Irati Formation is the name of a

geological formation A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics ( lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exp ...

of the

Paraná Basin The Paraná Basin ( pt, Bacia do Paraná, es, Cuenca del Paraná) is a large cratonic sedimentary basin situated in the central-eastern part of South America. About 75% of its areal distribution occurs in Brazil, from Mato Grosso to Rio Grande d ...

Brazil Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...

. It has previously been dated as

Late Permian Late may refer to: * LATE, an acronym which could stand for: ** Limbic-predominant age-related TDP-43 encephalopathy, a proposed form of dementia ** Local-authority trading enterprise, a New Zealand business law ** Local average treatment effect, ...

using

palynomorph Palynology is the "study of dust" (from grc-gre, παλύνω, palynō, "strew, sprinkle" and ''-logy'') or of "particles that are strewn". A classic palynologist analyses particulate samples collected from the air, from water, or from deposit ...

s, but is now dated as Early Permian using

zircon Zircon () is a mineral belonging to the group of nesosilicates and is a source of the metal zirconium. Its chemical name is zirconium(IV) silicate, and its corresponding chemical formula is Zr SiO4. An empirical formula showing some of t ...

ages obtained from

bentonite Bentonite () is an absorbent swelling clay consisting mostly of montmorillonite (a type of smectite) which can either be Na-montmorillonite or Ca-montmorillonite. Na-montmorillonite has a considerably greater swelling capacity than Ca-m ...

layers. The base of the formation has been dated at 278.4 ± 2.2 Ma.Da Costa, 2015, p.28Ventura Santos et al., 2006 Exposures of the Irati Formation are to be found in the South (

Geopark A geopark is a protected area with internationally significant geology within which sustainable development is sought and which includes tourism, conservation, education and research concerning not just geology but other relevant sciences. In 2 ...

of Paleorrota), southeastern

and in the states of

Goiás Goiás () is a Brazilian state located in the Center-West region. Goiás borders the Federal District and the states of (from north clockwise) Tocantins, Bahia, Minas Gerais, Mato Grosso do Sul and Mato Grosso. The state capital is Goi ...

, Mato Grosso,

São Paulo São Paulo (, ; Portuguese for ' Saint Paul') is the most populous city in Brazil, and is the capital of the state of São Paulo, the most populous and wealthiest Brazilian state, located in the country's Southeast Region. Listed by the Ga ...

, Paraná, Santa Catarina, Rio Grande do Sul and Mato Grosso do Sul. The formation is part of the

Passa Dios Group Passa may refer to: People * Chiara Passa (born 1973), Italian visual artist * Frank Passa (1916–2001), American luthier * François Jaubert de Passa (1785-1856), French engineer and politician Places * Passa, Pyrénées-Orientales, France * ...

, underlying the Serra Alta Formation and overlying the Palermo Formation. The formation has been deposited in a

restricted marine Restricted may refer to: *R rating (disambiguation), list of subjects where "R" stands for "Restricted" *18 rating, media rating designation sometimes called "Restricted" *Restricted (country club), historical use of the term in country clubs in t ...

environment Environment most often refers to: __NOTOC__ * Natural environment, all living and non-living things occurring naturally * Biophysical environment, the physical and biological factors along with their chemical interactions that affect an organism or ...

.Diduch, 2011, p.21 The Irati Formation, with a maximum thickness of , was defined and named by

White White is the lightest color and is achromatic (having no hue). It is the color of objects such as snow, chalk, and milk, and is the opposite of black. White objects fully reflect and scatter all the visible wavelengths of light. White o ...

in 1908.Da Costa, 2015, p.12

Fossil content

The formation is particularly famous for the occurrences of the

mesosaur Mesosaurs ("middle lizards") were a group of small aquatic reptiles that lived during the early Permian period, roughly 299 to 270 million years ago. Mesosaurs were the first known aquatic reptiles, having apparently returned to an aquatic life ...

s '' Mesosaurus tenuidiens'',Irati
at Fossilworks.org and ''

Stereosternum tumidum ''Stereosternum tumidum'' (meaning "rigid chest") (Stereos, Greek: “solid, firm”; Sternon, Greek: “chest, breastbone”) is an extinct genus of mesosaur marine reptile from the Early Permian of Brazil and also the Great Karoo Basin of South ...

''. Other fossils found in the formation are '' Myelontordoxylon camposii'',Diduch, 2011, p.24 and crustaceans of the genera '' Paulocaris'', '' Pygaspis'', '' Liocaris'', and '' Clarkecaris''.Diduch, 2011, p.23 It is considered time equivalent to the Whitehill Formation of the

Ecca Group The Ecca Group is the second of the main subdivisions of the Karoo Supergroup of geological strata in southern Africa. It mainly follows conformably after the Dwyka Group in some sections, but in some localities overlying unconformably over much ...

of the

Karoo Supergroup The Karoo Supergroup is the most widespread stratigraphic unit in Africa south of the Kalahari Desert. The supergroup consists of a sequence of units, mostly of nonmarine origin, deposited between the Late Carboniferous and Early Jurassic, a peri ...

of southern

Africa Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...

and the

Mangrullo Formation The Mangrullo Formation is an Early Permian (Artinskian) fossiliferous geological formation in northeastern Uruguay.Uruguay Uruguay (; ), officially the Oriental Republic of Uruguay ( es, República Oriental del Uruguay), is a country in South America. It shares borders with Argentina to its west and southwest and Brazil to its north and northeast; while bordering ...

.Piñeiro et al., 2012, p.299

References

Bibliography

* * * * {{cite LSA , last=Ventura Santos , first=Roberto , last2=Souza , first2=Paulo A. , last3=Souza de Alvarenga , first3=Carlos José , last4=Luiz Dantas , first4=Elton , last5=Martins Pimentel , first5=Marcio , last6=Gouveia de Oliveira , first6=Claudinei , last7=Medeiros de Araújo , first7=Laury , year=2006 , title=Shrimp U–Pb zircon dating and palynology of bentonitic layers from the Permian Irati Formation, Paraná Basin, Brazil , url= , journal= Gondwana Research , volume=9 , pages=456–463 , accessdate=2017-08-03 Geologic formations of Brazil Formations Permian System of South America Cisuralian Series Permian Brazil Shale formations Sandstone formations Oil shale formations Oil shale in Brazil Permian southern paleotemperate deposits Formations Formations Formations Formations Formations Formations Formations

Fossil content

See also

References

Bibliography