GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 1.1 - POSTER GNGTS 2023 Fig. 2 – LiDAR-derived DTM evidencing the paleosurface (green) capping the remnant of an ancient, suspended alluvial fan (2nd order depositional paleosurface, Lower-Middle Pleistocene in Robustelli and Muto, 2017). The surface is apparently offset by the MFF (red line; 11 m of vertical separation along blue dotted line). Black dotted line is the 10-m-spaced ERT across the scarp. Below is the topographic profile obtained from the DTM. Conglomerate thickness is deduced from field survey. To understand whether or not the 11 m offset between the two paleosurface flaps was due to faulting, we carried out a 10-m-spaced-electrodes Electrical Resistivity Tomography (ERT) that showed clearly a vertical contact at depth between bodies with different resistivity. Figure 3 displays the preliminary elaboration of the ERT (without topography), showing an upper body with high resistivity values (> 1000 Ohm*m), ~30-m-thick in the footwall, and up to ~60-m-thick in the hanging wall. Assuming that this high-resistivity body represents the paleofan gravels - as we surveyed in the field along the scarps bordering the surface - its bottom is displaced by ~25 m, roughly twice as much as that of the surface (11 m in Fig. 2).