SOME P RE-CAM BRIAN LITERATURE OF NORTH AMERICA 91 



ral features which favored the circulation of water. In Brazil, the 

 iron ores are the result of primary deposition, and while some 

 secondary concentration by leaching has taken place, it is local and 

 very subordinate. The fragmental ores of Brazil have no counter- 

 part in the Lake Superior region excepting in conglomerates at the 

 base of formations resting on ore deposits. Glacial erosion may 

 have removed large quantities of fragmental ore in the Lake 

 Superior region. 



Miller^ points out that certain pre-Cambrian stratigraphic units 

 of the Northwest Highlands of Scotland are similar to some of 

 Canada as indicated by the following table : 



Canada Scotland 



A. Keweenawan. A. Torridonian. 



B. Huronian with intrusives. B. Intrusives of Lewisan. A frag- 



mental series of quartzite, etc., 

 has been removed before Torri- 

 donian was deposited. 



C. Keewatin-Laurentian Complex. C. Lewisan. Fundamental Complex. 



Granite and gneiss, greenstone, Gneiss, hornblende and chloritic 



limestone, iron formation, etc. schists, limestone, and iron 



formation. 



Miller and Knight^ believe that the present use of the term 

 Laurentian as applied to the granites and granite gneisses intrusive 

 into the Keewatin but presumably not in the Lower Huronian may 

 have led to poorly based correlations. 



^W. G. Miller, "A Geological Trip in Scotland," Out. Bur. Mines, 20th Ann. 

 Rept., 1911, pp. 259-69. 



^W. G. Miller and C. W. Knight, "The Laurentian System," Ont. Bur. of Mines, 

 20th Ann. Kept., 1911, pp. 280-84. 



[To be continued] 



