30 
FLORIDA STATE GEOLOGICAL SURVEY. 
road, .the profiles show that there are considerable tracts of land which 
rise above the 200-foot contour, while Argyle, De Funiak Springs 
and Mossyhead are all above 250 feet—the last named being 264 feet 
above tide. It appears probable that at some localities near the Ala¬ 
bama line the surface may rise somewhat higher and small areas may 
exceed 300 feet. 
Rivers:—The drainage history of Florida has been somewhat 
complex, and the changes in relative positions of land and sea which 
have affected the stream are so closely interwoven with the general 
geologic and physiographic history that their full discussion is left for 
a subsequent report. At this time it is only necessary to note the 
general character of the streams and state briefly the factors which 
have produced the existing conditions. Some of the rivers are con¬ 
fined to the coastal lowlands where they assumed their courses in 
consequence of the initial slope of the land as it emerged from beneath 
the sea, and they are therefore known as consequent streams. Their 
positions are dependent upon the original slope of the surficial sand, 
and their channels are frequently winding. Wherever there were de¬ 
pressions in the sands, lakes were formed and some of the consequent 
streams consist of a chain of such lakes joined by more or less well 
defined channels. To this class belongs the Kissimmee-Caloosahatchee 
system with its numerous lakes. 
Wherever the consequent streams have removed the thin mantle 
of surficial sand and cut into the older formations they belong to the 
class known as superimposed streams. Thus the Caloosahatchee 
River .which in parts of its course has eroded a channel through the 
surface formations and into the underlying Pliocene and possibly 
Miocene marls, is superimposed upon the older formations. In like 
manner the St. Johns River north of Sanford has been superimposed 
upon the Pliocene and probably the Miocene rocks. The Manatee and 
Aucilla Rivers have in parts of their courses been superimposed upon 
the Oligocene formations. There are in Florida many other examples 
of consequent and superimposed streams and many of the rivers such 
as the St. Johns are in part consequent and in part superimposed. 
The rivers which cross both the older and younger geological 
formations existed before the deposition of the sands which form the 
surface of the lowlands. At that time they entered the sea at the 
edge of the present highland belt. Where they cross the highland 
these streams have broad, deep valleys floored with a deposit of al¬ 
luvium and are often bordered by prominent bluffs. In their courses 
across the uplands, they take a direction which was determined by 
the slope of the surface; but they have usually removed the surficial 
formations and cut deeply into the older rocks upon which they are 
superimposed. 
