The Floridan aquifer is the principal source of freshwater to wells in most of St. Johns County. The aquifer consists of a thick sequence of interbedded limestone and dolomite of Eocene age. The top of the Floridan aquifer, which is irregular throughout St. Johns County, ranges from less than 90 feet below sea level in the extreme southestern part to more than 360 feet below sea level in the northern part. (USGS)
Additional publication details
USGS Numbered Series
Altitude and generalized configuration of the top of the Floridan aquifer, St. Johns County, Florida
Water-Resources Investigations Report
1 map : col. ; 98 x 72 cm., folded in envelope 31 x 23 cm.