HILL : GEOLOGY OF JAMAICA. 175 



4 



the lower part of the IHue Mountain Series, and the Eichmond beds 

 of Jamaica. Concerning these he says : — 



" The Eocene conglomerates consist of sandstones, clay slates, and stratified 

 conglomerates. The latter predominate decidedly. The constituents of nearly 

 all these beds are almost exclusively of volcanic origin, and are to be attrib- 

 uted to the decomposition and erosion of the porphyritic and syenitic rocks, 

 especially the former. The porphyritic constituents have in the main imparted 

 the red color to this formation. The debris forming these conglomerates is 

 granite, especially syenite and porphyry, also trap, more rarely gneiss ; they 

 are united by a siliceous cement. Alongside of them are found limestone 

 pebbles, whose blue-gray or black color and Hippurite and Nerinea fossils in- 

 dicate that they belong to the Jurassic (?) limestone. The texture of the 

 various beds is loose, where no plutonic masses have exerted a hardening in- 

 fluence. The sedimentary origin, however, remains recognizable in the lines 

 of stratification and in the flat rounded pebbles. The strata, varying in thick- 

 ness from a few inches to several feet, always appear in regular arrangement. 

 At the surface this formation is frequently decomposed into local clays, shining 

 ochres, kaolin, various siliceous stones, agates, amethysts, and quartz. Such 

 surfaces, either high plateaus or mountain crests, always have a dreary red 

 appearance. The clay slates often show a well marked purple color. At the 

 base of this formation occur dark colored clay slates ; they seem to extend 

 back into the epoch of the Jurassic limestone. There they also grow more 

 rich in fossils, and show traces of plants, marine shells, and calcspar veins. Lig- 

 nite beds of small extent lie between the slates. The sandstones bear impres- 

 sions of leaves and stems. The higher clay slates are light brown or reddish, 

 and form thin beds of friable conglomerates, resting on massive gray sand- 

 stones. In the vicinity of eruptive rock the sandstone is hardened, becomes 

 crystalline and transformed into quartz ; elsewhere it is soft and friable. The 

 slate has been still more changed by heat, having become porphyritic. "When 

 exposed to the air, it crumbles, the sulphur, iron, and lime being separated and 

 forming with the aluminum two differently colored clays, red and gray, used 

 in industry." 



In Cuba the bituminous plant-bearing shales of Esperanza and other 

 points in Santa Clara province and in the vicinity of Havana, previously 

 noted by the writer ^ and others, occupy a position below the great 

 White Limestone Series corresponding to that of the Eichmond beds. 

 So far as is known the outcrops are not widely developed. 



In Porto Rico, the Virgin Islands, and St. Bartholomew, no attempt 

 has been made to separate this formation from the overlying equivalents 

 of the Cambridge beds, or to distinguish it from the Bluebeache, but 

 doubtless future study will reveal its presence there. 



* Notes on the Geology of the Island of Cuba, Cambridge, 1895, p. 246. 



