164 A Physical Description 



the plant impressions to be those of existing species. The 

 formation is probably a pliocene one, and the rolled pebbles 

 above suggest a drift like that in which the alluvial deposits 

 of gold are found in Victoria. The lignite is, however, not 

 usual. 



Other plant beds of tertiary age have been ably described 

 by Mr. R. M. Johnston. In the immediate vicinity of 

 Launceston and scattered over the westward plains there are 

 accumulations of water-worn gravel, one to three feet thick, 

 arranged in horizontal layers, and associated with clays and 

 tufa more or less laminated. The most extensively exposed 

 bed is on a railway cutting between Perth and Longford. 

 This is on a tableland about 115 feet above the present 

 channel of the South Esk, at Longford, and 630 feet above 

 the level of the sea. These beds are principally composed of 

 siliceous pebbles and gritty concretions, all more or less 

 water worn and cemented together. Opalized wood is 

 scattered throughout the whole of the gravelly accumula- 

 tions. With them are also associated pebbles of limestone, 

 derived from the carboniferous beds, and containing casts 

 of fossils characteristic of that formation. In the laminated 

 clays are found beds of lignite intercalated with beds of fine 

 blue clay, containing remains of water plants, fragments of 

 branches, twigs, and leaves, and occasional TJnio shells. In 

 a cutting beyond Breadalbane a section of tufaceous rock 

 is exposed, in which there are numerous fragments of 

 branches and trunks of trees disposed horizontally. These 

 are principally composed of lime. 



Mr. Johnston divides all the beds into the upper, middle, 

 and lower, which he thus characterises : — Lower beds : 

 Composed of series of beds of blue and white clays, 

 occasionally inter-laminated with thin bands of tenacious 

 clay, containing leaves, for the most part exogenous, and a 

 considerable portion coniferous. Myrtaceous forms do not 

 seem to predominate, but there are leaves very similar to 

 our finely pinnate acacias. In an exposed cliff section on 

 the North Esk, Mr. Johnston states that he found fragments 

 of Banksia and Eucalyptus, which, of course, would 

 approximate the deposits to the living flora. The middle 

 beds are chiefly composed of beds of clay and sand, with 

 leaf impressions. The upper beds are represented by the 

 low rounded hills and terraces flanking the present course of 

 the River Tamar. They are composed of alternate beds of 

 conglomerates, breccias, and gravels, and the detritus of the 



