The Agua de la Piedra Formation (FAP, Spanish names include ''Estratos de Agua de la Piedra'' and ''Complejo Volcano-sedimentario del Terciario inferior'')Combina et al., 1994, p.418 is a

Late Oligocene The Chattian is, in the geologic timescale, the younger of two ages or upper of two stages of the Oligocene Epoch/Series. It spans the time between . The Chattian is preceded by the Rupelian and is followed by the Aquitanian (the lowest stage ...

(

Deseadan The Deseadan ( es, Deseadense) age is a period of geologic time (29.0–21.0 Ma) within the Oligocene epoch of the Paleogene to the Early Miocene epoch of the Neogene, used more specifically within the SALMA classification of South America. It fo ...

in the SALMA classification) geologic

formation Formation may refer to: Linguistics * Back-formation, the process of creating a new lexeme by removing or affixes * Word formation, the creation of a new word by adding affixes Mathematics and science * Cave formation or speleothem, a secondar ...

of the

Malargüe Group The Malargüe Group is a group of geologic formations of the Neuquén Basin of the Mendoza, Neuquén, Río Negro and La Pampa Provinces in northern Patagonia, Argentina. The formations of the Malargüe Group range in age between the middle Camp ...

that crops out in the southernmost

Precordillera Precordillera is a Spanish geographical term for hills and mountains lying before a greater range, foothills. The term is derived from ''cordillera'' (mountain range)—literally "pre-mountain range"—and applied usually to the Andes. Some places ...

and northernmost

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 bas ...

in southern

Mendoza Province Mendoza, officially Province of Mendoza, is a province of Argentina, in the western central part of the country in the Cuyo region. It borders San Juan to the north, La Pampa and Neuquén to the south, San Luis to the east, and the republic o ...

, Argentina.Agua de la Piedra 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 ...

The strictly terrestrial tuffs and paleosols of the formation, geologically belonging to

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 gl ...

, have provided a wealth of mammal fossils of various groups at Quebrada Fiera, including '' Mendozahippus fierensis'', ''

Pyrotherium ''Pyrotherium'' ('fire beast') is an extinct genus of South American ungulate, of the order Pyrotheria, that lived in what is now Argentina and Bolivia, during the Late Oligocene.Coniopternium'' and '' Fieratherium''. Terror birds reminiscent of the

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 ...

Andrewsornis ''Andrewsornis'' is an extinct genus of giant flightless predatory birds of the family Phorusrhacidae or "terror birds" that lived in Oligocene Argentina. Fossils have been found in the Sarmiento Formation, and possibly the Agua de la Piedra ...

'' and indeterminate remains of the

phorusrhacid 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 ...

family have found in conjunction with the mammals.

Regional geology

The Agua de la Piedra is geologically part of the

, Argentina's most prolific onshore petroleum producing basin of northwestern

, and crops out in the geographical feature of the

Andean orogeny The Andean orogeny ( es, Orogenia andina) is an ongoing process of orogeny that began in the Early Jurassic and is responsible for the rise of the Andes mountains. The orogeny is driven by a reactivation of a long-lived subduction system along ...

; the Argentinian

of the higher

Andes The Andes, Andes Mountains or Andean Mountains (; ) are the longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range is long, wide (widest between 18°S – 20°S ...

in the

hinterland Hinterland is a German word meaning "the land behind" (a city, a port, or similar). Its use in English was first documented by the geographer George Chisholm in his ''Handbook of Commercial Geography'' (1888). Originally the term was associated ...

. The

, of which the Agua de la Piedra Formation is the uppermost unit, hosts among the most spectacular dinosaur fossils and nesting sites in the

Allen Formation The Allen Formation is a geological formation in Argentina whose strata date back to the Late Cretaceous (middle Campanian to early Maastrichtian.Salgado et al., 2007 Dinosaur remains are among the fossils that have been recovered from the formati ...

