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Installation et évolution de la plate-forme urgonienne (Hauterivien à Bédoulien) du Jura méridional aux chaînes subalpines (Ain, Savoie, Haute-Savoie) Sédimentologie, minéralogie,stratigraphie et paléogéographie et deuxième sujet : Dolomitisation,fracturation et porosité au voisinage d'une faille majeure (Urgonien du massif subalpin du Vercors)

Abstract : The study of the Hauterivian and Barremo- Bedoulian formations in Southern Jura and in the Northern subalpine chains , allowed defining and dating the main stages of emplacement and evolution of the Urgonian carbonated platform . Sedimentology : A model foracarbonated platform is propounded. It includes four paleogeographic domains : the basin, the outer slopes, the edge and the inner domain of the platform. Each of them is characterized by groups of facies comprising typical biological associations and microfauna. Mineralogy : This study involves (1) identification of the minerals (clays, quartz and goethite) contained in the sediments, (2) comparison between classes of mineralofacies and groups of microfacies, and (3) an original characterization of deposition environnents and of their evolution . It brought evidence for (1 ) a relation between nature of sediments and mineralogical associations, (2) a parallelism between mineralogical evolution and sequential evolution , (3) variations of paleogeographic context (asynchronous appearance or disappearance of minerals), and (4) refinement of the stratigraphy appearance of anomalies near stratigraphic limits) . Stratigraphy : From a paleontological point of view, two stratigraphic limits were accurately defined (Valanginian- Hauterivian and Lower Hauterivian- Upper Hauterivian ) From a sequential point of view, the sedimentary series studied, represented by a regressive megasequence , has been subdivided into eight major sequences, limited by important discontinuities . Concerning the correlations, the data obtained have been fitted into a regional framework, and accurate correspondences have been established between the Vercors and the Jura sections respectively. Paleogeography : Four main evolutionary stages of the platform have been recognized viz.: (1) several attempts at emplacement during the Hauterivian upon a morphology inherited from the ancient Valanginian platform , (2) slight withdrawed during the Lower Barremian, (3) maximal increase (appearance of protected anvironments) and stability during the Upper Barremian and (4) important withdrawed during the transition from Upper Barremian ta Bedoulian. SECOND SUBJECT : Through study of the Urgonian structural dolomitization close to a fault in the Vercors subalpine massif , the following factors are described : an early synsedimentary dolomitization and a structural dolomitization related to an ancient fracturation, a calcitization related to more recent fracturation systems, a dissolution inducing both intracrystalline porosity (connected with dedolomitization phenomena), intercrystalline or microfissural porosity.
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https://tel.archives-ouvertes.fr/tel-00523815
Contributor : Pascale Talour <>
Submitted on : Wednesday, October 6, 2010 - 1:44:10 PM
Last modification on : Wednesday, November 29, 2017 - 4:53:23 PM
Long-term archiving on: : Friday, January 7, 2011 - 2:36:17 AM

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  • HAL Id : tel-00523815, version 1

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Florence Viéban. Installation et évolution de la plate-forme urgonienne (Hauterivien à Bédoulien) du Jura méridional aux chaînes subalpines (Ain, Savoie, Haute-Savoie) Sédimentologie, minéralogie,stratigraphie et paléogéographie et deuxième sujet : Dolomitisation,fracturation et porosité au voisinage d'une faille majeure (Urgonien du massif subalpin du Vercors). Minéralogie. Université Scientifique et Médicale de Grenoble, 1983. Français. ⟨tel-00523815⟩

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