A PRELIMINARY MODEL OF SPELEOGENESIS IN THE HORN HOLLOW KARST SYSTEM, CARTER CAVES STATE RESORT PARK, NORTHEASTERN KENTUCKY

The Horn Hollow Karst system (HHK), located in Carter Caves State Resort Park (CCSRP) in northeastern Kentucky, is a typical fluviokarst system comprised of the surface and subterranean drainage system associated with the Horn Hollow Creek. The karst of CCSRP is poorly studied, lacking a process-based interpretation and speleogenetic history of the system. Based on cave morphology, hydrology, and geochemistry we have developed a preliminary model for the speleogenesis of the system.

We posit that a more extensive, ancestral karst system developed prior to the Last Glacial Maximum. Caves that appear to be remnants of larger systems occur throughout CCSRP and appear to be situated at several vertical levels coinciding with bedding contacts between adjacent carbonate units. In the upper reaches of HHK at least one complex of caves, at an area called the Horn Hollow Headwall, appears to be remnants of a previously connected system. The current surface channel, which alternates between losing and gaining reaches, passes through several dry reaches where the banks are bedrock and the channel cross-sections are very narrow. Many of these stream reaches contain large blocks of limestone displaying dissolutional features (e.g., anastomoses and scallops) that are associated with caves. We interpret these reaches as collapsed cave passages.

Caves actively transmitting water through the system fall into two categories. The first category tends to be more common in the upper reaches of HHK, near the contact between the overlying siliciclastic bedrock and the karstified carbonates. These caves appear to primarily direct water vertically down towards the phreatic zone. In some cases these caves are pits or steep-gradient canyon passages with a rapidly descending gradient. In two caves these passages can be followed to a transitional zone that leads to passages we interpret as phreatic. The second category of caves tends to display a phreatic morphology, with tubular passages that meander along bedding planes. These caves are most common in the lower reaches of the system near the terminal spring at H2O Cave. These caves also appear to be remnants of on older, more extensive cave system. Some flow path segments of the system are partially or wholly inaccessible. We hypothesize that these flow paths are following active caves representative of the second, phreatic category of caves.