GNGTS 2016 - Atti del 35° Convegno Nazionale

GNGTS 2016 S essione 1.1 133 Fig. 3a shows a thin section coming from a pocket of colluvium located along the main fault strand (Fig. 1e). At the mesoscale (Fig. 3a), the slide presents a set of sub-vertical fractures (corresponding to planar voids at the microscale) and some coarse fragments from the marly bedrock. At the microscale, the coarser elements of the micromass present a parallel sub-vertical orientation (Fig. 3b) aligned along tectonic strain axis. These stress features helped constraining one of the main tectonic deformation phases after the deposition of the colluvium, which has been involved in the displacement. Figs. 3c and 3d show thin sections sampled in correspondence of the fault gouge (Fig. 1e). The groundmass of the first slide (Fig. 3c) appears chaotic, with highly weathered soil fragments, coming from the colluvium and pinched in the weathered marl. The second slide (Fig. Fig. 1 – a) Location map of the studied sites (1: Monte Netto; 2: Pecetto di Valenza); the traces of the major frontal arcs of the N Appennines are also shown (from ITHACA database modified, https://goo.gl/55FwDH) ; b) geological sketch map of the Monte Netto area (modified after Livio et al. , 2014); the black box locates Fig. 1c; c) general view of the Monte Netto quarry wall, showing the south verging anticline analysed in detail: the box suggests the position of the sampled undisturbed block for the soil thin section shown in Fig. 2; d) geological map of the Pecetto di Valenza area (modified after Frigerio et al., in press): the location of the Pecetto site is indicated in the black box; e) general view of the Pecetto di Valenza section; the boxes indicate the position of samples collected for the soil thin sections shown in Fig. 3.