The deglacial history of surface and intermediate water of the Bering Sea - Cook, M. S.; Keigwin, L. D.; Sancetta, C. A. (Deep-Sea Research Part Ii-Topical Studies in Oceanography, 2005)
The lithology of deglacial sediments from the Bering Sea includes intervals of laminated or dysaerobic sediments. These intervals are contemporaneous with the occurrence of laminated sediments from the California margin and Gulf of California, which suggests widespread low-oxygen conditions at intermediate depths in the North Pacific Ocean. The cause could be reduced intermediate water ventilation, increased organic carbon flux, or a combination of the two. We infer abrupt decreases of planktonic foraminifer delta(18)O at 14,400 and 11,650 yr BP, which may be a combination of both freshening and warming. On the Shirshov Ridge, the abundance of sea-ice diatoms of the genus Nitzschia reach local maxima twice during the deglaciation, the latter of which may be an expression of the Younger Dryas. These findings expand the extent of the expression of deglacial millennial-scale climate events to include the northernmost Pacific. (c) 2005 Elsevier Ltd. All rights reserved.
995ksTimes Cited:51Cited References Count:52

The demise of the alga Botryococcus Braunii from a Norwegian fjord is due to early eutrophication - Smittenberg, R. H.; Baas, M.; Schouten, S.; Sinninghe-Damste, J. S. (The Holocene, 2005)
id: 1148

Detailed compositional analysis of gas seepage at the National Carbon Storage Test Site, Teapot Dome, Wyoming, USA - Klusman, Ronald W. (Applied Geochemistry, 2005)
id: 1038

Determination of microbial carbon sources in petroleum contaminated sediments using molecular 14C analysis - Slater, G. F.; White, H. K.; Eglinton, T. I.; Reddy, C. M. (Environmental Science and Technology, 2005)
id: 595

Determination of Microbial Carbon Sources in Petrolleum Contaminated Sediments Using Molecular 14C Analysis - Slater, G. F.; White, H. K.; Eglinton, T. I.; Reddy, C. M. (Environ. Sci. Technol, 2005)
id: 1225

Dissolved and particulate organic matter source-age characterization in river and estuarine outflow waters: a combined isotope and biochemical approach - Loh, A. N.; Bauer, J. E.; Canuel, E. A. (ASLO Summer Meeting, 2005)
id: 482

The early geological history of Long Island Sound - Varekamp, J. C.; Thomas, E. (AGU Fall meeting, 2005)
id: 744

Effects of natural sunlight on decomposition of estuarine dissolved organic C, N and P and bacterial growth - McCallister, S. L.; Bauer, J. E.; Kelly, J.; Ducklow, H. W. (Aquatic Microbial Ecology, 2005)
id: 1101

The environmental history of Long Island Sound with evidence for human impacts - Varekamp, J. C.; Thomas, E. (Living on the Edge Symposium, 2005)
id: 743

An equatorial harmonic of the high latitude 1500-year cycle - Russell, J. M.; Johnson, T. C. (Geophysical Research Letters, 2005)
id: 1006

An evaluation of 14C age relationships between co-occurring foraminifera, alkenones, and total organic carbon in continental margin sediments - Mollenhauer, Gesine; Kienast, Markus; Lamy, Frank; Meggers, Helge; Schneider, Ralph R.; Hayes, John M.; Eglinton, Timothy I. (Paleoceanography, 2005)
id: 492

Evidence from ophiolites, blueschists, and ultrahigh-pressure metamorphic terrances that the modern episode of subduction tectonics began in Neoproterozoic time - Stern, Robert J. (Geological Society of America, 2005)
id: 1551

Evidence from the Northeastern Atlantic basin for variability in the rate of the meridional overturning circulation through the last deglaciation - Gherardi, J. M.; Labeyrie, L.; McManus, J. F.; Francois, R.; Skinner, L. C.; Cortijo, E. (Earth and Planetary Science Letters, 2005)
A first study from the subtropical western Atlantic, using Pa-231/Th-230 ratios as a kinematic proxy for deep water circulation, provided compelling evidence for a strong link between climate and the rate of Meridional Overturning Circulation (MOC) over the last deglaciation. However, these results warrant confirmation from additional locations and water depths because the interpretation of the sedimentary Pa-231/Th-230 ratio in terms of circulation vigor can be biased by variations in particle flux and composition. We have measured Pa-231/Th-230 in a core from the Iberian margin, in the Northeastern Atlantic basin, and have compared these new results to the data from the western Atlantic basin. We find that the reduction in the circulation during H1 and YD and the subsequent increases first recognized in the sediment deposited on Ben-nuda Rise are also evident in the eastern basin, in a totally different sedimentary regime, confirming that sedimentary Pa-231/Th-230 ratios record basin-wide changes in deep water circulation. However, some differences between the eastern and western records are also recognized, providing preliminary evidence to differentiate between renewal rates in the two North Atlantic basins and between shallower and deeper overturning. Our results suggest the possible existence of two sources of Glacial North Atlantic Intermediate Deep Water (GNAIW), one in the south Labrador Sea and another west of Rockall Plateau. Both sources contributed to the meridional overturning but the two had different sensitivity to meltwater from the Laurentide and the Fermoscandian ice sheets during the deglaciation. These results indicate that additional information on the geometry and strength of the ventilation of the deep Atlantic can be obtained by contrasting the evolution of sediment Pa-231/Th-230 in different sections of the Atlantic Ocean. (C) 2005 Elsevier B.V. All rights reserved.
995vhTimes Cited:93Cited References Count:69

Evidence of past intense tropical cyclones from backbarrier salt pond sediments: A case study from Isla de Culebrita, Puerto Rico, USA - Donnelly, J. P. (Journal of Coastal Research, 2005)
Tropical cyclones pose a significant threat to lives and resources in heavily-populated regions and can extensivelymodify coastal landforms. In appropriate depositional environments a sedimentological record of past tropical cyclones can be preserved. Given the relative rarity of landfalling tropical cyclones and the shortness of the instrumental record, little is known about past patterns of hurricane activity. The development of long-term records of tropical cyclone activity will make it possible to examine how past climate change may have influenced the frequency, intensity, and locations (origin, tracks) of hurricanes. Previous work has shown that intense hurricane strikes produce a distinctive sedimentary signature that can be used to reconstruct long-term records of these events. Numerous coastal salt ponds and lagoons in eastern Puerto Rico and the U.S. Virgin Islands are well situated to receive allocthonous sediments during intense tropical cyclone landfalls. Coastal salt ponds, normally low-energy environments, are dominated by fine-grained organic sediments, with the exception of episodic deposition of coarser-grained mineral sediments from the beach and nearshore during extreme storms. Sediment obtained from a series of cores taken from Big Culebrita Salt Pond on the Isla de Culebrita, Puerto Rico reveal a record of flooding-induced sedimentation within mangrove and salt-pond sediments dating back more than 2000 years. Reconstructing the history of storm-surge deposition from backbarrier salt-pond sediments may allow for the reconstruction of a millennial-scale record of tropical cyclones for the northeastern Caribbean and other regions.
Sp. Iss. 42947fu Times Cited:16 Cited References Count:40
Keywords: Caribbean; climate; coast; deposits; florida; grain-size analysis; Holocene; hurricane; hurricanes; new-jersey; record; south-carolina; storm; tsunami

The Fe3+/ΣFe ratios of MORB glasses and their implications for mantle melting - Bezos, Antoine; Humler, Eric (Geochimica et Cosmochimica Acta, 2005)
The Fe3+/ΣFe ratio of 104 MORB glasses from the Pacific, the Atlantic, the Indian, and the Red Sea spreading centers have been determined using wet chemical Fe2+ analyses and electron microprobe FeOtotal measurements. The data provide a new estimate for the MORB oxygen fugacity (fO2) of 0.41 ± 0.43 (1sigma, N = 100) log units below the fayalite-magnetite-quartz buffer (FMQ), equivalent to a Fe3+/ΣFe = 0.12 ± 0.02 (1sigma, N = 104). This new fO2 estimate is 0.8 log units more oxidized than the average fO2 proposed by Christie et al. (1986) (FMQ-1.20 ± 0.44; Fe3+/ΣFe = 0.07 ± 0.01; N = 87). This slight difference may be related in part to the 3.5% underestimation of the Fe2+ concentration determined by Christie et al. (1986) compared with this study. MORB oxygen fugacity does not display any significant difference between the three main oceanic domains, or between enriched and depleted MORB. Yet, the iron red-ox state ratio shows a broad increase during fractional crystallization. Detailed study of magmatic suites highlights the lack of systematic Fe3+/ΣFe ratio fractionation during differentiation. Despite the large variations of inferred partial melting degrees (from 5 to 20%), the present data set does not provide any evidence of Fe3+/ΣFe relationships with partial melting proxies such as Na8.0. Based on the Fe3+ systematics during partial melting, it is suggested that the oxidation state of MORB reflects a “buffered mantle melting process” resulting in the apparent compatible behavior of Fe3+ during partial melting, and in the relatively constant Fe3+/ΣFe ratio irrespective of the extent of melting. This result implies that partial melting processes may be open relative to oxygen. We propose a model where the Fe3+/ΣFe ratio in the melt is buffered during partial melting. The MORB Fe2O3 systematics can be accounted for by using a fO2 of FMQ-1 that is equivalent to the average fO2 reported for abyssal peridotites.
id: 1578

Fluctuations in export productivity over the last century from sediments of a southern Chilean fjord (44 degrees S) - Sepulveda, J.; Pantoja, S.; Hughen, K.; Lange, C.; Gonzalez, F.; Munoz, P.; Rebolledo, L.; Castro, R.; Contreras, S.; Avila, A.; Rossel, P.; Lorca, G.; et al. (Estuarine Coastal and Shelf Science, 2005)
Here we present the first reconstruction of changes in surface primary production during the last century from the Puyuhuapi fjord in southern Chile, using a variety of parameters (diatoms, biogenic silica, total organic carbon, chlorins, and proteins) as productivity proxies. Two sediment cores from the head and the center of the fjord were analyzed and compared to gain insights on past changes in productivity in these two different depositional environments. Higher sedimentation rates found at the head of the fjord result from the combination of a shallower water column and a restricted circulation by the occurrence of a sill. Additionally, sediment mixing depths estimated from (210)Pb data suggest that suboxic conditions may dominate the bottom water and the sediment-water interface in this location.Productivity of the Puyuhuapi fjord during the last century was characterized by a constant increase from the late 19th century to the early 1980s, then decreased until the late 1990s, and then rose again to present-day values. The influence of rainfall on productivity was most noticeable during periods of low rainfall, which coincided with decreased overall productivity within the Puyuhuapi fjord. Simultaneous variations in productivity and rainfall in the study area suggest that marine productivity could respond to atmospheric-oceanic interactions at a local scale. At a regional scale, marine productivity of the area may be related to other large-scale processes such as the El Nino Southern Oscillation. (c) 2005 Elsevier Ltd. All rights reserved.
975sfTimes Cited:22Cited References Count:53

Foraminiferal isotope anomalies from northwestern Pacific marginal sediments - Ohkushi, K.; Ahagon, N.; Uchida, M.; Shibata, Y. (Geochemistry Geophysics Geosystems, 2005)
[1] We evaluated the influence of methane release from methane hydrate reservoirs in the northwestern Pacific continental margin on stable isotope values. We analyzed stable isotopes of foraminifera from a piston core collected at 1066-m water depth off eastern Hokkaido, northern Japan. Carbon isotope signals indicated that planktonic and benthic foraminifera in several glacial sediment layers in the core were highly depleted in C-13; both the planktonic and benthic foraminiferal delta C-13 values ranged from about -10 parts per thousand to -2 parts per thousand. Most foraminiferal tests in these horizons were brown as a result of postdepositional alteration. Foraminiferal oxygen isotopes fluctuated abnormally in the glacial sediment layers, showing small ( about 0.5 parts per thousand) positive shifts relative to normal glacial values. We attributed the positive shifts to authigenic carbonate formation in the foraminiferal tests. The authigenic carbonates have formed when rising methane, from methane hydrate in the sediment, became oxidized as it came in contact with dissolved sulfate near the seafloor. Episodic methane-release events may be associated with great plate-boundary earthquakes with epicenters near the coring site.
917qmTimes Cited:9 Cited References Count:48
Keywords: atmospheric processes : paleoclimatology; benthic foraminifera; California; carbon isotopes; corals; Foraminifera; gas-hydrate; kuril trench; marine geology and geophysics : marine sediments : processes and transport; methane hydrate; methane release; northwestern pacific ocean; sea-level record; tokachi-oki earthquake; western north pacific; Younger Dryas

From Pleistocene mariners to complex hunter-gatherers: the archaeology of the California Channel Islands - Rick, Torben C.; Erlandson, Jon M.; Vellanoweth, Rene L. (Journal of World Prehistory, 2005)
id: 581

A geoarchaeological chronology of Holocene dune building on San Miguel Island, California - Erlandson, J. M.; Rick, T. C.; Peterson, C. (Holocene, 2005)
A data base of 114 C-14 dates from 40 archaeological sites in San Miguel Island sand dunes provides a general chronology for Holocene dune building. Although rising seas have probably submerged earlier evidence, postglacial dune building on San Miguel began as early as 10 000 years ago. More intensive dune building dates to the middle and late Holocene, including large parabolic dunes that traverse the island and climb some of the highest landforms. Native American peoples lived on and altered island sand dunes for nearly 10 000 years, and native burning and other landscape alterations may have contributed to periodic destabilization of island dunefields. Accumulation of cultural debris also facilitated anthropogenic soil formation in many coastal localities, however, and over the millennia midden debris protected large expanses of the island's coastal perimeter from wind erosion. With the introduction of sheep c. AD 1850, destabilization and erosion of dune soils caused by overgrazing and other human impacts reached unprecedented levels, devastating the island's natural ecology. In recent decades, with the removal of sheep and other exotic animals from the island, the dunes have begun to restabilize.
992ziTimes Cited:23Cited References Count:31

