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Upper Huronian (Animikie). — This series has been 

 divided by Silver into the following divisions, 

 i. Black slate. 



2. Upper iron formation. 



3. Slate (somewhat calcareous.) 



4. Thin bedded impure limestones. 



5. Iron formation proper. 



6. Quartz conglomerate. 



The last of these is not more than six inches (15 cm.) in 

 thickness, where it has been seen in this vicinity and con- 

 sists of pebbles of vein quartz. 



The other five members of the series are reduced by 

 Mr. Smith to four divisions by omitting the thin bedded 

 limestones which, according to an analysis by Mr. A. G. 

 Burrows (8, p. 163), would appear to be ankerite in which 

 the iron has been oxidized to ferric oxide. Mr. Smith 

 looks upon these four divisions as representing one "con- 

 tinuous period of deposition during which the conditions 

 varied between those of chemical and probably also 

 organic sedimentation, producing the iron-bearing forma- 

 tions, and those of mechanical sedimentation with the 

 production of the slates." (6). 



The upper black slate has not been found around Loon 

 lake, though in other places it is well developed. The 

 upper iron formation is a thin bedded cherty iron carbonate 

 resembling in texture the jaspilite of the Vermilion and 

 Mesabi ranges in Minnesota. 'It varies in colour from 

 dark grey to very light-coloured, although the most 

 characteristic phase is a dark and light- 

 banded rock. '(6) 



The lower iron formation consists essentially of taconite, 

 and all stages in the formation of iron ore may be observed 

 in this formation. The slate between the upper and 

 lower iron formations has not been described nor has any 

 outcrop been located either on a published map or in 

 printed descriptions. 



Granite. — North of Loon lake is a series of hills of 

 granite intrusive into the rocks which have been assigned 

 to the Lower Huronian and the Keewatin. These hills 

 are dome shaped and have been denuded by glaciation. 

 That the original form of the intrusive mass was not mater- 

 ially different from the present form is shown by the 

 presence of contact breccia over the surface of the hills. 

 These masses are similar to if not identical in composition 



