STRATIGRAPHIC (AGE AND POSITION) AND STRUCTURAL PROBLEMS IN THE OCOEE BASIN

The Ocoee Supergroup was deposited during the post-565 Ma (?) successful Neoproterozoic–Cambrian rifting of Rodinia and opening of Iapetus. The basin extends from Johnson City, TN to Cartersville, GA and from the frontal Blue Ridge (BR) to the Hayesville fault. It is overlain by the Chilhowee Group and part of the Murphy sequence. The Chilhowee contains the rift-to-drift transition marking the opening of Iapetus. Thickness of the Ocoee ranges from zero near Johnson City to a maximum of ~15 km in the Great Smoky Mountains National Park. The Ocoee is divisible into the Snowbird Group that nonconformably overlies Grenvillian basement, the thick Great Smoky Group that may always be in fault contact with the Snowbird, and the Walden Creek Group that directly underlies the Chilhowee, but may conformably overlie both the Snowbird and Great Smoky Groups. Although mid-Paleozoic fossils have been reported in the Walden Creek Group, all reproducible localities lie within the Sandsuck Formation (Walden Creek Group), which is conformably overlain by the Chilhowee Group. The Walden Creek Group may represent the missing pre-Olenellus (Tommotian) Cambrian so well documented in the western US. The structure in the Park is complex, with faulting both before metamorphism and later during the Alleghanian. The structure SW of the Park is less complex with the frontal BR faulted syncline, and the NW-vergent Ducktown anticline, Murphy (-Alum Cave) syncline, and Ravensford anticline to the SE. Several large faults (Miller Cove, Rabbit Creek, Greenbrier?) are well mapped in the frontal BR from the Park southward and terminate against the Miller Cove fault. Several stratigraphic units (e.g., Elkmont Sandstone) project across the Little Tennessee River S of the Park into a poorly mapped area where different units project N from areas to the S mapped in detail. Several major faults project into this area from both directions. To the S and E, the Walden Creek Group conformably overlies the Great Smoky Group, and correlative rocks conformably overlie the Great Smoky Group in the Murphy syncline, with a major (Middle Ordovician?) unconformity near the top of the section. In progress detailed geologic mapping and C, O, and Sr isotopic analyses of carbonate rocks should tie together the structure and stratigraphy of the Ocoee basin.