i<So llic American Geologist. March. !«<> 
Winchell (N. H.),^ in 189 1, gives numerous details. The 
L^reat gabbros of the Cupriferous series and the Pewabic quartz- 
yte are regarded as lying below the Animikie. Large boulders 
of gabbro and of red syenite occur abundantly in the later 
traps of the Cupriferous. 
Winchell (N. H. and H. V.);'" in 1891, describe the iron 
ores of Minnesota. The gabbro of the Mesabi hills, red gran- 
ite, quartz porphyry and red felsite, are called the Norian for- 
mation. This lies below the Animikie, above which are the 
Keweenawan (Potsdam?) trap rocks, tufifs, red sandstones, 
and conglomerates. 
Bayley,'' in 1892, gives the results of a microscopic ex- 
amination of rocks from the vicinity of Akeley lake. The 
rocks designated Pewabic quartzyte by the Minnesota geol- 
ogists are granulitic phases of the gabbro and crystallized ag- 
gregates of quartz. None of them are sedimentary rocks. 
\'"an Hise,'" in 1892, reviews the literature up to that 
time upon the Archean and Algonkian of the lake Superior 
l)asin and accepts Irving's views of the Keweenawan. 
Grant,^^ in 1893, finds the gabbro lying upon the granite 
and mica schists from Birch to Kekequabic lakes. Many de- 
tailed observations are given. 
Winchell (H. V.),''* in 1893, places the gabbro above the 
Animikie slates and the Giant's range granite. 
Winchell (N. H.),^^ in 1893, divides the Keweenawan 
(Nipigon) into an upper and a lower division. The lower di- 
vision is divided into the Norian (gabbros and anorthosytes) 
and the traps and amygdaloidal rocks of the northwest coast 
of lake Superior. 
Grant.'" in 1893, finds that probably some of the gabbro 
contact rocks are part of the gabbro. while others are meta- 
morphosed sediments. 
Winchell (N. H.),'' in 1893, discusses the Norian of the 
Northwest. 
Lawson,^' in 1893, gives a petrographical description of 
the anorthosytes of the Minnesota coast of lake Superior. 
The anorthosytes are considered to represent, in part, the 
eroded surface of a pre-Keweenawan formation to which the 
name Carltonian is given. In the opinion of the author, the 
Keweenawan is not over 2,400 feet thick. 
