﻿Problems in Quehec Geology. 495 



limestone pebbles an abundant fauna of trilobites has 

 been found, which indicates that these have been derived 

 from the beds of the Georcjia series, though their source 



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does not readily appear. As the whole series has, how- 

 ever, been so faulted and overturned, it is presumable that 

 the lower members have been thrust upward and removed 

 by denudation. The gap in the sequence of formations 

 along the lower St. Lawrence may thus be explained, 

 though it is possible that a more careful search among 

 some of the oldest or lowest beds will yet result in the 

 discovery of strata holding a true lower Cambrian fauna 

 from which these pebbles have been derived. Certain 

 beds below the upper Sillery have already yielded very 

 ancient types of graptolites, as well as Cambrian forms of 

 trilobites. 



3rd. The Sillery has been conclusively shown by the 

 examination of a number of sections, both near the St. 

 Lawrence River, as well as at points inland, to represent 

 the lower part of the group, and there is a marked break 

 between these beds of red and green shale and sandstone, 

 which are the extension downward of the Levis beds and 

 the lower series of hard slates and quartzose strata. It is 

 at the base of the former portion that the coarse conglom- 

 erates, in the limestone pebbles of which the primordial 

 fossils are found, occur, so that these lower beds must 

 represent a lower or older portion of the Cambrian. 



As a result of the recent work in this area, therefore, 

 the Sillery formation is now transferred from its supposed 

 position above the Levis to the lower part of the series ; 

 and there appears to be a gradual upward passage from 

 the slates and conglomerates of this portion to the slates 

 and limestones of the Levis, the fossils in which are of 

 a more recent aspect and quite distinct as a whole in 

 character from those found in the lower division. 



The study of the Levis beds, and a careful discrimina- 

 tion of the fossils found in the pebbles of the associated 



