丹波帯II型地層群天ケ瀬砂岩層の堆積機構と堆積場

概要

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The Tamba Group in the southeastern part of the Tamba Belt, Southwest Japan, can be devided into two stratigraphic units. Type I and Type II suites, based on lithology and age. The Type II suite is distributed to the south of Kisenyama fault. It is composed mainly of Permo-Triassic chert and Early to Middle Jurassic sandstone and mudstone which include olistostorome. The layered sandstone (TIIb) at the Amagase area was studied sedimentologically in detail. The results as follows. Clasts of sandstones and conglomerates were transported by debris flow (planar fabric and nondeforming "plugs"), grain-flow (reverse grading), and density-modified grain flow. Layered sandstones show thinning and fining upward sequences in general. Orientations of quartz grains trend NEN-SWS in direction. From these results and petrographical deta it is concluded that the coarse clastic sediments of Amagase area were derived from the western continental arc and transported mainly by longitudinal currents from the southwest along the subduction zone in Early to Middle Turassir East Asia.
地学団体研究会の論文
1989-07-25