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Tectonique cassante de l'arc interne des Alpes occidentales; implications géodynamiques

Abstract : Brittle deformation in the inner western Alps reveals a predominance of extensional deformation: 75% of all the measured faults are normal, while 25% indicate strike-slip motions. This neogen deformation regime is synchronous with compressional tectonics recorded in external parts of the belt. Geomorphic features document a very recent and ongoing normal faulting activity within the western Alps.
200 new paleostress tensors, calculated using the Direct Inversion Method [Angelier 1990] have been merged with previous data (Simplon and the Briançon areas). A dominant extension direction is orogen-parallel oriented, materialized in the form fan like pattern faults. A minor part of faults indicate an orogen-perpendicular extension; this faulting style is best developed in the southern, and diminishes in importance northeastward. Transcurrent faults are observed all along the belt. Strike slip movement is younger than extension in the southern areas whereas it is older in the northern. Tensional paleostress axes of the transcurrent tensors are close to those of the extensional tensors.
Two stages in the late evolution of the Western Alps are deduced and geodynamic models are proposed:
- lateral extrusion to the South during the latest stages of collision with a general NW-ward advance, anticlockwise rotation of the Apulia and the opening of the Ligurian sea.
- gravitational equilibration and collapse related to the current absence of convergence between Apulia and Europe, with orogen-perpendicular extension.
The transition between these two regimes is probably of Pliocene age, related to the diminution of the convergence and the erosion rate increasing in the Alps.
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Contributor : Jean-Daniel Champagnac <>
Submitted on : Wednesday, February 16, 2005 - 4:04:23 PM
Last modification on : Thursday, November 19, 2020 - 3:54:26 PM
Long-term archiving on: : Friday, April 2, 2010 - 9:02:22 PM


  • HAL Id : tel-00008513, version 1



Jean-Daniel Champagnac. Tectonique cassante de l'arc interne des Alpes occidentales; implications géodynamiques. Géologie appliquée. Université Joseph-Fourier - Grenoble I; Université de Neuchâtel, 2005. Français. ⟨tel-00008513⟩



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