Mechanisms of mud extrusion on the Mediterranean Ridge Accretionary Complex

Drilling two mud domes on the Mediterranean Ridge during ODP Leg 160 has de monstrated that the eruption of mud breccia began at least 1.5 Ma ago. An e volution through extrusive building of a cone, followed by successive erupt ions of clast-bearing mud debris flows and subsequent subsidence can be ded uced for both domes. Results from permeability and shear strength tests, gr ain size analyses, sedimentary textures, and clast provenance provide clues concerning the mechanism of mud volcanism. The collision of Africa with Eu rasia resulted in backthrusting of the evaporite-dominated accretionary wed ge against a rigid backstop. This allowed egress of overpressured fluid-ric h mud of presumed Messinian age from the decollement, although many of the clasts may have originated from the overlying accretionary wedge.