THE COBALT SERIES; ITS CHARACTER AND ORIGIN 129 
square miles, but this is probably a mere fraction of its former 
extent for much Huronian, having the same lithological character 
and geological relationships, occurs in outlying districts such as 
that on Lake Chibougamau, about 300 miles to the northeastward. 
THE PRE-COBALT SERIES PALEOPLAIN 
Since the rocks comprising the Cobalt series have been but 
very’ gently folded, it follows that the surface upon which they 
were deposited has also not been greatly deformed, and that by 
the study of the contours of the contact of the basal conglomerate 
and the older complex, the stage, in physiographic development of 
the ancient erosion surface, at the time the deposition of the Cobalt 
series began, may be deciphered. The approximately uniform 
elevation, at which the junction of the Cobalt series and the older 
complex occurs throughout considerable areas, shows that the 
topography of the ancient surface was generally flat, but here and 
there hills consisting of rocks of the older complex occur which 
rise to elevations of 200 to 600 feet above the surrounding 
country and which must have had a still higher elevation prior 
to the deposition of the Cobalt series, for they have undergone 
denudation since that series was stripped from their surface. 
The ancient surface had therefore a range in elevation as great or 
greater than that of the region at present, but on the whole was 
probably more flat, the hills being local remnants which rose 
above the general level of erosion. This pre-Cambrian surface of 
denudation, therefore, represents a peneplain buried and later 
exposed and falls into the class of form known as a paleoplain. 
THE CONTACT OF THE COBALT SERIES AND THE OLDER COMPLEX 
The contact between the Cobalt series and the rocks of the 
older complex is peculiar in places, in that no definite line of 
junction can be seen, the underlying rock passing gradually 
upward into the basal conglomerate; in other places, however, 
the contact is very sharply defined, the conglomerate resting 
on a smoothly denuded surface. A striking example of this 
transitional relationship occurring at Baie des béres on the east 
shore of Lake Timiskaming has been described in detail by Barlow 
