Heavy mineral distributions in the surface sediments of the Osumi Strait, south of Kyushu, Japan

概要

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Heavy mineral analyses were made for 18 samples of marine surface sediments in the Osumi Strait, south of Kyushu, Japan. Hypersthene is the most abundant, common hornblende, augite and olivine are next among the non-opaque minerals. The amount of heavy minerals is rich in the southwestern part of the Strait. There is a tendency to decrease in the total amount of heavy minerals and in specific gravity of bulk sediments northeastward. Surface sediments tend to become finer in the same direction. The current velocity necessary to move the sediment grain is changed with the specific gravity at the same grain size, because the grains with higher specific gravity are less mobile than the grains with lower specific gravity. It is considered that the grains are transported to the direction toward which the sediments become lighter in specific gravity and finer in grain size. Therefore, surface sediments distributed in the Osumi Strait are moved from southwest to northeast. This direction is concordant with the dominant current direction in the Strait. This means that the sediments are transported by the ocean current, the Osumi Branch Current, one of the branches of the Kuroshio flowing through the Strait and that the sediment distribution is highly influenced by the current.
日本堆積学会の論文