Santa Barbara Basin Flood Layers: Impact on Sediment Diagenesis
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1.
California Institute of Technology
Abstract
The presence of gray layers, representing flood deposits, has previously been well documented in sediments obtained from Santa Barbara Basin, California. We studied geochemical aspects of these layers, in particular the carbon and sulfur contents and isotopic compositions, and found evidence of rapid pyrite formation. The data are consistent with complete (or nearly complete) sulfate consumption within the pore waters of a gray layer. This requires sulfate reduction rates (SRRs) that exceed the rate of resupply by diffusion, thus on the order of milimolar per day. The apparent rapidity of this diagenetic reaction is addressed. The net result is the precipitation of authigenic pyrite crystals enriched in 34S that become part of the sediment record. Thus, any interpretation of S isotope fluctuations in the marine sedimentary rock record obtained from pyrite must take into account the phenomena we describe and document here.
Copyright and License (English)
© 2019 Society for Sedimentary Geology. SEPM Special Publication No. 110.
Acknowledgement (English)
The authors acknowledge the contribution of many who provided insights and helped with analytical and collection tasks, including: F. Wu, J. West, J. Dolan, D. Hammond, F. Corsetti, and H.C. Li. Reviews by K. Marsaglia, R. Behl, D. Fike, and A. Paytan were most helpful. We thank Tony Morgan, Mike Ellis, and Chris Hendricks of the United Water Conservation District for enabling us to obtain a Santa Clara River sediment sample from the Freeman Diversion site. Funding support was provided by the Southern California Earthquake Center. This work was funded by NSF CA EAR-1033462 and USGS CA G12AC20038 to SCEC. As with all papers in this issue, we dedicate this to the fond memory of Donn Gorsline, his inspiration, friendship, mentoring, choice of food and beverage; all so influential to generations of geologists.
Funding (English)
Funding support was provided by the Southern California Earthquake Center. This work was funded by NSF CA EAR-1033462 and USGS CA G12AC20038 to SCEC.
Contributions (English)
The authors acknowledge the contribution of many who provided insights and helped with analytical and collection tasks, including: F. Wu, J. West, J. Dolan, D. Hammond, F. Corsetti, and H.C. Li. Reviews by K. Marsaglia, R. Behl, D. Fike, and A. Paytan were most helpful. We thank Tony Morgan, Mike Ellis, and Chris Hendricks of the United Water Conservation District for enabling us to obtain a Santa Clara River sediment sample from the Freeman Diversion site.
Data Availability
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Additional details
- Caltech groups
- Division of Geological and Planetary Sciences
- Series Name
- Special publication (SEPM (Society for Sedimentary Geology))
- Series Volume or Issue Number
- 110
- Publication Status
- Published