东北印度洋两类主要的深水沉积序列及其对喜马拉雅隆升的响应

Two types of deep-water sedimentary sequence in northeastern Indian Ocean and their response to the Himalayan Uplifts

东北印度洋存在两种典型的深水沉积序列,它们分别分布在盂加拉深海扇与东经90°海岭。深海扇以浊流沉积和半远洋沉积作用为主,沉积组份主要来自喜马拉雅山系直接剥蚀的物质材料;海岭以远洋沉积作用为主,沉积组份主要来自海洋环境下生成的钙质浮游生物壳体。两类沉积序列在物质组成和形成机理上存在着根本差别,但在聚积过程中都受到以喜马拉雅隆升为代表的构造运动的显著影响。本文应用DSDP218、ODP717、ODP758及其它来自东北印度洋的资料和样品,通过沉积学、微古生物学与古海洋学的综合研究,实现了9 Ma以来扇区近源相、远源相和岭区沉积记录中的事件对比。我们的工作表明,在东北印度洋所记录的众多与喜马拉雅山系隆升有关的地质事件中,3.5 Ma和0.8 Ma代表了最具规模和影响的两个演化阶段。

Two typical types of deep-water sedimentary sequence occur in the northeast Indian Ocean,which have been found on the Bengal fan and Ninetyeast Ridge, respectively. The turbidity and hemipelagic sedimentations are dominant in the Bengal fan, where the major composition of sediments are terrigenously derived from the denudation of Himalayan Mountains,while the pelagic sedimentation in the Ninetyeast ridge,where the major one from calcareous planktonic tests produced in ocean environment. Although there is an essential difference between them in material constituent and forming mechanism, both of two sedimentary sequences were deeply affected in their respective accumulation process by Himalayan tectonics. Using the data and samples of the holes DSDP218, ODP717,ODP758 and some others from the northern Indian Ocean, in the paper we make a comprehensive study of them in sedimentology, micropaleontology and paleoceanography and establish a correlation of geological events since 9 million years recorded in proximal fan, distal fan and ridge, respectively. Our results show that the most important and influential events took place at - 3.5 Ma and -0.8 Ma among all those episodes associated with the Himalayan uplifts.