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| Titel |
The U-Th isotopic composition of Australian aeolian deposits: implications for weathering and sediment transport timescales |
| VerfasserIn |
Heather Handley, Simon Turner, Paul Hesse, Puthiyaveetil Othayoth Suresh, Michael Turner |
| 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 |
250153446
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| Publikation (Nr.) |
 EGU/EGU2017-18423.pdf |
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| Zusammenfassung |
| In order to quantify how fast a landscape responds to tectonic, climatic and human factors,
accurate weathering rates and soil and/or sediment ages are required. The uranium-series
(U-series) isotopes are a valuable tool for deriving the timescales of weathering and erosion
processes. The impact of dust on calculated U-series isotope residence timescales of soil and
fluvial sediment has received little attention to date, despite the fact that the typical grain size
of aeolian material overlaps with that of interest in such studies, particularly for the
comminution approach (<50 microns). The potential of aeolian material to modify bulk soil
or fluvial U-series signatures will depend on its U-series isotopic ratios and its volume
percentage contribution to the deposit. We have determined the U-series isotopic ratios of
dust from the 2009 Sydney dust storm and of several aeolian deposits in Australia.
We show that there is significant isotopic disequilibria in the samples, which are
characterised by (230Th/238U) activity ratios > 1 and (234U/238U) activity ratios < 1. The
finer-grained fractions (<5 microns) have higher (230Th/238U) but comparable
(234U/238U) to the coarser-grained fractions (5-53 microns) of the same samples.
This study shows that the aeolian component cannot be assumed to be in isotopic
equilibrium and needs to be considered when calculating weathering and erosion
timescales. |
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