Resumen de Tectónica salina y escapes de fluidos en el Golfo de Cádiz
María C. Fernández Puga, Luis Somoza, Adolfo Maestro González, Juan Tomás Vázquez, A. Lowrie, Ricardo León, Víctor Díaz del Río Español
Deformations structures observed on migrated multifold and medium to high-resolution seismic lines (Air-gun, Sparker, Geopulse and 3.5 kHz) along the shelf and slopes of the Gulf of Cadiz provide geometric evidence for shale/salt tectonics and related seepages on the sea floor. The plastic layers involved in these processes are Triassic salt and undercompacted Early-Middle Miocene plastic marls (known generically as the "Olistostrome") along which the front of the advancing Betic-rifian accretionary wedge overthrust into the Gulf of Cadiz during Late Tortonian times. On the shelf, extensional faults are formed by basinward traslation the salt and its overburden with associated subsidence of minibasins, and consist dominantly of listric growth faults that dip basinward and sole out into a salt weld. Basinward traslation of the shelf sequence is balanced by salt extrusion and families of contractional faults on the upper slope, mainly basinward-vergent thrusts that ramp from a salt decollement. Salt bodies along toethrusts closed to (primary and/or secondary) welds that surface in the sea floor and supplied salt wedges: arcuate lobes of salt advancing basinward. Overpressure compartments generated beneath salt wedges provide avenues to that hydrocarbon gases, fluids (brine waters) and fluidized sediments flux upwards through contractional toe-thrust structures to seepages on the sea floor (mud volcanoes, salt/shale sheets...).
