Early Miocene freshwater diatom flora from the Yamato Rise, the Sea of Japan.

Fossil freshwater diatoms from tuffaceous–terrigenous deposits of the Yamato Rise, the Sea of Japan are described. The diatom flora includes 133 species and intraspecific taxa belonging to 44 genera. Species ofAulacoseira(19 taxa) andTetracyclus(17 taxa) are highly diversified, and species ofAulacoseiraandActinocyclusoccur very abundantly.Aulacoseirais mainly represented by extinct taxa, including those with elliptic valves that are characteristic of the Early Miocene (23–16 Ma). Such findings of numerous fossil freshwater diatoms in the Yamato Rise deposits strongly suggest that, during the Early Miocene, the Yamato Rise contained a lake basin within a terrestrial environment. Fifty-seven diatom taxa are illustrated. [ABSTRACT FROM PUBLISHER]