Gourlan, Alexandra T; Meynadier, Laure M; Allègre, Claude J; Tapponnier, Paul; Birck, Jean-Louis; Joron, Jean Louis (2010): Geochemistry of ODP Sites 121-758 and 121-757 [dataset publication series]. PANGAEA, https://doi.org/10.1594/PANGAEA.816396, Supplement to: Gourlan, AT et al. (2010): Northern Hemisphere climate control of the Bengali rivers discharge during the past 4 Ma. Quaternary Science Reviews, 29(19-20), 2484-2498, https://doi.org/10.1016/j.quascirev.2010.05.003
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Abstract:
Nd isotopes are useful tracers for paleoceanography due to the short Nd residence time in seawater and the large differences between the isotopic signatures of various geological reservoirs. Therefore, eNd variations reflect the geological history of individual oceanic basins.
Using a differential dissolution technique, which extracts Nd isotopes of seawater trapped in MnO2 coatings and carbonates in marine sediment, we measured almost two hundred samples from ODP Sites 758 and 757 in the Northern Bay of Bengal covering the last 4 Ma. For the first time, we have shown a covariation between epsilon-Nd and d18O over at least the last 800 ka. We also show that from 4 Ma to 2.6 Ma, epsilon-Nd is almost constant and starts to fluctuate at 2.6 Ma when northern glaciations increased. From 2.6 Ma to 1 Ma the fluctuation period is close to 40 ka while from 1 Ma to present it is dominantly 100 ka.
We attribute these findings to mixing between Himalayan river water (that ultimately originates as Indian summer monsoon rain) and normal Bay of Bengal seawater. Previous studies on seawater, using epsilon-Nd, d18O analyzed on planktonic foraminifera and sedimentary data, can be integrated into this model.
A simple quantitative binary mixing model suggests that the summer monsoon rain was more intense during interglacial than glacial periods. During last glacial episode, the monsoon trajectory was deviated to the east. At a large scale, the Indian monsoon is fully controlled by the variations in Northern Hemisphere climate but with a complex response function to this forcing.
Our study clearly establishes the large potential of Nd isotope data to evaluate the hydrological river regime during the Quaternary and its relationship with climate fluctuations, particularly when the sediment archive is sampled close to sediment sources.
Project(s):
Ocean Drilling Program (ODP)
Coverage:
Median Latitude: -0.217908 * Median Longitude: 89.816217 * South-bound Latitude: -17.024000 * West-bound Longitude: 88.181133 * North-bound Latitude: 5.384067 * East-bound Longitude: 90.361167
Date/Time Start: 1988-06-01T00:00:00 * Date/Time End: 1988-06-15T00:00:00
License:
Creative Commons Attribution 3.0 Unported (CC-BY-3.0)
Size:
4 datasets
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Datasets listed in this publication series
- Gourlan, AT; Meynadier, LM; Allègre, CJ et al. (2010): (Table 1) Chemical element concentrations in bulk and in acetic acid leachate samples from ODP Site 121-758. https://doi.org/10.1594/PANGAEA.816387
- Gourlan, AT; Meynadier, LM; Allègre, CJ et al. (2010): (Table 2) epsilon-Nd values for ODP Sites 121-758 and 121-157. https://doi.org/10.1594/PANGAEA.816385
- Gourlan, AT; Meynadier, LM; Allègre, CJ et al. (2010): (Table 3) Nd isotopic ratios of ancient seawater fraction of ODP Sites 121-758 and 121-757 samples. https://doi.org/10.1594/PANGAEA.816393
- Gourlan, AT; Meynadier, LM; Allègre, CJ et al. (2010): (Table 4) Strontium and Neodymium isotopic ratios of the detrital fraction from ODP Site 121-758. https://doi.org/10.1594/PANGAEA.816395