48 



Northern Hemisphere, and these are overlain by a newer 

 marine series, which the gentlemen mentioned referred to 

 the Miocene. <J ' 



Notwithstanding the considerable age of these deposits 

 and the oscillations of level to which they have been sub- 

 jected, they have, for the most part, preserved an almost 

 horizontal position. The inclination is usually inappreciable, 

 or where it occurs amounts to an angle of less than 5°, 

 giving evidence of a remarkable stability in the earth's crust 

 throughout wide areas in Australia, dating from remote 

 times. There is, however, in this State, one very interesting 

 exception to this rule, which is made the subject of the 

 present paper. 



In 1899, Mr. E. V. Clark, B.Sc, a graduate of the 

 Adelaide University, in some "Notes on the Cliffs separating 

 Aldinga and Myponga Bays," published in the Transactions 

 of the Royal Society of South Australia (vol. xxiv., p. 1), 

 drew attention to the disturbed area now under description. 

 He says, ''Three hundred yards further on Eocene again 

 appears overlying the Cambrian. It is here, however, much 

 inclined, dipping to the north-north-west at an angle of 50° 

 at first, increasing to 65°, and finally diminishing to 45°. It 

 extends seawards for a short distance as a reef, but owing to 

 the high dip it is of no great breadth. Due, however, 

 also to the great inclination, it is extremely regular, and for 

 150 yards or so where the cliffs take a bend and run approxi- 

 mately parallel to the direction of the strike (west-south-west) 

 it consists of a series of ridges, parallel to each other and to 

 the shore. One ridge in particular, though only 2 ft. wide, 

 is so uniform that it was keeping the sea inside at a height 

 of 15 in. to 18 in. higher than outside. In this the reef is 

 very different from that at the small patch of Eocene rocks 

 to the north, and to the reefs south of the Port Willunga 

 Jetty and at Blanche Point. In these cases, where the dip 

 of the rocks is low, the reef either presents a fairly level sur- 

 face or, if the rock is not quite uniform, a labyrinthine out- 

 crop, the projecting lines of greatest resistance to wear turn- 

 ing and twisting about extremely irregularly, as is so well 

 seen in the Miocene reef at Schnapper Point, south of Port 

 Willunga Jetty." 



<i) More recent investigations, in which the fauna living in 

 Australian waters have become better known by means of sea- 

 dredging, have reduced the number of supposed extinct species, 

 and it is possible that the question of the age of the Australian 

 marine Cainozoic beds may have to be. reconsidered, but tor con- 

 venience the terms adopted by the late Professor Tate and Mr. 

 Dennant have been used in this paper. 



