B\ H. I. JENSEN, D SC. 183^ 



The Newer Volcanic. 



The rocks are mainly basal* of a more or less por- 

 phyritic nature. They cover enormous areas of Eastern 

 Australia. In age they postdate the formation of the 

 Middle Tertiary peneplain, and the eruptions were in 

 progress during the great Pliocene uplift. The leads of 

 newer volcanics are consequently buried channels below 

 the peneplain level or resting immediately upon it : their 

 fossil contents are characterised by an abundance of fruits 

 and seeds similar to those of tropical Australia to-day. 

 Lauraceous types are characteristically absent. 



• The whole of the extensive basaltic plain of Western 

 Victoria, and many areas in Eastern Victoria belong to 

 the Newer Basalts. In this state eruptive activity con- 

 tinued, as in the Mount Gambler District of South Australia, 

 into late Pleistocene and recent times. Remains of the 

 Dingo (an animal presumed to have been introduced by 

 man) have been found in the tuff. 



On the Monaro in N.S. Wales and in the New England 

 extensive eruptions took place in late Pliocene or early 

 Pleistocene. Most of the Darling Downs basalts were 

 probably erupted at the same time. At the same time 

 extensive sheets were poured out in North Queensland 

 (as at Cairns, Atherton, Geraldton, &c.). 



Pleistocene and recent erosion has only had time 

 to slightly modify the original surface. There has been 

 no peneplain formed since these volcanic extravasations. 

 The very level nature of the Darling Downs, and of the 

 tableland on the Blackall Range and of the tablelands on 

 similar ranges is due to the fact that the lavas flowed over 

 a peneplain surface only, slightly dissected, and being of 

 a liquid nature, the lava outpourings made a level surface. 

 The eruptions were dominantly fissure eruptions. 



Early Tertiary peneplanation was followed by the 

 eruption of the Older Basalts, which usually cap deep 

 leads of this age. 



The Valuable Minerals of Eastern Australia. 



Closely connected with the petrology of our continent 

 is the study of our mineral deposits of economic value. 

 The genesis of ore deposits is also intimately bound up 

 with structural geology. 



