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| Titel |
Sr heterogeneity in \textit{Arctica islandica} shells and the potential use of Sr/Ca ratios as paleotemperature proxies |
| VerfasserIn |
Pascal Radermacher, Bernd R. Schöne, Elizabeth V. Nunn, Zhang Zengjie |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250042617
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| Zusammenfassung |
| Quantifiable paleotemperature data can help to verify predictions made by numerical climate
models. Traditionally, paleotemperature estimates are based on δ18O values of biogenic hard
parts. However, oxygen isotope values not only reflect changes in ambient temperature, but
also changes in δ18Owater, i.e. driven by freshwater influx, evaporation etc. Information
regarding the δ18Owater value of past environments is limited for the geological past. The
validity of published δ18O paleotemperature data can be tested using element-to-calcium
ratios of bivalve shells such as the long-lived ocean quahog, Arctica islandica. Preliminary
investigations suggest that Sr/Ca ratios of this species may provide more reliable
paleotemperature data. However, contemporaneously deposited shell portions within the
outer shell layer demonstrate at least a 30% variability in the Sr/Ca value. This study
presents Sr/Ca ratios measured by ICP-OES wet-chemical analyses. Significantly
different distributions of Sr/Ca ratios were recorded from the shell surface (over 1330
ppm), through the interior (850 ppm) and to the inner shell surface (1860 ppm).
Furthermore, this study showed that different shell crystal fabrics incorporate different
amounts of Sr into the CaCO3 lattice of the A. islandica shell. Disparate Sr distribution
could potentially be explained either by postdepositional diagenetic processes or
syndepositional processes during biomineralization (i.e. different amounts of Sr incorporated
into the shell). Understanding the mechanism of the observed Sr heterogeneity is
essential if Sr/Ca ratios are to be used confidently in paleotemperature reconstructions. |
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