STRUCTURAL ANALYSIS OF FOLD STRATA ALONG US HWY 641, WESTERN HIGHLAND RIM, LEXINGTON, TN

Here we present the preliminary structural analysis of a low amplitude fold structure observed in three road-cut outcrops within approximately two miles along US HWY 641, south of I-40 in the greater Lexington, Tennessee area. This structure does not appear on the previously published geologic map of the area, the Sugar Hill Quadrangle (1968), which was published prior to the construction of this highway. The three outcrops included in the analysis are located along the western Highland Rim of the Nashville Dome. Exposed in these outcrops are the carbonaceous dark gray to black, highly fissile Devonian- Mississippian Chattanooga Shale; the green-gray, glauconitic, fossiliferous shale and thin interbedded limestone of the Devonian Birdsong Shale Member of the Ross Formation; and the massive, light gray to reddish-gray, medium to coarse-grained limestone of the Silurian Decatur Formation. The Devonian Camden and Harriman Formations are not exposed in these outcrops, but would occur in stratigraphic succession between the Ross Formation and the Chattanooga Shale. All units outcrop at approximately the same elevation (+/- 10 m) along highway. The folded strata are best observed in the outcrop of the Decatur limestone where limbs of the fold dip up to 15 to 20 degrees to the north. Preliminary interpretations based on available data indicate the presence of a shallow northwestward plunging open fold and the possibility of a small displacement dip slip fault oriented NE-SW between the first and second outcrops. The structures within this area are likely related to the formation of the Nashville Dome.