essentially pyrite + minor elemental sulfur + minor acid volatile sulfides), which originates from the sulfate reduction process, was measured in selected squeeze-cake samples from sediments of Site 1119.
Interstitial waters from six Ocean Drilling Program (ODP) sites (Sites 1119-1124) from the southwestern Pacific Ocean (Fig. F1) were retrieved during Leg 181. Site 1119 (396 m water depth) was drilled close to the eastern shoreline of New Zealand's south island, Site 1120 (544 m water depth) is located on the shallow-water Campbell Plateau, and Site 1121 (4490 m water depth) on the Campbell "drift." Site 1122 (4432 m water depth) was drilled on the north flank of the abyssal Bounty Fan and Site 1123 (3290 m water depth) on the deep northeastern slopes of the Chatham Rise. Site 1124 (3957 m water depth) was positioned on the north-south-trending ridge of the Rekohu Drift (Fig. F1) (Carter, McCave, Richter, Carter, et al., 1999). Based on biostratigraphic criteria, sedimentation rates vary widely between 1.3 and 40 cm/k.y., and in composite, the recovered sediments span a time interval from the Late Cretaceous to the Holocene (Carter, McCave, Richter, Carter, et al., 1999).
Sulfur isotope signatures of dissolved sulfate in marine pore waters have been used as a valuable indicator for the occurrence of microbial sulfate reduction (e.g., Hartmann and Nielsen, 1969; Chanton et al., 1987; Böttcher et al., 2000). Despite the interest in the microbial activity of the deep biosphere (Parkes et al., 1994), only few studies have measured sulfur isotopes in pore waters of deep marine sediments (Zak et al., 1980; Brumsack et al., 1992; Böttcher et al., 1998, 1999; Rudnicki et al., 2001). In the present study, pore waters were retrieved from the six sites drilled during Leg 181 and analyzed for stable isotopes of dissolved sulfate (34S/32S), together with major and minor ions, as evidence for the activity of sulfate-reducing bacteria in the sediment-pore water system. Additionally, solid-phase total reduced inorganic sulfur ([TRIS] essentially pyrite + minor elemental sulfur + minor acid volatile sulfides), which originates from the sulfate reduction process, was measured in selected squeeze-cake samples from sediments of Site 1119.
