CONDITIONS UNDER WHICH THE WEST INDIAN, CENTRAL AMERICAN, 

 AND FLORIDIAN CORAL REEFS HAVE FORMED, AND THEIR BEAR- 

 ING ON THEORIES OF CORAL-REEF FORMATION. 



A brief review of the results obtained from a study of American 

 Tertiary and post-Tertiary corals in their relation to the larger prob- 

 lem of coral-reef formation in general will now be given. In a paper 

 recently published ^ I stated that in my opinion coral reefs should 

 be studied from at least the following standpoints: 



1. The corals themselves, to ascertain the ecologic conditions under which they 

 live or lived, and to distinguish the calcium carbonate secreted by corals from that 

 contributed through other agencies. 



2. A complex of geologic processes operating in the area must be studied, analyzed, 

 and evaluated — among these are the agencies other than corals whereby calcium 

 carbonate may be taken from the sea water, the probability of the solvent action of 

 sea water on calcium carbonate, the effects of winds, currents, and waves in build- 

 ing, shaping, and destroying banks, and in submarine planation. 



3. The stratigraphic and structural geology of the area, including a careful study 

 of the origin of the sedimentary rocks with which corals are associated. 



4. The physiography, especially that of the shore line, that of the land area adja- 

 cent to the shore, and that of the sea bottom from the shore to abyssal depths. 



In the subsequent discussion, after defining coral reef, brief atten- 

 tion wiU be given to the following topics: (1) The general ecology 

 of reef -forming corals; (2) the more striking hypotheses of the for- 

 mation of coral-reefs; (3) the conditions under which the American 

 Tertiary and Pleistocene reefs have formed and their importance 

 as constructional geologic agents; (4) the conditions under which 

 the hving reefs of the same area formed and their importance as 

 constructional agents; (5) coral reefs of the Pacific Ocean and com- 

 parison of them with the American fossil and hving reefs; (6) sum- 

 mary of conclusions. 



It is needless to say that, as an elaborate discussion of the subjects 

 mentioned would require a large volume, it is possible in the present 

 connection to give only summary statements. 



Definition of the Term "Coral Reef." 



As definitions are essential in this as in other discussions, the . 

 expression "coral reef" will be defined as foUows: 



A coral reef is a ridge or mound of limestone, the upper surface of which lies, or 

 lay at the time of its formation, near the level of the sea, and is predominantly com- 

 posed of calcium carbonate secreted by organisms, of which the most important are 

 corals.^ 



1 Some shoal-water corals from Murray Island (Australia), Cocos-Keeling Islands, and Panning Island, 

 Carnegia Inst. Washington Pub. 213, p. 54, 1918. 



2 Vaughan, T. W., Physical conditions under which Paleozoic coral reefs were formed, Bull. Geo). Soc- 

 America, vol. 22, p. 238, 1911. 



238 



