ORIGIN AND MORPHOLOGY OF LIMESTONE CAVES: A RETROSPECTIVE 27 YEARS LATER

Arthur N. Palmer’s 1991 recipient of the Geological Society of America’s Kirk Bryan Award, Origin and Morphology of Limestone Caves, set a gold standard for how we categorize and understand the development of caves. On August 2, 2018, Google Scholar recorded 975 citation of this paper by other works, a testament to its impact on the field of cave and karst science. In that paper, Art drew upon decades of caving across the world, building upon extensive experience in the Mitchell Plateau of Indiana and Mammoth Cave area of Kentucky, to associate key patterns of passage development and organization by recharge type and rock characteristics.

In the intervening quarter-century, cave and karst science has advanced dramatically. No longer are cave systems considered only a product of epigenetic processes. Diagenetic maturity of the limestone is of paramount importance, guiding the influence of littoral processes and geochemical interactions. Diagenetic evolution may lead to multigenerational karst, separated in time by upwards of 10⁸ years. Further, the locus and form of bedrock dissolution is more complex than the carbonate equilibrium reactions controlled by soil CO₂. Respiration, changing redox conditions, and mixing-driven undersaturation is controlled by a combination of microbial processes and gradients in groundwater temperature or solute concentration and may therefore occur throughout the aquifer.

This presentation summarizes advancements that highlight some evidence of non-epigenetic development of karst in both the Cumberland Plateau of southern Kentucky and in the Mitchell Plateau of Indiana. In the case of the Cumberland Plateau, the influence of shallow brines on carbon flux is considered. In the case of the Mitchell Plateau, the effect of evaporates on aquifer chemistry and the regional groundwater flow system is considered. In the case of both karst regions, these refined concepts provide additional insight into processes occurring in the critical zone of carbonate aquifers.