Holocene terebratulid brachiopods from the southern Brazilian Shelf (South Atlantic): Ecology, taphonomy, and time-averaging - Kowalewski, M.; Simoes, M. G.; Barbour-Wood, S. L.; Krause R.A, Jr.; Rodriguez, S. C.; Wehmiller, J. F.; Rodland, D. L.; Carroll, M. (Fifth International Brachiopod Congress, 2005)
id: 1171; Abstracts, p. 34-35

Impact of vegetation on sedimentary organic matter composition and polycyclic aromatic hydrocarbon attenuation - Gregory, S. T.; Shea, D.; Guthrie-Nichols, E. (Environ Sci Technol, 2005)
Results from natural and engineered phytoremediation systems provide strong evidencethatvegetated soils mitigate polycyclic aromatic hydrocarbon (PAH) contamination. However, the mechanisms by which PAH mitigation occurs and the impact of plant organic matter on PAH attenuation remain unclear. This study assessed the impact of plant organic matter on PAH attenuation in labile and refractory sediments fractions from a petroleum distillate waste pit that has naturally revegetated. Samples were collected in distinct zones of barren and vegetated areas to assess changes to organic matter composition and PAH content as vegetation colonized and became established in the waste pit. Sediments were fractionated into bulk sediment and humin fractions and analyzed for organic matter composition by isotope ratio mass spectrometry (delta (13)C), 13C nuclear magnetic resonance (13C NMR), delta 14C AMS (accelerator mass spectrometry), and percent organic carbon (%TOC). Gas chromatography mass spectrometry (GC/ MS) of lipid extracts of SOM fractions provided data for PAH distribution histograms, compound weathering ratios, and alkylated and nonalkylated PAH concentrations. Inputs of biogenic plant carbon, PAH weathering, and declines in PAH concentrations are most evidentfor vegetated SOM fractions, particularly humin fractions. Sequestered PAH metabolites were also observed in vegetated humin. These results show that plant organic matter does impact PAH attenuation in both labile and refractory fractions of petroleum distillate waste.
Gregory, Samuel TShea, Damian Guthrie-Nichols, Elizabeth eng Research Support, U.S. Gov't, Non-P.H.S. 2005/08/09 09:00 Environ Sci Technol. 2005 Jul 15;39(14):5285-92.
Keywords: Biodegradation, Environmental; Environmental Monitoring; Geologic Sediments/chemistry; Magnetic Resonance Spectroscopy; Mass Spectrometry; Plants; Polycyclic Aromatic Hydrocarbons/*isolation & purification/*metabolism; Refuse Disposal; Soil Pollutants/*isolation & purification/*metabolism

Increased productivity in the subantarctic ocean during Heinrich events - Sachs, J. P.; Anderson, R. F. (Nature, 2005)
Massive iceberg discharges from the Northern Hemisphere ice sheets, 'Heinrich events', coincided with the coldest periods of the last ice age. There is widespread evidence for Heinrich events and their profound impact on the climate and circulation of the North Atlantic Ocean, but their influence beyond that region remains uncertain. Here we use a combination of molecular fingerprints of algal productivity and radioisotope tracers of sedimentation to document eight periods of increased productivity in the subpolar Southern Ocean during the past 70,000 years that occurred within 1,000-2,000 years of a Northern Hemisphere Heinrich event. We discuss possible causes for such a link, including increased supply of iron from upwelling and increased stratification during the growing season, which imply an alteration of the global ocean circulation during Heinrich events. The mechanisms linking North Atlantic iceberg discharges with subantarctic productivity remain unclear at this point. We suggest that understanding how the Southern Ocean was altered during these extreme climate perturbations is critical to understanding the role of the ocean in climate change.
Sachs, Julian PAnderson, Robert FengResearch Support, Non-U.S. Gov'tResearch Support, U.S. Gov't, Non-P.H.S.England2005/04/29 09:00Nature. 2005 Apr 28;434(7037):1118-21.

Last deglaciation in the Okinawa Trough: Subtropical northwest Pacific link to Northern Hemisphere and tropical climate - Sun, Y. B.; Oppo, D. W.; Xiang, R.; Liu, W. G.; Gao, S. (Paleoceanography, 2005)
[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.
975ipTimes Cited:53 Cited References Count:55
Keywords: cal kyr bp; deep-ocean circulation; equatorial current; kuroshio current; late pleistocene; oxygen-isotope; planktonic-foraminifera; radiocarbon age calibration; south china sea; surface-water

The last glacial maximum: stability and change in an Andean cloud forest - Urrego, D. H.; Silman, M. R.; Bush, M. B. (Journal of Quaternary Science, 2005)
id: 458

Late-Quaternary lowstands of lake Bosumtwi, Ghana: evidence from high-resolution seismic-reflection and sediment-core data - Brooks, K.; Scholz, C. A.; King, J. W.; Peck, J.; Overpeck, J. T.; Russell, J. M.; Amoako, P. Y. O. (Palaeogeography Palaeoclimatology Palaeoecology, 2005)
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.
892ujTimes Cited:21Cited References Count:54

Latest Holocene evolution and human disturbance of a channel segment in the Hudson River Estuary - Klingbeil, A. D.; Sommerfield, C. K. (Marine Geology, 2005)
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).
942iaTimes Cited:11Cited References Count:49

Mid-Holocene hydrologic change and hypolimnion formation in Lake Erie - Clotts, R. A.; McCambridge, C. E.; Barrera, E.; Saylor, B. Z.; Palmer, D. F.; Coakley, J. P. (Journal of Great Lakes Research, 2005)
id: 688

Moving-wire device for carbon isotopic analyses of nanogram quantities of nonvolatile organic carbon - Sessions, A. L.; Sylva, S. P.; Hayes, J. M. (Anal Chem, 2005)
We describe a moving-wire analyzer for measuring 13C in dissolved, involatile organic materials. Liquid samples are first deposited and dried on a continuously spooling nickel wire. The residual sample is then combusted as the wire moves through a furnace, and the evolved CO2 is analyzed by continuous-flow isotope ratio mass spectrometry. A typical analysis requires 1 microL of sample solution and produces a CO2 peak approximately 5 s wide. The system can measure "bulk" delta13C values of approximately 10 nmol of organic carbon with precision better than 0.2 per thousand. For samples containing approximately 1 nmol of C, precision is approximately 1 per thousand. Precision and sensitivity are limited mainly by background noise derived from carbon within the wire. Instrument conditions minimizing that background are discussed in detail. Accuracy is better than 0.5 per thousand for nearly all dissolved analytes tested, including lipids, proteins, nucleic acids, sugars, halocarbons, and hydrocarbons. The sensitivity demonstrated here for 13C measurements represents a approximately 1000-fold improvement relative to existing elemental analyzers and should allow the use of many new preparative techniques for collecting and purifying nonvolatile biochemicals for isotopic analysis.
Sessions, Alex LSylva, Sean PHayes, John MengResearch Support, U.S. Gov't, Non-P.H.S.2005/10/15 09:00Anal Chem. 2005 Oct 15;77(20):6519-27.

The multi-centennial dynamics of an upwelling system revealed by stable isotope and trace element sclerochronology of amino-acid dated bivalve and brachiopod shells - Krause, R. A., Jr.; Barbour-Wood, S.; Romanek, C. S.; Kowalewski, M.; Simoes, M. G.; Wehmiller, J. F. (Geological Society of America Abstracts with Programs, 2005)
id: 717

Pre- and post-industrial environmental changes as revealed by the biogeochemical sedimentary record of Drammensfjord, Norway - Smittenberg, R. H.; Baas, M.; Green, M. J.; Hopmans, E. C.; Schouten, S.; Damste, J. S. S. (Marine Geology, 2005)
The biogeochemical sedimentary record of the anoxic Drammensfjord, Norway, was investigated on a decadal to centennial time scale over the last millennium, in order to reconstruct the pre-industrial fjord environment and ecosystem and human-induced environmental changes. The sediments were dated by a combination of C-14 and Pb-210 analysis and varve counting. Analysis of the bulk sedimentary parameters and of the biomarker distribution revealed that the sedimentary organic matter of the fjord is primarily of terrigetious origin, indicating that the fjord was oligotrophic or mesotrophic. The fjord's bottom water has been continuously euxinic since at least 1000 AD, but photic zone euxinia occurred only irregularly in the fjord. The organic matter flux and composition remained virtually invariable until the 18th century. After that time, the flux of material derived from coniferous trees started to increase, indicated by elevated concentrations of dehydroabietic acid and related compounds, but also by raising levels of C-24 n-alcohols and fatty acids. This marked the onset of sawmill activities in the hinterland. After the beginning of the industrial revolution, around 1850, the flux of organic waste from sawmills and paper mills increased substantially. It is suggested that slow bacterial degradation of this relatively nutrient-poor organic waste caused a gradual eutrophication trend, which is reflected in substantial increased bacterial and moderately increased other aquatic biomarker accumulation rates. After the industrial revolution, this trend accelerated and was possibly enhanced by a growing population of the area with accompanymg agricultural and domestic waste. This promoted primary productivity and changed the phytoplankton composition in the fjord.(C) 2004 Elsevier B.V. All rights reserved.
890unTimes Cited:23Cited References Count:105

Preliminary research results indicate modern sedimentation ont he continental slope seaward of theWaipoao River, New Zealand - Alexander, C. A.; Walsh, J. P.; Orpin, A. R.; Sumners, B. W.; Gerber, T. P.; Kuehl, S. A. (New Zealand Marine Science Society Annual Meeting, 2005)
id: 637

Progress on a Gas Ion Source for Continuous-Flow Accelerator Mass Spectrometry - Roberts, M. L.; Schneider, R. J.; von Reden, K. F.; Han, B. X.; Rosenheim, B. E.; Hayes, J. M. (10th International Conference on Accelerator Mass Spectrometry, 2005)
id: 768

The Puerto Bandera Moraines, Lago Argentino - Strelin, Jorge; Denton, George (Actas Del XVI Congreso Geologico Argentina, La Plata, 2005)
id: 573

Radiocarbon variability in the western North Atlantic during the last deglaciation - Robinson, L. F.; Adkins, J. F.; Keigwin, L. D.; Southon, J.; Fernandez, D. P.; Wang, S. L.; Scheirer, D. S. (Science, 2005)
We present a detailed history of glacial to Holocene radiocarbon in the deep western North Atlantic from deep-sea corals and paired benthic-planktonic foraminifera. The deglaciation is marked by switches between radiocarbon-enriched and -depleted waters, leading to large radiocarbon gradients in the water column. These changes played an important role in modulating atmospheric radiocarbon. The deep-ocean record supports the notion of a bipolar seesaw with increased Northern-source deep-water formation linked to Northern Hemisphere warming and the reverse. In contrast, the more frequent radiocarbon variations in the intermediate/deep ocean are associated with roughly synchronous changes at the poles.
Robinson, Laura FAdkins, Jess FKeigwin, Lloyd DSouthon, JohnFernandez, Diego PWang, S-LScheirer, Daniel SengResearch Support, Non-U.S. Gov'tResearch Support, U.S. Gov't, Non-P.H.S.2005/12/03 09:00Science. 2005 Dec 2;310(5753):1469-73. Epub 2005 Nov 3.

Recent and modern marine erosion on the New Jersey outer shelf - Goff, J. A.; Austin, J. A.; Gulick, S.; Nordfjord, S.; Christensen, B.; Sommerfield, C.; Olson, H.; Alexander, C. (Marine Geology, 2005)
Recent chirp seismic reflection data combined with multibeam bathymetry, backscatter, and analysis of grab samples and short cores provide evidence of significant recent erosion on the outer New Jersey shelf. The timing of erosion is constrained by two factors: (1) truncation at the seafloor of what is interpreted to be the transgressive ravinement surface at the base of the surficial sand sheet, and (2) truncation of apparently moribund sand ridges along erosional swales oriented parallel to the primary direction of modem bottom flow and oblique to the strike of the sand ridges. These observations place the erosion in a marine setting, post-dating the passage of the shoreface ravinement and the evolution of sand ridges that form initially in the near shore environment. Also truncated by marine erosion are shallowly buried, fluvial channel systems, formed during the Last Glacial Maximum and filled during the transgression, and a regional reflector "R" that is > &SIM; 40 kyr. Depths of erosion range from a few meters to > 10 m. The seafloor within eroded areas is often marked by "ribbon" morphology, seen primarily in the backscatter data as areas of alternating high and low backscatter elongated in the direction of primary bottom flow. Ribbons are more occasionally observed in the bathymetry; where observed, crests exhibit low backscatter and troughs exhibit high backscatter. Sampling reveals that the high backscatter areas of the ribbons consist of a trimodal admixture of mud, sand and shell hash, with a bimodal distribution of abraded and unabraded sand grains and microfauna. The shell hash is interpreted to be an erosional lag, while the muds and unabraded grains are, in this non-depositional environment, evidence of recent erosion at the seafloor of previously undisturbed strata. The lower-backscatter areas of the ribbon morphology were found to be a well-sorted medium sand unit only a few 10's of cm thick overlying the shelly/muddy/sandy material. Concentrations of well-rounded gravels and cobbles were also found in eroded areas with very high backscatter, and at least one of these appears to be derived from the base of an eroded fluvial channel. Seafloor reworking over the transgressive evolution of the shelf appears to have switched from sand ridge evolution, which is documented to &SIM; 40 m water depth, to more strictly erosional modification at greater water depths. We suggest that this change may be related to the reduction with water depth in the effectiveness of sediment resuspension by waves. Resuspension is a critical factor in the grain size sorting during transport by bottom currents over large bedforms like sand ridges. Otherwise, we speculate, displacement of sand by unidirectional currents will erode the seafloor. © 2005 Elsevier B.V. All rights reserved.
925kdTimes Cited:42Cited References Count:53

Source, timing and depositional environments of Paleochannel incision and infill on the New Jersey Shelf - Alexander, C.; Christensen, B.; Turner, J.; Goff, J.; Austin J.A, Jr.; Venherm, C.; Nordfjord, S.; Sommerfield, C.; Gulick, S.; Fulthorpe, C. (2005 National GSA Meeting, 2005)
id: 638

Status of the U. S. canary rockfish resource in 2005 - Methot, R.; Stewart, I. J. (Status of the Pacific Coast Groundfish Fishery Through 2005, Stock Assessment and Fishery Evaluation: Stock Assessments and Rebuilding Analyses, 2005)
id: 539

Subducting oceanic crust: The source of deep diamonds - Tappert, R.; Stachel, T.; Harris, J. W.; Muehlenbachs, K.; Ludwig, T.; Brey, G. P. (Geology, 2005)
Inclusions of majoritic garnet in diamonds from the Jagersfontein kimberlite formed at unusually great depths of similar to 250 to > 500 km in the asthenosphere and transition zone. The original host rocks were derived from a much shallower, basaltic (eclogitic) source. The presence of negative Eu anomalies in all majoritic garnets requires a crustal origin, thereby linking these very deep diamond sources to subducting oceanic crust. The carbon isotope values (delta(13)C) of the host diamonds fall within a narrow range at similar to -20%, which is fundamentally different from the broad range (-24% to -2%) and bimodal distribution of carbon isotopes of Jagersfontein diamonds that formed in the shallower lithosphere. This indicates that majoritic garnet-bearing diamonds at Jagersfontein inherited their light carbon isotopic composition directly from organic matter contained in a subducting slab. These diamonds were likely formed by direct conversion from graphite, well within the diamond stability field.
938hnTimes Cited:65Cited References Count:26

Terrace inundation as an autocyclic mechanism for parasequence formation: Galveston Estuary, Texas, USA - Rodriguez, A. B.; Anderson, J. B.; Simms, A. R. (Journal of Sedimentary Research, 2005)
Architecture of late Quaternary incised-valley fills is commonly attributed to the interplay between sea-level rise, sediment supply, and hydrodynamic processes. Inundation of fluvial terraces is commonly overlooked as an autocyclic mechanism for formation of parasequences. If the rate of sea-level rise and sediment supply is constant, architecture of terraced incised-valley fills will likely show backstepping parasequences. The control that variable antecedent topography has on architecture of incised-valley fills is examined in the Trinity incised valley, Texas. The Trinity valley is characterized by a series of downward-stepping terraces, and the Galveston Estuary formed above this irregular antecedent topography. Flooding surfaces, recognized in core by a decrease in sedimentation rates and a change from delta-plain to central-basin facies, formed at similar to -14 m, 8,200 cal. yr BP and similar to -10 m, 7,700 cal. yr BP, matching depths of the relatively flat fluvial terraces. Flooding surfaces formed rapidly and represent entire reorganization of the estuarine complex. Across the -10 m flooding surface, the river mouth and bay-head delta shifted landward at a rate of similar to 6.5 km per century and the associated barrier shoreline was stranded on the inner continental shelf, forming Heald Bank. Flooding surfaces formed as the rate of sea-level rise was decreasing, and are not associated with a decrease in sediment delivery to the estuary. As sea level inundates relatively flat fluvial terraces, rates of transgression rapidly increase, resulting in a sudden increase in accommodation space and an associated landward shift in coastal facies. Backstepping parasequences are inherent to the architecture of terraced incised-valley fills.
id: 2041; PT: J; UT: WOS:000230261600008

Toward a Neoproterozoic composite carbon-isotope record - Halverson, G. P.; Hoffman, P. F.; Schrag, D. P.; Maloof, A. C.; Rice, A. H. N. (Geological Society of America Bulletin, 2005)
Glacial deposits of Sturtian and Marinoan age occur in the well-studied Neoproterozoic successions of northern Namibia, South Australia, and northwestern Canada. In all three regions, the Marinoan glaciation is presaged by a large negative delta(13)C anomaly, and the cap carbonates to both glacial units share a suite of unique sedimentological, stratigraphic, and geochemical features. These global chronostratigraphic markers are the bases of a new correlation scheme for the Neoproterozoic that corroborates radiometric data that indicate that there were three glacial epochs between ca. 750 and 580 Ma. Intraregional correlation of Neoproterozoic successions in the present-day North Atlantic region suggests that glacial diamictite pairs in the Polarisbreen Group in northeastern Svalbard and the Tillite Group in eastern Greenland were deposited during the Marinoan glaciation, whereas the younger of a pair of glacials (Mortensnes Formation) in the Vestertana Group of northern Norway was deposited during the third (Gaskiers) Neoproterozoic glaciation. Gaskiers-aged glacial deposits are neither globally distributed nor overlain by a widespread cap carbonate but are associated with an extremely negative delta(13)C anomaly. The chronology developed here provides the framework for a new, high-resolution model carbon-isotope record for the Neoproterozoic comprising new delta(13)C (carbonate) data from Svalbard (Akademikerbreen Group) and Namibia (Otavi Group) and data in the literature from Svalbard, Namibia, and Oman. A new U-Pb zircon age of 760 +/- 1 Ma from an ash bed in the Ombombo Subgroup in Namibia provides the oldest direct time-calibration point in the compilation, but the time scale of this preliminary delta(13)C record remains poorly constrained.
960jtTimes Cited:414Cited References Count:174

14C activity and global carbon cycle changes over the past 50,000 years - Hughen, K.; Lehman, S.; Southon, J.; Overpeck, J.; Marchal, O.; Herring, C.; Turnbull, J. (Science, 2004)
A series of 14C measurements in Ocean Drilling Program cores from the tropical Cariaco Basin, which have been correlated to the annual-layer counted chronology for the Greenland Ice Sheet Project 2 (GISP2) ice core, provides a high-resolution calibration of the radiocarbon time scale back to 50,000 years before the present. Independent radiometric dating of events correlated to GISP2 suggests that the calibration is accurate. Reconstructed 14C activities varied substantially during the last glacial period, including sharp peaks synchronous with the Laschamp and Mono Lake geomagnetic field intensity minimal and cosmogenic nuclide peaks in ice cores and marine sediments. Simulations with a geochemical box model suggest that much of the variability can be explained by geomagnetically modulated changes in 14C production rate together with plausible changes in deep-ocean ventilation and the global carbon cycle during glaciation.
Hughen, KLehman, SSouthon, JOverpeck, JMarchal, OHerring, CTurnbull, Jeng2004/01/13 05:00Science. 2004 Jan 9;303(5655):202-7.

