GEOLOGICAL RECONNAISSANCE OF THE STIRLING RANGES. 107 



Pallinup River does not run strictly parallel with the 

 general axis of the Stirling Range, it is extremely probable 

 that the river course was brought into existence as a result 

 of the faulting which produced the range itself, and that 

 the river is therefore of the nature of a diverted stream, 

 and not as supposed by Jutson, 1 due to purely erosional 

 forces. 



Much more definite and instructive is the case of the 

 Gordon-Fraukland River System. The Gordon rises just 

 west of Broome Hill and runs southwards about parallel to 

 the Great Southern Railway to within a couple of miles 

 of Oanbrook. Here it suddenly turns off at right angles 

 and flows to the west-north-west in which direction it con- 

 tinues for 25 miles (direct measurement) until it readies 

 the valley of the Prankland River into which it falls at 

 right angles. The cause of the deflection is the influence 

 of the axis of elevation of the Stirling Range. The higher 

 peaks of the range extend only to the railway line, and the 

 country to the west is not perceptibly uplifted. It consists 

 of the normal crystalline rocks of the area, with the one 

 exception of Warriup Hill about 10 miles west of Oanbrook. 

 This isolated sugarloaf consists 2 of an outlier of the Stirling 

 Range Beds, and is built up of the same purplish ripple- 

 marked quartzites as the main range. In spite of the com- 

 paratively insignificant altitude of the country, the eleva- 

 tion in this area has been of such a character, and has 

 taken place at such a rate as to cause the complete deflec- 

 tion of the drainage. On the northern bank of the Gordon, 

 in its east and west portion heavy aggradation has taken 

 place, a feature which is conspicuously absent on the 

 southern side. 3 Both Pallinup and Gordon Rivers are 

 therefore diverted streams. 



1 Jutson, J. T. Bulletin Geological Survey of Western Australia, No. 

 61. p. 160. 



3 Fide M. Aurousseau (private communication). 



3 Fide W. K. Weller, (private communication). 



