674 



STRUCTURAL GEOLOGY OF NORTH AMERICA 



glomerates and sandstones. They have been involved in strong orogeny 

 along with the Cretaceous strata and are separated from the middle and 

 upper Eocene by a major unconformity. 



Middle and upper Eocene are found in all the provinces of the island. 

 In this series occur fine conglomerates, sandstones, limestones, marls, and 

 chalks. The Eocene deposits indicate a progressive deepening of the 

 depositional area. 



The Oligocene is very well represented. At least seven horizons have 

 been recognized in various parts of the island ranging from the lower 

 Oligocene to an Oligo-Miocene transitional one. It carries a large and 

 well-preserved fauna. The formation is predominantly lime in various 

 stages of induration, and coral reefs are common. The lowest known 

 Oligocene member is a marly shale. Roth Eocene and Oligocene contain 

 shale and some marl members that would afford admirable cap rock for 

 petroleum reservoirs. 



There was a continuity of deposition from the Oligocene into the lower 

 Miocene. During this period Cuba was submerged except for a few 

 islands. The general aspect was probably not greatly different from that 

 of the Lesser Antilles today, that is, a series of small islands. The deposi- 

 tion of this period is predominantly a hard limestone which has been 

 named the Guines. This limestone forms an interrupted collar nearly 

 around the island as far east as Camaguey, and crosses the island in two 

 low, flat saddles, one in Matanzas and the other in western Camaguey 

 Province. It lies unconformably upon almost all the preceeding forma- 

 tions. Except where folding has subjected it to erosion, the Guines lime- 

 stone masks the older formations. Geological data are here dependent on 

 geophysics and core drilling. 



Deposits of mid- and late Miocene age are limited to a few estuaries 

 that were inundated at the time. They are best developed around Matan- 

 zas Ray, Santiago de Cuba, and Manzanillo, and extend but a short dis- 

 tance inland from the coast. The remaining Tertiary deposits are but 

 small local patches along the coast. 



The Pleistocene record is confined to well-developed terraces in several 

 parts of the island and to a few scattered unimportant deposits along the 

 coast. 



The Upper Cretaceous and the Tertiary, except for the lower Eocene, 

 carry large and well-preserved faunas. These consist of Foraminifera, 

 Radiolaria, corals, echinoids, and mollusks. A noteworthy feature of the 

 Cuban fossil faunas, of both the Cretaceous and Tertiary, is that they are 

 definitely not North American. They are tropical faunas and form a part 

 of a Caribbean unit. This unit is in turn a part of the Mediterranean or 

 Tethyan fauna of the Old World. The Aptychus beds are a striking illus- 

 tration. Deposits with the same fauna, of the same lithologic aspect, at- 

 tributed to the same age are found in the Cape Verde Islands and in 

 Persia. Another equally striking illustration is that what appear to be the 

 same species of echinoid occur in the Eocene of both Cuba and Egypt. 



Igneous Rocks. Roth intrusive and extrusive rocks occur in Cuba. The 

 intrusives are both acid and basic. The acid rocks for the most part occur 

 in the southern half of the island. This is illustrated by a large granite 

 intrusion that borders the Trinidad Mountains on the north and by the 

 granite and other acid intrusions on the southern slope of the Sierra 

 Maestra. These intrusions are relatively not extensive. 



In contrast, the basic intrusions for the most part lie in the northern 

 half of the island and are by far the more prominent type. Most of the 

 basic rocks are serpentine. There is no agreement on the age of these 

 intrusions. Most of them occur in the Cretaceous terrane and appear to be 

 post-Cretaceous. Two are known in an Oligocene terrane and appear to 

 cut the limestone of that age. The very extensive intrusions of serpentine 

 and associated rocks in Santa Clara Province are thought to have accom- 

 panied the post-middle Eocene period of overthrusting. 



Lower Cretaceous volcanic activity was considerable. This is evidenced 

 by thick series of tuffs, volcanic breccia, and flows. At least 6000 feet 

 accumulated in the southern part of Habana Province. 



Except in Oriente Province, there is but little effusive volcanic material 

 in the Tertiary. In that province the middle Eocene deposits are largely 

 basaltic. The Sierra Maestra is composed of rocks of this material. Taber 

 (1934) estimates the thickness "to be over 4500 meters and possibly as 

 much as 6000 meters." 



The upper Eocene in Oriente Province is also basaltic in part, but much 

 less so than the middle Eocene. In Matanzas Province there are thin beds 



