Reconstruction of Quaternary paleoenvironment in the Indian and Western Pacific Oceans based upon floral analysis of calcareous nannofossils.

通过对四个岩芯中的钙质超微植物群进行分析，三个岩芯来自东印度洋的热带至温带地区，一个岩芯来自澳大利亚东南部的近海地区，以重建印度洋和西太平洋的第四纪古海洋学历史。结果表明：1）3种低透光性类群的相对丰度具有同步波动的特征，因此，深花囊藻（Florisphaera profunda）的地层变化可以准确地反映其在透光性水体中的稳定性。季风强度的100kyr周期性与轨道偏心率相对应，而F.profunda丰度的显著减少表明间冰期季风的显著减弱。3）冰期期间，Leeuwin海流的影响大大减弱，从西澳大利亚近海采集的两个中纬度岩心中F.profunda丰度的减少表明，4）过去14kyr来，列文海流一直在南大洋北方边缘流动，热带类群的完全消失证实了该海流在过去冰期的消失。

Calcareous nannoflora in four cores, three from the tropical to temperate regions of the eastern Indian Ocean and one from off-coast of SE Australia, were analyzed to reconstruct Quaternary paleoceanographic history of the Indian and Western Pacific Oceans. Followings are the major results of this investigation.1) Relative abundances of three lower-photic taxa fluctuated synchronously, thus the stratigraphic change in Florisphaera profunda, which is generally the only species preserved in deep sea sediment, was proven to be an accurate indicator of the strata stability in euphotic water.2) The percentage abundance of F.profunda indicates a ca. 100 kyr cyclicity of the monsoonal strength corresponding to the orbital eccentricity, and the significant reduction in F.profunda abundance indicates significant weakening of the monsoon during the interglacial periods.3) Influence of the Leeuwin Current lessened greatly during the glacial periods, and the reduction in F.profunda abundance in two mid-latitude cores taken from off-coast of the western Australia indicates a lower lower-photic temperature which was resulted by an increased influence of the Western Australian Current.4) The Leeuwin Current flows continuously at the northern margin of the Southern Ocean for the last 14 kyr, and the complete disappearance of tropical taxa confirmed the disappearance of the current during the past glacial periods.