) 



hill: geology of Jamaica. 197 



Owing to an outbreak of yellow fever the writer's studies of these 

 Gaudeloupean islands were limited to the briefest reconnoissance of 

 their general features as above enumerated, but they were sufficient to 

 warrant the deduction that the following details of the geology as set 

 forth by Duchassaing were in general correct.^ 



These beds consist of three formations, the oldest of which are 

 fossiliferous tuffs called by Jones ^ and DucTiassaing the " Pierre a 

 ravets " and " sables volcaniques remanies par la mer." This is com- 

 posed of yellow tuff very similar to the oldest stratified rocks of 

 Antigua, with few fossils, and the sands contain three species of Mol- 

 lusca which Cleve asserts with the enclosing strata greatly resemble 

 the Eocene beds of St. Bartholomew.^ Above these beds of sedi- 

 mentated igneous material there is a hard ringing limestone containing 

 Terebratula3. Still above the latter, and constituting the surface for- 

 mation of most of the Grande Terre are tufaceous marls very much 

 resembling those of Antigua, containing Foraminifera, Lunulites, and 

 many Mollusks, which Mr. Duchaissaing considered to be ''older Pliocene 

 in age." In these beds also occur three species of Echini which were 

 not considered as living in the adjacent waters. The latter beds at 

 oldest cannot antedate the Bowden or late Oligocene. Above these in 

 places are non-marine deposits of land wash in which were found the 

 famous human remains, and which also contain many fossil species of 

 land shells. 



The next and latest formation is the " Formation Madreporique *' of 

 Duchaissaing. This is true elevated reef rock or Soboruco, and bor- 

 ders all the coasts of Grande Terre as well as constitutes the outlying 

 islands of Marie Galante and Desirade.* 



These formations of Eocene and later age all overlie the detrital tuffs 

 of the old volcanoes of the Caribbee chain, and demonstrate the antiquity 

 of the vulcanism. 



These facts above presented lead me to the following conclusions con- 

 cerning the Caribbee Islands. Their geomorphology is entirely different 

 from that of the Antillean province except in those features on the Wind- 

 ward side recording the events of the last epochs of geologic time. No 



1 Bull Soc. Geol. France, 2(1 Ser., 1847, Vol. IV. Part II. pp. 1093-1100, and 2d 

 Ser., 1855, Vol. XII. pp. 753-757. 



^ Histoire physique des Antilles fran^aise, Paris, 1822. 



3 Op. cit., p. 44. 



* The reef formation of these two islands was also described by Maclure in 1817. 

 See Journ. Phila. Acad. Nat. Sci., Vol. I. p. 135. 



