Oceanic-continental convergence Fig21oceancont

The Andean orogeny ( es, Orogenia andina) is an ongoing process of

orogeny Orogeny is a mountain building process. An orogeny is an event that takes place at a convergent plate margin when plate motion compresses the margin. An ''orogenic belt'' or ''orogen'' develops as the compressed plate crumples and is uplifted t ...

that began in the Early Jurassic and is responsible for the rise of the

Andes mountains The Andes, Andes Mountains or Andean Mountains (; ) are the List of mountain ranges#Mountain ranges by length, longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range i ...

. The orogeny is driven by a reactivation of a long-lived subduction system along the western margin of

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the southe ...

. On a continental scale the

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...

(90 Ma) and

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 ...

(30 Ma) were periods of re-arrangements in the orogeny. Locally the details of the nature of the orogeny varies depending on the segment and the geological period considered.

Overview

Subduction orogeny has been occurring in what is now western South America since the break-up of the supercontinent

Rodinia Rodinia (from the Russian родина, ''rodina'', meaning "motherland, birthplace") was a Mesoproterozoic and Neoproterozoic supercontinent that assembled 1.26–0.90 billion years ago and broke up 750–633 million years ago. were probably ...

in the Neoproterozoic. 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 ' ...

Pampean, Famatinian and Gondwanan orogenies are the immediate precursors to the later Andean orogeny.Charrier ''et al''. 2006, pp. 113–114. The first phases of Andean orogeny in the

Jurassic The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The J ...

and

Early Cretaceous The Early Cretaceous ( geochronological name) or the Lower Cretaceous (chronostratigraphic name), is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 145 Ma to 100.5 Ma. Geology Pro ...

were characterized by

extensional tectonics Extensional tectonics is concerned with the structures formed by, and the tectonic processes associated with, the stretching of a planetary body's crust or lithosphere. Deformation styles The types of structure and the geometries formed depend on ...

, rifting, the development of

back-arc basin A back-arc basin is a type of geologic basin, found at some convergent plate boundaries. Presently all back-arc basins are submarine features associated with island arcs and subduction zones, with many found in the western Pacific Ocean. Most of ...

s and the emplacement of large

batholith A batholith () is a large mass of intrusive igneous rock (also called plutonic rock), larger than in area, that forms from cooled magma deep in Earth's crust. Batholiths are almost always made mostly of felsic or intermediate rock types, such ...

s. This development is presumed to have been linked to the subduction of cold

oceanic Oceanic may refer to: *Of or relating to the ocean *Of or relating to Oceania **Oceanic climate **Oceanic languages **Oceanic person or people, also called "Pacific Islander(s)" Places * Oceanic, British Columbia, a settlement on Smith Island, ...

lithosphere A lithosphere () is the rigid, outermost rocky shell of a terrestrial planet or natural satellite. On Earth, it is composed of the crust (geology), crust and the portion of the upper mantle (geology), mantle that behaves elastically on time sca ...

. During the mid to

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', the ...

(ca. 90 million years ago) the Andean orogeny changed significantly in character. Warmer and younger oceanic lithosphere is believed to have started to be subducted beneath South America around this time. Such kind of subduction is held responsible not only for the intense contractional deformation that different lithologies were subject to, but also the

uplift Uplift may refer to: Science * Geologic uplift, a geological process ** Tectonic uplift, a geological process * Stellar uplift, the theoretical prospect of moving a stellar mass * Uplift mountains * Llano Uplift * Nemaha Uplift Business * Uplif ...

and

erosion Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited. Erosion is distin ...

known to have occurred from the Late Cretaceous onward.

Plate tectonic Plate tectonics (from the la, label=Late Latin, tectonicus, from the grc, τεκτονικός, lit=pertaining to building) is the generally accepted scientific theory that considers the Earth's lithosphere to comprise a number of large te ...

reorganization since the mid-Cretaceous might also have been linked to the

opening Opening may refer to: * Al-Fatiha, "The Opening", the first chapter of the Qur'an * The Opening (album), live album by Mal Waldron * Backgammon opening * Chess opening * A title sequence or opening credits * , a term from contract bridge * , ...

of the South Atlantic Ocean. Another change related to mid-Cretaceous plate tectonic changes was the change of subduction direction of the oceanic lithosphere that went from having south-east motion to having a north-east motion at about 90 million years ago. While subduction direction changed it remained oblique (and not perpendicular) to the coast of South America, and the direction change affected several

subduction zone 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 ...

