BY FPvITZ NOETLING, M.A., PH.D. 109 



1913. 



basaltic leaf beds belong to the Palseogene, and as lie con- 

 siders the fossil if erous beds of Table Cape to be of Eocene 

 age, we mu&t infer that he attributes the same age to the 

 leaf bed series of the Deinvent valley. Under these cir- 

 cumstances the erosion of the old Derwent valley in which 

 the leaf bed series was deposited must have taken place 

 in Pre-Eocene times; in other words, it would date back 

 as far as the Cretaceous period. 



More recent researches, particularly of Victorian 

 geologists, have conclusively proved that Tate's views as to 

 the Eocene age of the Australian Tertiary Beds are no 

 longer tenable. All the Tertiaries of Australia are much 

 younger ; in fact, it appears very doubtful whether the 

 Eocene is represented at all in Australia. It is more than 

 probable that the Table Cape beds are of much younger 

 age than hitherto assumed, and consequently the leaf beds 

 of the Derwent are much younger than Eocene. If my 

 views are correct, they cannot be older than Pleistocene, 

 and we need not assume a Pre-Eocene erosion of the 

 Derwent valley if, as I believe, the leaf bed series were at 

 the time of their deposition in a much higher level than 

 they are now, and only came to their present position by 

 a downward movement which immediately preceded the 

 eruption of the Basalt. 



The Post-Pleistocene period represents, therefore, the 

 time during which the leaf bed series were raised from the 

 water, and it is probable that eruption of the Basalt took 

 place during the same period, though it is by no naeans im- 

 probable that the latter is somewhat younger- The 

 period following the eruption of the Basalt was a time of 

 extensive denudation which destroyed an enormous portion 

 of the Basalt ccne and a large portion of the leaf beds. 

 During the same period the Derwent valley was scooped 

 out. As the sea level was theii at its lowest, or nearly its 

 lowest, this stage must represent the time when Tasmania 

 was connected with the mainland of Australia. Towards 

 the end of the Pleistocene, long after the glaciers had dis- 

 appeared, a gradual rise of the sea level commenced, but 

 previous to final separation from the mainland the present 

 flora and fauna had settled in Tasmania. The remains of 

 the former fauna were a few isolated specimens of gigantic 

 mai-supials which found a haven of refuge in Northern 

 Tasmania, where they died out before tliey had time to 

 spread. The last to follow were the aborigines, and veiy 

 soon after their aiTival the rising sea had completely 

 severed Tasmania from the mainland. 