215-kyr sea-level oscillations from marine and continental layers in Argentarola cave speleothems (Italy) - Antonioli, F.; E, Bard; Silenzi, S.; Potter, E. K.; Improta, S. (Global and Planetry Changes, 2004)
Several Quaternary sea-level changes are recorded by speleothems in the Argentarola Cave (Italy), which is currently flooded by the Mediterranean Sea. Speleothems with a sequence of continental layers and marine biogenic overgrowths (serpulid colonies), all presently covered by living serpulids, were sampled at water depths between −3.5 and −21.7 m. The composite sequence contains five marine and four continental layers, formed over the last 215 ka. The Mediterranean Sea flooded the cave during two short periods of MIS 7 (7.3 and 7.1), as well as during an episode at the end of MIS 6 and during MIS 5, when a thick biogenic overgrowth grew during MIS 5.2 and 5.4. Thin continental layers also formed during the LGM. This final speleothem layer was interrupted during the Holocene sea-level rise, but at different times in each speleothem. A Holocene sea-level curve has been constructed from this same layer. A thin marine layer, found only in the deeper stalagmites at −21.5 and −21.7 m, is tentatively related to the short marine transgression of Termination II, after 145 ka BP and before MIS 5.5. The island of Argentarola lies in a tectonically stable area and our data generally agree with the results obtained by other authors on speleothems from the Bahamas. The data presented here are compared with the SPECMAP curve and other recently published sea-level curves.
id: 973
Keywords: Italy; Sea-level change; Submerged speleothems; Tyrrhenian sea

48,000 years of climate and forest change from a biodiversity hotspot - Bush, M. B.; Silman, M. R.; Urrego, D. H. (Science, 2004)
A continuous 48,000-year-long paleoecological record from Neotropical lower montane forest reveals a consistent forest presence and an ice-age cooling of ∼5° to 9°C. After 30,000 years of compositional stability, a steady turnover of species marks the 8000-year-long transition from ice-age to Holocene conditions. Although the changes were directional, the rates of community change were no different during this transitional period than in the preceding 30,000-year period of community stability. The warming rate of about 1°C per millennium during the Pleistocene-Holocene transition was an order of magnitude less than the projected changes for the 21st century.
id: 1016

Across-shelf sediment transport since the Last Glacial Maximum, southern California margin - Sommerfield, C. K.; Lee, H. J. (Geology, 2004)
Correlation of continental shelf-slope stratigraphy in Santa Monica Bay (southern California) with Ocean Drilling Program records for nearby slope-basin sites has illuminated the timing and scale of terrigenous sediment dispersal on margin since the Last Glacial Maximum (LGM). Marine flooding surfaces preserved in a transgressive sequence on the Santa Monica Shelf provide a key link between base-level elevation and sediment transport across shelf. Sediment-accumulation rates at slope-basin sites were maximal ca. 15-10 ka, well after the LGM, decreased during the 12-9 ka transition from fluvial-estuarine to fully marine conditions on the shelf, and decelerated throughout the Holocene to 30%-75% of their values at the LGM. The deceleration is interpreted to manifest a landward shift in the margin depocenter with the onset of transgressive sedimentation beginning when sea level surmounted the shelf edge ca. 13 ka, as predicted by sequence-stratigraphic models. However, the records make clear that factors other than base level modulated slope-basin accumulation rates during the deglaciation.
808fbTimes Cited:19Cited References Count:36

Age of the Palos Verdes submarine debris avalanche, southern California - Normark, W. R.; McGann, M.; Sliter, R. (Marine Geology, 2004)
id: 990

AMS 14C measurement and preparative techniques at NIES-TERRA - Yoneda, Minoru; Shibata, Yasuyuki; Tanaka, Atsushi; Uehiro, Takashi; Morita, Masatoshi; Uchida, Masao; Kobayashi, Toshiyuki; Kobayashi, Chiaki; Suzuki, Ryo; Miyamoto, Keisuke; Hancock, Boze; Dibden, Chris; et al. (Nuclear Instruments and Methods in Physics Research B, 2004)
The AMS facility at the National Institute for Environmental Studies (NIES) has now been operating for five years since 1997. This AMS-dedicated facility named NIES-TERRA (Tandem accelerator for Environmental Research and Radiocarbon Analysis) consists of a 5MV tandem Pelletron (15SDH-2), a solid ion source with sequential injection system, a gas ion source with a simultaneous injection system, and a gas ionization detector. Typical precision with 14C measurements is around 0.5% and the background level has been achieved at around 50 kBP. Our main target is radiocarbon in environmental sciences, while other cosmogenic isotopes (10Be and 26Al) have been measured. Recently we have improved our preparation laboratory to increase sample throughput. CO2 production and purification using a commercial elemental analyzer connected to cryogenic traps (EA–CT) were investigated. We used a modified elemental analyzer with a chemical trap for separation and this is expected to reduce memory effect and background in comparison with an analyzer using gas-chromatography. This newly designed EA–CT system showed high precision and accuracy. Source of background contamination was also discussed based on the analysis of various amounts of standard materials.
id: 1492

Anthropogenic eutrophication of Long Island Sound: effects on diatom communities through time - Cooper, S. R.; Thomas, E.; Varekamp, J. C.; Sangiorgio, F. (7th Biennial Long Island Sound reserach conference proceedings, 2004)
id: 1181

Characterization of Siberian Arctic coastal sediments: Implications for terrestrial organic carbon export - Guo, L. D.; Semiletov, I.; Gustafsson, O.; Ingri, J.; Andersson, P.; Dudarev, O.; White, D. (Global Biogeochemical Cycles, 2004)
Surface sediments were collected during the 2000 TransArctic Expedition along the Siberian Arctic coastline, including the Ob, Yenisey, Khatanga, Lena, and Indigirka estuaries. Sediments were characterized for elemental composition (total organic carbon, TOC, black carbon, BC, and total N, as well as major and trace elements), isotopic signature (delta(13)C, delta(15)N, Delta(14)C, epsilon(Nd), Sr-87/Sr-86), and organic molecular composition to better understand river export variations over the large spatial scale of the Siberian Arctic. On average, 79 +/- 9% of the total C in sediments was organic while 21 +/- 9% was inorganic. BC made up 9 +/- 4% of the TOC pool, with a general increasing trend from west to east along the Siberian coast. The combined Nd- and Sr-isotopes (epsilon(Nd) and Sr-87/Sr-86) were used to define two distinct sediment sources between east and west Siberian regions with the Khatanga River as a boundary. Data from pyrolysis-GC/MS of the sedimentary organic carbon (SOC) indicated an increase in the freshness of the organic matter from west to east on the Siberian Arctic coast, with increasing relative abundance of furfurals (polysaccharides) with respect to nitriles. Values for the delta(13)C of SOC ranged from -27.1% (mostly terrigenous) to -23.8%, while delta(15)N increased from east to west (3.1 to 5.2%) with a significant correlation with C/N ratio. Values for the Delta(14)C of SOC ranged from -805 to -279%, with a consistent trend increasing from the east (Indigirka River) to the west (Ob River). These D 14 C values corresponded to a 14 C age of 2570 +/- 30 yBP in the Ob estuary and 13,050 +/- 50 yBP in the Indigirka estuary. Most importantly, D 14 C values were significantly correlated with the ratio of BC/TOC (R-2 = 0.91, n = 6), consistent with the distribution pattern of increasing permafrost zone from the west to the east along the Siberian coast. Together, our results suggest that older OC was derived from the release of recalcitrant BC during permafrost thawing and riverbank and coastal erosion, likely enhanced by ongoing environmental changes in the northern ecosystem.
806knTimes Cited:99 Cited References Count:51
Keywords: arctic ocean; BLACK CARBON; climate; CO2; continental-shelf; flux; isotopic composition; lena river; MATTER; ocean; organic carbon; quantification; Sediment

Chronology of sediment deposition in Upper Klamath Lake, Oregon - Colman, S. M.; Bradbury, J. P.; McGeehin, J. P.; Holmes, C. W.; Sarna-Wojcicki, A. M.; Edgington, D. (Journal of Paleolimnology, 2004)
A combination of tephrochronology and 14C, 210Pb, and 137Cs measurements provides a robust chronology for sedimentation in Upper Klamath Lake during the last 45 000 years. Mixing of surficial sediments and possible mobility of the radio-isotopes limit the usefulness of the 137Cs and 210Pb data, but 210Pb profiles provide reasonable average sediment accumulation rates for the last 100–150 years. Radiocarbon ages near the top of the core are somewhat erratic and are too old, probably as a result of detrital organic carbon, which may have become a more common component in recent times as surrounding marshes were drained. Below the tops of the cores, radiocarbon ages in the center of the basin appear to be about 400 years too old, while those on the margin appear to be accurate, based on comparisons with tephra layers of known age.Taken together, the data can be combined into reasonable age models for each site. Sediments have accumulated at site K1, near the center of the basin, about 2 times faster than at site CM2, on the margin of the lake. The rates are about 0.10 and 0.05 cm/yr, respectively. The chronological data also indicate that accumulation rates were slower during the early to middle Holocene than during the late Holocene, consistent with increasing wetness in the late Holocene.
id: 182

The CO2-He-Ar-H2O systematics of the Manus back-arc basin: Resolving source composition from degassing and contamination effects - Shaw, A. M.; Hilton, D. R.; Macpherson, C. G.; Sinton, J. M. (Geochimica Et Cosmochimica Acta, 2004)
We report new stepped heating He, Ar, CO2 and water data on a petrogenetically diverse suite of lavas from the Manus back-arc basin, where a plume component has previously been identified. The aim of this study is to evaluate the superimposed effects of degassing and contamination in order to identify mantle source characteristics. CO2 abundances and carbon isotopes in both the vesicle ([CO2] up to 180ppm; delta(13)C as low as -33.6 parts per thousand) and glass ([CO2] up to 270ppm; delta(13)C as low as -34.3parts per thousand) phases reveal that samples have been modified by varying degrees of degassing. High water concentration samples (back-arc basin basalts (BABB) and arc type samples) show the highest degrees of degassing (i.e. lower delta(13)C values and lower CO2 contents). The results are modelled for both the glass and vesicle phases using batch and fractional degassing models. Parental melt compositions can be constrained to show the following CO2 concentration trend: are-type > BABB s.r. (southern rift) > MORB-2, E-MORB, X-BABB (extreme BABB), BABB > MORB-1 and MORB-smt. He-4/Ar-40* ratios of samples (14.6-1100) are consistent with residual volatiles from a degassed source. Variations in CO2/(3) He values are likely due to degassing, followed by contamination from a crustal source (either the subducting Solomon Sea Plate or the pre-existing crust through which the lavas erupt), as evidenced by high K2O/TiO2 ratios and low delta(13)C. The CO2/(3) He of the Manus plume is best estimated by the MORB-smt and MORB-1 samples at 3.1 +/- 0.6 X 10(9). This value is similar to previous estimates of plume CO2/(3) He values, which are either equal to or slightly greater than the upper mantle average of 2 X 10(9). Copyright (C) 2004 Elsevier Ltd.
813fdTimes Cited:30Cited References Count:76

A comparative analysis of time averaging for bivalves and brachiopods from a modern tropical shelf - Krause R.A, Jr.; Barbourl-Wood, S. L.; Wehmiller, J. F.; Kowalewski, M.; Simoes, M. G. (Geological Society of America, Abstracts with Programs, 2004)
36(5):383
id: 718

Compound-specific radiocarbon dating of the varved Holocene sedimentary record of Saanich Inlet, Canada - Smittenberg, R. H.; Hopmans, E. C.; Schouten, S.; Hayes, J. M.; Eglinton, T. I.; Damste, J. S. S. (Paleoceanography, 2004)
[1] The radiocarbon contents of various biomarkers extracted from the varve-counted sediments of Saanich Inlet, Canada, were determined to assess their applicability for dating purposes. Calibrated ages obtained from the marine planktonic archaeal biomarker crenarchaeol compared favorably with varve-count ages. The same conclusion could be drawn for a more general archaeal biomarker (GDGT-0), although this biomarker proved to be less reliable due to its less-specific origin. The results also lend support to earlier indications that marine crenarchaeota use dissolved inorganic carbon (DIC) as their carbon source. The average reservoir age offset DeltaR of 430 years, determined using the crenarchaeol radiocarbon ages, varied by +/-110 years. This may be caused by natural variations in ocean-atmosphere mixing or upwelling at the NE Pacific coast but variability may also be due to an inconsistency in the marine calibration curve when used at sites with high reservoir ages.
819piTimes Cited:18 Cited References Count:69
Keywords: british-columbia; compound-specific radiocarbon dating; crenarchaeol; ionization mass-spectrometry; marine-sediments; mediterranean sea; membrane-lipids; ne pacific; odp leg 169s; organic-matter; pacific-ocean; rapid isolation; Reservoir age; reservoir ages; saanich inlet

Dating the rise of atmospheric oxygen - Bekker, A.; Holland, H. D.; Wang, P. L.; Rumble, D.; Stein, H. J.; Hannah, J. L.; Coetzee, L. L.; Beukes, N. J. (Nature, 2004)
Several lines of geological and geochemical evidence indicate that the level of atmospheric oxygen was extremely low before 2.45 billion years (Gyr) ago, and that it had reached considerable levels by 2.22 Gyr ago. Here we present evidence that the rise of atmospheric oxygen had occurred by 2.32 Gyr ago. We found that syngenetic pyrite is present in organic-rich shales of the 2.32-Gyr-old Rooihoogte and Timeball Hill formations, South Africa. The range of the isotopic composition of sulphur in this pyrite is large and shows no evidence of mass-independent fractionation, indicating that atmospheric oxygen was present at significant levels (that is, greater than 10(-5) times that of the present atmospheric level) during the deposition of these units. The presence of rounded pebbles of sideritic iron formation at the base of the Rooihoogte Formation and an extensive and thick ironstone layer consisting of haematitic pisolites and oolites in the upper Timeball Hill Formation indicate that atmospheric oxygen rose significantly, perhaps for the first time, during the deposition of the Rooihoogte and Timeball Hill formations. These units were deposited between what are probably the second and third of the three Palaeoproterozoic glacial events.
id: 1534; Bekker, A Holland, H D Wang, P-L Rumble, D 3rd Stein, H J Hannah, J L Coetzee, L L Beukes, N J England Nature. 2004 Jan 8;427(6970):117-20.

Decline of surface temperature and salinity in the western tropical Pacific Ocean in the Holocene epoch - Stott, L.; Cannariato, K.; Thunell, R.; Haug, G. H.; Koutavas, A.; Lund, S. (Nature, 2004)
In the present-day climate, surface water salinities are low in the western tropical Pacific Ocean and increase towards the eastern part of the basin. The salinity of surface waters in the tropical Pacific Ocean is thought to be controlled by a combination of atmospheric convection, precipitation, evaporation and ocean dynamics, and on interannual timescales significant variability is associated with the El Nino/Southern Oscillation cycles. However, little is known about the variability of the coupled ocean-atmosphere system on timescales of centuries to millennia. Here we combine oxygen isotope and Mg/Ca data from foraminifers retrieved from three sediment cores in the western tropical Pacific Ocean to reconstruct Holocene sea surface temperatures and salinities in the region. We find a decrease in sea surface temperatures of approximately 0.5 degrees C over the past 10,000 yr, whereas sea surface salinities decreased by approximately 1.5 practical salinity units. Our data imply either that the Pacific basin as a whole has become progressively less salty or that the present salinity gradient along the Equator has developed relatively recently.
Stott, LowellCannariato, KevinThunell, RobertHaug, Gerald HKoutavas, AthanasiosLund, SteveengResearch Support, U.S. Gov't, Non-P.H.S.England2004/09/03 05:00Nature. 2004 Sep 2;431(7004):56-9.

Deglacial history of the Ecuadorian Andes and implication for climate variations: Preliminary results - Hall, M.; Rinterknecht, V. R.; Schaefer, J. M.; R, Seager; Greene, A. (Eos Trans. AGU Fall Meeting Supplement, 2004)
id: 1003

Episodic methane release events from Last Glacial marginal sediments in the western North Pacific - Uchida, M.; Shibata, Y.; Ohkushi, K.; Ahagon, N.; Hoshiba, M. (Geochemistry Geophysics Geosystems, 2004)
[1] According to recent observations of anomalous bottom-simulating reflections (BSR),the northwest Pacific marginal sediments around Japan main islands bear large abundances of methane hydrate [Satoh, 2002]. During the Last Glacial, direct and indirect evidence accumulated from geochemical data suggests that methane episodically released from hydrate trapped in the seafloor sediments [ Dickens et al., 1995; Hinrichs et al., 2003; Kennett et al., 2000]. Here we show that marginal sediments from the western North Pacific contain a hopanoid 17alpha( H), 21beta(H)-hop-22(29)-ene ( diploptene) derived from the activity of methanotrophic bacteria in water column and/or surface sediment during a warming period (Interstadial 3) in the Last Glacial. The carbon isotopic compositions of diploptene range between - 41.0parts per thousand and - 27.9parts per thousand ( relative to PDB). In the horizon indicative of a contribution of methanotrophic bacteria, foraminiferal isotope signals were also found with highly depleted C-13 compositions of planktonic foraminifera ( similar to - 1.9parts per thousand, PDB) and benthic foraminifera ( similar to - 0.8parts per thousand, PDB), suggesting indirect records of enhanced incorporation of C-13-depleted CO2 formed by methanotrophic process that use C-12-enriched methane as their main source of carbon. From combined isotopic data of molecular ( diploptene) and foraminifera, the most prominent signal of methane release was detected in the sediments deposited around 25.4 cal. kyr BP ( similar to 100 year time span), corresponding to the Interstadial 3. This is the first evidence of methane hydrate instability in the open western North Pacific during the Last Glacial. Considering the glacial-interglacial hydrographic conditions in this region, the instability of methane hydrate may be modulated by intermediate water warming and/or the lowering of sea level. Our results suggest that the western North Pacific marginal regions may be a profound effect on rapid global warming climate changes during the Last Glacial.
849mvTimes Cited:13 Cited References Count:73
Keywords: atmospheric composition and structure : geochemical cycles; atmospheric methane; carbon isotopes; carbon isotopic fractionation; climate-change; cold seeps; diploptene; Foraminifera; gas-hydrate; geochemistry : isotopic composition/chemistry; geochemistry : organic geochemistry; hydrocarbons; interglacial; intermediate water; methane hydrate; santa-barbara basin; sea sediments; subduction zone; western north pacific

Eutrophication of western Long Island Sound - Thomas, E.; Varekamp, J. C.; Acosta, Z.; Thaler, B.; Cooper, S.; Sangiorgio, F. (GSA Annual Meeting, 2004)
id: 739

Evaluation of ocean carbon cycle models with data-based metrics - Matsumoto, K.; Sarmiento, J. L.; Key, R. M.; Aumont, O.; Bullister, J. L.; Caldeira, K.; Campin, J. M.; Doney, S. C.; Drange, H.; Dutay, J. C.; Follows, M.; Gao, Y.; et al. (Geophysical Research Letters, 2004)
New radiocarbon and chlorofluorocarbon-11 data from the World Ocean Circulation Experiment are used to assess a suite of 19 ocean carbon cycle models. We use the distributions and inventories of these tracers as quantitative metrics of model skill and find that only about a quarter of the suite is consistent with the new data-based metrics. This should serve as a warning bell to the larger community that not all is well with current generation of ocean carbon cycle models. At the same time, this highlights the danger in simply using the available models to represent the state-of-the-art modeling without considering the credibility of each model.
811adTimes Cited:110 Cited References Count:17
Keywords: anthropogenic co2; pacific-ocean; radiocarbon

Evidence for Late Holocene earthquakes on the Utsalady Point Fault, northern puget lowland, Washington - Johnson, S. Y.; Nelson, A. R.; Personius, S. F.; Wells, R. E.; Kelsey, H. N.; Sherrod, B. L.; Okumura, K.; Koehler, R.; Witter, R. C.; Bradley, L. A.; Harding, D. J. (Bulletin of the Seismological Society of America, 2004)
Trenches across the Utsalady Point fault in the northern Puget Lowland of Washington reveal evidence of at least one and probably two late Holocene earthquakes. The "Teeka"' and "Duffers" trenches were located along a 1.4-km-long. 1- to 4-m-high, northwest-trending, southwest-facing. topographic scarp recognized from Airborne Laser Swath Mapping. Glaciomarine drift exposed in the trenches reveals evidence of about 95 to 150 cm of vertical and 200 to 220 cm of left-lateral slip in the Teeka trench. Radiocarbon ages from a buried soil A horizon and overlying slope colluvium alone, with the historical record of earthquakes suggest that this faulting occurred 100 to 400 calendar years B.P. (A.D. 1550 to 1850). In the Duffers trench, 370 to 450 cm of vertical separation is accommodated by faulting (similar to210 cm) and folding (similar to160 to 240 cm), with probable but undetermined amounts of lateral slip. Stratigraphic relations and radiocarbon ages from buried soil, colluvium. and fissure fill in the hanging wall suggest the deformation at Duffers is most likely from two earthquakes that occurred between 100 to 500 and 1100 to 2200 calendar years B.P., but deformation during a single earthquake is also possible. For the two-earthquake hypothesis, deformation at Teeka trench in the first event involved folding but not faulting. Regional relations suggest that the earthquake(s) were M greater than or equal to similar to6.7 and that offshore rupture may have produced tsunamis. Based on this investigation and related recent studies, the maximum recurrence interval for large ground-rupturing crustal-fault earthquakes in the Puget Lowland is about 400 to 600 years or less.
887giTimes Cited:18Cited References Count:46

A gas ion source for continuous-flow AMS - Schneider, R. J.; Kim, S. W.; von Reden, K. F.; Hayes, J. M.; Wills, J. S. C.; Griffin, V. S.; Sessions, A. L.; Sylva, S. (Proceedings of the Ninth International Conference on Accelerator Mass Spectrometry, 2004)
The first gas-fed ion source for radiocarbon AMS applications (without sputtering) has been operated at the Woods Hole NOSAMS Facility. A three-year, off-line test program resulted in positive carbon ion currents up to 1 mA and negative ion currents up to 80 μA. Recently, the compact, permanent-magnet microwave plasma ion source and magnesium vapor charge-exchange canal were coupled to the recombinator injector of the 2.5 MV Tandetron. When the ion source was operated on CO2 at a flow rate of about 200 μl per minute, negative carbon ion beams up to 20 μA were obtained, at an energy of 35 keV. Radiocarbon measurements were performed on standard reference gases and the dynamic response to square-wave pulses of gas was determined. Time constants in the ion source are less than 1 s, which should allow analysis of chromatographic peaks of CO2 with very little broadening. A combustion device has been constructed to generate CO2 for direct injection into the source. Argon carrier gas is used to buffer the pressure at one atmosphere in the sample gas injector. A dedicated ion-beam injector, with higher angular acceptance and higher transmitted currents, is being constructed for the AMS system.
id: 2104

A global ocean carbon climatology: Results from global data analysis project (GLODAP) - Kay, R. M.; Kozyr, A.; Sabine, C. L.; Lee, K.; Wanninkhof, R.; Bullister, J. L.; Feely, R. A.; Millero, F. J.; Mordy, C.; Peng, T. H. (Global Biogeochemical Cycles, 2004)
id: 527

H2-rich fluids from serpentinization: geochemical and biotic implications - Sleep, N. H.; Meibom, A.; Fridriksson, T.; Coleman, R. G.; Bird, D. K. (Proc Natl Acad Sci U S A, 2004)
Metamorphic hydration and oxidation of ultramafic rocks produces serpentinites, composed of serpentine group minerals and varying amounts of brucite, magnetite, and/or FeNi alloys. These minerals buffer metamorphic fluids to extremely reducing conditions that are capable of producing hydrogen gas. Awaruite, FeNi3, forms early in this process when the serpentinite minerals are Fe-rich. Olivine with the current mantle Fe/Mg ratio was oxidized during serpentinization after the Moon-forming impact. This process formed some of the ferric iron in the Earth's mantle. For the rest of Earth's history, serpentinites covered only a small fraction of the Earth's surface but were an important prebiotic and biotic environment. Extant methanogens react H2 with CO2 to form methane. This is a likely habitable environment on large silicate planets. The catalytic properties of FeNi3 allow complex organic compounds to form within serpentinite and, when mixed with atmospherically produced complex organic matter and waters that circulated through basalts, constitutes an attractive prebiotic substrate. Conversely, inorganic catalysis of methane by FeNi3 competes with nascent and extant life.
Sleep, N HMeibom, AFridriksson, ThColeman, R GBird, D KengResearch Support, U.S. Gov't, Non-P.H.S.2004/08/25 05:00Proc Natl Acad Sci U S A. 2004 Aug 31;101(35):12818-23. Epub 2004 Aug 23.

