The geology of

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 ...

includes ancient Precambrian basement rock affected by the

Grenville orogeny The Grenville orogeny was a long-lived Mesoproterozoic mountain-building event associated with the assembly of the supercontinent Rodinia. Its record is a prominent orogenic belt which spans a significant portion of the North American continent, f ...

, sediment filled basins from the Mesozoic and Cenozoic as well as newly uplifted areas in the Andes.

Geologic history, stratigraphy and tectonics

The oldest rocks in Argentina date to the

Precambrian The Precambrian (or Pre-Cambrian, sometimes abbreviated pꞒ, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of the ...

. Strontium, oxygen and carbon isotope data from carbonate rocks in the Sierra de Pie de Palo are part of an

ophiolite An ophiolite is a section of Earth's oceanic crust and the underlying upper mantle that has been uplifted and exposed above sea level and often emplaced onto continental crustal rocks. The Greek word ὄφις, ''ophis'' (''snake'') is found ...

unit related to the

, formed as cover rock in the Appalachian margin of the continent

Laurentia Laurentia or the North American Craton is a large continental craton that forms the ancient geological core of North America. Many times in its past, Laurentia has been a separate continent, as it is now in the form of North America, althoug ...

around 720 million years ago. These

Neoproterozoic The Neoproterozoic Era is the unit of geologic time from 1 billion to 538.8 million years ago. It is the last era of the Precambrian Supereon and the Proterozoic Eon; it is subdivided into the Tonian, Cryogenian, and Ediacaran periods. It is ...

age rocks are believed to have formed above much older

Archean The Archean Eon ( , also spelled Archaean or Archæan) is the second of four geologic eons of Earth's history, representing the time from . The Archean was preceded by the Hadean Eon and followed by the Proterozoic. The Earth Earth ...

craton rock. Throughout the late Proterozoic, sections of Argentina were part of a metamorphic mobile belt adjacent to the Brazilian Shield. Regional metamorphism produced

scheelite Scheelite is a calcium tungstate mineral with the chemical formula Ca W O4. It is an important ore of tungsten (wolfram). Scheelite is originally named after Swedish chemist K. Scheele (1742-1786). Well-formed crystals are sought by collectors a ...

belts and

wolframite Wolframite is an iron, manganese, and tungstate mineral with a chemical formula of that is the intermediate between ferberite ( rich) and hübnerite ( rich). Along with scheelite, the wolframite series are the most important tungsten ore minerals ...

in parts of San Luis and Cordoba Provinces. To the north, along the Bolivian border in the Altiplano, drilling has revealed Precambrian Hornblende Granoblastite and biotite Granoblastite formed from magma during the Grenville orogeny 1.05 billion years ago metamorphosed around 530 million years ago. Granitoid and metamorphic rocks elsewhere in the El Cristo area in the southern Tandilia Range experienced intense folding more than two billion years ago and then metamorphosed to

almandine Almandine (), also known as almandite, is a species of mineral belonging to the garnet group. The name is a corruption of alabandicus, which is the name applied by Pliny the Elder to a stone found or worked at Alabanda, a town in Caria in Asia M ...

grade on the sequence of

metamorphic facies A metamorphic facies is a set of mineral assemblages in metamorphic rocks formed under similar pressures and temperatures.Essentials of Geology, 3rd Edition, Stephen Marshak The assemblage is typical of what is formed in conditions corresponding ...

1.8 billion years ago. Brittle deformation, granite emplacement and chloritization occurred in the formation 900 million years ago. Extremely ancient trace fossils have been found in the Puncoviscana Formation in the northwest, which grades into

gneiss Gneiss ( ) is a common and widely distributed type of metamorphic rock. It is formed by high-temperature and high-pressure metamorphic processes acting on formations composed of igneous or sedimentary rocks. Gneiss forms at higher temperatures an ...

schist Schist ( ) is a medium-grained metamorphic rock showing pronounced schistosity. This means that the rock is composed of mineral grains easily seen with a low-power hand lens, oriented in such a way that the rock is easily split into thin flakes o ...

and

migmatite Migmatite is a composite rock found in medium and high-grade metamorphic environments, commonly within Precambrian cratonic blocks. It consists of two or more constituents often layered repetitively: one layer is an older metamorphic rock th ...

