Piedmont province of Southern Appalachians is comprised of exotic and North American terranes.

Many of the bounding faults between these terranes are wide ductile shear zones. many of which exhibit clear evidence of Alleghanian dextral motion.

Modoc Zone: an example of one of the faults in the EPFZ.

• mapped from near Columbia, S.C. to near Macon, Georgia.
• separates low grade greenschist facies Carolina terrance metasediments from an older basement terrane (the Savannah River terrane) to the South.
• Alleghanian age sill intrusions highly deformed, constraining age of dextral motion as being Alleghanian.
• disparity in geothermometers indicates there was a dip-slip 'normal' component.

EPFZ dextral motion is contemporaneous with Alleghanian thin-skinned folding and thrusting in the Valley and Ridge and Blue Ridge.

• suggests large scale decoupling of orogen parallel and orogen perpendicular motions.
• Alleghanian folds and the thin skinned character of the Piedmont sheets indicates there is Alleghaninan orogen perpendicular contraction also, so decoupling is partial.
• Brevard zone is approximate partitioning boundary.
• How do strike-slip faults connect to subhorizontal detachment suggested by COCORP work for much of the Piedmont?

Were orogen parallel motions due to oblique collision or due to escape tectonics?