Thin-skinned inversion tectonics at oblique basin margins: example of the western Vercors and Chartreuse Subalpine massifs (SE France)

Abstract

Abstract The western Vercors and Chartreuse Subalpine fold-and-thrust belts form part of the western Alpine foreland that wa sinvolved in Neogene compressive tectonics. The deformation front of the two massifs is superimposed on the western margin of the Mesozoic Southeast Basin, which was inverted in the Late Miocene. Obliquity between this NE-SW-directed basin margin and the WNW-ESE Alpine tectonic transport resulted in the development of en-échelon folds and thrusts at the leading edge of the massifs. The gradual change of the tectonic style from the Chartreuse to the southern Vercors belts denotes that the initial configuration of the basin as well as the rheological properties of the basal detachment layer strongly influenced the geometry and the kinematic evolution of the two fold belts. This paper presents the geometry of the inverted western Tethyan palaeomargin through a series of balanced cross-sections and attempts to evaluate the possible boundary conditions that controlled the development of the western Chartreuse and Vercors massifs and the lateral variations of the tectonic style in the study area. Results of an analogue modelling experiment simulating a thin-skinned inversion of an oblique platform-basin transition zone are compared with those of the field study and used to discuss the role of the palaeogeographic inheritance on both the initiation and orientation of thrust faults in décollement tectonics.