Paleomagnetic evidence of a drift of the Japanese main island during the paleogene period

Abstract

So far no paleomagnetic study of Paleogene rocks in Japan has been reported. In this paper paleomagnetic results are presented for Paleogene volcanic rocks which were taken from various localities in Southwest Japan. Thermal and alternating field demagnetization experiments have been carefully undertaken to clean the secondary unstable components in the natural remanent magnetization. From the result obtained it is shown that the Paleogene paleomagnetic pole deduced from Southwest Japan is appreciably far from that from the Eurasian continent. This fact might be well accepted as an additional proof supporting a hypothetical drift of the Japanese main island relative to the continent, since a certain time before the Cretaceous period, which was previously reported by the two authors. Such a drift of the Island should still continue during the Paleogene period until the Miocene epoch when the present geographic location of the Island was almost established.