Microfacies Analysis and Geochemical Evaluation of Campanian-Maastrichtian Limestone Along the Benin Flank, Southwestern Nigeria

Abstract

Outcrops of the Campanian-Maastrichtian limestone unit exposed along the Benin Flank in southwestern Nigeria, were sampled and analyzed in order to characterize the carbonate microfacies, determine chemical composition, mineralogy and depositional environment of the limestone unit. The investigation was undertaken by means of thin-section petrography, Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM/EDS), Energy Dispersive X-ray Fluorescence (ED-XRF) analysis and X-ray diffraction analysis. Three (3) carbonate microfacies were characterized, namely; wackestone, bioclastic wackestone-packstone and arenaceous proto-dolomite. The microfacies association characterizes sedimentation within shallow carbonate (lagoonal) marine setting. The results of major oxide geochemistry showed that the analyzed limestone samples are calcitic. The study findings highlighted the deposition of calcite limestone and arenaceous proto-dolomite of Campanian-Maastrichtian age along the Benin Flank within a shallow carbonate (lagoonal) marine environment.