HILL: GEOLOGY OF JAMAICA. 47 



4. Logie Green Beds. — Yellow clays, similar to those at Pennant's 

 Great House on the St. Thomas, containing fossil Rudistes. Exposed 

 at base of above section. Thickness of these clays indeterminate. 

 They are exposed intermittently as far as Trout Hall, and Mile Post 

 44 +100 ft. 



3. Frankenfiold Beds. — Beds twenty feet in thickness of large 

 igneous cobble stone of hornblende-andesite embedded in an ashen gray 

 matrix of tuff, grading down into, or possibly unconformable upon, a 

 great thickness of tuff without conspicuous pebbles. This formation 

 is exposed in superb cuts on both sides of Frankenfield between Mile 

 Posts 44-49. Towards Logie Green there are boulders of porphyry, 

 becoming smaller above. These beds may be from 500 to 1,000 feet 

 thick. Three hundred feet are exposed in the high hills back of 

 Trout Hall +500 ft. 



2. Limestone Beds. — Great masses of hard blue-white limestone 

 over 20 feet thick, with gigantic Rudistes, Actseonella, and corals. 

 Apparently bosses in the igneous conglomerate and tuffs. 



1. Yallahs Formation. — Conglomerate of porphyritic boulders. 

 Base concealed. This is the bottom of the section of the Blue 

 Mountain Series, as seen in Clarendon Parish. 



All the beds of the foregoing section have a very strong south dip 

 of ±30° beneath the white limestones on the south of the Clarendon 

 basin. 



This section does not agree with that given by Duncan and Wall, as 

 previously cited, in which the divide of the St. Thomas and Miuho 

 (Long Ridge) is represented as a hill of massive igneous rock protrud- 

 ing through and disturbing the sedimentaries. On the contrary, this 

 hill is composed of stratified tuff. 



The Clarendon section, although the best exposed on the island, does 

 not represent the Blue Mountain Series in its entirety, nor are its 

 facies everywhere uniform or continuous. Rocks similar to these com- 

 pose the material of all the higher mountains of the eastern half of 

 the island, but there they occur in such a disturbed condition that 

 the members cannot be easily differentiated. A greater thickness of the 

 lower conglomerates is exposed in the Blue Mountain districts. The 

 hiatus in the Clarendon section between the top of the Minho beds and 

 the Cambridge is elsewhere represented by the formation to be described 

 as the Richmond beds as best seen on the north side of the island. 

 Collectively the beds of the Clarendon section constitute the lower 



