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Advances in Regolith
In: Roach I.C. ed. Advances in Regolith, pp. 126-130. CRC LEME
126
LONGITUDINAL AND TRANSVERSE DUNES OF THE LAKE EYRE
BASIN
Kathryn E. Fitzsimmons
CRC LEME, Department of Geology, Australian National University, Canberra, ACT, 0200.
INTRODUCTION
Arid landscapes provide a sensitive record of environmental change. The geomorphic evolution of the
extensive desert dunefields of central Australia can be used as a proxy for climate change during the late
Quaternary period. The transverse and longitudinal dunes downwind of major playas are particularly
sensitive to small changes in both climate and hydrology. Understanding the interaction between the two
dune types is important for the interpretation of timing and conditions required for dune building.
At present, the evolution and dynamics of the Australian desert dunefields, which occupy well over one third
of the surface area of the continent, are poorly understood. This project aims to address at least part of this
issue by investigating a regional history of aeolian deposition and processes over time. The focus of this
study is on the geomorphology of the transverse and longitudinal dunes within the Strzelecki, Tirari and
southern Simpson Deserts, in particular those areas downwind of the major playa Lakes Frome, Callabonna,
Gregory and Eyre.
READING AEOLIAN LANDSCAPES: PROJECT METHODOLOGY
The Australian continental dunefield is a fossil landscape comprising stable dune forms, some with active
crests. Dune spacing, width, height and length vary across the basin and may be related to available sediment,
mineralogy, topography, vegetation and climatic conditions (Wasson et al. 1988). The stratigraphy of the
dunes, determined from eroded blowouts and rare section exposures, gives information about episodes of
dune activity and pedogenesis.
The regional landscape evolution will be interpreted based on multispectral, high resolution ASTER
(Advanced Spaceborne Thermal Emission and Reflection Radiometer) and Landsat7 satellite imagery.
Geomorphic maps of the region are currently being derived from these data. The comprehensive regional
coverage of landforms allows an overview of the spatial relationships between different landforms, in
particular classifications of longitudinal dunes, which are not able to be observed on the ground. The 15m
spatial resolution of the visible and near infrared bands of the recently acquired ASTER imagery is
particularly useful in delineating individual dune morphology in plan view. In addition, the spectral
characteristics of landform features may be identified using different combinations of the 14 and 7 spectral
bands of the ASTER and Landsat data, respectively. For example, images compiled from short-wave infrared
spectral bands in the ASTER dataset allow identification of areas where the water table is close to the surface
(Harper 2002).
Field observations will include studies of dune morphology and internal stratigraphy. The sedimentology of
the longitudinal and transverse dunes will also be investigated, yielding insights into the relationships
between grain size, mineralogy, sediment source and climatic conditions. Initial samples from selected
strategic dune sites have been taken for the preparation of oriented thin sections and grain mounts.
The geomorphic history will be placed within a chronologic framework based mainly on optical dating
techniques, with additional data from amino acid racemisation of bird eggshell found within the dune
stratigraphy. Initial reconnaissance activities have revealed several promising sites within the field area for
stratigraphic study and systematic luminescence dating sampling. The chemical preparation of this first set of
samples is underway, and will be discussed at the symposium in November. Dates derived using optical
dating techniques on samples from the Lake Frome region, presented in this abstract, are the result of
previous unpublished work by the author.
INTRODUCING THE DESERT DUNES OF THE LAKE EYRE BASIN
The Lake Eyre basin is a large internally drained basin encompassing a significant proportion of inland
Australia (1.2 million km
2
), and is defined by the drainage catchments of Lakes Eyre and Frome in
northeastern South Australia (S. DeVogel pers. comm.). The region is arid to semi-arid, and comprises
various desert landforms including large playas and widespread desert dunes. The large, dry playa Lakes
Eyre, Gregory, Blanche, Callabonna and Frome are linked by a network of creeks, smaller playas and
Advances in Regolith
K.E. Fitzsimmons. Longitudinal and transverse dunes of the Lake Eyre Basin.
127
depressions, and contain water only during rare occasions of excessive rainfall. The longitudinal dunefields
forming the Simpson, Tirari and Strzelecki Deserts occur downwind of this chain of extensive playas, which
encircle the upland region of the Flinders Ranges. The areas of interest to this study fall within those areas of
the Strzelecki and Tirari Deserts downwind of Lakes Frome, Callabonna and Gregory, the eastern edge of
Lake Eyre including the source bordering dunes of the Warburton Creek, and the northern section of the
Strzelecki Desert (Figure 1).
Longitudinal dunes
Longitudinal dunes are elongated
ridges of aeolian sediments, which
run parallel to the resultant vector of
the sand shifting winds (King
1960). The extensive longitudinal
dune systems of the Lake Eyre
basin vary in orientation, reflecting
variations in the resultant sand-
shifting wind direction at the time
of dune formation (Jennings 1968).
