University Of Tasmania
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A collection of papers mainly concerning the geological history of Tasmania with special reference to events during the palaeozoic era.

posted on 2023-05-27, 08:35 authored by Banks, M. R.(Maxwell R.)
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 ‚Äörocks 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."


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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). Thesis (D.Sc.)--University of Tasmania, 1977. Cover title: The geological history of Tasmania during the palaeozoic era. Includes bibliographies

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