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.^[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]

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 / -43.2; -69.1
Approximate paleocoordinates	40.6°S 30.0°W / -40.6; -30.0
Region	Chubut Province
Country	Argentina
Extent	Cañadón Asfalto Basin
Formation map and location, Shaded vertically

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]

Fossil content

Dinosaurs

Ornithischians

Ornithischians of the Cañadón Calcáreo Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Stegosauria Indet.[6]	Indeterminate			Humerus

Sauropods

Sauropods of the Cañadón Calcáreo Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Brachytrachelopan[3]	B. mesai			Partial articulated skeleton including a nearly complete presacral column	A short-necked dicraeosaurid sauropod
Tehuelchesaurus[3]	T. benitezii			Partial skeleton including skin impressions	A camarasaurid sauropod
Titanosauriformes Indet.[7]	Indeterminate			Humerus, chevron	Originally reported as a brachiosaurid[8]

Theropods

Sauropods of the Cañadón Calcáreo Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Abelisauridae Indet.[9]	Indeterminate			Cervical vertebra, fragmentary skeleton
Pandoravenator[5]	P. fernandezorum			Partial skeleton	A tetanuran theropod

Crocodylomorphs

Crocodylomorphs of the Cañadón Calcáreo Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Almadasuchus[10]	A. fragilis			Partial skull and postcranial skeleton.	A hallopodid crocodylomorph

Fish

Fishes of the Cañadón Calcáreo Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Condorlepis[11]	C. groeberi				A coccolepidid 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

Plant of the Cañadón Calcáreo Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Pararaucaria[12]	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