656 EDWARD STEIDTMANN 



Erosion has destroyed much ore. Some ore has been preserved 

 by folding and faulting. 



Miller and Knight's^ classification of the pre-Cambrian of 

 Ontario follows. 



Keweenawan 



Unconformity 

 Animikean 



Includes rocks called Animikie heretofore, also Logan's type 

 section, and the Cobalt and Ramsay Lake series. Minor 

 unconformities occur within the Animikean 

 Great unconformity 

 (Algoman granite and gneiss 

 Igneous contact) 



Laurentian of some authors, the Lorrain granite of Cobalt, and 

 the KiUarney granite of Lake Huron 

 Timiskamian 



Includes sedimentaries of various localities heretofore called 

 Huronian — also the Sudbury series of Coleman 

 Great unconformity 



Same order as that at base of Animikie 

 (Laurentian granite and gneiss) 



Igneous contact 

 T • f Grenville (sedimentary) 

 L^g^^^^^lKeewatin (igneous) 



The authors differ from Collins and Coleman in that the latter 

 recognize a twofold division of the Animikean group. Other differ- 

 ences are largely a matter of names and emphasis on the relative 

 importance of various features. Lawson, Coleman, and Collins 

 emphasize the unconformity at the base of the Animikean and 

 recognize two major groups. Miller and Knight stand alone in 

 concluding that the Grenville of southeastern Ontario is in part 

 interlayered, but largely above the Keewatin. Other authors are 

 either less confident or express doubt as to the position of the 

 Grenville. 



Parsons^ describes the productive iron deposits of the Michipi- 

 coten district. 



I W. G. Miller and C. W. Knight, "Revision of Pre-Cambrian Classification in 

 Ontario", Jour. GeoL, Vol. XXIII (1915), pp. 585-99- 



^ A. L. Parsons, "The Productive Area of the Michipicoten Iron Ranges 

 (Ontario)," Ontario Bur. Mines, Ann. Rept., Vol. XXIV (1915), Part I, pp. 185-213, 

 22 figs., 3 pis., maps. 



