REPORT OF INVESTIGATIONS NO. 42


surface is between the water. table of the nonartesian aquifer and
the piezometric surface of the Floridan aquifer. The clay beds
separating the aquifers are leaky as indicated by the conformance
of the fluctuations of the piezometric surfaces.

 FLORIDAN AQUIFER

 DESCRIPTION OF THE AQUIFER

 The Floridan aquifer is the principal source of artesian ground
water in Florida. In the Green Swamp area, the aquifer is exposed
at the surface in the western and northwestern parts and occurs
at depths ranging from 50 to more than 200 feet below land surface
in the eastern part, shown in figure 31.
 The Floridan aquifer is composed of marine limestones that have
been exposed to erosion and solution weathering. The formations
that comprise the aquifer in the Green Swamp area range in age
from middle Eocene to Oligocene (table 4). The Geologic cross
sections (fig. 8) show the limestone aquifer and the position of the
overlying plastic material.
 The top of the aquifer is highest (90 to 100 feet above msl) in
the west-central part of the area as shown in figure 32. The base
of the aquifer was determined by the first major occurrence of
gypsum. Apparently, the gypsum fills the pores in the lower part
of the Avon Park Limestone. The existing data indicate that the
aquifer is about 1,000 feet thick in the central part of the area.
 The transmissibility of the Floridan aquifer will vary depending
primarily on the occurrence of solution features such as caverns,
cavities, and pipes. The presence of dolomite in the limestone is an
indication of solution activity. Dolomite zones and cavities
generally occur in the Inglis Formation and the Avon Park
Limestone which are highly permeable. Logs of numerous wells in
the Green Swamp area indicate that a large percentage of the
cavities in the aquifer contain sand which reduces the transmissi-
bility. The low yields of some wells in the Lake Wales Ridge area
are attributed to sand-filled and clay-filled caverns.

 RECHARGE AND DISCHARGE

 The Floridan aquifer in the Green Swamp area is recharged by
 rainfall that percolates downward from the surface of the ground
 either through the nonartesian aquifer and aquiclude or directly