WAMSUTTA GROUP. 147 



horizon in this field, but on account of the intense folding', along with fault- 

 ing, it is not satisfactoiily determined to what extent the conglomerates are 

 duplicated. Some of the felsitic conglomerates pass into agglomerates, and 

 these into felsite breccias, well shown in the valley east of Oldtown. 



sandstones. — The sandstones of the area under discussion are of variable 

 texture, becoming coarse and feldspathic and thus approaching arkose 

 on one hand and grading into quartzites and shales by the separation of 

 the quartz and decomposed feldspar on the other hand. The reddish 

 quartzitic beds are well exposed on Robinson Hill and in general about the 

 village of North Attleboro. Their detailed representation on the map 

 accompanying this report has not been attempted. In the bend of the 

 sandstone ridges at Red Rock Hill, Mr. H. T. Burr found rain imprints on 

 the sandstone. 



shales. — The shales, or often slaty argillaceous sediments, of the for- 

 mation are well exposed in the valley between Reservoir Pond and Red 

 Rock Hill. Other exposures occur east of the village of North Attleboro. 

 Reservoir Pond appears to lie partly in a depression excavated along the 

 line of strike of these beds. The shales are frequently interrupted by 

 knobs and sills of felsite (see fig. 14). The. beds contain flattened stems of 

 calamites, as at Attleboro Falls, near Reservoir Pond, and east of Red Rock 

 Hill. 



THE CENTRAL FALLS AREA. 



The Central Falls area is not well exposed. The best outcrops are near 

 the High School in Central Falls. On the east, near the old post-road, con- 

 glomerates occur with slaty beds in nearly vertical attitudes. In Pawtucket 

 the beds are mostly red shales or slates at the same high angles. The 

 breadth of the formation decreases rapidly southward along the strike. At 

 the widest part it is as much as 1,000 feet. Its appearance in this part of 

 the field is evidently owing to compressed anticlines and synclines in the 

 highly inclined Carboniferous strata at the head of Narragansett Bay. 

 The structural relations of this area to that in North Attleboro are best 

 explained by an anticline arching over the conglomerates west of South 

 Attleboro. This view also supposes that some of the Coal Measures, i. e., 

 the Pawtucket shales, may be inferior in position to this southern extension 

 of the red beds. 



