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Rampes latérales et zones de transfert dans les chaînes plissées : géométrie, condition de formation et pièges structuraux associés

Abstract : On the basis of analogue modelling experiments we evidence that the development of transverse zones in fold-and-thrust belts is directiy related to a longitudinal variation of (1) the thickness of the allochthonous sequence and/or (2) the shear strength at the base of the prism. In cases of fold belts provided of a ductile decollement level, any oblique discontinuity within the detachment layer (i.e. abrupt thickness variation, presence of salt ridges ... ) controls the forming and the orientation of thrusts in the overlying britlle cover. Three natural examples of transfer zones taken in the Western Alpine foreland illustrate the observations derived from laboratory models : The northern and southern oblique fronts of the Jura arcuate belt are both located above a lateral disappearance of the Triassic decollement level (sedimentary pinch-out for the Southern Jura or normal faulting for the Northern Jura). Theses transverse segments display a finite deformation pattern combining compressive regime with wrench tectonics, as regional shortening directions are strongly deflected to trend nearly perpendicular to the strike of the transfer zone. The Western Vercors thrust belt corresponds to a transverse zone induced by the lateral thickening of the allochthonous cover, added to the presence of basal Triassic salt in the south of the massif. These variations along strike cause (1) the development of en-échelon folds at the frontal part of the belt and (2) the augmentation of the wave-length of imbricate thrust sheets, as the longitudinal decrease of the basal shear strength provokes a progressive reversai of the polarity of the belt from north to south.
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Contributor : Pascale Talour <>
Submitted on : Wednesday, November 21, 2012 - 4:43:06 PM
Last modification on : Tuesday, January 22, 2019 - 3:51:42 PM
Long-term archiving on: : Saturday, December 17, 2016 - 12:55:48 PM

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  • HAL Id : tel-00755680, version 1

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Yann Philippe. Rampes latérales et zones de transfert dans les chaînes plissées : géométrie, condition de formation et pièges structuraux associés. Tectonique. Université de Savoie, 1995. Français. ⟨tel-00755680⟩

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