Depósitos conglomeráticos da paleo-planície do Rio Tietê: evento de agradação fluvial na evolução da Depressão Periférica Paulista

• Autor(a) principal: Breda, Caio [UNESP]
• Data de Publicação: 2017
• Tipo de documento: Trabalho de conclusão de curso
• Idioma: por
• Título da fonte: Repositório Institucional da UNESP
• Texto Completo: http://hdl.handle.net/11449/203233; http://www.athena.biblioteca.unesp.br/exlibris/bd/capelo/2018-12-11/000909784.pdf
• topic: Sedimentação e depósitos; Geologia estratigráfica; Petrologia; Geologia estratigráfica - Cenozóico; Fácies (Geologia); Tietê, Rio (SP); São Paulo (Estado)

The conglomeratic Cenozoic deposits located in the sourroundings of the Laras district, in the city of Laranjal Paulista, SP, constitute packages of decametric thickness that consists of wide flat-topped hills (490 to 570 meters of altitude) developed on stratigraphic units of the Paraná Basin. The conglomerates lie in unconformable on the Teresina Formation (Permian) and, secondarily, on the Piramboia Formation (Permo-Triassic). The studied conglomeratic deposits are firstly described here and show mappable occurrence of the scale of 1: 25.000, so that they can constitute an independent lithostratigraphic unit. The deposits are essentially composed of poorly selected sandy matrix polymorphic orthoglomerates, sometimes ferricretized due to recent diagenetic processes. The conglomerates locally occur intercalated with pebbly sandstones with grooved cross stratification, forming channels with ten meters of lateral extension and many meters of thickness. The analysis of clasts provenance was carried out in four stations measuring in the entire length of the deposits, with the characterization of the lithologies and measurement of the major, minor and intermediate axes of 1,218 clasts. The results of gravel petrography show a higher frequency of lithotypes resistant to transport in the southeast portion of the area of occurrence of the deposits. Predominate clasts of silexites, quartzites and vein quartz, well rounded and oblate, suggesting transport over a long distance from the source area in the crystalline basement. In the northwestern portion, occurs less resistant litothypes and subangled clasts, represented by oolitic carbonates and coquinas, both silicified, predominate. These lithotypes suggest erosion of the Teresina Formation and short transport from the source area in Paleozoic terrains existing in the Paulista Peripheral Depression. Paleocurrent measurements measured in cross stratification and pebble imbrication indicate paleoflux...