STRUCTURAL FEATURES OF THE PRE-CAMBRIAN 189 



or more so than the folding along east-west axes. As these are the 

 most easterly areas studied, it is not known whether the cross- 

 folding represents merely a local crumpHng along some plane of 

 weakness or whether the areas are on the western edge of a region 

 folded along northeast and southwest axes. A study of the reports 

 and maps of the country to the east and north, however, makes the 

 latter supposition seem probable. 



1^ • [^ 



aranite Ryolite 



Geohgica/ Anticlma/ Syncfinel Dip 



Andesite 



3XIS and stritce Str 



Basalt -'/ r^ 



" I IS y- 



ike ^ 



Fig. 7. — The Eau Jaune-Obatogamau area 



The position and direction of the axes of folding are shown on 

 the map. The one set, corresponding with those in the other 

 areas described, strikes S. 70° E., apparently swinging in the 

 western part of the area to east. The other set strikes N. 35° E. 

 on Eau Jaune Lake, and N. 50° E. on Obatogamau Lake. The 

 succession and distribution of beds suggest that the larger structure 

 is that of a synclinorium whose axis has a northeasterly strike. The 

 rocks on the eastern side of the area are basalts. Andesites overlie 

 the basalts on the eastern side and outcrop also in the western part. 

 Their composition gradually becomes more acid toward the center, 



