EY H. C. RICHARDS. 131 



Mesozoic sediments. These sedimentary rocks are tenta- 

 tively regarded as belonging to the Walloon stage of the 

 Trias-Jura, so that the evidence here is certainly not in 

 favour of a contemporaneous age for the trachytic rocks 

 and the Walloon stage of the Trias-Jura, as has been 

 advocated. 



This question of age has been discussed at some length 

 and all the important pieces of evidence which have been 

 adduced in favour of a Trias-Jura age have been discussed. 

 The author is unable to accept the evidence for a Trias- 

 Jura age, but is firmly of the opinion that these rocks have 

 all been extruded during the Cainozoic era. 



The direct evidence as well as the indirect evidence 

 leads one to this conclusion, and the correlation with 

 similar extrusive material of Cainozoic age in New South 

 Wales and Victoria is strong confirmative evidence. 



The volcanic activitj- which resulted in the wide- 

 spread distribution of these volcanic rocks probably began 

 in the Lower Cainozoic and continued until the Upper 

 Cainozoic. 



(ill.) Ehyolitic Rocks, 



These occur as lava flows, plugs, dykes and pyro- 

 clastie accumulations. They were all formed during the 

 second great period of activity, and although they are 

 represented in nearly all parts of the field- where volcanic 

 rocks are encountered, the greatest development is in the 

 southern portion. 



Wearne and Woolnough^^ made reference to the 

 rhyolites of IMount Barney, ^Nlount ^Maroon, Mount Alford 

 and Glennie's Pulpit. Jensen-' also referred to these 

 rhyolites, but hitherto there has been no treatment of the 

 big development of the rhyolitic rocks in the southern and 

 south-eastern portions of the area. 



These rocks have resulted from central eruptions for 

 the most part, and setting aside the pyroclastic material 

 they usually occur more or less as isolated masses along 



^= Op. cit. 



^ Proe. Linn. Soc, N.S.W., xxxiv., p. 72 



