Analysis of gravity and aeromagnetic anomalies of the Central and southern parts of the Logone Birni region, Northern Cameroon

In this paper we study gravity and aeromagnetic anomalies and their relation to the surface geology in an area of the Logone Birni region. We present the magnetic and gravity anomaly maps and show the high frequencies residual maps obtained by Fourier transform filtering.
The region is mainly characterized by intense positive magnetic anomalies and very low and broad gravity variations. The amplitude of the magnetic anomalies varies from 0 to 300 nT whereas the gravity map shows values always negative between -5 and -70 mGal. The total gradient map of the residual aeromagnetic data depicts the main shallow high-intensity sources in the region, which could be ascribed to subsurface iron formation or to other volcanic rocks such as basalt concealed beneath the sedimentary cover.
The Euler deconvolution applied to the residual gravity and magnetic data clearly characterizes the sources, showing their location and depth. The gravity anomaly of Yagoua could be related to a sphere of maximum depth of about 9 Km. The Western boundary is confirm on Euler maps, defining the limit between the sedimentary cover and the crystalline basement.
Cluster solutions appearing around Waza could be related to a magnetic source body of a maximum depth of about 10 Km. A 2D forward modelling of gravity profiles extracted from the residual map suggests that the gravity lows in the regions surrounding Yagoua could be due to Tertiary and Quaternary rocks of great thickness.
Key words: gravity and aeromagnetic maps, residual gravity and aeromagnetic map analysis, total gradient; Euler deconvolution; Northern Cameroon.