113 
GEOLOGICAL NOTES ON THE CASTERTON AND COLERAINE 
DISTRICTS. 
By E. J. Dunn , F.G.S., Director , Geological Survey. 
Tertiary (Iron-Stone, Etc.). 
To the south and west of the Grampians the country in late Tertiary 
times consisted of a continuous plain, but since that period the Glenelg 
and Wannon Rivers have carved out extensive valleys, dales, and gullies, 
leaving remnants of the old plain to form the flat hill tops and plateaux. 
The general level of this marine plain was from 500 to 600 feet above 
sea-level. 
Southward from the Grampians a sheet of basalt extends almost to 
the coast. To the south-west and west of the Grampians the Tertiary rocks 
forming the old plain were composed of sand at the surface, then sand 
mixed with more or less pisolitic iron ore, and below this were clays of 
mottled appearance and also mottled red and grey soft sandstones and 
very calcareous beds in places filled with fossils. Where remnants of 
the plain survive the surface soil is sandy and of poor quality. 
In certain areas the iron ore becomes a prominent feature, and it is 
largely used for metalling the roads and also for the railway lines. About 
2J miles westward from Merino the iron ore has been excavated over acres 
of ground, and carried thence for use on the main roads. The sections 
disclose from 2 to 3 feet of loose pisolitic iron ore (iimonite), and below 
this from 2 to 3 feet of more compact Iimonite. It looks as though the 
lower portion had first aggregated and that at one period it was com¬ 
posed of loose pisolitic material, but as further deposition of the iron ore 
proceeded the interstices were filled in and the loose material bound to¬ 
gether into a solid mass. At present only this loose upper portion is re¬ 
moved, and the more solid, which would require to be first broken out and 
then broken up, is left; ultimately the whole will be removed. This 
material, as it comes from the gravel pits mixed with sand, would make 
a perfect concrete with the addition of a little cement, and could be used 
for building houses, walls, &c., and for culverts on the road. The value 
of this ore, as a source of iron, has been determined, as there appears to 
be vast quantities available. 
Iron Fe 
p 2 o 5 
h 2 o 
No, 229. No. 230. 
28-6% ... 44-6% 
O' 14 ... 028 
213 ... 2-8 
No. 229.—Pisolitic Iron, Gravel Pits, 2m. S. of Merino. 
No. 230.—Limonite. Same locality. 
Between Merino and Coleraine the road crosses a Tertiary plateau 
with pisolitic iron distributed through the sandy material just below the 
surface. Coleraine is built in the valley, about 300 feet below the 
plateau. 
At Casterton, on the north side of the Glenelg River, and about 2 
miles in a north-westerly direction from the town, there is another Ter¬ 
tiary plateau, and here also pisolitic iron ore is excavated for road¬ 
making. Its altitude above sea-level is about 640 feet. On the Har¬ 
row road, about 4 miles northerly from Casterton and 650 feet above 
sea-level, there are excavations for road material, and about 2 feet to 2J 
feet of pisolitic iron ore is shewn resting on another foot or so of more 
compact limonite. The size of the pisolitic material ranges from J inch 
