684 A. C. LANE AND A. E. SEAMAN 
Eozoic, Proterozoic, Archeozoic, and Archean, we are not prepared 
to give a final decision, but find the usage of Chamberlin and Salis- 
bury convenient. The terms Laurentian and Huronian have been 
used pretty continuously in the Lake Superior region, and always 
with almost the same practical application, so far as this state is con- 
cerned. We think, therefore, that we should in them follow Credner 
and Logan. It is at present agreed to divide the Huronian into three 
series. A question may arise whether the lowest of these series, 
which is considerably older than the other two, more eroded, and 
quite different in distribution, may not be the Grenville or Upper 
Laurentian. ‘There is, however, no local ambiguity involved, as it 
has always been mapped with the Huronian in this state. 
Eo-Huronian.—We use this term in preference to Lower Huron- 
ian, as that was applied to the eo-Huronian and mio-Huronian until 
the threefold division of the “‘Marquette” series was recognized. 
The Marquette Monograph calls it Lower Marquette. We had 
always called it Mesnard (formation or series).‘/ The U. S. and 
state survey now restrict this name to the basal member. 
a) Mesnard quartzite. Well exposed on Mt. Mesnard just south 
of Marquette, finely ripple marked, with about 250 feet of slaty flags 
toward the base, which is a conglomeritic and arkose quartzite. 
There are also brecciation beds, slate, quartzite, and cherty quart- 
zite toward the Kona dolomite above. 
It is at times much metamorphosed and sheared and may be 
confounded with underlying beds, and is at times cut by granites, 
but by no means as commonly as the Keewatin. We think, too, 
the granites cutting the Huronian have a different character, being 
much more inclined to a coarse porphyritic facies. 
b) Kona dolomite. This is a very well marked horizon around 
Goose Lake, but is represented, we believe, on all the ranges and in 
the original Huronian, being the Randville dolomite of the Menomi- 
nee Crystal Falls region, and the Bad River formation of the Gogebic 
Range.?_ But extensive erosion took place before the deposition 
of the mio-Huronian, generally removing the slates above it and 
often cutting deepanto the:dolomitess 74.555 ee 6oo ft. 
1 1892 Report, p. 65. 
2 Rominger’s “Marble” Series, Vol. IV, p. 56. 
