Candeleros Formation
Encyclopedia
The Candeleros Formation (formerly known as the Candeleros Member of the "Rio Limay Formation") is a geologic formation
that outcrop
s in Río Negro
, Neuquén
, and Mendoza
provinces of 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.
The type locality of the Candeleros Formation is Candeleros Hill in Neuquén province. 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 meters thick in some sections. Overall, the formation represents an ancient braided river
system, made up mostly of sandstone
s and conglomerate
s. There are also isolated sections that represent eolian (wind-blown) deposition, as well as siltstone
s deposited under swamp
conditions. Paleosol
s (soil deposits) are common in some sections as well.
Period: Late Cretaceous
Faunal stage
: early Cenomanian
Absolute Age
: ~100 to ~97 mya
The Candeleros Formation has a very diverse fossil fauna
, including:
There are also several trackway
sites and eggshell
s known from the Candeleros Formation, including theropods, sauropods, ornithopod
s, and pterosaur
s.
One of the most productive fossil
localities in the Candeleros is known as La Buitrera and is now well-known for producing many small tetrapod
skeletons with three-dimensional
preservation, although larger fossils, such as dinosaur
s, are rare. Much larger dinosaur fossils have been recovered from other sites in the formation, however, including one of the largest carnivore
s known, Giganotosaurus
. La Buitrera means, roughly, "the vulture
-roost"; the genus Buitreraptor
, a small bird-like dinosaur that must have been a predator of small vertebrates and possibly a scavenger was named after this.
Geologic formation
A formation or geological formation is the fundamental unit of lithostratigraphy. A formation consists of a certain number of rock strata that have a comparable lithology, facies or other similar properties...
that outcrop
Outcrop
An outcrop is a visible exposure of bedrock or ancient superficial deposits on the surface of the Earth. -Features:Outcrops do not cover the majority of the Earth's land surface because in most places the bedrock or superficial deposits are covered by a mantle of soil and vegetation and cannot be...
s in Río Negro
Río Negro Province
Río Negro is a province of Argentina, located at the northern edge of Patagonia. Neighboring provinces are from the south clockwise Chubut, Neuquén, Mendoza, La Pampa and Buenos Aires. To the east lies the Atlantic Ocean.Its capital is Viedma...
, Neuquén
Neuquén Province
Neuquén is a province of Argentina, located in the west of the country, at the northern end of Patagonia. It borders Mendoza Province to the north, Rio Negro Province to the southeast, and Chile to the west...
, and Mendoza
Mendoza Province
The Province of Mendoza is a province of Argentina, located in the western central part of the country in the Cuyo region. It borders to the north with San Juan, the south with La Pampa and Neuquén, the east with San Luis, and to the west with the republic of Chile; the international limit is...
provinces of Argentina
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...
. It is the oldest formation in the Neuquén Group
Neuquén Group
The Neuquén Group is a group of geologic formations found in Argentina. Rocks in the Neuquén Group fall within the Cenomanian to early Campanian stages of the Late Cretaceous Period, about 100 million to 80 million years in age...
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.
The type locality of the Candeleros Formation is Candeleros Hill in Neuquén province. This formation unconformably
Unconformity
An unconformity is a buried erosion surface separating two rock masses or strata of different ages, indicating that sediment deposition was not continuous. In general, the older layer was exposed to erosion for an interval of time before deposition of the younger, but the term is used to describe...
overlies the Lohan Cura Formation
Lohan Cura Formation
The Lohan Cura Formation is a geologic formation with outcrops in the Argentine provinces of Río Negro, Neuquén, and Mendoza. It is the second oldest Cretaceous terrestrial formation in the Neuquén Basin....
, and it is in turn overlain by the Huincul Formation
Huincul Formation
The Huincul Formation is a geologic formation that outcrops in Río Negro and Neuquén provinces of Argentina. It is the second formation in the Río Limay Subgroup, the oldest subgroup within the Neuquén Group...
