and chemical model of Lake Titicaca, Bolivia and Peru ER - TY - JOUR T1 - Late Quaternary water-level variations and vegetation history at Crooked Pond, southeastern Massachusetts JF - Quaternary Research Y1 - 2001 A1 - Shuman, B. A1 - Bravo, J. A1 - Kaye, J. A1 - Lynch, J. A. A1 - Newby, P. A1 - Webb, T. AB - Sediment cores collected along a transect in Crooked Pond, southeastern Massachusetts, provide evidence of water-level changes between 15,000 cal yr B.P. and present. The extent of fine-grained, detrital, organic accumulation in the basin, inferred from sediment and pollen stratigraphies, varied over time and indicates low water levels between 11,200 and 8000 cal yr B.P. and from ca. 5300 to 3200 cal yr B.P. This history is consistent with the paleohydrology records from nearby Makepeace Cedar Swamp and other sites from New England and eastern Canada and with temporal patterns of regional changes in effective soil moisture inferred from pollen data. The similarities among these records indicate that (1) regional conditions were drier than today when white pine (Pinus strobus) grew abundantly in southern New England (11,200 to 9500 cal yr B.P.); (2) higher moisture levels existed between 8000 and 5500 cal yr B.P., possibly caused by increased meridonal circulation as the influence of the Laurentide ice sheet waned; and (3) drier conditions possibly contributed to the regional decline in hemlock (Tsuga) abundances at 5300 cal yr B.P. Although sea-level rise may have been an influence, moist climatic conditions during the late Holocene were the primary reason for a dramatic rise in water-table elevations. (C) 2001 University of Washington. VL - 56 IS - 3 N1 - id: 1379; 493FU Times Cited:43 Cited References Count:41 JO - Late Quaternary water-level variations and vegetation history at Crooked Pond, southeastern Massachusetts ER - TY - JOUR T1 - Lake Erie: The Impact of Mid-Holocene Flooding by Upper Great Lake Waters JF - EOS, Transactions, American Geophysical Union Y1 - 2000 A1 - Kempthorne, R. A. A1 - Barrera, E. A1 - Coakley, J. P. A1 - Palmer, D. F. VL - 81 IS - 19 N1 - id: 248 ER - TY - JOUR T1 - Late glacial paleohydrology and vegetational change in Salada Medinana, Central Ebro Basin, Spain JF - Quarternary International Y1 - 2000 A1 - Valero-Garces, B. L. VL - 73/74 N1 - id: 382 ER - TY - JOUR T1 - A late Holocene pollen record from Torrey Pine State Reserve, California JF - Quaternary Research Y1 - 2000 A1 - Cole, K. L. A1 - Wahl, Eugene VL - 53 N1 - id: 214 ER - TY - CHAP T1 - Late Pleistocene and Holocene geological evolution of the central Penobscot River Valley: Surficial geology, geoarchaeology, and water supply (Book Section) T2 - Guidebook for Field Trips in Coastal and East-Central Maine: NEIGC 92nd Annual Meeting Y1 - 2000 A1 - Kelly, A. R. A1 - Dorion, C. C. A1 - Balco, G. A1 - Dieffenbacher-Krall, A. A1 - Garrett, P. A1 - Locke, D. A1 - Tolman, A. ED - Yates, M. G. JF - Guidebook for Field Trips in Coastal and East-Central Maine: NEIGC 92nd Annual Meeting CY - Orono, ME N1 - id: 152 ER - TY - CONF T1 - Late Quaternary sedimentary fluctuations of biogenic fluxes driven by climatic changes in the Southern Ocean--abstract T2 - XXV General Assembly of European Geophysical Society Y1 - 2000 A1 - Langone, L. A1 - Giglio, F. A1 - Ravaioli, M. A1 - Frignani, M. A1 - Marozzi, G. A1 - Rovatti, G. JF - XXV General Assembly of European Geophysical Society CY - Nice, France N1 - id: 288 ER - TY - JOUR T1 - Lipids as a Common Interest of Microorganisms and Geochemists (Commentary) JF - Proc. National Academy Sciences USE Y1 - 2000 A1 - Hayes, John M. VL - 98 N1 - id: 1778 ER - TY - CHAP T1 - Lomas de ocupacion en los Llanos de Moxos (Book Section) T2 - La Arqueologia de las Tierras Bajas Y1 - 2000 A1 - Erickson, Clark L. ED - Duran Coirolo, Alicia JF - La Arqueologia de las Tierras Bajas PB - Comision Nacional de Arqueologia, Ministerio de Educacion y Cultura CY - Montevideo, Uruguay N1 - id: 180 ER - TY - CHAP T1 - Los caminos prehispanicos de la amazonia boliviana (Book Section) T2 - Vias Precolombinas: los caminos, los ingenieros y los viajeros Y1 - 2000 A1 - Erickson, Clark L. ED - Herrera, Leonor JF - Vias Precolombinas: los caminos, los