Composition of bottom sediments from the Central Basin of the Indian Ocean

A study of petrographic and mineral compositions of 26 sediment cores from the western part of the Central Basin of the Indian Ocean has identified biogenic, terrigenous, volcanogenic, and authigenic sediment types formed in certain facies conditions. On the basis of bio- and paleomagnetic stratigraphy data from the cores sedimentation rates of different sediment types have been calculated. Modern and Pliocene-Pleistocene positions of the main facies boundaries (the critical depth of carbonate accumulation, the geochemical boundary between hemi- and miopelagic zones, the frontal boundaries of the equatorial belt of biogenic silica accumulation) have been determined. It has been shown that the sedimentary process during Pliocene-Quaternary had cycle variations characterized by successive changes of different sedimentation types - hemipelagic, miopelagic, and biogenic.针对取自印度洋中央盆地西部的26根沉积岩芯开展的岩石学与矿物组成研究，识别出了特定沉积相环境中形成的生源沉积物、陆源沉积物、火山源沉积物及自生沉积物四类沉积类型。基于各岩芯的生物地层与古地磁地层数据，研究计算了不同沉积类型的沉积速率。研究确定了主要相边界在现代及上新世-更新世时期的分布状态，包括碳酸盐堆积临界深度、半远洋与近远洋带的地球化学边界，以及生源硅质堆积赤道带的锋面边界。研究表明，上新世-第四纪期间的沉积过程存在周期性变化，其特征为半远洋沉积、近远洋沉积与生源沉积等不同沉积类型的连续更替。