802 GEOGRAPHY OF BLUR MTS. AND SYDNEY DISTRICT, 



shallowing very gradiuill}' for considerable distances from land; 

 thus wave-attack diminished in competency, and in the old 

 age of the cycle the submarine platform and the Jenolan pene- 

 plain would almost merge into one another. 



At the close of the cycle, then, the Jenolan Plain presented a 

 generally even surface removed but slightly above sea-level 

 (PL xxxix., fig. a) and diversified by gentle hills only; the coast 

 consisted of enormous gently curving beaches unbroken by 

 indentations. Sluggish rivers wandered over the plains, and 

 near their mouths were deflected from their normal consequent 

 courses by the dominant ocean current. The continental shelf 

 was of considerable width, the sea deepening oftshore for many 

 miles at an excessively slow rate. 



2. The Blue Mountain Plain (Cretaceous ?). 



The further formation of the Jenolan Plain, of which Sunny 

 Corner, the Stony Ridges, the Clear Creek Hills, Mts. Lambie, 

 Binda and Walker are to-day the insignificant remnants, was 

 interrupted b}^ a gentle tilting motion which carried the old plain 

 from sea-level on the east coast to a maximum height of 700 (?) 

 feet in the central portions (PI. xxxix., fig. b). A broad central 

 plateau was thus formed, having down-folded east and west 

 limbs. During the previous cycle, and also portion of the Blue 

 Mountain period, the centre of Australia was occupied by a 

 shallow sea, having a portion of its eastern shore in the neighbour- 

 hood of Moree, Narrabri and Dubbo. The new area thus secured 

 ma}^ have considerably advanced the land eastwards. In that 

 case it consisted essentially of a subaerial plain of denudation, 

 with a marginal plain of marine erosion, capped by off-shore 

 deposits. This capping of sediments would disappear early in 

 the cycle. The Trias-Jura sediments were also exposed some- 

 what, and subjected to subaerial denudation, although it is 

 probable they came, not into the sphere of pronounced central 

 elevation, but occupied low-pitched east and west limbs only. 



It has been suggested that the Blue ^Mountain Plain is one 

 with the Lithgow level, and that the surface is one of sedimenta- 



