THE LOWER HURONIAN. 329 



The normal iron-bearing Agawa formation — that which consists of the 

 chert, jasper, and iron bands, as, for instance, on the Wind Lake-Moose 

 Lake portage, and at the Canadian locahty on That Mans, Agawa, This 

 Mans and The Other Mans lakes — is identical, so far as its petrographic 

 character is concerned, with that which has alread}^ been described as the 

 Archean Soudan formation. In the course of the description of this formation 

 the conclusion was reached that this had been derived as the result of 

 alteration — the nature of which was also disciissed — from an original 

 cherty, iron-bearing carbonate. It is believed that this iron-bearing 

 Agawa formation was derived from the same kind of rock, and as the 

 result of processes analagous to those by which the Soudan formation was 

 produced. In the Soudan formation very little carbonate was found, 

 the reason being, very evidently, that the alteration had proceeded 

 so far that practically all of the carbonate had been changed. Some 

 carbonate-bearing bands were found associated with the jasjjers and 

 cherts on That ]Maiis Lake, and they bear a striking resemblance to the 

 carbonates in the Soudan formation. The carbonate-bearing phases of the 

 iron-bearing Agawa formation, to which reference has been made, contain 

 a comparatively high percentage of iron, as is shown by the very rich 

 brown ocherous crust which is found wherever the rocks have been 

 weathered. It is believed that this unaltered carbonate-bearing horizon 

 corresponds to the jasperized horizon, and that these unaltered rocks repre- 

 sent an earlier phase of the jasperized rocks, the alterations by which the 

 jaspers and cherts were produced not having taken place for some reason 

 as yet unexplained. 



RELATIONS TO OTHER FORMATIONS. 



In the preceding pages statements have already been made of the rela- 

 tions which these rocks bear to the adjacent formations, and the details will 

 be given under the heading "Interesting- localities." 



At this place the relations of the iron formation to the adjacent forma- 

 tions will be (concisely stated. In the first place, it is clear that the iron 

 formation lies above the Ogishke conglomerate, with which it has been 

 found in contact at several places. In every instance it lies above the con- 



