Paper No. 27
Presentation Time: 8:00 AM-12:00 PM
INTERPRETATION OF THE COLD SPRINGS FAULT ZONE, EASTERN GREAT SMOKY MOUNTAINS: GEOMETRY, KINEMATICS, CHRONOLOGY, AND METAMORPHIC CONDITIONS
The Cold Springs fault zone (CSFZ) typifies extensiveLate Paleozoic ductile deformation that overprints Precambrian (Grenville) and Early Paleozoic (Taconian) assemblages and fabrics. The CSFZ is mapped as cutting the core of the Cataloochee anticlinorium, and may hold clues to the formation of this major structure in the eastern Great Smoky Mountains. A field study was conducted in the northeast and central Cove Creek Gap (NC) and adjacent Lemons Gap 7.5 min. quadrangles, to document the kinematics of the fault zone, and characterize the deformation style and conditions of the Wading Branch formation within the CSFZ. A traverse along I-40 determined that the fault zone is approximately one kilometer in width. L, S, L-S, and S-C tectonites were derived from deformation of feldspathic siltstones, sandstones and conglomerates of the Wading Branch. Average foliation dips 42 to 145 with only minor variation. Average stretching lineations (e.g., elongate quartz pebbles, mineral streaks, feldspar trains) plunge 29 to 207, indicating reverse oblique slip. White micas form mica fish and shear bands. Highly strained (often blue) quartz occurs as fish, asymmetric grains, and ribbons several cm in length. Quartz exhibits sub-grain formation and dynamic recrystallization. Feldspars deform primarily by fracturing (locally forming bookshelf structure) and exhibit deformation twins, kink bands, pressure solution and locally dynamic recrystallization around grain rims. S-C fabrics are observed at the micro and macroscopic scale. Quartz and second generation biotite fill fractures in feldspars. Other metamorphic minerals include epidote, chlorite, and titanite (nucleating on ilmenite and defining elongate asymmetric trains of recrystallized aggregates), consistent with deformation at greenschist facies conditions. All kinematic indicators in oriented thin sections show thrust motion. The contrast in deformation behavior between quartz and feldspar and growth of biotite are consistent with temperatures at or above the closure temperature of fine-grained white mica. The late faulting increases the apparent outcrop width of the Snowbird Group. The fault was originally mapped to extend further southwest to the Cataloochee Valley, however, highly strained rocks were not observed there.