306 GEOLOGY OF THE NARRAGANSETT BASIN. 



appearance of some of the larger fragments suggests that they once formed 

 continuous beds intercalated in the coaly shale. In that case the occur- 

 rence of arkose in this shale is of interest. It will be remembered that 

 arkose is associated with coaly shales on Sachuest Neck. It is believed 

 there to overlie a greenish shale and conglomerate, possibly comparable 

 with the Little Compton green shales. It derived the materials for the 

 arkose in part from the coarse-grained granites on the south and east. 



The granite nearest to Bishop Rock is 2£ miles distant, at the southern 

 end of Jamestown, on Conanicut, and at the southern end of Newport Cliffs 

 and on the adjacent part of the neck. The nearest exposures of green 

 shales are on Goat Island, Rose Island, and Freebody Hill. Nowhere 

 can these rocks be brought in close relation with one another so that their 

 relative age may be determined. The arkose on Bishop Rock seems to 

 belong to a horizon not far from the coarse conglomerate on the western 

 side of Coddington Neck, and probably occur just beneath the same. Simi- 

 lar arkose occurs near the southern end of Coasters Harbor Island. 



COASTERS HARBOR ISLAND. 



The very coarse conglomerates, with pebbles often 1 foot and at times 

 2 feet long, so well shown on Miantonomy Hill, are again well shown on 

 Coasters Harbor Island. No elongation of the pebbles is observable here. 

 The strikes and dips are variable. The most southern exposure of conglom- 

 erate on the east side of the island has a strike N. 65° E., dip 40° to 50° 

 NW. North of a small indentation of the coast the strike remains N. 65° 

 E., but the dip becomes only 20° NW. Within a short distance north- 

 ward the strike changes to N. 80° W. and the dip becomes 60° NE., and 

 along the northeast coast the strike is N. 30° W. and at various locali- 

 ties the dip is 80° to 85° E. West of a small embayment the rocks of the 

 northern promontory of the island seem to be in part folded, and elsewhere 

 dip 80° W., striking N. 10° E. In an embayment west of this promon- 

 tory sandstone is exposed, the apparent dip, which may be cleavage, strik- 

 ing N. 35° E., dip southward. At the northwest angle of the island the 

 strike is N. 30° E., curving southward to N. 10° E. and N.-S., while 

 the dip is constantly eastward, about 40° E. northward, becoming less 

 southward. Southward carbonaceous sandstone and fine conglomerate are 

 faulted against the coarse conglomerate, which is almost horizontal, and 



