288 



The glacial remains at Hallett's Cove form a small outlier of a much more 

 extensive glacial field that is in evidence further to the southward. It embraces 

 the Cape Jervis peninsula south of the Willunga Ranges, the Inman and Hind- 

 marsh Valleys, Encounter Bay, the Mount Compass and Finniss River districts, 

 southern Yorke Peninsula, and parts of Kangaroo Island. The glacial beds 

 underlie the Lower Pliocene at Hallett's Cove, and also the Miocene in southern 

 Yorke Peninsula and in Kangaroo Island ; they rest upon either the Cambrian 

 or Pre-Cambrian in all cases where their base is shown. At the time of the 

 ice-flood the present drowned valley of Gulf St. Vincent was an upland valley 

 that held the main glacial stream, into which the tributary glaciers of the Inman 

 and other valleys, situated both east and west of the main glacier, delivered their 

 quota. Or if the ice was in the form of a continuous sheet, which is probable, 

 then no such valley need to be assumed. 



That the Permo-Carboniferous glaciation extended much further to the 

 northward than Hallett's Cove is probable from the extent of the ice-polished 

 pavement at the latter place, and also from the fact that the glacier path is 

 truncated by the present sea margins. Subaerial waste that was energetic 

 through long ages, the repeated incursions of the sea during Tertiary times, as 

 well as the periods of plateau formation, rifted segments, and block favilting, in 

 later times, are sufficient to account for the wiping out of the glacial evidences 

 and their non-appearance in the more northern situations of South Australia. 



( ?) Pre-Pliocene Beds in Section B. 



Between the boulder-clay and the fossiliferous Pliocene beds at the head 

 of the amphitheatre, at Hallett's Cove, are whitish and yellowish sands, some- 

 times argillaceous, which are of doubtful age. They are of uniform composi- 

 tion and free from stones. They come in, suddenly, at the northern side of 

 the amphitheatre, immediately underlying the Pliocene bed, which, latter, thins 

 out to the southward and its place is taken by the underlying sand bed which 

 becomes a conspicuous feature in the white, conical hill known as the "Sugar- 

 loaf." In the latter, it rests with a sharp division on the highly-coloured, reddish- 

 purple boulder clay. The two colours, in juxtaposition, make a very striking 

 contrast. The hill is capped by an outlying fragment of the Pleistocene mottled 

 clays. The white bed continues to show in the cliffs to the southward and is 

 also exposed in the uneven ground in front of the cliffs. 



In the deepest gutter cut by the rains within the limits of the Cove (a little 

 to the northward of the "Sugar-loaf") a section of the white bed is exposed 

 up to a thickness of about 60 feet. This bed in its upper portion is soft and 

 friable, but becomes more indurated at depth. In the thick section, just men- 

 tioned, it maintains a very uniform character, but towards the lower levels there 

 are thin streaks of the dark-red clay and, at the lowest level exposed, it is seen 

 to rest on the reddish-purple boulder clay that forms the base of the "Sugar- 

 loaf." The induration of the bed in its lower portion is not uniform, but shows 

 certain layers in relief, and, in common with the underlying boulder clay, dips 

 to the north-north-east at a low angle. 



The origin of this very considerable bed, sandwiched betweeen the glacial 

 till and the Lower Pliocene, is not very clear. The question is complicated by 

 the occurrence of a white sand bed that occupies a similar stratigraphical 

 relationship to the Lower Pliocene in other localities, further to the south, that 

 are in closer proximity to the freshwater beds that underlie the Miocene. So 

 far as the Hallett's Cove section is concerned the weight of the evidence seems 

 to point to its having some relation to the glacial conditions. It may have been 

 deposited during a late fluvio-glacial stage in the building up of the sediments ; 

 or, even later, by running water, acting on the glacial deposits by gentle currents. 



