COMPARATIVE STUDY OF THE CAPITANIAN (LATE GUADALUPIAN) FORAMINIFERAL FAUNAS IN THE LEPIDOLINA SHIRAIWENSIS ZONE OF THE AKIYOSHI LIMESTONE GROUP, SW JAPAN

Abstract

Middle Permian (Guadalupian) foraminiferal faunas in Japan are divided into the Akiyoshi, Chichibu, and Kurosegawa faunas based on the spatiotemporal distribution and phyletic evolution mainly of neoschwagerinid, verbeekinid, and schwagerinid fusulines. The Capitanian Akiyoshi Fauna of the Lepidolina shiraiwensis Zone in the Akiyoshi Limestone Group of the Akiyoshi Belt consists of 48 species assignable to 35 genera of foraminifers (17 species assignable to 13 genera of fusulines and 31 species to 22 genera of non-fusuline foraminifers). Fusulines in the fauna are represented by Lepidolina shiraiwensis, Sumatrina longissima, and Verbeekina douvillei . On the whole, the Capitanian Akiyoshi Fauna is as variable as the coeval Chichibu Fauna and somewhat less variable than the coeval Kurosegawa Fauna. The interrelation of variability and richness between the fusuline and non-fusuline foraminifers is locally controlled by ecological and depositional facies changes during the Capitanian. Taxonomic composition and richness of these three faunas throughout the Middle to Late Permian are related to environmental and faunal changes in the Panthalassan-originated seamounts and continental shelves in and around circum-Pacific regions. Twelve species assignable to nine genera including Parafusulina nagatoensis n. sp. are systematically described from the Lepidolina shiraiwensis Zone of the Akiyoshi Limestone Group.