P16C TUNES-3 final report for AMS 14C samples - Key, R. M.; Quay, P. (Ocean Tracer Laboratory Technical Report, 1996)
id: 1453

P16C TUNES-3 final report for AMS 14C samples (Report) - Key, R. M.; Quay, P. (Ocean Tracer Laboratory Tech. Report, 1996)
id: 1251

P16S17S TUNES-2 final report for AMS 14C samples - Key, R. M. (Ocean Tracer Laboratory Tech. Rep., 1996)
id: 1452

P16S17S TUNES-2 final report for large volume samples - Key, R. M. (Ocean Tracer Laboratory Tech. Rep., 1996)
id: 1451

P17C TUNES-1 final report for AMS 14C samples - Key, R. M. (Ocean Tracer Laboratory Tech. Report, 1996)
id: 1249

P17C TUNES-1 final report for large volume samples - Key, R. M. (Ocean Tracer Laboratory Tech. Rept, 1996)
id: 1449

P17E19S Final report for large volume samples and D14C measurements - Key, R. M. (Ocean Tracer Laboratory Tech. Rep., 1996)
id: 1455

P17N Final report for large volume samples - Key, R. M. (Ocean Tracer Laboratory Tech. Rep., 1996)
id: 1459

P19C Final report for large volume samples and D14C measurements - Key, R. M. (Ocean Tracer Laboratory Tech. Rep., 1996)
id: 1458

P6 final report for AMS 14C samples - Key, R. M. (Ocean Tracer Laboratory Tech. Rep., 1996)
id: 1456

The paleoecology and pH history of Ike Walton Lake and comparison with the recent history of Zee Lake. Report - Winkler, M. G. (Lac du Flambeau Water Resources Program Contract #1243, 1996)
id: 1325

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

PC17 TUNES-1 final report for AMS 14C samples - Key, R. M. (Ocean Tracer Laboratory Tech. Rept., 1996)
id: 1450

Petroleum Geochemistry and Geology - Hunt, John M. (W. H. Freeman & Company, 1996)
id: 1558

Post-bomb radiocarbon records of surface corals from the tropical Atlantic Ocean - Druffel, E. R. M. (Radiocarbon, 1996)
Delta(14)C records are reported for post-bomb corals from three sites in the tropical Atlantic Ocean. In corals from 18 degrees S in the Brazil Current, Delta(14)C values increased from ca.-58 parts per thousand in the early 1950s to +138 parts per thousand by 1974, then decreased to 110 parts per thousand by 1982 Shorter records from 8 degrees S off Brazil and from the Cape Verde Islands (17 degrees N) showed initially higher Delta(14)C values before 1965 than those at 18 degrees S, but showed lower rates of increase of Delta(14)C during the early 1960s. There is general agreement between the coral results and Delta(14)C of dissolved inorganic carbon (DIC) measured in seawater previously for locations in the tropical Atlantic Ocean. Delta(14)C values at our tropical ocean sites increased at a slower rate than those observed previously in the temperate North Atlantic (Florida and Bermuda), owing to the latter's proximity to the bomb C-14 input source in the northern hemisphere. Model results show that from 1960-1980 the Cape Verde coral and selected DIC Delta(14)C values from the North Equatorial Current agree with that calculated for the North Atlantic based on an isopycnal mixing model with a constant water mass renewal rate between surface and subsurface waters. This is in contrast to Delta(14)C values in Bermuda corals that showed higher post-bomb values than those predicted using a constant water mass renewal rate, hence indicating that ventilation in the western north Atlantic Ocean had decreased by a factor of 3 during the 1960s and 1970s (Druffel 1989).
Xd080Times Cited:25 Cited References Count:20
Keywords: atmosphere; banded corals; bermuda; C-14; pacific; rings; ventilation

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

Preparative capillary gas chromatographic isolation of individual compounds from complex matrices for radiocarbon dating - Eglinton, T. I.; Aluwihare, L. I.; Bauer, J. E.; Druffel, E. R. M.; McNichol, A. P. (Analytical Chemistry, 1996)
id: 1340

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. (Workshop on Applications of AMS to Global Climate Change, 1996)
id: 1768; 1

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, 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

Recession of the late Wisconsinan Ice Sheet from the northwestern White Mountains, New Hampshire (Book Section) - Thompson, W. B.; Fowler, B. K.; Flanagan, S. M.; Dorion, C. C. (New England Intercollegiate Geological Conference Guidebook for Field Trips in Northern New Hampshire and Adjacent regions of Maine and Vermont, 1996)
id: 18

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

Ryder Pond: A drought-induced natural acidification experiment - Winkler, M. G.; Portnoy, J. (Ecological Society of America (ESA) meeting, 1996)
id: 94

Seasonal oxygen depletion in continental-shelf waters of Louisiana; historical record of benthic foraminifers - Sen Gupta, B. K.; Turner, R. E.; Rabalais, N. N. (Geology, 1996)
id: 85

Seasonal variability of particulate organic radiocarbon in the northeastern Pacific - Druffel, Ellen R. M.; Bauer, J. E.; Williams, P. M.; Griffin, S.; Wolgast, D. (Journal of Geophysical Research, 1996)
id: 1239

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: Contribution from NOSAMS - McNichol, A. P.; Key, R.; Jones, G. (Supplement to Trans. Amer. Geophysical Union, 1996)
id: 1266

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

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

Surficial geology of the middle and upper continental slope, northern Gulf of Mexico; the important role of episodic fluid venting - Roberts, H. H. (AAPG Bulletin, 1996)
id: 1272

TIMS U-Th dated early Holocene sea-level record from submerged fossil reefs, southeast Florida margin - Lundberg, J.; Toscano, M. A. (Abstracts with Programs--Geological Society of America, 1996)
id: 1263

Uranium-series disequilibrium, sedimentation, diatom frustules, and paleoclimate change in Lake Baikal - Edgington, D. N.; Robbins, J. A.; Colman, S. M.; Orlandini, K. A.; Gustin, M. P. (Earth and Planetary Science Letters, 1996)
The large volume of water, approximately one-fifth of the total surface fresh water on the planet, contained in Lake Baikal in southeastern Siberia is distinguished by having a relatively high concentration of uranium (ca. 2 nM), and, together with the surface sediments, an unusually high U-234/U-238 alpha activity ratio of 1.95. About 80% of the input of 234 uranium to the lake, with a U-234/U-238 ratio of 2.0, comes from the Selenga River, Profiles of uranium, as well as the extent of isotopic disequilibrium in a 9 m sediment core collected on Academic Ridge, generally show high values during interglacial periods corresponding to high diatom frustule numbers (DiFr) and biogenic silica (BSi) data that have been reported elsewhere. During glacial periods (low DiFr and BSi), uranium progeny (U-234 and Th-230) were in secular equilibrium with low concentrations of their parent U-238. Radionuclide distributions were interpreted in terms of a quantitative model allowing for adsorption of riverine inputs of uranium onto two classes of sedimenting particles with differing U-238/Th-232 ratios and uranium progeny in secular equilibrium. If the U-234/U-238 activity ratio of adsorbed uranium has remained constant, mean sedimentation rates can be independently estimated as 3.6 +/- 0.6 and 3.7 +/- 0.9 cm . kyr(-1) for the decay of U-234 and in-growth of Th-230, respectively. These rates are consistent with a mean rate of 3.76 cm . kyr(-1), calculated by optimization of the correspondence between adsorbed U-238 and delta(18)O in dated oceanic sediments, The adsorbed uranium apparently tracks variable river flow during interglacials and is drastically reduced during periods of glaciation. Evidently, uranium has not been significantly redistributed within Baikal sediments over at least the past 250 kyr and is a unique, biologically non-essential, tracer for climate-sensitive processes, which provide their own internal geochronometers, potentially useful for ages up to 1 Myr BP.
Uz230Times Cited:61Cited References Count:29