-parallel faults including Atacama, Domeyko and Liquiñe-Ofqui.Charrier ''et al''. 2006, pp. 45–46. Paleogeography Gondwana - Late Cretaceous-Early Paleogene - around 85-63 Ma

Paleogeography Gondwana - Late Cretaceous-Early Paleogene - around 85-63 Ma

Low angle subduction or

flat-slab subduction Flat slab subduction is characterized by a low subduction angle (<30 degrees to horizontal) beyond the

seismogenic layer ...

has been common during the Andean orogeny leading to crustal shortening and deformation and the suppression of

arc volcanism A volcanic arc (also known as a magmatic arc) is a belt of volcanoes formed above a subducting oceanic tectonic plate, with the belt arranged in an arc shape as seen from above. Volcanic arcs typically parallel an oceanic trench, with the arc l ...

. Flat-slab subduction has occurred at different times in various part of the Andes, with northern Colombia (6–10° N), Ecuador (0–2° S), northern Peru (3–13° S) and north-central Chile (24–30° S) experiencing these conditions at present. The tectonic growth of the Andes and the regional climate have evolved simultaneously and have influenced each other. The topographic barrier formed by the Andes stopped the income of humid air into the present Atacama desert. This aridity, in turn, changed the normal superficial redistribution of mass via erosion and river transport, modifying the later tectonic deformation. In the Oligocene the

Farallon Plate The Farallon Plate was an ancient oceanic plate. It formed one of the three main plates of Panthalassa, alongside the Phoenix Plate and Izanagi Plate, which were connected by a triple junction. The Farallon Plate began subducting under the west c ...

broke up, forming the modern Cocos and

Nazca Nazca (; sometimes spelled Nasca; qu, Naska) is a city and system of valleys on the southern coast of Peru. It is also the name of the largest existing town in the Nazca Province. The name is derived from the Nazca culture, which flourished in ...

plates ushering a series of changes in the Andean orogeny. The new Nazca Plate was then directed into an orthogonal subduction with South America causing ever-since uplift in the Andes, but causing most impact 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 ...

. While the various segments of the Andes have their own uplift histories, as a whole the Andes have risen significantly in last 30 million years (

–present).

Orogeny by segment

Colombia, Ecuador and Venezuela (12° N–3° S)

Tectonic blocks of continental crust that had separated from northwestern South America in the Jurassic re-joined the continent in the Late Cretaceous by colliding obliquely with it. This episode of

accretion Accretion may refer to: Science * Accretion (astrophysics), the formation of planets and other bodies by collection of material through gravity * Accretion (meteorology), the process by which water vapor in clouds forms water droplets around nucl ...

occurred in a complex sequence. The accretion of the island arcs against northwestern South America in the Early Cretaceous led to the development of a

magmatic arc Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma is found beneath the surface of the Earth, and evidence of magmatism has also been discovered on other terrestrial planets and some natural sa ...

caused by subduction. The Romeral Fault in Colombia forms the suture between the accreted terranes and the rest of South America. Around the Cretaceous–

Paleogene The Paleogene ( ; British English, also spelled Palaeogene or Palæogene; informally Lower Tertiary or Early Tertiary) is a geologic period, geologic period and system that spans 43 million years from the end of the Cretaceous Period million yea ...

boundary (ca. 65 million years ago) the

oceanic plateau An oceanic or submarine plateau is a large, relatively flat elevation that is higher than the surrounding relief with one or more relatively steep sides. There are 184 oceanic plateaus in the world, covering an area of or about 5.11% of the ...

of the Caribbean large igneous province collided with South America. The subduction of the

as the oceanic plateau approached South America led to the formation of a magmatic arc now preserved in the Cordillera Real of Ecuador and the

Cordillera Central Central Cordillera refers to the New Guinea Highlands. Cordillera Central, meaning ''central range'' in Spanish, may refer to the following mountain ranges: * Cordillera Central, Andes (disambiguation), several mountain ranges in South America ** ...

of Colombia. In the Miocene an island arc and

terrane In geology, a terrane (; in full, a tectonostratigraphic terrane) is a crust fragment formed on a tectonic plate (or broken off from it) and accreted or " sutured" to crust lying on another plate. The crustal block or fragment preserves its own ...

