14 A. W. HOWITT ON THE PHYSICAL GEOGRAPHY AND 
to over twenty feet in width. A preliminary microscopic examina- 
tion of a number of these in thin sections has shown me that they 
are varieties of compact felstones, diorites, and basalts; but many 
have evidently undergone great mineral changes, partly due to 
metamorphism, which has, I believe, also generally affected the 
already metamorphosed schists, and partly due to alterations which 
have affected the dykes alone. I am, at present, unable to assign 
a classificatory position to these. 
Some of these intrusive dykes or masses are no doubt Paleozoic, 
but others are undoubtedly connected with the outflows of the Ter- 
tiary dolerites, which will be mentioned later *. 
Epidote is of frequent occurrence, both in the intrusive dykes and 
in the schists themselves, and forms a marked feature in the Omeo 
rocks. 
The subjoined sketches (fig. 3) will show the relations of such 
intrusive dykes to the schists and granites of Omeo. 
Fig. 3.—Aphanitic Dyke at Sandy Creek, Tambo River. 
OO 
X 
~~ 
ANOS ~ Aan 
~e 4 
an 
Ww es 
NZ . fe 
~~ cm 
s ~ -7 
a‘ Nae ~*~ 
' NU pains 
x 
» ~ * 
7 etc 
LG ~\ 2 6 fe 
7 eS v4 
* BSS 
“Nu 
~ 1 
os % 
a vv 
SN ‘ ss 
: aN 
ads | aC cs 
Ae NY 
ES ‘ 
\e 
Fy Ses ce 
GA oss AY 
A. Section. Dip N. 10° W. at 80°. B. Ground-plan. Strike N.80° W. 
The rock through which the dyke cuts is a metamorphic granite, 
These crystalline schists extend across the valley of Livingstone 
Creek towards the Omeo Plains, where they appear to pass into the 
argillaceous schists. These latter still distinctly show the former 
condition of the beds, being alternations of allered slates and sand- 
stones. The former have become spotted or nodular argillaceous 
schists; the latter quartzites. The connexion of these with the 
crystalline schists is seen in a gully near the Livingstone Swamp, 
from which I have taken the subjoined sketch (fig. 4). 
* Thave in this paper followed the suggestion made by Mr. Allport in his 
most valuable paper ‘‘On the Microscopic Structure and Composition of Bri- 
tish Carboniferous Dolerites,” read before the Geological Society of London, 
June 24, 1874 (p. 529 of the Quarterly Journal of the Society, vol. xxx. 
1874), and have used the term “dolerite” as including all those Tertiary vol- 
canic rocks of which basalt is the compact form, I have, however, still used 
the restricted term melaphyre in one instance. 
