The Ketreenairaii. — Winchell. 79 
cent. The lay of the ground and the perpendicular condition 
of the bluff necessitated a detour away from the river and the 
manner of union of the red conglomerate with the gray was 
not observed. This distinction besides was not established, 
although anticipated, until the specimens collected were sub- 
sequently being examined. The most convincing fact tending 
to show a difference of age between the lower and upper con- 
glomerates, at this place, was the discovery, among the peb- 
"bles collected from the upper, of a rounded fragment of iron 
pyrite which could be directly referred to the pyrite so abun- 
dant in the lower conglomerate. The writer was at first dis- 
posed to consider the lower conglomerate as the base of the 
Animikie,* but there is more reason to consider it the base of 
the Keweenawan and the equivalent of that at the base of 
Grand Portage island. The upper conglomerate and sand- 
stones must date from Keweenawan or post-Keweenawan time, 
since they consist almost wholly of Keweenawan debris. If 
this be correct the Keweenawan age separated the dates of 
their origin. The upper conglomerate passes upward into the 
sandstones at Fond du Lac. 
Prof. C. R. Van Hise has discovered lately a similar frag- 
niental base for the Keweenawan in Michigan. f It occurs 
also in Wisconsin. He describes it in one place as the top of 
the Penokee series, though that is a very anomalous assign- 
ment for such a conglomerate, and in another he makes it the 
base of the Keweenawan. This conglomerate, according to 
his description, is siliceous and coarsely pebbly, and contains 
only material that can be referred to pre-Keweenawan rocks. 
It is associated with a "red sandstone or quartz^^te," and is 
^'mingled with Keweenawan greenstones." 
Nos. 4 and 5 of Chamberlin's summary (above) are so 
closely related that they may be considered together, especially 
so as we do not wish here to call in question the Potsdam age 
of this upper, or "Eastern sandstone." They apjiertain to the 
structural features of the Keweenawan. 
Keeping in mind the fact that, as above shown, the Kewee- 
nawan was introduced not by eruptions of igneous rock, hut 
*See Twenty-third i-eport of the Minnesota survey, p. 2.39. 
tThe Penokee Iron-bearing series of Michigan and Wisconsin. Mou. 
XIX. U. S. Geol. Sur., pp. .326, m^ATu . 
