1897-98]. LATE FORMATIONS AND GREAT CHANGES OF LEVEL IN JAMAICA. 353 



tufaceous deposit is common on these rock islands. Sea caves excava- 

 ted in the walls of these islands were also seen. These terraces in part 

 mark the pauses in the post-Liguanea elevation of Jamaica. 



Coral Reefs. — As has been pointed out, the post-Liguanea elevation 

 reached an altitude of 120 feet, or possibly 200 feet on the northern side, 

 higher than now, as the streams cut channels to this depth, which have 

 since been drowned, (see page 350). Then followed the episode of 

 depression to about 25 feet below the present altitude, when coral reefs 

 and modern limestones began to be formed, which since then have been 

 raised from 10 to 25 feet, or locally more. The narrow reefs occupy a 

 considerable portion of the coast line on the northern side of the island, 

 and were specially studied to beyond Montego Bay. Where the corals 

 form the coast line, there are no beaches, except in coves. The floor of 

 Montego Bay is covered with a beautiful garden of corals, of both 

 massive and branching varieties. In part, the coral reefs which are 

 raised to form the coast limestone, may be replaced by shell beds 

 (Brown), and it is possible that some of the low fossiliferous shell bear- 

 ing marls seen west of Montego Bay belonged to this modern episode, 

 that is those beds which were not succeeded by other late formations. 

 Still some of the coast limestones are the remnants of the older forma- 

 tions, such as those near Orange Cove and Hopewell. 



Beaches. — The formation of the beaches is an interesting feature, as 

 they are the exact reproduction of the deserted beaches of the Great 

 Lake region of North America, but unlike the sandy Atlantic beaches at 

 least south of New York, and many other places noticed north-east of 

 that city. They form ridges from three to five feet above the sea, with 

 depressions behind them, and in composition they are made up of sand 

 and gravel, often somewhat coarse, derived from the harder portions of 

 the White Limestones, or older rocks brought down by the streams. 

 Along the Atlantic coast, all of the gravel has been ground to sand or 

 very fine material, before reaching the present coast, and the beach 

 ridges are not so sharply defined as in Jamaica. The Jamaican ridges 

 appear to be due in part to the presence of the gravel in large quanti- 

 ties, and also to the almost complete absence of tides. In the Lake 

 region the gravel has been derived from the boulder clay. The ridges 

 are often not more than 25 feet, or they may be 200 feet across their 

 crests. They are well developed between Hope Bay and Low Layton 

 volcano, also west of Buff Bay and at Annatto Bay. West of Buff 

 Bay a good representative of raised beaches may be seen. 



Another interesting beach is that in front of Kingston Harbour 



