Cañadón Calcáreo Formation

The Cañadón Calcáreo Formation is an Oxfordian to Kimmeridgian-aged geologic formation, from the Cañadón Asfalto Basin in Chubut Province, Argentina, a rift basin that started forming since the earliest Jurassic.Figari et al., 2015, p.142 It was formerly thought to date into the Cretaceous, but the age has been revised with Uranium–lead dating as likely being solely Late Jurassic in age.

It is a subunit of the Sierra de Olte Group, close to the city Cerro Condor in the Chubut Province of northwestern Patagonia, in southern Argentina. The formation is composed primarily of fluvial sandstones alongside shales and volcanic tuffites

The formation preserves fishes, crocodylomorphs and some dinosaur taxa, as well as conifers.

Geology

The Cañadón Calcáreo Formation is composed mainly of fluvial deposits, which are found close to the Cañadón Asfalto Formation. While originally thought to be part of the Cañadón Asfalto, there is a lack of calcareous rocks, and the geologic faulting and folding are weaker. The Cañadón Calcáreo Formation is overlain by the Chubut Group, the rocks of which lack synsedimentary deformation. The area of the Cañadón Calcáreo also includes lacustrine and palustrine rocks, including shales, pelites, psammites and coarse clastics.

Age The age of the Cañadón Calcáreo Formation was originally presumed to be Late Jurassic, probably Kimmeridgian to Tithonian in age. However, it has also been suggested to span the entire Late Jurassic, beginning in the Oxfordian, although this could also be because of the uncertainty of the youngest age Cañadón Asfalto Formation. A 2009 study of the palynology from a section of the formation revealed an age that was Hauterivian, which suggests that the formation extends from the Late Jurassic into the Early Cretaceous.

Fossil content

Dinosaurs

Ornithischians Ornithischians of the Cañadón Calcáreo Formation Genus Species Location Stratigraphic position Material Notes Images Stegosauria indet. Indeterminate Humerus An indeterminate stegosaur

Sauropods Sauropods of the Cañadón Calcáreo Formation Genus Species Location Stratigraphic position Material Notes ImagesBicharracosaurusB. dionidei Dionide 3 Partial skeletons consist of Cervical vertebrae A macronarian sauropod Brachytrachelopan B. mesai Partial articulated skeleton including a nearly complete presacral column A short-necked dicraeosaurid Diplodocidae Indet. Indeterminate Three dorsal vertebral centra and fragmentary scapula A diplodocid sauropod Tehuelchesaurus T. benitezii Partial skeleton including skin impressions A camarasaurid sauropod Titanosauriformes indet. Indeterminate Humerus, chevron A titanosauriform sauropod; originally reported as a brachiosaurid

Theropods Theropods of the Cañadón Calcáreo Formation Genus Species Location Stratigraphic position Material Notes Images Abelisauridae indet. Indeterminate Cervical vertebra, fragmentary skeleton A abelisaurid theropod Pandoravenator P. fernandezorum Partial skeleton A tetanuran theropod

Other reptiles Miscellaneous reptiles of the Cañadón Calcáreo Formation Genus Species Location Stratigraphic position Material Notes Images Almadasuchus A. fragilis Partial skull and postcranial skeleton A hallopodid crocodylomorph Rhynchocephalia indet. Indeterminate Lower Partial articulated postcranial skeleton A possible neosphenodontian

Fish Fishes of the Cañadón Calcáreo Formation Genus Species Location Stratigraphic position Material Notes Images Condorlepis C. groeberi A coccolepidid fish Luisiella L. feruglioi A luisiellid fish

Crustaceans Crustaceans of the Cañadón Calcáreo Formation Genus Species Location Stratigraphic position Material Notes Images Congestheriella C. rauhuti A clam shrimp Mandelstamia M. spp. A limnocytherid ostracodan Metacypris M. sp. A loxoconchidae ostracodan Pseudestherites P. sp. A clam shrimp Theryosinoecum T. barrancalensis minor A cytheroid ostracodan Timiriasevia T. sp. A limnocytherid ostracodan

Insects Insects of the Cañadón Calcáreo Formation Genus Species Location Stratigraphic position Material Notes Images Chironomidae indet. Indeterminate Neorthophlebidae indet. Indeterminate

Plants Plants of the Cañadón Calcáreo Formation Genus Species Location Stratigraphic position Material Notes Images Pararaucaria P. delfueyoi A pine

See also List of dinosaur-bearing rock formations Lotena Formation, contemporaneous formation of the Neuquén Basin Los Molles Formation, contemporaneous formation of the Neuquén Basin

References

Bibliography

Cañadón Calcáreo Formation

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