32G 
The American Geologist. 
May, 1891 
A critical re-exarnination of the region north of lake Huron is al- 
most absolutely necessary to further satisfactory progress. It 
has occurred to me that it might not be out of place for the Inter- 
national Congress of Geologists at its coming session to take cog- 
nizance of this necessity and nominate a commission to prose- 
cute the investigation of the field. The problem might be re- 
garded as an international one, the field being along the boundary 
and the interest equal on both sides, so that the commission might 
act in harmony with the United States and Canadian geological sur- 
veys. 
Prof. Van Hise finds as a result of his present classification of 
the lake Superior geological groups no use for the term Ontarian 
which I suggested some time ago as a useful if not necessary one 
to include the different rock groups of the upper Archaean. That 
classification being shown to be untenable the necessity for such 
a comprehensive term appears all the stronger from a consideration 
of Prof. Van Hise's table. There he places an irruptive uncon- 
formity between the Laurentian and the Coutchiching. This ir- 
ruptive unconformity occurs between the Laurentian and the 
system of strata of which the Coutchiching and Keewatin are con- 
stituent groups. This system comprising two, and possibly more, 
groups, seems to me to require a name, the necessity being even 
greater than the need of Algonkian to include Animikie and 
Keweenawan. 
As a substitute for Prof. Van Hise's table of classification I 
offer the following for the region northwest of lake Superior : 
PALAEO- 
ZOIC. 
Algonkian 
System. 
Keweenawan or Nipigon 
Group. 
Unconformity. 
Animikie Group. 
(Possibly Huronian.) 
Unconformity — Greatest erosion interval in American Geology. 
