Los Colorados Formation
The Los Colorados Formation is a sedimentary rock formation of the Ischigualasto-Villa Unión Basin, found in the provinces of San Juan and La Rioja in Argentina. The formation dates back to the Norian age of the Late Triassic.
| Los Colorados Formation Stratigraphic range: Norian ~227–213 Ma | |
|---|---|
 Los Colorados massif, La Rioja Province, Argentina | |
| Type | Geological formation |
| Unit of | Agua de la Peña Group |
| Underlies | Cerro Rajado Formation |
| Overlies | Ischigualasto Formation |
| Thickness | 600 m (2,000 ft) |
| Lithology | |
| Primary | Sandstone, siltstone, mudstone |
| Other | Conglomerate, gypsum |
| Location | |
| Coordinates | 29.8°S 67.9°W |
| Approximate paleocoordinates | 38.9°S 31.4°W |
| Region | San Juan & La Rioja Provinces |
| Country |  Argentina |
| Extent | Ischigualasto-Villa Unión Basin |
| Type section | |
| Named for | Los Colorados Massif |
  Los Colorados Formation (Argentina) | |
The up to 600 metres (2,000 ft) thick formation comprises sandstones, siltstones, mudstones and conglomerates with gypsum layers deposited in a fluvial to lacustrine environment. The formation is the uppermost stratigraphic unit of the Agua de la Peña Group, overlying the Lagerstätte of the Ischigualasto Formation. Los Colorados Formation is partly covered by the Cretaceous Cerro Rajado Formation, separated by an unconformity.
The formation is known for its fossils of early dinosaurs, including the coelophysoid Zupaysaurus and the "prosauropods" Coloradisaurus, Lessemsaurus, and Riojasaurus.[1] Magnetostratigraphic analysis suggests that the Los Colorados Formation was deposited between 227 and 213 million years ago.[2]
Description
Extent of the formation in the Ischigualasto-Villa Unión Basin
Los Colorados Formation is a unit with an approximate thickness of 600 metres (2,000 ft) of the Agua de la Peña Group in the Ischigualasto-Villa Unión Basin, where it is exposed in the Ischigualasto Provincial Park, a World Heritage site in Argentina. The formation gradually overlies the Ischigualasto Formation and is unconformably overlain by the Cretaceous Cerro Rajado Formation. The formation comprises red-colored, fine- to medium-grain–size sandstones together with siltstones and ancillary floodplain mudstones with early calcisol development. The formation was deposited in a fluvial to lacustrine environment.[2]
Fossil content
Anapsids
| Anapsids of Los Colorados Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Material | Notes | Images | |
|
Palaeochersis |
P. talampayensis |
[3][4] | ||||
Synapsids
| Synapsids of Los Colorados Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Material | Notes | Images | |
|
J. colorata |
[3] | |||||
Eucynodontia
| Eucynodonts of Los Colorados Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Material | Notes | Images | |
| Chaliminia | C. musteloides | [3] | ||||
Archosauromorphs
| Archosauromorphss of Los Colorados Formation | ||||
|---|---|---|---|---|
| Taxa | Location | Notes | Images | |
|
Genus:
|
La Rioja Province | [1][3] | ||
|
Genus:
|
Quebrada de los Jachaleros, El Salto (San Juan) | [3] |  | |
|
Genus:
|
[3][5] |  | ||
Crocodylomorpha
| Crocodylomorphs of Los Colorados Formation | ||||
|---|---|---|---|---|
| Taxa | Location | Notes | Images | |
|
Genus:
|
La Rioja Province | [6] | ||
|
Genus:
|
Quebrada de los Jachaleros, El Salto (San Juan) | [3][6] | ||
|
Genus:
|
Quebrada de los Jachaleros, El Salto (San Juan) | [3] |  | |
Dinosaurs
Indeterminate theropod remains present in the Provincia de la Rioja.[1]
| Dinosaurs of Los Colorados Formation | ||||
|---|---|---|---|---|
| Taxa | Location | Notes | Images | |
|
Genus:
|
La Rioja Province[1] | "Skull, adult"[3][7] | ||
|
Genus:
|
La Rioja Province[1] | "Partial cervical, dorsal, and sacral vertebrae, adult."[7] |  | |
|
Infraorder:
|
La Rioja & San Juan Provinces | Includes Strenusaurus procerus.[1] "Dorsals, caudals, partial fore- and hindlimb."[8] | ||
|
Genus:
|
Ischigualasto-Villa Unión Basin | Known from previously undescribed partial hindlimbs | ||
|
Genus:
|
La Rioja Province | [9][3][1] |  | |
|
Genus:
|
La Rioja Province | [3][1] |  | |
Ichnofossils
- cf. Brachychirotherium sp.[10]
- Chirotherium sp.[11][12]
See also
- List of dinosaur-bearing rock formations
- Quebrada del Barro Formation, contemporaneous fossiliferous formation of the Marayel-El Carrizal Basin just southeast of the Ischigualasto-Villa Unión Basin
- Caturrita Formation, contempeoraneous fossiliferous formation of the Paraná Basin, southeastern Brazil
- Chinle Formation, contemporaneous fossiliferous formation of Arizona
- Elliot Formation, contemporaneous fossiliferous formation of the Karoo Basin, South Africa
- Fremouw Formation, contemporaneous fossiliferous formation of Antarctica
References
- Weishampel et al., 2004, pp.527-528
- Kent et al, 2014, p.7959
- Arcucci et al., 2004, p.561
- 2 km NE of La Esquina at Fossilworks.org
- Von Baczko & Desojo, 2016, p.4
- Martínez et al., 2018, p.1
- "Table 12.1," in Weishampel et al., 2004. p.234
- "Table 12.1," in Weishampel, et al., 2004. Page 237.
