末次冰消期以来白令海盆的冰筏碎屑事件与古海洋学演变记录

通过对白令海盆中部BR02岩芯高分辨率的颜色、粒度和元素地球化学地层的研究发现:(1)该岩芯较为完整地记录了末次盛冰期结束以来(约16.3 ka BP)的多期冰筏碎屑事件,包括H1、OD、YD和北方2期,其中以H1和YD最为显著,反映了末次冰消期以来该地区海冰/冰山以及区域性冰川的消长变化;(2)BR02岩芯上部17—25 cm段出现富Mn、富Ba的氧化型沉积,说明在全新世高海面时期,白令海与北太平洋、北冰洋之间的水体交换达到极点,白令海环流加强,海盆底层水含氧状况明显改善,并引发海洋生产力增加;(3)CaO、Na2O、Sr、Zr及Na2O/K2O比值的分布说明,海盆冰筏碎屑主要来自富碳酸盐的育空河流域,其次为阿拉斯加半岛和阿留申群岛等火山岩区;岩芯上部Na2O/K2O比值的递增暗示10 ka BP以来与火山物质输运有关的北太平洋入流(阿拉斯加流)可能增加。

ICE-RAFTED DETRITUSEVENTS AND PALEOCEANOGRAPHIC RECORDS IN TNE BERING BASIN SINCE LAST DEGLACIATION

Based on the study of high resolution of sediment grain size, color reflectance and elemental stratigraphy of core BR02 dredged from the central part of the Bering Basin, we found: (1) Core BR02 provides perfect records for ice-rafted detritus (IRD) events happened since 16.3 ka Cal BP at the end of the Last Glacial Maximum including H1, OD, YD and Boreal2, among which H1 and YD are more significant. These IRD events all happened in the cold episodes or stadials, and indicated the changes in sea ice/iceberg condition in the sea and local glaciers in the surrounding lands. (2) The interval of Mn- and Ba-rich sediments at 17-25cm in the upper part of BR02 indicated water exchanges between the North Pacific-Bering Sea-the Arctic Ocean increased to the highest points during the Holocene high sea level period, which induced the circulation and seabed redox to change and marine productivity to increase in the Bering Basin; (3) the concentration of CaO, Na₂O, Sr, Zr and Na₂O/K₂O ratio indicated the IRD are derived mainly from the Yukon River drainage, and secondarily from the volcanic province including Alaska Peninsula and Aleutian Islands; Meanwhile, the gradual increase of Na₂O/K₂O ratio in the upper part of the core indicated the circulation especially the influences of the Alaska Current for sediments was enhanced since 10 ka BP.