Planktic foraminiferal oxygen isotopes, Mg/Ca and Mg/Ca-derived SST estimates of sediment core SO256_30-1 (GeoB22230-1). Oxygen isotope analyses were carried out by the isotope laboratory of MARUM, University of Bremen, on a Finnigan MAT 251 mass spectrometer, which is connected with automatic lines for carbonate preparation. Isotope data were calibrated against the international Vienna Pee Dee Belemnite (VPDB) standard by using an in‐house carbonate standard, which has been calibrated to the National Bureau of Standards 19 standard. The long‐term analytical standard deviation is below ±0.07‰. Sample preparation for Mg/Ca followed the procedure of Barker et al. (2003, doi:10.1029/2003GC000559). Mg/Ca measurements were performed at MARUM, University of Bremen, on an Agilent Technologies 700 Series Inductively Coupled Plasma Optical Emission Spectrophotometer (ICP-OES), which is connected to a Cetax ASX 520 autosampler. To convert Mg/Ca to temperature, we applied the species-specific Mg/Ca-temperature calibration of Anand et al. (2003; doi:10.1029/2002PA000846) with an assumed exponential constant of 0.09.