REPORT OF INVESTIGATIONS No. 40


limestone which contains shell fragments and abundant foraminifers.
The Tampa reaches a maximum thickness of 270 feet in southern Escam-
bia County. The Tampa contains several beds of clay which would re-
duce the effective porosity and permeability of the limestone. A few
wells in the southern part of the area obtain water from this limestone.
 The upper limestone is recharged mainly by rain that falls in
Conecuh, Escambia, and Monroe counties, Alabama. This is the area
where the upper limestone comes to the surface. Additional recharge
comes from downward leakage of water from the sand-and-gravel aqui-
fer in northern Escambia and Santa Rosa counties, Florida. The move-
ment of the water in the upper limestone is generally southward and
southeastward.
 The lower limestone of the Floridan aquifer in this area consists of
the Ocala Limestone and other limestones of Eocene age. The top of the
lower limestone, although an erosional unconformity, is a relatively flat
surface that dips gently toward the southwest (fig. 9). The lower lime-
stone rests unconformably upon shale and clay of middle Eocene age.
The lower limestone ranges in thickness from about 360 feet in central
Escambia County to as much as 1,200 feet in the northern part of Santa
Rosa County (fig. 6). Thus, unlike most sedimentary units along the
Gulf Coast, these limestones thin rather than thicken downdip. The
lower limestone is white to grayish cream and is rather soft and chalky.
Well samples contain as much as 30 percent very fine to very coarse
sand, but some of this probably caved from above during drilling. Sam-
ples also contain some gray clay. Lenses of hard light-gray shale occur
within the limestone, but these appear to be randomly distributed and
cannot be correlated from well to well over any great distance. Much of
this limestone consists of foraminifers, corals, bryozoans, ostracods, frag-
ments of echinoids and mollusks, and other fossils. Black phosphatic
grains are locally plentiful.
 Much of the Floridan aquifer in Escambia and Santa Rosa counties
 is composed of a porous and permeable coquina consisting of fossil
 fragments. This aquifer contains substantial quantities of ground water.
 Most of the water in both the upper and lower limestones of the Flori-
 dan aquifer is confined above and below by beds of relatively imperme-
 able clay. Ground water in the lower limestone is also derived mainly
 from precipitation that occurs 10 to 35 miles north of the area in
 Conecuh, Escambia, and Monroe counties, Alabama, where the lime-
 stone crops-out. The movement of water in the lower limestone is gen-
 erally to the south and southeast.