T. W. Vaughan — Origin of Barrier Coral Reef s. 133 



tion of barrier reefs to the last dominant change in the posi- 

 tion of strand line ; (3) are the reefs superposed on antecedent 

 platforms or are the platforms which the reefs margin or above 

 which they rise due to infilling and leveling behind reefs? 

 The following indicates the present status of information on 

 these subjects : 



1. Recent investigations conducted in Florida show not only 

 that submarine solution is not effective there, as all the bays, 

 sounds, and lagoons are being filled with sediment, which is 

 largely a bacterial precipitate as shown by the investigations of 

 Drew and Kellerman, but that according to analyses made by 

 Dole there is no free C0 2 in the sea water. These results 

 accord with the conclusions reached by numerous investigators 

 in the Pacific, which are that the more or less continuous walls 

 inclosing lagoons have been formed by constructional geologic 

 processes and that lagoon channels and atoll lagoons are not due 

 to submarine solution. 



2. Nearly all if not all the off-shore reefs in the western 

 Atlantic Ocean, the Caribbean Sea, and the Gulf of Mexico 

 have been investigated and, with the possible exception of the 

 reef off the southeast coast of Barbados, it is established that 

 they have been formed either during or subsequent to sub- 

 mergence. This is in accord with the results obtained in the 

 Pacific by Dana, Andrews, Hedley and Griffith Taylor, and 

 P. Marshall, and more recently by "W. M. Davis. 



3. R. T. Hill was apparently the first to recognize the rela- 

 tions of living reefs to submerged terraced surfaces. After 

 describing the elevated reefs of Jamaica, he says that " Jamaica 

 was once a more extensive land area than now with benched 

 and terraced margins which were submerged by subsidence" 

 and that "similar submerged plains are now occupied by the 

 growing reefs around the island." Andrews, in his article 

 which follows, gives the results of his studies of the Great 

 Barrier Reef of Australia, published in 1902, and of his in- 

 vestigations in the Fiji Islands.* After long continued studies 

 in Florida, in the Bahamas, in areas in Central America, and 

 in a number of the West Indian Islands, I will say that the 

 modern off-shore coral reefs of the western Atlantic Ocean, 

 the Gulf of Mexico, and the Caribbean Sea have grown upon 

 antecedent platforms, often on terraced surfaces, either during 

 or after submergence, where conditions are favorable for the 

 life of such reef-forming organisms. 



*It is gratifying to me that Mr. Andrews has essentially confirmed a 

 statement I published in 1914, which is that " a study of the charts of 

 barrier reef islands, as Viti Levu, Fijis, and Tahiti, Society Islands, show 

 that the platforms are independent of the presence of reefs, and therefore 

 the relations in these islands are similar to those indicated for barriers off 

 continental shores, for here the reefs are also superimposed on platforms 

 antedating their presence." 



