Samples were obtained from either those taken aboard JOIDES Resolution during Leg 160 or in the Bremen Ocean Drilling Program (ODP) Core Repository. On the ship, approximately one-quarter of a core in sapropel intervals and the surrounding sediments was sliced off the working halves, wrapped in plastic, and stored frozen until shipping. In the shore-based laboratory, the quarter cores were cut in 1-cm subsamples and freeze dried. Samples taken in the Core Repository consisted of 1-cm sediment intervals across sapropels and adjoining sediments collected with plastic scoops, which were also freeze dried upon arrival in Warnemünde. For each sample, we calculated the revised meters composite depth (rmcd) below seafloor based on the tables provided by Sakamoto et al. (1998).
The freeze-dried samples (~2-4 g dry weight) were subsequently split into subsamples. Two grams were wet sieved to obtain the >63-μm fraction, and the residue was used to pick up to 20 tests (sometimes samples were barren or contained less than 20 tests) of the planktonic foraminifer Globigerinoides ruber (white) for isotope analyses. This species is a shallow-dwelling planktonic foraminifer and the isotope signal of the calcite tests records global ice-volume variations, salinity, and temperature near the sea surface. The isotopic composition of oxygen and carbon in the calcite was analyzed with a Finigan MAT 251 mass spectrometer, and the measurement was calibrated against the Peedee Belemnite (PDB) reference scale through international isotope standards. The isotopic results are expressed in the usual notation delta = (Rs/Rst -1) * 1000, with Rs and Rst denoting the 13C/12C or 18O/16O ratios in the sample CO2 and the international standard, respectively. The standard deviation of the isotope analyses is ±0.02‰.
Age for each sample was calculated by linear interpolation between stratigraphic fix points (sapropel bases) as described in Emeis et al., (2003).
Because of limited sample material, we were not able to perform all analyses on all sapropels.
