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Transpressional deformations at lateral boundaries of propagating thrust-sheets: the example of the Meuse Valley Recess within the Ardennes Variscan fold-and-thrust belt (N France–S Belgium)

Abstract : The 3D kinematics of the fold–thrust structures within the Meuse Valley Recess (MVR) (Ardennes Variscan thrust belt, N France–S Belgium) have been investigated using an integrated approach combining geological mapping, cross-section analyses and studies of magnetic fabrics and paleomagnetic data at a total of 52 sites distributed within the study area. Fold–thrust geometries, strain distribution and thrust-sheet rotational patterns lead to a conceptual structural model illustrating natural deformation processes at lateral boundaries of propagating thrust-sheets. The MVR is shown to result from distributed transpressional deformation of the Ardennes Basal Thrust hanging wall above a buried lateral/oblique ramp inherited from the Lower–Middle Devonian extensional tectonics of the sedimentary wedge. This deep lateral/oblique discontinuity basically controls the thickness and basal friction of the Ardennes thrust wedge, thus resulting in contrasting thrust propagation west and east of the MVR. Out-of-plane strain within the transfer zone includes some varying components of normal-to-bedding shear and lateral shortening depending on the proximity with the buried lateral discontinuity. A gradient of lateral shortening is evidenced towards this discontinuity, thus acting as a buttress zone. We emphasize the high friction conditions prevailing along the lateral borders of the thrust sheets, which potentially result in drag effects during foreland-directed thrust propagation. Such additional shear strain is suggested to be accommodated by late pervasive thrust-sheet rotation and lateral broadening of the deformed zone subsequent to oblique folding close to the lateral/oblique boundary.
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https://hal-brgm.archives-ouvertes.fr/hal-03758314
Contributeur : Frédérique COUFFIGNAL Connectez-vous pour contacter le contributeur
Soumis le : mardi 23 août 2022 - 09:12:58
Dernière modification le : jeudi 25 août 2022 - 08:29:16

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Frédéric Lacquement, O. Averbuch, J.-L. Mansy, R. Szaniawski, M. Lewandowski. Transpressional deformations at lateral boundaries of propagating thrust-sheets: the example of the Meuse Valley Recess within the Ardennes Variscan fold-and-thrust belt (N France–S Belgium). Journal of Structural Geology, Elsevier, 2005, 27 (10), pp.1788-1802. ⟨10.1016/j.jsg.2005.05.017⟩. ⟨hal-03758314⟩

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