376 H. C. COOKE 



series elsewhere in northern Quebec from the reports. The Timis- 

 kaming, Sudbury, and Hastings series to the south and southwest 

 may possibly be of the same age, though a definite correlation cannot 

 now be made. 



The same difficulties obtain in the Mattagami series as in the 

 Grenville series with regard to a marine or non-marine origin. 

 Generally speaking, the composition of the two series is very similar, 

 that of an altered, rather impure sand, implying conditions of 

 rapid weathering and deposition without extended decomposition 

 of the rock constituents. All the arguments for and against a 

 marine origin that have been previously cited in the case of the 

 Grenville hold also in the case of the Mattagami series, with the 

 exception that the Mattagami series includes a heavy basal con- 

 glomerate of such thickness that a non-marine origin for this 

 member at least seems very probable. In the Lucky Strike area, 

 where the series has been greatly thinned by shearing, the present 

 thickness of the conglomerate band is approximately 300 feet. 

 In the Kenoniska area there are two bands of conglomerate, sepa- 

 rated by a thick, massive, basic greywacke, with very little trace 

 of bedding and holding an occasional pebble. The thickness of 

 the whole is very difficult to estimate on account of the probable 

 thickening of the formation at the nose of the fold by fiowage, 

 and uncertainty as to the plunge of the fold. A minimum estimate 

 by the writer, however, yielded a thickness here of at least 1,000 

 feet. According to Barrell, marine conglomerates are rarely over 

 100 feet in thickness. If this is true, the conglomerate member of 

 the Mattagami series is probably of non- marine origin. 



Diastrophism 



Certain considerations seem to indicate that the great dias- 

 trophic movements which followed the deposition of the Mattagami 

 series were connected with, or resulted in, the primary formation 

 of the great geosyncline of Hudson Bay. These may be summarized 

 as follows: 



I. If the Nemenjish and Mattagami series are considered 

 to be marine formations, their distribution indicates that the only 

 possible land mass which would supply the necessary sediments 

 must have occupied the present position of Hudson Bay. 



