Strontium stable isotope behaviour in foraminiferal calcite and the retrieval of marine records

Stevenson, E.; Burton, K. W.; Rickaby, R. E. M.; Parkinson, I. J.; Anand, P. and Hathorne, E. C. (2009). Strontium stable isotope behaviour in foraminiferal calcite and the retrieval of marine records. In: American Geophysical Union, Fall Meeting 2009, Dec 2009.


The strontium (88Sr/86Sr) stable isotope composition of seawater preserved in sedimentary foraminifera potentially provides key information on variations in the composition of material delivered by continental weathering and on changes in carbonate productivity over time. However, recent studies suggest a significant temperature dependent fractionation of Sr stable isotopes during the precipitation of calcium carbonate, which must be quantified before seawater records can be accurately retrieved [1, 2].
This study presents high-precision stable Sr isotope data (±10 ppm; 2 s.d.) for core-top planktonic foraminifera from sites in the South Atlantic covering a sea surface temperature range of ca. 18 - 28°C, and quaternary marine foraminiferal records from the SE Indian Ocean (core ). These results indicate that there is no signficiant variation in the stable isotope composition of an individual species across the temperature range studied here, but there are resolvable differences in the offset from seawater between species. In this case, seawater stable Sr isotope records can be reconstructed without the necessity of a temperature correction. The preliminary results for a glacial-interglacial planktonic foraminiferal record indicate that there are no resolvable variations in the stable isotope ratios over this time interval, indicating that there are no significant variations in the Sr isotope composition of continental runoff or carbonate productivity in the oceans over this time interval.

[1] Fietzke, J., Eisenhauer, A. (2006), Geochem. Geophys. Geosyst., 7, (8), 1-6 . [2] Ruggerburg, A., Fietzke, J., Liebetrau, V. Eisenhauer, A., Dullo, W-C., Freiwald, A. (2008). Earth Plan. Sci. Lett. 269, 570-575

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