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Datasets of project "Lamont-Doherty Earth Observatory, Columbia University"

Mostrando recursos 1 - 20 de 263

  1. Calcium carbonate preservation in the equatorial Pacific

    Prell, Warren L; Farrell, John W
    The Pliocene-Pleistocene history of CaCO3 preservation in the central equatorial Pacific is reconstructed from a suite of deep-sea cores and is compared to fluctuations in global ice volume inferred from delta18O records. The results are highlighted by: (1) a strong covariation between CaCO3 preservation and ice volume over 104 to 106 year time scales; (2) a long-term increase in ice volume and CaCO3 preservation since 3.9 Ma demonstrated by a deepening of the lysocline and the carbonate critical depth; (3) a dramatic shift to greater CaCO3 preservation at 2.9 Ma; (4) distinctive ice-volume growth and CaCO3 preservation events at 2.4...

  2. Estimates of sea surface temperatures in the Coral Sea

    Anderson, David M; Prell, Warren L; Barratt, N J
    The CLIMAP [1981] reconstruction of the Coral Sea found relatively little cooling (2°C) in the low latitudes (10°S) but a warming off Australia at about 25°S. The small low-latitude changes are of interest because terrestrial pollen and snowline data from the New Guinea highlands imply that surface temperatures may have been 6° to 9°C colder at the last glacial maximum (LGM). The purpose of this paper is to evaluate these conclusions on the basis of additional core sites, new oxygen isotope stratigraphy, and new sea surface temperature (SST) estimates using the modern analog technique (MAT). In the northern Coral Sea,...

  3. Geochemistry of foraminifera from sediment cores of the central California margin

    van Geen, Alexander; Fairbanks, Richard G; Dartnell, Peter; McGann, Mary L; Gardner, James V; Kashgarian, Michaele
    Under present climate conditions, convection at high latitudes of the North Pacific is restricted to shallower depths than in the North Atlantic. To what extent this asymmetry between the two ocean basins was maintained over the past 20 kyr is poorly known because there are few unambiguous proxy records of ventilation from the North Pacific. We present new data for two sediment cores from the California margin at 800 and 1600 m depth to argue that the depth of ventilation shifted repeatedly in the northeast Pacific over the course of deglaciation. The evidence includes benthic foraminiferal Cd/Ca, 18O/16O, and 13C/12C...

  4. (Table 1) Age determination of single species benthic and planktonic foraminifera from sediment core F2-92-P3

    van Geen, Alexander; Fairbanks, Richard G; Dartnell, Peter; McGann, Mary L; Gardner, James V; Kashgarian, Michaele

  5. (Table 1) Age determination of sediment core F2-92-P3

    van Geen, Alexander; Fairbanks, Richard G; Dartnell, Peter; McGann, Mary L; Gardner, James V; Kashgarian, Michaele

  6. Late Pleistocene oxygen isotope record of biognic silica

    Shemesh, Aldo; Burckle, Lloyd H; Hays, James D
    We determined the isotopic composition of oxygen in marine diatoms in eight deep-sea 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 delta18O can be used as a new paleocenographic tool to reconstruct past variations in surface water characteristics and to generate 18O -isotope-based stratigraphy for the Southern Ocean. The data indicate that diatom delta18O reflects sea surface temperature and seawater isotopic composition and that diatoms retain their isotopic signal on timescales of a least 430 ka. The delta18O analyses of different diatom assemblages reveal that...

  7. Age models and sedimentation rates of sites in the tropical Atlantic

    Verardo, David J; McIntyre, Andrew
    Late Pleistocene signals of calcium carbonate, organic carbon, and opaline silica concentration and accumulation are documented in a series of cores from a zonal/meridional/depth transect in the equatorial Atlantic Ocean to reconstruct the regional sedimentary history. Spectral analysis reveals that maxima and minima in biogenous sedimentation occur with glacial-interglacial cyclicity as a function of both (1) primary production at the sea surface modulated by orbitally forced variation in trade wind zonality and (2) destruction at the seafloor by variation in the chemical character of advected intermediate and deep water from high latitudes modulated by high-latitude ice volume. From these results...

  8. Stable isotope record of foraminifera from the Southern Ocean

    Lynch-Stieglitz, Jean; Fairbanks, Richard G; Charles, Christopher D
    Sediment cores from the southern continental margin of Australia are near the formation region of Antarctic Intermediate Water (AAIW) and Subantarctic Mode Water and record the changes in these water masses from the last glacial maximum through the present. Carbon and oxygen isotopes were measured on the benthic foraminiferal species Planulina wuellerstrorfi for both the Recent and last glacial maximum sections of the cores and were then used to reconstruct temperature and carbon isotopic water column profiles. The glacial oxygen isotope profile indicates a vertical temperature structure for this region similar to that in today's Subantarctic Zone. Although intermediate water...

  9. Organic carbon concentrations and Cd/Ca ratios of sediment core RC13-229

    Oppo, Delia W; Rosenthal, Yair
    A comparison of cadmium/calcium (Cd/Ca) records of benthic foraminifera from a deep Cape Basin and a deep eastern equatorial Pacific core suggests that over the past 400,000 years, the nutrient concentration of Circumpolar Deep Water (CPDW) has always been lower than that of the deep Pacific. The data further suggest that at the 100,000- and 23,000-year orbital periods, the contribution of North Atlantic Deep Water to CPDW is at a maximum during periods of ice growth and at a minimum during periods of ice decay. These results are not in agreement with results based on carbon isotope records of benthic...

