Stratified Sulfide Deposition in Modern and Ancient Environments

Present day sulfide deposition occurs in many environments. One is at tectonically active sites, such as the East Pacific Rise and the Red Sea where sulfides, formed most likely by high-temperature abiotic sulfate reduction, and metals are supplied by hydrothermal fluids. Another is in nonthermal restricted environments such as the Black Sea where sulfides form by bacterial sulfate reduction, but where extreme sulfide accumulation is prevented by a lack of reactable metals.