32 THE ROYAL SOCIETY OF CANADA 
These facts should be carefully borne in mind, for all the gold in 
the detrital and placer deposits in the Klondike has been derived directly 
from these altered rocks occurring in the immediate vicinity of the al- 
luvial deposits. 
Later Dynamic Geology.—We have seen that the Klondike area 
is an almost isolated mountain region which has been worn down to its 
present shape by atmospheric and stream agencies. The history of 
this area, and the processes by which it arrived at its present condition 
may be briefly stated as follows:— 
During the earlier part of the Tertiary epoch, probably about later 
Eocene times, the latest marine sediments were deposited, after which a 
period of elevation set in which raised the land above sea level. At 
this time, which was probably about the beginning of the Miocene age, 
all the rocks which had then been formed or deposited had assumed 
the crumpled and faulted condition in which they are at present found. 
A period of active denudation then began and continued until it 
had reduced the whole of the Yukon plateau, of which the Klondike 
area originally formed a part, to a vast peneplain, the remnants of 
which can still be seen in the vicinity of the Dome and at other places, 
at a present elevation of about 3,500 feet above the sea. Standing on 
some of the old imperfect terraces which occur at this elevation, the 
country is seen to extend in every direction with its higher points and 
ridges at approximately the same level, and with the valleys forming 
great trenches in the old peneplain. 
The period during which this peneplain was formed may be des- 
ignated as the “ First Cycle of Erosion” and we will call the peneplain 
itself the “ Dome Peneplain,”’ taking the name from the “ Dome,” the 
high rounded mountain at the head of Bonanza and Hunker creeks, 
which formed a little hill on the otherwise moderately even surface of 
the plain. This peneplain corresponds in a general way with the Kla- 
math Peneplain in California, which has been recently described by J. 8. 
Diller! of the United States Geological Survey from the Trinity river 
basin; through the Miocene rocks included in it in the Yukon territory 
are probably younger than any rocks that have been recognized in the 
Klamath Peneplain in California. 
After the Dome Peneplain was formed, possibly about the end of 
the Miocene period, the country was gradually elevated to a height of 
two thousand feet or more above the sea. Drainage along lines ap- 
proaching closely to those followed by the present streams was begun; 

1The Auriferous Gravels of the Trinity River Basin, California; J. S. Diller. 
U.S. Geological Survey, Bulletin 470, p. 14. 
