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Peru: Basic Geology and some neotectonics

ANDES , Nazca SubductionBelow South America

Typical oceanic vs continental subduction zone

but why typical as soon as we don’t know so much?

mercredi 14 juillet 2010

• Central ANDES = 5 countries .....Bolivia Peru Chile Argentina and Brazil....

• Politics and Geology... field access....... Bolivia first, then closed, Chile and Argentina.....then no pieces of land free of instruments...thus Peru now...

• Peru strongest points: overview, highly variable morphologies

• Widest, highest :High plateau ( 4000m ) , high chain ( 6500 m), canyons (2000m).... ....

• Subduction seismicity ( 1960, biggest..)

• Arid desertic Atacama vs tropical Amazonia

• Thérèse BOUYSSE-CASSAGNE ( Volcanoes, earthquakes ...

myths and culture , Healers of the Bolivian Andes....

The good devil, mining cults , lake Titicaca ; assimilating christianism ?...)

Geology , politics...culture of the Central Andes


• Data acquisition is going on, but Scientists are mainly discussing processes...

• Questions are :

- how did the Andes grow ? And where first?

- what is the main contribution to uplift ? Magmatic, tectonic, cimatic, distributed or focused shortening, mantle flow, lower lithospheric flow, delamination, tectonic erosion ?

- what happened on the western flank ? If nothing happened ...why?

- Extensional collapse ? Delamination ...See Barnes and Ehlers , 2009

• The South American margin, despite a geologic history of more than 200 million years of continuous subduction, did not begin to grow high topography until ~50 million years ago.

Andean geology


3900 KONO E? a•.: Mou•rrAiN BUILDING IN THE CENTRAL ANDES

HOW TO FORM

A HIGH PLATEAU?

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MAGMA ADDITION

FOLDING

ß ß

REPEATED THRUSTS

THERMAL EFFECTS CRUSTAL DOUBLING

Fig. 9. Processes which can form an extended plateau of high altitude (compare with a similar figure in Allmendinger [1986]. The three on the right involve some sort of crustal shortening, while the two on the left rely on the supply of volcanic material or heat from below.

Altiplano-Puna was formed there. The absence of a back arc

basin behind the Andes is another important feature, but we

think that the latter problem is closely related to the former. It

is well known that geologic features with sizes of about 200 km

or larger cannot be supported completely by the elastic stress in

the surficial layers. Yet, a substantial part of the Central Andes

is not in the equilibrium state now. Our gravity study showed that the Moho lies about 65 km below the Western Cordillera

and 55 km below the Eastern Cordillera, and the crustal

thickness changes smoothly between these two values below the

Altiplano [Fukao et al., this issue]. Since this indicates that

only the Western Cordillera and the western part of the Alti-

plano is compensated by the crust, some sort of support is

needed for the eastern half of the Altiplano and the Eastern Cor- dillera.

The problem of formation of high plateaus is a problem of

how to thicken the crust and how to support the excess load if

compensation is not complete. In either way, excess mass

should be supplied for the topography. A number of ways can

be conceived for this purpose (Figure 9). The three cartoons on

the right side of Figure 9 show thickening of crust due to shor-

tening. The folding model is what is inferred for the Chilean type subduction by Uyeda and Kanarnori [1979]. However, this model is not consistent with the fact that the observed deforma-

tion is very small in the Altiplano (Figure 5) and the east-west

asymmetry shown by the gravity data. The crustal thickening

by repeated underthrusting of the continental crust was the

mechanism suggested by Suarez et al. [1983]. However, such

motions are unlikely in the western half of the Central Andes.

The compressire stress regime only prevails in the Eastern Cor- dillera and the Amazonian foreland. Addition of subducted cru-

stal material was proposed by Rutland [1971], but this proposal

was based on the assumption of constant migration of the vol-

canic centers to the east with time. As this assumption was

denied, we may discard this process from the possible crustal shortening mechanisms.

The two cartoons on the left side of Figure 9 show ways to

thicken the crust or at least to make the surface topography

without shortening the crust. Volcanism is certainly a decisive

factor in the Western Cordillera, but does not appear so in the

east, where the crust appears to consist of Paleozoic to Meso-

zoic sedimentary and metamorphic rocks. Thermal expansion

was studied by Froidevaux and Isacks [1984] by assuming that

the Central Andes is essentially in equilibrium state. The idea

is that the topography should be compensated either by the crust

or by the lithosphere, because of the size of the Central Andes.

However, we think this rather unlikely because of the east-west

asymmetry; if the eastern part is supported by hot and lighter

lithosphere underneath, similarly hot or even hotter lithosphere

should exist under the Western Cordillera, leading to an over-

compensation of the surface load them.

We conclude that a single mechanism cannot create and sup-

port the topographic features of the Central Andes. Instead, we

propose that two different mechanisms operate simultaneously at

the western and eastern halves: magma addition and crustal

shortening (Figure 10). A combination of these two is the main

agent which contributed to make the Central Andes a unique

mountain chain associated with a subduction zone; e.g.,

existence of high plateaus of wide extent and absence of backarc basins.

In the western half of the Central Andes, a substantial amount

of magma has been added to the crust from below, thickening

the crust and raising the plateau without severely distorting the geologic formations. The reason for this is the shallow

(10ø-30 ø) and fast (about 10 cm/yr) subduction of the young Nazca plate, a situation which must have continued since the

Miocene (Figure 10). The subduction angle must have changed

in the past, reflecting the stress state of that time, but it stayed

in the shallow range because of the hot and buoyant nature of

the Nazca plate, and the trenchward advance of South America

[Uyeda and Kanarrmri, 1979]. When the slab descends shal-

lowly, magma may be generated in a wider Zone across the arc

(see Figure 7b), because the generation of magma is controlled

by the supply of water to the hot mantle by dehydration of

hydrous minerals and thus dependent on depth of the slab

[Tatsumi, 1986]. The strong coupling between the downgoing

slab and the overlying mantle induces secondary convection in

the mantle wedge [Toksoz and Bird, 1977], which helps magma

generation to occur in a wide zone by dragging the water-

bearing mantle material toward continental interiors [Tatsurni,

1986].

The continued shallow and fast subduction below the Central

Andes since the Miocene is consistent with the opening of the

Atlantic Ocean and the ages of the seafloor inferred from the

magnetic anomaly pattern analysis of the Nazca plate [Couch and Whitsett, 1981; Couch et al., 1981].

