Transpressional structuring of the High Atlas belt, Morocco

The High Atlas belt of Morocco is a doubly vergent intracontinental belt formed during Cenozoic convergence between the African and Eurasian plates. This belt is characterized by the simultaneous occurrence of high topographic elevation, minor crustal thickening and weak tectonic shortening, which are commonly explained by models of inversion tectonics and mantle upwelling. This paper aims to test the consistence of this type of model, presenting the results of a multi-scale tectonic study, including mapping of major faults and fault-slip data inversion, from key areas homogeneously distributed through the entire High Atlas. Our data highlight kinematic components parallel to the orogen trend, supporting a transpressional structuring. Integration between new tectonic data and available geophysical and thermochronologic constraints has allowed to extend to depth the main faults detected at the surface, resulting in the overall geometry of a positive flower structure. This scenario is the result of a long history of transpressional and transtensional reactivations of major lithospheric faults since the break-up of Pangea. Lithospheric-scale faults isolate independently-behaving lithospheric blocks characterized by different exhumation rates. In this framework, the compressive component of the transpressional geodynamic regime can produce the high topographic elevation of the High Atlas belt without crustal thickening.