Upper Pleistocene contourite deposits off the Capo Vaticano margin (southern Tyrrhenian Sea, Italy): interplay between down-slope and along-slope sedimentary processes

Both down-slope gravity currents and along-slope bottom currents are common phenomena occurring along most continental margins (Mulder et al., 2008), however mixed depositional systems related to these processes are yet poorly documented (e.g., Hernández-Molina et al., 2009). In semi-enclosed and tectonically active basins down-slope phenomena are more frequent; however, small contourite systems can be locally recognized. In this study, based on very high-resolution single-channel seismic profiles and multibeam bathymetric data, we investigate the upper slope and shelf deposits along the southern sector of the Capo Vaticano continental margin (Calabro-Tyrrhenian margin) where, between ~500 and 90m water depth, the stratigraphic record is characterized by hemipelagic, contourite, turbidite and mass wasting deposits formed in different upper Pleistocene eustatic cycles. The most recent part of the stratigraphic record has been analyzed by Martorelli et al. (2016), showing that during the last glacio-eustatic cycle, along-slope processes formed elongated drifts located on the upper continental slope and outer shelf, between -90 and -300 m. Here, contourite deposits and associated erosive elements indicate the presence of a northwestward geostrophic flow that can be related to the modified-LIW issued by the Messina Strait and it is likely that the activity of bottom-currents was intensified around the LGM period and during the successive sea-level rise. Downslope processes formed mass-transport deposits and turbidite systems with erosive channels, locally indenting the presentday shelf. Moreover, slide events affected the upper 10-20 m of the stratigraphic record, dismantling considerable volume of contourite sediment. The most striking mass wasting feature is the Capo Vaticano slide complex (the CVSC), which displays a large spatial coverage and is composed by several intersecting slide scars and overlapping deposits. The presence of high-amplitude reflectors within contourite deposits (i.e., potential weak layers), along with high post-glacial sedimentation rates estimated for contourite deposits and steep seaward flank of the drifts can act as a relevant predisposing/triggering factor for medium-large scale slope instability. In this study we highlight how a complex spatial and temporal interplay of along- and across slope processes can occur over a narrow area in a relatively short time-span (e.g., the post-glacial period), and that a similar interplay can be observed within pre LGM deposits. As a whole seismic data indicate that both these processes were relevant in shaping the study margin throughout the upper Pleistocene.