138 NOTES ON THE GEOLOGY OF LAKE ST. CLAIR. 
Lack oF PALZONTOLOGICAL EVIDENCE AS TO THE AGE OF 
THE Coat Hitt Coat MEAsurRES AND ASSOCIATED 
SANDSTONES. 
There is, however, another matter of great local importance 
which Mr. Officer’s paper reminds us of, viz., the doubtful 
age of the coal measutes which we know exist at Coal Hill, 
and the lack of knowledge regarding the positive existence 
of Lower and Upper Mesozoic formations succeeding the 
Permo-Carboniferous mudstones, of which we have here and 
elsewhere along the crests of the Great Plateau the most 
abundant evidence. Had Mr. Officer been more perfectly 
acquainted with our local wants in this respect (see “ Geol. of 
Tas.” p. 164), Iam sure his labours and observations would 
have been more profitable to science, as well as of more lasting 
satisfaction to himself. Let us hope that he may yet be 
encouraged to return to this interesting out-of-the-common 
track region, and direct his observations rather to fill up the 
blanks in our knowledge regarding the doubtful age of the 
Coal Hill coal measures, and also help us in discovering 
positive evidence (stratigraphical and paleontological) of the 
presence, or otherwise, with boundaries, of the rocks of 
Mesozoic Age of both upper and lower horizons, which are so 
familiar to us in similar situations in the more eastern 
elevated greenstone plateaux. Without paleontological 
evidence we can proceed no further at present, and it is 
unfortunate in this respect that Mr. Officer’s observations 
afford no light whatever.* As regards certain new aspects of 
portions of the greenstone plateau, my own observations 
during the last four or five years have again independently 
disposed me to regard with more favour the possible later or 
Post-Mesozoic age of the greenstones of the Great Plateau 
and elsewhere. My difficulty still exists as regards the 
apparent older greenstones lying between Blackman’s Bay 
and Adventure Bay. But I take this opportunity of 
acknowledging that my continued failure to detect the 
remains of undoubted greenstone rocks among the abundant 
erratics and derived conglomeratesjin our mudstones, together 
with the undoubted similarity of character of supposed older 
and later greenstones, have for the last year or two weighed 
strongly in my mind in favour of the later age of all our typical 
diabasic greenstone rocks, and I should not now be surprised 
in the least if reasons should soon be forthcoming which 
*It would be interesting to learn how Mr. Officer arrived at the knowledge that 
the whole of the Sandstones mapped by him as Carboniferous are really so. He 
does not support this conclusion by a single reference to the characteristic fossils, 
by which means alone can such a conclusion be accurately arrived at; for the 
Sandstones of Permo-Carboniferous Age and Lower Mesozoic Age in Tasmania are 
so sulla in lithological characters, that references so hazarded are pure guess- 
work, 
