378 GEOLOGY OF TPIE NAKKAGANSETT BASIN. 



The question suggests itself whether Indian Run represents another 

 syncline within the granite area which contains Carboniferous rocks. This 

 area has not been carefully investigated. The writer is inclined to consider 

 McSparran and Tower hills as marking the most western exposures of 

 Carboniferous rocks in the basin, without any attempt to assert, however, 

 that in times preceding the folding and subsequent denudation the Car- 

 boniferous rocks could not have extended farther westward. If it be 

 remembered that the Carboniferous deposits half a mile south of Bridge- 

 town and along southern Tower Hill owe their high inclination to folding, 

 it will be seen from a restoration of these beds to their original horizontal 

 attitudes that Carboniferous beds must have once extended farther west- 

 ward, making the western shore line pass west of Tower Hill; how much 

 farther west is not known. 



TIVERTON AEKOSE. 



From Steep Brook to Nannaquacket Pond. Along the pi'e-Cai'bonifei'OUS eSCarpment 



extending from Steep Brook to Tiverton Four Corners a number of expo- 

 sures of arkose occur. Since this escarpment consists almost entirely of 

 granite, any overlying basal Carboniferous rocks are apt to include arkose 

 beds. The latter were formerly well exposed at Steep Brook, but this is no 

 longer the case. A fine exposure occurs in Fall River, another at Town- 

 send Hill in the northwestern end of the town of Tiverton, one at the 

 quarry northeast of Tiverton railroad bridge, and there are several expo- 

 sures along the escarpment east of Nannaquacket Pond in Tiverton. In 

 all of these localities carbonaceous shales are more or less intimately asso- 

 ciated with the arkoses. At Steep Brook and Fall River these were fern 

 bearing. East of Nannaquacket Pond and at Fall River the arkoses and 

 coaly shales alternate repeatedly. At Steep Brook and the quarry northeast 

 of the Tiverton railroad bridge conglomerate beds occur in close connection 

 with the arkose series. The fact that these conglomerates contain quartzite 

 pebbles similar to those in the Natick conglomerates and that the pebbles 

 in places attain a length of 6 inches does not simplify the problem, since 

 pre-Carboniferous quartzites are practically unknown on the eastern side of 

 the basin. The pre-Carboniferous quartzites on the eastern side of the 

 basin may have been removed by subsequent erosion, but there is no good 

 reason for assuming their former existence here. The thickness of the 

 Tiverton arkose series is usually less than 100 feet and is nowhere known 

 to exceed 200 feet. 



