Abstract
The Miocene strata newly found near Mt. Mitsutoge is named the Kawaguchiko formation. The formation is confirmed to be upper Miocene in age and lies unconformably on the middle Miocene Nishikatsura formation. Judging from the fact that the Kawaguchiko formation abuts on highly inclined fault surfaces (the plane of unconformity), it was accumulated in the collapse basin which was surrounded by some large faults. One of them, the Katsuragawa fault, had developed just before the deposition of the Kawaguchiko formation.
