44 FLORIDA GEOLOGICAL SURVEY-SEVENTH ANNUAL REPORT. 
Analysis of the matrix of the land pebble phosphate. Sample from mine of 
the Prairie Pebble Phosphate Company near Mulberry. Air-dried sample. 
Moisture - .78 
Insoluble matter, sand, etc.- 25.18 
Phosphoric acid 26.73, equivalent to tri-calcium phosphate-58.38 
Iron and alumina_ 7.51 
Calcium oxide, 1.02, equivalent to calcium carbonate_2.32 
The relation of the Bone Valley formation to the Oligocene de¬ 
posits beneath is that of unconformity throughout. Of the other 
Pliocene formations of Florida, the Caloosahatchee and Nashua 
marls, it will not be necessary to speak at this time since they lie for 
the most part south and east of the phosphate area, and moreover 
have been described in the preceding reports of the Survey. 
PLEISTOCENE. 
The Pleistocene of southern Florida west of the Everglades is 
confined to deposits lying near the coast. Of these it will be neces¬ 
sary to consider only those in the stream valleys which hold the river 
pebble phosphate, the best known being the Peace Creek beds. 
Before continuing the description of the formations holding the 
phosphate deposits, however, it may be well to give some further 
account of the structure and g*eologic history of southern Florida. 
Fig. 3.—Mining river pebble phosphate on Peace Creek, 
