562 president's address. 



quartzite pebbles in tlie conglomerate at the Sturt Creek must 

 piobably have been derived from Pre-Cambrian rocks, but no well 

 marked basal breccia has as vet been found. 



The fossiliferous limestones of the Olenellus- Salterella zone in 

 South Australia show that the seas in Cambrian time teemed with 

 various forms of marine animal life, all the sub-kingdoms being 

 perhaps represented except the Echinodermata and the Verte- 

 bra ta. 



The Cambrian strata in the Macdonnell Ranges, where they are 

 seen in contact with the Lower Silurian rocks, were considerably 

 folded before the latter were formed, the axes of folding corre- 

 sponding closely with those of the Archaean Group. 



In Tasmania the folds run north-westerly. In South Australia 

 at Yorke's Peninsula their trend is N.E. by E. This N.E. folding 

 continues towards the N.E. until it meets the main axes of 

 folding coming from Tasmania from the S.E. and trending towards 

 the N.W. The folds, then, as they near Leigh's Creek trend 

 north-westerly, and as they approach the Macdonnell Ranges 

 swing round gradually to an east and west direction. 



In the Kimberley district the principal axes of folding appear 

 to run N.E. and S.W. parallel with part of the Archaean rocks in 

 the same neighbourhood. 



It must be borne in mind, however, that the principal direction 

 of folding of the Archa3an rocks at Kimberley is N.W. and S.E., 

 but Cambrian rocks have not been identified in this particular 

 locality, the King Leopold Range area, where the main axes of 

 the folds of the Archgean are visible. If hereafter Cambrian 

 rocks be found to exist there, their folds will no doubt be found 

 to correspond with those of the Archaean rocks, as is certainly the 

 case in the Macdonnell Ranges. The folding of the Cambrian 

 rocks and further simultaneous folding of the Archaean rocks 

 before the commencement of the Silurian Period must have had 

 the effect of increasing the land area, or area of very shallow 

 ocean. The sediments of the succeeding system the Silurian, of 

 vast area and thickness, imply an extensive surface brought 

 within reach of natural denuding agencies. 



