382 GEOLOGY OF THE NARRAGANSETT BASIN". 



The whitish rocks between the conglomerate ranges in the great 

 Paradise-Hanging Rock syncline resemble strongly the more quartzitic 

 exposures away from the shore, east of the Sakonnet River. 



Quartzites occur well exposed (1) west of Natick, (2) along a road a 

 short distance east of Natick, (3) southwest of the town, (4) along the 

 northern side of Bald Hill, (5) on a knoll directly east of that hill, and 

 elsewhere. Possibly various exposures west of East Greenwich, east of 

 Nonquit Pond, and in the neighborhood of Tiverton belong here. The 

 quartzites west of Natick have furnished the pebbles in the basal conglom- 

 erate of the Carboniferous. Pebbles of similar chai'acter occur also in all 

 the overlying conglomerates as far up as the Dighton conglomerate. 



In the quartzite pebbles of (1) the conglomerate between the Saun- 

 derstown sandstone series and (2) of the Aquidneck shale series on the 

 western side of Prudence Island fossil oboli occur. 1 They are found also 

 (3) in the conglomerates along Newport Cliffs, and (4) in the coarse 

 conglomerates at Eastons Point, (5) in the Paradise ridges, (6) along the 

 western shore exposures of the Sakonnet River, . and also (7) east of that 

 river north of Tiverton Four Corners. These oboli appear identical with 

 fossils from the passage beds between the Cambrian and Lower Ordovician 

 of Great Belle Island of Newfoundland. Hence they are either of late 

 Cambrian or early Lower Ordovician age. Notwithstanding the great 

 abundance of quartz pebbles with oboli, however, the quartzite containing 

 oboli has never been found in situ. It may be that the Natick quartzite is 

 a remnant of the old Cambrian quartzite, but since it contains no oboli this 

 can not be determined. 2 



Considering the great abundance of quartzite material in the coarse 

 Purgatory conglomerates, the quartzite must have once occurred in consid- 

 erable thickness over wide areas. It is not improbable that the quartzite 

 once occupied a considerable part of the area now occupied by pre- 

 Carboniferous granite. Subsequent erosion appeal's, however, to have- 

 effectually denuded these areas of the quartzite beds, excepting in isolated 

 localities, as at Natick. If the pebbles were derived from large exposures 



1 The following species hare so far been discovered in the quartzite pebhles derived from south- 

 eastern Rhode Island and Massachusetts: Oiolus (Lingulobolus) affinis, 0. (L.) spissus, and Obolus 

 (Lingulella) rogersi. 



-Charles D. Walcott, Brachiopod fauna of the quartzitic pebbles of the Carboniferous conglom- 

 erate of the Narragansett Basin, E. I.: Am. Jour. Sci., October, 1898, 3d series, Vol. VI, p. 3^7. 



