.4 Contribution to the Geologic History of the Floridian Plateau. 173 



At Miami, "samples from the wells of the water company show that 

 the oolite loses its typical appearance a few feet below sea-level and rests 

 on an irregularly cemented aggregate of shell fragments and quartz 

 sand." l 



The record of the well at Marathon, Key Vaca, revealed quartz sand 

 below 155 feet (see page 128). Some of these sands may be Pleistocene. 



Sands underlie the Lostman River limestone at a depth of 30 feet 

 at Everglade postoffice. 2 



Sanford reports a thickness of probably less than 50 feet for the 

 Kev West oolite 3 and mentions over 200 feet of quartz sand beneath it 4 

 on Big Pine Key. 



These records show sand beds underlying the Pleistocene limestones 

 as far south as Big Pine Key; some of the sands, the more northerly, are 

 surely Pleistocene, the more southerly may be partly Pleistocene and 

 partly Pliocene. 



THE FLORIDA OOLITES. 



The presence of two oolitic formations in Florida, the Miami and 

 Key West oolites, has been stated on preceding pages (pp. 130, 131) and 

 certain of their characters have already been given, viz.: their geologic 

 age, their general appearance, the structure of the granules, and their 

 areal distribution. As the object of the following remarks is to throw 

 such light as is possible on the origin of these deposits, a brief state- 

 ment will be made of the views of the principal previous students. 



Louis Agassiz 5 in his report for 1851 to Professor A. D. Bache, 

 Superintendent of the Coast Survey, says: 



The main islands of this group (west of Bahia Honda) are very flat, and 

 consist of thin layers of a regularly stratified and somewhat oolitical limestone, 

 evidently formed by deposits of limestone mud. 



E. B. Hunt 6 seemed to be of the opinion that the Key West oolite 

 might be partly due to the direct transformation of calcareous mud, or 

 to the transformation of calcareous sand lying above sea-level. 



Shaler considered the oolite a coral-reef rock and named that in the 

 vicinity of Miami the Miami Reef. 7 The oolite is distinctly not a coral- 

 reef rock, and Shaler's opinion is to be attributed to the fashion at that 

 time of considering practically all limestone in that area as having been 

 formed through the agency of corals. The differentiation 8 of varieties 

 of limestone had not then progressed so far as at present. 



The next important contribution to the subject came from Mr. 

 Alexander Agassiz in his "The Elevated Reef of Florida, 9 with notes on 



1 Florida Geol. Surv., 2d Ann. Report, p. 212, 1910. 



2 Sanford, op. at., p. 223. 



3 Op. cit., p. 220. 



4 Op. cit., p. 206. 



5 Mus. Comp. Zool., Mem., vol. vn, p. 19, 1880. 



6 Amer. Jour. Sci., 2d Ser., vol. xxxv, p. 203, 1863. 



7 Topography of Florida, Mus. Comp. Zool., Bull., vol. xvi, p. 143, 1890. 



8 Compare Mr. Agassiz's remarks in his "A Reconnaissance of the Bahamas 

 and of the Elevated Reefs of Cuba in the Steam Yacht Wild Duck, January to 

 April, 1893." (Mus. Comp. Zool., Bull., vol. xxvi, p. 179, 1894.) 



9 Mus. Comp. Zool., Bull., vol. xxvn, pp. 29-62, 26 plates, 1896. 



