DEFORMATIVE MOVEMENTS AND TtlElR RESULTS. 89 



Besides the epeirogenic and gentle uplifts, the coast ranges of Tertiary 

 rocks show much deformative movements since' the end of the Miocene 

 period, and in part much more recent, as shown by the character of the 

 elevated baselevel valleys. From the last subsidence Cuba has not yet 

 recovered, as the canyons forming outlets for the harbors are all far deeper 

 than could be formed at the level of the present outflows. To these sub- 

 jects reference is again made on page 90. 



Modern coralline Limestones or Reefs. 



The slightly submerged portions of the Cuban mass noted on page 69 

 are surmounted by coral reefs and mangrove islands. The most common 

 genera of corals are Meandrina, Astr<xa and Madre'pora. These reefs have 

 been brought above the surface of the sea during the last gentle uplift, 

 which in places appears to be still in progress. These raised reefs occur to 

 an elevation of 25 feet at Matanzas, but on the southern coast they do not 

 rise more than 10 feet, where they form the lowest terrace. The coral- 

 line rocks are fine, earthy, granular limestones, very porous, with a white 

 or stained color, and do not show bedding. While the mass is composed 

 of corals, there are very few or no mollusks or echinoderms in them. 

 These raised reefs have a structure quite unlike the Matanzas limestones, 

 which contain shells and only occasional masses of coral where fossils 

 are found. The reefs form only narrow fringes, varying from a few to 

 perhaps 200 yards wide. In front of the Trinidad mountains they are 

 absent, but the terrace is there present. 



Some Erosion Features. 



Very large, rounded blocks, having the appearance of erratics, occur 

 on the shores of Xagua fiord, but they are composed of the harder rocks 

 of the adjacent shores, rounded by the action of the waves, and stranded 

 upon the waterline. In many places north of Pan de Matanzas and in 

 other localities there are boulders of Tertiary limestone, of two feet or 

 more in diameter, resting upon the residual soil which conceals the 

 mother rock, but they appear to be the residual masses of the more 

 durable materials. Opposite Havana the decaying diorite gives rise to 

 rounded boulders of decomposition which resemble erratics. 



In the Yumuri and Trinidad valleys and elsewhere there are rounded 

 domes or hillocks from 100 to 300 feet high with the outlines of northern 

 drumlins. This external form is evidently the character assumed by 

 the incoherent strata subjected to atmospheric influences, irrespective of 

 latitude. Again, these hillocks form chains, with the outlines of the 

 osar, arising from the unequal erosion. 



