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"PhD Opportunity in Isotope Geochemistry at the University of Strasbourg –<br>
"Characterization and modeling of sediment transport in the alluvial plains<br>
coupling U- and Th-series disequilibria with B and Li stable isotopes"" has<br>
been updated by Damien Lemarchand on CZEN.org.<br>
<br>
The<br>
sediments carried by rivers keep the memory of their origin and the<br>
physico-chemical<br>
transformations resulting from the weathering reactions. However, using<br>
sedimentary records to reconstruct weathering conditions first requires a<br>
precise understanding of the mechanisms and parameters that control the<br>
geochemical<br>
signal recorded by sediments. In particular, it is critical to determine to<br>
what<br>
extent the geochemical variations measured in suspended sediments in rivers<br>
or<br>
deposited in floodplains are linked to changes in weathering conditions or to<br>
physico-chemical transformations occurring during transport and/or after<br>
their<br>
deposit. For this, a key point is to determine the timing of the production<br>
and<br>
transport of the sediments from the headwaters were there are produced to the<br>
floodplain where they are stored.<br>
<br>
The thesis<br>
project proposes to evaluate the potential of a study coupling<br>
geochronometric<br>
methods using the U- and Th-nuclides series (radioactive disequilibrium) and<br>
the analysis of “non-traditional” B and Li stable isotopes that give new<br>
information on the mechanisms underlying the formation and transformation of<br>
sediments in alluvial basins. These isotopic tools will be applied to the<br>
study<br>
of sediments from “model” rivers, including watersheds and alluvial<br>
basins already<br>
well studied. The objectives are: 1) using isotopic tools to trace the<br>
processes<br>
controlling the formation and transport of sediments in alluvial basins from<br>
the<br>
headwaters to the flood plains, and 2) to provide time constraints on these<br>
processes and focus especially on their response to changes in environmental<br>
conditions such as climate, agriculture, urbanization, and land use changes.<br>
<br>
This is a<br>
prospective study, which will give a spatio-temporal framework of the<br>
processes<br>
controlling the production and transport of the sediments at the scale of an<br>
alluvial system. This relationship between the weathering processes and their<br>
response to forcing parameters is still difficult to define even though it is<br>
essential to understand the role of sediment transfer in surface geochemical<br>
cycles.<br>
<br>
The PhD project will be undertaken under the supervision of D. Lemarchand and<br>
F. Chabaux at the University of Strasbourg<br>
<br>
project starts Oct. 2015<br>
<br>
The applicant should have a M.Sc. or equivalent, some knowledge of isotope<br>
geochemistry, chemical weathering. Experience in a clean lab and mass<br>
spectrometry will be appreciated<br>
<br>
Salary will be equivalent to the standard French Postgraduate Award stipend:<br>
∼16,500€<br>
<br>
If interested, send a cover letter and CV to Damien Lemarchand<br>
(<a href="mailto:lemarcha@unistra.fr" target="_blank">lemarcha@unistra.fr</a> [1]) and François Chabaux (<a href="mailto:fchabaux@unistra.fr" target="_blank">fchabaux@unistra.fr</a> [2])<br>
<br>
Deadline for applications (flexible) is 15 July 2015.<br>
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