The Ouarsenis “Grand Pic” : an exceptional example of a large-scale preserved halokinetic feature in the Western Tell (N. Algeria)

The Great Peak of Ouarsenis (“Grand Pic de l’Ouarsenis”) shows a spectacular geological structure that has intrigued geologists for more than a century. A stratigraphic pile comprising the entire Jurassic and lower Cretaceous levels is completely overturned for several kilometers. Various geological interpretations have been proposed, all of them within the framework of the Cenozoic compressional events responsible for the building of the Tell-Rif orogenic system. Based on a review of literature and field data, we propose a new interpretation in which early Mesozoic salt tectonics plays a major role. Salt activity is perceptible at the end of the Liassic and the Dogger but the main event, leading to the overturning of the lithostratigraphic succession dates from the Early Cretaceous. We tentatively correlate this event with a renewal of the extensive activity along the southern margin of the Tethys. The structures are then accentuated in the Cenozoic during the inversion of the margin and the building of the Tell system. The integration of the Early Cretaceous rifting in the geodynamics of North Africa is discussed.