The Ebro Continental Margin, Western Mediterranean Sea: Interplay between Canyon-Channel Systems and Mass Wasting Processes

Canals, M., Universitat de Barcelona, Spain; J.L. Casamor, Universitat de Barcelona, Spain; R. Urgeles, Universitat de Barcelona, Spain; G.Lastras, Universitat de Barcelona, Spain; D.G. Masson, Southampton Oceanography Centre, United Kindgon; S. Berné, IFREMER DRO/GM; Brest, France; and B. Alonso, UA Geociències Marines CSIC-UB, Dept. Geologia Marina i Oceanografia Física, Institut de Ciències del Mar, CSIC, Spain

Abstract

A comprehensive data set of the Ebro progradational margin, in the Western Mediterranean Sea, reveals that its Late Quaternary building results from complex interrelationships between canyon-channel related processes 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, is constituted by a turbidite system, which includes channel-levee complexes and base-of-slope non-channelised deposits. The data set highlights a variety of processes controlling the distribution of different sediment types. Those processes include channel abandonment, incision of inner channel courses, hanging valleys formation, retrogressive erosion, avulsion, channel wall sliding and channel spillover. Recurrent slides and associated debris flows wipe out the upper sediment cover of large segments of the margin and lead to extensive deposits at the base of the slope. These debris flows may cover large, about 2,000 km2, sectors of the sea-floor with thicknesses exceeding 40 m. The data show that debris flows can conceal large channel portions such as the the upper course of the mid-ocean type Valencia Channel which, in turn, collects several of the Ebro canyon-channel systems.

The modeling of the three-dimensional channel geometry provides a quantitative illustration of potential infill of these channels and corresponding volume lost due to mass-wasting processes.