Cerro Azul Formation Explained

Cerro Azul Formation
Type:	Geological formation
Period:	Tortonian
Age:	Tortonian (Huayquerian) ~
Prilithology:	Siltstone, sandstone
Otherlithology:	Conglomerate
Namedfor:	Cerro Azul, Epecuén Lake
Namedby:	Linares et al.
Year Ts:	1980
Region:	Buenos Aires & La Pampa Provinces
Country:	Argentina
Coordinates:	-35.7°N -64.7°W
Paleocoordinates:	-35.9°N -62.7°W
Underlies:	alluvium
Overlies:	Arroyo Chasicó Formation or Crystalline basement
Thickness:	54m (177feet) (outcrop) 180m (590feet) (subsurface)
Extent:	Colorado Basin
Map:	Cerro Azul Formation outcrop map.png

The Cerro Azul Formation (Spanish; Castilian: Formación Cerro Azul), 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.^{[1] [2]}

The fluvial and aeolian siltstones, sandstones and tuffs of the formation contain many mammals, such as Thylacosmilus and Macrauchenia, 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.^[3] The formation overlies crystalline basement or the Arroyo Chasicó Formation.^[4] The mammal assemblage of the Cerro Azul-Epecuén unit is the most diverse for the Huayquerian Late Miocene age, possibly ranging into the Pliocene.^[5] The formation is considered contemporaneous with the Río Negro Formation of the Colorado Basin.^{[6] [7]}

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 54m (177feet), although the unit reaches about 180m (590feet) in the subsurface.^[8]

The Cerro Azul Formation deposits were described by Linares et al. in 1980.^[3] 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.^[9]

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.^[10]

Large cylindrical sediment-filled structures, 115 of which interpreted as mammal burrows occur within the loess-paleosol sequence of the formation.^[11]

Fossil content

The following fossils have been recovered from the formation:^[1]

