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HvE – Regionale Geologie – WS 12/13

Modul Regionale Geologie (600156)WiSe 12/13

TM1 – Regionale Geologie ausgewählter Gebiete der Erde

Die Entwicklung der Anden – Teil 2:Hebung und Erosion

Hilmar von EynattenAbt. Sedimentologie/Umweltgeologie

HvE – Regionale Geologie – WS 12/13

What controls crustal thickening and uplift ?

- convergence Nazca/ SA plates- W-drift of South America- dip of subducted slab

- subduction erosion- upper-plate shortening- climate

Jaillard et al. 2002, Tectonophysics

what else…?

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Hoke & Garzione 2008, EPSL

Garzione et al. 2006, 2008: only the removal of dense eclogitic lower crust and mantle litho-sphere can generate uplift of such magnitudeand rapidity (i.e. ~3 km from ~10 to ~7 Ma)

shortening-thickening relation strongly variesalong orogenic strike; contribution of tectoniccontraction to crustal thickening may be as lowas 30% (e.g. Kley and Monaldi 1998)

Mamani et al. 2010: geochemical variation of magmatism in space and time support continuedcrustal thickening; i.e. no delamination, insteadshortening plus lower crust flow from areas of excess shortening to areas with low shortening; (Husson & Semperé 2003; Hartley et al. 2007)

→ additional mechanisms are required, such as:♦ magmatic addition/ basaltic underplating♦ lateral mass movement in the upper crust as

well as lower to mid crustal flow♦ delamination of dense lower crust/ upper m.

HvE – Regionale Geologie – WS 12/13

timing and mechanism(s) of uplift and crustalthickening in the Central Andes (15.5 – 20°S)

• ~45-25 Ma: onset of crustal shortening, thickening,and surface uplift

• 26-22 Ma: onset of voluminousmagmatic activity (16-19°S)

• ~10 Ma: major uplift phase inthe Late Miocene Oncken et al., 2006

elevations up to ~ 6 km, plateau-likeorogen (>4 km) at the leading edge of SA, up to 70 km thick crust, continuoussubduction since at least the Jurassic

Motivation:

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HvE – Regionale Geologie – WS 12/13

W E

km ~21°SElger et al. 2005, Tectonics

?

HvE – Regionale Geologie – WS 12/13

Approach:

Voigt et al. 2008

example 2: Late Miocene to Pliocene uplift & canyonincision, Western Flank, S-Peru

example 2: Late Eocene to Oligocene uplift & provenance change, Western Flank, N-Chile

example 3: Late Miocene to Pliocene uplift/ deformation vs. accumulation rates, Subandean Range/ Foreland, S-Bolivia

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sediment samples & potential source rocks

HM single-graingeochemistry

detrital zircon U/Pb geochronology

heavy mineral petrography

detrital zircon FT thermochronology

timing of Andean uplift large-scale processes

provenance model

cf. A. Decou

Approach:(example-1)

HvE – Regionale Geologie – WS 12/13

Decou 2011 (modified fromSempere et al. 2002 and INGEMMET)

Setting:CoastalCordillera

Western Cordillera

Moquegua forearc basin

500 m of sedimentin ~50 Ma

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HvE – Regionale Geologie – WS 12/13

Wotzlaw et al. 2011, Terra Nova

north

ern

Chi

le –

Bol

ivia

/ 18-

19°S

Corquesyncline

HvE – Regionale Geologie – WS 12/13

active arcBMC

Wotzlaw et al. 2011

W E

Mesozoic

Mesozoic HM: zircon, tourmaline, rutile + apa (no garnet !)

Azapa-Fm (Olig.) HM: epidote, hornblende, pyroxene + grt, zrc, rt, tou

Azurita-Fm (Olig.) HM: garnet + zrc, apa, px, hbl, (tou)WA

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HvE – Regionale Geologie – WS 12/13

Victor et al. 2004, Tectonics

HvE – Regionale Geologie – WS 12/13

Wotzlaw et al. 2011 (simplified after Kohler 1999 and Horton et al. 2001)

<30 Ma

23 Ma

Azapa Fm.Azapa Fm.

