Slope channel formation, evolution and backfilling in a wide shelf, passive continental margin (Northeastern Sardinia slope, Central Tyrrhenian Sea)

The sedimentary processes of the Caprera slope channel system (CSCS), located in the northern slope sector of the eastern Sardinian margin, have been reconstructed through the integrated interpretation of multibeam bathymetric data and seismic profiles. The CSCS is composed of three main slope channels (C0, C1, C2), and of a series of smaller V-shaped channel-forms, that show different morphologies and sedimentary infill. The southernmost C0 slope channel, is abandoned and its upper segment is completely buried and healed, whereas its lower segment is still evident in the bathymetry. On the contrary, the upper segments of the northernmost slope channels, C1 and C2, are characterized by an inner thalweg, erosional terraces, and internal levees. The channel bends feature complex erosive geomorphic elements, mainly controlled by the interaction of sediment gravity flows with the channel shape. The lower reaches of C1 and C2 slope channels have a flat floor, which is the result of the deposition of channel-wide sedimentary bodies. The present setting of the CSCS is indicative of a waning phase and a decreased volume of sediment gravity flows following a main waxing phase of channel excavation. This scenario can be interpreted as resulting from the decreased energy flow following the last glacial maximum. During low stand periods, river-fed sediment gravity flows had high energy and excavated the slope channels. During the present-day high stand, the main flows, resulting from the interaction between alongshore and cross-shelf currents had a downbasin depositional behavior and resulted in the complete healing, or partial backfilling of the slope channels.

► We describe three slope channels along a wide shelf, passive continental margin.
► Morphologies and internal architectures of the slope channels has been examinated.
► Sedimentary dynamics within the channels changes in response to sea level variations.
► In the slope channel bends erosional architectural elements predominate.
► A grain size control on the absence of fluvial-style point bars has been invoked.