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Bistrihutioii of Alliovial Gold. — The chief source of alluvial 

 gold iu South Australia is that of the high-level gravels 

 belouging to the later part of the Miocene epoch, which, from 

 the circumstance of their occurrence at considerable elevations 

 above the upper limits of the marine beds of Miocene age, we 

 have called " Upland Miocene." The best-known examples of 

 these gold drifts are those of Echunga and Barossa. Where 

 are the veins which supplied the gold of these drifts ? In 

 respect to the former area, some at least are known, but as 

 regards the latter, either they have been almost wholly removed, 

 or a large supply of gold has been derived from the denudation 

 of the inter-laminations of quartz which so frequently occur in 

 the micaceous schists of this area. If the drift-gold of Barossa 

 has been derived from the waste of known reefs, then must it 

 have been from a northern extension of the Lady Alice or from 

 those reefs immediately to the east of it ; but in nowise could 

 the drift deposits known as Barossa proper be derived from the 

 Malcolm's Barossa Reef, the position of which is incompatible 

 with such hypothesis. 



In the search for the sources of alluvial gold the geologist 

 comes to the aid of the gold prospector. He determines the 

 nature of the materials composing the drift, traces it to its 

 source, and maps out the hydrographical basin within which the 

 drift has been accumulated. In other words, he determines 

 the direction of the aqueous currents which brought the drift 

 and its gold. Locating in this way the source of the material, 

 the miner can concentrate his search over an area that was 

 formerly, if not now, veined with auriferous lodes, not neces- 

 sarily of restricted limits, probably otherwise, but nevertheless 

 deiinable. 



The Pliocene loams of our plains and the deeper-seated 

 gravel of the same epoch have not yielded gold ; but I am not 

 aware if any systematised prospecting has been conducted in 

 them. If gold had been removed from its rocky fastnesses by 

 pluvial action in Miocene times, why not, then, during the 

 2:)eriod of accumulation of the Pliocene drifts ? Theory 

 answers, " Perhaps more so." But the wide dispersal of the 

 sediments and of the inaccessibility of those portions most 

 likely to contain gold are serious obstacles to the successful 

 exploitation of these deposits for it. 



An example of a more modern gold drift is that of Biggs's 

 Plat, on the River Onkaparinga. Whether its gold be gathered 

 from the wreck of Miocene gold drifts or directly from aurifer- 

 ous veins in the immediate neighbourhood it is somewhat 

 difficult to answer, though I incline to the latter opinion. 

 Suffice it to say, however, that the period of accumulation of 

 the drift is comparatively of so recent date that it may be said 

 to be in course of formation. 



