Salt tectonics in and around the Nile deep-sea fan: Insights from the PRISMED II cruise

The recent PRISMED II geophysical survey has documented various styles of salt tectonics in and around the Nile deep-sea fan (Eastern Mediterranean Sea). The first main type of salt-related structures comprises listric normal growth faults and grabens, trending roughly perpendicular to the slope line of the Nile Cone. These faults and associated salt structures result from thin-skinned extension, driven by gravity gliding and spreading as a result of sediment loading of the Plio-Quaternary overburden above the Messinian evaporites, which acted as a decollement layer. The second major type of salt structures consists of lineaments that obliquely intersect the continental slope of the Nile deep-sea fan. These structures may have had some strike-slip movement, and salt diapirs grew reactively or were deformed by fault-block movement. In the western distal part of the Nile deep-sea fan, compressional tectonics of the adjacent Mediterranean Ridge caused the formation of a series of salt-cored folds and reverse faults above the Messinian evaporites. In the eastern distal part of the Nile Cone, sediment progradation progressively expelled salt northward, first forming small folds and tight diapirs, then a scarp of 400 m height around the Eratosthenes Seamount, corresponding to the basinward limit of salt deformation.