OF SANTO DOMIN"G^O. 



103 



CHAPTER VII. ■ - 



POSTPLIOCENE, ORCOAST FORMATION. 



A large proportion of the coast is fringed by a formation mucli more modern than 

 the preceding, usually as a narrow strip, though in some places extending back several 

 leagues. West of Azua only does it run into the interior, covering in this case at 

 least a part, possibly the whole of the San Juan Valley, and not improbably a portion 

 of the valley of the lakes. This, which may be called the coast formation, consists of 

 limestones, the debris of old coral reefs, shore gravels brought to the coast by rivers 

 still existing, beds of conglomerate resulting from the solidification of the last member, 

 and lastly, argillaceous and sandy beds having the same origin but owing their finer 

 texture to the greater distance from their primary soui'ce. - : • • 



Along the whole north coast the formation is represented exclusively by the lime- 

 stone, usually horizontal, though occasionally having a very low seaward dip. This 

 inclination is most marked east of Puerto Plata, and especially about Cabarete where 

 reefs and shoals run out many hundreds of feet, striking parallel with the general 

 trend of the coast and dipping at angles often not higher than 5°, and rarely as high 

 as 10°. At the eastern end of Samana, at Puerto Frances, there is a little horizontal 

 patch raised but a few feet above the sea level and bearing the brunt of the Atlantic 

 waves. It is honey-combed, caverned and worn into points and pinnacles so sharp 

 that it is diflGLcult to walk on the parts left bare by the waters. At one or two points 

 on the northern coast of the same peninsula, as for instance at point Cabron, the blue 

 Cretaceous limestone is broken down into angular fragments, such as would fall from 

 the face of a clitf, and are recemented by a stalactitic cement of this formation usually 

 of a pinkish color, making a pretty contrast. In the same vicinity wherever this 

 breccia does not occur the whole rock is more or less of the same color, although on 

 the southeast coast between Puerto Frances and Cape Balandra it forms bluffs inland 

 of a nearly pure white rock. 



Beginning at the end of the hills of the central chain where they reach the east 

 coast, the same limestone commences again and borders the entire southeast coast of 

 the Island to a point between the ISTigua and J^izao Rivers. Here it is so nearly 

 horizontal that no perceptible dip occui's. The whole mass seems to have been 

 elevated bodily. JSTo foldings or even undulations can be detected. The lithological 

 character is also exceedingly constant. The rock is evidently the bottom of a coral 

 sea. It contains a few corals, almost always of the massive forms, though these are 

 not generally disseminated, but occur rather in spots on the sites perhaps of pieces of 

 ancient reef. Occasionally in these collections a branching species may be found, but 



