Trace Fossils and Stratigraphy of Devonian Black Shale in East-Central Kentucky: ABSTRACT

Abstract

In recent years trace fossils have been studied in carbonate and siliceous rocks. Shales have largely been ignored. This study describes trace fossils from the anoxic Upper Devonian black shale in east-central End_Page 729------------------------------ Kentucky along the western margin of the Appalachian basin. Trace fossils occur where dolomite overlies black shale in the lower part of the Huron Member (basal New Albany or Ohio Shale). Cruziana, Zoophycos, Planolites, Phycodes, Chondrites (Type A), Trichichnus, Teichichnus, Laevicyclus, and a newly described large burrow form are common. Up section, trace fossils are found where gray shale overlies black shale in the upper lower part of the Huron Member (Teichichnus, Planolites, Chondrites-Type B, Rhizocorallium, and Zoophycos) and the Three Lick Bed (Chondrites-Types C and D, Planolites-like burrows, Zoophycos, and pyritic burrows). A combination of interpretations based on the stratigraphy, lithology sedimentary structures, and trace fossils suggests that the Devonian black shale was deposited in an upward-deepening sequence transgressive over the axis of the present Cincinnati arch in east-central Kentucky. The carbonate environment of the underlying Middle Devonian Boyle dolomite contains trace fossils and features suggestive of shallow water. At the beginning of the Upper Devonian, migration of black muds onto the platform rimming the Cincinnati arch allowed interbedding with the carbonates. Up section, the carbonate-black shale environment was replaced by entirely black shale deposition. Periodic oxygenation allowed brief periods of burrowing. Trace fossil correlation will be helpful in understanding the detailed stratigraphy within the mid-continent Upper Devonian black shale. End_of_Article - Last_Page 730------------