The KeiveeiKtird II. — ll'/jicfieU. 75 
[Crucial points in the geology of the Lake Superior region. No. 6.) 
THE KEWEENAWAN ACCORDING TO THE 
WISCONSIN GEOLOGISTS. 
By N. H. Winghell, Minneapolis, Minn. 
Concisely it may be said, at once, that the Wisconsin 
survey immediately reached definite ideas on these mooted 
questions of Lake Superior geology. That survey continued 
from 1873 to 1879, a period of six years. The whole state 
was reported and mapped in an incredibly short space of time. 
Its proximity to Michigan, where many of these rocks had 
been described, aided the geological corps in no small degree. 
They were aided still further in having the cooperation and 
active service of Prof. C. E. Wright and Maj. T. B. Brooks of 
Michigan, the latter already familiar with the problems in- 
volved, and the former still concerned with Michigan geology. 
The conclusions of this survey are summed up by Prof. 
Chamberlin in volume I of the final report, published in 1883. In 
general they are based on facts reported by the other geolo- 
gists and published in other parts of the final report. They 
are as follows, so far as they bear upon the questions we are 
considering : 
1. The Laurentian embraces gneiss and crystalline schists, 
micaceous and chloritic, and allied rocks. 
2. The Huronian is non-conformable upon the Laurentian, 
embracing all the known iron ore deposits, made up of quartz- 
ytes, black slates, often micaceous diorytes, limestones, con- 
glomerates and cherts, having a total thickness of at least 
13,000 feet. Quartz-porphyries overlie the quartzytes in cen- 
tral Wisconsin. These members constitute what has later 
been styled Upper Huronian, and are made the equivalent, 
after Selwyn, of those extensive deposits in Canada consisting 
of limestone, iron ores and carbonaceous shales, which were 
formerly classed with the Laurentian but have been sei)arated 
from it by Selwyn, as portions of the Huronian. It is non- 
conformable, but not strikingly so, with the overlying Kewee- 
nawan. It is associated with intrusive nuisses of granite, 
gabbro and dioryte. 
This conception of the Huronian is greatly different from 
that entertained by Brooks and Irving, who divitled it into 
twenty parts, and included in it the crystaMine schists and the 
Archean y;reenstones. 