When magma or mantle diapir ascends from the surface of

the slab, only a small part of the magma would reach the sur-

face. The rest is hindered form ascending to the surface by the compressire crust above and will either intrude in the crust or attach to the base of the lower crust and thicken it. This is

because most of the Andean crust has continuously been under

compressire stress regime since the Miocene. In the present

Western Cordillera, a tensional field locally occurs, and magma

can reach the surface, forming active volcanoes. Thus a clear

volcanic front is formed parallel to the Pacific coast of South

America. However, magma generation related to the formation

of the Central Andes must have been more widely distributed. A hot or at least warm mantle must extend further eastward as

suggested by the high heat flow observed there [Uyeda and

Watanabe, 1982]. Because of shallow subduction, magma will

be produced considerably inland behind the volcanic front,

Building a Plateau

Kono et al., 1989


• 3D feature

• EW cross sections

• NS variations

• History of the subducting plate but also of the upper plate

• .......

• I will focus on Central Andes, Northern part, in Peru ...

Andean geology


Central Andes

Northern Andes

Oceanic accreted terranes

Flat Slab

Short, lower Andes

North South Segmented Andes


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Submarine basins

Coastal «Cordillera»Central «depression»Western Cordillera

AltiplanoEastern Cordillera

SubAndes

Parallel to the Andes

Vega, 2002

Morphologic settings


Megard 1978

800 1000 DIST. (Km)

I I I I I I

I O 400 200 . 400 600

~' WLSTERN E A S T L R N COAST

C O R D . CO! D. I

-------

Pretty much the same now....

Once the uplift begon, nothing changed ?

Data from East to West , best known to less known

East West Segmented Andes ??

Garzione et al., 2008


Climate by promoting or inhibiting sedimentation, may help to focus the available plate-driving forces to portions of subducting plate boundaries, raising the local shear stresses to levels needed to support mountain belts with elevations 3 km.Lamb and davis,2003

Onset of Convective Rainfall During Gradual Late Miocene Rise of the Central Andes .Poulsen et al., 2010

Climatic Andes


• Mamani et al., 2010

Volcanic Andes

Mamani et al.

164 Geological Society of America Bulletin, January/February 2010

numerous isotopic ages published for the region and other information from the literature, and observed contact relationships and morphologi-cal criteria in the fi eld and on satellite images. A compilation of ages relative to the magmatic arcs recognized in this paper is given in the elec-tronic GSA Data Repository item (Table DR1).1

Three main periods of unequal durations help to summarize the long-term evolution of the ac-tive margin corresponding to the present-day Central Andean orocline:

(1) From the late Paleozoic (ca. 400? Ma) to the mid-Cretaceous (91 Ma), the margin dominantly underwent tectonic stretching, leading to the formation of an overall marine backarc basin.

(2) From the Late Cretaceous (91 Ma) to the mid-Oligocene (30 Ma), the magmatic arc was large enough to form a signifi cant, continuous relief, thus indicating incipient crustal thicken-ing. In contrast with the previous evolution, the backarc basin was occupied by mostly continen-tal environments. No clear and large-scale com-pressional structure is known from this period. It is noteworthy that ca. 45 Ma, the arc migrated

to the north by up to 200 km in the western part of the study area, and it occupied this position until ca. 30 Ma.

(3) The major crustal thickening typical of the Andean orogeny has developed since the mid-Oligocene (30 Ma), while the main arc has mi-grated back toward the trench (see following). Transpressional to compressional deformation developed in the northeastern Altiplano, East-ern Cordillera, and Subandean belt; in contrast, extensional, transtensional, and transpressional deformations have occurred in the forearc, arc, and southwestern Altiplano of southern Peru (Fig. 3; Sempere and Jacay, 2007, 2008). This tectonic development created a number of basins in the backarc, arc, and forearc and fragmented or terminated others, resulting in a somewhat complex stratigraphic record in time and space. This evolution possibly developed in relation with variations in the convergence rate, but not in the orientation of convergence, which has changed little since ca. 49 Ma (Pardo-Casas and Molnar, 1987).

Stretching the Margin: Late Paleozoic to Mid-Cretaceous (ca. 400? to 91 Ma)

The geological record relevant to this study starts with sedimentary deposits of Devonian to mid-Carboniferous age, which onlap mainly

1-Ga-old basement rocks. These strata are con-formably overlain by a thick but poorly known succession of dominantly basic volcanic and volcaniclastic rocks, referred to as the Chocolate Formation, which refl ect coeval arc construction and probably also backarc extension (Martínez et al., 2005). The thickness of this unit increases from !1 km in the paleobackarc to >3 km along the present-day coast.

No direct dating of the Chocolate Formation lavas has been achieved so far due to their perva-sive weathering. Stratigraphic relationships in the paleobackarc of southern Peru indicate that the Chocolate Formation conformably overlies strata of Middle to Late Carboniferous age (Pino et al., 2004; 2008, personal obs.), and it is conform-ably to gradually overlain by limestones that bear Sinemurian ammonites (ca. 195 Ma; Sempere et al., 2002). These relationships suggest that the unit spans at least the ca. 310–195 Ma interval, possibly with some internal hiatuses. However, this “Chocolate” magmatism continued well into the Jurassic along the present-day coastal area, refl ecting persistent activity of the arc system, while the backarc northeast of this arc under-went lithospheric thinning and signifi cant crustal downwarping. This backarc basin remained ma-rine during most of the ca. 195–91 Ma time inter-val, but it turned terrestrial between ca. 135 and ca. 115 Ma (Sempere et al., 2002). Maximum water depths were reached by 180–170 Ma, as in-dicated by sedimentary facies (Pino et al., 2004), suggesting that lithospheric thinning and tectonic stretching of the margin culminated at about that time. A poorly known episode of oblique trans-current deformation affected the backarc in the Early Cretaceous (Sempere et al., 2002).

In the Ilo area, the arc domain was the locus of a massive plutonic pulse between ca. 160 and ca. 150 Ma (Clark et al., 1990), leading to local growth of the Coastal Batholith; a further, major growth developed between 110 and 95 Ma by emplacement of more granitoids (Clark et al., 1990). The backarc record, however, testifi es to only very limited volcanic activity during the ca. 195–91 time interval, in contrast with the subsequent period (Callot et al., 2008).

