63 



]^OTES ON THE GEOLOGICAL STEUCTURE OF THE 

 NOETH-EAST COAST OF TASMANLi. 



Dear Sir, — I forward a few notes on the Geological 

 structure of the North East Coast, they are briefer than I had 

 intended, as in consequence of my having been so fully 

 occupied with my visit to the Fingal district, I have been 

 unable to attend to other matters, — I regret that I cannot as 

 yet lay before the Society my completed Geological map of 

 the district, this I hope to do at the next meeting, and in the 

 meanwhile shall confine myself to a few points which do not 

 necessitate illustration. 



At several meetings of the Society attention has been 

 directed to the controversy maintained among Geologists as 

 to the age of Austrahan coal, — and it will doubtless be 

 within the recollection of the members that I expressed my 

 opinion as to the coal in Tasmania belonging to two distinct 

 periods, assigning a later date to the age of Fingal, and 

 Douglas Eiver coal than to that of the Mersey, — a subor- 

 dinate point in the argument, was the relative age of the Coal 

 and the Greenstone, — and on this point 1 expressed an opinion 

 different from that of other Geologists. 



My own impression being thut the Coal formation was of 

 anterior origin to the Greenstone, and had been penetrated by 

 the latter, subsequent to its formation, — this opinion was 

 supported by the faulted nature of the formation, its general 

 distarbance near the Greenstone, and the mode of occurrence 

 of the latter in several instances in small isolated masses on 

 the very summit of some of the loftier ranges of the uj)per 

 Palaeozoic formation, the other view was that the Greenstone 

 was the older rock, and had formed a bold and rugged Coast 

 outline, jutting out into points and promontories affording 

 protection to bays and estuaries, within which the coal had 

 been accumulated. 



I am glad now to be able to furnish evidence corroborative 

 of my own view, and enclose a sketch of a Coast Section 

 exhibited near the mouth of the Tomahawk Eiver, upon the 

 North East Coast. Li this interesting locality we find in close 

 proximity no less than four formations, viz., Granite, Green- 

 stone, — an old Palaeozoic formation, and what I take to bo 

 Carboniferous or later Palaeozoic Sandstones. 



The granite is of a kind very common upon the coast — por- 

 phyritic in structure, and exhibiting large and distinct crystals 

 of pink and white felspar. 



It is traversed by porphjrry elvans. Near the junction 

 with the Greenstone these belong to two periods, in the sketch 

 appended, the direction of one of the elvans is from S. 55 W., 



