Y 
Ў 
FREE: INSTITUTE OF SGTENOR 
VEGETATION OF SOUTH FLORIDA 
northward. These outcrops, although scattered, probably extend north- 
ward into St. Lucie County, as depicted on the geologic map published in 
the Second Annual Report of the State Geologist of Florida. These lime- 
stones are covered by the sand dunes of the east coast, by the sands and peat 
of the Everglades, and in thickness vary from 1.52 m. (five feet) to 15.24 
m. (50 feet). Fora distance of 48 km. (30 miles) these limestone deposits 
help to define the eastern rim of the Everglades. 
The geologic map of Florida, published in the second report of the State 
Geological Survey (199), shows that the area immediately south of the 
sand hills at Delray, as far south as Cards Sound along the east coast, is 
characterized by outcrops of oölitic limestone designated as Miami-Key 
West oólite. The exposures were noted by army officers at the time of the 
Seminole war, by Tuomey, L. Agassiz, Shaler, A. Agassiz, and others. Buck- 
ingham Smith, as early as 1847, found many mollusk shells in the oólite 
at Miami River and determined the age of this deposit as post-Pliocene. 
The rock is perhaps younger than the Palm Beach limestone and is younger 
than the lower part of the Key Largo limestone. The thickness of the 
Miami-Key West oólite varies, according to the studies made in the drilling 
of wells. At Ft. Lauderdale it is four meters thick, at Dania 12 meters, 
at Miami 6 meters. These figures, making due allowance for the scanti- 
ness of the data and the unreliability of the well records, unless accompanied 
by samples, show that the maximum thickness may be 16 meters along the 
coastal outcrops and perhaps more inland. At Miami, the odlite rests on 
an irregularly cemented aggregate of shell fragments and quartz sand. It 
rests on “blue sand” at Dania and on sand at Ft. Lauderdale. Litho- 
logically the rock is a soft, white oölitic limestone, containing thin irregular 
layers of calcite separating less crystalline streaks, and is discolored by 
weathering, by the deposit of vegetal mould and the growth of lichens, 
mosses, and alge. It breaks with an irregular fracture, dresses nicely, 
hardens on exposure, and makes a good road and building stone. This 
oölite carries a varying proportion of small, irregular grains of quartz sand, 
which are more plentiful in the northern part of the area covered by Miami- 
Key West oölite. The Miami-Key West limestone, which extends to the 
edge of the Everglades and perhaps beyond, weathers into sharp angular 
fragments, which lie loosely on the surface, or it is eaten into pockets 
often filled with sand. The surface, therefore, is very rough and uneven, 