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

WOCE Pacific Ocean radiocarbon program - Key, R. M. (Radiocarbon, 1996)
Fieldwork for the World Ocean Circulation Experiment (WOCE) radiocarbon program was recently completed. Ca. 9000 samples were collected for analysis using both conventional B-counting techniques and the newer AMS technique. The mean uncertainty for the beta analyses is 3 parts per thousand; for AMS analyses, ca. 4.5 parts per thousand.
Xd080Times Cited:21 Cited References Count:40
Keywords: sciences-ams-facility

Age and paleoclimate of submerged late Pleistocene reef system, Southeast Florida shelf; implications for substage 5A sea level - Toscano, M. A.; Lundberg, J.; Hine, A. C. (Geological Society of America, 1995 annual meeting, 1995)
id: 1242; 6

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

Climate-Change - the North Pacific through the Millennia - Keigwin, L. D. (Nature, 1995)
Rz336Times Cited:6Cited References Count:14

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

Continental climate response to orbital forcing from biogenic silica records in Lake Baikal, Siberia - Colman, S. M.; Peck, J. A.; B, Karabanov E.; Carter, S. J.; Bradbury, J. P.; King, J. W.; Williams, D. F. (Nature, 1995)
id: 1357

Development and application of the mollusc Arctica islandicaas a paleoceanographic tool for the North Atlantic Ocean, Thesis - Weidman, C. R. (MIT, 1995)

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

The eastern chenier plain; an update on downrift coastal progradation associated with the building of a new Holocene delta lobe in the Mississippi delta complex - Roberts, Harry H.; Huh, O. K. (AAPG Bulletin, 1995)
id: 64

The effects of islands on the recession of the late Wisconsinan ice sheet margin in the De Geer Sea, Maine, Thesis - Donner, J. (University of Maine, 1995)

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

Evolution, environment, and isotope systematics of a glauconite deposit on the modern sea floor along the southeastern United States continental margin, Thesis - am Ende, B. A. (University of North Carolina, Chapel Hill, NC, 1995)
id: 1; Department of Geology

A first look at changes in Pacific 14C levels between GEOSECS and WOCE - Key, R. M.; Toggweiler, J. R. (International Association for the Physical Sciences of Oceans, General Assembly, 5-12 August 1995, Honolulu, Hawaii, 1995)
id: 40

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

The Hemispherical Ionizer Sputter Sources at the Woods Hole AMS Facility - von Reden, K. F. (29th Symposium of NorthEastern Accelerator Personnel, 1995)
id: 1671

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

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

Intracrystalline proteins in aragonite-needle mud from Florida Bay: an immunological and biogeochemica study, Thesis - Hawkins, Sharon (University of North Carolina at Chapel Hill, 1995)

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 Quaternary Paleolimnology of the Lake Winnebago Basin, Based on Ostracodes - Gruber, M. M. Smith G. L. (1995)
id: 910

Late Quaternary Relative Sea-Level Change in the Western Gulf of Maine - Evidence for a Migrating Glacial Forebulge - Barnhardt, W. A.; Gehrels, W. R.; Belknap, D. F.; Kelley, J. T. (Geology, 1995)
New radiocarbon-dated cores obtained by Vibracorers in the western Gulf of Maine confirm that a short-lived, relative sea-level lowstand of similar to-55 m occurred at 11-10.5 ka. These cores and younger salt-marsh data also reveal that rates of transgression varied throughout the Holocene, probably due to local variations in glacial isostasy. The isostatic component is resolved by subtracting published approximations of eustatic sea level from our well-determined observations of local relative sea level. A large peek in the isostatic curve coincides with the lowstand and is interpreted as a forebulge 20-25 m in amplitude. Forebulge migration is estimated at 7-11 km/100 yr, based on the timing of lowstands across the region.
Qr847Times Cited:69Cited References Count:32

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

The Marine Record of Deglaciation from the Continental-Margin Off Nova-Scotia - Keigwin, L. D.; Jones, G. A. (Paleoceanography, 1995)
Continental margin sediments off Nova Scotia accumulate at high rates (up to 360 cm kyr(-1)) and contain a history of millennial-scale environmental changes which are dominated by the proximity of the Laurentide ice sheet during the latest Quaternary. Using ratios of oxygen, accelerator mass spectrometer radiocarbon dating, micropaleontology, and sedimentology, we document these changes in six piston cores ranging in water depth from similar to 450 to similar to 4300 m. We find that maximum delta(18)O in N. pachyderma occurred about 15 ka and preceded the maximum abundance of this species in these cores by similar to 1000 years. Between 13 and 14 ka we find a second peak in abundance of N. pachyderma, minimum delta(18)O, and two pulses of ice rafting. The sediment lithology supports terrestrial studies which indicate that there was a general withdrawal of ice beyond the upper Paleozoic and Mesozoic red beds by 14 ka in southeastern Canada, so the ice rafting events between 13 and 14 ka probably reflect ice stream activity in the St. Lawrence valley. The Younger Dryas event is recognized as a peak in abundance of N. pachyderma and ice rafting (dated as similar to 11.3 ka), but meltwater discharge to the Gulf of St. Lawrence was either too small or occurred over too long a time to leave a distinct delta(18)O minium off Nova Scotia. At 7.1 ka, in the middle of Holocene warming, we find a third peak in abundance of N. pachyderma and another delta(18)O minimum but no ice rafting. We interpret these data as evidence of a late-occurring meltwater event which, if correct, could have originated in the Great Lakes, in the Labrador-Ungava region, or in both. The final millennial-scale phenomenon off Nova Scotia is the onset of ''Neoglaciation,'' marked by increased ice rafting and increased % N. pachyderma beginning about 5 kyr ago.
Th675Times Cited:85Cited References Count:77

Marsh accretion and relative sea level rise since AD 1000 - Varekamp, J. C.; E, Thoma (Geological Society of America, 1995 annual meeting, 1995)
id: 1290; 6

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

Mud volcanoes in the Gulf of Mexico; a mechanism for mixing sediments of different ages in slope environments - Kohl, Barry; Roberts, Harry H. (Gulf Coast Association of Geological Societies Transactions, 1995)
The extrusion of older, unconsolidated sediments onto the seafloor during the Quaternary is one explanation for frequent occurrences of displaced fossil microfaunas encountered at depth in wells drilled on the flanks of salt diapirs in the continental slope environment. Samples from mud volcanoes on the Louisiana continental slope were collected in 1992 and 1993 for foraminiferal studies by using the Johnson Sea-Link I & II manned submersibles. Age dating by use of planktonic foraminifera has shown that sediments ranging in age from middle Miocene to Pleistocene are being deposited on the modern seafloor by active mud vents/volcanoes. These sediments, when buried by modern pelagic or more rapidly deposited terrigenous clastics, would be anomalous when encountered in coreholes or exploratory wells. Vents, as shown by seismic sections, are associated with faults which provide the connection to older subsurface fine-grained sediments that are: 1) mobilized by gas and fluids, 2) carried to the surface, and 3) ejected onto the seafloor to form mud volcanoes and fine-grained sediment flows. The mud volcanoes are in water depths ranging from 300 to 690 meters located in Garden Banks Block 382, Green Canyon Blocks 143 and 272, and Mississippi Canyon Block 929. This study is part of an ongoing investigation of the geology around cold vents which support chemosynthetic faunal communities in the Gulf of Mexico. These results have important implications for age dating subsurface sediments encountered in wells and coreholes on the continental slope.
id: 63

Multiple Indicator Approach to Interpreting Abrupt Climate Changes in the North Atlantic. Program and Abstracts - Kellog, T. B.; Wright, J. D.; Kellogg, D. E.; Lagerklint, I. M.; French, P. L. (5th International Conference on Paleoceanography, 1995)
id: 96

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

North Atlantic Deep Water variability during stage 3 - Oppo, D. W.; Lehman, S. J.; Curry, J.; Lynch, Stieglitz; Fairbanks, R. G. (Eos, Transactions, American Geophysical Union, 1995)
id: 58

