GODWIN OKUMAGBE AIGBADON

This study examines the sedimentology, geochemical appraisal and palynofacies of the Maastrichtian–Paleocene Araromi Formation, situated in the eastern Dahomey Basin of southwestern Nigeria. The primary objectives is to evaluate the depositional environments, organic matter quality, and the hydrocarbon‐generation potential of the formation, thereby contributing to a broader understanding of the basin’s petroleum system.Integrated field observations and lithological analyses reveal an alternation of sandstones, shales, limestones, and siltstones, which collectively indicate a dynamic depositional system that evolved from fluvial to shallow marine settings. These facies transitions reflect varying energy conditions and sediment supply, suggesting periodic marine incursions during the late Maastrichtian to early Paleocene.Geochemical results show moderate to high Total Organic Carbon (TOC) values, accompanied by Hydrogen Index data consistent with a mixed assemblage of Type I and Type III kerogens. This mixture confirms the presence of both oil-prone and gas-prone organic matter, implying that the Araromi Formation possesses substantial potential for hydrocarbon generation under appropriate thermal maturity conditions.Palynofacies analyses further support these interpretations by revealing moderate palynological diversity. The presence of terrestrial pollen and spores, alongside abundant marine dinoflagellate cysts, confirms deposition during the late Maastrichtian to early Paleocene interval and indicates fluctuating terrestrial and marine influence. Amorphous organic matter dominates the offshore equivalents, suggesting deposition under reducing conditions that favored the preservation of hydrogen-rich organic material.Finally, the combined sedimentological, geochemical, and palynological evidence establishes the Araromi Formation as a significant source rock within the Dahomey Basin. The findings not only enhance understanding of the basin’s stratigraphic evolution and petroleum system but also highlight the formation’s relevance for future hydrocarbon exploration and development in southwestern Nigeria.