(Chocó terrane) collided against northwestern South America. This terrane forms parts of what is now Chocó Department and Western

Panamá Panama ( , ; es, link=no, Panamá ), officially the Republic of Panama ( es, República de Panamá), is a transcontinental country spanning the southern part of North America and the northern part of South America. It is bordered by Cost ...

. The

Caribbean Plate The Caribbean Plate is a mostly oceanic tectonic plate underlying Central America and the Caribbean Sea off the north coast of South America. Roughly 3.2 million square kilometers (1.2 million square miles) in area, the Caribbean Plate borders ...

collided with South America in the Early Cenozoic but shifted then its movement eastward.

Dextral Sinistral and dextral, in some scientific fields, are the two types of chirality ("handedness") or relative direction. The terms are derived from the Latin words for "left" (''sinister'') and "right" (''dexter''). Other disciplines use different ...

fault movement between the South American and Caribbean plate started 17–15 million years ago. This movement was canalized along a series of

strike-slip In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tectonic ...

faults, but these faults alone do not account for all deformation. The northern part of the

Dolores-Guayaquil Megashear The Dolores-Guayaquil Megashear ( es, Megafalla Dolores-Guayaquil ) is a first-order shear zone and fault zone in Northern South America. The megashear runs from the Gulf of Guayaquil in southwestern Ecuador, through Colombia, to Dolores in Venezu ...

forms part of the dextral fault systems while in the south the megashear runs along the suture between the accreted tectonic blocks and the rest of South America.

Northern Peru (3–13° S)

Long before the Andean orogeny the northern half of Peru was subject of the

s in the Neoproterozoic and

. Andean orogenic deformation in northern Peru can be traced to the Albian (Early Cretaceous). This first phase of deformation —the Mochica Phase— is evidenced in the

fold Fold, folding or foldable may refer to: Arts, entertainment, and media * ''Fold'' (album), the debut release by Australian rock band Epicure *Fold (poker), in the game of poker, to discard one's hand and forfeit interest in the current pot *Above ...

ing of

Casma Group The Casma Group ( es, Grupo Casma) is a stratigraphic group of Cretaceous (Albian to Cenomanian) sedimentary formations exposed along the coast and within the Cordillera Occidental near Casma, Peru. Description The sediments of the Casma Group ...

sediments near the coast. Sedimentary basins in western Peru changed from marine to continental conditions in the

as a consequence of a generalized vertical uplift. The uplift in northern Peru is thought to be associated with the contemporary accretion of the Piñón

in Ecuador. This stage of orogeny is called the Peruvian Phase. Besides coastal Peru the Peruvian Phase affected or caused crustal shortening along the Cordillera Oriental and the

tectonic inversion In structural geology inversion or basin inversion relates to the relative uplift of a sedimentary basin or similar structure as a result of crustal shortening. This normally excludes uplift developed in the footwalls of later extensional faul ...

of Santiago Basin in the Sub-Andean zone. The bulk of the Sub-Andean zone was however unaffected by the Peruvian Phase. After a period without much tectonic activity in the Early Eocene the Incaic Phase of orogeny occurred in the Mid and Late Eocene. No other tectonic event in the western Peruvian Andes compare with the Incaic Phase in magnitude. Horizontal shortening during the Incaic Phase resulted in the formation of the

Marañón fold and thrust belt The Marañón fold and thrust belt ( es, faja corrida y plegada del Marañón) is a long, northwest–southeast trending belt of deformed rocks located in the Andes of central Peru. The formation of the belt defines the Incaic Phase of the Andean ...

