Paleoenvironmental Study by the Mineralogical and Geochemical Analyses of the Deep-Sea Drilling Cores

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Mineralogical and geochemical studies carried out on the DSDP and ODP cores from the Gulf of Mexico, the Arabian Sea, and the Bengal Fan. The purpose of this study is to clarify the paleoenvironmental factors from the mineralogical and geochemical characteristics of these cores. The results obtained differ conspicuously. For example, the sediment columns of the Gulf of Mexico is characterized by the abundance of smectite and kaolinite. The sediments of the Arabian Sea is essentially characterized by the presence of palygorskite. The sediments of the Bengal Fan have indeed variable clay mineral compositions since the Early Miocene. The factors influencing the clay mineral compositions are such as geology, diagenetic transformation, soil formation, river runoff, sea currents, and climatology so on. For example, the sediment columns of the Gulf of Mexico are greatly influenced by the river runoff from the Mississippi which is the major source of the lithogenic minerals. The sediments of t … More he Bengal Fan have received a tremendus quantity of clastic minerals from the Burahmaputra which originates from the Himalayas. The authors point that the movements of the Himalayas are closely related to the vertical change in clay mineral compositions since the Early Miocene. The Arabian Sea sediments contain the palygorskite in various proportion of sedimentary columns and the proportion changes with geological time. In the same manner, the geochemical parameters such as the ratios of K/Al, Ti/Al, Fe/Al, Cr/Al, Zn/Al, Ni/Al. Si/Al, P/Al, Sr/Ca, and Cu/Al in sedimentary columns indicate the changes of environments in geological past and suggest the paleoenvironmental events. The present study shows that the relationshie between the clay minealogy and geochemistry in sedimentary columns is not neccessarily recognized each other but play a comelementary role. For example, the ratios of Fe/Al, Cr/Al, Ni/Al, and Zn/Al in sedimentary columns suggest that other lithogenic minerals except clay minerals are contained and closely related to the changes of sedimentary environments. Less