A Sub-Regional Hydrogeologic Framework for the Floridan Aquifer System n the Northern Coastal Areas of Georgia and Parts of South Carolina

The hydrogeologic framework for the Floridan aquifer system was revised for eight northern coastal counties in Georgia and five coastal counties in South Carolina as part of a regional assessment of water resources by the U.S. Geological Survey (USGS) Groundwater Resources Program.  In this study, selected well logs were compiled and analyzed to (1) determine the vertical and horizontal continuity of permeable zones that make up the aquifer system, and (2) define more precisely the thickness of confining beds that separate individual aquifer zones.  The results of the analysis indicate that permeable zones in the Floridan Aquifer system can be divided into (1) an upper group of extremely transmissive zones that correlate to the Ocala Limestone in Georgia and the Parkers Ferry Formation in South Carolina, and (2) a lower group of zones of relatively lower transmissivity that correlates to the middle part of the Avon Park formation in Georgia and updip clastic equivalent units of South Carolina.  This new subdivision simplifies the hydrogeologic framework originally developed by the USGS in the 1980’s and helps to improve the understanding of the physical geometry of the system for future modeling efforts.  Changes made to the framework in the Savannah-Hilton Head area are particularly important where permeable beds control the movement of saltwater contamination in that area.  The new framework will enable water-resource managers in Georgia and South Carolina to assess groundwater resources in a more uniform manner and help implementation of sound decisions when managing water resources in the aquifer system.