. An

unconformity An unconformity is a buried erosional or non-depositional surface separating two rock masses or strata of different ages, indicating that sediment deposition was not continuous. In general, the older layer was exposed to erosion for an interval o ...

cutting across the Marañón fold and thrust belt show the Incaic Phase ended no later than 33 million years ago in the earliest Oligocene. Nasa_anden

In the period after the Eocene the Northern Peruvian Andes were subject to the Quechua Phase of orogeny. The Quechua Phase is divided into the sub-phases Quechua 1, Quechua 2 and Quechua 3. The Quechua 1 Phase lasted from 17 to 15 million years ago and included a reactivation of Inca Phase structures in the Cordillera Occidental. 9–8 million years ago, in the Quechua 2 Phase, the older parts of the Andes in northern Peru were thrusted to the northeast. Most of the Sub-Andean zone of northern Peru deformed 7–5 million years ago (Late Miocene) during the Quechua 3 Phase. The Sub-Andean stacked in a thrust belt. The Miocene rise of the Andes in Peru and Ecuador led to increased

orographic precipitation Orography is the study of the topographic relief of mountains, and can more broadly include hills, and any part of a region's elevated terrain. Orography (also known as ''oreography'', ''orology'' or ''oreology'') falls within the broader discipl ...

along its eastern parts and to the birth of the modern

Amazon River The Amazon River (, ; es, Río Amazonas, pt, Rio Amazonas) in South America is the largest river by discharge volume of water in the world, and the disputed longest river system in the world in comparison to the Nile. The headwaters of t ...

. One

hypothesis A hypothesis (plural hypotheses) is a proposed explanation for a phenomenon. For a hypothesis to be a scientific hypothesis, the scientific method requires that one can test it. Scientists generally base scientific hypotheses on previous obse ...

links these two changes by assuming that increased precipitation led to increased

and this erosion led to filling the

Andean foreland basins The Andean foreland basins or Sub-Andean basins are a group of foreland basins located in the western half of South America immediately east of the Andes mountains. The Andean foreland basins in the Amazon River's catchment area are known as the A ...

beyond their capacity and that it would have been the basin over-sedimentation rather than the rise of the Andes that made

drainage basin A drainage basin is an area of land where all flowing surface water converges to a single point, such as a river mouth, or flows into another body of water, such as a lake or ocean. A basin is separated from adjacent basins by a perimeter, t ...

s flow to the east. Previously the interior of northern South America drained to the Pacific.

Bolivian Orocline (13–26° S)

Early Andean subduction in the Jurassic formed a volcanic arc in northern Chile known as La Negra Arc. The remnants of this arc are now exposed in the

Chilean Coast Range The Chilean Coastal Range ( es, Cordillera de la Costa) is a mountain range that runs from north to south along the Pacific coast of South America parallel to the Andean Mountains, extending from Morro de Arica in the north to Taitao Peninsula, ...

. Several

pluton In geology, an igneous intrusion (or intrusive body or simply intrusion) is a body of intrusive igneous rock that forms by crystallization of magma slowly cooling below the surface of the Earth. Intrusions have a wide variety of forms and com ...

s were emplaced in the Chilean Coast Range in the Jurassic and Early Cretaceous including the

Vicuña Mackenna Batholith The Vicuña Mackenna Batholith ( es, Batolito Vicuña Mackenna) is a group of plutons in the Chilean Coast Range of northern Chile. The plutons of the batholith formed (cooled from magma to rock) between the Early Jurassic and the Late Cretaceous ...

.Charrier ''et al''. 2006, pp. 47–48. Further east at similar latitudes, in Argentina and Bolivia, the Salta rift system developed during the Late Jurassic and the Early Cretaceous.

Pisco Basin Pisco Basin ( es, Cuenca de Pisco) is a sedimentary basin extending over in southwestern Peru.Solís Mundaca, 2018, p.1 The basin has a thick sedimentary fill, which is about half the thickness of more northern foreland basins in Peru. The old ...

