Miocene tectonic deformation of central Japan-Paleomagnetic evidence of intra-arc bending

Abstract

Recent paleomagnetic studies in the Kanto Mountains, central Japan, have revealed Miocene rotation of the east-wing of the bending structure of pre-Neogene geologic terranes. More than 90° colckwise rotation of the Kanto Mountains took place between 15 and 6 Ma. In contrast, Southwest Japan and it eastern part (Nohi area) have rotate clockwise through 47° and 13-17° around 15 Ma, respectively. This differential rotation represents an intra-arc deformation during the Miocene. In addition, the field investigations reveal that the Izu-Bonin arc has been colliding with central Japan since the Middle Miocene. Along whit this previous paleomagnetic results accompanied with geological studies in central Japan, it is concluded that lateral bending of central Japan occurred during 15 and 16 Ma in association with the collision between the southeastward drifting Japanese Islands and the northwestward migrating Izu-Bonin arc.