Abstract
The Mesozoic of the Osugi area in Mie Prefecture is divided into the Chichibu Terrane and the Shimanto Terrane. The Chichibu Terrane thrusts up to the Shimanto Terrane. Six units of sedimentary complexes are discriminated in the Chichibu Terrane, namely the Sannoko, Kitamatagawa, Okutamadani, Kuroishi, Daifugendake and Wasabidani complexes in tectonostratigraphically descending order, and in the southern margin of the Osugi area, the Obadanigawa and Akataki complexes are distributed in the Shimanto Terrane, whereas in the north part of the Osugi area, the Mayoidake Complex belonging to the Shimanto Terrane thrusts up to the Chichibu Terrane. Each complex of the Chichibu and Shimanto terranes is divided by thrust. For the Shimotakogawa Fault which has E-W strike, the southern geologic bodies were descended lower than the northern part. Furthermore the western geologic bodies in the Osugi area collapsed along the arcuate Kamataki Fault and the tuffite dyke swarm. In the Osugi area, all complexes attributed to the Chichibu Terrane were firstly formed as the accretionaly complexes during middle to late Jurassic. The complexes included to the Shimanto Terrane, were formed in late Cretaceous. The Mayoidake Complex thrust up to the Chichibu Terrane during Paleogene, and the southern geologic bodies were descended down by the Shimotakogawa Fault. The tuffite dyke swarm and Kamataki Fault were closely caused by the volcanic activity during middle Miocene.
