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KARST REGIONS OF TEXAS
Why divide Texas into karst regions? It aids in understanding the histories of karst areas. It helps us compare and contrast different karst styles and their relationships to regional geology and geomorphology. And it provides insight to the types and extents of caves to be found in each region.
The karst regions described here are delimited on several criteria: geomorphology and geomorphic history, stratigraphy, structure, cave density and types. Obviously, karst requires soluble rocks. Are these thin limestone beds interbedded with sandstone and shale (North Texas) or are they massive gypsum beds (Gypsum Plain)? Are they highly fractured with many joints and faults guiding cave orientations (Balcones Fault Zone) or are fractures less important to cave development (Maverick Basin)? Does the area consist of isolated, high-relief mountains (Block-faulted Ranges) or flat, low-relief plains (Northwest Texas)? Are the caves principally horizontal stream conduits (Lampasas Cut Plain) or vertical shafts which transmit water to humanly inaccessible conduits (Devils River Trend)? Clearly, distinct karst regions in Texas can be defined, as we have done below. We also describe a few areas of pseudokarst deserving notice. The regions and subregions are shown in a linked map of Texas karst and pseudokarst.
Texas karst regions are divided into three main categories
based on rock type. The carbonate regions include those areas where caves
are almost entirely formed in limestone or dolomite, although a few are
in interbedded gypsum. Gypsum area caves are mostly in gypsum, although
some caves are in interbedded dolomite. Pseudokarst regions contain caves
in rocks that are much less soluble than limestone or that formed by means
other than solution. Although isolated pseudo-karst caves occur throughout
Texas, only those areas with several caves of similar origin are presented.
Texas caves have developed from a highly diverse range of geologic conditions. Some areas stand out as exceptionally good cave-formers while others are cave-poor. Preliminary attempts to compare the density of caves within the regions outlined in this report demonstrates that this scale does not yield meaningful results. A more detailed analysis is needed. About 10,000 caves, sinkholes, and rock shelters are known in Texas. Surveys for new caves continue in many karst areas, and many caves have been added to the Texas Speleological Survey's database during the past ten years. This work should prove invaluable to better defining and delimiting the karst regions of Texas, and to advancing the conceptual basis of cave development.
Page updated 7/2014. Original page by A. Richard Smith and George Veni.