15 
GEOLOGY OF WINEGLASS BAY. 
(By W. H. CLEMES) 
On the eastern side of Frey cl net Penin¬ 
sula is a deep bay, called Wineglass or 
Thouin Bay, a gem set in the midst of 
rugged "ranite peaks of surpassing gran¬ 
deur. From our camping site we looked 
across the deep blue waters of the bay to 
a magnificent stretch of peaks of rosy 
granite, with a pure white beach stretch¬ 
ing crescent-wise beneath - a picture 
worthy of tlio pencil and brush of any 
artist. It seems almost desecration to 
analyse such a thing of beauty, and to 
probe and delve for its hidden secret, but 
the interests of science must be pleaded 
in extenuation. 
The granite belongs to an almost lost 
period of lime, as far as Tasmania is con¬ 
cerned, situated between the Silurian and 
Permo-carboniferous periods, when no 
sediments that can be recognised were 
laid clown. But, fortunately for Tas¬ 
mania, a great igneous intrusion took 
place, and huge masses of granite, both 
on the East and West Coasts of Tas¬ 
mania. forced and worked their way into 
the overlying strain, and consolidated 
deep down beneath the surface, biinging 
with them the rich stores of mineral 
wealth that have made our little island 
so famous. Subsequent denudation has 
exposed these rock masses, and given us 
such magnificent rugged scenery as only 
granite country can give. These rocks 
for the present have been placed in the 
Devonian period- 
A critical analysis of the rock itself 
cannot lie carried out without micro¬ 
scopic examination. The preparation of 
the slides is a lengthy process, and so 1 
must content myself with a few general 
remarks on composition and structure, as 
viewed in hand specimens. The rock ap¬ 
pears to consist principally of biotite 
mica, pink orthocluse felspar, and quartz. 
Mr. A. D. Maekay, in a former paper, 
also mentions Muscovite mica, plagioclase 
felspar, and chloride as accessories. The 
rock varies greatly in structure and com¬ 
position. On the southern side of the 
bay it is practically composed of a rich 
reddish-coloured felspar and quartz, little 
or no mica being present, but on the 
northern side in places black mica is the 
predominant mineral, and the felspar is 
almost while. Quartz is always present 
in abundance. 
Secondary veins are very noticeable, 
the granite composing them being much 
closer in texture, due to the squeezing it 
got in pushing its way up through the 
cracks and joints in the older rock The 
crystals are much smaller than in the 
normal granite, and approximate more 
to the micrograuitee. 
In many places the granite was inter¬ 
sected by gli nt veins of quartz, white to 
rose-coloured, with numerous nests of 
rock crystals. There were also dykes of 
diabase (?) cutting acioss the country in 
a north and south direction. This rock 
was highly porphyritic, and studded with 
great crystals of felspar, which had been 
absorb,' l during its passage up through 
the granite. The great cliffs to the south 
show signs of internal movement, which 
probably took place prior to consolida¬ 
tion. The vegetation on the whole is 
scanty, owing to the poorness of the soil, 
which is largely composed of quartz. 
Along the coastline the bare rock 
stretches up for a considerable height 
above high-water mark, an eloquent tri¬ 
bute to the force of the winter gales. 
In places the granite appeared as great 
boss-like masses, with smooth, rounded 
surfaces curiously streaked by descend¬ 
ing waters charged with mineral matter- 
In others it was columnar and much 
broken up, with great cracks running in 
all direct ions. In fact, the varied forms 
seemed endless, and the whole listrict 
would 'prove an almost linexhausitjfblie 
mine for geological research, that would 
well repay an enthusiastic geologist to 
exploit, tlie problems to be solved ap¬ 
pearing to be endless and varied. 
4/3035 