, around latitude 14° S, was subject to a

marine transgression A marine transgression is a geologic event during which sea level rises relative to the land and the shoreline moves toward higher ground, which results in flooding. Transgressions can be caused by the land sinking or by the ocean basins filling ...

in the

and Early Miocene epochs (25–16 Ma). In contrast Moquegua Basin to the southeast and the coast to south of Pisco Basin saw no transgression during this time but a steadily rise of the land. From the

Late Miocene The Late Miocene (also known as Upper Miocene) is a sub-epoch of the Miocene epoch (geology), Epoch made up of two faunal stage, stages. The Tortonian and Messinian stages comprise the Late Miocene sub-epoch, which lasted from 11.63 Ma (million ye ...

onward the region that would become the

Altiplano The Altiplano (Spanish for "high plain"), Collao (Quechua and Aymara: Qullaw, meaning "place of the Qulla") or Andean Plateau, in west-central South America, is the most extensive high plateau on Earth outside Tibet. The plateau is located at the ...

rose from low elevations to more than 3,000

m.a.s.l. Height above mean sea level is a measure of the vertical distance (height, elevation or altitude) of a location in reference to a historic mean sea level taken as a vertical datum. In geodesy, it is formalized as ''orthometric heights''. The com ...

It is estimated that the region rose 2000 to 3000 meters in the last ten million years.Charrier ''et al''. 2006, pp. 100–101. Together with this uplift several valleys incised in the western flank of the Altiplano. In the Miocene the Atacama Fault moved, uplifting the Chilean Coast Range and creating sedimentary basins east of it.Charrier ''et al''. 2006, p. 97. At the same time the Andes around the Altiplano region broadened to exceed any other Andean segment in width. Possibly about 1000 km of

has been lost due to lithospheric shortening. During subduction the western end of the

forearc Forearc is a plate tectonic term referring to a region between an oceanic trench, also known as a subduction zone, and the associated volcanic arc. Forearc regions are present along a convergent margins and eponymously form 'in front of' the vol ...

region flexured downward forming a giant

monocline A monocline (or, rarely, a monoform) is a step-like fold in rock strata consisting of a zone of steeper dip within an otherwise horizontal or gently-dipping sequence. Formation Monoclines may be formed in several different ways (see diagram) * ...

. By contrast the region east of the Altiplano is characterized by deformation and tectonics along a complex fold and thrust belt. Over-all the region surrounding the Altiplano and Puna plateaux has been horizontally shortened since 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' ...

. file:Lake-Titicaca-from-Ancohuma.JPG, left, 250px, The

and Lake Titicaca, its largest lake as seen from Janq'u Uma, Ancohuma. The uplift of the Altiplano plateau is one of the most striking features of the Andean orogeny. In southern Bolivia lithospheric shortening has made the Andean foreland basins, Andean foreland basin to move eastward relative to the continent at an average rate of ca. 12–20 mm per year during most of the Cenozoic. Along the Argentine Northwest the Andean uplift has caused Andean foreland basins to separate into several minor isolated intermontane sedimentary basins. Towards the east the piling up of crust in Bolivia and the Argentine Norwest caused a north-south

forebulge In geology, a forebulge is a flexural bulge in front as a result of a load on the lithosphere, often caused by tectonic interactions and glaciations. An example of forebulge can be seen in the Himalayan foreland basin, a result of the Indian-Euras ...

known as Asunción arch to develop in Paraguay. The uplift of the Altiplano is thought to be indebted to a combination of horizontal shortening of the crust and to increased temperatures in the mantle (thermal thinning). The bend in the Andes and the west coast of South America known as the

Bolivian Orocline An orocline — from the Greek words for "mountain" and "to bend" — is a bend or curvature of an orogenic (mountain building) belt imposed after it was formed. The term was introduced by S. Warren Carey in 1955 in a paper setting forth how comp ...

was enhanced by Cenozoic horizontal shortening but existed already independently of it. Besides direct causes the particular characteristics of the Bolivian Orocline–Altiplano region are attributed to a variety of deeper causes. These causes include a local steepening of the subduction angle of Nazca Plate, increased crustal shortening and plate convergence between the Nazca and South American plates, an acceleration in the westward drift of the South American Plate, and a rise in the

shear stress Shear stress, often denoted by (Greek: tau), is the component of stress coplanar with a material cross section. It arises from the shear force, the component of force vector parallel to the material cross section. ''Normal stress'', on the ot ...

