Late quaternary stratigraphy and sedimentology of the central North Atlantic: A progress report

The marine geological research program of the Department of Sedimentary Geology at the Free University of Amsterdam focuses on three areas: Banda Sea, central North Atlantic and the Mediterranean. Late Quaternary deep-sea cores taken in these areas are analysed in order to reconstruct changes in paleoceanography as reflected in the sedimentary record. Radiocarbon datings through the cores provide the necessary stratigraphie framework. The Utrecht tandem Accelerator Mass Spectrometer (AMS) allows radiocarbon dating on minutes samples (10–25 mg carbonate) and is therefore an excellent tool for core studies. This paper concentrates on results obtained from the central North Atlantic material. The Atlantic CaCO3 profile shows a maximum at the last climate optimum at 6 ka and a minimum at the last glacial maximum at 18 ka [1]. This is also observed in our material, and confirmed by radiocarbon dating. It is shown that sedimentation rates are distinctly higher during the period of deglaciation. The dating also provides a framework for the timing of the retreat of the polar front. A surface layer of pteropod shells covers parts of the Atlantic Ocean floor at about 3000 m depth. Many shells show Fe/Mn staining. The AMS technique allows dating of single shells, and proves that the stained specimens are considerably older than the unstained shells. Implications for this phenomenon and for the contribution of aragonite to the sediment are given