Holocene evolution of the east Texas coast and inner continental shelf: Along-strike variability in coastal retreat rates - Rodriguez, A. B.; Anderson, J. B.; Siringan, F. P.; Taviani, M. (Journal of Sedimentary Research, 2004)
The low gradient east Texas coast and inner-continental shelf, from Sabine Lake at the Texas-Louisiana border to the western end of Galveston Island, experienced extreme along-strike variations in rates of Holocene coastal retreat. Around 7.7 ka a barrier shoreline was located approximately 55 klm offshore. Toward the western end of Galveston Island, the shoreline retreated 55 km, occupying a position on the lagoon side of the Island by about 5.3 ka. Toward the Texas-Louisiana border, the shoreline retreated more gradually, occupying a position seaward of Sabine Bank by 5.3 ka. Between 4.7 ka and 2.8 ka the shoreline at Sabine Bank retreated -30 km, while Galveston Island prograded seaward. Bolivar Peninsula began to accrete around 1.5 ka. Heald and Sabine banks, located on the inner continental shelf above terraced fluvial deposits of the Trinity-Sabine incised valley, are the only preserved remnants of these former shoreline positions. Fluctuating rates of sea-level rise were not the forcing mechanism behind episodes of rapid shoreline retreat because these events were localized. Rather, along-strike variations in the rate of transgression were caused by the variable inner-shelf gradients, which increase towards the west, and the orientation of the Sabine incised valley and associated terraced fluvial deposits, which trend northeast-southwest (parallel to shore). As shorelines retreated over fluvial deposits, these served as local sand sources that enabled barrier islands to persist offshore, out of equilibrium with sea level. Once these sand sources became depleted, and/or sea level reached some critical threshold, barrier shorelines became stranded offshore as banks, and new shorelines formed landward. The geologic setting of coastal areas, specifically antecedent topography, plays a primary role in controlling coastal evolution. To accurately forecast long-term (centennial to millennial) coastal evolution, it is essential that impacts associated with variations in the underlying geology of coastal areas be incorporated into coastal forecasting models.
id: 2042; PT: J; UT: WOS:000221339900007

Holocene fault scarps near Tacoma, Washington, USA - Sherrod, B. L.; Brocher, T. M.; Weaver, C. S.; Bucknam, R. C.; Blakely, R. J.; Kelsey, H. M.; Nelson, A. R.; Haugerud, R. (Geology, 2004)
Airborne laser mapping confirms that Holocene active faults traverse the Puget Sound metropolitan area, northwestern continental United States. The mapping, which detects forest-floor relief of as little as 15 cm, reveals scarps along geophysical lineaments that separate areas of Holocene uplift and subsidence. Along one such line of scarps, we found that a fault warped the ground surface between A.D. 770 and 1160. This reverse fault, which projects through Tacoma, Washington, bounds the southern and western sides of the Seattle uplift. The northern flank of the Seattle uplift is bounded by a reverse fault beneath Seattle that broke in A.D. 900-930. Observations of tectonic scarps along the Tacoma fault demonstrate that active faulting with associated surface rupture and ground motions pose a significant hazard in the Puget Sound region.
765ehTimes Cited:50Cited References Count:22

Hydrologic variation during the last 170,000 years in the southern hemisphere tropics of South America - Fritz, S. C.; Baker, P. A.; Lowenstein, T. K.; Seltzer, G. O.; Rigsby, C. A.; Dwyer, G. S.; Tapia, P. M.; Arnold, K. K.; Ku, T. L.; Luo, S. D. (Quaternary Research, 2004)
Despite the hypothesized importance of the tropics in the global climate system, few tropical paleoclimatic records extend to periods earlier than the last glacial maximum (LGM), about 20,000 years before present. We present a well-dated 170,000-year time series of hydrologic variation from the southern hemisphere tropics of South America that extends from modem times through most of the penultimate glacial period. Alternating mud and salt units in a core from Salar de Uyuni, Bolivia reflect alternations between wet and dry periods. The most striking feature of the sequence is that the duration of paleolakes increased in the late Quaternary. This change may reflect increased precipitation, geomorphic or tectonic processes that affected basin hydrology, or some combination of both. The dominance of salt between 170,000 and 140,000 yr ago indicates that much of the penultimate glacial period was dry, in contrast to wet conditions in the LGM. Our analyses also suggest that the relative influence of insolation forcing on regional moisture budgets may have been stronger during the past 50,000 years than in earlier times. (C) 2003 University of Washington. All rights reserved.
776jhTimes Cited:98Cited References Count:43

Late Quaternary sedimentation and deformation in Santa Monica and Catalina Basins, offshore southern California - Normark, W. R.; Baher, S.; Sliter, R. (Geology and Tectonics of Santa Cataline Island and the California Continental Borderland, 2004)
id: 991

Mangrove ecocystem dynamics and elemental cycling at Twin Cays, Belize, during the Holocene - Wooller, M. J.; Behling, H.; Smallwood, B. J.; Fogel, M. (Journal of Quaternary Science, 2004)
Existing at the transition between the terrestrial environment and hydrosphere, mangroves are sensitive to environmental change (e.g. sea-level rise). We present pollen and stable isotope data from a core (TCC1) of continuous (10 m) mangrove peat from Twin Cays, ∼12 km off of the coast of Belize, Central America. Radiocarbon dates on fragments of mangrove leaves preserved in TCC1 show that the core provides an 8600 14C year record of mangrove ecosystem changes. Variation in the stable carbon and nitrogen isotope composition (δ13C = ∼−30 to −25‰; δ15N = ∼−6 to 2‰) of mangrove leaves imply that the stand structure and nutrient status of the mangroves at the site have changed during the Holocene. Pollen data from the same core show that the floral composition of the site has changed at points during the Holocene, most notably a brief (∼240 years) switch at ∼3860 14C yr BP to dominance by a species of Myrsine (not currently present at the site). Our results are consistent with significant environmental changes (either marked disturbance from hurricanes or fluctuations in sea-level) through the Holocene.
id: 1149
Keywords: Holocene; isotopes; pollen; mangroves; Palaeoecology

Mantle Samples Included in Volcanic Rocks: Xenoliths and Diamonds - Pearson, D. G.; Canil, D.; Shirey, S. B. (Treatise on Geochemistry, 2004)
id: 1575

Natural Radiocarbon Distribution in the Deep Ocean - Matsumoto, Katsumi; Key, Robert M. (Global Environmental Change in the Ocean and on Land, 2004)

Natural radiocarbon distribution in the deep ocean - Matsumoto, K.; Key, R. M. (Global Environmental Change in the Ocean and on Land, 2004)
id: 1050

Oceanic ventilation and biogeochemical cycling: Understanding the physical mechanisms that produce realistic distributions of tracers and productivity - Gnanadesikan, A.; Dunne, J. P.; Key, R. M.; Matsumoto, K.; Sarmiento, J. L.; Slater, R. D.; Swathi, P. S. (Global Biogeochemical Cycles, 2004)
[1] Differing models of the ocean circulation support different rates of ventilation, which in turn produce different distributions of radiocarbon, oxygen, and export production. We examine these fields within a suite of general circulation models run to examine the sensitivity of the circulation to the parameterization of subgridscale mixing and surface forcing. We find that different models can explain relatively high fractions of the spatial variance in some fields such as radiocarbon, and that newer estimates of the rate of biological cycling are in better agreement with the models than previously published estimates. We consider how different models achieve such agreement and show that they can accomplish this in different ways. For example, models with high vertical diffusion move young surface waters into the Southern Ocean, while models with high winds move more young North Atlantic water into this region. The dependence on parameter values is not simple. Changes in the vertical diffusion coefficient, for example, can produce major changes in advective fluxes. In the coarse-resolution models studied here, lateral diffusion plays a major role in the tracer budget of the deep ocean, a somewhat worrisome fact as it is poorly constrained both observationally and theoretically.
867xpTimes Cited:66 Cited References Count:42
Keywords: Biogeochemical cycles; bottom water formation; circulation models; diffusion; particle export; pycnocline; sensitivity; Temperature; vertical exchange; weddell sea; World Ocean

Organic carbon accumulation in the South Atlantic Ocean: 1st modern, mid-Holocene and Last Glacial distribution - Mollenhauer, Gesine; Schneider, Ralph R.; Jennerjahn, Tim; Muller, Peter J.; Wefer, Gerold (Global and Planetary Change, 2004)
id: 1704

Paleochannel incision and infill on the New Jersey shelf: timing, character and depositional environment - Alexander, C.; Christensen, C.; Goff, J.; Austin J.A, Jr.; Venherm, C.; Nordfjord, S.; Gulick, S.; Sommerfield, C.; Fulthorpe, C.; Schock, S. (2005 SE GSA Meeting, 2004)
id: 1120

Phylogenetically specific spearation of rRNA from prokaryotes for isotopic analysis - Pearson, Ann; Sessions, Alex L.; Edwards, Katrina J.; Hayes, John M. (Marine Chemistry, 2004)
id: 1805

Plans for Expanded 14C Analyses at the NOSAMS Facility--a status and progress report. 9th International Conference on Accelerator Mass Spectrometry, Nagoya, Japan, 9/2002 - von Reden, K.; Donoghue, J.; Elder, K.; Gagnon, A.; Gerlach, D.; Griffin, V. S.; Healy, R.; Long, P.; McNichol, A. P.; Percy, D.; Roberts, M. L.; Schneider, R. J.; et al. (Nuclear Instruments and Methods in Physics Research, 2004)
id: 1810

Quartz content and the quartz-to-plagioclase ratio determined by X-ray diffraction: a proxy for ice rafting in the northern North Atlantic? - Moros, M.; McManus, J. F.; Rasmussen, T.; Kuijpers, A.; Dokken, T.; Snowball, I.; Jansen, E.; Neilsen, T. (Earth and Planetary Science Letters, 2004)
id: 713

Quaternary sea level history of the United States - Muhs, D. R.; Wehmiller, J. F.; Simmons, K. R.; York, L. L. (The Quaternary period in the United States, Developments in Quaternary science, 2004)
id: 706

Radiocarbon ages of marine bimarkers and co-occurring foraminifera: evidence for differential particle transport on continental margins, Poster - Mollenhauer, Gesine; Eglinton, Timothy I.; Hayes, John M.; Kienast, Markus; Lamy, Frank; Meggers, Helge; Schneider, Ralph R. (Eighth International Conference on Palaeoceanography, 2004)
id: 549

Time averaging on a shallow subtropical shelf: the search for a taphomomic clock - Barbour-Wood, S. L.; Krause R.A, Jr.; Kowalewski, M.; Wehmiller, J. F.; Simoes, M. G. (Geological Society of America, Abstracts with Programs, 2004)
36(2):134
id: 719

Ventilation of the glacial deep Pacific Ocean - Broecker, W.; Barker, S.; Clark, E.; Hajdas, I.; Bonani, G.; Stott, L. (Science, 2004)
Measurements of the age difference between coexisting benthic and planktic foraminifera from western equatorial Pacific deep-sea cores suggest that during peak glacial time the radiocarbon age of water at 2-kilometers depth was no greater than that of today. These results make unlikely suggestions that a slowdown in deep-ocean ventilation was responsible for a sizable fraction of the increase of the ratio of carbon-14 (14C) to carbon in the atmosphere and surface ocean during glacial time. Comparison of 14C ages for coexisting wood and planktic foraminifera from the same site suggests that the atmosphere to surface ocean 14C to C ratio difference was not substantially different from today's.
Broecker, WallaceBarker, StephenClark, ElizabethHajdas, IrkaBonani, GeorgesStott, Lowelleng2004/11/13 09:00Science. 2004 Nov 12;306(5699):1169-72.

Western Long Island Sound: evidence from diatom studies of eutrophication and environmental change in the 19th centure - Cooper, S. R.; Thomas, E.; Varekamp, J. C.; Sangiorgio, F. (AERS fall meeting, 2004)
id: 736

14C activity and global carbon cycle changes over the past 50,000 years - Hughen, K. A.; Lehman, S. J.; Southon, J.; Overpeck, J. T.; Marchal, O.; Herring, C.; Turnbull, J. (Abstracts, 18th International Radiocarbon Conf., 2003)
id: 1079

A 1600-year history of the Labrador Current off Nova Scotia - Keigwin, L. D.; Sachs, J. P.; Rosenthal, Y. (Climate Dynamics, 2003)
A multicore from Emerald Basin, on the continental margin off Nova Scotia, has a modern C-14 age at the top, and other C-14 dates indicate a linear sedimentation rate of similar to30 cm/ka to 1600 calendar years BP. This rate is great enough to record century-to-millennial scale changes in the surface and deep (similar to250 m) waters in the basin that are influenced by the Labrador Current. We applied five proxies for seawater temperature changes to the sediments of Emerald Basin, including the percent abundance and the oxygen isotope ratio (delta(18)O) of the polar planktonic foraminifer N. pachyderma (s.), the unsaturation ratio of alkenones (U-37(k')) produced by prymnesiophyte phytoplankton, and the delta(18)O and Mg/Ca of benthic foraminifera. All five proxies indicate the ocean warmed suddenly sometime in the past 150 years or so. The exact timing of this event is uncertain because C-14 dating is inaccurate in recent centuries, but this abrupt warming probably correlates with widespread evidence for warming in the Arctic in the nineteenth century. Because the Canadian Archipelago is one of the two main sources for the Labrador Current, warming and melting of ice caps in that region may have affected Labrador Current properties. Before this recent warming, sea surface temperature was continually lower by 1-2 degreesC, and bottom water was colder by about 6 degreesC in Emerald Basin. These results suggest that there was no Medieval Warm Period in the coastal waters off Nova Scotia. Because there is also no evidence of medieval warming in the Canadian archipelago, it seems likely that coastal waters from Baffin Bay to at least as far south as Nova Scotia were continually cold for similar to1500 of the past 1600 years.
698thTimes Cited:25Cited References Count:31

Asynchronous alkenone and foraminifera records from the Benguela Upwelling System - Mollenhauer, Gesine; Eglinton, Timothy I.; Ohkouchi, Naohiko; Schneider, Ralph R.; Muller, Peter J.; Grootes, Pieter M.; Rullkotter, Jurgen (Geochimica et Cosmochimica Acta, 2003)
id: 1067

Calcium carbonate budget in the Atlantic Ocean based on water column inorganic carbon chemistry - Chung, S. N.; Lee, K.; Feely, R. A.; Sabine, C. L.; Millero, F. J.; Wanninkhof, R.; Bullister, J. L.; Key, R. M.; Peng, T. H. (Global Biogeochemical Cycles, 2003)
[1] Recent independent lines of evidence suggest that the dissolution of calcium carbonate (CaCO3) particles is substantial in the upper ocean above the calcite 100% saturation horizon. This shallow-water dissolution of carbonate particles is in contrast with the current paradigm of the conservative nature of pelagic CaCO3 at shallow water depths. Here we use more than 20,000 sets of carbon measurements in conjunction with CFC and C-14 data from the WOCE/JGOFS/OACES global CO2 survey to estimate in situ dissolution rates of CaCO3 in the Atlantic Ocean. A dissolution rate is estimated from changes in alkalinity as a parcel of water ages along an isopycnal surface. The in situ CaCO3 dissolution increases rapidly at the aragonite 100% saturation horizon. Estimated dissolution rates north of 40degreesN are generally higher than the rates to the south, which is partly attributable to the production of exported CaCO3 being higher in the North Atlantic than in the South Atlantic. As more CaCO3 particles move down the water column, more particles are available for in situ dissolution. The total water column CaCO3 dissolution rate in the Atlantic Ocean is determined on an annual basis by integrating estimated dissolution rates throughout the entire water column and correcting for alkalinity input of approximately 5.6 x 10(12) mol C yr(-1) from CaCO3-rich sediments. The resulting water column dissolution rate of CaCO3 for the Atlantic Ocean is approximately 11.1 x 10(12) mol C yr(-1). This corresponds to about 31% of a recent estimate (35.8 x 10(12) mol C yr(-1)) of net CaCO3 production by Lee [2001] for the same area. Our calculation using a large amount of high-quality water column alkalinity data provides the first basin-scale estimate of the CaCO3 budget for the Atlantic Ocean.
732egTimes Cited:44 Cited References Count:73
Keywords: alkalinity; anthropogenic co2; caco3 dissolution; calcium carbonate budget; chemical lysocline; Deep-sea; dioxide system; dissociation-constants; dissolution kinetics; dissolution of calcium carbonate; eastern north-atlantic; ocean carbon cycle; organic-carbon; pacific-ocean; saturation state of seawater

The Catfish Lake scarp: preliminary field data and implications for earthquake hazards posed by the Tacoma fault - Sherrod, B. L.; Nelson, A. R.; Kelsey, H. M.; Brocher, T. M.; Blakely, R. J.; Weaver, C. S.; Rountree, N. K.; Rhea, S.; Jackson, B. S. (U. S. Geological Survey Open-File Report, 2003)
id: 430

Changes in the 13C/12C of dissolved inorganic carbon in the ocean as a tracer of anthropogenic CO2 uptake - Quay, P.; Sonnerup, R.; Westby, T.; Stutsman, J.; McNichol, A. (Global Biogeochemical Cycles, 2003)
id: 1546

Changes of the 13C/12C of dissolved inorganic carbon in the ocean as a tracer of anthropogenic C)2 uptake - Quay, P. D.; Sonnerup, T.; Westby, J.; Stutsman, J.; McNichol, A. P. (Global Biogeochemical Cycles, 2003)
id: 1689

Climate and the collapse of Mayan civilization - Haug, G. H.; Gunther, D.; Peterson, L. C.; Sigman, D. M.; Hughen, K. A. (Science, 2003)
id: 556

A comparison of rates of time averaging between the bivalve Macoma cleryana and brachiopod Bouchardia rosea on a shallow subtropical shelf - Barbour-Wood, S. L.; Krause R.A, Jr.; Kowalewski, M.; Wehmiller, J. F.; Simoes, M. G.; Goodfriend, G. A. (Geological Society of America, Abstracts with Programs, 2003)
35(6):273
id: 720

