Regional and local paleostresses detected from orientations of clastic dikes around mud diapirs in the Miocene Tanabe Group, southwest Japan

Abstract

Forearc basin fills in southwest Japan feature mud diapirs and many associated clastic dikes. The orientations of the clastic dikes allow estimates to be made of the regional tectonic paleostress field at the time of intrusion, although local and episodic changes in stress states may have been induced by the mud diapir intrusions. In this study, regional and local stresses were resolved from the analysis of clastic dike orientations in the Miocene Tanabe Group, southwest Japan. A normal-faulting stress with a WNW-ESE tension axis was common to all sub-areas, suggesting that the stress was regional and had a tectonic origin. This stress is broadly consistent with the N-S-trending maximum horizontal compression axis along the forearc of southwest Japan that prevailed in the early Middle Miocene.