122 



and has summarized the literature, so that there is no neces- 

 sity for me to cover the ground he has so ably traversed. 

 These papers were not published at the time I was working in 

 South Australia. 



The choice of the Onkaparinga as the western limit of 

 the area under discussion is not an arbitrary one. The river 

 follows a distinct axis of earth-structure; it is, in fact, a 

 typical subsequent stream. West of it there is considerable 

 monotony in the rocks. The dominant types are soft quartz 

 schists (of the Mount Lofty series) and hard quartzites. 

 Here and there, as at Carey's Gully, and thence northward to 

 Forest Range, there is a strong belt of conglomerate con- 

 taining pebbles of titaniferous sandstone. Mr. Howchin has 

 shown this to be the basal bed of the Lower Cambrian, and 

 it will form a most useful datum-horizon for the detailed map- 

 ping of the area. On the Norton Summit-Woodside road 

 the conglomerate is interbedded ( ?) with an extremely tough 

 blue slate, vesicular in places, which is very much like the 

 non-boulder-bearing portions of the Sturt River glacial beds. 

 A little to the south of the Balhannah-Uraidla road the con- 

 glomerate is abruptly truncated by an east and west fault, 

 which causes it to abut against the blue slate. It appears 

 probable that this fault may be connected with the ore de- 

 position at the Balhannah Mine. 



Neither blue slate nor conglomerate appears in the rail- 

 way cuttings between Bridgewater and Ambleside. Almost 

 the whole of this stretch of country is occupied by soft friable 

 sandstone, of the Mount Lofty species. 



At Grunthal there occurs a well-marked shatter-zone. 

 The crushed rocks are much impregnated with iron, and in- 

 jected by large quartz veins. No doubt these phenomena are 

 responsible for the ore deposition at this point. A very pretty 

 example of extreme plication is shown by a series of slates 

 in the railway cutting close to the Ambleside down distant 

 signal. About a mile north-east of Ambleside there is ano- 

 ther occurrence of cellular blue slate, but it is doubtful 

 whether this is the same rock as that noted above at Forest 

 Range. 



Coming now to the area with which I wish more par- 

 ticularly to deal, I shall first describe in some detail the 

 partial sections afforded by several routes. 



Owing to the irregular way in which these lines of sec- 

 tion cross one another, it is difficult to devise any logical 

 method of presenting the observations. I shall, therefore, 

 give the details in approximately the order in which I ob- 

 served them. The first section to be described is that be- 

 tween Balhannah and Murray Bridge along the railway line. 



