Consideraciones geológicas y paleontológicas sobre el contacto de las formaciones Tatuí e Iratí (Pérmico), Cuenca de Paraná, Brasil

• Autores: Artur Chahud, Johanna Méndez Duque, Setembrino Petri
• Localización: Geología colombiana, ISSN 0072-0992, Vol. 35, Nº. 1, 2010, págs. 36-49
• Idioma: español
• Títulos paralelos:
  • Geologic and Paleontologic Considerations on the Contact of Tatuí and Irati Formations (Permian), Paraná Basin, Brazil
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• Resumen
  • español

    La Cuenca de Paraná está situada en el centro � oriente de América del Sur. Los sedimentos neopaleozoicos presentes al norte de la cuenca, en el Estado de São Paulo (Brasil), comprenden de base a tope las unidades litoestratigráficas: Itararé, Tatuí, Iratí y Corumbataí. La Formación Iratí es subdividida en dos miembros, Taquaral en la base y Assistência en el tope. El presente trabajo trata los afloramientos del centro este del Estado de São Paulo, del tope de la Formación Tatuí al Miembro Taquaral. La Formación Tatuí es exclusiva del Estado de São Paulo, parcialmente coetánea a las formaciones Palermo y Río Bonito de los Estados del sur de Brasil, formaciones litológicamente diferenciables. El Miembro Taquaral tiene un desarrollo más completo en el Estado de São Paulo. La litología de ambas unidades es aquí discutida. Los diferentes fósiles corresponden a restos de vertebrados, básicamente peces, crustáceos e icnofósiles, encontrados en los estratos más superiores de la Formación Tatuí, en el contacto del Miembro Taquaral.

  • English

    The Paraná Basin is located in the central � east part of South America. The thickest lithostratigraphic units of this basin were formed in the Late Palaeozoic. The neopalaeozoic sediments in the north of the river basin, in the State of São Paulo (Brazil), include from the base to the top the following lithostratigraphic units: Itararé, Tatuí, Irati (two members, Taquaral and Assistência) and Corumbataí. The Tatui Formation is recognized only in the São Paulo State.

    The lithologies of the Tatui Formation, in the studied area, are grouped into three facies: a) Hummocky fine sandstones, b) a varied lithology of sandstones, massive or thinly laminated, and siltstones and c) sandstones with ichnofossils. Two facies make up the Taquaral Member, the sandy one mostly located on the base of the unit and the shale facies. An unconformity separates the Tatui from the Taquaral sandy facies. The sandy facies is more common in outcrops even though the shale facies is thicker. The sandy facies is a high-energy transgressive lag, covering the Tatuí upper most beds. The lower energy deposits of the shale facies are overlain by the Assistência Member of the Iratí Formation. In this paper, the ichnofossils from the uppermost bed of the Tatui Formation, are reported for the first time. They are generated in a subaerial palaeoenvironment, attending the beginning of the Taquaral deposition. The main fossils from the Taquaral Member sandy facies are vertebrates; most of them bone fishes and Chondrichthyes (sharks and other cartilaginuous fishes). The crustacean Clarkecaris is the most characteristic fish of the Taquaral shale facies, some partly fossilized, few of them almost complete. Bonefishes are the only vertebrates found in this facies. No Chondrichthyes were recovered.