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Abstract

The sequence of interbedded mudstone, siltstone and very fine sandstone in the
Strahan Quadrangle, correlated with the Bell Shale is at least 500 m thick. Two broad
associations can be defined. The ratio of very fine sand to mud in the lower association
is between 3:2 and 2:3 whereas in the upper association only occasional thin
sandstone beds occur. Sedimentary structures such as lenticular bedding, symmetrical
ripple marks and the lack of deep water sedimentary features suggest that deposition
took place in shallow water. This is supported by palaeontological evidence. Some
scouring and upward fining beds suggest that deposition from waning currents occurred
sporadically within this environment.
The Bell Shale correlate has been folded during two phases. The first phase produced
folds plunging between 300 and 900 NW and the second phase produced folds
plunging shallowly WNW or ESE. Cleavage was developed only locally during each phase.
Folds of both phases produced a primary axial surface cleavage and the second phase
produced crenulation cleavage in some areas. The amplitude of folds produced during
the first phase decreases towards the centre of the basin. The locus of strain during
the second phase of deformation was along the Firewood Siding Fault. The existence
and timing of these deformation events demonstrates the uniformity in orientation of
Tabberabberan structures throughout north and western Tasmania.

Item Type:	Article
Authors/Creators:	Baillie, PW and Williams, PR
Keywords:	Tasmania, Hobart, Royal Society of Tasmania, RST, Van Diemens Land, natural history, science, ecology, taxonomy, botany, zoology, geology, geography, papers & proceedings, Australia, UTAS Library
Journal or Publication Title:	Papers and Proceedings of the Royal Society of Tasmania
ISSN:	0080-4703
Collections:	Royal Society Collection > Papers & Proceedings of the Royal Society of Tasmania
Additional Information:	Copyright Royal Society of Tasmania
Item Statistics:	View statistics for this item

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