Mud Vocanoes and Fluid Seepage in the Mediterranean Sea: A Regional Synthesis

Jean Mascle, Georges Mascle, Laurent Camera, and Laetitia Brosolo

Using various types of regional geophysical data, such as swath bathymetric mapping, derived backscatter images, seismic profiling, more locally geological sampling and a few results from near-bottom surveys and in situ sampling, we have mapped the proven and inferred mud volcanoes fields and areas of massive mud/fluid expulsion in the Mediterranean Sea and its vicinity. In the Mediterranean Sea mud and fluid expulsions are clearly not randomly distributed but are detected in two main structural settings, on few passive continental margin segments, and on sedimentary compressive wedges related to subduction/collision.

- Abundant mud cones, gas chimneys and pockmark fields characterize the Egyptian continental margin off Nile delta; there, they are detected mainly on the upper continental slope (locally on the shelf) where they appear linked to regional fault systems; they also occur in some specific areas at the foot of the continental slope, particularly in the North-Western sector of the margin where they are interfering with Messinian salt deposits to produce brines emitted directly on the sea floor through extensional faults. Few features, referred as mud volcanoes, have also been described in several regions of the Western Mediterranean Sea (notably Western Alboran Sea and Calabria margin).

Mud volcanoes fields are however particularly abundant along the various tectono-sedimentary wedges built in relation to subduction/ collision processes in the Mediterranean Sea, for example off Southern Calabria, in the socalled Calabria external arc, along the Mediterranean Ridge and, from place to place, within the Cyprus arc (running from the Anaximander mountains to the Hecate rise) or just outside in the Gulf of Cadiz. Over the Mediterranean ridge they are particularly located nearby its tectonic contacts with its backstop, implying close relationships with compression-induced overpressures, thrusting and faulting. A comparison with their repartition and the mapping of Messinian salt deep basins clearly show that mud and fluid expulsion do not occur where thick Messinian salt is present, except along continental slope where gravity tectonic has created the necessary conduits (e.g. Nile continental margin).

AAPG Search and Discovery Article #90161©2013 AAPG European Regional Conference, Barcelona, Spain, 8-10 April 2013