THE ROLE OF STRESS RELEASE FRACTURING IN THE DEVELOPMENT OF CAVERNOUSPOROSITY IN CARBONATE AQUIFERS

Stress relief fracturing provides the large mechanical apertures neede d for the development of conduit porosity in carbonate aquifers. Exami nation of valleys incised into Mississippian age limestones throughout the Appalachian plateaus has demonstrated a;consistent pattern taken in the development of conduits in these settings. Master conduits (cav es) are found beneath the valley walls in general, not directly beneat h the actual surface channel. Common features of the studied ''Cumberl and style'' caves are valley-parallel master conduit segments, excepti onal concordance of conduit orientation with minor surface topographic variations, development on distinct ''levels,'' and development in a downdip position from master surface streams. The recognition that the se conduits form along geologically young fracture systems of increase d aperture is a departure-from previous theories of cave origin. Prior theories have either explicitly or implicitly assumed that caves deve lop along joints and fractures of significant geologic age, related mo re to regional tectonic forces than to present-day topographic influen ces.