GEOLOGICAL RECONNAISSANCE OF THE STIRLING RANGES. 105 



brian age of all the granites in Australia west of a line 

 joining Adelaide to Cloncurry. 



If this suggestion can be verified it is obvious that the 

 Stirling Range Series must belong to some part, probably 

 the later portion, of the Pre-Cambrian. While I am pre- 

 pared to admit that the evidence from my suggested 

 generalisation is by no means conclusive, I consider that 

 the lithological character of the sediments, and the absence 

 of fossils are presumptive evidence in favour of great 

 antiquity of the beds. In connection with the lithological 

 features the fact must be borne in mind that south-western 

 Western Australia is an immense granite ''shield," and 

 that it appears to have suffered no orogenic disturbance 

 since extremely early geological times. The nearest 

 Palaoozoic sediments to the Stirling Ranges, namely the 

 Permo-Oarboniferous coal-measures of Collie and of the 

 Irwin River, and the associated marine beds in the latter 

 area, are largely unconsolidated sands and clays. The 

 contest between them and the homotaxial beds of Eastern 

 Australia is most striking. While a comparison between 

 the crystalline schists of South Australia and the Stirling 

 Range Series no doubt suggests the comparative youthful- 

 ness of the latter, a comparison with the rocks of the Collie 

 Coal Measures leads to exactly the opposite conclusion. 

 In my opinion the latter comparison is much the more 

 logical of the two, since it is obvious that Post Cambrian 

 orogenic movements on a grand scale have affected the 

 South Australian area. 



A very strong lithological resemblance exists between 

 the rocks of the Stirling Range and the Roper River Beds 

 and Mount McMinn Beds of the Northern Territory. 1 The 

 reddish or purplish colour of the beds (suggesting aridity 



1 Woolnough, W. G. Report on the Geology of the Northern Territory. 

 Bulletin of the Northern Territory, No. 4, (1913). 



