Altitude of the base of the surficial aquifer system in eastern Palm Beach, Martin, and St. Lucie counties, Florida, USGS WRIR 99-4214, fig. 1

The surficial aquifer system underlies Palm Beach, Martin, and St. Lucie Counties and primarily consists of sand, clay, silt, shell, and limestone of Holocene, Pleistocene, and Pliocene age. Its thickness is variable (decreasing westward and northward) and is estimated to be as much as 400 feet in Palm Beach County (Miller, 1987; Shine and others, 1989), 210 feet in Martin County (Miller, 1980), and 180 feet in St. Lucie County (Miller, 1980).The surficial aquifer system is composed of several stratigraphic units.

The maps shows the altitude of the base of the surficial aquifer system in Palm Beach, Martin, and St. Lucie counties in 1997-1998. The contour interval is 40 feet.