Hydrogeophysical characterization of the Bir Guendouz basin (SW Morocco): Insights into its relations to the Senegal-Mauritanian basin

The Senegal-Mauritanian Basin onshore is the largest among the northwest African Atlantic margin basins, covering approximately 350,000 km2 and extending from Morocco to Guinea Bissau. Although valuable information is provided on the Senegalese part, data on other parts of the basin are scarce. The study aims to visualise the subsurface structure and describe the distribution patterns of Meso-Cenozoic deposits in the Moroccan portion of the Senegalo-Mauritania basin. The dataset integrates information from 750 vertical electrical soundings, hydrogeological drilling data, and wireline logging into a Geographic Information System (GIS) platform and 3D modelling software. A new three-dimensional model has been created to represent the topmost layer of the Palaeozoic substratum. Additionally, thickness maps and geo-electric profiles have been developed for distinct geo-electric intervals, including the lower, middle, upper, and surface layers. The study presents the geometric properties of two aquifers, namely, the ''upper and lower'': the Continental Terminal sandy and sandstones, dating back to the upper Miocene to Pliocene period, and the Paleocene sand to shaly sand. The upper aquifer has a thickness of 20 m in the eastern region, whereas it thickens to nearly 100 m towards the west, approaching the coastline. Similarly, the lower aquifer's thickness ranges from 100 m to 400 m in the same direction. The resistivity values range from 5 to 240 Ω m, providing an average of 120 Ω m. Four discontinuities have been identified in the sections, which may indicate lateral facies modifications or synsedimentary faults, correlating with Atlantic margin structuration and Meso-Cenozoic sea-level variations. The parameters' range for various mappings, models, and quantitative descriptions of reservoir properties. The new structural and hydro-stratigraphic model provides novel insights for researching this critical area.