The Ebro margin, NW Mediterranean, has experienced significant sediment input during the Plio-Quaternary, which translates into extensive progradation. A conspicuous feature of the Ebro margin is a dense network of submarine canyons. These canyons are incised <500 m on the upper continental slope and evolve into channel-levee complexes at the base of the slope. The mechanisms by which those submarine canyons (and many others around the world oceans) form and evolve are still poorly constrained. A 40km x 60 km 3D seismic data set from the Ebro Margin sheds new light on the processes driving initiation and subsequent evolution of these features in sediment-flushed continental margins. From this dataset, it is apparent that major fluvial valleys excavated during the Messinan had little control on the subsequent submarine drainage network that developed after Zanclean reflooding. Amplitude and coherency attributes display Quaternary fluvial streams that reach the shelf edge during lowstand periods near submarine canyon heads. Coherency time slices show that proper canyons initiated in the early Pleistocene. These two facts suggest that transition from a climate dominated by the 41 kyr Earth precession cycles into a climate dominated by the 100 kyr obliquity of the Earth’s orbit and associated changes in sea-level amplitude were largely at the origin of the submarine canyons. From mid-Pleistocene times, development of submarine canyons was likely favored by 1) fluvial systems reaching the shelf edge during lowstands and 2) significantly increased sediment yield because rivers were prevented from establishing equilibrium state. Submarine canyonfill deposits and a series of paleo-canyons indicate net-accumulation of the canyons system and progradation with the reminder of the continental margin. The submarine canyons evolved into larger systems throughout Pleistocene, increasing their shelf drainage area and likely the magnitude and frequency of sediment flows

24e Réunion des Sciences de la Terre (RST Pau 2014), 27 au 31 Octobre 2014, Pau.- 1 page

Peer Reviewed