Trace Fossils and Depositional Environments of Upper Devonian Black Shales, East-Central Kentucky, U.S.A.
Douglas W. Jordan, 1985. "Trace Fossils and Depositional Environments of Upper Devonian Black Shales, East-Central Kentucky, U.S.A.", Biogenic Structures: Their Use in Interpreting Depositional Environments, H. Allen Curran
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Trace fossil assemblages are recognized in “anoxic” black shales and these assemblages are valuable in interpreting paleodepositional environments in shaly basins. Trace fossils in the Upper Devonian black shales of east-central Kentucky (Ohio or New Albany Shale) occur within and below dolomites, gray shale, and in black shale. A diverse suite of epifaunal and infaunal deposit-feeding traces is preserved in interbedded dolomite and shale of the lower part of the Huron Member. Planolites is the most common trace fossil and is associated with Chondrites (Type A), Zoophycos. Phycodes, Cruziana, Trichichnus, Teichichnus, Laevicyclus, and larged ribbed burrows. In interbedded gray and black shale of the lower part of the Huron Member, Planolites, Chondrites (Type B), Zoophycos. Teichichnus, and Rhizocorallium are common on black shale bedding planes. In gray and black shale interbeds of the Three Lick Bed, a less diverse assemblage of traces occurs, including Planolites-Wke burrows, Chondrites (Type C and Type D), and Zoophycos. These ichnogenera are included in Seilacher's (1967) Cruziana and Zoophycos ichnofacies.
Devonian black shales were deposited in an environment of deposition that was transgressive over the axis of the present Cincinnati Arch in east-central Kentucky. Sediments representing the shallow-water carbonate environment of the Middle Devonian Boyle Dolomite interfinger with Upper Devonian shales. Upsection, carbonates and black shales are replaced by black and gray shales. Black shales represent total anoxic conditions while gray shale represents periodic oxygenation events (possibly movement of the dysaerobic zone) which allowed burrowing to occur for short time intervals. At the beginning of the Early Mississippian, the depositional regime changed, and deltaic sands and prodeltaic muds replaced black mud deposition.