Ill 



or revived with the formation of valley in valley structure,, 

 as in Foreston Creek, near Gumeracha ; or they were reversed 

 altogether. Sixth Creek, flowing north from Uraidla into the 

 Torrens, seems to be a reversal of Cox's Creek flowing south 

 into the Onkaparinga. Further, the uplift and consequent 

 entrenchment and headward extension of the east and west 

 valleys (entrenched meanders of the Torrens River) brought 

 about the capture and reversal of portions of the meridional 

 streams. An excellent example of this was noted in Millen- 

 della Creek, near Palmer, by Mr. Howchin and the writer. 

 The former has a full description of it in preparation. Other 

 examples are shown by Rocky Gully,'( 14 ) near Murray Bridge, 

 Mount Barker Creek, Bull's Creek, etc. The recurrence of 

 earth movements at several periods probably accounts for 

 many puzzling features in the present drainage, particularly 

 the course of the Lower Onkaparinga. The occurrence of its 

 present valley cutting across the middle of the southward 

 sloping, Clarendon- Aldinga block, is very remarkable. Mr. 

 Howchin has shown that an older mouth lies considerably 

 south of its present opening. < 15 ) 



Many further problems await solution in this area, 

 which is one of the most interesting geologically and physio- 

 graphically in Australia. 



The writer's thanks are due to Mr. Howchin for his ever- 

 ready assistance and information freely given. 



Geological Department, 

 Sydney University, 

 March, 1911. 



DESCRIPTION OF PLATES. 



Plate XX. 

 Stereogram of the Mount Lofty Ranges. 



Plate XXI. 

 Map of the Mount Lofty Ranges to show the drainage 

 system. Notice how the original meridional drainage, the 

 streams of which are in matured valleys, has been broken into 

 numerous watersheds by capturing east and westerly gorges, de- 

 veloped consequent upon the uplift of the range. Mark particu- 

 larly the Wakefield, Light, Rhine, and Onkaparinga systems 

 and their relation to the lines of faulting. These faults have an 

 easterly downthrow on the eastern side and a westerly on the 

 western. The ends of the fault-lines shown are points beyond 

 which they have not been traced, or appear to pass into mono- 

 clinal folds, or to die out. The doubt as to the scarp nature of 

 the southern coast is explained in the text. 



(14) W. G. Woolnough, Trans. Roy. Soc, S.A., 1908, p. 124. 



(15) Geography of South Australia, p. 124. 



