Distribution and dike orientations of the lower Miocene volcanic rocks in the coastal area around the Hyogo-Tottori prefectural border, Japan

Abstract

Geological mapping and paleostress analysis were carried out in the coastal area around the border between Hyogo and Tottori prefectures in southwest Japan. The study area comprises volcanic rocks of the lower Miocene Yoka Formation of the Hokutan Group and the Kawabara Volcanic Member of the Tottori Group. The distribution of these rocks indicates they were emplaced into a >10-km length, E–W-trending basin that formed in response to normal faulting. The orientations of 63 syn-volcanic dikes were measured. Paleostress analysis of the dyke orientations indicates that the study area was under an extensional stress regime at the time of intrusion, consistent with previously reported paleostress data from the Hokutan Basin.