Evaluation of Depth to Magnetic Basement over Sokoto Basin, Northwestern Nigeria Using Spectral Fourier Analysis of High Resolution of Magnetic Data.

Abstract

Fourier analysis of high resolution of aeromagnetic (HRAM) data was carried out to evaluate depth to the magnetic basement of the entire Sokoto Basin in northwestern Nigeria to infer hydrocarbon potential for sustainable economy. The area covered is approximately 111,925 km2 and is bounded by latitudes 10.000 N and 14.000 N and longitudes 3.50 E and 7.000 E. It is covered by 38 sheets of aeromagnetic data joined to produce composite TMI map. The composite data was then divided into thirty seven sections of half degree by half degree for the purpose of two-dimensional spectral analysis in order to estimate the sedimentary depth underlain by the magnetic basement rock in the area. Results of the spectral analysis suggested the existence of two clear layers of magnetic sources which account for deeper and shallower magnetic sources. Linear segment from the low frequency portion of the spectral plot is due to deeper source effects. The deeper sources vary between 0.47 ± 0.04 km -3.08 ± 0.05 km with an average of 1.94 ± 0.07 km and these deeper sources represented by the low frequency component of the spectrum are considered to be the thickness of the sedimentary formation. The sedimentary thickness increases from the south to north. The shallower layer depths vary from 0.12 ± 0.03 km – 1.09 ± 0.07 km with an average of 0.47 ± 0.03 km represent the near surface sources. Lema with sedimentary thickness up to 3.0 km is a probable area for hydrocarbon generation and is recommended detailed seismic survey and soil sample tests. These results agree with earlier geophysical works done in parts of the area.