The Paleogene Tokibariyama Formation around Fuse，Oki Dogo Island is divided into 7 members．The lowest member is a talus basal conglomerate which shows the facies of sediments at a foot of a steep cliff，and lower members abut agaist steep wall of their basement rocks．These facts show that the sedimentary basin have resulted from depression caused by faulting．Volcanic clasts in debris flow deposits at the upper part of the talus basal conglomerate implies that near the study area any other volcano-pulutonic activity had taken placed prior to sedimentation of the talus basal conglomerate．Probably several volcano-pulutonic activities occured during the Tokibariyama Formation stage．