344 



TRANSACTIONS OF THE CANADIAN INSTITUTE. 



[Vol. v. 



PLEISTOCENE HISTORY. 



Epoch of Elevation. — After the Lay ton epoch of submergence, there 

 was a long period of high elevation, during which most of the Layton 

 series, forming fringes along the steep mountain sides close upon the 

 coast, was removed by denudation. Thus the formation does not 

 occur continuously round the island, and is only preserved in protected 

 districts or in some indentations entering the highlands. In the typical 

 locality, about Low Layton, the Layton series is greatly denuded, and 

 upon the eroded surfaces the Liguanea formation is deposited. In 

 many places the series appears to be covered by the succeeding loams 

 and gravels, without being exposed by later erosion. 



Apart from the degradation of the Layton formation, there was a 

 marked change in the character between the post-Layton and the 

 earlier epochs of erosion. This difference is represented by the deep 

 and more or less widened valleys, which dissected the old base planes 

 of erosion among the plateaus of White Limestones, and thus gave rise 

 to much of the ruggedness of the island. This feature is illustrated in 

 Figure 5. The higher margins represent portions of an elevated plateau, 

 which has been denuded so as to form numerous prominences of similar 

 height, separated by broad, undulating troughs and valleys, indicating 

 lower base levels than at present. The rocks are composed of the Old 

 Miocene " White Limestones." They have been subjected to denuda- 

 tion since their first elevation. Lower down the plateau, there are two 



Figure 5. ^Section across the Hope valley (east of Kingston), about three miles long, as viewed from 

 the north: — tn L (Long mountain, (Z-) 1528 feet above tide), old "White Limestone" topography; p p, 

 remains of early Pleistocene base-level outlines ; 1 1, base-level terrace formed during Liguanea epoch ; r, 

 canyon of recent date being cut below the Liguanea level (which is 550 feet above the sea). 



distinct base levels of more recent erosion, besides the modern gorge, 

 The stream is still deepening its channel, owing to the recent elevation 

 of the land. (See Plate vi., page 350). 



The feature of primary and secondary valleys and canyons is well 

 represented in the coast range plateau from Port Antonio to Annatto 



