ARENITOS FLÚVIO-EÓLICOS DA PORÇÃO SUPERIOR DA FORMAÇÃO PIRAMBÓIA NO CENTRO-LESTE PAULISTA

Abstract

Coarse and conglomeratic fluvial sandstones with varied thicknesses and geometries have been described in the literature and positioned at the lower portion of Botucatu Formation; more recently they were repositioned at the upper portion of Pirambóia Formation. These sandstones are here characterized with respect to their facies composition based on the description of excellent outcrops located in the vicinities of the cities of Itirapina, Descalvado and São Pedro, in the central-eastern portion of São Paulo State. Sedimentological log descriptions show a succession of very fine to coarse, poorly sorted sandstones, including conglomeratic beds, commonly exhibiting medium-scale trough-cross-stratifications. These sandstones have also been examined under optical microscopy and classified mainly as quartzarenites. The vertical and lateral relationships of these deposits revealed interesting fluvial-aeolian interaction, restricted to the upper portion of the Pirambóia Formation in the area. Itirapina Sandstones is the formal denomination for these sandstones deposited in alluvial mid-fans that were settled near the border of the basin, during the final episodes of Pirambóia sedimentation. In this context, braided fluvial deposits were continuously reworked by wind, which had intermingled aeolian deposits of dunes, interdunes and sand sheets to fluvial deposits.