Geochemical and hydrogeological contrasts between shallow and deeper aquifers in two villages of Araihazar, Bangladesh: Implications for deeper aquifers as drinking water sources - Zheng, Y.; van Geen, A.; Stute, M.; Dhar, R.; Mo, Z.; Cheng, Z.; Horneman, A.; Gavrieli, I.; Simpson, H. J.; Versteeg, R.; Steckler, M.; Grazioli-Venier, A.; et al. (Geochimica et Cosmochimica Acta, 2005)
Sediment and groundwater profiles were compared in two villages of Bangladesh to understand the geochemical and hydrogeological factors that regulate dissolved As concentrations in groundwater. In both villages, fine-grained sediment layers separate shallow aquifers ( 50 ka ago and a groundwater age of thousands of years. In the other village (Bay), the sediment is
id: 604; 999UZ Times Cited:59 Cited References Count:49

Geochemical characteristics of recent 2 ka mud on the inner shelf of the East China Sea - Xiao, S. B.; Li, A. C.; Jiang, F.; Xu, F. J.; Zheng, F.; Chen, Z. (GEOCHIMICA, 2005)
The particle size of DD2 in the northern part of the muddy area along the continental margin of the East China Sea was analyzed. AMS 14 C age test and the main elements, trace elements The relationship between the content of each element and the particle size was discussed and analyzed. The relationship between them was discussed by R factor analysis. Studies have shown that nearly 2 ka to DD2 The majority of the main elements and trace elements in the pores are stable; the content of most of the elements with the grain size becomes increasing, while the content of Sr and SiO 2 The decreasing tendency of CaO, Na 2 O, Hf, Zr and Ti is poor in particle size. The results of factor analysis show that the chemical composition of DD2 pore can be It is divided into four kinds of combination types: the main characteristics of the distribution of elements in sediments are reflected, and the samples are not treated by salt beforehand to cause the combination of main elements and trace elements The Zr, Hf and Nb elements are enriched in the specific particle size components (silt), and the addition of calcareous biological components and the redistribution of elements during early diagenesis Wait. The results show that Rb, Cu, Ni, V, P, Sc, Fe 2 O 3 , Cr, K 2 O, Nb, Co, Th, Ti and Al 2 O 3 are relatively inactive elements in DD 2 pores, They can be compared with the modern Yangtze River, the Yellow River sediments, for genetic analysis. The Ti J Zr and Cr J Th ratios indicate that the pore deposits are mainly derived from the granitic Source area.
id: 570
Keywords: East China Sea continental shelf; factor analysis; geochemical characteristics; particle size

Geologic implications of Late Quaternary isostatic adjustment in the Penobscot/Kennebec River system, Maine - Kelley, Alice R.; Kelly, Joseph T.; Belknap, Daniel F.; Gontz, Allen M. (Geological Society of America Abstracts with Programs, 2005)
id: 1173

Glacial water mass geometry and the distribution of d 13 C of SCO 2 in the western Atlantic Ocean - Curry, W. B.; Oppo, D. W. (Paleoceanography, 2005)
id: 416

Global methane emission through mud volcanoes and its past and present impact on the Earth's climate-a comment - Milkov, A. V.; Etiope, G. (International Journal of Earth Sciences, 2005)
940vyTimes Cited:11Cited References Count:15

Global ocean data analysis project (GLODAP): Results and data, ORNL/CDIAC-145, NDP-145 - Sabine, C. L.; Key, R. M.; Kozyr, A.; Feely, R. A.; Wanninkhof, R.; Millero, F. J.; Peng, T. H.; Bullister, J. L.; Lee, K. (2005)
id: 529

A high-resolution geochemical record from Lake Edward, Uganda Congo and the timing and causes of tropical African drought during the late Holocene - Russell, J. M.; Johnson, T. C. (Quaternary Science Reviews, 2005)
High-resolution analyses of the elemental composition of calcite and biogenic silica (BSi) content in piston cores from Lake Edward, equatorial Africa, document complex interactions between climate variability and lacustrine geochemistry over the past 5400 years. Correlation of these records from Lake Edward to other climatically-forced geochemical and lake level records from Lakes Naivasha, Tanganyika, and Turkana allows us to develop a chronology of drought events in equatorial East Africa during the late Holocene. Major drought events of at least century-scale duration are recorded in lacustrine records at about 850, 1500, similar to 2000, and 4100 cal year BP. Of these, the most severe event occurred between about 2050 and 1850 cal year BP, during which time Lake Edward stood about 15 in below its present level. Numerous additional droughts of less intensity and/or duration are present in the Lake Edward record, some of which may be correlated to other lacustrine climate records from equatorial East Africa. These events are superimposed on a long-term trend of increasingly and conditions from 5400 to about 2000 cal year BP, followed by a shift toward wetter climates that may have resulted from an intensification of the winter Indian monsoon. Although the causes of decade- to century-scale climate variability in the East African tropics remain obscure, time-series spectral analysis suggests no direct linkage between solar output and regional rainfall. Rather, significant periods of similar to 725, similar to 125, 63-72, 31-25, and 19-16 years suggest a tight linkage between the Indian Ocean and African rainfall, and could result from coupled ocean-atmosphere variability inherent to the tropical monsoon system. (c) 2004 Elsevier Ltd. All rights reserved.
933pzTimes Cited:63Cited References Count:74

High-resolution historical records from Pettaquamscutt River basin sediments; 2. Chronology and record of 137Cs released by the Chernobyl accident - Lima, A. L.; Hubeny, J. B.; Reddy, C. M.; King, J. W.; Hughen, K. A.; Eglinton, T. I. (Geochimica et Cosmochimica Acta, 2005)
id: 555

Holocene aminochronology and time-averaging fro Chesapeake Bay mulinia - Edwards, A. L.; Wehmiller, J. R.; Lockwood, R.; Kaufman, D.; Bright, J.; Cronin, T.; Willard, D. (Geological Society of America Abstracts with Programs, 2005)
id: 585

Holocene hydrologic variation at Lake Titicaca, Bolivia/Peru, and its relationship to North Atlantic climate variation - Baker, P. A.; Fritz, S. C.; Garland, J.; Ekdahl, E. (Journal of Quaternary Science, 2005)
A growing number of sites in the Northern Hemisphere show centennial- to millennial-scale climate variation that has been correlated with change in solar variability or with change in North Atlantic Circulation. However, it is unclear how (or whether) these oscillations in the climate system are manifest in the Southern Hemisphere because of a lack of sites with suitably high sampling resolution. In this paper, we reconstruct the lake-level history of Lake Titicaca, using the carbon isotopic content of sedimentary organic matter, to evaluate centennial- to millennial-scale precipitation variation and its phasing relative to sites in the Northern Hemisphere. The pattern and timing of lake-level change in Lake Titicaca is similar to the ice-rafted debris record of Holocene Bond events, demonstrating a possible coupling between precipitation variation on the Altiplano and North Atlantic sea-surface temperatures (SSTs). The cold periods of the Holocene Bond events correspond with periods of increased precipitation on the Altiplano. Holocene precipitation variability on the Altiplano is anti-phased with respect to precipitation in the Northern Hemisphere monsoon region. More generally, the tropical Andes underwent large changes in precipitation on centennial-to-millennial timescales during the Holocene. Copyright (C) 2005 John Wiley & Sons, Ltd.
id: 1095; 000CQ Times Cited:21 Cited References Count:46

Holocene molluscan aminostratigraphy of Chesapeake Bay sediments - Edwards, A. L.; Lockwood, R.; Wehmiller, J.; Cronin, T.; Kaufman, D.; Bright, J. (Geological Society of America Abstracts with Programs, 2005)
id: 586

The Holocene radiocarbon reservoir effect in the western Ross Sea - Hall, Brenda L.; Henderson, Gideon M.; Baroni, Carlo; Kellog, Thomas (Annual West Antarctic Ice Sheet Meeting, 2005)
id: 434

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

A hydrogen-rich early Earth atmosphere - Tian, F.; Toon, O. B.; Pavlov, A. A.; De Sterck, H. (Science, 2005)
We show that the escape of hydrogen from early Earth's atmosphere likely occurred at rates slower by two orders of magnitude than previously thought. The balance between slow hydrogen escape and volcanic outgassing could have maintained a hydrogen mixing ratio of more than 30%. The production of prebiotic organic compounds in such an atmosphere would have been more efficient than either exogenous delivery or synthesis in hydrothermal systems. The organic soup in the oceans and ponds on early Earth would have been a more favorable place for the origin of life than previously thought.
Tian, FengToon, Owen BPavlov, Alexander ADe Sterck, HengResearch Support, U.S. Gov't, Non-P.H.S.2005/04/09 09:00Science. 2005 May 13;308(5724):1014-7. Epub 2005 Apr 7.

Impact of millennial-scale Holocene climate variability on eastern North American terrestrial ecosystems: pollen-based climatic reconstruction - Willard, D. A.; Bernhardt, C. E.; Korejwo, D. A.; Meyers, S. R. (Global and Planetary Change, 2005)
We present paleoclimatic evidence for a series of Holocene millennial-scale cool intervals in eastern North America that occurred every similar to 1400 years and lasted similar to 300-500 years, based on pollen data from Chesapeake Bay in the mid-Atlantic region of the United States. The cool events are indicated by significant decreases in pine pollen, which we interpret as representing decreases in January temperatures of between 0.2 degrees and 2 degrees C. These temperature decreases include excursions during the Little Ice Age (similar to 1300-1600 AD) and the 8 ka cold event. The timing of the pine minima is correlated with a series of quasi-periodic cold intervals documented by various proxies in Greenland, North Atlantic, and Alaskan cores and with solar minima interpreted from cosmogenic isotope records. These events may represent changes in circumpolar vortex size and configuration in response to intervals of decreased solar activity, which altered jet stream patterns to enhance meridional circulation over eastern North America. (c) 2004 Elsevier B.V All rights reserved.
944zeTimes Cited:48Cited References Count:68

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.

Input of particulate organic and dissolved inorganic carbon from the Amazon to the Atlantic Ocean - Druffel, E. R. M.; Bauer, J. E.; Griffin, S. (Geochemistry Geophysics Geosystems, 2005)
We report concentrations and isotope measurements (radiocarbon and stable carbon) of dissolved inorganic carbon (DIC) and suspended particulate organic carbon (POC) in waters collected from the mouth of the Amazon River and the North Brazil Current. Samples were collected in November 1991, when the Amazon hydrograph was at its annual minimum and the North Brazil Current had retroflected into the equatorial North Atlantic. The DIC D 14 C results revealed postbomb carbon in river and ocean waters, with slightly higher values at the river mouth. The low DIC delta(13)C signature of the river end-member (-11%) demonstrates that about half of the DIC originated from the remineralization of terrestrially derived organic matter. A linear relationship between DIC and salinity indicates that DIC was mixed nearly conservatively in the transition zone from the river mouth to the open ocean, though there was a small amount (<= 10%) of organic matter remineralization in the mesohaline region. The POC Delta(14)C values in the river mouth were markedly lower than those values from the western Amazon region (Hedges et al., 1986). We conclude that the dominant source of POC near the river mouth and in the inner Amazon plume during November 1991 was aged, resuspended material of significant terrestrial character derived from shelf sediments, while the outer plume contained mainly marine-derived POC.
909pwTimes Cited:17 Cited References Count:21
Keywords: accumulation; amazon; C-14; carbon cycling; CO2; continental-shelf; poc; radiocarbon; river system; Sediment; total co(2); water

An investigation of accurate gas exchange measurements for determing a large river carbon isotope mass balance - Raymond, P. A.; McGillis, W. R.; Bauer, J. E.; Caraco, N. F.; Cole, J. J. (37th Liege International Colloquium on Gas Transfer at Water Survaces, 2005)
id: 490

The Island Chumash: Behavioral Ecology of a Maritime Society - Kennett, D. J. (University of California Press, 2005)
id: 1017

Isolation and Characterization of a Genetically Tractable Photoautotrophic Fe(II)-Oxidizing Bacterium, Rhodopseudomonaspalustris Strain TIE-1 - Jiao, Yongqin; Kappler, Andreas; Croal, Laura R.; Newman, Dianne K. (Applied and Environmental Microbiology, 2005)
id: 1576

On the isolation of elemental carbon (EC) for micro-molar 14C accelerator mass spectrometry: development of a hybrid reference material for 14C-EC accuracy asssurance, and a critical evaluation of the thermal optical kinetic (TOK EC isolation procedure - Currie, L. A.; Kessler, J. D. (Atmospheric Chemistry and Physics, 2005)
id: 631

Isotopic constraints on the fate of petroleum residues sequestered in salt marsh sedimetns - White, H. K.; Reddy, C. M.; Eglinton, T. I. (Environmental Science and Technology, 2005)
id: 969

Lacustrine loss-on-ignition recrods from the southern Uinta Mountains - Munroe, Jeffrey S. (Geological Society of America Abstracts with Programs, 2005)
id: 694

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 neogene and quaternary evolution of the northern Albermarle Embayment (mid-Atlantic continental margin, USA) - Mallinson, D.; Riggs, S.; Culver, S.; Thieler, R.; Foster, D. R.; Corbett, D. R.; Farrell, K.; J, Wehmiller (Marine Geology, 2005)
id: 1160

