Outcrop and petrographic lithofacies analyses of the Kanawa Member of Pindiga Formation, Northern Benue Trough, Nigeria: Implications for environment of deposition

Abstract

Understanding the depositional history of carbonate rocks is key to successful resource exploration and exploitation. The Kanawa Member of Pindiga Formation in the Gongola sub-basin of the northern Benue trough is a limestone-shale succession which has been a subject of research especially on the macro and micro fossil contents based on which the open marine environment of deposition has been inferred. However, the existing literature lacks clarity on the nature of the carbonate platform upon which the Kanawa Member was deposited. There are two primary aims of this study: 1) To investigate the macro (outcrop) and micro (thin-section) facies and 2) To ascertain depositional environment based on integrated macro and micro facies analyses. The method employed is detailed outcrop studies combined with thin-section microfacies analyses of the Ashaka quarry and Pindiga stream sections. Results reveal the presence of dark grey to black, fissile mudstone facies and limestone facies. The limestone facies is in turn divisible into three sub-facies including mudstone-wackestone, wackestone-packstone and packstone microfacies. The lithofacies are organised into two associations, namely 1) outer ramp and mid-ramp facies associations. The facies architecture depicted by these associations suggests deposition in homooclinal carbonate ramp setting. This study demonstrates that the combination of detailed outcrop and microfacies analyses leads to a better understanding of paleogeography of carbonate rocks which is relevant to resource exploration and exploitation.