54 
FLORIDA STATL GEOLOGICAL SURVEY. 
cene age. In the hard rock phosphate section there is at present 
no formation, other than the phosphate itself, overlying the Vicks¬ 
burg. However, there are good reasons, as already stated, for 
believing that the Upper Oligocene and some later formations, 
now found on the uplands bordering the phosphate belt, formerly 
extended across this area. Upper Oligocene deposits are found 
at the present time bordering the phosphate belt on the north, east 
and south, while on the west outliers of these formations may 
still be found in Levy and in Hernando Counties.* Remnants, 
apparently, of these formations have recently been observed by the 
writer on the hills near Morganville, west of the phosphate area 
in Marion County. 
Further support of the view that the Upper Oligocene deposits 
formerly extended across the phosphate belt is found in the topog¬ 
raphy of the area. The phosphate country has been reduced in 
elevation more or less by underground solution. The phosphate 
deposits of Alachua County are found at an elevation of from 75 
to 100 feet above sea, while passing to the east the plateau or 
uneroded section of this county rises to an elevation of 200 feet 
above sea. In Marion County the phosphates are found at an 
elevation of from 40 to 100 feet above sea, while both west and 
east of the phosphate belt, hills, the remnants of the former 
plateau, rise to an elevation of from 140 to 160 feet above sea. 
In Citrus County the hill country west of the phosphate area still 
retains a height of from 150 to 220 feet. The Upper Oligocene 
formations are found very generally on the east side of the phos¬ 
phate belt, while remnants, as already stated, are found on at least 
some of the hills on the west side of the area. 
Whether or not marine Miocene formerly extended across the 
present phosphate fields is undetermined. The character of the 
residue at some localities suggests Miocene material, although no 
actual proof of a former extent of the Miocene across this part 
of the State has yet been obtained. The marine Pliocene probably 
did not reach across this part of the State. Fresh water deposits 
of Pliocene and Pleistocene, however, are to be expected since 
"Florida Geological Survey, Second Annual Report, Map, 1909. 
