314 FLORIDA GEOLOGICAL SURVEY SIXTH ANNUAL REPORT. 



17. PENINSULAR LIME-SINK REGION. 

 (figures 82, 83) 



References. Harper i (221), Matson & Sanford (359-361, 408-412), Sellards, 

 3d Ann. Rep. 21-32, Sellards 2 (29), Sellards 3 (294-295 or 48-49), and U. S. soil 

 survey of the "Gainesville area" (by Rice & Geib, 1905). Illustrated in 2nd 

 Ann. Rep., pi. 4.1, 8.1; 4th, pi. 5.1. 



This well-marked 'region extends from a few miles north of 

 the Georgia line southward through the western half of the penin- 

 sula to Pasco County at least. About 2,000 square miles of it are 

 included in the arbitrary limits of this report. It bears some re- 

 semblance to the West Florida lime-sink region (no. 2), and still 

 more to the Bellair sand region (no. 12), but differs perceptibly 

 from both in its vegetation. 



Geology and Soils — The bed-rock here is the Vicksburg lime- 

 stone, which is overlaid in many places by formations of later age, 

 particularly the hard-rock phosphate beds (Alachua or Dunnellon 

 formation), and nearly everywhere by several feet of pale loamy 

 sand. The rock protrudes through the sand in many places, as 

 in regions 12 and 15. Clay often lies between the rock and sand, 

 especially northward, but exposures of it are rare, and consequently 

 its areal extent is not definitely known. All the hard-rock phosphate 

 mined in Florida comes from this region, and the soil probably con- 

 tains more phosphorus than the average, though no analyses of it 

 are available at this writing.* 



The salamander seems to be more abundant in this region than 

 anywhere else, and its hills, a foot or more in diameter and a few 

 inches high, are nearly always in sight in the drier soils, particular- 

 ly in early spring just after the woods are burned over. Ants, 

 gophers, and no doubt several other subterranean animals are com- 

 mon, and influence the soil in much the same way that the salaman- 

 der does. 



Topography and' Hydrography — This region has a character- 

 istic solution, or karst, topography (though possibly influenced some 

 by the wind, as suggested elsewhere), with a profusion of low hills 

 and basin-like depressions, the smallest of which are nearly circular. 



*In that part of the lime-sink region included in the "Gainesville area'' the 

 soil is nearly all classed as "Norfolk sand" in the government soil survey above 

 cited. But the two mechanical analyses of it given there both represent samples 

 from the hammock belt (no. 10), so that it would not be proper to quote them 

 here. 



