Two foraminiferal zones of Uvigerina akitaensis-Epistominella shimanesis Assemblage-zone and Uvigerina (s.1.)-Cyclammina cancellata Assemblage-zone, which are onginally recognized-in Miocene deposits of the centralpart of the Shimane Peninsula (Nomura,1986b), are also recognized in the argillaceous rocks distributed between Chikumiand Kasaura, eastem part of the peninsula.
The Josoji and Ushikiri formations of Kano and Yoshida (1985) comprise the U.akitaensis-E. shimanesis Assemblage-zone and the Furue Formation of them is represented by the U. segundoensis (s.1.)-C. cancellata Assemblage-zone.