Structural analysis of the alpine orogeny in the western High Atlas, Morocco: New insights through a multiscale approach

The Moroccan Atlas is an intracontinental chain resulted from an aborted rifting during the Mesozoic time, by an uplifting and moderate shortening during the Late Cretaceous-Cenozoic period. Several studies have highlighted the role of tectonic inversion in the evolution of the High Atlas Range, where strike-slip faults are commonly been considered as a main component of the alpine signature within the High Atlas belt. However, more recent works have focused on the geodynamic model of the evolution of the Atlas Range using different approaches. The structural history and chronology of events are still matter of debates. To contribute to the later, a combined meso and microstructural study was conducted in the western part of the chain. It provided an attempt to quantify paleo-stresses from structural analysis of the Permo-Triassic extensional phase to the tectonic reversal phases, acting from Cenozoic to present days.
This work highlighted two major tectonic phases: (1) the first represented by an extensive regime, with a sub-horizontal minimal stress σ3 oriented NE-SW and linked to the Central Atlantic occurrence. This stage is characterized by pull apart basins genesis in horst and graben morphology. (2) the second phase represented by a weakly tilted compression with a maximum stress σ1 oriented in set NNE-SSW to NNW-SSE. This compression began in the Tertiary, contemporary with the Africa and Europe collision. the related inversions are printed at the paleozoic basement/mesozoic cover interface from the Eastern area to the Jurassic-Cretaceous and Cenozoic plateaus in the West, passing through the Triassic detrital formations of the Argana corridor.
Keywords: Paleo-stress, Structural analysis, Tectonic inversion, Western high Atlas, Morocco, Alpine orogeny.