Paleomagnetic evidence for northward drift and clockwise rotation of the Izu-Bonin Forearc since the early Oligocene

Abstract

A paleomagnetic study was made on the deep-marine sediments and volcanic rocks drilled by ODP Leg 126 in the Izu-Bonin forearc region. Oligocene to early Miocene samples show 10° to 14° shallower paleolatitudes than those of the present. Middle Miocene to early Oligocene samples show progressive clockwise deflections (up to ~80°) in declination with time. These results suggest large northward drift and clockwise rotation of the Izu-Bonin forearc region since early Oligocene time. Considering previous paleomagnetic results from the other regions in the Philippine Sea, this motion may reflect large clockwise rotation of the whole Philippine Sea Plate over the past 40 m.y. -from Authors