54 



It is certain that the folding of the Cainozoic rocks was- 

 caused by earth movements on a large scale in which the 

 Willunga Ranges, as a whole, participated. These ranges 

 form the scarp-face (plate xi.) of an extensive upland 

 plateau that takes in most of the country to the southward. 

 The geological strike runs parallel with this scarp, in a north- 

 east and south-west direction, until it nears the coast, where 

 it turns more to the south and follows the general trend of 

 the coastline. This change in the strike can be seen even at 

 a distance, where the serrated outcrops of Cambrian limestone 

 pass over a round hill, known as Sugarloaf Hill, on the north 

 side of Boundary Creek. At a later stage in our enquiries 

 we shall find that this change of strike is an important 

 consideration in interpreting the geological facts — the strike 

 of the country instead of maintaining a straight course is 

 along two distinct lines, which, in their intersection form an 

 obtuse angle. 



Another point, which proves that the Willunga Range 

 movement formed a distinct tectonic unit, can be gathered 

 'from the sudden change that takes place in the dip of the 

 Eocene beds as they come into line with these ranges. At 

 Port Willunga, and for some miles to the south, the Eocene 

 limestones have a normal dip, and, even just in front of the 

 great Willunga scarp, they only roll to an extreme inclination 

 of 15°, but immediately they form a junction with the Cam- 

 brian of the Willunga Ranges they are thrown into a very 

 high angle of dip, which is suggestive that this high dip has 

 been occasioned by the elevation of the ranges, in which move- 

 ment the Cainozoic beds participated. 



In a study of the Cambrian beds which abut upon the 

 coast we find a confirmation of this view. In the cliffs facing 

 the sea, and for some distance back, the Cambrian slates are 

 greatly disturbed. They are intimately fractured in all 

 directions, rendering it most difficult to determine the true 

 dip. In the Boundary Creek, at about half a mile from its 

 outlet, the beds dip westerly at 48°. A ridge of hard purple 

 slates, between tides, situated near Waterfall Gully (No. 2), 

 shows a dip north-west at 70°. At the point of junction 

 between the Cambrian and Cainozoic beds, each of these 

 appear to have a dip of 80° westerly. This is probably a 

 false dip, so far as the Cambrian beds are concerned, for 

 there was certainly an initial unconformity of strata between 

 the latter and the newer series, and the apparent dip undoubt- 

 edly arises from master-joints, slides, and shear-cleavage that 

 have been induced by the earth-strains. These slides are 

 parallel to the coast, they conform to the high dip of the 

 Eocenes, and, as planes of weakness, give rise to frequent 



