The Cerro Azul Formation ( es, Formación Cerro Azul), in the Buenos Aires Province also described as Epecuén Formation, is a

geological 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 ...

Late Miocene The Late Miocene (also known as Upper Miocene) is a sub-epoch of the Miocene epoch (geology), Epoch made up of two faunal stage, stages. The Tortonian and Messinian stages comprise the Late Miocene sub-epoch, which lasted from 11.63 Ma (million ye ...

(

Tortonian The Tortonian is in the geologic time scale an age or stage of the late Miocene that spans the time between 11.608 ± 0.005 Ma and 7.246 ± 0.005 Ma (million years ago). It follows the Serravallian and is followed by the Messinian. The Torton ...

, or

Huayquerian The Huayquerian ( es, Huayqueriense) age is a period of geologic time (9.0–6.8 Ma) within the Late Miocene epoch of the Neogene, used more specifically within the SALMA classification. It follows the Mayoan The Mayoan ( es, Mayoense) age is ...

in the SALMA classification) age in the Colorado Basin of the

Buenos Aires Buenos Aires ( or ; ), officially the Autonomous City of Buenos Aires ( es, link=no, Ciudad Autónoma de Buenos Aires), is the capital and primate city of Argentina. The city is located on the western shore of the Río de la Plata, on South ...

and La Pampa Provinces in northeastern

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, th ...

.Cerro Azul Formation
in the

Paleobiology Database The Paleobiology Database is an online resource for information on the distribution and classification of fossil animals, plants, and microorganisms. History The Paleobiology Database (PBDB) originated in the NCEAS-funded Phanerozoic Marine Pale ...

Epecuén Formation
in the

The

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 fluviog ...

and aeolian

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, p ...

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

tuff Tuff is a type of rock made of volcanic ash ejected from a vent during a volcanic eruption. Following ejection and deposition, the ash is lithified into a solid rock. Rock that contains greater than 75% ash is considered tuff, while rock cont ...

s of the formation contain many mammals, such as ''

Thylacosmilus ''Thylacosmilus'' is an extinct genus of saber-toothed metatherian mammals that inhabited South America from the Late Miocene to Pliocene epochs. Though ''Thylacosmilus'' looks similar to the " saber-toothed cats", it was not a felid, like the ...

'' and ''

Macrauchenia ''Macrauchenia'' ("long llama", based on the now-invalid llama genus, ''Auchenia'', from Greek "big neck") was a large, long-necked and long-limbed, three-toed native South American mammal in the order Litopterna. The genus gives its name to its ...

'', reptiles, amphibians and fossils of

terror bird Phorusrhacids, colloquially known as terror birds, are an extinct clade of large carnivorous flightless birds that were one of the largest species of apex predators in South America during the Cenozoic era; their conventionally accepted temporal ...

s as well as ''

Argentavis ''Argentavis magnificens'' was among the largest flying birds ever to exist. While it is still considered the heaviest flying bird of all time, ''Argentavis'' was likely surpassed in wingspan by '' Pelagornis sandersi'' which is estimated to have ...

'', the largest flying bird ever discovered.

Description

The Cerro Azul Formation crops out in patches in the southwestern Buenos Aires Province and southeastern Pampa Province. The Epecuén Formation has been correlated to the Cerro Azul Formation in the early 2000s. The Cerro Azul and Epecuén Formations were named after the Cerro Azul ("Blue Hill") and Epecuén Lake where the formation crops out.Visconti et al., 2010, p.259 The formation overlies crystalline

basement A basement or cellar is one or more floors of a building that are completely or partly below the ground floor. It generally is used as a utility space for a building, where such items as the furnace, water heater, breaker panel or fuse box, ...

or the Arroyo Chasicó Formation.Visconti et al., 2010, p.262 The mammal assemblage of the Cerro Azul-Epecuén unit is the most diverse for the

age, possibly ranging into the

Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58Río Negro Formation of the Colorado Basin.Pérez, 2012, p.11Visconti et al., 2010, p.258 The unit is characterized by a monotonous succession of loess containing moderately developed

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 geolo ...

