Abstract
The Inumodorikyo Complex of the Southern Chichibu Belt in the eastern Kii Peninsula, Southwest Japan, consists of siliceous claystone, chert, dark green siliceous mudstone, and terrigenous clastic rocks, and is subdivided into the Nomata Belt on the north and Kuwanokidani Belt on the south by the north-dipping Nomata Thrust. Radiolarians recovered from the terrigenous clastic rocks show that the ages of the complex in the Nomata and Kuwanokidani Belts are, respectively, middle Bathonian to late Callovian (late Middle Jurassic) and late Callovian to Oxfordian (latest Middle to early Late Jurassic).
The structural analysis of the crush zone and fault rocks suggest that the Nomata Thrust really has a dominant reverse-slip component. NNE- to NE-trending high-angle faults cut the ENE-trending structures of the Inumodorikyo Complex as well as the middle Late Cretaceous accretionary complexes on the south. Moreover the strata of lower structural horizon widely expose on the east of the Nishiyamagawa - Kasagigawa Fault, which is one of the high-angle faults. Hence the high-angle faults are east-side-up, dip-slip faults and were likely active during latest Cretaceous to Paleogene time.
