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64 NCKRI Special Paper No. 1 In the eastern outskirts of the Eastern European craton, in the fore-Urals region, Russia, maze caves of hypogene origin are known in both limestones and gypsum. Kungurskaja Gypsum Cave (5.6 km) is a good example of an ascending maze considerably modified with lateral enlargement of passages by backflooding of the nearby Sylva River. Siberia In Siberia, a remarkable example is the 60.8 km long twodimensional network maze of Botovskaya Cave, developed in a Lower Ordovician limestone bed sandwiched between sandstone aquifers (Filippov, 2000; Figure 33 – top map). The area is now an entrenched and drained part of the Angaro-Lensky artesian basin. There are some other maze caves in the region, which likely share the same origin. Hypogene origin is suspected for a number of complex 3-dimensional caves known in other regions of Siberia in limestone (e.g. Dolganskaya Yama, 5.12 km long, developed with a vertical range of 125 m in the Riphean - Lower Cambrian limestones of the Vitim Upland) and conglomerates (e.g. Bol'shaya Oreshnaya Cave, 47 km long, developed with a vertical range of 250 m in the Ordovician carbonate conglomerates of the Eastern Sayan Upland; Figure 33 – bottom map). Caucasus, Central Asia and Middle East Hypogenic caves are found in both the Great Caucasus and the Minor Caucasus, throughout southwestern Russia, Georgia and Armenia. In the northern ridges of the Great Caucasus some deep sub-vertical caves display odd Figure 33. Maze caves in Siberia. Botovskaya Cave (upper map) is a 60.8-km long 2-dimensonal network maze in a Lower Ordovician limestone bed sandwiched between permeable sandstones in a stratified succession of the Angaro-Lensky artesian basin (Filippov, 2000). Bol'shaya Oreshnaya (lower map), Eastern Sayan is a 47 km long cave with a vertical range of 250 m in Ordovician carbonate conglomerates (map courtesy of Krasnoyarsk Speleo-Club). patterns and hydrothermal mineralization in their deep parts, although these aspects remain poorly studied. In the southern ridges, an outstanding cave of established hydrothermal origin (Dublyansky V., 1980) is Akhali Atoni Cave (Novoafonskaya) in Abkhazia, characterized
HYPOGENIC CAVE FEATURES by the huge volume of its chambers. In the Minor Caucasus, Armenia, an interesting hypogenic cave is Archeri (3.7 km long and 130 m deep), which is an inclined system of wide cavities at five levels along bedding planes and almost entirely lined with a crust of palisade hydrothermal calcite. Hypogenic caves, mainly produced by hydrothermal and sulfuric acid speleogenesis, are abundant throughout Central Asia (Turkmenistan, Uzbekistan, Tajikistan, and Kyrgystan). Opened by surface denudation, small relict caves are very common throughout the mountains of Tien Shan, Pamir, and Kopetdag. Some large caves are known, both fossil and active, e.g. Syjkyrdu Cave in Pamir, Cup- Coutunn/Promezhutochnaja, Geophizicheskaja, Khashim- Ouyuk, and other caves in the Kugitang Range in Tien Shan, and Bakharden Cave in Kopetdag. The longest cave in Iran, Ghar Alisadr (11.44 km), is developed in the Jurassic Sanandaj-Sirjan Formation. The cave has a joint-controlled maze pattern with passages in several levels and numerous ceiling cupolas (Laumanns et al, 2001). The cave contains numerous lakes representing the current water table and sluggish flow conditions, with lower parts of the cave extending below the water. No specific speleogenetic studies have been done for the cave so far, allowing inference about specific dissolution mechanisms involved. Based on available information about cave pattern and morphology, it is likely that Ghar Alisadr falls into the category of hypogenic transverse speleogenesis. In Israel, the hypogenic transverse speleogenesis concept has been successfully applied to interpret cave origins at a regional scale (Frumkin and Fischhendler, 2005) and to resolve some important issues of regional hydrogeology (Frumkin and Gvirtzman, 2006). These cited works are particularly instructive as they offer one of the few examples of a regional speleogenetic analysis based on extensive and consistent datasets and performed through a spectrum of paleohydrogeological conditions. Caves that have no genetic relationships to the surface are estimated to comprise about 95% of the caves in Israel. Many of them are network mazes; others are isolated chambers. Maze caves occur within the massive limestone and dolomite beds in upper sections of the late Cretaceous Judea Group (Bina Formation), beneath the overlying leaky confining Mt. Scopus Group (massive chalk and marls). Numerous maze caves (the longest is 3.45 km long) are distributed along the retreating edges of the confining cover and beneath the cover in the vicinity of deep underground faults and related flexures (Figure 34-A; Frumkin and Fischhendler, 2005). Caves are opened naturally by denudation and artificially by mining and construction holes. The lack of maze caves far away (>0.5 km) from the cover is due to erosional removal of the Bina Formation that contains them. Network patterns are arranged in several stories (up to three), forming 3-D systems. Stories are concordant with bedrock stratification, with horizontal networks in horizontal beds and inclined networks in inclined beds. Maze networks display many laterally blind terminations, abrupt changes in morphology and high passage density (Figure 36). The study of Frumkin and Gvirtzman (2006) in the western, still largely confined, sector of the same region has shown that hypogene transverse speleogenesis is currently operative in the confined area, being responsible for the “Ayalon Saline Anomaly” (ASA) at the central part of the major Yarkon-Taninim aquifer (Figure 34-B). Analysis of data from quarries and more than 10,000 boreholes suggests locally high porosity within the Bina Formation and shows that stratigraphic distribution of intercepted voids is similar to what is observed in the unconfined area (Figure 35). The analysis of hydrogeologic data indicates that the ASA contains “hot spots,” associated with transverse cave clusters of high permeability, through which warm-brackish groundwater rises to the upper aquifer section (Bina Formation). In these spots, water is substantially warmer and enriched in Cl and H2S, and has lower pH values as compared with waters a few hundred meters away. Other than maze caves, isolated chambers are also common for the region, occurring mainly in the more massive carbonates of the Weradim and Kefar Shaul units below the Bina Formation. They range between a few tens to a few hundred meters in their lateral dimensions and usually have a shaft or domepit rising upward from their ceilings, but tapering or terminating at certain higher intervals. Frumkin and Fischhendler (2005) attributed the chambers' origin to mixing dissolution in sluggish phreatic conditions below a water table, where downward vadose percolation locally occurs. This suggestion is based mainly on the uniform occurrence of isolated chambers through the whole area, including areas far away from the confining cover, where currently water table conditions prevail. However, chamber-type cavities also occur in the confined area (Frumkin and Gvirtzman, 2006), and some caves show combined maze-chamber patterns. An alternative model for chamber-type cavities is that they have also formed by rising flow as part of transverse threedimensional cave systems. Predominant association of mazes and chambers with different hydrostratigraphic units (Figure 35) is consistent with the role of vertical heterogeneities of initial porosity structure, as discussed in Section 3.4. Regular vertical variations in the distribution of elementary cave patterns are a common feature of 3-D hypogenic systems. The differences in the distribution between mazes and chambers within the exposed sections of the Judea Group can be explained by the fact that maze caves are exclusively associated with the Bina Formation, which is removed by denudation at some distance from the cover edge (see Figure 34-A). 65
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Hypogene Speleogenesis: Hydrogeolog
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Foreword In 1998, the National Cave
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Figure 33. Maze caves in Siberia: B
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