In northernmost Chile, the partly coeval La Negra Formation is locally up to 10 km thick and includes mainly andesitic lavas, as well as large plutonic bodies (Oliveros et al., 2006; Charrier et al., 2007). Whereas plutonism de-veloped over the 190–100 Ma interval, volcanic activity is recorded starting at 176 Ma, but it was particularly voluminous between 165 and 150 Ma (Oliveros et al., 2006). As in Peru, the arc in which this volcanic unit and related plu-tons were produced, as well as the backarc ba-sin, evolved in a markedly extensional context (Charrier et al., 2007).

Nazca R

idge

trench

Tacaza arc and backarc (30-24 Ma)

?Andahuaylas-Anta arc (45-30 Ma)

Huaylillas arc (24-10 Ma)

Lower Barroso arc (10-3 Ma)

Upper Barroso arc (3-1 Ma)

Frontal arc (<1 Ma)

Chocolate arc (~310-91 Ma)

Toquepala arc (91-45 Ma)

?

?

Quinsachata backarc

volcanism (<1 Ma)

Lima

Nazca

Peru

Bolivia

Chile

17°S

15°S

13°S

71°W73°W75°W77°W 69°W

N

100 km

Figure 2. Location, extension, and age (Ma) of the volcanic arcs and backarc areas distin-guished in southern Peru. The successive arcs approximately extended between the labeled lines of same color and thickness, drawn on the basis of dated outcrops and available geo-logical maps. Extension of Nazca Ridge (white dashed lines) is after Hampel (2002).

1GSA Data Repository item 2009161, ages and chemical analyses of central Andean igneous rocks, is available at http://www.geosociety.org/pubs/ft2009.htm or by request to [email protected].

From 91 Ma to 30 Ma, the magmatic arc was large enough to form a significant, continuous relief, thus indicating incipient crustal thickenIng. Migrated North between 45 and 30 Myrs; and retro migrated 30Myrs ago..

The major crustal thickening typical of the Andean orogeny has developed since the mid- Oligocene (30 Ma), while the main arc has migrated back toward the trench.

No delamination

Volcanic Andes

major- and trace-element data points, and 650 Sr-, 610 Nd-, and 570 Pb- isotopic analyses of Mesozoic-Cenozoic (190–0 Ma)


• Allochtonous accretion on the Western flank and ... brazilian carton on the Eastern flank

• Crustal thickening , extension, compression, post rifting...( thinning), slab flattening...

✦ Magmatism on both sides

✦ Tectonism on only one side?

✦ Migrating widening or narrowing volcanic arcs

✦ Distribution or localized processes..

Andean geology


• => Andes / Old Craton /deeper than 500km earthquakes in the slab : Striking Exact same shape?

• What define the bolivian Orocline ... Rotations Brazilian shield undethrusting or both?

USGS

«Old» craton


Ramos 2008

A long time ago...before the Andes

Martignole and Martelat, 2003.

Precambrian inliers, Mollendo-Camana Block

Inherited zircon in both domains suggests a c. 1900 Ma age for the protolith of the Arequipa massif.


• Paleomagnetic data

• Magnetic anomalies

• Geology

• Paleo volcanic arcs

• Geochemistry

• Rotation and formation of the Bolivian Orocline

• Low Andes

• Wetland...Sea East of the Central Andes

Lomize, 2008Sebrier et al., 1988Hoorn et al., 2010; Roperch et al, 2007

50 to 25 Myrs


Roperch et al., 2006

?

Paleomagnetic data

Allmendinger et al., 2005 shows that the same pattern is observed in GPS data.Some of the interseismic deformation field must reflect permanent deformation.

Rotations acquired PRIOR to shortening ( >25MA).


Eastern Andes


• Kley and Eisbacher, 1999, Eastern Andes and intial state before major uplift

• Sempere et al., 1994 ; 2002

• Ramos 2008

«Rift» and thinned Lithosphere pre 25Ma

This 110-Ma-long interval of lithospheric thinning ended 160 Ma ago with the onset of Cretaceous rift inversion in the Eastern Cordillera area.


J. Kley et al. / Tectonophysics 301 (1999) 75–94 85

Fig. 5. Different modes of continental extension produce different styles of foreland deformation upon later inversion. (a) Extension

is concentrated in a narrow marginal basin flanked by subsiding but largely unfaulted platforms. Inversion results in thin-skinned

thrusting of the platform sedimentary cover. (b) Extension affects a wide swath of the continental interior, creating a wide ‘continental

embayment’. Inversion results in normal fault reactivation and creates a thick-skinned thrust belt. See Fig. 6 for actual examples.

the particular structural style of the areas affected

by basement thrusts, it does not explain why those

areas become involved in foreland deformation at

all. There is a conspicuous link between basement

thrusts and thin-skinned thrust belts: Two of the three

major areas of basement thrusting in the Andes, in

the Huallaga and Pampeanas segments, lie foreland-

ward of thin-skinned thrust belts. Where both types

of deformation are well dated, basement thrusts and

thin-skinned thrusts can be seen to be partly co-

eval, with basement thrusts nucleating during the

late stages of thin-skinned deformation (Strecker et

al., 1989; Jordan et al., 1993). In both Peru and Ar-

gentina, the thrust front of the thin-skinned belts has

propagated up to the external limit of their respective

decollement levels (Mathalone and Montoya, 1995;

Zapata and Allmendinger, 1996), causing an increase

in shear strength at the base of the thrust wedge and

probably a drop in strain rates. This ‘blocking’ of

the thin-skinned thrust belts and an associated raise

in the horizontal stress acting on the foreland crust

may be another important factor in the formation of

basement thrusts.

The earlier proposed correlation of flat subduction

with basement thrusts (Jordan et al., 1983; Pilger,

1981) is somewhat weakened if the entire orogen

is considered. Although the major Peruvian and Ar-

gentinian examples do occur in the flat slab regions,

minor basement thrusts persist north of the northern

flat slab (Fig. 2b). More significantly, the spectacular

• Different modes of continental extension produce different styles of foreland deformation upon later inversion.

Eastern Andes, EC and SA


• Kley et al., 1997, De celles, Horton , Baby, McQuarrie ....... Balanced cross sections.......

• 25-0 Myrs, shortening EC first ( thick skinned ) and then followed by in the subandes ( Thin skinned )

Eastern Andes , SA


Shortening estimates in southern Peru

Geological Society of America Bulletin, May/June 2010 735

Subandean zone of Bolivia (Dunn et al., 1995; Baby et al., 1997; McQuarrie, 2002a; Barke and Lamb, 2006; McQuarrie et al., 2008).

