124 FLORIDA GEOLOGICAL SURVEY-TWELFTH ANNUAL REPORT 
tional samples should be obtained from wells in this section in or¬ 
der to determine more definitely both the lithology and the fossils 
of these formations. The casing in the two wells rests at 117 and 
124 feet respectively. Nevertheless, it is not impossible that the 
phosphate pebble in the samples below 115 .feet have fallen from 
above. 
A second area is marked off on the map, B, in which generally 
speaking the top of the Eocene limestones appear to lie below sea 
level, but at no place in excess of 200 feet below sea. These two 
areas, it will be noted, make up together a broad belt extending 
across and occupying all of the north central part of the peninsula 
from the Gulf to the Atlantic coasts. The data on which this belt 
is mapped is derived in part from surface exposures and in part 
from well records. The upper course of the Suwannee River in 
Florida is known to lie in a structurally low area since in follow¬ 
ing the course of this stream it passes towards the Gulf onto suc¬ 
cessively older formations. Since in Hamilton County the Alum 
Bluff Miocene is exposed at elevations not exceeding 75 feet above 
sea it is surmised that the Eocene will be found in this general area 
to lie below sea level. From numerous wells drilled at Jackson¬ 
ville it is known that the Eocene limestones there lie about 500 feet 
below sea level. On the other hand at Riverdale on the St. Johns 
River, about 35 miles south of Jacksonville, Eocene limestones are 
reached as indicated by well cuttings at about 211 feet below sea 
level; while at St. Augustine.the Ocala Eocene on the authority of 
Dr. W. H. Dali is placed at a depth of 224 feet from the surface 
or about 214 feet below sea level. 
In the well of Mr. Oliver Gibbs at Melbourne Beach, Eocene 
fossils were detected which from the log of the well appear to 
have come from the depth of 221 feet, the total depth of the well 
being 318 feet. At the intermediate points between Melbourne 
and St. Augustine on and near the coast the Eocene limestones lie 
so far as determined at a depth between 100 or somewhat less and 
200 feet below sea level. This is true of wells at Cocoa, where 
Eocene fossils have been taken from a well the total depth of which 
does not exceed 190 feet; at New Smyrna, where the Eocene ap¬ 
pears from well samples to have been reached at a depth of 105 
feet from the surface; at Daytona where from well logs it would 
seem that the Eocene is somewhat shallower than at New Smyrna, 
