North Atlantic (Rockall Plateau) coccolith assemblage data for MIS 5 of ODP Hole 162-980B

Calcareous nannoplankton analyses on late quaternary sediments from the eastern North Atlantic ODP Site 980 (55°29'N, 14°42'W) provide detailed insight into palaeoceanographic and palaeoclimatic changes that occurred throughout the Termination II and the adjacent interglacial of the Marine Isotope Stage (MIS) 5. This study presents the development of the coccolith assemblage throughout the interglacial MIS 5 towards the beginning of the glacial MIS 4 in the vicinity of the Rockall Plateau and investigates and characterises the impact of climatic and environmental variations on the coccolith assemblage distribution between 135 and 65 ky.

In general, the coccolith assemblage is dominated by Gephyrocapsa muellerae and Emiliania huxleyi, whilst significant changes in palaeoceanographic and palaeoclimatic conditions are mainly shown by variations of subordinate species. A drastic increase in coccolith accumulation rates and a change from a less to a higher diverse species assemblage indicate a rapid increase in surface water temperatures during the onset of MIS 5 from c. 127.5 ky on. Highest coccolith numbers, high numbers of taxa and a large diversity indicate highest coccolithophore primary productivity and peak interglacial conditions during MIS 5.5, which are due to the high influence of relatively warm surface water to this region. Coccolith numbers peak again around 120 ky and decline afterwards but stay above glacial levels. The two cooling events of MIS 5.4 and 5.2 interrupt the generally warm conditions and are indicated by lowered coccolith numbers, a drop of thermophile species and a reduction of the species diversity. Decreasing coccolith numbers and a slightly reduced diversity indicate that environmental conditions deteriorated towards the onset of MIS 4. The analysis of the coccolith assemblage reveals that not only the stadial events MIS 5.4 and 5.2 are characterised by colder conditions, but furthermore confirms the upcoming notion that MIS 5.5 was terminated by a slight short-term cooling of the surface water which occurred around 124 ky.

对北大西洋东部大洋钻探计划（Ocean Drilling Program, ODP）980站位（55°29′N，14°42′W）晚第四纪沉积物开展的钙板金藻（calcareous nannoplankton）分析，为第二冰期旋回终止期（Termination II）及紧邻的海洋同位素阶段（Marine Isotope Stage, MIS）5间冰期发生的古海洋与古气候演变提供了精细的认知。本研究揭示了洛克高原（Rockall Plateau）附近海域从海洋同位素阶段5间冰期向冰期MIS 4起始阶段的颗石藻（coccolith）组合演化过程，并探讨了135~65千年前气候与环境变化对颗石藻组合分布的影响并完成特征刻画。

总体而言，研究区颗石藻组合以穆勒桥石藻（Gephyrocapsa muellerae）与赫氏颗石藻（Emiliania huxleyi）为优势类群，而古海洋与古气候条件的显著变化主要通过次要物种的丰度变异体现。颗石藻堆积速率的急剧升高，以及物种组合从低多样性向高多样性的转变，指示了约127.5千年前以来MIS 5起始阶段表层海水温度的快速上升。MIS 5.5期间颗石藻丰度最高、类群数量最多且多样性最大，反映了当时颗石藻初级生产力达到峰值，且间冰期环境条件最优，这与该区域受相对温暖表层水的强烈影响密切相关。颗石藻丰度在约120千年前再次达到峰值，此后逐渐下降但仍维持在冰期水平之上。MIS 5.4与MIS 5.2两次降温冰阶事件打断了整体偏暖的气候背景，其识别标志为颗石藻丰度降低、喜温物种占比下降以及物种多样性降低。颗石藻丰度下降与多样性小幅降低，指示了向MIS 4起始阶段环境条件逐渐恶化。对颗石藻组合的分析显示，不仅MIS 5.4与MIS 5.2这两次冰阶事件以低温环境为特征，本研究还进一步证实了新近提出的学术观点：MIS 5.5的终止由约124千年前发生的表层海水短期小幅降温事件所主导。