Download PDF - Speleogenesis
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HYPOGENIC CAVE FEATURES<br />
Cueva de Villa Luz in Tabasco, Mexico, has received<br />
much attention during recent years as an example of active<br />
and dynamic, presently unconfined hypogenic development<br />
(Hose and Pisarowicz, 1999; Hose and Macalady, 2006).<br />
The cave is a 2-km long maze of passages lying almost<br />
horizontally 10-20 m below the surface, connected to it by<br />
numerous skylight entrances (Figure 51). The cave has<br />
more than 20 underground springs rising from conduits (up<br />
to 1 m x 2 m in width) in the floor and coalescing into a<br />
surface resurgence spring. Spring discharge (~270-300 L/s)<br />
is remarkably steady. Together with elevated temperature<br />
(28 o C) and high H2S and CO2 content of the water, this<br />
suggests a deep flow system possibly related to the<br />
magmatic system of El Chichon volcano, 50 km to the<br />
west. Springs inside the cave release H2S and CO2 into the<br />
cave atmosphere at concentrations that vary, respectively,<br />
from 1 to 120 ppm and from 0.03 to >3.2%. Replacement<br />
gypsum coats most walls throughout the cave. Fallen<br />
gypsum forms piles up to 1 m thick and is partially<br />
removed by the stream. The cave has many cupolas which<br />
are presumed to be actively growing due to chemical<br />
stoping. The origin of the cave is presumed to be largely<br />
due to subaerial dissolution at the stage of underground<br />
hypogenic springs (Hose and Macalady, 2006).<br />
Figure 51. Map of Cueva de Villa Luz, Tabasco, Mexico (from Hose<br />
and Pisarowicz, 1999).<br />
Sistema Zacatón (also known as Los Cenotes de<br />
Tamaulipas or Los Cenotes de Aldama) in the Sierra de<br />
Tamaulipas, northeastern Mexico, is one of the most<br />
outstanding examples of deep hypogenic karst, expressed as<br />
a series of extremely deep, phreatic megasinkholes, some of<br />
them being sealed with travertine precipitating at the water<br />
table (Figures 52 and 53, Plate 19 upper photo). Recently<br />
published results of the ongoing study of Sistema Zacatón<br />
provide a detailed description of the system and discussion<br />
of its origin (Gary et al., 2003; Gary and Sharp, 2006).<br />
Besides megasinkholes – deep phreatic shafts – the system<br />
also includes ramiform, currently vadose cave passages,<br />
sub-horizontal phreatic conduits, broad overland travertine<br />
flows and relict spring flow travertine. El Zacatón is the<br />
deepest of the sinkholes, and the second deepest underwater<br />
shaft in the world with its measured depth of at least 329 m<br />
(dove to -284 m).<br />
Figure 52. Profile view of southernmost sinkholes of Sistema<br />
Zacatón showing zones of varying water types and travertine<br />
morphology. The Verde pit is hypothesized to have a travertine<br />
floor formed during periods of low water-table levels (~50 m). This<br />
cap now serves as a flow barrier (from Gary and Sharp, 2006).<br />
Figure 53. Aerial photograph of Sistema Zacatón showing the<br />
major features of the area. Numerous travertine-filled sinkholes are<br />
labeled and water-filled areas appear as black. Water flows<br />
underground from El Zacatón to the resurgence of El Nacimiento<br />
through a phreatic cave passage and then flows overland until<br />
becoming dispersed through broad honeycomb travertine deposits<br />
south of the area (from Gary and Sharp, 2006).<br />
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