ELSEVIER FIRST PROOF MORP123 c0010 6.28 Evolution of Intrastratal Karst and Caves in Gypsum AB Klimchouk, Ukrainian Institute of Speleology and Karstology, Simferopol, Ukraine r 2012 Elsevier Inc. All rights reserved. 6.28.1 Introduction 2 6.28.2 Geological Occurrence of Evaporites 2 6.28.2.1 Occurrence of Sulfate Rocks 3 6.28.3 Evolutionary Types of Gypsum Karst 3 6.28.4 Speleogenesis in Gypsum in Different Types of Karst 4 6.28.4.1 Dissolution of Gypsum 4 6.28.4.2 Speleogenesis in Open Gypsum Karst 5 6.28.4.3 Speleogenesis in Intrastratal Gypsum Karst 5 6.28.5 Evolution of Intrastratal Gypsum Karst 8 6.28.5.1 Subjacent Gypsum Karst 8 6.28.5.2 Entrenched Gypsum Karst 8 6.28.5.3 Denuded Gypsum Karst 11 6.28.6 Other Evolutionary Types of Gypsum Karst: Open and Mantled 11 6.28.7 Regional Examples of Gypsum Karst Evolution: Inheritance and Zonality 12 6.28.8 Subsidence Hazards in Different Types of Gypsum Karst 12 References 12 Abstract The term ‘intrastratal karst’ denotes a series of evolutionary karst types corresponding to successive stages of karst devel- opment in a soluble rock while it moves back to exposure after being buried by younger strata. The major boundary conditions, the overall circulation pattern, and extrinsic factors and intrinsic mechanisms of karst development appear to change considerably between the stages, resulting in characteristic styles of cave development and surface karst morphology, particularly distinct in case of gypsum karst. As gypsum is much more soluble than carbonates, it does not survive long in outcrops beyond arid areas. Where gypsum is exposed to the surface with no substantial karstification formed during various stages of reburial, the devel- opment of epigene solution porosity in this rock is hindered due to the fast dissolution, being limited to flowpaths in which the breakthrough conditions can be attained quickly. However, karst processes in gypsum develop extensively in intrastratal karst settings, with inheritance from the deep-seated stage through the denuded one. Karstification may commence in any stage of intrastratal development, and during the next successive stage, the process, although in changed conditions, will be affected significantly by the preformed solution porosity. Speleogenesis in deep-seated gypsum karst is exclusively hypo- gene. In subjacent karst, both hypogene and epigene speleogenesis may operate depending on the locally prevailing flow regime, but hypogene speleogenesis still dominates. In entrenched and denuded karst types, speleogenesis is over- whelmingly epigenic, but it is greatly facilitated by the presence of solution porosity inherited from the previous stages. Diverse and expressive karst landforms related to subsurface conduits evolve through different stages of the intrastratal karst development. The subsidence hazard in regions underlain by gypsum differs substantially between the karst types, so that one can obtain a kind of integrated general hazard assessment by classifying a given individual karst according to its evolution state. In general, various types of intrastratal karst, subjacent karst in particular, are the most potent in generating subsidence problems, whereas exposed karst types, particularly open karst, are the least prone to subsidence. Glossary d0010 Breakthrough The moment in the early cave conduit development when dissolution has enlarged the fracture to the point where water can pass through the entire length of the fracture remaining considerably undersaturated. d0015 Confined aquifer An aquifer where groundwater is under pressure in a bed or stratum confined above and below by units of distinctly lower permeability. d0020 Epigene (karst, caves, and speleogenesis) The origin in the near-surface settings by downward recharge from the overlying or immediately adjacent surface. Klimchouk A.B., 2012. Evolution of intrastratal karst and caves in gypsum. In: Shroder, J., Jr., Frumkin, A. (Eds.), Treatise on Geomorphology. Academic Press, San Diego, CA, vol. 6, pp. xx–xx. [Please replace ‘xx’ by correct page number when available.] MORP 00123 1 Treatise on Geomorphology. Vol. 6. Shroder, J., Jr., Frumkin, A. (Eds.), Academic Press, San Diego, CA