10 Recent Advances and New Approaches in the Study of Faults and Shear Zones in Orogenic Systems (Posters)

Thursday, 28 March 2019
8:00 AM - 12:00 PM
Carolina Ballroom

MICROSTRUCTURAL OBSERVATIONS OF KINEMATICS AND DEFORMATION TEMPERATURES RECORDED IN THE CLYDE 7.5-MINUTE QUADRANGLE, WESTERN NORTH CAROLINA, USA: IMPLICATIONS FOR THE SOUTHWEST EXTENSION OF THE BURNSVILLE FAULT

Paper number: 10-2
Program: Theme Sessions
Time: 8:00 AM – 12:00 PM

Authors

Abstract

The Appalachians resulted from a complex series of orogenies associated with the formation and subsequent rifting of Rodinia and Pangea. Three major mountain building events are associated with the assembly of Pangea: the Ordovician Taconic, Silurian-Devonian Acadian, and the late Paleozoic Alleghanian orogenies. Deformation caused by these orogenies has been recorded in the Clyde 7.5-minute quadrangle within Haywood County, western North Carolina. The dextral Burnsville fault has been documented northeast of this quadrangle as an Acadian reactivation of the Taconic boundary between the Ashe Metamorphic Suite and Grenville basement rocks. This contact continues southwest into the Clyde quadrangle where it transitions into what has been mapped as a portion of the Taconic Hayesville fault. Field observations suggest that dextral shearing along the Burnsville fault continues into this quadrangle along these structures. The Acadian dextral shear zone is not offset by what has been mapped as the Alleghanian Fries and Chattahoochee thrust faults exposed north and south of these structures, respectively, suggesting that these structures may predate the Burnsville fault. This study presents new microstructural data to support these field observations. Microstructural shear sense indicators such as oblique quartz fabrics and mica fish support dextral strike slip shearing along the Burnsville fault. Deformation temperatures obtained from dynamic quartz recrystallization that occurred during deformation showed temperatures of ~400-500° C. Oblique quartz fabrics, mica fish, and rotated porphyroclasts suggest west-directed shearing north and south of the Burnsville fault along what has been mapped as the Fries and Chattahoochee thrusts, respectively. Quartz exhibits subgrain rotation and some grain boundary migration along these thrusts, indicating temperatures of ~500° C. These faults do not appear to offset the Burnsville fault which along with these deformation temperatures are consistent with west-directed shearing that predates the Burnsville fault.

Geological Society of America Abstracts with Programs. Vol. 51, No. 3

doi: 10.1130/abs/2019SE-327776

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