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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).
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