58 



of the Willunga scarp, as, for example, at Willunga and 

 Clarendon. It is therefore highly probable that the great 

 1902 earthquake was caused by a settlement along the north 

 and south trough-fault accompanied by sympathetic move- 

 ments along the tangential fissures. 



With the time data roughly diagnosed, it is instructive 

 to note the amount of denudation that has taken place in 

 the interval. The present coastline along the gulf is exceed- 

 ingly modern. Since the great earth movements above 

 described the sea has retreated from the gulfs and left them 

 dry and returned again — probably, more than once. At the 

 present time the coast, near Sellick's Hill, is in rapid retreat 

 before the advancing waves. There is a broad plain of 

 marine denudation on the shore which tells of recent loss of 

 land. All the exposed rocks in the cliffs — Cambrian slates, 

 Eocene limestones, and Pliocene clays — are easily operated 

 upon by the waves and as easily removed by the under- 

 tow. The encroachments on the land would be still more 

 rapid were it not for the wide floor of truncated limestones, 

 standing up on the beach in successive ridges, which break 

 much of the force of the waves before they reach the base 

 of the cliffs, but it cannot be long before this interesting 

 section will be entirely wiped out. 



A better gauge of the time that has elapsed, since the 

 uplift, may be found in a study of the amount of waste 

 that has occurred along the line of scarp. The Willunga 

 Ranges are deeply scored by running water, and, in their 

 varied sculpture, present a picturesque view from the opposite 

 sides of the valley ; but all the streams that drain the 

 northern face of the ranges are in a very juvenile stage of 

 development; they are all consequent streams, none are 

 sufficiently advanced to pirate their neighbours, and in no 

 instance has a stream intersected its watershed. The same 

 immature condition of stream development occurs on the 

 plateau and in the glacial districts of Mount Compass and 

 Nangkita, as noted in a paper that I have recently had the 

 honour of reading before this Society. < 3 ) 



The measure of denudation accomplished on the Wil- 

 lunga uplift, within a recognized period, may be used as a 

 standard of comparison with other uplifts, in other parts of 

 the State, by which we may infer their synchronism or rela- 

 tive age with respect to the Willunga movements. It is not 

 likely that these movements were strictly local, but rather 

 one phase of a complex and regional disturbance, in which, 



(3) Description of a New and Extensive Area of Permo- 

 Carboniferous Glacial Deposits in South Australia. Trans. Roy. 

 -Soc, S.A., vol. xxxiv., 1910, p. 234. 



