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Etude géologique des unités briançonnaises de Vanoise occidentale au sud-ouest de Pralognan (Savoie) : Evolution sédimentaire et structurale.

Abstract : This stratigraphic and structural study is based on a new detailed geological map (1/10 000°) of the briançonnais units that rest upon the Houiller massif, between the Péclet-Polset Massif, and the towns of Courchevel and Pralognan, in the Western Vanoise Massif. It aims to reconstruct the evolution of this part of the Briançonnais zone, from Triassic times, to the end of the Alpine orogeny. Stratigraphy. After deposition of the Early Triassic (Scythian) sandstones, a carbonate platform developed in the Middle Triassic, which deposited sedimentary sequences correlatable with those defined in other areas of the Briançonnais zone. Above the upper (9°) sequence, breccias layers locally seal important tectonic deformations, which would be of Carnian, or Liassic or early Middle Jurassic, age. The emergence of the Briançonnais domain during the Middle Liassic provoked large scale deformations, significant erosions, and karstic cavings. The Middle Jurassic transgression began with subaerial deposits (Bajocian-earliest Bathonian ?), first carbonated, then siliciclastic and aluminous. Then, internal carbonate shelf deposits (Bathonian), and limestones of outer shelf environments (Callovian) were deposited. The Late Jurasic Cretaceous period was marked by condensed pelagic deposits, marked by numerous and long-lasting hiatuses (latest Jurassic to Middle Cretaceous ?, latest Cretaceous to late Paleocene). The succession ends up with the appearance of shales and carbonated sandstones of probable Middle Eocene age. Structure. Five deformation phases have been identified : - thrusting of the carbonated Briançonnais cover upon the Houiller zone, - large scale, northward verging isoclinal folds deform the nappe stack, - East-verging thrusts and folds deform the prior structures, - South-East verging thrustings are associated with the senestral wrenching of the Chavière fault zone, - minor transcurrent and normal faults crosscut the area. As a conclusion, paleogeographic and tectonic reconstructions are proposed for the Briançonnais units of the Western Vanoise Massif.
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https://tel.archives-ouvertes.fr/tel-00502229
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Submitted on : Wednesday, August 21, 2013 - 10:51:36 AM
Last modification on : Friday, March 25, 2022 - 11:10:22 AM
Long-term archiving on: : Thursday, April 6, 2017 - 12:28:26 AM

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  • HAL Id : tel-00502229, version 2

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Etienne Jaillard. Etude géologique des unités briançonnaises de Vanoise occidentale au sud-ouest de Pralognan (Savoie) : Evolution sédimentaire et structurale.. Géologie appliquée. Université Joseph-Fourier - Grenoble I, 1984. Français. ⟨NNT : ⟩. ⟨tel-00502229v2⟩

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