GEOLOGICAL NOTES 
By \. N. LEWIS, M.C., LL.M. 
Sellout(*n Island has been known for 
the last hundred years to be of great, 
geological interest, and the members of 
the camp looked forward to a variety 
of geological studies in some respects 
unusual in Southern Tasmania. They 
were not disappointed. The granites 
proved a source of interest that could 
not be exhausted in many months. In 
addition there were coal measures and 
a variety of tectonic and physiographic 
features of interest. Only one day was 
available for the pursuit of geological 
studies on the island, but the few hour* 
spent at Cole and Wineglass Bays were 
by no means wasted. 
Sehouten Island has the distinction of 
lieing the subject of the first paper 
read before the Royal Society of Van 
Diemen’s Land by l)r. Joseph Milligan, 
the society’s first secretary, at its first 
meeting on August Id. I S IS. It was 
then one of tne known coal fields of 
Tasmania, and Dr. Milligan reported on 
its possibilities as a coal producer. A 
mine had been worked for several years, 
hut had been closed down for some 
t tne prior to 1848. 
The eastern half of the island is of 
granite, and the western half of coal 
measures intruded and overlain by dol- 
erlte (diabase). At Maria Island the 
granite is to be seen beneath the pertno- 
earboniferous strata. It is safe to say 
that the coal measures occupy a posi¬ 
tion stratiographlcally about 2000 feet 
above the top of the granite. To-day 
they are to he seen over a thousand feet 
below the top of the higher granite 
mountains. This indicates a fault on 
a major scale. The line of the fault 
is clearly distinguished, both from a 
distance and from close at hand. The. 
western hills, composed of dolerite. are 
gently rounded in contour and covered 
with a thick growth of fine gum trees. 
The eastern half of the island is a 
jumbled mass of ragged gran te crags, 
with !>are escarpments everywhere, and 
very stunted vegetation growing only 
in crevases. 
The fault runs across the island 
through the gap behind Mr, I'Vrgu-snn’s 
house. It has an angle of hade of about, 
Hkleg. to the westward. Seldom can 
a more perfect example of ground evi¬ 
dence of a fault be observed. From 
the top of the ridge in the centre of 
the island (here about 710 feet above 
sea level) a small creek bed descends 
down the hill in a north-westerly direc¬ 
tion. There is a quantity of rubble 
a coup'e of feet wide in its bed, then 
on the right bare granite rocks, and 
on the left the dolerite hillside rise 
steeply. The creek runs steeply down 
hill for 401t feet, along this fault, and 
not once does the nature of the rock 
on its right bank and on its left alter, 
neither tres[»iss into the preserves of 
the other. Half-way down the hill the 
stream turr s to the north-east, and 
leaves the fault, but the junction be¬ 
tween the granite and the dolerite can 
be seen still following the same line. 
This fault can lie traced north along 
the western shore of SchouLn Penin¬ 
sula. The point south of Ha/zards Bay 
is composed of dolerite similarly alter¬ 
ed oOOl) feet or more in its original ver¬ 
tical relationship with the older gran¬ 
ite. The fault can lie traced north 
through the East Coast coalfields, and 
south through Maria Island, where 
dolerite seen on the Parson and Clerk, 
dOOO feet above the base of the lime¬ 
stones. is at sea level at Cape 
Bourgainville. This great tectonic fea¬ 
ture is evidently responsible for tie 
trough now known as Flenrieu Bay. An¬ 
other fault forming the western side 
of the hay nan be seen in the straight 
escarpment of Cape Bernier. 
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