Diagênese de Arenitos do Grupo Bauru no Estado de São Paulo

In the state of São Paulo, the Bauru Group units cover about 47% of the territory, constituting an aquifer of great interest, in particular for public watersupply. In this study, core samples were taken for petrographic and diagenetic characterization of different units, seeking to improve the knowledge of the Bauru Aquifer System. The samples were submitted to analysis by optical microscopy and scanning electron microscopy. The units of this aquifer system are mostly subarkoses (67% of the samples), except the Marilia Formation, which is composed of sublitharenite and quartzarenite. These sandstones were submitted to shallow and low-intensity diagenesis. The main diagenetic phases identified were dissolution of the detrital minerals, notably feldspar and pyroxene, neoformation of clay minerals, iron oxi-hydroxide, calcite and analcime. Locally there is precipitation of quartz, feldspar and titanium oxide.