Lawson.] 



The Eparchcean Interval. 



55 



portions of the continent manv thousands of feet of strata, 

 comparable in volume to the aggregate volume of the Animikie 

 and Keweenawan, were laid down in Middle and Lower Cambrian 

 time. It is, therefore, easily within the limits of possibility 

 that these two series represent the Middle and Lower Cambrian. 

 I do not contend for a moment that they are of Cambrian age; 

 I merely point out that as a matter of fact they are only known 

 to be of pre-Upper Cambrian age, and that there remains an 

 element of doubt in designating them pre- Cambrian elastics 

 under the term Algonkian. However, setting that doubt aside 

 for the present, and assuming the truth of the hypothesis that 

 the Animikie and Keweenawan are pre-Cambrian, I am perfectly 

 willing to recognize the utility of the term Algonkian as a desig- 

 nation for the period of time represented by these two series. 



This limitation of the term Algonkian to these two series, 

 together with any others that may be discovered to be of pre- 

 Cambrian and post- Archaean age, appears to be unsatisfactory to 

 certain eminent geologists engaged in the study of Lake Superior 

 geology, and one of the most noteworthy features of the im- 

 portant body of literature which has appeared in the last ten 

 years on that region, has been the persistent and ingenious 

 attempts to make the term Algonkian straddle this great gap 

 between the Animikie and the Archaean. Even if the definition 

 of Algonkian as a term embracing all pre-Cambrian elastics 

 were not precluded by the previous establishment of the term 

 Archaean, it would seem most unfortunate, if not subversive of 

 all geological practice, to have a single term embrace formations 

 on either side of so vast a period of non-deposition as the 

 Eparehsean Interval. Properly restricted, the term Algonkian 

 should have a taxonomic value co-ordinate with Cambrian, 

 Silurian, Cretaceous, etc. But even if it were found desirable 

 to erect a new term co-ordinate with Paleozoic and Mesozoic, as 

 is the evident purpose of those who seek to have it displace 

 Archaean, the attempt to make the new term bridge the 

 Eparehaean Interval is indefensible. The intense disturbances 

 which inaugurated that interval and the erosion which it repre- 

 sents, taken into consideration with the vast geographical extent 

 of that erosion, constitute a break in the record of sedimentation 



