Ten years after - The WOCE AMS radiocarbon program - McNichol, A. P.; Schneider, R. J.; von Reden, K. F.; Gagnon, A. R.; Elder, K. L.; Key, R. M.; Quay, P. D. (Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions with Materials and Atoms, 2000)
The National Ocean Sciences Accelerator Mass Spectrometry (NOSAMS) Facility is measuring all of the samples collected as part of the US WOCE Program - over 13,000 samples. We designed our extraction lines so that we also measure precise, oceanographically useful delta C-13-Sigma CO2 values. We have completed the analysis of samples from the Pacific and Southern Oceans and are processing those from the Indian Ocean now. At present, this constitutes the world's largest AMS data set. Reviews of the Pacific radiocarbon data are available and demonstrate the increased penetration of the "bomb signal" into the water column since the 1970s. Stable isotope data are being combined with those collected as part of NOAA's Ocean-Atmosphere Carbon Exchange Study to study the ocean's role in the anthropogenic CO2 cycle. The relationship of delta C-13 to other chemical tracers, e.g., PO4, O-2 and chlorofluorocarbons, will further our understanding of basic oceanographic processes. We present preliminary results from these studies as well as investigate the relationship of C-14 to C-13 in the ocean. (C) 2000 Elsevier Science B.V. All rights reserved.
372jrTimes Cited:14Cited References Count:12

Tests of positive ion beams from a microwave ion source for AMS - Schneider, R. J.; von Reden, K. F.; Hayes, J. M.; Wills, J. S. C.; Kern, W. G. E.; Kim, S. W. (Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions with Materials and Atoms, 2000)
A test facility has been constructed to evaluate high-current positive ion beams from small gaseous samples for AMS applications. The major components include a compact permanent magnet microwave ion source built at the AECL Chalk River Laboratory and now on loan from the University of Toronto, and a double-focusing spectrometer magnet on loan from Argonne National Laboratory. Samples are introduced by means of a silica capillary injection system. Loop injection into a carrier gas provides a stable feed for the microwave driven plasma. The magnetic analysis system is utilized to isolate carbon ions derived from CO? samples from other products of the plasma discharge, including argon ions of the carrier gas. With a smaller discharge chamber, we hope to exceed a conversion efficiency of 14% for carbon ions produced per atom, which we reported at AMS-7. The next step will be to construct an efficient charge-exchange cell, to produce negative ions for injection into the WHOI recombinator injector. (C) 2000 Elsevier Science B.V. All rights reserved.
372jrTimes Cited:16Cited References Count:4

The tie-in of a varve-count chronology and radiocarbon dates: a method for addressing 14C-reservoir age - Schimmelmann, A.; Lange, Carina B. (Climate Conference, LDGO, 2000)
id: 199

Turbidite Megabeds in an Oceanic Rift Valley Recording Jokulhlaups of Late Pleistocene Glacial Lakes of the Western United States - Zuffa, G. G.; Normark, W. R.; Serra, F.; Brunner, C. A. (Journal of Geology, 2000)
Escanaba Trough is the southernmost segment of the Gorda Ridge and is filled by sandy turbidites locally exceeding 500 m in thickness. New results from Ocean Drilling Program (ODP) Sites 1037 and 1038 that include accelerator mass spectrometry (AMS) 14C dates and revised petrographic evaluation of the sediment provenance, combined with high-resolution seismic-reflection profiles, provide a lithostratigraphic framework for the turbidite deposits. Three fining-upward units of sandy turbidites from the upper 365 m at ODP Site 1037 can be correlated with sediment recovered at ODP Site 1038 and Deep Sea Drilling Program (DSDP) Site 35. Six AMS 14C ages in the upper 317 m of the sequence at Site 1037 indicate that average deposition rates exceeded 10 m/k.yr. between 32 and 11 ka, with nearly instantaneous deposition of one approximately 60-m interval of sand. Petrography of the sand beds is consistent with a Columbia River source for the entire sedimentary sequence in Escanaba Trough. High-resolution acoustic stratigraphy shows that the turbidites in the upper 60 m at Site 1037 provide a characteristic sequence of key reflectors that occurs across the floor of the entire Escanaba Trough. Recent mapping of turbidite systems in the northeast Pacific Ocean suggests that the turbidity currents reached the Escanaba Trough along an 1100-km-long pathway from the Columbia River to the west flank of the Gorda Ridge. The age of the upper fining-upward unit of sandy turbidites appears to correspond to the latest Wisconsinan outburst of glacial Lake Missoula. Many of the outbursts, or jokulhlaups, from the glacial lakes probably continued flowing as hyperpycnally generated turbidity currents on entering the sea at the mouth of the Columbia River.
id: 162; J Geol. 2000 May;108(3):253-274.

Use of Natural C-14 Measurements to Examine Benthic Food Webs - DeMaster, D. J.; Fornes, W. L.; Smith, C. R.; Plaia, G.; Blair, N. E.; Levin, L. A. (National AGU/ASLO Meeting, 2000)
id: 1367

Years of Sediment, Vegetation, and Water-Level Changes at the Makepeace Cedar Swamp, Southern Massachusetts - Newby, P. E.; Killoran, P.; Waldorf, M. R.; Shuman, B. N.; Webb, R. S.; Webb, T., III (Quaternary Research, 2000)
id: 231

2-Methylhopanoids as biomarkers for cyanobacterial oxygenic photosynthesis - Summons, R. E.; Jahnke, L. L.; Hope, J. M.; Logan, G. A. (Nature, 1999)
Oxygenic photosynthesis is widely accepted as the most important bioenergetic process happening in Earth's surface environment(1). It is thought to have evolved within the cyanobacterial lineage, but it has been difficult to determine when it began. Evidence based on the occurrence and appearance of stromatolites(2) and microfossils' indicates that phototrophy occurred as long ago as 3,465 Myr although no definite physiological inferences can be he made from these objects. Carbon isotopes and other geological phenomena(4,5) provide clues but are also equivocal, Biomarkers are potentially useful because the three domains of extant life-Bacteria, Archaea and Eukarya-have signature membrane lipids with recalcitrant carbon skeletons. These lipids turn into hydrocarbons in sediments and can be found wherever the record is sufficiently well preserved. Here we show that 2-methylbacteriohopanepolyols occur in a high proportion of cultured cyanobacteria and cyanobacterial mats, Their 2-methylhopane hydrocarbon derivatives are abundant in organic-rich sediments as old as 2,500 Myr. These biomarkers may help constrain the age of the oldest cyanobacteria and the advent of oxygenic photosynthesis. They could also be used to quantify the ecological importance of cyanobacteria through geological time.
223rtTimes Cited:510Cited References Count:28

87Sr/86Sr, delta 18O evolution of Phanerozoic seawater - Veizer, Jan; Davin, Ala; Azmy, Karem; Bruckschen, Peter; Buhl, Dieter; Bruhn, Frank; Carden, Giles A. F.; Diener, Andreas; Ebneth, Stefan; Godderis, Yves; Jasper, Torsten; Korte, Christoph; et al. (Chemical Geology, 1999)
id: 1603

The abundance of 13C in marine organic matter and isotopic fractionation in the global biogeochemical cycle of carbon during the past 800 Ma - Hayes, John M.; Strauss, Harald; Kaufman, Alan J. (Chemical Geology, 1999)
id: 1547

The Antarctic Radiocarbon Storage Ring - Schneider, Robert J.; McNichol, Ann P.; von Reden, Karl F.; Elder, Kathryn L.; Gagnon, Alan R.; Key, Robert M.; Quay, Paul D. (8th International Conference on Accelerator Mass Spectrometry, 1999)
id: 1791

Application of a compact microwave ion source to radiocarbon analysis - Schneider, R. J.; von Reden, K. F.; Hayes, J. M.; Wills, J. S. C. (The eighth international conference on heavy-ion accelerator technology, 1999)
The compact, high current, 2.45 GHz microwave-driven plasma ion source which was built for the Chalk River TASCC facility is presently being adapted for testing as a gas ion source for accelerator mass spectrometry, at the Woods Hole Oceanographic Institution accelerator mass spectrometer. The special requirements for producing carbon-ion beams from micromole quantities of carbon dioxide produced from environmental samples will be discussed. These samples will be introduced into the ion source by means of argon carrier gas and a silicon capillary injection system. Following the extraction of positive ions from the source, negative ion formation in a charge exchange vapor will effectively remove the argon from the carbon beam. Simultaneous injection of the three carbon isotopes into the accelerator is planned.
id: 1977
Keywords: carbon; ion sources; mass spectroscopy; spectrochemical analysis; tandem accelerators

Application of Compact Microwave Ion Source to Radiocarbon Analysis - Schneider, R. J.; von Reden, K. F.; Hayes, J. M.; Wills, J. S. C. (8th International Conference on Heavy Ion Accelerator Technology, 1999)
id: 1824

Cool surface waters of the subtropical North Pacific Ocean during the last glacial - Lee, K. E.; Slowey, N. C. (Nature, 1999)
One of the most controversial results of the CLIMAP(1,2) project's reconstruction of past sea surface temperature (SST) is that large areas of the subtropical Pacific Ocean were warmer during the last glacial period than they are today. This finding has important implications because SST patterns at low to subtropical latitudes strongly influence climate, and SST changes are closely linked with climate fluctuations(3-5). Until now, a lack of well-preserved, high-resolution marine sediment cores from the region has hindered efforts to confirm these unexpectedly high ice-age SST estimates. Here we use both the oxygen-isotope compositions and species assemblages of planktonic foraminifera in a shallow-water core with high deposition rates near Hawaii to estimate glacial SST of the subtropical North Pacific Ocean, Contrary to the CLIMAP results(2), our data indicate that the annual average SST in this region was similar to 2 degrees C cooler during the last glaciation than it is today, These results help to reconcile the marine SST record with inferences drawn from snowline depressions on Hawaii during the last glacial(3,6), and should ultimately yield improved estimates of global climate sensitivity by providing important new constraints on climate model simulations of ice-age cycles.
166knTimes Cited:31Cited References Count:29

Deep-sea sedimentary record of the late Wisconsin cataclysmic floods from the Columbia River - Brunner, C. A.; Normark, W. R.; Zuffa, G. G.; Serra, F. (Geology, 1999)
New results from Ocean Drilling Program Site 1037 and U.S. Geological Survey high-resolution seismic-reflection profiles confirm the great thickness, fast deposition rate, distant source, and convolute path of turbidites that fill the Escanaba Trough, the rift valley of the southernmost segment of the Gorda Ridge. Accelerator mass spectrometry C-14 measurements provide the first direct dating of the Escanaba Trough turbidites, demonstrating an average deposition rate faster than 10 m/k.y. between 32 and 11 ka and as fast as 15 m/k.y. during the oxygen isotope stage 2 lowstand, In the upper 60 m of sediment, the petrology of turbidite sand beds, which are as much as 12 m thick, show that the dominant source for the turbidites is from the Columbia River, which is more than 800 km to the north, rather than from the much closer rivers of northern California. New high-resolution seismic-reflection profiles show that, except for areas of very recent volcanism, the entire Escanaba Trough below 3200 m water depth is floored by the turbidite sequence that was cored in the upper 60 m at Site 1037B, The ages of the upper 120 m of turbidites correspond with the ages of channeled scabland deposits associated with latest Quaternary jokulhlaups from glacial Lake Missoula, The age and source characteristics suggest that these megaturbidite beds in Escanaba Trough are most likely deposits formed by hyperpycnally generated turbidity currents as the largest of the Lake Missoula floods entered the sea.
193qfTimes Cited:40Cited References Count:19

Deltas, radiocarbon dating, and measurements of sediment storage and subsidence - Stanley, D. J.; Hait, A. K. (Geology, 1999)
id: 1376

The distribution and carbon isotopic composition of dissolved organic matter in Florida Everglades (abstract) - Wang, Y.; Hsieh, Y. P.; Landing, W. M.; Salters, V.; Cooper, W.; Proctor, L. (The Sixth Symposium on Biogeochemistry of Wetlands, 1999)
id: 165

Environmental changes in the last centure in Little Trout Lake and Inkspot Bay, Lac du Flambeau Tribal Lands, Wisconsin. Preliminary Results Report - Winkler, M. G.; Sanford, P. R. (Water Resources Division, Lac du Flambeau Tribe, 1999)
id: 1320

Fractionation of hydrogen isotopes in lipid biosynthesis - Sessions, A. L.; Burgoyne, T. W.; Schimmelmann, A.; Hayes, J. M. (Organic Geochemistry, 1999)
Isotopic compositions of carbon-bound hydrogen in individual compounds from eight different organisms were measured using isotope-ratio-monitoring gas chromatography-mass spectrometry. This technique is capable of measuring D/H ratios at natural abundance in individual lipids yielding as little as 20 nmol of H-2, and is applicable to a wide range of compounds including hydrocarbons, sterols, and fatty acids. The hydrogen isotopic compositions of lipids are controlled by three factors: isotopic compositions of biosynthetic precursors, fractionation and exchange accompanying biosynthesis, and hydrogenation during biosynthesis. delta D values of lipids from the eight organisms examined here suggest that all three processes are important for controlling natural variations in isotopic abundance. n-Alkyl lipids are depleted in D relative to growth water by 113-262 parts per thousand, while polyisoprenoid lipids are depleted in D relative to growth water by 142-376 parts per thousand. Isotopic variations within compound classes (e.g., n-alkanes) are usually less than similar to 50 parts per thousand, but variations as large as 150 parts per thousand are observed among isoprenoid lipids from a single organism. Phytol is consistently depleted in D by up to 50 parts per thousand relative to other isoprenoid lipids. Inferred isotopic fractionations between cellular water and lipids are greater than those indicated by previous studies. (C) 1999 Elsevier Science Ltd. All rights reserved.
254efTimes Cited:281Cited References Count:26

A geostrophic transport estimate for the Florida Current from the oxygen isotope composition of benthic foraminifera - Lynch-Stieglitz, J.; Curry, W. B.; Slowey, N. (Paleoceanography, 1999)
We present a new method for the quantitative reconstruction of upper ocean flows for during times in the past. For the warm (T>5 degrees C) surface ocean, density can be accurately reconstructed from calcite precipitated in equilibrium with seawater, as both of these properties increase with decreasing temperature and increasing salinity. Vertical density profiles can be reconstructed from the oxygen isotopic composition of benthic foraminifera. The net volume transport between two vertical density profiles can be calculated using the geostrophic method. Using benthic foraminifera from surface sediment samples from either side of the Florida Straits (Florida Keys and Little Bahama Bank), we reconstruct two vertical density profiles and calculate a volume transport of 32 Sv using this method. This agrees well with estimates from physical oceanographic methods of 30-32 Sv for the mean annual volume transport. We explore the sensitivity of this technique to various changes in the relationship between temperature and salinity as well as salinity and the oxygen isotopic composition of seawater.
198xcTimes Cited:81Cited References Count:45

A high resolution ~15,000 year record of El-Nino driven alluviation in southwestern Ecuador - Rodbell, D. T.; Seltzer, G. O.; Anderson, D. M.; Abbott, M. B.; Enfield, D. B.; Newman, J. H. (Science, 1999)
id: 393

Holocene depositional patterns, neotectonics and Sundarban Mangroves in the western Ganges-Brahmaputra delta - Stanley, D. J.; Hait, A. (Jour. Coastal Res., 1999)
id: 229

Holocene surface faulting in the Seattle fault zone, Bainbridge Island, Washington - Nelson, A. R.; Pezzopane, S. K.; Bucknam, R. C.; Koehler, R. D.; Narwold, C. F.; Kelsey, H. M.; Sherrod, B. L.; LaPrade, W. T.; Wells, R. E.; Johnson, S. Y. (Seismological Research Letters, 1999)
id: 1404