between the Nazca and South American plates. This increase in shear stress could in turn be related to the scarcity of sediments in the

Atacama trench The Atacama Desert ( es, Desierto de Atacama) is a desert plateau in South America covering a 1,600 km (990 mi) strip of land on the Pacific coast, west of the Andes Mountains. The Atacama Desert is the driest nonpolar desert in the ...

which is caused by the arid conditions along Atacama Desert. Capitanio ''et al''. attributes the rise of Altiplano and the bending of the Bolivian Orocline to the varying ages of the subducted Nazca Plate with the older parts of the plate subducting at the centre of the orocline. As Andrés Tassara puts it the rigidity of the Bolivian Orocline crust is derivative of the thermal conditions. The crust of the western region (

) of the orocline has been cold and rigid, resisting and damming up the westward flow of warmer and weaker ductile crustal material from beneath the Altiplano. The Cenozoic orogeny at the Bolivian orocline has produced a significative

anatexis Anatexis (via Latin from Greek roots meaning "to melt down") is the partial melting of rocks. Traditionally, anatexis is used specifically to discuss the partial melting of crustal rocks, while the generic term "partial melting" refers to the part ...

of crustal rocks including metasediments and

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 ...

es resulting in the formation of peraluminous

magma Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma is found beneath the surface of the Earth, and evidence of magmatism has also been discovered on other terrestrial planets and some natural sa ...

s. These characteristics imply that the Cenozoic tectonics and magmatism in parts of Bolivian Andes is similar to that seen in collisional orogens. The peralumineous magmatism in Cordillera Oriental is the cause of the world-class

mineralization Mineralization may refer to: * Mineralization (biology), when an inorganic substance precipitates in an organic matrix ** Biomineralization, a form of mineralization ** Mineralization of bone, an example of mineralization ** Mineralized tissues are ...

s of the

Bolivian tin belt The Bolivian tin belt ( es, Cinturón estanifero boliviano, provincia estannifera boliviana) is a mineral-rich region in the Cordillera Oriental of Bolivia. Being a metallogenetic province the Bolivian tin belt is rich in tin, tungsten, silver an ...

. 250px, Tilted strata of the Yacoraite Formation at Serranía de Hornocal in northernmost Argentina. The Andean orogeny caused the tilting of these originally horizontal strata.">Principle of original horizontality">originally horizontal strata. The rise of the Altiplano is thought by scientist Adrian Hartley to have enhanced an already prevailing

aridity A region is arid when it severely lacks available water, to the extent of hindering or preventing the growth and development of plant and animal life. Regions with arid climates tend to lack vegetation and are called xeric or desertic. Most ar ...

or semi-aridity in Atacama Desert by casting a

rain shadow A rain shadow is an area of significantly reduced rainfall behind a mountainous region, on the side facing away from prevailing winds, known as its leeward side. Evaporated moisture from water bodies (such as oceans and large lakes) is carrie ...

over the region.

Central Chile and Western Argentina (26–39° S)

At the latitudes between 17 and 39° S the Late Cretaceous and Cenozoic development of the Andean orogeny is characterized by an eastward migration of the magmatic belt and the development of several foreland basins. The eastward migration of the arc is thought to be caused by

subduction erosion Tectonic erosion or subduction erosion is the loss of crust from an overriding tectonic plate due to subduction. Two types of tectonic erosion exist: frontal erosion at the outer margin of a plate and basal erosion at the base of the plate's cru ...

.Charrier ''et al''. 2006, p. 21. At the latitudes of 32–36° S —that is

Central Chile Central Chile (''Zona central'') is one of the five natural regions into which CORFO divided continental Chile in 1950. It is home to a majority of the Chilean population and includes the three largest metropolitan areas—Santiago, Valparaís ...

and most of Mendoza Province— the Andean orogeny proper began in the Late Cretaceous when

backarc basin A back-arc basin is a type of geologic Structural basin, basin, found at some convergent boundary, convergent plate boundaries. Presently all back-arc basins are submarine features associated with island arcs and subduction zones, with many found ...

s were inverted. Immediately east of the early Andes foreland basins developed and their flexural subsidence caused the ingression of waters from the Atlantic all the way to the front of the orogen in the

Maastrichtian The Maastrichtian () is, in the ICS geologic timescale, the latest age (uppermost stage) of the Late Cretaceous Epoch or Upper Cretaceous Series, the Cretaceous Period or System, and of the Mesozoic Era or Erathem. It spanned the interval from ...

