Abstract

This study investigates the depositional history and environmental conditions of sedimentary rocks exposed in Uhiere village, located in the Benin flank of Nigeria. Grain size analysis, heavy mineral analysis, and palynomorph assemblage studies were conducted on selected samples from the outcrop to gain insights into the formation of these sedimentary rocks. Grain size analysis showed that the sediments range from very fine grained to medium-grained with poor sorting, indicating deposition by low to moderate velocity currents alternating with quiet depositional regimes during which shales were deposited. Heavy mineral analysis and morphoscopic studies indicated an igneous and metamorphic source for the sediments and proximity to the source area. Palynomorph assemblage studies revealed an Eocene age for the sediments and suggested that they were deposited in a swampy or brackish environment. The lithological characteristics and palynomorph assemblage were consistent with the Ameki Formation, which represents the surface equivalence of the subsurface Agbada Formation in the Anambra Basin. The findings of this study contribute to the understanding of the depositional history and environmental conditions that led to the formation of these sedimentary rocks. The results suggest that the sediments were deposited in a paralic environment with alternating sand and shale units. The presence of heavy minerals and the proximity to the source area indicate a local sediment source. The Eocene age and palynomorph assemblage suggest a warm and humid climate with abundant vegetation. These findings are relevant for the exploration and exploitation of hydrocarbon resources in the Niger Delta sedimentary basin and provide insights into the paleoenvironmental conditions of the region.