AUSTRALASIA, NEW GUINEA, AND NEW ZEALAND 763 



periods of short-lived floods (sheet floods) which broke up the clays 

 and mixed them with the pebbles and grits carried downstream by 

 the local cloud-bursts or heavy rains. This appears also to have 

 been the opinion of Professor H. E. Gregory, of Yale, from an 

 examination by him in 1916 of the Sydney and Blue Mountain 

 exposures. The upper portion of the period appears to have 

 been one of greater precipitation in which actual lakes were in 

 existence. 



At Sydney, and a little south of that area, the Triassic beds dip 

 inland at a very gentle angle, but, as Carne has shown, the whole 

 southern area of these sediments has a dip averaging only from i° 

 to 2 . In the northeastern part of New South Wales, however, the 

 Mesozoic coal measures and the conglomerates dip from io° to 20 , 

 while in Southern Queensland they have been still more disturbed. 

 In the western portions of Eastern Australia, however, as also in 

 Western Australia, they lie practically horizontal. 



There appears to be no consensus of opinion among Australian 

 geologists as to the origin of the Hawkesbury beds. Rev. J. E. 

 Tenison Woods considered them to be of wind-blown origin 1 with 

 lakes and swamps between the dunes. 



In an unpublished paper R. S. Bonny considers them to be of 

 estuarine origin. On the whole they may be said to be continental 

 in origin, being formed in a sinking area mainly by water strains in 

 a rather dry period. 



Cretaceous. — The Cretaceous period marked a spilling over of 

 the ocean with the formation of great epicontinental seas, especially 

 during the Upper Cretaceous period. The area most affected was 

 the northern portion of the old heavy area separating Eastern and 

 Western Australia. It is probable that, during the Upper Cre- 

 taceous, the epicontinental sea extended from the Gulf of Carpen- 

 taria to the Southern Ocean. The eastern area occupied by the 

 Triassic sediments, however, consisted of dry land during the 

 Cretaceous. At the close of the period the whole center of Australia 

 appears to have been raised to a moderate height above sea-level. 

 Dunstan and Richards have recorded pronounced folding (40°-55°) 



1 "The Hawkesbury Sandstone," Proc. Jour. Roy. Soc. N.S. Wales, XVI (1882), 

 S3-9o- 



