Physiography of Yarra, etc. 481 



termed the Dandenong Fault. Whether this fault crosses the 

 Nepean Peninsula cannot at present be stated. 



A continuation south-westerly from Dandenong of the Croy- 

 don Senkungsfeld would account for the depression of the Car- 

 rum Swamp, and perhaps for the indentation of Port Phillip 

 from Mordialloc nearly to Sorrento. It also indicates a valley 

 extending from the Yarra at Brushy Creek mouth through 

 Croydon, Dandenong, the Carrum Swamp and, possibly, under 

 the waters of Port Phillip Bay, and dating from the time of the 

 uplift of the Nillumbik Peneplain. As will be subsequently 

 shown, the Yarra does not appear to have ever occupied this 

 valley. 



The Dandenong Fault may be a line along which repeated 

 movement may have taken place ; but we are here only con- 

 cerned as to its effect in the formation of the Croydon Sen- 

 kungsfeld. 



Dr. Hall (11, p. 204) apparently holds that the part of the 

 Dandenong Fault indicated by Selwyn was formed during the 

 drowning of the lower parts of the Yarra and other streams, 

 and the formation of Port Phillip Bay. The fault however 

 appears to date back at least to the uplift of the Nillumbik 

 Peneplain, the time of which is subsequently discussed, and 

 which was long prior to the formation of Port Phillip. 



Th.e Dandenong Fault and the boundaries of the Croydon 

 Senkungsfeld around the great mass of acid igneous rocks 

 forming the Dandenong Ranges and adjacent hills, suggest 

 that these igneous masses and those of Mounts Eliza and 

 Martha and Arthur's Seat are horsts. 



Mr. Griffith Taylor (12) and Mr. C. A. Sussmilch (13) have 

 explained some of the New South Wales topography by faults 

 and Senkungsfelder. Tlie writer's conclusions as to the origin 

 of the topography dealt with in this paper were arrived at 

 before perusing these interesting papers. 



The Yering Gorge. 



It has been stated above that the Yarra Fault mainly keeps 

 to the right bank of the Yarra River. An exception occurs 

 about two and a-half miles (in a direct line) to the east of the 



