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Paleoenvironmental evolution of the Yermak Plateau, Eastern Arctic Ocean during MIS 1-17(19?)

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Vogt, C. , Matthießen, J. , Knies, L. , Mackensen, A. , Nam, S. and Stein, R. (2004): Paleoenvironmental evolution of the Yermak Plateau, Eastern Arctic Ocean during MIS 1-17(19?) , 8th International Conference on Paleoceanography (ICP VIII), 5-10 Sept., Biarritz, France. .
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Abstract:

The Pleistocene paleoceanographic and paleoclimate development in the eastern Arctic Ocean is still widely unexplored due to contradictory stratigraphic models and sparsity of calc-areous or silious microfossils. We have selected ODP Hole 910 for a study because presence of some biogenic carbonate permits establishment of a relatively continuous stable oxygen isotope stratigraphy on planktic foraminifer Neogloboquadrina pachyderma sin. that is the basic stratigraphic tool in the Pleistocene. Furthermore, the Yermak Plateau is located in the path of relatively warm Atlantic waters, and its sediments record the dynamic coupling between the northernmost branch of the Gulf Stream and the Arctic Ocean. A multiproxy strategy is applied on the same sample set to reveal the synchronicity/ asynchronies of changes in the surface water regi-me and in the sediment supply and source areas.The revised chronostratigraphy indicates that the uppermost 20 m of Hole 910A range from Marine Isotope Stages (MIS) 17 to MIS 2. Several stratigraphic age fixpoints support the interpretation of the stable oxygen isotope record that is punctuated by numerous short-term meltwater events, often accompanied by an IRD increase and distinct changes in mineral assemblages. Organic-walled dinoflagellate cysts that have the best microfossil preservation potential establish a biostratigraphy calibrated vs the new chronostratigraphy and help to reconstruct the history of surface waters and sea-ice coverage and its interaction with the northern Barents Sea ice sheet developments. Planktic foraminifer assemblages are almost monospecific and often affectted by selective dissolution overprinting the paleorecord. Most samples analysed are productive suggesting that Atlantic water inflow into the Arctic Ocean was suppressed only for relatively short periods in the past 600,000 years. Presence of freshwater algae combined with a typical clay mineral assemblage rich in smectites in a number of samples suggests some freshwater supply from the Laptev and Kara Seas.The terrigenous minerals dolomite and siderite dominate the max. 4% carbonate content in most samples showing that only a rather small portion of bulk carbonate is of biological origin. Rock eval pyrolysis revealed that total organic carbon contents are predominately of terrestrial origin. Finally, our study will provide reference data sets records which can be compared to the new boreholes that will be drilled on the Lomonosov Ridge (Central Arctic Ocean) in the frame of the Arctic Coring Expedition (ACEX, IODP) in summer 2004.

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