162 THE GEOLOGY OF THE CANOBOLAS MOUNTAINS, 



Cargo Road oq the west. The highest point is the Old Man 

 Canobolas, which reaches an altitude of 4610 feet. The principal 

 peaks are as follows : — 



Old Man Canobolas ... 4610 feet. 



Towac (The Bald Knob)... 4500 „ 



Young Man Canobolas ... 4400 ,, 



The Pinnacle 4050 „ 



The Bald Hills (three) ... 4000 „ (about). 



Johnston's Pinnacle ... 3850 ,, 



Watt's Pinnacle 3810 „ 



The Bald Hills, Towac, and the Old Man Canobolas lie on a 

 definite north and south line, while the other peaks stand more 

 or less promiscuously to the east of this line. 



To the west of this line the tableland is much lower. At 

 Molong, for example, the altitude of the peneplain is only about 

 2000 feet. It is quite possible, therefore, that an important 

 fault may occur here, separating the Orange portion of the 

 uplifted peneplain from that part immediately to the west. 



That portion of these mountains which reaches above the 3000 

 feet level, consists entirely of volcanic rocks, lavas and tuffs, piled 

 up around several different volcanic vents. No distinct crater 

 rings remain. We have, then, an approximately level platform 

 of denuded Silurian and Devonian rocks, 3000 feet high, upon 

 which has been piled a series of lavas and tuffs to a maximum 

 height of 1600 feet above this level. These are, therefore, essen- 

 tially mountains of accumulation. The earlier lavas (comendites, 

 trachytes and andesites) have not been found below the 3000 feet 

 level, but the later basalts have flowed into and, in some cases, 

 filled the mature valleys on top of the tableland. In the 

 mountains the streams are all consequent streams, flowing by 

 direct courses to the tableland; and in most cases they have cut 

 fairly deep gorges into the volcanic rocks. Those flowing to the 

 north and east join the Macquarie River, those to the south and 

 v/est eventually join the Lachlan. 



