Abstract
We applied compound-specific sulfur isotope analysis (CSSIA) to organic matter (OM) extracted from ancient and immature organic-rich rocks from the Cretaceous Ghareb (Shefela Basin locality, Israel) and Miocene Monterey (Naples Beach locality, California, USA) Formations. Large variations in the δ34S values of different organosulfur compounds (OSCs), that reach up to 28‰ and 36‰, were observed in the Ghareb and Monterey samples, respectively. Additionally, some common OSCs in both locations showed consistent 34S trends relative to each other. The consistent enrichment in 34S of C35 hopane thiophene relative to iC20 thiophene in the studied sections probably resulted from differences in the timing of OM sulfurization. Reactive organic precursors quickly consume the most 34S-depleted reduced S, while less reactive species incorporate the heavier residual S at a later time. Despite the differences in the depositional environments, ages, and the initial δ34S values of the reduced S (represented by the δ34S of pyrite) between the Ghareb and the Monterey Formations, the sulfurization order of common organic compounds seems to be similar. All of the δ34S values of OSCs are 34S enriched relative to that of the coexisting pyrite with the exception of the C25 highly branched isoprenoid (HBI) thiophene in several samples from the Monterey Formation. The existence of 34S-depleted sulfurized HBI may point to OM sulfurization that occurred at or near the sediment-water interface during the deposition of the Monterey. Moreover, the δ34S of steroid sulfides shows an inverse trend with the pristane/phytane ratio, which may indicate that the sulfurization mechanism of these OSCs are affected by redox conditions. Further investigation of CSSI values in immature rocks from other basins may help constrain the OM sulfurization process, timescale, and depositional conditions and their possible use as paleoenvironmental proxies.
Original language | American English |
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Pages (from-to) | 20-44 |
Number of pages | 25 |
Journal | Geochimica et Cosmochimica Acta |
Volume | 274 |
DOIs | |
State | Published - 1 Apr 2020 |
Bibliographical note
Funding Information:We are grateful to Harold Vinegar and Yuval Bartov from IEI Ltd. for providing the core samples. The Monterey Formation samples were graciously provided by Paul Lillis of the U.S. Geological Survey. We appreciate the discussions with Shimon Feinstein, Sigal Abramovich, Ari Meilijson and Yoav Oved Rosenberg about the geology and stratigraphy of the study area and the help with the core sample selection. L.S. is grateful for Ph.D. scholarships from the Ministry of National Infrastructures, Energy and Water Resources of Israel, and the Harry and Sylvia Hoffman Fund. A.A. thanks the Israeli Science Foundation grant No. 1738/16 for partial support for this study. We appreciate the constructive and thoughtful comments by Paul Lillis, Pierre Adam, and two anonymous reviewers that greatly improved the paper. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
Funding Information:
We are grateful to Harold Vinegar and Yuval Bartov from IEI Ltd. for providing the core samples. The Monterey Formation samples were graciously provided by Paul Lillis of the U.S. Geological Survey. We appreciate the discussions with Shimon Feinstein, Sigal Abramovich, Ari Meilijson and Yoav Oved Rosenberg about the geology and stratigraphy of the study area and the help with the core sample selection. L.S. is grateful for Ph.D. scholarships from the Ministry of National Infrastructures, Energy and Water Resources of Israel, and the Harry and Sylvia Hoffman Fund. A.A. thanks the Israeli Science Foundation grant No. 1738/16 for partial support for this study. We appreciate the constructive and thoughtful comments by Paul Lillis, Pierre Adam, and two anonymous reviewers that greatly improved the paper. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
Publisher Copyright:
© 2020 Elsevier Ltd
Keywords
- Biomarkers
- C HBI thiophene
- Compound-specific S isotope analysis
- Organic S compounds
- Pyrite
- Sulfurization