Lineament mapping in the Edea area (Littoral, Cameroon) using remote sensing and gravimetric data: hydrogeological implications

The aim of this study is to map and analyze the lineament network in the Edéa, Cameroon, area using remote sensing and gravimetric data to determine their hydrogeological implications. Principal component analysis and directional filters applied to Landsat7 ETM+ and Shuttle Radar Topography Mission imagery, respectively, were used to extract remote sensing lineaments. Rose diagram of these lineaments highlights four families of lineaments along the N–S, E–W, NE–SW, and NW–SE directions. There are three major directions accounting for 74% of lineaments, including N0° to N10°, N20° to N30°, and N40° to N50°; and four minor directions (with 26% of the lineaments), including N60° N70°, N80° to N90°, N130° to N140°, and N150° to N160°. N20° to N90° directions correlate with those of major structures of the Oubanguides Complex, such as the Sanaga Fault and Central Cameroon Shear Zone. N130° to N140° direction corresponds to orientation of Shear Zones and blastomylonitic faults of Nyong Complex. Superposition of these lineaments on hydrographic network shows similarities between their directions, thus highlighting strong impact of tectonics on orientation of hydrographic network. The presence of numerous lineaments highlights strongly fractured subsoil, and their high density favors the circulation and accumulation of groundwater. Upward continuation and horizontal gradient maxima methods applied to Earth Gravitational Model 2008 data allowed the extraction of gravimetric lineaments, with a major N–S orientation, which correlates with general orientation of South Atlantic opening. Superposition of remote sensing lineaments and gravimetric lineaments highlights their parallelism, admitting that gravimetric structures are an extension in depth of surface structures defined by remote sensing.