180 THE BUILDING OF EASTERN AUSTRALIA 



great Tertiary peneplain of Eastern Australia, this pene- 

 plain having been excavated out of *' Older Volcanics,'* 

 palaeozoic and mesozoic rocks indifferently. They, there- 

 fore, lie on basalt capped hills dotting the peneplain. 



As examples, Andrews mentions Dargo High Plains, 

 Vic. ; Kiandra, Older Macquarie and Hawkesbury Leads 

 [Mount King George (0, Bald Hills, Hill End, etc.], Older 

 Ting ha and Emmaville Leads (N.S.W.) 



Skeats [25] describes numerous occurrences of Older 

 Volcanics in Eastern Victoria. According to this author 

 older basalts are not petrologically distinguishable from 

 the newer, except by their finer grain size and greater 

 decomposition. 



In New South Wales, the basalt of the Sydney basin, 

 found in dykes around Sydney, as necks at Hornsby, Pros- 

 pect, Minchinbury, Dundas, etc., and as more extensive 

 capping s on Mount Hay, Mt. Tomah, and Mount King George 

 in the Blue Mountains, are in part referable to this series. 

 These basalts have decidedly alkaline affinities, contain- 

 ing variously sodalite, analcite and hauyne. 



The Orange basalts underlying the alkaline pile of the 

 Canoblas must also be put in this class. They were 

 erroneously mapped by Mr. Sussmilch and myself as later 

 than the alkaline eruptions, but Mr. E. C. Andrews dis- 

 covered, by physiographic methods, that we must have 

 made a mistake, which was confirmed by Messrs. Andrews 

 and Sussmilch in subsequent studies in the field. These 

 basalts are in some instances characterised by the presence 

 of melilite and fayalite. Probably the melilite basalts 

 and the tuffs of Hobart and the Alkaline basalts of Shannon 

 Tier, Tasmania, are roughly contemporaneous. 



It has been demonstrated by Andrews [1], that many 

 of the New England basalts and much of the Darling 

 Downs basalts of Queensland belong to the Older Volcanics. 

 Mr. R. A. Wearne, B.A., and the wTiter have also seen 

 evidence in the Fassifern district of extensive intrusives 

 of basic magma in very late Mesozoic, or more probably 

 Early Tertiary time, before the Alkaline rocks of that dis- 

 trict were poured out. 



The Rhyolites of the Macpherson Ranges, between 

 Queensland and New South Wales, antedate in part at 

 least the extrusion of the Alkaline rocks. [15] From 



