The role of stress release fracturing in the development of cavernous porosity in carbonate aquifers

Abstract

Stress relief fracturing provides the large mechanical apertures needed for the development of conduit porosity in carbonate aquifers. Examination 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 (caves) are found beneath the valley walls in general, not directly beneath the actual surface channel. Common features of the studied "Cumberland style" caves are valley-parallel master conduit segments, exceptional 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 these conduits form along geologically young fracture systems of increased aperture is a departure from previous theories of cave origin. Prior theories have either explicitly or implicitly assumed that caves develop along joints and fractures of significant geologic age, related more to regional tectonic forces than to present-day topographic influences.

Concurrent tectonism and aquifer evolution >100,000 years recorded in cave sediments, Dinaric karst, Slovenia

“…In general, structural elements such as joints and faults have been considered to be passive templates upon which aquifer development (growth of fissures and conduits) may progress. However, very young jointing related to surface stresses has also been shown to guide conduit growth in certain settings (Sasowsky and White 1994). Researchers have used a variety of techniques to determine dates of fault movement near the surface in non-carbonate terrane (e.g.…”

Mixing of water in a carbonate aquifer, southern Italy, analysed through stable isotope investigations

“…This phenomenon causes an increased density of joints and bedding plane partings in the near-surface bedrock (Ferguson, 1967;Sasowsky & White, 1994). However, vertical heterogeneity can be further emphasised by mixing processes between groundwater and fresh infiltration water just below the water table of an unconfined aquifer.…”

Geomorphology and paleohydrology of Hurricane Crawl Cave, Sequoia National Park, California

“…Two entrances allow access to the cave through breakdown collapses near the upstream and downstream termini; these collapses likely relate to stress-relief fracturing along the canyon walls (e.g., Sasowsky and White, 1994). The cave has three perennial streams, although two have very low discharge, with base flows of less than 0.001 m 3 s −1…”