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Abstract

A geological study has been made of 130 square
miles of the Middle Dement Valley between New Norfolk
and Hamilton, Tasmania. A Permian sub-greywacke type
sequence consists of some 1300 feet of sandstone, siltstone,
mudstone and limestone, deposited on a stable to
mildly-unstable shelf. Disconformably overlying the
Permian are rocks belonging to the Triassic ystem
which have been grouped tentatively into three formations.
The Permian and Triassic are extensively and
complexly injected by dolerite and mineralogical variations
from the normal tholeiitic dolerite to granophyre
have been traced. Liquid immiscibility is present
towards the base of the sill. The Jurassic structure
Is interpreted as cauldron subsidence faulting accompanied
by dolerite intrusion as transgressive to concordant
sills, lopolithic near the root zone. Various
Tertiary faults combine to form a stepped graben, the
axis of which trends NW - SE on echelon, resulting in
the formation of a chain of lakes and lowlands. In
late Tertiary times, large outpouring of olivine basalt
and associated tuffs at least 350 feet thick overran
the lakes and filled the valley to a depth of some
hundreds of feet. The basalts have been mapped into several flows. Five periods of volcanism have been
recognized, the inter-basaltic periods being marked
by either lake sediments or fossil forests. The graben
faulting controlled the drainage pattern both during the
pre-basaltic times and subsequently.

Item Type:	Thesis - Unspecified
Authors/Creators:	Anandalwar, NA
Keywords:	Geology
Copyright Holders:	The Author
Copyright Information:	Copyright 1957 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 (M.Sc.)--University of Tasmania, 1958
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