The area consists of an autochthonous group, thrusting sheet, Klippen and Yokokura igneous group which intrudes the other three., The first group comprising the Upper Chichibu group of the Permo-Carboniferous age, late Jurassic Torinosu, Wealden Ryoseki and early Cretaceous Monobegawa series forms a complicate syncline and is thrust by the Decken-sheet which is composed chiefly of green phyllites., This somewhat resembles the Mikabu group in the rock-aspect and is appapently overlain by the Permo-Carboniferous formation in the same Decke., The Klippen are represented by the Permo-Carboniferous formations and the Kochigatani series the latter of which is a thin neritic deposit of the late Triassic period., The geologic structure of the area is complicated by folding, thrusting, faulting, and igneous intrusion., As the Halysites limestone bearing Imose formation thrusts on the Ryoseki or Monobegawa series on the south side and is intruded by granitic rock on the north, its stratigraphic position cannot actually be determined, but the limestone may possibly be located somewhere in a horizon below the green phyllitic rocks.,
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