Rotation of fabric elements in convergent shear zones, with examples from the southern Appalachians

John R. Pray, Donald T. Secor, Paul E. Sacks, Harmon D. Maher

Research output: Contribution to journalArticle

11 Citations (Scopus)

Abstract

Plane-strain shear zones between rigid walls which do not rotate but which converge and move laterally relative to each other are here-in referred to as convergent shear zones. Analysis of the deformation in convergent shear zones indicates the existence of two flow apophyses, one parallel to the shear zone wall and the other inclined to the wall. Modeling of the development of fabrics in convergent shear zones indicates the occurrence of stable orientations in which S and C′ do not rotate and are oppositely inclined to the shear-zone boundary. The stable C′ orientation is parallel to the inclined flow apophysis and also is parallel to the approach velocity vector of the opposing walls of the shear zone. If it can be demonstrated from field relationships that the walls of a shear zone were rigid and remained parallel, then the occurrence of a flow apophysis inclined in the direction of shear is diagnostic of convergent shear. S and C′ fabrics in the Ridge Road and Gundy Creek shear zones of the southern Appalachian Piedmont are interpreted to indicate a convergent shear regime with an approach velocity vector oriented ∼ 10-13° clockwise from the strike of the zones.

Original languageEnglish (US)
Pages (from-to)1023-1036
Number of pages14
JournalJournal of Structural Geology
Volume19
Issue number8
DOIs
StatePublished - Aug 1997

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shear zone
fabric
plane strain
piedmont
road
modeling

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  • Geology

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Rotation of fabric elements in convergent shear zones, with examples from the southern Appalachians. / Pray, John R.; Secor, Donald T.; Sacks, Paul E.; Maher, Harmon D.

In: Journal of Structural Geology, Vol. 19, No. 8, 08.1997, p. 1023-1036.

Research output: Contribution to journalArticle

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abstract = "Plane-strain shear zones between rigid walls which do not rotate but which converge and move laterally relative to each other are here-in referred to as convergent shear zones. Analysis of the deformation in convergent shear zones indicates the existence of two flow apophyses, one parallel to the shear zone wall and the other inclined to the wall. Modeling of the development of fabrics in convergent shear zones indicates the occurrence of stable orientations in which S and C′ do not rotate and are oppositely inclined to the shear-zone boundary. The stable C′ orientation is parallel to the inclined flow apophysis and also is parallel to the approach velocity vector of the opposing walls of the shear zone. If it can be demonstrated from field relationships that the walls of a shear zone were rigid and remained parallel, then the occurrence of a flow apophysis inclined in the direction of shear is diagnostic of convergent shear. S and C′ fabrics in the Ridge Road and Gundy Creek shear zones of the southern Appalachian Piedmont are interpreted to indicate a convergent shear regime with an approach velocity vector oriented ∼ 10-13° clockwise from the strike of the zones.",
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