427 



plain was developed but little above the level of the 

 surface of the sea. Floras during the Miocene appear to 

 have been uniform and of tropical to subtropical affinities, 

 besides being unlike those to be found in Australia to-day. 

 The Pliocene was partly a period of sedimentation and 

 partly of erosion. The flora of this period was unlike that 

 of the present day. 



The close of the Tertiary was marked by the develop- 

 ment of a great series of faults, whose main scarps parallel 

 the present continental margin, from Thursday Island in 

 the north to south-western Victoria on the south. The 

 great fault blocks produced by these dislocations are tilted 

 generally to the west, and thus the north and south river 

 courses are forced against the eastern scarps of the associ- 

 ated upfaulted blocks. Minor cross faults relieved the 

 general peripheral strain of the continents. An intensity 

 of movement was experienced at the angle formed in the 

 south-eastern corner of the continent, and here the maxi- 

 mum height of the plateaus is found. Typically the eastern 

 fall of the highlands is the steepest, and such fall occurs 

 in the form of large subparallel warps, block faults and 

 flexures. These are best developed in the south-east of 

 Australia, in eastern New England, and in northern 

 Queensland. The marvellous canons of the three regions 

 thus enumerated are due to the youthful dissection of these 

 fault blocks. 



The continental shelf is a portion of the coast line which 

 wasdownthrown in closing Ter1 lary t Lme and which has been 

 altered to a sloping terrace, first by wave erosion and 

 sedimentation, and secondly and much more recently, by 

 ■abmergence combined with erosion and sedimentation. To 

 this double set of activities also belongs the Great Barrier 

 Reef of North Queensland. 



