ABSTRACT
Stratigraphy on the eastern flank of the Southern Appalachian Blue Ridge near the Grandfather Mountain window is arranged in a series of fault-bounded lithotectonic belts stacked so that the structural section dips steeply southeast. The Fries block of the Blue Ridge thrust sheet overlies the Grandfather Mountain window along the Linville Falls fault. The Laytown belt overlies the Fries block along the Winding Stairs Mountain fault. The Brevard zone, bounded at its base by the Ripshin Mountain fault and bounded at its top by the Yadkin fault, lies on the Laytown belt. Augen gneiss and granitic gneiss of the Inner Piedmont, here called Henderson gneiss, sharply abuts the Brevard zone along the Yadkin fault. It is unlikely that any coherent stratigraphy exists in the Brevard zone.
All principal foliations in the Grandfather Mountain window, Blue Ridge thrust sheet, and Brevard zone are the result of the transposition of an earlier layering or foliation. Brevard zone mylonites commonly show isoclinally refolded isoclines. The mylonitic foliation there is the culmination of multiple deformation. Distinct zones in the Fries block contain a superimposed cleavage that results in locally transposed, mylonitic shear zones. These shear zones are sites for retrograde metamorphism and they are interpreted to be faults, possibly splays off a thrust that may emerge as the Linville Falls fault. Lineations were produced as a result of transposition. The principal lineation in the Grandfather Mountain window is older than the principal lineation in the Blue Ridge and the Brevard zone. Interpretations of shear sense in the Brevard zone based on orientations or reorientations of the lineations are not appropriate.
Shear across low angle oblique crenulation cleavage is consistently dextral in the Brevard zone. The cleavage event is interpreted to have occurred in the latter stages of late Paleozoic ductile deformation and retrograde metamorphism in the Brevard zone. The cleavage geometry suggests dextral strike-slip motion on the Brevard zone.
Theoretical models for irrotational structures in two-dimensional plane strain demonstrate that: (1) lines of material particles lying in an oblique irrotational orientation make an angle, a, with the shear zone boundaries whose vertex indicates the shear sense for the simple shear component and (2) the oblique irrotational direction could experience a component of simple shear equal in sign to that of the shear zone.

Bobyarchick, A.B., 1983. Structure of the Brevard Zone and Blue Ridge near Lenoir, North Carolina, with observations on oblique crenulation cleavage and a preliminary theory for irrotational structures in shear zones.  Unpublished PhD dissertation, State University of New York at Albany. 306pp., +x; 5 folded plates (maps)
University at Albany Science Library call number:  SCIENCE MIC Film QE 40 Z899 1983 B63
Copies of this PhD dissertation can be ordered from Proquest UMI

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