Temperature and carbonate ion effects on Mg/Ca and Sr/Ca ratios in benthic foraminifera: Aragonitic species Hoeglundina elegans

摘要: Received 16 March 2005; revised 20 June accepted 3 November published 21 February 2006. [1] Core top samples from Atlantic (Little Bahama Banks (LBB)) and Pacific (Hawaii Indonesia) depth transects have been analyzed in order to assess the influence of bottom water temperature (BWT) aragonite saturation levels on Mg/Ca Sr/Ca ratios aragonitic benthic foraminifer Hoeglundina elegans. Both H. elegans tests show a general decrease with increasing depth. Although at each site decreasing trends are consistent situ profile, LBB substantially higher than Indonesia Hawaii comparable depths greater difference observed Because we find no significant between results obtained ‘‘live’’ ‘‘dead’’ specimens, propose that these differences due primary effects metal uptake during test formation. Evaluation column properties suggests CO3 ion concentrations play an important role determining ratios. The effect is limited, however, only ([DCO3]aragonite) below 15 mmol kg � 1 . Above this level, exerts dominant effect. Accordingly, can be used reconstruct thermocline temperatures waters oversaturated respect mineral using following relationships: = (0.034 ± 0.002)BWT + (0.96 0.03) (0.060 (1.53 (for [DCO3]aragonite >1 5mmol ). standard error associated equations about ±1.1� C. Reconstruction deeper complicated because undersaturated waters, changes reflect combination [CO3] BWT. Overall, Sr/Ca, rather Mg/Ca, may more accurate proxy for reconstructing paleotemperatures.