ingenieros y los viajeros PB - Instituto Colombiano de Antropología y Historia CY - Bogata, Colombia N1 - id: 179 ER - TY - JOUR T1 - Low-level (submicromole) environmental 14C metrology JF - Nucl. Instr. and Meth. in Phys. Res. Y1 - 2000 A1 - Currie, L. A. A1 - Kessler, J. D. A1 - Marolf, J. V. A1 - McNichol, A. P. A1 - Stuart, D. R. A1 - Donoghue, J. C. VL - B IS - 172 N1 - id: 1713 ER - TY - CONF T1 - The Last Deglaciation in Southern Chile T2 - Development of Paleoceanography as a New Field of Science Y1 - 1999 A1 - Anderson, D. M. A1 - Archer, R. B. JF - Development of Paleoceanography as a New Field of Science CY - Stockholm VL - 27 N1 - id: 145 ER - TY - JOUR T1 - Late Pleistocene-Holocene sea-level change and the New Jersey coastline JF - Trans. Am. Geophys. Un. Y1 - 1999 A1 - Miller, K. G. A1 - Sugarman, P. J. A1 - Sheridan, R. E. A1 - Ashley, G. M. IS - Spring Meeting, 1999 N1 - id: 163 ER - TY - JOUR T1 - Late Quaternary stratigraphy of Marresale, Yamal Peninsula, Russia: new constraints on the footprint of the Eurasian ice sheet JF - Geology Y1 - 1999 A1 - Forman, S. L. A1 - Ingolfsson, O. A1 - Manley, W. F. A1 - Lokrantz, H. VL - 27 N1 - id: 370 ER - TY - JOUR T1 - Late Quaternary stratigraphy, Paleoclimate and neotectonism of the Persian (Arabian) Gulf region JF - Marine Geology Y1 - 1999 A1 - Uchupi, E. A1 - Swift, S. A. A1 - Ross, D. A. AB - The last glacial deposits in the Persian (Arabian) Gulf consist of a > 22,000 year old paralic terrigenous sequence in the Mesopotamia Shelf, the foredeep in front of the Iranian Zagros Mountains and the northern side of the Biaban Shelf. Elsewhere, the Gulf, and probably the Biaban Shelf, were mantled by > 30,000 year old carbonates. Comparison of C-14 data from foraminifera from the last glacial terrigenous unit in the foredeep off Iran with curves published by Hopley [Hopley, D., 1982. The Geomorphology of the Great Barrier Reef: Quaternary Development of Coral Reefs. Wiley, New York, 453 pp.] and Chapell et al. [Chapell, J., Omura, A., Tezer, E., McCulloch, M., Pandolfi, J., Ota, Y., Pillans, B., 1996. Reconciliation of late Quaternary sea levels derived from coral terraces at Huon Peninsula with deep sea oxygen isotope records. Earth Planet. Sci. Lett. 141, 227-236.] indicates that the region may have experienced uplift during the last glacial, whereas other geologic data indicate that the foredeep has had a history of continuous subsidence during the Cenozoic. A possible explanation for this discrepancy is that the foraminifera analyzed are not in place, but were reworked into shallower water during the Holocene transgression. However, the foraminifera analyzed do not display any evidence of wear, indicating that such transport was limited. A third alternative is that sea level during the last glacial was much higher than indicated by the curves of Hopley and Chapell et al.At the peak of the last glaciation 21,000 to 20,000 years ago, when sea level was 120 m lower than now, the Gulf was a waterless basin and deposition was negligible. On the Biaban Shelf, the Holocene transgressive sequence resting unconformably on last glacial sediments consists of 14,000 year old carbonates, a > 11,000 year old terrigenous delta on the northern end of the Biaban Shelf and 11,000-10,000 year old intertidal-tidal aragonite deposited in a dry climate. On the northeast side of the Gulf, the last glacial sediments are covered by 10,000 to 7000 year old aragonite muds (younging toward the northwest). Resting on the aragonites on the Biaban Shelf and on the northeast and northwest sides of the Gulf are marls deposited under the present humid climate. The southwest side of the Gulf continued to be a site of carbonate deposition throughout the Holocene. Comparison of AMS C-14 measurements of the late Holocene marls with the sea level curve of Fairbanks [Fairbanks, R.G., 1989. A 17,000 year glacio-eustatic sea level record; influence of glacial melting rates and the Younger Dryas event and deep-ocean circulation. Nature 342, 637-642.] indicates that the axial zone of the Gulf off Iran experienced subsidence during the Holocene. This subsidence coupled with a rapid rise in sea level during a major glacial melt 9500 to 8500 