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

2006; Sociedade Brasileira de Geologia; Volume: 36; Issue: 2 Linguagem: Inglês

10.5327/rbg.v36i2.1229

2317-4889

Maria Rita Caetano-Chang, Fu Tai Wu,

Geological formations and processes

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 Piramboia 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 Sao Pedro, in the central-eastern portion of Sao 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 Piramboia 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 Piramboia 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.