Structural Geometries, Fabrics, and Stratigraphic Relationships in the Cades Cove Region, Great Smoky Mountains National Park, Tennessee

The major structure in the Cades Cove area of the western Great Smoky Mountains is best explained as a polydeformed recumbent fold (nappe) within Precambrian Ocoee Series rocks of the Rabbit Creek thrust sheet. The Elkmont Sandstone, southeast of Cades Cove, is upright and gently southeast dipping and represents the hinterland limb of the thrust nappe. The Cades Sandstone, which is lithologically similar to the Elkmont, occurs northwest of the Coalen Ground thrust and is gently southeast dipping and overturned.

Petrographic investigation of thin sections from Cades and Elkmont units reveals very different textures. Cades samples commonly contain large, fractured potassium feldspar grains within a strong ribbon quartz fabric. Pressure-solution features and subgrain development in quartz are also prominent here. In contrast, Elkmont samples generally contain undeformed potassium feldspar, with a general absence of ribbon quartz and subgrain development in quartz. The Cades is much more highly deformed than the Elkmont and represents the overturned forelimb of the thrust nappe.

Strain analysis supports rock fabric data by presence of average tectonic strains (Rs values) in the

XZ plane of 3.0:1 in the Cades Sandstone versus 1.7:1 in the Elkmont Sandstone. High tectonic strains near the Rabbit Creek thrust trace are attributed to Rabbit Creek thrust emplacement. Strain analysis data, in conjunction with rock fabrics, are the principal structural bases for the nappe hypothesis.

The thrust nappe was emplaced along the Rabbit Creek thrust, which is the western most (foreland) expression of an early (Greenbrier?) deformational event in this region. Mylonitic fault zones in the nappe core, formerly interpreted to be stratigraphic contacts, cut through the Rabbit Creek thrust sheet and represent out-of-the-anticline thrusts. The later Great Smoky thrust either re-activated the Rabbit Creek thrust plane or cut up into the Rabbit Creek thrust sheet in the Cades Cove region.