Hawkins — Notes on the Geology of Rhode Island. 439 



while there is little or no evidence of the relative age of 

 this granite gneiss series where it is adjacent to the green 

 schists of Little Compton, R. L, it is the writer's opinion 

 that they do intrude and include these schists. 



The pre- Carboniferous age of the Northbridge granite 

 gneiss is established beyond doubt by its relations to the 

 Carboniferous sediments in the area south of Woonsocket. 

 From the latter city, a long narrow area of siliceous sedi- 

 mentary rocks, the southward extension of the "Belling- 

 ham Series" of Warren and Powers, 6 called by the 

 present writer the Woonsocket Basin Series, mentioned 

 and outlined in the Report of the . Natural Resources 

 Survey of Rhode Island for 1909, and so named, extends 

 from the Massachusetts line for a distance of thirteen 

 miles into Rhode Island. These sedimentary rocks 

 resemble the Carboniferous sediments of the Narragan- 

 sett basin (compare analyses in Table I), although they 

 are much more thoroughly metamorphosed than the latter, 

 being in places changed into biotite schists ; but their age 

 is established by a few fragmentary imprints of stems of 

 Cordaites, obtained by the writer from a railroad cut just 

 west of Woonsocket and northeast of Woonsocket Hill. 

 The structure of the granite gneiss bordering this basin, 

 as indicated by the dip and strike of its foliation, shows 

 that the Woonsocket Basin sediments occupy the eroded 

 summit of an anticline with slightly northward pitching 

 axis in the Northbridge and Milford granite gneisses (see 

 map, fig* 1). For a distance of several miles south of 

 Woonsocket the border of the sediments is indistinguish- 

 able from the granite gneiss of the side of the basin, the 

 former grading into the latter through arkosic beds 

 (which are best shown on the west side of the basin just 

 north of West Greenville, R. I. ) . South of the Waterman 

 Reservoir, north of North Scituate, is exposed a great 

 thickness of Carboniferous sedimentary arkoses, basal 

 beds of the series, containing large amounts of blue 

 quartz grains which are especially typical of the Milford 

 granite gneiss and at times are also present in the 

 Northbridge. The Carboniferous sediments have been 

 removed by erosion south of North Scituate, although the 

 structural basin persists to South Scituate, where on 

 account of the pitch of the anticlinal axis, it disappears. 



6 Warren and Powers, op. cit., 448-449. 



