TRANSACTIONS OF WAGNER 

 1594 



-^^^ TERTIARY FAUNA OF FLORIDA 



THE FLORIDIAN MIOCENE. 



After the elimination of the Oligocene series from the so-called Miocene 

 of Florida we have remaining practically only one series of beds which has 

 been identified over a considerable area of northern Florida. The Miocene 

 appears as a soft limestone rock in the vicinity of Jacksonville, and has been 

 traced by material from artesian wells on the east side of the peninsula as far 

 south as Lake Worth. The layers of fossiliferous marl in the vicinity of the 

 Chipola River, at Alum Bluff, and other localities in Western Florida are usu- 

 ally less than thirty feet in thickness, but counting unfossiliferous clays, etc., it 

 has been estimated that the rocks of this age in Florida may have attained to 

 a thickness of some five hundred feet or less. The localities where it has been 

 noticed and the knowledge of the distribution of this series of beds are sum- 

 marized in Bulletin 84 of the United States Geological Survey, pp. 124-7, 1892. 

 Later and fuller information in regard to the beds in northwest Florida will be 

 found in the Bulletin of the Geological Society of America, v., pp. 147-170, 

 1894. The Miocene as regarded in the present Memoir was discriminated by the 

 writer from the Oligocene with which it had up to that time been erroneously 

 united in the " Proceedings of the United States National Museum," xix.. No. 

 mo, pp. 303-4, 1896, and in a " Table of North American Tertiary Horizons" 

 in the " Eighteenth Annual Report of the United States Geological Survey," 

 pp. 323-348, a paper handed in for publication in 1895 but not printed until 

 1898. Long previously, however, the writer had pointed out the important 

 characters which separated these two groups and designated them as Old or 

 subtropical, and Newer or cold-water Miocene. Marine deposits of the latter or 

 true Miocene age have not been shown to exist anywhere in the Antillean region 

 south of Lake Worth, Florida. 



As I have on various occasions insisted, the faunal gap between the upper- 

 most Oligocene (Oak Grove) and the Chesapeake or Miocene is the most sud- 

 den, emphatic, and distinct in the whole post-Cretaceous history of our south- 

 eastern Tertiary, and indicates physical changes in the surrounding region, if 

 not in Florida itself, sufficient to alter the course of ocean currents and wholly 

 change the temperature of the waters on our southern coast. 



Some indications of the approaching change are seen in the Oak Grove 

 fauna, but, while that is united by thirty-four per cent, of its species with the 

 fauna of the antecedent Chipola beds, its contribution to the fauna of the 

 succeeding Chesapeake is three species, and these of a kind which recalls the 

 inflexible organization of the goose cited by Darwin. Practically the conditions 

 amount to a complete change of fauna as well as of the character of the fauna. 



