58 GEOLOGICAL RECONNAISSANCE OF THE DOMINICAN REPUBLIC. 



EOCENE SERIES. 



The Eocene rocks in the Dominican Republic, though widely distributed, 

 are almost exclusively limestones. Eocene limestone has been recognized 

 on both the north and south slopes of the Cordillera Septentrional, on the 

 south slope of the Sierra de Ocoa, and farther east, near Banf, in the 

 Province of Santo Domingo. Similar Eocene limestone forms a large part 

 of the Sierra de Bahoruco and the Sierra de Neiba, and probably also of 

 the Sierra de Martin Garcfa. Patches of limestone along the northern 

 slope of the Cordillera Central are supposed but not proved to be of Eocene 

 age. 



The relations of the Eocene limestone to the underlying deposits are not 

 definitely known, but limestone of Eocene age overlies deposits apparently 

 of Cretaceous age in the southern scarp of the Cordillera Septentrional near 

 Damajagua, northwest of Navarrete. At Las Lajas, on the Ferrocarril 

 Central Dominicano, between Bajabonico and Altamira, Eocene limestone 

 and sandstone apparently lie directly on sheared greenish hornstone and 

 banded slate of the basal complex. At this locality the rocks of the basal 

 complex are vertical and strike N. 40° W.; the Eocene beds have the same 

 strike, but dip southward about 60°. Other exposures in the vicinity of 

 Las Lajas show that a conglomerate immediately overlies the rocks of the 

 basal complex. Apparently the limestone and sandstone from which 

 Eocene Foraminifera were collected (see list on p. 105, station 8708) are 

 interbedded with the conglomerate. 



The only identified fossils that have been obtained from the Eocene of 

 the Dominican Republic are Foraminifera, which are listed on pages 105-106. 

 A sufficient number of recognizable species have been identified to establish 

 close correlations with the Eocene deposits of the Republic of Haiti and 

 of the other islands of the West Indies. 



The thickness of the Eocene limestones in the Dominican Republic is 

 unknown. In Haiti, according to T. W. Vaughan, a considerable thickness 

 of Eocene limestone occurs at Cape Haitien and in the mountains between 

 Plaisance and Ennery. Similar limestone composes the main mountain 

 mass from Ennery to Gonaives, thence to Artibonite Valley, and between 

 St. Marc and the north side of the Cul-de-Sac. For this Eocene limestone, 

 as exposed between Plaisance and Ennery, he proposes the name Plaisance 

 limestone. The type exposure is at an altitude of 705 meters up the 

 mountain from Plaisance toward Ennery. Typical fossils are Ortho- 

 phragmina, Conulites, and other Foraminifera. Southeast of Port-au- 

 Prince, on the road to Furcy, W. F. Jones 1 reports a thickness of at least 

 8,000 feet (2,438 meters) of limestone which he refers to the Eocene and 

 Oligocene. That any of this great thickness of limestone is younger than 



» Jones, W. F., Jour. Geol., vol. 26, p. 733, 1918. 



