Recent Canyon Activity Resulting From the Confining of Dense Bottom Currents: the Bari Canyon Example (Central Mediterranean)

Submarine canyons are commonly active during sea-level low stands when sediment sources, such as deltas or littoral cells, are close to the canyon heads and, consequently, large amounts of sediment are delivered through slumps and turbidity currents. Bari Canyon (South Adriatic, Central Mediterranean) was impacted by turbidity currents and repeated mass transport events during sea-level low stands, while it is flushed by cold and dense water mass flowing down-canyon during the modern sea level high stand. The cold and dense water mass forms in the North Adriatic shelf through winter cooling and flows off-shelf into the Bari Canyon at the end of the winter season. Bari Canyon is a broad entrenched erosional feature, within which a 20km long asymmetric channel levee complex, formed during the Last Glacial, remains active during part of the post-glacial sea-level rise. Currently, Bari Canyon presents two main conduits, emanating from a broad crescent-shaped head region on the shelf break, and presents a marked asymmetry, with the right flank (southern) higher and steeper (about 800 m in relief and more than 30° steep) than the left flank. As a consequence, the steady-state contour-parallel bottom currents, flowing along the South Adriatic slope from the north, enters the canyon and interacts with its complex topography. These contour-parallel currents defines areas of preferential deposition on the up-current side of pre-existing morphological reliefs with variable origin and extent. The cold-dense water mass flowing down-canyon has enough energy to erode or prevent deposition within the canyon axes and contribute to the aggradation of a channel levee complex formed during the last glacial stage of canyon evolution. Moreover, the down-canyon flowing water mass is responsible for the post-glacial evolution of a field of up-current migrating mud waves, located at the canyon exit in about 900m water depth.