Expedition 395C: Reykjanes Ridge planktonic foraminifer biostratigraphy and assemblages

第395 C远征队将在冰岛南部的雷克雅内斯海岭（Reykjanes Ridge）海底采集一系列岩芯。岩芯将由火山岩（所谓的“基底”）组成，上面覆盖着长期积累的沉积物。这些岩心提供了一种研究过去地质时期北大西洋的方法。预计发现的最古老的沉积物大约有3500万年的历史，当时气候要温暖得多，北方的冰很少。该项目将重建北大西洋气候条件在这一长时期内以及在冰河时代周期等较短期变化中的变化。关于冰岛火山热点对北大西洋海底几何形状和洋流方向可能产生的影响的各种想法将得到检验，有必要为沉积岩提供准确的年代测定。这一具体项目是研究一组被称为有孔虫的浮游生物化石，有孔虫产生一种由碳酸钙制成的硬壳，生存在海底。由于浮游生物进化迅速，因此可以将任何沉积物样本中的物种与其他参考地点进行比较，以确定大致的年龄。例如，目前看来，一些亚热带物种正随着温暖的表面气流向北移动。最新的沉积物将被检查，看看这是否正在发生。通过记录亚热带和极地物种的相对丰度，将以同样的方式跟踪地质历史中的寒冷和温暖气候阶段。

Expedition 395C will recover a series of drill cores from the sea bed on a feature known as the Reykjanes Ridge south of Iceland. The cores will consist of volcanic rocks (the so-called 'basement') overlain by sediments which have accumulated over long periods of time. The cores provide a way of studying the North Atlantic Ocean in the geological past. The oldest sediments recovered are expected to be about 35 million years old at which time climate was much warmer and there was very little ice in the northern hemisphere. The project will reconstruct how climatic conditions have changed in the North Atlantic over this long period and also over shorter term changes such as the ice age cycles. Various ideas about the possible influence of the Iceland volcanic hotspot on North Atlantic sea floor geometry and the direction of ocean currents will be tested.It is necessary to provide accurate age dating for the sedimentary rocks. This specific project is to study a group of fossil plankton known as foraminifers which produce a hard shell made of calcium carbonate which survives on the sea floor. Because the plankton evolve rapidly it is possible to compare the species in any given sediment sample with reference sites elsewhere to determine the approximate age.Planktonic foraminifers also respond to climate change. For instance, at the present time it appears that some sub-tropical species are moving further north with warmer surface currents. The very latest sediments will be examined to see if this is happening. Cold and warm climate phases in the geological past will be tracked in the same way by documenting the relative abundance of subtropical and polar species.