Late-glacial and Holocene record of lake levels of Mathews Pond and Whitehead Lake, northern Maine, USA - Dieffenbacher-Krall, A. C.; Nurse, A. M. (Journal of Paleolimnology, 2005)
Paleohydrology studies at Mathews Pond and Whitehead Lake in northern Maine revealed synchronous changes in lake levels from about 12,000 C-14 yrs BP to the present. We analyzed gross sediment structure, organic and carbonate content, mineral grain size, and macrofossils of six cores from each of the two lakes, and obtained 72 radiocarbon dates. Interpretation of this paleo-environmental data suggests that the lateglacial and Younger Dryas climate was dry, and lake levels were low. Early Holocene lake levels were considerably higher but declined for an interval from about 8000 to 7200 14 C yrs BP. Sediment of both lakes contains evidence of a dry period at similar to 7400 C-14 yrs BP (8200 cal yr). Lake levels of both sites declined abruptly about 4800 14 C yrs BP and remained low until 3000 14 C yrs BP. Modern lake levels were achieved only within the past 600 years. The west-to-east, time-transgressive nature of lake-level changes from several sites across northeastern North America suggests periodic changes in atmospheric circulation patterns as a driving force behind observed moisture balance changes.
953ghTimes Cited:21Cited References Count:81

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

Long range transport of biomass aerosol to Greenland: Multi-spectroscopic investigation of particles deposited in the snow - Currie, L. A.; Kessler, J. D.; Fletcher, R. A.; Dibb, J. E. (Journal of Radioanalytical and Nuclear Chemistry, 2005)
Recent developments in radiometrics and mass spectrometry techniques for ultra-sensitive analysis of radionuclides in the marine environment are reviewed. In the radiometrics sector the dominant development has been the utilization of large HPGe detectors in underground laboratories with anti-cosmic or anti-Compton shielding for the analysis of short and medium-lived radionuclides in the environment. In the mass spectrometry sector, applications of inductively coupled plasma mass spectrometry (ICP-MS) and accelerator mass spectrometry (AMS) for the analysis of long-lived radionuclides in the environment are the most important recent achievements. The recent developments do not only considerably decrease the detection limits for several radionuclides (up to several orders of magnitude), but they also enable to decrease sample volumes so that sampling, e.g., of the water column can be much easier and more effective. A comparison of radiometrics and mass spectrometry results for the analysis of radionuclides in the marine environment shows a reasonable agreement - within quoted uncertainties, for wide range of activities and different sample matrices analyzed.
899oqTimes Cited:2Cited References Count:28

Long term calibration of the Noble gas temperature system in a shallow unconfined Pleistocene aquifer - Hall, C. M.; Castro, M. C.; Lohmann, K. C.; Ma, L. (Eos Trans. AGU Fall Meeting Supplement, 2005)
id: 438

Microbial transformations of organic matter in black shales and implications for global biogeochemical cycles - Petsch, S. T.; Edwards, K. J.; Eglinton, T. I. (Geobiology: Objectives, Concepts, Perspectives, 2005)
id: 758

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

Millennial scale variability in tropical South American vegetation during the last glaciation - Hughen, K. A.; Drenzek, N.; Bice, M.; Eglinton, T. I. (Eos Trans. AGU, 86(52), Fall Meeting Suppl., 2005)
id: 563

Molecular and stable isotope compositions of natural gas hydrates: A revised global dataset and basic interpretations in the context of geological settings - Milkov, A. V. (Organic Geochemistry, 2005)
A global dataset of molecular and stable isotope compositions of gases released from 209 different specimens of natural gas hydrate is presented and discussed. The 26 hydrate-bearing areas from 21 geographic regions are grouped into high gas flux (HGF) settings, low gas flux (LGF) settings and hydrated gas accumulations (HGA). Methane (CH4) is the most abundant hydrate-bound gas, while CO2 and C2+ hydrocarbon gases are frequently present in small amounts. Non-hydrocarbon gases, such as H2S, are uncommon. The stable isotope composition of hydrate-bound gases varies significantly (e.g., delta(13)C of CH4 from -74.7 to -39.60 parts per thousand), suggesting that gases of both microbial and thermogenic origin form gas hydrates. Hydrate-bound gases are derived from autochthonous [Located predominantly within the gas hydrate stability zone (GHSZ)] and allochthonous (located in deep sediments) sources. The occurrence and concentration of gas hydrates in sediments are controlled not by the origin of gases, but rather by their sources, which in turn strongly depend on geological setting. Allochthonous gases (microbial and/or thermogenic) dominate in HGF and HGA settings where they are focused in the shallow GHSZ along faults, within mud volcanoes, in permeable carrier beds and other geological features from underlying petroleum systems. Relatively high concentrations of gas hydrate (average 5-15% of pores and locally up to 100 parts per thousand of volume) occurring over small areas are typical of HGF and HGA settings. In contrast, autochthonous and diffuse allochthonous gases (mostly microbial) occur in stratigraphically and structurally simple LGF settings and result in relatively low concentrations of gas hydrate (average similar to 2% of pores in the GHSZ) spread over large areas. The major implication of this finding is that successful prediction of resource and geohazard potential of gas hydrates is possible only if regional petroleum systems extending well below the GHSZ are properly evaluated. In addition to the diagnosis of origins and sources of hydrate-bound gases, molecular and isotopic data help to better identify hydrate-bearing intervals and provide valuable insights into the dynamics of hydrate-bearing sites. (C) 2005 Elsevier Ltd. All rights reserved.
929dvTimes Cited:101Cited References Count:138

Morphodynamics and evolution of Danube delta - Giosan, L.; Vespremeanu, E.; Donnelly, J. P.; Bhattacharya, J.; Buonaiuto, F. (Journal of Sedimentary Research, 2005)
id: 499

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

Multiple sources for late-Holocene tsunamis at Discovery Bay, Washington State, USA - Williams, H. F. L.; Hutchinson, I.; Nelson, A. R. (Holocene, 2005)
Nine muddy sand beds interrupt a 2500- yr- old sequence of peat deposits beneath a tidal marsh at the head of Discovery Bay on the south shore of the Strait of Juan de Fuca, Washington. An inferred tsunami origin for the sand beds is assessed by means of six criteria. Although all the sand beds contain marine diatoms and almost all the beds display internal strati. cation, the areal extent of the oldest beds is too limited to confirm their origin as tsunami deposits. The ages of four beds overlap with known late Holocene tsunamis generated by plate- boundary earthquakes at the Cascadia subduction zone. Diatom assemblages in peat deposits bracketing these four beds do not indicate concurrent change in elevation at Discovery Bay. Diatoms in the peat bracketing a tsunami bed deposited about 1000 cal. yr BP indicate a few decimeters of submergence, suggesting deformation on a nearby upper- plate fault. Other beds may mark tsunamis caused by more distant upper- plate earthquakes or local submarine landslides triggered by earthquake shaking. Tsunamis from both subduction zone and upper- plate sources pose a significant hazard to shoreline areas in this region.
894xjTimes Cited:37Cited References Count:67

Natural variability in skeletal growth rate, stable isotopes, and Sr/Ca composition in two species of Pacific sclerosponges (Acnathocheatetes wellsi and Astroclera welleyana) - Grottoli, A. G.; Adkins, J. F.; Moots, K. (Benthic Ecology Meetings, 2005)
id: 1135

Noble gases and stable isotopes in a shallow aquifer in southern Michigan: Implications for noble gas paleotemperature reconstructions for cool climates - Hall, C. M.; Castro, M. C.; Lohmann, K. C.; Ma, L. (Geophysical Research Letters, 2005)
Noble gas data from the Glacial Drift, the shallowest aquifer in southern Michigan confirm findings by Ma et al. (2004) that modern noble gas temperatures (NGTs) are systematically below the current mean annual air temperature (MAAT) which, in turn, is similar to the ground temperature of these recharge waters. By tracking noble gas concentrations as well as stable isotope ratios through an autumn, winter, spring and into summer, we show that although water in this aquifer is modern, noble gases do not track the atmosphere on a short time scale. Specifically, excess He-3 and He-4 indicate that the gas environment at the water table is integrating conditions over years or decades rather than weeks or months. Our results are interpreted using various NGT interpretational models and possible mechanisms for the production of low apparent NGTs are discussed.
968qnTimes Cited:26 Cited References Count:14
Keywords: water

Once spilled, still found: metal contamination in Connecticut wetlands and Long Island Sound sediment from historic industries, Chapter 9 - Varekamp, J. C.; Mecray, E. L.; Zierzow, T. (Our Changing Coasts, 2005)
id: 724

One-year record of organic and elemental carbon in fine particles in downtown Beijing and Shanghai - Yang, F.; He, K.; Ye, B.; Chen, X.; Cha, L.; Cadle, S. H.; Chan, T.; Mulawa, P. A. (Atmospheric Chemistry and Physics, 2005)
Weekly PM2.5 samples were collected for one year ( 1999 - 2000) in Beijing and Shanghai and the carbonaceous species analyzed to investigate and compare their time series patterns and possible sources in the two biggest cities of China. Weekly carbonaceous concentrations varied in wide ranges with 8.6 - 59 mu g m(-3) for OC and 1.5-25.4 mu g m(-3) for EC in Beijing, and with 5.1 - 38.4 mu g m(-3) for OC and 2.3 - 13.0 mu g m(-3) for EC in Shanghai. Similar weekly and seasonal variations of OC and EC concentrations were found in each city though major combustion sources presented source-dependent emission characteristics and seasonal differences in emission amount for carbonaceous species. Both OC and EC maintained much higher concentrations in late fall through winter, probably due to enhanced emissions coupled with unfavorable meteorological conditions. In Beijing, the C-14 analysis of limited samples suggested there was a significant contribution ( 33 - 48%) of modern carbon to the total fine carbonaceous PM burden with higher fractions in the harvest seasons. The high mass ratios of excessive potassium to EC in both Beijing and Shanghai also indicated that biomass burning had important contribution to fine carbonaceous particles.
936dsTimes Cited:77Cited References Count:45

Organic matter inputs and metabolism in a large river estuary (the Hudson): Insights from natural abundance isotopes and whole system metabolism - Caraco, N. F.; Cole, J. J.; Raymond, P. A.; Bauer, J. E. (American Society of Limnology and Oceanography, 2005)
id: 478

Otolith science entering the 21st century - Campana, S. E. (Marine and Freshwater Research, 2005)
A review of 862 otolith-oriented papers published since the time of the 1998 Otolith Symposium in Bergen, Norway suggests that there has been a change in research emphasis compared to earlier years. Although close to 40% of the papers could be classifed as ‘annual age and growth’ studies, the remaining papers were roughly equally divided between studies of otolith microstructure, otolith chemistry and non-ageing applications. A more detailed breakdown of subject areas identified 15 diverse areas of specialisation, including age determination, larval fish ecology, population dynamics, species identification, tracer applications and environmental reconstructions. For each of the 15 subject areas, examples of representative studies published in the last 6 years were presented, with emphasis on the major developments and highlights. Among the challenges for the future awaiting resolution, the development of novel methods for validating the ages of deepsea fishes, the development of a physiologically-based otolith growth model, and the identification of the limits (if any) of ageing very old fish are among the most pressing.
id: 1044

The Paleoproterozoic snowball Earth: a climate disaster triggered by the evolution of oxygenic photosynthesis - Kopp, R. E.; Kirschvink, J. L.; Hilburn, I. A.; Nash, C. Z. (Proc Natl Acad Sci U S A, 2005)
Although biomarker, trace element, and isotopic evidence have been used to claim that oxygenic photosynthesis evolved by 2.8 giga-annum before present (Ga) and perhaps as early as 3.7 Ga, a skeptical examination raises considerable doubt about the presence of oxygen producers at these times. Geological features suggestive of oxygen, such as red beds, lateritic paleosols, and the return of sedimentary sulfate deposits after a approximately 900-million year hiatus, occur shortly before the approximately 2.3-2.2 Ga Makganyene "snowball Earth" (global glaciation). The massive deposition of Mn, which has a high redox potential, practically requires the presence of environmental oxygen after the snowball. New age constraints from the Transvaal Supergroup of South Africa suggest that all three glaciations in the Huronian Supergroup of Canada predate the Snowball event. A simple cyanobacterial growth model incorporating the range of C, Fe, and P fluxes expected during a partial glaciation in an anoxic world with high-Fe oceans indicates that oxygenic photosynthesis could have destroyed a methane greenhouse and triggered a snowball event on time-scales as short as 1 million years. As the geological evidence requiring oxygen does not appear during the Pongola glaciation at 2.9 Ga or during the Huronian glaciations, we argue that oxygenic cyanobacteria evolved and radiated shortly before the Makganyene snowball.
Kopp, Robert EKirschvink, Joseph LHilburn, Isaac ANash, Cody ZengResearch Support, Non-U.S. Gov'tResearch Support, U.S. Gov't, Non-P.H.S.2005/08/03 09:00Proc Natl Acad Sci U S A. 2005 Aug 9;102(32):11131-6. Epub 2005 Aug 1.

