Petrographic and geochemical constraints on petrofacies, provenance and tectonic setting of the upper cretaceous sandstones, Northern Bida Basin, north-central Nigeria

Abstract

The petrographic and geochemical compositions of the Campanian-Maastrichtian siliciclastic sediments in the northern Bida Basin, North-central Nigeria were investigated with the aim to determine the petrofacies, their provenance and tectonic settings. The mineral composition of the samples selected from the 10 sub-facies in the study area is characterized by abundant quartz (predominantly of monocrystalline quartz) and minor feldspar, rock fragments and heavy minerals. The framework grains are angular, sub-angular to sub-rounded and well sorted with the quartz varieties exhibiting euhedral to subhedral, non-undulose to undulose characteristics. The modal composition reveals the sediments as quartzarenite to sublitharenite with minor sub-arkoses and also reflects felsic rocks derived within passive margin paleotectonics as provenance. Geochemical proxies obtained based on major, trace and rare earth elements data; Al2O3/TiO2, SiO2/Al2O3, K2O/Al2O3, La/Th, La/Co, Th/Co, La/Sc, Cr/Th, Zr/Nb and Zr/Th with chondrite-normalized REE patterns, light REE enrichment, heavy REE flat pattern and negative Eu anomalies revealed sediments derivation mainly from felsic source rocks. A higher Zr/Sc and Zr/Hf ratio with Th/Sc and Zr/Sc binary plot suggest considerable zircon enrichment in the source areas. Discrimination plots; log(K2O/Na2O) versus SiO2, TiO2 versus (Fe2O3+MgO), Al2O3/SiO2 versus (Fe2O3+MgO) and SiO2/20-(K2O+Na2O)-(TiO2+Fe2O3+MgO), La/Y versus Sc/Cr, La-Th-Sc, Th-Sc-Zr/10 of the analyzed sandstones suggest that source rocks may lie in the passive continental margin, before sediment transport and deposition in the basin by fluvial modes. This study suggests a passive paleotectonic setting for the Precambrian Basement Complex consisting of two igneous source materials from which the sediments are derived and supplied to the study area.