BY R. M. JOHNSTON, F.L.S. 201 



are also abundant in the older terraces of the stanniferous 

 region in the vicinity of Gladstone, Moorina, and Ringa- 

 rooma. 



Similar deposits exist in Victoria and New South Wales, 

 and the same difficulties in respect of classification are 

 there also experienced. The descriptions of local geologists 

 in Victoria and New South Wales in respect of these 

 Australian deposits are quite applicable to Tasmania. For 

 example, if we take the graphic description of the Neogene 

 rocks of New South Wales, so ably given by the Head of 

 the Geological Department, Mr, G. S. Wilkinson, we may 

 see that the relationship and character of the rocks and 

 the difficulties of classification are very similar. At page 

 67 of the publication issued by the Mines Department 

 (1882. — Notes on the Geology of New South Wales), Mr. 

 Wilkinson writes : — 



" Now the remains of old river beds do actually occur 

 upon these high lands (above the 800 feet level), but as 

 no fossils have been found in them, it is doubtful whether 

 they belong to the Miocene or Pliocene periods. Without 

 the aid of fossils or of natural sections showing the relation 

 of these deposits to older or newer formations, there will 

 always be a difficulty in determining their age. In fact 

 it will almost be impossible to draw a hard and fast line 

 between them, as the subaerial conditions of the Miocene 

 period continued into the Pliocene ; for, during the 

 Upper Miocene, Pliocene, and Pleistocene periods the 

 land appears to have been gradually rising, and, of course, 

 subject to continued atmospheric denudation, which varied 

 occasionally in intensity. During this long period the 

 valleys were gradually eroded, though at intervals they 

 were partly filled with fiuviatile deposits and flows of lava, 

 and then eroded to deeper levels. Thus in every large 

 valley, as that in which the Macquarie drains, we find at 

 different elevations terraces of gravel and alluvium which 

 mark the successive levels of the valleys during the in- 

 tervals when the denuding agencies were not sufficiently 

 powerful to prevent the accumulation of such deposits. 

 The more ancient of these fiuviatile drifts are sometimes 

 covered with basalt, showing that these old valleys, during 

 their erosion, were at different times modified by the 

 flowing into them of lava through which the drainage 

 water either cut a fresh channel or was diverted, and 



