hill: geology of Jamaica. 195 



accumulation represent portions of the windward sea bottom whicli 

 was brought up by uplifts of the main chain. 



This main or interior chain is composed of piled up volcanic debris, 

 and upon the islands of Guadeloupe and St. Vincent there have been 

 active volcanic eruptions in historic time, 1797 in the former and 1812 

 in the latter. Soufrieres, hot springs, etc., show that this activity is 

 only slumberingly quiescent in nearly all these islands. Besides most 

 of them still possess upon their summits one or more true craters, 

 while Saba and St. Eustatius are composed of simple crater cones now 

 quiescent. While tliese facts attest recent eruptivity in the islands, 

 there is much evidence presaging the conclusion that the present 

 vulcanism is merely the survival of that which began much earlier in 

 geologic history. 



The configuration and structure show that their history extends back 

 to considerable antiquity. In the first place while the protuberance 

 of all these islands is largely due to extrusive piling up, the present 

 detailed configuration expressed in steep coastal bluffs, benches, slopes, 

 and canyons, is produced by erosion, which has required considerable 

 time for development. True crater shapes, except in St. Eustatius and 

 St. Christopher, are exceptional, and are merely secondary summit 

 features in the other islands, occurring parasitically upon masses of old 

 eroded volcanic debris reaching a height of 4,000 feet. Secondly, they 

 are all composed largely of vast piles of old tufi's and trachytic debris 

 of many eruptive epochs, like the volcanic heights of the Costa Rican 

 plateau, which indicate long continuation of the volcanism since com- 

 paratively remote geologic epochs, reaching back most probably to the 

 Eocene time. 



In St. Christopher, St. Eustatius, Guadeloupe, Martinique, St. Lucia, 

 and Granada, disturbed fossiliferous beds of Pleistocene or recent age 

 are found interbedded in volcanic debris of the lower slopes at altitudes 

 of two or three hundred feet above the sea, showing that uplifting as 

 well as extrusion has in part produced the present eminences, and that 

 vulcanism existed in Pleistocene time. 



The fossils mentioned are hardly older than Pliocene, and are most 

 probably Pleistocene, and their border-like position shows that the 

 greater mass of the islands were ejected in previous epochs. 



So much for the main chain of the Caribbees considered by them- 

 selves, but the eastern belt, of the compound type, owe their present 

 position above sea level to the erogenic uplifts which affected the 

 Caribbean area in later geologic time. Guadeloupe and Antigua are the 



