Cerro Azul Formation

The Cerro Azul Formation (), also described as Epecuén Formation, is a geological formation of Late Miocene (Tortonian, or Huayquerian in the SALMA classification) age in the Colorado Basin of the Buenos Aires and La Pampa Provinces in northeastern Argentina.Cerro Azul Formation in the Paleobiology DatabaseEpecuén Formation in the Paleobiology Database

The fluvial and aeolian siltstones, sandstones and tuffs of the formation contain many mammals, such as Thylacosmilus and Huayqueriana, reptiles, amphibians and fossils of terror birds as well as Argentavis, 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 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 Huayquerian Late Miocene age, possibly ranging into the Pliocene.Carrillo et al., 2015, p.5 The formation is considered contemporaneous with the Río 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 paleosols. In particular, the formation is considered to represent 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 evidence 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.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 are interpreted as mammal burrows, occur within the loess-paleosol sequence of the formation.Cardonatto & Melchor, 2018, p.1

Locations 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

Paleofauna Amphibians Taxa Species Presence Abundance Description Images NotesCeratophrynidaeC. sp. Quehué Nicoli, 2017 LepidobatrachusL. sp. Birds Cathartid Taxa Species Presence Abundance Description Images Notes ArgentavisA. magnificens Carhué An associated partial skeleton with portions of the skull, right quadrate, and parts of the legs and arms. A giant teratornithidae bird Vizcaino & Fariña, 1999

Phorusrhacids Taxa Species Presence Abundance Description Images Notes DevincenziaD. pozzi Carhué ProcariamaP. simplex Salinas de Hidalgo Vezzosi, 2012 Phorusrhacidae indet.

Tinamou

Taxa Species Presence Abundance Description Images Notes EudromiaE. sp. Salinas de Hidalgo NothuraN. sp. Bajo GiulianiEl GuanacoSalinas de Hidalgo Cenizo et al., 2012

Rheidae Taxa Species Presence Abundance Description Images Notes RheaR. sp. Salinas de Hidalgo

Mammals Carnivora Taxa Species Presence Abundance Description Images NotesCyonasuaC. brevirostris Salinas de Hidalgo A procyonid mammal. C. prebrevirostris Salinas de Hidalgo C.sp. Telén Sparassodonts Taxa Species Presence Abundance Description Images Notes BorhyaenidiumB. musteloides Salinas de Hidalgo DimartiniaD. pristina Arroyo Chasicó A left dentary and its associated teeth A thylacosmiliform ThylacosmilusT. atrox El GuanacoQuehuéSalinas de Hidalgo A saber-toothed thylacosmilid Borhyaenidae indeterminate. Telén

Didelphimorphs Taxa Species Presence Abundance Description Images Notes Didelphinaeindet. Telén HyperdidelphysH. pattersoni El GuanacoTelén H. sp. Salinas Grandes de Hidalgo Goin & Pardiñas, 1996 LutreolinaL. sp. Salinas de Hidalgo Sparassocynidae indet. Telen ThylamysT. pinei Laguna Chillhué T. zetti Estancia RéArroyo Guaminí ThylatheridiumT. dolgopolae El GuanacoQuehuéTelén Goin & Montalvo, 1988 T. hudsoni Bajo GiulianiTelén T. sp. Estancia RéTelén ZygolestesZ. tatei Bajo Giuliani

Polydolopimorphia Taxa Species Presence Abundance Description Images Notes ArgyrolagusA. rusconii Bajo GiulianiEl GuanacoBarrancas Coloradas Goin et al., 2000 Argyrolagidae indet. Telén Lelvunlagus L. rusconii Cerro Patagua, Bajo Giuliani, and Laguna Epecuén Cranial material, partial mandibles, and isolated teeth An argyrolagid PliolestesP. venetus Bajo GiulianiLaguna Chillhué

Rodents Taxa Species Presence Abundance Description Images Notes AbrocomaA. antiqua Estancia Ré Montalvo et al., 2016CardiatheriumC. aff. orientalis Laguna ChillhuéLaguna Guatraché Vucetich et al., 2014 CardiomysC. sp. Salinas de Hidalgo ChasichimysC. bonaerense Cerro Patagua Verzi, 1999 C. scagliai Laguna Chillhué C. sp. Bajo Giuliani Caviidae indet. Barrancas de Sarmiento ClyomysC. aff. sp. Barrancas Coloradas Ctenomyidae indet. Telén DolicaviaD. sp. Grünbein Cantera Seminario Echimyidae indet. Telén Hydrochoeridae indet. Salinas de Hidalgo Neocavia N. pampeana Estancia El Recado Montalvo & Rocha, 2003 Lagostomus L. pretrichodactyla Salinas de Hidalgo L. (Lagostomopsis) sp. Grünbein Cantera SeminarioBarrancas de SarmientoEstancia RéSalinas de Hidalgo Neocavia N. sp. Grünbein Cantera Seminario Neophanomys N. pristinus Estancia Don MarianoQuehué Verzi et al., 2011 N. sp. Estancia Ré PalaeocaviaP. sp. Grünbein Cantera SeminarioBarrancas de SarmientoEstancia Ré PalaeoctodonP. aff. simplicidens Bajo Giuliani Montalvo & Casadio, 1988 PampamysP. emmonsae Laguna ChillhuéBajo GiulianiEstancia Ré Verzi et al., 2008Verzi et al., 1995PhtoramysP. hidalguense Barrancas ColoradasSalinas de Hidalgo Pascual et al., 1965P. cf. hidalguense Grünbein Cantera Seminario P. sp. Estancia Ré ProctenomysP. simpsoni El GuanacoBarrancas Coloradas Verzi et al., 1991 Protabrocoma P. chasicoensis Telén Octodontoideaindet. Estancia Ré Cerdeño et al., 2017 OrthomycteraO. sp. Grünbein Cantera SeminarioSalinas de Hidalgo ReigechimysR. octodontiformis Bajo GiulianiEstancia Ré R. plesiodon Laguna Chillhué Verzi et al., 1994 R. simplex Bajo Giuliani Sostillo et al., 2014TetrastylusT. araucanus Salinas de Hidalgo Tetrastylus sp. Telén TheridomysopsT. parvulus Telén XenodontomysX. ellipticus Grünbein Cantera SeminarioBarrancas de Sarmiento Deschamps, 2005

