THE GREAT FAULT TROUGHS OF THE ANTILLES iii 



related to the tectonic lines of Central America and southeastern 

 Mexico. 



Another group of tectonic lines, prominent in the Greater 

 Antilles, trends northwest and southeast. The principal mountains 

 of Jamaica, composed of intensely folded Cretaceous rocks trend 

 about N. 70° W. parallel to the northeast coast; the Grand Hilera 

 or Sierra Cibao extend across the Island of Haiti in a northwest- 

 southeast direction from a point near Cape Engano to Mole St. 

 Nicolas, and the axis of elongation of Cuba from the Windward 

 Passage almost to Habana also follows this trend. Vaughan infers 

 that a fault runs northeast from Cape Cruz but the evidence is 

 meager.^ 



Another old structural direction, which seems to have no relation 

 to the present topography, is indicated by the north-south strike of 

 the crystalKne rocks exposed on the Isla de Pinos lying south of 

 western Cuba.^ 



The Antillean fault zones cut across the earlier trend lines which 

 seem to be due chiefly to folding, and, because of their recency as 

 well as the magnitude of the displacements, they dominate the 

 present topography. Transverse faulting seems to be rare, and 

 it has had little or no effect on the topography. The irregular 

 coast lines at the east and west ends of the various islands are in 

 marked contrast to the rectilinearity of many of the coast lines that 

 run east and west. 



Berkey has suggested that Porto Rico is a large fault block 

 uplifted along the southern margin and tilted toward the north 

 with breaks at each end. In support of this hypothesis he mentions 

 the unsymmetrical position of the main drainage divide, which is 

 nearer the south coast; the comparatively abrupt termination of 

 the island at both ends; and the absence of the younger limestone 

 margin from these coasts although it is fairly continuous along the 

 north coast and about half of the south coast.^ 



' T. W. Vaughan, "Fossil Corals from Central America, Cuba, and Porto Rico, 

 with an Account of the American Tertiary, Pleistocene, and Recent Coral Reefs," 

 U.S. Nat. Mus. Bull. 103 (1919), pp. 288-89. 



^ C. W. Hayes, T. W. Vaughan, and A. C. Spencer, "Report on a Geological 

 Reconnaissance of Cuba," Washington, 1901. 



3C. P. Berkey, op. ciL, pp. 40-41. 



