171 



ox TlIK TOPOGRAPJIY ANY) CEOLOGY 



The cle\^ation of Sainana is unimportant, I'esemljliiig- in this respect the eastei'n 

 end of the main chain, to which it also bears a greater resemblance in the details of 

 its structure than to the more centi'al portions. The highest points and the region of 

 greatest disturbance are alike at and near its eastern end, and the fact of the Cre- 

 taceous strata approaching a more nearly horizontal position towards the west, 

 together with the greater development of the Tertiary in the same direction, seem to 

 indicate that in the yet unexploi-ed eastern end of the Monte Cristi range at most but 

 a trifling amount of the older formation will be discovered, - 



Immediately adjoining the Gran Estero the land is low, much of it is marshy, 

 and the rocks are covei'ed with river alluvium ; but approaching Port Jackson, 

 Tertiary hills came in, and the only rock found is a very compact limestone more or 

 less nearly white, usually with a pinkish tinge, and containing Orhitoides. It is 

 nearly horizontal, with a trifling northern dip. Only in the higher hills between this 

 point and Canitas are any of the older rocks discovered, and here they foi-m but a 

 narrow belt. East of Port Jackson this limestone gradually narrows and finally runs 

 out to a point on the coast underlaid by the uptilted Cretaceous ; but in the interioi" 

 it forms a series of basins more or less interrupted and flanking the northern face of 

 the highest ridge. It is thei-e horizontal and occasionally fossilifei'ous. Along the 

 south coast the formation is continued around the west end of the hills and borders 

 their southern base, past Canitas and los Robalos almost to Punta Mangle. Here it 

 is represented by a nari'ow strip, but instead of the limestone, an older member makes 

 its appearance. The Cluayubin shales with all of their ordinary characteristics form 

 all of the flat or low I'olling land between the base of the hills and the shore of the 

 bay. 



Owing to the roughness of the surface and the scanty population thei'C is no i"oad 

 across the island between the Canitas trail and one which crosses from the mouth of 

 the Limon nearly south to los Robalos. At the former point the rock is a dark blue 

 limestone, semi-crystalline, and dips north about 30°. Unlike the Cibao range, the 

 greater part of Samana is made up of limestone and mica slate, both of which rocks 

 are I'are elsewhere and the latter is especially exceptional. Abundant proof exists 

 that the mica slate is always sedimentary in origin. It is always interstratified with 

 rocks of that class, and one .curious instance occurs east of Santa Barbara where in 

 the same block the transition occurs from this to limestone within a couple of feet. 

 But to return to the section. In following up the ridge parallel with the river the 

 dip of the strata becomes higher and beds of sandstone and mica slate appear, gradu- 

 ally becoming vertical and then assuming a southern dij). Passing the anticlinal, a 



