240 GEOLOGY OF THE FARRAGANSETT BASIN. 



the dark-bluish shales of Conanicut. The color banding is usually very pro- 

 nounced, and since the contortion and folding of strata is less, the general 

 strike and dip of the rocks can be readily determined. These shaly rocks 

 differ considerably from the Conanicut shales, however, in the more fre- 

 quent presence of sandy courses, varying from 1 inch to 8, 12, and even 20 

 inches in thickness. These have usually been less affected by cleavage. 

 There are also distinctly conglomeratic beds present, although these, except 

 in the case of two beds, occur only in very thin layers. Darker, more 

 coaly phases are present in the shales, more carbonaceous than any 

 observed on Conanicut. The general color of the shales on the shore, 

 where not moistened by water, is often, for rather long stretches, a peculiar 

 silvery green, which resembles some phases of the greenish shales at Eas- 

 tons Point. The darker shales are frequently ottrelitic. Notwithstanding 

 all these differences, a person acquainted with the varying aspect of this 

 series will readily satisfy himself as to its identity with the Conanicut shales. 



The general strike for a distance south of the wharf is N. 10° E., dip 

 70° W. About five-sixths of a mile south of the light-house the shale is 

 darker, more carbonaceous, and ottrelitic. Farther south thin conglom- 

 erate beds show stretched pebbles, usually not exceeding half an inch in 

 length. Yet farther to the south more carbonaceous black shales occur close 

 to the inward curve along the shore. Farther on there is conglomerate 

 with pebbles an inch long, and a little over a mile south of the light-house 

 a 3-foot layer of conglomerate is found with pebbles often 3£ inches long. 

 The pebbles are usually greenish, as though lithologically similar to the 

 shales; they are rarely quartzitic. Still farther southward more ottrelitic 

 dark shale is seen. Fine color banding is often shown. Cross bedding is 

 common in the coarser sandstones. Thin conglomeratic layers begin to 

 be more frequent. Near this point the continuous exposures cease. At the 

 southern end of these exposures the strike is N. 20° E., the dip still 70° to 

 80° W. 



At the next exposure southward there occurs a more carbonaceous 

 form of the shale, black and ottrelitic. Strike N. 28° E., dip 60° to 70° 

 W. The next exposure, more greenish, gives again strike N. 13° E., dip 

 88° W. Banded, slightly ottrelitic shales form the last exposure, If miles 

 south of the light-house; strike N. 33° E., dip 80° W. 



