444 Hawkins — Notes on the Geology of Rhode Island. 



with a pitching geo- synclinal and -anticlinal structure of 

 Alpine proportions in southern and western Rhode Island 

 (see map, fig. 1). The largest and most clearly denned 

 fold in the granite, concerning whose anticlinal or syn- 

 clinal nature no conclusion can be reached, on account of 

 insufficient and ill-defined exposures, curves sharply 

 around the resistant mass of the Preston gabbro in the 

 adjacent part of Connecticut. The latter gabbro mass is 

 included in the granite gneiss ; hence the observed phe- 

 nomena might be attributed to actual flow of the granite 

 about the inclusion, or to later shear effects about the 

 resistant gabbro body during regional metamorphism. 

 The present writer favors the latter hypothesis because 

 the foliation in the granite gneiss seems to be connected 

 with the presence of feldspar phenocrysts and augen best 

 explained as secondary in origin due to such regional 

 deformation. If this latter supposition be true, then a 

 kind of deformation greatly different from and probably 

 vastly older than the folds of the Appalachians to the 

 westward is indicated. This deformation swings east- 

 ward toward the Narragansett Basin; it then turns 

 northward and extends in this direction through northern 

 Rhode Island and into Massachusetts, and northeastward 

 apparently to Boston Bay, forming a complicated series 

 of synclinal and anticlinal folds, one of the latter, after 

 deep erosion of the mountain mass in pre-Carboniferous 

 times, being filled with the Carboniferous sediments of 

 the Woonsocket Basin. It appears that the Carbon- 

 iferous sediments of the Narragansett Basin were sim- 

 ilarly laid down at this time in a more deeply and widely 

 eroded structural basin between the mass of deformed 

 granites just described and the very similarly deformed 

 granites of the eastern side of the Narragansett Basin. 

 Along the foliation caused by the deformation the West- 

 erly granite 8 found its way upward, the intrusion fol- 

 lowing an east-west line along the Connecticut and 

 Rhode Island shore and appearing probably in the small 

 north-south granite sill at Foster, and farther north, and 

 possibly in the vicinity of a small outcrop of a granite of 

 similar appearance on the Rhode Island-Massachusetts 

 line. The "Westerly granite is massive and does not 

 share in the gneissic structure which is so typical of the 



8 For a new analysis of the Westerly granite, see Table III, analysis 

 no. 23. 



