(Appendix) Mineral composition of ODP Leg 128 sandstone samples

Deep drilling in the Japan Sea during Legs 127 and 128 resulted in recovery of volcanic lithic sandstones from Leg 127, Sites 796 and 797, and feldspathic sandstones from Leg 128, Site 799. Petrographic and geochemical analyses of sandstone framework grains define source-rock lithology and the tectonic setting of the source areas that furnished the framework constituents of these sandstones. Our analyses indicate 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 in 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. Volcanic, metamorphic, and sedimentary source rocks also furnished detritus to this site. The principal source of sediment for Site 799 sandstones was probably the granitic and sedimentary rocks of Kita-Yamato Bank, which lies nearby to the west of Site 799 on Yamato Rise. Minor amounts of volcanic detritus, which was probably shed from Yamato Bank east of Site 799, also reached Site 799. The sandstones from Sites 796, 797, and 799 were deposited at upper to middle bathyal depths by turbidity currents.