I solve boundary-value problems for an idealized thrust block moving over a detachment surface and ramp, and produce theoretical bed-duplication folds in the thrust block that closely resemble the Powell Valley anticline in the southern Appalachian Mountains. The anticline is narrow and rounded if the translation is small, and broad and flat-topped if the translation is large. The limbs of the anticline are symmetric if drag is zero. Drag along the ramp part of the detachment surface can explain the asymmetry of dips of the two limbs of the Powell Valley anticline, particularly if drag between relatively competent rocks in opposition at the ramp causes an initial anticline to form as the thrust block begins to move, and then drag reduces markedly as relatively soft shales at the base of the block were thrust over competent rocks in the ramp.