Petroleum and Coal Pet Coal (2023); 65(1): 138-152 ISSN 1337-7027 an open access journal Article Open Access Spectral Depth Estimation of the Magnetic Basement in Parts of the Benue Trough Using High-Resolution Aeromagnetic Data: Implication for Hydrocarbon Prospectivity I. A. Omenikolo 1, 2 *, A. I. Opara 2 , C. N Okereke 2 , D. O. Ikoro 2 , T. T. Emberga 1 , C. C. Agoha 2 , and C.N. Nwokeabia 3 1 Department of Physics/Electronics, Federal Polytechnic Nekede, P.M.B. 1036, Owerri, Nigeria 2 Department of Geology, Federal University of Technology, P.M.B. 1526 Owerri, Nigeria 3 Department of Applied Geophysics, Nnamdi Azikwe University Awka, Nigeria Received April 23, 2022, Accepted November 8, 2022 Abstract Spectral analysis of high-resolution airborne magnetic data of part of Benue Trough was used to estimate the depths of anomalous magnetic sources within the study area. This paper was aimed at the determination of sedimentary thickness of the study area and to infer favourable areas for possible petroleum exploration. Several data enhancement techniques were used to digitally enhance the data to improve the signal-to-noise ratio. The total magnetic intensity was subjected to regional - residual separation using polynomial fitting of the first order, with the residual field revealing magnetic intensity values ranging from -79.8 to -16.5nT. Several clusters of circular magnetic anomaly closures with very clear amplitudes which occur especially in the northern and mid part of the area revealed edges of intrusive bodies. The structures observed within the location from the residual maps revealed dominant trends in the NE-SW and N-S direction. The result of 2D spectral analysis revealed a two-depth model, with the depth to the first layer (D1) varying from 0.135 km to 0.200 km with an average depth of 0.158 km while second layer depth (D2) varies from 2.585 km to 4.878 km with the average depth of 3.415 km. This result therefore, indicates that the average basement depth of the study area as deduced from power spectrum inversion is about 3.415km. The mean sedimentary thickness of 3.415km obtained and the near absence of intrusive bodies especially in the northern part of the study area thus reveal favourable conditions for hydrocarbon exploration. Keywords: Basement depth; Aeromagnetic data; Spectral analysis; Benue trough; Hydrocarbon exploration. 1. Introduction The magnetic method is one of the most common geophysical techniques that is well established and commonly applied for geological mapping, hydrocarbon, and mineral exploration [1-2] . The magnetic method generally measures variations in the Earth’s magnetic field and investigates the subsurface geology based on anomalies in the geomagnetic field which are the resultant effects of the magnetic properties of the underlying rocks. It is applied in estimating the depth to magnetic source bodies, sedimentary thickness and to delineate subsurface structures. It is also useful for locating buried magnetic ore bodies due to their magnetic susceptibilities [3] . Aeromagnetic survey is one of the most frequently used airborne geophysical survey and has been recognized as a principal mapping tool for geological bodies that are strongly magnetized [4] . Previous scholars have demonstrated that basement depth and structure can be accurately delineated using airborne magnetic data [5-8] . Spectral analysis is a well-established technique and generally applied in magnetic and gravity surveys for estimating depths to anomalous bodies [5-8] . This is based on the principle that a magnetic force exerted at the surface of a magnetized body produces magnetic signatures at all points. Application of 2-D spectral in- version to the interpretation of potential field data is now usually applied for basement depth determination established [9] . Different studies have therefore carried out magnetic basement 138