Tarjados Formation Explained

Tarjados Formation
Type:Geological formation
Period:Ladinian
Age:Early-Mid Triassic
~
Prilithology:Sandstone
Otherlithology:Conglomerate
Namedfor:Sierra de Los Tarjados
Namedby:Romer & Jensen
Year Ts:1966
Region:La Rioja Province
Coordinates:-29.8°N -67.8°W
Paleocoordinates:-48°N -38.9°W
Unitof:Paganzo Group
Underlies:Chañares Formation
Overlies:Talampaya Formation
Thickness:Up to 250m (820feet)
Extent:Ischigualasto-Villa Unión Basin

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.

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 250m (820feet),[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

Bibliography

Notes and References

  1. http://www.fossilworks.org/cgi-bin/bridge.pl?a=collectionSearch&collection_no=174112 Talampaya National Park
  2. Caselli, 1998, p.22
  3. Balabusic et al., 2001, p.14
  4. http://www.fossilworks.org/cgi-bin/bridge.pl?action=collectionSearch&geological_group=Paganzo&formation=Tarjados Tarjados Formation
  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