Empirical partition coefficients for Sr and Ca in marine barite: Implications for reconstructing seawater Sr and Ca concentrations

[1] A robust record of fluctuations in seawater Sr and Ca concentrations is critical for understanding the long-term global carbon cycle as it is influenced by the history and location of carbonate precipitation, chemical weathering, and hydrothermal activity. Such a record is also necessary for interpretation of paleoceanographic records (temperature, productivity) derived from carbonate sources (e.g. Sr/Ca, Mg/Ca, Li/Ca). Marine barite, an inorganic phase preserved in oxic, deep-sea sediments, may record seawater Sr and Ca concentrations. Using core top barite samples we have derived the partition coefficients for Sr (D-Sr = 2.9 x 10(-5)), Ca (D-Ca = 1.9 x 10(-8)), and Sr/Ca (D-Sr/Ca = 1.6 x 10(3)) in barite. The natural variability of core top marine barite Sr/Ca, Sr/Ba, and Ca/Ba ratios, selected from different ocean basins, is 10.1%, 15.0%, and 16.3%, respectively. Since estimates of Cenozoic fluctuations in seawater Sr/Ca ratios are large (possibly greater than 80%) relative to the variability recorded in core tops, marine barite may be used to reconstruct seawater Sr/Ca ratios, and Sr and Ca concentrations, using empirically derived partition coefficients.