422 JPROCEEDINGS OF SECTION C. 



(3) In other insjtances known horizons of the Cambrian rocks can 

 be traced from their unaltered condition into the region of contact, 

 where they are powerfully affected and altered. This has been noted 

 in the case of the Cambrian glacial beds and equivalents of the Tapley's 

 Hill slates, at Umberatana, on the eastern side of the Flinders Ranges, 

 and at Olary, on the Petersburg and Cockburn railway line, not far 

 from the New South Wales border. In the Kapunda district a 10-mile 

 section can be followed, where it includes the Mitcham quartzites and 

 the till beds, in the Camel's Hump Range, four miles north-west of 

 Kapunda ; the Tapley's Hill slates, in the neighborhood of Kapunda ; 

 and the Brighton limestone series, in the Kapunda marbles, in a position 

 where the igneous zone is not far distant. 



(4) The most distinctive horizons of the lower beds of the Cambrian 

 on the western side are, in ascending order — (a) Felspathic and ilmenite 

 grits and sandstones {= Aldgate beds) ; (b) the lower limestone (= River 

 Torrens limestone) ; (c) the thick quartzite {= Black Hill and 

 Mount Lofty quartzite). These respective horizons are separated 

 by phyllites and lesser quartzites. The three divisions mentioned are 

 virell defined in their lithological characteristics and stratigraphical 

 relationships. Similar beds in the same order of succession have been 

 determined by cross-sections on the eastern side of the axis in the 

 following localities, (b) viz., Philcox Hill, between Mount Barker and 

 Strathalbyn ; Mount Barker Springs, near Mount Barker ; Reefton, 

 near Woodside ; Mount Torrens, near the head of the Onkaparinga 

 Valley ; and Springfield, near Williamstown. The interstratified 

 phyllites of the western side are represented mostly by fine-grained 

 mica schists or micaceous flags on the eastern. 



(5) The highly altered character of the beds on the eastern side 

 can be satisfactorily explained by the very great extent of the igneous 

 zone, and the corresponding potentiality for effecting metamorphic 

 results. The great development of plutonic rocks on that side indicates 

 that the associated sedimentary rocks were at one time deep-seated, 

 and under geothermal conditions which must have been equal to the 

 production of regional metamorphism on a grand scale. On the assump- 

 tion that the beds thus metamorphosed are of Cambrian age, it will 

 follow that the intruding granitic veins and bosses of the eastern side 

 are Post-Cambrian. At the same time, it is highly probable that some 

 of the igneous outcrops, especially on the western side of the State, 

 are of Pre-Cambrian age. 



6 Detailed descriptions of these sections are in course of preparation. 



