218 PROCEEDINGS OF THE PALEONTOLOGICAL SOCIETY 



though incomplete, are sufficiently exact to block out the major features of 

 the topography and geology. 



The Cordillera Central, a rugged mountain system, extends from the eastern 

 end of the island westward into Haiti. It is flanked on the north by the 

 Cibao Valley, a fertile valley extending from iSaman^ Bay to Manzanilla Bay. 

 The Cordillera Setentrional, containing some peaks 4,000 feet high, lies be- 

 tween the Cibao Valley and the Atlantic. South of the Cordillera Central a 

 coastal plain borders the Caribbean as far west as Calderas Bay. The Azua 

 Plain and the great Valley of San Juan separate the Cordillera Central 

 from the mountains of the Sierra de Neiba and the Sierra de Martin Garcia. 

 Lake Enriquillo, 144 feet below sealevel, occupies part of the depression called 

 the Enriquillo Basin, between the Sierra de Neiba on the north and the Sierra 

 de Bahoruco on the south. Little is known of the southern peninsula. 



The basal complex, consisting chiefly of metamorphic and igneous rocks, is 

 similar to the corresponding formations of Cuba, Porto Rico, and the Virgin 

 Islands. It makes up a large part of the Cordillera Central and Samana 

 Peninsula. Rocks of known Cretaceous age occur in the southern part of the 

 Cordillera Central, between Santo Domingo City and Azua, and in the faulted 

 front range of the Cordillera Setentrional near Demajagua. 



The Tertiary formations and their supposed equivalents are named in the 

 correlation table. All the names of Dominican formations in the table are 

 new except the Cercado formation and the Gurabo formation, which were 

 very recently proposed by Dr. Maury .^ Lower and Middle Eocene sediments 

 appear to be lacking in Santo Domingo, but from Upper Eocene upward there 

 is a nearly complete sequence. Limestone of Upper Eocene age is widely 

 distributed on both sides of the Cordillera Central, but appears to be most 

 extensively developed in the mountains of Barahona Province. Two forma- 

 tions of Oligocene age in the north have been given names, and rocks of the 

 same age have been found also in the south. The Lower and Middle Miocene 

 are represented by the thick series of conglomerates, silts, and coralliferous 

 limestones comprising the Yaque group, and the upper Miocene, not at present 

 known elsewhere in the AVest Indies, appears to have left its trace in the 

 gypsum, salt, and clastic sediments of the Las Salinas formation. The Las 

 Matas gravels are supposed to be of Pliocene age, but no fossils have been 

 found in them. 



Pleistocene deposits — gravels, soft limestones ("caliche"), and raised coral 

 reefs and beaches — are widel.v distributed around the island. 



In addition to rocks of igneous origin included within the basal complex, 

 there is a considerable variety of eruptive and dike rocks, tuffs, and ag- 

 glomerates, the youngest of which is not older than Pleistocene. These late 

 igneous rocks are most conspicuous in the Province of Azua. 



Faults are numerous and outline many of the topographic features. Fold- 

 ing, except in the basal complex, is less important. 



C. .T. Manry : Science, new series, volume 50, December 20, 1019, page 591. 



