112 W. G. WOOLNOUGH. 



The abrupt termination of botli Stirlings and Porongrups 

 on the east indicates that the zone of movement has been 

 limited in that direction by a fault which originally had a 

 downthrow to the west, but which has since taken its part 

 in the relative uplift of both ranges. 



Summary of Conclusions. 



The Stirling Ranges consist of a mass of ripple-marked 

 and current bedded quartzites alternating with fine-grained 

 slates possessing for the most part almost horizontal strati- 

 fication. Locally, very considerable crumpling, sometimes 

 associated with overthrusting lias occurred. On the north, 

 south and east the Stirling Range Series is probably faulted 

 heavily, and comes into contact with older gneissic granites 

 and greenstones. On the west the contact is an igneous 

 one, the granites being more recent than the sediments. 

 For this reason it is believed that the age of the sedimentary 

 series may be Pre-Oambrian. 



While the sediments must have been preserved from 

 denudation in a senkungsfeld, it is probable that the latest 

 differential movement has resulted in the uplift of the 

 sediments. In this movement extensive rearrangement of 

 drainage systems has occurred. The Pallinup and Gordon 

 rivers are explained as diverted streams, while an area of 

 internal drainage has been formed to the north of the 

 Stirling Ranges. The great "passes" through the range 

 are regarded as "air gaps" produced by stream erosion 

 during the penultimate period of the earth movement. 



