302 GEOLOGY OF THE IJ^AERAGANSETT BASIK 



coarse conglomerate ridges. The largest of these are on the eastern side of 

 the region here described. The great ridge west of the Hanging Eock 

 ridge is composed almost entirely of trap, but shows toward the north, on 

 its eastern face, toward the upper portion of the ridge, a number of long 

 inclusions of the quartzitic slate which it in general intersects. This 

 quartzitic rock is also shown on the western side of the same trap ridge, 

 near its highest elevation; it also is exposed on the eastern side of the next 

 ridge westward, and probably once occupied the valley separating the 

 two ridges. This western ridge is also composed almost entirely of trap 

 rock, the dike rock forming the top and the entire western face of the 

 ridge. Toward the north a lower ridge of trap is found between the 

 other two. West of the western of the lofty trap ridges is the reservoir. 

 At a very low stage of the water in the reservoir an island is exposed 

 which is composed chiefly of the quartzitic sandstone, but which also 

 shows trap on the western side. Crossing the eastern brook entering the 

 reservoir from the north, a trap dike is encountered, then quartzitic slate, 

 then more trap. Northward these ti^ap exposures increase in elevation 

 and form the eastern side of a low ridge lying approximately along the 

 middle of the reservoir valley. Near the northern end of this region 

 inclusions of the quartzitic slate can be seen in the trap. The slate is found 

 also west of thistrap ridge. 



The Paradise-Hanging Rock valley is undoubtedly occupied alto- 

 gether by the quartzitic slate, intersected by coarse trap, the quartzitic slate 

 forming the valleys and the trap the ridges. 



In the present state of knowledge on the subject, no place for these 

 quartzitic schists can be found in the Carboniferous series. They either 

 overlie or underHe these rocks, and owing to their resemblance to rocks else- 

 where with confidence adjudged pre-Carboniferous, they are also considered 

 older than Carboniferous, and are beHeved to have been left as a great 

 triangular mass, bounded east and west by fault planes along which the 

 Carboniferous strata dropped down. Whether the diabasic rock preceded 

 or anteceded the period of deposition of Carboniferous rocks is not known. 

 Attention should, however, be drawn in this connection to the frequency of 

 dike action in the pre-Carboniferous shales of the Newport Neck region^ 

 and to a less degree in the green pre-Carboniferous rocks of Sachuest Neck 

 and in the Conanicut Carboniferous shale series. 



All of these interpretations of the geological structure of the exposures 



