384 The American Geologist. June, i89i 
■clearly indicated in the text of my paper.* Aside from the matter of 
the signification of Laurentian, the one difference of importance in the 
successions is that I place as a part of the Animikie the Upper Kamin- 
istiquia and equivalent rocks. These Lawson would regard as a part of 
his Keewatin. But he appears to have overlooked the fact that I dis- 
tinctly suggest that between these series there may be an additional 
unconformity. f 
Lawson objects to 'my placing the Keewatin as post-Archean and the 
Coutchiching as Archean on the ground that both of these have been 
intruded by subsequent granite-gneiss which he has denominated Lau- 
rentian. It is wholly new to me that an intrusive which cuts two prior 
series of rocks can give information as to the structural relations and 
relative ages of those two series. Dr. Lawson would hardly think of 
binding with the Triassic of Connecticut and New Jersey the adjacent 
pre-Cambrian crystalline rocks because they are both cut by numerous 
dykes of the same age. 
On the south shore of lake Superior it has been repeatedly maintained 
by Brooks, Pumpelly, Irving, Chamberlin, and others, that the clastic 
series rest upon a thoroughly crystalline granite-gneiss-schist complex 
with an intervening great unconformity. In this part of the lake 
Superior region, from their point of view, subsequent to a portion of the 
elastics, there have also been granitic and gneissic intrusions. North- 
west of lake Superior, Lawson's work has shown that similar intrusives 
cover large areas and include much of what has there been designated 
as Laurentian. Agreeing with Foster, Whitney, Wadsworth, Herrick, 
and the published reports of Rominger, Lawson has generalized as did 
some of these writers, that because a part of the granite-gneiss is intru- 
sive later than the sedimentaries, it is all of this origin. 
From recent work of others, ilie manuscript report of which I have 
seen, it appears probable that Lawson has overlooked that northwest of 
lake Superior, as on the south shore, and not far from Rainy lake, there 
is also a granite-gneiss-schist complex which is more ancient than and 
served as a basement upon which the fragmentals were deposited. This 
oversight may be due either to the fact that this basement complex does 
not appear in the districts which Lawson has studied in detail, or pos- 
sibly cleavage may be so prominently developed in these districts as to 
have made it difficult to discover these relations. Because a part of the 
granite-gneiss northwest of lake Superior is an intrusive, is no evidence 
that another part of it is not more ancient than any of the sedimentaries. 
Thus, notwithstanding Lawson's surprise, I think that there still is 
found a large part of the preexistent basement in the Lake Superior 
region upon which the clastic series were deposited, a position which I 
do not hold dogmatically, but as according best with present evidence. 
The problem from my point of view is simply more complex than Lawson 
has believed. All of his facts are true, as well as the like facts of Fos- 
ter, Whitney, and others, and there is the additional great fact of a 
granite-gneiss-schist complex more ancient than the recognized clastic 
*Ibid, p. 134. tlbid, p. 126. 
