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NCKRI Special Paper No. 1
Figure 16. Examples of polygonal (above: Yellow Jacket Cave in
the Yates Formation) and systematic (below: fragment of
Lechuguilla Cave survey) network patterns in the same region,
Guadalupe Mountains, USA. Yellow Jacket: simplified map from
the original survey drawn by D.Belski, courtesy of the Pecos Valley
Grotto. Lechuguilla: fragment from the original survey drawn by
P.Bosted, courtesy of the US National Park Service.
Irregular chambers can be isolated cavities, or parts of
composite patterns. In hypogenic settings they form in two
situations: 1) by buoyant dissolution at the bottom of the
cave formation, commonly evaporites, where a major
aquifer immediately underlies it; 2) where the recharge
from below is localized and flow and transverse
speleogenesis in the cave formation is guided by prominent
fractures. In the latter case, chamber development is
commonly induced by intersection of the vertical flow path
with a lateral flow-conducting horizon (stratiform
permeability system) that enhances dissolution through
mixing mechanisms. Irregular chambers in hypogenic karst
can attain very large dimensions, such as directly
documented cavities in evaporites of southern Harz,
Germany (cavities of the “schlotten” type; Kempe, 1996),
the Big Room in Carlsbad Cavern, or the indirectly
documented (via drilling) hydrothermal cavity in the
Archean and Proterozoic marbles in southern Bulgaria
with a maximum vertical dimension of 1340 m and an
estimated volume of 237.6 million m 3 (Sebev, 1970;
Dubljansky,V. 2000), probably the largest known,
although not accessible, cave chamber on Earth. It is likely
that hypogenic megasinkholes associated with
hydrothermal systems, such as Sistema El Zacatón in
Mexico (Gary and Sharp, 2006; see Plate 19 and Section
4.5) or obruks (local name in Turkey for cenote-like
sinkholes) in the Konya Basin, Turkey (Plate 19) are
collapse features over giant chambers. However, it is also
possible that they are rising dissolution shafts.
Isolated passages or crude clusters of passages also
form in two situations: 1) in a manner similar to chambers,
by buoyant dissolution at the bottom of the cave formation,
where there is some initial linear guidance (by fractures or
other kinds of weaknesses) but little or no forced flow
across the formation; 2) by forced or mixed flow across a
thin bed, where fracturing is scarce. In the former case
some big irregular passage-like cavities may form, often
associated with chambers, exemplified again by some
“schlottens” in the South Harz (Kempe, 1996). In the latter
case isolated slot-like passages or crude clusters of
passages form, such as those intercepted by mines in the
Neogene limestones in the southern Ukraine (see Figure
31).
Rising shafts are outlets of deep hypogenic systems
and commonly hydrothermal. A type example is the 392 m
deep Pozzo del Merro near Rome, Italy, presumably
formed by rising thermal water charged with CO2 and H2S.
It shows the morphology of a rising shaft (Figure 27), in
contrast with the roughly cylindrical morphology of the
sinkholes of Sistema El Zacatón in Mexico (see below),
where hydrothermal cavities at depth are thought to open
to the surface through collapse.
Consideration of hypogenic cave patterns only in plan
view can be misleading, giving a false impression of
seemingly two-dimensional structures in the case of
laterally extensive network or spongework mazes. Further
confusion arises from the fact that in many relict
hypogenic mazes sediment fill obscures the “root”
morphology at the passage floors, and that minor bottom
features are rarely documented while surveying large maze
caves even when they are recognizable. First recognized in
the Western Ukrainian gypsum mazes and subsequently
found in many maze caves around the world, both in
limestone and gypsum, are numerous feeding conduits at
lower levels, scattered throughout maze patterns at the
master story (Figure 20; see Sections 4.2 and 4.4). With
these feeders and their lower conduits, even largely
horizontal laterally extensive maze patterns become
complex three-dimensional structures.
Complex 3-D cave structures may develop within a
rather thin formation (e.g. two- to four-story mazes in the
western Ukraine confined within the 16-20 m thick gypsum
formation) or extend through a vertical range of several
hundred meters (e.g. Monte Cucco system, Central Italy:
930 m; Lechuguilla Cave in the Guadalupe Mountains,
New Mexico, USA: 490 m). These complex 3-D structures
often display a staircase arrangement of stories within a
system, with cave areas at different stories shifted relative
to each other (as discussed in section 3.5; see Figures 12
and 13), or have feeders at the lower level randomly or
systematically distributed throughout the single master
passage network. Some vertically extensive caves in the
Guadalupe Mountains have prominent feeders as large