306 REPORTS OF RESEARCH COMMITTEES. 



Tasmania had been in doiibt. The late Mr. Twelvetrees had 

 provisionally placed them at the .top of the Permo-Carboni- 

 ferous series as they obviously intruded the lower members of that 

 series at Port Cygiiet, but had hitherto not been proved to be 

 intrusive into the late mesozoic diabase or other rocks younger 

 than the Permo Carboniferous. The paper describes a dyke of 

 alkali poTphyry, similar to some of the Port Cygnet rocks, which 

 was observed at Little Oyster Cove, Kettering, to intersect the 

 diabase. The age of this rock and probably those of the related 

 rocks at Port Cygnet and elsewhere in the district is therefore 

 regarded as pest diabase, i.e., post-mesozoic. A co-mparison is 

 made of the alkali rocks of South-eastern Tasmania with other 

 Australian occurrences, whose age is known in some cases to be 

 probably mid-Cainczoic. On grounds cf general petrographic 

 similarity it is believed that the alkali rocks m South-eastern 

 Tasmania are to be referred to the same geological period. 



Y icfoi'la. 



The writer read a short paper on the tertiary alkali rocks of 

 Victoria at the Melbourne meeting of the British Association in 

 1914, which is published under section C. In it a brief synopsis 

 is given of what was known up to that time of the distribution 

 of alkali rocks in Victoria. Apart from occurrences described 

 by the writer in the Brisbane volume of the Australasian Assceia- 

 tion in 1909, in a Presidential address on the Volcanic Rocks of 

 Victoria, and a note by the writer on the occurrence of nepheline 

 in dykes at Omeo, in the Sydney volume in 1911, and the publica- 

 tion by Dr. Summers and the writer of a Geological Survey Eulle- 

 tm 24, on the rocks of the Mo^mt Macedon area, certain additional 

 types and localities are referred to. Further work at Omeo showed 

 that all the alkali recks are probably Cainozoic in age, and that 

 surrounding a central plug of solvsbergite there occur lavas of 

 sccriaceous anoithoclase trachyte, and numerous more or less 

 radial dykes. Most of these are trachytic, some contain quartz, 

 one at least is a bostonite and seven prove to be dykes of nepheline 

 phonolite. These occurrences have not yet been fully described. 

 The resemblance of the rocks of Mt. Leinster, in North-eastern 

 Victoria, to those of Omeo, and to some C'f those of the Macedon 

 district is referred to. About 14 miles north-east from Mansfield, 

 in North-central Victoria and about 3 miles from Tolmie, in the 

 Tclmie highlands a volcanic hill, known locally as Gallows Hill, has 

 been shown by the writer to consist of lava flows of nej^heline 

 phonolite of probably late Cainczoic age. A nepheline phonolite 

 has also been recognised from Barwite, east of Mansfield, but 

 it is not known whether the rock is " in situ," and no detailed 

 account of these rocks has yet been published. 



In the paper before the British Association the question of 

 the relation of these alkali rocks of Victoria toi Cainozoic elevatory 

 movements of a plateau is tentatively discussed. 



