[Abstract]

The Moritayama Lava lies in the adjacent area of Sambe Volcano, and has been thought as a part of Miocene basement rocks. Radiometric age determinations are carried out on the Moritayama Lava, and 0.9+-0.2 Ma (fission-track ED-2 method) and 1.01+-0.03 Ma (whole rock K-Ar method) are obtained. These data indicate that the Moritayama Lava is the first stage volcanic product of the Sambe Volcano at early Pleistocene time.

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