372 i?. D. Irving — Is there a Huronian Group ? 



must cover two or more groups itself; it must be of the same 

 rank with Paleozoic, Mesozoic, and Cenozoic. 



To follow out the idea that is contained in these three terms, 

 the new term should have some reference to the life-conditions 

 of these early times. That life existed during the accumula- 

 tion of the pre-Cambrian fragmentals seems to me to admit of 

 no question. For proof of this I will not appeal to the high 

 development of the first Cambrian fauna, nor to the fossil or 

 fossil-like forms which have been found in the quartzites of 

 southwestern Minnesota, in the Keweenaw series of Lake 

 Superior, in the pre-Cambrian quartzites of Newfoundland, and 

 in the Grand-Canon series of Arizona; nor will I advance the 

 usual arguments in favor of an Archaean life. I will only 

 bring forward the wide-spread occurrence, within the Huronian 

 of the Lake-Superior province, of two materials whose organic 

 origin would seem to be beyond question. I refer to the car- 

 bonaceous shales and to the iron carbonates — or derivatives 

 from iron carbonates — often associated with them. It is some- 

 what singular that these materials have been largely ignored 

 in the various discussions that have taken place during many 

 years past as to the existence or non-existence of life in pre- 

 Cambrian times. It is true that the iron oxide accumulations 

 of the Archaean have been used in this connection very often ; 

 but a doubt always remains as to whether these may not pos- 

 sibly be of chemical origin. In the case of the iron carbonates 

 associated with carbonaceous shales in the Huronian, however, 

 it does not seem that any such question can arise, since, as I 

 have tried to show elsewhere, this association is one for which 

 we can imagine no possible explanation other than that gener- 

 ally given to account for the association of similar materials at 

 various higher geological horizons, notably the coal measures. 

 Again, the carbonaceous shales themselves, taken alone, furnish 

 an equally strong argument; for, while a doubt as to an organic 

 origin for the graphite masses of the Archaean may perhaps be 

 entertained, no such doubt can be admitted with regard to 

 these shale.*, the carbonaceous matter of which is mingled with 

 argillaceous fragmental material, whose accumulation in water 

 by the ordinary processes of sedimentation must be taken as 

 certain. Moreover, this carbonaceous matter, in the case of 

 those shales which are separate from the iron carbonate accum- 

 ulations, as well as in those that are associated with this car- 

 bonate, seems often to be distinctly organic matter, that is to say, 

 is hydro-carbonaceous. We need not question, then, the exist- 

 ence of life during the accumulation of part if not all of the 

 pre-Cambrian fragmentals. The nature of the life that then 

 existed, however, we know practically nothing about, since, 

 with the exception of those few doubtful forms already re- 