Composition and syngeneity of molecular fossils from the 2.78 to 2.45 billion-year-old Mount Bruce Supergroup, Pilbara Craton, Western Australia - Brocks, J. J.; Buick, R.; Logan, G. A.; Summons, R. E. (Geochimica Et Cosmochimica Acta, 2003)
Shales of very low metamorphic grade from the 2.78 to 2.45 billion-year-old (Ga) Mount Bruce Supergroup, Pilbara Craton, Western Australia, were analyzed for solvent extractable hydrocarbons. Samples were collected from ten drill cores and two mines in a sampling area centered in the Hamersley Basin near Wittenoom and ranging 200 km to the southeast, 100 km to the southwest and 70 km to the northwest. Almost all analyzed kerogenous sedimentary rocks yielded solvent extractable organic matter. Concentrations of total saturated hydrocarbons were commonly in the range of 1 to 20 ppm ( mug/g rock) but reached maximum values of 1000 ppm. The abundance of aromatic hydrocarbons was similar to1 to 30 ppm. Analysis of the extracts by gas chromatography-mass spectrometry (GC-MS) and GC-MS metastable reaction monitoring (MRM) revealed the presence of n-alkanes, mid- and end-branched monomethylalkanes, omega-cyclohexylalkanes, acyclic isoprenoids, diamondoids, tri- to pentacyclic terpanes, steranes, aromatic steroids and polyaromatic hydrocarbons. Neither plant biomarkers nor hydrocarbon distributions indicative of Phanerozoic contamination were detected. The host kerogens of the hydrocarbons were depleted in C-13 by 2 to 21parts per thousand relative to n-alkanes, a pattern typical of, although more extreme than, other Precambrian samples. Acyclic isoprenoids showed carbon isotopic depletion relative to n-alkanes and concentrations of 2alpha-methylhopanes were relatively high, features rarely observed in the Phanerozoic but characteristic of many other Precambrian bitumens. Molecular parameters, including sterane and hopane ratios at their apparent thermal maxima, condensate-like alkane profiles, high mono- and triaromatic steroid maturity parameters, high methyladamantane and methyldiamantane indices and high methylphenanthrene maturity ratios, indicate thermal maturities in the wet-gas generation zone. Additionally, extracts from shales associated with iron ore deposits at Tom Price and Newman have unusual polyaromatic hydrocarbon patterns indicative of pyrolytic dealkylation.The saturated hydrocarbons and biomarkers in bitumens from the Fortescue and Hamersley Groups are characterized as 'probably syngenetic with their Archean host rock' based on their typical Precambrian molecular and isotopic composition, extreme maturities that appear consistent with the thermal history of the host sediments, the absence of biomarkers diagnostic of Phanerozoic age, the absence of younger petroleum source rocks in the basin and the wide geographic distribution of the samples. Aromatic hydrocarbons detected in shales associated with iron ore deposits at Mt Tom Price and Mt Whaleback are characterized as 'clearly Archean' based on their hypermature composition and covalent bonding to kerogen. Copyright (C) 2003 Elsevier Ltd.
741dvTimes Cited:124Cited References Count:102

Compound specific radiocarbon dating of alkenones: methodological considerations and applications in paleoceanography - Mollenhauer, Gesine; Eglinton, Timothy I.; Schneider, Ralph R.; Meggers, Helge; Lamy, Frank; Ohkouchi, Nao; Hayes, John M. (18th International Radiocarbon Conference, 2003)
id: 1070

Continuous-Flow Accelerator Mass Spectrometry - Roberts, M. L.; Benthien, A.; Schneider, R. J.; von Reden, K. F.; Hayes, J. M. (International Symposium on Radiation Physics, 2003)
id: 1683

Contrasting He-C relationships in Nicaragua and Costa Rica: insights into C cycling through subduction zones - Shaw, A. M.; Hilton, D. R.; Fischer, T. P.; Walker, J. A.; Alvarado, G. E. (Earth and Planetary Science Letters, 2003)
We report He-3/He-4 ratios, relative He, Ne, and CO2 abundances as well as delta(13)C values for volatiles from the volcanic output along the Costa Rica and Nicaragua segments of the Central American arc utilising fumaroles, geothermal wells, water springs and bubbling hot springs. CO2/He-3 ratios are relatively constant throughout Costa Rica (av. 2.1 X 10(10)) and Nicaragua (av. 2.5 X 10(10)) and similar to arcs worldwide (similar to1.5 X 10(10)). delta(13)C values range from -6.8parts per thousand (MORB-like) to -0.1parts per thousand (similar to marine carbonate (0parts per thousand)). He-3/He-4 ratios are essentially MORB-like (8 +/- R-A) with some samples showing evidence of crustal He additions - water spring samples are particularly susceptible to modification. The He-CO2 relationships are consistent with an enhanced input of slab-derived C to magma sources in Nicaragua ((L+S)/M = 16; where L, M and S represent the fraction of CO2 derived from limestone and/or marine carbonate (L), the mantle (M) and sedimentary organic C (S) sources) relative to Costa Rica ((L+S)/M = 10). This is consistent with prior studies showing a higher sedimentary flux to the arc volcanics in Nicaragua (as traced by Ba/La, Be-10 and La/Yb). Possible explanations include: (1) offscraping of the uppermost sediments in the Costa Rica forearc, and (2) a cooler thermal regime in the Nicaragua subduction zone, preserving a higher proportion of melt-inducing fluids to subarc depths, leading to a higher degree of sediment transfer to the subarc mantle. The absolute flux Of CO2 from the Central American arc as determined by correlation spectrometry methods (5.8 X 10(10) mol/yr) and CO2/He-3 ratios (7.1 X 10(10) mol/yr) represents approximately 14-18% of the amount of CO2 input at the trench from the various slab contributors (carbonate sediments, organic C, and altered oceanic crust). Although the absolute flux is comparable to other arcs, the efficiency Of CO2 recycling through the Central American are is surprisingly low (14-18% vs. a global average of similar to50%). This may be attributed to either significant C loss in the forearc region, or incomplete decarbonation of carbonate sediments at subarc depths. The implication of the latter case is that a large fraction of C (up to 86%) may be transferred to the deep mantle (depths beyond the source of arc magmas). (C) 2003 Elsevier B.V. All rights reserved.
725paTimes Cited:98Cited References Count:50

Eutrophication and carbon sources in Chesapeake Bay over the last 2700 yr: human impacts in context - Bratton, John F.; Colman, Steven M.; Seal, Robert R. (Geochimica et Cosmochimica Acta, 2003)
To compare natural variability and trends in a developed estuary with human-influenced patterns, stable isotope ratios (δ13C and δ15N) were measured in sediments from five piston cores collected in Chesapeake Bay. Mixing of terrestrial and algal carbon sources primarily controls patterns of δ13Corg profiles, so this proxy shows changes in estuary productivity and in delivery of terrestrial carbon to the bay. Analyses of δ15N show periods when oxygen depletion allowed intense denitrification and nutrient recycling to develop in the seasonally stratified water column, in addition to recycling taking place in surficial sediments. These conditions produced 15N-enriched (heavy) nitrogen in algal biomass, and ultimately in sediment. A pronounced increasing trend in δ15N of +4‰ started in about A.D. 1750 to 1800 at all core sites, indicating greater eutrophication in the bay and summer oxygen depletion since that time. The timing of the change correlates with the advent of widespread land clearing and tillage in the watershed, and associated increases in erosion and sedimentation. Isotope data show that the region has experienced up to 13 wet-dry cycles in the last 2700 yr. Relative sea-level rise and basin infilling have produced a net freshening trend overprinted with cyclic climatic variability. Isotope data also constrain the relative position of the spring productivity maximum in Chesapeake Bay and distinguish local anomalies from sustained changes impacting large regions of the bay. This approach to reconstructing environmental history should be generally applicable to studies of other estuaries and coastal embayments impacted by watershed development.
id: 541

Field and laboratory data from an earthquake history study of the Waterman Point fault, Kitsap County, Washington - Nelson, A. R.; Johnson, S. Y.; Kelsey, S. K.; Wells, R. E.; Sherrod, B. L.; Bradley, L. A.; Okumura, K.; Bogar, R. (U. S. Geological Survey Miscellaneous Field Studies, 2003)
id: 429

Global MORB chemistry compilation at the segment scale - Su, Y.; Langmuir, C. H. (Database available at http://www.petdb.org., 2003)
id: 1600

Isotopic and geochemical assessment of in situ biodegradation of chlorinated hydrocarbons - Kirtland, B. C.; Aelion, C. M.; Stone, P. A.; Hunkeler, D. (Environ Sci Technol, 2003)
Currently there is no in situ method to detect and quantify complete mineralization of chlorinated hydrocarbons (CHCs) to CO2. Combined isotopic measurements in conjunction with traditional chemical techniques were used to assess in situ biodegradation of trichloroethylene (TCE) and carbon tetrachloride (CT). Vadose zone CHC, ethene, ethane, methane, O2, and CO2 concentrations were analyzed using gas chromatography over 114 days at the Savannah River Site. delta13C of CHC and delta13C and 14C of vadose zone CO2, sediment organic matter, and groundwater dissolved inorganic carbon (DIC)were measured. Intermediate metabolites of TCE and CT accounted for < or = 10% of total CHCs. Delta13C of cis-1,2-dichloroethylene (DCE) was always heavier than TCE indicating substantial DCE biodegradation. 14C-CO2 values ranged from 84 to 128 percent modern carbon (pMC), suggesting that plant root-respired CO2 was dominant. 14C-CO2 values decreased over time (up to 12 pMC), and contaminated groundwater 14C-DIC (76 pMC) was substantially depleted relative to the control (121 pMC). 14C provided a direct measure of complete CHC mineralization in vadose zone and groundwater in situ and may improve remediation strategies.
Kirtland, Brian CAelion, C MarjorieStone, Peter AHunkeler, DanielengResearch Support, Non-U.S. Gov'tResearch Support, U.S. Gov't, Non-P.H.S.2003/10/04 05:00Environ Sci Technol. 2003 Sep 15;37(18):4205-12.

Late Holocene earthquakes on the Toe Jam Hill fault, Seattle fault zone, Bainbridge Island, Washington - Nelson, A. R.; Johnson, S. Y.; Kelsey, H. M.; Wells, R. E.; Sherrod, B. L.; Pezzopane, S. K.; Bradley, L. A.; Koehler, R. D.; Bucknam, R. C. (Geological Society of America Bulletin, 2003)
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.
740qwTimes Cited:41Cited References Count:53

Magnitude and variability of Holocene sediment accumulation in Santa Monica Bay, California - Sommerfield, C. K.; Lee, H. J. (Mar Environ Res, 2003)
The spatial variability of Holocene (past 10,000 years) sediment accumulation in Santa Monica Bay (California) was examined to identify controls sediment trapping in a bathymetrically complex coastal embayment and to provide geologic context for the post-industrial sedimentary record and associated pollution gradients. Sediment chronologies based on downcore AMS 14C dates were used to quantify long-term (millennia) accumulation rates in an effort to elucidate particle-transport pathways and sinks. Sediment accumulation rates for the full range of bayfloor environments (50-630 m water depths) range from 22 to 102 mg/cm(2)/year (15-88 mm/100 year), have an overall mean of 51+/-21 mg/cm(2)/year (1 sigma, n=11), and are comparable to rates reported for adjacent borderland basins. Maximal accumulation rates on the Malibu shelf and within a reentrant to Redondo canyon are interpreted to reflect (1) proximity to sediment sources and (2) localized oceanographic and topographic conditions conducive to sediment trapping and deposition. The 14C-derived accumulation rates are 2-10 times lower than rates determined through (210)Pb geochronology for the same sites in a related study, revealing that Holocene sediment accumulation has been non-steady-state. Santa Monica Bay is an important sink for suspended matter; averaged over the past several millennia a mass of sediment equivalent to 10-80% of the modern annual river supply is sequestered yearly. Net influx of suspended matter derived from the adjacent Palos Verdes shelf is evinced by a concentration gradient of p,p'-DDE in bayfloor sediments, whereas the distribution of anthropogenic silver suggests transport from Santa Monica shelf to the southeastern boundary of the bay. The results of this study provide new insight to the long-term fates of particulate matter in Los Angeles coastal waters.
Sommerfield, Christopher KLee, Homa JengResearch Support, U.S. Gov't, Non-P.H.S.England2003/03/22 04:00Mar Environ Res. 2003 Jul-Aug;56(1-2):151-76.

Maps and data from a trench investigation of the Utsalady Point fault, Whidbey Island, Washington - Johnson, S. Y.; Nelson, A. R.; Personius, S. F.; Wells, R. E.; Kelsey, H. M.; Sherrod, B. L.; Okumura, K.; Koehler, R., III; Witter, R. C.; Bradley, L. A.; Harding, D. J. (U. S. Geological Survey Miscellaneous Field Studies, 2003)
id: 996

Microbial dolomite crusts from the carbonate platform off western India - Rao, V. P.; Kessarkar, P. M.; Krumbein, W. E.; Krajewski, K. P.; Schneider, R. J. (Sedimentology, 2003)
The occurrence of Late Pleistocene dolomite crusts that occur at 64 m depth on the carbonate platform off western India is documented. Dolomite is the most predominant mineral in the crusts. In thin section, the crust consists of dolomitized microlaminae interspersed with detrital particles. Under scanning electron microscopy, these laminae are made up of tubular filaments or cellular structures of probable cyanobacterial origin. Dolomite crystals encrust or overgrow the surfaces of the microbial filaments and/or cells; progressive mineralization obliterates their morphology. Well-preserved microbial mats, sulphide minerals (pyrrhotite and marcasite) and the stable isotope composition of dolomite in the crusts indicate hypersaline and anoxic conditions during dolomite formation. The crusts are similar to dolomite stromatolites, and biogeochemical processes related to decaying microbial mats under anoxic conditions probably played an important role in dolomite precipitation. The dolomite is therefore primary and/or very early diagenetic in origin. The dolomite crusts are interpreted to be a composite of microbial dolomite overprinted by early burial organic dolomite. The results of this study suggest that a microbial model for dolomite formation may be relevant for the origin of ancient massive dolomites in marine successions characterized by cryptalgal laminites. The age of the crusts further suggests that the platform was situated at shallow subtidal depths during the Last Glacial Maximum.
724ejTimes Cited:19Cited References Count:69

Quantitative estimates of time-averaging in terebratulidbrachiopod shell accumulations from a modern tropical shelf - Carroll, M.; Kowalewski, M.; Simoes, M. G.; Goodfriend, G. A. (Paleobiology, 2003)
Quantitative estimates of time-averaging in marine shellaccumulations available to date are limited primarily toaragonitic mollusk shells. We assessed time-averaging in Holoceneassemblages of calcitic brachiopod shells by direct dating ofindividual specimens of the terebratulid brachiopod Bouchardiarosea. The data were collected from exceptional (brachiopod-rich)shell assemblages, occurring surficially on a tropical mixedcarbonate-siliciclastic shelf (the Southeast Brazilian Bight, SWAtlantic), a setting that provides a good climatic andenvironmental analog for many Paleozoic brachiopod shell beds ofNorth America and Europe. A total of 82 individual brachiopodshells, collected from four shallow (5-25 m) nearshore (
id: 2231; Source type: scholarlyjournals; Object type: Article; Object type: Feature; CSAUnique: BONE5712965; AccNum: 5712965; DOI: 10.1043/0094-8373(2003)029(0381:QEOTIT)2.0.CO;2; ISSN: 0094-8373; Peer Reviewed: true

Radiocarbon ages of marine biomarkers and co-occurring foraminifera: evidence for differential particle transport on continental margins - Mollenhauer, Gesine; Eglinton, Timothy I.; Hayes, John M.; Keinast, Markus; Lamy, Frank; Meggers, Helge; Schneider, Ralph R. (AGU Fall Meeting 2003, 2003)
id: 1069

Sea-level changes and depositional environments in the Izmit Gulf, eastern Marmara Sea, during the late glacial-Holocene period - Cagatay, M. N.; Gorur, N.; Polonia, A.; Demirbag, E.; Sakinc, M.; Cormier, M. H.; Capotondi, L.; McHugh, C.; Emre, O.; Eris, K. (Marine Geology, 2003)
Offshore and onshore stratigraphic studies, together with high-resolution shallow seismic reflection profiling and multibeam bathymetric mapping, were carried out in the western and central part of the Izmit Gulf. These studies indicate that the Izmit Gulf was a lacustrine environment as part of the Marmara 'Lake' during the late glaciation and early deglaciation until similar to12 kyr BP, when the Marmara Basin was inundated by the Mediterranean waters. Correlation of C-14-dated onshore and offshore stratigraphic units in the Western Izmit Gulf indicates that generally coarse late glacial sediments overlie a marked erosional surface formed during the low water level of the Marmara 'Lake'. These coarse sediments are succeeded by 10.4-7 kyr BP old transgressive, and by late Holocene post-transgression mud units. The bathymetry and sub-bottom Chirp profiles clearly show that the paleoshoreline of the Gulf was located at -85 m, having been controlled by the bedrock sill depth of the Canakkale Strait. Another paleoshoreline observed at -65 m on the northern margin of the Western Izmit and Karamursel basins was probably formed during the Younger Dryas sea-level stillstand. The shelf areas during this time were colonized by bioherms, which were subsequently drowned and disappeared after a further rise of the sea level. The presence of a -65 in marine paleoshoreline in the Karamursel Basin indicates that the sill restricting this basin to the west was much deeper than its present -55 in level and was located further south. The Golcuk Basin, restricted by a -38 in sill to its west, was probably not flooded by marine waters until similar to9 kyr BP. (C) 2003 Published by Elsevier B.V.
749gpTimes Cited:52Cited References Count:30

Sedimentology and age control of late Quaternary New Jersey shelf deposits - Alexander, C.; Sommerfield, C.; Austin J.A, Jr.; Christensen, B.; Fulthorpe, C.; Goff, J.; Gulick, S.; Nordfjord, S.; Nielson, D.; Schock, S. (AGU Fall 2003 Meeting, 2003)
id: 636

Suitability of glycerin-preserved otoliths for age validation using bomb radiocarbon - Campana, S. E.; Stanley, R. D.; Wischniowski, S. (Journal of Fish Biology, 2003)
The effect of glycerin storage on the bomb radiocarbon content of otoliths was determined experimentally. Storage in either pre- or post-bomb glycerin had no detectable effect on the bomb radiocarbon content of either pre- or post-bomb otoliths. Therefore bomb-dated age validation studies need not be restricted to freshly-collected samples or dry otoliths, implying that the large numbers of glycerin-archived otoliths around the world are suitable for age validation studies using bomb radiocarbon. (C) 2003 The Fisheries Society of the British Isles.
734gqTimes Cited:5Cited References Count:9

A 6100 14C year record of El Nino activity from the Galapagos Islands - Riedinger, M. A.; Steinitz-Kannan, M.; Last, W. M.; Brenner, M. (Journal of Paleolimnology, 2002)
id: 1485

Abundant brachiopods on a tropical, upwelling-influenced shelf (Southeast Brazilian Bight, South Atlantic - Kowalewski, M.; Simeos, M. G.; Carroll, M.; Rodland, D. L. (Palaios, 2002)
Rhynchonelliform brachiopods were diverse and often dominant benthos of tropical seas in the Paleozoic. In contrast, they are believed to be rare in open habitats of modern oceans, especially at low latitudes. This study documents numerous occurrences of rhynchonelliform brachiopods on a modern tropical shelf, particularly in areas influenced by upwelling. Extensive sampling of the outer shelf and coastal bays of the Southeast Brazilian Bight revealed dense populations of terebratulid brachiopods (>103 individuals / m2 of seafloor) between 24° and 26°S. On the outer shelf, brachiopods are more abundant than bivalves and gastropods combined. However, brachiopod diversity is low: only four species belonging to the genera Bouchardia, Terebratulina, Argyrotheca, and Platidia were identified among over 16000 examined specimens. Brachiopods occur preferentially on carbonate bottoms and include two substrate-related associations: Bouchardia (40–70% CaCO3 weight content) and Terebratulina-Argyrotheca (70–95% CaCO3). All four species display a broad bathymetric range that contrasts with a narrow depth tolerance postulated for many Paleozoic rhynchonelliforms. The most abundant populations occur in the depth range between 100 and 200 m, and coincide with zones of shelf-break upwelling, where relatively colder and nutrient-rich water masses of the South Atlantic Central Water are brought upward by cyclonic meanders of the South Brazil Current (a western boundary current that flows poleward along the coast of Brazil). This is consistent with previous biological and paleontological studies that suggest upwelling may play a role in sustaining brachiopod-dominated benthic associations. The presence of abundant brachiopods in the open habitats of the tropical shelf of the western South Atlantic contrasts with current understanding of their latitudinal distribution and points to major gaps in our knowledge of their present-day biogeography. The ecological importance of rhynchonelliform brachiopods in modern oceans and their role as producers of biogenic sedimentary particles may be underestimated.
id: 1416

The Antarctic ice sheet during the last glacial maximum and its subsequent retreat histroy: a review - Anderson, J. B.; Shipp, S. S.; Lowe, A. L.; Wellner, J. S.; Mosola, A. (Quaternary Science Reviews, 2002)
An emerging body of evidence from studies of the last glacial/interglacial cycle suggests that the East and West Antarctic ice sheets have not advanced and retreated in concert. The West Antarctic ice sheet advanced to the outer shelf in most regions during the Last Glacial Maximum (LGM). The retreat from the shelf commenced shortly after the LGM and continued into the late Holocene. The West Antarctic Ice Sheet in Ross and Amundsen seas slid across a deforming bed, at least during the final phases of extended glaciation. This implies that at this time the ice sheet had a low profile. Differences in the number and locations of grounding-zone wedges and smaller grounding zone features from trough to trough imply that individual West Antarctic Ice Sheet ice streams retreated episodically. Details concerning the expansion, retreat, and behavior of the East Antarctic Ice Sheet (EAIS) are more sparse. The picture emerging is that the EAIS did not expand to the continental shelf edge during the LGM; rather, it achieved a maximum extent of a mid-shelf position in some locations, while in other areas the ice terminus was situated near its present location. The timing of retreat along sectors within the EAIS appears diachronous, and in places occurred prior to the LGM. The Antarctic Peninsula shelf contained considerably more ice during the LGM than previously proposed. The results presented in this paper support more recent published ice-sheet models that call for greater contributions of melting ice from West Antarctica, including the Antarctic Peninsula, to the post-glacial rise in sea level.
id: 1126

