Miocene intra-arc bending at an arc-arc collision zone, central Japan |
| |
| Authors: | Masaki Takahashi Kazuo Saito |
| |
| Institution: | Fuel Resources Department, Geological Survey of Japan, Tsukuba, Ibaraki 305, Japan;Department of Earth and Environmental Sciences, Yamagata University, Yamagata 990, Japan |
| |
| Abstract: | Abstract Recent paleomagnetic studies are reviewed in an effort to clarify the relationship between the intra-arc deformation of central Japan and the collision tectonics of the Izu-Bonin Arc. The cusp structure of the pre-Neogene terranes of central Japan, called the Kanto Syntaxis, suggests a collisional origin with the Izu-Bonin Arc. The paleomagnetic results and newly obtained radiometric ages of the Kanto Mountains revealed the Miocene rotational history of the east wing of the Kanto Syntaxis. More than 90° clockwise rotation of the Kanto Mountains took place after deposition of the Miocene Chichibu Basin (planktonic foraminiferal zone of N.8: 16.6–15.2 Ma). After synthesizing the paleomagnetic data of the Japanese Islands and collision tectonics of central Japan, it appears that approximately a half rotation (40–50°) probably occurred at ca 15 Ma in association with the rapid rotation of Southwest Japan. The remainder (50-40°) continued until 6 Ma, resulting in the sharp bent structure of the pre-Neogene accretionary complexes (Kanto Syntaxis). The latter rotation seems to have been caused by the collision of the Izu-Bonin Arc on the northwestward migrating Philippine Sea Plate. |
| |
| Keywords: | central Japan collision tectonics intra-arc deformation Miocene paleomagnetism tectonic rotation |
|
|
