182 President's address — section c. 



country which, commencing in New South Wales, occupies at the 

 boundary a breadth of about 20 miles near the head of the River 

 Murray. The western limits include the Cobber as Mountain, and runs 

 south to Mount Nowa Nowa, near the head of L. Tyers, while the 

 eastern boundary is parallel to and slightly eastward of the Snowy 

 River. 



Outlying areas included with this series occur near the valley of 

 the Mitta Mitta River, and near Corryong, in the extreme N.E. of the 

 State. 



A series of rocks near Whitfield in countrj^ Delatite has been 

 correlated by Kitson (7-1) with this group, but for reasons given later 

 I prefer to group them with the dacite and quartz-porphyry series. 

 The highest elevations in the Snowy River porphyry series occur near 

 the N.S. Wales boundary, the Cobberas, for example, being over 

 6,000 ft. in height, and the general level falls southwards till at about 

 1,000 ft. above sea level the rocks are hidden beneath the Tertiary 

 coastal belt of S.E. Gippsland. The scenery is rugged in the more 

 elevated areas, while gorges and Avaterfalls occur in parts of the 

 course of the SnoT\n^ River and some of its tributaries. 



Geological Relations (See Sections, Plate II., Fig. 1). 



The rocks of this series consist of acid lavas and fragmental 

 rocks, in places over 2,000 ft. in thickness, ejected from a series 

 of Palaeozoic volcanoes which Howitt describes as probably de- 

 veloped along meridional fissures in the Lower Palaeozoic rock 

 foundations near a subsiding coast line. The age and character of 

 this foundation for the volcanic rocks varies. In places it consists 

 of the complex of g-neisses and schists possibly of Archoean age. Else- 

 whei'e it consists of Ordovician sediments and of granitic rocks. Near 

 the Limestone River Howitt (58) describes the poi-phyries as resting 

 on the upturned edges of shales and intercalated limestones and 

 marbles. These yielded obscure fossils which McCoy described as 

 probably U. Silurian, and on this account Howitt regarded the 

 porphyries as of Post-Silurian age. The evidence of the relations of 

 the two series in this area is not very clear, and there is some doubt 

 as to the age of the limestone, which may possibly be related to the 

 Mid-Devonian series of Buchan and Bindi. It is therefore difficult to 

 speak precisely of the age of the base of the poi'phyries, especially as 

 Howitt describes the boundary with the older rocks in some parts as 

 a fault junction. We can speak more positively of the relations of the 

 upper part of the series with the overlying sediments. Near Buchan, 

 Bindi, and one or two other areas the volcanic rocks are succeeded by 

 marine limestones containing typical middle Devonian fossils, and in 

 some localities a gradual passage occurs between the volcanic tuffs 

 and ashes of the Snowy River porphyries through calcareous felsite 

 breccias and submarine tuff's into typical marine limestones. It is 

 clear therefore that the upper stratigraphical limit of the 

 porphyries is Mid-Devonian. The lower limit is certainly Post- 

 Ordovician, and possibly Post-Silurian. No Lower Devonian sedi- 

 ments are known in Victoria, and the Snowy River porphyries 

 are generally regarded as occupying that horizon. Until the rela- 

 tions of this series with the underlying rocks, however, can be more 



