366 GEOLOGY OF THE NABKAGANSETT BASIN. 



greenish shales northward. This apparently corroborates the evidence in 

 favor of a general southward pitch of the rocks in southern Aquidneck. 



Owing to the typical development of the coarse conglomerate series at 

 Purgatory, and its already well-known occurrence as shown by frequent 

 references in geological literature, the name Purgatory conglomerate is chosen 

 to designate those coarse conglomerates which are supposed to belong to 

 the same horizon. 



Identity of the Purgatory and the Sakonnet River western shore coarse conglomerate. There COlud 



be no closer lithological resemblance than that between the conglomer- 

 ates exposed between Black Point and Smiths Beach along the Sakonnet 

 River or East Passage and the similar beds in the Purgatory and western 

 Paradise regions. The lithological character of the slaty and quartzose 

 pebbles, the inclosed oboli, 1 the great size of the pebbles, the alternation 

 of the coarse conglomerates with sandstones, the same varieties of medium- 

 grained granite pebbles and the same infrequency of granite as compared 

 with quartzitic pebbles, and many other points easily recognized in the 

 field, all suggest the identity of the two series. The presence of Aquidneck 

 shales in the region northwest of Black Point and the eastward dip of the 

 coarse conglomerate suggest superposition of the coarse conglomerate upon 

 the Aquidneck shales. 



Possible syncline between the two western Paradise ridges of conglomerate. The Pui'^atOl'V 



and western Paradise exposures and the Sakonnet River western shore 

 exposures just mentioned dip eastward. In order to place them at the same 

 horizon, it seems necessary to imagine at least one syncline somewhere 

 between the two lines of exposure. The main ridge of the Paradise region, 

 forming its western boundary, evidently dips eastward, most, of the dips 

 being between 40° and 60°. East of the same, separated by a grassy val- 

 ley, is another lower conglomerate ridge, with a few very steep eastward 

 dips, and a greater number of very steep westward dips, which can be best 

 summarized as steep, nearly vertical, clips. This variation of dips between 

 the two ridges admits of the suggestion that there is a syncline between 

 them. Following the strike of the nearly vertically dipping ridge north- 

 ward, exposures Avith almost vertical dips soon cease. Eastward-dipping 

 exposures, however, continue to occur northward, suggesting that if there is 



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

 erates of the Narragausett Basin, R. I. : Am. Jour. Sci., October, 1S98, 3d series, Vol. VI, p. 327. 



