158 GEOLOGY OF THE NARRAGANSETT BASIN. 



Several small faults exist in the North Attleboro area between Robin- 

 son Hill and South Attleboro. These dislocations are indicated by the 

 offset of diabase dikes along their line of strike, by the occurrence of beds 

 in blocks, and also by the exposures in which the dislocation may be 

 traced. In front of the house of Mr. H. Rhodes, about 1£ miles northeast 

 of South Attleboro, reddish sandstones are brought against the red slates, 

 but this relation is probably due to local unconformity rather than to a 

 fault. 



FLORA OF THE WAMSUTTA GROUP. 



So far as the observations of the present survey go, the sole fossils 

 found in the red shales and sandstones of this series by Dr. Foerste and 

 myself are a species of calamites and a cordaites. As a whole, the strata 

 are prevailingly barren, a characteristic of red rocks everywhere. Enough 

 of the flora is known, however, taken together with the stratigraphy, to 

 warrant placing the beds in the Carboniferous section of the Narragansett 

 Basin. This fully confirms the views of Crosby and Barton expressed in 

 1880. 



The geographical conditions under which the beds were laid down 

 seem to have been incompatible with the accumulation of plant remains in 

 the area of sedimentation, rather than that there is any difficulty in preserv- 

 ing fossils of this kind in red beds. In places abundant traces of calamites 

 occur in the form of good impressions without a trace of Carbonaceous 

 matter. In other localities the impressions of single stems are black with 

 carbon, and had enough of these fragments been accumulated in one plane 

 a black shale layer, if not a deposit of coal, must undoubtedly have resulted. 



There are reasons for believing that southward beyond the limits of 

 the red beds plant remains were accumulating at this early stage in the 

 Carboniferous of the Rhode Island area. The general absence of fossils 

 in this series appears to have been due to a control exercised by the 

 peculiar processes concerned in the deposition of the series itself. The pres- 

 ence of quartz-porphyry pebbles along with masses of this rock and the 

 related felsite, which appear to have come into their present relation to the 

 strata before the deposition of the Coal Measures in this part of the field, 

 suggests that volcanic action may have affected the formation of sediments 

 in a way to be locally unfavorable to the growth and preservation of plants. 



