274 GEOLOGY OF THE NARRAGANSETT BASIK 



border passes southward from the stone bridge, rounds the granites and 

 schists north of Nannaquacket Point, and then continues southward, east of 

 the pond. In that case the pre-Carboniferous range of exposures between 

 Gould Island and Common Fence Point must have been brought to their 

 present position by means of a fault bringing up these rocks from below. 

 At least there is no evidence that the Gould Island-Common Fence Point 

 range of exposures formed an island in the Carboniferous seas. 



This explanation makes it unnecessary to hypothesize any connection 

 between the Common Fence Point range of granites and the Bristol Neck 

 granite area above the water surface in Carboniferous times. 



EASTERN BORDER OF THE CARBONIFEROUS BASIN SOUTH OF 

 TIVERTON FOUR CORNERS. 



Half a mile south of Tiverton Four Corners granite is exposed on the 

 northwest side of the hill, south of the brook entering Nonquit Pond from 

 the east. The granite continues to be exposed southward for a short dis- 

 tance, when greenish rock, having the appearance of a very fine-grained 

 sandstone, occurs. Its schistosity is N. 40° E., dip 45° SE., and there is a 

 probability that this should be taken as the strike and dip of the bedding. 

 This rock is exposed along the apparent strike at a number of places on the 

 northwest side of the hill. A quarter of a mile southeast, along the road- 

 side, the granite is abundantly exposed. The granite has been sheared so 

 as to present a pseudo-gneissoid structure with a northeasterly strike. The 

 granite and the fine-grained rock are pre-Carboniferous. The eastern border 

 of the Carboniferous area probably extends from Tiverton Four Corners 

 east of Nonquit Pond and west of the granite hill southward. 



The granite is well exposed along the southern end of the hill north- 

 east of Tiverton Four Corners, almost east of the church north of Tiverton. 

 On the east side of Borden Brook the granite has been considerably sheared 

 in a direction about N. 30° E. The granite of this region contains in 

 places abundant phenocrysts of feldspar from 1 to 2 inches in diameter, and 

 these have been sheared to a lenticular form, producing a sort of augen- 

 gneiss. Where the shearing was more marked the black mica increased in 

 quantity. Extreme shearing reduced the granite in places to a biotitic 

 schist, whose real character it is not possible to recognize in the case of 

 .every exposure. Gradations from one into the other can, however, be found. 



