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66 NCKRI Special Paper No. 1 Figure 34. A = Geological section across the Judean arch, Israel. Symbols in boxes: 1 = Cenozoic; 2 = Senonian – early Cenozoic (mostly chalk, confining unit); 3 = dolomite and limestone: Amminadav to Bina Formations of late Cenomanian – Turonian age, with locations of maze caves (X) and chamber caves (O); 4 = Cretaceous dolomite, limestone, and marl, older than Amminadav Formation. B = Schematic east-west hydrogeological cross-section showing the conceptual model for groundwater flow and hypogenic transverse speleogenesis, the Yarkon-Taninim aquifer and the ASA zone. This cross-section runs roughly parallel to the above section of the Judean arch, but ~ 15 km to south. White arrows = thermal water; black arrow = non-thermal fresh water. Combined from Frumkin and Fischhendler (2005) and Frumkin and Gvirtzman (2006). Figure 35. Stratigraphic section of Cretaceous formations in the Samaria Mountains, Israel (left) and a quarry in the confined zone (right) showing distribution of caves. The Judea Group consists of karstified dolomite and limestone with thin-bedded marl intercalations; Menuha Formation, composed of chalk and marl, is a confining unit. The histogram with the quarry section represents an arbitrary sample of voids encountered by the quarry from 1997 to 1999, the best available approximation of actual void frequency in the ASA zone in the confined flow area. Combined from Frumkin and Fischhendler (2005) and Frumkin and Gvirtzman (2006).
HYPOGENIC CAVE FEATURES Figure 36. Maps of typical caves in the Turonian limestone. Network maze patterns commonly develop at two or three levels. Cave entrances are artificial. Broken lines on the Aneva Cave plan are rifts at the bottom of passages. Combined from Frumkin and Fischhendler (2005) and Frumkin and Gvirtzman (2006). A few papers describing karst and caves in Saudi Arabia, Qatar and other regions of the Arabian Peninsula (e.g. Amin and Bankher, 1997; Peters et al., 1990; Sadiq and Nasir, 2002; Hussain et al., 2006) give strong evidence in favor of a hypogenic transverse origin of karst features, although not interpreting them in this way. The vast regional multi-story (eleven aquifers) artesian system comprises alternating sulfate, carbonate and clastic beds within the Mesozoic and Cenozoic Arab, Hith, Silaiy, Aruma, Umm Ar Radhuma, Rus, Dammam and Hofuf formations. This offers extremely suitable conditions for transverse speleogenesis. Numerous caves are mainly fissure- and slot-like passages or clusters of passages (“ghar” caves); some are clear rectilinear mazes. None of the caves show any genetic relationship with the surface. The regional artesian system discharges via numerous springs at the Gulf area, many of them being vertical pits (“ayns”) through which groundwater rises from horizontal passage clusters at the base (Hötzl et al., 1978). Amin and Bankher (1997) and Sadiq and Nasir (2002) implied that karst and caves in the area were formed epigenetically during past humid epochs of the Plio-Pleistocene. Hussain et al. (2006) suggested that network caves in the Upper Miocene calcareous sandstone in the Jabal Al Qarah area (Figure 37), which are being truncated now by denudational lowering, have developed due to weathering and enlargement of the fracture systems. The photographs in this paper show, in fact, very characteristic morphologies of confined maze caves, now in the process of un-roofing. It is argued here that, based on available information about regional litho- and hydrostratigraphy, hydrogeology, and cave patterns and morphology, the dominant mode of karst development in that region is probably hypogenic transverse speleogenesis. Numerous deep collapse sinkholes described in the region (e.g. Amin and Bankher, 1997; Sadiq and Nasir, 2002), some with unexplored caves at the base, are clearly related to regionally operating contemporary artesian speleogenesis rather than to presently inactive epigenic cave systems formed during past epochs of humid climates, as commonly assumed for the region. A hypogenic transverse origin could be assigned to Magharet Qasir Hafeet Cave in the Jebel Hafeet ridge in the United Arab Emirates, described by Waltham and Fogg (1998). The cave has rift-like passages at depths of almost 100 m, connected to the surface through a series of vertical joints and shafts of apparently rising morphology. It occurs at the crest of an eroded anticline, in limestones that were confined by a clay-marl sequence in the past. Although initially a conventional phreatic origin was suggested for this cave (Waltham and Fogg, 1998), the possibility of per ascensum hydrothermal origin has been later acknowledged (Waltham and Jeannin, 1998). Figure 37. Plan view and cross-sections (insets) of Jabal Al Qarah caves formed in the calcareous sandstone of the Upper Miocene Hofuf Formation, northeastern Saudi Arabia (adapted from Hötzl et al., 1978, and Hussain et al., 2006). Africa Hydrothermal caves in massive Cretaceous limestones, including complex 3-D and network maze systems, are reported from northern Algeria (Collignon, 1983, 1990) and northern Namibia (Martini and Marais, 1996). Quinif and Dupuis (1989) described the artesian karst system of Ziaka in Zaire. Ziaka Cave is an emergence of the system explored by divers. It has the characteristic morphology of confined caves with numerous cupolas. The piezometric surface of the aquifer is higher than the base level of the Kwilu River. Maze caves are common throughout the Transvaal Basin in South Africa, in the carbonates of the Malmani Subgroup of late Archaean age (2.5-2.6 billion years). Sterkfontein Cave is the best documented example (Martini et al., 2003), well known for the hominin fauna found in a breccia fill. It is also an informative example of 67
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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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