Post-Variscan tectonics in eastern Anti-Atlas (Morocco).

New field data integrated by fission-track (FT) analysis unravel an innovative scenario for the post-Variscan evolution of the eastern Anti-Atlas. This area, unaffected by Meso-Cenozoic tectonics according to most workers, is crosscut by crustal faults bearing evidence of a polyphase deformation history. Apatite FT ages, ranging between 284 and 88 Ma, point to fast Neogene exhumation and unravel contrasting cooling paths across major faults. Results show that the study area was buried beneath 2 km of allochthonous Variscan units, now eroded. The eastern Anti-Atlas acted as the southern shoulder of the Atlasic rift in the Mesozoic, and underwent a dextral transpressional structuring of Neogene age followed by sub-meridian shortening. The southern front of Atlasic deformation is therefore located inside the Anti-Atlas region, and it is still active.