Tectonic control on the morphology of the subcircular structure of El Mdaouar (Saharan Atlas,Algeria): insights from geological and remote sensing data

El Mdaouar subcircular structure is located in the eastern Saharan Atlas (Algeria) at 35° 05′ N and 4° 19′ 30″ E, about 20 km southwest of the town of Bou Saada. Its diameter is about 3.2 km and shows a raised rim that stands high above the surrounding terrain. We have carried out a combining remote sensing (Landsat 8 OLI image and Shuttle Radar Topography Mission (SRTM) data) and geological field investigation of the El Mdaouar subcircular structure in order to study its morphology and to determine its origin. In the absence of evidence of magmatism, diapirism, and impact on this structure, a tectonic deformation is the most likely in the origin of this subcircular feature. The counterclockwise rotational motion of the layers explains the morphology of the structure. This rotational motion is probably the result of a combination of the movement of the faults which pass through the structure, in particular two NE-SW strike-slip faults and a NW-SE fault, which marks the eastern limit of the El Mdaouar structure. The NE-SW trending of the structure indicates a NW-SE compressional event, which corresponds to that of the Atlasic phase. This event occurred in the Late Eocene (35 Ma), which is the best estimation of the age of the El Mdaouar structure.