Organic chemistry of sediments of the Peru margin

High concentrations of organic matter in diatomaceous muds, its thermal immaturity, and the presence of abundant hydrogen-containing organic compounds lead to the conclusion that organic matter is not limiting for reduced sulfur formation.

Rather, high degrees of iron pyritization at Site 680 limit pyrite accumulation in sediments from this shelf site. The low degree of iron pyritization and nearly complete reduction of dissolved sulfate at Site 688 suggest that a lack of interstitial sulfate is limiting pyrite formation there. Although factors that limit the formation of sedimentary iron sulfide are different at each site, the resulting average reduced-sulfur concentrations are remarkably similar (0.85 wt.% at Site 680 and 0.86 wt.% at Site 688).