Journal and Proceedings of
The Royal Society of New South Wales
Volume 120 Parts 3 and 4 [Issued May, 1988]
CONTENTS
AUTHORS & TITLES
PAGES
Veevers, J.J., Earth History of the Southeast Indian Ocean and the Conjugate Margins
of Australia and Antarctica
57-70
(Clarke Memorial Lecture, 1987)
Dulhunty, J.A., Middlemost, E.A.K. and Beck, R.W., Potassium-Argon Ages,
Petrology and Geochemistry of Some Mesozoic Igneous Rocks in Northeastern New 71-90
South Wales
Akpododje, E.G., The Mineralogical Relationship between some Arid Zone Soils and
their Underlying Bedrocks at Fowlers Gap Station, New South Wales (NSW) Australia
Riley, S.J. and Henry, H.M., A Geophysical Survey of Culoul and Mellong Creek Valley
Fills: Implications for Valley Development in Sandstone Terrain
Henry, H.M., Mellong Plateau, Central Eastern New South Wales: an Anomalous
Landform
Brophy, J.J., Lassak, E.V. and Boland, D.J., Volatile Leaf Oils of the Two Subspecies
of Melaleuca acacioides F. Muell.
Katz, M.B., Analysis of a Small-Scale Fault at Bingi Bingi, NSW, and speculations on
its relationship to a Large-Scale Transform Fault of the Tasman Sea
91-99
101-115
117-134
135-139
141-146
ABSTRACTS OF THESES:
[Opening in a new page]
Pollard, G.H., A Stochastic Analysis of Scoring Systems
Gibbons, D.S., Ultra-Violet and Tactile Pollination Guides of Some Fabaceae
147
148
pp.57-70
Earth History of the Southeast Indian Ocean and the Conjugate Margins of Australia
and Antarctica
J. J. Veevers
[Clarke Memorial Lecture, delivered to the Royal Society of New South Wales, 5th August, 1997,
at Macquarie University.]
Abstract. Australia and Antarctica occupied the eastern part of Gondwanaland until their
breakup by the growth of the Southeast Indian Ocean in the mid-Cretaceous (96 Ma). The
growth of the ocean was preceded by a stage of separation of the land areas of the continents
that started in the mid-Jurassic (160 Ma). This separation was effected by 360 km of extension
(6 mm/year) by normal and listric faulting in a 600 km wide zone represented today by the
submerged continental margins. In the first phase of seafloor spreading, from the midCretaceous to the Eocene (45 Ma), the Southeast Indian ocean grew to a width of 500 km at the
slow rate of 10 mm/year, and in the second phase grew another 2600 km at a fast rate of
60 mm/year. Even so, Australia and Antarctica remained side by side along the N-trending
transform faults in the east until the Oligocene (35 Ma). With their subsequent definitive
separation, the Circum-Antarctic Current was able to flow unimpeded through the oceanic gap
with the result that Antarctica became isolated from the surface water of the rest of the world
ocean and this contributed to its intense glaciation.
Return to Top
pp.71-90
Potassium-Argon Ages, Petrology and Geochemistry of some Mesozoic Igneous Rocks
in Northeastern New South Wales
J.A. Dulhunty, E.A. Middlemost and R.W. Beck
Abstract. Twelve specimens of volcanic and subvolcanic rocks were collected from outliers in
the Wellington-Muswellbrook-Narrabri region of northeastern N.S.W. They were originally
assumed to be of Tertiary age as they occurred in close field association with volcanic rocks of
established Tertiary age. However, anomalies were perceived as to their possible misconceived
age relative to ages of erosion surfaces onto which they were extruded, and sediments into which
they were intruded. K-Ar dating proved all specimens collected to be of Mesozoic age, and the
establishment of high-level Mesozoic erosion surfaces, previously regarded as Tertiary, has
simplified some aspects of landscape development in northeastern N.S.W.
The 12 specimens are all silica undersaturated alkaline rocks that have many geochemical,
mineralogical and petrographic similarities. The more primitive basanites, alkali basalts, hawaiites
and tephrites all plot as a coherent group in the "within-plate" field on the Ti-Y-Zr discriminant
diagram. Spidergrams illustrate the broad chemical similarities among the least differentiated
specimens. This study augments the concept that there was widespread alkaline volcanism in
northeastern N.S.W. over an extensive period during the Mesozoic.
