A PRELIMINARY MAP SHOWING THE DISTRIBUTION OF SOLUTION CAVES IN CARBONATE AND EVAPORITE-BEARING GEOLOGIC UNITS IN THE UNITED STATES

Classifying geologic map units based on reported solution caves can aid in better delineating our karst landscapes. Carbonate and evaporite rocks with potential for development of karst features underlay the surface of about 18% of the United States. Through a State by State and unit-by-unit search for reports on the occurrence of solution caves within areas of soluble rocks delineated by State, Commonwealth, Territorial, and island geologic bedrock maps covering the entire USA, we produced a preliminary map showing the distribution of rocks containing solution caves. Sources of cave occurrence information include various publicly accessible on-line data and hard-copy publications.

Each carbonate or evaporite map unit is classified and displayed as: Yes, ADJ, or NR. “Yes” indicates that solution caves have been reported from somewhere within that map unit. “ADJ” indicates that although no cave reports were found, caves are reported from the same or equivalent units in adjacent states. “NR” indicates no reports of caves were found (but does not preclude the possibility of caves).

This map version is flawed due to several variables, including: (1) our information on specific cave locations is limited as we did not attempt to use proprietary cave location databases, (2) cavers often do not document the lithostratigraphic unit in which the cave occurs in trip reports or on cave maps, (3) some states classify state geologic map units by age and depositional setting (e.g. “lower Paleozoic marine rocks”) making those units difficult to correlate with cave reports, and (4) geologic unit boundaries often do not match across state boundaries for various reasons.

While not showing actual cave locations, these map unit classifications broadly delineate areas with potential for cave openings exposed at the surface. These data can be used for national and regional scale portrayal and analyses of speleogenic trends and comprise a large subset of the potential distribution of obligate cave biota. Mapped soluble rock units that contain caves reflect areas that have undergone speleogenesis by either hypogenetic or epigenetic processes. Cavernous areas of the arid and semi-arid western United States are more likely to have been affected by hypogenetic processes, or by epigenetic processes under wetter antecedent climates.