GEOLOGICAL RECONNAISSANCE OF THE STIRLING RANGES. 99 



powerful overthrusting force from south to north. In some 

 instances the slip-faulting produces a pseudo-ripple-marking 

 on the rock surfaces. This, however, is easily distinguish- 

 able from true ripple-marking which is also extensively 

 developed in the same beds. Sometimes cases may be found 

 where the primary and secondary irregularities are shown 

 in a single specimen, producing a decidedly complicated 

 structure. 



Mount Hassell shows fine rock exposures at its summit. 

 Some of these exhibit perhaps the most beautifully pre- 

 served ripple marks in the district. On the spot their dip 

 is inappreciable, but from Toolbrunup a general east-north- 

 easterly inclination can be detected. On the lower slopes 

 suggestions of steep and irregular dips are probably to be 

 explained as due to jointing, induration or slip, though 

 they may be connected with the disturbance which pro- 

 duced the steep dips in Yungermere. 



In the "cock's-comb" ridge of Toolbrunup there is a 

 decided synclinal structure; though the dips are all very 

 slight there is an inclination towards the central peak from 

 each side. Towards the end of the south-western ridge 

 there is a good deal of contortion and dips of 45° towards 

 the central ridge are to be observed. There is probably a 

 fault hereabouts. In the long spur south of Toolbrunup 

 and separated from it by a deep gorge, dips, which may be 

 those of false bedded layers, tend south 20° east at 24°. At 

 the summit of this ridge where it joins the transverse spur 

 which connects it with main mountain, the dip of the ripple 

 marked surface, and therefore undoubtedly the true dip, is 

 north 17° east at 44°. One hundred yards to the north- 

 west the dip is north 39° west at 69°, less than a quarter of 

 a, mile away towards the south, the inclination is about 

 south south-east and amounts to not more than 8°. There 

 is therefore a very decided plane of disturbance at this 



