For the present study, samples have been taken each 5 cm in the upper 13 m (Samples 175-1087A-1H-1, 0-3 cm, to 2H-4, 30-32 cm) to obtain a time resolution of ~2 k.y. in the stable isotope records. A break of 40 cm occurs between Cores 1H and 2H (from Samples 175-1087A-1H-6, 51-53 cm, and 2H-1, 20-22 cm). Each sample was disintegrated in distilled water and washed on a 63-µm sieve, cleaned in an ultrasonic bath to remove fine particles, filtered, and dried. The foraminifers were then selected from the >250-µm size fraction. An average number of 10 to 12 individuals of each species was picked to obtain the weight of 200 to 250 µg that is necessary for stable isotope analyses. Stable isotope analyses were performed on the three planktonic foraminifer species Globigerina bulloides, Globigerinoides ruber, and Globorotalia inflata and on the benthic foraminifer species Cibicides wuellerstorfi.
CO2 gas is extracted from the carbonate of the foraminifers at 90°C with dehydrated phosphoric acid on the automatic device, coupled with a triple collector Optima-Isogas mass spectrometer. The analytical precision is 0.01. With each 12 samples, two reference carbonates are included, giving a reproducibility of measurements made on this reference of ±0.02 for both 18O and 13C values. Standard deviations of three to four separated analyses of the same foraminiferal species calculated from a series of 50 samples are ±0.1 for 18O and 13C.
All analytical data from Hole 1087A are listed in Table T1.