10 Notes on the Diabase Rocks 



It may be said that the floods which, during the past ten 

 years, have swept out the streams, in many cases to the bed 

 rock, in the North Gippsland mountains, have opened up a 

 storehouse of facts bearing upon some of the most interesting 

 as well as difficult problems of petrography. 



Description of the Rocks. 



In the preceding paper on the Buchan Beds* I was led, 

 from an examination of the much-altered olivine-bearing 

 rocks at the Murendel River, to regard them as representing 

 basalts, and I also regarded all the basic igneous rocks, both 

 at the Murendel and Back Creek, as belonging to the same 

 group. I now proceed to give the results obtained from a 

 more complete and extended examination in the field, and a 

 careful analytical examination of the samples I had collected. 



The sketch section given here extends from Moore's 

 Crossing, at the Snowy River, to a little west of the Muren- 

 del galena mine. The line of section and the Snowy and 

 Buchan Rivers rudely represent an equilateral triangle, the 

 junction of the rivers being at the apex. The length of the 

 section is about three miles. In order to give as complete a 

 view as possible of the various rock masses crossed, and also 

 of their relations to each other, I have found it advisable to 

 repeat some of the features given in a section at p. 131 in 

 the previous paper. 



The section commences on the eastern side of the Snowy 

 River, at Moore's Crossing. At this place there is a some- 

 what larger outlier of the Buchan limestones than usual. 

 On the western side, for some miles up and down the river, 

 the principal rock is a dark-coloured (dark brown to nearly 

 black) massive igneous rock. On the eastern side the lime- 

 stones preponderate, and on the western side these igneous 

 rocks. But on both sides there are numerous places where 

 the contact of both rocks can be well observed. This dark- 

 coloured igneous rock is evidently akin to that which, at the 

 Back Creek, underlies the limestones, and also in that locality 

 extends over much of the eastern side of the Buchan River. 

 It decomposes into a moderately good soil, and it weathers 

 into harsher and more rugged masses than is usual with the 

 basalts and dolerites of Gippsland. This harsh character is 



* Progress Report Geological Survey of Victoria, Part V., p. 117. 