Installation and First Results of a 134-Sample MC-SNICS Ion Source at NOSAMS - von Reden, K. F.; Schneider, R. J.; McNichol, A. P.; Elder, K. F.; Gagnon, A. R. (8th International Conference on Accelerator Mass Spectrometry, 1999)
id: 1802

Installation of a 134-Sample MC-SNICS Ion Source at NOSAMS and first results - von Reden, Karl F.; Bellino, Mary; Long, Patricia; Schneider, Robert J.; Loger, Roger (Accelerator Mass Spectrometry, Proceedings of the Eighth International Conference on Accelerator Mass Spectrometry, 1999)
id: 1724

Late Pleistocene-Holocene sea-level change and the New Jersey coastline - Miller, K. G.; Sugarman, P. J.; Sheridan, R. E.; Ashley, G. M. (Trans. Am. Geophys. Un., 1999)
id: 163

Late Quaternary stratigraphy, Paleoclimate and neotectonism of the Persian (Arabian) Gulf region - Uchupi, E.; Swift, S. A.; Ross, D. A. (Marine Geology, 1999)
The last glacial deposits in the Persian (Arabian) Gulf consist of a > 22,000 year old paralic terrigenous sequence in the Mesopotamia Shelf, the foredeep in front of the Iranian Zagros Mountains and the northern side of the Biaban Shelf. Elsewhere, the Gulf, and probably the Biaban Shelf, were mantled by > 30,000 year old carbonates. Comparison of C-14 data from foraminifera from the last glacial terrigenous unit in the foredeep off Iran with curves published by Hopley [Hopley, D., 1982. The Geomorphology of the Great Barrier Reef: Quaternary Development of Coral Reefs. Wiley, New York, 453 pp.] and Chapell et al. [Chapell, J., Omura, A., Tezer, E., McCulloch, M., Pandolfi, J., Ota, Y., Pillans, B., 1996. Reconciliation of late Quaternary sea levels derived from coral terraces at Huon Peninsula with deep sea oxygen isotope records. Earth Planet. Sci. Lett. 141, 227-236.] indicates that the region may have experienced uplift during the last glacial, whereas other geologic data indicate that the foredeep has had a history of continuous subsidence during the Cenozoic. A possible explanation for this discrepancy is that the foraminifera analyzed are not in place, but were reworked into shallower water during the Holocene transgression. However, the foraminifera analyzed do not display any evidence of wear, indicating that such transport was limited. A third alternative is that sea level during the last glacial was much higher than indicated by the curves of Hopley and Chapell et al.At the peak of the last glaciation 21,000 to 20,000 years ago, when sea level was 120 m lower than now, the Gulf was a waterless basin and deposition was negligible. On the Biaban Shelf, the Holocene transgressive sequence resting unconformably on last glacial sediments consists of 14,000 year old carbonates, a > 11,000 year old terrigenous delta on the northern end of the Biaban Shelf and 11,000-10,000 year old intertidal-tidal aragonite deposited in a dry climate. On the northeast side of the Gulf, the last glacial sediments are covered by 10,000 to 7000 year old aragonite muds (younging toward the northwest). Resting on the aragonites on the Biaban Shelf and on the northeast and northwest sides of the Gulf are marls deposited under the present humid climate. The southwest side of the Gulf continued to be a site of carbonate deposition throughout the Holocene. Comparison of AMS C-14 measurements of the late Holocene marls with the sea level curve of Fairbanks [Fairbanks, R.G., 1989. A 17,000 year glacio-eustatic sea level record; influence of glacial melting rates and the Younger Dryas event and deep-ocean circulation. Nature 342, 637-642.] indicates that the axial zone of the Gulf off Iran experienced subsidence during the Holocene. This subsidence coupled with a rapid rise in sea level during a major glacial melt 9500 to 8500 years ago, when global sea level rose from -50 to -28 m, led to the replacement of marl with a shallow (8-25 m) water fauna by a 'deep' (> 50 m) water one. Similar measurements and other geologic data indicate that the Mesopotamia Shelf and the mouth of the Mesopotamian Depression on the northwest side of the Gulf underwent both subsidence and uplift during the Cenozoic. These vertical oscillations, however, were more subdued than these in the foredeep off iran. The Arabian Shelf along the Gulfs southwest side appears to have experienced minor uplift during the Cenozoic. (C) 1999 Elsevier Science B.V. All rights reserved.
214vaTimes Cited:31Cited References Count:58

Late Wisconsian deep-sea sedimentary record from convulsive geologic events, Northeast Pacific - Serra, Francesca; Normark, William R.; Zuffa, Gian Gaspare; Brunner, Charlotte A. (IAS 19 Regional Meeting of Sedimentology, 1999)
id: 1471

Marine and meteoric diagenesis of pleistocene carbonates from a nearshore submarine terrace, Ohau, Hawaii - Sherman, C. E.; Fletcher, C. H.; Rubin, K. H. (Journal of Sedimentary Research, 1999)
id: 298

Marine and meteoric diagenesis of Pleistocene carbonates from a nearshore submarine terrace, Oahu, Hawaii - Sherman, C. E.; Fletcher, C. H.; Rubin, K. H. (Journal of Sedimentary Research, 1999)
The nearshore slope of Oahu consists of a shallowly dipping shelf extending from the shoreline out to the similar to -20 m contour, where there is a sharp break in slope down to similar to -30 m, Limestones recovered in a series of short cores taken from this nearshore terrace are typical of shallow-marine reef environments and comprise either a branching-coral or massive-coral facies, The composition as well as shoreward zonation of facies suggests that the terrace represents an in situ fossil reef complex. Th-U ages of in situ corals are all Pleistocene and suggest that the bulk of the feature formed during marine oxygen isotope stage 7. Later accretion along the seaward front of the terrace occurred during marine oxygen isotope substages 5a and/or 5c. Deposition during these interglacial highstands has not previously been documented in the sea-level record on Oahu,Although the diagenetic record in the cored samples is incomplete, three periods of diagenesis are identified: early shallow marine, meteoric, and post-meteoric shallow marine. Early shallow-marine diagenesis includes cementation by aragonite and Mg calcite in an active marine phreatic zone and predominantly micritization in a stagnant marine phreatic zone. Meteoric processes occurred in the vadose zone and include precipitation of calcite (needle fibers, meniscus cements, micritic networks), neomorphism, and dissolution. All limestones are now in an active marine phreatic zone. Evidence of post-meteoric shallow-marine diagenesis is found in last-generation Mg calcite cements and internal sediments occurring directly on limestone substrates that have otherwise been stabilized to calcite. The present seafloor is undergoing extensive biological and physical erosion. No Holocene limestones were recovered. Petrographic and geochemical signatures of subaerial exposure and meteoric diagenesis are recognized within the upper several centimeters of all cores. Thus, the present seafloor in the study area is a flooded Pleistocene subaerial exposure surface.
A237cq Times Cited:42 Cited References Count:79
Keywords: barrier-reef; calcite; corals; fringing-reef; Holocene; oxygen isotopes; platform; recrystallization; sea-level; stabilization

Methane-consuming archaebacteria in marine sediments - Hinrichs, K. U.; Hayes, J. M.; Sylva, S. P.; Brewer, P. G.; DeLong, E. F. (Nature, 1999)
Large amounts of methane are produced in marine sediments but are then consumed before contacting aerobic waters or the atmosphere. Although no organism that can consume methane anaerobically has ever been isolated, biogeochemical evidence indicates that the overall process involves a transfer of electrons from methane to sulphate and is probably mediated by several organisms, including a methanogen (operating in reverse) and a sulphate-reducer (using an unknown intermediate substrate). Here we describe studies of sediments related to a decomposing methane hydrate. These provide strong evidence that methane is being consumed by archaebacteria that are phylogenetically distinct from known methanogens. Specifically, lipid biomarkers that are commonly characteristic of archaea are so strongly depleted in carbon-13 that methane must be the carbon source, rather than the metabolic product, for the organisms that have produced them. Parallel gene surveys of small-subunit ribosomal RNA (16S rRNA) indicate the predominance of a new archael group which is peripherally related to the methanogenic orders Methanomicrobiales and Methanosarcinales.
Hinrichs, K UHayes, J MSylva, S PBrewer, P GDeLong, E FengResearch Support, Non-U.S. Gov'tResearch Support, U.S. Gov't, Non-P.H.S.England1999/05/11 02:03Nature. 1999 Apr 29;398(6730):802-5.

New Developments at the NOSAMS Facility - von Reden, K. F.; Schneider, R. J.; McNichol, A. P.; Hayes, J. M.; Pearson, A.; Eglinton, T. I. (Proceeding of the International Workshop on Frontiers in Accelerator Mass Spectrometry, 1999)
id: 1723(JISTEC)

New Developments at the NOSAMS Facility - von Reden, K. F.; Schneider, R. J.; McNichol, A. P.; Hayes, J. M.; Pearson, A.; Eglinton, T. I. (International Workshop on Frontiers in Accelerator Mass Spectrometry, 1999)
id: 1679

The North Atlantic's 1-2 kyr climate rhythm: Relation to Heinrich events, Dansgaard/Oeschger cycles and the Little Ice Age (Book Section) - Bond, G. C.; Showers, W.; Elliot, M.; Evans, M.; Lotti, R.; Hajdas, I.; Bonani, G.; Johnson, S. (Mechanisms of global climate change at mellennial time scales, 1999)
id: 216

The overturning circulation of the glacial Atlantic: A view from the top - Lynch-Stieglitz, J.; Curry, W. B.; Slowey, N.; Schmidt, G. A. (Reconstructing Ocean History: A Window into the Future, 1999)
id: 1364

The overturning circulation of the glacial Atlantic: A view from the top - Lynch-Stieglitz, J.; Curry, W. B.; Slowey, N. C. (Sixth International Conference on Paleoceanography, 1999)
id: 1337

Paleoclimate of Southwestern China for the past 50,000 yr inferred from lake sediment records - Hodell, D. A.; Brenner, M.; Kanfoush, S. L.; Curtis, J. H.; Stoner, J. S.; Song, X. L.; Yuan, W.; Whitmore, T. J. (Quaternary Research, 1999)
Long sediment cores (12.5 and 13.5 m) from two lakes in Yunnan Province were used to infer the paleoclimate of southwest China over the past 50,000 yr, During the Holocene and marine isotope stage (MIS 3), bio-induced carbonate precipitation and organic matter (OM) production was high, suggesting warm temperatures and high primary productivity. In contrast, sediment inorganic carbon (IC) and organic carbon (OC) concentrations were low in last glacial deposits from 38,000 to 12,000 cal yr B.P., indicating cool temperatures and low productivity. The 50,000-yr record has alternating peaks of carbonate and coarse-grain (>38 mu m) quartz that reflect warm, moist interglacial or interstadial conditions alternating with cold, dry glacial or stadial conditions, respectively. Spectral analysis of the carbonate and quartz signals reveals power concentrated at periods of 7200 and 8900 cal yr, respectively, that may reflect a nonlinear climate response to precessional forcing at a time of reduced eccentricity modulation (McIntyre and Molfino, 1996). Oxygen isotope values of calcite from Yunnan lake cores indicate the summer monsoon was weak during the last glaciation from 50,000 to 12,000 cal yr B.P. The summer monsoon intensified between 12,000 and 8000 cal yr B.P., but weakened gradually in response to insolation forcing during the mid-to-late Holocene. Our results support the Overpeck ef al. (1996) model that posits a weak summer monsoon during the last glaciation that responded nonlinearly to insolation forcing when its intensity was affected by Eurasian snow cover and ice-sheet extent. The summer monsoon intensified and responded linearly to seasonal insolation forcing in the Holocene when ice volume diminished. (C) 1999 University of Washington.
255ltTimes Cited:85Cited References Count:58

Rapid strand-plain accretion in the northeastern Nile Delta in the 9th century A. D. and the demise of the port of Pelusium - Goodfriend, G. A.; Stanley, D. J. (Geology, 1999)
id: 177

Reconstructing the oceanic 13C Suess effect - Sonnerup, R. E.; Quay, P. D.; McNichol, A. P.; Bullister, J. L.; Westby, T. A.; Anderson, H. L. (Global Biogeochemical Cycles, 1999)
id: 1710

Registro micropaleontologico de los cambios naturales y antropicos (500 anos BP-presente) en us ecosistema de lagoon (Doninos, NO Peninsula Iberica) - Bao, R.; Santos, L.; Sanchez-Goni, M. F. (Actas XV Jornadas Sociedad Espanola de Paleontologia, 1999)
id: 151

A Silent Tandetron AMS System - von Reden, Karl F.; Schneider, Robert J. (Symposium of North Eastern Accelerator Personnel, October 13-15, 1997, SNEAP XXXI, 1999)
id: 1722

The speciation and sources of dissolved phosphorus in the Everglades (Report) - Copper, W.; Hsieh, Y. P.; Landing, W. M.; Proctor, L.; Salters, V.; Wang, Y. (1999)
id: 1348

Ten Years After--The WOCE AMS Radiocarbon Program - McNichol, A.; Schneider, R.; von Reden, K.; Gagnon, A.; Elder, K.; Key, R.; Quay, P. (8th International Conference on Accelerator Mass Spectrometry, 1999)
id: 1757

Terminal Proterozoic Mid-Shelf Benthic Microbial Mats in the Centralian Supervasin and their Environmental Significance - Logan, Graham A.; Calver, Clive R.; Gorjan, Paul; Summons, Roger E.; Hayes, John M.; Walter, Malcolm R. (Geochimica et Cosmochimica Acta, 1999)
id: 1734

Weaker Gulf Stream in the Florida straits during the last glacial maximum - Lynch-Stieglitz, J.; Curry, W. B.; Slowey, N. (Nature, 1999)
As it passes through the Florida Straits, the Gulf Stream consists of two main components: the western boundary flow of the wind-driven subtropical gyre and the northward-flowing surface and intermediate waters which are part of the 'global conveyor belt' compensating for the deep water that is exported from the North Atlantic Ocean(1), The mean flow through the Straits is largely in geostrophic balance and is thus reflected in the contrast in seawater density across the Straits(2). Here we use oxygen-isotope ratios of benthic foraminifera which lived along the ocean margins on the boundaries of the Florida Current during the Last Glacial Maximum to determine the density structure in the water and thereby reconstruct transport through the Straits using the geostrophic method-a technique which has been used successfully for estimating present-day flow(3). Our data suggest that during the Last Glacial Maximum, the density contrast across the Florida Straits was reduced, with the geostrophic flow, referenced to the bottom of the channel, at only about two-thirds of the modern value. If the wind-driven western boundary flow was not lower during the Last Glacial Maximum than today, these results indicate a significantly weaker conveyor-belt component of the Gulf Stream compared to present-day values. Whereas previous studies based on tracers suggested that deep waters of North Atlantic origin were not widespread during glacial times, indicating either a relatively weak or a shallow overturning cell, our results provide evidence that the overturning cell was indeed weaker during glacial times.
264pcTimes Cited:122Cited References Count:31

A 25,000-year tropical climate history from bolivian ice cores - Thompson, L. G.; Davis, M. E.; Mosley-Thompson, E.; Sowers, T. A.; Henderson, K. A.; Zagorodnov, V. S.; Lin, P.; Mikhalenko, V. N.; Campen, R. K.; Bolzan, J. F.; Cole-Dai, J.; Francou, B. (Science, 1998)
Ice cores that were recovered from the summit of Sajama mountain in Bolivia provide carbon-14-dated tropical records and extend to the Late Glacial Stage (LGS). Oxygen isotopic ratios of the ice decreased 5.4 per mil between the early Holocene and the Last Glacial Maximum, which is consistent with values from other ice cores. The abrupt onset and termination of a Younger Dryas-type event suggest atmospheric processes as the probable drivers. Regional accumulation increased during the LGS, during deglaciation, and over the past 3000 years, which is concurrent with higher water levels in regional paleolakes. Unlike polar cores, Sajama glacial ice contains eight times less dust than the Holocene ice, which reflects wetter conditions and extensive snow cover.
ThompsonDavis Mosley-Thompson Sowers Henderson Zagorodnov Lin Mikhalenko Campen Bolzan Cole-Dai Francou eng 1998/12/04 03:02 Science. 1998 Dec 4;282(5395):1858-64.