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 report on the archaeology and paleoecology of the Abalone Rocks Estuary, Santa Rosa Island, California - Rick, T. C.; Kennett, D. J.; Erlandson, J. M. (Proceedings of the Sixth California Islands Symposium, 2005)
id: 468

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

Provenance analysis of mud along the Min-zhe coast since 2 ka BP - Xiao, S. B.; Li, A. C.; Jiang, F. (Acta Sedimentologica Sinica, 2005)
id: 567

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

Radiocarbon dating and the "old shell" problem: direct dating of artifacts and cultural chronologies in coastal and other aquatic regions - Rick, T. C.; Vellanoweth, R. L.; Erlandson, J. M. (Journal of Archaeological Science, 2005)
Archaeologists have long recognized the problem of the "old wood" effect in radiocarbon dating charcoal and wood samples, the age of which may be hundreds of years older than their use by humans. Such problems have resulted in significant changes in how most researchers select wood and charcoal samples for C-14 dating, with many now using relatively short-lived carbonized materials for dating. Despite the significant strides made in our understanding of the potential biases of the "old wood" effect, little emphasis has been placed on the possible impacts of dating "old shell" in archaeological deposits. The use of marine shell for C-14 dating is widespread in coastal areas around the world, including a growing emphasis on the dating of individual shell artifacts via Accelerator Mass Spectrometry (AMS). In dating shell artifacts, we have obtained several dates older than associated C-14 dates for short-lived subsistence remains from the same deposits, including great disparities (> 10,000 years) and more subtle differences (>= 100 years). These discrepancies appear to be due to the use of old shells by humans to make beads and other artifacts, including shells collected from fossil deposits, older archaeological sites, and beaches. The problems caused by the use of old shells to make beads and other artifacts are surmountable through careful sample selection, analysis of multiple 14 C dates on a variety of materials, and proper calibration procedures. (c) 2005 Elsevier Ltd. All rights reserved.
970xgTimes Cited:33Cited References Count:40

Radiocarbon dating of alkenones from marine sediments: I. Isolation protocol - Ohkouchi, N.; Xu, L.; Reddy, C. M.; Montlucon, D.; Eglinton, T. I. (Radiocarbon, 2005)
The chemical and isotopic compositions of long-chain (C-36-C-39) unsaturated ketones (alkenones), a unique class of algal lipids, encode surface ocean properties useful for paleoceanographic reconstruction. Recently, we have sought to extend the utility of alkenones as oceanic tracers through measurement of their radiocarbon contents. Here. we describe a method for isolation of alkenones from sediments as a compound class based on a sequence of wet chemical techniques. The steps involved, which include silica gel column chromatography, urea adduction, and silver nitrate-silica gel column chromatography, exploit various structural attributes of the alkenones. Amounts of purified alkenones estimated by GC/FID measurements were highly correlated with CO2 yields after sample combustion, indicating purities of greater than 90% for samples containing >= 100 mu g C. The degree of alkenone unsaturation (U-37(K')) also varied minimally through the procedure. We also describe a high-performance liquid chromatography (HPLC) method to isolate individual alkenones for molecular-level structural and isotopic determination.
993nkTimes Cited:13 Cited References Count:22
Keywords: AMS; carbon; indicators; proxy; records; tool

Radiocarbon dating of alkenones from marine sediments: II. Assessment of carbon process blanks - Mollenhauer, G.; Montlucon, D.; Eglinton, T. I. (Radiocarbon, 2005)
We evaluate potential process blanks associated with radiocarbon measurement of microgram to milligram quantities of alkenones at the National Ocean Sciences Accelerator Mass Spectrometry (NOSAMS) facility. Two strategies to constrain the contribution of blanks to alkenone C-14 dates were followed: 1) dating of samples of known age and 2) multiple measurements of identical samples. We show that the potential contamination associated with the procedure does not lead to a systematic bias of the results of alkenone dating to either younger or older ages. Our results indicate that alkenones record Delta(14)C of ambient DIC with an accuracy of approximately 10 parts per thousand. A conservative estimate of measurement precision is 17 parts per thousand for modern samples. Alkenone C-14 ages are expected to be reliable within 500 yr for samples younger than 10,500 C-14 yr.
993nkTimes Cited:13 Cited References Count:20
Keywords: c-14 ams; organic-compounds; records; samples; system; tool

Radiocarbon dating of alkenones from marine sediments-III. Influence of solvent extractions procedures on 14C measurements of foraminifera - Ohkouchi, N.; Eglinton, T. I.; Hughen, K. A.; Roosen, E.; Keigwin, L. (Radiocarbon, 2005)
id: 554

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.

Rapid lateral particle transport in the Argintine Basin: Th-230 and molecular C-14 Evidence, Poster - Mollenhauer, Gesine; McManus, J. F.; Benthien, A.; Muller, P. J.; Eglinton, T. I. (EGU General Assembly, 2005)
id: 548

Rapid viscoelastic uplift in southeast Alaska caused by post-Little Ice Age glacial retreat - Larsen, C. F.; Motyka, R. J.; Freymueller, J. T.; Echelmeyer, K. A.; Ivins, E. R. (Earth and Planetary Science Letters, 2005)
Our observations show that extreme uplift in southeast Alaska began about 1770 AD, with relative sea level (RSL) change to 5.7 m and current uplift rates to 32 mm/yr. This region experienced widespread glacial melting following the Little Ice Age (LIA), with the collapse of the Glacier Bay Icefield alone equivalent to 8 mm of global sea level rise. Geodynamic modelling links the uplift to post-LIA isostatic rebound, with the extreme uplift signal and a priori knowledge of ice load changes requiring the presence of a low viscosity asthenosphere (3.7 X 10(18) Pa s). These crustal deformations are triggered by climate change through glacier wastage. (c) 2005 Elsevier B.V. All rights reserved.
968ijTimes Cited:109Cited References Count:44

Reassessing human settlement on the south coast of San Miguel Island, California: The use of 14C dating as a reconnaissance tool - Braje, Todd J.; Erlandson, Jon M.; Rick, Torben C. (Radiocarbon, 2005)
Californias San Miguel Island contains over 600 archaeological sites, some occupied as early as 12,000 yr ago and most located along the islands north coast. Archaeologists have long believed the south coast to have been marginal or largely uninhabited. Burial of some landforms by sand dunes deposited after historical overgrazing, the lack of systematic survey, and a dearth of radiocarbon dating have also contributed to an underestimation of the intensity of human land use along the south coast of San Miguel Island. Our recent reconnaissance and dating of shell middens on the islands south coast indicate more intensive occupation than previously thought, with numerous south coast sites spanning at least the past 9000 yr, and demonstrate the utility of combining systematic archaeological reconnaissance and radiometrics in reconstructions of human settlement and historical ecology in coastal environments.
id: 579

Recent 2000-year geological records of mud in the inner shelf of the East China Sea and their climatic implications - Xiao, S. B.; Li, A. C.; Jiang, F. Q.; Li, T. G.; Huang, P.; Xu, Z. K. (Chinese Science Bulletin, 2005)
AXIS(14)C dating and grain-size analysis for Core DD2, located at the north of the Yangtze River-derived mud off the Zhejiang-Fujian coasts in the inner shelf of the East China Sea, provide us a high-resolution grain-size distribution curve varying with depth and time. Data in the upper mud layer of Core DD2 indicate that there are at least 9 abrupt grain-size increasing in recent 2000 years, with each corresponding very well with the low-temperature events in Chinese history, which might result from the periodical strengthening of the East Asian Winter Monsoon (EAWM), including the first-revealed maximum temperature lowering event at around 990 a BP. At the same time, the finer grain size section in Core DD2 agrees well with the Sui-Tang Warming Period (600-1000 a AD) defined previously by Zhu Kezhen, during which the climate had a warm, cold and warm fluctuation, with a dominated cooling period of 750-850 a AD. The Little Ice Age (LIA) can also be identified in the core. It starts around 1450 a AD and was followed by a subsequent cooling events at 1510, 1670 and 1840 a AD. Timing of these cold events revealed here still needs to be further verified owing to some current uncertainty of dating we used in this study.
923yeTimes Cited:20Cited References Count:58

Recent 8 ka mud records of the East Asian Winter Monsoon from the inner shelf of the East China Sea - Xiao, S. B.; Li, A. C.; Chen, M. H.; Liu, J. P.; Jiang, F. G.; Li, T. G.; Xie, Q.; Xiang, R.; Chen, Z. (Earth Science - Journal of China University of Geosciences, 2005)
id: 569

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

Redox stratification and anoxia of the early Precambrian oceans: Implications for carbon isotope excursions and oxidation events - Aharon, P. (Precambrian Research, 2005)
An updated compendium of delta(13)C data offer compelling evidence that delta(13)C positive excursions of unsurpassed magnitude in the recorded Earth history (> 8 parts per thousand, and up to 18 parts per thousand PDB) occurred in the early Proterozoic (the Lomagundi event). Questions whether or not these unprecedented positive VC shifts were contemporaneous in various basins and represent local or global events remain unresolved. The framework of major geologic events that occurred in the Paleoproterozoic argues against a Snowball Earth scenario as a backdrop to these exceptional C-13-enrichments. Substantial increases of carbon flux ratio (F-o/F-c, eight times the Phanerozoic average) and organic carbon burial rate (F-o, three times the Phanerozoic average) are required to account for the observed C-13-enrichments under steady-state and dynamic equilibrium modes, respectively. These enhanced ratios and rates are conditional on the availability of a flux of nutrients to the contemporaneous biota producers in excess of the riverine flux, and a decoupling of the P and C cycles. It is argued that these two conditions were met between 2.25 and 2.11 Ga in a redox-stratified ocean with weak upwelling and sluggish meridional surface circulation. The alternative, that the major disturbance in the terrestrial carbon cycle occurred in a rapidly ventilated ocean, is assessed as being unlikely. A large pulse of O-2 equivalent to six to seven times the present terrestrial oxygen budget was rapidly scavenged and spent in the oxidation of reduced Fe and S transported to the shelves by rivers. This contention is consistent with data inferring low oxygen levels (10(-5) to 10(-2) PAL) in the Paleoproterozoic atmosphere and the occurrence of ocean anoxia until the late Precambrian. (c) 2005 Elsevier B.V. All rights reserved.
id: 1585; 940DR Times Cited:19 Cited References Count:78

Sedimentation and carbon burial on the northern California continental shelf: the signatures of land-use change - Leithold, E. L.; Perkey, D. W.; Blair, N. E.; Creamer, T. N. (Continental Shelf Research, 2005)
The burial of organic carbon (OC) on continental margins is strongly coupled to the supply and accumulation of inorganic mineral particles. It follows that carbon burial on the margins should be impacted by changes in riverine sediment delivery, yet these impacts have not been well documented. In this study, an similar to2000-year record of sedimentation and carbon burial on the continental shelf offshore from the Eel River in northern California was examined. The record reveals a 6-11-fold increase in the rate of sediment accumulation on the mid-shelf beginning about 1955, and a concomitant decrease in grain size and increase in flood-layer preservation. At the same time. the age of buried wood fragments abruptly decreased and their stable carbon isotopic composition became enriched in C-13. We argue that these changes can be explained largely as the result of altered land use in the Eel watershed during the past century and its impacts on shelf sediment dispersal processes.Sedimentary OC on the Eel shelf consists primarily of discrete wood fragments associated with coarse-silt- and sandsized particles, and of organic matter strongly bound to clay-sized mineral grains. The clay fraction is a particularly sensitive recorder of environmental change in the Eel system. Above the 1995 horizon, the clay fraction shows an abrupt decrease in OC concentration and loading (OC content normalized to particle surface area) attendant with the increased accumulation rate. Kerogen carbon constitutes a relatively constant proportion of the clay-associated OC throughout the similar to2000-year record. Increases in mass wasting and input of bedrock material following the onset of intensive industrial logging in the Eel watershed may have resulted in a lower loading of terrestrial plant OC in the clay fraction deposited after 1955 as suggested by isotopic mass balance calculations.The Eel River is representative of small mountainous watersheds worldwide that deliver a major portion of the sediment and carbon flux to the margins and that have been strongly impacted by land-use change during the past century. Our results suggest that such changes leave a distinctive mark in both the sedimentological and geochemical records preserved offshore. (C) 2004 Elsevier Ltd. All rights reserved.
894cyTimes Cited:29Cited References Count:109

On the sedimentological origin of downcore variations of bulk sedimentary nitrogen isotope ratios - Kienast, M.; Higginson, M. J.; Mollenhauer, G.; Eglinton, T. I.; Chen, M. T.; Calvert, S. E. (Paleoceanography, 2005)
The bulk sedimentary nitrogen isotopic composition of two cores from nearby sites on the northern slope of the South China Sea (Site 17940 and Ocean Drilling Program (ODP) Site 1144) differs by up to >2‰ during the last glacial period. Given their close proximity, both core sites are located in the same biogeographic zone and nutrient regime, and it is thus unlikely that this offset is due to a true gradient in surface ocean conditions. In an attempt to resolve this offset, we have investigated the possible effects of two sedimentological parameters that can affect bulk sedimentary δ15N, namely, the variable contribution of inorganic N to bulk N in the sediment and the grain-size dependence of bulk δ15N. We find that neither effect, singly or in combination, is sufficient to explain the significant δ15N offset between the two down-core records. By elimination the most likely explanation for the observed discrepancy is a different origin of both the organic and inorganic nitrogen at each site. This study adds to the growing body of evidence highlighting the complex nature and origin of the sedimentary components in sediment drifts, such as ODP Site 1144.
id: 1066

Solar influence on the Indian summer monssoon during the Holocene - Gupta, Anil K.; Das, Moumita; Anderson, David M. (Geophysical Research Letters, 2005)
id: 535

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

Submerged paleoshorelines in the southern and western Black Sea - implications for inundated prehistoric archaeological sites - Coleman, Dwight F.; Ballard, Robert D. (The Black Sea Flood Questions: Changes in Coastline, Climate, and Human Settlement, 2005)
id: 1058

The supply and preservation of ancient and modern components of organic carbon on the Canadian Beaufort Shelf of the Arctic Ocean - Goñi, M. A.; Yunker, M. B.; Macdonald, R. W.; Eglinton, T. I. (Marine Chemistry, 2005)
id: 757

Ten years of compound-specific radiocarbon analysis - Ingalls, A. E.; Pearson, A. (Oceanography, 2005)
id: 504

