Análise petrográfica e proveniência do Arenito Pedreira, Jurássico Superior da Bacia do Paraná, sul do Brasil

In the south-west portion of the Parana Basin, there is a unit informally called Pedreira Sandstone. In order to define the stratigraphic relations and to characterize this unit, two boreholes were evaluated and representative samples were selected for petrographic analysis and modal counting of the constituents in order to define its provenance. The Pedreira Sandstone was deposited between the Botucatu Formation by overlapped unconformity and the Rio do Rastro Formation, with which it has erosive contact. It is composed of a succession of fining-upward cycles consisting of conglomerate sandstones, sandy conglomerates sandstone packages with tangential cross-bedding and low angle crossbedding, sandstones with ripple marks and laminated pelites respectively. The sandstones are classified as lithic arkoses and arkoses, have a medium selection, with a high ratio of feldspar and quartz grains. The diagenetic features characterize eodiagenesis and mesodiagenesis conditions, with dry continental climate features. The provenance analysis points to sources associated with a dissected magmatic arc and the lithoclasts described are similar to the rocks found in the Dom Feliciano Belt located further south on the Tijucas terranes and Pelotas Batholith. These data suggest a source area near the deposition area and allows accepting that the NW-SE direction uplift of the Rio Grande Arc is responsible for the provision of sediments for the formation of the Pedreira Sandstone.