Fission-track ages of the volcanic ash layers in the Osaka Group, northwest part of Awaji island, Japan

Abstract

Fission track ages of zircon crystals were determined for To 1 and A 2-1 volcanic ash layers of Osaka Group in the northwest of Awaji island. The fission track ages obtained are follows : To-1 volcanic ash layer 2.4±0.6 Ma A 2-1 volcanic ash layer 2.2±0.5 Ma A 2-1 volcanic ash layer is correlated to Asano 2 volcanic ash layer. These ages indicates that the Osaka Group in this study area is correlated to the lower to lowermost part of Osaka Group.