POSITION OP SAKONNET SANDSTONES. 365 



structure of this region, occur the shale, sandstone, and fine conglomerate 

 beds, forming the Sakonnet sandstones east of the river, from the shore 

 west of Windmill Hill almost as far as Browns Point, The thickness of the 

 sandstones along this part of the shore must amount to at least 300 feet, 

 but no accurate measurements were obtained. 



Underlying the coarse conglomerate of High Hill Point is more sand- 

 stone and small-pebbled conglomerate. Immediately beneath the Fogland 

 Point conglomerate is greenish shale. The exposures south of Corys 

 Wharf, consisting of bluish shale with some sandstone, approach more 

 nearly to some of the Aquidneck exposures west of the Sakonnet River 

 than any other exposures known on the eastern side of the bay. They 

 undoubtedly belong beneath the coarse conglomerate, and lie at about the 

 same horizon as some of the Sakonnet sandstones farther southward. 



Sakonnet sandstones within the Aquidneck shales, in transition to the coarse conglomerate. The 



Sakonnet sandstones are here placed with the Aquidneck shales, owing to 

 the frequent intercalation of shales, and because the dividing line is more 

 readily drawn above than below the sandstones. At the same time these 

 sandstones, with the interbedded small-pebbled conglomerate layers, are 

 undoubtedly introductory to the coarse conglomerate series above. 



Coarse conglomerate forming the latest Carboniferous rocks in the southern part of the Narragansett 



Basin. — The various coarse conglomerate exposures mentioned form the 

 summit. of the rocks of Carboniferous age in the localities where they are 

 found. Under these circumstances the temptation is very great to consider 

 them all as being of the same general horizon. 



Purgatory conglomerate as a typical exposure. The position of the COai'Se COllglom- 



erate at Eastons Point is perhaps the best defined. It occurs on both sides 

 of the anticline forming the point, and the exposures on the eastern side of 

 the anticline containing the famous Purgatory chasm can be readily traced 

 northward to the high conglomerate ridges forming the western side of the 

 Paradise region northwest of the reservoir. The southward pitch of this 

 anticline is the best assurance that this coarse conglomerate occupies a 

 higher position than shales of the Aquidneck series. 



The upper green shales occur on Slate Hill at an elevation of 260 feet 

 About a mile southward they occur at a level of 180 feet. At Eastons 

 Point a restoration of the syncline would probably give a somewhat lower 

 elevation to that part of the section which most nearly corresponds to the 



