HILL: GEOLOGY OF JAMAICA. 49 
again, as in the canyon of Plantain Garden River in Portland, where the 
Cretaceous rocks of Jamaica were first noted by Barrett,! a single 
Stratum of limestone is interbedded between overlying and underlying 
tuffs, conglomerates, and clays. Sawkins noted in southwest Portland 
“thin beds of Cretaceous limestone, interstratified with thick porphy- 
ritic breccias and conglomerates, enclosing contemporaneous trap rocks.” ? 
The writer tried to visit all the localities mentioned, three of which, 
Clarendon, Jerusalem Mountain, Westmoreland Parish, and Bath, in 
St. Thomas, may bo taken as typical. These are in the central, western, 
and eastern portion of the island respectively.! 
Jerusalem Mountain Section. — In at least one locality Cretaceous 
limestones occur in extensive beds. This is near the extreme west end 
of the island at Jerusalem Mountain in the parish of Westmoreland. 
This was probably sufficiently remote from the centres of igneous activ- 
ity to permit undisturbed oceanic conditions and continuous growth of 
life. Jerusalem Mountain is a low, isolated hill standing 570 feet above 
the sea and about 500 feet above the surrounding valley plains. It is 
“omposed entirely of Cretaceous limestones and dull yellow clays, except 
at its eastern base, where the Tertiary limestones rest unconformably 
Against it, probably by faulting. The rocks dip slightly to the east. 
Here we made the following section: — 
Later Formations at Foot of the Hill. 
IV. Yellow shale resembling Richmond beds, with beds of lime- reet. 
me; weathers into purple colors . . . ... +... . 98 
IIT. Minho Beds. Purple clays and blotched shales dipping east 60 
II. “White limestone " in bluish shale, fossils Tertiary? . . . 50 
I. Level of valley plain of Mount gle, Alluvium v . . 00 
Section of the Hill. 
VI. 14. Summit of brown marls with Alectryonate oyster in 
thin limestone slabs, Pholadomya, ete. . . een 
V. 13. Yellowish limestone with small fossils 15 
12. Red purple clay Or ad ie, S1U 
ll. Dimension layers one foot thiek, of impure limestone with 
Aleetryonato oyster sou niv o nues osi c TU 
Lo, Yellow marl . . .. u ee ZH 
9. White fossiliferous limestone, Caprice, « . . . . . 0 
1 Quart. Jour. Geol. Soc, London, Vol. XVI. pp. 324-326, 
? Jamaican Reports, p. 74. 
VOL, XXXIV. 4 
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