SAMPLING AND ANALYTICAL METHODS

Interstitial water samples were squeezed from whole-were found at almost all whole-round samples immediately after retrieval of the core using the standard ODP titanium/stainless-steel squeezer (Manheim and Sayles, 1974). The retrieved pore waters were subsequently analyzed on board ship for salinity, pH, alkalinity, sulfate, chloride, lithium, potassium, sodium, calcium, magnesium, strontium, manganese, ammonium, phosphate, and silica using the methods described in Gieskes et al. (1991). Sulfur and oxygen isotope measurements of dissolved sulfate were determined on pore waters previously used for shipboard alkalinity determinations. Therefore, dissolved sulfide, if present, was removed from the aqueous solution. The sulfate was precipitated quantitatively as BaSO₄ by the addition of barium chloride, washed with deionized water, and dried at 110°C. Sulfur isotope ratios (³⁴S/³²S) of BaSO₄ were analyzed by combustion-isotope-ratio-monitoring mass spectrometry (C-irmMS) as described by Böttcher et al. (1998). About 0.4 mg BaSO₄ was combusted in an elemental analyzer (Carlo Erba EA 1108) connected to a Finnigan MAT 252 mass spectrometer via a Finnigan MAT Conflo II split interface. The liberated SO₂ gas was transported in a continuous stream of He (5.0 grade). Filtered samples for carbon isotopes of dissolved inorganic carbonate species and oxygen isotopes of water measurements were sealed in glass ampules immediately after recovery and stored in the dark. For carbon isotope determination of dissolved inorganic carbonate species, 1-2 mL of water was drawn with a syringe immediately after breaking the seal of the ampule. Then it was injected into a previously evacuated vacutainer containing 0.1 mL of 100% phosphoric acid. The evolved CO₂ was cryogenically purified on a vacuum line and measured using a Fisons-Optima mass spectrometer calibrated with the NBS-19 standard. The accuracy and precision of the method were determined by multiple measurements of a solution of sodium bicarbonate of known isotopic composition. Reproducibility of the method is ±0.3. Oxygen isotope measurements on water were conducted using an automated equilibration device with a reproducibility of ± 0.06. Oxygen isotope measurements on BaSO₄ were performed at the Marie Curie-Skolodowska University of Lublin, Poland, according to the method described by Mizutani (1971). Stable sulfur, oxygen, and carbon isotope ratios are presented using the -notation with respect to the Vienna-Canyon Diablo troilite standard (V-CDT), Vienna-Standard Mean Ocean Water (V-SMOW), and the Vienna-Peedee-Belemnite standard (V-PDB), respectively. A ³⁴S value of +20.59 was obtained for the NBS-127 (BaSO₄) standard (Böttcher et al., 1997). The measured ¹⁸O value of +9.53 for NBS-127 agrees with the proposed value of +9.34 ± 0.32 (Gonfiantini et al., 1995).