Land-Based High-Resolution Seismic Reflection Image Of A Karst Sinkhole And Solution Pipe On Fort George Island, Duval County, Northeastern Florida

Monitoring of the drinking-water wells that tap the upper Floridan aquifer, indicate<br>increases in chloride concentration at some wells while at other nearby wells chloride<br>concentration are unchanged. One explanation for this is that geologic features (fracture zones,<br>joints, solution channels, and paleosinkholes) in the underlying carbonate strata of the Floridan<br>aquifer system have breached the semi-confining units, thus allowing warmer and more saline<br>water to flow upward and mix with fresh water production aquifers. A reconnaissance seismic<br>reflection survey was conducted at Fort George Island, Duval County, Florida, to determine if a<br>modified Mini-Sosie high-resolution seismic reflection technique, which has been successfully<br>used to image near-surface faults in urban areas, could be used to image karst hydrogeologic<br>features in this area.<br>We acquired good quality data in this survey within a depth range of 30-400 m. The<br>interpreted profiles of two perpendicular lines provide a clear image of geologic-karst<br>deformation in the form of a solution pipe and overlying buried sinkhole feature.