WAMSUTTA GROUP. 153 



spur of the railroad into the trap locality would necessitate building a 

 bridge or trestle across Abbots Run. From a point half a mile north of 

 the station, it would require about 4,000 feet of track to reach the ledge. 



Quartz-porphyries, felsites, and granophyres. Intimately aSSOCiated with tile l'ed 



rocks of the Wamsutta group is a series of acid ig-neous rocks of felsitic and 

 granophyric structure, the distribution of which is parallel with that of the 

 diabase dikes just described, and, like the former, these rocks occur in knobs, 

 whether true bosses or faulted and disjointed dike-like masses being not 

 easily determined. In general they are limited to the horseshoe fold, and 

 do not accompany the Wamsntta group eastward along the northern 



Fig. 14.— Section through JVlsite knob iu Attleboro. Massachusetts. (See table below.) 



margin of the basin nor in the Norfolk County Basin beyond the narrows 

 in Wrentham. The felsites are usually of a reddish color. 



A cross section (fig. 14) of one of these knobs south of Reservoir Pond 

 illustrates the general character of the association with the Wamsutta group. 



The succession, beginning on the east, is : 



Section south of Reservoir Pond. 



Feet. 



Sandstone (red, pebbly) and shale (red) 40 



Diabase 40 



Felsite 10 



Conglomerate, red 8 



Felsite, in large knob 50 



(Western contact not seen.) 



