66 Papers from the Marine Biological Laboratory at Tortiigas. 



COMPARISONS OF THE FLORIDA REEF TRACT WITH SOME OTHER 

 CORAL REEF AREAS. 



In order to compare the relations of the barrier reef of Florida with 

 the last change of sea-level in Cuba and in Andros Island, Bahamas, the 

 following statements will be made: Hayes, Vaughan, and Spencer^ have 

 shown, as is evidenced by the pouch-shaped harbors of the Cuban coast 

 and filled channels, such as the submerged filled channel in Havana Harbor, 

 that the last movement of the Cuban coast has been downward with refer- 

 ence to sea-level. As an account of the Cuban reefs would be out of place 

 here, reference is made to that published by A. Agassiz.^ The platform on 

 which the Cuban reefs grow has been brought to its present position by 

 subsidence. The great barrier reef of Andros Island, Bahamas, as I have 

 shown,' occupies the outer edge of a depressed platform. Therefore the 

 Floridian, Andros, and Cuban reefs all have a similar relation to the oscilla- 

 tion of sea-level, as in each instance there has been elevation antecedent 

 to depression which has brought the platforms on which the reefs stand 

 into their present positions. 



There is, however, in one important respect, a difference between the 

 relations of the Recent reefs of Florida, Andros Island, Bahamas, and of 

 those of Cuba to Pleistocene oscillation. The oscillations in Florida and 

 Andros Island have taken place without notable differential crustal move- 

 ments; while in Cuba there was notable deformation accompanying the 

 oscillations. The Pleistocene terraces rise in height toward the eastern 

 end of Cuba in Orlente Province, where altitudes of about 600 feet are 

 attained near Cape Maisi; while in Santa Clara, Matanzas, and Havana 

 provinces terraces on the north side are distinct and rise in several steps to 

 heights of about 200 feet, but are absent or indistinct on the southern side.'* 

 These facts show that there has been pronounced tilting in late Pleistocene 

 time. In Barbados Pleistocene reefs extend to 1,000 feet in elevation. 



By working out the salient features in the development of the Florida 

 reefs and instituting comparisons with the West Indies a basis has been 

 supplied for explaining certain puzzling relations of the reefs in the Tropical 

 Pacific. A. Agassiz discovered that in the Paumotuan atolls the Recent 

 corals were growing as a thin crust on an older limestone foundation. His 

 explanation of the formation of the atolls by the destruction of the interior 

 of a limestone mass must be discarded, as they were certainly not formed 

 in that manner but by constructional agencies. There was evidently a 

 period of atoll formation in the Paumotus previous to the growth of the 

 Recent corals, which have established themselves on an atoll basement 

 already prepared for them. A great development of Pleistocene (and per- 

 haps late Tertiary) coral reefs in the tropical Pacific has been proven in the 

 most convincing way. 



1 Report on a geological reconnaissance of Cuba, made under the direction of General Leonard Wood, 

 Military Governor, 1901. Report of tiie Military Governor for 1901. 



• Bull. Mus. Comp. Zool., vol. 26, pp. 133-136. 1894. 



• Cam. Inst. Wash. Year Book, No. 11, p. 154, 1912; Cam. Inst. Wash. Pub. 182, page 50, 1913. 



• Hayes, Vaughan, and Spencer, Geological reconnaissance of Cuba, pp. 18-20. 