Birth of the modern Chesapeake Bay estuary between 7.4 and 8.2 ka and implications for global sea-level rise - Bratton, John F.; Colman, Steven M.; Thieler, E. Robert; Seal, Robert R. (Geo-Marine Letters, 2002)
Two major pulses of sea-level rise are thought to have taken place since the last glacial maximum — meltwater pulses (mwp) 1A (12 cal ka) and 1B (9.5 cal ka). Between mwp 1B and about 6 cal ka, many of the complex coastal ecosystems which ring the world’s oceans began to form. Here we report data for rhenium, carbon isotopes, total organic carbon, and fossil oysters from Chesapeake Bay which span the transition from fresh to brackish water conditions in the bay in the mid-Holocene. These data constrain sea-level change and resulting environmental change in the bay. They indicate that the transition was rapid, and that it was produced by (1) a third pulse of rapid eustatic sea-level rise, or (2) a geometry of the prehistoric Chesapeake Bay basin which predisposed it to a nonlinear response to a steadily rising sea level. Similar nonlinear changes in vulnerable coastal environments are likely to take place in the future due to polar warming, regardless of the timing or rate of sea-level rise.
id: 540

Bomb radiocarbon and anthropogenic CO2 in ocean biogeochemical models - Matsumoto, K.; Sarmiento, J.; Key, R.; Slater, C.; Sabine, C. (AGU/ASLO Conference, 2002)
id: 320

Changes in the 13C/12C of dissolved inorganic carbon in the ocean as a tracer of anthropogenic CO2 uptake - Quay, P. D.; Sonnerup, R.; Westby, T.; Stutsman, J.; McNichol, A. P. (Global Biogeochemical Cycles, 2002)
id: 1715

Chemical and carbon isotopic evidence for the source and fate of dissolved organic matter in the northern Everglades - Wang, Y.; Hsieh, Y. P.; Landing, W. M.; Choi, Y. H.; Salters, V.; Campbell, D. (Biogeochemistry, 2002)
id: 616

Composition, age, provenance of organic matter in N. W. African dust over the Atlantic Ocean - Eglinton, T. I.; Eglinton, G.; Dupont, L.; Montlucon, D.; Sholkovitz, E.; Reddy, C. M. (Geochemistry, Geophysics, Geosystems G3, 2002)
id: 611

Compositional characterization of prehistoric ceramics: A new approach - Kennett, D. J.; Sakai, S.; Neff, H.; Gossett, R.; Larson, D. O. (Journal of Archaeological Sciences, 2002)
id: 474

A Critical Evaluation of Interlaboratory Data on Total, Elemental, and Isotopic Carbon in the Carbonaceous Particle Reference Material, NIST SRM 1649a - Currie, L. A.; Benner, B. A., Jr.; Kessler, J. D.; Klinedinst, D. B.; Klouda, G. A.; Marolf, J. V.; Slater, J. F.; Wise, S. A.; Cachier, H.; Cary, R.; Chow, J. C.; Watson, J.; et al. (J Res Natl Inst Stand Technol, 2002)
Because of increased interest in the marine and atmospheric sciences in elemental carbon (EC), or black carbon (BC) or soot carbon (SC), and because of the difficulties in analyzing or even defining this pervasive component of particulate carbon, it has become quite important to have appropriate reference materials for intercomparison and quality control. The NIST "urban dust" Standard Reference Material((R)) SRM 1649a is useful in this respect, in part because it comprises a considerable array of inorganic and organic species, and because it exhibits a large degree of ((14)C) isotopic heterogeneity, with biomass carbon source contributions ranging from about 2 % (essentially fossil aliphatic fraction) to about 32 % (polar fraction). A primary purpose of this report is to provide documentation for the new isotopic and chemical particulate carbon data for the most recent (31 Jan. 2001) SRM 1649a Certificate of Analysis. Supporting this is a critical review of underlying international intercomparison data and methodologies, provided by 18 teams of analytical experts from 11 institutions. Key results of the intercomparison are: (1) a new, Certified Value for total carbon (TC) in SRM 1649a; (2) (14)C Reference Values for total carbon and a number of organic species, including for the first time 8 individual PAHs; and (3) elemental carbon (EC) Information Values derived from 13 analytical methods applied to this component. Results for elemental carbon, which comprised a special focus of the intercomparison, were quite diverse, reflecting the confounding of methodological-matrix artifacts, and methods that tended to probe more or less refractory regions of this universal, but ill-defined product of incomplete combustion. Availability of both chemical and (14)C speciation data for SRM 1649a holds great promise for improved analytical insight through comparative analysis (e.g., fossil/biomass partition in EC compared to PAH), and through application of the principle of isotopic mass balance.
Currie, L ABenner, B A JrKessler, J DKlinedinst, D BKlouda, G AMarolf, J VSlater, J FWise, S ACachier, HCary, RChow, J CWatson, JDruffel, E R MMasiello, C AEglinton, T IPearson, AReddy, C MGustafsson, OQuinn, J GHartmann, P CHedges, J IPrentice, K MKirchstetter, T WNovakow, TPuxbaum, HSchmid, Heng2002/01/01 00:00J Res Natl Inst Stand Technol. 2002 Jun 1;107(3):279-98. doi: 10.6028/jres.107.022. Print 2002 May-Jun.

Differences in 14C age between stratigraphically associated charcoal and marine shell from the archaic period site of kilometer 4, southern Peru: old wood or old water? - Kennett, D. J.; Ingram, B. L.; Southon, J. R.; Wise, K. (Radiocarbon, 2002)
id: 1023

The dynamics of pore water dissolved organic carbon and the fate of organic matter in anoxic marine sediments: As assessment using carbon isotopes and ultrafiltration. PhD thesis - Seagle, Carol A. (University of North Carolina at Chapel Hill, 2002)

El Nino-like pattern in Ice Age Tropical Pacific Sea surace temperature - Koutavas, Athanasios; Lynch-Stieglitz, Jean; Marchitto, Thomas M.; Sachs, Julian P. (Science, 2002)
Sea surface temperatures (SSTs) in the cold tongue of the eastern equatorial Pacific exert powerful controls on global atmospheric circulation patterns. We examined climate variability in this region from the Last Glacial Maximum (LGM) to the present, using a SST record reconstructed from magnesium/calcium ratios in foraminifera from sea-floor sediments near the Galápagos Islands. Cold-tongue SST varied coherently with precession-induced changes in seasonality during the past 30,000 years. Observed LGM cooling of just 1.2°C implies a relaxation of tropical temperature gradients, weakened Hadley and Walker circulation, southward shift of the Intertropical Convergence Zone, and a persistent El Niño–like pattern in the tropical Pacific. This is contrasted with mid-Holocene cooling suggestive of a La Niña–like pattern with enhanced SST gradients and strengthened trade winds. Our results support a potent role for altered tropical Pacific SST gradients in global climate variations.
id: 644

Field and laboratory data from an earthquake history study of the Toe Jam Hill fault, Bainbridge Island, Washington - Nelson, A. R.; Johnson, S. Y.; Wells, R. E.; Kelsey, H. M.; Pezzopane, S. K.; Sherrod, B. L.; Bradley, L. A.; Iii, Koehler R. D.; Bucknam, R. C.; Haugerud, R. A.; LaPrade, W. T. (U.S. Geological Survey Open-File Report, 2002)
id: 428

Field and Laboratory data from an earthquake history study of the Toe Jam Hill fault, Bainbridge Island, Washington - Nelson, A. R.; Johnson, S. Y.; Wells, R. E.; Pezzopane, S. K.; Kelsey, H. M.; Sherrod, B. L.; Bradley, L. A.; Koehler, R. D., III; Bucknam, R. C.; Haugerud, R. A.; LaPrade, W. T. (U.S. Geological Survey Open-File Report 02-60, 2002)
id: 259

Holocene moisture changes and fire frequency at Rio Rubens Bog, Southern Patagonia - Huber, U. M.; Markgraf, V. (Fire History, 2002)
id: 233

In situ calcium carbonate dissolution in the Pacific Ocean - Feely, R. A.; Sabine, C. L.; Lee, K.; Millero, F. J.; Lamb, M. F.; Greeley, D.; Bullister, J. L.; Key, R. M.; Peng, T. H.; Kozyr, A.; Ono, T.; Wong, C. S. (Global Biogeochemical Cycles, 2002)
Over the past several years researchers have been working to synthesize the WOCE/JGOFS global CO(2) survey data to better understand carbon cycling processes in the oceans. The Pacific Ocean data set has over 35,000 sample locations with at least two carbon parameters, oxygen, nutrients, CFC tracers, and hydrographic parameters. In this paper we estimate the in situ CaCO(3) dissolution rates in the Pacific Ocean water column. Calcium carbonate dissolution rates ranging from 0.01-1.1 mumol kg(-1) yr(-1) are observed in intermediate and deepwater beginning near the aragonite saturation horizon. In the North Pacific Intermediate Water between 400 and 800 m, CaCO(3) dissolution rates are more than 7 times faster than observed in middle and deep water depths (average=0.051 m mol kg(-1) yr(-1)). The total amount of CaCO(3) that is dissolved within the Pacific is determined by integrating excess alkalinity throughout the water column. The total inventory of CaCO(3) added by particle dissolution in the Pacific Ocean, north of 40degreesS, is 157 Pg C. This amounts to an average dissolution rate of approximately 0.31 Pg C yr(-1). This estimate is approximately 74% of the export production of CaCO(3) estimated for the Pacific Ocean. These estimates should be considered to be upper limits for in situ carbonate dissolution in the Pacific Ocean, since a portion of the alkalinity increase results from inputs from sediments.
649rqTimes Cited:86 Cited References Count:60
Keywords: anthropogenic co(2); anthropogenic co2; aragonite saturation; atmospheric carbon; caco(3) dissolution; calcite saturation; carbonate lysocline; chemical lysocline; coccolithophore emiliania-huxleyi; indian-ocean; north pacific; organic-matter; Pacific Ocean; panama basin; particulate matter

Inorganic carbon in the Indian Ocean: Distribution and dissolution processes - Sabine, C. L.; Key, R. M.; Feely, R. A.; Greeley, D. (Global Biogeochemical Cycles, 2002)
This study uses nearly 25,000 carbon measurements from the WOCE/JGOFS global CO2 survey to examine the distribution of dissolved inorganic carbon (DIC) and total alkalinity (TA) in the Indian Ocean. Shallow and intermediate distributions of inorganic carbon do not strictly follow temperature and salinity because of differing surface gradients and vertical biological processes that work to modify the circulation derived features. Anthropogenic CO2 has increased the shallow DIC by as much as 3%, decreasing the vertical DIC gradient. Deep ocean DIC and TA increase toward the north because of the decomposition and dissolution of organic and inorganic particles. Calcite saturation depths range from 2900-3900 m with the deepest saturation depth in the central Indian Ocean. Variations of aragonite saturation depth (200-1400 m) are similar to calcite, but the deepest saturations are in the southwestern Indian Ocean. The shallowest aragonite saturation depths are found in the Bay of Bengal. In the northern Arabian Sea and Bay of Bengal, the current aragonite saturations are 100 and 200 m shallower, respectively, than in preindustrial times. Estimates of carbonate dissolution rates on isopycnal surfaces range from 0.017 to 0.083 mumol kg(-1) yr(-1) in deep waters. Upper water column dissolution rates range from 0 to 0.73 mumol kg(-1) yr(-1), with a local maximum occurring in intermediate waters just below the aragonite saturation horizon. Dissolution is also generally higher north of the Chemical Front at 10-20degreesS. There is some evidence for significant sedimentary sources in the northern Indian Ocean.
643rkTimes Cited:50 Cited References Count:72
Keywords: alkalinity; anthropogenic co2; arabian sea; calcium carbonate; Carbon cycle; dioxide system; dissociation; indian ocean; pressure; saturation state; SEAWATER; Temperature; thermodynamics; total alkalinity; total co2; water

A late glacial-Holocene tephrochronology for glacial lakes in southern Ecuador - Rodbell, D. T.; Bagnato, S.; Nebolini, J. C.; Seltzer, G. O.; Abbott, M. B. (Quaternary Research, 2002)
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.
555kpTimes Cited:25Cited References Count:23

Late-Quaternary lowstands of Lake Titicaca: evidence from high-resolution seismic data - D'Agostino, K.; Seltzer, G.; Baker, P.; Fritz, S.; Dunbar, R. (Palaeogeography Palaeoclimatology Palaeoecology, 2002)
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.
560qxTimes Cited:31 Cited References Count:33
Keywords: Andes; bolivian altiplano; central andes; climatic-change; Holocene; lacustrine; lake level change; lake titicaca; level; malawi; Peru; record; seismic reflection data; tropical paleoclimate; tropical south-america

Ocean circulation: thermohaline circulation - Toggweiler, J. R.; Key, R. M. (Encyclopedia of Ocean Sciences, 2002)
id: 521

Ocean ventilation and sedimentation since the glacial maximum at 3 km in the western North Atlantic - Keigwin, L. D.; Schlegel, M. A. (Geochemistry Geophysics Geosystems, 2002)
[1] Stable isotope, sedimentological, and radiocarbon data from cores at similar to 3 km water depth on the Blake Ridge, western subtropical North Atlantic, reveal the history of deep water ventilation since the last glacial maximum (LGM). Bulk sediment accumulation rates varied locally by a factor of 2 under the influence of bottom currents in this sediment drift environment, but the sand flux, mostly foraminifera, was nearly identical at a given time. This suggests that the rain rate of foraminifera (mostly planktonic) was constant, that transport of foraminifera was negligible, and that current-controlled differences in clay and silt transport drive bulk accumulation. In two of the cores, flux peaks in the benthic foraminifera Cibicidoides and Uvigerina peregrina occurred during the Younger Dryas (YD) cold event, and at 18.2, 19.6, 21.1, 25.0, and 28.1 ka. Radiocarbon measurements on those benthic foraminifera show the ventilation age of bottom waters was similar to 1000 years during the YD, and for older events it was as great as 2000 years. These results contrast with Holocene ventilation, which was similar to 500 years and 700 years at 1500 years and similar to 7100 years before present, respectively.
565rlTimes Cited:26 Cited References Count:43
Keywords: abyssal circulation; benthic foraminifera; c-14 ages; Calibration; climate-change; deep-water; Holocene; Last glacial maximum; ocean ventilation; radiocarbon; radiocarbon age; sea; sediment drifts; Younger Dryas

Plans for expanded 14C analyses at the NOSAMS facility - a status and progress report - von Reden, K. F.; Donoghue, J.; Elder, K.; Gagnon, A.; Gerlach, D.; Griffin, V.; Healy, R.; Long, P.; McNichol, A.; Percy, D.; Roberts, M. L.; Schneider, R. J.; et al. (International Conference on Accelerator Mass Spectrometry, 2002)
id: 1685

Possible biological or physical explanations for decadal scale trends in North Pacific nutrient concentrations and oxygen utilization - Keller, K.; Slater, R. D.; Bender, M.; Key, R. M. (Deep-Sea Research Part Ii-Topical Studies in Oceanography, 2002)
We analyze North Pacific GEOSECS (1970s) and WOCE (1990s) observations to examine potential decadal trends of the marine biological carbon pump. Nitrate concentrations ([NO3]) and apparent oxygen utilization (AOU) decreased significantly in intermediate waters (by -0.6 and -2.9 mu mol kg(-1) respectively, at sigma (theta) = 27.4 kg m(-3), corresponding to approximate to 1050 m). In shallow waters (above roughly 750 m) [NO3-] and AOU increased, though the changes were not statistically significant. A sensitivity study with an ocean general circulation model indicates that reasonable perturbations of the biological carbon pump due to changes in export production or remineralization. efficiency are insufficient to account for the intermediate water tracer trends. However, changes in water ventilation rates could explain the intermediate water tracer trends and would be consistent with trends of water age derived from radiocarbon. Trends in AOU and [NO3-] provide relatively poor constraints on decadal scale trends in the marine biological carbon pump for two reasons. First, most of the expected changes due to decadal scale perturbations of the marine biota occur in shallow waters, where the available data are typically too sparse to account for the strong spatial and temporal variability. Second, alternative explanations for the observed tracer trends (e.g., changes in the water ventilation rates) cannot be firmly rejected. Our data analysis does not disprove the null-hypothesis of an unchanged biological carbon pump in the North Pacific. (C) 2001 Published by Elsevier Science Ltd.
507ceTimes Cited:24 Cited References Count:71
Keywords: anthropogenic co2 invasion; atmospheric co2; carbon-cycle; el-nino; hydrographic data; organic-matter; redfield ratios; sargasso-sea; subtropical gyre; vertical fluxes

Precambrian marine carbonate isotope database: Version 1.1 - Shields, G.; Veizer, J. (Geochemistry Geophysics Geosystems, 2002)
[1] We present a compilation of strontium, carbon, and oxygen isotope compositions of roughly 10,000 marine carbonate rocks of Archean - Ordovician age (3800 Ma - 450 Ma). The Precambrian Marine Carbonate Isotope Database (PMCID) has been compiled from 152 published and 3 unpublished articles and books of the past 40 years. Also included are 30 categories of relevant "metadata'' that allow detailed comparisons and quality assessments of the isotope data to be made. The PMCID will be updated periodically as new data and better age constraints come to light. Here we outline the structure of the first published version of the database and its inherent merits and limitations.
561enTimes Cited:103 Cited References Count:26
Keywords: 1010 geochemistry : chemical evolution; 1030 geochemistry : geochemical cycles (0330); 1040 geochemistry : isotopic composition/chemistry; 1050 geochemistry : marine geochemistry (4835,4850); calcite; carbonates; cycle; dolomite; evolution; Geochemistry; isotope stratigraphy; oceans; precambrian; SEAWATER; sediments; strontium; sulfur; time

Prehistoric cereamics in the upper James River region of the northeastern plains - Toom, Dennis L.; Schneider, Frederick E. (Conference on the ceramics of the northeastern plains and adjacent areas, 2002)
id: 1436

Prehistoric horticulture in the northeastern plains - Schneider, Frederick E. (Plains Anthropologist, 2002)
id: 1437

Radiocarbon dating of alkenones in sediments from the Namibian continental margin - Mollenhauer, Gesine; Eglinton, Timothy I.; Ohkouchi, Nao; Grootes, Pieter M.; Muller, Peter J.; Rullkotter, Jurgen; Schneider, Ralph R. (European Geophysical Society, XXVII General Assembly, 2002)
id: 546

Rapid isolation of biomarkers for compound specific radiocarbon dating using high-performance liquid chromatography and flow injection analysis - atmoospheric pressure chemical ionisation mass spectrometry - Smittenberg, R. H.; Hopmans, E. C.; Schouten, S.; Sinninghe-Damste, J. S. (Journal of Chromatography A, 2002)
id: 669

Shelf record of climatic changes in flood magnitude and frequency, north-coastal California - Sommerfield, C. K.; Drake, D. E.; Wheatcroft, R. A. (Geology, 2002)
Continental-shelf deposits off the Eel River, north-coastal California, document a recent increase in the magnitude and frequency of major hydrologic floods (greater than or equal to10 yr recurrence interval). The shelf record reveals a sudden, three-fold increase in sedimentation rate ca. 1954 and a concomitant increase in the frequency of preserved flood beds. Comparison of sedimentary and river-discharge records reveals that major floods after ca. 1950 had a more pronounced effect on coastal sediment delivery and accumulation offshore than previous recorded events of similar magnitude, and that stratigraphic preservation of flood events is highly dependent on flood frequency and net sedimentation rate. We contend that this change in marine sedimentation is a response to documented climatic phenomena that have increased the frequency of major floods throughout the western United States during the past half century, together with intrabasinal impacts of extreme floods in 1955 and 1964. Anthropogenic increase in watershed-sediment production is a probable secondary factor.
551ucTimes Cited:46Cited References Count:34

Stable chlorine and carbon isotopic compositions of selected semi-volatile organochlorine compounds - Drenzek, N. J.; Tarr, C. H.; Eglinton, T. I.; Heraty, L. J.; Sturchio, N. C.; Shiner, V. J.; Reddy, C. M. (Organic Geochemistry, 2002)
To assess whether the isotopic composition of semi-volatile organochlorine compounds (SVOCs) may be a useful tool, we measured the bulk delta(37)Cl and delta(13)C values of several pesticides and Aroclor mixtures from different suppliers. Overall, the delta(37)Cl and delta(13)C values ranged from -5.10 to + 1.22% and -31.63 to -22.39%, respectively. These values are narrower than the ranges observed previously for volatile organic contaminants (VOCs). In particular, the isotopic compositions of the Aroclor mixtures were very tightly constrained for both chlorine and carbon, We also observed that SVOCs synthesized from hexachlorocyclopentadiene had the most enriched delta(37)Cl values. These data provide a baseline for future work employing isotope ratios to study the environmental fate of SVOCs. (C) 2002 Elsevier Science Ltd. All rights reserved.
545bnTimes Cited:41 Cited References Count:25
Keywords: aroclors; fractionation; hydrocarbons; intrinsic bioremediation; samples; solvents; trichloroethene

Super ENSO and global climate oscillations at millennial time scales - Stott, L.; Poulsen, C.; Lund, S.; Thunell, R. (Science, 2002)
The late Pleistocene history of seawater temperature and salinity variability in the western tropical Pacific warm pool is reconstructed from oxygen isotope (delta18O) and magnesium/calcium composition of planktonic foraminifera. Differentiating the calcite delta18O record into components of temperature and local water delta18O reveals a dominant salinity signal that varied in accord with Dansgaard/Oeschger cycles over Greenland. Salinities were higher at times of high-latitude cooling and were lower during interstadials. The pattern and magnitude of the salinity variations imply shifts in the tropical Pacific ocean/atmosphere system analogous to modern El Nino-Southern Oscillation (ENSO). El Nino conditions correlate with stadials at high latitudes, whereas La Nina conditions correlate with interstadials. Millennial-scale shifts in atmospheric convection away from the western tropical Pacific may explain many paleo-observations, including lower atmospheric CO2, N2O, and CH4 during stadials and patterns of extratropical ocean variability that have tropical source functions that are negatively correlated with El Nino.
Stott, LowellPoulsen, ChristopherLund, SteveThunell, Roberteng2002/07/13 10:00Science. 2002 Jul 12;297(5579):222-6.