years ago, when global sea level rose from -50 to -28 m, led to the replacement of marl with a shallow (8-25 m) water fauna by a 'deep' (> 50 m) water one. Similar measurements and other geologic data indicate that the Mesopotamia Shelf and the mouth of the Mesopotamian Depression on the northwest side of the Gulf underwent both subsidence and uplift during the Cenozoic. These vertical oscillations, however, were more subdued than these in the foredeep off iran. The Arabian Shelf along the Gulfs southwest side appears to have experienced minor uplift during the Cenozoic. (C) 1999 Elsevier Science B.V. All rights reserved. VL - 160 IS - 1-2 N1 - 214vaTimes Cited:31Cited References Count:58 JO - Late Quaternary stratigraphy, Paleoclimate and neotectonism of the Persian (Arabian) Gulf region ER - TY - CONF T1 - Late Wisconsian deep-sea sedimentary record from convulsive geologic events, Northeast Pacific T2 - IAS 19 Regional Meeting of Sedimentology Y1 - 1999 A1 - Serra, Francesca A1 - Normark, William R. A1 - Zuffa, Gian Gaspare A1 - Brunner, Charlotte A. JF - IAS 19 Regional Meeting of Sedimentology CY - Copenhagen VL - Abstracts N1 - id: 1471 ER - TY - JOUR T1 - Linking the 10Be continental record of Lake Baikal to marine and ice archives for the last 50 ka: Implication for the global dust-aerosol input JF - Geophysical Research Letters Y1 - 1999 A1 - Aldahan, A. A1 - Possnert, G. A1 - Peck, J. A1 - King, J. A1 - Colman, S. AB - We present here a 10Be profile from the continental sediments of Lake Baikal (the world's largest fresh water lake), which, for the first time, shows the ≈ 40 ka 10Be enhancement and a pattern that strongly matches those from the marine and ice records for the last 50 ka. This finding provides a new horizon for global and regional correlation of continental archives. Additionally, our VADM-predicted 10Be production confirms and further strengthens a common global cause (geomagnetic field intensity) for the change in atmospheric 10Be over the last 50 ka. We also show that most of the 10Be inventory to the lake has been provided by riverine input, but with a significant addition from direct precipitation and dust-aerosol fallout. We estimate a higher dust-aerosol contribution of 10Be during the Holocene and interstadial stage 3 (22–50 ka) as compared with the glacial period (12–22 ka). VL - 26 N1 - id: 1353 JO - Linking the 10Be continental record of Lake Baikal to marine and ice archives for the last 50 ka: Implication for the global dust-aerosol input ER - TY - JOUR T1 - Long-term fluxes and budget of ferric iron: implication for the redox states of the Earth's mantle and atmosphere JF - Earth and Planetary Science Letters Y1 - 1999 A1 - Lecuyer, C. A1 - Ricard, Y. AB - Net flux of ferric iron from the subducted oceanic crust to the mantle has been estimated to constrain the evolution of the redox state of the Earth's mantle. The main mechanism responsible for the transfer of ferric iron towards the mantle is the production of magnetite during the hydrothermal alteration of the oceanic crust. Both modeling and compilation of chemical data lead to a flux of 21 x 10(3) kg s(-1) of ferric iron transported by the subducted oceanic crust. The net flux of ferric iron towards the deep mantle is estimated to be 12 x 10(3) kg s(-1) when corrected from the production rates of basic magmas at oceanic ridges, island arcs, and hot spots. We discuss several hypotheses. Ferric iron could react at depth with reduced species that buffer the redox state of the mantle to its present-day value. One possible mechanism could be the reaction of this ferric iron with the core that would have been reduced by only 500 m since 2 Ga. At the opposite, we may also consider that ferric iron accumulates in the deep mantle, being possibly accepted by the structure of spinel, garnet, and perovskite. The transfer of ferric iron from subducted slabs to the mantle contributes from 10 to 25% in the global budget of the ferric iron component of the mantle. The long-term loss of ferric iron from the Earth's surface may be considered as a plausible mechanism to regulate the photosynthetic production of molecular oxygen. (C) 1999 Elsevier Science B.V. All rights reserved. VL - 165 IS - 2 N1 - 160gtTimes Cited:87Cited References Count:66 JO - Long-term fluxes and budget of ferric iron: implication for the redox states of the Earth's mantle and atmosphere ER - TY - CONF T1 - Late Holocene climatic variability in Central America: evidence from lacustrine sediments in the Peten, Guatemala and implications for Maya cultural evolution; Procedings of the PEP 1 T2 - PEP 1 (Pole-Equator-Pole, Paleoclimate of the Americas) Y1 - 1998 A1 - Rosenmeier, M. F. A1 - Hodell, D. A. A1 - Martin, J. B. A1 - Brenner, M. A1 - Curtis, J. H. JF - PEP 1 (Pole-Equator-Pole, Paleoclimate of the Americas) CY - Merida, Venezualla N1 - id: 141 ER - TY - CONF T1 - Late Pleistocene Mammuthus primigenious from coastal mMaine T2 - 33rd annual meeting, Geological Society of America, Northeastern Section Y1 - 1998 A1 - Hoyle, B. G. A1 - Fisher, D. C. A1 - Dorion, C. C. A1 - Churchill, L. L. A1 - W, Borns H., Jr. A1 - Nelson, R. E. JF - 33rd annual meeting, Geological Society of America, Northeastern Section PB - Geological Society of America CY - Portland, ME N1 - id: 21 ER - TY - JOUR T1 - Le torbiditi dell'Escanaba Trough (Juan de Fuca Plate, Pacifico nordorientale): registrazione sedimentaria di piene fluviali catastrofiche del Fiume Columbia durante le fasi di deglaciazione tardo quaternaria JF - Giornale di Geologia Y1 - 1998 A1 - Brunner, C. A. A1 - Normark, W. R. A1 - Zuffa, G. G. A1 - Serra, F. VL - 60 N1 - id: 1470 JO - Le torbiditi dell'Escanaba Trough (Juan de Fuca Plate, Pacifico nordorientale): registrazione sedimentaria di piene fluviali catastrofiche del Fiume Columbia durante le fasi di deglaciazione tardo quaternaria ER - TY - CONF T1 - Late Plains Woodland Occupation of the Kirschenman III Site in the James River Valley, North Dakota T2 - 1997 Plains Conference, 55th Annual Meeting of the Plains Anthropological Society Y1 - 1997 A1 - Toom, Dennis L. JF - 1997 Plains Conference, 55th Annual Meeting of the Plains Anthropological Society CY - Boulder, CO N1 - id: 204 ER - TY - CHAP T1 - Late Quaternary climate, fire, and vegetation dynamics (Book Section) T2 - Sediment Records of Biomass Burning and Global Change Y1 - 1997 A1 - Winkler, M. G. ED - Clark, J. S. JF - Sediment Records of Biomass Burning and Global Change PB - Springer-Verlag CY - Berlin N1 - id: 134 ER - TY - THES T1 - Late quaternary evolution of the Central Texas shelf: Sequence Stratigraphic Implications, Thesis Y1 - 1997 A1 - Eckles, Brenda AB - This study documents the evolution of the interdeltaic central Texas continental shelf over the last 350,000 years. The dataset consists of high-resolution seismic data, platform boring descriptions, oxygen isotope analyses, and radiocarbon dates. A strong correlation exists between seismic facies and lithofacies enabling seven stages of evolution to be mapped. The distribution of these facies is primarily controlled by fourth-order glacio-eustatic cycles. Seismic stratigraphy, oxygen isotope analyses, and radiocarbon dating were integrated to develop an independent sea-level curve for the area. Longshore and surface currents transport large volumes of sand into the area which is deposited as widespread, thick $(>$10 meters) barrier-bar highstand sand bodies on the inner shelf. Sediments are deposited and preserved in a repetitive manner during each glacio-eustatic cycle. This implies a predictable pattern of deposition, therefore, allowing for the development of depositional models that can be applied to ancient deposits in the exploration for hydrocarbons. VL - Dissertation/Thesis ER - TY - JOUR T1 - Late Quaternary Western Atlantic Paleoceanography and terrigenous sedimentation on the Amazon Fan: a view from delta d180 and d13C of planktonic foraminifera and bulk organic matter d13C JF - Proceedings of the Ocean Drilling Program: Scientific Results Y1 - 1997 A1 - Schneider, R. R. A1 - Muller, P. J. A1 - Schlunz, B. A1 - Segl, M. A1 - Showers, W. J. A1 - Wefer, G. VL - 155 N1 - id: 1278 ER - TY - JOUR T1 - Lignin phenols in sediments of Lake Baikal, Siberia: application to paleoenvironmental studies JF - Organic Geochemistry Y1 - 1997 A1 - Orem, W. H. A1 - Colman, S. M. A1 - Lerch, H. E. AB - Sediments from three cores obtained