Reconstructing water mass exchange and climate variability in the northernmost Atlantic and Arctic oceans during the beginning of the Quaternary
During the first 16 months of the project surface sediments of the proposed ODP/IODP cores and from nearby locations (Fig. 1) were sampled. The leaching method to extract the seawater derived radiogenic Nd and Pb isotope signatures from the early diagenetic ferromanganese coatings of the sediments (...
| Main Authors: | , , |
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| Format: | Conference Object |
| Language: | unknown |
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2011
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| Online Access: | https://oceanrep.geomar.de/id/eprint/12900/ http://www.geo.uni-potsdam.de/icdp_homepage/downloads/Abstractband_M%C3%BCnster_2011a.pdf |
| Summary: | During the first 16 months of the project surface sediments of the proposed ODP/IODP cores and from nearby locations (Fig. 1) were sampled. The leaching method to extract the seawater derived radiogenic Nd and Pb isotope signatures from the early diagenetic ferromanganese coatings of the sediments (Gutjahr et al., 2007) was extensively tested and, where necessary, improved for the different core locations by comparison of core top data to the modern dissolved bottom water Nd isotope signatures in the same areas (Lacan and Jeandel, 2004; Andersson et al., 2008). These test results for sediments in the N-Atlantic (at or near Site 984), the Norwegian-Greenland Seas (near Site 907) and on the Yermak-Plateau in the Fram Strait (Site 911) (Fig. 2) showed that the data of ODP Site 911 gave Nd isotope signatures closest to the modern ocean bottom water signatures, which was supported by Sr isotope signatures very close to seawater in the same leachates. The Nd isotope results of Sites 907 were slightly too radiogenic and those of Site 984 were significantly too radiogenic compared with expected values from deep water data although it has to be stated that there are no direct deepwater data available for Sites 907 and 984. We suspect that small amounts of basaltic ash with highly radiogenic Nd isotope signatures originating from Iceland were dissolved and responsible for the positive offset. This was further tested by extracting and analyzing the seawater Nd isotope data from the carbonate shells of planktonic and benthic foraminifera, which yielded more negative and in the case of site 907 fully realistic numbers, whereas for site 984 the numbers still seem slightly too positive. Based on these results downcore samples covering the proposed time period of the past 5 million years were obtained at the IODP-Core Repository in Bremen and the first Nd and Pb isotope data set was produced for ODP Site 911 (900 m water depth). It is located NW of Svalbard on the southeastern slope of the Yermak Plateau in the Fram Strait. The ... |
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