ABSTRACT
The Guaraní Aquifer System (G.A.S.) is one of the world’s most important fresh groundwater reservoirs. It lies under four South American countries: Argentina, Brazil, Paraguay and Uruguay, which use this resource for several purposes with very different exploitation levels. This great transboundary aquifer is situated in aeolian and fluvial sandstone of Triassic-Jurassic age, usually covered by basalt formations from the Cretaceous, which provide a high degree of confinement. Due to the vast extent of the aquifer, this paper focuses on the border area between Argentina and Uruguay. An analysis of the geological and hydrochemical data available for this area made it possible to delineate zones with different characteristics. In addition, it was possible to evaluate the feasibility of deep thermal groundwater being present towards the southwest portion of the G.A.S. in Argentina, where the boundary has not yet been defined.
