Plancton foraminifera, biostratigraphy and palaeoclimatology across the Eocene/Oligocene boundary in Loburg 1/90 borehole (Sachsen-Anhalt)

Loburg 1/90钻孔（德国Sachsen-Anhalt）较完整地记录了古北海东南部始新世/渐新世过渡层。目前，几组科学家正在对这段时间内全球气温下降的原因进行多学科研究。我们自己的稳定同位素研究已经表明，当时的北海盆地已经存在这样一个相当大的温度下降，但其确切的地层位置一直在激烈的讨论中（并且有相互矛盾的意见）。在以前的一个项目中，我们使用底底有孔虫进行生物地层学研究，我们已经能够反驳以前的观点，并将温度下降的时间定在一个略高于始新世/渐新世边界的地层区间，这将与特提斯和北海之间古地理联系的中断相吻合，因此（通过波兰）温暖的特提斯水团流入。在这个项目的研究中，我们已经能够通过使用植物有孔虫的新生物地层学来支持这些观点。此外，我们还能够将始新世/渐新世边界定年到上Schönwalde组的最上部。关于洋流与南极冰川作用对dO18曲线影响的分离（领先值与较重值）的其他信息已从方解石壳的Mg/Ca分析中得出（指向与上述相同的解释）。在我们对Loburg有孔虫研究的最后阶段，我们打算进行更多的Mg/Ca测量（同样是为了破译相互之间对dO18趋势的两种可能影响），并使用锶同位素地层学来确认（如果可能的话）我们从有孔虫（底栖和塑料）中得出的地层学结论。该项目的最终目标是基于一套跨学科和可靠的数据，总结解释古北海在始新世/渐新世过渡时期的古气候和古海洋演化。

Borehole Loburg 1/90 (Sachsen-Anhalt, Germany) records the Eocene/Oligocene transition beds of the southeastern part of the ancient North Sea quite completely. The worldwide temperature drop of that interval of time is currently under multidisciplinary investigation by several groups of scientists. Our own stable isotope research has already shown that such a considerable temperature drop has alreay existed in the North Sea Basin of that time, but its exact stratigraphic position has been under intensive discussion (and with conflicting opinions). Using benthic foraminifera for biostratigraphy in a former project, we have already been able to contradict previous opinions and date the time of the temperature drop into a stratigraphical interval somewhat above the Eocene/Oligocene boundary, which would coincide with the interruption of the palaeogeographic connection between the Tethys and the North Sea and thus the inflow (via Poland) of warm Tethyan watermasses.During this project´s research, we have been able to support these views by our new biostratigraphy using plancton foraminifera. Moreover, we have been able to date the Eocene/Oligocene boundary into the uppermost part of the Upper Schönwalde Formation. Additional information about the separation of ocean current vs. antarctic glaciation influences onto the dO18 curve (leading vs. heavier values) has been derived from Mg/Ca analysis of calcite shells (pointing to the same explication as described above). In the final phase of our research on the Loburg foraminifera, we intend to carry out more Mg/Ca measurements (again in order to decipher the two possible influences onto the dO18 trend from each other) and also use strontium isotope stratigraphy in order to confirm (if possible) our stratigraphical conclusions derived from the foraminifera (both benthic and planctic). Final goal of the project is a summarizing interpretation, based on a set of interdisciplinary and solid data, of the palaeoclimatic and palaeooceanographic evolution of the ancient North Sea across the Eocene/Oligocene transition.