Visean – Moscovian conodont biostratigraphy of the Ko-yama Limestone Group, Akiyoshi Belt, SW Japan

Carboniferous clastic carbonates associated with basaltic pyroclasts and spicular chert beds in the lower part of the Ko-yama Limestone Group contain the Visean –Moscovian conodont succession of Gnathodus semiglaber (late Visean), Gnathodus praebilineatus – Lochriea multinodosa (late Visean), Lochriea ziegleri – Gnathodus girtyi girtyi s.l. (early Serpukhovian), Neoganthodus symmetricus – Idiognathodus primulus (middle – late Bashkirian), and Idiognathoides convexus – Gondolella clarki (early Moscovian). The FAD of Lochriea ziegleri marks the Visean/Serpukhovian boundary in the section. The middle – late Bashkirian Neoganthodus symmetricus – Idiognathodus primulus Fauna is a mixed fauna containing reworked Serpukhovian and older elements possibly related to an erosional event after the Early Bashkirian global eustatic low-stand. The revision of conodont zonal correlation in the Akiyoshi Belt was examined with the Mississippian/Pennsylvanian boundary considering the FAD of Declinognathodus noduliferus in the previously proposed zones in the similar Hina, Atetsu, Akiyoshi and Omi limestone groups. Idiognathodus craticulinodosus n. sp. was described as the middle – late Bashkirian to early Moscovian index.