ARKOSE OF WESTERN BORDER OF BASIN. 377 



extended from the shore exposures near Saunderstown and the Bonnet over 

 unbroken areas as far west at least as McSparran and Tower hills, and 

 covered even Boston and Little necks as far south as Narragansett Pier. 

 The basal Carboniferous of these regions probably rested upon an extensive 

 pre-Carboniferous granite area. In consequence of folding, the pre-Carbon- 

 iferous granite was raised toward the west of the Tower and McSparran 

 escarpments and along the area now occupied by Little and Boston necks, 

 while the Carboniferous was lowered into a synclinal tract lying between 

 these two regions along the Cove and the Pattaquamscott, and was by 

 later denudation severed from the Carboniferous east of Boston Neck. 



There is undoubted evidence of faulting in the Carboniferous area 

 east of Boston Neck. The temptation is very great to account for the 

 alternation of granite and Carboniferous rock, in part at least, by faulting. 

 Some of the occurrences of detrital, presumably Carboniferous, masses in 

 the granite areas, however — for instance, those at Narragansett Pier and at 

 Clump Rocks light-house — could be explained as cases of Carboniferous 

 rocks once overlying the granites, but subsequently broken up and folded 

 in with the granites, or faulted down into them by later disturbances, only 

 remnants of the Carboniferous rocks remaining, owing to denudation. Or 

 else they must be considered as fragments of Carboniferous rocks cauo-ht 

 up by post-Carboniferous granites. Unfortunately, post-Carboniferous 

 granites are not known anywhere in the field here investigated. 



Where the Carboniferous rocks are traversed by dike-like rocks, the 

 latter on closer examination almost invariably turn out to be pegmatitic in 

 structure, so that the pegmatites are, as a rule, readily identified as post- 

 Carboniferous. These coarse pegmatites traverse the Carboniferous rocks 

 rather frequently south of Hazzard's quarry and Saunderstown as far as the 

 region northwest of the cove, and are especially well exposed at Watsons 

 Pier (PI. XXV; see also Pis. XVIII and XIX, pp. 242, 244). But the 

 mass of pegmatite southwest of Wesquage Pond, on the hill, seems to 

 belong to the Boston Neck series of exposures, and appears to connect 

 with pre-Carboniferous granites as though the latter were in reality post- 

 Carboniferous. The conditions are perplexing and require more study. It 

 may be that careful observations might lead to more definite results, but 

 to the writer conclusive data seem to be lacking, although he considers the 

 general mass of granites as pre-Carboniferous. 



