GEOLOGY OF NORTH GIPPSLAND, VICTORIA. 17 
in rapidity of change and in the nature of the change itself. In 
examining any of the isolated granite areas, the Silurian strata are 
found in the neighbourhood to maintain their general direction of 
strike and dip until in near proximity to the granite, where they 
exhibit signs of pressure and of alteration. The beds.are thrust in 
all directions, and extensively broken up by irregular joints. Granite 
veins are found to traverse these contact-margins, showing in 
different localities the same general features, and especially the 
distinct contact of the sedimentary rock and the granite vein, as 
clearly as elsewhere the contact of the granite with the mass of 
intrusive dykes is shown. The stratified rocks themselves are 
greatly altered, either resembling fine-textured gneissose or mica- 
ceous schists, or forming dense crystalline rocks in which the 
planes of deposit can barely be distinguished by wavy lines of 
various shades of colour. The extreme form of this series is Horn- 
fels. The changes resulting in the former series of alterations seem 
to be heralded by a micatization of the rocks; in the latter by the 
appearance of chiastolite-like markings, which can often be still 
distinctly recognized in an enlarged form in the Hornfels. 
A microscopic examination of thin sections of the Hornfels series 
has led me to believe that, in some cases, the markings I have 
referred to are probably due rather to the somewhat different 
aggregation of materials than to the introduction of fresh elements 
into the rock masses. 
Sometimes both forms of alteration are seen in the same area, and 
occasionally in near proximity, as at Dargo Flat, where the mica- 
ceous alterations are seen, especially on the northern margin (Dargo 
River), and the indurated rock series on the south side (Orr's 
Creek). 
These alterations of adjacent rocks extend for uncertain distances 
from the visible granite surfaces; and I think that this may be 
accounted for on the belief that the granite continues nearer to the 
present surface in some directions than in others—in other words, 
that it is due to the granite surface being as highly uneven under- 
ground as we see it to be where denudation has laid it bare. 
In some- parts of North Gippsland the rock masses which have 
apparently been invaded by granites do not present so much the 
alterations I have described as a general silicification of the strata, 
by which great portions have assumed the character of quartzites, 
as, for instance, Delegete Hill and the Bowen Mountain. But it 
seems to me significant of some connexion between the changes 
seen and the appearances of invasion by the granites, that the 
intensity of those alterations in the sedimentary strata varies in an 
inverse proportion to the distance of the former. But in these 
tracts there are also places where the rock masses present just such 
alteration as I have before mentioned ; for instance, Marriott’s 
Mountain, where the Silurian slates and sandstones have, near the 
granite, assumed a finely gneissose appearance. 
The annexed section (fig. 5), sketched from a cutting in Orr’s Creek, 
Dargo Flat, will illustrate the contact appearances generally seen: 
Q.J.G.8. No. 137. C 