, 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 meters thick in some sections. Overall, the formation represents an ancient braided river
Braided river
A braided river is one of a number of channel types and has a channel that consists of a network of small channels separated by small and often temporary islands called braid bars or, in British usage, aits or eyots. Braided streams occur in rivers with high slope and/or large sediment load...
system, made up mostly of sandstone
Sandstone
Sandstone is a sedimentary rock composed mainly of sand-sized minerals or rock grains.Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust. Like sand, sandstone may be any colour, but the most common colours are tan, brown, yellow,...
s and conglomerate
Conglomerate (geology)
A conglomerate is a rock consisting of individual clasts within a finer-grained matrix that have become cemented together. Conglomerates are sedimentary rocks consisting of rounded fragments and are thus differentiated from breccias, which consist of angular clasts...
s. There are also isolated sections that represent eolian (wind-blown) deposition, as well as siltstone
Siltstone
Siltstone is a sedimentary rock which has a grain size in the silt range, finer than sandstone and coarser than claystones.- Description :As its name implies, it is primarily composed of silt sized particles, defined as grains 1/16 - 1/256 mm or 4 to 8 on the Krumbein phi scale...
s deposited under swamp
Swamp
A swamp is a wetland with some flooding of large areas of land by shallow bodies of water. A swamp generally has a large number of hammocks, or dry-land protrusions, covered by aquatic vegetation, or vegetation that tolerates periodical inundation. The two main types of swamp are "true" or swamp...
conditions. Paleosol
Paleosol
In the geosciences, paleosol can have two meanings. The first meaning, common in geology and paleontology, refers to a former soil preserved by burial underneath either sediments or volcanic deposits , which in the case of older deposits have lithified into rock...
s (soil deposits) are common in some sections as well.
Age
Era: MesozoicMesozoic
The Mesozoic era is an interval of geological time from about 250 million years ago to about 65 million years ago. It is often referred to as the age of reptiles because reptiles, namely dinosaurs, were the dominant terrestrial and marine vertebrates of the time...
Period: Late Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
Faunal stage
Faunal stage
In chronostratigraphy, a stage is a succession of rock strata laid down in a single age on the geologic timescale, which usually represents millions of years of deposition. A given stage of rock and the corresponding age of time will by convention have the same name, and the same boundaries.Rock...
: early Cenomanian
Cenomanian
The Cenomanian is, in the ICS' geological timescale the oldest or earliest age of the Late Cretaceous epoch or the lowest stage of the Upper Cretaceous series. An age is a unit of geochronology: it is a unit of time; the stage is a unit in the stratigraphic column deposited during the corresponding...
Absolute Age
Geochronology
Geochronology is the science of determining the age of rocks, fossils, and sediments, within a certain degree of uncertainty inherent to the method used. A variety of dating methods are used by geologists to achieve this, and schemes of classification and terminology have been proposed...
: ~100 to ~97 mya
Vertebrate paleofauna
Fauna
Fauna or faunæ is all of the animal life of any particular region or time. The corresponding term for plants is flora.Zoologists and paleontologists use fauna to refer to a typical collection of animals found in a specific time or place, e.g. the "Sonoran Desert fauna" or the "Burgess shale fauna"...
, including:
- fishFishFish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
- frogFrogFrogs are amphibians in the order Anura , formerly referred to as Salientia . Most frogs are characterized by a short body, webbed digits , protruding eyes and the absence of a tail...
s - sphenodontiaSphenodontiaSphenodontia is an order of lizard-like reptiles that includes only one living genus, the tuatara , and only two living species...
ns - primitive snakeSnakeSnakes are elongate, legless, carnivorous reptiles of the suborder Serpentes that can be distinguished from legless lizards by their lack of eyelids and external ears. Like all squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales...
s (including Najash) - several turtleTurtleTurtles are reptiles of the order Testudines , characterised by a special bony or cartilaginous shell developed from their ribs that acts as a shield...
s (including 2 species of Prochelidella) - abundant crocodiliaCrocodiliaCrocodilia is an order of large reptiles that appeared about 84 million years ago in the late Cretaceous Period . They are the closest living relatives of birds, as the two groups are the only known survivors of the Archosauria...
ns (including a species of AraripesuchusAraripesuchusAraripesuchus is a genus of extinct crocodyliform whose species existed during the Cretaceous period of the late Mesozoic era some 125 to 65 million years ago. They are generally considered to be notosuchians , characterized by their varied teeth types and distinct skull elements...
) - rebbachisaurid sauropods (LimaysaurusLimaysaurusLimaysaurus is a herbivorous rebbachisaurid sauropod dinosaur from the Lower Cretaceous of northwestern Patagonia.Limaysaurus includes a single type species, Limaysaurus tessonei, which was originally referred to the genus Rebbachisaurus as Rebbachisaurus tessonei by Jorge Calvo and Leonardo...
and NopcsaspondylusNopcsaspondylusNopcsaspondylus is a genus of rebbachisaurid sauropod dinosaur from the Coniacian-age Candeleros Formation of Neuquén, Argentina. It is based on a now-lost back vertebra described by Nopcsa in 1902 but not named at the time...
