Formation and deformation processes of late Paleogene sedimentary basins in southern central Hokkaido, Japan: Paleomagnetic and numerical modeling approach

Abstract

Formation and deformation processes of the late Paleogene sedimentary basins related to a strike-slip fault system in southern central Hokkaido are described by a combination of paleomagnetic study and numerical analysis. After correction of the Miocene counter-clockwise rotation associated with back-arc opening of the Japan Sea, paleomagnetic declination data obtained from surface outcrops in the Umaoi and Yubari areas show significant easterly deflections. Although complicated differential rotation is anticipated as a result of recent thrust movements, clockwise rotation in the study areas is closely linked with development of the Paleogene Minami-naganuma Basin as a pull-apart depression along the north-south fault system. Numerical modeling suggests that 30 km of strike-slip is required to restore the distribution and volume of the Minami-naganuma Basin. The relative slip rate on the long-standing fault system is about 10 mm/yr, which corresponds to global-scale plate motion. It has inevitably caused regional rearrangement of the eastern Eurasian margin. A rotation field simulated by simplified dextral motion using dislocation modeling basically accords with the paleomagnetic data around the pull-apart basin. © 2009 Blackwell Publishing Asia Pty Ltd.