SOME STRATIGRAPHIC AND STRUCTURAL FEATURES 

 OF THE PRE-CAMBRIAN OF NORTHERN QUEBEC 



H. C. COOKE 

 Geological Survey of Canada, Ottawa 



. PART II 



DETAILED AREAL DESCRIPTIONS 



In the following descriptions the structures of the separate areas 

 studied will be briefly stated, with the conclusions as to succession 

 which were made in each area. Fig. 3 shows the relative positions 

 of the areas described. In the Opawika, Father's Lake, Windy- 

 Lake, and Eau Jaune-Obatogamau areas, where the rocks are 

 largely of the basal lava series, or Abitibi volcanics, the determina- 

 tions of the structure were in each case the result of a large number 

 of observations, using the methods described, on the attitude of 

 the lava flows over as wide an area as the nature of the work per- 

 mitted. The results of each determination by any one of the 

 methods described were checked whenever possible by the applica- 

 tion of one or more of the other* criteria as well. No other strati- 

 graphic methods were applied or, in fact, were applicable. For the 

 sake of brevity, therefore, the methods of determination of the 

 structure in the separate instances will not be stated, as this would 

 only involve unnecessary repetition. 



The Opawika area. — The Opawika area (Fig.4) borders the Opa- 

 wika River near its junction with the Waswanipi River. It includes 

 the northern portion of Tush Lake, Opawika Lake, and the Opawika 

 River from Opawika Lake down to Sturgeon fall. The rocks are 

 a series of closely folded lavas and tuffs and are unusually well 

 exposed. The axes of the folds strike N. 75° E., but their plunge 

 was not determined. The approximate position of these axes is 

 shown on the map. The southernmost fold, on Tush Lake, 

 is an anticline, the southern limb of which is cut off by granite. 

 The axis of the syncKne to the north follows approximately the 