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

Group	Clade	Taxa	Location	Images	Notes
Mammals		Cyonasua brevirostris	Salinas de Hidalgo		align=center
		C. prebrevirostris	Salinas de Hidalgo		align=center
		Cyonasua sp.	Telén		align=center
		Borhyaenidium musteloides	Salinas de Hidalgo		align=center
		Thylacosmilus atrox	El Guanaco Quehué Salinas de Hidalgo		align=center
			Telén		align=center
	Rodents	Abrocoma antiqua	Estancia Ré		align=center	^[12]
		Cardiatherium aff. orientalis	Laguna Chillhué Laguna Guatraché		align=center	^[13]
		Chasichimys bonaerense	Cerro Patagua		align=center	^[14]
		C. scagliai	Laguna Chillhué		align=center
		Neocavia pampeana	Estancia El Recado		align=center	^[15]
		Lagostomus pretrichodactyla	Salinas de Hidalgo		align=center
		Neophanomys pristinus	Estancia Don Mariano Quehué		align=center	^[16]
		Palaeoctodon aff. simplicidens	Bajo Giuliani		align=center	^[17]
		Pampamys emmonsae	Laguna Chillhué Bajo Giuliani Estancia Ré		align=center	^[18] ^[19]
		Phtoramys hidalguense	Barrancas Coloradas Salinas de Hidalgo		align=center	^[20]
		Proctenomys simpsoni	El Guanaco Barrancas Coloradas		align=center	^[21]
		Reigechimys octodontiformis	Bajo Giuliani Estancia Ré		align=center
		R. plesiodon	Laguna Chillhué		align=center	^[22]
		R. simplex	Bajo Giuliani		align=center	^[23]
		Tetrastylus araucanus	Salinas de Hidalgo		align=center
		Theridomysops parvulus	Telén		align=center
		Xenodontomys ellipticus	Grünbein Cantera Seminario Barrancas de Sarmiento		align=center	^[24]
		Phtoramys cf. hidalguense	Grünbein Cantera Seminario		align=center
		Cardiomys sp.	Salinas de Hidalgo		align=center
		Chasichimys sp.	Bajo Giuliani		align=center	^[25]
		Dolicavia sp.	Grünbein Cantera Seminario		align=center
		Lagostomus (Lagostomopsis) sp.	Grünbein Cantera Seminario Barrancas de Sarmiento Estancia Ré Salinas de Hidalgo		align=center
		Neocavia sp.	Grünbein Cantera Seminario		align=center
		Neophanomys sp.	Estancia Ré		align=center
		Orthomyctera sp.	Grünbein Cantera Seminario Salinas de Hidalgo		align=center
		Palaeocavia sp.	Grünbein Cantera Seminario Barrancas de Sarmiento Estancia Ré		align=center
		Phtoramys sp.	Estancia Ré		align=center
		Protabrocoma sp.	Telén		align=center
		Tetrastylus sp.	Telén		align=center
		aff. Clyomys sp.	Barrancas Coloradas		align=center
			Barrancas de Sarmiento		align=center
			Telén		align=center
			Telén		align=center
			Salinas de Hidalgo		align=center
			Estancia Ré		align=center	^[26]
		Aspidocalyptus castroi	Robilote Field Salinas de Hidalgo		align=center	^[27]
		Coscinocercus brachyurus	Robilote Field Salinas de Hidalgo		align=center
		C. marcalaini	Robilote Field Salinas de Hidalgo		align=center
		Hoplophractus tapinocefalus	Laguna de los Paraguayos Salinas de Hidalgo		align=center	^[28]
		Plohophorus araucanus	Salinas de Hidalgo		align=center
		Proscelidodon gracillimus	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		align=center	^[29] ^[30] ^[31] ^[32]
		Aspidocalyptus sp.	Telén		align=center
		Coscinocercus sp.	Telén		align=center
		Eosclerocalyptus sp.	Laguna La Paraguaya		align=center
		Eumysops sp.	Laguna Chillhué		align=center
		Hoplophorus sp.	Telén		align=center
		Hoplophractus sp.	Telén		align=center
		Plesiomegatherium sp.	Salinas de Hidalgo		align=center
		cf. Aspidocalyptus sp.	Grünbein Cantera Relleno Sanitario Level 2		align=center
		cf. Pseudoplohophorus sp.	Grünbein Cantera Relleno Sanitario Level 2		align=center
			Laguna La Paraguaya Salinas Grandes de Hidalgo		align=center
			Telén		align=center
		Chasicotatus ameghinoi	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		align=center	^[33] ^[34]
		Chasicotatus cf. peiranoi	Grünbein Cantera Relleno Sanitario Level 2		align=center
		Chorobates 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		align=center
		Doellotatus chapadmalensis	El Recado Salinas de Hidalgo		align=center	^[35]
		D. inornatus	Laguna Chillhué Estancia Don Mariano Grünbein Cantera Seminario Puesto Colorado Ruta 14 El Guanaco El Recado Laguna Guatraché Loventué Quehué Barrancas Coloradas Estancia Ré Telén Salinas de Hidalgo		align=center
		D. cf. praecursor	Grünbein Cantera Seminario		align=center
Macrochorobates chapalmalensis		El Guanaco Barrancas Coloradas		align=center
M. scalabrinii		Laguna Chillhué Estancia Don Mariano Telen Loventué Quehué Salinas de Hidalgo		align=center
Macroeuphractus morenoi		Grünbein Cantera Relleno Sanitario Level 2 Puesto Colorado Laguna Chillhué Telen El Recado Laguna Guatraché Loventué Quehué Barrancas Coloradas Estancia Ré Salinas de Hidalgo		align=center
M. retusus		Salinas de Hidalgo		align=center
Proeuphractus limpidus		Laguna Chillhué Telén		align=center
Vetelia perforata		Cerro Patagua Cerro de los Guanacos Telén		align=center
Zaedyus pichiy		Laguna Chillhué Telen Quehué		align=center
Chasicotatus sp.		El Recado		align=center
Chorobates sp.		Grünbein Cantera Seminario		align=center
Doellotatus sp.		Laguna La Paraguaya		align=center
Macrochorobates sp.		Grünbein Cantera Relleno Sanitario Level 2 El Recado		align=center
Paleuphractus sp.		Salinas de Hidalgo		align=center
Proeuphractus sp.		Laguna Chillhué Cerro Patagua Telen El Recado Laguna Guatraché Quehué Salinas de Hidalgo		align=center
	Hyperdidelphys pattersoni	El Guanaco Telén		align=center
	Thylamys pinei	Laguna Chillhué		align=center
	T. zetti	Estancia Ré Arroyo Guaminí		align=center
	Thylatheridium dolgopolae	El Guanaco Quehué Telén		align=center	^[36]
	T. hudsoni	Bajo Giuliani Telén		align=center
	Zygolestes tatei	Bajo Giuliani		align=center
	Hyperdidelphys sp.	Salinas Grandes de Hidalgo		align=center	^[37]
	Thylatheridium sp.	Estancia Ré Telén		align=center
		Telén		align=center
	Lutreolina sp.	Salinas de Hidalgo		align=center
		Telen		align=center
Ungulates	Diplasiotherium pampa	Bajo Giuliani Laguna Chillhué Salinas de Hidalgo		align=center	^[38]
	Eoauchenia cingulata	Robilote Field Salinas de Hidalgo		align=center
	E. primitiva	El Guanaco		align=center
	Epecuenia thoatherioides	Robilote Field Salinas de Hidalgo		align=center
	Huayqueriana cristata	Robilote Field		align=center
	Macrauchenia latidens	Salinas de Hidalgo		align=center
	cf. Brachytherium cuspidatum	Telén Salinas de Hidalgo		align=center
	Neobrachytherium sp.	Bajo Giuliani Salinas de Hidalgo		align=center
	Promacrauchenia sp.	Grünbein Cantera Relleno Sanitario Level 2 Salinas de Hidalgo		align=center
		Bajo Giuliani Telén		align=center
		Telén		align=center
	Hemihegetotherium achataleptum	Cerro Patagua Eduardo Castex Cerro de los Guanacos Puesto Colorado Bajo Giuliani Laguna Chillhué Loventué Salinas de Hidalgo		align=center	^[39]
	H. lazai	Salinas de Hidalgo		align=center
	Paedotherium bonaerense	Barrancas de Sarmiento		align=center
	Paedotherium minor	Laguna La Paraguaya Estancia Ré Salinas de Hidalgo		align=center
	Paedotherium cf. minor	Grünbein Cantera Seminario		align=center
	Pisanodon nazari	Salinas de Hidalgo		align=center
	Pseudotypotherium carhuense	Robilote Field Salinas de Hidalgo		align=center
	Tremacyllus impressus	Grünbein Cantera Seminario Bajo Giuliani Laguna Chillhué Salinas Grandes de Hidalgo Quehué Barrancas Coloradas		align=center	^[40]
	Typotheriodon grandis	Robilote Field		align=center
	Typotheriopsis minimus	Robilote Field		align=center
	Paedotherium sp.	Bajo Giuliani Laguna Chillhué Estancia Ré		align=center	^[41]
		Laguna La Paraguaya Telén		align=center	^[42]
	Argyrolagus rusconii	Bajo Giuliani El Guanaco Barrancas Coloradas		align=center	^[43]
		Telén		align=center
	Pliolestes venetus	Bajo Giuliani Laguna Chillhué		align=center
Birds		Devincenzia pozzi	Carhué		align=center
		Procariama simplex	Salinas de Hidalgo		align=center	^[44]
		Phorusrhacidae indet.	Laguna Guatraché Carhué		align=center
		Argentavis magnificens	Carhué		align=center	^[45]
		Eudromia sp.	Salinas de Hidalgo		align=center
		Nothura sp.	Bajo Giuliani El Guanaco Salinas de Hidalgo		align=center	^[46]
		Rhea sp.	Salinas de Hidalgo		align=center
Reptiles		Tupinambis sp.	Telén		align=center	^[47]
			Telén		align=center
			Salinas de Hidalgo		align=center	^[48]
Amphibians		Lepidobatrachus sp.	Quehué		align=center	^[49]