CRUSTAL THICKENING BUDGET

To determine if the shortening in our cross section accounts for the crustal area of the oro-gen, we predict the amount of shortening that would be needed to account for the crustal area in

Airy isostatic equilibrium and then compare the shortening predictions to our measured values. We made predictions assuming initial crustal thicknesses of 35, 40, and 45 km. Due to the his-tory of Permian-Triassic rifting in the region, an average global crustal thickness of ~35–40 km (Bassin, et al., 2000), and a crustal thickness of ~35–40 km in the foreland of the Andean Plateau , we assume that a 35–40-km-thick crust best represents the starting conditions. Previous

work, however, has assumed a 40–45 km initial crustal thickness, so we include calculations us-ing this initial condition for comparison (e.g., Beck et al., 1996; Kley and Monaldi 1998).

Isostasy Crustal Area Calculations

South of Peru, at ~20°S, broadband seismic studies suggest that the topography of the An-dean Plateau is in Airy isostatic equilibrium

A A!

185 km

10 km

0 km

–10 km

–20 km

Preferred shortening estimate 123 km

A A!

185 km

10 km

0 km

–10 km

–20 km

décollement dip requiredby mapped stratigraphy is steeper than minimum 1°

Minimum shortening estimate 58 km

basement shortening is much less thanoverlying strata requiring matching basementshortening to west

A A!

185 km

10 km

0 km

–10 km

–20 km

Maximum shortening estimate 333 km

basement involved deformation required here

Hanging-wall cutoff hererestores to footwall cutoff hererequiring the majority of slip on one structureextra area due to steeper

décollement that needsto be filled with deformed strata

depth of footwall flat to match hanging-wallramp creates a mismatch of thickness in the thrust sheet

Figure 6. Variations in the way shortening is accommodated in our preferred, minimum, and maximum shortening estimates. Annotations indicate problems with the kinematics in the maximum and minimum shortening estimates. Stratigraphic color key is given in Figure 2.DeCelles and Horton, 2003 suggests 500km of total shortening since Paleocene...enough to

explain the crustal thickenning and they suggest altiplano and western shortening is included.

Gotberg, et al., 2010

Eastern Andes , SA


Vertical or Horizontal ?

Baby et al., 1997

Dorbath et al., 1993


• Carlier et al.,2005

Vertical ?

The Altiplano of southern Peru displays a large spectrum of Cenozoic potassic and ultrapotassic mafic rocks that delineate two deep lithospheric mantle blocks

Those blocks have undergone different depletion and enrichment events and favour a vertical limit between EC and SA

25-23, 7-5,2-0Myrs old


AC

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12°

64°66°70°72°

14°

16°

24°

26°

28°

A

L

T

I

P

L

A

N

O

P

U

N

A

EC

AL

WC

WC

PrCPU

SB

SP

EC

EC

IA

SA

La Paz

Cuzco

Potosi

A

B2 !/std. error region

1 !/std. error region

4 67

5

paleobotany

paleoclimate correction

Age (Ma)

Pla

teau

ele

vati

on

(km

)

0510152025

1

0

2

3

4 modern

5

13

14

15del18O

16

17

18

clumped 13C-18O

1

21

21

11

4

19

520

13-18

7

6

12

8 2

9

10

22

3

?

Uplift

1.7 ± 0.7 kmsince 12-9 Ma

2.7 ± 0.4 km 10.3 - 6.7 Ma

2.3 -3.4 kmsince

11-10 Ma

3 - 4.3 kmsince

21-14 Ma

>2 kmAP elev by19-13 Ma

1-3 km since25-18? Ma

3.2 km since25-19 Ma

1.1 km since25 Ma

>2 km since~16-11 Ma

>2 km since~25-16 Ma

5000 km 250

Elev7000

0 m

Figure 7Barnes & EhlersBlack & white print version, color online version

Figure 7

Barnes and Ehlers, 2009

• Neogene uplift

• But ˜1000m Andes

• existed before 25Ma.

• Plateau but West ?

• Smoother gradual uplift?

Uplift of the plateau, Central Andes


Tavera et al., 2002Dorbath et al., 1991 West/East cross section

NSFor 12 Myrs , entered North of Peru and then southeastward migration

«small» ridge in comparison to Carnegie (Ecuador ) but much bigger than Juan Fernandez ridge ( Chile )

Older plate ?Oblique? Tectonic erosion from below?

Uplift and then subsidence on the coastal area

But didn’t reach southern Peru yet.

12 Myrs ago....Subduction of the nazca ridge


KoNo œT ,st,.: MOUNTan• BUILDINO IN THE CENTRAL ANDES 3901

Western Cordillera Altiplano Eastern Cordillera primarily small deformation primarily uplift

magmatic growth by compression

small deformation r.r • faults and folds nearly isostatic • not isostatic

++++++++ •

+++++++ • •

• ++++++++++++ •

buoyant young • ,&, • ,•,--- ,.-- ,• , *-., heated mantle oceanic plate •ø•'!,.,.'""•t • c '-- • '• • and crust

_ stro.ng coupling "•*.•o6'•,,•' ..., "-, __, • secondary convection lar e thrust events large thrust events • • • • induced by subduction

• • (carries heat upward

.,._•• •ind volcanic line) wide zøne• - • •

magma generation • •

Fig. 10. A cartoon showing the processes operating in the formation of the Central Andes. Not to scale.

although it does not appear on the surface due to the overlying

compressive crust. Accretion of such volcanic materials is the

main reason for the thickening of the crust observed in the Cen-

tral Andes, especially in the Altiplano and the Western Cordil- lera.

In the Eastern Cordillera and Andean foreland basin, there is

little evidence for extensive magma intrusion dubrig the Ceno-

zoic age. Instead, thick Paleozoic rocks have been extensively

folded and faulted. Crustal seismic activity shows hohzontal

compression almost perpendicular to the mountain axis. The

sub-Andes foreland basin is formed by a series of folds and

west dipping reverse faults active from at least Pliocene time to

the present [Suarez et al., 1983; Allmendinger, 1986]. Such evi-

dence suggests that crustal shortening due to westward compres-

sion from the Brazilian shield is a major agent of the mountain

building in the Eastern Cordillera. Perhaps the Andean crustal

block is heated from below even in its eastern part and it is on the whole hotter and softer than the Brazilian shield block.

