FOLDING OF I5ASEMENT COMPLEX AND MARQUETTE SERIES. 569 



to the northeast. The frag-mental formations thus appear to plunge under 

 the Arcliean islands on the south sides of" the areas and to lie above them 

 on the north sides. The infolded character of the Upper Marquette and 

 Lower ^larquette series is illustrated by the isoclinal overfolds along the 

 north half of the noi'th-south quarter line of sec. 21, T. 47 N., It. 27 W. 

 (Atlas Sheet XXVI). Here a north-south section at one place shows the 

 Negaunee formation; above this, in its proper position, is the Goodrich 

 quartzite; and then there appears above this again the Negaunee formation. 

 At the west end of the Jackson mine also the isoclinal overfolds of the 

 Goodrich quartzite and the Negaunee iron formation are beautifully shown 

 (Atlas Sheet XXVIII). However, the best locality of all to illustrate the 

 isoclinal overfolds is in sec. 30, T. 48 N., 11. 28 W. (Atlas Sheet XVIII). 

 Here the infolding is between the granite of the Northern Complex and the 

 Lower Marquette Ajibik quartzite and Siamo slate. A section at the most 

 favorable place passes from the Siamo slate to the Archean granite, then 

 again to the Siamo slate, froin this to the Ajibik quartzite, into the Archean 

 granite, in turn into the Ajibik quartzite, granite, Ajibik quartzite, granite, 

 Ajibik quartzite, and probably following this, although topography rather 

 than exposures indicates it, come again the Siamo slate, the Ajibik quartz- 

 ite, and the Archean. For the whole of this distance the dips are to the 

 south. Two islands of Archean are cut off from the main area. The quartz- 

 ites and slates occupy the valleys, while the granite is more resistant and 

 occupies the higher land. Controlled by the western pitch, the tongues 

 of quartzite which project into the Archean die out to the east, and open 

 out to the west. We have here, then, the conjoint eftect of the close 

 isoclinal overfolding due to the north-south pressure and the great north- 

 south folding caused by east-west pres.sure which gives all of the formations 

 a westerly pitch. As for the major part of the district the north-south folds 

 are more open and the east-west folds more conspicuous, the latter may be 

 designated the major folding, and the former folds may be considered as 

 cross folds which give the east-west folds a pitch. 



The western major north-south anticline at the east end of Michigamme 

 Lake causes the Marquette rocks to here contract; but to the west, in pass- 

 ing toward the next syncline, these Algonkian rocks open out into a broad 



