GEOGRAPHIC FEATURES OF THE CRETACEOUS. 75 



In the Yumuri valley, east of Colon, in the Santa Clara district, etcetera, 

 these Cretaceous deposits are seen in narrow belts, where they have been 

 exposed b}^ denudation. 



GEOGRAPHIC FEATURES OF THE CRETACEOUS PERIOD. 



The general absence of sedimentary and calcareous formations beneath 

 the Cretaceous sands and the widespread foundation of igneous rocks 

 under them lead to the inference that Cuba was subjected to extensive 

 erosion during at least the earlier Cretaceous period, if not before. How- 

 ever, the topography then produced has been generally obliterated so as 

 not to be prominent in the later physical conditions of the Antillean region. 

 The pre-Cretaceous baselevel character of Cuba bears a close resemblance 

 to the pre-Cretaceous baselevel plains of the southern states, which were 

 composed of Archean rocks and extended far seaward of their present 

 limits. Indeed, it would not be a violent suggestion to suppose that the 

 continent extended to Cuba just before the commencement of the Cre- 

 taceous period. 



Whether the post-Cretaceous elevation was at the close of that period 

 or in the earlier Eocene has not been determined, for some of the semi- 

 crystalline limestones provisionally grouped with the Cretaceous forma- 

 tions may belong to the later period. The degradation which affected 

 the Cretaceous accumulations was much less energetic than that preced- 

 ing the deposition of these rocks, as the sands and other rocks, although 

 easily denuded, are yet both extensive and of considerable thickness- 

 The preservation of the soft Cretaceous deposits is in strong contrast to 

 the general removal of hard rocks, like those of Trinidad mountains, dur- 

 ing the earlier period of erosion. 



Where not covered by the Tertiary limestones the Cretaceous forma- 

 tions are generally concealed beneath the black or mulatto, residual soils 

 formed by the decay of the calcareous rocks or the accumulation of the 

 more recent sands and gravels. 



Eocene and Miocene History. 

 local geologic characteristics. 



In general. — Resting upon the greatly disturbed and eroded surfaces 

 belonging to the Cretaceous sj^stem there are extensive beds of limestones 

 with which some mechanical deposits are associated. These Tertiary 

 rocks constitute widespread formations of considerable, but variable, 

 thickness, as they have been subjected to enormous denudation subse- 

 quent to their deposition. 



While these Tertiary beds can, upon paleontologic grounds, be sepa- 



XI— Bull. Geol. Soc. Am., Vol. 7, 1895. 



