56 



most elevated, outlier of the Eocene beds in South Australia, 

 occurs as a small patch on the Hindmarsh Tiers, near the 

 middle of this elevated plateau (see inset map, plate x.). 

 It is exposed in the head waters of the Hindmarsh River, 

 near Mr. Maslin's, and ten miles distant, in a straight line,, 

 south-east from the outcrop on the coast. The beds are under 

 alluvial cover and only seen in creek sections, so that their 

 lateral extent is uncertain. The stone is highly fossiliferous, 

 of a pinkish colour, and consists of a very pure limestone with 

 secondary deposition of calcium carbonate in the interspaces. 

 The old furnace, used for smelting the iron ore from Mount 

 Cone, is in close proximity to the outcrop and the Eocene 

 limestone was used as a flux in the process. The height which 

 these beds occupy above sea-level is probably between 900 ft. 

 and 1,000 ft. The height of Mount Cone, not quite three 

 miles distant, is given, officially, as 1,380 ft. The Eocene 

 beds, in other places, rarely exceed the 200-ft. limit of alti- 

 tude, so that this outlier on the Hindmarsh plateau is several 

 hundreds of feet higher than any other outcrop of these rocks 

 known in South Australia, and it therefore supplies an 

 indirect proof that the Willunga segment has undergone an 

 uplift relatively to the surrounding areas. This interesting 

 •outlier also clearly indicates a former extension of the lower 

 Cainozoic marine series over the area of what, at present, 

 forms the Hindmarsh Tiers plateau, and was, probably, 

 originally conterminous with beds of the same age on the 

 Murray Plains, as well as those on the west in the neigh- 

 bourhood of the gulfs. Of this great upland sheet of marine 

 limestones this little outlier has alone survived to tell the 

 tale. 



Geological Age of the Earth Movements. 

 The geological age of these earth movements can be 

 •defined within certain limits. They were certainly post 

 Eocene, as the beds of this age have been profoundly 

 affected by the tectonic movements. The relationship 

 they bear to the Miocene is not so clear. The Mio- 

 cene beds usually rest directly on the Eocene — sometimes with 

 a slight stratigraphical unconformity. This is the case at 

 Port Willunga. At Sellick's Hill, however, only the basal 

 beds of the Eocene occur in the cliffs, while the higher strata, 

 at a high dip, pass seawards and disappear below sea- level. 

 If the Miocene beds occupied the same position in relation 

 to the Eocene at Sellick's Hill that they do on the coast 

 further north, they have been placed beyond the range of 

 observation. This is unfortunate, as it leaves the question 

 of the relationship which these great crust movements bore to 

 Miocene times, undefined. It is possible that the movements 



