Hypogene Processes in the Balcones Fault Zone Edwards Aquifer in South-Central Texas, a New Conceptual Model to Explain Aquifer Dynamics
Most existing aquifer models are epigenic and implicitly or explicitly assume that circulating meteoric waters formed the Edwards Aquifer. The initial karstification is assumed to have occurred along paleokarst features that originated during an initial subaerial exposure. Such paleokarst features created zones of enhanced permeabilites that allowed the deep circulation of waters and the formation of the present aquifer.
However, epigenic processes do not adequately explain many features in the Edwards Aquifer. For example, large voids that are isolated from epigenetic processes formed deep in the aquifer by mixing corrosion. Acidic water is generated by oxidation of sulfides and intrusion of CO2 from below, and possibly from hydrocarbon sources. In addition, the Edwards Aquifer displays characteristics that are difficult to accommodate in epigenic models. Examples include the wide distribution of high permeabilities, extreme depth of circulation and the extremely high yields of most wells.
Recent data and new interpretations suggest hypogenic processes have contributed to the formation of the Edwards Aquifer (Klimchouk, 2007). Klimchouk concludes that rising waters from depth are important agents of karst development and this model explains many hitherto crypic features in the Edwards Aquifer.