498 L. C. Johnson — Phosphate Fields of Florida. 



of any kind. Some distance off, however, to the westward of 

 the former and about four miles west of Waldo, is a small ex- 

 posure known as the Preston Marl, near old Fort Harlee ; and 

 seven or eight miles still farther northwestward in Bradford 

 County, is another large sink. Both these exhibit formations 

 of Miocene age. The small streams also, which traverse 

 these flat woods, including Santa Fe river and several of its 

 affluents, and Lockloosa creek rising by several small branches 

 from the eastern end of Lake Santa Fe, have in them or in 

 their immediate valleys, driftlike sediments, containing casts of 

 fossils similar to those of Waldo. These flatwoods are said to 

 have a general elevation of about 150 feet above tide water. 



It is well to acknowledge here in advance, the assistance 

 derived from the topograpical sheets of the Geological Survey. 



Between Nunan Lake, and the great Alachua Sink or Lake, 

 to the westward, are a number of exposures of clays, and phos- 

 phatic sandstones, — the latter being known as the Gainesville 

 " Paving-rock." These may be regarded as alteration products 

 of older Miocene beds. Fossils are rare ; but traces exist of a 

 Venus, a Fecten, and there is no scarcity of reptilian bones. 

 Teeth of sharks and rays are quite numerous. In other parts 

 of the region having this structure, and the tufa-Wke Gaines- 

 ville Paving-rock, there are ferruginous marly sands with chal- 

 cedonized oyster shells not distinguishable from O. Virginiana, 

 and there are also abundant patches of the large coral Astrea 

 Floridana (or bella.) The contour lines of the Survey give 

 the elevations of these deposits of the coral, and oysters and 

 Gainesville rock at 70-100 feet. 



At the great Alachua Sink, twenty feet lower than the 

 lowest Gainesville rock of the adjoining hills, the formation is 

 Eocene of the Yicksburg type. 



For ten or twelve miles westward of this sink, and of Lake 

 Nunan, the same relative position of the strata continues, with 

 a constant gain to the Eocene rocks ; until they reach the eleva- 

 tion of near 100 feet, and the Gainesville rock disappears, or 

 becomes very thin and represented by its alternate clay. This 

 probably signifies a small dip of the Eocene to the eastward ; in 

 which direction, it sinks under Miocene clays and marls. 



The region south of Gainesville, a distance of ten miles, is 

 one of apparent depression. Within it are contained Payne's 

 Prairie — lately Lake Alachua* — the Kanapaha Prairie, and the 

 Hogtown and Sugarfoot Prairies and Sinks. To the southeast 

 of Payne's Prairie lie series of ponds and small cypress 



* Alachua Lake wasaprare, from the oldest record, till 1878, when after 

 great rains it became a lake of 40 sq. miles. Again in June, 1891, after a series 

 of four dry years, it suddenly dried off. Immense numbers of fish were taken or 

 destroyed. And now, July, 1892, after a month of heavy rains, the water is 

 reclaiming possession of the flats 



