hill: geology of JAMAICA. 



51 



Sawkins), here composed of volcanic tuff with conchoidal fracture and 

 weathering into rusty red clays, metamorphosed shale, and occasional 



m 



W:^MK:>^^m^''^^^<>^y^ vmy^n^^m 



Figure 15. Barrett's Section, near Bath. 



pieces of contained impure Hmestone. About a mile up the Plantain 

 Garden Kiver the stream has a steep V-sliaped canyon surrounded by 

 hills. A new highway which is being constructed shows fine cuts of the 

 prevalent Minho formation. In this we found exposures of hard strata 

 of Cretaceous limestone, aggregating several feet in thickness, but the 

 vegetation was so thick that the latter fact could not be determined 

 positively. 



I 



Figure 16. Plantain Garden River Section at Bath. c. Trappean Material 

 above, b. Cretaceous Limestone, a. Trappean Material below b. 



Below the limestone (b) are altered shales and decomposed volcanic 

 conglomerates, some of which weather into dark colored chocolate or 

 vermilion colors. 



In nearly all the localities of the Jamaican Survey, with the excep- 

 tion of the Jerusalem exposure, the limestones have the appearance of 

 localized beds in the midst of the general material of the Blue Mountain 

 Series,^ and not of widely extending or persistent strata. 



These beds occupy no persistent horizon but occur at various inter- 

 vals in the great aggregation of deposits. Our observations incline us to 

 agree with Sawkins,^ that " it would appear from the occurrence of the 

 limestone in detached places that it originally formed isolated reefs." 



The marls succeed the bedded limestones in ascending series, and 

 vary from 50 feet to an inch in thickness as seen in the clays along the 

 Minho, at Ballard's above Clarendon, at Pennant's Great House, and 

 Trout Hall. In general, these clays contain fossils which represent 

 intermittent life colonies which have found temporary habitation in 

 periods of quiescence during the irregular deposition marking the forma- 

 tion of the earlier part of the Blue Mountain Series. 



1 Barrett, Quart. Jour. Geol. Soc. London, 1860, Vol. XVI. pp. 325, 326. 



2 The Metamorphosed Series, Trappean Series, Black Shale, and Conglomerate 

 of Sawkins. 



