Sedimentological and Compositional Studies of Itori Well, Eastern Dahomey Basin, Southwestern Nigeria

Abstract

This study investigates subsurface samples from the Itori well in the eastern Dahomey Basin using sedimentological and compositional method to interpret the depositional environment, tectonic framework, and provenance of the sequence. Eighteen limestone and two sandstone samples were examined through thin-section petrography and geochemical techniques, including major oxide, trace element, and rare earth element analysis. Petrographic results classify the sandstones as Quartz Arenites, while the carbonate units represent two microfacies: Sandy bioclastic packstone and Bioclastic wackstone-packstone. Geochemically, the sandstones are dominated by SiO , Al O , Fe O , 2 2 2 3 2 3 TiO , and CaO (~95 wt%), with trace concentrations (<1 wt. %) of MgO, Na O, and K O; Similar oxide trends were 2 2 observed in the limestones. Elemental ratios such as (Th/Sc and Cr/Th) indicate intermediate to felsic provenance. 2 2 Furthermore, K O/Na O againstSiO discrimination plots, suggest deposition within theactive and passive 2 continental margins. Paleo-environmental indicatorsratio such as; (V/Cr and Sr/Ba) revealed deposition under oxicconditions characterized by high salinity and productivity. It can be deduced that the sandstone is a productsof recycled basement rocks, under passive and active continental margins with low weathering conditions while the limestone reflects depositionin shallow marine origin with terrigenous influx.