484 ./. T. Jutson: 



slopes of the ridges. Moreover, the actual position of the axis 

 appears to be that of an original water-parting. Were this 

 due to denudation since the last great uplift, we should expect 

 much more irregularity in its outline than at present exists. 



In addition, differential uplift is indicated bv the formation 

 of the Croydon Senkungsfeld. 



It is possible however that the slopes to the north and south 

 of the Mitcham Axis may have been formed prior to the last 

 great uplift, and not disturbed by that movement. This aspect 

 will be dealt with under the section describing the monadnocks. 

 of " Pinemont," Croydon Hill and Burt's Hill. 



The Slow Uplift of the Nillumbik Peneplain and 

 the Fopmep Character of the Yarra River. 



The last great uplift of the land that took place was the 

 elevation of the Nillumbik Peneplain. We have seen from the 

 evidence of the Mitcham Axis and the Brushy Creek and Yarra 

 Faults and their scarps, that such uplift was differential. The 

 Yering Gorge furnishes us with evidence that the uplift was 

 also extremely slow and gradual. 



The river here pierces the scarp and hence the gorge. At 

 its entrance and its exit, the gorge is bounded (on the left side 

 of the river) by an alluvial flat. Between the two flats, the 

 scarp descends on to a long, low ridge which steadily rises in a 

 south-easterly direction. The scarp of the Yarra Fault is here 

 about 200 feet above the low ridge at its base, and this low 

 ridge is about 70 feet above the river. Taking a section in a 

 south-easterly direction, there is first the Yarra Plateau, then 

 the deep, narrow Yering Gorge, then the fault scarp descend- 

 ing to a low ridge, and then the latter rising gently towards 

 the south-east. The plan and section of this part of the 

 country accompanying this paper illustrate the matter. 



It is clear that the river could not have formed the gorge 

 while the country possessed any resemblance to its present 

 contour. It is equally clear that if the Yarra Fault Scarp had 

 been rapidly formed, the river could not have cut the gorge, 

 but must have taken the then lowest part of the country — viz.. 



