Geophysical study of the Kribi-Campo sedimentary sub-basin By the modelling of gravity data

Abstract

A new gravity survey is carried out in the Kribi-Campo sub-basin in South Cameroon located between latitudes 2˚20’ N - 3˚20’ N and longitudes 9˚15’ E - 10˚00’ E. The data are incorporated to the existing ones, analyzed and modeled in order to elucidate the subsurface structure of the area. The area is characterized in its north-western, southwestern and southeastern parts by considerably high positive anomalies indicative of the presence of dense intrusive bodies. The observed high and low gradient zones are indicative of major and minor faults. We find that, 1) from the analysis of the gravity residual anomaly map, the high positive anomalies observed in the Kribi and Lolabe-Campo areas are the signature of a shallow dense intrusions; 2) the results obtained from the 2D spectral analysis on anomaly grids give a depth to the basement rocks of the basin from 0.60 km to 3.93 km. This represents the thickness of the sedimentary formations overlying the basement; 3) from the multi-scale analysis of the maxima of the horizontal gradient, the Kribi intrusion is confined between depths of 0.5 km and 5.2 km with a density contrast of 0.07 g.cm-3 and the Lolabe-Campo intrusion between 0.5 and 2.8 km with a density contrast of 0.13 g.cm-3. 4) the results of the application of the ideal body solution and the 2.5D modelling to the Lolabe-Campo intrusion suggest that the emplacement, breaking up and separation of the intrusive igneous body was the outcome of two tectonic events corresponding to an upward vertical translational tectonic movement followed by an anticlockwise rotational faulting tectonic movement. 5) The 3D model the Kribi dense intrusive igneous block is surrounded by sedimentary formations to the south-west and metamorphic formations to the north-east. The interpretation of the structural map, the 2.5D and 3D models could serve as a guide in the investigation and exploitation of oil, gas and mineral sources in the study area, facilitating the location of points favorable to their existence. These results could also serve as a guide in the identification of risk areas, help in identifying the direction of fluid flow in the subsurface. The interpretation of the sedimentary thickness values can serve to identify areas with the highest mineral and hydrocarbon production potentials which correspond to areas with the highest sedimentary thickness