Calcareous Nannofossil of the Takatsukayama Member of the Meimi Formation in the Eastern Part of the Harima Plain, Western Japan

Abstract

The Takatsukayama Member of the Meimi Formation is distributed at the western foothill sof the Rokko Mountains, western Japan, and has been known as a Middle Pleistocene deposit intercalating a marine clay bed. Calcareous nannofossil assemblages in marine clay sediments were analyzed to clarif ythe biostratigraphi cage of the marine clay bed. The assemblages were dominated by Gephyrocapsa caribbeanica and G. oceanica together with the small type of Gephyrocapsa spp., while Pseudoemiliania lacunosa (the last appearance datum of 0.41 Ma) and Emiliania huxleyi (the first appearance datum of 0.25 Ma) were absent in all sediment samples. This result is consistent with our previous inference that the marine bed of the Takatsukayama Member was deposited during the period corresponding to the oxygen isotope stage 11 as derived from the eruption age (ca. 0.4 Ma) of the Takatsukayama volcanic ash layer.