A 3D geometric model of the Cenomanian-Turonian aquifer in the Souss Massa plain: Combination of geophysics and hydrogeological boreholes database

Abstract

The Souss-Massa plain is located in the southwest of Morocco within a depression, bordered by the Anti Atlas domain to the south and the High Atlas domain to the north. This region contains a shallow Plio-Quaternary aquifer predominantly composed of fluvio-lacustrine sediments and two deeper aquifers. The first deep aquifer is within continental Neogene conglomerates and the second and most important one is within Cenomano-Turonian limestones. These aquifers are treated by water scarcity due to arid climate, increasing water demand and overexploitation especially for agriculture. The Cenomano-Turonian like most deep aquifers is considered a fossil aquifer due to lower recharge and must be protected from exploitation. Previous studies are conducted for this aquifer but there is still a lack of knowledge about their geometry and spatial extent. Hence, this study's objective is to identify the depth and geometry of the Turonian aquifer and to create its 3D geometric model. To achieve this goal, a combination of direct and indirect methodologies was employed, based on the data derived from different boreholes, alongside the analysis and interpretation of geoelectric sections established across the plain. The results reveal the absence of Cenomano-Turonian formations in the southeastern part of the basin In the central part, this formation is present, with maximum depth and thickness of around 920 and 410 meters, respectively. Toward the northwest (High Atlas), this formation elevates towards the surface with a minimum depth of 10 meters and a thickness around 30 meters. The average thickness of the Cenomano-Turonian aquifer is approximately 100 meters. To safeguard and conserve this aquifer, it is important to refrain from drilling deep boreholes, especially in the central part of the basin where the aquifer is considerably deep and undergoes a limited recharge. This study aims to guide decision-making for sustainable water management.