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Tectonic map of the southern and central Appalachians: A tale of three orogens and a complete Wilson cycle

By
Robert D. Hatcher, Jr.
Robert D. Hatcher, Jr.
1
Department of Earth and Planetary Sciences and Science Alliance Center of Excellence, University of Tennessee, Knoxville, Tennessee 37996-1410, USA
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Brendan R. Bream
Brendan R. Bream
2
Department of Earth and Environmental Sciences, Vanderbilt University, Nashville, Tennessee 37235, USA
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Arthur J. Merschat
Arthur J. Merschat
3
Department of Earth and Planetary Sciences and Science Alliance Center of Excellence, University of Tennessee, Knoxville, Tennessee 37996-1410, USA
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Published:
January 01, 2007

A new tectonic map of the southern and central Appalachians incorporates modern field and structural-stratigraphic, geochronologic (mostly sensitive high-resolution ion microprobe–reverse geometry, SHRIMP–RG, and Sm-Nd), geochemical, and geophysical data to identify crustal boundaries and blocks. Major tectonic units include the ∼735 Ma Laurentian failed rift, ∼565 Ma rifted margin sedimentary-volcanic assemblage deposited on Grenvillian and pre-Grenvillian crust, the Laurentian platform, and a series of distal Laurentian terranes (Cowrock, Cartoogechaye, Tugaloo-Chopawamsic-Potomac) accreted to Laurentia during the Taconian (Ordovician) or Neoacadian (Late Devonian–early Mississippian) orogenies. The Dahlonega gold belt consists of more proximal metasandstone and pelitic schist; it also contains Ordovician arc volcanic rocks, and a mixed detrital zircon suite of Laurentian and Gondwanan, or Penokean, affinity. The newly recognized Cat Square terrane contains Laurentian, Avalonian, and 430 Ma detrital zircons, and is considered a remnant ocean basin that closed during Acadian-Neoacadian accretion of the Carolina superterrane. The Pine Mountain terrane (southernmost exposed Appalachians) consists of Grenvillian basement and a cover sequence bearing Gondwanan or Penokean detrital zircons. The Carolina superterrane contains numerous peri-Gondwanan terranes that were deformed, metamorphosed, and amalgamated prior to 530 Ma, then accreted to Laurentia during the Neoacadian along the central Piedmont suture. The Raleigh-Goochland terrane contains blocks of Laurentian basement and cover that moved SW (dextrally) out of the collision zone to the north as the Theic ocean closed north to south during the early Alleghanian orogeny. This event also produced the Kiokee-Raleigh belt high-grade metamorphic core in the eastern Piedmont, and includes faults of the Pine Mountain window. The latter is framed by Alleghanian thrust and dextral faults formed at different crustal depths (times?). Subsurface components of the southern and central Appalachians are recognized in potential field and limited drill data. The Carolina superterrane extends beneath the Coastal Plain—possibly eastward to the East Coast magnetic anomaly. South of the Carolina superterrane and north of the Wiggins suture is the Brunswick (Charleston) terrane, another peri-Gondwanan terrane. The east–west Alleghanian Wiggins suture with the Suwannee terrane is recognizable to the south beneath Georgia and Alabama in potential field data, truncating all Appalachian structures and older crustal blocks west of the Appalachians. South of the suture, African basement and cover lie in the eastern Florida subsurface, while to the west are other Gondwanan or peri-Gondwanan components that may have originally connected with Yucatan.

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GSA Memoirs

4-D Framework of Continental Crust

Robert D. Hatcher, Jr.
Robert D. Hatcher, Jr.
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Marvin P. Carlson
Marvin P. Carlson
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John H. McBride
John H. McBride
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José R. Martínez Catalán
José R. Martínez Catalán
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Geological Society of America
Volume
200
ISBN print:
9780813712000
Publication date:
January 01, 2007

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