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

Tsunami history of an Oregon coastal lake reveals a 4600 yr record of great earthquakes on the Cascadia subduction zone - Kelsey, H. M.; Nelson, A. R.; Hemphill-Haley, E.; Witter, R. C. (Geological Society of America Bulletin, 2005)
Bradley Lake, on the southern Oregon coastal plain, records local tsunamis and seismic shaking on the Cascadia subduction zone over the last 7000 yr. Thirteen marine incursions delivered landward-thinning sheets of sand to the lake from nearshore, beach, and dune environments to the west. Following each incursion, a slug of marine water near the bottom of the freshwater take instigated a few-year-to-several-decade period of a brackish (<= 4 parts per thousand salinity) lake. Four additional disturbances without marine incursions destabilized sideslopes and bottom sediment, producing a suspension deposit that blanketed the lake bottom.Considering the magnitude and duration of the disturbances necessary to produce Bradley Lake's marine incursions, a local tsunami generated by a great earthquake on the Cascadia subduction zone is the only accountable mechanism. Extreme ocean levels must have been at least 5-8 m above sea level, and the cumulative duration of each marine incursion must have been at least 10 min. Disturbances without marine incursions require seismic shaking as well.Over the 4600 yr period when Bradley Lake was an optimum tsunami recorder, tsunamis from Cascadia plate-boundary earthquakes came in clusters. Between 4600 and 2800 cal yr B.P., tsunamis occurred at the average frequency of similar to 3-4 every 1000 yr. Then, starting similar to 2800 cal yr B.P., there was a 930-1260 yr interval with no tsunamis. That gap was followed by a similar to 1000 yr period with 4 tsunamis. In the last millennium, a 670-750 yr gap preceded the A.D. 1700 earthquake and tsunami. The A.D. 1700 earthquake may be the first of a new cluster of plate-boundary earthquakes and accompanying tsunamis.Local tsunamis entered Bradley Lake an average of every 390 yr, whereas the portion of the Cascadia plate boundary that underlies Bradley Lake ruptured in a great earthquake less frequently, about once every 500 yr. Therefore, the entire length of the subduction zone does not rupture in every earthquake, and Bradley Lake has recorded earthquakes caused by rupture along the entire length of the Cascadia plate boundary as well as earthquakes caused by rupture of shorter segments of the boundary. The tsunami record from Bradley Lake indicates that at times, most recently similar to 1700 yr B.P., overlapping or adjoining segments of the Cascadia plate boundary ruptured within decades of each other.
938hsTimes Cited:103Cited References Count:73

Two abundant bioaccumulated halogenated compounds are natural products - Teuten, E. L.; Xu, L.; Reddy, C. M. (Science, 2005)
Methoxylated polybrominated diphenyl ethers (MeO-PBDEs) have been found bioaccumulated in the tissues of a variety of aquatic animals and at concentrations comparable to those of anthropogenic halogenated organic compounds, including polychlorinated biphenyls (PCBs). The origin of the MeO-PBDEs has been uncertain; circumstantial evidence supports a natural and/or an industrial source. By analyzing the natural abundance radiocarbon content of two MeO-PBDEs isolated from a True's beaked whale (Mesoplodon mirus), we show that these compounds were naturally produced.
Teuten, Emma LXu, LiReddy, Christopher MengResearch Support, Non-U.S. Gov'tResearch Support, U.S. Gov't, Non-P.H.S.2005/02/12 09:00Science. 2005 Feb 11;307(5711):917-20.

Unusually high helium fluxes in the shallow Marshall aquifer in southern Michigan: implications for cross-formational flow and salinity sources - Ma, L.; Castro, M. C.; Hall, C. M.; Walter, L. M. (Eos Trans. AGU Fall Meeting Supplement, 2005)
id: 437

Using comprehensive two-dimensional gas chromatography retention indices to estimate environmental partitioning properties for a complete set of diesel fuel hydrocarbons - Arey, J. S.; Nelson, R. K.; Xu, L.; Reddy, C. M. (Analytical Chemistry, 2005)
Comprehensive two-dimensional gas chromatography (GC x GC) provides nearly complete composition data for some complex mixtures such as petroleum hydrocarbons. However, the potential wealth of physical property information contained in the corresponding two-dimensional chromatograms is largely untapped. We developed a simple but robust method to estimate GC x GC retention indices for diesel-range hydrocarbons. By exploiting n-alkanes as reference solutes in both dimensions, calculated retention indices were insensitive to uncertainty in the enthalpy of gas-stationary-phase transfer for a suite of representative diesel components. We used the resulting two-dimensional retention indices to estimate the liquid vapor pressures, aqueous solubilities, air-water partition coefficients, octanol-water partition coefficients, and vaporization enthalpies of a nearly complete set of diesel fuel hydrocarbons. Partitioning properties were typically estimated within a factor of 2; this is not as accurate as some previous estimation or measurement methods. However, these relationships may allow powerful and incisive analysis of phase-transfer processes affecting petroleum hydrocarbon mixtures in the environment. For example, GC x GC retention data might be used to quantitatively deconvolve the effects of water washing and evaporation on environmentally released diesel fuels.
id: 1700; 985UM Times Cited:30 Cited References Count:56

Volatiles in subduction zone magmas: concentrations and fluxes based on melt inclusion and volcanic gas data - Wallace, P. J. (Journal of Volcanology and Geothermal Research, 2005)
Owing to advances in microanalytical techniques over the last 15 years, there is a growing database on the volatile contents of subduction-related magmas as recorded in melt (glass) inclusions trapped in phenocrysts in volcanic rocks. Basaltic. magma from subduction zones show a wide range of water contents, ranging from as high as 6-8 to <0.5 wt.% H2O. Variations are related in some places to primary factors such as proximity to the arc front or extent of subduction-related mantle enrichment inferred from trace element systematics. Some low values of H2O in melt inclusions result from shallow degassing before crystallization and entrapment of inclusions. The dissolved CO2 contents of melt inclusions from basaltic arc lavas range from Mow detection (similar to25 ppm) to nearly 2500 ppm. This variability is caused by degassing of low-solubility CO2 before inclusions are trapped. The estimated primary CO2 content of arc basaltic magma inferred front global arc volcanic CO2 emissions and magma flux is >3000 ppm, suggesting that no melt inclusions sample undegassed arc magmas. The Cl and S contents of arc basaltic magmas are greater than midocean ridge basalts, indicating that these volatiles are also recycled from subducted sediment and altered oceanic crust back into the mantle wedge. Comparison of the fluxes of volatiles subducted back into the mantle along subduction zones and returned from the mantle to the surface reservoir (crust, ocean, and atmosphere) via magmatism suggests that there is an approximate balance for structurally bound H2O and Cl. In contrast, similar to50% of subducted C appears to be returned to the deep mantle by subduction, but uncertainties are relatively large. For S, the amount returned to the surface reservoir by subduction zone magmatism is only similar to15-30% of the total amount being subducted. Dacitic and rhyolitic magmas in arcs contain 1-6 wt.% H2O, a range that overlaps considerably with the values for basaltic magmas. Either basaltic parents for these differentiated magmas are relatively H2O-poor, or intermediate to silicic arc magmas form through open-system processes involving variable amounts of crustal melting, mixing with basalt and basaltic differentiates, and fluxing of CO2-rich vapor from mafic magma recharged into silicic magma bodies. Consideration of H2O-CO2 relations and gaseous SO2 emissions for intermediate to silicic arc magmas shows that such magmas are typically vapor-saturated during crystallization in the middle to upper crust. Gas emissions thus reflect migration and accumulation of volatiles within complex open magmatic systems. (C) 2004 Elsevier B.V. All rights reserved.
889fwTimes Cited:418Cited References Count:157

When did oxygen appear in the atmosphere? - Ono, Shuhei (Geological Society of America, 2005)
id: 1577

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.

The 14C AMS system at the University of Georgia - Roberts, M. L.; Culp, R. A.; Dvoracek, D. K.; Hodgins, G. W. L.; Neary, M. P.; Noakes, J. E. (Nuclear Instruments and Methods in Physics Research, 2004)
id: 1809

The 14C AMS system at The University of Georgia - Roberts, M. L.; Culp, R. A.; Dvoracek, D. K.; Hodgins, G. W. L.; Neary, M. P.; Noakes, J. E. (Proceedings of the Ninth International Conference on Accelerator Mass Spectrometry, 2004)
The Center for Applied Isotope Studies at the University of Georgia has installed a compact 14C accelerator mass spectrometry (AMS) system manufactured by the National Electrostatics Corporation, Middleton, Wisconsin. The system utilizes a 134 sample ion source and a 500 kV Pelletron. In terms of cost and size, the new system is a significant advance over previous technology. Details and performance of the new system will be presented.
id: 2103

14C Measurements - Tanner, R. L.; Parkhurst, W. J.; McNichol, A. P. (Aerosol Science & Technol, 2004)
id: 972

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

50,000-Year-Old Plant May Warn of Death of Tropical Ice Caps - Thompson, Lonnie (Newswise, 2004)
id: 1224

An 8700 year old shell midden from the south coast of San Miguel Island, California - Braje, Todd J.; Erlandson, Jon M.; Rick, Torben C. (Current Research in the Pleistocene, 2004)
id: 1091

Abrupt tropical vegetation response to rapid climate changes - Hughen, K. A.; Eglinton, T. I.; Xu, L.; Makou, M. (Science, 2004)
Identifying leads and lags between high- and low-latitude abrupt climate shifts is needed to understand where and how such events were triggered. Vascular plant biomarkers preserved in Cariaco basin sediments reveal rapid vegetation changes in northern South America during the last deglaciation, 15,000 to 10,000 years ago. Comparing the biomarker records to climate proxies from the same sediment core provides a precise measure of the relative timing of changes in different regions. Abrupt deglacial climate shifts in tropical and high-latitude North Atlantic regions were synchronous, whereas changes in tropical vegetation consistently lagged climate shifts by several decades.
Hughen, Konrad AEglinton, Timothy IXu, LiMakou, MatthewengResearch Support, Non-U.S. Gov't2004/05/25 05:00Science. 2004 Jun 25;304(5679):1955-9. Epub 2004 May 20.

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

Advective controls on the age of marine sedimentary organic matter - Mollenhauer, Gesine; Eglinton, Timothy I.; Hayes, John M. (Gordon Research Conference Organic Geochemistry, 2004)
id: 1068

Age and preservation of Amphistegina (foraminifera) in Hawaiian beach sand: implication for sand turnover rate and resource renewal - Resig, J. M. (Marine Micropaleontology, 2004)
Radiocarbon dating of tests of Amphistegina spp. from the surface sand of Hawaiian beaches has revealed ages up to 1500 years or more. Preservation is related to age: the residual umbos are older than the intact tests. The antiquity of some of the tests suggests that predictions of a sand turnover rate of less than 100 years time based on Amphistegina productivity studies are in error and that the majority of tests produced in nearshore environments of Hawaii do not accumulate on the beach. (C) 2003 Elsevier B.V. All rights reserved.
id: 178; 800DG Times Cited:3 Cited References Count:30

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

Alabama Gulf Coast groundwaters: 4He and 14C as groundwater-dating tools - Carey, Anne; Dowling, Carolyn B.; Poreda, Robert J. (Geology, 2004)
Analyses of 4He and 14C in groundwaters from a Miocene quartz aquifer on the Alabama Gulf Coast show the usefulness of 4He for dating these Holocene groundwaters. In this aquifer system of low alkalinities and low pHs, radiocarbon ages can be used without model correction. The groundwaters studied ranged from 42.3% to 95.5% modern carbon and yielded uncorrected ages of 375–6790 yr. Radiogenic 4He ages ranged from >50–7500 yr.
id: 1222
Keywords: 14C; 4He; age dating; Baldwin County Alabama; groundwater

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

Anthropogenic influences on benthis foraminiferal faunas in Long Island Sound - Thomas, E.; Varekamp, J. C.; Thaler, B.; Acosta, Z. (7th Biennial Long Island Sound reserach conference, Program and Abstracts, 2004)
id: 1183

Archean Tectonics 2004: A review - Van Kranendonk, M. (Precambrian Research, 2004)
id: 1601

Artifacts from a submerged prehistoric site on the Coos Bay Estuary, southern Oregon coast - Minor, Rick; Nelson, Alan R. (Journal of California and Great Basin Anthropology, 2004)
id: 993

Assessing sources and agesof organic matter supporting river and estuarine bacterial production: a multiple isotope (Delta14C, delta13C and delta15N) approach - McCallister, S. L.; Bauer, J. E.; Cherrier, J. C.; Ducklow, H. W. (Limnology and Oceanography, 2004)
id: 1153

A backbarrier overwash record of intense storms from Brigantine, New Jersey - Donnelly, J. P.; Butler, J.; Roll, S.; Wengren, M.; Webb, T. (Marine Geology, 2004)
Analysis of aerial photographs and historic charts indicates that the barrier beach at Brigantine, NJ has migrated landward 300 to 400 m since 1869, primarily as a result of overwash during hurricanes and winter storms. A series of vibracores from the backbarrier salt marsh reveals a millennial-scale stratigraphic record of overwash deposition. Carbon-14 (C-14) and Cesium-137 (Cs-137) radioisotopic methods were used to date over-wash deposits (washovers). The ages of recent washovers are consistent with deposition during intense storms in 1938, 1944, 1950, and 1962. An additional overwash deposit recovered in five of the sediment cores was likely deposited by an intense hurricane strike in 1821 or possibly in 1788. Two prehistoric overwash fans were likely deposited by intense storms striking the New Jersey Coast in the 7th to l4th centuries and 6th to 7th centuries A.D. The landward barrier migration indicates that the older overwash sediments were likely transported a considerably greater distance than the more recent overwash fans. The greater distance of transport may indicate that the prehistoric storms that deposited overwash fans across the study site were more intense than the most intense storm to strike this coast in the historic period, the hurricane of 182 1. The spatially variable occurrence of overwash deposition at this site points to a need for multisite stratigraphic surveys of extensive stretches of the coast in order to develop reliable records of past intense storm frequency from backbarrier environments. (C) 2004 Elsevier B.V. All rights reserved.
Sp. Iss. SI853thTimes Cited:74Cited References Count:37

