The leads of the "Older" and "Newer Volcanics " may be 

 distinguished both by their geographical position and their fossil 



(a) Fossil Contents.— The Leads of the "Older Volcanics" are 

 characterised by the presence of abundant plant leaves. Among 

 these the lauraceous types appear to predominate in the Victorian 

 area at least. Fruits and seeds are, however, characteristically 



The Leads of the " Newer Volcanics " are characterised by the 

 presence of abundant fruits and seeds showing affinities with 

 tropical plant types of the present day. Lauraceous leaves are, 

 however, characteristically absent. 



(b) Geographical Position. — Leads of the "Older Volcanic*. " 

 These buried channels usually possess basaltic cappings, and they 

 commonly occur as basalt-capped hills dotting the great Tertiary 

 Peneplain of Eastern Australia. The peneplain has been excavated 

 out of basalts, Paleozoic complexes, and Mesozoic rocks indiffer- 

 ently, and the miners frequently exploit the old leads themselves 

 for their possible mineral (gold, tin and diamonds) contents by 

 means of levels driven in from the hillsides. 



Examples.— Dargo High Plains (Vic); Kiandra, Older Mac- 

 quarie and Hawkesbury Leads [Mount King George (?), Bald 

 Hills, Hill End, etc.], Older Tinghaand Emmaville Leads (N.S.W.) 



Leads of "Younger Volcanics." — These buried river channels lie 

 beneath the peneplain surface. They have been buried under 

 basalt floods. The basalts themselves have suffered great denuda- 

 tion and broad mature valleys have been formed in their mass, 

 leaving isolated hills of basalt dotting the rolling surface, due to 

 the post-basaltic erosion, nevertheless the leads themselves underlie 

 the peneplain surface thus made. The leads are exploited by 

 means of shafts sunk either in the peneplain surface or on the 

 gentle hill slopes. 



