PRE-CAMBRIAN OF NORTHERN ONTARIO AND QUEBEC 327 



degrees north except within 2 miles of the northern edge where 

 they are steeply north or vertical. The dips of the northern edge 

 are due to overturned folding, as the writer has shown/ If the 

 series as mapped is all one, its thickness in Quebec is at least 

 ,22,000 feet, unless the outcrops have been repeated by folding; but 

 Wilson records no southward dips. On the contrary, the width of 

 the conglomerate-greywacke band, the descriptions of which cor- 

 respond so closely with those of the Timiskaming of Ontario, is 

 uniformly about 2 miles, or very little greater than that of the 

 Timiskaming to the west. While it is possible therefore that the 

 series does increase in thickness from 2,600 to 22,000 feet by 

 depositional processes within less than 15 miles, the writer considers 

 it more likely, in view of the other evidence, that only the band of 

 conglomerate and greywacke along the north edge of the series as 

 mapped is of Timiskaming age, while much or all of the biotite 

 schists and amphiboUte to the south of this band belongs to the 

 older sedimentary series. 



ORIGIN OF TIMISKAMING SERIES 



The well-stratified nature of the Timiskaming sediments, 

 especially of the upper members of the series, such as the argillites 

 of Larder Lake, indicates that they have been laid down in a 

 body of standing water. The well-rounded pebbles in the basal 

 conglomerate indicate fairly long-continued wear, while the 

 angularity of the fragmental material, in the beds above the 

 proximate base, and its unsorted character indicate either that it 

 has not been carried far before deposition, or else that if carried 

 far the transportation has been very rapid, such as would be afforded 

 by torrential streams from a mountainous area. The unde- 

 composed character of the particles composing the greywackes, 

 etc., indicate rapid removal of detritus after disintegration, such as 

 occurs in any district where there is no vegetation to hold the rock 

 particles in place long enough for decomposition to take place. 

 The great thickness of the basal conglomerate in places and its 

 rapid variations in thickness are characteristic of continental or 

 subaerial deposits as also is the cross-bedding frequently to be 



^Ibid., p. 200. 



