Delineating deep aquifers structures using magnetotelluric and airborne magnetic data: Voltaian Basin, Ghana

This study combines airborne magnetic and magnetotelluric (MT) surveys to enhance deep subsurface geologic characterization and groundwater prospecting in the Voltaian Sedimentary Basin (VSB) in Ghana. A comprehensive analysis of airborne magnetic data delineated potential subsurface lineaments, which subsequently informed the selection of sites for magnetotelluric (MT) field investigations. Resistivity maps derived from both 3D depth slices and 1D inversions of the magnetotelluric profiles, and jointly interpreted with lineaments from airborne magnetic, defined a deep zone of low resistivity formation indicating a probable groundwater-bearing zone. The resistivity signature of the structure is comparable to that of a unit in which a 132 l/min-yielding research borehole in close proximity is completed. This promising conductive layer is approximately 30 m thick at a depth of 260 m below ground level and is about 45 km long. This has presented new insights into the stratigraphic thickness of the two regionally significant geological formations: the Panabako and Poubogou Formations. The new data suggest thicker units than are currently known in the current literature. This finding is significant and will affect the current understanding of the geology and groundwater resource productivity of the Voltaian Basin.