80 
FLORIDA GEOLOGICAL SURVEY-I4TH ANNUAL REPORT 
the surface drainage this dome is believed to be indicated by the very 
pronounced westward bend in the Suwannee River. In Hamilton Coun¬ 
ty, north of Rive Oak, the Alum Bluff formation as seen in the banks 
of the Suwannee River lies at a lower level than near Live Oak. The 
data on which this area is determined as structurally a dome has been 
presented in the Thirteenth Annual Report of the Florida Survey, page 
16, 1921. 
OCALA AREA 
A considerable area in central peninsular Florida consisting of Ala¬ 
chua, Marion, Levy and Sumter Counties, and a part of Columbia and 
Union Counties is included in a large structural dome or geanticline. In 
this area, which may be known as the Ocala Area, the Oligocene appar¬ 
ently is wanting, and the Alum Bluff Miocene which formerly covered 
all or nearly all of the area now is found only locally, often existing as 
remnants. The Eocene limestones are either at the surface in this area 
or are sufficiently near the surface to be occasionally exposed in sinks, 
so that the Eocene may be regarded as the country rock of this part of 
the state. 
As already noted, wells in this area will start either in the Alum Bluff, 
Miocene, or in the Eocene. The thickness of the Tertiary formations is 
very moderate. The Alum Bluff may in places attain a thickness of as 
much as 100 feet, while the Eocene, according to the records which we 
now have, rarely exceeds 100 or 200 feet in thickness. Next beneath the 
Eocene, according to Cushman, is the Lower Cretaceous, the Upper 
Cretaceous being absent. No well as yet drilled in this area is known 
certainly to have passed through the Cretaceous. 
The following record of a deep well in Sumter County indicates the 
character and probable age of the formations in central peninsular Flor¬ 
ida to a depth of 3,090 feet: 
Well of Dundee Petroleum Company, Sec. 36, T. 20 S., R. 22 E., about four miles 
northeast of Bushnell, Sumter County. Samples collected by L. W. Hudson, driller, 
submitted by H. B. Goodrich, Geologist. Well begun July, 1917, completed Feb¬ 
ruary, 1918. From the surface to 380 feet no samples were taken. This interval, 
however, consists chiefly or entirely of limestones. 
Depth in feet. 
Limestone, no fossils observed; nearly white, breaks into angular frag¬ 
ments........ 380 
Limestone, apparently no fossils, except one echinoid; nearly white, not 
crystallized .......;.... 385 
