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.[1]
Description
The type locality of the Candeleros Formation is Candeleros Hill in Neuquén Province, after which the formation was named by Wichmann in 1929.[2] 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.[3]
The Candeleros Formation is almost 300 metres (980 ft) 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.[1][3]
Fossil content
The Candeleros Formation has a very diverse fossil fauna, including:
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).[9]
A partial skeleton consisting of a series of four vertebrae from the lower back, as well as 27 tail vertebrae, divided up into two series from separate parts of the tail. The vertebrae from the middle part of its tail had elongated centra. Elements of the pelvis were also discovered, including two ischia and a pubis bone, along with rib fragments and an incomplete humerus and femur.
The holotype consists of a partial left femur, distal portions of left and right tibiae, right fibula, proximal tarsals of both ankles, a nearly complete right metatarsus, proximal and distal parts of the left metapodials, and left pedal digit III.
Several paratypes consist of fragments of two premaxillae with three pairs of teeth; a piece of upper right jawbone with a tooth; pieces of seventeen vertebrae; fourteen sacral vertebrae; twenty caudal vertebrae; pieces of two shoulder blades; an upper back corner of a right raven's jawbone; the tops of three ulna; the end of a spoke bone; eight hand claws; pieces of a left femur; five upper shafts of pubic bones; five partial femurs; the tops of two left tibias; the underside of a right tibia; a right tibia; pieces of five metatarsals; fifteen phalanges, separately eight-foot claws and pieces of rib.
Paratypes consist of a partial skull without skull roof, basicranium, and squamosals, a partial left lower jaw with damaged teeth, and an incomplete skull with a relatively complete right lower jaw missing some teeth.
A small insectivorous mammal that belongs to the Meridiolestida family.
^Baez, 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.
^Riguetti FJ, Apesteguía S, Pereda-Suberbiola X. A new Cretaceous thyreophoran from Patagonia supports a South American lineage of armored dinosaurs. Sci Rep. 2022 Aug 11;12(1):11621. doi: 10.1038/s41598-022-15535-6. PMID: 35953515; PMCID: PMC9372066.
Wichmann, R (1929). "Los Estratos con Dinosaurios y su techo en el este del Territorio del Neuquén ("The dinosaur-bearing strata and their upper limit in eastern Neuquén Territory")". Dirección General de Geología, Minería e Hidrogeología Publicación. 32: 1–9.