. The Andes at the latitudes of 32–36° S experienced a sequence of uplift in the Cenozoic that started in the west and spread to the east. Beginning about 20 million years ago in the

the

Principal Cordillera Principal Cordillera ( es, Cordillera Principal) is the Andean mountain range that makes up the boundary between Central Chile and neighbouring areas of Argentina. It is also a continental divide between the Atlantic and the Pacific watersheds. ...

(east of Santiago) began an uplift that lasted until about 8 million years ago. From the Eocene to the early Miocene, sediments accumulated in the Abanico Extensional Basin, a north-south elongated basin in Chile that spanned from 29° to 38° S. Tectonic inversion from 21 to 16 million years ago made the basin to collapse and the sediments to be incorporated to the Andean cordillera.Charrier ''et al''. 2006, pp. 93–94. Lavas and volcanic material that are now part of Farellones Formation accumulated while the basin was being inverted and uplifted. The Miocene

continental divide A continental divide is a drainage divide on a continent such that the drainage basin on one side of the divide feeds into one ocean or sea, and the basin on the other side either feeds into a different ocean or sea, or else is endorheic, not ...

was about 20 km to the west of the modern water divide that makes up the Argentina–Chile border. Subsequent river incision shifted the divide to the east leaving old flattish surfaces hanging. Compression and uplift in this part of the Andes has continued into the present. The Principal Cordillera had risen to heights that allowed for the development of valley glaciers about 1 million years ago. Before the Miocene uplift of the Principal Cordillera was over, the

Frontal Cordillera The Frontal Cordillera ( es, Cordillera Frontal) is a mountain range in western Argentina that forms part of the Andes. It extends in a north–south direction in the provinces of La Rioja La Rioja () is an autonomous community and province i ...

to the east started a period of uplift that lasted from 12 to 5 million years ago. Further east the

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 ...

was uplifted in the last 10 million years and the

Sierras Pampeanas The Sierras Pampeanas (also called Central Sierras or Pampas Sierras) (English: Pampas Mountains) is a geographical region of Argentina. The Sierras Pampeanas are a chain of mountains that rise sharply from the surrounding pampa region of ...

has experienced a similar uplift in the last 5 million years. The more eastern part of the Andes at these latitudes had their geometry controlled by ancient faults dating to the San Rafael orogeny of the

. The

Sierras de Córdoba The Sierras de Córdoba is a mountain range in central Argentina, located between the Pampas to the east and south and the Chaco to the north and east. Most of the range is located in Córdoba Province, except for the southwestern margin whic ...

(part of the Sierras Pampeanas) where the effects of the ancient

Pampean orogeny The Pampean orogeny ( es, orogenia pampeana) was an orogeny active in the Cambrian in the western margin of the ancient landmass of Gondwana. The orogen's remains can now be observed in central Argentina, in particular at the Sierras de Córdoba an ...

can be observed, owes it modern uplift and relief to the Andean orogeny in the late

Cenozoic The Cenozoic ( ; ) is Earth's current geological era, representing the last 66million years of Earth's history. It is characterised by the dominance of mammals, birds and flowering plants, a cooling and drying climate, and the current configura ...

. Similarly the

San Rafael Block The San Rafael Block or San Rafael Massif (Spanish: ''Bloque de San Rafael'' or ''Macizo de San Rafael'') is an uplifted area in central Mendoza Province, Argentina. The San Rafael Block is both a geographic and a tectonic unit. From a tectonostra ...

