Paleomagnetic directions of a volcanic and sedimentary sequence of the Kani Basin, ranging from 22 to 16 Ma, show a clockwise declination shift of about 50¿. This result implies that detectable rotation of Southwest Japan did not occur in this period, but after 16 Ma. The initial opening of the Japan Sea before 16 Ma might have caused a southeastward translation of Southwest Japan, which was then followed by clockwise rotation between 16 and 14 Ma. ¿American Geophysical Union 1991