Depositional age based on calcareous nannofossil biostratigraphy of the Miocene Uchiono Formation exposed in Daigo Town, Ibaraki Prefecture, Japan.

Abstract

Calcareous nannofossil assemblages in mudstone samples from the Miocene Uchiono Formation exposed in Daigo Town, Ibaraki Prefecture, Japan, were examined for the depositional ages. Five samples obtained from four sites yielded calcareous nannofossils indicating CN3 or CN4 zones, which are dated to 17.65–13.60 Ma (early–middle Miocene). These results are consistent with previous studies of radiometric ages of pyroclastic rocks as well as diatom biostratigraphy.