The Candeleros Formation (formerly known as the Candeleros Member of the "Río Limay Formation") is a

geologic formation A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics ( lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exp ...

that crops out in the Río Negro,

Neuquén Neuquén (; arn, Nehuenken) is the capital city of the Argentine province of Neuquén and of the Confluencia Department, located in the east of the province. It occupies a strip of land west of the confluence of the Limay and Neuquén rive ...

, and Mendoza provinces of northern

Patagonia Patagonia () refers to a geographical region that encompasses the southern end of South America, governed by Argentina and Chile. The region comprises the southern section of the Andes Mountains with lakes, fjords, temperate rainforests, and ...

Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, t ...

. 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 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.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 A braided river, or braided channel, consists of a network of river channels separated by small, often temporary, islands called braid bars or, in English usage, '' aits'' or ''eyots''. Braided streams tend to occur in rivers with high sedime ...

system, made up mostly of

sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates ...

s and

conglomerate Conglomerate or conglomeration may refer to: * Conglomerate (company) * Conglomerate (geology) * Conglomerate (mathematics) In popular culture: * The Conglomerate (American group), a production crew and musical group founded by Busta Rhymes ** Co ...

s. There are also isolated sections that represent eolian (wind-blown) deposition, as well as

siltstone Siltstone, also known as aleurolite, is a clastic sedimentary rock that is composed mostly of silt. It is a form of mudrock with a low clay mineral content, which can be distinguished from shale by its lack of fissility.Blatt ''et al.'' 1980, ...

s 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 Fauna is all of the animal life present in a particular region or time. The corresponding term for plants is ''flora'', and for fungi, it is '' funga''. Flora, fauna, funga and other forms of life are collectively referred to as ''biota''. Zoo ...

, including: * dipnoan fish (including '' Ceratodus argentinus'') *

frog A frog is any member of a diverse and largely carnivorous group of short-bodied, tailless amphibians composing the order Anura (ανοὐρά, literally ''without tail'' in Ancient Greek). The oldest fossil "proto-frog" '' Triadobatrachus'' is ...

s * Rhynchocephalians (including '' Priosphenodon avelasi'' and ''

Tika giacchinoi ''Tika'' is an extinct genus of sphenodontian from the Late Cretaceous Candeleros Formation of Argentina. The type species is ''Tika giacchinoi''. It is considered to be closely related to the tuatara, (''Sphenodon punctatus''), and a member of t ...

'') * primitive

snake Snakes are elongated, limbless, carnivorous reptiles of the suborder Serpentes . Like all other squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales. Many species of snakes have skulls with several more j ...

s (including '' Najash rionegrina'') * several

turtle Turtles are an order of reptiles known as Testudines, characterized by a special shell developed mainly from their ribs. Modern turtles are divided into two major groups, the Pleurodira (side necked turtles) and Cryptodira (hidden necked ...

s (including 2 species of ''

Prochelidella ''Prochelidella'' is an extinct genus of Early to Late Cretaceous chelid turtles from the Bajo Barreal, Candeleros, Cerro Barcino and Portezuelo Formations of the Cañadón Asfalto, Golfo San Jorge and Neuquén Basins in Patagonia, Argentin ...

'') *

rebbachisaurid Rebbachisauridae is a family of sauropod dinosaurs known from fragmentary fossil remains from the Cretaceous of South America, Africa, North America, Europe and possibly Central Asia. Taxonomy In 1990 sauropod specialist Jack McIntosh included t ...

sauropod Sauropoda (), whose members are known as sauropods (; from '' sauro-'' + '' -pod'', 'lizard-footed'), is a clade of saurischian ('lizard-hipped') dinosaurs. Sauropods had very long necks, long tails, small heads (relative to the rest of their ...

s ('' Limaysaurus'', '' Nopcsaspondylus'' and '' Rayososaurus'') * titanosaurian sauropods (including '' Andesaurus'' and a second unnamed huge titanosaur'') * abelisaurid

theropod Theropoda (; ), whose members are known as theropods, is a dinosaur clade that is characterized by hollow bones and three toes and claws on each limb. Theropods are generally classed as a group of saurischian dinosaurs. They were ancestrally ...

s ('' Ekrixinatosaurus'' and unnamed formCanale et al., 2016) * the carcharodontosaurid (''

Giganotosaurus ''Giganotosaurus'' ( ) is a genus of theropod dinosaur that lived in what is now Argentina, during the early Cenomanian age of the Late Cretaceous period, approximately 99.6 to 95 million years ago. The holotype specimen was discovered in the ...

'') * a

dromaeosaurid Dromaeosauridae () is a family of feathered theropod dinosaurs. They were generally small to medium-sized feathered carnivores that flourished in the Cretaceous Period. The name Dromaeosauridae means 'running lizards', from Greek ('), meaning ...

theropod ('' Buitreraptor gonzalezorum'') * an alvarezsauroid theropod ('' Alnashetri'') * a basal coelurosaurian (''

Bicentenaria ''Bicentenaria'' (meaning "two hundred year anniversary"; named after the 200th anniversary of the 1810 May Revolution in Argentina) is a genus of carnivorous coelurosaurian theropods which lived during the early Late Cretaceous (about 90 mi ...

'') * Iguanodonts * a

basal Basal or basilar is a term meaning ''base'', ''bottom'', or ''minimum''. Science * Basal (anatomy), an anatomical term of location for features associated with the base of an organism or structure * Basal (medicine), a minimal level that is nec ...

thyreophoran Thyreophora ("shield bearers", often known simply as "armored dinosaurs") is a group of armored ornithischian dinosaurs that lived from the Early Jurassic until the end of the Cretaceous. Thyreophorans are characterized by the presence of body ...

('' Jakapil'') * cladotherian mammals (including ''

Cronopio dentiacutus ''Cronopio'' is an extinct genus of small insectivorous mammal known from the early Late Cretaceous of the Río Negro region in Argentina. Its only species is ''Cronopio dentiacutus''.ichnofossils of '' Sousaichnum monettae'', '' Limayichnus major'', '' Bonaparteichnum tali'', '' Bressaniichnus patagonicus'', '' Deferraiichnum mapuchense'', '' Abelichnus astigarragae'' and '' Picunichnus benedettoi''Leonardi, 1994, p.79 In

2021 File:2021 collage V2.png, From top left, clockwise: the James Webb Space Telescope was launched in 2021; Protesters in Yangon, Myanmar following the coup d'état; A civil demonstration against the October 2021 coup in Sudan; Crowd shortly after t ...

, fossil material of a giant

titanosaur Titanosaurs (or titanosaurians; members of the group Titanosauria) were a diverse group of sauropod dinosaurs, including genera from all seven continents. The titanosaurs were the last surviving group of long-necked sauropods, with taxa still th ...

sauropod, distinct from '' Andesaurus'' and probably exceeding '' Patagotitan'' in size, was described from the formation by Otero ''et al.'' (2021).Otero et al., 2021

References

Bibliography

* * * * * * {{cite LSA , last=Wichmann , first=R , year=1929 , title=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") , journal=Dirección General de Geología, Minería e Hidrogeología Publicación , volume=32 , pages=1–9 Geologic formations of Argentina Cretaceous Argentina Sandstone formations Aeolian deposits Fluvial deposits Paludal deposits

Description

Fossil content

See also

References

Bibliography