, the lowermost stratigraphic unit of the

group A group is a number of persons or things that are located, gathered, or classed together. Groups of people * Cultural group, a group whose members share the same cultural identity * Ethnic group, a group whose members share the same ethnic iden ...

. The

Jagüel Formation The Jagüel Formation is a geological formation, located in Patagonia, Argentina. It underlies the Roca Formation and overlies the Allen Formation. All of these formations belong to the Malargüe Group. Its name was coined by Windhausen in 1914. ...

, overlying the Allen Formation, hosts the

Cretaceous–Paleogene boundary The Cretaceous–Paleogene (K–Pg) boundary, formerly known as the Cretaceous–Tertiary (K–T) boundary, is a geological signature, usually a thin band of rock containing much more iridium than other bands. The K–Pg boundary marks the end of ...

and has provided fossils of marine reptiles including

mosasaur Mosasaurs (from Latin ''Mosa'' meaning the 'Meuse', and Greek ' meaning 'lizard') comprise a group of extinct, large marine reptiles from the Late Cretaceous. Their first fossil remains were discovered in a limestone quarry at Maastricht on th ...

sHoja 3969-II Neuqúen, 2007 and the marine turtle '' Euclastes meridionalis''. The Roca Formation, overlying the Jagüel Formation shows evidence of Atlantic waters depositing the evaporites, claystones and limestones of the formation.Archuby et al., 2016Malamuián & Náñez, 2011 The Neuquén Basin started forming in the latest Jurassic as one of the

rift basin In geology, a rift is a linear zone where the lithosphere is being pulled apart and is an example of extensional tectonics. Typical rift features are a central linear downfaulted depression, called a graben, or more commonly a half-graben wi ...

s resulting from the break-up of

Pangea Pangaea or Pangea () was a supercontinent that existed during the late Paleozoic and early Mesozoic eras. It assembled from the earlier continental units of Gondwana, Euramerica and Siberia during the Carboniferous approximately 335 million y ...

. While the earlier formations in the basin are mostly distal terrestrial in nature, the Agua de la Piedra Formation is a unique combination of purely terrestrial influence (paleosols) with the early Andean volcanism in the form of tuffs.

Oligocene South America

Climate

Oligocene South America differed quite substantially from the Eocene period preceding it. Isolated from Gondwana for 70 million years, the continent had developed widespread lush forests with their own specific faunas. The climate drastically cooled at the Eocene-Oligocene boundary with global cooling as a result of the formation of the

Antarctic Ocean The Southern Ocean, also known as the Antarctic Ocean, comprises the southernmost waters of the World Ocean, generally taken to be south of 60° S latitude and encircling Antarctica. With a size of , it is regarded as the second-small ...

current. The South American landscape became more arid than in the Eocene with ongoing volcanism related to the Andean orogeny affecting the local climates.

Oligocene fauna

The Oligocene of South America is characterized by the arrival of the first

monkeys Monkey is a common name that may refer to most mammals of the infraorder Simiiformes, also known as the simians. Traditionally, all animals in the group now known as simians are counted as monkeys except the apes, which constitutes an incomple ...

, possibly rafting from Africa, which in the Oligocene was significantly removed from South America. The first rodents had arrived to the island continent in the Late Eocene before,Vassallo & Antenucci, 2015, p.6 perhaps using similar methods of transoceanic transport. The rodents of South America diversified in the Oligocene. Cabeza Blanca, where the

Sarmiento Formation The Sarmiento Formation (Spanish: ''Formación Sarmiento''), in older literature described as the Casamayor Formation, is a geological formation in Chubut Province, Argentina, in central Patagonia, which spans around 30 million years from the mid- ...

outcrops, has provided the richest and most diverse Oligocene fauna of South America.Vucetich et al., 2015, p.21 The cooler Oligocene climate led to the wide-spread extension of

savanna A savanna or savannah is a mixed woodland-grassland (i.e. grassy woodland) ecosystem characterised by the trees being sufficiently widely spaced so that the canopy does not close. The open canopy allows sufficient light to reach the ground to ...

