368 



H. C. COOKE 



probably to be considered only as secondary folds on the flanks of 

 the large regional major folds, parallelism is not to be expected 

 between them, as the strike of the axes of such secondary folds is 

 governed by the general strike of the strata at the point where they 

 occur. The extension of data of the foregoing type over a large 

 region will enable the nature of the great regional folds to be worked 

 out; but this cannot be done now, as the area under discussion, 

 though large, is small compared with the size of the Labrador 

 peninsula. 



Area 



Kenoniska. . . 

 Lucky Strike.. 



Brock 



Opawika 



Father's Lake. 

 Windy Lake . . 

 Nemenjish. . . 

 Eau Jaune.. . . 

 Mattagami. . . 

 Pontiac 



Structure 



Anticline 



Anticline 



Anticline 



An-Sy-An 



Syncline 



Monocline 



Probable anticline 

 Probable anticline 



Strike of Axis 



75° E. 

 75° E. 



N. 85° E. 



75 E. 



75° E. 

 E.-W. 

 N. 60° E. 

 S. 70° E. 

 N. 80° E. 

 E.-W. E. 



The general parallelism of axes indicates that the regional 

 folding was not caused by the hydrostatic pressures of batholithic 

 intrusions, but by a compressive stress affecting large areas uni- 

 formly; while the lack of shear in the granites shows that the fold- 

 ing occurred before their intrusion. This conclusion does not of 

 course invalidate the possibility that the intrusions followed the 

 folding very closely. 



The folding may therefore be dated as post-Mattagami and 

 pre-batholithic. It resulted in the formation of close folds with an 

 east-west axial trend and cross folds of a much more open type. 

 The cross folding has given a plunge of some 20" to the axes of the 

 major folds. 



In addition to the post-Mattagami folding movement, some 

 evidence exists that there was an earlier folding, affecting not the 

 region under discussion, but that to the south, the borders of the 

 continental segment, in Grenville time. This accompanied or 

 closely followed the intrusion of the earlier granite, but preceded 

 the intrusion of the anorthosite. In the Adirondacks, Gushing/ 



^ Reports of the New York State Museum. 



