La structure du rif externe (Maroc): mise au point sur le rôle des décrochements des chevauchements et des glissements gravitaires

Abstract

Regional structural field evidence in the Temsamane area, forming the eastern part of the Rifian external zones, indicate that deformation of this area results from N75° left lateral wrenching. The structural data do not fit the nappe interpretation pointed out in Western part of external zone. A review of the geological frame appears necessary; it forms the subject of the present paper. Structurally, the external zones are subdivided into three groups of tectonic units: (a) the olistostromes and associated gravity-driven nappes which crop out all around the Rifian belt (‘slided external Rif’); (b) The tectonic windows situated beneath olistostromes and nappes (‘basal external Rif’); (c) The central area bounded by NW-SE thrust faults in the Western parts of the belt and by N75° (then N45°) wrench faults in the Eastern parts (‘Central Rif’). Concerning the paleogeographic evolution, the deposits of external Rif show a different evolution from their direct foreland but comparable with areas actually situated far eastward: (a) the ‘tellian-like domain’ shows basinal-type facies similar to facies of the epitellian nappes into Algeria b, (b) the ‘Ker Ker-like domain’ shows platform facies similar to facies known in West Algerian and Northeast Moroccan forelands. Thus, structural and paleogeographic data show that the all external zones of Rif moved westward along the African margin before sliding southward.