GEOLOGY OF FLORIDA 299 



Florida. On this map there is indicated an area in the west central 

 part of the peninsula, marked "A," in which the top of the Eocene 

 limestones, when present, lies at or above sea-level. The data for 

 placing the eastern margin of this area are very limited, and the 

 bomidaries are necessarily very roughly approximated. In the lake 

 region of Clay County in particular it is possible that the Eocene 

 may lie closer to the surface than is here indicated. 



A second area, " B , " is marked off on the map, in which generally 

 speaking the top of the Eocene limestones appears to lie below sea- 

 level, but at no place in excess of 200 feet below sea. These two 

 areas, it will be noted, together make up 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 following the 

 course of this stream it passes toward the Gulf to successively 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 Jacksonville it is known 

 that the Eocene limestones there lie about 5oo»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 indi- 

 cated by well cuttings, at about 211 feet below sea-level; while at 

 St. Augustine the Ocala Eocene, on the authority of Dr. W. H. Dall, 

 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 intermediate points between Melbourne and St. 

 Augustine, on and near the coast the Eocene limestones lie, so far as 

 determined, at depths 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 appears from 



