Evolution tectono-sédimentaire et caractérisation des niveaux de décollement dans le Bassin stéphanien de Graissessac (sud du Massif Central, France)

Abstract : The Stephanien Graissessac basin located on the Southem edge of the french Massif Central, is one of a series of Carboniferous intramontane extensional basins. It is located immediately at the North of the Espinouse detachment fault oriented N100°E. It shows a geometry characterized by a spread half-graben structured by a progressively discordant dissymmetrical syncline. The Stephanian Graissessac basin is characterized by filling composed of fluviatile deposits and coal bearing strata in the East, which passes laterally to alluvial fans in the West. Tectono-sedimentary analysis highlights the narrow control exerted by the Espinouse bordering normal fault structuring the half-graben basin. This reveals two types of structuring. At the basin scale, synsedimentary deformation is characterized by network of normal syn- to post-lithification faults, whitch defined by a coaxial deformation regime, associated at N40°E stretching direction. In the eastem part of the basin, this extensional structuration coexist with overfold structures tilted towards the south. These structures are characterized by a no-coaxial deformation regime related to a gravity-induced tectonic decollement, located on the principals coal measure. This structuration is closely associated at the half-graben shaped basin and tilted stephanian unit towards the south. The integration of all structural and microtectonic data shows that the extensional syn-sedimentary structuration of the Stephanian Graissessac basin is associated through time with an anti-clockwise progressive rotation of the main direction of extension successively from the azimuth N40°E to the azimuth N160°E. At the regional scale, the whole of the data allows to characterize an extensional tectonic regime and to integrate the Graissessac stephanian basin within the framework of the late-orogenic extensional variscan belt in the french Massif Central.
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Theses
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http://docnum.univ-lorraine.fr/prive/SCD_T_1999_0171_BELHANNACHI.pdf
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Submitted on : Thursday, March 29, 2018 - 10:50:47 AM
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Hamza Belhannachi. Evolution tectono-sédimentaire et caractérisation des niveaux de décollement dans le Bassin stéphanien de Graissessac (sud du Massif Central, France). Sciences de la Terre. Université Henri Poincaré - Nancy 1, 1999. Français. ⟨NNT : 1999NAN10171⟩. ⟨tel-01747088⟩

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