Impact of the Messinian Salinity Crisis and Related Residual Bathymetric Relief on the Structural Evolution of the Nile Deep-Sea Fan, Eastern Mediterranean

Loncke, Lies¹, Gaullier Virginie², Mascle Jean³, Vendeville Bruno⁴, Camera Laurent³ (1) Université de Picardie Jules Verne, Amiens, France (2) Université de Perpignan, Perpignan, France (3) Observatoire Océanologique de Villefranche-sur-Mer, Villefranche-sur-mer, France (4) Université de Lille 1, Villeneuve d’Ascq, France

The Messinian salinity crisis had two main consequences on the structural evolution of the Mediterranean basins and margins. First, deposition of large volumes of halite-rich evap­orites led to vigorous salt tectonics during Plio-Quaternary times. Second, intense erosion modified the physiography of the margins and introduced rheological contrasts within the sedimentary overburden (mobile evaporites versus non-mobile, clastic evaporites). The Nile deep-sea fan has a complex present-day deformation pattern: this includes structures typi­cal of salt-bearing margins (upslope growth faults, minibasins, diapirs, and contractional folds and thrusts). However, the strike of some of these salt-related structures, and the pres­ence in the eastern province of a 200 km long, NW-SE-trending tectonic corridor suggest that there is some deep-seated controls. Combined analysis of seismic data and physical experiments have shed light on how the Messinian paleobathymetry has influenced the fan’s later evolution. First, the paleobathymetry controlled the boundary between a downslope mobile zone (underlain by salt) and an upslope, non-mobile zone (made of Messinian bad­lands and detrital cones). This boundary, which is partly structurally controlled, is sinuous and is marked presently by the upslope limit of growth-faults, whose traces are parallel to this limit (hence oblique to the slope direction). Second, paleo-Messinian topographic highs located in the basin, such as the Eratosthenes seamount have acted as rigid buttresses that later influenced the pattern and movement directions during gravity spreading and gliding.

Therefore, the only deep-seated control acting on the actual physiography, lies in inherited paleo-Messinian relief interfering with salt tectonics.