Abstract
Fission track (FT) ages were determined for 14 tuff samples from the Miocene Mizunami and Iwamura groups in southeastern Gifu Prefecture, Central Japan. On the basis of FT ages for the Mizunami Group, the Hongo Formation was deposited ca. 17 Ma, and the Akeyo Formation was deposited at ∼17—16 Ma. For the Iwamura Group, the depositional age of the Agi Formation was found to be ca. 20—18 Ma and the lower part of the Toyama Formation was deposited at ∼17—16 Ma. Depositional FT ages for the Akeyo and Toyama formations are almost 1 Myr younger than their fossil ages.
