Interaction of geomorphology and tectonics in the evolution of the Orobic Alps (central Southern Alps)

Although numerical and physical models clearly demonstrated the dynamic coupling of tectonic evolution with surface processes, the landscape is still often interpreted as the result of the climatic action only. Valley patterns in mountain areas are often related to glacial and fluvial erosion, without considering the influence of structures. The aim of this work is to find out the relationships between tectonics and geomorphology to get an evolutionary model of the Orobic Alps (Central Southern Alps, Italy). The structural model is based on previous authors’ works, cross-sections (traditional and balanced) and interpretation of existing data. This analysis allowed the reconstruction of the alpine deformation phases and of the relative chronology of structures. Geomorphology and Quaternary geology field-data, aerial photos-DEMs interpretation and evaluations of the erosion rates gave informations on the landscape evolution. Sandbox experiments helped to understand the linkage between structures and morphologies, kinematic and erosion. The integration of structural and geomorphological analysis showed the close relationship between valley evolution and tectonics. The contemporaneous evolution of valleys and relieves has been demonstrated: the initial valley pattern was created during the alpine deformation phases together with the structures. Weathering and gravity acted during and after the orogenesis dismantling part of the relief. Rivers and glaciers played a minor role, mainly transporting and depositing the debris previously produced, rather then actively eroding the valleys. Therefore, the Orobic Alps landscape is mostly inherited by the structural shaping of the surface during the alpine deformation phases.