Tectonic styles affecting the frontal part of the Jura (dashed rectangles) as functions of the Triassic décollement friction angle and of the lower crust friction angle ϕ_LC. In the South, on cross-section A, the tectonics is either inactive (dark grey), thin-skinned (blue) or reaching beyond the Jura front (light grey). Towards the North-East, the Jura evolves to a thick-skinned style on cross-sections D and E, activating the Triassic décollement (green) or not (yellow). On cross-sections B and C, both thin- or thick-skinned tectonics are possible (black dots in the graph C correspond to the examples of Fig. 3). These results suggest that a thick-skinned front cross-cuts the Jura belt (see Fig. 5).