502 L. ('. -Johnson — Phosphate Fields of Florida. 



tion as vet observed — at Belleview on the Florida Central and 

 Peninsula railroad, 12 miles south of Ocala. The remains are 

 chalcedonized oyster shells. As related by the manager of the 

 mine they are associated with the "plate-rock" next the 

 shoulders of Eocene limestone. As observed by the writer in 

 an abandoned pit, where it was said they had been numerous, 

 the shells of Ostrea Virginiana were still adhering to the 

 rock, evidently undisturbed since the day they attached them- 

 selves, and grew there. 



B. Genesis of the Plate-RocJc Deposits. 



The problems presented by the foregoing facts are : (a) To 

 account for compact phosphate ; (h) To account for the " soft- 

 phosphate" phase; (c) To account for the presence therein of 

 "_£>?« fe-?v<?&." 



Peninsular Florida first appeared above water in early Mio- 

 cene times, in the form of numerous small islands of Eocene 

 limestone, stretched along what would later be the Gulf coast 

 — corresponding in position to parts of the present counties — 

 Suwanee, Columbia, Lafayette, Levy, Hernando, Citrus, Pasco, 

 Sumter, and the western parts of Marion and Allachua. 

 Twenty miles eastward of this main line facing the Gulf, was 

 this smaller cluster of islets we have under consideration, then 

 braving the Atlantic. Denudation of these islands by the sea 

 imparted to them at many points the water-worn low bluffs 

 with pinnacles, such as are visible on any part of the present 

 coast composed of rocks like these. Notably may be instanced, 

 St. Mark's Bay, and Deadman's Bay, of the Gulf side. Upon 

 shores of this nature were laid down the deposits described in 

 the foregoing pages. 



The varieties of this class of phosphates in Marion County 

 alone, comprise in mining language "hard rock," "laminated- 

 rock," "'plate-rock" and " soft- phosphate." 



The explanation offered herewith of the genesis of these 

 phosphates, is based upon the hypothesis of the original depo- 

 sition of guano. 



In a rainless region the deposits would have remained in 

 form similar to those of the Chincha islands. In the present 

 case in a region of much rain and great moisture, the guano 

 beds became converted into the phosphates here encountered. 

 The arrangement of land and sea in the Miocene age rendered 

 the deposition of immense deposits of guano quite possible. 

 Only upon such secure island homes, away from the predatory 

 animals of the continent, could the sea-birds have successfully 

 maintained their breeding grounds. The waters of such an 

 archipelago at that age teemed with life, which with the rich 

 vegetation of warm shallow seas afforded ample food. 



