and their Contact Zones. 19 



I have observed, when tracing round the boundary of 

 regional metamorphism at Omeo, the constant recurrence 

 near it of tracts of intrusive granites and felsites, but as yet 

 I have not been able to identify such intrusions within the 

 Omeo schists themselves. So far as I have yet examined, it 

 seems certain that all these granites and felsites are of an 

 age younger than the Omeo schists which they adjoin, and 

 at Bindi, where alone some Upper palceozoic rocks still 

 remain, I have found these latter resting upon them. 



It becomes, therefore, an exceedingly interesting, and as 

 regards dynamical and chemical geology, an important 

 question for consideration, what connection there may be 

 between the intrusion of these igneous masses and regional 

 metamorphism. I can now, however, only refer thus briefly 

 to the question, and leave it for future consideration. 



The intrusive igneous rocks of Swift's Creek, which I 

 have taken as the subject of this essay, are situated exactly 

 in the passage of the normal Silurian formation into the 

 regional schists of Omeo, and are, therefore, an example of 

 the above statements. 



Although it can be shown that these intrusive masses are 

 all younger than the Omeo schists, it is not easy to point out 

 the precise period to which they belong. They are generally 

 found protruding from the denuded Lower palceozoic forma- 

 tions as mountain masses, or when the sediments are hard 

 and silicious, they form eroded basins. At Swift's Creek 

 there are no younger formations to aid in determining the 

 geological age. At Bindi, however, as I have said, at a few 

 miles distance there is a similar occurrence of intrusive 

 igneous rocks which is overlaid by Devonian sediments.* In 

 this instance, therefore, the age is fixed as between the close 

 of the Silurian and the middle of the Devonian periods. 

 Elsewhere similar intrusive masses as Mount Taylor, near 

 Bairnsdale, are found capped by Upper Devonian beds.*f- 

 The Swift's Creek granites and diorites are, in fact, part of 

 that rock formation of North Gippsland upon which the 

 Upper palceozoic sediments were laid down. 



* Report of Progress of the Geological Survey of Victoria, Part IV., p. 158, 

 Schedule of Report on Fossil Specimens, by Professor M'Coy, Nos. 4083 to 

 4131. 



f The Devonian Rocks of North Gijipsland, by A. W. Howitt. Report of 

 Progress of the Geological Survey of Victoria, Part III.; also, Schedule of 

 Reports on Fossil Specimens, by Professor M'Coy. Progress Report G. S. V. 

 Part IV. No. 2687, p. 155, and No. 3295, p. 156. 



