Geomorphological, oceanographical and benthic characteristics of Gazul mud volcano in the Spanish Middle Slope of the Gulf of Cádiz

The seabed morphology and the sub-bottom characteristics of a sector of the Gulf of Cádiz continental slope have been analyzed from different data sets. The morphological characteristics, the type of sediments and dominant benthic species of Gazul mud volcano and adjacent areas have been studied. The morphological characteristics identified were grouped in fluid escape related features, bottom current features, mass movement features, structural features and biogenic related features. Additionally, dominant benthic species associated to fluid escape and seepage, hard substrates or soft bottoms have also been indicated in these features. A bottom current velocity analysis allowed relating the morphological features with the different sedimentary and oceanographic processes as well as the benthic habitats and that currently occur in the mud volcano and nearby areas. The major factor controlling these features and their associated benthic habitats is the interaction of deep water masses with the seafloor topography. At high velocities, authigenic carbonates can be exhumed and colonized by sessile suspensivorous species associated with hard substrates such as cold-water corals, anthipatarians and large sponges. Mounds and diapiric ridges are found on the depressions and they could be relict structures. Living corals have been found on raised zones, revealing different oceanographic condition and strong enough currents to favour the availability of nutrients and organic particles. Chemosymbiotic organisms are very scarce at the summit and old remains of Lucinoma asapheus indicating past higher seepage activity.Versión del edito