AMS measurement of - von Reden, K. F.; McNichol, A. P.; Pearson, A.; Schneider, R. J. (Sixteenth International Radiocarbon Conference, 1998)
id: 1643

AMS Measurement of small samples with high-current system: (Proceedings of the 16th International Radiocarbon Conference, 1997) - von Reden, K. F.; McNichol, A.; Pearson, A.; Schneider, R. (Radiocarbon, 1998)
id: 1815

A Correction for Aberrations in the Woods Hole Recombinator - Schneider, R. J.; von Reden, K. F. (Symposium of North-Eastern Accelerator Personnel, SNEAP 1996, 1998)
id: 1823

A Correction for Aberrations in the Woods Hole Recombinator. Symposium of North-Eastern Accelerator Personnel - Schneider, Robert J.; McNichol, Ann P.; von Reden, Karl F.; Elder, Kathryn L.; Gagnon, Allan R.; Key, Robert M.; Quay, Paul D. (World Scientific, 1998)
id: 1664

A Correction for Aberrations in the Woods Hole Recombinator. Symposium of North-Eastern Accelerator Personnel - Schneider, R. J.; von Reden, K. F. (World Scientific, 1998)
id: 1793

Decadal to millennial variability of fluviomarine sedimentation on the northern California continental shelf - Sommerfield, C. K. (EOS, 1998)
id: 1328

Environmental changes since deglaciation in Voyageurs National Park: A summary for park personnel in Holocene Paleoenvironnments in Western Great Lakes Park. Report - Winkler, M. G.; Sanford, P. R. (National Park Service, 1998)
id: 129

High-precision Measurements of 14C as a Circulation Tracer in the Pacific, Indian, and Southern Oceans with Accelerator Mass Spectrometry (AMS) - von Reden, K. F.; Peden, J. C.; Schneider, R. J.; Bellino, M.; Donoghue, J.; Elder, K. L.; Gagnon, A. R.; Long, P.; McNichol, A. P.; Morin, T.; Stuart, D.; Hayes, J. M.; et al. (8th International Conference on Heavy Ion Accelerator Technology, 1998)
id: 1636

High-precision radiocarbon age calibration for terrestrial and marine samples - Stuiver, M.; Reimer, P. J.; Braziunas, T. F. (Radiocarbon, 1998)
Single-year and decadal radiocarbon tree-ring ages are tabulated and discussed in terms of C-14 age calibration. The single-year data form the basis of a detailed 14C age calibration curve for the cal AD 1510-1954 interval ("cal" denotes calibrated). The Seattle decadal data set (back to 11,617 cal sp, with 0 sp = AD 1950) is a component of the integrated decadal INTCAL98 C-14 age curve (Stuiver et al. 1998). Atmospheric C-14 ages can be transformed into C-14 ages of the global ocean using a carbon reservoir model. INTCAL98 C-14 ages, used for these calculations, yield global ocean C-14 ages differing slightly from previously published ones (Stuiver and Braziunas 1993b). We include discussions of offsets, error multipliers, regional C-14 age differences and marine C-14 age response to oceanic and atmospheric forcing.
155qrTimes Cited:705 Cited References Count:31
Keywords: ad 1950-500 bc; c-14 data; decadal calibration; reservoir ages; time scale

How much deep water is formed in the Southern Ocean? - Broecker, W. S.; Peacock, S. L.; Walker, S.; Weiss, R.; Fahrbach, E.; Schroeder, M.; Mikolajewicz, U.; Heinze, C.; Key, R.; Peng, T. H.; Rubin, S. (Journal of Geophysical Research-Oceans, 1998)
Three tracers are used to place constraints on the production rate of ventilated deep water in the Southern Ocean. The distribution of the water mass tracer PO4* ("phosphate star") in the deep sea suggests that the amount of ventilated deep water produced in the Southern Ocean is equal to or greater than the outflow of North Atlantic Deep Water from the Atlantic. Radiocarbon distributions yield an export flux of water from the North Atlantic which has averaged about 15 Sv over the last several hundred years. CFC inventories are used as a direct indicator of the current production rate of ventilated deep water in the Southern Ocean. Although coverage is as yet sparse, it appears that the CFC inventory is not inconsistent with the deep water production rate required by the distributions of PO4* and radiocarbon. It has been widely accepted that the major part of the deep water production in the Southern Ocean takes place in the Weddell Sea. However, our estimate of the Southern Ocean ventilated deep water flux is in conflict with previous estimates of the flux of ventilated deep water from the Weddell Sea, which lie in the range 1-5 Sv. Possible reasons for this difference are discussed.
Zz547Times Cited:115Cited References Count:44

Le torbiditi dell'Escanaba Trough (Juan de Fuca Plate, Pacifico nordorientale): registrazione sedimentaria di piene fluviali catastrofiche del Fiume Columbia durante le fasi di deglaciazione tardo quaternaria - Brunner, C. A.; Normark, W. R.; Zuffa, G. G.; Serra, F. (Giornale di Geologia, 1998)
id: 1470

Manzala lagoon, Nile delta, Egypt: modern sediment accumulation based on radioactive tracers - Benninger, L. K.; Suayah, I. B.; Stanley, D. J. (Environmental Geology, 1998)
This study was undertaken to determine whether recent anthropogenic changes in the Nile basin have affected the modern rate of sediment accumulation in the Nile delta. Excess (210)pb, Cs-137, and Pu-239,Pu-240 were used to develop a sediment chronology for a core from central Manzala lagoon, the delta sector which has had the highest average rate of sediment accumulation during the Holocene (to about 0.7 cm year(-1)). Excess Pb-210 was detected in the top 32 cm of the core, yielding an accumulation rate of 1.2 cm year(-1), higher than the mean rate for the Holocene. A high Cs-137/Pu-239,Pu-240 ratio requires a reactor source (possibly Chernobyl) for these nuclides. Low concentrations of excess (210)pb and weapons-fallout nuclides precluded recognition of changes in sediment accumulation rate in Manzala lagoon during this century and may limit the use of tracer radionuclides for modern sediment chronology in the Nile delta.
id: 1283; Zq055 Times Cited:9 Cited References Count:37

Microscale AMS 14C Measurement at NOSAMS - Pearson, Ann; McNichol, Ann P.; Schneider, Robert J.; von Reden, Karl F. (16th International 14C Conference, 1998)
id: 1502

Microscale AMS 14C measurements at NOSAMS - Pearson, A.; McNichol, A. P.; Schneider, R. J.; von Reden, K. F.; Zheng, Y. (Radiocarbon, 1998)
id: 1621

Microscale AMS 14C measurements at NOSAMS: (Proceedings of the 16th International Radiocarbon Conference, 1997) - Pearson, A.; McNichol, A. P.; Schneider, R. J.; von Reden, K. F.; Zheng, Y. (Radiocarbon, 1998)
id: 1814

Microscale AMS (super 14) C measurement at NOSAMS - Pearson, Ann; McNichol, Ann P.; Schneider, Robert J.; von Reden, Karl F.; Zheng, Yan (University of Arizona, Department of Geosciences, Tucson, AZ, United States (USA), 1998)
Techniques for making precise and accurate radiocarbon accelerator mass spectrometry (AMS) measurements on samples containing less than a few hundred micrograms of carbon are being developed at the NOSAMS facility. A detailed examination of all aspects of the sample preparation and data analysis process shows encouraging results. Small quantities of CO (sub 2) are reduced to graphite over cobalt catalyst at an optimal temperature of 605 degrees C. Measured (super 14) C/ (super 12) C ratios of the resulting targets are affected by machine-induced isotopic fractionation, which appears directly related to the decrease in ion current generated by the smaller sample sizes. It is possible to compensate effectively for this fractionation by measuring samples relative to small standards of identical size. Examination of the various potential sources of background (super 14) C contamination indicates that the sample combustion process is the largest contributor, adding ca. 1 mu g of carbon with a less-than-modern (super 14) C concentration.
id: 2237; Source type: conferencepapers&proceedings; Object type: Article; Object type: Conference Paper; Copyright: GeoRef, Copyright 2007, American Geological Institute.; CSAUnique: 1999-044438; AccNum: 1999-044438; ISSN: 0033-8222; CODEN: RACAAT
Keywords: 03; absolute age; accelerator mass spectroscopy; accuracy; C-14; C-14/C-12; carbon; Carbon dioxide; combustion; data processing; Geochronology; graphite; isotope fractionation; isotopes; mass spectroscopy; mathematical methods; methods; native elements; radioactive isotopes; sample preparation; size; spectroscopy; Stable isotopes

Overview of the eruption of Soufriere Hills volcano, Montserrat, 18 July 1995 to December 1997 - Young, S. R.; Sparks, R. S. J.; Aspinall, W. P.; Lynch, L. L.; Miller, A. D.; Robertson, R. E. A.; Shepherd, J. B. (Geophysical Research Letters, 1998)
The onset of phreatic volcanic activity at the Soufriere Hills volcano, Montserrat on 18 July 1995 followed a three-year period of heightened volcano-seismic activity beneath the island. Phreatic explosions gave way to continuous eruption of juvenile andesitic magma in the form of a lava dome on or around 15 November 1995. Magma production rate has varied, leading to changes in eruptive style. An explosive eruption on 17 September 1996 followed a period of enhanced dome growth and large-scale gravitational collapses from its eastern flank. Increasing dome volume led to stressing and overtopping of the confining crater walls to the southwest, north and west during early 1997. Sustained high magma production rate since June 1997 has led to three periods of major gravitational dome collapses followed by vulcanian explosive eruptions. Dome growth re-started immediately after the cessation of the latest of these explosive phases in October 1997 and continues as of December 1997.
119mkTimes Cited:102Cited References Count:7

Preparation for continuous flow accelerator mass spectrometry Radiocarbon - Schneider, R. J.; Hayes, J. M.; von Reden, K. F.; McNichol, A. P.; Eglinton, T.; Wills, J. S. C. (Radiocarbon, 1998)
id: 1623

Proceedings of the 30th Symposium of Northeastern Accelerator Personnel - Woods Hole, 1996 - von Reden, K. F.; Schneider, R. J. (World Scientific, 1998)
id: 1674

The Proceedings of the 30th Symposium of North-Eastern Accelerator Personnel - von Reden, K. F.; Schneider, R. J. (30th Symposium of North-Eastern Accelerator Personnel, 1998)

Proceedings of the 8th International Conference on Heavy Ion Accelerator Technology - Schneider, R. J.; von Reden, K. F.; Hayes, J. M.; Wills, J. S. C. (American Institute of Physics, Conference Proceeding Series, 1998)
id: 1624; submitted

Pyroclastic stratigraphy of the Soufriere Hills volcano, Montserrat - Implications for the present eruption - Roobol, M. J.; Smith, A. L. (Geophysical Research Letters, 1998)
The stratigraphy of the Soufriere Hills volcano is dominated by dense-andesite block and ash flow deposits. Forty-one radiocarbon ages permit a reconstruction of the eruptive history over the past 31,000 years. A single stratigraphic member yielding radiocarbon ages of 22,000 to 20,000 years B.P. is composed of block and ash flow deposits with semi-vesiculated clasts concentrated in the upper third of each deposit. The present eruption is also producing block and ash flow deposits with both dense and semi-vesiculated clasts. It marks a return to a more explosive driven type of activity as occurred 22,000 to 20,000 years ago. Deposits of this member have a broad sheet-like form and volumes in excess of any produced so far by the present eruption.
119mkTimes Cited:24Cited References Count:9

Ritual, Power, and the Development of a Complex Society: The Island of the Sun and the Tiwanaku State, Thesis - Seddon, Matthew T. (University of Chicago, 1998)

Sea-level rise on eastern China's Yangtze delta - Chen, Z. Y.; Stanley, D. J. (Journal of Coastal Research, 1998)
The Yangtze delta is a densely populated, low-lying region highly vulnerable to flooding, high tides and typhoons. All previous studies indicated that relative sea level was higher from similar to 7500-4000 yrs. BP, then lowered and stabilized at about present msl during the past 3000 yrs. To the contrary, we find that sea level has been rising relative to the southern Yangtze delta plain based on new sea-level data derived from dated peats, reassessment of earlier sea-level curves and measurement of delta plain subsidence and analysis of prehistoric habitat bases from similar to 7000 to 3000 yrs. BP. Consequences of this relative rise include difficulty in expelling water from the low-lying delta plain to the coast and associated flood damage. Emplacement of the 3-Gorges Dam on the Yangtze will control flooding of the Yangtze river but decrease sediment accumulation on the delta plain that, in turn, is likely to accelerate saline inundation of this vital breadbasket.
Yt592Times Cited:46 Cited References Count:27
Keywords: delta flooding; Holocene; neolithic sites; peat; radiocarbon dates; relative sea level; sea-level curve; subsidence; taihu lake; yangtze delta

Status Report of the National Ocean Sciences AMS Facility at Woods Hole Oceanographic Institution: Operations and Recent Developments - Bellino, M.; von Reden, K. F.; Schneider, R. J.; Peden, J. C.; Donoghue, J.; Elder, K. L.; Gagnon, A. R.; Long, P.; McNichol, A. P.; Odegaard, A. P.; Stuart, D.; Handwork, S.; et al. (15th International Conference on the Applications of Accelerators in Research and Industry, 1998)
id: 1647

(super 14) C AMS measurements of - von Reden, Karl F.; McNichol, Ann P.; Pearson, Ann; Schneider, Robert J. (University of Arizona, Department of Geosciences, Tucson, AZ, United States (USA), 1998)
The NOSAMS facility at Woods Hole Oceanographic Institution has started to develop and apply techniques for measuring very small samples on a standard Tandetron accelerator mass spectrometry (AMS) system with high-current hemispherical Cs sputter ion sources. Over the past year, results on samples ranging from 7 to 160 mu g C showed both the feasibility of such analyses and the present limitations on reducing the size of solid carbon samples. One of the main factors affecting the AMS results is the dependence of a number of the beam optics parameters on the extracted ion beam current. The extracted currents range from 0.5 to 10 mu A of (super 12) C (super -) for the sample sizes given above. We here discuss the setup of the AMS system and methods for reliable small-sample measurements and give the AMS-related limits to sample size and the measurement uncertainties.
id: 2239; Source type: conferencepapers&proceedings; Object type: Article; Object type: Conference Paper; Copyright: GeoRef, Copyright 2007, American Geological Institute.; CSAUnique: 1999-044459; AccNum: 1999-044459; ISSN: 0033-8222; CODEN: RACAAT
Keywords: 03; absolute age; accelerator mass spectroscopy; C-14; carbon; dilution; Geochronology; ions; isotopes; mass spectroscopy; precision; radioactive isotopes; sample preparation; spectroscopy; volume

Target preparation for continuous flow accelerator mass spectrometry - Schneider, R. J.; Hayes, J. M.; von Reden, K. F.; McNichol, A. P.; Eglinton, T. I.; Wills, J. S. C. (Radiocarbon, 1998)
For very small samples, it is difficult to prepare graphitic targets that will yield a useful and steady sputtered ion beam. Working with materials separated by preparative capillary gas chromatography, we have succeeded with amounts as small as 20 mu g C. This seems to be a practical limit, as it involves 1) multiple chromatographic runs with trapping of effluent fractions, 2) recovery and combustion of the fractions, 3) graphitization and 4) compression of the resultant graphite/cobalt matrix into a good sputter target. Through such slow and intricate work, radiocarbon ages of lignin derivatives and hydrocarbons from coastal sediments have been determined. If this could be accomplished as an "online" measurement by flowing the analytes directly into a microwave gas ion source, with a carrier gas, then the number of processing steps could be minimized. Such a system would be useful not just for chromatographic effluents, but for any gaseous material, such as CO2 produced from carbonates. We describe tests using such an ion source.
1 Sp. Iss. SI113kt Times Cited:11 Cited References Count:10
Keywords: gas; ion-source

