LANDSCAPE RESPONSE TO THE INTERACTION BETWEEN TECTONICS AND DIAPIRISM IN THE EASTERN BRANCHE OF THE SOUTH RIFIAN RIDGES (NORTHERN MOROCCO)

The South Rifian Ridges (SRR) are active thrust faults and folds, which have accommodated the expulsion of the Rif belt, Northern Morocco, as an active edge, in response to the continued motion between the African and European plates. Recent activity results in the complex and interesting tectonic structure of the Eastern arc of the SRR, where the most important diapir occurs. Nevertheless, factors controlling the landscape response to present day activity remain poorly defined.

We intend to evaluate and understand the variation in tectonic activity and their influence on the landscape evolution through the application of geomorphic and surface indices. They include: the mountain front sinuosity (S_mf), valley floor width-to-height ratio (V_f), drainage basin asymmetry factor (AF), hypsometric integral, surface roughness (SR), surface index (SI), normalized steepness index (K_sn), longitudinal river profile and χ as an indicator of drainage network disequilibrium. All these parameters are related to channel incision and the drainage configuration.

Our results suggest that folds related faults in the area produce differential uplift with a relatively high degree of tectonic activity along the Eastern part, especially in Dehar N’Sour dome, Nesrani and Takerma-Kannoufa anticlines. The halokinesis process accounts for the elevation of the area, and this in turn could be explained as being promoted by the NE-SW striking fault systems, which are still active. By contrast, the northwestern part is dominated by gorges that are interpreted as a consequence of active folding and faulting.

The active faults exert a strong influence on the morphology of the Fert El Bir anticline inducing the Khoumane river deflection, while other streams exhibit rejuvenation, piracy process and water divide migration.