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

Paleosol evidence of anthropogenic impact on late Holocene landscape instability around an Anasazi site in Kane County, Utah - Kulp, T. R.; Rigsby, C. A. (Abstracts with Programs - Geological Society of America, 1995)
id: 1271

Possible Role of Climate in the Collapse of Classic Maya Civilization - Hodell, D. A.; Curtis, J. H.; Brenner, M. (Nature, 1995)
THE Maya civilization developed around 3,000 years ago in Mesoamerica, and after flourishing during the so-called Classic period, it collapsed around 750-900 AD(1). It has been speculated(2-6) that climate change may have played a part in this collapse. But efforts to reconstruct the last three millennia of Mesoamerican climate using palynological methods have met with equivocal success, because human-mediated deforestation has altered regional vegetation in ways that mimic climate shifts, making it difficult to discriminate between natural and anthropogenic changes(7-15). Here we use temporal variations in oxygen isotope and sediment composition in a 4.9-m sediment core from Lake Chichancanab, Mexico, to reconstruct a continuous record of Holocene climate change for the central Yucatan peninsula. The interval between 1,300 and 1,100 yr up (AD 800-1,000) was the driest of the middle to late Holocene epoch, and coincided with the collapse of Classic Maya civilization, This continuous climate proxy record thus provides evidence of climate deterioration in the Maya region during the terminal Classic period.
Rb101Times Cited:439Cited References Count:41

Radiocarbon Ages of Pre-Bomb Clams and the Hard-Water Effect in Lakes Michigan and Huron - Rea, D. K.; Colman, S. M. (Journal of Paleolimnology, 1995)
Five radiocarbon ages, all determined by accelerator mass spectrometry, have been obtained for two pre-bomb bivalves from Lake Michigan and one from Lake Huron. After correcting those ages for the fractionation of C-14 in calcite and for the radioactively inert CO2 in the atmosphere, we find residual ages, caused by the hard water effect, of about 250 years for Lake Michigan and 440 years for Lake Huron.
Rq668Times Cited:22Cited References Count:13

Routine 14C AMS at 0.2% precision - Do we need it, can it be done? - von Reden, K. F. (109th American Chemical Society National Meeting, 1995)
id: 945

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

A Sea-Level Rise Curve from Guilford, Connecticut, USA - Nydick, K. R.; Bidwell, A. B.; Thomas, E.; Varekamp, J. C. (Marine Geology, 1995)
High-resolution stratigraphic studies based on sediment chemistry, lithology, macroflora, and benthic foraminiferal assemblages in three peat cores from coastal salt marshes at Guilford, Connecticut, show that coastal marshes are ephemeral environments. Marsh-wide environmental variations were common, and century-long episodes of relative submergence alternated with emergence. Despite about 2 m of relative sea-level rise (RSLR) in Connecticut over the last 1500 years, the marshes have expanded both landwards and seawards, and marsh accretion has been outpaced only marginally by RSLR.We used radiocarbon dating and the level of anthropogenic markers (metal pollution, as dated with Pb-210) in the cores for age control. For most of the last 1000 years the rate of RSLR was between 1.3 and 1.8 mm/yr, but over the last 300-400 years it increased to 2.9-3.3 mm/yr, and has been faster than the accretion rate, especially in the middle marsh. The net-submergence rate or ''submergence index'' (ratio of the rate of RSLR and marsh-accretion rate) averaged about 1.15 over the last 1000 years, and increased to about 1.5 over the last 200 years.The rate of RSLR was very sluggish during the early part of the Little Ice Age, but we found a slightly higher rate during the Little Climate Optimum; this excursion is close to the noise level, however. The most significant observation is that RSLR increased strongly around A.D. 1650. The onset of this acceleration falls in the middle to end of the Little Ice Age, and thus preceded the period of modern global warming that started late last century and that has been tentatively correlated with anthropogenic emissions of greenhouse gases.
Rl477Times Cited:71Cited References Count:81

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

Suborbital Timescale Variability of North-Atlantic Deep-Water during the Past 200,000 Years - Oppo, D. W.; Lehman, S. J. (Paleoceanography, 1995)
We generated similar to 200-kyr-long proxy records of surface and deepwater variability from a subpolar North Atlantic core (V29-202), enabling us to assess the linkage between surface and deepwater changes on suborbital timescales. In particular, we used a benthic delta(13)C record to evaluate the deep water response to Dansgaard-Oeschger temperature oscillations and to Heinrich events, times of massive iceberg delivery to the North Atlantic. We found that the reduction of North Atlantic Deep Water (NADW) production was generally associated with cold or dropping sea surface temperatures (SSTs) as indicated by planktonic foraminiferal assemblages. The NADW contribution to the site did not drop appreciably during Heinrich events H4 through H2, probably because these events followed intervals of prolonged surface cooling already characterized by low rates of NADW production. By contrast NADW reduction appears to have been synchronous with H5. SST rise associated with both Dansgaard-Oeschger oscillations and Heinrich events was usually accompanied by increasing NADW strength. In a few cases the NADW recovery appeared to lag the SST rise; however, the apparent delay is most likely an artefact of the sedimentary record (low concentrations of benthic foraminifera). As a result of low benthic foraminiferal abundances during stage 6, the stage 6 benthic foraminiferal delta(13)C record is of lower resolution than the younger part of the record. The stage 6 proxy records for surface hydrography nevertheless reveal millennial-scale oscillations similar to those seen in stage 3. The available delta(13)C data suggest that NADW weakened in association with the cold portions of stage 6 SST oscillations. We also sought to confirm a recent study which concluded that there was little NADW variability during the peak of the last interglaciation, marine oxygen isotope substage 5e (Eemian). Isotope stage 5 was marked by a trend of increasing benthic delta(13)C in V29-202. Rising delta(13)C through isotope stage 5 is also seen in tropical surface water records and at some deep Atlantic sites and may reflect the common derivation of these water masses. Variations of greater than or equal to 0.5 parts per thousand superimposed on this rising delta(13)C trend within substage 5e in V29-202 are so far not evident in tropical feed waters and may therefore indicate that NADW production was weaker during the late than mid-Eemian.
Rx409Times Cited:145Cited References Count:39

Systematic decrease of high delta 13C values with burial in late archaean (2.8 Ga) diagenetic dolomite: evidence for methanogenesis from the Crixas Greenstone Belt, Brazil - Dix, G. R.; Thomson, M. L.; Longstaffe, F. J.; McNutt, R. H. (Precambrian Research, 1995)
id: 1589

Tree Survival and Growth on Land Reclaimed in Accord with Public-Law-95-87 - Chaney, W. R.; Pope, P. E.; Byrnes, W. R. (Journal of Environmental Quality, 1995)
The objective of this study was to determine survival and growth of black walnut (Juglans nigra L.) and northern red oak (Quercus alba L.) 12 yr after planting on a surface-mined site in southern Indiana reclaimed according to specifications of Public Law 95-87, the Surface Mining Control and Reclamation Act of 1977. A stocking level adequate to meet the requirements for forest land use (1112 trees/ha, or 450 trees/acre) was attained only for black walnut and only if competing ground cover vegetation was controlled in the tree rows. Height of both tree species was significantly greater when ground cover vegetation was controlled during the first 2 yr, but the growth rate, approximately 10 cm/yr, was very slow.
Rj934Times Cited:17 Cited References Count:18

Two-step deglaciation of the southeastern Barents Sea - Polyak, L.; Lehman, S. J.; Gataulin, V.; Jull, A. J. T. (Geology, 1995)
id: 62

Using sclerochronology of the mollusc Arctica islandica as a paleoceanographic tool - Marchitto, T. M.; Jones, G. A.; Goodfriend, G. A.; Weidman, C. R.; Jirikowic, J. (5th International Conference on Paleoceanography, 1995)
id: 1294

