Geophysical investigation of the possible extension of Ifewara fault zone beyond Ilesa area, southwestern Nigeria

Abstract

High-resolution aeromagnetic data (HRAD) of parts of the southwestern and north-central Nigeria between 7° 30′ N – 8° 30′ N and 4° 30′ E – 5° 30′ E have been analyzed with a view to investigate the possible extension of Ifewara fault zone beyond Ilesa area. Analyses of the filtered HRAD by analytic signal amplitude (ASA), horizontal gradient magnitude (HGM), first vertical derivative (FVD), and Euler deconvolution (ED) methods were combined to delineate the locations, strikes, and dip directions of the subsurface structures in the area. The inferred structural map and the associated rose diagram indicate that the area is bisected by a number of major and minor faults that trend NE-SW, ENE-WSW, E-W, NW-SE, WNW-ESE, NNE-SSW, and NNW-SSE, among which the NE-SW trending faults predominate. The Ifewara and other major fault zones were clearly delineated. The mapped Ifewara faults trend between NNE-SSW and NE-SW directions and extend from the southwestern part (Ilesa area) to the extreme of north-eastern part of the study area. The study concluded that the Ifewara fault zones exist and do not terminate in the southwestern part of Nigeria but further extends to the northern part, possibly to Nupe basin and Zungeru area.