CHAPTER V. 



METAMORPHIC AND IGNEOUS ROCKS. 



By F. C. Calkins. 



METAMORPHIC SEDIMENTARY ROCKS. 



All the metamorphic sedimentary rocks represented in the collection 

 made in the Dominican Republic belong to the basal complex in the prov- 

 inces traversed by the Cordillera Central and in Samana Peninsula. They 

 do not include all the rocks that are here assigned to the basal complex, 

 nor some of the distinctly tuffaceous sediments mentioned on page 55, 

 which may be Cretaceous. The term "sedimentary rocks" as here used 

 includes tuffaceous material. 



The most intensely metamorphosed specimen is D. C. 23a, a silvery- 

 looking micaceous schist from the Province of La Vega. This rock has 

 undergone "regional" metamorphism, and seems to be much older than 

 Cretaceous. The same may be said of the marbles from Samana Peninsula 

 and the Province of Santiago, which are gray to white and are markedly 

 crystalline. These marbles contain mica and probably other metamorphic 

 minerals, which cause certain layers to stand out in relief on weathered 

 surfaces. A much lower degree of alteration is shown by a reddish lime- 

 stone, supposedly Cretaceous, from the vicinity of Bani. 



There are several specimens of pale-green chloritic schist that resemble 

 altered tuff, especially R. 6, which exhibits vestiges of brecciated texture. 



The absence of sediments resembling quartzite is rather noteworthy. 

 Specimens of metamorphic sedimentary rocks. 



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