[TYRRELL] PRE-CAMBRIAN GOLDFIELDS OF CENTRAL CANADA 



93 



Huronian 



Nipissing Diabase, 

 Sudbury Norite, etc. 



Intrusive Contact 

 Whitewater Series. 

 Cobalt Series 



Unconformity 

 Bruce Series 



Great Unconformity 



Batholitic granite intrusives 



Intrusive contact 



Sudbury Series 

 pre-Huronian \ Temiskaming Series 



Fabre Series, et . 



Unconformity 



Granite Intrusives 



Keewatin Group 



Mr. Collins points out clearly that it was Sir William Logan's 

 intention to subdivide the Pre-Cambrian rocks of the Canadian Shield 

 into a lower, highly metamorphosed or close folded portion which he 

 called "Laurentiajt,"' and an upper sedimentary and comparatively 

 little altered portion composed of rocks usually lying much more 

 nearly horizontal than vertical which he called "Huronian." 



Sir William Logan's own first characterization of these two great 

 subdivisions is as follows: 



^"In the same report (1845-6) is mentioned, among the Azoic 

 rocks, a formation occurring on Lake Temiscamang, and consisting of 



^ Sir W. E. Logan. On the Division of the Azoic rocks of Canada into the 

 Huronian and Laurentian. Can. Jour. Ser. II, Vol. 2, pp. 439-442. Nov., 1857. 



