Role of preexisting faults in the structural configuration of the South Rifian Ridges, Northern Morocco: Contribution of isobase maps and gravity data

Abstract

The South Rifian Ridges are located in northern Morocco, to the south of the Gibraltar Arc, and constitute a portion of the south Rifian corridor in the Rif belt front. These active fault-related folds, separated by the Volubilis piggy back basin, were structured since the Late Miocene due to the reactivation of Triassic graben fault systems in the context of the Eurasia-Africa convergence.

For the first time, a combination of morphotectonic and gravity analysis coupled with field Kinematic data have been used to characterize the main structures responsible for the Late Miocene to recent evolution of the area.

The morphotectonic analysis based on the dynamics of drainage network analysis allowed the isobase lineament mapping to depict a general view of the tectonic framework of the South Rifian Ridges. The interpretation of gravity data, including maps derived from the Bouguer and residual anomalies, allowed subsurface geometric features characterization and revealed buried salt diapirs to establish a new structural map. Evidenced structures confirm previously interpreted ones and support the presence of new masked faults, with the presence of compressional and extensive deformations. The main inferred structures are the NW-SE oriented buried Prerif Nappe fronts. Rooted faults related to the main ridges show reverse displacement and are expressed by high-angle reverse faults, while the NW oriented normal faults within Volubilis basin, in the field, are probably related to an active subsidence. This event is related to the current NW-SE continental collision, within a context of transition from thin to thick skinned tectonics. Our results shed light on the Miocene to Quaternary tectonics that have taken part in the closure of the South Rifain marine gateway.