THE GEOLOGICAL SECTION OF MICHIGAN 683 
U. S. Geological Survey as Archean (the basement and fundamental 
complex); by Wadsworth as the Cascade formation. Yet a glance 
at the various geological maps of Lake Superior shows that, however 
different the connotation, or meaning, and the theories of the various 
writers as to relationships, the areas and rocks denoted were mainly 
the same. 
Of other terms the ‘‘Mona” series is referred to by Foster and 
Whitney (p. 35), in the European sense, similar, but probably not 
identical, with the sense of the term used in the Marquette Mono- 
graph. ‘That and “Kitchi” are intended to be synonymous terms, 
but include some areas of extra highly metamorphosed Huronian. 
The term Mareniscan (Van Hise Monograph, 19, p. 473), appears 
to be a later synonym of Keewatin and it was decided by the joint 
committee to prefer the latter, but should further discoveries make a 
local Michigan term needful, may be used, as Wadsworth’s term 
Cascade is later and included, we believe, disparate things. The 
“Palmer gneiss” appears to be a sheared facies of some of the Huron- 
ian members up to the Siamo slate. It is only fair, however, to be 
ready in regard to so difficult a group as the earliest rocks, to accept 
a term even though there be some slight inconsistency or error made 
by the author, provided only that they are not so great as to destroy 
its usefulness by making uncertain its general application. 
Huronian.—The name under which the pre-Cambrian rocks have 
been assembled in this state has varied. Among the earliest writers 
who derived their information from direct observation was Credner, 
then Professor Pumpelly’s assistant, who published a paper in 
Volume II of this survey, and whose thesis for the doctorate was on 
Die Gliederung der eozoischen (vorsilurischen) Formations-Gruppe 
Nord-Amertkas’, which is, as far as I know, the first original work 
published after that of Foster and Whitney. Douglass Houghton’s 
“metamorphic” rocks were in the Huronian. Foster and Whitney, 
in spite of themselves, divided the formations to be considered, class- 
ing them all as Azoic, into granitic rocks (chap. iii); iron ores and 
associated rocks (chap. iv). Credner calls them all Eozoic, and 
divides them into Huronian and Laurentian, and the same divisions 
are used by Brooks and Pumpelly. As between the terms Azoic and 
t Published at Halle, 1869. 
