Paleomagnetism and fission-track geochronology on the Goto and Tsushima Islands in the Tsushima Strait area: implications for the opening mode of the Japan Sea

Abstract

Paleomagnetism of Neogene rocks in the Goto Islands and fission-track (FT) geochronology of Miocene igneous rocks in the Goto and Tsushima Islands were investigated in order to reveal Miocene tectonics in the Tsushima Strait area. The results, in conjunction with previously-reported paleomagnetic data in the Tsushima Islands, suggest that the Goto Islands were rotated at the early to middle Miocene before about 15 Ma and that the CCW of the Tsushikma islands occurred after about 15 Ma. The CCW rotations of these islands imply that the Tsushima Strait area did not belong to the Southest Japan block in terms of clock-wise (CW) rotation at about 15 Ma, constraining the western margin of the CW-rotated block. -from Authors