Provenance of Miocene sandstones from ODP sites in the Japan Sea

Abstract

Ocean Drilling Program (ODP) scientists recovered Miocene sandstones at three drill sites in the Japan Sea during Leg 127/128 operations in the summer of 1989. Shipboard examination determined that these sandstones were deposited at upper to middle bathyal depths by turbidity currents. Subsequent petrographic and geochemical analyses of sandstone samples from these sites show that upper Miocene sandstones from Site 796 in the northeastern part of the Japan Basin were derived from a dominantly pyroclastic volcanic source or sources that lay in an undissected magmatic arc on or near southwestern Hokkaido, Japan. Lower Miocene sandstones from Site 797, located in Yamato Basin southeast of Yamato Rise, were also derived mainly from a volcanic source area. This source area lay in an undissected to transitional magmatic arc that was probably located near west-central Honshu, Japan, and that included some metamorphic, sedimentary, and plutonic source rocks. Lower Miocene sandstones at Site 799, which lies in the southwestern end of Kita-Yamato Trough on Yamato Rise, were derived primarily from granitic source rocks, with minor contribution of detritus from volcanic, metamorphic, and sedimentary source rocks. The principal source of sediment for Site 799 sandstones was probably the granitic rocks of Kita-Yamato Bank, which lies nearby to the west of Site 799 on Yamato Rise.