Geology and configuration of the base of the Tertiary limestone aquifer system, southeastern United States

The Tertiary limestone aquifer system of the southeastern United States is a thick sequence of carbonate rocks that vary in age land that are hydraulically connected in varying degrees. A map is presented that shows at the altitude and configuration of base of the aquifer system. The age and lithology of the different low-permeability materials that mark the base of the system are delineated and briefly described. Several types of geologic structures that affect the configuration of the base of the system may be readily recognized. (USGS)