The biogeochemical cycling of sulfur in two distinct redox regimes

Biogeochemical cycling of sulfur provides a valuable tool for deciphering the varying redox conditions in marine and terrestrial environments throughout the history of the earth. This study addresses the cycling of sulfur in two distinct redox environments. These environments preserve diagnostic sulfur geochemical fingerprints that can be used to recognize similar environments throughout the geologic record.; The Leicester Pyrite Member, within the Devonian Appalachian Basin, is unique in that it is a detrital metal sulfide lag formed and preserved during times of atmospheric oxygenation. Geochemical results, including framboidal pyrite distributions and the delta34S of iron sulfides, suggest that during times of atmospheric oxygenation, pyrite reworking and detrital lag formation require unusual high-energy but low-oxygen conditions at pycnocline depths within a subaqueous marine setting.; The Gulf of Mexico provides the opportunity to address the biogeochemical cycling of sulfur in environments where active methane hydrate dissociation occurs along with active hydrocarbon seepage. Results include the recognition of diagnostic sulfur geochemical proxies that can be applied to recognize similar environments throughout geologic history. Furthermore carbon and oxygen isotope compositions of carbonates provides the necessary tool to determine the dominate carbon source being utilized by the biological communities coupled to sulfur cycling.