HILL: GEOLOGY OF JAMAICA. 03 



cessivG reefs is Lest shown on the west end of tlie nortli coast between 

 Montego Bay and Lncea in the parish of Hanover. 



Extensive patches of Soboruco border the coast two miles east of Port 

 Antonio. This is made up entirely of large coral heads ^ and super- 

 ficially consolidated into rough jagged surfaces. It forms a low bluff 

 about ten feet high, which is being undermined by wave action. It 

 extends back from the water only a short distance, and numerous in- 

 dentations have been cut into it by the sea. There are similar ex- 

 posures on both sides of Williamsfield Harbor, making the coast line for 

 two or three miles. The horizontal surface of these constitutes a bench 

 against the line of back coast hills, here composed of yellow Pliocene 

 marl. In places in this vicinity the Soboruco is backed by swamps 

 lying between it and the hills. These swamps may have once been 

 lagoons attending the landward side of the Soboruco when it was a reef 

 in the sea. On Plate XXVIII. is an illustration of the Soboruco bench 

 in this vicinity, which shows in the foreground the jagged indurated 

 surfaces of the rock, and in the middle ground and distance the under- 

 mining bluff and w^ave indented incisions. Plate XXIX. shows the 

 composition and structure of the Soboruco, here made up of large in- 

 dividuals of reef making corals. The Soboruco of the east end of the 

 island is unconformable upon the Montpelier white limestones, the 

 Bowden, and the Manchioneal formations. 



The straight east coast of the island which extends to Point Morant 

 is reached after passing Northeast Point. At the mouth of Priest- 

 man's River a cross section exposing the entire thickness of aii elevated 

 reef is seen on both sides of the river for a considerable distance back 

 from the sea, where it forms a vertical scarp some 25 feet in thickness. 

 It overlies the yellow Manchioneal marls in which the present stream- 

 way is situated. This exposure of Soboruco is made up of gigantic 

 reef coral heads and its surface constitutes a wide flat bench extending 

 from the sea to the back coast mountains. The top of this old reef is 

 about 70 feet above the sea, an altitude equal to the level of the Hope- 

 well old reef formation on the west side of the north coast, and the 

 greatest height at which any undoubted reef rock is known to occur 

 on the island. 



The Priestman's River terrace extends a considerable distance towards 

 Black River. South of the latter as far as Holland Bay its level is 

 continued by a baselevelled plain underlain by the older limestones, 



^ The species of corals from the localities mentioned are all given in the paleon- 

 tologic portion of this pnpcr. 



