Recycling History, Maturity, Paleoweathering, and Paleoclimatic Conditions of the Campano-Maastrichtian Sandstones in the Northern Bida Basin, Nigeria

Abstract

Abstract The Campanian-Maastrichtian sandstone and siltstone facies of the Bida and Enagi formations, northern Bida Basin Nigeria were logged and sampled. The study aims to evaluate the sandstone's petrographic, mineralogical, and bulk geochemical compositions. This is towards exemplifying sediment recycling, maturity, paleoweathering history, and the prevailing paleoclimatic conditions during depositions in the parts of Bida Basin. Petrography result reveals framework modal composition of Bida Formation sandstones as Q93.51−100F0−2.60L/R0 − 3.90 whereas the Enagi Formation sandstones constituents includes Q84.42−98.72F0−3.75L/R1.18−15.58, thus the Bida Formation sandstones are classified as mostly quartzarenite with minor sublitharenite whereas Enagi Formation sandstone are basically classified as sublitharenite with minor quartzarenite varieties. Mineralogical composition from the X-ray diffractions revealed higher kaolinite contents among the mineral constitutes with relatively high quartz contents while muscovite, anatase and iron-rich minerals (goethite and hematite) were recorded in trace amounts and this suggests significant post-depositional weathering prior to reworking. Higher geochemical weathering indices values, including chemical index of alteration (CIA), chemical index of weathering (CIW), plagioclase index of alteration (PIA), and chemical proxy for alteration (CPA), as well as the ternary A-CN-K and A-CNK-FM plots for both Bida and Enagi formations, suggest an intense weathering and reworking at the source area during late Cretaceous. Geochemical proxies, weathering indices and plots show that the compositionally mature to super mature sediments were deposited under warm, temperate to tropical humid climatic paleoclimatic settings. The light rare earth elements (LREE) enrichment relative to heavy rare earth elements (HREE) and low negative europium (Eu/Eu*) anomaly values with geochemical discrimination plots revealed that the sandstones were sourced from a felsic rocks’ provenance within a passive margin paleotectonic settings. This study concluded that the Campano-Maastrichtian Bida and Enagi formations siliciclastic sediments in the northern Bida sub-Basin, northcentral Nigeria were subjected to extreme weathering, during a warm, temperate to tropical humid climate with the dominance of semi-humid and only brief semi-arid conditions.