Strike-slip influenced rift systems: the case study of the Moroccan Atlas system

The High Atlas is an aborted rift system along NW Africa that formed during the Mesozoic break-up of Pangaea and was inverted during the Alpine Orogeny. In contrast to the well-studied inversion, the Triassic-Jurassic rifting, synchronous to the Atlantic and the Tethyan opening, is still not fully understood. Orthogonal rifting is proposed to be active during the Triassic to early Early Jurassic, and was followed by an oblique extensional phase. The timing of this change in the kinematic of rifting is poorly constrained. Restoration of the Atlantic-Tethys triple junction suggests sinistral motion during the Middle Jurassic, which reactivated NE-SW trending Hercynian structures in a transtensional manner.

The Atlas system is a great field analogue to study and analyse extensional systems influenced by strike-slip tectonics since the well exposed syn-rift structures and sediments have been weakly affected by the contraction during the late Cenozoic Alpine inversion.

This work investigates the kinematic and geometry of the oblique rifting phase, the stress and strain variation lengthwise along the Atlas rift system, the relationship between the Triassic-Early Jurassic orthogonal rift structures, the Middle Jurassic strike-slip structures, and the potential synchronous volcanism occurring during the Middle Jurassic. This contribution highlights the fieldwork results of significant outcrops that we used to constrain the restoration of the rift system, evaluate extension and transtension, and produce a conceptual model of how strike-slip tectonics can influence the evolution of continental rifting.