AAPG Southwest Section

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Novel Biomarkers for Interpreting Depositional Environment and Organic Distributions in the Woodford Shale


Recent work in the Oklahoman Woodford Shale has shown marked geochemical variability in terms of organic type and preservation, reflecting the discrete changes in depositional setting throughout the Upper Devonian-Lower Mississippian formation. Such heterogeneities are seen both sequentially and regionally as a function of the dynamic history of marine transgression, alternating circulation patterns, fluctuating marine and continental organic input, and intermittent events of photic zone euxinia (PZE) through laterally varied depositional conditions.

A well-preserved, 80-foot Interstate-35 outcrop in Carter County, Oklahoma provides a unique opportunity to investigate detailed geochemical and stratigraphic trends across the Upper Woodford. A biomarker study was conducted to assess complexities of the Woodford's deposition, with a particular focus on the relationship between sequence stratigraphy, organic input, euxinic episodes, and the Frasnian-Famennian mass extinction. A more thorough understanding of mechanisms that link these characteristics of the Woodford Shale may help predict the occurrence of high organic content and preservation.