The Bajada Colorada 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 ...

of the southern Neuquén Province in the

Neuquén Basin Neuquén Basin ( es, Cuenca Neuquina) is a sedimentary basin covering most of Neuquén Province in Argentina. The basin originated in the Jurassic and developed through alternating continental and marine conditions well into the Tertiary. The ba ...

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 ...

. The formation belongs to the

Mendoza Group Mendoza may refer to: Places Argentina * Greater Mendoza, the name given to the large urban conurbation around the city of Mendoza * Mendoza, Argentina, the capital of the province of Mendoza * Mendoza Department, subdivision of the Mendoza Provi ...

and is

Late Berriasian In the geological timescale, the Berriasian is an age/ stage of the Early/Lower Cretaceous. It is the oldest subdivision in the entire Cretaceous. It has been taken to span the time between 145.0 ± 4.0 Ma and 139.8 ± 3.0 Ma (million years ago ...

to Early Valanginian in age. The formation is renowned for preserving fossil remains of '' Bajadasaurus pronuspinax'', a genus of

dicraeosaurid Dicraeosauridae is a family of diplodocoid sauropods who are the sister group to Diplodocidae. Dicraeosaurids are a part of the Flagellicaudata, along with Diplodocidae. Dicraeosauridae includes genera such as '' Amargasaurus'', '' Suuwassea'', ...

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...

s named after the formation.

Description

The Bajada Colorada Formation, first defined by Roll in 1939, pertains to the

.Moyano Bohórquez, 2004 It overlies the Quintuco and Picún Leufú Formations and is overlain by the

Agrio Formation The Agrio Formation is an Early Cretaceous geologic formation that is up to thick and is located in the southern Mendoza Province and northern-central Neuquén Province, in the Neuquén Basin of northwestern Patagonia, Argentina.Weaver, C. E. ( ...

. The contact with the Agrio Formation is

discordant The adjective discordant ('conflicting, disagreeing, at variance') may describe: Earth science * Discordant rock, one that cuts across the existing bedding: as in one of the main types of igneous intrusion, or as in the sedimentary clastic dike ...

and the unconformity has been dated to 134 Ma.Leanza, 2005, p.151 The formation is laterally equivalent with the

Mulichinco Formation The Mulichinco Formation is a geological formation in Argentina. It is Valanginian in age and is predominantly terrestrial, being deposited at a time of marine regression in the Neuquén Basin, and predominantly consists of siliciclastic rocks. ...

.Howell et al., 2005, p.4 The formation comprises red and greenish-brown, fine to coarse grained conglomerates and thick-bedded

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 with well developed bands of light brown

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 and reddish, pinkish grey and purple-reddish

claystone Mudrocks are a class of fine-grained siliciclastic sedimentary rocks. The varying types of mudrocks include siltstone, claystone, mudstone, slate, and shale. Most of the particles of which the stone is composed are less than and are too sm ...

s.Leanza et al., 2011, p.120 The formation was deposited in a

fluvial In geography and geology, fluvial processes are associated with rivers and streams and the deposits and landforms created by them. When the stream or rivers are associated with glaciers, ice sheets, or ice caps, the term glaciofluvial or fluv ...

environment Environment most often refers to: __NOTOC__ * Natural environment, all living and non-living things occurring naturally * Biophysical environment, the physical and biological factors along with their chemical interactions that affect an organism or ...

, and the paleoenviroment resembled a

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 with well-preserved channels and

paleosol In the geosciences, paleosol (''palaeosol'' in Great Britain and Australia) is an ancient soil that formed in the past. The precise definition of the term in geology and paleontology is slightly different from its use in soil science. In geol ...

s.Gallina et al., 2014, p.2 X-ray diffraction studies of sediments belonging to the Bajada Colorada Formation have revealed the presence of

smectite A smectite (from ancient Greek ''σμηκτός'' smektos 'lubricated'; ''σμηκτρίς'' smektris 'walker's earth', 'fuller's earth'; rubbing earth; earth that has the property of cleaning) is a mineral mixtures of various swelling sheet sil ...

