106 GEOLOGY OF THE NAERAGANSETT BASIS. 



to refer to the rocks, exclusive of the igneous intrusives, as the Blackstone 

 series. On lithological grounds, which have some support in the stra- 

 tigraphy, the series may be divided into the Cumberland quartzites, the 

 Ashton schists, and the Smithfield limestones. 



CUMBERLAND QUARTZITES. 



Bands of quartzite occur as discontinuous outcrops at several localities. 

 The principal of these is traceable from the southern side of Sneech Pond, 

 along the main street southeastward for a mile and a half in the village of 

 Cumberland Hill. The width of outcrop varies from 500 to 1,500 feet. 

 Another small exposure occurs on the same general trend 2 miles north of 

 Ashton. A broad belt of outcrops of the rock occurs hi the valley of the 

 Blackstone from Cumberland village southeastward. The quartzite is 

 interbedded with schists or green slates in alternations of varying thickness. 

 The dip of the structure is NE. at angles from 50° upward. 



At Albion Mr. F. C. Schrader has observed fragments of the quartzite 

 in a siliceous and quartzitic schist striking about N. 41° W. and dipping 

 50° NE. Just west of this outcrop, and separated from it by a small ravine, 

 is a large outcrop of the quartzite. The presumption here is that of an 

 unconformable relation of the Ashton schists upon the quartzite. The 

 quartzite is lithologically the same as the Cumberland rock. The fragments 

 of the quartzite in the Ashton schists are sometimes somewhat worn. The 

 schist in the bold bluff on the east of Sneech Pond also contains small, 

 rounded, and broken fragments of the quartzite. These facts, together 

 with the siliceous character of the slates and schists, indicate that they were 

 derived from the erosion of a quartzite terrane. Some evidence of probable 

 unconformity of dip at the Albion locality also points to the conclusion 

 that the more massive quartzite beds of the Blackstone series are older 

 than the Ashton schists. 



Limited exposures of quartzite occur along the border in the western 

 part of Providence at Manton. The quartzites are prevailingly brownish- 

 yellow in color wherever they occur, are generally granulated by crushing, 

 and are glossy by reason of the development of some sericite. Their 

 occurrence in lenses and along strike lines, together with the probability 

 that they are older than the Ashton schists, seems to indicate that the 



