Sea floor morphology and Plio-Quaternary sedimentary cover of the Mallorca Channel, Balearic Islands, western Mediterranean

A complete multibeam coverage of the sea floor of Mallorca Channel, in the western Mediterranean, was recorded during the Spanish Exclusive Economic Zone surveys in 1995, 1996 and 1997. These data, combined with previous high-resolution seismic reflection profiles, allow an assessment of the geomorphology of the area. The channel seafloor is disrupted by a fault complex and pockmarks. Motion along the faults split the sea floor into a series of undulations separated by narrow V-shaped notches. Faulting may be a consequence of recent seaward gravitational sliding that occurred along a soft surface at the top of a late Messinian–early Pliocene unit and a late Messinian evaporite. These units have been tilted during recent subsidence of the Mallorca Channel at the same time that the insular shelf was uplifted along a fault at the shelfʹs edge. The set of pockmarks in the channel sequence were probably formed by the expulsion of gas of hydrothermal origin, and expulsion may have been enhanced by the faulting. This gas seepage could be an additional factor leading to sediment instability.