Interplay of fluvial incision and rockfalls in shaping periglacial mountain gorges

Fluvial incision is the consequence of landscape readjustment to combined tectonic and climatic processes. In southwestern Alps (Haute Provence Geopark), deep gorges incised by Bès River attest efficient erosional processes at front Alpine mountain range. This catchment stands in a peripheral position, out glaciated domain during last glacial periods, which makes it suitable quantify fluvial related glacier-free environment. this paper, we combine high resolution 3D topographic mapping situ produced cosmogenic 36Cl dating gorge (the “Clue de Barles” Gorge). First, very high-resolution modeling from aerial drone surveys permits map erosion markers on walls accurately determine shielding factor for Cosmic Ray Exposure (CRE) dating. Secondly, CRE age distribution highlights two distinct geomorphic domains along vertical profile: i) higher section characterized clusters similar ages, interpreted as paraglacial rockfall events; ii) lower shows increasing ages with height, are ascribed occurring rate 0.15 mm/yr since 25 ka, 2 ka. Our results Clue Barles, compared other sites South French highlight that: morphology result combination both lateral gravitational processes, mean Quaternary least twice than further east formerly Alps.