SALMA correlations

Huayquerian correlations in South America

Formation	Cerro Azul																Map
Basin																	align=center rowspan=17
Cardiatherium	align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center
Lagostomus	align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center
Macroeuphractus	align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center
Proeuphractus	align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center
Pronothrotherium	align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center
Pseudotypotherium	align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center
Thylacosmilus	align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center
Xotodon	align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center
	align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center
	align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center
Rodents	align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center
Reptiles	align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center
Birds	align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center			align=center		align=center		align=center		align=center
Terror birds	align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center
	align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center
	Aeolian-fluvial	Fluvio-deltaic			Fluvial						Fluvio-lacustrine	Fluvial			Fluvio-lacustrine	Fluvio-deltaic
Volcanic						Yes

See also

• South American land mammal ages
• Honda Group
• Ituzaingó Formation
• Pebas Formation
• Urumaco

References

Bibliography

Geology

Paleontology

Notes and References

1. https://paleobiodb.org/classic/displayStrata?geological_group=&formation=Cerro%20Azul&group_formation_member=Cerro%20Azul Cerro Azul Formation
2. https://paleobiodb.org/classic/displayStrata?geological_group=&formation=Epecu%C3%A9n&group_formation_member=Epecu%C3%A9n Epecuén Formation
3. Visconti et al., 2010, p.259
4. Visconti et al., 2010, p.262
5. Carrillo et al., 2015, p.5
6. Pérez, 2012, p.11
7. Visconti et al., 2010, p.258
8. Cardonatto & Melchor, 2018, p.2
9. http://www.fossilworks.org/cgi-bin/bridge.pl?a=collectionSearch&collection_no=141939 Caleufú
10. Verzi & Montalvo, 2008, p.285
11. Cardonatto & Melchor, 2018, p.1
12. Montalvo et al., 2016
13. Vucetich et al., 2014
14. Verzi, 1999
15. Montalvo & Rocha, 2003
16. Verzi et al., 2011
17. Montalvo & Casadio, 1988
18. Verzi et al., 2008
19. Verzi et al., 1995
20. Pascual et al., 1965
21. Verzi et al., 1991
22. Verzi et al., 1994
23. Sostillo et al., 2014
24. Deschamps, 2005
25. Verzi, 1999
26. Cerdeño et al., 2017
27. Cabrera, 1939
28. Zurita & Aramayo, 2007
29. Montalvo et al., 2020
30. Rovereto, 1914
31. Goin, 1997
32. Ortega, 1967
33. Urrutia et al., 2008
34. Esteban et al., 2000
35. Esteban et al., 2003
36. Goin & Montalvo, 1988
37. Goin & Pardiñas, 1996
38. Schmidt et al., 2018
39. Cerdeño & Montalvo, 2002
40. Sostillo et al., 2018
41. Cerdeño et al., 2017
42. Cardonatto & Melchor, 2018, p.16
43. Goin et al., 2000
44. Vezzosi, 2012
45. Vizcaino & Fariña, 1999
46. Cenizo et al., 2012
47. Montalvo et al., 2008
48. De la Fuente et al., 2018
49. Nicoli, 2017