HILL: GEOLOGY OF JAMAICA. 81 



mation. In this region the Cobre formation is very much honeycombed, 

 and weathers into blood-red soils. At one place where laborers were 

 blasting unusually large masses of the limestone, specimens from its in- 

 terior were secured, which clearly showed the red iron blotches in the 

 interstitial cavities. 



There are a number of isolated outliers of this formation standing in 

 the midst of the Liguanea and other plains composed of later alluvium 

 in the parishes of St. Catherine and Clarendon, as shown in Figure 26. 



T— *— I — —r ' I ' I • ! ■ I ■ -I ■ -^-' T -■ . '■ . -^ ■ ' I -I I I ' — r-- I -r 



Figure 26. Outlier of Limestone in Liguanea Plain, near Spanishtown. 

 a a, Cobre Limestone, b h, Kingston Formation. 



These are of the type known in America as monadnocks. Two of these 

 may be conveniently seen on the Kingston road a mile or two east of 

 Spanishtown.^ These consist of the same limestone as that seen in the 

 Bog Walk section (see Fig. 25). 



At the convict quarry back of Rock Fort, about four miles east of 

 Kingston, where Long Mountain bluffs against the seacoast, a superb 

 exposure of limestone has been made by quarrying. It is so lumpy 

 that it is worked by the pick and used for road metal. Under the 

 microscope it is composed of numerous undetermined species of Forami- 

 nifera, entirely different from those of the Montpelier and Cambridge 

 beds. In the western group of parishes, forming the county of Corn- 

 wall, it may constitute the summit formation and pointed hills of the 

 cockpit country. This idea is suggested by the lithologic aspects of 

 the rocks comprising these hills, and from outcrops in Manchester along 

 the highlands bordering the Montego Bay Railway. Close research has 

 not been made to determine this. A prominent feature of the Cobre 

 formation is the blood-red residual subsoils which everywhere result 

 from its surface decay. 



From the Bog Walk section it is evident that the Cobre formation 

 lies stratigraphically above the supposed Moneague beds at Ewarton 



^ Lennox (Jamaican Reports, pp. 149-151) described the formation of these hills 

 under tlie name of the " Port Henderson Limestone." 



VOL. XXXIV. 6 



