GEOGRAPHIC FEATURES OF THE PLEISTOCENE PERIOD. 



87 



so that while Cuba was reduced in size it was not so dismembered as in 

 the Matanzas epoch of subsidence. 



The elevation of the island succeeding the formation of the Zapata 

 loams and gravels appears to have reached about 200 feet above the 

 present altitude, thus enlarging the Cuban mass. This elevation is in- 

 ferred by the depth of the canyons which form the outlets of the harbors 

 and extend across the slightly submerged coastal shelves. During this 

 epoch of elevation the amount of erosion was considerable, but it did not 

 exceed more than from one-fifteenth to one-fiftieth of that of the pre- 

 Zapata epoch. 



Another subsidence followed the excavation of the outlets of the har- 

 bors, carrying the island down to depths necessary to allow the forma- 

 tion of the terraces, and during the subsequent rise the building of the 

 modern coralline reefs ; but these two subjects will be considered by 

 themselves. 



Terraces, Sea-caves and Kifts. 



north coast of the island. 



The most elevated terraces seen are those on Pan de Matanzas, carved 

 out of the Tertiary limestone at an elevation between 1,000 and 1,100 

 feet above tide, as shown in figures 



7 and 8. The summit of the moun- ^^^ "" 



tain ridge rises to 1,277 feet. At 

 about 700 feet there is another con- 

 spicuous terrace, and between 350 

 and 400 feet the low divide between 

 the peaks corresponds to another 

 water-level. The highest terrace is strongly marked on the northern 

 side of the more western mountain. At the level of the terraces there 

 are also sea-caves and occasional rifts (see a, figure 8) or narrow ravines 

 through the ridge which may not be more than a few hundred yards 



across. The deep depression be- 

 tween the Pan and the western 

 ridge has been broadened by late 

 current action. There are many 

 such rifts, and they mark tide- 

 level as plainly as the terraces 

 record the deserted shores. 

 On both sides of the ridges there are baselevel plains at about 400 feet^ 

 and out of that on the northern side of the Pan, the Yumuri valley was 

 excavated. These baselevel plains are of more recent origin than the 

 Matanzas epoch, but older than the Zapata. At the outlet of Matanzas 



Figure •]. — Pan de Matanzas from the South. 

 Horizontal and vertical scales the same. 



■Pctn. cLeAfatamcLS 



Figure S. — Pan de Matanzas from the North. 



Showing terraces and sea-caves (the dark 

 spots) and rifts at a and c. 



