28; 



The interval between these headlands has been excavated to an unknown depth 

 and filled up with morainic material to a height of 100 feet above sea level, 

 with overlaps on the Cambrian rocks at either side of the Cove. This morainic 

 material, together with more recent deposits overlying it, has yielded more 

 readily to atmospheric waste than the harder Cambrian rocks of the locality, 

 giving rise to a retreat of the cliffs and much broken ground within the area, 

 and has exposed some very large erratics. Near the head of the Cove there 

 are two large cuboidal erratics, belonging to the siliceous limestones of the 

 Tapley's Hill Series, situated close together, and, unitedly, measure 9 feet in 

 length. 



In the lower positions, within the Cove, the ground moraine, or till, is the 

 leading feature ; and, at the higher levels, in addition to the boulder clay, there 

 are fluvio-glacial deposits in the form of fine-grained mud, sands, and gravels. 

 The latter features are well developed on the sea face, towards the southern side 

 of the Cove before reaching the Field River. Many of the stones in these beds 

 are well scratched. So far as observed, the polished floor is limited to the 

 cliffs on the northern side of the Cove. The Cove ends on the southern side 

 with a thick body of boulder clay banked up against the Cambrian purple slates. 



Some very large erratics occur on the beach, where they are more or less 

 either obscured, or exposed, by the varying amount of sand left by the waves. 

 Towards the Field River, and between tides, there are about half a dozen large 

 erratics gathered from the Cambrian (or ( ?) Proterozoic) tillite which are 

 grouped together ; and on the beach, to the southward of the Field River, is the 

 largest granite erratic of the vicinity, measuring 8 feet in length, of the Victor 

 Harbour type, and is surrounded by a great field of erratics, of many kinds, 

 and some of exceptional size. 



The erratics contained in the till at Hallett's Cove give us some clue to the 

 respective routes by which the ice travelled to the Cove. Among the travelled 

 stones are numerous porphyritic granites from Victor Harbour district, which 

 probably came by the Inman Valley, and, passing over the water parting of the 

 Bald Hills, united with the main glacier near the site of Normanville. The 

 fine-grained schists that form the lower cliffs of Cape Jervis are also well repre- 

 sented, and many of them are strongly glaciated. Rocks that outcrop nearer to 

 Hallett's Cove — the impure siliceous limestone and the older moraines of the 

 (?) Cambrian tillite, that occur between the Field River and the Onkaparinga — 

 have been quarried out and transported by the ice-plough and form some of 

 the largest of the erratics both on the beach and within the limits of the Cove. 

 Some of the boulder clay, near the head of the Cove, is of a deep purple colour, 

 having been ploughed up from the outcrops of the purple slates in the immediate 

 neighbourhood — no more definite proof of the nature of the glaciation, as land 

 ice, could possibly occur than these examples of local erosion. The Victor 

 Harbour granite and the Cape Jervis schists that were delivered at Hallett's Cove 

 indicate glaciers of not less than 50 miles in length. 



The evidences of glacial action do not extend far beyond the southern limits 

 of the Cove. Some particularly large erratics of the impure limestones that 

 underlie the Brighton limestones occur on the beach, to the southward of the 

 Field River, some of which are speckled with veins of calcite, and what is 

 probably the largest erratic of the locality, also belonging to the impure limestone 

 series, occupies a conspicuous position on the edge of the sea-cliff, about half 

 a mile to the southward of the Cove. Its present position is suggestive of a 

 "perched block," but when this great erratic was stranded on the retreat of the 

 ice, the cliff in its present form, of course, did not exist. Near to this large 

 erratic the glacial evidences of the neighbourhood appear to end. 