Un registro de 6,000 anos de manifestaciones intensas del fenomeno de El Nino en sedimentos de lagunas de las Islas Galapagos - Steinitz-Kannan, M.; Riedinger, M. A.; Last, W. M.; Brenner, M.; Miller, M. C. (Bulletin de l'Institut Francais d'Etudes Andines, 1998)
id: 196

Western Great Lakes paleoecology study, global climate change initiative. In Holocene Paleoenvironments in Western Great Lakes Parks. Report - Winkler, M. G.; Sanford, P. R. (National Park Service & USGS Biological Resources Div., Northern Prairie Wildlife Research Center, 1998)
id: 130

Yangtze delta inundation and the discontinuity between Neolithic and younger cultures, China - Stanley, D. J.; Chen, Z.; Song, J. (Geoarchaeology, 1998)
id: 228

14C AMS measurement of C AMS measurement of C AMS measurement of - von Reden, K.; McNichol, A.; Pearson, A.; Schneider, R. (16th International Radiocarbon Conference, Groningen, 1997)
id: 952

An abrupt drowning of the Black Sea shelf - Ryan, W. B. F.; Pitman, W. C.; Major, C. O.; Shimkus, K.; Moskalenko, V.; Jones, G. A.; Dimitrov, P.; Gorur, N.; Sakinc, M.; Yuce, H. (Marine Geology, 1997)
During latest Quaternary glaciation, the Black Sea became a giant freshwater lake. The surface of this lake drew down to levels more than 100 m below its outlet. When the Mediterranean rose to the Bosporus sill at 7,150 yr BP1, saltwater poured through this spillway to refill the lake and submerge, catastrophically, more than 100,000 km(2) of its exposed continental shelf. The permanent drowning of a vast terrestrial landscape may possibly have accelerated the dispersal of early neolithic foragers and farmers into the interior of Europe at that time. (C) 1997 Elsevier Science B.V.
Xj245Times Cited:283Cited References Count:35

AMS measurements of the 14C distribution in the Pacific Ocean - von Reden, K. F.; McNichol, A. P.; Peden, J. C.; Elder, K. L.; Gagnon, A. R.; Schneider, R. J. (Nuclear Instruments and Methods in Physics Research, 1997)
id: 1673

AMS measurements of the 14C distribution in the Pacific Ocean - von Reden, K. F.; McNichol, A. P.; Peden, J. C.; Elder, K. L.; Gagnon, A. R.; Schneider, R. J. (Proceedings of the Seventh International Conference on Accelerator Mass Spectrometry, 1997)
id: 1644; B123

Biostratigraphy and sedimentation rates of the Amazon Deep Sea Fan - Mikkelsen, N.; Maslin, M.; Firaudeau, J.; Showers, W. J. (Proceedings of the Ocean Drilling Program: Scientific Results, 1997)
id: 71

Carbon isotopic fractionation associated with lipid biosynthesis by a cyanobacterium: relevance for interpretation of biomarker records - Sakata, S.; Hayes, J. M.; McTaggart, A. R.; Evans, R. A.; Leckrone, K. J.; Togasaki, R. K. (Geochim Cosmochim Acta, 1997)
For the cyanobacterium Synechocystis UTEX 2470, grown photoautotrophically to a logarithmic stage of growth, the total lipid extract is depleted in 13C by 4.8% relative to average biomass. Depletions observed for acetogenic (straight-chain) lipids range from 7.6 (hexadecanoic acid) to 9.9% (a C16 n-alkyl chain bound in a polar-lipid fraction), with a mass-weighted average of 9.1%. Polyisoprenoid lipids fall into two isotopic groups, with phytol, diplopterol, and diploptene depleted by 6.4-6.9% and bishomohopanol (produced from the extracts by the preparative degradation of bacteriohopanepolyol) depleted by 8.4%. Analysis of the pattern of depletions indicates that two carbon positions in each C5 biomonomer leading to polyisoprenoid products are probably depleted in 13C relative to average biomass. The depletion of bacteriohopanepolyol relative to other polyisoprenoids can be ascribed to changes that occur over the life of each cell: (1) the 13C content of carbon flowing to lipid biosynthesis decreases as the cell size increases and (2) a greater proportion of the bacteriohopanepolyol which, unlike other polyisoprenoids, is present mainly in the cytoplasm rather than in membranes and is synthesized when cells are larger. Chlorophyll a is depleted relative to average biomass by O.7%. Given the observed depletion of 13C in phytol, the heteroaromatic, chlorophyllide portion of chlorophyll must be enriched in 13C by 2.7%. This enrichment is large relative to that in chlorophyllides produced by eukaryotes and may be related to a parallel enrichment of 13C in cyanobacterial glutamic acid. As in many previous investigations of cyanobacterial lipids, long-chain n-alkanes (C22-C29) are found in the extracts. They are, however, enriched in 13C relative to biomass and have isotopic compositions suggesting that they are contaminants of petrochemical origin. Available results indicate that cyanobacterial lipids will be depleted relative to dissolved CO2 that has served as a carbon source by 22-30% and that a wider range of depletions will be characteristic of eukaryotic products. The absence of long-chain n-alkanes in cyanobacteria reduces the possibility that petroleum ever formed from pre-eukaryotic sedimentary debris.
Sakata, SHayes, J M McTaggart, A R Evans, R A Leckrone, K J Togasaki, R K eng Research Support, U.S. Gov't, Non-P.H.S. 1997/01/01 00:00 Geochim Cosmochim Acta. 1997;61(24):5379-89.
Keywords: *Biomass; Acetic Acid/metabolism; Alkanes/*analysis/chemistry; Biomarkers/chemistry; carbon isotopes; Carbon/*chemistry; Chlorophyll/metabolism; Cyanobacteria/chemistry/*metabolism; Geologic Sediments/*chemistry; Lipids/*biosynthesis; NASA Discipline Exobiology; Non-NASA Center; Palmitic Acid/metabolism; Phytol/metabolism; Pigments, Biological/metabolism

Climate variation and the rise and fall of an Andean civilization - Binford, M. W.; Kolata, A. L.; Brenner, M.; Janusek, J. W.; Seddon, M. T.; Abbott, M.; Curtis, J. H. (Quaternary Research, 1997)
Paleolimnological and archaeological records that span 3500 years from Lake Titicaca and the surrounding Bolivian-Peruvian altiplano demonstrate that the emergence of agriculture (ca. 1500 B.C.) and the collapse of the Tiwanaku civilization (ca. A.D. 1100) coincided with periods of abrupt, profound climate change, The timing and magnitude of climate changes are inferred from stratigraphic evidence of lake-level variation recorded in C-14-dated lake-sediment cores. Paleolake levels provide estimates of drainage basin water balance. Archaeological evidence establishes spatial and temporal patterns of agricultural field use and abandonment. Prior to 1500 B.C., aridity in the altiplano precluded intensive agriculture. During a wetter period from 1500 B.C. to A.D. 1100, the Tiwanaku civilization and its immediate predecessors developed specialized agricultural methods that stimulated population growth and sustained large human settlements, A prolonged drier period (ca. A.D. 1100-1400) caused declining agricultural production, field abandonment, and cultural collapse. (C) 1997 University of Washington.
Wu887Times Cited:148Cited References Count:53

Consistent Fractionation of 13C in Nature and in the Laboratory: Growth-rate Effects in Some Haptophyte Algae - Bidigare, Robert R.; Fluegge, Arnim; Freeman, Katherine H.; Hanson, Kristi L.; Hayes, John M.; Hollander, David; Jasper, John P.; King, Linda L.; Laws, Edward A.; Milder, Jeffrey; Millero, Frank J.; Pancost, Richard; et al. (Global Biogeochemical Cycles, 1997)
The carbon isotopic fractionation accompanying formation of biomass by alkenone-producing algae in natural marine environments varies systematically with the concentration of dissolved phosphate. Specifically, if the fractionation is expressed by єP ≈ δe − δp, where δe and δp are the δ13C values for dissolved CO2 and for algal biomass (determined by isotopic analysis of C37 alkadienones), respectively, and if Ce is the concentration of dissolved CO2, μmol kg−1, then b = 38 + 160*[PO4], where [PO4] is the concentration of dissolved phosphate, μM, and b = (25 − єp)Ce. The correlation found between b and [PO4] is due to effects linking nutrient levels to growth rates and cellular carbon budgets for alkenone-containing algae, most likely by trace-metal limitations on algal growth. The relationship reported here is characteristic of 39 samples (r2 = 0.95) from the Santa Monica Basin (six different times during the annual cycle), the equatorial Pacific (boreal spring and fall cruises as well as during an iron-enrichment experiment), and the Peru upwelling zone. Points representative of samples from the Sargasso Sea ([PO4] ≤ 0.1 μM) fall above the b = f[PO4] line. Analysis of correlations expected between μ (growth rate), єp, and Ce shows that, for our entire data set, most variations in єp result from variations in μ rather than Ce. Accordingly, before concentrations of dissolved CO2 can be estimated from isotopic fractionations, some means of accounting for variations in growth rate must be found, perhaps by drawing on relationships between [PO4] and Cd/Ca ratios in shells of planktonic foraminifera.
id: 1727

A correction for aberrations in the WHOI Recombinator Injector - von Reden, K. F.; Schneider, R. J. (Symposium of North Eastern Accelerator Personnel, 1997)

Corrections for contamination background in AMS 14C measurements - Brown, T. A.; Southon, J. R. (Nuclear Instruments and Methods in Physics Research B, 1997)
Measurements of ratios were made on samples of Oxalic Acid and 14C “dead” materials spanning the mass range from 10 μg to ∼1 mg. These measurements have allowed the determination of both the amount, and the 14C content, of the contaminant carbon introduced during sample processing in our laboratory. These data were used to correct measured ratios obtained from ANU Sucrose and “∼ one-half-life old” test samples for the influence of the contaminant. The test samples spanned the 10 μg to ∼1 mg mass range and the corrections were made using three different formulae. The results obtained from these calculations allow the accuracy of these background correction formulae to be evaluated.
id: 1493

Determination of the radiocarbon ages of individual PAH extracted from urban aerosol and marine sediment - Pearson, A.; Eglinton, T. I.; McNichol, A. P.; Currie, L. A.; Schneider, R. J.; von Reden, K. F.; Benner, B. A.; Wise, S. A. (16th International Radiocarbon Conference, 1997)
id: 951

Eastern Mississippi Delta; late Wisconsin unconformity, overlying transgressive facies, sea level and subsidence - Stanley, D. J.; Warne, A. G.; Dunbar, J. B. (Engineering Geology, 1997)
id: 79

Eruption of Soufriere Hills Volcano in Montserrat - Young, S. R.; Sparks, S.; Robertson, R.; Lynch, L.; Aspinall, W. (EOS, 1997)
On July 18,1995, the Soufriere Hills volcano in Montserrat erupted for the first time in recorded history. The eruption began with intense fumarolic venting and phreatic explosions following 3 years of elevated seismicity. An andesite lava dome emerged on November 15, 1995, and continued to grow, with several periods of copious pyroclastic flow generation and an explosive eruption on September 17, 1996. The largest pyroclastic flows to date (on June 25, 1997) and a period of vulcanian explosions with fountain collapse (during early August 1997) indicate continued escalation of the eruption.
id: 99

Evidence for earliest olive oil production in submerged settlements off the Carmel coast, Israel - Galili, E.; Stanley, D. J.; Sharvit, Y.; Weinstein, E. M. (Journal of Archaeological Science, 1997)
Thousands of crushed olive stones with olive pulp are concentrated in pits at the Kfar Samir prehistoric settlement off the Carmel coast south of Haifa. Observations at this site, and at other Late Neolithic to Early Chalcolithic offshore settlements in this region, record an olive-oil technology that began along the Carmel coastal plain as early as 6500 years ago. This is about 500 years earlier than previously held. These new finds help define the technology of olive-oil production and refine the chronological definition of cultural units along the southern Levant coast during the 7th millenniumbp, a time of major transition between the end of the Neolithic and beginning of the Chalcolithic.
id: 81

The first trans-Arctic 14C section: comparison of the mean ages of the deep waters in the Eurasian and Canadian basins fo the Arctic Ocean - Schlosser, Peter; Kromer, Bernd; Ekwurzel, Brenda; Bonisch, Gerhard; McNichol, Ann; Schneider, Robert; von Reden, Karl; Ostlund, H. G.; Swift, J. H. (Nuclear Instruments and Methods in Physics Research, 1997)
id: 67

The first trans-Arctic 14C section: comparison of the mean ages of the deep waters in the Eurasian and Canadian Basins of the Arctic Ocean; in Proceedings of the 7th International Conference on Accelerator Mass Spectrometry - Schlosser, P.; Kromer, B.; Ekwurzel, B.; Bonisch, G.; McNichol, A.; Schneider, R.; von Reden, K.; Ostlund, H.; Swift, J. (Nuclear Instruments and Methods, 1997)
id: 1751

A high-resolution paleoenvironmental record from Bainbridge Crater Lake, Galapagos Islands - Reidinger, M.; Steinitz-Kannan, M.; Last, W.; Brenner, M. (Wurzburger Geographische Manuscripte, Heft, 1997)
id: 356

Hold-up and memory effect for carbon in a compact microwave ion source - Schneider, R. J.; vonReden, K. F.; Wills, J. S. C.; Diamond, W. T.; Lewis, R.; Savard, G.; Schmeing, H. (Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions with Materials and Atoms, 1997)
The production of C+ in a microwave ion source injected with a gaseous CO2 sample has been investigated as an alternative to sample graphitization, A continuous flow of argon gas maintained the discharge, and 20 mu L Of CO2 gas at approximately 1 atm was pulsed into the source through a sample valve closely coupled to the plasma chamber, The C+ component of the beam fell to 1% of its original intensity less than 10 s after the valve was operated. in a separate experiment, the microwave ion source was operated with pure CO2 feed gas and the extracted beam was magnetically analyzed. Efficient breakup of the molecules was observed. These results are considered promising for such applications as accelerator mass spectrometry of C isotopes in gaseous samples.
Wt653Times Cited:13Cited References Count:7

An isotopic biogeochemical study of Neoproterozoic and Early Cambrian sediments from the Centralian Superbasin, Australia - Logan, G. A.; Summons, R. E.; Hayes, J. M. (Geochim Cosmochim Acta, 1997)
Organic matter from Neoproterozoic and Early Cambrian sediments of the Amadeus and Officer basins of the Centralian Superbasin, Australia, has been studied for biomarker distributions and the carbon isotopic compositions of kerogen and individual hydrocarbons. These sediments represent both shallow and deep water marine facies in the older sections and marine and saline lacustrine carbonate deposits in the Cambrian. Hydrocarbon biomarker patterns were found to be quite consistent with the known sedimentary environments and provide valuable insights into the biogeochemical changes which accompanied the transition from a microbially-dominated ocean to the early stages of metazoan radiation. In particular, carbon isotopic data for n-alkyl and isoprenoid lipids presented here, and in earlier studies, showed a reversal in carbon isotopic ordering between the Proterozoic and Phanerozoic. By comparison with the delta 13C of kerogen, n-alkyl lipids from deep-water Proterozoic sediments were enriched in 13C and appear to be derived mainly from heterotrophs whilst open marine Phanerozoic counterparts are 13C depleted and evidently derived mainly from autotrophs. Data from the samples studied here are consistent with a model invoking a change in the redox structure of the ocean, possibly aided by the innovation of faecal pellets.
Logan, G ASummons, R E Hayes, J M eng Research Support, U.S. Gov't, Non-P.H.S. 1997/01/01 00:00 Geochim Cosmochim Acta. 1997;61(24):5391-409.
Keywords: Alkanes/analysis/chemistry; Animals; australia; biomarkers; carbon isotopes; Carbon/analysis/*chemistry; Cyanobacteria; Eukaryota; Feces; Fossils; Geologic Sediments/*analysis/chemistry; Hydrocarbons/analysis; NASA Discipline Exobiology; Non-NASA Center; Paleontology; phytoplankton; SEAWATER; Terpenes/analysis; Zooplankton

