From Wikipedia, the free encyclopedia
Seamless Wikipedia browsing. On steroids.
Every time you click a link to Wikipedia, Wiktionary or Wikiquote in your browser's search results, it will show the modern Wikiwand interface.
Wikiwand extension is a five stars, simple, with minimum permission required to keep your browsing private, safe and transparent.
Irati Formation is the name of a geological formation of the Paraná Basin in Brazil. It has previously been dated as Late Permian using palynomorphs, but is now dated as Early Permian using zircon ages obtained from bentonite layers. The base of the formation has been dated at 278.4 ± 2.2 Ma.[1][2] Exposures of the Irati Formation are to be found in the South (Geopark of Paleorrota), southeastern Brazil and in the states of Goiás, Mato Grosso, São Paulo, Paraná, Santa Catarina, Rio Grande do Sul and Mato Grosso do Sul.[1] The formation is part of the Passa Dios Group, underlying the Serra Alta Formation and overlying the Palermo Formation. The formation has been deposited in a restricted marine environment.[3] The Irati Formation, with a maximum thickness of 80 metres (260 ft), was defined and named by White in 1908.[4]
| Irati Formation | |
|---|---|
| Stratigraphic range: Early Permian ~ | |
 The Irati Formation belongs to the Gondwana I megasequence | |
| Type | Geological formation |
| Unit of | Passa Dois Group |
| Underlies | Serra Alta Formation (Paraná Basin) Teresina Formation (Pelotas Basin) |
| Overlies | Palermo Formation |
| Area | 1,000,000 km2 (390,000 sq mi) |
| Thickness | up to 80 m (260 ft) |
| Lithology | |
| Primary | Black shale |
| Other | Sandstone |
| Location | |
| Coordinates | 25.5°S 50.7°W |
| Region | Paraná & Pelotas Basins Goiás, Mato Grosso do Sul, Mato Grosso, São Paulo, Paraná, Santa Catarina, Rio Grande do Sul |
| Country |  Brazil |
| Type section | |
| Named by | White |
| Year defined | 1908 |
| Approximate paleocoordinates | 45.8°S 29.7°W |
 The Paraná Basin in South America | |
The formation is particularly famous for the occurrences of the mesosaurs Mesosaurus tenuidiens,[5] and Stereosternum tumidum. Other fossils found in the formation are Myelontordoxylon camposii,[6] and crustaceans of the genera Paulocaris, Pygaspis, Liocaris, and Clarkecaris.[7] It is considered time equivalent to the Whitehill Formation of the Ecca Group of the Karoo Supergroup of southern Africa and the Mangrullo Formation of Uruguay.[8]