Return to Top
pp.91-99
The Mineralogical Relationship between some Arid Zone Soils and their Underlying
Bedrocks at Fowlers Gap Station, New South Wales (N.S.W.) Australia
E. G. Akpokodje
Abstract. The clay mineralogy of metasedimentary quartzites, phyllitic shales and their overlying
desert loam soils from Fowlers Gap Station, Australia, were studied. The mineralogic variations
in the rock sequence may be attributed to broad changes in both provenance and the
environment of deposition. The smectite, illite and chlorite found in the soils formed on the
phyllitic shales were all inherited from the bedrock. Kaolinite, on the other hand, is the
weathering product developed under a subtropical climate in the Tertiary. The same clay
minerals, except chlorite, also occur in the soils developed on the crest and colluvial slopes of the
quartzites. Kaolinite was inherited from the bedrock, whereas significant proportions of the
smectite and illite are considered to have been partly formed from the intercalated clay and the
closely associated phyllitic shales, where they occur as relics on the weathered Tertiary surface.
Return to Top
pp.101-115
A Geophysical Survey of Culoul and Mellong Creek Valley Fills: Implications for Valley
Development in Sandstone Terrain
S.J. Riley and H.M. Henry
Abstract. Geophysical surveys of the Mellong Plateau valley fills supplemented and calibrated
against limited drilling revealed a system of wide valleys with up to 10 metres of fill. Streams with
dimensions similar to those that presently occupy the valley floors may have excavated the
valleys. If they did then there has been a complex history of valley aggradation and incision with
the most recent period being one of aggradation.
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pp.117-134
Mellong Plateau, Central Eastern New South Wales: An Anomalous Landform
H.M. Henry
Abstract. The Mellong Plateau, between Colo Heights and Putty in central eastern New South
Wales, lies east of the topographically higher Lapstone Monocline (Fig. 1); through the latter the
plateau's creeks drain west in transverse valleys against the regional topographic gradient. In spite
of its location on top of the Macdonald River – Wollemi Creek drainage divide, the plateau is
extensively alluviated, large swamps occurring on all main creeks and tributaries. The plateau's
anomalously low relief; wide, shallowly incised valleys; valley-side embayments; and westerlyflowing transverse drainage are described. More than 200 samples of fill were collected to depths
up to 10 m; 71 of these were analysed granulometrically. Clay beds were less common in the fill
than anticipated; clayey and muddy sand predominated. Difficulties were experienced in
determining the alluvium/colluvium and bedrock boundaries, so seismic and resistivity methods
were used to supplement drilling, and a limited coring programme was undertaken with thinsection examination of core fabrics. Alternative explanations of Mellong Plateau transverse
drainage are discussed. Gaps in present knowledge, e.g. the age of the Lapstone Monocline,
speculative existence of a vanished former cover, do not permit any positive conclusion, but
genetic diversity seems indicated.
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pp.135-139
Volatile Leaf Oils of the Two Subspecies of Melaleuca acacioides R Muell.
J.J. Brophy, E.V. Lassak and D.J. Bolland
Abstract. An examination of the volatile leaf oils of two recently described subspecies of
Melaleuca acacioides, ssp. acacioides and ssp. alsophila, has shown substantial chemical differences
between them. Subspecies acaciaides from northern Queensland is almost exclusively
sesquiterpenic with α- and β-selinenes accounting for about 80% of the oil, whilst subspecies
alsophila from northern Western Australia is almost entirely monoterpenoid in character with pcymene, geranial and terpinen-4-ol, each approximately 20%, as its main oil components.
Return to Top
pp.141-146
Analysis of a Small-Scale Fault at Bingi Bingi, N.S.W., and Speculations on its
Relationship to a Large-Scale Transform Fault of the Tasman Sea
M.B Katz
Abstract. South of Moruya, at Bingi Bingi Point, N.S.W., a NW trending aplite dyke of the
Devonian Tuross Head Complex has been sinistrally drag folded by a ENE steeply dipping fault.
A structural analysis of the faulted, drag folded dyke provides a preliminary solution that
speculates by scale transfer, that the fault may be part of a Riedel shear system related to
movements along a transform fault developed during the opening of the Tasman Sea which
subsequently controlled later mafic dykes emplaced during the rifting of Australia from
Antarctica.