CHAPTER IX. 



THE PURGATORY CONGLOMERATE. 



Coarse conglomerate overlying the Aquidneck shale series. The KillgStOWn Sei'ieS is OVei'- 



lain by a considerable thickness of shales, here termed the Aquidneck 

 series. These shales retain their shaly characteristics and bluish-black color 

 to within a very short distance of the base of the overlying' coarse conglom- 

 erate at Coasters Harbor Island, Coddington Point, and Miantonomy Hill. 



Farther eastward, near the top of the Portsmouth syncline, at Slate 

 Hill and southwestward, and to a less degree on both sides of the Eastons 

 Point anticline, the upper portion of the shale series has a more greenish 

 color, and at the first and last mentioned localities this upper greenish shale 

 evidently lies immediately under the coarse conglomerate of these regions. 



At Taggarts Ferry the bluish Aquidneck shales are exposed in the 

 stream bed entering the bay from the west, within a very short distance 

 from the shore. Overlying these shales is a variable series composed of 

 bluish shales, carbonaceous shales, black fine-grained sandstones, less car- 

 bonaceous and coarser-grained sandstones, and conglomerates with the 

 pebbles usually small. These occur in alternating beds, and have already 

 been described under the name of Sakonnet sandstones. Immediately over- 

 lying them is coarse conglomerate. 



The dark-blue Aquidneck shales are well exposed at the Glen. South- 

 ward along the shore the shales are usually more black and carbonaceous. 

 Just before reaching Black Point an overlying series of dark shales, dark 

 carbonaceous fine-grained sandstones, and very small-pebbled conglomerate 

 comes in, representing a more northern variety of the Sakonnet sandstones. 

 Overlying these sandstones is the same coarse conglomerate which was 

 mentioned in describing the exposures at Taggarts Ferry. 



East of the Sakonnet River there are no exposures of the typical 

 Aquidneck shale variety, but the coarse conglomerates occur, and immedi- 

 ately beneath the latter, according to this interpretation of the geological 



