BY H. I. JENSEN, D.SC. 169 



^are like our Triassic rocks, very poor in fossils, and indicate 

 deposition in a semi-brackish sea. The Devonian sediments, 

 where not of organic origin, point to acidic eruptions and 

 intrusions in this and the previous period. 



(6) The late Carboniferous Avas a period of most 

 intense folding and faulting, accompanied b}'^ igneous 

 intrusions and volcanic eruptions of strongly acidic 

 character. 



(7) The Permo-Carboniferous was a period of general 

 subsidence, accompanied by erosion of the lands and the 

 piling up of sediments in the ocean. Volcanic eruptions 

 took place far and wide in the regions of heavy sedimenta- 

 tion, and the lavas were all of an intermediate to basic 

 nature. 



Towards the end of this period the super-elevation of 

 some landmass lying to the south-west of Tasmania, caused 

 an Australian ice age. Evidences obtain at Bacchus 

 Marsh, Victoria; Hallett's Cove, and other places in S.A., 

 Lochinvar and Branxton in N.S.W.. Bowen in Queensland, 

 and the Irwin and Gascojme Coalfields in W.A. [4 and 5] 



In the foregoing notes, the following two points are of 

 special interest :— 



(1) The Continent moved in an easterly direction 

 throughout the Palaeozoic, and by the end of the Permo- 

 Carboniferous, had captured more than the whole of the 

 present continent, including many deep ocean parts. This 

 is satisfactory evidence that Penc k's theory of the 

 permanency of ocean basins doe.< not hold. n 



(2) Andesite indicates a subsiding and rhyolite a. "> J^ ' 

 rising area. V^ "* 



The Mesozoic. 



The Mediterranean Sea of Australia, shown on Figs. 

 7, 8, 9, commenced in the Permo-Carboniferous period, 

 during which it was probably connected with the ocean 

 by a south passage. Its oceanic connection to the south 

 ceased with the dawn of the Mesozoic. 



In the Triassic and in the Trias-Jura, it is probable 

 that the main mountain ranges of Australia lay some 

 distance out in the present Pacific Ocean, in the direction 

 of New Zealand. Regional uplift took place over most 

 of the coal-basin (Permo-Carboniferous) area. The 

 upward movement was not of equal intensity in all parts. 



