Thin-skin tectonics in the Essaouira basin (western High Atlas, Morocco): evidence from seismic interpretation and modelling

Abstract In the Essaouira basin, detailed re-examination of seismic profiles and the use of modelling computer programs based on widely accepted concepts in fold kinematics has allowed us to set additional kinematic constraints on the geometry of the structures in this area. Forward modelling, conducted with the help of computer programs, was carried out in order to find the best kinematic pathway accounting for the geometry of the folds. We have observed two main geometrical types: fault-bend folds and a fault-propagation fold. Simple fault-bend folds were observed at the Tabelaouart, Oued Tahria, Bouzergoun and N’dark anticlines. All the ramps are located within the Triassic formations and have variable height. However, the ramps in the western structures have a northerly dip, whereas the eastern anticlines have grown upon southerly-dipping ramps. The amount of displacement is variable. Complex fault-bend folds occur at the Amsitten anticline, developed upon three major fault planes. Finally, an example of fault-propagation folding was observed at the Jeer anticline. In conclusion, the cover in the Essaouira basin appears decoupled from its basement in most structures, and its kinematics follows a ramp-flat geometry. From the oil exploration point of view, we believe that the whole tectonics of the Essaouira basin has to be reviewed on the basis of geometrical analysis, in order to improve the knowledge on the potential targets.