130 E, 0. Teale: 



our knowledge is so fragmentary that at the best, our ideas can only 

 be largely conjectural. 'It may, nevertheless, be stimulating to fur- 

 ther research to attempt to formulate some picture of the earth 

 history of this ancient era. 



It will be seen that the same area along the Mansfield-Wellington 

 belt, marks the site successively of marine deposition in Upper 

 Cambrian, Upper Ordovician and Silurian times, with probable 

 intervening periods of sub-aerial denudation. The Cambrian rocks 

 also indicate contemporaneous volcanic action of a basic nature, the 

 extent of which is unknown. Devonian times were ushered in with 

 the outbreak of great igneous activity, the greatest volcanic period 

 of Palaeozoic times in this part of Australia. Rocks of this age, 

 however, are better developed in certain other parts of Victoria. 

 This region wais then mainly a land area, for the volcanic accumu- 

 lations appear to have been almost entirely sub-aerial. Whether 

 marine conditions supervened here as they did along the Snowy 

 River belt is not knoAvn, for no Middle Devonian limestones have yet 

 been recognised, but in late Devonian or early Lower Carboniferous 

 times, a large trough, at least 100 miles long and possibly fifty 

 miles wide was developed and occupied by a fresh water lake. The 

 early lacustrine sedimentation which was thus initiated was accom- 

 panied in its early stage by energetic volcanic activity, both' effusive- 

 and explosive, and of a highly acidic nature. Long after this 

 rhyolitic outburst had ceased, and as deposition proceeded, there 

 w^ere successive outpourings of basic lavas, mostly of no great thick- 

 ness, and these in turn became covered with later sediments belong- 

 ing to the same period. 



The succession along the Snowy River is less complete. No Cam- 

 brian, Silurian, or Lower Carboniferous sediments are known, but 

 the volcanic accumulations of Lower Devonian times indicate very 

 great igneous activity, which was succeeded by marine invasion in 

 Middle Devonian into basins and troughs in the " Snowy River 

 Porphyries.'^ 



The history recorded in these zones implies a sequence of powerful 

 earth movements of various kinds to be discussed later. Even a 

 casual look at the geological map of Victoria reveals a general sub- 

 parallelism of the Palaeozoic formations,, with a prevailing northly 

 trend, and a little closer investigation indicates that certain belts 

 have had a more varied history, therefore implying zones of greater 

 unrest or instability, along which movements, also in some cases, 

 igneous activities, have been periodically repeated. It has been 



