K-Ar ages of the Lavas from Kirigamine Volcano, Central Japan

Oikawa, Teruki; Nishiki, Kuniaki*

The authors will report two K-Ar ages of volcanic rocks from the Kirigamine Volcano, which composes the uppermost part of the Enrei Formation. Based on the newly obtained ages, previously reported radiometric ages, and volcanostratigraphic data, we identify activity periods of 1.3 to 0.75Ma for Kirigamine Volcano. And, we estimate that the Oiwake Volcanic Graben field by Kirigamine Volcano formed rapidly at ca 0.85Ma. Judging from the previous studies and this study, the duration of the activity of the Enrei Formation is mainly ca.1.5 to 0.75 Ma.