Isotopic stratigraphy of Amazon Fan sediments - Showers, W. J.; Schneider, R.; Mikkelsen, N.; Maslin, M. (Proceedings of the Ocean Drilling Program: Scientific Results, 1997)
id: 1277

Late Quaternary Western Atlantic Paleoceanography and terrigenous sedimentation on the Amazon Fan: a view from delta d180 and d13C of planktonic foraminifera and bulk organic matter d13C - Schneider, R. R.; Muller, P. J.; Schlunz, B.; Segl, M.; Showers, W. J.; Wefer, G. (Proceedings of the Ocean Drilling Program: Scientific Results, 1997)
id: 1278

Mass transport deposits of Amazon Fans - Piper, D. J.; Pirmez, C.; Flood, R.; Long, D.; Manely, P.; Normark, W.; Showers, W. (Proceedings of the Ocean Drilling Program: Scientific Results, 1997)
id: 1279

Mediterranean deltas: subsidence as a major control of relative sea-level rise - Stanley, D. J. (Bulletin de l'Institut oceanographique(Monaco), 1997)
id: 1284

Paleoceanographic Variability on a Millennial Scale: A High Resolution Record of the Latest Deglaciation from the Blake Outer Ridge, Western North Atlantic, Thesis - Schlegel, Mary Ann (1997)

Paleoclimatic implications of silicieous microfossil succession in late Quaternary sediments in Lake Baikal, Siberia - Julius, M. L.; Stoermer, E. F.; Colman, S. M.; Moore, T. C. (Journal of Paleolimnology, 1997)
id: 1354

Paleoecological research at Isle Royale, Apostle Islands, and Voyageurs National Parks. Report - Winkler, M. G.; Sanford, P. R. (1997)
id: 1321

Paleolimnology research at Isle Royale, Apostle Island, and Voyageurs National Parks - Winkler, M. G.; Sanford, P. R. (USGS Biological Resources Division, Global Change Research Program, 1997)
id: 1299

Postglacial relative sea level history from sediment and diatom rcords of emerged coastal lakes, north-central Kola Peninsula, Russia - Snyder, J. A.; Forman, S. L.; Mode, W. N.; Tarasov, G. A. (Boreas, 1997)
id: 379

Preliminary paleoecology study of Salt Pond and Nauset Lagoon, Cape Cod National Seashore (Report) - Cole, K.; Winkler, M. G.; Sanford, P. R. (National Park Service, North Atlantic Region, 1997)
id: 131

Preliminary results of the first scientific drilling on Lake Baikal, Buguldeika site, southeastern Siberia - Colman, S.; Grachev, M.; Hearn, P.; Horie, S.; Kawai, T.; Kuzmin, M.; Logachov, N.; Fialkov, V.; Gorigljad, A.; Tomilov, B.; Khakhaev, B.; Kochikov, S.; et al. (Quaternary International, 1997)
The Baikal Drilling Project (BDP) is a multinational effort to investigate the paleoclimatic history and tectonic evolution of the Baikal sedimentary basin during the Late Neogene. In March 1993 the Baikal drilling system was successfuly deployed from a barge frozen into position over a topographic high, termed the Buguldeika saddle, in the southern basin of Lake Baikal. The BDP-93 scientific team, made up of Russian, American and Japanese scientists, successfully recovered the first long (>100 m) hydraulic piston cores from two holes in 354 m of water. High quality cores of 98 m (Hole 1) and 102 m (Hole 2), representing sedimentation over the last 500,000 years, were collected in 78 mm diameter plastic liners with an average recovery of 72% and 90%, respectively. Magnetic susceptibility logging reveals an excellent hole-to-hole correlation. In this report the scientific team describes the preliminary analytical results from BDP-93 hole 1 cores. Radiocarbon dating by accelerator mass spectrometry provides an accurate chronology for the upper portion of Hole 1. Detailed lithologic characteristics, rock magnetic properties and inorganic element distributions show a significant change to the depositional environment occuring at 50 m subbottom depth, approximately 250,000 BP. This change may be due to uplift and rotation of the horst block in the Buguldeika saddle. The sedimentary section above 50 m is pelitic with varve-like laminae, whereas the section below 50 m contains a high proportion of sand and gravel horizons often organized into turbidite sequences. Accordingly, high resolution seismic records reveal a change in sonic velocity at this depth. It is inferred that sedimentation prior to 250 ka BP was from the west via the Buguldeika river system. After 250 ka BP the Buguldeika saddle reflects an increase in hemipelagic sediments admired with fine-grained material from the Selenga River drainage basin, east of Lake Baikal. Variations in the spore-pollen assemblage, diatoms, biogenic silica content, rock magnetic properties, clay mineralogy and organic carbon in the upper 50 m of BDP-93-1 reveal a detailed record of climate change over approximately the last 250,000 years. These variables alternate in a pattern characteristic of glacial/interglacial climatic fluctuations. The present age model suggests that the climate signal recorded in Lake Baikal sediments is similar to Late Quaternary signals recorded in Chinese loess sections and in marine sediments. Copyright (C) 1996 INQUA/Elsevier Science Ltd
Vq100Times Cited:44 Cited References Count:29
Keywords: asia; tectonics

Recent subsidence of the northern Suez canal - Stanley, D. J.; Goodfriend, G. A. (Nature, 1997)
Xm528Times Cited:16Cited References Count:10

Regional, Holocene records of the human dimension of global change: Sea-level and land-use change in prehistoric Mexico - Sluyter, A. (Global and Planetary Change, 1997)
Regional, Holocene records hold particular relevance for understanding the reciprocal nature of global environmental change and one of its major human dimensions: ''sustainable agriculture'', i.e., food production strategies which entail fewer causes of and are less susceptible to environmental change. In an epoch of accelerating anthropogenic transformation, those records reveal the protracted regional causes and consequences of change (often agricultural) in the global system as well as informing models of prehistoric, intensive agriculture which, because of long tenures and high productivities, suggest strategies for sustainable agricultural in the present. This study employs physiographic analysis and the palynological, geochemical record from cores of basin fill to understand the reciprocal relation between environmental and land-use change in the Gulf of Mexico tropical lowland, focusing on a coastal basin sensitive to sea-level change and containing vestiges of prehistoric settlement and wetland agriculture. Fossil pollen reveals that the debut of maize cultivation in the Laguna Catarina watershed dates to ca. 4100 BC, predating the earliest evidence for that cultivar anywhere else in the lowlands of Middle America. Such an early date for a cultivar so central to Neotropical agroecology and environmental change, suggests the urgency of further research in the study region. Moreover, the longest period of continuous agriculture in the basin lasted nearly three millennia (ca. 2400 BC-AD 550) despite eustatic sea-level rise. Geochemical fluxes reveal the reciprocity between land-use and environmental change: slope destabilization, basin aggradation, and eutrophication. The consequent theoretical implications pertain to both applied and basic research. Redeploying ancient agroecologies in dynamic environments necessitates reconstructing the changing operational contexts of putative high productivity and sustainability. Adjusting land use in the face of global warming and eustatic sea-level rise necessitates understanding sediment influxes to coastal basins which, in turn, depend on vegetation, climate, and land use in watersheds.
Wk148Times Cited:17Cited References Count:116

Target preparation for continuous flow accelerator mass spectrometry - Schneider, R. J.; Hayes, J. M.; Eglinton, T. I.; McNichol, A. P.; von Reden, K. F. (16th International Radiocarbon Conference, 1997)
id: 953

Target preparation for continuous flow accelerator mass spectrometry - Schneider, R. J.; Hayes, J. M.; von Reden, K. F.; McNichol, A. P.; Eglinton, T. I. (Radiocarbon, 1997)
id: 1661

Target preparation for continuous flow accelerator mass spectrometry: (Proceedings of the 16th International Radiocarbon Conference, 1997) - Schneider, R. J.; Hayes, J. M.; von Reden, K. F.; McNichol, A. P.; Eglinton, T. (Radiocarbon, 1997)
id: 1752

Western Great Lakes Paleoecology Study. Report - Winkler, M. G.; Sanford, P. R. (National Biological Service Global Climate Change Initiative, 1997)
id: 1322

Western Great Lakes regional paleoenvironmental changes: island and inland contrasts - Winkler, M. G.; Sanford, P. R.; Cole, K. L.; Flakne, R. L. (Ecological Society of America Bulletin, 1997)
id: 1301

AMS measurements of the 14C distribution in the Pacific Ocean - von Reden, K. F.; McNichol, A. P.; Schneider, R. J. (7th International Conference on Accelerator Mass Spectrometry, 1996)
id: 950; 1

Cape May site report - Miller, K. G.; Liu, C.; Browning, J. V.; Pekar, S.; Sugarman, P.; Van Fossen, M. C.; Mullikin, L.; Queen, D.; Feigenson, M. D.; Aubry, M. P.; Burckle, L. D.; Powars, D.; et al. (Proc. ODP, Init. Repts, 1996)
id: 55

Catastrophic discharge of fluvial sediment to the ocean; evidence of jokulhlaups events in the Alsek Sea Valley, Southeast Alaska (USA) - Milliman, J. D.; Snow, J.; Jaeger, J.; Nittrouer, C. A. (International symposium on Erosion and sediment yield; global and regional perspectives, 1996)
id: 28

Character, paleoenvironment, rate of accumulation, and evidence for seismic triggering of Holocene turbidites, Canada Abyssal Plain, Arctic Ocean - Grantz, A.; Phillips, R. L.; Mullen, M. W.; Starratt, S. W.; Jones, G. A.; Naidu, A. S.; Finney, B. P. (Marine Geology, 1996)
Four box cores and one piston core show that Holocene sedimentation on the southern Canada Abyssal Plain for the last 8010 +/- 120 yr has consisted of a continuing rain of pelagic organic and ice-rafted elastic sediment with a net accumulation rate during the late Holocene of less than or equal to 10 mm/1000 yr, and episodically emplaced turbidites 1-5 m thick deposited at intervals of 830 to 3450 yr (average 2000 yr). The average net accumulation rate of the mixed sequence of turbidites and thin pelagite interbeds in the cores is about 1.2 m/1000 yr.Physiography suggests that the turbidites originated on the Mackenzie Delta or its clinoform, and delta(13)C values of -27 to -25 parts per thousand in the turbidites are compatible with a provenance on a delta. Extant displaced neritic and lower slope to basin plain calcareous benthic foraminifers coexist in the turbidite units. Their joint occurence indicates that the turbidites originated on the modern continental shelf and entrained sediment from the slope and rise enroute to their final resting place on the Canada Abyssal Plain. The presence of Middle Pleistocene diatoms in the turbidites suggests, in addition, that the turbidites may have originated in shallow submarine slides beneath the upper slope or outer shelf. Small but consistent differences in organic carbon content and delta(13)C values between the turbidite units suggest that they did not share an identical provenance, which is at least compatible with an origin in slope failures.The primary provenance of the ice-rafted component of the pelagic beds was the glaciated terrane of northwestern Canada; and the provenance of the turbidite units was Pleistocene and Holocene sedimentary deposits on the outer continental shelf and upper slope of the Mackenzie Delta. Largely local derivation of the sediment of the Canada Abyssal Plain indicates that sediment accumulation rates in the Arctic Ocean are valid only for regions with similar depositional sources and processes, and that these rates cannot be extrapolated regionally. The location of an elliptical zone of active seismicity over the inferred provenance of the turbidites suggests that they were triggered by large earthquakes.Distal turbidite sediment accumulation rates were more than two orders of magnitude greater than pelagic sediment accumulation rates on the Canada Abyssal Plain during the last 8000 years. This disparity reconciles the discrepancy between the high accumulation rates assumed by some for the Arctic Ocean because of the numerous major rivers and large ice sheets that discharge into this small mediterranean basin and the low pelagic sedimentation rates that have been reported from the Arctic Ocean.
Uy014Times Cited:36Cited References Count:46

Chemical Composition of Volcanic Gases - Giggenbach, W. F. (Monitoring and Mitigation of Volcano Hazards, 1996)
id: 1590

Dating of explosive volcanic events associated with dome growth at Soufriere Hills volcano, Montserrat - Young, S. R.; Hoblitt, R. P.; Smith, A. L.; Devine, J. D.; Wadge, G.; Shepherd, J. B. (Proceedings of the Special Symposium on Volcanism in Montserrat, Second Caribbean Conference on Natural Hazards and Hazard Management, 1996)
id: 1306

Deep water formation and exchange rates in the Arctic Ocean: Implications from the distribution of 14C - Schlosser, P.; Kromer, B.; Ekwurzel, B.; Boenisch, G.; McNichol, A.; Schneider, R.; von Reden, K.; Oestlund, G. (7th International Conference on Accelerator Mass Spectrometry, 1996)
id: 947; 1

Direct U-Th dating of marine sediments from the two most recent interglacial periods - Slowey, N. C.; Henderson, G. M.; Curry, W. B. (Nature, 1996)
A KNOWLEDGE of the age of marine sediments is necessary to determine the timing of events and rates of processes in the marine realm, and the relationships among marine and other climatically sensitive records. The establishment of an accurate chronology for Pleistocene marine sediments beyond the range of radiocarbon dating (approximately the past 45 kyr) has therefore been a goal of palaeoceanographers for decades. Early attempts(1,2) based on measurements of the radionuclides Th-230 and Pa-231 mere beset with problems, and subsequent studies focused on tying fluctuations in marine sediment oxygen-isotope records to events such as the formation of col al reef terraces and changes in the Earth's magnetic polarity(3,4), and tuning the resultant chronologies to the Earth's orbitally driven insolation variations(5-8). But these chronologies (especially the age and duration of the last interglacial period) have been challenged by several studies(9-12), raising questions about the fundamental cause of Pleistocene climate fluctuations. Here we report the direct U-Th dating of aragonite-rich marine sediments from the Bahamas, and present an accurately dated marine oxygen-isotope record for the last two interglacials. We obtain dates of 120-127 kyr BP for the last interglacial and 189-190 kyr np for the late stage 7 interglacial. These dates are in accord with the general theory of orbitally forced climate fluctuations and demonstrate the potential of our direct-dating approach for developing an absolute chronology for the Pleistocene marine oxygen-isotope record.
Vh315Times Cited:39Cited References Count:40

Effects of turbidity flows on organic matter accumulation, sulfate reduction, and methane generation in deep-sea sediments on the Iberia Abyssal Plain - Meyers, P. A.; Silliman, J. E.; Shaw, T. J. (Organic Geochemistry, 1996)
Non-steady-state sedimentation has affected preservation of organic matter in a Pliocene-Pleistocene turbidite sequence sampled by the Ocean Drilling Program at four closely spaced drill sites on the Iberia Abyssal Plain. Organic carbon concentrations average ca. 0.7% in sediments from Sites 897 and 898 and ca. 0.4% at Sites 899 and 900. Headspace concentrations of interstitial methane exceed 100,000 ppm in sediments from Sites 897 and 898 but are essentially zero in those from Sites 899 and 900. Methane concentrations do not rise until interstitial sulfate concentrations are virtually depleted, suggesting the presence of deep in situ methanogenic bacterial activity at Sites 897 and 898 and its absence at Sites 899 and 900. Two factors associated with the turbidity flows that created the sedimentary sequence evidently influenced post-depositional diagenesis at these sites. The principal factor is that the rapidly deposited turbidite sequences at Sites 897 and 898 protected organic matter from early oxic degradation and thereby permitted subsequent anoxic degradation to proceed. In contrast, organic matter in the more slowly deposited turbidites at Sites 899 and 900 was oxidized soon after deposition and was therefore not available for later microbial utilization. A lesser factor is that the turbidity flows may have obtained their entrained organic matter from different environments and consequently delivered organic matter with different characteristics. Both factors contributed to heterogeneity of the types and amounts of organic matter that accumulated in these deep-sea sediments, and this variability has influenced subsequent sulfate reduction and methanogenesis. Copyright (C) 1996 Elsevier Science Ltd.
Wd943Times Cited:22Cited References Count:33

