DEUQUA 2014 Innsbruck 62 The Marocche rock avalanches, Trentino Italy Susan Ivy-Ochs 1 , Silvana Martin 2 , Paolo Campedel 3 , Alfio Viganò 3 , Silvio Alberti 2 , Manuel Rigo 2 , Christof Vockenhuber 1 1 ETH, Ion Beam Physics, ivy@phys.ethz.ch , 2 University of Padua, Geosciences Department, silvana.martin@unipd.it , 3 Geological Survey of the Province of Trento, Trento , Italy , alfio.vigano@retesismicatrento.org Numerous rock avalanche deposits of undetermined age are located along the Adige and Sarca valleys (Trentino, Italy) of the Eastern Alps. With a view to understanding predisposition and triggering factors, thus ultimately paleoseismicity in the region, we are studying several of the largest rock avalanches. The Marocche di Dro is one of the most extensive of these deposits with an area of 13 km 2 and an estimated volume of about 109 m 3 . The Marocche deposits cover the lower Sarca Valley north of Lake Garda for a length of more than 8 km. There up to seven rock avalanches with release areas on both sides of the valley have been mapped by various authors. The rock avalanches developed within carbonate rocks of Mesozoic age, mainly limestones of the Jurassic Calcari Grigi Group. The main scarps are located on the western side of the Sarca Valley, along the steep faces of Mt. Brento and Mt. Casale. The presence of these scarps is strictly related to the Southern Giudicarie and the Trento - Cles fault systems. The former is here constituted by regular NNE - directed ESE - vergent thrust faults. The latter has been reactivated as normal faults. These complicated structural relationships favored complex failure mechanisms, including rock slide and massive collapse. At the Marocche di Dro itself, based on morphostratigraphy, vegetation differences, and degree of karst development on the boulders, we differentiated two large rock avalanches: the Marocca di Kas in the south and the Marocca (s.s.) in the northern sector. Preliminary 36Cl exposure dating results for boulders of the two deposits suggests middle and late Holocene ages. The latter are in part comparable with post-Roman ages proposed by Trener in 1924 based on the presence of artifacts at the base of the younger deposits. Zitate Trener GB . 1924 : Geologia delle Marocche . A.Scotoni, Trento : 25 - 33