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Pere Puig, Institute of Marine Sciences, CSIC, Barcelona, Spain
Ruth Durán, Institute of Marine Sciences, CSIC, Barcelona, Spain
Araceli Muñoz, TRAGSATEC-Secretaria General de Pesca, Madrid, Spain
Elena Elvira, TRAGSATEC-Secretaria General de Pesca, Madrid, Spain
Jorge Guillén, Institute of Marine Sciences, CSIC, Barcelona, Spain
Submarine canyon-head morphologies and inferred sediment transport processes in the Alías-Almanzora canyon system (SW Mediterranean)

Submarine canyons are morphological incisions into continental margins that act as major conduits of sediment from shallow- to deep-sea regions, involving different sediment transport processes and triggering mechanisms operating at various time-scales. Canyon head regions are key areas for understanding the shelf-to-canyon sedimentary dynamics and assessing the predominant hydrodynamic and sedimentary processes shaping their morphology. High-resolution multibeam bathymetries were conducted along the main thalwegs of the Alías-Almanzora submarine canyon system to recognize their specific morphological features. Various canyon head morphologies were observed at 80-90 m water depth, incising the outer shelf off the Almanzora River prodelta. A direct connection from the river is evidenced by the coalescence of cyclic steps on the prodelta deposits and their continuation towards the Almanzora canyon head. This suggests the occurrence of flood events causing hyperpycnal flows that progressed directly into the canyon. Processes linked to seepage and groundwater sapping also seems evident in this prodelta, which results in pockmark alignments and formation of elongated narrow canyon heads. At the southern limit of the prodeltaic deposits another type of canyon head results from the formation and merging of linear gullies. These have been interpreted as the morphological expression of the distal off-shelf transport of flood-related hyperycnal flows, potentially transformed into wave-supported sediment gravity flows. Most of the canyon heads of this canyon system, however, are found at much shallower water depths (10-20 m), some of them being disconnected from any major river source, but showing a continuation in land with intermittent creeks that experience flash flood events. They cut into the infralittoral prograding wedge, displaying feeder channels with oval depressions indicative of sediment littoral drift interception. Some tributaries show crescent shaped bedforms over the shelf and along their axis, which have been observed until a water depth of 80 m and interpreted as the result of storm-induced sediment gravity flows. An instrumented mooring was deployed from October 2014 to April 2015 to monitor the contemporary sediment transport processes through a canyon axis with bedforms. No flash floods or major storms occurred during the deployment period and the sedimentary dynamics was governed high-frequency current fluctuations along the canyon, which caused several minor down-canyon transport events.

Theme 1: Canyon processes in the space-time continuum (formation, evolution, circulation)
Oral Presentation
canyon head morpphology, sediment transport, hyperpycnal flow, crescent-shaped bedforms