The Australian Alpine knot is just the topographic feature 

 which might be expected from tin's assumption. Thus 

 Tasmania and the associated continental shelf formed a 

 horst against which the southern forces were delivered 

 from the centre and the Alpine knot would result from the 

 interference both of the horst and of the strong suboceanic 

 forces from the Southern and South Pacific Oceans. 



In this interpretation the main forces are considered as 

 coming from the Antaivt ie and south-eastern oceanic areas 

 and the minor ones as coming from the central "negative" 

 (dense or sinking) area to form a reversed overthrust 

 towards the oceans. The influence of the Tasmanian horst 

 is seen on the Victorian highlands; the direct influence of 

 the Antarctic thrusts on the West Australian horst is seen 

 in the concave curve of south-western Australia and the 

 associated Jeffreys Deep and the heights of Arnheim Land 

 and the McDonnell Ranges appear to be arranged on the 

 eastern margin of the great Westralian horst, a horst which 

 may be seen to have formed a " positive" (buoyant) element 

 since Archean time. 



The discussion of trie outer Australasian arcs is not here 

 considered. Fig. 1 illustrates a scheme of forces which 

 appears to accord with the facts of observation. 



Great Barrier Reef and Harbours— The Great Barrier 

 Reef was initiated by the activities of the Kosciusko Period 

 which resulted in the submergence of the late Tertiary 

 shoreline. The continental shelf thus appears to represent 

 a strip flexed or faulted below sea level. In North Queens- 

 land the sulmi<Ti:ein'r doubtless was caused by faulting. 

 Coral growths attached themselves to the sinking shore- 

 line in the Queensland area and formed a great barrier 

 reef. During the more recent submergence the shore was 

 Bti]] farther depressed, and the Barrier Reef increased in 

 width and depth until it attained its present portions. The 



