Two new short-ranged Calcidiscus species from the offshore marine Neogene Niger Delta sequences

摘要

Two new species, Calcidiscus salamis sp. nov. and C. odebodea sp. nov. are described from the marine offshore Niger Delta Neogene sequence. Calcidiscus salamis is structurally similar to C. fuscus but has a closed central area. Calcidiscus odebodea differs from C. leptoporous in having strongly curved sutures. The new forms consistently occur throughout the Late Miocene to Early Pliocene offshore eastern and western Niger Delta sequences. They have the same stratigraphic range: NN11-NN13 zones (Messinian to Zanclean). The combination of their widespread geographic occurrence and short stratigraphic range makes them excellent index species for the high-resolution biostratigraphy of the Niger Delta marine offshore sequences where most Calcidiscus forms have much longer ranges. KEYWORDS: Calcareous nannofossil, Biostratigraphy, Calcidiscus, Niger Delta.