REVIEWS 893 



but it contains in addition many new features of interest. Atten- 

 tion will be directed only to such conclusions as are new or vary 

 from those given in the preceding reports. 



In the Vermilion district the great Stuntz conglomerate and 

 equivalent rocks have been found to lie unconformably under 

 the Animikie series, which has been referred to the Upper 

 Huronian by the United States Geological Survey, and thus the 

 Stuntz conglomerate is correlated with the Lower Huronian 

 series instead of with the Upper Huronian, as in former reports. 

 The underlying greenstones, green schists, and iron formation, 

 the latter of sedimentary origin, are thus thrown into the 

 Archean. 



In the Mesabi district the Keewatin of the Minnesota Sur- 

 vey, which was in large part classed as "Archean" by the United 

 States Geological Survey and recognized by all as being uncon- 

 formably below the Animikie, is subdivided on the basis of recent 

 work in the district by C. K. Leith into an upper series of gray- 

 wackes, slates and conglomerates, correlated with the Lower 

 Huronian, and a lower basement complex, consisting mainly of 

 greenstones and green schists, correlated with the Archean. 

 This correlation is based on the equivalence of the Animikie 

 with the Upper Huronian long maintained by geologists of the 

 United States Geological Survey. 



In the Marquette district certain jaspers and associated 

 cherty and slaty rocks found intimately associated with the 

 basement rocks of the Archean, and previously supposed to be 

 Huronian rocks infolded with the Archean, are now themselves 

 called Archean. 



In the Michipicoten district of Canada the iron formation, 

 and associated greenstones and green schists, are correlated 

 respectively with the iron formation with associated green- 

 stones and green schists of the Vermilion district, and are there- 

 fore classed as Archean. 



The iron ores of the Lake Superior region are supposed to have 

 originated from iron carbonate in all districts outside of the 

 Mesabi. In the Mesabi district the ores have mainly resulted 

 from the alteration of a green ferrous silicate in small granules 



