A Middle Silurian thin-skinned style of deformation is documented in the southeastern corner of the Lachlan Fold Belt. Thrusts are south to southeast verging and are mainly localized within or at the base of an Upper Ordovician incompetent black shale and also in inferred underlying Lower Ordovician turbidites. The eastern margin of the thrust belt is a later regional high-angle reverse fault that corresponds to the I-S line. We suggest that the thin-skinned structures developed on a cryptic terrane of old, rigid continental crust (identified by previous granitoid source data) surrounded by less rigid crust. Such areally restricted thrust belts may occur in the inboard parts of other fold belts and may form at different times in their evolution.