Late Ediacaran–Cambrian structures and their reactivation during the Variscan and Alpine cycles in the Anti-Atlas (Morocco)

• Most Anti-Atlas majorfaults are inherited from the Pan-African Belt collapse.
• They controlled the late Ediacaran–Cambrian rifting and Devonian extension.
• Their Variscan inversion is complete in western Anti-Atlas, partial in the east.
• Anti-Atlas suffered Triassic-Jurassic uplift then Cretaceous shallow subsidence.
• Its present elevation results from the late Eocene–Neogene Rif–Atlas orogeny.

The post-Pan-African evolution of the northern border of the West African Craton is largely controlled by the remobilisation of Late Neoproterozoic basement faults. The Upper Ediacaran volcanic and volcano-sedimentary sequences of the Ouarzazate Group show dramatic and rapid thickness changes, consistent with active extensional faulting associated with post-orogenic collapse and incipient continental rifting. The geometry and kinematics of these faults differ from west to east in the Anti-Atlas. N- to NE-trending faults dominate in western Anti-Atlas in response to E–W to NW–SE pure extension, while a transtensive opening regime characterize the central (Bou Azzer) and eastern (Saghro–Ougnate) Anti-Atlas.The marine incursion in the west-central Anti-Atlas during the late Ediacaran–Early Cambrian occurred without major geodynamical break between the continental Ouarzazate Group and marine sediments of the Adoudou Fm. Extensional tectonics went on during the Early Cambrian, being concentrated in the western and central parts of the belt. From Middle Cambrian to Lower Devonian and mainly due to thermal subsidence, the Anti-Atlas basement was buried under marine sediments with dominant south-derived detrital input. Basement faults control the distribution of subsiding versus shallow areas. During the Middle–Late Devonian, the dislocation of the Saharan platform occurred, mainly in the eastern Anti-Atlas where Precambrian faults were also remobilized during the Early Carboniferous.During the Variscan orogeny, the Paleozoic series of the Anti-Atlas basin were involved in folding tectonics, concomitant with the uplift of Proterozoic basement blocks bounded by inherited basement faults. The pre-existing rift-related faults were variably inverted across the Anti-Atlas. In the westernmost part of the belt, Variscan shortening induced positive inversions along the remobilized basement faults, but in some cases, some faults preserved an apparently normal throw. Some hidden basement faults accommodate the Variscan shortening by strike-slip movement expressed by en echelon fold pattern in the overlying cover.The Mesozoic-Cenozoic evolution of the Anti-Atlas is again marked by the reactivation of the basement faults. During the Triassic, the Anti-Atlas belongs to the uplifted shoulder of the Atlasic-Atlantic rift zone. Remobilisations of paleofaults again play a significant role in the weak burial of the Anti-Atlas during the Late Cretaceous–Eocene before the Neogene exhumation related to the Africa–Europe collision. Hence the structural evolution of the Anti-Atlas during the Paleozoic to Present times has been heavily dependent on the fault pattern inherited from the Late Ediacaran–Cambrian rifting evolution at the northern fringe of the WAC, already deeply affected by the Pan-African orogeny.