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. The formation overlies crystalline basement or the Arroyo Chasicó Formation. The mammal assemblage of the Cerro Azul-Epecuén unit is the most diverse for the HuayquerianLate Miocene age, possibly ranging into the Pliocene. The formation is considered contemporaneous with the Río Negro Formation of the Colorado Basin.
The unit is characterized by a monotonous succession of loess containing moderately developed paleosols. In particular, the formation is considered as representing the interval between 10 and 5.7 Ma. The maximum exposed thickness in outcrop is 54 metres (177 ft), although the unit reaches about 180 metres (590 ft) in the subsurface.
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.
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.
Large cylindrical sediment-filled structures, 115 of which interpreted as mammal burrows occur within the loess-paleosol sequence of the formation.
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
Laguna Chillhué Estancia Don Mariano Cerro Patagua Cerro El Chancho Cerro de los Guanacos Puesto Colorado Estancia Quiñi-Malal Bajo Giuliani El Guanaco Telen El Recado Laguna Guatraché Loventué Quehué Barrancas Coloradas Estancia Ré Salinas de Hidalgo
C. cf. peiranoi
Grünbein Cantera Relleno Sanitario Level 2
C. sp.
El Recado
Chorobates
C. villosissimus
Laguna Chillhué Estancia Don Mariano Grünbein Cantera Relleno Sanitario Level 2 Puesto Colorado Ruta 14 Estancia Quiñi-Malal El Guanaco Telen El Recado Loventué Quehué Estancia Ré Salinas de Hidalgo
Estancia Don Mariano Huayquerías de San Carlos Laguna Epecuén Bajo Giuliani Laguna Chillhué Loventué Salinas Grandes de Hidalgo Quehué Barrancas Coloradas Estancia Ré Arroyo Guaminí Laguna de los Paraguayos Carhué
Visconti, Graciela; Melchor, Ricardo N.; Montalvo, Claudia I.; Umazano, Aldo M.; De Elorriaga, Elena E. (2010), "Anáisis litoestratigráfico de la Formación Cerro Azul (Mioceno Superior) de la Provincia de La Pampa", Revista de la Asociación Geológica Argentina, 67: 257–265
Paleontology
Montalvo, C. I.; Miño Boilini, A. R.; Sostillo, R.; Cerdeño, E.; Cardonatto, M. C.; Bonini, R. A. (2020), "The Scelidotheriinae Proscelidodon gracillimus (Xenarthra: Mylodontidae) from the Cerro Azul Formation (late Miocene), Argentina: Ontogenetic variability and taxonomy", Journal of South American Earth Sciences, 102754 102754, Bibcode:, doi:
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Sostillo, R.; Cerdeño, E.; Montalvo, C. (2018), "Taxonomic implications of a large sample of Tremacyllus (Hegetotheriidae: Pachyrukhinae) from the late Miocene Cerro Azul Formation of La Pampa, Argentina", Ameghiniana, 55 (4): 407–422, doi:, hdl:
Cerdeño, E.; Montalvo, C. I.; Sostillo, R. (2017), "Deciduous dentition and eruption pattern in late Miocene Pachyrukhinae (Hegetotheriidae, Notoungulata) from La Pampa Province, Argentina", Historical Biology, 29 (3): 359–375, Bibcode:, doi:, hdl:
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Carrillo, Juan D.; Forasiepi, Analía; Jaramillo, Carlos; Sánchez Villagra, Marcelo R. (2015), "Neotropical mammal diversity and the Great American Biotic Interchange: spatial and temporal variation in South America's fossil record", Frontiers in Genetics, 5: 1–11, doi:, PMC , PMID
Sostillo, Renata; Montalvo, Claudia I.; Verzi, Diego H. (2014), , Ameghiniana, 51 (4): 284–294, Bibcode:, doi:
Vucetich, M. G.; Deschamps, C. M.; Vieytes, E. C.; Montalvo, C. I. (2014), "Late Miocene Capybaras from Argentina: Skull Anatomy, Taxonomy, Evolution, and Biochronology", Acta Palaeontologica Polonica, 59: 517–535
Cenizo, M. M.; Tambussi, C. P.; Montalvo, C. I. (2012), "Late Miocene continental birds from the Cerro Azul Formation in the Pampean region (central-southern Argentina)", Alcheringa: An Australasian Journal of Palaeontology, 36 (1): 47–68, Bibcode:, doi:, hdl:
Vezzosi, Raúl Ignacio (2012), "First record of Procariama simplex Rovereto, 1914 (Phorusrhacidae, Psilopterinae) in the Cerro Azul Formation (upper Miocene) of La Pampa Province; remarks on its anatomy, palaeogeography and chronological range", Alcheringa: An Australasian Journal of Palaeontology, 36 (2): 157–169, Bibcode:, doi:, hdl:
Verzi, D. H.; Vieytes, E. C.; Montalvo, C. I. (2011), "Dental evolution in Neophanomys (Rodentia, Octodontidae) from the late Miocene of central Argentina", Geobios, 44 (6): 621–633, Bibcode:, doi:
Montalvo, C. I.; Melchor, R. N.; Visconti, G.; Cerdeño, E. (2008), "Vertebrate taphonomy in loess-palaeosol deposits: A case study from the late Miocene of Central Argentina", Geobios, 41 (1): 133–143, Bibcode:, doi:
Verzi, D. H.; Montalvo, C. I. (2008), "The oldest South American Cricetidae (Rodentia) and Mustelidae (Carnivora): Late Miocene faunal turnover in Central Argentina and the Great American Biotic Interchange", Palaeogeography, Palaeoclimatology, Palaeoecology, 267 (3–4): 284–291, Bibcode:, doi:
Verzi, D. H.; Montalvo, C. I.; Deschamps, C. M. (2008), "Biostratigraphy and biochronology of the Late Miocene of central Argentina: Evidence from rodents and taphonomy", Geobios, 41 (1): 145–155, Bibcode:, doi:
Urrutia, J. J.; Montalvo, C. I.; Scillato Yané, G. J. (2008), "Dasypodidae (Xenarthra, Cingulata) de la Formación Cerro Azul (Mioceno tardío) de la provincia de La Pampa, Argentina", Ameghiniana, 45: 289–302
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Zurita, A. E.; Aramayo, S. A. (2007), "New remains of Eosclerocalyptus tapinocephalus (Cabrera) (Mammalia, Xenarthra, Glyptodontidae): description and implications for its taxonomic status", Rivista Italiana di Paleontologia e Stratigrafia, 113: 57–66
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Esteban, G. I.; Nasif, N. L.; Montalvo, C. I. (2000), "Nuevos registros de Dasypodidae (Xenarthra) del Mioceno tardío de la provincia de La Pampa, Argentina", Revista Espanola de Paleontología, 16: 77–87
Verzi, D.H (1999), "The dental evidence on the differentiation of the ctenomyine rodents (Caviomorpha, Octodontidae, Ctenomyinae)", Acta Theriologica, 44: 263–282, doi:
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Cabrera, A (1939), "Sobre Vertebrados Fósiles del Plioceno de Adolfo Alsina", Revista del Museo de La Plata, 2: 3–35
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