Fig. 3.

Estimation of calcification temperature. Calibration curves for Mg/Ca derived from multispecies datasets of planktic foraminifera based on core-top samples (A) (17) and sediment trap samples (B) (18). The curve (B) is extended to warmer temperatures with a dashed line. The 2 stippled horizontal lines represent the average Mg/Ca values for the juvenile and adult chambers as analyzed by SIMS. The horizontal solid arrows show the temperature offset between the 2 calibration curves, whereas the dashed vertical arrows indicate the derived average calcification temperatures. The Inset shows a picture of a juvenile (I) and an adult (II) S. globigerus specimen (SI Text).