丹波地帯の古生界(その3) : 京都市北方大森・雲ケ畑地域の古生層

Abstract

In this report, the authors have dealt with the stratigraphy, litho-facies, and geological structure of the Palaeozoic formations, that are distributed in the northern part of Kyoto City, which is located at the eastern part of the district described in Part II. The sequence of the Palaeozoic formations is as follows (in descending order): The Ohmori The Kumogahata synclinal area synclinal area l. Sandstone formation 1750 m 1750 m k. Chert formation 210m 1200m j. Shale-sandstone formation 1000m 4000 m + i. Chert formation 800-250 m 600-400 m h. Schalestein formation 50-300 m 100 m g. Shale-sandstone formation 1500 m + The thickness of the entire formations measured in this district attains to 5310-4800 m at the Ohmori synclinal area and to 7650-7450 ra at the Kumogahata synclinal area. Some fusulinids fossils, namely Pseudoschwagerina sp. and Pseudofusulina sp., were collected from a few limestone-lentils in the f-schalestein formation. So the greater part of the formations in this district is regarded to be Lower to Middle Permian in age. The formations form as a whole a synclinal structure named "Shuzan syncline" by MATSUSHITA (1953). It has been cleared that the syncline was composed of two minor synclines plunging to the west and to the north-west and an anticline also plunging to the west. The thickness of clastic formations obviously increases four to ten times from the wings of minor synclines towards their axial parts. The variation in thickness is related to the original amounts of sediments. We have also referred to the sedimentary features of some bedded cherts collected from the surveyed area.