When the soft Andes block is pushed by the hard block of the

Brazilian shield, intense deformation would occur in the Andes

block but is concentrated in the region near the colliding boun-

dary. A similar situation occurs in the Himalaya where defor-

mation is concentrated near the boundary between hard and soft

blocks [Moltmr and Tapponnier, 1979]. We consider that the

resultant crustal shortening and thickening with possible

underthrusting of the Brazilian shield block are the main reason

for the uplifting of the Eastern Cordillera.

The two processes are strongest at both ends, but extend to

the east or west, losing their strengths gradually. The superpo-

sition of the two different processes is responsible for the crea-

tion and maintenance of the intermediate plateau, the Altiplano- Puna. Sediment fill from both eastern and western mountain

ranges must have been substantial [James, 1971b], but this is a

secondary effect compared with the former two processes.

Thus our model of the mountain uplifting can be summarized

as follows. Because of the relatively shallow subduction of the

young oceanic plate, magma is generated in an extensive area

above the descending slab. Accretion of magmatic material into

the crust is most extensive at the volcanic front and progres-

sively decreases eastward. The Andes block, even at its eastern

end, is heated and softened by the extensive volcanism and is

pushed westward by the hard block of the Brazilian shield. The

deformation due to this push is severest at the Amazonian fore-

land basin and the Eastern Cordillera, but also extends to the

west with decreasing magnitude. These two mountain ranges

thus represent two extreme cases in the process of mountain

uplifting. The superposition of asymmetric processes to form a

relatively symmetric feature, the Altiplano-Puna, is the essential

property of the Central Andes.

DISCUSSION

[James, 1971b] considered that the intrusion of melt into the

crust beneath the Western Cordillera and the resultant crustal

dilatation produced continentward compression to form thrust and fold mountains in the Eastern Cordillera. It is not evident

why the volcanic matehals intruding under the Western Cordil-

lera can apply a compressive force to such a remote place as the

Eastern Cordillera. Besides its physical implausibility, this

mechanism is inconsistent with the fact that intense folding and reverse faulting occur on the eastern flank and not on the

western flank of the Western Cordillera. The concept of the

Altiplano as an intermontane valley filled by eroded matehals

from both mountains is also not convincing, since the topo-

graphic shape of the Altiplano is essentially trapezoidal (Figure

2) and not a "valley" between two high mountain chains. His

Kono et al., 1989

KONO œ? AL: MOUNTAIN BoreDtoO IN THE CœYmAL ANDF. S 3897

xx• z• x

.... I .... I .... I .... I .... [ .... I .... [ .... I .... [ .... I'•

.... I .... I .... I .... I .... I .... I .... I .... I .... [ .... I

lO0 200 300 400 500 600 '700 800 900 !000

DIS;TRNCE [KFI]

4000

2000

o

-2ooo

-4ooo

-6000

•oo

-lOO

-200

-300

-400

-500

(•

,s-

z

rn

Fig. 6. Gravity anomalies obtained for the route Nazca-Puerto Maldonado, which spans from the Pacific coast through the Western and Eastern Cordillera and the Altiplano and continues to the flat land of the Amazon fiver, where the height is only about 200 m [Fukao et al., this issue]. From top to bottom, station height (dots) and heights of grid points in a 100-km belt containing the traverse route, Bouguer gravity anomaly on land [Fukao et al., this issue] and free air anomaly on the sea [Hayes, 1966], and the crustal structure model.

[1971] suggested tectonic erosion as an important element of his

model of the Central Andes partly because of this apparent age

progression from west to east. However, most of the volcanic

rocks associated with the Altiplano are of Cenozoic age. Recent

radiomelric age determinations show no definite trend in the

ages of the Cenozoic volcanic rocks in the Altiplano [e.g.,

Baker and Francis, 1978; Thorpe and Francis, 1979; Kaneoka

and Guevara, 1984]. Even a reverse trend in age progression (west to east} was found in the volcanic rocks of southwestern

Bolivia [Kussmaul et al., 1977]. With the addition of newer age

data, it now appears that the important thing about the distribu-

tion of volcanic rocks in the Central Andes is not the regular

age progression but the wide occurrence as noted by James

[1971b]. Ignimbrites of Miocene age show especially wide dis-

tribution and are the evidence of the very strong volcanic

activity in the late Tertiary [Rutland et al., 1965; Guest, 1969;

Francis and Rundle, 1976; Kussmaul et al., 1977; Baker and

Francis, 1978; Baker, 1981; Lahsen, 1982; Francis et al.,

1983]. Some center of volcanic activity may have lasted several

million years [e.g., Kaneoka and Guevara, 1984]. The locations

of volcanic centers seem to have moved not in a systematic but

in a random manner with age.

Figure 8 shows the distribution of active volcanoes and vol-

canic centers younger than Miocene [International Association

of Volcanology and Chemistry of the Earth's Interior,

(IAVCEI), 1979]. For Argentina, Figure 8b was supplemented

by the volcanic centers younger than 10 Ma reported by Froide-

vaux and /sacks [1984] using Landsat imagery, because that

Gravimetry

Magmatic thickening fits the gravity on the western side if you consider that no shortening occured west...


Kendrick et al., 2001

GPS , partitionning.... West...?

c


2002

?

?

?


Western Andes, forearc


Carlos Benavente, INGEMMET, Peru

Hernando Tavera, IGP, PEru

Saillard Marianne, LMTG, Toulouse France

Claire David, IRSN , France

Sarah Hall, UC Santa Cruz, USA

Daniel Farber, UCSC/LLNL, USA

Tectonic activity on the western side of the Andes

Faults Transpressionnal and reverse


Carlos Benavente, INGEMMET, Peru

Hernando Tavera, IGP, PEru

Saillard Marianne, LMTG, Toulouse France

Claire David, IRSN , France

Sarah Hall, UC Santa Cruz, USA

Daniel Farber, UCSC/LLNL, USA

Tectonic activity on the western side of the Andes

Topographic cross section

Faults Transpressionnal and reverse


Offshore/Onshore ODP,DSDP and Oil companies

Onshore, low interest on Tertiary deposits and lower on Quaternary... Now everybody is gathering data,

ages, and stratigraphy in order to constrain the forearc evolution.

Major Cannyons, ......no tectonics neither analysis of crustal seismicity.


