452 Loughlin — Intrusive Granites and Associated 



writer has not visited every outcrop in the area, but has studied 

 the continuous exposures along the shore of the Bay, and all 

 the exposed granite contacts, and has examined thin sections of 

 the several rock types represented. 



Granite. — The various granite exposures include types iden- 

 tical in texture, mineral composition, and structural relations 

 with the several members of the Sterling series (including the 

 Westerly granite). These types and their relations to one 

 another are perfectly shown in the continuous granite ledge 

 which extends along the shore of the Bay from Narragansett 

 Pier for two miles southward. There is, in addition to the 

 types previously mentioned, a pegmatitic muscovite granite 

 which, as will be shown presently, is a contact phase of the 

 Sterling batholith, and is transitional into those pegmatites 

 which were previously interpreted as post-Carboniferous.* 

 Muscovite variations are present in the areas previously 

 described, but only in the Kingstown area are they conspicuous 

 and important. The feldspars of the muscovite granite are the 

 same in character and composition as those of the other types. 

 Schist inclusions are found in all the granite types. 



Normal and porphyritic Sterling granite, moderately to 

 highly gneissoid, are the prevailing types in the Kingstown 

 area. They comprise the body of the two-mile exposure along 

 the shore, and are exposed to the north on Rose, McSparren, 

 and Hammond Hills. Exposures are few at intervening points, 

 but are of the same types of granite. Small pegmatite dikes, 

 more or less muscovitic, are of common occurrence. The 

 northern part of this area also overlaps the southern limits of 

 the area previously mapped as pre-Cambrian (see p. 448) ; but 

 here again, owing to the general lack of local evidence, it is 

 impossible to choose between the differing interpretations. 

 Weathered schist inclusions are found on McSparren Hill, but 

 the presence of these alone is not convincing evidence. 



Definite evidence, however, is afforded east of Wakefield, at 

 the bend of Indian Run, in an exposed contact with quartz- 

 biotite schist, the metamorphic sediments of the Narragansett 

 Basin. The granite a short distance from the contact is red, 

 distinctly gneissoid, and irregularly porphyritic. Both its 

 megascopic and microscopic characters are identical with those 

 of the Sterling granite types of Connecticut. As the contact 

 is approached, the gneissoid character is obscure or absent, 

 and pegmatitic segregations are numerous. Distinct dikes of 

 pegmatite are also present, cutting the granite. The adjacent 

 schist is penetrated by many pegmatitic apophyses, most of 

 which follow the foliation plains. 



A mile eastward, along the southeast slope of Tower Hill, 

 *U. S. G. S. Mon. XXXIII, p. 377. 



