Fusuline biostratigraphy and paleontology of the Akasaka Limestone, Gifu Prefecture, Japan

Abstract

In the Akasaka Limestone, the following 9 fusuline zones are proposed in ascending order: (1) Parafusulina granum-avenae Zone, (2) Neoschwagerina (Cancellina) nipponica Zone, (3) N. simplex Zone, (4) Pseudodoliolina ozawai Zone, (5) N. craticulifera Zone, (6) N. margaritae Zone, (7) Yabeina igoi Zone, (8) Y. globosa Zone and (9) Codonofusiella cf. kueichowensis Zone.

New findings and ideas resulted from the present investigation are the following: (1) Yabeina multiseptata is discovered for the first time in the limestone beds of the Yabeina igoi Zone in association with Y. igoi. (2) Reichelina changhsingensis is found from the upper part of the Neoschwagerina margaritae Zone indicating its first appearance as upper Murgabian. According to this finding, Reiclielina changhsingensis may no longer be an index species of the Dzhulfian.

In the fusuline paleontology, "septal pocket", an important but virtually unknown biocharacter attaching on the antethecal portion of the septa of some neoschwagerinids, is introduced and discussed in detail. Stratigraphic, taxonomic and phylogenetic significance of this biocharacter may stimulate new areas of research interest.

Totally 39 species of 10 fusuline genera are discriminated from the limestone. Among the species identified, 20 species assignable to the genus Neoschwagerina and 6 to Yabeina are systematically described.