Backbarrier sedimentary records of intense hurricane landfalls in the northeastern United States - Donnelly, J. P.; Iii, Webb T. (Hurricanes and Typhoons: Past, Present, and Potential, 2004)
id: 500

Benthic foraminifera in the changing ecosystem of Long Island Sound, abstract - Thaler, B.; Thomas, E.; Varekamp, J. C. (EOS Trans. AGU, 2004)
id: 1182

Busted balls shell midden (CA-SMI-606): an early coastal site on San Miguel Island, California - Erlandson, Jon M.; Rick, Torben C.; Batterson, Melissa R. (North American Archaeologist, 2004)
id: 583

Carbonatization of oceanic crust by the seafloor hydrothermal activity and its significance as a CO2 sink in the Early Archean - Nakamura, K.; Kato, Y. (Geochimica Et Cosmochimica Acta, 2004)
Early Archean (3.46 Ga) hydrothermally altered basaltic rocks exposed near Marble Bar, eastern Pilbara Craton, have been studied in order to reveal geological and geochemical natures of seafloor hydrothermal carbonatization and to estimate the CO2 flux sunk into the altered oceanic crust by the carbonatization. The basaltic rocks are divided into basalt and dolerite, and the basalt is further subdivided into type I, having original igneous rock textures, and type II, lacking these textures due to strong hydrothermal alteration. Primary clinopyroxene phenocrysts are preserved in some part of the dolerite samples, and the alteration mineral assemblage of dolerite (chlorite + epidote + albite +/- quartz actinolite) indicates that the alteration. condition was typical greenschist facies. In other samples, all primary minerals were completely replaced by secondary minerals, and the alteration mineral assemblage of the type I and type II basalts (chlorite + K-mica + quartz + carbonate minerals +/- albite) is characterized by the presence of K-mica and carbonate minerals and the absence of Ca-Al silicate minerals such as epidote and actinolite, suggesting the alteration condition of high CO2 fugacity. The difference of the alteration mineral assemblages between basalt and dolerite is probably attributed to the difference of water/rock ratio that, in turn, depends on their porosity.Carbonate minerals in the carbonatized basalt include calcite, ankerite, and siderite, but calcite is quite dominant: The delta(13)C values of the carbonate minerals are -0.3 +/- 1.2parts per thousand and mostly within the range of marine carbonate; indicating that the carbonate minerals were formed by seafloor hydrothermal alteration and that carbonate carbon in the altered basalt was derived from seawater. Whole-rock chemical composition of the basaltic rocks is essentially similar to that of modern mid-ocean ridge basalt (MORB) except for highly mobile elements such as K2O, Rb, Sr, and Ba. Compared to the least altered dolerite, all altered basalt samples are enriched in K2O, Rb, and Ba, and are depleted in Na2O, reflecting the presence of K-mica replacing primary plagioclase. In addition, noticeable CO2 enrichment is recognized in the basalt due to the ubiquitous presence of carbonate minerals, but there was essentially neither gain nor loss of CaO. This suggests that the CO2 in the hydrothermal fluid (seawater) was trapped by using Ca originally contained in the basalt. The CaO/CO2, ratios of the basalt are generally the same as that of pure calcite, indicating that Ca in the basalt was almost completely converted to calcite during the carbonatization, although Mg and Fe were mainly redistributed into noncarbonate minerals such as chlorite.The carbon flux into the Early Archean oceanic crust by the seafloor hydrothermal carbonatization is estimated to be 3.8 X 10(13) mol/yr, based on the average carbon content of altered oceanic crust of 1.4 X 10(-3) mol/g, the alteration depth of 500 m, and the spreading rate of 1.8 X 10(11) cm(2)/yr. This flux is equivalent to or greater than the present-day total carbon flux. It is most likely that the seafloor hydrothermal carbonatization played an important role as a sink of atmospheric and oceanic CO2 in the Early Archean: Copyright (C) 2004 Elsevier Ltd.
869juTimes Cited:55Cited References Count:67

Carbon-isotopic shifts associated with heterotrophy and biosynthetic pathways in direct- and indirect-developing sea urchins - Villinski, J. C.; Hayes, J. M.; Villinski, J. T.; Brassell, S. C.; Raff, R. A. (Marine Ecology Progress Series, 2004)
Natural abundances of C-13 were measured in bulk biomass and in individual lipids isolated from 2 species of sea urchins, Heliocidaris erythrogramma and H. tuberculata, and from calcareous and green benthic algae on which they were feeding. Planktonic larvae of H. erythrogramma are lecithotrophic whereas those of H. tuberculata are planktotrophic. The organisms were collected from a subtidal environment in Botany Bay, Sydney, Australia. The biomass of both consumers was enriched in C-13 relative to their diets by up to 1.8parts per thousand. The carbon skeletons of sterols from the urchins derive at least in part from de novo biosynthesis by the urchins. Depending on chain length and degree of unsaturation, carboxylic acids from the urchins derive from de novo blosynthesis (14:0, unsaturated acids), from the diet (18:0), or from both these sources (16:0). H. tuberculata synthesizes a greater distribution and proportion of unsaturated carboxylic acids. Odd-C and branched-chain carboxylic acids derive in part from bacterial sources and are enriched in C-13 relative to algal lipids and depleted relative to those in urchins. Only H. erythrogramma, which uses wax esters-as storage lipids in its relatively large and buoyant eggs, produces significant quantities of n-alkanols; n-alkanols in H, tuberculata derive from the diet. In terms of molecular distributions and isotopic compositions, the lipids in fecal matter from both heterotrophs resemble those of the diet rather than those of the urchins.
847vnTimes Cited:4Cited References Count:34

CA-SMI-548: A 9500 year old shell midden at Running Springs, San Miquel Island, California - Erlandson, Jon M.; Rick, Torben C.; Vellanoweth, Rene L.; Largaespada, Tony (Emerging from the Ice Age: Early Holocene Occupations on the Central California Coast, 2004)
id: 584

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

Co2 and 3He in hydrothermal plumes: implications for mid-ocean ridge CO2 flux - Resing, Joseph A.; Lupton, John E.; Feely, Richard A.; Lilley, Marvin D. (Earth and Planetary Science Letters, 2004)
id: 1518

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

Collapse and rapid resumption of Atlantic meridional circulation linked to deglacial climate changes - McManus, J. F.; Francois, R.; Gherardi, J. M.; Keigwin, L. D.; Brown-Leger, S. (Nature, 2004)
The Atlantic meridional overturning circulation is widely believed to affect climate. Changes in ocean circulation have been inferred from records of the deep water chemical composition derived from sedimentary nutrient proxies, but their impact on climate is difficult to assess because such reconstructions provide insufficient constraints on the rate of overturning. Here we report measurements of 231Pa/230Th, a kinematic proxy for the meridional overturning circulation, in a sediment core from the subtropical North Atlantic Ocean. We find that the meridional overturning was nearly, or completely, eliminated during the coldest deglacial interval in the North Atlantic region, beginning with the catastrophic iceberg discharge Heinrich event H1, 17,500 yr ago, and declined sharply but briefly into the Younger Dryas cold event, about 12,700 yr ago. Following these cold events, the 231Pa/230Th record indicates that rapid accelerations of the meridional overturning circulation were concurrent with the two strongest regional warming events during deglaciation. These results confirm the significance of variations in the rate of the Atlantic meridional overturning circulation for abrupt climate changes.
McManus, J FFrancois, RGherardi, J-MKeigwin, L DBrown-Leger, SengResearch Support, Non-U.S. Gov'tResearch Support, U.S. Gov't, Non-P.H.S.England2004/04/23 05:00Nature. 2004 Apr 22;428(6985):834-7.

Comments on potential geologic and seismic hazards affecting coastal Ventura County, CCalifornia - Ross, S. D. Boore; Fisher, M.; Frankel, A.; Geist, E.; Hudnut, K.; Kayen, R.; Lee, H.; Normark, W. R.; Wong, F. (U. S. Geological Survey OFR 1004-1286, 2004)
id: 420

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

The constancy of upper mantle fO2 through time inferred from V/Sc ratios in basalts - Li, Zheng-Xue Anser; Lee, Cin-Ty Aeolus (Earth and Planetary Science Letters, 2004)
id: 1580

Controls on the variability of organic matter and dissolved inorganic carbon ages in northeast U.S. rivers - Raymond, P. A.; Bauer, J. E.; Caraco, N. F.; Cole, J. J.; Longworth, B. E.; Petsch, S. T. (Marine Chemistry, 2004)
id: 967

Coupling instrumental and geological records of sea-level change: Evidence from southern New England of an increase in the rate of sea-level rise in the late 19th century - Donnelly, J. P.; Cleary, P.; Newby, P.; Ettinger, R. (Geophysical Research Letters, 2004)
We construct a high-resolution relative sea-level record for the past 700 years by dating basal salt-marsh peat samples above a glacial erratic in an eastern Connecticut salt marsh, to test whether or not the apparent recent acceleration in the rate of sea-level rise (SLR) is coeval with climate warming. The data reveal an average SLR rate of 1.0 +/- 0.2 mm/year from about 1300 to 1850 A. D. Coupling of the regional tide-gauge data (1856 to present) with this marsh-based record indicates that the nearly three-fold increase in the regional rate of SLR to modern levels likely occurred in the later half of the 19th century. Thus the timing of the observed SLR rate increase is coincident with the onset of climate warming, indicating a possible link between historic SLR increases and recent temperature increases.
806kkTimes Cited:94 Cited References Count:20
Keywords: accretion; cal yr ad; climate-ocean variations; connecticut; long-island sound; salt-marsh

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.

Deep global cycling of carbon constrained by the solidus of anhydrous, carbonated eclogite under upper mantle conditions - Dasgupta, R.; Hirschmann, M. M.; Withers, A. C. (Earth and Planetary Science Letters, 2004)
We present partial melting experiments that constrain the near solidus phase relations of carbonated eclogite from 2 to 8.5 GPa. The starting material was prepared by adding 5 wt.% CO2 in the form of a mixture of Fe-Mg-Ca-Na-K carbonates to an eclogite from Salt Lake crater, Oahu, Hawaii and is a reasonable approximation of carbonated oceanic crust from which siliceous hydrous fluids have been extracted during subduction. Melt-present versus melt-absent conditions are distinguished based on textural criteria. Garnet and clinopyroxene appear in all the experiments. Between 2 and 3 GPa, the subsolidus assemblage also includes ilmenite+/-calcio-dolomite(ss)+/-CO2, whereas above the solidus (1050-1075 degreesC at 3 GPa) calcio-dolomitic liquid appears. From 3 to 4.5 GPa, dolomite(ss) is stable at the solidus and the near-solidus melt becomes increasingly dolomitic. The appearance of dolomite above 3 GPa is accompanied by a negative Clapeyron slope of the solidus, with a minimum located between 995 and 1025 degreesC at ca. 4 GPa. Above 4 GPa, the solidus rises with increasing pressure to 1245+35 degreesC at 8.5 GPa and magnesite becomes the subsolidus carbonate. Dolomitic melt coexists with magnesite+garnet+cpx+rutile along the solidus from 5 to 8.5 GPa.Comparison of our results to other recent experimental studies [T. Hammouda, High-pressure melting of carbonated eclogite and experimental constraints on carbon recycling and storage in the mantle, Earth Planet. Sci. Lett. 214 (2003) 357-368; G.M. Yaxley, G.P. Brey, Phase relations of carbonate-beating eclogite assemblages from 2.5 to 5.5 GPa: implications for petropnesis of carbonatites, Contrib. Mineral. Petrol. 146 (2004) 606-6191 shows that carbonate minerals are preserved in anhydrous or slightly hydrous carbonated eclogite to temperatures >1100 and >1200 degreesC at 5 and 9 GPa, respectively. Thus, deep subduction of carbonate is expected along any plausible subduction geotherm. If extrapolated to higher pressures, the carbonated eclogite solidus is likely to intersect the oceanic geotherm at a depth close to 400 km. Carbonated eclogite bodies entering the convecting upper mantle will thus release carbonate melt near the top of the mantle transition zone and may account for anomalously slow seismic velocities at depths of 280-400 km. Upon release, this small volume, highly reactive melt could be an effective agent of deep mantle metasomatism. Comparison of the carbonated eclogite solidus with that of peridotite-CO2 shows a shallower solidus-geotherm intersection for the latter. This implies that carbonated peridotite is a more likely proximal source of magmatic carbon in oceanic provinces. However, carbonated eclogite is a potential source of continental carbonatites, as its solidus crosses the continental shield geotherm at ca. 4 GPa. Transfer of eclogite-derived carbonate melt to peridotite may account for the geochemical characteristics of some oceanic island basalts (OIBs) and their association with high CaO and CO2. (C) 2004 Elsevier B.V. All rights reserved.
864qyTimes Cited:192Cited References Count:49

