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LONGITUDINAL AND TRANSVERSE DUNES OF THE LAKE EYRE BASIN

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Abstract

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
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.
ResearchGate has not been able to resolve any citations for this publication.
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Examines sediments and morphology within major colour zones which have been interpreted as the result of progressive reddening and ageing of sand grain coatings downwind from sources of sand. Also the processes of sediment mobilization for dune construction are examined. The hypothesis of downwind ageing of dune sand is critically tested and found to be inadequate.-after Author
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As a contribution to understanding the morphogenesis of the Australian continental dunefield, maps are presented of the main types of dunes, their orientation and mean spacing using the best available sources of data. Major features on previous maps of the Australian dunefield are verified and new information has been obtained. The anticlockwise whorl of dunes has been found to close on both its eastern and western ends. Dunes extend as far north as 16°S and over large parts of the far south‐west of Western Australia. Distributions of dune types are related to former vegetation cover, climate, supply of sand and directional variability of formative winds. Previously documented relationships between dune spacing, height, equivalent sand thickness (EST) and the texture of surfaces over which sand is transported are used to partially explain the map of mean dune spacings. The spatial distribution of EST, and mineralogic and sedimentologic evidence show that aeolian sediment in the Australian dunefield has travelled only short distances.
Thesis
This study of the Australian continental dunefields focuses on the origin of the sand-sized material presently in the dunes and on the distances of its transport within and between dunefields. The sand dunes which currently make up the Australian continental dunefields are part of a sedimentary system which has been developed over millions of years. This system has received sediment from large numbers of protosource areas both within and outside the present margins of Australia. Some of these protosource areas underlie the current dunefields while others are hundreds of kilometres away, indicating significant distances of sand transport. Each individual dunefield comprises material from several different protosource areas. Material from certain protosources is widespread over the entire desert, while that from others is found concentrated only in particular regions. It is suggested that the mechanisms for the transport of sand from these protosource areas into the sedimentary basins currently underlying many of the dunefields involved tluvial activity and marine transgressions and regressions. Most of this sedimentary transport is believed to have occurred prior to the change to a more arid climatic regime in Australia during the Late Tertiary. Following this climatic change and commonly coincident with periods of glaciation, the Australian continental dunefields have been formed through the vertical . corrasion of local/underlying sedimentary material, accompanied by lateral .displacement of sand and upward growth of nearby ridges. Very little evidence has been found in this study to suggest significant distances of aeolian transport of sand. The main function of wind in the Australian dunefields is thought to be in the shaping of dunes. At the present time, the Australian continental dunefield is largely stabilised, and all but the crests of dunes are covered by vegetation, thereby reducing the possibility of aeolian transport. The determination of protosource areas for the desert sands has been based predominantly on U-Pb SHRIMP studies of zircon grains separated from the sand samples. This method provides direct evidence on provenance, albeit the provenance of zircon grains and not bulk sand samples. Studies of the oxygen-isotope values of quartz have also provided useful information on sand protosource areas, although this technique was hampered by the large numbers of protosource areas involved and by the presence of small amounts of low-temperature quartz in many samples. Characterisation of sands from the major dunefield areas in Australia in terms of their physical and mineralogical properties shows that there are significant differences in these parameters across individual dunefields. These differences are commonly found in sands from dunes overlying the boundaries between different underlying rock types. The apparent lack of mixing between sands derived from different underlying rock types indicates that transport within dunefields has not been substantial. On a wider scale, despite the possibility of the long-distance aeolian transport of sand around the continental "whorl" of the Australian dunefields, there appears to have been only a limited amount of such transport between dunefields. Similarities between the characteristics of sands from dunes directly overlying basement areas and the properties of the basement areas themselves, suggest that dune sands were derived from the weathering of the underlying bedrock, and could therefore be considered as remnant lag deposits. Dunes in these areas tend to be smaller, more scattered, and in many cases, merge with sand plains. In contrast to this, the major dunefield areas in Australia overlie sedimentary basins where sand supply is plentiful. In general, there has been negligible recent (post Late Tertiary) sedimentary input to the Australian continental dunefields. The exception to this is in the Simpson, Strzelecki and Tirari Deserts, where rivers and creeks flowing into the Lake Eyre Drainage Basin have deposited small amounts of sediment. After its fluvial deposition, this material has not been transported significant distances within the dunefields and is concentrated in areas near the rivers and creeks. In some areas of the southeastern Simpson and Strzelecki Deserts however, it is thought that limited amounts of aeolian transport of sand occur, although this is considered to be an exception to the general stability of the dunefields and is only very localised.
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A variety of transverse dune types occurs on the eastern margins of lake basins across southern Australia. Known collectively as 'lunettes', these range in composition through quartz-rich, sandy clay, gypseous clay to nearly pure gypsum. The origin of the pure quartz dunes formed under lake-full conditions, is distinct from that of the clay or gypsum-rich variety which formed by deflation from adjacent lake floors. In the lunette forming processes the role of salts and groundwater is critical. Descriptions of modern examples from Texas provide analogues of clay dune building that affected hundreds of small basins across southern Australia during late Pleistocene time at the height of the last glacial episode.-from Author
Regional and economic geology of the Mt Painter province. Department of Mines Geological Survey of South Australia, Bulletin 43 Geologic and geomorphic applications of ASTER satellite imagery, northern Flinders Ranges, South Australia. BSc (Hons) Thesis, School of Earth Sciences
  • R P H Blissett A
  • K L Harper
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.
Lunettes as indices of hydrologic change: A review of Australian evidence Geomorphology of the Mallee region in semi-arid northern Victoria and western New South Wales
  • References Bowler
  • J M Bowler
  • J M Magee
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.
The provenance of the Australian continental dunefields Australian National University, unpublished Dune sediment types, sand colour, sediment providence and hydrology in the Simpson-Strzelecki dunefield, Australia Eolian sediments and processes
  • Pell S D J Wasson R
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.
Regional and economic geology of the Mt Painter province. Department of Mines Geological Survey of South Australia
  • P Coats R
  • H Blissett A
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.