226 Charles Feaner : 



the village of Greendale northward beyond the Main Divide of 

 Victoria. 



The existence of this fault was, the writer learns, suspected by 

 Messrs. Hart and Baragwanath, but no references to it occur in 

 the geological records of this State. In January, 1915, the Univer- 

 sity Geological Survey Party, under Professor Skeats, gave critical 

 attention to the scarp, and clearly demonstrated its existence as a 

 fault for some six miles, in the parish of Blackwood. The writer 

 has sincei extended these observations to the west and the east, and 

 has been permitted by Professor Skeats, and by Mr. Herman, 

 Director of Geological Survey, to embody in this paper the evi- 

 dence collected by the Survey Party referred to. 



The whole of this area is known to be traversed by faults, run- 

 ning at all varieties of angles both across and with the strike. By 

 far the most definite are the E.-W. series, as proved in the under- 

 ground workings at Blackwood. W. H. Ferguson (ref. 18, pp. 5 

 and 26) records twelve "cross courses" (E.-W. faults), within a 

 distance of three miles, in the Blackwood field. They are all verti- 

 cal or moderately inclined, and in some instances the fissures are 

 filled by dyke material, one being over 100 feet wide. The move- 

 ment does not seem to have been very marked in most cases, and in 

 many fractures there was no movement at all. 



It would seem futile to endeavour to approximate an age for 

 such faults and fractures as a whole, seeing that tliese lower Ordo- 

 vician rocks have been the sufferers of every thrust and screw and 

 •crush to which this part of the lithosphere has been subjected since 

 those lower palaeozoic times. There can be no doubt that the frac- 

 tures and faults had their origin at many and various times, and 

 that along any one ancient fracture line, movements may have 

 occurred at every period of diastrophism since then. 



There is a peculiar and interesting generalization which has been 

 put forward concerning several areas of Victoria, viz. : — 



(1) N.-S. dykes are acid. 



(2) E.-W. dykes are basic. 



Accepting as part of our creed that the devonian was par excel- 

 lence the period of activity of acid magmas, and the tertiary as the 

 chief period of the uprising of basic material, there would 

 seem to be appreciable a further generalization to the effect 

 that the E.-W. fractures were largely post-devonian, and the N.-S. 

 fractures largely pre-carboniferous in origin. Many other factors 

 and many other areas will need to be investigated before any 

 ■generalization of value can be arrived at, but in a section dealing 

 with the age of faults the idea was thought worthy of mention. 



