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Los Colorados Formation

Summary

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
TypeGeological formation
Unit ofAgua de la Peña Group
UnderliesCerro Rajado Formation
OverliesIschigualasto Formation
Thickness600 m (2,000 ft)
Lithology
PrimarySandstone, siltstone, mudstone
OtherConglomerate, gypsum
Location
Coordinates29°48′S 67°54′W / 29.8°S 67.9°W / -29.8; -67.9
Approximate paleocoordinates38°54′S 31°24′W / 38.9°S 31.4°W / -38.9; -31.4
RegionSan Juan Province
La Rioja Province
CountryArgentina
ExtentIschigualasto-Villa Unión Basin
Type section
Named forLos Colorados Massif
Los Colorados Formation is located in Argentina
Los Colorados Formation
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 edit

 
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 edit

Anapsids edit

Anapsids of Los Colorados Formation
Genus Species Location Material Notes Images

Palaeochersis

P. talampayensis

[3][4]

Synapsids edit

Synapsids of Los Colorados Formation
Genus Species Location Material Notes Images
Chaliminia C. musteloides [3]
Jachaleria J. colorata  
Tessellatia T. bonapartei [5]

Archosauromorphs edit

Archosauromorphs of Los Colorados Formation
Taxa Location Notes Images

Genus:

  1. F. tenax
 La Rioja Province [1][3]

Genus:

  1. N. engaeus
 Quebrada de los Jachaleros, El Salto (San Juan) [3]
 

Genus:

  1. R. tenuisceps
 [3][6]
 

Crocodylomorpha edit

Crocodylomorphs of Los Colorados Formation
Taxa Location Notes Images

Genus:

  1. C. abelini
 La Rioja Province [7]  

Genus:

  1. H. leali
 Quebrada de los Jachaleros, El Salto (San Juan) [3][7]

Genus:

  1. P. jachaleri
 Quebrada de los Jachaleros, El Salto (San Juan) [3]
 

Dinosaurs edit

Indeterminate theropod remains present in the Provincia de la Rioja.[1]

Dinosaurs of Los Colorados Formation
Taxa Location Notes Images

Genus:

  1. C. brevis
 La Rioja Province[1] "Skull, adult"[3][8]

Genus:

  1. L. sauropoides
 La Rioja Province[1] "Partial cervical, dorsal, and sacral vertebrae, adult."[8]
 

Infraorder:

  1. Indeterminate remains
 La Rioja & San Juan Provinces Includes Strenusaurus procerus.[1] "Dorsals, caudals, partial fore- and hindlimb."[9]

Genus:

  1. P. podocitus
 Ischigualasto-Villa Unión Basin Known from previously undescribed partial hindlimbs

Genus:

  1. R. incertus
 La Rioja Province [10][3][1]
 

Genus:

  1. Z. rougieri
 La Rioja Province [3][1]
 

Ichnofossils edit

See also edit

References edit

  1. ^ a b c d e f g h Weishampel et al., 2004, pp.527-528
  2. ^ a b Kent et al, 2014, p.7959
  3. ^ a b c d e f g h i j Arcucci et al., 2004, p.561
  4. ^ 2 km NE of La Esquina at Fossilworks.org
  5. ^ Gaetano, L. C.; Abdala, F.; Seoane, F. D.; Tartaglione, A.; Schulz, M.; Otero, A.; Leardi, J. M.; Apaldetti, C.; Krapovickas, V.; Steimbach, E. (2022). "A new cynodont from the Upper Triassic Los Colorados Formation (Argentina, South America) reveals a novel paleobiogeographic context for mammalian ancestors". Scientific Reports. 12 (1): Article number 6451. Bibcode:2022NatSR..12.6451G. doi:10.1038/s41598-022-10486-4. PMC 9038739. PMID 35468982.
  6. ^ Von Baczko & Desojo, 2016, p.4
  7. ^ a b Martínez et al., 2018, p.1
  8. ^ a b "Table 12.1," in Weishampel et al., 2004. p.234
  9. ^ "Table 12.1," in Weishampel, et al., 2004. Page 237.
  10. ^ Ezcurra, 2017
  11. ^ Río de los Tarros tracksite at Fossilworks.org
  12. ^ Leonardi, 1994, p.25
  13. ^ Leonardi locality 15 at Fossilworks.org

Bibliography edit

  • 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 edit

 
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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