Proceedings of the 12th International INQUA meeting on paleoseismology, active tectonic and archaeoseismology

476 PATA Days 2024 M E T H O D S We acquired a high-resolution (0.5 m pixel size) digital surface model from Pléaides satellite images (provided by CNES through the ISIS program) using the software freewareMicMac® at the scale of the whole Sansepolcro basin (Fig.1). In addition, we acquired a high-resolution (0.2 m pixel size) DTM LiDAR on a smaller area (1.45 km2 Fig.2). We used the Lidar DTM to map the paleosurfaces and fault alignments and perform a quantitative geomorphological analysis. We projected the gullies and the risers of the paleosurfaces on several topographic profiles parallel to the drainage using GMT®. This analysis allows quantifying fault topographic displacement and gullies incisions and comparing the slope of gullies and surfaces to understand the morphotectonic significance of the mapped features. To perform the dating of the investigated paleosurfaces we used the Cosmogenic nuclides methodology. Surface exposure dating using in situ-produced cosmogenic nuclides is a relatively young and powerful tool in Quaternary geochronology (Pousse-Beltran et al. 2022; Moulin et al. 2016;). To date the exposure of the displaced paleosurfaces using in situ-produced cosmogenic nuclides, we systematically collected limestone pebbles within three different depth pits at the top of the paleosurfaces (two at the hanging wall of the Anghiari fault and one at its footwall). The sample preparation was performed following the procedure described by Stone et al. (1996) and modified by Schlagenhauf et al. (2011). Both 36Cl and Cl concentrations were obtained on each sample by isotope dilution accelerator mass spectrometry at the national French Accelerator mass spectrometry facility (Accélérateur pour les Sciencesde la Terre, Environnement, Risques; Centre de Recherche et d’Enseignement des Géosciences de l’Environnement, ASTER-CEREGE, Aix-en-Provence)measuring both the 36Cl/35Cl and the 35Cl/37Cl ratios.We calculated 36Cl cosmic-ray exposure ages using the Excel® spreadsheet of Schimmelpfennig et al. (2009) and the 36Cl production rate for spallation of Ca, reference to sea level and high latitude (SLHL), of 42.2 ± 4.8 atoms 36Cl (g · Ca)−1 · yr−1 (Schimmelpfennig et al., 2011) with the time- invariant scaling method by Stone (2000). Exposure ages were calculated using the time-independent Stone (2000) scaling functions for all cosmogenic nuclides. The density was measured at each site, collecting, and weighing a certain amount of sediment. Figure 2. DTM LIDAR (0.2 m/pixel) and geomorphological interpretation. Fig. 2:DTM LIDAR (0.2 m/pixel) and geomorphological interpretation.