Composition and Texture of Surface Sediment Indicating the Depositional Environments off Northeast Taiwan


Surfacial sediments of 27 piston cores, 14 gravity cores and 5 dredged samples were taken from an offshore area of northeastern Taiwan for delineating the depositional features beneath the Kuroshio Current and around the southwestern edge of the East China Sea. The turn of direction from the Kuroshio Current in this area has resulted primarily from the effect of an ascent of the seafloor. The China coast current has spread coarse sediment in the East China Sea, composed primarily of quartz, feldspar and mafic minerals toward the area of 26¢XN, 122¢XE. Fine sediments may, however, be distributed beyond the east of 123¢XE. Rock fragments and mafic minerals have been concentrated in the north of Taiwan, as delivered by the Kuroshio Current. Two upwellings have possibly deposited calcareous biogeneous materials on the seafloor: one being located at the south of the depositional boundary in which the sediments are derived from mainland China; and the other one being located at 25.6¢XN, 122.4¢XE just on top of the Lan-Yan Fan. In the Okinawa Trough, the sediments beneath the path of the main Kuroshio flow have been shown here to be composed of non-biogenic, fine-grained mud.

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