Climatic, tectonic and volcanic controls of sediment supply to an Oligocene Foredeep basin: The Val d'Aveto Formation (Northern Italian Apennines)

The Val d'Aveto Formation is a turbidite sequence deposited in the Northern Apennines during the Oligocene (32-29 Ma). The occurrence of calcareous, siliciclastic, volcaniclastic and carbonatoclastic deposits makes the Val d'Aveto Formation a natural laboratory to study the interplay among climate, tectonics and volcanism in a subduction-related context. Eight logs have been studied in order to reconstruct the stratigraphic architecture of the succession. Ten different facies (one limestone senso lato facies, four siliciclastic facies, four volcaniclastic facies and one carbonatoclastic facies) have been recognized on the basis of their different sedimentary features, microtextures and matrix compositions (through thin section analysis and X-ray powder diffraction). For the first time, syn-volcanic facies (pyroclastic density current and epiclastic deposits) have been distinguished from post-volcanic facies in the volcaniclastic facies. Compositional trends of sandy to muddy detritus, together with image analyses on gravel dimensions, highlight spatial and temporal persistence of the syn-depositional volcanic activity across the source-to-sink system. Lithological and petrographic analyses on the gravel size fraction of the siliciclastic and volcaniclastic detritus point out a SE France provenance and reveal the strong influence that tectonics has on sediment production. The comparison between the geodynamic evolution of the source area and the stratigraphic evolution of the Val d'Aveto Formation can help unravel the importance of climate on the redistribution of tectonically produced sediments and shaping of the resulting submarine fan.