122 Van Hise — Attempt to harmonize some apparently 



Above the upper quartzite, which is the base of the Upper 

 Marquette Series, follow the black slates (sometimes carbon- 

 aceous), graywackes, and mica- schists, together of great thick- 

 ness. These appear a short distance wrst of ISTegaunee; for 

 some six or eight miles east of Lake Michigamme cover a 

 larger area than the members of the series below the uncon- 

 formity, and about Michigamme Lake have a great development. 

 In these upper slates are locally belts of chert, associated with 

 which are ore-bodies of considerable size, among which as 

 types maybe cited the Wetmore, Dalliba and Beaufort. These 

 ores are, however, of a very different character from those 

 which occur in the red banded jasper already described, being 

 always soft, and oftentimes more or less limonitic. Our study 

 has not extended far enough so that we feel certain on which 

 side of the break some of the mines of the Marquette district 

 occur. Among such are those of Teal Lake, which we feel 

 inclined at present to place in the upper series. 



It is thus plain that in the Marquette district we have, as 

 maintained by Brooks, at least two ore-bearing horizons ; nut 

 only this, but these horizons are separated by a great uncon- 

 formity and therefore belong to different series of rocks. 

 Those upon the lower side of this break, in the exceedingly 

 contorted jasper, in the schistose character of its quartzites, 

 and in the general assumption of a semi-crystalline character, 

 show the evidence of profound dynamic action. In the upper 

 series, on the contrary, the folding has not been intense ; the 

 fragmental character of the slates and quartzites under the 

 microscope is evident at a glance, and no indication of great 

 dynamic action is seen. While subsequent to the deposition 

 of the upper series, the whole region has been subjected to a 

 new folding, great enough in places to give the later series a 

 dip of 60° or 70° as at the Goodrich, it has not suffered since 

 that time such intense dynamic movements as has produced 

 the more thoroughly crystalline and folded character of the 

 earlier series. 



Unconformity in the Vermilion Lake district. — Near Ver- 

 milion Lake, while we have not yet discovered the same struc- 

 tural evidence of a physical break between the iron-bearing 

 and an overlying newer series, there occurs a wide belt of con- 

 glomerate which overlies the iron formation and contains very 

 numerous fragments from that formation, as indicated by 

 Irving in the paper already cited. A similar conglomerate, 

 containing red jasper fragments and having a wide extent, 

 occurs at Ogishki Manissi Lake.* This rock is also found at 

 points intermediate between Vermilion Lake and Ogishki 

 Manissi. 



* Enlargements of Hornblende Fragments, C. R. Van Hise: this Journal, III, 

 xxx, 232, 1885. 



