PSEUDOKARST CONDUIT CHARACTERIZATION IN A SANDSTONE SILTSTONE AQUIFER, IN STILLWATER, OKLAHOMA

Pseudokarst conduits are poorly characterized when compared to their carbonate karst cousins due to their small size and complex groundwater biogeochemistry. This study aims to quantify the chemical exchange between a sandstone siltstone pseudokarst matrix and the conduits flowing through the aquifer. This study integrates geochemical and geophysical data to evaluate conduit chemical exchange. Results demonstrate that groundwater fluids at the site are composed of two fluids mixing in a fracture zone with pseudokarst conduits along a bedding plane. Temporal electrical resistivity imaging was used to evaluate the flow system in relation to the location of the chemical samples. The results suggest mixing between the conduits and the matrix during storm events and the evolution of the rock body to generate a clay unit in the fracture zone. The results also suggest strong temporal variability in geochemistry that requires active storm monitoring of flow through the generally low permeability aquifer.