142 



GEOLOGY OF THE NARRAGANSETT BASES. 



BED ROOK AREAS. 



There are eight areas in the northern part of the basin in which reddish 

 rocks have a surface exposure, and in these they are brought to the surface 

 by strong folding. 1. In North Attleboro and the adjoining towns of Wren- 

 tham, Massachusetts, and Cumberland, Rhode Island, a large horseshoe- 

 shaped area wrapping about a knob of granitite in Hoppin Hill and the 

 North Attleboro Cambrian outcrops. 2. A small lens-shaped area extending 

 northeastward from Central Falls, Rhode Island, into Massachusetts. 3. A 

 still smaller area south of the last, extending northeastward from the gorge 



Area now exposed Area probably now covered Area probably eroded owoy 



— *■ Directions in which the formation decreases in thickness 

 T Possible exposures 



Fig. 11 Map showing distribution of red sediments. 



of the Blackstone in Pawtucket. 4. A characteristic elongate narrow area 

 extending along the northern margin of the main basin and traceable as far 

 as the North River in the town of Hanover. This area is probably con- 

 nected at the west with the succeeding. 5. The largest area of all, extend- 

 ing from No. 1, near Sheldonville, northward and eastward to Braintree, 

 forming the greater part of the strata in the Norfolk County Basin. There 

 are exposures in (6) Attleboro and (7) Rehoboth, and one in (8) Norton, 

 which may belong to a different horizon. I shall begin the account of these 

 fields with the area along the northern border of the main basin. 



