The Neotectonic Deformation of the Eastern Rif Foreland (Morocco): New Insights from Morphostructural Analysis

The Rif Cordillera, an Alpine orogen in the Western Mediterranean, was developed by the interaction of Eurasian and African (Nubia) plates. Neotectonic deformations of the Rif foreland influence the relief, especially in post-nappe basins and their boundaries with Jurassic and Cretaceous carbonate mountain massifs, and they contribute to highlighting the recent evolution of the Cordillera. The topographic and hydrological lineaments of these basins were characterised on the basis of multi-scale morphostructural data analysis, supported by digital mapping and GIS. They were correlated with geological structures, essentially with fractures. The outcrops of the Upper Tortonian and Messinian deposits depict well-defined geometric shapes with roughly rectilinear boundaries, as defined by their contacts with the massive and rigid rocks of the Jurassic and Cretaceous series. Upper Tortonian deposits evidence major regional N70°E and N40°E lineaments, which are obliquely intersected by late structures. Messinian N120°E and N25°E lineaments, associated with N140°E lineaments, are also recognised. The interpretation of these lineaments as faults indicates the activity of two systems of transtensive sinistral and then dextral brittle shearing that correspond to two episodes of neotectonic deformation that played a decisive role in shaping the reliefs of the Eastern Rif. These deformations are particularly relevant to isolate basins and likely have a key role during the closure of the South Rifian corridor during the Mediterranean Messinian Salinity crisis.