356 GEOLOGY OF THE NARRAGANSETT BASIN. 



GOULD ISLAND OF THE MIDDLE PASSAGE. 



The strike of the strata composing Gould Island is generally north- 

 south. Plumbago and coaly shales form almost all of the shore exposures 

 on the eastern shore for a little more than half the length of the island, 

 going southward. Farther south carbonaceous shales continue to appear, 

 but sandstone, in part conglomeratic, also makes its appearance. The peb- 

 bles of the more conglomeratic layers are very small. The dips are chiefly 

 east, but very irregular, and the most northern dip appears to be westward, 

 while the strata about a fourth of the length of the island north of its 

 southern end are nearly vertical. 



SOUTHERN THIRD OF AQUIDNECK ISLAND. 



South of the line connecting Coddington Point and Black Point, includ- 

 ing the southern third of Aquidneck Island, the typical dark-blue and 

 greenish-blue shales of the Aquidneck series are not often exposed (see foot- 

 note on page 372). The top of the series is exposed at Eastons Point, but 

 presents features which it is desirable to discuss in connection with other 

 exposures farther north that seem to belong to the same horizon. This will 

 be done under the next heading. 



UPPER GREEN SHALES OF THE AQUIDNECK SERIES. 



The great mass of shales exposed on Aquidneck or Rhode Island 

 undoubtedly constitute a single series. Considering their thickness and 

 their considerable geographical distribution, they present decided litho- 

 logical uniformity. Along the middle of Aquidneck Island, however, the 

 upper part of the shale is greenish in color, in contrast to the chiefly dark- 

 blue fissile shales underneath. These green shales are well exposed (1) 

 for a mile along the western road from Newport to Bristol Ferry, south- 

 west of Butts Hill, on the western side of the Portsmouth syncline. They 

 are seen again (2) half a mile southwest of the top of Quaker Hill, on the 

 eastern side of the syncline. The green shales include near the top more 

 sandy layers and sandstones, followed higher up by the sandstones and 

 conglomerates of the conglomerate series. At (3) Slate Hill and for over 

 a mile southwestward along the road green shales are again exposed. The 

 coarse conglomerate series which is supposed once to have overlain them is 



