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.