PROCEEDINGS OF SECTIOX C. 457 



]5._S0ME PROBLEMS OF AUSTRALIAN GLACIATIONS. 



By T: W. EDGE WORTH DAVID, B.A., F.R.S.. Professor of Geology, 

 University, Sydney. 



In view of the fact that the Glacial Research Committee of this 

 Association has now been in existence for just 15 years, and has accumu- 

 lated a considerable amount of evidence relating to at least three Ice 

 Ages through which Australasia has passed, it may not be inopportune 

 to now summarise the evidence with a view partly to suggest special 

 lines of inquiry and partly to formulate certain working hypotheses. 

 The latter, while to a certain extent speculative, may perhaps be found 

 of use in directing the attention of geological workers to what, as it 

 appears to the author, are salient points requiring further study. 



Of the three proved glacial epochs, viz. — The Lower Cambrian, 

 the Permo- Carboniferous, and the Pleistocene, the oldest may be 

 considered first. 



LOWER CAMBRIAN. 



The evidence so far adduced by Mr. Howchin appears to the 

 author to point to the following conclusions : — 



L The widespread distribution of this till for 300 miles of longi- 

 tude and for 450 miles from north to south, from lat. 29° 40' S. to lat. 

 36° S., suggests that the ice gathered on a plateau of comparatively 

 low relief. 



2. As shown already by Mr. Howchin, the ice probably moved from 

 south to north. 



3. The presence of casts of what appear to be radiolarian shells 

 in the Tapley's Hill shales, overlying the glacial beds, suggests that the 

 ice came down very close to sea-level, even to sea-level, near the lati- 

 tude of Adelaide in Lower Cambrian time. 



4. Glacial conditions became less marked as the tropic was ap- 

 proached, and as the ice front would be more or less at right angles 

 to the general trend of the movement of the ice, the area glaciated in 

 Lower Cambrian time in the Australasian region was approximately 

 concentric to the present South Pole of the earth. 



Obviously the evidence on this important point is as yet rather 

 slender ; but, as far as it goes, it appears to the author to point in the 

 direction above indicated. 



5. Inasmuch as glaciers and ice-sheets usually grow to windward, 

 going out. as it were to meet their food supply, and we have seen that 

 the ice in Lower Cambrian time in South Australia moved from south 

 to north, the winds which fed its gathering grounds with snow probably 

 came from the north or the north-west, and therefore were derived 

 from the southern anticyclone belt of that period.- If this conclusion 

 is correct the southern anticyclone belt may not have beeia, as it now 

 is, a comparatively dry belt, but probably yielded large supplies of 

 snow to a plateau of moderate elevation lying to the south of the present 

 southern coastline of Australia. It is to be noted that the present 



