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| Titel |
Early diagenetic overprint in Caribbean sediment cores and its effect on the geochemical composition of planktonic foraminifera |
| VerfasserIn |
M. Regenberg, D. Nürnberg, J. Schönfeld, G.-J. Reichart |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 4, no. 6 ; Nr. 4, no. 6 (2007-11-12), S.957-973 |
| Datensatznummer |
250001992
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| Publikation (Nr.) |
 copernicus.org/bg-4-957-2007.pdf |
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| Zusammenfassung |
| Early diagenetic features are noticed in the vicinity of carbonate platforms.
Planktonic foraminifera of two tropical Atlantic deep-sea sediment cores show
the strict relation between micro-scale euhydral crystallites of inorganic
precipitates, higher oxygen isotope values and Mg/Ca ratios, and lower Sr/Ca
ratios than expected for their pelagic environment in the time interval of
~100 000–550 000 calendar years before present. Laser ablation Mg/Ca
(Sr/Ca) of crystallite-bearing foraminiferal chamber walls revealed
4–6 times elevated (2–3 times depleted) ratios, when ablating the
diagenetic overgrowth. Crystalline overgrowth in proportion of 10–20% are
estimated to cause the observed geochemical alteration. The extent of
foraminiferal Mg/Ca alteration, moreover, seems to be controlled by the
composition of the bulk sediment, especially the content of high-magnesium
calcite. Anomalous ratios of >6 mmol/mol only occur, when high-magnesium
calcite has dissolved within the sediment. The older parts (back to
~800 kyrs) of the records are characterized by similar trends of Mg/Ca
and Sr/Ca. We discuss possible scenarios to accommodate the obtained
geochemical information. |
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