Ghost-rock karstification and cave system modelling in the Middle Atlas, Morocco

This research presents the first comprehensive investigation of ghost-rock karstification and its relationship with the development of caves in the Middle Atlas Mountains of Morocco, focusing on a region previously overlooked in karst research in North Africa and the Mediterranean. Although the phenomenon of ghost rocks karstification has been widely investigated in Europe, its geographic distribution, formation, and hydrogeological implications remain undocumented in North Africa. To bridge this knowledge gap, remote sensing, structural analysis based on the Geographic Information System (GIS), extensive fieldwork, petrographic analysis, and three-dimensional (3D) modeling of cave development; were adopted. The spatial organization of the caves located in the El Menzel Causse in in the Central Middle Atlas, analyzed through GIS and remote sensing data, reflects a strong influence of regional structural features, such as the North Middle Atlas Fault, and hydrological systems, including the Sebou River. Field surveys indicated that this form of karstification occurs in two phases: deep isovolumetric chemical weathering of the host rock, followed by the selective mechanical evacuation of the resulting alterite. The petrographic analysis reveals a weathering gradient from unaltered Liassic dolomites to altered facies within the cavities, exhibiting extensive dedolomitization, pronounced recrystallization, and notable dissolution, indicative of the initial phases of karstification in ghost rocks. In summary, this study presents a novel conceptual framework to elucidate cave formation in tectonically active carbonate landscapes in Africa and the Mediterranean region by reconstructing the multi-phase history of ghost rock karstification.