Imagerie géophysique des structures de la zone de pitoa-figuil (Nord-Cameroun) par inversion conjointe des données aeromagnetiques et gravimétriques

Abstract

Independent and joint interpretations of aeromagnetic and gravity data were carried out in the Pitoa-Figuil region in Northern Cameroon. The aim was to highlight the major lineaments controlled by the geodynamics of the Benue trough and which are totally or partially buried in geological formations. Various data processing techniques have been applied, namely upward continuation, horizontal gradient magnitude, vertical derivative, and analytic signal. This led to the mapping of lineaments in general and the mapping of faults in particular, whose main directions are NE-SW, E-W, NW-SE, and ENE-WSW. The depth of these faults was estimated by Euler deconvolution for the magnetic method and multi-scale analysis of the horizontal gradient of the vertical derivative for the gravity method. It appears that the depth of faults varies between 2 and 8 km. In this depth range, a tectonic trough that we named Pitoa-Figuil trough (FPF) was highlighted following the NE-SW direction. The 2.75D modeling proposed geological models which revealed the stratigraphy of the study area and the average depth of the top of the bedrock which is approximately 8 km. This stratigraphy has shown that the Pitoa-Figuil trough contains small sedimentary reservoirs consisting essentially of sandstones and schistose clays. Independent and joint 3D inverse models brought out the presence of anomalous bodies on the Pitoa-Figuil axis. The geometry and the depth of these bodies revealed that the Pitoa-Figuil trough is deeper in its southern part than in its northern part. This information associated with its NE-SW trend allowed us to conclude that this trough was generated by the emplacement of the Benue tectonic trough and therefore, is a consequence of the opening of the Atlantic Ocean. The nature and thickness of the sediments contained in the Pitoa-Figuil trough as well as the presence of numerous deep faults, make this trough a potential site for accumulation of hydrocarbons.