Section IV, 1917 [39] Trans. R.S.C. 



Frozen Muck in the Klondike District, Yukon Territory, Canada. 

 By J. B. Tyrrell, F.R.S.C. 



(Read May Meeting, 1917). 



At the meeting of this Society, in May, 1912, 1 presented a paper 

 with the title "The Gold of the Klondike," in which were discussed 

 the formation of the valleys in that far northern district, the modes 

 in which the gravels had been deposited on the benches or terraces 

 and in the alluvial bottom lands of those valleys, and the natural 

 processes by which the grains or pellets of gold had been collected in 

 the lower portion of these gravels, in restricted longitudinal bands 

 locally known as Paystreaks. In that paper special attention was 

 devoted to the gravel itself and to the gold contained in it. But 

 overlying the gravel in the bottoms of the valleys there is a peculiar 

 deposit known as "muck," which, as far as I am aware, is only found in 

 Arctic or sub-Arctic regions. A consideration of the character and 

 mode of formation of this "muck" may be of interest to the geologists, 

 and perhaps also to the botanists, of this Society. 



As pointed out in my paper mentioned above, the Klondike 

 district was subjected throughout long geological ages to more or less 

 continuous erosion, and plains and deep valleys were formed in it in 

 alternate succession. 



In the Miocene Epoch, at the close of the First Cycle of Erosion, the 

 Dome Peneplain was produced, fragments of which can be recognized 

 on many of the higher hills and ridges throughout the country. 

 The Second Cycle of Erosion, during which deep and wide valleys 

 were excavated in the Dome Peneplain, has usually been considered 

 to have occurred during Pliocene times, but in the light of the facts 

 here presented as to the Pilocene age of the Third, or next succeeding 

 Cycle of Erosion, it will be necessary to consider the Pecond Cycle 

 either as of early Pliocene or possibly of Miocene age. At the end of 

 the Second Cycle the bottoms of the wide matured valleys that had 

 just been formed, were covered with deep deposits of well rounded 

 gravels which are usually referred to as the "White Channel Gravels." 



After the deposition of these gravels the Third Cycle of Erosion 

 began and continued to the end of Pliocene times. During it some of the 

 streams, as for instance Bonanza Creek, cut deep narrow valleys or 

 gorges into the floors of the pre-existing valleys. The work of erosion 

 during this Cycle was somewhat irregular and intermittent so that 



