1864.] 



DUNCAN AND WALL JAMAICA. 



formation of the succeeding deposits ; but in one or two instances, in 

 Clarendon, conglomerates are observed conformable to the Cretaceous 

 marls at an angle of 60°. In other locahties it is difBcult or im- 

 possible to determine the relations of the Conglomerate and Cre- 

 taceous groups. This is especially the case in the highly mountainous 

 eastern parts of Jamaica, where traces of almost obliterated Hippurites 

 and other Cretaceous fossils are detected in strata which, from their 

 confused position, could not otherwise be classified stratigraphically. 



The Cretaceous Corals about to be described came from the marls 

 and Cretaceous sands at Trout Hall and Mount Hindmost, in the 

 parish of Upper Clarendon. 



The Conglomerate (Eocene) series is very extensively developed in 

 Jamaica: it consists of a lower member whicli is a trvie conglomerate, 

 formed by boulders and fragments of the hardest porphyries, and of 

 rounded veinstones ; and of an upper, which consists of shaly and 

 sandj^beds with small pebbles, or even of merely granular fragments. 

 Occasionally masses of the Cretaceous Hmestone, with altered shales 

 and sandstones, are observed in the lower member. The group is at 

 least 3000 feet thick in some places, and it fills up the space between 

 the Cretaceous series and the base of the Miocene. The term Con- 

 glomerate-group may appear objectionable, but the character is 

 almost exclusively conglomeratic in the typical district of Clarendon, 

 and in several other localities. In Clarendon the various beds suc- 

 ceed each other conformably, from the base to the summit •; but the 

 repeated disturbances of other districts render the sequence both 

 ■obscure and uncertain. The lower member is unfossiiiferous ; but 

 in the upper, for instance, at Port Maria and at Tailahs valley, Corals 

 and fragments of SheUs are found. 



Pig. 3. — Section through the Concjlomerate-series in the parishes of 



S.W. Metcalfe and St. Mary. Near Port Maria N.R 



(fossil Corals). 



a. Coast limestone. 

 3. Sands and shales, 

 5. Conglomerates. 



8, Igneous rocks. 

 V Conglomerate-group. (Eocene.) 



The Port Maria beds consist of conglomerates, shales, and sands ; 

 and the YaUahs valley and other parts of the Blue Mountain district 

 are occupied by dark carbonaceous shales, which are sometimes 

 calcareous. It is extremely rare to find any determinable fossils in 

 this group, for its beds are generally much disturbed, often vertical, 

 and are cut up and altered by dykes. 



The next formation, in ascending order, comprises marls, sands, 

 and various calcareous beds, limited in places to a yellow limestone 

 of a few feet in thickness, and at others expanding into a great 

 succession of marls, sands, and calcareous beds, which are not always 

 conformably superposed on the subjacent conglomerates. Numerous 



