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The tectono-thermal evolution of the central Appalachian Orogen: Accretion of a peri-Gondwanan(?) Ordovician arc

By
Howell Bosbyshell
Howell Bosbyshell
Department of Geology & Astronomy, West Chester University of Pennsylvania, 700 South High Street, West Chester, Pennsylvania 19383, USA
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LeeAnn Srogi
LeeAnn Srogi
Department of Geology & Astronomy, West Chester University of Pennsylvania, 700 South High Street, West Chester, Pennsylvania 19383, USA
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Gale C. Blackmer
Gale C. Blackmer
Pennsylvania Geological Survey, 3240 Schoolhouse Road, Middletown, Pennsylvania 17057, USA
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William S. Schenck
William S. Schenck
Delaware Geological Survey, 257 Academy Street, University of Delaware, Newark, Delaware 19716-7501, USA
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Ryan Mathur
Ryan Mathur
Department of Geology, Juniata College, 1700 Moore Street, Huntingdon, Pennsylvania 16652, USA
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Victor Valencia
Victor Valencia
School of the Environment, PO Box 642812, Washington State University, Pullman, Washington 99164-2812, USA
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Published:
January 01, 2015

Abstract

Recent detrital zircon results in both the central Appalachians and New England demonstrate that middle Ordovician, ‘Taconic’ island arcs, long considered to be peri-Laurentian, are built upon or associated with rock of Gondwanan affinity. This trip will visit granulite-facies orthogneiss of the Wilmington Complex, a 475–480 Ma magmatic arc, and the adjacent Wissahickon Formation. The Wissahickon Formation is intruded by and interlayered with meta-igneous rocks with arc affinity and contains detrital zircon populations characteristic of both Gondwanan and Laurentian sources. The Chester Park Gneiss, now known to have detrital zircon age spectra which match the Gondwana-derived Moretown Terrane in New England, is also featured. The trip will examine contact relationships between arc and Laurentian rocks and a newly discovered location where metapelitic rock contains garnet with crystallographically oriented rutile inclusions, possibly indicative of ultrahigh-temperature or ultrahigh-pressure metamorphism. We will discuss similarities between rocks of the central and northern Appalachians and evaluate a new model wherein the central Appalachian rocks were originally part of the Taconic arc in New England and were translated by strike-slip deformation to their present position in the orogen.

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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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