170 THE BUILDING OF EASTERN AUSTRALIA 



But this fold is of such a gentle nature, and the dips 

 produced so slight, that the movement may be more aptly 

 described as Andrews has done as plateau uplift 

 [Andrews, I]. 



No superheated magmas have yet worked their way 

 up in these sediments and caused expansion and intense 

 folding, but very late Tertiary faults have produced 

 Senkungsfeldt areas (as described by Sussmilch, 11], some 

 of which may, perhaps, in a future period, become so 

 squeezed as to be intensely folded. Up to the present, 

 the uplift has affected the superficial strata only so far 

 as to produce in them faults and great masterjoints. As 

 shown by Sussmilch (op cit) and T. G. Taylor [21], the 

 direction of the rivers of Southern N.S.W. is induced by 

 these faults, while in the present writer's opinion, the great 

 canons which dissect the Southern coastg,l tablelands and 

 Blue Mountains of N.S.W. follow principally great joint 

 cracks of the sandstones. These joint cracks, as seen by 

 the writer at Ettrema Canon, often coincide in position 

 with Palseozoic faults, and may owe their origin to slight 

 displacements along these old fault lines. Joints and 

 faults in a homogeneous formation constitute the lines of 

 weakness, along which streams are able to work down and 

 dissect a plateau. 



Folding of a compressive nature in an area like that 

 of the Blue Mountains of N.S.W., is very deepseated, and, 

 in the writer's opinion, pressure is exerted in the deeper 

 portions of the earth's crust from the sea, towards the land, 

 from the great subsiding basin of the Tasman Sea towards 

 the Continent. In this respect, the writer agrees with 

 Hedley, and disagrees with Andrews, who believes that 

 the continent exerts a pressure in the direction of the 

 ocean. The contour of the east coast of Australia would 

 seem to lend colour to Andrews' hypothesis, but, as 

 pointed out by Hedley, in an interesting discussion, the 

 apparent convex curve of the East Australian coast becomes 

 two concave curves if we analyse the soundings in the 

 adjoining Pacific Ocean, for a bar of shallow water runs 

 from Point Danger eastwards in the direction of Fiji. 



The deepseated landward pressure in itself largely 

 accounts for the buoying-up of the Continent. 



