PEBBLE PHOSPHATE DEPOSITS. 
45 
STRUCTURE OF SOUTHERN FLORIDA. 
THICKNESS AND SUCCESSION OF FORMATIONS. 
With regard to the thickness and succession of the formations 
underlying the pebble phosphate deposits in southern Florida, the 
best record that is at present available is that which has been ob¬ 
tained through the study of samples from wells drilled at and near 
Tiger Bay by the Palmetto Phosphate Company, at Christina by the 
Phosphate Mining Company, and at Fort Myers by the Ohio 1 Well 
Drilling Company. 
Description of samples from well No. 3 of the Palmetto Phosphate Com¬ 
pany, Tiger Bay, Florida. 
Depth of sample from the surface. 
73 feet. The rock at this depth is a light colored phosphatic marl or limestone. 
In texture and appearance it is like the marl which lies beneath the land 
pebble phosphates. The phosphate is in the form of smooth, rounded black, 
brown, and white pebbles. While this is the prevailing material of the sam¬ 
ple, at least one fragment consists of clear grained quartz, held together by 
a phosphatic or calcareous cement and resembling Alum Bluff sands. Acid 
test showed this piece to be but slightly if at all calcareous. There are 
also some fragments of dark blue hard rock which effervesce but slightly 
in acid. No fossils were seen in this sample. 
85 feet. This is also a phosphatic marl or limestone. It is similar to the 73- 
foot sample except that it is lighter in color, being light gray or nearly 
white. The phosphatic pebbles are mostly black in color, the black pebble 
in the light colored marl giving a grayish cast to the rock. The hard blue 
rock that effervesces scarcely at all in acid is rather more abundant in this 
than in the preceding sample. This hard rock also contains black phos¬ 
phate pebbles and it is probable that it is merely a silicified phase of the 
marl. Some casts of fossils but no determinable specimens. A considerable 
amount of clear grained siliceous sand is seen among the finer material. 
150 feet. The material at this depth is also calcareous and phosphatic. The 
phosphate pebbles are black or brown and are smooth and rounded. The 
rock contains numerous small cavities giving it a porous appearance. Only 
one fossil is seen, this being part of a small gastropod. 
160 feet. A phosphatic limestone or marl with some fossil gastropods and bi¬ 
valves preserved as casts. The rock at this depth is in general similar to 
the 150-foot sample. The fossils seem more abundant perhaps because the 
sample is larger. The phosphate pebbles are black, brown, and white in 
color. 
180 feet. Compact brown, phosphatic limestone. The phosphate pebbles are not 
abundant in this limestone and are in the form of small black pebbles im¬ 
bedded in the rock. While the rock is prevailingly compact some porous 
fragments are seen. A few broken fossils preserved as casts. 
