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354 



THE AZOIC SYSTEM AND ITS SUBDIVISIONS. 



wliicli I have now sliown are really only the westward extension of the diorites 

 hornblende schists and mica- slates oi* Lanark and Renfrew counties, or, in 

 other words, of Groups I., II. and III. But these last, as we Lave also shown, 

 are simply a low portion of the gneiss and limestone scries which has always 

 been lopked upon as typical Laurentian. Cousetiuently, we are Anally led to 

 the important conclusion that the Hastings series is not, as it has up to the 

 present been considered, the most recent, but rather the oldest portion of the 

 great system of rocks we have been investigating from the year 18GG to 1875 

 inclusive. Further, it was clear that this great crystalline, gneiss and lime- 

 stone series rested upon a still older gneiss series, in which no crystalline lime- 

 stones had yet been discovered. This series is referred to as Division A in the 

 Report of Progress, 18GG-G9, where, however, limestones arc, incorrectly, men- 

 tioned as occurring in it. It . . . ., is the rock which may be said to form the 

 back-bone of Eastern Ontario, and the nucleous around which have been de- 

 posited all succeeding formations. This, then, is undoubtedly Archaean and 

 Lower Laurentian, and consequently the crystalline limestones and gneisses 

 constitute a series which would come in beneath Sir W. E. Logan's Upper Lau- 

 rentian or Labradorite series. As regards the existence of this latter as a dis- 

 tinct formation, however, I entertain grave doubts." (l. c, p. 254.) 



As a reason for these doubts be points to several localities where he 

 says the labradorite (Norian) rock is iutcrstratificd with the limestones 

 of this scries, and to others where it is conformable with the Hastings 

 series. Mr. Vennor concludes : — 



''So far, then, my investigations in Eastern Ontario show but three great 

 divisions or groups of rocks, namely : — 



'* 1. A great gneissic and sycnitic series, without limestones. 



"2. A thinner gneissic series with labradorites and limestones. 



" 3. Lower Silurian (Potsdam to Trenton)." (l. c, p. 277.) 



In 1877 Mr. Vennor said (Am. Jour. Sci., 1877, (3 ) XIY. 313-316) : 



" We find that there still exists a great Azoic formation, consisting of syenite 

 and gneiss (?) without crystalline limestones. In this there arc but little indi- 

 cations of stratification. Occasionally a limited surface presents an approach 

 to an obscure stratification, but this does not appear to be due to the deposition 

 of sediment.' This rock forms the back-bone of Canada. On it there has been 

 deposited a great series of gneisses, schists, slates, crystalline limestones and 

 dolomites, which, although heretofore grouped with the former, is clearly dis- 

 tinct and unconformable Eozoon danadense belongs undoubtedly in the 



main to the highest band of crystalline limestone yet found I may 



simply state that I consider both the Huronian and Upper Laurentian of Sir 

 W. e! Logan to belong rightly to ray second division, which I nmst for the 



present call Upper Laurentian I have found Labradorite rocks clearly 



interstratified with several of my bands of limestone, and I lUil entirely to dis- 



