562 THE GEOLOGY OF THE WARRUMBUNGLE MOUNTAINS, 



mountains round Bugaldi Creek, at Gowang and numerous- 

 other places. 



The Volcanic Bocks include (a) light grey arfvedsonite trachytes 

 which form the main balk of the mountains in the heart of the 

 group, such as Timor, Mobara, Siding Spring Mountain, Berum 

 Buckle, Mount Caraghnan, Needle Mountain, The Bluff, 

 Wombalong (Terra-Terra or EKmouth) and The Spire. 



(b) Dark bluish cegirine trachytes, nepheline-segirine phonolites 

 and allied rocks, capping the arfv^edsonite rock in places, as on 

 Mount Caraghnan, and extending all round them in a sheet now 

 dissected by gorges and wider creek valleys; the AVarrumbungle 

 Range north of the Castlereagh River from Timor to Coona- 

 barabran is capped with this rock, as is also the ridge known as 

 Naman Ledges; Tooraweanah Mountain, the Dillys (south of 

 Tooravveanah), the Ridge Pole S.W. of Tannabar, Mount 

 Tannabar and most of the spurs north of the Warrumbungle 

 Range, such as Kalga Range, the Bugaldi Spur and the Yarra- 

 man Spur, have similar cappings. 



(c) Grey nosean and pseudoleucite phonolites at Mount Bingy 

 Grumble, Berum Buckle and round the base of Mount Caraghnan. 



(d) Trachydolerite with sodalite, olivine, augite, fegirine and 

 soda felspars at Uargon Creek covering much of the tableland 

 south of Black Mountain, and forming part of The Spire pinnacle 

 (Tonduron). The rock which forms the butte-like hills of the 

 Forked Mountain and Nandi near Coonabarabran is closely 

 related. 



(e) Melilite basalts or basanites at Billy King's Creek, a couple 

 of miles south of Coonabarabran. 



(f) Sodalite basalt at Mount Gowang, The Spire, and other 

 places, a differentiation-product of the trachydolerite. 



(g) Ordinary andesites and basalts capping the other rocks in 

 places, as on tlie top of Mount Wombalong (Exmouth), and 

 spreading over a much wider area. 



Sequence. — The sequence of the lavas seems to have been in 

 general from the more acid to the more basic; and they merge 

 into one another in such a way that there can be no doubt that 



