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doi:10.2204/iodp.proc.320321.220.2018

Methods and materials

A low-resolution (approximately one sample every ~60,000 y) subsurface temperature record was generated from the Mg/Ca values of Globorotalia tumida. G. tumida were picked from the 355–425 m size fraction. Approximately 15 individuals (N = 4–29) were crushed and cleaned for minor elemental analyses. Samples were cleaned using a standard protocol that included repetitive Milli-Q water and methanol rinses, oxidative and reductive cleaning steps, and a weak acid leach (Martin and Lea, 2002; Rosenthal and Lohmann, 2002). Cleaned samples were measured on a PerkinElmer Optima 8300 inductively coupled plasma–optical emission spectrometer (ICP-OES) (Wara et al., 2003). Long-term Mg/Ca mmol/mol reproducibility for a liquid consistency standard and foraminifer standard are 3.32 ± 0.030 mmol/mol (1σ; N = 434) and 3.75 ± 0.180 mmol/mol (1σ; N = 115), respectively. Mg/Ca values were converted to subsurface temperatures using a species-specific G. tumida temperature calibration (Mohtadi et al., 2011). The age model is based on gamma ray attenuation density correlation with nearby Ocean Drilling Program (ODP) Site 851 (M. Lyle, pers. comm., 2015).

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