GEOPHYSICAL INVESTIGATIONS IN DETERMINING THE EXTENT OF KARST FEATURES SOUTH OF SPRINGFIELD, MISSOURI

Old Spanish Cave in Missouri is a collapsed cave located on the southwestern edge of the Ozark Dome. The Paleozoic formations in the Ozark Dome are susceptible to the formation of karst features. Karst features are more common in the near-surface Mississippian carbonate units, but also occur within the Ordovician carbonate units. Old Spanish Cave has lost passages that near surface geophysical methods could be useful in determining the location and nature of.

There are a variety of geophysical methods that can be used to investigate karst features, including electrical resistivity, gravity, seismic refraction, and very low frequency electromagnetics. While all these methods are useful in imaging karst features, electrical resistivity methods have been shown to be the most useful in deciphering sinkholes and caves. To investigate the known and lost cave passages of Old Spanish Cave, and related sinkholes and faults within Mississippian carbonates of southwest Missouri, a series of two-dimensional electrical resistivity profiles will be collected using the Schlumberger array. The data will be collected using 64 electrodes with varying electrode spacing. Terrain data will be collected to include in modeling. The data will be modeled using a robust two-dimensional inversion method. The inversion parameters will be varied to determine the statistically most reasonable model. To constrain the inversion models, seismic refraction data will be collected and modeled, which will provide thicknesses of the overlying soil layer and location of karst features.