Thermoluminescence ages of Quaternary volcanic rocks of the Doroyu Area, Akita, Japan.

The Kijiyama Pyroclastic Flow Deposits is proposed for a new formation name in the Doroyu area. It is supported by field and laboratory observations on rocks and minerals, and thermoluminescence (TL) dating results. Ages of 27 pyroclastic flow and lava samples show the clear succession of the Okumiyayama Volcanics, the Kabutoyama Pyroclasitic Flow Deposits, the Kijiyama Pyroclastic Flow Deposits and the Takamatsudake Volcanics in ascending order. The ages of them are 2.12 Ma, 1.16 Ma, 305 ka and 232 ka for averages of 5, 9, 10 and 2 samples, respectively. Eruption centers of the Kabutoyama and Kijiyama Pyroclastic Flows were estimated from a field geological survey. The distribution of a Ouaternary lacustrine formation, which has been considered as a part of the Tertiary Sanzugawa Formation, was newly recognized from the TL age of rock fragment.