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Abstract:

The intense development of the theory and criteria of identification of hypogenic speleogenesis during last few years has stimulated re-interpretation of karst phenomena in many regions of the world. Recent research strongly suggest that solution features in the Piedmont Range of the Crimean Mountains, previously believed as being the result of epigenic karstification, were in fact formed in hypogenic environment due to ascending transverse flow in a stratified artesian system. Tectonically, the Piedmont Range of Crimea is an edge of the Scythian Plate, uplifted and partially eroded along the regional fault separating the plate from the folded region of the Mountain Crimea. The Cretaceous and Paleogene sequence is dipping 5 to 20o to north and north-west, where it plunges beneath the Neogene cover. It is exposed within the Piedmont Range as a series of distinct cuestas generally faced to south-east. Karst features are represented by 26 caves and abundant and diverse solution forms at the cuesta escarps. Most of karst features develop in two distinct limestone units of Paleocene (Danian) and Eocene but some are present in the underlying Maastrichtian unit of Cretaceous. There are strong and systematic evidences that the caves have hypogenic origin and that most of solution features at the escarps are remnants of morphologies of hypogenically karstified fractures, which walls are now exposed due to the block-fall retreat of the escarps. The features in various beds demonstrate strong lithostratigraphic control in their distribution and are vertically stacked into transverse complexes. Caves are fracturecontrolled, linear, or crude maze clusters, demonstrating the complete suit of morphologies indicative of hypogenic origin. Isolated cavities, expressed in the contemporary escarps as grottos and niches, as well as zones of spongework porosity, developed where laterally conductive beds of higher initial porosity were crossed by vertical fractures that once conducted rising fluids from a regional flow system.

The Piedmont Range of Crimea was a part of the Plain Crimea artesian basin during the post-Eocene time till the late Pliocene. Uplift and initial erosional entrenchment in the middle through late Pliocene caused the pattern of tectonically and geomorphologically guided zones of upward cross-formational discharge and hypogenic speleogenesis to establish. Further valley entrenchment in the region during Pleistocene shaped up the modern cuesta-like relief and drained the Cretaceous-Paleogene sequence. Hypogenically karstified fractures and caves, which are sub-parallel to valleys, provide zones of structural weakness along which blocks fall at the cuesta escarps exposing relict hypogenic morphologies.

The Piedmont Crimea Range, with its perfect and extensive exposures of the hypogenically karstified sequence, provides outstanding possibilities for studying patterns and morphologies of hypogenic speleogenesis, which is important for understanding its hydrogeological functioning and roles in the reservoir formation, especially in implication to the adjacent Plain Crimea artesian basin.