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| Titel |
Exploring the controls on element ratios in middle Eocene samples of the benthic foraminifera Oridorsalis umbonatus |
| VerfasserIn |
C. F. Dawber, A. K. Tripati |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1814-9324
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| Digitales Dokument |
URL |
| Erschienen |
In: Climate of the Past ; 8, no. 6 ; Nr. 8, no. 6 (2012-12-07), S.1957-1971 |
| Datensatznummer |
250005980
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| Publikation (Nr.) |
 copernicus.org/cp-8-1957-2012.pdf |
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| Zusammenfassung |
| Culturing studies and empirically based core top calibrations have
been used to infer that elemental ratios in benthic foraminifera can be used
as proxies to reconstruct past variations in bottom water temperature and
saturation state (Δ [CO32−]).
However the mechanisms linking elemental ratios to these
parameters are poorly constrained. Here, we explore the environmental
parameters influencing the incorporation of B, Li, Sr and Mg in
Oridorsalis umbonatus in early Cenozoic sediments from Ocean Drilling Program Site 1209. We
investigate the influence of middle Eocene variations in intermediate water Δ [CO32−] using relationships developed
from core top samples. The fidelity of bottom water Δ[CO32−] reconstructions based on single element
ratios is assessed by comparing the X/Ca-based reconstructions to each other
and to carbon cycle proxy records (benthic foraminifera δ13C, organic carbon content, foraminifera dissolution
indices), and a seawater δ18O reconstruction for Site
1209. Discrepancies in the reconstructed Δ[CO32−] values based on these different metal
ratios suggest that there are still gaps in our understanding of the
parameters influencing X/Ca and demonstrate that caution is required when
interpreting palaeo-reconstructions that are derived from a single elemental
ratio. The downcore record of O. umbonatus Mg/Ca
does not exhibit any similarities with the Li/Ca, B/Ca and Sr/Ca records,
suggesting that the environmental parameters influencing Mg/Ca may be
different for this species, consistent with temperature as the strongest
control on this elemental ratio. This hypothesis is supported by the
coefficients of multiple linear regression models on published Mg/Ca
data. An incomplete understanding of the controls on elemental incorporation
into benthic foraminifera hinders our ability to confidently quantify
changes in saturation state using single X/Ca reconstructions over a range
of timescales. |
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