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

AMS C14 Dating of the Holocene Climatic Optimum in the North Pacific and Atlantic Oceans - Kuzmin, Y. V.; Jones, G. A.; Elder, K. L. (EOS,Transactions,American Geophysical Union, 1994)
id: 913

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

Application of AMS 14C dating to continental margin sediments off Nova Scotia - Keigwin, L. D.; Jones, G. A. (Eos, Transactions, American Geophysical Union, 1994)
id: 1247

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

An assessment of the effect of chemical scavenging within hydrothermal plumes upon ocean geochemistry - Kadko, D. (Earth and Planetary Science Letters, 1994)
id: 1594

Automated Sample Processing at the National Ocean Sciences Ams Facility - Cohen, G. J.; Hutton, D. L.; Osborne, E. A.; vonReden, K. F.; Gagnon, A. R.; McNichol, A. P.; Jones, G. A. (Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions with Materials and Atoms, 1994)
The high throughput and high precision requirements for the NOSAMS facility have made it essential to automate many of the stages in sample processing. These automated procedures increase the sample capacity for the lab while reducing errors in sample preparation. Automation has also allowed sample histories to be recorded and saved in Sybase, a relational data base.
Nv547Times Cited:9Cited References Count:1

Biogenic Silica in Lake Baikal Sediments - Results from 1990-1992 American Cores - Carter, S. J.; Colman, S. M. (Journal of Great Lakes Research, 1994)
The Lake Baikal Paleoclimate Project is a joint Russian-American program established to study the paleoclimate of Central Asia. During three summer field seasons, duplicate Russian and American coves were taken at a number of sites in different sedimentary environments in the lake. Eight cores returned to the U.S. were quantitatively analyzed for biogenic silica using a single-step 5-hour alkaline leach, followed by dissolved silicon analysis by inductively-coupled-plasma atomic-emission spectroscopy. Sediments of Holocene age in these cores have biogenic silica maxima that range from about 15 to 80 percent. An underlying zone in each core with low biogenic-silica concentrations (0 to 5 percent) dates from the last glacial maximum. The transition from the last glaciation to the present interglaciation, recorded by biogenic silica, began about 13,000 years ago. Biogenic silica profiles from these cores appear to be a good measure of past diatom productivity and a useful basis for paleoclimatic interpretations.
Px453Times Cited:46 Cited References Count:20
Keywords: accumulation; Holocene; Lake Baikal; marine-sediments; opal; Paleoclimate; sediments; silica

Carbon and Radiocarbon in the Northeast Pacific: Implications for Abyssal Ventilation and Biogenic Input - Key, R. M.; Rooth, C. G. A.; Feely, R. (15th International Radiocarbon Conference, Glasgow, Scotland, 1994)
id: 911

Chronology, sedimentology, and faunal assemblages of glaciomarine sediments in Maine - Dorion, C. C. (Geological Society of America, Abstracts with Programs, 1994)
id: 17

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

Control and automation of the Accelerator Mass Spectrometry Facility at Woods Hole Oceanographic Institution - Cohen, G. C.; von Reden, K. F. (Symposium of Northeastern Accelerator Personnel, 1994)
id: 1649

The Deep-water Radiocarbon Minimum in the Northeastern Pacific Ocean; Early WOCE Results - Key, R. M.; Toggweiller, J. R. (EOS, Transactions, American Geophysical Union; Ocean Sciences Mtg., San Diego, Feb.21-25, 1994, 1994)
id: 912

Deglaciation, Lake Levels, and Meltwater Discharge in the Lake-Michigan Basin - Colman, S. M.; Clark, J. A.; Clayton, L.; Hansel, A. K.; Larsen, C. E. (Quaternary Science Reviews, 1994)
The deglacial history of the Lake Michigan basin, including discharge and routing of meltwater, is complex because of the interaction among (1) glacial retreats and re-advances in the basin (2) the timing of occupation and the isostatic adjustment of lake outlets and (3) the depositional and erosional processes that left evidence of past lake levels. In the southern part of the basin, a restricted area little affected by differential isostasy, new studies of onshore and offshore areas allow refinement of a lake-level history that has evolved over 100 years. Important new data include the recognition of two periods of influx of meltwater from Lake Agassiz into the basin and details of the highstands gleaned from sedimentological evidence. Major disagreements still persist concerning the exact timing and lake-level changes associated with the Algonquin phase, approximately 11,000 BP. A wide variety of independent data suggests that the Lake Michigan Lobe was thin, unstable, and subject to rapid advances and retreats. Consequently, lake-level changes were commonly abrupt and stable shorelines were short-lived. The long-held beliefs that the southern part of the basin was stable and separated from deformed northern areas by a hinge-line discontinuity are becoming difficult to maintain. Numerical modeling of the ice-earth system and empirical modeling of shoreline deformation are both consistent with observed shoreline tilting in the north and with the amount and pattern of modern deformation shown by lake-level gauges. New studies of subaerial lacustrine features suggest the presence of deformed shorelines higher than those originally ascribed to the supposed horizontal Glenwood level. Finally, the Lake Michigan region as a whole appears to behave in a similar manner to other areas, both local (other Great Lakes) and regional (U.S. east coast), that have experienced major isostatic changes. Detailed sedimentological and dating studies of field sites and additional development of geophysical models offer hope for reconciling the field data with our understanding of earth theology.
Qq080Times Cited:30Cited References Count:48

The deglaciation of southeastern Washington County, Maine. Thesis - Kaplan, M. (University of Maine, Orono, 1994)

The development of the Gull Pond Chain of Lakes and the Herring River Basin in the Cape Cod National Seashore. Report - Winkler, M. G. (1994)
id: 93

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 geology of the Penobscot River basin between Millinocket and Medway (Book Section) - Weddle, T. K.; Lowell, T. V.; Dorion, C. C. (New England Intercollegiate Geological Conference Guidebook for Field Trips in North Central Maine, 1994)
id: 19

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

Global methanotrophy at the Archean-Proterozoic transition - Hayes, J. M. (Early Life on Earth. Nobel Symposium, 1994)
id: 1565

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 resolution sediment changes on the Pleistocene NJ upper slope - Christensen, B. A.; Hoppie, B. W.; Miller, K. G.; Thunell, R. C.; Le, J. (Eos, Transactions, American Geophysical Union, 1994)
id: 53

High-latitude ocean radiocarbon time histories from AMS-dating of long-lived molluscs - Weidman, C. R.; Jones, G. A. (AGU Ocean Sciences Meeting, 1994)
id: 90

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

High-Resolution Climate Records from the North-Atlantic during the Last Interglacial - McManus, J. F.; Bond, G. C.; Broecker, W. S.; Johnsen, S.; Labeyrie, L.; Higgins, S. (Nature, 1994)
THE two deep ice cores recovered by the GRIP(1) and GISP(2) projects at Summit, Greenland, agree in detail over the past 100,000 years(3) and demonstrate dramatic climate variability in the North Atlantic region during the last glacial, before the current period of Holocene stability. This glacial climate instability has subsequently been documented in the marine sedimentary record of surface-ocean conditions in the North Atlantic(4). Before 100 kyr ago the two ice core records are discrepant, however, casting doubt on whether the oxygen isotope fluctuations during the last interglacial (Eemian) seen in the GRIP core(1,5) represent a true climate signal. Here we present high-resolution records of foraminiferal assemblages and ice-rafted detritus from two North Atlantic cores for the interval 65 kyr to 135 kyr ago, extending the surface-ocean record back to the Eemian. The correlation between our records and the Greenland ice-core records is good throughout the period in which the two ice cores agree, suggesting a regionally coherent climate response. During the Eemian, our marine records show a more stable climate than that implied by the GRIP ice core, suggesting that localized phenomena may be responsible for the variability in the latter record during the Eemian.
Ph254Times Cited:313Cited References Count:25

A history of past earthquakes in the Puget Sound area recorded in Holocene sediments from Lake Washington - Karlin, R. E.; Abella, S. E. B. (Open-File Report, U. S. Geological Survey, 1994)
id: 31

