SECOND ANNUAL REPORT-STRATIGRAPHIC GEOLOGY. 
159 
cene deposits is by far the most common material, though locally 
fragments of rock derived from some of the older geological forma¬ 
tions predominate. Such rock has been noted by Heilprin 1 on the 
Chassahowitzka River, and by Dali 2 at various points along the west 
coast south of Tampa. An admixture of recent and extinct fossils 
sometimes results from the erosion and redeposition of the older 
formations. 
Aeolian Deposits:—The aeolian deposits consist of sand in the 
lorm of dunes, ridges or more or less irregular hillocks. These occur 
in many localities from the northern line of the State southward to 
Ihe vicinity of Lake Okeechobee; but are best developed along the 
(ast coast. In the interior, ridges and dunes are seldom conspicuous. 
This is probably to be ascribed to the topography, vegetation and 
climatic conditions. During a large part of the year the ground water 
stands very near the surface, especially where the relief is slight and 
* this serves to keep the sand moist and prevent its being blown about 
by the wind. 
Another factor which hinders the formation of dunes in the in¬ 
terior is the general absence of strong winds blowing from a single 
direction. This is well shown by contrast with the islands along the 
east coast where the prevailing winds from the northeast have re¬ 
sulted in the formation of dunes which in places attain a height of 
over 50 feet as far south as Dade County. And finally, the presence 
of a luxuriant subtropical vegetation not only protects Ihe sand from 
the direct force of the wind but also tends to hold it in place by means 
of a matting of roots and stems. 
Chemical DepositsIn a region where solution is so prominent, 
chemical deposits would naturally be expected, but aside from the 
extreme southern end of the State such deposits do not appear to be 
important. The chemical deposits are of two classes, one being formed 
from underground water where it emerges in the form of springs, 
and the other being deposited in crevices and caverns beneath the 
surface. The spring deposits vary with the character of the material 
carried in solution. The waters containing hydrogen sulphide de¬ 
posit sulphur which appears as a white flocculent material coating the 
plants and earth at the point of emergence. Other waters deposit 
carbonate of lime, or hydrated iron oxide (limonite). Examples of 
the deposition of sulphur may be found at almost any sulphur spring 
or well, but lime and iron deposits are less common. The subject of 
1 Heilprin, Angelo. Explorations on the West Coast of Florida, Wag. Free 
Inst. Sci., vol. i, 1887, pp. 57-58. 
2 Dali, Wm. H., Neocene of North America, U. S. Geol. Survey, Bull. 84, 
1892, p. 153. 
