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Abstract

Rocks of the Parmeener Super-group (Late Carboniferous to Late
Triassic) of Tasmania rest with angular unconformity or nonconformity
on a basement of folded Precambrian to Early Devonian sedimentary
rocks and Late Devonian to Early Carboniferous granitic rocks.
Within the basement, geanticlines of Precambrian rocks are
overlain by a Middle and early Late Cambrian "eugeosynclinal"
association associated with ultramafic rocks and a silicic volcanic
"arc." After Late Cambrian movements, especially around the
Tyennan Geanticline, local marine silts formed and were followed by
widespread alluvial fan deposits derived from the recently uplifted
geanticlines. The alluvial fan deposits initiated shallow, stable
shelf deposition of shelly sediments in central and western Tasmania
which continued into the Late Ordovician. Subsequently an alternation
of sandstone and siltstone deposition under less stable conditions
continued into the Early Devonian.
From Early Ordovician to Early Devonian unstable shelf deposits
of turbidite type were formed and are now found in north-eastern
Tasmania.
Earlier rocks were folded during the several phases of the
Tabberabberan Orogeny in Early and Middle Devonian time. Subsequently
granitic batholiths and some ore bodies were emplaced.
Deposition of the Parmeener Super-group in the "Tasmania Basin"
began in the Late Carboniferous as an extensive ice sheet covering a
basement with a relief of several hundred metres began to melt.
After this initial glacial episode, deposition of the Parmeener Supergroup
may be considered as an alternation of shallow marine and continental, largely fluviatile, deposition.
Silt was the commonsediment formed in the sea but sands, rare gravels and calcareous
rocks were also deposited. The marine sediments are fossiliferous,
in places richly so. The marine sediments are characterised
throughout by the presence of megaclasts which can be demonstrated
to be dropstones, and of glacial origin in at least some cases.
The fossils are numerous but not so taxonomically diverse as in contemporaneous
•rocks elsewhere in Australia. This also suggests a
cooler sea than elsewhere. Coal occurs at two main levels in the
Permian part of the Super-group and suggests a humid (and probably
cool) climate. From Late Permian to Late Triassic inclusive,
Tasmania was the site of extensive fluvial plains supporting
vegetation initially glossopterid but subsequently filicalean,
corystospermacean and then cycadalean. The climate was probably
humid during this interval except for a short period early in the
Triassic when red beds and abundant clay pellet conglomerates suggest
at least temporary dessication. The clay-pellet conglomerates
contain tetrapod bones in many places, the tetrapods suggesting a
land connection with South Africa, India and southern China.
At some time after deposition the beds of the Parmeener Supergroup
were folded into a broad syncline with minor local folds.
Dolerite intrusions during the Jurassic and faulting during the
Tertiary, especially the Early Tertiary, disrupted the Parmeener
Super-group. Pleistocene glaciation in central and western Tasmania
has stripped rocks of the Parmeener Super-group from older rocks and
super-imposed Pleistocene glacial features on a Late Carboniferous
glacial surface.

Item Type:	Thesis - Unspecified
Authors/Creators:	Banks, M. R.(Maxwell R.)
Keywords:	Geology, Stratigraphic, Geology
Copyright Holders:	The Author
Copyright Information:	Copyright 1976 the Author - The University is continuing to endeavour to trace the copyright owner(s) and in the meantime this item has been reproduced here in good faith. We would be pleased to hear from the copyright owner(s).
Additional Information:	Thesis (D.Sc.)--University of Tasmania, 1977. Cover title: The geological history of Tasmania during the palaeozoic era. Includes bibliographies
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