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

罗堡1/90井(德国萨克森-安哈尔特)较完整地记录了古北海东南部始新世/渐新世过渡层。几个科学家小组目前正在对这段时间内全球气温下降的情况进行多学科研究。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降，但其确切的地层位置一直在激烈的讨论中(并有相互矛盾的意见)。在以前的一个项目中，利用海底有孔虫进行生物地层学研究，我们已经能够与以前的观点相矛盾，并将气温下降的时间定在始新世/渐新世界线上方的一个地层区间内，这将与特提斯和北海之间的古地理联系中断，从而导致温暖的特提斯水团(经由波兰)流入。在这个项目的S研究期间，我们已经能够通过使用有孔虫的新的生物地层学来支持这些观点。此外，我们已经能够确定始新世/渐新世界线进入上Schönwalde组的最上面部分。关于洋流与南极冰川作用对dO18曲线(领先与较大值)的影响的分离的其他信息来自方解石壳的镁/钙分析(指向与上述相同的解释)。在我们对罗堡有孔虫研究的最后阶段，我们打算进行更多的镁/钙测量(同样是为了破译彼此对dO18趋势的两种可能的影响)，并使用锶同位素地层学来证实(如果可能的话)我们从有孔虫(海底和平面)得出的地层学结论。该项目的最终目标是基于一组跨学科和可靠的数据，对始新世/渐新世过渡时期古代北海的古气候和古海洋演化进行总结解释。

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.