Karst Aquifers - Hydrogeology: Objectives, Methods, Applications - page 52

emerge due to eustatic changes or tectonic uplift. The karstifi cation of a
limestone region can therefore be spread over thousands of years. The
double motor driving karstifi cation is on the one hand chemical, and on
the other hand hydraulic. The chemical driver is mineral undersaturation.
The hydraulic driver is the potential energy between catchment and
discharge areas, capable of transporting undersaturation downstream below
ground. The evolution of this potential energy over time can be induced by
increased permeability, an orogeny, neotectonics, or eustatic variations. The
polyphasic genesis of karst regions makes them into geometrically complex
environments (alternating phases of down cutting and equilibrium with the
local base level), which translates into the modifi cation of drainage patterns
over time (plugging of passageways, re-excavation, circulation reversals).
Figure 26 Polyphase karst system.