The Keii'eeiunc((ti. — W inclicU. 85 
series than Archean, but whatever their age they are likel}^ to 
occur at many points throughout the ai*ea of the southern 
complex, or surrounding it, and there woukl in that case be 
no plausible reason to exclude their debris from that conglom- 
erate. As to the basic eruptives in this conglomerate it would 
probably not be questioned that they may have been derived 
from the volcanics of the "Penokee series" lately described by 
Van Hise in that immediate neighbf)rhood.* The additional 
case, therefore, cited by Van Hise, seems not to strengthen the 
hypothesis of the separateness of the Eastern sandstone from 
the Keweenawan. In the light of what is now" known of the 
wide extension of a basal siliceous conglomerate at the bottom 
of the Keweenawan, it seems to the writer quite reasonable to 
refer this conglomerate to that horizon — especially so since all 
those conglomerates in the Lake Superior region that can be 
referred unmistakably to a higher horizon in the series consist 
wholly, or largely, of Kew^eenawan debris. Its persistence after 
the erosion and recession of the Keweenawan trap range to its 
present line of strike might be reasonably expected for many 
miles further south. It must have been affected, and perhaps at 
first covered hy the diabasic floods, and so hardened that in its 
low lying positions it would be almost as durable as the neigh- 
boring granite. 
Finally, it may ba said that all the cited individual cases 
of non-conformity are defective as proof of an extended ero- 
sion interval between the upper part of the Keweenawan, 
which consists of sandstones quite similar to the horizontal 
sandstones, and those horizontal sandstones. According to 
Irving's estimate the upper fragmental member of the Ke- 
weenaw^an rocks, in which no trap layers sire fouiul, consists 
of sandstones and shales, usually reddish, which reach tiie ag- 
gregate thickness of 12,000 or 15,000 feet.f It is claimed on 
the foregoing evidence that between these and the horizontal 
sandstones the age of the Taconic, or Lower Cambrian, must 
be included. This is the fundamental idea on which tlie whole 
structure of the "Correlation papers" of Walcott atul Van 
His3 is based so far as they discuss the gJology of this region. 
*Bulletm Geo). Soc. Am., vol. v, p. 425. 
tCopper-ljearing rocks of lake Sujierior, Mon. v, U. S. Geol. Sur., p. 
151. 
