Student supported: 1 Student AssistantThe distinction of partially dissolved from compact carbonate rocks and from the alluvial overburden is a major problem in geological engineering and water resources. Geoelectrical depth soundings after Schlumberger were applied over karst terraines in three locations of the Ozarks in Missouri. The zone of dissolved carbonate rock shows intermediate resistivities between low values for the overburden and extremely high values for the compact rock. The main part of the investigation was directed towards solving the underground flow and disappearance of Logan Creek near Ellington, Missouri. Combined geoelectrical and gravity surveys under consideration of some near surface seismic refractions indicate zones of increased depth and degree of dissolution at the Ellington Fault. A detailed gravity profile across the fault shows a negative anomaly with a minimum of -2.0 mgal, which extends over approximately 3 miles with large lateral gradients. A theoretical model can explain the anomaly if the depth of the cavernous limestone has a maximum of 350 feet and if the bulk volume of fissures and stream channels amounts to 15 percent. The coincidence between the fault and the negative anomaly suggests that ruptures along fault planes weakened the rock so that chemical dissolution from surface waters had a greater penetration.Project # A-065-MO Agreement # 14-31-0001-382
