Paleobiogeographic affinities and paleoecological significance of paleogene ostracods from Eastern Benin Basin, Southwestern Nigeria

Ditch cutting samples from the studied section of the RC-4 Hole, eastern Benin (Dahomey) Basin were studied for their ostracod content. 3671 ostracod fauna belonging to 22 species were recovered and analysed with a view to determining ostracod paleobiogeographic affinities and paleoecological conditions within this part of the basin during the Paleogene. Ostracod assemblages of the studied section bear close affinities to those of some North and West African basins. Species such as Bairdia ilaroensis, Leguminocythereis spp., Bairdia malzi, Paracosta kefensis, Xestoleberis tunisiensis, Buntonia jordanica, Aegyptiana duwiensis and Leguminocythereis lokossaensis identified from the RC-4 hole suggest shallow neritic conditions. Paracosta kefensis and Paracosta parakefensis occur in high abundance indicating marine upwelling conditions. Many of the species recovered in this study have also been identified from Iullemeden and southern Tethys basins (e.g. Sirte Basin) suggesting ostracod migration from Benin Basin (Gulf of Guinea) to southern Tethys basins through the Paleogene shallow Trans – Saharan Seaway. A distinct ostracod turnover at the top of the limestone unit (Ewekoro Formation) is related to the Paleoceneo Eocene Thermal Maximum (PETM) – a climatic phenomenon characterised by 5 – 8 C global temperature rise at the end of the Paleocene.