282 BULLETIN OF THE 



III. RESUME AND CONCLUSION. 



The known geologic history of Cuba may be stated as follows : — 



1. In Pre-Tertiary times an old land existed, almost as extensive in 

 area as the present island. Whether this old land was insular, multi- 

 insular, or connected with other Antillean areas or the mainland, I will 

 not speculate. The submarine topography indicates that it was not. 

 Its composition ami structure, however, show that it was an area of 

 active vulcanism accompanied by great metamorphism and eruptive 

 flows. If there are preserved in it any traces of Pre-Tertiary sedi- 

 mentation they are largely overwhelmed and almost obliterated by the 

 vulcanism, metamorphism, and later erosion. Paleozoic, Triassic, Jurassic, 

 and Cretaceous sediments have been reported by De Castro ^ in localities, 

 but their physical history is unknown. 



2. It is also certain that during Tertiary times, embracing the Eocene 

 and Xeocene periods, this ancient nncleal land, with all of its geographic 

 outlines, completely subsided beneath sea level, and that it was covered 

 with limestone sediments, which were organically derived from the sea, 

 not the island itself, for there is no semblance of limestone material in 

 the rocks of the Pi'e-Tertiary land which could have furnished material 

 for the Tertiary rocks. That this subsidence was profound we may 

 reasonably conclude from the thickness of the older nucleal region, now 

 visibly covered by the limestone beds, which have been horizontallv ele- 

 vated to a heiglit of at least two thousand feet. In other words, the 

 Pre-Tertiary subsidence may have been at least to an equal depth. 

 Durin": this epoch of Tertiary subsidence a thousand feet of Tertiary 

 limestone were accumulated over the old nucleal island. 



3. After the close of Tertiary times the Tertiary sediments were 

 greatly warped and folded, concurrently with an emergence of the land 

 from the sea. This movement was orogenic. 



4. Following this began the epoch of epeirogenic or regional elevation. 

 During' Pleistocene time the island underwent the first of these upward 

 impulses to its present height, with the exception of about six hundred 

 feet represented in still later movements. This older Pleistocene or 

 Yunque elevation raised the main area to a height of at least two thou- 

 sand feet in its eastern half, and fifteen hundred feet in its western half. 

 How much higher it extended we cannot tell, so great has been the 

 erosion. This elevation was so rapiii and general thi-oughout the island 



1 Op. cit. 



