Expedition 395C: Reykjanes Ridge planktonic foraminifer biostratigraphy and assemblages

395C探险队将在冰岛南部被称为雷克扬斯山脊的海床上打捞出一系列钻芯。岩心将由火山岩(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。发现的最古老的沉积物预计约有3500万年前，当时气候要温暖得多，北半球几乎没有冰。该项目将重建北大西洋气候条件在这段漫长的时期内以及在冰河时代周期等较短期变化中的变化情况。关于冰岛火山热点可能对北大西洋海底几何形状和洋流方向的影响的各种想法将得到检验。提供沉积岩的准确年龄是必要的。这个特定的项目是为了研究一组被称为有孔虫的浮游生物化石，这些浮游生物产生一种由碳酸钙制成的坚硬的外壳，这种外壳存活在海底。因为浮游生物进化很快，所以有可能将任何给定沉积物样本中的物种与其他地方的参考地点进行比较，以确定大约的年龄。浮游有孔虫也对气候变化做出反应。例如，目前一些亚热带物种似乎正在随着地表暖流进一步向北移动。将对最新的沉积物进行检查，以确定是否发生了这种情况。通过记录亚热带和极地物种的相对丰富程度，将以同样的方式跟踪地质过去的冷暖气候阶段。

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.