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Sheath folds in pelitic schists of the Tia complex of the Yarrowitch block are described. Multiple deformations and their kinematic interpretation in the complex are re-examined. Two major mesoscopic deformation cycles (D1 and D2) are identified. D1 is associated with the formation of sheath folds and probably represents the earliest deformation in the region which occurred during high P/T metamorphism of 310-320 Ma. D2 formed asymmetrical open～gentle fold with veins of biotite-quartz during the Tia granodiorite emplacement of 265 Ma. The sheath folds seem to have occurred along a nappe boundary between the Oxley and Brackendale metamorphics.