PRESERVATION OF A LONG-LIVED FLUVIAL SYSTEM IN A MOUNTAIN CHAIN: THE TAGLIAMENTO VALLEY (SOUTHEASTERN ITALIAN ALPS)

摘要

The continental succession filling the valley of the Tagliamento River (eastern Southern Alps) is one of the best examples of long-lived fluvial system in the Alpine Chain. The sedimentary record, divided into a number allostratigraphic units, covers the Messinian-Quaternary time interval and allows the unravelling of the evolution of the drainage basin in the most tectonically active sector of the Alps. The timing of the tectonic activity was compared with the ages of the sedimentary units and its influence on the sedimentation along the valley, and the preservation of the sedimentary bodies was evaluated. After the deep incision determined by the Messinian Salinity Crisis the sedimentation along the valley was firstly driven by thelate Zanclean marine transgression; subsequently the strike-slip deformation along the valley, caused by the western segment of the Idrija Fault, created reaches of local subsidence, in which there were unit superposition, or uplift, where the units are nested. Strike-slip movement contributed to the northeastern migration of the trunk valley at its present location. Finally, the onset of the Quaternary glaciations determined the increase of sediment discharge of the catchment and enhanced the erosion during the glacier advances.