These aquifers consist of semiconsolidated sand interbedded with silt, clay, and minor carbonate rocks.
Porosity is intergranular, and the hydraulic conductivity of the aquifers is moderate to high.
The aquifers underlie the Coastal Plains of the eastern and southern United States, and they are of fluvial, deltaic, and shallow marine origin. Accordingly, some aquifers are local whereas others extend over hundreds of square kilometers. Water in topographically high recharge areas is unconfined, but, it becomes confined as it moves coastward. Discharge is by upward leakage to shallower aquifers or to saltwater bodies in coastal areas. Because flow is sluggish near the ends of regional flow paths, the aquifers commonly contain unflushed saline water in their deeply buried, downdip parts.