Skip to Main Content
Book Chapter

Blue Ridge–Inner Piedmont geotraverse from the Great Smoky fault to the Inner Piedmont: Upper crust to upper-lower crust, terranes, large faults, and sutures

By
Arthur J. Merschat
Arthur J. Merschat
U.S. Geological Survey, Reston, Virginia 20192, USA
Search for other works by this author on:
Robert D. Hatcher, Jr.
Robert D. Hatcher, Jr.
Department of Earth and Planetary Sciences and Science Alliance Center of Excellence, University of Tennessee, Knoxville, Tennessee 37996, USA
Search for other works by this author on:
J. Ryan Thigpen
J. Ryan Thigpen
Department of Earth and Environmental Sciences, University of Kentucky, Lexington, Kentucky 40506, USA
Search for other works by this author on:
Elizabeth A. McClellan
Elizabeth A. McClellan
Department of Geology, Radford University, P.O. Box, 6939, Radford, Virginia 24142, USA
Search for other works by this author on:
Published:
March 29, 2018
08 January 2018

ABSTRACT

The southern Appalachian orogen is a Paleozoic accretionary-collisional orogen that formed as the result of three Paleozoic orogenies, Taconic, Acadian and Neoacadian, and Alleghanian orogenies. The Blue Ridge–Piedmont megathrust sheet exposes various crystalline terranes of the Blue Ridge and Inner Piedmont that record the different effects of these orogenies. The western Blue Ridge is the Neoproterozoic to Ordovician Laurentian margin. Constructed on Mesoproterozoic basement, 1.2–1.0 Ga, the western Blue Ridge transitions from two rifting events at ca. 750 Ma and ca. 565 Ma to an Early Cambrian passive margin and then carbonate bank. The Hayesville fault marks the Taconic suture and separates the western Blue Ridge from distal peri-Laurentian terranes of the central and eastern Blue Ridge, which are the Cartoogechaye, Cowrock, Dahlonega gold belt, and Tugaloo terranes. The central and eastern Blue Ridge terranes are dominantly clastic in composition, intruded by Ordovician to Mississippian granitoids, and contain ultramafic and mafic rocks, suggesting deposition on oceanic crust. These terranes accreted to the western Blue Ridge during the Taconic orogeny at 462–448 Ma, resulting in metamorphism dated with SHRIMP (sensitive high-resolution ion microprobe) U-Pb ages of metamorphic zircon. The Inner Piedmont, which is separated from the Blue Ridge by the Brevard fault zone, experienced upper amphibolite, sillimanite I and higher-grade ­metamorphism during the Acadian and Neoacadian orogenies, 395–345 Ma. These events also affected the eastern Blue Ridge, and parts of the western Blue Ridge. The Acadian and Neoacadian orogeny is the result of the oblique collision and accretion of the peri-Gondwanan Carolina superterrane overriding the Inner Piedmont. During this collision, the Inner Piedmont was a forced mid-crustal orogenic channel that flowed NW-, W-, and SW-directed from underneath the Carolina superterrane. The Alleghanian orogeny thrust these terranes northwestward as part of the Blue Ridge–Piedmont megathrust sheet during the collision of Gondwana (Africa) and the formation of Pangea.

You do not currently have access to this article.
Don't already have an account? Register

Figures & Tables

Contents

GSA Field Guides

Geology at Every Scale: Field Excursions for the 2018 GSA Southeastern Section Meeting in Knoxville, Tennessee

Annette Summers Engel
Annette Summers Engel
Search for other works by this author on:
Robert D. Hatcher, Jr.
Robert D. Hatcher, Jr.
Search for other works by this author on:
Geological Society of America
Volume
50
ISBN electronic:
9780813756509
Publication date:
March 29, 2018

GeoRef

References

Related

A comprehensive resource of eBooks for researchers in the Earth Sciences

This Feature Is Available To Subscribers Only

Sign In or Create an Account

This PDF is available to Subscribers Only

View Article Abstract & Purchase Options

For full access to this pdf, sign in to an existing account, or purchase an annual subscription.

Subscribe Now