Expanded Small Sample Capabilities at NOSAMS: Preparation and Analysis of Conventional Graphite Targets Containing 0.15 mg Carbon - Pearson, A.; McNichol, A. P.; Schneider, R. J.; von Reden, K. F. (7th International Conference on Accelerator Mass Spectrometry, 1996)
id: 946; 1

Fluxes of mantle and subducted carbon along convergent plate boundaries - Sano, Y.; Williams, S. N. (Geophysical Research Letters, 1996)
The potential impact of increases in atmospheric CO2 is a topic of considerable controversy. Even though volcanic emission of CO2 may be very small as compared to anthropogenic emissions, evaluation of natural degassing of CO2 is important for any model of the geochemical C cycle and evolution of the Earth's atmosphere. We report here the mantle C flux in subduction zones based on He and C isotopes and CO2/He-3 ratios of high-temperature volcanic gases and medium- and low-temperature fumaroles in circum-Pacific volcanic regions. The calculated volcanic C flux of 3.1x10(12) mol/a from subduction zones is larger than the flux of 1.5x10(12) mol/a from mid-ocean ridges, while contributions from the mantle in subduction zone is only 0.30x10(12) mol/a, equivalent to about 20% of the C flux in mid-ocean ridges. Since the estimated mantle C flux in hot spot regions is insignificant, 0.029x10(12) mol/a, we propose that the global mantle C flux is 1.8x10(12) mol/a in total. The flux, if accumulated over 4.5 billion year of geological time, amounts to 8.3x10(21) mol which agrees well with 9x10(21) mol of the present inventory of C at the Earth's surface. This may support a continuous degassing model of C or the idea that subducted C is recycled into the lower mantle.
Vl370Times Cited:137Cited References Count:39

Gas venting and late Quaternary sedimentation in the Persian (Arabian) Gulf - Uchupi, E.; Swift, S. A.; Ross, D. A. (Marine Geology, 1996)
High resolution 3.5 kHz echo sounding profiles and piston cores were used to reconstruct the microtopography and late Quaternary depositional history of the Persian Gulf. Perversive throughout the seafloor of the Gulf is an extensive network of pockmarks formed by seepages of thermogenic gas. These gas seeps and bottom water exiting the Gulf via the Strait of Hormuz are the most significant processes controlling present-day sedimentation in the region. Erosion by these seeps has been so intense in the Baiban Shelf in the Strait of Hormuz as to create a ''hoodoo'' like terrain on the outer shelf. The surfical geology of the Gulf documents a short lived transgression 29,400 to 22,800 years ago during the Wisconsin regression which began 125,000 years ago, the Wisconsin regressive maxima when sea level dropped to -120/-130 m about 21,000/20,000 years ago and the climate was dry and eolian and paralic sedimentation characterized the Gulf, the Holocene transgression 18,000 to 12,000 years ago when the climate was more humid than during the climax of the Wisconsin regression, a dry phase 12,000 to 9000 years ago when the Persian Gulf was a site of eolian and carbonate deposition, and the present sediment cycle during the last 9000 years under a more humid regime. It was during the present cycle that southeast trending marl lobes were deposited off Iran, Arabia acquired its hyper-arid climate about 3000 years ago and the Gulf attained its present configuration about 1000 years ago as a result of the construction of the Tigris Euphrates Delta at its head and tectonism and aggradation along its Arabian and Iranian flanks.
Tv774Times Cited:49Cited References Count:82

Holocene paleoclimatic changes in the Lake Winnebago basin, east-central Wisconsin - Haase, Alisa A.; Smith, G. L.; Hardacker, E. P. (Abstracts with Programs - Geological Society of America, 1996)
id: 77

Informe Final: Geocronologia de las aquas subterraneas del Salar Punta Negra, Antofagasta, II Region. Preparado para Minera Escondida Ltda. (Report) - Salamanca, Marco (Minera Escondid Ltda, 1996)
id: 181

Isolation of Individual Organic Compounds for AMS Radiocarbon Analysis--A Novel Approach - Eglinton, T. I.; McNichol, A. P.; Benitez-Nelson, B. C.; Pearson, A.; von Reden, K. F.; Schneider, R. J.; Bauer, J. E.; Druffel, E. R. M. (Radiocarbon, 1996)
id: 1650

Isolation of Individual Organic Compounds for AMS Radiocarbon Analysis -- A Novel Approach - Eglinton, T. I.; McNichol, A. P.; Benitez-Nelson, B. C.; Pearson, A.; von Reden, K. F.; Schneider, R. J.; Bauer, J. E.; Druffel, E. R. M. (7th International Conference on Accelerator Mass Spectrometry, 1996)
id: 1800; 1

Kinematic Effects in the Sputtering of Carbon Isotopes - Schneider, R. J.; Hartman, J.; von Reden, K. F.; McNichol, A. P. (7th International Conference on Accelerator Mass Spectrometry, 1996)
id: 1801; 1

Kinematic Effects in the Sputtering of Carbon Isotopes - Schneider, R. J.; Hartman, J.; von Reden, K. F.; McNichol, A. P. (Radiocarbon, 1996)
id: 1660

Large-volume WOCE radiocarbon sampling in the Pacific Ocean - Stuiver, M.; Ostlund, H. G.; Key, R. M.; Reimer, P. J. (Radiocarbon, 1996)
At the University of Miami Tritium Laboratory and the University of Washington Quaternary Isotope Laboratory, more than 1000 large-volume Pacific Ocean radiocarbon samples were measured for the WOCE program. Here we present a comprehensive data set, and a brief discussion of our findings.
Xd080Times Cited:12 Cited References Count:8
Keywords: geosecs

Molecular breakup of CO2 and hold-up time in a microwave ion source - Wills, J. S. C.; Diamond, W. T.; Lewis, R. A.; Schmeing, H.; von Reden, K. F.; Schneider, R. J. (1996)
id: 949

Neolithic migrations as a function of sea level-controlled topography in the Yangtze Delta, China - Stanley, D. J.; Chen, Zhongyuan (Geology, 1996)
id: 1282

Paleoecology of the Everglades National Park Paper - Winkler, M. G.; Sanford, P. R.; Kaplan, S. W. (Florida Bay Science Conference, 1996)
id: 1298

Paleoecology of the Everglades National Park. Report - Winkler, M. G.; Sanford, P. R.; Kaplan, S. (National Park Service, Everglades National Park, 1996)
id: 1324

A preliminary palynological study of the late Pleistocene to Holocene history of the Lake Winnebago basin, Wisconsin - Ormseth, B. L.; Smith, G. L. (Abstracts with Programs - Geological Society of America, 1996)
id: 76

Progress of the NOSAMS Facility WOCE 14C Data Analysis - von Reden, K. F.; McNichol, A. P.; Schneider, R. J. (Radiocarbon, 1996)
id: 1672

Progress of the NOSAMS Facility WOCE 14C data analysis - von Reden, K. F.; McNichol, A. P.; Schneider, R. J. (7th International Conference on Accelerator Mass Spectrometry, 1996)
id: 948; 1

Progress of the NOSAMS Facility WOCE 14C Data Analysis - von Reden, K. F.; McNichol, A. P.; Schneider, R. J. (Workshop on Applications of AMS to Global Climate Change, 1996)
id: 1768; 1

Progress of the NOSAMS Facility WOCE 14C Data Analysis, Workshop on Applications of AMS to Global Climate Change - von Reden, K. F.; McNichol, A. P.; Schneider, R. J. (Workshop on Applications of AMS to Global Climate Change, 1996)
id: 954; 8

Progress of the NOSAMS facility WOCE (super 14) C data analysis - von Reden, K. F.; McNichol, A. P.; Schneider, Robert J. (University of Arizona, Department of Geosciences, Tucson, AZ, United States (USA), 1996)
id: 2242; Source type: conferencepapers&proceedings; Object type: Article; Object type: Conference Paper; Copyright: GeoRef, Copyright 2007, American Geological Institute.; CSAUnique: 1999-071631; AccNum: 1999-071631; ISSN: 0033-8222; CODEN: RACAAT
Keywords: 02D; 07; accelerator mass spectroscopy; C-14; carbon; Isotope geochemistry; isotopes; mass spectroscopy; Oceanography; Pacific Ocean; progress report; radioactive isotopes; report; sea water; spectroscopy

Radiocarbon measurements of atmospheric volatile organic compounds: Quantifying the biogenic contribution - Klouda, G. A.; Lewis, C. W.; Rasmussen, R. A.; Rhoderick, G. C.; Sams, R. L.; Stevens, R. K.; Currie, L. A.; Donahue, D. J.; Jull, A. J. T.; Seila, R. L. (Environmental Science & Technology, 1996)
The radiocarbon (C-14) abundance of atmospheric volatile organic compounds (VOC) gives a quantitative estimate of contributions from biomass and fossil-mass sources, important information for effective regulation of ozone precursors. We report here details of a methodology to perform such measurements and the first exploratory C-14 results on VOC fractions separated from two composited urban tropospheric air samples, collected during the summer (1992) in Atlanta, GA. The upper limit of the percentage of VOC originating from biomass sources during the morning and evening hours in Atlanta were 9 and 17%, respectively, measurements reported at the 95% confidence level. However, due to the level of the process blank and its uncertainty, in both cases the percentage can be as low as zero. The results of these experiments, designed to (i) evaluate the entire [C-14]VOC measurement process and (ii) obtain reliable estimates of biogenic contributions to atmospheric VOC, emphasize how important controls are throughout this multi-step chemical process to ensure quality data.
Uc413Times Cited:26Cited References Count:25

Reworking and discontinuities in Holocene sedimentation in the Nile Delta: Documentation from amino acid racemization and stable isotopes in mollusk shells - Goodfriend, G. A.; Stanley, D. J. (Marine Geology, 1996)
The late Holocene sedimentary history of the northwestern edge of the Nile Delta is reconstructed from amino acid racemization, radiocarbon, and stable isotope analysis of a series of bivalve shells from a core taken at the edge of Lake Maryut near Alexandria. Amino acid racemization, confirmed by radiocarbon and stable isotope analysis, indicates that in many parts of the core mixed-age mollusk assemblages are present. Dating of the time of sediment accumulation at various levels in the core is therefore based on the age of the youngest shells, which are identified by amino acid racemization analysis (lowest D/L values). AMS radiocarbon analysis is used to determine the ages of the shells, except for the most recent sediments (last 100 yr), for which aspartic acid racemization provides more precise ages.Amino acid racemization analysis of 59 shells from 21 levels in the 4.8 m Holocene sequence in the core enabled identification of a large hiatus. Holocene sedimentation started at ca. 2400 BC, apparently corresponding to a westward shift of the course of the Canopic Nile distributary which lies to the east. Deposition continued at a rate of 1.4 mm per year, ceasing at ca. 550 BC, at which time the Canopic Nile shifted eastward again and subsequently became defunct. A marine connection during this period is indicated by stable isotope values of shells. Sediment accumulation began again only at the end of the 19th century, when a series of irrigation canals was connected to the Lake Maryut basin. Stable isotope values indicate a strong freshwater influence. Deposition has continued to the present at a very high rate (19 mm per year) due to supply of sediments by agricultural activity.The relative ease with which racemization analyses can be carried out permits detailed analysis of core chronostratigraphy, leading to more accurate reconstruction of core chronology: hiatuses can be pinpointed and documented, and age mixtures can be identified, with appropriate individual shells being selected for AMS radiocarbon analysis. Aspartic acid racemization analysis permits dating of samples from the last several hundred years, a period for which radiocarbon analyses provide poor precision.
Tv774Times Cited:35Cited References Count:30

Sediment dispersal along northern Israel coast during the early Holocene: Geological and archaeological evidence - Stanley, D. J.; Galili, E. (Marine Geology, 1996)
geological and archaeological study of finds at Atlit-Yam, a Pre-Pottery Neolithic settlement submerged off the Carmel coast of northern Israel, provides new information on sediment provenance and dispersal in the southern Levant. Clay mineral analyses of mud-rich samples collected in a water well (ca. 8100-7550 yrs B.P.) at this site are useful for determining the early Holocene circulation pattern along this margin. Analyses record the predominance of fluvial sediment from proximal Carmel highland sources to the east, as indicated by illite, and of marine sediment from the north and northeast, as indicated by kaolinite. This north-to-south coastal transport is in marked contrast to the present south-to-north dispersal pattern where smectite-rich Nile material is derived from distal sources and carried hundreds of kilometers to the Carmel margin. The interpreted coastal circulation pattern indicates that although the modern Nile delta, major source of sediment in the eastern Mediterranean, had begun to form about 8000-7500 yrs ago, it had not yet begun to supply substantial amounts of sediment to as far north as the Carmel coast by the time the water well was abandoned. The Atlit-Yam site serves as a unique geochronologic gauge valuable for interpreting climatic, oceanographic and sedimentologic conditions in the SE Mediterranean which, as recently as 7500 yrs ago, were markedly different than those prevailing at present.
Ue849Times Cited:13Cited References Count:30

Sedimentary carbon-isotope systematics on the Amazon shelf - Sommerfield, C. K.; Nittrouer, C. A.; DeMaster, D. J. (Geo-Marine Letters, 1996)
Sedimentary carbon systematics on the Amazon continental shelf were investigated using C-14 and delta(13)C measurements of sedimentary organic materials. Mass balance calculations indicate that the C-14 content of modern shelf muds results from burial of old (similar to 5000 yr BP) terrestrial soil carbon and bomb-C-14-enriched marine carbon, implying that most of the bomb-labeled riverine particulate carbon is not buried on the shelf. The C-14 signature of Amazon shelf deposits records the effects of both biogeochemical and sedimentary processes active in this dynamic environment.
Ty588Times Cited:12Cited References Count:33

Sedimentology of the Krakatau 1883 submarine pyroclastic deposits - Mandeville, C. W.; Carey, S.; Sigurdsson, H. (Bulletin of Volcanology, 1996)
The majority of tephra generated during the paroxysmal 1883 eruption of Krakatau volcano, Indonesia, was deposited in the sea within a 15-km radius of the caldera. Two syneruptive pyroclastic facies have been recovered in SCUBA cores which sampled the 1883 subaqueous pyroclastic deposit. The most commonly recovered facies is a massive textured, poorly sorted mixture of pumice and lithic lapilli-to-block-sized fragments set in a silty to sandy ash matrix. This facies is indistinguishable from the 1883 subaerial pyroclastic flow deposits preserved on the Krakatau islands on the basis of grain size and component abundances. A less common facies consists of well-sorted, planar-laminated to low-angle cross-bedded, vitric-enriched silty ash. Entrance of subaerial pyroclastic flows into the sea resulted in subaqueous deposition of the massive facies primarily by deceleration and sinking of highly concentrated, deflated components of pyroclastic flows as they traveled over water. The basal component of the deposit suggests no mixing with seawater as inferred from retention of the fine ash fraction, high temperature of emplacement, and lack of traction structures, and no significant hydraulic sorting of components. The laminated facies was most likely deposited from low-concentration pyroclastic density currents generated by shear along the boundary between the submarine pyroclastic flows and seawater. The Krakatau deposits are the first well-documented example of true submarine pyroclastic flow deposition from a modern eruption, and thus constitute an important analog for the interpretation of ancient sequences where subaqueous deposition has been inferred based on the facies characteristics of encapsulating sedimentary sequences.
Uk310Times Cited:57Cited References Count:59

