74 



thick limestone's, or, possibly, is nipped in by a fault; the 

 beds seem to bifurcate about the spot. The limestone ex- 

 posed on the eastern side of the road has the appearance of 

 a shallow syncline. The great mass of limestone that forms 

 the main part of the "Big Hill" comes up from the Eren- 

 gunda Creek (see under Section VIII.). In its purest por- 

 tions it forms a white and grey marble (dip N. 30° E. 

 at 30°), with remains of Archaeocyathinae. The best fossili- 

 ferous horizon is in the upper beds, near the public road. 



[The observations at this point join on to those given in 

 the traverse from Blinman to the "Big Hill," in Section 

 VIII.] 



XVI. Visit to the Grindstone Range, Balcoracana 

 Creek, and the Wilkawillina Gorge. 



This trip was in a southerly and south-westerly direction 

 from Wirrealpa Station. Going in a south-westerly direction, 

 the track was over flaggy sandstones. At 1 mile distant, 

 in small creek, soft sandy flags were exposed, showing false 

 bedding: dip W. at 25°. At 3 miles out, descending to a 

 valley (three-quarters of a mile in width), the exposures 

 were still sandy flags, much false bedded : dip E. 20° S. 

 at 35°. In a dry creek, near the centre of the valley, 

 sandstone and flags havo a dip E. 20° N. at 35°. After 

 crossing the valley and ascending a small rise, I passed over 

 into the Balcoracana Creek. This creek, which is the most 

 important waterway in the neighbourhood, takes its rise in 

 The Bunkers, which are a continuation of the Nildottie 

 Ranges that occur on the southern side of Patawarta. There 

 was a strong flow of water in the creek at the time of passing. 



On the southern side of the Balcoracana Creek is situated 

 the Grindstone Range, or the "Little Bunkers." These form 

 an isolated range of hills, about 3 miles from Wirrealpa, and 

 are intersected, at one end, by the Balcoracana Creek. They 

 consist of purple sandstones and shales, the latter, wasting 

 more rapidly than the former, produce an outline of peaks 

 and depressions, from which feature they have received the 

 name of "bunkers," on account of their resemblance to the 

 main range of The Bunkers, on their western side. The 

 "white cliff," or the "grindstone cliff," in the range, is 

 formed of a sharp fine-grained sandstone, wliich is used locally 

 for making grindstones, from which the range has received 

 its secondary name: strike S. 20° W., dip easterly at 63°. 



Went up stream, in the Balcoracana Creek, to the junction 

 of small creek which comes in from the north-east. The 

 main creek channel, almost immediately, going up stream 

 turns due west and makes a gorge that penetrates the high 



