146 GEOLOGY OF THE NAREAGANSETT BASIN. 



from this point to the northern border of the main basin seems to have the 

 form of an overturned syncline, as shown in fig. 12. 



From Robinson Hill the red conglomerates, sandstones, and shales can 

 be traced southward, with strikes conforming in direction to the general 

 distribution of the formation, to Reservoir Pond, thence to Rattlesnake Hill 

 and skirting the northern banks of Fourmile Brook. The formation thence 

 trends in a southwesterly direction to South Attleboro. Good exposures 

 may be seen in Red Rock Hill. Immediately west of Washington street 

 and south of Allen road, the sandstones and conglomerates may be seen 

 turning north-northwestward, whence they continue in that general direc- 

 tion as a broad area of red rocks with occasional exposures as far north as 

 the vicinity of Burnt Swamp Corner. A well-marked occurrence of these 

 rocks is found between Abbots Run and Millers River. 



The stratigraphy of the area immediately west of the Blake Hill fault 

 block in Plainville, and thence northward to the Sheldonville narrows, is 

 imperfectly understood. About a mile north of the southwest corner of 

 the block, the Wamsutta beds occur in a well. Between this locality and 

 the Blake Hill schoolhouse, 1 mile southeast of Burnt Swamp Corner, gray 

 Carboniferous beds appear in an unknown relation to the red beds above 

 referred to. From the schoolhouse a strip of red conglomerates extends 

 southwestward toward the main belt of these rocks, Avhich here skirt the 

 western border. The varying strikes and the repetition of isolated red and 

 gray outcrops northward in the direction of Red Brush Hill render the 

 structure of this region difficult of interpretation, since the gray beds may 

 belong below or above the red beds, and criteria for the determination of 

 their position are there absent. The boundary line drawn upon the 

 accompanying map (PL XVII) between the red and gray series in this 

 region is therefore wholly conjectural. It is probable that the rocks are 

 thrown into closed folds. 



conglomerates. — The conglomerates are composed mainly of waterworn 

 pebbles of greenish quartzite. One pebble in the outcrops in the valley of 

 Abbots Run contained several Obolus shells, which, according to Walcott, 

 are upper Cambrian. Granitic pebbles are common, and locally there is a 

 large proportion of felsite. Stretching and fracturing of pebbles under the 

 pressure of strong folding is evident from point to point in the more dis- 

 turbed areas. It is probable that conglomerates occur on more than one 



