110 GEOLOGY OF LOWER MESOZOIC ROCKS OF QUEENSLAND, 



the Australian Continent, a land about 1,800 miles east and 

 west and 2,200 miles north and south, was folded into a series 

 of parallel ridges trending north-west and south-east, nearly all 

 of which went down more and more beneath the level of the sea 

 to a maximum depth of about four miles and an average depth 

 of between one and two and a half miles. Small parts of the 

 ridges still protrude above the ocean (at least New Caledonia), 

 but most of what we see are the volcanoes that have built them- 

 selves up above the folded rocks to the level of the sea." 



This statement gives a general outline of the geological history' 

 of this region, but the stress laid on the Jurassic as a period of 

 folding does not appear to be justified. As far as our present 

 knowledge goes, the periods during which folding-forces have 

 been effective since the Carboniferous are Permian (Permo-Car- 

 boniferous), late Cretaceous, and possibly late Cainozoic. The 

 Permian strata of New South Wales indicate folding with axes 

 approximately N. by W.; the Triassic, Jurassic, and Lower Cre- 

 taceous all show a general stratigraphical conformity, and have 

 all been affected to the same extent by a folding which was later 

 than Lower Cretaceous and earlier than Cainozoic, the direction 

 of the axes of folding being about N.30°W.; the Cainozoic rocks 

 in the Ipswich District have been subject to a minor folding- 

 movement with approximately meridional axes. 



It is also noted that, in New Caledonia, Triassic, Jurassic, and 

 Cretaceous strata are apparently conformable, and have all been 

 subject to subsequent overthrusting from the north-east. This 

 strengthens the conclusion that the more important folding did. 

 not take place till after the deposition of the Cretaceous. 



It appears, then, that there were transgressions in Triassic 

 time (1) from the east, extending as far west as New Caledonia, 

 and (2) from the south, forming the Gulf of Queensland. During 

 Jurassic, the eastern coast remained in much the same position, 

 the Gulf of Queensland disappeared or was very much reduced, 

 and the sea transgressed in Western Australia parallel to the 

 present western coast, and also in New Guinea to the Strickland 

 River district; during this time, also, the extent of the basins. 



