GEOLOGICAL RECONNAISSANCE OF THE STIRLING RANGES. 95 



slight irregularities of tlie surface as not to be measurable 

 by clinometer on the rock exposures themselves. Deter- 

 minations of dip are obtainable with certainty only on the 

 slopes and summits of the peaks where extensive rock 

 outcrops occur in situ. On the foothills and lowlands 

 the rocks are so much broken and covered by angular 

 rubble that it is extremely difficult, and often impossible, 

 to determine with certainty whether what is apparently a 

 dip surface is a true dip, current bedding, jointing or local 

 superficial disturbance. The extreme density of the scrub 

 is also a factor which renders the measurement of a con- 

 tinuous geological section impossible in the course of a 

 reconnaissance like the present investigation. 



While the general horizontality of the stratification is so 

 outstanding a feature, there are, nevertheless, abundant 

 and very striking exceptions to the general rule. Where 

 dips were measured with certainty they are indicated on 

 the map. Broadly, there is a very decided tendency for 

 southerly dips on the northern side of the range and for 

 northerly ones on the southern side, so that the structure, 

 as a whole, is markedly synclinal. 



In Ellen Peak the stratification is practically horizontal. 

 In the peaks of the five summits of Isongerup the same 

 structure is exhibited. In Pyungoorup there is a general 

 southerly dip of about 10°. Bluff Knoll and Ooyanarup are 

 seen from a little distance to possess a gentle synclinal 

 structure. At closer quarters this apparent regularity 

 is found to be subject to local disturbances. In the mag- 

 nificent precipice on the northern side of the range at 

 Ooyanarup the dip of the ripple marked quartzite is south 

 30° east at 25°, and, in the lower parts of the cliff, the 

 bedding is highly contorted, with a strong suggestion of 

 overfolding towards the north. In the low gap in the crest 

 of the range near by the ripple marked surfaces are hori- 

 zontal. 



