COMPARATIVE STUDY OF DOLOMITIZATION AND ITS EFFECTS ON CAVE MORPHOLOGY: EXAMPLES FROM KENTUCKY

Conduits in karst typically develop along bedding planes, faults, and fractures. However, the diagenetic evolution of porosity and permeability, via cementation and dissolution in the host rock, also controls groundwater flow and subsequent conduit development. To explore why the presence of dolomite in a carbonate succession does not have a consistent relationship with cave passage development, we studied the cave-wall morphology and petrology of the cave-hosting carbonates in the Mammoth and Edward Mountain cave systems in Kentucky. These cave systems are located on opposite sides of the Cincinnati Arch, a paleogeographic/structural feature separating the Illinois and Appalachian Basins. Even though both cave systems are hosted in Mississippian carbonates of similar paleo-environments, differences in post-depositional tectonic movements on opposing sides of the arch resulted in a divergence in burial history and corresponding diagenetic evolution. At Mammoth Cave, on the margin of the Illinois Basin, stratiform reflux or sabkha dolomites underwent burial recrystallization by hot fluids. Here, the dolomite beds do not exert an important control on passage development. At Edward Mountain, on the margin of the Appalachian Basin, irregularly shaped dolomite bodies protrude into cave passages to varying degrees; the protrusion is more or less pronounced if encased in soft, porous wackestone or hard, tight grainstone, respectively. These dolomite bodies are the product of complex diagenesis and were likely recrystallized by cold meteoric fluids during relative sea-level lowstands accompanied by extensive calcite replacement and cementation. This process resulted in a mixed mineralogy and rough surfaces of the dolomite bodies compared to the surrounding homogenous, smooth limestone. The variation of surface texture in the dolomite is likely the result of differential dissolution of the less soluble dolomite and the more soluble calcite during cave passage development. The porosity-permeability contrast between the dolomite and the surrounding limestone appears to be an important factor in the development of larger-scale morphology, whereas the mineralogy appears to be important for the development of finer-scale texture of the cave wall.