Paper No. 4-2
Presentation Time: 8:40 AM
EMPLACEMENT KINEMATICS OF TWO LARGE HORSES ALONG THE GREAT SMOKY FAULT IN THE PARKSVILLE 7.5-MINUTE QUADRANGLE, SOUTHEASTERN TENNESSEE
The Great Smoky fault (GSF) separates Blue Ridge geology to the east from Valley and Ridge geology to the west. The GSF is the largest fault in the southern Appalachians, and, based on geologic and seismic-reflection data, has some 400 km of displacement. The GSF displays a marked change in strike from SE TN into NW GA of ~045 to ~010 in the Parksville 7.5-minute quadrangle in SE TN, some 80 km (50 mi) E of Chattanooga. This quadrangle contains good to excellent exposure on both sides of the GSF, with Neoproterozoic to Lower Cambrian rocks (Walden Creek and Chilhowee Groups) to the E and Cambrian to Middle Ordovician rocks (Rome Fm., and Conasauga, Knox, and Chickamauga Groups) to the W. The Parksville quadrangle is currently being mapped to collect sufficient lithologic and structural data to produce a detailed geologic map to better understand the emplacement kinematics of the Chilhowee Group horses and Blue Ridge thrust sheet. This mapping revises a reconnaissance geologic map by Sutton, which was part of an earlier University of Tennessee dissertation. Along the GSF are two large horses of Cambrian Chilhowee Group rocks, the smaller of which (at the TVA Ocoee #1 Dam) may contain a thinned Chilhowee Group sequence. Studying these horses may provide new insight into the emplacement history of the Blue Ridge-Great Smoky thrust sheet and why the strike of the frontal Blue Ridge changes abruptly in this area. Core samples and thin sections of the Chilhowee Group horse at the GSF beneath Ocoee #1 display intense brittle and semi-ductile deformation, highly strained quartz, stylolites in the quartzite, along with other complex microfabrics not seen elsewhere along the fault, in the horses, or in Chilhowee sandstones. Initial data suggest that the frontal Blue Ridge hanging wall either fragmented as it ramped over strong platform sedimentary rocks, or picked off the horses down dip to the SE, leading to emplacement of the two horses, possibly causing the change in strike of the GSF and footwall. Alternatively, this curvature may be a relict of the Neoproterozoic Laurentian continental margin, and the horses were picked off in transit from a cryptic rift basin containing Chilhowee Group rocks.