Abstract
The geologic settings of the Shimanto Terrain in the Kii Peninsula, the properties of coarser elastics and these source areas, and sedimentary structures were described in brief. The main geosynclinal stage of the Shimanto Terrain is from the Cretaceous to the lower Miocene and is divided into two sub-stages, that is, the Cretaceous and the Paleogene to the lower Miocene. The sediments of the former sub-stage (the Hidakagawa group) have eugeosynclinal sedimentary facies and the latter (the Muro group) miogeosynclinal. From, the viewpoint of tectonics, the difference between them is remarkable. Sediments of the Shimanto geosyncline are chiefly turbidites. Paleocurrent analysis by sole marks shows that the sediments of the Hidakagawa group were mostly supplied by longitudinal currents of the east to west and west to east trends, and those of the Muro group were mainly supplied longitudinally as in the case of the Hidakagawa group, and partly from north and from south by lateral currents. The northern provenance are the Acid Volcanics of the Inner Zone, the Ryoke Complex, the Paleozoics of the Chichibu Terrain and the Torinosu-group and its correlatives. The southern source area must have existed in the Pacific Ocean. The paleocurrent data and the discovery of the orthoquartzite gravels from the Muro group at the southern end of the peninsula suggest the existence of a missing former-land to the south of the Shimanto Terrain. These were discussed in some detail.
