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Master Thesis

Tectonique d'inversion et glissements gravitaires en milieu sous marin, effet de la mobilité du bloc ibérique (Vercors méridional, Haut Diois & Dévoluy occidental

Abstract : The Dévoluy massif (French Western Alps) was located at the toe of the Cretaceous Vercors platform margin. It shows a sharp unconformity separating the lower and upper Cretaceous pelagic sediments. The Jurassic and lower Cretaceous beds are folded and cut by a rugged erosional surface overlain by the Senonian sediments. The area has been later deformed within the Alpine foreland. The pre-Senonian folding phase, which consist of N-S shortening, is classically assigned to the Pyrenean-Provence orogeny, but an alternative interpretation has been recently proposed (Michard et al., submitted), which involves large-scale gravity sliding from the Vercors platform margin. In order to test these hypotheses, the study focuses on two normal faults which have been affected by N-S shortening during Late Cretaceous: one is closer from the platform edge in an area which remained feeded by carbonate clastic sediments during inversion (a), the other one in a farther area which suffered sea-bottom degradation (b).
- a) In the Glandage area, the Senonian beds onlap an older (Albian-Cenomanian) normal fault scarp, and coeval compressional deformation is shown by erosional toplaps.
- b) In the Clausis area, the coeval sediments are partly missing due to deep truncation of the compressional structures by submarine erosion. The erosion surface is covered by Late Cretaceous (Campanian) turbidites.
The comparison of these two areas allows to propose the following succession of events:
1- After Valanginian : NW-SE extension possibly of gravitational origin as a consequence of the enhancement of the SE-dipping platform-basin slope.
2- During latest Albian or Cenomanian : N-S extension producing the S-dipping Glandage and Clausis normal faults.
3- After Middle Turonian : N-S shortening affecting the previous normal faults and producing a regional E-W trending folds network, dominantly north-recumbent.
4- Before Campanian : in the eastern area (Dévoluy), gravity-driven N-S extension overprints the folded sea-bottom coeval with significant removal of lower Cretaceous rocks. The sliding criteria are dominantly north-directed and not consistent with the platform margin morphology, which suggests the occurrence of a submarine slope created by inversion (3).
5- The whole area is finally covered by marine Campanian-Maastrichtian sediments (from slope fans to turbidites) then involved in younger Alpine deformation stages.
From geodynamic point of view, the Senonian inversion fits with the kinematics of the Iberian plate through the earliest Pyrenean-Provence compressional phase.
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Submitted on : Tuesday, January 12, 2010 - 10:36:02 AM
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Vincent Franzi. Tectonique d'inversion et glissements gravitaires en milieu sous marin, effet de la mobilité du bloc ibérique (Vercors méridional, Haut Diois & Dévoluy occidental. Tectonique. 2009. ⟨dumas-00446138⟩

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