31

W

E

Central depression

Coastal Cordillera

Western Cordillera


• Desert Varnish

• Two distinct surfaces

Quaternary dynamic forearc ? Upper forearc

10Be dating of abandoned and reincised surfaces

Hall et al., 2008


• Desert Varnish

• Two distinct surfaces

Quaternary dynamic forearc ? Upper forearc

10Be dating of abandoned and reincised surfaces

Hall et al., 2008


Cerro El Huevo 492 mNW SE

NWSE Cerro Tres HermanasUplifted marine terraces ( Be10 datation ) Quaternary < 1Ma

⇒ 15 levels

Quaternary dynamic forearc ? Coastal forearc

Saillard et al., in revisionmercredi 14 juillet 2010

34

Pliocene marine sediments

Quaternary marine deposits

Marine terrace re incised in a marine terrace

Regard et al., 2010mercredi 14 juillet 2010

Hidden structures , volcano clastic cover for 50Myrs

Audin et al., submitted


• Onlyclue:DistancebetweentheCretaceousArc(CoastalCordillera)andthepresentdaytrench(SolerandSebrierarguesthetectonicerosionoccurredmorethan40Myrsago).

• butitseemsthatthefore‐arcbasinshavemaintainedtheirpresentgeometryatleastsincethemid‐orlateEocene(ThornburgandKulm,1981;Macharéandothers,1986;Macharé,1987),sothattectonicerosionatthetrenchcannotbeinvokedatleastforthelast40m.y.CliftarguefortectonicerosionnorthofParacas.PostNazcaridge?

• South,Ivoteforanaccretionnaryprism...Andsplayfaults?

• Everybodymapnormalfaults(sueprVicialdetachmentsdiruptingthesurface)butonly«old»(ienoprecisionindepth)refractionproVilesareavailable

Offshore:Tectonic erosion at the trench and underplating?

Kulm et al., 1981Clift et al., 2002


2.3. MARCO GEOLOGICO Y ESTRUCTURAL DEL BORDE OESTE DEL

ALTIPLANO 43

Figura 2.11: Marco tectonico conocido de la Precordillera del Codo de Arica.

En la Precordillera de la region de Tacna, en Peru (18!S), Tosdal et al. [1984] refieren

la existencia de la flexura de Huaylillas, que serıa la continuacion hacia el Norte del

Anticlinal de Oxaya del Norte de Chile. Esta flexura habrıa actuado contemporaneamente

con la depositacion de las ignimbritas de la Formacion Altos de Camilaca entre 25 y 18

Ma [Sebrier et al., 1985].

En la Precordillera del Norte de Chile, el denominado Sistema de Cabalgamientos de

Tavera et al., 2007; Mw5.4, 17km

Onshore: Tertiary to Quaternary active faults


Local and temporal seismic networks: Subduction seismicity82

CAPITULO 3. ANALISIS DE LA SISMICIDAD DEBAJO DEL ANTE-ARCO Y DEL

ARCO VOLCANICO DEL OROCLINO DE LOS ANDES CENTRALES

figura 3.15 especıfica tambien las redes locales y regionales que registraron estos datos.

Estos datos se adquirieron en periodos distintos:

- en 1981 en la region de Camana-Arequipa, Sur del Peru,

- en 2003 en la region de Tacna-Moquegua, Sur del Peru

- y entre 1996 y 2003 en el Norte de Chile.

Figura 3.15: Eventos locales de magnitud mL ! 4,0, registrados por las redes locales temporales en1981 y en 2003 y por las redes permanentes entre 1981-2004 y entre 1996-2003, procesados en este

trabajo y en trabajos anteriores. El rectangulo rojo ilustra el area de ruptura del terremoto de Arequipa.

La flecha azul representa la brecha sısmica del Oroclino. Las lıneas negras representan la orientacion

de las secciones ortogonales a la fosa. La topografıa y la batimetrıa son de Sandwell and Smith [1997]

ETOPO de 2 minutos de angulo, muestreadas a 30 segundos de angulo.

La figura 3.16 presenta las mismas secciones perpendiculares a la fosa E1, E2, E3, E4, E5, E6

que la figura 3.14. No aparece la seccion E7 ya que los datos locales procesados en esta zona

3.3. ANALISIS DE LA DISTRIBUCION ESPACIAL DE LA SISMICIDAD DEL

OROCLINO DE LOS ANDES CENTRALES 83

estan afuera de la cobertura de la red.

Figura 3.16: Secciones ortogonales a la fosa con los eventos locales registrados por la red permanente

RESISTE de Arica entre 1996 y 2003, por la red temporal de la region Tacna-Moquegua del Sur del

Peru instalada en 2003, por la red temporal de la region Camana-Arequipa del Sur del Peru instalada

en 1981 y por la red nacional de Peru.

La exageracion vertical de la topografıa y de la batimetrıa explica que hayan 2 escalas: la escala de la

izquierda que corresponde a la profundidad de los eventos graduada cada 20 km, la de la derecha, a la

topografıa y a la batimetrıa graduada cada 6 km. La ubicacion geografica de las secciones se encuentra

en la figura 3.15.

David PhD 2007


Local and temporal seismic networks: Subduction seismicity82



figura 3.15 especıfica tambien las redes locales y regionales que registraron estos datos.

Estos datos se adquirieron en periodos distintos:

- en 1981 en la region de Camana-Arequipa, Sur del Peru,

- en 2003 en la region de Tacna-Moquegua, Sur del Peru

- y entre 1996 y 2003 en el Norte de Chile.

Figura 3.15: Eventos locales de magnitud mL ! 4,0, registrados por las redes locales temporales en1981 y en 2003 y por las redes permanentes entre 1981-2004 y entre 1996-2003, procesados en este

trabajo y en trabajos anteriores. El rectangulo rojo ilustra el area de ruptura del terremoto de Arequipa.

La flecha azul representa la brecha sısmica del Oroclino. Las lıneas negras representan la orientacion

de las secciones ortogonales a la fosa. La topografıa y la batimetrıa son de Sandwell and Smith [1997]

ETOPO de 2 minutos de angulo, muestreadas a 30 segundos de angulo.

La figura 3.16 presenta las mismas secciones perpendiculares a la fosa E1, E2, E3, E4, E5, E6

que la figura 3.14. No aparece la seccion E7 ya que los datos locales procesados en esta zona

3.3. ANALISIS DE LA DISTRIBUCION ESPACIAL DE LA SISMICIDAD DEL

OROCLINO DE LOS ANDES CENTRALES 83

estan afuera de la cobertura de la red.