Test of negative ion beams from a microwave ion source with a charge exchange canal for accelerator mass spectrometry applications - Kim, S. W.; Schneider, R. J.; von Reden, K. F.; Hayes, J. M.; Wills, J. S. C. (Review of Scientific Instruments, 2002)
A test facility has been constructed to evaluate negative ion beams from small gaseous samples for accelerator mass spectrometry applications. The positive ion beams from the microwave ion source are passed into a charge-exchange canal (CXC) where the ions exchange electrons with magnesium vapor and become negatively charged. Positive molecular ions were: either neutralized or broken up into atomic ions and neutral atoms and molecules by collision processes. Most of the resulting particles were suspected to be neutrals. In studies with injections of CO2 pulses, the resulting positive and negative C-12 current peaks gave a 0.09% yield of C- ions from CO2 molecules, which includes a charge-exchange efficiency of 10%. Since nitrogen does not form a stable negative ion, N-14 background is virtually eliminated after the beam goes through the CXC, which is necessary for radiocarbon measurements. (C) 2002 American Institute of Physics.
2522wyTimes Cited:8Cited References Count:7

Vapour undersaturation in primitive mid-ocean-ridge basalt and the volatile content of Earth's upper mantle - Saal, A. E.; Hauri, E. H.; Langmuir, C. H.; Perfit, M. R. (Nature, 2002)
The analysis of volatiles in magmatic systems can be used to constrain the volatile content of the Earth's mantle and the influence that magmatic degassing has on the chemistry of the oceans and the atmosphere. But most volatile elements have very low solubilities in magmas at atmospheric pressure, and therefore virtually all erupted lavas are degassed and do not retain their primary volatile signatures. Here we report the undersaturated pre-eruptive volatile content for a suite of mid-ocean-ridge basalts from the Siqueiros intra-transform spreading centre. The undersaturation leads to correlations between volatiles and refractory trace elements that provide new constraints on volatile abundances and their behaviour in the upper mantle. Our data generate improved limits on the abundances of carbon dioxide, water, fluorine, sulphur and chlorine in the source of normal mid-ocean-ridge basalt. The incompatible behaviour of carbon dioxide, together with the CO(2)/Nb and CO(2)/Cl ratios, permit estimates of primitive carbon dioxide and chlorine to be made for degassed and chlorine-contaminated mid-ocean-ridge basalt magmas, and hence constrain degassing and contamination histories of mid-ocean ridges.
Saal, Alberto EHauri, Erik HLangmuir, Charles HPerfit, Michael RengEngland2002/10/09 04:00Nature. 2002 Oct 3;419(6906):451-5.

Were glacial iceberg surges in the North Atlantic triggered by global climatic warming? - Moros, M.; Kuijpers, A.; Snowball, I.; Lassen, S.; Backstrom, D.; Gingele, F.; McManus, J. F. (Marine Geology, 2002)
id: 712

WOCE radiocarbon IV: Pacific Ocean results; P10, P13N, P14C, P18, P19 & S4P - Key, R. M.; Quay, P. D.; Schlosser, P.; McNichol, A. P.; von Reden, K. F.; Schneider, R. J.; Elder, K. L.; Stuiver, M.; Ostlund, H. G. (Radiocarbon, 2002)
The World Ocean Circulation Experiment, carried out between 1990 and 1997, provided the most comprehensive oceanic survey of radiocarbon to date. Approximately 10,000 samples were collected in the Pacific Ocean by U.S. investigators for both conventional large volume P counting and small volume accelerator mass spectrometry analysis techniques. Results from six cruises are presented. The data quality is as good or better than previous large-scale surveys. The C-14 distribution for the entire WOCE Pacific data set is graphically described using mean vertical profiles and sections, and property-property plots.
591keTimes Cited:33Cited References Count:56

Woodlands in ancient and modern times in the territory of Sagalassos - Vermoere, M.; Vanhecke, L.; Paulissen, E.; Waelkens, M.; Smets, E. (Sagalassos VI. Report on the survey and excavation campaigns of 1998, 1999 and 2000, 2002)
id: 346

A 700 year sedimentary record of intense hurricane landfalls in southern New England - Donnelly, Jeffrey P.; Bryant, Sarah Smith; Butler, Jessica; Dowling, Jennifer; Fan, Linda; Hausmann, Neil; Newby, Paige; Shuman, Bryan; Stern, Jennifer; Westover, Karlyn; Webb, Thompson, III (GSA Bulletin, 2001)
id: 1343

Accumulation rates and sources of sediments and organic carbon on the Palos Verdes shelf based on multiple radioisotopic tracers (137Cs, 239,240Pu, 210Pb, 234Th, 238U and 14C) - Santschi, P. H.; Guo, L.; Asbill, S.; Allison, M.; Kepple, B.; Wen, L. S. (Marine Chemistry, 2001)
We report here bioturbation and sediment accumulation rates determined from replicate sediment cores at four different sampling sites on the Palos Verdes shelf, Southern California, using bomb fallout and natural radionuclides (137Cs, 239,240Pu, 210Pb, 234Th, and 14C), along with supporting measurements of organic carbon (OC), porosity and granulometry. Present-day particle reworking, on time scales of several months, is restricted to the upper 3 cm, with rates ranging from 13 to 200 cm2/year, as deduced from 234Thxs profiles. There is little evidence that particle reworking reached depths significantly greater than 5 cm. Post-1963 (or post-1971) sediment accumulation rates ranged from 0.7 to 1.4 g/cm2/year (equivalent to 1.1–1.8 cm/year for surficial sediments), as calculated from Pu and Cs isotope profiles, with little change over time or distance from the outfall. Lateral transport of older sediment and multiple sediment sources on the Palos Verdes shelf is suggested from radiocarbon measurements on foraminifera and bulk sedimentary organic matter at two sampling sites, which showed variable, old and refractory sources of OC. Pre-1953 sediments accumulated at rates that were at least 0.4 g/cm2/year (≥0.3 cm/year), based on 210Pbxs dating. Given the abundance of sediment sources to the Palos Verdes shelf, the high sedimentation rates, and shallow particle mixed layers, contaminant-enriched layers should continue to move deeper into the sediments.
id: 1309

Amino acid composition and diagenesis in the shells of terebratulid brachiopod Bouchardia rosea (SW Atlantic) - Carroll, M.; Kowalewski, M.; Simeos, M. G.; Goodfriend, G. A. (Geological Society of America Abstracts with Programs, 2001)
id: 1417

Benthic remineralization and burial of biogenic SiO2, CaCO3, organic carbon, and detrital material in the Southern Ocean along a transect at 170oW - Sayles, F. L.; Martin, W. R.; Chase, Z.; Anderson, R. F. (Deep-Sea Res., 2001)
id: 276

Bomb 14C versus anthropogenic CO2 in OCMIP ocean biogeochemical models - Matsumoto, K.; Sarmiento, J. L.; Key, R. M.; Slater, R. D.; Sabine, C. L. (Global Change Open Science Conference, 2001)
id: 1446

Brachiopod shell taphonomy in subtropical siliciclastic environments: preliminary field results - Simoes, M. G.; Kowalewski, M.; Carroll, M.; Rodland, D. L.; Mello, L. H. C. (Reuniao Anal de Sociedade Brasileira de Paleontologia, Paleo-2001, 2001)
id: 281

Carbon dioxide cycling and implications for climate on ancient Earth - Sleep, N. H.; Zahnle, K. (Journal of Geophysical Research-Planets, 2001)
The crustal Urey cycle of CO2 involving silicate weathering and metamorphism acts as a dynamic climate buffer. In this cycle, warmer temperatures speed silicate weathering and carbonate formation, reducing atmospheric CO2 and thereby inducing global cooling. Over long periods of time, cycling of CO2 into and out of the mantle also dynamically buffers CO2. In the mantle cycle, CO2 is outgassed at ridge axes and island arcs, while subduction of carbonatized oceanic basalt and pelagic sediments returns CO2 to the mantle. Negative feedback is provided because the amount of basalt carbonatization depends on CO2 in seawater and therefore on CO2 in the air. On the early Earth, processes involving tectonics were more vigorous than at present, and the dynamic mantle buffer dominated over the crustal one. The mantle cycle would have maintained atmospheric and oceanic CO2 reservoirs at levels where the climate was cold in the Archean unless another greenhouse gas was important. Reaction of CO2 with impact ejecta and its eventual subduction produce even lower levels of atmospheric CO2 and small crustal carbonate reservoirs in the Hadean. Despite its name, the Hadean climate would have been freezing unless tempered by other greenhouse gases.
395tjTimes Cited:185Cited References Count:101

Chronology of the Palmer Deep Site, Antarctic Peninsula: A Holocene Paleoenvironmental reference for the circum-Antarctic - Domack, E. W.; Leventer, A.; Dunbar, R.; Taylory, R.; Brachfeld, S.; Sjunneskog, C. (The Holocene, 2001)
id: 119

Chronology of the Palmer Deep Site, Antarctic Peninsula: A Holocene Paleoenvironmental reference for the circum-Antarctic - Domack, E. W.; Leventer, A.; Dunbar, R.; Taylor, R.; Brachfeld, S.; Sjunneskog, C. (The Holocene, 2001)
Palmer Deep sediment cores are used to produce the first high-resolution, continuous late Pleistocene to Holocene time-series from the Antarctic marine system. The sedimentary record is dated using accelerator mass spectrometer radiocarbon methods on acid insoluble organic matter and foraminiferal calcite. Fifty-four radiocarbon analyses are utilized in the dating which provides a calibrated timescale back to 13 ka BP. Reliability of resultant ages on organic matter is assured because duplicates produce a standard deviation from the surface age of less than laboratory error (i.e., ±50 years). In addition, surface organic matter ages at the site are in excellent agreement with living calcite ages at the accepted reservoir age of 1260 years for the Antarctic Peninsula. Spectral analyses of the magnetic susceptibility record against the age model reveal unusually strong periodicity in the 400,–200 and 50-70 year frequency bands, similar to other high-resolution records from the Holocene but, so far, unique for the circum-Antarctic. Here we show that comparison to icecore records of specific climatic events (e.g., the ’Little Ice Age‘, Neoglacial, Hypsithermal, and the Bølling/Allerød to Younger Dryas transition) provides improved focus upon the relative timing of atmosphere/ocean changes between the northern anid southern high latitudes.
id: 1319

Climatic significance of large lakes on the Altiplano of South America - Baker, P. A.; Seltzer, G. O.; Fritz, S. C.; Rigsby, C. A.; Dwyer, G. S. (EOS, Transactions, American Geophysical Union, 2001)
id: 333

Comparative analysis of methane-oxidizing archaea and sulfate-reducing bacteria in anoxic marine sediments - Orphan, V. J.; Hinrichs, K. U.; Ussler, W.; Paull, C. K.; Taylor, L. T.; Sylva, S. P.; Hayes, J. M.; DeLong, E. F. (Appl Environ Microbiol, 2001)
The oxidation of methane in anoxic marine sediments is thought to be mediated by a consortium of methane-consuming archaea and sulfate-reducing bacteria. In this study, we compared results of rRNA gene (rDNA) surveys and lipid analyses of archaea and bacteria associated with methane seep sediments from several different sites on the Californian continental margin. Two distinct archaeal lineages (ANME-1 and ANME-2), peripherally related to the order Methanosarcinales, were consistently associated with methane seep marine sediments. The same sediments contained abundant (13)C-depleted archaeal lipids, indicating that one or both of these archaeal groups are members of anaerobic methane-oxidizing consortia. (13)C-depleted lipids and the signature 16S rDNAs for these archaeal groups were absent in nearby control sediments. Concurrent surveys of bacterial rDNAs revealed a predominance of delta-proteobacteria, in particular, close relatives of Desulfosarcina variabilis. Biomarker analyses of the same sediments showed bacterial fatty acids with strong (13)C depletion that are likely products of these sulfate-reducing bacteria. Consistent with these observations, whole-cell fluorescent in situ hybridization revealed aggregations of ANME-2 archaea and sulfate-reducing Desulfosarcina and Desulfococcus species. Additionally, the presence of abundant (13)C-depleted ether lipids, presumed to be of bacterial origin but unrelated to ether lipids of members of the order Desulfosarcinales, suggests the participation of additional bacterial groups in the methane-oxidizing process. Although the Desulfosarcinales and ANME-2 consortia appear to participate in the anaerobic oxidation of methane in marine sediments, our data suggest that other bacteria and archaea are also involved in methane oxidation in these environments.
Orphan, V JHinrichs, K UUssler, W 3rdPaull, C KTaylor, L TSylva, S PHayes, J MDelong, E FengComparative StudyResearch Support, Non-U.S. Gov'tResearch Support, U.S. Gov't, Non-P.H.S.2001/04/03 10:00Appl Environ Microbiol. 2001 Apr;67(4):1922-34.

Composition of hydrothermal vent microbial communities as revealed by analyses of signature lipids, stable carbon isotopes, and Aquificales cultures - Jahnke, Linda L.; Eder, Wolfgang; Huber, Robert; Hope, Janet M.; Hinrichs, Kai-Uwe; Hayes, John M.; Des Marais, David J.; Cady, Sherry L.; Summons, Roger E. (Applied and Environmental Microbiology, 2001)
id: 1783

Compound-specific D/H ratios of lipid biomarkers from sediments as a proxy for environmental and climatic conditions - Sauer, P. E.; Eglinton, T. I.; Hayes, J. M.; Schimmelmann, A.; Sessions, A. L. (Geochimica Et Cosmochimica Acta, 2001)
Hydrogen isotope ratios (D/H) of lipid biomarkers extracted from aquatic sediments were measured to determine whether they can be used as a proxy for D/H of environmental water. Values of deltaD were determined by using a recently developed isotope-ratio-monitoring gas chromatograph-mass spectrometer system (irmGCMS) and were confirmed by conventional hydrogen isotopic measurements (i.e., combustion followed by reduction) on individual compounds isolated by preparative capillary gas chromatography. Diverse lipids (alkanes, n-alkanols, sterols, and pentacyclic triterpenols) were analyzed to examine hydrogen-isotopic controls on lipids of varying origin and biosynthetic pathway. For algal sterols (24-methylcholest-3 beta -ol, 24-ethylcholest-5,22-dien-3 beta -ol, and 4,23,24-trimethylcholesterol, or dinosterol), the fractionation between sedimentary lipids and environmental water was -201 +/- 10 parts per thousand and was similar in both marine and freshwater sites. In a sediment from a small lake in a forested catchment, triterpenols from terrestrial sources were enriched in D by 30 parts per thousand relative to algal sterols. Apparent fractionation factors for n-alkyl lipids were smaller than those of triterpenols and were more variable, probably reflecting multiple sources for these compounds. We conclude that hydrogen-isotopic analyses of algal sterols provide a viable means of reconstructing D/H of environmental waters. Results are less ambiguous than reconstructions based on analyses of kerogen or other operationally defined organic matter fractions. Copyright (C) 2001 Elsevier Science Ltd.
395npTimes Cited:209Cited References Count:64

Correction of H3+ contributions in hydrogen isotope ratio monitoring mass spectrometry - Sessions, A. L.; Burgoyne, T. W.; Hayes, J. M. (Anal Chem, 2001)
Two fundamentally different approaches, termed "pointwise" and "peakwise," are currently used to correct hydrogen isotope ratio monitoring data for the presence of H3+ ion contributions. Consideration of the underlying assumptions shows that the peakwise approach is valid only for peaks with the same functional shape and only when background signals do not vary. The pointwise correction is much more versatile and can be used even when peak shapes and sizes, as well as background signals, vary significantly. It is not exact and is limited in accuracy by (1) the signal-broadening effects of electronic time constants, (2) the analog-to-digital conversion frequency, and (3) the highest frequency of the sample signal. To minimize errors for typical gas chromatographic signals, time constants of <500 ms and analog-to-digital sampling intervals of < or =250 ms are needed. Errors are further minimized by matching sample and standard peaks in both amplitude and D/H ratio. Using the pointwise algorithm, we demonstrate that a series of 14 homologous n-alkanes varying in concentration over a 5-fold range can be analyzed with a mean precision of 2.3 per thousand and no systematic errors.
Sessions, A LBurgoyne, T W Hayes, J M eng 2001/02/24 12:00 Anal Chem. 2001 Jan 15;73(2):192-9.

Dating modern deltas: progress, problems and prognostics - Stanley, D. J. (Annual Review of Earth and Atmospheric Sciences, 2001)
Radiocarbon dating is the method most frequently used to date Holocene deltaic sequences, but less than one quarter of 14C dates are within ±500 years of predicted age. Such dates tend to be unreliable, in other words, often too old and commonly inverted upsection, and core sample dates obtained near deltaic plain surfaces may be as old as mid- to late Holocene. Stratigraphic irregularities result primarily from downslope reworking of upland alluvial sediment, with displacement of “old carbon” in the sediment that accumulates in lower valleys and deltaic plains. Use of dates that are too old results in inaccurately calculated rates (most often too low) of relative sea-level rise and/or land subsidence. More reliable timing of deltaic sediment requires a multiple-method dating approach, including, where possible, identification of associated archaeological material. Developing an accurate dating strategy is a critical step for implementing reliable coastal protection measures needed for the rapidly increasing human populations in these low-lying, vulnerable nearshore settings.
id: 1378

Deposition of Bomb C-14 in Continental Slope Sediments: Use of Radiocarbon in Understanding Benthic Food Web Dynamics - DeMaster, D. J.; Blair, N. E.; Smith, C. R.; Fornes, W. L.; Thomas, C. J.; Plaia, G. (Aquatic Sciences Meeting, ASLO, 2001)
id: 1368

Determination of the the H3 factor in hydrogen isotope ratio monitoring mass spectrometry - Sessions, A. L.; Burgoyne, T. W.; Hayes, J. M. (Anal Chem, 2001)
The H3 factor, K, is a parameter required in high-precision, mass spectrometric analyses of hydrogen isotopic abundances. When H2 is used as the sample gas, R* = R - Ki2, where R* is the true HD/H2 ratio, R is the observed (mass 3)/(mass 2) ion-current ratio, and i2 is the ion current at mass 2. Four different methods for the determination of K were defined and tested under conditions characteristic of isotope ratio monitoring systems. Three of these were peak-based. The fourth employed steady flows of H2 from a conventional inlet system. Results obtained using the latter method were more precise (standard deviation of K = 0.1 versus approximately 0.6 ppm mV(-1) for the peak-based methods). However, use of the resulting values of K for correction of isotope ratio monitoring GC/MS results led to systematic errors as large as 9 per thousand, whereas use of the peak-based values led to no systematic errors. Values of K were only weakly dependent on the pressure of He, declining approximately 5% for each 10-fold increase in P(He). Small variations in partial pressures of H2O and CH4, potential contaminants under isotope ratio monitoring conditions, had no significant effect on values of K.
Sessions, A LBurgoyne, T W Hayes, J M eng 2001/02/24 12:00 Anal Chem. 2001 Jan 15;73(2):200-7.