Holocene neotectonic deformation and earthquake history in sediments from Lake Washington - Karlin, R.; Holmes, M.; Abella, S. (Abstracts with Programs - Geological Society of America, 1994)
id: 32

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

Integrated Dating Techniques to Determine the Age of a Glauconite Deposit on the Modern Seafloor - am Ende, B. A.; Paull, C. K.; Benninger, L. (EOS, Transactions,American Geophysical Union, 1994)
id: 901

Internal and External Checks in the Nosams Sample Preparation Laboratory for Target Quality and Homogeneity - Osborne, E. A.; McNichol, A. P.; Gagnon, A. R.; Hutton, D. L.; Jones, G. A. (Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions with Materials and Atoms, 1994)
In the NOSAMS sample preparation laboratory (SPL) we have developed rigorous internal procedures aimed at ensuring that sample preparation introduces as little error into our analyses as possible and identifying problems rapidly. Our three major CO2 preparation procedures are: stripping inorganic carbon from seawater, hydrolyzing CaCO3, and oxidizing organic matter. For seawater, approximately 10% of our analyses are standards or blanks which we use to demonstrate extraction of virtually all the inorganic carbon. Analysis of the stable carbon isotopic composition of the CO2 extracted from our standards indicates a precision of better than 0.15-0.20 parts per thousand. We also routinely process C-14-free CO2 in our stripping lines to demonstrate the absence of a significant process-dependent blank. For organic combustions and CaCO3 hydrolyses, we use the carbon yield (% organic carbon (OC) or % CaCO3 by weight) as a check on our sample procedures. We have analyzed the blank contribution of these procedures as a function of sample size. Our organic carbon blank is constant at approximately 0.4% modem for samples containing greater than 1 mg C and our carbonate blank is less than 0.2% modern for samples containing more than 0.5 mg C. We use a standard Fe/H-2 catalytic reduction to prepare graphite from CO2. We check the completeness of our reactions with the pressure data stored during the reaction as well as use a robot to determine a gravimetric yield. All graphite undergoes a visual inspection and is rejected if any heterogeneities are present. We have recombusted graphite made from CO2 with deltaC-13 values ranging from -42 to 1 parts per thousand and determined that the deltaC-13 of the recombusted carbon agrees with that from the pure gas to within 0.05 parts per thousand, demonstrating little or no fractionation during the treatment of the sample. The deltaC-13 we measure on the CO2 generated from more than 75% of our samples is compared to the deltaC-13 measured on the AMS as a further check of our procedures. As further external checks, we analyzed the International Atomic Energy Association (IAEA) samples during the establishment of our laboratory and are presently participating in the third international radiocarbon intercalibration (TIRI) exercise.
Nv547Times Cited:14Cited References Count:5

La Curva Di Risalta Del Mare Tirreno Negli Ultimi 40 KA Ottenuta Mediante Datazioni Di Speleotemi Sommersi E Dati Archeologici - Alessio, M.; Allegri, L.; Antonioli, F.; Belluomini, G.; Improta, S.; Manfra, L.; Martinez, M. P. (International Meeting on Underwater Geology, 1994)
id: 899

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

The limnological and climate history of Lake Michigan from ostracode, stable-isotope, and magnetic susceptibility records - Forester, R. M.; Colman, S. M.; Reynolds, R. L.; Jones, G. A.; Keigwin, L. D.; Foster, D. S. (Journal of Great Lakes Research, 1994)
id: 1358

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 modern limnology of the interdunal Provincelands Ponds in the Cape Cod National Seashore. Technical Report. Final Report - Winkler, M. G. (National Park Service, North Atlantic Region, 1994)
id: 136

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

Paleoceanographic conditions of the late Wisconsinan marine transgression and regression in eastern coastal Maine: stable isotopic evidence. Thesis - Kreutz, K. J. (University of Maine, 1994)

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

Radiocarbon Chronology of Black-Sea Sediments - Jones, G. A.; Gagnon, A. R. (Deep-Sea Research Part I-Oceanographic Research Papers, 1994)
Accelerator Mass Spectrometer (AMS) radiocarbon analyses have been made on 102 samples from 12 sediment cores and 23 samples from two water column profiles. These materials, collected during the first leg of the 1988 joint U.S.-Turkish Black Sea Expedition, provide the most comprehensive radiocarbon chronology of Black Sea sediments vet attempted. Radiocarbon analyses from carefully collected box cores and a molluse shell collected live in 1931 suggest the prebomb surface waters had a DELTAC-14 value of -55 parts per thousand (460 years) and that the maximum detrital correction for radiocarbon ages of Unit I sediments is 580 years for the organic carbon and 260 years for the carbonate fractions. Evidence does not support the 1430-2000 year pre-bomb surface water and/or detrital corrections argued for in past studies. The best estimates for the age of the beginning of the final invasion of the coccolithophore Emiliania huxleyi (Unit 1/2 boundary of Ross and DEGENS, 1974, The Black Sea-geology, chemistry and biology, pp. 183-199) and the age of the first invasion of E. huxleyi (Unit I/II boundary of HAY et al., 1991, Deep-Sea Research, 38, S1211-S1235) are 1635 +/- 60 and 2720 +/- 160 years BP, respectively. Sapropel formation began at approximately 7540 +/- 130 years BP at all depths in the basin, a pattern in disagreement with those predicted by existing time-evolution models of sapropel formation for this basin. Our data suggest that the oxic-anoxic interface has remained relatively stable throughout the Holocene, is controlled largely by the physical oceanography of the basin, and has not evolved as assumed by previous workers.
Nm252Times Cited:121Cited References Count:44

Radiocarbon Dating of Marine Deposits on Submerged Speleothems and Sea-Level Oscillation - Alessio, M.; Allegri, L.; Antonioli, F.; Belluomini, G.; Improta, S.; Manfra, L. (15th International Radiocarbon Conference, 1994)
id: 900

Radiocarbon studies of particulate organic carbon in the eastern North Pacific Ocean - Druffel, E. R. M.; Bauer, J. E.; Williams, P. M.; Griffin, S.; Wolgast, C. Lee; Wakeham, S. G. (1994 ocean sciences meeting, 1994)
id: 1240; 3

Radiocarbon Studies of Particulate Organic Carbon in the Eastern North Pacific Ocean - Druffel, E. R. M.; Griffin, S.; Bauer, J. E.; Williams, P. M.; Wolgast, D. M.; Lee, C. (15th International Radiocarbon Conference, Glasgow, Scotland, 1994)
id: 907

Radiocarton Dating of Pollen by Accelerator Mass Spectrometry - Brown, Thomas Alexander (University of Washington, 1994)
id: 1494; Geophysics Program

Rapid analysis of seawater samples at the National Ocean Sciences Accelerator Mass Spectrometry Facility, Woods Hole, MA - McNichol, A. P.; Jones, G. A.; Hutton, D. L.; Gagnon, A. R.; Key, R. M. (Radiocarbon, 1994)
id: 305

The Rapid Preparation of Seawater Sigma-Co2 for Radiocarbon Analysis at the National Ocean Sciences Ams Facility - McNichol, A. P.; Jones, G. A.; Hutton, D. L.; Gagnon, A. R.; Key, R. M. (Radiocarbon, 1994)
We have established a laboratory for extracting Sigma CO2 from seawater samples for AMS analysis of the radiocarbon content. The seawater samples are collected at sea, poisoned and stored until analysis in the laboratory. Each sample is acidified; the inorganic carbon is stripped out as CO2 with an inert carrier gas and then converted to graphite. We present results for Buzzards Bay surface H2O and Na2CO3 standards that demonstrate we strip > 98% of inorganic carbon from seawater. Stable isotope analyses are performed to better than 0.2 parts per thousand, and the reproducibility of C-14 measurements on Buzzards Bay seawater is better than 13 parts per thousand. Finally, we compare data from samples collected in 1991 to those collected in the 1970s and to large volume samples.
Pz926Times Cited:61 Cited References Count:14
Keywords: accelerator mass-spectrometry; C-14; samples

