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HE Late Cretaceous-Early Eocene carbonate sequences of the White Desert of Egypt exhibit amazing complex paleo-humid karst landforms, so it was declared as a nature-protected area since 2002. Two karst depressions of El Sheikh Abdallah and the Crystal Mountain (Qaret El Sheikh Abdallah) are identified by detailed fieldwork and GIS morphometric analysis of the digital elevation model of the northern part of the White Desert. These depressions are verified as two separate karst uvalas between the major karst poljes of El Bahariya and Farafra karst territory with northeast alignment. The sea-level drops and uplifting phases of the carbonate sequences of the uvalas, associated with the major compressional events of the Syrian arc (Cretaceous-Paleogene) and Oligo-Miocene extensional tectonics in north Egypt caused the development of three major stratigraphic breaks (fossilized paleo-karst surfaces) of Late Cretaceous-Palaeocene, Palaeocene-Early Eocene, and post-Early Eocene (Oligocene-Miocene). Along these fossilized surfaces, paleokarst features and sediments are detected and described. El Sheikh Abdallah and the Crystal Mountain depressions (uvalas) are also dominated by exposed (surface) complex karst features such as unroofed caves, widened joints, sinkholes, collapse breccia's, and solution channels, together with sporadic remains of uncovered autochthonous and allochthones paleo-cave sediments. The recognized stratigraphic breaks and their paleokarst features and the subsequent surface denudation helped to propose a morphotectonic evolutionary model for the exposed karst landscape and the denuded karst features of El Sheikh Abdallah-Crystal Mountain uvalas.

Mazzini et al.Hydrothermal Venting in the Western Desert and the deformed structures located within the strike-slip zone suggest that faulting controlled the emplacement and the final shape of some of the hydrothermal vents. We speculate that this system may represent a palaeo sediment-hosted hydrothermal system and could be related to the opening of the Red Sea.