36 



Past Climatic Changes, ^with Special Refer- 

 ence TO THE Occurrence of a Glacial 

 Epoch in Australia. 



By Gattx ScorLAR, Corr. Mem. 



[Read July 7, August 4.] 

 [abridged.] 



Introduction. — Of tlie many complex problems witli which the- 

 South Australian geologist and scientist have to deal none 

 probably are more shrouded in the hidden mysteries of nature 

 than those to which the above heading refers. That the forma- 

 tion known as the "drift deposits," constituting the Adelaide 

 plain and other places, was a consequence of those climatic- 

 changes which were embraced by the period of the last glacia- 

 tion of the southern hemisphere, I think geologists who have 

 thoroughly studied these beds are fully agreed ; but whether 

 they, especially those comprised along the western seaboard of 

 the colony, were laid down whilst the Australian Continent 

 stood at a much greater elevation than now, or whilst in a more 

 depressed state than it now is, is a subject worthy of careful 

 investigation. 



Traces of a Glacial Epoch in South Australia. — Instances of 

 supposed ice markings, arising from the effects of actual glacial 

 action or otherwise in connection with the Adelaide chain and 

 adjacent seaboard, have been observed and noted from time to 

 time by various geologists. Mr. Selwyn ("Geological iSTotes of 

 a Journey in South Australia," p. 4) directs attention to a 

 point in the valley of the Inman where he says : — "I observed 

 a smooth striated and grooved rock surface presenting every 

 indication of glacial action. The bank of the creek showed a 

 section of clay and coarse gravel, or drift composed of frag- 

 ments of all sizes irregularly imbedded in the clay. The direction 

 of the grooves and scratches is east and west in parallel lines, 

 or nearly at right angles to the strike of the rocks, and though 

 they follow the course of the stream, I do not think that they 

 could have been produced by the action of water forcing 

 pebbles and boulders detached from the drift along the bed of 

 the stream." Mr. Selwyn likewise notifies that this was the 

 only instance of the kind he had seen in Australia, and though 

 somewhat struck with the similarity of the markings to those 

 he had formerly seen as ice markings in the mountain valleys- 

 of Xorth AVales, he seemed, nevertheless, to retain a doubt in 



