[Abstract]

Quaternary volcanic products erupted from five volcanoes located in the central part of the Hida Mountain Range. In the central part of Hida Mountain RangeThese are, following five volcanoes are distributed as a few km3 stratovolcano: the Kaminorouka Volcanic Rocks, the Warimodake Andesite, and eruptives from, the Iwagokekotani Volcano, the Kumonotaira Volcano, the Warimodake Volcano and the Washibaike vVolcanoes. We have determined the K-Ar ages for 5 specimens five lava samples collected from the above volcanoes except forwithout the Washibaike Volcano. The K-Ar ages are measured for separated groundmass from the lavas. Based on the newly obtained obtained 5 K-Ar ages for separated groundmass, previously reported seven 9 radiometric ages, and volcanostratigraphic data, we identify activity periods of each centers. These are: following active periods of the each volcanoes are ledca. 0.9Ma for: Iwagokekotani Volcano (0.9 MaÅ}), 0.4 -0.2Ma for the Kaminorouka Volcanic Rocks (0.4-0.2 Ma), 0.3-0.1Ma for Kumonotaira Volcano, ca. 0.3Ma for Warimodake andesite, (0.3-0.1 Ma) and 0.12-0.01Ma for Washibaike Volcano, most of which are in the late early Pleistocene to the late Pleistocene. (0.12-0.01? Ma) from older to younger. As deposition of the Kumonotaira Grabel Bed occur simultaneously with the early activity of Kaminorouka Volcano (ca. 0.4-0.3 Ma), it may be inferred that the activity causes damming up of the old Kurobegawa River and then the Kumonotaira Gravel Bed are accumulated.

e-mail:

oikawa.teruki@jnc.go.j