SOME STRATIGRAPHIC AND STRUCTURAL FEATURES 



OF THE PRE-CAMBRIAN OF NORTHERN 



QUEBEC 



H. C. COOKE 



PART IV 



DIASTROPHISM 



The evidence cited in the preceding pages indicates that previ- 

 ous to the end of the period of deposition of the Mattagami series 

 no general orogenic movements took place in this region, but that 

 such movements as occurred were of the gentle, epeirogenic type. 

 After the deposition of the Mattagami series, intense orogenic 

 movements went on, which folded the Mattagami and Nemenjish 

 series and the Abitibi volcanics closely, and converted a large 

 proportion of them into schists. By some writers this folding 

 has been supposed to have accompanied the intrusion of the granite, 

 and been caused by the hydrostatic pressure of the upwelling 

 magma. Were this the case, the remnants of the older series should 

 have dominantly synclinal or monoclinal structures, and there 

 would be no general correspondence between the axes of the folds 

 of the different remnants. Such a condition appears to obtain in 

 the Grenville-granite complex in the Adirondacks, according to 

 W. J. Miller.' However, it does not appear to be the case through- 

 out Ontario and Quebec, where no dominantly synclinal or mono- 

 clinal structure exists, and where there appear to be a definite 

 subparallelism of the axes of folding over considerable areas. 



A tabulation of the areas which have been discussed, with their 

 general structure and the strike of their axes of folding as nearly 

 as determinable, is given on page 368. 



The parallelism of the axes of folding of the different, rather 

 widely separated areas is remarkable. All, it will be observed, 

 fall within between N. 75° E. and S. 70° E. As the folds are 



'W. J. Miller, Jour. GeoL, XXIV (1916), 587. 



367 



