The Candeleros 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.Sánchez et al., 2006
Description The type locality of the Candeleros Formation is Candeleros Hill in Neuquén Province, after which the formation was named by Wichmann in 1929.Wichmann, 1929 This formation unconformably overlies the Lohan Cura Formation, and it is fused with the Huincul Formation, also a unit of the Neuquén Group. The sediments of the latter are of lighter greenish and yellow colors and the fused boundary between the Candeleros and Huincul formations is easily recognizable.Leanza et al., 2004
The Candeleros Formation is almost 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. The base of the formations age is correlated to the "Violaceous Sandstones" whose age is estimated at 98.6 ± 2.5 Ma. In 2010, Tunik and colleagues estimated the youngest maximum depositional age of the Candeleros Formation around 98.6 ± 2.5 Ma based on the youngest single grain from the underlying Rayoso Formation, supporting the proposed Cenomanian age. However, Ignacio J. Maniel and colleagues criticized the reliability of this dating method in 2026, since potential contamination or loss of lead isotopes can result in a dating over 10 million years younger than the actual maximum depositional age; the authors suggested that the Candeleros Formation is most certainly dated to the early Albian age, approximately 111.4 ± 1.1 Ma, using zircon U-Pb dating based on the youngest statistical population and maximum likelihood age of four samples (one tuff and three basal sandstones) from the Candeleros Formation and a single tuff sample from the overlying Huincul Formation, the latter of which was also dated to the Albian at approximately 106.2 ± 1.0 Ma.
Fossil content
The Candeleros Formation has a very diverse fossil fauna, including fish, frogs, mammals, rhynchocephalians, snakes, turtles, notosuchians, pterosaurs, and abundant dinosaurs including rebbachisaurid and titanosaurian sauropods and diverse theropods, and the enigmatic armored Jakapil.
Ichnofossils found in the formation include those assigned to Sousaichnum monettae, Limayichnus major, Bressaniichnus patagonicus, Deferraiichnum mapuchense, and Picunichnus benedettoi.Leonardi, 1994, p. 79
Fish Taxa Species Locality Member Material Notes Images Ceratodus C. argentinusUpper A lungfish
Amphibians Taxa Species Locality Member Material Notes Images AvitabatrachusBaez, Ana & Trueb, Linda & Calvo, Jorge. (2000). The earliest known pipoid frog from South America: A new genus from the Middle Cretaceous of Argentina. Journal of Vertebrate Paleontology. 20. 490-500. 10.1671/0272-4634(2000)020%5B0490:TEKPFF%5D2.0.CO;2. A. uliana El GiganteLower Fragmentary skull and postcranial skeleton A pipimorph frog
Dinosaurs Ornithischians Taxa Species Locality Member Material Notes Images Jakapil J. kaniukura Cerro Policía Upper A partial skeleton including several osteoderms and a complete lower jaw Possibly a basal thyreophoran
Sauropods Taxa Species Locality Member Material Notes Images Andesaurus A. delgadoiNear Villa El ChoconLower A partial skeleton A basal titanosaurian sauropod Campananeyen C. fragilissimus Barda Atravesada de Las CampanasLower A fragmentary skeleton A rebbachisaurid sauropod Limaysaurus L. tessoneiUpper A rebbachisaurid sauropod Nopcsaspondylus N. alarconensisleft bank of Limay RiverA single lost vertebra A dubious rebbachisaurid sauropod Rayososaurus R. agrioensis Agrio del MedioUpper A left scapula, an almost complete right scapular blade, and the distal three-quarters of a left femur. A rebbachisaurid sauropod Titanosauria IndeterminateUpper A giant titanosaurian sauropod, probably exceeding Patagotitan in size
Theropods Taxa Species Locality Member Material Notes ImagesAbelichnus A. astigerrae A footprint Alnashetri A. cerropoliciensis La BuitreraUpper Several skeletal remains, from complete to incomplete An alvarezsauroid Bicentenaria B. argentina Ezequiel Ramos Mexia ReservoirUpper Much of a skeleton A coelurosaur Buitreraptor B. gonzalezorum La BuitreraUpper Several partial skeletons A dromaeosaurid Ekrixinatosaurus E. novasi Bajo del Añelo Upper A partial skeleton An abelisaurid Giganotosaurus G. carolinii Los Candeleros and Villa El Chocón Upper/Lower A partial skull and a disarticulated postcranial skeleton, a dentary, and teeth. Found in the upper part of the formation. A carcharodontosaurid
Pterosaurs Taxa Species Locality Member Material Notes Images Azhdarchidae Indeterminate Ezequiel Ramos Mexía Reservoir Upper A partial cervical vertebra An azhdarchid
Other reptiles Taxa Species Locality Member Material Notes Images Antusuchus A. rionegrinus La Buitrera A holotype specimen, MPCA PV 1294, consists of an articulated skull and lower jaw and the second individual, MPCA PV 1295, is represented by the middle to posterior parts of a skull A peirosaurid notosuchianAraripesuchusA. buitreraensis La Buitrera, Cerro Policía and El Pueblito.Upper Multiple skull specimens. A small notosuchian crocodyliform A manzanensisUpper A partial skull and lower jawA. patagonicus El Chocón.Lower An anterior half of the skull with an articulated mandible, lacking the most anterior portion of the rostrum and also preserves part of the postcranium Najash N. rionegrinaUpper A basal snake Priosphenodon P. avelasi Upper An eilenodontine rhynchocephalian Tika T. giacchinoiUpper A sphenodontine rhynchocephalian
Mammals Taxa Species Locality Member Material Notes Images Cronopio C. dentiacutus La Buitrera Upper Skull bones and teeth A small meridiolestidan mammal
Turtles Taxa Species Locality Member Material Notes ImagesProchelidellaP. buitreraensisUpperA small chelid turtleElkanemysE. pritchardiUpperA bothremydid turtle
See also List of fossil sites Bajo Barreal Formation, contemporaneous fossiliferous formation of the San Jorge Basin Cerro Fortaleza Formation, contemporaneous fossiliferous formation of the Austral Basin Alcântara Formation, contemporaneous fossiliferous formation of the São Luís-Grajaú Basin, Brazil List of dinosaur bearing rock formations
References
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