Avaliação hidrogeológica da formação Serra dos Martins nas Microrregiões do Seridó Oriental e Curimataú Ocidental da Paraíba: Contribuições da Geofísica e Hidroquímica

Abstract

Groundwater is an important freshwater reserve on the planet. The Brazilian Northeast, especially the State of Paraíba, is marked by low rainfall and geology mostly composed of igneous and metamorphic rocks that do not favor water storage. In the micro-regions of Seridó Oriental and Curimataú Occidental, the Serra dos Martins Sedimentary For mation occurs, which deserves to be highlighted in the local context, given the possi bility of meeting the population's water demands. This formation is locally little known in terms of its hydrogeological potential. Therefore, the present study aimed to charac terize this formation from a geological/geophysical, hydrogeological and water quality perspective. Two areas were researched, named as follows: (i) Serra dos Martins Sed imentary Formation in Barra de Santa Rosa/Cuité (with approximately 3,145 hectares) and (ii) Serra dos Martins Sedimentary Formation in Nova Floresta/Picuí/Cuité (with approximately 10,721 hectares ). The geophysical survey carried out was through the method of electroresistivity, totaling 14 interpreted geophysical lines. For the petro physical analysis, 14 rock samples were collected, which allowed estimating the aver age porosity of the formation in the studied sectors. The hydrogeological data were obtained from SIAGAS (Groundwater Information System) of the Geological Survey of Brazil, and also through field registration. The hydrochemical characterization was car ried out by collecting water samples from 38 wells with subsequent analysis in the laboratory. The Serra dos Martins Formation in the study area is approximately 80 meters thick, and the aquifer itself is at a depth of 30 meters, with a thickness of around 50 meters. Petrophysical tests show an average porosity of 20.3% in the Barra de Santa Rosa/Cuité area and 8.15% in Nova Floresta/Picuí/Cuité. In both sedimentary occurrences, the waters have a slightly acidic pH and in terms of salinity they are clas sified as Slightly Brackish, which in many situations makes direct human consumption unfeasible.