Isotopic composition and speciation of sulfur in the Miocene Monterey Formation: Reevaluation of sulfur reactions during early diagenesis in marine environments

Journal Article · Sat Feb 01 04:00:00 EST 1992 · Geochimica et Cosmochimica Acta; (United States)

DOI:https://doi.org/10.1016/0016-7037(92)90096-2· OSTI ID:5358169

Zaback, D A; Pratt, L M ^[1]

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1. Indiana Univ., Bloomington (United States)

The timing and pathways of early diagenetic sulfur transfer from dissolved species in pore waters to solid inorganic and organic compounds in sediments have been studied in the Miocene Monterey Formation, Santa Maria Basin (onshore), California. Correlation between concentrations of total organic carbon (TOC) and total sulfur (TS), in addition to concentrations of titanium, aluminum, total iron, and reactive iron, have been used to infer organic matter reactivity, redox conditions, and relative rates of clastic and biogenic input for each lithofacies. Isotopic compositions of six sulfur species (acid-volatile, disulfide, kerogen, bitumen, sulfate, and elemental) have provided information regarding relative timing of sulfur incorporation, sulfate diffusivity in the upper centimeters of the sediments, and the sources of sulfur for individual species. Consistent ordering of isotopic values for sulfur species (disulfide < acid-volatile sulfide {le} kerogen) indicates that pyrite precipitated nearest to the sediment-water interface under mildly reducing conditions and with little or no decrease in sulfate concentration relative to seawater. Enrichment of {sup 34}S in acid-volatile sulfide and kerogen sulfur resulted from formation of these species at greater depths or in restricted micro-environments under more reducing conditions and with low concentrations of porewater sulfate. The formation of acid-volatile sulfide after pyrite but during early diagenesis is significant because it implies more strongly reducing conditions than are generally recognized in deep-water marine sediments.

• OSTI ID: 5358169
• Journal Information: Geochimica et Cosmochimica Acta; (United States), Journal Name: Geochimica et Cosmochimica Acta; (United States) Vol. 56:2; ISSN GCACA; ISSN 0016-7037
• Country of Publication: United States
• Language: English

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