Geoscience reports of Shimane University

number of downloads : ?
Geoscience reports of Shimane University 14
1995-12-25 発行


The Tokibariyama Formation in the central part of the Oki-Dogo Island
Adachi, Katsuhiko
Komuro, Hiroaki
Murakami, Hisashi
The Tokibadyama Formation of Late Oligocene to Early Miocene in the central part of Oki Dogo Island mainly consists of felsic to andesitic volcanic rocks and volcaniclastic rocks.It is divided into three members ; the Nakadani Andesite,Choshigawa Rhyolite and Chikaishigawa Andesite Members,in ascending order.The upper part of Choshigawa Rhyolite Member contains intercalated lacustrine shale beds.The Chikaishigawa Andesite Member mainly consists of two pyroxene andesite and clinopyroxene andesite lavas with autobrecciation,partly of andesitic volcaniclastic rocks and olivine basalt lavas.
Most of faults and fold axes strike NE-SW to ENE-WSW.These structural trends may represent the regional stress field during Oligocene.