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The distribution of layer parallel shortening fabrics in the Appalachian foreland of New York and ‘Pennsylvania: Evidence for two non-coaxial phases of the Alleghanian orogeny

By
Peter Geiser
Peter Geiser
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Terry Engelder
Terry Engelder
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Published:
January 01, 1983

This paper presents a structural interpretation of a part of the central and northern Appalachian foreland using the correlation in orientation of such deformation features as mechanical twins, solution cleavage, crenulation cleavage, pencils, joints, and deformed fossils. Such a correlation suggests that, within the central Appalachians, the Alleghanian orogeny consists of two major phases: a deformation possibly as old as Pennsylvanian, herein called the Lackawanna phase, and a second deformation, termed the Main phase of Permian or younger age. Effects of the Lackawanna phase deformation are found mainly in the Hudson River Valley and Pocono plateau, while effects in the Main phase deformation are found throughout the Valley and Ridge and Alleghany Plateau. The Lackawanna phase is interpreted as the product of strike-slip motion, possibly between the Avalon microcontinent and North America. The Main phase may record the final convergence of Africa against North America and accreted terranes.

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GSA Memoirs

Contributions to the Tectonics and Geophysics of Mountain Chains

Robert D. Hatcher, Jr.
Robert D. Hatcher, Jr.
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Harold Williams
Harold Williams
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Isidore Zietz
Isidore Zietz
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Geological Society of America
Volume
158
ISBN print:
9780813711584
Publication date:
January 01, 1983

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