390 MORLEY E. WILSON 
Lake Huron-Lake Timiskaming-Lake Mistassini region, pre- 
Cambrian sedimentary rocks occur here and there, which were 
laid down upon the surface of a basement complex. This of course 
does not make it necessary that the original Huronian rocks, the 
Cobalt series and the rocks described-as Huronian in the Chibou- 
gamau district, are wholly contemporaneous. In fact this is 
scarcely probable since there are two series present* in the original 
Huronian group of rocks and, as far as known, only one elsewhere. 
Nevertheless it is evident that all of these younger sediments were 
derived from similar sources, that they originated under somewhat 
similar conditions, that their history since their deposition has been 
similar, and that the floor upon which they were deposited was the 
Same. 
THE LAKE SUPERIOR REGION 
Having shown that an early pre-Cambrian paleoplain extends 
throughout such a wide area of country in northwestern Quebec 
and northeastern Ontario, two questions now present themselves: 
(x) does this pre-Huronian erosion plane extend throughout the 
Lake Superior region, and (2) what rocks in that area correspond 
to the basement complex of the Lake Huron—Lake Timiskaming— 
Lake Mistassini region ? 
From the geological reports which have been published with 
regard to various districts in northern Ontario and the adjacent 
portions of United States to the west of Lake Superior, it is known 
that throughout the wide area of country which extends from the 
Timiskaming region to the Vermilion district in Minnesota, there 
is a basal (pre-Animikie) complex composed in part of volcanic 
rocks and in part of granite and gneiss, and in almost every locality 
where detailed work has been carried on—on the east shore of 
Lake Superior near Batchawana bay,’ in the Michipacoten district, 
near Heron bay on the northeast shore of Lake Superior,‘ in the 
Nipigon district,’ in the vicinity of Port Arthur,° in the region 
« According to C. R. Van Hise, Bull. Geo. Soc. Am., p. 5, 1908. 
2 Ann. Rep. Ont. Bur. of Mines, p. 127, 1892. 
3 [bid., pp. 152-85, 1902. 4 [bid., p. 127, 1892. 
5 [bid., 1908, 1909; National Transcontinental Railway between Lake Nipigon and 
Sturgeon Lake (Geol. Surv. Dept. of Mines, Can.), 1908; Geology of the Nipigon 
Basin, Memoir No. 1 (Geol. Surv. Dept. of Mines, Can.), roo. 
6 Ann. Rep. Ont. Bur. of Mines, pp. 254-60, 1905. 