from distinct depositional environments in Lake Baikal, Siberia were analyzed for organic carbon, total nitrogen and lignin phenol concentration and composition. Results were used to examine changes in paleoenvironmental conditions during climatic cycles of the late Quaternary (<125 ka). Average organic carbon, and total nitrogen concentrations, atomic C/N ratios and organic carbon accumulation rates were significantly higher in the Holocene compared with the late Pleistocene, reflecting overall warmer temperatures and increased runoff during the Holocene. A Holocene maximum in organic carbon was observed at about 6 ka, and may represent the warmest/wettest period of the Holocene. At one site (Academician Ridge) pronounced late Pleistocene maxima in organic carbon and biogenic silica were observed at about 80-85 ka, probably indicative of an interstadial period with enhanced aquatic productivity. Total sedimentary lignin phenol contents were generally lower in the late Pleistocene compared to the Holocene, but with several peaks in concentration during the late Pleistocene. These late Pleistocene peaks in total sedimentary lignin content (dated at about 80, 50 and 30 ka) directly precede or occur during peaks in sedimentary biogenic silica contents. These periods likely represent relatively warm interstadial times, with increased precipitation producing the observed increase in terrestrial runoff and aquatic productivity. Lignin phenol ratios (S/V, C/V and P/V) were used to examine changes in terrestrial vegetation type resulting from changes in paleoenvironmental conditions during the late Pleistocene. A degree of caution must be used in the interpretation of these ratios with regard to vegetation sources and paleoenvironmental conditions, because of potential compositional changes in lignin resulting from biodegradation. Nevertheless, results show that long glacial periods were characterized by terrestrial vegetation composed of a mix of non-woody angiosperm vegetation and minor gymnosperm forest. Shorter interstadial periods are defined by a change to dominant gymnosperm forest and were observed at about 80, 75, 63, 50 and 30 ka, ranging from about 2-6 kyr in duration. These interstadial periods of the late Pleistocene defined by lignin phenol ratios generally occur during longer periods of enhanced sedimentary biogenic silica content (about 10-15 ka in duration), providing corroborative evidence of these warm interstadial periods. (C) 1997 Elsevier Science Ltd. VL - 27 IS - 3-4 N1 - Yq252Times Cited:29Cited References Count:61 JO - Lignin phenols in sediments of Lake Baikal, Siberia: application to paleoenvironmental studies ER - TY - CONF T1 - The "Lake" of Mayran: Reconstructing an Environmental History from Alluvial, Lacustrine, and Soils Records in Northern Mexico T2 - Annual Meeting, Sociedad Mexicana de Antropologia Y1 - 1996 A1 - Butzer, K. W. Frederick C. D. Cordova C. E. Butzer E. K. Abbott y J. T. JF - Annual Meeting, Sociedad Mexicana de Antropologia CY - Tepic (Noyarit) N1 - id: 903; Symposium: "El Hombre y el Lago: Ayer y Hoy" ER - TY - JOUR T1 - Large-volume WOCE radiocarbon sampling in the Pacific Ocean JF - Radiocarbon Y1 - 1996 A1 - Stuiver, M. A1 - Ostlund, H. G. A1 - Key, R. M. A1 - Reimer, P. J. KW - geosecs AB - At the University of Miami Tritium Laboratory and the University of Washington Quaternary Isotope Laboratory, more than 1000 large-volume Pacific Ocean radiocarbon samples were measured for the WOCE program. Here we present a comprehensive data set, and a brief discussion of our findings. VL - 38 SN - 0033-8222 IS - 3 N1 - Xd080Times Cited:12 Cited References Count:8 JO - Radiocarbon ER - TY - JOUR T1 - Late holocene coastal plain stratigraphy and sea-level history at Hanalei, Kauai, Hawaiian islands JF - Quaternary Research Y1 - 1996 A1 - Calhoun, R. S. A1 - Fletcher, C. H. AB - Fluvial, marine, and mixed fluvial-marine deposition on the coastal plain of Hanalei Bay on the north shore of Kauai, Hawaii, records a middle- to late-Holocene fall of relative sea level. Radiocarbon dating of the regression boundary preserved in the stratigraphy of the coastal plain documents a seaward shift of the shoreline beginning at least 