Xenarthrans Cingulata Taxa Species Presence Abundance Description Images Notes AspidocalyptusA. castroi Robilote FieldSalinas de Hidalgo Cabrera, 1939A. sp. Telén A. cf. sp. Grünbein Cantera Relleno Sanitario Level 2 ChasicotatusC. ameghinoi Laguna ChillhuéEstancia Don MarianoCerro PataguaCerro El ChanchoCerro de los GuanacosPuesto ColoradoEstancia Quiñi-MalalBajo GiulianiEl GuanacoTelenEl RecadoLaguna GuatrachéLoventuéQuehuéBarrancas ColoradasEstancia RéSalinas de Hidalgo Urrutia et al., 2008Esteban et al., 2000 C. cf. peiranoi Grünbein Cantera Relleno Sanitario Level 2 C. sp. El Recado ChorobatesC. villosissimus Laguna ChillhuéEstancia Don MarianoGrünbein Cantera Relleno Sanitario Level 2Puesto ColoradoRuta 14Estancia Quiñi-MalalEl GuanacoTelenEl RecadoLoventuéQuehuéEstancia RéSalinas de Hidalgo Chorobates sp. Grünbein Cantera Seminario CoscinocercusC. brachyurus Robilote FieldSalinas de Hidalgo C. marcalaini Robilote FieldSalinas de Hidalgo C. sp. Telén DoellotatusD. chapadmalensis El RecadoSalinas de Hidalgo Esteban et al., 2003 D. inornatus Laguna ChillhuéEstancia Don MarianoGrünbein Cantera SeminarioPuesto ColoradoRuta 14El GuanacoEl RecadoLaguna GuatrachéLoventuéQuehuéBarrancas ColoradasEstancia RéTelénSalinas de Hidalgo D. cf. praecursor Grünbein Cantera Seminario D. sp. Laguna La Paraguaya EosclerocalyptusE. sp. Laguna La Paraguaya EumysopsE. sp. Laguna Chillhué Glyptodontidae indet. Laguna La ParaguayaSalinas Grandes de Hidalgo HoplophorusH. sp. Telén Hoplophractus H. tapinocefalus Laguna de los ParaguayosSalinas de Hidalgo Zurita & Aramayo, 2007H. sp. Telén MacrochorobatesM. chapalmalensis El GuanacoBarrancas Coloradas M. scalabrinii Laguna ChillhuéEstancia Don MarianoTelenLoventuéQuehuéSalinas de Hidalgo MacroeuphractusM. morenoi Grünbein Cantera Relleno Sanitario Level 2Puesto ColoradoLaguna ChillhuéTelenEl RecadoLaguna GuatrachéLoventuéQuehuéBarrancas ColoradasEstancia RéSalinas de Hidalgo M. retusus Salinas de Hidalgo M. sp. Grünbein Cantera Relleno Sanitario Level 2El Recado PaleuphractusP. sp. Salinas de Hidalgo PlohophorusP. araucanus Salinas de Hidalgo ProeuphractusP. limpidus Laguna ChillhuéTelén P. sp. Laguna ChillhuéCerro PataguaTelenEl RecadoLaguna GuatrachéQuehuéSalinas de Hidalgo PseudoplohophorusP. cf. sp. Grünbein Cantera Relleno Sanitario Level 2 VeteliaV. perforata Cerro PataguaCerro de los GuanacosTelén ZaedyusZ. pichiy Laguna ChillhuéTelenQuehué

Pilosans Taxa Species Presence Abundance Description Images Notes Mylodontidae indet. Telén PlesiomegatheriumP. sp. Salinas de Hidalgo ProscelidodonP. gracillimus Estancia Don MarianoHuayquerías de San CarlosLaguna EpecuénBajo GiulianiLaguna ChillhuéLoventuéSalinas Grandes de HidalgoQuehuéBarrancas ColoradasEstancia RéArroyo GuaminíLaguna de los ParaguayosCarhué Montalvo et al., 2020Rovereto, 1914Goin, 1997Ortega, 1967 McdonaldocnusM. bondesioi

Litopterns