168 THE BUILDING OF EASTERN AUSTRALIA 



In this way the great accumulation of sediments round 

 the margin of the old continent Avould be raised into 

 mountain ranges, the continent advancing a few hundred 

 miles in the direction of the former sea in each geological 

 period. 



The sediments of one geological period in this way 

 became raised into a marginal buttress of mountain ranges 

 in the next geological period. These mountain ranges in 

 their turn would become subject to denudation, and the 

 material derived from them would accumulate on the 

 new continental shelf and in the adjoining deep ; in its 

 turn this new area of sedimentation would become a 

 continental margin. 



This view is opposed to the doctrine of Permanency 

 of Ocean Basins advanced by that eminent geologist, 

 Penck, but it derives strong support from the geological 

 history of Eastern Australia. [For further discussion see 

 12]. 



Ocean basis are subsiding segments of the earth's 

 crust, whose downward movement is probably due to 

 rigid connection with the shrinking interior of the crust. 

 In their downward sag, these segments sink from levels 

 of lower earth temperature to those of higher temperature, 

 with the result that such segments are fused below, and by 

 reason of their expansion exert a lateral pressure on 

 adjoining segments. In this way is produced a creep in 

 the zone of rock flowage from the subsiding segments 

 towards the rising segments. The displaced magmas become 

 injected into cavities (maculae), zones of no strain, and 

 fractures in the continental margins, the rocks in which 

 become heated by the injected magmas and consequently 

 expand. A period of mountain building and folding, due 

 to igneous injection as outlined by Reg. A. Daly [18], 

 may therefore succeed or accompany the uplift and folding, 

 due to rise of isogeotherms. 



Mountain building by igneous injection, seems to have 

 gone on extensively in the late Palseozoic and early 

 Mesozoic in the New England area of New South Wales. 



Folding only takes place in the superficial strata of 

 a rising area (undergoing expansion due to rise of 

 isogeotherms) under particular conditions, namely, when 

 the area is a sunken fault block relatively left behind in the 



