Paleocene ichthyofauna and paleoenvironmental setting, Imo Formation, southeastern Nigeria

Paleocene ichthyofauna and paleoenvironmental setting, Imo Formation, southeastern Nigeria

Stevens N J; Eastman J T; Odunze S O; Cooper L N; Obi G C

Neues Jahrbuch Fur Geologie Und Palaontologie-Abhandlungen

2011

2011-06

The Paleogene vertebrate fossil record of Nigeria has until recently been limited to marine deposits in the Eocene-age Ameki Formation. New work in the Imo Formation of southeastern Nigeria has revealed a diverse ichthyofauna of Paleocene age. The Imo Formation overlies the Nsukka Formation, and underlies the Ameki Formation. The uppermost bone-bearing interval of the Imo Formation is separated from the overlying Ameki Formation by a NW-SE trending, shorefacetidally-influenced sandstone ridge that dominates the Ozuitem-Umuahia landscape. The Ameki beds outcrop to the west of the sandstone ridge, whereas the Imo outcrops to the east. Fossils described herein were recovered from an interval of interstratified crudely laminated clay/shale and calcareous lenses of well-sorted sandstone/siltstone which outcrops to the east of the sandstone ridge in the Bende District. The fauna is represented by at least seven taxa, including an actinopterygian, five chondrichthyans (represented by one ray and four shark species), and Cylindracanthus, an enigmatic incertae sedis taxon. Five of the species in the Imo fauna appear to have survived into the Eocene, whereas the remaining two are hitherto undocumented in younger faunas of Nigeria.

Actinopterygii; Chondrichthyes; early Cenozoic; marine environments; Nigeria; paleobiogeography; paleoecology; Paleontology; sequence stratigraphy

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