332 TRANSACTIONS OF THE CANADIAN INSTITUTE. [VOL. W 



that this series once covered even a much larger area than at present. 

 In spite of the great thickness of the Hmestones, simple or complex 

 valleys from one to five miles wide have been cut through them ; and 

 the seaward margins of the highlands have suffered so much denuda- 

 tion that the lower beds of the formation have been exposed even where 

 they dip outward from the plateau. The solvent action of the tropical 

 rains produces a much more rapid degradation of the rocks than occurs 

 in the temperate latitudes. The exaggerated amount of erosion of 

 these limestones is referred to in order to point out the improbability 

 of ever finding the higher beds of the series, though some must have been 

 deposited, and thus the stratigraphical gap in the geological succession 

 is greater than the interval of time which the break represents. Ac- 

 cordingly, as there is only the older portion of the series preserved, it is 

 necessary to look for a somewhat later date in order to determine the 

 period when the land was first raised high enough to suffer denudation. 

 This elevation was the last uplift accompanied by any considerable dis- 

 turbance of the horizontality of the strata. Indeed, the " White Lime- 

 stones " have their beds highly tilted and often occur in sharp folds, 

 with occasional faults. This structure is shown in many canyons of the 

 streams crossing the formation. These physical disturbances occurred 

 immediately before the Mio-PHocene period of denudation. 



However characteristic the name, it is confusing, for the term 

 " White Limestones " has been given to different formations on various 

 islands and the continent. The Jamaican geologists were contradictory 

 as to the age of the " White Limestones." However, these strata 

 represent a physical and almost a lithological unit. They have close 

 analogies in Cuba, Santo Domingo and elsewhere, and they are the last 

 great development of limestones in the West Indies, although uncon- 

 formably succeeded by other accumulations. It is from the physical 

 standpoint that the formation is most important in this study. From 

 the appearance of the contained fossils, the series is doubtless complex, 

 and probably separable into Eocene and lower Miocene or (Oligocene) 

 formations. While in places the Eocene beds may not have been 

 deposited at the base of the great mass of rocks, in other localities the 

 overlying beds have been so removed as to expose the lower formation, 

 but the older Miocene (or Oligocene) beds seem to prevail. 



In this geomorphic study, the important feature is that the great 

 denudation of the island was subsequent to the disposition of these 

 older Miocene limestones. 



It was the prevailing impression among the Jamaican geologists that 



