Structural inheritance and cenozoic stress fields in the Jura fold-and-thrust belt (France)

Abstract

Based on an analysis of 8000 minor fault-slip data in the Jura Mountains (France), we discuss the influence of pre-existing discontinuities on the development of fold-and-thrust belts. We present palinspastic maps showing the stress fields and active faults during the Cenozoic pre-orogenic events in the Jura belt prior to the main Late Miocene fold-and-thrust tectonics. During the Eocene, a N -S strike-slip regime produced a few NNE -SSW sub-vertical strike-slip faults in the central external Jura and a few E -W reverse faults in the eastern Jura near the future frontal thrust. During the Oligocene, an average WNW -ESE extension, with irregular stress trajectories, resulted in normal faulting along N -S to NE -SW trends in the external part of the belt, WNW -ESE trends along the future northern and northeastern frontal thrust, and NW -SE trends in the internal Jura. The Late Miocene tectonics began with a strike-slip regime with a fan-shaped compressional trajectory. It was followed by a stress field with similar stress direction, but local r 2 /r 3 stress permutation resulted in strike-slip regime domains contrasting with reverse regime domains. Stress deflections and permutations occurred near inherited cover and basement discontinuities. Major deformation zones, like the Jura frontal thrust onto the foreland, the thrust of the internal central Jura onto the external Jura, and the narrow deformation bands within the flat-lying plateaus formed close to the inherited faults. The structural style of the Jura belt thus partly mimics the pre-orogenic fault pattern. Stress deflections point to the pre-orogenic faults, express the indentation process of the Jura by its hinterland, and highlight successive slip events along major faults during the fold-and-thrust tectonics. This case study illustrates the relevance of minor fault-slip studies for characterizing both the pre-orogenic tectonics and the kinematics of the deformation. D

Alpine paleostress reconstruction and active faulting in Western Iberia

“…δA, angular deviations of the stress solutions for each fault population [44]. nucleation of a later deformation [2,49]. The reactivation of pre-existing basement discontinuities produces stress deflections and principal stress axis permutations [50,51].…”

“…Within the Iberian microplate, as in the rest of the Eurasian Plate, the Variscan basement crops out extensively. Studies dealing with paleostress reconstructions in areas with Mesozoic, Cenozoic * E-mail: loreant@geo.ucm.es and recent sedimentary rocks are abundant [1][2][3][4][5]. Nevertheless, in extensive intraplate areas where the basement is dominant, only a few studies have attempted to determine the post-Variscan paleostress orientations.…”

Tectonic evolution around the Mont Terri rock laboratory, northwestern Swiss Jura: constraints from kinematic forward modelling

“…Butler et al 2006;Giambiagi et al 2003). Deformation events predating thrust-belt initiation affect the geometry of the basal décollement horizon, potentially even offsetting it, and lead to the formation of fractures and faults that can act as pre-existing zones of mechanical weakness during thrust-belt formation (Laubscher 1985(Laubscher , 1987Homberg et al 2002;Ustaszeswki and Schmid 2007;Madritsch et al 2008). In 2003, Freivogel and Huggenberger proposed an initial interpretation of the deep structures beneath the Mont Terri rock laboratory based on a balanced cross section of the Mont Terri anticline along the Mont Terri motorway tunnel.…”

Contemporaneous multi-scale structures in the Montagne des Mémises (Préalpes du Chablais, Haute-Savoie, France)

“…similarly, we propose that both the strike-slip and normal faulting in the Montagne des Mémises occurred during the same large-scale folding event. similar extension, parallel to the fold axes (like σ 3 ), has been observed in the Préalpes romandes (Mosar 1991, Mettraux & Mosar 1989) and in the Jura (Homberg 2002), but in these cases it was not possible to analyze the bedding plane-faulting rela- tionships. In the Montagne des Mémises, the relation between the bedding planes and the faulting suggests that the faulting was contemporaneous with the folding.…”

“…However, previous studies did not include bedding plane orientations, thereby limiting the comparisons that can be made with our results. two types of stress regime have been recognised in Late Miocene rocks in the Jura Mountains (Homberg 1997, Homberg et al 2002: a strike-slip regime (σ 1 = NW-sE and σ 3 = NE-sW) and a reverse regime (σ 1 = NW-sE and σ 2 = NE-sW). Due to the low dip of the bedding planes, it was impossible to carry out such an analysis for the Montagne des Mémises localities.…”