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

A rock-magnetic record from Lake Baikal, Siberia: Evidence for Late Quaternary climate change - Peck, J. A.; King, J. W.; Colman, S. M.; Kravchinsky, V. A. (Earth and Planetary Science Letters, 1994)
id: 15

The Role of the Deep-Ocean in North-Atlantic Climate-Change between 70-Kyr and 130-Kyr Ago - Keigwin, L. D.; Curry, W. B.; Lehman, S. J.; Johnsen, S. (Nature, 1994)
THE suggestion(1) that changes in North Atlantic Deep Water (NADW) production are linked through surface heat flux to the atmospheric temperature over Greenland is supported by earlier indications(2,3) that NADW production decreased during glacial times, and by the subsequent finding(4-6) that it declined during the Younger Dryas cool period at the end of the last glaciation. Changes in North Atlantic surface temperatures have been found? to mirror high-frequency temperature changes recorded in Greenland ice cores over the past 80 kyr, but the connection to abyssal circulation has yet to be established, except for one or two isolated oscillations(8,9). Here we present carbon and oxygen isotope analyses of benthic foraminifera in a high-resolution North Atlantic deepsea sediment core for the period 70-130 kyr ago. These data allow us to reconstruct the history of NADW production, which shows a close correlation with Greenland climate variability for much of this time interval, suggesting that the climate influence of NADW variability was widespread. We see no evidence, however, for changes in NADW production during substage 5e (the Eemian interglacial period), in contrast with recent ice-core data(10) which suggest severe climate instability in Greenland during this time period. Our results may support suggestions, based on data from a second ice core, that this apparent instability is am artefact caused by ice flow(11). Alternatively, the Eemian climate instability may have had a different origin from the subsequent climate events.
Ph254Times Cited:159Cited References Count:32

A Sediment Budget for Southern Lake-Michigan - Source and Sink Models for Different Time Intervals - Colman, S. M.; Foster, D. S. (Journal of Great Lakes Research, 1994)
We have constructed a sediment budget for the southern Lake Michigan basin for sand and for mud during three time periods: the past 100, 5,000, and 10,000 years. For the modern (100-year) sediment budget, accountable sediment sources add up to 93 percent of the calculated sinks. The mud budget has a source deficit of about 40%, probably due to errors in mu&sand ratios and (or) to other sources not included in our model, especially erosion of the lake floor, which accompanies bluff recession. Two terms dominate the modem sediment-budget equation: (1) bluff erosion, which is an order of magnitude larger than either rivers or aerosols as a source, and (2) deposition in the deep basin, which is more than two orders of magnitude greater as a sink than suspended sediment transport out of the basin. About half of the sand derived from bluff erosion is deposited in the deep lake; the other half must be deposited in nearshore sand bodies, beaches, and dunes. Despite the uncertainties in our estimates of sediment sources and sinks, the attempt to reconstruct sediment budgets for time intervals of 100, 5,000, and 10,000 years leads to important insights about erosion and sedimentation processes. Bluff erosion is the dominant source of both sand and mud in the basin. The deep lake floor is the primary sink for mud, whereas both the deep lake and nearshore areas are important sinks for sand. On a long-term basis, rates of bluff erosion have progressively decreased and are apparently independent of anthropogenic effects. Rates of sediment accumulation in the lake basin mirror the decrease in rates of bluff erosion for prehistoric time, but have increased markedly since human settlement, probably because of anthropogenic effects on river and aerosolic inputs.
Nl348Times Cited:17 Cited References Count:29
Keywords: deposition; erosion; Holocene; lake michigan; sediment budget; sediments

Sensing plant community and climate change by charcoal-carbon isotope analysis - Winkler, M. G. (Ecoscience, 1994)
Mass spectrometric carbon isotope (delta C-13) analyses of charcoal-carbon found in lake sediments provide evidence of paleoclimate and paleovegetation independent of pollen. By chemically separating the microscopic charcoal-carbon, which originates from upland fires, from total carbon in lake, ocean, or ice cores, changes in C-3/C-4 biomass of upland plant communities can be measured, wet or dry climates identified, and the evolution of specific plant assemblages traced. In the North American Midwest, delta C-13 values of lake sediment charcoal-carbon from Lake Mendota, Wisconsin, U. S. A., document two shifts from C-3 (forests) to C-4 (prairie grasses) plants since deglaciation: an abrupt change at about 8.5 ka (8 500 years BP) and a longer duration change between 6 and 3 ka. A pine-savannah is interpreted for the earlier date while oak-savannah dominated the landscape between 6 and 3 ka. C-4 biomass, which was almost non-existent in the region before 8.5 ka, increased to more than 50% between 6 and 3 ka. Spruce-tundra parkland evident in the Midwest before about 12 ka contained no C-4 grasses and was probably similar in composition to modern North American tundra-parkland which has no C-4 biomass. The climate inferred from the delta C-13 data compares well with climate inferred from pollen and sediment data from the same core and supports climate model simulations of decreased effective moisture during the middle Holocene in the North American Midwest. The delta C-13 results also suggest future landscape changes should greenhouse-gas warming occurs. Savannah, with increased C-4 biomass, could again become prevalent in the North American Midwest.
V19xpTimes Cited:10 Cited References Count:44
Keywords: c-3/c-4 plants; midwestern u. s.; paleoclimatology; paleovegetation; sediment charcoal; stable carbon isotopes

Sources of Urban Contemporary Carbon Aerosol - Hildemann, L. M.; Klinedinst, D. B.; Klouda, G. A.; Currie, L. A.; Cass, G. R. (Environmental Science & Technology, 1994)
Emissions from the major sources of fine carbonaceous aerosol in the Los Angeles basin atmosphere have been analyzed to determine the amounts of the C-12 and C-14 isotopes present. From these measurements, an inventory of the fossil carbon and contemporary carbon particle emissions to the Los Angeles atmosphere has been created. In the winter, more than half of the fine primary carbonaceous aerosol emissions are from sources containing contemporary carbon, including fireplaces, charbroilers, paved road dust, cigarette smoke, and brake lining dust, while in the summer at least one-third of the carbonaceous particle emissions are contemporary. Using a mathematical model for atmospheric transport, predictions are made of the atmospheric fine particulate fossil carbon and contemporary carbon concentrations expected due to primary source emissions. Model predictions are in reasonable agreement with the measured radiocarbon content of the fine ambient aerosol samples. It is concluded that the high fraction of contemporary carbon measured historically in Los Angeles is not due to local emission sources of biogenic material; rather, it is due to a combination of local anthropogenic pollution sources and background marine aerosol advected into the city.
Pe258Times Cited:111Cited References Count:45

Subsidence in the Mississippi River Delta - Important influences of valley filling by cyclic deposition, primary consolidation phenomena, and early diagenesis - Roberts, H. H.; Bailey, A.; Kuecher, G. J. (Transactions of the Gulf Coast Association of Geological Societies, 1994)
id: 1273