- Ezcurra, 2017
- Río de los Tarros tracksite at Fossilworks.org
- Leonardi, 1994, p.25
- Leonardi locality 15 at Fossilworks.org
Bibliography
- Arcucci, A.B.; C.A. Marsicano, and A.T. Caselli. 2004. Tetrapod association and palaeoenvironment of the Los Colorados Formation (Argentina): a significant sample from western Gondwana at the end of the Triassic. Geobios 37. 557–568. Accessed 2019-03-28.
- Von Baczko, Maria Belén, and Julia Brenda Desojo. 2016. Cranial Anatomy and Palaeoneurology of the Archosaur Riojasuchus tenuisceps from the Los Colorados Formation, La Rioja, Argentina. PLoS ONE 11. 1–30. Accessed 2019-03-29.
- Ezcurra, Martín D. 2017. A new early coelophysoid neotheropod from the Late Triassic of northwestern Argentina. Ameghiniana 54. Abstract. Accessed 2019-03-26.
- Kent, Dennis V.; Paula Santi Malnis; Carina E. Colombi; Oscar A. Alcober, and Ricardo N. Martínez. 2014. Age constraints on the dispersal of dinosaurs in the Late Triassic from magnetochronology of the Los Colorados Formation (Argentina). Proceedings of the National Academy of Sciences 111. 7958–7963. Accessed 2018-09-08.
- Leonardi, Giuseppe. 1994. Annotated Atlas of South America Tetrapod Footprints (Devonian to Holocene) with an appendix on Mexico and Central America, 1–248. Ministerio de Minas e Energia - Companhia de Pesquisa de Recursos Minerais, Geological Service of Brazil. Accessed 2019-03-25.
- Martínez, Ricardo N.; Oscar A. Alcober, and Diego Pol. 2018. A new protosuchid crocodyliform (Pseudosuchia, Crocodylomorpha) from the Norian Los Colorados Formation, northwestern Argentina. Journal of Vertebrate Paleontology 38. 1–12. Accessed 2019-03-28.
- Weishampel, David B.; Peter Dodson, and Halszka Osmólska (eds.). 2004. The Dinosauria, 2nd edition, 1–880. Berkeley: University of California Press. Accessed 2019-02-21. ISBN 0-520-24209-2
Further reading
 |
Wikimedia Commons has media related to Los Colorados Formation. |
- A. B. Arcucci and R. A. Coria. 2003. A new Triassic carnivorous dinosaur from Argentina. Ameghiniana 40(2):217-228
- J. F. Bonaparte. 1999. Evolución de las vértebras presacras en Sauropodomorpha [Evolution of the presacral vertebrae in Sauropodomorpha]. Ameghiniana 36(2):115-187
- J. F. Bonaparte and J. A. Pumares. 1995. Notas sobre el primer craneo de Riojasaurus incertus (Dinosauria, Prosauropoda, Melanorosauridae) del Triasico Superior de La Rioja, Argentina [Notes on the first skull and jaws of Riojasaurus incertus (Dinosauria, Prosauropoda, Melanorosauridae), Late Triassic of La Rioja, Argentina]. Ameghiniana 32(4):341-349
- J. F. Bonaparte. 1981. Descripción de "Fasolasuchus tenax" y su significado en la sistematica y evolución de los thecodontia. Revista del Museo Argentino de Ciencias Naturales "Bernardino Rivadavia" 3(2):55-101
- J. F. Bonaparte. 1978. Coloradia brevis n. g. et n. sp. (Saurischia–Prosauropoda), dinosaurio Plateosauridae de la Formacion Los Colorados, Triasico Superior de La Rioja, Argentina [Coloradia brevis n. g. et n. sp. (Saurischia–Prosauropoda), a plateosaurid from the Upper Triassic Los Colorados Formation of La Rioja, Argentina]. Ameghiniana 15(3-4):327-332
- J. F. Bonaparte. 1971. Los tetrapodos del sector superior de la Formacion Los Colorados, La Rioja, Argentina (Triásico Superior) [The tetrapods of the upper part of the Los Colorados Formation, La Rioja, Argentina (Upper Triassic)]. Opera Lilloana 22:1-183
- J. F. Bonaparte. 1969. Dos nuevas "faunas" de reptiles triasicos de Argentina [Two new reptilian "faunas" of the Argentine Triassic]. Gondwana Stratigraphy (IUGS Symposium, Buenos Aires) 2:283-306
- J. B. Desojo and A. M. Baez. 2007. Cranial morphology of the Late Triassic South American archosaur Neoaetosauroides engaeus: evidence for aetosaurian diversity. Palaeontology 50:267-276
- J. B. Desojo and A. M. Baez. 2005. El esqueleto postcraneano de Neoaetosauroides (Archosauria: Aetosauria) del Triásico Superior del centro-oeste de Argentina. Ameghiniana 42:115-126
- M. D. Ezcurra and C. Apaldetti. 2012. A robust sauropodomorph specimen from the Upper Triassic of Argentina and insights on the diversity of the Los Colorados Formation. Proceedings of the Geologists' Association 123:155-164
- A. G. Martinelli and G. W. Rougier. 2007. On Chaliminia musteloides (Eucynodontia: Tritheledontidae) from the Late Triassic of Argentina, and a phylogeny of Ictidosauria. Journal of Vertebrate Paleontology 27:442-460
- G. W. Rougier, M. S. de la Fuente, and A. B. Arcucci. 1995. Late Triassic turtles from South America. Science 268:855-858
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