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The most significant morphologic feature of almost all continental margins are submarine canyons. For sediments, submarine canyons represent the gateway and pathway form the continent and adjacent continental shelf to the deep sea. Nevertheless the mechanisms by which submarine canyons form and evolve on continental margins are still poorly constrained. One of the most accepted and early hypothesis sustained that submarine canyons are related to subaerial incisions, carved during sea level lowstands. In the Mediterranean basins a period of extremely low sea level occurred during the Messininan Salinity Crisis (MSC).
Due to the MSC the continental margins were carved subaerially from the present coastline to almost the base of the continental slope. 3D seismic data from the Ebro margin allow to study in detail the incisions associated with the MSC and their subsequent evolution. Mapping of several horizons and analysis of seismic facies allow to visualize the relationship between the Messinian paleo-releif, the subsequently deposited sedimentary sequences and later incisions on the margin by submarine canyons. It appears that the MSC incisions were filled by a rapidly prograding margin that lacked significant incisions from submarine canyons. As the margin developed, incisions started to form and these hold no apparent relationship with the incisions carved during the MSC. A time model based on seismic stratigraphy indicates that the present day incisions on the continental slope are relatively recent features. In addition, none of the incisions, past and present, extended along the whole continental shelf, therefore indicating that canyon formation is decoupled from onshore fluvial dynamics. The most important mechanism controlling onset of canyons and subsequent evolution in the Ebro margin appears to be erosion by submarine landslides and turbidity currents.
This research was funded by the "Ministerio de Educación y Ciencia" through grant CTM2007-64880 (EDINSED3D). 3D Seismic data was kindly provided by British Gas.
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