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| Titel |
Strontium isotopic record of signatures of Holocene fluvial sediments in the Loire valley, France |
| VerfasserIn |
P. Négrel, W. Kloppman, M. Garcin, D. Giot |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1027-5606
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| Digitales Dokument |
URL |
| Erschienen |
In: Hydrology and Earth System Sciences ; 6, no. 5 ; Nr. 6, no. 5, S.849-858 |
| Datensatznummer |
250003770
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| Publikation (Nr.) |
 copernicus.org/hess-6-849-2002.pdf |
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| Zusammenfassung |
| The distribution of Sr
contents and isotopes of strontium Sr in the labile fraction of sediments from a
channel fillings infill in the Middle Loire alluvial plain is used to highlight
aspects of the evolution of the basin over the period from 10 000 yr. BP to the
present. The acid extractable matter (AEM) in the sediment samples is variable
in amount and in trace element contents. Carbonates and Fe–Mn oxyhydroxides
are the principal carrying phases in the labile fraction. The historical record
of 87Sr/86Sr ratio variations in AEM shows two components.
In the first, the AEM is consistently low (around 10%) and the
87Sr/86Sr
ratios range from around 0.7086 to 0.710. This corresponds to the hydrous Fe-Mn
oxides endmember. Fe–Mn oxyhydroxides originate from the Massif Central and
their 87Sr/86Sr ratios display a larger range than present
day Fe–Mn oxides. Furthermore, the mixing proportions between Fe–Mn oxides
generated on granitoids and on basalts fluctuated only weakly in the past. The
second component has greater AEM (20–50%) and the
87Sr/86Sr
ratio is almost constant at 0.709–0.7095. This corresponds to a carbonate
endmember, clearly different from present day carbonates and may reflect the
influence of both authigenic and detrital origins.
The low 87Sr/86Sr
ratio suggests a dominantly authigenic source for the carbonate endmember; this
may be linked to groundwater inputs, although a minor influence from a secondary
detrital source cannot be discounted. This reflects a different functioning of
the river between deposition in the channel and the present day.
Keywords: River Loire, Holocene, fluvial dynamics, geochemistry, strontium isotopes |
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