and other

grassland A grassland is an area where the vegetation is dominated by grasses (Poaceae). However, sedge (Cyperaceae) and rush (Juncaceae) can also be found along with variable proportions of legumes, like clover, and other herbs. Grasslands occur natur ...

biome A biome () is a biogeographical unit consisting of a biological community that has formed in response to the physical environment in which they are found and a shared regional climate. Biomes may span more than one continent. Biome is a broader ...

s. In the Early Oligocene, these rodents inhabited open and arid landscapes with wind-blown dust and grasslands environments.Ojeda et al., 2015, p.123

Monkeys and rodents

The oldest confirmed

New World monkey New World monkeys are the five families of primates that are found in the tropical regions of Mexico, Central and South America: Callitrichidae, Cebidae, Aotidae, Pitheciidae, and Atelidae. The five families are ranked together as the Ceboidea ( ...

fossils stem from the Deseadan formations

Salla Salla (''Kuolajärvi'' until 1936) ( smn, Kyelijävri) is a municipality of Finland, located in Lapland. The municipality has a population of () and covers an area of of which is water. The population density is . The nearby settlement of S ...

in presently Andean Bolivia (the approximately weighing '' Branisella boliviana'' and '' Szalatavus attricuspis'' half the size of ''Branisella'') and the heavy ''

Canaanimico ''Canaanimico'' is an extinct genus of medium-sized New World monkeys from the Late Oligocene (approximately 26.5 Ma, Deseadan in the SALMA classification) fossiliferous fluvio-lacustrine Chambira Formation of the Ucayali Basin in Amazonian P ...

'' from the

Chambira The Chambira River is a major tributary of the Marañón River, and has been the traditional territory of the Urarina peoples for at least the past 350 years, if not longer. Located in the Amazon jungle of Peru, otherwise known as the Selva, the Ch ...

of Amazonian Peru.Silvestro et al., 2017, p.14 The rodents had arrived in the Late Eocene and diversified greatly during the Deseadan following the appearance of '' Andemys'' with species ''A. frassinettii'' and ''A. termasi'' in the

Tinguirirican The Tinguirirican ( es, Tinguiririquense) age is a period of geologic time (36.0–29.0 Ma) within the Late Eocene and Early Oligocene epochs of the Paleogene, used more specifically within the SALMA classification in South America. It follows th ...

(

Abanico Formation Abanico Formation ( es, Formación Abanico) is a thick sedimentary formation exposed in the Andes of Central Chile. The formation has been deposited in a timespan from the Eocene to the Miocene. Abanico Formation's contact with the overlying Mi ...

;

Tinguiririca fauna The fossil Tinguiririca fauna, entombed in volcanic mudflows and ash layers at the onset of the Oligocene, about 33-31.5 million years ago, represents a unique snapshot of the history of South America's endemic fauna, which was extinguished when ...

Caviomorph Caviomorpha is the rodent infraorder or parvorder that unites all New World hystricognaths. It is supported by both fossil and molecular evidence. The Caviomorpha was for a time considered to be a separate order outside the Rodentia, but is now a ...

s arrived in Patagonia during the latest Eocene or early Oligocene, and by the Late Oligocene they were highly diversified, with representatives of the four main lineages. A great morphological disparity, at least in tooth morphology, was then acquired mainly by the development of hypsodonty in several lineages. The early evolution of each of the major clades was complex, especially for chinchilloids and octodontoids. The first stages of the evolution of cavioids are more obscure because they are recognized through the relatively derived Deseadan species of

Cavioidea Caviomorpha is the rodent infraorder or parvorder that unites all New World hystricognaths. It is supported by both fossil and molecular phylogeny, molecular evidence. The Caviomorpha was for a time considered to be a separate order outside the R ...

