BY H. I. JENSEN, D.SC. 167 



that period, though the area may have remained sub- 

 merged for a while after. 



Hence I deduce from the horizontal nature of Permo- 

 Carboniferous beds at Mt. Barney [15], that in this period, 

 or just before it, subsidence came to an end in this region ; 

 it does not follow that sedimentation must cease at the 

 same time. It may persist for a whole geological period 

 longer. 



Queensland underwent the same general types of 

 movement as New South Wales durijng the Palaeozoic era. 

 In the early Triassic, the super-elevation of some earth 

 segments, such as New England, caused down warpings 

 of slight amplitude, and in the depressions thus formed 

 were the Triassic and Cretaceous rocks deposited. 



Causes of Folding. 



It has been argued that throughout the Palaeozoic 

 periods- the ancestral Australian Continent was continually 

 adding to itself on the eastern side. Adopting Kelvin's 

 hypothesis of the origin of the continents, we may regard 

 this original Australia or Gondwana Land as a floater, that 

 is a portion of the earth's C(rust, which consisted of acid 

 magma, and was specifically light, and therefore raised 

 by flotation above the heavier magmas, or buoyed up by 

 the heavier basic magmas beneath. As erosion was con- 

 tinually making it specifically lighter, and the detritus 

 resulting from erosion was being piled up in adjoining seas, 

 the process of erosion had the effect of causing continued 

 elevation of the continental area and subsidence for a long 

 period at least in the adjoining basins. 



The elevation of the continental area would cease 

 when the underlying basic portions of the earth's crust had 

 consolidated and fallen under the influence of secular 

 contraction. 



The subsidence of the seabasins would cease when 

 sufficient sediments had been heaped together for the 

 depressed isogeotherms to reassert themselves. 



The gradual rise of temperature in this great mass 

 of cool sediments would cause first a general uplift, and, 

 later, if upward expansion did not afford sufficient relief 

 of pressure, folding of the sediments would ensue. 



