Sr/Ca in multiple species of planktonic foraminifera: implications for reconstructions of seawater Sr/CA

Elderfield, H., Cooper, M. and Ganssen, G. (2000) Sr/Ca in multiple species of planktonic foraminifera: implications for reconstructions of seawater Sr/CA. Geochemistry, Geophysics, Geosystems, 1, Art.1017. (doi:10.1029/1999GC000031).

Abstract

Sr/Ca ratios were measured on eight species of planktonic foraminifera from a core top transect of the North Atlantic. Five of the species (Globigerinoides ruber, Globigerina bulloides, Neogloboquadrina pachyderma, Globigerinoides sacculifer, Globigerinella siphonifera) show remarkably little within-species variability in Sr/Ca (1.2 ± 0.1%). Three globorotaliid species (Globorotalia hirsuta, Globorotalia inflata, Globorotalia truncatulinoides) show somewhat greater variability (3–7%). Interspecies variations are of ?10%. The variability in globorotaliid Sr/Ca is explained either by a greater temperature sensitivity than for other species or by depth-dependent dissolution. Other than this effect, the overwhelming control on foraminiferal Sr/Ca appears to be seawater Sr/Ca. In contrast, time series Sr/Ca records of four species from a North Atlantic sediment core over a glacial-interglacial cycle show very significant differences. N. pachyderma shows large-amplitude changes in Sr/Ca (9.7%), in phase with ?18O, whereas G. ruber shows the smallest amplitude changes (2.6%) out of phase with ?18O and most similar to model predictions for temporal changes in seawater Sr/Ca. Records of G. inflata and G. bulloides are intermediate (amplitude changes of 3.3–4.7%) and out of phase with ?18O. The lack of coherence in the time series records between the species shows that factors in additional to changing seawater Sr/Ca must affect planktonic foraminiferal Sr/Ca.

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Contributors

Author: M. Cooper

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