A synthesis of post-glacial diatom records from Lake Baikal - Bradbury, J. Platt; Bezrukova, Ye V.; Chernyaeva, G. P.; Colman, S. M.; Khursevich, G.; King, J. W.; Likoshway, Y. V. (Journal of Paleolimnology, 1994)
The biostratigraphy of fossil diatoms contributes important chronologic, paleolimnologic, and paleoclimatic information from Lake Baikal in southeastern Siberia. Diatoms are the dominant and best preserved microfossils in the sediments, and distinctive assemblages and species provide inter-core correlations throughout the basin at millennial to centennial scales, in both high and low sedimentation-rate environments. Distributions of unique species, once dated by radiocarbon, allow diatoms to be used as dating tools for the Holocene history of the lake. Diatom, pollen, and organic geochemical records from site 305, at the foot of the Selenga Delta, provide a history of paleolimnologic and paleoclimatic changes from the late glacial (15 ka) through the Holocene. Before 14 ka diatoms were very rare, probably because excessive turbidity from glacial meltwater entering the lake impeded productivity. Between 14 and 12 ka, lake productivity increased, perhaps as strong winds promoted deep mixing and nutrient regeneration. Pollen evidence suggests a cold shrub — steppe landscape dominated the central Baikal depression at this time. As summer insolation increased, conifers replaced steppe taxa, but diatom productivity declined between 11 and 9 ka perhaps as a result of increased summer turbidity resulting from violent storm runoff entering the lake via short, steep drainages. After 8 ka, drier, but more continental climates prevailed, and the modern diatom flora of Lake Baikal came to prominence. On Academician Ridge, a site of slow sedimentation rates, Holocene diatom assemblages at the top of 10-m cores reappear at deeper levels suggesting that such cores record at least two previous interglacial (or interstadial?) periods. Nevertheless, distinctive species that developed prior to the last glacial period indicate that the dynamics of nutrient cycling in Baikal and the responsible regional climatic environments were not entirely analogous to Holocene conditions. During glacial periods, the deep basin sediments of Lake Baikal are dominated by rapidly deposited clastics entering from large rivers with possibly glaciated headwaters. On the sublacustrine Academician Ridge (depth = 300 m), however, detailed analysis of the diatom biostratigraphy indicates that diastems (hiatuses of minor duration) and (or) highly variable rates of accumulation complicate paleolimnologic and paleoclimatic reconstructions from these records.
id: 16
Keywords: Climate change; diatoms; Holocene; Lake Baikal; paleolimnology; palynology

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

Tic, Toc, Dic, Doc, Pic, Poc - Unique Aspects in the Preparation of Oceanographic Samples for C-14 Ams - McNichol, A. P.; Osborne, E. A.; Gagnon, A. R.; Fry, B.; Jones, G. A. (Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions with Materials and Atoms, 1994)
The radiocarbon content of discrete carbon pools (total (T), dissolved (D), and particulate (P) inorganic (I) and organic (O) carbon (C)) is a useful tracer of carbon cycling within the modem and past ocean. The isolation of different carbon pools in the ocean environment and conversion to CO2 presents unique analytical problems for the radiocarbon chemist. In general, isolation and preparation of inorganic carbon presents few problems; dissolved carbon is easily extracted by acidifying the sample and stripping with an inert gas. Carbon is also readily isolated from particulate carbonate samples; in this case, CO2 is prepared by hydrolysis of the substrate with phosphoric acid. The isolation and preparation of organic carbon presents a much greater problem. Dissolved organic carbon (DOC) must first be isolated from DIC and then oxidized in the presence of very high salt concentrations. We present results from a closed-tube combustion method in which the DIC-free seawater is evaporated to dryness, transferred to a clean combustion tube, and oxidized overnight at 550-degrees-C. Combustion of total organic carbon (TOC) in sediments with a high inorganic carbon content is also difficult. Removal of CaCO3 with acid leaves severely deliquescent salts which, if not thoroughly dried, cause combustion tubes to explode. Removal of the salts by rinsing can also remove significant amounts of organic matter. Finally, we present results from a local coastal region.
Nv547Times Cited:82Cited References Count:9

Two episodes of meltwater influx from glacial Lake Agassiz into the Lake Michigan basin: Contrasts in climatic and oceanographic effects - Colman, S. M.; Keigwin, L. D.; Forester, R. M. (Geology, 1994)
id: 189

AMS Pulse, Supplement 1993 - NOSAMS, / (National Ocean Sciences Accelerator Mass Spectrometry Facility, 1993)

AMS Pulse Vol. 1, No. 4, Spring 1993 - NOSAMS, / (National Ocean Sciences Accelerator Mass Spectrometry Facility, 1993)

AMS Pulse Vol. 2, No. 1, Summer 1993 - NOSAMS, / (National Ocean Sciences Accelerator Mass Spectrometry Facility, 1993)

Ams-Graphite Target Production Methods at the Woods-Hole Oceanographic Institution during 1986-1991 - Gagnon, A. R.; Jones, G. A. (Radiocarbon, 1993)
In July 1986, an AMS radiocarbon target preparation laboratory was established at the Woods Hole Oceanographic Institution to produce graphite to be analyzed at the NSF-Accelerator Facility for Radioisotope Analysis at the University of Arizona (Tucson). By June 1991, 923 graphite targets had been prepared and 847 analyzed. Our lab procedures during this time included the careful documentation of weights of all starting samples, catalysts and final graphite yields, as well as the volume of CO2 gas evolved during CaCO3 hydrolysis or closed-tube organic carbon combustions. From these data, we evaluate the methods used in general and in our lab.
Lg927Times Cited:12 Cited References Count:14
Keywords: accelerator mass-spectrometry; facility; ocean; radiocarbon; samples; sediments

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

Dating the Climatic Optimum with AMS - Elder, K. L. (AMS Pulse, The National Ocean Sciences Accelerator Mass Spectrometry Facility Newsletter, 1993)
id: 1645

Deep-sea sediments reveal - Lehman, Scott J.; Keigwin, L. D. (Oceanus, 1993)
id: 1248

Development of the mollusc Artica islandica as a paleoceanographic tool for reconstructing annual and seasonal records of 14C and delta 18O in the mid- to high- latitude North Atlantic Ocean - Weidman, C. R.; Jones, G. A. (International Symposium on Applications of Isotope Techniques in the Study of Past and Current Environmental Changes in the Hydrosphere and the Atmosphere, 1993)
id: 1292

First results in from Pacific 14C Program - Key, R. M.; Toggweiler, J. R. (WOCE Notes, 1993)
id: 39

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

A history of past earthquakes recorded in Holocene sediments from Lake Washington - Karlin, R.; Abella, S. (Eos, Transactions, American Geophysical Union, 1993)
id: 30

Internal and external checks in the NOSAMS Sample Preparation Laboratory for target quality and homogeneity - McNichol, A. P.; Gagnon, A. R.; Osborne, E. A.; Hutton, D. L.; Jones, G. A. (6th International Conference on Accelerator Mass Spectrometry, 1993)
id: 958

Laboratory automation at the National Ocean Sciences AMS Facility - Cohen, G. J.; Hutton, D. L.; von Reden, K. F.; Osborne, E. A.; McNichol, A. P.; Jones, G. A. (6th Internation Conference on Accelerator Mass Spectrometry, 1993)
id: 927

Methods for data screening, flagging and error analysis at the National Ocean Sciences AMS Facility - Schneider, R. J.; Jones, G. A.; McNichol, A. P.; von Reden, K. F.; Elder, K. L.; Kessel, E. D. (6th International Conference on Accelerator Mass Spectrometry, 1993)
id: 933

The National Ocean Sciences Accelerator Mass Spectrometry Facility - Jones, G. A.; McNichol, A. P.; von Reden, K. F.; Schneider, R. J. (WOCE Notes, 1993)
id: 1639

The National Ocean Sciences Accelerator Mass Spectrometry Facility and the WOCE Hydrographic Program. Measurement of 14C in seawater by AMS - McNichol, A. P.; Jones, G. A.; Schneider, R. J.; von Reden, K. F.; Key, R. M. (Third Scientific Meeting, Oceanography Society, 1993)
id: 1656

The National Ocean Sciences Accelerator Mass Spectrometry Facility (WOCE) - Jones, G. A.; McNichol, A. P.; von Reden, K. F.; Schneider, R. J. (WOCE Notes, 1993)
id: 1651

The National Ocean Sciences AMS Facility at Woods Hole Oceanographic Institution - Jones, G. A.; Schneider, R. J.; von Reden, K. F.; McNichol, A. P.; Gagnon, A. R.; Cohen, G. J.; Osborne, E. A.; Hutton, D. L.; Kessel, E. D.; Elder, K. L. (6th International Conference on Accelerator Mass Spectrometry, 1993)
id: 930

