Devonian extension of the Pan-African crust north of the West African craton, and its bearing on the Variscan foreland deformation: evidence from eastern Anti-Atlas (Morocco)

The Anti-Atlas belt belongs to the northern fringe of the West African craton, moderately deformed during the Variscan orogeny south of the Meseta Block. Field-based investigations into the stratigraphy and structure of the Palaeozoic cover have been performed in the eastern part of Anti-Atlas, with emphasis on the Devonian terranes. The Pan-African basement, which crops out in the Ougnat massif, was fragmented into a mosaic of tilted blocks during a sequence of extensional faulting events that occurred from Cambrian to (mostly) Late Devonian times. The Devonian normal fault pattern indicates a multi-directional extension, with a dominant northward direction. The Variscan compression resulted in the inversion of the palaeofaults as strike-slip–reverse faults, the kinematics of which points to a NE-trending regional direction of shortening, probably Permian in age. The occurrence of the Late Devonian palaeofault array accounts for the thick-skinned style of the (eastern) Anti-Atlas belt. The Devonian paleogeography of the Anti-Atlas can be correlated with that of the Meseta, but the lack of any Late Devonian compressional event in the Anti-Atlas shows that the two domains were not mechanically coupled at that time.