Sédimentation sous contrôle tectonique de la plateforme sud Setifienne

Abstract

The studied area is constituting a hinge zone, at the convergence of the Alpine's range internal zones of Eastern Algeria and the Atlasic domain. It is centred on the South-Setifian platform, which is the western extension of the Constantinois neritic pier. Stratigraphically, the detailed lithostratigraphic analysis of the outcrops allowed the revising of the bio-lithostratigraphic schema of the meridional south-setifian facies and northern aurésian facies. In this context, some formations and units have been adopted and biostratigraphically repositioned, others have been identified for the first time. Sedimentologically, the microfacies’ analysis of the sedimentary series has revealed that: - Jurassic facies characterize a platform medium that is progressively evolving according to tectonics, subsidence and eustatism whose joint actions are influencing the carbonate production. - Cretaceous facies refer to two types of platform: a detrital platform and a carbonate platform, the influence of which is controlled by the sedimentary dynamics and the dominant energetic action. - The Neogenic facies have a continental aspect with, in some places, a Molechfor biofacies and / or a Rhodalgal biofacies, which are translate as a filling of paleovalleys. Structurally, the structural style of the north aurésian autochthonous Mountains is characterized by a succession of folds oriented E-W to NE-SW, affected by numerous faults which, most often, bring out the limestone massifs in horst. Among these brittle accidents, NWSE dextral strik-slip faults, which limit the shear zones, are the most numerous and most apparent. In the shear zone that joins the Messaouda massif to the Mestaoua massif, the dextral recesses, arranged in echelon, induce a virgation, also dexterally of the fold axes. The overlapping series, located in the south of the Messaouda Massif and SW of the Mestaoua Massif, represent the inverse flanks of anticlinal structures. All these structural dispositifs reveal fold-fault structures. However, a ramp and landing structure, supported by the surface geometry, can be envisaged. In this case, the shortening is fully or partially accommodated by folding. Thus, the present structures oblige not to envisage a tangential tectogenesis of regional amplitude.