Structural Analysis Using Integrated Aeromagnetic Data and Landsat Imagery in a Basement Complex Terrain, Southwestern Nigeria

Abstract

In this study, different digital format data sources including aeromagnetic and remotely sensed (Landsat ETM+) data were used for structural and tectonic interpretation of the southwestern part of Ilesha, Osun State, Nigeria. Aeromagnetic data were analyzed using advanced processing techniques (Spectral analysis, deconvolution). The aeromagnetic interpretation was carried out using the Butterworth filter, reduction to equator, derivative filters and Euler deconvolution. The results were improved by the study of enhanced Landsat ETM+ images and correlated with the extracted surface lineaments. Two main lineament sets are observed in the study area. The major lineaments strike NW-SE, NE-SW and the minor E-W. General coincidence of both landsat and aeromagnetic lineaments trends were observed in the study area, reflecting the real continuous fractures in the depth. The 3D Euler deconvolution and radial spectral analysis applied to locate and estimate the depth to anomalous bodies, shows varying depth between 48 m and 280 m. The map revealed the presence of major and minor faults, fractures as well as rock boundaries with the frequency of fracturing. This suggests that the major fractures and faults in the area are deep seated within the basement formation since that the spectral analysis enhances the anomalies associated with deep magnetic sources. The processed image displays the lineaments trending NE-SW directions.  The new structural map derived from the combined aeromagnetic data and landsat imagery, provides an effective tool for analyzing subsurface structure in the region.