COASTAL GEORGIA

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USGS IN YOUR STATE

USGS Water Science Centers are located in each state.

Coastal Georgia Sound Science Initiative

Geology and groundwater resources

The coastal area of Georgia and adjacent parts of Florida and South Carolina is blanketed and underlain by sand, clay, and other clastic rocks that overlie limestone and dolostone at varying depth. The sequence of sedimentary strata is thickest and most deeply buried in the Brunswick area and southward into northeastern Florida, where more than 500 feet of sand and clay overlie more than 2,000 feet of limestone and dolostone. The sequence is thinner and at shallower depths toward the north in the Savannah, Georgia, and Hilton Head Island, South Carolina, areas where the carbonate rocks are 50–150 feet below land surface and are less than 500 feet thick.

A - Surficial aquifer

Overlying the Floridan aquifer system are layers of clay, thin limestone beds, and sand that yield small quantities of water that can be an alternative or supplemental source of water to the Upper Floridan aquifer. Uppermost of these units is the sandy surficial aquifer, present throughout the coastal area, supplying water mostly for domestic and small-scale irrigation uses.

B - Brunswick aquifer

Underlying the surficial aquifer are the sandy upper and lower Brunswick aquifers, present mostly in the Glynn County area, supplying water for irrigation, public, and some small industry use. Clay and other low-permeability strata confine the underlying Floridan aquifer system.

C - Floridan aquifer system

The Floridan aquifer system consists of carbonate rocks of varying permeability, and in the coastal area, has been divided into the Upper and Lower Floridan aquifers. The Upper Floridan is the aquifer of choice in the coastal area because it lies at relatively shallow depth, has high water-yielding capabilities, and yields water of good quality. Although the Lower Floridan aquifer contains highly permeable zones, its utilization is limited by the excessive depth and locally poor water quality. In the southern part of the Georgia coastal area and in northeastern Florida, the Lower Floridan aquifer contains an extremely permeable water-bearing zone called the Fernandina permeable zone. The Fernandina permeable zone contains highly saline water in the southern part of coastal Georgia, and is the source of saltwater contamination in the Brunswick area.