Download PDF - Speleogenesis
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2<br />
NCKRI Special Paper Series No.1<br />
either solute or thermal density differences is important in<br />
hypogenic speleogenesis.<br />
In identifying hypogenic caves, the primary criteria<br />
are morphological (patterns and meso-morphology) and<br />
hydrogeological (hydrostratigraphic position and<br />
recharge/flow pattern viewed from the perspective of the<br />
evolution of a regional groundwater flow system).<br />
Elementary patterns typical for hypogenic caves are<br />
network mazes, spongework mazes, irregular chambers<br />
and isolated passages or crude passage clusters. They<br />
often combine to form composite patterns and complex 3-<br />
D structures. Hypogenic caves are identified in various<br />
geological and tectonic settings, and in various<br />
lithologies. Despite these variations, resultant caves<br />
demonstrate a remarkable similarity in cave patterns and<br />
meso-morphology, which strongly suggests that the<br />
hydrogeologic settings were broadly identical in their<br />
formation. Presence of the characteristic morphologic<br />
suites of rising flow with buoyancy components is one of<br />
the most decisive criteria for identifying hypogenic<br />
speleogenesis, which is much more widespread than was<br />
previously presumed. Hypogenic caves include many of<br />
the largest, by integrated length and by volume,<br />
documented caves in the world.<br />
The refined conceptual framework of hypogenic<br />
speleogenesis has broad implications in applied fields and<br />
promises to create a greater demand for karst and cave<br />
expertise by practicing hydrogeology, geological<br />
engineering, economic geology, and mineral resource<br />
industries. Any generalization of the hydrogeology of<br />
karst aquifers, as well as approaches to practical issues<br />
and resource prospecting in karst regions, should take into<br />
account the different nature and characteristics of<br />
hypogenic and epigenic karst systems. Hydraulic<br />
properties of karst aquifers, evolved in response to<br />
hypogenic speleogenesis, are characteristically different<br />
from epigenic karst aquifers. In hypogenic systems, cave<br />
porosity is roughly an order of magnitude greater, and<br />
areal coverage of caves is five times greater than in<br />
epigenic karst systems. Hypogenic speleogenesis<br />
commonly results in more isotropic conduit permeability<br />
pervasively distributed within highly karstified areas<br />
measuring up to several square kilometers. Although<br />
being vertically and laterally integrated throughout<br />
conduit clusters, hypogenic systems, however, do not<br />
transmit flow laterally for considerable distances.<br />
Hypogenic speleogenesis can affect regional subsurface<br />
fluid flow by greatly enhancing initially available crossformational<br />
permeability structures, providing higher<br />
local vertical hydraulic connections between lateral<br />
stratiform pathways for groundwater flow, and creating<br />
discharge segments of flow systems, the areas of lowfluid<br />
potential recognizable at the regional scale.<br />
Discharge of artesian karst springs, which are modern<br />
outlets of hypogenic karst systems, is often very large and<br />
steady, being moderated by the high karstic storage<br />
developed in the karstified zones and by the hydraulic<br />
capacity of an entire artesian system. Hypogenic<br />
speleogenesis plays an important role in conditioning<br />
related processes such as hydrothermal mineralization,<br />
diagenesis, and hydrocarbon transport and entrapment.<br />
An appreciation of the wide occurrence of hypogenic<br />
karst systems, marked specifics in their origin,<br />
development and characteristics, and their scientific and<br />
practical importance, calls for revisiting and expanding<br />
the current predominantly epigenic paradigm of karst and<br />
cave science.