Análise estrutural da região de Picada Grande como suporte para a prospecção de água subterrânea, Caçapava do Sul, RS

Abstract

The municipality of Caçapava do Sul has rural communities that suffer from a lack of water supply during periods of drought. This work was carried out in one of the communities affected by the periodic lack of water in the interior of the municipality, in the Picada Grande region. Its aim is to verify, from the point of view of structural geology, promising areas for groundwater prospecting that have previously been studied from a geophysical point of view, using the electroresistivity method, defining points of water potential for drilling deep tube wells. With the use of remote sensing techniques to identify lineaments on a regional scale, combined with structural surveys on a field scale, as well as the compilation and integration of previous databases, it was possible to present point and geological-structural maps, stereograms and an integrating section and thus understand the ductile and rutile deformation and the control they exert on the fissure aquifer in the study area. The study area contains predominantly foliated syenogranites (Caçapava do Sul Granitic Complex) in the west and schists of metavolcanic origin in the central-east, with low to medium angle foliations to the east, in line with the contact between the units. Sandstones (Maricá Group) occur subordinately to the east. The rocks show predominantly high-angle fractures in a NE-SW and NW-SE direction. Several pieces of field evidence suggest that the NE-SW structures present near the contact, in a N- S direction, control the flow of groundwater, and the intersection of the contact with the N-S lineament (010-190) probably plays a role as a recharge area for groundwater occurrences previously recognized by geophysical analyses, which highlights the importance of preserving it from a hydrogeological point of view.