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306 FLORIDA GEOLOGICAL SURVEY-SEVENTH ANNUAL REPORT. 
SOILS. 
The underlying geological formations of Pinellas County belong 
to the Upper Oligocene. These are exposed at a number of different 
points in the county. At Bay View and a few other places the ex¬ 
posures consist of a hard impure limestone, while in other places 
plastic dark-colored clays are found. These materials, however, in¬ 
fluence the soil in but a comparatively small part of the county. 
The county as a whole is covered with a mantle of fine sand sev¬ 
eral feet in thickness. At Clearwater the bluff along the bay exposes 
a section of this deposit, which shows it to be 12 to 15 feet thick. 
The deposit is deepest in the northern part of the county and in 
many places gives evidence of having been drifted about by the wind. 
This action, together with the uneven dissolution of the underlying 
limestone, has’ given the region a more varied topography than is 
found farther south. Most of the soils have been derived from this 
sandy deposit. 
Difference in topography and depth of the sandy mantle has 
given rise to two broad groups of soils—those that are well drained 
and those having poor natural drainage. The poorly drained soils 
predominate in number and extent, there being but two types that 
have ample natural drainage—the Norfolk fine sand and the Leon 
fine sand. The surface soils of the county are fine in texture, and 
with one exception—a silty clay loam of small development—they 
fall into two'classes: The fine sand and fine sandy loam. 
The soils of Pinellas County are in general designated by local 
terms descriptive of their topographic features and forest growth. 
To the highest and excessively drained types the term “sand hill” 
is applied. The forest growth, now almost entirely removed, origi¬ 
nally consisted of longleaf pine. Blackjack oak has taken possession 
of some of this land. The hilly phase of the Norfolk fine sand occu¬ 
pies these elevations. 
“Scrub” is a local term given to hills and ridges of the Leon fine 
sand, rolling phase. It supports a dense growth of shortleaf pine, 
locally called “spruce pine,” and a thick undergrowth of rosemary, 
palmetto, and low-growing shrubs and vines, and has a very low 
agricultural value. 
“Piny woods land” and “high hammock land” are equivalent 
terms used to designate that' class of land in which drainage is suffi¬ 
ciently well established to permit citrus fruit growing, and other 
forms of agriculture. Vegetation on such areas consists of longleaf 
