Hawkins — Notes on the Geology of Rhode Island. 115 



Sterling and the Northbridge, and forms welded contacts 

 at times across the gneissic banding of the former. But 

 the field evidence shows clearly that the enormous pre- 

 Carboniferous deformation, above described, affected the 

 Sterling, Northbridge, and Milford granite gneisses all 

 alike, together with the ancient quartzites and basic rocks 

 included in them. It is therefore indicated that all of 

 these granite gneisses are of pre-Oarboniferous age. 



Loughlin has sought to demonstrate the post-Car- 

 boniferous age of the Northbridge granite gneiss in 

 northeastern Connecticut, stating that it intrudes the Put- 

 nam gneiss, which he considers to be Carboniferous, 9 

 since it "has been traced northward into Massachusetts, 

 where it is represented by the Bolton gneiss. This rock 

 at Worcester, Mass., has been shown by Perry and 

 Emerson to lie conformably with quartzite and fos- 

 siliferous phyllite of known Carboniferous age, and is 

 regarded by them as Carboniferous. " But geological 

 conformity seems to have little value in this region as a 

 means of establishing identity of age. This is brought 

 forcibly to our attention by the discovery of Carbonifer- 

 ous sediments on the eastern slope of Woonsocket Hill, 

 in perfect apparent conformity with the finely exposed 

 white quartzite of Cambrian or possibly earlier age 

 which forms the backbone of the hill. Moreover, the 

 writer, as already stated, has found the Northbridge 

 granite gneiss in pre-Carboniferous relations along the 

 Woonsocket Basin, and has followed it from thence west- 

 ward through the northwestern part of Rhode Island into 

 Connecticut, throughout which area, though the outcrops 

 are widely scattered and the granite gneiss is modified in 

 different ways, it preserves its essential characteristics. 

 At a point a mile south of the hamlet of West Gloucester, 

 R. L, on the Putnam Pike, at the base of the southwestern 

 slope of a hill of Northbridge granite gneiss, the latter 

 may be seen as apparently well-defined sills in a quartz- 

 ite. This quartzite is the Plainfield quartz schist, 10 which 

 Rice and Gregory 11 regard as "only a prominent and 



9 Loughlin, G. F., Conn. State. Geol. and Nat. Hist, Surv., Bull. 13, 146- 

 148, 1910. This formation is mapped by Emerson (op. cit., 79) as gneiss 

 of "Age Undetermined." 



10 Westboro ("Grafton") quartzite of Emerson, which he finds to lie 

 unconformably upon the Northbridge granite gneiss. 



n Eice, W. N., and Gregory, H. E., Conn. State Geol. & Nat. Hist. Surv., 

 Bull. 6, 134, 1906. 



