Fig. 11

Rose diagram showing the azimuths of striations measured on >400 strained pebbles in the whole area. The computation of all the measured pebbles shows a bimodal distribution of shortening direction (N156°E and N11°E). The mean striation value of the whole measured dataset is N7°E, and the bisector direction of the two principal modes is of N175°E. The bimodal distribution is correlated with the two main fault directions (see Fig. 12). This data strongly suggests that pebble deformation is controlled by localization along the fault direction. Striations appear by pressure-dissolution processes due to the incrustation of quartz sand onto the pebble surface. The absence of any striations in the direction perpendicular to the main shortening axis reflects a pure stylolithic incrustation in the N–S direction, while oblique pebble surfaces undergo sliding + incrustation producing the striations