Recent mass-movement processes on the Ebro continental slope (NW Mediterranean)

13 pages, 8 figures, 2 tables.

Mass-movement is an important process controlling the sedimentary structure and growth patterns of the Ebro continental slope during recent time (at least Quaternary). About 37% of the slope surface is affected by mass-movement features, which are variable in distribution, size and morphology. The northern and central sectors are mainly affected by erosive canyons with gullies on their upper courses and massive and chaotic slump bodies on the middle and lower courses; the southern sector is mainly affected by large-scale slides (>10 km), and debris-flow deposits. In the three sectors, the slope is also locally affected by small-scale slides (<4 km long). The overall development of mass-movement features on the Ebro continental slope has been favoured by the local tectonism and the high sedimentation rates on the upper slope sediments, which correspond to regressive deltaic deposits. Under these conditions, the possible triggering mechanisms of the mass-movement features are the gravity loading, earthquakes, and the impinging of storm and internal waves onto the seafloor during the lowstand stages. The spatial distribution, the variability in the types of mass-movement and the post-failure evolution are influenced by several independent factors. These factors include the uneven volume of sediment supply, the frequency of failures, the sediment thickness involved in the failures, the slope gradients and the proximity to earthquake epicenters.

This work was founded by the European Commission ANAXIMANDER project (EVK3-2001-00123), and by the ‘Ministerio de Ciencia y Tecnología’ MARCONI (REN2000-0336-C03) project, MARSIBAL (REN2001-3868-C03) project and NT1999-1462-E. The support of these people and institutions is gratefully acknowledged. David Casas thanks the Generalitat de Catalunya for the PhD Grant (1999FI 00002CSIC PG). We also thank David G. Roberts and anonymous journal reviewer for their helpful comments and editorial assistance.

Peer reviewed