THICKNESS OF THE CARBONIFEROUS. 209 



strata between the granitic base and the top of the Dighton group. The 

 evidence on which this estimate is based is as follows: 



From the south bank of the Taunton River north of Steep Brook to 

 the axis of the Dighton-Swansea syncline there is a section from the base 

 to the uppermost beds of the series. The distance along this line perpen- 

 dicular to the strike is approximately 3 miles, and the dip of the beds is 

 generally steep; it may be assumed to be as high as 45°. This gives 11,198 

 feet as the thickness of the strata remaining along this margin of the basin. 



Between the axes of the Dighton-Swansea and the Taunton synclines 

 is a distance of 6 miles. The intervening beds, in anticlinal position, 

 though very imperfectly exposed, nowhere exhibit in the few exposures 

 available for interpretation foldings or thrusts likely to diminish or increase 

 the estimate of thickness based on measurements across the interval between 

 the two synclinal axes. The dips on the southern side of the anticlinal 

 axes are very steep, mainly above 45°; the dips on the northern side are 

 much less steep, mainly below 45°. The lowest beds exposed anywhere 

 along the anticlinal axis lie above the basal beds of the Carboniferous; 

 so that estimates along this line must necessarily fall short of the base. 

 Assuming 45° as the average dip over this anticlinal section, and since the 

 beds over half the distance between the adjacent synclines have 3 miles of 

 outcrop as before, we obtain the same amount as on the southern side of the 

 Dighton-Swansea syncline. Inasmuch as this estimate of about 11,200 

 feet is a minimum and does not reach the base, it is probable that the beds 

 increase in thickness toward the middle and now deeper part of the basin. 



Northward from the Taunton syncline to the northern border near 

 Mansfield there is certainly one anticlinal area, and another syncline in 

 the Mansfield coal basin ; but there are no exposures of the upper conglom- 

 erate series along "this line, and the outcrops are totally inadequate for 

 making even minimum estimates of thickness. 



West of the line of section above described an approximate estimate 

 of thickness can be founded upon the strata exposed between the western 

 end of the Taunton syncline in Seekonk and the axis of the Attleboro syn- ■ 

 cline. From the Perrin's anticline, where there is a probable overthrust of 

 the beds on the south, to the axis of the adjacent Attleboro syncline there 

 is a fairly continuous exposure of outcrops, ranging in inclination from 45°, 

 for a few hundred feet on the south, to nearly vertical for most of the 

 thon xxxni 14 



