BY FRITZ NOETLING, M.A., PH.D. 107 



1913. 



3. Breccia (a period of intense denudation), and termi- 

 nat-ed by the deposition .of 



4. Well stratified leaf beds. (Tlie agencies producing the 

 Breccia must have continued during the formation of the 

 leaf beds, because layers of Breccia are intercalated in the 

 leaf beds.) 



.5. Pause in the deposition of sedimentary rocks, dur- 

 ing which the leaf bed series (including all the beds from 

 2 to 4) were laid dry. (It is veiy probable that during this 

 process the leaf bed series acquire the remarkable regular 

 dip towards south.) 



6. Partial destruction of the leaf beds by volcanic ex- 

 plosions, followed immediately by the erujotion of Basaltic 

 magma of probably very low temperature. 



7. Dislocation of the leaf bed series and the overlying 

 Basalt by faults striking in an approximate north-western 

 direction, and having a northern dip, going hand in hand 

 with the destruction of the Basalt cone. 



8. Period of extensive denudation and erosion of the 

 bed of the Derwent below the present sea level. (Sea level 

 lower than at tlie present day.) 



9. Deposition of arenaceous beds on Basalt at Droughty 

 Point. 



10. Rise of sea to its present level. (Partial filling 

 up of the Derwent valley with sea water.) 



11. Formation of hill wash consisting of volcanic 

 debris, ashes, etc., representing the present day soil. 



12. Formation of shell deposits by the aborigines. 



13. Present day deposits. 



All these events can be traced with the greatest 

 acciu'acy, and they must have followed each other in the 

 above order. There can be not the slightest doubt tliat the 

 period during which the Breccia was deposited in the 

 lower parts of the Derwent valley must represent a period 

 of most active denudation in other parts of Tasmania. 

 Great masses of angular debris of sedimentary rocks mixed 

 with well rounded blocks of Diabase were quickly moved 

 and redeposited at convenient places. This period of 

 great activity was followed by one of comparative rest, 

 during which a fine silt was deposited which preserved the 

 impression of delicate leaves floating about in the water. 

 Occasional relapses of the fonner energetic denudation 

 must have occurred, however, during this period, resulting 



