HISTORICAL REVIEW OF THE GEOLOGY OB" MICHIGAN. 189 



bearing or Hiironiaii series. Over this (juestion there lias been also a 

 long controversy, participated in by various writers, and it cannot yet 

 be said to be fully settled. I believe, however, that we are within sight 

 of agreement on the great essentials. Mr. Van Hise is preparing a final 

 monograph on the iron ores of Lake Superior, and I think that in that 

 he will assume a position with which I can coincide in all the essential 

 fundamentals. I copy from his report on the iron ore deposits of the 

 Lake Superior Kegion in the Twenty-first Annual Report, a table slightly 

 modified, the modifications which I have nmde being indicated by 

 italics. It will be noticed that he has already introduced the possibility 

 of sediments and iron bearing formations into the lowest division, — his 

 Archean, — my Laurentian, which is a modification of his earlier position, 



Cambrian Lake Superior Sandstone. 



(Unconformity) 



Michigamme formation (locally replaced by Clarks- 

 burg volcanic formation). One might divide the Mich- 

 igamme sedimentary formation into three parts: (a) 



TT TT • /TT upper slate member, (b) iron-bearing member, (c) lower 



Upper Huronian, (Upper, {'^ member. 

 Marquette Series.) ' 



Rominger's 



Lake Hanbury? 



1 



Ishpeming formation, consisting of two members: the 

 Bijiki schist (in western part of district), and the Good- 

 rich quartzite, containing detrital ores at its base. 



(Unconformity)' 



Middle Huronian. *' . Negaunee formation. (The chief iron bearing forma- 



' tion 



Rominger's | Siamo slate, containing, interstratified amygdaloid. 



Quinnesec? [Ajibik quartzite. 



( Unconformity) 



Lower Huronian, (Lower ( Wewe Slate. 



Marquette Series.) \ Kona dolomite. 



Rominger's Norway? ( Mesnard quartzite. 



(Unconformity) 



f Granite, syenite, peridotite. 



I Kitchi schist and Mona schist, the latter banded, and 

 (Laurentian.) ■( in a few places containing narrow bands of iron bearing 



I formation. 

 [ Palmer gneiss. 



The iron bearing series and all three members of the Huronian have 

 in many places been folded and a slaty cleavage produced which has 

 been mistaken for the original bedding. They are probably least dis- 

 turbed to the west in the Gogebic Range, where they occur in a fairly 

 regular band with Laurentian rocks to the south and the Copper-bear- 

 ing rocks to the north. Above them and generally unconformable come 

 the rocks of the Copper-bearing series. Their distribution was fairly 

 iu-curately outlined by Dr. Houghton and his assistants, — Burt and 

 Hubbard — and it is summarized in the work of Foster and Whitney. 

 Their mineralogical character was quite accurately determined by Koch 

 and in fact, except for fine distinctions,' is very simple. We have a 

 series of flows of lava ; the center massive, the top originally porous and 

 full of bubbles which are generally filled in so as to produce a spotted 

 appearance. The commonest minerals are augite and a lime-soda feld 



