On the Paleogene Sandstone Dikes in the Muroto District, Shikoku Island, Southwest Japan

Abstract

In the Paleogene rocks of the Muroto district sandstone dikes are found in many localities. They occur invariably within shaly flysch-type rocks and not essentially associated with slumping. The material of the dikes was filled into fissures from above and/or below. In addition the paper deals with the origin of the dikes and their deformation. Fissuring in the desposits was probably caused by an underwater earthquake. The sandstone dikes show not only ptygmatic folding by the compaction of the surrounding rocks, but also are folded, faulted, and fractured through later orogenic movements, depending on their initial attitude.