Composition, provenance and tectonic setting of Eze-Aku Sandstone facies in the Afikpo Synclinorium, Southern Benue Trough, Nigeria

Field study, petrographic and major element geochemical composition of the Eze-Aku Sandstone facies outcropping in the Afikpo Synclinorium, southeastern Nigeria, were utilized in this study. The aim is to interpret the provenance and tectonic setting for sandstones in the sedimentary basin. Field observation shows alternating sequence of parallel sandstone ridges trending NE-SW and shales which represent the low-lying plains in the area. Four major sandstone facies were identified: massive conglomeritic sandstone facies, laminated sandstone facies, bioturbated sandstone facies and cross-bedded sandstone facies. Ternary plots for framework elements (quartz, feldspar and rock fragments) from petrography of the sandstones indicate the sandstones as arkosic and subarkosic arenites. Tectonic setting discrimination diagrams plotted based on major element oxides revealed continental block provenance dominantly in a passive continental margin. Petrographic and geochemical results indicate large amounts of detritus were derived principally from plutonic igneous rocks with minor contribution from metamorphic source region, probably from Obudu Plateau, Oban and Cameroon Massifs.