Characterization of Depositional Environment within Parts of Benin Formation, Akwa Ibom State, Nigeria Using Vertical Electrical Sounding Technique

This study presents a comprehensive interpretation of the depositional environment within the Benin Formation in Akwa Ibom State, Southeastern Nigeria, based on Vertical Electrical Sounding (VES) data integrated with borehole lithologic information. This study investigated the spatial variability of subsurface lithologies and their electrical resistivity signatures to reconstruct sedimentary facies and depositional settings. The VES data, acquired across key local government areas, reveal stratigraphic layering indicative of a fluviodeltaic depositional system, dominated by coarse- to fine-grained sand, gravel beds, and interbedded clay lenses. The lithostratigraphic interpretation delineates proximal braided fluvial facies transitioning into meandering river systems with floodplain deposits. The presence of resistivity values ranging from <100 Ωm (indicative of clay and silty sands) to >1500 Ωm (characteristic of coarse sand and gravel) supports the identification of high-energy channel fills and overbank deposits. Emphasis was placed on correlating resistivity signatures with sedimentary facies and curve types to delineate fluvial depositional systems and hydrogeological conditions. The VES data revealed stratigraphic sequences comprising high-resistivity coarse sands and gravels, interlayered with low-resistivity clay lenses. Curve types such as KHK, HK, and KH dominate the area, indicating multiple aquifer zones, including confined, semi-confined, and unconfined systems. These hydrostratigraphic interpretations support a fluviodeltaic model transitioning from braided to meandering systems, with implications for groundwater availability and environmental planning. The results provide a valuable framework for water resource management and geotechnical assessment in this region. This study offers insight into the paleoenvironmental conditions that control sediment supply and distribution, informing hydrogeological modeling and resource exploration within the region.