VOLUBILIS PIGGY-BACK BASIN DEVELOPMENT IN RESPONSE TO GROWING FAULT-RELATED FOLDS, FROM THE SOUTH RIFIAN RIDGES, NORTHERN MOROCCO

The volubilis piggy back basin, in the front of the Rif belt, northern Morocco, is a subsided area, as a continuation of the deformational orogenic ridges, related to the present-day African and Eurasian convergence. The latters have been classically interpreted as active thrusts and folds-related faults, since the middle Miocene-early Tortonian.

For the first time, by morphotectonic studies, we analysed the topography development of the basin and drainage system response to this activity.

Our results proved the influence of active tectonics in the drainage network and topography of volubilis basin. The young phase is indicated by a less dissected planation surface comparing to the ridges that we interpret to be a cuesta landform, as well as the ε-shaped hypsometric curve of the khoumane river.This latter drains the continuation of the basin and the eastern arc, where the tectonic activity is the most concentrated. Based on swath analysis, the general trend of tilting was characterized and was attributed to the recent tectonic movement combined with folds growth of the ridges.