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

为了重建印度洋和西太平洋的第四纪古海洋学历史，对东印度洋热带温带地区的3个岩心和澳大利亚东南部近海的1个岩心的钙质超微植物群进行了分析。研究的主要结果如下：1)三个低光速类群的相对丰度同步波动，因此深部浮游藻类的地层变化被证明是真光水中地层稳定性的准确指标。深部浮游动物通常是保存在深海沉积物中的唯一物种。2)深部浮游动物的百分比丰度表明与轨道偏心率对应的季风强度的周期性约为100 KYR，而深部浮游植物丰度的显著降低表明间冰期季风显著减弱。3)在冰期，勒温洋流的影响大大减弱。而取自西澳大利亚近海的两个中纬度岩心深水海流丰度的降低表明，由于西澳洋流的影响增加，导致了较低的低光温。4)近14KYR以来，南大洋北缘持续流动的勒文流，热带类群的完全消失证实了过去冰期海流的消失。

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.