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Modélisation 3D de l'interface socle varisque-couverture alpine dans le Massif du Pelvoux (Hautes Alpes, France)- Tectonique des socles et bassins à la limite secondaire-tertiaire.

Abstract : The Pelvoux massif (External Crystalline Massif, western Alps) belongs to the palaeopassive margin of the Tethys. It is a relevant area for the study of superimposed structures: evidences of the Tethyan rifting and the Alpine shortening can be observed. The Aiguille de Morges, Puy des Pourroys and Vallon massifs are pinches of mesozoic cover sediments on the crystalline basement. The basement - cover contact is, therefore, clearly visible in these massifs. This contact can be used as a marker of the finite deformation at an orogenie scale. Two stages of deformation have been recognized in the alpine cycle by geometric and kinematic studies. A first NE-SW shortening stage is followed by a E-W shortening deformation. By comparison with neighbouring areas led to propose that the first stage Dl is of late Cretaceous - early Eocene age, related to the "pyreneo-provencal" event. The D2 stage is late Oligocene. The characterization of these two episodes gives additional constraints on the geodynamic models. The crystalline basement was reactivated along pre-existing faults and developped kilometric-scale folds in respons to the Dl shortening whereas the mesozoic sediments were folded at all scales. This mechanical division is partly related to the distribution of fluids: these were diffuse in the sediments cover, but concentrated along big mylonitics fauIts of the basement, along wich the deformation concentrated. This deformation is contemporaneous with temperature conditions about 300 to 400 °C, and pressions ranging from 2 to 4 kbars, according to the mineralogic association of chlorite - muscovite - albite - pumpellyite on the SI plane in the basement. The Dl shortening is mainly responaible for the actual structure of the Morges massif. This hypothesis about the 3D geometry of the Morges massif is illustrated by a 3D surfacic model which was built using STRIM software. The model was restored using a 3D surfacic unfolding method (Unfold). The results of unfolding are in agreement with the main NE-SW compression Dl. This study shows that in the South-Pelvoux, the cover - basement contact becomes subvertical at depth. This geometry is consistent with that inferred from the ECORS seismic profile in the extemal part of the Alps
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Submitted on : Monday, August 27, 2012 - 8:46:48 AM
Last modification on : Wednesday, November 20, 2019 - 2:53:46 AM
Long-term archiving on: : Friday, December 16, 2016 - 7:44:00 AM

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  • HAL Id : tel-00614882, version 2

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Joëlle Lazarre. Modélisation 3D de l'interface socle varisque-couverture alpine dans le Massif du Pelvoux (Hautes Alpes, France)- Tectonique des socles et bassins à la limite secondaire-tertiaire.. Sciences de la Terre. Université Claude Bernard - Lyon I, 1997. Français. ⟨NNT : ⟩. ⟨tel-00614882v2⟩

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