Characterization of overbanking features on the lower reach of the Gioia-Mesima canyon-channel system (southern Tyrrhenian Sea) through integration of morpho-stratigraphic data and physical modelling

The collection of high-resolution multibeam bathymetry, single-channel seismic profiles, TOBI side scan sonardata, gravity cores allowed the characterization of the main morpho-sedimentary processes acting along thelower reach of the shelf-indenting Gioia-Mesima canyon-channel system (GMS) and the surrounding continentalslope (southern Tyrrhenian Sea). This last area, developing across a depth range of 1000–1700 m, shows acomplex morphology due to the interaction between downslope gravitative processes (mainly turbidite sheetflows) and abrupt changes in slope gradients related to tectonically-controlled scarps. Particularly, severalerosive-depositional features (levee deposits, sediment undulations, channels) have been related to overflowprocesses from the northern flank of the GMS, although the lower reach of the GMS is characterized by strongentrenchment (canyon height ranging from 120 to 270 m) and low sinuosity. Morphological and seismic stratigraphydata indicate that the distribution and dimension of these features vary in response both to theproximity to the external levee of the GMS and to the topographic gradient of the lower continental slope.Particularly, we were able to discriminate between a gently sloping sector (on average 1.5°) dominated bysedimentary bypass of the turbidity currents and a steeper sector (about 3°), where the erosional capability ofthese currents seems to increase. Indeed, three channels, 4,3–6,5 km long and up to 20 m deep, incise this steepersector, running parallel to each other at a distance of 1250–1500 m. To support the capability of overbankingflow in producing these channels, we used a physical model for the ignition of turbidity currents that providesrealistic values for the ignitive state of the overbanking turbidity flows. More generally, the methodologicalapproach used in this study may be useful to provide constraints on the genesis and evolution of erosive-depositionalfeatures in other tectonically-controlled margins, where sedimentary gravity flows interact with anuneven morphology.