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| Titel |
Dune formation on the Cooper Creek floodplain, Strzelecki Desert, Australia
- first results of morphodynamic simulations |
| VerfasserIn |
Mateusz Kryger, Olaf Bubenzer, Eric Parteli |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250143973
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| Publikation (Nr.) |
 EGU/EGU2017-7746.pdf |
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| Zusammenfassung |
| Linear Dunes, which align longitudinally to the resultant wind vector, are the prevailing type
of the south-north trending and partially vegetated dunes in the Strzelecki Desert, Australia.
However, particularly on the Cooper Creek floodplain near Innamincka, striking complex
dune features consisting of transversely oriented east-west trending dunes occur. These
transverse dunes extend over several kilometers and are superimposed by linear dunes that
elongate northwards and are separated by sandy swales.
The aeolian features in the Strzelecki Desert are the result of interrelated late quaternary
aeolian and fluvial activity and serve, thus, as archives providing information about variations
in palaeoclimate and potential changes in fluvial sediment supply and wind strength and
directionality. However, since the dunes are currently mostly stabilized by vegetation, it is
uncertain whether their formation can be explained by the contemporary wind systems. To
understand the dynamic processes underlying the genesis of the dune field in the Strzelecki
Desert, the role of vegetation and the wind regimes leading to the observed dune patterns
must be elucidated.
Here we investigate the formative processes of the dune features occurring on the Cooper
Creek floodplain by means of morphodynamic modeling of aeolian sand transport and dune
formation in presence of vegetation growth. Our simulations show that a source-bordering
dune can be formed out of the sediments of seasonally exposed sandbars of the
palaeo-Cooper system by a unidirectional wind, which explains the emergence of the
transverse dunes in the field. Moreover, a shift in the wind regime to obtuse bidirectional
wind flows combined with a rapid decrease in the vegetation cover leads to the
formation of linear dunes on the surface and in the lee of the transverse dunes.
These linear dunes elongate over several kilometers downwind as a result of the
seasonal wind changes. The dune shapes obtained in our simulations agree well with
the real dune morphologies when a low vegetation growth rate is applied in the
model.
Although geochronological investigations, reported in the literature, on the Cooper
Creek floodplain did not show the linear dunes declining in age downwind (which
suggests the adjacent swales or the transverse dune to be the sediment source), our
simulations show that strikingly similar linear dune morphologies can be obtained by
sediment influx due to saltation alone. In this case, the bars of the palaeo-Cooper
system might as well have served as the sediment source for the formation of the
linear dunes. Therefore, our results suggest that a long-distance transport extension
model could also explain the linear dune formation, while previous geochronological
investigations supported the wind-rift vertical extension and wind-rift vertical accretion
models.
The morphodynamic simulations may thus not only help to reconstruct the
palaeoenvironment of the northern Strzelecki Desert, but also provide insights for the
interpretation of the sediment archives located on the Cooper Creek alluvial fan. |
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