Influence of the Meso-Cenozoic tectonics on groundwater and surface water flows in the Skoura hydrogeological basin (folded Middle Atlas, Morocco)

Abstract

The Skoura hydrogeological basin, part of the Folded Middle Atlas Mountain range, is located 30 km NE of Boulemane city and 50 km SE of Sefrou city. It is limited to the North and North-East by the Aichoun reliefs, to the West by the North Middle Atlas Fault (NMAF) and to the South by the Tichoukt ridge. It corresponds to a collapsed area resulting from polyphase tectonics succeeding from the Upper Miocene to present day. Its location between two major structural lines favors the accumulation and runoff of all precipitated water. This work aims to identify the geological structures which guide groundwater and surface water flows. The geological mapping and the measurements of the water points capturing the water table, have allowed to reconstitute the geodynamic evolution of this basin on one hand, and to identify the various aquifers containing the water table on the other hand. The Skoura water table circulates within four aquifer systems represented by Liassic carbonates, Bathonian sandstones, Vallesian lacustrine limestone and the Plio-Quaternary fluvio-lacustrine deposits. The impermeable substratum of each reservoir layer is respectively represented from bottom to top by Triassic-Liassic red claystones, Bathonian versicolored marls, Vallesian lacustrine claystones and Upper Miocene marls. The superposition of the piezometric map with the fracturing map shows that the groundwater flow axis is multidirectional. Groundwater flows along faults and fracture, following two main directions converging towards the Mdaz River. A first flow from SW to NE characterizing the upstream part of the hydrogeological basin and a second flow from West to East which covers its central part. Concerning surface water flows, they are guided by the submeridian and transverse faults, as well as by the two major faults (NMAF and the Tichoukt Fault) which have played a major role in the genesis and evolution of the Oued Mdaz valley.