Ford C.D., 2003, Perspectives in karst hydrogeology and cavern genesis

Sourse: School of Geography and Geology, McMaster University Hamilton, ON L8S 4K1 Canada. E-mail: dford@mcmaster.ca
Keywords: karst aquifers, karst hydrogeology, cave origin
Rubric Name: Evolution of karst systems

Abstract: Hydrogeology and speleology both began during the 19th Century. Their approaches to limestone aquifers diverged because hydrogeologists tend to measure phenomena at very local scales between drilled wells and generalize from them to basin scales, while speleologists study the large but sparse conduits and then infer conditions around them. Convergence of the two approaches with modem computing should yield important genetic models of aquifer and cave.

Genesis of common cave systems by dissolution is a three-dimensional problem, best broken down into two-dimensional pairs for purposes of analysis. Historically, the dimensions of length and depth have received most attention, especially the question of the location of principal cave genesis with respect to the water table. Between 1900 and 1950, different scientists proposed that caves develop principally (1) in the vadose zone; (2) at random depth in the phreatic zone; (3) along the water table in between. Empirical evidence suggests that these differing hypotheses can be reconciled by a four-state model in which the frequency of penetrable fissuration controls the system geometry.

For the dimensions of length and breadth (plan patterns) there is widespread agreement that dendritic (or branchwork) patterns predominate in common caves. Irregular networks or anastomose patterns may occur as subsidiary components. When hydraulic conditions in a fissure are anisotropic (the usual case), dissolutional conduit development is competitive: local hydraulic gradients are reoriented toward the first conduits to break through to outlet points, redirecting others toward them in a cascading process. Plan patterns are most complex where there have been multiple phases ("levels") of development in a cave system in response to such effects as river channel entrenchment lowering the elevation of springs.

Read full text