Estimates of anthropogenic carbon uptake from four three-dimensional global ocean models - Orr, J. C.; Maier-Reimer, E.; Mikolajewicz, U.; Monfray, P.; Sarmiento, J. L.; Toggweiler, J. R.; Taylor, N. K.; Palmer, J.; Gruber, N.; Sabine, C. L.; Le Quere, C.; Key, R. M.; et al. (Global Biogeochemical Cycles, 2001)
We have compared simulations of anthropogenic CO2 in the four three-dimensional ocean models that participated in the first phase of the Ocean Carbon-Cycle Model Intercomparison Project (OCMIP), as a means to identify their major differences. Simulated global uptake agrees to within +/- 19%, giving a range of 1.85 +/-0.35 Pg C yr(-1) for the 1980-1989 average, Regionally, the Southern Ocean dominates the present-day air-sea flux of anthropogenic CO2 in all models, with one third to one half of the global uptake occurring south of 30 degreesS. The highest simulated total uptake in the Southern Ocean was 70% larger than the lowest. Comparison with recent data-based estimates of anthropogenic CO2 suggest that most of the models substantially overestimate storage in the Southern Ocean; elsewhere they generally underestimate storage by less than 20%. Globally, the OCMIP models appear to bracket the real ocean's present uptake, based on comparison of regional data-based estimates of anthropogenic CO2 and bomb C-14. Column inventories of bomb C-14 have become more similar to those for anthropogenic CO2 with the time that has elapsed between the Geochemical Ocean Sections Study (1970s) and World Ocean Circulation Experiment (1990s) global sampling campaigns. Our ability to evaluate simulated anthropogenic CO2 would improve if systematic errors associated with the data-based estimates could be provided regionally.
417rwTimes Cited:187Cited References Count:64

The history of South American tropical precipitation for the past 25,000 years - Baker, P. A.; Seltzer, G. O.; Fritz, S. C.; Dunbar, R. B.; Grove, M. J.; Tapia, P. M.; Cross, S. L.; Rowe, H. D.; Broda, J. P. (Science, 2001)
Long sediment cores recovered from the deep portions of Lake Titicaca are used to reconstruct the precipitation history of tropical South America for the past 25,000 years. Lake Titicaca was a deep, fresh, and continuously overflowing lake during the last glacial stage, from before 25,000 to 15,000 calibrated years before the present (cal yr B.P.), signifying that during the last glacial maximum (LGM), the Altiplano of Bolivia and Peru and much of the Amazon basin were wetter than today. The LGM in this part of the Andes is dated at 21,000 cal yr B.P., approximately coincident with the global LGM. Maximum aridity and lowest lake level occurred in the early and middle Holocene (8000 to 5500 cal yr B.P.) during a time of low summer insolation. Today, rising levels of Lake Titicaca and wet conditions in Amazonia are correlated with anomalously cold sea-surface temperatures in the northern equatorial Atlantic. Likewise, during the deglacial and Holocene periods, there were several millennial-scale wet phases on the Altiplano and in Amazonia that coincided with anomalously cold periods in the equatorial and high-latitude North Atlantic, such as the Younger Dryas.
id: 369; Baker, P A Seltzer, G O Fritz, S C Dunbar, R B Grove, M J Tapia, P M Cross, S L Rowe, H D Broda, J P New York, N.Y. Science. 2001 Jan 26;291(5504):640-3.

Hydrology, vegetation, and climate change in the southern Everglades during the Holocene - Winkler, M. G.; Sanford, P. R.; Kaplan, S. W. (Bulletin of American Paleontology, 2001)
Paleoecological study of 18 AMS-dated sediment cores from the southern Everglades provides evidence of a shifting mosaic of biotic communities in the past similar to those on the Everglades landscape today. Our results also indicate initiation of Everglades peatlands at 5900 yr B. P., the importance of fire (from charcoal analysis) as a structuring agent in the tropical Everglades, evidence of past plant communities (Isoetes marshes) not present in the modern landscape, and the introduction of exotic plants (Schinus, Casuarina, etc.) today. Past vegetation changes are documented by pollen and sclereid changes. Past water level changes are documented by plant community changes, diatom species and habitat changes, sponge spicule changes, and by intervals of peat (wet) or marl (dry) deposition in the sediment cores. Marl deposition dominates today at these sites in the southern Everglades, a long-term trend exacerbated by human impacts. The Everglades may become less complex in the near future as introduced plants outcompete native vegetation and decreased water levels result in decreased peat production. A rewatering plan must include both wet and dry seasonal cycles in order to preserve the shifting mosaic nature of the landscape and to maintain the Everglades as a functional habitat for both plants and animals.
id: 125

Installation of a 134-sample MC-SNICS at the NOSAMS facility and first results - Bellino, Mary; von Reden, Karl F.; Schneider, Robert J.; Long, Patricia Long; Healy, Richard (Symposium of NorthEastern Accelerator Personnel, Oak Ridge National Lab., USA, October 25-28, 1999, 2001)
id: 1718

Isotopes as tracers of the oceanic circulation: results from the world ocean circulation experiment - Schlosser, P.; Jenkins, W. J.; Key, R.; Lupton, J. (International Conference on the Study of Environmental Change Using Isotope Techniques, I.A.E.A., 2001)
id: 318

Late quaternary climate and hydrology of tropical South America inferred from an isotopic and chemical model of Lake Titicaca, Bolivia and Peru - Cross, S. L.; Baker, P. A.; Seltzer, G. O.; Fritz, S. C.; Dunbar, R. B. (Quaternary Research, 2001)
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.
452lzTimes Cited:50Cited References Count:46

Late Quaternary water-level variations and vegetation history at Crooked Pond, southeastern Massachusetts - Shuman, B.; Bravo, J.; Kaye, J.; Lynch, J. A.; Newby, P.; Webb, T. (Quaternary Research, 2001)
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.
id: 1379; 493FU Times Cited:43 Cited References Count:41

A marine record of holocene climate events in tropical South America - Haug, G. H.; Hughen, K. A.; Sigman, D. M.; Peterson, L. C.; Rohl, U. (Science, 2001)
id: 1466

Multiple anthropogenic tracer distributions in the ocean - Sabine, C. L.; Key, R. M.; Bullister, J. L.; Feely, R. A.; Lamb, M. F.; Millero, F. J.; Wanninkhof, R.; Peng, T. H.; Lee, K.; Kozyr, A.; Gruber, N. (Sixth International CO2 Conference, 2001)
id: 319

Ocean Circulation and Climate - Schlosser, P.; Bullister, J. L.; Fine, R.; Jenkins, W. J.; Key, R.; Lupton, J.; Roether, W.; Smethie, W. M., Jr. (Observing and Modelling the Global Ocean, 2001)
id: 309

Ocean process tracers: Radiocarbon - Key, R. M. (Encyclopedia of Ocean Sciences, 2001)
id: 310

Persistent solar influence on North Atlantic climate during the Holocene - Bond, G.; Kromer, B.; Beer, J.; Muscheler, R.; Evans, M. N.; Showers, W.; Hoffmann, S.; Lotti-Bond, R.; Hajdas, I.; Bonani, G. (Science, 2001)
Surface winds and surface ocean hydrography in the subpolar North Atlantic appear to have been influenced by variations in solar output through the entire Holocene. The evidence comes from a close correlation between inferred changes in production rates of the cosmogenic nuclides carbon-14 and beryllium-10 and centennial to millennial time scale changes in proxies of drift ice measured in deep-sea sediment cores. A solar forcing mechanism therefore may underlie at least the Holocene segment of the North Atlantic's "1500-year" cycle. The surface hydrographic changes may have affected production of North Atlantic Deep Water, potentially providing an additional mechanism for amplifying the solar signals and transmitting them globally.
id: 1397; Bond, G Kromer, B Beer, J Muscheler, R Evans, M N Showers, W Hoffmann, S Lotti-Bond, R Hajdas, I Bonani, G New York, N.Y. Science. 2001 Dec 7;294(5549):2130-6. Epub 2001 Nov 15.

Pollen record of the last 500 years from the Doninos coastal lagoon (NW Iberian Peninsula): Changes in the pollinic catchment size versus paleoecological interpretation - Santos, L.; Bao, R.; Goni, M. F. S. (Journal of Coastal Research, 2001)
Pollen, diatom, charcoal and sedimentological analyses of a 4.20-m long core collected in the margin of the Doninos coastal lagoon, northwest Iberian Peninsula, provide information about the environmental evolution of this lagoon during the last 530 yr BP. During this time period, local environmental changes, such as changes in the sand-barrier permeability, alluvial sedimentation and/or anthropogenic activity, played a major role in the evolution of this coastal system. This scenario allows us to test the degree the pollinic signal recorded in the sediments of coastal lagoons is reshaped by the influence of local processes.Diatom and sedimentological data as well as historical archives indicate the development of a lacustrine system at the bottom of the sequence. Therefore, the coring site might be included in the lagoon itself. Pollen data seems to reflect the regional vegetation as a consequence of the large pollinic catchment area. Local Castanea cultivation and anthropogenic deforestation are also recorded. At the top of the sequence, diatom facies suggest increased marine influence at this time as a consequence of the more common events of breaching of a retrograding barrier. This, plus natural silting up by alluvial sedimentation and man-induced drying up of the lagoonal margins, lead to a progressive decrease in the water body extension. The coring point is now outside of the lagoon, implying a reduction in the pollinic catchment area that gave rise to a gradual increase in the local pollinic rainfall of periphytic vegetation. From the pollen diagram of this coastal deposit signatures of regional vegetation are swamped by local pollen input. The fluctuations in the percentages of the different pollen taxa are related to the complex interaction between basin size, human activities and breaching of the barrier. Caution must therefore be taken with direct paleoclimatic inferences from pollinic studies in coastal lagoons as an alternative where other continental deposits are lacking.
479bdTimes Cited:6 Cited References Count:46
Keywords: charcoal; coastal lagoon; diatoms; human impact; Late Holocene; late-holocene; nw iberian peninsula; pollen; representation; source area; vegetation; vegetation history

Post-glacial eruptive history of the western volcanic zone, Iceland - Sinton, John M.; Gronvold, Karl (EOS Trans. Amer. Geophys. Union, 2001)
id: 355

Radiocarbon and stable carbon isotopic evidence for transport and transformation of DOC, DIC and CH4 in a northern Minnesota peatland - Chasar, L. S.; Chanton, J. P.; Glaser, P. H.; Siegel, D. I.; Rivers, J. S. (Global Biogeochemical Cycles, 2001)
id: 98

A Silent Tandetron AMS System - von Reden, K. F.; Schneider, R. J. (Proceedings of the 31st SNEAP, 2001)
id: 1680

A solid state 13C NMR study of kerogen degradation during black shale weathering - Petsch, S. T.; Smernik, R. J.; Eglinton, T. I.; Oades, J. M. (Geochim. Cosmochim. Acta, 2001)
id: 277

Stratigraphic Development of a Northeastern South Carolina Barrier Island: Waites Island - Wright, E.; Harris, M. S.; Sapp, A.; Lewis, K.; Kruse, S.; Edgar, T. (Geological Society of America National Meeting, Abstracts with Program, 2001)
id: 1410

Subdivision of glacial deposits in southeastern Peru based on pedogenic development and radiometric ages - Goodman, A. Y.; Rodbell, D. T.; Seltzer, G. O.; Mark, B. G. (Quaternary Research, 2001)
The Cordillera Vilcanota and Quelccaya Ice Cap region of southern Peru (13 degrees 30'-14 degrees 00'S; 70 degrees 40'-71 degrees 25'W) contains a detailed record of late Quaternary glaciation in the tropical Andes, Quantification of soil development on 19 moraine crests and radiocarbon ages are used to reconstruct the glacial history. Secondary iron and day increase linearly in Quelccaya soils and clay accumulates at a linear rate in Vilcanota soils, which may reflect the semicontinuous addition of eolian dust enriched in secondary iron to all soils. In contrast, logarithmic rates of iron buildup in soils in the Cordillera Vilcanota reflect chemical weathering; high concentrations of secondary iron in Vilcanota tills may mask the role of eolian input to these soils. Soil-age estimates from extrapolation of field and laboratory data suggest that the most extensive late Quaternary glaciation occurred >70,000 yr B.P. This provides one of the first semiquantitative age estimates for maximum ice extent in southern Peru and is supported by a minimum-limiting age of similar to 41,520 C-14 yr B.P. A late glacial readvance culminated similar to 16,650 cal yr B.P. in the Cordillera Vilcanota, Following rapid deglaciation of unknown extent, an advance of the Quelccaya Ice Cap occurred between similar to 13,090 and 12,800 cal yr B.P., which coincides approximately with the onset of the Younger Dryas cooling in the North Atlantic region. Moraines deposited <394 cal yr B.P. in the Cordillera Vilcanota and <300 cal yr B.P. on the west side of the Quelccaya Ice Cap correlate with Little Ice Age moraines of other regions. (C) 2001 University or Washington.
452lzTimes Cited:27Cited References Count:51

Thirty thousand year record of climate from the Galapagos Islands and links with high latitudes - Koutavas, A.; Lynch-Stieglitz, J.; Sachs, J. P.; Marchitto, T. M. (EOS, 2001)
Fall Meeting Supplement F737
id: 255

Time-Averaging in articulate brachiopod accumulations: A quantitative estimate of temporal resolution from a Holocene tropical shelf (Southern Brazil) - Carroll, M.; Kowalewski, M.; Simoes, M. G.; Goodfriend, G. A. (North American Paleontological Convention, Programs and Abstracts, 2001)
id: 1418

Tropical climate changes at millennial and orbital timescales on the Bolivian Altiplano - Baker, P. A.; Rigsby, C. A.; Seltzer, G. O.; Fritz, S. C.; Lowenstein, T. K.; Bacher, N. P.; Veliz, C. (Nature, 2001)
Tropical South America is one of the three main centres of the global, zonal overturning circulation of the equatorial atmosphere (generally termed the 'Walker' circulation1). Although this area plays a key role in global climate cycles, little is known about South American climate history. Here we describe sediment cores and down-hole logging results of deep drilling in the Salar de Uyuni, on the Bolivian Altiplano, located in the tropical Andes. We demonstrate that during the past 50,000 years the Altiplano underwent important changes in effective moisture at both orbital (20,000-year) and millennial timescales. Long-duration wet periods, such as the Last Glacial Maximum—marked in the drill core by continuous deposition of lacustrine sediments—appear to have occurred in phase with summer insolation maxima produced by the Earth's precessional cycle. Short-duration, millennial events correlate well with North Atlantic cold events, including Heinrich events 1 and 2, as well as the Younger Dryas episode. At both millennial and orbital timescales, cold sea surface temperatures in the high-latitude North Atlantic were coeval with wet conditions in tropical South America, suggesting a common forcing.
id: 388

U-Th dating of carbonate platform and slope sediments - Henderson, G. M.; Slowey, N. C.; Fleisher, M. Q. (Geochimica Et Cosmochimica Acta, 2001)
Absolute chronology of marine sediment beyond the C-14 age range provides a test for models of climate change and has many other applications. U-Th techniques have been used for such chronology by dating corals, but extending these techniques to marine sediment is complicated by the presence of significant initial Th-230-both in detrital material and scavenged from seawater. In this study, we investigate four methods of solving the initial Th-230 problem for a particular type of marine sediment-the aragonite-rich sediments of carbonate platforms and slopes. Bulk sediment U-Th analyses can be corrected for initial Th to yield ages with approximate to2 to 3 kyr precision for highstand periods when sediment aragonite contents are particularly high. Uncertainty on the corrections causes inadequate precision for sediment from other periods, however. Removal of scavenged Th before analysis would enable a dramatic increase in this precision but has not proved successful despite a range of chemical leach approaches. Using heavy liquids to separate the various carbonate minerals found in Bahamas sediment enables an isochron approach to correct for initial Th, but the presence of initial Th from two sources requires correction or removal of one source of initial Th before the other is deconvolved by the isochron. Quantitative removal of detrital material before isochron analysis proves a successful approach. Such isochron data demonstrate that, although sediment remains closed to U-Th on a centimetre scale, nuclides are moved from grain to grain by alpha -recoil. Such intergrain exchange is expected to be observed in all sediments containing mineral grains with different U concentrations. Measured U-234/U-238 allows the recoil movement to be corrected and results in isochron ages with precision sometimes as low as 3 kyr. The accuracy of this approach has been proved by dating samples within the 14C age range. Sediments spanning the penultimate deglaciation have also been dated. After a small correction for bioturbation, the age for this event is found to be 135.2 +/- 3.5 ka. TWs date is approximate to8 kyr before the peak in northern hemisphere insolation and suggests that deglaciation is initiated by a mechanism in the southern hemisphere or tropics. This isochron approach shows considerable promise for dating of sediments older than this event, which will provide further information about the timing and mechanisms of global climate change. Copyright (C) 2001 Elsevier Science Ltd.
462zlTimes Cited:49Cited References Count:44

Validation of compound-specific 14C dating using the varved sedimentary record of Saanich Inlet, Canada - Smittenberg, R. H.; Hopmans, E. C.; Eglinton, T. I.; Hayes, J. M.; Whiticar, M. J.; Schouten, S.; Sinninghe Damsté, J. S. (Proceedings of the 20th international meeting on organic geochemistry, 2001)
id: 270

d13C values and radiocarbon dates of microbial biomarkers as tracers fro carbon recycling in peat deposits - Pancost, R. D.; van Geel, B.; Baas, M.; Damste Sinninghe, J. S. (Geology, 2000)
id: 1330

Environmental changes in the last centure in Little Trout Lake, Inkspot Bay, Great Corn and Little Corn Lakes, Lac du Flambeau Tribal Lands, Wisconsin. Report - Winkler, M. G.; Sanford, P. R. (2000)
id: 128

Evidence from U-Th dating against Northern Hemisphere forcing of the penultimate deglaciation - Henderson, G. M.; Slowey, N. C. (Nature, 2000)
Milankovitch proposed that summer insolation at mid-latitudes in the Northern Hemisphere directly causes the ice-age climate cycles. This would imply that times of ice-sheet collapse should correspond to peaks in Northern Hemisphere June insolation. But the penultimate deglaciation has proved controversial because June insolation peaks 127 kyr ago whereas several records of past climate suggest that change may have occurred up to 15 kyr earlier. There is a clear signature of the penultimate deglaciation in marine oxygen-isotope records. But dating this event, which is significantly before the 14C age range, has not been possible. Here we date the penultimate deglaciation in a record from the Bahamas using a new U-Th isochron technique. After the necessary corrections for alpha-recoil mobility of 234U and 230Th and a small age correction for sediment mixing, the midpoint age for the penultimate deglaciation is determined to be 135 +/- 2.5 kyr ago. This age is consistent with some coral-based sea-level estimates, but it is difficult to reconcile with June Northern Hemisphere insolation as the trigger for the ice-age cycles. Potential alternative driving mechanisms for the ice-age cycles that are consistent with such an early date for the penultimate deglaciation are either the variability of the tropical ocean-atmosphere system or changes in atmospheric CO2 concentration controlled by a process in the Southern Hemisphere.
HendersonSloweyengEngland2000/03/15 09:00Nature. 2000 Mar 2;404(6773):61-6.

