Investigation of basement fault propagation in Chad Basin of Nigeria using high resolution aeromagnetic data

Abstract

This study was conducted to investigate the basement fault propagation into the overlying sedimentary cover in parts of the Nigerian sector of Chad Basin. The Total Magnetic Intensity (TMI) map was compiled from the digital aeromagnetic data and was reduced to the equator to produce the Reduced-to-Equator (RTE) map. Residual Magnetic Intensity (RMI) map of the study area was obtained after the removal of regional trend from the RTE data. Regional-residual separation of the RMI map was carried out using upward continuation filtering technique adopting the depths obtained from spectral analysis to produce magnetic anomaly maps associated with the basement and intra-sedimentary magnetic sources. The maxima of the Horizontal Gradient Magnitude (HGM) of the basement and intra-sedimentary magnetic anomaly maps were computed and used to delineate faults that produced the structural maps of the basement and the intra-sedimentary column, respectively. Upward continuation of the RMI map at various altitudes and the maxima of their HGM were used to highlight faults from shallow to deep depths, as well as their strikes and dips. Both major and minor faults dominated the study area. The faults strike in the directions NE-SW (Pan-African trend), ENE-WSW, NW-SE, and E-W. Two profiles were drawn on the basement and intra-sedimentary maps, respectively, to model the subsurface structures. The results of this study revealed that the sedimentary section was affected by the tectonics of the underlying basement, with faults propagating from the basement upwards into the sedimentary cover. These faults constitute potential structural traps for oil accumulation or conduit for oil migration.