Tarjados Formation

The Tarjados Formation is an Early to Middle Triassic geologic formation in the Ischigualasto-Villa Unión Basin of La Rioja Province in northwestern Argentina. The red to whitish sandstones and conglomerates of the formation were deposited in an arid fluvial environment. The formation overlies the Talampaya Formation and is overlain by the Chañares Formation of the Agua de la Peña Group.

Tarjados Formation
Stratigraphic range: Early-Mid Triassic
~252–236 Ma
Sandstones in Talampaya National Park
TypeGeological formation
Unit ofPaganzo Group
UnderliesChañares Formation
OverliesTalampaya Formation
ThicknessUp to 250 m (820 ft)
Lithology
PrimarySandstone
OtherConglomerate
Location
Coordinates29.8°S 67.8°W / -29.8; -67.8
Approximate paleocoordinates48.0°S 38.9°W / -48.0; -38.9
RegionLa Rioja Province
Country Argentina
ExtentIschigualasto-Villa Unión Basin
Type section
Named forSierra de Los Tarjados
Named byRomer & Jensen
Year defined1966
Tarjados Formation (Argentina)

The formation has provided fossils of an archosaur and a kannemeyeriid dicynodont, both not yet placed in a dedicated genus. The formation crops out in the Talampaya National Park, which was designated a UNESCO World Heritage Site in 2000.[1]

Description

The formation was first defined by Romer and Jensen in 1966,[2] based on a type section exposed in the Sierra de Los Tarjados.[3] The Tarjados Formation, as the underlying Talampaya Formation, belongs to the Paganzo Group.[4]

The formation is exposed in the Talampaya National Park of La Rioja Province. The Tarjados Formation is overlain by the Chañares Formation, separated by a regional unconformity.[5]

The formation, reaching a maximum thickness of 250 metres (820 ft),[6][7] comprises red to greenish grey sandstones,[8] deposited in an eolian and playa-lacustrine to fluvial environment.[9] The sediments were deposited under arid,[10] or semi-arid conditions.[9]

The formation has provided fossils of an archosaur and a kannemeyeriid dicynodont, both not yet placed in a dedicated genus.[11][12]

See also

References
  1. Talampaya National Park at Fossilworks.org
  2. Caselli, 1998, p.22
  3. Balabusic et al., 2001, p.14
  4. Tarjados Formation at Fossilworks.org
  5. Balabusic et al., 2001, p.26
  6. Aceituno Cieri et al., 2015, p.60
  7. Monetta et al., 2000, p.648
  8. Monetta et al., 2000, p.644
  9. Ezcurra et al., 2015, p.476
  10. Balabusic et al., 2001, p.28
  11. Ezcurra et al., 2015, p.478
  12. Ezcurra et al., 2015, p.479

Bibliography

Further reading
  • Bonaparte, J.F. 1978. El Mesozóico de América de Sur y sus Tetrapodos - The Mesozoic of South America and its tetrapods. Opera Lilloana 26. 1–596.
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