4800-4580 cal yr B.P. and continuing until at least 2160-1940 cal yr B.P. Marine sands stranded in the backshore and coastal plain environment are buried by fluvial floodplain and channel sands, silts, and muds. In places, erosion at the regression contact exposed older marine sands thus increasing the hiatus at the regression disconformity, The shoreline regression is best explained as the result of a fall in relative sea level. The age and elevation of the cored regression boundary at sites that have not been influenced by erosion are consistent with a middle-to late-Holocene highstand of relative sea level as predicted by geophysical models of whole Earth deformation related to deglaciation. (C) 1996 University of Washington. VL - 45 IS - 1 N1 - Uf728Times Cited:21Cited References Count:35 JO - Late holocene coastal plain stratigraphy and sea-level history at Hanalei, Kauai, Hawaiian islands ER - TY - CHAP T1 - Late Quaternary deep circulation in the western equatorial Atlantic (Book Section) T2 - The South Atlantic: Present and Past Circulation Y1 - 1996 A1 - Curry, W. B. ED - Berger, W. JF - The South Atlantic: Present and Past Circulation N1 - id: 1336 ER - TY - THES T1 - Late Quaternary stratigraphy, sea-level history and paleoclimatology of the southeast Florida outer continental shelf, Thesis Y1 - 1996 A1 - Toscano, M. A. PB - University of South Florida CY - St. Petersburg, FL VL - Unpublished Ph.D. dissertation ER - TY - JOUR T1 - The Little Ice Age and Medieval Warm Period in the Sargasso Sea JF - Science Y1 - 1996 A1 - Keigwin, L. D. AB - Sea surface temperature (SST), salinity, and flux of terrigenous material oscillated on millennial time scales in the Pleistocene North Atlantic, but there are few records of Holocene variability. Because of high rates of sediment accumulation, Holocene oscillations are well documented in the northern Sargasso Sea. Results from a radiocarbon-dated box core show that SST was approximately 1°C cooler than today approximately 400 years ago (the Little Ice Age) and 1700 years ago, and approximately 1°C warmer than today 1000 years ago (the Medieval Warm Period). Thus, at least some of the warming since the Little Ice Age appears to be part of a natural oscillation. VL - 274 SN - 1095-9203 (Electronic)0036-8075 (Linking) UR - https://www.ncbi.nlm.nih.gov/pubmed/8929406 IS - 5292 N1 - Keigwineng 1996/11/29 Science. 1996 Nov 29;274(5292):1504-8. ER - TY - JOUR T1 - A long pollen record from lowland Amazonia: Forest and cooling in glacial times JF - Science Y1 - 1996 A1 - Colinvaux, P. A. A1 - DeOliveira, P. E. A1 - Moreno, J. E. A1 - Miller, M. C. A1 - Bush, M. B. AB - A continuous pollen history of more than 40,000 years was obtained from a lake in the lowland Amazon rain forest. Pollen spectra demonstrate that tropical rain forest occupied the region continuously and that savannas or grasslands were not present during the last glacial maximum. The data suggest that the western Amazon forest was not fragmented into refugia in glacial times and that the lowlands were not a source of dust. Glacial age forests were comparable to modern forests but also included species now restricted to higher elevations by temperature, suggesting a cooling of the order of 5 degrees to 6 degrees C. VL - 274 IS - 5284 N1 - Vk748Times Cited:350Cited References Count:42 JO - A long pollen record from lowland Amazonia: Forest and cooling in glacial times ER - TY - JOUR T1 - Late Pleistocene Oxygen-Isotope Records of Biogenic Silica from the Atlantic Sector of the Southern-Ocean JF - Paleoceanography Y1 - 1995 A1 - Shemesh, A. A1 - Burckle, L. H. A1 - Hays, J. D. AB - We determined the isotopic composition of oxygen in marine diatoms in eight deepsea cores recovered from the Atlantic sector of the Southern Ocean. The analytical reproducibility and core-to-core consistency of the isotopic signal suggests that diatom delta(18)O can be used as a new paleocenographic tool to reconstruct past variations in surface water characteristics and to generate O-18 -isotope-based stratigraphy for the Southern Ocean. The data indicate that diatom delta(18)O reflects sea surface temperature and seawater isotopic composition and that diatoms retain their