丹波地帯の古生界(その1) : 京都府北桑田郡京北町東部の古生層

Abstract

Studies of the Late Palaeozoic eugeosyncline in Japan have taken effort based on the researches chiefly of the formations on South Kitakami belt and the formations of calcareous facies in Southwest Japan. In the Tanba belt, Upper Palaeozoic formations of non-calcareous facies develop extensively and typically, and have been studied by several geologists. The central district in the belt, however, has been far behind other districts in the research of the strata, owing to paucity of the fossils, monotonous character of the lithology, and the complicated geologic structure which makes geological survey very troublesome. In this study, the way of investigation of sequence of these strata was examined. The internal sedimentary structures of the clastic beds, the character of crevices in the bedded chert, and the relation among the manganese ore bed and the chert beds, etc., were noticed as proofs of the stratigraphyical sequence of the strata. Thus, the sequence of the Palaeozoic formations was determined in descending order as follows. g. shale-sandstone formation 220m+ f. schalstein formation 600〜1200m e. shale formation 750m d. chert-shale formation 500〜640m c. shale formation 500〜600m b. chert formation 670〜700m a. shale formation 350m+ A limestone lens of the schalstein (f) yields Pseudo-fusulina sp.. The Palaeozic formations in this district is regarded, as a whole, to belong to Permian in age, and can be correlated to the middle and the lower part of "the Tanba group" of SAKAGUCHI (1952). There are several synclines and anticlines in this district extending in the direction of about E-W. Many faults develop extending in the direction of ENE-WSW, and WNW-ESE in this district.