Electrical imaging of an alluvial aquifer at the Antinaco-Los Colorados tectonic valley in the Sierras Pampeanas, Argentina

The Antinaco-Los Colorados valley is a wide N–S tectonic depression, located between the Sa. de Velazco and the Sa. de Famatina, both ranges belonging to the Sierras Pampeanas thick-skinned deformation province in Argentina. From previously reported magnetotelluric (MT) data, it is known that the thickness of the sedimentary sequences may reach up to 8 km in the central zone of this basin. In particular, the Quaternary-to-recent alluvial filling contains an aquifer complex of great importance for this semiarid zone providing water for irrigation and also for human consumption. To obtain information about the electrical structure of the alluvial cover, 17 vertical electric soundings were carried out along an E–W traverse profile extending from one side of the valley to the other. A geoelectrical model is proposed taking into account complementary hydrogeological and geophysical information. In this model, the various layers which could contain fresh water are identified and the level of the water table inferred from the model is almost coincident with that observed from existing wells in the surveyed zone.