, as well as conglomerates, pelagic clay and volcanic rocks. Large areas of Argentina were part of the supercontinent

Gondwana Gondwana () was a large landmass, often referred to as a supercontinent, that formed during the late Neoproterozoic (about 550 million years ago) and began to break up during the Jurassic period (about 180 million years ago). The final stages ...

, inferred from detrital

zircon Zircon () is a mineral belonging to the group of nesosilicates and is a source of the metal zirconium. Its chemical name is zirconium(IV) silicate, and its corresponding chemical formula is Zr SiO4. An empirical formula showing some of the r ...

grains.

Paleozoic (539-251 million years ago)

In the

Paleozoic The Paleozoic (or Palaeozoic) Era is the earliest of three geologic eras of the Phanerozoic Eon. The name ''Paleozoic'' ( ;) was coined by the British geologist Adam Sedgwick in 1838 by combining the Greek words ''palaiós'' (, "old") and ' ...

, Argentina was located at a point in western Gondwana where the current African and South American cratons joined.

Graywacke Greywacke or graywacke (German ''grauwacke'', signifying a grey, earthy rock) is a variety of sandstone generally characterized by its hardness, dark color, and poorly sorted angular grains of quartz, feldspar, and small rock fragments or lit ...

samples from the Puncoviscana Formation have zircon age patterns that suggest the crystals eroded out of active-margin mountain belts in the Brazilian Shield. Ice ages occurred in the

Carboniferous The Carboniferous ( ) is a geologic period and system of the Paleozoic that spans 60 million years from the end of the Devonian Period million years ago ( Mya), to the beginning of the Permian Period, million years ago. The name ''Carbonifero ...

and

Early Permian 01 or '01 may refer to: * The year 2001, or any year ending with 01 * The month of January * 1 (number) Music * '01 (Richard Müller album), 01'' (Richard Müller album), 2001 * 01 (Son of Dave album), ''01'' (Son of Dave album), 2000 * 01 (Urban ...

in two main glacial periods. Carboniferous glacial deposits are well preserved in the San Eduardo Group in the western side of the Precordillera. The discovery of glacial deposits and marine sediments far east of the main deposits suggests that global changes in climate and latitude played a bigger role than altitude in the ice ages. The Rio Blanco Basin and Paganzo Basin in western Argentina include sedimentary sequences that from bottom to top include marine sediments, an erosional surface with conglomerate, fluvial and shallow marine deposits, shale and diamictite, as well as shallow marine and glacial outwash deposits.

Mesozoic (251-66 million years ago)

During the

Mesozoic The Mesozoic Era ( ), also called the Age of Reptiles, the Age of Conifers, and colloquially as the Age of the Dinosaurs is the second-to-last era of Earth's geological history, lasting from about , comprising the Triassic, Jurassic and Cretaceo ...

, basins formed in what would become the Andean foothills, due to strike-slip movement and continental extension. The Choiyoi Group is a remnant of bimodal magmatism along a Paleozoic terrane suture. As the breakup of Gondwana began, narrow half-grabens filled with volcaniclastic rocks and the Pampa de Agnia Basin formed along the Gastre fault system. The Magallenes Basin experienced rifting and the Chon Aike province witnessed intraplate volcanism during the acceleration of the breakup around 180 to 165 million years ago, as the Weddell Sea opened. Explosive volcanism occurred in back arc basins through the Jurassic and low oxygen conditions prevailed in the Neuquen Basin sedimentary environment. Compressional tectonic forces were the norm in Argentine Tierra del Fuego. The volcanite and breccia of the Lemaire Formation, deep marine

andesite Andesite () is a volcanic rock of intermediate composition. In a general sense, it is the intermediate type between silica-poor basalt and silica-rich rhyolite. It is fine-grained (aphanitic) to porphyritic in texture, and is composed predomi ...

