Sedimentary Geochemistry of Campanian-Maastrichtian sandstones at the Agbaja Plateau, southern Bida Basin, Nigeria: Implications for provenance, paleotectonics and palaeoenvironmental reconstruction

Abstract

The sandstones in the Bida Basin exposed at Agbaja Plateau were profiled and sampled. The samples were analyzed for major, trace and rare earth elements. The study aims to provide insight into the Late Cretaceous palaeogeography within the context of geochemical proxies. The results show that the sandstones are of felsic origin and deposited in passive margin setting. The palaeoclimatic condition varied with less humidity in the early history of the basin (Campanian) but warmer and more humid later in the Maastrichtian. The sandstones in the upper part of the section are intensively weathered with more pervasive weathering in the Maastrichtian sandstones compared to the basal Campanian sandstones. The scenario is interpreted to be reflective of more humidity and marine incursion from both the Tethys Sea and the South Atlantic Ocean. Generally, the sandstones units were deposited dominantly in oxic setting with the older sandstone showing more oxic condition than the younger sandstones which may be responsible for improved paleoproductivity in the younger sandstones. The sandstones units are characterized by dominant marine organic matter diluted by high continental detritus. The transition from basal arkosic sandstone to upper arenitic sandstone is marked by low temperature regime at Campanian-Maastrichtian boundary. The study revealed that the southern Bida Basin belongs to the West Africa Rift System that was probably inundated by Tethys Sea and south Atlantic Ocean in the Late Cretaceous.