A Billion Years of Deformation in the Central Appalachians: Orogenic Processes and Products
Downloaded from fieldguides.gsapubs.org on October 15, 2015 The Geological Society of America Field Guide 40 2015 A billion years of deformation in the central Appalachians: Orogenic processes and products Steven J. Whitmeyer Department of Geology and Environmental Science, James Madison University, Harrisonburg, Virginia 22807, USA Christopher M. Bailey Department of Geology, College of William & Mary, Williamsburg, Virginia 23187, USA David B. Spears Virginia Department of Mines, Minerals, and Energy, Division of Geology and Mineral Resources, Charlottesville, Virginia 22903, USA ABSTRACT The central Appalachians form a classic orogen whose structural architecture developed during episodes of contractional, extensional, and transpressional defor- mation 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 fi eld 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 Vir- ginia, 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 fore- land that were folded, faulted, and cleaved in the late Paleozoic, to brittle extensional structures that overprint many of these rocks.
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