Geochemistry, mineralogy and isotopes at DSDP Hole 62-464

The relationships between mineralogical and geochemical data on the three successive sedimentary facies at Deep Sea Drilling Project Site 464 are studied. The evolution of siliceous biogenic sediments is derived from the analyses of one Fe-Ti smectite concretion, and of siliceous aggregates occurring in the pelagic "brown clays." Along the sedimentary section, the trace elements enriching the authigenic silicates and the Fe-Mn oxyhydroxides vary, depending on the marine environment. The proportion of clays and carbonates into the siliceous deposits controls the diagenetic evolution of silica making up the quartz aggregates from the "brown clay" or the cristobalite cherts.

Methanogenic activity in sediments from DSDP Leg 64 Holes

We detected methanogenic bacterial activity in 6 of 12 sediment samples from Deep Sea Drilling Project (DSDP) locations in the Gulf of California.When samples were incubated anaerobically for three weeks at temperatures of 10 or 22°C, we found activity to sediment depths of about 12 meters. The methanogenic bacteria were inhibited by CHCl3 or 2-bromoethanesulfonic acid and were generally stimulated by H2.