250 STRATIGRAPHY 



85° S. by Mr. J. C. H. Mingaye, F.C.S., Government Analyst and Assayer to the 

 Department of Mines, New South Wales : — 



The fact that the coal is slightly hydrous is suggestive of its bemg not older 

 than Newer Palgeozoic. In Australia it is exceptional to find coal seams as old 

 as the Permo-Carboniferous j^eriod containing more than about 1 per cent, of 

 hygroscopic moi.sture. The chemical composition of the coal therefore suggests an 

 age not older than Late Paleozoic. On the other hand, the degree of induration 

 of this unfaulted plateau sandstone suggests a fahly high geological antiquity. 

 H. T. Ferrar has shown on one of his sections that Beacon Sandstones are intruded 

 by the pink granites, a statement which we had not an opportunity of confirming. 

 In this case the induration may be explained as simply the result of contact 

 metamorphism. There can be no doubt w^iatever that it has been very strongly 

 and extensively intruded by vast sills of quartz-dolerite. This of course will have 

 produced a great deal of quartzite as the result of contact metamorphism. Similar 

 contact metamorphism has been recorded in the case of the Permo-Carboniferous 

 and Trias-Jura rocks of Tasmania, where they too have been invaded by immense 

 sills of quartz-dolerite. Indeed so like is the general appearance of much of the 

 south-east coast of Tasmania to that of the jalateau sandstone regions of Ross Sea, 

 than an observer familiar with Tasmanian geology would at once be inclined to 

 correlate the Beacon Sandstone formation with the Trias-Jura of Tasmania, and in 

 the light of the most recent evidence such a correlation would not appear unreason- 

 able. We think, therefore, that our original suggestion that the Beacon Sandstone 

 formation may be of Gondwana Age may be provisionally accepted. Certainly a 

 considerable induration of the rocks, in view of their comparatively undisturbed 

 state, suggests an age for them wholly ante-dating the Tertiary and probably 

 ante-dating the Cretaceous as well. It is of course possible that the actual coal- 

 bearing formation which lies near the top of the Beacon Sandstone may be of 

 distinctly newer age than the Beacon Sandstone proper underlying it, but as far 

 as we were able to observe the whole series is perfectly conformable, and therefore 

 to be referred probably to one and the same system.* 



■*■ It has been proved recently by Taylor and Debenham's discoveries on the last Scott Expedition that 

 at Granite Harbour, at all events, the lower part of the gi-eat sandstone formation is of Devonian Age, 

 as argued by Dr. A. S. Woodward on the evidence of fossil fish plates collected by the above geologists. 