Figura 3.16: Secciones ortogonales a la fosa con los eventos locales registrados por la red permanente

RESISTE de Arica entre 1996 y 2003, por la red temporal de la region Tacna-Moquegua del Sur del

Peru instalada en 2003, por la red temporal de la region Camana-Arequipa del Sur del Peru instalada

en 1981 y por la red nacional de Peru.

La exageracion vertical de la topografıa y de la batimetrıa explica que hayan 2 escalas: la escala de la

izquierda que corresponde a la profundidad de los eventos graduada cada 20 km, la de la derecha, a la

topografıa y a la batimetrıa graduada cada 6 km. La ubicacion geografica de las secciones se encuentra

en la figura 3.15.

David PhD 2007

104



Figura 3.28: Mecanismos focales determinados a partir de los eventos registrados por la red perma-

nente del Norte de Chile [David et al., 2002].

En la seccion a (figura 3.30), el mecanismo focal asociado a un sismo a 20 km de profundidad

debajo del frente precordillerano corresponde a un movimiento normal.

En la seccion b (figura 3.30), caracterizada por el mayor numero de mecanismos focales, se

puede observar varios tipos de mecanismos focales. Es difıcil encontrar algun patron que pueda

explicar esta variedad ya que los tipos de mecanismos no presentan correlaciones directas ni

con la profundidad, ni con la unidad morfoestructural debajo de las cuales se encuentran.


39High obliquity > 30° , where does the partitionning go?

Normal faults in the volcanic arc and on the Altiplano do not reflect necesarly extension but a rotating σ1 (stretching lower than 1percent) Sebrier et al., 1985

Normal faults // trench, extension and collapse?


Onshore: Western Cordillera piedmont

Reverse faults// to the trench

Sempere 2010mercredi 14 juillet 2010

41

South PeruESC Image/NASA

Coastal Cordillera

Central basin

OE

Active Reverse fault systemsMore and more vertical…..

// to the margin Compressive component


Audin et al., submittedmercredi 14 juillet 2010

Reverse fault systems// to the trench

Compressive component

500m


Audin et al., submittedmercredi 14 juillet 2010

Fig. 1. Geodynamic setting of the Arica Bend. Main faults, greatest (Mw!8.0)interplate subduction earthquakes of XIX and XX centuries, the interplate seismicgap of the Arica Bend and the Aroma earthquake and its aftershocks including themain one: Chiapa earthquake are represented. Inverted triangles correspond to thepermanent Arica network.

some ones, like the Aroma Quebrada, reaches depth of 800 m. The easternpart is separated from the western part by a main flexure, the Aroma flexureand is characterized by large surfaces dipping to the west. These surfaces aredissected by numerous WSW-ENE fossil quebradas about 100 m deep, andlarge quebradas (like Aroma, Sotoca), 500 to 900 deep. The substratum isformed by di!erent units ranging from upper Devonian and lower Carbonif-erous to Cretaceous. The oldest one is the Quebrada Aroma formation, 1000to 1500 m thick, where oceanic metasediments are interbedded with phyllitesand sandstones. It is unconformably covered by the Quebrada Coscaya for-mation, about 1200 m thick. The lower part (800 m) is composed of metriclayers of sandy agglomerates and conglomerates with intercalations of oceanicsedimants. The Cenozoic formations cover the Paleozoic and Mesozoic unitswith an angular unconformity. The Altos de Pica formation has a maximumthickness of about 600 m to the west of the Aroma flexure. It is formed ofignimbrites, conglomerates and breccia and is dated from upper Oligocene tolower Miocene. The El Diablo formation, which constitutes the surface of thePre-Cordillera, is more than 400 m thick at the western border of the Pre-

5

Crustal faults in the foerarcRe Activated after a subduction

earthquake ( M>8)


Fig. 2. Increase of Precordilleran crustal micro-events after the Arequipaearthquake. The map (a) represents the Precordileran and Cordilleran events oc-curred between June and December 2001. The histograms represent the tempo-ral distribution of the crustal microseismicity in the Arica Bend Precordillera andCordillera (b) between 1996-2003 and (c) in 2001, between January and December.

4.1 The Aroma earthquake, July 24, 2001, Mw = 6.3

The Aroma earthquake depth determined by NEIC and Harvard is 15 km.Engdahl et al. [1998] ’s catalog gives a depth value of 13.2 km. A teleseismic7

David, 2007mercredi 14 juillet 2010

Onshore: Coastal Cordillera

Reverse and normalPerpendicular to the

trench faults

4.1. EL SISTEMA TECTONICO DE LA CORDILLERA DE LA COSTA Y LA

SISMICIDAD ASOCIADA 133

Figura 4.1: Sismicidad cortical entre 0 y 25 km de profundidad debajo de la Cordillera de la Costa del Codo de

Arica y las cuatro estructuras tectonicas estudiadas, Pisagua, Atajana, Arica y Chololo. Las estructuras indicadas

por lineas delgadas corresponden a lineamientos visibles sobre imagenes topograficas, vistas en terreno, pero no

estudiadas. Las estructuras cuya cinematica es conocida ha sido especificada, con triangulos negros, la falla es

inversa manteando hacia la punta del triangulo, con rectangulos negros, la falla es normal manteando del lado

del rectangulo, y con flechas, las fallas son transcurrentes. La cinematica ha sido caracterizada por este estudio y

tomada de Allmendinger et al. [2005a]. La microsismicidad esta representada por cırculos de tamano pequeno. El

mecanismo focal corresponde a un sismos de magnitud Mw = 5.8 con localizacion del ISC. El color de los eventos

sısmicos y de los mecanismos focales representan la profundidad.

24 de Marzo de 2007, Mw = 5,8, localizado por el NEIC a 30 km de profundidad. Dado el error

de localizacion, puede que este sismo haya ocurrido en la falla Pisagua que mantea hacia el Sur.

El mecanismo focal asociado indica un movimiento inverso, lo que concuerda con las evidencias

Pliocenas de la cinematica de la falla Pisagua. Esto sugiere que esta falla sigue activa con la

misma cinematica que hace algunos millones de anos. Con respecto a los planos nodales, son

de alto angulo (los manteos son de 41!y de 50!) y se orientan casi E-W (los acimuts son de

David, 2007mercredi 14 juillet 2010

Normal faults , perpendicular to the trench

Active, some lateral components2

001



Normal faults , perpendicular to the trench

Active, even offshore on the margin

Linked somehow to the NS subduction segmentation ?

