10 



Preliminary Note on the Existence of 

 Glacial Beds of Cambrian Age in South 

 Australia. 



By Walter Howchin, F.G.S. 



[Read April 2, 1901.] 



It has recently been my good fortune to discover in our 

 local rocks a glacial "till" of very remote geological age, and of 

 great extent in its stratigraphical outcrop. As the forma- 

 tion in question has been proved at intervals over a line of 

 strike that exceeds 200 miles, considerable time will be in- 

 volved in making the detailed observations requisite for a full 

 treatment of the subject. I have, therefore, concluded it 

 was best to place before this society, at the earliest oppor- 

 tunity, a preliminarv note giving the outlines of this interest- 

 ing discovery. 



During the past year I have paid several visits to the valley 

 of the Sturt River, about seven miles from Adelaide, where 

 the formation referred to first attracted my attention. The 

 Sturt crosses the Adelaide main road near the Flagstaff 

 Hotel, at the base of Tapleys Hill. About a mile up stream 

 from this point the glacial beds are exposed, and for a con- 

 siderable distance occupy the bed and banks of the river. 

 The outcrop is about a mile and three-quarters wide, and 

 include cuttings on the Hills railway line, as well as the 

 quarry of the Metropolitan Brick Works Company, on its 

 eastern limits. 



The glacial beds rise from beneath the thick banded shales 

 of Tapley's Hill, and are underlain by the shales and 

 quartzites of the Mitcham and Glen Osmond series. 



The lithological features of the beds are very distinctive, 

 and when once observed can be easily recognised, even in small 

 fragments. As a rule the formation exhibits an unstratified 

 mass, with a mudstone base, and carries stones from the size 

 of small grit, up to erratics several feet in diameter. These- 

 are distributed through the mass without order, and at all 

 angles, frequently producing a local contortion in the finer 

 sediment immediately adjacent to them. In places the mud- 

 stone is replaced with irregular and unstratified masses of 

 sandstones or coarse grits. It is often impossible to trace 

 the line of junction between the mudstones and these 



