Sedimentology, Geochemistry, and Paleoenvironment of the Sandstones of Enagi Formation exposed at Kutigi, Northern Bida Basin, Nigeria

Abstract

This study investigates the geology, geochemistry, and paleoenvironment of the Enagi Formation sandstones exposed at Kutigi in the Northern Bida Basin, North-Central Nigeria, using grain size analysis, thin-section petrography, X ray diffraction (XRD), and X-ray fluorescence (XRF). The sandstones exhibit mean grain sizes of 0.17–1.94 ö, ranging from medium to coarse-grained textures. Sorting values vary between 0.67 ö (well sorted) and 1.19 ö (poorly sorted), skewness ranges from - 0.38 (very negatively skewed) to +1.14 ö (very positively skewed), while kurtosis is mainly mesokurtic to leptokurtic (0.79–1.16). Mineralogically, the sandstones comprise an average of 79.7% quartz (dominated by monocrystalline grains), 6.2% feldspar, and 14.3% rock fragments. XRD results indicate abundant clay minerals, with geochemical data showing relatively low SiO contents (45.65–58.89%) and elevated Al O 2 2 3 (14.9–26%). Provenance analysis suggests a mixed granitic and metamorphic source. Sedimentary structures, including bioturbation, clay drapes, cross-bedding, and laminated facies, indicate deposition within braided fluvial channels, floodplains, and shallow marine to lagoonal/deltaic settings. Texturally and mineralogically, the sandstones are classified as sub-litharenite to feldspathic litharenite, with immature to sub-mature compositions. The high clay content (notably kaolinite) and relatively low quartz suggest limited reservoir quality, with poor to fair porosity and potential for diagenetic cementation at depth. Overall, the Enagi Formation sandstones reflect deposition in a dynamic fluvio-deltaic to shallow marine system, sourced from diverse crystalline terrains. Their reservoir potentia3333 is moderate, with implications for hydrocarbon accumulation and groundwater exploration in the Northern Bida Basin.