Candeleros Formation

Candeleros Formation
Stratigraphic range: Cenomanian
Type Geological formation
Unit of Neuquén Group
Underlies Huincul Formation
Overlies Lohan Cura Formation
Thickness 300m
Lithology
Primary Sandstone
Other Conglomerate
Eolian
Siltstone
Paleosol
Location
Region Neuquén Province
Country  Argentina
Type section
Named for Candeleros Hill

The Candeleros Formation (formerly known as the Candeleros Member of the "Rio Limay Formation") is a geologic formation that outcrops in Río Negro, Neuquén, and Mendoza provinces of Argentina. It is the oldest formation in the Neuquén Group and belongs to the Rio Limay Subgroup. Formerly that subgroup was treated as a formation, and the Candeleros Formation was known as the Candeleros Member.[1]

The type locality of the Candeleros Formation is Candeleros Hill in Neuquén province.[2] This formation unconformably overlies the Lohan Cura Formation, and it is in turn overlain by the Huincul Formation, also a unit of the Neuquén Group. The sediments of the latter are of lighter greenish and yellow colors and the boundary between the Candeleros and Huincul formations is easily recognizable.[3]

The Candeleros Formation is almost 300 meters thick in some sections. Overall, the formation represents an ancient braided river system, made up mostly of sandstones and conglomerates. There are also isolated sections that represent eolian (wind-blown) deposition, as well as siltstones deposited under swamp conditions. Paleosols (soil deposits) are common in some sections as well.[4]

Age

Era: Mesozoic
Period: Late Cretaceous
Faunal stage: early Cenomanian
Absolute Age: ~100 to ~97 mya

Vertebrate paleofauna

Reconstruction of Giganotosaurus carolinii
Skeleton of Buitreraptor gonzalezorum, the "vulture raptor" from the Candeleros Formation.

The Candeleros Formation has a very diverse fossil fauna, including:

Pterosaurs

Pteraichnus is found in Late Jurassic Strata of the Rio Limay group,[6] while substantial pterosaur remains are found on the La Buitrera Late Cretaceous strata.[7][8]

Pterosaurs of the Rio Limay Formation
Taxa Presence Description Images

Ichnogenus:
  • Present at Lake Ezequiel Ramos Mexia in the Candeleros Member.[6]
  • Specimens housed at Museo de Ciencias Naturales de la Universidad Nacional del Comahue.[6]
Pterosaurs of the La Buitrera Formation
Taxa Presence Description Images
  • The holotype (MPCN-PV 101) is a distal portion of a right ulna.
  • Housed at Museo de Ciencias Naturales de la Universidad Nacional del Comahue.
  • A proximal part of the left ulna. It is considerably larger than the other pterosaurs in the formation.
  • Housed at Museo Municipal “Ernesto Bachmann”, Villa El Chocón, Neuquén, Argentina
  • Holotype (MPCN-PV 102) is a partially preserved right wing represented by an almost complete ulna (fused to the radius) articulated with proximal and distal syncarpals, metacarpal IV and the proximal part of the first wing phalanx. It shows a peculiar combination of features including the syncarpal shape, a high ulna (preserved)/IV metacarpal and WF1 (preserved)/Mc IV ratios that allows its recognition as a basal pterosaur.
  • Housed at Museo Municipal “Ernesto Bachmann”, Villa El Chocón, Neuquén, Argentina

There are also several trackway sites and eggshells[1] known from the Candeleros Formation, including theropods, sauropods, ornithopods, and pterosaurs.

One of the most productive fossil localities in the Candeleros is known as La Buitrera and is now well known for producing many small tetrapod skeletons with three-dimensional preservation, although larger fossils, such as dinosaurs, are rare. Much larger dinosaur fossils have been recovered from other sites in the formation, however, including one of the largest carnivores known, Giganotosaurus. La Buitrera means, roughly, "the vulture-roost"; the genus Buitreraptor, a small bird-like dinosaur that must have been a predator of small vertebrates and possibly a scavenger was named after this.

See also

Footnotes

  1. 1 2 Sánchez et al. (2006)
  2. ↑ Wichmann (1929)
  3. ↑ Leanza et al. (2004)
  4. ↑ Leanza et al. (2004), Sánchez et al. (2006)
  5. ↑ "Small-sized abelisaurid (Theropoda: Ceratosauria) remains from the Upper Cretaceous of northwest Patagonia, Argentina". Cretaceous Research. 62: 18–28. doi:10.1016/j.cretres.2016.02.001.
  6. 1 2 3 4 5 Lockley, M.; Harris, J.D.; and Mitchell, L. 2008. "A global overview of pterosaur ichnology: tracksite distribution in space and time." Zitteliana. B28. p. 187-198. ISSN 1612-4138.
  7. 1 2 Haluza, A. Y Apesteguía, S, Pterosaur remains (Archosauria, Ornithodira) from the early Late Cretaceous of "La Buitrera", Río Negro, Argentina, Jornada; XXIII Jornadas Argentinas de Paleontología de Vertebrados; 2007
  8. 1 2 Alejandro Haluza, Juan I. Canale, A PARTIAL PTEROSAUR ULNA FROM THE CANDELEROS FORMATION (NEUQUÉN GROUP), LATE CRETACEOUS OF ARGENTINA, Historia Natural 2013

References

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