Abstract 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 the late 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.

The Paleogene turbiditic sedimentation in the eastern Southern Alps represents the sedimentary response to tectonic activity related to the Mesoalpine phase, which involved the surrounding chains from Paleocene time onward. Field and petrographic analyses have allowed us to classify these turbiditic successions as multisource deposits, as demonstrated by the common presence of allochemical, mainly bioclastic detritus, associated with different types of terrigenous arenites. For all units, field data suggest more proximal sources for allochemical supply and distal sources for terrigenous material, characterized by the presence of chert, carbonate rocks, and metamorphic rock fragments. All the investigated successions display transparent heavy mineral associations, marked by the common presence of chrome spinel, alkaline amphibole, staurolite, epidote, and zoisite, which point to similar metamorphic sources. The location of the source of metamorphic rock fragments is uncertain, but inputs from the internal Dinaric belt are possible. The source of the allochemical detritus was located in the nearby reactivated Friuli Platform.

Abstract The Upper Cretaceous Helminthoid Flysch (HF) of the Northern Apennines consists of thick and regionally widespread deep-water carbonate turbidite successions, deposited during the initial stages of Alpine collision. The HF spans the time from Turonian to Early Eocene and is mainly composed of intrabasinal carbonate ooze mixed with clay; siliciclastic terrigenous beds are also present, but they are a volumetrically minor component of the successions. Petrographic and sedimentological signatures indicate that the HF was deposited in distinct basins located below the carbonate compensation depth. Bulk composition and heavy minerals of terrigenous beds indicate provenance from different crustal levels of the European and Adria plates. The petrographic and palaeobathymetric characteristics of these turbidites indicate the coexistence of an active-margin tectonic setting, a palaeogeographical position suitable for carbonate ooze production and storage, and limited supply of terrigenous detritus into the basin. Palaeotectonic reconstructions and stratigraphic data suggest that Adria represented a vast repository of penecontemporaneous carbonate mud; the presumably intense seismic activity related to the pre-collisional Alpine orogeny promoted large-scale failures of shelf and/or slope biogenic muddy sediments, resulting in the deposition of a large volume of carbonate turbidites. Only occasionally, turbidity currents probably linked to exceptional fluvial floods generated pure terrigenous beds with different petrographic signatures for each HF succession.