Deglacial δ18O and hydrologic variability in the tropical Pacific and Indian Oceans (original) (raw)

Cleaning techniques for foraminifera for Mg/Ca analyses include water and methanol rinses, but techniques vary as to whether they include oxidative and reductive steps [Boyle and Keigwin, 1985/6; Rosenthal et al., 1997] or only an oxidative step [Barker et al., 2003]. The difference in cleaning technique has been found to affect Mg/Ca ratios. Barker et al. [2003] found the reductive step lowers Mg/Ca ratios by approximately 10%, and an interlaboratory comparison study estimated the reductive step lowered Mg/Ca by 15% [Rosenthal et al., 2004]. Recent work by Arbuszewski et al. [2010] found the difference to be 8-9%. Mg/Ca values were converted to temperature using the Anand multispecies equation [Anand et al., 2003] as this calibration is relatively data rich. The equation was adjusted to account for the fact that the Anand calibration was based on foraminifera that had been cleaned only with an oxidative step. We assume the reductive step reduces Mg/Ca values by approximately 10%: Original Anand Multi-species equation: Mg/Ca = 0.38exp(0.090T) Modified Anand equation: Mg/Ca + 0.1Mg/Ca = 0.38e 0.09T or Mg/Ca = 0.345exp(0.090T) Mg/Ca samples from cores GeoB10029-4 [Mohtadi et al., 2010], GeoB10038-4

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