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

Deglacial sea surface temperatures of the western tropical Pacific: A new look at old coral - Cohen, A. L.; Hart, S. R. (Paleoceanography, 2004)
Using Secondary Ion Mass Spectrometry ( SIMS) ion microprobe techniques, we generated annual Sr/Ca cycles with subweekly resolution from chunks of Porites coral retrieved from a Tahiti barrier reef drill core (149degreesW, 17degreesS), representing the period 13,650 to 13,100 years B.P. The centers of pristine skeletal septa were selectively targeted with a 10 mum diameter ion beam spot, avoiding adjacent pore spaces occupied by secondary aragonite needles. Applying a Sr/Ca-sea surface temperature (SST) calibration equation derived from modern Tahiti Porites having the same low growth rate as the fossil specimens, we obtained SSTs similar to0.5degrees-1.5degreesC cooler during the Bolling-Allerod relative to the present day, with no significant change in seasonality. On the contrary, we estimate that analysis of bulk samples would yield excessively cool Sr/Ca-based SST estimates due to the occupation by secondary aragonite crystals of up to 50% of the skeletal pore space in the ancient samples. We find that growth rate effects on coral Sr/Ca further depress the apparent mean annual derived SSTs (by >3degreesC) and amplify the apparent seasonality by selectively enhancing wintertime cooling. Our microscale analysis of pristine skeleton and application of an appropriate growth-dependent calibration yield Sr/Ca-derived SSTs that are in good agreement with those derived from Mg/Ca ratios of calcitic foraminifera which indicate a continuous postglacial warming of the western tropical Pacific, in phase with the warming of the tropical Atlantic.
885czTimes Cited:30 Cited References Count:37
Keywords: bolling-allerod; climate-change; coral sr/ca; diagenesis; ion microprobe; last deglaciation; paleotemperature proxy; radiocarbon; record; sea surface temperature; sr/ca; strontium; symbiotic coral; trace-elements; tropical pacific

Dynamics of tidal salt barren formation and the record of present-day sea level change - Hsieh, Y. P. (The Ecogeomorphology of Tidal Marshes, American Geophysical Union, 2004)
id: 1164

Early diagenetic remineralization of sedimentary organic C in the Gulf of Papua deltaic complex (Papua New Guinea): Net loss of terrestrial C and diagenetic fractionation of C isotopes - Aller, R. C.; Blair, N. E. (Geochimica et Cosmochimica Acta, 2004)
Oceania supplies similar to40% of the global riverine flux of organic carbon, approximately half of which is injected onto broad continental shelves and processed in shallow deltaic systems. The Gulf of Papua, on the south coast of the large island of New Guinea, is one such deltaic clinoform complex. It receives similar to4 Mt yr(-1) particulate terrestrial organic carbon with initial particle C-org loading similar to0.7 mg m(-2). C-org loading is reduced to similar to0.3 mg m(-2) in the topset-upper foreset zones of the delta despite additional inputs of mangrove and planktonic detritus, and high net sediment accumulation rates of 1-4 cm yr(-1) . Carbon isotopic analyses (delta(3)C, Delta(14)C) of SigmaCO(2) and C-org demonstrate rapid (
id: 976; 813FD Times Cited:44 Cited References Count:72

The early history of Long Island Sound - Varekamp, J. C.; Thomas, E.; Groner, M. (7th Biennial Long Island Sound research conference, Program/Abstracts, 2004)
id: 741

Enhanced marine productivity off western North America during warm climate intervals of the past 52 kyr - Ortiz, J. D.; O'Connell, S.; DelViscio, J.; Dean, W. E.; Carriquiry, J.; Marchitto, T. M.; Zheng, Y.; van Geen, A. (Geology, 2004)
id: 603

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

The eutrophication of Long Island Sound, abstract - Varekamp, J. C.; Lugolobi, F.; Thomas, E.; Mecray, E.; Buchholtz ten Brink, M. R. (EOS Trans. AGU, 2004)
id: 740

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

Evidence of historical wet period deposits in central Long Island Sound: source and transport processes based on mercury profiles and sedimentology - Carey, D. A.; Varekamp, J. C. (7th biennial Long Island Sound research conference, Program and abstrracts, 2004)
id: 734

The evolution of the Earth surface sulfur reservoir - Canfield, D. E. (American Journal of Science, 2004)
The surface sulfur reservoir is in intimate contact with the mantle. Over long time scales, exchange with the mantle has influenced the surface reservoir size and possibly its isotopic composition. Processes delivering sulfur to the Earth surface from the mantle include volcanic outgassing, hydrothermal input, and ocean crust weathering. The sulfide fixed in ocean crust as a consequence of hydrothermal sulfate reduction, and subduction of sedimentary sulfides, represent return pathways of sulfur to the mantle. The importance of these different pathways in influencing the size of the surface sulfur reservoir depends on the particulars of ocean and atmosphere chemistry. During times of banded iron formation when the oceans contained dissolved iron, sulfide from submarine hydrothermal activity was precipitated on the seafloor and subsequently subducted back into the mantle and, therefore, had little impact on the surface sulfur reservoir size. With sulfidic ocean bottom water conditions, which may have occurred through long stretches of the Mesoproterozoic and Neoproterozoic, significant amounts of sulfide is subducted into the mantle. When the oceans are oxic, sulfide subduction is unimportant, and an additional source, ocean crust weathering, delivers sulfur to the Earth surface. Thus, under oxic conditions the surface environment accumulates sulfur, and probably has for most of the last 700 million years.Mass balance modeling suggests that the surface sulfur reservoir may have peaked in size in the early Mesoproterozoic, declined to a minimum in the Neoproterozoic, and increased to its present size through the Phanerozoic. The exchange of sulfur between the mantle and the surface environment can also influence the isotopic composition of the surface reservoir. Modeling shows that the subduction of S-34- depleted sulfur through the Mesoproterzoic could have significantly increased the average delta(34)S of the surface reservoir into the late Neoproterozoic. The preserved isotope record through the Neoproterozoic is well out of balance, with the average delta(34)S for sulfate and sulfide both exceeding the modem crustal average. This imbalance could be explained, at least partly, if the crustal average was more S-34-enriched than at present, as the modeling presented here suggests.
889sqTimes Cited:142Cited References Count:59

Export of young terrigenous dissolved organic carbon from rivers to the Arctic Ocean - Benner, R.; Benitez-Nelson, B.; Kaiser, K.; Amon, R. M. W. (Geophysical Research Letters, 2004)
Soils in the drainage basins of Arctic rivers are a major global reservoir of aged organic carbon. The fate of this old carbon is of growing concern as the effects of climate change become more evident in the Arctic. We report natural abundance C-14 data indicating that dissolved organic carbon (DOC) from several Eurasian and North American rivers is predominantly young and largely derived from recently-fixed C in plant litter and upper soil horizons. Concentrations of dissolved lignin phenols, unique organic tracers of terrestrial plant material, and C-14 content in DOC were strongly correlated throughout the Arctic Ocean, indicating terrigenous DOC is mostly young and widely distributed in polar surface waters. These young ages of terrigenous DOC in rivers and the ocean indicate little of the old carbon stored in Arctic soils is currently being mobilized in the dissolved component of continental runoff.
id: 646; 806KJ Times Cited:60 Cited References Count:34

Fate of mercury in Long Island Sound - Varekamp, J. C. (Newsday Magazine, 2004)

Flexible strategies for resource defense on the northern channel islands of California: An agent-based model - Kennett, D. J.; Clifford, R. (The Archaeology of Insularity: Examining the Past in Island Environments, 2004)
id: 470

From bedrock to burial: the evolution of particulate organic carbon across coupled watershed-continental margin systems - Blair, N. E.; Leithold, E. L.; Aller, R. C. (Marine Chemistry, 2004)
Deltas sequester nearly half of the organic carbon (OC) buried in the marine environment. The composition of the buried organic matter reflects both watershed and seabed processes. A conceptual model is presented that describes the evolution of particulate organic carbon (POC) as it travels from its terrestrial source to its burial at sea. Alterations to the POC occur primarily in bioactive reservoirs, such as soils and the surface mixed layer (SML) of the seabed, where new organic matter can be added and older material degraded. Bypassing or rapid passage through the reservoirs is a key parameter because it avoids change. The Eel River of northern California and the Amazon River systems illustrate the importance of reservoir transit time and storage in determining the character of POC delivered to the continental margin. The Eel exemplifies a bypass system. Mass-wasting processes on land deliver unaltered bedrock along with OC derived from extant vegetation directly to the river channel without significant storage in soils. Rapid burial on the shelf occurs as a result of flood events. As a consequence, the buried material appears to be a simple mixture of carbon derived from kerogen (bedrock C), and modem terrestrial and marine sources. This is predicted to be a characteristic of the many similar short rivers on active margins that supply >40% of the fluvial sediment to the world's ocean. Extensive storage and processing of OC in lowland soils is a characteristic of the large Amazon watershed. Upland POC compositions are either overprinted or replaced by lowland sources. Upon delivery to the shelf, over half of the riverine POC is lost as a result of residence in sediment layers that are periodically reworked over time scales of days to months. The addition of fresh reactive marine OC, exposure to oxygen, and the regeneration of metal oxidants during resuspension events fuel the oxidation of the niverme organic matter. The nature of the watershed-shelf processes likely produce a complex mixture of organics possessing a continuum of ages and reactivities. The model illustrates the need to develop tools to measure residence times of particles in the various reservoirs so that the behavior of POC can be calibrated as it moves through a sedimentary system. The ultimate goal is to be able to use the organic geochemistry of soils and sediments to quantitatively infer the history of processes that determine both the composition and amount of POC present in different depositional environments. (C) 2004 Elsevier B.V. All rights reserved.
id: 978; 882IA Times Cited:50 Cited References Count:118

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

Glacial intermediate water ventilation in the northwestern Pacific based on AMS radiocarbon dating - Ohkushi, K.; Uchida, M.; Ahagon, N.; Mishima, T.; Kanematsu, T. (Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions with Materials and Atoms, 2004)
C-14 ages of benthic foraminifera and planktonic foraminifera in sediment core PC4 (41degrees07.10'N, 142degrees24.17'E) collected from the northwestern Pacific were measured by accelerator mass spectrometry. The purpose of this study was to investigate the changes in intermediate water ventilation in the northwestern Pacific during the last glacial period. We used age differences between benthic foraminifera and planktonic foraminifera from the same sediment horizons to estimate the ventilation time of intermediate water. Planktonic C-14 ages show that the core recorded paleoenvironmental changes during the last 35 kyr. Glacial benthic-planktonic age differences were smaller in the early deglacial period (15000-17000 cal yr BP) than in the period (19000-30000 cal yr BP) before and during the last glacial maximum. The results at intermediate depths are consistent with those from a Pacific deep-water site. (C) 2004 Elsevier B.V. All rights reserved.
852jtTimes Cited:7Cited References Count:13

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

Great earthquakes and tsunamis of the past 2000 years at the Salmon River estuary, central Oregon coast, USA - Nelson, A. R.; Asquith, A. C.; Grants, W. C. (Bulletin of the Seismological Society of America, 2004)
Four buried tidal marsh soils at a protected inlet near the mouth of the Salmon River yield definitive to equivocal evidence for coseismic subsidence and burial by tsunami-deposited sand during great earthquakes at the Cascadia subduction zone. An extensive, landward-tapering sheet of sand overlies a peaty tidal-marsh soil over much of the lower estuary. Limited pollen and macrofossil data suggest that the soil suddenly subsided 0.3-1.0 m shortly before burial. Regional correlation of similar soils at tens of estuaries to the north and south and precise C-14 ages from one Salmon River site imply that the youngest soil subsided during the great earthquake of 26 January A.D. 1700. Evidence for sudden subsidence of three older soils during great earthquakes is more equivocal because older-soil stratigraphy can be explained by local hydrographic changes in the estuary. Regional C-14 correlation of two of the three older soils with soils at sites that better meet criteria for a great-earthquake origin is consistent with the older soils recording subsidence and tsunamis during at least two great earthquakes. Pollen evidence of sudden coseismic subsidence from the older soils is inconclusive, probably because the amount of subsidence was small (<0.5 m). The shallow depths of the older soils yield rates of relative sea-level rise substantially less than rates previously calculated for Oregon estuaries.
855anTimes Cited:18Cited References Count:80

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 development of the Yellow River's subaqueous delta, North Yellow Sea - Liu, J. P.; Milliman, J. D.; Gao, S.; Cheng, P. (Marine Geology, 2004)
id: 650

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

Holocene relative sea-level history of the Southern Victoria Land Coast, Antarctica - Hall, B. L.; Baroni, C.; Denton, G. H. (Global and Planetary Change, 2004)
More than 130 radiocarbon dates of penguin remains and guano, sealskin, shells, and seaweed from raised beach ridges afford relative sea-level information for southern Victoria Land. A new relative sea-level curve suggests that the final unloading of grounded ice from the coast took place about 6600 C-14 years BP, in keeping with previous estimates of the timing of deglaciation. Since this time, the coast has experienced 32 m of relative sea-level fall at rates ranging from 2 to 15 mm/year, consistent with glacioisostatic rebound. (C) 2004 Elsevier B.V. All rights reserved.
845idTimes Cited:40Cited References Count:25

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

Inhibited eclogite formation: The key to the rapid growth of strong and buoyant Archean continental crust - Bjornerud, M. G.; Austrheim, H. (Geology, 2004)
Subduction is the principal mechanism by which the hydrosphere and interior of Earth interact. Today, subduction involves the dehydration of ocean crust at depths of 60-120 km depending on the age of the slab. Release of the water leads to generation of arc magmas (future continental crust), and the slab is then transformed into denser eclogite that helps to pull more of the slab into the trench. However, it is unlikely that the first continental crust formed this way. Growing geochemical evidence indicates that large volumes of continental crust were produced over a short period of time in the Archean, when the planet was probably too hot for modern plate tectonics to operate. A significant increase in the kinetics of eclogite-forming reactions may have been the key to the transition from Archean to modern tectonics. Under the higher geothermal gradients of the Archean, tectonically buried ocean crust would have been severely dehydrated before reaching eclogite facies pressures. Because rapid eclogitization is dependent on water as a medium for advective ion transport, the very shallow dehydration in the Archean may have inhibited the formation of eclogite facies minerals. The importance of water in eclogite metamorphism is illustrated by a complex of partly eclogitized malic granulites in Holsnoy, western Norway, in which reaction progress was limited by the availability of water. When water is scarce or absent, metastable granulite facies mineral assemblages can persist at eclogite facies depths owing to the extremely slow reaction kinetics when diffusion is the only chemical transport mechanism. Such dehydrated but uneclogitized mafic crust would have been very strong and too buoyant to sink into the mantle, and it may have formed the substrate for the first continental lithosphere.
id: 1507; 851PG Times Cited:12 Cited References Count:29

