PENNSYLVAKIAN ROCKS 447 



luetaiiiurpliosed, wliei'cas the Naj-vagaiisett series lias beeu folded with but 

 little shearing. 



XARKA GANSE TT SERIES 



The northeastern edge of the ISTarragansett Basin is in the area south 

 of Sheldonville, Massachusetts^ and east of Diamond Hill, Ehode Island, 

 at the northeastern edge of the area mapped in the southern end of the 

 >forfolk Basin. The j^arragansett series consists, according to Wood- 

 worth, of four formations: 



Dighton group, 

 Pawtucket formation,^® 

 Wam_sutta red beds, 

 Pondville arkoses, 



arranged in the order of their stratigraphic position. 



In the area mapped in this paper the Pawtucket and Wamsutta f oijbia- 

 tions are ctposed, the former along a narrow strip south of the Diam_ond 

 Hill felsite and the latter on the east of this strip and of the Diam-ond 

 Hill felsito." 



The structure of the Narragansett series in a section from_ Arnolds 

 Mills westward is m_onoclinal, the beds dipping southwest at an angle of 

 about 30 degrees and striking north 75 degrees west. They are cut off 

 by the north-south fault running west of Diamond Hill. Near Sheldon- 

 ville the strike is nearly parallel to the northeast-southwest fault and the 

 dip is about 40 degrees north. 



The existence of these faults is proven by the dips of the strata near 

 them. The downthrow has apparently been on the side of the Narragan- 

 sett series. The north-south fault past Diamond Hill was mapped by 

 Woodworth. He also drew a north-south fault east of Sheldon ville 

 which is shown on the map accompanying this paper. The steep cliff of 

 •Joes Eock granite northeast of Sheldonville, and on this fault line, ap- 

 pears to substantiate the existence of the fault. 



The Wamsutta red beds consist of red conglomerates, shales, and sand- 

 stones. The rocks have been tilted and compressed, as is shown by some 

 of the conglomerates in which the pebbles have been dented or flattened 

 b}'' each other. Near the reservoir east of Diamond Hill there are nu- 

 merous exposures of moderately coarse conglomerates and some inter- 

 bedded red shales. The pebbles in the conglomerate vary in size to about 

 4 inches in length, but on the average they are one inch in length. They 



i« The term Pawtucket formation is introduced in place of the "Coal Measures" of 

 Woodworth in order to avoid confusion with the Coal Measures of other localities. 

 1' Monograph U. S. Geol. Survey No. 33, plate 17. 