chlorite The chlorite ion, or chlorine dioxide anion, is the halite with the chemical formula of . A chlorite (compound) is a compound that contains this group, with chlorine in the oxidation state of +3. Chlorites are also known as salts of chl ...

illite Illite is a group of closely related non-expanding clay minerals. Illite is a secondary mineral precipitate, and an example of a phyllosilicate, or layered alumino-silicate. Its structure is a 2:1 sandwich of silica tetrahedron (T) – alumina ...

and

kaolinite Kaolinite ( ) is a clay mineral, with the chemical composition Al2 Si2 O5( OH)4. It is an important industrial mineral. It is a layered silicate mineral, with one tetrahedral sheet of silica () linked through oxygen atoms to one octahed ...

Fossil content

The formation has provided fossils of:Bajada Colorada locality
at

Fossilworks Fossilworks is a portal which provides query, download, and analysis tools to facilitate access to the Paleobiology Database, a large relational database assembled by hundreds of paleontologists from around the world. History Fossilworks was cre ...

.org * '' Bajadasaurus pronuspinax'' * ''

Leinkupal laticauda ''Leinkupal'' is a genus of diplodocine sauropod known from the Early Cretaceous (Late Berriasian to Early Valanginian stage) of the Bajada Colorada Formation, southeastern Neuquén Basin in the Neuquén Province of Argentina. It contains a ...

'' *'' Ninjatitan zapatai'' *

Abelisauridae Abelisauridae (meaning "Abel's lizards") is a family (or clade) of ceratosaurian theropod dinosaurs. Abelisaurids thrived during the Cretaceous period, on the ancient southern supercontinent of Gondwana, and today their fossil remains are fou ...

indet. *

Abelisauroidea Abelisauroidea is typically regarded as a Cretaceous group, though the earliest abelisauridae remains are known from the Middle Jurassic of Argentina (classified as the species Eoabelisaurus mefi) and possibly Madagascar (fragmentary remains of ...

indet. *

Ankylosauria Ankylosauria is a group of herbivorous dinosaurs of the order Ornithischia. It includes the great majority of dinosaurs with armor in the form of bony osteoderms, similar to turtles. Ankylosaurs were bulky quadrupeds, with short, powerful limbs ...

indet. *

Deinonychosauria Deinonychosauria is a clade of paravian dinosaurs which lived from the Late Jurassic to the Late Cretaceous periods. Fossils have been found across the globe in North America, Europe, Africa, Asia, South America, and Antarctica,Case, J.A., Mart ...

indet. *

Megalosauridae Megalosauridae is a monophyletic family of carnivorous theropod dinosaurs within the group Megalosauroidea. Appearing in the Middle Jurassic, megalosaurids were among the first major radiation of large theropod dinosaurs. They were a relatively ...

indet. *

Tetanurae Tetanurae (/ˌtɛtəˈnjuːriː/ or "stiff tails") is a clade that includes most Theropoda, theropod dinosaurs, including Megalosauroidea, megalosauroids, Allosauroidea, allosauroids, Tyrannosauroidea, tyrannosauroids, Ornithomimosauria, ornitho ...

indet.

References

Bibliography

* * * * * {{cite LSA , last=Moyano Bohórquez , first=Fernando , year=2004 , title=Los sistemas sedimentarios de la Formación Bajada Colorada (Cretácico Temprano) en el sur de la Cuenca Neuquina, Argentina , url=http://naturalis.fcnym.unlp.edu.ar/id/20120126000088 , publisher=

Universidad Nacional de La Plata The La Plata National University ( es, Universidad Nacional de La Plata, UNLP) is one of the most important Argentine national universities and the biggest one situated in the city of La Plata, capital of Buenos Aires Province. It has over 90 ...

, pages=1–250 , accessdate=2019-02-14 Geologic formations of Argentina Lower Cretaceous Series of South America Cretaceous Argentina Berriasian Stage Valanginian Stage Sandstone formations Conglomerate formations Fluvial deposits Formations Paleontology in Argentina Geology of Neuquén Province Geology of Patagonia

Description

Fossil content

See also

References

Bibliography