Isotopic order, biogeochemical processes, and earth history - Goldschmidt Lecture, Davos, Switzerland, August 2002 - Hayes, J. M. (Geochimica Et Cosmochimica Acta, 2004)
The impetus to interpret carbon isotopic signals comes from an understanding of isotopic fractionations imposed by living organisms. That understanding rests in turn on studies of enzymatic isotope effects, on fruitful concepts of isotopic order, and on studies of the distribution of (13)C both between and within biosynthetic products. In sum, these studies have shown that the isotopic compositions of biological products are governed by reaction kinetics and by pathways of carbon flow.Isotopic compositions of individual compounds can indicate specific processes or environments. Examples include biomarkers which record the isotopic compositions of primary products in aquatic communities, which indicate that certain bacteria have used methane as a carbon source, and which show that some portions of marine photic zones have been anaerobic. In such studies, the combination of structural and isotopic lines of evidence reveals relationships between compounds and leads to process-related thinking. These are large steps. Reconstruction of the sources and histories of molecular fossils redeems much of the early promise of organic geochemistry by resolving and clarifying paleoenviron-mental signals. In turn, contemplation of this new information is driving geochemists to study microbial ecology and evolution, oceanography, and sedimentology. Copyright (C) 2004 Elsevier Ltd.
813fdTimes Cited:17Cited References Count:70

Late Archean Microbial Ecology: An Integration of Molecular, Isotopic, and Lithologic Studies - Eigenbrode, Jennifer (PH.D. thesis, Earth Sciences, the Pennsylvania State University, 2004)
id: 1581

A late Pleistocene-Holocene noble gas paleotemperature record in southern Michigan - Ma, L.; Castro, M. C.; Hall, C. M. (Geophysical Research Letters, 2004)
Noble gas temperatures (NGTs) and C-14 derived ages in groundwaters of the Michigan Basin reveal a ground temperature of similar to1degreesC toward the end of the Last Glacial Maximum (LGM) suggesting that groundwater recharge occurred under the Laurentide Ice Sheet (LIS) cover. In addition to the general warming observed since the LGM, the NGT record indicates an abrupt warming event between similar to12.8 and 11.1 kyrs BP, correlative to the Bolling-Allerod (BOA) warm phases. Ice-sheet-linked changes in freshwater delivery to the North Atlantic, together with changes in the North Atlantic Deep Water (NADW) circulation are possible causes of such abrupt climate shifts in northeastern US. Pleistocene waters yielding the lowest NGTs have the highest delta(18)O and deltaD values, suggesting an atmospheric circulation pattern distinct from today, with a stronger moisture component from the Gulf of Mexico, possibly due to the presence of the LIS which weakened the Pacific westerly flow.
881pcTimes Cited:31Cited References Count:24

Late Quaternary deposition in the Inner Basins of the California Continental Borderland: Part A. Santa Monica Basin - Normark, W. R.; McGann, M. (U. S. Geological Survey Scientific Investigations Report 2004, 2004)
id: 417

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

Late-glacial climate as inferred from chironomid assemblages in lake sediments from Aroostook County, northeastern Maine - Chase, G. (University of Maine, 2004)

Long Island Sound: diatoms from sediment cores as part of environmental and ecological change studies, abstracts - Cooper, S. R.; Thomas, E.; Varekamp, J. C. (Mid-Atlantic ecology conference: sustainable landscapes, 2004)
id: 735

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

Mercury contamination in wetlands - Varekamp, J. C. (Meeting of the Atlantic Chaopter of the Soc. of Env. Toxicology and Health, 2004)
id: 742

Mercury in Connecticut and Long Island Sound: impact of historic hatting industries - Bronsther, R.; Welsh, P.; Varekamp, J. C. (American Geophyscial Union, Joint Assembly, 2004)
id: 733

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

A new Holocene relative sea-level curve for Terra Nova Bay, Victoria Land, Antarctica - Baroni, C.; Hall, B. L. (Journal of Quaternary Science, 2004)
More than 100 radiocarbon dates of penguin guano and remains, shells and seal skin afford ages for raised beaches adjacent to Terra Nova Bay, Antarctica. These dates permit construction of a new relative sea-level curve that bears on the timing of deglaciation. Recession of the Ross Sea ice-sheet grounding line from Terra Nova Bay occurred no earlier than 7200 C-14 yr (8000 cal. yr) BP. Retreat along the Victoria Land coast may have been rapid, possibly contributing to eustatic sea-level rise centred at ca. 7600 cal. yr BP. The presence of a significant amount of ice remaining in the Ross Sea Embayment in Holocene time lessens the chance that Antarctica contributed significantly to meltwater pulse 1A several thousand years earlier. Copyright (C) 2004 John Wiley Sons, Ltd.
833xiTimes Cited:38Cited References Count:36

New insights into the burial history of organic carbon on the early Earth - Bjerrum, C. J.; Canfield, D. E. (Geochemistry Geophysics Geosystems, 2004)
[1] The isotope record of organic matter and calcium carbonate is often used to infer the burial history of organic carbon through time. As organic carbon burial is widely held to control long-term oxygen production, the isotope record also relates to the production rates of oxygen on Earth. Current interpretations of the record suggest a long-term consistency in the proportion of total carbon buried as organic carbon (f ratio), with some important periods of much higher burial proportions. The isotope record is analyzed here with a new carbon isotope mass balance model, which considers submarine hydrothermal weathering of ocean crust as a significant removal pathway of inorganic carbon. With this model the f ratio is considerably reduced if isotopically depleted inorganic carbon is precipitated during hydrothermal weathering and if hydrothermal weathering dominates inorganic carbon removal from the surface environment. In contrast to previous calculations, our analysis of the carbon isotope record shows that organic carbon burial in the Archean accounted for only between 0% and 10% of the total carbon burial. These low burial proportions would have contributed to a slow accumulation of atmospheric oxygen in the Archean.
id: 1506; 846RU Times Cited:14 Cited References Count:44

Nitrogen isotopic ratio records the eutrophication history of Long Island sound - Altabet, M.; Varekamp, J. C. (American Geophyscial Union, Joint Assembly, 2004)
Increasing coastal population and industrialization has led to the steady degradation of the Long Island Sound (LIS) environment. Increased nutrient loading from sewage inputs has resulted in eutrophication and decreased summertime subsurface oxygen concentration particularly at its western end. It is critical to develop a detailed history of these environmental changes, both to understand causative processes and for design of optimal and cost effective remediation plans. We are developing a detailed time line of environmental changes in LIS over the last few centuries based on the study of geochemical and paleo-ecological proxies in geographically distributed sediment cores. Sediment nitrogen isotopic ratio (d15N) in particular is being used as an indicator of perturbations of the nitrogen biogeochemistry. Higher d15N is expected from sewage inputs as well as from the initiation of subsurface denitrification during low O2 conditions. Contemporary correlation between eutrophication intensity and d15N is seen in sediment core top data which show a substantial 4 per mil increase in d15N going from eastern to western LIS. This observation is consistent with greater nutrient loading toward New York City with its greater coastal population density. Downcore data from a site in western LIS show 4 per mil lower d15N prior to 200 years ago, documenting the point at which significant anthropogenic impact began. Increasing d15N over the last 200 years correlate with productivity proxies and other proxies for anthropogenic influence
id: 732

NotCal04-Comparison/Calibration 14 C records 26-50 cal kBP - van der Plicht, J.; Beck, J. W.; Bard, E.; Baillie, M. G. L.; Blackwell, P. G.; Buck, C. E.; Friedrich, M.; Guilderson, T. P.; Hughen, K. A.; Kromer, B. (Radiocarbon, 2004)
id: 399

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

Pacific halibut (Hippoglossus stenolepis) chronology of bomb radiocarbon in otoliths from 1944-1981 and a validation of ageing methods - Piner, K. P.; Wischniowski, S. G. (Journal of Fish Biology, 2004)
id: 1063

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

Paleoclimate. A better radiocarbon clock - Bard, E.; Rostek, F.; Menot-Combes, G. (Science, 2004)
id: 974; Bard, Edouard Rostek, Frauke Menot-Combes, Guillemette New York, N.Y. Science. 2004 Jan 9;303(5655):178-9.

The paleo-environmental history of Long Island Sound as traced by organic carbon, biogenic silica and stable isotope/trace element studies in sediment cores - Varekamp, J. C.; Thomas, E.; Lugolobi, F.; Buchholtz ten Brink, M. R. (6th Biennual LIS Res. Conf. Proc., 2004)
id: 1174

Paleoproductivity indicators in Long Island Sound - Andersen, N.; Varekamp, J. C. (American Geophyscial Union, Joint Assembly, 2004)
Oxygen depletion in bottom waters is considered to be the most pressing environmental problem affecting Long Island Sound (LIS). Summer anoxia occurs as a result of two factors: 1) Stratification of the water column due to warming of the shallow water preventing mixing and thus homogeneous distribution of oxygen. 2) Eutrophication resulting in increased primary productivity leading to a greater oxygen demand in the bottom waters as the larger amount of organic matter decays. The goal of this project is to create a paleoproductivity record for LIS and to attempt to link recent increases in productivity with anthropogenic nutrient sources, most notably wastewater treatment plant effluent. Two cores, WLIS-75 from the western narrows and B1GGC1 from near the mouth of the Housatonic River, have been analyzed for biogenic silica (BSi), total carbon, nitrogen, and sulfur. The BSi data was obtained through analyses of timed sequential extracts from an alkaline solution that reacted with the sediment at 85 C. Sediment densities were calculated from measured core water contents and assumed dry rock densities. A preliminary age model was developed using the onset of mercury pollution (about 1820 AD) as a reference point. At around 1800, the C, N, S and BSi concentrations all start to increase. In WLIS-75, BSi was higher throughout the core compared to core B1GGC1, suggesting an overall higher rate of productivity in the western section of LIS. In both cores the mass accumulation rates of BSi, C, N, and S increased exponentially over the last 300 years. A coarse layer was deposited around 1950-1960 in core WLIS-75, and is marked by abundant coarse debris of rocks and coal fragments. This layer may represent a flood deposit or stem from local (illegal?) dumping; its presence impacts the data for the last 30-40 years of the core. A strong correlation between total S and total C is observed, suggesting that Sulfide formation is limited by the amount of labile organic matter present. The data from the two cores show strong evidence for eutrophication over the last 200 years, with a strong increase in the N supply.
id: 1180

The Phanerozoic Carbon Cycle - Berner, Robert A. (Oxford University Press, 2004)
id: 1555

Photosynthetic microbial mats in the 3,416-Myr-old ocean - Tice, M. M.; Lowe, D. R. (Nature, 2004)
Recent re-evaluations of the geological record of the earliest life on Earth have led to the suggestion that some of the oldest putative microfossils and carbonaceous matter were formed through abiotic hydrothermal processes. Similarly, many early Archaean (more than 3,400-Myr-old) cherts have been reinterpreted as hydrothermal deposits rather than products of normal marine sedimentary processes. Here we present the results of a field, petrographic and geochemical study testing these hypotheses for the 3,416-Myr-old Buck Reef Chert, South Africa. From sedimentary structures and distributions of sand and mud, we infer that deposition occurred in normal open shallow to deep marine environments. The siderite enrichment that we observe in deep-water sediments is consistent with a stratified early ocean. We show that most carbonaceous matter was formed by photosynthetic mats within the euphotic zone and distributed as detrital matter by waves and currents to surrounding environments. We find no evidence that hydrothermal processes had any direct role in the deposition of either the carbonaceous matter or the enclosing sediments. Instead, we conclude that photosynthetic organisms had evolved and were living in a stratified ocean supersaturated in dissolved silica 3,416 Myr ago.
Tice, Michael MLowe, Donald RengResearch Support, Non-U.S. Gov'tResearch Support, U.S. Gov't, Non-P.H.S.England2004/10/01 05:00Nature. 2004 Sep 30;431(7008):549-52.

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

Prehistoric marine mammal overkill in the northeastern Pacific: A review of new evidence - Jones, T. L.; Hildebrandt, W. R.; Kennett, D. J.; Porcasi, J. J. (Journal of California and Great Basin Anthropology, 2004)
id: 469

Present status of radiocarbon calibration and comparison records based on Polynesian corals and Iberian Margin sediments - Bard, E.; Menot-Combes, G.; Rostek, F. (Radiocarbon, 2004)
In this paper, we present updated information and results of the radiocarbon records based on Polynesian corals and on Iberian Margin planktonic foraminifera. The latter record was first published by Bard et al. (2004a,b), with the subsequent addition of some data by Shackleton et al. (2004). These data sets are compared with the IntCal98 record (Stuiver et al. 1998) and with data sets based on other archives, such as varves of Lake Suigetsu (Kitagawa and van der Plicht 1998, 2000), speleothems from the Bahamas (Beck et al. 2001), and Cariaco sediments (Hughen et al. 2004). Up to 26,000 cal BP, the Iberian Margin data agree within the errors of the other records. By contrast, in the interval between 33,000 and 41,000 cal BP, the Iberian Margin record runs between the Lake Suigetsu and Bahamian speleothem data sets, but it agrees with the few ImCal98 coral data and the Cariaco record.
956zfTimes Cited:30Cited References Count:33