257 



etc, in which direction the Pre-Canibrian beds are largely 

 penetrated by granitic intrusions, some of which are of great 

 width. 



South Para. — The junction can be studied near Menzies' 

 JBarossa Mine, and in the South Para River, where very fine 

 sections occur. The older rocks in this district develop a 

 very characteristic augen-gneiss structure. They form the 

 country rock at the Princess Alice Mine, and have been quar- 

 ried to form the weir of the Barossa Reservoir. 



Tanunda. — The felsjoathic grits are quarried near the 

 township, and the older series is developed, under a great 

 variety of lithological features, in the Tanunda Creek. 



Yorke Peninsula. — The western limits of the Cambrian 

 series are indicated on Yorke Peninsula by features closely 

 analogous to those on the eastern side. At Ardrossan fels- 

 pathic grits of Cambrian age rest unconformably on pegma- 

 tites and graphic granite. At Winulta Creek a coarse quartz 

 conglomerate is seen to overlie similar granitic rocks. At 

 Port Hughes, near Moonta, there is a coarse conglomerate and 

 siliceous gritty quartzites outcropping on the beach. The 

 included pebbles are nearly all quartz ana rounded, similar 

 to those of Winulta Creek. In certain zones the rock has 

 been greatly cracked, and subsequently filled with quartz. 

 These quartz veins run through matrix and pebbles quite in- 

 differently. Dip, north, 20" west at 12°. No floor was visible, 

 but granitic rocks outcrop at no great distance from the 

 exposure. 



X. — Pre=Cambrian Complex (Archaean). 



The fundamental rocks which underlie the Cambrian 

 series have been but slightly investigated. They occur as 

 inliers of the Cambrian beds, sometimes several miles in 

 extent. They are frequently in an advanced stage of decom- 

 position, and in consequence have suffered extensive denuda- 

 tion and are reduced to low situations. Their study involves 

 many difficult problems, but is of more than ordinary inter- 

 est, as they will, no doubt, throw light on the early condi- 

 tions of the Australian continent and the development of its 

 orographic features. 



The Pre-Cambrian rocks consist primarily of a sedimen- 

 tary series, but these have been so altered under metamorphic 

 action as frequently to obliterate their stratigraphical boun- 

 daries. They have been subjected to successive eruptive and 

 intrusive conditions, which have profoundly modified both the 

 texture and structure of the beds. In the central axes of the 

 Mount Lofty and Barossa Ranges they include extensive areas 

 ■of granitoid rocks, mostly under the forms of aplite and peg- 



