Morpho-structural features of episodic mud volcanism in the Gulf of Cádiz

A morpho-structural analysis of several mud volcanoes on the Moroccan Atlantic margin (Gulf of Cadiz) is presented. Multibeam data (bathymetry and backscatter), very high resolution seismic profiles from ultra-high resolution topographic parametric sounder (TOPAS) and gravity core data have been used. Analysis reveals an episodic mud extrusion dynamic evidenced by the presence: (1) levels of mud breccia interbedded between hemipelagic layers, (2) lobated and terraced profiles with different backscatter values, (3) crater-like depressions and/or internal domes with patches of very high backscatter values. This episodic dynamic is framed in an evolutionary model constituted by periods of high activity of mud extrusions separated by quiescence ones. Depending on the tectonic setting and oceanographic conditions, a wide possibility of sedimentological and geomorphological features can take place in quiescent periods. Latent periods are located between active and quiescence ones, and are characterized by occurrence of gravitational collapses, landsliding and the precipitation of authigenic carbonates and polimetalic nodules and crusts.