The Ebro Continental Margin, Western Mediterranean Sea: Interplay Between Canyon-Channel Systems and Mass Wasting Processes
Published:December 01, 2000
M. Canals, J.L. Casamor, R. Urgeles, G. Lastras, A.M. Calafat, D.G. Masson, S. Berné, B. Alonso, 2000. "The Ebro Continental Margin, Western Mediterranean Sea: Interplay Between Canyon-Channel Systems and Mass Wasting Processes", Deep-Water Reservoirs of the World, Paul Weimer
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A comprehensive swath bathymetry and high resolution seismic reflection data set of the Ebro progradational margin, in the Western Mediterranean Sea, reveals that its Late Quaternary development results from an interplay between channel-related and mass-wasting processes.
The Ebro continental margin is mainly fed by the terrigenous input of the Ebro River. The continental slope and rise, extending down to 1,300-1,800 m, has been built by multiple turbidite systems, which include channel-levee complexes and base-of-slope non-channelized deposits. Our data set shows a variety of processes controlling the distribution of different sediment types. These processes include channel abandonment, incision of inner channel courses, formation of hanging valleys, retrogressive erosion, avulsion, channel wall sliding, and channel spillover. Recurrent slides wipe out the upper sediment cover of large segments of the margin and lead to extensive mass transport deposits at the base of the slope. The youngest of these deposits, AMS 14C dated at 10,000 years BP, is the BIG’95 debris flow covering 2,000 km2 and thicknesses locally exceed 40 m. The data show that landslide deposits can conceal large channel portions such as the upper course of the mid-ocean type Valencia Channel, which downstream drains several of the Ebro canyon-channel systems. The modeling of the three-dimensional channel geometry illustrates the potential infill of these channels and thus the sediment volumes transferred downslope by mass transport processes.
Recurrent slope failures in the Ebro margin represent catastrophic events that interrupt the “normal” development of canyon-channel systems and channel-levee complexes. Slope failures rejuvenate the slope both by destroying upper canyon-channel courses and filling preexisting channel lower courses. Combined with canyon-channel erosional-depositional processes they create pathways for new canyon-channel systems to form thus modifying depocentre locations.