Paleoniagnetism Study of Pliocene to Pleistocene Volcanic Rocks in Southwest Japan

Abstract

The directions of natural remanent magnetization of about 300 volcanic rock specimens collected from Southwest Japan of which ages range from Pliocene to Pleistocene were measured. The mean pole positions calculated from the results agree with the present geographic north pole within an oval of 95% confidence. This fact suggests that there were no considerable movement of paleomagnetic pole position during Pliocene and Pleistocene in Southwest Japan, and that Southwest Japan did not change its geographical situation since Pliocene epoch. Furthermore, the volcanic rocks of remote localities used in the study can be correlated much more exactly with one another by the aid of comprehensive knowledges, such as their stratigraphy, absolute age determined by isotope method and the paleomagnetic polarity change of their remanent magnetization.