east of the Andes and south of Sierras Pampeanas was raised in the Miocene during the Andean orogeny. In broad terms the most active phase of orogeny in area of southern Mendoza Province and northern Neuquén Province (34–38° S) happened in the Late Miocene while

occurred east of the Andes. At more southern latitudes (36–39° S) various Jurassic and Cretaceous

s from the Pacific are recorded in the sediments of

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 the Late Cretaceous conditions changed. A

marine regression A marine regression is a geological process occurring when areas of submerged seafloor are exposed above the sea level. The opposite event, marine transgression, occurs when flooding from the sea covers previously-exposed land. Evidence of marine ...

occurred and the fold and thrust belts of Malargüe (36°00 S), Chos Malal (37° S) and Agrio (38° S) started to develop in the Andes and did so in until

times. This meant an advance of the orogenic deformation since the Late Cretaceous that caused the western part of

to stack in the Malargüe and Agrio fold and thrust belts. In the

the western part of the fold and thrust belt was subject to a short period of

whose structures were inverted in the

. After a period of quiescence the Agrio fold and thrust belt resumed limited activity in the Eocene and then again in the Late Miocene. In the south of Mendoza Province the Guañacos fold and thrust belt (36.5° S) appeared and grew in the

Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58Pleistocene 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 ...

consuming the western fringes of the Neuquén Basin.

Northern Patagonian Andes (39–48° S)

Southern Patagonian Andes (48–55° S)

The early development of the Andean orogeny in southernmost South America affected also the

Antarctic Peninsula The Antarctic Peninsula, known as O'Higgins Land in Chile and Tierra de San Martín in Argentina, and originally as Graham Land in the United Kingdom and the Palmer Peninsula in the United States, is the northernmost part of mainland Antarctic ...

. In southern Patagonia at the onset of the Andean orogeny in the

created the Rocas Verdes Basin, a

whose southeastern extension survives as the Weddell Sea in Antarctica. In the

the tectonic regime of Rocas Verdes Basin changed leading to its transformation into a compressional

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 ...

–the

Magallanes Basin The Magallanes Basin or Austral Basin is a major sedimentary basin in southern Patagonia. The basin covers a surface of about and has a NNW-SSE oriented shape. The basin is bounded to the west by the Andes mountains and is separated from the Malv ...

– in the

. This change was associated with an eastward move of the basin

depocenter A depocenter or depocentre in geology is the part of a sedimentary basin where a particular rock unit has its maximum thickness. Depending on the controls on subsidence and the sedimentary environment the location of basin depocenters may vary with ...

and the

obduction Obduction is a geological process whereby denser oceanic crust (and even upper mantle) is scraped off a descending ocean plate at a convergent plate boundary and thrust on top of an adjacent plate. When oceanic and continental plates converge, ...

of ophiolites. The closure of Rocas Verdes Basin in the Cretaceous is linked to the high-grade metamorphism of

Cordillera Darwin Metamorphic Complex The Cordillera Darwin Metamorphic Complex is a geologic complex composed chiefly of metamorphic rocks located in southern Tierra del Fuego. It has been suggested that the Cordillera Darwin Metamorphic Complex is analogous to the Eastern Andes Me ...

in southern

Tierra del Fuego Tierra del Fuego (, ; Spanish for "Land of the Fire", rarely also Fireland in English) is an archipelago off the southernmost tip of the South American mainland, across the Strait of Magellan. The archipelago consists of the main island, Isla G ...

. As the Andean orogeny went on, South America drifted away from Antarctica during the Cenozoic leading first to the formation of an isthmus and then to the opening of the Drake Passage 45 million years ago. The separation from Antarctica changed the tectonics of the Fuegian Andes into a transpressive regime with

transform fault A transform fault or transform boundary, is a fault along a plate boundary where the motion is predominantly horizontal. It ends abruptly where it connects to another plate boundary, either another transform, a spreading ridge, or a subductio ...

s. About 15 million years ago in the

the Chile Ridge begun to subduct beneath the southern tip of Patagonia (55° S). The point of subduction, the

triple junction A triple junction is the point where the boundaries of three tectonic plates meet. At the triple junction each of the three boundaries will be one of three types – a ridge (R), trench (T) or transform fault (F) – and triple junctions can b ...

has gradually moved to the north and lies at present at 47° S. The subduction of the ridge has created a northward moving "window" or gap in the asthenosphere beneath South America.Charrier ''et al''. 2006, p. 112.