Magnesium and strontium compositions of Recent benthic foraminifera from the Coral Sea, Australia and Prydz Bay, Antarctica

Abstract

Analyses of the Mg/Ca and Sr/Ca ratios of the modern benthic foraminifera, Cibicides wuellerstorfi (epifaunal) and Uvigerina species (infaunal) from the Coral Sea, and Cibicides refulgens (epifaunal) and Trifarina angulosa (infaunal) from Prydz Bay, Antarctica revealed relationships with temperature that have possible applications for reconstructions of bottom-water paleotemperatures. A positive relationship exists between the Mg/Ca and Sr/Ca ratios of Cibicides wuellerstorfi and Cibicides refulgens and ambient temperatures, at least within the range of - ̊ 2 and 6°C. For the correlation between Mg/Ca compositions and temperature the r 2 values range from 0.78 ( C. wuellerstorfi alone) to 0.88 ( C. wuellerstorfi and C. refulgens together). At present, the Mg/Ca-temperature relationship must be regarded as tentative because of significant overlap of standard error values. The relationship between the Sr/Ca compositions of C. wuellerstorfi and bottom-water temperature yields an r 2 value of 0.95. These results indicate that Sr/Ca and possibly Mg/Ca ratios of Cibicides wuellerstorfi may provide useful information for the assessment of paleotemperature. Single-species data are presently insufficient to assess the influence of ambient temperature on trace-element compositions of Uvigerina species. Trifarina angulosa may have Mg/Ca compositions which are positively related to temperature, but Sr/Ca values seem unaffected by temperature. This may be due to pore-water influences on infaunal tests or to vital effects. Although more modern data are needed, our present results suggest that Sr/Ca ratios and possibly Mg/Ca ratios of some benthic foraminifera have the potential to be useful paleothermometers, at least within a temperature range of −2 to 6°C.