Abstract
The main regional aquifer of South America is the Guarani Aquifer System (SAG), it is made up mainly of the psamitic Piramboia and Botucatu formations (Brazil), Misiones (Paraguay and Argentina) and Taquarembo (Uruguay), with a maximum thickness of 600m. The aquifer system lies unconformable over different Paleozoic formations and is covered by extensive basaltic flows of Early Cretaceous age. The aquifer is not a homogeneous blanket sandstone, but composed of facies association whose geometry and architectural elements allow to subdivide it in flows units. These units have different hydraulic conductivity and as consequence different hydrodynamic and hydrochemical behavior. Stratigraphic analysis using field and well data allows to construct a model of depositional systems and reservoirs properties distribution. The aquifer is divided in tree main flow unities: dune (DU), interdune (ID) and channel (CH); and secondary, two others: crevasse (CR), and lacustrine and flood plain (FF). Each one has facies characteristics, and the grain distribution allow inferring the effective porosity and permeability. Botucatu DU presents average hydraulic conductivity one order o magnitude grater than Piramboia interdune, meaning ten times the potential of water flow velocity. The humid interdune blanket sands bellow Botucatu and interbeded in the Piramboia dunes may be considered a strong aquitard. The space distributions of the unities have a direct effect in quality and flow of water inside the regional aquifer. The data and results lead to the recognition of five main regional stratigraphic domains around the Parana basin
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