66 



A stronger bed of limestone, 10 ft. in thickness, under- 

 lies the fossiliferous beds, just mentioned, and makes a low 

 ridge that can be followed by the eye for a long distance. The 

 limestone has undergone differential weathering from the pre- 

 sence of siliceous material which shows in relief as blotches, 

 casts, and reticulations of an arenaceous character. No organic 

 structure could be detected in these objects in relief, but 

 some of them strongly suggested casts of Pteropods and other 

 organisms. The limestone is laminated at some levels and is 

 subnodular. Near the homestead, on its northern side, the 

 bed has a dip to the S.E., from which point it gradually 

 curves round to the S., then S.W., then W. 20° S. at 20°, 

 then W. 20° N. at 40°, from which point it makes a strike, 

 for about a mile, parallel with the eastern side of the old 

 road, then makes a sharp twist in the form of the letter S. 

 At IJ miles from the homestead, at a small creek where the 

 road makes a sharp turn to the north, the beds dip W. 20° S. 

 at 80°. About 100 yards from this point the beds are cut 

 by a dip fault and the purple flags are thrown against the 

 faulted face. The purple shales dip S. 20° W. at 65°. The 

 limestone is thrown 53 yards to the S.W., when the dip is 

 S. 20° W. at 70°. On the southern side, the oolitic lime- 

 stones and Girvanella bed that occur near the Wirrealpa 

 homestead, show on the rise, with a dip W. 20° N. at 65°. 

 These overlying beds are evidently faulted against the lower, 

 as the strike is divergent. On the low rise situated between 

 the small creek and a larger one, at this point, a great number 

 of fragments of the Archaeocyathinae limestone occur, no 

 doubt brought down with the alluvium of the creeks. 



X. Up a Tributary of Wirrealpa Creek. 



The main ereek passes the station house on its south- 

 eastern side, the bed of which is thickly strewn with boulders 

 and gravel. Near the bottom end of small creek that is a 

 tributary to the Wirrealpa Creek, on the western side of the 

 "Trig" Hill, bleached and rotten purple shales have a dip 

 of 90°. In going up the creek the dip decreases. A few 

 hundreds of yards up, shelving purple sandstones, etc., are 

 seen in quarry, with a dip S. at 23°. Massive purple sand- 

 stones dip S.W. at 18°. Higher up, where the creek bifur- 

 cates, the right-hand branch exposes a 15-in. bluish limestone 

 and a 3-ft. earthy limestone, with a shale bed between : dip 

 W.N.W. at 34°. ' At 300 yards up the left-hand branch there 

 is a bar of limestone with wavy and concentric structure 

 having a dip W.N.W. About a quarter of a mile up this 

 creek, several large loose stones, up to 2 ft. in diameter, con- 

 taining Archaeocyathinae remains, rest on a bar of limestone, 

 but the latter does not appear to contain similar remains. 



