264 EEPORTS OP COMMITTEES. 



a large boulder obtained in situ from the Lower Cambrian boulder 

 beds at Petersburg, and some smaller boulders. These specimens 

 were seen by many scores of expert glacialists at the above meetings, 

 and not a single doubt was expressed as to the glacial origin of their 

 grooves and striae. 



The secretary would strongly advocate, in any further investiga- 

 tions on this subject, those who may question the glacial origin of the 

 Sturt beds — go first to Petersburg, to that less disturbed and less 

 crushed area, where the glacial evidences are clear and undoubted, 

 and then work down southwards towards the more disturbed area of 

 the Sturt Gorge. The continuity of the beds must then become ap- 

 parent. 



Readers interested in this question are advised to compare with 

 Mr. Howchin's evidences of the Great Lower Cambrian Ice Age in South 

 Australia the description of the more recently discovered Cambrian 

 glacial beds near Ichang, just above the head of navigation of the 

 Yangtse River in China. 



See Chamberlin & Salisbury's Geology, vol. ii., Earth History, p. .273 ; also 

 Year Book, No. 3, Carnegie last., p. 282. 



SOUTH AUSTRALIA. 



2.— CAMBRIAN AND (?) PERMO-CARBONIFEROUS 

 GLACIATION. 



By WALTER HOWCUIN, F.O.S. 



There are two extensively developed series of glacial deposits in 

 South Australia, widely separated in relation to geological time. These 

 have been respectively made the subjects of reports by this committee 

 at different times. Since the last report was presented (in 1902) some 

 additional data have been obtained in relation to each of these periods, 

 which will be briefly summarised. 



I. — Glacial Beds of Cambrian Age. a 

 1. Aqe of the Beds. — The stratigraphical relationships of the glacial 

 beds are now sufficiently defined to fix their geological age as definitely 

 Lower Cambrian. A general description of the Cambrian series of 

 South Australia is reserved for another paper to be read before this 

 Section ; but the position of the beds in question may be briefly ex- 

 plained as follows : — The Cambrian rocks form a very thick series, 

 which may be divided, lithologically, into two parts — {a) an upper 

 (which is much the thicker portion), consisting mostly of red-colored 

 rocks ; {h) and a lower, chiefly characterised by siliceous quartzites 

 and phyllites. Near the top of the upper set of beds are some fossi- 

 liferous limestones, with ArchceocyathincB reefs, Cambrian trilobites, 



a See Howchin on the Geology of the Mount Lofty Ranges, Part II., Trans. 

 Roy. Soc, S. Aus., 1906, p. 228. 



