272 GEOLOGY OF THE I^AEEAGAXSETT BASIN. 



contact between the granite and the overlying Carboniferous rocks is again 

 well shown. The clastic rocks consist of a series of interbedded arkoses and 

 coaly shales, sometimes one, sometimes the other kind of rock forming the 

 contact with the granite. The contact line is usually very distinct. The 

 same strike of N. 85° W., dip 60° S., is shown. The arkose and granite con- 

 tact can be followed as far as the creek entering Nannaquacket Pond from the 

 east. From the pond southward it evidently takes a more southex'ly course, 

 following the eastern side 'Of the low land west of the granite hill, and then 

 following the valley of a small brook as far as Tiverton Four Corners, 



North of Nannaquacket Pond normal granite occurs, as already de- 

 scribed. Still farther north a white fine-grained micaceous schist is 

 exposed over a considerable area, until farther northward the granite 

 appears again. The whitish micaceous schist may be followed eastward 

 across the north-south road. It forms the southern end of the hill north 

 of Sin and Flesh Brook and occurs along the northern brancli of the 

 stream It also occurs south of the brook, the line of contact with the 

 granite crossing south of the ice-house pond. West of this pond, along 

 the road, the schist has been brecciated so as to resemble at first sight a 

 conglomerate. In places this rock looks very much like a very fine-grained 

 aplite made schistose by shearing. East of the ice house, between the 

 branches of the brook and also south of the south branch, a greenish schist, 

 often containing a dark-greenish hornblendic-looking mineral, is common. 

 The granite north of this schist area not uncommonly also shows the eifect 

 of shearing and has a sort of gneissoid structure. The schist area has not 

 been thoroughly studied. This will later, however, be desirable in order 

 to learn whether the present eastern border of the Carboniferous area north 

 of Nannaquacket Pond is due to the topography of the early Carboniferous 

 sea bottom or is a result of subsequent sliding of the more northern pre- 

 Carboniferous granite to the westward. 



OOXJXiD ISXjAjN*!). 



The main mass of the island consists of a very fine-grained rock, vary- 

 ing in color. In some places it is white, with minute black specks, prob- 

 ably biotite; in others it is light bluish gray or dark blue; in still others it 

 is gray, but contains many light-colored blotches. This rock has been 

 extensively brecciated by a shearing action which took place in a direction 



