A study of earth dynamics using deep sea drilling and borehole logging

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This study investigated ocean floor and earth dynamics using deep sea drilling samples, borehole logging and ocean floor observatory though participation to Ocean Drilling Program (ODP). Five major areas of contributions can be pointed out.(1) Evolution of ocean floorIt was confirmed that emplacement of oceanic plateau was related to mantle plume activity. Ontong Java Plateau was emplaced at120 Ma within a very short time.(2) Subduction zone studyDrilling in the Nankai Trough showed that the evolution of accretionary prism is largely influence incoming sediment types especially the types of clay minerals.(3) Environmental changesDeep water circulation played a key role in environmental valiability in the earth system. During the Cretaceous, the ocean was highly stratified.(4) Deep biosphere and gas hydrateDeep microbial community lives at depth close to 1000m and temperature up to 90 degrees. Deep microbial activity is closely related to methanogenesis and sulfate reduction. The discovery of this deep biospehre should have profound influence on our understanding of the earth system.