BY H. I. JENSEN. 849 



watershed between Bullawa Creek and Spring Creek. In this 

 razorback the coarse conglomerate bed is met with at an altitude 

 of 2,000-2,100 feet, about 200 feet higher than one mile south. 

 This means a dip of 1 in 25 to the south, or of about 5° to the 

 S.E. 



Kangaroo Gully is interesting because of the occurrence there 

 of a type of porphyritic basalt with phenocrysts of plagioclase up 

 to two inches in length. The basalt penetrates sandstone and 

 apparently also trachytic tuffs. It is similar to basalts found 

 elsewhere in the Nandewars intruding and capping the trachytes, 

 being alkaline and without olivine. Both in hand-specimen and 

 under the microscope the Nandewar post-trachytic basalts 

 resemble the Sandilands Ranges basalt. On the east side of 

 Kangaroo Gully there is a high trachyte ridge commencing in 

 the Sugarloaf, N.N.W. of Ningadhun. The trachyte of the ridge 

 caps trachytic tuffs, which again overlie sandstone. The trachyte 

 is therefore a flow which has infilled an old valley. On the 

 western side of the gully the formation consists of tuffs and 

 breccias. In the Triassic (?) sandstones north of Kangaroo 

 Gully there are carbonaceous shales but no fossils. The dips 

 are somewhat disturbed. 



East of Kangaroo Gully occurs a sill-like or laccolitic mass of 

 arfvedsonite trachyte porphyritic in anorthoclase. To the north 

 this merges into an eruptive conical mass. 



The ascent of Ningadhun from the N.N. W. is interesting, 

 inasmuch as various kinds of alkaline volcanic rock are met with 

 in well defined sheets as shown in Fig. 2. Ningadhun rock itself 

 is a plug left by the removal of surrounding tuffs. Behind 

 Ningadhun on Yullundunida there is a slanting dyke-like razor- 

 back dipping sharply to the S. E. It appears to be a relic of a 

 surface-flow from Ningadhun capping the tufl's now removed by 

 denudation (Plate 4). About half-a-mile N.N. W. of Ningadhun 

 there is a sugarloaf of arfvedsonite trachyte which represents a 

 plug in a parasitic vent. 



The sandstone beds north of Bullawa Creek have a sliccht 

 N.W. dip. The S.E. dip so general on the other side of the 



