574 THE MARQUETTE IRONBEAEIiSfG DISTBICT. 



the different foi'mations and between dissimilar beds of each formation. 

 As these layers were rubbed over one another schistosity was developed 

 parallel to the bedding in many places. The unconformable contact 

 between the Upper Marquette and Lower Marquette series was one of 

 the greatest planes of movement, and adjacent to it the rocks of both 

 were rendered schistose. The contact between the Ai-chean and the 

 Lower Marquette series was another such plane of movement, and at many 

 places a considerable zone at the base of the Lower Marquette series 

 was transformed into a schist, as was also a zone of the rocks of the 

 Archean immediately below. Where the lower quartzite was thin, as in the 

 Republic tongue, this change affected the entire basal formation. In other 

 places, where the folding was less severe, the rocks still plainly show clastic 

 characters. 



These statements as to the adjustment between the layers and the 

 development of schistosity parallel to the bedding do not fully apply to 

 the nearly homogeneous Michigamme and other slates. There apparently 

 occurred in these formations an actual flowage, the whole acting in a way 

 as plastic material; consequently there is frequently a discrepancy between 

 the cleavage or schistosity and the bedding. Oftentimes it happens that the 

 schistosity nearly coiTCsponds with the bedding on one side of a fold and cuts 

 across it upon the other (tig. 16). In this case the complicated character of 

 the folding and the reduplications of the beds are particularly likely to be 

 overlooked. In the crystalline rocks constituting the Basement Complex 

 the north-south pressure was the predominating force, and a nearly vertical 

 schistosity has been extensively developed with an approximately east-west 

 strike. This is particularly conspicuous in the case of the volcanic rocks 

 which, like the Michigamme slate, were approximately homogeneous. The 

 whole mass was mashed together, and flowage resulted in well-developed 

 schistosity. 



During the time in which the dynamic forces were at work — that is, 

 while the folds, fractures, cleavage, and schistosity were being formed — 

 chemical and molecular forces were active, and from the old minerals new 

 minerals were developing. Also other mineral material was being deposited 

 in the interstices. Thus we have quartzites or quartz-schists in place of the 