) - titanosaurian sauropods (including AndesaurusAndesaurusAndesaurus is a genus of basal titanosaurian sauropod dinosaur which existed during the middle of the Cretaceous Period in South America. Like most sauropods, it would have had a small head on the end of a long neck and an equally long tail...
) - a carcharodontosaurid theropod (GiganotosaurusGiganotosaurusGiganotosaurus is a genus of carcharodontosaurid dinosaur that lived around 97 million years ago during the early Cenomanian stage of the Late Cretaceous Period. It included some of the largest known terrestrial carnivores, slightly larger than the largest Tyrannosaurus, but smaller than the...
) - a dromaeosaurid theropod (BuitreraptorBuitreraptorBuitreraptor is a predatory dromaeosaurid theropod dinosaur from the Cretaceous of Argentina.Buitreraptor was described in 2005. The type species is Buitreraptor gonzalezorum...
) - cladotheriaCladotheriaCladotheria is a group of mammals that is defined as including the ancestor of Dryolestoidea, Peramuridae and Zatheria .-External links:* * -Further reading:Zofia Kielan-Jaworowska, Richard L...
n mammalMammalMammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
s
Pterosaurs
Pteraichnus found in Late Jurassic Strata of the Rio Limay group.| Pterosaur Pterosaur Pterosaurs were flying reptiles of the clade or order Pterosauria. They existed from the late Triassic to the end of the Cretaceous Period . Pterosaurs are the earliest vertebrates known to have evolved powered flight... s of the Rio Limay Formation |
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Ichnogenus:
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There are also several trackway
Fossil trackway
A fossil trackway is a type of trace fossil, a trackway made by an organism. Many fossil trackways were made by dinosaurs, early tetrapods, and other quadrupeds and bipeds on land...
sites and eggshell
Eggshell
An eggshell is the outer covering of a hard-shelled egg and of some forms of eggs with soft outer coats.- Insect eggs :Insects and other arthropods lay a variety of styles and shapes of eggs. Some have gelatinous or skin-like coverings, others have hard eggshells. Softer shells are mostly protein....
s known from the Candeleros Formation, including theropods, sauropods, ornithopod
Ornithopod
Ornithopods or members of the clade Ornithopoda are a group of ornithischian dinosaurs that started out as small, bipedal running grazers, and grew in size and numbers until they became one of the most successful groups of herbivores in the Cretaceous world, and dominated the North American...
s, and pterosaur
Pterosaur
Pterosaurs were flying reptiles of the clade or order Pterosauria. They existed from the late Triassic to the end of the Cretaceous Period . Pterosaurs are the earliest vertebrates known to have evolved powered flight...
s.
One of the most productive fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
localities in the Candeleros is known as La Buitrera and is now well-known for producing many small tetrapod
Tetrapod
Tetrapods are vertebrate animals having four limbs. Amphibians, reptiles, birds and mammals are all tetrapods; even snakes and other limbless reptiles and amphibians are tetrapods by descent. The earliest tetrapods evolved from the lobe-finned fishes in the Devonian...
skeletons with three-dimensional
Three-dimensional space
Three-dimensional space is a geometric 3-parameters model of the physical universe in which we live. These three dimensions are commonly called length, width, and depth , although any three directions can be chosen, provided that they do not lie in the same plane.In physics and mathematics, a...
preservation, although larger fossils, such as dinosaur
Dinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...
s, are rare. Much larger dinosaur fossils have been recovered from other sites in the formation, however, including one of the largest carnivore
Carnivore
A carnivore meaning 'meat eater' is an organism that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of animal tissue, whether through predation or scavenging...
s known, Giganotosaurus
Giganotosaurus
Giganotosaurus is a genus of carcharodontosaurid dinosaur that lived around 97 million years ago during the early Cenomanian stage of the Late Cretaceous Period. It included some of the largest known terrestrial carnivores, slightly larger than the largest Tyrannosaurus, but smaller than the...
. La Buitrera means, roughly, "the vulture
New World vulture
The New World Vulture or Condor family Cathartidae contains seven species in fivegenera, all but one of which are monotypic. It includes five vultures and two condors found in warm and temperate areas of the Americas....
-roost"; the genus Buitreraptor
Buitreraptor
Buitreraptor is a predatory dromaeosaurid theropod dinosaur from the Cretaceous of Argentina.Buitreraptor was described in 2005. The type species is Buitreraptor gonzalezorum...
, a small bird-like dinosaur that must have been a predator of small vertebrates and possibly a scavenger was named after this.