The Saltville thrust sheet in the southwest Virginia portion of the Appalachian foreland fold and thrust belt generally has very little penetrative deformation. At the southern termination of Walker Mountain however, a continuous 10-15 km zone along strike is highly strained and polydeformed. In this area a NW-trending mesoscopic solution cleavage and associated buckle folds are obliquely superimposed on the regional northeast structural trend. Values of penetrative strain, determined from syntectonic fibrous mineral growths in pressure fringes, vary along strike and vertically within the thrust sheet and indicate up to 50% shortening approximately orthogonal to cleavage. Fibers are virtually straight and undeformed reflecting a nearly coaxial strain history associated with cross-structural evolution. The cross-structures deform the Saltville sheet as well as the leading edge of the Pulaski sheet and were not rotated into their present orientation, but were initiated and evolved oblique to the northwest direction of tectonic transport. Cross-structural development is best explained by the oblique propagation of a portion of the frontal-tip of the evolving Saltivlle thrust in response to varying degrees of detachment. The variable ease with which the decollement was able to migrate through the rocks created zones of differential movement in the overlying sheet and the generation of locally high strains in the tip region. Spatial variation in strain and in the orientation of structural elements may be used to delineate zones of differential thrust movement. / M.S. / Bibliography: leaves 57-65.