Holocene cirque glacier activity in Western Spitsbergen, Svalbard: sediment records from pro-glacial Linnevatnet - Snyder, J. A.; Werner, A.; Miller, G. H. (The Holocene, 2000)
id: 234

Holocene hydrological reconstructions from stable isotopes and paleolimnology, Cordillera Real, Bolivia - Abbott, M. B.; Wolfe, A. P.; Aravena, R.; Wolfe, A. P.; Seltzer, G. O. (Quarternary Science Reviews, 2000)
Multiproxy analyses of sediment cores from Lago Taypi Chaka Kkota (LTCK) Cordillera Real, Bolivia, provide a record of drier conditions following late Pleistocene deglaciation culminating in pronounced aridity between 6.2 and 2.3 ka B.P. Today LTCK is a glacial-fed lake that is relatively insensitive to changes in P–E because it is largely buffered from dry season draw-down through the year-round supply of glacial meltwater. This was not the case during the middle to late Holocene when glaciers were absent from the watershed. Lake-water δFull-size image (<1 K) values inferred from δFull-size image (<1 K) analysis of sediment cellulose range from −12.9 to −5.3‰ and average −8.7‰ between 6.2 and 2.3 ka B.P. Modern lake-water δFull-size image (<1 K) from LTCK averages −14.8‰ which is compatible with the δFull-size image (<1 K) value of −14.3‰ for the surface sediment cellulose. Analyses of δFull-size image (<1 K) from modern surface waters in 23 lakes that span the range from glacial-fed to closed basin vary from −16.6 to −2.5‰. This approximates the magnitude of the down-core shift in δFull-size image (<1 K) values in LTCK during the middle to late Holocene from −12.9 to −5.3‰. Strong paleohydrologic change during the middle Holocene is also evident in diatom assemblages that consist of shallow-water, non-glacial periphytic taxa and bulk organic δFull-size image (<1 K) and δFull-size image (<1 K) that show increases likely resulting from degradation of lacustrine organic matter periodically exposed to subaerial conditions. Neoglaciation began after 2.3 ka B.P. as indicated by changes in the composition of the sediments, lower δFull-size image (<1 K) values, and a return to diatom assemblages characteristic of the glacial sediments that formed during the Late Pleistocene. Collectively, these data indicate that the past 2.3 ka B.P. have been the wettest interval during the Holocene. Millennial-scale shifts in the paleohydrologic record of LTCK during the early to middle Holocene conform to other regional paleoclimatic time-series, including Lake Titicaca and Nevado Sajama, and may be driven by insolation and resultant changes in atmospheric circulation and moisture supply. In contrast, an apparent 1200-year lag in the onset of wetter conditions at LTCK (2.3 ka B.P.) compared to Lake Titicaca (3.5 ka B.P.) provides evidence for variable sub-regional hydrologic response to climate change during the middle to late Holocene.
id: 1206

Implementazione di sistemi di datazione con il 14C ed estensione all 'impiego di piccole quantita di materiale, Thesis - Salvatore, Improta (Universita degli studi di Roma La Sapienza, 2000)

The Indian Ocean 13C Suess effect - Sonnerup, R. E.; Quay, P. D.; McNichol, A. P. (Global Biogeochemical Cycles, 2000)
id: 1816

Installation of a 134-sample MC-SNICS ion source at NOSAMS and first results - von Reden, K. F.; Bellino, M.; Long, P.; Schneider, R. J.; Loger, R. (Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions with Materials and Atoms, 2000)
In April 1999, the National Ocean Sciences AMS (NOSAMS) facility received the shipment of a 134-sample MC-SNICS ion source from the National Electrostatics Corporation (NEC). It replaced one of the two 59-sample spherical ionizer sources (US-AMS Model 3090A, HVEE Model 846). In this paper, we will describe the adaptation of the NEC ion source to the US-AMS/HVEE recombinator injector at NOSAMS. This is the first lime that the two leading sputter ion source designs are directly comparable on the same system. We will present ion beam optics calculations for both in comparison with measured results. Once fully operational, the new ion source will assume all of the sputter sample measurements at NOSAMS, while the remaining 59-sample source will be replaced by the newly developed microwave gas ion source. One of the most desirable features of the MC-SNICS design is the smaller cathode geometry. At comparable extracted currents, the surface diameter of the pressed samples is reduced from 1.5 to 1 mm. A new, automatic sample pressing procedure is being developed for this design. This will improve the capability for preparing and analyzing smaller sputter samples (carbon weight <100 <mu>g). Our US-AMS cathodes showed considerable reduction in the extracted currents when the sample diameter was reduced to 1 mm, even with samples of normal size (>200 mug C). (C) 2000 Elsevier Science B.V. All rights reserved.
8th International Conference on Accelerator Mass SpectrometrySEP 06-10, 1999 VIENNA, AUSTRIA
Keywords: AMS; beam extraction/injection; C-14; ion sources; ocean; pacific

Isotopic evidence for Late Glacial and Holocene climatic change in the tropical Andes - Seltzer, G.; Rodbell, D.; Burns, S. (Geology, 2000)
id: 1338

Low-level (submicromole) environmental 14C metrology - Currie, L. A.; Kessler, J. D.; Marolf, J. V.; McNichol, A. P.; Stuart, D. R.; Donoghue, J. C. (Nucl. Instr. and Meth. in Phys. Res., 2000)
id: 1713

Mapping of C4 plant input from North West Africa into North East Atlantic Sediments - Huang, Yongsong; Dupont, Lydie; Sarnthein, Michael; Hayes, John M.; Eglinton, Geoffrey (Geochimica et Cosmochima Acta, 2000)
id: 1777

Mass spectra of sn-2hydroxyarchaeol, a Polar-lipid Biomarker for Anaerobic Methanotrophy - Hinrichs, Kai-Uwe; Pancost, Richard D.; Summons, Roger E.; Sprott, G. Dennis; Sylva, Sean P.; Sinninghe-Damste, Jaap S.; Hayes, John M. (Geochem. Geophys. Geosyst., 2000)
id: 1735

Memorial to Henry G. Thode, 1910-1997 - Shaw, Denis M.; Epstein, Sam; Hayes, John M. (Geological Society of America Memorials, 2000)
id: 1737

Molecular and isotopic analysis of anaerobic methane-oxidizing communities in marine sediments - Hinrichs, K. U.; Summons, R. E.; Orphan, V.; Sylva, S. P.; Hayes, J. M. (Organic Geochemistry, 2000)
Convergent lines of molecular, carbon-isotopic, and phylogenetic evidence have previously indicated (Hinrichs, K.U., Hayes, J.M., Sylva, S.P., Brewer. P.G.. DeLong, E.F., 1999. Methane-consuming archaebacteria in marine sediments. Nature 398, 802-805.) that archaea are involved in the anaerobic oxidation of methane in sediments from the Eel River Basin. offshore northern California. Now, further studies of those same sediments and of sediments from a methane seep in the Santa Barbara Basin have confirmed and extended those results. Mass spectrometric and chromatographic analyses of an authentic standard of sn-2-hydroxyarchaeol (hydroxylated at C-3 in the sn-2 phytanyl moiety) have confirmed our previous, tentative identification of this compound but shown that the previously examined product was the mono-TMS, rather than di-TMS, derivative. Further analyses of C-13-depleted lipids, appreciably more abundant in samples from the Santa Barbara Basin, have shown that the archaeal lipids are accompanied by two sets of products that are only slightly less depleted in C-13. These are additional glycerol ethers and fatty acids. The alkyl substituents in the ethers (mostly monoethers, with some diethers) are non-isoprenoidal. The carbon-number distributions and isotopic compositions of the alkyl substituents and of the fatty acids are similar, suggesting strongly that they are produced by the same organisms. Their structures, n-alkyl and methyl-branched n-alkyl, require a bacterial rather than archaeal source. The non-isoprenoidal glycerol ethers are novel constituents in marine sediments but have been previously reported in thermophilic, sulfate- and nitrate-reducing organisms which lie near the base of the rRNA-based phylogenetic tree. Based on previous observations that the anaerobic oxidation of methane involves a net transfer of electrons from methane to sulfate, it appears likely that the non-archaeal, C-13-depleted lipids are products of one or more previously unknown sulfate-reducing bacteria which grow syntrophically with the methane-utilizing archaea. Their products account for 50% of the fatty acids in the sample from the Santa Barbara Basin. At all methane-seep sites examined, the preservation of aquatic products is apparently enhanced because the methane-oxidizing consortium utilizes much of the sulfate that would otherwise be available for remineralization of materials from the water column. Crown Copyright (C) 2000 Published by Elsevier Science Ltd. All rights reserved.
384quTimes Cited:204Cited References Count:49

The N and W Iceland Shelf: insights into Last Glacial Maximum ice extent and deglaciation based on acoustic stratigraphy and basal radiocarbon AMS dates - Andrews, J. T.; Hardardottir, J.; Helgadottir, G.; Jennings, A. E.; Geirsdottir, A.; Sveinbjornsdottir, A. E.; Schoolfield, S.; Kristjansdottir, G. B.; Smith, L. M.; Thors, K.; Syvitski, J. P. M. (Quaternary Science Reviews, 2000)
We present 32 AMS radiocarbon dates collected from sediments obtained during cruises of CSS Hudson (1993, RV Jan Mayen (1996), and Bjarni Saemundsson (1997). The radiocarbon dates were obtained on samples from the basal part of sediment cores collected across an area between 64 and 67 degrees N and 18-29 degrees W. Core sites were based on 3.5 kHz acoustic subbottom surveys. The 3.5 kHz subbottom profiles indicate that several of the troughs contain greater than or equal to 30 m of Quaternary sediment. At many sites, the acoustic surveys suggest the presence of one or more strong reflectors which can be traced over extended areas ( > 100 km) of the seafloor. These may represent large-scale volcanic ash falls, such as the Vedde ash and its correlatives, as well as other regionally significant tephras. We report dates from seven areas; (1) Northern troughs - Eyjafjardarall, Hunafloadjup, and Reykjafjardarall: (2) Hunafloi area and inner shelf and fjords; (3) Djupall area; (4) Isafjardardjup area; (5) Kolluall; (6) western shelf break and slope; and 7) Jokuldjup. The dates range in age from Marine Isotope Stages 3-1. Five cores have basal dates greater than or equal to 16 ka and thus provide information on the timing and environments during the deglaciation, Several dates of similar to 12 ka indicate that the inner shelf may have been largely ice-free by that time. Estimates of average sediment accumulation rates vary between 4 and 90 cm/kyr, with modal estimates of 30-30 cm/kyr, (C) 2000 Elsevier Science Ltd. All rights reserved.
298udTimes Cited:71Cited References Count:75

A New Estimate of the Holocene Lowstand Level of Lake Titicaca and Implications for Tropical Paleohydrology - Cross, S. C.; Baker, P. A.; Seltzer, G. O.; Fritz, S. C. (The Holocene, 2000)
id: 1339

The NOSAMS sample preparation laboratory in the next millenium: Progress after the WOCE program - Gagnon, A. R.; McNichol, A. P.; Donoghue, J. C.; Stuart, D. R.; von Reden, K. (Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions with Materials and Atoms, 2000)
Since 1991, the primary charge of the National Ocean Sciences AMS (NOSAMS) facility at the Woods Hole Oceanographic Institution has been to supply high throughput, high precision AMS C-14 analyses for seawater samples collected as part of the World Ocean Circulation Experiment (WOCE). Approximately 13,000 samples taken as part of WOCE should be fully analyzed by the end of Y2K. Additional sample sources and techniques must be identified and incorporated if NOSAMS is to continue in its present operation mode.A trend in AMS today is the ability to routinely process and analyze radiocarbon samples that contain tiny amounts (<100 <mu>g) of carbon. The capability to mass-produce small samples for C-14 analysis has been recognized as a major facility goal. The installation of a new 134-position MC-SNICS ion source, which utilizes a smaller graphite target cartridge than presently used, is one step towards realizing this goal. New preparation systems constructed in the sample preparation laboratory (SPL) include an automated bank of 10 small-volume graphite reactors, an automated system to process organic carbon samples, and a multi-dimensional preparative capillary gas chromatograph (PCGC). (C) 2000 Elsevier Science B.V. All rights reserved.
372jrTimes Cited:20Cited References Count:12

Oceanic uptake of CO2 re-estimated through d13C in WOCE samples - Lerperger, M.; McNichol, A. P.; Peden, J.; Gagnon, A. R.; Elder, K. L.; Kutschera, W.; Rom, W.; Steier, P. (Nuclear Instruments and Methods in Physics Research, 2000)
id: 1817

An Ocean-Wide DIC-13 Data Set - McNichol, A P; Quay, P D; Stuart, D R; Sonnerup, R E; Key, R M (2000 Ocean Sciences Meeting, San Antonio, TX (USA), 24-28 Jan 2000, 2000)
High quality DIC-13 measurements were made throughout the world's oceans at the University of Washington (UW) and the National Ocean Sciences Accelerator Mass Spectrometry (NOSAMS) Facility during both the OACES and WOCE programs. We are currently merging these two data sets which represent 25000 individual DIC- 13 measurements from 1260 stations. We will present the inter-laboratory calibration and standardization data. Based on 135 measurements on CO2 gas extracted at UW, the mean offset between the two labs is 0.01 o/oo, similar to the offset observed from an exchange of DIC standards (0.012 o/oo). Stations measured by both laboratories will also be examined for offsets, although one comparison in the Indian Ocean shows no significant differences. We will present our progress towards a global atlas of DIC-13, primarily maps of the merged data sets in the Pacific, Southern, and Indian Oceans. In this poster we will concentrate on regions that have been under-sampled in the past, e.g. the Southern Ocean. Additionally, we will examine the relationship of DIC-13 to PO4 and to DIC-14. A preliminary analysis of DIC-13 and PO4 from three WOCE lines in the Pacific indicates that the expected relationship is observed in the deep waters and that the data from different water masses occupy well-defined regions of the graph. We are examining the potential for using the relationship between DIC-14 and DIC-13 to improve our understanding of the penetration of bomb radiocarbon into the ocean as well as fundamental processes in the deep ocean. The relationship is complex yet the data from shallow to intermediate depths (100 to 1000m) follow two distinct parallel lines that are related to the hemisphere in which
Date revised - 2007-04-01SuppNotes - Abstracts available.Last updated - 2016-12-21
Keywords: carbon cycling; Carbon dioxide; Deep water; dissolved inorganic carbon; ISW, Indian Ocean; Marine; Mass Spectrometry; Ocean circulation; Phosphates; PS, Antarctic Ocean; Q2 09146:TSD distribution, water masses and circulation; Stable isotopes; Standardization; Water masses; World Ocean; World Ocean Circulation Experiment (WOCE)

An ocean-wide DIC-13 data set - McNichol, A. P.; Quay, P. D.; Stuart, D. R.; Sonnerup, R. E.; Key, R. M. (AGU Ocean Sciences Meeting, 2000)
id: 1444

Postglacial and Late Holocene earthquakes on the Toe Jam strand of the Seattle fault, Bainbridge Island Washington - Nelson, A. R.; Johnson, S. Y.; Pezzopane, S. K.; Wells, R. E.; Kelsey, H. M.; Sherrod, B. L.; Koehler, R. D.; Bradley, L. A.; Bucknam, R. C.; LaPrade, W. T.; Cox, J. W.; Narwold, C. F. (Geological Society of America Abstracts with Programs, 2000)
id: 258

Postglacial climate and vegetation history, north-central Kola Peninsula, Russia: pollen and diatom records from Lake Yarnyshnoe-3 - Snyder, J. A.; MacDonald, G. M.; Forman, S. L.; Tarasov, G. A.; Mode, W. N. (Boreas, 2000)
A sediment core from Lake Yamyshnoe-3 (69 degrees 04'N; 36 degrees 04'E), an emerged coastal lake from the tundra of the north-central Kola Peninsula, has been analyzed for fossil pollen and diatoms. The pollen record shows the Younger Dryas event marked by increasing Artemisia coupled with decreases in Poaceae, Cyperaceae and Salix at c. 10 700 to 10 000 BP. This core provides the first well-defined palynological record of the Younger Dryas event on the Kola Peninsula. Stomates from Pinus were recovered from the core interval between 8000 and 6000 BP. The stomates, coupled with elevated values of pine pollen, indicate that Pinus sylvestris grew near the arctic coastline of the central Kola Peninsula in the middle Holocene. However, the small number of stomates suggests that pines were not plentiful. The diatom record from the core reflects basin isolation from the sea and indicates additional limnological changes during the climate transition between c. 5000 and 4000 BP. The broadly similar climate and vegetation history on the north-central Kola Peninsula and in Fennoscandia demonstrates the propagation of late glacial and Holocene climate events from the North Atlantic region into the Eurasian Arctic.
378dxTimes Cited:28 Cited References Count:82
Keywords: atlantic; finnish lapland; Holocene; late pleistocene; norway; sea; sediments; varanger-peninsula; western part; younger-dryas

Processes and rates of Holocene sedimentation in Santa Monica Bay, CA - Sommerfield, C. K.; Lee, H. J. (EOS, 2000)
id: 139

Quantitative estimates of time-averaging in articulate brachiopod accumulations from a Holocene tropical shelf (Southern Brazil) - Carroll, M.; Kowalewski, M.; Simoes, M. G.; Goodfriend, G. A. (Geological Society of America Abstracts with Programs, 2000)
id: 124

Radiocarbon calibration and abruptchanges in atmospheric 14Cconcentration during Marine Isotope Stage 3 - Hughen, K. A.; Southon, J.; Lehman, S. J.; Peterson, L. C.; Overpeck, J. T. (American Geophysical Union, 2000)
id: 327

Radiocarbon dated Pinus sylvertis L. wood from beyond treeline on the Kola Peninsula, Russia - MacDonald, G. M.; Gervalis, B.; Snyder, J. A.; Tarasov, G. A.; Borisova, O. A. (The Holocene, 2000)
Radiocarbon dates were obtained from 24 samples of Pinus sylvestris L. (Scots pine) wood recovered from sites beyond the modern conifer tree-line on the Kola Peninsula of Russia. Twenty-one of the samples came from the shallow waters and eroding peats at the edges of two small lakes at 68°439N, 35°109E, located north of the modern conifer tree-line. Three samples came from a small pond located above the modern elevational limits of Pinus sylvestris at 68°259N, 35°199E. The radiocarbon dates indicate that pine trees grew approximately 20 km north of the mapped modern limits of the species from 6680 BP to 3830 BP. Pine trees were also growing some 40 m above their modern elevational limits between 5890 BP and 3450 BP. Nineteen of the samples date from 6680 BP to 5070 BP, suggesting that the density of trees north of the modern tree-line was greatest between 7000 and 5000 BP. The timing of tree-line advance and greatest density on the Kola Peninsula are in agreement with the results of similar studies from northern Fennoscandia which indicate that maximum northern and elevational extension of tree-line occurred between 7000 BP and 4000 BP. The general agreement between tree-line reconstructions suggests that the climatic changes that promoted mid-Holocene tree-line extension along the North Atlantic margins in northern Fennoscandia propagated eastward to the Kola Peninsula. The late timing of initial pine expansion on the Kola and in adjacent northern Fennoscandia remains problematic and may relate to lower winter insolation, temperature regimes in the adjacent oceans or slow rates of migration.
id: 376

Radiocarbon dates in China's Holocene Yangtze delta: record of sediment storage and reworking, not timing of deposition - Stanley, D. J.; Chen, Z. (Journal Coastal Res., 2000)
id: 230

Radiocarbon dating the artifically contained surfaces of the Rhone deltaic plain, southern France - Stanley, D. J. (Journal Coastal Res., 2000)
id: 1377

The radiocarbon gradient at the Antarctic Polar Front - Schneider, R. J.; McNichol, A. P.; von Reden, K. F.; Elder, K. L.; Gagnon, A. R.; Key, R. M.; Quay, P. D.; Schlosser, P. M. (AGU Ocean Sciences Meeting, 2000)
id: 317

Rapid ice margin fluctuations during the Bolling/Allerod and Younger Dryas intervals in the Peruvian Andes - Rodbell, D. T.; Seltzer, G. O. (Quaternary Research, 2000)
id: 392

Rapid ice margin fluctuations during the Younger Dryas in the tropical Andes - Rodbell, D. T.; Seltzer, G. O. (Quaternary Research, 2000)
Radiocarbon dated lacustrine sequences in Peru show that the chronology of glaciation during the late glacial in the tropical Andes was significantly out-of-phase with the record of climate change in the North Atlantic region. Fluvial incision of glacial-lake deposits in the Cordillera Blanca, central Peru, has exposed a glacial outwash gravel; radiocarbon dates from peat stratigraphically bounding the gravel imply that a glacier advance culminated between similar to 11,280 and 10,990 C-14 yr B.P.; rapid ice recession followed. Similarly, in southern Peru, ice readvanced between similar to 11,500 and 10,900 C-14 yr B.P. as shown by a basal radiocarbon date of similar to 10,870 C-14 yr B.P. from a lake within 1 ion of the Quelccaya Ice Cap. By 10,900 C-14 yr B.P, the ice front had retreated to nearly within its modern limits. Thus, glaciers in central and southern Peru advanced and retreated in near lockstep with one another. The Younger Dryas in the Peruvian Andes was apparently marked by retreating ice fronts in spite of the cool conditions that are inferred from the partial derivative O-18 record of Sajama ice. This retreat was apparently driven by reduced precipitation, which is consistent with interpretations of other paleoclimatic indicators from the region and which may have been a nonlinear response to steadily decreasing summer insolation. (C) 2000 University of Washington.
388erTimes Cited:61Cited References Count:66

Responces of a saline lake ecosystems in semi-arid regions to irrigation and climate variability. The history of Salada Chiprana, Central Ebro Basin, Spain - Valero-Garces, B. L.; Navas, A.; Machin, J.; Stevenson, T.; Davis, B. (Ambio, 2000)
id: 385

Stable chlorine isotopic compositions of aroclors and aroclor-contaminated sediments - Reddy, C. M.; Heraty, L. J.; Holt, B. D.; Sturchio, N. C.; Eglinton, T. I.; Drenzek, N. J.; Xu, L.; Lake, J. L.; Maruya, K. A. (Environmental Science & Technology, 2000)
An exploratory investigation was conducted to evaluate if stable chlorine isotopic ratios of polychlorinated biphenyls (PCBs) could be useful in studying the processes that determine their transport and fate in the environment First, we determined the variability of delta(37)Cl in the source materials for PCBs. Second, we determined if the delta(37)Cl values of contaminated environmental samples fell outside the range in source variability. The isotopic variability among the source materials (Aroclors) was rather small; delta(37)- Cl values ranged from -3.37 to -2.11% (mean and standard deviation, -2.78 +/- 0.39%, n = 12). There was no correlation between the delta(37)Cl values and percentages of chlorine in the mixtures. We also found very similar values in several Clophen mixtures and one Phenoclor. The delta(37)Cl values in the total PCBs isolated from Aroclor-contaminated sediments from the Hudson River, New Bedford Harbor, and Turtle River Estuary ranged from -4.54 to -2.25% (n = 19). While most of the delta(37)Cl values were within 2 standard deviations of the mean Aroclor value (our assumed estimate for overall source variability), two of the PCB contaminated sediment samples from New Bedford Harbor did appear to be isotopically distinct. The PCBs in these sediments had lower amounts of less chlorinated congeners (when compared to the source material) and were likely isotopically affected by alteration processes that preferentially removed these congeners. Compound specific measurements of two congeners in Aroclor 1268 suggest that there are no large congener-specific differences in the stable chlorine isotope ratios in Aroclors. This study shows that the delta(37)Cl Values of PCBs may be a potentially useful diagnostic tool in studying the transport and fate of PCBs and indicates that additional research is warranted.
330rcTimes Cited:39Cited References Count:16

Ten years after - the WOCE AMS radiocarbon program - McNichol, A. P.; Schneider, R. J.; von Reden, K. F.; Gagnon, A. R.; Elder, K. L.; Key, R. M.; Quay, P. D. (Accelerator Mass Spectrometer Conference, 2000)
id: 316