Calcareous Microfossil Biostratigraphy of the Uppermost Cenozoic Formations Distributed in the Coast of the Japan Sea

Abstract

The calcareous nannofossil and the foraminiferal assemblages of the uppermost Cenozoic formations distributed in the Oga Peninsula and the Akita area are described. Among twelve calcareous nannofossil biohorizons recognized in the Quarternary sequences in the North Atlantic Ocean during DSDP-IPOD Leg 94 (TAKAYAMA and SATO, 1987), seven calcareous nannofossil biohorizons are detected in this area. In the Oga Peninsula, the upper Funakawa and the lowest Kitaura formations are late Pliocene, and the middle to upper Kitaura and the Wakimoto formations are Pleistocene in age based on the results of DSDP-IPOD Leg 94. The Tentokuji and the Sasaoka formations, the uppermost marine sediments in the Akita area are late Pliocene in age. Consequently, the Tentokuji and the Sasaoka formations in the Akita area are correlative with the upper Funakawa to the lowest Kitaura formations in the Oga Peninsula.