An investigation into Nd and Sr isotopes in marine sediment and their application to paleoceanography
Studies of past ocean circulation and, in particular, the behaviour of North Atlantic Deep Water (NADW), are crucial to improving understanding of the potential links between the oceans and climate-change. Previously, conventional paleoceanographic proxies have provided a wealth of information conce...
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| Format: | Thesis |
| Language: | English |
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University of Southampton
2002
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| Online Access: | https://eprints.soton.ac.uk/464772/ https://eprints.soton.ac.uk/464772/1/874454.pdf |
| Summary: | Studies of past ocean circulation and, in particular, the behaviour of North Atlantic Deep Water (NADW), are crucial to improving understanding of the potential links between the oceans and climate-change. Previously, conventional paleoceanographic proxies have provided a wealth of information concerning deep ocean circulation throughout the Late Quaternary. However, development of additional, novel tracers continues to help improve our understanding of this complex natural environment. In this thesis, the use of radiogenic isotopes (Sr and Nd) as paleoceanographic proxies has been investigated. The study has focused on five sediment cores from the southeast Atlantic (Angola and Cape Basins), a key areas for monitoring the behaviour of NADW over glacial-interglacial time-scales. In these sediments, the Sr and Nd isotopic compositions of both detrital and Fe-Mn oxyhydroxide fractions have been analysed to investigate evidence for changes in deep ocean circulation in the SE Atlantic throughout the Late Quaternary. A sequential leading procedure for marine sediments has been developed which can be used to separate both Fe-Mn oxides and the detrital fraction for isotopic analysis. For any given sample, this procedure allows one to make use of two independent paleoceanographic proxies: a) the isotopic composition of the detrital fraction - as a tracer of the provenance and flow trajectory of local bottom-water at the time of deposition; b) the isotopic composition of the Fe-Mn component - taken to record the isotopic composition of contemporaneous deep-water. This study has demonstrated an exciting potential for the future use of radiogenic isotopes (Nd, Hf?, Os?) in marine sediments for paleoceanographic investigations. While the case for detrital/provenance determinations may be relatively straightforward, isotopic investigations of Fe-Mn fractions may be more problematic - specifically one should pay particular attention to the diagenetic/redox history of any samples under consideration. |
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