Structural analysis and reconstruction of the Late Hercynian paleostress in the Aouli inlier (Upper Moulouya massif, Morocco)

The Aouli inlier is part of the Upper Moulouya Massif located at the junction of the Middle Atlas and the central High Atlas, where outcrop a Paleozoic basement and an unconformably overlying Meso-Cenozoic cover. The aim of this paper is to describe the main fault and fracture systems that contributed to the structuring of the region during its tectonic evolution, as well as the reconstruction of the paleostress fields during the Late Hercynian period. This was achieved using a multidisciplinary approach with field surveys and measurements associated with stress tensor calculations. The structural analysis allowed us to distinguish the main faults affecting the Paleozoic basement and its Meso-Cenozoic cover on a multi-kilometer scale, as well as secondary faults whose influence can only be observed at the scale of a few hundred meters to a few kilometers. The spatial distribution of these faults shows the following directional systems: (i) the NNE-SSW to NE-SW system; (ii) the ENE-WSW to E-W system; (iii) the WNW-ESE to NW -SE system; and (iv) the NNW-SSE to N-S system. The reconstruction of the Late Hercynian paleostress fields allowed us to highlight a brittle deformation phase consistent with a regional strike-slip to transpressional tectonic regime. This phase is characterized by a subhorizontal to horizontal maximal & sigma;1 stress axis with a submeridian direction, and a minimal & sigma;3 axis also subhorizontal to horizontal with a subequatorial direction. This tectonic regime is responsible for NNE-SSW to NE-SW sinistral strike-slip faults, NW-SE dextral strike-slip faults, and ENE-WSW to E-W reverse faults with strike-slip component, as well as the development of submeridian tension gashes.

Automated summary

The aim of this paper is to analyze the main faults and fracture systems in the Aouli inlier and reconstruct the paleostress fields during the Late Hercynian period. The study reveals the presence of multiple directional fault systems and a tectonic regime consistent with regional strike-slip and transpressional deformation. The findings contribute to a better understanding of the tectonic evolution of the region.