Role of Fracturing in the Organization of the Karst Features of Azrou Plateau (Middle Atlas,Morroco) Studied by Remote Sensing Imagery

Karst formation geometry can be controlled by fractures and faults, and by other lithologies. Here we show the organization of kastic collapse features related to structures and to extensive basaltic lava flows in the Middle Atlas of Morocco. A lineament map of major faults and fractures has been created for the Middle Atlas using Landsat 7 ETM⁺ satellite images. This shows a dominant NE–SW regional direction and less prominent NNW–SSE and ENE–WSE directions. All these directions coincide with the alignments of karstic depressions that have formed in the Liassic limestones. The basaltic flows covering these formations on the Middle Atlas limestone plateau, have allowed the generation of cryptokarst, geometrically organized a long these major lineament directions. Karst landforms probabaly existed before the eruption of the lavas, but there were partly invaded by intrusions and volcanism. The extensive basaltic flows allowed for increased infiltration, and subsurface water flow, increasing the rate of kast formation after eruptions. Some basins show evidence of increased subsidence after lava emplacement (Aguelmam Sidi Ali Lake) and some maar-like craters also have subsided after eruption, by karts formation. We lay out the structural and lithological controls on Karstic formation in an intraplate volcanic field based on limestones and evaporites.