HILL: GEOLOGY OF JAMAICA. 47 
4. Logie Green Beds. — Yellow clays, similar to those at Pennant's 
Great House on tho St. Thomas, containing fossil Rudistes. Exposed 
at baso of above section. Thickness of these clays indeterminate. 
They are exposed intermittently as far as Trout Hall, and Mile Post 
ee ae lotes dea a OA, 
3. Frankenfield 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 
ig 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 
thiek, Three hundred feet aro exposed in the high hills back of 
ES Edo ne qon so v voc MIR 
2. Limestone Beds. — Great masses of hard blue-white limestone 
Over 20 feet thick, with gigantic Rudistes, Actxonella, and corals. 
Apparently bosses in the igneous conglomerate and tuffs. 
l. 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 agreo with that given by Duncan and Wall, as 
Previously cited, in which the divide of the St. Thomas and Minho 
(Long Ridge) is represented as a hill of massive igneous rock protrud- 
Mg through and disturbing the sedimentaries. On the contrary, this 
hill ig 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 
iatus in the Clarendon section between the top of the Minho beds and 
the Cambridge is elsewhere represented by the formation to be described 
*8 the Richmond beds as best seen on the north side of the island. 
Collectively the beds of the Clarendon section constitute the lower 
