Irati Formation

Irati Formation
Irati Formation
Stratigraphic range: Early Permian; ~278.4–270 Ma PreꞒ Ꞓ O S D C P T J K Pg N
	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°30′S 50°42′W / 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°48′S 29°42′W / 45.8°S 29.7°W
	; The Paraná Basin in South America

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]

Fossil content

Color key

Taxon	Reclassified taxon	Taxon falsely reported as present	Dubious taxon or junior synonym	Ichnotaxon	Ootaxon	Morphotaxon

Notes
Uncertain or tentative taxa are in small text; ~~crossed out~~ taxa are discredited.

Reptiles of the Irati Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Image
Brazilosaurus	B. sanpauloensis				A mesosaurid mesosaur
Mesosaurus	M. tenuidiens				A mesosaurid mesosaur
Stereosternum	S. tumidum				A mesosaurid mesosaur

Crustaceans of the Irati Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Iraticaris	I. damiani
Myelontordoxylon	M. camposii
Permocaris	P. purperae
Pittinucaris	P. wuerdigae

Da Costa, Guilherme Estevam (2015), Fácies sedimentares e composição de folhelhos da Formação Irati (Eopermiano) da Bacia do Paraná na região de Bom Retiro, Leste de Santa Catarina (PDF), Universidade Federal de Santa Catarina, UFSC, pp. 1–67, retrieved 2017-08-03
Diduch, Ana Paula (2011), Descrição de Crustacea Malacostraca da Formação Irati, Permiano Superior, Bacia do Paraná, Brasil (PDF), Universidade Federal do Paraná, UFPR, pp. 1–52, retrieved 2017-08-03
Piñeiro, G.; Ramos, A.; Goso, C.S.; Scarabino, F.; Laurin, M. (2012), "Unusual Environmental Conditions Preserve a Permian Mesosaur-Bearing Konservat-Lagerstätte from Uruguay", Acta Palaeontologica Polonica, 57 (2): 1–299, doi:10.4202/app.2010.0113
Ventura Santos, Roberto; Souza, Paulo A.; Souza de Alvarenga, Carlos José; Luiz Dantas, Elton; Martins Pimentel, Marcio; Gouveia de Oliveira, Claudinei; Medeiros de Araújo, Laury (2006), "Shrimp U–Pb zircon dating and palynology of bentonitic layers from the Permian Irati Formation, Paraná Basin, Brazil", Gondwana Research, 9 (4): 456–463, Bibcode:2006GondR...9..456S, doi:10.1016/j.gr.2005.12.001