The National Ocean Sciences AMS System at Woods Hole Oceanographic Institution - von Reden, K. F.; Jones, G. A.; Schneider, R. J.; McNichol, A. P. (European Community Workshop on Tracers in Physical Oceanography, 1993)
id: 935

Neo-Atlantic Climatic Episode and the Middle Missouri Villagers - Toom, D. L. (51st Plains Anthropological Conference, 1993)
id: 918

A new high-temporal resolution paleoceanographic tool for the northern North Atlantic: the mollusc Arctica islandica - Weidman, C. R.; Jones, G. A. (International Council for the Exploration of the Sea (ICES) Statutory Meeting, 1993)
id: 1295; 17

Optimized data analysis for radiocarbon dating - Sequin, F. H.; Schneider, R. J.; Jones, G. A.; von Reden, K. F. (6th International Conference on Accelerator Mass Spectrometry, 1993)
id: 934

Performance characteristics of the 3MV tandetron AMS system at the National Ocean Sciences AMS Facility - von Reden, K. F.; Schneider, R. J.; Cohen, G. J.; Jones, G. A. (6th International Conference on Accelerator Mass Spectrometry, 1993)
id: 936

Plankton Environment and Marine Sediment Record of the Archipelago de Magallanes, Chile - Anderson, D. M.; Archer, R. B. (EOS,Transactions,American Geophysical Union, 1993)
id: 902

Progress report for the WOCE radiocarbon program - Key, R. M.; Toggweiler, J. R. (WOCE Notes, 1993)
id: 322

Putting Ourselves to the Test: Analysis of the IAEA Intercomparison Samples - McNichol, A. P. (AMS Pulse, 1993)
id: 1612

Radiocarbon ages from two submerged strandline features in the western Gulf of Maine and a sea-level curve for the northeastern Massachusetts coastal region - Oldale, R. N.; Colman, S. M.; Jones, G. A. (Quaternary Research, 1993)
id: 10

Radiocarbon dating of Lake Baikal sediments--A progress report - Colman, S. M.; Kuptsov, V. M.; Jones, G. A.; Carter, S. J. (Russian Geology and Geophysics, 1993)
id: 191

Radiocarbon time histories from long-lived molluscs using accelerator mass-spectrometry - Weidman, C. R.; Jones, G. A. (6th International Conference on Accelerator Mass Spectrometry, 1993)
id: 1296

Role of the United States National Ocean Sciences Accelerator Mass Spectrometry Facility in Global Climate Change Studies - Jones, G. A.; Schneider, R. J.; von Reden, K. F.; McNichol, A. P. (International Symposium on Applications of Isotope Techniques in Studying Past and Current Environmental Change in the Hydrosphere and the Atmosphere, 1993)
id: 928

Sampling the marine gashydrate reservoir: Assessing the methane inventory, internal dynamics, and potential of methane discharges to the atmosphere. Final progress report - Paull, C. (California University, 1993)
id: 59

A shell-derived time history of bomb 14C on Georges Bank and its Labrador Sea implications - Weidman, C. R.; Jones, G. A. (Journal of Geophysical Research, 1993)
Bomb-produced radiocarbon has been used in the past as an important tracer of ocean circulation and as a valuable tool for calculating CO2 air-sea exchange. However, previous studies of the ocean's time-varying bomb 14C record have been confined exclusively to analyzing banded corals, and thus their application has been limited to the lower latitudes. The first time history of bomb 14C from the high-latitude North Atlantic Ocean is obtained from a 54-year-old mollusc specimen, (Bivalvia) Arctica islandica, which was collected live from Georges Bank (41°N) in 1990. The annual growth bands of its shell were analyzed for Δ14C using accelerator mass spectrometry, producing a Δ14C time history from 1939 to 1990. The depleted condition of the Georges Bank bomb 14C signal relative to two coral-derived North Atlantic Δ14C time histories suggests a significant deepwater source for the waters on Georges Bank. Supported by previous work linking the origin of waters on Georges Bank to the Labrador Sea, the Δ14C budget on Georges Bank is modeled as Labrador Sea water, which largely becomes confined to the shelf and partially equilibrates with the atmosphere during a 1-year transit time from the Labrador Sea to Georges Bank. This model is also used to estimate a time history of bomb 14C for the Labrador Sea. Prebomb Δ14C values calculated for the surface Labrador Sea suggest that a greater inventory of bomb 14C has accumulated here than has previously been reported. However, the estimated prebomb average Δ14C (−70.6‰) for this period is nearly identical to the −70‰ previously calculated for the prebomb source of North Atlantic Deep Water and is in agreement with Transient Tracers in the Ocean subsurface tritium data from the central Labrador Sea. Deduced variations in the ventilation and/or 14CO2 uptake rates in the Labrador Sea correspond with observed changes in surface salinity of the Labrador Sea, suggesting a reduction in deepwater formation during the late 1960s and 1970s.
id: 88

The 59-sample, hemispherical ionizer ion sources at the Woods Hole Accelerator Mass Spectrometer - von Reden, K. F. (Twelfth International Conference on the Application of Accelerators in Research and Industry, 1992)
id: 1797

Abundances and Isotopic Compositions of Carbon and Sulfur Species in Whole Rock and Kerogen Samples - Strauss, H.; Moore, T. B. (The Proterozoic Biosphere, 1992)
id: 1599

Accelerator Mass-Spectrometry - Tracking Carbon in the Marine-Environment - Schneider, R. J.; Jones, G. A. (Oceanus, 1992)
Kl777Times Cited:0 Cited References Count:0

The AMS Accelerator at Woods Hole Oceanographic Institution - Schneider, R. J.; von Reden, K. F.; Cohen, G. J.; Jones, G. A. (Symposium of North Eastern Accelerator Personnel, 1992)
id: 1794

AMS Pulse Vol. 1, No. 3, Winter 1992 - NOSAMS, / (National Ocean Sciences Accelerator Mass Spectrometry Facility, 1992)

AMS Pulse Vol. 1, Nos. 1 and 2, Fall 1992 - NOSAMS, / (National Ocean Sciences Accelerator Mass Spectrometry Facility, 1992)

Application of AMS to Oceanography: Progress at the National Ocean Sciences AMS Facility (abstract) - McNichol, A. P.; Jones, G. A.; Schneider, R. J.; von Reden, K. F. (AMS Symposium Division of Nuclear Chemistry and Technology, 203rd American Chemical Society National Meeting, 1992)
id: 1796

Climatic History and Darwinian Causes of High Amazonian Diversity - Colinvaux, P. (8th International Palynological Congress, Aix-en-Provence, France, 1992)
id: 904

Geochemistry of Precambrian carbonates: IV. Early Paleoproterozoic (2.25 +/-0.25 Ga) seawater - Veizer, J.; Clayton, K. R. N.; Hinton, R. W. (Geochimica et Cosmochimica Acta, 1992)
id: 1602

Illumination of a Black-Box - Analysis of Gas-Composition during Graphite Target Preparation - McNichol, A. P.; Gagnon, A. R.; Jones, G. A.; Osborne, E. A. (Radiocarbon, 1992)
We conducted a study of relative gas composition changes of CO2, CO and CH4 during the formation of graphite targets using different temperatures, catalysts and methods. Reduction with H-2 increases the reaction rate without compromising the quality of the AMS target produced. Methane is produced at virtually any temperature, and the amount produced is greater at very low temperatures. The reduction of CO to graphite is very slow when H-2 is not included in the reaction.
Kf389Times Cited:63 Cited References Count:10
Keywords: deposition

Initial Dating and Paleoenvironmental Results From Lake Baikal, Southeastern Siberia - Colman, S. M.; Karabanov, E. B.; Williams, D. F.; Hearn, P. P., Jr.; King, J. W.; Orem, W. H.; Bradbury, J. P.; Shanks, W. C., III; Jones, G. A.; Carter, S. J. (Abstracts With Programs of the American Quaternary Association, 1992)
id: 905