Estimation of Magnetic Basement Depth of Oyo Area from Aeromagnetic Data

Abstract

This work involves the application of airborne magnetic data over Oyo town and its environ on geographical latitudes of 7°30'N to 8° 00' N and longitudes of 3° 30' E to 4° 00' E south western Nigeria. The main
objective of this study is to define the depth to the crystalline basement in the study area by means of the magnetic automated processing techniques. Locations and depths to magnetic contacts were estimated from the total intensity magnetic field using Horizontal gradient magnitude (HGM), Analytic signal amplitude (ASA) and Local wavenumber (LWN). The digitized magnetic intensity data of Oyo area, south western Nigeria was analyzed to estimate depths to magnetic sources as well as source locations. The total magnetic intensity values ranges from -143.8 nT to 147.0 nT suggesting contrasting rock types in the basement complex. The magnetic basement depth results ranges from 0.528 km to 4.85 km for ASA, 0.674 km to 2.28 km for HGM while 0.0993 km to 1.69 km for the LWN method which overestimated source depths when compared with HGM and ASA functions. Thus, Oyo and its environs is dominated with basement rocks and have considerable variations both in the physical characteristics of rocks and
structural geometries.

Keywords: Aeromagnetic; Local wavenumber; upward continuation; Geological structure; Magnetic susceptibility