130 MORLEY E. WILSON 
and Ferrier! Examples of the sharply defined contacts have been 
described by W. H. Collins and by the writer.’ 
THE ORIGIN OF THE COBALT SERIES 
HYPOTHESES PROPOSED 
The Cobalt series has, in recent years, been the object of 
special study by those geologists engaged in fieldwork in the 
Timiskaming region for the purpose of procuring evidence which 
would confirm or disprove the glacial hypothesis which has been 
strongly advocated by A. P. Coleman in a number of recent publi- 
cations. With this object in view, the writer, while in the field, 
paid special attention to those characteristics of the various mem- 
bers of the series which might have a bearing on the conditions 
under which they were deposited, hoping in that way to reach some 
definite conclusions as to their origin. 
That the conditions under which the series was deposited 
were unusual is indicated by the various modes of origin which 
have been suggested from time to time, by the geologists who have 
studied these rocks in the field. Owing to the fact that the earlier 
geologists did not distinguish the Cobalt series from the underlying 
Abitibi group? (Keewatin), the conglomerate was thought to be 
closely related to the lavas of the underlying basement and were 
said to be of pyroclastic origin,’ although it was noted that many 
fragments of granite and other plutonic rocks were present. In 
1905, A. P. Coleman in his report® on the Sudbury nickel field, 
= “On the Relations and Structures of Certain Granites and Associated Arkoses 
on Lake Timiskaming, Canada,” Rep. B.A.A.S., Toronto (1897), pp. 656-60; Ann. 
Rep. Geol. Surv. Can. (1897), pp. 195-99, I. 
2“Pre], Rep. on Gowganda District, Ont.” Geol. Surv. Bran., Dept. of Mines, 
Can. (1909), p. 31; ““The Larder Lake District, Ont., and Adjoining Portions of 
Pontiac County, Que.” Mem. 17, Geol. Surv., Dept. of Mines, Can., 1910. 
3 Amer. Jour. Sci., XXIII, 187-92; Bull. Geol. Soc. Amer., XIX, 347-66; Jour. 
Geol., XVI, 149-58. 
4The name Abitibi group is here used for those surficial rocks of the older 
complex occurring in the Timiskaming region, whose stratigraphical and structural 
relations are as yet unknown. 
5 Ann. Rep., Can. Geol. Surv., X (1897), 96. 
6 Ann. Rep. Bur. of Mines, Ont., XIV (1905), Pt. 3, p. 1280. 
