42 FLORIDA GEOLOGICAL SURVEY SIXTH ANNUAL REPORT. 



Smith, who in 1847 examined the oolitic limestone in the vicinity 

 of Miami and along the Miami River. The locality was subse- 

 quently visited by Agassiz, Tuomey and others of the early geolo- 

 gists, and the age of the rocks correctly determined as Pleistocene. 

 The limestones bordering the Everglades west of Palm Beach and 

 at the extreme southern end of the peninsula were examined in 

 1908 by Samuel Sanford, supplementing similar investigations made 

 in 1887 by Joseph Wilcox, and together with the rocks found west 

 of Palm Beach, were described in the Second Annual Report of 

 the Florida Geological Survey. The limestone west of Palm Beach 

 v/as there designated as the Palm Beach Limestone, while that 

 found bordering the Gulf coast at the southern end of the Ever- 

 glades was named the Lostman's River Limestone. 



On the west side of the Everglades along the Caloosahatchee 

 River there is found a shell marl formation of Pliocene age first 

 described in 1887 by Angelo Heilprin and known as the Caloosa- 

 hatchee marl. This marl, remarkable for the number, size and 

 excellent preservation of the fossil shells which it contains, dis- 

 appears from view beneath later formations at Fort Thompson 

 near the head of the Caloosahatchee River. 



The formations lying above the Caloosahatchee marl at Fort 

 Thompson consists of hard and soft limestones, shell and clay 

 marls. The principal limestone seen at this locality is a hard 

 almost flinty rock containing an abundance of the fresh-water 

 snail, Planorbis. Both above and below this limestone stratum, 

 are shell marls, some of which are of fresh-water and some of 

 marine origin. The most persistent of these marls is a shell 

 stratum resting directly upon the limestone and having a thickness 

 of about two feet. The predominating fossil in this stratum, the 

 small Chione cancellata, is a species which prefers shallow water, 

 frequently living between low and high tide. Above this marine 

 shell marl is a fresh-water clayey marl which contains an abundance 

 of the remains of the pond snails. These deposits in which marine 

 marls alternate with fresh-water marls and limestones indicate 

 that at the time of their formation this part of Florida was being 

 gradually elevated above sea. The elevation of the land area as 

 is usual in such cases, progressed slowly with minor fluctuations, 

 permitting the formation of fresh and brackish water lagoons, in 

 which the fresh-water marls accumulated, then by a minor subsi- 



