﻿42 JV. S. Shale? 1 — Geology of Cobseook Bay District, Me. 



It appears from the distribution of these contemporaneous 

 deposits of volcanic nature that the center of eruption was to 

 the northeastward of this district and that the intensity of 

 its effects diminished toward the southwest. There is some 

 reason to believe that this field of volcanic material is the 



ffightide 



Sections on Deny's River. 

 Fig. 3. — A, stratified volcanic ash. B, dark colored shales. C, ash beds as 



before. D, fragmental trap. 

 Fig. 4. — A, volcanic breccia. B, shales. C, felsite. D. indurated sandstone. 



E, banded felsite. F, drift. 



extension of the ash-bed district which is known to occur near 

 St. Johns, New Brunswick. The preliminary study of this 

 Cobseook district has sufficed to show that in about this same 

 horizon there are very extensive sheets of lava which were 

 possibly surface flows, though afterwards buried beneath sub- 

 sequently formed deposits. Of these the most important is a 

 great mass of reddish felsite which occupies a wide field in the 

 northern part of Moose Island and probably extends beneath 

 the bays in this neighborhood. Besides this extensive sheet 

 there is another, of the same general character, seen in the hill 

 crowned by the old earthwork fort near the middle of Moose 

 Island. The latter sheet of felsite is apparently interbedded in 

 slates of Silurian age. 



Section on shore N. of Red Island. 

 A, gray slabs and flags. B, greenish diorite. C, red felsite. D, high tide mark. 



The felsites of this region also appear in dykes having a 

 general north and south trend, which traverse all the other for- 

 mations of this district; being perhaps the latest intrusions 



