Structural mapping of the Goulfey-Tourba (West and Central African Rift) sedimentary basin using high-resolution gravity data

Abstract

The Goulfey-Tourba sedimentary basin (GTSB) is a portion of the West and Central African Rift System whose studies on its structural geology remain very limited. Belonging to the vast semi-arid Sahelian region, this sedimentary basin covers several localities in Cameroon and Chad, whose economic and social activities are highly impacted by the shortage of drinking water. In this work, a new look is taken at the geological features of this local sedimentary region. To perform this, a preliminary synthetic study is carried out to assess the performance of some classic and recent edge detection methods. The effectiveness of the recent Improved Logistic (IL) method is approved, given its ability to highlight low amplitude and deep features with a refined resolution. A regional/residual separation was applied to Bouguer gravity disturbances to avoid blurring some upper crustal structures by high-frequency anomalies. The effectiveness of this regional/residual separation has been validated by checking the absence of ringing artifacts (Gibbs phenomenon). The application of the IL method on residual gravimetric disturbances of the study area revealed a series of lineaments not yet identified by previous scientific studies. The results show a slight fracturing of the basement, with geological features mainly trending in an NW-SE direction. A newly identified geological discontinuity continuously crosses the study area from 12o45'N latitude to the southeast. Utilizing a modified and recent form of the Euler deconvolution theory (Improved Tilt-Euler method) has enabled the detection of several density sources in the GTSB, most of which correlate well with the lineaments outlined by the IL method. The improved Tilt-Euler method results show anomalous sources at more than 6 km depth beneath the Bodélé sedimentary series of the Upper Tertiary. The Euler’s linear solutions attributed to basement fractures show an average depth of 1 km. These results are undoubtedly a major contribution to refining the research of hydrogeological resources in this Sahelian area.