WIE SEAS O MLAS SITE. IAOXCIEE SIS ING. 19 
basic gabbros and quartzose rocks like those referred to above as 
“‘quartzites”’ in the account of the geology of Akeley Lake. 
Hence it was concluded that the ‘‘ Pewabic quartzite,” as described 
Jrom the Akeley Lake region, could not be used as a definite horizon 
for correlation purposes, since so much of it is gabbro. This opin- 
ion is still held; but the writer may have been mistaken in his views 
regarding the origin of the quartzose rocks interbanded with the 
gabbros. None of those seen, are, in their present condition, frag- 
mental sediments, nor can any trace of clastic grains be detected 
inthem. Nevertheless, it is possible that they may be re-crystal- 
lized quartz rocks. 
The basic layers interbanded with the quartzose ones are, 
however, not “‘tufaceous, eruptive fragmental elements,”* and 
cannot be a part of any distinct horizon to which the name Pewa- 
bic quartzite may be applied. These bands are igneous and 
are not chemical sediments, nor are they metamorphosed 
quartzites. 
The main purpose of the paper referred to, however, was not 
the discussion of the Pewabic quartzite. It was the determina- 
tion of the age of the gabbro, and upon this question it was 
supposed to have added some evidence in opposition to the 
view that the gabbro is of Animikie age, although Professor 
Winchell? was inclined to regard its evidence as favorable to 
that view. 
The descriptions of the granulitic and basic gabbros so closely 
associated with the normal gabbro show that these rocks are not 
sediments, but are parts of the gabbro, and hence cannot be used 
for determining the age of the latter rock. 
If the quartzose rocks with which they are interbanded are 
metamorphosed Animikie strata then the proof of the post- 
* PROFESSOR N. H. WINCHELL: Footnote, 19th Ann. Rep. Geol. Survey Minn., 
p. 210. 
2 “Of course the intent of Professor Bayley’s paper is to establish the idea of Pro- 
fessor Irving that the gabbro flood is later than the Animikie rather than near the 
bottom of it, where the Minnesota geologists have placed it, but its purport confirms 
the Minnesota geologists in their conclusions.”— Professor Winchell, in footnote 
referred to. 
