Paleontology and depositional environments of the Tatuí and Irati formations (Permian) in the Ponte Nova Farm, Ipeúna, state of São Paulo

Abstract

The Paraná Basin, located at the center-eastern South America, exhibits a thick succession of Late Paleozoic deposits. Two early Permian formations are present in the State of São Paulo, Brazil: Tatuí (the oldest) and Irati. Two members make up the Irati Formation - the Taquaral (the oldest) and Assistência. This paper discusses the facies of the upper Tatuí Formation and Taquaral Member, and their fossil content, mainly at the Ponte Nova Farm. This locality exhibits well-preserved outcrops of both units, with informative data on the facies relationships and their fossils. Crustaceans and vertebrates are presented at both the Tatuí and Taquaral beds. Different facies were recognized at Ponte Nova Farm, based on lithosomes, fossils and their relationships. In this context, a complex six facies architecture displayed at this locality allowed the formulation of a paleoenvironment hypothesis for the generation of the Tatuí Formation. The fine cross-bedded sandstone with subordinate planeparallel strata (facies 1) might have been laid down by a rather topographic mild coastal environment. Facies 2 is the result of low energy slack water subenvironment passing to facies 3, a high energy water system. The facies 4 is the result of an encroaching coastal environment over the continent. Taquaral facies 5 might be the result of a very high energy, body of water, becoming very quieter later, when facies 6 was deposited.