Geophysical Study of Fervenca and 2-D Apparent Resistivity Models

From the hydrogeological point of view the Fervença region is characterised by two aquifers, one in porous media, superficial and installed in Quaternary and Cretaceous formations, and the other, eventually deeper, installed in Jurassic carbonate formations, known as the Bairrada Karstic System. Although of strategic importance of these aquifers for local water supply and for agriculture use, there are not comprehensive studies and information about the thickness of the overlaying formations and the structure of the carbonate formations. The present research aims of clarifying these questions using geophysical prospecting methods. An integrated approach is used including apparent resistivity soundings, seismic refraction profiles and the available boreholes information in the region. A set of interpretation material was developed for simple 2D models and thus pseudosections for alpha resistivity and for the ratio beta/gamma resistivities using Wenner tripotential measurements are presented, in order to be used for the interpretation of the present and future field data.Finally the integration of all data suggests a structural model for the region and an evaluation of the thickness.