PHYSIOGRAPHY OF THE SOUTHERN TABLELAND OF N.S.W. 335 



and quartz porphyries. The surface of this tableland is a 

 peneplain cut out of these rocks, and subsequently elevated 

 to its present altitude. It is proposed to call this erosion 

 level the Monaro peneplain. The isolated hills and ridges 

 which rise above this peneplain include the following, these 

 being the only ones whose altitudes are available to the 

 writer : — 



Height above Height above 



sea-level. peneplain level. 



Barren Jack Mountain ... 3,162 feet ... 1,162 feet 



NarruDgullen (?) ... 

 Bowning Hill 

 Black Mountain ... 

 Mount Ainslie 

 Spring Trig. Station 

 Oaroll Trig. Station 

 Parson Trig. Station 



3,411 „ ... 1,411 



2,608 „ ... 608 



2,756 „ ... 756 



2,762 „ ... 762 



2,904 „ ... 904 



2,811 „ ... 811 



2,659 „ ... 659 



Goodradigbee Trig. Station 2,632 „ ... 632 „ 



It is probable, as will be discussed later, that these are 

 remnants of two distinct erosion levels, one from 700 to 

 800 higher, and the other about 1,300 feet higher than the 

 Monaro peneplain. For purposes of convenience the former 

 will be referred to as the Mount Ainslie peneplain, and the 

 latter as the Barren Jack peneplain, it being understood 

 however that the existence of these as two distinct erosion 

 levels needs confirmation. 



Intrenched in the Yass-Canberra tableland are the valleys 

 of the Murrumbidgee River and its tributaries, cut out 

 during the existing cycle of erosion. Where the course of 

 these streams is through soft rocks, as at Taemas, the 

 valleys have reached the early mature stage of their 

 development (see Plate 12,f\g. 1), but where they are in hard 

 rock as at Barren Jack, the valleys are typical V-shaped 

 gorges (see Plate 10). 



