THE KLONDIKE GOLD DISTIMCT. 287 



to have had an elevation above the sea of, say, 7,000 or 8,000 ft., and 

 it seems to have maintained its stabihfy for a very long period, during 

 which the old ciystalline rocks became deeply decayed and eroded, 

 while the softened niatenal was excavated on a large scale: by almost 

 imiumerable brooks and soroei streams of greater size. The result 

 was that the average altitude of the surface was reduced by denuda- 

 tion to the extent of perhaps 5,000 ft. Thus the smooth-sided moun- 

 tains and valleys of the Klondike country were produced. After a 

 great lapse of time, and while the slopes of the valley were deeply 

 covered with the mixed debris from the disintegration of the softer 

 and harder rocks, a gradual subsidence of the land took place, and 

 was followed by a general elevation to an altitude exceeding that of 

 the former surface by about 600 ft. The gradual subsidence of the 

 land gave the incoming sea an opportunity to wash and modify the 

 disintegrated rocky materials all the way up from the lowest to the 

 highest levels, to round off the angles of the harder fragments, and 

 to arrange them at many altitudes into beds which are sometimes of 

 great thickness, even up to 100 and even 200 ft. 



The White Channel gravels, described further on, belong to this 

 period. The re-elevation to a height of aboiit 600 ft. above the level, 

 wliich had been so long maintained before the submergence permitted 

 the retiring sea. to cut tlie White Channel and other old gi'avels into 

 terraces and beaches ; and the increased height at which the land now 

 stood enabled the streams in the Klondike district to deepen their 

 valleys by about the same amount. The contrast between the steep 

 sides and the angularity of the new valleys and the smooth and more 

 gentle: slopes of the old ones is easily recognised. 



Source of the Pi;Acer Gold. 



An attempt will now be made to interpret the surface indications 

 in regard to the later geological history of the Klondike distiict, and 

 to tiy to account for tlie richness of its placers. 



The investigations of Mr. R. G. McConnell and Mr. J. B. Tyrrell, 

 which extended over several seasons, have shown that, during and 

 sirice the Pliocene epoch, more events and changes have taken place in 

 that territory than might have been supposed possible, and all of these 

 involved time. The evidences of some of these, such as the invasion 

 of the district by the Klondike River at a certain period, an event of 

 great geological interest, could only ha^^e been detected by experienced 

 geologii-ts. The numerous phenomena which have occurred during the 

 Pliocene and Post Pliocene epochs in the Yukon region indicate a more 

 varied history, and also the lapse of a greater lengtli of time than had 

 heretofore been suspected. 



The small veins of quartz which liave been mentioned in 

 describing the Klondike rocks are quite abundant in almost every 

 part of the district. Nearly all of them are white, and they are 

 usually hyaline, but many havei developed a finelj^-granular structure. 

 They are generally short and lenticular in form and vary from mere 

 threads up to several inches in thickness and occasionally reach a foot 

 or more. They often occur in groups, the individual veins of which are 

 nearly parallel to one another and to the lamination, but veins are 

 also found which form angles with both the dip and the strike of 

 the schistosity. In the universal disintegration and waste of the 



