THE LAUDERBACK RIDGE FAULT BEND FOLD AT GREEN GAP, WHITEOAK MOUNTAIN, TENNESSEE

Appalachian orogenic sequences in the vicinity of Whiteoak Mountain range from the Ordovician to the Pennsylvanian. Collision between North America and Africa during the Alleghanian also resulted in heaving Paleozoic strata to a wedge. Deformation in the wedge resulted in imbricate thrust that young to the northwest. The thrust faults may be associated with folds, such as fault bend folds, due to differences in rock compliance to deformation forces. Outcrops along I-75 at Green Gap across the Whiteoak Mountain contain the Lauderback Ridge (LR) on the southeast and the Whiteoak Ridge on the northwest. The LR exposes the complexly deformed frontal limb of a fault bend fold. In contrast, capped by the Upper Devonian Chattanooga shale, strata dip gently to the southeast at the Whiteoak Ridge. This ridge extends southeast into Georgia, where it is called the Taylor Ridge.

The LR has a short lateral extent on a map view. It lies north of Grindstone, Tennessee. At Grindstone, Pennsylvanian rocks are preserved on the southeast side of Whiteoak Ridge. At Green Gap, the strata within the LR dip very steeply and young to the northwest. A gentler fault bend fold above a sliver of fault northwest of the LR is also viewable at Green Gap. Great pressure was likely applied in forming the steep limb of the LR at Green Gap, which displays a complex variety of folds and faults. Layers of sandstone and limestone interbedded with shale are buckled, and the axes of folds verge in different directions. Some strata are fractured and faulted in synthetic or antithetic directions and hanging wall blocks either moved up or down in contraction or extensional settings. This buckling has thickened the Silurian Rockwood Formation by about 20 % at the LR compared to that at whiteoak Ridge (Wilson, 1986). Previous workers further described the structure at Green Gap as synclinorium by combing the NW dipping limb at LR with the SE dipping strata at Whiteoak Ridge.