56 
Geology and Physical Geography: 
The Moroka River is a branch of the Mitchell, and heads from 
a broad valley between Mount ‘Wellington and Castle Hill, whence 
it flows north through precipitous ranges for tho greater part of 
its length, finally turning to tho east and joining the main river. 
A bold lofty spur, starting from Castle Ilill, runs north between 
the Moroka and tho Mitchell Rivers, and its terminal point before 
descending to their junction is the Snowy Bluff. At tho Snowy 
Bluff a section was noted by Mr. Howitt and myself, showing 
over 2,000 feet of well exposed layers, having a slight southerly 
inclination, and resting on the abraded edges of the nearly vertical 
Silurian rocks. Here, again, the lowest beds, immediately on the 
Silurian, are conglomerates and conglomeritic sandstones, on 
which rest quartziferons and porphyritic felsites and massive 
bedded felstones, clearly contemporaneous, followed by alterna- 
tions of laminar and rubbly shales, sandstones, grits, rubbly 
mudstones, and conglomerates, with intercalated contemporaneous 
layers of basalt (melaphyre); the uppermost bed noted is a coarse 
conglomeritic sandstone. (Fig. 18.) 
These Upper Palaeozoic rocks constitute the Snowy Bluff, 
Mount Kent, and Castle Hill Range, and the country westward of 
it; the lower eastern slope of the range, towards the Wonnongatta, 
being Silurian and Granite. 
The boundary line between the Upper Palaeozoic and the older 
rocks from Castle Hill to Freestone Creek has not been examined; 
but there is no reason for doubting tho general identity in geolo- 
gical position of the Snowy Bluff beds with those of Freestone 
and Iguana Creeks, which have been shown to bo of Upper 
Devoniau age. 
At the Avon River, where it emerges from the mountainous 
country, above its junction with Valencia Creek, occur varying 
bauds of thick and thin bedded fissile, purple, brown, and 
yellowish micaceous sandstones, and purple or brick-red rubbly 
mudstones, “ cornstones,” with other varieties of sedimentary 
rocks, the whole forming a group known as the “ Avon Sand- 
stones,” in some of the red and yellow sandstones of which was 
found the LepidodcJtdron ( Bergeria ) Australe, figured and de- 
scribed by Professor McCoy in the first Decade of his Prodromus 
of Victorian Paleontology. Professor McCoy expresses a strong 
opinion as to the Lower Carboniferous aspect of this fossil plant- 
impression ; and, from my own observations, I am inclined to 
believe that the bods in which it is found are among the upper- 
most of the group, and younger than, though conformable with, 
the Upper Devonian beds of Freestone and Iguana Creeks. It is 
highly probable, therefore, judging from their etratigraphicai 
position, that the Avon Sandstones are — as indicated by Professor 
McCoy, on paleontological evidence — of Lower Carboniferous age, 
or passage beds in that direction upwards from the Upper 
Devonian beds. 
