Ezeaku Formation Calcarenaceous Sandstone Facies at Abini, Cross River State, Nigeria

Abstract

Mineralogical and paleocurrent studies of Amasiri Sandstone, a member of Ezeaku Group outcropping as a ridge in Abini were done to determine the quantitative values of component minerals for proper designation of the facies of sandstone and the direction of paleocurrent. Sampling, paleocurrent measurements, petrographic and X-ray diffraction (XRD) analyses were employed to achieve results. Three highly indurated beds of white fine – medium, angular - subrounded grained sandstones were observed. The basal and second beds had thin laminations, whereas the third was massive. The sandstone is found to be hybrid facies, it is not a quartz arenite neither a calcareous sandstone. Calcite (CaCo3) is the most abundant mineral ranging from 43% - 66%, with an average of 51.39%. Calcite is seen occurring as skeletal grains and sparry calcite, corroding, and replacing quartz grains. Quartz (SiO2) ranges from 3% - 37.6% with an average of 17.22%, occurring as detrital quartz and authigenic quartz overgrowth. Monocrystalline and polycrystalline quartz occur, with monocrystalline dominating. Feldspars such as albite, plagioclase, sanidine and orthoclase occur, with the potasssic feldspars dominating. Silica, calcite, and iron oxide were the observed cementing materials. The paleocurrent direction is in the SE. The angularity of the grains implies a source area with close proximity. Therefore, the source area could be inferred to be the Oban Massif or and the Cameroun Mountains.