  10. Age determination and radionuclides of sediment cores from the Western Atlantic

    Broecker, Wallace S; Lao, Yong; Klas, Mieczyslawa; Clark, Elizabeth; Bonani, Georges; Ivy, Susan; Chen, Chin
    The CO2 record for air bubbles from the Byrd Station ice core suggest a drawdown in the ocean-atmosphere carbon reservoir during the early Holocene. Such a drawdown would require a corresponding increase in the CO3= ion concentration in the deep sea. We report here the results of a search in Atlantic sediments for evidence that the lysocline showed a corresponding deepening. While both the pteropod and the calcite preservation records we have obtained are consistent with expectation, they are not conclusive.

  11. Sedimentology and stable isotope ratios of the northwest Pacific

    Lyle, Mitchell W; Zahn, Rainer; Prahl, Frederick G; Dymond, Jack R; Collier, Robert W; Pisias, Nicklas G; Suess, Erwin
    The Multitracers Experiment studied a transect of water column, sediment trap, and sediment data taken across the California Current to develop quantitative methods for hindcasting paleoproductivity. The experiment used three sediment trap moorings located 120 km, 270 km, and 630 km from shore at the Oregon/California border in North America. We report here about the sedimentation and burial of particulate organic carbon (Corg) and CaCO3. In order to observe how the integrated CaCO3 and Corg burial across the transect has changed since the last glacial maximum, we have correlated core from the three sites using time scales constrained by both...

  12. Biogenic opal, carbonat concentrations and stable oxygen isotope ratios of foraminifera from sediment cores of the Southern Ocean

    Charles, Christopher D; Froelich, Philip N; Zibello, Michael A; Mortlock, Richard A; Morley, Joseph J
    We present records of biogenic opal percentage and burial rate in 12 piston cores from the Atlantic and Indian sectors of the Southern Ocean. These records provide a detailed, quantitative description of changing patterns of opal deposition over the last 450 kyr. The striking regional coherence of these records suggests that dissolution in the deep sea and sediment pore waters does not obscure the surface productivity signal, and therefore these opal time series can be used in combination with other surface water tracers to make inferences about the chemistry and circulation of the Southern Ocean under different global climate conditions....

  13. Pollen records and stable isotope ratios of benthic foraminifera from sediment cores of the Sea of Okhotsk

    Morley, Joseph J; Heusser, Linda E; Shackleton, Nicholas J
    In two cores with oxygen isotope stratigraphy from the southern Okhotsk Sea, marine pollen and siliceous microfauna record concurrent late glacial through Holocene variations in regional terrestrial and marine environments. Glacial vegetation around the southern Okhotsk basin, which resembles the present tundra/steppe of the northwest coast of this marginal sea, yields to spruce-dominated boreal forests during the glacial/interglacial transition. Temperate forest components, such as oak, peak during the mid-Holocene. Decreasing oak accompanied by increasing spruce reflects the effect of global cooling on local vegetation during the last 4 kyr. Although the radiolarian fauna in the Okhotsk Sea samples is similar...

  14. Pollen records and stable isotope ratios of benthic foraminifera from sediment cores of the Sea of Okhotsk

    Morley, Joseph J; Heusser, Linda E; Shackleton, Nicholas J
    In two cores with oxygen isotope stratigraphy from the southern Okhotsk Sea, marine pollen and siliceous microfauna record concurrent late glacial through Holocene variations in regional terrestrial and marine environments. Glacial vegetation around the southern Okhotsk basin, which resembles the present tundra/steppe of the northwest coast of this marginal sea, yields to spruce-dominated boreal forests during the glacial/interglacial transition. Temperate forest components, such as oak, peak during the mid-Holocene. Decreasing oak accompanied by increasing spruce reflects the effect of global cooling on local vegetation during the last 4 kyr. Although the radiolarian fauna in the Okhotsk Sea samples is similar...

  15. (Table 3) Pollen record of sediment core V32-161

    Morley, Joseph J; Heusser, Linda E; Shackleton, Nicholas J

  16. (Table 3) Pollen record of sediment core V32-161

    Morley, Joseph J; Heusser, Linda E; Shackleton, Nicholas J

  17. (Table 3) Pollen record of sediment core V32-159

    Morley, Joseph J; Heusser, Linda E; Shackleton, Nicholas J

  18. (Table 3) Pollen record of sediment core V32-159

    Morley, Joseph J; Heusser, Linda E; Shackleton, Nicholas J

  19. Age models and stable isotope record of sediment cores from the Atlantic Ocean

    Oppo, Delia W; Fairbanks, Richard G
    The high-resolution delta18O and delta13C records of benthic foraminifera from a 150,000-year long core from the Caribbean Sea indicate that there was generally high delta13C during glaciations and low delta13C during interglaciations. Due to its 1800-m sill depth, the properties of deep water in the Caribbean Sea are similar to those of middepth tropical Atlantic water. During interglaciations, the water filling the deep Caribbean Sea is an admixture of low delta13C Upper Circumpolar Water (UCPW) and high delta13C Upper North Atlantic Deep Water (UNADW). By contrast, only high delta13C UNADW enters during glaciations. Deep ocean circulation changes can influence atmospheric...

  20. Estimates of annual mean surface temperatures in the late Quaternary of the tropical Atlantic

    Mix, Alan C; Ruddiman, William F; McIntyre, Andrew
    At least two modes of glacial-interglacial climate change have existed within the tropical Atlantic Ocean during the last 20,000 years. The first mode (defined by cold glacial and warm interglacial conditions) occurred symmetrically north and south of the equator and dominated the eastern boundary currents and tropical upwelling areas. This pattern suggests that mode 1 is driven by a glacial modification of surface winds in both hemispheres. The second mode of oceanic climate change, defined by temperature extremes centered on the deglaciation, was hemispherically asymmetrical, with the northern tropical Atlantic relatively cold and the southern tropical Atlantic relatively warm during...

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