turbidite A turbidite is the geologic deposit of a turbidity current, which is a type of amalgamation of fluidal and sediment gravity flow responsible for distributing vast amounts of clastic sediment into the deep ocean. Sequencing Turbidites wer ...

of the Yahgan Formation, and slope mudstones of the Beauvoir Formation were metamorphosed in the Rocas Verdes Marginal Basin. The Malvinas and Austral basins originated during uplift of the region in the

Campanian The Campanian is the fifth of six ages of the Late Cretaceous Epoch on the geologic timescale of the International Commission on Stratigraphy (ICS). In chronostratigraphy, it is the fifth of six stages in the Upper Cretaceous Series. Campanian s ...

Cenozoic (66 million years ago-present)

250px, Tilted strata of the Yacoraite_Formation_at_Serranía_de_Hornocal_in_northernmost_Argentina._The_ Yacoraite_Formation_at_Serranía_de_Hornocal_in_northernmost_Argentina._The_Andean_orogeny">Serranía_de_Hornocal.html"_;"title="Yacoraite_Formation_at_Serranía_de_Hornocal">Yacoraite_Formation_at_Serranía_de_Hornocal_in_northernmost_Argentina._The_Andean_orogeny_caused_the_tilting_of_these_Principle_of_original_horizontality.html" ;"title="Andean_orogeny.html" ;"title="Serranía_de_Hornocal.html" ;"title="Yacoraite Formation at Serranía de Hornocal">Yacoraite Formation at Serranía de Hornocal in northernmost Argentina. The Andean orogeny">Serranía_de_Hornocal.html" ;"title="Yacoraite Formation at Serranía de Hornocal">Yacoraite Formation at Serranía de Hornocal in northernmost Argentina. The Andean orogeny caused the tilting of these Principle of original horizontality">originally horizontal strata. The Andean orogeny has been a dominant process through the Cenozoic in Argentina. Rifting and fault (geology)), strike-slip faulting in weak Cretaceous magmatic arc rocks was reactivated with the

subduction Subduction is a geological process in which the oceanic lithosphere is recycled into the Earth's mantle at convergent boundaries. Where the oceanic lithosphere of a tectonic plate converges with the less dense lithosphere of a second plate, the ...

of the Nazca Plate under South America around nine million years ago. Uplift began around seven million years ago in the Sierra Pampeanas, a group of reverse fault-bounded Precambrian and Paleozoic rocks in the central Andes

foreland basin A foreland basin is a structural basin that develops adjacent and parallel to a mountain belt. Foreland basins form because the immense mass created by crustal thickening associated with the evolution of a mountain belt causes the lithospher ...

. To the south, in Tierra del Fuego, turbidites accumulated in the basins formed in the late Cretaceous, producing the

Paleocene The Paleocene, ( ) or Palaeocene, is a geological epoch (geology), epoch that lasted from about 66 to 56 mya (unit), million years ago (mya). It is the first epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), E ...

Río Claro Group, the

Eocene The Eocene ( ) Epoch is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene' ...

La Despedida Group and the

Oligocene The Oligocene ( ) is a geologic epoch of the Paleogene Period and extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that define the epoch are well identified but the ...

Cabo Domingo Group. Outside of Antarctica, the chronology of the Patagonian glaciers is the best documented in the Southern Hemisphere. Glaciation began around seven million years ago in the

Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recen ...

and

Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58Great Patagonian Glaciations in the early

Pleistocene The Pleistocene ( , often referred to as the ''Ice age'') is the geological Epoch (geology), epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fina ...

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 and

loess Loess (, ; from german: Löss ) is a clastic, predominantly silt-sized sediment that is formed by the accumulation of wind-blown dust. Ten percent of Earth's land area is covered by loess or similar deposits. Loess is a periglacial or aeolian ...

formed in the Pampas, very similar to sediments in northern China although less well preserved.

References

{{South America topic, Geology of