"3 5 



6 FLORIDA GEOLOGICAL SURVEY SIXTH ANNUAL REPORT. 



19. EAST FLORIDA FLATVVOODS. 

 (figures 85, 86) 



References. Gillmore (974), Harper i (224-225, 250-251, 272, 287-290), 

 Harper 3 (229-232, 235), Matson & Clapp (29, 108-113), Matson & Sanford 

 (126, 267-270, 283-287, 296-301, 273-2,7^, 394-398). Sellards & Gunter 2 (126, 135- 

 137, 141-143), Smith 2 {2^0-22,2), and U. S. soil surveys of the "Gainesville area" 

 (1905), "Jacksonville area" (1911), and Bradford Co. (1914). Illustrated in 

 2nd Ann. Rep., pi. 6.2; 3d, pi. lo.i, 14.3, 23.1, 28, fig. 24; 4th, fig. 3; sth, pi. 13.3, 

 14. 1. 



The flatwoods of northeastern Florida extend northward along 

 the coast to the vicinity of the Savannah River, where their char- 

 acter gradually changes. Going inland in Georgia this region passes 

 gradually at a distance of 50 to 100 miles from the coast into the 

 Altamaha Grit region or rolling wire-grass country, which is a 

 direct continuation of the West Florida pine hills already described 

 (region 7). In the area under consideration these flatwoods cover 

 about 5,300 square miles. Farther south there is nothing exactly 

 similar, for the extensive flatwoods of peninsular Florida differ in 

 several ways. 



Geology and Soils — Fossiliferous marly strata are exposed on 

 the banks of a few creeks and rivers in the eastern half of this 

 region, and have been mapped as Miocene. Throughout the greater 

 part of the area the marl seems to be overlaid by several feet of 

 essentially non-calcareous sandy clay, and that in turn by a few 

 feet or inches of grayish sand, which is regarded by some as a 

 distinct Pleistocene formation and by others as a mere product of 

 weathering. In many places, however, particularly on Trail Ridge 

 (described under Topography, below) the sand passes at a depth of 

 two or three feet into blackish "hardpan," and in such places there 

 are usually no excavations deep enough to disclose whether clay is 

 present beneath the hardpan or not. Another variation in the ar- 

 rangement of the surface formations (if the sand and clay be re- 

 garded as such) is that within 25 miles of the coast there are many 

 low spots where the vegetation seems to indicate the proximity of 

 marl to the surface, and consequently the sand and clay must be 

 thin or wanting. 



The sand which forms the surface everywhere except in the 

 marly spots and where covered by muck or peat is fine-grained and 

 usually rather dark-colored from admixture of vegetable matter. 

 In all three of the government soil surveys above cited the most 

 extensive type of soil in the flatwoods is called "Portsmouth fine 



