Paleocene Ostracods Of The Eastern Dahomey Basin Of Nigeria: Implications For Paleoenvironmental, Paleobiogeographic And Hydrocarbon Exploration Efforts

Abstract

This study investigates the paleoenvironmental conditions, paleo-biogeographic affinities, and paleoecological significance of Paleocene ostracods from the Ewekoro Formation in the eastern Dahomey Basin, Nigeria. Less attention has been given to ostracods study in Nigeria. The research aimed at understanding the paleoecological and paleobiogeographic distributions of the ostracods from borehole data in the eastern Dahomey Basin of Nigeria and their relationship to other African basins. The carbonates samples were analysed using sedimentological and micropaleontological methods. Eleven carbonates samples that were carefully collected from borehole BH-22 and processed based on Nagy et al. (1988) procedure were used for this study, yielding 18 well-preserved ostracod species. These species include Soundanella laciniosa triangulata, Bardia ilaroensis, Nigeroloxoconcha acgyptiaca, Paracosta kefensis, Xestoleberis tunisiensis, and others. The identified assemblages reflect a heterogenous neritic zone, ranging from high-energy nearshore to low-energy outer neritic settings. Species such as Bardia ilaroensis and Nigeroloxoconcha aegyptiaca, indicate shallow marine or estuarine environments, while Cytherella species suggest deeper, low-energy conditions. The paleobiogeographic distribution supports a Trans-Saharan Seaway connection during the Paleocene–Eocene, linking the Southern Tethys and West African provinces. Ostracod species between the eastern Dahomey Basin and regions in North Africa, the Middle East, and other parts of West Africa indicate significant faunal interchange. For hydrocarbon exploration in the basin, the limestone units and interbedded light grey sandstone of the Ewekoro Formation suggest potential reservoirs, while black shales indicate potential source rock. The identified ostracods provide biostratigraphic markers enhancing the predictability of reservoir and source rock distribution in the basin.