114 



from Wcarrenben and N. of Royston Head, gneiss appears ; this 

 is intruded by granite-veins carrying wolfram. The base of 

 West Cape, Reef Head, Cape Spencer, south side of Rhino Head, 

 and the coast-line between Hillock Point and Point Yorke is 

 composed of metamorphic rock, more or less granitoid. 



In all the above exposures, and these are all that are known 

 on the coast, "^ the archfiean rocks do not in any instance rise to 

 more than about 20 feet above sea-level, though the Pleistocene 

 sands are piled up upon them to heights up to 200 feet or so. 

 Archiean rocks were brought to view in a well-sinking about 

 three miles inland from Point Souttar, and apparently at not 

 much above sea-level. 



IV. General Remarks. 



The Great Salt-Marsh is a deserted sea-way, whether by the 

 formation of the barriers of blown-sand at its seaward boundaries, 

 or by a moderate elevation, I cannot decide without accurate 

 levelling, and the same uncertainty applies to the other low-level 

 tracts in Southern Yorke-Peninsula ; though it is more probable 

 that some slight elevation of the land has taken place, so as to be 

 in accord with the evidences of accurate levels taken on other 

 parts of the South Australian coast-line. The whole country is 

 devoid of water-courses, and everywhere the land rises abruptly 

 from the shore. 



The islets in Pondalowie Bay and those off Cape Spencer, and 

 the Althorpes, are wholly or nearly so made of tabular masses of 

 Pleistocene sandstones, from which it may be inferred that they 

 are remnants of a more extended coast-line. 



Wedge Island and the others of the Gambler Group, as also 

 many off the Port Lincoln coast, are of the same nature ; which 

 leaves no choice but to regard them either as parts of a former 

 land-connection between Southern Yorke-Peninsula and Eyre- 

 Peninsula and perhaps Kangaroo Island, or that they are rem- 

 nants of larger insular masses. 



In pre-pleistocene times, the majority at least of the Archaean 

 outcrops were submerged reefs or low islets constituting an archi- 

 pelago of very considerable area. This condition must have 

 been followed by elevation sufficiently great to form a beach-line 

 commensurate with the amount of the present degraded material, 

 the whole then became fused together by sand-drifts and a junc- 

 tion with Yorke-Peninsula was effected. To-dav erosion has 



* The Government Geologist, in liis Geological Map of South Australia, 

 1886, shows a continuous outcrop of igneous rock from Corney Point to 

 Point Yorke — this exaggeration may have been necessitated ])y the small 

 scale of the map ; the rest of the area under consideration is uniformly 

 coloured to represent Tertiary. 



