BASIS OF PRE-CAMBRIAN CORRELATION LAK) 
United States geologists in reference to the succession and relation of the pre- 
Cambrian series of Canada. So far as there are differences they will appear 
below. 
The elucidation of the pre-Cambrian succession for the Lake Superior region, 
which term as here used includes the great tract extending from the Lake of the 
Woods to north of Lake Huron and south to the Paleozoic rocks, has been the 
work of many men extending through many years. In 1892, when Bulletin S6 
of the United States Geological Survey, on the Archean and Algonkian appeared, 
the Lake Superior succession, as now recognized, had been fully worked out,! 
with the exception that what was then called the Lower Huronian has since been 
found to comprise two series; also the series now called Keewatin was called 
Mareniscan, but was properly defined. Some years after the publication of this 
bulletin, Mr. A. E. Seaman discovered the unconformity mentioned in the lower 
Huronian of the Marquette district. As soon as this discovery was made it was 
appreciated that the two divisions of the Huronian in the original Huronian area 
worked out by Pumpelly, Leith, and myself, correspond with the two divisions 
in the Marquette district. The classification of the pre-Cambrian as thus devel- 
oped was fully accepted by the International Geological Committee in 1904, and 
the table giving the succession was published by Leith in 1904, and by the com- 
mittee in 1905, as follows:? 
CAMBRIAN 
Upper sandstones, etc., of Lake Superior 
Unconformity 
PRE-CAMBRIAN 
Keweenawan (Nipigon) 
Unconformity 
Upper (Animikie) 
Unconformity 
Huronian ( Middle 
Unconformity 
Lower 
Unconformity 
_ Keewatin 
Eruptive contact 
Laurentian 
This succession is repeated by Dr. Adams in his communication, except that 
the unconformities are omitted, and it is extended to the entire Canadian pre- 
Cambrian region. 
It is indeed gratifying to have completely accepted for the great Canadian 
pre-Cambrian area the succession which has been worked out for the Lake 
Superior region, but Dr. Adams implies that his classification rests upon a sounder 
basis than the same classification offered by others since ‘‘drawing evidence from 
the area as a whole rather than from a few restricted areas on its southern border.” 
But unhappily for the contention of Dr. Adams, it is still true that the Lake 
Superior region is the only very extensive area in which the detailed geology has 
tC. R. Van Hise, “Archean and Algonkian,” Bull. 86, U.S. G.S., p. 195. 
2 Journal of Geology, Vol. XIII, p. 104. 
