Middle Permian foraminifers of the Izuru and Nabeyama Formations in the Kuzu area, central Japan Part 2. Schubertellid and ozawainellid fusulinoideans, and non-fusulinoidean foraminifers

Abstract

Middle Permian Izuru and Nabeyama Formations in the Kuzu area, central Japan are divisible into three zones based on the stratigraphic distribution of larger fusulinoideans: the lower Parafusulina nakamigawai Zone, the middle Parafusulina yabei Zone, and the upper Parafusulina tochigiensis Zone. Although schubertellid and ozawainellid fusulinoideans and non-fusulinoidean foraminifers are accessary in comparison with dominant schwagerinid fusulinoideans, 56 species assignable to 25 genera and a few more indeterminate genera are distinguished in these three zones. Their taxonomic diversity is very low in the lower zone, and becomes higher in the middle zone and highest in the upper zone. The difference of their variety well agrees with lithologic change of limestone in these three zones. There are no remarkable differences in the faunal composition of schubertellid and ozawainellid fusulinoideans and non-fusulinoidean foraminifers between the Izuru and Nabeyama Formations and other contemporaneous limestones of Japan. The similar faunal composition of these groups shows a striking contrast to the provinciality of the schwagerinids and neoschwagerinids of the Izuru and Nabeyama Formations. Six species of schubertellid fusulinoideans newly proposed herein are systematically described and discussed. They are Schuberetella? karasawensis, Schubertella? minutisphaera, Codonofusiella ashioensis, Codonofusiella elongata, Codonofusiella nabeyamensis, and Dunbarula oviformis.