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

该项目的主要目标是(1)建立吐鲁尼亚至桑托尼亚(晚白垩世早期)的底层水古温度记录，(2)重建赤道大西洋的古海洋学条件，以及(3)解决晚白垩世早期是否存在显著的冰盖和/或短期冷却阶段的问题。为了达到这一目的，我们打算分析底栖有孔虫的氧同位素组成。选择了ODP207段(1259和1261)的两个井眼。岩心沉积物主要由富含有机碳的粘土岩组成，并含有海底有孔虫，显示出玻璃状保存。这种保存状态为计划中的调查提供了理想的条件，并允许计算可靠的古温度。此外，德梅拉拉隆升在了解白垩纪中晚期海洋温度和白垩纪深水形成机制方面占有中心地位。这项调查的另一个重要方面是与同一时间间隔的太平洋进行比较。这将通过研究来自DSDP站点305和463的材料来实现。该项目的其他目标是：(1)完善同位素地层学，(2)确定底水水源可能的短期变化，以及(3)核实同位素信号的物种间和物种特定变化。

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.