INVESTIGATING THE RELATIONSHIP BETWEEN INHERITED GEOLOGIC FRAMEWORK AND SALTWATER INTRUSION ON ST. CATHERINES ISLAND, GEORGIA

Since the late 1800s, the oldest cities on the Georgia coast have been withdrawing water from the confined Floridan Aquifer System. As the population has grown, a cone of depression has formed extending from Savannah, GA to St. Catherines Island, GA, a barrier island ~50 km southeast of Savannah. On St. Catherines Island, the cone of depression has altered the vertical and horizontal gradients causing saltwater intrusion into the Upper Floridan Aquifer from the Lower Floridan Aquifer through joints, faults, or solution collapse features. Previous studies from the southern and central areas of the island have found evidence of joints, solution collapse features, and a fault that may span across the island. A thorough investigation of the geologic framework of the north end of the island has yet to be conducted. Therefore, the purpose of this study is to use ground penetrating radar and electrical resistivity tomography, to identify if faults and other saltwater intrusion pathways are present on the north end of the island. Thus, we present a preliminary geophysical interpretation for the north end of the island. This research can inform a better understanding of the geology and hydrogeology of barrier islands, which could lead to a better understanding of potential saltwater intrusion pathways in similar settings.