The Crust beneath Morocco: From the Surface Topography to the Upper Mantle

Abstract

The most characteristic topographic features of Morocco are the Atlas Mountains and the Rif Cordillera. These two orogenic belts are the response of different geodynamic processes acting at lithospheric scale caused by the complex plate interaction between Africa and Europe. It is a broad zone of deformation that includes: the Betics, the Rif Cordillera, the Alboran basin and, the Gibraltar arc. The area is characterized by a relatively large amount of earthquake activity at various depths. Within the last decade a large international effort have been devoted to the area to constrain the structure, composition and tectonic scenario from south of the Atlas to the Betics, across the Rif cordillera and the Alboran basin. Multidisciplinary research included: earthquake recording with broad band temporal deployments and, controlled source seismic acquisition of wide-angle seismic reflection data. A transect from Merzouga across the Gibraltar Arc and into the Iberian Peninsula and, a nearly regular grid of BB were acquired. The data constrains the litospheric structure and provides seismic P-wave velocity models from the coast across the Rif and the Atlas. The crust features a moderate crustal root (40 km) differing from the 35 km thickness value observed at both sides. Travel time inversion positions the root just south of the High Atlas defining a thrusted mantle wedge. A prominent crustal root (over 50 km) located beneath the external Rif is identified by the wide-angle data and receiver function studies. To the east the crust thins rapidly by 20 km across the Nekkor fault zone. On shore-offshore records reveal complexities in the transition to the Alboran basin.