Palaeozoic Ge0logy of Victoria. 73 



showed a succession of iuliers ranging from Cambrian to Silurian^ 

 surrounded by a ring of Upper Palaetizoic sediments with associ- 

 ated acid and basic lava flows. Important broad structural and 

 tt;ctonic considerations involving palaeozoic geology generally there- 

 fore, became involved. 



On the first expedition of renewed exploration in April, 1915, L 

 was accompanied by my father, Mr. A. 0. Thiele, who had been 

 a constant helper throughout the numerous field trips to this area. 

 Mr. Herman, Director of the Geological Survey, also kindly 

 arranged for Mr. J. Caldwell, one of the officers of the Survey, tO' 

 join the party as a field assistant, and I am greatly indebted ta 

 the willing and able help rendered by both these persons. 



Various unavoidable difficulties, due partly to the season and 

 partly to the rough nature of the country, prevented the com- 

 pletion of tlie work before the wet season set in, and as the district 

 was unsuitable for winter field work, it was decided to choose 

 another region in the meantime, offering unsolved problems likely 

 to bear in some way with! those of the Wellington region. 



The district, therefore, between Nowa Nowa at the head of Lake 

 Tyers and Buchan, was chosen, for it included two occurrences 

 believed by Mr. Dunn tu be of Heathcotian age, one in Boggy 

 Creek and the other in the I'ara Range (19), south-east from 

 Buchan. 



In Boggy Creek, just north of Nowa Ni)wa, Mr. Dunn had stated 

 that diabases associated with cherts occurred and in the Mount 

 Tara goldfields he had recognised cherts. Both these occurrences, 

 had been included in the Heathcotian on purely lithological 

 grounds, but the relationship to the surrounding rocks had not 

 been worked out. This district further offered an opportunity of 

 studying a portion of the important belt of igneous rocks known 

 as the " Snowy River Porphyries," thus affording scope to discuss 

 the Palaeozoic volcanic history generally, of which the Wellington 

 series form an important chapter. 



These various journeys through Gippsland provided also some 

 interesting physiographical studies, so that the extent of the work 

 has gradually groAvn until it includes a number of distinct prob- 

 lems wliich will now be considered in turn. 



WELLINGTON DISTRICT. 



Tlu Palaeozoic Geology. — Thn? Wellington region forms part of 

 one of the important major tectonic and structural zones of Vic- 

 toria, which may le conveniently termed the Mansfield-Welling- 



