Sediment composition of the Central Arctic Ocean@en

The sediment composition of deep-sea cores from the central Arctic Ocean, the Fram Strait, and the Yermak Plateau was analyzed for several parameters to reconstruct the history of marine paleoenvironment and terrestrial glaciation in the last 200,000 years. Layers with high amounts of coarse, terrigenous ice-rafted debris (IRD) and often high contents of smectite were deposited during extensive glaciations in northern Eurasia, when ice sheets reached the northern continental margins of the Barents and Kara seas and discharged icebergs into the Arctic Ocean. Intercalated layers with relatively low IRD and smectite contents, but abundant planktic foraminifers in the coarse fraction were deposited during periods of Atlantic Water inflow to the Arctic Ocean and seasonally open waters (leads) in a sea ice cover with only few icebergs in the Arctic Ocean. High IRD contents in the sediments reflect the presence of ice sheets on the Kara and Barents seas shelves and the hinterland during the entire oxygen isotope stage 6 (ca 190-130 ka), in substage 5b (ca 90-80 ka), at the stage boundary 5/4 (around 75 ka), and in late stage 4/early stage 3 (ca 65-50 ka). These results are in excellent correlation with those from recent field work in northern Scandinavia, European Russia, Siberia, and on the shelves. Relatively low amounts of IRD in central Arctic Ocean sediments from the Late Weichselian glacial maximum (ca 24-18 ka) correlate well with the recent reconstruction of a very limited eastern ice sheet extension during this time. […]本研究对北冰洋中部、弗拉姆海峡（Fram Strait）及耶尔马克高原（Yermak Plateau）的深海岩芯沉积物组成开展多参数分析，旨在重建过去20万年以来的海洋古环境与陆地冰川作用历史。在北欧亚大陆发生大规模冰川作用时期，冰盖延伸至巴伦支海与喀拉海北部大陆边缘，并向北冰洋释放冰山，此时沉积物中富集粗粒陆源冰筏碎屑（ice-rafted debris, IRD）及高含量蒙脱石（smectite）的地层得以沉积。而当大西洋水流入北冰洋、北极海冰覆盖中仅存在少量冰山且存在季节性开放水域（冰间湖，leads）时，沉积形成的夹层地层中冰筏碎屑与蒙脱石含量相对较低，但粗粒组分中浮游有孔虫（planktic foraminifers）丰富。沉积物中高含量的冰筏碎屑，反映了氧同位素6期（约190~130 ka）、5b亚期（约90~80 ka）、5/4阶段边界（约75 ka）以及4期晚期/3期早期（约65~50 ka）期间，喀拉海与巴伦支海陆架及其腹地存在冰盖。上述研究结果与近期在斯堪的纳维亚北部、欧洲俄罗斯、西伯利亚及各陆架开展的野外调查结果高度吻合。晚威斯康星冰盛期（约24~18 ka）北冰洋中部沉积物中较低的冰筏碎屑含量，也与近期重建的该时期东部冰盖扩张范围极为有限的结论高度一致。[...]