88 
FLORIDA GEOLOGICAL SURVEY—THIRD ANNUAL REPORT. 
exceeding 190 feet, while at Melbourne Beach, 150 miles south 
of St. Augustine, its depth in one well was found to be 221 feet. 
Passing to the south from this point the Vicksburg dips rapidly. 
At Palm Beach, 100 miles farther south, this limestone was reach¬ 
ed at a depth of approximately 1,000 feet, *a dip of about 750 feet 
in 100 miles or 7 >4 feet per mile. The Vicksburg was not reached 
in a well 700 feet deep drilled by the Florida East Coast Railway 
Company at Marathon Key, 175 miles south of Palm Beachj 
At Key West, however, the formation is believed to have been 
reached at a depth of 700 feet.t 
It is thus seen that the Vicksburg forms a broad arch extending 
from central Florida to the Atlantic Ocean. St. Augustine lies 
near the north slope of this arch, while Melbourne, as nearly as 
can be determined, lies near the south slope. On either side of 
the arch the limestone dips at a moderate rate. On the north side 
of the arch the maximum depth recorded in Florida is 500 feet. 
Passing to the south a maximum of. approximately 1,000 feet is 
recorded at Palm Beach. While the occurrence of this formation 
is thus known in a general way the data are as yet imperfect. 
In view of the importance of the Vicksburg as an artesian 
water reservoir the depth at which it is to be expected is a matter 
of very great importance and it is to be hoped that well drillers 
will find it possible to keep accurately labeled well samples in order 
to determine more definitely the distribution of this formation. 
APALACHICOLA GROUP. 
The Apalachicola group of formations is of a much less uniform 
character than the Vicksburg and is also of less importance in 
connection with the water supply. A full description of this group 
of formations will be found in the preceding Annual Report of 
this Survey, pp. 67-106. 
The formations which make up the Apalachicola group include 
the Chattahoochee and Alum Bluff formations, well exposed along 
the Apalachicola River; the Hawthorne formation in central Flor¬ 
ida; and the Tampa formation in southern Florida. The relative 
position of three of these, the Chattahoochee, the Hawthorne and 
the Tampa formations has not been definitely determined, and they 
may be largely contemporaneous. The Alum Bluff formation lies 
above the Chattahoochee formation. The limestone of this group 
consists largely of impure clayey material which upon decay 
*Darton, N. H.; Amer. Journ. Sci. (3) XLI, p. 105-6, 1891. 
■{•Florida Geol. Survey. Second Annual Report, p. 206, 1909. 
ijiHovey, E. O. Mus. Comp. Zool. Bull. XXVIII, pp. 65-91, 1896. 
