K-Ar ages of Middle and Late Pleistocene lavas from the Rishiri Volcano, off northern Hokkaido, Japan

Abstract

K-Ar ages of 0.07±0.02Ma, 0.09±0.02Ma, 0.50±0.31Ma, and 0.09±0.04Ma were newly obtained for the Ponmoshirito lava dome, Oshidomari pon’yama lava dome, Oshidomari lava and Minamihama lava respectively, from the Rishiri Volcano off north Hokkaido, Japan. Data for three of the lavas (not the Oshidomari lava) confirm an eruptive history in which the initial stage of volcanic activity lasted from 130 to 70ka.