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HYPOGENIC CAVE FEATURES
Amazing Maze Cave (the cave name) is a very densely
packed 3-D network maze with 9 km of passages surveyed
to date. It was originally opened by a road cut in a lowrelief
hill within a broad valley of Edwards Plateau
outliers. Most of the passages lie at a single level but three
or more other levels, connected by outlet/feeder structures,
can be distinguished in the cave within a 22 m thick
stratified section of the Fredericksburg Formation,
Cretaceous Edwards Group (Figure 43; Elliott and Veni,
1994). The cave has no features indicative of downward
percolation, considerable lateral flow or water table action.
Instead, the morphologic suite of rising flow is perfectly
represented in the cave (Plates 4; 9, F and H). Many
passages on the master level contain massive bodies of
microcrystalline gypsum, commonly coated with calcite
crust. This gypsum is similar to the secondary gypsum
known from the Guadalupe Mountains caves, indicative of
a sulfuric acid dissolution mechanism. Gypsum masses in
Amazing Maze Cave have numerous “vents” in them,
which are morphologically continuous with feeders below.
Some of these holes have gypsum blisters at the top.
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Figure 42. Robber Baron
Cave, Texas, USA, a maze
cave in Cretaceous limestone,
above the confined zone of the
Edwards Aquifer. Survey: San
Antonio Grotto, 1976-77 (from
Veni, 1989).
Gypsum masses do not fill passages from side to side but
occupy central sections, leaving wide gaps between the
gypsum body and walls. They were apparently formed
under water-filled conditions. During our examination of
the cave we found massive occurrences of endellite of
intense purple color in several parts of the cave. In the
main occurrence, endellite rims a feeder in a small passage
at the upper level developed along a diffusely permeable
bed (Plate 4-D). Identification of endellite has been
confirmed by SEM and elemental analysis by M. Spilde
(University of New Mexico). All of these characteristics
strongly suggest the confined transverse origin of Amazing
Maze Cave, in which, at least during some episodes,
dissolution by sulfuric acid had contributed to
speleogenesis through mixing of uprising H2S-bearing
waters with oxygenated waters flowing laterally through
some more transmissive beds. The cave is located above
the White and Backed Oil Field, and a source of sulfates
could be evaporitic beds in the Trinity Group below.
The presence of the massive gypsum and endellite in a
typical stratiform maze cave, which was apparently formed