378 T. W. E. DAVID, F. B. GUTHRIE, AND W. G. WOOLNOUGH. 



The older basalts of Victoria are in part of Eocene age, and in 

 part, according to Messrs. Hall and Pritchard, 1 perhaps older, 

 possibly Upper Cretaceous. The nepheline rock of Kosciusco may 

 therefore, be also of Cretaceous, or at all events of Upper Mesozoic 

 age. This conclusion is rendered the more probable by a com- 

 parison of the age of the trachyte lavas of the Canoblas near 

 Orange, and of the Warrumbungle Mountains near Coonabarabran 

 in New South Wales. These last appear to be slightly older than 

 most of the Tertiary basalts of New South Wales, perhaps Eocene 

 or older. 2 



Moreover, the relations of the soda-syenite of the Gib Rock near 

 Bowral, New South Wales, to the Tertiary basalts of the sarne 

 neighbourhood appears to be somewhat similar, the soda rock 

 being somewhat older than the basalts. Evidence is as yet want- 

 ing as to the exact age of the rock in New South Wales, which 

 above all others hitherto described mostly closely resembles the 

 nepheline rock of Kosciusko, viz. that of Barigan. It is clear 

 however, from Mr. Carne's account that the nepheline rock of 

 Barigan has intruded the Triassic Hawkesbury Series as well as 

 the underlying Permo-Carboniferous coal measure formation, and 

 is therefore Post-Triassic in age.' 



In Queensland the trachyte lavas and trachytic volcanic necks 

 of the Glass House Mountains, between Brisbane and Maryborough 

 and the trachyte agglomerates of the district west of Port Mackay 

 appear to be slightly older than most of the Tertiary basalts of 

 Queensland. As described in the report by Mr. A. Gibb Maitland* 

 the trachytic agglomerates of the Port Mackay district are to be 

 referred to the geological horizon of the Desert Sandstone, the 

 age of the latter being considered to be either Upper Cretaceous 

 or Cretaceo-Tertiary. 



Messrs. W. H. Twelvetrees and F. W. Petterd in their inter- 

 esting account of the Port Cygnet soda-bearing rocks of Tasmania 



1 Proc. Eoy. Soc. Vict., Vol. vn., pp. 188 and 195, 1894. 



2 Proc. Linn. Soc. N. S. Wales, 1896, Pt. 2, June 24th, p. 265. 



3 Geological Features and Mineral Resources of the Port Mackay 

 District — Parliamentary Paper C.A. 93, 1889. 