Longitudinal dunes are oriented
west-southwest to east-northeast in
the south of the region near Lake
Frome, rotate towards the north near
Moomba in the central Strzelecki
dunefield, and extend north-
northwest in the downstream
Warburton Creek area.
Longitudinal dunes converge at “Y”
shaped junctions within the longer
dune systems and at points of
upwind dune genesis close to the
transverse dunes (Bowler & Magee
1978). Convergence occurs in the
downwind direction, and indicates
the termination of individual ridges
and dune amalgamation, possibly
due to a diminishing sediment
supply (King 1960). The processes
responsible for dune convergence
and their implications for desert
dune dynamics are not well understood, and further work on their geomorphology is required.
The sedimentological characteristics of the longitudinal dunes in the Lake Eyre basin are variable, ranging
from relatively pale, clay rich dunes in areas proximal to the playas and lunettes, to strongly red, dominantly
quartz sand dunes east of the Strzelecki Creek and in the northern Simpson Desert (Wasson 1983). The
internal stratigraphy of longitudinal dunes preserves at least two phases of dune building and subsequent
pedogenesis depending on location within the basin (Figure 2). Modern active crests are common throughout
the region, and vary in thickness depending on the season and location.
Transverse dunes
Transverse dunes, by definition, are oriented perpendicular to the resultant sand shifting winds, and occur
within the dunefields, generally immediately downwind of playas, creeks and clay flats. Transverse dunes
within the region include lunettes, as described below, and source bordering dunes, which border the
downwind banks of the largely ephemeral streams within the basin.
Lunettes are large clay rich dunes, crescentic in outline, forming along the downwind shorelines of lakes and
playas which are, or have been, subject to fluctuating groundwater levels. Unstable hydrologic conditions
such as these allow the efflorescence of salts in the capillary zone of the water table, resulting in the
formation of sand sized clay pellets which are then transported by wind, together with other mobile particles,
to form a transverse dune (Bowler 1983). The lunettes downwind of most large playas are compound
features, incorporating clay rich lunette-type morphologies overlying quartz rich shoreline dunes formed by
Figure 1: northeast South Australia, including the major playas and
Strzelecki, Tirari and southern Simpson Desert dunefields (after Coats
& Blissett 1971). General longitudinal dune orientation is indicated.
Study areas are highlighted in grey.
Advances in Regolith
K.E. Fitzsimmons. Longitudinal and transverse dunes of the Lake Eyre Basin.
128
wave action during high lake levels (Figure 3). In some areas, such as the eastern (downwind) Lake Frome
region, multiple transverse dune systems have developed. Each lunette system comprises several smaller
parallel transverse dune crests. These are interpreted to represent different generations of lunette development
as the lake basin diminished in size over time. This interpretation is supported by ASTER satellite imagery
which shows longitudinal dunes, of varying lengths depending on the distance from Lake Frome, generating
downwind from the transverse dunes.
Figure 3: environmental conditions required for the formation of: A. Quartz rich shoreline dunes; B. Saline
clay dunes; C. Soil profiles developed on the surface of a clay lunette. Adapted from Bowler (1983).
Figure 2: a schematic cross section of a typical longitudinal dune in the Lake Eyre basin. This particular
example was observed in the Lake Frome region. The internal structures of palaeosols overlying the
palaeodune sediments, and a modern mobile crest, are outlined.
Advances in Regolith
K.E. Fitzsimmons. Longitudinal and transverse dunes of the Lake Eyre Basin.
129
RECONNAISSANCE AND PAST WORK
This project is still in its initial stages; therefore limited data are available for discussion within this abstract.
A study of the local geomorphology of the northeast Lake Frome area, including a chronology using optical
dating, was undertaken in 2002. Significant observations arising from that work are summarized here.
Observations arising from preliminary reconnaissance and sampling carried out in the Innamincka area in
May this year is briefly discussed below.
Lake Frome
In the area northeast of Lake Frome, four transverse dune systems are clearly delineated on satellite images,
and are oriented approximately north-south. Crests become more irregular towards the east of these large
lunette systems and develop into parabolic forms oriented to the northeast. These forms appear to be a hybrid
between transverse and longitudinal dune, and strongly indicate a genetic morphological relationship
between the two major dune types. Individual longitudinal dunes appear to derive from different crestal lines
within the lunette system, implying different stages of initiation of the longitudinal forms.