Audin et al., 2008 ; Calderon 2008



N

Blind Thrust Morphology... hidden


N

Blind Thrust Morphology... hidden


N

Onshore: Central depression

Hall et al. submittedmercredi 14 juillet 2010

N



N



N





Wind Gap

Water Gap


Calientes Pliocene formation, folded

Benavente , 2009mercredi 14 juillet 2010

Active channel, Quaternary to recent terraces

Calientes hot springsTrench: paleoseismic record

Benavente , 2009mercredi 14 juillet 2010

Incision Summary:


T1 3m: 41.6 ± 9.4 kaT2 10m: 218 ± 20.6 kaT3 20m: 541 ± 67.8 ka

Incision Rate: 0.04-0.09 mm/yr

Incision Summary:


T1 25m: 195 ± 29 kaT1 25m: 193 ± 28 ka

Incision Rate: 0.1 ± 0.03mm/yr

T1 3m: 41.6 ± 9.4 kaT2 10m: 218 ± 20.6 kaT3 20m: 541 ± 67.8 ka


Incision Summary:


T1 28m: 51.1 ± 25.3 ka Incision Rate: 0.5 mm/yr

T1 25m: 195 ± 29 kaT1 25m: 193 ± 28 ka


T1 3m: 41.6 ± 9.4 kaT2 10m: 218 ± 20.6 kaT3 20m: 541 ± 67.8 ka


Incision Summary:




T1 25m: 195 ± 29 kaT1 25m: 193 ± 28 ka


T1 3m: 41.6 ± 9.4 kaT2 10m: 218 ± 20.6 kaT3 20m: 541 ± 67.8 ka


Incision Summary:




T1 25m: 195 ± 29 kaT1 25m: 193 ± 28 ka


T1A 43m: 170 ± 29.9 kaT1A 79m: 201 ± 22.6 kaT2B 98m: 445 ± 35.3 ka


T1 3m: 41.6 ± 9.4 kaT2 10m: 218 ± 20.6 kaT3 20m: 541 ± 67.8 ka


Incision Summary:


0.3mm/yr

Uplift rates Summary:


• Pleistocene age surfaces exist within the forearc which yield erosion rates <0.1m/Ma

• Active structures yield uplift rates ranging from 0.05 - 0.5 mm/yr

• Contractile structures accommodate compressional stresses within the forearc of southern Peru

• Incision rates during the past ~600 ka are consistent with incision rates calculated for periods during the last 10Ma.


9

around 1 mm yr–1, the entire western and central Altipl-ano experienced shortening in the Oligocene (35–25 Ma)with local shortening rates of 0.1 to 3.0 mm yr–1 (not re-solved in Western Altiplano for lack of exposure). Thisstage was followed by an early Miocene lull in deforma-tion, but shortening resumed with distinct local accelera-tion to some 1.7–3.0 mm yr–1 (west and center) in the middleto late Miocene (20–10 Ma). In most of the Altiplano, rateswere higher during the later stage while the Eastern Altipl-ano exhibits the opposite relationship. At 7–8 Ma, deforma-tion ceased nearly everywhere except for the continuationof very slow dextral slip on the Precordilleran Fault System.

In contrast to this evolution, the Eastern Cordillera de-formed over a long time span starting some 40 million years

ago (cf. Müller et al. 2002; Ege 2004; Horton 2005 for rel-evant data). Deformation spread from its center to the eastand west with a maximum shortening rate of 6–9 mm yr–1

between 30 and 17 Ma. Deformation practically ceased be-tween 12 and 8 Ma, as evidenced by the formation of theSan Juan del Oro surface (Gubbels et al. 1993; Kennan et al.1995). During this period, the Subandean fold and thrustbelt was initiated. It propagated eastwards somewhat dis-continuously, as recently established by Echavarria et al.(2003), with shortening rates at some 8–14 mm yr–1 and withmaximum rates occurring around 7 and 2 Ma. The currentshortening rate at this latitude, established by GPS measure-ments, is 9 ± 1.5 mm yr–1 (Bevis et al. 2001; Klotz et al. 2001)and is focused nearly entirely at the present deformation

Fig. 1.4. Distribution of deformation ages across the Southern Central Andes (21° S) based on published and own data (modified from Elgeret al. 2005). a Compilation of deformation ages: Western Flank (Victor et al. 2004), Precordillera (Haschke and Günther 2003), Altiplano(Elger et al. 2005; Ege 2004; Silva-González 2004), Eastern Cordillera (Gubbels et al. 1993; Müller et al. 2002), Interandean (Kley 1996; Ege2004), and Subandean (Kley 1996). b Balanced cross section at 21° S compiled from Victor et al. (2004; Altiplano West Flank), Elger et al.(2005; Altiplano), and Müller et al. (2002, Eastern Cordillera and Subandean), Moho and Andean Low Velocity Zone (ALVZ) from receiverfunction data (Yuan et al. 2000). Line drawing in the middle crust indicates locations of strong reflectivity in the ANCORP seismic line (cf.ANCORP working group 2003). c Estimates of maximum and minimum periods of active faulting and related folding in the units buildingthe Altiplano. d Cumulative shortening rates of the thrust systems building the plateau calculated from fault activity periods and heave;bold line delineates average shortening rate based on sliding average of three million year sampling width

Chapter 1 · Deformation of the Central Andean Upper Plate System – Facts, Fiction, and Constraints for Plateau Models

Oncken, 2006

Megard, 1978

Rigid ?


CONCLUSION Continental plateaus, such as the Altiplano-Puna plateau in the central Andes, are the result of exceptional tectonic and climatic conditions.

A number of different mechanisms may be operating at the same time but which ones ? In the Andes, there is an active magmatic arc, the Brazilian craton is underthrusting the eastern flank, both thin- and thick-skinned deformation is found throughout the plateau. Climatic factors affect the growth of the plateau, where internally-drained basins appears to be important.

The Andean Plateau probably results from a combination of different, interacting mechanisms. Initial crustal thickening may result in weak, gravitationally unstable crust, which could lead to lithospheric delamination, lower crustal flow and even extensional collapse, ok but not everywhere along the Andes....

Plateaus also create their own arid climate, leading to internal drainage, which may help sustain plateau morphology. Shortening alone explain the crustal thickening.


Cooperation in Earth Sciences in Peru

• INGEMMET

• IGP, INRENA

• Universities UNI, San Marcos,

• Univ. Cuzco, Tacna, Arequipa

• UNALM La Agraria Lima

• Petroperu

• IMARPE,SENAHMI
