350 C. A. SUSSMILCH. 



Description of the Valley of the Murrumbidgee River. 

 — From Barren Jack to Canberra the river is entrenched 

 in the Yass-Oanberra tableland; its valley varies from a 

 typical V-shaped gorge, where it cuts through resistant 

 rocks, to the early mature type with narrow flood plains, 

 but steep valley walls, where it has been cut out of the 

 softer rocks. At Taemas the bed of the stream is still 

 1,000 feet above sea level and about 900 feet below the 

 surface of the tableland. Four or Ave distinct erosion 

 levels (rock benches) occur on the sides of the valley, indi- 

 cating that the elevation which rejuvenated this stream 

 was probably an intermittent one. Since the beginning of 

 the elevation which produced the tableland, the river has 

 then, along this part of its course cut out a valley 900 feet 

 in depth, and still youthful in character; while it still has 

 to cut its bed downwards to a considerable depth before 

 base level is reached. From Michelago to Bunyan Hill 

 (near Oooma) the valley is shallow and mature, the river 

 flowing practically on the surface of the Monaro peneplain 

 except for a few miles between Colinton and Bredbo, where 

 it flows in a gorge about 500 to 600 feet in depth — a gorge 

 cut through some of the residuals of the Mount Ainslie 

 peneplain. Throughout this part of its course it flows 

 at the foot of the Murrumbidgee fault escarpment and 

 on its western bank receives only one tributary of any 

 importance, the Gap Creek, which lies at the bottom of a 

 deep gorge ; but on its eastern bank, numerous tributaries 

 such as Bredbo Creek and the Umaralla River occur. These 

 head back to the main divide and all occupy — for miles 

 away from their junction with the Murrumbidgee River — 

 broad mature valleys, which are heavily aggraded. 



It is here that the Murrumbidgee River flows through 

 the Colinton Senkungsfeld a feature which has usually 

 been looked upon as an ordinary river valley. If this were 

 the case, what has been described in these notes as the 



