II8 FLORIDA GEOLOGICAL SURVEY-TWELFTH ANNUAL REPORT 
thickness. Both the Nashua and Caloosahatchee formations so 
far as known, are thin and may not exceed 50 or 100 feet. 
PLEISTOCENE. 
The Pleistocene formations of Florida include river, alluvial 
and marine deposits. Alluvial Pleistocene deposits are widely dis¬ 
tributed over the State, especially in the stream valleys. In places 
these stream deposits contain vertebrate and invertebrate fossils. 
Among localities that have afforded important collections of verte¬ 
brates are Peace Creek, the Caloosahatchee River, and the drain¬ 
age canals. At Vero in St. Lucie County a drainage canal cutting 
through a stream bed has afforded an especially interesting collect¬ 
ing locality for vertebrates, land and fresh water invertebrates and 
marine invertebrates. This locality has been fully described in the 
Eighth, Ninth and Tenth Annual Reports of the Survey. 
The marine or chiefly marine Pleistocene deposits of the State 
have been described under the heading of Palm Beach Limestone, 
Miami Oolitic Limestone, Key Largo Limestone, Key West Lime¬ 
stone, Lostman’s River Limestone, and Ft. Thompson beds. The 
five first named are all of marine origin. The Ft. Thompson beds 
include an alternation of fresh water and marine deposits. All of 
these deposits are found in southern Florida and the interrelation 
of the several named units remains to be determined on more de¬ 
tailed stratigraphic work than has as yet been done. The Ft. 
Thompson beds are described in a paper included in the present 
volume. The other limestones are described in detail in the Second 
Annual Report of this Survey. 
GEOLOGIC SKETCH MAP. 
The accompanying sketch map shows in a general way the sur¬ 
face distribution of the Florida formations. Owing to the small 
scale of the map it has been necessary to combine the formations. 
It is also impracticable to show limited exposures, such for in¬ 
stance as the exposures of the Ocala Eocene on the Chipola River 
near Marianna, or of the Claiborne Eocene on the Choctawhatchee 
River near the Georgia-Florida State line. Out-liers and rem¬ 
nants of some of the formations are omitted for the same reason. 
