Tectonic evolution of the Alpine orogen

Jacques Charvet ISTO, Orléans, France

06-04-2012 Carpathian belt

Dinarides

Alps Balkan

Apennines Str. Sketch Alps

European margin: Ext: Outer zone; V: Valais zone; P: Penninic=Inner zones; Apulian margin: AA: Austro-Alpine; SA; South-Alpine; FH: Helminthoid Flysch Oph: Ophiolite Schematic structural map of the Alps

Central Alps Eastern Alps

Southern Alps

Western Alps Schematic diagram (Central and Eastern Alps) showing the piling of European, oceanic, and Austroalpine and South-Alpine unitsApulian plate = Adria

Austroalpine units South-Alpine units

Po basin molasse Oceanic units

European units Molassic foreland basin European plate European foreland Gosau beds

Handy et al 2010 EASTERN AND SOUTHERN ALPS Hohe Tauern Structural sketch of Eastern Alps tectonic window European Penninic units Northern Calcareous Alps

European basement Vienna

HP Metamorphic units (Eocene)

Eastern Alps

Southern Alps The peri-Adriatic Line (Fault) : a dextral strike-slip fault between the Southern Alps and the Eastern and Central Alps

Oligocene granite Structural map of Southern Alps N-S cross-sections of Southern Alps

Tauern window

Basement-Pz T - K III

EUROPE ADRIA Post-thrusting Messinian beds

Inner zones CENTRAL ALPS Str. Sketch Alps

Central Alps

European margin: Ext: Outer zone; V: Valais zone; P: Penninic; Apulian margin: AA: Austro-Alpine; SA; South-Alpine; FH: Helminthoid Flysch Oph: Ophiolite Cross-section through Central Alps

Prealps: stack of nappes of Sesia Zone: AA various origins or Europe? Matterhorn

Ivrea Zone: Apulia Oligocene Oligocene HT Bergell metamorphism granitoid

Metamorphic map of Tessin area WESTERN ALPS Str. Sketch Alps

Western Alps

Ophiolitic suture

European margin: Ext: Outer zone; V: Valais zone; P: Penninic; Apulian margin: AA: Austro-Alpine; SA; South-Alpine; FH: Helminthoid Flysch Oph: Ophiolite Structural map of Western Alps

Penninic Front

Inner crystalline massif Outer crystalline massif Possible deep structure of Western Alps along the ECORS-CROP profile Lithostratigraphy Handy et al 2010 Structural map of Western Alps

6 3

Penninic Front 4 1 Inner crystalline massif Outer crystalline massif

5

2 1 Eybens 2 Bonnette pass 2 Bonnette pass, block-bearing Upper Eocene flysch 3 Lautaret Chenaillet, pillow-lavas 4 4 Chenaillet-Gondran, oceanic sediments 5 Jausiers, Barcelonnette; Helminthoid Flysch on Jurassic 6 Petit St Bernard pass Geodynamic evolution

Rifting and ocean spreading Norian Ornon Dauphinois tilted blocks Ornon pass

Taillefer fault, Chalp d’Ornon Europe paleomargin

European margin Ocean Neo-Tethys

Handy et al 2010

Alpine Tethys

Vardar obduction Schematic cross-section through the main Alpine structural units, showing their paleo-geographic origin

Apulia, Europe Intermediate block Adria K1 Valais Ocean Briançonnais Liguro-Piemontais Ocean

J3 Valaisan rift

T3-J1 Liguro- Piemontais rift Handy et al 2010 Geodynamic evolution

Metamorphic record of subduction and collision Handy et al. 2010 Subduction stage Metamorphic zonation of Western Alps P-T-t paths of main units of Inner zones on the transect Digne-Dora Maira

Comparison of uplift speeds for several units of Inner Zones Oberhänsli and Bousquet 2011 Collision stage Berger et al. 2011 Berger et al. 2011 Comparison Western-Central Alps Oberhänsli and Bousquet 2011 Oberhänsli and Bousquet 2011

Berger et al. 2011 Chenaillet Structural sketch map of Briançonnais and W dip surrounding zones between Briançon Outer zone and Ubaye H Fl Br

H Fl

Tectonic window Section through Inner Zones of Western Alps: from Helminthoïds Flysch nappe to « Schistes Lustrés »

Back-thrusting

H Fl Geodynamic evolution

Summary Handy et al 2010 Handy et al 2010 Handy et al 2010

Handy et al 2010 Opening of the Bay of Biscay

Handy et al 2010

Building of Eo- Alpine orogen

Independent Adria plate Piemont ocean subduction

Unconformable Gosau deposits

Handy et al 2010 Collision

Handy et al 2010

Last Dinaric thrusting

Apenninic thrusting Handy et al 2010 Handy et al 2010 CONCLUSIONS

Criteria of collisional belt: -Ophiolitic suture -Stack of nappes -High pressure metamorphism -Foreland molassic basin Criteria lacking or poorly developed: -Magmatic arc -Thermal overprint due to crustal thickening: Eastern Alps -Post-collisional crustal melting: Eastern Alps Peculiarities: -Outer zone (lower plate) well preserved -Huge basement nappe of the upper plate -Interaction of numerous small plates

During its evolution, stage of accretionary orogen, with subduction and exhumation of HP units before final collision Difference between oceanic closure and end of deformation THANKCONCLUSIONS YOU

Criteria of collisional belt: -Ophiolitic suture -Stack of nappes -High pressure metamorphism -Foreland molassic basin Criteria lacking or poorly developed: -Magmatic arc -Thermal overprint due to crustal thickening -Post-collisional crustal melting Peculiarities: -Outer zone (lower plate) well preserved -Huge basement nappe of the upper plate

During its evolution, stage of accretionary orogen, with subduction and exhumation of HP units before final collision

Cross-section and reconstruction at Late Jurassic Paleo-geographic units at the beginning of Late Jurassic

Europe

Valais rift

Apulia

Oberhänsli and Bousquet 2011