VO GEOLOGY OF TASMANIA. 



material, which never succeeded in reaching the surface, or 

 if it did, its superficial, subaerial portion has been removed 

 by denudation. The masses now visible, as at Mount Wel- 

 lington, and crowning the Tiers, may be looked upon as huge 

 laccolites and sills. Up to the present, no evidences of lava 

 flow have been found in the structure of this rock. It is 

 devoid of ore-deposits. 



Tertiary. 



A great stratigraphic break exists between the Mesozoic 

 and the succeeding strata. The Tertiary system cannot be 

 subdivided as in Europe. Mr. R. M. Johnston has pro- 

 posed the two divisions, palaeogene and neogene, which are 

 here adopted. According to this arrangement, the Ter- 

 tiaries will be subdivided, as follows : — 



Neogene ( = approximately to pliocene)-^ 



4. Glacier moraines of the Western highlands. 

 River terraces and estuarine deposits. 



Paleogene ( = Eocene to miocene) — 



3. Basalt lavas. 



2. Fluviatile and lacustrine clays and sands, tin-ore 



drifts and leads. 

 1. Fossiliferous marine beds at Table Cape (= Eocene). 



1. The researches of J. Dennant and the late Professor 

 Ralph Tate have shown the marine fossiliferous beds at 

 Table Cape to be of Eocene age. These strata are covered 

 with the basalt, which, in the Island, appears to separate 

 the lower from the upper Tertiaries. 



2. The extensive lacustrine deposits within the watershed, 

 of the Tamar and its tributaries were described long ago by 

 Mr. Johnston, under the apt title of sediments of the Laun- 

 ceston Tertiary basin. They cover an area of 600 square 

 miles, and embrace the pre-basaltic or palaeogene clays and 

 sands, which are spread all over that part of the Island, as 

 well as the post-basaltic, or neogene, valley terraces. The 

 thickness of these beds is from 900 to 1000 feet. 



At Launceston, the ferruginous sands and clays of the 

 Windmill Hill are palaeogene. They contain fossil impres- 

 ■ sions of the plant genera, Betula, Fagtis, Quercus, Giiinamo- 

 nmm, Banksia. At Dilston, Windermere, and Muddy 

 Creek similar beds occur. At Carr Villa, the boring-core 

 showed an impression of Betula at a depth of 500 feet. A 

 bore at Belmont went down in the palaeogene sandstones and 