isotopic signal on timescales of a least 430 ka. The delta(18)O analyses of different diatom assemblages reveal that the isotopic signal is free of species effects and that the common Antarctic species have the same water-opal fractionation. The transition from the last glacial maximum (LGM) to the Holocene is fully recorded in high sedimentation rate cores. An O-18 enrichment during the LGM, a post-LGM meltwater spike and an input of meltwater during the late Holocene are the main isotopic features observed in down core records. The origin of this meltwater was very likely melting icebergs and/or continental ice or by melting sea ice that had accumulated snow. The most pronounced meltwater effects are recorded in cores that are associated with the Weddel gyre. Our results provide the basis for extending isotope studies to oceanic regions devoid of carbonate; further, isotopic stratigraphies may be constructed for records and regions where they were previously not possible. VL - 10 IS - 2 N1 - Rd382Times Cited:82Cited References Count:23 JO - Late Pleistocene Oxygen-Isotope Records of Biogenic Silica from the Atlantic Sector of the Southern-Ocean ER - TY - CONF T1 - Late Pleistocene to Holocene Diatom Assemblages of the Lake Winnebago Basin, Wisconsin T2 - North-Central/South-Central Section, Geological Society of America Y1 - 1995 A1 - Smith, S. R. Smith G. L. JF - North-Central/South-Central Section, Geological Society of America CY - Lincoln, Nebraska VL - 27 N1 - id: 915 ER - TY - JOUR T1 - Late Pleistocene to Holocene paleolimnolgy of the Lake Winnebago Basin, based on ostracods JF - Abstracts with Programs - Geological Society of America Y1 - 1995 A1 - Gruber, M. M. A1 - Smith, G. L. VL - 27 IS - 3 N1 - id: 75 ER - TY - CONF T1 - Late Pleistocene to Holocene Paleolimnology of the Lake Winnebago Basin, Based on Ostracods T2 - North-Central/South-Central Section,Geological Society of America Y1 - 1995 A1 - Gruber, M. M. A1 - Smith, G. L. JF - North-Central/South-Central Section,Geological Society of America CY - Lincoln, Nebraska VL - 27 N1 - id: 909 ER - TY - CONF T1 - Late Quaternary Depositional History of the Lake Winnebago Basin T2 - North-Central/South_Central Section, Geological Society of America Y1 - 1995 A1 - Fitzgerald, T. M. A1 - Smith, G. L. JF - North-Central/South_Central Section, Geological Society of America CY - Lincoln, Nebraska VL - 27 N1 - id: 908 ER - TY - JOUR T1 - Late Quaternary Paleolimnology of the Lake Winnebago Basin, Based on Ostracodes Y1 - 1995 A1 - Gruber, M. M. Smith G. L. N1 - id: 910 ER - TY - JOUR T1 - Late Quaternary Relative Sea-Level Change in the Western Gulf of Maine - Evidence for a Migrating Glacial Forebulge JF - Geology Y1 - 1995 A1 - Barnhardt, W. A. A1 - Gehrels, W. R. A1 - Belknap, D. F. A1 - Kelley, J. T. AB - New radiocarbon-dated cores obtained by Vibracorers in the western Gulf of Maine confirm that a short-lived, relative sea-level lowstand of similar to-55 m occurred at 11-10.5 ka. These cores and younger salt-marsh data also reveal that rates of transgression varied throughout the Holocene, probably due to local variations in glacial isostasy. The isostatic component is resolved by subtracting published approximations of eustatic sea level from our well-determined observations of local relative sea level. A large peek in the isostatic curve coincides with the lowstand and is interpreted as a forebulge 20-25 m in amplitude. Forebulge migration is estimated at 7-11 km/100 yr, based on the timing of lowstands across the region. VL - 23 IS - 4 N1 - Qr847Times Cited:69Cited References Count:32 JO - Late Quaternary Relative Sea-Level Change in the Western Gulf of Maine - Evidence for a Migrating Glacial Forebulge ER - TY - CONF T1 - Late Wisconsinan stratigraphy and deglaciation chronology of the lower Aroostook River Valley, Maine T2 - Geological Society of America, Northeastern Section, 30th annual meeting Y1 - 1995 A1 - Strasser, J. C. A1 - Weddle, T. K. A1 - Dorion, C. C. JF - Geological Society of America, Northeastern Section, 30th annual meeting CY - Cromwell, Connecticut VL - 27 N1 - id: 1238 ER - TY - CONF T1 - La Curva Di Risalta Del Mare Tirreno Negli Ultimi 40 KA Ottenuta Mediante Datazioni