Brittle tectonic feature in the external part of the Variscan belt (Eastern Anti-Atlas, Morocco): A combined field and remote sensing approach

Located in the external part of the Variscan belt, the Ougnat massif in the eastern Anti-Atlas of Morocco represents one of the repeatedly deformed inliers from the Precambrian onward. This study presents a detailed structural analysis covering the outcrops of Precambrian basement and Paleozoic cover in the Ougnat massif. The interpretation is carried through remote sensing-based lineament mapping in this arid area. The methodology entails processing a Landsat-8 OLI satellite image using a Directional Filter to accentuate the various structural lineaments across different scales. A Digital Elevation Model (DEM) is used to map all major structural lineaments.

The analysis led to the identification of 4719 lineaments extracted manually, as well as 2330 lineaments extracted automatically from the first vector of the principal component (PCA1). Moreover, 213 major lineaments, mainly related to large morphological structures, were identified from the digital elevation model (DEM). All lineaments are organized along four main directions, NE-SW to ENE-WSW, ESE-WNW to SE-NW, and NNW-SSE to N-S. Mapped fault networks are more common in the Precambrian basement than in the Paleozoic cover, indicating the higher mechanical strength and rigid rheology of the Pan-African basement rocks. Many previously identified or suspected faults have been confirmed, others have been extended, and new major faults have been revealed. These structures reflect a long tectonic history, with multiple reactivation phases from the Precambrian to the present day. The results provide new insights into the structural evolution of the Ougnat massif and its broader tectonic framework within the Variscan belt.