Candeleros Formation

The Candeleros Formation (formerly known as the Candeleros Member of the "Río Limay Formation") is a geologic formation that crops out in the Río Negro, Neuquén, and Mendoza provinces of northern Patagonia, 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.

Description
The type locality of the Candeleros Formation is Candeleros Hill in Neuquén Province, after which the formation was named by Wichmann in 1929. 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.

The Candeleros Formation is almost 300 m thick in some sections. Overall, the formation represents a part of the ancient Kokorkom desert with 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.

Fossil content
The Candeleros Formation has a very diverse fossil fauna, including:
 * dipnoan fish (including Ceratodus argentinus)
 * frogs (including Avitabatrachus)
 * Rhynchocephalians (including Priosphenodon avelasi and Tika giacchinoi)
 * primitive snakes (including Najash rionegrina)
 * several turtles (including 2 species of Prochelidella)
 * an azhdarchid pterosaur, the oldest known from South America
 * rebbachisaurid sauropods (Limaysaurus, Nopcsaspondylus and Rayososaurus)
 * titanosaurian sauropods (including Andesaurus and a second unnamed huge titanosaur, though possibly Argentinosaurus)
 * abelisaurid theropods (Ekrixinatosaurus and unnamed form )
 * a carcharodontosaurid (Giganotosaurus)
 * a dromaeosaurid theropod (Buitreraptor gonzalezorum)
 * an alvarezsauroid theropod (Alnashetri)
 * a basal coelurosaur (Bicentenaria)
 * Iguanodonts (including Bonaparteichnium)
 * a notosuchian (Araripesuchus)
 * a basal thyreophoran (Jakapil)
 * cladotherian mammals (including Cronopio dentiacutus)
 * ichnofossils of Sousaichnum monettae, Limayichnus major, Bonaparteichnum tali, Bressaniichnus patagonicus, Deferraiichnum mapuchense, Abelichnus astigarragae and Picunichnus benedettoi

In 2021, fossil material of a giant titanosaur sauropod, distinct from Andesaurus and probably exceeding Patagotitan in size, was described from the formation by Otero et al. (2021).

Amphibians

 * Frogs

Reptiles

 * Rhynchocephalians

Saurischians

 * Sauropods


 * Theropods