Palaeodune sediments within both the longitudinal and transverse dunes have a significant clay component,
derived from the clay-rich interdune swales and elongate clay flats. This has important hydrologic
implications requiring relatively high water tables to assist in clay deflation for the formation not only of
transverse lunettes, but also longitudinal dunes. Dune mineralogy also comprises a dominant quartz fraction,
with the addition of minor fresh feldspars and heavy minerals. The presence of feldspars indicates young
aeolian sediments relatively close to their original source rock, and the proximity of this area to the
crystalline rocks of the northern Flinders Ranges strongly suggests these to be the source. Studies of dune
provenance (Pell 1994) support this conclusion. The preservation of laminations within both transverse and
longitudinal dune sediments indicates that the sediments were deposited rapidly.
Optically stimulated luminescence dating has defined a chronology of a representative longitudinal and
transverse dune within the Lake Frome region (Figure 4).
Three palaeodune horizons were sampled within a
transverse dune and yielded ages of approximately >100ka (saturated), 57ka and 22-14.5ka (from base to top
of horizon). Ages of approximately 35ka and 11ka were derived from samples within two palaeodune
horizons of a longitudinal dune, the former sample representing a palaeosol which was correlated with the
middle (57ka) dune horizon of the transverse dune. The horizons dated at approximately 57ka and 20ka allow
a tentative correlation with increased aeolian activity elsewhere on the Australian continent, and glacial
periods interpreted from ice core data in Antarctica. The last major dune building event around 11ka yielded
the most precise dates, and suggests a significant change to arid conditions conducive to dune building. Other
regions of Australia do not yet reflect similar dune building events; this episode therefore warrants further
investigation, and may have significant implications for climatic and environmental evolution.
Figure 4. Optical
ages, sample
locations and
stratigraphy of a
representative
longitudinal and
transverse dune
in the northeast
Lake Frome area.
Advances in Regolith
K.E. Fitzsimmons. Longitudinal and transverse dunes of the Lake Eyre Basin.
130
Innamincka
The Innamincka area is located toward the downwind margins of the Strzelecki Desert, and is a region
containing an interesting juxtaposition of landform types visible on both satellite imagery and in the field.
Close to the township of Innamincka, the Strzelecki Creek diverges southwards from the main, east flowing,
Cooper Creek channel, and forms the western margin of the longitudinal dunefield. The formation of linear
dunes is apparently halted to the south of Innamincka by a noticeable rise in the topography, observed as low
relief gibber plains. The longitudinal dunes bound by the south of this plain, west of the Strzelecki Creek,
exhibit highly variable morphologies, from closely spaced, highly disorganized forms converging frequently
at “Y” shaped junctions, to widely spaced, more regular ridges overlying a gibber substrate and regular, more
closely spaced dunes more typical of the Strzelecki dunefield at a broader scale. More detailed investigation
of this complex geomorphology using high spatial resolution satellite imagery is planned, and will augment
field work to be conducted in the area in October this year. An understanding of the factors influencing
longitudinal dune morphology will be gained as a result of this work, which will also be placed within a
chronologic framework using optical dating.
REFERENCES
BOWLER J.M. 1983. Lunettes as indices of hydrologic change: A review of Australian evidence.
Proceedings of the Royal Society of Victoria 95, 147-168.
BOWLER J.M. & MAGEE J.W. 1978. Geomorphology of the Mallee region in semi-arid northern Victoria
and western New South Wales. Proceedings of the Royal Society of Victoria 90, 5-25.
COATS R.P. & BLISSETT A.H. 1971. Regional and economic geology of the Mt Painter province.
Department of Mines Geological Survey of South Australia, Bulletin 43.
HARPER K.L. 2002. Geologic and geomorphic applications of ASTER satellite imagery, northern Flinders
Ranges, South Australia. BSc (Hons) Thesis, School of Earth Sciences, University of Melbourne,
unpublished.
JENNINGS J.N. 1968. A revised map of the desert dunes of Australia. Australian Geographer 10, 408-409.
KING D. 1960. The sand ridge deserts of South Australia and related aeolian landforms of the Quaternary
arid cycles. Transactions of the Royal Society of South Australia 83, 99-108.
PELL S.D. 1994. The provenance of the Australian continental dunefields. PhD Thesis, Research School of
Earth Sciences, Australian National University, unpublished.
WASSON R.J. 1983. Dune sediment types, sand colour, sediment providence and hydrology in the Simpson-
Strzelecki dunefield, Australia. In: BROOKFIELD M.E. & AHLBRANDT T.S. eds. Eolian
sediments and processes. Elsevier Science Publishers, Amsterdam, 165-195.
WASSON R.J., FITCHETT K., MACKEY B. & HYDE R. 1988. Large-scale patterns of dune type, spacing
and orientation in the Australian continental dunefield. Australian Geographer 19(1), 89-104.
Acknowledgments: This research is supported by an Australian Postgraduate Award and CRC LEME
Scholarship. Thanks also to Dr John Magee (ANU) for valuable reconnaissance and augering assistance in
the field, and to Barton Smith (ex-University of Melbourne) for guidance with the optical dating last year.
