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. 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, 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.

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.