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

由于西南季风的影响，阿拉伯半岛近海出现了强烈的上升流，但据推测，在冰期季风强度将显著减弱。为了了解植物群与第四纪气候之间的关系，在沿海上升流强烈发育的地点(723A柱)和中等上升流发生的另一地点(722A&B柱)对钙质超微化石进行了研究。在代表最后270 Ky的序列中。在723A岩芯，低透光率生物的相对丰度的地层变化与三角洲的变化是一致的。然而，在间冰期增加的地层趋势与Molfino和McIntyre模型相矛盾，后者认为丰度在垂直混合的光学带中下降。在722站位1.0~0.2 Ma之间，深水螺类的相对丰度在冰期期间显著增加，但在最近20英里的变化趋势与723站位的情况完全相反。正如预期的那样，热带太平洋上升流中常见的小胎盘在其地层变化方面与温暖的GePhyrocapsa物种表现出相反的趋势。然而，这些记录与深井的地层变化没有明显的关系。观测到的钙质超微化石的变化与冰期/间冰期旋回的总体趋势不一致。

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