108 GEOLOGY OF LOWER MESOZOIC ROCKS OF QUEENSLAND, 



The Jurassic rocks of Victoria and Tasmania are freshwater 

 deposits, and probably extended some distance east of the present 

 coast. The Jurassic strata of New^ South Wales and Queensland 

 extend right to the extreme north of the latter State, and there 

 are marine Jurassic strata in New Guinea (Strickland River). 

 This seems to indicate that these Jurassic rocks were laid down 

 in a large basin, which had some outlet to the north. Another 

 point which strengthens this, and is against the existence of the 

 Gulf of Queensland during the Jurassic period, is the enormous 

 amount of sediment represented by the continuous Jurassic strata 

 of New South Wales and Queensland. These beds must average 

 some thousands of feet in thickness over an area of some hundreds 

 of thousand square miles, and must represent denudation of a 

 large area. That the drainage to this basin was limited on the 

 north, west, and south, is easily shown, for, in these directions, 

 we know the regions of synchronous deposition, and the divides 

 separating these from the Walloon basin do not allow of a very 

 extensive area from which the sediments may have been derived. 

 There is left, then, only extension to the south-east and east to 

 any very large extent, and, if this was the case, there seems little 

 possibility of the existence of the Gulf of Queensland. 



These considerations have governed the drawing up of Text, 

 fig. 5 (p. Ill) showing the distribution of land and sea during 

 Jurassic time. 



The Thomson Trough, which lies to the east of Australia, may 

 have been of comparatively recent origin. The east coast of 

 Australia has been subject to folding since Lower Cretaceous, 

 and to considerable faulting during Cainozoic; and it does not 

 seem improbable that the Thomson Trough is a result of these 

 movements. Schuchert* concludes his study of continental 

 fracturing and diastrophism in Oceania thus: "To sum up, we 

 may say that the bottom of the Pacific Ocean in the region of 

 greater Australasia seemingly became more and more mobile 

 with the Lower Carboniferous and especially during the Jurassic 

 and Cretaceous. During this very long time, the eastern half of 

 * Amer. Journ. of Science, xlii., 1916, p. 104. 



