Integrated remote sensing data and field investigations for geological mapping and structural analysis. The case of SW Tichoukt ridge (Middle Atlas, Morocco)

Boulemane area is one of the important key sectors to understand the evolution of the central Middle Atlas of Morocco. It is a junction area of three Cretaceous/Paleogene unconformable sedimentary basins on the Triassic -Jurassic deposits. This work is a combination of remote sensing results (optical and radar data) supported by field observations to accurate a high-precision geological map of the study area. For this purpose, we used two types of images that are the radar image (Sentinel-1 data) and the optical multispectral images: Landsat 8 OLI (Optical Land Imager) and Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER). The two multispectral images have been spatially enhanced using the panchromatic band of the HRG-2 (High Geometric Resolution) sensor of SPOT 5, allowing the production of high spatial resolution images (5m).The colored compositions that were chosen using OIF (Optimum Index Factor), and PCA (Principal Component Analysis) allowed good discrimination of the main rock. Moreover, ASTER thermal bands have allowed the delimitation of large outcrops of yellow sandstone, conglomerate, phosphate and gypsum based on their thermal emissivity.Structural lineaments are manually extracted from Sentinel-1 radar images after applying directional filters, analyzing Landsat 8 OLI, ASTER high-resolution multispectral images, and interpreting the spatial juxtaposition of lithological features after digitizing the final lithological map.The extracted structural lineaments are grouped into major systems mainly oriented NE-SW, and NW-SE. The NE-SW system is constituted by faults inherited from the Paleozoic basement. The NW-SE transverse system is constituted by faults newly developed during the Middle Liassic.