PALEOGEOGRAPHIC SUMMARY 623 



deformation in Cuba, rendering it highly probable, if not certain, that 

 the major tectonic trends of Cuba are as old as the Paleozoic. Although 

 no Paleozoic rocks have been identified in Jamaica, the inference appears 

 warranted that Jamaica itself dates back to late Paleozoic, as it has been 

 shown by Sapper that the west end of the tectonic features represented in 

 Mosquito and Eosalind banks and Jamaica already existed in late Paleo- 

 zoic time. The Cuban and Jamaican trends meet in Haiti and continue 

 through Porto Rico to the Virgin Islands, while Saint Croix, which is 

 closely related in its geologic features to the Virgins, was probably at one 

 time a member of that group and has been separated from them by fault- 

 ing of comparatively late geologic date. There is no direct evidence of 

 the existence at this time of any of the Caribbean Islands, but certain 

 relations suggest that at least parts of the Caribbean Arc may be old. 

 Saint Croix stands on the western end of a ridge between 600 and 700 

 fathoms deep, on the eastern end of which is Saint Christopher. This 

 ridge extends northward to the Saint Martin Plateau, eastward to Anti- 

 gua and Barbuda, and southward from the latter islands through Guade- 

 loupe, Saint Lucia, and the Grenadines to South America. These rela- 

 tions suggest that the eastern perimeter of the Caribbean basin may have 

 been outlined in late Paleozoic time. 



From the preceding statement it is evident that the principal tectonic 

 lines of the perimeters of the Gulf of Mexico and Caribbean Sea existed 

 at the close of the Paleozoic. The northern, western, and southern 

 boundaries had been outlined and the major transverse trends had also 

 been formed — the more northern through Oaxaca and Chiapas, including 

 the northward trending Coxcomb Mountains of British Honduras; the 

 more southern through Honduras and Nicaragua. The first may have 

 connected along the axis of the Coxcomb Mountains with Cuba and thence 

 with Haiti; the second probably connected with Jamaica, Haiti, Porto 

 Rico, and the Virgin Islands, and there are vague suggestions that the 

 Caribbean Arc also existed. As the positive and negative areas so early 

 outlined dominated the tectonic development during later geologic time, 

 the subsequent history consists in tracing the modification of these old 

 features. 



CENOZOIG 



The Cenozoic history may be summarized as follows : 

 Eocene and Oligocene. — The West Indian Islands, because no old Eo- 

 cene sediments are known in any of them except Trinidad, which is South 

 American in its affinities, are supposed to have stood above sealevel at 

 that time. In Cuba and Jamaica there are Upper Cretaceous and upper 

 Eocene sediments without the intervention of lower Eocene deposits. 



