Reconstructing the Gorte and Spiaz de Navesele Landslides, NE of Lake Garda, Trentino Dolomites (Italy)

We applied a multi-method approach to reconstruct the Gorte rock avalanche (85-95 Mm3)located at the northeastern end of Lake Garda. The combination of field mapping, characterizationof bedrock discontinuities, Dan3D-Flex runout modeling and dating of boulders with cosmogenic36Cl supports the conclusion that the deposits stem from a single rock avalanche at 6.1 0.8 ka. TheGorte event may have triggered the Spiaz de Navesele-Salto della Capra landslide (3.2 Mm3), whosedeposits cover the southern end of the Gorte deposits. First-order controls on detachment were theNNE-SSW- and WNW-ESE-oriented fractures in the limestone bedrock, related to the Giudicarieand Schio-Vicenza fault systems, respectively. Dan3D-Flex runout modeling sufficiently reproducedthe Gorte rock avalanche, which involved detachment and sliding of a quasi-intact block, likely alongmarly interbeds, followed by rapid disintegration. The frictional rheology in the source area andthe turbulent frictional rheology (Voellmy) in the remaining part best replicate the observed depositextent and thickness. Heavy precipitation that occurred at that time may have contributed to failure atGorte. Nonetheless, its timing overlaps with the nearby (<15 km) Dosso Gardene (6630-6290 cal BP)and Marocca Principale (5.3 0.9 ka) landslides, making a seismic trigger plausible.