.Vucetich et al., 2015, p.11 The Oligocene (Tinguirirican and Deseadan SALMAs plus La Cantera fauna) has a rich record of caviomorphs showing a greater morphological disparity than older faunas. Representatives of the four superfamilies, with the archetypal dental features that characterize species of the subsequent SALMAs, can be clearly recognized, at least since the Deseadan SALMA. Although a few genera (e.g., ''Andemys'', '' Branisamys'') cannot be assigned with certainty to any supra generic taxa. The Acaremyidae were likely a group of austral differentiation. The first representatives, the Deseadan '' Platypittamys brachyodon'', '' Galileomys baios'' and '' Changquin woodi'',Vucetich et al., 2014, p.692 attest to its differentiation into several lineages.Vucetich et al., 2015, p.18

Oligocene volcanism

Early Andean volcanism in the Southern Cone of South America dating to the Oligocene has been found in: * Estratos de PupunahueElgueta et al., 2000Alfaro & Gantz, 1997Villablanca et al., 2003 * Estratos de San Pedro * Caleta Chonos Formation * Cheuquemó Formation * Temuco FormationMella & Quiroz, 2010 * Oxaya FormationGarcía et al., 1999Zeilinger et al., 2015 * Ancud Volcanic Complex * Cerro Ratones

Description

The formation comprises the "Rodados Lustrosos" level, formed by clastic heterogeneous conglomerates in a silty matrix, considered as the stratigraphic evidence of the Pehuenche orogenic phase of the Andean orogeny, followed by uniform sequences, variable in thickness, of whitish-ocher

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 ...

aceous

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 with concretions and whitish-gray tuffs with intercalations of pyroclastic deposits.Schmidt et al., 2019, p.370 The upper part of the Agua de la Piedra Formation consists of of white-grayish tuffs and tobaceous paleosols, with laminated or massive parallel stratification constitute the fossiliferous level of Quebrada Fiera.Cerdeño, 2012, p.378 The formation overlies the Pircala-Coihueco Formation.

Depositional environment

The studied profiles of the Agua de la Piedra Formation show large lateral lithological varieties, typical of

alluvial fan An alluvial fan is an accumulation of sediments that fans outwards from a concentrated source of sediments, such as a narrow canyon emerging from an escarpment. They are characteristic of mountainous terrain in arid to semiarid climates, but a ...

depositional setings. The climate during deposition has been estimated to be semi-arid and the differential thicknesses of facies associations within the Agua de la Piedra Formation may represent the infill of minibasins in the forming foreland of the

. Sedimentary loading can enhance the effect of tectonic forces in foreland basins. The variety in volcanic fragments and composition indicates local ash fall caused by contemporaneous volcanism in the area of deposition.Combina et al., 1994, p.420 2017 research on the Deseadan fauna (late Oligocene) from Quebrada Fiera, south of Mendoza Province, Argentina, evidences a rich mammal assemblage that shows the existence of common elements with Deseadan faunal associations of Patagonia and those of lower latitudes such as Salla, Bolivia, as well as endemic taxa of different groups.Hernández Pino et al., 2017, p.195 Endemism refers to Notohippidae (''Mendozahippus fierensis''), Leontiniidae (''Gualta cuyana''), Homalodotheriidae (''Asmodeus petrasnerus'') and Metatheria (''Fieratherium sorex''); to these mammals a new terrestrial snail has been added in 2016.Miquel & Cerdeño, 2016 Faunal data published in 2019 confirm the Deseadan age, but as per 2020, absolute dating is lacking for Quebrada Fiera.

Paleontological significance

Quebrada Fiera

The Quebrada Fiera site is situated in the Malargüe Department,Quebrada Fiera
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 southern Mendoza Province, Argentina, in the foothills of the Andes Range. The fossiliferous levels are located at around at elevation. The site was discovered during a geological prospection carried out by

Yacimientos Petrolíferos Fiscales YPF S.A. (, formerly ; English: "Fiscal Oilfields") is a vertically integrated, majority state-owned Argentine energy company, engaged in oil and gas exploration and production, and the transportation, refining, and marketing of gas and petr ...