Di Speleotemi Sommersi E Dati Archeologici T2 - International Meeting on Underwater Geology Y1 - 1994 A1 - Alessio, M. A1 - Allegri, L. A1 - Antonioli, F. A1 - Belluomini, G. A1 - Improta, S. A1 - Manfra, L. A1 - Martinez, M. P. JF - International Meeting on Underwater Geology CY - Palinuro N1 - id: 899 ER - TY - JOUR T1 - Lake-Level History of Lake-Michigan for the Past 12,000 Years - the Record from Deep Lacustrine Sediments JF - Journal of Great Lakes Research Y1 - 1994 A1 - Colman, S. M. A1 - Forester, R. M. A1 - Reynolds, R. L. A1 - Sweetkind, D. S. A1 - King, J. W. A1 - Gangemi, P. A1 - Jones, G. A. A1 - Keigwin, L. D. A1 - Foster, D. S. KW - lake michigan KW - ostracodes KW - radiocarbon KW - sedimentology KW - sediments KW - southern AB - Collection and analysis of an extensive set of seismic-reflection profiles and cores from southern Lake Michigan have provided new data that document the history of the lake basin for the past 12,000 years. Analyses of the seismic data, together with radiocarbon dating, magnetic, sedimentologic, isotopic, and paleontologic studies of core samples, have allowed us to reconstruct lake-level changes during this recent part of the lake's history.The post-glacial history of lake-level changes in the Lake Michigan basin begins about 11.2 ka with the fall from the high Calumet level, caused by the retreat of the Two Rivers glacier, which had blocked the northern outlet of the lake. This lake-level fall was temporarily reversed by a major influx of water from glacial Lake Agassiz (about 10.6 ka), during which deposition of the distinctive gray Wilmette Bed of the Lake Michigan Formation interrupted deposition of red glaciolacustrine sediment. Lake level then continued to fall, culminating in the opening of the North Bay outlet at about 10.3 ka. During the resulting Chippewa low phase, lake level was about 80 m lower than it is today in the southern basin of Lake Michigan. The rise of the early Holocene lake level, controlled primarily by isostatic rebound of the North Bay outlet, resulted in a prominent, planar, transgressive unconformity that eroded most of the shoreline features below present lake level. Superimposed on this overall rise in lake level, a second influx of water from Lake Agassiz temporarily raised lake levels an unknown amount about 9.1 ka. At about 7 ka, lake level may have fallen below the level of the outlet because of sharply drier climate. Sometime between 6 and 5 ka, the character of the lake changed dramatically, probably due mostly to climatic causes, becoming highly undersaturated with respect to calcium carbonate and returning primary control of lake level to the isostatically rising North Bay outlet. Post-Nipissing (about 5 ka) lake level has fallen about 6 m due to erosion of the Port Huron outlet, a trend around which occurred relatively small (+/- approximately 2 m), short-term fluctuations controlled mainly by climatic changes. These cyclic fluctuations are reflected in the sedimentological and sediment-magnetic properties of the sediments. VL - 20 SN - 0380-1330 IS - 1 N1 - Nl348Times Cited:47 Cited References Count:29 JO - J Great Lakes Res ER - TY - JOUR T1 - Latest Quaternary Sedimentation in the Kerch Strait Area of the Black Sea Shelf: Response to Glacial Sea Level Fluctuation JF - EOS,Transactions,American Geophysical Union Y1 - 1994 A1 - Major, C. O. A1 - Ryan, W. B. F. A1 - Pitman, W. C., III A1 - Shimkus, K. M. A1 - Jones, G. A. A1 - O'Connell, S. VL - 75 IS - 16 N1 - id: 914 ER - TY - JOUR T1 - The limnological and climate history of Lake Michigan from ostracode, stable-isotope, and magnetic susceptibility records JF - Journal of Great Lakes Research Y1 - 1994 A1 - Forester, R. M. A1 - Colman, S. M. A1 - Reynolds, R. L. A1 - Jones, G. A. A1 - Keigwin, L. D. A1 - Foster, D. S. VL - 20 N1 - id: 1358 ER - TY - CONF T1 - Laboratory automation at the National Ocean Sciences AMS Facility T2 - 6th Internation Conference on Accelerator Mass Spectrometry Y1 - 1993 A1 - Cohen, G. J. A1 - Hutton, D. L. A1 - von Reden, K. F. A1 - Osborne, E. A. A1 - McNichol, A. P. A1 - Jones, G. A. JF - 6th Internation Conference on Accelerator Mass Spectrometry CY - Canberra, Australia N1 - id: 927 ER -