SECOND ANNUAL, REPORT—SOUTHERN ERORIDA. 
207 
OLIGOCENE. 
Foraminifera of the genus Orbitoides that characterize the Vicks¬ 
burg group were found in drillings from the wells at Palm Beach and 
Key West. The top of the limestone may lie about 950 feet below the 
surface at Palm Beach and 700 feet below at Key West. An east¬ 
ward dip of the limestone is indicated by the records of wells east of 
Fort Myers, but evidence to show the amount of dip is meager. A 
southern prolongation of the anticlinal fold of west central Florida 
is probable, but can not be established from the known data. i 
Thickness:—Samples from the Palm Beach well showed Orbito¬ 
ides for 312 feet, samples from the Key West well showed the same 
fossils for 1100 feet. It is fairly certain that the Key West well was 
not cased to below 1000 feet; hence little reliance can be placed on 
the samples from 1000 to 2000 feet, so carefully examined and de¬ 
scribed by Hovey. Thus there is no evidence to establish the thick¬ 
ness of the Vicksburg group there, though Hovey noted changes in 
the character of the limestones at 475 and 2000 feet. There is no 
evidence to establish the thickness of Oligocene beds above the Vicks¬ 
burg group, which were probably penetrated over eighty feet at Indian 
Key Channel. 
MIOCENE AND PLIOCENE. 
Lithology:—A comparison of records from points so widely 
separated as Palm Beach, Key Vaca and Buck Key shows a surpris¬ 
ing thickness of beds composed largely of quartz sand, and contra¬ 
dicts the old belief that the southern end of the peninsula rests on a 
solid limy foundation. Between the surficial limestones and the lime¬ 
stones of Upper Oligocene age are 200 to 700 feet of unconsolidated 
material that is siliceous, rather than calcareous. The succession of 
limy beds at Key West is explainable by remoteness from the main¬ 
land and consequently from the source of the quartz sands. 
Thickness:—No deep well in southern Florida has proved de¬ 
finitely the thickness of Miocene and Pliocene sediments at a given 
point, and it is doubtful if any well that may be drilled will show 
Miocene deposits sharply separated from Pliocene, or if wells in most 
of the region will afford a basis for separating the Miocene from the 
upper beds of the Oligocene. Hence the total combined thickness of 
the Pliocene and Miocene beds is likely to remain conjectural. It 
may amount to 800 feet at Miami, and 516 feet at Indian Key Channel. 
Source of Siliceous Material:—Some of the Miocene and Pliocene 
sands probably represent siliceous grains derived by weathering and 
erosion from the Upper Oligocene and Lower Oligocene limestones. 
Much more of it may have worked south along the east and west coast 
