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To promote a wider use of S and Z buckle folds in field-based structural studies, we first formulate three conditions under which quasi-cylindrical segments of gentle to close S and Z folds indicate the sense of finite-shear components. Based on our results of shear-sense mapping, we then assess the validity of published geological hypotheses in well-exposed parts of the western Grenville Province and the Southern Appalachians. Near the Central metasedimentary belt boundary of southeastern Ontario, which is widely interpreted as a 1090–1050 Ma ductile thrust, most orogen-normal, southeasterly plunging, gentle to close folds in the main foliation prove to have S style. This attests to a regional component of orogen-parallel sinistral shear that probably postdates the ductile thrusting. In gneisses and schists of the northern Inner Piedmont, six deformation events (D1–D6) are recognized by other workers. We focus attention mainly on early Alleghanian, orogen-parallel folds (F3) and associated mineral-shape fabrics in the Salem-Sunset area, western Inner Piedmont of South Carolina. Here, the orientation and S and Z style of mesoscopic F3 features attest to an orogen-normal component of distributed thrust shear, and thereby strengthen the case for northwest-directed displacements of ductile thrust sheets during early stages of the Alleghanian orogeny.

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