174 Papers from the Marine Biological Laboratory at Tortugas. 



the Geology of Southern Florida by Leon S. Griswold." Mr. Agassizr 

 has presented the salient features of his conclusions as follows: 



I was quite surprised on examining a bluff about lo feet in height, extending 

 eastward from Cocoanut Point toward the mouth of the Miami River, to find that 

 it consisted of ceolian rocks which have covered the elevated reef in many places. 

 On the low shores these aeohan rocks are honeycombed and pitted and might be 

 readily mistaken for decomposed reef rocks; but they contain no corals. This 

 looks as if the lower southern extremity of Florida, the Everglade tracts, was a 

 huge shallow sink, or a series of more or less connected sinks, into which sand had 

 been blown, forming low dunes which have little by little been eroded, and which 

 former observers had mistaken in some localities for reef rock. The material for 

 these dunes coming from the now elevated reef or the beach rock at a time when 

 it was either a fringing or a barrier reef along the former coast line of Florida, all 

 of which, back of the reef, has little by little been eroded by the mechanical and 

 solvent action of the sea, leaving on the mainland only an occasional outcrop of 

 the elevated reef as observed by Professor L. Agassiz and vShaler. The outer line 

 of reef has also been elevated. 



There are in this view several points that need to be emphasized: 

 (i) The Miami oolite is not a coral reef rock. (2) It is of aeolian origin. 

 (3) In southern Florida a huge sink existed, into which the material of 

 the oolite was blown. (4) The source of wind-blown sand was either 

 the now elevated reef or the beach rock at a time when it was either a 

 fringing or a barrier reef along the former coast-line of Florida. (5) The 

 bays and sounds are due to the mechanical and solvent action of the 

 sea. What is of particular concern here is the supposed aeolian origin 

 of the oolite and the source of the material. The discussion of the " huge 

 shallow sink" and the formation of the bays and sounds may be laid 

 aside for the present. 



A careful reading of the text of Mr. Agassiz 's remarks does not 

 reveal the criteria by which he determined the oolite to be aolian; he 

 has merely given his opinion. In his foot-notes to Mr. Griswold's " Notes 

 on the Geology of Southern. Florida," although dissent from Griswold 

 is expressed, still no criteria are given for distinguishing between water- 

 laid and aeolian cross-bedded calcareous deposits. At the bottom of 

 page 52 is the statement: "This bluff is a most distinctly marked aeolian 

 rock exposure, with characteristic knife-edge stratification." A com- 

 parison of plate XV of Mr. Agassiz's report on the Bahamas with plate 

 XIX of Griswold's "Notes" will show considerable similarity in structure 

 of the Bahaman and Floridian materials. 



Griswold in his " Notes on the Geology of Southern Florida," already 

 cited, says concerning the origin of the oolite: 



The low undulations of the land surface in the pine belt can scarcely be 

 accepted as evidence of former dunes. They would well accord, however, with the 

 inequalities of a sea floor like the present one between the keys and the mainland. 

 The cross-bedding and oolitic structure favor neither water nor wind as the primary 

 agent in the construction of the rock. Therefore, since the land appears to be very 

 young, being almost without soil and surface drainage ways, the topography favors 

 an origin for the limestone in water. 



Sellards has published the opinion that the Miami oolite is a marine 

 formation.' 



* Florida Geol. Surv., ist Ann. Report, p. 22, 1908. 



