Document Type
Thesis
Abstract
The Appalachian belt of eastern Laurentia records evidence of three Paleozoic deformation events: the Taconic, Acadian, and Alleghanian orogenies. Paleozoic deformation folded and thrusted the Blue Ridge province of Virginia. Discrete, anastomosing high-strain zones that cut the Blue Ridge anticlinorium’s Grenvillian basement core accommodated thrusting of at least one of these Paleozoic events. A segment of the Blue Ridge high-strain zones is mapped though Greene County, Virginia, and cuts two gneissic granitoid plutons. White mica, biotite, chlorite, and recrystallized quartz define the mylonitic foliation. The zone is 0.5 —1 km wide, strikes northeast, and dips moderately to the southeast. A top to the northwest reverse sense of shear is recorded by tails on quartz and perthite porphyroclasts. Based on biotite formation and quartz recrystallization, the high-strain zone deformed at greenschist facies temperatures (350-400°C). From structural relations of the Blue Ridge rocks and the cooling history suggested by new “’Ar/*’Ar data, deformation is estimated at having occurred at a crustal depth of 15 + 5 km. Previous suggestions for the timing of deformation along these zones have been largely based on field relations. “°Ar/*’Ar geochronology dates the age of deformation in the Blue Ridge high-strain zones as occurring during the early Alleghanian (320-330 Ma). K-feldspar spectra suggest Blue Ridge basement rocks cooled below 150°C at ~200 Ma. This could be an extended cooling from 350-150°C during exhumation of the Blue Ridge core from ~320 to ~200 Ma. The data could also be interpreted as a reheating of the system due to hydrothermal heat transfer from Mesozoic dikes intruded into the Blue Ridge region at this time.
Date Awarded
2005
Department
Geology
Advisor 1
Christopher M. Bailey
Recommended Citation
Wooton, Kathleen M., "The Nature and Timing of Deformation in th Ble Ridge Province, Greeme County, Virginia" (2005). Geology Senior Theses. William & Mary. Paper 146.
https://scholarworks.wm.edu/geologyseniors/146
