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HYPOGENIC CAVE FEATURES
in the Segovia (Fort Lancaster) Formation of the
Cretaceous Edwards Group (Kastning, 1983; Onac et al.,
2001). The lower stories lie within massive dolomitic
marly units and have generally larger dimensions than the
upper stories. The upper stories with denser maze
development lie within more porous beds separated by a
marly unit. Cupolas at the uppermost story open up into a
distinct bed of touching-vugs type porosity (“burrowed
bed”), which probably served as a “receiving aquifer”
during the ascending formation of the cave (Figure 9).
Most of the cave lies beneath that vuggy bed, which is
overlain by the thick unit of massive limestone that
provides a caprock. Another maze cave in the vicinity,
Felton Cave (2.05 km), is in many respects similar to
Caverns of Sonora but has more diverse trends of passages
(Kastning, 1983).
Figure 44. Map of Caverns of Sonora (by G. Veni and P. Sprouse;
adapted from Elliott and Veni, 1994).
The cave perfectly displays the morphologic suite of
rising flow (Plates 4-G, 6-B and 9 A, C and G). Passages at
different stories are often co-planar, with rift-like or oval
connections between stories. Smaller connections are
domepits from the perspective of a lower story. Where
passages at different stories are not co-planar, they are
connected by steep passages with a rising sequence of
dome-like forms. Ceilings, especially at upper levels,
demonstrate complex half-tube/pendant morphology. The
morphology of Caverns of Sonora bears strong imprints of
dissolution by multiple buoyant currents and shows no
appreciable modification by a water table or epigenic
recharge.
Speleogenesis of Caverns of Sonora had been
interpreted by Kastning (1983) in terms of a classic
epigenic concept, assuming passage development by
lateral flow recharged from above, with progressive
shifting from upper levels to lower levels, in response to
lowering of base levels. The ascending hypogenic origin
of the Caverns of Sonora, besides morphological and
hydrostratigraphic considerations, is strongly corroborated
by the recent finding of metatyuyamunite, a uraniumvanadium
mineral diagnostic of sulfuric acid dissolution
(Onac et al., 2001). The cave was formed under confined
conditions in the mixing zone between deep-seated H2Sbearing
warm fluids and an oxygenated shallow flow
system.
The origin of the major caves in the Guadalupe
Mountains, New Mexico, USA, including some of the
largest caves in the United States such as Carlsbad Cavern
(43.2 km long, 315 m deep) and Lechuguilla Cave (193.4
km long, 490 m deep), is firmly attributed to sulfuric acid
speleogenesis (e.g., among others, Davis, 1980; Hill, 1987,
2000a, 2000b; Palmer and Palmer, 2000a; Palmer, 2006).
The caves are formed in carbonate reef and backreef
formations of Permian age, exhumed during several
episodes of uplift (of which the Cenozoic is believed to be
the main one) from beneath largely evaporitic sediments of
the adjacent Delaware Basin (Figure 45). Most of these
caves are developed near the reef-forereef contact in the
largely massive Capitan Formation and the reef-backreef
contact between the Capitan and prominently bedded
Seven Rivers and Yates Formations (DuChene and
Martinez, 2000), but some caves or parts of caves lie
within the backreef succession. Caves are scattered along
the mountain ridge, which plunges from southwest (from
elevations up to 2767 m) to northeast (to elevations of
about 1000 m) for about 70 km. Many of these caves have
stratigraphically-conformable multi-story maze patterns,
network or spongework, or both, but some caves display
complex vertically extended 3-D structures that include
maze and chamber elements at many loosely defined
stories, and sub-vertical conduits connecting them (Figures
16, 17, and 46). The caves show no genetic relationships
with the surface and fit most other criteria for ascending
transverse caves (Section 4.1). It is apparent that
Guadalupian caves, or their segments, utilized various
kinds of original porosity available throughout different
members of the rock succession, including syndepositional
faults and fractures (Koša and Hunt, 2006), other
syndepositional features such as teepees (Plate 16),
paleokarstic cavities and zones, uplift-related
discontinuities, and vuggy porosity. Depending on their
nature and position within the geological structure, various
porosity systems (and hence respective cave elements) can
be distributed conformably within the stratigraphy or be
discordant to the bedrock structure.
Although caves in the region have received much
scientific attention during the last 30 years, speleogenesis
in the Guadalupe Mountains still has many controversial
aspects. A comprehensive overview of speleogenesis in the
Guadalupe Mountains and discussion of relevant issues is
clearly beyond the scope of this book. But this case is
treated here more extensively compared to other entries in
this section because the Guadalupes are a prime reference
region of hypogenic speleogenesis, and interpretations of
their speleogenesis are highly important in illustrating
hypogenic processes.
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