Quaternary rock avalanches in the Apennines. New data and interpretation of the huge clastic deposit of the L'Aquila Basin (central Italy)

In this paper we inferred the origin of a huge clastic deposit (i.e. L'Aquila Breccia) which widely crops out within the L'Aquila intermontane basin, a tectonic depression in central Apennines, that is bounded by seismogenic active faults, as demonstrated by the earthquake occurred on April 6, 2009 (Mw 6.1). The genesis of this deposit is still debated in the literature: for this reason, a number of methods have been applied, mainly aimed at evidencing its geomorphological and sedimentological features, as well as at defining its geometry and volume through cross sections constrained by borehole data and field observations. On the basis of the obtained results, we identified such deposit as resulting from a Quaternary rock avalanche event. In particular, the rock avalanche would have detached during the cold climate phases of late Middle Pleistocene from the southern slope of the Gran Sasso Range, a sector characterized by the presence of numerous DGSD-related landforms. We performed morphometric analyses of the Gran Sasso slope, in order to define the potential source area of the inferred rock avalanche and, according to the results, the volume estimated from this area (about 108 m3) is coherent with the volume calculated for the preserved rock avalanche deposit. Furthermore, we analyzed the main features of the deposit (i.e. age and morphometric parameters) also in the light of similar rock avalanche events occurred in the same region during the Quaternary, with the aim of discussing potential analogues and better understanding the role of gravity-induced processes in the Quaternary morpho-evolution of the Apennine chain.