70 
FLORIDA GEOLOGICAL SURVEY. 
his sketch illustrating the structure of the peninsula, 
likewise indicates its anticlinal structure. 
The fact that the marine, deposits in Florida are 
drained of salt originally present in the interstices of the 
rock for nearly a thousand feet below sea level, as indi¬ 
cated by bored wells, together with solution cavities at 
considerable depth, led Shaler (181) to postulate an eleva¬ 
tion of the peninsula at some time since its formation to 
not less than 800 to 1000 feet. 
McGee’s memoir on the Lafayette formations (138) 
contain^ the writer’s conclusions as to the history of 
the coastal plains during late geographical times. Pre¬ 
vious to the formation of the Lafayette the coastal plains, 
in the opinion of McGee, had been for a long time quies¬ 
cent. In order to account for the Lafayette formation 
McGee, like Hilgard, finds it necessary to postulate an 
extensive submergence, involving the entire coastal 
plains. It is, however, considered as not absolutely cer¬ 
tain that southern Florida was submerged (p. 509). 
Following the Lafayette deposits an elevation occurred 
bringing the southern coastal plains much above their 
present level. Previous to the Lafayette deposits canyons 
were cut by rivers across the coastal plains. McGee 
estimates this elevation as 200 to 700 feet above the 
present level. A re-submergence, not so extensive as that 
of the Lafayette, but involving Florida, is indicated, in 
the view of McGee, by the presence of the Columbia sands 
on top of the Lafayette. A Post-Columbian high level 
period, followed 1 by subsidence to the present level, closes 
the history of the coastal plains. 
In regard to the supposed elevation of land north of 
the Gulf of Mexico postulated by Spencer, Upham and 
others to account for the glacial epoch, Dali (45) main¬ 
tains that for Florida, at least, no such elevation oc¬ 
curred. Canyons and sculpturing of the topography 
such as would necessarily have occurred in the soft Flor¬ 
ida formation, being absent. 
