﻿J¥. S. Shale?" — Geology of Cobscook. Bay District, Me. 51 



plants, and so far has furnished no trace of fossils which could 

 have been formed in marine deposits. I do not propose at 

 present to consider the age of the Perry series, as the problem 

 is one of peculiar difficulty and requires a much more extended 

 study than I have been able to give to it. 



We shall see in the subjoined account of the fossils from 

 several horizons of the Cobscook series that what appear to be 

 the uppermost beds of that series contain an assemblage of 

 forms which belong in the Devonian section. These fossils are 

 in a very thick section of blackish slates resembling in certain 

 features the Devonian black shales of the Mississippi valley and 

 the basin of the great lakes. These beds, like their presumed 

 western equivalents, probably were deposited in the waters of a 

 deep sea at a considerable* distance from the main land, yet in a 

 time that cannot be. very far separated from these Moose Isl- 

 and shales, as I have termed the black shales of this series. 

 The Perry sandstones were deposited in conditions that show 

 that they were made on the mainland or in an estuary basin. 

 Thus the elevation which followed the deep subsidence occur- 

 ring in the time of the Moose Island blaek shale, appears to 

 have brought this part of the continent above the sea level, 

 while in the Ohio basin it only served to shallow the water and 

 bring the shore nearer than it was before.* 



Although these conclusions as to the divisions of the rocks 

 in the regions near Eastport must be subject to review 

 after a more thorough knowledge of this district is attained, 

 they are sufficient to show that the oscillation of levels 

 of this district and the data attainable from the composition of 

 the sediment, will afford some important clues to the geological 

 history of the continent. It should be said that these divisions 

 of the rocks in and about the Cobscook district are presented 

 with much hesitancy ; although it may be found in the end to 

 be extremely imperfect, it will at least serve as a basis on 

 which to build a more critical study of the rocks of this region. 



Fossiliferous Horizons of the Cobscook series. 



We turn now to the problems connected with the strati- 

 graphic equivalency of the various divisions of the Cobscook 

 series. It has also been noticed that the very great amount of 

 igneous injections and the extensive erosion to which this dis- 

 trict has been subjected has made it very difficult to determine 

 the stratigraphical relations of the fragmentary sections which 

 remain. This problem is still further complicated by the diffi- 

 culty which is found in using the fossils contained in the rocks 



* It may be incidentally suggested that the conglomerates and sandstones of 

 the Perry series should be compared with the deposits of the Catskill period of 

 the Hudson district. 



