Stable isotope analyzes on benthic foraminifera from the Late Cretaceous (Turonian - Santonian) of Demerara Rise (ODP Leg 207) and comparison with the Pacific Ocean

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The principal objectives of this project are (1) to establish a bottom-water paleotemperature record for the Turonian to Santonian (early Late Cretaceous), (2) to reconstruct the paleoceanographic conditions of the equatorial Atlantic, and (3) to address the question if there are significant ice sheets and/or short-term cooling phases during the early Late Cretaceous. In order to achieve this, it is intended to analyze the oxygen isotopic composition of benthic foraminifera. Two boreholes of ODP Leg 207 (Sites 1259 &1261) have been chosen. The cored sediments consist mostly of TOC-rich claystones and contain benthic foraminifera which show a glassy preservation. This status of preservation provides ideal conditions for the planned investigations and allows the calculation of reliable paleotemperatures. Furthermore, Demerara Rise occupies a central position for understanding mid- to Late Cretaceous ocean temperatures and the mechanisms of Cretaceous deep-water formation. Another important aspect of this investigation is a comparison with the Pacific Ocean for the same time interval. This will be achieved by studying material from DSDP Sites 305 and 463. Further objectives of this project are: (1) to refine the isotope stratigraphy, (2) to define possible short-term changes in bottom-water sources, and (3) to verify inter-species and species-specific variations in the isotope signals.