Deformation of the Japanese Islands as inferred from Rock Magnetism

Abstract

Summary Results are presented of the directions of magnetization for twentyeight sets of rocks collected from different parts of Japan. The directions for rocks of Pre‐Tertiary age from south‐west Japan differ systematically from those from north‐east Japan. It is suggested that the difference is due to the deformation of the Japanese Islands in the late Mesozoic or early Tertiary. Because of the deformation, it is not possible to infer the accurate position of the geomagnetic dipole with respect to Japan for Pre‐Tertiary times.

Miocene clockwise rotation of southwest Japan and formation of curvature of the Median Tectonic Line: Paleomagnetic implications

“…Clockwise deflected paleomagnetic directions in Late Cretaceous to Paleogene rocks of southwest Japan (SW Japan) were first reported by Kawai et al [1961]. Later paleomagnetic studies established that SW Japan experienced clockwise rotation in Miocene times [e.g., Otofuji, 1996 …”

Timing of Rotational Motion of Southwest Japan Inferred from Paleomagnetism of the Setouchi Miocene Series

“…The past paleomagnetic studies done before 1970's have already revealed that remanent magnetization of the Cretaceous and Paleogene rocks in Southwest Japan shows significant declination shift relative to those in Northeast Japan (KAWAI et al, 1961;1971), and to those in the Korean Peninsula (YASKAWA, 1975). The pioneer workers suggested that the declination shift was caused by a clockwise rotation of Southwest Japan.…”

Magnetic Anomalies in the Sea of Japan

“…From the analysis of the paleomagnetic data in Japan, KAWAI et al (1961KAWAI et al ( , 1969KAWAI et al ( , 1971 concluded that the northeastern and southwestern parts of Honshu island rotated counterclockwisely and clockwisely, respectively, around a hinge in the central part of Honshu island at some time between Cretaceous and Upper Tertiary. This concept was further elaborated by additional paleomagnetic and age data from both the southwestern MATSUDA, 1983, 1984) and northeastern Japan (OTOFUJI et al, 1985;TOSHA, 1984).…”