Geomorphology of the NE Sicily continental shelf controlled by tidal currents, canyon head incision and river-derived sediments

• We illustrate the small-scale geomorphologic variability of continental shelves.
• Shelf development is driven by spatial variations in sediment supply by rivers.
• Channelized river deltas directly connect with canyon heads.
• In the relict outer shelf, past coastal systems provide hints on ancient landscapes.
• Oceanographic processes redistribute sediment forming tidal current sandwaves.

The NE Sicily continental shelf, imaged by multibeam bathymetry data and CHIRP/sparker seismic profiles, is less than 5 km-wide, and is located in a tectonically active margin characterized by strong regional uplift rates. In this paper, we show how variations of geomorphic elements in the study area are tied to spatial and temporal changes in the driving forces that control the seafloor processes. This study demonstrates that the geomorphology of continental shelves can vary over very short spatial scales depending on the uneven distribution of sediment supply from rivers and sediment transfer both across and along the shelf by oceanographic currents. In the northeastern part, three sandwave fields were mapped in the highstand sediment wedge that, due to the small size of rivers, is restricted to the inner shelf. The sandwave fields are found in proximity of the Messina Straits, a shallow water sill with strong tidal currents between the Tyrrhenian and the Ionian Seas. The bedform fields have sandwaves of variable shape, wavelength and orientation, reflecting along-shelf variations of tidal current strength and sediment grain size distribution. In the southwestern shelf, rivers are larger and form deltas that shape a considerable part of the shelf, often having their distal, still channelized delta front at the shelf edge. In some cases, deltas are built close to the heads of canyons and a large volume of the river-borne sediments is directly fed to the deep sea through delta front terminal distributary channels. Where rivers are small, the outer shelf lacks recent river borne sediment and presents a relict morphology consisting of submerged coastal systems formed during previous sea-level lowstands. The tectonics of the study area mainly consist of structures that have a NNE–SSW trend similar to the extensional faults responsible for the Siculo-Calabrian Rift Zone in the nearby emerged areas. Our study extends the area affected by the regional deformation belt into the NE Sicily offshore.

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