Elevating Geoscience in the Southeastern United States: New Ideas about Old Terranes—Field Guides for the GSA Southeastern Section Meeting, Blacksburg, Virginia, 2014
This volume includes 10 field guides that explore the diverse geology of the southern and central Appalachians. These guides examine both ancient rocks and modern landscape processes, highlighting new research ideas regarding these old terranes. Three guides focus on the geology of the Appalachian Plateau and Valley and Ridge, considering topics such as the enigmatic Eocene igneous rocks, the gas-rich Marcellus and Millboro Shales, and new models for karst formation. The 2011 M5.8 Mineral, Virginia, earthquake literally shook up our understanding of the Piedmont and two guides focus on new research in the epicentral region. Two guides take in the Paleozoic to Proterozoic geology of the Blue Ridge province. The volume is rounded out by three guides focused on Mesozoic geology, including the world-class Lagerst–tte fauna in the Dan River basin, a unique uranium deposit at Coles Hill, Virginia, and the tectonics of the Scottsville Basin.
Key structural and stratigraphic relationships from the northeast end of the Mountain City window and the Mount Rogers area, Virginia–North Carolina–Tennessee
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Published:January 01, 2014
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CiteCitation
Arthur J. Merschat, Scott Southworth, Elizabeth McClellan, Richard P. Tollo, Douglas W. Rankin, Seth Hooper, Samantha Bauer, 2014. "Key structural and stratigraphic relationships from the northeast end of the Mountain City window and the Mount Rogers area, Virginia–North Carolina–Tennessee", Elevating Geoscience in the Southeastern United States: New Ideas about Old Terranes—Field Guides for the GSA Southeastern Section Meeting, Blacksburg, Virginia, 2014, Christopher M. Bailey, Lorrie V. Coiner
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Abstract
Recent field and associated studies in eight 7.5-minute quadrangles near Mount Rogers in Virginia, North Carolina, and Tennessee provide important stratigraphic and structural relationships for the Neoproterozoic Mount Rogers and Konnarock formations, the northeast end of the Mountain City window, the Blue Ridge–Piedmont thrust sheet, and regional faults.
Rocks in the northeast end of the Mountain City window constitute an antiformal syncline. Overturned Konnarock and Unicoi formations in the window require a ramp-flat geometry in the hanging wall of the Blue Ridge thrust sheet or stratigraphic pinch-out of the Konnarock Formation. Undulose and ribbon quartz, fractured feldspars, and mylonitic foliations from the Stone Mountain and Catface faults indicate top-to-NW motion, and ductile deformation above ∼300 °C along the base of the Blue Ridge thrust sheet on the southeast side of the window. The Stone Mountain fault was not recognized northeast of Troutdale, Virginia. The Shady Valley thrust sheet is continuous with the Blue Ridge thrust sheet.
The ∼750 Ma Mount Rogers Formation occurs in three volcanic centers in the Blue Ridge thrust sheet. Basal clastic rocks of the lower Mount Rogers Formation nonconformably overlie Mesoproterozoic basement in the northeasternmost Razor Ridge volcanic center, but the basal contact in parts of the Mount Rogers and Pond Mountain volcanic centers is strongly tectonized and consistent with a NW-directed, greenschist-facies high-strain zone. The contact between the Mount Rogers Formation and Konnarock Formation is nonconformable, locally faulted. Metarhyolite interbedded with lacustrine and fluvial rocks suggests that volcanism and glaciation were locally coeval, establishing an age of ∼750 Ma for the Konnarock Formation, a pre-Sturtian glaciation.
Multiple greenschist-facies, high-strain zones crosscut the Blue Ridge thrust sheet including the Fries high-strain zone (2–11 km wide). Foliations across the Fries and Gossan Lead faults have similar orientations and top-to-NW contractional deformation.
- absolute age
- Appalachians
- Blue Ridge Province
- Cambrian
- Chilhowee Group
- contraction
- crystallization
- dates
- deformation
- ductile deformation
- faults
- field trips
- foliation
- guidebook
- Lower Cambrian
- magmatism
- Mesoproterozoic
- Neoproterozoic
- nesosilicates
- North America
- North Carolina
- orientation
- orogeny
- orthosilicates
- outcrops
- Paleozoic
- phenocrysts
- Piedmont
- Precambrian
- Proterozoic
- road log
- silicates
- strain
- tectonics
- Tennessee
- thrust sheets
- U/Pb
- United States
- upper Precambrian
- Virginia
- windows
- zircon
- zircon group
- southwestern Virginia
- Mountain City Window
- Mount Rogers Formation
- Fries Fault
- Mount Rogers
- Gossan Lead Fault
- Konnarock Formation
- French Broad Massif