Submarine Landslides and Contourite Drifts Along the Pianosa Ridge (Corsica Trough, Mediterranean Sea)

摘要

The Corsica Trough between the island of Corsica and the mainland of Italy is dominated on its western side by turbidite channel-lobe systems fed by high-gradient rivers during glacial epochs, while the eastern side is markedly different. It is flanked by the Pianosa Ridge, a prominent tectonic structure confining the distal reaches of turbidite lobes and it is characterized by the development of contourite drifts with evident seafloor expression. The southern part of the Pianosa Ridge hosts a submarine landslide called 'Pianosa Slump' (PS, 6 km long, 14 km wide). Multichannel Sparker and Chirp profiles reveal the internal geometry of the PS, formed by two sediment bodies of up to 0.85 and 0.34 km~3. A buried submarine landslide below the PS shows that mass wasting is a recurrent process in this area. Preliminary results suggest that submarine landslides have volumes and ages comparable with those of turbidite lobes from the Golo turbidite system and contribute actively to their confinement and to basin filling. Relatively steep gradients, rapid contourite drift accumulation during times of sea level lowstands, and fluid escape from distal turbidite sandy lobes are the main factors conducive to seafloor instability.