I 



HILL : GEOLOGY OF JAMAICA. 37 



land Eidge of Clarendon, which constitutes the southern peninsula of 

 the island, and at another by the extensive outliers of the Limestone 

 Plateau known as the Healthshire and Port Henderson Hills, opposite 

 the Naval Station of Port Ptoyal. The latter are conspicuous features 

 to the west as one enters Kingston Harbor. The Braziletto Hills of 

 Clarendon extend into this plain, almost separating it into eastern and 

 western divisions. The term Liguanea is restricted in local usage to 

 that portion of the plain lying east of this prolongation. The interior 

 margin of the plain terminates against the steep white limestone topog- 

 raphy, except just north of Kingston, where it abuts against the Blue 

 Mountain ridges proper. This interior margin is over 800 feet high 

 near Constant Springs, whence it slopes rapidly to the sea at Kingston, 

 six and a half miles distant. 



In comparison with regions underlain by other formations, the physical 

 aspect of this plain is arid and sterile. The flora, including thorny 

 acacias and cactus, tends towards the chapparal type so character- 

 istic of the Rio Grande Plain of Mexico and Texas, and presents a 

 striking contrast to the deciduous tropical flora of the remainder of 

 the island. To the west the next extensive plain of this character, 

 known as the Pedro Plain in St. Elizabeth, indents the land to the 

 east and north of Black River Bay. Its estimated area is over 100 

 squai'e miles. This is analogous to the Plain of Liguanea, except 

 that it contains much marshy ground, and the gravel formation is accom- 

 panied by marls. Back of Savanna-la-Mar there is another extensive 

 plain of this type, which continues inward nearly one half the dis- 

 tance across the island. This is cut entirely out of the limestone hills, 

 and, inasmuch as there is little gravel in the back country, the formation 

 is of a marly nature. This plain is fully 100 square miles in area. On 

 the west it is almost connected by a narrow arm with the marslies which 

 border the western coast of the island. Plains of this character are sin- 

 gularly absent from the north side except at Montego Bay adjacent to 

 the mouth of Montego River, where they are more feebly developed than 

 on the south coast. 



The history of the Liguanea type of Plains is a record of four dis- 

 tinct events : (1) the original cutting out of the topographic matrix 

 during an antecedent period of base levelling; (2) the filling in of 

 the debris which composes the present surface material of the plains ; 

 (3) the elevation of the plains into their present position above the sea; 

 and (4) th'e cutting of the modern streamw\ays acroae them. The sur- 



face formation of these plains is clearly deposited iiUfpre-eroded valleys 



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