74 president's address — section c. 



while elevation was in progress, extensive outbursts occurred 

 of basaltic lavas and tuffs. A slight subsidence followed, 

 succeeded by re-elevation, and then on the slowly rising 

 coastal areas eruptions took place of the newer basalts, the 

 volcanic centres progressively shifting their position south- 

 wards as the shore-line, owing to the elevation of the land, 

 gradually receded in the same direction. 



In Tasmania, during the Tertiary era eruptions of basalt 

 and basalt tuffs occurred on a large scale, as described by Mr. 

 R. M. Johnston, F.L.S.* At Breadalbane forests of conifers 

 and angiosperms are stated to have been overwhelmned by 

 the lava. 



In the neighbourhood of Launceston the felspathic basalts 

 are considered by Mr. Johnston to belong to the Older 

 Tertiary period. 



At One-Tree Point, near Hobart, traces have been dis- 

 covered of a bone breccia imbedded in the cooHng joints of a 

 partly denuded surface of an older flow of basalt, and capped 

 by a solid sheet of newer basalt. The breccia is stated to 

 contain bones and teeth belonging to marsupials of the 

 following genera : — Hypsiprymnus, Phalangista, and Phas- 

 colomys. 



The occurrence of nepheline in the Tertiary basalts of 

 Tasmania, as described by Mr. Johnston, is not yet certainly 

 established, as the author was informed by Mr. Johnston and 

 Professor G. H. F. Ulrich, of Dunedin tJniversity. 



At present the information available is insufficient to justify 

 any conclusion as to whether the volcanic outbursts in 

 Tasmania in Tertiary time were subsequent to heavy sedi- 

 mentation, or whether they took place during an elevation 

 or during a depression of the land. In the case, how- 

 ever, of the Tertiary lacustrine beds in the neighbourhood 

 of Launceston, which are capped by basalts over con- 

 siderable areas, there is evidence of subsidence having 

 taken place previous to the eruption of the basalt, to the 

 extent of, perhaps, several hundred feet. At the bore for 

 coal at Belmont, near Longford, in the centre of this basin, 

 the Tertiary beds were proved to have a thickness of at least 

 894 feet,t Tertiary fossil-wood being found down to that 

 depth. The whole of this thickness of sediment accumulated 

 before the eruption of the basalt, and, as the surface-level at 

 the Belmont bore is probably not more than 700 feet above 



* Geology of Tasmania : R. M. Johnston, F.L.S., p. 273. 

 t Loc. cit., pp. 275-276. 



