Current Understanding of the Eastern Dahomey Basin: Consensus, Controversies, and Future Research Gaps

Abstract

The Eastern Dahomey Basin, the Nigerian sector of the wider Dahomey (Benin) Embayment that fringes the Gulf of Guinea, has attracted more than five decades of geological enquiry, yet its stratigraphic nomenclature, structural geometry, petroleum potential and groundwater systems remain incompletely reconciled across the published literature. This review synthesises the current state of knowledge on the basin's tectonic evolution, lithostratigraphy, geophysical architecture, petroleum system elements, hydrogeological framework and geochemical character, drawing on peer-reviewed studies published largely within the past decade alongside foundational works that established the basin's structural and stratigraphic framework. Consensus has been reached on the broad tectono-stratigraphic staging of the basin into pre-rift, rift, transitional and post-rift megasequences, and on the presence of a shallow, saline-vulnerable coastal aquifer system that supplies a substantial share of groundwater demand in southwestern Nigeria. Persistent controversies concern the precise position of the basement–sediment boundary, the true source of the extensive bituminous sand deposits along the eastern flank of the basin, the viability of a self-contained petroleum system independent of migration from the Niger Delta, and the stratigraphic correlation between the onshore and offshore sectors of the embayment. The review identifies research gaps relating to three-dimensional basin modelling, integrated onshore–offshore seismic stratigraphy, long-term aquifer monitoring, and the application of machine-learning-assisted geochemical prediction to frontier exploration. Recommendations for future research are outlined, together with an assessment of the limitations inherent in the present body of literature.