We selected three to eight well-preserved specimens of the benthic foraminiferal species Cibicidoides wuellerstorfi and/or Cibicidoides mundulus from the size fraction >250 μm. In 29 samples, only 1-2 specimens were analyzed and in 12 samples the species Uvigerina spp. or Hoeglundina elegans were measured, when C. wuellerstorfi and C. mundulus were rare or absent. Tests were broken into large fragments and cleaned in ethanol in an ultrasonic bath, then dried at 40°C. Measurements were performed with a Finnigan MAT 253 mass spectrometer coupled online to a Carbo-Kiel IV device for automated CO2 preparation from carbonate samples at the Leibniz Laboratory for Radiometric Dating and Stable Isotope Research, Christian-Albrechts-University Kiel. Samples were reacted by individual acid addition (99% H3PO4 at 75°C). The external standard error is better than ±0.08‰ and ±0.05‰ for δ18O, based on international standards. Results were calibrated using the National Institute of Standard and Technology (NIST) (Gaithersburg, Maryland) carbonate isotope standard NBS (National Bureau of Standard) 19, and the international carbonate standard IAEA (International Atomic Energy Agency) 603 and reported on the Vienna PeeDee Belemnite (VPDB) scale. Duplicate measurements of 32 samples show an average standard deviation of 0.08‰ for δ18O. We applied a correction factor of −0.64‰ to Uvigerina δ18O and of -1.26‰ for Hoeglundina δ18O to normalize values to C. wuellerstorfi δ18O.
