344 C. A. SUSSMILCH. 



ago. To the west it is bounded by the Murrumbidgee 

 tableland, and to the east by the Tinderry tableland, both 

 4,000 feet or more in altitude. To the north it expands 

 and merges into the Yass-Oanberra tableland, while to the 

 south it merges into the Berridale tableland. This section 

 of the southern tableland was tilted during uplift and the 

 Monaro peneplain which has an elevation of about 3,000 

 feet at the junction with the Berridale tableland is inclined 

 towards the north, so that where it joins the Yass-Oanberra 

 tableland the altitude is only about 2,000 feet. As will be 

 shown later, this tilting has had an important influence in 

 modifying the drainage systems. Residuals of the Mount 

 Ainslie peneplain are numerous ; in the neighbourhood of 

 Bredbo and Oolinton they are so crowded together as to 

 mask the true nature of the Monaro peneplain, which here 

 consists of broad, flat-bottomed mature valleys separated 

 by ridges 600 to 700 feet in altitude. This locality has 

 every appearance of having been a main divide during the 

 previous cycle of erosion. 



It is the Murrumbidgee and Tinderry faults which sepa- 

 rate this Senkungsf eld from the Murrumbidgee and Berridale 

 fault blocks to the west and the Tindery tableland to the 

 east. 



G. The Fault Escarpments.— When an area with an 

 approximately level surface is separated during elevation 

 into two portions by faulting, that portion which has 

 suffered least elevation will naturally form a temporary 

 base level for the streams which flow to it from the higher 

 portion. Such rejuvenated streams starting at the fault 

 escarpment where they will have a steep grade, begin to 

 entrench themselves in their old courses and cut down their 

 valleys to the new base level. If the uplift and faulting 

 are of comparatively recent geological age, the extent to 

 which the streams have cut back into the higher tableland 



