The impact of margin shaping processes on the architecture of the Sardinian and Sicilian margin submarine depositional systems within the Tyrrhenian Sea

The Tyrrhenian Sea was formed through rifting due to back-arc extension above the subducting Ionian oceanic slab. Within the basin and the surrounding regions, extensional processes were diachronous, first affecting the Sardinian margin and then migrating southeastward toward the Sicilian margin and the Calabrian margin and the western side of the Italian peninsula. Thus, at the Sardinia passive margin, tectonic activity has been quiescent since the Early Pliocene, whereas extensional processes are ongoing at the Sicilian margin. As a result, the different geological setting of the associated hinterland areas has had a large impact on the present-day depositional systems along the two margins. At the Sardinian margin, a relatively large spacing of river entry points results in widely spaced submarine slope canyons that feed isolated submarine fans in the intraslope basins. At the Sicilian margin, as a consequence of smaller river drainage basins, canyons are very close together along the slope and feed base-of-slope coalescing sedimentary bodies, creating an apron consisting of channel levee deposits and channel-mouth lobes. Hinterland local tectonic regime also influences the nature of the deep-sea depositional systems along each of the margins. Generally, the small, radial fans of the Sardinian margin lie basinward of narrow shelf regions, where a direct fluvial input of coarse-grained sediments to the canyon heads can be inferred. The large elongated Caprera fan, in contrast, forms in an area where the shelf is wider and can efficiently trap much of the coarse-grained fraction of throughput sediments. At the Sicilian apron, in the areas facing the depressed regions, with smaller continental uplift rates, the Gioia basin channel levee system is actively aggrading. On the other hand, destructive processes, resulting in widespread mass-wasting deposits, are affecting the Sicilian apron, where high uplift rates are affecting the adjacent land areas.