Stable and radio-carbon isotope measurements in the Pacific Ocean; contributions from NOSAMS - McNichol, A. P.; von Reden, K. F.; Schneider, R. J.; Key, R. M.; Jones, G. A. (American Geophysical Union, Washington, DC, United States (USA), 1996)
id: 2240; Source type: conferencepapers&proceedings; Object type: Article; Object type: Conference Paper; Copyright: GeoRef, Copyright 2007, American Geological Institute.; CSAUnique: 1997-047916; AccNum: 1997-047916; ISSN: 0096-3941; CODEN: EOSTAJ
Keywords: 02D; 07; accelerator mass spectroscopy; C-13/C-12; C-14; carbon; chemical analysis; geochemical indicators; high-resolution methods; Isotope geochemistry; isotope ratios; isotopes; marine geology; mass spectroscopy; National Ocean Sciences Accelerator Mass Spectrometry; NOSAMS; Oceanography; Pacific Ocean; radioactive isotopes; radioactive tracers; sampling; sea water; spectroscopy; Stable isotopes; tracers; Woods Hole Oceanographic Institution

Stable and radiocarbon isotope measurements in the Pacific Ocean: Contributions from NOSAMS - McNichol, A. P.; von Reden, K. F.; Schneider, R. J.; Key, R. M.; Jones, G. A. (AGU/ASLO 1996 Ocean Sciences Meeting, 1996)
id: 960

WOCE AMS Radiocarbon I: Pacific Ocean results (P6, P16, and P17) - Key, R. M.; Quay, P. D.; Jones, G. A.; McNichol, A. P.; von Reden, K. F.; Schneider, R. J. (Radiocarbon, 1996)
AMS radiocarbon results from the World Ocean Circulation Experiment in the Pacific Ocean show dramatic changes in the inventory and distribution of bomb-produced 14C since the time of the GEOSECS survey (8/73-6/74). Nearsurface 4C values for the eastern portion of both the northern and southern subtropical gyres decreased by 25-50%, with the change being greater in the north. Equatorial near-surface values have increased by ca. 25%. Changes in the 250-750-m depth range are dramatically different between the northern and southern basins. The intermediate and mode waters of the southern basin have increased by as much as 75%o since GEOSECS. Waters of similar density in the northern hemisphere are not exposed to the Southern Ocean circulation regime and are significantly less ventilated, showing maximum changes of ca. 50%.
id: 38

Amazon continental margin high resolution records of the penultimate interglacial - Showers, W. J.; Genna, B.; Price, P. (Eos, Transactions, American Geophysical Union, 1995)
id: 1276

Amazon Continental Margin High Resolution Records of Western Tropical Atlantic circulation over the past 130 ky - Showers, William J.; Genna, Bernard; Price, Pamela (International Conference of Paleoceanography, 1995)
id: 1280

Climatically Linked Carbon-Isotope Variation during the Past 430,000 Years in Southern-Ocean Sediments - Singer, A. J.; Shemesh, A. (Paleoceanography, 1995)
We use the isotopic composition of carbon from organic matter enclosed within diatom frustules as a proxy for paleoproductivity and paleo-dissolved carbon dioxide concentrations in ocean surface waters. A Southern Ocean record from south of the Antarctic Polar Front and spanning 430,000 years of carbon isotopic variation in diatomaceous organic matter is presented for the first time. The most refractory diatomaceous organic matter fraction was extracted and analyzed to avoid problems associated with diagenesis. The results clearly indicate cyclic changes in organic carbon isotopic ratios, with C-13 depleted values associated with all of the last five glacial periods, reflecting changes in surface water properties and primary productivity. Changes in dissolved carbon dioxide concentrations are the most probable cause of these cycles, but the possible effect of seawater pH changes cannot be excluded.
Rd382Times Cited:54Cited References Count:43

Coastal Massachusetts Pond Development - Edaphic, Climatic, and Sea-Level Impacts since Deglaciation - Winkler, M. G.; Sanford, P. R. (Journal of Paleolimnology, 1995)
Kettle ponds in the Cape Cod National Seashore in southeastern Massachusetts differ in their evolution due to depth of the original ice block, the clay content of outwash in their drainage basins, and their siting in relation to geomorphic changes caused by sea-level rise, barrier beach formation, and saltmarsh development. Stratigraphic records of microfossil, carbon isotope, and sediment changes also document late-glacial and Holocene climatic changes.The ponds are separated into 3 groups, each of which follow different development scenarios. Group I ponds date from the late-glacial. They formed in clay-rich outwash, have perched aquifers and continuous lake sediment deposition. The earliest pollen and macrofossil assemblages in Group I pond sediments suggest tundra and spruce-willow parklands before 12 000 yr B.P., boreal forest between 12 000 and 10 500 yr B.P., bog/heath initiation and expansion during the Younger Dryas between 11 000 and 10 000 yr B.P., northern conifer forest between 10 500 and 9500 yr B.P., and establishment of the Cape oak and pitch pine barrens vegetation after 9500 yr B.P. Sedimentation rate changes suggest lowered freshwater levels between 9000 and 5000 yr B.P. caused by decreased precipitation on the Atlantic Coastal Plain. Lake sediment deposition began in the middle Holocene in Group II ponds which formed in clay-poor outwash. These ponds date from about 6000-5000 yr B.P. In these ponds sediment deposition began as sea level rose and the freshwater lens intersected the dry basins. The basal radiocarbon dates of these ponds and stable carbon isotope analyses of the pond sediments suggest a sea-level curve for Cape Cod Bay. Holocene topographic changes in upland and the landscape surrounding the ponds is reconstructed for this coastal area.Group III ponds in the late Holocene landscape of the Provincelands dunes originated as interdunal bogs about 1000 yr B.P. and became ponds more recently as water-levels increased. Feat formation in the Provincelands reflects climatic changes evident on both sides of the Atlantic region.
Td951Times Cited:1Cited References Count:62

Developments at the NOSAMS Facility During 1995 - von Reden, K. F.; Cohen, G. J.; Dalton, M. J.; Peden, J. C.; Schneider, R. J. (Symposium of Northeastern Accelerator Personnel, 1995)
id: 1799

Environmental History of the Lake Winnebago Basin: 15,000 Years Ago to 1850 - Smith, G. L. Fitzgerald T. M. Gruber M. M. Smith S. R. (Wisconsin Academy of Sciences, Arts and Letters, 125th Annual Conference, 1995)
id: 916

Geological framework, processes, and rates of subsidence in the Mississippi River delta plain - Penland, P. Shea; Jeffress, Williams S.; Roberts, Harry H.; Bailey, Alan; Kuecher, Gerald J.; Suhayda, Joseph N.; Ramsey, Karen E. (AAPG Bulletin, 1995)
id: 65

Glacial-Interglacial Differences in Circulation and Carbon Cycling within the Upper Western North-Atlantic - Slowey, N. C.; Curry, W. B. (Paleoceanography, 1995)
We investigated glacial-interglacial changes in the circulation and carbon cycling in the western North Atlantic subtropical gyre using hydrographic data and downcore records of the stable isotopic compositions of individual shells of Bahamian benthic foraminifera. Potential temperature-salinity-depth relations show that modern thermocline (similar to 200-1000 m) and deep (similar to 1000-2000 m) waters in the Providence Channels, Bahamas, originate in the Sargasso Sea and are typical of the subtropical gyre. Gradients in the stable isotopic compositions of late Holocene Planulina and Cibicidoides species from the bank margins (similar to 400 to 1500 m depth) reflect temperature, nutrient, and isotopic gradients of modern subtropical gyre waters. The difference between the delta(18)O of glacial maximum and late Holocene foraminifera is similar to 2.1 parts per thousand for the upper 900 m of the water column and similar to 1.6 parts per thousand for deeper waters, indicating that these waters were similar to 4 degrees C and similar to 2 degrees C cooler, respectively, during glacial time. The glacial temperature gradient (dT/dz) was similar to today, while the base of the thermocline was similar to 100 m shallower. These results differ significantly from our earlier results from multiple shell delta(18)O analyses, which implied upper thermocline waters were only similar to 1 degrees C cooler and dT/dz was greater during the glacial maximum. The difference occurs because bioturbation adversely affects multiple shell analyses of glacial-aged samples from shallow water depths. At all depths above 1500 m, foraminiferal delta(13)C are greater during the glacial maximum than the late Holocene by at least 0.1 to 0.2 parts per thousand (as much as 0.6 parts per thousand in the lower thermocline), indicating that nutrient concentrations throughout the thermocline were reduced and there was no oxygen minimum zone during the glacial maximum. This suggests greater, more uniform ventilation of the thermocline. Results of single and multiple shell delta(13)C analyses of glacial age foraminifera compare favorably because samples most affected by mixing correspond to water depths where the glacial-interglacial change of delta(13)C was small. Cooler upper ocean waters during the glacial maximum reflect cooler temperatures at the ocean surface where isopycnal surfaces outcrop, including large areas of the subtropical ocean. A shallower thermocline base is consistent with southward migration of the northern edge of the subtropical gyre or increased mode water production. Enhanced thermocline ventilation is consistent with more vigorous winds and all isopycnal surfaces outcropping in the area of Ekman downwelling.
Rm032Times Cited:80Cited References Count:86

Improvements in procedural blanks at NOSAMS: Reflections of improvements in sample preparation and accelerator operation - McNichol, A. P.; Gagnon, A. R.; Osborne, E. a; Hutton, D. L.; von Reden, K. F.; Schneider, R. J. (15th International 14C Conference, 1995)
id: 1641; 15th International Radiocarbon Conference, Glasgow, Scotland, August 15-19, 1994

Improvements in procedural blanks at NOSAMS: Reflections of improvements in sample preparation and accelerator operation - McNichol, A. P.; Gagnon, A. R.; Osborne, E. A.; Hutton, D. L.; vonReden, K. F.; Schneider, R. J. (Radiocarbon, 1995)
During the four years the Sample Preparation Laboratory (SPL) at the National Ocean Sciences Accelerator Mass Spectrometer (NOSAMS) Facilty has been in operation we have accumulated much data from which we can assess our progress. We evaluate our procedural blanks here and describe modifications in our procedures that have improved our analyses of older samples. In the SPL, we convert three distinct types of samples-seawater, CaCO3 and organic carbon-to CO2 prior to preparing graphite for the accelerator and have distinct procedural blanks for each procedure. Dissolved inorganic carbon (Sigma CO2) is extracted from acidified seawater samples by sparging with a nitrogen carrier gas. We routinely analyze ''line blanks'' by processing CO2 from a C-14-dead source through the entire stripping procedure. Our hydrolysis blank, IAEA C-1, is prepared by acidifying in vacuo with 100% H3PO4 at 60 degrees C overnight, identical to our sample preparation. We use a dead graphite, NBS-21, or a commercially available carbon powder for our organic combustion blank; organic samples are combusted at 850 degrees C for 5 h using CuO to provide the oxidant. Analysis of our water stripping data suggests that one step in the procedure contributes the major portion of the line blank. At present, the contribution from the line blank has no effect on our seawater analyses (fraction modern (fm) between 0.7 and 1.2). Our hydrolysis blanks can have an fm value as low as 0.0006, but are more routinely between 0.0020 and 0.0025. The fm of our best organic combustion blanks is higher than those routinely achieved in other laboratories and we are currently altering our methods to reduce it.
Ud868Times Cited:16 Cited References Count:6
Keywords: SPECTROMETRY

Late Pleistocene Oxygen-Isotope Records of Biogenic Silica from the Atlantic Sector of the Southern-Ocean - Shemesh, A.; Burckle, L. H.; Hays, J. D. (Paleoceanography, 1995)
We determined the isotopic composition of oxygen in marine diatoms in eight deepsea cores recovered from the Atlantic sector of the Southern Ocean. The analytical reproducibility and core-to-core consistency of the isotopic signal suggests that diatom delta(18)O can be used as a new paleocenographic tool to reconstruct past variations in surface water characteristics and to generate O-18 -isotope-based stratigraphy for the Southern Ocean. The data indicate that diatom delta(18)O reflects sea surface temperature and seawater isotopic composition and that diatoms retain their isotopic signal on timescales of a least 430 ka. The delta(18)O analyses of different diatom assemblages reveal that the isotopic signal is free of species effects and that the common Antarctic species have the same water-opal fractionation. The transition from the last glacial maximum (LGM) to the Holocene is fully recorded in high sedimentation rate cores. An O-18 enrichment during the LGM, a post-LGM meltwater spike and an input of meltwater during the late Holocene are the main isotopic features observed in down core records. The origin of this meltwater was very likely melting icebergs and/or continental ice or by melting sea ice that had accumulated snow. The most pronounced meltwater effects are recorded in cores that are associated with the Weddel gyre. Our results provide the basis for extending isotope studies to oceanic regions devoid of carbonate; further, isotopic stratigraphies may be constructed for records and regions where they were previously not possible.
Rd382Times Cited:82Cited References Count:23

Late Pleistocene to Holocene Diatom Assemblages of the Lake Winnebago Basin, Wisconsin - Smith, S. R. Smith G. L. (North-Central/South-Central Section, Geological Society of America, 1995)
id: 915

Late Pleistocene to Holocene paleolimnolgy of the Lake Winnebago Basin, based on ostracods - Gruber, M. M.; Smith, G. L. (Abstracts with Programs - Geological Society of America, 1995)
id: 75

Late Pleistocene to Holocene Paleolimnology of the Lake Winnebago Basin, Based on Ostracods - Gruber, M. M.; Smith, G. L. (North-Central/South-Central Section,Geological Society of America, 1995)
id: 909

Late Quaternary Depositional History of the Lake Winnebago Basin - Fitzgerald, T. M.; Smith, G. L. (North-Central/South_Central Section, Geological Society of America, 1995)
id: 908

Late Wisconsinan stratigraphy and deglaciation chronology of the lower Aroostook River Valley, Maine - Strasser, J. C.; Weddle, T. K.; Dorion, C. C. (Geological Society of America, Northeastern Section, 30th annual meeting, 1995)
id: 1238

Measurements of the OX-II/OX-1 ratio as a quality control parameter at NOSAMS - Schneider, R. J.; McNichol, A. P.; Nadeau, M. J.; von Reden, K. F. (Radiocarbon, 1995)
id: 1630

Measurements of the OX-II/OX-I ratio as a quality control parameter at NOSAMS - Schneider, R. J.; McNichol, A. P.; Nadeau, M. J.; von Reden, K. F. (15th International Radiocarbon Conference, 1995)
id: 944

Negative ion sources for dating a very small radiocarbon samples - Nadeau, M. J.; Schneider, R. J.; von Reden, K. R. (15th International Radiocarbon Conference, 1995)
id: 943

Origin of Carbon in Fumarolic Gas from Island Arcs - Sano, Y.; Marty, B. (Chemical Geology, 1995)
We have measured He-3/He-4 ratios, delta(13)C-values and CO2/He-3 ratios of fumaroles and hot spring gases in three volcanic areas in Japan. The He-3/He-4 ratios, delta(13)C-values and CO2/He-3 ratios vary from 2.02 R(atm) to 7.55 R(atm) -9.7 parts per thousand to -2.7 parts per thousand and from 7.74.10(9) to 1.18.10(11), respectively. Based on these data and those in the literature, we present the first quantitative estimates of the upper mantle, sediment and limestone including slab components in CO2 of volcanic and hydrothermal fluids from subduction zones. Taking compiled C isotopic data of limestone and organic sediment, assuming that the CO2/He-3 ratio and delta(13)C-value of mid-ocean ridge basalt (MORB) are representative of the upper-mantle component, and that later isotopic and elemental fractionations are minimal, it is possible to deconvolve each fraction of C on the basis of simple mixing equations. Up to 20% of the carbon in high-temperature volcanic gases in subduction zones is derived from a MORB-type source, while the major fraction of the gases is attributable to CO2 produced by decarbonation of subducted marine limestone and slab carbonate.
Qc329Times Cited:227Cited References Count:46

