Art. Y. — Notes on the Diabase Rocks of the Buchan 



District. 



Contributed by A. W. Howitt, F.G.S. 



[Read 19th May, 1881.] 



Introduction. 



In papers previously published in the Reports of Progress 

 of the Geological Survey of Victoria,* on the Devonian 

 rocks of North Gippslancl, I gave some particulars as to those 

 formations which collectively constitute, at Buchan, the 

 Middle Devonian group, and whose geological age is deter- 

 mined by the characteristic marine fossils of the Buchan 

 limestones. 



In the last-published communication on this subject*)* I 

 desired to describe and to bring into relation with each 

 other the members of that group of rocks which I provi- 

 sionally termed the Buchan Beds. I was led to make that 

 more special examination by certain doubtful features which 

 my previous more general examination had shown, and this 

 again brought other appearances into view which required 

 further elucidation. It even then remained uncertain 

 whether certain dark-coloured basic igneous rocks at Back 

 Creek and the Murendel River were intrusive into the 

 Buchan Beds, or were older than some of them, and therefore 

 contemporaneous members of the group. 



I was not able at the time to completely satisfy myself on 

 this point, but I inclined to regard them as being intrusive, 

 and therefore younger than the whole of the Buchan Beds. 

 Since then I have had an opportunity of examining this 

 group of beds in detail over a wider area. 



The following notes are the result of that examination, 

 both as to the localities themselves in the field, and subse- 

 quently of the rock samples I then collected. 



* Report of Progress of the Geological Survey of Victoria, Parts III. and V. 

 f Same, Part V., p. 117. 



C 



