丹波帯砂岩の特性

概要

論文の詳細を見る
The Tamba belt in the Inner Zone of Southwest Japan consists of two distinctive tectono-stratigraphic units, the Type I (Late Jurassic) and Type II (Late Triassic〜Middle Jurassic) suites. The latter is divided into three subunits, TIIa, TIIb and TIIc, according to differences of their age and lithology. These suites and subunits have a sort of upward-coarsening sequence of accretionary prism. Sandstone sequence of the Type I suite is composed of rather distal turbidites. On the contrary, that of the Type II suite exhibits more proximal feature. Petrography of sandstone in each suite and subunit was examined. Sandstone of the Type I suite is more quartzose than that of the Type II suite, and is assumed to be derived from a continental source area widely occupied by basement rocks. The sandstone composition of the Type II suite gradually change from lithic (TIIc) to feld-spathic (TIIa) as the age of deposition becomes younger. This alteration is due to the geologic change of the source area by some reason, for example, erosion.
地学団体研究会の論文
1989-03-25