Paleodischarge events on the Amazon Fan during the last glacial - Showers, William J.; Genna, Bernard; Price, Pamela; Flood, Roger; Piper, David (AGU Annual Fall Meeting, 1995)
id: 1281

Sampling Cruise 6, North Atlantic Tracer Release Experiment, R/V Seward Johnson, Cruise 9404 - Ledwell, J. R.; Donoghue, T.; Donoghue, J.; Sundermeyer, M. (Woods Hole Oceanographic Institution, 1995)
id: 1754

Status of understanding of the saturated-zone ground-water flow system at Yucca Mountain, Nevada, as of 1995, Report - Steinkampf, W. C. (1995)
id: 1285

Stratigraphic Evidence of Changes in Amazon Shelf Sedimentation during the Late Holocene - Sommerfield, C. K.; Nittrouer, C. A.; Figueiredo, A. G. (Marine Geology, 1995)
Late Holocene sedimentation on the Amazon shelf was investigated using a combination of seismic, sedimentological, and geochronological methods. Piston cores collected in the subaqueous delta region during A Multidisciplinary Amazon Shelf Sediment Study (AmasSeds) penetrated a regionally traceable (1.25 x 10(4) km(2)) seismic discontinuity, which corresponds to a dense relict-mud reflector overlain by acoustically transparent sediment. Distinct offsets in profiles of wet-bulk density, P-wave velocity, and Pb-210 activity are noted in cores at the reflector horizon (unconformity), signifying a past change in sedimentation conditions on the shelf. Bulk-sediment C-14 dating indicates net depositional conditions for the subaqueous delta from >1800 yr B.P. to 700 yr B.P. and a net erosional phase from about 700 yr B.P. to 100 yr ago. Sedimentological evidence of the erosional phase includes lag deposits and burrows present at the unconformity surface in piston cores. The deposits above and below the unconformity are similar with respect to grain-size parameters and sedimentary structures, suggesting that environmental conditions during the two depositional periods were similar. According to C-14 dates of coastal deposits, the shoreline of Amapa State, Brazil served as a major depocenter of Amazon mud during the erosional phase on the shelf. Pb-210 geochronology indicates that the most recent phase of sediment accumulation in the study area commenced about 100 yr ago, resulting in rapid progradation of topset deposits and burial of relict strata. In the present environment, oceanographic and meteorologic processes cause along-shelf variations in sediment dispersal and depositional patterns, and about 1400 km(2) of the erosional relict deposits are still exposed at the seabed. The short time scales over which Amazon shelf strata respond to changes in the physical environment preclude the influence of relative sea-level cyclicity on recent sedimentation patterns. During the late Holocene, sedimentation and strata formation on the Amazon shelf are linked to fluvial, oceanographic and meteorologic processes that affect sediment supply, deposition and erosion.
Rt489Times Cited:33Cited References Count:65

Variability in the Benguela Current upwelling system over the past 70,000 years - Summerhayes, C. P.; Kroon, D.; Rosell-Mele, A.; Jordan, R. W.; Schrader, H. J.; Hearn, R.; Villanueva, J.; Grimali, J. O.; Eglinton, G. (Progress in Oceanography, 1995)
This study was designed to see if the intensity and location of upwelling in the Benguela Current Upwelling System off Namibia changed significantly during the last 70,000 years. Most of the analytical work focused on geochemical, micropalaeontological and stable isotopic analyses of a 6.5m long combined pilot and piston core, PGPC12, from 1017m on the continental slope close to Walvis Bay. The slope sediments are rich in organic matter. Most of it is thought to represent deposition beneath a productive shelf edge upwelling system, but some is supplied by downslope near-bottom flow of material probably resuspended on the outer continental shelf. Temporal changes in upwelling intensity as represented by fluctuations in the accumulation of organic matter do not show the simple 'classical' pattern of less upwelling and lower productivity in interglacials and more upwelling and higher productivity in glacials, but instead show a pattern of higher frequency fluctuations. The broad changes in organic carbon accumulation reach maxima at times when the earth-sun distance was greatest, indicating that this accumulation responded to changes in the precession index; at these times monsoons would have been weakest and Trade Winds strongest. Maximum accumulation of organic matter on the slope occurred in the last interstadial (isotope stage 3), and coincided with coldest sea surface temperatures as recorded by alkenone data (U(37)(k)), and by nannofossil assemblages. It is attributed largely to increased productivity in situ, rather than the lateral supply of material eroded from older organic rich deposits exposed by the lowering of sealevel at that time. The enhanced productivity is attributed to a strengthening of upwelling-favourable winds in this area in response to the minimal solar insolation typical of this period. Diatoms generally are not abundant in these sediments, so appear to be unreliable indicators of productivity over the continental slope. When sealevel was lowest (isotope stages 2 and 4) organic matter previously deposited on the continental shelf was eroded and dumped on the continental slope; this reworked material constitutes up to 43% of the flux of organic matter to the slope at these times. This process did not affect the slope in stage 3, when sealevel fell by only 50m. The accumulation of terrigenous material was highest in stages 2 and 4. The available data suggest that the terrigenous influx at those times was primarily aeolian. We interpret this to mean that more of the winds then came from the east ('Berg' winds), bringing an influx of aeolian dust from the hinterland; these easterlies were less favoarable for upwelling than were the more southerly Trade Winds that dominated during stage 3. Carbonate accumulation was least in stages 2 and 4, largely in response to dissolution induced by CO(2)-rich bottom waters.
V07zbTimes Cited:100Cited References Count:147

Ventilation of the deep Pacific Ocean - Key, R. M.; Rooth, C.; Ostlund, G.; Stuiver, M. (Supplement to Trans. American Geophysic. Union, 1995)
id: 41

Analysis of a large hydrochemical data base for the Death Valley region, Nevada and California - Perfect, D. L.; Steinkampf, W. C.; Turner, A. K. (Eos, Transactions, American Geophysical Union, 1994)
id: 1286

The Application of AMS to Organic Geochemistry--Constraints Imposed by Sample Preparation and Machine Operations - McNichol, A. P.; von Reden, K. F.; Schneider, R. J.; Jones, G. A. (EOS, Transactions of the American Geophysical Union, 1994)
id: 1798

Comparative-Study of Fe-C Bead and Graphite Target Performance with the National-Ocean-Science-Ams (Nosams) Facility Recombinator Ion-Source - Klinedinst, D. B.; McNichol, A. P.; Currie, L. A.; Schneider, R. J.; Klouda, G. A.; vonReden, K. F.; Verkouteren, R. M.; Jones, G. A. (Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions with Materials and Atoms, 1994)
An accelerator mass spectrometry (AMS) experiment was designed to investigate C-14 target performance for two target types over a range of isotopic concentrations and sample sizes, with a special focus on the ability to measure C-14 in environmental samples having only microgram amounts of carbon. The findings were positive, showing that precision, accuracy, and stability were adequate to determine C-14 to 1% or better in samples containing as little as 25 mug carbon. Satisfactory Poisson uncertainty and target stability were demonstrated down to a level of 7 mug carbon, but experimental data showed that accurate measurements at that level require detailed knowledge of blank variability and mass dependence of the modern carbon calibration factor.
Nv547Times Cited:23Cited References Count:13

Constraints Imposed by Sample Preparation and Machine Operations - McNichol, A. P.; von Reden, K. F.; Schneider, R. J.; Jones, G. A. (EOS, Transactions of the American Geophysical Union, 1994)
id: 937

Contamination in Boston Harbor and Massachusetts Bay - Bothner, M. H.; Butman, B.; Signell, R. P. (United States Geological Survey Yearbook, 1994)
id: 1231

Do AMS measurements approach a Gaussian distribution? - Jirikowic, J. L.; Schneider, R. J.; von Reden, K. F.; Jones, G. A. (15th International Radiocarbon Conference, 1994)
id: 940

Glacial/interglacial slope sedimentation changes on the Pleistocene NJ margin, ODP Site 904A - Christensen, B. A.; Thunell, R.; Miller, K. G.; Smith, N.; Cockrell, K. (Eos, Transactions, American Geophysical Union, 1994)
id: 54

High Precision Sea Water 14C Analyses at the National Ocean Sciences AMS Facility - von Reden, K. F.; Jones, G. A.; Schneider, R. J.; McNichol, A. P. (EOS, Transactions of the American Geophysical Union, 1994)
id: 939

High-precision AMS radiocarbon measurements of central Arctic Ocean seawaters - Jones, G. A.; Gagnon, A. R.; Schneider, R. J.; von Reden, K. F.; McNichol, A. P. (Nuclear Instruments and Methods in Physics Research, 1994)
id: 52

High-precision sea water 14C analyses by accelerator mass spectrometry. 15th International Radiocarbon Conference, Glasgow, Scotland, August 15-19 - von Reden, K. F.; Jones, G. A.; Schneider, R. J.; McNichol, A. P. (EOS, Transactions of the American Geophysical Union, 1994)
id: 941

Hydrochemical data base for the Death Valley region, California and Nevada - Perfect, D. L.; Faunt, C. C.; Steinkampf, W. C.; Turner, A. K. (Open-File Report--U. S. Geological Survey, 1994)
id: 1287

Lake-Level History of Lake-Michigan for the Past 12,000 Years - the Record from Deep Lacustrine Sediments - Colman, S. M.; Forester, R. M.; Reynolds, R. L.; Sweetkind, D. S.; King, J. W.; Gangemi, P.; Jones, G. A.; Keigwin, L. D.; Foster, D. S. (Journal of Great Lakes Research, 1994)
Collection and analysis of an extensive set of seismic-reflection profiles and cores from southern Lake Michigan have provided new data that document the history of the lake basin for the past 12,000 years. Analyses of the seismic data, together with radiocarbon dating, magnetic, sedimentologic, isotopic, and paleontologic studies of core samples, have allowed us to reconstruct lake-level changes during this recent part of the lake's history.The post-glacial history of lake-level changes in the Lake Michigan basin begins about 11.2 ka with the fall from the high Calumet level, caused by the retreat of the Two Rivers glacier, which had blocked the northern outlet of the lake. This lake-level fall was temporarily reversed by a major influx of water from glacial Lake Agassiz (about 10.6 ka), during which deposition of the distinctive gray Wilmette Bed of the Lake Michigan Formation interrupted deposition of red glaciolacustrine sediment. Lake level then continued to fall, culminating in the opening of the North Bay outlet at about 10.3 ka. During the resulting Chippewa low phase, lake level was about 80 m lower than it is today in the southern basin of Lake Michigan. The rise of the early Holocene lake level, controlled primarily by isostatic rebound of the North Bay outlet, resulted in a prominent, planar, transgressive unconformity that eroded most of the shoreline features below present lake level. Superimposed on this overall rise in lake level, a second influx of water from Lake Agassiz temporarily raised lake levels an unknown amount about 9.1 ka. At about 7 ka, lake level may have fallen below the level of the outlet because of sharply drier climate. Sometime between 6 and 5 ka, the character of the lake changed dramatically, probably due mostly to climatic causes, becoming highly undersaturated with respect to calcium carbonate and returning primary control of lake level to the isostatically rising North Bay outlet. Post-Nipissing (about 5 ka) lake level has fallen about 6 m due to erosion of the Port Huron outlet, a trend around which occurred relatively small (+/- approximately 2 m), short-term fluctuations controlled mainly by climatic changes. These cyclic fluctuations are reflected in the sedimentological and sediment-magnetic properties of the sediments.
Nl348Times Cited:47 Cited References Count:29
Keywords: lake michigan; ostracodes; radiocarbon; sedimentology; sediments; southern

Latest Quaternary Sedimentation in the Kerch Strait Area of the Black Sea Shelf: Response to Glacial Sea Level Fluctuation - Major, C. O.; Ryan, W. B. F.; Pitman, W. C., III; Shimkus, K. M.; Jones, G. A.; O'Connell, S. (EOS,Transactions,American Geophysical Union, 1994)
id: 914

Methods for Data Screening, Flagging and Error Analysis at the National-Ocean-Sciences-Ams-Facility - Schneider, R. J.; Jones, G. A.; McNichol, A. P.; vonReden, K. F.; Elder, K. L.; Huang, K.; Kessel, E. D. (Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions with Materials and Atoms, 1994)
All data collection, from sample submittal through processing into targets and AMS analysis, is integrated within a large relational database (Sybase). Over 50 tables are linked through key fields. Through structured queries, the information is analysed and presented for a wide variety of applications. Benefits include enhanced quality control, more complete reports to users and more accurate transfer of data among the several laboratories on the network.
Nv547Times Cited:14Cited References Count:4

The National Ocean Sciences Accelerator Mass Spectrometry Facility: Recent Developments - Schneider, R. J.; Jones, G. A.; von Reden, K. F.; McNichol, A. P. (EOS, Transactions of the American Geophysical Union, 1994)
id: 938

ODP Initial Reports, Leg 150X - Miller, K. G.; Liu, C.; Browning, J. V.; Pekar, S. F.; Sugarman, P. J.; Van Fossen, M. C.; Mullikin, L.; Queen, D.; Feigenson, M. D.; Aubry, M. P.; Burckle, L. D.; Powars, D.; et al. (Ocean Drilling Program, 1994)
id: 1347

Optimized Data Analysis for AMS Radiocarbon Dating - Séguin, F. H.; Schneider, R. J.; Jones, G. A.; von Reden, K. F. (Nuclear Instruments & Methods in Physics Research Section B - Beam Interactions with Materials and Atoms, 1994)
id: 1617; PBS Record: 240; (03) FH Seguin/Mit/Cambridge, MA 02139 USA (42) English Article (44) NV547

A paleoenvironmental study of the southern Champlain Sea, Thesis - Schlegel, Mary Ann (MIT, 1994)

Performance Characteristics of the 3-MV Tandetron AMS System at the National Ocean Sciences AMS Facility - von Reden, K. F.; Schneider, R. J.; Cohen, G. J.; Jones, G. A. (Nuclear Instruments & Methods in Physics Research Section B - Beam Interactions with Materials and Atoms, 1994)
id: 1619; PBS Record: 60; (03) KF Vonreden/Woods Hole Oceanog Inst/Natl Ocean Sci Accelerator/Mass Spectrometry Facil/Woods Hole, MA 02540 USA (42) English Article (44) NV547
Keywords: ACCELERATOR MASS-SPECTROMETER

Progress at the Woods Hole AMS Facility - Schneider, R. J. (13th International Conference on the Applications of Accelerators in Research and Industry, 1994)
id: 964

Redifinition of the "Blake Event" based on new paleomagnetic results from deep sea sediments of the Blake-Bahama Outer Ridge - Henyey, S.; Lund, S. P.; Schwart, M.; Keigwin, L. (Eos, Transactions, American Geophysical Union, 1994)
id: 33

Thermocline Ventilation Rates in the North Pacific - Sonnerup, R. E.; Quay, P. D.; Bullister, J. L.; Key, R. M.; McNichol, A. P.; Jones, G. A. (American Geophysical Union, San Francisco, 1994)
id: 917

Comparative study of Fe-C Bead vs. graphite target performance with the NOSAMS Facility recombinator ion source - Kleindinst, D. B.; McNichol, A. P.; Currie, L. A.; Jones, G. A.; Verkouteren, R. M.; von Reden, K. F.; Klouda, G. A.; Schneider, R. J. (6th International Conference on Accelerator Mass Spectrometry, 1993)
id: 931

The high-precision AMS 14C program on seawater at the National Ocean Sciences AMS Facility - von Reden, K. F.; Jones, G. A.; Schneider, R. J.; McNichol, A. P. (European Community Workshop on Development of Ocean Tracer Measurements, 1993)
id: 1767

High-precision AMS radiocarbon measurements of seawater at the National Ocean Sciences AMS Facility - Jones, G. A.; Schneider, R. J.; McNichol, A. P.; von Reden, K. F. (6th International Conference on Accelerator Mass Spectrometry, 1993)
id: 929