Figure 2.

Calibration of δ¹¹B of T. sacculifer as measured by N-TIMS versus δ¹¹B of borate in seawater (data in Table S1). Culture data [Sanyal et al., 2001 and this study] define the slope of the relationship. Core top δ¹¹B data are offset from the culture relationship, where the offset can be explained by secretion of gametogenic calcite at greater water depth. This offset (0.84‰) is subtracted from the intercept of the culture regression to define the sedimentary calibration of δ¹¹B_{T. sacculifer} calcite to δ¹¹B borate. Linear regression is a York fit [York et al., 2004, Matlab script York_fit.m] which incorporates x and y uncertainty for each datum; slope and intercept uncertainties are 2σ.