A structural analysis of metasedimentary rocks of the Ocoee Supergroup above the Great Smoky overthrust in southeast Tennessee

Mesoscopic and microscopic fabrics in the upper Tellico River area indicate a polyphase deformation plan. Major deformational events include an episode of folding during the Taconic orogeny and a period of folding and thrusting during the later Paleozoic Appalachian orogeny. Three major phases of deformation are recognized. The first phase e (D,) produced F, folds with an axial plane slaty cleavage (s,). of overprinting F crenulation cleavage. Some F, formation. Macroscopic F. folds and large thrust faults form the The folds warp pre-existing structures by faulting at deeper structural levels. Faulting can be related to both D continuum of thrusting. . Regional metamorphism (M,) was coeval with D, and most likely spanned a greater time interval than the associated F, folding event. Weaker pulses of metamorphism are development. Metamorphic minerals indicate that a late, low pressure metamorphism is superposed upon the regional metamorphic event.

Results of this study indicate that F, folds formed under a minimum of 9 km of overburden. folds, however, formed at various depth levels. Associated thrust faults indicate a progressive event involving both folding and thrusting. The latest structures observed, however, are thrust faults discordant to folding. Although transport zone fabrics are preserved locally, most observed fabrics of the Great Smoky thrust zone formed under frontal zone conditions. Conjugate shear with a large, right lateral antithetic component and fold discordant, westerly thrusting are major features of the thrusts. The Alaculsy Valley fault, forming the eastern boundary of the frontal thrust zone, differs in style. It contains pervasive small mesoscopic folds of polyphase origin; axial planes of the folds are rotated from southeast to northwest dips in the hanging wall. Above the Alaculsy Valley fault, Taconic structures are well developed in a central fold belt in the foothills. These structures southeastward. The southeastern portion of the study area, the mountain belt, shows increasing structural complexity and polyphase deformation. . Tectonic thickening by development of thrust splays. is probably responsible for development of the Great Smoky anticlinorium and the uplift of progressively higher grade metamorphic rocks to the surface. The Sassafras Ridge thrust overrides much of the mountain belt. Small macroscopic F folds in the hanging wall of the sheet are discordant to thrusting. Fault fabrics are similar to those developed in the frontal thrust zone and indicate that the Sassafras Ridge thrust formed during emplacement of the Great Smoky overthrust.