Shale Shaker Vol 72, No 4 July-August 2021

An IntactThirty Four Foot Long Petrified Log in theWoodford Shale, Oklahoma: AQuestion of Preserving Geological Heritage By: AndrewCullen, Independent Geoscientist, Norman, OK; David Hull, Devon Energy, Oklahoma City, OK; MollyTurko,TurkoTectonics & Structural Geology, Edmond, OK Oil and Gas Exploration An Intact Thirty Four Foot Long Petrified Log in the Woodford Shale, Oklahoma: A Question of Preserving Geological Heritage Abstract This short note documents our recent find of an intact, large (at least 34ft/10m long and 3.5ft/1.5m wide) silicified Callixylon log in the Woodford Shale in an inactive quarry on the Lawrence Uplift in Pontotoc County, Oklahoma. In terms of length this trunk likely sets a global record for Devonian age petrified wood. Petrification has preserved exquisite features such as internal vascular tissue, bark, and differential compaction around the rafted log after it sank into a euxenic water bottom. We believe this fossil represents an important piece of Oklahoma’s geological heritage and ask the question “If and how it should be preserved?”

Introduction The Late Devonian-Early Mississippian Woodford Shale crops out on the flanks of the Arbuckle anticline, on a horst block known as the Lawrence Uplift, and in the Criner Hills south of Ardmore (Figures 1a, 1b). Because it is a world-class petroleum source rock, an excellent unconventional reservoir, and serves as the top seal for structural traps; the Woodford Shale has

long attracted the attention of oil and gas operators, as well as the academic com- munity (Johnson and Cardott, 1992 and papers therein; Slatt et. al, 2018). The Woodford Shale’s high-gamma signature enables easy identification on wireline logs which facilitates using it as a regional mapping horizon that show the Woodford Shale was deposited on a major unconfor- mity, thus providing critical evidence for establishing a timeline regional tectonic

events. The Devonian Period is a critical time in the evolution of Earth’s biosphere marked by the initial colonization by a di- verse assemblage of vascular plants, such as lycophytes and ferns that formed the planet’s first forests (see review by Paw - lik, et al., 2020). The development of thick soils and increased chemical weathering provided more nutrients into rivers likely triggering eutrophication and subsequent anoxia on the shelf (Algeo and Scheckler,

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