156 
FLORIDA STATE GEOLOGICAL SURVEY. 
have not been transported far, and, in many instances, the lack of 
definite arrangement of the layers renders the recognition of an 
unconformity very uncertain. The interpretation of the observations 
is also subject to considerable unreliability because it is difficult to say 
whether such unconformities as are seen are general or merely local. 
Thickness of the Pleistocene:—In Florida, the beds of Quaternary 
age vary greatly in thickness; and, in some localities, they are wholly 
wanting. The variation in thickness is due to uneven deposition on a 
surface which had been more or less dissected by erosion. The gray 
sands are commonly not more than 3 or 4 feet thick, but in places 
they rise in sand dunes 40 or 50 feet high and near the coast they 
thicken rapidly, hence, their maximum thickness is over 50 feet. 
The thickness of the coquina is difficult to determine because sec¬ 
tions. showing the base are rare and well records are frequently un¬ 
reliable—the driller often reporting as “coquina” any rock which is 
soft and contains abundant shell fragments. However, at St. Augus¬ 
tine it is known to attain a thickness of over 30 feet and at various 
points along the east coast sections from 3 to 10 or 12 feet may be seen. 
Where the shell marls are exposed, they seldom attain a thickness 
of more than 3 or 4 feet; but if we include the non-fossiliferous gray 
sand immediately overlying them, these figures will usually be in¬ 
creased three or four fold. The data supplied by well samples 
indicate that the Quaternary along the east coast varies in thickness 
from about 40 feet at Jacksonville to over 70 feet at West Palm Beach 
and more than 100 feet at Miami. 
Along the west coast the information is much less satisfactory, 
and it is probable that from the Manatee River northward nearly to 
Carrabelle the Quaternary is usually less than 30 feet thick though in 
places it exceeds 50 feet. At Carrabelle the “Sopchoppy limestone” 
was encountered at about 50 feet, but some of the overlying sands 
and clays may be older than the Quaternary. Westward in the 
vicinity of Pensacola, there is a great thickness of sands with some 
thin clay beds. While it has been impossible to get satisfactory col¬ 
lections of fossils from the wells that penetrate these sands, it appears 
probable that the Quaternary may attain a thickness of several hun¬ 
dred feet near the coast. 
At Kissimmee in the south-central part of the peninsula, the pre¬ 
sence of Pleistocene fossils in a well at a depth of 100 feet probably 
indicates that the beds thicken toward the south. This conclusion has 
been verified by the work of Mr. Sanford whose report appears in a 
subsequent chapter. 
On the uplands of the peninsula the yellow sand is commonly 
thicker than the white. It has been penetrated to a depth of over 50 
feet in the vicinity of Lakeland, and, at other localities in the south 
