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A billion years of deformation in the central Appalachians: Orogenic processes and products

By
Steven J. Whitmeyer
Steven J. Whitmeyer
Department of Geology and Environmental Science, James Madison University, Harrisonburg, Virginia 22807, USA
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Christopher M. Bailey
Christopher M. Bailey
Department of Geology, College of William & Mary, Williamsburg, Virginia 23187, USA
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David B. Spears
David B. Spears
Virginia Department of Mines, Minerals, and Energy, Division of Geology and Mineral Resources, Charlottesville, Virginia 22903, USA
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Published:
January 01, 2015

Abstract

The central Appalachians form a classic orogen whose structural architecture developed during episodes of contractional, extensional, and transpressional deformation from the Proterozoic to the Mesozoic. These episodes include components of the Grenville orogenic cycle, the eastern breakup of Rodinia, Appalachian orogenic cycles, the breakup of Pangea, and the opening of the Atlantic Ocean basin. This field trip examines an array of rocks deformed via both ductile and brittle processes from the deep crust to the near-surface environment, and from the Mesoproterozoic to the present day.

The trip commences in suspect terranes of the eastern Piedmont in central Virginia, and traverses northwestward across the Appalachian orogen through the thick-skinned Blue Ridge basement terrane, and into the thin-skinned fold-and-thrust belt of the Valley and Ridge geologic province. The traverse covers a range of deformation styles that developed over a vast span of geologic time: from high-grade metamorphic rocks deformed deep within the orogenic hinterland, to sedimentary rocks of the foreland that were folded, faulted, and cleaved in the late Paleozoic, to brittle extensional structures that overprint many of these rocks. Stops include: the damage zone of a major Mesozoic normal fault, composite fabrics in gneiss domes, transpressional mylonites that accommodated orogen-parallel elongation, contractional high-strain zones, and overpressured breccia zones in the Blue Ridge, as well as folds, thrusts, and back thrusts of the Alleghanian foreland.

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Contents

GSA Field Guide

Tripping from the Fall Line: Field Excursions for the GSA Annual Meeting, Baltimore, 2015

David K. Brezinski
David K. Brezinski
Maryland Geological Survey 2300 St. Paul Street Baltimore, Maryland 21218, USA
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Jeffrey P. Halka
Jeffrey P. Halka
Maryland Geological Survey 2300 St. Paul Street Baltimore, Maryland 21218, USA
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Richard A. Ortt, Jr.
Richard A. Ortt, Jr.
Maryland Geological Survey 2300 St. Paul Street Baltimore, Maryland 21218, USA
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Geological Society of America
Volume
40
ISBN electronic:
9780813756400
Publication date:
January 01, 2015

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