Maxima of interstitial water and gas parameters in ODP Leg 182 sediments

At three sites (1127, 1129, and 1131), high contents of H2S (to 15%), CH4 (50%), and CO2 (70%) were also encountered. These levels of H2S are the highest yet reported during the history of either the Deep Sea Drilling Project or the Ocean Drilling Program.

The high concentrations of H2S and CH4 are associated with anomalous Na+/Cl- ratios in the pore waters. Although hydrates were not recovered, and despite the shallow water depth of these sites (200-400 m) and relative warm bottom water temperatures (11-14°C), we believe that these sites possess disseminated H2S-dominated hydrates. This contention is supported by calculations using the measured gas concentrations and temperatures of the cores, and depths of recovery.