The crustal structure of the westcentral Pyrenees revisited : Inferences from a new kinematic scenario

Antonio Teixell (1) , Pierre Labaume (2) , Yves Lagabrielle (3)

1 Department of Geology
2 Géosciences Montpellier
3 Systèmes Tectoniques

Crustal-scale models for the Pyrenees based on ECORS reflection profiles have around 20 years now. In recent years, new understandings were gained on the reconstruction to the preorogenic times, namely a scenario of extreme crustal attenuation and mantle exhumation ; in turn, this has implications on the interpretation of the present-day structure, as new models for the chain must consider feedbacks between the mid-Cretaceous hyperextension and the Pyrenean inversion. On the Wcentral Pyrenean traverse, the southern part comprises 3 S-vergent basement thrust units, the Lakora, Gavarnie and Guarga units, flanked by the detached cover of the Jaca piggyback basin and the Ebro basin, where the Mesozoic is thin and Late Cretaceous-Tertiary synorogenic carbonate and detrital sequences record a southward depocenter migration. To the N, the Chaînons Béarnais belt (CB) is a system of Jurassic to Lower Cretaceous carbonate anticline ridges separated by synclines with thick Albian-Cenomanian flysch, covered to the north by Upper Cretaceous flysch sequences. The CB is thrust southwards together with the Lakora thrust unit and northwards onto the Aquitaine basin. CB folding largely results from the rising and squeezing of diapirs initiated during the Jurassic-Early Cretaceous extension. Pieces of crust and mantle lifted in the diapirs attest that the CB derive from a Cretaceous domain of hyperextended continental crust and exhumed mantle. Moho reflections in the ECORS-Arzaq profile constrain the present deep structure. Restoration leads to a Mesozoic cover detachment over the N-Iberian and S-European margins. Inversion began by subduction of the exhumed mantle and folding and pop-up thrusting of the CB cover onto the margins. From the mid-late Eocene onwards, continental collision was accommodated by wedging and thrust stacking in the Iberian crust, involving the piggyback formation of S-vergent basement thrusts in the upper crust, and the northward subduction of the lower crust.

Domains: Earth Sciences

Antonio Teixell, Pierre Labaume, Yves Lagabrielle. The crustal structure of the westcentral Pyrenees revisited : Inferences from a new kinematic scenario. 24 ème Réunion des sciences de la Terre 2014, Oct 2014, Pau, France. pp.230. ⟨insu-01080831⟩