Cañadón Calcáreo Formation

Cañadón Calcáreo Formation
Stratigraphic range: Oxfordian-Tithonian
~160–150 Ma

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Cañadón Calcáreo Formation; Stratigraphic range: Oxfordian-Tithonian; ~160–150 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Type	Geological formation
Unit of	Sierra de Olte Group
Underlies	Los Adobes Formation
Overlies	Cañadón Asfalto Formation
Lithology
Primary	Sandstone
Other	Shale, tuffite
Location
Location	Patagonia
Coordinates	43.2°S 69.1°W
Approximate paleocoordinates	40.6°S 30.0°W
Region	Chubut Province
Country	Argentina
Extent	Cañadón Asfalto Basin
	; Formation map and location, Shaded vertically

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.[1] 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.[2][3][4]

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[3]

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

Geology

The Cañadón Calcáreo Formation is composed mainly of fluvial deposits, that 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 is 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.[4]

Age

The age of the Cañadón Calcáreo Formation was originally presumed to be Late Jurassic, probably Kimmeridgian to Tithonian in age.[3] 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.[3][5] 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.[4]

Dinosaurs

An unnamed brachiosaurid sauropod is also known from the Cañadón Calcáreo Formation. It is known from a single humerus.[6]

A stegosaurian is too known, also from a humerus.[7]

Dinosaurs reported from the Cañadón Calcáreo Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Brachytrachelopan[3]	B. messai[3]	Patagonia	Cerro Condor	Partial articulated skeleton including a nearly complete presacral column.[3]	A dicraeosaurid sauropod closer to Dicraeosaurus than Amargasaurus.[3]
Pandoravenator[5]	P. fernandezorum[5]	Central Patagonia	Chubut[5]	Partial skeleton.[5]	Basal tetanuran close to the base of Averostra.[5]
Tehuelchesaurus[3]	T. benitezii[3]	Patagonia	Cerro Condor[3]	Partial skeleton including skin impressions.[3]	Sauropod proposed to be related to Omeisaurus, but more likely a camarasauromorph.[3]

Crocodylomorphs

Crocodylomorphs of the Cañadón Calcáreo Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Almadasuchus[8]	A. figarii[8]	Patagonia	Cerro Condor[8]	Partial skull and postcranial skeleton.[8]	A non-crocodyliform crocodylomorph. The type species is Almadasuchus figarii. Sediments alternatively referred by different authors to the Cañadón Calcáreo Formation or to the Puesto Almada Member of the Cañadón Asfalto Formation.[8]

Fishes

Fishes of the Cañadón Calcáreo Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Condorlepis[9]	C. groeberi[9]	Patagonia	Cerro Condor[9]	Almost complete skeleton.[9]	A coccolepidid, a member of Chondrostei; a new genus for "Oligopleurus" groeberi Bordas (1943).[9]

Plants

Plants of the Cañadón Calcáreo Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Pararaucaria[10]	P. delfueyoi[10]	Patagonia	Chubut[10]	Conifer seed cones.[10]	A member of Coniferales belonging to the family Cheirolepidiaceae, a species of Pararaucaria.[10]

References

Figari et al., 2015, p.142
Cúneo, Rubén; Ramezani, Jahandar; Scasso, Roberto; Pol, Diego; Escapa, Ignacio; Zavattieri, Ana M.; Bowring, Samuel A. (November 2013). "High-precision U–Pb geochronology and a new chronostratigraphy for the Cañadón Asfalto Basin, Chubut, central Patagonia: Implications for terrestrial faunal and floral evolution in Jurassic". Gondwana Research. 24 (3–4): 1267–1275. doi:10.1016/j.gr.2013.01.010. ISSN 1342-937X.
Novas, F.J. (2009). The Age of Dinosaurs in South America. Indiana University Press. pp. 1–458. ISBN 978-0253352897.
Volkheimer, W.; Gallego, O.F.; Cabaleri, N.G.; Narváez, P.L.; Silva Nieto, D.G.; Páez, M.A. (2009). "Stratigraphy, palynology, and conchostracans of a Lower Cretaceous sequence at the Cañadón Calcáreo locality, Extra-Andean central Patagonia: age and palaeoenvironmental significance". Cretaceous Research. 30 (2009): 270–282. doi:10.1016/j.cretres.2008.07.010.
Rauhut, O.; Pol, D. (2017). "A theropod dinosaur from the Late Jurassic Cañadón Calcáreo Formation of Central Patagonia, and the evolution of the theropod tarsus". Ameghiniana. 54 (5): 539–566. doi:10.5710/AMGH.12.10.2017.3105. S2CID 134945437.
Rauhut, O.W. (2006). "A brachiosaurid sauropod from the late Jurassic Cañadón Calcáreo Formation of Chubut, Argentina". Fossil Record. 9 (2): 226–237. doi:10.1002/mmng.200600010.
Rauhut, O. W. M.; Carballido, J. L.; Pol, D. (2021). "First Osteological Record of a Stegosaur (Dinosauria, Ornithischia) from the Upper Jurassic of South America". Journal of Vertebrate Paleontology. in press: e1862133. doi:10.1080/02724634.2020.1862133.
Diego Pol; Oliver W. M. Rauhut; Agustina Lecuona; Juan M. Leardi; Xing Xu; James M. Clark (2013). "A new fossil from the Jurassic of Patagonia reveals the early basicranial evolution and the origins of Crocodyliformes". Biological Reviews. 88 (4): 862–872. doi:10.1111/brv.12030. PMID 23445256. S2CID 14648168.
Adriana López-Arbarello; Emilia Sferco; Oliver W.M. Rauhut (2013). "A new genus of coccolepidid fishes (Actinopterygii, Chondrostei) from the continental Jurassic of Patagonia". Palaeontologia Electronica. 16 (1): 7A.
Escapa, I.H.; Cúneo, N.R.; Rothwell, G.; Stockey, R.A. (2013). "Pararaucaria delfueyoi sp. nov. from the Late Jurassic Cañadón Calcáreo Formation, Chubut, Argentina: Insights into the Evolution of the Cheirolepidiaceae" (PDF). International Journal of Plant Sciences. 174 (3): 458–470. doi:10.1086/668612. hdl:11336/1531.

Bibliography

Figari, Eduardo G.; Roberto A. Scasso; Rubén N. Cúneo, and Ignacio Escapa. 2015. Estratigrafía y evolución geológica de la Cuenca de Cañadón Asfalto, Provincia del Chubut, Argentina. Latin American Journal of Sedimentology and Basin Analysis 22. 135–169. Accessed 2018-09-10.