HURONIAN FORMATIONS, TIMISKAMING REGION. 
27 
The unconformity below the Bruce series represents the 
most important known Pre-Cambrian erosion interval in Timis- 
kaming region. The formations above and below it are also 
distinctly unlike, in degree of diastrophic disturbance and 
metamorphism. Accordingly it is taken as the plane of sepa- 
ration of an upper, Huronian system from a residual older portion 
of the Pre-Cambrian which remains to be classified. To this 
imperfectly known part the temporary designation pre-Huronian 
is applied. The opportunity is taken to reiterate that the pre- 
Huronian is not regarded as co-ordinate with the Huronian, and 
that merely a dual division of the Pre-Cambrian is not intended. 
It is deemed entirely possible that the pre-Huronian may ulti- 
mately be subdivided into two or more parts each co-ordinate 
with the Huronian. 
The upward extension of the Huronian in this region must 
remain somewhat in abeyance until the relations existing be- 
tween the Cobalt and Whitewater series can be discovered. 
Only one area of Whitewater series rocks is known and this is 
so completely circumscribed and isolated from other sedimentary 
rocks by the Sudbury laccolith that, until another, more favour- 
ably situated area is discovered, the position of this series remains 
unproven. 
