Analysis of the relationship between development of the Monsoon-induced upwelling and calcareous nannoflora

由于西南季风的影响，阿拉伯半岛近海形成了强烈的上升流，但季风强度在冰期明显减弱。为了了解第四纪气候与植物区系的关系，我们在723A和722a两处进行了钙质纳米化石的研究。在表示最后270个Ky的序列中。723A岩芯低光生物Florisphaera profunda相对丰度的地层变化与三角洲^<18>的变化一致。然而，在间冰期增加的地层趋势与Molfino和Mcintyre模型相矛盾，该模型认为丰度在垂直混合的光带中下降。此外，在冰期中期，寒性Gephyrocapsa种类急剧增加，但在冰期极大期，暖性Gephyrocapsa种类占主导地位。在1.0 ~ 0.2 Ma之间，722站点的相对丰度在冰期期间有所增加，但在近20 Ma期间，723站点的趋势完全相反。正如预期的那样，在热带太平洋上升流中常见的小placiths在其地层变化中表现出与温暖的Gephyrocapsa物种相反的趋势。然而，这些记录与深孔藻的地层变化之间没有明显的关系。钙质纳米化石的变化与冰期/间冰期旋回的总趋势不一致

Because of the SW Monsoon, strong upwelling develops at the off coast of Arabian Peninsula, but the monsoon strength is postulated to be significantly weakened during glacial periods. In order to understand the relationship between the flora and the Quaternary climate, calcareous nannofossils were studied at a site where a strong coastal upwelling develops (Core 723A) and at another site where a moderate upwelling occurs (Core 722A&B). In the sequence representing the last 270 Ky. At Core 723A, the stratigraphic change in relative abundance of the lower-photic dweller Florisphaera profunda is concordant with that of delta ^<18>O.The stratigraphic trend, increasing in the interglacial periods, however is contradictory to the Molfino and Mcintyre Model that says the abundance drops in a vertically mixing photic zone. Moreover, although a cold Gephyrocapsa species sharply increased in the middle part of the glacials, a warm Gephyrocapsa species took over the dominance during the glacial maximums.Between 1.0 and 0.2 Ma at Site 722, the relative abundance of F.profunda increased during the glacials, but the trend is a complete opposite for the last 20 m.y., as was observed at Site 723. As expected, small placoliths that are common in the tropical Pacific upwelling exhibited a reversed trend in their stratigraphic variation with that of the warm Gephyrocapsa species. There is, however, no obvious relationship between these records and the stratigraphic variation of F.profunda. The observed changes in calcareous nannofossil are not concordant with the general trend of glacial/interglacial cycles