Neogene kinematics in the Japan Sea region and volcanic activity of the northeast Japan Arc

Abstract

Deep sea drilling in the Japan Sea during ODP Legs 127 and 128 brought new constraints to the timing and dynamics of backarc opening. The nature and age of the oceanic basement as well as the recovered lithology allow us to present new reconstructions from 25 Ma to the present. The Japan Sea opened as a complex pull-apart basin in a dextral shear zone that extends more than 2000 km from Central Japan to Northern Sakhalin. Oceanic crust was emplaced in the northern part of the Japan Basin, and highly extended arc crust in the Tsushima and Yamato basins. Westward propagation of oceanic spreading was active in the early Miocene. Correlations between volcanic events and tectonic phases are observed, and the hypothesis that variations in the character of volcanism during the Neogene in Northeast Japan can be due to changes in the tectonic status of the arc crust other than deep-seated variations in the mantle is explored. The migration of the volcanic front through time from 30 Ma to the present is discussed with respect to tectonic processes. -from Authors