HILL : GEOLOGY OF JAMAICA. 89 



the Rio Cobre and largely white limestone debris to the west of that 

 stream. 



It has been successively accumulated through several geologic epochs, 

 and may ultimately be classified into several distinct terraines. For 

 the present, however, we shall recognize but two principal stages, — an 

 older one, to which tlie name of Kingston will be applied, and a newer 

 one, which will be called the Montego. 



The Kingston formation is the oldest of the formations of old gravel 

 and other alluvium occurring upon the plains of the Liguanea type. 

 This is the formation upon whicli the city of Kingston and suburbs are 

 built, including the strip of land known as the Palisades, and the plain 

 extending back of Kingston to the foot of the mountains (see Plates VI. 

 and XIX.). The material consists of boulders, gravel, and pebble of 

 varying sizes, usually very angular, and representing every known 

 material of the Blue Mountain Series. These are embedded in a matrix 

 of dull red arenaceous clay, producing a chocolate soil and derived from 

 the Minho beds so conspicuously exposed in situ in the mountains 

 north of Kingston. 



The thickness of this formation is unknown, but over 200 feet are 

 exposed in the thalweg of Ilope Kiver, and probably fully this thickness 

 is concealed. It is even likely that it may be nearly a thousand feet in 

 places. 



To the west in St. Catherine the material is similar in composition to 

 all the rocks of the mother region drained by the Cobre. Sometimes 

 it grades into a true marine marl, including some white limestone 

 debris. 



Concerning the origin of this material in St. Andrew, there is no 

 doubt but it has been deposited by Hope River, as it debouched from 

 the mountains. While most of the material was originally estuarine, 

 some of its upper layers w^ere made by talus fan deposits similar to 

 those now seen in the arid region of North America where the moun- 

 tain streams debouch upon the desert plains. 



As a whole, it represents excessive deposition, first as estuarine or 

 littoral material during an epoch when the coasts were submerged, and 

 later talus deposits of subsequent epochs, when the land was rapidly 

 rising and stream erosion was very active, as discussed more fully in 

 Part I., p. 39, of this paper. The alluvial deposits in the bottom of the 

 larger interior basins are also closely synchronous with the Kingston 

 formation, and it is probable that these basins are products of the same 

 great erosion epoch which preceded the Kingston deposition. 



