Irati Formation
Encyclopedia
Irati Formation is the name of a geological formation of Brazil
.
It has previously been dated as Upper Permian
using palynomorph
s but is now dated as Lower Permian using zircon
ages obtained from bentonite
layers. Exposures of the Irati Formation are to be found in the South (Geopark
of Paleorrota
), southeastern Brazil
and in the states of Goias
and Mato Grosso do Sul
.
The Irati Formation is particularly famous for its mesosaur
occurrences
.
It is considered time equivalent to the Whitehill Formation of the Ecca Group of the Karoo Supergroup of southern Africa.
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
.
It has previously been dated as Upper Permian
Permian
The PermianThe term "Permian" was introduced into geology in 1841 by Sir Sir R. I. Murchison, president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with Edouard de Verneuil; Murchison asserted in 1841 that he named his "Permian...
using palynomorph
Palynomorph
Palynomorph is the geological term used to describe a particle of a size between five and 500 micrometres, found in rock deposits and composed of organic material such as chitin, pseudochitin and sporopollenin...
s but is now dated as Lower Permian using zircon
Zircon
Zircon is a mineral belonging to the group of nesosilicates. Its chemical name is zirconium silicate and its corresponding chemical formula is ZrSiO4. A common empirical formula showing some of the range of substitution in zircon is 1–x4x–y...
ages obtained from bentonite
Bentonite
Bentonite is an absorbent aluminium phyllosilicate, essentially impure clay consisting mostly of montmorillonite. There are different types of bentonite, each named after the respective dominant element, such as potassium , sodium , calcium , and aluminum . Experts debate a number of nomenclatorial...
layers. Exposures of the Irati Formation are to be found in the South (Geopark
Geopark
A Geopark is defined by the United Nations Educational, Scientific and Cultural Organization in its UNESCO Geoparks International Network of Geoparks programme as follows:...
of Paleorrota
Paleorrota
Paleorrota , is a geopark located in the center of the Brazilian state of Rio Grande do Sul. The rocks and fossils found along the route date back to the times when there was only one supercontinent Pangaea....
), southeastern Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
and in the states of Goias
Goiás
Goiás is a state of Brazil, located in the central part of the country. The name Goiás comes from the name of an indigenous community...
and Mato Grosso do Sul
Mato Grosso do Sul
Mato Grosso do Sul is one of the states of Brazil.Neighboring Brazilian states are Mato Grosso, Goiás, Minas Gerais, São Paulo and Paraná. It also borders the countries of Paraguay and Bolivia to the west. The economy of the state is largely based on agriculture and cattle-raising...
.
The Irati Formation is particularly famous for its mesosaur
Mesosaur
Mesosaurs 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 aquatic reptiles, having apparently returned to an aquatic lifestyle from more terrestrial ancestors...
occurrences
.
It is considered time equivalent to the Whitehill Formation of the Ecca Group of the Karoo Supergroup of southern Africa.