The Tarjados Formation is an

Early Early may refer to: Places in the United States * Early, Iowa, a city * Early, Texas, a city * Early Branch, a stream in Missouri * Early County, Georgia * Fort Early, Georgia, an early 19th century fort Music * Early B, stage name of Jamaican d ...

Middle Triassic In the geologic timescale, the Middle Triassic is the second of three epoch (geology), epochs of the Triassic period (geology), period or the middle of three series (stratigraphy), series in which the Triassic system (stratigraphy), system is di ...

geologic

formation Formation may refer to: Linguistics * Back-formation, the process of creating a new lexeme by removing or affixes * Word formation, the creation of a new word by adding affixes Mathematics and science * Cave formation or speleothem, a secondary ...

in the

Ischigualasto-Villa Unión Basin The Ischigualasto-Villa Unión Basin () is a small sedimentary basin located in the Argentine Northwest, Argentina. It is located in the southwestern part of La Rioja Province and the northeastern part of San Juan Province. The basin borders the ...

of La Rioja Province in northwestern

Argentina Argentina, officially the Argentine Republic, is a country in the southern half of South America. It covers an area of , making it the List of South American countries by area, second-largest country in South America after Brazil, the fourt ...

. The red to whitish

sandstone Sandstone is a Clastic rock#Sedimentary clastic rocks, clastic sedimentary rock composed mainly of grain size, sand-sized (0.0625 to 2 mm) silicate mineral, silicate grains, Cementation (geology), cemented together by another mineral. Sand ...

s and conglomerates of the formation were deposited in an arid

fluvial A river is a natural stream of fresh water that flows on land or inside caves towards another body of water at a lower elevation, such as an ocean, lake, or another river. A river may run dry before reaching the end of its course if it ru ...

environment. The formation overlies the

Talampaya Formation The Talampaya Formation is an Early Triassic (Olenekian) geologic formation in the Ischigualasto-Villa Unión Basin of La Rioja Province in northwestern Argentina. The pink to red sandstones of the formation represent the oldest sedimentary un ...

and is overlain by the

Chañares Formation The Chañares Formation is a Carnian-age geologic formation of the Ischigualasto-Villa Unión Basin, located in La Rioja Province, Argentina. It is characterized by drab-colored fine-grained volcaniclastic claystones, siltstones, and sandstones ...

of the Agua de la Peña Group. The formation has provided fossils of an

archosaur Archosauria () or archosaurs () is a clade of diapsid sauropsid tetrapods, with birds and crocodilians being the only extant taxon, extant representatives. Although broadly classified as reptiles, which traditionally exclude birds, the cladistics ...

and a kannemeyeriid

dicynodont Dicynodontia is an extinct clade of anomodonts, an extinct type of non-mammalian therapsid. Dicynodonts were herbivores that typically bore a pair of tusks, hence their name, which means 'two dog tooth'. Members of the group possessed a horny, t ...

, both not yet placed in a dedicated

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

. The formation crops out in the

Talampaya National Park Talampaya National Park () is a National Parks of Argentina, national park located in the east/centre of La Rioja Province (Argentina), La Rioja Province, Argentina. It was designated a provincial reserve in 1975, a national park in 1997, and a U ...

, which was designated a

UNESCO The United Nations Educational, Scientific and Cultural Organization (UNESCO ) is a List of specialized agencies of the United Nations, specialized agency of the United Nations (UN) with the aim of promoting world peace and International secur ...

World Heritage Site World Heritage Sites are landmarks and areas with legal protection under an treaty, international treaty administered by UNESCO for having cultural, historical, or scientific significance. The sites are judged to contain "cultural and natural ...

in 2000.Talampaya National Park
at

Fossilworks Fossilworks was a portal which provides query, download, and analysis tools to facilitate access to the Paleobiology Database, a large relational database assembled by hundreds of paleontologists from around the world. History Fossilworks was cr ...

.org

Description

The formation was first defined by Romer and Jensen in 1966,Caselli, 1998, p.22 based on a

type section In geology, a stratotype or type section is the physical location or outcrop of a particular reference exposure of a stratigraphic sequence or stratigraphic boundary. If the stratigraphic unit is layered, it is called a stratotype, whereas the ...

exposed in the Sierra de Los Tarjados.Balabusic et al., 2001, p.14 The Tarjados Formation, as the underlying

, belongs to the Paganzo Group.Tarjados Formation
at

.org The formation is exposed in the

of La Rioja Province. The Tarjados Formation is overlain by the

, separated by a regional

unconformity An unconformity is a buried erosional or non-depositional surface separating two rock masses or strata of different ages, indicating that sediment deposition was not continuous. In general, the older layer was exposed to erosion for an interval ...

.Balabusic et al., 2001, p.26 The formation, reaching a maximum thickness of ,Aceituno Cieri et al., 2015, p.60Monetta et al., 2000, p.648 comprises red to greenish grey

s,Monetta et al., 2000, p.644 deposited in an eolian and playa-lacustrine to

environment.Ezcurra et al., 2015, p.476 The sediments were deposited under arid,Balabusic et al., 2001, p.28 or semi-arid conditions. The formation has provided fossils of an

and a kannemeyeriid

, both not yet placed in a dedicated

.Ezcurra et al., 2015, p.478Ezcurra et al., 2015, p.479

References

Bibliography

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Description

See also

References

Bibliography

Further reading