The present study concentrates on the interpretation of Vertical Electrical Soundings (VES) and well logs to understand the geometry and the functioning of the Ghardimaou multilayered aquifer, a potential target for water supply in the Mejerda basin (Tunisia). The analysis of isobath and isopach maps established in this study, shows a tectonic influence on the reservoirs structure; the Villafranchian folding and the NE-SW, and E-W normal faulting in the recent Quaternary created an aquifer system compartmentalized by raised and tilted blocks. Geoelectrical cross sections reveal that this structure influences the thickness of permeable formations and the groundwater circulation. These results will be useful for rationalizing the future hydrogeological research that will be undertaken in the Mejerda basin.

Résumé Une étude géophysique par sondages électriques (SE) a été menée dans la région de Ghardimaou (Tunisie) en vue de caractériser la structure de l'aquifère superficiel, cible potentielle pour l'alimentation en eau. L'interprétation des coupes géoélectriques et des cartes des isobathes et des isopaques, établies dans cette étude, permet de mettre en évidence un aquifère compartimenté en blocs soulevés et affaissés. Contrôlée par le plissement Villafranchien et par la réactivation des accidents NE-SO et E-O en failles normales lors du Quaternaire récent, cette structuration influence l'épaisseur des formations perméables et la circulation des eaux souterraines. Les résultats obtenus amènent à repenser les schémas hydrogéologiques locaux en vue d'une exploitation intensive de l'aquifère superficiel.Mots clefs aquifère superficiel; aquifère compartimenté; géophysique; sondages électriques; Tunisie New elements on the structure of the Ghardimaou superficial aquifer (Tunisia): electrical geophysics resultsAbstract A geophysical survey, by electrical sounding (ES), was undertaken in the Ghardimaou region, Tunisia, with the aim of characterizing the structure of the superficial aquifer, a potential target for water supply. The interpretation of the geoelectrical cross-sections, isobath and isopach maps established in this study, highlighted a compartmentalized aquifer in raised and subsided blocks. Controlled by the Villafranchian folding and the NE-SW and E-W normal faults of the recent Quaternary, this structure influences the thickness of permeable formations and the circulation of groundwater. The results obtained lead us to reconsider the local hydrogeological diagrams with a view to intensive exploitation of the superficial aquifer.

A geoelectrical survey was carried out in order to better understand the subsurface geology of the metamorphic massif of Hairech (Tunisia). Over 50 Schlumberger electrical soundings were performed using a maximum electrode spacing of 3000 m. The carried out qualitative interpretation of resistivity distributions for various depths is based on apparent resistivity maps that were constructed for different AB spacings.Quantitatively, the measured resistivity values were one-dimensionally interpreted. The already drilled boreholes and the position of some electrical soundings on geological outcrops have been helpful for electrical data calibration.The results of the vertical electrical soundings reveal that the metamorphic Hairech massif, correspond to a folded structure which is affected by deep trending east-west to northeast-southwest faults.