[TYRRELL] FROZEN MUCK IN THE KLONDIKE 45 



gravel from the sides of the valleys would have been renewed, and the 

 beds of muck which had been formed up to that time would have 

 been everywhere buried under beds of gravel, and a refreezing of the 

 country would have been necessary to allow for the formation of later 

 beds of muck. But no such general bed of gravel between earlier 

 and later beds of muck exists, and we must therefore conclude that 

 the ground has remained frozen continuously from the beginning of 

 the period of perennial frost down to the present. Was there an 

 earlier period of frozen ground during Pleistocene times ? Certainly 

 not since the valleys w^ere excavated to their present depths. If there 

 had been such a cold period , evidences of it would need to be looked 

 for in the muck of the lower terraces on Bonanza Creek, or in the 

 muck of Sulphur Creek or of some of the other tributaries of Indian 

 River, or in the valley of Indian River itself. All these streams cut 

 out very shallow^ valleys during the Pliocene Epoch, and it is possible 

 that earlier and later layers of muck separated by beds of gra\^el 

 might have been preserved in their valleys. 



Conclusions. 



We have thus seen that the deposit which is known as "Muck" 

 in the Klondike District is a dark coloured bed of frozen vegetable 

 material, partly transported and partly in place, which was formed 

 while the rocks and soil of the country were permanently frozen, and 

 while the supply of ordinary alluvial material was cut off. That the 

 process of its formation started in a period of great cold in early 

 Glacial times; and that its formation has gone on continuously and 

 uninterruptedly down to the present. 



If the cold period when the muck beds began to be formed was 

 at the beginning of the First Glacial Period, then the gravels of the 

 alluvial bottom lands, which underlie the muck would be Pre Glacial 

 in age. From this it would be necessary to conclude that the valleys 

 holding these gravels were excavated before the Glacial or Pleistocene 

 Epoch, and that these valleys are therefore of Pliocene age. 



When the cold period began, the country appears to have been 

 fairly thickly populated with mammoth, mastodon, bison, elk, moose, 

 horses, bears, etc., for the bones of these animals are found in large 

 numbers in the underlying gravels and in the bottom of the muck; 

 but the climate would seem to have soon become too inhospitable for 

 them, and their remains are very scarce in the higher portions of the 

 muck and fmally disappear from it altogether. 



To the eye of one w^ho is not a trained botanist the trunks and 

 limbs of trees and fragments of moss which occur in the muck from 

 top to bottom look very much like the plants that are growing on the 



