GEOLOGIC MAP OF THE SOUTHERN ERWIN QUADRANGLE, TENNESSEE APPALACHIANS

We present a geologic map of the southern section of the 7.5’ Erwin Quadrangle at a scale of 1:24,000. This geologic map is produced with data collected in fieldwork during June 2017. This map area in the Appalachians in Northeast Tennessee contains the synclinal transition of a foreland-dipping duplex to a hinterland-dipping duplex.

The exposed units mapped in this area are Cambrian and Precambrian in age. The Cambrian units include the Honaker Dolomite, the Rome Formation, the Shady Dolomite, and the Chilhowee Group containing the Erwin, Hampton, and Unicoi Formations. The Precambrian units mapped are the Snowbird and Sandsuck Formations of the Ocoee Series. This area contains the northeastern-most occurrence of the Ocoee Series. In the east part of the map, in the town of Erwin, Tennessee, two thrusts are mapped of the foreland-dipping duplex. Duplex horses there contain the Hampton through Rome Formations dipping northwest from about 55° to 70°, with the northwestern-most sequence topped by Honaker Dolomite. To the west, on Rich Mountain, we map the folding foreland of the duplex, where Unicoi and Ocoee are dipping to the southeast around 20° to 50° with some internal folding. This is thrust onto a slice of Erwin and Hampton to the northwest, which is generally dipping south to southeast at 30° to 45° and is then thrust onto Shady Dolomite.

This new map adds strike and dip data to an overlooked area, with a gap in research at this scale between Bumpus Cove and Buffalo Mountain to the north, Limestone Cove to the northeast, and the Chestoa Quadrangle to the south. This new structural data will be compared to the broader-scale structure of the foreland-dipping duplexes near Limestone Cove and help constrain the development of this geometry. Also, our new stratigraphic observations help differentiate the Ocoee between the Sandsuck and Snowbird Formations where it was previously mapped as simply undifferentiated Ocoee here at its northeastern-most occurrence.