1 62 FLORIDA GEOLOGICAL SURVEY I3TH ANNUAL REPORT 



sand any irregularities that might tend to be formed by erosion, 

 burrowing animals, uprooted trees, etc.* 



Lake basins. The hills of the lake region are interspersed with 

 many saucer-like basins of various sizes and depths, some dry and 

 some containing water. Just how these basins were formed is an 

 unsolved problem. Some have ascribed them to solution and some 

 to the action of strong ocean currents when the land was sub- 

 merged! but neither explanation fits all the facts. Basins of some- 

 what similar outline but usually shallower are very common in the 

 lime-sink region, and as some of those are known to have been 

 formed by a sudden caving in of the roof of a subterranean passage 

 and the subsequent smoothing of the sides by rain and wind, it may 

 be assumed that most of them originated in some such way. But 

 in the lake region sinks, caves, and other solution phenomena are 

 very rare, and no one seems to have ever observed the beginning 

 of one of the basins in question. They could hardly have been 

 scooped out by the wind or the elevations around them piled up by 

 waves, either, for many of the hills have a hard clay substratum 

 in them considerably above the bottom of the basins. And lake? 

 a short distance apart often differ considerably in elevation, show- 

 ing that they rest on an irregular surface of clay or some other 

 impervious material. 



Lime-sinks. This term is used for several different things. 

 Some lime-sinks are small drj^ sandy basins of the kind just de- 

 scribed, with no visible outlet, while others have rock outcropping 

 in them and a hole at the bottom through which water escapes, 

 and some have steep banks and are more or less permanently filled 

 with water, which is usually bluish from dissolved limestone. The 

 dry sandy type is most common in the lime-sink region and the 



*It seems probable that the wind has had a much larger share in shapin.j 

 the topography of the uplands of peninsular Florida than is commonly realized. 

 Although the sand does not move noticeably on windy days, except in culti- 

 vated fields (and even there there is little evidence of drifting after the wind 

 dies down), in the course of centuries any minor irregularities must Ijo prctiy 

 thoroughly smoothed out. 



tSee pages 150-156 of the paper on the topography of Florida by Prof. 

 Shaler, cited on the preceding page. 



