216 WwW. R. BROWNE. 
this valley 4 miles along the Mittagang road and flows 
N.N.EH. across a level plain to join Rock Flat Creek. Oon- 
siderable alluvium marks the confluence of the two streams. 
Rock Flat Creek has cut for itself a fairly wide valley. 
It shows evidence of having shifted its bed somewhat to 
the east in recent times. From about the 6-mile peg on 
the Kydra Road, as one looks north there can be seen a 
long ridge of quartz-porphyry forming the left bank of the 
valley evidently carved out by the creek in the past. The 
present course of the stream however is upwards of half a 
mile to the east of this ridge. Again, the gravels along 
Numeralla Road to which reference has already been made 
give evidence of easterly movement. Rock Flat Creek 
joins the Umaralla River 4 miles nearly due east of the 
S-bend in the Murrumbidgee. 
The history of the present topography has been referred 
to by Griffith Taylor,* and discussed in greater detail by 
Sussmilch.? Briefly, the region forms part of what was in 
late Tertiary times a peneplain area—the Monaro pene- 
plain—the occasional isolated elevations being residuals of 
a former peneplain—the Mount Ainslie peneplain. This 
Monaro peneplain has undergone differential uplift, the 
area in the N.W. which has been roughly indicated above 
forming part of the Berridale fault-block, with probably 
a slight tilt down towards the south, and bounded on the 
east by asteep escarpment—the Murrumbidgee fault-scarp, 
indicated in Fig. 2. This escarpment crosses the Murrum- 
bidgee near Pearman’s Hill, and continues south, gradually 
merging, as it nears Cooma, into the general level of the 
country. To the east of the fault-scarp the country has 
been less elevated, and farther north this relatively 
depressed area is rather narrow, forming the Colinton 
senkungsfeld. It broadens considerably towards the south 
' Loc.. cit. swp. 2 Loe. cit. sup. 
