FOLDING OF BASEMENT OOMFLEX AXJ) ^NIAlfQUETTE SERIES. 567 



crown — that Is, for tlie eastern (! or 8 miles of the (hstrict — suj)eruiiposed 

 upon it folds of the second order, making this part of the fold an anti- 

 clinorium. These secondary folds have lengths varying fidiu 1 to several 

 miles, and therefore a given formation may be repeated in an east- west 

 direction along the present plain of denudation. The other major anti- 

 cline belonging to this system of folds is one running north and south 

 thi-ough the east end of Michigamme Lake. From this line the Algonkian 

 belt l)roadens to the east and to the west. It then follows that all of the 

 district between the center of range 25 west and the east end of Lake 

 Michigamme may be regarded as a great north-south syncline. 



The major part of the district has been affected, however, by much 

 more powerful pressure in a north-south direction, so that the folds in an 

 east-west direction are much more conspicuous than the north-south folds of 

 greater wave length and greater amplitude. The conspicuous character 

 of these folds has, in fact, led to neglecting the effect of the folding in the 

 other direction, and thus one of the most important clews to the distribution 

 of the formations was unnoticed. As a result of the north-south pi-essure, 

 the Upper and Lower Marquette series together have been bent into a 

 great synclinorium. At the east end of the district the Mesnard quartzite 

 is overturned at one place and dips under the Southern Comjjlex at an 

 angle c)f SC. The strikes of most exposures are mainly controlled by the 

 east-west folding, but at the east and west ends of the areas of the forma- 

 tions the larger north-south folds already described control the strike. In 

 passing to the west from Lake Superior, on the south side of the district, 

 from Lake Mary to Goose Lake and somewhat beyond, the secondary north- 

 south folds and the primary east-west folds are of about equal amplitude, 

 although the east-west folds are closer and give higher dips. As a conse- 

 quence of these two sets of folds some belts strike north and south, some 

 east and west, and some in intermediate directions, thus giving, at first sight, 

 an apparently lawless distribution of the formations; but when the char- 

 acter of the folding is understood the distribution is perfectly explained. 

 From the north-south line running through Goose Lake to the west line 

 of range 28 west is the area in which the Marquette series have the 

 greatest width. For this part of the district it appears that the less rigid 