s. In particular, the formation is considered as representing the interval between 10 and 5.7 Ma. The maximum exposed thickness in outcrop is , although the unit reaches about in the subsurface.Cardonatto & Melchor, 2018, p.2 The Cerro Azul Formation deposits were described by Linares et al. in 1980. They are discontinuous along the whole occupied area in the provinces of La Pampa and Buenos Aires. They are composed of silts, sandy silts and very thin silty sands, reddish and brown colored, with a homogeneous and compact general aspect, and frequent carbonate nodules and evidences of pedogenic processes. Visconti et al. (2010) interpreted them as eolian deposits characterized by loessic materials, with a high percentage of lithic fragments and volcaniclastic sediments.Caleufú
at

Fossilworks Fossilworks is a portal which provides query, download, and analysis tools to facilitate access to the Paleobiology Database The Paleobiology Database is an online resource for information on the distribution and classification of fossil animals ...

.org The sediments and their fauna belong to a sedimentary and faunal cycle, which followed the withdrawal (around 10 Ma) of a widespread marine transgression that extended from central Argentina, to western Uruguay and southern Paraguay and Brazil, the "Paraná Sea" or ''mar paranense'' in Spanish.Verzi & Montalvo, 2008, p.285 Large cylindrical sediment-filled structures, 115 of which interpreted as mammal burrows occur within the loess-paleosol sequence of the formation.Cardonatto & Melchor, 2018, p.1

Fossil content

The following fossils have been recovered from the formation: Locations: ;La Pampa * Barrancas Coloradas - Cerro Azul Formation - La Pampa * Caleufú - Cerro Azul Formation - La Pampa * Cerro El Chancho - Cerro Azul Formation - La Pampa * Cerro Patagua - Cerro Azul Formation - La Pampa * Estancia Don Mariano - Cerro Azul Formation - La Pampa * Estancia El Recado - Cerro Azul Formation - La Pampa * Estancia Ré - Cerro Azul Formation - La Pampa * El Guanaco - Cerro Azul Formation - La Pampa * Huayquerías de San Carlos - Cerro Azul Formation - La Pampa * Laguna Chillhué - Cerro Azul Formation - La Pampa * Laguna Guatraché - Cerro Azul Formation - La Pampa * Quehué - Cerro Azul Formation - La Pampa * Salinas Grandes de Hidalgo - Cerro Azul Formation - La Pampa * Telen - Cerro Azul Formation - La Pampa ;Buenos Aires * Bajo Giuliani - Cerro Azul Formation - Buenos Aires * Barrancas de Sarmiento - Cerro Azul Formation - Buenos Aires * Eduardo Castex - Cerro Azul Formation - Buenos Aires * Estancia los Médanos - Cerro Azul Formation - Buenos Aires * Estancia Quiñi-Malal - Cerro Azul Formation - Buenos Aires * Grünbein Cantera Seminario - Cerro Azul Formation - Buenos Aires * Grünbein Cantera Seminario Level 2 - Cerro Azul Formation - Buenos Aires * Laguna Epecuén - Cerro Azul Formation - Buenos Aires * Laguna La Paraguaya - Cerro Azul Formation - Buenos Aires * Puesto Colorado - Cerro Azul Formation - Buenos Aires * Ruta 14 - Cerro Azul Formation - Buenos Aires * Arroyo Guaminí - Epecuén Formation - Buenos Aires * Carhué - Epecuén Formation - Buenos Aires * Laguna de los Paraguayos - Epecuén Formation - Buenos Aires * Robilote Field - SE of Epecuén lagoon & E of Laguna de Epecuén - Epecuén Formation - Buenos Aires * Salinas Grandes de Hidalgo - Epecuén Formation - Buenos Aires

SALMA correlations

References

Bibliography

;Geology * * ;Paleontology * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * {{cite LSA , last=Rovereto , first=C , year=1914 , title=Los Estratos Araucanos y sus fósiles , journal= Anales del Museo de Historia Natural de Buenos Aires , volume=25 , pages=1–24 Geologic formations of Argentina Miocene Series of South America Tortonian Huayquerian Neogene Argentina Sandstone formations Siltstone formations Conglomerate formations Aeolian deposits Fluvial deposits Lacustrine deposits Fossiliferous stratigraphic units of South America Paleontology in Argentina Formations Formations

Description

Fossil content

SALMA correlations

See also

References

Bibliography