238 GEOLOGY OF THE NAEEAGANSETT BASIN. 



points the cross bedding is well marked. Thin but elongated pockets of 

 ottrelitic coaly shale are found in places not far northward. Within 2,700 

 feet of the wharf scattered pebbles, sometimes 3£ inches long, not at all 

 flattened, occur in the sandstone. In a few of these pebbles oboli were 

 found. The oboli occur again northward in a thin layer of conglom- 

 erate, the pebbles of which are sometimes 1£ inches long. The oboli are 

 found once again, about 700 feet north of the first-mentioned locality, 

 in pebbles scattered through the sandstone. The gray sandstone is not 

 infrequently banded with more carbonaceous layers. Farther north long, 

 thin fragments of carbonaceous shale occur in small conglomerate layers. 

 A little more than three-quarters of a mile from the wharf the flattened ■ 

 leaf-like plant remains occur, such as are found at Hills Grove, Warwick, 

 and Silver Springs, East Providence. The outcrops along the shore cease 

 about a mile north of the wharf. Northeastward of this, in the field, a 

 sandy outcrop, probably belonging in the next higher series, occurs. In 

 general, the series here described is composed of sandstones. The absence 

 of coaly shale layers in it does not signify much, since the vertical section 

 here exposed probably does not exceed 50 feet. 



The occurrence of a shaly series over that of sandstones all along the 

 line of outcrop has already been noticed. This shale series is well exposed 

 along the long inward curve of shore north of the wharf. The lower 

 courses immediately over the sandstone look very much like the dark-blue 

 shales of the Conanicut series, but frequently contain ottrelite and are 

 banded with more frequent and much larger layers of a very fine grained 

 sandstone, which has been less affected by shearing. Above these beds 

 occur decidedly coaly shales, often siliceous from the presence of minute 

 clastic quartz grains. Above these again occur the fissile dark-blue shales. 

 The color banding of the shales is often very well shown, and since there 

 has been no crumpling, or violent folding, it indicates the strike and dip very 

 well. The strike averages N. 20° E., and the dip is about 35° E. The upper 

 dark-blue fissile shales are exposed at a number of points halfway up the 

 hillside east of the wharf. The very coaly black shales form the shore 

 south of the wharf for a distance of over a mile. It must not be imagined 

 from this that the coaly shales are perfectly distinct from the dark-blue 

 members; on the contrary, they are interbedded with the dark-blue shales 

 at various levels, but nowhere else in the series is so much coaly shale 