(YPF) in the late 1970s (Gorroño et al., 1979). Later on, other fossil bearing levels were found at the southern side of the ravine, located at around , elevation. The site is one of five recognized fossiliferous sites in Mendoza Province, with Divisadero Largo, where the

Santacrucian The Santacrucian age is a period of geologic time (17.5 – 16.3 Ma) within the Early Miocene epoch of the Neogene, used more specifically with SALMA classification in South America. It follows the Colhuehuapian and precedes the Friasian age. ...

Mariño Formarion is found, Huaquerías, defining the

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 and precedes the Montehermosan age. ...

in the Huayquerías Formation, the Aisol Formation of central Mendoza and the Uspallata Group and Carrizal Formations in the north of the province.Cerdeño, 2012, p.376 The geological characterization and the preliminary faunal list were published by Gorroño et al. (1979). The faunal assemblage was then assigned to the Late Oligocene (Deseadan SALMA) based on the presence of two typical representatives of the Deseadean fauna of Patagonia; ''

Pyrotherium ''Pyrotherium'' ('fire beast') is an extinct genus of South American ungulate, of the order Pyrotheria, that lived in what is now Argentina and Bolivia, during the Late Oligocene.Proborhyaena gigantea'' , both also found in the Puesto Almendra member of the

.Gran Blanca
in the

The species

epithet An epithet (, ), also byname, is a descriptive term (word or phrase) known for accompanying or occurring in place of a name and having entered common usage. It has various shades of meaning when applied to seemingly real or fictitious people, di ...

'' Mendozahippus fierensis'' and genus '' Fieratherium'' refer to Quebrada Fiera.Cerdeño & Reguero, 2015Seoane & Cerdeño, 2014Cerdeño & Vera, 2014a

Fossil content

The formation has provided fossils of:

SALMA correlations

The Deseadan South American land mammal age (SALMA) is equivalent to the

Arikareean The Arikareean North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology (NALMA), typically set from 30,600,000 to 20,800,000 years BP, a period of . It is usuall ...

in the

North American land mammal age The North American land mammal ages (NALMA) establishes a geologic timescale for North American fauna beginning during the Late Cretaceous and continuing through to the present. These periods are referred to as ages or intervals (or stages when ref ...

(NALMA) and the

Harrisonian The Harrisonian North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology (NALMA), typically set from 24,800,000 to 20,600,000 years BP, a period of . It is usual ...

in the 2000 version of the classification. It overlaps with the

Hsandagolian The Hsandagolian age is a period of geologic time (33.9 – 23.03 Ma) within the Oligocene epoch of the Paleogene used more specifically with Asian Land Mammal Ages. It follows the Kekeamuan and precedes the Tabenbulakian age. The Ulangochuian ...

of Asia and the MP 25 zone of Europe, the Waitakian and the Landon epoch of New Zealand.

References

Bibliography

;General * * ;Regional geology * * * * * * * * ;Oligocene volcanism * * * * * * * * ;Paleontology * CC-BY icon

Material was copied from this source, which is available under
Creative Commons Attribution 3.0 International License
* * * * CC-BY icon

Material was copied from this source, which is available under
Creative Commons Attribution 4.0 International License
* * * * * * * * * * * * * ;New World monkeys * * * ;Terror birds * * * * * * ;South American rodents * * ** ** ** * * *

Regional correlations

;Mariño Formation * ;Rancahué Formation * * ;Río Guillermo Formation * ;Deseado Formation * * ;Sarmiento Formation * * * * * * * * * * ;Salla Formation * * * ;Lacayani fauna * ;Fray Bentos Formation * * ;Moquegua Formation * * ;Chambira Formation * * * ;Barzalosa Formation * * ;Tremembé Formation * * * ;Las Cascadas Formation *