~10 Ma

23-24 Ma

20 Ma

20 Ma

~35 Ma

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HvE – Regionale Geologie – WS 12/13

Wotzlaw et al. 2011

tourmalinegeochemistry

→ tourmaline is derived almost exclusively from recycling of Mesozoic sediments

HvE – Regionale Geologie – WS 12/13

Wotzlaw et al. 2011

→ garnet reveals mixed provenance for the Azapa-Fm (forearc) from the BMC as well as magmatic rocks (and their contact aureoles);

and local/regional pro-venance for the Azurita-Fm. from Uyaraniequivalent basement

garnetgeochemistry

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Wotzlaw et al. 2011

rutile geochemistry

→ rutile from Azapa-Fm.underlines significant contribution from BMC (in addition to recycling of Mesozoic siliciclastics)

BMCpeak-T

HvE – Regionale Geologie – WS 12/13

Wotzlaw et al. 2011

zircon U/Pb geochronology

→Azapa-Fm U/Pb ages reveal mainly erosion of Mesozoic substratum including Toquepala arc intrusives plus minor Eocene/early Oligocene volcanism;

while Azurita-Fmzircons yield exclusively Grenville-Sunsas ages (1.0-1.2 Ga) reflecting local Uyarani-type basement

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Wot

zlaw

2009

HvE – Regionale Geologie – WS 12/13

Jurassic – Early Cretaceous

Late Cretaceous – PaleogeneWotzlaw et al. 2011, Terra Nova

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Late Eocene

Early-Middle EoceneEocene arc volcanism (lower Lupica Fm.?)

Oligocene

Wotzlaw et al. 2011

HvE – Regionale Geologie – WS 12/13

Victor et al. 2004, Tectonics

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Sch

ildge

net

al.

2007

, Geo

logy

example 2: canyon incision, S-Peru

HvE – Regionale Geologie – WS 12/13

Schildgen et al. 2007, Geology

Cotahuasi-Ocona Canyon

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1 km, 60-9 Ma: ~0.02 mm/a

1 km, 9-5 Ma: ~0.25 mm/a

after 5 Ma to ~2 Ma: ~0.5 mm/a

Schildgen et al. 2007, Geology

HvE – Regionale Geologie – WS 12/13

example 3: Foreland basinSubandean Ranges, S-Bolivia

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HvE – Regionale Geologie – WS 12/13Uba et al. 2009, EPSL

HvE – Regionale Geologie – WS 12/13Uba et al., 2009, EPSL

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Uba et al. 2009, EPSL

HvE – Regionale Geologie – WS 12/13Uba et al., 2009, EPSL

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Jaillard et al. 2002, Tectonophysics

Late Miocene to Pliocene uplift & canyon incision starting at ~9 Ma, mainly relatedto warping of the western margin of the Andean plateau (Western Flank, S-Peru)

Late Eocene to Oligocene uplift & provenancechange, establishment of an effective E-W drainage divide, mainly related to upper crustal shortening (Western Flank, N-Chile & S-Peru)

Late Miocene (~ 12 to 6 Ma) pulse in shortening, foreland propagation, and

sedimentation rates (Subandean Range/ Foreland basin, S-Bolivia)

HvE – Regionale Geologie – WS 12/13

Decou A, von Eynatten H, Mamani M, Sempere T, Wörner G (2011): Cenozoic forearcbasin sediments in Southern Peru (15-18°S): Stratigraphic and heavy mineral constraints for Eocene to Miocene evolution of the Central Andes. Sedimentary Geology, 237, 55-72.

Wotzlaw JF, Decou A, von Eynatten H, Wörner G , Frei D (2011): Jurassic to Paleogenetectono-magmatic evolution of northern Chile and adjacent Bolivia from detrital zircon U-Pbgeochronology and heavy mineral provenance. Terra Nova, 23(6), 399-406 .

References:

Jaillard E, Herail G, Monfret T, Wörner G (2002): Andean geodynamics: main issues and contributions from the 4th ISAG, Göttingen. Tectonophysics, 345, 1-15.

Uba CE, Kley J, Strecker MR, Schmitt AK (2009): Unsteady evolution of the Bolivian Subandean thrust belt: The role of enhanced erosion and clastic wedge progradation. Earth and Planetary Science Letters, 281, 134-146.

Schildgen TF, Hodges KV, Whipple KX, Reiners, Pringle MS (2007): Uplift of the western margin of the Andean plateau revealed from canyon incision history, southern Peru. Geology, 35, 523-526.