REVIEWS 163 



A. P. Coleman. " Rock Basins of Helen Mine, Michipicoten, Canada." 

 Bulleti7t of the Geological Society of America, Vol. XLIII (1902), pp. 



293-304. 



Colemiin discusses the origin of the roclc basins of Beyer and Sayer's Lakes of 

 the Michipicoten district of Canada, the former containing the Helen iron-ore body. 

 He holds the lake basins to have resulted from the solution of the iron-bearing rocks 

 long before glacial time. 

 A. B. WiLLMOTT. "The Nomenclature of the Lake Superior Formations." 



Journal of Geology, Vol. X (1902), pp. 67-76. 



Willmott discusses the nomenclature of the Lake Superior formations, this being 

 practically a consideration of Van Hise's "Iron-Ore Deposits of the Lake Superior 

 Region." ' He argues principally against the correlation of the Animikie series with 

 the Upper Huronian of the original Huronian area. He states that there can be no 

 doubt that Logan in 1863 included within his Huronian two series — the one typically 

 represented by the banded jaspers, the other by the slate conglomerate and the jasper 

 conglomerate. This has been uniformly followed from that time forward by all 

 Canadian geologists, and by many American, the vertical green schists and their 

 interbedded banded jaspers being considered Lower Huronian. Professor Willmott 

 doubts the advisability of attempting the separation of the green volcanics and sedi- 

 ments, except in limited areas of economic value. Here each would be given forma- 

 tional names, just as Van Hise has done with the Ely greenstone and the Soudan iron 

 formation. In other places the volcanics and eruptives will take the name of the 

 sediment with which they are associated. The lowest sedimentary series of the Lake 

 Superior region is the Lower Huronian. These sediments were included in the areas 

 mapped. as Huronian by Logan in 1863, and, although not actually found in place by 

 him, were recognized from their fragments, and to him should be given the credit. As 

 so used, the term "Lower Huronian" is nearly equivalent to the term "Archaean" as 

 used by Van Hise, and the term "Upper Huronian" is equivalent to Van Hise's 

 " Lower Huronian." Accordingly, the Animikie, or the Upper Huronian of Van Hise, 

 is younger than the original Huronian series. That the Animikie is later than the 

 true Upper Huronian or original Huronian may be shown in the following ways : 



1. Stratigraphically it is the third series of sediments upwards from the bottom 

 of the geological column in the Lake Superior region ; the Upper Huronian is the 

 second. 



2. Lithologically, the two series are quite different, and so presumably are of dif- 

 ferent age. There is very little conglomerate at the base of the Animikie ; in the 

 Huronian the quartzites, slate conglomerates, and jasper conglomerates are of great 

 thickness. The oolitic jaspers found in the Animikie are quite absent from the 

 Huronian. The shales, so important in the Animikie, are almost unknown in the 

 Huronian. The laccolitic sills of the Animikie are lacking in the Original Huronian. 



3. Structurally, the two series are usually said to be alike in that both lie flat and 

 undisturbed. While this is quite true of the Animikie, it is only partially true of the 

 Huronian north of the Georgian Bay, and is untrue of the Upper Huronian about 

 Batchawana and Michipicoten. Coleman^ and Murray 3 have described cases of 



' C. R. Van Hise, " The Iron Ore Deposits of the Lake Superior Region," 

 Tiventy-first Annual Report of the U. S. Geological Survey, Part HI, pp. 305-434. 

 ^Bureau of Mines, Ontario, 1901, p. 189. 

 '^ Geological Survey of Canada, 1858, p. 95. 



