Abstract

Abstract

The study investigated the subsurface tectonic framework and structural disposition of the basement/sedimentary transition zone in the southeastern part of Bauchi, Northeastern Nigeria, to delineate the basal and lateral contacts and unravel some of the hydrogeological and engineering challenges in such areas. The method deployed involved analysis of high-resolution aeromagnetic (HRAM) data, through the application of several filtering techniques. The transformation techniques applied include reduction to pole, second vertical derivative techniques analytic signal, and Euler deconvolution. Euler depths result range of 1 to 200 m coincides with region where basement rocks outcrop on the surface while depth range between 0 and −800 m correspond to sedimentary terrain (Kerri-Kerri Fm.) or part of the area where the basement rocks are overlain by thick overburden sediments. The 2-D depth model around the transition zone showed high variability as it ranged from 0 to -500 m owing to the presence of basement highs and depressions. The basement highs are usually characterized by impermeable rocks with poor aquifer characteristics and are responsible for the failure of boreholes in these zones. The basement depressions, however, constitute good groundwater prospects depending on the hydrological properties of the sedimentary infill. The general orientation of lineaments in the area revealed NW-SE, NE-SW, and ENE-WSW, with minor N-S and E-W trends, suggesting a pan-African origin. The occurrence of lineaments in parts of the contact zones also contributes to the groundwater prospects. The erratic bedrock relief exhibited by the study area is also detrimental to foundation of pavement structures as it undermines their durability. Therefore, a detailed site investigation is crucial in such geological contact zones prior to the erection of structures. Additionally, vertical electrical soundings are recommended before borehole drilling to ascertain the suitability of these hydrogeologically complex zones.

Key words: structural disposition, euler deconvolution, basement depressions, lineaments, groundwater prospects