A COMPARATIVE INTEGRATED GEOPHYSICAL STUDY OF THE HORSE SHOE CHIMNEY CAVE, COLORADO BEND STATE PARK, TEXAS

Integrated geophysical studies were performed over a known cave in Colorado Bend State Park (CBSP), Texas. We applied several geophysical methodologies such as resistivity profiling, ground penetrating radar (GPR), microgravity, hammer seismics, and ground conductivity measurements in an effort to distinguish which geophysics method worked most effectively and efficiently in detecting the presence of the cave. Shallow karst features within the Ellenberger Limestone are common throughout the CBSP region. The Horse Shoe Chimney Cave (HSCC) which is part of a larger network of cave systems in the Ellenberger Limestone in CBSP provides a good control environment for this research.

A 50 x 50 meter grid, with 5 m spaced traverses was designed around the entrance to the cave. Resistivity, seismic, ground conductivity, and GPR data were collected, cleaned and processed with the aid of commercial software packages. Microgravity data were collected, drift and topographic corrections applied, and processed for density anomalies. A traditional cave survey was conducted after geophysical data collection, to avoid any bias in initial data collection. The survey of the cave also served the purpose of ground truthing. Preliminary results indicate the microgravity and resistivity techniques worked most efficiently, while the other methods showed varying levels of effectiveness.