In present day paleoclimate research one of the most pressing challenges is the reconstruction of atmospheric CO2 concentrations. A variety of proxies for several components of the marine inorganic carbon system have been developed in this context (e.g. B isotopes, B/Ca, U/Ca) to allow reconstruction of past seawater pH, alkalinity etc., and thereby facilitate estimates of past atmospheric pCO2. Based on culture experiments using the benthic foraminifera Ammonia sp. we describe a positive correlation between Sr/Ca and the carbonate system, namely DIC/ bicarbonate ion concentration. Foraminiferal Sr/Ca ratios provide potentially additional constraints on the carbonate system proxy, because the analysis of foraminiferal carbonate Sr/Ca is straightforward and not easily contaminated. Applying our calibration to a published dataset of paleo-Sr/Ca suggests the validity of Sr/Ca as a carbonate system proxy. Furthermore, we explore how our data can be used to advance conceptual understanding of the foraminiferal biomineralization mechanism.
Keul N., Langer G., Thoms S., Jan de Nooijer L., Reichart G.-J. & Bijma J., in press. Exploring foraminiferal Sr/Ca as a new carbonate system proxy. Geochimica et Cosmochimica Acta. Article (subscription required).
